Lanlan Sun

Nitrogen-doped porous carbon/Co3O4 nanocomposites as anode materials for lithium-ion batteries.

A simple and industrially scalable approach to prepare porous carbon (PC) with high surface areas as well as abundant nitrogen element as anode supporting materials for lithium-ion batteries (LIBs) was developed. Herein, the N-doped PC was prepared by carbonizing crawfish shell, which is a kind of food waste with abundant marine chitin as well as a naturally porous structure. The porous structure can be kept to form the N-doped PC in the pyrolysis process. The N-doped PC-Co3O4 nanocomposites were synthesized by loading Co3O4 on the N-doped PC as anode materials for LIBs. The resulting N-doped PC-Co3O4 nanocomposites release an initial discharge of 1223 mA h g(-1) at a current density of 100 mA g(-1) and still maintain a high reversible capacity of 1060 mA h g(-1) after 100 cycles, which is higher than that of individual N-doped PC or Co3O4. Particularly, the N-doped PC-Co3O4 nanocomposites can be prepared in a large yield with a low cost because the N-doped PC is derived from abundant natural waste resources, which makes it a promising anode material for LIBs.

Metal/metal oxide nanostructures derived from metal–organic frameworks

Metal–organic frameworks (MOFs) have important potential applications in gas separation, storage and purification, and also for use as electrode materials, catalysts, sensors and in drug-delivery systems. There has been increasing interest in the synthesis of micro- and nanostructures based on MOFs, particularly on the improvement of their versatility and the simplification of synthesis procedures. This paper reviews the use of MOFs as matrices for solid-state decomposition and in the synthesis of metal/metal oxide micro- and nanostructures, porous carbon and composite materials.

Metal organic framework-derived anthill-like Cu@carbon nanocomposites for nonenzymatic glucose sensor

A novel nonenzymatic glucose sensor was constructed based on anthill-like Cu@carbon nanocomposites which were derived from a Cu-based metal organic framework by a simple thermolysis method. The final nanocomposites were characterized by scanning electron microscopy, thermogravimetric analysis, X-ray powder diffraction and electrochemical techniques. The results showed that the derived nanocomposites maintained the morphology of the original materials upon thermolysis, while the produced Cu nanoclusters were embedded in three-dimensional carbon frameworks and presented an anthill-like structure. Since the final products gave a sufficiently large specific surface area, good catalytic activity towards the oxidation of glucose and appropriate pores for electrolyte transfer, the resultant glucose sensor based on the anthill-like Cu@carbon nanocomposites showed a wide linear range of 0.2–8.0 mM and a low detection limit of 29.8 μM. The low cost, simple preparation and good catalytic activity of anthill-like Cu@carbon nanocomposites render them promising candidates as electrode materials for the construction of novel nonenzymatic sensors.

Hierarchical Cu–Co–Ni nanostructures electrodeposited on carbon nanofiber modified glassy carbon electrode: application to glucose detection

Hierarchical Cu–Co–Ni nanostructures (Cu–Co–Ni NSs) attached to carbon nanofibers (CNFs) modified glassy carbon electrode (GCE) was prepared by electrodeposition. Scanning electron microscopy results indicated that many hierarchical Cu–Co–Ni NSs were formed and uniformly dispersed on the CNFs/GCE surface. The electrochemical behavior and electrocatalytic performance of the Cu–Co–Ni NSs/CNFs/GCE towards the oxidation of glucose were evaluated by cyclic voltammograms, chronoamperometry and amperometric methods. The results revealed that Cu–Co–Ni NSs/CNFs/GCE has a good electrocatalytic activity for glucose oxidation and could be used as a nonenzymatic glucose sensor. The sensor showed an acceptable linear range from 0.01 to 4.30 mM with a sensitivity of 104.68 μA mM cm−2, and a detection limit of 3.05 μM (S/N = 3). The good catalytic activity, high sensitivity, good selectivity and stability rendered the Cu–Co–Ni NSs/CNFs/GCE to be a promising electrode for constructing a nonenzymatic glucose sensor.

Fabrication, characterization, and application in surface-enhanced Raman spectrum of assembled type-I collagen-silver nanoparticle multilayered films.

In this paper, we report a facile method for the fabrication of type-I collagen-silver nanoparticles (Ag NPs) multilayered films by utilizing type-I collagen as a medium. These samples were characterized by UV-vis spectra photometer, atomic force microscopy, scanning electron microscopy, and Fourier transform IR spectrum. Experimental results show that collagen molecules serve as effective templates to assemble Ag NPs into multilayer films. These samples exhibit high surface-enhanced Raman scattering (SERS) enhancement abilities. For example, EF(nu(cc)) (EF means enhancement factor) at 1592 cm(-1) in the SERS spectrum of 4-aminothiophenol on seven-layered substrates was calculated to be 1.81 x 10(5), which is larger than that reported in several literatures. The EFs increased as the layer number of multilayer films increases.

