Mercury Ions In Water Research Articles

Tailoring polythiophene nanocomposites with MnS/CoS nanoparticles for enhanced SERS detection of mercury ions in water

The excessive emission of heavy metal ions from industrial processes poses a serious threat to both the environment and human health. This study presents a novel approach using PTh-MnS/CoS NPs for the selective and sensitive detection of Hg2+ ions in water. Such detection is crucial for safeguarding human health, protecting the environment, and assessing toxicity. The fabrication method employs a simple and efficient chemical precipitation technique, combining polythiophene, MnS, and CoS NPs to create active substrates for SERS. The MnS@Hg2+ exhibits a distinct Raman shift at 938 cm−1, enabling specific identification and showing the highest responsiveness among the studied semiconductor substrates with a detection limit of only 1 nM. This investigation shows reliable and practical SERS detection for mercury ions. The RSD ranged from 0.49 % to 9.8 %, and recovery rates varied from 96 % to 102 %, showing selective adsorption of Hg2+ ions on the synthesized substrate.

The trace detection of Hg2+ by flexible electrochemical biosensor based on covalent organic framework synergistic amplified strategy

Mercury (II) ion (Hg2+) is highly toxic, which is harmful to the environment and human health. Hg2+ electrochemical detection method lacks high sensitivity and convenience. Thus, we fabricated a new-style flexible sandwich biosensor for ultra-sensitive identification of trace mercury ions in water. A large number of gold nanoparticles (AuNPs) were electrodeposited on the flexible electrode as the sensing interface, and the Au-functionalized covalent organic framework (COF) nanocomposites adsorbed a large amount of methylene blue (MB) were used as the signal amplifier. COF/Au provided a large specific surface area, which was easier to assemble with mercaptan functionalized capture DNAs (cDNA) aptamers via S-Au bonds for selective recognition of mercury, to improve the conductivity and electrochemical performance. Meanwhile, gold nanoparticles (AuNPs), MB and reporter DNA (rDNA) were anchored to COF to fabricate the COF/Au/MB/rDNA probe. The prepared COF based probe exhibited a large surface area, excellent electrical signal response, and good environmental compatibility. After incubation with Hg2+, rDNA was tightly bound to cDNA via thymidine-Hg2+-thymine pairing (T-Hg2+-T). Thus, the COF based probe was specifically connected to the flexible interface to generate electrical signals. Experimental results indicated that the biosensor exhibited wider linear response range of 0.1 pM to 100 nM Hg2+, and lower detection limit of 45.2 fM (3σ/k). In addition, the prepared ligand sensor also showed reliable detection performance in real water samples.

Construction of cellulose-based hybrid hydrogel beads containing carbon dots and their high performance in the adsorption and detection of mercury ions in water

Cellulose-based adsorbents have been extensively developed in heavy metal capture and wastewater treatment. However, most of the reported powder adsorbents suffer from the difficulties in recycling due to their small sizes and limitations in detecting the targets for the lack of sensitive sensor moieties in the structure. Accordingly, carbon dots (CDs) were proposed to be encapsulated in cellulosic hydrogel beads to realize the simultaneous detection and adsorption of Hg (II) in water due to their excellent fluorescence sensing performance. Besides, the molding of cellulose was beneficial to its recycling and further reduced the potential environmental risk generated by secondary pollution caused by adsorbent decomposition. In addition, the detection limit of the hydrogel beads towards Hg (II) reached as low as 8.8 × 10−8 M, which was below the mercury effluent standard declared by WHO, exhibiting excellent practicability in Hg (II) detection and water treatment. The maximum adsorption capacity of CB-50 % for Hg (II) was 290.70 mg/g. Moreover, the adsorbent materials also had preeminent stability that the hydrogel beads could maintain sensitive and selective sensing performance towards Hg (II) after 2 months of storage. Additionally, only 3.3% of the CDs leaked out after 2 weeks of immersion in water, ensuring the accuracy of Hg (II) evaluation. Notably, the adsorbent retained over 80% of its original adsorption capacity after five consecutive regeneration cycles, underscoring its robustness and potential for sustainable environmental applications.

