Electrochromic devices such as smart windows have received extensive attention from researchers in related fields in the materials industry. Tungsten trioxide (WO3) is an n-type semiconductor and a promising material due to its high transparency, good coloration efficiency, and low response times. The electrochromic performance of WO3 depends strongly on its particle size, morphology, and structure. However, low electrical conductivity of WO3 can give rise to poor electrochromic performance of the device. 

Due to global industrial growth and increased emissions of particular gases (such as NO2, H2S or VOC), indoor and outdoor air quality monitoring has become a major issue today. These gases in sufficiently high concentrations bring a negative effect to the environment and human healthy.

In recent years, tungsten-molybdenum (W-Mo) alloys have attracted great interest as high-temperature materials for various applications. W-Mo alloy has excellent performance in preventing corrosion of molten zinc, and can be used at higher temperatures than molybdenum or molybdenum alloys. It is used for zinc liquid temperature measuring tube, zinc liquid pump rotor, and some corrosion-resistant parts of zinc smelting furnace. Because of its high melting point, ablation resistance, and flame retardancy to solid particles. tungsten-molybdenum alloy can also be used for the air rudder and protective cover of solid rocket motors. In addition, it is also used in the production of stirring tools in the glass industry, the manufacture of thin film transistors, the sputtering target for flat screen coating and the treatment of molten metal.

As a member of the antibiotic family, nitrofurazone (NFZ) is commonly used to treat burned skin, scratches, and wounds. However, it may cause physical or functional defects in the human embryo or fetus. If it is ingested by humans through the food chain, it can also cause cancer. Therefore, it is prohibited from being used in humans and animals worldwide. As people pay more and more attention to environmental pollution and human health, it is necessary to develop a suitable and sensitive platform to detect NFZ in the environment and water bodies.

Recently, researchers have prepared WO3/CuMnO2 nanocomposite for photoelectrochemical detection of nitrofurazone has been applied for photoelectrochemical detection of nitrofurazone (NFZ). The preparation process is as below:

WO3 nanotiles were synthesized by using CTAB assisted hydrothermal method. In this synthesis, about 2 g of Na2WO4 and a certain amount of CTAB were dissolved in 70 ml of DI water and stirred for an hour to homogenize. To this solution, concentrated HNO3 was added carefully by dropwise to adjust the pH to 3. Finally, the solution was transferred into a 100 ml Teflon-Autoclave hydrothermal pot, and the reaction was initiated at 80 °C for 12 h. The obtained product was washed several times with ethanol and water repeatedly. The received light yellowish powder sample was dried at 80 °C over 24 h and was kept into calcination for 4 h at 450 °C.

The CuMnO2 nanoparticles were prepared by a simple and facile ultrasound-assisted hydrothermal method. For the synthesis, about 360 mg of Cu(NO3)2·3H2O and 380 mg of Mn(NO3)2·3H2O were added in 80 ml of DI water and sonicated for an hour. Then the solution was transferred into 100 ml Teflon autoclave and sealed tightly. Then the hydrothermal reaction was carried out at 120 °C for 24 h. The obtained reddish-brown precipitate was washed with alcohol and DI water several times and oven-dried at 80 °C for 12 h.

The CuMnO2 decorated WO3 nanotiles were prepared by following a simple impregnation method. For the synthesis, 100 mg of WO3 was dispersed in 15 ml of ethyl alcohol by sonication for 30 min. Then aliquot of CuMnO2 particles was added next to the dispersion and again subjected to sonication for 30 min. The resulting dispersion was heated on a hot plate at 120 °C until the complete evaporation of the alcohol medium. The final product was oven-dried at 75 °C for further applications. During the preparation, X weight percentages of CuMnO2 (X = 5, 10, 15, 20, 25) were added to the WO3 dispersion and the obtained composites were named accordingly as WO3/CuMnO2-5, WO3/CuMnO2-10, WO3/CuMnO2-15, WO3/CuMnO2-20, and WO3/CuMnO2-25 respectively.

In conclusion, WO3/CuMnO2 nanocomposite for photoelectrochemical detection of nitrofurazone has been successfully prepared and has been applied for photoelectrochemical detection of nitrofurazone (NFZ). The photoelectrochemical NFZ sensing performance of WO3/CuMnO2 nanocomposite was 1.9 times higher than that of as-synthesized pure WO3 nanotiles. The resulting higher photoelectrochemical performance of the nanocomposite is due to more visible light absorption ability and synergy from p-n heterojunction formation. The designed WO3/CuMnO2 nanocomposite sensor gives satisfactory photocurrent signals for the detection of NFZ in the range of 0.015–32 μM with the detection limit (LOD) of 1.19 nM. The practical applicability of the nanocomposite sensor was monitored in pork liver and tap water samples.