ABSTRACT
To understand the limitations occurring during enzymatic hydrolysis of cellulosic materials in renewable energy production, we used wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), X-ray microtomography, and transmission electron microscopy (TEM) to characterize submicrometer changes in the structure of microcrystalline cellulose (Avicel) digested with the Trichoderma reesei enzyme system. The microtomography measurements showed a clear decrease in particle size in scale of tens of micrometers. In all the TEM pictures, similar elongated and partly ramified structures were observed, independent of the hydrolysis time. The SAXS results of rewetted samples suggested a slight change in the structure in scale of 10-20 nm, whereas the WAXS results confirmed that the degree of crystallinity and the crystal sizes remained unchanged. This indicates that the enzymes act on the surface of cellulose bundles and are unable to penetrate into the nanopores of wet cellulose.
Subject(s)
Cellulases/metabolism , Cellulose/chemistry , Cellulose/ultrastructure , beta-Glucosidase/metabolism , Aspergillus niger/enzymology , Cellulose/metabolism , Hydrolysis , Microscopy, Electron, Transmission , Particle Size , Scattering, Small Angle , Trichoderma/enzymology , X-Ray Diffraction , X-Ray MicrotomographyABSTRACT
The aim of this research was to explore the use of amine-containing polymeric and low-molar-mass organic protecting agents in the preparation of copper nanoparticles. Particles were synthesized using poly(ethylene imine) (PEI) or tetraethylenepentamine (TEPA) as protecting agents. The resulting particles were studied with UV-vis spectrometry, thermogravimetry, scanning electron microscopy, and transmission electron microscopy, wide-angle X-ray scattering with heating, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The average crystal sizes for the particles were at room temperature 8.5 and 19.4 nm for PEI and TEPA, respectively, and some surface oxidation was observed. The particles were sintered on paper, and the resistance and resistivity were measured. For Cu/PEI samples, the protecting agent was removed upon sintering at relatively low temperatures (between 150 and 200 degrees C). At this temperature range, particles exhibited a rapid increase in the crystal size. Sintered particles exhibited high conductivity, indicating that these kinds of materials might find use in paper-based printing.
