Green synthesis of carbon nanodots (CNDs) moderated by flavonoid extracts from Moringa oleifera leaves and co-doped sulfur/nitrogen (NS – CNDs – Fla) and their potential for heavy metals sensing application

Green synthesis of carbon nanodots (CNDs) moderated by flavonoid extracts from Moringa oleifera leaves and co-doped sulfur/nitrogen (NS – CNDs – Fla) and their potential for heavy metals sensing application | 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 Green synthesis of carbon nanodots (CNDs) moderated by flavonoid extracts from Moringa oleifera leaves and co-doped sulfur/nitrogen (NS – CNDs – Fla) and their potential for heavy metals sensing application Sriati Wahyudi, Ivan Rizoputra, Camellia Panatarani, Ferry Faizal, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4747067/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 25 Sep, 2024 Read the published version in Journal of Fluorescence → Version 1 posted 8 You are reading this latest preprint version Abstract Moringa oleifera is the “ magic tree ” which contains many bioactive compounds such as flavonoids, especially in its leaves. Natural flavonoids and glycosides with specific components of structure can bind to metal ions. The content of bioactive compounds such as total flavonoids found in Moringa oleifera leaves is 172.10 mg/g. In addition, carbon (47.34%), nitrogen (51.67%), and sulfur (0.99%) are also the main composition. Then, the carbon nanodots (CNDs) synthesized in this research were moderated by flavonoid extract from Moringa oleifera using the hydrothermal method. The technique is easy, ecologically friendly, and requires neither specialized device or reagents. In practice, the CNDs produced are almost circular, with an average diameter of 3.49 nm. Furthermore, we enhanced synthesis CNDs - Fla with heteroatoms of nitrogen (N) and sulfur (S). They display a broad excitation-emission spectrum, excitation-dependent emission, and extraordinary fluorescence. Therefore, the synthesis of CNDs using flavonoids from Moringa oleifera as precursors would be a great potential candidate for the development of novel types of heavy metals sensing. Carbon Nano Dots (CNDs) Moringa oleifera leave Heteroatoms Fluorescence Detection of heavy metals Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Carbon nano dots (CNDs) are fluorescent carbon nanoparticles, the most recent addition to the nanocarbon family, which are fast developing as promising candidates and has continued to garner interest since discovered in 2004. CNDs are amorphous, belonging to the zero-dimensional (0D) carbon nanomaterial, and their mean diameter is less than 10 nanometers [1], [2]. The most popular methods for pleasantly synthesis CNDs include electrochemical oxidation, hydrothermal treatment, laser ablation, arc- discharge, microwave, and ultrasonic synthesis [3], [4]. Hydrothermal is the most often employed due to the easiest carbonation synthesis of CNDs applications, low-toxicity, inexpensive, and homogenous sizes of particles gets accomplished [5], [6]. Generally, CNDs have fascinating and distinctive properties, including great water solubility, fluorescence, simple functionalization, great photobleaching, non-toxic characteristics [7], edge effects leading to the sensors [8], [9], reduction of CO 2 [10] and supercapacitors [11]. CNDs present a compelling substitute for photocatalysts because of their favorable redox properties, strong photo-responsiveness (bright fluorescence and extensive absorbance), and biocompatibility [12], [13]. Furthermore, utilizing green synthesis makes CND produce easier by reducing the use of hazardous and carcinogenic solvents. Natural and environmentally friendly carbon precursors, including acids made of organic matter [14], fruits juice [15], and waste of foods such as peels of banana [6] and watermelon [10], have already been utilized. Green synthesis from natural products provides considerable benefits in terms of sustainable, renewable, environmentally friendly, and affordable raw materials that utilizes parts of plants, such as leaves [16]–[18], fruits [19], peels [6], [10], flowers [20], or microorganisms [21]. Therefore, using a green method and carefully selecting precursors with significant physical and biological value increases the probability of successfully fabricating CNDs. Moringa oleifera leaves is one of the precursors can be a suitable natural resource to develop CNDs. In addition to satisfying the urgent requirement for the large-scale manufacture of CNDs, the utilization of plant parts as green materials encourages the development of sustainable applications. Plant components lack the requirement for separately chemical for doping, surface passivation, or post modification since they include an abundance of proteins, carbohydrates, amino compounds, and other macromolecules which are sufficient for CND surface functioning [22]. Even though the field of plant component derived CNDs is abundant with prospects, there are still a lot of challenges to overcome in order fully explore the incredible power of these compounds. Large precursor compositions can lead to variability in CNDs generated from plant parts, therefore separation and purification need to be thoroughly investigated [23]. To achieve for development in the space, relationships between physicals (e.g., size, shape) and chemicals (e.g., carbon, nitrogen, flavonoid), the features of CNDs, including their resulting optical properties (for example, peak excitation/emission wavelength), and functionality against diverse applications should be proved. Thus, the types of natural product, synthesis processes, and post-treatment procedures all affect the characteristics of CNDs made utilizing natural product as precursors. Finally, although the produced CNDs have a wide range of applications, including selective sensing metal ions [24], few actual applications and a thorough mechanism are described [9]. Subsequently is still plenty of opportunity to perform research on this emerging field to investigate more renewable green carbon precursors, create more heteroatom-doped CNDs with much higher quality, and broaden the CNDs applications. Specifically, CNDs can help address some of the contemporary issues that are becoming a growing concern to humans, such as protecting the environment and disease diagnosis [25]. Moringa oleifera is also known as the " miracle tree " or the " tree of life " due to every part of the plant is advantageous for both people and animals. Its leaves, roots, bark, seeds, and fruit can be utilized for a variety of purposes, such as food, medicinal, and purifying of water. This plant is native to northern India and can also be found in other tropical and subtropical regions [26], [27], which involves Indonesia. Moringa oleifera leaves contain a wide range of bioactive substances, such as potassium, calcium, phosphorus, iron, protein, vitamins A, C, and E, β-carotene, carotenoids, and polyphenols [28], [29], oxidase, catalase, alkaloids, glucosinolates, isothiocyanates, tannins, and saponins [30]–[32], each share favorable effects on humans [33]. An abundance of bioactive substances can have medicinal properties, such as hypotension, anticancer, antioxidant, anti-inflammatory antibiotics, skin infections, anemia, wounds, scratches, irritation, a sign of aging, malaria, and fever caused by typhoid, diarrhea, intestinal obstruction, hepatoprotective colitis, hypocholesterolemia, and hypoglycemic activity [34], [35]. The polyphenol concentration of Moringa oleifera varies depending on the portion of the plant. Dried Moringa oleifera leaves are high in polyphenols, with flavonoids and phenolic acids being the primary components. Flavonoids effectively reduce oxygen harmful free radicals from the entire body, hence improving cardiovascular and cerebrovascular illnesses. Furthermore, metal chelation is widely considered as another mechanism of flavonoid antioxidant activity. In several systems of biology that contain a variety of biomolecules and are linked to vital physiological processes in humans, metal ions are a significant component. The antioxidant characteristics and biological effects of quercetin can also be altered by its interaction with metal ions. Due to a metal ion can function as a free radical acceptor, ligands that are coordinated with or combined with them can have their biological activity increased. It should be a desirable alternative to provide an abundant feedstock for material science research. Therefore, extract flavonoid from Moringa oleifera leave can be an alternative green synthesis of CNDs from natural product. Herein, Moringa oleifera was transformed into fluorescent carbon nanodots and sulfur/nitrogen co-doped CNDs using a one-pot green hydrothermal method. Simple post-treatment way of centrifugated and filtering with 0.22 µm micro syringe was devised to reduce undesired outcomes in CNDs products. Determine of flavonoid total of Moringa oleifera leave applied before synthesis CNDs. Further, characterization such as UV-visible spectroscopy, photoluminescence (PL) spectroscopy, Energy Dispersive X-Ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and high resolution-transmission electron microscopy (HR-TEM) were employed to analyze of the as-prepared CNDs. Based on the characterization results, a credible mechanism for heavy metal-induced PL quenching of CNDs was proposed ( Figure 1 ). Toward our understanding, this is the first work to investigation into the synthesis of CNDs from extract flavonoid Moringa oleifera leave, and conjugation of the CNDs with nitrogen/sulfur (NS – CNDs - Fla). Overall, the synthesis approach is fast, consistent, and measurable, reaching in the fabrication of CNDs that have outstanding photoluminescence characteristics and non-toxicity, establishing CNDs as an intriguing potential substitute as well as the corresponding applications. 2. Materials and methods 2.1. Materials Fresh Moringa oleifera leaves were collected from trees growing in local area of Probolinggo, Indonesia. The experiment was conducted using deionized water (DI). Thiourea were purchased from Sigma Aldrich as nitrogen (N) and sulfur (S) sources. Furthermore, the chemicals employed were anhydrous ethanol, Pb (NO 3 ) 2 (99%), CuSO 4 .5H 2 O (99%), and HgCl 2 (98%) were purchased from chemist stores in local market. The chemical compounds were analytical grade and utilized without further purification. 2.2. Methods 2.2.1. Extractions of flavonoid from Moringa oleifera Flavonoid extraction was prepared using a described approach with some modifications [36]. Moringa oleifera leaves were smashed manually after being dried at room temperature. The sample was extracted using the maceration method with 70% ethanol at room temperature for a duration of three days with occasional shaking. The extract underwent filtration, and the resultant liquid flavonoid extract was subsequently evaporated using a rotary evaporator. The resulting extracts were freeze-dried and then utilized for further investigation. 2.2.2. The determination of the total flavonoid content from Moringa oleifera leaves The aluminum chloride colorimetric method with modifications has been employed for determining total flavonoids [37]. Quercetin (10 mg) was dissolved in ethanol (96%) and diluted to 100, 75, 50 and 25 μg/mL. Then 0.5 mL of each solution was mixed with 1.5 mL of 96% ethanol, 0.1 mL of 10% aluminum chloride, 0.1 mL of 1 M sodium acetate and 2.8 mL of DI-water. The mixture was incubated at room temperature for 30 minutes with intermittent shaking. Furthermore, absorbance measurements were carried out with maximum absorption (415 nm). The total flavonoids were determined as mean ± SD (n = 3) and then expressed as quercetin equivalent weight (QE) in 100 mg of extract from dry powder. 