Alumina nanoparticles were synthesized from locally available high alumina clay, obtained from Giro in Kabbi State, through acid leaching with sol-gel method. The clay was leached with hydrofluoric acid and the aluminous solution produced was used as precursor to synthesis nanoparticles through sol gel process. The composition and structure of the clay and the particles produced were characterized using Fourier Transform Infrared (FTIR), X-ray diffraction and fluorescence Spectroscopic techniques, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). From the analyses, the clay sample was observed to be high in alumina and predominantly Kaolinitic in nature. During the sol-gel process, effective flocculation was obtained at slightly alkaline pH range (7.6 to 8.0) and a relative moderate temperature of 80oC. The result also shows that the aging time of the gel affected the size of the particles produced during the process, and the particles are mainly nano-alumina.
Synthesis of Zinc oxide nanoparticles (ZnONPs) using plant extract was carried out in this work because of its advantages over other method of synthesis namely; simplicity, environmental friendliness and elimination of toxic chemicals. Fresh Siam leaf extract was characterized over a period of 10 days to study the effect of time on the optical photon energy absorption properties. ZnONPs was synthesized and deposited on substrate by spin-coating method and characterized by UV-vis spectroscopy, Fourier transform infra-red spectroscopy, Scanning Electron microscopy, and Energy Dispersive X-ray. ZnONPs thin film device was then fabricated to study the electrical properties. From UV-vis spectroscopic result, as the time (day) increased, there was an increase in the value of the transmittance and corresponding reduction in photon energy absorption. FTIR result gives the functional groups and absorption number at 3448.04cm−1 O-H single bond, 2524.85cm−1 C-H bond, 1437.15 cm−1, 880.59 cm−1, 729.06 cm−1, 433.44 cm−1 Zn-OH and Zn-O variety of single bond. The surface morphology shows large grain size. Energy band gap of ZnONPs was approximately 3.7 eV. The fabricated ZnONPs thin film device under illumination has efficiency of 2.010/0. From the morphology, optical, and electrical properties of the ZnONPs thin film and device, it could be a suitable material for crystalline solar cells as photoanode.
Current advancements in nanotechnology appear to open a more efficient, stable, and cheaper way of producing solar cells to replace the too expensive means of inorganic solar cells production. The creation of nanoscale materials for advanced structures has led to a growing research interest in the area of photovoltaic energy conversion using photovoltaic devices. This research investigates the impact of annealing temperature on the optical properties of silver nanoparticles-doped titanium (IV) oxide thin film (TiO2:AgNPs) deposited by spin-coating method on glass substrate. AgNPs were prepared using the leaf extract of Gliricidia sepium as a reducing agent for silver nitrate. Deposition of TiO2:AgNPs composite solution was performed in different volume ratio. Deposition of TiO2:AgNPs volume ratio (1: 0.2) was performed with different spin-coating speed for 30 seconds at 7 different thicknesses. Characterization of the optical properties of thin films was carried out by using a UV-vis single beam spectrophotometer; this was used to calculate the absorbance and the bandgap energy. Sixteen 16 samples of TiO2:AgNPs deposited at 1000 rpm on the glass substrate were annealed at temperature range of 50 to 425 °C with step of 10 °C interval in a tubular furnace. It was observed from the results that the peak absorption of photon energy occurred at 375 °C in the visible spectrum of the wavelength band. The optimal thickness for peak absorbance of the TiO2:AgNPs blend layer occurred at 115 nm in the visible spectrum and at the corresponding spin speed of 1000 rpm. The optimized fabrication process with blend layer thickness of 115 nm yielded the best absorbance at an annealed temperature of 375 °C in the visible spectrum. The volume ratio of (1:0.2) gave the peak absorption at 0.75 au. At 1000 rpm with the corresponding thickness of 115 nm, TiO2:AgNPs blend has the peak absorbance. The energy band gap of the blend thin film is 3.58 eV at 375 °C in the visible spectrum of wavelength band. The result obtained showed that AgNPs enhanced light absorption, broadened absorption spectral range and thermal stability of titanium (IV) oxide film. The result can be used as a guideline in the design and fabrication of solar cells.
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