Why is it in the News?

A new low-cost sensor made of metal oxide nanoparticles-reduced graphene oxide composite can detect formalin adulteration in fishes at room temperature in a non-invasive way. The sensor shows long-term stability with a low detection limit.

Context:

• A sensor designed for the detection of formalin in fish has been developed by the Nanomaterials and Nanoelectronics Laboratory at Guwahati University, Assam.
• The formalin sensor utilizes a composite of tin oxide-reduced graphene oxide, synthesized through a process involving the wet chemical approach for Graphene Oxide (GO) and the hydrothermal route followed by calcination for the tin oxide-reduced graphene oxide composite (rGO-SnO2).
• Testing of the sensor has been conducted both at the laboratory scale and on fish procured from the fish markets in the Guwahati region, specifically targeting potential adulteration.
• This groundbreaking research has received support from DST-PURSE (Promotion of University Research and Scientific Excellence) and has been documented in the journal ACS Appl. Nano Mater.
• Research Support: The research behind this innovative sensor is backed by DST-PURSE (Promotion of University Research and Scientific Excellence).

About Non-Invasive Formaldehyde Sensor:

• This non-invasive formaldehyde sensor incorporates a composite of tin oxide-reduced graphene oxide (rGO-SnO2) as its key materials.
  • While reduced graphene oxide (rGO) has been widely utilized for detecting various toxic gases and volatile organic compounds (VOCs), tin oxide (SnO2) has demonstrated notable efficacy in formaldehyde detection, both in its pristine form and when combined with different compounds, including graphene.
  • This combination is favoured for its heightened stability and sensitivity to low concentrations of formaldehyde.
• Synthesis Process: The fabrication process involves a wet chemical approach for the production of graphene oxide (GO), followed by the hydrothermal route and subsequent calcination to synthesize the tin oxide-reduced graphene oxide composite (rGO-SnO2).
• Comparison with Existing Sensors: Unlike commercial formalin sensors for fish, which are primarily electrochemical-based or colorimetric-based and often invasive, this novel sensor, made from metal oxide nanoparticles and reduced graphene oxide, offers a cost-effective and non-invasive method for detecting formalin adulteration in fishes at room temperature.
• Challenges with Existing Sensors: Traditional electrochemical sensors, though widely used, tend to be expensive, and colourimetric sensors, while more cost-effective, share the invasive nature of their electrochemical counterparts. Both face challenges related to low-level and selective detection.
• Significance of the New Sensor: The development of gas sensors based on 2D materials, such as graphene, opens up new possibilities for the effective detection of toxic vapours at room temperature.
  • These sensors hold promise for accurately detecting formalin emanating from adulterated food products.

What is Formaldehyde?

• Formaldehyde (CH?O) is an odorless, colorless gas with high toxicity and flammability under standard room temperature conditions.
• Primary Applications:
  • Production of fertilizers, paper, plywood, and certain resins.
  • Utilized as a food preservative.
  • Found in glues, resins, dyes, textiles, disinfectants, building materials, automotive components, embalming processes, and laboratory settings.
  • Incorporated into household items like antiseptics, medications, and cosmetics.
• Potential Health Effects:
  • Exposure to formaldehyde may result in irritation of the skin, throat, lungs, and eyes. Additionally, formaldehyde is recognized as a carcinogenic substance.