Synthesis and characterization of Silver-Histidine complex and L-Histidine capped Ag-NPs in Buffer System, Electrochemical and Antibacterial Properties

Synthesis and characterization of Silver-Histidine complex and L-Histidine capped Ag-NPs in Buffer System, Electrochemical and Antibacterial Properties | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Synthesis and characterization of Silver-Histidine complex and L-Histidine capped Ag-NPs in Buffer System, Electrochemical and Antibacterial Properties D. S. GHARBUDE, A. G. KORE, L. M. KASHID This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9030666/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Silver-Histidine complex and L-Histidine capped silver nanoparticles (AgNPs) were chemically synthesized. Their properties were compared and thoroughly characterized using UV-visible spectroscopy, FTIR, XRD, SEM, EDAX, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). In the UV-visible spectrum, the silver-histidine complex showed an absorption peak in the lower wavelength region, which was attributed to ligand metal interaction. In contrast, L-Histidine capped AgNPs displayed a clear surface plasmon resonance (SPR) band at around 420–450 nm, thus confirming the formation of metallic Ag nanoparticles.FTIR spectra of histidine demonstrated the main functional groups, such as -NH stretching (3200–3400 cm), C = O stretching (~ 1650 cm), and imidazole -CN vibrations (1400–1500 cm), with evident changes pointing to coordination and surface capping.XRD pattern of Ag-NPs showed four well, separated diffraction peaks centered at 2θ values near 38, 44, 64, and 77 which correspond to (111), (200), (220), and (311) planes of face, centered cubic silver, respectively. The average particle size was calculated to be 22 and 40 nm by the Debye Scherrer equation.SEM pictures of the complex showed an aggregated morphology whereas capped Ag-NPs were spherical and the nanoparticles were evenly spread. EDAX analysis verified that the elements C, N, O, and Ag were present; among them, silver was significantly enriched in the nanoparticles system. Electrochemical studies such as CV and LSV were conducted and the results revealed well, defined redox peaks along with a significant increase in the current response of Ag-NPs, which is indicative of an efficient electron transfer process. The assessment of the antimicrobial property of L-Histidine capped Ag-NPs compared to Ag-Complex against Escherichia coli and Staphylococcus aureus revealed that, first, the bacteria were effectively inhibited and, second, the antibacterial activity of L-Histidine capped Ag, NPs was significantly higher. In short, this study essentially provides the evidence that the nanoparticles were successfully synthesized and that they have superior properties of morphology, electrochemistry, and antimicrobial activities as compared to Silver-Histidine complex. spectrum inhibit. Morphology electrochemistry Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 INTRODUCTION Silver, based materials have been the focus of materials science and bioinorganic chemistry for decades, mainly due to their exceptional physicochemical versatility and their widely studied biological activity. Among the noble metals, silver stands out as the only metal which is chemically stable and at the same time highly effective as an antimicrobial agent, thus it is extremely useful for applications in healthcare, environmental protection, catalysis, and electrochemical systems 1 , 2 , 3 .By selecting silver for the size reduction down to the Nano scale dimension, initially, the functionalities of the latter have been significantly boosted because silver nanoparticles (Ag-NPs) are considered to have an enhanced surface reactivity, tunable electronic properties, and a higher rate of interaction with biological entities when compared to bulk silver 4 , 5 .Consequently, Ag-NPs are presently the number one most exhaustively studying nanomaterials acutely in the forefront of research 6 , 7 .The overcrowding of the world for the efficient antimicrobial materials due to antimicrobial resistance, hospital, acquired infections, and the immediate need to the safer biomedical devices has in a great way increased the interest in silver based nanomaterials 8 .Ag-NPs are able to eliminate microorganisms through several different synergistic mechanisms. These include the rupture of the bacterial membranes, interference with enzymes inside the cells, induction of oxidative stress, and attachment to the genetic material 9 .These multiple pathway strategies not only reduce the odds of bacteria developing drug resistance but also differentiate silver, based systems from commonplace antibiotics 10 . 11 . 12 . 13 . Surface functionalization has become an essential technique for improving the stability, biocompatibility, and the overall functional performance of silver nanoparticles. One of the approaches to doing this is through ligand, mediated surface, specific modification which would allow for tunable growth of nanoparticles, provide control of surface charge and regulate interaction with the surrounding media. During the search for stabilizing agents, biologically derived ligands, more specifically amino acids, have been the centerpiece of most research owing to their low toxicity, a great variety of structures, and they can coordinate metal centers through heteroatom donor sites 14 .Functionalization of amino acids both stabilizes Ag-NPs and at the same time decorates the protein surfaces with bioactive functionalities which lead to better interaction with biological targets 15 .L-Histidine is a very interesting molecule here due to its one, of, a, kind chemical structure and the fact it is a biologically significant molecule. It is thus good for coordinating metal ions and also gives the nanomaterials resulting biocompatibility and stabilization 16 .One of the Special characteristics of Histidine is its imidazole side chain which has a strong binding affinity with metal ions and exhibits coordination behavior, which is dependent on pH, of the metal ion. This imidazole group enables Histidine to establish a strong interaction with silver ions and silver surfaces via coordination of nitrogen donor, while amino and carboxylate groups can participate in multi, dentate binding 17 , 18 . Histidine is thus capable of easily making strong silver Histidine coordination complex and serves as a very efficient capping ligand for silver nanoparticles 19 , 20 . These properties distinguish Histidine from the majority of other amino acids and render it a highly versatile ligand for silver, based coordination and nanostructure systems 21 .Silver Histidine complexes exemplify coordination compounds at the crossroads of traditional inorganic chemistry and bioinorganic materials science. Unlike their free forms, Ag ions coordinated with Histidine ligands terminals undergo changes in their electronic environment and redox properties, thus influencing not only the chemical stability but also the biological activity of the metal center 22 , 23 .Subsequently, such complexes are great models for metal, bimolecular interaction studies and unravel how biologically relevant ligands may alter silver, ion behavior 24 .Various studies have demonstrated that silver-Histidine complexes exhibited antimicrobial properties to a significantly greater extent than free silver ions, and thus the coordination chemistry plays a critical role in the mechanism of bioactive silver systems. Furthermore, except for the binuclear coordination compounds, Histidine is a main contributor to the surface modification of silver nanoparticles. L-Histidine capped Ag-NPs are a mixture of silver's intrinsic antimicrobial capability and the stabilizing and bio, functional advantages of amino acid capping. Histidine modification of metallic particles prevents their aggregation, increases the stability of the colloid, and enables the control of surface chemistry, which is crucial for obtaining consistent biological and electrochemical results. Besides, Histidine exposed on the surface of nanoparticles helps in the attachment of microbial membranes through electrostatic attraction and coordination, assisted binding, which results in higher antimicrobial effectiveness 27 , 28 . The biological potential of Histidine capped Ag-NPs in the biological system is not only their antimicrobial activity. More and more studies are revealing that such nanoparticles have antioxidant, anticancer, and anti, inflammatory properties which are related to their ability to regulate reactive oxygen species production and influence cellular signaling pathways 29 , 30 .Actually, Histidine capping has been found to be a great Biocompatibility enhancer and it also significantly reduces nonspecific cytotoxicity when compared with the parent Ag-NPs, thus offering a solution to one of the major problems faced in the use of silver nanomaterials for biomedicine 31 , 32 .Other than their biological relevance, silver, Histidine systems carry a lot of electrochemical importance as well. The binding of Histidine to silver surfaces results in changes in electron transfer kinetics at the interface, and the distribution of surface charge, which are key factors in electrochemical sensing and analytical applications 33 , 34 . Histidine, decorated silver materials provide enhanced surface availability and more reliable signal transduction, thus they can be employed for the electrochemical detection of bio-molecules and metal ions. It is a must to explore the electrochemical features of silver, Histidine complexes and Histidine, capped Ag-NPs before making a correlation between material structure and its functional attributes 35 .So, silver-Histidine coordination systems in conjunction with L-Histidine, capped silver nanoparticles constitute a fusion of coordination chemistry, nanotechnology, and bio, functional material design. The use of amino acids as ligands and stabilizers goes along with the green chemistry principles as it offers environment, friendly, sustainable, and biologically compatible alternatives to the conventional synthetic capping agents 36 , 37 . Recent research reports point to the growing importance of such nature, inspired approaches in the fabrication of high, performance nanomaterials at minimum environmental and biological hazards levels 38 . EXPERIMENTAL Materials and Methods Investigators utilized the reagents of analytical grade and no one was re, purified. AgNO 3 was the source of silver ions. L-Histidine was the ligand that coordinated and stabilized. The silver ions were reduced to metallic Ag by NaBH 4 .It was decided to make reaction environment stable by an acetate buffer which was made from sodium acetate and acetic acid and the pH was adjusted by diluted sodium hydroxide or acetic acid. Double, distilled water was used in all the solution preparations. For the determination of antibacterial activity, nutrient agar was used as the growth medium and streptomycin was used as the standard drug. General Procedure: Synthesis of Ag–Histidine Complex All the experiments were conducted in 0.04 M sodium acetate buffer kept at pH 5 and at 60 0 C with a magnetic stirrer at 400 rpm. To prepare the Ag-Histidine complex, 10 mL of 0.01 M silver nitrate (AgNO 3 ) was combined with 10 mL of 0.02 M L-Histidine solution with constant stirring. The reaction was left to continue for around 4 hours at a constant temperature. In the meantime, the formation of a yellowish suspension was observed which the indication of the silver Histidine coordination complex was. The product obtained was separated by centrifugation at 4000 rpm for 15 minutes. The precipitate obtained was first washed with ethanol and then with double, distilled water two times to get rid of the unreacted precursors and soluble impurities. The purified sample was then dried for 12h at 100 0 C and kept for further physicochemical characterization. Synthesis of L-Histidine Capped Silver Nanoparticles (Ag-NPs) L-Histidine capped silver nanoparticles were prepared by first using the Complexation procedure. After stirring for 10 minutes the reaction mixture