RESUMEN
Perovskite-based SrSnO3 nanostructures doped with indium are prepared via a facile chemical precipitation method. Prepared nanostructures are used to assemble the dye-sensitized solar cells (DSSCs), and their photovoltaic response and electrochemical impedance spectra are measured. The synthesized samples are subjected to structural, morphological, optical, and magnetic properties. The X-ray diffraction pattern confirms the single-phase orthorhombic (Pbnm) perovskite structure. Local structural and phonon mode variations are examined by Raman spectra. Electron micrographs disclose the nanorods. The elements (Sr, Sn, O, and In) and the existence of oxygen vacancies are identified by X-ray photoelectron spectroscopy analysis. Surface area analysis demonstrates the higher surface area (11.8 m2/g) for SrSnO3 nanostructures. Optical absorption spectra confirm the good optical behavior in the ultraviolet region. The multicolor emission affirms the presence of defects/vacancies present in the synthesized samples. The appearance of interesting ferromagnetic behavior in the prepared samples is due to the presence of F-center exchange interactions. Under the irradiation (1000 W/m2) of simulated sunlight, the DSSC fabricated by 3% In-doped SrSnO3 exhibits the highest η of 5.68%. Hence, the blocking layers prepared with pure and indium-doped samples could be the potential candidates for DSSC applications.
RESUMEN
ZnO nanorods and Mn/ZnO microflowers with nano-sized petals exhibit singly ionized oxygen vacancies, V. This is strongly supported by a green photoluminescence emission at 2.22 eV and an EPR g value of 1.953, both of which are suppressed greatly after annealing in an oxygen atmosphere. A strong red emission observed during exposure to X-rays reveals the presence of F(+) centres as a consequence of the V. Mn/ZnO displayed enhanced H2 generation with visible light exposure, when compared to pure ZnO and annealed Mn/ZnO in the visible region, which directly correlated with the oxygen vacancy concentration. There is an interesting correlation between the intensities of the EPR lines at the g-value of 1.953 due to the oxygen vacancies, the intensity of light emitted from the exposure to X-rays, the intensity of the photoluminescence due to oxygen vacancies and the quantity of H2 produced by the photocatalytic effect when comparing the three different nanomaterials, viz. pure ZnO, Mn/ZnO before and after annealing, all having been made exactly by the same methodologies.
RESUMEN
Silver doped zinc oxide nanoparticles are synthesized by a solution combustion method. The samples characterized by a variety of spectroscopic and other techniques clearly reveal the presence of silver nanoparticles as well as silver clusters. The silver in the two forms was identified by careful deconvolution of X-ray photoelectron spectral results. Their formation was also confirmed by the presence of plasmons, the concentration and energy of which increase on increasing silver input, indicating the presence of perpendicular excitons since aggregates of clusters are known to shift the plasmon resonances depending on their topologies. Further confirmation of clusters came from EPR (electron paramagnetic resonance), HRSEM (high resolution scanning electron microscopy) and HRTEM (high resolution transmission electron microscopy); direct proof for clusters came from matrix assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectral measurements. The antimicrobial activity of the silver doped zinc oxide polymer nanocomposites as biomedical devices are measured by zone of inhibition. Also, samples coated on paper disk with acacia binder are evaluated by a disk diffusion method. While pure zinc oxide does not show any antimicrobial property, the activity of silver-doped zinc oxide is comparable to that of commercial antibiotics and found to be related to nanoparticulate silver. Similarly, the microbial adherence to the surface of polymer nanocomposite which mimics a biomedical device also was influenced by nanoparticles of silver. The photocatalytic water treatment was carried out using silver carrying nanoparticles with Rhodamine-B and 4-chlorophenol as model pollutants. The increased photocatalytic activity of silver containing zinc oxide as compared to pure zinc oxide nanoparticles is attributed to the synergistic display of the properties of silver nanoparticles and clusters in zinc oxide. This activity depends upon the dispersion of silver nanoparticles over the zinc oxide lattice where charge separation plays a dominant role. The mechanisms for both photocatalysis and antimicrobial activity are discussed.