Blue TiO2 polymorph: An efficient material for dye-sensitized solar cells fabricated using a low-temperature sintering process

Recently,surface-disordered or non-stoichiometric TiO_2,such as blue TiO_2(B-TiO_2),has received much attention owing to its unique properties,such as structural disorder near the surface and the existence of Ti~(3+)ions and oxygen vacancies.Therefore,surface-disordered TiO_2has been applied for microwave absorption,photocatalysis,in photoelectrochemical sensors and rechargeable lithium-ion batteries.In this work B-TiO_2,a polymorph consisting of nanoparticles,nanotubes and nanosheets,was successfully synthesized and employed as a semiconductor layer in dye-sensitized solar cells(DSSCs)fabricated using a low-temperature heat treatment process(120°C).Based on the analyses of the experimental results regarding the structure and those from the characterization of B-TiO_2,and its application to DSSCs,it has been found that the B-TiO_2 material has an effect on electron-hole pair separation.The conversion efficiency of the B-TiO_2 DSSC(BTiO_2-DSSC)was 6.18%,whereas that of the TiO_2-P25 DSSC(P25-DSSC)was 3.61%,and that of the TiO_2 polymorph DSSC(PTiO_2-DSSC)which is the precursor of B-TiO_2 was 4.51%.     

Fabrication of a TiO2-P25/(TiO2-P25+TiO2 nanotubes) junction for dye sensitized solar cells

The dye sensitized solar cell（DSSC）, which converts solar light into electric energy, is expected to be a promising renewable energy source for today’s world. In this work, dye sensitized solar cells, one containing a single layer and one containing a double layer, were fabricated. In the double layer DSSC structure, the under-layer was TiO₂-P25 film, and the top layer consisted of a mixture of TiO₂-P25 and TiO₂ nanotubes. The results indicated that the efficiency of the DSSC with the double layer structure was a significant improvement in comparison to the DSSC consisting of only a single film layer. The addition of TiO₂-P25 in the top layer caused an improvement in the adsorption of dye molecules on the film rather than on the TiO₂ nanotubes only. The presence of the TiO₂ nanotubes together with TiO₂-P25 in the top layer revealed the enhancement in harvesting the incident light and an improvement of electron transport through the film.     

Efficient inactivation of Staphylococcus aureus by silver and copper loaded photocatalytic titanate nanotubes

One dimensional titanate nanotubes(TNTs) were synthesized by microwave assisted alkaline hydrothermal process. The process was followed by UV-photodeposition of Ag and Cu on the surface of TNTs to enhance the photocatalytic activity in visible light spectrum. The loading of Ag and Cu(single and combination mode)offered a new insight to inactivate multi-drug resistant micro-organisms. The antibacterial properties of these samples were studied on Gram positive bacteria, Staphylococcus aureus(S. aureus) using well diffusion method.The TNTs with Ag and Cu loading showed a clear zone of inhibition after overnight incubation of S. aureus. The bacterial inactivation efficiency of nanoparticles in the visible light was further analyzed by kill kinetics. TNTs with Ag and/or Cu loading showed a significant reduction in bacterial growth. Cu co-loaded with Ag sample showed the highest inactivation efficiency within 90 min of visible light irradiation. To elucidate the mechanism of bactericidal properties of samples under visible light irradiation, the formation of reactive oxygen species(ROS), particularly, superoxide radical anion was determined by nitro blue tetrazolium(NBT) assay and the protein degradation by each samples were measured. Based on overall results, it was observed that the Cu coloaded with Ag on TNTs samples were found to be more effective as compared to either Ag or Cu loaded TNTs. It provides new avenues for utilizing the combination of Cu and Ag for enhancing the antimicrobial efficacies for different nanoparticles.     

The effect of laser surface texturing on the tribological performance of different Sialon ceramic phases

A tribological performance was carried out on different types of hot press Sialon ceramics regarding the phases, i.e., the α-Sialon phase, the β-Sialon phase, and the α/β-Sialon composite phase. The different phases of Sialon ceramics were analyzed by XRD patterns. For the tribological performance, the Sialon ceramics were laser textured and the starved lubrication method was applied with different dimple pitches under a load of 10 N at room temperature. The material having a dimple pitch of 200 mm shows the lowest coefficient of friction. The α/β-Sialon composite phase shows the least coefficient of friction i.e. 0.04 and 0.1 for the textured and polished(without being textured) samples, respectively. The Sialon ceramics show mild wear and therefore, the wear rate of the steel ball(mating partner) was taken into account for the wear analysis. The α-Sialon phase having a higher hardness shows the least wear in comparison to the α/β-Sialon composite phase and the β-Sialon phase.