Post-synthetic modification on metal organic frameworks composite for efficient removal and sensitive detection of mercury ions in water

Post-synthetic modification (PSM) technique is employed on the optimization of metal organic frameworks (MOFs) composites. In this work, a new Zr-MOF derived from UiO-66 is prepared and used as efficient adsorbents for mercury removal from water and able to detect mercury ions with excellent selectivity. It is observed that the fluorescence intensity of UiO-66-An exhibits good linearity across the concentration range of 0.5–2.5 μM and the detection limit of mercury is calculated to be as low as 2.67 × 10-8 M which is below the effluent standard declared by WHO. Furthermore, the removal efficiency of UiO-66-An for Hg (II) can still maintain 64.8 % after 5 cycles of adsorption–desorption process. In addition, the adsorption capacity of the adsorbent is determined to be as high as 303.03 mg/g for mercury, indicating the successful integration of adsorptive and detective functions together on a single adsorbent material which is beneficial for practical application in mercury management.

Revealing the interaction forms between Hg(II) and group types (–Cl, –CN, –NH2, –OH, –COOH) in functionalized Poly(pyrrole methane)s for efficient mercury removal

To explore the impact of different functional groups on Hg(II) adsorption, a range of poly(pyrrole methane)s functionalized by –Cl, –CN, –NH2, –OH and –COOH were synthesized and applied to reveal the interaction between different functional groups and mercury ions in water, and the adsorption mechanism was revealed through combined FT-IR, XPS, and DFT calculations. The adsorption performance can be improved to varying degrees by the incorporation of functional groups. Among them, the oxygen-containing functional groups (–OH and –COOH) exhibit stronger affinity for Hg(II) and can increase the adsorption capacity from 180 mg g−1 to more than 1400 mg g−1 at 318 K, with distribution coefficient (Kd) exceeding 105 mL g−1. The variations in the capture and immobilization capabilities of functionalized poly(pyrrole methane)s predominantly stem from the unique interactions between their functional groups and mercury ions. In particular, oxygen-containing –OH and –COOH effectively capture Hg(OH)2 through hydrogen bonding, and further deprotonate to form the –O–Hg–OH and –COO–Hg–OH complexes which are more stable than those obtained from other functionalized groups. Finally, the ecological safety has been fully demonstrated through bactericidal and bacteriostatic experiments to prove the functionalized poly(pyrrole methane)s can be as an environmentally friendly adsorbent for purifying contaminated water.

A doubly interpenetrated 3D nickel metal-organic framework for selective and sensitive turn-on sensing Hg2+ ions in water

Developing efficient fluorescent sensors for Hg2+ ions is significant due to the highly toxic and hazardous nature of Hg2+. Therefore, a novel nickel-metal framework [Ni-(Bibt)2-(ttpda)0.5] based on hybrid ligands 4,7-bis(1H-imidazol-1-yl)benzo[c][1,2,5]thiadiazole (Bibt) and 5,5′-(1,3,6,8-Tetraoxo-1,3,6,8-tetrahydrobenzo[lmn]-3,8-phenanthroline-2,7-diyl)diisophthalic acid (H4ttpda), briefly named as NiBT, was constructed, which exhibited a doubly interpenetrated 4, 6-connected fsc 3D network and a simplified topological symbol of {44∙610∙8}{44∙62}. In addition, NiBT showed high solvent and thermal stability, and pH durability (2.0 - 12.0). Moreover, NiBT could be used as a sensor for mercury ions in water with several favorable features including turn-on fluorescence changes, rapid response (within 30 s), high selectivity and sensitivity (LOD: 8.7 nM), broad pH response scope (4.0 - 11.0), and reusability (5 times). The sensing mechanism could be mainly attributed to the interactions between the Hg2+ and Bibt ligand by coordination with N atoms in the frameworks.

Synthesis of a water-stable CsPbBr3 perovskite for selective detection of mercury ion in water.

By using the method of low-temperature crystallization, CsPbBr3 perovskite nanocrystals (PNCs) coated with trifluoroacetyl lysine (Tfa-Lys) and oleamine (Olam) were synthesized in aqueous solution. The structure of the CsPbBr3 PNCs was characterized by many methods, such as ultraviolet (UV)-visible absorption spectrophotometer, fluorescence spectrophotometer, transmission electron microscopy (TEM), and X-ray diffraction (XRD) pattern. The fluorescence emission of the CsPbBr3 PNCs is stable in water for about 1 day at room temperature. It was also found that the fluorescence of the PNCs could be obviously and selectively quenched after the addition of mercury ion (Hg2+ ), allowing a visual detection of Hg2+ by the naked eye under UV light illumination. The fluorescence quenching rate (I0 /I) has a good linear relationship with the addition of Hg2+ in the concentration range 0.075 to 1.5 mg/L, with a correlation coefficient (R2 ) of 0.997, and limit of detection of 0.046 mg/L. The fluorescence quenching mechanism of the PNCs was determined by the fluorescence lifetime and X-ray photoelectron spectroscopy (XPS) of the PNCs. Overall, the synthesis method for CsPbBr3 PNCs is simple and rapid, and the as-prepared PNCs are stable in water that could be conveniently used for selective detection of Hg2+ in the water environment.

