Colorimetric detection of chromium (VI) ion using poly(N-phenylglycine) nanoparticles acting as a peroxidase mimetic catalyst

Colorimetric detection of Cr(VI) in water using tetramethyl benzidine (TMB) as an indicator

Hexavalent chromium (CrVI) poses a serious risk to both human and environment health. Hence, a simple, robust, and efficient analytical method must be developed to monitor the presence of Cr(VI) in the environment. The current investigation concentrated on the colorimetric detection of Cr(VI) using TMB as indicator in the presence of H2O2. The study found that Cr(VI) reacts with H2O2 to generate hydroxyl radicals which oxidize TMB in a concentration dependent manner. Under optimized conditions, the method obtained a good linearity range (0.025-0.5 mg/L, r2 = 0.9944) with LOD and LOQ of 0.009 mg/L and 0.029 mg/L, respectively. The technique was further improved by the addition of EDTA in the sample preparation protocol to reduce the false positive result by the presence of ions like Cu2+, Fe3+, etc. The study recorded improved Cr(VI) recoveries (81.73-111.40 %) at different fortification levels (0.1-0.5 mg/L). Under optimized conditions, the EDTA added method obtained a good linear response (r2 = 0.9952) with a detection limit of 0.023 mg/L which is less than the prescribed limits by WHO (0.05 mg/L) and US EPA (0.1 mg/L) for drinking water. The developed analytical method is very simple without use of any nanomaterial and the results with natural water samples show that it has the potential for real-time detection of Cr(VI) in the environment.

A colorimetric and electrochemical dual-mode system for identifying and detecting varied Cr species based on fungus-like porous CoS nanosensor

The differentiation of valence states plays a crucial role in determining the toxicity of chromium (Cr) in environmental samples. In this work, two modes of colorimetric and electrochemical analytical methods based on a fungus like porous CoS (FP CoS) nanosensor were developed for rapid, specific, and portable detection trace/ultra-trace chromium species (Cr(VI) and Cr(III)). The FP CoS exhibited peroxidase activity as a nanozyme for the colorimetric detection of Cr(VI), catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to a blue oxidation product (oxTMB) in the presence of Cr(VI) instead of unstable H2O2 as an oxidizer at room temperature over existing methods. Based on the promotion of colorimetric reaction by increasing in Cr(VI) concentration, an effective colorimetric detection of Cr(VI) method was established with a detection limit (LOD) low to 3.93 μg L-1 and unique selectivity for Cr(VI) over 21 interfering ions (containing 15 metal ions and 6 anions). Innovatively, Cr(VI) could be reduced to Cr(III) without TMB, then selectively enriched by redox reaction with FP CoS. Hence, Cr (III) can be selectively and effectively enriched by FP CoS applying voltage, and then detected using cyclic voltammetry, with a lower LOD of 0.116 μg L-1 and high sensitivity ignoring background interferences. By integrating the dual-mode detection channel, the FP CoS nanosensor offers a convenient and flexible method for simultaneously determining Cr(VI), Cr(III), and total chromium in diverse samples.

Uncovering an effecient binary system as a chemosensor for visual and fluorescence detection of chromium (VI) in water samples

There is an urgent requirement for the development of sensitive and quick sensors to monitor chromium (VI) due to its substantial carcinogenic and mutagenic properties. A coexisting system of coumarin 334 and diphenylcarbazide (C334/DPC) was used in this study as a fluorescent chemosensor to detect Cr(VI) ions. Upon the addition of Cr(VI), a purple chelate complex (Cr(III)-diphenylcarbazone) was produced, which resulted from the quantitative reaction between Cr(VI) ions and diphenylcarbazide (DPC), whereas no interaction between Cr(VI) and coumarin 334 took place. More interestingly, the absorption spectra of purple (Cr(III)-diphenylcarbazone) complex (λmax = 540 nm) were overlapped with emission and excitation spectra of coumarin 334 (λex/em = 453/492), resulting in the efficient quenching of coumarin 334 (C334) via the inner filter effect. Furthermore, the semi-quantitative estimation of Cr(VI) ion concentration may be achieved by visually watching the progressive color transformation of the probe from yellow to red after the addition different concentration of Cr(VI). The calibration plot for determination of Cr(VI) by this method is ranging from 0.048 to 268 μM. DFT calculations were conducted to enrich our understanding about the mechanism of action. This approach demonstrates an excellent selectivity and sensitivity for Cr(VI) including a detection limit of 48 nM. The new sensor was successfully applied to water samples (tap, mineral, and waste waters). The accuracy was confirmed by the atomic absorption spectroscopy.

