Spectroscopic sensing of eight metal ions in aqueous solutions using silver nanoparticles

Spectroscopic sensing of eight metal ions in aqueous solutions using silver nanoparticles | 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 Spectroscopic sensing of eight metal ions in aqueous solutions using silver nanoparticles Selvaraj Tamilselvan, Rathnavelu Murali Soniya, Raguraman Vasantharaja, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-1246304/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 Anthropogenic releases from different outlets of industry, municipal sewage and the road traffic can give rise to higher concentrations of the heavy metals in the food commodities which imposes a threat to human health and environment. A simple silver nanoparticle (Ag NPs) used for the sensing of heavy metal ions, Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ in aqueous solution is described by qualitative and quantitatively using spectroscopic tool. FE-SEM and TEM images confirmed that the particles are spherical in shape with an average diameter of 23.4 nm. In presence of heavy metal ions with Ag NPs, a new peak at around 925, 898, 643, 665, 688, and 838 nm of Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ and Zn 2+ appeared in addition to the peak found at 410 nm of Ag NPs. Further, the addition of Ni 2+ and Pb 2+ metal ion solution with Ag NPs increased the SPR band from 410 nm to 436 and 462 nm respectively. Citrate functionalized Ag NPs are aggregated in solution in the presence of divalent metal ions by an ions-template chelating process and easily measurable change in the UV-vis absorption spectrum of the particles. Further, studies also confirmed the interaction of Ag NPs with metal ions using FT-IR spectroscopy. The proposed method was found to be useful for simple UV-vis spectroscopic sensing of metal ions in aqueous solutions and real contaminated samples. Silver nanoparticles Heavy metal ions UV-vis spectroscopy FT-IR spectroscopy sensing 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 Figure 13 Introduction Heavy metals are commonly defined as elements that have a density at least 5 times higher than of water. Their presence in the soil can be of natural and anthropogenic origin. Due to natural processes in the earth's crust, the soil usually contains low concentrations of heavy metals. However, different anthropogenic activities lead to an increase of heavy metals concentration above the natural level in aquatic ecosystems. As heavy metals are not biodegradable, they accumulate in the environment and enter the food chain as bioaccumulation. Further, excessive intake of heavy metals into living organisms causes many harmful consequences, including death (Zwolak et al. 2019 ). Various heavy metals such as Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ are reported to be potential environmental pollutants and causing various problems such soil, aquatic organisms, plants, animals and human at trace ppm level concentrations (Sheet et al. 2014 ; Fajardo et al. 2019 ). So far, quite a few reports are available for the detection/sensing of metal ions using various analytical techniques (Nolan and Lippard 2008 ; Ray 2010 ; Aragay et al. 2011 ; Singh et al. 2021 ) and conventional methods for heavy metal quantitative measurement include atomic absorption spectroscopy (AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS) and electrochemical sensing platforms (Kumeria et al. 2013 ) offer excellent sensitivity, multi-element analysis but, they are high expensive, time consuming, skill dependent and use non-portable accessories. In recent years, nanomaterials-based sensing/detection of metal ions due to their optical properties with high extinction co-efficient at the visible region for improving the performance of sensors in terms of sensitivity, limit of detection, selectivity and reproducibility (Zheng et al. 2004 ; Prosposito et al. 2020 ; Wang et al. 2020 ). So far, several reports are available for the sensing/detection of toxic metal ions using various synthetic (biogenic, physical and chemical) methods. For instance, Kim et al ( 2001 ) reported the sensing of spectroscopically silent heavy metal ions (Pb 2+ ) using 11-mercaptoundecanoic acid stabilized gold nanoparticles. Wang et al ( 2010 ) reported the detection of Hg 2+ ions using unmodified silver nanoparticles and mercury specific oligonucleotides used as sensors (Zheng et al. 2004 ). Green synthesized silver nanoparticles using aqueous extract of Hedysarum alpinum plant used for calorimetrically detection of Hg 2+ . Zhou et al ( 2012 ) reported silver nanoparticles co-functionalized with 4-mercapto benzoic acid and melamine as a probe for colorimetric detection of Mn 2+ . Green synthesis of L-tyrosine-stabilized silver nanoparticles under ambient sunlight irradiation for colorimetric detection of heavy metal ions (Hg 2+ and Pb 2+ ) as reported. Recently, Wang et al ( 2020 ) reported that the carrageenan stabilized silver nanoparticles for effective detection of Cu 2+ and S 2− ions in aqueous solution. In the present investigation, sodium citrate stabilized silver nanoparticles for sensing/detection of various metal ions (Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ ) in aqueous solution using UV-vis spectroscopic technique. Further, metal ion interactions with silver nanoparticles were studied using FT-IR spectroscopy. Materials And Methods Synthesis of Ag NPs Synthesis of silver nanoparticles using sodium citrate as reducing agents was done according to the literature procedure (Kamat et al. 1998) with slight modification. Briefly, 100 mL of AgNO 3 (10 mg) aqueous solution and heated until it begins to boil. 2 mL of