Colorimetric detection of H2O2 based on the enhanced peroxidase mimetic activity of nanoparticles decorated Ce2(WO4)3 nanosheets

Superior peroxidase-like activities of InVO4 hollow nanocuboid assemblies for colorimetric detection of hydrogen peroxide and glucose

In this work, InVO4 hollow nanocuboid assemblies (IVHNs) with larger specific surface area were synthesized by a facile one-pot hydrothermal method, which were utilized as artificial biomimetic catalysts. In the presence of hydrogen peroxide (H2O2), the IVHNs nanozyme enchantingly displayed an extraordinary peroxidase-like performance, inducing the oxidation of the chromogenic compound 3,3',5,5'-tetramethylbenzidine (TMB) to generate a blue oxide. Kinetics analysis unequivocally demonstrated that the catalytic behavior of IVHNs conformed to the Michaelis-Menten mechanism, and ·O2- radicals played a vital role in the catalytic process according to the active species capture experiments. Given the exceptional catalytic performance of IVHNs, a colorimetric sensing platform was successfully established for rapid and accurate detection of H2O2 and glucose. The concentrations of H2O2 and glucose were positively correlated with the absorbance of TMB oxide in the linear ranges of 1-25 μM and 10-100 μM with the detection limit of 0.092 μM and 0.96 μM, respectively. Enriched by its exquisite stability, selectivity, and anti-interference ability, the colorimetric sensing system bestowed its success upon qualitative detection of H2O2 and glucose in real samples. This study not only unveils a novel nanozyme boasting remarkably efficient catalytic prowess, but also pioneers a rapid and straightforward approach for environmental analysis and clinical diagnosis.

Rational designing of ZIF-67-derived Co3O4 nanocomposite with hierarchical porous structure and extensive peroxidase mimetic activities for highly sensitive colorimetric detection of nitrite in drinking water

A simple, fast, and cost-effective colorimetric nitrite (NO2-) sensor based on ZIF-67-derived Co3O4 nanocomposite (ZCo-2 NC) structure has been developed. The prepared colorimetric sensor (ZCo-2 NC) was employed to sensitively detect NO2- in drinking water system by the exhibition of promising peroxidase-mimicking nanozyme-like features. The sensor manifest well-determined sensing response with excellent linear and wide range of NO2- sensitivity (0.001-0.810 μM). The lower detection-limit (LOD) and lower quantification-limit (LOQ) were 0.14 ± 0.05 nM and 0.72 ± 0.05 nM, respectively, which is far below the US-EPA limit (21.7 μM). Further, the sensor also provides strong selectivity response to NO2-, better reversibility (12 cycles), and commendable stability of 10 weeks. In addition, it also perceived astonishing practicality towards NO2- in real water samples. Thus, this study opens a new pathway for the sensitive detection of NO2- in drinking water for future endeavor.

Oxidized 3,3',5,5'-tetramethylbenzidine nanobelts enhance colorimetric sensing of H2O2

Herein, oxidized 3,3',5,5'-tetramethylbenzidine (oxTMB) nanobelts were developed to enhance the colorimetric and paper-based sensing of H2O2. It was found that the minor component of Fe2+ in Na2SO4 reagent could catalyze the oxidization of TMB by H2O2 into positively charged oxTMB, which was further assembled into dark blue oxTMB nanobelts via electrostatic interaction with SO42-. The extinction originating from the absorption and scattering of oxTMB nanobelts was utilized to quantitatively detect H2O2 with a wide linear detection range (1.0-300 μM) and a low limit of detection (0.48 μM). In addition, no coffee-ring effect was observed in the test zone of the paper-based colorimetric array, which was beneficial to judge the color by naked eye. Finally, the colorimetric method was applied to detect H2O2 in contact lens care solution. This work not only proposed a new colorimetric sensing platform for H2O2, but also highlighted the minor component in the reagent might influence the experimental result.

