On-chip generation and detection of electrochemiluminescence

A miniaturized and fully integrated probe for analytical assays based on electrochemiluminescence (ECL) is proposed. It combines both, the electrode transducer and the photodetector in a single 5x6 mm(2) silicon chip. The device accommodates two identical cells, each consisting of a gold interdigitated microelectrode array (IDA) resting on top of a pn photodiode, and of which one is used as an active cell and the other as a dummy. Light-intensity measurements are taken in a differential mode to increase the overall system performances. The device was characterized using ruthenium (II) tris(2,2'-bipyridyl) and tripropylamine as model system. The influence of both, the pH and the electrode to electrode distance on the response was investigated. The highest signal intensities were detected in a phosphate buffer solution of pH 7.5 and an IDA gap of 0.8 mu m. Excellent correlation was achieved between the peak light intensity and the concentration of the ruthenium complex over a 0.5-50 mu M concentration range. (C) 1998 Elsevier Science B.V.