Donor-acceptor Ratio Research Articles

Temperature- and pH-modulated Förster resonance energy transfer for establishment of white light emission

Heteroatom doping is an efficient approach for increasing fluorescence efficiency of carbon dots (CDs). Co-doping with heteroatoms may add additional active sites to CDs and expand their different capabilities. A simple and low-cost hydrothermal method was used to prepare nitrogen- and also nitrogen- and sulfur-rich CDs-decorated graphene oxide, NCDs-GO and N,SCDs-GO, respectively. The as-prepared hybrid CDs-GO samples are responsive to pH and temperature variations, implying pH and temperature-dependent fluorescence properties. The different properties of the CDs-GO hybrids were investigated using transmission electron microscopy and also energy-dispersive X-ray, Raman, and Fourier transform infrared spectroscopies. The ternary mixture of N,SCDs-GO, poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA), and rhodamine B (RB) was also used to detect pH changes via the Förster resonance energy transfer (FRET) process, where N,SCDs-GO and RB play the role of donor and acceptor, respectively, in the PDMAEMA aqueous solution medium. Fluorescence and ultraviolet–visible spectroscopies were used to assess the feasibility and efficiency of the FRET process. The donor–acceptor ratio was changed to get the broadly adjustable photoluminescence emission from blue to red, and especially white light. The aqueous ternary mixture has a wide range of potential applications in pH sensing, temperature monitoring, and anticounterfeiting. This colloidal system with controllable fluorescence and white light emission was used to design anticounterfeiting inks for security-marking of wood samples.

Solvent-Free Organic Liquids: An Efficient Fluid Matrix for Unexplored Functional Hybrid Materials.

ConspectusThe invention of solvent-free organic liquids (SOLs) was serendipitous. However, the curiosity-driven research in the later stage delivered new soft materials with exciting optical, and optoelectronic properties along with appealing physical characteristics suitable for the futuristic applications. A slight change in the molecular design resulted in a drastic change in the physical state of molecules demonstrating monomer-like features in the bulk. The basic idea of core isolation has been successful in delivering new SOLs with attractive functional properties. The unique fluid matrix associated with SOLs offers a tremendous opportunity for making hybrid materials by simple mixing. The chance to study the fundamentally important electron transfer, energy transfer, charge transfer interactions, triplet-state emissions, and even detailed NMR experiments in the solvent-free neat state is the major attraction of SOLs. Usually, solvents and their polarity control such molecular properties, and in the case of SOLs, it avoids the use of solvents to study such fundamentally important properties. Besides, SOLs protect the triplet emitters and excited state processes involving triplet states from quenchers and make the analysis possible under ambient conditions.Our effort in this direction was focused on tuning the ground and excited state properties by transforming conventional organic molecules to SOLs and further value addition by preparing the hybrid SOLs. We developed a series of hybrid SOLs, exploring room-temperature phosphorescence, thermally activated delayed fluorescence, charge or energy transfer between donor and acceptor SOLs, selective explosive sensing, etc. A slight variation in the chemical structure or optoelectronic properties of the individual components imparted exciting optical features for the hybrid SOLs. It includes nonemissive charge transfer, tunable emission exciplex, room temperature phosphorescence, and thermally activated delayed fluorescence SOLs. The liquid matrix of donor SOLs accommodated varying amounts of acceptor SOLs to tune the ground and excited state features. In all examples of donor-acceptor-based hybrid SOLs, even a low amount of acceptor, such as a donor-acceptor ratio of 1000:1, can cause pronounced optical properties. Hence, the evaluation of the optical properties of SOLs, especially, in the absence of solvents is so special that it avoids the interference of solvent molecules. Still, the major drawback of SOLs remains unsolved until we report polymerizable SOLs. Although a large variety of SOLs have been reported in the literature, the long-lasting problem of surface stickiness of SOLs was resolved by polymerizable SOLs. It enabled the development of flexible, foldable, and stretchable large-area luminescent films suitable for lighting and display devices. In this Account, we summarize our work on SOLs, hybrid SOLs, polymerizable SOLs, and the application of SOLs in selective sensing of explosives. Finally, an outlook on the feasibility of luminescent polymerizable SOLs in futuristic applications is provided.