Preparation of ultra-sensitive and selective hydrogen peroxide-based colorimetric sensor using highly exfoliated g-C3N4 nanosheets with peroxidase-like activity

A highly sensitive, portable, rapid, and accurate colorimetric sensing method is presented. It is based upon exfoliated g-C3N4 nanosheets (E-g-C3N4 NSs), having peroxidase nanozyme-like properties. The as-prepared catalyst (E-g-C3N4 NSs) tends to oxidize the colorless tetramethyl-benzidine (TMB) into oxidized-TMB in the presence of hydrogen peroxide (H2O2) generating a dark blue color and corresponding ultraviolet visible-spectral changes following a Michaelis-Menten kinetic. The prepared colorimetric sensor exhibited response within the range 0.001-0.450 μM having R2 value of 0.999 and a detective limit (LOD) of 0.15 ± 0.04 nM. Furthermore, the sensor also displayed outstanding selectivity, ample stability (10 weeks), and excellent practicability in real sample applications. All these outstanding properties were highly attributed to the large surface area with exposed actives sites, high surface energy, and large conductive structure of E-g-C3N4 NSs. For comparison of the catalytic study, we have also explored the sensing mechanism of B-g-C3N4, using the same optimized experimental conditions. Resultantly, we concluded that the proposed sensor (E-g-C3N4 NSs) will gain considerable attention for on-site environmental and health monitoring in future endeavor.

Effect of precipitant on pro-oxidative and antibacterial properties of CeO2 nanoparticles - an experimental study

In this study, the synthesis of pro-oxidative cerium-oxide nanozymes (CeO2 NZs) is reliably performed via the co-precipitation method using ceric ammonium nitrate as a precursor and ammonium carbonate as a precipitating agent. Different samples of CeO2 NZs were prepared by varying the amount of the precipitant. The synthesized NZs were characterized by ultraviolet-visible (UV-vis) spectroscopy, particle size analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM) and then checked for their pro-oxidative (peroxidase and oxidase) activity. Furthermore, we studied the NZ kinetics and antibacterial properties of synthesized samples.

Biocompatible Palladium Nanoparticles Prepared Using Vancomycin for Colorimetric Detection of Hydroquinone

Hydroquinone poses a major threat to human health and is refractory to degradation, so it is important to establish a convenient detection method. In this paper, we present a novel colorimetric method for the detection of hydroquinone based on a peroxidase-like Pd nanozyme. The vancomycin-stabilized palladium nanoparticles (Van-Pd_n NPs, n = 0.5, 1, 2) were prepared using vancomycin as a biological template. The successful synthesis of Van-Pd_n NPs (n = 0.5, 1, 2) was demonstrated by UV-vis spectrophotometry, transmission electron microscopy, and X-ray diffraction. The sizes of Pd nanoparticles inside Van-Pd_0.5 NPs, Van-Pd₁ NPs, and Van-Pd₂ NPs were 2.6 ± 0.5 nm, 2.9 ± 0.6 nm, and 4.3 ± 0.5 nm, respectively. Furthermore, Van-Pd₂ NPs exhibited excellent biocompatibility based on the MTT assay. More importantly, Van-Pd₂ NPs had good peroxidase-like activity. A reliable hydroquinone detection method was established based on the peroxidase-like activity of Van-Pd₂ NPs, and the detection limit was as low as 0.323 μM. Therefore, vancomycin improved the peroxidase-like activity and biocompatibility of Van-Pd₂ NPs. Van-Pd₂ NPs have good application prospects in the colorimetric detection of hydroquinone.

