Post-annealing reinforced hollow carbon nitride nanospheres for hydrogen photosynthesis

A Core-Shell-Satellite Structured Fe3 O4 @g-C3 N4 -UCNPs-PEG for T1 /T2 -Weighted Dual-Modal MRI-Guided Photodynamic Therapy

Reactive oxygen species (ROS) produced in the specific tumor site plays the key role in photodynamic therapy (PDT). Herein, a multifunctional nanoplatform is designed by absorbing ultrasmall upconversion nanoparticles (UCNPs) on mesoporous graphitic-phase carbon nitride (g-C₃ N₄ ) coated superparamagnetic iron oxide nanospheres, then further modified with polyethylene glycol (PEG)molecules (abbreviated as Fe₃ O₄ @g-C₃ N₄ -UCNPs-PEG). The inert g-C₃ N₄ layer between Fe₃ O₄ core and outer UCNPs can substantially depress the quenching effect of Fe₃ O₄ on the upconversion emission. Upon near-infrared (NIR) laser irradiation, the UCNPs convert the energy to the photosensitizer (g-C₃ N₄ layer) through fluorescence resonance energy transfer process, thus producing a vast amount of ROS. In vitro experiment exhibits an obvious NIR-triggered cell inhibition due to the cellular uptake of nanoparticles and the effective PDT efficacy. Notably, this platform is responsive to magnetic field, which enables targeted delivery under the guidance of an external magnetic field and supervises the therapeutic effect by T₁ /T₂ -weighted dual-modal magnetic resonance imaging. Moreover, in vivo therapeutic effect reveals that the magnetism guided accumulation of Fe₃ O₄ @g-C₃ N₄ -UCNPs-PEG can almost trigger a complete tumor inhibition without any perceived side effects. The experiments emphasize that the excellent prospect of Fe₃ O₄ @g-C₃ N₄ -UCNPs-PEG as a magnetic targeted platform for PDT application.

Novel g-C3N4/CoO Nanocomposites with Significantly Enhanced Visible-Light Photocatalytic Activity for H2 Evolution

Novel g-C₃N₄/CoO nanocomposite application for photocatalytic H₂ evolution were designed and fabricated for the first time in this work. The structure and morphology of g-C₃N₄/CoO were investigated by a wide range of characterization methods. The obtained g-C₃N₄/CoO composites exhibited more-efficient utilization of solar energy than pure g-C₃N₄ did, resulting in higher photocatalytic activity for H₂ evolution. The optimum photoactivity in H₂ evolution under visible-light irradiation for g-C₃N₄/CoO composites with a CoO mass content of 0.5 wt % (651.3 μmol h^-1 g^-1) was up to 3 times as high as that of pure g-C₃N₄ (220.16 μmol h^-1 g^-1). The remarkably increased photocatalytic performance of g-C₃N₄/CoO composites was mainly attributed to the synergistic effect of the junction or interface formed between g-C₃N₄ and CoO.

A Composite Polymeric Carbon Nitride with In Situ Formed Isotype Heterojunctions for Highly Improved Photocatalysis under Visible Light

Introducing heterojunction is an effective way for improving the intrinsic photocatalytic activity of a graphitic carbon nitride (GCN) semiconductor. These heterostructures are mostly introduced by interfacing GCN with foreign materials that normally have entirely different physicochemical properties and show unfavorable compatibility, thus resulting in a limited improvement of the photocatalytic performance of the resultant materials. Herein, a composite polymeric carbon nitride (CPCN) that contains both melon-based GCN and triazine-based crystalline carbon nitride (CCN) is prepared by a simple thermal reaction between lithium chloride and GCN. Thanks to the intimate contact and good compatibility between GCN and CCN, an in situ formed heterojunction acts as a driving force for separating the photogenerated charge carriers in CPCN. As a result, CPCN exhibits a significantly improved photocatalytic performance under visible light irradiation, which is, respectively, 10.6 and 5.3 times as high as those of the GCN and CCN alone. This well designed isotype heterojunction by a coupling of CCN presents an effective avenue for developing efficient GCN photocatalysts.

