Green synthesis of Au nanoparticles immobilized on halloysite nanotubes for surface-enhanced Raman scattering substrates

Abstract

A facile and green route was introduced to synthesize Au nanoparticles immobilized on halloysite nanotubes (AuNPs/HNTs) used for surface-enhanced Raman scattering substrates. The naturally occurring HNTs were firstly functionalized with a large amount of -NH(2) groups by N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (AEAPTES), which possesses one lone electron pair and will "anchor" Au ions to form a chelate complex. Then, with the addition of tea polyphenols (TP), the Au ions were reduced on the surface of the previously formed Au-NH(2) chelate complex to form AuNPs. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE-SEM) observations indicate that a large amount of AuNPs were synthesized on HNTs. The AuNPs are irregularly spherical and densely dispersed on HNTs and the diameter of the nanoparticles varies from 20 to 40 nm. The interactions between AuNPs and -NH(2) groups were verified by X-ray photoelectron spectroscopy (XPS) and the results showed that the functional groups can "anchor" AuNPs through the chelating effect. The as-prepared AuNPs/HNTs nanomaterials with several nanometers gaps among nanoparticles were used as a unique surface-enhanced Raman scattering substrate, which possessed strong and distinctive Raman signals for R6G, indicating the remarkable enhancement effect of the AuNPs/HNTs.

Fabrication of Gold Nanoparticles Modified Carbon Nanofibers/Polyaniline Electrode for H2O2Determination

“…These values are consistent with JCPDS: 65-2870, which indexed as the (111), (200), (220)and (311) crystal planes of AuNPs, respectively, indicating that crystalline Au had been formed on the CPANFs 42. …”

Physicochemical characterization of organosilylated halloysite clay nanotubes

“…17 In a distinct work, the organosilane N-2-aminoethyl-3-aminopropyltrimethoxysilane (AEAPTMS) was used in the functionalization of HNTs to allow immobilizing Au nanoparticles to be subsequently used as a surface-enhanced Raman scattering substrate, showing a remarkable enhancement effect due to the synergy between the Au nanoparticles and the HNTs. 19 In another application, HNTs functionalized with bis(triethoxysilylpropyl)-tetrasulphide (TESPT) were used to improve the dispersion and physical properties of a natural rubber matrix. 1 Functionalized HNTs have also been used as supports for catalytic active species (metal complexes and metallic nanoparticles), although not in so great extent as other clay minerals, such as K10-montmorillonite.…”

Hybrid Materials Based on Bentonite Functionalized with Amine Groups via the Hydrolytic Sol-Gel Method

“…9,26,27 As for the spectra of BEN-APTS, BEN-TMPT, and BEN-TMPO (spectra b-d in Figure 2), they display bands between 2929 and 2795 cm -1 , ascribed to CH/NH groups, and at 1567 and 1330 cm -1 , ascribed to amine groups (NH 2 ). The FTIR spectra indicated functionalization of bentonite with the alkoxides.…”

“…1 Several works have reported on clay modification and on clay adsorption capacity for environmental use as adsorbents. [2][3][4][5][6][7][8][9][10][11][12] In addition, clay materials can undergo intercalation reactions and/or functionalization of its interlayers and/or surface area, to afford hybrid materials. The -OH groups present in the clay edges will react with silane through condensation reactions via the sol-gel method.…”