Dynamic optical nonlinearities in free base tetrapyridylporphyrin ( H 2 TPyP ) solutions were inv... more Dynamic optical nonlinearities in free base tetrapyridylporphyrin ( H 2 TPyP ) solutions were investigated at 532 nm with the Z-scan technique. We observed a reverse saturable absorption process that was found to have a fast contribution related to the singlet population and a slow accumulative contribution arising from the triplet population. The optical excitations and subsequent relaxations can be interpreted with a five-energy-level diagram that allows determination of the excited states photophysical parameters such as triplet and singlet absorption cross-sections and the intersystem crossing time.
Herein we report on the full experimental measurement of the two-photon absorption circular dichr... more Herein we report on the full experimental measurement of the two-photon absorption circular dichroism spectra of (S)-(-)-1,1'-bi(2-naphthol) and (R)-(+)-1,1'-bi(2-naphthol), their analysis, and theoretical support. The finding of new nonlinear optical fingerprints in chiral molecules offers new opportunities in the recognition and understanding of optically active systems in regions where CD could present strong limitations.
In this article, we present a new and simple, yet efficient, two-step approach to synthesize 4,4&... more In this article, we present a new and simple, yet efficient, two-step approach to synthesize 4,4'-bis(dibutylaminostyrylstyryl)-2,2'-bipyridine with high yield, as well as its linear and nonlinear optical characterizations in THF and toluene solutions. We show that its one- and two-photon absorption spectra are similar in both solvents. Nevertheless, the relaxation processes of this compound exhibit dependence on the solvent polarity. The one- and two-photon induced fluorescence signal of this molecule in solution reveals that its excited state is highly stabilized in THF solution rather than in toluene. Analysis of the fluorescence quantum yield, lifetime, and radiative and nonradiative decay rates are in agreement with Lippert's model for solute-solvent interactions. The optical measurements demonstrate that this dye is a promising candidate for multiphoton fluorescence imaging, optical limiting, and dye lasers.
Two-photon absorption cross-section spectrum of a π-conjugated polymer obtained using the white-l... more Two-photon absorption cross-section spectrum of a π-conjugated polymer obtained using the white-light continuum Z-scan technique. [Applied Physics Letters 88, 021911 (2006)]. SL Oliveira, DS Corrêa, L. De Boni, L. Misoguti, SC Zilio, CR Mendonça. Abstract. ...
This Article reports a combined experimental and theoretical analysis on the one and two-photon a... more This Article reports a combined experimental and theoretical analysis on the one and two-photon absorption properties of a novel class of organic molecules with a π-conjugated backbone based on phenylacetylene (JCM874, FD43, and FD48) and azoaromatic (YB3p25) moieties. Linear optical properties show that the phenylacetylene-based compounds exhibit strong molar absorptivity in the UV and high fluorescence quantum yield with lifetimes of approximately 2.0 ns, while the azoaromatic-compound has a strong absorption in the visible region with very low fluorescence quantum yield. The two-photon absorption was investigated employing nonlinear optical techniques and quantum chemical calculations based on the response functions formalism within the density functional theory framework. The experimental data revealed well-defined 2PA spectra with reasonable cross-section values in the visible and IR. Along the nonlinear spectra we observed two 2PA allowed bands, as well as the resonance enhancement effect due to the presence of one intermediate one-photon allowed state. Quantum chemical calculations revealed that the 2PA allowed bands correspond to transitions to states that are also one-photon allowed, indicating the relaxation of the electric-dipole selection rules. Moreover, using the theoretical results, we were able to interpret the experimental trends of the 2PA spectra. Finally, using a few-energy-level diagram, within the sum-over-essential states approach, we observed strong qualitative and quantitative correlation between experimental and theoretical results.
