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In this work, the linear and nonlinear optical properties of three Imidazo[4-5,b]pyridine derivatives were investigated The results show an increase in the fluorescence quantum efficiency and 2PA cross-section due to substituent groups.

In this work, the spectroscopic properties of Imidazo[1,2-a]pyridine derivatives were investigated, as well as the two-photon absorption process. An increase in the 2PA cross-section was shown with the different structures of the molecules.

Linear and nonlinear optical properties of the PDI BSA molecule was performed in a solvent binary mixture aiming biological applications. Preliminary results showed that the 2PA cross-section is similar regardless the system, monomeric or aggregated.

In this work, the spectroscopic properties of Perylene were studied in different solvents, applying the Lippert equation. It has been observed that polar solvents have a more significant effect on the optical properties of Perylene.

Three-dimensional microstructures with selective properties have often been developed for optical and photonic applications. The simplest way to achieve optically active structures is by the functionalization of host matrices using, for instance, organic dyes. Laser fabrication techniques, such as two-photon polymerization, allow manufacturing devices quickly, with high resolution, without shape limitation, among other many advantages. In this work, we demonstrate the fabrication of three-dimensional microstructures via two-photon polymerization, using azobenzene-based dyes as photoinitiator, the compound responsible for absorbing the light and start the polymerization. When a high photoinitiator concentration is used (for instance 1.00 wt%), a significant amount of dye remains unchanged into the final structures, and its optically induced birefringence could be investigated. Therefore, the azobenzene-based dye acts, at the same time, as the photoinitiator and functionalizer.

The hyper-Rayleigh scattering technique was used to determine the first order hyperpolarizability β of magnetic nanoparticles dispersed on colloidal solutions. Pulse trains of mode-locked pulses of 100 ps on an a Q-switcher envelope of 150 ns emitted by a Nd:YAG laser, centered on 1064 nm, were used since this method allows measurements as a function of the incident beam intensity without the need of external elements. In order to determine the procedure to measure second-order optical nonlinearities on magnetic nanoparticles and avoid cumulative effects during the measurements, that lasts between to consecutive pulse trains, the results were studied for different values of the Q-switcher repetition rate, from 5 Hz to 800 Hz. Since cumulative effects were verified for higher values of repetition rates, all measurements were performed at the rate of 30 Hz. Therefore, the first-order hyperpolarizability β was measured in the presence and absence of external magnetic field of magnitude H = 800 G. The linear attenuation spectrum was determined and didn't change with the appliance of magnetic field since large aggregates of nanoparticles were not formed. Nonlinear scattering measurements were performed in the case were the laser light polarization was parallel and perpendicular to the external field lines, employing a half-wave plate to change the light polarization state. In the absence of magnetic field, βH=0 = 8:5(1)×10-28 cm5/esu, while in their presence of magnetic field, β = 9:8(2)×10-28 cm5/esu and β⊥ = 8:1(1)×10-28 cm5/esu, showing an anisotropy β-β⊥/β of about 17%.

Rhodamine 6G-doped TEOS-derived xerogels containing different concentrations of TiO2 nanoparticles with average diameter of about 350 nm were designed to study random laser action. Due to the decantation of TiO2 nanoparticles during the sol–gel process, the obtained xerogels samples exhibits an inhomogeneous TiO2 distribution, with a higher concentration at one of the sample surfaces. By pumping the samples at each of the surfaces at a time with a ps-laser at 532 nm, differences in the emission behavior were observed. The higher concentration of TiO2 in one side of the sample, which occurs during its preparation, was shown to play an important role in the random laser energy threshold and emission spectra, depending on what side of the sample the excitation takes place. The difference in the laser threshold shows that the way scatterers are volumetrically distributed can increase or decrease the pump energy required for laser action.

