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.

Nearly 20% of water pollution is caused by the leather and textile industries. Textile wastewater contains a lot of organic pollutants, including dyes that are widely used in industry. At the same time, printing and dyeing wastewater has also caused water problems and health problems.

Diethyl phthalate (DEP) is an odorless, colorless, oily liquid. It is used to make plastics, pesticides, cosmetics, and aspirin, as well as toothbrushes, auto parts, toys, tools and food packaging. At the same time, DEP has a negative impact on human health and causes environmental problems.

In the past decade, the application of semiconductor powder as a photocatalytic degradation of organic pollutants in water has received widespread attention. Titanium dioxide (TiO2) suppresses amazing photocatalytic properties, including high activity, chemical stability, and low cost. However, the photocatalytic activity of TiO2 (with a band gap of 3.2 eV, excited by photons with a wavelength of less than 387 nm) is still limited by UV wavelength irradiation, so the photocatalytic process cannot effectively occur during sunlight irradiation. 4% of the total solar spectrum radiation is in the ultraviolet region.

Combustion equipment and automobiles are the major sources of NOx gas including nitrogen dioxide (NO2). These gases have negative effects on the human health and can also cause acid rain. Therefore, effective adsorption materials should be used to sense and detect these gases in the atmosphere.

Oxide nanomaterials are used to develop advanced photovoltaic materials, photocatalysts, and smart devices. Among metal oxides, tungsten oxide (WO3) is an n-type semiconductor with a small bandgap of 2.6 eV and unique thermal, optical, physical, chemical, and electrical properties. These properties have led to many applications in chemical and selective catalysis, sensors, fuel cells, color change, and pollutant adsorption. WO3 is considered a suitable candidate for the photodegradation of organic pollutants in the visible light region.

Tungsten trioxide (WO3) is an n-type semiconductor oxide that possesses a large bandgap in the range of 2.6–3.0 eV and has the potential for a variety of applications such as electrochemical devices, photovoltaic devices, photocatalytic devices, electrochromic devices, dye-sensitized solar cells, optical devices, field-emission displays, and gas sensors. Meanwhile, with the development of one-dimensional nanostructures, dimensionality and size of the materials have also been regarded as critical factors that may bring some novel and unexpected properties.

Tungsten trioxide (WO3) has been extensively studied due to its affinity for visible light, chemical inertness, thermal stability, and harmlessness. These excellent properties make this material useful for solar-related applications such as photocatalysts, solar cells, water splitting, and hydrogen generation.

Semiconductor metal oxides (SMOs) are highly potent gas sensors for gaseous detection in terms of screening of air eminence, low expenditure on synthesis and sensing property that can be modified. The semiconductor metal oxide gas sensor is considered the most capable gas-sensing device due to its high sensitivity, fast response, low cost, and small size.