Modified cellulose paper with photoluminescent acrylic copolymer nanoparticles containing fluorescein as pH-sensitive indicator.

Herein, novel fluorescein mono-acrylate (Flu-Ac) was synthesized and copolymerized with methyl methacrylate and glycidyl methacrylate to produce epoxy-functionalized latex nanoparticles. Fluorescent cellulose paper was then obtained by dip-coating and subsequent heat treatment. Synthesis of Flu-Ac, its incorporation efficiency into the epoxy-functionalized nanoparticles (almost 92 %), spherical morphology of the particles and their sizes (89-93 nm), and optical properties were studied comprehensively. SEM micrographs showed effective wetting of the cellulose fibers with uniform diffusion and deposition of the prepared functional nanoparticles through the establishment of physical and chemical interactions. Visual and spectroscopic emission intensity of the impregnated cellulose paper (λ of 529 nm) were enhanced by increasing pH of the solution (from 2 to14) as a consequence of the transformation of cationic fluorescein to its neutral and anionic form. These observations depicted that such fluorescent cellulose substrates could be exploited in reusable indicators with good ability for sensing pH of solutions with diverse acidity or basicity.