In the present report TiO2 nanoparticles co-doped with iron and different mol % of silver have been successfully synthesized by sol-gel route and studied by X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDX), UV-visible absorption spectroscopy (UV-Vis), Photoluminescence spectroscopy (PL), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), and FTIR spectroscopy. The XRD data analysis confirms the formation of mixed phases of TiO2 (anatase) and Ag2O phase. The crystalline size was vary from 48.0 nm to 44.6 nm determined from XRD further verified from TEM micrograph. The EDXS measurements suggest that iron is completely incorporated however silver has not incorporated into TiO2 matrix. The optical band gap of the prepared nanoparticles was calculated by UV-Visible absorption spectroscopy using Tauc-Davis and Mott expression and found to varying from 2.92 to 2.30 eV. The absorption bands in the UV-visible spectra shift towards higher wave length region and appearance of emission bands in PL spectra confirms the formation of energy substates in the forbidden gap of the prepared samples. TEM micrographs showed that prepared nanoparticles are somewhat spherical in shape. The formation of different functional groups and bonds in the structure of synthesized nanoparticles as observed in FTIR spectra helps in degradation of organic dyes (congo red and methyl orange) and enhance the photocatalytic activity under visible light. It is observed that the higher doping concentration of silver causes to decrease the band gap energy as a result the carrier recombination rate decreases and therefore enhance the degradation efficiency.

Cobalt, Iron & Cerium co-doped Co x Fe 0.02 Ce 0.02 Ti 0.96- x O 2 ; x = 0.02, 0.03 & 0.04 mol % nanoparticles were fabricated by following sol-gel process. Characterization of synthesized samples was carried out through X-ray diffraction, UV-visible and Fourier transform infrared spectroscopy, Transmission electron and Field-emission scanning electron microscopy and Electron dispersive X-ray spectroscopy. Anatase phase of fabricated nanoparticles was estimated by XRD and further verified by EDXS measurements. Using Debye Scherrer's formula the particle size of synthesize d nanoparticles calculated was 24.8 to 10.3 nm. With growing cobalt concentration ( x ) shifting of absorption edge towards region of higher wave length correspond to blue shift as noticed from UV – Visible absorption spectra indicate the generation of energy sub states within forbidden gap and reduction in energy band gap from 2.57 eV to 1.69 eV. Structural formation of the synthesized nanoparticles was studied by FTIR spectroscopy which confirm that formed TiO 2 nanoparticles have stable anatase pahse. Photocatalytic degradation activity against congo red and methyl orange dyes was detected by visible light illumination. Observations showed that with rise in cobalt concentration ( x ) the photocatalytic activity rises which is ascribed to decreasing rate of carrier recombination and increasing surface area of the fabricated nanoparticles.

Undoped TiO2 and Mo/N co-doped TiO2 nanoparticles have been fabricated by sol gel technique. The average particle size of nanoparticles was calculated from the line broadening of (101) peak of XRD pattern and further verified by High Resolution Transmission Electron Microscopy (HRTEM) are in good agreement. The decrease in particle size 28.5 to 15.0 nm was observed with increase of molybdenum concentration. The surface morphology of all samples was studial by Field Emission Scanning Electron Microscopy shows small agglomeration. The optical band gap energy was calculated using UV-visible absorption spectroscopy and found to decrease in increase of doping concentration. The presence of defect levels caused by oxygen vacancies has been confirmed by Photoluminescence spectra. The emission bands observed at 453.9, 470.6, 485.7, 495.8 and 535 mu could be arising from surface states. The phase composition and elemental analysis of synthesized samples was estimated from Energy dispersive X-ray spectroscopy. The effect of doping concentration on structural formation was studied by FTIR spectroscopy. The Photocatalytic activity of synthesized samples for degradation of Congo red (CR) and Methyl orange (MO) dyes as standard pollutants was investigated under visible light source. The increase in doping concentration causes enhance in photocatalytic activity of the synthesized nanoparticles which is attributed from the decrease in electron-hole pair recombination rates. The degradation efficiency against congo red dye is very high compared to methyl orange dye. These observations suggest that co-doped synthesized nanoparticles are suitable for complete degradation of congo red dye and are not able to degrade methyl orange dye.

