Metal-organic Frameworks- Based Electrochemical Sensors

Metal-organic frameworks(MOFs) are a new class of porous materials, which have unique physicochemical properties, such as ease of functionalization, large surface area, extra high porosity, open metal sites, etc. In this paper, nickel(II) terephthalic acid Ni(pdc), nickel(II) benzene-1,4-dicarboxylate metal-organic frameworks/single-walled carbon nanotube(Ni(bdc)/SWCNT), manganese(II) benzene-1,4-dicarboxylate metal-organic frameworks/single-walled carbon nanotube(Mn(bdc)/SWCNT) composite were prepared and characterized by scanning electron microscopy(SEM), fourier-transform infrared(FT-IR) and X-ray diffraction(XRD) methods, using to construct highiy sensitive and selective electrochemical sensors. The preared biosensors were used for electrochemical determination of glucose and Pb2+. The main works is concisely described as followed:(1) In this work, nickel(II) terephthalic acid(Ni(bdc)) metal organic-frameworks(MOFs)was synthesized through a facile template-free hydrothermal method. Then the hybrid material of Ni(bdc) and chitosan(CS) was cast on the glassy carbon electrode(GCE) to get a modified electrode(Ni(bdc)-CS). Cyclic voltammetric methods were used to investigate the catalytic properties of the sensor. Meanwhile, the electrocatalytic oxidation to glucose of biosensor was also investigated. The electrochemical study showed that the Ni(bdc) metal organic-frameworks exhibited the high catalytic effect on the glucose oxidation. Under optimized conditions, the oxidation peak currents for glucose electro-oxidation were linearly to concentrations in the range of 20.0 μmol/L ~ 5.9 mmol/L, the detection limit of the sensor was 4.4 μmol/L(signal-to-noise ratio(S/N) of 3).(2) A novel composite consisted of nickel(II) benzene-1,4-dicarboxylate metal-organic frameworks(Ni(bdc)) and single-walled carbon nanotube(SWCNT) was synthesized by ultrasonication, showing excellent water dispersibility and stability. Then the composite was dropped on a glassy carbon electrode to prepare a modified electrode(Ni(bdc)-SWCNT-CS/GCE), and used to fabricate an enzyme-free amperometric glucose. Cyclic voltammetric and amperometric methods were used to investigate the catalytic properties of the sensor for glucose electro-oxidation in alkaline media. Under optimized conditions, the enzymeless sensor exhibited excellent performance for glucose analysis selectively, offering a much wider linear range(from 20.0 μmol/L to 5.0 mmol/L), an extremely low detection limit(4.4 μmol/L, signal-to-noise ratio(S/N) of 3), highly sensitivity and selectivity. Importantly, the combination of large specific surface area and high electrical conductivity makes Ni(bdc)-SWCNT-CS/GCE highly promising as an electrocatalyst platform.(3) A novel composite consisted of manganese(II) benzene-1,4-dicarboxylate metal-organic frameworks(Mn(bdc)) and SWCNT was synthesized via a one-step chemical synthesis approach for fabricated Pb2+ sensor. Then the composite was cast on a glassy carbon electrode to prepare a modified electrode(Mn(bdc)-SWCNT-CS/GCE). A novel differential pulse anodic stripping voltammetry was developed for determination of lead. The main parameters, including supporting electrolyte, p H, accumulation potential and deposition time have been investigated in detail. Under the optimum conditions, the oxidation peak current displayed a good linear relationship with Pb2+ concentration over a range from 0.1 μmol/L to 14.0 μmol/L with the limit of detection 0.038 μmol/L based on S/N = 3.