Baoping Lu

Porous Co3O4 Nanorods–Reduced Graphene Oxide with Intrinsic Peroxidase-Like Activity and Catalysis in the Degradation of Methylene Blue

A facile two step process was developed for the synthesis of porous Co3O4 nanorods-reduced graphene oxide (PCNG) hybrid materials based on the hydrothermal treatment cobalt acetate tetrahydrate and graphene oxide in a glycerol-water mixed solvent, followed by annealing the intermediate of reduced graphene oxide-supported Co(CO3)0.5(OH)·0.11H2O nanorods in a N2 atmosphere. The morphology and microstructure of the composites were examined by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and Raman spectroscopy. It is shown that the obtained PCNG have intrinsic peroxidase-like activity. The PCNG are utilized for the catalytic degradation of methylene blue. The good catalytic performance of the composites could be attributed to the synergy between the functions of porous Co3O4 nanorods and reduced graphene oxide.

In situ controllable growth of CoFe2O4 ferrite nanocubes on graphene for colorimetric detection of hydrogen peroxide

A facile method is proposed for the synthesis of cubic CoFe2O4 ferrite–reduced graphene oxide nanocomposite sheets (rGO–CFs), using poly(N-vinyl-2-pyrrolidone) as the reductant and stabilizer. The rGO–CFs functioned as efficient peroxidase mimetics and were successfully applied for colorimetric assay. The morphology and composition of the rGO–CFs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. Significantly, the peroxidase-like activity of the rGO–CFs followed typical Michaelis–Menten kinetics and showed a good affinity to 3,3,5,5-tetramethyl benzidine. Under optimum conditions, the colorimetric assay showed a lower detection limit (S/N = 3) of 0.3 μM when compared with that of other nanoparticle based colorimetric assays. Furthermore, the cubic nanostructured rGO–CFs exhibited better stability than horseradish peroxidase when they were exposed to solutions with different solvents and temperatures. These excellent properties made the cubic nanostructured rGO–CFs an ideal candidate for a wide range of potential applications as peroxidase mimetics.

One-pot solvothermal synthesis of graphene-supported TiO2 (B) nanosheets with enhanced lithium storage properties

A facile process was developed for the synthesis of graphene-supported TiO2 (B) nanosheets (GTBN) composite based on the hydrothermal treatment titanium (III) chloride and graphene oxide in an ethylene glycol. The morphology and microstructure of the composites were examined by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectroscopy. The obtained GTBN show a high thermal stability and the phase transformation of TiO2 (B) to anatase can be prevented by graphene after pyrolysis of GTBN at 350°C for 2h. Furthermore, GTBN exhibited high rate performance and stability of lithium ion batteries, due to the enhanced conductivity of the electrode and accommodation to volume/strain changes during lithium insertion-extraction.

Facile synthesis of Au@Fe3O4–graphene and Pt@Fe3O4–graphene ternary hybrid nanomaterials and their catalytic properties

Graphene-based sheets that possess a unique nanostructure and a variety of fascinating properties are appealing as promising nanoscale building blocks of new composites. Herein, we present a general and effective approach for the preparation of metal oxide–graphene (metal oxide–G, metal oxide = Fe3O4, ZnO and Cu2O) by in situ nucleation and growth of metal oxide on the surface of graphene in tetraethylene glycol (TEG) solution. TEG, a nontoxic and environmentally friendly agent, acts as both solvent and reductant. Furthermore, the Fe3O4–G was employed as a two dimensional support for loading noble metal nanoparticles (Au or Pt) to synthesize Au@Fe3O4–G and Pt@Fe3O4–G ternary hybrid materials. The as-obtained Au@Fe3O4–G exhibited excellent catalytic activity in the reduction of 4-nitrophenol by NaBH4, and the Pt@Fe3O4–G showed remarkable electrocatalytic performance for hydrazine oxidation. We believe that the hybrid catalysts fabricated by this simple, efficient method have great potential for applications in other fields, such as electrochemical energy storage, sensors, and so on.

Facile synthesis of three dimensional hierarchical Co-Al layered double hydroxides on graphene as high-performance materials for supercapacitor electrode.

A facile simple hydrothermal method combined with a post-solution reaction is developed to grow interconnected three dimensional (3D) hierarchical Co-Al layered double hydroxides (LDHs) on reduced graphene oxide (rGO). The obtained 3D hierarchical rGO-LDHs are characterized by field emission scanning electron microscopy, X-ray diffraction, and X-ray photo-electron spectroscopy. As LDHs nanosheets directly grow on the surface of rGO via chemical covalent bonding, the rGO could provide facile electron transport paths in the electrode for the fast Faradaic reaction. Moreover, benefiting from the rational 3D hierarchical structural, the rGO-LDHs demonstrate excellent electrochemical properties with a combination of high charge storage capacitance, fast rate capability and stable cycling performance. Remarkably, the 3D hierarchical rGO-LDHs exhibit specific capacitance values of 599 F g(-1) at a constant current density of 4 A g(-1). The rGO-LDHs also show high charge-discharge reversibility with an efficiency of 92.4% after 5000 cycles.

Reversible detection of vancomycin using peptide-functionalized cantilever array sensor.

