Photo-mediated optimized synthesis of silver nanoparticles for the selective detection of Iron(III), antibacterial and antioxidant activity

Visible Periodic Piezoelectric Domains in Silk Fibroin for Neurite-Orientated Extension

The development of visible periodic piezoelectric domains is highly attractive but challenging to overcome the homogeneous distribution and lack of visualization of the electric field on traditional piezopolymers. This work reports an in situ synthesis to create customized silver patterns with micron-level distinguishability. This method serves to form visible periodic piezoelectric domains and endows the silk fibroin (SF) piezoelectric generator with maximum root mean square current, energy density, and voltage of 5.1 mA, 6.7 W m-2 and 529.5 mV, respectively, under an ultrasound intensity of 1.0 W cm-2. The oriented piezoelectric electric field is periodically distributed into the SF film with ultrasound-driven assistance and remarkably regulates neurite directional growth, length, and gene expression. Additionally, these piezoelectric domains enable the direct and timely observation of the electric field's effect on neurites by biological microscopy. This approach paves the way for great potential in tailored electric stimulation for cell biology and medical engineering.

Antioxidant Efficacy of Green-Synthesized Silver Nanoparticles Promotes Wound Healing in Mice

Developing an efficient and cost-effective wound-healing substance to treat wounds and regenerate skin is desperately needed in the current world. Antioxidant substances are gaining interest in wound healing, and green-synthesized silver nanoparticles have drawn considerable attention in biomedical applications due to their efficient, cost-effective, and non-toxic nature. The present study evaluated in vivo wound healing and antioxidant activities of silver nanoparticles from Azadirachta indica (AAgNPs) and Catharanthus roseus (CAgNPs) leaf extracts in BALB/c mice. We found rapid wound healing, higher collagen deposition, and increased DNA and protein content in AAgNPs- and CAgNPs (1% w/w)-treated wounds than in control and vehicle control wounds. Skin antioxidant enzyme activities (SOD, catalase, GPx, GR) were significantly (p < 0.05) increased after 11 days CAgNPs and AAgNPs treatment. Furthermore, the topical application of CAgNPs and AAgNPs tends to suppress lipid peroxidation in wounded skin samples. Histopathological images evidenced decreased scar width, epithelium restoration, fine collagen deposition, and fewer inflammatory cells in CAgNPs and AAgNPs applied wounds. In vitro, the free radical scavenging activity of CAgNPs and AAgNPs was demonstrated by DPPH and ABTS radical scavenging assays. Our findings suggest that silver nanoparticles prepared from C. roseus and A. indica leaf extracts increased antioxidant status and improved the wound-healing process in mice. Therefore, these silver nanoparticles could be potential natural antioxidants to treat wounds.

Preparation of temperature-responsive nanomicelles with AIE property as fluorescence probe for detection of Fe3+ and Fe2

Temperature-responsive nanomicelles with aggregation induced emission (AIE) property were prepared by the host-guest complexation of ferrocene functionalized tetraphenyl (TPE-Fc) and β-cyclodextrin-poly (N-isopropylacrylamide) (β-CD-(PNIPAM)₇). The AIE chromophore TPE-Fc bound to the hydrophobic cavity of cyclodextrin serves as the core of micelles, and temperature sensitive PNIPAM serves as the shell to give the micelles good solubility. The size of the nanomicelles is about 100 nm. At the excitation wavelength of 340 nm, the strongest fluorescent emission peak was 421 nm. The introduction of cyclodextrin star polymer increased the fluorescence intensity of nanomicelles, thus improving the recognition of probe to Fe³⁺ and Fe²⁺. The fluorescent probe can quickly detect Fe³⁺ and Fe²⁺ in water within 5 min even in the presence of various interfering ions. The detection limits of Fe³⁺ and Fe²⁺ were 1.04 μM and 0.78 μM, respectively in the range of 10-90 μM. The formation of complex between the probe and Fe³⁺/Fe²⁺ was supported by Job's plot. The probe was successfully applied to the detection of Fe³⁺and Fe²⁺ in actual water sample with a good recovery. In addition, a possible sensing mechanism for the interaction of iron ions with amide bond groups of nanomicelles was proposed.