Single-atom nanozymes: Emerging talent for sensitive detection of heavy metals

In recent years, the increasingly severe pollution of heavy metals has posed a significant threat to the environment and human safety. Heavy metal ions are highly non-biodegradable, with a tendency to accumulate through biomagnification. Consequently, accurate detection of heavy metal ions is of paramount importance. As a new type of synthetic nanomaterials, single-atom nanozymes (SANs) boast exceptional enzyme-like properties, setting them apart from natural enzymes. This unique feature affords SANs with a multitude of advantages such as dispersed active sites, low cost and variety of synthetic methods over natural enzymes, making them an enticing prospect for various applications in industrial, medical and biological fields. In this paper, we systematically summarize the synthetic methods and catalytic mechanisms of SANs. We also briefly review the analytical methods for heavy metal ions and present an overall overview of the research progress in recent years on the application of SANs in the detection of environmental heavy metal ions. Eventually, we propose the existing challenges and provide a vision for the future.

Novel Nucleic Acid-Assisted Ion-Responsive ECL Biosensor Based on Hollow AuAg Nanoboxes with Excellent SPR and Effective Coreaction Acceleration

Novel hollow AuAg nanoboxes (AuAg NBs) were designed for an innovative electrochemiluminescence (ECL) sensor to ultrasensitively detect Pb2+ and Hg2+ with the aid of DNAzyme and "thymine-Hg2+-thymine" ("T-Hg2+-T") structure. AuAg NBs are employed as an excellent surface plasma resonance (SPR) source, as well as an effective coreaction accelerator for the CoNi NFs/S2O82- system to greatly improve ECL performance. To detect Pb2+, the DNAzyme catalyzes the cleavage of ribonucleic acid targets into numerous small nucleic acid fragments, leading to an ECL signal. When Hg2+ is added, the thymine-thymine (T-T) mismatches of the Hg2+ aptamer bind Hg2+ to form the "T-Hg2+-T" structure, which not only inhibits the SPR process but also produces a large steric hindrance, thus quenching the ECL signal and allowing quantification of Hg2+. The novel ECL sensor quantifies Pb2+ in the range of 0.1 fM to 0.1 μM with a limit of detection of 0.07 fM and Hg2+ in the range of 10 pM to 1 μM with a LOD of 4.07 pM.

Ultrathin porous PdCu metallenezymes as oxidase mimics for colorimetric analysis

Ultrathin porous and highly curved two-dimensional PdCu alloy metallene are shown to be highly efficient oxidase mimics. Serving as intrinsic oxidase mimic, the ultrathin porous structure of the PdCu metallenezymes could effectively utilize all the Pd atoms of the metallenezymes during catalytic reactions. By using the oxidation capability of 3,3'5,5'-tetramethylbenzidine as distinctive chromogenic substrate, the PdCu metallenezymes was used as oxidase-like mimics for determination of total antioxidant capacity (TAC) of vitamin C containing real products including fresh orange juice, commercial beverages, Vitamin C tablets and dermo-cosmetic products. AAP was hydrolyzed using ALP to generate AA and the corresponding ALP activity was successfully detected in the 0-100 U/L range with a lowest detection limit of 0.9 U/L. This study demonstrates the significant catalytic performance and oxidase-like activity of PdCu metallene nanozyme providing a strategy to develop a TAC assay for the assessment of antioxidant food quality as well as oxidative stress in skin and health care products.