was placed in an ice bath to slow the kinetics of the reaction and avoid uncontrolled nucleation. While the pH was kept at 5,30 mL of 0.02 M sodium Borohydrate (NaBH 4 ) solution was added drop, wise as a reducing agent under continuous stirring. Upon the reduction, the mixture of the reaction was converted gradually in colour from pale yellow to dark brown within about 1 hour, which indicated the formation of silver nanoparticles as a result of surface Plasmon resonance. The nanoparticles were separated by centrifugation at 7500 rpm for 30 min, and then they were washed several times with ethanol and distilled water to get rid of the residual by, products and impurities. Afterward, the purified nanoparticles were dried and stored for further characterization and analyses. Instrumentation: Characterization Techniques: The electrochemical behavior of the Silver-Histidine complex was comprehensively analyzed by cyclic Voltammetry (CV) and linear sweep Voltammetry (LSV) on a STAT-20 electrochemical workstation (EC, Proyog, India). The electrochemical cell consisted of a glassy carbon electrode (GCE) as the working electrode, a platinum wire as the auxiliary (counter) electrode, and an Ag/AgCl electrode as the reference electrode. Voltammograms were obtained by scanning the potential in both anodic and cathodic directions and within the potential window of 0.0 to + 1.0 V at a scan rate of 60 mV/s. linear sweep Voltammetry was used for the potential change from 0.0 to + 1.0 V at the same scan rate. All the tests were done in 0.04 M acetate buffer solution (pH 5).The UV-visible absorption of the silver-Histidine complex was investigated with a (Shimadzu UV-1800 series spectrophotometer). Spectra were recorded over the (200 nm to 800 nm) range to find ligand, to, metal charge transfer (LMCT) and possible d-d electronic transitions. Functional groups and coordination interactions were recognized by FTIR spectroscopy which was carried out on a Shimadzu (Shimadzu UV, 1800 series spectrophotometer) spectrometer (ENG 230 V). Spectra were recorded within the range 4000 − 400 cm - .X-ray diffraction (XRD) (Malvern Panalytical Empyrean DY3280 diffract meter.) analysis was used to determine the crystalline structure, phase purity, and structural parameters of the samples was used for the measurements. The surface morphology and micro structural features were investigated by scanning electron microscopy (SEM). The elemental composition was confirmed by energy, dispersive X-ray spectroscopy (EDAX). Both SEM and EDAX analyses were performed on the TESCAN CLARA series scanning electron (TESCAN, Czech Republic). RESULTS AND DISCUSSION Cyclic Voltammetry (CV) : The electrochemical interaction between Silver and Histidine was thoroughly characterized by cyclic Voltammetry (CV) and linear sweep Voltammetry (LSV) in 0.04 M acetate buffer (pH 5.0) at a scanning rate of 60 mV/s. The gradual addition of Histidine (0.0-0.5 mL) resulted in a significant reduction of the peak current and a systematic negative shift of the anodic peak potential in both methods, which was interpreted as the formation of a stable Ag-Histidine coordination complex. In CV, the anodic peak potential moved from 0.481 V to 0.424 V, a change which was highly linear and could be represented by the regression equation E =-0.114x + 0.481 (R = 0.979). On the other hand, LSV exhibited a change from 0.487 V to 0.419 V with an even better linear correlation, E =-0.137x + 0.487 (R = 0.987), revealing a higher sensitivity towards ligand metal interaction. The Cathodic shifting of the peak potential and the decrease of the peak current are in agreement with Ag binding to the imidazole nitrogen of Histidine, which alters the redox environment, decreases the amount of free silver ions, and changes the electron transfer kinetics at the electrode interface. Both methods showed excellent linear dependence, indicating that the Complexation process is concentration, dependent and can be potentially analytically applicable. Cyclic Voltammetry (CV): The electrochemical interaction between Silver and Histidine was thoroughly characterized by cyclic Voltammetry (CV) and linear sweep Voltammetry (LSV) in 0.04 M acetate buffer (pH 5.0) at a scanning rate of 60 mV/s. The gradual addition of Histidine (0.0-0.5 mL) resulted in a significant reduction of the peak current and a systematic negative shift of the anodic peak potential in both methods, which was interpreted as the formation of a stable Ag-Histidine coordination complex. In CV, the anodic peak potential moved from 0.481 V to 0.424 V, a change which was highly linear and could be represented by the regression equation E =-0.114x + 0.481 (R = 0.979). On the other hand, LSV exhibited a change from 0.487 V to 0.419 V with an even better linear correlation, E =-0.137x + 0.487 (R = 0.987), revealing a higher sensitivity towards ligand metal interaction. The Cathodic shifting of the peak potential and the decrease of the peak current are in agreement with Ag binding to the imidazole nitrogen of Histidine, which alters the redox environment, decreases the amount of free silver ions, and changes the electron transfer kinetics at the electrode interface. Both methods showed excellent linear dependence, indicating that the Complexation process is concentration, dependent and can be potentially analytically applicable. UV-Visible Spectrum:- Pure L-Histidine in sodium acetate buffer (pH 5) shows typical absorption bands of approximately 210 and 250 nm in its UV-visible spectrum. The bands are due to n → σ* and n → π* electronic transitions of imidazole ring and amino (-NH 2 ) groups in the Histidine molecule. There is no absorption in the visible region, thus free Histidine is neither plasmonic nor an extended chromophoric system. Upon binding of Ag ions, the UV band pattern significantly alters and the silver, Histidine complex exhibits a band at 290 to 310 nm, which is a characteristic of ligand, to, metal charge transfer (LMCT) between nitrogen atoms in the imidazole ring and the silver ions. Furthermore, the UV bands are slightly broadened and shifted as compared to those of pure Histidine, which is a clear sign of binding between Ag and imidazole nitrogen, and possibly also the amino group. At this pH-5, Histidine can be considered a perfect chelates ligand as it can stabilize silver ions in solution through N, donor interactions. The metallic silver nanoparticles formation is evident with the help of a strong and broad absorption band in the visible region, which is centred at 395 nm, and corresponds to the surface Plasmon resonance (SPR) of Ag nanoparticles. This SPR band is due to the conduction electrons collective oscillation on the nanoparticles surface when excited by the incident light. The broad character of the band is a signature of nanoscale particle formation with some size distribution. For L-Histidine capped Ag nanoparticles, the SPR band is accompanied by a red shift and is located in the region of 420–430 nm. This red shift relative to the uncapped Ag nanoparticles indicates surface modification and an increase in the local refractive index around the particles caused by Histidine adsorption. The stabilizing effect of Histidine consequently prevents aggregation and regulates particle growth. Moreover, the weak absorption around 300 nm corresponds to the surface, bound Histidine molecules. The relatively sharper and more stable SPR band is indicative of successful L-Histidine capping and that it is a suitable biocompatible stabilizing agent that improves dispersion and prevents excessive aggregation of the nanoparticles. FTIR Spectrum: The FTIR spectra of pure L-Histidine depict NH stretching of the amino group in association with hydrogen, bonded OH vibrations revealed by a broad absorption band in the region of 3200–3400 cm − 1 . A very strong band that muscle can be found at about 1600–1620 cm − 1 is the one resulting from the asymmetric stretching vibration of the carboxylate (COO − ) group, while the symmetric stretching vibration is near 1390–1410 cm − 1 . The extent of difference between these two bands is a perfect confirmation of the zwitterionic form of Histidine. Also, the peaks between1000-1100cm − 1 can be assigned to -CN stretching and imidazole ring vibrations, thus, proving the presence of nitrogen, containing groups capable to coordinate metal. When the Ag-Histidine compound is generated, significant changes are gone in the COO − asymmetric and symmetric stretching bands showing that Ag ions form a bond with carboxylate oxygen atoms. The -NH stretching band gets wider and is a little bit shifted, which is an indication that amino and imidazole nitrogen atoms also take part in coordination. In addition, a faint band seen in the lower frequency region near 500–600 cm − 1 is assigned to Ag-N bond vibrations, thus silver-Histidine complex formation is confirmed. The FTIR spectrum of bare Ag nanoparticles only shows very faint and broad absorption bands that are mainly caused by surface, adsorbed species or a small degree of surface oxidation. The lack of peaks related to strong organic functional groups suggests that the nanoparticles surface is predominantly metallic. In the case of L-Histidine capped Ag nanoparticles, the -NH stretching band stays wide but exhibits a minor shift compared to pure Histidine, thus confirming the surface interaction. The asymmetric and symmetric COO − stretching bands are present with only minor positional changes which imply that the carboxylate groups remain involved in stabilizing the particles. Besides the main imidazole vibrations, low, frequency bands around 500–600 cm − 1 also appear, thus corroborating a strong Ag-N interaction. These spectral differences very clearly indicate that L-Histidine indeed binds to and caps the silver nanoparticles surface. X-Ray Diffraction(XRD): The XRD pattern of the synthesized silver nanoparticles shows four distinct diffraction peaks at 2θ = 38 0 , 44 0 , 64 0 , and 77 0 .The most intense peak at 38 0 is indexed to the (111) crystallographic plane and represents the fcc silver that is most stable thermodynamically and the dominant reflection. The peak at 44 is assigned to the (200) plane, and the peaks at 64 and 77 refer to the (220) and (311) planes, respectively. The positions of these diffraction peaks are perfectly consistent with those of the standard JCPDS card for metallic silver; hence, the crystalline structure of Ag nanoparticles is confirmed. The remarkably high intensity of the (111) peak shows the preferential orientation and high crystalline of the nanoparticles. The obvious broadening of all the diffraction peaks is indicative of the nano, crystalline nature of the material. By using the Debye Scherrer formula, the crystallite size is found to be on the nanometer scale, thus confirming particulate formation. For L-Histidine capped Ag nanoparticles, one can observe the same typical fcc peaks at 2θ Positions, and thus it is confirmed that the capping does not change the crystal structure of silver. Nonetheless, more peaks broadening is observed with an additional slight decrease in peak intensity, which is a sign that there is less crystallite growth due to stabilization at the surface by Histidine molecules. Most significantly, there are no peaks of silver oxide (Ag-O) or any other impurity phases, thus the phase purity is confirmed and silver nanoparticles are effectively protected by L- Histidine. Table.1.XRD peak Position and Corresponding Miller indices (hkl) of L-Histidine capped Ag-NPs nanoparticles indexed to the face-centre cubic (fcc) structure of metallic Silver (hkl) 2θ θ Cos θ FWHM 0 β radian d(A 0 ) D (nm) 111 38.14 19.04 0.945 0.4695 0.00819 2.36 17.9 200 44.27 22.13 0.927 0.3814 0.00665 2.05 22.5 220 64.45 32.22 0.846 0.382 0.00667 1.44 24.6 311 77.48 38.74 0.78 0.2769 0.00483 1.23 36.8 Scanning Electron Microscopy (SEM): Field Emission Scanning Electron Microscopy (FESEM) analysis was conducted to explore the surface features and particle distribution of the synthesized materials. The FE-SEM image of the Ag-Histidine complex displays abnormal, aggregated, and non, uniform structures, which substantiate