Advances in green materials derived from wood for detecting and removing mercury ions in water

The issue of mercury pollution in environmental remediation has garnered significant attention due to its severe health hazards to humans. Various strategies have been devised to mitigate the impact of toxic mercury ions, including coagulation, ion exchange, adsorption, membrane technology, and electrochemical treatment. Among these approaches, adsorption has emerged as an efficient and widely employed method for the uptake of low concentrations of mercury ions. It offers convenient operation, high removal efficiency, and facile regeneration of the adsorbent. Wood, being the most abundant renewable and sustainable bioresource, has garnered attention as a promising material for treating heavy metal wastewater. This is attributed to its unique physical and chemical characteristics, encompassing hierarchical pores, aligned channels, active functional groups, biodegradability, and cost-effectiveness. However, a comprehensive examination of the cutting-edge applications of wood and wood-derived biopolymers in the detection and removal of mercury ions from wastewater has yet to be undertaken. Consequently, this article presents a chronological overview of recent advancements in materials and structures derived from bulk wood and its constituents, including cellulose, lignin, hemicellulose, and tannin, with a specific focus on their utility in detecting and eliminating mercury from water sources. Subsequently, the most promising techniques and strategies involving wood and wood-derived biopolymers in addressing the predicament of mercury pollution are explored. Furthermore, this piece offers insights into the existing challenges and future prospects concerning environmentally friendly materials derived from wood, aiming to foster the development of cost-effective mercury adsorbents and detection devices.

Preparation of Self‐Assembled Starch‐Based Organometallic Polymers and Their Efficient Adsorption of Mercury Ion in Water

AbstractHerein, a newly‐developed material called Thiourea@WOx/Starch Polymer (TH@WOx/SP) is prepared by a one‐pot and high yield solvothermal method. It is not only equipped with porous structure but also has a superior adsorption capacity. The relevant characterizations and adsorption performance are analyzed by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Zeta potential analysis, and differential pulse voltammetry (DPV). Surprisingly, with its abundant active sites, the TH@WOx/SP reveals its excellent adsorption capacity for heavy metal and organics dye, as high as 2201.16 mg g−1 for Hg(II) and 175.01 mg g−1 for methylene blue (MB), finished within 30 and 90 min, respectively. These satisfactorily fast and high adsorption capacities not only come down to its concave–convex structure, but also to its enriched functional groups serving as anchor sites for Hg(II) and MB. The adsorption mechanism of Hg(II) and MB on TH@WOx/SP is carefully evaluated, which can be attributed to covalent coordination, ion exchange, π–π interactions, hydrogen bonds, and electrostatic attraction. This work designs a new strategy to develop a novel porous metal organic polymer adsorbents and demonstrates its prospective application in the field of adsorption.

Recyclable Multifunctional Magnetic Fe3O4@SiO2@Au Core/Shell Nanoparticles for SERS Detection of Hg (II)

Mercury ions can be enriched along the food chain and even low concentrations of mercury ions can seriously affect human health and the environment. Therefore, rapid, sensitive, and highly selective detection of mercury ions is of great significance. In this work, we synthesized Fe3O4@SiO2@Au three-layer core/shell nanoparticles, and then modified 4-MPy (4-mercaptopyridine) to form a SERS sensor. Mercury ions in water can be easily captured by 4-MPy which were used as the reporter molecules, and the concentration of mercury ions can be evaluated based on the spectral changes (intensification and reduction of peaks) from 4-MPy. After the mercury ion was combined with the pyridine ring, the peak intensity at 1093 cm−1 increased with the concentration of mercury ion in the range of 10 ppm–1 ppb, while the Raman intensity ratio I (416 cm−1)/I (436 cm−1) decreased with the increase of mercury ion concentration. This magnetically separatable and recyclable SERS sensor demonstrates good stability, accuracy, and anti-interference ability and shows the potential to detect actual samples. Furthermore, we demonstrate that the probe is applicable for Hg2+ imaging in macrophage cells.