A reversible detection method for vancomycin was developed utilizing the cantilever array sensor functionalized by a designed peptide consisting of a cysteine (Cys-), a space linker (-Gly-Gly-Gly-Gly-) and a molecular recognition ligand (-L-Lys-D-Ala-D-Ala). It was found that the peptide space linker was necessary and important for the response of the cantilever array sensor. The sensing cantilevers in the array were functionalized with the peptide while the reference cantilevers were modified by 6-mercapto-1-hexanol (MCH) to eliminate the influence of environmental disturbances. The binding between vancomycin and the peptide induced a change of surface stresses in the sensing cantilevers resulting in a differential deflection between the sensing and reference cantilevers. The reciprocal of the differential deflection is linear with the reciprocal of vancomycin concentration within the range of 2 μM to 100 μM (R=0.993) at a detection limit of 0.2 μM (S/N=3). The reversible detection can be realized just by regenerating the sensing cantilevers with running buffer solution. Other antibiotics such as doxycycline, streptomycin, and kanamycin have negligible effect on the response of the sensor. The sensor can also be utilized for reversible detection of vancomycin in serum background, which clearly indicates the potential of the sensor for vancomycin detection in real biological samples.

CoxFe3−xO4 hierarchical nanocubes as peroxidase mimetics and their applications in H2O2 and glucose detection

A facile approach was proposed for the synthesis of hierarchical CoxFe3−xO4 nanocubes (CF nanocubes), using Prussian Blue (PB) as precursor. The method consists of the synthesis of hierarchical cobalt–iron Prussian blue analogues (PBAs) through the reaction of PB nanocubes with CoCl2 in a water bath and subsequently calcining the corresponding PBA precursor. The obtained CF nanocubes were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and N2 adsorption–desorption isotherm measurements. It is found that the hierarchical CF nanocubes have a large specific surface area (108 m2 g−1). Considering the hierarchical structure and the doping of Co in Fe3O4 are beneficial for the catalytic activity of the catalyst, an efficient and simple colorimetric biosensor for H2O2 and glucose was fabricated using CF nanocubes as a peroxidase mimetic. The good catalytic activity and low-cost make the hierarchical CF nanocubes a useful biocatalyst for a wide range of potential applications in medicine and biotechnology.

Facile Fabrication of SERS Arrays through Galvanic Replacement of Silver onto Electrochemically Deposited Copper Micropatterns

Scatter me: A fast and cost-effective approach for the fabrication of surface-enhanced Raman scattering (SERS) arrays is developed. The method applied combines microcontact printing, electrodeposition, and galvanic replacement without the need for expensive instruments and intricate processing. The as-prepared arrays show excellent SERS activity and high reproducibility for Rhodamine 6G.

Electrochemical sensing platform based on Schiff-base cobalt(II)/single-walled carbon nanohorns complexes system

Single-walled carbon nanohorns (SWNHs), distinguished by their high purity and unique structure, were noncovalently functionalized with Schiff-base cobalt(II) (Co-salen) for the first time. Cyclic voltammogram of Co-salen/SWNHs display a pair of redox peaks with a formal potential of +0.15 V in 0.1 M phosphate buffer solution (pH 7.0). A novel bifunctional electrochemical sensor for hydrazine oxidation and hydrogen peroxide reduction are presented based on the composite modified electrode. Using amperometry, the linear relationship of hydrazine was found to be in the range from 1 to 96 μM with a sensitivity of 2.4 μA mM−1, the detection limit is 0.1 μM (S/N = 3). The linear relationship of hydrogen peroxide is in the range from 50 to 4600 μM with a sensitivity of 1.8 μA mM−1, the detection limit is 10 μM (S/N = 3). The hybrid material provides a good electrochemical sensing platform and has potential applications in environment analysis and biosensors.

Study of the interactions between the key spore coat morphogenetic proteins CotE and SpoVID.

The capability of Bacillus subtilis spores to withstand extreme environmental conditions is thought to be conferred especially by their outermost proteinaceous protective layer, called the spore coat. Of the over 70 proteins that form the spore coat, only a small subset of them affect its morphogenesis, they are referred to as morphogenetic proteins. In this study we investigated the interaction between two spore coat morphogenetic proteins SpoVID and CotE. SpoVID is involved in the process of spore surface encirclement by individual coat proteins, these include CotE, which controls the assembly of the outer coat layer. Both proteins were proposed to be recruited to a common protein scaffold, but their direct association has not been previously shown. Here we studied the interactions between CotE and SpoVID in vitro for the first time by using molecule recognition force spectroscopy, which allows the detection of piconewton forces between conjugated biological pairs and also facilitates the investigation of dynamic processes. The most probable CotE-CotE unbinding force was 49.4±0.1pN at a loading rate of 3.16×10³ pN/s while that of SpoVID-CotE was 26.5±0.6pN at a loading rate of 7.8×10² pN/s. We further analyzed the interactions with the bacterial two hybrid system and pull-down experiments, which also indicate that SpoVID interacts directly with CotE. In combination with the previously identified direct contacts among SpoIVA, SpoVID and SafA, our data imply that the physical association of key morphogenetic proteins forms a basic skeleton where other coat proteins could be attached.