This work describes the development of two advanced sensor platforms based on different spectroscopic techniques. The first, and the primary focus of this work, is an enhanced generic multi-analyte sensor platform for fluorescence-based sensors and the second is an absorbance-based portable sensor for the detection of nitrates in groundwater. A generic multi-analyte sensor platform can be applied to a broad range of areas such as food packaging and blood gas analysis. A multi-analyte optical sensor platform for enhanced capture of fluorescence was modelled, designed and fabricated. The sensor platform was developed using a range of microfabrication techniques. Films sensitive to oxygen, relative humidity and carbon dioxide respectively were developed for the context of indoor air-quality monitoring. Deposition methods for printing the sensor solutions onto the sensor platforms were also investigated. The sensor films and platforms were integrated into a working sensor chip with both a fluorescence intensity and phase fluorometric detection system. An absorbance-based portable sensor for the detection of nitrates in groundwater was also developed. This was based on the direct absorbance of UV-light by the nitrate ion. Other contaminants, which could be found in groundwater and interfere with the nitrate detection, such as humic acid and chlorides, were investigated and compensated for.