Luyi Sun

Preparation of α-zirconium phosphate nanoplatelets with wide variations in aspect ratios

Synthetic α-zirconium phosphate (α-ZrP) layer structures have been prepared via three different approaches. By controlling the concentration of reactants, temperature, pressure, and using a complexing agent, α-ZrP with a wide variation in aspect ratios has been prepared. Synthetic α-ZrP can be easily intercalated by amines and then exfoliated in epoxy to prepare polymer nanocomposites. Nanocomposites that contain exfoliated α-ZrP nanoplatelets with wide variations in aspect ratios can be utilized as model systems to study the structure–property relationship in polymer nanocomposites.

A critical review on the heterogeneous catalytic oxidation of elemental mercury in flue gases.

Nowadays, an increasing attention has been paid to the technologies for removing mercury from flue gases. Up to date, no optimal technology that can be broadly applied exists, but the heterogeneous catalytic oxidation of mercury is considered as a promising approach. Based on a brief introduction of the pros and cons of traditional existing technologies, a critical review on the recent advances in heterogeneous catalytic oxidation of elemental mercury is provided. In this contribution, four types of Hg oxidation catalysts including noble metals, selective catalytic reduction (SCR) catalysts, transition metals, and fly ash have been summarized. Both the advantages and disadvantages of these catalysts are described in detail. The influence of various acidic gases including SO2, SO3, NH3, NOx, HCl, Cl2, etc. have been discussed as well. We expect this work will shed light on the development of heterogeneous catalytic oxidation of elemental mercury technology in flue gases, particularly the synthesis of novel and highly efficient Hg(0) oxidation catalysts.

Electrically Conductive Polypropylene Nanocomposites with Negative Permittivity at Low Carbon Nanotube Loading Levels

Polypropylene (PP)/carbon nanotubes (CNTs) nanocomposites were prepared by coating CNTs on the surface of gelated/swollen soft PP pellets. The electrical conductivity (σ) studies revealed a percolation threshold of only 0.3 wt %, and the electrical conductivity mechanism followed a 3-d variable range hopping (VRH) behavior. At lower processing temperature, the CNTs formed the network structure more easily, resulting in a higher σ. The fraction of γ-phase PP increased with increasing the pressing temperature. The CNTs at lower loading (0.1 wt %) served as nucleating sites and promoted the crystallization of PP. The CNTs favored the disentanglement of polymer chains and thus caused an even lower melt viscosity of nanocomposites than that of pure PP. The calculated optical band gap of CNTs was observed to increase with increasing the processing temperature, i.e., 1.55 eV for nanocomposites prepared at 120 °C and 1.70 eV prepared at 160 and 180 °C. Both the Drude model and interband transition phenomenon have been used for theoretical analysis of the real permittivity of the nanocomposites.

Graphene quantum dots: versatile photoluminescence for energy, biomedical, and environmental applications

Photoluminescence is one of the most outstanding features of graphene quantum dots. Because of their versatile photoluminescence, large surface area, high photostability, low cytotoxicity, and excellent biocompatibility, graphene quantum dots show promising applications in various fields, and herein they have become the research focus in recent years. In this review article, we summarize the latest research progress of graphene quantum dots, focusing on their photoluminescence features and promising applications. This article also summarizes the most recent researches on the upconversion by the use of a femtosecond laser. Perspectives on this topic were presented on the basis of the current research status. We hope that this article could help gain an in-depth understanding of photoluminescent graphene quantum dots, and herein stimulate continued interest and endeavors in this research area.

Silica nanoparticles and frameworks from rice husk biomass.

Biogenic silica nanoparticles (25-30 nm in diameter) were synthesized from rice husks. The characterizations revealed that the silica nanoparticles were composed of smaller primary particles (ca. 4.2 nm in diameter), and their clustering led to a porous structure with a surface area of 164 m(2)/g. Under the controlled melting catalyzed by K(+), such silica nanoparticle clusters can gradually fuse to form semicrystalline porous silica frameworks with tunable pore size and structural integrity.

