Showing papers by "Wenrong Yang published in 2017"

Effect of Different Binders on the Electrochemical Performance of Metal Oxide Anode for Lithium-Ion Batteries.

Abstract: When testing the electrochemical performance of metal oxide anode for lithium-ion batteries (LIBs), binder played important role on the electrochemical performance. Which binder was more suitable for preparing transition metal oxides anodes of LIBs has not been systematically researched. Herein, five different binders such as polyvinylidene fluoride (PVDF) HSV900, PVDF 301F, PVDF Solvay5130, the mixture of styrene butadiene rubber and sodium carboxymethyl cellulose (SBR+CMC), and polyacrylonitrile (LA133) were studied to make anode electrodes (compared to the full battery). The electrochemical tests show that using SBR+CMC and LA133 binder which use water as solution were significantly better than PVDF. The SBR+CMC binder remarkably improve the bonding capacity, cycle stability, and rate performance of battery anode, and the capacity retention was about 87% after 50th cycle relative to the second cycle. SBR+CMC binder was more suitable for making transition metal oxides anodes of LIBs.

Recent advances in cobalt phosphide based materials for energy-related applications

Abstract: With the imminent exhaustion of fossil fuels and increasing global energy demands, great effort has been made to design and develop functional materials for exploiting clean renewable energy sources and developing more efficient energy storage systems. Cobalt phosphide is a rapidly rising star on the horizon of highly efficient catalysts with numerous research activities worldwide. In this review, we summarize recent research progress made in cobalt phosphide-based materials as efficient catalysts for hydrogen production and fuel cells, and as electrode materials for batteries. The impacts of phosphorus content on the electrocatalytic activity and other significant structural designs of cobalt phosphides for improving the performance are discussed. Finally, current challenges and future directions for cobalt phosphide-based materials are discussed.

MXene: a potential candidate for yarn supercapacitors.

Abstract: The increasing developments in wearable electronics demand compatible power sources such as yarn supercapacitors (YSCs) that can effectively perform in a limited footprint. MXene nanosheets, which have been recently shown in the literature to possess ultra-high volumetric capacitance, were used in this study for the fabrication of YSCs in order to identify their potential merit and performance in YSCs. With the aid of a conductive binder (PEDOT-PSS), YSCs with high mass loading of MXene are demonstrated. These MXene-based YSCs exhibit excellent device performance and stability even under bending and twisting. This study demonstrates that MXene is a promising candidate for YSCs and its further development can lead to flexible power sources with sufficient performance for powering miniaturized and/or wearable electronics.

Fabrication of an arbitrary-shaped and nitrogen-doped graphene aerogel for highly compressible all solid-state supercapacitors

Abstract: Herein, we report a new template method for fabricating an arbitrary-shaped compressible nitrogen-doped graphene aerogel (GA). The as-prepared GA remains stable under a maximum compressive strain of 90% or after 50 compression/release cycles at a strain of 80%. The compressible nitrogen-doped GA is used as an electrode to fabricate an all solid-state graphene aerogel supercapacitor (GASC). The as-assembled GASC shows a specific capacitance of 150 F g−1 at a current density of 0.3 A g−1 and a long cycle life with 85.1% capacitance retention after 10 000 cycles at 1 A g−1. In addition, the compressible GASC displays stable electrochemical performance under different compressive strains (0%, 25%, 50% and 75%) or after 100 compression/release cycles under a compressive strain of 50%. The present work highlights the first example of fabricating an arbitrary-shaped compressible GA. Furthermore, the as-obtained GASC overcomes the limitation of previous work which required the assistance of other materials to maintain the mechanical properties. This simple template method for the fabrication of compressible and robust GA electrodes could have enormous potential for high performance compressible energy storage devices.

Transforming doxorubicin into a cancer stem cell killer via EpCAM aptamer-mediated delivery.

Abstract: Chemotherapy-resistant cancer stem cells (CSCs) are a major obstacle to the effective treatment of many forms of cancer. To overcome CSC chemo-resistance, we developed a novel system by conjugating a CSC-targeting EpCAM aptamer with doxorubicin (Apt-DOX) to eliminate CSCs. Incubation of Apt-DOX with colorectal cancer cells resulted in high concentration and prolonged retention of DOX in the nuclei. Treatment of tumour-bearing xenograft mice with Apt-DOX resulted in at least 3-fold more inhibition of tumour growth and longer survival as well as a 30-fold lower frequency of CSC and a prolonged longer tumourigenic latency compared with those receiving the same dose of free DOX. Our data demonstrate that a CSC-targeting aptamer is able to transform a conventional chemotherapeutic agent into a CSC-killer to overcome drug resistance in solid tumours.

