Chemical, Thermal, and Ultrasonic Stability of Hybrid Nanoparticles and Nanoparticle Multilayer Films

Abstract

Gold nanoparticles stabilized by thiolates derived from normal and ω-functionalized alkane-and arenethiols (HS(CH 2 ) n CH 3 , HS(CH 2 ) 10 COOH, HS(CH 2 ) 11 OH, HSC 6 H 4 NH 2 , HSCH 2 CH 2 C 6 H 5 , and HSCH 2 C 6 H 4 C(CH 3 ) 3 ) were synthesized. Differences in their chemical and ultrasonic stabilities were studied using UV-vis spectroscopy. The results showed that these stabilities of monolayer-protected nanoparticles were greatly influenced by the structure and functionality of the monolayer surrounding a nanoparticle core. The selective functionalization of the nanoparticle allowed us to prepare hybrid nanostructures (nanoparticle multilayer assemblies) with different compositions and functionalities. This paper also presents an investigation of the chemical, thermal, and ultrasonic treatments of these nanoparticle multilayer assemblies. The results suggest that the linkers used to build nanoparticle multilayer films govern the overall stability of hybrid nanostructures.

Preparation of Gold Nanoisland Arrays from Layer-by-Layer Assembled Nanoparticle Multilayer Films

“…The COOH-functionalized gold nanoparticles (MUA-NPs: average molecular formula of Au314L91) used for the film preparation were synthesized by the following methods. [33][34][35] Hexanethiolateprotected gold nanoparticles were first synthesized using a convenient two-phase synthesis known as the Schiffrin reaction. Briefly, AuCl4…”

“…The incorporation of COOH-functional groups to the monolayer involved a modification of the hexanethiolate-protected gold nanoparticles by ligand-replacement. 34,35 In the exchange reaction, the incoming 11-mercaptoundecanoic acid (MUA) ligands replaced the hexanethiolate ligands on nanoparticles in THF by an associative reaction. The relative concentration of incoming ligands was carefully controlled for the synthesis of nanoparticles to have ~ 20% of COOH functional groups in the monolayers.…”

“…The silanization procedure started with glass microscope slides that were cleaned in a "piränha" solution (3/1 H2SO4/H2O2), rinsed thoroughly with distilled water, and placed in a 100 mL isopropyl alcohol solution containing 1 mL of MPTS and 1 mL of nanopure water. 35 (Caution: Pirahha solution reacts violently with organic materials and should be handled with extreme care.) After heating for 30 min, the glass slides were rinsed with ethanol, blown dry with N2, and allowed to dry in a 100 o C oven for at least 30 min.…”

“…To build the gold nanoparticle multilayers onto glass slides, the MPTS-functionalized glass slides were placed in the ethanol solution containing MUA-NPs (~ 2.2 ± 0.8 nm in diameter) for 24 hours. 35 Then, the slides were alternately placed in the aqueous solution containing PAH and in the nanoparticle solution for ten minutes each to build the second layer of the gold nanoparticle films. This last procedure was repeated three or five more times to build five or eight layers, respectively, of the gold nanoparticle multilayer films.…”

Reactivity of Au25 clusters with Au3+

“…Most of these studies have been on monolayer protected clusters (MPCs), which are typically nanoparticles with diameters larger than 2 nm. Stability of nanoparticles depends on the chemical constitution and the shape of the core as well as the structure and the functionality of the ligands surrounding them [1]. It is reported that gold nanoparticles stabilized by monolayers of arenethiols have less thermodynamic stability than those stabilized by alkanethiols [2].…”