改性钛基PbO2电极的制备及其对COD的快速检测

通过制备Ti/α/β-PbO₂、Ti/Ag/β-PbO₂这两种含有不同中间层的钛基二氧化铅电极来探究电催化氧化技术快速测定葡萄糖模拟废水中有机物(COD)含量的可行性。为了评估两种电极的各项性能,首先采用扫描电镜(SEM)、X射线衍射(XRD)对电极进行形貌表征,其次进行电化学性能测试包括线性伏安曲线(LSV)、塔菲尔曲线(Tafel)、循环伏安曲线(CV)以及交流阻抗测量分析。结果表明,Ti/α/β-PbO₂电极表面晶体结构更加均匀,晶粒尺寸偏小,具有更大的电活性表面积。Ti/α/β-PbO₂电极的析氧电位为1.77 V,为·OH的产生提供良好条件。在Tafel、CV测试中,Ti/α/β-PbO₂电极的交换电流密度i₀及比电容C_p分别为0.0995 A·cm^-1、0.004098 F·cm^-1均高于Ti/Ag/β-PbO₂电极,说明Ti/α/β-PbO₂电极的耐腐蚀性以及释放电子的能力优异。最终选用Ti/α/β-PbO₂电极为工作电极。Ti/α/β-PbO₂电极检测COD的最佳条件为：氧化电位1.30 V、电解时间150 s、电解液浓度0.03 mol·L^-1 硝酸钠(NaNO₃)。电化学法与比色消解法测定COD的相关系数可达0.9909,同时具有良好的重现性与相关性,COD的检测范围为0 mg·L^-1 ~ 500 mg·L^-1。在误差允许的范围内可以替代标准的重铬酸钾法,为实现COD的在线快速检测提供参考价值。     

2,4-二羟基苯乙酮缩异烟酰腙的实验和DFT理论研究:合成、晶体结构和性质及量化计算

合成了一种酰腙类Schiff碱2,4-二羟基苯乙酮缩异烟酰腙(C₁₄H₁₃N₃O₃,H₂L),经元素分析、红外光谱、紫外光谱、荧光光谱和热重分析等技术手段进行了表征。 用X射线单晶衍射测定了它的晶体结构,该晶体属单斜晶系,C2/c空间群,晶胞参数a=2.0102(2) nm,b=0.75891(8) nm,c=1.9530(2) nm,α= 90°,β=111.481(12)°,γ=90°,V=2.7725(5) nm³,Z=4,D_c=1.4292 g/cm³,R₁=0.0422,wR₂=0.1113,F(000)=1256。 同时进行了量子化学计算研究。 使用Gaussian09量子化学程序包, 在密度泛函理论(DFT)的B3LYP/6-31G(d)水平,对化合物的分子结构进行全参数优化计算,获得了热力学参数和几何结构参数,对分子的总能量及前线分子轨道、Mulliken电荷分布进行了分析讨论;同时,用TD-DEF方法计算了化合物的电子吸收光谱和荧光发射光谱。     

α,β,γ,δ,ε,η-Bi2O3电子结构和光学性质的第一性原理研究

基于密度泛函理论的CASTEP模块研究了α, β, γ, δ, ε和η-Bi₂O₃晶型, 计算分析了其几何结构、 能带结构、 电子态密度和光学性质. 结果表明, α, ε和η相均为层状结构, 其中, α和ε相为单层—Bi—O—结构, 而η相为双层—Bi—O—结构; β, γ和δ相为—Bi_m—O_n—交错结构, 其中δ相交错尤为密集, 呈现导体特性. 各晶相的导带均由Bi 6p态构成, 价带由O_2p态起主导作用. 电势电位分析结果表明, 6种晶相价带电位均在H₂O/O₂之下, 具有强氧化能力, 与实验报道的光催化氧化能力大小顺序γ-Bi₂O₃>β-Bi₂O₃>α-Bi₂O₃>δ-Bi₂O₃一致, 而导带还原电位低于H₂/H₂O, 预测纯Bi₂O₃很难具备催化产氢能力. 光学性质分析发现, γ和δ相的起始响应波长较大, 说明其应具备红外激发的性质. 这些结果可为获得偏红外激发和较宽光谱响应的Bi₂O₃材料研究提供理论基础, 为研发和应用Bi₂O₃及其复合物提供重要的指导.     

