Silver nanoprisms embedded in a polymeric matrix for energy saving glazing

Abstract

According to the data from government institutions (Energy Information Administration, 2012), the consumption of energy will show an average growth of 42.5% by 2035 from the heating, ventilation and air conditioning devices solely (Perez-Lombard et al., 2008). For this reason the interest in technologies that can reduce the consumption of energy for heating or cooling houses is growing. In particular, the glazing of houses could offer great potential for energy saving as these elements of the building envelopment still have a margin for improvement. Currently, the research is focusing on stopping the heat exchange through radiative transfer. The problems of the current technologies are associated with the high costs and the colour they give to windows. Technologies using nanoparticles have started to emerge and have shown promise as methods for absorbing the radiation which passes through the glazing. Thanks to the unique control over their size and shape dependent properties, their absorbance can be moved to lower energy and this can satisfy both the requirements of stopping the heat carrying radiation and still providing a good illumination. Through the wide range of nanoparticle materials, sizes and shapes, silver triangular nanoprisms are a promising candidate for further research due to their strong absorption in the near infrared region. As their synthesis and the control over their geometrical properties are challenging using conventional batch-based macro reactor systems, a novel microreactor system was developed in this study in order to continuously produce silver triangular nanoprisms and monitoring their optical properties by mean of integrated spectroscopy techniques. By using sol-gel chemistry, the particles were coated with a shell of SiO2 which can further be functionalised with various chemical functional groups such as thiol and allyl. Coated particles were then embedded in polymeric matrix (i.e. poly(methylmethacrylate), or PMMA) with covalent interactions between the polymer and the functional groups attached to the silica shell surface. Finally, the composite solutions were casted onto a glass-slide and the optical performance was evaluated using spectroscopic methodologies. Compared to similar composite materials, the systems herein reported offers several advantages, such as the low coloration in the visible spectrum and no risk of aggregation of the metal nuclei once they are dispersed in the polymer matrix. The use of a microreactor can also grant good control over high volumes of such colloids, opening to the possibility for a large scale production of such materials.

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ORCID for Xunli Zhang: orcid.org/0000-0002-4375-1571

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