A Fluorescence Intensity Ratiometric Fiber Optics–Based Chemical Sensor for Monitoring pH

Abstract

Accurate determination of pH is essential, yet a single technology is relied upon for almost all pH measurements. Here, a new optical pH sensor is described. Two highly photostable fluorescent dyes with a polymerizable side chain are incorporated into a composite polymer that allows for fast transport of protons. A pH‐responsive dye and a reference dye with limited response to pH are used, thus allowing for determining pH using a ratiometric fluorescence intensity response. The sensor material—dyes covalently attached in the composite polymer—is deposited on a polycarbonate hemiwicking substrate, and immobilized on the inside of a shaker flask. In this manner, two robust pH optodes with pKa values of 5.30 and 6.11 are prepared. The pH‐responsive composite materials are addressed using fiber optics, and the response is recorded on a fiber spectrometer. The optodes are shown to have low drift, fast response time, no leachables, and the sensor is shown to work in heterogeneous media exemplified with coffee, beer, and cola.

Evaluation of Ebselen-azadioxatriangulenium as redox-sensitive fluorescent intracellular probe and as indicator within a planar redox optode

“…In summary, we have shown that triangulenium-based dyes can be converted to redox probes by linking them to a redox sensitive motif. High photostability, long decay times and high yield synthesis are some of the arguments to further investigate triangulenium based indicators for sensor development [41,[50][51][52] as well as imaging purposes.…”

Review of Structural Health Monitoring Techniques in Pipeline and Wind Turbine Industries

“…While only a few research studies have examined DCS [119,[121][122][123], chemical sensing materials are being studied for a wider variety of optical fiber applications, which could theoretically be used for the production of DCS to track corrosive external factors. For compatibility with OFS, there are a number of pH-sensing materials, including localized surface plasmon resonance (LSPR) Au or Ag nanoparticles (NP) integrated composites (Figure 13a) [124][125][126], organic dyes [127][128][129][130][131][132], fluorescent molecules [133][134][135][136][137], polymers [138][139][140][141], pH-sensitive hydrogel [142][143][144][145], etc. The pH value of the solution independent of the material embedded in the matrix is observed to be more integrated with the silica matrix coating [124,146].…”

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

“…However, the decrease of the band at 660 nm is due to the overlap with the peak 595nm, as it has been confirmed DMQA has no fluorescence response to pH when it is in the gel phase. 41 The normalized and smoothed fluorescence spectra were shown in Figure S5, and the pH is evaluated by the ratiometric signal of the integrated peak areas (DAOTA/DMQA). By monitoring the sensors response to pH, we could see the responses are reversible and repeatable (Figure S6).…”

“…21,40 We have described an organically modified silicon sol-gel that solves many of these issues, when it comes to creating a competitive optical pH sensor. 3,18,[41][42][43] The resulting sensor material has good chemical, photochemical and thermal stability as well as fast diffusion of H + , while excluding all other ions. The sensor material has the capacity to fully encapsulate the pH responsive dye, the ability to firmly stick to polymer and glass substrate, a long shelf-life and is fully biocompatible.…”