Investigation of ground and excited state photophysical properties of gadolinium phthalocyanine

Author(s)

Vivas, Marcelo G. ^[1] ; de Boni, Leonardo ^[1] ; Gaffo, Luciana ^[2] ; Mendonca, Cleber R. ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Fis Sao Carlos, Sao Carlos, SP - Brazil

^[2] Univ Estadual Oeste Parana, Ctr Engn & Ciencias Exatas, Toledo, PR - Brazil

• Document type: Journal article
• Source: DYES AND PIGMENTS; v. 101, p. 338-343, FEB 2014.
• Web of Science Citations: 17

Abstract

In this present work, we investigated the singlet excited state absorption (ESA) spectrum and intersystem crossing dynamics of gadolinium phthalocyanine (GdPc) in toluene. For that, we employed the femtosecond wavelength-tunable Z-scan and picosecond Pulse Train Fluorescence (PTF) techniques to determine, respectively, the singlet ESA cross-section on a wide spectral range (from 460 up to 740 nm) and the intersystem crossing time (singlet triplet transition). We observed that the ESA spectrum presents distinct absorption behaviors, i.e., saturable (SA) and reverse saturable absorption (RSA). We have also been able to identify regions in which the excited state absorption cross-section has the same magnitude as the ground state one (at 600 and 720 nm). The RSA effect was observed for wavelengths shorter than 600 nm and longer than 720 nm, while SA occurs in the Q-band region, located between 600 and 720 rim. To describe the main singlet singlet transitions, we measured the fluorescence decay time and employed a rate equation model considering a three-energy-level-diagram. Ratios between excited and ground state absorption cross-section from 0.4 to 4 were observed along the ESA spectrum. From these results, we calculated the transition dipole moment between the excited states for the main electronic transitions of GdPc. To obtain the intersystem crossing time, we incorporated an additional level in our model and used the PTF technique to probe the population transfer to the triplet state. Our results pointed out that the intersystem crossing time is higher than 300 ns, which corresponds to a maximum triplet quantum yield of 1.5%. (C) 2013 Elsevier Ltd. All rights reserved. (AU)

• FAPESP's process: 11/12399-0 - Femtosecond pulses applied to nonlinear optics: spectroscopy, pulse shaping and microfabrication
• Grantee: Cleber Renato Mendonça
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 11/06489-6 - EFFECT OF THE ULTRASHORT PULSE POLARIZATION ON THE TWO-PHOTON ABSORPTION OF ORGANIC COMPOUNDS
• Grantee: Marcelo Gonçalves Vivas
• Support Opportunities: Scholarships in Brazil - Post-Doctoral