sodium citrate (30 mg) solution was added, and heating continued till the color was yellowish brown color which indicates formation of Ag NPs nanoparticles. Characterization of Ag NPs The formation of Ag NPs was monitored using a UV-visible spectrophotometer (Shimadzu UV-1800) in the range of 200-1000 nm. Particle’s size and shape of the citrate reduced Ag NPs were determined using FE- SEM (Supra 55-Carl Zeiss, Germany) and TEM (FEI Technai, instruments) operating at an accelerating voltage of 120kVA. Sensing/ detection of Metal ions The spectroscopic detection of aqueous heavy metal ions was studied using Ag NPs solution at room temperature. To demonstrate the effect of heavy metal ions on Ag NPs, 1 mL concentrations of heavy metal ions were added one at a time to 500 µL of Ag NPs and the resulting mixture was then allowed to stand for 10 min at room temperature, during which the colour change depending upon the metal ions. The intensity of this colour gradually increased with the increase of heavy metal ion concentration. UV-Vis absorption spectra from all samples were analyzed carefully to correlate the changes of SPR spectra with respect to concentrations of Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ using UV-visible Spectrophotometer (UV 1800) Shimadzu, Japan. Spectra of the adsorbents before and after Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ binding were recorded with a FT-IR analysis using a PerkinElmer 1600 infra-red spectrometer with a pellet of powered potassium bromide. Results And Discussion Addition of sodium citrate into the beakers containing aqueous solution of AgNO 3 led to the change in the colour of the solution from colorless to brownish yellow within reaction duration due to excitation of surface plasmon resonance (SPR) vibrations in Ag NPs. The colour of the solution is brownish yellow indicating formation of Ag NPs (Figure 1 inset). Ag NPs synthesized using sodium citrate were analyzed by UV spectra of Plasmon resonance band observed at 410 nm (Figure 1 ) (Zia et al. 2016 ). SEM micrograph shows the morphology of the Ag NPs which are spherical and well dispersed (Figure 2 a). TEM results showed well dispersed spherical particles with a size of ca. 23.4 nm in diameter (Figure 2 b&c). The spectroscopic detection of metal ions Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ at the fixed concentrations of 500 µL of a 1 × 10 −5 M were added to Ag NPs solution and the corresponding changes of the absorption coefficient were observed from brownish yellow to light blue color (Figure 3 a-h) (Kamel et al. 2019 ; Boruah et al. 2019 ). In presence of heavy metal ions with Ag NPs, a new peak at around 925, 898, 643, 665, 688, and 838 nm of Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ and Zn 2+ appeared in addition to the peak found at 410 nm of Ag NPs (Figure 4 a-e, h). Further, the addition of Ni 2+ and Pb 2+ metal ion solution with Ag NPs increased the SPR band from 410 nm to 436 and 462 nm respectively (Figure 4 f, 4 g). Even though Pb interacts with Ag NPs surface plasmon resonance (SPR) peak at 436 near to Ag NPs similar reported (Anambiga et al. 2013 ). Ag NPs undergo agglomeration upon exposure to increasing concentrations of heavy metal ions. Color change occurred due to the aggregation between Ag NPs with metal ions (Xiong and Li 2008 ). The ability of silver nanoparticles to form agglomeration caused the SPR to broaden and shift to longer wavelengths (Sulistiawaty et al. 2015 ). In particular Hg 2+ ions interact with Ag NPs precipitation and the SPR band absorbance at 410 nm. Besides, the colour of the Ag NPs became transparent immediately when added to the Hg 2+ ions solution. In contrast, increasing the concentration of Ag NPs to Hg 2+ solution changed colour into yellow precipitate (Uddin et al. 2017 ). Similarly, the Ag NPs were interacting with Hg 2+ and Mn 2+ ions, a blue shift in the SPR band was observed by UV-vis spectroscopy detection. Hg 2+ ions were added to the Ag NPs solution and the colour of the solution changed from yellow to colorless. This interaction is due to oxidation of Ag 0 to Ag + during the process of reduction of Hg 2+ ions (Annadhasan et al. 2014 ). FT-IR measurements were carried out to identify the interaction of Ag NPs and metal ions. FT-IR spectra of Ag NPs functional groups 2924, 2856, 2338, 1714, 1638 cm −1 respectively, CdSO 4 and CdSO 4 + Ag NPs show several significant absorption peaks such as 2956, 2128, 1638 and 2327, 1639 cm −1 disappears in CdSO 4 + Ag NPs. The peaks 2338 shifted into 2339 (Figure. 5a-c). FT-IR spectra of Ag NPs, CuSO 4 , CuSO 4 + Ag NPs, absorption peaks at 2924, 2855 and 2448, 2092 cm −1 were disappeared in CuSO 4 +AgNPs and new peaks at 2956 shifted into 2969, 1737 shifted into 1738 (Figure 6 ). Similar study of FeO nanoparticles observation confirms a successful modification of the surface of the nanoparticles with Cd and Cu ions (Klekotka et al. 2018 ). There were significant changes on the FT-IR spectrum of Ag NPs after interaction with FeSO 4 ions. The Ag NPs and FeSO 4 absorption peaks at 2956, 2855, 2338, 2128, 1714, 2326, 1642 cm −1 were appearing but disappeared in the FeSO 4 + Ag NPs whereas new peaks appeared at 2926, besides the peak at 2924 shifted into 2916 (Figure 7 ). The FT-IR spectrum of Ag NPs, HgCl 2 and HgCl 2 + Ag NPs was represented in Figure 8 . The presence of a sharp absorption band at 2956, 2125, 2188 and 2097 cm −1 in Ag NPs and HgCl 2 . HgCl 2 + Ag NPs new peak 2855, 1737 shifted into 2853, 1738. FT-IR spectral data revealed absorption peaks at 2956, 2338, 2128, 1737, 1714 and 2199 cm −1 were present in Ag NPs and MnCl 2 . Whereas the peak at 2855, 1638 shifted into 2853, 1640 present in MnCl 2 + Ag NPs (Figure. 