As a fascinating conjugated polymer, graphitic carbon nitride (g-C3N4) has become a new research hotspot and drawn broad interdisciplinary attention as a metal-free and visible-light-responsive photocatalyst in the arena of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability, and “earth-abundant” nature. This critical review summarizes a panorama of the latest progress related to the design and construction of pristine g-C3N4 and g-C3N4-based nanocomposites, including (1) nanoarchitecture design of bare g-C3N4, such as hard and soft templating approaches, supramolecular preorganization assembly, exfoliation, and template-free synthesis routes, (2) functionalization of g-C3N4 at an atomic level (elemental doping) and molecular level (copolymerization), and (3) modification of g-C3N4 with well-matched energy levels of another semiconductor or a metal as a cocatalyst to form heterojunction nanostructures. The constructi...

Graphitic Carbon Nitride (g-C3N4)-Based Photocatalysts for Artificial Photosynthesis and Environmental Remediation: Are We a Step Closer To Achieving Sustainability?

Plasmons in strongly coupled metallic nanostructures.

Optical antennas are devices that convert freely propagating optical radiation into localized energy, and vice versa. They enable the control and manipulation of optical fields at the nanometre scale, and hold promise for enhancing the performance and efficiency of photodetection, light emission and sensing. Although many of the properties and parameters of optical antennas are similar to their radiowave and microwave counterparts, they have important differences resulting from their small size and the resonant properties of metal nanostructures. This Review summarizes the physical properties of optical antennas, provides a summary of some of the most important recent developments in the field, discusses the potential applications and identifies the future challenges and opportunities.

Antennas for light

An overview of the recent developments in the field of cylindrical vector beams is
provided. As one class of spatially variant polarization, cylindrical vector beams
are the axially symmetric beam solution to the full vector electromagnetic wave
equation. These beams can be generated via different active and passive methods.
Techniques for manipulating these beams while maintaining the polarization symmetry
have also been developed. Their special polarization symmetry gives rise to unique
high-numerical-aperture focusing properties that find important applications in
nanoscale optical imaging and manipulation. The prospects for cylindrical vector
beams and their applications in other fields are also briefly discussed.

Cylindrical vector beams: from mathematical concepts to applications

A review on g-C3N4-based photocatalysts

The generation of sustainable and stable semiconductors for solar energy conversion by photoredox catalysis, for example, light-induced water splitting and carbon dioxide reduction, is a key challenge of modern materials chemistry. Here we present a simple synthesis of a ternary semiconductor, boron carbon nitride, and show that it can catalyse hydrogen or oxygen evolution from water as well as carbon dioxide reduction under visible light illumination. The ternary B–C–N alloy features a delocalized two-dimensional electron system with sp 2 carbon incorporated in the h-BN lattice where the bandgap can be adjusted by the amount

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Carbon-doped BN nanosheets for metal-free photoredox catalysis

Ternary boron carbon nitride (BCN) semiconductors have been developed as emerging metal-free photocatalysts for visible-light reduction of CO2, but the achieved efficiency is still not satisfying. Herein, we report that the CO2 photoreduction performance of a bulk BCN semiconductor can be substantially improved by surface engineering with CdS nanoparticles. The CdS/BCN photocatalysts are characterized completely by diverse tests (e.g., XRD, FTIR, XPS, DRS, SEM, TEM, N2 sorption, PL, and transient photocurrent spectroscopy). Performance of the CdS/BCN heterostructures is evaluated by reductive CO2 conversion reactions with visible light under benign reaction conditions. Compared with bare BCN material, the optimized CdS/BCN photocatalyst exhibits a 10-fold-enhanced CO2 reduction activity and high stability, delivering a considerable CO production rate of 12.5 μmol h–1 (250 μmol h–1 g–1) with triethanolamine (TEOA) as the reducing agent. The reinforced photocatalytic CO2 reduction activity is mainly assigne...

Boron Carbon Nitride Semiconductors Decorated with CdS Nanoparticles for Photocatalytic Reduction of CO2

The development of water oxidation catalysts (WOCs) to cooperate with light-energy transducers for solar energy conversion by water splitting and CO2 fixation is a demanding challenge. The key measure is to develop efficient and sustainable WOCs that can support a sustainable photocatalyst to reduce over-potentials and thus to enhance reaction rate of water oxidation reaction. Cobalt has been indentified as active component of WOCs for photo/electrochemical water oxidation, and its performance relies strongly on the contact and adhesion of the cobalt species with photoactive substrates. Here, cobalt is homogeneously engineered into the framework of pristine graphitic carbon nitride (g-C3 N4 ) via chemical interaction, establishing surface junctions on the polymeric photocatalyst for the water oxidation reaction. This modification promotes the surface kinetics of oxygen evolution reaction by the g-C3 N4 -based photocatalytic system made of inexpensive substances, and further optimizations in the optical and textural structure of Co-g-C3 N4 is envisaged by considering ample choice of modification schemes for carbon nitride materials.

Dispersing molecular cobalt in graphitic carbon nitride frameworks for photocatalytic water oxidation.

We demonstrate here that two-dimensional boron nitride (h-BN) nanosheets can be employed as a robust supporting substrate to incorporate function metal oxides. The Cu2O@h-BN composites are thus obtained by dispersing Cu2O octahedrons on the surfaces of h-BN nanosheets. The −OH and −NH groups on the surfaces of h-BN nanosheets are found to be beneficial for anchoring Cu2O octahedrons. Moreover, the Cu2O@h-BN composites exhibit superior activity for the reduction of p-nitrophenol to pure Cu2O crystals and h-BN nanosheets. The h-BN component in the composites plays a critical role in the formation and adsorbing of the p-nitrophenolate ions, and, at the same time, Cu2O components react with brohydride ions and transfer a surface hydrogen species and electrons, resulting in the reduction of p-nitrophenol into p-aminophenol. Our results provide a new approach for the rational design and development of metal oxides composites and open the way to a range of important applications of h-BN-based materials.

Dispersed Cu2O Octahedrons on h-BN Nanosheets for p-Nitrophenol Reduction

In-depth understanding the dye sensitization process over the semiconductor is the key issue for the applications of dye-sensitized solar cells, hydrogen production, and environmental remediation. This work addresses the role of high-quality BiOCl nanoplates in the photosensitization process. It is found that there exists a strong interaction between Rhodamine B and BiOCl nanoplates, which greatly improves the electronic conductivity for interfacial electron injection. The fluorescence emission of Rhodamine B is thus markedly suppressed by the addition of BiOCl suspension, resulting from the electron injection from excited Rhodamine B into the conduction band of BiOCl nanoplates. Moreover, benefitting from the proper conduction band edge potential of BiOCl nanoplates, the injected electrons can be trapped by the surface absorbed O2 to generate reactive oxygen species, resulting in the high photosensitization activity for the Rhodamine B degradation under visible light irradiation.

Caijin Huang

Papers

Carbon-doped BN nanosheets for metal-free photoredox catalysis

Boron Carbon Nitride Semiconductors Decorated with CdS Nanoparticles for Photocatalytic Reduction of CO2

Dispersing molecular cobalt in graphitic carbon nitride frameworks for photocatalytic water oxidation.

Dispersed Cu2O Octahedrons on h-BN Nanosheets for p-Nitrophenol Reduction

Insights into the photosensitivity activity of BiOCl under visible light irradiation