Liangming Wei

Synthesis of Polymer—Mesoporous Silica Nanocomposites

Polymer nanocomposites show unique properties combining the advantages of the inorganic nanofillers and the organic polymers. The mesoporous silica nanofillers have received much attention due to their ordered structure, high surface area and ease for functionalization of the nanopores. To accommodate macromolecules, the nanopores lead to unusually intimate interactions between the polymer and the inorganic phase, and some unusual properties can be observed, when compared with nonporous fillers. Whereas many review articles have been devoted to polymer/nonporous nanofiller nanocomposites, few review articles focus on polymer/mesoporous silica nanocomposites. This review summarizes the recent development in the methods for synthesizing polymer/mesoporous silica nanocomposites based on the papers published from 1998 to 2009, and some unique properties of these composites are also described.

A non-enzymatic glucose sensor based on the composite of cubic Cu nanoparticles and arc-synthesized multi-walled carbon nanotubes

A sort of non-enzymatic glucose sensor is fabricated based on a composite of cubic Cu nanoparticles and arc-synthesized multi-walled carbon nanotubes (MWCNTs) by using a substrate-enhanced electroless deposition (SEED) method. The common glassy carbon (GC) electrode is replaced by the cylindrical deposit that contains abundant MWCNTs as a support electrode. These cylindrical deposits can be synthesized by arc discharge in low pressure air atmosphere. The Cu-MWCNTs electrode shows significantly electrocatalytic activity to the oxidation of glucose in 0.1M NaOH alkaline solution. The amperometric responses to glucose reveal that the fast response achieves within 1s, the sensitivity is 922μAmM(-1)cm(-2) with a wide linear in the 0.5-7.5mM concentration range, and the detection limit is 2.0μM. The sensor also exhibits high stability and specificity to glucose. Due to the simplicity of the sensor preparation, Cu-MWCNTs electrodes are a good candidate for reliable glucose determination.

Preparation of high aspect ratio nickel oxide nanowires and their gas sensing devices with fast response and high sensitivity

NiO p-type semiconducting nanowires with high aspect ratios up to approximately 2000 have been prepared by chemical reduction under assistance of magnetic fields and subsequent heat treatment method. The diameter of NiO nanowires is about 150 nm and the length can be up to 300 μm. Ni nanowires have been prepared from a structure of Ni nanospheres at atmospheric pressure. Transformation from Ni nanowires to NiO semiconducting nanowires via in situ chemical oxidation process in open air have been conducted by undergoing a process of an amorphous oxidation. Heat treatment results in significant influence on the grain size in the NiO nanowire structure. NiO nanowires with crystalline grain size of about 12 nm is characteristic with a band gap energy of about 4.20 eV, which is larger than the bulk NiO material (3.65 eV). Meanwhile, we find that the optical band gap energy gradually increases with the decrease of the crystalline grain size. NiO nanowires with different grain sizes have been used to fabricate arrays for a gas sensor under an external magnetic field. NH3 gas sensing capability at room temperature by NiO nanowire arrays is characteristic for its high sensitivity, fast response, rapid recovery and good reproducibility.

Dissolving and biodegradable microneedle technologies for transdermal sustained delivery of drug and vaccine

Microneedles were first conceptualized for drug delivery many decades ago, overcoming the shortages and preserving the advantages of hypodermic needle and conventional transdermal drug-delivery systems to some extent. Dissolving and biodegradable microneedle technologies have been used for transdermal sustained deliveries of different drugs and vaccines. This review describes microneedle geometry and the representative dissolving and biodegradable microneedle delivery methods via the skin, followed by the fabricating methods. Finally, this review puts forward some perspectives that require further investigation.

Zinc-doped nickel oxide dendritic crystals with fast response and self-recovery for ammonia detection at room temperature

Nanoscale Zn-doped NiO dendritic crystals with a Christmas-tree-like structure, have been successfully synthesized via an electrolytic approach combined with subsequent high temperature oxidation. The trunks have lengths in the range 6–10 μm with diameters varying from 190 nm to 200 nm, and the branches have lengths in the range 1–3 μm with diameters varying from 150 nm to 180 nm. Microstructure characterization indicated that the solubility limit of zinc ions in the NiO lattice sites was lower than 7 mol%. We systematically investigated the gas sensing properties of the Zn-doped NiO sensors for NH3 gas detection at room temperature. The sensor with doped NiO dendritic crystals gave 5–8 times faster responses and 30–50 times faster recovery speeds than the sensor with pristine NiO dendritic crystals, which is important for the practical application of this NiO sensor. The fast response and recovery speeds could be attributed to the effective electron transfer between the doped NiO dendritic crystal networks and the ammonia molecules. Moreover, we found that the doped NiO sensors have excellent reproducibility, reversibility, stability and selectivity toward NH3 gas over other organic gases. Lastly, a possible gas sensing mechanism of NiO dendritic crystal sensors was discussed.

