Abstract
This article details the preparation of hollow gold-silver nanoshells (GS-NSs) coated with tunably thin silica shells for use in plasmon-enhanced photocatalytic applications. Hollow GS-NSs were synthesized via the galvanic replacement of silver nanoparticles. The localized surface plasmon resonance (LSPR) peaks of the GS-NSs were tuned over the range of visible light to near-infrared (NIR) wavelengths by adjusting the ratio of silver nanoparticles to gold salt solution to obtain three distinct types of GS-NSs with LSPR peaks centered near 500, 700, and 900 nm. Varying concentrations of (3-aminopropyl)trimethoxysilane and sodium silicate solution afforded silica shell coatings of controllable thicknesses on the GS-NS cores. For each type of GS-NS, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images verified our ability to grow thin silica shells having three different thicknesses of silica shell (~2, ~10, and ~15 nm) on the GS-NS cores. Additionally, energy-dispersive X-ray (EDX) spectra confirmed the successful coating of the GS-NSs with SiO2 shells having controlled thicknesses. Extinction spectra of the as-prepared nanoparticles indicated that the silica shell has a minimal effect on the LSPR peak of the gold-silver nanoshells.
Highlights
Harvesting solar energy and storing it in the form of a chemical, such as hydrogen, has garnered significant interest for renewable energy because it is the most abundant and free energy source available on earth [1,2]
We have successfully synthesized hollow gold-silver nanoshells coated with silica shells of varying thicknesses by tuning the concentration of (3-aminopropyl)trimethoxysilane and sodium silicate solutions
Our strategy proceeded via the synthesis of silver nanoparticles in the size range of 60–80 nm using a modified KI-assisted citrate procedure followed by the formation of hollow gold-silver nanoshells via galvanic replacement
Summary
Harvesting solar energy and storing it in the form of a chemical, such as hydrogen, has garnered significant interest for renewable energy because it is the most abundant and free energy source available on earth [1,2]. Of particular interest is the water-splitting reaction, for which the standard Gibbs free energy to produce hydrogen from water is greater than 237 kJ/mol and is equivalent to the wavelength of light in the range of 500–1100 nm [4]. Various composites have been aggressively explored for use in water-splitting reactions due to their ability to absorb across the broad range of wavelengths in the solar spectrum [5]. Most of the aforementioned metal oxide materials respond most efficiently to UV light, owing to their large bandgap (higher than 3.2 eV), while the bulk of solar radiation reaching the surface of the earth lies
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