Optically Matched Semiconductor Quantum Dots Improve Photophosphorylation Performed by Chloroplasts

A natural–artificial hybrid system was constructed to enhance photophosphorylation. The system comprises chloroplasts modified with optically matched quantum dots (chloroplast–QD) with a large Stokes shift. The QDs possess a unique optical property and transform ultraviolet light into available and highly effective red light for use by chloroplasts. This favorable feature enables photosystem II contained within the hybrid system to split more water and produce more protons than chloroplasts would otherwise do on their own. Consequently, a larger proton gradient is generated and photophosphorylation is improved. At optimal efficiency activity increased by up to 2.3 times compared to pristine chloroplasts. Importantly, the degree of overlap between emission of the QDs and absorption of chloroplasts exerts a strong influence on the photophosphorylation efficiency. The chloroplast–QD hybrid presents an efficient solar energy conversion route, which involves a rational combination of a natural system and an artificial light‐harvesting nanomaterial.     

Exposing the Origins of Irreproducibility in Fluorine NMR Spectroscopy

Fluorine chemistry has taken a pivotal role in chemical reaction discovery, drug development, and chemical biology. NMR spectroscopy, arguably the most important technique for the characterization of fluorinated compounds, is rife with highly inconsistent referencing of fluorine NMR chemical shifts, producing deviations larger than 1 ppm. Herein, we provide unprecedented evidence that both spectrometer design and the current unified scale system underpinning the calibration of heteronuclear NMR spectra have unintentionally led to widespread variation in the standardization of ¹⁹F NMR spectral data. We demonstrate that internal referencing provides the most robust, practical, and reproducible method whereby chemical shifts can be consistently measured and confirmed between institutions to less than 30 ppb deviation. Finally, we provide a comprehensive table of appropriately calibrated chemical shifts of reference compounds that will serve to calibrate ¹⁹F spectra correctly.     

Symmetric Eighth Algebraic Order Methods with Minimal Phase-Lag for the Numerical Solution of the Schrödinger Equation

In this paper some new eighth algebraic order symmetric eight-step methods are introduced. For these methods a direct formula for the computation of the phase-lag is given. Based on this formula, the calculation of free parameters is done in order the phase-lag to be minimal. The new methods have better stability properties than the classical one. Numerical illustrations on the radial Schrödinger equation indicate that the new method is more efficient than older ones.     

替代衬底上的碲镉汞长波器件暗电流机理

基于暗电流模型,通过变温I-V分析长波器件(截止波长为9~10μm)的暗电流机理和主导机制.实验对比了不同衬底、不同成结方式、不同掺杂异质结构与暗电流成分的相关性.结果表明,对于B+离子注入的平面结汞空位n~+-on-p结构,替代衬底上的碲镉汞(HgCdTe)器件零偏阻抗(R0)在80 K以上与碲锌镉(CdZnTe)基碲镉汞器件结阻抗性能相当.但替代衬底上的HgCdTe因结区内较高的位错,使得从80 K开始缺陷辅助隧穿电流(I_(tat))超过产生复合电流(I_(g-r)),成为暗电流的主要成分.与平面n~+-on-p器件相比,采用原位掺杂组分异质结结构(DLHJ)的p~+-on-n台面器件,因吸收层为n型,少子迁移率较低,能够有效抑制器件的扩散电流.80 K下截止波长9.6μm,中心距30μm,替代衬底上的p~+-on-n台面器件品质参数(R0A)为38Ω·cm2,零偏阻抗较n-on-p结构的CdZnTe基碲镉汞器件高约15倍.但替代衬底上的p+-on-n台面器件仍受体内缺陷影响,在60 K以下较高的Itat成为暗电流主导成分,其R0A相比CdZnTe基n~+-on-p的HgCdTe差了一个数量级.     

Blue-phase liquid crystal display with insulating protrusion

In order to lower the saturation voltage and enhance the transmittance of in-plane switching blue-phase liquid crystal display (IPS-BPLCD), IPS-BPLCD with insulating protrusion is proposed. The single-protrusion (only set on the top of pixel electrode) and double-protrusion (set on the top of pixel and common electrodes) structures are investigated in this work. The potential distribution changes when the protrusion is used. There is a thicker transverse electric field in BPLC range, because the stronger electric field at the edges of the electrodes is decentralised into BPLC range. As a result, the saturation voltage is reduced from 36.3 V to 28.9 V when the double-protrusion structure is used, and transmittance is increased by ~20%. The contrast ratio is larger than 1000:1 in 60° viewing cone using a half-wave biaxial film. Both single-protrusion and double-protrusion structures have the uniform gamma curves at large oblique viewing angles. Moreover, the off-axis image distortion index is 0.1590 at 60º polar angle when zigzag electrodes are used.     

