We report a new production pathway for a variety of metal oxide nanocrystallites via submerged illumination in water: submerged photosynthesis of crystallites (SPSC). Similar to the growth of green plants by photosynthesis, nanocrystallites shaped as nanoflowers and nanorods are hereby shown to grow at the protruded surfaces via illumination in pure, neutral water. The process is photocatalytic, accompanied with hydroxyl radical generation via water splitting; hydrogen gas is generated in some cases, which indicates potential for application in green technologies. Together with the aid of ab initio calculation, it turns out that the nanobumped surface, as well as aqueous ambience and illumination are essential for the SPSC method. Therefore, SPSC is a surfactant-free, low-temperature technique for metal oxide nanocrystallites fabrication.
Stainless steel nanoparticles or 'nanoballs' have been synthesised using submerged glow-discharge plasma. Transmission electron microscopy showed that the nanoballs are uniformly spherical and size distribution estimation showed that their diameters are below 200 nm. The decomposition of methylene blue solution under ultraviolet light with the wavelength of 354 nm was observed in the presence of stainless steel nanoballs. A mixture of stainless steel nanoballs and 0.1% methylene blue dye was irradiated with ultraviolet light. The concentration of methylene blue was reduced to baseline level in 72 hours. This shows that the stainless steel nanoballs have photocatalytic ability. In stainless steel nanoballs, methylene blue showed two different decomposition pathways; showing fast and slow reactions. Also, methylene blue was oxidised into sulphoxide before reducing into lighter by-products. X-ray diffraction analysis has shown that the nanoballs consist of Fe 2 O 3 and Cr 2 O 3 , which are photocatalytically active species.
Stainless steel has shown potential as a catalytic material in bulk form. However, it only becomes active in an aqueous acidic environment and elevated temperatures. This study aims to produce stainless steel nanoparticles that have high photocatalytic activity in a neutral medium and at room temperature and to elucidate the photocatalytic activity mechanism of the nanoparticles. Spherical, photocatalytic nanoparticles called "nanoballs" were synthesized by the submerged glow-discharge method. Stainless steel SUS316L grade wire was used as the cathode, platinum mesh was used as the anode while the electrolyte was potassium carbonate. The nanoballs were obtained after centrifuging and washing with water. The physical characteristics of the photocatalytic nanoballs were analysed by scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The nanoballs were mixed with methylene blue and irradiated with ultraviolet light for the evaluation of photocatalytic reaction. The photodecomposition samples were determined using UV-vis spectrometry. The by-products of the photodecomposition were evaluated using mass spectrometry. The results show that stainless steel nanoballs have photocatalytic activity when irridiated with ultraviolet light at room temperature. Submerged glow-discharge plasma method can synthesize nanoparticles rapidly using only metal wires as the electrode.
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