. The dynamic nonlinear absorption of a chloroform solution of chlorophyll A was investigated u... more . The dynamic nonlinear absorption of a chloroform solution of chlorophyll A was investigated using the Z-scan technique with picosecond pulses at 532 nm. The nonlinear absorption exhibits a reverse saturation, indicating a strong intersystem crossing (singlet–triplet) process. The time evolution of the optical nonlinearity, modeled by means of a five-level energy diagram, allows the determination of excited-state cross sections and
Quantum chemical calculations were carried out to explain the observed shifts in the absorption s... more Quantum chemical calculations were carried out to explain the observed shifts in the absorption spectrum of different azo-aromatic compounds due to changes in the dihedral angle of the azo-group. Our results reveal that the π−π∗ transition presents a hypsochromic shift and an oscillator strength drop upon increase of the dihedral angle. Nevertheless, the n−π∗ transition exhibits the opposite behavior. This effect is attributed to the reduction in the π−electron conjugation length of the molecule. Experimentally, we performed temperature dependence measurements of the linear absorption spectrum. Both the theoretical and experimental results demonstrate that small energy changes are mirrored in the electronic transitions of conjugated linear molecules.
Excited state dynamics, particularly intersystem crossing, of a set of meso-substituted porphyrin... more Excited state dynamics, particularly intersystem crossing, of a set of meso-substituted porphyrins bearing different electron–donor and acceptor groups was studied by pulse train fluorescence technique. Triplet quantum yield was found to be critically dependent on the nature of meso-substituents in the porphyrin system. Porphyrins with meso methoxyphenyl groups were found to show high triplet quantum yields ([Formula: see text] between 0.70 and 0.81). Moreover, the quantity of methoxyphenyl groups and the substitution pattern directly influence [Formula: see text]. Alternatively, porphyrins attached to nitrophenyl group possess low triplet quantum yield values (~0.3). The observed structure-properties relationships suggest new ways for tuning the optical properties of porphyrins via chemical modification.
2005 Quantum Electronics and Laser Science Conference, 2005
Page 1. Nonlinear Absorption Spectrum in Perylene Derivatives SL Oliveira, L. de Boni, DS Corrêa,... more Page 1. Nonlinear Absorption Spectrum in Perylene Derivatives SL Oliveira, L. de Boni, DS Corrêa, L. Misoguti, SC Zílio, and CR Mendonça Departamento de Física e Ciência dos Materiais, Instituto de Física de São Carlos, CP ...
This paper reports on the static and dynamic first-order hyperpolarizabilities of a class of push... more This paper reports on the static and dynamic first-order hyperpolarizabilities of a class of push-pull octupolar triarylamine derivatives dissolved in toluene. We have combined hyper-Rayleigh scattering experiment and the coupled perturbed Hartree-Fock method implemented at the Density Functional Theory (DFT) level of theory to determine the static and dynamic (at 1064 nm) first-order hyperpolarizability (βHRS) of nine triarylamine derivatives with distinct electron-withdrawing groups. In four of these derivatives, an azoaromatic unit is inserted and a pronounceable increase of the first-order hyperpolarizability is reported. Based on the theoretical results, the dipolar/octupolar character of the derivatives is determined. By using a polarizable continuum model in combination with the DFT calculations, it was found that although solvated in an aprotic and low dielectric constant solvent, due to solvent-induced polarization and the frequency dispersion effect, the environment substa...
This article reports on a comprehensive study of the two-photon absorption (2PA) properties of si... more This article reports on a comprehensive study of the two-photon absorption (2PA) properties of six novel push-pull octupolar triarylamine compounds as a function of the nature of the electron-withdrawing groups. These compounds present an octupolar structure consisting of a triarylamine core bearing two 3,3'-bis(trifluoromethyl)phenyl arms and a third group with varying electron-withdrawing strength (H < CN…
Latin America Optics and Photonics Conference, 2010
ABSTRACT We use pulse-shaping of femtosecond pulses to coherent control the synthesis of gold nan... more ABSTRACT We use pulse-shaping of femtosecond pulses to coherent control the synthesis of gold nanoparticles induced by two-photon absorption. Applying distinct phase masks to the pulse, we were able to shift the plasmon absorption band.