Zipped data sets relative to the article "Tuning hyper-Rayleigh scattering amplitude on magnetic colloids by means of an external magnetic field", https://doi.org/10.1364/JOSAB.35.002681

This work reports on the singlet excited-state absorption spectrum of sodium-copper chlorophyllin using three distinct methods of Z-Scan measurement: white-light continuum Z-Scan technique ranging from 470 to 780 nm, tunable Z-Scan technique with femtosecond pulses (490–700 nm) and 532 nm Z-Scan technique with 100 ps pulse width. A transition from reverse saturation absorption (RSA) to saturable absorption (SA) was observed at 570 nm, and at 532 nm RSA was tested showing potential application as optical limiting device. Pump-probe technique was used to measure lifetime of the first singlet excited state (22 ps) and no evidence of triplet conversion was observed.

The influence of the environment on the excited state transitions of meso-tetrakis(p-sulfonatophenyl) porphyrin (TPPS) is reported. TPPS was investigated in protonated and non-protonated forms, and in the presence of the cationic cetyltrimethylammonium bromide (CTAB) micelles. The singlet excited-state absorption spectra were measured by using the white-light continuum Z-scan technique and the triplet–triplet absorption spectra were acquired employing an association of laser flash photolysis and Z-scan techniques. Our results show that the perseveration of the molecular symmetry, upon excitation, depends on the state of multiplicity of the molecules, as well as on the environment and structural characteristics of the porphyrin. Additionally, it was observed that for excited molecules, the ring distortion caused by the protonation of porphyrin ring has great influence on the changes observed for the symmetry and vibronic structure. The results clearly show that the porphyrin investigated is a promising candidate for optical limiting applications for all investigated environments.

Hintergrund Auf Grund mangelnder histopathologischer Differenzierungsmoglichkeit ist eine eindeutige Identifizierung eines Mykoseerregers nur selten moglich. Um das Erregerspektrum bei einer zephalen Mykose besser erfassen zu konnen, ist das Einbeziehen weiterer Methoden erforderlich.

The two-photon absorption (2PA) of five symmetrical fluorenone-based molecules is studied by femtosecond wavelength-tunable Z-scan, as well as quantum-chemical calculations. The molecules are transparent for wavelengths greater than 500 nm and two main one-photon absorption bands are observed in the blue region; one weak, centered at 450 nm, and a stronger one at approximately 360 nm. We observed a strong 2PA band located around 720 nm with maxima 2PA cross-sections between 100 and 230 GM. Quantum chemical calculations employing the response function formalism were performed at the Density Function Theory level to support the interpretation of the experimental nonlinear spectra.

We investigate the excited state intramolecular proton transfer dynamic for a salophen derivative chromophore by using white-light continuum femtosecond pump-probe and quantum chemical calculations within the DFT framework.

Two-photon absorption cross-section spectra of nine Fluorenone-based composites were measured using the open-aperture Z-Scan technique. Their maxima cross-sections values are between 100 and 230 GM at around 710 nm, which are desired for applications as cellular probes.

The α-synuclein gene (SNCA) plays a major role in the aetiology of Lewy body disease (LBD) including Parkinson's disease (PD). Point mutations and genetic alterations causing elevated gene expression are causally linked to familial PD. To what extent epigenetic changes play a role in the regulation of α-synuclein expression and may contribute to the aetiology of sporadic LBD is a matter of debate. We analysed the methylation state of the promoter region and a CpG-rich region of intron 1 of α-synuclein in several brain regions in sporadic LBD and controls using 454 GS-FLX-based high-resolution bisulphite sequencing. Our results indicate that there are significant differences in the level of methylation between different brain areas. The overall methylation levels in the promoter and intron 1 of α-synuclein are rather low in controls and-in contrast to previously reported findings-are not significantly different from LBD. However, single CpG analysis revealed significant hyper- and hypomethylation at different positions in various brain regions and LBD stages. A slight overall increase in methylation related to LBD patients' age was detected.

