Evanescent-Field Spectroscopy using Structured Optical Fibers: Detection of Charge-Transfer at the Porphyrin-Silica Interface (original) (raw)
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Photochemical properties of porphyrin films covering surfaces of tapered optical fibers
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We report the fabrication and characterization of tapered fibers covered with porphyrin monolayer films prepared by Langmuir-Blodgett (LB) deposition method. The studied molecule was 10 mol-% 5,10,15,20- tetrakis(pentafluorophenyl)porphyrin (PFP) entrapped in an octadecylamine (ODA) matrix. PFP molecules, deposited on plane glass surfaces, have relatively long fluorescence lifetime (~ 4 ns) together with high fluorescence efficiency. Therefore, such photoactive materials, example of which are PFP molecules, hold much promise for the development of chemical sensors and efficient light harvesting devices.
Merging porphyrins and structured optical fibres: future technology for chemical sensors
19th International Conference on Optical Fibre Sensors, Pts 1 and 2, 2008
Spectroscopic characterisation of water soluble porphyrins using a structured optical fibre are presented and discussed. Porphyrin thin-films were also fabricated inside the holes of structured fibres. The thin-films self-assemble inside the fibres leading to energy coupling between the molecules. These are the first steps towards future chemically tailored optical fibre sensors for molecular detection.
Water-soluble porphyrin detection in a pure-silica photonic crystal fiber
Optics Letters, 2006
Aqueous solutions of the water-soluble porphyrin 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinatomanganese(III) acetate were inserted into the holes of a photonic crystal fiber, and the porphyrin absorption bands were identified. Results were obtained for three concentrations. The porphyrins in water show no surface interactions with the silica walls of the capillary channels. We discuss the implications for future hybrid electronic and photonic fiber devices.
Fluorescent porphyrins trapped in monolithic SiO 2 gels
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Macrocyclic molecules play key roles in basic processes in living organisms. Free bases and the metal complexes of porphyrins exhibit a wide range of important optical properties. In these systems the position of the most intense absorption band depends on the peripheral substituents of the macrocycle. Sol-gel methods have generally allowed the successful trapping of porphyrins into inorganic networks. The materials obtained are strong and transparent monolithic gels, but in the majority of cases the red fluorescence of the porphyrins disappears with ageing. We have evaluated the effect of the type and spatial disposition of the substituents in the porphyrin macrocycle periphery on key optical properties, with particular emphasis on the conservation of red fluorescence when porphyrins are simply trapped or covalently bonded to the inorganic matrix. Here, we report the use of the sol-gel procedures to obtain monolithic gels with the hydroxyl-or amino-substituted α, β, γ , δ-tetraphenylporphyrins, (H 2 T(S)PP), simply trapped or covalently bonded to the SiO 2 matrix.
2010
We propose and demonstrate, through simulation and experiment, how the interaction of an optical field within a waveguide designed for chemical sensing and, more generally, evanescent field spectroscopy can be enhanced substantially by strategic deposition of high index surface layers. These layers draw out the optical field in the vicinity of probing and take advantage of field localisation through optical impedance matching. Localisation of the evanescent field to the inner layer in turn is accompanied by whispering gallery modes within the channels of a structured cylindrical waveguide, further enhancing sensitivity. A novel demonstration based on self-assembled layers made up of TiO 2 within a structured optical fibre is demonstrated, using a simple porphyrin as the spectroscopic probe. This technique offers optimisation of the limitations imposed on practical waveguide sensors that are highly sensitive but nearly always at the expense of low loss. The principles have potential ramifications for nanophotonics more generally and these are discussed. OCIS codes: (000.0000) General; (000.2700) General science, (999.9999) nanophotonics; (999.9999) nanotechnology; (999.9999) optical localisation; (999.9999) TiO 2 ; (999.9999) nanolayers; (999.9999) structured optical fibers; (999.9999) photonic crystal fibers; (999.9999) (photonic crystal waveguides; (999.9999) porphyrins; (999.9999) evanescent field spectroscopy; (999.9999) chemical sensing; (999.9999) waveguides; (999.9999) optical fibers; (999.9999) self-assembly; (999.9999) whispering gallery mdoes
Spectral fingerprinting of porphyrins for distributed chemical sensing
Journal of Porphyrins and Phthalocyanines, 2009
We have synthesized a series of tetrakis(arylvinylene)phthalocyanines from the corresponding phthalonitriles. According to 1 H and 19 F NMR data, the cis-or trans-conformations of the starting materials retain du ring condensation, thus phthalocyanines formed are in all-cis or all-trans form. The cis-trans photoisomerization occurs easily for phthalonitriles, while phthalocyanines retain their conformations under UV beam.
