Shunsheng Cao

A temperature-responsive nanoreactor.

An originally designed temperature-responsive nanoreactor is reported. The nanoreactor is made of Ag nanoparticles and a functional polymer composite of poly(acrylamide) (PAAm) and poly(2-acrylamide-2-methylpropanesulfonic acid) (PAMPS). At a relatively low temperature (e.g., 20 °C), this nanoreactor displayed weak reactivity because of the interpolymer complexation between PAAm and PAMPS, which largely restricted the access of reactants to the encapsulated Ag nanoparticles. On the contrary, at a relatively high temperatures (e.g., 40 °C), the nanoreactor demonstrated significant catalytic activity resulting from the dissociation of the interpolymer complexation between PAAm and PAMPS, which allowed reactants to get access to the encapsulated Ag nanoparticles. By taking account of previously reported PNIPAm-based nanoreactors, which show inverse temperature response, i.e., reactivity decreases whilst temperature increases, this temperature-responsive nanoreactor would greatly facilitate and enrich the increasing studies on smart nanomaterials, generating numerous applications in a wide range of areas, such as catalysis and sensing.

Unique double-shelled hollow silica microspheres: template-guided self-assembly, tunable pore size, high thermal stability, and their application in removal of neutral red

A novel type of monodisperse and double-shelled hollow silica microspheres was reported. This unique double-shelled structure was fabricated using a consecutive template-guided self-assembly. Cationic poly(styrene) (CPS) particles prepared by emulsifier-free polymerization were first used as the template to coat with tetraethylorthosilicate (TEOS) in the presence of coupling agent methacryloxypropyltrimethoxysilane (MPS), forming the core/shell type of CPS/SiO2 particles. The resulting CPS/SiO2 particles were further used as the template and in situ polymerized with styrene, a cationic co-monomer 2-(methacryloyl)ethyltrimethyl ammonium chloride (DMC), followed by electro-statically guided self-assembly and polymerization of TEOS on the surface, generating the sandwich-like CPS/SiO2/CPS/SiO2 particles. Finally, the unique double-shelled hollow silica spheres were produced by one-step removal of the CPS core and CPS layer from the sandwich-like particles. The structure of the monodisperse and intact double-shelled hollow silica microspheres was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET), Elemental Analysis (EA), and 29Si Nuclear Magnetic Resonance (29Si-NMR). Unlike previously reported hollow silica microspheres which have one single shell, the novel silica microspheres have two shells, enabling improved thermal stability and larger BET surface area. Notably, the interior cavity and shell-to-shell distance can be effectively tuned simply by controlling the interior CPS core diameter and the outer CPS template layer. The absorption and separation of the neutral red (NR) in synthesized hollow silica spheres showed favorable adsorption behavior, such as higher absorbent amount of dye and lower rate of dye desorbed for NR in comparison to single-shelled hollow silica, which thereby makes it potentially more applicable in environmental separation and adsorption.

The Fabrication and Progress of Core-Shell Composite Materials

Core-shell materials, in which a layer or multilayer of inorganic or organic material surrounds an inorganic or organic particle core, have been investigated both as a means to improve the stability and surface chemistry of the core particle and as a way of accessing unique physical and chemical properties that are not possible from one material alone. As a result, the fabrication of core-shell particles is attracting a great deal of interest because of their unique properties and potential applicability in catalysis, semiconductors, drug delivery, enzyme immobilization, molecular recognition, chemical sensing, etc. As evidenced by the literature described and discussed in this review, a basic understanding of the mechanism and recent progress in production methods have enabled the fabrication of core-shell particles with unique and tailored properties for various applications in materials science.

Preparation and antibacterial activities of hollow silica–Ag spheres

Hollow silica spheres with round mesoporous shells were synthesized by core-shell template method, using monodispersed cationic polystyrene particles as core, and TEOS (tetraethoxysilane) as the silica source to form shell. After calcination at 550°C, uniform spheres with a thin shell of silica and hollow interior structures. Transmission electron microscopy results showed that the size of the spheres is about 700 nm in diameter with narrow distribution. In addition, the spheres have a high surface area of 183 m(2)/g. The spheres were subsequently used as silver-loading substrates and the silver loaded spheres were tested in antimicrobial study against gram negative bacteria Eschrichia coli in vitro. The hollow silica-Ag spheres proved significantly higher antibacterial efficacy against E. coli as compared to that of the common silica-Ag particles.

The Preparation and Enzyme Immobilization of Hydrophobic Polysiloxane Supports

Enzymes are versatile biocatalysts and find increasing applications in many areas. The major advantages of using enzymes in biocatalytic transformations are their chemo-, regio-, and stereospecificity, as well as the mild reaction conditions that can be used. However, even when an enzyme is identified as being useful for a given reaction, its application is often hampered by its lack of long-term stability under process conditions, and also by difficulties in recovery and recycling. For ease of application and stabilization purposes, enzymes are often immobilized on solid supports. Among support matrices, hydrophobic biomaterials have been extensively used as supports for enzyme immobilization because the hydrophobic interactions not only can effectively increase the amount of enzyme immobilization, but also exhibit higher activity and retention of activity compared with hydrophilic supports. On the other hand, polysiloxane can evidently increase the amount of enzyme immobilization because of its hydrophobicity and strong affinity with enzyme. Therefore, this research details the first preparation and use of a hydrophobic polysiloxane support for enzyme immobilization in which the structural and functional characteristics of new supports have been investigated by using glucose oxidase (GOD) and a simple Fentons assay method, and extremely interesting features were revealed. The results showed that the amount of GOD immobilization and the stability of GOD loaded, which are fundamental properties for enzyme separation and purification, can be significantly improved by adsorption. Moreover, the results indicated that hydrophobic polysiloxane supports can effectively increase the enzymatic affinity and durability of GOD, and decrease the rate of GOD desorbed.

