Synthesis of Au Nanoparticles Assisted by Linker-Modified TiO₂ Nanoparticles

Abstract

Plasmonic nanoparticles, especially gold ones, have been widely employed as photosensitizers in photoelectrovoltaic or photocatalytic systems. To improve the system's performance, a greater interaction of the nanoparticles with the semiconductor, generally TiO, is desired. Moreover, this performance is enhanced when an efficient covering of TiO surface by the sensitizer is achieved. The Brust-Schiffrin-like methods are of the most employed approaches for nanoparticles synthesis. In a traditional approach, the reduction of the gold precursor is performed in the presence of a stabilizer (typically a thiol molecule) free in solution. A second step in which the obtained nanoparticles are anchored to the semiconductor surface is necessary in the case of photosensitive applications. Drawbacks like steric hindrance turn more difficult the covering of the semiconductor's surface by nanoparticles. In this paper, we report a variation of this methodology, where the linker is previously anchored to the TiO nanoparticles surface. The resulting system is employed as the stabilizer in the gold reduction step. This strategy is carried out in aqueous media in two simple steps. A great covering of the titania surface by gold nanoparticles is achieved in all cases and the gold nanoparticles in the resulting nanoaggregate might be useful for photoelectrovoltaic or photocatalytic applications.

Highly efficient hydrogen evolution reaction, plasmon-enhanced by AuNP-l-TiO2NP photocatalysts

“…However, no significant morphological differences were found for the same Au:linker proportions. 29 It is worth to highlight that in all cases the as-prepared nanoaggregates showed an efficient covering of the semiconductor's surface by the AuNPs, as well as high quality AuNPs regarding morphology and light harvesting properties. In consequence, an effective sensibilization of the semiconductor is achieved.…”

“…Moreover, the highest density of AuNPs coverage was obtained for proportion 2. 29 This factor enhances the catalytic effect of nanoaggregates from proportion 2, while the greater absorption yields improves the activity in the case of other two proportions. Urbach energies (Eu) were also determined to complement the optical characterization of these materials.…”

“…AuNPs-L-TiO2NPs catalysts were prepared according to a variant of Brust-Schiffrin approach, previously reported by our group. 29 Briefly, 50 mg of commercial TiO2 (Degussa P25, ≥ 99%, Merck) was dispersed by sonication in 50 mL of acidified Milli-Q water (pH = 1.69, 85 μL of concentrated HCl). Then, 30 mmol of thiol was added and the mixture was kept under vigorous stirring for 30 min.…”

“…In addition, the crystalline structure of Au in the nanoparticles is also appreciated in the HRTEM micrograph (inset in Figure 2A) and the corresponding detected from live Fast Fourier Transform. 29 It is interesting to check if the different structures of the three linkers could affect the photo-catalytic properties of the nanoaggregates in a H2 evolution photoreaction. Hence, three proportions were used Please do not adjust margins…”

“…27 In addition, it has been reported that AuNPs-decoration of TiO2 assisted by linker led to an increase in the photocatalytic activity of the resulting system in comparison to a TiO2 directly decorated with Au nanoparticles. 28 In a previous work, we reported the synthesis of gold nanoparticleslinker-TiO2 nanoparticles nanoaggregates (AuNPs-L-TiO2NPs), employing a novel variant 29 of the Brust-Shiffrin approach. 30 The asprepared nanoaggregates showed an efficient covering of the semiconductor's surface by the AuNPs, as well as appropriate AuNPs sizes for effective sensibilization.…”