Optical Chemosensors based on Spiropyran-Doped Polymer Nanoparticles for Sensing pH of Aqueous Media

Abstract

Photochromic polymers, which are prepared by the incorporation of photochromic compounds into polymer matrices, show fluorescence emission along with color change under UV light irradiation. Polymer nanoparticles yield high chromic properties at low chromophore loadings, as they have a large surface area to absorb a high level of light irradiation. Particle size is a significant parameter to control optical properties, where the decrease of particle size results in a high light absorption and efficiency of photochromism and fluorescence emission. Reverse atom transfer radical polymerization was used to synthesize methyl methacrylate homopolymer and its copolymers with different comonomers to yield polymers with a narrow molecular weight distribution. Spiropyran was doped to the polymeric nanoparticles during nanoprecipitation to yield photochromic polymer nanoparticles. Particle size below 100 nm for the photochromic nanoparticles was shown by dynamic light scattering. Morphology investigation with microscopic analysis showed spherical morphology for nanoparticles. The photochromic properties of the polymer nanocarriers were studied in both acidic and alkaline media. The results indicated that the pH of the media as well as the copolymer composition significantly affect the optical properties. Therefore, the photochromic polymer nanoparticles could have potential applications as optical pH chemosensors by colorimetric and fluorometric detection mechanisms. The nanoparticles with hydroxyl- or amine-functional groups were shown to be highly efficient for pH chemosensor applications. Finally, photochromic cellulosic papers prepared from the photochromic polymer nanoparticles were highly applicable in the detection of acid vapors.

Soap-Free Emulsion Composed of Polymer Solutions and an Aqueous Clay Suspension

“…As an application of the emulsion, photochromism was investigated. Photochromism which is a phenomenon of photocoloration and thermal- (or photo-) decoloration, is useful phenomena for optical recording and smart materials . The emulsion containing the photochromic molecule was red, and the color faded out by visible light irradiation, as shown in Figure b, showing the negative photochromism.…”

Synthesis and Application of Fluorescent Polymer Micro‐ and Nanoparticles

“…Recently, the same authors reported the fabrication of photochromic polymer nanoparticles doped with spiropyran for pH sensing. [ 98 ] It was found that the optical properties could be affected by media’ pH and copolymer composition, thus, based on the colorimetric and fluorescence detection mechanisms, the potential application of photochromic polymer nanoparticles as optical pH chemical sensors could be realized.…”

“…[97] In the work published by Roghani-Mamaqani and coworkers, photochromic polymer nanoparticles doped with spiropyran were prepared by nanoprecipitation and served as optical pH chemosensors. [98] Specifically, PMMA homopolymer and its two copolymers were synthesized by reverse atom transfer radical polymerization (RATRP). It should be pointed out that RATRP could not only control the molecular weight of the polymers, but also overcome the catalyst' oxidation, as well as generate different charges on the surface of the subsequently prepared photochromic nanoparticles.…”

Development of pH sensing colloidal nanoparticles and oil/water separating electrospun membranes containing oxazolidine from functional polymers

“…2,4 Variation of ionic strength and pH of media can alter the photochromism properties and fluorescence emission of the nanoparticles, which can be used in pH sensing applications. [23][24][25][26][27] Paek et al prepared polymer-quantum dot nanoparticles which respond to acidic range of pH variations. The results indicated that the color and fluorescence emission of the samples change under different acidic pHs.…”