Application Of Metal Composites And Conjugated Polymer For Electrochemical Sensors

Electrochemical sensor is the most common detection device in the field of electrochemistry, owing to its high sensitivity, fast response, low price, and facile miniaturization. Currently, developing a novel electrochemical sensor with high sensitivity and stability is an essential aspect in electrochemical analysis. With the rapid development of technology, many kinds of materials including nanoparticles, metal particles, bioactive molecules, and conducting polymers have been used in electrochemical sensors. These novel materials give the sensor not only an enhanced sensitivity, but also some special functions.Composites, which combined with the property of each single material in it, can be used as electrocatalysts for sensor fabrication. The composites not only preserve the properties of each single-layer material, but also exhibit more advantages due to the synergetic effect. And more importantly, the performances of composites can be adjusted easily according to the experimental purposes by choosing proper single-layer material. In recent years, the metal composites are most widely used materials in electrochemistry. Various metal composites with high electrocatalytic activities can be achieved by combining the advantages of metal and substrate. And these metal composites based sensors tend to show enhanced sensing performances. On other hand, stability is an important measure of a sensor. Compared with coating or dipping method, electrochemical polymerization is a preferable method because the obtained polymerization film has good stability. Conjugated polymer has an extended π-orbital system, through which electrons can move from one end of the polymer to the other. The delocalization of electron induces conjugated polymer unusual properties such as electrical conductivity, low ionization potential, and high electron affinity. Therefore, conjugated polymer can be used for electrochemical sensor fabrication. Based on the above analysis, this paper aims at the preparation of electrochemical sensors with metal composites and conjugated polymers for drug and glucose sensing.1. A copper-poly(cysteine)(Cu-poly(Cys)) composite is achieved via a simple electrochemical method and subsequently exploited as an electrocatalyst for nitromidazole compound detection. This Cu-poly(Cys) composite combines the catalytic activity of copper and the stability of polymer, exhibiting electrocatalytic activity to the reduction of nitromidazole compound. The proposed sensor with high sensitivity and stability can be feasibly applied to detect nitromidazole compound in practical samples.2. A facile molecularly imprinted sensor for metronidazole electrochemical sensing is developed. In this sensor, the copper–melamine complex(Cu–Mel) is used as the functional monomer and metronidazole as the template. The electrochemical activity as well as film forming ability of the functional monomer can be enhanced by the use of Cu–Mel instead of melamine. During the imprinting process, the redox-active center containing copper is introduced into the composite, thus improving its sensitivity. And the recognition sites formed in the composite have the capability to distinguish target molecules through their size, shape, and functional group, thus improving its selectivity. Under optimum experimental conditions, the proposed sensor shows a good selectivity for metronidazole with a low detection limit of 0.12 μM.3. The propeller-like monomer, N,N’,N’’-1,3,5-tricarbazoloylbenzene(TCB), containing a phenyl ring as the central core and three carbazoles as the peripheral functional groups is synthesized. Subsequently, the polymer of TCB(poly(TCB), PTCB), is achieved via the electrochemical polymerization method and exploited as an electrocatalyst for non-enzymatic glucose detection. The rigid conjugated backbone of polycarbazole is beneficial for formation of a porous polymer with high physicochemical stability. Nitrogen-containing conjugated structure makes the polymer electron-rich, which may enhance the interaction between analyte and polymer. The electrocatalytic activity of carbazolyl unit still remains with the polymer. Therefore, the PTCB based sensor exhibits wide linear range, low detection limit, and stable response for glucose sensing.4. The starburst monomer, 4,4’,4’’-tri(N-carbazolyl)-triphenylamine(TCT), containing a triphenylamine as the central core and three carbazoles as the peripheral functional groups is designed and synthesized. Subsequently, the polymer of TCT(poly(TCT), PTCT) is achieved via the electrochemical polymerization method and exploited as an electrocatalyst for non-enzymatic glucose detection. The response to glucose is linear in the concentration range of 1.0–6000 μM. This strategy possesses two features superior to traditional methods. Firstly, this non-enzymatic glucose sensor effectively avoids the drawbacks of enzyme electrodes, including the insufficient stability and reproducibility. The second advantage is the use of non-metallic electrocatalysts for glucose oxidation, which can minimize the interference by toxic metal ions.