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1.
Chemistry ; 25(46): 10954-10964, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31215691

RESUMO

Epicocconone 1 is a natural chromophore isolated from the fungus Epicoccum nigrum that has shown applications in proteomics and fluorescent microscopy thanks to its unique pro-fluorescence properties. The modification of the skeleton of the natural product by replacing the triene side chain by a fluorenyl scaffold can noticeably increase the fluorophore's absorption coefficient. The synthesis of the analogues of the natural product has been made possible by the use of a palladium-catalyzed carbonylation reaction, allowing the construction of the ß-keto-dioxinone key intermediate. Two-photon absorption cross-section measurements of the fluorenyl epicocconone analogues show a structure dependency with values ranging from 60 to 280 GM and live cell imaging show intense staining of intracellular vesicle-like structures around the nucleus.


Assuntos
Benzopiranos/química , Fluorenos/química , Corantes Fluorescentes/química , Furanos/química , Cetonas/química , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Animais , Benzopiranos/síntese química , Catálise , Fluorenos/síntese química , Corantes Fluorescentes/síntese química , Furanos/síntese química , Cetonas/síntese química , Imagem Óptica/métodos , Células PC12 , Paládio/química , Ratos
2.
Chemistry ; 25(38): 9026-9034, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-30972809

RESUMO

Two trispicolinate 1,4,7-triazacyclonane (TACN)-based ligands bearing three picolinate biphotonic antennae were synthetized and their Yb3+ and Gd3+ complexes isolated. One series differs from the other by the absence (L1 )/presence (L2 ) of bromine atoms on the antenna backbone, offering respectively improved optical and singlet-oxygen generation properties. Photophysical properties of the ligands, complexes and micellar Pluronic suspensions were investigated. Complexes exhibit high two-photon absorption cross-section combined either with NIR emission (Yb) or excellent 1 O2 generation (Gd). The very large intersystem crossing efficiency induced by the combination of bromine atom and heavy rare-earth element was corroborated with theoretical calculations. The 1 O2 generation properties of L2 Gd micellar suspension under two-photon activation leads to tumour cell death, suggesting the potential of such structures for theranostic applications.

3.
J Phys Chem B ; 117(34): 9877-81, 2013 Aug 29.
Artigo em Inglês | MEDLINE | ID: mdl-23879840

RESUMO

We experimentally demonstrate that some peptides and proteins lend themselves to an elementary analysis where their first hyperpolarizability can be decomposed into the coherent superposition of the first hyperpolarizability of their elementary units. We then show that those elementary units can be associated with the amino acids themselves in the case of nonaromatic amino acids and nonresonant second harmonic generation. As a case study, this work investigates the experimentally determined first hyperpolarizability of rat tail Type I collagen and compares it to that of the shorter peptide [(PPG)10]3, where P and G are the one-letter code for Proline and Glycine, respectively, and that of the triamino acid peptides PPG and GGG. An absolute value of (0.16 ± 0.01) × 10(-30) esu for the first hyperpolarizability of nonaromatic amino acids is then obtained by using the newly defined 0.087 × 10(-30) esu reference value for water. By using a collagen like model, the microscopic hyperpolarizability along the peptide bond can be evaluated at (0.7 ± 0.1) × 10(-30) esu.


Assuntos
Aminoácidos/química , Colágeno Tipo I/química , Colágeno/química , Peptídeos/química , Animais , Colágeno/metabolismo , Colágeno Tipo I/metabolismo , Peptídeos/metabolismo , Estrutura Secundária de Proteína , Ratos
4.
J Phys Chem Lett ; 4(19): 3330-6, 2013 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-26705821

RESUMO

Multiexciton absorption cross sections are important for analysis of a number of experiments, including multiple exciton generation and stimulated emisson. We present a rigorous method to determine these cross sections using transient absorption (TA) measurements. We apply the method to CdSe quantum dots (QDs) and core-shell (CdSe)ZnS QDs. The method involves measuring TA dynamics for various excitation intensities over a broad time range and analyzing the experiments in terms of a kinetic multiexciton model taking into account all contributions to the signal. In this way, we were able to quantify exciton and multiexciton absorption cross sections at different spectral positions. The absorption cross sections decrease with increasing number of excitations, qualitatively in agreement with the state-filling effective mass model but showing a slower decrease. The cross sections for single-exciton to biexciton absorption range between 57 and 99% of the ground to single-exciton cross section.

5.
J Phys Condens Matter ; 24(12): 124104, 2012 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-22395007

RESUMO

We have measured the first hyperpolarizabilities of thioalkane capped silver and gold metallic nanoparticles. The values found are ß(AgC 12-10 nm) = (2.10 ± 0.23) × 10(-26) esu for 10 nm diameter silver nanoparticles and ß(AuC 18-18 nm) = (3.37 ± 0.08) × 10(-26) esu for 18 nm diameter gold nanoparticles at the fundamental wavelength of 784 nm. By comparison to the corresponding values reported for citrate capped silver and gold metallic nanoparticles, after size corrections, decreases by factors of 4.3 and 6.5 respectively are observed. These decreases are tentatively attributed to the bonds formed between the gold and silver surface atoms and the sulfur atoms of the capping layer.

6.
Nano Lett ; 12(3): 1697-701, 2012 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-22375818

RESUMO

We show that sensing in the nonlinear optical regime using multipolar surface plasmon resonances is more sensitive in comparison to sensing in the linear optical regime. Mie theory, and its extension to the second harmonic generation from a metallic nanosphere, is used to describe multipolar second harmonic generation from silver metallic nanoparticles. The standard figure of merit of a potential plasmonic sensor based on this principle is then calculated. We finally demonstrate that such a sensor is more sensitive to optical refraction index changes occurring in the vicinity of the metallic nanoparticle than its linear counterpart.


Assuntos
Metais/química , Modelos Químicos , Modelos Moleculares , Nanosferas/química , Nanosferas/ultraestrutura , Ressonância de Plasmônio de Superfície/métodos , Simulação por Computador , Luz , Espalhamento de Radiação
7.
Opt Express ; 17(14): 11450-6, 2009 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-19582060

RESUMO

Short lived plasma channels generated through filamentation of femtosecond laser pulses in air can be revived after several milliseconds by a delayed nanosecond pulse. Electrons initially ionized from oxygen molecules and subsequently captured by neutral oxygen molecules provide the long-lived reservoir of low affinity allowing this process. A Bessel-like nanosecond-duration laser beam can easily detach these weakly bound electrons and multiply them in an avalanche process. We have experimentally demonstrated such revivals over a channel length of 50 cm by focusing the nanosecond laser with an axicon.


Assuntos
Lasers , Óptica e Fotônica , Ar , Elétrons , Desenho de Equipamento , Oxigênio/química , Fatores de Tempo
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