Fabrication of Aptamer-based Field Effect Transistor Sensors for Detecting Mercury Ions

This study presents an extended gate aptamer-based FET sensor for the detection of mercury ions in water. Heavy metal contamination in water can pose a severe threat to human health, and mercury ions are particularly dangerous as they can accumulate in the human body and cause serious health problems. The sensor provides high selectivity and sensitivity, even in the presence of other heavy metals, and achieves a detection limit of 0.2 ppm using a 500 μm x 500 μm gate sensing area. This cost-effective and efficient method can contribute to the mitigation of environmental pollution and the protection of public health.

Dansyl-labelled cellulose as dual-functional adsorbents for elimination and detection of mercury in aqueous solution via aggregation-induced emission

Dansyl chloride fluorophore exhibits typical aggregation induced fluorescence emission behavior in acetone/water solution. To realize the integration of detective and adsorptive functions, dansyl chloride is covalently immobilized on cellulose substrate to fabricate an efficient adsorbent for mercury ions in water. The as-prepared material exhibits excellent fluorescence sensing performance exclusively for Hg (II) with the presence of other metal ions. A sensitive and selective fluorescence quenching across the concentration range of 0.1–8.0 mg/L is observed with a detection limit of 8.33 × 10−9 M as a result of the inhibition of aggregation induced emission caused by the coordination between adsorbent and Hg (II). Besides, the adsorption properties for Hg (II) including the influence of initial concentration and contact time are investigated. Langmuir model and pseudo-second-order kinetics are demonstrated to fit well with the adsorption experiment for the uptake of Hg (II) by the functionalized adsorbent, also, intraparticle diffusion kinetic model is proved to aptly describe the Hg (II) removal in aqueous solution. In addition, the recognition mechanism is considered to originate from the Hg (II) triggered structural reversals of naphthalene ring units which are verified by the X-ray photoelectron spectroscopy and density functional theory calculation. Moreover, the synthesis method used in this work also provides a strategy for the sensing application of organic sensor molecules with AIE properties in which the aggregated behavior could be appropriately realized.

Highly fluorescent hydroxyl groups functionalized graphitic carbon nitride for ultrasensitive and selective determination of mercury ions in water and fish samples

Heavy metal ion pollution is always a serious problem worldwide. Therefore, monitoring heavy metal ions in environmental water is a crucial and difficult step to ensure the safety of people and the environment. A mercury ion (Hg2+) fluorescence probe with excellent sensitivity and selectivity is described here. The functionalized graphitic carbon nitride nanosheets (T/G-C3N4) fluorescence probe was fabricated using melamine as a precursor by the pyrolysis technique, followed by a rapid KOH heat treatment method for 2 min. The chemical structure and morphology of the T/G-C3N4 probe were characterized using multiple analytical techniques including UV–Vis, SEM, XPS, XRD, and fluorometer spectroscopy. Geometry optimization of T/G-C3N4 as a modified probe was performed to assess its stability and interaction ability with Hg(II) via using the density function approach. The T/G-C3N4 probe showed a linear response based on quenching over the range 0–1.25 × 103 nM Hg(II); the detection limit was 27 nM. The remarkable sensitivity of T/G-C3N4 towards the Hg2+ ions was explained by the intense coordination and fast chelation kinetics of Hg2+ with the NH2, CN, C=N, and OH groups of T/G-C3N4 nanoprobe. The T/G-C3N4 probe demonstrates exceptional selectivity for Hg2+ ions among other metal ions including (Na+, Ag+, Mg2+, Fe2+, Fe3+, Co2+, Ni2+, Cd2+, K+, Ca2+, Cu2+, Pb2+, Mn2+ and Hg2+) and over a broad pH range (6–10), together with remarkable long-term fluorescence stability in water (> 30 days) and minimal toxicity. T/G-C3N4 was used to detect and quantify Hg2+ ions in tuna and mackerel fish and the results compared to ICP-AES. The results obtained offer a new simple and green technique for the design of multifunctional fluorescent probe appropriate for environmental applications.Graphical

