pH is a fundamental parameter controlling physicochemical processes in environmental systems. Cloud droplet pH controls the dissolution of important micronutrients (iron, phosphorus) which in turn affects the biological carbon pump and ultimately global climate. Using bulk cloud/fog water pH measurements to represent the whole pH spectrum can potentially lead to large errors in climate models. Optochemical sensors (optodes and nanosensors) have been developed for numerous analytes and applications. Optodes for pH however, are typically limited to biomedical applications due to their small pH sensing range (2 – 4 pH units). In this work, pH sensing optodes were developed ultimately combined into a single pH sensing optode with an extended range of pH 1-11. The optode material properties were re-designed to allow for the collection, storage and analysis of individual droplets on the sensor surface. Core-shell pH nanosensors were also developed and used to map the pH distribution within the model organism Daphnia magna, the pH along the gut was found to range from pH 5.8 – 7.2. Finally, a device (electrostatic precipitator) for collecting individual cloud/fog droplets was designed and constructed. The electrostatic precipitator was used in conjunction with the optodes to deposit and measure pH in standard (artificial) cloud/fog droplets under laboratory conditions.