Preparation and Characterization ZnO Nanorods for Photocatalyst Application

Zinc oxide (ZnO) nanorods are prepared onto glass substrates via chemical bath deposition method. ZnO nanoparticles is prepared onto glass substrate to act as a seed layer for grown ZnO NRs. Field Emission Scanning Electron Microscope (FESEM) image confirmed that the grown rods have hexagonal shape covered the surface of substrate. Further, the prepared ZnO NRs appeared good crystallinity according to X-ray diffraction method. The absorption edge for seeds nanoparticles layer appeared at wavelength of 362nm (3.42 eV) while it was at around 479nm (3.27 eV) nm for the grown ZnO NRs. The grown ZnO NRs showed two emission peaks at 381nm and 540nm corresponding to near band-to-band electron-hole recombination and oxygen vacancies, respectively. Degradation rate of methylene blue (MB) dye was 0.01% after 1h of illumination by UV light and increased to 71.4% after 4h of illumination.

Synthesis of Heterostructure of ZnO@MOF-46(Zn) to Improve the Photocatalytic Performance in Methylene Blue Degradation

The heterostructure of ZnO and MOF-46(Zn) was synthesized to improve the photocatalytic performance of ZnO and prove the synergistic theory that presented the coexistence of ZnO and MOF-46(Zn), providing better efficiency than pure ZnO. The heterostructure material was synthesized by using prepared ZnO as a Zn2+ source, which was reacted with 2-aminoterephthalic acid (2-ATP) as a ligand to cover the surface of ZnO with MOF-46(Zn). The ZnO reactant materials were modified by pyrolysis of various morphologies of IRMOF-3 (Zn-MOF) prepared by using CTAB as a morphology controller. The octahedral ZnO obtained at 150 mg of CTAB shows better efficiency for photodegradation, with 85.79% within 3 h and a band gap energy of 3.11 eV. It acts as a starting material for synthesis of ZnO@MOF-46(Zn). The ZnO/MOF-46(Zn) composite was further used as a photocatalyst material in the dye (methylene blue: MB) degradation process, and the performance was compared with that of pure prepared ZnO. The results show that the photocatalytic efficiency with 61.20% in the MB degradation of the heterostructure is higher than that of pure ZnO within 60 min (90.09% within 180 min). The reason for this result may be that the coexistence of ZnO and MOF-46(Zn) can absorb a larger range of energy and reduce the possibility of the electron–hole recombination process.

Innovative Ag–TiO2 Nanofibers with Excellent Photocatalytic and Antibacterial Actions

Ag–TiO2 nanostructures were prepared by electrospinning, followed by calcination at 400 °C, and their photocatalytic and antibacterial actions were studied. Morphological characterization revealed the presence of one-dimensional uniform Ag–TiO2 nanostructured nanofibers, with a diameter from 65 to 100 nm, depending on the Ag loading, composed of small crystals interconnected with each other. Structural characterization indicated that Ag was successfully integrated as small nanocrystals without affecting much of the TiO2 crystal lattice. Moreover, the presence of nano Ag was found to contribute to reducing the band gap energy, which enables the activation by the absorption of visible light, while, at the same time, it delays the electron–hole recombination. Tests of their photocatalytic activity in methylene blue, amaranth, Congo red and orange II degradation revealed an increase by more than 20% in color removal efficiency at an almost double rate for the case of 0.1% Ag–TiO2 nanofibers with respect to pure TiO2. Moreover, the minimum inhibitory concentration was found as low as 2.5 mg/mL for E. coli and 5 mg/mL against S. aureus for the 5% Ag–TiO2 nanofibers. In general, the Ag–TiO2 nanostructured nanofibers were found to exhibit excellent structure and physical properties and to be suitable for efficient photocatalytic and antibacterial uses. Therefore, these can be suitable for further integration in various important applications.

2D Perovskites for Biological Sensors

2D perovskite’s quantum confinement and superlattices enhance electron and hole recombination which maximizes the photoluminescence quantum efficiency for optical devices. However, only a few works have been reported for biological applications, especially, DNA associated. Contemporary gene-editing science through CRISPR technology is advantageous as all types of nucleic acid chains such as RNA, single-stranded DNA, and double-stranded DNA can be modified. There are numerous reports that base pairs of nucleic acids are nonpolar and 2D perovskites that are capped with aliphatic chains possibly can operate as an optical sensor for detecting a specific sequence of DNA. Here, we demonstrate organic-inorganic halide 2D perovskite’s – capped with eight carbon long aliphatic chains – optical and structural properties. Self-assembly of tin-based perovskites showed near-unity photoluminescence quantum yield but had poor stability in water or ambient condition due to hydrolysis whereas lead-based perovskites showed less PL but were stable in water at high concentration. 2D perovskites’ unique multiple emission peaks at different wavelengths, water stability, and intensity discrepancy when conjugated in nucleoside dispersed solution were studied. However, complex multiple directionalities of PL emission, water stability by concentration, minor PL intensity or wavelength discrepancy, and toxicity followed by the lead source for the perovskites are conflicting with robust and convenient detection technique for the DNA.

Characteristics of Perovskite Solar Cells with Methylammonium Iodide-Added Anti-Solvent

The perovskite film—manufactured via a one-step method—was superficially improved through an anti-solvent process to increase solar cell efficiency. Although perovskite synthesis proceeds rapidly, a significant amount of lead iodide residue remains. Well-placed lead iodide in perovskite grains prevents electron–hole recombination; however, when irregularly placed, it interferes with the movement of electron and holes. In this study, we focused on improving the crystallinity of the perovskite layer, as well as reducing lead iodide residues by adding a methylammonium halide material to the anti-solvent. Methylammonium iodide in chlorobenzene used as an anti-solvent reduces lead iodide residues and improves the crystallinity of formamidinium lead iodide perovskite. The improved crystallinity of the perovskite layer increased the absorbance and, with reduced lead iodide residues, increased the efficiency of the perovskite solar cell by 1.914%.