As a typical exhaust gas from industry and automobiles, nitrogen dioxide (NO2) not only causes environmental problems, but also affects the human health. Tungsten trioxide (WO3) is an n-type semiconductor oxide, which has proven to be particularly suitable for detecting NO2 gas.

Dye-sensitized solar cell (DSSC) is one of the most popular renewable energy equipment, which has been studied for its light weight, simple manufacturing process, low cost, transparency, good plasticity, and environmental friendliness. The photoanode is one of the main factors affecting the energy conversion efficiency of DSSCs. The efficiency of DSSC-based titanium dioxide (TiO2) is significantly limited by the high interface photogenerated electron-hole recombination rate and the low electron mobility of the TiO2 photoanode.

The main source for water and soil pollutions is hazardous colorants in waste water discharged from textile industries. Rhodamine B (RhB) is the most used dye in the textile industries hence it is widely considered as a typical water pollutant. Among the several methods available today, the removal of Rhodamine B dye from the textile waste water via photocatalytic degradation has received much attention from researchers because it can convert the Rhodamine B dye into water, carbon di-oxide and mineral acids without creating secondary pollutants.

Aromatic nitration has long been an important process in industrial chemistry, because nitroaromatic products are widely used as dyes, pesticides, solvents, drugs, and intermediates for the manufacture of synthetic dyes and other chemicals. Traditionally nitration is carried out by using mixture of concentrated nitric acid (98%) and sulphuric acid in the proportion of 1:2. However the process produces large quantity of dilute sulphuric acid which leads to environmental pollution.