A new microwave plasma assisted sol-gel (MPAS) technique was adopted to produce Titanium dioxide (TiO 2 ) photocatalyst by using pure and mixed stabilizers. The crystalline phases, composition, bandgap energy and surface morphology of TiO 2 were studied through SEM, XRD, FT-IR, UV-Visible spectroscopy and photoluminescence spectroscopy. The average particle size of MPAS synthesized TiO 2 nanoparticles remained smaller than the simple sol-gel method while bandgap energy increased by 40 %. The rutile content and crystallinity of nanoparticles were also found higher in MPAS synthesized TiO 2 than the simple sol-gel method. The type of stabilizer only effected the particle size but not the phase transformations of TiO 2 nanoparticles. TiO 2 photocatalyst with band gap of 3.06 eV was used to degrade methylene blue dye in water under the exposure of open atmosphere argon plasma jet. UV radiation intensity of the plasma jet at a distance of 2 cm was 576 μW/cm 2 , which reduced to 149 μW/cm 2 at 10 cm. The plasma jet produced some highly reactive species and UV radiations. The reactive species reacted with dye molecules while UV radiations promoted the activity of TiO 2 . The dye degradation efficiency of the process, under the combined effect of reactive species and TiO 2 activity, reached to 95 % after 30 min of plasma exposure time.

This study investigated the production of Cu2+-doped CoFe2O4 nanoparticles (CFO NPs) using a facile sol−gel technique. The impact of Cu2+ doping on the lattice parameters, morphology, optical properties, and electrical properties of CFO NPs was investigated for applications in electrical devices. The XRD analysis revealed the formation of spinel-phased crystalline structures of the specimens with no impurity phases. The average grain size, lattice constant, cell volume, and porosity were measured in the range of 4.55–7.07 nm, 8.1770–8.1097 Å, 546.7414–533.3525 Å3, and 8.77–6.93%, respectively. The SEM analysis revealed a change in morphology of the specimens with a rise in Cu2+ content. The particles started gaining a defined shape and size with a rise in Cu2+ doping. The Cu0.12Co0.88Fe2O4 NPs revealed clear grain boundaries with the least agglomeration. The energy band gap declined from 3.98 eV to 3.21 eV with a shift in Cu2+ concentration from 0.4 to 0.12. The electrical studies showed that doping a trace amount of Cu2+ improved the electrical properties of the CFO NPs without producing any structural distortions. The conductivity of the Cu2+-doped CFO NPs increased from 6.66 × 10−10 to 5.26 × 10−6 ℧ cm−1 with a rise in Cu2+ concentration. The improved structural and electrical characteristics of the prepared Cu2+-doped CFO NPs made them a suitable candidate for electrical devices, diodes, and sensor technology applications.

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Titanium dioxide (TiO2) nanoparticles have attracted the attention of research community due to their novel functionalities as compared to the bulk material. TiO2 is an excellent photocatalyst due to its high photosensitivity, nontoxicity, high refractive index, strong oxidizing ability, high stability, wide band gap and high resistance to photochemical. The main objective of this study was to investigate the influence of microwave (MW) plasma treatment on TiO2 nanoparticles synthesized using sol-gel method. TiO2 nanoparticles were obtained through sol-gel method at ambient temperature. The suspension was heated at 300 °C for 2 hours to evaporate the organic content. The obtained nanoparticles were placed in partially vacuumized chamber for MW plasma treatment. The plasma treatment is a promising technique for oxidation of nanomaterials. Both plasma treated and untreated samples were evaluated with X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Visible spectroscopy for crystallite size, crystal phases, band gap energy and surface morphology. The obtained results confirmed the existence of anatase and rutile phases of TiO2 with smaller particle size within the range of 0.2 to 14 nm. The particles were of aggregated and trigonal shapes. The MW Plasma treatment improved the photocatalytic activity of TiO2 nanoparticles by raising their band gap energy and reducing the grain size.

In this study, TiO 2 nanopowders were prepared by combining the surfactant assisted sol-gel method with microwave plasma calcination. Plasma calcination was performed just for 20-30 min for reducing the calcination time and ensuring the energy efficient synthesis of photocatalyst. The mixed anatase-rutile phased TiO 2 nanoparticles were obtained under these synthesis conditions. The band gap energy of the photocatalyst decreased by 40% on microwave plasma calcination. The surfactants were found to be ineffective on phase transformations of synthesized TiO 2 . FTIR analysis confirmed the absorption of O-Ti-O band stretching between 415 and 420 cm −1 . The hydroxyl bands (OH) were observed to be less stretched after plasma calcination. The conventionally calcined HA-Ti, NA-Ti and MS-Ti samples showed band gap energies of 5.09 eV, 4.88 eV and 5.06 eV, respectively. The band gap energy of plasma calcined MTHA-Ti, MTNNA-Ti and MTMS-Ti samples was calculated about 4.92 eV, 3.11 eV and 4.96 eV, respectively. The combined effect of photocatalyst, plasma reactive species and UV radiations promoted the degradation efficiency of the methylene blue dye. Under DC plasma jet exposure, the maximum degradation efficiency of 95% was achieved after 30 min of plasma exposure time. The catalyst retained about 93-95% degradation efficiency after five cycles of dye degradation.