Facile Controlled Synthesis of Pd-ZnO Nanostructures for Nitrite Detection.

The electrocatalytic characteristics of nanostructures are significantly affected by surface structure. The strict regulation of structural characteristics is highly beneficial for the creation of novel nanocatalysts with enhanced electrocatalytic performance. This work reports a nitrite electrochemical sensor based on novel flower-like Pd-ZnO nanostructures. The Pd-ZnO nanocatalysts were synthesized through a simple hydrothermal method, and their morphology and structure were characterized via field-emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Their electrocatalytical performance in the nitrite oxidation reaction was studied via cyclic voltammetry (CV) and the amperometric technique. Compared to pure ZnO and Pd nanoparticles, the Pd-ZnO nanostructures exhibited enhanced electrochemical performance in the nitrite oxidation reaction. In order to investigate the relationships between the structures of Pd-ZnO nanocatalysts and the corresponding electrocatalytic performances, different surface morphologies of Pd-ZnO nanocatalysts were fabricated by altering the solution pH. It was found that the flower-like Pd-ZnO nanostructures possessed larger effective surface areas and faster electron transfer rates, resulting in the highest electrocatalytic performance in the nitrite oxidation reaction. The designed nitrite sensor based on flower-like Pd-ZnO displayed a wide concentration linear range of 1 µM-2350 µM, a low detection limit of 0.2 µM (S/N of 3), and high sensitivity of 151.9 µA mM-1 cm-2. Furthermore, the proposed sensor exhibited perfect selectivity, excellent reproducibility, and long-time stability, as well as good performance in real sample detection.

Plasmonic SERS Biosensor Based on Multibranched Gold Nanoparticles Embedded in Polydimethylsiloxane for Quantification of Hematin in Human Erythrocytes.

This work reports a plasmonic surface-enhanced Raman scattering (SERS) biosensor that allows for quantitative analysis of hematin in erythrocytes without the need of separating it from hemoglobin (Hb). The biosensor exploits the tunable localized surface plasmon resonance (LSPR) characteristics of multibranched gold nanoparticles (M-AuNPs) and the strong plasmon coupling between an Au thin film and a flexible substrate consisting of M-AuNPs embedded in polydimethylsiloxane (PDMS) (i.e., M-AuNP-embedded PDMS substrate). In the assay, the hematin (or hematin-containing erythrocyte hemolysate) was deposited on Au film surface and covered with M-AuNP-embedded PDMS. Strong SERS signals were generated under excitation at 785 nm; the signals were sensitive to hematin concentration but not to several common coexisting biological substances. The intensities of the SERS signal (at 1623 cm-1) displayed a wide linear range using hematin concentrations in a range of at least ∼1.5 nM-1.1 µM; the limit of detection (LOD) was ∼0.03 ± 0.01 nM at a signal/noise (S/N) of 3. This assay is simple and sensitive without tedious separation procedures, thereby saving time and enhancing efficiency. This biosensor can be used to determine hematin concentration in human erythrocyte cytosols giving concentrations of ∼18.5 ± 4.5 (by averaging eight samples) and 51.5 ± 6.2 µM (by averaging three samples) for healthy and sickle erythrocytes, respectively, making it a potential application in clinical detection.

Adsorption of phosphate ions from aqueous solutions by a CeO2 functionalized Fe3O4@SiO2 core-shell magnetic nanomaterial.

Phosphate is generally considered to be one of the nutrients for plants which may cause eutrophication of the aquatic environment. In this study, a CeO2-functionalized Fe3O4@SiO2 core-shell magnetic nanomaterial (denoted as Fe3O4@SiO2-CeO2) was prepared and used as the adsorbent to remove phosphate from water. The adsorbents were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and N2 adsorption/desorption isotherms. Characterization results show that the particle size is around 8.63 nm, Brunauer-Emmett-Teller (BET) surface area is 179.7 m2 · g-1 and the pore volume is 0.39 cm3 · g-1 for magnetite Fe3O4@SiO2-CeO2. The adsorbents could be rapidly separated under an external magnetic field. Batch adsorption tests show that the Fe3O4@SiO2-CeO2 adsorbent exhibited high adsorption affinity for phosphate. Additionally, phosphate adsorption isotherms over the adsorbents could be well described by the Langmuir model, suggesting monolayer adsorption, and phosphate adsorption kinetics followed the pseudo-second-order kinetics. Moreover, increasing pH led to suppressed phosphate adsorption, and phosphate adsorption slightly increased with ionic strength.

Bimetallic Pt-Au nanocatalysts electrochemically deposited on graphene and their electrocatalytic characteristics towards oxygen reduction and methanol oxidation.