2.2.3. Synthesis of CNDs and NS-CNDs-Fla using hydrothermal method Carbon nanodots (CNDs) of Moringa oleifera were synthesized by hydrothermal method. As received Moringa oleifera leaves were dried at room temperature. Before the synthesis of CNDs, dehydrated Moringa oleifera leaves were ground to powder. Ground greenish Moringa oleifera powder then extracted with maceration method and following by freeze dry to obtain dried flavonoid extract of Moringa oleifera leaves. Flavonoid dried extract (0.5 g) was dissolved in 50 mL of deionized water followed by the stirrer for 15 minutes, then it was transferred to the hydrothermal autoclave and was heated at a constant temperature of 200 °C for 8 hours. Subsequently, the autoclave was allowed to cool down to room temperature. The suspension was dissolved in anhydrous ethanol and followed by the centrifuged at 10,000 rpm for 15 minutes to remove the large un-dissolved particles. The supernatant was filtered using 0.22 µm micro syringe filter for further purification. The purified CNDs was transferred to the glass vial and stored for further characterization. For NS - CNDs - Fla, 0.5 g flavonoid dried extract and 0.5 g of thiourea dissolved in 50 mL of deionized water followed by the stirring for 15 minutes, then it was transferred to the hydrothermal autoclave and was heated at a constant temperature of 200 °C for 8 hours. After reaction, the mixture was cooled down, and was then centrifuged at 10,000 rpm for 15 minutes to get the supernatants, which was purified via a 0.22 µm micro syringe filter for further purification. Finally, NS – CNDs – Fla was obtained for further characterization. Figure 2 illustrates the synthesis methods of two CNDs. The hydrothermal method has proven to be straightforward and effective, and it has been the most often used strategy for CND development [38]. All the preparation procedures were consistent with the previously mentioned the strategy. 2.2.4. Characterizations of CNDs The optical properties of CNDs were studied using the UV-visible spectrophotometer (Shimadzu UV-1800, Duisburg, Germany) and photoluminescence (PL) spectroscopy (FP-6500, JASCO, Japan). The size distribution and morphology of CNDs were characterized by a Thermofisher Scientific Fei Tecnai G2 Supertwin transmission electron microscopy (HR-TEM, ILRC Universitas Indonesia). Fourier transform infrared spectra (FTIR) of CNDs were recorded to identify the functional groups on to the surface of CNDs (PerkinElmer Spectrum 100). The zeta potential measurements were obtained using a Horiba Scientific SZ 100z/Nano Particle Size Analyzer. The elemental composition of CNDs was evaluated by energy-dispersive X-ray spectroscopy (EDS, JEM-2300F, JEOL) at Central Laboratory, Universitas Padjadjaran, Indonesia. 2.2.5. Procedure for metal ions sensing The stock solutions of three metal ions (Pb 2+ , Cu 2+ , and Hg 2+ ) were respectively prepared, and were further diluted with deionized water to obtain a final concentration of 1 µM, 10 µM, 50 µM, 100 µM, 500 µM, and 1000 µM. Each of the metal ion solution was mixed with CNDs (3.0 mL), stirred, and incubated for 15 min at room temperature. The fluorescence spectra of the suspensions were then measured using the fluorescence spectrophotometer to determine the fluorescence intensities. For CNDs – Fla, fluorescence was excited at 365 nm and emitted at 440 nm. The fluorescence excitation and emission wavelengths for NS - CNDs - Fla were 340 nm and 435 nm, respectively. The intensity of fluorescence emissions at these wavelengths for each sample has been determined. 3. Results and discussions 3.1. Flavonoid and EDS studies Total flavonoids represent the total amount of flavonoid compounds from plant extract such as moringa oleifera leaves. As explained, Moringa oleifera extract was high in phenolic components, such as quercetin, kaempferol, and rutin, flavonoid compounds [39], [40]. In this study the total flavonoid test results were 172.10 mg QE/g sample. Determination of total flavonoids using gallic acid and quercetin standards where the calibration curve equation obtained respectively was y = 0.005x + 0.161 (R 2 = 0.992). This confirms that Moringa leaves are rich in flavonoid content. The EDS spectrums are graphs of the X-rays received at each energy level indicated. They show peaks that correlate to the different levels of energy received from X-rays. The EDS's abscissa axis represents the ionization energy pathway, whilst the ordinate axis represents the counts per second of CND intensity [41]. Each peak is associated with a certain element, such as carbon (C), nitrogen (N), or sulfur (S). Figure 3 represents a study of the compositional constituents in CNDs extract flavonoid of Moringa oleifera leaves, the picture reveals a carbon content of 47.343%, nitrogen of 51.670%, and sulfur of 0.986%. A greater peak in the spectrum indicates the most prominent element in the sample. The presence of these elements in the sample confirms that synthesized sample is comprised of CNDs. 3.2. HR-TEM and FTIR studies As explained previously, CNDs are a novel type of carbon nanomaterials with a diameter of less than 10 nm. In this work, the hydrothermal process was carried out at 200 0 C for 8 h. Figure 4 shows an HR-TEM image of as-prepared CNDs. CNDs are revealed to be monodispersed particles in a spherical form with a diameter of less than 10 nm. In addition, CNDs have crystalline or polymeric structures as indicated by graphite lattice d-spacing of 0.22 nm in the insert of Figure 4(a). Furthermore, Figure 4(b) depicts the corresponding size distribution histogram, which shows that the overall distribution of particle sizes range between 2.25 nm and 4.75 nm, with an average size of 3.49 nm. To confirm the presence of various carbon-oxygen functional groups on Moringa oleifera CNDs, we performed FTIR spectroscopy, as depicted in Figure 5 . Both samples have similar IR bands in the range of 600–1500 cm −1 , which are caused by C–O, C–S, and C–H stretching vibrations [42]. The FTIR spectrum corresponds to functional groups, such as vibration bands at 3321 cm -1 and 1031 cm -1 respectively representing hydroxyl groups (-OH) and C-O-C according to the initial material. The relative intensity of the two vibration bands is very strong, indicating that the group is related to flavonoids in the CNDs-Fla structure. Apart from that, the vibration bands –CH (2945 cm –1 , 2833 cm –1 , and 1449 cm –1 ), C=C (1660 cm –1 ) are also very clearly visible and unique vibration bands such as =CH (663.40 cm –1 ) in the spectrum of CNDs confirmed the presence of flavonoid-related functional groups [43]. Furthermore, a new band at C–S (1110 cm −1 ) and two other bands at 1652 cm −1 and 1450 cm −1 , represent the typical stretching modes of C=N and C–N. This indicates the successful synthesis of N and S co-doped CNDs. 3.5. Zeta Potential of CNDs The Zeta potential is an essential parameter used to determine the surface charge of CNDs in a aqueous solution. The Zeta potential indicates the total electric charge on the surface of the CNDs and NS - CNDs - Fla which aim to evaluate the stability of carbon nano dots. Herein, the Zeta potential of CNDs - Fla is −10.9 mV indicates that the CNDs have a negative surface charge. While the zeta potential of NS - CNDs - Fla −11.6 mV, showing the enhanced stability with addition of nitrogen and sulfur in CNDs as given in Figure 6 . This negative charge is caused by the presence of functional groups or chemical species on the CNDs' surfaces that ionize in solution, resulting in an accumulation of negatively charged particles around the CNDs. Carbon nanodots (CNDs) have a negative charge due to the presence of surface functional groups, which results in negative zeta potential values for both zeta potential. The negative sign of the zeta potential reveals negatively charged residues, which are required for good dispersion stability of CNDs [44]. 3.6. UV-Visible and PL intensity of CNDs The optical properties were studied as revealed by the characteristic UV-Vis spectra of the CNDs. In Figure 7 show the UV–visible absorption spectra of developed CNDs - Fla and NS - CNDs - Fla, respectively. UV–visible spectra of prepared CNDs - Fla significant peaks at about 280 nm should be ascribed to π–π* transition due to sp 2 aromatic π-domains of C = C bonds within the CNDs, this is corresponding to some other earlier findings. [45], [46]. Similarly, the absorption spectra of NS - CNDs - Fla show more pronounced peaks around 265 nm, which correspond to the π-π* transition caused by the presence of sp2 aromatic π-domains. Heteroatom doping in CND structures alters their electrical characteristics via modifying the band-gap and optical absorbance [47]. Therefore, the prepared NS - CNDs - Fla exhibited increased optical absorption, as illustrated in Figure 7 (line orange). Furthermore, as shown in Figure 8 , the fluorescence spectra illustrate the behavior of the CNDs and providing further details on their optical properties. In Figure 8 (a) and 8 (c) displays the photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the synthesized CNDs - Fla and NS - CNDs - Fla. In this case, it was observed that the CNDs - Fla and NS - CNDs -Fla exhibited strong blue luminescence at a wavelength of 440 nm and 436 nm, respectively. On the other hand, the PLE spectrum depicts the absorbed light, demonstrating the energy levels at which CNDs was able to absorb photons and transition to greater energy states. Then, the CNDs - Fla sample exhibits an absorption peak at 365 nm, leading to the emission of light at 440 nm, while NS - CNDs - Fla at the excitation 340 nm with the emission of light at 436 nm. In Figure 8 (b) and 8 (d) show the excitation-dependent photoluminescence spectra of a CNDs - Fla and NS - CNDs - Fla samples, together with the associated colors recognized under various excitation settings. In this research provides a thorough grasp of how CNDs behave to different excitation wavelengths. 3.7. Selectivity and sensitivity of metal ions detection Selectivity and sensitivity are essential factor in designing an effective sensors for detection of heavy metals in aqueous solutions. Herein, we investigated by introducing different metal ions into CNDs - Fla and NS - CNDs - Fla, such as Cu 2+ , Hg 2+ , dan Pb 2+ . Variations concentration of heavy metals solution was added to the CNDs - Fla and NS - CNDs - Fla. The PL spectra were obtained at an excitation wavelength of 365 nm and 340 nm for the CNDs - Fla and NS - CNDs - Fla, respectively. Figure 9 depicts the ratio of the intensity of PL when various concentration of heavy metals was added to CNDs - Fla (I) to the intensity of Pl in a blank sample (I 0 ). It was observed that adding heavy metals significantly reduced the intensity ratio. As a result, CNDs - Fla demonstrated high selectivity for Cu 2+ . Then, the sensitivity toward heavy metals was analyzed by adding different concentrations (0–1000 µM) of heavy metals to CNDs - Fla and recording the PL responses at 365 nm excitation wavelength. The intensity of PL was found to decrease as heavy metal ions concentrations increased. It indicates that CNDs - Fla were also sensitive to Cu 2+ . In our current study, we hypothesize on the selective binding ability of CND-Fla due to the creation of Cu 2+ specific flavonoid motifs on its edges during the production of CNDs from flavonoid extracts. Furthermore, flavonoids and polyphenolic chemicals including gallic acid, catechol, pyrogallol, and their derivatives have been shown to form complexes with heavy and transition metal cations [48]. Similarly, selectivity and sensitivity experiments for the various heavy metals were conducted on produced NS - CNDs - Fla. In Figure 10 , Cu 2+ ions demonstrated considerable PL quenching of NS- CNDs - Fla as compared to the other heavy metals. NS - CNDs - Fla is composed primarily of N-related and O-related functional groups that act as electron donors and have a high binding affinity for Cu 2+ ions as compared to other heavy metals [49]. 