Monoclinic VO2 nanoparticles are of interest due to the material's thermochromic properties, however, direct synthesis routes to VO2 nanoparticles are often inaccessible due to the high synthesis temperatures or long reaction times required. Herein, we present a two-step synthesis route for the preparation of monoclinic VO2 nanoparticles using Continuous Hydrothermal Flow Synthesis (CHFS) followed by a short post heat treatment step. A range of particle sizes, dependent on synthesis conditions, were produced from 50 to 200 nm by varying reaction temperatures and the residence times in the process. The nanoparticles were characterised by powder X-ray diffraction, Raman and UV/Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The nanoparticles were highly crystalline with rod and sphere-like morphologies present in TEM micrographs, with the size of both the rod and spherical particles being highly dependent on both reaction temperature and residence time. SEM micrographs showed the surface of the powders produced from the CHFS process to be highly uniform. The samples were given a short post synthesis heat treatment to ensure that they were phase pure monoclinic VO2, which led to them exhibiting a large and reversible switch in optical properties (at near-IR wavelengths), which suggests that if such materials can be incorporated into coatings or in composites, they could be used for fenestration in architectural applications.

This report describes the first Aerosol Assisted Chemical Vapour Deposition (AACVD) of photocatalytic titanium dioxide thin films embedded with synthetic hydroxyapatite, [Ca10(PO4)(OH)2], nanoparticles. The hydroxyapatite nanoparticles were prepared using a low temperature continuous hydrothermal flow synthesis method; analysis of the hydroxyapatite powder showed that it was phase pure and that the as-prepared material was made up of nanoneedles as expected. The nanoparticles were then embedded into TiO2 coatings using the AACVD technique by suspending them in a solution of the titania precursor (titanium tetraisopropoxide). Results showed that the hydroxyapatite, although present in very low concentrations in the coatings (not detectable by XRD or Raman spectroscopy), heavily affected their morphology, depending on their concentration in the precursor solution. Tests of the photocatalytic activity of the composite films showed that the inclusion of the hydroxyapatite led to an increase in the photodegradation (up to 50 % higher for methylene blue degredation) and that the materials were photostable.2 This study shows that TiO2 coatings embedded with hydroxyapatite nanoparticles have potential as highly efficient photocatalysts.

Cobalt oxide (Co 3 O 4 ) nanoparticles were synthesized from aqueous solutions of cobalt(II) acetate using a laboratory scale continuous hydrothermal flow synthesis reactor incorporating a confined jet (co-axial) mixer. By changing the concentration of the precursor combined with operating under flow rate conditions expected to result in a laminar or turbulent mixing, the size of the crystallites could be controlled in the range of 6.5 to 16.5 nm (median). A quench stream was employed to rapidly cool down the nascent stream of nanoparticles and to elucidate the mechanisms of nucleation and growth. The results show a clear correlation between increasing precursor concentration and crystallite size, which at lower concentrations in particular decreased in laminar flow and increased in turbulent flow. The smallest particles of 6.5 nm (median) were produced at a precursor concentration of 0.1 M (at a rate of 20 g.h -1 ). The materials were characterized using a range of analytical methods including powder X-ray diffraction and transmission electron microscopy. Figure. Parameters of the size distribution (D10, D50 and D90) of cobalt oxide nanoparticles vs. precursor concentration (logarithmic scale). D10, D50 and D90 are the tenth, fiftieth and ninetieth percentile of the size distribution, respectively. Cobalt oxide (Co 3 O 4 ) nanoparticles were synthesized from aqueous solutions of cobalt(II) acetate using a laboratory scale continuous hydrothermal flow synthesis reactor incorporating a confined jet (co-axial) mixer. By changing the concentration of the precursor combined with operating under flow rate conditions expected to result in a laminar or turbulent mixing, the size of the crystallites could be controlled in the range of 6.5 to 16.5 nm (median). A quench stream was employed to rapidly cool down the nascent stream of nanoparticles and to elucidate the mechanisms of nucleation and growth. The results show a clear correlation between increasing precursor concentration and crystallite size, which at lower concentrations in particular decreased in laminar flow and increased in turbulent flow. The smallest particles of 6.5 nm (median) were produced at a precursor concentration of 0.1 M (at a rate of 20 g.h -1 ). The materials were