Excited state absorption and excited state dynamics of indocyanine-green (ICG) dissolved in dymethyl sulfoxide were measured using white-light continuum Z-scan (WLCZScan) and white-light continuum pump–probe (WLCPP) techniques. The excited state absorption spectrum, obtained through Z-scan measurements, revealed saturable absorption (SA) for wavelengths longer than 630 nm, while reverse saturable absorption (RSA) appeared, as indicated by a band at approximately 570 nm. Both processes were modeled by a three-energy-level diagram, from which the excited state cross-section values were determined. SA and RSA were also observed in pump–probe experiments, with a recovery time in the hundreds of picoseconds time scale due to the long lifetime of the first excited state of ICG. Such results contribute to the understanding of ICG optical properties, allowing application in photonics and medicine. Copyright © 2010 John Wiley & Sons, Ltd.

Two-photon absorption spectra of a triarylamine compounds dissolved in toluene were measured using the well-known Z-scan technique, employing 120-fs laser pulse-width. According to the results, an extra band located at around 900 nm was observed only for triarylamine with azoaromatic units. On the other hand, a shift in the two-photon absorption band for triarylamine, with and without azoaromatic units, is observed when different electron donor/acceptors groups are changed. The fitting of the spectra, using sum-over-states model, allowed us to obtain the spectroscopic parameters of each molecule, which appears to be in reasonable agreement with molecules presenting similar structural moieties.

This work investigates the two-photon absorption spectrum of perylene tetracarboxylic derivatives using the white-light continuum Z-scan technique. Perylene derivatives present relatively high two-photon absorption cross-section, which makes them attractive for applications in photonics. Because of the spectral resolution of the white-light continuum Z-scan, we were able to observe a well defined structure in the two-photon absorption spectrum, composed by two distinct peaks. These peaks, as well as the resonant enhancement of the nonlinearity, were modeled using the sum-over-states approach considering a four-level energy diagram with two final two-photon states. The existence of such states was confirmed using the response function formalism within the DFT framework.

This Letter studies the degenerate two-photon absorption (2PA) spectra of three diazoaromatic compounds using Z-scan with fs-pulses. The 2PA spectra exhibit resonant enhancement of the nonlinearity as the excitation approaches the linear absorption. The absence of 2PA to the ππ ∗ band is related to the weaker donor/acceptor groups, and lower symmetry of diazoaromatic compounds, in agreement with our semi-empirical calculations. The higher magnitude of the 2PA cross-section, in comparison with single azoaromatics, demonstrates the positive effect of increasing conjugation. The decrease of 2PA cross-section with temperature is attributed to thermally induced torsions, which decreases the effective conjugation of diazoaromatic molecules.

The excited state dynamics of Zn 2+ , Fe 3+ , and Mn 3+ meso-tetra(sulfonatophenyl) porphyrin complexes were investigated with a Z-scan technique at 532 nm using 70 ps and 120 fs single pulses and 200 ns pulse trains of a Q-switched and mode locked laser. We determined the characteristic interconversion and intersystem crossing times, quantum yields of the excited S 1 state, and S 1 → S n and T 1 → T n transition cross-sections. The ground state cross-sections were obtained using UV-vis absorption spectroscopy, and a five-energy-level diagram was used to yield the photophysical parameters mentioned previously.

We carried out experiments of induced birefringence via two-photon absorption in spin-coated films of the conjugated polymer poly[2-[ethyl-[4-(4-nitro-phenylazo)-phenyl]-amino]-ethane (3-thienyl)ethanoate], PAzT, at 680 and 775 nm. This process allows recording in the bulk because of the spatial confinement of the birefringence provided by the two-photon absorption. The induced birefringence is associated with molecular reorientation caused by the two-photon induced isomerization of the azochromophores attached to the polymer backbone. In addition, the two-photon absorption spectrum of PAzT was measured to help selecting the excitation wavelength for two-photon absorption induced birefringence.

