Lexin Zhang

Fabrication of Hierarchical Layer-by-Layer Assembled Diamond-based Core-Shell Nanocomposites as Highly Efficient Dye Absorbents for Wastewater Treatment

The effective chemical modification and self-assembly of diamond-based hierarchical composite materials are of key importance for a broad range of diamond applications. Herein, we report the preparation of novel core-shell diamond-based nanocomposites for dye adsorption toward wastewater treatment through a layer-by-layer (LbL) assembled strategy. The synthesis of the reported composites began with the carboxyl functionalization of microdiamond by the chemical modification of diamond@graphene oxide composite through the oxidation of diamond@graphite. The carboxyl-terminated microdiamond was then alternatively immersed in the aqueous solution of amine-containing polyethylenimine and carboxyl-containing poly acrylic acid, which led to the formation of adsorption layer on diamond surface. Alternating (self-limiting) immersions in the solutions of the amine-containing and carboxyl-containing polymers were continued until the desired number of shell layers were formed around the microdiamond. The obtained core-shell nanocomposites were successfully synthesized and characterized by morphological and spectral techniques, demonstrating higher surface areas and mesoporous structures for good dye adsorption capacities than nonporous solid diamond particles. The LbL-assembled core-shell nanocomposites thus obtained demonstrated great adsorption capacity by using two model dyes as pollutants for wastewater treatment. Therefore, the present work on LbL-assembled diamond-based composites provides new alternatives for developing diamond hybrids as well as nanomaterials towards wastewater treatment applications.

Graphene Oxide-Polymer Composite Langmuir Films Constructed by Interfacial Thiol-Ene Photopolymerization

The effective synthesis and self-assembly of graphene oxide (GO) nanocomposites are of key importance for a broad range of nanomaterial applications. In this work, a one-step chemical strategy is presented to synthesize stable GO-polymer Langmuir composite films by interfacial thiol-ene photopolymerization at room temperature, without use of any crosslinking agents and stabilizing agents. It is discovered that photopolymerization reaction between thiol groups modified GO sheets and ene in polymer molecules is critically responsible for the formation of the composite Langmuir films. The film formed by Langmuir assembly of such GO-polymer composite films shows potential to improve the mechanical and chemical properties and promotes the design of various GO-based nanocomposites. Thus, the GO-polymer composite Langmuir films synthesized by interfacial thiol-ene photopolymerization with such a straightforward and clean manner, provide new alternatives for developing chemically modified GO-based hybrid self-assembled films and nanomaterials towards a range of soft matter and graphene applications.

Self-Assembled AgNP-Containing Nanocomposites Constructed by Electrospinning as Efficient Dye Photocatalyst Materials for Wastewater Treatment

The design and self-assembly of graphene oxide (GO)-based composite membranes have attracted enormous attention due to their wide application in nanomaterial and environmental fields. In this work, we have successfully developed a strategy to fabricate new composite membranes based on poly(vinyl alcohol)/poly(acrylic acid)/carboxyl-functionalized graphene oxide modified with silver nanoparticles (PVA/PAA/GO-COOH@AgNPs), which were prepared via thermal treatment and the electrospinning technique. Due to the strong π-π forces and strong electrostatic interactions of GO–COOH sheets, the prepared composite membranes and their lager surface areas were modified by scores of AgNPs, which demonstrated that a high-efficiency photocatalyst removed the organic dyes from the aqueous solutions. The prepared PVA/PAA/GO-COOH@AgNPs nanocomposite membranes showed a remarkable photocatalytic capacity in the catalytic degradation of the methylene blue dye solutions. Most importantly, the whole process was easy, mild, and eco-friendly. Additionally, the as-prepared membranes could be repeatedly used after the catalytic reaction.

Fabrication of tunable hierarchical MXene@AuNPs nanocomposites constructed by self-reduction reactions with enhanced catalytic performances

