TY - BOOK
T1 - Fluorescenec Properties of HPLC-purified DNA-stabilized Silver Clusters
AU - Bogh, Sidsel Ammitzbøll
PY - 2018
Y1 - 2018
N2 - DNA-stabilized silver clusters (AgDNAs) are a new type of fluorophores where small groups of silver (< 25 atoms) are protected from agglomeration into larger silver particles by the presence of DNA strands, acting as ligands. AgDNAs are exciting as fluorophores due to their DNA sequence dependent tunable absorption and emission properties, their small sizes (< 2 nm) and their good biocompatibility. Besides these features AgDNAs possess significant Stokes shifts and many of them fluoresce in the red or near-infrared, which makes them promising as fluorophores for bioimaging applications. Despite these intriguing properties of AgDNAs there is still a significant lack of knowledge about the structure of the fluorophores and how changes in the stabilizing DNA sequences govern changes in optical properties of the synthesized silver clusters. These challenges limit the tailoring of AgDNAs with specific optical properties for different applications. In the research presented in this thesis, silver clusters synthesized in different DNA sequences were investigated with the objective of enhancing our knowledge of AgDNAs. Due to heterogeneity of the synthesis product all fluorescent AgDNAs were purified by HPLC prior to any experiments. The main focus of the research has been on the excited state properties and electronic structure of silver clusters stabilized in both novel and previously discovered DNA scaffolds. To investigate these properties time-resolved fluorescence techniques have been theprimary tool. We found that some AgDNAs undergo spectral relaxation of the excited state on a time-scale similar to the fluorescence lifetime, which causes the emission spectra to red-shift as a function of fluorescence detection time. For the AgDNAs where spectral relaxation occur the fluorescence intensity decay is multi-exponential, whereas in AgDNAs that undergo relaxation faster the intensity decay has a mono-exponential character. This indicates that the flexibility of the stabilizing DNA scaffold affects the relaxation dynamics of the AgDNAs and that the silver clusters are inherently coupled to the DNA. This interplay between silver clusters and DNA in AgDNAs leads to excited state properties that are significantly different from those of common organic fluorophores.
AB - DNA-stabilized silver clusters (AgDNAs) are a new type of fluorophores where small groups of silver (< 25 atoms) are protected from agglomeration into larger silver particles by the presence of DNA strands, acting as ligands. AgDNAs are exciting as fluorophores due to their DNA sequence dependent tunable absorption and emission properties, their small sizes (< 2 nm) and their good biocompatibility. Besides these features AgDNAs possess significant Stokes shifts and many of them fluoresce in the red or near-infrared, which makes them promising as fluorophores for bioimaging applications. Despite these intriguing properties of AgDNAs there is still a significant lack of knowledge about the structure of the fluorophores and how changes in the stabilizing DNA sequences govern changes in optical properties of the synthesized silver clusters. These challenges limit the tailoring of AgDNAs with specific optical properties for different applications. In the research presented in this thesis, silver clusters synthesized in different DNA sequences were investigated with the objective of enhancing our knowledge of AgDNAs. Due to heterogeneity of the synthesis product all fluorescent AgDNAs were purified by HPLC prior to any experiments. The main focus of the research has been on the excited state properties and electronic structure of silver clusters stabilized in both novel and previously discovered DNA scaffolds. To investigate these properties time-resolved fluorescence techniques have been theprimary tool. We found that some AgDNAs undergo spectral relaxation of the excited state on a time-scale similar to the fluorescence lifetime, which causes the emission spectra to red-shift as a function of fluorescence detection time. For the AgDNAs where spectral relaxation occur the fluorescence intensity decay is multi-exponential, whereas in AgDNAs that undergo relaxation faster the intensity decay has a mono-exponential character. This indicates that the flexibility of the stabilizing DNA scaffold affects the relaxation dynamics of the AgDNAs and that the silver clusters are inherently coupled to the DNA. This interplay between silver clusters and DNA in AgDNAs leads to excited state properties that are significantly different from those of common organic fluorophores.
UR - https://rex.kb.dk/permalink/f/h35n6k/KGL01012015371
M3 - Ph.D. thesis
BT - Fluorescenec Properties of HPLC-purified DNA-stabilized Silver Clusters
PB - Department of Chemistry, Faculty of Science, University of Copenhagen
ER -