Controllable 3D Flower-Like Ag-CF Electrodes as Flexible Marine Electric Field Sensors with High Stability

Construction of three-dimensional (3D) flower-like nanostructures with controlled morphologies has emerged as an attractive tool by scientists in the marine electric field sensor research field due to their peculiar structural features. Herein, novel 3D flower-like Ag-CF capacitive composite electrodes have been created by an eco-friendly water-bath strategy via AgNO₃ as a sliver source and subsequently compounded with carbon fibers (CFs) pretreated by thermal oxidation. A series of electrode samples with various morphologies obtained by modulating different reaction times and temperatures bring about the dominant formation mechanism of these nanostructures and the influence behavior on the CF electrode in detail. Especially, the 3D flower-like Ag-CF electrode shows a large surface area acquired under the conditions of 80 °C and 15 min, which can provide more electroactive sites in electrochemical analysis and exhibit a maximum areal specific capacitance of 619.75 mF·cm^-2 at a scanning speed of 10 mV·s^-1. This is mainly due to the synergistic behavior of the unique 3D flower-like morphology and the large specific surface area of CFs. Furthermore, a cylinder-shaped Ag-CF sensor is designed, which delivers a superior potential difference of 33.08 μV, a potential difference drift of 18.62 μV/24 h for 30 days, and a self-noise of 0.92 nV/rt (Hz)@1 Hz. In this work, the intriguing synthesis strategy can be a promising facile approach to manufacture the controllable 3D flower-like Ag-CF electrode for electric field sensor applications.

Phytofabrication and Characterisation of Zinc Oxide Nanoparticles Using Pure Curcumin

Zinc oxide and curcumin, on their own and in combination, have the potential as alternatives to conventional anticancer drugs. In this work, zinc oxide nanoparticles (ZnO NPs) were prepared by an eco-friendly method using pure curcumin, and their physicochemical properties were characterised. ATR-FTIR spectra confirmed the role of curcumin in synthesising zinc oxide curcumin nanoparticles (Green-ZnO-NPs). These nanoparticles exhibited a hexagonal wurtzite structure with a size and zeta potential of 27.61 ± 5.18 nm and -16.90 ± 0.26 mV, respectively. Green-ZnO-NPs showed good activity towards studied bacterial strains, including Escherichia coli, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. The minimum inhibitory concentration of Green-ZnO-NPs was consistently larger than that of chemically synthesised ZnO NPs (Std-ZnO-NPs) or mere curcumin, advocating an additive effect between the zinc oxide and curcumin. Green-ZnO-NPs demonstrated an efficient inhibitory effect towards MCF-7 cells with IC50 (20.53 ± 5.12 μg/mL) that was significantly lower compared to that of Std-ZnO-NPs (27.08 ± 0.91 μg/mL) after 48 h of treatment. When Green-ZnO-NPs were tested against Artemia larvae, a minimised cytotoxic effect was observed, with LC50 being almost three times lower compared to that of Std-ZnO-NPs (11.96 ± 1.89 μg/mL and 34.60 ± 9.45 μg/mL, respectively). This demonstrates that Green-ZnO-NPs can be a potent, additively enhanced combination delivery/therapeutic agent with the potential for anticancer therapy.

Nanomaterials photocatalytic activities for waste water treatment: a review

Water is necessary for the survival of life on Earth. A wide range of pollutants has contaminated water resources in the last few decades. The presence of contaminants incredibly different dyes in waste, potable, and surface water is hazardous to environmental and human health. Different types of dyes are the principal contaminants in water that need sudden attention because of their widespread domestic and industrial use. The toxic effects of these dyes and their ability to resist traditional water treatment procedures have inspired the researcher to develop an eco-friendly method that could effectively and efficiently degrade these toxic contaminants. Here, in this review, we explored the effective and economical methods of metal-based nanomaterials photocatalytic degradation for successfully removing dyes from wastewater. This study provides a tool for protecting the environment and human health. In addition, the insights into the transformation of solar energy for photocatalytic reduction of toxic metal ions and photocatalytic degradation of dyes contaminated wastewater will open a gate for water treatment research. The mechanism of photocatalytic degradation and the parameters that affect the photocatalytic activities of various photocatalysts have also been reported.

