title: Multidentate surface ligand exchange for the immobilization of CdSe/ZnS quantum dots and surface quantum dot-oligonucleotide conjugates.
abstract: A method for synthesizing multidentate thiol ligands on fused silica surfaces (e.g., optical fibers) was developed for the immobilization of CdSe/ZnS quantum dots (QDs) capped with hydrophilic or hydrophobic ligands. This work was motivated by the poor stability of QDs immobilized via monodentate thiol ligands and the need for stable immobilization strategies in the development of sensor technologies based on QDs. Multi-dentate immobilization was able to withstand washing protocols, and surface ligand exchange occurred via self-assembly through the zinc-metal affinity interaction. Atomic force and scanning electron microscopy images suggested that the QDs were immobilized at high density, approximately 2-4 x 10 (13) cm (-2). It was possible to immobilize one, two, or three colors of QD. Upon immobilization, 1-2 nm bathochromic shifts in the PL spectra were observed. This was attributed to both ligand exchange and the change in local environment. The change in environment was accompanied by a decrease in PL lifetime. Self-assembly of immobilized QD-oligonucleotide and QD-avidin conjugates was also demonstrated. These conjugates were able to hybridize with complementary oligonucleotide and bind biotin, respectively. This versatile immobilization chemistry is an important step in the development of surface-based QD nanosensors. Such technology requires QDs to be immobilized such that they remain accessible to target molecules in solution.
authors.affiliation: Department of Chemical and Physical Sciences, University of Toronto, Mississauga ON L5L 1C6, Canada.
authors.forename: W Russ
authors.initials: WR
authors.lastname: Algar
authors.forename: Ulrich J
authors.initials: UJ
authors.lastname: Krull
mesh_terms: D015374:Biosensing Techniques; D001710:Biotin / Q000737:chemistry; D019187:Cadmium Compounds / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology / Q000379:methods*; D009841:Oligonucleotides / Q000737:chemistry; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry*; D012822:Silicon Dioxide; D013440:Sulfides / Q000737:chemistry*; D013499:Surface Properties; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D008024:Ligands; D009841:Oligonucleotides; D018036:Selenium Compounds; D013440:Sulfides; D017967:Zinc Compounds; D001710:Biotin; D012822:Silicon Dioxide; C058667:cadmium selenide; C031238:zinc sulfide