真空加热和电子束辐照改性处理g-C_3N_4光催化剂

将真空加热与电子束辐照两种改性后处理过程引入非金属光催化剂类石墨相氮化碳(graphitic carbon nitride,g-C_3N_4)的性能改善中.这两种后处理方法都能有效地改善g-C_3N_4的光催化特性,不过电子束辐照方法更具有破坏性,会在一定程度上改变g-C_3N_4光催化剂本身的化学键和能带结构.根据后处理的实施参数,真空热处理(6.7±0.7 Pa,4 d,200?C)可以将原始的g-C_3N_4可见光光催化性能提高2.5倍,而电子束辐照(800 kGy,1.8 MeV,8 mA·s^(-1))可以提高至4.5倍.光催化循环实验显示了改性后光催化剂的循环稳定性,也保证了这两种后处理方式的进一步实施.

Recent Advances of Graphitic Carbon Nitride-Based Structures and Applications in Catalyst, Sensing, Imaging, and LEDs

The graphitic carbon nitride(g-C_3N_4) which is a two-dimensional conjugated polymer has drawn broad interdisciplinary attention as a low-cost, metal-free, and visible-light-responsive photocatalyst in the area of environmental remediation. The g-C_3N_4-based materials have excellent electronic band structures, electron-rich properties, basic surface functionalities, high physicochemical stabilities and are ‘‘earth-abundant.'' This review summarizes the latest progress related to the design and construction of g-C_3N_4-based materials and their applications including catalysis, sensing,imaging, and white-light-emitting diodes. An outlook on possible further developments in g-C_3N_4-based research for emerging properties and applications is also included.

Efficient Photoelectrochemical Water Splitting by g-C_3N_4/TiO_2 Nanotube Array Heterostructures

Well-ordered TiO_2 nanotube arrays(TNTAs)decorated with graphitic carbon nitride(g-C_3N_4) were fabricated by anodic oxidization and calcination process.First, TNTAs were prepared via the anodic oxidation of Ti foil in glycerol solution containing fluorinion and 20%deionized water. Subsequently, g-C_3N_4 film was hydrothermally grown on TNTAs via the hydrogen-bonded cyanuric acid melamine supramolecular complex. The results showed that g-C_3N_4 was successfully decorated on the TNTAs and the g-C_3N_4/TNTAs served as an efficient and stable photoanode for photoelectrochemical water splitting. The facile deposition method enables the fabrication of efficient and low-cost photoanodes for renewable energy applications.

DFT‑Guided Design and Fabrication of Carbon‑Nitride‑Based Materials for Energy Storage Devices:A Review

Carbon nitrides(including CN,C2N,C3N,C3N4,C4N,and C5N)are a unique family of nitrogen-rich carbon materials with multiple beneficial properties in crystalline structures,morphologies,and electronic configurations.In this review,we provide a comprehensive review on these materials properties,theoretical advantages,the synthesis and modification strategies of different carbon nitride-based materials(CNBMs)and their application in existing and emerging rechargeable battery systems,such as lithium-ion batteries,sodium and potassium-ion batteries,lithium sulfur batteries,lithium oxygen batteries,lithium metal batteries,zinc-ion batteries,and solid-state batteries.The central theme of this review is to apply the theoretical and computational design to guide the experimental synthesis of CNBMs for energy storage,i.e.,facilitate the application of first-principle studies and density functional theory for electrode material design,synthesis,and characterization of different CNBMs for the aforementioned rechargeable batteries.At last,we conclude with the challenges,and prospects of CNBMs,and propose future perspectives and strategies for further advancement of CNBMs for rechargeable batteries.

