Starch-derived carbon quantum dots: Unveiling structural insights and photocatalytic potential as a bio-sourced metal-free semiconductor

The optical appeal and sustainability of carbon quantum dots (CQDs) have led to these nanoparticles swiftly gaining attention and emerging as a new, multifunctional class of nanomaterials. This work centers on the hydrothermal preparation of CQDs utilizing starch, an abundant and renewable biopolymer, as the precursor. Extensive characterization via spectroscopy and microscopy techniques revealed that the starch-derived CQDs exhibit a spherical nanoscale morphology averaging a ~ 4 nm diameter, demonstrating a red-orange photoluminescence emission. Diffuse reflectance spectroscopic analysis verified their semiconductor behavior, with an estimated direct band gap of 4.1 eV comparable to conventional semiconductors. The prepared CQDs demonstrated considerable promise as metal-free, semiconductor photocatalysts for degrading aqueous dye pollutants under UV irradiation. High photodegradation efficiencies of 45.11 %, 62.94 %, and 91.21 % were achieved for Acid Blue 21, Reactive Blue 94, and Reactive TB 133 dyes, respectively. Systematic investigations of critical process parameters like pH, CQDs dosage, dye concentration, and contact time provided vital insights into the photocatalytic mechanism. The bio-sourced CQD nanomaterials offer a sustainable pathway for effective environmental remediation.