Development and characterisation of nanotemplated carbon monoliths in analytical chemistry
He, Xiaoyun (2014) Development and characterisation of nanotemplated carbon monoliths in analytical chemistry. PhD thesis, Dublin City University.
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A novel approach has been developed to fabricate a hierarchical nanotemplated carbon monolithic rod (NTCM) by using C60-fullerene modified silica fullerene C60 (C60) modified silica gels (FMS) as hard templates and resorcinol-formaldehyde (RF) copolymer as carbon precursor. The influence of using the C60 modified template was systematically studied using various physiochemical characterisation techniques in comparison with the unmodified counterpart carbon monolith blank (CM blank). This carbon/carbon monolithic composite, NTCM, possessed a higher specific surface area of 435 m2 g-1 with an integrated open hierarchical porous structure consisting of a tri-modal pore distribution. Due to its high surface area, high pore volume and graphite-like nature, it was used to modify the surfaces of boron doped diamond electrodes for hydrogen peroxide detections. The separation of three phenols on an in-house prepared CM blank column in reversed phase liquid chromatography demonstrated that this type carbon monolith has good selectivity for small polar aromatic compounds and poor separation efficiency due to strong affinity between the analytes and stationary phase. Subsequently, CM blank and NTCM in a rod form were tested as SPE sorbents for phenols adsorption. The adsorption kinetics showed that the CMs had good selectivity with very slow adsorption kinetics and lower adsorption capacity than the other common carbonaceous sorbent reported due to the capillary diffusion effect in the broad cross-section of the sorbents. Then the ground CM blank and NTCM powders were used for the adsorption of methylene blue (MB) in aqueous environment. Their adsorption kinetics, Langmuir isotherms, pH and temperature effects were intensely studied. The overall kinetics of both sorbents in a powder form showed much faster than in the rod form. The experimental results showed ground CM blank was a significantly better sorbent material for MB removal in water than NTCM with good reusability. For obtaining carbon monoliths of required shape for actual applications, CO2 laser ablation in a continuous mode was used to cut two CM blank and NTCM rods under control conditions to produce discs with controlled dimensions. Adsorption studies confirmed the changes in surface chemistry and morphology in these resultant laser cut carbon monolithic discs (LCMs). The results showed laser cut is a good technique for cutting the fragile and porous carbon monoliths with intriguing structure and morphology.
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