the formation of a coordinated complex rather than isolated nanoparticles. The surface is quite rough with clustered morphology. On the other hand, FE, SEM images of L-Histidine capped silver nanoparticles demonstrate the formation of almost spherical and evenly distributed nanoparticles. Despite the fact that a small cluster can be seen, the particles are pretty much evenly scattered, indicating that Histidine molecules are efficiently capping the particle surface. In terms of morphology, the nanoparticles are smooth surfaced and have nanoscale dimensions. The particle size distribution histogram also verifies the nanoscale nature of the synthesized nanoparticles. The size distribution covers approximately from 10 nm to 60 nm, with the majority of particles in the 20–40 nm segments. The average particle size worked out is about ~ 30 nm, which means that nucleation and growth were well controlled during the synthesis. The rather narrow size distribution indicates that L-Histidine functions well as a capping agent, restricting particle growth and avoiding excessive aggregation. (particles size-40 nm) (particles size-22 nm) Energy Dispersive X-ray Analysis (EDAX): The EDS elemental analysis confirms the conversion of Ag-Histidine coordination complex into L-Histidine capped silver nanoparticles. Ag-Histidine complex mainly contains carbon (45.0 wt%, 56.4 at%), nitrogen (30.2 wt%, 32.4 at%), and oxygen (9.7 wt%, 9.1 at%) while silver only accounts for 15.1 wt% and 2.1 atomic and N in considerable quantities reveal that the Histidine ligand, which includes an imidazole ring, amino group (-NH 2 ), and carboxyl group (-COOH), is the major part of the structure. The extremely small atomic fraction of silver suggests that Ag is mostly in ionic form (Ag) and thus is coordinated to the nitrogen atoms of the imidazole and amino groups, with the carboxylate oxygen possibly involved in an interaction. The fact that elements from the ligands are much more abundant than silver is a strong indication of a metal-ligand coordination complex being formed rather than a metallic nanoparticles system. The homogeneous spreading of C, N, and O also points to silver ion chelating and stabilization within the Histidine framework effectively. the elemental composition of the L-Histidine capped Ag-NPs changes dramatically. Silver becomes the most abundant component, making up 81.8 wt% and 35.0 atomic%, whereas carbon (11.3 wt%), nitrogen (3.7 wt%), and oxygen (3.2 wt%) are only present in very small amounts. This highly significant increase in silver level confirms the Ag ions were converted into metallic Ag and silver nanoparticles were formed. The lower figures for %C, N, and O further support the idea that Histidine is not the main structure in the bulk but is acting as a capping and stabilizing agent on the surface. The minor presence of nitrogen and oxygen helps to justify that Histidine molecules are adsorbed on the nanoparticles surface through coordination of the imidazole nitrogen or amino groups with the metallic silver core. Therefore, the change in composition from ligand, dominated to metal, dominated structure perfectly demonstrates nanoparticles formation, with Histidine serving as the organic shell that inhibits aggregation and increases stability. In general, the differential EDAS data provide very strong evidence for the reactivity of the coordination complex to a surface, functionalized metallic nanoparticles system. Table 2 EDAX elemental analysis of the Ag-Histidine complex and L-Histidine-capped Ag-NPs synthesized in acetate buffer (pH 5) Element Ag–Histidine complex L-Histidine capped AgNPs Shell Weight % MDL Atomic % Weight % MDL Atomic % C K 45.0 0.06 56.4 11.3 0.25 43.4 N K 30.2 0.17 32.4 3.7 0.54 12.2 O K 9.7 0.13 9.1 3.2 0.54 9.4 Ag L 15.1 0.05 2.1 81.8 0.26 35.0 Antimicrobial Activity of Silver-Histidine and L-Histidine Capped Silver Nanoparticles: The antimicrobial property of the Silver-Histidine complex and L-Histidine Capped Silver Nanoparticles were tested against bacteria Escherichia coli (Gram, negative) and Staphylococcus aureus (Gram, positive) through the agar well diffusion method. The complex and Nanoparticles showed a clear zone of inhibition (ZOI) of about 13, 16 mm against E.coli and 11, 14 mm against S. aureus, thus confirming the significant antibacterial effect on both bacterial strains. The main reason for the antibacterial action is the coordinated Ag ions that disrupt the negatively charged cell membrane components of bacteria, thus increasing permeability and causing damage to the membrane. Silver ions in E. coli dismantle the top lip polysaccharide membrane and also disturb membrane, bound enzymes, whereas in S. aureus Ag ions pass through the thick peptidoglycan layer and then get attached to thiol groups of essential proteins, which lead to enzyme inactivation and DNA replication inhibition. Also, the formation of reactive oxygen species (ROS) causes oxidative stress in bacterial cells, thus, killing them. The value of ZOI observed indicates that the Silver, Histidine complex has moderate and L-Histidine capped Silver nanoparticles shows More than Ag-Histidine complex antibacterial activity against both types of bacteria (Gram, negative and Gram, positive) which is due to sustained silver ion release and microbial cell component interaction. Comparative Zone of Inhibition (mm): Table 3 Antimicrobial activity of Ag-Histidine complex and L-Histidine-capped AgNPs synthesized in acetate buffer (pH 5). Sample E. coli (Gram −) S.Aureus sp. (Gram +) Silver–Histidine complex 13 mm 11 mm L-Histidine capped AgNPs 16 mm 14 mm CONCLUSION Ag-Histidine complex and L-Histidine capped Ag nanoparticles were supported by a set of complementary spectroscopic and morphological investigations. UV-visible spectral recordings showed a typical surface Plasmon resonance (SPR) band at about 395–430 nm region, which is an indicator of the production of metallic Ag nanoparticles. Besides, the shift of the Histidine absorption bands suggested the coordination of Ag ions with the Histidine molecule. Further, FTIR inspection exposed major alterations of -NH, COO − , and imidazole group vibrations, which strongly suggested the role of Histidine in metal binding and the final effect of capping on the surface of newly formed particles.XRD results revealed separate diffraction peaks such as (111), (200), (220), and (311) that belong to the silver face, centered cubic crystal planes, thereby confirming the crystalline attribute of the nanoparticles. Three, dimensional SEM micrographs displayed quasi, spherical shaped and moderately aggregated particles and nanosized dimensions. On the other hand, the obtained particle size distribution analysis indicated that the average particle size mainly fell within the 40 nm interval. Overall, all these data undeniably showed that crystalline L-Histidine, functionalized silver nanoparticles with controlled nanoscale morphology were synthesized successfully. As a highlight, both Escherichia coli and Staphylococcus aureus strains were inhibited by the Silver-Histidine complex which resulted in visible zones of inhibition, thereby confirming substantial antimicrobial property of the complex. The anti, bacterial property observed can, thus, be mainly attributed to the mechanism of the controlled release of Ag ions which permeabilize the bacterial cell membranes, lead to the loss of enzymatic activity, and finally cause oxidative stress inside microbial cells. Despite the fact that the antimicrobial activity is moderate relative to metallic silver nanoparticles, the complex still manages to provide a sustained release of ions and to effectively inhibit both Gram, negative and Gram, positive bacteria. This study demonstrates that the Silver, Histidine complex is an excellent antimicrobial agent that can be used in various biomedical and antimicrobial material developments. Declarations ACKNOWLEDGMENT The authors gratefully acknowledge VidyaPratishthans Arts, Science and Commerce College, Baramati,Pune, Maharashtra, India for providing the necessary research facilities to carry out this work. CONFLICT OF INTERESTS The authors declare that they have no conflict of interest. AUTHOR CONTRIBUTIONS All the authors contributed significantly to this manuscript, participated in reviewing/editing, and approved the final draft for publication. The research profile Open Access: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Citethisarticleas: KanchanRaniandJ.B.Dahiya, RasayanJ. Chem. ,19(1),1-9(2026), https://doi.org/10.317 88/RJC.2026.1919443 References K.B.A. Ahmed, V. Anbazhagan, R. Uthandakalaipandian, Silver nanoparticles: Preparation, characterization, and applications. J. Nanosci. Nanotechnol. 16 (3), 2526–2537 (2016). https://doi.org/10.1166/jnn.2016.10830 M. Rai, A. Yadav, A. Gade, Silver nanoparticles as a new generation of antimicrobials. Biotechnol. Adv. 27 (1), 76–83 (2014). https://doi.org/10.1016/j.biotechadv.2008.09.002 X.F. Zhang, Z.G. Liu, W. Shen, S. Gurunathan, Silver nanoparticles: Synthesis, characterization, properties, applications, and therapeutic approaches. Int. J. Mol. Sci. 17 (9), 1534 (2020). .https://doi.org/10.3390/ijms17091534 A.C. Burdușel et al., Biomedical applications of silver nanoparticles. J. Nanobiotechnol. 16 , 1–36 (2018). https://doi.org/10.1186/s12951-018-0332-z S. Prabhu, E.K. Poulose, Silver nanoparticles: Mechanism of antimicrobial action. Int. Nano Lett. 2 , 32 (2012). https://doi.org/10.1186/2228-5326-2-32 (2025). Mechanistic insights and therapeutic innovations in engineered nanomaterial-driven disruption of biofilm dynamics. RSC Adv. https://doi.org/10.1039/D5RA01711D (2025). Mechanistic insights and therapeutic innovations in engineered nanomaterial-driven disruption of biofilm dynamics. RSC Adv. https://doi.org/10.1039/D5RA01711D C.L. Ventola, The antibiotic resistance crisis. Pharm. Ther. 40 (4), 277–283 (2015) J.S. Kim et al., Antimicrobial effects of silver nanoparticles. Nanomedicine. 3 (1), 95–101 (2007). https://doi.org/10.1016/j.nano.2006.12.001 Khalifa et al., 2025) (E. coli and S. aureus resist silver nanoparticles via an identical mechanism, but through different pathways, 2023) (Antibacterial Properties of Silver Nanoparticles Embedded on Polyelectrolyte, Hydrogels Based on α-Amino Acid Residues, 2023) (Silver Nanoparticle-Based Combinations with Antimicrobial Agents against Antimicrobial-Resistant Clinical Isolates, 2024) (Hayat et al., 2025, pp. 42460–42478) Sun et al., 2021) However, the direct application of uncapped AgNPs is often limited by aggregation, instability in biological environments, and concerns related to nonspecific cytotoxicity (Ivask., 2014; Mukherjee., 2014) P. Singh et al., Biological synthesis of nanoparticles. Adv. Colloid Interface Sci. 256 , 39–58 (2018). https://doi.org/10.1016/j.cis.2018.03.004 (Biosynthesis of Silver Nanoparticles Functionalized with Histidine and Phenylalanine Amino Acids for Potential Antioxidant and Antibacterial Activities, 2023, pp. 28556–28565) (Anticancer Potential of L-Histidine-Capped Silver Nanoparticles against Human Cervical Cancer Cells (SiHa), 2021, pp. 118–125)levance L. Alderighi et al., Coordination chemistry of histidine. Coord. Chem. Rev. 184 , 311–318 (1999). https://doi.org/10.1016/S0010-8545(98)00224-0 E.P. Ivanova et al., Natural amino acids as metal ligands. RSC Adv. 4 , 46993–47003 (2014). https://doi.org/10.1039/C4RA06767H G. Shumi, T.B. Demissie et al., Biosynthesis of silver nanoparticles functionalized with histidine. ACS Omega. 8 , 24371–24386 (2023). https://doi.org/10.1021/acsomega.3c01910 M.A. Raza et al., Amino acid capped silver nanoparticles. Mater. Chem. Phys. 258 , 123879 (2021). .https://doi.org/10.1016/j.matchemphys.2020.123879 Y.S. Lee, S.H. Kim, S.H. Kim, S.H. Kim, S.H. Kim, Spectroscopic analysis of L-histidine adsorbed on gold and silver nanoparticle surfaces investigated by surface-enhanced Raman scattering. SpectrochimicaActa Part. A: Mol. Biomol. Spectrosc. 68 (5), 1240–1245 (2007). https://doi.org/10.1016/j.saa.2007.01.019 I. Kostova, Metal complexes as antimicrobial agents. Curr. Med. Chem. 13 , 1085–1107 (2006). https://doi.org/10.2174/092986706776360961 M.J. Panzner et al., Bioinorganic silver complexes. Dalton Trans. 