Yang Tian

Electrochemical in-vivo sensors using nanomaterials made from carbon species, noble metals, or semiconductors

AbstractElectrochemical analytical methods have the advantages of simplicity, direct measurements, and ease of miniaturization which pave the way for real time detection and sensing. However, the complexity of living systems usually requires electrochemical sensors to display high selectivity, sensitivity, accuracy, biocompatibility and stability over time. Nanomaterials possess attractive properties in terms of surface modification, catalysis, and functionality. These open new avenues with respect to electrochemical enzymatic determination of neurochemicals such as dopamine, serotonin and ascorbate, biological small molecules such as H2O2 and metal ions such as copper(II) in-vivo. Three properties of nanomaterials make their use particularly attractive, namely the larger surface-to-volume ratio area, their unique surface, and the ease of electron transfer between enzymes and electrodes. These properties make them more sensitive, selective and stable. The article is subdivided into sections that cover applications of the following materials: carbonaceous materials (mainly carbon nanotube), noble metal particles (mainly gold and platinum particles), and semiconductor (mainly metal oxide) nanomaterials. A conclusion and outlook section addresses current chances and limitations. The review contains 99 references. FigureThree attractive properties of nanomaterials: the larger surface-to-volume ratio area, unique surface, and facilitating the electron transfer between enzyme and electrode, can improve the analytical performance of electrode, fulfilling the requirements in sensitivity, selectivity and stability for in vivo electrochemistry.

Earthworm-like N, S-Doped carbon tube-encapsulated Co9S8 nanocomposites derived from nanoscaled metal–organic frameworks for highly efficient bifunctional oxygen catalysis

Herein, a novel earthworm-like N, S-doped carbon nanotube-encapsulated Co9S8 hybrid was developed using the metal–organic framework (MOF) UiO-66-NH2 as a nanoscaled template via an immiscible two-phase incorporation. Highly efficient heteroatom-doping in graphene stacking generated a number of joints in the nanotubes, which harvested numerous defects as active sites for oxygen catalysis. Moreover, the Co9S8 nanoparticles were found to be tightly defined in the graphitic carbon shell, which were triggered by the spatial confinement of UiO-66-NH2. This nanostructure greatly enhanced the reaction kinetics and the stability of the catalyst. The carbon nanotube-Co9S8 composites via pyrolysis at 800 °C (Co9S8@CT-800) showed highly bifunctional catalytic activity for O2 catalysis processes. The low overpotential for ORR obtained for Co9S8@CT-800 was comparable to that of commercial Pt/C, and the small Tafel slope of 72 mV dec−1 for OER was better than that obtained for conventional RuO2. Density functional theory calculations revealed that the high activity of the developed nanocomposites for oxygen electrocatalysis in an alkaline medium was attributed to the synergistic effects of Co9S8 and the N-doped graphitic shell.

An Electrochemical Biosensor with Dual Signal Outputs: Toward Simultaneous Quantification of pH and O2 in the Brain upon Ischemia and in a Tumor during Cancer Starvation Therapy

Herein, we develop a novel method for designing electrochemical biosensors with both current and potential signal outputs for the simultaneous determination of two species in a living system. Oxygen (O2 ) and pH, simple and very important species, are employed as model molecules. By designing and synthesizing a new molecule, Hemin-aminoferrocene (Hemin-Fc), we create a single electrochemical biosensor for simultaneous detection and ratiometric quantification of O2 and pH in the brain. The reduction peak current of the hemin group increases with the concentration of O2 from 1.3 to 200.6 μm. Meanwhile, the peak potential positively shifts with decreasing pH from 8.0 to 5.5, resulting in the simultaneous determination of O2 and pH. The Fc group can serve as an internal reference for ratiometric biosensing because its current and potential signals remain almost constant with variations of O2 and pH. The developed biosensor has high temporal and spatial resolutions, as well as remarkable selectivity and accuracy, and is successfully applied in the real-time quantification of O2 and pH in the brain upon ischemia, as well as in tumor during cancer therapy.