Achieving narrowband emissions with tunable colors for multiple resonance-thermally activated delayed fluorescence materials: effect of boron/nitrogen number and position.

The boron/nitrogen (B/N)-based multiple resonance-thermally activated delayed fluorescence (MR-TADF) materials with tunable colors have attracted widespread attention owing to their great potential in next-generation display, white lighting, and imaging applications. Numerous MR-TADF emitters with different B/N number and position have been reported to realize full-color narrowband emissions. To gain a better understanding of the effect of B/N number and position on the photo-electronic properties, geometric and electronic properties, Huang-Rhys factors and reorganization energies, charger transfer and absorption/emission properties were analyzed in detail to determine the structure-property relationship for the investigated molecules. The calculated results show that the molecules with para-atoms having the same electronic characteristics (para-B-π-B/para-N-π-N) exhibited smaller structural relaxations upon excitation, and the molecules with increased B/N atoms showed more obvious short-range charge transfer (SRCT) properties. Besides, the para-B-π-N and para-B-π-B/para-N-π-N substructures could reduce and enhance the donor and acceptor strengths, respectively, leading to tunable HOMO-LUMO gaps and emission colors. Such theoretical insights well rationalize the experimental results, revealing that the small reorganization energy and dominant SRCT property should be two key factors in realizing narrowband emissions of MR-TADF materials. These findings and understandings could give an in-depth insight into the structure-property relationship, providing molecular design strategies for the exploration of narrowband MR-TADF materials with tunable emission colors.

Surfactant-enhanced anoxic degradation of polycyclic aromatic hydrocarbons (PAHs) in aged subsurface soil at high temperature (60 °C).

Thermally enhanced anoxic biodegradation is emerging as a promising method for removing PAHs from subsurface soil. However, some PAHs still remain in soil following remediation with thermally enhanced anoxic degradation due to low bioavailability of these residual PAHs. The effects of five surfactants (Tween 80, TX 100, Brij 30, SDS, and SDBS) on the desorption of PAHs, anoxic degradation of PAHs, and native bacteria in soil at high temperature (60 °C) were evaluated in this study. The desorption of PAHs in soil increased as surfactant concentration increased. Low doses of surfactants (0.08%, w/w) enhanced the growth of potential PAHs degrading bacteria and promoted the anoxic degradation of PAHs, whereas high doses of surfactants (0.3%-0.8%, w/w) displayed the opposite effect, and the degree of inhibition increased with increasing surfactant concentration. The results also indicated that the inhibitory effect of anionic surfactants (SDS and SDBS) on microbial growth and PAHs degradation is stronger than that of nonionic surfactants (Tween 80, TX 100 and Brij 30) at the same concentration. These results suggest a feasible way of enhancing the anoxic degradation of PAHs in soil where heat cannot be effectively utilized when in situ thermal desorption (ISTD) technology is used.

Constructing high-performance TADF polymers from non-TADF monomers: a computational investigation.

Thermally activated delayed fluorescence (TADF) polymers excelling in simple, low-cost and large-area solution process ability have attracted tremendous attention recently, but it remains a great challenge for the design of such materials due to the lack of reliable molecular construction guidelines. Here we perform a systematic computational investigation on the construction of TADF polymers from non-TADF monomers to elucidate the effects of polymerization sites, substituent positions and substituent types. The results indicate that the polymerization of 3,6-carbazole-based monomers with different substituents is efficient to build TADF polymers due to their facile π-conjugation extendability. Especially, polymers with para-phenyl-substituted monomers are promising in light of their separated frontier molecular orbitals for small ΔEST with favorable energy levels, bipolar charge transport properties and relatively strong absorption/emission intensity, which should be highly attractive for experimental investigations. These findings and insights are important in revealing the structure-property relation of TADF polymers made from non-TADF monomers with important clues for understanding the construction mechanism and molecular design principles of TADF polymers.

Effect of menthone and related compounds on skin permeation of drugs with different lipophilicity and molecular organization of stratum corneum lipids.

