Metal organic framework MIL-53(Fe) as an efficient artificial oxidase for colorimetric detection of cellular biothiols.

Biothiols play critical roles in many biological processes and their aberrant is related to a variety of syndromes. A simple and reliable colorimetric method is developed in this work for biothiols detection based on an oxidase mimic, a metal organic framework (MOF) MIL-53(Fe), and a peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB). In this design, MIL-53(Fe) is utilized to catalyze the conversion of TMB to a blue colored 3,3',5,5'-tetramethylbenzidine diimine, which can be read on a spectrophotometer at 652 nm. The oxidation-induced blue color generation can be efficiently inhibited by biothiols, thus a colorimetric analytical method is proposed for biothiols detection based on the above system. Under optimal conditions, a linear relationship in a range from 1 to 100 µM and a limit of detection (LOD) at 120 nM are achieved with Cys as a model target. The developed platform is further applied to evaluate cellular biothiols in normal (RWPE-1) and cancer (LNCap) cell lines, revealing that the overall biothiols level in LNCap is much higher than that in RWPE-1. This work renders a powerful tool for identifying cancer cells in a simple manner for biomedical diagnosis associated with biothiols.

Constructing high effective nano-Mn3(PO4)2-chitosan in situ electrochemical detection interface for superoxide anions released from living cell.

Monitoring superoxide anions in living cells have attracted much academic and biomedical interest due to their important role in metabolic processes. Herein, we confined ultra-small nano-Mn3(PO4)2 in chitosan and designed a unique puffy woven sphere consisted by nanowires. Further constructed an effective in situ detection chip using the as-synthesized nano-Mn3(PO4)2-chitosan for electrochemical sensing of superoxide anions from murine breast tumor cells (4T1). The excellent biocompatibility of chitosan and large size of the Mn3(PO4)2-chitosan spheres greatly reduced the damage and toxicity of the detection interface to the living cells, while the ultra-small nano-Mn3(PO4)2 in chitosan could effectively catalyze the superoxide anions released from cells. The nano-Mn3(PO4)2-chitosan-based sensor exhibited high sensitivity (1.6 µA µM-1), low detection limit (9.4 nM at S/N = 3) and good selectivity for O2•-. After cell culture on the surface of nano-Mn3(PO4)2-chitosan based electrode. As a miniature analytical and sensing platform, results further suggest that the prepared chip offers a more sensitive detective superoxide anions (O2•-) released from 4T1 cell lines than traditional electron paramagnetic resonance (EPR) analysis.

Center-iodized graphene as an advanced anode material to significantly boost the performance of lithium-ion batteries.

Iodine edge-doped graphene can improve the capacity and stability of lithium-ion batteries (LIBs). Our theoretical calculations indicate that center-iodization can further significantly enhance the anode catalytic process. To experimentally prove the theoretical prediction, iodine-doped graphene materials were prepared by one-pot hydrothermal and ball-milling approaches to realize different doping-sites. Results show that the center-iodinated graphene (CIG) anode exhibits a remarkably high reversible capacity (1121 mA h g-1 after 180 cycles at 0.5 A g-1), long-cycle life (0.01% decay per cycle over 300 cycles at 1 A g-1) and high-rate capacity (374 mA h g-1 after 800 cycles at 8 A g-1), which greatly improves the performance of the edge-iodinated graphene anode and these results are in good agreement with the theoretical analysis. More importantly, the CIG anode also delivers a high-rate capacity and excellent cycling stability (279 mA h g-1 after 500 cycles at 10 A g-1) in full-cells. Both the theoretical analysis and experimental investigation reveal the enhancement mechanism, in which the center-iodization increases the surface charge for fast electron transfer rate, improves the conductivity for charge transport and rationalizes the pore structure for enhanced mass transport and ion insertion/desertion, thus resulting in a high rate capacity and long cycle life. This work not only discloses the critical role of catalytic sites including both amounts and site positions but also offers great potential for high-power rechargeable LIB applications.

Design and synthesis of Co-N-C porous catalyst derived from metal organic complexes for highly effective ORR.

In this work, we reported a novel and slack rose-like metal organic precursor designed by coordinating p-phenylenediamine with cobalt ion. After subsequent pyrolysis and acid etching process, the as-prepared Co-N-C catalyst delivered a superior catalytic activity and long-term durability. Further applied in the Zn-air battery, it also displayed a comparable performance with 20% Pt/C.

Nanostructured cobalt phosphates as excellent biomimetic enzymes to sensitively detect superoxide anions released from living cells.

Monitoring superoxide anion radicals in living cells has been attracting much academic and industrial interest due to the dual roles of the radicals. Herein, we synthesized a novel nanostructured cobalt phosphate nanorods (Co3(PO4)2 NRs) with tunable pore structure using a simple and effective micro-emulsion method and explored their potential utilization in the electrochemical sensing of superoxide anions. As an analytical and sensing platform, the nanoscale biomimetic enzymes Co3(PO4)2 NRs exhibited excellent selectivity and sensitivity towards superoxide anion (O2•-) with a low detection limit (2.25nM), wide linear range (5.76-5396nM), and long-term stability. Further, the nanoscale biomimetic enzyme could be efficiently applied in situ to electrochemically detect O2•- released from human malignant melanoma cells and normal keratinocyte, showing excellent real time quantitative detection capability. This material open up exciting opportunities for implementing biomimetic enzymes in nanoscale transition metal phosphates and designing enzyme-free biosensors with much higher sensitivity and durability in health and disease analysis than those of natural one.

