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Optofluidic hollow-core photonic crystal fibre

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If you have a question about this talk, please contact Catherine Pearson.

Liquid-filled hollow-core photonic crystal fibres (HC-PCF) are excellent optofluidic microreactors in which light propagates in well-defined modes at the centre of a microchannel [1]. They enable efficient photochemistry, photo-switching, and photocatalysis at optical powers that are five orders of magnitude lower than in conventional reactors [1]. In addition, sample volumes in HC-PCF can be as small as a few nL per cm interaction length while meter-long optical paths enable sensitive absorption, fluorescence, and Raman spectroscopy.

In my talk, I will discuss how optofluidic HC-PCF can help improve our understanding of photochemical and electrochemical processes relevant to the green energy transition.

First, we demonstrate an operando Raman spectroscopy method that tracks the chemistry of liquid electrolytes during battery cycling. An optofluidic hollow-core fibre is integrated into a working Li: ion cell and used to analyse sub-microlitre electrolyte samples at different stages of the charge-discharge cycle by background-free Raman spectroscopy. The observed changes in electrolyte composition are related to the solid electrolyte interphase (SEI) formation and can reveal early signs of battery degradation [2].

Second, we use HC-PCF, connected to microfluidic coupling cells, to optimise photocatalytic “solar-fuel” generation in hybrid colloidal systems that combine molecular catalysts with particulate light absorbers. We focus on carbon-nanodots, one of the most promising light-absorber materials, due to their unique combination of scalability, biocompatibility, water solubility, and stable optical properties [3]. Key to improving their performance in solar catalysis are charge-transfer processes that we investigate and optimise through fibre-based absorption [4], fluorescence [8], and Raman spectroscopy [9].

Finally, I will briefly discuss how holographic spatial light modulation techniques can be used to excite higher-order modes in HC-PCFs, with the aim to selectively probe surface- and bulk processes within optofluidic microreactors [7,8].

This talk is part of the Seminars for the Centre for Environmental and Industrial Flows series.

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