Multifunctional Nanocomposite Thin Films by Aerosol-Assisted CVD** By Michael E.A. Warwick, Charles W. Dunnill, and Russell Binions* The aerosol-assisted (AA)CVD reaction of titanium isopropoxide and a solution of preformed tin dioxide nanoparticles leads to the production of titanium dioxide/tin dioxide nanocomposite thin films on glass substrates. Scanning electron microscopy (SEM) studies show that film composition and morphology are linked, with larger island sizes being observed as more tin dioxide nanoparticles are incorporated into the films. Reflectance measurements performed on the nanocomposite thin films show an increase in reflection in the infrared (IR) portion of the spectrum with increased tin dioxide nanoparticle incorporation. Photocatalysis experiments indicate that the nanocomposite films are photo-active with irradiation by 365 nm light. The nanocomposite thin films display both low-emissivity and self-cleaning functionalities; and as such they are multifunctional. Keywords: AACVD, Nanocomposites, Thin films 1. Introduction The production of nanocomposite thin films has recently received a great deal of attention, [1] with the majority of work published focusing on incorporating noble metal nanoparticles into metal oxide matrices. [2–9] The incorpora- tion of nanoparticles can lead to films with improved single functionality. [10] This has led to advances in a variety of areas including glazing, semi-conductors, anti-bacterials, and catalysis. [11] Relatively little focus has been on the incorporation of metal oxide nanoparticles, [12–14] and as yet virtually no attention has been directed to using nanopar- ticles to produce multifunctional films whereby the thin film matrix has a separate and independent functionality to the incorporated nanoparticles. Nanocomposite thin films have been produced using a variety of methodologies such as sol-gel, multi-target magnetron sputtering, and CVD. [8,10,15] In each of these cases the nanoparticles are generated in-situ, which limits the amount of control over the nanoparticle composition, size, and shape achievable. AACVD has been utilized to deposit preformed nanoparticles from solution, [16] allowing for much greater control of the subsequent properties of the composite, although in this work no properties of the thin film matrix are reported. AACVD uses a solution aerosol to transport precursors to a heated substrate. The method was initially developed for use where more traditional atmospheric pressure (AP)CVD routes were inapplicable due to precursor non- volatility or thermal instability. AACVD has no such restrictions and a wide variety of precursors, such as ionic precursors and metal oxide clusters, have been used. [17,18] In this paper, we report the use of an AACVD process utilizing preformed tin oxide nanoparticles and titanium isopropoxide in toluene to produce thin films of titanium dioxide with incorporated tin oxide nanoparticles. Titanium dioxide was chosen as a matrix as it is a well-known and relatively easy to characterize photocatalyst. [19] Tin oxide nanoparticles were chosen as tin oxide is known to have a high IR reflectivity, that titanium dioxide does not, and finds use in solar control coatings. [20] By combining the two we have produced films that are both photocatalytic and IR reflective, thus demonstrating that it is possible to generate truly multifunctional thin films using this methodology. This particular example may be of use in the glazing industry to reduce energy usage in terms of heating requirements as a result of the low-e component (SnO 2 ), as well as being self cleaning as a result of the photocatalytic component (TiO 2 ); however this method ought to be generally applicable and represents a new strategy for the production of multi- functional thin films and nanocomposites. 2. Results and Discussion Composite TiO 2 /SnO 2 nanoparticle films were grown by the use of AACVD from preformed SnO 2 nanoparticles and titanium isopropoxide in toluene. The films from the DOI: 10.1002/cvde.201006841 Full Paper [*] Dr. R. Binions, M. E. A. Warwick, C. W. Dunnill Department of Chemistry, University College London, Christopher Ingold Laboratories 20 Gordon Street, London WC1H 0AJ (United Kingdom) E-mail: uccarbi@ucl.ac.uk [**] RB thanks the Royal Society for a Dorothy Hodgkin fellowship. Mr. Kevin Reeves is thanked for invaluable assistance with electron micro- scopy. Pilkington-NSG are thanked for the provision of glass substrates. Prof. Ivan Parkin is thanked for the loan of CVD equipment. Dr. David J. Morgan is thanked for performing XPS as part of the EPSRC access to research equipment initiative (grant number EP/F019823/1). 220 wileyonlinelibrary.com ß 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Chem. Vap. Deposition 2010, 16, 220–224