Xianbo Lu

Porous nanosheet-based ZnO microspheres for the construction of direct electrochemical biosensors.

Nanosheet-based ZnO microsphere with porous nanostructures was synthesized by a facile chemical bath deposition method followed by thermal treatment, which was explored for the construction of electrochemical biosensors. Spectroscopic and electrochemical researches revealed the ZnO-based composite was a biocompatible immobilization matrix for enzymes with good enzymatic stability and bioactivity. With advantages of nanostructured inorganic-organic hybrid materials, a pair of stable and well-defined quasi-reversible redox peaks of hemoglobin was obtained with a formal potential of -0.345 V (vs. Ag/AgCl) in pH 7.0 buffer. Facilitated direct electron transfer of the metalloenzymes with an apparent heterogeneous electron transfer rate constant (k(s)) of 3.2s(-1) was achieved on the ZnO-based enzyme electrode. Comparative studies demonstrated the nanosheet-based ZnO microspheres were more effective in facilitating the electron transfer of immobilized enzyme than solid ZnO microspheres, which may result from the unique nanostructures and larger surface area of the porous ZnO. The prepared biosensor displayed good performance for the detection of H(2)O(2) and NaNO(2) with a wide linear range of 1-410 and 10-2700 microM, respectively. The entrapped hemoglobin exhibits high peroxidase-like activity for the catalytic reduction of H(2)O(2) with an apparent Michaelis-Menten constant (K(M)(app)) of 143 microM. The nanosheet-based ZnO could be a promising matrix for the fabrication of direct electrochemical biosensors, and may find wide potential applications in biomedical detection and environmental analysis.

Nanographene-based tyrosinase biosensor for rapid detection of bisphenol A.

Hydrophilic nanographene (NGP) prepared by ball milling of graphite was used as the support to construct a novel tyrosinase biosensor for determination of bisphenol A (BPA). The performances of the nanographene-based tyrosinase biosensor were systematically compared with those of multiwall carbon nanotubes (MWNTs) modified tyrosinase biosensors. The results indicated that the nanographene-based tyrosinase biosensor provided significant advantages over MWNTs-based tyrosinase biosensor in term of response, repeatability, background current and limit of detection (LOD), which could be attributed to its larger specific surface area and unique hierarchical tyrosinase-NGP nanostructures. The nanographene-based tyrosinase biosensor displayed superior analytical performance over a linear range from 100 nmol L(-1) to 2000 nmol L(-1), with LOD of 33 nmol L(-1) and sensitivity of 3108.4 mA cm(-2)M(-1). The biosensor was further used for detecting BPA (leaching from different vessels) in tap water, and the accuracy of the results was validated by high performance liquid chromatography (HPLC). The nanographene-based tyrosinase biosensor proved to be a promising and reliable tool for rapid detection of BPA leached from polycarbonate plastic products and for on-site rapid analysis of emergency pollution affairs of BPA.

Polybrominated diphenyl ethers in sediments of the Daliao River Estuary, China: levels, distribution and their influencing factors.

The concentrations, compositional profiles, possible sources of polybrominated diphenyl ethers (PBDEs) in sediments of the Daliao River Estuary as well as the factors influencing the distribution of PBDEs were investigated. The total concentrations of PBDEs ranged from 0.13 to 1.98 ng g(-1)d.w. BDE209 was the dominating congener in all sediment samples, indicating the pollution of PBDEs in the Daliao River Estuary mainly came from the use of deca-BDE commercial mixtures. The intrusion of sea waters promoted the deposition of the colloid-associated PBDEs in the estuary. There were significantly negative correlations between PBDE concentration in sediment with pH value and salinity in the bottom water. The higher river flow in the flood season (summer) obviously accelerated the transport of PBDEs, and thereby increased the risk of PBDE contamination to the deep ocean. Moreover, a positive correlation between TOC and PBDE distributions was observed, suggesting that TOC regulated the distributions of PBDEs in sediments of Daliao River Estuary.

