Nanoparticle assembled microcapsules for application as pH and ammonia sensor

The encapsulation of molecular probes in a suitable nanostructured matrix can be exploited to alter their optical properties and robustness for fabricating efficient chemical sensors. Despite high sensitivity, simplicity, selectivity and cost effectiveness, the photo-destruction and photo-bleaching are the serious concerns while utilizing molecular probes. Herein we demonstrate that hydroxy pyrene trisulfonate (HPTS), a pH sensitive molecular probe, when encapsulated in a microcapsule structure prepared via the assembly of silica nanoparticles mediated by poly-l-lysine and trisodium citrate, provides a robust sensing material for pH sensing under the physiological conditions. The temporal evolution under continuous irradiation indicates that the fluorophore inside the silica microcapsule is extraordinarily photostable. The fluorescence intensity alternation at dual excitation facilitates for a ratiometic sensing of the pH, however, the fluorescence lifetime is insensitive to hydrogen ion concentration. The sensing scheme is found to be robust, fast and simple for the measurement of pH in the range 5.8–8.0, and can be successfully applied for the determination of ammonia in the concentration range 0–1.2 mM, which is important for aquatic life and the environment.

HPTS encapsulated nanoparticle assembled microcapsule is exploited as dual excitations ratiometic pH sensor. This nanoparticle assembled microcapsule based fluorescence sensor can determine ammonia and offers a robust, simple and fast sensing material.Figure optionsDownload as PowerPoint slideHighlights
► A novel HPTS encapsulated nanoparticle assembled microcapsule is developed.
► Its dual excitation facilitates a ratiometic pH sensor.
► It is successfully applied for the determination of ammonia.
► It provides a robust, simple and fast sensing material.