Sr2+ doped TiO2; SrxTi1−x O2; x = 0.12, 0.16 & 0.20 mol % nanoparticles have been synthesized by hydrothermal method. The X-ray diffraction (XRD) data analysis confirms the formation of mixed anatase phase of strontium doped TiO2 nanoparticles. The crystallite size vary from 35.4 nm to 25.5 nm was estimated from the FWHM of (101) peak of TiO2 in X-ray diffraction spectra. The UV-Vis absorption spectroscopy was used to determine optical band gap energy and calculated values to be 2.96, 2.57 & 2.37 eV respectively. The formation of defect levels caused by oxygen vacancies were confirmed by Photoluminescence spectroscopy. The emission bands observed at 453, 464, 470, 483 and 494 nm in photoluminescence spectra could be arising from surface states appears in forbidden region of TiO2. The effect of doping on structural formation is verified by Fourier-transform-infrared spectroscopy. The photocatalytic degradation efficiency of synthesized nanoparticles against both dyes congo red and methyl orange (both used as model pollutant) was studied under visible light source of wavelength ranging 400-700 nm and found to increase with increase in dopant concentration. The increase in photocatalytic degradation activity of synthesized nanoparticles is attributed to decrease in photo induced charge carrier recombination rate arises from the decrease in energy band gap.

In present paper pure and Ni-N-codoped TiO2 nanoparticles have been synthesized via sol gel technique. Crystal phase formation of as synthesized nanoparticles was determined from x-ray diffraction which confirms the existence of anatase phase of TiO2. The average crystalline size was determined from x-ray diffraction and estimated from Transmission Electron Micrographs found to vary from 24.8 nm to 10.2 nm. The morphology was studied by Field Emission Scanning Electron Microscopy and reveals that the synthesized nanoparticles are highly crystalline, spherical and small agglomerated. It is observed that on doping the agglomeration decreases and is due to relative rates of growth process. The band gap energy was calculated from UV–visible absorption spectroscopy and found to be 3.12, 1.81, 1.69 and 1.53 eV respectively. The appearance of emission bands at 453, 470, 483 and 494 nm in Photoluminescence spectra could be arising from defect energy states caused by oxygen vacancies within the forbidden region of TiO2.The structural formation of the synthesized nanoparticles is investigated from Fourier-transform-infrared and Energy dispersive x-ray spectroscopy measurements. Photocatalytic degradation efficiency of as synthesized nanoparticles against two different dyes (Congo red and Methyl orange) was investigated under visible light source of wavelength 420–520 nm and is found to increase with dopant concentration (x). It is observed that the increase in Photocatalytic degradation efficiency of synthesized nanoparticles is attributed to decrease in carrier recombination rate arises from the decrease in band gap energy. On the basis of these observations it is concluded that the increase in Photocatalytic activity is due to increase in surface area arises from the decrease in average crystalline size of the synthesized nanoparticles.

Cobalt & Copper doped CoxCu0.05Ti0.95-xO2; x = 0.04, 0.08 & 0.12 mol % nanoparticles have been prepared by sol-gel technique and characterized by X-ray diffraction, Electron dispersive X-ray spectroscopy, UV-visible spectroscopy, Fourier transform infrared and Field-emission scanning electron microscopy. The X-ray diffraction and EDXS measurements confirm the formation of anatase phase of TiO2 nanoparticles. The average particle size of the prepared nanoparticles was calculated from X-ray diffraction using Debye Scherrer’s formula and found to be 16.4, 14.9, 13.1 nm respectively. The absorption edge in observed UV–Vis absorption spectra shifted to higher wavelength region correspond to blue shift indicates the decrease in band gap energy from 2.87eV to 1.90 eV on increasing cobalt concentration. The presence of strong chemical bonding and functional groups present at the interface of TiO2 nanoparticles observed in FTIR spectra confirm the formation of stable anatase phase of TiO2 nanoparticles. The photocatalytic activities of the prepared samples for methyl orange (MO) and congo red (CR) was investigated under visible light irradiation. It is observed that increase in dopant concentration enhance the photocatalytic activity is attributed to narrow band gap and increase in surface area of the synthesized nanoparticles.