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In this thesis, an investigation on the influence of iron impurities on the optical properties of zeolites and the luminescence properties of silver-exchanged zeolites was performed. The main source of these impurities originates from the source materials used in the synthesis procedures, therefore, a comparative study on the optical purity between commercial zeolites and self-synthesized zeolites was performed. First, the influence of different synthesis procedures on the topology and crystal morphology of the self-made zeolites was determined. The followed procedures differed in silica source, organic template and overall batch composition. Each procedure contained multiple samples with a different crystallization time. Second, the presence of absorbing species, such as iron and organic components, was determined using DRS and ESR measurements. The DRS analysis gives direct information on the amount of absorbing species and the absorption region of the impurities. The relative concentration of iron in the zeolite was determined by ESR. Some of the self-synthesized samples were also subject to a post-synthesis treatment before the silver-exchange to extract the unavoidable trace amounts of iron impurities. After analyzing the physiochemical characteristics, the zeolites were exchanged with silver ions and a further thermal activation step was used to form the emissive silver clusters. These silver species are typically excited with UV light yielding a visible light emission and the corresponding quantum efficiency of emission (EQE) and the influence of the zeolite purity on it was studied in detail. In order to measure the EQE in a correct fashion, the exact position of the excitation and emission maxima of the silver-exchanged were determined using spectrofluorimeter. Based on the EQE and the 2D excitation-emission spectra obtained for the different samples the effect of several parameters, such as impurities, zeolite topology and counter-balancing ion on the l...