9). FT-IR spectra of Ag NPs, NiSO 4 and NiSO 4 + Ag NPs based on the functional groups 2924, 2856, 2338, 1714, 1638 cm −1 and 3293, 2332, 1638 cm −1 peaks were present and 2332, 2128, 1714, 1638 cm −1 peaks were disappeared in Ag NPs and NiSO 4 . While 3459, 3016, 2132 and 1434 cm −1 peaks were present in NiSO 4 + Ag NPs. 2128 cm −1 line is observed in p-polarization and is absent in s-polarization shifted into 2132 –C≡C– stretch and the presence of a broad absorption band at 3392 and 3459cm −1 can be attributed the –OH stretching presented due to the adsorption of water in air when FT-IR sample disks were prepared in an open air (Figure 10 ). FT-IR analysis on Ag NPs, Pb(NO) 3 and Pb(NO) 3 + Ag NPs reveals that the peaks at 2956, 2924, 2855, 2338, 2398 and 1768 cm −1 were present [Ag NPs, Pb(NO) 3 ] but disappear in the Pb(NO) 3 + Ag NPs. The broad absorption peak 2128, 1638 shifted into 2125 cm −1 , 1654 cm −1 confirms the formation of Pb-Ag NPs complex (Figure 11 ) (Kamel et al. 2019 ; Anambiga et al. 2013 ). FT-IR absorption peaks at 2128, 1714 and 1616 cm −1 were present in Ag NPs and ZnSO 4 whereas disappear in ZnSO 4 + Ag NPs. A ZnSO 4 + Ag NPs new peak appears at 2871 and 1980. The peaks were 2338, 2077 and 1737 cm −1 shifted into 2340, 2079 and 1741 cm −1 (Figure 12 ). Based on the present study and previous literature report, the conceivable predicted mechanisms of Ag NPs interaction with metal ions which is shown in Figure 13 . Conclusions Herein, we report the Ag NPs as a cost-effective sensor for the detection of toxic metal ions in water. The spectroscopic tool such as UV-vis spectroscopy was used for detection and of various heavy metal ions (Cd 2+ , Cu 2+ , Fe 2+ , Hg 2+ , Mn 2+ , Ni 2+ , Pb 2+ and Zn 2+ ) in aqueous medium with the detection limits of nM concentrations and easily visualized with the naked eye by the rapid color change from a brownish yellow to light blue color observed. From the noteworthy mention that spectral changes and fast colour changes of ions with the addition of nanoparticles, we conclude that ions can potentially become a selective detection for the qualitative detection of the used nanoparticles and could be used as a visual marker. Declarations Acknowledgements The authors (KG) thankful to the DST‐FIST (SR/FST/ESI‐145/2016) for infrastructure support to carry out this work and management of Sathyabama Institute of Science and Technology, Chennai for their constant support in research activities. Ethics approval and consent to participate Not applicable. Consent to Participate Not applicable. Consent to Publish Not applicable. Authors contribution S. Tamilselvan: Methodology, Investigation, Validation; R.M. Soniya: Investigation, Formal analysis, Data curation; R. Vasantharaja: Formal analysis, Review & editing; M. Kannan: Validation, Resources, Writing - review & editing; S. Supriya: Formal analysis, Resources; K. Govindaraju: Conceptualization, Project administration, Writing - review & editing. Funding Not applicable. Competing interests The authors declare no competing interests. Availability of data and materials The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. References Anambiga IV, Suganthan V, Raj NAN, Kumar TSS (2013) Colorimetric detection of lead ions using glutathione stabilized silver nanoparticles. 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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-1246304","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":79893933,"identity":"d79d78f9-f10c-4103-88ec-d5c0766f1498","order_by":0,"name":"Selvaraj Tamilselvan","email":"","orcid":"","institution":"Sathyabama Institute of Science and Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Selvaraj","middleName":"","lastName":"Tamilselvan","suffix":""},{"id":79893934,"identity":"2ba15c72-53ce-4cdd-b6fc-60100a94defb","order_by":1,"name":"Rathnavelu Murali Soniya","email":"","orcid":"","institution":"Sri Venkateswara College of Pharmacy","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Rathnavelu","middleName":"Murali","lastName":"Soniya","suffix":""},{"id":79893935,"identity":"204947e1-cc02-49eb-90f4-d9edc7a5b001","order_by":2,"name":"Raguraman Vasantharaja","email":"","orcid":"","institution":"Sathyabama Institute of Science and Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Raguraman","middleName":"","lastName":"Vasantharaja","suffix":""},{"id":79893936,"identity":"f8364a63-fa11-4d32-9b69-ac5cde761331","order_by":3,"name":"Malaichamy Kannan","email":"","orcid":"","institution":"Tamil Nadu Agricultural University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Malaichamy","middleName":"","lastName":"Kannan","suffix":""},{"id":79893937,"identity":"bff7a0f6-5be2-4ecc-b22d-aa7f29a1dc53","order_by":4,"name":"Subrahmanian Supriya","email":"","orcid":"","institution":"Sathyabama Institute of Science and Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Subrahmanian","middleName":"","lastName":"Supriya","suffix":""},{"id":79893938,"identity":"619bb892-1067-498e-97f1-edaaa9809f0a","order_by":5,"name":"Kasivelu Govindaraju","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYJCCAwxsDAz8IFZCAfFaDBgkG0BaDIi2B6jF4ACIQYwWefcew8MFZX8SN59fnfjhgQGDPL/YAfxaDM+cMTg845xB4rYbbzdLAB1mOHN2AgEtM9ISDvO2gbSc3QDSkmBwm1gtm2ec3fyDKC3yEskHwFo28PduI84WA57DBw7znDM2nnGDd5tFgoEEYb/Itzc2f+Ypk5Pt7z+7+eaPCht5fmlCthyAsSTAKiXwKwfb0gBj8R/ArWoUjIJRMApGNgAAuENIECjUVC0AAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-9687-2174","institution":"Sathyabama Institute of Science and Technology","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Kasivelu","middleName":"","lastName":"Govindaraju","suffix":""}],"badges":[],"createdAt":"2022-01-10 12:46:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-1246304/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-1246304/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":17853235,"identity":"159e8d56-a9ed-4939-9f23-10151aaa132d","added_by":"auto","created_at":"2022-02-01 18:24:30","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":68407,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUV–Vis spectra of sodium citrate mediated synthesized Ag NPs. Inset shows citrate mediated synthesized Ag NPs.