Xiaolong Xu

A templateless, surfactantless, simple electrochemical route to a dendritic gold nanostructure and its application to oxygen reduction.

A templateless, surfactantless, simple electrochemical route to prepare dendritic gold nanostructure is reported. The morphology, composition, and structure of as-prepared dendritic gold nanostructure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The whole nanostructure was constructed by pristine metallic gold. The formation mechanism related to experimental conditions was discussed. The synthesis promises indium tin oxide (ITO) electrode can be easily modified with the dendritic pristine gold nanostructure. The as-prepared modified ITO electrode has excellent catalytic activity to oxygen reduction in neutral KCl solution.

Direct toxicity assessment of toxic chemicals with electrochemical method.

Electrochemical measurement of respiratory chain activity is a rapid and reliable screening for the toxicity on microorganisms. Here, we investigated in-vitro effects of toxin on Escherichia coli (E. coli) that was taken as a model microorganism incubated with ferricyanide. The current signal of ferrocyanide effectively amplified by ultramicroelectrode array (UMEA), which was proven to be directly related to the toxicity. Accordingly, a direct toxicity assessment (DTA) based on chronoamperometry was proposed to detect the effect of toxic chemicals on microorganisms. The electrochemical responses to 3,5-dichlorophenol (DCP) under the incubation times revealed that the toxicity reached a stable level at 60 min, and its 50% inhibiting concentration (IC50) was estimated to be 8.0 mg L(-1). At 60 min incubation, the IC50 values for KCN and As2O3 in water samples were 4.9 mg L(-1) and 18.3 mg L(-1), respectively. But the heavy metal ions, such as Cu2+, Pb2+ and Ni2+, showed no obvious toxicity on E. coli. With the exception of Hg2+, it showed 40.0 mg L(-1) IC50 value when E. coli was exposed to its solution for 60 min. The lower sensitivity of DTA for the heavy metal ions could be attributed to the toxicological endpoint and the experimental conditions used. All results suggest that the DTA is a sensitive, rapid and inexpensive alternative to on-site water and wastewater toxic analysis.

Self-standing non-noble metal (Ni–Fe) oxide nanotube array anode catalysts with synergistic reactivity for high-performance water oxidation

The oxygen evolution reaction (OER) is coupled with a number of important cathodic processes, for instance water splitting for hydrogen production and other energy storage devices based on O2–H2O chemistries such as metal–air batteries and unitized regenerative fuel cells, but they are limited by the slow kinetics. Attempts to solve this problem have received wide attention recently. However, accessing and stabilizing high-oxidation-state catalytically active species to further improve the high performance for the OER has been considered a huge challenge. Here, we report a Ni–Fe oxide-based nanotube array electrode, novel in design, with strong durability and excellent and synergistically enhanced catalytic performance for the OER. The OER electrode, with a nanotube array nanostructure, shows the remarkable features of a small overpotential of 0.28 V, favourable electrode kinetics and high stability, comparing favorably with the reported performances of the best OER electrocatalysts (IrO2), which is attributed to the formation and stabilization of the favourable OER catalytically active species NiOOH that is produced and reinforced by the introduction of Fe into nanostructured materials. This feasible strategy affords a new strategy for the development of effective and robust OER electrodes.

A biofilm reactor-based approach for rapid on-line determination of biodegradable organic pollutants.

A new analytical approach utilizing a biofilm reactor (BFR) for rapid online determination of biochemical oxygen demand (BOD) was proposed and experimentally validated. The BFR was fabricated via a cultivation process using naturally occurring microbial seeds from locally collected wastewaters. The resultant BFR displays a remarkable rate of biodegradation towards a wide spectrum of organic substrates, capable of degrading over 20% of biodegradable organic substrates within 100 s. More importantly, the BFR exhibits a superior indiscriminative biodegradation feature, enabling a precise prediction of BOD values of total biodegradable organics based on experimentally determined BOD values from partial degradation processes without a need for on-going calibration. The proposed approach was systematically validated using a range of individual organic substrates, their mixtures, synthetic samples and wastewaters. Highly significant linear correlations between the BFR and the standard BOD(5) methods were obtained from diversified synthetic samples (r=0.988, p=0.000, n=45) and wastewaters (r=0.983, p=0.000, n=40). Near unity slope values of the principal axis of the correlation ellipse were obtained from all tested samples, suggesting both methods were essentially measuring the same BOD value. The reported method could be a useful online monitoring tool for determination of biodegradable organic pollutants.

A fluorescent ELISA based on the enzyme-triggered synthesis of poly(thymine)-templated copper nanoparticles

Inspired by the ALP-triggered hydrolysis of the substrate ascorbic acid 2-phosphate as well as the product ascorbate-controlled generation of polyT-CuNPs with bright red fluorescence, we have developed a novel, selective and sensitive fluorescence turn-on assay for ALP activity sensing. Based on the conventional ELISA platform and commercially available antibody-ALP conjugates, an unconventional fluorescent ELISA system has been rationally developed and successfully applied in the quantitative measurement of model antigen proteins using fluorescence spectroscopy and a naked-eye readout under ultraviolet light.

Bifunctional plasmonic colloidosome/graphene oxide-based floating membranes for recyclable high-efficiency solar-driven clean water generation

Utilizing plasmonic nano-particles/structures for solar water evaporation has aroused increasing interest; however, large-scale methods are desired to boost the efficiency and improve the practicality of solar steam generation. We developed a membrane-supported floating solar steam generation system based on graphene oxide and a multiscale plasmonic nanostructure; the latter is a micrometer-sized colloidosome that was assembled from hollow and porous Ag/Au nanocubes. By taking advantage of multiscale plasmonic coupling of the particles, an extremely high solar thermal conversion efficiency up to 92% at 10 kW·m−2 (with a water evaporation rate reaching 12.96 kg·m−2·h−1) can be achieved. The TiO2 nanoparticle-modified floating system is also capable of high-efficiency dye degradation in organic-polluted water, rendering such a membrane system recyclable and scalable for practical and versatile solar-driven generation of clean water.

Single glass nanopore-based regenerable sensing platforms with a non-immobilized polyglutamic acid probe for selective detection of cupric ions

A single glass capillary nanopore-based sensing platform for rapid and selective detection of cupric ions is demonstrated by utilizing polyglutamic acid (PGA) as a non-immobilized probe. The detection is based on the significant decrease of ionic current through nanopore and the reversal of ion current rectification responses induced by the chelated cupric ions on the probes when in the presence of cupric ions. PGA shows high selectivity for detecting cupric ions rather than other metal ions. The sensitivity of the sensing platform can be improved about 1-2 orders of magnitude by employing asymmetric salt gradients during the measurements. And the PGA-based nanopore sensing platform shows excellent regenerability for Cu(2+) sensing applications. In addition, the method is found effective and reliable for the detection of cupric ions in real samples with small volume down to 20 μL. This nanopore-based sensing platform will find promising practical applications for the detection of cupric ions.