DNAzyme Based Nanomachine for in Situ Detection of MicroRNA in Living Cells

Abstract: The capability of in situ detection of microRNA in living cells with signal amplification strategy is of fundamental importance, and it will open up a new opportunity in development of diagnosis and prognosis of many diseases. Herein we report a swing DNA nanomachine for intracellular microRNA detection. The surfaces of Au nanoparticles (NPs) are modified by two hairpin DNA. We observe that one DNA (MB2) will open its hairpin structure upon partial hybridization with target miR-21 after entering into cells, and the other part of its hairpin structure could further react with the other hairpin DNA (MB1) to form a Zn2+-specific DNAzyme. This results in the disruption of MB1 through shearing action and the release of fluorescein Cy5. To provide an intelligent DNA nanomachine, MB2 is available again with the shearing action to bind with MB1, which provides effective signal amplification. This target-responsive, DNA nanomachine-based method showed a detection limit of 0.1 nM in vitro, and this approach could b...

Size-dependent Effects of Gold Nanoparticles on Osteogenic Differentiation of Human Periodontal Ligament Progenitor Cells.

Abstract: Gold nanoparticles (AuNPs) have been reported to promote osteogenic differentiation of mesenchymal stem cells and osteoblasts, but little is known about their effects on human periodontal ligament progenitor cells (PDLPs). In this study, we evaluated the effects of AuNPs with various diameters (5, 13 and 45 nm) on the osteogenic differentiation of PDLPs and explored the underlying mechanisms. 5 nm AuNPs reduced the alkaline phosphatase activity, mineralized nodule formation and expression of osteogenic genes, while 13 and 45 nm AuNPs increased these osteogenic markers. Compared with 13 nm, 45 nm AuNPs showed more effective in promoting osteogenic differentiation. Meanwhile, autophagy was up-regulated by 13 and 45 nm AuNPs but blocked by 5 nm AuNPs, which corresponded with their effects on osteogenic differentiation and indicated that autophagy might be involved in this process. Furthermore, the osteogenesis induced by 45 nm AuNPs could be reversed by autophagy inhibitors (3-methyladenine and chloroquine). These findings revealed that AuNPs affected the osteogenic differentiation of PDLPs in a size-dependent manner with autophagy as a potential explanation, which suggested AuNPs with defined size could be a promising material for periodontal bone regeneration.

A novel method to decorate Au clusters onto graphene via a mild co-reduction process for ultrahigh catalytic activity

Abstract: To achieve high catalytic activity and stability with low noble-metal loadings on special supports has triggered much research interest in the past few years. Herein, a mild co-reduction strategy was exploited to fabricate glutathione decorated Au clusters (with a size of ∼1.4 nm) on reduced graphene oxide (Au@HSG-rGO) with low Au loadings and high catalytic activity in an aqueous medium. The resultant Au@HSG-rGO complex exhibited 20.8 times higher catalytic activity than Au nanoparticle supported graphene for catalysis of the reduction of 4-nitrophenol (4-NP). The Au@HSG-rGO was packed in a filtering platform to afford a fixed-bed system, with which the catalytic conversion reached 96.03% for 0.2 mM 4-NP solution at a flow rate of 1 mL min−1. In addition, the poly(2-(dimethylamino) ethyl acrylate) modified Au@HSG-rGO (Au@HSG-rGO-PDMAEA) via π–π stacking interactions exhibited good recyclability and tunable catalytic activity and only showed slight loss of activity after recycling five times. The PDMAEA served as forest-like shelters to efficiently protect the Au@HSG clusters from aggregation and also endowed the system with enhanced stability and temperature-controlled catalytic activity. Meanwhile, the Au@HSG-rGO showed excellent electrocatalytic activity for the oxygen reduction reaction in alkaline electrolytes. This simple, economical and mild strategy could be generalized to the preparation of other metal cluster complexes for broad catalytic and analytical applications.

Monolithically integrated CoP nanowire array: An on/off switch for effective on-demand hydrogen generation via hydrolysis of NaBH4 and NH3BH3

Abstract: The issues of hydrogen generation and storage have hindered the widespread use and commercialization of hydrogen fuel cell vehicles. It is thus highly attractive, but the design and development of highly active non-noble-metal catalysts for on-demand hydrogen release from alkaline NaBH4 solution under mild conditions remains a key challenge. Herein, we describe the use of CoP nanowire array integrated on a Ti mesh (CoP NA/Ti) as a three-dimensional (3D) monolithic catalyst for efficient hydrolytic dehydrogenation of NaBH4 in basic solutions. The CoP NA/Ti works as an on/off switch for on-demand hydrogen generation at a rate of 6,500 mL/(min·g) and a low activation energy of 41 kJ/mol. It is highly robust for repeated usage after recycling, without sacrificing catalytic performance. Remarkably, this catalyst also performs efficiently for the hydrolysis of NH3BH3.