\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/a8c5e8873e363b235eb2877d.png"},{"id":17853561,"identity":"45ec5ac8-5f64-4983-9b0f-e54c13329d12","added_by":"auto","created_at":"2022-02-01 18:30:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":755386,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea) SEM image; b\u0026amp;c) TEM images of sodium citrate mediated synthesized Ag NPs.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/e12a798d979a40943ebc93ca.png"},{"id":17853236,"identity":"a6b58fd7-8900-431c-ac9c-aa650b685c17","added_by":"auto","created_at":"2022-02-01 18:24:30","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1447956,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePhotograph showing the visual observation of before and after addition of Ag NPs with metal ions solutions (a) Cd\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e, (b) Cu\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e, (c) Fe\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e, (d) Hg\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e, (e) Mn\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e, (f) Ni\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e, (g) Pb\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e and (h) Zn\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e ions\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/cb2ed745fdd2401db1aa30c7.png"},{"id":17853475,"identity":"7bbeb7b8-9fda-4ab3-ba54-3d6dd5b928e1","added_by":"auto","created_at":"2022-02-01 18:27:31","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":214311,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUV–Vis spectra of before and after addition of AgNPs with metal ions solutions interaction (a) Cd\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e; (b) Cu\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e; (c) Fe\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e; (d) Hg\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e; (e) Mn\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e; (f) Ni\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e; (g) Pb\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e and (h) Zn\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/278456647f9286c6766dabce.png"},{"id":17853477,"identity":"2240f997-ee58-4bce-94c2-f27f8257073f","added_by":"auto","created_at":"2022-02-01 18:27:31","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":629260,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) CdSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Cd\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig5.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/7168805ff91b1b4f4b7d5f60.png"},{"id":17853473,"identity":"e64b8a09-9979-4e07-9266-fdb29d6de659","added_by":"auto","created_at":"2022-02-01 18:27:31","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":61356,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) CuSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt; (c) AgNPs interaction with Cu\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+ \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal ion\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig6.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/c832f93701e5997802d7f434.png"},{"id":17853116,"identity":"19ef7b60-c024-4972-889c-072a61645a8e","added_by":"auto","created_at":"2022-02-01 18:21:30","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":59747,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) FeSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Fe\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig7.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/f62c62cb42c9f6fd3f8a88b7.png"},{"id":17853118,"identity":"ad193549-9aa9-4cc5-94cf-63ca527ab87b","added_by":"auto","created_at":"2022-02-01 18:21:30","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":70935,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) HgCl\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Hg\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig8.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/119e666b0ff381800fdb8322.png"},{"id":17853239,"identity":"0664a98f-f1f5-4eff-934a-6564d24d5029","added_by":"auto","created_at":"2022-02-01 18:24:31","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":55454,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) MnCl\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Mn\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"fig9.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/f71c7442ab7d03173bf7e39d.png"},{"id":17853122,"identity":"a0322b98-029c-4cf0-87c4-5d43b29b0f42","added_by":"auto","created_at":"2022-02-01 18:21:31","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":82678,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) NiSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Ni\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig10.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/d03a4cf7bc38df0c4cf5e085.png"},{"id":17853476,"identity":"1101aaa8-7ef3-49b3-b9e1-a0882085ecf8","added_by":"auto","created_at":"2022-02-01 18:27:31","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":59199,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) Pb(NO)\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Pb\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig11.