Functionalized Nanoparticles for Detection of Pesticides and Toxic Metal Ions: A Comprehensive Review

The emerging technology of nanotechnology has fundamentally changed the approach to environmental monitoring, especially in the process of pesticides and toxic metal ions detection in various environmental and biological samples. It is the functionalised nanoparticles (particularly gold and silver) which have emerged as a potent sensing surface, due to their unique physicochemical properties including large surface areas, surface plasmon resonance at the limit and tuneable optical results. This is a review of recent advances in the detection methodologies of substances in the nanoparticle-based detection of pesticides and toxic metal ions with emphasis on functionalisation strategies and sensing mechanisms along with practical applications. Conventional methods of analysis of pesticides and heavy metals, although accurate, are often time consuming, expensive and require use of advanced equipment and highly skilled employees. Compared to these, nanoparticle-based colourimetric sensors are fast, cost-efficient, and on-site applications with a visual output, which makes them highly applicable in the field and in environmentally limited conditions. The review critically analyzes a diversity of functionalised nanoparticles, such as carbon based, metal based, metal-oxide based and metal-organic framework based nanomaterials, with their synthesis protocols, characterisation mechanisms and detection mechanisms. Specific focus is made on the multimodal sensing strategies, a combination of colourimetric, fluorescent, electrochemical and surface enhanced Raman spectroscopies techniques, thus providing increased sensitivity and selectivity. The new developments in technology in nanozymes, aptamer-functionalised nanoparticles and portable sensors integrated into smartphones are mentioned. The current issues that have also been discussed in the review include matrix interference, reproducibility, standardisation and long-term stability of nanoparticle-based sensors. Future trends especially the incorporation of artificial intelligence, a microfluidic platform and point-of-care testing devices are addressed. This tedious examination is informative to the researcher involved in the manufacturing of next generation nanoparticles based sensors in environmental and food safety monitoring.