TAILIEUCHUNG - New Perspectives in Biosensors Technology and Applications Part 13

Tham khảo tài liệu 'new perspectives in biosensors technology and applications part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 352 New Perspectives in Biosensors Technology and Applications 5. Ligand-exchange processes in core-shell nanoparticle systems Growing interests in bioassays providing transduction of bioinformation to optical and electronic signals have recently been observed in conjunction with stimulating developments in synthesis of highly efficient quantum-dots and functionalized gold nanoparticles AuNP Bain et al. 1989 Hostetler et al. 1999 . Kinetic studies show that ligand-exchange process in a self-assembled monolayer SAM film is basically a Langmuirian pseudo-first-order process and is based on the random place-exchange proceeding evenly on the entire surface of AuNP. This process may be influenced by such slow steps as surface diffusion hydrogen bond breaking or slow desorption. The improvement of the rate of metal nanoparticle functionalization is then highly desired. In this work we have described phenomena which are the key factors for the design of biosensors with fabrication of nanoparticle-enhanced sensory film and other applications such as the photodynamic cancer therapy or colorimetric assays for heavy metals. These phenomena relate to the speed of the film formation and modification of the film composition. In the proposed methodology we have employed a biomolecule homocysteine Hcys as the ligand replacing citrate capping of AuNP5nm and glutathione GSH which can act as the moderator for one-step ligand-exchange processes. The ultra-fast functionalization of gold nanoparticles process was monitored using RELS spectroscopy. It proceeds through the nucleation and avalanche growth of ligand-exchange domains in the self-assembled monolayer film on a gold nanoparticle surface Scheme 2 . Scheme 2. Schematic view of the hydrogen bonded citrate SAM basal film and the nucleation and growth of a hydrogen bonded Hcys-ligand domain on an edge of a citrate-capped AuNP. To distinguish between Hcys-dominated AuNP and GSH-dominated AuNP the pH dependence of RELS was analyzed. .

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