Dispersion and Stability Studies of Resorcinarene-Encapsulated Gold Nanoparticles

Abstract

Two resorcinarene surfactants with sulfur-functionalized headgroups have been evaluated for their ability to stabilize dispersions of midnanometer (16−87 nm)-sized gold particles in organic solvents. Citrate-stabilized colloidal gold nanoparticles were extracted from aqueous solutions into toluene or chloroform by tetrabenzylthiol resorcinarene 1 or tetraarylthiol resorcinarene 2. The nanoparticle dispersions were subjected to various conditions and monitored for changes in plasmon absorption intensity. The stability of the dispersions was dependent on the chemisorptive properties of the surfactant headgroup, with tetrabenzylthiol 1 being the more effective dispersant. Nanoparticles encapsulated by 1 were also highly robust, demonstrated good resistance to alkanethiol-induced flocculation, and could be redispersed after repeated precipitations in polar solvents. Surface-enhanced Raman scattering analysis and X-ray photoelectron spectroscopic studies confirmed significant differences in the chemisorptive properties of tetrathiols 1 and 2, indicating that surface passivation is an important factor in the dispersibility of colloidal gold nanoparticles in nonpolar solvents.

Calixarene‐Encapsulated Nanoparticles: Self‐Assembly into Functional Nanomaterials

“…38,39 Moreover, resorcinarene tetrathiols 6 and especially 7 were capable of extracting colloidal Au nanoparticles from aqueous solutions. { These classic 'Faraday sols' are easily produced in the 10-100 nm size range with narrow size distributions and are endowed with size-dependent optical properties, but their organization into well-defined ensembles had never been systematically addressed because of difficulties in dispersion control.…”

“…Colloidal Au particles as large as 87 nm could be dispersed in chloroform-THF mixtures by tetrabenzylthiol resorcinarene 7. 39 The stability of the nanoparticles encapsulated by tetrathiols 6 and 7 was also evaluated against alkanethiolinduced precipitation in organic solvents. Both systems were far more stable than the nanocrystals coated with resorcinarenes 1 or 2, but 7 was significantly more robust in its chemisorption than 6 and could maintain a long dispersion half-life (t 1/2 y1 month) in the presence of alkanethiols at ambient temperature (see Fig.…”

“…This can be controlled by using an ion-exchange resin to minimize the ionic strength of the colloidal suspensions prior to introducing the surfactant. 39,41 Even so, a sublayer of adsorbed electrolyte remains; if the surfactant is not aggressive enough to completely displace the adsorbed ions, the encapsulated nanoparticles will not be fully extracted to the organic phase but instead be confined to the aqueous interface. { These effects are illustrated in Fig.…”

Spectroscopy-based study on the interaction between gold nanoparticle and poly(vinylpyrrolidone) molecules in a non-hydrocolloid

“…In this regard, various bottom-up approaches, such as UV irradiation [6,7,15], chemical [3][4][5][6], thermochemical [3,6], sonochemical [3,6], and electrochemical reduction [16], have been reported for the synthesis of stable Au NPs of controlled shapes and sizes. Gold NPs of various structural architectures (e.g., rods, plates, disks, cubes, spheres, and stars) can be synthesized by proper manipulation of experimental parameters in the presence of surface-capping agents in the form of surfactants [3,17], polymers [3][4][5][6][7], and dendrimers [3,6]. However, among the various encapsulating agents, a macroscopic ligand especially a hydrophilic polymer like poly(vinylpyrrolidone) (PVP) is widely used in the synthesis of NMNPs [4][5][6]18,19].…”

Intense quenching of fluorescence intensity of poly(vinyl pyrrolidone) molecules in presence of gold nanoparticles

“…The formation of GNPs in a non-hydrocolloid was confirmed by UVvisible, X-ray photoemission spectroscopy (XPS), and transmission electron microscope (TEM). An organic solvent was chosen in this work because such medium founds to provide low interfacial energies needed for a high degree of control during solution and surface processing is required for synthesis of nano colloids (Balasubramaniam et al 2002). Also it was reported that Au-NPs synthesized in an organic medium offer excellent control over size and possess superior processability (Sugunan et al 2005).…”