A molybdenum disulfide/gold nanorod composite-based electrochemical immunosensor for sensitive and quantitative detection of microcystin-LR in environmental samples

Abstract: A sensitive electrochemical immunosensor based on a molybdenum disulfide (MoS 2 ) and gold nanorods (AuNRs) composite was developed for the detection of microcystin-LR (MC-LR). The immunosensor was constructed by immobilizing MC-LR antibody on the MoS 2 /AuNRs nanocomposite modified gold electrode. Using a competitive immunoassay format, the coated MC-LR antibody competed for MC-LR antigen with added target MC-LR, forming an antibody-antigen immunocomplex. Subsequently, horseradish peroxidase-labeled anti-MC-LR antibody (HRP-Ab 2 ) was captured and detected. Under optimal conditions, the immunosensor exhibited a linear response to MC-LR ranging from 0.01 to 20 μg L −1 with a detection limit of 5 ng L −1 at a signal to noise of 3. This electrochemical immunosensor showed good performance with high sensitivity, good stability, accepted reusability and promising applications in routine water quality monitoring for various toxins.

Graphene-Oxide-Based Enzyme Nanoarchitectonics for Substrate Channeling

Abstract: The controlled spatial organization or compartmentalization of multi-enzyme cascade reactions to transfer a substrate from one enzyme to another for substrate channeling on scaffolds has sparked increasing interest in recent years. Here, we use graphene oxides to study the dependence of the activity of cascade reactions in a closely packed, randomly immobilized enzyme system on a 2 D scaffold. We first observe that the hydrophobicity of graphene oxides and various enzyme architectures for co-immobilized systems are important attributes for achieving high product-conversion rates. A transient time close to 0 s can be achieved if enzymes are randomly immobilized close to one another, owing to direct molecular channeling. This contributes to overcoming complications regarding control of the spatial arrangement of the enzymes. Furthermore, a fabricated bienzyme paper can be used for glucose detection with high stability, reusability, and enhanced substrate channeling. Our findings provide new guidance for enzyme orientation on 2 D scaffolds, which may be extrapolated to other multienzyme cascade systems.

Ultrasensitive electrochemical biosensor for silver ion based on magnetic nanoparticles labeling with hybridization chain reaction amplification strategy

Abstract: Silver ion (Ag+) is a highly toxic heavy metal ion to aquatic organisms and accumulates in the human body via the food chain. Therefore, fast and accurate detection of Ag+ in water and food resources has become a critical issue within the scope of human health. Herein, we developed an ultrasensitive electrochemical biosensor for detection of Ag+ based on magnetic Fe3O4@gold core-shell nanoparticles (Fe3O4@Au NPs) labeling with hybridization chain reaction (HCR) amplification strategy. In this sensing strategy, the magnetic Fe3O4@Au NPs were selected for labeling with HCR product and enrichment on the surface of magnetic gold electrode. Thiolated-oligonucleotide (S1) was firstly immobilized on the surface of Fe3O4@Au NPs through Au–S chemical bond. In the presence of Ag+, cytosine-rich DNA oligonucleotide S2 hybridized with S1 to form an intramolecular duplex, in which Ag+ can selectively bind to cytosine–cytosine mismatches forming C–Ag+–C complex. The exposed stem of the C–Ag+–C complex opened two alternating ferrocene-labeled DNA hairpins (H1 and H2) in turn and triggered HCR to form a supersandwich DNA structure on the surface of Fe3O4@Au NPs. The HCR products modified Fe3O4@Au NPs were brought to the surface of magnetic gold electrode for direct electrochemical measurements. The proposed strategy led to a low detection limit of 0.5 fM and a wide dynamic range of 1 fM–100 pM for target Ag+. The developed biosensor was highly selective and its practical applicability in tap water and lake water samples was also investigated with a satisfactory result.