Efficient long lifetime room temperature phosphorescence of carbon dots in a potash alum matrix

It was found that upon dispersing the carbon dots (CDs) into a KAl(SO4)2·x(H2O) matrix, the CD composite powders showed a long phosphorescence lifetime of 707 ms and an average lifetime of 655 ms. This strategy would provide a novel route for achieving efficient long lifetime room temperature phosphorescence of CDs.

Advances with microRNAs in Parkinson’s disease research

Parkinson’s disease (PD) is the second-most common age-dependent neurodegenerative disorder and is caused by severe degeneration of dopaminergic neurons in the substantia nigra pars compacta. Unfortunately, current treatment only targets symptoms and involves dopamine replacement therapy, which does not counteract progressive degeneration. MicroRNAs (miRNAs) are a class of small RNA molecules implicated in post-transcriptional regulation of gene expression during development. Recent studies show that miRNAs are playing an important role in the pathophysiology of PD. miRNA-based therapy is a powerful tool with which to study gene function, investigate the mechanism of the disease, and validate drug targets. In this review, we focus on the recent advances of the use of miRNAs in the pathogenesis of PD.

A new strategy to prepare N-doped holey graphene for high-volumetric supercapacitors

N-doped holey graphene (N-HG) was successfully prepared by a novel “Bottom-up” strategy with scalable and low cost characteristics. The as-obtained N-HG possessed amounts of in-plane holes, a high specific surface area (1602 m2 g−1), a high nitrogen content and could be easily stacked to form a high density carbon monolith which presented a maximum volumetric capacitance of 397 F cm−3 for supercapacitors.

Poly (acrylic acid sodium) grafted carboxymethyl cellulose as a high performance polymer binder for silicon anode in lithium ion batteries

The design of novel binder systems is required for the high capacity silicon (Si) anodes which usually undergo huge volume change during the charge/discharge cycling. Here, we introduce a poly (acrylic acid sodium)-grafted-carboxymethyl cellulose (NaPAA-g-CMC) copolymer as an excellent binder for Si anode in lithium ion batteries (LIBs). The NaPAA-g-CMC copolymer was prepared via a free radical graft polymerization method by using CMC and acrylic acid as precursors. Unlike the linear, one-dimensional binders, the NaPAA-g-CMC copolymer binder is expected to present multi-point interaction with Si surface, resulting in enhanced binding ability with Si particles as well as with the copper (Cu) current collectors, and building a stable solid electrolyte interface (SEI) layer on the Si surface. The NaPAA-g-CMC based Si anode shows much better cycle stability and higher coulombic efficiency than those made with the well-known linear polymeric binders such as CMC and NaPPA.

Hydrogel Microneedle Arrays for Transdermal Drug Delivery

Stratum corneum is the main obstacle for drugs to pass through the skin. Microneedles are composed of arrays of micro-projections formed with different materials, generally ranging from 25–2000 μm in height. Microneedles straightly pierce the skin with its short needle arrays to overcome this barrier. Microneedles can be divided into several categories, for instance, solid microneedles, coated microneedles, and hollow microneedles and so on. However, all these types have their weak points related to corresponding mechanisms. In recent years, pioneering scientists have been working on these issues and some possible solutions have been investigated. This article will focus on the microneedle arrays consisting of hydrogels. Hydrogels are commonly used in drug delivery field. Hydrogel microneedles can be further divided into dissolving and degradable microneedles and phase transition microneedles. The former leaves drug with matrix in the skin. The latter has the feature that drugs in the matrix are delivered while the remaining ingredients can be easily removed from the skin after usage. For drugs which are required to be used every day, the phase transition microneedles are more acceptable. This article is written in order to summarize the advantages of these designs and summarize issues to be solved which may hinder the development of this technology.