Facile transformation of low cost melamine–oxalic acid into porous graphitic carbon nitride nanosheets with high visible-light photocatalytic performance

The high visible-light photocatalytic performance of porous g-C₃N₄nanosheets were prepared by using a long strip-like structure of melamine–oxalic acid (MO) as a precursor.

Ultrathin g-C3N4 nanosheets with an extended visible-light-responsive range for significant enhancement of photocatalysis

Ultrathin graphitic carbon nitride (UGCN) nanosheets with an extended region of visible light response and enhanced surface area were constructed for a significant enhancement in photocatalysis.

MnPSe3 Monolayer: A Promising 2D Visible-Light Photohydrolytic Catalyst with High Carrier Mobility

The 2D material single-layer MnPSe₃ would be a promising photocatalyst for water splitting, as indicated by the proper positions of band edges, strong absorption in visible-light spectrum, broad applicability (pH = 0 - 7), and high carrier mobility.

Hollow porous carbon nitride immobilized on carbonized nanofibers for highly efficient visible light photocatalytic removal of NO

With the deterioration of air quality, great efforts were devoted to designing various photocatalysts for effective removal of NOx in air. However, the present photocatalysts have a fatal problem of low photocatalytic efficiency. In this work, a hollow porous carbon nitride nanosphere coupled with reduced graphene oxide (HCNS/rGO) was exploited as a visible-light photocatalyst to remove nitrogen monoxide in air at a low concentration (600 ppb level) under irradiation of an energy saving lamp. HCNS/rGO showed a NO removal ratio of 64%, which was superior to that of most other visible-light photocatalysts. The excellent photocatalytic ability of HCNS/rGO originates from the hollow porous morphology of HCNS and the grafted rGO on the surface. HCNS/rGO was immobilized on porous carbonized polymer nanofibers to obtain a photocatalytic membrane without affecting photocatalytic efficiency. Furthermore, the membrane showed excellent photochemical stability and recyclability.

Novel mesoporous P-doped graphitic carbon nitride nanosheets coupled with ZnIn2S4 nanosheets as efficient visible light driven heterostructures with remarkably enhanced photo-reduction activity

In this report, we rationally designed and fabricated P-C3N4/ZnIn2S4 nanocomposites by in situ immobilizing ZnIn2S4 nanosheets onto the surface of mesoporous P-doped graphite carbon nitrogen (P-C3N4) nanosheets in a mixed solvothermal environment; their application to the photoreduction of 4-nitroaniline was used to estimate the photocatalytic performance. Different to the template route, here the mesoporous P-C3N4 nanosheets were prepared with a template-free strategy. The as-fabricated P-C3N4/ZnIn2S4 nanocomposites were systematically characterized by analyzing the phase structure, chemical components, electronic and optical properties and separation of charge carrier pairs. More importantly, these P-C3N4/ZnIn2S4 heterostructures have been proven to be highly efficient visible light responsive photocatalysts for photo-reduction, and meanwhile exhibit excellent photo-stability during recycling runs. The sufficient evidence reveals that the significantly improved photocatalytic performance is mainly attributed to the more efficient charge carrier separation based on the construction of a close heterogeneous interface. This work may provide new insights into the utilization of P-C3N4/ZnIn2S4 nanocomposites as visible light driven photocatalysts for comprehensive organic transformations in the field of fine chemical engineering.

Design, synthesis and applications of core-shell, hollow core, and nanorattle multifunctional nanostructures

