Oxygen (O2) molecule is of paramount importance in nature, and it takes part in several biological and chemical activities such as energy generation, cellular respiration, and food deterioration, to name a few. Detection of O2 concentration is of extreme importance in many application fields to monitor the above-mentioned activities. In the last decade, optical oxygen sensors have become a popular research topic due to the need for continuous, reversible, and non-destructive O2 sensing. Rational design of O2 sensing materials, optimal integration of reporter luminophore chemistry with the other sensor components (encapsulation matrix, support material, additives), and simple fabrication procedures are the main bottlenecks and challenges in producing simple and affordable optical O2 sensors with stable and predictable sensing performance. The traditional approach, such as developing metal ion-based luminophores and integrating these sensing units into organic/inorganic matrix have shown their utility in many optical O2 sensor systems. However, a high degree of toxicity of metal ions hampers the effective use of such systems in many application areas. Therefore, it is crucial to develop purely organic optical O2 sensors to overcome the above-mentioned problem. Although a few studies investigate the O2 sensing performance of organic optical O2 sensors, their lack of O2 sensitivity range and poor reversibility are two main drawbacks of these sensors. In this thesis, I study improving the O2 sensitivity range of organic optical O2 sensors with good sensing reversibility by developing diamine-based organic O2 sensing material and embedding these indicators within a polymer matrix.