Peroxidase Mimetic Activity Research Articles

Ultrasensitive Pd nano catalyst as peroxidase mimetics for colorimetric sensing and evaluation of antioxidants and total polyphenols in beverages and fruit juices

Herein, we developed a new Pd NP from the aq extract of Elsholtzia blanda Benth. flower that showed efficient peroxidase mimetic activity. The catalytic mechanism was confirmed through colorimetric analysis. The optimizations of temperature, concentration, PH and time were done to find out the best procedure to implement the intrinsic catalytic activity in practical applications. Michaelis-Menten constants were evaluated for both TMB and H2O2 substrate to investigate the affinity of Pd NP towards them. Km was observed to be 42.35 mM for H2O2 and 0.0076 mM for TMB. Antioxidants were sensed using the peroxidase mimetic property up to nanomolar levels with a LOD = 0.78 nM for Gallic acid 0.85 nM for Tannic acid. The method was further implemented in comparing the radical scavenging power of different phenolic compounds. Smart-phone based analysis was done for observing the change in colour which could further be utilized as an analytical tool for study the antioxidant activity. R-Square values of 0.97 and 0.96 for detection of gallic acid and tannic acid respectively suggest good linearity of the plot. Lastly, the system was utilized in the evaluation of total antioxidant capacity (TAC) and total phenolic content (TPC) in commercially available juices and beverages.

Introducing hierarchical hollow MnO2 microspheres as nanozymes for colorimetric determination of captopril.

A simple sensor was developed for the colorimetric determination of captopril (CPT). Herein, hierarchical hollow MnO2 microspheres (HH-MnO2) were applied as nanozymes with peroxidase-mimetic activity. Free cation radicals with a strong absorption signal (λmax at 653nm) were generated via a redox reaction between 3, 3', 5, 5'-tetramethylbenzidine (TMB) and HH-MnO2. Captopril could successfully prevent the generation of blue-colored free cation radicals. The influence of CPT concentration on the absorption of the generated radicals was monitored by UV-Vis spectroscopy. The corresponding linear concentration range was from 1.0 to 30.0μgmL-1 (4.6-138.1μmolL-1), and the detection limit was found to be 0.26μgmL-1 (1.2μmolL-1). As a practical usage, the developed sensor was effectively utilized to measure the content of CPT in pharmaceutical formulations.

Cobalt-Doped Carbon Quantum Dots with Peroxidase-Mimetic Activity for Ascorbic Acid Detection through Both Fluorometric and Colorimetric Methods.

In this work, we fabricated cobalt-doped carbon quantum dots (Co-CQDs) by a one-pot hydrothermal method with cobalt tetraphenylporphyrin and 1,2-ethanediamine as precursors. The morphology and structure of the Co-CQDs were characterized through transmission electron microscopy, X-ray diffraction spectra, Fourier transform infrared, and X-ray photoelectron spectra. The Co-CQDs emitted intense blue luminescence under ultraviolet irradiation and exhibited a typical excitation-dependent emission property. Moreover, they can act as a fluorescent probe for the detection of Fe3+ and ascorbic acid (AA) with high selectivity and sensitivity through an "on-off-on" mode. The limit of detection (LOD) of Fe3+ was measured as 38 μM (S/N = 3). The quenched emission of carbon quantum dots can be recovered with the addition of ascorbic acid (AA) to the Co-CQDs/Fe3+ system. The change of fluorescence was linear with the concentration of AA (0.6-1.6 mM) with the LOD of 18 μM. Furthermore, the Co-CQDs exhibited high oxidase-like catalytic behavior, which could convert transparent 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB by dissolved oxygen. After adding ascorbic acid to the Co-CQDs/TMB system, the blue color of the solution faded due to the reduction of blue ox-TMB to colorless TMB. Based on this phenomenon, the Co-CQDs were capable of detecting AA (10-400 μM) with the LOD of 0.27 μM. The fluorometric and colorimetric assays based on the Co-CQDs for the AA detection were then successfully applied in fresh fruits. Furthermore, the high biocompatibility of the Co-CQDs against HeLa cells was verified by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Thus, the Co-CQDs could be used as a powerful tool for the detection of AA in real samples through a dual-mode method.