Ag2S QDs integration with MnO2 nanosheets for the sensitive detection of Cr (VI) via the redox reaction induced photoelectrochemical variation

The heavy metal Cr (VI) will remain, accumulate, and migrate after entering the environment or ecosystem, causing serious harm to the environment. Here, a photoelectrochemical sensor was developed for Cr (VI), utilizing the Ag₂S quantum dots (QDs) and MnO₂ nanosheets as photoactive components. By introducing Ag₂S QDs with a narrow gap, a staggered energy level match is created which effectively prevents the carrier recombination in MnO₂ nanosheets, resulting in an enhanced photocurrent response. In the presence of the electron donor, l-ascorbic acid (AA), the photocurrent of the Ag₂S QDs and MnO₂ nanosheets modified photoelectrode is further enhanced. As AA has the ability to convert Cr (VI) to Cr (Ⅲ), the photocurrent may decline due to the decrease in the electron donors when Cr (VI) is added. This phenomenon can be utilized for the sensitive detection of Cr (VI) over a wider linear range (100 pM-30 μM) with a lower detection limit of 6.46 pM (S/N = 3). This work using the strategy that the targets induced the variations of the electron donor shows the advantages of good sensitivity and nice selectivity. The sensor holds many advantages such as simple fabrication process, economical material expense, and consistent photocurrent signals. It also holds significant potential for environmental monitoring and serves as a practical photoelectric sensing approach for detecting Cr (VI).

Synthesis of multicolor silver nanostructures for colorimetric sensing of metal ions (Cr3+, Hg2+ and K+) in industrial water and urine samples with different spectral characteristics

In this work, we have synthesized four different color (yellow, orange, green, and blue (multicolor)) silver nanostructures (AgNSs) by chemical reduction method where silver nitrate, sodium borohydride and hydrogen peroxide were used as reagents. The as-synthesized multicolor AgNSs were successfully functionalized with bovine serum albumin (BSA) and applied as a colorimetric sensor for the assaying of metal cations (Cr³⁺, Hg²⁺, and K⁺). The addition of metal ions (Cr³⁺, Hg²⁺, and K⁺) into BSA functionalized AgNSs (BSA-AgNSs) causes the aggregation of BSA-AgNSs, and are accompanied by visual color changes with red or blue shift in the surface plasmon resonance (SPR) band of BSA-AgNSs. The BSA-AgNSs show different SPR characteristic for each metal ions (Cr³⁺, Hg²⁺, and K⁺) with exhibiting different spectral shift and color change. The yellow color BSA-AgNSs (Y-BSA-AgNSs) act as a probe for sensing Cr³⁺, orange color BSA-AgNSs (O-BSA-AgNSs) act as probe for Hg²⁺ ion assay, green color BSA-AgNSs (G-BSA-AgNSs) act as a probe for the assaying of both K⁺ and Hg²⁺, and blue color BSA-AgNSs (B-BSA-AgNSs) act as a sensor for colorimetric detection of K⁺ ion. The detection limits were found to be 0.26 μM for Cr³⁺ (Y-BSA-AgNSs), 0.14 μM for Hg²⁺ (O-BSA-AgNSs), 0.05 μM for K⁺ (G-BSA-AgNSs), 0.17 μM for Hg²⁺ (G-BSA-AgNSs), and 0.08 μM for K⁺ (B-BSA-AgNSs), respectively. Furthermore, multicolor BSA-AgNSs were also applied for assaying of Cr³⁺, and Hg²⁺ in industrial water samples and K⁺ in urine sample.

Ultrafast colorimetric detection of Cr(VI) based on competition of 8-HQ to Cr(VI) and TMB oxides using GO/AuNPs nanocomposites as peroxidase mimic

Rapid detection of ultra-trace heavy metal chromium is very important for ecological environment. Herein, a rapid colorimetric assay was constructed for detecting hexavalent chromium (Cr(VI)) in environment water through the strong peroxidase mimicking activity of graphene oxide/gold nanoparticles (GO/AuNPs) nanocomposites and competition of Cr(VI) to 3,3',5,5'-tetramethylbenzidine (TMB) oxides and 8-hydroxyquinoline (8-HQ). Cr(VI) could effectively prevent the reaction between 8-HQ and TMB oxides to restore the blue color of the system. The detection limit for Cr(VI) was as low as0.018 µM by spectroscopic absorption. Paper-based colorimetric analysis had the detection limit of0.153 µM. The high sensitivity was basically due to the strong peroxidase mimicking activity of GO/AuNPs nanocomposite from synergistic coupling action and the firm chelation between 8-HQ and Cr(VI) from inner-sphere surface complexation. The detection results for real water sample showed that the analysis had feasibility in practical application. It is worth mentioning that the assay is performed by one-step mixing mode at room temperature, and a single test can be completed in half a minute. Indeed, this work not only provided an extremely easy method for real-time detecting Cr(VI) in the environment, but also verified the vitality of colorimetric strategy based on the strong peroxidase mimicking activity and competitive reaction.

