The enhanced photocatalytic activity of ultrasonic spray reduction of silver nanoclusters over lamellar graphite carbon nitride: Interface reaction, theoretical calculation and degradation pathway

Role of transition metals in coinage metal nanoclusters for the remediation of toxic dyes in aqueous systems

A difficult issue in chemistry and materials science is to create metal compounds with well-defined components. Metal nanoclusters, particularly those of coinage groups (Cu, Ag, and Au), have received considerable research interest in recent years owing to the availability of atomic-level precision via joint experimental and theoretical methods, thus revealing the mechanisms in diverse nano-catalysts and functional materials. The textile sector significantly contributes to wastewater containing pollutants such as dyes and chemical substances. Textile and fabric manufacturing account for about 7 × 105 tons of wastewater annually. Approximately one thousand tons of dyes used in textile processing and finishing has been recorded as being discharged into natural streams and water bodies. Owing to the widespread environmental concerns, research has been conducted to develop absorbents that are capable of removing contaminants and heavy metals from water bodies using low-cost technology. Considering this idea, we reviewed coinage metal nanoclusters for azo and cationic dye degradation. Fluorometric and colorimetric techniques are used for dye degradation using coinage metal nanoclusters. Few reports are available on dye degradation using silver nanoclusters; and some of them are discussed in detailed herein to demonstrate the synergistic effect of gold and silver in dye degradation. Mostly, the Rhodamine B dye is degraded using coinage metals. Silver nanoclusters take less time for degradation than gold and copper nanoclusters. Mostly, H2O2 is used for degradation in gold nanoclusters. Still, all coinage metal nanoclusters have been used for the degradation due to suitable HOMO-LUMO gap, and the adsorption of a dye onto the surface of the catalyst results in the exchange of electrons and holes, which leads to the oxidation and reduction of the adsorbed dye molecule. Compared to other coinage metal nanoclusters, Ag/g-C3N4 nanoclusters displayed an excellent degradation rate constant with the dye Rhodamine B (0.0332 min-1). The behavior of doping transition metals in coinage metal nanoclusters is also reviewed herein. In addition, we discuss the mechanistic grounds for degradation, the fate of metal nanoclusters, anti-bacterial activity of nanoclusters, toxicity of dyes, and sensing of dyes.

Degradation characteristics of p-nitrophenol and atenolol by carbon nitride modified by graphene quantum dots

Photocatalysis is a promising technology for wastewater treatment. It is of great significance to find catalysts with high photoactivity. In this paper, a catalyst with high photocatalytic degradation efficiency to organic wastewater, carbon nitride modified by graphene quantum dots (SCN-GQDX), is prepared by supramolecular self-assembly thermal polycondensation method and doping graphene quantum dots (GQDs). The results show that SCN-GQD0.5 has the best catalytic performance, and its photocatalytic degradation efficiency to organic pollutants can reach 86% and still remains above 83% after five cycles, which shows the modified carbon nitride has high catalytic efficiency and stability. In a word, SCN-GQDX is a highly efficient, non-toxic and stable photocatalyst for organic pollutants in wastewater.