Hemoglobin entrapped within a layered spongy Co3O4 based nanocomposite featuring direct electron transfer and peroxidase activity

Layered Co3O4 nanoflakes with spongy nanostructure were synthesized for the first time. The porous, layered spongy nanostructure of Co3O4 is advantageous for the immobilization of proteins and enzymes, which were integrated with conductive polymer Nafion to form a biocompatible Nafion–Co3O4 organic–inorganic hybrid material. Hemoglobin (Hb) was chosen as a model protein to investigate the nanocomposite. FTIR spectroscopy revealed that Hb entrapped in the composite film could retain its essential secondary structure. With advantages of organic–inorganic hybrid materials, dramatically facilitated direct electron transfer of Hb and excellent bioelectrocatalytic activity towards H2O2 were demonstrated. The small apparent Michaelis–Menten constant (0.136 mM) and the high sensitivity (396 mA cm−2 M−1) of the film electrode indicated that Hb in the composite film possessed high enzyme-like peroxidase activity. The Co3O4-based hybrid material could be used efficiently for the entrapment of redox-active proteins and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biomedical devices.

3D metal-organic framework as highly efficient biosensing platform for ultrasensitive and rapid detection of bisphenol A

As is well known, bisphenol A (BPA), usually exists in daily plastic products, is one of the most important endocrine disrupting chemicals. In this work, copper-centered metal-organic framework (Cu-MOF) was synthesized, which was characterized by SEM, TEM, XRD, FTIR and electrochemical method. The resultant Cu-MOF was explored as a robust electrochemical biosensing platform by choosing tyrosinase (Tyr) as a model enzyme for ultrasensitive and rapid detection of BPA. The Cu-MOF provided a 3D structure with a large specific surface area, which was beneficial for enzyme and BPA absorption, and thus improved the sensitivity of the biosensor. Furthermore, Cu-MOF as a novel sorbent could increase the available BPA concentration to react with tyrosinase through π-π stacking interactions between BPA and Cu-MOF. The Tyr biosensor exhibited a high sensitivity of 0.2242A M(-1) for BPA, a wide linear range from 5.0×10(-8) to 3.0×10-6moll(-1), and a low detection limit of 13nmoll(-1). The response time for detection of BPA is less than 11s. The proposed method was successfully applied to rapid and selective detection of BPA in plastic products with satisfactory results. The recoveries are in the range of 94.0-101.6% for practical applications. With those remarkable advantages, MOFs-based 3D structures show great prospect as robust biosensing platform for ultrasensitive and rapid detection of BPA.

Electrochemical biosensing platform based on amino acid ionic liquid functionalized graphene for ultrasensitive biosensing applications.

In this study, a facile non-covalent method was developed for preparing water-soluble graphene with excellent electronic conductivity. Room temperature ionic liquids (ILs) with high ionic conductivity were used for the non-covalent surface functionalization of graphene through π-π stacking interactions. Compared to other ILs used, amino acid ionic liquids (AAILs) were found to be the most effective for improving the dispersion of graphene in water phase. Electrochemical and spectroscopic results confirmed that the obtained AAIL functionalized GR can retain the excellent electronic conductivity of pristine graphene without damaging the graphene lattice. The obtained water-soluble graphene (GR-AAIL) was exemplified to fabricate an electrochemical biosensor using tyrosinase as a model enzyme, and the sensitivity (12,600 mA cm(-2) M(-1)) of GR-AAIL based biosensor was about 17 times higher than that of graphene oxide and other nanomaterial based biosensor, displaying its unprecedented high sensitivity for biosensing. The detection limit for catechol (one important environmental pollutant) reached as low as 8 nM with a response time of 3s and a linear range from 25 nM to 11,100 nM. The AAIL-GR based biosensor also demonstrated good reproducibility, repeatability, selectivity, long-term stability and high recovery for catechol detection. Amino acid ionic liquid functionalized graphene proves to be a robust and versatile electrochemical biosensing platform for fabricating biosensors with excellent performance.

Graphitized macroporous carbon microarray with hierarchical mesopores as host for the fabrication of electrochemical biosensor.

A novel graphitized ordered macroporous carbon (GMC, pore size approximately 380 nm) with hierarchical mesopores (2-30 nm) and high graphitization degree was prepared by nickel-catalyzed graphitization of polystyrene arrays. The obtained GMC possessed high specific surface area, large pore volume, and good electrical conductivity, which was explored for the enzyme entrapment and biosensor fabrication by a facile method. With advantages of novel nanostructure and good electrical conductivity, direct electrochemistry of hemoglobin (a model protein) was observed on the GMC-based biocomposite with a formal potential of -0.36 V (vs. Ag/AgCl) and an apparent heterogeneous electron transfer rate constant (k(s)) of 1.2 s(-1) in pH 7.0 buffer. Comparative studies revealed that GMC offered significant advantages over carbon nanotubes (CNTs) in facilitating direct electron transfer of entrapped Hb. The fabricated biosensor exhibited good sensitivity (101.6 mA cm(-2) M(-1)) and reproducibility, wide linear range (1-267 microM), low detection limit (0.1 microM), and good long-term stability for H(2)O(2) detection. GMC proved to be a promising matrix for enzyme entrapment and biosensor fabrication, and may find wide potential applications in biomedical detection and environmental analyses.

