Highly ordered mesoporous silica film nanocomposites containing gold nanoparticles for the catalytic reduction of 4-nitrophenol

Abstract

We report that transparent mesostructured silica/gold nanocomposite materials with an interpore distance of 4.1 nm, as-synthesized from a templated sol–gel synthesis method using discotic trinuclear gold(I) pyrazolate complex, were successfully utilized for the fabrication of thin film mesoporous silica nanocomposites containing gold nanoparticles. The material exhibited a highly ordered hexagonal structure when subjected to a thermal hydrogen reduction treatment at 210 °C. In contrast, when the material was subjected to calcination as a heat treatment from 190 to 450 °C, the thin film nanocomposites showed an intense d 100 X-ray diffraction peak. Moreover, gold nanoparticles inside the thin film nanocomposites were confirmed by the presence of the d 111 diffraction peak at 2θ = 38.2°, a surface plasmon resonance peak between 500–580 nm, and the spherical shape observed in the transmission electron microscope images, as well as the visual change in color from pink to purple. Interestingly, by simply dipping the material into a reaction solution of 4-nitrophenol at room temperature, the highly ordered structure of the as-fabricated silica/gold nanoparticle thin film composite after thermal hydrogen reduction at 210 °C resulted in an improved catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol compared to the material calcined at 250 °C. Such catalytic activity is due to the presence of gold nanoparticles of smaller size in the silicate channels of the highly ordered mesoporous film nanocomposites.

Fluorescent Noncovalent Organic Framework for Supporting Gold Nanoparticles as Heterogeneous Catalyst with Merits of Easy Detection and Recycle

“…− or H 2 adsorbs onto the active sites of AuNPs surface, and then transforms to the surface-hydrogen species that is the actual reductant for reacting with substrates. [42] Generally, AuNPs@CMC-TPEA would promote the catalysis in the following aspects: 1) the geometric and size-specific electronic structures gain AuNPs with superior catalytic activity than the bulk metal and molecular compounds; [16][17][18][19][20][21][22][23][24][25][26] 2) the cationic property of the CTA stabilizer improves the catalytic activity of AuNPs in the reduction by BH 4 − , as compared to those of thiols-capped AuNPs and anionic surfactants stabilized AuNPs, which is attributed to the electrostatic attraction between the cationic CTA and the anionic species (BH 4 − and also substrates), [43] referring to following the Langmuir−Hinshelwood mechanism; [44][45][46] 3) the porous structure of CMC-TPEA provides high surface-to-volume ratio, facilitating the AuNPs catalyzed reactions. In the following, we will present the catalytic activity of AuNPs@CMC-TPEA in the reduction of some nitrobenzene and dye compounds.…”

“…[11,12] In the past decades, with virtues of good biocompatibility and low toxicity, gold NPs (AuNPs) havereceived considerable attention and shown great potential applications in the fields of catalysis, biology, optics, and nanotechnology. [13][14][15] Under the motivation by the geometric and size-specific electronic structures, AuNPs can perform good catalysis on some reduction reactions, [16][17][18][19][20][21][22][23][24] aerobic oxidation, [25] carbon-carbon bond formation, [26] etc. However, similar to the other nanoscale materials, two major concerns are presented for using AuNPs as catalysts, which are the agglomeration under heating conditions and hard recycling for repeating use.…”

Novel mesoporous silica nanocarriers containing gold; a rapid diagnostic tool for tuberculosis

“…MSNs can also be used as a carrier for antimicrobial agents. The major pathology of the TB is kind of pulmonary infection, where MSNs have been proved efficient therapeutic cargos for aerosol delivery and are promising choice for treating respiratory diseases [22][23][24][25].…”

Temperature-Dependent X-Ray Studies of Discotic Hexagonal Columnar Mesophases in Trinuclear Gold(I) Pyrazolate Complex

“…Figure 2. The structure of trinuclear gold complexes with a) two phenyl group with each substituted with two aliphatic (decyloxy) chains, b) heptyl substituent groups, c) octyl substituent groups and d) amphiphilic side chain [12][13][14] In this work, [Au3Pz3]C10TEG was chosen as the subject matter as it was proven to exhibit room temperature liquid crystalline properties and its thin film metal nanocomposites have been successfully utilized in various applications including metal ion sensors [15], starting precursor for formation of gold nanoparticles [16,17], phosphorescence sensing and temperature imaging [18], as well as catalysis [19]. In addition, apart from using polarized optical microscope (POM), X-ray scattering experiment was mainly used as the technique to monitor the real-time structural changes of [Au3Pz3]C10TEG as this method is very useful in investigating the LCs behaviour of compounds as being reported elsewhere [20][21][22].…”