Ultrafine and well dispersed silver nanocrystals on 2D nanosheets: synthesis and application as a multifunctional material for electrochemical catalysis and biosensing

DNA Nanotechnology for Cancer Diagnosis and Therapy

Cancer is one of the leading causes of mortality worldwide, because of the lack of accurate diagnostic tools for the early stages of cancer. Thus, early diagnosis, which provides important information for a timely therapy of cancer, is of great significance for controlling the development of the disease and the proliferation of cancer cells and for improving the survival rates of patients. To achieve the goals of early diagnosis and timely therapy of cancer, DNA nanotechnology may be effective, since it has emerged as a valid technique for the fabrication of various nanoscale structures and devices. The resultant DNA-based nanoscale structures and devices show extraordinary performance in cancer diagnosis, owing to their predictable secondary structures, small sizes, and high biocompatibility and programmability. In particular, the rapid development of DNA nanotechnologies, such as molecular assembly technologies, endows DNA-based nanomaterials with more functionalization and intellectualization. Here, we summarize recent progress made in the development of DNA nanotechnology for the fabrication of functional and intelligent nanomaterials and highlight the prospects of this technology in cancer diagnosis and therapy.

Boron doped graphene wrapped silver nanowires as an efficient electrocatalyst for molecular oxygen reduction

Metal nanowires exhibit unusually high catalytic activity towards oxygen reduction reaction (ORR) due to their inherent electronic structures. However, controllable synthesis of stable nanowires still remains as a daunting challenge. Herein, we report the in situ synthesis of silver nanowires (AgNWs) over boron doped graphene sheets (BG) and demonstrated its efficient electrocatalytic activity towards ORR for the first time. The electrocatalytic ORR efficacy of BG-AgNW is studied using various voltammetric techniques. The BG wrapped AgNWs shows excellent ORR activity, with very high onset potential and current density and it followed four electron transfer mechanism with high methanol tolerance and stability towards ORR. The results are comparable to the commercially available 20% Pt/C in terms of performance.

Enhancing the specificity of polymerase chain reaction by graphene oxide through surface modification: zwitterionic polymer is superior to other polymers with different charges

Graphene oxides (GOs) with different surface characteristics, such as size, reduction degree and charge, are prepared, and their effects on the specificity of polymerase chain reaction (PCR) are investigated. In this study, we demonstrate that GO with a large size and high reduction degree is superior to small and nonreduced GO in enhancing the specificity of PCR. Negatively charged polyacrylic acid (PAA), positively charged polyacrylamide (PAM), neutral polyethylene glycol (PEG) and zwitterionic polymer poly(sulfobetaine) (pSB) are used to modify GO. The PCR specificity-enhancing ability increases in the following order: GO-PAA < GO-PAM < GO-PEG < GO-pSB. Thus, zwitterionic polymer-modified GO is superior to other GO derivatives with different charges in enhancing the specificity of PCR. GO derivatives are also successfully used to enhance the specificity of PCR for the amplification of human mitochondrial DNA using blood genomic DNA as template. Molecular dynamics simulations and molecular docking are performed to elucidate the interaction between the polymers and Pfu DNA polymerase. Our data demonstrate that the size, reduction degree and surface charge of GO affect the specificity of PCR. Based on our results, zwitterionic polymer-modified GO may be used as an efficient additive for enhancing the specificity of PCR.

Reversibly Switching Silver Hierarchical Structures via Reaction Kinetics

Here we report a study on controllable synthesis of hierarchical silver structures via regulating reaction kinetics. Silver particles with various morphologies are synthesized by a solution-based reduction approach at the addition of amino acids. The amino acid is used to coordinate with silver ions to slow down the reduction of silver ions. With the increase of glycine concentration, the morphologies of silver particles switch from dendrites, to flowers and to compacted spheres, which is attributed to the decrease of reaction rate as a result of the coordination. Three more amino acids are examined and confirms the role of reaction kinetic in shaping silver particles. Furthermore, by increasing the concentration of the reductant, the silver morphologies change from compact spheres to loose flowers as a result of the increase of reaction rate. Therefore the silver hierarchical structure can be reversibly switched by reaction kinetics. The silver particles synthesized are tested for surface enhanced Raman scattering (SERS) property and the dendritic particles present a remarkable SERS activity. This study shows that reaction kinetics is a powerful tool to tune hierarchical structures of silver particles, which is expected to be transferable to other material systems.

Fabrication of bimetallic Cu/Au nanotubes and their sensitive, selective, reproducible and reusable electrochemical sensing of glucose

Herein, we report a facile two-step approach to produce gold-incorporated copper (Cu/Au) nanostructures through controlled disproportionation of the Cu(+)-oleylamine complex at 220 °C to form copper nanowires and the subsequent reaction with Au(3+) at different temperatures of 140, 220 and 300 °C. In comparison with copper nanowires, these bimetallic Cu/Au nanostructures exhibit their synergistic effect to greatly enhance glucose oxidation. Among them, the shape-controlled Cu/Au nanotubes prepared at 140 °C show the highest electrocatalytic activity for non-enzymatic glucose sensing in alkaline solution. In addition to high sensitivity and fast response, the Cu/Au nanotubes possess high selectivity against interferences from other potential interfering species and excellent reproducibility with long-term stability. By introducing gold into copper nanostructures at a low level of 3, 1 and 0.1 mol% relative to the initial copper precursor, a significant electrocatalytic enhancement of the resulting bimetallic Cu/Au nanostructures starts to occur at 1 mol%. Overall, the present fabrication of stable Cu/Au nanostructures offers a promising low-cost platform for sensitive, selective, reproducible and reusable electrochemical sensing of glucose.

Hydroxyl-rich nanoporous carbon nanosheets synthesized by a one-pot method and their application in the in situ preparation of well-dispersed Ag nanoparticles

Nanoporous carbon nanosheets (CNSs) with high surface area have been synthesized by pyrolysis of organic–inorganic precursor. The CNSs with rich hydroxyl groups display remarkable reactivity and capability for in situ loading ultrafine Ag NPs.