CxNy: New Carbon Nitride Organic Photocatalysts

The search for metal-free and visible light-responsive materials for photocatalytic applications has attracted the interest of not only academics but also the industry in the last decades. Since graphitic carbon nitride (g-C3N4) was first reported as a metal-free photocatalyst, this has been widely investigated in different light-driven reactions. However, the high recombination rate, low electrical conductivity, and lack of photoresponse in most of the visible range have elicited the search for alternatives. In this regard, a broad family of carbon nitride (CxNy) materials was anticipated several decades ago. However, the attention of the researchers in these materials has just been awakened in the last years due to the recent success in the syntheses of some of these materials (i.e., C3N3, C2N, C3N, and C3N5, among others), together with theoretical simulations pointing at the excellent physico-chemical properties (i.e., crystalline structure and chemical morphology, electronic configuration and semiconducting nature, or high refractive index and hardness, among others) and optoelectronic applications of these materials. The performance of CxNy, beyond C3N4, has been barely evaluated in real applications, including energy conversion, storage, and adsorption technologies, and further work must be carried out, especially experimentally, in order to confirm the high expectations raised by simulations and theoretical calculations. Herein, we have summarized the scarce literature related to recent results reporting the synthetic routes, structures, and performance of these materials as photocatalysts. Moreover, the challenges and perspectives at the forefront of this field using CxNy materials are disclosed. We aim to stimulate the research of this new generation of CxNy-based photocatalysts, beyond C3N4, with improved photocatalytic efficiencies by harnessing the striking structural, electronic, and optical properties of this new family of materials.

Mixing States of Aerosol Particles in Urban Haze

<p>Secondary organic aerosols (SOA) are a large fraction of PM<sub>2.5</sub> mass and contribute to extreme haze events, reducing visibility and impairing human health, especially in the Northern China Plain. It has been observed that laboratory generated and field collected SOA material can undergo liquid-liquid phase separation (LLPS), however this has never been directly observed in single ambient aerosol particles. Oligomers are a significant component of atmospheric SOA typically having a molecular mass of >200 g mol<sup>-1</sup>. These large molecules can be produced via multiphase chemical processes and, when soluble in the aerosol phase, may lead to interesting phase separation behavior.</p><p>We conducted a campaign in Beijing during which PM<sub>2.5</sub> was analyzed using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) to observe oligomers at significant quantities. Aerosol particle samples collected before, during and at the peak of a pollution event were targeted. We have evidence that oligomers were the result of multiphase chemistry at high relative humidity. Single particles were probed for chemical morphology and mixing states using X-ray spectro-microscopy to characterize the numbers of particles mixed with inorganic matter, organic matter or soot. Using an environmental microchamber, we subjected single ambient particles to humidity cycles and observed any LLPS to occur. We also quantify the humidity required for LLPS to occur. Our data links oligomeric material having different solubility than e.g. inorganic hygroscopic components with LLPS, giving rise to a clear constraint for urban haze. The results will give statistically significant information about particle mixing state for aerosol population having different oligomer content, humidity history, LLPS behavior and pollution levels.</p>

Preparation of Pineapple Leaf Cellulose Membrane

In this study, the pineapple leaf cellulose membrane was prepared after being dissolved in ionic liquid (1-butyl-3-methylimidazolium chloride ([Bmim]Cl)) and high pressure microfluidization process. The chemical morphology and structure of cellulose membrane were measured by scanning electron microscope (SEM), fourier transformed infrared spectra (FT-IR), extension test and thermogravimetric analysis (TGA). Resules indicated that after microfluidizer, the surface of membrane became smoother, however the tensile strength and thermal stability of cellulose membrane was decreased due to the shearing action of microfluidizer. This would broad the application of cellulose membrane widely.