Dynamic optical nonlinearities in free base tetrapyridylporphyrin ( H 2 TPyP ) solutions were inv... more Dynamic optical nonlinearities in free base tetrapyridylporphyrin ( H 2 TPyP ) solutions were investigated at 532 nm with the Z-scan technique. We observed a reverse saturable absorption process that was found to have a fast contribution related to the singlet population and a slow accumulative contribution arising from the triplet population. The optical excitations and subsequent relaxations can be interpreted with a five-energy-level diagram that allows determination of the excited states photophysical parameters such as triplet and singlet absorption cross-sections and the intersystem crossing time.
Herein we report on the full experimental measurement of the two-photon absorption circular dichr... more Herein we report on the full experimental measurement of the two-photon absorption circular dichroism spectra of (S)-(-)-1,1&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-bi(2-naphthol) and (R)-(+)-1,1&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-bi(2-naphthol), their analysis, and theoretical support. The finding of new nonlinear optical fingerprints in chiral molecules offers new opportunities in the recognition and understanding of optically active systems in regions where CD could present strong limitations.
In this article, we present a new and simple, yet efficient, two-step approach to synthesize 4,4&... more In this article, we present a new and simple, yet efficient, two-step approach to synthesize 4,4&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-bis(dibutylaminostyrylstyryl)-2,2&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-bipyridine with high yield, as well as its linear and nonlinear optical characterizations in THF and toluene solutions. We show that its one- and two-photon absorption spectra are similar in both solvents. Nevertheless, the relaxation processes of this compound exhibit dependence on the solvent polarity. The one- and two-photon induced fluorescence signal of this molecule in solution reveals that its excited state is highly stabilized in THF solution rather than in toluene. Analysis of the fluorescence quantum yield, lifetime, and radiative and nonradiative decay rates are in agreement with Lippert&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s model for solute-solvent interactions. The optical measurements demonstrate that this dye is a promising candidate for multiphoton fluorescence imaging, optical limiting, and dye lasers.
Two-photon absorption cross-section spectrum of a π-conjugated polymer obtained using the white-l... more Two-photon absorption cross-section spectrum of a π-conjugated polymer obtained using the white-light continuum Z-scan technique. [Applied Physics Letters 88, 021911 (2006)]. SL Oliveira, DS Corrêa, L. De Boni, L. Misoguti, SC Zilio, CR Mendonça. Abstract. ...
This Article reports a combined experimental and theoretical analysis on the one and two-photon a... more This Article reports a combined experimental and theoretical analysis on the one and two-photon absorption properties of a novel class of organic molecules with a π-conjugated backbone based on phenylacetylene (JCM874, FD43, and FD48) and azoaromatic (YB3p25) moieties. Linear optical properties show that the phenylacetylene-based compounds exhibit strong molar absorptivity in the UV and high fluorescence quantum yield with lifetimes of approximately 2.0 ns, while the azoaromatic-compound has a strong absorption in the visible region with very low fluorescence quantum yield. The two-photon absorption was investigated employing nonlinear optical techniques and quantum chemical calculations based on the response functions formalism within the density functional theory framework. The experimental data revealed well-defined 2PA spectra with reasonable cross-section values in the visible and IR. Along the nonlinear spectra we observed two 2PA allowed bands, as well as the resonance enhancement effect due to the presence of one intermediate one-photon allowed state. Quantum chemical calculations revealed that the 2PA allowed bands correspond to transitions to states that are also one-photon allowed, indicating the relaxation of the electric-dipole selection rules. Moreover, using the theoretical results, we were able to interpret the experimental trends of the 2PA spectra. Finally, using a few-energy-level diagram, within the sum-over-essential states approach, we observed strong qualitative and quantitative correlation between experimental and theoretical results.
