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1.
J Fluoresc ; 32(4): 1299-1308, 2022 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-35362933

RESUMO

Dropcast films produced from blends solutions of phenazine 1,2,3-triazole molecules in very low concentrations in a 1,3-Bis (N-carbazolyl) benzene (mCP) matrix were investigated at room tem-perature. The mCP acts as an optically inert matrix, having no influence on the emission properties of the guest molecules. Its conductive properties ensure the blend films as completely organic active layers. The fluorescent and phosphorescent emissions of the guest molecules in blue, green, red and also in white are relatively intense, without the need to mix different organic materials. The excitation of the system occurs directly by the incident laser beam on the films. The steady-state spectroscopy for the blue monomer and green dimer singlet fluorescence emissions were investigated. The analysis of their temporal decays was done using a different approach based on the Exponentially Modified Gaussian function. The phosphorescent emissions of the triplet steady-states, in the orange or in the red wavelength regions, were observed to be correlated, respectively, to the formation of guest monomers or to the guest dimers singlet states.

2.
J Org Chem ; 86(1): 264-278, 2021 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-33306394

RESUMO

Rhodium(III) catalysis enabled C-H/N-H alkyne annulation of nonsymmetric imidazole derivatives. This study encompasses the synthesis of imidazoles from a naturally occurring quinoidal compound and their use for the preparation of rigid π-extended imidazole derivatives with outstanding fluorescence. Our study also brings to light the photophysical aspects and the mechanism of the reaction studied via computational calculations. This method provided an efficient and versatile tool for the synthesis of fluorescent compounds with a wide range of chemical and biological applications.

3.
Phys Chem Chem Phys ; 21(39): 21966-21971, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31552960

RESUMO

Dropcast films of very low concentration domains of phenazine 1,2,3-triazole molecules, blended in a Zeonex matrix, were studied by steady-state fluorescence as a function of temperature. These domains, randomly spread in the volume of the films, presented emission characteristics of singlet and triplet states coming from different molecular conformations. Emissions of singlet monomers, dimers or more complex aggregates, as well two distinct triplet phosphorescent bands, were observed to appear concomitantly or in isolated forms. From the analysis of the experimental results, the additional red-shifted phosphorescent band appeared as a consequence of the formation of dimer and/or more complex aggregated states. The emission characteristics of both phosphorescent bands were classified as coming from ensembles of a few interactive molecules. This statement was assumed based on the absence of replica modes of vibrational spin-orbit interactions.

4.
Phys Chem Chem Phys ; 21(7): 3814-3821, 2019 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-30698176

RESUMO

Phenazine derivative molecules were studied using steady state and time resolved fluorescence techniques and demonstrated to lead to strong formation of aggregated species, identified as dimers by time dependent density functional theory calculations. Blended films in a matrix of Zeonex®, produced at different concentrations, showed different contributions of dimer and monomer emissions in a prompt time frame, e.g. less than 50 ns. In contrast, the phosphorescence (e.g. emission from the triplet state) shows no significant effect on dimer formation, although strong dependence of the phosphorescence intensity on concentration is observed, leading to phosphorescence being quenched at higher concentration.

5.
Phys Chem Chem Phys ; 19(5): 3473-3479, 2017 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-27824176

RESUMO

The optical properties of phenazine derivative probe solutions involving intersystem crossing from singlet to triplet states were investigated by time resolved spectroscopy. The room temperature phosphorescence emission presented different time responses when Cd2+ ions were bound to the probe chemical structure. The complex exciplex formation observed to occur in this case was not directly responsible for the change in the phosphorescence lifetime. This was more influenced by the new molecular conformation and modified spin-orbit coupling imposed by the binding of the Cd2+ ions to the phenazine molecules.

6.
J Hazard Mater ; 401: 123713, 2021 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-33113722

RESUMO

Herein, the structural defects of metal-free polymeric carbon nitrides were controlled by making use of different precursors in their syntheses, i.e. melamine (CN-M) and thiourea (CN-T), as well as a 1:1 mixture of them (CN-1M:1 T). By controlling the structural defects, the electronic, morphological and chemical properties were modified. Additionally, the activities of synthesized PCNs were evaluated for amoxicillin photodegradation under visible light irradiation (16 mW cm-2). The results of photocatalytic tests showed that CN-T material has better efficiency (100 % removal within 48 h), which is directly related to the greater number of defects present in its structure with consequent improvement of electron-hole pairs separation efficiency. The CN-T material showed excellent stability with only 13 % decrease in its photocatalytic activity after the third cycle. A mechanism for amoxicillin degradation by CN-T was proposed based on the ESI-MS and the in situ EPR allied with spin trapping method investigations.


Assuntos
Amoxicilina , Grafite , Catálise , Luz , Nitrilas , Fotólise
7.
Beilstein J Nanotechnol ; 9: 963-974, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29600157

RESUMO

The influence of graphene and retinoic acid (RA) - a π-conjugated organic semiconductor - interface on their hybrid system is investigated. The physical properties of the interface are assessed via scanning probe microscopy, optical spectroscopy (photoluminescence and Raman) and ab initio calculations. The graphene/RA interaction induces the formation of a well-organized π-conjugated self-assembled monolayer (SAM) at the interface. Such structural organization leads to the high optical emission efficiency of the RA SAM, even at room temperature. Additionally, photo-assisted electrical force microscopy, photo-assisted scanning Kelvin probe microscopy and Raman spectroscopy indicate a RA-induced graphene doping and photo-charge generation. Finally, the optical excitation of the RA monolayer generates surface potential changes on the hybrid system. In summary, interface-induced organized structures atop 2D materials may have an important impact on both design and operation of π-conjugated nanomaterial-based hybrid systems.

8.
J Phys Condens Matter ; 18(32): 7529-42, 2006 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-21690866

RESUMO

A correlation between thermal, optical and morphological properties of self-sustained films formed from blends of poly(3-hexylthiophene) (P3HT) and thermoplastic polyurethane (TPU), with 1, 10 and 20 wt% of P3HT in TPU, is established. Images of scanning electron microscopy (SEM) show the formation of domains of P3HT into the TPU matrix, characterizing the blend material as heterogeneous. The heat capacity (C(p)) dependence on P3HT contents was investigated in a large temperature interval. In the region of the TPU glass transition, the difference between the experimental and predicted ΔC(p) values is more pronounced for the 1 wt% case, which strongly suggests that in this case there is a higher influence of the P3HT chains on the TPU matrix. The SEM images for the 1 wt% blended film present the formation of the smallest P3HT domains in the TPU matrix. The relatively high reduction of the PL intensity of the pure electronic transition peak in the 1 wt% blended film, in comparison to the other blended films and also to a pure P3HT film, favours the assumption that the smallest P3HT domains are at the origin of a more structural disordered character. This fact is in agreement with the results obtained by Raman spectroscopy and also by photoluminescence resolved by polarization in stretched self-sustained films, showing an ample correlation between morphological, thermal and optical properties of these blended materials. In addition, the thermoplastic properties of the polyurethane configure very good conditions for tensile drawing of P3HT and other conjugated polymer molecules.

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