Visible Light Excitation of CdSe Nanocrystals Triggers the Release of Coumarin from Cinnamate Surface Ligands
摘要:
The photochemical properties of organic ligands on the surface of nanocrystalline CdSe particles were examined. A number of thiols carrying a substituted cinnamate tail was synthesized. In solution, these cinnamate compounds undergo light-induced ( 374 nm) E-Z isomerization, followed by a nonphotolytic lactonization to give highly fluorescent coumarin. The cinnamate-thiols were successfully exchanged onto the CdSe nanocrystal, and the photochemical behavior of these conjugates was studied. Upon aerobic photolysis at 374 nm, the surface cinnamates released coumarin accompanied by rapid nanocrystal degradation. This degradation was not observed under similar anaerobic conditions or when the organic ligands did not contain the cinnamate group. Surprisingly, very similar results were obtained upon irradiation at visible wavelengths at which the cinnamate has no absorption. With the aid of UV-visible absorption spectroscopy, fluorescence spectroscopy, and electrochemistry, a unified theory for both the increased photoinstability of the nanocrystal as well as the coumarin release was proposed. It involves cinnamate radical anions on the CdSe surface, formed upon electron transfer from the excited nanocrystal to the surface cinnamate, undergoing E-Z isomerization. Practically, this results in the remarkable ability to release coumarin from nanocrystal ligands simply by exciting the nanocrystal with visible light. This new photorelease protocol not only aids in the understanding of fundamental nanocrystal-ligand interactions but may also offer new opportunities in the areas of drug delivery and imaging.
Gold Glyconanoparticles: Synthetic Polyvalent Ligands Mimicking Glycocalyx-Like Surfaces as Tools for Glycobiological Studies
作者:África G Barrientos、Jesús M. de la Fuente、Teresa C. Rojas、Asunción Fernández、Soledad Penadés
DOI:10.1002/chem.200204544
日期:2003.5.9
methodology is described for tailoring sugar-functionalised gold nanoclusters (glyconanoparticles) that have 3D polyvalent carbohydrate display and globular shapes. This methodology allows the preparation of glyconanoparticles with biologically significant oligosaccharides as well as with differing carbohydrate density. Fluorescent glyconanoparticles have been also prepared for labelling cells in biological
作者:Jouliana M. El Khoury、Xiaoli Zhou、Liangti Qu、Liming Dai、Augustine Urbas、Quan Li
DOI:10.1039/b901826c
日期:——
Organo-soluble photoresponsive azothiol monolayer-protected gold nanorods were synthesized; the resulting gold nanorods encapsulated by thiols on their entire surface with strong covalent Au–S linkages were very stable in both organic solvents and in the solid state without aggregation or decomposition.
Functional aliphatic polyesters and nanoparticles prepared by organocatalysis and orthogonal grafting chemistry
作者:Angela L. Silvers、Chia-Chih Chang、Todd Emrick
DOI:10.1002/pola.26114
日期:2012.9.1
used for postpolymerizationmodification of diblock copolymers possessing alkene groups on one block and alkyne groups on the other block. The polyesters were crosslinked using azide/alkyne cycloaddition, by reaction of α,ω‐diazides with the pendent alkynes on the polyester backbone. This gave polyester nanoparticles possessing alkene functionality, which were subjected to further modification using thiol‐ene
An efficient and convenient synthesis of unsymmetrical disulfides from thioacetates
作者:Slawomir Lach、Sebastian Demkowicz、Dariusz Witt
DOI:10.1016/j.tetlet.2013.10.056
日期:2013.12
We have developed convenient methods for the synthesis of functionalized unsymmetrical dialkyl disulfides under mild conditions in very good yields. The designed method is based on the reaction of (5,5-dimethyl-2-thioxo-1,3,2-dioxaphosphorinan-2-yl)-disulfanyl derivatives 1 with functionalized alkyl thiolate anions, generated in situ from thioacetates 2 and sodium methoxide or butylamine. The developed
AuBr3 mediated glycosidations: synthesis of tetrasaccharide motif of the Leishmania donovani lipophosphoglycan
作者:Gopalsamy Sureshkumar、Srinivas Hotha
DOI:10.1007/s10719-012-9400-7
日期:2012.5
Tetrasaccharide cap present in lipophosphoglycan of the Leishmania donovani responsible for visceral Leishmaniaisis is synthesized as a fully protected propargyl glycoside. AuBr3 mediated selective glycosylation of propargyl 1,2-orthoester in the presence of propargyl glycoside is employed as a key step to obtain propargyl containing oligomers. Further, propargyl tetrasaccharide is connected with a long chain hydrocarbon containing azidothiol functionality situated at two terminal ends via ‘click’ reaction.