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Solar vapour generation technology has emerged as a promising approach for reducing the global problem of water shortage issues via the solar water interfacial evaporation technique utilised for water purification. However, achieving superior light absorption and a high evaporation rate in a solar evaporator remains challenging. Here, we show that high solar interfacial water evaporation rates can be achieved using a natural and sustainable biomaterial, diatom frustules, decorated with silver nanoparticles made using a one-pot synthesis method. The species of diatom selected for this study was Actinocyclus sp. that has complex nano- and micro-structured surfaces and air pores that lead to multiple light scattering. The absorptance before and after silver nanoparticle coating was measured after creating a thin frustule layer on a hydrophobically treated quartz substrate. It was found that the cleaned and uncoated frustules had zero absorptance from 400 nm to 1200 nm. However, silver nanoparticles coated frustules showed a large broadband absorptance up to 90 % from 400 nm to 1200 nm, covering most of the solar spectrum, due to localised surface plasma resonance and multiple light scattering in the air pores. The frustules were floated on the surface of a water droplet for solar water interfacial evaporation rate measurements. A high evaporation rate of 5.4 kg m−2 h−1 under 1 sun irradiation was found for silver nanoparticles decorated frustules and for a droplet volume of 10 mm3. This is significantly larger than that found for frustules without silver nanoparticles or bare water where the evaporation rates were 1.7 kg m−2 h−1 and 1.2 kg m−2 h−1, respectively. Moreover, increasing the number of floating frustules per drop resulted in a factor of 1.67 enhancement. Our results show that research into silver nanoparticle decorated frustules can potentially provide a novel route for fabricating a high-performance solar vapour generator. [Display omitted] [ABSTRACT FROM AUTHOR]

Single-layer silver nanoparticles have been grown on quartz substrates by a one-pot synthesis method using tannic acid as a reducing agent. The area filling fraction and average nanoparticle sizes were found to depend on the tannic acid pre-treatment and silver nitrate reduction times. Increasing these two parameters enabled single-layer silver nanoparticles to be fabricated with area filling fractions and average nanoparticle sizes that were controlled from 7.2% to 50%, and from 25 nm to 40 nm, respectively. The silver nanoparticles were anchored onto the quartz surface by a tannic acid layer bonded to silanol groups. Localized surface plasmonic resonance from the silver nanoparticles was observed where the peak wavelength was controlled by the synthesis conditions. Surface enhanced Raman scattering, and surface enhanced photoluminescence were also observed. Our one-pot method to produce single-layer silver nanoparticles offers a promising approach for applications in plasmonic microdevices and biosensors. [Display omitted] • One-pot synthesis method for growing Ag nanoparticle single layers on quartz. • Controllable area filling fractions and average nanoparticle sizes. • Surface enhanced Raman scattering and photoluminescence were observed. [ABSTRACT FROM AUTHOR]