Laser damage threshold of hydrophobic up-conversion carboxylated nanocellulose/SrF2:Ho composite films functionalized with 3-aminopropyltriethoxysilane

Abstract

Luminescent nanocomposite films, containing SrF 2 :Но up-conversion particles, were prepared by two different protocols from aqueous dispersions of TEMPO-oxidized cellulose nanofibrils (TOCNF) functionalized with 3-aminopropyltriethoxysilane (APS) without the use of organic solvents at pH = 4.0-4.5 and 9.0-9.5, respectively. Proposed synthetic protocols included formation of the films by drying the dispersions containing pre-hydrolyzed APS adsorbed onto TOCNF and SrF 2 :Но particles followed by heating at 105 °C. Hydrophobic (water contact angle 101 ± 2°), strong, and translucent TOCNF/SrF 2 :Но-APS films were prepared by casting from a solution at pH = 4.0-4.5. Scanning electron microscopy, energy-dispersive X-ray spectroscopy with element mapping, Fourier-transform infrared spectroscopy, X-ray diffraction methods confirmed homogeneous distribution of up-conversion particles in TOCNF matrices as well as the grafting of linear polysiloxanes via the condensation of silanol groups and OH-groups on the surface of TOCNF. Differential scanning calorimetry and thermogravimetry data confirmed an increase in thermal stability of the APS modified nanocomposite films obtained at pH = 4.0-4.5.Hydrophobic TOCNF/SrF 2 :Но-APS nanocomposite films exhibited an intense red luminescence in the visible spectrum range ( 5 I 7 level excitation of Ho 3+ ions with 1912 nm laser irradiation) as well as two-times higher laser damage threshold compared to unmodified TOCNF/SrF 2 :Но films. TOCNF/SrF 2 :Но films can be used for visualization 2 μm laser radiation in medicine and long-distance atmosphere monitoring.

High lignin content cellulose nanofibrils obtained from thermomechanical pulp

“…Cellulose nanofibrils (CNF), obtained from various cellulose sources, attracted attention of modern researchers as "green alternative" for plastics used in polymer composites, packaging materials, optoelectronic and electronic materials, detectors, medicine and healthcare, etc. [1][2][3][4][5][6][7][8][9][10]. For the first time, CNFs were obtained by mechanical fibrillation of cellulose fibers in high-pressure homogenizer in 1983 [11,12].…”