Nanostructured Organosilicon Luminophores Research Articles

Novel Approach to the Synthesis of Bithiophenesilane Dendrimers with Efficient Intramolecular Energy Transfer

A synthetic scheme allowing the preparation of nanostructured organosilicon luminophores of branched or dendritic structure with up to 18 bithiophenesilane donor fragments and one central acceptor fragment has been elaborated. This universal scheme has been successfully upscaled to 20 g of the product, and its efficiency has been verified by the synthesis of two earlier unknown bithiophenesilane dendrimers with dense molecular shell and the central acceptor fragment, 1,4-bis(5-phenylthienyl-2-yl)benzene. The synthesis of more branched dendrimers under the Suzuki reaction conditions has led to the formation of the side products with the rupture of the Si–C(thiophene) bond, not typical of the synthesis of analogous compounds with lower branching degree under the same conditions.

Study of the fast calorimeter prototype for modern e+e− factories

Modern e+ e− factories with high luminosity require fast response of the detector subsystems to suppress severe beam background. The prototype of the electromagnetic calorimeter based on the counter with a pure CsI crystal, novel wavelength shifter with nanostructured organosilicon luminophores and avalanche photodiodes Hamamatsu S8664-55 is discussed. Results of detection of cosmic particle signals by such a prototype are reported.

Ultrafast intramolecular energy transfer in a nanostructured organosilicon luminophore based on p-terphenyl and 1,4-bis(5-phenyloxazol-2-yl)benzene

Förster theory allows quantitative description of the ultrafast intramolecular energy transfer observed experimentally within nanostructured organosilicon luminophores (NOLs).

Synthesis of Nanostructured Organosilicon Luminophores Based on Phenyloxazoles

A series of nanostructured organosilicon luminophores (NOLs) composed of a central 1,4-bis(5-phenyl-1,3-oxazol-2-yl)benzene (POPOP) acceptor chromophore and various peripheral p-terphenyl and 2,5-diphenyl-1,3-oxazole donor fragments have been synthesized for the first time using van Leusen reaction and direct palladium-catalyzed C-arylation of oxazole ring. Due to different functionalities of the silicon branching centers, NOLs with different donor-acceptor ratios have been obtained. The synthesized structures are expected to possess good optical characteristics for use in photonics and optoelectronics.

Study of the fast calorimeter prototype for the Super Charm-Tau Factory

Modern e+e− factories with high luminosity require fast response time of the detector subsystems to collect the data efficiently and suppress severe beam background. The prototype of the electromagnetic calorimeter based on the counter made of pure CsI crystal, novel wavelength shifter with nanostructured organosilicon luminophores and avalanche photodiodes Hamamatsu S8664-55 is discussed. Results of the measurement of the basic characteristics of the counter are presented.

Novel highly efficient blue-emitting branched oligoarylsilanes

In this work synthesis and study of novel nanostructured organosilicon luminophores (NOLs) based on p-terphenyl and POPOP (1,4-bis(5-phenyloxazol-2-yl) benzene) moieties with unique optical properties is reported. NOLs are branched molecules composed from a donor-acceptor-donor framework with different optical bandgap luminescence moieties connected via silicon atoms. As a result effective intramolecular Förster resonance energy transfer can be observed. The main advantages of such materials in comparison with conventional organic luminophores are high molar absorption coefficient, excellent photoluminescence quantum yield, fast luminescence decay time, good processability and low toxicity. Using NOLs in plastic scintillators, widely utilized for radiation detection and in elementary particles discoveries, led to significant improving their efficiency, which combines both high light output and fast decay time. In the best samples the scintillation light yield was 20% higher in comparison with the standard commercially available plastic scintillator UPS-89.

Development of a New Class of Scintillating Fibres with Very Short Decay Time and High Light Yield

We present first studies of a new class of scintillating fibres which are characterised by very short decay times and high light yield. The fibres are based on a novel type of luminophores admixed to a polystyrene core matrix. These so-called Nanostructured Organosilicon Luminophores (NOL) have high photoluminescense quantum yield and decay times just above 1 ns. A blue and a green emitting prototype fibre with 250 μm diameter were produced and characterised in terms of attenuation length, ionisation light yield, decay time and tolerance to x-ray irradiation. The well-established Kuraray SCSF-78 and SCSF-3HF fibres were taken as references. Even though the two prototype fibres mark just an intermediate step in an ongoing development, their performance is already on a competitive level. In particular, their decay time constants are about a factor of two shorter than the fastest known fibres, which makes them promising candidates for time critical applications.