Co‐reactant Electrogenerated Chemiluminescence of Iridium(III) Complexes Containing an Acetylacetonate Ligand

Abstract: We examine the electrogenerated chemiluminescence (ECL) of three Ir(C∧N )2(acac) complexes, where acac=acetylacetonate anion and C∧N =2-phenylpyridine (ppy), 2-phenylbenzothiazole (bt), or 2-phenylquinoline (pq) anions, with tri-n-propylamine co-reactant in acetonitrile under a range of chemical and instrumental conditions; this follows somewhat conflicting recent claims of the ECL intensities from complexes of this type. Relevant electrochemical, spectroscopic, and ECL properties are evaluated in direct comparison with those of Ir(ppy)3 and [Ru(bpy)3](PF6)2, as well as data from previous publications. DFT calculations on the Ir(C∧N )2(acac) complexes show the HOMOs to be composed of both the metal and the C∧N ligand, and the LUMOs almost exclusively on the C∧N ligand. The ECL intensities of the Ir(C∧N )2(acac) complexes (relative to [Ru(bpy)3](PF6)2) were dependent on experimental conditions and, in some cases, the ECL intensities reported for iridium complexes may have been derived using conditions that unintentionally disadvantaged the reference electrochemiluminophore.

One-side non-covalent modification of CVD graphene sheet using pyrene-terminated PNIPAAm generated via RAFT polymerization for the fabrication of thermo-responsive actuators

Abstract: Thermo-responsive graphene-polymer films have been obtained by the modification of large CVD graphene films with pyrene-terminated poly( N -isopropylacrylamide) (PNIPAAm) via non-covalent π-π stacking interactions. Pyrene-terminated PNIPAAm was prepared by reversible addition fragmentation chain transfer (RAFT) polymerization using a pyrene-functionalized RAFT agent. Since PNIPAAm possesses a lower critical solution temperature (LCST) of 32 °C, the as-prepared graphene-PNIPAAm films could be reversibly deformed as a result of the morphology response of PNIPAAm to the environmental temperature variation. In addition, the thermo-triggered deformation of the graphene-PNIPAAm films was observed to be reversible and controllable by manipulation of the environmental temperature. Atomic force microscopy (AFM) and high-resolution SEM analysis evidenced the successful attachment of the PNIPAAm on the graphene surface. The thickness of the polymer was revealed by high-resolution scanning electron microscopy (SEM). The successful stepwise fabrication of the CVD graphene-polymer composite films was also characterized using Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). These thermo-responsive composite films would be highly desirable for a wide range of applications, such as thermo-responsive actuators, a thermo-responsive intelligent switch was fabricated using these thermo-responsive graphene composite films.

The Influence of Inflammatory Cytokines on the Proliferation and Osteoblastic Differentiation of MSCs

Abstract: Background: Mesenchymal stem cells (MSCs) have been widely researched for the function of wound repair and bone regeneration. Numerous evidence have proved that MSCs can differentiate towards osteoblasts, and enhance bone formation, and then directly promote the process of bone regeneration. Objective: The researchers’ interest in MSCs focuses on the potential of differentiating towards osteoblasts. They suggest that these applications can be significantly influenced by different kinds of inflammatory cytokines. In particular, in the process of bone regeneration, MSCs and inflammatory cytokines interact with each other, and promote the process of bone healing. In this review, we attempt to summarize several inflammatory cytokines that may have influence on the osteogenic differentiation of MSCs, including interleukin 1 (IL-1), IL-6, IL-10, IL-17, tumor necrosis factor-α (TNF-α ), and interferon-γ (INF-γ ), bone morphogenetic proteins(BMPs). Finally, some perspective of the behavior of MSCs in response to inflammatory cytokines are discussed.

Self-supported Cu(OH)2@Co2CO3(OH)2 core-shell nanowire array as a robust catalyst for ammonia-borane hydrolysis.

Abstract: High hydrogen content and long-term stability in aqueous solutions make ammonia-borane (AB) a promising hydrogen-storage material. It is highly attractive but still challenging to develop efficient catalysts for real-time and controllable hydrogen release from AB solution under mild conditions. Herein, we describe the use of a three-dimensional hierarchical Cu(OH)2@Co2CO3(OH)2 core–shell nanowire array on copper foam (denoted as Cu(OH)2@Co2CO3(OH)2/CF) as a highly efficient catalyst for hydrolytic dehydrogenation of AB. The Cu(OH)2@Co2CO3(OH)2/CF works as an on/off switch for on-demand hydrogen generation with a low activation energy of 44.3 KJ mol−1 and a turnover frequency of 39.72 mol(H2)/mol(cat.)/min. It also maintains activity and integration after long-term usage.

