Incorporating Fluorescent Nanomaterials in Organically Modified Sol-Gel Materials – Creating Single Composite Optical pH Sensors

Optical sensors hold the promise of providing the coupling between the tangible and the digital world that we are currently experiencing with physical sensors. The core of optical sensor development lies in materials development, where specific requirements of opposing physicochemical properties create a significant obstacle. The sensor material must provide dye retention, while ensuring porosity for analyte transport. The sensor material must provide hydrophobic pockets for dyes to ensure high signal intensity, while remaining fully hydrophobic to measure in water. We have previously reported optical sensors, where we compromised on sensor manufacturing by using a double-layer composite. Here, we report a composite organically modified sol-gel (ORMOSIL) polymer, where polystyrene (PS) nanoparticles (NPs) have been incorporated. This allows all the opposing requirements on optical sensor materials to be fulfilled, and by introducing a hydrophobic reference dye in the fully hydrophobic compartments of the sensor material we show that we can incorporate any hydrophobic fluorophore in this material, even those which are suffering from quenching in water. In this work, PS NPs with 1,13-dimethoxyquinacridinium (DMQA) were immobilized in a composite sol-gel material with pH responsive diazaoxatriangulenium (DAOTA) dyes prior to curing. The multicomponent sensor composite was cured on a polycarbonate hemiwicking substrate, and the resulting fluorescence intensity ratiometric optical pH sensor was shown to have excellent performance. We expect that this type of composite sensor materials will allow the creation of next generation industrial chemosensors.<br /

A Reproducible and Scalable Method for Producing Fluorescent Polystyrene Nanoparticles

In this work polystyrene nanoparticles (PS NPs) were fabricated from an emulsion of PS/toluene in water using various surfactants, and purified via dialysis in a simple procedure. The synthesis process was carried out at room temperature, without hazardous chemicals, and with a workload of 5 hours. The investigation was performed to evaluate the limits for production of PS NPs with comparable properties. A robust PS NP synthesis procedure was developed, repeated, and tested by three independent researches. The procedure was up-scaled to prove the applicability of the method and the NPs were prepared with four different hydrophobic dyes. All products were found to be comparable, and it was concluded that the method reported here can provide PS NPs with or without dye dopants, and that it provides access to PS NPs with an average diameter of 25 nm in a reproducible size distribution