Cu(II)-Grafted Carbon Nitride Quantum Dots with High Crystallinity for Photoelectrochemical Detection Application

Graphitic Carbon Nitride Enters the Scene: A Promising Versatile Tool for Biomedical Applications

Graphitic carbon nitride (g-C3N4), since the pioneering work on visible-light photocatalytic water splitting in 2009, has emerged as a highly promising advanced material for environmental and energetic applications, including photocatalytic degradation of pollutants, photocatalytic hydrogen generation, and carbon dioxide reduction. Due to its distinctive two-dimensional structure, excellent chemical stability, and distinctive optical and electrical properties, g-C3N4 has garnered a considerable amount of interest in the field of biomedicine in recent years. This review focuses on the fundamental properties of g-C3N4, highlighting the synthesis and modification strategies associated with the interfacial structures of g-C3N4-based materials, including heterojunction, band gap engineering, doping, and nanocomposite hybridization. Furthermore, the biomedical applications of these materials in various domains, including biosensors, antimicrobial applications, and photocatalytic degradation of medical pollutants, are also described with the objective of spotlighting the unique advantages of g-C3N4. A summary of the challenges faced and future prospects for the advancement of g-C3N4-based materials is presented, and it is hoped that this review will inspire readers to seek further new applications for this material in biomedical and other fields.

Microwave-assisted preparation of yellow fluorescent graphitic carbon nitride quantum dots for trace tetracycline-specific detection

Tetracycline (TC) is extensively utilized in livestock breeding, aquaculture, and medical industry. TC residues seriously harm food security, the environment, and human health. There is an urgent need to exploit a highly efficient and sensitive testing method to monitor TC residue levels in aquatic environments. In this study, graphitic carbon nitride quantum dots (g-CNQDs) were successfully synthesized by a one-step microwave-assisted method using citric acid and urea as precursors. The as-prepared g-CNQDs with size of 1.25-3.75 nm exhibited bright yellow fluorescence at 523 nm when excited at 397 nm. Interestingly, this characteristic fluorescence emission of g-CNQDs could be selectively and efficiently quenched by TC. Based on this phenomenon, for TC detection was successfully explored and applied in real water samples. Wide linear scope of 7-100 μM, low detection limit (LOD) of 0.48 μM, satisfactory recovery of 97.77%-103.4%, and good relative standard deviation (RSD) of 1.05-5.87% were obtained. Mechanism investigations revealed that the static quenching and the inner filter effect (IFE) were responsible for this fluorescence quenching between g-CNQDs and TC. This work not only provided a facile approach for g-CNQDs synthesis but also constructed a g-CNQDs-based fluorescent sensor platform for the highly sensitive and selective detection of TC in aquatic environments.

Highly Hydrophilic and Defective Carbon Nitride for Enhanced Photocatalytic Hydrogen Evolution

Graphitic carbon nitride (g-C3N4), as a kind of nonmetallic low-cost photocatalyst, has great potential in photocatalytic hydrogen (H2) evolution, but its poor hydrophilicity and nonwetting extremely limit its H2 evolution efficiency. Herein, highly hydrophilic and defective g-C3N4 photocatalysts (NH3-CN-P as a representative example) have been fabricated on the basis of the strategy of joint phosphorus doping and ammonia stripping. The dopant of phosphorus prefers to occupy the C atoms bonded to -NH2 groups in the g-C3N4 skeleton, which is conducive to the formation of N defects caused by the effects of electronegativity and charge balance. Moreover, ammonia stripping plays a dual role in exposing plentiful two-dimensional defective planar structure and implanting the hydrophilic groups on the surface. As expected, the photocatalytic H2 evolution property of NH3-CN-P reaches 11.31 mmol g-1 h-1, with an apparent quantum yield of 17.9% at 420 nm, outperforming the majority of the reported g-C3N4-based photocatalysts.

