Photoelectrochemical Sensing Based on Zr鄄MOFs for Homocysteine Detection北大核心CSCD

Due to the independent form of the light source and detection system, photoelectrochemical (PEC) sensor has the advantages of low background, high sensitivity and simple operation. So far, PEC systems have been widely used in the fields including the actual detection of metal ions, biological antibodies or antigens in environmental pollutants. When the photosensitive material is irradiated by a light source with an energy being equal to or greater than its band gap, electrons (e-) transition occurs from the valence band to the conduction band, leaving a hole (h+), at the same time, the generated electron-hole pair (e-/h+) separate, and migrate to the electrode surface and electrolyte to generate photocurrent or photovoltage. When the target analyte is added, it will interact with its recognition molecule, and affect the separation or migration process of the charge, thereby, causing a change in the photocurrent. Metal organic framework (MOF) is a material composed of metal ions and organic linking groups. They have adjustable porosity, functional surface and massive conjugate back bone. These unique characteristics of MOF have been extensively explored in various fields. Zr-MOFs were synthesized use 4-carboxyphenylporphyrin (TCPP) as the ligand, and metal zirconium (Zr) as the coordination metal. Using Zr-MOFs as the photoelectrically active material, a cathode photoelectrochemical sensor was constructed to detect homocysteine (Hcy). A three-electrode system, consisting of Zr-MOFs/FTO electrode, Pt electrode and Ag/AgCl electrode, was inserted into 0.01 mol窑L-1 HEPES solution to prepare the sensor. An aqueous solution of homocysteine was added to the electrolyte, allowing it to stand for 5 min. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the reaction process and the electron transfer process between optoelectronic materials. When the Xe lamp with 姿 > 420 nm is used to irradiate Zr-MOFs, electrons (e-) in the valence band transfer to the conduction band, and holes (h+) are generated in the valence band, thereby, generating light current. The addition of homocysteine will hinder the transfer of electrons, causing the cathode photocurrent to be decreased. The prepared sensor had good linear responses in the ranges of 10 ~ 100 nmol窑L-1 and 100 ~ 1000 nmol窑L-1, and the detection limit was 2.17 nmol窑L-1. The sensor also exhibited good stability and selectivity. The prepared cathode photoelectric sensor could sensitively and efficiently detect homocysteine in milk. The studied high-performance photoelectric active materials and chemical sensing platforms may be important for the design of other chemical sensing platforms and the development of PEC applications. © 2021 Authors. All rights reserved.     

A novel method to prepare SPR sensor chips based on photografting molecularly imprinted polymer

A novel method to prepare surface plasmon resonance(SPR) sensor chips based on grafted imprinted polymer is explored. Benzophenone photografting system is used to grow molecularly imprinted polymer(MIP) films from the modified surface of gold substrate.The surface morphology and thickness of MIP films were investigated by scanning electronic microscope(SEM).The adsorption properties of sensor chip were studied by SPR spectroscopy.The results demonstrate that nano-MIP films can be constructed on the surface of gold substrate with the good adsorption of template molecules.     

Imprinted Polymeric Film-Based Sensor for the Detection of Dopamine Using Cyclic Voltammetry

The imprinted polymeric film was synthesized on the glass-carbon electrodes dlrectly. The response to the template molecule-dopamine and other molecules with similar structure was measured by cyclic voltammetry. The response of dopamine on imprinted electrode was much higher than that of other molecules,because of the existing of micro-cavities in polymeric rdm fitting with the size and shape of dopamine in the imprinted polymer.Experimental results showed that dopamlne can be enriched by the imprinted film, therefore increasing the sensitivity of the sensor. The imprinted film could also efface the interference of ascorbic acid, indicating that dopamine can be determined with a large excess of ascorbic acid.     