4. Conclusions CNDs - Fla and NS-CNDs - Fla were successfully synthesized from Moringa oleifera leaves using hydrothermal, as confirmed by EDS, FTIR, and HR-TEM measurements. The average diameter of CNDs is 3.49 nm and shows graphite lattice with d-spacing of 0.22 nm. The synthesized CNDs Fla and NS-CNDs Fla exhibited strong photostability, high fluorescence, and great water solubility. Because of heteroatom doping, which offers large number of active sites and the synergistic impact between each element, the NS - CNDs - Fla displayed higher PL intensity and photostability than the CNDs - Fla. This resulted in radiative recombination of the trapped electron-hole pairs. The elimination of additional surface functional groups that alter the PL property causes the non-radiative self-trapped electrons on the surface of CNDs to disappear as surface passivation rises. Therefore, compared to CNDs - Fla, the NS - CNDs - Fla exhibits excitation-independent PL emission due to its higher surface passivation from heteroatom doping. The addition of heavy metals in CNDs – Fla and NS – CNDs - Fla exhibits the significant result i.e., “Turn-off” intensity of PL based on mechanisms dynamic quenching. Therefore, flavonoid compound from Moringa oleifera should be great a potential candidate good precursor for sensing and other application based on carbon nano dots (CNDs). Declarations Author Contribution Sriati Wahyudi : Investigation, writing - original draft preparation, data curation, formal analysis, and visualization.Ivan Rizoputra : Visualization. Camellia Panatarani : Data analysisFerry Faizal : Review and editing of the manuscript. Ayi Bahtiar : Conceptualization, methodology, supervision, data analysis, and review. All authors reviewed the manuscript. Funding: This research was funded by the Ministry of Research, Technology and Higher Education Indonesia, through research scheme Doctoral Dissertation Program (PDD-DIKTI), contract number 3841/UN6.3.1/PT.00/2024 dated on June 13, 2024. Institutional Review Board Statement: Not applicable Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Acknowledgments: This research project is supported Functional Nano Powder University Center of Excellence (FiNder U-CoE) is a Research Centre at Universitas Padjadajaran. References S. Sharma, A. Umar, S. Sood, S. K. Mehta, and S. K. Kansal, “Photoluminescent C-dots: An overview on the recent development in the synthesis, physiochemical properties and potential applications,” J. Alloys Compd. , vol. 748, pp. 818–853, 2018, doi: 10.1016/j.jallcom.2018.03.001. I. Y. Goryacheva, A. V. Sapelkin, and G. B. Sukhorukov, “Carbon nanodots: Mechanisms of photoluminescence and principles of application,” TrAC - Trends Anal. Chem. , vol. 90, pp. 27–37, 2017, doi: 10.1016/j.trac.2017.02.012. Y. Wang, J. Sun, B. He, and M. Feng, “Synthesis and modification of biomass derived carbon dots in ionic liquids and their application: A mini review,” Green Chem. Eng. , vol. 1, no. 2, pp. 94–108, 2020, doi: 10.1016/j.gce.2020.09.010. N. Ullal, K. Muthamma, and D. Sunil, “Carbon dots from eco-friendly precursors for optical sensing application: an up-to-date review,” Chemical Papers . Springer, 2022. doi: 10.1007/s11696-022-02353-3. R. Khan, A. Qureshi, M. Azhar, Z. U. Hassan, S. Gul, and S. Ahmad, “Recent Progress of Fluorescent Carbon Dots and Graphene Quantum Dots for Biosensors: Synthesis of Solution Methods and their Medical Applications,” J. Fluoresc. , 2024, doi: 10.1007/s10895-024-03809-3. R. Atchudan, T. N. Jebakumar Immanuel Edison, M. Shanmugam, S. Perumal, T. Somanathan, and Y. R. Lee, “Sustainable synthesis of carbon quantum dots from banana peel waste using hydrothermal process for in vivo bioimaging,” Phys. E Low-Dimensional Syst. Nanostructures , vol. 126, no. April 2020, p. 114417, 2021, doi: 10.1016/j.physe.2020.114417. M. Mondal and S. Pramanik, “A mechanism for excitation-dependent emission from carbon nanodots,” Mater. Lett. X , vol. 18, no. December 2022, p. 100195, 2023, doi: 10.1016/j.mlblux.2023.100195. X. Sun and Y. Lei, “Fluorescent carbon dots and their sensing applications,” TrAC - Trends Anal. Chem. , vol. 89, pp. 163–180, 2017, doi: 10.1016/j.trac.2017.02.001. D. J. Fan, D. L. Kang, P. D. Di Liu, and P. D. S. Zhang, “Modification of Carbon Dots for Metal-Ions Detection,” ChemistrySelect , vol. 8, no. 19, 2023, doi: https://doi.org/10.1002/slct.202300062. W. . Dwandaru, E. K. Sari, W. Widyawidura, and D. S. Khaerudini, “Carbon nanodots from watermelon peel as co2absorbents in biogas,” Vopr. Khimii i Khimicheskoi Tekhnologii , vol. 2021, no. 4, pp. 41–49, 2021, doi: 10.32434/0321-4095-2021-137-4-41-49. S. S. Patil, A. G. Bhosale, S. S. Kundale, T. D. Dongale, and S. A. Vanalakar, “Enhancing capacitance performance of functional group assisted carbon quantum dots derived from turmeric plant waste,” Carbon Trends , vol. 15, no. May, p. 100370, 2024, doi: 10.1016/j.cartre.2024.100370. A. Rehman, A. Daud, and M. F. Warsi, “Nanostructured maghemite and magnetite and their nanocomposites with graphene oxide for photocatalytic degradation of methylene blue,” Mater. Chem. Phys. , vol. 256, no. July, p. 123752, 2020, doi: 10.1016/j.matchemphys.2020.123752. G. S. Das, J. P. Shim, A. Bhatnagar, K. M. Tripathi, and T. Y. Kim, “Biomass-derived Carbon Quantum Dots for Visible-Light-Induced Photocatalysis and Label-Free Detection of Fe(III) and Ascorbic acid,” Sci. Rep. , vol. 9, no. 1, pp. 1–9, 2019, doi: 10.1038/s41598-019-49266-y. S. Yang, K. Wang, X. Wang, and X. Sun, “Organic acid participation strategy for the synthesis of highly fluorescent carbon dots and their application in dual-mode determination of copper ions,” Appl. Surf. Sci. , vol. 505, no. July 2019, p. 144567, 2020, doi: 10.1016/j.apsusc.2019.144567. M. Lu, Y. Duan, Y. Song, J. Tan, and L. Zhou, “Green preparation of versatile nitrogen-doped carbon quantum dots from watermelon juice for cell imaging, detection of Fe3+ ions and cysteine, and optical thermometry,” J. Mol. Liq. , vol. 269, pp. 766–774, 2018, doi: 10.1016/j.molliq.2018.08.101. S. Tang, Y. Liu, H. Opoku, and M. Gregorsson, “Fluorescent carbon dots from birch leaves for sustainable electroluminescent devices,” Green Chem. , vol. 25, no. 23, pp. 9884–9895, 2023, doi: 10.1039/d3gc03827k. K. kanthi Gudimella, G. Gedda, and P. S. Kumar, “Novel synthesis of fluorescent carbon dots from bio-based Carica Papaya Leaves: Optical and structural properties with antioxidant and anti-inflammatory activities,” Environ. Res. , vol. 204, no. PA, p. 111854, 2022, doi: 10.1016/j.envres.2021.111854. Y. Shao, C. Zhu, Z. Fu, and K. Lin, “Green synthesis of multifunctional fluorescent carbon dots from mulberry leaves (Morus alba L.) residues for simultaneous intracellular imaging and drug delivery,” J. Nanoparticle Res. , vol. 22, no. 8, 2020, doi: 10.1007/s11051-020-04917-4. V. N. Mehta, S. Jha, and H. Basu, “One-step hydrothermal approach to fabricate carbon dots from apple juice for imaging of mycobacterium and fungal cells,” Sensors Actuators, B Chem. , vol. 213, pp. 434–443, 2015, doi: 10.1016/j.snb.2015.02.104. O. G. Rojas-Valencia, M. Regules-Carrasco, J. Hernández-Fuentes, C. M. R. S. Germán, M. Estrada-Flores, and E. Villagarcía-Chávez, “Synthesis of blue emissive carbon quantum dots from Hibiscus Sabdariffa flower: Surface functionalization analysis by FT-IR spectroscopy,” Materialia , vol. 19, no. July, p. 101182, 2021, doi: 10.1016/j.mtla.2021.101182. H. Bahrulolum, S. Nooraei, N. Javanshir, and H. Tarrahimofrad, “Green synthesis of metal nanoparticles using microorganisms and their application in the agrifood sector,” J. Nanobiotechnology , vol. 19, no. 1, pp. 1–26, 2021, doi: 10.1186/s12951-021-00834-3. M. Zulfajri, G. Gedda, and C. J. Chang, “Cranberry Beans Derived Carbon Dots as a Potential Fluorescence Sensor for Selective Detection of Fe3+ Ions in Aqueous Solution,” ACS Omega , vol. 4, no. 13, pp. 15382–15392, 2019, doi: 10.1021/acsomega.9b01333. W. Meng, X. Bai, B. Wang, Z. Liu, S. Lu, and B. Yang, “Biomass-Derived Carbon Dots and Their Applications,” Energy Environ. Mater. , vol. 2, no. 3, pp. 172–192, 2019, doi: 10.1002/eem2.12038. S. Wahyudi, J. Abdul Aziz, F. Faizal, and A. Bahtiar, “Improved mercury ions (Hg2+) detection by composite silver nanoparticles (AgNPs) and nitrogen - Sulfur co-doped carbon dots (N, S-CDs),” Results Mater. , vol. 21, no. December 2023, p. 100551, 2024, doi: 10.1016/j.rinma.2024.100551. M. Zulfajri, H. N. Abdelhamid, S. Sudewi, and S. Dayalan, “Plant part-derived carbon dots for biosensing,” Biosensors , 2020, doi: 10.3390/bios10060068. S. V. Patil, B. V. Mohite, K. R. Marathe, N. S. Salunkhe, V. Marathe, and V. S. Patil, “Moringa Tree, Gift of Nature: a Review on Nutritional and Industrial Potential,” Curr. Pharmacol. Reports , vol. 8, no. 4, pp. 262–280, 2022, doi: 10.1007/s40495-022-00288-7. A. Pareek, M. Pant, M. M. Gupta, and P. Kashania, “Moringa oleifera: An Updated Comprehensive Review of Its Pharmacological Activities, Ethnomedicinal, Phytopharmaceutical Formulation, Clinical, Phytochemical, and Toxicological Aspects,” Int. J. Mol. Sci. , vol. 24, no. 3, 2023, doi: 10.3390/ijms24032098. S. Sreelatha and P. R. Padma, “Antioxidant activity and total phenolic content of Moringa oleifera leaves in two stages of maturity,” Plant Foods Hum. Nutr. , vol. 64, no. 4, pp. 303–311, 2009, doi: 10.1007/s11130-009-0141-0. P. P. M. Ferreira, D. F. Farias, J. T. D. A. Oliveira, and A. D. F. Carvalho, “Moringa oleifera : bioactive compounds and nutritional potential,” Rev. Nutr. , vol. 21, no. 4, pp. 431–437, 2008. C. Martin, G. Martin, A. Garcia, T. Fernández, E. Hernández, and y J. Puls, “Potential Applications of Moringa oleifera. A critical review,” Pastos y Forrajes , vol. 36, no. 2, pp. 150–158, 2013. R. K. Saini, I. Sivanesan, and Y. S. Keum, “Phytochemicals of Moringa oleifera: a review of their nutritional, therapeutic and industrial significance,” 3 Biotech , vol. 6, no. 2, pp. 1–14, 2016, doi: 10.1007/s13205-016-0526-3. M. Vergara-Jimenez, M. M. Almatrafi, and M. L. Fernandez, “Bioactive components in Moringa oleifera leaves protect against chronic disease,” Antioxidants , vol. 6, no. 4, pp. 1–13, 2017, doi: 10.3390/antiox6040091. S. J. Stohs and M. J. Hartman, “Review of the safety and efficacy of Moringa oleifera,” Phyther. Res. , vol. 29, no. 6, pp. 796–804, 2015, doi: 10.1002/ptr.5325. H. S. Hamed and Y. S. El-Sayed, “Antioxidant activities of Moringa oleifera leaf extract against pendimethalin-induced oxidative stress and genotoxicity in Nile tilapia, Oreochromis niloticus (L.),” Fish Physiol. Biochem. , vol. 45, no. 1, pp. 71–82, 2019, doi: 10.1007/s10695-018-0535-8. Y. Zhu, Q. Yin, and Y. Yang, “Comprehensive Investigation of Moringa oleifera from Different Regions by Simultaneous,” Molecules , vol. 25, no. 1, p. 676690, 2020. B. Vongsak, P. Sithisarn, S. Mangmool, S. Thongpraditchote, Y. Wongkrajang, and W. Gritsanapan, “Maximizing total phenolics, total flavonoids contents and antioxidant activity of Moringa oleifera leaf extract by the appropriate extraction method,” Ind. Crops Prod. , vol. 44, pp. 566–571, 2013, doi: 10.1016/j.indcrop.2012.09.021. C. C. Chang, M. H. Yang, H. M. Wen, and J. C. Chern, “Estimation of total flavonoid content in propolis by two complementary colometric methods,” J. Food Drug Anal. , vol. 10, no. 3, pp. 178–182, 2002, doi: 10.38212/2224-6614.2748. S. Wahyudi, A. Bahtiar, C. Panatarani, Anas, and Risdiana, “Recent advanced carbon dots derived natural products and aptasensor-based carbon dots for detection of pesticides,” Sens. Bio-Sensing Res. , vol. 41, no. July, p. 100576, 2023, doi: 10.1016/j.sbsr.2023.100576. Y. Y. Wang, C. Peng, and Y. Zhang, “Optimization, identification and bioactivity of flavonoids extracted from Moringa