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/5f32f8d0e8c0b19cfbe5cf96.png"},{"id":17853125,"identity":"04a5e1a7-9953-4ee8-9db5-9fed95cc81a9","added_by":"auto","created_at":"2022-02-01 18:21:31","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":90508,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFT-IR spectra of (a) AgNPs; (b) ZnSO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e4\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003emetal salt and (c) AgNPs interaction with Zn\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e metal ion\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig12.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/c3d6868a98dca8948b0c8fd0.png"},{"id":17853243,"identity":"82b8232c-c97f-4566-9225-0a889382a8f2","added_by":"auto","created_at":"2022-02-01 18:24:31","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":176881,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematic illustration of Ag nanoparticles interaction with metal ions\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"fig13.png","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/e0246a1f13999898c9b5487a.png"},{"id":19357691,"identity":"b1181a2f-dfa3-43b2-9330-de9275e78c98","added_by":"auto","created_at":"2022-03-18 06:35:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4063526,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-1246304/v1/1f9ed1a1-8e72-4bcd-82fc-d593a2d4aefc.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eSpectroscopic sensing of eight metal ions in aqueous solutions using silver nanoparticles \u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eHeavy metals are commonly defined as elements that have a density at least 5 times higher than of water. Their presence in the soil can be of natural and anthropogenic origin. Due to natural processes in the earth's crust, the soil usually contains low concentrations of heavy metals. However, different anthropogenic activities lead to an increase of heavy metals concentration above the natural level in aquatic ecosystems. As heavy metals are not biodegradable, they accumulate in the environment and enter the food chain as bioaccumulation. Further, excessive intake of heavy metals into living organisms causes many harmful consequences, including death (Zwolak et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Various heavy metals such as Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e are reported to be potential environmental pollutants and causing various problems such soil, aquatic organisms, plants, animals and human at trace ppm level concentrations (Sheet et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Fajardo et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). So far, quite a few reports are available for the detection/sensing of metal ions using various analytical techniques (Nolan and Lippard \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2008\u003c/span\u003e; Ray \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2010\u003c/span\u003e; Aragay et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Singh et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and conventional methods for heavy metal quantitative measurement include atomic absorption spectroscopy (AAS), atomic fluorescence spectrometry (AFS), inductively coupled plasma mass spectrometry (ICP-MS) and electrochemical sensing platforms (Kumeria et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) offer excellent sensitivity, multi-element analysis but, they are high expensive, time consuming, skill dependent and use non-portable accessories.\u003c/p\u003e \u003cp\u003eIn recent years, nanomaterials-based sensing/detection of metal ions due to their optical properties with high extinction co-efficient at the visible region for improving the performance of sensors in terms of sensitivity, limit of detection, selectivity and reproducibility (Zheng et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Prosposito et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Wang et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). So far, several reports are available for the sensing/detection of toxic metal ions using various synthetic (biogenic, physical and chemical) methods. For instance, Kim et al (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2001\u003c/span\u003e) reported the sensing of spectroscopically silent heavy metal ions (Pb\u003csup\u003e2+\u003c/sup\u003e) using 11-mercaptoundecanoic acid stabilized gold nanoparticles. Wang et al (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2010\u003c/span\u003e) reported the detection of Hg\u003csup\u003e2+\u003c/sup\u003e ions using unmodified silver nanoparticles and mercury specific oligonucleotides used as sensors (Zheng et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2004\u003c/span\u003e). Green synthesized silver nanoparticles using aqueous extract of \u003cem\u003eHedysarum alpinum\u003c/em\u003e plant used for calorimetrically detection of Hg\u003csup\u003e2+\u003c/sup\u003e. Zhou et al (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) reported silver nanoparticles co-functionalized with 4-mercapto benzoic acid and melamine as a probe for colorimetric detection of Mn\u003csup\u003e2+\u003c/sup\u003e. Green synthesis of L-tyrosine-stabilized silver nanoparticles under ambient sunlight irradiation for colorimetric detection of heavy metal ions (Hg\u003csup\u003e2+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e) as reported. Recently, Wang et al (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) reported that the carrageenan stabilized silver nanoparticles for effective detection of Cu\u003csup\u003e2+\u003c/sup\u003e and S\u003csup\u003e2\u0026minus;\u003c/sup\u003e ions in aqueous solution. In the present investigation, sodium citrate stabilized silver nanoparticles for sensing/detection of various metal ions (Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e) in aqueous solution using UV-vis spectroscopic technique. Further, metal ion interactions with silver nanoparticles were studied using FT-IR spectroscopy.