Synthesis of Monometallic (Au and Pd) and Bimetallic (AuPd) Nanoparticles Using Carbon Nitride (C₃N₄) Quantum Dots via the Photochemical Route for Nitrophenol Reduction

Abstract

In this study, we report the synthesis of monometallic (Au and Pd) and bimetallic (AuPd) nanoparticles (NPs) using graphitic carbon nitride (g-CN) quantum dots (QDs) and photochemical routes. Eliminating the necessity of any extra stabilizer or reducing agent, the photochemical reactions have been carried out using a UV light source of 365 nm where CN QD itself functions as a suitable stabilizer as well as a reducing agent. The g-CN QDs are excited upon irradiation with UV light and produce photogenerated electrons, which further facilitate the reduction of metal ions. The successful formation of Au, Pd, and AuPd alloy nanoparticles is evidenced by UV-vis, powder X-ray diffraction, X-ray photon spectroscopy, and energy-dispersive spectroscopy techniques. The morphology and distribution of metal nanoparticles over the CN QD surface has been systematically investigated by high-resolution transmission electron microscopy (HRTEM) and SAED analysis. To explore the catalytic activity of the as-prepared samples, the reduction reaction of 4-nitrophenol with excellent performance is also investigated. It is noteworthy that the synthesis of both monometallic and bimetallic NPs can be accomplished by using a very small amount of g-CN, which can be used as a promising photoreducing material as well as a stabilizer for the synthesis of various metal nanoparticles.

Carbon‐Dot‐Based Heterojunction for Engineering Band‐Edge Position and Photocatalytic Performance

“…Figure a,b shows UV–vis spectra of the reaction mixture (containing 5 mg CDs@Ag 3 PO 4 ) at different time intervals and the same temperature (0 °C) without and with visible irradiation, respectively. By contrast, the maximum absorbance peak at 400 nm, which is assigned to the characteristic absorbance peak of 4‐NP, decreases much slowly without visible irradiation as well as no obvious absorbance peak at 297 nm. Under the visible light, however, the absorbance peak at 400 nm gradually decreases as the visible irradiation time proceeds, simultaneously accompanied by the increase in intensity of the 297 nm peak attributed to 4‐AP .…”

“…By contrast, the maximum absorbance peak at 400 nm, which is assigned to the characteristic absorbance peak of 4‐NP, decreases much slowly without visible irradiation as well as no obvious absorbance peak at 297 nm. Under the visible light, however, the absorbance peak at 400 nm gradually decreases as the visible irradiation time proceeds, simultaneously accompanied by the increase in intensity of the 297 nm peak attributed to 4‐AP . As a result, almost complete conversion of 4‐NP to 4‐AP was achieved within 20 min irradiation.…”

“…After the addition of a catalyst, the reduction of 4‐NP is initiated, which can be visualized by tracking the gradual decrease in intensity of the 400 nm absorption peak. This process is accompanied by the appearance of a new peak at 297 nm attributed to 4‐AP . This successive decrease in intensity of the 400 nm peak is generally considered for the kinetic investigation of the conversion of 4‐NP to 4‐AP, and is easily monitored using UV–vis spectroscopy .…”

“…This successive decrease in intensity of the 400 nm peak is generally considered for the kinetic investigation of the conversion of 4‐NP to 4‐AP, and is easily monitored using UV–vis spectroscopy . Presently, the catalytic reduction of 4‐NP most often uses metallic catalysts, including free or immobilized metallic nanoparticles and alloys . Gazi and Ananthakrishnan first offered an example of metal‐free catalytic reduction of 4‐NP under visible light irradiation .…”

Highly Efficient Photo‐Reduction of p‐Nitrophenol by Protonated Graphitic Carbon Nitride Nanosheets

“…Moreover, in comparison to the numerous investigation interests on other photocatalytic reactions by g‐CN or g‐CN based composites, fewer studies have been reported on photo‐reduction of PNP. And, in most cases g‐CN was only used as photo‐reduction medium or supporter to prepare or load noble metal catalysts …”