基于一维双螺旋链的锌配合物的合成与荧光性能

选择配体N,N'-双(3-吡啶)丙二酰胺(3-bpma)、1,4-对苯二乙酸(H₂pda)和硝酸锌在水热条件下,自组装制备了一个基于双螺旋链的三维超分子锌配合物[Zn(3-bpma)(pda)]_n(1),并通过红外光谱、元素分析、热重分析和X射线单晶衍射分析进行了晶体结构表征。 单晶结构分析表明标题锌配合物是正交晶系,Pna21空间群,晶胞参数a=1.62512(11) nm,b=1.15947(8) nm,c=1.19282(8) nm,α=90°,β=90°,γ=90°,V=2.2476(3) nm³,M_r=513.80,D_c=1.518 g/cm³,Z=4,F(000)=1056,R₁=0.0381,wR₂=0.0669。 金属锌离子被两种桥连配体3-bpma和pda连接形成一种一维双螺旋链状结构,相邻的链间进一步通过氢键作用拓展成为三维超分子网络结构。 标题锌配合物具有强荧光发射特性,而且其对不同的有机溶剂分子和金属离子有显著的荧光传感特性,可以作为检测硝基苯的高灵敏性荧光传感材料。 CCDC:1811967     

双金属氮化物NiMoN析氢催化剂制备及其电解海水析氢性能的研究

电解水制氢是最具潜力的绿氢制备技术, 而高效析氢反应(HER)催化剂的开发对其大规模推广意义重大. 选用氯化镍和钼酸铵为镍源和钼源, 通过原位生长法获得NiMo双金属催化剂前驱体, 再以二腈二胺为氮源, 高温氮化-程序升温法制备了一系列NiMo_xN@NC催化剂(x代表钼酸铵和氯化镍的物质的量比), 并对催化剂进行了结构、形貌以及金属价态表征. 分别在1 mol/L KOH碱液以及模拟海水中分析了析氢(HER)性能. 结果表明, 碱液中NiMo_xN@NC催化剂均具有良好的电荷转移速率(R_ct<1 Ω), 具有较好的内在催化活性(Tafel斜率103~168 mV/dec). 其中, NiMo_0.75N@NC催化剂具有最高的极限电流(–178 mA/cm²), 最小的过电势η₁₀=0.164 V, η₁₀₀=0.448 V), 最高的内在催化活性, Tafel斜率只有103 mV/dec, 且具有较好的稳定性. 在海水中, 在10 mA/cm²和40 mA/cm²的负载电流下, NiMo_0.75N@NC催化剂依旧表现出了较好的稳定性.     

三环已基锡L-扁桃酸酯配合物的合成、结构及性质

三环己基氢氧化锡与L-扁桃酸(物质的量比1:1)在苯和乙醇混合溶剂中反应合成了三环己基锡L-扁桃酸酯。 经X射线衍射方法测定了其晶体结构,配合物属斜方晶系,空间群为P2₁2₁2₁,晶体学参数a=0.80825(4) nm,b=1.77151(8) nm,c=1.8385(2) nm,α=β=γ=90°,V=2.6324(2) nm³,Z=4,D_c=1.310 g/nm³,μ(MoKα)=9.92 cm^-1,F(000)=1080,R₁=0.0472,wR₂=0.1341。 中心锡原子与环己基碳原子和氧原子构成畸型四面体。 对其结构进行量子化学从头计算,探讨了配合物的稳定性、分子轨道能量以及一些前沿分子轨道的组成特征。 研究了配合物的热稳定性、电化学性能、圆二色谱和体外抗癌活性。     

