An Enzyme-Free Amperometric Sensor Based on Self-Assembling Ferrocene-Conjugated Oligopeptide for Specific Determination of L-Arginine

Main observation and conclusion An enzyme-free amperometric sensor based on a heptadecapeptide possessing an electroactive ferrocene(Fc)linker as ferrocene-Gly-Gly-Gly-Gly-Phe-Gly-His-Ile-His-Glu-Gly-Tyr-Gly-Gly-Gly-Gly-Lys-(CH_(2))_(4)-dithiocyclopentane self-assembled on gold substrate was designed and fabricated for specific determination of L-arginine(L-Arg).The detection mechanism is based on conformational change of surface-immobilized peptide induced by the target L-Arg,which was confirmed via SEM,TEM,AFM,XPS,and SPR studies.The binding affinity and the recognition feasibility of immobilized specific and non-specific peptides were also assessed using electrochemical impedance spectroscopy(EIS),cyclic voltammetry(CV),and differential pulse voltammetry(DPV).The proposed method can serve as“signal-on”sensor for detection of L-Arg down to 31 pmol/L with broad linear range(0.0001 to 10μmol/L).Furthermore,the Fc-conjugated specific peptide sensor was successfully applied to the determination of L-Arg in pig serums with a recovery rate of 97.5%—106.9%,and its test results are in good agreement with that of chromatographic instrument,evidencing that the oligopeptide-based sensor can be served as a simple and enzyme-free biosensing platform towards L-Arg for future application.

Highly Sensitive and Selective Amperometric Sensor for Iodate Based on 9,10-Phenanthrenequinone Derived Graphene

We reported on a new amperometric sensor for the sensitive and selective determination of iodate in table salt. The iodate sensor was constructed by the integration of a novel nanocomposite which was made from 9,10-phenanthrenequinone（PQ） and graphene（GP） with a glassy carbon electrode（GCE）. The synthesized graphene and the nanocomposite were well characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, Fourier transform infrared（FTIR） spectroscopy and Raman spectroscopy. We fully studied the electrochemical beha- vior and kinetic characteristics of the PQ/GP nanocomposite at GCE. The PQ/GP electrode shows a good electrochemical catalytic activity towards the reduction of iodate, which makes itself a sensitive and selective electrochemical sensor for iodate. The iodate sensor displays a high sensitivity（1.04 p.A.tamol.L-1）, a low detection limit（1.0X 10-8 mol/L）, a rapid response（less than 2 s）, and a broad linear range（from 5.0X 10-8 mol/L to 6.0X 10-3 mol/L ）. In addition, the sensor is interference free. The practical application of the proposed sensor was tested by the detection of iodate in table salt.

A Novel Amperometric Nitric Oxide Sensor Based on Polythionine/Nation Modified Glassy Carbon Electrode

A novel amperometric sensor for the determination of nitric oxide was developed by coating polythionine / nation on a glassy carbon electrode. This sensor exhibited a great enhancement to the oxidation of nitric oxide. The oxidation peak currents were linear to the concentration of nitric oxide over the wide range from 3.6×10^-7 to 6.8×10^-5 mol·L^-1, and the detection limit was 7.2×10^-8 mol·L^-1. Experimental results showed that this nitric oxide sensor possessed excellent selectivity and longer stability. NO releasing from rat kidney was monitored by this sensor.

A CMOS detection chip for amperometric sensors with chopper stabilized incremental △∑ ADC

This paper presents a low noise complimentary metal-oxide-semiconductor（CMOS） detection chip for amperometric electrochemical sensors.In order to effectively remove the input offset of the cascaded integrators and the low frequency noise in the modulator,a novel offset cancellation chopping scheme was proposed in the Incremental AS analog to digital converter（IADC）.A novel low power potentiostat was employed in this chip to provide the biasing voltage for the sensor while mirroring the sensor current out for detection.The chip communicates with FPGA through standard built in I2 C interface and SPI bus.Fabricated in 0.18-μm CMOS process,this chip detects current signal with high accuracy and high linearity.A prototype microsystem was produced to verify the detection chip performance with current input as well as micro-sensors.

A Study on the Full-Solid-State Electrochemical Systems for Amperometric Carbon Dioxide Gas Sensor Devices

A new type of solid polymer electrolyte based on polyacrylonitrile (PAN )-dimethylsulfoxide (DMSO)-tetrabutylammonium perchlorate (TBAP) system has been prepared. The ionic conductivities of such solid-electrolytes reach values as high as 10-4 S. cm-1 at room temperature. At proper content of each component in the solid-electrolyte the polymeric film has a porous network microstructure of three dimen-sions,and exhibits a good level of mechanical properties and dimensional stability. The full-solid-state elec-trochemical cell contains two coplanar electrodes coated by a thin layer of PAN-DMSO-TBAP solid-elec-trolyte: a Au microdisk as working electrode and a Ag ring counter/reference electrode. This study has shown that the integrated two-electrode assembly can be directly used for the amperometric solid-state car-bon dioxide gas sensor devices,and it shows good response characteristics for direct amperometric determi-nation of the CO2 concentration in the gas phase. Also, such full-solid-state amperometric sensor devices possess their own original advantages.

Fabrication of nanocomposite electrochemical sensors with poly(3,4-ethylenedioxythiophene)conductive polymer and Au nanoparticles adsorbed on carboxylated nanocrystalline cellulose

Au nanoparticles(AuNPs)were prepared by reducing HAuCl4 with NaBH4,and then adsorbed uniformly on the surface of carboxylated nanocrystalline cellulose(CNCC).The obtained AuNPs/CNCC particles were doped into a conductive polymer of poly(3,4-ethylenedioxythiophene)(PEDOT)to yield a highly conductive nanocomposite,which was deposited onto a glassy carbon electrode(GCE)by an electrochemical method.The PEDOT/AuNPs/CNCC nanocomposite showed low electrochemical impedance and good electrocatalytic activity toward ascorbic acid.Based on this novel nanocomposite material,an amperometric sensor was developed for the detection of ascorbic acid with a detection limit as low as 0.29μM.When operated at-0.15 V,the sensor detected ascorbic acid in the range of 0.88μM to 15000μM.

A high precision CMOS weak current readout circuit

This paper presents a high precision CMOS weak current readout circuit.This circuit is capable of converting a weak current into a frequency signal for amperometric measurements with high precision and further delivering a 10-bit digital output.A fast stabilization-enhanced potentiostat has been proposed in the design, which is used to maintain a constant bias potential for amperometric biochemical sensors.A technique based on source voltage shifting that reduces the leakage current of the MOS transistor to the reverse diode leakage level at room temperature was employed in the circuit.The chip was fabricated in the 0.35 μm chartered CMOS process, with a single 3.3 V power supply.The interface circuit maintains a dynamic range of more than 100 dB.Currents from 1 pA to 300 nA can be detected with a maximum nonlinearity of 0.3% over the full scale.