\u003c/p\u003e"},{"header":"Materials And Methods","content":"\u003cp\u003e\u003cstrong\u003eSynthesis of Ag NPs \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSynthesis of silver nanoparticles using sodium citrate as reducing agents was done according to the literature procedure (Kamat et al. 1998) with slight modification. Briefly, 100 mL of AgNO\u003csub\u003e3\u003c/sub\u003e (10 mg) aqueous solution and heated until it begins to boil. 2 mL of sodium citrate (30 mg) solution was added, and heating continued till the color was yellowish brown color which indicates formation of Ag NPs nanoparticles. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCharacterization of Ag NPs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe formation of Ag NPs was monitored using a UV-visible spectrophotometer (Shimadzu UV-1800) in the range of 200-1000 nm. Particle\u0026rsquo;s size and shape of the citrate reduced Ag NPs were determined using FE- SEM (Supra 55-Carl Zeiss, Germany) and TEM (FEI Technai, instruments) operating at an accelerating voltage of 120kVA.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSensing/ detection of Metal ions \u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe spectroscopic detection of aqueous heavy metal ions was studied using Ag NPs solution at room temperature. To demonstrate the effect of heavy metal ions on Ag NPs, \u003cbr\u003e 1 mL concentrations of heavy metal ions were added one at a time to 500 \u0026micro;L of Ag NPs and the resulting mixture was then allowed to stand for 10 min at room temperature, during which the colour change depending upon the metal ions. The intensity of this colour gradually increased with the increase of heavy metal ion concentration. UV-Vis absorption spectra from all samples were analyzed carefully to correlate the changes of SPR spectra with respect to concentrations of Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e using UV-visible Spectrophotometer (UV 1800) Shimadzu, Japan. Spectra of the adsorbents before and after Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+ \u003c/sup\u003ebinding were recorded with a FT-IR analysis using a PerkinElmer 1600 infra-red spectrometer with a pellet of powered potassium bromide.\u003c/p\u003e"},{"header":"Results And Discussion","content":"\u003cp\u003eAddition of sodium citrate into the beakers containing aqueous solution of AgNO\u003csub\u003e3\u003c/sub\u003e led to the change in the colour of the solution from colorless to brownish yellow within reaction duration due to excitation of surface plasmon resonance (SPR) vibrations in Ag NPs. The colour of the solution is brownish yellow indicating formation of Ag NPs (Figure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e inset). Ag NPs synthesized using sodium citrate were analyzed by UV spectra of Plasmon resonance band observed at 410 nm (Figure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) (Zia et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). SEM micrograph shows the morphology of the Ag NPs which are spherical and well dispersed (Figure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). TEM results showed well dispersed spherical particles with a size of ca. 23.4 nm in diameter (Figure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb\u0026amp;c).\u003c/p\u003e \u003cp\u003eThe spectroscopic detection of metal ions Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e at the fixed concentrations of 500 \u0026micro;L of a 1 \u0026times; 10\u003csup\u003e\u0026minus;5\u003c/sup\u003e M were added to Ag NPs solution and the corresponding changes of the absorption coefficient were observed from brownish yellow to light blue color (Figure \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea-h) (Kamel et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Boruah et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In presence of heavy metal ions with Ag NPs, a new peak at around 925, 898, 643, 665, 688, and 838 nm of Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e appeared in addition to the peak found at 410 nm of Ag NPs (Figure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea-e, h). Further, the addition of Ni\u003csup\u003e2+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e metal ion solution with Ag NPs increased the SPR band from 410 nm to 436 and 462 nm respectively (Figure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef, \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg). Even though Pb interacts with Ag NPs surface plasmon resonance (SPR) peak at 436 near to Ag NPs similar reported (Anambiga et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). Ag NPs undergo agglomeration upon exposure to increasing concentrations of heavy metal ions. Color change occurred due to the aggregation between Ag NPs with metal ions (Xiong and Li \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). The ability of silver nanoparticles to form agglomeration caused the SPR to broaden and shift to longer wavelengths (Sulistiawaty et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). In