Luminescence Studies and some of Its Applications

Lanthanide luminescence has wide applicability in both solid and solution state luminescence studies. The process of ligand sensitized luminescence has not only enhanced the lanthanide fluorescence but also found wider applicability in the field of immunoassay and drug delivery apart from probing the site of binding or complexation. The lanthanide fluorescence enhancement not only depends on the complexing ability of the ligand but also depends on the position of the complexing/binding site. A study of the Terbium luminescence with a number of aromatic acid ligands brings out the role of the position of the carboxylic group in the aromatic ligand. The aromatic acid ligands like bdiketones enhance the lanthanide by nearly three orders of magnitude but use of a secondary ligand like TOPO in a micellar environment enhances further the lanthanide luminescence by another order. The complexation of lanthanide is not restricted to the simple ligands with a carboxylic group as it can complex with large molecules like DNA and in the process the DNA itself can be estimated. However here, use of TOP does not enhance any luminescence as the DNA molecule is too large to be contained within the micellar cavity to entrap the lanthanide complex. Apart from its applicability in the medical science, the lanthanide luminescence can also be applied in the industrial environment. In the power industry, the cooling water system plays a major role with respect to microbial corrosion. The sulphur reducing bacteria is a common species found in almost all the cooling water systems of India though Iron bacteria is found only in selected sites. The bacterial population is generally found through the colony counting methodology and for the first time we have reported the luminescence/fluorescence from the Iron bacteria in the cooling water system. Though the luminescence from Iron bacteria is recorded, its luminescence intensity visa vis its population is yet to be standardised despite the fact that the originating moiety with respect to Iron bacteria luminescence is the Tryptophan. Another important application of luminescence in recent times is in the field of Industrial Safety. The development of afterglow phosphors that emit light in absence of an exciting source for 8-10 hours has revolutionized the industrial Safety. In addition to it studies have indicated that white light emission also can be obtained from the afterglow phosphors. Another industrial application of luminescence is in the field of power plant chemistry where the flow through condenser is few meter cube of water per second. In the event of biofouling, the better way of getting practical information in the field is the measurement water flow through the condenser. However, this is an uphill task as flow meters are generally not available to measure the water flow of this magnitude and here the application luminescence is handy. This manuscript discusses the application of luminescence in all these fields. 1. LANTHANIDE FLUORESCENCE