Phase transfer of hydrophilic, cyclodextrin-modified gold nanoparticles to chloroform solutions

A Novel Approach to Molecular Recognition Surface of Magnetic Nanoparticles Based on Host-Guest Effect

A novel route has been developed to prepared beta-cyclodextrin (beta-CD) functionalized magnetic nanoparticles (MNPs). The MNPs were first modified with monotosyl-poly(ethylene glycol) (PEG) silane and then tosyl units were displaced by amino-beta-CD through the nucleophilic substitution reaction. The monotosyl-PEG silane was synthesized by modifying a PEG diol to form the corresponding monotosyl-PEG, followed by a reaction with 3-isocyanatopropyltriethoxysilane (IPTS). The success of the synthesis of the monotosyl-PEG silane was confirmed with (1)H NMR and Fourier transform infrared (FTIR) spectroscopy. The analysis of FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the immobilization of beta-CD onto MNPs. Transmission electron microscopy (TEM) indicated that the beta-CD functionalized MNPs were mostly present as individual nonclustered units in water. The number of beta-CD molecules immobilized on each MNP was about 240 according to the thermogravimetric analysis (TGA) results. The as-prepared beta-CD functionalized MNPs were used to detect dopamine with the assistance of a magnet.

Conversion of the surface property of oleic acid stabilized silver nanoparticles from hydrophobic to hydrophilic based on host-guest binding interaction

This paper describes a general method to change the surface property of the oleic acid stabilized silver nanoparticles and successful tranferring of the silver nanoparticles from the organic phase into the aqueous phase. By vigorous shaking of a biphasic mixture of the silver organosol protected with oleic acid and p-sulfonated calix[4]arene (pSC4) aqueous solution, it is believed that an inclusion complex is formed between oleic acid molecules and pSC4, and the protective layer of the silver nanoparticles shifts from hydrophobic to hydrophilic in nature, which drives the transfer of silver nanoparticles from the organic phase into the aqueous phase. The efficiency of the phase transfer to the aqueous solution depends on the initial pSC4 concentration. The pSC4-oleic acid inclusion complex stabilized nanoparticles can be stable for long periods of time in aqueous phase under ambient atmospheric conditions. The procedure of phase transfer has been independently verified by UV-vis, transmission electron microscopy, Fourier transform infrared, and 1H nuclear magnetic resonance techniques.

Face preferred deposition of gold nanoparticles on α-cyclodextrin/octanethiol inclusion compound

The preferred deposition of gold nanoparticles (Au NPs) onto microcrystal faces of alpha-cyclodextin/octanethiol inclusion compound was obtained. The immobilization of Au NPs is caused by the spatial replacing of the citrate shell of the NPs by the free dangling SH groups of the guest molecule.

Unusual fluorescence enhancement of a novel carbazolyldiacetylene bound to gold nanoparticles

A novel carbazolyldiacetylene derivative of 5-[1,2]dithiolan-3-ylpentanoic acid 1,6-bis((N-carbazol-3-yl)methyl)-2,4-hexadiyne ester (DCHD-HS) was synthesized. DCHD-HS showed unusual fluorescence enhancement when it was bound to gold nanoparticles. The studies also showed that varied solvents and ratios of ligand/gold particles that served as the driving forces to control aggregation resulted in emission enhancement. A rational explanation for this phenomenon was discussed and elucidated.

A general phase transfer protocol for synthesizing alkylamine-stabilized nanoparticles of noble metals

The ethanol-mediated phase transfer protocol was extended herein to prepare alkylamine-stabilized nanoparticles of several noble metals by transferring them from aqueous environment into toluene. This method relies on the use of ethanol as a mediator to provide and maintain adequate contact between dodecylamine and metal nanoparticles during the transfer process and involves first mixing the metal hydrosols and an ethanol solution of dodecylamine and then extracting the dodecylamine-stabilized metal nanoparticles into toluene. Alkylamine-stabilized Ag, Pd, Rh, Ir and Os nanoparticles with 7.09, 3.45, 6.89, 2.42 and 4.52 nm in diameter, respectively, could be prepared this way. The self-assembly of dodecylamine-stabilized Ag and Rh nanoparticles was also detected by transmission electron microscopy (TEM).

Improved biocompatibility of surface functionalized dendrimer-entrapped gold nanoparticles

A general approach to modifying preformed dendrimer-entrapped Au nanoparticles with different functionalities is proved to improve their biocompatibility.

Formation of gold@polymer core-shell particles and gold particle clusters on a template of thermoresponsive and pH-responsive coordination triblock copolymer

Template synthesis of various morphological gold colloidal nanoparticles using a thermoresponsive and pH-responsive coordination triblock copolymer of poly(ethylene glycol)-b-poly(4-vinylpyridine)-b-poly(N-isopropylacrylamide) is studied. The template morphology of the thermoresponsive and pH-responsive coordination triblock copolymer, which can be tuned by simply changing the pH or temperature of the triblock copolymer aqueous solution, ranges from single chains to core-corona micelles and further to micellar clusters. Various morphological gold colloidal nanoparticles such as discrete gold nanoparticles, gold@polymer core-shell nanoparticles, and gold nanoparticle clusters are synthesized on the corresponding template of the triblock copolymer by first coordination with gold ions and then reduction by NaBH4. All three resultant gold colloidal nanoparticles are stable in aqueous solution, and their sizes are 2, 10, and 7 nm, respectively. The gold@polymer core-shell nanoparticles are thermoresponsive. The gold nanoparticle cluster has a novel structure, and each one holds about 40 single gold nanoparticles.