Enhanced CH4 selectivity in CO2 photocatalytic reduction over carbon quantum dots decorated and oxygen doping g-C3N4

Graphitic carbon nitride(g-C3N4,CN)exhibits inefficient charge separation,deficient CO2 adsorption and activation sites,and sluggish surface reaction kinetics,which have been recognized as the main barriers to its application in CO2 photocatalytic reduction.In this work,carbon quantum dot(CQD)decoration and oxygen atom doping were applied to CN by a facile one-step hydrothermal method.The incorporated CQDs not only facilitate charge transfer and separation,but also provide alternative CO2 adsorption and activation sites.Further,the oxygen-atom-doped CN(OCN),in which oxygen doping is accompanied by the formation of nitrogen defects,proves to be a sustainable H^+ provider by facilitating the water dissociation and oxidation half-reactions.Because of the synergistic effect of the hybridized binary CQDs/OCN addressing the three challenging issues of the CN based materials,the performance of CO2 photocatalytic conversion to CH4 over CQDs/OCN-x(x represents the volume ratio of laboratory-used H2O2(30 wt.%)in the mixed solution)is dramatically improved by 11 times at least.The hybrid photocatalyst design and mechanism proposed in this work could inspire more rational design and fabrication of effective photocatalysts for CO2 photocatalytic conversion with a high CH4 selectivity.

Fluorescent light enhanced graphitic carbon nitride/ceria with ultralow-content platinum catalyst for oxidative decomposition of formaldehyde at ambient temperature

The complete decomposition of formaldehyde(HCHO) at ambient temperature is the most potential strategy for HCHO elimination from indoor environment.Herein,extra low content of Pt nanoparticles(0.025 wt%)supported on water-solubility carbon nitride/ceria(Pt/gC_(3)N_(4)@CeO_(2)) was prepared for gaseous HCHO removal at ambient temperature in a simulated indoor environment.Fluorescent light(8 W) illumination could visibly boost the complete decomposition of HCHO into CO_(2) over Pt/gC_(3)N_(4)@CeO_(2).The cooperative effect in the distinct heterostructure and plenty of surface reactive oxygen species contribute primarily to the enhanced catalytic performance of Pt/g-C_(3)N_(4)@CeO_(2).Moreover,the possible mechanism of HCHO oxidation over Pt/g-C_(3)N_(4)@CeO_(2) assisted by the fluorescent light irradiation was proposed based on the physicochemical and optical characterization as well as the result of in situ diffuse reflectance infrared Fourier transform spectra.This work might shed some light on the potential application of the versatile catalysts for ambient-temperature catalytic decomposition of HCHO by making full use of the indoor energies.

Template-free large-scale synthesis of g-C3N4 microtubes for enhanced visible light-driven photocatalytic H2 production

A template-free hydrothermal-assisted thermal polymerization method has been developed for the large-scale synthesis of one-dimensional （1D） graphitic carbon nitride （g-C3N4） microtubes. The g-C3N4 microtubes were obtained by simple thermal polymerization of melamine-cyanuric acid complex microrods under N2 atmosphere, which were synthesized by hydrothermal treatment of melamine solution at 180℃ for 24 h. The as-obtained g-C3N4 microtubes exhibited a large surface area and a unique one-dimensional tubular structure, which provided abundant active sites for proton reduction and also facilitated the electron transfer processes. As such, the g-C3N4 microtubes showed enhanced photocatalytic H2 production activity in lactic acid aqueous solutions under visible light irradiation （A 〉 420 nm）, which was - 3.1 times higher than that of bulk g-C3N4 prepared by direct thermal polymerization of the melamine precursor under the same calcination conditions.

Visible-light-driven enhanced antibacterial and biofilm elimination activity of graphitic carbon nitride by embedded Ag nanoparticles

Semiconductor nanomaterials with photocatalytic activity have potential for many applications. An effective way of promoting photocatalytic activity is depositing noble metal nanoparticles （NPs） on a semiconductor, since the noble metal NPs act as excellent electron acceptors which inhibit the quick recombination of the photoexcited electron-hole pairs and thereby enhance the generation of reactive oxygen species （ROS）. Herein, a highly effective platform, graphitic carbon nitride （g-C3N4） nanosheets with embedded Ag nanopartides （Ag/g-C3N4）, was synthesized by a facile route. Under visible light irradiation, the ROS production of Ag/g-C3N4 nanohybrids was greatly improved compared with pristine g-C3N4 nanosheets, and moreover, the nanohybrids showed enhanced antibacterial efficacy and ability to disperse bacterial biofilms. We demonstrate for the first time that the Ag/g-C3N4 nanohybrids are efficient bactericidal agents under visible light irradiation, and can also provide a new way for biofilm elimination. The enhanced antibacterial properties and biofilm-disrupting ability of Ag/g-C3N4 nanohybrids may offer many biomedical applications.

