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Long-lived NIR emission in sulfur-doped zeolites due to the presence of [S3]2- clusters
Publication . Viola, Catarina; Laia, César A. T.; Outis, Mani; Ferreira, Luís F. V.; Alves, Luís C.; Teixeira, Miguel; Folgosa, Filipe; Lima, João C.; Ruivo, Andreia; Avó, João; DQ - Departamento de Química; LAQV@REQUIMTE; VICARTE - Vidro e Cerâmica para as Artes; Instituto de Tecnologia Química e Biológica António Xavier (ITQB); Elsevier
The exploration of novel long-lived near-infrared (NIR) luminescent materials has attracted significant attention due to their applications in optical communications, anticounterfeiting, and bioimaging. However, these materials usually present low photoluminescence quantum yields and low photo- and chemical stability. Novel emitters that overcome these limitations are in demand. In this study, NIR emission was achieved using widely available, sustainable, and non-toxic materials through the synthesis of sulfur-doped zeolites, with different S/Cl ratios. With a combination of computational calculations (TD-DFT) and spectroscopic data, this emission was assigned to the radiative decay of excited triplet states of [S3]2- clusters, which resulted in a remarkably high Stokes shift (1.97 eV, 440 nm) and an average decay time of 0.54 ms. These new materials present high stability, external quantum efficiency of up to 17%, and a long-lived NIR emission, placing these compounds in a unique position to be used in applications demanding NIR emitters.
Luminescent tetranuclear gold(I) dibenzo[g,p]chrysene derivatives: Effect of the environment on photophysical properties
Publication . Caparrós, Francisco J.; Outis, Mani; Jung, Yongsik; Choi, Hyeonho; Lima, João Carlos; Rodríguez, Laura; LAQV@REQUIMTE; DQ - Departamento de Química; MDPI - Multidisciplinary Digital Publishing Institute
A new 2,7,10,15-tetraethynyldibenzo[g,p]chrysene ligand (1) and two tetranuclear gold(I) derivatives containing PPh3 (3) and PMe3 (4) phosphines were synthesized and characterized by 1H and 31P NMR, IR spectroscopy, and high-resolution mass spectrometry. The compounds were studied in order to analyze the effect of the introduction of gold(I) on the supramolecular aggregation and photophysical properties. Absorption and emission spectra displayed broad bands due to the establishment of π π interactions as an indication of intermolecular contacts and the formation of aggregates. A decrease of the recorded quantum yield (QY) of the gold(I) derivatives was observed compared to the uncomplexed ligand. The introduction of the complexes into poly methyl methacrylate (PMMA) and Zeonex 480R matrixes was analyzed, and an increase of the measured QY of 4 in Zeonex was observed. No phosphorescent emission was detected.
Luminescent compounds with Delayed Fluorescence in Aggregate State for Imaging Applications
Publication . Gomes, Liliana Jorge; Moro, Artur; Avó, João
Visual stimulation through colour is one of the most powerful tools to get and process
information easily. In the world of chemical compounds, this type of knowledge could
be reached using fluorescence. However, a major disadvantage of this process is its small
lifetime that can limit, for example, the local cell-imaging information using conventional
fluorescent probes.
To overcome this problem, TADF (Thermally Activated Delayed Fluorescence) com pounds are a possible solution since their lifetime range could reach micro- or even
milliseconds. TADF compounds were firstly recognized for their ability to maximize
internal quantum efficiency of OLEDs but now they are also known for their capacity
of bioluminescent probing. The major concerns of using TADF compounds in biologic
systems are their low solubility, low biocompatibility, poor efficiency in polar media and
high susceptibility to oxygen in triplet state. Therefore, we designed a series of com pounds which can exhibit TADF in the aggregate state - Aggregation Induced Delayed
Fluorescence (AIDF), as a possible solution to overcome these limitations. For the aim
of this work, Diphenyl sulfoxide-based and Quinoxaline-based units acceptors and its
relatives were synthetised with success.
Diphenyl sulfoxide derivatives were confirmed unstable towards fluorescence irradia tion. As a consequence of that, TADF was not able to be confirmed. However, diphenyl
sulfoxide derivatives have shown signs of AEE (Aggregation enhanced emission).
Nonetheless, the presence of aggregate states has been observed. A quinoxaline deriva tive was also studied. In this case, the TADF and aggregate states phenomenons have
been experimentally verified. And, instead of AIE-TADF, AEE-TADF was confirmed.
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/QUI-QFI/32007/2017