ABSTRACT
This chapter deals briefly with several topics related to ECL and its applications that were not covered in the previous chapters. It concludes with some ideas about future work in ECL.
II. LOW LEVEL EMISSION AND INVERSE PHOTOEMISSION
There are numerous examples of cases where very low levels of light are recorded during an ECL experiment, when the conditions, such as the applied potential range, seem inconsistent with accepted models for ECL. Such is the case for so-called preannihilation ECL mentioned in Chapter 1. One must be aware, however, that there are a number of processes that can produce low-level emission and that current technology allows the detection of light at exceedingly low levels. Thus trace impurities, either in the solution originally or formed in a decomposition reaction of an electrogenerated species, can sometimes act as coreactants. Weak chemiluminescence results from reactions of many organic compounds with oxygen [1]. In addition, there are a number of artifacts, such as the accumulation in solution of reaction products from the counter electrode or insufficient shielding of the counter electrode to prevent its possible light
emission from being detected by the photomultiplier or CCD, that can lead to reports of ECL at a working electrode under conditions that are difficult to explain. In general, one should be very cautious about experiments that produce apparent ECL at very low levels.
