POS08 – Semyon Bodian

Fibre-Optic Ultrasound Probes Coated with CuInS2 Quantum Dot-PDMS Films

Semyon Bodian1,4*, Richard J Colchester1,4, Tom Macdonald5, Kathryn Welsby3, Ross Gordon3, Martha Briceno de Gutierrez3, Paul Collier3, Ivan Parkin2, Adrien Desjardins1,4, Sacha Noimark1,2,4

1Department of Medical Physics & Biomedical Engineering, University College London, London, United Kingdom

2Department of Chemistry, University College London, London, United Kingdom

3Johnson Matthey Ltd, Sonning, United Kingdom

4Wellcome/EPSRC Centre for Interventional and Surgical Sciences, University College London, London, United Kingdom

5Department of Chemistry, Imperial College London. London, United Kingdom

*email: zccasbo@ucl.ac.uk

 

Abstract

The novel electronic structures of Quantum Dots (QDs), based on their nano-scale dimensions, have made them a novel component of many applications across scientific and technological fields. The customisation of a QD’s band-gap via its synthesis allows the tailoring of both the absorption and photoluminescence profiles. In addition, QDs exhibit high quantum yields of photoluminescence which has justified their use in light-emitting diodes (LEDs) and liquid-crystal displays (LCDs) both of which have been employed in flat-screen televisions1. Various types of QDs including CdSe and CdTe have been utilised as biological in-vivo imaging agents resulting from their greater photostabilities compared to conventional dyes. However, due to qualms regarding the high toxicities of these QDs, particularly the Cd2+ species, has prevented their wide-spread inclusion in in-vivo imaging devices2. Our works consists on using nanocomposite materials in multimodality imaging probes for use in minimally-invasive surgery.  Specifically, our imaging probes include all-optical fibre-optic ultrasound (US) transducers composed of multi-component films deposited on the distal ends of optical fibres. The micrometre-sized diameters of these fibres facilitate their integration into surgical devices such as needles and catheters providing in-vivo US imaging of delicate anatomical features such as blood vessels3. We have employed non-toxic CuInS2 QDs in our composite films, embedding them within a medical-grade polydimethylsiloxane (PDMS) elastomer. These films have been shown to generate high US pressures and wide bandwidths suitable for clinical US imaging. Our approach exploits the low quantum yields of CIS QDs which generate heat through the photoacoustic effect rather than photoluminescence following their excitation by the laser light. In addition, the selective absorption of the input laser light by the CIS-PDMS film facilitates US imaging using the absorbed wavelengths whilst those transmitted are used for photoacoustic imaging. The dual-modality imaging provided by these fibre-optic probes offers a greater range of information to clinicians than available previously using single modality imaging.  The films are prepared in a two-step fabrication. Fibres are first dip-coated into a paste of CIS QDs, prepared previously by evaporating off the toluene solvent. A PDMS overlayer is then dip-coated on top, producing a sub 50 μm-thick bilayer film. Microscope images reveal orange-red convex coatings with smooth and homogenous morphologies. Fibre-optic CIS- PDMS have generated US pressures and bandwidths of up to 3.7 MPa and 18.01 MHz, respectively, measured 1.5 mm at a laser fluence of 153 mJ cm-2. Currently, we are new composite films with shelled CIS QDs (CuInS2/ZnS) QDs to determine the effects of the shell has on the film’s generated US. This will hopefully elucidate the photodynamics of the QDs, determining which non-radiative pathways are undertaken and enabling us to optimise their properties to refine their imaging capabilities.

References:

[1] Y. Shirasaki et al. Nature Photonics 7 (2013) 13

[2] T.S Hauck et al. Small 6 (2010) 138

[3] R.K. Poduval et al Applied Physics Letters (2017) 223700

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