The objective of this article was to investigate the enhancing effect of menthone, menthol and pulegone on the transdermal absorption of drugs with different lipophilicity and probe their mechanisms of action at molecular level. Five model drugs, namely osthole, tetramethylpyrazine, ferulic acid, puerarin and geniposide, which were selected based on their lipophilicity denoted by logKo/w, were tested using in vitro permeation studies in which Franz diffusion cells and rat skin were employed. Infrared spectroscopy and molecular dynamic simulation were used to investigate the effect of these enhancers on the stratum corneum (SC) lipids, respectively. Three compounds could effectively promote the transdermal absorption of drugs with different lipophilicity, and the overall promoting capacities were in the following increasing order: pulegone < menthol < menthone. The penetration enhancement ratio was roughly in parabolic curve relationships with the drug lipophilicity after treatment with menthol or menthone, while the penetration enhancement effect of pulegone hardly changed with the alteration of the drug lipophilicity. The molecular mechanism studies suggested that menthone and menthol enhanced the skin permeability by disordering the ordered organization of SC lipids and extracted part of SC lipids, while pulegone appeared to promote drug transport across the skin only by extracting part of SC lipids.

[Matrix formulation of chaizhi cataplasma optimized by D-optimal mixture design combined with multiple mechanical indicators and its in vitro evaluation].

To optimize the matrix formulation of Chaizhi cataplasma (CC) and investigate its release and transdermal absorption properties in vitro. The optimized matrix formulation of cataplasma containing liquid herbal extract is determined by using D-optimal mixture design, with initial bonding strength, endurance bonding strength and gel strength as the evaluating indicators. Modified Franz diffusion cells were used to study the in vitro release and transdermal absorption of geniposide in CC. The optimized matrix formulation of CC contained NP700, aluminum glycinate, tartaric acid, glycerin, PVPK90 and water (9∶0.7∶0.8∶30∶5∶30.5). Cumulative release rate of geniposide in CC was (77.02±3.73)% in 24 h. The percutaneous penetration rate of geniposide was 7.25 µg•cm⁻²â€¢h⁻¹ and the 24 h permeated amount was (156.22±4.90) µg•cm⁻². The optimized CC prepared by the D-optimal mixture design showed a good adhesion and formability. The in vitro release of the geniposide in CC was in accordance with the first order equation, while its in vitro transdermal absorption was close to the zero order equation.

[Preparation and optimization of zhitong micro-emulsion formula].

To prepare Zhitong micro-emulsion in this study, with the empirical formula of Zhitong preparation as the model medicine, the essential oil in the formula as the oil phase, and the water decoction as the water phase. The types of surfactant and co-surfactant were investigated. The changes in micro-emulsion conductivity and construction, the water percentage in the micro-emulsion system, the changing curve of conductivity and the fine pseudo-ternary phase diagram of micro-emulsion were drawn to determine the surfactant-co-surfactant mass ratio (K(m)). Subsequently, the D-mixture design was used to optimize Zhitong Micro-emulsion formula, with particle size and surface tension of micro-emulsion as the indexes. Finally, efforts were made to determine part of physical parameters of Zhitong micro-emulsion and preliminarily detect its stability. The results showed that the micro-emulsion was optimal with the EL-35-tween 20 ratio of 4:1 in surfactant, whereas the absolute ethyl alcohol was recommended as the co-surfactant. The ratio between surfactant and co-surfactant (K(m)) was 1.5. The finalized micro-emulsion formula contains 12% surfactant, 8% co-surfactant, 70% 1 g x mL(-1) water decoction and 8% oil. The results of the preliminary stability experiment showed a better stability of Zhitong micro-emulsion.

Manipulating Multiple Resonance-Charge Transfer Hybrid Proportion for Developing Red Narrowband Thermally Activated Delayed Fluorescence Materials.

