Guicun Li

Electrochemical DNA biosensor based on chitosan/nano-V2O5/MWCNTs composite film modified carbon ionic liquid electrode and its application to the LAMP product of Yersinia enterocolitica gene sequence.

A new electrochemical DNA biosensor was fabricated by using a V(2)O(5) nanobelts (nano-V(2)O(5)), multi-walled carbon nanotubes (MWCNTs) and chitosan (CTS) nanocomposite materials modified carbon ionic liquid electrode (CILE) as the working electrode. The CILE was prepared by using N-hexylpyridinium hexafluorophosphate (HPPF(6)) as the binder with the graphite powder. The CTS-V(2)O(5)-MWCNTs/CILE was used as the basal electrode for the immobilization of the single-stranded DNA (ssDNA) probe. After the hybridization with the target ssDNA sequence, the electrochemical indicator of methylene blue (MB) was used to monitor the hybridization reaction. Experimental data indicated that the synergistic effect of nano-V(2)O(5) and MWCNTs increased the amounts of ssDNA adsorbed on the electrode surface and resulted in the corresponding increase of the electrochemical responses. This DNA biosensor combined the advantages such as the biocompatibility of V(2)O(5) nanobelt, the excellent electron transfer ability of MWCNTs, the good film-forming ability of CTS and the high conductivity of CILE. Under the optimal conditions differential pulse voltammetry (DPV) was used to record the electrochemical response of MB and the specific ssDNA sequence could be detected in the concentration range from 1.0x10(-11) to 1.0x10(-6) mol L(-1) with the detection limit as 1.76x10(-12) mol L(-1) (3sigma). The DNA biosensor showed good stability and discrimination ability to the one-base and three-base mismatched ssDNA sequence. The loop-mediated isothermal amplification (LAMP) product of Yersinia enterocolitica gene sequence in pork meat was detected by the proposed method with satisfactory result, suggesting that the CTS-V(2)O(5)-MWCNTs/CILE had the potential for the sensitive detection of specific gene sequence.

Nitrogen- and oxygen-containing activated carbon nanotubes with improved capacitive properties

Nitrogen- and oxygen-containing activated carbon nanotubes have been successfully synthesized via a high temperature carbonization of polypyrrole (PPy) nanotubes followed by chemical activation. The first carbonization step ensures the formation of amorphous carbon nanotubes, which are more stable than PPy to preserve the nanotube morphology during the subsequent chemical activation process. The obtained activated carbon nanotubes with high nitrogen (19.8 wt%) and oxygen contents (11.1 wt%) show enlarged specific areas of 705.9 m2 g−1 compared to that of the pristine carbon nanotubes (212.4 m2 g−1). As expected, the activated carbon nanotubes exhibit enhanced capacitance properties, such as an enlarged specific capacity (384.9 F g−1 at 0.5 A g−1), excellent rate capability (201 F g−1 at 50 A g−1), and more stable cyclic stability (only 2.4% of specific capacitance loss after 500 cycles) due to its abundant micropores, high specific areas and abundant interfacial functional groups. This method is facile, low cost and enables easy production of large quantities, and can be expected to open up new opportunities in designing high-performance carbon electrode materials for supercapacitors.

Mesoporous hydrogenated TiO2 microspheres for high rate capability lithium ion batteries

Mesoporous hydrogenated TiO2 microspheres were synthesized via a simple hydrogenation treatment process, and showed twice the rate capability compared to that of mesoporous TiO2 microspheres at 20 C due to the combination of the short lithium ion diffusion path and the high electronic conductivity of the mesoporous hydrogenated TiO2 framework.

Hierarchical hollow microspheres assembled from N-doped carbon coated Li4Ti5O12 nanosheets with enhanced lithium storage properties

Hierarchical hollow microspheres composed of N-doped carbon coated Li4Ti5O12 nanosheets (NC-LTO) have been synthesized on a large scale by a facile low-temperature solution-based approach combined with high temperature calcination. The primary Li4Ti5O12 nanosheets show zigzag morphology with a typical thickness of about 5.0 nm, which are uniformly coated with N-doped carbon layers. When evaluated for lithium storage capacity, the NC-LTO hollow microspheres display enhanced electrochemical energy storage performances compared to the pristine hollow microspheres composed of Li4Ti5O12 nanosheets (A-LTO), including high capacity (181.4 mA h g−1 at 0.5 C), excellent rate capability (140.8 mA h g−1 at 20 C), and good cyclic stability (92.8% capacity loss after 100 cycles at 20 C). The reasons for these improvements are explored in terms of the increased electronic conductivity and the facilitation of lithium ion transport arising from the introduction of N-doped carbon layers and the thin zigzag Li4Ti5O12 nanosheets.

One‐Dimensional V2O5@Polyaniline Core/Shell Nanobelts Synthesized by an In situ Polymerization Method

Uniform one-dimensional V(2) O(5) @polyaniline core/shell nanobelts have been fabricated by a simple in-situ polymerization method in the absence of any surfactant and additional initiator. The influences of pH and additional initiator on the morphology of the resulting products are investigated. The pH value is important for the formation of V(2) O(5) @polyaniline core/shell nanobelts, which preserve the original morphology of V(2) O(5) nanobelts. With a decrease in the pH value to 0 the original morphology of the V(2) O(5) nanobelts is destroyed. When ammonium peroxydisulfate is used, some separated polyaniline nanofibers are formed. The formation of the V(2) O(5) @polyaniline core/shell nanobelts can be related to the in-situ polymerization of aniline monomer by etching V(2) O(5) nanobelts. The electrochemical lithium intercalation/deintercalation of V(2) O(5) @polyaniline core/shell nanobelts is investigated by cyclic voltammograms.

