Yongshun Huang

In Situ Ion Exchange Synthesis of Strongly Coupled Ag@AgCl/g-C3N4 Porous Nanosheets as Plasmonic Photocatalyst for Highly Efficient Visible-Light Photocatalysis

A novel efficient Ag@AgCl/g-C3N4 plasmonic photocatalyst was synthesized by a rational in situ ion exchange approach between exfoliated g-C3N4 nanosheets with porous 2D morphology and AgNO3. The as-prepared Ag@AgCl-9/g-C3N4 plasmonic photocatalyst exhibited excellent photocatalytic performance under visible light irradiation for rhodamine B degradation with a rate constant of 0.1954 min(-1), which is ∼41.6 and ∼16.8 times higher than those of the g-C3N4 (∼0.0047 min(-1)) and Ag/AgCl (∼0.0116 min(-1)), respectively. The degradation of methylene blue, methyl orange, and colorless phenol further confirmed the broad spectrum photocatalytic degradation abilities of Ag@AgCl-9/g-C3N4. These results suggested that an integration of the synergetic effect of suitable size plasmonic Ag@AgCl and strong coupling effect between the Ag@AgCl nanoparticles and the exfoliated porous g-C3N4 nanosheets was superior for visible-light-responsive and fast separation of photogenerated electron-hole pairs, thus significantly improving the photocatalytic efficiency. This work may provide a novel concept for the rational design of stable and high performance g-C3N4-based plasmonic photocatalysts for unique photochemical reaction.

Rationally designed 1D Ag@AgVO3 nanowire/graphene/protonated g-C3N4 nanosheet heterojunctions for enhanced photocatalysis via electrostatic self-assembly and photochemical reduction methods

1D Ag@AgVO3 nanowire/graphene/protonated g-C3N4 nanosheet (Ag@AgVO3/rGO/PCN) heterojunctions are fabricated via a simple electrostatic self-assembly process followed by a photochemical reduction method. In this hybrid structure, 1D Ag@AgVO3 nanowires penetrate through 2D nanosheets (graphene and PCN), forming a 3D hybrid photocatalyst, which is applied as an efficient visible light driven photocatalyst for organic pollutant degradation. Its enhanced photocatalytic activity is ascribed to the well-known electronic conductivity of 2D graphene, the intense visible light absorption of 1D Ag@AgVO3 nanowires, large surface areas and rapid photogenerated charge interface transfer and separation. Our results provide a facile way to fabricate hierarchical g-C3N4-based photocatalysts in a controlled manner and highlight promising prospects by adopting an integrative 1D and 2D nanomaterial strategy to design more efficient semiconductor-based composite photocatalysts with high photocatalytic activities and a wide spectral response toward environmental and energy applications.

Formation of Fe3O4@MnO2 ball-in-ball hollow spheres as a high performance catalyst with enhanced catalytic performances

While the synthesis of heterogeneous catalysts is well established, it is extremely challenging to fabricate complex hollow structures with mixed transition metal oxides. Herein, we report a facile in situ growth process of SiO2@Fe3O4@MnO2, followed by an etching method to synthesize a hierarchical hollow structure, namely Fe3O4@MnO2 ball-in-ball hollow spheres (Fe3O4@MnO2 BBHs). The as-prepared Fe3O4@MnO2 BBHs were applied to degrade methylene blue (MB) by catalytic generation of active radicals from peroxymonosulfate (PMS), exhibiting the merits of excellent catalytic performance, easy separation, good stability and recyclability. In this architecture, the degradation process can be divided into three layers. The outer hierarchical MnO2 nanosheets could accumulate and transport the pollutants by electrostatic interactions and catalyze the generation of active radicals for degradation. Both the inner MnO2 nanosheets and the outer Fe3O4 hollows could produce active radicals to accelerate the pollutant degradation. The active catalytic sites also existed in the inner Fe3O4 hollows, which could further degrade the highly concentrated pollutants in the hollows. This work provides new strategies for the controllable synthesis of complex hollow structures and their application in environmental remediation.

Applications of conjugated polymer based composites in wastewater purification

The increasing water demand and the worldwide shortage of clean water call for new technologies for wastewater treatment, of which adsorption is a simple and efficient method to remove organic and inorganic pollutants from contaminated water. Conjugated polymers, particularly for polyaniline, polypyrrole, polythiophene and their derivatives/analogues, have been widely applied in wastewater purification due to their unique properties, such as easy synthesis, porous structure, tunable morphology, good electrorheological property, unique redox chemistry, non-toxicity, etc. This review summarizes potential solutions to wastewater treatment by utilizing conjugated polymer composites as adsorbents. The adsorption phenomenon is briefly introduced, followed by its mechanism investigation techniques. Detailed discussions are focused on the adsorption advantages of polyaniline, polypyrrole and polythiophene based composites to conventional materials. The remaining challenges are also mentioned.

