Mingtao Zheng

Fabrication of Reduced Graphene Oxide and Sliver Nanoparticle Hybrids for Raman Detection of Absorbed Folic Acid: A Potential Cancer Diagnostic Probe

Reduced graphene oxide (RGO) and silver nanoparticle (AgNP) hybrids (RGO-AgNP) were prepared by a facile one-pot method using Poly (N-vinyl-2-pyrrolidone) as reductant and stabilizer. Folic acid (FA) molecules were attached to the RGO-AgNP by physisorption for targeting specific cancer cells with folate receptors (FRs) and using as Raman reporter molecules. The internalization of the FA loaded RGO-AgNP (RGO-AgNP-FA) inside the FRs-positive cancer cell was confirmed by confocal laser scanning and transmission electron microscopy. The Raman signals of the FA in live cancer cells were detected by confocal Raman spectroscope at 514 nm excitation, indicating that the RGO-AgNP-FA material has great potential as a Raman probe for cancer diagnosis in vitro.

Microtube bundle carbon derived from Paulownia sawdust for hybrid supercapacitor electrodes.

The structure and capacitive properties of microtube bundle carbons (MTBCs) from carbonization of paulownia sawdust (PS) followed by NaOH activation were investigated. Morphology analyses indicated that MTBCs had abundant micropores and mesopores with a high specific surface area of about 1900 m(2) g(-1). Cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy studies demonstrated the excellent charge storage, transfer capability, and low impedance of MTBCs. The specific capacitance of MTBCs-4 was as high as 227 F g(-1) at 2 mV s(-1). Experimental results indicated that MTBCs provide smooth charge-transfer pathways for the ions in electrolytes and gateways to micropores and mesopores in the bulk. The hybrid supercapacitor model of MTBCs based on electrical double-layer capacitors and electrostatic capacitors was discussed and demonstrated. MTBCs are electrostatic capacitors at low frequency current, and may provide the pathways for easy accessibility of efficient charge transmission and high energy storage.

Amorphous Ni–Co Binary Oxide with Hierarchical Porous Structure for Electrochemical Capacitors

A simple and outstanding approach is provided to fabricate amorphous structure Ni-Co binary oxide as supercapacitors electrode materials. We can easily obtain porous Ni-Co oxides composite materials via chemical bath deposition and subsequent calcination without any template or complicate operation procedures. The amorphous porous Ni-Co binary oxide exhibits brilliant electrochemical performance: first, the peculiar porous structure can effectively transport electrolytes and shorten the ion diffusion path; second, binary composition and amorphous character introduce more surface defects for redox reactions. It shows a high specific capacitance up to 1607 F g(-1) and can be cycled for 2000 cycles with 91% capacitance retention. In addition, the asymmetric supercapacitor delivers superior energy density of 28 W h kg(-1), and the maximum power density of 3064 W kg(-1) with a high energy density of 10 W h kg(-1).

Hierarchical NiO mesocrystals with tuneable high-energy facets for pseudocapacitive charge storage

Mesocrystals are advantageous in providing a large specific surface and favorable transport properties, and have been extensively studied for energy-related applications including supercapacitors, solar cells, lithium-ion batteries, and catalysis. However, the practical applications of mesocrystals are hindered by many obstacles, such as high cost, complicated synthesis processes, and utilization of deleterious additives. Herein, we report a facile one-step and additive-free route for the controllable synthesis of NiO mesocrystals (NOMs) with a cuboctahedral morphology and layered hierarchical structures consisting of self-assembled NiO nanosheets. When employed as an electrode material for supercapacitors, the as-prepared NOMs exhibited an exceptional electrochemical performance such as an ultrahigh reversible specific capacity of ca. 1039 F g−1 at a current density of 1.0 A g−1 and excellent cycling stability (ca. 93% capacitance retention after 10u2006000 charge/discharge cycles). Moreover, an all-solid-state hybrid supercapacitor based on hierarchical NOMs and three-dimensional nitrogen-doped graphene manifested a high energy density of 34.4 W h kg−1 at a power density of 150 W kg−1 in 2.0 M KOH aqueous electrolyte. These results further demonstrate the potential of NiO mesocrystals as a promising electrode material by constructing a hierarchical mesostructure, which can improve the electrochemical performance for energy storage. The outstanding electrochemical performance may be attributed to their hierarchical mesostructure that can effectively enhance the electrical conductivity and avoid the aggregation of NiO nanosheets, and the exposed {100} facets with a high electrochemical activity.

