Executive Summary : | Unravelling the non-contact, color-coded methods for monitoring the crucial physical parameter such as temperature is vital for continuous monitoring of temperature, the places where the conventional thermometers could not be used, wearable devices, to probe the exothermic or endothermic reactions that happen in the biological systems. In this regard, colorimetric or fluorescence changes against the temperature are an ideal pathway owing to the sensitivity of the technique, availability of numerous molecules and nanomaterials, and easy visualization without the requirement of any sophisticated instruments. The principle behind the changes in the absorption, absorbance, and or fluorescence is driven by the alternations in the ground or excited state properties of the molecules against the temperature and it would be possible to develop a quantitative structure-property relationship between these parameters. Thus, this proposal aims the development of organic fluorescent molecular-thermometers for wearable and biological applications. Although significant progress has been made, there remain some challenges to be addressed. For instance, conventional organic fluorophores are impotent to provide remarkable signal changes within a given temperature range and are prone to photo-bleaching upon continuous light irradiation; moreover, some of the fluorescence parameters (e.g., intensity and bandwidth) are easily affected by their residing environment, thereby limiting the sensitivity and accuracy of nano-thermometers. Thermo responsive polymers can amplify the signal responses of organic fluorophores to temperature variation by displaying a remarkable change in local hydrophobicity during phase transition. However, the broad transition temperature and slow transition process arising from the compositional heterogeneity compromise the sensitivity and responsiveness. In addition, most organic nano thermometers only rely on a single fluorescence parameter to reflect temperature variation, which does not allow for multi-parameter validation to ensure the reliability of temperature sensing. As such, it is still necessary to improve the sensitivity, reliability, and responsiveness of organic fluorescent nano-thermometers. Considering the above facts, this proposal aims to develop pyrene derivatives as molecular thermometer since pyrene is a well-known, versatile fluorescent molecule, ease of functionalization with judicious choice of substituents, and higher photostability. The changes in the -conjugation between the pyrene and substituents, electron or charge transfer process against the temperature will be used as a basis for the molecular thermometer. Further, the developed molecules could be incorporated as a probe in a wearable device and also in probing temperature in biological samples. |