BSA-stabilized silver nanoclusters for efficient photoresponsive colorimetric detection of chromium(VI)

Hexavalent chromium is a highly toxic substance, which will pose a serious threat to human life and health and the entire ecosystem. Therefore, it is crucial to establish a simple and rapid detection method for hexavalent chromium. In this work, we fabricated bovine serum albumin-stabilized silver nanocluster (BSA-Ag₁₃ NC) which exhibited photoresponsive oxidase-like activity, catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to the blue oxidized state TMB (oxTMB) in a short time. Interestingly, 8-hydroxyquinoline (8-HQ) can significantly inhibit the color reaction of TMB oxidation while Cr(VI) can interact specifically with 8-HQ to restore this chromogenic reaction. Based on the above facts, a colorimetric sensing system for detecting Cr(VI) was developed. The sensing system shows a wide linear range, and good selectivity, with a low detection limit of 2.32 nM. Moreover, this sensing system could be successfully applied to the detection of Cr(VI) in lake water, tap water, and sewage with satisfactory results.

Ultrafast colorimetric detection of Cr(VI) using Fe3O4@polydopamine/Prussian blue composites as a highly efficient peroxidase mimic

A recyclable peroxidase mimic Fe₃O₄@polydopamine/Prussian blue (Fe₃O₄@PDA/PB) composite was facilely prepared by coating PDA on an Fe₃O₄ nanoparticle core and in situ growth of PB nanoparticles on a PDA shell. The prepared Fe₃O₄@PDA/PB composite exhibited excellent peroxidase-like activity and can catalytically oxidize the colorless colorimetric substrate 3,3',5,5'-tetramethylbenzidine (TMB) into a blue colored product in the presence of H₂O₂ at 30 °C in 1 min. The catalytic mechanism was deduced to be the nanozyme-promoted generation of a hydroxyl radical (·OH), and the catalytic behavior followed the typical Michaelis-Menten kinetics. Based on Cr(VI)-boosted peroxidase-like activity of Fe₃O₄@PDA/PB, a simple and fast colorimetric method for detection of Cr(VI) was developed. Under the optimum conditions, the colorimetric method exhibited wider linear range (100 nM to 140 μM), low LOD (51.1 nM), good selectivity and short detection time (1 min). Moreover, the feasibility of the proposed colorimetric method was evaluated by determination of Cr(VI) in spiked tap water and lake water samples. Good recoveries (95.2-102.9%) and low relative standard deviations (RSDs) (1.6-4.4%) were obtained, showing great promise for practical use.

Morphology Adjustment and Optimization of CuS as Enzyme Mimics for the High Efficient Colorimetric Determination of Cr(VI) in Water

Metal sulfide is often utilized as a catalyzed material to form colorimetric response system for some heavy metal detection. While the aggregation effect and conventional morphology limited the catalyzed efficiency. Herein, a robust method based on morphology adjustment was proposed to improve the dispersibility and catalytic performance of CuS. The results demonstrated when the solvent ratio of ethylene glycol and dimethyl sulfoxide arrived at 3:1, it displayed an optimal structure which is like a patulous flower. Meanwhile, an optimal surface binding energy (ΔE) of 120.1 kcal/mol was obtained via theoretical calculation model. The flower-like structure caused a 2-fold increase in the catalytic level. Subsequently, the CuS was employed to make colorimetric detection of Cr(VI) in water. The assay results exhibited a linear range of the Cr(VI) from 60 to 340 nM, the limit of detection was 1.07 nM. In the practical tests for Qianhu lake water, the spiked recoveries were 93.6% and 104% with the RSD of 4.71% and 3.08%. Therefore, this CuS-based colorimetric method possesses a satisfactory application prospect for the Cr(VI) determination in water.

