Self-supporting covalent organic framework membranes synthesized through two different processes: solvothermal annealing and solvent vapor annealing.

Rigid, freestanding covalent organic framework (COF-1) membranes have been synthesized from 1,4-benzenediboronic acid (BDBA) precursors using two different approaches: room temperature solvent-vapour annealing (SVA) and solvothermal annealing (SA). Characterization of films using Fourier-transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and various microscopies shows that the films obtained through the two different routes vary in their retained BDBA proportion, crystal size and macroscale morphology. Gas adsorption measurements give specific surface areas of 579 ± 7 m2 g-1 and 739 ± 11 m2 g-1 respectively, suggesting that the average porosity of these films is competitive with bulk-synthesized COF-1 particles. The films have a stratified structure, with a dense, thin top layer and a thicker, sponge-like base layer. Using nanoindentation, we measured the Young's modulus at the top surface of the SVA and SA films to be 3.64 ± 1.20 GPa and 3.33 ± 0.12 GPa respectively, with the smaller uncertainty for the SA film attributed to a more uniform morphology. These measurements provide useful experimental data pertaining to COF-1 mechanical properties, furnishing information relevant to the use of these free-standing membranes in applications such as gas filtration or storage.

Interactions of iodoperfluorobenzene compounds with gold nanoparticles.

Understanding the interactions of small molecules with gold nanoparticles is important for controlling their surface chemistry and, hence, how they can be used in specific applications. The interaction of iodoperfluorobenzene compounds with gold nanoparticles was investigated by UV-Vis difference spectroscopy, surface enhanced Raman spectroscopy (SERS) and Synchrotron X-ray photoelectron spectroscopy (XPS). Results from UV-Vis difference spectroscopy demonstrated that iodoperfluorobenzene compounds undergo charge transfer complexation with gold nanoparticles. SERS of the small molecule-gold nanoparticle adducts provided further evidence for formation of charge transfer complexes, while Synchrotron X-ray photoelectron spectroscopy provided evidence of the binding mechanism. Demonstration of interactions of iodoperfluorobenzene compounds with gold nanoparticles further expands the molecular toolbox that is available for functionalising gold nanoparticles and has significant potential for expanding the scope for generation of hybrid halogen bonded materials.

Interactions between alginate and chitosan biopolymers characterized using FTIR and XPS.

This study investigates alginate-chitosan polyelectrolyte complexes (PECs) in the form of a film, a precipitate, as well as a layer-by-layer (LbL) assembly. The focus of this study is to fully characterize, using the complementary techniques of Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) in combination with solution stability evaluation, the interactions between alginate and chitosan in the PECs. In the FTIR spectra, no significant change in the band position of the two carbonyl vibrations from alginate occurs upon interaction with different ionic species. However, protonation of the carboxylate group causes a new band to appear at 1710 cm(-1), as anticipated. Partial protonation of the amine group of chitosan causes the appearance of one new band ( approximately 1530 cm(-1)) due to one of the -NH3+ vibrational modes (the other mode overlaps the amide I band). Importantly, the position of the two main bands in the spectral region of interest in partly protonated chitosan films is not dependent on the extent of protonation. XPS N 1s narrow scans can, however, be used to assess the degree of amine protonation. In our alginate-chitosan film, precipitate, and LbL assembly, the bands observed in the FTIR correspond to the species -COO- and -NH3+, but their position is not different from each of the single components. Thus, the conclusion of the study is that FTIR cannot be used directly to identify the presence of PECs. However, in combination with XPS (survey and narrow N 1s scans) and solution stability evaluation, a more complete description of the structure can be obtained. This conclusion challenges the assignment of FTIR spectra in the literature.

Introducing amine functionalities on a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) surface: comparing the use of ammonia plasma treatment and ethylenediamine aminolysis.

Amine functionalities were introduced onto the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by applying radio frequency ammonia plasma treatment and wet ethylenediamine treatment. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) for chemical composition and Raman microspectroscopy for the spatial distribution of the chemical moieties. The relative amount of amine functionalities introduced onto the PHBV surface was determined by exposing the treated films to the vapor of trifluoromethylbenzaldehyde (TFBA) prior to XPS analysis. The highest amount of amino groups on the PHBV surface could be introduced by use of ammonia plasma at short treatment times of 5 and 10 s, but no effect of plasma power within the range of 2.5-20 W was observed. Ethylenediamine treatment yielded fewer surface amino groups, and in addition an increase in crystallinity as well as degradation of PHBV was evident from Fourier transform infrared spectroscopy. Raman maps showed that the coverage of amino groups on the PHBV surfaces was patchy with large areas having no amine functionalities.