47 , 13010–13020 (2018). https://doi.org/10.1039/C8DT02741A Y. You, C. Zhang, Interaction between silver ions and histidine. J. Clin. Rehabilitative Tissue Eng. Res. 14 (29), 5498–5504 (2010). https://doi.org/10.3969/j.issn.1673-8225.2010.29.042 S.Y. Liau et al., Silver compounds in wound care. J. Appl. Microbiol. 83 , 433–438 (1997). https://doi.org/10.1046/j.1365-2672.1997.00253.x S. Medici et al., Silver coordination compounds. Coord. Chem. Rev. 284 , 329–350 (2015). https://doi.org/10.1016/j.ccr.2014.09.002 Le B. Ouay, F. Stellacci, Antibacterial activity of functionalized nanoparticles. Nano Today. 10 (3), 339–354 (2015). https://doi.org/10.1016/j.nantod.2015.04.002 M. Rai et al., AgNP interaction with microbes. Appl. Microbiol. Biotechnol. 100 , 459–475 (2016). https://doi.org/10.1007/s00253-015-6905-4 H. Katas et al., Biocompatibility of capped AgNPs. Arab. J. Chem. 11 , 676–683 (2018). https://doi.org/10.1016/j.arabjc.2015.06.019 M. Akter et al., Cytotoxicity of silver nanoparticles. Part. Fibre Toxicol. 15 , 18 (2018). .https://doi.org/10.1186/s12989-018-0253-4 C. Beer et al., Surface chemistry effects on nanoparticle toxicity. Langmuir. 28 , 7240–7247 (2012). https://doi.org/10.1021/la2041687 S. Gurunathan et al., Biocompatibility of AgNPs. Colloids Surf. B 135 , 407–417 (2015). https://doi.org/10.1016/j.colsurfb.2015.07.043 J. Wang et al., Electrochemical applications of silver nanomaterials. ElectrochimicaActa. 247 , 785–795 (2017). https://doi.org/10.1016/j.electacta.2017.07.019 S. Chen et al., Amino acid-modified electrodes. Biosens. Bioelectron. 126 , 208–215 (2019). https://doi.org/10.1016/j.bios.2018.10.060 Zhao et al., 2021) P.T. Anastas, J.C. Warner, Green chemistry: Theory and practice (Oxford University Press, 1998) Iravani et al., 2014) O.V. Kharissova et al., Green synthesis of metal nanoparticles. Trends Biotechnol. 37 , 190–203 (2019). https://doi.org/10.1016/j.tibtech.2018.08.007 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9030666","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":617689787,"identity":"b5ecd3ba-dfbd-4f14-8694-0a9138a8f7e4","order_by":0,"name":"D. S. GHARBUDE","email":"","orcid":"","institution":"Savitribai Phule Pune University","correspondingAuthor":false,"prefix":"","firstName":"D.","middleName":"S.","lastName":"GHARBUDE","suffix":""},{"id":617689788,"identity":"62ee52fa-bf9f-4ed3-a282-acc94452286d","order_by":1,"name":"A. G. KORE","email":"","orcid":"","institution":"Savitribai Phule Pune University","correspondingAuthor":false,"prefix":"","firstName":"A.","middleName":"G.","lastName":"KORE","suffix":""},{"id":617689789,"identity":"5e3d36f2-1520-4813-aa3c-ca594e8cdee8","order_by":2,"name":"L. M. KASHID","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYBACPgY2BgbGBgnGfhAvoYAILWwwLTMbQFoMiNfCwLjhAIhLlBaxY4kff+6wkN18fnXihwcGDPL8YgcIaJFOOyzNe0bCeNuNt5slgA4znDk7gZCW9AZpxjaJxG03zm4AaUkwuE1YS/PPn0Atm2ec3fyDSC1pxyR4gVo28PduI9aWtDRroBbjGTd4t1kkGEgQ9gu/dJrxzZ9tdbL9/Wc33/xRYSPPL01ACwJIgFVKEKscbN8BUlSPglEwCkbBSAIA2ZtC2+teDycAAAAASUVORK5CYII=","orcid":"","institution":"Savitribai Phule Pune University","correspondingAuthor":true,"prefix":"","firstName":"L.","middleName":"M.","lastName":"KASHID","suffix":""}],"badges":[],"createdAt":"2026-03-04 13:11:47","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9030666/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9030666/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106423987,"identity":"d95d0c9b-88c8-4d68-8cc3-aff948d0db4f","added_by":"auto","created_at":"2026-04-08 11:44:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":250514,"visible":true,"origin":"","legend":"\u003cp\u003emechanism of synthesis of Ag-Histidine Complex and L-Histidine capped Ag-NPs.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/d9486cbf8d47f0301d35fa74.png"},{"id":106423970,"identity":"27b885c8-31ca-40a7-b985-d0448cadb3d2","added_by":"auto","created_at":"2026-04-08 11:44:16","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":261999,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Cyclic Voltammogramgrams of Ag-Histidine (b) Linearity of Ag-Histidine (R\u003csup\u003e2\u003c/sup\u003e=0.9999)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/c63f98919a9a24600d49cc2d.png"},{"id":106423971,"identity":"cb7b4032-e5af-4780-8a09-97ad4bc0bf90","added_by":"auto","created_at":"2026-04-08 11:44:16","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":246864,"visible":true,"origin":"","legend":"\u003cp\u003e(a)Linear Sweep Voltammogramgrams of Ag-Histidine\u0026nbsp; (b)Linearity of Ag-Histidine (R\u003csup\u003e2\u003c/sup\u003e=0.9998)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/bd2771b1da3c7e4491234f24.png"},{"id":106423978,"identity":"784f8531-b0c7-4f22-b900-614007e130ca","added_by":"auto","created_at":"2026-04-08 11:44:21","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":197995,"visible":true,"origin":"","legend":"\u003cp\u003eUV-visible Spectra of (a)L-Histidine(b)Ag-Histidine (c)Ag-NPs(d)L-Histidine capp Ag-NP\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/fb7b2640f1575266e05118e2.png"},{"id":106423980,"identity":"238016ef-f81f-481f-948b-b5438fdcf76f","added_by":"auto","created_at":"2026-04-08 11:44:22","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":333557,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR Spectra of (a)L-Histidine(b)Ag-Histidine complex (c)Ag-NPs,(d)L-Histidine capped Ag-NPs\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/a86443b6e9d703b56955253c.png"},{"id":106424011,"identity":"e9947b6c-9241-49ee-ba4f-963585e8d2f0","added_by":"auto","created_at":"2026-04-08 11:44:30","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":134571,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of (a)L-Histidine(b)Ag-Histidine complex (c)Ag-NPs,(d) L-Histidine capped Ag-NPs\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/7db5e8d32a21dfd40f3242a4.png"},{"id":106424009,"identity":"2d61a495-c8bb-49e3-889d-ea54d1fd93a8","added_by":"auto","created_at":"2026-04-08 11:44:30","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":394752,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Ag-cysteine complex (particles size-40 nm)\u003c/p\u003e\n\u003cp\u003e(b) L-cysteine capped AgNPs (particles size-22 nm)\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/71bb96918e2597baa22f232f.png"},{"id":106423986,"identity":"2d090687-debb-4ab8-9deb-f5763c6cfbb7","added_by":"auto","created_at":"2026-04-08 11:44:22","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":455964,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Ag-Histidine complex \u0026nbsp;(b)L-Histidine capped Ag -Nanoparticles\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/16d0cfbe7cb8f59bdd31fca3.png"},{"id":106423981,"identity":"f222d86a-3a82-4f5e-bae4-88def305a99f","added_by":"auto","created_at":"2026-04-08 11:44:22","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":1085908,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) Ag-Histidine complex (b) Elemental Analysis of Ag-Histidine\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/762218993c5fe049014bf5af.png"},{"id":106424010,"identity":"73eee93b-8044-4e08-8118-0c4f59de19af","added_by":"auto","created_at":"2026-04-08 11:44:30","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":971773,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(a) L-Histidine capped AgNPs \u0026nbsp;\u0026nbsp;(b) Elemental Analysis of L-Histidine capped AgNPs\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/d2e0858ad95b68e6c9422981.png"},{"id":106424012,"identity":"81d3df78-b168-4761-bd3f-fd5a8e0ba99e","added_by":"auto","created_at":"2026-04-08 11:44:30","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":133203,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig.10. Elemental analysis: (a) Ag-Histidine compl (b)L-Histidine capped Ag-Histidine complex\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/e9832584e0711c7756019563.png"},{"id":106423972,"identity":"129238b1-eccd-450c-8c45-7ffbad3fd35b","added_by":"auto","created_at":"2026-04-08 11:44:17","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":89203,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFig.11. Zone of Inhibition : (a) E.Coli (b) S.Aureas\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/74a468d25ab1bc43e1301803.png"},{"id":107461153,"identity":"d8ee6d45-59b5-49f2-9a9e-0999ea6fb00c","added_by":"auto","created_at":"2026-04-21 16:55:42","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5266923,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9030666/v1/72e61ed1-8c51-47cc-b9ac-dff0ea511722.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Synthesis and characterization of Silver-Histidine complex and L-Histidine capped Ag-NPs in Buffer System, Electrochemical and Antibacterial Properties","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eSilver, based materials have been the focus of materials science and bioinorganic chemistry for decades, mainly due to their exceptional physicochemical versatility and their widely studied biological activity. Among the noble metals, silver stands out as the only metal which is chemically stable and at the same time highly effective as an antimicrobial agent, thus it is extremely useful for applications in healthcare, environmental protection, catalysis, and electrochemical systems\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.By selecting silver for the size reduction down to the Nano scale dimension, initially, the functionalities of the latter have been significantly boosted because silver nanoparticles (Ag-NPs) are considered to have an enhanced surface reactivity, tunable electronic properties, and a higher rate of interaction with biological entities when compared to bulk silver\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.Consequently, Ag-NPs are presently the number one most exhaustively studying nanomaterials acutely in the forefront of research\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e.The overcrowding of the world for the efficient antimicrobial materials due to antimicrobial resistance, hospital, acquired infections, and the immediate need to the safer biomedical devices has in a great way increased the interest in silver based nanomaterials\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e.Ag-NPs are able to eliminate microorganisms through several different synergistic mechanisms. These include the rupture of the bacterial membranes, interference with enzymes inside the cells, induction of oxidative stress, and attachment to the genetic material\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e.These multiple pathway strategies not only reduce the odds of bacteria developing drug resistance but also differentiate silver, based systems from commonplace antibiotics\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e.\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e.\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e.\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Surface functionalization has become an essential technique for improving the stability, biocompatibility, and the overall functional performance of silver nanoparticles.