Synthesis of Urchin-like VO2 Nanostructures Composed of Radially Aligned Nanobelts and Their Disassembly

Urchin-like VO(2)(B) nanostructures composed of radially aligned nanobelts have been synthesized by the homogeneous reduction reaction between peroxovanadic acid and oxalic acid under hydrothermal conditions. The influences of synthetic parameters, such as reaction times and the concentration of oxalic acid, on the morphologies and crystals of the resulting products have been investigated. The formation of VO(2)(B) nanostructures undergoes a reduction-dehydration phase-transition and disassembly process. As the reaction time increases from 2 to 6 h, the diameters of urchin-like V(10)O(24) x 12 H(2)O nanostructures increase from 1-2 microm to 3-6 microm. After 12 h, urchin-like V(10)O(24) x 12 H(2)O nanostructures can be transformed in situ into VO(2)(B) nanostructures composed of radially aligned nanobelts, which can be described by a possible reduction-dehydration phase-transition process. The urchin-like VO(2)(B) nanostructures are disassembled into dissociated VO(2)(B) nanobelts with the reaction time increased to 24 h. The shapes of the dissociated VO(2)(B) nanobelts can be controlled by adjusting the concentration of oxalic acid.

Morphology-controlled synthesis of hematite hierarchical structures and their lithium storage performances

A series of hematite hierarchical structures, including amorphous hierarchical spheres with varied internal polycrystalline structures, single-crystalline nanoflakes and co-aligned micro-layered structures, have been fabricated by simply controlling the reaction time in a one-step hydrothermal procedure. In the early stages of the reaction, an Ostwald ripening process dominates the successive occurrence of single-shell, double-shell and yolk–shell spheres, which reoccur in reverse order under the effect of an H+ etching process on prolonging the reaction time. Afterwards, the oriented attachment mechanism takes charge of the formation of single-crystalline nanoflakes and co-aligned micro-layered structures at the expense of the previously formed spheres. It is found that the different adsorption configuration of the hydroxyl groups in different crystallographic planes is of fundamental importance to the morphology evolution from nanoflakes to micro-layered structures. The electrochemical measurements of these hierarchical structures show that their lithium storage properties are closely related to their crystallinity and morphology. The amorphous-based architectures exhibit quite similar electrochemical properties regardless of their morphologies, whereas the crystallized architectures present morphology-dependent electrochemical properties. Also, well-crystallized electrodes facilitate the access of lithium-ions and thus possess superior lithium storage performances, whether in the initial charge–discharge cycling or in the subsequent cyclic capacity retention.

Ti3+ self-doped Li4Ti5O12 nanosheets as anode materials for high performance lithium ion batteries

Ti3+ self-doped Li4Ti5O12 (S-LTO) nanosheets have been synthesized via a facile solvothermal approach combined with hydrogenation treatment. The thickness and lateral dimension of Li4Ti5O12 nanosheets are 10–20 nm and 100–400 nm, respectively. The Ti3+ species and/or oxygen vacancies are well introduced into the crystal structures of Li4Ti5O12 after hydrogen reduction, resulting into an enhancement in the electronic conductivity and the modified surface electrochemical activity. When evaluated for lithium storage capacity, the S-LTO nanosheets exhibit enhanced electrochemical energy storage performances compared to the pristine Li4Ti5O12 (P-LTO) nanosheets, including high capacity (165.6 mA h g−1 at 0.5 C), excellent rate capability (119.6 mA h g−1 at 20 C), and good cyclic stability (95.3% capacity retention after 100 cycles at 10 C). The improvement of lithium storage performances is ascribed to the increased electronic conductivity and the shortened lithium ion diffusion paths arising from the introduction of Ti3+ species and the ultrathin thickness of S-LTO.

Styrene hydrogenation performance of Pt nanoparticles with controlled size prepared by atomic layer deposition

Highly dispersed Pt sub-nanoparticles supported on carbon nanotubes (CNTs) with well-controlled size have been prepared by atomic layer deposition. Their particle size distribution was characterized by TEM. The obtained Pt sub-nanoparticles exhibit unusual catalytic performance for styrene hydrogenation. It is revealed that the turnover frequency (TOF) of the Pt/CNTs catalysts for this reaction correlated well with the Pt particle size. The highest TOF was obtained with the Pt/CNTs catalyst having an average Pt particle size around 0.5–0.7 nm.

Preparation and characterization of polyethylene/TiO2 nanocomposites

The rheological behaviour, dispersion, crystallization behavior, mechanical properties, fracture surface morphology of polyethylene (PE)/TiO2 nanocomposites prepared by melt compounding were investigated using rheometer, energy dispersive X-ray spectrometer (EDX), polarized microscopy, impact tester, universal testing machine and field-emission scanning electron microscopy (FE-SEM). The rheological analysis indicated a fine dispersion of TiO2 during the melt compounding. The large scaled surface dispersion of TiO2 nanoparticles was revealed by the EDX composition distribution maps. The introduction of 2.0 wt% TiO2 in composites improved the mechanical properties significantly compared to neat PE, and resulted in 45% increase in notched impact strength. Moreover, the further analysis and discussion showed the mechanical properties of the composites were controlled by the dispersion conditions of TiO2 and its nucleating effect on PE crystallization.