The present work aims the development of photoluminescence based analytical methods for the determination of toxic analytes (methylmercury and formaldehyde) and for temperature sensing. The probes and methods proposed allow, under adjusted conditions, selective determinations with competitive limits of detection and simple procedures when compared to those methods reported in literature. In terms of temperature sensing, probes performed with sensitivity and prompt reversibility in solutions, also showing good potential when immobilized in polymeric films. In the first part of this work the preparation, characterization and studies of spectroscopic properties of a trivalent rare earth beta-diketonate complex [Eu(tta)4](Et3NH) is presented aiming to produce a method to enable the determination of methylmercury in produced water. The structural characteristic of the complex along with a liquid-liquid extraction procedure enable high selectivity towards the analyte and limit of detection (LOD) of 0.059 micrograma L-1. The second part of this work aimed to develop new nitrogen-doped silver modified graphene quantum dots (N-GQDs-Ag) that, after structural and optical characterization, was used as a probe to determine formaldehyde contamination in milk. Selectivity was achieved by probing formaldehyde in the vapor phase as the N-GQDs-Ag dispersion was used in a headspace single-drop microextraction procedure. Limit of detection in milk was 5.5 x 10-3 g L-1. Finally, [Eu(tta)4](Et3NH), N-GQDs-Ag and the recently reported benzothiadiazole derivative 4-(4-methoxyphenoxy)-7-styrylbenzo[c][1,2,5]thiadiazole (LASOC 460) were evaluated as probes for the sensing of temperature variation with better performance for the N-GQDs-Ag.