. The dynamic nonlinear absorption of a chloroform solution of chlorophyll A was investigated u... more . The dynamic nonlinear absorption of a chloroform solution of chlorophyll A was investigated using the Z-scan technique with picosecond pulses at 532 nm. The nonlinear absorption exhibits a reverse saturation, indicating a strong intersystem crossing (singlet–triplet) process. The time evolution of the optical nonlinearity, modeled by means of a five-level energy diagram, allows the determination of excited-state cross sections and
Quantum chemical calculations were carried out to explain the observed shifts in the absorption s... more Quantum chemical calculations were carried out to explain the observed shifts in the absorption spectrum of different azo-aromatic compounds due to changes in the dihedral angle of the azo-group. Our results reveal that the π−π∗ transition presents a hypsochromic shift and an oscillator strength drop upon increase of the dihedral angle. Nevertheless, the n−π∗ transition exhibits the opposite behavior. This effect is attributed to the reduction in the π−electron conjugation length of the molecule. Experimentally, we performed temperature dependence measurements of the linear absorption spectrum. Both the theoretical and experimental results demonstrate that small energy changes are mirrored in the electronic transitions of conjugated linear molecules.
Excited state dynamics, particularly intersystem crossing, of a set of meso-substituted porphyrin... more Excited state dynamics, particularly intersystem crossing, of a set of meso-substituted porphyrins bearing different electron–donor and acceptor groups was studied by pulse train fluorescence technique. Triplet quantum yield was found to be critically dependent on the nature of meso-substituents in the porphyrin system. Porphyrins with meso methoxyphenyl groups were found to show high triplet quantum yields ([Formula: see text] between 0.70 and 0.81). Moreover, the quantity of methoxyphenyl groups and the substitution pattern directly influence [Formula: see text]. Alternatively, porphyrins attached to nitrophenyl group possess low triplet quantum yield values (~0.3). The observed structure-properties relationships suggest new ways for tuning the optical properties of porphyrins via chemical modification.
2005 Quantum Electronics and Laser Science Conference, 2005
Page 1. Nonlinear Absorption Spectrum in Perylene Derivatives SL Oliveira, L. de Boni, DS Corrêa,... more Page 1. Nonlinear Absorption Spectrum in Perylene Derivatives SL Oliveira, L. de Boni, DS Corrêa, L. Misoguti, SC Zílio, and CR Mendonça Departamento de Física e Ciência dos Materiais, Instituto de Física de São Carlos, CP ...
This paper reports on the static and dynamic first-order hyperpolarizabilities of a class of push... more This paper reports on the static and dynamic first-order hyperpolarizabilities of a class of push-pull octupolar triarylamine derivatives dissolved in toluene. We have combined hyper-Rayleigh scattering experiment and the coupled perturbed Hartree-Fock method implemented at the Density Functional Theory (DFT) level of theory to determine the static and dynamic (at 1064 nm) first-order hyperpolarizability (βHRS) of nine triarylamine derivatives with distinct electron-withdrawing groups. In four of these derivatives, an azoaromatic unit is inserted and a pronounceable increase of the first-order hyperpolarizability is reported. Based on the theoretical results, the dipolar/octupolar character of the derivatives is determined. By using a polarizable continuum model in combination with the DFT calculations, it was found that although solvated in an aprotic and low dielectric constant solvent, due to solvent-induced polarization and the frequency dispersion effect, the environment substa...
This article reports on a comprehensive study of the two-photon absorption (2PA) properties of si... more This article reports on a comprehensive study of the two-photon absorption (2PA) properties of six novel push-pull octupolar triarylamine compounds as a function of the nature of the electron-withdrawing groups. These compounds present an octupolar structure consisting of a triarylamine core bearing two 3,3'-bis(trifluoromethyl)phenyl arms and a third group with varying electron-withdrawing strength (H < CN…
Latin America Optics and Photonics Conference, 2010
ABSTRACT We use pulse-shaping of femtosecond pulses to coherent control the synthesis of gold nan... more ABSTRACT We use pulse-shaping of femtosecond pulses to coherent control the synthesis of gold nanoparticles induced by two-photon absorption. Applying distinct phase masks to the pulse, we were able to shift the plasmon absorption band.
Uploads
Papers by Leonardo Boni