particular Hg\u003csup\u003e2+\u003c/sup\u003e ions interact with Ag NPs precipitation and the SPR band absorbance at 410 nm. Besides, the colour of the Ag NPs became transparent immediately when added to the Hg\u003csup\u003e2+\u003c/sup\u003e ions solution. In contrast, increasing the concentration of Ag NPs to Hg\u003csup\u003e2+\u003c/sup\u003e solution changed colour into yellow precipitate (Uddin et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Similarly, the Ag NPs were interacting with Hg\u003csup\u003e2+\u003c/sup\u003e and Mn\u003csup\u003e2+\u003c/sup\u003e ions, a blue shift in the SPR band was observed by UV-vis spectroscopy detection. Hg\u003csup\u003e2+\u003c/sup\u003e ions were added to the Ag NPs solution and the colour of the solution changed from yellow to colorless. This interaction is due to oxidation of Ag\u003csup\u003e0\u003c/sup\u003e to Ag\u003csup\u003e+\u003c/sup\u003e during the process of reduction of Hg\u003csup\u003e2+\u003c/sup\u003e ions (Annadhasan et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2014\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFT-IR measurements were carried out to identify the interaction of Ag NPs and metal ions. FT-IR spectra of Ag NPs functional groups 2924, 2856, 2338, 1714, 1638 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e respectively, CdSO\u003csub\u003e4\u003c/sub\u003e and CdSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs show several significant absorption peaks such as 2956, 2128, 1638 and 2327, 1639 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e disappears in CdSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs. The peaks 2338 shifted into 2339 (Figure. 5a-c). FT-IR spectra of Ag NPs, CuSO\u003csub\u003e4\u003c/sub\u003e, CuSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs, absorption peaks at 2924, 2855 and 2448, 2092 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e were disappeared in CuSO\u003csub\u003e4\u003c/sub\u003e+AgNPs and new peaks at 2956 shifted into 2969, 1737 shifted into 1738 (Figure \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Similar study of FeO nanoparticles observation confirms a successful modification of the surface of the nanoparticles with Cd and Cu ions (Klekotka et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). There were significant changes on the FT-IR spectrum of Ag NPs after interaction with FeSO\u003csub\u003e4\u003c/sub\u003e ions. The Ag NPs and FeSO\u003csub\u003e4\u003c/sub\u003e absorption peaks at 2956, 2855, 2338, 2128, 1714, 2326, 1642 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e were appearing but disappeared in the FeSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs whereas new peaks appeared at 2926, besides the peak at 2924 shifted into 2916 (Figure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The FT-IR spectrum of Ag NPs, HgCl\u003csub\u003e2\u003c/sub\u003e and HgCl\u003csub\u003e2\u003c/sub\u003e + Ag NPs was represented in Figure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The presence of a sharp absorption band at 2956, 2125, 2188 and 2097 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e in Ag NPs and HgCl\u003csub\u003e2\u003c/sub\u003e. HgCl\u003csub\u003e2\u003c/sub\u003e + Ag NPs new peak 2855, 1737 shifted into 2853, 1738. FT-IR spectral data revealed absorption peaks at 2956, 2338, 2128, 1737, 1714 and 2199 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e were present in Ag NPs and MnCl\u003csub\u003e2\u003c/sub\u003e. Whereas the peak at 2855, 1638 shifted into 2853, 1640 present in MnCl\u003csub\u003e2\u003c/sub\u003e + Ag NPs (Figure. 9). FT-IR spectra of Ag NPs, NiSO\u003csub\u003e4\u003c/sub\u003e and NiSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs based on the functional groups 2924, 2856, 2338, 1714, 1638 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e and 3293, 2332, 1638 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e peaks were present and 2332, 2128, 1714, 1638 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e peaks were disappeared in Ag NPs and NiSO\u003csub\u003e4\u003c/sub\u003e. While 3459, 3016, 2132 and 1434 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e peaks were present in NiSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs. 2128 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e line is observed in p-polarization and is absent in s-polarization shifted into 2132 \u0026ndash;C\u0026equiv;C\u0026ndash; stretch and the presence of a broad absorption band at 3392 and 3459cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e can be attributed the \u0026ndash;OH stretching presented due to the adsorption of water in air when FT-IR sample disks were prepared in an open air (Figure \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e). FT-IR analysis on Ag NPs, Pb(NO)\u003csub\u003e3\u003c/sub\u003e and Pb(NO)\u003csub\u003e3\u003c/sub\u003e + Ag NPs reveals that the peaks at 2956, 2924, 2855, 2338, 2398 and 1768 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e were present [Ag NPs, Pb(NO)\u003csub\u003e3\u003c/sub\u003e] but disappear in the Pb(NO)\u003csub\u003e3\u003c/sub\u003e + Ag NPs. The broad absorption peak 2128, 1638 shifted into 2125 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, 1654 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e confirms the formation of Pb-Ag NPs complex (Figure \u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e) (Kamel et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Anambiga et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). FT-IR absorption peaks at 2128, 1714 and 1616 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e were present in Ag NPs and ZnSO\u003csub\u003e4\u003c/sub\u003e whereas disappear in ZnSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs. A ZnSO\u003csub\u003e4\u003c/sub\u003e + Ag NPs new peak appears at 2871 and 1980. The peaks were 2338, 2077 and 1737 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e shifted into 2340, 2079 and 1741 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e (Figure \u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e). Based on the present study and previous literature report, the conceivable predicted mechanisms of Ag NPs interaction with metal ions which is shown in Figure \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e13\u003c/span\u003e.