Sensitive and selective molecularly imprinted electrochemical sensor based on multi-walled carbon nanotubes for doxycycline hyclate determination

An electrochemical sensor for doxycycline hyclate(DC)detection with high sensitivity and good selectivity is reported.The sensor was fabricated by electro-polymerization of molecularly imprinted polymers(MIPs)in the presence of DC onto multi-walled carbon nanotubes modified glassy carbon electrode(MWCNTs/GCE).The MWCNTs can significantly increase the current response of the sensor,leading to enhanced sensitivity.The MIPs provide selective recognition sites for DC detection.The experimental parameters,such as the polymer monomer concentration,supporting electrolyte pH,the time for electro-polymerization and the incubation time of the sensor with DC were optimized.Under optimized experimental conditions,the sensor displayed a linear range of 0.05μmol/L-0.5μmol/L towards DC detection,with the detection limit of 1.3×10^-2μmol/L.The sensor was successfully applied for recovery test of DC in human serum samples.     

利用Cu0/多壁碳纳米管纳米复合物修饰玻碳电极快速非酶法检测葡萄糖和果糖(英文)

A nonenzymatic electrochemical sensor for glucose and fructose was fabricated that contained a glassy carbon electrode modified with a copper oxide (CuO)/multiwalled carbon nanotube (MWCNT) nanocomposite. The electrochemical properties of the CuO/MWCNT‐modified glassy carbon electrode were investigated. Two distinguishable anodic peaks were observed around 0.30 and 0.44 V corresponding to the oxidation of glucose and fructose, respectively, at the surface of the modified electrode. The detection limits for glucose and fructose were both 0.04 mmol/L. The sensor was used to simultaneously determine the concentrations of glucose and fructose in hydrolyzed sucrose samples, and to measure glucose in blood serum samples, demonstrating its potential as a nonenzymatic carbohydrate sensor.     

Rapid,simple and selective determination of 2,4-dinitrophenol by molecularly imprinted spin column extraction coupled with fluorescence detection

A rapid, simple and selective method based on molecularly imprinted, spin column extraction coupled with fluorescence detection was successfully established for the determination of 2,4-dinitrophenol in serum samples. The 2,4-dinitrophenol imprinted polymers exhibited highly selective recognition for the template molecule and the maximum adsorption capacity was 138.9 mg/g. The results indicated that when water is used as the loading solution, only 2,4-dinitrophenol could be adsorbed on the spin column without the remaining structural analogs（2-nitrophenol, 4-nitrophenol and phenol）. After eluting with acetonitrile/acetic acid（9/1, v/v）, 2,4-dinitrophenol in serum samples could be determined by using the fluorescence spectrometer, based on the fluorescence enhancement of fluorescein by the template molecule. Under the optimal conditions, the spiked recovery ranged from 95.8% to 103.4% and the detection limit was 1 nmol/L. The results confirmed the reliability and practicality of the protocol and revealed a good perspective of this method for biological sample analysis.     

Glucose biosensor based on new carbon nanotube-gold-titania nano-composites modified glassy carbon electrode

In this paper, a novel biosensor was prepared by immobilizing glucose oxidase （GOx） on carbon nanotube-gold-titania nanocomposites （CNT/Au/TiO2） modified glassy carbon electrode （GCE）. SEM was initially used to investigate the surface morphology of CNT/Au/TiO2 nanocomposites modified GCE, indicating the formation of the nano-porous structure which could readily facilitate the attachment of GOx on the electrode surface. Cyclic voltammogram （CV） and electrochemical impedance spectrum （EIS） were further utilized to explore relevant electrochemical activity on CNT]Au/TiO2 nanocomposites modified GCE. The observations demonstrated that the immobilized GOx could efficiently execute its bioelectrocatalytic activity for the oxidation of glucose. The biosensor exhibited a wider linearity range from 0.1 mmol L-1 to 8 mmol L^-1 glucose with a detection limit of 0.077 mmol L^- 1.     

Electrochemical sensor for Cd2+ and Pb2+ detection based on nano-porous pseudo carbon paste electrode

An electrochemical sensor based on self-made nano-porous pseudo carbon paste electrode (nano-PPCPE) has been successfully developed, and used to detect Cd²⁺ and Pb²⁺. The results showed that the electrodes can quantitatively detect trace Cd²⁺ and Pb²⁺, and with satisfied limit of detection, which has great significance in electrochemical analysis and detection.     

