Mechanistic insights of mercury ion detection and its influence on time monitored hydrodynamic size of Capsicum Annumm C derived silver nanoparticles during colorimetric nano-sensing

The presence of hazardous mercury ions (Hg²⁺) in industrial waste not only contaminates water reservoirs but also influence badly on human skin if its amount exceeds the allowed limit in cosmetics. It is still very challenging to develop a selective and sensitive Hg²⁺ sensor to protect environment as well as human health. In this work, we demonstrated a robust and facile synthesis for the development of silver nanoparticles (AgNPs) from Capsicum annumm C. (CA) extract as bio-reductant and stabilizer. Different experimental parameters were optimized i.e., effect of volume, pH and heating time via UV-Vis spectrophotometer to achieve the stable CA-AgNPs. The phytochemical bio-functionality, crystallinity and size controlled CA-AgNPs with prominent blue shifted surface plasmon resonance (SPR) band at 396 nm with golden yellow color were obtained. The size of the fabricated CA-AgNPs was reported an average of approximately 11–22 nm of spherical shape which act as a selective and sensitive conventional colorimetric sensor probe. The sensor efficiently respond as decrease in color and SPR band with blue shift due to Hg²⁺ ions detection even under the interference of other ions. The CA-AgNPs sensor displays an outstanding linear calibration response with increase in Hg²⁺ ions concentration range from 1 to 10 µM and lowest LOD of 0.17 µM with satisfactory percentage recoveries from 96 % to 98.5 %. The mechanism of Hg²⁺ ions detection were described on the basis of change in hydrodynamic size and zeta potential of the CA-AgNPs with time from 0 to 30 minutes of interaction.