Detection of Trace Hg(II) in Cosmetics and Aqueous Solution by a Gold Nanospikes Electrochemical Sensor

An ultrasensitive and rapid electrochemical detection of trace Hg(II) sensor was developed. The significantly amplified electrochemical signals was caused by the high specific surface area of the electrochemical sensor. Scanning electron microscopy showed that the gold nanospikes were 200 ∼ 300 nm in length and 50 nm in diameter. The electrochemical properties of sensor were characterized by square wave voltammetry. Experimental parameters were optimized using square wave stripping voltammetry. The linear range of sensor for Hg(II) is 3 × 10−10 mol l−1 ∼ 7 × 10−7 mol l−1 and the limit of detection is 1 × 10−10 mol l−1. Hg(II) was successfully quantified in river water and cosmetics. The original Hg(II) in loose powder, Sunblock and whitening lotion using the high ratio surface area electrochemical sensor determination were found to be 2.234, 2.056 and 2.347 mg kg−1 respectively. The results are within the range of standard values, the RSD are 1.7%, 1.5% and 2.1%, respectively. HRSA Au electrode sensor displays high sensitive, excellent stability, reproducibility, especially more convenient than ICP-MS and AFS verification methods. We look forward to the possibility that the HRSA Au electrode sensor can be used for real-time monitoring of Mercury ions in water and cosmetics in the future.

Highly selective fluorescent probe for detecting mercury ions in water.

Mercury ion (Hg2+) is a well-known toxic heavy metal. It has become one of the most significant environmental pollutants in the world because of its serious physiological toxicity, persistence, easy migration, and high bioconcentration. Thus, the development of methods for monitoring Hg2+ is indispensable. Herein, we have designed and synthesized a new fluorescent probe, TPH, for the detection of Hg2+ in the water environment. The TPH probe could quantitatively detect Hg2+ between 0 and 5 μM (LOD = 16 nM), with a linear range of 0-2.5 μM. In addition, the TPH probe was used to monitor Hg2+ in water samples successfully. Thus, this probe is suitable for monitoring Hg2+ in the actual water environment.

Biomass valorization of walnut shell into biochar as a resource for electrochemical simultaneous detection of heavy metal ions in water and soil samples: Preparation, characterization, and applications

Lately, due to its accessibility and eco-friendliness, walnut shell biochar (WS-BC) is gaining attention as an electrode material component in the electrochemical detection of water pollutants. The overall performance of WS-BC is reliant on the nature of raw biomass and the production methods as well. In our concept, biochar, prepared from raw walnut shell (WS) by pyrolysis, was added to a carbon paste electrode (CPE), and poly-tyrosine (p-Tyr) was electrodeposited on the surface of the BC-doped electrode. The conditions of the elaboration of the electrode, such as pH, potential, and the number of deposition cycles, pH were optimized. The obtained p-Tyr-BC-CPE platform was tested for the determination of cadmium, lead, copper, and mercury ions in water and soil samples, using square wave voltammetry (SWV). The raw WS biomass and its BC were examined by thermal analysis (TG-DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX) techniques. The synergistic effects of the coexistence of the WS-BC and the thin film of p-Tyr, for the detection of traces of heavy metal ions were investigated by electrochemical tests. The electrochemical characterization of the unmodified and modified electrodes was performed using the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods, while the Cd2+, Pb2+, Cu2+, and Hg2+ detection experiments were studied using the CV and SWV techniques. The optimized experimental conditions for the p-Tyr-BC-CPE platform were evaluated. The obtained electrochemical results showed that the p-Tyr-BC-CPE platform produced excellent sensitivity toward the heavy metal ions: LOD of 0.086, 0.175, 0.246, and 0.383 nM for Cd(II), Pb(II), Cu(II) and Hg(II), respectively. The modified electrode platform displayed high selectivity, stability, and good reproducibility.

