Electrochemical Hydrogen Peroxide Sensor Based on Macroporous Silicon

Kinetic detection of hydrogen peroxide in single horseradish peroxidase-concentrated silica particle using confocal fluorescence microspectroscopic measurement

In the present study, we propose a scheme for detecting H2O2 by using horseradish peroxidase (HRP) adsorbed onto single silica particles and fluorescence microspectroscopy. When the silica particles were immersed in an HRP solution, the HRP concentration in the silica particles increased by a factor of 690 compared to that in the bulk aqueous solution because HRP was adsorbed on the silica surface. When a single particle containing HRP was added to a mixed solution of H2O2 and Amplex Red, fluorescence from resorufin, which was produced by the reaction of HRP, H2O2, and Amplex Red, was observed. The fluorescence from the resorufin in the particles increased after a single particle was added to the solution, and the release of resorufin was observed. As the concentration of H2O2 (CH2O2) decreased, the time it takes for fluorescence intensity to reach its maximum was shorter. The detection limit for H2O2 in the present system was 980 nM. The reaction behavior of a single silica particle was evaluated using a spherical diffusion model, which explains the approximate concentration change of resorufin in the silica particle. The proposed method has the advantages of simple sample preparation and detection, low sample consumption, and a short detection time.

A Core–Shell Au@TiO2 and Multi-Walled Carbon Nanotube-Based Sensor for the Electroanalytical Determination of H2O2 in Human Blood Serum and Saliva

A hydrogen peroxide (H₂O₂) sensor was developed based on core–shell gold@titanium dioxide nanoparticles and multi-walled carbon nanotubes modified glassy carbon electrode (Au@TiO₂/MWCNTs/GCE). Core–shell Au@TiO₂ material was prepared and characterized using a scanning electron microscopy and energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), atomic force microscopy (AFM), Raman spectroscopy, X-ray diffraction (XRD) and Zeta-potential analyzer. The proposed sensor (Au@TiO₂/MWCNTs/GCE) was investigated electrochemically using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The analytical performance of the sensor was evaluated towards H₂O₂ using differential pulse voltammetry (DPV). The proposed sensor exhibited excellent stability and sensitivity with a linear concentration range from 5 to 200 µM (R² = 0.9973) and 200 to 6000 µM (R² = 0.9994), and a limit of detection (LOD) of 1.4 µM achieved under physiological pH conditions. The practicality of the proposed sensor was further tested by measuring H₂O₂ in human serum and saliva samples. The observed response and recovery results demonstrate its potential for real-world H₂O₂ monitoring. Additionally, the proposed sensor and detection strategy can offer potential prospects in electrochemical sensors development, indicative oxidative stress monitoring, clinical diagnostics, general cancer biomarker measurements, paper bleaching, etc.

Colorimetric assay based on horseradish peroxidase/reduced graphene oxide hybrid for sensitive detection of hydrogen peroxide in beverages

We reported a simple and sensitive colorimetric assay for detection of hydrogen peroxide (H₂O₂) based on the oxidation of 2,2׳-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) by UV-Vis spectroscopy method. The reduced graphene oxide (rGO) was prepared using green tea extract as bio-reducing and stabilizer agent and decorated by horseradish peroxidase (HRP). The surface of Au interface was modified with HRP-rGO hybrid. The formation of HRP-rGO hybrid was confirmed by cyclic voltammetry, scanning electron microscopy (SEM), energy-dispersive X-ray Spectroscopy (EDX) and Raman spectroscopy·H₂O₂ can be catalysed by HRP-rGO hybrid and converted into water and oxygen. The ABTS substrate takes up oxygen to form a green coloured product that has absorption peaks at 421, 655 nm and 737 nm. The colour development is linearly dependent on HRP in the range of 4-50 µg/L. The color of the green product solution is stable for 20 min. The absorption intensity is strongly related to the hydrogen peroxide concentration. The absorption intensity of the formed product scaled linearly with the hydrogen peroxide concentration in the ranges of 0.3-20 µM and 20-8000 µM with a detection limit of ≈15 nM could be achieved. The biosensor with excellent limit detection and wide linear ranges was adapted to monitor H₂O₂ in different beverages.

ZnO Films Incorporation Study on Macroporous Silicon Structure

In the present work, we developed hybrid nanostructures based on ZnO films deposited on macroporous silicon substrates using the sol–gel spin coating and ultrasonic spray pyrolysis (USP) techniques. The changes in the growth of ZnO films on macroporous silicon were studied using a UV-visible spectrometer, an X-ray diffractometer (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). XRD analysis revealed the beneficial influence of macroporous silicon on the structural properties of ZnO films. SEM micrographs showed the growth and coverage of ZnO granular and flake-like crystals inside the pores of the substrate. The root mean square roughness (RMS) measured by AFM in the ZnO grown on the macroporous silicon substrate was up to one order of magnitude higher than reference samples. These results prove that the methods used in this work are effective to cover porous and obtain nano-morphologies of ZnO. These morphologies could be useful for making highly sensitive gas sensors.

Gold Nanoframe Array Electrode for Straightforward Detection of Hydrogen Peroxide

The nanostructuring of a sensing membrane is performed through colloidal nanosphere lithography (NSL) techniques with a tiny polystyrene nanobead template 100 nm in size. The solvent ratio adjustment has been proven to be effective in assisting the monolayer deposition of small templating particles with minimal defects. Two distinct structures, namely, a billowy gold nanostructure (BGN) where the nanobead template is left unetched and a gold nanoframe array (GNA) with a regular ring-like structure after template removal, are used for the extended-gate field-effect transistor (EGFET) electrodes. The GNA structure generates an electroactive surface area significantly (~20%) larger than its geometrical area as well as a greater surface roughness than the BGN. When integrated with the portable constant voltage–constant current (CVCC) FET circuitry for pH screening to determine the optimized measurement conditions for H2O2 sensing, the GNA sensing membrane also shows more improved Nernstian sensitivity at ~50 mV/pH than the BGN electrode. The more optimized sensitivity is then proven using the GNA in the detection of H2O2, the most common representative reactive oxygen species (ROS) involved in the environment, food, and neurodegenerative diseases, such as Parkinson´s and Alzheimer´s diseases. The GNA electrode has a sensitivity of 70.42 mV/log µM [H2O2] and a limit of detection (LoD) of 1.183 µM H2O2. The integrated ion sensing system employing unique, highly ordered gold array gate electrodes and a portable CVCC circuit system has shown a stable real-time output voltage signal, representing an alternative to bulky conventional FET devices for potential on-site H2O2 detection.