Novel plant extract-chitosan nanocomposite (SCE/ChNPs) biosensor for trace level arsenic sensing in water samples using quartz crystal microbalance with dissipation monitoring

Abstract This study introduces a novel green biosensor for ultra-low arsenic detection in water, combining Saussurea costus ethanolic extract (SCE) with chitosan nanoparticles (ChNPs) in a Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) system. The SCE/ChNPs were characterized using AFM, SEM, TEM, DLS, and zeta potential measurements, revealing a mean particle size of 37.0 ± 2.0 nm, spherical morphology, and a stable colloidal system with −28.3 mV surface charge. The QCM-D-based biosensor demonstrated exceptional performance with a detection limit of 0.05 ppb, significantly below the WHO guideline for arsenic in drinking water. It exhibited a linear response from 0.1 to 10 ppb (R 2 = 0.99) and high selectivity against potential interferents. The sensor showed a rapid 10 s response time and maintained stability over five adsorption–desorption cycles. Validation in spiked tap water samples yielded results comparable to ICP spectroscopy, confirming the sensor’s applicability in complex matrices. This eco-friendly approach offers advantages over conventional methods, including high sensitivity, rapid response, and potential for on-site analysis. The synergistic combination of plant extract and biodegradable nanoparticles presents a sustainable solution for heavy metal sensing. Further research on long-term stability and field testing could lead to practical tools for monitoring arsenic contamination in water resources, contributing to public health and environmental safety.