Partial Energy Transfer Research Articles

Unraveling the Phase Behavior of Water Confined in Nanochannels through Positron Annihilation

Water confined in cylindrical pores of silica with a diameter of 2 nm was studied by positron annihilation lifetime spectroscopy. Instead of freezing at 273 K, the glass-like transition through the viscous state to the solid phase was observed in the wide temperature range of 225–188 K. Reducing the vapor pressure over confined water allowed us to obtain the negative pressure pn = −164 MPa in liquid water, and the phase transition temperature range changed to 234–189 K. The temperature dependence of the ortho-positronium (o-Ps) lifetime in water under pn became consistent with the surface tension as in most liquids, as opposed to the anomalous temperature dependence in water under the saturated vapor pressure. This indicates a reduction in the number of hydrogen bonds in confined water under pn. On this basis, to explain the anomalous temperature dependence, we propose a hypothesis of a partial energy transfer to distant water molecules via the OH-stretching modes instead of repelling the molecules surrounding o-Ps. Our results indicate that thermally generated defects in the confined ice are accompanied by permanent defects, which predominate in the ice formed under pn. Both types of defects have the same volume of 70 Å3, which is much greater than in hexagonal ice Ih. We conjecture that the defects are larger due to the influence of the silanol groups on the structure of solid water. These observations imply that the structure of confined ice differs significantly from that of bulk ice and the vapor pressure influences its formation.

Polar Lanthanide Anthracene Complexes Exhibiting Magnetic, Luminescent and Dielectric Properties

AbstractMultifunctional molecular materials combining magnetic, luminescent and dielectric properties are attractive for potential applications in spintronics and molecular devices. Herein we report three isostructural mononuclear lanthanide phosphonates, namely, Ln(NO3)3(2‐deap)3 [Ln=Dy (1Dy), Er (2Er), Yb (3Yb), 2‐deap=diethyl anthrancen‐2‐ylphosphonate] which crystallize in polar space group Pna21. Magnetic studies revealed field‐induced slow magnetization relaxation for 1Dy and 3Yb, but not for 2Er down to 1.8 K. Theoretical calculations were conducted to rationalize the magneto‐structural relationship. The photoluminescent properties are also dependent on the lanthanide ion. For 1Dy, luminescence was observed only in the visible region mainly originating from the ligand. For 2Er, luminescence was observed only in the near‐infrared (NIR) region due to a complete energy transfer from the ligand to the ErIII ion. Regarding to 3Yb, luminescence was observed in both visible and NIR regions suggesting a partial energy transfer from the ligand to YbIII ion. Dielectric and piezoelectric measurements were performed on single crystals of 3Yb, which confirmed the presence of high dielectric anisotropy and weak piezoelectric response.

A Water-Stable Tb-MOF As a Rapid, Accurate, and Highly Sensitive Ratiometric Luminescent Sensor for the Discriminative Sensing of Antibiotics and D2O in H2O.

The design and development of self-calibrating ratiometric luminescent sensors for the fast, accurate, and sensitive discrimination and determination of pollutants in wastewater is highly desirable for public and environmental health. Herein, a 3D porous Tb(III)-based metal-organic framework (MOF), {[Tb(HL)(H2O)2]·x(solv)}n (1), was facilely synthesized using a urea-functionalized tetracarboxylate ligand, 5,5'-(((1,4-phenylenebis(azanediyl))bis(carbonyl))bis(azanediyl))diisophthalic acid (H4L). The activated framework showed a good water stability in both aqueous solutions at a wide pH range of 2-14 and simulated antibiotic wastewaters. Interestingly, this Tb-MOF exhibited dual luminescence owing to the partial energy transfer from the antenna H4L to Tb3+. More importantly, activated 1 (1a) that was dispersed in water showed a fast, accurate, and highly sensitive discrimination ability toward antibiotics with a good recyclability, discriminating three different classes of antibiotics from each other via the quenching or enhancement of the luminescence and tuning the emission intensity ratio between the H4L ligand and the Tb3+ center for the first time. Simultaneously, 1a is a ratiometric luminescent sensor for the rapid, accurate, and quantitative discrimination of D2O from H2O. Furthermore, this complex was successfully used for the effective determination of antibiotics and D2O in real water samples. This work indicates that 1a represents the first ever MOF material for the discriminative sensing of antibiotics and D2O in H2O and promotes the practical application of Ln-MOF-based ratiometric luminescent sensors in monitoring water quality and avoiding any major leak situation.