With the evolution of nanoscience and nanotechnology, studies have been focused on manipulating nanoparticle properties through the control of their size, composition, and morphology. As nanomaterial research has progressed, the foremost focus has gradually shifted from synthesis, morphology control, and characterization of properties to the investigation of function and the utility of integrating these materials and chemical sciences with the physical, biological, and medical fields, which therefore necessitates the development of novel materials that are capable of performing multiple tasks and functions. The construction of multifunctional nanomaterials that integrate two or more functions into a single geometry has been achieved through the surface-coating technique, which created a new class of substances designated as core-shell nanoparticles. Core-shell materials have growing and expanding applications due to the multifunctionality that is achieved through the formation of multiple shells as well as the manipulation of core/shell materials. Moreover, core removal from core-shell-based structures offers excellent opportunities to construct multifunctional hollow core architectures that possess huge storage capacities, low densities, and tunable optical properties. Furthermore, the fabrication of nanomaterials that have the combined properties of a core-shell structure with that of a hollow one has resulted in the creation of a new and important class of substances, known as the rattle core-shell nanoparticles, or nanorattles. The design strategies of these new multifunctional nanostructures (core-shell, hollow core, and nanorattle) are discussed in the first part of this review. In the second part, different synthesis and fabrication approaches for multifunctional core-shell, hollow core-shell and rattle core-shell architectures are highlighted. Finally, in the last part of the article, the versatile and diverse applications of these nanoarchitectures in catalysis, energy storage, sensing, and biomedicine are presented.

Temperature-Dependent Photoluminescence of g-C3N4: Implication for Temperature Sensing

We report the temperature-dependent photoluminescence (PL) properties of polymeric graphite-like carbon nitride (g-C3N4) and a methodology for the determination of quantum efficiency along with the activation energy. The PL is shown to originate from three different pathways of transitions: σ*-LP, π*-LP, and π*-π, respectively. The overall activation energy is found to be ∼73.58 meV which is much lower than the exciton binding energy reported theoretically but ideal for highly sensitive wide-range temperature sensing. The quantum yield derived from the PL data is 23.3%, whereas the absolute quantum yield is 5.3%. We propose that the temperature-dependent PL can be exploited for the evaluation of the temperature dependency of quantum yield as well as for temperature sensing. Our analysis further indicates that g-C3N4 is well-suited for wide-range temperature sensing.

Graphitic carbon nitride nanoribbon for enhanced visible-light photocatalytic H2 production

Chemical scissors provide a new vision to manufacture unique carbon nitride nanostructures with improved photocatalytic performance.

(NH4)2SO4-assisted polycondensation of dicyandiamide for porous g-C3N4 with enhanced photocatalytic NO removal

A facile (NH₄)₂SO₄-modified polycondensation strategy was developed for thin porous g-C₃N₄ with highly enhanced visible light photocatalytic NO removal.

Facile fabrication of metal-free urchin-like g-C3N4 with superior photocatalytic activity

Spherical urchin-like graphitic carbon nitride nanoparticles were fabricated and exhibited almost 12 times higher activity during RhB photodegradation.

An overview of the structural, textural and morphological modulations of g-C3N4 towards photocatalytic hydrogen production

This study highlights the recent trends in the structural, textural and morphological variations of g-C₃N₄ for visible-light-induced hydrogen evolution.

Facile preparation of semimetallic WP2 as a novel photocatalyst with high photoactivity

Searching for inexpensive and earth-abundant photocatalysts with high activities has attracted considerable research in recent years. Semimetallic tungsten diphosphide (WP₂) micro-particles are explored as a novel photocatalyst at the first time.

Ammonia-induced robust photocatalytic hydrogen evolution of graphitic carbon nitride

We report a new and effective method to prepare high activity graphitic carbon nitride (g-C3N4) by a simple ammonia etching treatment. The obtained g-C3N4 displays a high BET surface area and enhanced electron/hole separation efficiency. The hydrogen evolution rates improved from 52 μmol h(-1) to 316.7 μmol h(-1) under visible light.

A facile method of activating graphitic carbon nitride for enhanced photocatalytic activity

Activated graphitic carbon nitride (g-C3N4) with enhanced photocatalytic capability under visible light irradiation was fabricated by using a facile chemical activation treatment method. In the chemical activation, a mixed solution of hydrogen peroxide and ammonia was employed. The yield can reach as high as 90% after the activation process. The activation process did not change the crystal structure, functional group, morphology and specific surface area of pristine g-C3N4, but it introduced H and O elements into the CN framework of g-C3N4, resulting in a broader optical absorption range, higher light absorption capability and more efficient separation of photogenerated electrons and holes. The photoactivity was investigated by the degradation of rhodamine B (RhB) under visible light irradiation. As compared to the pristine g-C3N4, the activated g-C3N4 exhibited a distinct and efficient two-step degradation process. It was found that the RhB dye in the activated g-C3N4 was mainly oxidized by the photogenerated holes. It is believed that sufficient holes account for the two-step degradation process because they would significantly improve the efficiency of the N-de-ethylation reaction of RhB.