The burgeoning demand for clean and energy-efficient fuel cell system requires electrocatalysts to deliver greater activity and selectivity. Bimetallic catalysts have proven superior to single metal catalysts in this respect. This work reports the preparation, characterization, and electrocatalytic characteristics of a new bimetallic nanocatalyst. The catalyst, Pt-Au-graphene, was synthesized by electrodeposition of Pt-Au nanostructures on the surface of graphene sheets, and characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the molar ratio between Pt and Au precursors. The electrocatalytic characteristics of the nanocatalysts for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) were systematically investigated by cyclic voltammetry. The Pt-Au-graphene catalysts exhibits higher catalytic activity than Au-graphene and Pt-graphene catalysts for both the ORR and the MOR, and the highest activity is obtained at a Pt/Au molar ratio of 2:1. Moreover, graphene can significantly enhance the long-term stability of the nanocatalyst toward the MOR by effectively removing the accumulated carbonaceous species formed in the oxidation of methanol from the surface of the catalyst. Therefore, this work has demonstrated that a higher performance of ORR and the MOR could be realized at the Pt-Au-graphene electrocatalyst while Pt utilization also could be greatly diminished. This method may open a general approach for the morphology-controlled synthesis of bimetallic Pt-M nanocatalysts, which can be expected to have promising applications in fuel cells.

Electrochemical approach for detection of extracellular oxygen released from erythrocytes based on graphene film integrated with laccase and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid).

This work develops a novel electrochemical approach for detection of the extracellular oxygen released from human erythrocytes. The sensing is based on the bioelectrocatalytic system of graphene integrated with laccase (Lac) and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) toward the reduction of oxygen. ABTS and laccase are assembled on the surface of graphene, which is synthesized by a chemistry route, utilizing the pi-pi and electrostatic interactions of these components. Transmission electron microscopy (TEM), atomic force microscopy (AFM), and FT-IR spectroscopy demonstrate that graphene has been successfully synthesized, and ABTS and laccase have been effectively assembled on a graphene surface with the formation of Lac-ABTS-graphene hybrid. The voltammetric results indicate that ABTS can be used as a redox mediator when it is in immobilized form. The hybrid deposited on the glassy carbon (GC) electrode is demonstrated to be a good bioelectrocatalyst for the reduction of oxygen with inherent enzyme activity, accepted stability, high half-wave potential (ca.670 mV vs NHE), and unimpeded electrical communication to the copper redox sites of laccase. Therefore, this study has not only established a novel approach of detection of extracellular oxygen but also provided a general route for fabricating a graphene-based biosensing platform via assembling enzymes/proteins on a graphene surface.

Electrochemical detection of hepatitis C virus based on site-specific DNA cleavage of BamHI endonuclease.

We have developed a new electrochemical approach for qualitative and quantitative detection of hepatitis C virus (HCV) based on the site-specific DNA cleavage of BamHI endonuclease.

Raman observation of a molecular signaling pathway of apoptotic cells induced by photothermal therapy.

Plasmonic nanoparticle (NP)-mediated photothermal therapy (PPTT) has been explored as a minimally invasive approach to cancer therapy and has progressed from concept to the early stage of clinical trials. Better understanding of the cellular and molecular response to PPTT is crucial for improvement of therapy efficacy and advancement of clinical application. However, the molecular mechanism underlying PPTT-induced apoptosis is still unclear and under dispute. In this work, we used nuclear-targeting Au nanostars (Au NSs) as both a photothermal agent to specifically induce apoptosis in cancer cells and as a surface enhanced Raman spectroscopy (SERS) probe to monitor the time-dependent SERS spectra of MCF-7 cells which are undergoing apoptosis. Through SERS spectra and their synchronous and asynchronous SERS correlation maps, the occurrence and dynamics of a cascade of molecular events have been investigated, and a molecular signaling pathway of PPTT-induced apoptosis, including release of cytochrome c, protein degradation, and DNA fragmentation, was revealed, which was also demonstrated by metabolomics, agarose gel electrophoresis, and western blot analysis, respectively. These results indicated that PPTT-induced apoptosis undergoes an intrinsic mitochondria-mediated apoptosis pathway. Combined with western blot results, this intrinsic mitochondria-mediated apoptosis pathway was further demonstrated to be initiated by a BH3-only protein, BID. This work is beneficial for not only improving the fundamental understanding of the molecular mechanism of apoptosis induced by PPTT but also for guiding the modulation of PPTT to drive forward its clinical application.

A graphene-amorphous FePO4 hollow nanosphere hybrid as a cathode material for lithium ion batteries.

Amorphous FePO(4) hollow nanospheres were directly grown on graphene for use as a cathode material in lithium ion batteries. This hybrid exhibits high rate capability and good cycle stability because of efficient Li(+) ion diffusion through the thin wall of the hollow nanospheres and fast electron transport through the graphene.