oleifera leaves by deep eutectic solvent,” Food Biosci. , vol. 47, no. March, 2022, doi: 10.1016/j.fbio.2022.101687. P. Wei, Y. Zhang, Y. Y. Wang, and J. F. Dong, “Efficient extraction and excellent activity of flavonoid from Moringa oleifera leaves and its microencapsulation,” Lwt , vol. 184, no. June, 2023, doi: 10.1016/j.lwt.2023.115021. A. Barhoum, M. L. García-Betancourt, H. Rahier, and G. Van Assche, Physicochemical characterization of nanomaterials: Polymorph, composition, wettability, and thermal stability . Elsevier Inc., 2018. doi: 10.1016/B978-0-323-51254-1.00009-9. H. Ding, J. S. Wei, and H. M. Xiong, “Nitrogen and sulfur co-doped carbon dots with strong blue luminescence,” Nanoscale , vol. 6, no. 22, pp. 13817–13823, 2014, doi: 10.1039/c4nr04267k. R. M. Silverstein and F. X. Webster, “Spectrometric Identification Of Organic Compounds 6th Edition,” John Wiley & Sons Ltd , vol. 6. pp. 1–482, 1996. W. Li, S. Wang, and Y. Li, “One-step hydrothermal synthesis of fluorescent nanocrystalline cellulose/carbon dot hydrogels,” Carbohydr. Polym. , vol. 175, pp. 7–17, 2017, doi: 10.1016/j.carbpol.2017.07.062. Z. L. Wu, P. Zhang, M. X. Gao, and C. F. Liu, “One-pot hydrothermal synthesis of highly luminescent nitrogen-doped amphoteric carbon dots for bioimaging from bombyx mori silk – natural proteins,” Mater. Chem. B , vol. 10, no. 207890, p. 4118, 2013, [Online]. Available: https://pubs.rsc.org/en/content/articlelanding/2013/tb/c3tb20418a L. Shi, X. Li, Y. Li, and X. Wen, “Naked oats-derived dual-emission carbon nanodots for ratiometric sensing and cellular imaging,” Sensors Actuators, B Chem. , vol. 210, pp. 533–541, 2015, doi: 10.1016/j.snb.2014.12.097. N. Sohal, B. Maity, and S. Basu, “Recent advances in heteroatom-doped graphene quantum dots for sensing applications,” RSC Adv. , vol. 11, no. 41, pp. 25586–25615, 2021, doi: 10.1039/d1ra04248c. M. McDonald, I. Mila, and A. Scalbert, “Precipitation of metal ions by plant polyphenols: Optimal conditions and origin of precipitation,” J. Agric. Food Chem. , vol. 44, no. 2, pp. 599–606, 1996, doi: 10.1021/jf950459q. J. Lin, X. Huang, E. Kou, and W. Cai, “Carbon dot based sensing platform for real-time imaging Cu2+ distribution in plants and environment,” Biosens. Bioelectron. , vol. 219, no. August 2022, p. 114848, 2023, doi: 10.1016/j.bios.2022.114848. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Published Journal Publication published 25 Sep, 2024 Read the published version in Journal of Fluorescence → Version 1 posted Editorial decision: Revision requested 29 Jul, 2024 Reviews received at journal 28 Jul, 2024 Reviewers agreed at journal 23 Jul, 2024 Reviewers agreed at journal 23 Jul, 2024 Reviewers invited by journal 23 Jul, 2024 Editor assigned by journal 18 Jul, 2024 Submission checks completed at journal 18 Jul, 2024 First submitted to journal 16 Jul, 2024 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-4747067","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":333169817,"identity":"94258f42-ff20-42e7-aea8-769fd86870bb","order_by":0,"name":"Sriati Wahyudi","email":"data:image/png;base64,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","orcid":"","institution":"Universitas Padjadjaran","correspondingAuthor":true,"prefix":"","firstName":"Sriati","middleName":"","lastName":"Wahyudi","suffix":""},{"id":333169818,"identity":"5d1de72b-e555-4236-a92b-5a0ca1c55943","order_by":1,"name":"Ivan Rizoputra","email":"","orcid":"","institution":"Institut Teknologi Sepuluh Nopember","correspondingAuthor":false,"prefix":"","firstName":"Ivan","middleName":"","lastName":"Rizoputra","suffix":""},{"id":333169819,"identity":"2bcd6998-25c4-4ff9-b5ca-05a72c28fa6c","order_by":2,"name":"Camellia Panatarani","email":"","orcid":"","institution":"Universitas Padjadjaran","correspondingAuthor":false,"prefix":"","firstName":"Camellia","middleName":"","lastName":"Panatarani","suffix":""},{"id":333169820,"identity":"5274fe70-f7e2-442f-b739-9b0d6a280241","order_by":3,"name":"Ferry Faizal","email":"","orcid":"","institution":"Universitas Padjadjaran","correspondingAuthor":false,"prefix":"","firstName":"Ferry","middleName":"","lastName":"Faizal","suffix":""},{"id":333169821,"identity":"1f0d6853-ca72-46b4-b695-f23d4d565cdb","order_by":4,"name":"Ayi Bahtiar","email":"","orcid":"","institution":"Universitas Padjadjaran","correspondingAuthor":false,"prefix":"","firstName":"Ayi","middleName":"","lastName":"Bahtiar","suffix":""}],"badges":[],"createdAt":"2024-07-16 04:59:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4747067/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4747067/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10895-024-03931-2","type":"published","date":"2024-09-25T15:58:10+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":62334894,"identity":"1411f37b-9889-4a8e-91b2-7638131d635b","added_by":"auto","created_at":"2024-08-13 05:03:58","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":783069,"visible":true,"origin":"","legend":"\u003cp\u003eThe schematic illustration of CNDs and NS – CNDs - Fla from extract flavonoid \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves and application quenching fluorescence with heavy metal ions\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/f4d66d80c39a6a676eeda787.png"},{"id":62334542,"identity":"da1240f0-2a3e-4a89-ae52-507ade216e69","added_by":"auto","created_at":"2024-08-13 04:55:58","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":515727,"visible":true,"origin":"","legend":"\u003cp\u003eThe schematic illustration shows the synthesis of CNDs from \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves via hydrothermal method\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/48cb648114ed87b02a5dfdba.png"},{"id":62333965,"identity":"dd7de952-c049-455f-9be7-548e1b44ad97","added_by":"auto","created_at":"2024-08-13 04:47:58","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":158695,"visible":true,"origin":"","legend":"\u003cp\u003ePoint beam EDS spectra of as synthesized CNDs.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/f28e95caebde9125f82d0a90.png"},{"id":62334893,"identity":"c1a58108-ad9f-4fc5-88ad-b70829ecbfb2","added_by":"auto","created_at":"2024-08-13 05:03:58","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1050350,"visible":true,"origin":"","legend":"\u003cp\u003e(a).\u003cstrong\u003e \u003c/strong\u003eHRTEM images of CNDs with scale bar of 5 nm (inset: graphitic core lattice of CNDs), and (b) particle size distribution.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/bd68ef78952e9ff9196d595f.png"},{"id":62334543,"identity":"15a52e85-d275-484c-ac93-e4ded369769d","added_by":"auto","created_at":"2024-08-13 04:55:58","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":85402,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectra for CNDs-Fla and NS-CNDs-Fla\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/77fcf61a562651e448bfa4a1.png"},{"id":62335572,"identity":"01117e40-28da-430a-ae46-1861dda0b7a2","added_by":"auto","created_at":"2024-08-13 05:19:58","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":117748,"visible":true,"origin":"","legend":"\u003cp\u003eZeta potential of (a) CNDs - Fla and (b) NS – CNDs – Fla\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/f6b9f2a6841716dacb9d3bbf.png"},{"id":62333968,"identity":"3d0a9f0b-7bff-4426-8e23-fecf0bf57b72","added_by":"auto","created_at":"2024-08-13 04:47:58","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":91143,"visible":true,"origin":"","legend":"\u003cp\u003eUV – visible spectra of CNDs - Fla and NS – CNDs – Fla\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/ef736ba27a67778c98a5c2e6.png"},{"id":62334547,"identity":"6747525a-a4f9-4eb6-ae3b-716cbd9fb4fb","added_by":"auto","created_at":"2024-08-13 04:55:58","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":347685,"visible":true,"origin":"","legend":"\u003cp\u003eThe photoluminescence (PL) and photoluminescence excitation (PLE) spectra of CNDs – Fla (a) and NS – CNDs – Fla (c) and excitation-dependent photoluminescence spectra of CNDs – Fla (b) and NS – CNDs – Fla (d).\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/c46a5e9bb96d45854fde140e.png"},{"id":62333972,"identity":"1f01b064-55c7-4a04-99b8-334f5b45b210","added_by":"auto","created_at":"2024-08-13 04:47:58","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":242487,"visible":true,"origin":"","legend":"\u003cp\u003ePhotoluminescence spectra of CNDs - Fla solution with varied metal ions concentrations (a) Hg\u003csup\u003e2+\u003c/sup\u003e, (b) Pb\u003csup\u003e2+\u003c/sup\u003e and (c) Cu\u003csup\u003e2+\u003c/sup\u003e, (d–f) are linear relationship between Ln (I/I\u003csub\u003e0\u003c/sub\u003e) to metal ions concentration from Hg\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Cu\u003csup\u003e2+\u003c/sup\u003e, respectively.\u003cbr\u003e\n\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/e62d4cb1c9eae90aafe56aa7.png"},{"id":62333974,"identity":"7c21730c-393a-4877-a090-962c51ab914b","added_by":"auto","created_at":"2024-08-13 04:47:58","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":232441,"visible":true,"origin":"","legend":"\u003cp\u003ePhotoluminescence spectra of NS - CNDs - Fla solution with varied metal ions concentrations (a) Hg\u003csup\u003e2+\u003c/sup\u003e, (b) Pb\u003csup\u003e2+\u003c/sup\u003e and (c) Cu\u003csup\u003e2+\u003c/sup\u003e, (d–f) are linear relationship between Ln (I/I\u003csub\u003e0\u003c/sub\u003e) to metal ions concentration from Hg\u003csup\u003e2+\u003c/sup\u003e, Pb\u003csup\u003e2+\u003c/sup\u003e and Cu\u003csup\u003e2+\u003c/sup\u003e, respectively.\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/fb009c220ffe24c37254a92b.png"},{"id":65628174,"identity":"b3f729ce-605c-4f63-b339-7129ab83c937","added_by":"auto","created_at":"2024-09-30 16:18:18","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3999709,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4747067/v1/42931fd4-f7f7-4912-abe8-2b585251568d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Green synthesis of carbon nanodots (CNDs) moderated by flavonoid extracts from Moringa oleifera leaves and co-doped sulfur/nitrogen (NS – CNDs – Fla) and their potential for heavy metals sensing application","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCarbon nano dots\u003cem\u003e\u0026nbsp;\u003c/em\u003e(CNDs) are fluorescent carbon nanoparticles, the most recent addition to the nanocarbon family, which are fast developing as promising candidates and has continued to garner interest since discovered in 2004. CNDs are amorphous, belonging to the zero-dimensional (0D) carbon nanomaterial, and their mean diameter is less than 10 nanometers\u0026nbsp;[1], [2]. The most popular methods for pleasantly synthesis CNDs include electrochemical oxidation, hydrothermal treatment, laser ablation, arc- discharge, microwave, and ultrasonic synthesis\u0026nbsp;[3], [4]. Hydrothermal is the most often employed due to the easiest carbonation synthesis of CNDs applications, low-toxicity, inexpensive, and homogenous sizes of particles gets accomplished\u0026nbsp;[5], [6]. Generally, CNDs have fascinating and distinctive properties, including great water solubility, fluorescence, simple functionalization, great photobleaching, non-toxic characteristics\u0026nbsp;[7], edge effects leading to the sensors\u0026nbsp;[8], [9], reduction of CO\u003csub\u003e2\u003c/sub\u003e [10]\u0026nbsp;and supercapacitors\u0026nbsp;[11]. CNDs present a compelling substitute for photocatalysts because of their favorable redox properties, strong photo-responsiveness (bright fluorescence and extensive absorbance), and biocompatibility\u0026nbsp;[12], [13]. Furthermore, utilizing green synthesis makes CND produce easier by reducing the use of hazardous and carcinogenic solvents. Natural and environmentally friendly carbon precursors, including