Unveiling the multifaceted applications of magnetically responsive chitosan capped ZnS QDs for sensing and annihilation of pharmaceutical drugs

The persistence of active pharmaceutical ingredients in water bodies has lead to detrimental impacts on public health as well as deteriorated aquatic resources at breakneck pace. To address this, highly fluorescent chitosan capped ZnS QDs (CZS QDs) were integrated with nickel ferrite nanoparticles (NF NPs) through ultrasonic assisted method to yield a series of magnetically responsive CZS-xNF nanohybrids (x = 5, 10, 15 and 20 wt% of NF). The successful fabrication of nanohybrids were affirmed through various techniques such as Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS), high resolution transmission electron microscopy (HRTEM), vibrating sample magnetometer (VSM) and diffused reflectance spectroscopy (DRS). The dual applicability of CZS-xNF nanohybrid was witnessed for the detection of pharma-ceutical waste by fluorescence sensing and their concomitant annihilation via visible light driven photo-degradation reactions. The developed nanohybrid showed exceptional selectivity towards tetracycline antibiotics, with ultra-low limit of detection of 0.53 mu M for tetracycline (TC) and 0.30 mu M for minocycline (MC), respectively. The fluorescent sensor was also analysed for trace level detection of tetracyclines in real water samples that showed satisfactory recoveries of 90-106%, depicting practical applicability of sensor. Additionally, the excellent photocatalytic features of synthesized nanohybrid prompted their use in photodegradation of TC and MC and a superior photocatalytic performance was achieved in comparison to CZS QDs. The enhanced photocatalytic performance of CZS-xNF nanohybrid can be attributed to type-I charge transfer mechanism, which resulted in efficient charge separation and reduced photo-induced recombination rate of charge carriers. The nanohybrids were recyclable up to four cycles after being utilized in sensing and photocatalysis, thus offering a promising strategy for environmental remediation through synchronized sensing and extirpation of pharmaceutical waste.