Polyvinylpyrrolidone

All the chemicals used for the synthesis were of analytical grade and used directly without any purification. CQDs were synthesized using the waste pulp of Citrus limetta. TiO₂ nanofibres were prepared using polyvinylpyrrolidone (PVP, average MW 1 300 000), ethanol, acetic acid, and titanium tetraisopropoxide (Ti[OCH(CH₃)₂]₄) procured from Loba Chemie. For the plasmonic nanostructure and CQD synthesis: silver nitrate and chloroauric acid were procured from Sigma Aldrich. Methylene blue (MB) that was studied for dye degradation experiments was also procured from Sigma Aldrich. Pharmaceutical drug, erythromycin, for pharmaceutical degradation experiments was procured from the nearby medical store. Millipore corporation grade water system (Milli-Q, 18.2 MΩ) was used to perform all studies and preparation of standard solutions.

The maximum integrity chemicals were purchased for this research purpose. L-tryp (purity 99.5%) was purchased from Sigma-Aldrich (China), l-glutamic acid (monosodium salt) (purity 99%) from Sisco Research Laboratories Pvt. Ltd (India), Copric sulfate pent hydrate (purity 99%) and polyvinyl pyrrolidone (PVP) from Loba Chemie Pvt Ltd (india), Hydrogen peroxide from Pt. Smart Lab (Indonesia). Type I with resistivity <18 MΩ double distilled ultrapure water was made from Evoqua (Germany) and was used during total experiments. A supporting electrolyte of phosphate-buffered saline (PBS) was purchased from Sigma Aldrich (China). Moreover, analytical grade reagents and chemicals were used in this experiment with high purity. Each electrolyte solution was deoxygenated for 5 min before voltammetry measurement.