Biomass-derived Carbon Quantum Dots for Visible-Light-Induced Photocatalysis and Label-Free Detection of Fe(III) and Ascorbic acid

Abstract

Visible-light-driven photocatalysts prepared using renewable resources are crucial but challenging to develop for the efficient degradation of organic pollutants, which is required to solve ever-increasing water deterioration issues. In this study, we report a visible-light-responsive photocatalyst for the efficient degradation of methylene blue (MB) as a model pollutant dye. Green-emissive carbon quantum dots (CQDs) were synthesized from pear juice via a facile, scalable, one-pot solvothermal process. The as-synthesized CQDs exhibit superior photocatalytic activity under visible-light irradiation owing to their efficient light absorption, electron transfer, and separation of photogenerated charge carriers, facilitating ~99.5% degradation of MB within 130 min. A possible mechanism for the photocatalysis is proposed on the basis of comprehensive active species trapping experiments. Furthermore, the CQDs were used in a specific sensitive assay for Fe(III) and ascorbic acid (AA), even with interference from other metal ions. The fluorescence emission of CQDs was “turned off” specifically upon binding of Fe(III) and “turned on” with AA. The prepared CQDs represent efficient photocatalysts and fluorescent probes that are not restricted by toxicity, cost, or lack of scalability.

Methylene blue decolorizing bacteria isolated from water sewage in Yogyakarta, Indonesia

“…Many technologies have been employed to eliminate the contamination of methylene blue in the environment. Recently, physicochemical approaches, including photocatalysis, physiochemical adsorption, and non-thermal plasma technology, have garnered popularity due to its high efficiency and degradation percentage (Das et al 2019;Myung et al 2019;Wu et al 2019). However, high complexity, low economic feasibility, and disposal problems by some of these methods hinder their broad application, especially in a developing country (Zhou et al 2019).…”

Facile Synthesis of “Boron-Doped” Carbon Dots and Their Application in Visible-Light-Driven Photocatalytic Degradation of Organic Dyes

“…For example, Yu et al reported C-dots/TNS and C-dots/P25 composites with excellent photocatalytic activity for the degradation of RhB; however, there was no activity when C-dots were used alone [52]. Recently, some encouraging studies have shown that C-dots alone could possess good to excellent photocatalytic activity toward the degradation of organic dyes (Table 1, entries 5-10); however, various factors including limited light absorption, extra surface doping, as well as tedious separation have limited the practical applications of C-dots in these studies [58][59][60][61][62][63]. For instance, C-dots prepared by Srivastava and co-workers could only utilize light with a specific wavelength for the catalytic degradation of MB [59].…”

“…Due to the rich presence of surface defects (i.e., surface functionalities) on C-dots, some of the excited carriers are trapped, and the recombination of e - and h + are hindered. As a result, the organic dyes could be oxidized by the h + directly to cause the degradation, which is well known [ 62 ]. In the meantime, some of the e − could be captured by oxygen dissolved in solution, forming super oxide radicals (i.e., •O 2 − ); some of the h + could interact with surface-adsorbed H 2 O to form hydroxyl radicals (i.e., •OH).…”

“…In the meantime, some of the e − could be captured by oxygen dissolved in solution, forming super oxide radicals (i.e., •O 2 − ); some of the h + could interact with surface-adsorbed H 2 O to form hydroxyl radicals (i.e., •OH). Reactive oxygen species (ROS) such as super oxide •O 2 − [ 63 ] and hydroxyl radical •OH [ 62 , 92 ] are known to degrade organic dyes.…”

“…To realize the efficient degradation of organic dyes, C-dots have to be integrated in metal-based heterostructures [50][51][52][53][54][55][56][57]. Recently, some encouraging reports demonstrated the efficient photocatalytic degradation of organic dyes by C-dots alone [58][59][60][61][62][63][64]; however, various factors including limited light absorption, extra surface doping, and tedious separation significantly limited their practical applications.…”