Laser-Induced Graphene-based Flexible Substrate with Photothermal Conversion and Photoresponse Performance on Polyimide Film

Graphene-based flexible electronic devices are widely used in photoelectric components and photodetectors. However, it remains a huge challenge to fabricate graphene-based flexible devices efficiently and economically. Compared with the flexible electronic devices made by combining the flexible film with metal and semiconductor materials, the graphene-based flexible substrate (GFS) can be efficiently and conveniently induced by laser direct writing on the flexible film. In this paper, the GFS with a resistance of as low as 15 Ω was successfully induced by CO2 laser on a polyimide (PI) film in one step, and the GFS surface covered with carbon nanoparticles (GFSC) with a resistance of 25 Ω was further induced by femtosecond (fs) laser reprocessing. Benefiting from the laser-induced porous graphene structure, the absorptivity of GFS is up to 90% in the wavelength range of 200-2000 nm. The formation of carbon nanoparticles on the GFSC surface further improves the absorptivity to 97.5% in a wide spectral range. Under white light irradiation of 1 sun, the surface temperature of GFS reaches 65.7 °C and that of GFSC is up to 70.8 °C within 2 min. Under the irradiation of a light-emitting diode (LED) with a central wavelength of 365 nm, the highest photoresponsivity of GFS and GFSC was 8.8 and 1.3 mA/W, respectively. The response time and recovery time of GFS are 8 and 7.3 s, and those of GFSC are 8.3 and 6.7 s, respectively. Importantly, GFSC has a more stable photoresponse performance due to the better electron capture and transfer capability of carbon nanoparticles. It is believed that GFS and GFSC have great application potential in flexible photodetectors and sensors.

A Comprehensive Review on Graphitic Carbon Nitride for Carbon Dioxide Photoreduction

Inspired by natural photosynthesis, harnessing the wide range of natural solar energy and utilizing appropriate semiconductor-based catalysts to convert carbon dioxide into beneficial energy species, for example, CO, CH₄ , HCOOH, and CH₃ COH have been shown to be a sustainable and more environmentally friendly approach. Graphitic carbon nitride (g-C₃ N₄ ) has been regarded as a highly effective photocatalyst for the CO₂ reduction reaction, owing to its cost-effectiveness, high thermal and chemical stability, visible light absorption capability, and low toxicity. However, weaker electrical conductivity, fast recombination rate, smaller visible light absorption window, and reduced surface area make this catalytic material unsuitable for commercial photocatalytic applications. Therefore, certain procedures, including elemental doping, structural modulation, functional group adjustment of g-C₃ N₄ , the addition of metal complex motif, and others, may be used to improve its photocatalytic activity towards effective CO₂ reduction. This review has investigated the scientific community's perspectives on synthetic pathways and material optimization approaches used to increase the selectivity and efficiency of the g-C₃ N₄ -based hybrid structures, as well as their benefits and drawbacks on photocatalytic CO₂ reduction. Finally, the review concludes a comparative discussion and presents a promising picture of the future scope of the improvements.

Ternary heterostructures of 1D/2D/2D CuCo2S4/CuS/Ti3C2 MXene: Boosted amperometric sensing for chlorpyrifos

Multicomponent heterogeneous Ti₃C₂ transition metal carbide (MXene)-based materials are receiving extensive research attention due to their interesting synergistic interactions and catalytic properties. However, the morphology-controllable synthesis of heterostructures as structural stabilizers for Ti₃C₂ MXene remains a challenge owing the complicated synthesis procedure. In this work, a kind of ternary heterogeneous nanomaterials CuCo₂S₄/CuS/Ti₃C₂ MXene with a nanorod/nanoplate/nanosheet hybrid architecture is constructed through a one-step low-temperature solvothermal method. The well-designed ternary one-dimensional (1D)/two-dimensional (2D)/2D CuCo₂S₄/CuS/Ti₃C₂ MXene heteromaterials exhibit synergistic improvements in substrate-catalyzed reactions for electrochemical acetylcholinesterase (AChE) biosensor. The Michaelis-Menten constant for the Nafion/AChE/CuCo₂S₄/CuS/Ti₃C₂ MXene/GCE biosensor is 228 μM, which is smaller than ones reported in previous literatures, indicating a higher affinity of the fabricated enzyme biosensor to acetylthiocholine chloride. The biosensor exhibits a well linear relationship with chlorpyrifos concentration ranging from 2.852 × 10^-12 M to 2.852 × 10^-6 M. The multicomponent 1D/2D/2D CuCo₂S₄/CuS/Ti₃C₂ MXene heteromaterial may shine a light in more electrochemical applications.