Transient Brewster angle reflectometry of spiropyran monolayers.
Photochem Photobiol Sci
; 9(2): 141-51, 2010 Feb.
Article
en En
| MEDLINE
| ID: mdl-20126787
ABSTRACT
Brewster angle reflectometry has been developed as a tool for determining the absorbance and refractive index changes in molecular monolayers containing spiropyran. The method is sensitive to changes in both the real and imaginary parts of the refractive index in the monolayers. It was used to monitor the conversion of spiropyran to merocyanine and the reversal of this reaction when the molecules were immobilised on quartz using silane coupling. An analytical solution of Fresnel formula allowed the transient reflectometry data to be converted into transient absorption information. Absorbances of transients as low as approximately 10(-6) were possible using the current apparatus with a single laser pulse transient measurement. It was found that spiropyran photoconverted to merocyanine with an efficiency of approximately 0.1. The photochemical reversion of converted merocyanine to spiropyran occurred with efficiencies of 0.03-0.2 and this was probably site dependent. It was found that the thermal conversion from merocyanine to spiropyran was slow and even after 10 min there was no significant thermal reversion. This measurement was possible because the real part of the refractive index of the monolayer could be monitored with time using an off-resonance probe at a wavelength where the merocyanine did not absorb light meaning that the probe did not photobleach the sample. Thus our method also provides a non-intrusive method for probing changes in molecules in thin films.
Texto completo:
1
Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Benzopiranos
/
Indoles
/
Nitrocompuestos
Idioma:
En
Revista:
Photochem Photobiol Sci
Asunto de la revista:
BIOLOGIA
/
QUIMICA
Año:
2010
Tipo del documento:
Article