Zhifeng Yi

Superhydrophobic and Superoleophilic Micro-Wrinkled Reduced Graphene Oxide as a Highly Portable and Recyclable Oil Sorbent

The potential of superhydrophobic and superoleophilic microwrinkled reduced graphene oxide (MWrGO) structures is here demonstrated for oil spill cleanup. The impact of the thickness of MWrGO films on the sorption performance of three different oils was investigated. Water contact angles across the MWrGO surfaces were found to exceed 150°, while oil could be easily absorbed by the microwrinkled structures of MWrGO within seconds after contact. Although the oil surface diffusion rate was not found to be dependent on the thickness of the graphene oxide films, the oil sorption capacity was the largest with the thinner MWrGO films due to the high surface area resulting from their fine surface texture. Furthermore, the composite films can be repeatedly used for at least 20 oil sorption-removal cycles without any notable loss in selectivity and uptake capacity. These MWrGO/elastomer composite films could be applied as a potential candidate material for future oil spill cleanup.

Reinforcement of natural rubber with core-shell structure silica-poly(methyl methacrylate) nanoparticles

A highly performing natural rubber/silica (NR/SiO2) nanocomposite with a SiO2 loading of 2wt% was prepared by combining similar dissolve mutually theory with latex compounding techniques. Before polymerization, double bonds were introduced onto the surface of the SiO2 particles with the silane-coupling agent. The core-shell structure silica-poly(methyl methacrylate), SiO2- PMMA, nanoparticles were formed by grafting polymerization of MMA on the surface of the modified SiO2 particles via in situ emulsion, and then NR/SiO2 nanocomposite was prepared by blending SiO2-PMMA and PMMA-modified NR (NR-PMMA). The Fourier transforminfrared spectroscopy results show that PMMA has been successfully introduced onto the surface of SiO2, which can be well dispersed in NR matrix and present good interfacial adhesion with NR phase. Compared with those of pure NR, the thermal resistance and tensile properties of NR/SiO2 nanocomposite are significantly improved.

Functionalized Mesoporous Silica Nanoparticles with Redox-Responsive Short-Chain Gatekeepers for Agrochemical Delivery

The controlled release of salicylic acid (SA), a key phytohormone, was mediated by using a novel decanethiol gatekeeper system grafted onto mesoporous silica nanoparticles (MSNs). The decanethiol was conjugated only to the external surfaces of the MSNs through glutathione (GSH)-cleavable disulfide linkages and the introduction of a process to assemble gatekeepers only on the outer surface so that the mesopore area can be maintained for high cargo loading. Raman and nitrogen sorption isotherm analyses confirmed the successful linkage of decanethiol to the surface of MSNs. The in vitro release of SA from decanethiol gated MSNs indicated that the release rate of SA in an environment with a certain amount of GSH was significantly higher than that without GSH. More importantly, in planta experiments showed the release of SA from decanethiol gated MSNs by GSH induced sustained expression of the plant defense gene PR-1 up to 7 days after introduction, while free SA caused an early peak in PR-1 expression which steadily decreased after 3 days. This study demonstrates the redox-responsive release of a phytohormone in vitro and also indicates the potential use of MSNs in planta as a controlled agrochemical delivery system.

Silver metal nano-matrixes as high efficiency and versatile catalytic reactors for environmental remediation

Nano-porous metallic matrixes (NMMs) offer superior surface to volume ratios as well as enhanced optical, photonic, and electronic properties to bulk metallic materials. Such behaviours are correlated to the nano-scale inter-grain metal domains that favour the presence of electronic vacancies. In this work, continuous 3D NMMs were synthesized for the first time through a simple diffusion-reduction process whereby the aerogel matrix was functionalized with (3-Mercaptopropyl)trimethoxysilane. The surface energy of the silica monolith templates was tuned to improve the homogeneity of the reduction process while thiol functionalization facilitated the formation of a high density of seeding points for metal ions to reduce. The diameter of NMMs was between 2 and 1000 nm, corresponding to a silver loading between 1.23 and 41.16 at.%. A rates of catalytic degradation kinetics of these NMMS which is three orders of magnitude higher than those of the non-functionalized silver-silica structures. Furthermore, the enhancement in mechanical stability at nanoscale which was evaluated by Atomic Force Microscopy force measurements, electronic density and chemical inertness was assessed and critically correlated to their catalytic potential. This strategy opens up new avenues for design of complex architectures of either single or multi-metal alloy NMMs with enhanced surface properties for various applications.

Mesoporous silica nanoparticles enhance seedling growth and photosynthesis in wheat and lupin

The application of mesoporous silica nanoparticles (MSNs) as a smart delivery system to agricultural crops is gaining attention but the release of nanoparticles into the environment may pose a potential threat to biological systems. We investigated the effects of MSNs on the growth and development of wheat and lupin plants grown under controlled conditions. We report a dramatic increase in the growth of wheat and lupin plants exposed to MSNs. We also found that, in leaves, MSNs localised to chloroplasts and that photosynthetic activity was significantly increased. In addition, absorption and cellular distribution of MSNs by the two plant species following root uptake were observed using scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). Following uptake of MSNs at 500 and 1000 mg L(-1), there was enhancement of seed germination, increased plant biomass, total protein and chlorophyll content. Treatment of both species with MSNs at the highest concentration (2000 mg L(-1)) did not result in oxidative stress or cell membrane damage. These findings show that MSNs can be used as novel delivery systems in plants and that over the range of concentrations tested, MSNs do not have any negative impacts on plant growth or development.