A simple and large-scale method to prepare flexible hollow graphene fibers for a high-performance all-solid fiber supercapacitor

Abstract: Herein, we develop a spray deposition process for the production of flexible and conductive hollow graphene fibers (HGFs). Firstly, a graphene oxide suspension is spray-coated on silk fibers, which act as a template, followed by the reduction of GO into RGO using HI as the reductant. This simple method gets rid of the picky conditions and complicated process for the fabrication of graphene fibers (GFs) which possess good flexibility, conductivity and a hollow structure. A flexible all-solid hollow graphene fiber supercapacitor (HGFS) is assembled using the as-prepared HGFs and shows an excellent specific capacitance of 76.1 F g−1 (127.4 mF cm−2, 48.5 F cm−3) at a current density of 1 A g−1, excellent rate capability (over 87% retention at 5 A g−1) and high cycling stability with only 9.5% capacitance decay over 2000 recycles at a scan rate of 100 mV s−1. This simple large-scale template method for the preparation of flexible and conductive HGF electrodes could promise broad prospects for high-performance energy storage applications, particularly for next-generation wearable electronic devices.

Direct transfer of graphene and application in low-voltage hybrid transistors

Abstract: A novel scotch tape assisted direct transfer of graphene onto different flexible and rigid substrates, including paper, polyethylene terephthalate, flat and curved glass, SiO2/Si, and a solution-processed high-k dielectric layer is presented. This facile graphene transfer process is driven by the difference in adhesion energy of graphene with respect to tape and a target substrate. In addition, the graphene films transferred by scotch tape are found to be cleaner, more continuous, less doped and higher-quality than those transferred by PMMA. Based on that, the tape transferred graphene is employed as a carrier transport layer in oxide thin-film transistors (TFTs) with different gate dielectrics (i.e., SiO2 and high-k ZrO2). The In2O3/graphene/SiO2 TFTs exhibit a high electron mobility of 404 cm2 V−1 s−1 and a high on/off current ratio of 105, while the counterpart In2O3/graphene/ZrO2 TFTs exhibit improved electron transport properties at an ultra-low operating voltage of 3 V, which is 20 times lower than that of SiO2-based devices. In contrast, the ZrO2-based TFTs with PMMA-transferred graphene exhibit no detective electrical properties. Therefore, the proposed scotch tape assisted transfer method will be particularly useful for the production of graphene films and other two-dimensional materials in more cost-effective and environmentally friendly modes for broad practical applications beyond graphene-based field-effect transistors (GFETs).

Characterization and Molecular Mechanism of Peptide-Conjugated Gold Nanoparticle Inhibiting p53-HDM2 Interaction in Retinoblastoma

Abstract: Inhibition of the interaction between p53 and HDM2 is an effective therapeutic strategy in cancers that harbor a wild-type p53 protein such as retinoblastoma (RB). Nanoparticle-based delivery of therapeutic molecules has been shown to be advantageous in localized delivery, including to the eye, by overcoming ocular barriers. In this study, we utilized biocompatible gold nanoparticles (GNPs) to deliver anti-HDM2 peptide to RB cells. Characterization studies suggested that GNP-HDM2 was stable in biologically relevant solvents and had optimal cellular internalization capability, the primary requirement of any therapeutic molecule. GNP-HDM2 treatment in RB cells in vitro suggested that they function by arresting RB cells at the G2M phase of the cell cycle and initiating apoptosis. Analysis of molecular changes in GNP-HDM2-treated cells by qRT-PCR and western blotting revealed that the p53 protein was upregulated; however, transactivation of its downstream targets was minimal, except for the PUMA-BCl2 and Bax axis. Global gene expression and in silico bioinformatic analysis of GNP-HDM2-treated cells suggested that upregulation of p53 might presumptively mediate apoptosis through the induction of p53-inducible miRNAs.

Study on triazophos adsorption behavior on the multi-walled carbon nanotubes

Abstract: A commercial multi-walled carbon nanotube (MWCNT) was selected as an adsorbent to remove triazophos, which is a representative insecticide. The MWCNT was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy. The effect of initial pH value, ionic strength and adsorbent dosage on the adsorption capacity of triazophos was optimized. The adsorption behaviors of triazophos on MWCNT including adsorption kinetics, isotherms and thermodynamics were investigated. The results demonstrated that the adsorption kinetics belonged to the pseudo-second-order and the adsorption rate constant was up to 1.7586 g/min; correlation coefficient was above 0.997. The Freundlich model fits better than Langmuir model, and the maximum adsorption capacity was 42.02 mg/g. The adsorption of triazophos onto MWCNT was thermodynamically feasible and spontaneous.