Study of Highly Sensitive Formaldehyde Sensors Based on ZnO/CuO Heterostructure via the Sol-Gel Method

Abstract

Formaldehyde (HCHO) gas sensors with high performance based on the ZnO/CuO heterostructure (ZC) were designed, and the sensing mechanism was explored. FTIR results show that more OH− and N–H groups appeared on the surface of ZC with an increase in Cu content. XPS results show that ZC has more free oxygen radicals (O*) on its surface compared with ZnO, which will react with more absorbed HCHO molecules to form CO2, H2O and, electrons, accelerating the oxidation-reduction reaction to enhance the sensitivity of the ZC sensor. Furthermore, electrons move from ZnO to CuO in the ZC heterostructure due to the higher Fermi level of ZnO, and holes move from CuO to ZnO until the Fermi level reaches an equilibrium, which means the ZC heterostructure facilitates more free electrons existing on the surface of ZC. Sensing tests show that ZC has a low detection limit (0.079 ppm), a fast response/recovery time (1.78/2.90 s), and excellent selectivity and sensitivity for HCHO detection at room temperature. In addition, ambient humidity has little effect on the ZC gas sensor. All results indicate that the performance of the ZnO sensor for HCHO detection can be improved effectively by ZC heterojunction.

A review on the synthesis and applications of sustainable copper-based nanomaterials

“…[414][415][416] Acetic acid and formaldehyde chemicals are widely used in foods, photography, pharmaceuticals and fermentation, which are highly volatile organic compounds that cause clinical symptoms such as burning in the nose and throat, coughing and wheezing in acute effects at low concentrations. 417,418 Thus, a variety of gas sensors has been reported in the literature, including solid electrolyte gas sensors, electrochemical gas sensors, metal oxide semiconductor (MOS) sensors, catalytic combustion gas sensors and other types of gas sensors. 408,419 Copper and copper-based NM sensors are sensitive to detect a wide range of pollutants and noxious gases even at low ppm and ppb concentrations (Table 10).…”

Paving the Way for a Green Transition in the Design of Sensors and Biosensors for the Detection of Volatile Organic Compounds (VOCs)

“…Other recent sustainable approaches for the preparation of sensors for formaldehyde detection include the use of largely available and inexpensive materials such as tin and zinc [ 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 ], the second most abundant element in the Earth’s crusts, i.e., silicon [ 129 , 130 ], the use of biomass-derived materials, such as bacterial cellulose [ 131 ] or egg-white [ 132 ].…”

Approaches to Formaldehyde Measurement: From Liquid Biological Samples to Cells and Organisms

“…The third group includes genetically-encoded sensors that were developed for living cells and organisms. However, the variety of methods for FA assessment is not limited to those mentioned above: there are numerous other approaches for analysis of air samples using graphene- and metal oxide-based nanomaterial gas sensors [ 37 , 38 , 39 , 40 , 41 ], optical FA-sensors [ 42 ] and others that are out of the scope of this review.…”