MXene, a new type of two-dimensional layered transition metal carbide material differing from graphene, demonstrates intriguing chemical/physical properties and wide applications in recent years. Here, the preparation of the self-assembled MXene-gold nanoparticles (MXene@AuNPs) nanocomposites with tunable sizes is reported. The nanocomposites are obtained via the self-reduction reactions of MXene material in a HAuCl4 solution at room temperature. The sizes of the Au particles can be well-controlled by regulating the self-reduction reaction time. They can greatly influence the catalytic behaviors of the MXene@AuNPs composites. MXene@AuNPs composites with optimized reduction time show high catalytic performances and good cycle stability for model catalytic reactions of nitro-compounds, such as 2-nitrophenol and 4-nitrophenol. This work demonstrates a new approach for the preparation of tunable MXene-based self-assembled composites.摘要MXene是一种不同于石墨烯的新型层状二维过渡金属碳化物材料, 近年来表现出有趣的化学、 物理性能并被广泛应用. 本文报道了结构新颖且尺寸可调的自组装层状MXene@AuNPs纳米复合材料的制备方法. 在室温下MXene@AuNPs纳米复合材料可通过MXene材料在HAuCl4溶液中的自还原反应制备. 控制自还原反应的时间可精确地调节Au粒子的颗粒尺寸. 而金纳米颗粒的粒径对MXene@AuNPs复合材料的催化性能具有很大的影响. 适当自还原时间下得到的MXene@AuNPs复合材料表现出对模型硝基化合物(如4-NP和2-NA)催化反应很高的催化性能和良好的循环稳定性. 本研究工作为基于MXene自组装复合材料的制备与调控提供了新方法.

Preparation and dye removal capacities of porous silver nanoparticle-containing composite hydrogels via poly(acrylic acid) and silver ions

In this work, hierarchical porous composite hydrogels of poly(acrylic acid)–silver/silver nanoparticles (PAA–Ag/AgNPs) were successfully prepared by an in situ coordination and self-assembly process. The obtained composite PAA–Ag/AgNPs hydrogels were achieved through different coordination times between PAA and silver ions in the self-assembly process. These as-formed hydrogels were characterized by various morphological and spectroscopy techniques. Interestingly, unique 3D porous network structures in the nanocomposite hydrogels were demonstrated, due to which the as-obtained composite hydrogels demonstrate good removal capacities in accordance with both a pseudo-first-order model and a pseudo-second-order model for three model dyes. Thus, the present obtained composite hydrogels provide new alternatives for developing hybrid hydrogels and nanomaterials for removal of organic dye pollutants from aqueous environments in wastewater treatment applications.

Preparation and adsorption capacity evaluation of graphene oxide-chitosan composite hydrogels

Graphene oxide (GO)-chitosan composite hydrogels were successfully prepared via the self-assembly of chitosan molecules and GO. These as-prepared hydrogels were characterized by different techniques. The morphology of the internal network structure of the nanocomposite hydrogels was investigated. The adsorption capacity results demonstrate that the prepared GObased composite hydrogels can efficiently remove three tested dye molecules, Congo red, methylene blue and Rhodamine B, from wastewater in accordance with the pseudo-second-order model. The dye adsorption capacity of the obtained hydrogels is mainly attributed to the GO sheets, whereas the chitosan molecule was incorporated to facilitate the gelation process of the GO sheets. The present study indicates that the as-prepared composite hydrogels can serve as good adsorbents for wastewater treatment as well as the removal of harmful dyes.中文摘要本文通过壳聚糖分子与氧化石墨烯(GO)的自组装成功制备了GO-壳聚糖复合水凝胶, 并对该水凝胶进行了表征. 研究发现复合水凝胶中存在网状微观结构. 吸附性能结果表明制得的基于GO的复合水凝胶可以有效地从废水中去除三种测试染料分子, 同时符合准二阶模型. 该水凝胶的染料吸附能力主要来源于GO片层, 而壳聚糖分子促进了GO片层的凝胶化过程. 目前的研究结果表明制备的复合水凝胶可以作为良好的吸附剂应用于废水处理以及有害染料去除等领域.

Hierarchical AuNPs-Loaded Fe3O4/Polymers Nanocomposites Constructed by Electrospinning with Enhanced and Magnetically Recyclable Catalytic Capacities

Gold nanoparticles (AuNPs) have attracted widespread attention for their excellent catalytic activity, as well as their unusual physical and chemical properties. The main challenges come from the agglomeration and time-consuming separation of gold nanoparticles, which have greatly baffled the development and application in liquid phase selective reduction. To solve these problems, we propose the preparation of polyvinyl alcohol(PVA)/poly(acrylic acid)(PAA)/Fe3O4 nanocomposites with loaded AuNPs. The obtained PVA/PAA/Fe3O4 composite membrane by electrospinning demonstrated high structural stability, a large specific surface area, and more active sites, which is conducive to promoting good dispersion of AuNPs on membrane surfaces. The subsequently prepared PVA/PAA/Fe3O4@AuNPs nanocomposites exhibited satisfactory nanostructures, robust thermal stability, and a favorable magnetic response for recycling. In addition, the PVA/PAA/Fe3O4@AuNPs nanocomposites showed a remarkable catalytic capacity in the catalytic reduction of p-nitrophenol and 2-nitroaniline solutions. In addition, the regeneration studies toward p-nitrophenol for different consecutive cycles demonstrate that the as-prepared PVA/PAA/Fe3O4@AuNPs nanocomposites have outstanding stability and recycling in catalytic reduction.

