Tailoring a Zinc Oxide Nanorod Surface by Adding an Earth‐Abundant Cocatalyst for Induced Sunlight Water Oxidation

Abstract

Herein, a detailed investigation of the surface modification of a zinc oxide (ZnO) nanorod electrode with FeOOH nanoparticles dispersed in glycine was conducted to improve the water oxidation reaction assisted by sunlight. The results were systematically analysed in terms of the general parameters (light absorption, charge separation, and surface for catalysis) that govern the photocurrent density response of metal oxide as photoanode in a photoelectrochemical (PEC) cell. ZnO electrodes surface were modified with different concentration of FeOOH nanoparticles using the spin‐coating deposition method, and it was found that 6‐layer deposition of glycine‐FeOOH nanoparticles is the optimum condition. The glycine plays an important role decreasing the agglomeration of FeOOH nanoparticles over the ZnO electrode surface and increasing the overall performance. Comparing bare ZnO electrodes with the ones modified with glycine‐FeOOH nanoparticles an enhanced photocurrent density can be observed from 0.27 to 0.57 mA/cm2 at 1.23 VRHE under sunlight irradiation. The impedance spectroscopy data aid us to conclude that the higher photocurrent density is an effect associated with more efficient surface for chemical reaction instead of electronic improvement. Nevertheless, the charge separation efficiency remains low for this system. The present discovery shows that the combination of glycine‐FeOOH nanoparticle is suitable and environmentally‐friend cocatalyst to enhance the ZnO nanorod electrode activity for the oxygen evolution reaction assisted by sunlight irradiation.

Electrochemical Immunosensors Based on Zinc Oxide Nanorods for Detection of Antibodies Against SARS-CoV-2 Spike Protein in Convalescent and Vaccinated Individuals

“…SEM images of ZnONRs show that the rods have a hexagonal shape with an average diameter of 490 nm, as shown in Figures F and A. The results are consistent with studies previously published by the group , and other researchers. − After SARS-CoV-2 recombinant spike protein immobilization, visual morphological changes were observed. The surface of the nanorods does not look smooth; it seems to be covered, indicating that an optimal immobilized protein profile was achieved (Figure B).…”

“…SEM images of ZnONRs show that the rods have a hexagonal shape with an average diameter of 490 nm, as shown in Figures 2F and 3A. The results are consistent with studies previously published by the group 61,79 and other researchers. 80−82 After SARS-CoV-2 recombinant spike protein immobilization, visual morphological changes were observed.…”

ZnO-Based Electrochemical Immunosensor to Assess Vaccine-Induced Antibody-Mediated Immunity against Wild-Type and Gamma SARS-CoV-2 Strains

“…The SEM images in Figure 3 A,B demonstrate that ZnONRs are highly dense and grown on the surface of FTO glass substrates. The high-magnification SEM image in Figure 3 C reveals that the ZnONRs obtained possess a hexagonal morphology, with an average diameter of approximately 200–300 nm, consistent with results reported elsewhere [ 16 , 22 , 29 ]. SEM images of the FTO-ZnONRs/spike WT and the FTO-ZnONRs/spike P.1 electrodes are presented in Figure 3 D,E, respectively.…”

“…Glycine was used as an agent to prevent non-specific antibody binding on the device surface and to have a low dielectric constant [ 18 , 19 , 20 , 21 ]. In previous work, we have demonstrated that the glycine coating works directly on the ZnO nanorods since it has a good affinity for carboxylic groups [ 22 ]. A volume of 20 μL of serum sample diluted 1:500 ( v / v ) in PBS (pH 7.4) was incubated for 1 h on the electrode surface, rinsed to wash away the unbound material (non-specific antibodies), and subsequently dried.…”