Enhanced Luminescence Based Response towards pH in Highly Acidic Environments by the Silver Nanoparticles and Ionic Liquids

Correct measurement of the pH in highly acidic environments is still a challenge. In such conditions most of the pH indicators suffer from instability in air or leaching from host matrices due to the solubility considerations. In this work, two different fluorescent probes were used along with silver nanoparticles (AgNPs) and ionic liquid (IL) in the polymeric matrices for sensing of the pH in harsh conditions. The pH sensitivities of the probes were tested after exposure to strong acid vapors by steady-state, lifetime based and kinetic mode measurements. The sensing materials were fabricated in form of thin films and electrospun nanofibers. The ionic liquid; 1-butyl-3-methylimidazolium tetrafluoroborate was exploited as additive to enhance the stability as well as response towards pH. Spectral changes were tested in a large scale; between pH3.00-12.00. Utilization of the dyes in ethyl cellulose and polymethyl methacrylate along with AgNPs in form of electrospun fibers resulted in many advantages such as enhanced long term stability, sensitivity and improvement in all sensor dynamics. Sensing characteristics of the offered designs were tested after exposed to vapors of HCl, H2SO4 and HNO3, respectively.