| The development of nanomaterials and nanotechnology has been brought great revolution in physics, chemistry, biology and computer science. Nanomaterials become a hot spot of research due to their excellent electronic, optic and catalytic properties. Now, more and more attentions have been paid on preparation and application of nanomaterials composites.4-parapheneol, as one of the severely toxic substituted phenols, has threatened the healthy of people. Dopamine is one of the most important neurotransmitters which play vital role in the function of central nervous, renal, hormonal and cardiovascular system. L-Histidine plays a significant role in the growth and repair of tissues as well as in controlling the transmission of metal elements in biological bases. Therefore, it’s urgent to explore novel methods to sensitively and selectively measure the concentration of the molecules. However, due to the complexity of environment and biological conditions, several problems limits the effective detection of small molecules, such as merely low concentrations, severe interference from the coexist analogues. To overcome these problems, molecularly recognition technology, such as molecularly imprinted technology or radical, molecule and biomolecule modified technology, was applied in bioassay and biosensing.In this article, we focus on developing novel electrochemical sensors and fluorescent sensors to sensitive and selective detect small molecules (4-NP, DA, His). Novel nanomaterials such as graphene oxide, graphene quantum dot, DNA-scaffolded silver nanoclusters, were utilized in the studies. In some parts, molecule recognition technology was applied for promoting the selectivity and sensitivity of analytical methods. This article was divided into four chapters as follows: Chapter1. overviewThis part gave a comprehensive overview for the development and applications of several novel nanomaterials, such as graphene, graphene quantum dot and DNA-scaffolded silver nanoclusters. We put emphasis on the applications of nanomaterials in biosensing areas. Moreover, we introduce two important molecule recognition technologies in biosensors:molecularly imprinted technology and radical, molecule or biomolecule modified technology. These technologies were used for enhanced the ability of biosensors in molecule recognition. Finally, we expounded the significance and main contents of our article.Chapter2. A novel composite of graphene quantum dots and molecularly imprinted polymer for fluorescent detection of paranitrophenolIn this chapter, a novel composite of MIP-coated GQDs was successfully fabricated and an eco-friendly fluorescent sensor was constructed to selectively detect4-NP based on this composite. In the4-NP sensing system, GQDs acted as fluorophores and imprinted silica film provided specific binding sites for analytes. The novel composites were characterized by FT-IR and TEM. The fluorescence of MIP-coated GQDs was greatly quenched when interacted with4-NP. The results of experiments indicated that the MIP-coated GQDs composite combines the merits of imprinted silica materials and GQDs, showing fast kinetics, special binding sites, and improved fluorescence. The novel fluorescent sensor realized specific and selective detection of4-NP from its interferents. Moreover, the MIP-coated GQDs sensor had a wider linear range from0.02-3.00μg mL/1, and a low detection limit of0.009μg mL-1(S/N=3). The optical sensor was applied to the determination of4-NP in real water samples with satisfactory results.Chapter3. A selective dopamine biosensor based on graphene oxide and molecular imprinted polymers doped carbon paste electrodeIn this chapter, a graphene oxide doped molecular imprinted carbon paste electrode (GO-MIPs-CPE) was prepared by incorporating appropriate amounts of graphene oxide (GO) and molecular imprinted polymers in a paste mixture. GO, with excellent electro-catalysis and large area, has been demonstrated a good candidate for potential applications and electrode doping. Molecularly imprinted polymers (MIPs) possess high selectivity and affinity for the target molecule. Firstly, we prepared GO and MIPs doped carbon paste electrode (GO-MIPs-CPE) at optimized conditions. GO-MIPs-CPE was construct a electrochemical sensor for DA detection. Compared with GO-NIPs-CPE, GO-MIPs-CPE has a specific affinity to the template DA over other analogues, such as norepinephrine (NE), epinephrine (EP), ascorbic acid (AA), and uric acid (UA). The proposed method based on GO-MIPs-CPE had a wide linear range from0.05to300.0μM, with a detection limit low to0.02μM (S/N=3). Moreover, the sensor was also applied to the determination of DA in injections and human urine samples with satisfactory results.Chapter4. DNA-scaffolded silver nanoclusters/Cu2+ensemble:use as a turn-on fluorescent probe for histidineIn this chapter, a new type of rapid, sensitive, and selective fluorescence turn-on assay was developed for detection of histidine using DNA-scaffolded silver nanoclusters/Cu2+ensemble (DNA-AgNCs/Cu2+). Cu2+was first bound to the nucleic acid of the DNA-AgNCs forming DNA-AgNCs/Cu2+ensemble and then liberated to solution via the highly specific interaction between the histidine and Cu2+in the presence of histidine. The fluorescence of DNA-AgNCs was greatly quenched with the addition of Cu2+, then the DNA-AgNCs/Cu2+ensemble exhibited marvelous fluorescent enhancement in the presence of histidine, which showed the possibility for constructing the turn-on chemosensor of histidine. Compared to other methods, this approach promises high sensitivity, simplicity in design, and convenient operation, minimized organic solvents. The ultra-high selectivity demonstrated the feasibility of the assay for detecting histidine in sophisticated physical environment. The fitting range of the proposed assay is from0to100μM, with a detection limit of1.4μM (S/N=3). The protocol was evaluated by analysis of artificial urine sample with good recoveries and showed great potential for practical application. |
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