具有丰富晶界的铜催化剂在气-液平衡扩散电极上高效电还原CO_(2)制C_(2)H_(4)

电催化二氧化碳还原反应(CO_(2)RR)可以将二氧化碳转化为具有高经济价值的碳氢化合物,被认为是实现碳中和并缓解能源危机的一种有潜力的技术.铜(Cu)作为一种最有应用前景的非贵金属催化剂之一,表现出较高的催化CO_(2)RR转化为多碳产物(C_(2+))的活性.然而,电催化CO_(2)还原成C_(2+)产物涉及一个动力学过程缓慢的C-C偶联反应,这导致C_(2+)产物的选择性较低,电流密度低,阻碍了其在工业电解槽中的实际应用.同时,CO_(2)RR产物的选择性不仅取决于热力学速率决定步骤,还取决于传质控制动力学.CO_(2)RR发生在固-气-液三相反应界面,气-液的平衡扩散可以有效抑制析氢竞争反应,进而提高CO_(2)RR的反应效率.本文设计合成了一种富晶界的Cu纳米带催化剂,并构建了气-液平衡扩散的电极结构,用于高效电催化二氧化碳还原制备乙烯(C_(2)H_(4)).以一种碱式碳酸铜(Cu_(2)CO_(3)(OH)_(2))纳米带为前驱体,在原位电化学还原条件下,前驱体中的Cu2+离子获得电子被还原为金属Cu,而释放的CO_(3)2-和OH-混合阴离子调节金属Cu的生长.生成的Cu纳米带由细小的纳米颗粒堆积而成,并暴露出大量的由Cu(111),Cu(200)和Cu(220)晶面形成的富晶界结构(GBs).同时,在CO_(2)RR测试中发现催化剂层的厚度是影响CO_(2)和电解质传质的关键因素.通过调整催化层厚度,CO_(2)和电解质可以同时到达催化剂表面,参与到CO_(2)RR中,实现了气-液平衡扩散,有效抑制了氢析出副反应.在晶界效应和气-液平衡扩散的协同作用下,优化后的电极在电流密度为700 mA cm^(-2)时,对C_(2)H_(4)和C_(2+).产物的法拉第效率分别高达67.2%和82.1%.此外,C_(2)H_(4)的部分电流密度可高达505 mA cm^(-2),高于大多数文献报道的结果.原位拉曼光谱和衰减全内反射表面增强红外吸收光谱结果表明,丰富的晶;界结构增强了CO_(2)在催化剂表面的活化,显著促进了*CO中间体的形成和吸附,加速了C-C偶联过程形成*OCCO和*OCCOH中间体,提高了C_(2)H_(4)和其他C_(2+)产物的产率.综上,本文设计了一种高活性Cu催化剂和电极结构,为高效电催化CO_(2)还原为C_(2)H_(4)等C_(2+)产物提供参考.

Cu-Zn-based alloy/oxide interfaces for enhanced electroreduction of CO_(2) to C_(2+) products

The electrochemical CO_(2)reduction reaction to produce multi-carbon(C_(2+)) hydrocarbons or oxygenate compounds is a promising route to obtain a renewable fuel of high energy density.However,producing C_(2+)at high current densities is still a challenge.Herein,we develop a Cu-Zn alloy/Cu-Zn aluminate oxide composite electrocatalytic system for enhanced conversion of CO_(2)to C_(2+)products.The Cu-Zn-Al-Layered Double Hydroxide(LDH) is used as a precursor to decompose into uniform Cu-Zn oxide/Cu-Zn aluminate pre-catalyst.Under electrochemical reduction,Cu-Zn oxide generates Cu-Zn alloy while Cu-Zn aluminate oxide remains unchanged.The alloy and oxide are closely stacked and arranged alternately,and the aluminate oxide induces the strong electron interaction of Cu,Zn and Al,creating a large number of highly active reaction interfaces composed of 0 to+3 valence metal sites.With the help of the interface effect,the optimized Cu_(9)Zn_(1)/Cu_(0.8)Zn_(0.2)Al_(2)O_(4)catalyst achieves a Faradaic efficiency of 88.5% for C_(2+)products at a current density of 400 mA cm^(-2)at-1.15 V versus reversible hydrogen electrode.The in-situ Raman and attenuate total reflectance-infrared absorption spectroscopy(ATR-IRAS) spectra show that the aluminate oxide at the interface significantly enhances the adsorption and activation of CO_(2)and the dissociation of H2O and strengthens the adsorption of CO intermediates,and the alloy promotes the C-C coupling to produce C_(2+)products.This work provides an efficient strategy to construct highly active reaction interfaces for industrial-scale electrochemical CO_(2)RR.