A Highly Selective and Sensitive Nano-Silver sol Sensor for Hg2+ and Fe3+: Green Preparation and Mechanism

The development of highly selective and highly sensitive nanometer colorimetric chemical sensors is an urgent requirement in the immediate detection of heavy metal ions. In this work, silver-nanoparticle (Ag NPs)-based chemosensors were prepared by a simple and green method, in which the silver nitrate, carboxymethyl cellulose sodium (CMS) and Polyvinylpyrrolidone (PVP), and glucose are used as the silver source, double stabilizer and green reductant, respectively. The obtained colloidal CMS/PVP-Ag NPs showed a high dispersibility and stability, and creating a high selectivity and sensitivity to detect Hg2+ and Fe3+ with remarkable and rapid color variation. Low limits of detection (LOD) of 7.1 nM (0–20 μM) and 15.2 nM (20–100 μM) for Hg2+ and 3.6 nM for Fe3+ were achieved. More importantly, the CMS/PVP-Ag NPs has a high sensitivity even in a complex system with multiple heavy ions, the result of the practical ability to detect Hg2+ and Fe3+ in tap water and seawater reached a rational range of 98.33~104.2% (Hg2+) and 98.85~104.80% (Fe3+), indicating the great potential of the as-prepared nanocomposites colorimetric chemosensor for practical applications.

Biosynthesis of silver nanoparticles using Lawsonia inermis and their biomedical application

Developing biosynthesis of silver nanoparticles (Ag‐NPs) using plant extract is an environmentally friendly method to reduce the use of harmful chemical substances. The green synthesis of Ag‐NPs by Lawsonia inermis extract and its cellular toxicity and the antimicrobial effect was studied. The physical and chemical properties of synthesised Ag‐NPs were investigated using UV‐visible spectroscopy, infrared spectroscopy, X‐ray diffraction (XRD), scanning, and transmission electron microscopy. The average size of Ag‐NPs was 40 nm. The XRD result shows peaks at 2θ = 38.07°, 44.26°, 64.43°, and 77.35° are related to the FCC structure of Ag‐NPs. Cytotoxicity of synthesised nanoparticles was evaluated by MTT toxicity test on breast cancer MCF7 cell line. Observations showed that the effect of cytotoxicity of nanoparticles on the studied cell line depended on concentration and time. The obtained IC₅₀ was considered for cells at a dose of 250 μg/ml. Growth and survival rates decreased exponentially with the dose. Antimicrobial properties of Ag‐NPs synthesised with extract were investigated against Escherichia coli, Salmonella typhimurium, Bacillus cereus, and Staphylococcus aureus to calculate the minimum inhibitory concentration and the minimum bactericidal concentration of (MBC). The results showed that the synthesised Ag‐NPs and the plant extract have antimicrobial properties. The lowest concentration of Ag‐NPs that can inhibit the growth of bacterial strains was 25 μg/ml.

Light-Emitting-Diode-Assisted, Fungal-Pigment-Mediated Biosynthesis of Silver Nanoparticles and Their Antibacterial Activity

Nanoparticle synthesis, such as green synthesis of silver nanoparticles (AgNPs) using biogenic extracts, is affected by light, which changes the characteristics of particles. However, the effect of light-emitting diodes (LEDs) on AgNP biosynthesis using fungal pigment has not been examined. In this study, LEDs of different wavelengths were used in conjunction with Talaromyces purpurogenus extracellular pigment for AgNP biosynthesis. AgNPs were synthesized by mixing 10 mL of fungal pigment with AgNO₃, followed by 24 h exposure to LEDs of different wavelengths, such as blue, green, orange, red, and infrared. All treatments increased the yield of AgNPs. The solutions exposed to blue, green, and infrared LEDs exhibited a significant increase in AgNP synthesis. All AgNPs were then synthesized to determine the optimum precursor (AgNO₃) concentration and reaction rate. The results indicated 5 mM AgNO₃ as the optimum precursor concentration; furthermore, AgNPs-blue LED had the highest reaction rate. Dynamic light scattering analysis, zeta potential measurement, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to characterize the AgNPs. All LED-synthesized AgNPs exhibited an antimicrobial potential against Escherichia coli and Staphylococcus aureus. The combination of LED-synthesized AgNPs and the antibiotic streptomycin demonstrated a synergistic antimicrobial activity against both bacterial species.