Polymeric-coated Fe-doped ceria/gold hybrid nanocomposite as an aptasensor for the catalytic enhanced colorimetric detection of 2,4-dinitrophenol

The Meisenheimer charge transfer reaction has, for many years, been the predominant mode of interaction to detect explosive compounds via the naked eye. However, this method is majorly sensitive to 2,4,6-trinitrotoluene and insensitive to many other explosive compounds. In this work, we report on the development of a novel aptamer-based amphiphilic polymer-coated Fe-doped ceria/gold (Au) hybrid nanocomposite (NC) as a peroxidase mimetic nanozyme for explosive colorimetric detection. Polymeric-Fe-doped ceria NC was synthesized and incorporated in-situ in the hydrothermal synthetic pot of citrate-Au nanoparticles to form a polymer-Fe-doped ceria/Au NC. A streptavidin (strep)-biotinylated DNA aptamer (B-Apt) binding complex was immobilised on the polymer-Fe-doped ceria/Au NC surface and the modified NC was used as a functional nanozyme in a peroxidase mimic assay to catalyse the oxidation of 3,3′,5,5′-tetramethylbenzidine by H2O2. Screening of several explosives showed that 2,4-dinitrophenol (DNP) bonded with higher affinity to the aptamer based on the selective greenish colorimetric catalytic reaction observed. The peroxidase mimetic activities of several nanozymes were tested and our analysis showed that the polymer-Fe-doped ceria/Au NC generated enhanced catalytic activity for DNP detection. Several optimisation reactions including the kinetic reaction mechanism was conducted and a limit of detection of 0.45 µg/mL (2.4 µM) was obtained for DNP recognition. The peroxidase mimetic strep-B-Apt-polymer-Fe-doped ceria/Au NC biosensor was successfully applied for the detection of DNP in tap water and river water with satisfactory recoveries in the range of 97–117%.

Ratiometric fluorescent sensor based on 2D MOF nanosheets modified by DNA for sensitive detection of Hg2+

Mercury is highly toxic and can accumulate throughout the food cycle, leading to water contamination and foodstuffs pollution. Therefore, increasing attention has been paid to explore effective detection of Hg2+. Here, we report a sensitive Hg2+ sensor based on single-stranded DNA (ssDNA) modified two-dimensional (2D) MOF nanosheets by a ratiometric fluorescent method. The chosen 2D MOF nanosheets possess intrinsic peroxidase-like catalytic ability, ssDNA adsorption and fluorescence quenching. We demonstrate that the adsorption of ssDNA can significantly improve the peroxidase mimetic activity of 2D MOF nanosheets, enhancing the fluorescence of substrate Amplex Red. Taking advantages of the favorable characteristics above, we fabricate an efficient Hg2+ sensor. In the presence of Hg2+, the ssDNA is released from 2D MOF nanosheets, which results in a decreasing of peroxidase mimetic activity of 2D MOF nanosheets and a fluorescence enhancement of attached fluorophore. A linear relationship between ratiometric fluorescence of substrate and fluorophore and Hg2+ concentrations is obtained. The detection limit is 5 nM, which is much lower than the maximal contamination level in drinking water (30 nM) by Word Health Organization. These findings show 2D MOF based ratiometric fluorescent sensor is a convenient and efficient strategy to detect Hg2+.

UV-light-actuated in-situ preparation of paper@ZnCd quantum dots for paper-based enzymatic nanoreactors

Quantum dots (QDs) have been widely applied in the analytical field including sensitive fluorescent assays on paper-based devices. A facile in-situ synthesis of QDs after a simple reagent deposition on paper could enable a rapid low-cost fabrication of QD–modified paper with a variety of properties and purposes such as enzymatic nanoreactors. Herein, for the first time, fluorescent ZnCd QDs were prepared by in-situ synthesis in the paper matrix using thiol-containing precursors and irradiation by UV light. A successful creation of the immobilized ZnCd QDs on paper (paper@ZnCd QDs) was monitored by their intrinsic fluorescence while their peroxidase mimetic activity was evaluated by a catalytic reaction between H2O2 and a substrate (3,3′,5,5′-tetramethylbenzidine, TMB) producing a blue coloured product of charged transfer complex of TMB (oxTMB). From three thiol precursors investigated, the insulin precursor provided a greater activity than glutathione (GSH) and both considerably larger than BSA. Finally, a QDs precursor mixture deposition onto the paper matrix was evaluated by the peroxidase-mimetic activity, which was comparable with a reference method. The in-situ preparation of paper@ZnCd QDs is simple, rapid and ‘green’, with potential in biomedical applications primarily as fluorescence imaging agent and enzyme mimetic paper-based nanoreactors.

