Simultaneous determination of neodymium, erbium and holmium in rare earth mixtures with 2-phenyltrifluoroacetone and octylphenol poly(ethyleneglycol) ether by third-derivative spectrophotometry

The complexes of the rare earth metals with 2-phenyltrifluoroacetone in the presence of TX-100 are reported. The characteristic absorbances of neodymium, holmium and erbium complexes can be increased by factors of 8.5, 31 and 15 respectively, compared to those of the cholrides. The third-derivative spectra have been used to eliminate the interference of cerium, and the sensitivities are increased again by factors of 7.4, 5.5 and 6.5. A method for the direct determination of neodymium, erbium and holmium in rare earth mixtures is proposed.     

Single Atoms of Iron on MoS2 Nanosheets for N2 Electroreduction into Ammonia

Efforts have been devoted to achieving a highly efficient artificial synthesis of ammonia (NH₃). Reported herein is a novel Fe-MoS₂ catalyst with Fe atomically dispersed onto MoS₂ nanosheets, imitating natural nitrogenase, to boost N₂ electroreduction into NH₃ at room temperature. The Fe-MoS₂ nanosheets exhibited a faradic efficiency of 18.8 % with a yield rate of 8.63 μg mg_cat.⁻¹ h⁻¹ for NH₃ at −0.3 V versus the reversible hydrogen electrode. The mechanism study revealed that the electroreduction of N₂ was promoted and the competing hydrogen evolution reaction was suppressed by decorating the edge sites of S in MoS₂ with the atomically dispersed Fe, resulting in high catalytic performance for the electroreduction of N₂ into NH₃. This work provides new ideas for the design of catalysts for N₂ electroreduction and strengthens the understanding about N₂ activation over Mo-based catalysts.     

Bond energy, aromatic stabilization energy and strain in IPR fullerenes

Various models applied to DFT structures and energies of 2-D and 3-D aromatic molecules shed new light on the effects of strain and aromaticity in these systems. The cyclic pi electron delocalisation does not stabilize the fullerene C60 formation; and 5-6 and 6-6 CC bonds have near-identical bond stretch potentials.     

反式共轭类碳烯CH_2CH—CHC∶LiF的构型及异构化反应

用MP2 / 6 - 31G 解析梯度方法研究了反式共轭类碳烯CH2CH—CHC∶LiF的结构 .得到 3个平衡构型和 2个异构化反应的过渡态 .计算结果表明 ,反式共轭类碳烯有两种比较稳定的平衡构型 .分析了各平衡构型的结构特点及稳定性 ,给出了各种平衡构型及过渡态结构的Mulliken集居数 ,并讨论了两种稳定构型的化学活性     

联萘衍生物的磺化反应研究

研究了1-和2-苯基萘, 1, 1'-和2, 2'-联萘, 2, 2-二羟基-, 2, 2'-二甲氧基和-2, 2'-甲基磺酰氧基-1, 1'-联萘等七种萘衍生物和三氧化硫的磺化反应。1-苯基萘和1, 1'-联萘的磺化先发生在4位上, 第二取代位置为6和7位。2-苯基萘和2, 2'-联萘均首先得到8位磺酸取代物, 进一步磺化得到8, 4'-和8, 8'-二磺酸取代物。2, 2'-二甲氧基-1, 1'-联萘以13:87的比例得到3位和6位磺酸取代物。2, 2'-二甲磺酰氧基-1, 1'-联萘以58:42的比例得到5位和6位磺酸取代物。2, 2'-二羟基-1, 1'-联萘的等摩尔磺化得到比例为35:65的5位和6位磺酸取代物, 和大于6摩尔的SO~3反应则以62:38的比例得到5位和6位磺酸取代物。     

n-Hexane dehydrocyclization over Pt?Ni supported on alumina catalysts

Pt–Ni/-Al₂O₃ catalysts have been prepared and studied in n-hexane dehydrocyclization. The selectivity for benzene and toluene, a chain lengthening product formation was improved by Ni and correlated with its content.

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Pt–Ni/-Al₂O₃ -. Ni . Ni , .

     

Role of tin in a PtSb alloy and a Pt-Sn/Al2O3 reforming catalyst

The conversion of n-hexane was studied on a Pt-Sn/Al₂O₃ catalyst, a PtSn alloy and on the corresponding Pt catalysts. The results indicate the same catalytic effect of tin in supported and unsupported catalysts. It is concluded that the role of tin is connected with alloy formation.

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- Pt-Sn/Al₂O₃, PtSn Pt-. . , .

     

A High－efficiency Preparation, Properties and Structure of （R, S ）－and （ S, S）－Pyrrolidine－2－carboxylic Acid 3,5－Dioxa－4－boracvclo.hepta [ 2,1－α; 3,4－α′] dinaphthalen－4－yl Esters

A highly-efficient preparative procedure for ( R, S )- and ( S, S)-pyrroHdine-2-carboxyHc acid 3,5-dioxa-4-boracyclohepta[2, 1-α ; 3,4-α′] dlnaphthalen-4-yl esters [ namely ( R, S )-BNBAP and (S, S )-BNBAP] is described and the crystal structure of (R, S )-BNBAP was obtained. The data indicate that ( R, S )-BNBAP is a spirocyclic inner borate salt with almost normal te-trahedral configuration. This structural form may be the basic reason for their high chemical, optical and thermodynamic sta-bility.     

1.3μm高增益偏振无关应变量子阱半导体光放大器

采用低压金属有机化学气相外延法 (LP MOVPE)生长并制作了 1 3μm脊型波导结构偏振无关半导体光放大器 (SOA) ,有源区为基于四个压应变量子阱和三个张应变量子阱交替生长的混合应变量子阱 (4C3T)结构 ,压应变阱宽为 6nm ,应变量 1 0 % ,张应变阱宽为 11nm ,应变量 - 0 95 % ;器件制作成 7°斜腔结构以有效抑制腔面反射。半导体光放大器腔面蒸镀Ti3 O5/Al2 O3 减反 (AR)膜以进一步降低腔面剩余反射率至 3× 10 -4以下 ;在 2 0 0mA驱动电流下 ,光放大器放大的自发辐射 (ASE)谱的 3dB带宽大于 5 0nm ,光谱波动小于 0 4dB ,半导体光放大器管芯的小信号增益近 30dB ,在 12 80～ 1340nm波长范围内偏振灵敏度小于 0 6dB ,饱和输出功率大于 10dBm ,噪声指数 (NF)为 7 5dB。