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1.
ACS Nano ; 2020 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-32543172

RESUMO

In this contribution, we focused on integrating a phenylene-bridged dibenzodiazahexacene dimer (o-DAD), which is singlet fission (SF) active, onto single-walled carbon nanotubes (SWCNTs) as a low-energy sink for energetically low lying excited states that stem from SF. Spectroscopic and microscopic assays assisted in documenting that SWCNT/o-DAD feature high stability in THF as a result of electronic interactions between the individual constituents. For example, statistical Raman analysis underlined n-doping of SWCNTs in the presence of o-DAD. Fluorescence spectroscopy prompted an energy transfer between the individual constituents, a conclusion that was exclusively derived from the quenching of the o-DAD-centered fluorescence. Excitation spectroscopy with a focus on the SWCNT fluorescence confirmed independently this conclusion by showing o-DAD-centered features. Our work was rounded off by time-resolved transient absorption measurements with SWCNT/o-DAD, in which evidence was gathered for the sequential o-DAD-centered SF with an efficiency of 112% followed by a unidirectional energy transfer from o-DAD to SWCNT and a rapid deactivation. The energy transfer efficiency from SF products such as (S1S0)CT and 1(T1T1) exceeded the 100% threshold with values of 115%, which is conventionally found in energy transfer schemes.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32492240

RESUMO

Red-emissive π-expanded diketopyrrolopyrroles (DPPs) with fluorescence reaching λ=750 nm can be easily synthesized by a three-step strategy involving the preparation of diketopyrrolopyrrole followed by N-arylation and subsequent intramolecular palladium-catalyzed direct arylation. Comprehensive spectroscopic assays combined with first-principles calculations corroborated that both N-arylated and fused DPPs reach a locally excited (S1 ) state after excitation, followed by internal conversion to states with solvent and structural relaxation, before eventually undergoing intersystem crossing. Only the structurally relaxed state is fluorescent, with lifetimes in the range of several nanoseconds and tens of picoseconds in nonpolar and polar solvents, respectively. The lifetimes correlate with the fluorescence quantum yields, which range from 6 % to 88 % in nonpolar solvents and from 0.4 % and 3.2 % in polar solvents. A very inefficient (T1 ) population is responsible for fluorescence quantum yields as high as 88 % for the fully fused DPP in polar solvents.

3.
J Phys Chem A ; 2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32567862

RESUMO

Triplet-excited-state energies of perylene-monoimides (PMIs) lie in the range 1.12 eV ± 2 meV when compared to singlet-excited-state energies of about 2.39 eV ± 2 meV; therefore, the corresponding naphthalene-linked PMI-Dimer was investigated as a novel singlet-fission (SF) material. Ultrafast transient absorption measurements demonstrated the (S1S0)-to-1(T1T1) transformation and the involvement of a mediating step in the overall 1(T1T1) formation. The intermediate is a charge-transfer state that links the initial (S1S0) with the final 1(T1T1), and imposes charge-transfer character on both, which are thus denoted (S1S0)CT and 1(T1T1)CT. At room temperature, the decorrelation and stability of 1(T1T1)CT is affected by the geminate triplet-triplet recombination (G-TTR) of the two triplets. Independent confirmation for G-TTR to afford up-converted (S1S0)UC in fsTA and nsTA measurements with PMI-Dimer, came from probing PMI-Monomer (T1)s in triplet-triplet annihilation up-conversion (TTA-UC). The G-TTR channel, active in the PMI-Dimer at room temperature, is suppressed by working at either low temperatures (∼140 K) or in polar solvents (benzonitrile): Both scenarios assist in stabilizing (T1T1)CT. As a consequence, the triplet quantum yields are 4.2% and 14.9% at room temperature and 140 K, respectively, in 2-methyltetrahydrofuran.

4.
Angew Chem Int Ed Engl ; 59(3): 1113-1117, 2020 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-31647593

RESUMO

Singlet fission has emerged as a promising strategy to avoid the loss of extra energy through thermalization in solar cells. A family of dimers consisting of nitrogen-doped pyrene-fused acenes that undergo singlet fission with triplet quantum yields as high as 125 % are presented. They provide new perspectives for nitrogenated polycyclic aromatic hydrocarbons and for the design of new materials for singlet fission.

5.
Nanoscale ; 11(46): 22286-22292, 2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31730142

RESUMO

A porphyrazine featuring complementary absorption to a pentacene dimer was chosen to fill the absorption gap of the latter in the range of 450 to 600 nm to realize panchromatic absorption through the visible region out to ca. 700 nm. Of even greater relevance is the quantitative intramolecular Förster resonance energy transfer (i-FRET) to funnel energy to the pentacene moieties, where efficient intramolecular singlet fission (i-SF) converts the singlet excited state into the corresponding triplet excited states. Remarkably, the triplet quantum yield either via direct excitation or via indirect i-FRET is up to 200% ± 20% in polar solvents.