acids made of organic matter\u0026nbsp;[14], fruits juice\u0026nbsp;[15], and waste of foods such as peels of banana\u0026nbsp;[6]\u0026nbsp;and watermelon\u0026nbsp;[10], have already been utilized. Green synthesis from natural products provides considerable benefits in terms of sustainable, renewable, environmentally friendly, and affordable raw materials that utilizes parts of plants, such as leaves\u0026nbsp;[16]\u0026ndash;[18], fruits\u0026nbsp;[19], peels\u0026nbsp;[6], [10], flowers\u0026nbsp;[20], or microorganisms\u0026nbsp;[21]. Therefore, using a green method and carefully selecting precursors with significant physical and biological value increases the probability of successfully fabricating CNDs. \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves is one of the precursors can be a suitable natural resource to develop CNDs. In addition to satisfying the urgent requirement for the large-scale manufacture of CNDs, the utilization of plant parts as green materials encourages the development of sustainable applications. Plant components lack the requirement for separately chemical for doping, surface passivation, or post modification since they include an abundance of proteins, carbohydrates, amino compounds, and other macromolecules which are sufficient for CND surface functioning\u0026nbsp;[22]. Even though the field of plant component derived CNDs is abundant with prospects, there are still a lot of challenges to overcome in order fully explore the incredible power of these compounds. Large precursor compositions can lead to variability in CNDs generated from plant parts, therefore separation and purification need to be thoroughly investigated\u0026nbsp;[23]. To achieve for development in the space, relationships between physicals (e.g., size, shape) and chemicals (e.g., carbon, nitrogen, flavonoid), the features of CNDs, including their resulting optical properties (for example, peak excitation/emission wavelength), and functionality against diverse applications should be proved. Thus, the types of natural product, synthesis processes, and post-treatment procedures all affect the characteristics of CNDs made utilizing natural product as precursors. Finally, although the produced CNDs have a wide range of applications, including selective sensing metal ions\u0026nbsp;[24], few actual applications and a thorough mechanism are described\u0026nbsp;[9]. Subsequently is still plenty of opportunity to perform research on this emerging field to investigate more renewable green carbon precursors, create more heteroatom-doped CNDs with much higher quality, and broaden the CNDs applications. Specifically, CNDs can help address some of the contemporary issues that are becoming a growing concern to humans, such as protecting the environment and disease diagnosis\u0026nbsp;[25].\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMoringa oleifera\u0026nbsp;\u003c/em\u003eis also known as the \u0026quot;\u003cem\u003emiracle tree\u003c/em\u003e\u0026quot; or the \u0026quot;\u003cem\u003etree of life\u003c/em\u003e\u0026quot; due to every part of the plant is advantageous for both people and animals. Its leaves, roots, bark, seeds, and fruit can be utilized for a variety of purposes, such as food, medicinal, and purifying of water. This plant is native to northern India and can also be found in other tropical and subtropical regions\u003cem\u003e\u0026nbsp;\u003c/em\u003e[26], [27], which involves Indonesia. \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves contain a wide range of bioactive substances, such as potassium, calcium, phosphorus, iron, protein, vitamins A, C, and E, \u0026beta;-carotene, carotenoids, and polyphenols [28], [29], oxidase, catalase, alkaloids, glucosinolates, isothiocyanates, tannins, and saponins [30]\u0026ndash;[32], each share favorable effects on humans [33]. An abundance of bioactive substances can have medicinal properties, such as hypotension, anticancer, antioxidant, anti-inflammatory antibiotics, skin infections, anemia, wounds, scratches, irritation, a sign of aging, malaria, and fever caused by typhoid, diarrhea, intestinal obstruction, hepatoprotective colitis, hypocholesterolemia, and hypoglycemic activity [34], [35]. The polyphenol concentration of \u003cem\u003eMoringa oleifera\u003c/em\u003e varies depending on the portion of the plant. Dried \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves are high in polyphenols, with flavonoids and phenolic acids being the primary components. Flavonoids effectively reduce oxygen harmful free radicals from the entire body, hence improving cardiovascular and cerebrovascular illnesses. Furthermore, metal chelation is widely considered as another mechanism of flavonoid antioxidant activity. In several systems of biology that contain a variety of biomolecules and are linked to vital physiological processes in humans, metal ions are a significant component. The antioxidant characteristics and biological effects of quercetin can also be altered by its interaction with metal ions. Due to a metal ion can function as a free radical acceptor, ligands that are coordinated with or combined with them can have their biological activity increased. It should be a desirable alternative to provide an abundant feedstock for material science research. Therefore, extract flavonoid from Moringa oleifera leave can be an alternative green synthesis of CNDs from natural product.\u003c/p\u003e\n\u003cp\u003eHerein, \u003cem\u003eMoringa oleifera\u003c/em\u003e was transformed into fluorescent carbon nanodots and sulfur/nitrogen co-doped CNDs using a one-pot green hydrothermal method. Simple post-treatment way of centrifugated and filtering with 0.22 \u0026micro;m micro syringe was devised to reduce undesired outcomes in CNDs products. Determine of flavonoid total of \u003cem\u003eMoringa oleifera\u003c/em\u003e leave applied before synthesis CNDs. Further, characterization such as UV-visible spectroscopy, photoluminescence (PL) spectroscopy, Energy Dispersive X-Ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and high resolution-transmission electron microscopy (HR-TEM) were employed to analyze of the as-prepared CNDs. Based on the characterization results, a credible mechanism for heavy metal-induced PL quenching of CNDs was proposed (\u003cstrong\u003eFigure 1\u003c/strong\u003e). Toward our understanding, this is the first work to investigation into the synthesis of CNDs from extract flavonoid \u003cem\u003eMoringa oleifera\u003c/em\u003e leave, and conjugation of the CNDs with nitrogen/sulfur (NS \u0026ndash; CNDs - Fla). Overall, the synthesis approach is fast, consistent, and measurable, reaching in the fabrication of CNDs that have outstanding photoluminescence characteristics and non-toxicity, establishing CNDs as an intriguing potential substitute as well as the corresponding applications.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cp\u003e\u003cem\u003e2.1. Materials\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFresh\u003cem\u003e\u0026nbsp;Moringa oleifera\u003c/em\u003e leaves were collected from trees growing in local area of Probolinggo, Indonesia. The experiment was conducted using deionized water (DI). Thiourea were purchased from Sigma Aldrich as nitrogen (N) and sulfur (S) sources. Furthermore, the chemicals employed were anhydrous ethanol, Pb (NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(99%), CuSO\u003csub\u003e4\u003c/sub\u003e.5H\u003csub\u003e2\u003c/sub\u003eO (99%), and HgCl\u003csub\u003e2\u003c/sub\u003e (98%) were purchased from chemist stores in local market. The chemical compounds were analytical grade and utilized without further purification.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2. Methods\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2.1. Extractions of flavonoid from Moringa oleifera\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFlavonoid extraction was prepared using a described approach with some modifications [36]. \u003cem\u003eMoringa oleifera\u0026nbsp;\u003c/em\u003eleaves were smashed manually after being dried at room temperature. The sample was extracted using the maceration method with 70% ethanol at room temperature for a duration of three days with occasional shaking. The extract underwent filtration, and the resultant liquid flavonoid extract was subsequently evaporated using a rotary evaporator. The resulting extracts were freeze-dried and then utilized for further investigation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2.2. The determination of the total flavonoid content from Moringa oleifera leaves\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe aluminum chloride colorimetric method with modifications has been employed \u0026nbsp;for determining total flavonoids [37]. Quercetin (10 mg) was dissolved in ethanol (96%) and diluted to 100, 75, 50 and 25 \u0026mu;g/mL. Then 0.5 mL of each solution was mixed with 1.5 mL of 96% ethanol, 0.1 mL of 10% aluminum chloride, 0.1 mL of 1 M sodium acetate and 2.8 mL of DI-water. The mixture was incubated at room temperature for 30 minutes with intermittent shaking. Furthermore, absorbance measurements were carried out with maximum absorption (415 nm). The total flavonoids were determined as mean \u0026plusmn; SD (n = 3) and then expressed as quercetin equivalent weight (QE) in 100 mg of extract from dry powder.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2.3. Synthesis of CNDs and NS-CNDs-Fla using hydrothermal method\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eCarbon nanodots (CNDs) of \u003cem\u003eMoringa oleifera\u003c/em\u003e were synthesized by hydrothermal method. As received \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves were dried at room temperature. Before the synthesis of CNDs, dehydrated \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves were ground to powder. Ground greenish \u003cem\u003eMoringa oleifera\u003c/em\u003e powder then extracted with maceration method and following by freeze dry to obtain dried flavonoid extract of \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves. Flavonoid dried extract (0.5 g) was dissolved in 50 mL of deionized water followed by the stirrer for 15 minutes, then it was transferred to the hydrothermal autoclave and was heated at a constant temperature of 200 \u0026deg;C for 8 hours. Subsequently, the autoclave was allowed to cool down to room temperature. The suspension was dissolved in anhydrous ethanol and followed by the centrifuged at 10,000 rpm for 15 minutes to remove the large un-dissolved particles. The supernatant was filtered using 0.22 \u0026micro;m micro syringe filter for further purification. The purified CNDs was transferred to the glass vial and stored for further characterization.\u003c/p\u003e\n\u003cp\u003eFor NS - CNDs - Fla, 0.5 g flavonoid dried extract and 0.5 g of thiourea dissolved in 50 mL of deionized water followed by the stirring for 15 minutes, then it was transferred to the hydrothermal autoclave and was heated at a constant temperature of 200 \u0026deg;C for 8 hours. After reaction, the mixture was cooled down, and was then centrifuged at 10,000 rpm for 15 minutes to get the supernatants, which was purified via a 0.22 \u0026micro;m micro syringe filter for further purification. Finally, NS \u0026ndash; CNDs \u0026ndash; Fla was obtained for further characterization.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 2\u003c/strong\u003e illustrates the synthesis methods of two CNDs. The hydrothermal method has proven to be straightforward and effective, and it has been the most often used strategy for CND development [38]. All the preparation procedures were consistent with the previously mentioned the strategy.