Multiple resonance thermally activated delayed fluorescence (MR-TADF) materials have attracted increasing attention because of their 100% exciton utilization capability and narrowband emissions. However, it remains a formidable challenge to develop such red materials. Herein, we perform a theoretical investigation on the design of red narrowband TADF materials via manipulating the MR-charge transfer (CT) hybrid proportion by regulating the types of MR cores and peripheral electron-donating units. The results indicate that the MR-CT proportion in the excited states is closely relevant to the frontier molecular orbital (FMO)/hole-electron overlap, which is mainly determined by the dihedral angle between the MR cores and the peripheral units for the MR donor-acceptor molecules. The electron-donating ability of the peripheral substituents has little influence on the FMO/hole-electron overlap. Finally, c1-a and c2-a with red narrowband emissions were revealed. These findings with rich physical insights into the structure-property relationship should provide important clues for designing red narrowband optoelectronic materials.

Multicolor hyperafterglow from isolated fluorescence chromophores.

High-efficiency narrowband emission is always in the central role of organic optoelectronic display applications. However, the development of organic afterglow materials with sufficient color purity and high quantum efficiency for hyperafterglow is still great challenging due to the large structural relaxation and severe non-radiative decay of triplet excitons. Here we demonstrate a simple yet efficient strategy to achieve hyperafterglow emission through sensitizing and stabilizing isolated fluorescence chromophores by integrating multi-resonance fluorescence chromophores into afterglow host in a single-component copolymer. Bright multicolor hyperafterglow with maximum photoluminescent efficiencies of 88.9%, minimum full-width at half-maximums (FWHMs) of 38 nm and ultralong lifetimes of 1.64 s under ambient conditions are achieved. With this facilely designed polymer, a large-area hyperafterglow display panel was fabricated. By virtue of narrow emission band and high luminescent efficiency, the hyperafterglow presents a significant technological advance in developing highly efficient organic afterglow materials and extends the domain to new applications.

Microwave collimation based on zero index metamaterials with Dirac point.

The microwave zero index metamaterials (ZIMs) can be realized by loading lumped elements into two-dimensional transmission lines (TLs) with Dirac cones whose linear dispersion can appear around the center of the Brillouin zone. Based on Snell's law, the refracted angle of waves nearly equals zero when a point source radiates from the ZIM TL into the double positive (DPS) one in the ZIM-DPS TL structure. Experimental results demonstrate that at Dirac point the curved wavefronts in the ZIM region are transformed into planar ones in DPS region.

Energy transport in a metamaterial subwavelength open-cavity resonator.

We present a theoretical and experimental investigation into the energy transport in a conjugate matched bilayer consisting of ε-negative (ENG) and µ-negative (MNG) slabs. It is proved that the conjugated matched ENG/MNG bilayer is a subwavelength open-cavity resonator, in which the resonance frequency is determined by the complete tunneling condition, and the Q factor increases exponentially with the slab thickness. It is revealed that the wave is not evanescent inside the bilayer, but it is a hybrid of a traveling wave and a reactive standing wave. It is also manifested during the transient wave propagation that the reactive field energy stored inside the bilayer is provided by the incident wave.

Rabi splitting induced by a metamaterial plasmon cavity.

We studied the surface plasmon resonance properties of transverse electric (TE) wave in a µ-negative (MNG) material/dielectric/µ-negative (MNG) material waveguide with a finite length which works as a subwavelength cavity. The wavelength of the surface plasmon becomes shorter when decrease the thickness of the dielectric core and decrease the plasma frequency of MNG material. The resonance in this cavity can be understood as a Fabry-Perot resonance caused by the reflection of the TE guided mode at the entrance and the exit surfaces. The electromagnetic fields and power flow are concentrated around the dielectric core at the resonant frequency, the magnetic field is maximized at the dielectric core entrance and exit. When a subwavelength magnetic resonator is put at the core entrance and the resonance frequency is tuned to the plasmon cavity mode, Rabi splitting and Rabi oscillation can appear because of the strong coupling between this resonator and the cavity mode.

Electromagnetic tunneling in a sandwich structure containing single negative media.