Im-SCC-FRET: improved single-cell-based calibration of a FRET system.

We recently developed a SCC-FRET (single-cell-based calibration of a FRET system) method to quantify spectral crosstalk correction parameters (β and δ) and system calibration parameters (G and k) of a Förster resonance energy transfer (FRET) system by imaging a single cell expressing a standard FRET plasmid with known FRET efficiency (E) and donor-acceptor concentration ratio (RC) (Liu et al., Opt. Express30, 29063 (2022)10.1364/OE.459861). Here we improved the SCC-FRET method (named as Im-SCC-FRET) to simultaneously obtain β, δ, G, k and the acceptor-to-donor extinction coefficient ratio (ε A ε D), which is a key parameter to calculate the acceptor-centric FRET efficiency (EA), of a FRET system when the range of β and δ values is set as 0-1. In Im-SCC-FRET, the target function is changed from the sum of absolute values to the sum of squares according to the least squares method, and the initial value of β and δ estimated by the integral but not the maximum value spectral overlap between fluorophore and filter. Compared with SCC-FRET, the experimental results demonstrate that Im-SCC-FRET can obtain more accurate and stable results for β, δ, G, and k, and add the ratio ε A ε D, which is necessary for the FRET hybrid assay. Im-SCC-FRET reduces the complexity of experiment preparation and opens up a promising avenue for developing an intelligent FRET correction system.

Photosynthetic Function of Wheat Genotypes With Different Donor-Acceptor Ratio in Water Deficiency

The article presents the results of studies of the intensity of photosynthesis of wheat genotypes at various donor-acceptor ratios. Field experiments were carried out in the optimal irrigation regime and under drought conditions, the object of research was wheat genotypes: Barakatli 95, Vugar, Garagylchyg 2 and Gyrmyzy bugda. An artificial change in the donor-acceptor ratios in the plant, in combination with environmental factors, including the effect of drought, has a certain effect on the intensity of photosynthesis. When exposed to drought, the intensity of photosynthesis naturally decreases in both leaves. The removal of one layer of leaves leads to an increase in the intensity of photosynthesis in the leaves of the other layer, and when half the ear is removed, on the contrary, a decrease in the intensity of photosynthesis is observed both in the 7th and 8th leaves.

How hydrogen bond donor acceptor ratio and water content impact heterogeneity in microstructure and dynamics of N,N-diisooctylacetamide and decanol based hydrophobic deep eutectic solvent

Recently hydrophobic deep eutectic solvents (HDESs) have emerged as a potential green alternative media for the extraction of compounds from aqueous environment, and their increased importance as water immiscible solvent has attracted researchers to gain more insights into this domain. The present study employs atomistic molecular dynamics simulations to elucidate the microscopic structural organization, dynamics, and crucial interactions in N,N-diisooctylacetamide (DOA) plus decanol (DEO) based HDES at different mole ratios of the hydrogen bond donor (HBD) and acceptor (HBA). The analysis of simulated X-ray and neutron scattering structure functions reveals a nanoscale heterogeneous structural organization in the HDES at all compositions. The genesis for this heterogeneity can be derived from the polarity alternation peaks of partial structure functions in the low-q region. Polarity ordering in DOA:DEO (1:2) HDES is observed at longer length-scales in comparison to that in DOA:DEO (1:1) and DOA:DEO (2:1) HDESs. Moreover, the liquid morphologies are portrayed by nano-polar domains ingrained into the apolar environment depicting polar and apolar self-segregation. The analysis of angle-resolved radial distribution functions suggests that the microstructures of these HDESs are dominated by a strong DEO-DEO and DEO-DOA hydrogen bonding interactions. Slower decay of the hydrogen bond autocorrelation function corresponding to DOA-DEO suggests stronger hydrogen bonding in DOA-DEO than DEO-DEO. The translational mobility of both the components decreases as the DOA concentration increases. The DEO molecules exhibit faster diffusion in bulk HDES than the DOA molecules. A small water content in the HDES leads to slightly enhanced segregation of polar and apolar environments in the HDESs. We observe that water molecules interfere with the hydrogen bonding network of DOA and DEO by establishing hydrogen bond with them, thereby reducing the strength of DEO-DEO and DOA-DEO hydrogen bond interactions. The hydration also causes slightly faster hydrogen bond relaxation dynamics, indicating the weakening of hydrogen bond interactions between the constituent species of the HDESs.

