Abstract
In this work, the Stöber process was applied to produce uniform silica nanoparticles (SNPs) in the meso-scale size range. The novel aspect of this work was to control the produced silica particle size by only varying the volume of the solvent ethanol used, whilst fixing the other reaction conditions. Using this one-step Stöber-based solvent varying (SV) method, seven batches of SNPs with target diameters ranging from 70 to 400 nm were repeatedly reproduced, and the size distribution in terms of the polydispersity index (PDI) was well maintained (within 0.1). An exponential equation was used to fit the relationship between the particle diameter and ethanol volume. This equation allows the prediction of the amount of ethanol required in order to produce particles of any target diameter within this size range. In addition, it was found that the reaction was completed in approximately 2 h for all batches regardless of the volume of ethanol. Structurally coloured artificial opal photonic crystals (PCs) were fabricated from the prepared SNPs by self-assembly under gravity sedimentation. Figureᅟ Electronic supplementary materialThe online version of this article (doi:10.1007/s11051-016-3691-8) contains supplementary material, which is available to authorized users.
Highlights
Spherical silica particles with uniform size, shape and composition have been used in various applications such as ceramics (Sacks and Tseng 1984), chromatography (Unger et al 2000), coatings (Leder et al 2002) and more recently in the field of photonic crystals (PCs) or colloidal crystals (Xia et al 2000; López 2003)
Natural precious opals are a typical example of PCs as they consist of highly ordered silica nanoparticles (SNPs) with diameters typically ranging between 150 and 400 nm (Jones et al 1964; Sanders 1964; Darragh et al 1976)
It has been proved that particle diameter decreases monotonically as temperature increases (Bogush et al 1988)
Summary
Spherical silica particles with uniform size, shape and composition have been used in various applications such as ceramics (Sacks and Tseng 1984), chromatography (Unger et al 2000), coatings (Leder et al 2002) and more recently in the field of photonic crystals (PCs) or colloidal crystals (Xia et al 2000; López 2003). A set of seven batches of uniform SNPs were successfully produced with particle diameters ranging from 70 to 400 nm and with a polydispersity index (PDI), for all but one sample, of less than 0.1 Under these fixed conditions, it was found that the final size has a negative correlation with the volume of ethanol used in the recipe. A Malvern Zetasizer Nano S dynamic light scattering (DLS) device was used to measure the particle size and size distribution of the SNPs. The growth rates of the silica particles in the solution were analysed using DLS, as the technique provides an effective way to measure the particle size directly from an original silica suspension with little sample preparation required such as drying or gold coating
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