R. Shwetharani

Photoactive titania float for disinfection of water; evaluation of cell damage by bioanalytical techniques.

A photoactive float was fabricated with the modified titania to cause a feasible disinfection of water, contaminated with E. coli. The commercially available titania was doped with neodymium by pulverization technique to enhance its activity in sunlight and a multiapproach technique was used to evaluate the extended efficiency of the doped sample. X‐ray diffraction patterns depicted the retention of anatase phase on doping and the existence of neodymium was confirmed by the energy dispersive atomic X‐ray analysis and the X‐ray photoelectron spectroscopy. Transmission electron microscopy and Bruner–Emmett–Teller analysis depicted a marginal increase in the particle size and a decrease in the surface area, respectively. Doping induces semiconductor behavior with lower band energy that could respond to visible light and exhibit better disinfection activity. The “f” and “d” transitions of the lanthanide in doped sample caused new electronic behavior of trapping/detrapping effect together with bandgap narrowing. The amount of malondialdehyde, protein, DNA and RNA released on destruction of E. coli was observed to be 0.915 × 10−3 μg mL−1, 859.912 μg mL−1, 20.173 μg mL−1 and 1146.073 μg mL−1, respectively. The above analytical methods along with standard plate count method substantiated the enhanced disinfection efficiency of the doped sample in sunlight.

Excellent hydrogen evolution by a multi approach via structure–property tailoring of titania

Photocatalytic water splitting by solar energy is an ideal economic method for hydrogen generation. An attempt has been made to overcome the main barriers of photocatalytic hydrogen evolution (these being rapid recombination of electron–hole pairs, the process of back reaction and poor activation of titania by visible light) by the usage of Fe-induced titania. The method facilitates a cage like mesoporous structure and an effective surface level doping. The induction of dopants and formation of coupled semiconductor oxides of well matched band energy contribute favorably to the rise of mid bands and the perfect alignment of their energy levels, leading to a shallow trapping and detrapping of electrons, necessary for efficient charge separation and transfer. Decrease in the band gap energy to ∼2.0 eV and hence the extended light absorption in modified titania, together with a shift in band edge potentials (caused by pH variation), results in an activated titania, desirable for enhanced visible light hydrogen evolution. The modified nanostructure shows an excellent hydrogen evolution of 255 mmol g−1 h−1, one of the highest reported so far. Sodium acetate acts as a good sacrificial agent in preventing the back reaction. Characterization techniques like spectroscopy (XRD, UV, reflectance, EDX, XPS and PL) and microscopy (FESEM and HRTEM) have been used to evidence the presence of Fe as dopant/as oxide and to study the structure–property tailoring that occurs during chemical modification.

La activated high surface area titania float for the adsorption of Pb(II) from aqueous media

Currently, the world faces alarming challenges of heavy metal contamination, which are hazardous to humans and the environment because of their toxicity even in trace concentrations. Lead is one of the harmful heavy metal contaminants and has poisonous effects on human health. The present research investigation describes the adsorption of toxic Pb(II) on an immobilized adsorbent with a highly smaller crystallite size along with enhanced surface area and pore volume of La doped TiO2 synthesized from a simple co-precipitation method. Induction of dopant La3+ was confirmed by XPS with a smaller particle size of 25 nm as compared to TiO2 of 80 nm. The La doped TiO2 shows an enhanced surface area of 97.246 m2 g−1 compared to TiO2 of 17.2 m2 g−1 due to the introduction of oxygen vacancies leading to increased surface roughness and thus shows significant improvement in the adsorption of Pb(II) in comparison with TiO2 at basic pH due to the negative charge on La doped TiO2. A suitable optimized pH was examined and the Pb(II) adsorption study was measured using atomic absorption spectroscopy.