Highly sensitive and convenient aptasensor based on Au NPs@Ce-TpBpy COF for quantitative determination of zearalenone

In this work, an aptasensor based on a portable U-disk electrochemical workstation in combination with a screen-printed electrode (SPE) is demonstrated for the quantitative determination of zearalenone (ZEN). The aptamer is immobilized on Au NPs@Ce-TpBpy COF (Covalent organic frameworks), which is modified on the surface of glassy carbon electrode. ZEN specifically binds to ZEN aptamer, which hinders the electron transfer and decreases the catalytic current of Au NPs@Ce-TpBpy COF for the reduction of hydrogen peroxide, measured by chronoamperometry (i-t). The quantitative detection of ZEN toxin is realized by a decrease of the catalytic current (ΔI). Under the optimal experimental conditions, the aptamer sensor exhibited excellent sensitivity, selectivity, reproducibility. A wide linear range of 1 pg mL-1-10.0 ng mL-1 with a detection limit of 0.389 pg mL-1 (at 3σ) was obtained. The linear equation is ΔI = 0.401 lg c + 1.948 with a correlation coefficient of 0.9906. The recovery is in the range of 93.0-104.7% for the cornflour samples. The proposed method offers a new strategy for the rapid, inexpensive, and real-time detection of ZEN.

In-situ generation of highly active and four-in-one CoFe2O4/H2PPOP nanozyme: Mechanism and its application for fast colorimetric detection of Cr (VI)

Nanozymes have been widely utilized in colorimetric sensors and developing nanomaterials with multienzyme functions have more application prospects due to their cascaded catalytic efficiency. Here, a unique organic-inorganic nanocomposite CoFe₂O₄/H₂PPOP was synthesized by depositing CoFe₂O₄ nanocubes on a fully conjugated porphyrin-based porous organic polymer (H₂PPOP) in situ. CoFe₂O₄/H₂PPOP revealed outstanding tetra-enzyme-like activities, namely oxidase-like, peroxidase-like, catalase-like and superoxide dismutase-like activities. Compared with pure CoFe₂O₄ nanocubes, the catalytic activities of CoFe₂O₄/H₂PPOP were significantly boosted because of the large surface area and extended conjugated structure of H₂PPOP, abundant active substances (CoFe₂O₄) on the surface and the effective electronic transfer between CoFe₂O₄ and H₂PPOP. Based on the oxidase-like activity of CoFe₂O₄/H₂PPOP, a colorimetric platform was constructed for Cr (VI) with a wide linear range (0.6-100 μM) and a low detection limit (26 nΜ). Further utilizing the double oxidase-like and peroxidase-like activities, a more sensitive colorimetric platform with a faster detection speed for Cr (VI) was realized with the LOD as low as 2 nΜ. This work opens up a new way to prepare multi-enzyme active nanozyme and excavates its potential for detecting environmental pollutants.

Effective PDT/PTT dual-modal phototherapeutic killing of bacteria by using poly(N-phenylglycine) nanoparticles

This study investigated, for the first time, the antimicrobial properties of polyethylene glycol-functionalized poly(N-phenylglycine) nanoparticles (PNPG-PEG NPs). PNPG-PEG NPs exhibit high extinction coefficient in the near-infrared (NIR) region; they can convert light energy into heat energy with high thermal transformation efficiency. Additionally, they can generate cytotoxic reactive oxygen species (ROS) upon light irradiation. Also, PNPG-PEG NPs are not cytotoxic. All these properties make them appropriate for combined dual-modal photothermal and photodynamic therapies. The antibacterial activity of PNPG-PEG NPs was assessed using Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) pathogenic strains. The results revealed that NIR light (810 nm) irradiation for 10 min could kill effectively the planktonic bacteria and destroy Escherichia coli and Staphylococcus aureus biofilms. The results demonstrated that PNPG-PEG NPs represent a very effective nanoplatform for killing of pathogenic bacteria.

