Nanoscale Au-ZnO Heterostructure Developed by Atomic Layer Deposition Towards Amperometric H2O2 Detection

Novel Synthesis of Sensitive Cu-ZnO Nanorod-Based Sensor for Hydrogen Peroxide Sensing

We aimed to synthesize sensitive electrochemical sensors for hydrogen peroxide sensing by using zinc oxide nanorods grown on a fluorine-doped tin oxide electrode by using the facial hydrothermal method. It was essential to keep the surface morphology of the material (nanorods structure); due to its large surface area, the concerned material has enhanced detection ability toward the analyte. The work presents a non-enzymatic H₂O₂ sensor using vertically grown zinc oxide nanorods on the electrode (FTO) surfaces with Cu nanoparticles deposited on zinc oxide nanorods to enhance the activity. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-Ray (EDX), X-ray diffraction (XRD), and electrochemical methods were used to characterize copper–zinc oxide nanorods. In addition to the high surface area, the hexagonal Cu-ZnO nanorods exhibited enhanced electrochemical features of H₂O₂ oxidation. Nanorods made from Cu-ZnO exhibit highly efficient sensitivity of 3415 μAmM⁻¹cm⁻² low detection limits (LODs) of 0.16 μM and extremely wide linear ranges (0.001–11 mM). In addition, copper-zinc oxide nanorods demonstrated decent reproducibility, repeatability, stability, and selectivity after being used for H₂O₂ sensing in water samples with an RSD value of 3.83%. Cu nanoparticles decorated on ZnO nanorods demonstrate excellent potential for the detection of hydrogen peroxide, providing a new way to prepare hydrogen peroxide detecting devices.

Au nanoparticles decorated ZnO/ZnFe2O4 composite SERS-active substrate for melamine detection

Surface-enhanced Raman scattering (SERS) based on plasmonic metal nanoparticles and semiconductors has been used as performance-enhancing structures for sensing trace chemicals. We have selected a case of oxide functional oxide organic nanostructure between ZnFe₂O₄ and ZnO, denoted as ZZF. By decorating such nanostructure with AuNPs, to identify R6G in varying concentrations (10^-6 M - 10^-12 M), an enhancement factor of 1.6 × 10⁸ was observed. The material was used for the identification of melamine in the concentration range of 0.39 μM-7.92 μM. This high-performance nanocomposite provides improved melamine sensitivity towards SERS and the limit of detection as low as 0.39 μM. The Au-ZZF SERS substrate can yield a SERS enhancement factor of 1.37 × 10⁷. The experimental performance demonstrates that excellent SERS enhancement is due to electrons movement within ZZF and Au nanoparticles. Owing to its easy and effective synthesis methodology, this sensitive and specific SERS substrate is a promising technique to detect trace chemicals. We further study the best energetically favorable orientation of melamine molecules over the substrate leading to the SERS activity using density functional theoretical study.

Dual Transduction of H2O2 Detection Using ZnO/Laser-Induced Graphene Composites

Zinc oxide (ZnO)/laser-induced graphene (LIG) composites were prepared by mixing ZnO, grown by laser-assisted flow deposition, with LIG produced by laser irradiation of a polyimide, both in ambient conditions. Different ZnO:LIG ratios were used to infer the effect of this combination on the overall composite behavior. The optical properties, assessed by photoluminescence (PL), showed an intensity increase of the excitonic-related recombination with increasing LIG amounts, along with a reduction in the visible emission band. Charge-transfer processes between the two materials are proposed to justify these variations. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy evidenced increased electron transfer kinetics and an electrochemically active area with the amount of LIG incorporated in the composites. As the composites were designed to be used as transducer platforms in biosensing devices, their ability to detect and quantify hydrogen peroxide (H2O2) was assessed by both PL and CV analysis. The results demonstrated that both methods can be employed for sensing, displaying slightly distinct operation ranges that allow extending the detection range by combining both transduction approaches. Moreover, limits of detection as low as 0.11 mM were calculated in a tested concentration range from 0.8 to 32.7 mM, in line with the values required for their potential application in biosensors.