Biogenic Silver Nanoparticles of Clinacanthus nutans as Antioxidant with Antimicrobial and Cytotoxic Effects

Silver nanoparticles (AgNPs) previously synthesised using leaf (AgNP-L) and stem (AgNP-S) extracts of Clinacanthus nutans (C. nutans) were tested to evaluate antimicrobial, antioxidant, and cytotoxicity activities. The AgNPs showed good inhibition against bacteria, but not fungi. The inhibition results showed the highest activity against Staphylococcus aureus (S. aureus) with 11.35 mm (AgNP-L) and 11.52 mm (AgNP-S), while the lowest inhibition was against Escherichia coli (E. coli) with 9.22 mm (AgNP-L) and 9.25 mm (AgNP-S) in the disc diffusion method. The same trend of results was noted in the well diffusion method. The IC50 of AgNP-L and AgNP-S in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays was 417.05 μg/mL and 434.60 μg/mL, as well as 304.31 μg/mL and 326.83 μg/mL, respectively. Ferric reducing power (FRAP) assay showed that AgNP-L [872.389 μmol/L Fe(II)] and AgNP-S [612.770 μmol/L Fe(II)] exhibited significantly (p < 0.05) greater antioxidant activities than leaf extract (CNL) [152.260 μmol/L Fe(II)] and stem extract (CNS) [110.445 μmol/L Fe(II)] of C. nutans. The AgNPs were also proven to possess cytotoxic effects on the breast (MCF-7), cervical (HeLa), and colon (HT-29) cancer cells in a dose-dependent manner. AgNP-S and AgNP-L showed significantly (p < 0.05) higher cytotoxicity against MCF-7 (117.43 μg/mL) and HT-29 (78.47 μg/mL), respectively. In conclusion, the biosynthesised AgNPs from aqueous extract leaves and stem of C. nutans have demonstrated promising potential towards antioxidant, antimicrobial, and cytotoxicity activities.

Biosynthesis of CuO nanoparticles using aqueous extract of herbal tea (Stachys Lavandulifolia) flowers and evaluation of its catalytic activity

Plant derived biogenic synthesis of nanoparticles (NP) has been the recent trend in material science as featured sustainable catalysts. A great deal of the current nanocatalytic research has been oriented on the bio-inspired green catalysts based on their wide applicability. In this context, CuO NPs are synthesized following a green approach using an herbal tea (Stachys Lavandulifolia) flower extract. The phytochemicals contained in it were used asthe internal reductant without applying harsh chemicals or strong heat. The derived nanoparticles also got stabilized by the biomolecular capping. The as-synthesized CuO NPs was characterized over FT-IR, FE-SEM, EDS, TEM, XRD, TGA and UV–Vis spectroscopy. These NPs were exploited as a competent catalyst in the aryl and heteroaryl C–heteroatom (N, O, S) cross coupling reactions affording outstanding yields. The nanocatalyst was isolated and recycled in 8 consecutive runs with reproducible catalytic activity. Rigidity of the CuO/S. Lavandulifolia nanocomposite was further justified by leaching test and heterogeneity test.

Photo-mediated optimized synthesis of silver nanoparticles using the extracts of outer shell fibre of Cocos nucifera L. fruit and detection of its antioxidant, cytotoxicity and antibacterial potential

Presently, photo-mediated optimized synthesis of SNPs (CS-AgNPs) was carried out with the help of aqueous extracts of coconut (Cocos nucifera) outer shell fibre. Green synthesis of CS-AgNPs was undertaken under laboratory light conditions and characterized by several standard techniques such as UV–visible spectrophotometer (UV–Vis), X-ray diffraction pattern (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDX). UV–Vis spectra displayed a surface plasmon resonance peak at 468 nm equivalent to CS-AgNPs, and the FT-IR spectra confirmed the association of biological molecules from the extract in the synthesis process. The SEM image data confirmed the round and circular nature of CS-AgNPs. The EDX data presented the elemental configuration with a solid peak at 3 KeV that matched with the Ag. The synthesized CS-AgNPs exhibited substantial cytotoxicity potential against the HepG2 cells with (effective concentration (IC₅₀) value of 15.28 µg/ml along with robust antioxidant potential, with respect to its 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging (IC₅₀ of 96.39 µg/ml) and reducing assay (IC_0.5 of 209.96 µg/ml). The CS-AgNPs demonstrated encouraging antimicrobial potential against four different pathogenic bacteria and one Candida sp. with inhibition zone diameter ranged between 8.87 and 13.07 mm. Overall, the existing investigation suggested that CS-AgNPs can be an attractive, cost-effective, and environment-friendly candidate for its possible uses in the food, cosmetics, and therapeutic fields.

