Abstract
Owing to their unique optical properties, colloidal quantum dots (QDs) have attracted much attention as versatile fluorescent markers with broad biological and physical applications. On the other hand, DNA-based assembly has proven to be a powerful bottom-up approach to create designer nanoscale objects and to use these objects for the site-directed arrangement of guest components. To achieve good colloidal stability and accurate positioning of QDs on DNA templates, robust QD surface functionalization is crucial. Here, we present a simple and reliable conjugation method for the direct attachment of DNA molecules to QDs. Phosphorothiolated regions of chimera oligonucleotides are attached and incorporated into a ZnS layer freshly growing in situ on QDs that were rendered water soluble with hydrophilic ligands in a prior step. The reaction can be completed in a 2 mL plastic tube without any special equipment. The utility of these DNA-labeled QDs is demonstrated via prototypical assemblies such as QDs dimers with various spacings and chiral helical architectures.
Highlights
Colloidal semiconductor quantum dots (QDs), in comparison to organic fluorophores, offer several advantages, such as a broader excitation spectra, a narrow and sharply defined emission peak, a longer fluorescence lifetime, orders of magnitude higher photochemical stability, and high resistance to photobleaching [1]
As the crystal structure of an individual QD is crucial for its intrinsic properties, a rigorous understanding of the structure–property relationship will allow researchers to optimize QD synthesis and to obtain designed photonic properties in an iterative manner
Spherical QDs, one-dimensional (1D) quantum nanorods (NRs), and intricately branched nanocrystals have been successfully synthesized with high uniformity through kinetic shape control [16,17,18,19]
Summary
Colloidal semiconductor quantum dots (QDs), in comparison to organic fluorophores, offer several advantages, such as a broader excitation spectra, a narrow and sharply defined emission peak, a longer fluorescence lifetime, orders of magnitude higher photochemical stability, and high resistance to photobleaching [1]. QDs are often considered to be artificial atoms and, as a result of the quantum confinement effect, possess exceptional tunability of their electronic energy levels [2,3,4,5] Their excitation recombination energies, recombination rates, and the spatial distributions of electrons and holes can be carefully engineered by controlling the size, shape, crystal structure, and composition of the constituent materials. Despite their potential toxicity [6,7] and slow diffusion due to their large physical sizes compared with organic dyes [8], QDs have received considerable attention for various applications in bio-imaging, real-time tracking, and therapeutic drug delivery [9,10,11]. Assembled QDs thereby enable a range of studies, such as plasmon–exciton interactions for excitation and emission enhancement, carrier–carrier interactions, and nanoscale spin and energy transfers [20,21,22,23]
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