Danhong Huayu Koufuye combined with metformin attenuated diabetic retinopathy in Zucker diabetic fatty rats

AIM: To evaluate effects of Danhong Huayu Koufuye(DHK, a Chinese medicinal formulae) alone or combined with metformin on diabetic retinopathy(DR) in Zucker diabetic fatty(ZDF) rats, an animal model of obese type-2 diabetes, and then to investigate the mechanisms.·METHODS: ZDF(fa/fa) rats were administered with vehicle(distilled water), metformin, DHK, and DHK plus metformin. Electrophysiological and histological analysis were applied to evaluated effects of DHK alone or combined with metformin on DR. The levels of fasting blood glucose(FBG) and glycosylated hemoglobin(Hb A1c) in blood were measured to evaluate the antihyperglycemic activity of DHK. Furthermore, levels of nitric oxide(NO), malondialdehyde(MDA) and activities of superoxide dismutase(SOD), glutathione peroxidase(GSH-Px) in serum were measured to study effects of DHK on oxidative stress in ZDF rats. In addition, body weight, lipidic indexes and insulin level were also assessed.·RESULTS: DHK combined with metformin significantly reversed the prolongation of latency times of flash electroretinogram(FERG) and oscillatory potentials(OPs)in diabetic rats. Furthermore, DHK alone or combined with metformin showed a remarkable suppression of retinal neovascularization and amelioration of retinal internal limiting membrane morphology. Moreover, DHK alone or plus metformin reduced FBG(P <0.05), Hb A1c(P <0.01) and MDA(P <0.01) levels in diabetic rats. In addition, reductions in levels of triglycerides(TG)(P <0.01)and low density lipoprotein cholesterol(LDL-c)(P <0.01 and P <0.05, respectively) were also observed in diabetic rats treated with DHK alone or plus metformin.· CONCLUSION: DHK in combination with metformin had a preventive and therapeutic effect on DR in type-2diabetic rats, and the possible mechanisms may be alleviating hyperglycemia, reducing oxidative stress and improving lipid metabolism.

冬凌草甲素对人宫颈癌HeLa细胞线粒体凋亡途径的影响

目的观察冬凌草甲素对人宫颈癌HeLa细胞凋亡的影响,并探讨其诱导HeLa细胞线粒体凋亡的机制。方法体外培养HeLa细胞,分别以0μmol/L(设为空白对照组)、5μmol/L、10μmol/L、25μmol/L、50μmol/L、100μmol/L冬凌草甲素处理12 h、24 h、36 h、48 h,CCK-8法检测HeLa细胞活力,计算IC50。以0μmol/L、5μmol/L、10μmol/L、25μmol/L冬凌草甲素处理HeLa细胞24 h,采用Annexin V/PI双染法和TUNEL染色分别检测HeLa细胞凋亡;JC-1染色检测线粒体膜电位(Δψm)改变;Western blotting检测细胞色素c(Cyt c)、B细胞淋巴瘤-2因子(Bcl-2)、Bcl-2相关X蛋白(Bax)的表达;比色法检测半胱氨酸蛋白酶-3(Caspase-3)、半胱氨酸蛋白酶-9(Caspase-9)活性。结果冬凌草甲素抑制HeLa细胞细胞活力呈剂量-时间依赖效应(P<0.05),其12 h、24 h、36 h、48 h的IC50分别为95.63μmol/L、32.24μmol/L、19.58μmol/L和4.13μmol/L;与空白对照组比较,5μmol/L、10μmol/L、25μmol/L冬凌草甲素组HeLa细胞凋亡率和凋亡指数升高(P<0.05);与空白对照组比较,5μmol/L、10μmol/L、25μmol/L冬凌草甲素组HeLa细胞Δψm降低(P<0.05);与空白对照组比较,5μmol/L、10μmol/L、25μmol/L冬凌草甲素组HeLa细胞Cyt c、Bax表达升高(P<0.05),Bcl-2、Bcl-2/Bax比值降低(P<0.05);与空白对照组比较,5μmol/L、10μmol/L、25μmol/L冬凌草甲素组HeLa细胞Caspase-3、Caspase-9活性升高(P<0.05)。结论冬凌草甲素可诱导HeLa细胞凋亡,其机制可能是通过线粒体凋亡途径实现。

