One-pot synthesis and characterisation of alkyl functionalised silicon nanoparticles, using an inverse micelle based method.
Silicon nanoparticles (SiNPs) are subject to research in a variety of fields and their synthesis is of increasing importance. A simple, cheap and easily scalable solution based synthesis method of alkyl terminated SiNPs is reported here. The produced SiNPs were imaged with a transmission electron microscope and have a spherical silicon core approximately 5 nm in diameter. The particles also show a strong blue photoluminescence (PL) emission at 420 nm; demonstrating a stability of luminescence over long periods of time. Further study of these particles indicated the presence of alkoxy impurities in the surface chemistry. This was caused by the introduction of alcohol to the system in order to quench the lithium aluminium hydride (LiAlH4) reducing agent. Because of this problem a further refined synthesis approach is reported, whereby suitable modification and optimisation of the reaction mechanism encourages more desirable surface capping, and a much lower surface oxide level. This is accomplished by the introduction of anhydrous copper (II) chloride (CuCl2) as an alternative to alcohol. However, this approach greatly increased the amount of solid by-product from the reaction and thus complexity of purification, resulting in a decreased overall yield. The optical properties of SiNPs are of particular interest, since the root cause of particular emissions is not well understood. The alkyl-SiNPs synthesised were subjected to testing of surface chemistry and elemental composition through x-ray photoelectron spectroscopy (XPS), and previously reported correlations between V photoluminescence and the presence of nitrogen and oxygen containing species was shown not to be true in the case of these particles. The one-pot chemical synthesis method for alkyl terminated SiNPs investigated and reported here is simple, cheap and easily scalable. In addition, toxic reagents involved in other contemporary synthesis methods for similar particles are not required. The SiNPs produced are of consistent size and high stability, with a strong photoluminescence emission. The simplicity of the synthesis ensures that the method can be easily employed in the future to introduce other more complex surface groups and this method has the potential to greatly combat the inherent problems in large scale SiNP synthesis.
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