PART I: Fluorescent Sensors for the Detection of Toxic Elements and Environmentally-Related Pollutants 1. Introduction 2. Strategies to improve sensitivity and selectivity PART II: Detection of Toxic Pollutants 3. Alkali and alkaline earth Metal sensing 4. Heavy Metals Sensing 5. Radio Nuclide Sensing 6. Anion Sensing 7. Gas Sensing 8. Volatile Organic Compound Sensing 9. Nitroaromatics Sensing 10. Biological molecules Sensing 11. Food toxins sensing 12. Miscellaneous Species Sensing 13. Challenges and future Prospects in fluorescent optical sensing