A capacitive sensor based on molecularly imprinted polymers and poly(p-aminobenzene sulfonic acid) film for detection of pazufloxacin mesilate

A novel capacitive sensor for pazufloxacin mesilate (pazufloxacin) determination was developed by electropolymerizing p-aminobenzene sulfonic (p-ABSA) and molecularly imprinted polymers (MIPs), which was synthesized through thermal radical copolymerization of metharylic acid (MAA) and ethyl-ene glycol dimethacrylate (EGDMA) in the presence of pazufloxacin template molecules, on the gold electrode surface. Furthermore, 1-dedecanethiol was used to insulate the modified electrode. Alter-nating current (ac) impedance experiments were carried out with a Model IM6e to obtain the capaci-tance responses. Under the optimum conditions, the sensor showed linear capacitance response to pazufloxacin in the range of 5 ng·mL-1 to 5 μg·mL-1 with a relative standard deviation (RSD) 5.3% (n=7) and a detection limit of 1.8 ng·mL-1. The recoveries for different concentration levels of pazufloxacin samples varied from 94.0% to 102.0%. Electrochemical experiments indicated the capacitive sensor exhibited good sensitivity and selectivity and showed excellent parameters of regeneration and stabil-ity.     

Preparation and Electrochemical Characters of Parathion Molecule Imprinted Polymeric Sensors

A sensitive, fast and low-cost molecular imprinted polymeric sensor for quantitative determination of parathion was prepared with chitosan(CS) as function matrix and parathion(PT) as template molecule via constant potential electrochemical deposition. Sensitive response was obtained with a detection limit of 1.0×10–7 mol/L and an excellent recognition for PT was achieved due to the good memory capacity of the sensor. The developed sensor exhibited good fabrication reproducibility and acceptable stability, w...     

Glucose Biosensor Based on Carbon/PVC-COOH/Ferrocene Composite with Covalently Immobilized Enzyme

A carbon/PVC-COOH/ferrocene composite electrode used for the determination of glucose has been prepared. The ferrocene acted as mediator was incorporated into the PVC-COOH polymer and the leakage could be prevented. The presence of carboxyl groups on the electrode surface allowed immobilizing enzyme via EDC and NHS. The ratio of PVC-COOH to graphite powder （w/w） has been studied. Amperometric determination of glucose has been performed at potential of 0.30 V vs SCE. The response time was 〈 15 s. The linear response range was of 0.1-20 mmol/L with a detection limit of 48μmol/L.     

An electrochemical aptasensor based on cu2+-induced signal amplification strategy for the detection of ochratoxin aEI北大核心CSCD

A novel electrochemical aptasensor based on a Cu2+-induced signal amplification strategy was constructed for the rapid, sensitive and specific detection of ochratoxin A （OTA）. The OTA aptamer with poly （T） was hybridized with the captured DNA probe on the electrode surface. In the presence of Cu2+ and ascorbic acid, the end of poly（T） was used as a template to in situ grow copper nanoclusters （Cu NCs）. In the absence of targeted OTA, the gold electrodes after decorating Cu NCs were immersed into an acidic environment to release Cu2+. After enriching Cu2+ at a potential of − 1.6 V, the strongest current value of copper was recorded by measuring differential pulse voltammetry （DPV）. In the presence of OTA, the OTA aptamer was tightly bound to the target OTA. The OTA aptamer broke away from the electrode to reduce the growth of Cu NCs, resulting in lower DPV current response. This proposed method was employed to detect OTA with linear range from 0.1 to 50.0 ng/mL, and the detection limit was 41.2 pg/mL. The Cu2+-induced electrochemical aptasensor can be further applied in the analysis of target OTA in coffee solution samples. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Immobilization and Characterization of Glucose Oxidase on Single-Walled Carbon Nanotubes and Its Application to Sensing Glucose