A novel nonenzymatic hydrogen peroxide sensor based on three-dimensional porous Ni foam modified with a Pt electrocatalyst

A novel nonenzymatic hydrogen peroxide (H2O2) sensor was simply prepared by depositing Pt nanoparticles (Pt NPs) onto Ni foam using UV-irradiation. Scanning electron microscopy was applied to characterize the changes of morphologies with UV-irradiation time. Energy dispersive spectroscopy confirmed that the Pt NP–Ni foam was mainly composed of Pt and Ni. The Pt NP–Ni foam electrode shared the unique advantages of Pt NPs (such as the good electrocatalytic activity) and Ni foam (such as the high electric conductivity, large surface area and high porosity). Its application in H2O2 detection, surprisingly, showed the high sensitivity and low detection limit. The linear range was from 0.005 to 0.85 mM. The sensitivity was 829 μA cm−2 mM−1 and the detection limit was 0.3 μM (S/N = 3). The H2O2 sensor also showed long-term stability. Therefore, the sensor is more suitable for the detection of H2O2 concentration.

Atomic force microscopy and surface-enhanced Raman scattering detection of DNA based on DNA-nanoparticle complexes

We report a simple method for the label-free detection of double-stranded DNA using surface-enhanced Raman scattering (SERS). We prepared cetyltrimethylammonium bromide (CTAB)-capped silver nanoparticles and a DNA-nanoparticle complex by adding silver nanoparticles to lambda-DNA solutions. In the present study, the utilization of CTAB-capped silver nanoparticles facilitates the electrostatic interaction between DNA molecules and silver nanoparticles; at the same time, the introduction of DNA avoids adding aggregating agent for the formation of nanoparticle aggregates to obtain large enhancement of DNA, because the DNA acts as both the probe molecules and aggregating agent of Ag nanoparticles. Atomic force microscopy (AFM) studies show that the morphology of DNA-Ag nanoparticle complexes seems to be determined by the concentrations of the DNA and the nanoparticles. Surface-enhanced Raman scattering (SERS) studies show that the morphology of the complexes plays a significant role in the intensity of SERS signals of DNA, and the best signal enhancement of DNA can be obtained by fine-tuning the experimental parameters. The SERS spectrum affords important structural information about the bases, phosphate backbone, and the conformation of DNA after mixing the DNA solutions with the Ag sol.

Type I collagen-mediated synthesis of noble metallic nanoparticles networks and the applications in Surface-Enhanced Raman Scattering and electrochemistry

In this paper, we demonstrated an effective environmentally friendly synthesis route to prepare noble metallic (Au, Ag, Pt and Pd) nanoparticles (NPs) networks mediated by type I collagen in the absence of any seeds or surfactants. In the reactions, type I collagen served as stabilizing agent and assembly template for the synthesized metallic NPs. The hydrophobic interaction between collagen and mica interface as well as the hydrogen bonds between inter- and intra-collagen molecules play important roles in the formation of collagen-metallic NPs networks. The noble metallic NPs networks have many advantages in the applications of Surface-Enhanced Raman Scattering (SERS) and electrochemistry detection. Typically, the as-prepared Ag NPs networks reveal great Raman enhancement activity for 4-ATP, and can even be used to detect low concentration of DNA base, adenine, without any label step. Furthermore, the cyclic voltammograms showed Pt NPs networks have good electrocatalytic ability for the reduction of O(2).

Surface-Relevant Regulable DNA Toroids Induced by Dopamine

Dopamine (2-(3,4-dihydroxyphenyl)ethylamine) is known as a natural chemical neurotransmitter and is also a cytotoxic and genotoxic molecule for cell apoptosis. In this work, the interaction of DNA with dopamine was investigated. Though the electrostatic interaction of DNA and dopamine was weak in aqueous solution, dopamine condensed circular pBR322 DNA into toroids on the mica surface cooperatively with ethanol. The formed DNA toroids came from the shrinking of DNA that was driven by ethanol-enhanced DNA-dopamine electrostatic interaction. The size of the DNA toroids could be modulated by varying the concentration of dopamine. This study offers useful information about the DNA condensation induced by monovalent cations and the sample preparation for AFM measurement and application. On the other hand, this work provides the potential strategies to prepare morphology and size controllable DNA condensates, which have valuable applications in gene transfection and nanotechnology.

Atomic Force Microscopic Study of Low Temperature Induced Disassembly of RecA−dsDNA Filaments

The assembly and disassembly of RecA-DNA nucleoprotein filaments on double-stranded DNA (dsDNA) or single-stranded DNA (ssDNA) are important steps for homologous recombination and DNA repair. The assembly and disassembly of the nucleoprotein filaments are sensitive to the reaction conditions. In this work, we investigated different morphologies of the formed nucleoprotein filaments at low temperature under different solution conditions by atomic force microscopy (AFM). We found that low temperature and long keeping time could induce the incomplete disassembly of the formed nucleoprotein filaments. In addition, when the formed filaments were kept at -20 degrees C for 20 h with 1,4-dithiothreitol (DTT), the integrated filaments disassembled. It was similar to the case under the same condition without anything added. However, when glycerol was used as a substitute for DTT, there was no obvious disassembly at the same condition. Oppositely, when the formed filaments were kept at 4 degrees C for 20 h, the disassembly with additional DTT was not as obvious as the case at -20 degrees C for 20 h, whereas the case with additional glycerol disassembled. The experiments indicated the effect of cold denaturation on the interaction of DNA and RecA. Meanwhile, the study of these phenomena can supply guidelines for the property and stability of RecA as well as the relevant roles of influencing factors to RecA and DNA in further theoretical studies.