Plasmonic substrates for surface enhanced Raman scattering

As an advanced analytical tool, surface-enhanced Raman scattering (SERS) has broad applications in identification of colorants in paints and glazes, hazard detection to ensure food safety, biomedicine and diagnosis, environmental monitoring, detection of explosives and forensic science. In this review, main types of plasmonic substrates, which include solid substrate with metallic nanostructures and chemically synthesized noble metal colloids, and their fabrication methods are reviewed. The design principles for fabrication of ultrasensitive plasmonic substrates for SERS are presented on the basis of published literature. Finally, various applications of SERS substrates are described, indicating the potential of this technique in practical applications. As an ultrasensitive detection method, SERS is at the core of a rapidly expanding research field.

Inorganic nanoparticles/metal organic framework hybrid membrane reactors for efficient photocatalytic conversion of CO2

Photocatalytic conversion of carbon dioxide (CO2) to useful products has potential to address the adverse environmental impact of global warming. However, most photocatalysts used to date exhibit limited catalytic performance, due to poor CO2 adsorption capacity, inability to efficiently generate photoexcited electrons, and/or poor transfer of the photogenerated electrons to CO2 molecules adsorbed on the catalyst surface. The integration of inorganic semiconductor nanoparticles across metal organic framework (MOF) materials has potential to yield new hybrid materials, combining the high CO2 adsorption capacity of MOF and the ability of the semiconductor nanoparticles to generate photoexcited electrons. Herein, controlled encapsulation of TiO2 and Cu-TiO2 nanoparticles within zeolitic imidazolate framework (ZIF-8) membranes was successfully accomplished, using rapid thermal deposition (RTD), and their photocatalytic efficiency toward CO2 conversion was investigated under UV irradiation. Methanol and carbon monoxide (CO) were found to be the only products of the CO2 reduction, with yields strongly dependent upon the content and composition of the dopant semiconductor particles. CuTiO2 nanoparticle doped membranes exhibited the best photocatalytic performance, with 7 μg of the semiconductor nanoparticle enhancing CO yield of the pristine ZIF-8 membrane by 233%, and methanol yield by 70%. This work opens new routes for the fabrication of hybrid membranes containing inorganic nanoparticles and MOFs, with potential application not only in catalysis but also in electrochemical, separation, and sensing applications.

Delivery of Abscisic Acid to Plants Using Glutathione Responsive Mesoporous Silica Nanoparticles.

An intracellular glutathione (GSH) responsive phytochemical delivery system based on thiol gated mesoporous silica nanoparticles (MSNs) was developed and tested on the model plant Arabidopsis thaliana. In the present study, monodispersed MSNs with particle diameters of ~20 nm and pore sizes of ~2.87 nm were synthesized and modified. Abscisic acid (ABA), a key phytohormone, was entrapped in the mesopores of MSNs and then the pore entrances of MSNs were covered with decanethiol gatekeepers through GSH-cleavable disulfide linkages. An in vitro release test of ABA from decanethiol gated MSNs proved that there was efficient loading and entrapment of phytochemicals in the absence of a GSH redox trigger. Most importantly, in planta experiments demonstrated that GSH-mediated release of ABA from the pores of MSNs significantly reduced the leaf stomatal aperture and inhibited water loss of treated plants. Moreover, compared with the usage of free ABA, the controlled release of the encapsulated phytohormone from MSNs markedly prolonged the expression of the ABA inducible marker gene (AtGALK2) and finally, improved the drought resistance ability of Arabidopsis seedlings under drought stress. Therefore, the concept of using short-chain molecules as gatekeepers to encapsulate biomolecules in MSNs was demonstrated. The application of MSNs with redox-responsive gatekeepers has been shown in this study to be a potential and efficient technique to deliver phytochemicals into plants and release them in a controllable fashion.

Tailored Mesoporous Silica Nanoparticles for Controlled Drug Delivery: Platform Fabrication, Targeted Delivery, and Computational Design and Analysis.

Mesoporous silica nanoparticles (MSNs) are exceptionally promising drug carriers for controlled drug delivery systems because their morphology, pore structure, pore volume and pore size can be well tailored to obtain certain drug release profiles. Moreover, they possess the ability to specifically transport and deliver anti-cancer drugs when targeting molecules are properly grafted onto their surface. MSNs based drug delivery systems have the potential to revolutionize cancer therapy. This review provides a comprehensive overview of the fabrication, modification of MSNs and their applications in tumour-targeted delivery. In addition, the characterization and analysis of MSNs with computer aided strategies were described. The existing issues and future prospective concerning the applications of MSNs as drug carriers for controlled drug delivery systems were discussed.

Single step synthesis of Schottky-like hybrid graphene - titania interfaces for efficient photocatalysis

The development of 2D nanomaterial coatings across metal surfaces is a challenge due to the mismatch between the metal microstructure and the nanoscale materials. The naturally occurring thin oxidative layer present across all metal surfaces, may lead to low adherence and connectivity. In this paper, graphene/titania/Titanium hybrid films were for the first time fabricated by a single step chemical vapour deposition process across Titanium foils. The presence of graphene as a dopant was found to enhance the photocatalytic performance of the final products, applied to the degradation of organic molecules and to lead to Schottky-like junction formation at the metal/oxide interface. These Schottky junctions, where vacancies are present across the titania material due to the graphene doping and where Ti3+ ions are predominantly located, yield enhanced catalytic performance. The highest degradation rate was found to be 9.66 × 10−6 min−1, achieved by the sample grown at 700 °C for 5 min, which was 62% higher than the sample just treated at that temperature without graphene growth. This work provides evidence that graphene may be grown across pure Titanium metal and opens new avenues in biomedical devices design, tribological or separation applications.