ABSTRACT
Pretreatments with aqueous protic ionic liquid (PIL)-ethanolamine bis(oxalate) ([MEA][(HOA)(H2OA)]), combined with ultrasonic disintegration, were employed in cellulose nanofibril (CNF) production from pulp fibers. The optimization of pretreatment parameters is crucial for obtaining the maximum CNF yield. The response surface methodology was used to design the pretreatment conditions for preparing CNFs. This method consists of four factors: pretreatment time (A, 2-4 h), pretreatment temperature (B, 100-120 °C), liquid-to-solid ratio (C, 60-80 g g-1), and PIL content (D, 20-40%). The predicted CNF yield (Y) followed a quadratic multinomial regression equation represented by Y = 84.43 + 3.59A + 8.22B + 2.22C - 2.13D - 0.85AB + 2.83AC + 5.95AD + 0.43BC - 2.98BD + 4.25CD - 6.04A2 - 18.23B2 - 4.98C2 - 7.39D2. The regression equation exhibited high model fit to the experimental CNF yields as evidenced by a determination coefficient of 0.9764. Results showed that a maximum CNF yield of 86.2% was obtained in the case with the following conditions: pretreatment temperature of 112 °C, pretreatment time of 3.2 h, liquid-to-solid ratio of 83 g g-1, and PIL content of 29%. CNFs with high crystalline index (64.0%) and thermal stability (Tmax = 348 °C) were prepared. This work favors the development of low cost PIL-based pretreatment systems for the clean production of CNFs.
ABSTRACT
Two silylated BODIPY derivatives were synthesized, characterized and used for the fabrication of the dye-encapsulated silica nanoparticles. The fluorophores were covalently incorporated into the silica matrix to minimize any fluorophore leakage. The synthesized fluorophore-doped nanoparticles were stable in aqueous solution and monodisperse with diameters of 20-25 nm. By incorporating the two BODIPY dyes simultaneously at a controlled ratio, silica nanoparticles with switchable emitting wavelengths were achieved with a change in the excitation wavelength. Thus by using the dual-fluorophore-doped nanoparticles, two-color imaging was demonstrated with minimal background signal by employing an appropriate excitation light source and appropriate excitation/emission filter sets. Further, the surfaces of the dual-fluorophore-doped nanoparticles were functionalized with folic acid to allow for the recognition of HeLa cells which over-express the folate receptors.