Bimetal-organic-frameworks-derived yolk-shell-structured porous Co2P/ZnO@PC/CNTs hybrids for highly sensitive non-enzymatic detection of superoxide anion released from living cells.

We report a general approach for the synthesis of yolk-shell-structured porous dicobalt phosphide/zinc oxide@porous carbon polyhedral/carbon nanotube hybrids (Co2P/ZnO@PC/CNTs) derived from bimetal-organic frameworks, and explore their potential utilization in the electrochemical sensing of superoxide anions. Beyond our expectation, the trace level of O2˙- released from living cells has also been successfully captured by our designed sensor. The presented strategy for the controlled design and synthesis of bimetal-organic frameworks-derived functional nanomaterials offers prospects of developing highly active electrocatalysts in non-enzyme sensors.

Platanus hispanica-inspired design of Co-carbon nanotube frameworks through chemical vapor deposition: a highly integrated hierarchical electrocatalyst for oxygen reduction reactions.

In this communication, a novel platanus hispanica-like, highly integrated hierarchical electrocatalyst, with Co-carbon nanotubes anchored through porous Co embedded carbon sphere frameworks (Co-CNTFs), was fabricated using a chemical vapor deposition (CVD) method. More importantly, the prepared Co-CNTFs demonstrate even better activity than commercial Pt electrocatalysts in an alkaline medium. This presented CVD approach provides an effective way to grow metal-CNTs in situ through various metal-complex-derived functional nanomaterials and can be expanded to metallic oxide, metallic sulfide, and metallic phosphide, among others, to introduce carbon nanotube frameworks with a multitude of potential applications.

Carbon nanotubes implanted manganese-based MOFs for simultaneous detection of biomolecules in body fluids.

Metal-organic frameworks (MOFs) have recently attracted much interest in electrochemical fields due to their controlled porosity, large internal surface area, and countless structural topologies. However, the direct application of single component MOFs is limited since they also exhibit poor electronic conductivity, low mechanical stability, and inferior electrocatalytic ability. To overcome these problems, we implanted multi-walled carbon nanotubes (MWCNTs) into manganese-based metal-organic frameworks (Mn-BDC) using a one-step solvothermal method and found that the introduction of MWCNTs can initiate the splitting of bulky Mn-BDC into thin layers. This splitting is highly significant in that it enhances the electronic conductivity and electrocatalytic ability of Mn-BDC. The constructed Mn-BDC@MWCNT composites were utilized as an electrode modifying material in the fabrication of an electrochemical sensor and then were used successfully for the determination of biomolecules in human body fluid. The sensor displayed successful detection performance with wide linear detection ranges (0.1-1150, 0.01-500, and 0.02-1100 µM for AA, DA and UA, respectively) and low limits of detection (0.01, 0.002, and 0.005 µM for AA, DA and UA, respectively); thus, this preliminary study presents an electrochemical biosensor constructed with a novel electrode modifying material that exhibits superior potential for the practical detection of AA, DA and UA in urine samples.

Self-assembly of three-dimensional interconnected graphene-based aerogels and its application in supercapacitors.

Homogeneously distributed self-assembling hybrid graphene-based aerogels with 3D interconnected pores, employing three types of carbohydrates (glucose, ß-cyclodextrin, and chitosan), have been fabricated by a simple hydrothermal route. Using three types of carbohydrates as morphology oriented agents and reductants can effectively tailor the microstructures, physical properties, and electrochemical performances of the products. The effects of different carbohydrates on graphene oxide reduction to form graphene-based aerogels with different microcosmic morphologies and physical properties were also systemically discussed. The electrochemical behaviors of all graphene-based aerogel samples showed remarkably strong and stable performances, which indicated that all the 3D interpenetrating microstructure graphene-based aerogel samples with well-developed porous nanostructures and interconnected conductive networks could provide fast ionic channels for electrochemical energy storage. These results demonstrate that this strategy would offer an easy and effective way to fabricate graphene-based materials.

A green and facile route for constructing flower-shaped TiO2 nanocrystals assembled on graphene oxide sheets for enhanced photocatalytic activity.

We have demonstrated an environmentally friendly in situ assembly method for the preparation of novel three-dimensional TiO2/graphene oxide (TiO2/GO) nanostructures with favorable flower-shaped architectures. Very little information on such a morphology of TiO2/GO nanostructures is available in the literature. The as-synthesized sample was characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, N2 adsorption-desorption measurements and Raman spectroscopy. Also the TiO2/GO composites exhibited enhanced photocatalytic properties.

Environment-friendly biomimetic synthesis of TiO2 nanomaterials for photocatalytic application.

We have demonstrated an environment-friendly biomimetic synthesis method for the preparation of TiO(2) nanomaterials with different crystal phases and morphologies. This is the first time that it has been found that the crystal phase of TiO(2) can be controlled just by using different biotemplates, and cannot be changed by calcination up to 750 °C. In our experiment, anatase TiO(2) was obtained by using yeast and albumen templates, while rutile TiO(2) was formed by using dandelion pollen as the template.