Modification of cellulose paper with photoluminescent acrylic copolymer nanoparticles containing fluorescein as pH-sensitive indicator

In this study, fluorescein mono-acrylate (Flu-Ac) was copolymerized with methyl methacrylate and glycidyl methacrylate to prepare epoxy-functionalized fluorescent latex nanoparticles through semi-continuous emulsion polymerization. The fluorescent nanoparticles were coated on cellulose substrate through dip-coating technique and subsequent heat treatment. Chemical structure and incorporation efficiency of Flu-Ac into the fluorescent acrylic coplymer nanoparticles (average particle size of 93 nm) w:as char:acterized by FTIR and HNMR analyses. SEM images demonstrate efficient coating of the cellulose fibers with fluorescent nanoparticles as a result of hydrogen bonding and probable ring-opening of the epoxy groups by hydroxyl group of cellulose. Images of fluorescent cellulose paper and fluoremetry analysis showed an enhanced visual fluorescence and spectroscopic emission intensity (λmax of 529 nm) by increasing the pH of surrounding solution. This was attributed to the transformation of cationic fluorescein dye to the neutral and also highly fluorescent anionic form. These observations revealed that the prepared fluorescent cellulose paper could be exploited as reusable pH-sensitive indicators. In this study, fluorescein mono-acrylate (Flu-Ac) was copolymerized with methyl methacrylate and glycidyl methacrylate to prepare epoxy-functionalized fluorescent latex nanoparticles through semi-continuous emulsion polymerization. The fluorescent nanoparticles were coated on cellulose substrate through dip-coating technique and subsequent heat treatment. Chemical structure and incorporation efficiency of Flu-Ac into the fluorescent acrylic coplymer nanoparticles (average particle size of 93 nm) w:as char:acterized by FTIR and HNMR analyses. SEM images demonstrate efficient coating of the cellulose fibers with fluorescent nanoparticles as a result of hydrogen bonding and probable ring-opening of the epoxy groups by hydroxyl group of cellulose. Images of fluorescent cellulose paper and fluoremetry analysis showed an enhanced visual fluorescence and spectroscopic emission intensity (λmax of 529 nm) by increasing the pH of surrounding solution. This was attributed to the transformation of cationic fluorescein dye to the neutral and also highly fluorescent anionic form. These observations revealed that the prepared fluorescent cellulose paper could be exploited as reusable pH-sensitive indicators.