Multi-enzyme activity of three layers FeOx@ZnMnFeOy@Fe-Mn organogel for colorimetric detection of antioxidants and norfloxacin with smartphone

In this study, the FeOx@ZnMnFeOy@Fe-Mn bimetallic organogel (FO@ZMFO@FM-MOG) with three layers structure was synthesized. It presented outstanding multi-enzyme (peroxidase, oxidase and catalase) activities. The systematical characterization results showed that Zn and Mn on the surface of FO@ZMFO@FM-MOG were nearly disappeared, and thus a large amount of Fe exposed as the active species. Accordingly, the high ratio of Fe2+/Fe3+ for FO@ZMFO@FM-MOG was conductive to the electron transfer and enzyme activity. Moreover, the multiple detection platforms were constructed based on the different nanozyme activities. As for the peroxidase-mimetic activity, citric acid (CA) and norfloxacin (NOR) were monitored continuously on the basis of the turn on–off-on signal change due to the electron transfer abilities and hydroxyl radicals (•OH) formation. The linear range of 0.415–6.21 μM was obtained with a low detection limit of 79 nM, which was rarely detecting citric acid by nanozyme. And the low detection limit of 52 nM for NOR was superior to the most published NOR assays in nanozyme field. Furthermore, an oxidase platform for gallic acid (GA) was also established due to superoxide anions (O2•−) generation. It should be noted that the smartphone detection platforms for CA and NOR were established successfully for on-site analysis. This study provided multifunctional detection platform for valuating CA, NOR and GA in food quality and environment monitoring.

Determination of Cr(VI) based on the peroxidase mimetic catalytic activity of citrate-capped gold nanoparticles.

Highly negatively charged gold nanoparticles (AuNPs) are shown to havestrong simulated oxidase activity and effectively boosted the oxidation of enzyme substrate 3,3',5,5'-tetramethylbenzidine (TMB) by hexavalent chromium ion Cr(VI), resulting in the formation of oxidation product with blue color. Based on this, a facile colorimetric assay was developed to detect Cr(VI) at a range 0.008~0.156mg/L with r= 0.996. The detection limit was estimated to be 0.52μg/L. In addition, the colorimetric assay showed high selectivity against 28 other interfering ions. It was performed at room temperature and required about half an hour including the preparation of AuNPs. The assay was successfully applied to the determination of Cr(VI) in spiked water samples, and recoveries in the range 95.00-105.40% were obtained. This work paves a way for design of high performance sensor based on highly active nanozymes and also provides an extremely practical analytical tool for the monitoring of Cr(VI) in the environment.

Eco-Friendly Synthesis of SnO2-Cu Nanocomposites and Evaluation of Their Peroxidase Mimetic Activity.

The enzyme mimetic activity of nanomaterials has been applied in colorimetric assays and point-of-care diagnostics. Several nanomaterials have been exploited for their peroxidase mimetic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. However, an efficient nanomaterial for the rapid and strong oxidation of TMB remains a strategic challenge. Therefore, in this study, we developed copper-loaded tin oxide (SnO2-Cu) nanocomposites that rapidly oxidize TMB. These nanocomposites have strong absorption at 650 nm and can be used for highly sensitive colorimetric detection. An environmentally friendly (green), rapid, easy, and cost-effective method was developed for the synthesis of these nanocomposites, which were characterized using ultraviolet-visible, energy-dispersive X-ray, and Fourier-transform infrared spectroscopy, as well as scanning electron microscopy. This is the first green synthesis of SnO2-Cu nanocomposites. Their enzyme mimetic activity, which was first studied here, was found to be strongly dependent on the temperature and pH value of the solution. The synthesized nanocomposites have the advantages of low cost, high stability, and ease of preparation for enzyme mimetic applications. Hence, SnO2-Cu nanocomposites are a promising alternative to peroxidase enzymes in colorimetric point-of-care diagnostics.