The negatively charged （at pH 8.2） glucose oxidase （GOx, pI ca. 4.2） was assembled onto the surface of single-walled carbon nanotubes （SWNT）, which was covered （or wrapped） by a layer of positively charged polyelectrolyte poly（dimethyldiallylammonium chloride） （PDDA）, via the electrostatic interaction forming GOx-PDDASWNT nanocomposites. Fourier transform infrared （FTIR）, UV-Vis and electrochemical impedance spectroscopy （EIS） were used to characterize the growth processes of the nanocomposites. The results indicated that GOx retained its native secondary conformational structure after it was immobilized on the surface of PDDA-SWNT. A biosensor （Nafion-GOx-PDDA-SWNT/GC） was developed by immobilization of GOx-PDDA-SWNT nanocomposites on the surface of glassy carbon （GC） electrode using Nafion （5%） as a binder. The biosensor showed the electrocatalytic activity toward the oxidation of glucose under the presence of ferrocene monocarboxylic acid （FcM） as an electroactive mediator with a good stability, reproducibility and higher biological affinity. Under an optimal condition, the biosensor could be used to detection of glucose, presenting a typical characteristic of Michaelis-Menten kinetics with the apparent Michaelis-Menten constant of KM^app ca. 4.5 mmol/L, with a linear range of the concentration of glucose from 0.5 to 5.5 mmol/L （with correlation coefficient of 0.999） and the detection limit of ca. 83 μmol/L （at a signal-to-noise ratio of 3）. Thus the biosensor was useful in sensing the glucose concentration in serum since the normal glucose concentration in blood serum was around 4.6 mmol/L. The facile procedure of immobilizing GOx used in present work would promote the developments of electrochemical research for enzymes （proteins）, biosensors, biofuel cells and other bioelectrochemical devices.     

Electrochemical sensing of DNA immobilization and hybridization based on carbon nanotubes/nano zinc oxide/chitosan composite film

A novel electrochemical DNA biosensor based on zinc oxide （ZnO） nanoparticles and multi-walled carbon nanotubes （MWNTs） for DNA immobilization and enhanced hybridization detection is presented. The MWNTs/nano ZnO/chitosan composite film modified glassy carbon electrode （MWNTs/ZnO/CHIT/GCE） was fabricated and DNA probes were immobilized on the electrode surface. The hybridization events were monitored by differential pulse voltammetry （DPV） using methylene blue （MB） as an indicator. The sensor can effectively discriminate different DNA sequences related to PAT gene in the transgenic corn, with a detection limit of 2.8× 10^-12 mol/L of target sequence.     

A nonenzyme glucose sensor based on Cu/Ni/CMWCNTs nanocompositesEI北大核心CSCD

Copper-nickel bimetallic nanoparticles decorated on carboxylated multi-walled carbon nanotubes （Cu/Ni/CMWCNTs）were prepared by using a simple one-pot solvothermal method,which was then employed to construct a highly sensitive non-enzymatic glucose sensor. The modified electrode showed high sensitivity and stability in glucose detection,which was mainly attributed to the synergistic effect of the compact copper-nickel nanocomposite and carboxylated multi-walled carbon nanotubes that possessing high specific surface area to increase the number of active sites and to improve the electrocatalytic activity of the modified electrode. The phase structure and morphology of the material were characterized by X-ray diffraction and scanning electron microscope; the electrochemical performance of the sensor was studied by cyclic voltammetry and chronoamperometry. The sensor had a sensitivity of 1949.1 μµA·L/（mmol·cm2）for glucose detection in the linear range of 1.0-8000 μµmol/L at a potential of 0.55 V,and the detection limit was 0.2 μµmol/L. The sensor was also applied to measure the concentration of glucose in serum samples. The developed nanocomposites sensor has the potential prospect to monitor blood glucose. © 2023, Youke Publishing Co.,Ltd. All rights reserved.     

Preparation and Cyclic Voltammetry Characterization of Cu—dipyridyl Imprinted Polymer

Polymer capable of specific binding to Cu-dipyridyl complex was prepared by molecular imprinting technology. The binding specificity of the polymer to the template (Cu-dipyridyl complex) was in vestigated by cyclic voltametric scanning using the carbon paste electrode modified by polymer particles in phosphate buffer solution. Factors that influence rebinding of the imprinted polymer were explored. The result demonstrated that the cycllic voltammetry was an efficient approach to explore interactions between template and imprinted polymers.     

