纳米尺度超声显影微囊的制备及性能表征

采用双乳液-溶剂挥发法制备了内部包封氟碳液体的聚乳酸-甲氧基聚乙二醇两嵌段共聚物(MePEG-b-PLA)基超声显影纳米微囊; 用2种不同嵌段比的MePEG-b-PLA共聚物研究共聚物组成与纳米囊性能的关系; 选用聚乙烯醇(PVA)、 羧甲基葡聚糖(CMG)和壳聚糖(CS) 3种乳化剂对纳米囊表面进行亲水性修饰. 对所制备纳米囊的粒径、 Zeta电位、 形貌和水溶液稳定性进行了表征. 结果表明, 利用质量分数为1%的PVA和质量分数为1%的CMG组成的复配乳化剂和m(MePEG)∶m(PLA)= 1∶3的聚合物制得的纳米囊的平均粒径为432.9 nm, 水溶液稳定性优良. 利用超声仪对纳米囊体外超声显影性能进行研究, 结果表明, 所得聚乳酸-甲氧基聚乙二醇纳米囊具有更好的中心成像区域灰度值和更持久的体外超声显影效果. 结合3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)比色法研究证实该纳米囊具有低细胞毒性. 在超声影像学领域具有良好的应用前景.     

A kinetics-controlled coating method to construct 1D attapulgite @ amorphous titanium oxide nanocomposite with high electrorheological activity

A new kind of one-dimension attapulgite (APG) @ titanium oxide nanoparticles was prepared via kinetics-controlled coating method. By simply altering the ammonia content and reaction time to control the kinetics of hydrolysis and condensation of tetra-n-butyl titanate (TBOT) in ethanol/ammonia mixtures, amorphous titanium oxide nanoparticles can adhere to the APG rods firmly, and the thickness of uniform amorphous titanium oxide shells can be adjusted from 0 to 40 nm. The obtained APG@ titanium oxide nanorods were applied as a new electrorheological (ER) fluid, which showed a promising ER activity. The yield stresses of the APG@ titanium oxide nanorod (40-nm shell thickness) ER fluid under electric field was 2.1 times of the granular titanium oxide ER fluid and 4.1 times of the APG ER fluid. And, the APG@ titanium oxide nanorod ER fluid also exhibited distinctly improved suspended stability.     

The pressure tunning Raman and IR spectral studies on the multinuclear metal carbyne complexes

The Raman and infrared (IR) spectra of four tungsten metal carbyne complexes I, II, IV and V [Cl(CO)2(L)W[triple bond]CC6H4[triple bond](C[triple bond]CC6H4)n[triple bond]N[triple bond]C[triple bond]]2M (L = TMEDA, n = 0, M = PdI2 or ReCl(CO)3; L = DPPE, n = 1, M = PdI2 or ReCl(CO)3) were studied at high external pressure. Their pressure-induced phase transitions were observed near 20kbar (complexes I), 15 kbar (complexes II), 25 kbar (complex IV) and 30 kbar (complex V). The pressure-induced phase transition likely is first order in complex I and the pressure-induced phase transitions of complexes II, IV and V are mostly second order. The pressure sensitivities d nu/dp of nu(W[triple bond]C) are high in the low-pressure phase area and very low in the high-pressure phase area due to the pressure strengthening pi back-bonding from metal W to pi* orbital of C[triple bond]O in fragment Cl(CO)2(L)W[triple bond]C. The pressure strengthening metal pi back-bonding from metal Re or Pd to pi* orbital of C[triple bond]O or C[triple bond]N also happened to both of central metal centers of NCPd(I2)CN in complex I and NCReCl(CO)3CN in complex II.     

A 3D Hydroxylated MXene/Carbon Nanotubes Composite as a Scaffold for Dendrite‐Free Sodium‐Metal Electrodes

Sodium metal is a promising anode, but uneven Na deposition with a dendrite growth seriously impedes its application. Herein, a fibrous hydroxylated MXene/carbon nanotubes (h‐Ti₃C₂/CNTs) composite is designed as a scaffold for dendrite‐free Na metal electrodes. This composite displays fast Na⁺/electron transport kinetics and good thermal conductivity and mechanical properties. The h‐Ti₃C₂ contains abundant sodiophilic functional groups, which play a significant role in inducing homogeneous nucleation of Na. Meanwhile, CNTs provide high tensile strength and ease of film‐forming. As a result, h‐Ti₃C₂/CNTs exhibit a high average Coulombic efficiency of 99.2 % and no dendrite after 1000 cycles. The h‐Ti₃C₂/CNTs/Na based symmetric cells show a long lifespan over 4000 h at 1.0 mA cm^?2 with a capacity of 1.0 mAh cm^?2. Furthermore, Na‐O₂ batteries with a h‐Ti₃C₂/CNTs/Na anode exhibit a low potential gap of 0.11 V after an initial 70 cycles.     