Influence of chemical structure of branched and dendritic organosilicon luminophores on their optical and thermal properties

AbstractSynthesis and investigation of optical and thermal properties of a homologous series of highly luminescent nanostructured organosilicon luminophores (NOLs) containing different donor to acceptor ratio (D:A) are reported. Each of the NOL consists of a 1,4-bis(5-phenylthienyl-2-yl)benzene (PTPTP) acceptor unit and four, six or twelve 2,2′-bithienyl donor fragments connected to each other through two or six silicon atoms. These complex molecules show a “molecular antenna” effect with high efficiency of intramolecular energy transfer about 97-98% combined with excellent photoluminescence (PL) quantum yield of 84-91% and fast PL decay time of 0.90-0.95 ns. A significant increase of the molar extinction coefficient from 94 000 to 257 000 M

Nanostructured organosilicon luminophores in highly efficient luminescent down-shifting layers for thin film photovoltaics

We use a new type of solution processed luminescent molecules – nanostructured organosilicon luminophores (NOLs) – in printed luminescent down-shifting layers for photovoltaic light harvesting. We show that NOLs exhibit a high luminescent efficiency of 82–90% when added into two chemically different polymer matrices that are commonly used for photovoltaic encapsulation: polyvinyl butyral and ethylene-vinyl acetate. The coated layers are optimized to maximize both UV absorbance and visible light emission and transmittance. Attaching the luminescent layers onto a CIGS solar cell significantly improves the external quantum efficiency in the UV region: from 1% to 55%at 360nm. As a result, the short circuit current density and power conversion efficiency increase by up to 3.2–4.3%. After experimental verification of our optical simulation model, we employ it to determine the ideal molecular structure of NOLs for luminescent down-shifting applied to CIGS.

A novel highly efficient nanostructured organosilicon luminophore with unusually fast photoluminescence

For the first time successful experimental and theoretical treatments of nanostructured organosilicon luminophores (NOLs) with unique optical properties are considered.

Study of a pure CsI crystal readout by APD for Belle II end cap ECL upgrade

A scintillation counter consisting of a pure CsI crystal and avalanche photodiodes (Hamamatsu APD S8664-55 and S8664-1010) has been studied for the upgrade of the end cap electromagnetic calorimeter of Belle II detector. An essential increase of the light output was achieved with wavelength shifters based on nanostructured organosilicon luminophores.

Nanostructured Organosilicon Luminophores for Effective Light Conversion in Organic Light Emitting Diodes

AbstractFull characterization of nanostructured organosilicon luminophores NOL4 and NOL5 based on the donor 2,2’-bithiophene and acceptor 1,4-bis(2,2′- bithiophene-5-yl)benzene units in dilute solutions and thin films by UV-Vis spectroscopy, DSC, TGA and X-ray techniques was reported. It was found that usage of these molecules as dopants (10–20 wt%) to the electroactive polyfluorene host in organic light-emitting devices (OLEDs) leads to the efficient spectral long wavelength shifting of the electroluminescence and an increase of the OLED performance as compared to the devices based on pristine polyfluorene, NOL4 and NOL5.

Novel Cross-Linked Luminescent Silicone Composites Based on Reactive Nanostructured Organosilicon Luminophores

New functional silyl hydride and vinyl containing methylphenylsiloxane oligomers were synthesized by a polycondensation reaction in the active medium being the solvent, the catalyst and the reactant simultaneously. Hydrosilylation of them in the presence of 0.1 - 3 wt. % of novel reactive nanostructured organosilicon luminophores (NOLs) containing different central luminescent and 2,2’-bithienyl peripheral light harvesting fragments with terminal undecylenic groups led to crosslinked silicone composites with valuable luminescence in different regions of the visible spectrum (blue, yellow or red). Investigation of their optical properties revealed that their absorption and luminescence spectra correspond to those of the diluted solutions of the reactive NOLs used. These findings indicate the absence of any aggregation of NOLs in the crosslinked silicon composites confirming their excellent optical quality. High thermal stability of the reactive NOLs (up to 370 ∘C in argon) and the silicones themselves indicate their great potential for creation of highly efficient thermo and radiation resistant plastic scintillators.

Nanostructured organosilicon luminophores and their application in highly efficient plastic scintillators.

Organic luminophores are widely used in various optoelectronic devices, which serve for photonics, nuclear and particle physics, quantum electronics, medical diagnostics and many other fields of science and technology. Improving their spectral-luminescent characteristics for particular technical requirements of the devices is a challenging task. Here we show a new concept to universal solution of this problem by creation of nanostructured organosilicon luminophores (NOLs), which are a particular type of dendritic molecular antennas. They combine the best properties of organic luminophores and inorganic quantum dots: high absorption cross-section, excellent photoluminescence quantum yield, fast luminescence decay time and good processability. A NOL consists of two types of covalently bonded via silicon atoms organic luminophores with efficient Förster energy transfer between them. Using NOLs in plastic scintillators, widely utilized for radiation detection and in elementary particles discoveries, led to a breakthrough in their efficiency, which combines both high light output and fast decay time. Moreover, for the first time plastic scintillators, which emit light in the desired wavelength region ranging from 370 to 700 nm, have been created. We anticipate further applications of NOLs as working elements of pulsed dye lasers in photonics, optoelectronics and as fluorescent labels in biology and medical diagnostics.