In this paper, the electromagnetic (EM) tunneling phenomenon in a sandwich structure consisting of an mu-negative (MNG) medium, air, and an epsilon-negative (ENG) medium is investigated by means of the transfer-matrix method and microwave experiments. Both results demonstrate that by properly choosing parameters, EM waves can efficiently tunnel through a long distance over several hundreds times the length of the device. Unlike in the ENG-MNG slabs, the electric and the magnetic field of the tunneling mode is interestingly separated and localized at the interface of MNG-air and ENG-air, respectively. Therefore, this structure may be important for potential applications in wireless information and energy transmission, for its high efficiency, security, and health.

Experimental observation of Rabi splitting in effective near-zero-index media in the microwave regime.

We report the observation of a strong coupling between an artificial "atom" and localized interface mode in the microwave regime. Transmittance is experimentally measured for the effective near-zero-index paired structures containing epsilon -negative and mu -negative materials made of composite right- and left-handed transmission lines. When the atom is embedded in the interface, because of the strong coupling between the atom and the interface mode, a Rabi splitting of 0.12GHz is observed, which is in good agreement with numerical simulations. Different from the usual Rabi splitting observed in conventional cavities, the splitting modes in the effective zero-index media are invariant with the scaling change of the length.

Experimental investigation of interface states in photonic crystal heterostructures.

Optical Tamm states, a kind of interface modes, are also called Tamm plasmon-polaritons. They are experimentally observed in photonic heterostructures based on microstrip transmission lines. The position of optical Tamm states can be designed exactly under effective impedance match and effective phase shift match conditions. Our results show that the photonic band gaps can have the effect of negative-permittivity or negative-permeability media in constructing the interface modes. The simulations and experimental results agree with each other quite well.

Charge mobility retrieval approach from apparent charge packet movements based on the negative differential resistance theory.

Space charge migration characteristics play an important role in the evaluation of polymer insulation performance. However, an accurate description of charge carrier mobility in several typical insulating polymers such as polyethylene, polypropylene is currently not available. Recently, with the observation of a series of negative charge packet movements associated with the negative differential resistance characteristic of charge mobility in LDPE films, the extraction of charge mobility from the apparent charge packet movement has been attempted using appropriate methods. Based on the previous report of the successful derivation of charge mobility from experimental results using numerical methods, the present research improves the derivation accuracy and describes the details of the charge mobility derivation procedure. Back simulation results under several typical polarizing fields using the derived charge mobility are exhibited. The results indicate that both the NDR theory and the simulation models for the polyethylene materials are reasonable. A significant migration velocity difference between the charge carrier and the charge packet is observed. Back simulations of the charge packet under several typical polarizing fields using the obtained E-v curve show good agreement with the experimental results. The charge packet shapes during the migrations were also found to vary with the polarizing field.

Experimental study of photonic crystals consisting of E-negative and mu-negative materials.

E-negative (ENG) and mu-negative (MNG) materials are successfully fabricated by using composite right/left-handed transmission line. The ENG and MNG materials are opaque in experiments, but the completely tunneling phenomenon occurs in the ENG-MNG pair, if the wave impedance and the effective phase shift of ENG and MNG materials are under the conditions of match, respectively. We experimentally confirmed that the photonic crystals consisting of ENG and MNG materials can possess left-handed propagation modes and right-handed propagation modes within forbidden gaps. At the same time, the Bragg gaps for the band-gap indices m=+/-1 and the zero effective phase (zero-Phi(eff)) gaps were also observed. The experimental results agree extremely well with the simulations.

Observation of the Zero Doppler Effect.

The normal Doppler effect has well-established applications in many areas of science and technology. Recently, a few experimental demonstrations of the inverse Doppler effect have begun to appear in negative-index metamaterials. Here we report an experimental observation of the zero Doppler effect, that is, no frequency shift irrespective of the relative motion between the wave signal source and the detector in a zero-index metamaterial. This unique phenomenon, accompanied by the normal and inverse Doppler effects, is generated by reflecting a wave from a moving discontinuity in a composite right/left-handed transmission line loaded with varactors when operating in the near zero-index passband, or the right/left-handed passband. This work has revealed a complete picture of the Doppler effect in metamaterials and may lead to potential applications in electromagnetic wave related metrology.