A promising electrochemical biosensing platform based on graphitized ordered mesoporous carbon

Three dimensional ordered graphitized mesoporous carbon GMC-6 (pore diameter ∼6 nm) and GMC-13 (pore diameter ∼13 nm), prepared by a nickel-catalyzed template-assisted method, were explored systematically for the construction of enzyme-based electrochemical biosensors. Comparative studies revealed that GMC-6 offer significant advantages over GMC-13 and graphitized multiwalled carbon nanotubes (CNTs) in facilitating the direct electron transfer of entrapped hemoglobin and improving the performance of fabricated biosensors. The possible factors that affect the biosensing performance of these carbon materials were evaluated comprehensively and comparatively based on the characterization of their physical parameters. The biosensor based on GMC-6 displayed excellent analytical performance over a wide linear range along with good stability and selectivity for the detection of hydrogen peroxide. The “entrapment” immobilization mode and “interspace confinement effect” (by restraining the unfolding or conformational change of enzyme molecules from inactivation) provided by GMC can result in pore-size-dependent enzymatic stability and bioactivity, which might be a crucial factor for the superior biosensing performance of GMC-6 to that of CNTs and GMC-13. Graphitized ordered mesoporous carbons with good pore size matching for enzymes proved to be a promising electrochemical biosensing platform.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in soils and sediments from Daliao River Basin, China

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) were analyzed in surface sediments and top soils collected from 30 sites in Daliao River Basin. The concentrations of PCDD/F ranged from 0.28 to 29.01 ng TEQ kg(-1) dw (mean value, 7.45 ng TEQ kg(-1)dw) in sediments, and from 0.31 to 53.05 ng TEQ kg(-1)dw (mean value, 7.00 ng TEQ kg(-1)dw) in soils. PCDD/F pollution in sediments from the mid- and downstream sections of Hun River was found to be relatively heavy, and the levels of PCDD/F contamination in paddy soils were generally higher than those of upland soils. Using multivariate statistical analysis, the PCDD/F homologue and congener profiles of all soil and sediment samples were compared with those of suspected PCDD/F sources. The results showed that, PCDD/F contamination in most sediments of Hun River should mainly originated from the production of organochlorine chemicals, while metal smelting was the important potential source of PCDD/F in the drainage area of Taizi River. PCDD/F contamination in paddy soils should be simultaneously attributed to the polluted water irrigation and the organochlorine pesticide application.

Destruction of Polychlorinated Aromatic Compounds by Spinel-Type Complex Oxides

Destruction of polychlorinated aromatic compounds was carried out over spinel-type catalysts XY2O4 (where X = Mg, Ca, Cu, Ni, Zn, and Y = Al, Fe). The catalysts were characterized by XRD, nitrogen adsorption-desorption isotherms and FTIR. The performance of these catalysts toward the decomposition of hexachlorobenzene (HCB) and octachlorodibenzo-p-dioxin (OCDD) was evaluated in a closed system. The spinel-type catalyst with mesoporous structure demonstrated high catalytic activity for the hydrodechlorination of polychlorinated aromatic compounds. Among them, the copper-aluminum spinel (CuAl2O4), specifically calcined at 600 degrees C, exhibited the best activity. More than 85% dechlorination efficiency of HCB and 99% decomposition of polychlorinated dibenzodioxin (PCDD) were achieved at 250 degrees C for 30 min over the above catalyst which was more effective than the corresponding metallic copper and copper oxide catalysts during the thermal degradation of polychlorinated aromatic compounds. The correlation of catalytic performance to structural characteristics is discussed based on the detailed characterization. The simple preparation procedure and reasonable cost of the spinel-type catalysts present a good potential for the thermal treatment of polychlorinated aromatic pollutants at lower temperatures.