Green Synthesis of Gold Nanoparticles Capped with Procyanidins from Leucosidea sericea as Potential Antidiabetic and Antioxidant Agents

In this study, procyanidins fractions of dimers and trimers (F1-F2) from the Leucosidea sericea total extract (LSTE) were investigated for their chemical constituents. The total extract and the procyanidins were employed in the synthesis of gold nanoparticles (Au NPs) and fully characterized. Au NPs of 6, 24 and 21 nm were obtained using LSTE, F1 and F2 respectively. Zeta potential and in vitro stability studies confirmed the stability of the particles. The enzymatic activity of LSTE, F1, F2 and their corresponding Au NPs showed strong inhibitory alpha-amylase activity where F1 Au NPs demonstrated the highest with IC₅₀ of 1.88 µg/mL. On the other hand, F2 Au NPs displayed the strongest alpha-glucosidase activity at 4.5 µg/mL. F2 and F2 Au NPs also demonstrated the highest antioxidant activity, 1834.0 ± 4.7 μM AAE/g and 1521.9 ± 3.0 μM TE/g respectively. The study revealed not only the ability of procyanidins dimers (F1 and F2) in forming biostable and bioactive Au NPs but also, a significant enhancement of the natural products activities, which could improve the smart delivery in future biomedical applications.

Interaction of Ag+ with soil organic matter: Elucidating the formation of silver nanoparticles

Naturally silver nanoparticles (AgNPs) have been widely observed in ore deposits, coal, natural water and soil environment. Identifying the source of these naturally AgNPs could be helpful for the elucidation of the geochemical cycle of Ag⁺ and AgNPs. This paper presents the formation of AgNPs by reducing Ag⁺ in the presence of soil organic matter (SOM) under various environmentally relevant conditions. The formation of AgNPs associated with various SOM (peat humic acid (PHA), peat fulvic acid (PFA), and commercial humic acids (HA-1 and HA-2)) was determined and compared. The physicochemical properties of the tested SOM were studied by electron paramagnetic resonance (EPR) and attenuated total reflection-infrared (ATR-FTIR) techniques. The formation of AgNPs depended on reductive reactions mediated by SOM. Other influential parameters that influenced the formation of AgNPs included concentrations of Ag⁺ and SOM and the reaction temperature on AgNPs. The produced AgNPs were characterized by transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The mean hydrodynamic diameters of AgNPs associated with PHA and PFA were in range from 2.5 to 15 nm, which were smaller than that produced from HA-1 and HA-2 in the range from 20 to 120 nm. Two different Ag states, i.e., Ag₂O and Ag⁰ species, were observed by XPS technique. The results indicated that the formation of AgNPs depends largely on the types and the properties of natural organic matter. These findings have important implications for the fate of AgNPs under the soil environment.

Green synthesis of Au nanoparticles using an aqueous extract of Stachys lavandulifolia and their catalytic performance for alkyne/aldehyde/amine A3 coupling reactions

High reaction rate and easy availability make green synthesis of metal nanoparticles noticeable. In the present study, gold nanoparticles with wide applications in different fields were synthesized by an ecofriendly method at room temperature using Stachys lavandulifolia extract as the reducing agent. Properties of the synthesized gold nanoparticles (GNP) were identified by different analytical techniques including: UV-Vis absorption spectroscopy verified presence of Au NPs in the solution while functional groups of its extract and synthesized Au NPs were determined by FT-IR. Its crystalline analysis with a fcc plane was verified by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) determined elements in the sample. Surface morphology, diverse shapes and sizes of the Au NPs were shown by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). Beginning and end destruction temperatures of the Au/S. lavandulifolia NPs were determined by thermal gravimetric analysis (TGA). The Au nanoparticles were capped with extracts, preventing them from oxidation and agglomeration and were used as an efficient heterogeneous nanocatalyst for a three-component reaction of amines, aldehydes, and alkynes (A3 coupling). A diverse range of propargylamines were obtained in good yields. Furthermore, the separation and recycling of Au/S. lavandulifolia NPs was very simple, effective, and economical.