Terahertz polarization conversion and sensing with double-layer chiral metasurface

The terahertz(THz)resonance,chirality,and polarization conversion properties of a double-layer chiral metasurface have been experimentally investigated by THz time domain spectroscopy system and polarization detection method.The special symmetric geometry of each unit cell with its adjacent cells makes a strong chiral electromagnetic response in this metasurface,which leads to a strong polarization conversion effect.Moreover,compared with the traditional THz transmission resonance sensing for film thickness,the polarization sensing characterized by polarization elliptical angle(PEA)and polarization rotation angle(PRA)shows a better Q factor and figure of merit(FoM).The results show that the Q factors of the PEA and PRA reach 43.8 and 49.1 when the interval film is 20µm,while the Q factor of THz resonance sensing is only 10.6.And these PEA and PRA can play a complementary role to obtain a double-parameter sensing method with a higher FoM,over 4 times than that of resonance sensing.This chiral metasurface and its polarization sensing method provide new ideas for the development of high-efficiency THz polarization manipulation,and open a window to the high sensitive sensing by using THz polarization spectroscopy.

Microstructure and magnetocaloric properties of partially crystallized Gd_(60)Co_(30)Fe_(10)amorphous alloy prepared by different solidification cooling rates

The Gd_(60)Co_(30)Fe_(10)alloy ribbons with different solidification cooling rates were prepared by modifying the melt-spinning speed of 6.0,12.5,25.0 and 50.0 m·s^(-1)·With cooling rate decreasing,the(Fe,Co)5 Gd and hcp-Gd nanocrystalline was in situ precipitated among the amorphous matrix,which resulted in the composition change of the amorphous phase.Because of the only slight amount of crystalline phase in Gd_(60)Co_(30)Fe_(10)alloys,the magnetic and magnetocaloric properties mainly depend on the amorphous phase,and all the magnetic entropy change versus temperature(|Δ|SMI-T)curves are table-like,indicating the suitability for Ericsson cycle.The magnetic transition temperature of the Gd_(60)Co_(30)Fe_(10)alloy at a melt-spinning speed of 6.0 m·s^(-1) shifted obviously to the lower value with the applied magnetic fields increasing.The peak value of magnetic entropy change(|ΔSMpk|)is 2.19 J·kg^(-1)·K^(-1)at217 K under the magnetic field change of 0-2 T,and the table-like region is 200-230 K.It was proved that the moderate reduction of the cooling rate will not deteriorate the magnetocaloric performance of the Gd_(60)Co_(30)Fe_(10)ribbons seriously.

Near-infrared and mid-infrared semiconductor broadband light emitters

Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications,especially for optical coherence tomography systems.Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications,the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices.Owing to the relatively weak amplified spontaneous emission,as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures,it is even more challenging to obtain desirable mid-infrared broadband light emitters.There have been great efforts in the past 20 years to pursue high-efficiency broadband optical gain and very low reflectivity in waveguide structures,which are two key factors determining the performance of broadband light emitters.Here we describe the realization of a high continuous wave light power of 420 mW and broadband width of 4130 nm with near-infrared broadband light emitters and the first mid-infrared broadband light emitters operating under continuous wave mode at room temperature by employing a modulation p-doped InGaAs/GaAs quantum dot active region with a‘J’-shape ridge waveguide structure and a quantum cascade active region with a dual-end analogous monolithic integrated tapered waveguide structure,respectively.This work is of great importance to improve the performance of existing near-infrared optical coherence tomography systems and describes a major advance toward reliable and costeffective mid-infrared imaging and sensing systems,which do not presently exist due to the lack of appropriate low-coherence mid-infrared semiconductor broadband light sources.