A new non-invasive, low-cost sensor with long-term stability and a low detection limit is based on reduced graphene oxide composite with metal oxide nanoparticles, and it can detect formalin adulteration in fish at room temperature.
The act of adding illicit or dangerous materials to food in order to extend its shelf life or give it a more enticing appearance is known as food adulteration. A colourless, strong gas called formaldehyde finds application in numerous industrial processes. It is also used as a food preservative in certain dishes, most notably fish in underdeveloped nations. However, because formaldehyde is a known carcinogen, its use in food is prohibited in many nations.
Fish formalin sensors that are sold commercially are mostly colorimetric or electrochemical in nature. Although they are costly, electrochemical sensors are widely used. However, both approaches are intrusive. Furthermore, two significant problems with these sensors are selective detection and low-level detection. A new method for efficiently detecting toxic vapours at room temperature has been made possible by the development of gas sensors based on 2D materials. These sensors may be able to identify formalin that has evaporated from tainted food items.
The Nanomaterials and Nanoelectronics Laboratory, led by Dr Hemen Kumar Kalita, Assistant Professor, Department of Physics, Guwahati University, Assam, has created a formalin sensor that is both economical and effective. It uses a composite of graphene oxide and reduced tin oxide to detect the presence of formalin in fish that have been tampered with.
The oxidised form of graphene, known as graphene oxide (GO), is highly soluble in solutions and readily manipulated chemically with metals, metal oxides, and polymers. However, GO’s low electrical conductivity presented a problem, which the researchers solved by creating the tin oxide-reduced graphene oxide composite (rGO-SnO2).
Tin oxide (SnO2) has been thoroughly studied for formaldehyde detection in its purest form and by combining it with various compounds, including graphene, due to its high stability and high sensitivity toward low concentrations of formaldehyde. Reduced graphene oxide (rGO) has been used to detect various toxic gases and volatile organic compounds (VOCs).
The wet chemical approach was used by the researchers to create graphene oxide (GO), and the hydrothermal route was used to create tin oxide-reduced graphene oxide composite (rGO-SnO2), which was then calcined. They discovered that the reduced graphene oxide sensor decorated with tin oxide was capable of sensing formaldehyde vapour at room temperature.
The sensor has been tested on fish from the Guwahati region’s fish markets as well as fish available in lab scale. The ACS Applied Nano Materials journal published the research that was funded by DST-PURSE (Promotion of University Research and Scientific Excellence). The sensor was found to be able to identify formalin in a large number of fish sample units that were imported from areas outside the state of Assam. The non-invasive formalin detection is of utmost importance in this work. A prototype that could be considered a breakthrough in the field of food adulteration is currently being designed in the lab.