Donor-Acceptor Co-Adsorption Ratio Controls the Structure and Electronic Properties of Two-Dimensional Alkali-Organic Networks on Ag(100).

The results are presented of a detailed combined experimental and theoretical investigation of the influence of coadsorbed electron-donating alkali atoms and the prototypical electron acceptor molecule 7,7,8,8-tetracyanoquinodimethane (TCNQ) on the Ag(100) surface. Several coadsorption phases were characterized by scanning tunneling microscopy, low-energy electron diffraction, and soft X-ray photoelectron spectroscopy. Quantitative structural data were obtained using normal-incidence X-ray standing wave (NIXSW) measurements and compared with the results of density functional theory (DFT) calculations using several different methods of dispersion correction. Generally, good agreement between theory and experiment was achieved for the quantitative structures, albeit with the prediction of the alkali atom heights being challenging for some methods. The adsorption structures depend sensitively on the interplay of molecule-metal charge transfer and long-range dispersion forces, which are controlled by the composition ratio between alkali atoms and TCNQ. The large difference in atomic size between K and Cs has negligible effects on stability, whereas increasing the ratio of K/TCNQ from 1:4 to 1:1 leads to a weakening of molecule-metal interaction strength in favor of stronger ionic bonds within the two-dimensional alkali-organic network. A strong dependence of the work function on the alkali donor-TCNQ acceptor coadsorption ratio is predicted.

Enhanced reverse inter-system crossing process of charge-transfer stated induced by carrier balance in exciplex-type OLEDs

The reverse inter-system crossing (RISC, CT<sup>3</sup> → CT<sup>1</sup>) process in charge transfer (CT<sup>1</sup> and CT<sup>3</sup>) states is an effective approach to improving the energy utilization rate of excited states, and precise control and full use of the RISC process have important scientific significance and application prospect for fabricating and realizing the efficient exciplex-type organic light-emitting diodes (OLEDs). The conventional exciplex-type OLEDs based on m-MTDATA: Bphen have received extensive attention among researchers owing to the fact that the energy difference between CT<sup>1</sup> and CT<sup>3</sup> around zero promotes the efficient occurrence of RISC process. But up to now, only transient photoluminescence can infer the existence of RISC process in experiment, which is quite unfavorable for the comprehensive understanding and application of this process to design high-performance OLEDs. Fortunately, in this paper, a series of balanced and unbalanced exciplex-based devices are prepared by changing the donor-acceptor blending ratio in the emitting layer (<i>x</i>% <i>m</i>-MTDATA:<i>y</i>% Bphen; <i>x</i>%, <i>y</i>% is the weight percent) and the carrier density flowing through the device. The RISC process of CT states is directly observed via analyzing fingerprint magneto-conductance (MC) traces of the balanced device at room temperature, and the balanced device has higher electroluminescence (EL) efficiency than the unbalanced device. Specifically, the low-field MC curves of unbalanced device only show an inter-system crossing (ISC) line shape, whereas those from the balanced exciplex device present an RISC line shape at low bias-current and the conversion into an ISC line shape with the further increase of bias current. The line shape transition from RISC to ISC is attributed to the triplet-charge annihilation (TQA) process caused by excessive charge carries under high bias current. Combining the physical microscopic mechanism of device, the above-mentioned MC curves of various exciplex devices can be explained as follows: under the same bias current, extra holes or electrons are generated in the emitter layer of unbalanced devices due to the mismatch of donor-acceptor molecular concentrations. These superfluous holes or electrons will react with the CT<sup>3</sup> state, which aggravates the TQA process in the device and weakens the RISC process in which the CT<sup>3</sup> state participates. That is to say, there are strong TQA process and weak RISC process in unbalanced exciplex device. Contrarily, the strong RISC process and weak TQA process in the balanced exciplex device are beneficial to the occurrence of delayed fluorescence, resulting in its EL efficiency higher than that of the unbalanced device. This work not only deepens the physical understanding of the influence of donor-acceptor blending ratio on the carrier balance in exciplex devices, but also paves the way for designing highly efficient OLED by fully employing the RISC process of balanced device.

