Jozef Hodyl PhD Thesis - Theses - Flinders University

4.2 Characterisation of modified silica materials4.2.1 Techniques used for characterisation of silica materialsCharacterisation of the silica based materials was performed by established literaturemethods utilising 13 C Cross Polarisation Magic Angle Spinning Nuclear MagneticResonance ( 13 C CPMAS NMR) and Diffuse Reflectance Infrared Fourier Transform207, 209, 210(DRIFT) infrared spectroscopy.Loading capacities for all the prepared silica materials were determined bymicroanalytical calculation of the carbon content for the linker materials; and both153, 211the carbon and nitrogen content for silica immobilised macrocyclic materials.Thermal decomposition of the materials at 800 o C was also employed to establish theextent of functionalisation on the silica surface. 2124.2.2 Diffuse Reflectance Infrared Fourier Transform spectroscopyDiffuse Reflectance Infrared Fourier Transform (DRIFT) is an effectivespectroscopic technique for qualitative analysis of surface species on solid materialsfor which normal infrared spectra may be difficult to acquire. 213-215 For this reason,DRIFT spectroscopy was used as a qualitative tool to assess the changes to thesurface of dried silica gel as stepwise modifications were chemically imparted. Thesespectral frequency changes are manifest in the DRIFT spectral traces displayed in,Figure 4.5, demonstrating the transition from pure silica gel, through attachment ofthe GPS linker, to attachment of a macrocyclic species to the linker.The expected absorption frequencies for the dried silica gel, Trace A, are visiblewith an additional band at 3739 cm -1for the v (OH) frequency of isolated silanolgroups freed of hydrogen bonding by the removal of physisorbed water from thesurface by thermal pre-treatment. 216-21977