4PA) cross-section spectra for poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) chloroform solution, which exhibits values comparable to other materials reported in the literature. A resonant enhancement was observed in the 3PA spectrum for excitation wavelengths with one-third of the energy (1200 nm) of the one-photon state. From the applications point of view, the nonlinear absorption spectrum can help to select the operation wavelength for a given device, indicating, for instance, the spectral region in which the nonlinear response is highest. Moreover, we also observed three- and four-photon excited fluorescence, suggesting MEH-PPV could be used as the active medium in up-conversion fluorescence devices. The multiphoton absorp

The understanding of excited states of conjugated polymers is of great interest for photonics, especially for fabricating electroluminescent and optical devices. This work concerns the excited state absorption of three conjugated polymers: poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV), poly[2-[ethyl-[4-(4-nitro-phenylazo)-phenyl]-amino]-ethane-(3-thienyl)-ethanoate] (PAzT), and poly(3-octyl-thiophene) (POT). The nonlinear spectra from 450 nm up to 700 nm for the three polymers were obtained by means of the white-light continuum Z-scan technique. Saturation of absorption was observed due to the ground state depletion for the three polymers. In addition to this effect, we also observed a small excited state absorption for POT. The absorption from the first to a higher excited state is negligible for MEH-PPV and PAzT. In contrast, POT presented absorption for a higher excited state, which allowed the determination of its excited state absorption cross-section.

In this work, we studied the nonlinear absorption dynamics of indocyanine green (ICG) in dimethyl sulfoxide (DMSO) at 532 nm. Single pulse and pulse train Z-scan techniques were used to obtain singlet and triplet states dynamics, which were analyzed with a three- and five-energy level diagram, respectively. The excited singlet state absorption cross-section was determined to be 75 times higher than the ground state one, giving rise to reverse saturated absorption. Reverse saturated absorption also occurs from the triplet state, after its population through an intersystem crossing process, whose characteristic time is 4 ns. The triplet state absorption cross-section determined is 31 times higher than the ground state one. The high excited singlet and triplet states absorption cross-sections of ICG indicates its use in application requiring reverse saturated absorption, such as sensitizer for photodynamic therapy and optical limiting.

This work reports the degenerate two-photon absorption spectrum for a series of Salen complexes possessing two azo dye units. The observed spectra peak at 1000 nm, twice the wavelength of the linear absorption peak, and increase monotonically to the blue due to resonant enhancement of the non linearity. The two-photon absorption properties of these molecules were found to be an additive effect of chromophores and independent of the metal ions. The two-photon absorption spectra were described with a sum-over-states model, from which the transition dipole moment and dipole moment change were determined and compared with quantum chemistry calculation.

In this paper we present optical anisotropy induced by 150-fs laser pulses operating at 775 nm in poly(methyl methacrylate) (PMMA) films doped with Disperse Red 13 (DR13). Two-photon absorption of DR13 induces reversible birefringence in the sample, a feature associated with the molecular orientation caused by isomerization of the azochromophores. No irreversible anisotropy, associated with photobleaching of the chromophore was observed. The slope of 2 obtained for the induced birefringence as a function of the excitation irradiance corroborates the two-photon nature of the process.

This work investigates the two-photon absorption (2PA) spectrum of all-trans retinoic acid (ATRA) in DMSO solution, employing the wavelength-tunable Z-scan and white-light pump-probe techniques with femtosecond pulses. Our results showed that ATRA presents two 2PA allowed bands at 280 nm (2hν = 560 nm) and 365 nm (2hν = 730 nm) with 2PA cross-section values of 34 GM and 40 GM, respectively. The 2PA band at 280 nm was ascribed to the transition from ground to high energy excited states with contribution from the real intermediate excited state (11Bu+-like). The 2PA band at 365 nm was attributed to an overlap of 11Bu+-like and 21Ag−-like excited states, which are essential to describe the photochemical processes that this class of organic materials play in nature. Through solvatochromic measurements and by using the two-energy level approach, we found that the 11Bu+-like and 21Ag−-like states contribute, respectively, 48% and 52% of the lowest energy 2PA band of ATRA in DMSO solution. From femtosecond transient spectroscopy we verified that when ATRA is excited at 775 nm (2PA excitation) its excited state absorption (ESA) spectrum presents a red-shift of ∼5.5 nm in comparison to the same spectrum excited at 387.5 nm (1PA excitation), corroborating the interpretation about the 2PA spectrum for the ATRA in DMSO.