A cavitand-based supramolecular artificial light-harvesting system with sequential energy transfer for photocatalysis.

A novel artificial light-harvesting system, featuring sequential energy transfer processes, has been successfully constructed, which demonstrated white light emission through a precise adjustment of the donor-acceptor ratio. To better mimic natural photosynthesis, the system is employed as a nanoreactor for the photocatalysis of a cross-dehydrogenative coupling (CDC) reaction in aqueous solution.

Study of the efficiency of chemiluminescence resonance energy transfer system based on hemin/G-quadruplex DNAzyme catalysis by chemiluminescence imaging

For designing and constructing a highly efficient CRET system, it is extremely important to systematically study the effects of reactants and the catalysts on the efficiency. In this paper, we investigated the effects of reactants and the catalyst hemin/G-quadruplex DNAzyme concentration, donor-acceptor ratio and distance on the CRET efficiency by CL imaging. The CRET system was based on hemin/G-quadruplex DNAzyme catalyzed luminol analogue L012 and hydrogen peroxide CL system, taking luminol analogue L012 as the energy donor and a quenching dye DABCYL labelled on the catalyst hemin/G-quadruplex instead of the donor as the energy acceptor. Our study showed that the concentrations of the CL reactants had no significant effect on the efficiency, while the concentration of the catalyst hemin/G-quadruplex had a great effect on the CRET efficiency. When the ratio of the energy donor to the acceptor was as high as 250, the efficiency was only reduced by 5.1%, which was quite different from that of FRET. In addition, a DNA double-stranded structure was designed at the end of G-quadruplex to control the distance between the donor and the acceptor. When the acceptor DABCYL was separated by different linker lengths (1, 5, 10, 20, and 30 base pairs) from the catalyst and the donor L012 molecules, the corresponding CRET efficiencies were 86.0%, 75.1%, 25.7%, 14.0%, and 5.0%, respectively. CL imaging was successfully used to study the efficiency of CRET with high throughput, low sample consumption, and high sensitivity. Our strategy would be beneficial to design and construct a highly efficient CRET system, enabling the interdisciplinary applications of CRET.

Mechanism leading to semi-insulating property of carbon-doped GaN: Analysis of donor acceptor ratio and method for its determination

Carbon impurities in GaN form both acceptors and donors. Donor-to-acceptor ratios (DARs) determine the semi-insulating behavior of carbon-doped GaN (GaN:C) layers and are still debated. Two models are discussed; both can theoretically achieve semi-insulating behavior: the dominant acceptor model (DAM, DAR<1) and the auto-compensation model (ACM, DAR=1). We perform a capacitance–voltage analysis on metal/GaN:C/nGaN (n-doped GaN) structures, exhibiting Fermi-level pinning in GaN:C, 0.7 eV above the valence band maximum. This observation coupled with further interpretation clearly supports the DAM and contradicts the ACM. Furthermore, we reveal a finite depletion width of a transition region in GaN:C next to nGaN, where carbon acceptors drop below the Fermi level becoming fully ionized. Calculation of the potential drop in this region exhibits DAR values of 0.5–0.67 for GaN:C with total carbon concentrations of 1018 cm−3 and 1019 cm−3. Based on those results, we re-evaluate formerly published density functional theory (DFT)-calculated formation energies of point defects in GaN. Unexpectedly, growth in thermodynamic equilibrium with the bulk carbon phase contradicts our experimental analysis. Therefore, we propose the consideration of extreme carbon-rich growth conditions. As bulk carbon and carbon cluster formation are not reported to date, we consider a metastable GaN:C solid solution with the competing carbon bulk phase being kinetically hindered. DFT and experimental results agree, confirming the role of carbon at nitrogen sites as dominant acceptors. Under N-rich conditions, carbon at gallium sites is the dominant donor, whereas additional nitrogen vacancies are generated under Ga-rich conditions.