6.
J Am Chem Soc ; 141(15): 6191-6203, 2019 04 17.
Artigo em Inglês | MEDLINE | ID: mdl-30854854

RESUMO

We have designed and used four different spacers, denoted A-D, to connect two pentacenes and to probe the impact of intramolecular forces on the modulation of pentacene-pentacene interactions and, in turn, on the key steps in singlet fission (SF), that is, the 1(S1S0)-to-1(T1T1) as well as 1(T1T1)-to-5(T1T1) transitions by means of transient absorption and electron paramagnetic resonance measurements. In terms of the 1(S1S0)-to-1(T1T1) transition, a superexchange mechanism, that is, coupling to a higher-lying CT state to generate a virtual intermediate, enables rapid SF in A-D. Sizeable electronic coupling in A and B opens, on one hand, an additional pathway, that is, the population of a real intermediate, and changes, on the other hand, the mechanism to that of hopping. In turn, A and B feature much higher 1(T1T1) quantum yields than C and D, with a maximum value of 162% for A. In terms of the 1(T1T1)-to-5(T1T1) transition, the sizable electronic coupling in A and B is counterproductive, and C and D give rise to higher 5(T1T1)-to-(T1 + T1) quantum yields than A and B, with a maximum value of 85% for D.

7.
Nanoscale ; 8(19): 10113-23, 2016 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-27122097

RESUMO

We show unambiguous and compelling evidence by means of pump-probe experiments, which are complemented by calculations using ab initio multireference perturbation theory, for intramolecular singlet fission (SF) within two synthetically tailored pentacene dimers with cross-conjugation, namely XC1 and XC2. The two pentacene dimers differ in terms of electronic interactions as evidenced by perturbation of the ground state absorption spectra stemming from stronger through-bond contributions in XC1 as confirmed by theory. Multiwavelength analysis, on one hand, and global analysis, on the other hand, confirm that the rapid singlet excited state decay and triplet excited state growth relate to SF. SF rate constants and quantum yields increase with solvent polarity. For example, XC2 reveals triplet quantum yields and rate constants as high as 162 ± 10% and (0.7 ± 0.1) × 10(12) s(-1), respectively, in room temperature solutions.

8.
Vector Borne Zoonotic Dis ; 12(12): 1065-7, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23199275

RESUMO

Neotrombicula autumnalis is the most common species of the family Trombiculidae that parasitizes dogs, cats, and humans in Europe. Besides the skin lesions it may cause, this mite is a possible vector of Anaplasma phagocytophilum and Borrelia burgdorferi sensu lato. Two cases of N. autumnalis infestation in a cat and a dog in the island of Corfu, Greece, and 1 case of infestation in a cat living in Limassol, Cyprus, are presented. To the best or our knowledge, these are the first cases of feline and canine trombiculosis reported in both countries, and their appearance in islands points out to the possibility of introduction through importation of infested dogs and cats. For this reason, parasiticides that are effective for both the treatment and prevention of trombiculosis should be recommended for all dogs and cats that live in areas where the parasite is present as well as for all traveling pets.


Assuntos
Antiparasitários/uso terapêutico , Doenças do Gato/diagnóstico , Doenças do Cão/diagnóstico , Trombiculíase/veterinária , Trombiculidae/classificação , Animais , Doenças do Gato/parasitologia , Gatos , Chipre , Doenças do Cão/parasitologia , Cães , Feminino , Grécia , Humanos , Ivermectina/análogos & derivados , Ivermectina/uso terapêutico , Larva , Masculino , Pirazóis/uso terapêutico , Resultado do Tratamento , Trombiculíase/diagnóstico , Trombiculíase/parasitologia , Trombiculidae/efeitos dos fármacos
9.
Arch Esp Urol ; 55(5): 539-41, 2002 Jun.
Artigo em Espanhol | MEDLINE | ID: mdl-12174421

RESUMO

OBJECTIVE: To present a case of a 16-year-old male patient with primary enuresis refractory to conservative treatment. METHODS/RESULTS: Radiologic and urodynamic tests revealed posterior urethral valves that were treated by transurethral fulguration. The patient was cured of both enuresis and infravesical obstruction and remains disease-free 3 years after the operation with no impact on his sexual function. CONCLUSIONS: Posterior urethral valves are very rarely diagnosed in adolescents and adults. Very few cases have been published in the literature. To our knowledge, the case described herein is the first case presenting with persistent primary enuresis.


Assuntos
Eletrocoagulação , Enurese/etiologia , Uretra/anormalidades , Adolescente , Anormalidades Congênitas/diagnóstico , Anormalidades Congênitas/cirurgia , Humanos , Masculino , Radiografia , Uretra/diagnóstico por imagem , Urodinâmica
10.
Arch. esp. urol. (Ed. impr.) ; 55(5): 539-541, jun. 2002.
Artigo em Espanhol | IBECS | ID: ibc-13250

RESUMO

Objetivo: Presentar un caso clínico de un varón de 16 años de edad cuyo único síntoma era la enuresis nocturna primaria, resistente al tratamiento farmacológico. Método/resultados: Tras la exploración radiológica y el estudio urodinámico se llegó a la conclusión de la existencia de válvulas congénitas de uretra posterior. El tratamiento consistió en resecar las válvulas por vía transuretral con recuperación tanto de la enuresis, como de la obstrucción infravesical. Conclusión: El diagnóstico de válvulas de uretra posterior es excepcional en jóvenes así como en adultos. En la bibliografía internacional se han publicado muy pocos casos, siendo éste el primero que se presenta con enuresis nocturna como síntoma único (AU)


Assuntos
Adolescente , Masculino , Humanos , Eletrocoagulação , Uretra , Urodinâmica , Anormalidades Congênitas , Enurese
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