Luminescence-Sensitive Surfaces Bearing Ratiometric Nanoparticles for Bacteria Growth Detection

pH is one of the most fundamental parameters describing the quality of an aqueous solution. We developed a ratiometric fluorescent platform to monitor pH not only in solution but also on surfaces: our nanoprobe is based on fluorescent nanoparticles (FNPs) with a red-emitting BODIPY core and a pH-sensitive fluorescein derivative grafted on the outer shell. We demonstrated that a limited but controlled Fo''rster resonance energy transfer occurs between two fluorophores. Such pH-sensitive and ratiometric FNPs could be grafted on a silanized glass surface, still permitting the measurement of pH with good sensitivity and allowing the monitoring of Escherichia coli growth through optical measurements in physiological pH range.