Bowan Wu

Acetylsalicylic acid electrochemical sensor based on PATP–AuNPs modified molecularly imprinted polymer film

A novel electrochemical sensor based on molecularly imprinted polymer film has been developed for aspirin detection. The sensitive film was prepared by co-polymerization of p-aminothiophenol (p-ATP) and HAuCl(4) on the Au electrode surface. First, p-ATP was self-assembled on the Au electrode surface by the formation of Au-S bonds. Then, the acetylsalicylic acid (ASA) template was assembled onto the monolayer of p-ATP through the hydrogen-bonding interaction between amino group (p-ATP) and oxygen (ASA). Finally, a conductive hybrid membrane was fabricated at the surface of Au electrode by the co-polymerization in the mixing solution containing additional p-ATP, HAuCl(4) and ASA template. Meanwhile, the ASA was spontaneously imprinted into the poly-aminothiophenol gold nanoparticles (PATP-AuNPs) complex film. The amount of imprinted sites at the PATP-AuNPs film significantly increases due to the additional replenishment of ASA templates. With the significant increasing of imprinted sites and doped gold nanoparticles, the sensitivity of the molecular imprinted polymer (MIP) electrode gradually increased. The molecularly imprinted sensor was characterized by electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV). The linear relationships between current and logarithmic concentration were obtained in the range from 1 nmol L(-1) to 0.1 μmol L(-1) and 0.7 μmol L(-1) to 0.1 mmol L(-1). The detection limit of 0.3 nmol L(-1) was achieved. This molecularly imprinted sensor for the determination of ASA has high sensitivity, good selectivity and reproducibility, with the testing in some biological fluids also has good selectivity and recovery.

A novel molecularly imprinted impedimetric sensor for melamine determination

A novel molecularly imprinted (MIP) impedimetric sensor was promoted for selective detecting melamine (MEL). The Au electrode modified with MIP poly (2-mercaptobenzimidazole) (PMBI) was prepared by electrochemical polymerization of 2-mercaptobenzimidazole (2-MBI) with cyclic voltammetry (CV) in the presence of template molecule MEL. The surface morphology and structure of MIP PMBI are characterized by atomic force microscopy (AFM), infrared spectra (IR), electrochemical impedance spectroscopy (EIS), and CV. The main driving force of recognition is the π-donor-acceptor interaction between MEL and PMBI. The imprinted electrode could avoid the interference successfully. In addition, a linear response curve was obtained from 1.0×10(-8) M to 5.0×10(-5) M, with the detection limit of 3.0×10(-9) M. The sensor exhibits remarkable advantages, such as higher sensitivity, wider linear range and lower detection limit. The effective method has a potential application to monitor nonelectrochemically active substances in food analysis in the future.

Determination of explosives based on novel type of sensor using porphyrin functionalized carbon nanotubes

The hydroxide of meso-tetraphenylporphyrin derivatives functionalized carbon nanotubes (CNTs) was fabricated in our research to explore the interaction between porphyrin and explosive. It was turned out that in the formation of grid porphyrin film, carbon nanotubes as a cruciul base materials promoted the electron transfer rate. Most of important, the results also showed that the electrochemical response was enhanced through increasing the number of -OH substitution in porphyrin. Such information provides the platform for a practical strategy for rational design of the sensor of explosives.

Heterogeneous Consecutive Electron Transfer at Graphite Electrodes under Steady State

In this report, the theory based on thin-layer cyclic voltammetry (TLCV) for consecutive electron transfer (ET) across the interface between two immiscible electrolyte solutions (ITIES) is well developed and experimentally verified. The voltammetric responses to multistep electron transfer at the ITIES are predicted by numerical simulations. Moreover, the impact of empirical parameters on the shape of the multistep current-voltage curve has been examined. The results obtained not only give information regarding the effect of the concentration ratio of the reactants in two phases and the thin-layer thickness on multistep electron transfer, but also prove the excellent agreement between simulations and experiments. The model system of two-step electron transfer of ZnTPP/[Fe(CN)₆]⁴⁻ was studied, indicating that the Bulter-Volmer (B-V) theory is suitable for the consecutive electron transfer. Thus, TLCV is demonstrated to be a useful means for investigating the kinetics of heterogeneous consecutive ET.

A molecularly imprinted electrochemical enzymeless sensor based on functionalized gold nanoparticle decorated carbon nanotubes for methyl-parathion detection

Functionalized gold nanoparticles (FuAuNP) have potential applications because of their specific functional groups. p-Aminothiophenol (p-ATP) possesses double functional groups that can be used to form an S–Au bond and oligoaniline. Based on molecular imprinting technology and electrochemical technology, a novel enzymeless methyl-parathion (MP) sensor has been constructed with nanocomposites. The template molecule (MP) is embedded in the imprinting sites by p-ATP molecular self-assembly and FuAuNP electro-polymerization. The imprinting effective sites and the conductive performance are improved by gold nanoparticles decorated carbon nanotube nanocomposites (AuNP–MCNT). The linear relationships between peak current and MP concentration are obtained in the range from 0.1 to 1.1 ng mL−1 and 1.1 to 11 ng mL−1, respectively. The detection limit can be achieved as low as 0.08 ng mL−1 (3σ) with relative standard deviation of 3.8% (n = 5). This sensor was also applied for the detection of MP in apples and vegetables, with average recoveries between 95.2% and 105.7% (RSD < 5%). The results mentioned above show that the novel electrochemical sensor is an ideal device for the real-time determination of MP in real samples.

A valuable visual colorimetric and electrochemical biosensor for porphyrin.

Porphyrin is able to specifically combine with phosphorus, thus a novel bifunctional sensing platform for determination of porphyrin by visual colorimetry and electrochemistry was demonstrated. A pretreated gold sheet (or electrode) with 2-mercatpoethanol (2-ME) was chemically modified by POCl(3) to obtain the surface phosphate active sites. The different stages of modified electrode were characterized by electrochemical impedance spectroscopy (EIS). The 1:1 cationic sitting-atop (SAT) complex P(V)-porphyrin was formed due to the high affinity of the modified gold sheet (or electrode) towards the porphyrin, resulting in electron transfer resistance increase of the electrode surface. Meanwhile, a dramatic color changing from burgundy to dark green of porphyrin solution was observed with the naked-eye within 3s. Whats more, this was reflected by the notable change of the Soret band of porphyrin when using UV-vis. Two sensing systems provide different sensitivity for porphyrin analysis. With visual colorimetry, porphyrin can be detected at a level of 1.0×10(-6) M, whereas the detection limit of porphyrin is 3.0×10(-8) M using the EIS method. The practical application of the sensor to determination of pheophytin which was obtained from fresh spinach leaves has been accomplished. The results demonstrate the facility and effectivity of our introduced bifunctional biosensor for quantitative analysis of porphyrin.