Modulation of FRET efficiency by donor-acceptor ratio in co-condensed fluorophore-silica nanoconjugates

Förster resonance energy transfer (FRET) in nanocomposites is an important step in many applications. In order to maximize the amount of energy transferred from donor, D, to an acceptor, A, it is essential to minimize self-quenching of the donor. In the present work, fluorescein (D) and rhodamine B (A) are covalently bound into silica nanoshells (C-dye-SNS) with varying D:A ratio where the amount of A has been held constant. The total number of dye molecules is varied from 24 to 140 per nanoshell keeping the number of A molecules at ~13 ​± ​2 molecules per particle. In these conditions, FRET is found to be governed by the D:A ratio. An energy transfer process associated with maximum efficiency of 77% with time constant of 130 ps has been observed in these nanoconjugates. Fast fluorescence decays for D and corresponding risetime for A are observed in the present systems, unlike in those with high concentration of D and A (~1000 molecules/nanoshell). Thus, the presently used dye concentrations are found to be more appropriate than the higher concentration used earlier.

Highly Selective Vapor and Liquid Phase Transfer Hydrogenation of Diaryl and Polycyclic Ketones with Secondary Alcohols in the Presence of Magnesium Oxide as Catalyst

MgO has been shown to catalyze an almost quantitative hydrogen transfer from 2-octanol as the hydrogen donor to benzophenone to form benzhydrol, a useful intermediate product in the pharmaceutical industry. The hydrogen transfer from a series of alcohols to the carbonyl group of benzophenone, its ten derivatives, four polycyclic ketones, and 2-naphthyl phenyl ketone was carried out in liquid (LP) or vapor phase (VP). The dependence of reactivity on the structure of the hydrogen donor, reaction temperature, donor-acceptor ratio, amount of catalyst, and the type and position of substituents has been established. For both reaction modes, optimal conditions for selective synthesis of the alcohols were determined and side reactions were investigated. The results indicate that the reactivity of the ketone is suppressed by the presence of a methyl substituent in the ortho position to a much greater extent in LP mode. A scale-up was demonstrated in the liquid phase mode.

NIR-II pH Sensor with a FRET Adjustable Transition Point for In Situ Dynamic Tumor Microenvironment Visualization.

Monitoring the pH in tumor lesions provides abundant physiological information. However, currently developed pH sensors only achieve sensitive detection in the settled response region around the pH transition point (pHt ). To realize tumor pH monitoring with high sensitivity within a wider response region, reported here are serial pHt adjustable sensors (pTAS) that simply regulate the component ratio of second near-infrared (NIR-II) emission aza-BODIPY (NAB) donor and pH sensitive rhodamine-based pre-acceptor (NRh) in Förster resonance energy transfer system. Combining the pH response regions of pTAS, a twofold widened pH detection range (6.11-7.22) is obtained compared to the pHt settled sensor (6.38-6.94). With an adjustable pHt , in vivo tumor pH increase and decrease processes could be dynamically visualized through dual-channel ratiometric bioimaging within the NIR-II window, with a coefficient of variation under 1 % compared to the standard pH meter.

Information theoretic FRET calibration on the cell surface

A new method of flow cytometric dual-laser FRET calibration is presented based on an information theoretical description of the FRET signals. This method belongs to the so called two-channel or ratiometric FRET methods, whose crucial and common element is the determination of a calibration factor called α (alpha- or G-factor), to place the detected FRET signal on the absolute scale of efficiency. Generally α is determined by extra cell samples labeled with only donor and only acceptor, where the donor-acceptor ratio is known. Alternatively, when the donor-acceptor ratio is not known, standard donor-acceptor FRET pairs of known FRET efficiency can also be used for determining α. In our approach, there is no need for extra information presented by the known acceptor-to-donor ratio or the standard FRET efficiency. Our approach proceeds solely on the signals of the interested FRET-pair applying only a single FRET sample, not necessitating extra ones. The missing information of extra cell samples is replaced by an information theoretic balance equation written for the actual FRET sample. Our method has been proven to be robust, inasmuch as both donor and acceptor appear in adequate levels in the FRET sample used for finding α.

