Electrochemiluminescence devices based on Novel materials for Biosensors

The main objective of this thesis was to discover highly efficient, cost effective and environmental friendly electrode material for the detection of Ruthenium Tris Bypiridil (Ru(bpy)32+) using ElectroChemiLuminescence (ECL) technique. In this regard different novel materials, Carbon NanoTubes (CNT), Bismuth oxide (Bi2O3), Bismuth oxychloride (BiOCl), Bi2O3/CNT composite, BiOCl/CNT composite, Carbon Fiber (CF), Silicon Carbide (SiC) and Biomass material, have been utilized as a working electrode (WE) in the ECL analysis. Throughout the ECL experiments, gold (Au) were used as an auxiliary electrode and silver/silver chloride (Ag/AgCl) were used as a reference electrode. Concerning CNT working electrode, self-standing cylindrical-shaped Multi-Walled Carbon NanoTubes (MWCNT) were grown by means of chemical vapour deposition (CVD) system. The bundles were initially back contacted with copper wire and then encapsulated into epoxy resin to provide electrical insulation. During the measurements, it was observed that emission of light is periodic and it last for hundreds of voltammetric cycles. The efficiency was found out to be far better than commercially used Glassy Carbon (GC) working electrode, used as a benchmark. The only problem with CNT was the non-reproducibility which we don’t have in case of GC. The analysis showed that, even they are not cost-effective and environmental friendly; they are highly efficient and can be considered as disposable electrode material for ECL based biosensor platforms. On the other hand, different bismuth based materials were investigated as a WE in ECL experiments. Initially, Bi2O3, BiOCl and their composite with CNT were used to make different kind of pellets and then the process of electrical connection and encapsulation was performed. The ECL analysis showed that it is possible to have light emission with all bismuth based working electrodes but with lower intensities. Bismuth is considered to be cheap and less toxic then glassy carbon but the efficiency of bismuth based electrodes were found out to be lesser than glassy carbon. CF is now reached to a maturity level and they represent a growing industry with multitude of applications. Due to large surface area and high electrical conductivity, CF is widely used as electrode material for various applications. In order to exploit these properties, CF was also used as WE for ECL analysis. During the analysis, it has been noticed that the light emission were almost constant with very low deviation. The light emission with CF electrode was found to be even better than the standard glassy carbon electrode (GCE) used as benchmark. Sensitivity, bio-compatibility and low cost are the main characteristics which make CF a potential candidate for the future biosensor platforms. The superior bio-electric properties of SiC make it an ideal candidate for bio-electrodes. The SiC is considered to be one of the most favourable bio-compatible materials due to its hydrophilicity and rich surface chemistry. In this work three different kinds of SiC material; (1) SiC with SiO2 shell (2) SiC without SiO2 shell (3) SiC thin film, were used as working electrodes. The light emission with all these electrodes was found to be quite strong and stable in time. Biomass, are considered to be one of the best resources for the production of cost-effective and environmental friendly products. These solid wastes have the peculiarity of producing low ash and high carbon contents through the process of pyrolyzation and activation. In this work we have used Bamboo and Pistachio Nut Shells (PNS), two biomass materials, as a precursor for making working electrodes. Bamboo sticks were initially pyrolyzed, using metal oxide chemical vapour deposition (MOCVD) system. This work was carried out in order to prove the possibility of using less expensive carbon based electrodes for ECL analysis. It has also been showed the possibility of making electrodes through biomass materials. Initially bamboo was pyrolyzed in an argon fluxed oven at 850°C. In order to attain a high amount of purity, the surface of the resulted pyrolysed bamboo sticks were cleaned with an acid attack. The purity was later confirmed by XPS and TGA analysis. The experimental analysis showed that the bamboo electrodes have outstanding electrochemical properties than standard GC electrodes, even if they are lacking good reproducibility. The tubular structure of bamboo was found to be a vital factor for such higher ECL emissions and stability. In order to use PNS as working electrode in ECL experiments, initially, it was carbonized at 500°C for 2 hours by using Chemical Vapour Deposition (CVD) apparatus. Consequently, the Carbonized Pistachio Nut Shells (CPNS) were activated with KOH at 900°C in Argon atmosphere. Field Emission Scanning Electron Microscopy (FESEM) analysis confirmed the grain size, structural porosity, activation with KOH and elemental composition. The experimental analysis showed that the ECL efficiency and stability with CNPS electrodes are comparable with GC electrodes but like bamboo they are also lacking good reproducibility. The very low cost of the raw material combined with such good results make them good candidates for future ECL based disposable biosensor platforms.