Partial Energy Transfer Model of Lamb Waves Scattering in Materially Isotropic Waveguides

The scattering phenomena of the fundamental antisymmetric Lamb wave mode with a horizontal notch enabling the partial energy transfer (PET) option is addressed in this paper. The PET functionality for a given waveguide is realized using the material interface. The energy scattering coefficients are identified using two methods, namely, a hybrid approach, which utilizes the finite element method (FEM) and the general orthogonality relation, and the semi-analytical approach, which combines the modal expansion technique with the orthogonal property of Lamb waves. Using the stress and displacement continuity conditions on the present (sub)waveguide interfaces, one can explicitly derive the global scattering matrix, which allows detailed analysis of the scattering process across the considered interfaces. Both methods are then adopted on a simple representation of a surface breaking crack in the form of a vertical notch, of which a certain section enables not only the reflection of the incident energy, but also its nonzero transfer. The presented results show very good conformity between both utilized approaches, thus leading to further development of an alternative technique.

Partial energy transfer from blue TADF sensitizer to orange fluorescent dopant for prolonging device lifetime

White organic light-emitting diodes (WOLEDs) with thermally activated delayed fluorescence-sensitized fluorescence (TSF) have aroused wide attention, considering their potential for attaining ultimate high efficiency and long lifetime with pure organic fluorescent emitters. To develop high-performance TSF-based WOLEDs, an efficient energy transfer system is built by combining a conventional host, a stable blue delayed fluorescence sensitizer, and an orange fluorescent dopant in a single-emissive-layer. Transient photoluminescence measurements decipher the Förster resonance energy transfer process with the high exciton utilization and the suppressed Dexter energy transfer in the single-emissive-layer. The TSF-based WOLEDs achieve a maximum external quantum efficiency of 20.9% and the balanced white emission with color coordinates of (0.31, 0.41) because of the partial energy transfer from blue sensitizer to the fluorescent dopant. Moreover, the TSF-WOLEDs exhibit a half-lifetime of ~2,800 h at an initial brightness of 1,000 cd m−2, which can be further improved to >12,000 h by implementing the stacked structure and light outcoupling enhancement techniques. The prolonged device stability is because the TSF system can effectively prevent exciton leakage and suppress the accumulation-caused exciton-annihilation.

Ternary Polymer Solar Cells with High Open Circuit Voltage containing Fullerene and New Thieno[3',2',6,7][1]Benzothieno[3,2‐b]Thieno[3,2‐g][1]Benzothiophene‐based Non‐fullerene Small Molecule Acceptor

Herein, the synthesis of a new medium bandgap nonfullerene acceptor DBTBT‐IC consisting of di‐benzothieno [3,2‐b][1]‐benzothiophene DBTBT as the central donor unit and IC as terminal acceptor units and its use as the acceptor for the fabrication of single binary and ternary polymer solar cells is reported. DBTBT‐IC exhibits a medium optical bandgap of about 1.65 eV. When paired with the wide bandgap‐conjugated polymer PDTNIT as donor, the polymer solar cells based on the optimized PDTNIT:DBTBT‐IC active layer realized a power conversion efficiency of 12.34% (short‐circuit current = 8.06 mA cm−2, open‐circuit voltage = 1.12 V, and fill factor (FF) = 0.62) which is higher than that for the PDTNIT:PC71BM counterpart, i.e., 9.08 % (short‐circuit current=14.58 mA cm−2, open‐circuit voltage = 0.93 V, and FF = 0.67). When a small amount of PC71BM was introduced into the host PDTNIT:DBTBT‐IC binary layer, the polymer solar cell based on the optimized PDTNIT:PC71BM:DBTBT‐IC (1:0.3:0.9) ternary active layer attained an excellent power conversion efficiency of about 15.92 %, mainly due to the increase in short‐circuit current and FF. The increase in the short‐circuit current may be associated with the broader absorption profile of the ternary active layer as compared with the binary counterparts and more efficient exciton utilization, due the partial energy transfer from PC71BM to DBTBT‐IC.

Фотолюминесценция низкоразмерных композитных структур полиметилметакрилат/(Zn,Cd,Mn,Eu)S

A colloidal technology for the synthesis and doping of low-dimensional structures based on zinc and cadmium sulfides directly in the medium of an acrylic monomer is implemented in the process of obtaining optically transparent compositions of polymethylmethacrylate/(Zn,Cd,Mn,Eu)S. It is shown that the photoluminescence of the compositions is associated with a system of levels of structural defects of semiconductor particles located in its band gap, which are formed during successive doping of ZnS and CdS layers with Mn2+ and Eu3+ ions, and with intraband 5D0 → 7F1,2,4 transitions of 4f-electrons of Eu3+ ions. Photoluminescence excitation it occurs as a result of the transition of electrons from the valence band of a semiconductor to the levels of defects in its structure and partial energy transfer to the excited energy levels of Eu3+ ions.

