Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy
A series of fluorescent compounds (rhodamine 101, cresyl violet, oxazine 1, and tris(2,2′-bipyridyl)-ruthenium(II) chloride hexahydrate) were used as molecular probes in titania gels. Sols and gels of pH = 2.5 and 3.5 were prepared using standard methods. Absorption and emission spectra and fluoresc...
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1997
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07437463_v13_n14_p3665_Marchi http://hdl.handle.net/20.500.12110/paper_07437463_v13_n14_p3665_Marchi |
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paper:paper_07437463_v13_n14_p3665_Marchi2023-06-08T15:44:48Z Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy Marchi, María Claudia Aldabe Bilmes, Sara Alfonsina Dora Negri, Ricardo Martin Absorption spectroscopy Aging of materials Alcohols Anisotropy Emission spectroscopy Fluorescence Friction pH effects Quantum theory Titanium oxides Viscosity Water Steady state fluorescence anisotropy Titania gels Gels A series of fluorescent compounds (rhodamine 101, cresyl violet, oxazine 1, and tris(2,2′-bipyridyl)-ruthenium(II) chloride hexahydrate) were used as molecular probes in titania gels. Sols and gels of pH = 2.5 and 3.5 were prepared using standard methods. Absorption and emission spectra and fluorescence quantum yields of the probes were measured at room temperature. Fluorescence intensity and steady-state fluorescence anisotropy, 〈r〉, were measured for cresyl violet and oxazine 1 at controlled temperature between 25 and 95 °C as function of aging. The local environment of Rh101, Rbpy, CV, and Ox1 in the gels at 25 °C is essentially aqueous. Among these compounds, only CV and Ox1 are appropriate for fluorescence anisotropy studies in titania gels of low pH. Parameters for the calculation of the local friction, ξ, inside the cavities were obtained from previous experimental data or by modeling a symmetrical molecule as prolate ellipsoid. For CV, the comparison of the fluorescence anisotropy data in microheterogeneous systems and homogeneous solutions can be directly performed, because its rotational dynamics has been very well characterized in water and alcohols. The fluorescence anisotropy and photophysical parameters of Ox1 in water and alcohols are less known, but the symmetry properties allows us to obtain analytical expressions for the rotational correlation times and for the local friction. Even when the bulk viscosity of the gel increases, there is a minor restriction for the rotation of the fluorescent probes, indicating that the gel is composed of a rigid network with solvent-filled cavities of volumes larger than 500-600 Å 3 . The similarity of the values of ξ for both probes is a strong validation for the model used for Ox1 and allows Ox1 to be used as an alternative to CV for the method. Fil:Marchi, M.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Bilmes, S.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Negri, R.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 1997 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07437463_v13_n14_p3665_Marchi http://hdl.handle.net/20.500.12110/paper_07437463_v13_n14_p3665_Marchi |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Absorption spectroscopy Aging of materials Alcohols Anisotropy Emission spectroscopy Fluorescence Friction pH effects Quantum theory Titanium oxides Viscosity Water Steady state fluorescence anisotropy Titania gels Gels |
| spellingShingle |
Absorption spectroscopy Aging of materials Alcohols Anisotropy Emission spectroscopy Fluorescence Friction pH effects Quantum theory Titanium oxides Viscosity Water Steady state fluorescence anisotropy Titania gels Gels Marchi, María Claudia Aldabe Bilmes, Sara Alfonsina Dora Negri, Ricardo Martin Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| topic_facet |
Absorption spectroscopy Aging of materials Alcohols Anisotropy Emission spectroscopy Fluorescence Friction pH effects Quantum theory Titanium oxides Viscosity Water Steady state fluorescence anisotropy Titania gels Gels |
| description |
A series of fluorescent compounds (rhodamine 101, cresyl violet, oxazine 1, and tris(2,2′-bipyridyl)-ruthenium(II) chloride hexahydrate) were used as molecular probes in titania gels. Sols and gels of pH = 2.5 and 3.5 were prepared using standard methods. Absorption and emission spectra and fluorescence quantum yields of the probes were measured at room temperature. Fluorescence intensity and steady-state fluorescence anisotropy, 〈r〉, were measured for cresyl violet and oxazine 1 at controlled temperature between 25 and 95 °C as function of aging. The local environment of Rh101, Rbpy, CV, and Ox1 in the gels at 25 °C is essentially aqueous. Among these compounds, only CV and Ox1 are appropriate for fluorescence anisotropy studies in titania gels of low pH. Parameters for the calculation of the local friction, ξ, inside the cavities were obtained from previous experimental data or by modeling a symmetrical molecule as prolate ellipsoid. For CV, the comparison of the fluorescence anisotropy data in microheterogeneous systems and homogeneous solutions can be directly performed, because its rotational dynamics has been very well characterized in water and alcohols. The fluorescence anisotropy and photophysical parameters of Ox1 in water and alcohols are less known, but the symmetry properties allows us to obtain analytical expressions for the rotational correlation times and for the local friction. Even when the bulk viscosity of the gel increases, there is a minor restriction for the rotation of the fluorescent probes, indicating that the gel is composed of a rigid network with solvent-filled cavities of volumes larger than 500-600 Å 3 . The similarity of the values of ξ for both probes is a strong validation for the model used for Ox1 and allows Ox1 to be used as an alternative to CV for the method. |
| author |
Marchi, María Claudia Aldabe Bilmes, Sara Alfonsina Dora Negri, Ricardo Martin |
| author_facet |
Marchi, María Claudia Aldabe Bilmes, Sara Alfonsina Dora Negri, Ricardo Martin |
| author_sort |
Marchi, María Claudia |
| title |
Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| title_short |
Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| title_full |
Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| title_fullStr |
Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| title_full_unstemmed |
Microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| title_sort |
microviscosity in the cavities of titania gels studied by steady-state fluorescence anisotropy |
| publishDate |
1997 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_07437463_v13_n14_p3665_Marchi http://hdl.handle.net/20.500.12110/paper_07437463_v13_n14_p3665_Marchi |
| work_keys_str_mv |
AT marchimariaclaudia microviscosityinthecavitiesoftitaniagelsstudiedbysteadystatefluorescenceanisotropy AT aldabebilmessaraalfonsinadora microviscosityinthecavitiesoftitaniagelsstudiedbysteadystatefluorescenceanisotropy AT negriricardomartin microviscosityinthecavitiesoftitaniagelsstudiedbysteadystatefluorescenceanisotropy |
| _version_ |
1768542087285833728 |