E.s.c.a. studies of the nitration and denitration of cellulosic materials

The use of sample positioning to control defect creation by oxygen plasma in isotopically labelled bilayer graphene membranes

Monolayer and isotopically labelled bilayer graphene membranes were prepared on grids for transmission electron microscopy (TEM). In order to create defects in the graphene layers in a controlled way, we studied the sensitivity of the individual graphene layers to the oxygen plasma treatment. We tested samples with different configurations by varying the order of the transfer of layers and changing the orientation of the samples with respect to the plasma chamber. Using Raman spectroscopy, HRTEM and X-ray photoelectron spectroscopy, we demonstrated defect formation and determined the quantity and chemical composition of the defects. By keeping the sample structure and the setup of the experiment unchanged, the significant role of the sample orientation with respect to the chamber was demonstrated. The effect was accounted for by the variation of the accessibility of the sample surface for the reactive species. Therefore, this effect can be used to control the degree of damage in each layer, resulting in differing numbers of defects present on each side of the sample.

Monolayer and isotopically labelled bilayer graphene membranes were prepared on grids for transmission electron microscopy (TEM).

X-Ray Photoelectron Spectroscopy Characterization of Polyaniline-Cellulose Ester Composite Membranes

X-ray photoelectron spectroscopy (XPS) is a promising technique employed for the study of conducting polymers and their composites. XPS was used to study the surface chemistry of polyaniline-mixed cellulose ester (PANI-ME) composite membranes prepared by various chemical oxidative polymerization techniques such as insitu solution, vapour phase polymerizations and aniline polymerization using a two-compartment permeation cell. Hydrolytic degradation of surface deposited PANI and scission of cellulosic chains due to x-ray irradiation inside the XPS chamber influenced the quantification of polyaniline deposition levels as well as oxidation and doping states in PANI-ME membranes. N1s core level spectra allowed characterization of the PANI deposition level, its oxidation state and x-ray induced cellulosic ring cleavage. C1s and O1s core level spectra revealed PANI hydrolysis at the membrane surface. These degradation phenomena influence the performance of PANI composite membranes used specifically in electrodiffusion applications. It was shown that successful quantification of PANI deposition levels and its oxidation state on microporous mixed cellulose ester membranes using XPS could be realized by incorporating the degradation effects in the characterization results.