Wide-angle Spectrally Selective Perfect Absorber by Utilizing Dispersionless Tamm Plasmon Polaritons.

We theoretically investigate wide-angle spectrally selective absorber by utilizing dispersionless Tamm plasmon polaritons (TPPs) under TM polarization. TPPs are resonant tunneling effects occurring on the interface between one-dimensional photonic crystals (1DPCs) and metal slab, and their dispersion properties are essentially determined by that of 1DPCs. Our investigations show that dispersionless TPPs can be excited in 1DPCs containing hyperbolic metamaterials (HMMs) on metal substrate. Based on dispersionless TPPs, electromagnetic waves penetrate into metal substrate and are absorbed entirely by lossy metal, exhibiting a narrow-band and wide-angle perfect absorption for TM polarization. Our results exhibit nearly perfect absorption with a value over 98% in the angle of incidence region of 0-80 degree.

Puerarin and betahistine treatment of vertebrobasilar ischemia vertigo: A meta-analysis of randomized controlled trials.

The present meta-analysis aimed to evaluate the effectiveness and safety of puerarin co-treatment with betahistine in treating vertebrobasilar ischemia (VBI) vertigo. A total of 6 medical databases were searched, identifying randomized controlled trials (RCTs) of VBI vertigo performed until August 2014 that investigated a combined treatment of puerarin with betahistine or with other conventional drugs. The quality of the literature was evaluated using the Cochrane Collaboration's tool for assessing risk of bias, and Rev Man 5.0 software was used for statistical analysis and evaluation. The present study included 7 RCTs, involving a total of 664 subjects, and revealed a statistically significant increase in efficacy between the control and the experimental group (odds ratio [OR], 4.99; 95% confidence interval [CI], 3.05 to 8.15). The average blood flow velocity within the vertebrobasilar arteries increased following treatment with puerarin and betahistine compared with that of the control groups (OR, 7.59; 95% CI, 6.19 to 9.00); however, no difference was detected between these groups in the average flow velocity within the left vertebral artery (OR, 6.17; 95% CI, 5.22 to 7.13). The frequency of adverse reactions in the experimental group was lower (OR, 0.75; 95% CI, 0.32 to 1.77) compared with the control group. Combined puerarin and betahistine regimens were more effective in treating VBI vertigo compared with other, conventional drugs; effectively alleviating the associated symptoms, including dizziness and increased average blood flow velocity within the vertebrobasilar arteries, without causing an increased number of serious side effects. However, the efficacy and safety of puerarin and betahistine use in treating VBI vertigo requires additional investigation.

On-line monitoring the extract process of Fu-fang Shuanghua oral solution using near infrared spectroscopy and different PLS algorithms.

An on-line near infrared (NIR) spectroscopy monitoring method with an appropriate multivariate calibration method was developed for the extraction process of Fu-fang Shuanghua oral solution (FSOS). On-line NIR spectra were collected through two fiber optic probes, which were designed to transmit NIR radiation by a 2mm flange. Partial least squares (PLS), interval PLS (iPLS) and synergy interval PLS (siPLS) algorithms were used comparatively for building the calibration regression models. During the extraction process, the feasibility of NIR spectroscopy was employed to determine the concentrations of chlorogenic acid (CA) content, total phenolic acids contents (TPC), total flavonoids contents (TFC) and soluble solid contents (SSC). High performance liquid chromatography (HPLC), ultraviolet spectrophotometric method (UV) and loss on drying methods were employed as reference methods. Experiment results showed that the performance of siPLS model is the best compared with PLS and iPLS. The calibration models for AC, TPC, TFC and SSC had high values of determination coefficients of (R(2)) (0.9948, 0.9992, 0.9950 and 0.9832) and low root mean square error of cross validation (RMSECV) (0.0113, 0.0341, 0.1787 and 1.2158), which indicate a good correlation between reference values and NIR predicted values. The overall results show that the on line detection method could be feasible in real application and would be of great value for monitoring the mixed decoction process of FSOS and other Chinese patent medicines.