Emission-tunable probes using terbium(III)-doped self-activated luminescent hydroxyapatite for in vitro bioimaging

Lanthanide ion (Ln3+)-doped nanoscale hydroxyapatites (nHAp) with tunable luminescence have attracted increasing attention due to their potential applications as useful biomedical tools (e.g., imaging and clinical therapy). In this study, we reported that doping Terbium (III) ions (Tb3+) in self-activated luminescent nHAp via a facile hydrothermal reaction, using trisodium citrate (Cit3−), generates unique emission-tunable probes known as Cit/Tb-nHAp. The morphology, crystal phase, and luminescence properties of these Cit/Tb-nHAp probes are studied in detail. Moreover, the results demonstrate that the luminescence of self-activated nHAp originates from the carbon dots trapped within the nHAp crystals, in which partial energy transfer occurs from carbon dots (CDs) to Tb3+. The color tunability is successfully achieved by regulating the addition of Cit3−. Biocompatibility study indicates that when co-cultured with C6 glioma cells in vitro for 3 days, ≤800 ppm Cit/Tb-nHAp is not cytotoxic for C6 glioma cells. We also present in vitro data showing efficient cytoplasmic localization of transferrin conjugated Cit/Tb-nHAp into C6 glioma cells by fluorescence cell imaging. We have successfully engineered Cit/Tb-nHAp, a promising biocompatible agent for future in vitro and in vivo fluorescence bioimaging.

Interaction between Bax and Bcl-XL proteins confirmed by partial acceptor photobleaching-based FRET imaging

Exact interaction mechanism between Bax and Bcl-XL, two key Bcl-2 family proteins, is an interesting and controversial issue. Partial acceptor photobleaching-based quantitative fluorescence resonance energy transfer (FRET) measurement, PbFRET, is a widely used FRET quantification method in living cells. In this report, we implemented pixel-to-pixel PbFRET imaging on a wide-field microscope to map the FRET efficiency ([Formula: see text] images of single living HepG2 cells co-expressing CFP-Bax and YFP-Bcl-XL. The [Formula: see text] value between CFP-Bax and YFP-Bcl-XL was 4.59% in cytosol and 11.31% on mitochondria, conclusively indicating the direct interaction of the two proteins, and the interaction of the two proteins was strong on mitochondria and modest in cytosol.

One-pot synthesis of a white-light emissive bichromophore operated by aggregation-induced dual emission (AIDE) and partial energy transfer.

Merocyanine-triarylamine bichromophores are readily synthesized by sequentially Pd-catalyzed insertion-alkynylation-Michael-Suzuki four-component reactions. White-light emissive systems form upon aggregation in 1 : 99 and 0.1 : 99.9 vol% CH2Cl2-cyclohexane mixtures, ascribed to aggregation-induced dual emission (AIDE) in combination with partial energy transfer between both chromophore units as supported by spectroscopic studies.

Adaptive and Guest Responsive Supramolecular Porous Framework: Solvent Modulated Energy Transfer toward Fingerprint Sensing

A solvent responsive, dynamic, three-dimensional supramolecular porous host has been synthesized and structurally characterized. The structural flexibility is realized by the guest responsive structural transformation and also by the different gas and solvent vapor adsorption studies. Noncovalent encapsulation of fluorescein dye into the framework resulted in dual emission through host-to-guest partial energy transfer which is utilized for solvent sensing. Diffusion of solvents modulates the structural arrangement and energy transfer.

2D-BCNO with Eu3+: partial energy transfer and direct natural white light for LEDs

2D-BCNO transfers some energy to excite Eu3+ ions and together they generate white light.

Diversity-Oriented Synthesis and Optical Properties of Bichromophoric Pyrrole-Fluorophore Conjugates.