Peroxidase-mimetic activity of FeOCl nanosheets for the colorimetric determination of glutathione and cysteine

Forthe first time the enzyme mimic activity of iron oxychloride (FeOCl) nanosheets has been studied. The intrinsic peroxidase-mimetic activity of the nanosheets in the presence of H2O2 was approved by the efficient oxidation of tetramethylbenzidine (TMB). The Michaelis-Menten constant of the nanosheets toward TMB was about six times lower than that of natural horseradish peroxidase. The superiority of the nanosheets' catalytic property ascribes to their H2O2 activation ability. Based on the inhibition of the nanozymes' catalytic reaction, an assay was developedfor the quantitative measurement of glutathione (GSH) and cysteine (Cys). The linear range for both biomolecules was over the range of 3-33 μM. The LOD values (3σ/slope) for GSH and Cys were 2.23 μM and 2.76 μM, respectively. Importantly, we succeeded in colorimetric discrimination of GSH and Cys kinetically. We achieved high selectivity toward GSH and Cys. This work extends the feasibility of using FeOCl as nanozymes to construct biosensors, colorimetric probes for medical diagnosis, and nanozyme-based cancer therapy.

Analyte-triggered citrate-stabilized Au nanoparticle aggregation with accelerated peroxidase-mimicking activity for catalysis-based colorimetric sensing of arsenite

Arsenite is a well-known toxic species widely distributed in many matrices, and exploring reliable and facile methods for its detection is always desired for environmental analysis and food safety control. Here we propose a catalytic colorimetric assay of arsenite based on the analyte inducing the aggregation of citrate-stabilized Au nanoparticles (AuNPs) with promoted peroxidase-mimicking activity. Originally, highly dispersed AuNPs with a mean size of ∼20 nm show negligible enzyme-like activity. However, when a small amount of arsenite is added, it triggers the rapid aggregation of AuNPs via the interactions between the analyte and the stabilizer citrate on AuNP surface, and it is further observed that the formed AuNP agglomerate can exhibit significantly accelerated peroxidase-mimetic activity to catalyze the 3,3′,5,5′-tetramethylbenzidine chromogenic reaction with the participation of H2O2. Based on this phenomenon, a facile colorimetric strategy with catalytic signal amplification was established for the efficient sensing of arsenite. With the catalysis-based strategy, arsenite in a wide range (0.0111.67 mg/L) was linearly determined with a detection limit lower than the standard approved by the US EPA and the EEA. Stable and reliable measurement of the analyte in various water matrices was also verified, promising our assay’s great potential in practical applications.

Fe-doped MoS2 nanomaterials with amplified peroxidase mimetic activity for the colorimetric detection of glutathione in human serum

In this paper, transition metal-doped MoS2 2D materials have been explored for the colorimetric detection of glutathione based on peroxidase mimetic activity. We have synthesized (hydrothermal) and characterized various doped MoS2. Among them, Fe-doped MoS2 flowers exhibit excellent peroxidase-mimetic activity over MoS2 by inducing the oxidation of chromogenic substrate and results in a blue color charge transfer product. Property of this nanomaterial is exploited for efficacious detection of Glutathione level in the buffer as well as in serum samples which follows the steady-state kinetics for peroxidase mimetic activity and exhibits stability over harsh environmental conditions. The developed sensor shows good linearity for glutathione detection in the range 1–30 μM with a significant limit of detection (0.577 μM). The Fe-doped MoS2 with excellent mimetic activity is utilized to develop noble-metal free, high-performance, low-cost peroxidase mimetic activity for onsite detection of glutathione in the real sample.

"Light-on" Colorimetric Assay for Ascorbic Acid Detection via Boosting the Peroxidase-like Activity of Fe-MIL-88

A label-free "light-on" colorimetric assay for ascorbic acid (AA) determination is unprecedentedly devised by regulating the intrinsic peroxidase-mimetic activity of the Fe-MIL-88. AA can reduce Fe(III) presented in Fe-MIL-88 to Fe(II), which will dramatically promote the hydroxyl radicals (·OH) conversion efficiency of H2O2 through a Fenton reaction, and effectually accelerate the Fe-MIL-88 catalyzed chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB)-H2O2. Redox reaction between AA and H2O2 also can produce ·OH and promote this chromogenic reaction. Thus, quantification of AA is realized via determining the enhanced colorimetric signals. The linear range is 0.5 − 40 μM with a detection limit of 0.12 μM. Furthermore, the straightforward yet effective colorimetric strategy with the merits of simplicity, cost-effectiveness, high accuracy, specificity, and sensitivity is widely utilized to determine the concentrations of AA in serological tests.