The nonlinear absorption of poly[2-[ethyl-[4-(4-nitro-phenylazo)-phenyl]-amino]-ethane(3-thienyl)ethanoate], PAzT, was investigated using single pulse and pulse train open aperture Z-scan techniques to discriminate between fast and accumulative nonlinearities. We observed an induced transparency for excitation with picosecond laser pulses at resonant conditions, which was attributed to the azobenzene moieties attached to the polymer backbone. The fast transparency is caused mainly by the build up of molecules in the first excited state that have a negligible absorption cross-section compared to the ground state. When using pulse trains, the nonlinear response is mainly due to the accumulation of molecules in the cis configuration, which presents a ground state cross-section slightly smaller than that of trans. The cumulative effect arises from a combination of the less intense excitation and longer lifetime of the cis population. We believe that the process observed here makes PAzT an attractive polymer for photonics applications, such as optical switches and storage devices.

The whole set of photophysical characteristics of the metal-free water-soluble meso-tetrakis(p-sulfonatophenyl) porphyrin (TPPS4) in its protonated and nonprotonated states in homogeneous aqueous solutions and in the presence of cationic cetyltrimethylammonium bromide micelles (CTAB) was investigated with nonlinear optical Z-scan technique, UV–vis absorption and fluorescence spectroscopies, time-resolved fluorescence and flash-photolysis. The characteristics were: the cross-sections of the ground (σ0) and the excited singlet (σS) and triplet (σT) states; the rate constants of intersystem-crossing (kisc), internal conversion (kic) and radiative one (kr); the quantum yields (Φfl and ΦT) and lifetimes (τS and τT) of singlet and triplet states and quantum yield of internal conversion (Φic). The study was realized at pH 7.0 and 4.0, where TPPS4 in homogeneous solutions is nonprotonated and biprotonated, respectively. It was observed that, in spite of the fact that protonation changes all these characteristics, their values for TPPS4 bound with CTAB micelles were at both pH close to those of nonprotonated porphyrin in the solution. It is due to the fact that binding with CTAB shifts the pK of TPPS4 from 5.0 in homogeneous solution to 2.5 in the micellar one and the bound porphyrin appears in nonprotonated state at both pH used. We can conclude also that the change of the quality of the environment from homogeneous aqueous solution to the micellar one affects weakly the TPPS4 photophysical characteristics when it is not protonated.

In this work we have measured the nonlinear absorption spectrum of ytterbium bis-phthalocyanine (YbPc2) in chloroform solution employing the Z-scan technique with white-light continuum (WLC) pulses. Two distinct excited state absorption behaviors were observed: a saturable absorption (SA) at the Q-band region and a reverse saturable absorption (RSA) around 530 nm. A threeenergy-level diagram was used to explain the experimental results, leading to the excited state absorption cross-section determination from 500 up to 675 nm. � 2005 Elsevier B.V. All rights reserved.

Nonlinear absorption dynamics of Zn(2+), Cu(2+), and Ni(2+) tetrapyridyl porphyrins in chloroform/methanol solutions were investigated at 532 nm with the Z-scan technique. Additional techniques such as UV-vis absorption spectroscopy and time-resolved fluorescence were used to obtain parameters that are important for the analysis of the population dynamics. A marked difference was observed in the nonlinear absorption and excited-state dynamics of closed (ZnTPyP)- and open-shell metalloporphyrins (CuTPyP and NiTPyP). ZnTPyP presents a reverse saturable absorption whose dynamics can be completely described by means of a simple five-energy-level diagram. On the other hand, CuTPyP and NiTPyP have a different excited-state dynamics, presenting a saturable absorption behavior and faster relaxation rates that were attributed to the presence of unfilled d shells of the central ion.