Self-Assembly and Drug Release Capacities of Organogels via Some Amide Compounds with Aromatic Substituent Headgroups

In this work, some amide compounds with different aromatic substituent headgroups were synthesized and their gelation self-assembly behaviors in 22 solvents were characterized as new gelators. The obtained results indicated that the size of aromatic substituent headgroups in molecular skeletons in gelators showed crucial effect in the gel formation and self-assembly behavior of all compounds in the solvents used. Larger aromatic headgroups in molecular structures in the synthesized gelator molecules are helpful to form various gel nanostructures. Morphological investigations showed that the gelator molecules can self-assembly and stack into various organized aggregates with solvent change, such as wrinkle, belt, rod, and lamella-like structures. Spectral characterizations suggested that there existed various weak interactions including π-π stacking, hydrogen bonding, and hydrophobic forces due to aromatic substituent headgroups and alkyl substituent chains in molecular structures. In addition, the drug release capacities experiments demonstrated that the drug release rate in present obtained gels can be tuned by adjusting the concentrations of dye. The present work would open up enormous insight to design and investigate new kind of soft materials with designed molecular structures and tunable drug release performance.

Hierarchical electrospun nanofibers treated by solvent vapor annealing as air filtration mat for high-efficiency PM2.5 capture

Recently, air pollution has become more serious and started to have a dramatic effect on the health of humans in many large cities. Generally, outdoor personal protection, such as commercial masks, cannot effectively prevent the inhalation of many pollutants. Particulate matter (PM) pollutants are a particularly serious threat to human health. Here we introduce a new efficient air filtration mat that can be used for outdoor protection. The new efficient air filter’s nanocomposite materials were successfully fabricated from poly(ε-caprolactone)/polyethylene oxide (PCL/PEO) using an electrospinning technique and solvent vapor annealing (SVA). SVA treatment endows the wrinkled fiber surface and enhances the PM2.5 capture capacity of protective masks. This nanowrinkled air filtration mat can effectively filter PM2.5 with a removal efficiency of 80.01% under seriously polluted conditions (PM2.5 particle concentration above 225 mgm−3). Our field test in Qinhuangdao indicated that the air filtration mat had a high PM2.5 removal efficiency under thick haze. Compared to commercial masks, the fabricated SVA-treated PCL/PEO air filter mat demonstrated a simpler and ecofriendly preparation process with excellent degradation characteristics, showing wide potential applications with a high filtration efficiency.摘要空气污染特别是颗粒物(PM)污染, 已经威胁到人类的身体健康, 因而引起了全世界的高度关注. 人们在室外可通过口罩进行个人防 护, 然而一般的商业口罩起不到好的防护效果. 本文利用静电纺丝技术和溶剂蒸汽退火(SVA)方法制备了新型高效的聚(ε-己内酯)/聚环氧 乙烷(PCL/PEO)空气过滤纳米纤维. 通过SVA处理, 纤维表面变得褶皱, 增强了对PM2.5的捕获效率. 在重度污染状况(PM2.5颗粒浓度 >225 mg m−3)下, 这种纳米褶皱空气过滤膜的移除效率达80.01%. 秦皇岛雾霾天实地测量表明, 空气过滤膜能高效移除PM2.5. 与商业口 罩相比, 本文经过SVA处理后的PCL/PEO空气过滤膜具有制备方法简单、环境友好且易降解的特性, 在高效过滤膜领域有潜在应用.

Preparation of MoS2-based polydopamine-modified core–shell nanocomposites with elevated adsorption performances

New molybdenum disulfide (MoS2)-based core–shell nanocomposite materials were successfully prepared through the self-assembly of mussel-inspired chemistry. Characterization by Fourier transform infrared, thermogravimetric analysis, scanning electron microscope and transmission electron microscopy revealed that the surface of the flaked MoS2 was homogeneously coated with a thin layer of polydopamine (PDA). Dye adsorption performances of the synthesized MoS2–PDA nanocomposites were investigated at different pH values and reaction times. Compared with pure MoS2 nanosheets, the obtained core–shell nanocomposites showed elevated adsorption performances and high stability, indicating their potential applications in wastewater treatment and composite materials.