title: Photonic crystal fibre as an optofluidic reactor for the measurement of photochemical kinetics with sub-picomole sensitivity.
abstract: Photonic crystal fibre constitutes an optofluidic system in which light can be efficiently coupled into a solution-phase sample, contained within the hollow core of the fibre, over long path-lengths. This provides an ideal arrangement for the highly sensitive monitoring of photochemical reactions by absorption spectroscopy. We report here the use of UV/vis spectroscopy to measure the kinetics of the photochemical and thermal cis-trans isomerisation of sub-picomole samples of two azo dyes within the 19-μm diameter core of a photonic crystal fibre, over a path length of 30 cm. Photoisomerisation quantum yields are the first reported for "push-pull" azobenzenes in solution at room temperature; such measurements are challenging because of the fast thermal isomerisation process. Rate constants obtained for thermal isomerisation are in excellent agreement with those established previously in conventional cuvette-based measurements. The high sensitivity afforded by this intra-fibre method enables measurements in solvents in which the dyes are too insoluble to permit conventional cuvette-based measurements. The results presented demonstrate the potential of photonic crystal fibres as optofluidic elements in lab-on-a-chip devices for photochemical applications.
authors: EaStCHEM School of Chemistry, King's Buildings, The University of Edinburgh, Edinburgh, EH9 3JJ, United Kingdom.
authors: Gareth O S
authors: GO
authors: Williams
authors: Jocelyn S Y
authors: JS
authors: Chen
authors: Tijmen G
authors: TG
authors: Euser
authors: Philip St J
authors: PS
authors: Russell
authors: Anita C
authors: AC
authors: Jones
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D004396:Coloring Agents / Q000737:chemistry*; D007536:Isomerism; D007700:Kinetics; D008027:Light; D055095:Optics and Photonics / Q000295:instrumentation* / Q000379:methods; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; C556349:Disperse Orange 1; C009850:azobenzene