We present an experimental investigation on the photophysical properties of meso-tetra(sulfonatophenyl) porphyrin (TPPS4 )i n its bi-protonated and deprotonated states in water solutions at pH 4.0 and 7.0, respectively. The Z-scan technique at 532 nm with single 70 ps pulses as well as with pulse trains, was used in association with other complementary techniques such as UV–Vis absorption spectroscopy and time resolved fluorescence. The saturation behavior and the time evolution of nonlinear optical absorption were analyzed with a five-energy-level diagram. Photophysical parameters such as ground and excited states absorption crosssections, together with the fluorescence lifetime and intersystem crossing time were determined. � 2005 Elsevier B.V. All rights reserved.

Two- and three-photon excited fluorescence and its optimization via pulse shaping was studied in a novel classes of Y-shaped chromophores with large nonlinear absorption cross section

Nonlinear optical properties of phenyl/−NH2 end-capped tetraaniline in dimethyl sulfoxide solutions were investigated as a function of the tetraaniline concentration for both doped and undoped samples. We employed the single beam Z-scan technique with 70-ps-duration pulses at 532 nm, in association with others complementary techniques such as UV−vis absorption spectroscopy and time-resolved fluorescence. Our results show that both the nonlinear refractive index and the nonlinear absorption diminish for the doped sample, following the same behavior of the absorption coefficient.

Nonlinear absorption dynamics of oxidized cytochrome c in water solution was investigated at 532 nm with Z-scan and pump–probe techniques. The optical characterization of this compound is very important owing to its similarity with hematoporphyrin-based drugs commonly used in photodynamic therapy for cancer treatment. We observed a saturable absorption process related to the excited singlet population, followed by a fast decay to the ground state. The optical excitation and subsequent relaxation were interpreted with a three-energy-level diagram, allowing the first singlet excited-state absorption cross section and lifetime determination.

Here we present, a two-photon absorption (2PA) study in Fe2+ and Fe3+ oxidation states of cytochrome c molecule in water solution, using the femtosecond Z-scan technique with pulses from 560 to 850 nm. No qualitative difference was observed in the 2PA process for the two Fe oxidation states. The 2PA cross-sections, for both samples, increase as the wavelength approaches the absorption band, in agreement with the resonant denominator in the sum-over states model, presenting a maximum value of approximately 1000 GM at about 600 nm.

Knowledge about the nonlinear absorption spectra of materials used in photonic devices is of paramount importance in determining their optimum operation wavelengths. It is well-know that resonances enhance the nonlinear response of a material, but in this case, slow excited states processes, propagation losses, and photodegradation can take place, which are known to be deleterious for photonic applications. With this concern, we have studied the nonlinear degenerate spectrum of poly(MEH-PPV) using femtosecond laser pulses from 460 to 1000 nm. Such a wide band spectrum has never been investigated in previous works reported in the literature. We were able to distinguish between a strong two-photon absorption (2PA) mechanism at nonresonant conditions and a saturated absorption (SA) that overcomes the 2PA process as we approach the absorptive region. The results were fitted with rate equations obtained from an energy level model.

This work reports on the two-photon absorption (2PA) cross-section for bis (n-butylimido) perylene (BuPTCD), bis (benzimidazo) perylene (AzoPTCD), bis (benzimidazo) thioperylene (Monothio BZP), bis (phenethylimido) perylene (PhPTCD), bis (benzylimido) perylene (BePTCD) and n-pentylimido-benzimidazo perylene (PAzoPTCD) solutions measured using the Z-scan technique with femtosecond laser pulses at 775 nm. All perylene derivatives studied present large 2PA cross-sections, only comparable to the best ones reported in the literature. The experimental 2PA cross-sections obtained for each PTCD compound are in good agreement with a simplified sum-over-state calculation. The results of the present work indicates perylene derivatives as promising materials for two-photon applications.

We report on the two-photon absorption (2PA) cross-section for eight azoaromatic compounds in dimethyl sulfoxide solutions, using the Z-scan technique with femtosecond laser pulses at 775 nm. The 2PA cross-sections of these molecules are of the order of (1–6)×10 −50 cm 4 s photon −1 . A correlation was established between the molecular structure and the two-photon absorption process, which makes it possible to develop molecular design strategies to create structures with suitable two-photon absorption coefficients.