\u003c/p\u003e \u003cp\u003eOne of the approaches to doing this is through ligand, mediated surface, specific modification which would allow for tunable growth of nanoparticles, provide control of surface charge and regulate interaction with the surrounding media. During the search for stabilizing agents, biologically derived ligands, more specifically amino acids, have been the centerpiece of most research owing to their low toxicity, a great variety of structures, and they can coordinate metal centers through heteroatom donor sites\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e.Functionalization of amino acids both stabilizes Ag-NPs and at the same time decorates the protein surfaces with bioactive functionalities which lead to better interaction with biological targets\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.L-Histidine is a very interesting molecule here due to its one, of, a, kind chemical structure and the fact it is a biologically significant molecule. It is thus good for coordinating metal ions and also gives the nanomaterials resulting biocompatibility and stabilization\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.One of the Special characteristics of Histidine is its imidazole side chain which has a strong binding affinity with metal ions and exhibits coordination behavior, which is dependent on pH, of the metal ion. This imidazole group enables Histidine to establish a strong interaction with silver ions and silver surfaces via coordination of nitrogen donor, while amino and carboxylate groups can participate in multi, dentate binding\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Histidine is thus capable of easily making strong silver Histidine coordination complex and serves as a very efficient capping ligand for silver nanoparticles \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. These properties distinguish Histidine from the majority of other amino acids and render it a highly versatile ligand for silver, based coordination and nanostructure systems \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.Silver Histidine complexes exemplify coordination compounds at the crossroads of traditional inorganic chemistry and bioinorganic materials science. Unlike their free forms, Ag ions coordinated with Histidine ligands terminals undergo changes in their electronic environment and redox properties, thus influencing not only the chemical stability but also the biological activity of the metal center \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e.Subsequently, such complexes are great models for metal, bimolecular interaction studies and unravel how biologically relevant ligands may alter silver, ion behavior\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.Various studies have demonstrated that silver-Histidine complexes exhibited antimicrobial properties to a significantly greater extent than free silver ions, and thus the coordination chemistry plays a critical role in the mechanism of bioactive silver systems. Furthermore, except for the binuclear coordination compounds, Histidine is a main contributor to the surface modification of silver nanoparticles. L-Histidine capped Ag-NPs are a mixture of silver's intrinsic antimicrobial capability and the stabilizing and bio, functional advantages of amino acid capping. Histidine modification of metallic particles prevents their aggregation, increases the stability of the colloid, and enables the control of surface chemistry, which is crucial for obtaining consistent biological and electrochemical results. Besides, Histidine exposed on the surface of nanoparticles helps in the attachment of microbial membranes through electrostatic attraction and coordination, assisted binding, which results in higher antimicrobial effectiveness \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe biological potential of Histidine capped Ag-NPs in the biological system is not only their antimicrobial activity. More and more studies are revealing that such nanoparticles have antioxidant, anticancer, and anti, inflammatory properties which are related to their ability to regulate reactive oxygen species production and influence cellular signaling pathways \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.Actually, Histidine capping has been found to be a great Biocompatibility enhancer and it also significantly reduces nonspecific cytotoxicity when compared with the parent Ag-NPs, thus offering a solution to one of the major problems faced in the use of silver nanomaterials for biomedicine\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e.Other than their biological relevance, silver, Histidine systems carry a lot of electrochemical importance as well. The binding of Histidine to silver surfaces results in changes in electron transfer kinetics at the interface, and the distribution of surface charge, which are key factors in electrochemical sensing and analytical applications \u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHistidine, decorated silver materials provide enhanced surface availability and more reliable signal transduction, thus they can be employed for the electrochemical detection of bio-molecules and metal ions. It is a must to explore the electrochemical features of silver, Histidine complexes and Histidine, capped Ag-NPs before making a correlation between material structure and its functional attributes\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e.So, silver-Histidine coordination systems in conjunction with L-Histidine, capped silver nanoparticles constitute a fusion of coordination chemistry, nanotechnology, and bio, functional material design. The use of amino acids as ligands and stabilizers goes along with the green chemistry principles as it offers environment, friendly, sustainable, and biologically compatible alternatives to the conventional synthetic capping agents \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e,\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Recent research reports point to the growing importance of such nature, inspired approaches in the fabrication of high, performance nanomaterials at minimum environmental and biological hazards levels\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"EXPERIMENTAL","content":"\n\u003ch3\u003eMaterials and Methods\u003c/h3\u003e\n\u003cp\u003eInvestigators utilized the reagents of analytical grade and no one was re, purified. AgNO\u003csub\u003e3\u003c/sub\u003e was the source of silver ions. L-Histidine was the ligand that coordinated and stabilized. The silver ions were reduced to metallic Ag by NaBH\u003csub\u003e4\u003c/sub\u003e.It was decided to make reaction environment stable by an acetate buffer which was made from sodium acetate and acetic acid and the pH was adjusted by diluted sodium hydroxide or acetic acid. Double, distilled water was used in all the solution preparations. For the determination of antibacterial activity, nutrient agar was used as the growth medium and streptomycin was used as the standard drug.\u003c/p\u003e\n\u003ch3\u003eGeneral Procedure:\u003c/h3\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eSynthesis of Ag\u0026ndash;Histidine Complex\u003c/h2\u003e \u003cp\u003eAll the experiments were conducted in 0.04 M sodium acetate buffer kept at pH 5 and at 60\u003csup\u003e0\u003c/sup\u003eC with a magnetic stirrer at 400 rpm. To prepare the Ag-Histidine complex, 10 mL of 0.01 M silver nitrate (AgNO\u003csub\u003e3\u003c/sub\u003e) was combined with 10 mL of 0.02 M L-Histidine solution with constant stirring. The reaction was left to continue for around 4 hours at a constant temperature. In the meantime, the formation of a yellowish suspension was observed which the indication of the silver Histidine coordination complex was. The product obtained was separated by centrifugation at 4000 rpm for 15 minutes. The precipitate obtained was first washed with ethanol and then with double, distilled water two times to get rid of the unreacted precursors and soluble impurities. The purified sample was then dried for 12h at 100\u003csup\u003e0\u003c/sup\u003e C and kept for further physicochemical characterization.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eSynthesis of L-Histidine Capped Silver Nanoparticles (Ag-NPs)\u003c/h3\u003e\n\u003cp\u003eL-Histidine capped silver nanoparticles were prepared by first using the Complexation procedure. After stirring for 10 minutes the reaction mixture was placed in an ice bath to slow the kinetics of the reaction and avoid uncontrolled nucleation. While the pH was kept at 5,30 mL of 0.02 M sodium Borohydrate (NaBH\u003csub\u003e4\u003c/sub\u003e) solution was added drop, wise as a reducing agent under continuous stirring. Upon the reduction, the mixture of the reaction was converted gradually in colour from pale yellow to dark brown within about 1 hour, which indicated the formation of silver nanoparticles as a result of surface Plasmon resonance. The nanoparticles were separated by centrifugation at 7500 rpm for 30 min, and then they were washed several times with ethanol and distilled water to get rid of the residual by, products and impurities. Afterward, the purified nanoparticles were dried and stored for further characterization and analyses.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eInstrumentation:\u003c/h3\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eCharacterization Techniques:\u003c/h2\u003e \u003cp\u003eThe electrochemical behavior of the Silver-Histidine complex was comprehensively analyzed by cyclic Voltammetry (CV) and linear sweep Voltammetry (LSV) on a STAT-20 electrochemical workstation (EC, Proyog, India). The electrochemical cell consisted of a glassy carbon electrode (GCE) as the working electrode, a platinum wire as the auxiliary (counter) electrode, and an Ag/AgCl electrode as the reference electrode. Voltammograms were obtained by scanning the potential in both anodic and cathodic directions and within the potential window of 0.0 to +\u0026thinsp;1.0 V at a scan rate of 60 mV/s. linear sweep Voltammetry was used for the potential change from 0.0 to +\u0026thinsp;1.0 V at the same scan rate. All the tests were done in 0.04 M acetate buffer solution (pH 5).The UV-visible absorption of the silver-Histidine complex was investigated with a (Shimadzu UV-1800 series spectrophotometer). Spectra were recorded over the (200 nm to 800 nm) range to find ligand, to, metal charge transfer (LMCT) and possible d-d electronic transitions. Functional groups and coordination interactions were recognized by FTIR spectroscopy which was carried out on a Shimadzu (Shimadzu UV, 1800 series spectrophotometer) spectrometer (ENG 230 V). Spectra were recorded within the range 4000\u0026thinsp;\u0026minus;\u0026thinsp;400 cm\u003csup\u003e-\u003c/sup\u003e.X-ray diffraction (XRD) (Malvern Panalytical Empyrean DY3280 diffract meter.) analysis was used to determine the crystalline structure, phase purity, and structural parameters of the samples was used for the measurements. The surface morphology and micro structural features were investigated by scanning electron microscopy (SEM). The elemental composition was confirmed by energy, dispersive X-ray spectroscopy (EDAX). Both SEM and EDAX analyses were performed on the TESCAN CLARA series scanning electron (TESCAN, Czech Republic).\u003c/p\u003e \u003c/div\u003e"},{"header":"RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eCyclic Voltammetry (CV) :\u003c/h2\u003e \u003cp\u003eThe electrochemical interaction between Silver and Histidine was thoroughly characterized by cyclic Voltammetry (CV) and linear sweep Voltammetry (LSV) in 0.04 M acetate buffer (pH 5.0) at a scanning rate of 60 mV/s. The gradual addition of Histidine (0.0-0.5 mL) resulted in a significant reduction of the peak current and a systematic negative shift of the anodic peak potential in both methods, which was interpreted as the formation of a stable Ag-Histidine coordination complex. In CV, the anodic peak potential moved from 0.481 V to 0.424 V, a change which was highly linear and could be represented by the regression equation E =-0.114x\u0026thinsp;+\u0026thinsp;0.481 (R\u0026thinsp;=\u0026thinsp;0.979). On the other hand, LSV exhibited a change from 0.487 V to 0.419 V with an even better linear correlation, E =-0.137x\u0026thinsp;+\u0026thinsp;0.487 (R\u0026thinsp;=\u0026thinsp;0.987), revealing a higher sensitivity towards ligand metal interaction. The Cathodic shifting of the peak potential and the decrease of the peak current are in agreement with Ag binding to the imidazole nitrogen of Histidine, which alters the redox environment, decreases the amount of free silver ions, and changes the electron transfer kinetics at the electrode interface. Both methods showed excellent linear dependence, indicating that the Complexation process is concentration, dependent and can be potentially analytically applicable.