Search results for "luminescence."
showing 10 items of 1568 documents
Triazolopyridopyrimidines: an emerging family of effective DNA photocleavers. DNA binding. Antileishmanial activity.
2015
Triazolopyridopyrimidines 3-phenyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine (1a), 6,8-di(pyridin-2-yl)-[1,2,3]triazolo[1',5':1,6]pyrido[2,3-d]pyrimidine (1b) and 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine (1c) were prepared and their electrochemical and luminescence properties were studied in depth. The DNA binding ability of this series of compounds has been investigated by means of UV-vis absorption and fluorescence titrations, steady-state emission quenching with ferrocyanide as well as viscosity measurements. Results have shown that triazolopyridopyrimidine 1a interacts strongly at DNA grooves. This compound also displays pref…
Triplet–Triplet Annihilation Upconversion in a MOF with Acceptor‐Filled Channels
2019
Abstract Photon upconversion has enjoyed increased interest in the last years due to its high potential for solar‐energy harvesting and bioimaging. A challenge for triplet–triplet annihilation upconversion (TTA‐UC) processes is to realize these features in solid materials without undesired phase segregation and detrimental dye aggregation. To achieve this, we combine a palladium porphyrin sensitizer and a 9,10‐diphenylanthracene annihilator within a crystalline mesoporous metal–organic framework using an inverted design. In this modular TTA system, the framework walls constitute the fixed sensitizer, while caprylic acid coats the channels providing a solventlike environment for the mobile a…
A crystalline and free-standing silver thiocarboxylate thin-film showing high green to yellow luminescence
2016
The simple direct synthesis of Cu(ii) and Ag(i) salts and thiobenzoic acid under ambient conditions allows the preparation of two bidimensional coordination polymers [M(TB)] (TB = thiobenzoate; M = Cu (1) or Ag (2)). Their electrical and luminescent properties show that these are multifunctional materials. Interestingly 1 and 2 undergo a reversible solubilization process. This unusual feature and their simple preparation allow us to prepare a crystalline and free-standing thin-film of 2, using an interfacial procedure, which shows a remarkable thermochromic luminescence.
Luminous lip-prints as criminal evidence.
2005
Luminescence is specially a useful property for the search of invisible evidences at the scene of a crime. In the latent fingerprints particular case, there are at one's disposal fluorescent reagents for their localization. The study of latent lip prints (that is lip prints from protective lipstick, or permanent or long-lasting lipstick that do not leave any visible marks) is more recent than fingerprints study. Because of the different composition of both types of prints, different reagents have been tried out on their developing. Although, lysochromes are particularly useful reagents to obtain latent lip prints, it may occur on coloured or multicoloured surfaces, the developing is not per…
Gallium Concentration Optimisation of Gallium Doped Zinc Oxide for Improvement of Optical Properties
2021
The research has been supported by project ERA.NET RUS_ST2017-05 (Latvia) and No. 18-52-76002 (Russia). The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union’s Hori-zon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming-Phase2 under grant agreement No. 739508, project CAMART².
In situobservation of the generation and annealing kinetics of E ′ centres induced in amorphous SiO2by 4.7 eV laser irradiation
2011
The kinetics of E' centers induced in silica by 4.7eV laser irradiation was investigated observing in situ their optical absorption band at 5.8 eV. After exposure the defects decay due to reaction with diffusing molecular hydrogen of radiolytic origin. Hydrogen-related annealing is active also during exposure and competes with the photo-induced generation of the centers until a saturation is reached. The concentrations of E' and H2 at saturation are proportional, so indicating that the UV-induced generation processes of the two species are correlated. These results are consistent with a model in which E' and hydrogen are generated from a common precursor Si-H.
Present and Perspectives of Photoactive Porous Composites Based on Semiconductor Nanocrystals and Metal-Organic Frameworks
2021
This review focuses on the recent developments in synthesis, properties, and applications of a relatively new family of photoactive porous composites, integrated by metal halide perovskite (MHP) nanocrystals and metal-organic frameworks (MOFs). The synergy between the two systems has led to materials (MHP@MOF composites) with new functionalities along with improved properties and phase stability, thus broadening their applications in multiple areas of research such as sensing, light-harvesting solar cells, light-emitting device technology, encryption, and photocatalysis. The state of the art, recent progress, and most promising routes for future research on these photoactive porous composit…
Acylated triterpene saponins from Silene jenisseensis
1995
Abstract From the roots of Silene jenisseensis a new trans-p-methoxycinnamoyl triterpene saponin has been isolated along with its cis-p-methoxycinnamoyl isomer as an inseparable mixture. Their structures were established by chemical means and spectroscopic methods including 1D- and 2D-homonuclear and heteronuclear correlation NMR spectroscopy as 3-O-[β- d -galactopyranosyl -(1 → 2)-β- d -glucuronopyranosyl ]-28-O-[β- d -glucopyranosyl -(1 → 2)-α- l - rhamnopyranosyl -(1 → 2)-β- d -4-O-trans-p- methoxycinnamoyl-fucopyranosyl ] quillaic acid and its cis-isomer, respectively. They did not show any activity in the in vitro chemoluminescence granulocytes assay, but exhibited only a weak inhibito…
Colour centres in LiBaF3
1997
Abstract The X-ray-induced optical absorption (OA) and the spectra of magnetic circular dichroism (MCD) followed by optically detected EPR (ODEPR) have been investigated in undoped LiBaF3 crystals. According to ODEPR, the absorption bands in the spectral region 470–770 nm correspond to the F-type centres, whereas the absorption band at 420 nm is assigned to the hole centres. The redistribution of electrons to the thermal more stable F-type centres indicates that all types of colour centres are annealed in the course of the thermal release of electrons from F-type centres, accompanied by a thermostimulated luminescence.
Dysprosium-Based Ionic Liquid Crystals: Thermal, Structural, Photo- and Magnetophysical Properties
2009
[C12mim]3[DyBr6] (C12mim = 1-dodecyl-3-methylimidazolium) represents a new material with interesting luminescent behavior as well as mesomorphic and magnetic properties. The compound was found to show thermotropic liquid crystalline behavior and forms smectic mesophases which were investigated by hot-stage polarizing optical microscopy and differential scanning calorimetry. The emission color of [C12mim]3[DyBr6] can be tuned from white to orange-yellow by the choice of the excitation wavelength. Sample excitation with λex = 366 nm leads to the blue-whitish luminescence from the imidazolium cation itself. With λex = 254 nm the common Dy(III) emission is observed which mainly arises from the …