Made available in DSpace on 2018-12-11T16:47:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-06-01 A Rhodamine B-doped 3-glycidoxypropyltrimethoxysilane (GPTS)/tetraethyl orthosilicate (TEOS)-derived organic/silica monolithic xerogel with excellent optical properties was prepared and its potential as a random laser host investigated. This hybrid material has a non-porous organic/inorganic morphology with silica-rich nanoparticles of less than 10 nm in diameter homogeneously dispersed within the matrix. Random laser emission with incoherent feedback, centered at 618 nm, was observed from Rhodamine B incorporated into the monolithic xerogel when excited by a 532 nm pulsed laser. This hybrid system is shown to be very promising for the development of a new class of random laser-based integrated devices, with applications ranging from optical bio-imaging to sensing. Departamento de Física Universidade Federal de Sergipe Departamento de Física Unesp - Universidade Estadual Paulista Departamento de Física Universidade Federal de São Carlos Instituto de Física de São Carlos Universidade de São Paulo, CP 369 Departamento de Física Unesp - Universidade Estadual Paulista

Due to the lack of histopathological differentiation the unequivocal identification of fungal pathogens is rarely possible. In order to understand the pathogen spectrum causing cephalic mycosis the use of alternative methods is essential.In a retrospective study 24 formalin-fixed, paraffin-embedded (FFPE) samples from patients with histologically confirmed cerebral or cephalic mycosis were analyzed with molecular biological methods.In two samples obtained during the patients' lifetime human as well as fungal DNA was detected, making an unambiguous diagnosis possible. For tissue that had been fixed over a longer period, detection of human and fungal DNA was possible merely in 60% and 47 % of the samples, respectively. Most frequently diagnosed were aspergillosis (n = 9), followed by mucormycosis (n = 2) and imported blastomycosis (n = 1).Using biopsy material a DNA analysis seems promising although only with limited success using brain samples taken at autopsy which have been fixed over a longer period. For unambiguous retrospective diagnostics of pathogens when cephalic mycosis is suspected, the sample extraction for postmortem diagnostics should be performed prior to a long period of formalin fixation.

In this report we investigate the two-photon absorption circular-linear dichroism (2PA-CLD) of two chiral molecules based on phenylacetylene moieties employing the Z-scan technique with polarization control

This work reports on the optical nonlinearities of a newly synthesized pyrazole derivative, namely ( E )-1-(4-chlorophenyl)-4-(2-nitrovinyl)-1 H -pyrazole. The Z-scan technique with femtosecond laser pulses was used to determine the two-photon absorption (2PA) cross-section spectrum, which presents a maximum of 67 GM at 690 nm. We have combined hyper-Rayleigh scattering (HRS) experiments and second-order Moller–Plesset perturbation theory (MP2) calculations to study the first hyperpolarizability ( β HRS ). It was found that the MP2/6-311+G(d) model, taking into account solvent and dispersion effects, provides the β HRS value of 40 × 10 −30 cm 5 /esu for the compound, in good agreement with the experimental result of 45 ± 2 × 10 −30 cm 5 /esu.

This work reports on the photophysical properties of zinc porphyrins meso -tetrakis methylpyridiniumyl (Zn 2+ TMPyP) and meso -tetrakis sulfonatophenyl (Zn 2+ TPPS) in homogeneous aqueous solutions and in the presence of sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide (CTAB) micelles. The excited-state dynamic was investigated with the Z-scan technique, UV–Vis absorption, and fluorescence spectroscopy. Photophysical parameters were obtained by analyzing the experimental data with a conventional five-energy-level diagram. The interaction of the charged side porphyrin groups with oppositely charged surfactants can reduce the electrostatic repulsion between porphyrin molecules leading to aggregation, which affected the porphyrin characteristics such as absorption cross-sections, lifetimes and quantum yields. The interaction between anionic ZnTPPS with cationic CTAB micelles induced the formation of porphyrin J-aggregates, while this effect was not observed in the interaction of ZnTMPyP with SDS micelles. This difference is, probably, due to the difference in electrostatic repulsion between the porphyrin molecules. The insights obtained by these results are important for the understanding of the photophysical behavior of porphyrins, regarding potential applications in pharmacokinetics as encapsulation of photosensitizer for drug delivery systems and in its interaction with cellular membrane.