Hierarchical FeTiO3-TiO2 hollow spheres for efficient simulated sunlight-driven water oxidation

Oxygen generation is the key step for the photocatalytic overall water splitting and considered to be kinetically more challenging than hydrogen generation. Here, an effective water oxidation catalyst of hierarchical FeTiO3-TiO2 hollow spheres are prepared via a two-step sequential solvothermal processes and followed by thermal treatment. The existence of an effective heterointerface and built-in electric field in the surface space charge region in FeTiO3-TiO2 hollow spheres plays a positive role in promoting the separation of photoinduced electron-hole pairs. Surface photovoltage, transient-state photovoltage, fluorescence and electrochemical characterization are used to investigate the transfer process of photoinduced charge carriers. The photogenerated charge carriers in the hierarchical FeTiO3-TiO2 hollow spheres with a proper molar ratio display much higher separation efficiency and longer lifetime than those in the FeTiO3 alone. Moreover, it is suggested that the hierarchical porous hollow structure can contribute to the enhancement of light utilization, surface active sites and material transportation through the framework walls. This specific synergy significantly contributes to the remarkable improvement of the photocatalytic water oxidation activity of the hierarchical FeTiO3-TiO2 hollow spheres under simulated sunlight (AM1.5).

An Amorphous Carbon Nitride Photocatalyst with Greatly Extended Visible-Light-Responsive Range for Photocatalytic Hydrogen Generation

Amorphous carbon nitride (ACN) with a bandgap of 1.90 eV shows an order of magnitude higher photocatalytic activity in hydrogen evolution under visible light than partially crystalline graphitic carbon nitride with a bandgap of 2.82 eV. ACN is photocatalytically active under visible light at a wavelength beyond 600 nm.

Tuning the morphology of g-C3N4 for improvement of Z-scheme photocatalytic water oxidation

Solar-driven water oxidation is the key step for overall water splitting that efficiently harvests and converts solar energy into fuels; the development of a highly efficient photocatalyst that can mediate water oxidation has become an appealing challenge. Herein, we report a facile two-step process to decorate silver phosphate (Ag3PO4) particles on different types of graphitic carbon nitrides (g-C3N4) as composite photocatalysts for water oxidation. For all the Ag3PO4/g-C3N4 materials, an in situ Z-scheme is created by the generation of Ag nanoparticles which act as a cross-linking bridge between Ag3PO4 and g-C3N4 in the composite, resulting in better charge separation and higher catalytic performance. A detailed analysis emphasizes the importance of the g-C3N4 on the chemical, photophysical, and catalytic properties of the composite materials. Our results show that the alteration of the morphology dominates the performance of the composite materials.

Hollow spheres consisting of Ti0.91O2/CdS nanohybrids for CO2 photofixation

Multilayer hollow spheres consisting of alternating ultrathin Ti_0.91O₂ nanosheets and CdS nanoparticles have achieved a redox mediator-free artificial Z-scheme for photocatalytic reduction of CO₂ into CH₄, which was proved by indirect optical transition effect.

The function-led design of Z-scheme photocatalytic systems based on hollow carbon nitride semiconductors

Hollow conjugated polymer nanospheres mimicking thylakoids act as a host scaffold that coassemble with CdS and Au as an electron mediator to construct an artificial Z-scheme photosynthesis system, which shows a highly efficient performance in photocatalytic water-splitting and CO₂reduction reaction under the irradiation of visible light.

Shell-engineering of hollow g-C3N4 nanospheres via copolymerization for photocatalytic hydrogen evolution

Aromatic monomers have been grafted onto photocatalytic hollow carbon nitride nanospheres via copolymerization to strengthen their optical and electronic properties.