苯酚和草酸二甲酯酯交换合成碳酸二苯酯反应产物的气相色谱-质谱分析

采用气相色谱-质谱联用、程序升温方法对苯酚和草酸二甲酯酯交换合成碳酸二苯酯反应产物进行了分析。实现了对钛酸四丁酯催化苯酚和草酸二甲酯二甲酯酯交换合成草酸二苯酯反应的主产物草酸二苯酯、中间产物甲基苯基草酸酯、副产物丁基苯基草酸酯、2-甲基丁醛、正丁醚及草酸二苯酯脱羰基生成碳酸二苯酯反应产物的定性，验证了苯酚和草酸二甲酯酯交换合成碳酸二苯酯反应分三步进行的反应模式。     

乙烷在V2O5(001)表面深度氧化反应机理的周期性密度泛函理论研究

采用周期密度泛函理论研究了V₂O₅ (001)表面乙烷深度氧化过程.结果表明,乙醛是主要的副产物,且脱附态的乙醛能很容易被氧化成乙酸,但多数乙醛在从表面脱附前已被氧化成CO_x.显然,在乙烷氧化脱氢反应的最终产物CO_x主要来源于乙醛.     

通过调变碳纳米管大π体系与含氧官能团的共轭作用以改变碳纳米管的催化性能

选取碳纳米管(CNT)催化剂催化丙烷氧化脱氢作为模型反应,通过系统研究CNT上多种活性氧位的微观结构,以及对其电子结构的表征,发现通过调控CNT大π体系与含氧官能团之间的共轭效应可以改变CNT的催化活性.CNT体系充当一个电子存储器,通过活性位与CNT的离域效应向活性位提供或夺取电子改变反应活性.对于丙烷氧化脱氢,当电子从CNT流向官能团时,第一步C-H断键活性提高,但反应过程中生成的中间体过于稳定将导致CNT催化剂活性位被占据,从而抑制第二步C-H活化生成丙烯.反之,当电子从官能团流向CNT时,第一步C-H断键活性较低,生成的中间体较不稳定,较易生成丙烯.因此,可以通过调控CNT与官能团之间的电子共轭效应来平衡两步C-H键的活化.这些结果有助于从微观尺度上理解CNT催化剂活性的来源,并为制备高活性CNT催化剂提供理论指导.     

Efficient selective oxidation of alcohols to aldehydes catalyzed by a morpholinone nitroxide

Efficient chemoselective oxidation of primary alcohols to the corresponding aldehydes is described. The transformation is promoted by a catalytic morpholinone nitroxide radical catalyst which can be easily synthesized. A broad range of substrates including aromatic and aliphatic primary alcohols are converted with excellent yields under mild conditions. The control experiments reveal that the morpholinone nitroxide can be used as a selective oxidant for primary alcohols in the presence of secondary alcohols.     

Active Diluent-Anion Synergy Strategy Regulating Nonflammable Electrolytes for High-Efficiency Li Metal Batteries

High-energy Li metal batteries (LMBs) consisting of Li metal anodes and high-voltage cathodes are promising candidates of the next generation energy-storage systems owing to their ultrahigh energy density. However, it is still challenging to develop high-voltage nonflammable electrolytes with superior anode and cathode compatibility for LMBs. Here, we propose an active diluent-anion synergy strategy to achieve outstanding compatibility with Li metal anodes and high-voltage cathodes by using 1,2-difluorobenzene (DFB) with high activity for yielding LiF as an active diluent to regulate nonflammable dimethylacetamide (DMAC)-based localized high concentration electrolyte (LHCE-DFB). DFB and bis(fluorosulfonyl)imide (FSI⁻) anion cooperate to construct robust LiF-rich solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI), which effectively stabilize DMAC from intrinsic reactions with Li metal anode and enhance the interfacial stability of the Li metal anodes and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes. LHCE-DFB enables ultrahigh Coulombic efficiency (98.7 %), dendrite-free, extremely stable and long-term cycling of Li metal anodes in Li || Cu cells and Li || Li cells. The fabricated NCM811 || Li cells with LHCE-DFB display remarkably enhanced long-term cycling stability and excellent rate capability. This work provides a promising active diluent-anion synergy strategy for designing high-voltage electrolytes for high-energy batteries.     

Sul-containing fluorinated polyimides for optical waveguide device

Novel sul-containing fluorinated polyimides have been synthesized by the reaction of 2,2′-bis-(trifluoromethyl)-4,4′-diaminodiphenyl sulfide (TFDAS) with 1,4-bis-(3,4-dicarboxyphenoxy)benzene dianhydride (HQDPA), 2,2′-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), 4,4′-oxydiphthalicanhydride (ODPA) or 3,4,3′,4′-biphenyl-tetracarboxylic acid dianhydride (s-BPDA). The fluorinated polyimides, prepared by a one-step polycondensation procedure, have good solubility in many solvents, such as N-methyl-2-pyrrolidinone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), cyclohexanone, tetrahydrofuran (THF) and m-cresol. The molecular weights (M_n's) and polydispersities (M_n/M_w's) of polyimides were in the range of 1.24 × 10⁵ to 3.21 × 10⁵ and 1.59–2.20, respectively. The polymers exhibit excellent thermal stabilities, with glass-transition temperatures (T_g) at 221–275 °C and the 5% weight-loss temperature are above 531 °C. After crosslinking, these polymers show higher thermal stability. The films of polymers have high optical transparency. The novel sul-containing fluorinated polyimides also have low absorption at both 1310 and 1550 nm wavelength windows. Rib-type optical waveguide device was fabricated using the fluorinated polyimides and the near-field mode pattern of the waveguide was demonstrated.