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2.4. Characterizations of CNDs\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe optical properties of CNDs were studied using the UV-visible spectrophotometer (Shimadzu UV-1800, Duisburg, Germany) and photoluminescence (PL) spectroscopy (FP-6500, JASCO, Japan). The size distribution and morphology of CNDs were characterized by a Thermofisher Scientific Fei Tecnai G2 Supertwin transmission electron microscopy (HR-TEM, ILRC Universitas Indonesia). Fourier transform infrared spectra (FTIR) of CNDs were recorded to identify the functional groups on to the surface of CNDs (PerkinElmer Spectrum 100). The zeta potential measurements were obtained using a Horiba Scientific SZ 100z/Nano Particle Size Analyzer. The elemental composition of CNDs was evaluated by energy-dispersive X-ray spectroscopy (EDS, JEM-2300F, JEOL) at Central Laboratory, Universitas Padjadjaran, Indonesia.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e2.2.5. Procedure for metal ions sensing\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe stock solutions of three metal ions (Pb\u003csup\u003e2+\u003c/sup\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e, and Hg\u003csup\u003e2+\u003c/sup\u003e) were respectively prepared, and were further diluted with deionized water to obtain a final concentration of 1 \u0026micro;M, 10 \u0026micro;M, 50 \u0026micro;M, 100 \u0026micro;M, 500 \u0026micro;M, and 1000 \u0026micro;M. Each of the metal ion solution was mixed with CNDs (3.0 mL), stirred, and incubated for 15 min at room temperature. The fluorescence spectra of the suspensions were then measured using the fluorescence spectrophotometer to determine the fluorescence intensities. For CNDs \u0026ndash; Fla, fluorescence was excited at 365 nm and emitted at 440 nm. The fluorescence excitation and emission wavelengths for NS - CNDs - Fla were 340 nm and 435 nm, respectively. The intensity of fluorescence emissions at these wavelengths for each sample has been determined.\u003c/p\u003e"},{"header":"3. Results and discussions","content":"\u003cp\u003e\u003cem\u003e3.1. Flavonoid and EDS studies\u003c/em\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eTotal flavonoids represent the total amount of flavonoid compounds from plant extract such as moringa oleifera leaves. As explained, \u003cem\u003eMoringa oleifera\u003c/em\u003e extract was high in phenolic components, such as quercetin, kaempferol, and rutin, flavonoid compounds [39], [40]. In this study the total flavonoid test results were 172.10 mg QE/g sample. Determination of total flavonoids using gallic acid and quercetin standards where the calibration curve equation obtained respectively was y = 0.005x + 0.161 (R\u003csup\u003e2\u003c/sup\u003e = 0.992). This confirms that Moringa leaves are rich in flavonoid content.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe EDS spectrums are graphs of the X-rays received at each energy level indicated. They show peaks that correlate to the different levels of energy received from X-rays. The EDS\u0026apos;s abscissa axis represents the ionization energy pathway, whilst the ordinate axis represents the counts per second of CND intensity [41]. Each peak is associated with a certain element, such as carbon (C), nitrogen (N), or sulfur (S). \u003cstrong\u003eFigure 3\u003c/strong\u003e represents a study of the compositional constituents in CNDs extract flavonoid of \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves, the picture reveals a carbon content of 47.343%, nitrogen of 51.670%, and sulfur of 0.986%. A greater peak in the spectrum indicates the most prominent element in the sample. The presence of these elements in the sample confirms that synthesized sample is comprised of CNDs.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.2. HR-TEM and FTIR studies\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAs explained previously, CNDs are a novel type of carbon nanomaterials with a diameter of less than 10 nm. In this work, the hydrothermal process was carried out at 200 \u003csup\u003e0\u003c/sup\u003eC for 8 h. \u003cstrong\u003eFigure 4\u003c/strong\u003e shows an HR-TEM image of as-prepared CNDs. CNDs are revealed to be monodispersed particles in a spherical form with a diameter of less than 10 nm. In addition, CNDs have crystalline or polymeric structures as indicated by graphite lattice d-spacing of 0.22 nm in the insert of Figure 4(a). Furthermore, Figure 4(b) depicts the corresponding size distribution histogram, which shows that the overall distribution of particle sizes range between 2.25 nm and 4.75 nm, with an average size of 3.49 nm.\u003c/p\u003e\n\u003cp\u003eTo confirm the presence of various carbon-oxygen functional groups on \u003cem\u003eMoringa oleifera\u003c/em\u003e CNDs, we performed FTIR spectroscopy, as depicted in \u003cstrong\u003eFigure 5\u003c/strong\u003e. Both samples have similar IR bands in the range of 600\u0026ndash;1500 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, which are caused by C\u0026ndash;O, C\u0026ndash;S, and C\u0026ndash;H stretching vibrations\u0026nbsp;[42]. The FTIR spectrum corresponds to functional groups, such as vibration bands at 3321 cm\u003csup\u003e-1\u003c/sup\u003e and 1031 cm\u003csup\u003e-1\u003c/sup\u003e respectively representing hydroxyl groups (-OH) and C-O-C according to the initial material. The relative intensity of the two vibration bands is very strong, indicating that the group is related to flavonoids in the CNDs-Fla structure. Apart from that, the vibration bands \u0026ndash;CH (2945 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, 2833 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, and 1449 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e), C=C (1660 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) are also very clearly visible and unique vibration bands such as =CH (663.40 cm\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) in the spectrum of CNDs confirmed the presence of flavonoid-related functional groups\u0026nbsp;[43]. Furthermore, a new band at C\u0026ndash;S (1110 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e) and two other bands at 1652 cm\u003csup\u003e\u0026minus;1\u0026nbsp;\u003c/sup\u003eand 1450 cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e, represent the typical stretching modes of C=N and C\u0026ndash;N. This indicates the successful synthesis of N and S co-doped CNDs.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.5. Zeta Potential of CNDs\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe Zeta potential is an essential parameter used to determine the surface charge of CNDs in a aqueous solution. The Zeta potential indicates the total electric charge on the surface of the CNDs and NS - CNDs - Fla which aim to evaluate the stability of carbon nano dots. Herein, the Zeta potential of CNDs - Fla is \u0026minus;10.9 mV indicates that the CNDs have a negative surface charge. While the zeta potential of NS - CNDs - Fla \u0026minus;11.6 mV, showing the enhanced stability with addition of nitrogen and sulfur in CNDs as given in \u003cstrong\u003eFigure 6\u003c/strong\u003e. This negative charge is caused by the presence of functional groups or chemical species on the CNDs\u0026apos; surfaces that ionize in solution, resulting in an accumulation of negatively charged particles around the CNDs. Carbon nanodots (CNDs) have a negative charge due to the presence of surface functional groups, which results in negative zeta potential values for both zeta potential. The negative sign of the zeta potential reveals negatively charged residues, which are required for good dispersion stability of CNDs\u0026nbsp;[44].\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.6. UV-Visible and PL intensity of CNDs\u003c/em\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe optical properties were studied as revealed by the characteristic UV-Vis spectra of the CNDs. In \u003cstrong\u003eFigure 7\u0026nbsp;\u003c/strong\u003eshow the UV\u0026ndash;visible absorption spectra of developed CNDs - Fla and NS - CNDs - Fla, respectively. \u0026nbsp; UV\u0026ndash;visible spectra of prepared CNDs - Fla significant peaks at about 280 nm should be ascribed to \u0026pi;\u0026ndash;\u0026pi;* transition due to sp\u003csup\u003e2\u003c/sup\u003e aromatic \u0026pi;-domains of C = C bonds within the CNDs, this is corresponding to some other earlier findings. [45], [46]. Similarly, the absorption spectra of NS - CNDs - Fla show more pronounced peaks around 265 nm, which correspond to the \u0026pi;-\u0026pi;* transition caused by the presence of sp2 aromatic \u0026pi;-domains. Heteroatom doping in CND structures alters their electrical characteristics via modifying the band-gap and optical absorbance [47]. Therefore, the prepared NS - CNDs - Fla exhibited increased optical absorption, as illustrated in Figure 7 (line\u0026nbsp;\u003cbr\u003eorange).\u003c/p\u003e\n\u003cp\u003eFurthermore, as shown in \u003cstrong\u003eFigure 8\u003c/strong\u003e, the fluorescence spectra illustrate the behavior of the CNDs and providing further details on their optical properties. In Figure \u003cstrong\u003e8 (a)\u003c/strong\u003e and \u003cstrong\u003e8 (c)\u003c/strong\u003e displays the photoluminescence (PL) and photoluminescence excitation (PLE) spectra of the synthesized CNDs - Fla and NS - CNDs - Fla. In this case, it was observed that the CNDs - Fla and NS - CNDs -Fla exhibited strong blue luminescence at a wavelength of 440 nm and 436 nm, respectively. On the other hand, the PLE spectrum depicts the absorbed light, demonstrating the energy levels at which CNDs was able to absorb photons and transition to greater energy states. Then, the CNDs - Fla sample exhibits an absorption peak at 365 nm, leading to the emission of light at 440 nm, while NS - CNDs - Fla at the excitation 340 nm with the emission of light at 436 nm. In \u003cstrong\u003eFigure 8 (b)\u003c/strong\u003e and \u003cstrong\u003e8 (d)\u003c/strong\u003e show the excitation-dependent photoluminescence spectra of a CNDs - Fla and NS - CNDs - Fla samples, together with the associated colors recognized under various excitation settings. In this research provides a thorough grasp of how CNDs behave to different excitation wavelengths.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e3.7. Selectivity and sensitivity of metal ions detection\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eSelectivity and sensitivity are essential factor in designing an effective sensors for detection of heavy metals in aqueous solutions. Herein, we investigated by introducing different metal ions into CNDs - Fla and NS - CNDs - Fla, such as Cu\u003csup\u003e2+\u003c/sup\u003e, Hg\u003csup\u003e2+\u003c/sup\u003e, dan Pb\u003csup\u003e2+\u003c/sup\u003e. Variations concentration of heavy metals solution was added to the CNDs - Fla and NS - CNDs - Fla. The PL spectra were obtained at an excitation wavelength of 365 nm and 340 nm for the CNDs - Fla and NS - CNDs - Fla, respectively.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFigure 9\u003c/strong\u003e depicts the ratio of the intensity of PL when various concentration of heavy metals was added to CNDs - Fla (I) to the intensity of Pl in a blank sample (I\u003csub\u003e0\u003c/sub\u003e). It was observed that adding heavy metals significantly reduced the intensity ratio. As a result, CNDs - Fla demonstrated high selectivity for Cu\u003csup\u003e2+\u003c/sup\u003e. Then, the sensitivity toward heavy metals was analyzed by adding different concentrations (0\u0026ndash;1000 \u0026micro;M) of heavy metals to CNDs - Fla and recording the PL responses at 365 nm excitation wavelength. The intensity of PL was found to decrease as heavy metal ions concentrations increased. It indicates that CNDs - Fla were also sensitive to Cu\u003csup\u003e2+\u003c/sup\u003e. In our current study, we hypothesize on the selective binding ability of CND-Fla due to the creation of Cu\u003csup\u003e2+\u003c/sup\u003e specific flavonoid motifs on its edges during the production of CNDs from flavonoid extracts. Furthermore, flavonoids and polyphenolic chemicals including gallic acid, catechol, pyrogallol, and their derivatives have been shown to form complexes with heavy and transition metal cations [48]. Similarly, selectivity and sensitivity experiments for the various heavy metals were conducted on produced NS - CNDs - Fla. In \u003cstrong\u003eFigure 10\u003c/strong\u003e, Cu\u003csup\u003e2+\u003c/sup\u003e ions demonstrated considerable PL quenching of NS- CNDs - Fla as compared to the other heavy metals. NS - CNDs - Fla is composed primarily of N-related and O-related functional groups that act as electron donors and have a high binding affinity for Cu\u003csup\u003e2+\u003c/sup\u003e ions as compared to other heavy metals [49].