ABSTRACT
Evaluating candidates for novel materials with high nonlinear absorption properties for applications as biomarkers is a very important field of research. In this context, experimental and computational information on the two-photon absorption (TPA) properties of the dye IR780 is shown. The two-photon absorption data from 850 to 1000 nm for IR780 and other two well-known dyes, taken as reference, are presented. The experimental data were collected via an implementation of the two-photon induced fluorescence technique, while the quantum chemical data were produced by implementing DFT (Density-functional theory) methods. The data presented here supplement the paper "Two-photon absorption spectrum and characterization of the upper electronic states of dye IR780" by Guarin et al. (2021).
ABSTRACT
In this work, the full two-photon absorption (2PA) spectrum of cyanine dye IR780 in methanol was measured and some important properties of the upper excited electronic states were investigated. Specifically, two IR780 2PA bands of intensities nearing 140 and 2800 Goeppert-Mayer (GM) were found. In order to determine the optical properties of the upper electronic singlet states, a deconvolution of the absorption peaks in the UV region of the spectrum was made. Based on this, properties such as transition dipole moments, oscillator strengths, absorption maxima in the UV-vis spectra, S2-S1 vibrational couplings and predictions of the lifetime of the second excited state were calculated. Moreover, by combining experimental and computational results, the 2PA transitions were assigned to the upper excited states S2 and S4. Cross-section magnitudes, positions and shapes of the 2PA bands have been satisfactorily explained with a four-state model that comprises the singlet states S1, S2 and S4. From these results, the cyanine investigated in the present work could be used as a novel and interesting moiety for more complex systems that respond to two-photon excitation.
