Synthesis and characterization of nano fibrillated cellulose/Cu₂O films; micro and nano particle nucleation effects

Cubic, truncated cubic and spherical nano and micro particles of Cu₂O, can be selectively deposited onto nano fibrilated cellulose gels by the modulated alkaline reduction of Cu²⁺ ions aided by the cellulose's reducing end groups. The role of the cellulose's reducing end groups and that of externally added carbohydrate reducing agents, towards inducing various Cu₂O morphologies, is discussed with respect to the detailed nucleation effects leading to micro and nano Cu₂O particle deposition on NFC. When the reducing end groups are provided only by the cellulose's chain ends, supersaturation effects seem to be affecting the Cu₂O nucleation mechanism. However, the Cu₂O nucleation considerations were altered when mobile reducing end groups were provided by adding dextrose in the system, promoting additional particle nucleation sites. Furthermore, the effort offered the possibility to quantitatively determine the number of accessible reducing end groups (-CHO) present in NFC, expressed in mmol/g. The optical properties of the created NFC/Cu₂O films were examined by UV-vis absorption measurements, revealing band gaps ranging between 2.02-2.25 eV. The accumulated understanding expands the utility window and opens new directions for the novel utilization of nano-fibrillated cellulose, and more specifically toward semiconductor applications.