Study On Nanostructures Based Ru（bpy）₃²⁺ Solid-State Electrochemiluminescence Sensors

Electrochemiluminescence (abbreviated ECL), combining chemiluminescence and electrochemistry, is a powerful analytical technique. This technique makes use of electrochemically formed excited state to generate optical signal when the ecited state returns to its ground state. Therefore, the ECL has the advantages of high sensitivity from electrochemiluminescence and potential controllability from electrochemistry, and has becoming an important and active research field in modern bioanyltical chemistry. Among the ECL species, the first reported ruthenium bipyridine complex and its derivatives have been proved to be the most valuable and potential applicable optical probes. However, these species are expensive, and solution phase based ECL sensors find their limited application. While immobilization of Ru(bpy)32+onto electrode surfaces forming solid-state ECL could save the cost, and simplify the experimental design. Therefore, solid-state ECL has been extensively applied to construct gene, immunosensors, and used as sensitive optical detector coupled to microfluidics systems and microarray sensors. So far, many methods have been proposed to immobilize Ru(bpy)32+, including entrapment, adsorption, self-assembly and coating. However, the solid-state ECL sensors using the above methods are not stable and controllable due to the easy leakage and uncertainty of optical generating species in the solid state phase. To these issues to be addressed, this doctoral thesis will concentrate on developing effective method to immoblize ECL species, increasing functional density, designing novel ECL probes with high sensitivity and stability. The results can be summarized as following:1. One-step immobilization of Ru(bpy)32+in silica matrix for the construction of solid-state electrochemiluminescence sensor with excellent performanceAn electrochemically induced sol-gel process has been proposed to efficiently immobilize Ru(bpy)32+in a three-dimensional (3D) porous silica film matrix on a glassy carbon electrode (GCE). In this electrochemically process, electrolysis of GCE from a solution containing ammonium fluorosilicate and Ru(bpy)32+at cathodic potential voltage reduces water to hydroxyl ions and hydrogen bubbles. The former product catalyzes the hydrolysis of ammonium fluorosilicate to form silica film efficiently encapsulated with Ru(bpy)32+ complex and the simultaneously evolved hydrogen bubbles act as dynamic soft template in forming porous silica matrix. In this approach, large quantity of Ru(bpy)32+ ions can be efficiently encapsulated in the porous silica matrix, and the porous structure offers good mass transport path, accordingly, the fabricated Ru(bpy)32+ solid-state electrochemiluminescence sensor shows high sensitivity and stability towards the determination of tri-n-propylamine (TPA). The present approach is promising for various molecules and nanoparticles encapsulation and could find wide application in construction of sensors and biofuel cells.2. Enhanced electrochemiluminescence efficiency of Ru(Ⅱ) derivative covalently linked carbon nanotubes hybridNowdays, one-dimensional nanostructured materials have been widely studied due to their potential applications in nano-scaled optical and electrical devices. As one of the representative materials, carbon nanotubes (CNTs) with unique structural, superior mechanical and excellent electronical properties, have been extensively explored for numerous applications in field emission, molecular electronics, and biomedicine. The applications can be further broadened by functionalizing the surface properties of CNTs. On the other hand, electrochemiluminescence (ECL) has been proven to be a powerful detection technique. The ECL signal may be significantly improved by immobilizing luminophores on electrode surfaces, forming solid state ECL detectors. A number of approaches have been attempted. However, such ECL detectors usually lack long-term stability due to the leakage of the luminophores. The ruthenium complex was used as a model molecule for constructing high performance solid state ECL sensors. In order to covalently bind this luminophore to CNTs, a Ru(bpy)3 derivative with free amine group was synthesized. The covalent reaction between the amine group of Ru(bpy)3 derivative and the carboxyl group from the functional carbon nanotubes results in successful immobilization of luminophores on carbon nanotubes. The resulted Ru-CNTs hybrid shows good electrochemical activity and ca. 17 times higher luminescence quantum efficiency than the adsorbed Ru(bpy)3 derivative on CNTs. The Ru-CNTs based ECL sensor exhibits high stability toward determination of TPA with a detection limit as low as 8.75 pM, which is 3 orders of magnitude lower than that of reported film. The present Ru-CNTs hybrid could be used as both electrochemical and luminescent labels for ultrasensitive bioanalysis.3. Synthesis and characterization of a novel type ruthenium bipyridine derivativesMany species can produce electrochemiluminescence, among which Ru(bpy)32+ and its derivatives are first reported and most widely studied. Self-assembly refers to the organization of two-dimensional (2D) arrays and three-dimensional (3D) networks by attractive forces or chemical bond formation. Solution-based self-assembly has been reported to provide a means for the integration of functional mesoscopic devices and macroscopic materials. Room-temperature ionic liquids (RTILs) are widely known as functional materials and media with promising applications, especially as a new "green" solvent, due to the excellent conductivity, low melting temperature, uninflammability, more widely potential window of electrochemical stability than any other supporting electrolytes. In this section, a ruthenium derivative Ru(bpy)3(BPh4)2 was synthesized via a solution-based self-assembly strategy. The properties of the resultant complex have been characterized using UV-Vis spectroscopy, NMR, flurescence spectroscopy and electrochemical methods. It is found that the complex has excellent electrochemical activity and electrochemiluminescence properties when dissolved in RTILs. The electrochemiluminescence can be effectively enhanced by using TPA as coreactant. The present novel complex is promising for the construction of ECL sensors in organic phase.