Juanrong Chen

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.

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.

Recent advances in silica-based biosensors: a review

Silica has become a common platform for various catalytic and chemical reactions, biosensor, and drug release owing to its low toxicity, chemical and physical stabilities, large surface area, tunable pore sizes, and well-defined surface chemistry. Therefore, biomolecules encapsulated within a porous silica host has provoked significant interest in the development, application, and market of silica-based biosensors due to its potential application in analytic chemistry and biological science. Considerable progresses have been achieved in past few decades. This review focuses primarily on such advances in synthesis and applications of silica-based biosensors, especially emphasizing development which has occurred in the last 10 years, further driving readers to understand and construct various silica-based biosensors with high sensitivity and high stability.

A facile synthesis of hollow TiO2 photocatalyst with high amount of carbon exhibiting efficient visible-light photocatalytic performance

ABSTRACTA facile approach was developed for the synthesis of hollow TiO2 photocatalyst with a high amount of carbon (C/TiO2). The method mainly includes the following steps: the preparation of cationic polystyrene spheres (CPSs), deposition of TiO2 precursor, and the pyrolysis of CPS in an N2 atmosphere at 450 °C (close system). The structure and morphology of C/N-TiO2 were characterized by using TEM, XRD, XPS, and UV-Vis spectroscopy. The results confirm that the carbon is coated on the surface of the photocatalysts, substantially enhancing the visible-light harvesting and accelerating the separation of the photo-generated electrons/holes. Interestingly, the formed C/TiO2 effectively narrows the bandgap of TiO2, manifesting excellent photocatalytic activities for degradation of MB and Rh B under visible-light irradiation than commercial P25. Therefore, our findings demonstrate that C/TiO2 is a more promising candidate as visible-light photocatalysts for potential applications.

Hierarchically-structured SiO 2 -Ag@TiO 2 hollow spheres with excellent photocatalytic activity and recyclability

A new protocol for constructing sandwich-like SiO2-Ag@TiO2 hollow spheres (SAT) is introduced, in which SiO2 acts as an efficient support for the Ag nanoparticles (Ag NPs) immobilization, while TiO2 maintains its hierarchical structure and prevents the aggregation of Ag NPs during the photocatalytic reaction. As a photocatalytic agent, the inner and outer surfaces of TiO2 can be fully occupied by pollutants molecules because of its unique structure, which faster boosts the photo-generated electrons to transfer the substrates, leading to an enhanced photocatalytic performance. Compared with Ag NPs deposited on the surface of SiO2@TiO2 (STA), the as-synthesized SAT exhibits a markedly enhanced visible-light and UV light activity than STA for degrading tetracycline and traditional dyes. The excellent photocatalytic performances are ascribed to the enhanced transport paths of photo-generated electrons, reduced recombination probability of e-/h+ pairs, and decreased threat of oxidation and corrosion. Especially, the SAT still maintains its photocatalytic efficiency after five consecutive runs even though the sample is recovered under visible-light irradiation, far beyond the reusability of STA under the same conditions. Therefore, the outstanding photocatalytic activity and excellent recyclability make SAT more potential to purify aquatic contaminants and to meet the demands of future environmental issues.

Carbon-Doped Hollow Titania with Tuneable Shell Architecture for Supercapacitors

A new trend in supercapacitor research has focussed on the construction of inexpensive electrode materials with high capacitor performances. In this study, we demonstrate the successful preparation of carbon-doped hollow titania spheres. The as-prepared titania spheres not only exhibit an advantage over existing methods because they are created in situ by directly carbonizing cationic polystyrene templates without the addition of carbon precursors, but also feature a narrow pore size distribution and a tuneable shell architecture. When the materials were applied as supercapacitor anodes, the electrochemical results reveal the superior performances of the supercapacitors over that of commercial P25. The higher performances were attributed to carbon doping. Thus, the reported C-doped hollow titania shows more potential as electrode materials for high-performance supercapacitors.

The Fabrication and Progress of Hollow Structures

The fabrication of hollow particles is one of the fastest-growing fields of materials research, owing to their potential applications in catalysis, chromatography, separation, coatings, protection of bioactive agents, microelectronics and electrooptics. As reported in recent studies, a variety of chemical and physicochemical methods have been employed to prepare hollow spheres with hierarchical and well-defined morphologies. For this, a basic understanding of the mechanism and recent advances in the fabrication of hollow spheres is discussed, along with outstanding challenges, issues, and potentially future opportunities. Evidently, it will enable the development in the fabrication of hollow particles with unique and tailored properties.