Efficient Dye-Sensitized Solar Cells Based on Nanoflower-like ZnO Photoelectrode

Boosting H2O2 generation by shortening the charge migration distance in BiPO4 nanocrystals

The photocatalytic production of H2O2 has gained recognition as an economical and eco-friendly technology, but it suffers from limitations such as low production rates and difficulty in achieving high concentrations. This study was designed to overcome these limitations by preparing BiPO4 nanocrystals (BIP NCs) via high-temperature hydrolysis, and X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that BIP NCs with particle sizes of 8.5 ± 3 nm were synthesized. In a photocatalytic performance test, only H2O and O2 were used to produce H2O2, resulting in an accumulation of H2O2 of up to 30.44 mM·g-1, as measured with the potassium titanium oxalate method; this value was 3.13 times greater than that of bulk BiPO4 (BIP-B). The resulting nanocrystals demonstrated superior electron-hole transport and separation efficiency compared to those of BIP-B, and H2O2 was formed in a one-step two-electron process. Furthermore, a film composed of a gas diffusion layer (GDL) and BIP NCs provided continuous accumulation of H2O2; a concentration of 7.23 mM was achieved after 96 h of reaction, and the stability of the film was confirmed by comparing scanning electron microscopy (SEM) images obtained before and after the reaction. Construction of a nanocrystalline structure to enhance the activities of photocatalysts and films and achieve continuous accumulation of H2O2 will provide insights into the photocatalytic production of highly concentrated H2O2.

Application of Zinc Oxide nanoflowers in Environmental and Biomedical Science

Zinc oxide (ZnO) nanostructures can be synthesized in nanoforms of spheres, rods, flowers, disks, walls, etc., among which nanoflowers have gained special attention due to their versatile biomedical and pollutant remedial applications in waste water and air. ZnO nanoflowers have an ultrasmall size with a huge surface area to volume ratio due to their hexagonal petal structures which render them superior compared to the nanoparticles of other shapes. The ZnO nanoflowers have bandgap energy equivalent to a semiconductor that makes them have unique photophysical properties. We have used the appropriate keywords in Google Scholar and PubMed to obtain the recent publications related to our topic. We have selected the relevant papers and utilized them to write this review. The different methods of synthesis of ZnO nanoflowers are chemical vapor deposition, facile hydrothermal, thermal evaporation, chemical reduction, bio route of synthesis, and solvothermal method, etc. which are mentioned in this review. ZnO nanoparticles are used in paints, cosmetics, and other products due to their high photocatalytic activity. The different applications of ZnO nanoflowers in the diagnosis of disease biomarkers, biosensors, catalysts, and the therapeutic process along with wastewater remediation and gas sensing applications will be discussed in this review.

Yolk-shell ZnO@C-CeO2 ternary heterostructures with conductive N-doped carbon mediated electron transfer for highly efficient water splitting

Herein, carbon-incorporated yolk-shell ZnO@C-CeO₂ ternary heterostructures are employed as visible light responsive photocatalyst for highly efficient photoelectrochemical (PEC) water splitting. Compared to conventional ZnO/CeO₂ semiconductors, introduction of a thin PDA shell layer assures the generation of a conductive N-doped graphitic carbon layer after a calcination post-treatment with mesoporous hollow morphologies. The evaluation of PEC water splitting performance of ZnO@C-CeO₂ photoanodes reveals the maximum photocurrent density as 7.43 mA/cm² at 1.18 V RHE under light whereas almost no response is recorded at dark. These superior PEC H₂ evolution performance strongly implies efficient charge separation, facilitated charge transfer between photoanode and electrolyte interface as well as within the semiconductor bulk by means of rapid electron transfer ability of N-doped graphitic carbon layer and prolong life time of light inside yolk-shell structure. Furthermore, considerable depression in PL intensity of ZnO@C-CeO₂ photoanodes compared to ZnO clearly reveals a higher photon absorption due to the reflection of light in hollow region and increase in electron hole separation efficiency. Moreover, plausible Z-scheme charge transfer mechanism using ZnO@C-CeO₂ photoanodes under visible light illumination is verified using radical trapping experiments and X-ray photoelectron spectroscopy (XPS) methods, suggesting new generation of heterostructures for sufficient conversion of sunlight to H₂ fuels.

Hierarchical NiO/CMK-3 Photocathode for a p-Type Dye-Sensitized Solar Cell with Improved Photoelectrochemical Performance and Fast Hole Transfer

The sluggish photoelectrochemical performance of p-type dye-sensitized solar cells (p-DSSCs) has hindered its commercial use. In this work, we introduce a novel hierarchical nanocomposite of NiO nanoparticles anchored on highly ordered mesoporous carbons CMK-3 (NiO/CMK-3). Using CMK-3 as a backbone effectively prevented the self-aggregation of NiO nanoparticles and subsequently increased the total specific surface area of the composite for more dye adsorption. The interconnected conductive networks of CMK-3 also served as a split-flow high-speed channel, which was beneficial for hole spin-flow to accelerate hole transfer. The hierarchical NiO/CMK-3 photocathode improved the photovoltaic conversion efficiency to 1.48% in a cell with a Cobalt(II)/(III) electrolyte and a PMI-6T-TPA dye.

Synthesis, Characterization, and Three-Dimensional Structure Generation of Zinc Oxide-Based Nanomedicine for Biomedical Applications

Zinc oxide (ZnO) nanoparticles have been studied as metal-based drugs that may be used for biomedical applications due to the fact of their biocompatibility. Their physicochemical properties, which depend on synthesis techniques involving physical, chemical, biological, and microfluidic reactor methods affect biological activity in vitro and in vivo. Advanced tool-based physicochemical characterization is required to identify the biological and toxicological effects of ZnO nanoparticles. These nanoparticles have variable morphologies and can be molded into three-dimensional structures to enhance their performance. Zinc oxide nanoparticles have shown therapeutic activity against cancer, diabetes, microbial infection, and inflammation. They have also shown the potential to aid in wound healing and can be used for imaging tools and sensors. In this review, we discuss the synthesis techniques, physicochemical characteristics, evaluation tools, techniques used to generate three-dimensional structures, and the various biomedical applications of ZnO nanoparticles.