Bioinspired Synthesis of Carbon Dots/g-C₃N₄ Nanocomposites for Photocatalytic Application

Abstract

This study reports a fast and green preparative strategy to synthesize water soluble and fluorescent carbon quantum dots (CQDs) through hydrothermal method by using low cost organic waste of human fingernails as the carbon precursor for the first time. The coupling of CQD with pure carbon nitride (g-C3N4) was further explored to enhance the latter’s performance in photocatalysis of 2,4-dicholorophenol (2,4-DCP), a toxic and recalcitrant compound mostly released from industrial effluent. Such coupling overcame the weakness of pure g-C3N4 in photocatalysis process by broadening its visible light absorption and promoting the charge separation. As a result, the removal rate of CQD/ g-C3N4(10) was up to 71.53%, which was approximately 1.5 times higher than that of pure g-C3N4 under sunlight irradiation. The morphological structure, optical properties and chemical compositions of CQDs/g-C3N4 composites were characterized using various spectroscopic techniques including field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray (EDX) and Ultraviolet-visible diffuse reflectance spectra (UV-DRS).

Fabrication and Characterization of Highly Efficient As-Synthesized WO3/Graphitic-C3N4 Nanocomposite for Photocatalytic Degradation of Organic Compounds

“…This result was also reported by J.Y. Tai et al [ 31 ]. For the indirect bandgap, we noted a slight change from 2.56 eV for the pure g-C 3 N 4 changing to 2.6, 2.65, 2.66, 2.86, to 2.71 eV for the 0.5, 0.1, 0.05, 0.01, and 0.001 WO 3 -doped g-C 3 N 4 composite, respectively.…”

A Review on Synthesis and Physicochemical Properties-Photocatalytic Activity Relationships of Carbon Quantum Dots Graphitic Carbon Nitride in Reduction of Carbon Dioxide

“…CQDs can potentially operate as electron acceptors or donors [11,15]. CQDs are nanoparticles with a size below 10 nm [42,49] Moreover, oxygenated functional groups such as hydroxyl, carbonyl (C=O), epoxides, and amino are present on the surface of CQDs [18,42,49]. The oxygenated functional group enables CQDs to interact with inorganic, organic, polymeric, and biological materials, resulting in enhanced adsorption, surface passivation, and accessible surface modification [42,49].…”

“…According to the previous study, the recombination of e --h + will affect photocatalytic activity. The fabrication of g-C3N4 with CQDs alters and improves the defects by increasing the photocatalytic activity and light absorption range, preventing the recombination of e --h + , and improving the quantum efficiency of pure g-C3N4 [15,18,19]. Another intriguing experiment with a CQDs/g-C3N4 hybrid demonstrated a photodegradation rate three times higher than that of pure g-C3N4.…”

“…Additionally, the exceptional electrical characteristics of CQDs offer applications in optoelectronics, catalysis, and sensing. When paired with the g-C3N4, its role as electron acceptors or donors in redox processes makes it suited for photocatalytic applications [16][17][18]. CQDs/g-C3N4 is a metal-free photocatalyst that has drawn attention since Kang et al released their work on stable visible-light water splitting using carbon nanodots and carbon nitride (C3N4).…”

A Review on Carbon Quantum Dots Modified g-C3N4-Based Photocatalysts and Potential Application in Wastewater Treatment

“…Importantly, the photostability of the g-C 3 N 4 /CQDs nanocomposite was also significantly bettered wherein the photocatalytic performance of the photocatalyst endured up to five successive consecutive cycles under light illuminations (Figure 4c). Additionally, a g-C 3 N 4 /CQDs nanocomposite was fabricated through a simple hydrothermal approach and displayed outstanding degradation activity of 71.53% towards 2,4-dichlorophenol, 1.5-fold greater than bare g-C 3 N 4 [62]. Henceforth, from the above discussion it can be concluded that the best efficacy of the photocatalyst was attributed to CQDs, which acted as electron sinks and hamper the recombination of charge pairs with enhanced separation rate.…”