Enhancing Gas Adsorption In Sensors：Au–Pt Nanoparticles and Methylated Coordination Cages

Abstract

This thesis investigates two nanostructured materials, bimetallic gold platinum (AuPt) nanoparticles and a methylated cobalt(II)/iron(II) coordination cage, for their potential use in gas sensors designed to detect acetone, a key biomarker for non-invasive glucose monitoring. The AuPt nanoparticles were synthesized using a modified co-reduction method based on Britto’s procedure. The synthesis was optimized to achieve uniform and well-dispersed nanoparticles through precise control of reaction time and washing steps. The nanoparticles were characterized using SEM and, EDX, to confirm their morphology, composition, and crystal structure. They were immobilized on quartz substrates through silane functionalization, and UV–Vis spectroscopy was used to verify both immobilization and acetone vapor adsorption. A clear spectral shift observed after acetone exposure confirmed successful adsorption on the nanoparticle surface, indicating their suitability for gas sensing applications. In parallel, methylated Co(II) and Fe(II) coordination cages were synthesized through subcomponent self-assembly and characterized using NMR and UV–Vis spectroscopy. The immobilization of Co(II) cages on glass and silicon substrates was verified using UV–Vis and TOF-SIMS. The data is consistent with successful immobilization of the cages on both glass and silicon surfaces. Notably, this study demonstrates for the first time that this particular cage has been successfully adsorbed onto glass and silicon substrates. Gas exposure experiments were performed on the Fe(II) cage solutions and analyzed by NMR; however, no significant spectral changes were detected, likely due to gas dissipation or weak interactions at ambient conditions. Overall, the study presents promising results for the AuPt nanoparticles, while preliminary findings for the coordination cages indicate the need for further optimization. These results contribute to the development of nanostructured mate- rials for more sensitive and selective gas-sensing technologies aimed at advancing non-invasive diagnostic methods.