High photocatalytic activity of hierarchical SiO2@C-doped TiO2 hollow spheres in UV and visible light towards degradation of rhodamine B

Ongoing research activities are targeted to explore high photocatalytic activity of TiO2-based photocatalysts for the degradation of environmental contaminants under UV and visible light irradiation. In this work, we devise a facile, cost-effective technique to in situ synthesize hierarchical SiO2@C-doped TiO2 (SCT) hollow spheres for the first time. This strategy mainly contains the preparation of monodisperse cationic polystyrene spheres (CPS), sequential deposition of inner SiO2, the preparation of the sandwich-like CPS@SiO2@CPS particles, and formation of outer TiO2. After the one-step removal of CPS templates by calcination at 450°C, hierarchical SiO2@C-doped TiO2 hollow spheres are in situ prepared. The morphology, hierarchical structure, and properties of SCT photocatalyst were characterized by TEM. SEM, STEM Mapping, BET, XRD, UV-vis spectroscopy, and XPS. Results strongly confirm the carbon doping in the outer TiO2 lattice of SCT hollow spheres. When the as-synthesized SCT hollow spheres were employed as a photocatalyst for the degradation of Rhodamine B under visible-light and ultraviolet irradiation, the SCT photocatalyst exhibits a higher photocatalytic activity than commercial P25, effectively overcoming the limitations of poorer UV activity for many previous reported TiO2-based photocatalysts due to doping.

Design and Synthesis of Hierarchical SiO2@C/TiO2 Hollow Spheres for High-Performance Supercapacitors

TiO2 has been widely investigated as an electrode material because of its long cycle life and good durability, but the relatively low theoretical capacity restricts its practical application. Herein, we design and synthesize novel hierarchical SiO2@C/TiO2 (HSCT) hollow spheres via a template-directed method. These unique HSCT hollow spheres combine advantages from both TiO2 such as cycle stability and SiO2 with a high accessible area and ionic transport. In particular, the existence of a C layer is able to enhance the electrical conductivity. The SiO2 layer with a porous structure can increase the ion diffusion channels and accelerate the ion transfer from the outer to the inner layers. The electrochemical measurements demonstrate that the HSCT-hollow-sphere-based electrode manifests a high specific capacitance of 1018 F g-1 at 1 A g-1 which is higher than those for hollow TiO2 (113 F g-1) and SiO2/TiO2 (252 F g-1) electrodes, and substantially higher than those of all the previously reported TiO2-based electrodes.

Recognition of proteins and peptides: Rational development of molecular imprinting technology

The creation of tailor-made receptors which are able to recognize molecular targets with high affinity and selectivity has attracted much attention in the field of chemistry, physics, and biology. Molecular imprinting has proved to be an effective technique for generating specific recognition sites in synthetic polymers. The synthesis of molecular imprinted polymers specific for proteins and peptides has been a focus for many scientists working in the area of molecular recognition, since the creation of synthetic polymers that can specifically recognize biomacromolecules is a very challenging but potentially extremely rewarding work. These polymers with specificity for biological macromolecules have considerable potential for applications in the areas of solid phase extraction, catalysis, medicine, clinical analysis, drug delivery, environmental monitoring, and sensors. In this review, the authors discuss the developed approaches associated with the imprinting of peptides and proteins, and provide an overview of the significant progress achieved within this field. Finally, the possible mechanism of the molecular imprinting and recognition has been discussed.

Stimuli-responsive controlled release and molecular transport from hierarchical hollow silica/polyelectrolyte multilayer formulations

The smart designing of polymer hybrid carriers with a selective property will play a pivotal role in improving patient care and simplifying treatment regimes in the clinic. The controlled drug release of biomolecules from thin film coatings provides a simple pathway to offer complex localized in vivo dosing. In this investigation, we showed that it is possible to take advantage of the structure of hierarchically structured hollow silica/polymer hybrid system to control drug release. Drug-loaded polyelectrolyte multilayer films were developed using layer-by-layer assembly, incorporating the surface of the hierarchically structured hollow silica spheres. In comparison to the conventional hollow silica system, the synthesized formulation exhibited an enhanced stability, higher drug loading and better residual capacity of biomolecules. This rationally integrated architecture was demonstrated to be a very effective and controllable carrier for the drug release by changing the pH value. In addition, the developed system presented a highly selective molecular transport of doxorubicin hydrochloride (DOX), a model anti-cancer agent, at different pH values; moreover, it could be further applied to tailor cell viability, making it more promising for advanced drug therapy.

The Fabrication and Development of Molecularly Imprinted Polymer-based Sensors for Environmental Application

The detection of specific molecules as markers of disease, health status, environmental monitoring, and food quality means that MIP-based sensors for these targets attract increasing attention due to their practical significance and their potential application in analytical chemistry. Therefore, considerable endeavors have been devoted to fabricate and develop a variety of MIP sensor platform with high selectivity, sensitivity, and robustness. This review focuses primarily on synthetic strategies and environmental MIP-based sensors, especially emphasizing the development that has occurred in the last decades, in order to help readers to understand and fabricate various optimized MIPs.