Surface photochemistry: 3,3'-dialkylthia and selenocarbocyanine dyes adsorbed onto microcrystalline cellulose.
In this work, thia and selenocarbocyanines with n-alkyl chains of different length, namely with methyl, ethyl, propyl, hexyl and decyl substituents, were studied in homogeneous and heterogeneous media for comparison purposes. For both carbocyanine dyes adsorbed onto microcrystalline cellulose, a remarkable increase in the fluorescence quantum yields and lifetimes were detected, when compared with solution. Contrary to the solution behaviour, where the increase in the n-alkyl chains length increases to a certain extent the fluorescence emission Φ(F) and τ(F), on powdered solid samples a decrease of Φ(F) and τ(F) was observed. The use of an integrating sphere enabled us to obtain absolute Φ(F)'s for all the powdered samples. The main difference for liquid homogeneous samples is that the increase of the alkyl chain strongly decreases the Φ(F) values, both for thiacarbocyanines and selenocarbocyanines. A lifetime distribution analysis for the fluorescence of these dyes adsorbed onto microcrystalline cellulose, evidenced location on the ordered and crystalline part of the substrate, as well as on the more disordered region where the lifetime is smaller. The increase of the n-alkyl chains length decreases the photoisomer emission for the dyes adsorbed onto microcrystalline cellulose, as detected for high fluences of the laser excitation, for most samples.
Molecular Physical Chemistry Center, and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
Luís F
LF
Vieira Ferreira
Molecular Physical Chemistry Center, and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
Diana P
DP
Ferreira
Molecular Physical Chemistry Center, and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
Paulo
P
Duarte
Molecular Physical Chemistry Center, and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.|School of Technology and Business, Polytechnic Institute of Portalegre, Lugar da Abadessa, Apt 148, 7301-901 Portalegre, Portugal.
A S
AS
Oliveira
Molecular Physical Chemistry Center, and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
E
E
Torres
Molecular Physical Chemistry Center, and IN-Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Technical University of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.|School of Technology and Business, Polytechnic Institute of Portalegre, Lugar da Abadessa, Apt 148, 7301-901 Portalegre, Portugal.
I
I
Ferreira Machado
CICS - Health Sciences Research Center, Beira Interior University, Av. Infante D. Henrique, 6200-506 Covilhã, Portugal.
P
P
Almeida
Department of Chemistry and Chemistry Center, Trás-os-Montes e Alto Douro University, Apartado 1013, 5001-801 Vila Real, Portugal.
Lucinda V
LV
Reis
Department of Chemistry and Chemistry Center, Trás-os-Montes e Alto Douro University, Apartado 1013, 5001-801 Vila Real, Portugal.
Paulo F
PF
Santos
D000327:Adsorption; D002232:Carbocyanines / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D011789:Quantum Theory; D026082:Singlet Oxygen / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D002232:Carbocyanines; D005456:Fluorescent Dyes; D026082:Singlet Oxygen; D002482:Cellulose; C109691:microcrystalline cellulose