Electrochemical performance and storage mechanism study of conjugate donor–acceptor organic polymers as anode materials of lithium-ion battery

The low redox potential of conjugated donor–acceptor (D–A) type polymer due to strong electron interaction between donor units and acceptor units is benefit to increase the power density, which is suitable to serve as the anode materials of lithium-ion battery. In this paper, the D–A type polymers containing phenanthraquinone (PQ) as acceptor unit and thiophene as donor unit was used as anode materials of lithium-ion battery. Three polymers with different content of donor unit are synthesized to study the effects of donor unit content on the electrochemical properties. It is found that the low content of donor unit in the polymer is benefit to the specific capacities, but not benefit to the rate capability of the electrode. The polymers with the donor–acceptor ratio of 1:1, 2:1 and 3:1 display discharge specific capacity of 737 mAh•g−1, 552 mAh•g−1 and 499 mAh•g−1 at the current density of 72 mA•g−1, respectively. The rate capability of polymer with higher donor–acceptor ratio is better due to its lower band gap and better conductivity. The three D–A type molecules all have perfect cycle stability and stable molecular structure. For a situation of C=C group in aromatic rings partly stored lithium ions, one simple method is proposed for the first time to confirm the exactly lithium ion storage sites by using the Natural Bond Orbital (NBO) analysis. It is found that the lithium ions are mainly stored in the PQ units (redox sites A, RSA) and the thiophene units adhered to the PQ unit directly (redox sites B, RSB), while the thiophene units not adhere to the PQ units did not storage Li-ion.

Molecular engineering of polymeric carbon nitride based Donor-Acceptor conjugated copolymers for enhanced photocatalytic full water splitting

Research based on the full water splitting via heterogenous semiconducting photocatalyst is a significant characteristic nevertheless challenging for determining the energy and environmental crises. With respect to this, a photocatalytic water splitting by visible light through heterojunction semiconductors has been anticipated as a route to the sustainable energy.For the first time, we integrate a potential conjugated donor–acceptor (DA) co-monomer such as 2, 3-dichloroquinoxaline (DCQ) within the structure of polymeric carbon nitride (PCN) by a facile one-pot co-polymerization process. The DCQ which is acting as an organic motif that simulates a nucleophilic attack on the hosting PCN semiconductor which extends into a long chain of the polymer having enormous surface area and remarkable photocatalytic activity for H2 and O2 evolution as compared to the parental CNU.The supremacy of molecular geometry with DA ratio is effectively studied by absorbent, calculated band gap and migration of electrons on the photocatalytic performance of as-synthesized CNU-DCQx co-polymer. The density functional theory (DFT) calculation deliver supplementary evidence for the positive incorporation of DCQ in to the PCN matrix with reduced band gap upon copolymerization.Further, the hydrogen evolution rate (HER) for pure CNU with 14.2 μmol/h while for CNU-DCQ18.0 it is estimated at 124.9 μmol/h which remarkably fueled almost eight times more than blank sample. Similarly, the oxygen evolution rate (OER) analysis indicates the production 0.2 μmol/h (visible) and 1.5 μmol/h (non-visible) for CNU. However, the OER of copolymerized CNU-DCQ18.0 is found to be 1.9 μmol/h (visible) and 12.8 μmol/h (non-visible) which almost nine times higher than parental CNU.Hence, the output of this work reflects as an important step on the way to tailor-designed and elucidate the promising role of D-π-A system for the rational motifs of productive photocatalysts for forthcoming request.

Luminescent Solar Concentrators Based on Energy Transfer from an Aggregation-Induced Emitter Conjugated Polymer.

