Improved Membrane Performance Via Photothermal Heating Through Incorporation of Noble Metal Nanoparticles

Noble metal nanoparticles (NPs) strongly absorb light and turn it into heat very efficiently. This phenomenon becomes especially strong under surface plasmon resonance, at the wavelength where the light resonates with the collective oscillations of the electron gas at the surface of nanoparticles[1]. The photothermal heating has already been applied in photothermal imaging and sensing, drug release and tumor destruction [2-4], even though for thermally process nanostructured polymeric materials [5].

Our group proposed to apply the photothermal heating effect of noble metal NPs in membrane separation technology for the purpose of increasing fluxes in an energy efficient way while without significant lowering selectivities. Noble metal NPs release heat under laser irradiation; the heat then diffuses away from the NPs and leads to an elevated temperature of the surrounding media. Membranes can thus be locally heated by light irradiation when noble metal NPs are embedded in the polymer matrix.

In previous work, Vanherck et al. prepared gold NPs containing solvent resistant nanofiltration (SRNF) membranes based on polyimide and cellulose acetate. The membrane fluxes clearly increased by a factor which up to 4 under laser irradiation, without even lowering selectivity [6, 7].Recently this idea was extended to hydrophobic PDMS SRNF membranes [8]. This concept is now also being applied in other membrane separation processes, such as pervaporation(PV) and gas separation(PV). However, the expensive gold NPs and the complicated laser devices limit its large scale application.

The present study aims at using cheaper silver NPs as an alternative for gold NPs, using LED light as an energy efficient and cheaper alternative for laser devices. Polymeric membranes containing silver NPs were thus prepared and applied in SRNF, PV, and GS. Application feasibilities of the technique for membrane separations are discussed, including requirements for feed, potential application fields and scaling-up issues.

Reference:

[1] A.O. Govorov, H.H. Richardson, Generating heat with metal nanoparticles, Nano Today, 2 (2007) 30-38.

[2] I.H. El-Sayed, X. Huang, M.A. El-Sayed, Surface Plasmon Resonance Scattering and Absorption of anti-EGFR Antibody Conjugated Gold Nanoparticles in Cancer Diagnostics:  Applications in Oral Cancer, Nano Letters, 5 (2005) 829-834.

[3] K.-S. Lee, M.A. El-Sayed, Gold and Silver Nanoparticles in Sensing and Imaging:  Sensitivity of Plasmon Response to Size, Shape, and Metal Composition, The Journal of Physical Chemistry B, 110 (2006) 19220-19225.

[4] C. Jiang, S. Markutsya, Y. Pikus, V.V. Tsukruk, Freely suspended nanocomposite membranes as highly sensitive sensors, Nat Mater, 3 (2004) 721-728.

[5] S. Maity, J.R. Bochinski, L.I. Clarke, Metal Nanoparticles Acting as Light-Activated Heating Elements within Composite Materials, Advanced Functional Materials, 22 (2012) 5259-5270.

[6] K. Vanherck, S. Hermans, T. Verbiest, I. Vankelecom, Using the photothermal effect to improve membrane separations via localized heating, Journal of Materials Chemistry, 21 (2011).

[7] K. Vanherck, I. Vankelecom, T. Verbiest, Improving fluxes of polyimide membranes containing gold nanoparticles by photothermal heating, Journal of Membrane Science, 373 (2011) 5-13.

[8] Y. Li, T. Verbiest, I. Vankelecom, Improving the flux of PDMS membranes via localized heating through incorporation of gold nanoparticles, Journal of Membrane Science