Made available in DSpace on 2013-08-28T14:11:18Z (GMT). No. of bitstreams: 1 WOS000306176100050.pdf: 941781 bytes, checksum: 0a65cb652272365b995e599725226bb0 (MD5) Made available in DSpace on 2013-09-30T19:23:22Z (GMT). No. of bitstreams: 2 WOS000306176100050.pdf: 941781 bytes, checksum: 0a65cb652272365b995e599725226bb0 (MD5) WOS000306176100050.pdf.txt: 28470 bytes, checksum: 95caaa4a695d9a105845fe9382f889a2 (MD5) Previous issue date: 2012-07-02 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:34:10Z No. of bitstreams: 2 WOS000306176100050.pdf: 941781 bytes, checksum: 0a65cb652272365b995e599725226bb0 (MD5) WOS000306176100050.pdf.txt: 28470 bytes, checksum: 95caaa4a695d9a105845fe9382f889a2 (MD5) Made available in DSpace on 2014-05-20T15:34:10Z (GMT). No. of bitstreams: 2 WOS000306176100050.pdf: 941781 bytes, checksum: 0a65cb652272365b995e599725226bb0 (MD5) WOS000306176100050.pdf.txt: 28470 bytes, checksum: 95caaa4a695d9a105845fe9382f889a2 (MD5) Previous issue date: 2012-07-02 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) AFOSR from USA Glasses containing metallic nanoparticles are promising materials for technological applications in optics and photonics. Although several methods are available to generate nanoparticles in glass, only femtosecond lasers allow controlling it three-dimensionally. In this direction, the present work investigates the generation of copper nanoparticles on the surface and in the bulk of a borosilicate glass by fs-laser irradiation. We verified the formation of copper nanoparticles, after heat treatment, by UV-Vis absorption, transmission electron microscopy and electron diffraction. A preferential growth of copper nanoparticles was observed in the bottom of the irradiated region, which was attributed to self-focusing in the glass. (c) 2012 Optical Society of America Univ São Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, UNESP, BR-14801907 Araraquara, SP, Brazil Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Instrumentacao Agr, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, UNESP, BR-14801907 Araraquara, SP, Brazil

Experimental and theoretical studies on the two-photon absorption properties of two oxazole derivatives: 2,5-diphenyloxazole (PPO) and 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) are presented. The two-photon absorption cross-section spectra were determined by means of the Z-scan technique, from 460 up to 650 nm, and reached peak values of 84 GM for PBD and 27 GM for PPO. Density Functional Theory and response function formalism are used to determine the molecular structures and the one- and two-photon absorption properties and to assist in the interpretation of the experimental results. The Polarizable Continuum Model in one-photon absorption calculations is used to estimate solvent effects.

This paper reports the synthesis of Au nanoparticles by 30-fs pulses irradiation of a sample containing HAuCl4 and chitosan, a biopolymer used as reducing agent and stabilizer. We observed that it is a multi-photon induced process, with a threshold irradiance of 3.8 × 10(11) W/cm2 at 790 nm. By transmission electron microscopy we observed nanoparticles from 8 to 50 nm with distinct shapes. Infrared spectroscopy indicated that the reduction of gold and consequent production of nanoparticles is related to the fs-pulse induced oxidation of hydroxyl to carbonyl groups in chitosan.

In this report, we investigate the polarization effect (linear, elliptical and circular) on the two-photon absorption (2PA) properties of a chiral compound based in azoaromatic moieties using the femtosecond Z-scan technique with low repetition rate and low pulse energy. We observed a strong 2PA modulation between 800 nm and 960 nm as a function the polarization changes from linear through elliptical to circular. Such results were interpreted employing the sum-over-essential states approach, which allowed us to model the 2PA circular-linear dichroism effect and to identifier the overlapping of the excited electronic states responsible by the 2PA allowed band.