Synthesis of flower like zinc oxide nanostructure and its application as a photocatalyst

Nanocomposite of starch, gelatin and itaconic acid-based biodegradable hydrogel and ZnO/cellulose nanofiber: A pH-sensitive sustained drug delivery vehicle

In recent years, hydrogels as drug carriers have been receiving great interest due to their ability to change their behavior in response to one or more external stimuli. However, their initial burst release profile limits their practical applications. Therefore, we prepared a bio-based hydrogel nanocomposite (HNC) using starch, itaconic acid, acrylic acid and gelatin in the presence of CNF/ZnO-based nanohybrid (ZONH) and used it to evaluate the pH-sensitive drug release properties in different pH solutions. The prepared HNCs were analyzed using various spectroscopic and microscopic techniques. The BET analysis and swelling test of the HNC indicated improved porosity and swelling capacity due to the addition of ZONH. From the drug release study, sustained drug release rate was observed at pH 4 than those at pH 7.4 and 9, indicating controlled release as well as pH responsive behavior of the HNC. Moreover, the drug released HNC was reused as a photocatalyst for dye degradation and achieved good degradation (%). The antibacterial activity of ZONH and HNC was observed against EC and SA bacterial strains from the antibacterial test. In summary, the prepared HNC can be considered as a potential sustainable DDS for biomedical applications as well as a photocatalyst for dye contaminated water treatment.

Tuning the Microstructures of ZnO To Enhance Photocatalytic NO Removal Performances

Effective removal of kinetically inert dilute nitrogen oxide (NO, ppb) without NO₂ emission is still a challenging topic in environmental pollution control. One effective approach to reducing the harm of NO is the construction of photocatalysts with diversified microstructures and atomic arrangements that could promote adsorption, activation, and complete removal of NO without yielding secondary pollution. Herein, microstructure regulations of ZnO photocatalysts were attempted by altering the reaction temperature and alkalinity in a unique ionic liquid-based solid-state synthesis and further investigated for the removal of dilute NO upon light irradiation. Microstructure observations indicated that as-tuned photocatalysts displayed unique nucleation, diverse morphologies (spherical nanoparticles, short and long nanorods), defect-related optical characteristics, and enhanced carrier separations. Such defect-related surface-interface aspects, especially V_o″-related defects of ZnO devoted them to the 4.16-fold enhanced NO removal and 2.76 magnitude order decreased NO₂ yields, respectively. Improved NO removal and toxic product inhabitation in as-tuned ZnO was disclosed by mechanistic exploitations. It was revealed that regulated microstructures, defect-related charge carrier separation, and strengthened surface interactions were beneficial to active species production and molecular oxygen activation in ZnO, subsequently contributing to the improved NO removal and simultaneous avoidance of NO₂ formation. This investigation shed light on the facile regulation of microstructures and the roles of surface chemistry in the oxidation of low concentration NO in the ppb level upon light illumination.

Substrate free ultrasonic-assisted hydrothermal growth of ZnO nanoflowers at low temperature

ZnO nanoflowers (NFs) have been synthesised using a simple cost effective ultrasonic-assisted hydrothermal method at low temperature of 95 °C. Here the NFs consist of petal-like arrangement of several hexagonal-shaped nanorods, the length and diameter of which lie in a range of 100–150 nm and 30–70 nm, respectively. ZnO NFs possess hexagonal wurtzite phase, high crystallinity and strong absorption in the UV region. The optical band gap 3.25 eV of these NFs estimated by two different ways is found to be nearly the same. Room temperature photoluminescence spectrum reveals that the ZnO NFs exhibit dominant UV emission and three major emissions in the visible i.e. violet, blue–green and yellow. NFs are promising nanostructures for application in environment related sensors and antimicrobial activity.

Synthesis of Vertically-Aligned Zinc Oxide Nanowires and Their Application as a Photocatalyst

Vertically aligned zinc oxide (ZnO) nanowires were hydrothermally synthesized on a glass substrate with the assistance of a pre-coated ZnO seeding layer. The crystalline structure, morphology and transmission spectrum of the as-synthesized sample were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and ultraviolet-visible (UV-Vis) spectrophotometry, respectively, indicating a wurzite ZnO material of approximately 100 nm wire diameter and absorbance at 425 nm and lower wavelengths. The photocatalytic activity of the sample was tested via the degradation of methyl orange in aqueous solution under UV-A irradiation. The synthesized nanowires showed a high photocatalytic activity, which increased up to 90% degradation in 2 h as pH was increased to 12. It was shown that the photocatalytic activity of the nanowires was proportional to the length to diameter ratio of the nanowires, which was in turn controlled by the growth time and grain size of the seed layer. Estimates suggest that diffusion into the regions between nanowires may be significantly hindered. Finally, the reusability of the prepared ZnO nanowire samples was also investigated, with results showing that the nanowires still showed 97% of its original photoactivity after ten cycles of use.

A joint experimental and theoretical study on ZnO nanocomposites synthesised by a liquid deposition method

ZnO was grown on mordenite zeolite, activated carbon and alumina substrates by a liquid deposition method. The photocatalytic activity of the synthesised samples was elucidated using the photodegradation of Acid Blue 92 (AB92) dyes as a test pollutant under UV light irradiation. Supports play a key role in AB92 photodegradation and significantly improve the photocatalytic activity of ZnO. Different supports form additional transport channels and provide an effective pathway for the charge carriers. The supports effectively construct porous structures with more active sites. Hence, the higher photocatalytic activity of supported catalysts is attributed to the large surface area and charge carrier separation. Bader's AIM theory showed that the strength and nature of intermolecular interactions between ZnO and the various supports is different. All geometry structures were optimised with B3LYP/6-31g (d) level theory. The performed local reactivity descriptors determined the reactive sites in molecules, demonstrating the mechanism for the enhanced photocatalytic activity of the composites. Both experimental and theoretical results confirm that the insertion of ZnO nanoparticles on the supports enhances electron transfer between ZnO and the catalyst surface, thus inhibiting charge recombination. The highest photocatalytic activity was observed for ZnO/MOR nanocomposite due to its high surface area, unique structure of MOR and photonic efficiency.

Photocatalytic degradation of the antibiotic levofloxacin using highly crystalline TiO2 nanoparticles

Highly crystalline TiO₂ (anatase) nanoparticles were synthesized by a facile sol–gel method for the photocatalytic degradation and inhibition of the commonly used antibiotic drug, levofloxacin.