Sulfur@graphene oxide core–shell particles as a rechargeable lithium–sulfur battery cathode material with high cycling stability and capacity

Sulfur@GO core–shell composites were prepared by the self-assembly of sulfur particles stabilized by a cationic surfactant and anionic graphene oxide nanosheets through electrostatic interaction. Due to the effective entrapment of polysulfide intermediates by the GO shell, the composites exhibit high cycling stability with 81% capacity maintenance over 210 cycles as the cathode for Li–S batteries.

Large-Scale and Controllable Synthesis of Graphene Quantum Dots from Rice Husk Biomass: A Comprehensive Utilization Strategy

In this work, rice husk biomass was utilized as an abundant source to controllably prepare high-quality graphene quantum dots (GQDs) with a yield of ca. 15 wt %. The size, morphology, and structure of the rice-husk-derived GQDs were determined by high-resolution transmission electron microscopy, atomic force microscopy, and Raman spectroscopy. The as-fabricated GQDs can be stably dispersed in water, exhibiting bright and tunable photoluminescence. A cell viability test further confirmed that the GQDs possess excellent biocompatibility, and they can be easily adopted for cell imaging via a facile translocation into the cytoplasm. It is worth noting that mesoporous silica nanoparticles were also synthesized as a byproduct during the fabrication of GQDs. As such, our strategy achieves a comprehensive utilization of rice husks, exhibiting tremendous benefits on both the economy and environment.

Sulfonic acid-functionalized α-zirconium phosphate single-layer nanosheets as a strong solid acid for heterogeneous catalysis applications.

Solid acids have received considerable attention as alternatives to traditional corrosive and hazardous homogeneous acids because of their advantages in practical applications, including their low corrosion of equipment and high catalytic activity and recyclability. In this work, a strong solid acid was prepared by anchoring thiol group terminated chains on layered α-zirconium phosphate (ZrP) single-layer nanosheets, followed by oxidation of thiol groups to form sulfonic acid groups. The obtained solid acids were thoroughly characterized and the results proved that sulfonic acid group terminated chains were successfully grafted onto the ZrP nanosheets with a high loading density. Such a strong solid acid based on inorganic nanosheets can be well-dispersed in polar solvents, leading to high accessibility to the acid functional groups. Meanwhile, it can be easily separated from the dispersion system by centrifugation or filtration. The strong solid acid can serve as an effective heterogeneous catalyst for various reactions, including the Bayer-Villiger oxidation of cyclohexanone to ε-caprolactone in the absence of organic solvents.

Bio-inspired sensitive and reversible mechanochromisms via strain-dependent cracks and folds

A number of marine organisms use muscle-controlled surface structures to achieve rapid changes in colour and transparency with outstanding reversibility. Inspired by these display tactics, we develop analogous deformation-controlled surface-engineering approaches via strain-dependent cracks and folds to realize the following four mechanochromic devices: (1) transparency change mechanochromism (TCM), (2) luminescent mechanochromism (LM), (3) colour alteration mechanochromism (CAM) and (4) encryption mechanochromism (EM). These devices are based on a simple bilayer system that exhibits a broad range of mechanochromic behaviours with high sensitivity and reversibility. The TCM device can reversibly switch between transparent and opaque states. The LM can emit intensive fluorescence as stretched with very high strain sensitivity. The CAM can turn fluorescence from green to yellow to orange as stretched within 20% strain. The EM device can reversibly reveal and conceal any desirable patterns.

Aqueous phase preparation of graphene with low defect density and adjustable layers

Graphene sheets with an adjustable number of layers and a low defect density were prepared by exfoliation of microwave-assisted expanded graphite in the aqueous phase with the assistance of cetyltrimethylammonium bromide. The graphene sheets exhibit excellent film-formation ability, showing potential applications in optical and electrical device fields.