The mild reaction conditions of the palladium-copper coupling-isomerization reaction open a highly convergent, chromogenic route to blue emissive pyrroles in the sense of a consecutive four-component reaction. By virtue of this strategy a phenol derivative can be readily accessed, which can be transformed in a level-2 transformation to a library of bichromophoric pyrrol-fluorophore conjugates by facile alkylation with fluorophore halides. The photophysics of the underlying blue emitter derivative and the conjugates is studied by absorption and emission spectroscopy, furnishing intramolecular energy transfer at short distances as well as competing fluorescence quenching. In some cases partial energy transfer results in the occurrence of dual emission, for instance seen as magenta-rose emission arising from blue and red orange luminescence. The experimental photophysical studies are rationalized by DFT and TD-DFT calculations.

Low Inhomogeneous Broadening of Excitonic Resonance in MAPbBr3 Single Crystals.

We present an optical study of MAPbBr3 single crystal grown from solution. The crystal Pm3m symmetry was confirmed by electron backscatter diffraction. Our major attention was focused on optical effects related to the excitonic states in MAPbBr3. Photoluminescence temperature dependence of narrow exciton resonance showed encouragingly low inhomogeneous broadening Γ ≈ 0.5 meV that allows one to distinguish the signals from free excitons and those arising from recombination of excitons localized on defects. Excitonic origin of the resonance was proved by its superlinear pump intensity dependence, in contrast to the linear behavior of the defect-assisted recombination bands. For the first time, the phonon replicas originating from free exciton recombination accompanied by partial energy transfer to the phonons were observed in high-resolution PL spectra and confirmed by independent low-temperature Raman scattering experiments. In turn, low-temperature, low-frequency Raman scattering studies let us resolve the structure of the low-frequency phonon spectrum.

Saturated and Stable White Electroluminescence from Linear Single Polymer Systems Based on Polyfluorene and Mono-Substituted Dibenzofulvene Derivatives

The development of new electroluminescent copolymer based materials for white polymer light emitting diodes (WPLED) with special emphasis on the conceptual novelty of utilizing aggregation-induced emission enhancement (AIEE) active or dual state emitting, monosubstituted dibenzofulvene (M-DBF) derivatives 4-(5-fluoren-9-ylidenemethyl-thiophen-2-yl)-7-(4-methoxy-phenyl)-benzo[1,2,5]thiadiazole (DT) or 4-[5-(4-fluoren-9-ylidenemethyl-phenyl)-thiophen-2-yl]-7-(4-methoxy-phenyl)-benzo[1,2,5]thiadiazole (DP) as orange/red fluorophores into polyfluorene (PF) main chain is demonstrated. The mol % of these M-DBF monomer based special small π-system has been optimized as low as 0.0003, 0.0006, and 0.001% in the poly[2,7-(9,9′-dioctylfluorene)-co-4-(5-fluoren-9-ylidenemethyl-thiophen-2-yl)-7-(4-methoxy-phenyl)-benzo[1,2,5]thiadiazole (WDT) and poly[2,7-(9,9′-dioctylfluorene)-co-4-[5-(4-fluoren-9-ylidenemethyl-phenyl)-thiophen-2-yl]-7-(4-methoxy-phenyl)-benzo[1,2,5] thiadiazole (WDP) copolymers, respectively. We report the utilization of “dual emission” peaks from PFO and M-DBFs in the blue and orange region that enabled the fabrication of bias-independent WPLEDs which is fundamentally very important and highly challenging in the case of linear polymers. These copolymers showed excellent solubility in organic solvents viz. CHCl3, THF, toluene, p-xylene, etc. The synthesized copolymers were characterized by UV–vis and photoluminescence (PL) spectroscopy, and WPLEDs with ITO/PEDOT:PSS/WDP or WDT/TPBi/LiF/Al configurations were fabricated to study their electroluminescence (EL) properties. Partial energy transfer has been achieved by adjusting the PFO and DT or DP concentrations in the single polymer main chain leading to the white emission in a facile manner. The copolymers WDP-1 and WDT-1 gave saturated white emission with CIE coordinates of (0.31, 0.33) and (0.35, 0.34) at 8–14 voltages and exhibiting excellent voltage independent emission. The highest luminous efficiencies of 7.82 and 4.57 cd A–1 were achieved for WDP and WDT polymers with the highest brightness values of 9753 and 7436 cd m–2, respectively.

