Ultrathin structure of oxygen doped carbon nitride for efficient CO2photocatalytic reduction.

Photocatalytic conversion of carbon dioxide into fuels and valuable chemicals is a promising method for carbon neutralization and solving environmental problems. Through a simple thermal-oxidative exfoliation method, the O element was doped while exfoliated bulk g-C3N4into ultrathin structure g-C3N4. Benefitting from the ultrathin structure of g-C3N4, the larger surface area and shorter electrons migration distance effectively improve the CO2reduction efficiency. In addition, density functional thory computation proves that O element doping introduces new impurity energy levels, which making electrons easier to be excited. The prepared photocatalyst reduction of CO2to CO (116µmol g-1h-1) and CH4(47µmol g-1h-1).

Tumor-Microenvironment-Induced Degradation of Ultrathin Gadolinium Oxide Nanoscrolls for Magnetic-Resonance-Imaging-Monitored, Activatable Cancer Chemotherapy.

The development of biodegradable inorganic nanoparticles with a tumor microenvironment-activated therapeutic mode of action is urgently needed for precision cancer medicine. Herein, the synthesis of ultrathin lanthanide nanoscrolls (Gd2 O3 NSs) is reported, which biodegrade upon encountering the tumor microenvironment. The Gd2 O3 NSs showed highly controlled magnetic properties, which enabled their high-resolution magnetic resonance imaging (MRI). Importantly, Gd2 O3 NSs degrade in a pH-responsive manner and selectively penetrate tumor tissue, enabling the targeted release of anti-cancer drugs. Gd2 O3 NSs can be efficiently loaded with an anti-cancer drug (DOX, 80 %) and significantly inhibit tumor growth with negligible cellular and tissue toxicity both in vitro and in vivo. This study may provide a novel strategy to design tumor microenvironment-responsive inorganic nanomaterials for biocompatible bioimaging and biodegradation-enhanced cancer therapy.

Preparation of Structure Vacancy Defect Modified Diatomic-Layered g-C3 N4 Nanosheet with Enhanced Photocatalytic Performance.

Structure self-modification of graphitic carbon nitride (g-C3 N4 ) without the assistance of other species has attracted considerable attention. In this study, the structure vacancy defect modified diatomic-layered g-C3 N4 nanosheet (VCN) is synthesized by thermal treatment of bulk g-C3 N4 in a quartz tube with vacuum atmosphere that will generate a pressure-thermal dual driving force to boost the exfoliation and formation of structure vacancy for g-C3 N4 . The as-prepared VCN possesses a large specific surface area with a rich pore structure to provide more active centers for catalytic reactions. Furthermore, the as-formed special defect level in VCN sample can generate a higher exciton density at photoexcitation stage. Meanwhile, the photogenerated charges will rapidly transfer to VCN surface due to the greatly shortened transfer path resulting from the ultrathin structure (≈1.5 nm), which corresponds to two graphite carbon nitride atomic layers. In addition, the defect level alleviates the drawback of enlarged bandgap caused by the quantum size effect of nano-scaled g-C3 N4 , resulting in a well visible-light utilization. As a result, the VCN sample exhibits an excellent photocatalytic performance both in hydrogen production and photodegradation of typical antibiotics.

Ultrathin and Highly Tough Hydrogel Films for Multifunctional Strain Sensors.

With good flexibility and biocompatibility, hydrogel-based sensors have been widely used in human motion detection, artificial intelligence, human-machine interface, and other fields. Previous research on hydrogel-based sensors has focused on improving the mechanical properties and signal transmission sensitivity. With the development of human smart devices, there is an increasing demand for hydrogel sensor comfort and more application functions, such as ultrathin structures and recognition functions for contact surfaces, which are realized with higher requirements for the thickness, flexibility, friction resistance, and biocompatibility of hydrogels. Inspired by the ultrathin and flexible characteristics of human organ biofilms, we constructed conductive hydrogel films by using the flim-casting and glycerol-H2O secondary hydration methods. This ultrathin structure enables the hydrogel films to have a high elongation at break of 523.3%, a stress of 3.5 MPa, and a good friction resistance. Combined with the excellent sensing properties (gauge factor = 2.1 and a response time of 200 ms), the hydrogel film-based sensor can not only record human motion signals but also recognize the surface texture and roughness of objects, such as glass, brushes, wood, and sandpaper with mesh sizes of 80, 50, and 24, accurately. In addition, this hydrogel film has a series of excellent properties such as UV shielding, antiswelling ability, and good biocompatibility. This research provides a novel way for the development of emerging soft-material smart devices, such as hydrogel-based electronic skin and soft robots.

Directing photocatalytic pathway to exceedingly high antibacterial activity in water by functionalizing holey ultrathin nanosheets of graphitic carbon nitride.

Metal-free polymeric carbon nitride (C3N4) photocatalysts offer attractive technological advantages over the conventional transition metal oxides or sulfides -based photocatalysts in water disinfection, but their antimicrobial activities are limited by their rapid charge carrier recombination and low specific surface areas. By controlling photocatalytic pathways, we obtained in amino-rich holey ultrathin g-C3N4 nanosheets (AHUCN) a highly efficient inactivation rate against E-coli, which is the highest among the monolithic g-C3N4 and exceeds the antibacterial performance of the most of the previously reported g-C3N4-based photocatalysts. Both the experiments and theoretical calculations demonstrated that the high photocatalytic disinfection performance of AHUCN was derived from the synergistic advantages of their unique holey ultrathin structure and the amino - rich surface in controlling the charge separation and transfer, and most importantly in increasing the photo-production of the dominant antibacterial species, H2O2. From the analysis of the reactive oxygen species and rotating disk electrode (RDE) measurements, it was found that the presence of abundant surface amino groups enabled the switch of the oxygen-reduction pathway from the two-step single-electron indirect reduction on holey ultrathin g-C3N4 nanosheets (HUCN) to the one-step two-electron direct reduction on AHUCN. The switch of the H2O2 production pathway not only facilitated the separation of photogenerated electron-hole pairs but also promoted the generation of reactive oxygen species, greatly enhancing photocatalytic disinfection efficiency.

Nanostructure Engineering of Graphitic Carbon Nitride for Electrochemical Applications.

Graphitic carbon nitride with ordered two-dimensional structure displays multiple properties, including tunable structure, suitable bandgap, high stability, and facile synthesis. Many achievements on this material have been made in photocatalysis, but the advantages have not yet been fully explored in electrochemical fields. The bulk structure with low conductivity impedes charge-transfer kinetics during electrochemical processes. Excessive nitrogen content leads to insufficient charge transfer, while bulk structures produce tortuous channels for mass transport. Some attempts have been made to address these issues by nanostructure engineering, such as ultrathin structure design, heterogeneous composition, defect engineering, and morphology control. These structure-engineered nanomaterials have been successfully applied in electrochemical fields, including ionic actuators, flexible supercapacitors, lithium-ion batteries, and electrochemical sensors. Herein, a timely review on the latest advances in graphitic carbon nitride through various engineering strategies for electrochemical applications has been summarized. A perspective on critical challenges and future research directions is highlighted for graphitic carbon nitride in electrochemistry on the basis of existing research works and our experimental experience.