Molecularly imprinted optical probe based on in-situ CoFe2O4/CNDs for monitoring 2,4,6-para trinitrophenol in aqueous medium with integrated smartphone detection

Assessing TNP in actual water samples is essential to reduce its harmful impacts on human health and aquatic ecosystems. This study details the development of an innovative and sustainable dual-mode optical biosensor that employs Cobalt ferrite magnetic nanoparticles (CF-MNPs), Carbon nanodots (CNDs), and molecularly imprinted polymers (MIPs) for the precise and sensitive identification of 2,4,6-para trinitrophenol (TNP) in water-based environments. The plant-derived CNDs from Piper longum demonstrate improved fluorescence properties, leading to a notable enhancement in the sensor's performance. The CF-MNPs/CNDs/MIP composite improves the selectivity and sensitivity of the optical sensing probe by promoting efficient electron transfer with TNP. The dual-mode biosensing platform integrates fluorescence and colorimetric detection, leveraging the peroxidase-mimicking activity of CF-MNPs/CNDs/MIPs to oxidize TMB for a visual colorimetric response. The biosensor demonstrates exceptional analytical capabilities, reaching a limit of detection (LOD) of 1.09 nM (fluorescence) and 3.07 nM (colorimetry). Furthermore, the analysis of real samples exhibited remarkable reliability, achieving a recovery rate of 101 %. To improve portability and field applicability, an RGB-based smartphone sensing method was incorporated, achieving a limit of detection 10 nM, facilitating rapid and economical on-site identification of TNP. This study presents a sustainable, highly selective, and ultrasensitive dual-mode optical biosensor, providing a strong foundation for real-time environmental monitoring of water contaminants.