Simple additive-free method to manganese monoxide mesocrystals and their template application for the synthesis of carbon and graphitic hollow octahedrons.

Mesocrystals are of great importance owing to their novel hierarchical microstructures and potential applications. In the present work, a simple additive-free method has been developed for the controllable synthesis of manganese monoxide (MnO) mesocrystals, in which cheap manganese acetate (Mn(Ac)2) and ethanol were used as raw materials without involving any other expensive additives such as surfactants, polyelectrolyte, or polymers. The particle size of the resulting MnO mesocrystals is tunable in the range 400-1500 nm by simply altering the concentration of Mn(Ac)2 in ethanol. The percentage yield of the octahedral MnO mesocrystals is about 38 wt % with respect to the starting Mn(Ac)2. The selective adsorption of oligomers, which was resulted from the polymerization of ethanol, acted as an important role for the mesocrystal formation. A mechanism involving the oriented aggregation of MnO nanoparticle subunits and the subsequent ripening process was proposed. Moreover, for the first time, the as-synthesized MnO mesocrystals were employed as a novel template to fabricate functional materials with an octahedral morphology including MnO@C core/shells, carbon, and graphitic hollow octahedrons. This method shows the importance of mesocrystals not only for the field of material research but also for the application in functional materials synthesis.

Facile one-step and high-yield synthesis of few-layered and hierarchically porous boron nitride nanosheets

Few-layered boron nitride nanosheets (BNNSs) have attracted increasing research interest in the past few years due to their unique material properties. However, the lack of a reliable scale-up production method is an inhibiting issue for their practical applications. In this work, we report a facile one-step and high-yield method for the synthesis of few-layered and hierarchically porous BNNSs through simultaneous etching and in situ nitridation of calcium hexaboride (CaB6) by ammonium chloride under moderate conditions. The output of the few-layered BNNSs is as high as 1.4 g with respect to 1.06 g of starting CaB6 crystals. Transmission electron microscopy and atomic force microscopy characterizations confirm the successful synthesis of few-layered BNNSs, most of which are layered with a thickness less than 3 nm (layer number < 10). The as-prepared BNNSs exhibit a high specific surface area (492–795 m2 g−1) and a high pore volume (0.34–0.50 cm3 g−1). In addition, the as-resulted BNNSs exhibit high and tuneable H2 uptakes from 1.48 to 2.18 wt% at 77 K and at a relatively low pressure of 1.0 MPa, thus guiding the further search of materials for H2 storage. Our results suggest that the simultaneous etching and in situ nitridation of metallic borides is a facile and effective method for reliable production of few-layered BNNSs with hierarchical porosity for potential applications such as gas storage and functional composites.

Using hydrogen peroxide to mediate through a one-step hydrothermal method for the fast and green synthesis of N-CDs

A facile and green approach for preparation of photoluminescent nitrogen-doped carbon dots (N-CDs) is reported, using cheap and extensively available cocoon silk as raw material. The use of H2O2 leads to the enhanced formation of N-CDs. The N-CDs have been synthesized in a short time (50 minutes), and have a high fluorescence quantum yield (24.0%). A small amount of H2O2 solution plays a vital role in shortening the reaction time, which is a brand new way to synthesize N-CDs with the help of H2O2, with both reactants and products being environmentally friendly. The prepared N-CDs are collected by removing the insoluble materials through simple filtration rather than dialysis. As far as we know, this is the first report of N-CDs being synthesized simply with the help of H2O2 solution. The prepared N-CDs solution is sensitive to pH changes, which means they have promise for application in the pH detection area.