Hemin-assisted synthesis of peroxidase-like Fe-N-C nanozymes for detection of ascorbic acid-generating bio-enzymes

Revealing the relationship between composition and enzyme-like activities is essential for the rational designs of nanozymes and related assays with improved performances. Here, a series of Fe-N co-doped porous carbon (Fe-N-C) nanozymes containing different Fe contents have been successfully prepared by facilely pyrolyzing hemin trapped zeolitic-imidazolate-frameworks (Hemin@ZIF-8). The special doping agent hemin will endow Fe-N-C with exceptionally high peroxidase-mimetic activities due to the hierarchically porous structure, high specific surface area, and high dispersed Fe-Nx sites. Notably, the optimal Fe55-N-C nanozymes are used to detect bio-enzymes, by taking alkaline phosphatase (ALP) as a model, based on the inhibition of nanozymatic activity by ascorbic acid (AA). A linear activity range of 0.05–20 U/L is obtained with a low detection limit of 0.03 U/L, which is superior to the most published optical ALP assays. This work provides not only a new method for the design of the transition metal-N-C nanozyme with enhanced peroxidase-like activity but also a promising strategy for the detection of ascorbic acid-generating bio-enzymes with the assistance of specific substrates.

Colorimetric determination of D-penicillamine based on the peroxidase mimetic activity of hierarchical hollow MoS2 nanotubes

A colorimetric assay was designed for the detection of D-penicillamine (D-PA). In this work, hierarchical hollow molybdenum disulfide nanotubes (HH-MoS2) were implemented as peroxidase mimetic catalysts. The pink-colored free cation radicals were generated through oxidation of N,N-diethyl-p-phenylenediamine (DPD) by hydrogen peroxide under the catalytic activity of HH-MoS2. The main role of HH-MoS2 was the enhancement of cation radical generation, thereby, improving the sensitivity of the sensor. In the presence of D-PA, the oxidation reaction of DPD was inhibited and the absorption bands of the cation radicals (at 510 and 551 nm) diminished while a new absorption band appeared at 475 nm. Good linearity between the absorbance ratio (A551/A475) and D-PA concentration in the range of 7.0-60.0 μg mL−1 was acquired and a detection limit of 0.63 μg mL−1 was achieved. As a practical application, this colorimetric sensor was successfully used to determine the D-PA content of the pharmaceutical formulation.

Peroxidase- and UV-triggered oxidase mimetic activities of the UiO-66-NH2/chitosan composite membrane for antibacterial properties.

In this study, UiO-66-NH2 metal-organic framework (MOF) nanoparticles with peroxidase and oxidase mimetic activities were incorporated into a chitosan (CS) matrix by a simple and environmentally friendly method. The UiO-66-NH2/CS composite membrane possesses the peroxidase mimicking activity in the presence of traces of H2O2, thus resulting in good antibacterial properties. Intriguingly, 30 min of UV pre-irradiation of the UiO-66-NH2/CS composite membrane, in the absence of H2O2, still leads to a good antibacterial activity. This was attributed to the oxidase mimetic activity and the peroxidase mimicking activity of UiO-66-NH2. In such a way, the side effects of direct exposure to UV irradiation and H2O2 can be avoided for wound-healing treatments. The antibacterial mechanism was further proved by antibacterial experiments, TMB·2HCl color development experiments, reactive oxygen species generation tests and electron spin resonance tests. As a potential medical antibacterial dressing, in vitro membranes were also investigated.

Fast colorimetric sensing of H2O2 and glutathione based on Pt deposited on NiCo layered double hydroxide with double peroxidase-/oxidase-like activity

The Pt/NiCo layered double hydroxides nanocomposites (Pt/NiCo-LDH NCs) have been successfully prepared by a one-pot hydrothermal method. Pt/NiCo-LDH was demonstrated to possess an excellent peroxidase-like activity together with a weak oxidase-like activity, evaluating in virtue of rapid catalytic oxidization of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) by H2O2 into a blue oxidation product (oxTMB) only in 30 s. The short response time is very important for designing colorimetric sensors to realize real time detection. The catalytic behaviors of Pt/NiCo-LDH followed the Michaelis-Menten kinetics, possessing a good affinity towards both TMB and H2O2. The catalytic mechanism of Pt/NiCo-LDH is due to OH radicals from decomposing of H2O2. Based on the high peroxidase mimetic activity of Pt/NiCo-LDH, a rapid and convenient colorimetric sensing platform for H2O2 and glutathione has been successfully constructed. Under optional conditions, the colorimetric platform shows a sensitive response to H2O2 and glutathione in the linear range of 10–90 mM and 50–500 mM with a limit of detection of 0.76 mM and 3.77 mM, respectively.