\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eCNDs - Fla and NS-CNDs - Fla were successfully synthesized from \u003cem\u003eMoringa oleifera\u003c/em\u003e leaves using hydrothermal, as confirmed by EDS, FTIR, and HR-TEM measurements. The average diameter of CNDs is 3.49 nm and shows graphite lattice with d-spacing of 0.22 nm. The synthesized CNDs Fla and NS-CNDs Fla exhibited strong photostability, high fluorescence, and great water solubility. Because of heteroatom doping, which offers large number of active sites and the synergistic impact between each element, the NS - CNDs - Fla displayed higher PL intensity and photostability than the CNDs - Fla. This resulted in radiative recombination of the trapped electron-hole pairs. The elimination of additional surface functional groups that alter the PL property causes the non-radiative self-trapped electrons on the surface of CNDs to disappear as surface passivation rises. Therefore, compared to CNDs - Fla, the NS - CNDs - Fla exhibits excitation-independent PL emission due to its higher surface passivation from heteroatom doping. The addition of heavy metals in CNDs \u0026ndash; Fla and NS \u0026ndash; CNDs - Fla exhibits the significant result i.e., \u0026ldquo;Turn-off\u0026rdquo; intensity of PL based on mechanisms dynamic quenching. Therefore, flavonoid compound from \u003cem\u003eMoringa oleifera\u003c/em\u003e should be great a potential candidate good precursor for sensing and other application based on carbon nano dots (CNDs).\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSriati Wahyudi : Investigation, writing - original draft preparation, data curation, formal analysis, and visualization.Ivan Rizoputra : Visualization. Camellia Panatarani : Data analysisFerry Faizal : Review and editing of the manuscript. Ayi Bahtiar : Conceptualization, methodology, supervision, data analysis, and review. All authors reviewed the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This research was funded by the Ministry of Research, Technology and Higher Education Indonesia, through research scheme Doctoral Dissertation Program (PDD-DIKTI), contract number 3841/UN6.3.1/PT.00/2024 dated on June 13, 2024. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInstitutional Review Board Statement:\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent Statement:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement:\u0026nbsp;\u003c/strong\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e This research project is supported Functional Nano Powder University Center of Excellence (FiNder U-CoE) is a Research Centre at Universitas Padjadajaran.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eS. Sharma, A. Umar, S. Sood, S. K. Mehta, and S. K. Kansal, \u0026ldquo;Photoluminescent C-dots: An overview on the recent development in the synthesis, physiochemical properties and potential applications,\u0026rdquo; \u003cem\u003eJ. Alloys Compd.\u003c/em\u003e, vol. 748, pp. 818\u0026ndash;853, 2018, doi: 10.1016/j.jallcom.2018.03.001.\u003c/li\u003e\n\u003cli\u003eI. Y. Goryacheva, A. V. Sapelkin, and G. B. Sukhorukov, \u0026ldquo;Carbon nanodots: Mechanisms of photoluminescence and principles of application,\u0026rdquo; \u003cem\u003eTrAC - Trends Anal. Chem.\u003c/em\u003e, vol. 90, pp. 27\u0026ndash;37, 2017, doi: 10.1016/j.trac.2017.02.012.\u003c/li\u003e\n\u003cli\u003eY. Wang, J. Sun, B. He, and M. Feng, \u0026ldquo;Synthesis and modification of biomass derived carbon dots in ionic liquids and their application: A mini review,\u0026rdquo; \u003cem\u003eGreen Chem. Eng.\u003c/em\u003e, vol. 1, no. 2, pp. 94\u0026ndash;108, 2020, doi: 10.1016/j.gce.2020.09.010.\u003c/li\u003e\n\u003cli\u003eN. Ullal, K. Muthamma, and D. Sunil, \u0026ldquo;Carbon dots from eco-friendly precursors for optical sensing application: an up-to-date review,\u0026rdquo; \u003cem\u003eChemical Papers\u003c/em\u003e. Springer, 2022. doi: 10.1007/s11696-022-02353-3.\u003c/li\u003e\n\u003cli\u003eR. Khan, A. Qureshi, M. Azhar, Z. U. Hassan, S. Gul, and S. Ahmad, \u0026ldquo;Recent Progress of Fluorescent Carbon Dots and Graphene Quantum Dots for Biosensors: Synthesis of Solution Methods and their Medical Applications,\u0026rdquo; \u003cem\u003eJ. Fluoresc.\u003c/em\u003e, 2024, doi: 10.1007/s10895-024-03809-3.\u003c/li\u003e\n\u003cli\u003eR. Atchudan, T. N. Jebakumar Immanuel Edison, M. Shanmugam, S. Perumal, T. Somanathan, and Y. R. Lee, \u0026ldquo;Sustainable synthesis of carbon quantum dots from banana peel waste using hydrothermal process for in vivo bioimaging,\u0026rdquo; \u003cem\u003ePhys. E Low-Dimensional Syst. Nanostructures\u003c/em\u003e, vol. 126, no. April 2020, p. 114417, 2021, doi: 10.1016/j.physe.2020.114417.\u003c/li\u003e\n\u003cli\u003eM. Mondal and S. Pramanik, \u0026ldquo;A mechanism for excitation-dependent emission from carbon nanodots,\u0026rdquo; \u003cem\u003eMater. Lett. X\u003c/em\u003e, vol. 18, no. December 2022, p. 100195, 2023, doi: 10.1016/j.mlblux.2023.100195.\u003c/li\u003e\n\u003cli\u003eX. Sun and Y. Lei, \u0026ldquo;Fluorescent carbon dots and their sensing applications,\u0026rdquo; \u003cem\u003eTrAC - Trends Anal. Chem.\u003c/em\u003e, vol. 89, pp. 163\u0026ndash;180, 2017, doi: 10.1016/j.trac.2017.02.001.\u003c/li\u003e\n\u003cli\u003eD. J. Fan, D. L. Kang, P. D. Di Liu, and P. D. S. Zhang, \u0026ldquo;Modification of Carbon Dots for Metal-Ions Detection,\u0026rdquo; \u003cem\u003eChemistrySelect\u003c/em\u003e, vol. 8, no. 19, 2023, doi: https://doi.org/10.1002/slct.202300062.\u003c/li\u003e\n\u003cli\u003eW. . Dwandaru, E. K. Sari, W. Widyawidura, and D. S. Khaerudini, \u0026ldquo;Carbon nanodots from watermelon peel as co2absorbents in biogas,\u0026rdquo; \u003cem\u003eVopr. Khimii i Khimicheskoi Tekhnologii\u003c/em\u003e, vol. 2021, no. 4, pp. 41\u0026ndash;49, 2021, doi: 10.32434/0321-4095-2021-137-4-41-49.\u003c/li\u003e\n\u003cli\u003eS. S. Patil, A. G. Bhosale, S. S. Kundale, T. D. Dongale, and S. A. Vanalakar, \u0026ldquo;Enhancing capacitance performance of functional group assisted carbon quantum dots derived from turmeric plant waste,\u0026rdquo; \u003cem\u003eCarbon Trends\u003c/em\u003e, vol. 15, no. May, p. 100370, 2024, doi: 10.1016/j.cartre.2024.100370.\u003c/li\u003e\n\u003cli\u003eA. Rehman, A. Daud, and M. F. Warsi, \u0026ldquo;Nanostructured maghemite and magnetite and their nanocomposites with graphene oxide for photocatalytic degradation of methylene blue,\u0026rdquo; \u003cem\u003eMater. Chem. Phys.\u003c/em\u003e, vol. 256, no. July, p. 123752, 2020, doi: 10.1016/j.matchemphys.2020.123752.\u003c/li\u003e\n\u003cli\u003eG. S. Das, J. P. Shim, A. Bhatnagar, K. M. Tripathi, and T. Y. Kim, \u0026ldquo;Biomass-derived Carbon Quantum Dots for Visible-Light-Induced Photocatalysis and Label-Free Detection of Fe(III) and Ascorbic acid,\u0026rdquo; \u003cem\u003eSci. Rep.\u003c/em\u003e, vol. 9, no. 1, pp. 1\u0026ndash;9, 2019, doi: 10.1038/s41598-019-49266-y.\u003c/li\u003e\n\u003cli\u003eS. Yang, K. Wang, X. Wang, and X. Sun, \u0026ldquo;Organic acid participation strategy for the synthesis of highly fluorescent carbon dots and their application in dual-mode determination of copper ions,\u0026rdquo; \u003cem\u003eAppl. Surf. Sci.\u003c/em\u003e, vol. 505, no. July 2019, p. 144567, 2020, doi: 10.1016/j.apsusc.2019.144567.\u003c/li\u003e\n\u003cli\u003eM. Lu, Y. Duan, Y. Song, J. Tan, and L. Zhou, \u0026ldquo;Green preparation of versatile nitrogen-doped carbon quantum dots from watermelon juice for cell imaging, detection of Fe3+ ions and cysteine, and optical thermometry,\u0026rdquo; \u003cem\u003eJ. Mol. Liq.\u003c/em\u003e, vol. 269, pp. 766\u0026ndash;774, 2018, doi: 10.1016/j.molliq.2018.08.101.\u003c/li\u003e\n\u003cli\u003eS. Tang, Y. Liu, H. Opoku, and M. Gregorsson, \u0026ldquo;Fluorescent carbon dots from birch leaves for sustainable electroluminescent devices,\u0026rdquo; \u003cem\u003eGreen Chem.\u003c/em\u003e, vol. 25, no. 23, pp. 9884\u0026ndash;9895, 2023, doi: 10.1039/d3gc03827k.\u003c/li\u003e\n\u003cli\u003eK. kanthi Gudimella, G. Gedda, and P. S. Kumar, \u0026ldquo;Novel synthesis of fluorescent carbon dots from bio-based Carica Papaya Leaves: Optical and structural properties with antioxidant and anti-inflammatory activities,\u0026rdquo; \u003cem\u003eEnviron. Res.\u003c/em\u003e, vol. 204, no. PA, p. 111854, 2022, doi: 10.1016/j.envres.2021.111854.\u003c/li\u003e\n\u003cli\u003eY. Shao, C. Zhu, Z. Fu, and K. Lin, \u0026ldquo;Green synthesis of multifunctional fluorescent carbon dots from mulberry leaves (Morus alba L.) residues for simultaneous intracellular imaging and drug delivery,\u0026rdquo; \u003cem\u003eJ. Nanoparticle Res.\u003c/em\u003e, vol. 22, no. 8, 2020, doi: 10.1007/s11051-020-04917-4.\u003c/li\u003e\n\u003cli\u003eV. N. Mehta, S. Jha, and H. Basu, \u0026ldquo;One-step hydrothermal approach to fabricate carbon dots from apple juice for imaging of mycobacterium and fungal cells,\u0026rdquo; \u003cem\u003eSensors Actuators, B Chem.\u003c/em\u003e, vol. 213, pp. 434\u0026ndash;443, 2015, doi: 10.1016/j.snb.2015.02.104.\u003c/li\u003e\n\u003cli\u003eO. G. Rojas-Valencia, M. Regules-Carrasco, J. Hern\u0026aacute;ndez-Fuentes, C. M. R. S. Germ\u0026aacute;n, M. Estrada-Flores, and E. Villagarc\u0026iacute;a-Ch\u0026aacute;vez, \u0026ldquo;Synthesis of blue emissive carbon quantum dots from Hibiscus Sabdariffa flower: Surface functionalization analysis by FT-IR spectroscopy,\u0026rdquo; \u003cem\u003eMaterialia\u003c/em\u003e, vol. 19, no. July, p. 101182, 2021, doi: 10.1016/j.mtla.2021.101182.\u003c/li\u003e\n\u003cli\u003eH. Bahrulolum, S. Nooraei, N. Javanshir, and H. Tarrahimofrad, \u0026ldquo;Green synthesis of metal nanoparticles using microorganisms and their application in the agrifood sector,\u0026rdquo; \u003cem\u003eJ. Nanobiotechnology\u003c/em\u003e, vol. 19, no. 1, pp. 1\u0026ndash;26, 2021, doi: 10.1186/s12951-021-00834-3.\u003c/li\u003e\n\u003cli\u003eM. Zulfajri, G. Gedda, and C. J. Chang, \u0026ldquo;Cranberry Beans Derived Carbon Dots as a Potential Fluorescence Sensor for Selective Detection of Fe3+ Ions in Aqueous Solution,\u0026rdquo; \u003cem\u003eACS Omega\u003c/em\u003e, vol. 4, no. 13, pp. 15382\u0026ndash;15392, 2019, doi: 10.1021/acsomega.9b01333.\u003c/li\u003e\n\u003cli\u003eW. Meng, X. Bai, B. Wang, Z. Liu, S. Lu, and B. Yang, \u0026ldquo;Biomass-Derived Carbon Dots and Their Applications,\u0026rdquo; \u003cem\u003eEnergy Environ. Mater.\u003c/em\u003e, vol. 2, no. 3, pp. 172\u0026ndash;192, 2019, doi: 10.1002/eem2.12038.\u003c/li\u003e\n\u003cli\u003eS. Wahyudi, J. Abdul Aziz, F. Faizal, and A. Bahtiar, \u0026ldquo;Improved mercury ions (Hg2+) detection by composite silver nanoparticles (AgNPs) and nitrogen - Sulfur co-doped carbon dots (N, S-CDs),\u0026rdquo; \u003cem\u003eResults Mater.\u003c/em\u003e, vol. 21, no. December 2023, p. 100551, 2024, doi: 10.1016/j.rinma.2024.100551.\u003c/li\u003e\n\u003cli\u003eM. Zulfajri, H. N. Abdelhamid, S. Sudewi, and S. Dayalan, \u0026ldquo;Plant part-derived carbon dots for biosensing,\u0026rdquo; \u003cem\u003eBiosensors\u003c/em\u003e, 2020, doi: 10.3390/bios10060068.