13.56 MHz/2 MHz柱状感性耦合等离子体参数的对比研究

通过Langmuir双探针和发射光谱诊断方法,对比研究了驱动频率为13.56 MHz和2 MHz柱状感性耦合等离子体中电子密度和电子温度的径向分布规律.结果表明:在高频和低频放电中,输入功率的增加对等离子体参数产生了不同的影响,高频放电中主要提升了电子密度,低频放电中则主要提升了电子温度.固定气压为10 Pa,分别由高频和低频驱动时,电子密度的径向分布均为"凸型".而电子温度的分布差异比较明显,高频驱动时,电子温度在腔室中心较为平坦,在边缘略有上升;低频驱动时,电子温度随径向距离的增加而逐渐下降.为了进一步分析造成这种差异的原因,在相同放电条件下采集了氩等离子体的发射光谱图,利用分支比法计算了亚稳态粒子的数密度,发现电子温度的径向分布始终与亚稳态粒子的径向分布相反.继续升高气压到100 Pa,发现不论高频还是低频放电,电子密度的径向分布均从"凸型"转变为"马鞍形",较低气压时电子密度的均匀性有了一定的提升,但低频的均匀性更好.     

双金属(Sn/Ni)掺杂多孔硅微球的液相合成与电化学储锂性能

使用廉价的硅铝合金前驱体,通过简单的化学沉积方法制备了新型双金属(Sn/Ni)掺杂多孔硅微球(pSi@SnNi)。pSi@SnNi复合材料的三维多孔结构可以缓冲硅在锂化过程中的巨大体积膨胀,增加储锂活性位点。双金属(Sn/Ni)的掺杂可以提高硅的电子导电性,改进pSi的结构稳定性。由于其独特的组成和微观结构,具有适当Sn/Ni含量的pSi@SnNi复合材料显示了较大的可逆储锂容量(0.1 A·g^-1下为2 651.7 mAh·g^-1)、较高的电化学循环稳定性(1 A·g^-1下400次循环后为1 139 mAh·g^-1)和优异的倍率性能(2.5 A·g^-1下为1 235.8 mAh·g^-1)。     

Seeking magneto-structural correlations in easily tailored pentagonal bipyramid Dy(III) single-ion magnets

Science China Chemistry - Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating, especially for single-molecule magnets (SMMs). Herein a family of...     

野黄芩素的制备、纯化与结构表征

提出一种简便的由灯盏花植物制备野黄芩素的方法.首先从灯盏花植物中提取灯盏花乙素,再通过水解制得野黄芩素粗品,经硅胶柱层析纯化,得高纯度野黄芩素.所得野黄芩素经高效液相色谱法测定,纯度达98％,其结构为IR、UV、MS、13C NMR和1H NMR所确证.     

改变激发环境调控Ho3+离子的上转换发光特性

稀土掺杂上转换发光材料的发光特性不仅依赖于基质材料本身,而且与其激发条件密切相关.本文主要是以Ho^3+离子为研究对象,在NaYF4和LiYF4这两种不同的基质中,研究其在不同激发条件下的上转换发光特性.通过共聚焦显微光谱测试系统,对比Ho^3+离子在NaYF4和LiYF4微米晶体中的发光特性.实验结果发现:Ho^3+离子在这两种不同基质中均展现出较强的荧光发射.然而,当激发功率增加时,在单颗粒个LiYF4微米晶体中,当激发功率增加时,Ho^3+离子则发射出较强绿光及微弱的红光,红绿比变化并不明显,其蓝光发射强度也相对较弱.当激发这两种微米粉末晶体时,结果发现:Ho^3+离子均发射较强的绿光发射并伴有微弱红光发射,两种晶体中的发射特性极其相似.由此可见,在常规测试条件下,一些特殊发光现象是很难被观测到的.同时,通过对其光谱特性的分析,对Ho^3+离子的发光机理进行了研究.     

聚碱式氯化铝制备实验探索

通过改进的制备方案,在常温下成功制备聚碱式氯化铝。无论在制备方法上还是在净水效果上,改进后的聚碱式氯化铝的制备方案都优于现有教材采用的实验方案。     

Suppressing the weakly bound states in the photoassociation dynamics by a frequency cut-off laser pulse

The photoassociation dynamics of ultracold lithium atoms controlled by a cut-off pulse has been investigated theoretically by solving numerically the time-dependent Schrödinger equation using the mapped Fourier grid method. The frequency components of the laser pulse close to the atomic resonance are partly cut off. Compared with the typical Gauss-type pulses, the cut-off pulse is helpful to suppress efficiently the weakly bound states and prepare the associated molecules in the lower vibrational states. Especially, the dependence of photoassociation probability on the cut-off position of the laser pulse is explored.     

Tertiary-Amine-Initiated Synthesis of Acyl Fluorides from Carboxylic Acids and CF3SO2OCF3

A convenient method for deoxyfluorination of aromatic and aliphatic carboxylic acids with CF₃SO₂OCF₃ in the presence of a suitable base at room temperature has been developed. The reaction allows a straightforward access to a variety of acyl fluorides and proves that CF₃SO₂OCF₃ is an effective deoxyfluorination reagent for carboxylic acids. The method features simplicity, expeditiousness, high efficiency, ease of handling, good functional group tolerance, a wide range of substrates, excellent yields of products, compatibility of many amine initiators, use of environmentally friendly reagents, and effortless removal of byproducts. This reaction represents the first utilization of trifluoromethyl trifluoromethanesulfonate as a fluorination reagent.     

Enhancing single-molecule magnet behavior of linear Co<Superscript>II</Superscript>-Dy<Superscript>III</Superscript>Co<Superscript>II</Superscript> complex by introducing bulky diamagnetic moiety

Single-molecule magnets (SMMs) are regarded as promising candidates for ultrahigh-density storage, quantum information processing and molecular spintronics. It is a crucial challenge for chemists to modulate magnetic dynamics of SMMs. Here, we successfully synthesized two 3d-4f polynuclear compounds [Co₂Dy(TTTT^Cl)₂(MeOH)]NO₃·3MeOH (1) and [Co₂Dy(TTTT^Cl)₂ (MeOH)][Co(HTTTT^Cl)](NO₃)₂·2.5MeOH·2H₂O (2), where H₃TTTT^Cl=2,2′,2′′-(((nitrilotris(ethane-2,1-diyl)) tris(azanediyl)) tris(methylene))tris-(4-chlorophenol). On applying the approach by co-crystallization of bulky diamagnetic moiety, the effective energy barrier enhances from 401 K (1) to 536 K (2), which are both among the highest d-f heterometallic SMMs.     

Application of arylsulfonium salts as arylation reagents

Arylsulfonium salts are versatile arylation reagents for the synthesis of functional molecules. This digest focuses on the recent advances on the transition metal-mediated or -free arylation using the stable arylsulfonium salts or the metastable arylsulfonium intermediates as arylation agents.