Characterization of functionalised porphyrin films using synchrotron radiation
Applied Surface Science, 2005
Porphyrins and C 60 are strategic materials for the fabrication of nanoscale molecular devices by virtue of their optical, photoelectro-chemical and chemical properties. We have developed procedures to immobilise cobalt tetra-butyl-phenyl porphyrins (CoTBPPs) on gold surfaces via ligation to self-assembled monolayers of aromatic aminothiophenols (4-ATP). We have used synchrotron radiation photoemission and near-edge X-ray absorption, NEXAFS, to characterise such films, both in their native state, and with ligated fulleropyrrolidines N-methyl-2-(p-pyridyl)-3,4-fulleropyrrolidine (Py-C 60), forming charge-separation complexes which may have applications in solar cells. While photoemission spectra appear dominated by the individual CoTBPP and Py-C 60 components, we observe an apparent signature of charge separation in fulleropyrrolidine NEXAFS spectra.
Photoinduced Electron Transfer in Self-Assembled Monolayers of Porphyrin−Fullerene Dyads on ITO
Langmuir, 2005
Two porphyrin-fullerene dyads were synthesized to form self-assembled monolayers (SAMs) on indiumtin oxide (ITO) electrode, with either ITO-porphyrin-fullerene or ITO-fullerene-porphyrin orientations. The dyads contain two linkers for connecting the porphyrin and fullerene moieties and enforcing them essentially to similar geometries of the donor-acceptor pair, and two linkers to ensure the attachment of the dyads to the ITO surface with two desired opposite orientations. The transient photovoltage responses (Maxwell displacement charge) were measured for the dyad films covered by insulating LB films, thus ensuring that the dyads interact only with the ITO electrode. The direction of the electron transfer was from the photoexcited dyad to ITO independent of the dyad orientation. The response amplitude for the ITO-fullerene-porphyrin structure, where the primary intramolecular electron-transfer direction coincides with the direction of the final electron transfer from the dyad to ITO, was 25 times stronger than that for the opposite ITO-porphyrin-fullerene orientation of the dyad. Static photocurrent measurements in a liquid electrochemical cell, however, show only a minor orientation effect, indicating that the photocurrent generation is controlled by the processes at the SAM-liquid interface. (1) (a) Delmarre, D.; Meallet, R.; Bied-Charreton, C.; Pansu, R. B. van der Boom, M. E.; Abbotto, A.; Beverina, L.; Marks, T. J.; Pagani, G. A. Langmuir 2001, 17, 5939. (f) Schuster, D. I.; Cheng, P.; Jarowski, P. D.; Guldi, D. M.; Luo, C.; Echegoyen, L.; Pyo, S.; Holzwarth, A. R.; Braslavsky, S. E.; Williams, R. M.; Klihm, G. J. Am. Chem. Soc. 2004, 126, 7257. (g) Hasobe, T.; Imahori, H.; Fukuzumi, S.; Kamat, P. V. J. Phys. Chem. 2003, 107, 12105. (h) Hasobe, T.; Kamat, P. V.; Troiani, V.; Solladie, N.; Ahn, T. K.; Kim, S. K.; Kim, D.; Kongkanand, A.; Kuwabata, S.; Fukuzumi, S. J. Phys. Chem. B 2005, 109, 19. (2) (a) Wolf, M. O.; Fox, M. A. Langmuir 1996, 12, 955. (b) Weber, R.; Winter, B.; Hertel, I. V.; Stiller, B.; Schrader, S.; Brehmer, L.; Koch, N.