Precious-Metal Nanoparticles Anchored onto Functionalized Halloysite Nanotubes

Abstract

Natural halloysite nanotubes (HNTs) were functionalized with a silane coupling agent with the aim of tuning the loading rate and dispersion of precious-metal nanoparticles. The samples were characterized by FTIR spectroscopy, TEM, and XPS. The results indicated that a large number of precious-metal nanoparticles were anchored on the surface of the silanized HNTs, with an average diameter of ∼3 nm. The functionalized HNTs contain a large number of functional groups (−NH 2 or −SH groups) that have one lone electron pair and can form a chemical bond complex with nanoparticles. Because of bond formation between the nanoparticles and the functional groups, most of the nanoparticles (NPs) are anchored by the functional groups, resulting in the formation of nanoparticle−functional group complexes. Bond formation between the nanoparticles and the functional groups was demonstrated, and furthermore, atomic-level interfaces for NPs anchored onto functionalized HNTs were depicted. The chemical immobilization of precious-metal nanoparticles onto silanized HNTs could avoid particle aggregation and movement, thus leading to a higher catalytic efficiency.

Physicochemical characterization of organosilylated halloysite clay nanotubes

“…6 Pt nanoparticles were uniformly immobilized into APTES functionalized HNTs and were subsequently tested in the catalytic hydrogenation of styrene to ethylbenzene with 100% substrate conversion after 180 min; however, the catalytic activity slowly decreased with the increasing number of reaction cycles because of the low recovery of the catalyst. 23 Finally, raw HNTs were used as intrinsic acid catalysts in methylic and ethylic esterifications of lauric acid with substrate conversions of 95.0 % and 87.1 % for the methylic and ethylic esterifications, respectively. 24 In the present work, pristine HNTs were functionalized with several organosilanes with different functional groups (-NH 2 , -NH-(CH 2 ) 2 -NH 2 , -SH, -Br, -C 6 H 6 , -C=C) in aprotic and anhydrous media, Scheme 1, with the ultimate goal of being used as linkers or reactive groups for the immobilization of metal complexes/other active phases (metal and metal oxide nanoparticles) with catalytic activity.…”

Non-enzymatic sensor based on a glassy carbon electrode modified with Ag nanoparticles/polyaniline/halloysite nanotube nanocomposites for hydrogen peroxide sensing

“…Halloysite nanotube (HNTs) is a super-fine clay material (Al 2 Si 2 O 5 (OH) 4 ·nH 2 O), which exhibits interesting features of hollow nanotubular structure, good hydrophilicity, tunable surface chemistry, thermal stability and low cost [17]. Halloysite nanotube (HNTs) is a super-fine clay material (Al 2 Si 2 O 5 (OH) 4 ·nH 2 O), which exhibits interesting features of hollow nanotubular structure, good hydrophilicity, tunable surface chemistry, thermal stability and low cost [17].…”

“…Their novel physical and chemical properties provided opportunities for advanced applications in many fields [18]. HNTs functionalized with organosilane can effectively increase the amounts of metal particles loaded and improve the adhesion between the metal particles and the support [17]. Furthermore, compared to carbon nanotubes, HNTs were economically available natural materials and had many unique characteristics including different outside and inside chemical properties.…”

Substitutional Doping for Aluminosilicate Mineral and Superior Water Splitting Performance

“…A number of techniques have been used to enhance the functionalities of support materials, such as polymer coating [14, 15], carbon coating [8], and atomic doping [16–19]. Doped aluminosilicate minerals can form in nature, but their synthesis in a laboratory allow for various properties with the specified dopants [20–23].…”