Detecting mercury ions in water using a low-cost colorimetric sensor derived from immobilized silver nanoparticles on a paper substrate

The exceptional and specific reactivity of mercury ions (Hg2+) toward plasmonic silver nanoparticles (AgNPs) in aqueous media has motivated the need to develop innovative, low-cost, portable, and robust sensors to help address the detrimental effects of heavy metal contamination particularly in rural communities. In this paper, we present the plasmonic and colorimetric sensing of Hg2+ using a paper-based sensing material derived from thiamine-functionalized (ThAgNPs) that were immobilized on a commercial filter paper. Plasmonic AgNPs with a surface plasmon resonance peak at 420 nm and a size of about 21.3 nm were synthesized by a chemical reduction technique. Fourier transform infrared spectroscopy revealed the characteristic functional groups of thiamine in the spectra of AgNPs, thereby confirming the functionalization of AgNPs. The successful integration of ThAgNPs onto the Whatman filter paper (WFP) matrix was confirmed by the UV–vis and SEM-EDX results. An evident color change from yellowish to white was manifested by the fabricated WFP-ThAgNP sensor in the presence of Hg2+ with an appreciable detection of up to 0.5 µM using the naked eye. The colorimetric response of the sensor was also found to be selective towards Hg2+ after testing with different metal ions. Moreover, the response was consistent for tap, and creek water samples spiked with Hg2+. The results of this work provide a promising baseline technology for the development of an affordable, fast, portable, and reliable sensor that can be used for on-site detection and monitoring of Hg2+ levels in the water.

A Benzothidiazole-Based Reversible Fluorescent Probe with Excellent Performances in Selectively and Sensitively Sensing of Hg2+ in Water

The development of mercury ion selective fluorescent probe is significant because it is one of toxic heavy metals and poses great risks and hazards to human health. Herein, we develop a mercury ion-selective fluorescent probe, namely IB, based on imidazole decorated benzothiadiazole that obtained by a facile palladium catalytic C-N coupling reaction. IB exhibits high selectivity and sensitivity towards mercury ion in water with nearly 32-fold fluorescent enhancement. The detection limit is calculated to be 0.93 nmol/L. In addition, the sensing of mercury ion can be conducted in a wide pH scope ranging from 4.0 to 10.0. Subsequently, the mercury ion elicits fluorescence of IB solution can be quenched by the addition of cyanide anions, showing "off-on-off" fluorescence transformation with at least 5 cycles, demonstrating the reversible sensing ability of IB. Furthermore, an INHIBIT logical detector has been developed using mercury ion and cyanide anions as inputs and fluorescence of IB as output. Significantly, IB can be utilized for mercury ion detection in real water sample.

Detection and Removal of Mercury Ions in Water by a Covalent Organic Framework Rich in Sulfur and Nitrogen

Hg/Hg(II) is deemed to be the most toxic heavy metal to humans. Therefore, designing suitable adsorbents to simultaneously achieve high capacity, rapid mercury adsorption, and fluorescence detection is still an important challenge in overcoming Hg2+ pollution. Here, we report a flexible alkylamine covalent organic framework (TpTSC), which has been used as an efficient adsorbent and achieves the dual-functional application of TpTSC for Hg2+, with a fluorescence detection limit of 2 ppm and simultaneously a removal capacity of 1035 mg g–1. It can remove 10 ppm mercury solution to below 2 ppb (drinking water standard) within 10 min, and the removal rate is as high as 99.98%. To a certain extent, it exceeds the recently reported thioether or thiol functionalized adsorbents. The kinetic study shows that TpTSC displays a very high Kd value, with Kd = 1.2 × 109 mL g–1, which has a strong affinity for mercury. In addition, TpTSC displays a good recycling capacity, with a removal rate of over 90% after five cycles. In conclusion, sulfur modification is a useful strategy for developing dual-functional COFs to simultaneously remove and detect toxic heavy metal ions.

Colorimetric sensing of mercury ions using green synthesized silver nanoparticles from Trigonella foenum (Linnaeus)

Mercury ion sensing is an essential technology in water polluted countries especially India, China, south east Asian countries etc. This type of technology heavily relies on nano-sensing with silver nanoparticles. Colorimetric sensors are optical sensors that change color in response to an external input. A colorimetric sensor was developed to detect hazardous mercury ions in water. Silver nanoparticles will lose its UV–Vis absorption intensity when combined with mercury ions. Plant extract of Trigonella foenum (Linnaeus) was used to prepare silver nanoparticles in this study. Having a cubic form and an average crystallite size of 27.24 nm, the silver nanoparticles are widely distributed. Nanoparticles were found to be crystalline and has a cubic phase of geometry, as demonstrated by XRD and SEM investigation. Using biosynthesized Ag nanoparticles, we demonstrate very sensitive and specific colorimetric detection of the mercury ion (Hg2+).