Synthesis, Characterization, and Colorimetric Sensing of Zr4+, and Fluorometric Sensing of Cd2+, and Biological Application of Tetrahydroquinoxaline-Capped AgNPs.

Here, we put forth the synthesis, characterization of 2,3-diphenyl-5,6,7,8-tetrahydroquinoxaline stabilized silver nanoparticles (AgNPs) DTQ@AgNPs by a coprecipitation method. Additionally, Schiff base is employed as an N, N-donor ligand to regulate the shape of NPs. The effective production and stability of the nanocomposite were validated by extensive morphological (SEM, TEM, and XRD), thermal (TGA and DTG), and spectroscopic (UV-visible, FTIR, NMR, and fluorescence) investigations. DTQ@AgNPs acts as a dual-mode chemosensor for the sensitive and selective colorimetric detection of Zr⁴⁺ and fluorometric detection of Cd²⁺ ions with detection limits of 0.80 and 0.69 µM, respectively. The successful detection of Cd²⁺ in actual water samples with excellent recovery rates and low relative standard deviations has confirmed the practical application of the suggested sensor DTQ@AgNPs. Furthermore, the fabricated test strips enabled rapid, on-site colorimetric detection of Zr⁴⁺, demonstrating field-level usability. The nanocomposite DTQ@AgNPs also displayed significant antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa, suggesting promising biomedical relevance. Its significance in biological systems is further supported by the detection of Cd²⁺ in the presence of BSA protein.