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eCyclic Voltammetry (CV):\u003c/h2\u003e \u003cp\u003eThe electrochemical interaction between Silver and Histidine was thoroughly characterized by cyclic Voltammetry (CV) and linear sweep Voltammetry (LSV) in 0.04 M acetate buffer (pH 5.0) at a scanning rate of 60 mV/s. The gradual addition of Histidine (0.0-0.5 mL) resulted in a significant reduction of the peak current and a systematic negative shift of the anodic peak potential in both methods, which was interpreted as the formation of a stable Ag-Histidine coordination complex. In CV, the anodic peak potential moved from 0.481 V to 0.424 V, a change which was highly linear and could be represented by the regression equation E =-0.114x\u0026thinsp;+\u0026thinsp;0.481 (R\u0026thinsp;=\u0026thinsp;0.979). On the other hand, LSV exhibited a change from 0.487 V to 0.419 V with an even better linear correlation, E =-0.137x\u0026thinsp;+\u0026thinsp;0.487 (R\u0026thinsp;=\u0026thinsp;0.987), revealing a higher sensitivity towards ligand metal interaction. The Cathodic shifting of the peak potential and the decrease of the peak current are in agreement with Ag binding to the imidazole nitrogen of Histidine, which alters the redox environment, decreases the amount of free silver ions, and changes the electron transfer kinetics at the electrode interface. Both methods showed excellent linear dependence, indicating that the Complexation process is concentration, dependent and can be potentially analytically applicable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eUV-Visible Spectrum:-\u003c/h2\u003e \u003cp\u003ePure L-Histidine in sodium acetate buffer (pH 5) shows typical absorption bands of approximately 210 and 250 nm in its UV-visible spectrum. The bands are due to n \u0026rarr; σ* and n \u0026rarr; π* electronic transitions of imidazole ring and amino (-NH\u003csub\u003e2\u003c/sub\u003e) groups in the Histidine molecule. There is no absorption in the visible region, thus free Histidine is neither plasmonic nor an extended chromophoric system. Upon binding of Ag ions, the UV band pattern significantly alters and the silver, Histidine complex exhibits a band at 290 to 310 nm, which is a characteristic of ligand, to, metal charge transfer (LMCT) between nitrogen atoms in the imidazole ring and the silver ions. Furthermore, the UV bands are slightly broadened and shifted as compared to those of pure Histidine, which is a clear sign of binding between Ag and imidazole nitrogen, and possibly also the amino group. At this pH-5, Histidine can be considered a perfect chelates ligand as it can stabilize silver ions in solution through N, donor interactions. The metallic silver nanoparticles formation is evident with the help of a strong and broad absorption band in the visible region, which is centred at 395 nm, and corresponds to the surface Plasmon resonance (SPR) of Ag nanoparticles. This SPR band is due to the conduction electrons collective oscillation on the nanoparticles surface when excited by the incident light. The broad character of the band is a signature of nanoscale particle formation with some size distribution. For L-Histidine capped Ag nanoparticles, the SPR band is accompanied by a red shift and is located in the region of 420\u0026ndash;430 nm. This red shift relative to the uncapped Ag nanoparticles indicates surface modification and an increase in the local refractive index around the particles caused by Histidine adsorption. The stabilizing effect of Histidine consequently prevents aggregation and regulates particle growth. Moreover, the weak absorption around 300 nm corresponds to the surface, bound Histidine molecules. The relatively sharper and more stable SPR band is indicative of successful L-Histidine capping and that it is a suitable biocompatible stabilizing agent that improves dispersion and prevents excessive aggregation of the nanoparticles.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eFTIR Spectrum:\u003c/h2\u003e \u003cp\u003eThe FTIR spectra of pure L-Histidine depict NH stretching of the amino group in association with hydrogen, bonded OH vibrations revealed by a broad absorption band in the region of 3200\u0026ndash;3400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. A very strong band that muscle can be found at about 1600\u0026ndash;1620 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is the one resulting from the asymmetric stretching vibration of the carboxylate (COO\u003csup\u003e\u0026minus;\u003c/sup\u003e) group, while the symmetric stretching vibration is near 1390\u0026ndash;1410 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The extent of difference between these two bands is a perfect confirmation of the zwitterionic form of Histidine. Also, the peaks between1000-1100cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e can be assigned to -CN stretching and imidazole ring vibrations, thus, proving the presence of nitrogen, containing groups capable to coordinate metal. When the Ag-Histidine compound is generated, significant changes are gone in the COO\u003csup\u003e\u0026minus;\u003c/sup\u003e asymmetric and symmetric stretching bands showing that Ag ions form a bond with carboxylate oxygen atoms. The -NH stretching band gets wider and is a little bit shifted, which is an indication that amino and imidazole nitrogen atoms also take part in coordination. In addition, a faint band seen in the lower frequency region near 500\u0026ndash;600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is assigned to Ag-N bond vibrations, thus silver-Histidine complex formation is confirmed. The FTIR spectrum of bare Ag nanoparticles only shows very faint and broad absorption bands that are mainly caused by surface, adsorbed species or a small degree of surface oxidation. The lack of peaks related to strong organic functional groups suggests that the nanoparticles surface is predominantly metallic. In the case of L-Histidine capped Ag nanoparticles, the -NH stretching band stays wide but exhibits a minor shift compared to pure Histidine, thus confirming the surface interaction. The asymmetric and symmetric COO\u003csup\u003e\u0026minus;\u003c/sup\u003e stretching bands are present with only minor positional changes which imply that the carboxylate groups remain involved in stabilizing the particles. Besides the main imidazole vibrations, low, frequency bands around 500\u0026ndash;600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e also appear, thus corroborating a strong Ag-N interaction. These spectral differences very clearly indicate that L-Histidine indeed binds to and caps the silver nanoparticles surface.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eX-Ray Diffraction(XRD):\u003c/h2\u003e \u003cp\u003eThe XRD pattern of the synthesized silver nanoparticles shows four distinct diffraction peaks at 2θ\u0026thinsp;=\u0026thinsp;38\u003csup\u003e0\u003c/sup\u003e, 44\u003csup\u003e0\u003c/sup\u003e, 64\u003csup\u003e0\u003c/sup\u003e, and 77\u003csup\u003e0\u003c/sup\u003e.The most intense peak at 38\u003csup\u003e0\u003c/sup\u003e is indexed to the (111) crystallographic plane and represents the fcc silver that is most stable thermodynamically and the dominant reflection. The peak at 44 is assigned to the (200) plane, and the peaks at 64 and 77 refer to the (220) and (311) planes, respectively. The positions of these diffraction peaks are perfectly consistent with those of the standard JCPDS card for metallic silver; hence, the crystalline structure of Ag nanoparticles is confirmed. The remarkably high intensity of the (111) peak shows the preferential orientation and high crystalline of the nanoparticles. The obvious broadening of all the diffraction peaks is indicative of the nano, crystalline nature of the material. By using the Debye Scherrer formula, the crystallite size is found to be on the nanometer scale, thus confirming particulate formation. For L-Histidine capped Ag nanoparticles, one can observe the same typical fcc peaks at 2θ Positions, and thus it is confirmed that the capping does not change the crystal structure of silver. Nonetheless, more peaks broadening is observed with an additional slight decrease in peak intensity, which is a sign that there is less crystallite growth due to stabilization at the surface by Histidine molecules. Most significantly, there are no peaks of silver oxide (Ag-O) or any other impurity phases, thus the phase purity is confirmed and silver nanoparticles are effectively protected by L- Histidine.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTable.1.XRD peak Position and Corresponding Miller indices (hkl) of L-Histidine capped Ag-NPs nanoparticles indexed to the face-centre cubic (fcc) structure of metallic Silver\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e(hkl)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2θ\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eθ\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCos θ\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFWHM \u003csup\u003e0\u003c/sup\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eβ radian\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003ed(A\u003csup\u003e0\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eD (nm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e111\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e38.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e19.04\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.945\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.4695\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.00819\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2.36\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e17.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e44.27\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e22.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.927\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.3814\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.00665\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e22.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e220\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e64.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e32.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.846\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.382\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.00667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.44\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e24.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e311\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e77.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e38.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.2769\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.00483\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e36.