Fluorometric Detection of Thiamine Based on Hemoglobin-Cu3(PO4)2 Nanoflowers (NFs) with Peroxidase Mimetic Activity.

Component analysis plays an important role in food production, pharmaceutics and agriculture. Nanozymes have attracted wide attention in analytical applications for their enzyme-like properties. In this work, a fluorometric method is described for the determination of thiamine (TH) (vitamin B1) based on hemoglobin–Cu3(PO4)2 nanoflowers (Hb–Cu3(PO4)2 NFs) with peroxidase-like properties. The Hb–Cu3(PO4)2 NFs catalyzed the decomposition of H2O2 into ·OH radicals in an alkaline solution that could efficiently react with nonfluorescent thiamine to fluoresce thiochrome. The fluorescence of thiochrome was further enhanced with a nonionic surfactant, Tween 80. Under optimal reaction conditions, the linear range for thiamine was from 5 × 10−8 to 5 × 10−5 mol/L. The correlation coefficient for the calibration curve and the limit of detection (LOD) were 0.9972 and 4.8 × 10−8 mol/L, respectively. The other vitamins did not bring about any obvious changes in fluorescence. The developed method based on hybrid nanoflowers is specific, pragmatically simple and sensitive, and has potential for application in thiamine detection.

A Colorimetric Assay for the Detection of Glucose and H2O2 Based on Cu-Ag/g-C3N4/ZIF Hybrids with Superior Peroxidase Mimetic Activity.

In this work, we report the synthesis of Cu-Ag bimetallic nanopartiles and g-C3N4 nanosheets decorated on zeolitic imidazolate framework-8 (ZIF-8) to form a Cu-Ag/g-C3N4/ZIF hybrid. The hybrid was synthesized and characterized by Transmission electron microscopy (TEM), Fourier transformed infrared (FTIR), the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Cu-Ag/g-C3N4/ZIF hybrid has intrinsic peroxidaselike catalytic activity towards the oxidation of TMB in the presence of H2O2. The situ synthesis of Cu-Ag bimetallic nanopartiles on 2D support such as g-C3N4 nanosheets would significantly enhance the peroxidaselike catalytic properties of individual Cu-Ag bimetallic nanopartiles and the g-C3N4 nanosheets. After loading of Cu-Ag bimetallic nanopartiles and g-C3N4 nanosheets on the ZIF-8, the hybrids exhibited superior peroxidaselike catalytic activity and good recyclability. Then, this method was applied for detecting glucose in human serum, owing the significant potential for detection of metabolites with H2O2-generation reactions.

Enhanced Peroxidase Mimetic Activity of Magnetic Porous Carbon (MPC) Utilized in Colorimetric Sensing of Hg (II) Ions in Aqueous Medium

AbstractA new sensitive colorimetric sensor was designed to investigate the presence of Hg2+ in aqueous solution by using Fe3O4 NP impregnated on carbon nanocomposite(MPC) synthesized from MIL88 A which possess an excellent peroxidase mimicking activity that brings oxidation of 3, 3’, 5, 5’‐ tetramethylbenzidine (TMB) under the influence of hydrogen peroxide (H2O2) to produce blue colour in the solution. The solution was decolorized by the addition of Glutathione (GSH) which restores the TMB radical cations and ceased the oxidation reaction. Addition ofHg2+ ions to the solution bring back a strong blue colour due to the strong affinity of Hg 2+ with the thiol groups of GSH which promote the oxidation of TMB in the solution. Based on these strategies, we have developed a sensitive andselective colorimetric sensor for the determination of Hg (II) in aqueous solution with the detection limit value of 236 pM and a linear relationship of R2=0.994. The proposed mechanism was successfully implemented for the detection of mercury in real water samples for environmental applications.