OPT'2007, 20 - 22 June 2007, Kharkiv, Ukraine New trends in analytical applications of aqueous electrogenerated chemiluminescence Yu. T. Zholudov, M. M. Rozhitskii Kharkov National University of Radio Electronics, Kharkov, Ukraine Abstract: We give brief overview of new approaches and amphiphilic molecules and polymers. Since most known technologies for fabrication of electrochemiluminescent (ECL) inaqueous electrochemiluminescers do not form Langmuir devices for different application. New method of ECL generation in monolayers at the air/water interface they should be included aqueous mediums as well as results of recent experiments and their into electrochemicaly inert matrix of amphiphilic molecules or potential applications, including highly sensitive optical analysis of polymer. liquid mediums, will be presented and discussed. polymer. In our study we used LB films of polymeric matrix Electrogenerated chemiluminescence (ECL) is a kind of non- polymethylmethacrylate (PMMA) with incorporated optically excited luminescence due to sequential electrochemiluminescer rubrene deposited onto transparent electrochemical and recombination processes in ITO covered glass electrodes. The electrochemical and ECL electrochemiluminescent device during electrolysis in solutions measurements were done in bidistilled water with of organic luminescers [1]. Mentioned phenomenon can be tripropylamine (TPA) as a coreactant and LiCl04 as a used as powerful analytical tool in biology, medicine, ecology supporting electrolyte in usual three electrode electrochemical . - - ~~~~~~~cell using c clic voltammetr method Fi . 1 The 75 mm and other areas. With the emergence of new fabrication g y ry m (g ) technologies the miniature ECL sensors became widely spread ITO coated glass substrates with deposited LB films of rubrene [2, 3]. served as working electrodes of the cell. The potential scan vas Classical ECL systems are mostly based on nonaqueous done in the range 0 - +1.25 V vs. Ag/AgCl reference electrode ECL compositions and use recombination ECL processes, i.e. at 100 mV/s. Platinum foil was used as an auxiliary electrode. the excited luminescer molecules are produced from Electrochemical Potentiostat recombination of radical ions electrogenerated at the electrode. m r The appearance of aqueous ECL, important for different pg biomedical and ecological applications, was due to discovery of water soluble electrochemiluminescers (first of all luminol - XI Y rcorde 3-amino-phtalhydrazide and ruthenium tris(2,2'-bipyridine) 2 complex, other ruthenium and osmium complexes are much i 1 3 less spread) as well as due to utilization of ECL reactions with WI X o coreactants. The latter solves the problem of simultaneous generation of electrochemiluminescer's radical anions and cations that is difficult due to narrow available potential window of the water (caused by its electrolysis decomposition). ECL reactions with coreactants allow using only one form of radical ion - cation or anion generated on the electrode, the corresponding counter-ion is produced by the Fig. 1. Scheme of experimental setup. 1 - working coreactant due to its oxidation/reduction by electrode and/or electrode; 2 - reference electrode; 3 -auxiliary electrode. radical ion of the electrochemiluminescer. We have investigated substrates covered with 1, 3, 5, 15 and In order to overcome limitations implied by aqueous ECL 50 LB monolayers of PMMA containing 20 molar percents of systems there can be used immobilization Of rubrene. Results for maximal electrochemical current and ECL electrochemiluminescer at the working electrode of the ECL photocurrent for different samples of ITO electrodes are given cell. This can be done by different methods that allow on Fig. 4. It is clearly seen that the curve of electrochemical deposition of organic films. The examples of ECL from the current through the films has several regions with different films on the electrode containing electrochemiluminescer slope. This can be explained by interplay between different molecules are known [4-7]. In our previous works [8] we mechanisms of charge transfer through LB films with proposed deposition of Langmuir-Blodgett (LB) films with incorporated electroactive molecules (rubrene) [9]: transfer of incorporated electrochemiluminescers on the working electrode charge through molecular orbitals of rubrene due to its of ECL sensor to allow use of water-insoluble oxidation/reduction, tunneling of charge through the whole electrochemiluminescers which considerably extend range of film, direct oxidation/reduction of coreactant at the electrode substances that can be used for ECL generation. LB method due to its diffusion through pinholes or its penetration into LB allows deposition of ordered monomolecular films of film if the latter has insufficient packaging of molecules 29