Surface-imprinted polymers in microfluidic devices

Molecularly imprinted polymers are generated by curing a cross-linked polymer in the presence of a template. During the curing process, noncovalent bonds form between the polymer and the template. The interaction sites for the noncovalent bonds become "frozen" in the cross-linking polymer and maintain their shape even after the template is removed. The resulting cavities reproduce the size and shape of the template and can selectively reincorporate the template when a mixture containing it flows over the imprinted surface. In the last few decades the field of molecular imprinting has evolved from being able to selectively capture only small molecules to dealing with all kinds of samples. Molecularly imprinted polymers (MIPs) have been generated for analytes as diverse as metal ions, drug molecules, environmental pollutants, proteins and viruses to entire cells. We review here the relatively new field of surface imprinting, which creates imprints of large, biologically relevant templates. The traditional bulk imprinting, where a template is simply added to a prepolymer before curing, cannot be applied if the analyte is too large to diffuse from the cured polymer. Special methods must be used to generate binding sites only on a surface. Those techniques have solved crucial problems in separation science as well as chemical and biochemical sensing. The implementation of imprinted polymers into microfluidic chips has greatly improved the applicability of microfluidics. We present the latest advances and different approaches of surface imprinting and their applications for microfluidic devices.     

Surface plasmon resonance sensor chips for the recognition of bovine serum albumin via electropolymerized molecularly imprinted polymers

In this paper,a surface plasmon resonance(SPR)sensor chip for detection of bovine serum album(BSA)was prepared by electropolymerization of 3-aminophenylboronic acid(3-APBA)based on molecularly imprinted polymer(MIP)technique.The surface morphology of MIP and non-imprinted(NIP)flms were characterized by scanning electroscopy(SEM).SEM images exhibited nanoscale cavities formed on the MIP films surface homogeneously due to the removal of BSA templates.The effects of pH,ion strength of rebinding BSA,the specific binding and selective recognition were studied for MIP films.Results indicated that the BSA-imprinted films exhibited a good adsorption of template protein(0.02–0.8 mg/mL)in0.05 mol/L sodium phosphate buffer at pH 5.0 with the limit of detection(LOD)of 0.02 mg/mL.     

Electorchemical Studies of Cytochrome c on Electodes Modified by Single—Wall Carbon Naotubes

Single-wall carbon nanotubes(SWNTs) modified gold electrodes were prepared by using two different methods.The electrochemical behavior of cytochrome c on the modified gold electrodes was investigated.The first kind of SWNT-modified electrode (noted as SWNT/Au electrode)was prepared by the adsorption of carboxylterminated SWNTs from DMF dispersion on the gold electrode.The oxidatively processed SWNT tips were covalently modified by coupling with amines (AET) to form amide linkage.Via Au-S chemical bonding,the self-assembled monolayer of thiol-unctionalized nanotubes on gold surface was fabricated so as to prepare the others SWNT-modified electrode (noted as SWNT/AET/Au electrode).It was shown from cyclic voltammetry cxperiments that cytochrome c exhibited direct electrochemical responses on the both electrodes, but only the current of controlled diffusion existed on the SWNT/Au electrode while both the currents of controlled diffusion and adsorption of cytochrome c occurred on the SWNT/AET/Au electrode.Photoelastic Modulation Infared Reflection Absorpthion Spectroscopy (PEM-IRRAS) and Quartz Crystal Microbalance (QCM) were employed to verify the adsorption of SWNTs on the gold electrodes.The results proved that SWNTs could enhance the direct electron transfer proecss between the electrodes and redox proteins.     

在3,4-二羟基肉桂酸介质中以多壁碳纳米管为传感器电催化检测L-半胱氨酸(英文)

A highly sensitive electrochemical sensor was prepared for the determination of L-cysteine using a modified multiwall carbon nanotubes paste electrode in the presence of 3,4-dihydroxycinnamic acid(3,4-DHCA) as a mediator, based on an electrocatalytic process. The results indicate that the electrode is electrocatalytically efficient for the oxidation of L-cysteine in the presence of 3,4-DHCA. The interaction between the mediator and L-cysteine can be used for its sensitive and selective determination. Using chronoamperometry, the catalytic reaction rate constant was calculated to be 2.37 × 102 mol–1 L s–1. The catalytic peak current was linearly dependent on the L-cysteine concentration in the range of 0.4–115 μmol/L. The detection limit obtained by linear sweep voltammetry was 0.25 μmol/L. Finally, the modified electrode was examined as a selective, simple, and precise new electrochemical sensor for the determination of L-cysteine in real samples.