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eHerein, we report the Ag NPs as a cost-effective sensor for the detection of toxic metal ions in water. The spectroscopic tool such as UV-vis spectroscopy was used for detection and of various heavy metal ions (Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e) in aqueous medium with the detection limits of nM concentrations and easily visualized with the naked eye by the rapid color change from a brownish yellow to light blue color observed. From the noteworthy mention that spectral changes and fast colour changes of ions with the addition of nanoparticles, we conclude that ions can potentially become a selective detection for the qualitative detection of the used nanoparticles and could be used as a visual marker.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors (KG) thankful to the DST‐FIST (SR/FST/ESI‐145/2016) for infrastructure support to carry out this work and management of Sathyabama Institute of Science and Technology, Chennai for their constant support in research activities.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate \u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate \u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish \u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors contribution \u003c/strong\u003eS. Tamilselvan: Methodology, Investigation, Validation; R.M. Soniya: Investigation, Formal analysis, Data curation; R. Vasantharaja: Formal analysis, Review \u0026amp; editing; M. Kannan: Validation, Resources, Writing - review \u0026amp; editing; S. Supriya: Formal analysis, Resources; K. Govindaraju: Conceptualization, Project administration, Writing - review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding \u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests \u003c/strong\u003eThe authors declare no competing interests. \u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials \u003c/strong\u003eThe datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnambiga IV, Suganthan V, Raj NAN, Kumar TSS (2013) Colorimetric detection of lead ions using glutathione stabilized silver nanoparticles. 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Water Air Soil Poll 230:164\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":"Silver nanoparticles, Heavy metal ions, UV-vis spectroscopy, FT-IR spectroscopy, sensing ","lastPublishedDoi":"10.21203/rs.3.rs-1246304/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-1246304/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAnthropogenic releases from different outlets of industry, municipal sewage and the road traffic can give rise to higher concentrations of the heavy metals in the food commodities which imposes a threat to human health and environment. A simple silver nanoparticle (Ag NPs) used for the sensing of heavy metal ions, Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e, Ni\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+ \u003c/sup\u003ein aqueous solution is described by qualitative and quantitatively using spectroscopic tool. FE-SEM and TEM images confirmed that the particles are spherical in shape with an average diameter of 23.4 nm. In presence of heavy metal ions with Ag NPs, a new peak at around 925, 898, 643, 665, 688, and 838 nm of Cd\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, Fe\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, Mn\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e appeared in addition to the peak found at 410 nm of Ag NPs. Further, the addition of Ni\u003csup\u003e2+\u003c/sup\u003e and Pb\u003csup\u003e2+\u003c/sup\u003e metal ion solution with Ag NPs increased the SPR band from 410 nm to 436 and 462 nm respectively. Citrate functionalized Ag NPs are aggregated in solution in the presence of divalent metal ions by an ions-template chelating process and easily measurable change in the UV-vis absorption spectrum of the particles. Further, studies also confirmed the interaction of Ag NPs with metal ions using FT-IR spectroscopy. The proposed method was found to be useful for simple UV-vis spectroscopic sensing of metal ions in aqueous solutions and real contaminated samples.\u0026nbsp;\u003c/p\u003e","manuscriptTitle":"Spectroscopic sensing of eight metal ions in aqueous solutions using silver nanoparticles","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2022-02-01 18:21:28","doi":"10.21203/rs.3.rs-1246304/v1","editorialEvents":[{"type":"communityComments","content":1}],"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":"affd8b01-56d9-4a0f-ba17-45f16a8ad82c","owner":[],"postedDate":"February 1st, 2022","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2022-03-18T06:35:24+00:00","versionOfRecord":[],"versionCreatedAt":"2022-02-01 18:21:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-1246304","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-1246304","identity":"rs-1246304","version":["v1"]},"buildId":"ehx78VzkSd0WSzXnipQa-","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}