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. 2025 May 3;15(9):692.
doi: 10.3390/nano15090692.

Scalable Production and Multifunctional Coating of Gold Nanostars for Catalytic Applications

Silvia Nuti  1 , Adrián Fernández-Lodeiro  2 , Inmaculada Ortiz-Gómez  3 , Carlos Lodeiro  1   4 , Javier Fernández-Lodeiro  1   4
Affiliations

Scalable Production and Multifunctional Coating of Gold Nanostars for Catalytic Applications

Silvia Nuti et al. Nanomaterials (Basel). .

Abstract

Gold nanostars (AuNSTs) stabilized with adenosine monophosphate (AMP) were synthesized using a scalable method, achieving a 30-fold yield increase compared to previous studies using AMP as a shaping agent, while also reducing the reaction time to 3 h. The AuNSTs were coated with mesoporous silica (mSiO2) via a robust approach, producing the AuNSTs@mSiO2 nanoparticles (NPs) with tunable thicknesses and consistent optical properties for a range of morphologies. The NPs were additionally coated with platinum (Pt) before synthesizing the mSiO2 layer, facilitating a comparative analysis of catalytic activity. The catalytic performance of the bare AuNSTs, the AuNSTs@mSiO2, and the AuNSTs@Pt@mSiO2 was evaluated through methylene blue reduction, confirming the gold core as the primary catalytic source. The AuNSTs@Pt@mSiO2 exhibited enhanced activity, highlighting the potential of the mSiO2 coatings. Additionally, solid-phase catalytic tests using 3,3',5,5'-tetramethylbenzidine (TMB) on cellulose discs demonstrated the effectiveness of these NPs under diverse conditions. These findings showcase the versatility and broad catalytic potential of silica-coated NPs for solution- and solid-phase applications.

Keywords: catalysis; gold; mesoporous silica coating; nanostars; platinum.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Normalized Extinction spectra (A); Transmission Electron Microscopy Images of the AuNSTs obtained by the original protocol (B); expansion of the concentration (×4) (C); and expansion of volume (×30) (D).
Figure 2
Figure 2
Schematic representation of the characterization of the silica coating (A). TEM Images of the AuNSTs@mSiO2 obtained using [TEOS] of 1.6 (B), 2.2 (C), 2.9 (D) mM. TEM images of the AuNSTs@mSiO2 obtained repeating the coating process with a TEOS concentration of 6.7 mM three times (E). Representative extinction spectra of the AuNSTs@mSiO2 obtained with 1.6 and 2.2 mM of TEOS (F).
Figure 3
Figure 3
Time-dependent UV-visible spectra for the catalytic reduction of methylene blue by AuNSTs (A); and AuNSTs@mSiO2 with two different silica thicknesses (B,C), with the inset showing the plot of time dependent absorbance at 662 nm.
Figure 4
Figure 4
Transmission electron microscopy (TEM) images of the AuNSTs@Pt at different magnifications (A,B). High-resolution TEM image, with the inset showing a zoomed-in view of the region marked by the dotted box, highlighting an interplanar distance of 0.227 nm corresponding to the Pt(111) plane (C). High-angle annular dark-field (HAADF) image (D), with EDS elemental maps showing Au in red (E) and Pt in green (F). TEM images of the AuNSTs@Pt@mSiO2 NPs at different magnifications (G,H). Time-dependent UV-visible spectra for the catalytic reduction of methylene blue by AuNSTs@Pt@SiO2NPs, with the inset showing the plot of time dependent absorbance at 662 nm (I).
See this image and copyright information in PMC

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