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eScanning Electron Microscopy (SEM):\u003c/h2\u003e \u003cp\u003eField Emission Scanning Electron Microscopy (FESEM) analysis was conducted to explore the surface features and particle distribution of the synthesized materials. The FE-SEM image of the Ag-Histidine complex displays abnormal, aggregated, and non, uniform structures, which substantiate the formation of a coordinated complex rather than isolated nanoparticles. The surface is quite rough with clustered morphology. On the other hand, FE, SEM images of L-Histidine capped silver nanoparticles demonstrate the formation of almost spherical and evenly distributed nanoparticles. Despite the fact that a small cluster can be seen, the particles are pretty much evenly scattered, indicating that Histidine molecules are efficiently capping the particle surface. In terms of morphology, the nanoparticles are smooth surfaced and have nanoscale dimensions. The particle size distribution histogram also verifies the nanoscale nature of the synthesized nanoparticles. The size distribution covers approximately from 10 nm to 60 nm, with the majority of particles in the 20\u0026ndash;40 nm segments. The average particle size worked out is about\u0026thinsp;~\u0026thinsp;30 nm, which means that nucleation and growth were well controlled during the synthesis. The rather narrow size distribution indicates that L-Histidine functions well as a capping agent, restricting particle growth and avoiding excessive aggregation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(particles size-40 nm) (particles size-22 nm)\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eEnergy Dispersive X-ray Analysis (EDAX):\u003c/h2\u003e \u003cp\u003eThe EDS elemental analysis confirms the conversion of Ag-Histidine coordination complex into L-Histidine capped silver nanoparticles. Ag-Histidine complex mainly contains carbon (45.0 wt%, 56.4 at%), nitrogen (30.2 wt%, 32.4 at%), and oxygen (9.7 wt%, 9.1 at%) while silver only accounts for 15.1 wt% and 2.1 atomic and N in considerable quantities reveal that the Histidine ligand, which includes an imidazole ring, amino group (-NH\u003csub\u003e2\u003c/sub\u003e), and carboxyl group (-COOH), is the major part of the structure. The extremely small atomic fraction of silver suggests that Ag is mostly in ionic form (Ag) and thus is coordinated to the nitrogen atoms of the imidazole and amino groups, with the carboxylate oxygen possibly involved in an interaction. The fact that elements from the ligands are much more abundant than silver is a strong indication of a metal-ligand coordination complex being formed rather than a metallic nanoparticles system. The homogeneous spreading of C, N, and O also points to silver ion chelating and stabilization within the Histidine framework effectively. the elemental composition of the L-Histidine capped Ag-NPs changes dramatically. Silver becomes the most abundant component, making up 81.8 wt% and 35.0 atomic%, whereas carbon (11.3 wt%), nitrogen (3.7 wt%), and oxygen (3.2 wt%) are only present in very small amounts. This highly significant increase in silver level confirms the Ag ions were converted into metallic Ag and silver nanoparticles were formed. The lower figures for %C, N, and O further support the idea that Histidine is not the main structure in the bulk but is acting as a capping and stabilizing agent on the surface. The minor presence of nitrogen and oxygen helps to justify that Histidine molecules are adsorbed on the nanoparticles surface through coordination of the imidazole nitrogen or amino groups with the metallic silver core. Therefore, the change in composition from ligand, dominated to metal, dominated structure perfectly demonstrates nanoparticles formation, with Histidine serving as the organic shell that inhibits aggregation and increases stability. In general, the differential EDAS data provide very strong evidence for the reactivity of the coordination complex to a surface, functionalized metallic nanoparticles system.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eEDAX elemental analysis of the Ag-Histidine complex and L-Histidine-capped Ag-NPs synthesized in acetate buffer (pH 5)\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eElement\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c5\" namest=\"c3\"\u003e \u003cp\u003eAg\u0026ndash;Histidine complex\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c8\" namest=\"c6\"\u003e \u003cp\u003eL-Histidine capped AgNPs\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eShell\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eWeight %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMDL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eAtomic %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eWeight %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMDL\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eAtomic %\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e45.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e56.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e11.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e43.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e32.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e12.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e9.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e9.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eL\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e81.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e35.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eAntimicrobial Activity of Silver-Histidine and L-Histidine Capped Silver Nanoparticles:\u003c/h2\u003e \u003cp\u003eThe antimicrobial property of the Silver-Histidine complex and L-Histidine Capped Silver Nanoparticles were tested against bacteria Escherichia coli (Gram, negative) and Staphylococcus aureus (Gram, positive) through the agar well diffusion method. The complex and Nanoparticles showed a clear zone of inhibition (ZOI) of about 13, 16 mm against E.coli and 11, 14 mm against S. aureus, thus confirming the significant antibacterial effect on both bacterial strains. The main reason for the antibacterial action is the coordinated Ag ions that disrupt the negatively charged cell membrane components of bacteria, thus increasing permeability and causing damage to the membrane. Silver ions in E. coli dismantle the top lip polysaccharide membrane and also disturb membrane, bound enzymes, whereas in S. aureus Ag ions pass through the thick peptidoglycan layer and then get attached to thiol groups of essential proteins, which lead to enzyme inactivation and DNA replication inhibition. Also, the formation of reactive oxygen species (ROS) causes oxidative stress in bacterial cells, thus, killing them. The value of ZOI observed indicates that the Silver, Histidine complex has moderate and L-Histidine capped Silver nanoparticles shows More than Ag-Histidine complex antibacterial activity against both types of bacteria (Gram, negative and Gram, positive) which is due to sustained silver ion release and microbial cell component interaction.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003eComparative Zone of Inhibition (mm):\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAntimicrobial activity of Ag-Histidine complex and L-Histidine-capped AgNPs synthesized in acetate buffer (pH 5).\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eE. coli\u003c/em\u003e (Gram \u0026minus;)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eS.Aureus\u003c/em\u003e sp. (Gram +)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSilver\u0026ndash;Histidine complex\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eL-Histidine capped AgNPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e16 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14 mm\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eAg-Histidine complex and L-Histidine capped Ag nanoparticles were supported by a set of complementary spectroscopic and morphological investigations. UV-visible spectral recordings showed a typical surface Plasmon resonance (SPR) band at about 395\u0026ndash;430 nm region, which is an indicator of the production of metallic Ag nanoparticles. Besides, the shift of the Histidine absorption bands suggested the coordination of Ag ions with the Histidine molecule. Further, FTIR inspection exposed major alterations of -NH, COO\u003csup\u003e\u0026minus;\u003c/sup\u003e, and imidazole group vibrations, which strongly suggested the role of Histidine in metal binding and the final effect of capping on the surface of newly formed particles.XRD results revealed separate diffraction peaks such as (111), (200), (220), and (311) that belong to the silver face, centered cubic crystal planes, thereby confirming the crystalline attribute of the nanoparticles. Three, dimensional SEM micrographs displayed quasi, spherical shaped and moderately aggregated particles and nanosized dimensions. On the other hand, the obtained particle size distribution analysis indicated that the average particle size mainly fell within the 40 nm interval. Overall, all these data undeniably showed that crystalline L-Histidine, functionalized silver nanoparticles with controlled nanoscale morphology were synthesized successfully. As a highlight, both Escherichia coli and Staphylococcus aureus strains were inhibited by the Silver-Histidine complex which resulted in visible zones of inhibition, thereby confirming substantial antimicrobial property of the complex. The anti, bacterial property observed can, thus, be mainly attributed to the mechanism of the controlled release of Ag ions which permeabilize the bacterial cell membranes, lead to the loss of enzymatic activity, and finally cause oxidative stress inside microbial cells. Despite the fact that the antimicrobial activity is moderate relative to metallic silver nanoparticles, the complex still manages to provide a sustained release of ions and to effectively inhibit both Gram, negative and Gram, positive bacteria. This study demonstrates that the Silver, Histidine complex is an excellent antimicrobial agent that can be used in various biomedical and antimicrobial material developments.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eACKNOWLEDGMENT\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge VidyaPratishthans Arts, Science and Commerce College, Baramati,Pune, Maharashtra, India for providing the necessary research facilities to carry out this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCONFLICT OF INTERESTS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAUTHOR CONTRIBUTIONS\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll the authors contributed significantly to this manuscript, participated in reviewing/editing, and approved the final draft for publication. The research profile\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOpen Access:\u0026nbsp;\u003c/strong\u003eThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCitethisarticleas:\u003c/strong\u003e KanchanRaniandJ.B.Dahiya,\u003cem\u003eRasayanJ. Chem.\u003c/em\u003e,19(1),1-9(2026), https://doi.org/10.317 88/RJC.2026.1919443\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eK.B.A. Ahmed, V. Anbazhagan, R. Uthandakalaipandian, Silver nanoparticles: Preparation, characterization, and applications. J. Nanosci. Nanotechnol. \u003cb\u003e16\u003c/b\u003e(3), 2526\u0026ndash;2537 (2016). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1166/jnn.2016.10830\u003c/span\u003e\u003cspan address=\"10.1166/jnn.2016.10830\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Rai, A. Yadav, A. Gade, Silver nanoparticles as a new generation of antimicrobials. Biotechnol. Adv. \u003cb\u003e27\u003c/b\u003e(1), 76\u0026ndash;83 (2014). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.biotechadv.2008.09.002\u003c/span\u003e\u003cspan address=\"10.1016/j.biotechadv.2008.09.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eX.F. Zhang, Z.G. Liu, W. Shen, S. Gurunathan, Silver nanoparticles: Synthesis, characterization, properties, applications, and therapeutic approaches. Int. J. Mol. Sci. \u003cb\u003e17\u003c/b\u003e(9), 1534 (2020). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e.https://doi.org/10.3390/ijms17091534\u003c/span\u003e\u003cspan address=\".10.3390/ijms17091534\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eA.C. Burdușel et al., Biomedical applications of silver nanoparticles. J. Nanobiotechnol. \u003cb\u003e16\u003c/b\u003e, 1\u0026ndash;36 (2018). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/s12951-018-0332-z\u003c/span\u003e\u003cspan address=\"10.1186/s12951-018-0332-z\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS. Prabhu, E.K. Poulose, Silver nanoparticles: Mechanism of antimicrobial action. Int. Nano Lett. \u003cb\u003e2\u003c/b\u003e, 32 (2012). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1186/2228-5326-2-32\u003c/span\u003e\u003cspan address=\"10.1186/2228-5326-2-32\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e(2025). Mechanistic insights and therapeutic innovations in engineered nanomaterial-driven disruption of biofilm dynamics. RSC Adv. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/D5RA01711D\u003c/span\u003e\u003cspan address=\"10.1039/D5RA01711D\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e(2025). Mechanistic insights and therapeutic innovations in engineered nanomaterial-driven disruption of biofilm dynamics. RSC Adv. