Mild chemical processes of various analytes and detection methods involving revolutionary strategies in the fields of analytical chemistry, biology and environmental sciences have been extensively developed. This critical review focuses on representative examples of mild chemical processes that can be used in fluorescent chemodosimeters for ion sensing (anions and cations). A systematisation according to the type of reaction mechanism is established. Numerous examples including extensions combined with catalytic and material sciences applicable in fluorescence imaging and water treatment are also discussed (151 references). This critical review focuses on advances in various mild chemical processes that can form the basis of fluorescent chemodosimeters for anions and cations, as well as catalytic and material science application in fluorescence imaging and water treatment.