Phytic acid-doped poly-N-phenylglycine potato peels for removal of anionic dyes: investigation of adsorption parameters

In this work, we report on enhanced adsorption of anionic dyes, Reactive Blue 49 (RB 49) and Direct Blue 199 (DB 199), using a phytic acid-doped poly-N-phenylglycine@potato peel (PA-PPG@PP) nanocomposite material.

CuS nanoparticles-enhanced luminol-O2 chemiluminescence reaction used for determination of paracetamol and vancomycin

A new chemiluminescence (CL) method was proposed to measure two widely used drugs, including paracetamol (PCM) and vancomycin (VAN). The CL reaction used was the CuS nanoparticles (CuS NPs)-luminol-O₂ system. In this system, CuS NPs played the role of catalyst and increased the CL intensity. CuS NPs were easily synthesized by quick-precipitation. CuS NPs were characterized by spectroscopic techniques, and the mean size of NPs was estimated to be about 9 nm. In the developed CL methods, PCM and VAN decreased the CL intensity. In the proposed method, the linear concentration ranges were 4.0 × 10^-5-4.0 × 10^-4 mol L^-1 of PCM and 2.0 × 10^-5-6.0 × 10^-4 mol L^-1 of VAN. The limit of detections were 2.9 × 10^-5 mol L^-1 and 8.9 × 10^-6 mol L^-1 for PCM and VAN, respectively. The relative standard deviations (RSD) of the CL method were 2.99 and 4.31 (n = 6) for the determination of 3.0 × 10^-4 mol L^-1 PCM and VAN, respectively. It was also shown that the CL methods can measure PCM and VAN concentrations in various real samples.

Au-assisted polymerization of conductive poly(N-phenylglycine) as high-performance positive electrodes for asymmetric supercapacitors

Herein, a novel conductive poly(N-phenylglycine) (PNPG) polymer was successfully prepared, byin situelectrochemical polymerization method (+0.75 VversusAg/AgCl) for 10 min, on flexible stainless-steel plate coated with a thin Au film (Au/SS) to serve as a binder-free pseudocapacitive PNPG/Au/SS electrode for energy storage devices. Compared to the electrode without Au coating, PNPG/Au/SS electrode exhibited better electrochemical performance with larger specific capacitance (495 F g^-1at a current density of 2 A g^-1), higher rate performance and lower resistance, which are good indications to act as a positive electrode for asymmetric supercapacitor devices. Combined with activated carbon as a negative electrode, an asymmetric supercapacitor device was constructed. It displayed a specific capacitance of 38 F g^-1at a current density of 0.5 A g^-1and an energy density of 5.3 Wh kg^-1at a power density of 250 W kg^-1. Experimentally, two asymmetric supercapacitor devices were connected in series to power a home-made windmill continuously for 8 s, revealing the high potential of this novel conductive polymer material for energy storage application.

Colorimetric Detection of Chromium(VI) Ions in Water Using Unfolded-Fullerene Carbon Nanoparticles

Water pollution caused by hexavalent chromium (Cr(VI)) ions represents a serious hazard for human health due to the high systemic toxicity and carcinogenic nature of this metal species. The optical sensing of Cr(VI) through specifically engineered nanomaterials has recently emerged as a versatile strategy for the application to easy-to-use and cheap monitoring devices. In this study, a one-pot oxidative method was developed for the cage opening of C60 fullerene and the synthesis of stable suspensions of N-doped carbon dots in water-THF solutions (N-CDs-W-THF). The N-CDs-W-THF selectively showed variations of optical absorbance in the presence of Cr(VI) ions in water through the arising of a distinct absorption band peaking at 550 nm, i.e., in the transparency region of pristine material. Absorbance increased linearly, with the ion concentration in the range 1-100 µM, thus enabling visual and ratiometric determination with a limit of detection (LOD) of 300 nM. Selectivity and possible interference effects were tested over the 11 other most common heavy metal ions. The sensing process occurred without the need for any other reactant or treatment at neutral pH and within 1 min after the addition of chromium ions, both in deionized and in real water samples.

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 have strong 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 0.008~0.156 mg/L with r = 0.996. The detection limit was estimated to be 0.52 μg/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.