CdSe/ZnS Nanocrystals with Dye‐Functionalized Polymer Ligands Containing Many Anchor Groups

Abstract

Colloidal semiconductor nanocrystals (NCs) are color tunable inorganic fluorophores, which consist of an inorganic core and an outer shell of molecular ligands.[1] While the optical properties can be adjusted by the composition [2] and the size of the core, [3] the ease with which the NCs can be chemically processed is mainly governed by the molecular structure of the ligands. In this context we define a ligand as consisting of three parts: a functional anchor group that attaches to the inorganic NC surface, an outer functional group, and a spacer in between. The architecture of the ligand is of major importance for assembling the NCs into larger supramolecular structures [4] or conjugating them to biological samples where they serve as fluorescence labels.[5] For these purposes it is essential that both the anchor and outer functionality can form strong chemical bonds. We will address this problem by introducing a novel type of polymer ligand, where the bond strength is increased by the presence of multiple anchor groups. Since our model ligands are decorated with dye molecules, we can employ fluorescence resonance energy transfer (FRET) to study the formation and stability of the NC-dye couples, where the NCs are the donors and the dyes the acceptors [6,7] . Based on the ensemble absorption and fluorescence spectra, the amount of dye attached to a given NC [6] and the average distance between the NC and the dye molecules can be estimated.[8] However, since the relative orientation and structure of the FRET couples can differ significantly from one complex to the next, we extend our measurements to single NC-dye complexes. Our experiments clearly show that static and dynamic heterogeneities occur in the ensemble of NC-dye couples, a result which is of importance for a FRET-based analysis of intermolecular distances.The CdSe/ZnS core-shell NCs are synthesized by an established method [3,9] in the presence of phosphonic acids [10] and trioctylphosphine oxide (TOPO) as ligands. The surface molecules can be subsequently cross linked to form multianchor ligands to stabilize the ligand shell.

Complete Quenching of CdSe Nanocrystal Photoluminescence by Single Dye Molecules

“…[12] In this previous work, the nanocrystal was passivated with trioctylphosphine oxide (TOPO) ligands and the conjugate was found to be photochemically unstable. As a result of the instability, the energy transfer efficiency could not be quantified.…”

Batch defluoridation appraisal of aluminium oxide infused diatomaceous earth

“…The classical co-precipitation method has been extensively applied to the enrichment of metal ions [12] and the synthesis of functionalized materials [13]. Thus, this method was adopted for the synthesis of the AD sample used in the batch defluoridation process.…”

Functional Inorganic Nanohybrids for Biomedical Diagnosis

“…Other polymers contained a mixture of aliphatic side chains and others with primary amines at their ends can bind to the nanoparticle surface through the amino groups. [40] Additionally, poly(acrylic acid) modified with free thiol and amino groups at the ends of the side chains was demonstrated as coating for quantum dots to form a thin shell with little effect on the quantum yield of the coated particles. The hydrophobic-hydrophilic block-copolymers formed in micellar structure dispersible in solvent were also used for the coating of the nanoparticles.…”