| A biosensor can be defined as a device that incorporates a biological sensing element combined with a transducer. The biosensor is usually composed of three parts: a detector, a transducer and a signal conditioner. Biosensors, which connect a biological recognition to a physical or chemical transduction, have proved to be promising the advantage in the field of food analysis, environmental monitoring, drug delivery and diagnosis ofhealth related issues, toxicity measurement, protein engineering, DNA sequencing, genetic analysis, cellular localization, cell identifi cation and sorting, detection of pathogens and so on. There are many types of biosensor, electrochemical and fluorescence sensors have attracted great attention due to their simple operation, high detection sensitivity, good selectivity and easy miniaturization. In order to improve the response performance of these two kinds of sensor, the introduction of carbon nanomaterial is a good choice. Graphene materials have stimulated intense research and development in the field of sensing due to its attractive properties. Due to their low-cost and good biocompatibility properties, carbon dots have recently attracted considerable research interest in a wide range of application. We successfully constructed two kinds of graphene-based electrochemical biosensors and a kind of carbon dots-based fluorescent sensors and studied their application in the detection of biological molecules. Paper main content is as follows:(1) After a brief overview of biosensor, two kinds of carbon materials:graphene and carbon dots were introduced. Then the contribution of these kinds of materials in electrochemistry and fluorescence was summarized, respectively. Finally, the outline and innovation of this dissertation were proposed.(2) Multilayer films containing graphene (Gr) and chitosan (CS) were prepared on glassy carbon electrodes with layer-by-layer (LBL) assembly technique. After being characterized with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM), the electrochemical sensor based on the resulted films was developed to simultaneously determine dopamine (DA) and uric acid (UA). The LBL assembled electrode showed excellent electrocatalytic activity towards the oxidation of DA and UA. In addition, the self-assembly electrode possessed an excellent sensing performance for detection of DA and UA with a linear range from 0.1 μM to 140 μM and from 1.0 uM to 125 μM with the detection limit as low as 0.05 μM and 0.1 μM based on S/N=3, respectively.(3) We demonstrate a highly efficient method to fabricate pencil lead/graphene core-shell electrode (PGCE) as a multifunctional sensor platform via in situ electrochemical exfoliation of pencil lead in sodium sulfate aqueous. The gradual formation of graphene deformed from graphite on pencil lead surface not only provide a large surface area, a fast electron transportation for the target species, but also effectively create an integration of graphene-graphite detection system without complex process of electrode modification. When dopamine was chosen as the testing sample, its determination can be sensitively achieved with a detection limit of 29 nM (S/N=3), even in the presence of high concentrations of interfering materials such as ascorbic acid and uric acid.(4) Carbon nanodots (CDs) were first fabricated by one-pot theremal treatment of glucose and glycine. We demonstrate a novel fluorescent sensor for multi-molecule detection based on the selectivity quenching of Fe3+ and polymer nanodots CDs. The oxygenants such as hydrogen peroxide (H2O2), potassium permanganate (KMnO4), and potassium dichromate (K2Cr2O7) could be detected by the decrease of the fluorescence intensity for the formation of Fe3+- CDs when they were present in the system of Fe2+- CDs. Similarly, the reducers could be detected according to the increased fluorescence intensity as they were existed in the system of Fe3+-CDs. We choose H2O2 as an example and the detection limit is calculated to be 0.0612 μM. |
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