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/D5RA01711D\u003c/span\u003e\u003cspan address=\"10.1039/D5RA01711D\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC.L. Ventola, The antibiotic resistance crisis. Pharm. Ther. \u003cb\u003e40\u003c/b\u003e(4), 277\u0026ndash;283 (2015)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ.S. Kim et al., Antimicrobial effects of silver nanoparticles. Nanomedicine. \u003cb\u003e3\u003c/b\u003e(1), 95\u0026ndash;101 (2007). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.nano.2006.12.001\u003c/span\u003e\u003cspan address=\"10.1016/j.nano.2006.12.001\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhalifa et al., 2025) (E. coli and S. aureus resist silver nanoparticles via an identical mechanism, but through different pathways, 2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e(Antibacterial Properties of Silver Nanoparticles Embedded on Polyelectrolyte, Hydrogels Based on α-Amino Acid Residues, 2023)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e(Silver Nanoparticle-Based Combinations with Antimicrobial Agents against Antimicrobial-Resistant Clinical Isolates, 2024) (Hayat et al., 2025, pp. 42460\u0026ndash;42478)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun et al., 2021) However, the direct application of uncapped AgNPs is often limited by aggregation, instability in biological environments, and concerns related to nonspecific cytotoxicity (Ivask., 2014; Mukherjee., 2014)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eP. Singh et al., Biological synthesis of nanoparticles. Adv. Colloid Interface Sci. \u003cb\u003e256\u003c/b\u003e, 39\u0026ndash;58 (2018). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.cis.2018.03.004\u003c/span\u003e\u003cspan address=\"10.1016/j.cis.2018.03.004\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e(Biosynthesis of Silver Nanoparticles Functionalized with Histidine and Phenylalanine Amino Acids for Potential Antioxidant and Antibacterial Activities, 2023, pp. 28556\u0026ndash;28565)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003e(Anticancer Potential of L-Histidine-Capped Silver Nanoparticles against Human Cervical Cancer Cells (SiHa), 2021, pp. 118\u0026ndash;125)levance\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eL. Alderighi et al., Coordination chemistry of histidine. Coord. Chem. Rev. \u003cb\u003e184\u003c/b\u003e, 311\u0026ndash;318 (1999). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0010-8545(98)00224-0\u003c/span\u003e\u003cspan address=\"10.1016/S0010-8545(98)00224-0\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eE.P. Ivanova et al., Natural amino acids as metal ligands. RSC Adv. \u003cb\u003e4\u003c/b\u003e, 46993\u0026ndash;47003 (2014). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/C4RA06767H\u003c/span\u003e\u003cspan address=\"10.1039/C4RA06767H\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eG. Shumi, T.B. Demissie et al., Biosynthesis of silver nanoparticles functionalized with histidine. ACS Omega. \u003cb\u003e8\u003c/b\u003e, 24371\u0026ndash;24386 (2023). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/acsomega.3c01910\u003c/span\u003e\u003cspan address=\"10.1021/acsomega.3c01910\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM.A. Raza et al., Amino acid capped silver nanoparticles. Mater. Chem. Phys. \u003cb\u003e258\u003c/b\u003e, 123879 (2021). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e.https://doi.org/10.1016/j.matchemphys.2020.123879\u003c/span\u003e\u003cspan address=\".10.1016/j.matchemphys.2020.123879\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eY.S. Lee, S.H. Kim, S.H. Kim, S.H. Kim, S.H. Kim, Spectroscopic analysis of L-histidine adsorbed on gold and silver nanoparticle surfaces investigated by surface-enhanced Raman scattering. SpectrochimicaActa Part. A: Mol. Biomol. Spectrosc. \u003cb\u003e68\u003c/b\u003e(5), 1240\u0026ndash;1245 (2007). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.saa.2007.01.019\u003c/span\u003e\u003cspan address=\"10.1016/j.saa.2007.01.019\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eI. Kostova, Metal complexes as antimicrobial agents. Curr. Med. Chem. \u003cb\u003e13\u003c/b\u003e, 1085\u0026ndash;1107 (2006). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.2174/092986706776360961\u003c/span\u003e\u003cspan address=\"10.2174/092986706776360961\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM.J. Panzner et al., Bioinorganic silver complexes. Dalton Trans. \u003cb\u003e47\u003c/b\u003e, 13010\u0026ndash;13020 (2018). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1039/C8DT02741A\u003c/span\u003e\u003cspan address=\"10.1039/C8DT02741A\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eY. You, C. Zhang, Interaction between silver ions and histidine. J. Clin. Rehabilitative Tissue Eng. Res. \u003cb\u003e14\u003c/b\u003e(29), 5498\u0026ndash;5504 (2010). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.3969/j.issn.1673-8225.2010.29.042\u003c/span\u003e\u003cspan address=\"10.3969/j.issn.1673-8225.2010.29.042\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS.Y. Liau et al., Silver compounds in wound care. J. Appl. Microbiol. \u003cb\u003e83\u003c/b\u003e, 433\u0026ndash;438 (1997). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1046/j.1365-2672.1997.00253.x\u003c/span\u003e\u003cspan address=\"10.1046/j.1365-2672.1997.00253.x\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS. Medici et al., Silver coordination compounds. Coord. Chem. Rev. \u003cb\u003e284\u003c/b\u003e, 329\u0026ndash;350 (2015). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.ccr.2014.09.002\u003c/span\u003e\u003cspan address=\"10.1016/j.ccr.2014.09.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLe B. Ouay, F. Stellacci, Antibacterial activity of functionalized nanoparticles. Nano Today. \u003cb\u003e10\u003c/b\u003e(3), 339\u0026ndash;354 (2015). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.nantod.2015.04.002\u003c/span\u003e\u003cspan address=\"10.1016/j.nantod.2015.04.002\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Rai et al., AgNP interaction with microbes. Appl. Microbiol. Biotechnol. \u003cb\u003e100\u003c/b\u003e, 459\u0026ndash;475 (2016). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1007/s00253-015-6905-4\u003c/span\u003e\u003cspan address=\"10.1007/s00253-015-6905-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eH. Katas et al., Biocompatibility of capped AgNPs. Arab. J. Chem. \u003cb\u003e11\u003c/b\u003e, 676\u0026ndash;683 (2018). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.arabjc.2015.06.019\u003c/span\u003e\u003cspan address=\"10.1016/j.arabjc.2015.06.019\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eM. Akter et al., Cytotoxicity of silver nanoparticles. Part. Fibre Toxicol. \u003cb\u003e15\u003c/b\u003e, 18 (2018). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e.https://doi.org/10.1186/s12989-018-0253-4\u003c/span\u003e\u003cspan address=\".10.1186/s12989-018-0253-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eC. Beer et al., Surface chemistry effects on nanoparticle toxicity. Langmuir. \u003cb\u003e28\u003c/b\u003e, 7240\u0026ndash;7247 (2012). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1021/la2041687\u003c/span\u003e\u003cspan address=\"10.1021/la2041687\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS. Gurunathan et al., Biocompatibility of AgNPs. Colloids Surf. B \u003cb\u003e135\u003c/b\u003e, 407\u0026ndash;417 (2015). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.colsurfb.2015.07.043\u003c/span\u003e\u003cspan address=\"10.1016/j.colsurfb.2015.07.043\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJ. Wang et al., Electrochemical applications of silver nanomaterials. ElectrochimicaActa. \u003cb\u003e247\u003c/b\u003e, 785\u0026ndash;795 (2017). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.electacta.2017.07.019\u003c/span\u003e\u003cspan address=\"10.1016/j.electacta.2017.07.019\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eS. Chen et al., Amino acid-modified electrodes. Biosens. Bioelectron. \u003cb\u003e126\u003c/b\u003e, 208\u0026ndash;215 (2019). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.bios.2018.10.060\u003c/span\u003e\u003cspan address=\"10.1016/j.bios.2018.10.060\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZhao et al., 2021)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eP.T. Anastas, J.C. Warner, \u003cem\u003eGreen chemistry: Theory and practice\u003c/em\u003e (Oxford University Press, 1998)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIravani et al., 2014)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eO.V. Kharissova et al., Green synthesis of metal nanoparticles. Trends Biotechnol. \u003cb\u003e37\u003c/b\u003e, 190\u0026ndash;203 (2019). \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.tibtech.2018.08.007\u003c/span\u003e\u003cspan address=\"10.1016/j.tibtech.2018.08.007\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"spectrum, inhibit. Morphology, electrochemistry","lastPublishedDoi":"10.21203/rs.3.rs-9030666/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9030666/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSilver-Histidine complex and L-Histidine capped silver nanoparticles (AgNPs) were chemically synthesized. Their properties were compared and thoroughly characterized using UV-visible spectroscopy, FTIR, XRD, SEM, EDAX, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). In the UV-visible spectrum, the silver-histidine complex showed an absorption peak in the lower wavelength region, which was attributed to ligand metal interaction. In contrast, L-Histidine capped AgNPs displayed a clear surface plasmon resonance (SPR) band at around 420–450 nm, thus confirming the formation of metallic Ag nanoparticles.FTIR spectra of histidine demonstrated the main functional groups, such as -NH stretching (3200–3400 cm), C = O stretching (~ 1650 cm), and imidazole -CN vibrations (1400–1500 cm), with evident changes pointing to coordination and surface capping.XRD pattern of Ag-NPs showed four well, separated diffraction peaks centered at 2θ values near 38, 44, 64, and 77 which correspond to (111), (200), (220), and (311) planes of face, centered cubic silver, respectively. The average particle size was calculated to be 22 and 40 nm by the Debye Scherrer equation.SEM pictures of the complex showed an aggregated morphology whereas capped Ag-NPs were spherical and the nanoparticles were evenly spread. EDAX analysis verified that the elements C, N, O, and Ag were present; among them, silver was significantly enriched in the nanoparticles system. Electrochemical studies such as CV and LSV were conducted and the results revealed well, defined redox peaks along with a significant increase in the current response of Ag-NPs, which is indicative of an efficient electron transfer process. The assessment of the antimicrobial property of L-Histidine capped Ag-NPs compared to Ag-Complex against Escherichia coli and Staphylococcus aureus revealed that, first, the bacteria were effectively inhibited and, second, the antibacterial activity of L-Histidine capped Ag, NPs was significantly higher. In short, this study essentially provides the evidence that the nanoparticles were successfully synthesized and that they have superior properties of morphology, electrochemistry, and antimicrobial activities as compared to Silver-Histidine complex.\u003c/p\u003e","manuscriptTitle":"Synthesis and characterization of Silver-Histidine complex and L-Histidine capped Ag-NPs in Buffer System, Electrochemical and Antibacterial Properties","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-08 11:43:24","doi":"10.21203/rs.3.rs-9030666/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"63541d50-a95c-495d-b6bf-2d1e46bdaad2","owner":[],"postedDate":"April 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-21T16:53:29+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-08 11:43:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9030666","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9030666","identity":"rs-9030666","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}