Catalyzing polysulfide conversion by g-C3N4 in a graphene network for long-life lithium-sulfur batteries

The practical application of lithium-sulfur batteries with a high energy density has been plagued by the poor cycling stability of the sulfur cathode, which is a result of the insulating nature of sulfur and the dissolution of polysulfides. Much work has been done to construct nanostructured or doped carbon as a porous or polar host for promising sulfur cathodes, although restricting the polysulfide shuttle effect by improving the redox reaction kinetics is more attractive. Herein, we present a well-designed strategy by introducing graphitic carbon nitride （g-C3N4） into a three-dimensional hierarchical porous graphene assembly to achieve a synergistic combination of confinement and catalyzation of polysulfides. The porous g-CBN4 nanosheets in situ formed inside the graphene network afford a highly accessible surface to catalyze the transformation of polysulfides, and the hierarchical porous graphene-assembled carbon can function as a conductive network and provide appropriate space for g-C3N4 catalysis in the sulfur cathode. Thus, this hybrid can effectively improve sulfur utilization and block the dissolution of polysulfides, achieving excellent cycling performance for sulfur cathodes in lithium-sulfur batteries.

Amine-rich carbon nitride nanoparticles:Synthesis,covalent functionalization with proteins and application in a fluorescence quenching assay

Carbon nitride nanoparticles (CNNPs) have been employed as fluorescent sensing tools owing to their unique features, e.g. low cost production, high stability in water and high photoluminescence quantum yield. Here, an easy and versatile synthetic approach was exploited to design fluorescent nanoparticles with surface functionalities suitable for covalent binding to bioligands. High hydrophilic, brightly fluorescent CNNPs, rich of superficial amines, were obtained from the thermal condensation of urea and lysine (CNNP^Lys) and by tuning the precursor ratio and the heating time. Structure and size of the functionalized nanoparticles were characterized through infrared (IR) spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). Their optical properties were studied by ultraviolet-visible (UV-Vis) and fluorescence spectroscopy. The superficial primary amino groups, furnished by the lysine co-precursor, enabled for covalently linking CNNP^Lys to model proteins. The CNNP^Lys-protein conjugates excited under UV irradiation emit in the 400-450 nm visible range (quantum yield 24%). The applicability of CNNP^Lys as novel fluorescent probes was demonstrated by a fluorescence quenching assay, in which gold nanoparticles (GNPs) were attached to Staphylococcal protein A and employed to quench the CNNP^Lys fluorescence by Forster resonant energy transfer (FRET). The quenching occurred upon formation of the specific binding between the GNP-linked protein A and CNNP^Lys-tagged immunoglobulins, while the inhibition of the binding resulted in the recovery of CNNP^Lys luminescence. The synthetic strategy, based on combining a "conjugated polymer"-forming unit (urea) and a co-precursor able to provide the desired functional group (lysine), allows designing innovative materials for the development of new generation fluorescence biosensors in which easily functionalized fluorophores are needed.

Recent Advances in Graphitic Carbon Nitride-Based Chemiluminescence,Cataluminescence and Electrochemiluminescence

Graphitic carbon nitride(g-C3N4)has attracted considerable attention due to its special structure and properties,such as its good chemical and thermal stability under ambient conditions,low cost and non-toxicity,and facile synthesis.Recently,g-C3N4-based sensors have been demonstrated to be of high interests in the areas of sensing due to the unique optical,electronic and catalytic properties of g-C3N4.This review focuses on the most salient advances in luminescent sensors based on g-C3N4,chemiluminescence,cataluminescence and electrochemiluminescence methods are discussed.This review provides valuable information for researchers of related areas and thus may inspire the development of more practical and effective approaches for designing two-dimensional(2D)nanomaterial-assisted luminescent sensors.