Antioxidant, antimicrobial and cytotoxic potential of silver nanoparticles synthesized using flavonoid rich alcoholic leaves extract of Reinwardtia indica

The present work discusses the establishment of a green route for the rapid synthesis of silver nanoparticles (AgNPs) using an alcoholic extract of Reinwardtia indica (AERI) leaves which act as a reducing as well as a capping agent. The change in color from yellowish green to dark brown confirmed the synthesis of AgNPs. A characteristic surface plasmon resonance (SPR) band at 436 nm advocated the presence of AgNPs. The synthesis process was optimized using one factor at a time approach where 1.0 mM AgNO₃ concentration, 5 mL 0.4% (v/v) of AER inoculum dose and 30 min of sunlight exposure were found to be the optimum conditions. The synthesized AgNPs was characterized by several characterizing techniques such as HR- TEM, SAED, HR-SEM, EDX, XRD, FTIR and AFM analysis. For evaluation and comparison of AgNPs with AERI used human pathogen E. coli, P. aeurogenosa, S. aeurus and C. albicans for antimicrobial, for cytotoxicity study SiHa cell line at concentration of (10, 50, 100, 250 and 500 µg mL^-1) and for enzymatic assay superoxide dismutase, catalase, malondialdehyde and glutathione peroxidase method were used. The size of nanoparticle in the range of 3-15 nm was confirmed TEM, spherical shape by SEM and crystal lattice nature by XRD. AFM results revealed the 2 D and 3 D pattern of particle scatter nature on the surface. This protocol as simple, rapid, one step, eco-friendly, nontoxic and AgNPs showed strong antimicrobial activity as well as cytotoxic potential in comparison to AERI.

Bactericidal Properties of Plants-Derived Metal and Metal Oxide Nanoparticles (NPs)

Nanoparticles (NPs) are nano-sized particles (generally 1–100 nm) that can be synthesized through various methods. The wide range of physicochemical characteristics of NPs permit them to have diverse biological functions. These particles are versatile and can be adopted into various applications, particularly in biomedical field. In the past five years, NPs’ roles in biomedical applications have drawn considerable attentions, and novel NPs with improved functions and reduced toxicity are continuously increasing. Extensive studies have been carried out in evaluating antibacterial potentials of NPs. The promising antibacterial effects exhibited by NPs highlight the potential of developing them into future generation of antimicrobial agents. There are various methods to synthesize NPs, and each of the method has significant implication on the biological action of NPs. Among all synthetic methods, green technology is the least toxic biological route, which is particularly suitable for biomedical applications. This mini-review provides current update on the antibacterial effects of NPs synthesized by green technology using plants. Underlying challenges in developing NPs into future antibacterials in clinics are also discussed at the present review.

Enhanced electron transfer mediated detection of hydrogen peroxide using a silver nanoparticle–reduced graphene oxide–polyaniline fabricated electrochemical sensor

The current study aims at the development of an electrochemical sensor based on a silver nanoparticle–reduced graphene oxide–polyaniline (AgNPs–rGO–PANI) nanocomposite for the sensitive and selective detection of hydrogen peroxide (H₂O₂).

Green synthesis of silver nanoparticle for the selective and sensitive colorimetric detection of mercury (II) ion

An ecofriendly and zero cost approach has been developed for the photoinduced synthesis of more stable AgNPs using an aqueous extract of Murraya koenigii (AEM) as a reducing and stabilizing agent. The exposed reaction mixture of AEM and AgNO₃ to sunlight turned dark brown which primarily confirmed the biosynthesis of AgNPs. The biosynthesis was monitored by UV-vis spectroscopy which exhibited a sharp SPR band at 430nm after 30min of sunlight exposure. The optimum conditions for biosynthesis of AgNPs were 30min of sunlight exposure, 2.0% (v/v) of AEM inoculuam dose and 4.0mM AgNO₃ concentration. TEM analysis confirmed the presence of spherical AgNPs with average size 8.6nm. The crystalline nature of the AgNPs was confirmed by XRD analysis where the Bragg's diffraction pattern at (111), (200), (220) and (311) corresponded to face centered cubic crystal lattice of metallic silver. The surface texture was analyzed by AFM analysis where the average roughness of the synthesized AgNPs was found 1.8nm. FTIR analysis was recorded between 4000 and 400cm^-1 which confirmed the involvement of various functional groups in the synthesis of AgNPs. On the basis of the linear relationship between SPR band intensity and different concentration of Hg²⁺, the synthesized AgNPs can be used for colorimetric detection of Hg²⁺ with a linear range from 50nm to 500μM. Based on experimental findings, an oxidation-reduction mechanism between AgNPs and Hg²⁺ was also proposed.