Luminescent solar concentrators (LSCs) are solar-harvesting devices fabricated from a transparent waveguide that is doped or coated with lumophores. Despite their potential for architectural integration, the optical efficiency of LSCs is often limited by incomplete harvesting of solar radiation and aggregation-caused quenching (ACQ) of lumophores in the solid state. Here, we demonstrate a multilumophore LSC design that circumvents these challenges through a combination of nonradiative Förster resonance energy transfer (FRET) and aggregation-induced emission (AIE). The LSC incorporates a green-emitting poly(tetraphenylethylene), p-O-TPE, as an energy donor and a red-emitting perylene bisimide molecular dye (PDI-Sil) as the energy acceptor, within an organic–inorganic hybrid diureasil waveguide. Steady-state photoluminescence studies demonstrate the diureasil host induced AIE from the p-O-PTE donor polymer, leading to a high photoluminescence quantum yield (PLQY) of ∼45% and a large Stokes shift of ∼150 nm. Covalent grafting of the PDI-Sil acceptor to the siliceous domains of the diureasil waveguide also inhibits nonradiative losses by preventing molecular aggregation. Due to the excellent spectral overlap, FRET was shown to occur from p-O-TPE to PDI-Sil, which increased with acceptor concentration. As a result, the final LSC (4.5 cm × 4.5 cm × 0.3 cm) with an optimized donor–acceptor ratio (1:1 by wt %) exhibited an internal photon efficiency of 20%, demonstrating a viable design for LSCs utilizing an AIE-based FRET approach to improve the solar-harvesting performance.

Energy‐Transfer Random Laser: Replica Symmetry Breaking in FRET‐Assisted Random Laser Based on Electrospun Polymer Fiber (Ann. Phys. 9/2019)

In article number 1900066, Zhijia Hu and co-workers investigate a FRET-assisted random laser based on an electrospun polymer fiber. They find that the FRET efficiency can be controlled by modulating the donor–acceptor ratio. Meanwhile, the statistical association between the random laser with other complex physical systems is illustrated by experimental evidence of the replica symmetry breaking in a random laser with multiple energy levels.

Replica Symmetry Breaking in FRET‐Assisted Random Laser Based on Electrospun Polymer Fiber

AbstractSpin‐glass theory has been widely introduced to describe the statistical behaviors in complex physical systems. By analogy between disorder photonics and other complex systems, the glassy behavior, especially the replica symmetry breaking (RSB) phenomenon, has been observed in random lasers. However, previous studies only analyzed the statistical properties of the random laser systems with single gain material. Here, the first experimental evidence of the glassy behavior in a random laser with complex energy level structure is reported. This novel random laser is demonstrated based on the electrospun polymer fibers with the assistance of Förster resonance energy transfer (FRET). The electrospinning technology employed in the experiment herein promises high‐volume production of random laser devices with multiple energy levels, enabling the comprehensive investigation of lasing properties in multi‐energy level random laser system. Clear paramagnetic phase and spin‐glass phase are observed in the FRET‐assisted random laser under different pump energies. The RSB phase transition is verified to occur at the laser threshold, which is robust among the random lasers with different donor–acceptor ratio. The finding of RSB in FRET‐assisted random laser provides a new statistical analysis method toward the laser system with complex energy level, for example, quantum cascade laser.

Donor acceptor ratio effect on P3HT:PCBM nanoparticulate organic photovoltaic device performance

The Effect of blending ratio between Poly (3-hexylthiophene) (P3HT) as donor electron and phenyl C61 butyric acid methyl ester (PCBM) on Nanoparticulate Organic Photovoltaic has been investigated. A series of P3HT:PCBM nanoparticle dispersions with blending ratio by mass of P3HT:PCBM 2:1, 1:1, and 1:2 were prepared as an active layer of nanoparticulate organic photovoltaic devices. The highest efficiency of booth pre-annealed and annealed P3HT:PCBM nanoparticulate organic photovoltaic devices is at blending ratio of 1:1. The highest efficiency was driven by the highest current density (Jsc) and the highest fill factor (FF) indicating that optimal balance between charge generation and charge transport occurred at blending ratio of 1:1.