SEMINAR: Bayliss Seminar Series

Nanotechnology is developing as an industry, with nanoparticles finding their way into products. It is important to keep the potential industry production in mind when synthesising nanoparticles in the laboratory. Industry prefers continuous flow reactors as they have benefits in efficiency, cost and safety over traditional batch methods used to synthesise nanoparticles. Furthermore, it is important to consider the environmental impact of your synthesis avoiding toxic compounds and reducing the energy requirements of your methods while you are developing it. In this work a new type of chemical processor, the Ig noble prize winning vortex fluidic device (VFD) was investigated for its applicability to the continuous flow production of nanoparticles. The VFD is a dynamic thin film reactor that uses a rapidly rotating 10 mm diameter glass tube to produce a turbulent thin film where nanoparticle synthesis can occur. The control of nanoparticle synthesis was investigated through the modification of the machine parameters of rotation speed and angle of device to the horizontal.

A UV/Vis spectrometer was attached to the VFD for online monitoring. To calibrate the spectrometer the film thickness at various spin speeds and angles was measured. It was found that the film thickness changed with rotation speed and angle in accordance with the centripetal and gravitational forces. The segregation index of the VFD was measured using an Iodate-iodine chemical probe. The measured segregation index was ≈ 0.15 for all spin speeds and angles other than 0o for which the segregation index was closer to 0.1. The segregation index corresponds to a mixing time of ≈ 0.1 seconds, which is much slower than the SDP and similar to the mixing time of a vigorously mixed stirred tank.

To test the ability of the VFD to control the synthesis of nanoparticles two non-toxic, room temperature precipitation reactions were trialled; superparamagnetic magnetite nanoparticles (Fe3O4) and anisotropic fluorescent lanthanide phosphate (LnPO4) nanorods. To facilitate the outflow of these nanoparticles from the VFD two molecular weights of polyvinylpyrrolidone (PVP) were used 40 thousand (PVP40) and 360 thousand (PVP360).

Magnetite nanoparticles with an average size ≈10 nm were synthesised at all spin speeds, both PVP molecular weights, and at 0o and 45o for PVP360. The mean size of particles produced by batch methods were only slightly larger at 11-12 nm. However, particles produced on the VFD had superior magnetic properties. Lanthanide phosphate nanorods and radial aggregates of nanorods called dandelions were synthesised with controllable aggregation states on the VFD with the use of the PVP polymer. Batch methods produced only short LnPO4 nanorods. On the VFD dandelions were produced at moderate speeds but broke apart at 9000 rpm. Within the VFD It was proposed that high shear first promotes then disrupts the production of the dandelions. The VFD shows promise in the control of the synthesis of nanoparticles through the wrapping the particles in the polymer and control over the aggregation of particles rather than improvements in mixing that was expected for the continuous flow thin film processor.