Nanosensor for the detection of bromothymol blue dye and its removal from wastewater by sustainable methods†

This study introduces the environmentally friendly synthesis of Ag₂O, TiO₂, and Ni-doped SnO₂ nanoparticles (NPs) and their application in detecting and removing bromothymol blue (BTB) dye from wastewater. The unique electronic properties and quantum size effects of NPs allow them to surpass conventional materials. Characterization of the synthesized nanoparticles was conducted through spectroscopic and voltammetric techniques. TiO₂ NPs, in conjunction with amine-functionalized multiwalled carbon nanotubes (NH₂-fMWCNTs) enhanced the sensitivity of the transducer, while electrochemical impedance spectroscopy confirmed effective charge transport through the designed sensing platform. The sensor was found to exhibit the qualities of repeatability, specificity, and reproducibility, achieving a detection limit of 0.1 nM for BTB dye. For wastewater purification from BTB, Ag₂O NPs were employed as a photocatalyst and the photocatalytic degradation monitored with electronic absorption spectroscopy revealed a 92% degradation of BTB dye within 30 minutes. Furthermore, Ni-doped SnO₂ NPs were utilized for the adsorptive removal of the dye, demonstrating a maximum adsorption capacity of 90.90 mg g⁻¹. The adsorption mechanism adhered to the Langmuir model at lower BTB concentrations and the Freundlich model at higher concentrations, with kinetics aligning with the intra-particle diffusion model. This research underscores the promise of electrocatalytic and photocatalytic nanomaterials as scalable, sustainable, and eco-friendly approaches to combat water pollution.