Hybrid 0D–2D Nanoheterostructures: In Situ Growth of Amorphous Silver Silicates Dots on g-C3N4 Nanosheets for Full-Spectrum Photocatalysis

The smaller particle sizes, better dispersion, and more heterojunction interfaces can enhance the photocatalytic performance of photocatalysts. Herein, ultradispersed amorphous silver silicates/ultrathin g-C3N4 nanosheets heterojunction composites (a-AgSiO/CNNS) with intimate interfacial coupling effect were synthesized through the facile in situ precipitation of ultrafine a-AgSiO (∼5.2 nm) uniformly dispersed on the entire surface of hierarchical ultrathin CNNS. In this process, the ultrathin CNNS not only perform as the support to form heterostructures but also are employed as dispersant to confine the aggregation of a-AgSiO nanoparticles. Notably, the optimum photocatalytic activity of a-AgSiO/CNNS-500 composite is ∼36 and 13 times higher than that of CNNS toward the degradation of rhodamine B and tetracycline, respectively. The excellent photocatalytic activity can be attributed to the synergistic interactions of heterojunction with strong interfacial coupling effect, improved visible light absorbance, abundant heterojunction interfaces, and fully exposed reactive sites, which originate from the well-defined nanostructures such as uniform packing of the ultrasmall a-AgSiO, the intimate and maximum coupling interfaces between a-AgSiO and CNNS. We believe that such an easy and scalable synthetic strategy can be further extended to the fabrication of other ultrafine semiconductors coupled with g-C3N4 for increasing its photocatalytic performance.

Rice husks as a sustainable silica source for hierarchical flower-like metal silicate architectures assembled into ultrathin nanosheets for adsorption and catalysis

Metal silicates have attracted extensive interests due to their unique structure and promising properties in adsorption and catalysis. However, their applications were hampered by the complex and expensive synthesis. In this paper, three-dimensional (3D) hierarchical flower-like metal silicate, including magnesium silicate, zinc silicate, nickel silicate and cobalt silicate, were for the first time prepared by using rice husks as a sustainable silicon source. The flower-like morphology, interconnected ultrathin nanosheets structure and high specific surface area endowed them with versatile applications. Magnesium silicate was used as an adsorbent with the maximum adsorption capacities of 557.9, 381.3, and 482.8mg/g for Pb2+, tetracycline (TC), and UO22+, respectively. Ni nanoparticles/silica (Ni NPs/SiO2) exhibited high catalytic activity and good stability for 4-nitrophenol (4-NP) reduction within only ∼160s, which can be attributed to the ultra-small particle size (∼6.8nm), good dispersion and high loading capacity of Ni NPs. Considering the abundance and renewability of rice husks, metal silicate with complex architecture can be easily produced at a large scale and become a sustainable and reliable resource for multifunctional applications.

Removal of uranium(VI) from aqueous solution by magnetic yolk–shell iron oxide@magnesium silicate microspheres

Yolk–shell microspheres with magnetic Fe3O4 cores and hierarchical magnesium silicate shells (Fe3O4@MS) have been successfully synthesized by combining the versatile sol–gel process and hydrothermal reaction. The as-prepared Fe3O4@MS microspheres were then assessed as the adsorbent for uranium(VI) removal from water, and could be easily separated by an external magnetic field. Influencing factors to adsorb uranium(VI) were investigated, including pH, ionic strength and coexisted ions, amount of adsorbent and equilibrium time. The results indicated that uranium(VI) adsorption on Fe3O4@MS microspheres was strongly dependent on pH and the ionic strength. The maximum adsorption capacity for uranium(VI) was calculated to be 1.51 × 10−5 mol g−1 based on the Langmuir model and the experimental data fitted the Langmuir model (R2 = 0.999) better than the Freundlich model (R2 = 0.954). The as-prepared sub-microspheres showed their potential applications as adsorbent for highly efficient removal of heavy metal ions from wastewater.

Adsorption, Aggregation, and Deposition Behaviors of Carbon Dots on Minerals

The increased production of carbon dots (CDs) and the release and accumulation of CDs in both surface and groundwater has resulted in the increasing interest in their research. To assess the environmental behavior of CDs, the interaction between CDs and goethite was studied under different environmental conditions. Electrokinetic characterization of CDs suggested that the ζ-potential and size distribution of CDs were affected by pH and electrolyte species, indicating that these factors influenced the stability of CDs in aqueous solutions. Traditional Derjaguin-Landau-Verwey-Overbeek theory did not fit well the aggregation process of CDs. Results of the effects of pH and ionic strength suggested that electronic attraction dominated the aggregation of CDs. Compared with other minerals, hydrogen-bonding interactions and Lewis acid-base interactions contributed to the aggregation of CDs, in addition to van der Waals and electrical double-layer forces. Adsorption isotherms and microscopic Fourier transformed infrared spectroscopy indicated that chemical bonds were formed between CDs and goethite. These findings are useful to understand the interaction of CDs with minerals, as well as the potential fate and toxicity of CDs in the natural environment, especially in soils and sediments.

Theoretical studies on the pyrolysis of thiocarbonates

Abstract Theoretical studies were carried out to investigate the pyrolysis of O-methyl S-alkyl and S-methyl O-alkyl thiocarbonates, where alkyl groups referred to ethyl, isopropyl and t -butyl groups. Eight possible pathways were found, of which three pathways would generate the alkene products. Not only thermal elimination pathways were calculated, other possible mechanisms, such as rearrangements and nucleophilic substitutions, were also considered. MP2/6-31G(d) level was employed to carry out the calculation and the progress of the reactions was followed by the Wiberg bond indices.

Polydopamine Integrated Nanomaterials and Their Biomedical Applications.

In the past few decades, the applications of nanomaterials in biologic systems have become one of the most studied areas. Many novel syntheses and processing methods have been developed to generate nanomaterials to enhance biomedical applications. Among those methods, polydopamine (PDA) integrated nanomaterials have attracted considerable interest for various types of biomedical applications. This concise review outlines the basic chemistry and material science regarding PDA and discusses its successful applications in drug delivery, biosensing, antifouling and antimicrobial activities, as well as its interaction with cells.