A Stereolithography‐Based 3D Printed Hybrid Scaffold for In Situ Cartilage Defect Repair

Damage to articular cartilage can over time cause degeneration to the tissue surrounding the injury. To address this problem, scaffolds that prevent degeneration and promote neotissue growth are needed. A new hybrid scaffold that combines a stereolithography‐based 3D printed support structure with an injectable and photopolymerizable hydrogel for delivering cells to treat focal chondral defects is introduced. In this proof of concept study, the ability to a) infill the support structure with an injectable hydrogel precursor solution, b) incorporate cartilage cells during infilling using a degradable hydrogel that promotes neotissue deposition, and c) minimize damage to the surrounding cartilage when the hybrid scaffold is placed in situ in a focal chondral defect in an osteochondral plug that is cultured under mechanical loading is demonstrated. With the ability to independently control the properties of the structure and the injectable hydrogel, this hybrid scaffold approach holds promise for treating chondral defects.     

A Zero‐Dimensional Organic Seesaw‐Shaped Tin Bromide with Highly Efficient Strongly Stokes‐Shifted Deep‐Red Emission

The synthesis and characterization is reported of (C₉NH₂₀)₂SnBr₄, a novel organic metal halide hybrid with a zero‐dimensional (0D) structure, in which individual seesaw‐shaped tin (II) bromide anions (SnBr₄^2?) are co‐crystallized with 1‐butyl‐1‐methylpyrrolidinium cations (C₉NH₂₀⁺). Upon photoexcitation, the bulk crystals exhibit a highly efficient broadband deep‐red emission peaked at 695 nm, with a large Stokes shift of 332 nm and a high quantum efficiency of around 46 %. The unique photophysical properties of this hybrid material are attributed to two major factors: 1) the 0D structure allowing the bulk crystals to exhibit the intrinsic properties of individual SnBr₄^2? species, and 2) the seesaw structure enabling a pronounced excited state structural deformation as confirmed by density functional theory (DFT) calculations.     

Chiral imines prepared from 1-(2-aminoalkyl)aziridines as novel chiral shifts reagents for efficient recognition of acids

Optically pure, chiral imines synthesized from the corresponding aldehydes and 1-(2-aminoalkyl)aziridines in good chemical yields, have been assessed as an NMR chiral shift reagents for effective discrimination of the signals of some acids (mandelic acid and its derivatives and N-protected amino acid). The title compounds have proven to be very useful for the determination of enantiomeric purity and absolute configuration of the aforementioned acid derivatives.     

Density Functional Study on the Reactivity of Carbenes Toward 1,2‐H Shifts

The 1,2‐H shift reactions of simple carbenes (CH₂Y‐C‐X) have been studied using density functional theory (DFT). The influence of the substituent X and Y groups on the activation energy (Ea) of 1,2‐H shifts were examined. The ‘by stander’ Y substituents lower E_a in the order of Me, F > Cl, Br > H. Our analysis shows that the X effect is more significant than the by stander Y effect. X substitutions increase E_a of carbenes in the order of F > Cl > Br > Me > H. The influence of X on E_a is governed by the singlet‐triplet energy separation (ΔE_S‐T) of the carbene, i.e., E_a of a carbene is larger as its ΔE_S‐T in creases due to an X substitution. The X effect was also found to be related to the magnitude of the exothermicity: Ea of reaction is smaller when the reaction is more exothermic. Origin of the Y effect is attributed to the inter play between two factors: ‘lateness’ of transition state on the potential energy surface, and the exothermicity of the reaction.     

13C Nuclear magnetic resonance spectra of cyclodextrin monomers,derivatives and their complexes with methyl orange

Low molecular mass fractions of water soluble -, -, and -cyclodextrin epichlorohydrin polymer products (cdx-Ep) were characterized by¹³C nuclear magnetic resonance. The derivatives proved not to be polymers, but substituted cdx having one or two glyceryl groups per one glucose at the C-2, C-3 and C-6 positions. Spectra of analogous hydroxy-propyl -cdx indicate that the degree of substitution is rather higher at the C-6 position. Methyl orange (MO) was included into nine kinds of cdx having different inner diameters and hydrophobic torus heights; -, -, and -cdx monomers, 2, 6-dimethyl and 2, 3, 6-trimethyl -cdx, water soluble -, -, and -cdx-Ep and ethyleneglycol-bis(epoxy-propyl) ether products. The inclusion shifts were compared with each other and with the dioxane-induced solvent shift of MO. TheN, N-dimethyl-aniline side of MO shifted to a higher field site with the increase of the inner diameter in cdx. By substituting cdx with ether groups of different length, the mechanism of inclusion formation remains substantially the same, but by lengthening the hydrophobic cavity, the hydrophobic interaction becomes stronger, as a better resemblance of inclusion shifts and solvent shifts can be observed.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.