\u003c/li\u003e\n\u003cli\u003eS. V. Patil, B. V. Mohite, K. R. Marathe, N. S. Salunkhe, V. Marathe, and V. S. Patil, \u0026ldquo;Moringa Tree, Gift of Nature: a Review on Nutritional and Industrial Potential,\u0026rdquo; \u003cem\u003eCurr. Pharmacol. Reports\u003c/em\u003e, vol. 8, no. 4, pp. 262\u0026ndash;280, 2022, doi: 10.1007/s40495-022-00288-7.\u003c/li\u003e\n\u003cli\u003eA. Pareek, M. Pant, M. M. Gupta, and P. Kashania, \u0026ldquo;Moringa oleifera: An Updated Comprehensive Review of Its Pharmacological Activities, Ethnomedicinal, Phytopharmaceutical Formulation, Clinical, Phytochemical, and Toxicological Aspects,\u0026rdquo; \u003cem\u003eInt. J. Mol. Sci.\u003c/em\u003e, vol. 24, no. 3, 2023, doi: 10.3390/ijms24032098.\u003c/li\u003e\n\u003cli\u003eS. Sreelatha and P. R. Padma, \u0026ldquo;Antioxidant activity and total phenolic content of Moringa oleifera leaves in two stages of maturity,\u0026rdquo; \u003cem\u003ePlant Foods Hum. Nutr.\u003c/em\u003e, vol. 64, no. 4, pp. 303\u0026ndash;311, 2009, doi: 10.1007/s11130-009-0141-0.\u003c/li\u003e\n\u003cli\u003eP. P. M. Ferreira, D. F. Farias, J. T. D. A. Oliveira, and A. D. F. Carvalho, \u0026ldquo;Moringa oleifera : bioactive compounds and nutritional potential,\u0026rdquo; \u003cem\u003eRev. Nutr.\u003c/em\u003e, vol. 21, no. 4, pp. 431\u0026ndash;437, 2008.\u003c/li\u003e\n\u003cli\u003eC. Martin, G. Martin, A. Garcia, T. Fern\u0026aacute;ndez, E. Hern\u0026aacute;ndez, and y J. Puls, \u0026ldquo;Potential Applications of Moringa oleifera. A critical review,\u0026rdquo; \u003cem\u003ePastos y Forrajes\u003c/em\u003e, vol. 36, no. 2, pp. 150\u0026ndash;158, 2013.\u003c/li\u003e\n\u003cli\u003eR. K. Saini, I. Sivanesan, and Y. S. Keum, \u0026ldquo;Phytochemicals of Moringa oleifera: a review of their nutritional, therapeutic and industrial significance,\u0026rdquo; \u003cem\u003e3 Biotech\u003c/em\u003e, vol. 6, no. 2, pp. 1\u0026ndash;14, 2016, doi: 10.1007/s13205-016-0526-3.\u003c/li\u003e\n\u003cli\u003eM. Vergara-Jimenez, M. M. Almatrafi, and M. L. Fernandez, \u0026ldquo;Bioactive components in Moringa oleifera leaves protect against chronic disease,\u0026rdquo; \u003cem\u003eAntioxidants\u003c/em\u003e, vol. 6, no. 4, pp. 1\u0026ndash;13, 2017, doi: 10.3390/antiox6040091.\u003c/li\u003e\n\u003cli\u003eS. J. Stohs and M. J. Hartman, \u0026ldquo;Review of the safety and efficacy of Moringa oleifera,\u0026rdquo; \u003cem\u003ePhyther. Res.\u003c/em\u003e, vol. 29, no. 6, pp. 796\u0026ndash;804, 2015, doi: 10.1002/ptr.5325.\u003c/li\u003e\n\u003cli\u003eH. S. Hamed and Y. S. El-Sayed, \u0026ldquo;Antioxidant activities of Moringa oleifera leaf extract against pendimethalin-induced oxidative stress and genotoxicity in Nile tilapia, Oreochromis niloticus (L.),\u0026rdquo; \u003cem\u003eFish Physiol. Biochem.\u003c/em\u003e, vol. 45, no. 1, pp. 71\u0026ndash;82, 2019, doi: 10.1007/s10695-018-0535-8.\u003c/li\u003e\n\u003cli\u003eY. Zhu, Q. Yin, and Y. Yang, \u0026ldquo;Comprehensive Investigation of Moringa oleifera from Different Regions by Simultaneous,\u0026rdquo; \u003cem\u003eMolecules\u003c/em\u003e, vol. 25, no. 1, p. 676690, 2020.\u003c/li\u003e\n\u003cli\u003eB. Vongsak, P. Sithisarn, S. Mangmool, S. Thongpraditchote, Y. Wongkrajang, and W. Gritsanapan, \u0026ldquo;Maximizing total phenolics, total flavonoids contents and antioxidant activity of Moringa oleifera leaf extract by the appropriate extraction method,\u0026rdquo; \u003cem\u003eInd. Crops Prod.\u003c/em\u003e, vol. 44, pp. 566\u0026ndash;571, 2013, doi: 10.1016/j.indcrop.2012.09.021.\u003c/li\u003e\n\u003cli\u003eC. C. Chang, M. H. Yang, H. M. Wen, and J. C. Chern, \u0026ldquo;Estimation of total flavonoid content in propolis by two complementary colometric methods,\u0026rdquo; \u003cem\u003eJ. Food Drug Anal.\u003c/em\u003e, vol. 10, no. 3, pp. 178\u0026ndash;182, 2002, doi: 10.38212/2224-6614.2748.\u003c/li\u003e\n\u003cli\u003eS. Wahyudi, A. Bahtiar, C. Panatarani, Anas, and Risdiana, \u0026ldquo;Recent advanced carbon dots derived natural products and aptasensor-based carbon dots for detection of pesticides,\u0026rdquo; \u003cem\u003eSens. Bio-Sensing Res.\u003c/em\u003e, vol. 41, no. July, p. 100576, 2023, doi: 10.1016/j.sbsr.2023.100576.\u003c/li\u003e\n\u003cli\u003eY. Y. Wang, C. Peng, and Y. Zhang, \u0026ldquo;Optimization, identification and bioactivity of flavonoids extracted from Moringa oleifera leaves by deep eutectic solvent,\u0026rdquo; \u003cem\u003eFood Biosci.\u003c/em\u003e, vol. 47, no. March, 2022, doi: 10.1016/j.fbio.2022.101687.\u003c/li\u003e\n\u003cli\u003eP. Wei, Y. Zhang, Y. Y. Wang, and J. F. Dong, \u0026ldquo;Efficient extraction and excellent activity of flavonoid from Moringa oleifera leaves and its microencapsulation,\u0026rdquo; \u003cem\u003eLwt\u003c/em\u003e, vol. 184, no. June, 2023, doi: 10.1016/j.lwt.2023.115021.\u003c/li\u003e\n\u003cli\u003eA. Barhoum, M. L. Garc\u0026iacute;a-Betancourt, H. Rahier, and G. Van Assche, \u003cem\u003ePhysicochemical characterization of nanomaterials: Polymorph, composition, wettability, and thermal stability\u003c/em\u003e. Elsevier Inc., 2018. doi: 10.1016/B978-0-323-51254-1.00009-9.\u003c/li\u003e\n\u003cli\u003eH. Ding, J. S. Wei, and H. M. Xiong, \u0026ldquo;Nitrogen and sulfur co-doped carbon dots with strong blue luminescence,\u0026rdquo; \u003cem\u003eNanoscale\u003c/em\u003e, vol. 6, no. 22, pp. 13817\u0026ndash;13823, 2014, doi: 10.1039/c4nr04267k.\u003c/li\u003e\n\u003cli\u003eR. M. Silverstein and F. X. Webster, \u0026ldquo;Spectrometric Identification Of Organic Compounds 6th Edition,\u0026rdquo; \u003cem\u003eJohn Wiley \u0026amp; Sons Ltd\u003c/em\u003e, vol. 6. pp. 1\u0026ndash;482, 1996.\u003c/li\u003e\n\u003cli\u003eW. Li, S. Wang, and Y. Li, \u0026ldquo;One-step hydrothermal synthesis of fluorescent nanocrystalline cellulose/carbon dot hydrogels,\u0026rdquo; \u003cem\u003eCarbohydr. Polym.\u003c/em\u003e, vol. 175, pp. 7\u0026ndash;17, 2017, doi: 10.1016/j.carbpol.2017.07.062.\u003c/li\u003e\n\u003cli\u003eZ. L. Wu, P. Zhang, M. X. Gao, and C. F. Liu, \u0026ldquo;One-pot hydrothermal synthesis of highly luminescent nitrogen-doped amphoteric carbon dots for bioimaging from bombyx mori silk \u0026ndash; natural proteins,\u0026rdquo; \u003cem\u003eMater. Chem. B\u003c/em\u003e, vol. 10, no. 207890, p. 4118, 2013, [Online]. Available: https://pubs.rsc.org/en/content/articlelanding/2013/tb/c3tb20418a\u003c/li\u003e\n\u003cli\u003eL. Shi, X. Li, Y. Li, and X. Wen, \u0026ldquo;Naked oats-derived dual-emission carbon nanodots for ratiometric sensing and cellular imaging,\u0026rdquo; \u003cem\u003eSensors Actuators, B Chem.\u003c/em\u003e, vol. 210, pp. 533\u0026ndash;541, 2015, doi: 10.1016/j.snb.2014.12.097.\u003c/li\u003e\n\u003cli\u003eN. Sohal, B. Maity, and S. Basu, \u0026ldquo;Recent advances in heteroatom-doped graphene quantum dots for sensing applications,\u0026rdquo; \u003cem\u003eRSC Adv.\u003c/em\u003e, vol. 11, no. 41, pp. 25586\u0026ndash;25615, 2021, doi: 10.1039/d1ra04248c.\u003c/li\u003e\n\u003cli\u003eM. McDonald, I. Mila, and A. Scalbert, \u0026ldquo;Precipitation of metal ions by plant polyphenols: Optimal conditions and origin of precipitation,\u0026rdquo; \u003cem\u003eJ. Agric. Food Chem.\u003c/em\u003e, vol. 44, no. 2, pp. 599\u0026ndash;606, 1996, doi: 10.1021/jf950459q.\u003c/li\u003e\n\u003cli\u003eJ. Lin, X. Huang, E. Kou, and W. Cai, \u0026ldquo;Carbon dot based sensing platform for real-time imaging Cu2+ distribution in plants and environment,\u0026rdquo; \u003cem\u003eBiosens. Bioelectron.\u003c/em\u003e, vol. 219, no. August 2022, p. 114848, 2023, doi: 10.1016/j.bios.2022.114848.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-fluorescence","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jofl","sideBox":"Learn more about [Journal of Fluorescence](https://www.springer.com/journal/10895)","snPcode":"10895","submissionUrl":"https://submission.nature.com/new-submission/10895/3","title":"Journal of Fluorescence","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Carbon Nano Dots (CNDs), Moringa oleifera leave, Heteroatoms, Fluorescence, Detection of heavy metals","lastPublishedDoi":"10.21203/rs.3.rs-4747067/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4747067/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cem\u003eMoringa oleifera\u003c/em\u003e is the “\u003cem\u003emagic tree\u003c/em\u003e” which contains many bioactive compounds such as flavonoids, especially in its leaves. Natural flavonoids and glycosides with specific components of structure can bind to metal ions. The content of bioactive compounds such as total flavonoids found in \u003cem\u003eMoringa oleifera\u003c/em\u003eleaves is 172.10 mg/g. In addition, carbon (47.34%), nitrogen (51.67%), and sulfur (0.99%) are also the main composition. Then, the carbon nanodots (CNDs) synthesized in this research were moderated by flavonoid extract from \u003cem\u003eMoringa oleifera\u003c/em\u003e using the hydrothermal method. The technique is easy, ecologically friendly, and requires neither specialized device or reagents. In practice, the CNDs produced are almost circular, with an average diameter of 3.49 nm. Furthermore, we enhanced synthesis CNDs - Fla with heteroatoms of nitrogen (N) and sulfur (S). They display a broad excitation-emission spectrum, excitation-dependent emission, and extraordinary fluorescence. Therefore, the synthesis of CNDs using flavonoids from \u003cem\u003eMoringa oleifera\u003c/em\u003e as precursors would be a great potential candidate for the development of novel types of heavy metals sensing.\u003c/p\u003e","manuscriptTitle":"Green synthesis of carbon nanodots (CNDs) moderated by flavonoid extracts from Moringa oleifera leaves and co-doped sulfur/nitrogen (NS – CNDs – Fla) and their potential for heavy metals sensing application","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-13 04:47:53","doi":"10.21203/rs.3.rs-4747067/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-07-29T11:52:11+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-07-28T13:48:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"52775469346816785587383345667202216729","date":"2024-07-23T16:51:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"181784168490707897183022215101431060700","date":"2024-07-23T13:03:56+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-07-23T12:22:25+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-07-18T19:50:23+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-07-18T19:50:07+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Fluorescence","date":"2024-07-16T04:56:54+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-fluorescence","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jofl","sideBox":"Learn more about [Journal of Fluorescence](https://www.springer.com/journal/10895)","snPcode":"10895","submissionUrl":"https://submission.nature.com/new-submission/10895/3","title":"Journal of Fluorescence","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"72348358-62af-41e2-a004-44de40f94ada","owner":[],"postedDate":"August 13th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-09-30T16:11:52+00:00","versionOfRecord":{"articleIdentity":"rs-4747067","link":"https://doi.org/10.1007/s10895-024-03931-2","journal":{"identity":"journal-of-fluorescence","isVorOnly":false,"title":"Journal of Fluorescence"},"publishedOn":"2024-09-25 15:58:10","publishedOnDateReadable":"September 25th, 2024"},"versionCreatedAt":"2024-08-13 04:47:53","video":"","vorDoi":"10.1007/s10895-024-03931-2","vorDoiUrl":"https://doi.org/10.1007/s10895-024-03931-2","workflowStages":[]},"version":"v1","identity":"rs-4747067","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4747067","identity":"rs-4747067","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}