Temperature Sensitive Emission Color Tuning and White Light Emission in Segmented OPV Polymer: Perylene Bisimide Supramolecular Complex

An oligo(phenylenevinylene) (OPV) based segmented polymer (POPV) and its small molecule model compound (SOPV) were designed with a carboxyl functionality in the side chain. The polymer and small molecule were complexed with pyridine functionalized perylene bisimide (UPBIPy) and the properties of the donor: acceptor (D:A) complexes were compared. Both polymer and small molecule D:A complexes formed lamellar morphologies in the <10 nm length scale, which could be visualized by TEM and AFM imaging. The flexibility of the segmented polymer architecture imparted special properties to the polymer and its complex. The polymer complex (POPVC) exhibited white light emission with CIE color coordinates (0.27, 0.32) due to partial energy transfer from POPV to UPBIPy. The analogous model OPV complex (SOPVC) continued to show characteristic blue OPV emission in the complex also. The higher sensitivity of polymers toward temperature was made use of to tune the emission color in the complex from white (0.27, 0.32) at 30 °C to yellow-green (0.29, 0.31) at 100 °C and back to white (0.27, 0.31) upon cooling to 30 °C. Such a temperature sensitive emission color tuning was not observed in the small molecule complex under identical conditions.

Star-Shaped Single-Polymer Systems with Simultaneous RGB Emission: Design, Synthesis, Saturated White Electroluminescence, and Amplified Spontaneous Emission

A three-armed star-shaped single-polymer system comprising tris(4-(3-hexyl-5-(7-(4-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazol-4-yl)thiophen-2-yl)phenyl)amine (TN) as red emissive cores, benzothiadiazole (BT) as green emissive dopants, and polyfluorene (PF) as blue arms was successfully developed, in which the construction of the star-shaped architectures can depress intermolecular interactions and concentration quenching. The thermal, photophysical, electrochemical, electroluminescent, and amplified spontaneous emission (ASE) properties of the synthesized polymers are systematically investigated. The modulation of the doping concentration of TN and BT can guarantee the partial energy transfer in a star-shaped single-polymer system, further achieving saturated white emission. Consequently, a current efficiency of 2.41 cd A–1 and Commission Internationale d’Eclairage (CIE) coordinates of (0.34, 0.35) were recorded for TN-R3G4 with 0.03 mol % red core and 0.04 mol % green dopants. The saturated white emiss...

Energy transfer and formation of long-lived (3)MLCT states in multimetallic complexes with extended highly conjugated bis-terpyridyl ligands.

Multimetallic complexes with extended and highly conjugated bis-2,2':6',2''-terpyridyl bridging ligands, which present building blocks for coordination polymers, are investigated with respect to their ability to act as light-harvesting antennae. The investigated species combine Ru(II)- with Os(II)- and Fe(II)-terpyridyl chromophores, the latter acting as energy sinks. Due to the extended conjugated system the ligands are able to prolong the lifetime of the (3)MLCT states compared to unsubstituted terpyridyl species by delocalization and energetic stabilization of the (3)MLCT states. This concept is applied for the first time to Fe(II) terpyridyl species and results in an exceptionally long lifetime of 23 ps for the Fe(II) (3)MLCT state. While partial energy (>80%) transfer is observed between the Ru(II) and Fe(II) centers with a time-constant of 15 ps, excitation energy is transferred completely from the Ru(II) to the Os(II) center within the first 200 fs after excitation.

Multiple emissive triarylborane-A2H2 and triarylborane-Zn-A2H2 porphyrin conjugates.

Triarylborane-A2H2 (1) and triarylborane-Zn-A2H2 porphyrins (2) have been synthesized by acid catalyzed condensation of 4-dimesitylboryl-benzaldehyde and dipyrromethane under ambient conditions. Compounds 1 and 2 showed multiple emission bands upon excitation at the triarylborane dominated absorption region (350 nm). Detailed experimental and computational studies show that the multiple emission features of 1 and 2 arise as a result of a partial energy transfer from the donor (triarylborane) to the acceptor (porphyrin) moieties. Compounds 1 and 2 showed very high selectivities towards fluoride ions compared to other competing anions.

White Light from a Light-Emitting Electrochemical Cell: Controlling the Energy-Transfer in a Conjugated Polymer/Triplet-Emitter Blend.

We report on the attainment of broadband white light emission from a host-guest light-emitting electrochemical cell, comprising a blue-emitting conjugated polymer as the majority host and a red-emitting small-molecule triplet emitter as the minority guest. An analysis of the energy structure reveals that host-to-guest energy transfer can be effectuated by both Förster and Dexter processes, and through a careful optimization of the active material composition partial energy transfer and white emission is accomplished at a low guest concentration of 0.5%. By adding a small amount of a yellow-emitting conjugated polymer to the active material, white light emission with a high color rendering index of 79, and an efficiency of 4.3 cd/A at significant luminance (>200 cd/m(2)), is realized.