Few-Atom Silver Clusters as Fluorescent Reporters - Advanced Fluorescence Reporters in Chemistry and Biology - page 307

Few-Atom Silver Clusters as Fluorescent
Reporters

Isabel D´ez and Robin H.A. Ras

Abstract Silver clusters, composed of only a few silver atoms, have remarkable
optical properties based on electronic transitions between quantized energy levels.
They have large absorption coefficients and fluorescence quantum yields, in com-
mon with conventional fluorescent markers. But importantly, silver clusters have
an attractive set of features, including subnanometer size, nontoxicity and photo-
stability, which makes them competitive as fluorescent markers compared with
organic dye molecules and semiconductor quantum dots. In this chapter, we review
the synthesis and properties of fluorescent silver clusters, and their application as
bio-labels and molecular sensors. Silver clusters may have a bright future as
luminescent probes for labeling and sensing applications.

Keywords Fluorescent marker Nanoclusters Nanodots Nanoscale metal

Quantum dots

Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
2 Metal Clusters: The Missing Link Between Single Atoms
and Plasmonic Nanoparticles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
4 Synthesis of Fluorescent Silver Clusters in Various Scaffolds
and Their Application as Bio-Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
4.1 DNA Oligonucleotides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
4.2 Proteins and Peptides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
4.3 Polymers and Dendrimers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
4.4 Transfer of Silver Clusters Between Scaffolds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323