Langmuir-Blodgett monolayers of gold nanoparticles with amphiphilic shells from V-shaped binary polymer arms

Gold nanoparticles functionalized with amphiphilic polybutadiene-poly(ethylene glycol) (PB-PEG) V-shaped arms formed stable Langmuir monolayers at the air-water and the air-solid interfaces. At these interfaces, the binary arms vertically segregated into a dense polymer corona, which surrounded the gold nanoparticles, preventing their large-scale agglomeration and keeping individual nanoparticles well-separated from each other and forming flattened, pancake nanostructures. The presence of both PEG and PB chains in the close proximity to the gold core was confirmed by surface enhanced Raman spectroscopy, whereas the AFM phase contrast images revealed the presence of 2 nm gold cores surrounded by the polymer shell with the diameter of 11 nm. We suggest that the amphiphilic shell drives their spontaneous organization into discrete 2D pancake-like hybrid structures that measured up to 10 microm in diameter and had a high packing density of gold clusters.

Enantiodifferentiating Photocyclodimerization of 2-Anthracenecarboxylic Acid Mediated by γ-Cyclodextrins with a Flexible or Rigid Cap

[reaction: see text] A series of modified gamma-cyclodextrins (CDs) with a flexible or rigid cap, synthesized and used as chiral supramolecular hosts for mediating the enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid, significantly improved the chemical and optical yields of chiral head-to-head cyclodimer 3, while the gamma-CD with a rigid cap dramatically inverted the stereochemical outcomes and further improved the enantioselectivities of both head-to-tail and head-to-head dimers 2 and 3.

The tuneable complexation of gold nanoparticles

Mixed monolayer protected gold nanoparticles have been fabricated incorporating 1,5-dialkyloxynaphthalene moieties that are capable of forming complexes with the tetracationic cyclophane cyclobis(paraquat-p-phenylene); electrochemical reduction of the cyclophane or the addition of tetrathiafulvalene results in disassembly of the complexes.

A new 19-metal-atom cluster [(Me2PhP)10Au12Ag7(NO3)9] with a nearly staggered–staggered M5 ring configuration

New mixed metal clusters with M19 metal frameworks have been synthesized by NaBH4 reduction of Au(NO3)(PMe2Ph) together with AgNO3 in ethanol. Single crystal X-ray diffraction has revealed Au12Ag7 and Au17Ag2 metal skeletons for these clusters, which are best described in terms of bicapped pentagonal antiprismatic cages with a staggered-staggered M(5) ring configuration. These clusters connect the missing link between M13 icosahedral and M25 biicosahedral clusters providing a view of the cluster growth process. A TEM image of this cluster has been observed, which has clearly demonstrated single-sized nano-particles of less than 1.0 nm.

A metal nanoparticle-based supramolecular approach for aqueous biphasic reactions

beta-cyclodextrin immobilized on Pd nanoparticles was successfully employed as an efficient phase-transfer catalyst in aqueous biphasic hydrogenation reactions.

Towards nanomedicine with a supramolecular approach: a review

A review dedicated mainly to the results obtained by the authors on the use of cyclodextrin (CD) derivatives on protein (enzyme) stabilization through covalent and non-covalent interactions (host-guest supramolecular interactions) is presented here. This latter procedure served to introduce a new method for enzyme immobilization on metallic surfaces that can be used to prepare biosensors and therapeutic nanodevices. The surfaces of gold (and silver) electrodes and nanoparticles were modified with sulphur-containing cyclodextrin derivatives. The protein (enzyme) was then supramolecularly immobilized on the modified surface when one or more of its bulky hydrophobic moieties was included into the CD cavity. The protein can also be modified with a typical CD guest, such as adamantane, to achieve a more stable immobilization. Different examples are presented, such as a biosensor based on monolayers of adamantane-modified cytochrome c and a bienzymatic nanodevice comprising gold nanoparticles stabilized with CD associated to catalase and superoxide dismutase modified with complementary host-guest residues. The possibilities of this new approach for the development of biosensors and therapeutic nanodevices are analyzed.

Surfactant layering on mixed monolayer-protected gold clusters

Positively-charged monolayer protected gold clusters (MMPCs) were mixed with sodium dodecyl sulfate (SDS). At lower SDS concentration, the initially water-soluble particles became organic-soluble while remaining discrete. Upon further addition of SDS, the particles aggregate and become water-soluble. NaCN decomposition, TEM, and DLS characterization reveal the morphology and properties of these encapsulated assemblies.

Supramolecular control of complexation-induced fluorescence change of water-soluble, β-cyclodextrin-modified CdS quantum dots

The fluorescence of beta-cyclodextrin-modified CdS quantum dots can be reversibly tuned by introducing different substrates in aqueous media.