Batch and Flow Synthesis of CeO2 Nanomaterials Using Solid-state Microwave Generators

Microwave-assisted synthesis in combination with flow synthesis offers an interesting approach to develop faster and more sustainable procedures for the preparation of homogeneous nanomaterials. Recently, solid-state generators of microwaves appeared as a tool with improved control over power and frequency. Cerium oxide, despite its excellent catalytic activity, has not been prepared before using solid-state generators or microwave-assisted flow chemistry. We report a procedure for the preparation of nanoparticulated CeO₂ (around 4 nm) under 2.45 GHz microwaves in only 30 s. The materials are further calcined at 800 °C to increase particle size, with a better defined particle size and crystallinity. The procedure was tested in batch at pH 11 and 12 and diverse potencies, and the products were characterized by TEM, XRD, DLS, and N₂ adsorption–desorption isotherms. The materials were similar at the diverse pH values and potencies. XRD confirms the crystallinity of the CeO₂ material with a fluorite-like structure. They are composed of particles around 40 nm that aggregate as structures of around 100 nm. The procedure was successfully adapted to flow synthesis, obtaining materials with structure and properties equivalent to batch synthesis. The batch and flow materials offer peroxidase properties, opening the door for their use as ROS scavengers.

Recent Trends in Biosensors for Environmental Quality Monitoring

The monitoring of environmental pollution requires fast, reliable, cost-effective and small devices. This need explains the recent trends in the development of biosensing devices for pollutant detection. The present review aims to summarize the newest trends regarding the use of biosensors to detect environmental contaminants. Enzyme, whole cell, antibody, aptamer, and DNA-based biosensors and biomimetic sensors are discussed. We summarize their applicability to the detection of various pollutants and mention their constructive characteristics. Several detection principles are used in biosensor design: amperometry, conductometry, luminescence, etc. They differ in terms of rapidity, sensitivity, profitability, and design. Each one is characterized by specific selectivity and detection limits depending on the sensitive element. Mimetic biosensors are slowly gaining attention from researchers and users due to their advantages compared with classical ones. Further studies are necessary for the development of robust biosensing devices that can successfully be used for the detection of pollutants from complex matrices without prior sample preparation.

Peroxidase-Like Platinum Clusters Synthesized by Ganoderma lucidum Polysaccharide for Sensitively Colorimetric Detection of Dopamine

The sensitive and selective detection of dopamine (DA) is very important for the early diagnosis of DA-related diseases. In this study, we reported the colorimetric detection of DA using Ganoderma lucidum polysaccharide (GLP) stabilized platinum nanoclusters (Pt_n-GLP NCs). When Pt₆₀₀-GLP NCs was added, 3,3’,5,5’-tetramethylbenzidine (TMB) was rapidly catalyzed and oxidized to blue oxTMB, indicating the peroxidase-like activity of Pt₆₀₀-GLP NCs. The catalytic reaction on the substrate TMB followed the Michaelis-Menton kinetics with the ping-pong mechanism. The mechanism of the colorimetric reaction was mainly due to the formation of hydroxyl radical (•OH). Furthermore, the catalytic reaction of Pt₆₀₀-GLP NCs was used in the colorimetric detection of DA. The linear range for DA was 1–100 μM and the detection limit was 0.66 μM. The sensitive detection of DA using Pt-GLP NCs with peroxidase-like activity offers a simple and practical method that may have great potential applications in the biotechnology field.

Expedite Fluorescent Sensor Prototype for Hydrogen Peroxide Detection with Long-Life Test Substrates

We report a practical fluorescent sensor device for the trace amount detection of hydrogen peroxide vapor. In this paper, we have significantly improved the performance of fluorescence analysis for the detection of peroxides by solving the problems of packaging and storage of active materials and transferring the chemical experiment phenomenon to the actual project output. The fluorescent sensor molecule, test substrates, mixing methods, and the way to improve the life time are carefully studied. Combined with the design of circuit and programming, a field-test prototype was designed for peroxide explosives and its performance and algorithm were screened and optimized. In the detection of traces of H₂O₂ generated by ultraviolet separation or leaked as inherent impurities, the high-efficiency and rapid detection of peroxide-based explosives is achieved. The detection limit of H₂O₂ is expected to reach 2 ppb, and the response time can reach <0.5 s.