芘基查尔酮的合成及三阶非线性光学性质

合成了一种新的具有潜在应用价值的非线性光学(NLO)有机材料1-(芘-1-基)-3-(4-二甲氨基苯基)丙烯酮(PMAK),并通过 NMR、IR、MS和元素分析等技术手段进行了表征。 采用溶液Nd:YAG激光技术测定了PMAK的三阶非线性光学性质并确定了相关参数。 纳秒实验结果:折射率n₂=-3.5×10^-17 m²/W,吸收系数β=7.0×10^-10 m/W,极化率χ⁽³⁾=2.54×10^-11 esu,分子超极化率γ=3.44×10^-30 esu;皮秒实验结果:n₂=-2.8×10^-18 m²/W,β=8.3×10^-11 m/W,χ⁽³⁾=2.49×10^-12 esu,γ=3.33×10^-31 esu。     

一种新型钼钒多酸化合物的合成、结构与荧光性能

采用水热技术,合成了一种新型四帽Keggin结构多酸化合物[H₃Mo₈^ⅥV₈^ⅣO₄₀(AsO₄)](en)₂(4,4-bipy)₇·9H₂O(en:乙二胺;bipy:联吡啶)(1),并对化合物进行了元素分析、红外光谱、X射线光电子能谱和X射线单晶结构分析。 晶体结构分析表明, 化合物属三斜晶系,P1空间群,晶胞参数a=1.47395(5) nm,b=1.48172(6) nm,c=1.62881(7) nm,α=66.16(3)°,β=87.15(2)°,γ=63.42(1)°,V=2.8723(2) nm³,Z=1,R₁=0.0728,wR₂=0.2014。 化合物由四帽Keggin多酸阴离子、4,4'-联吡啶、乙二胺和结晶水分子构成,化合物分子间存在大量的氢键,使化合物1形成3-D超分子结构。 荧光测试表明,化合物1能发出较强的荧光,有可能成为潜在的光活性材料。     

三维多孔MnOx@In2O3立方盒子的构筑及储锌性能

锰基氧化物作为锌离子电池正极具有高比容量和低成本等优点, 但在电化学循环过程中不可逆相变、 锰的溶解和电极/电解质界面不稳定导致其在小电流密度、 深度放电条件下的循环性能差. 针对以上问题, 合成了三维(3D)多孔MnO_x立方盒子, 并在其表面包覆In₂O₃层, 获得3D多孔MnO_x@In₂O₃立方盒子. 结果显示, MnO_x@In₂O₃立方盒子具有大量孔径约10 nm左右的孔, 有利于H⁺和Zn²⁺的快速传输; In₂O₃包覆层均匀包覆于3D多孔MnO_x立方盒子的孔壁上, 有利于抑制MnO_x在电化学循环过程中的不可逆相变和锰的溶解, 稳定电极/电解质界面. 电化学测试结果表明, 该3D多孔MnO_x@In₂O₃电极在0.3 A/g的小电流密度、 深度放电条件下能稳定循环400次以上, 容量保持260 mA·h/g; 在1. 8 A/g电流密度下可稳定循环4000次以上, 容量保持81 mA·h/g; 即使在高电流密度6.0 A/g下仍保持73.4 mA·h/g的高可逆容量. 恒电流间隙滴定(GITT)和循环伏安测试结果表明, 3D多孔MnO_x@In₂O₃电极比3D多孔MnO_x具有更高的离子扩散速率, 有利于提升其高倍率容量. 电化学阻抗谱结果表明, 3D多孔MnO_x@In₂O₃电极具有比3D多孔MnO_x更稳定的电极/电解质界面, 有利于提升其循环寿命. 2000次循环后的扫描电子显微镜(SEM)结果表明, MnO_x@In₂O₃电极表面仍分布少量In₂O₃, 以确保电极/电解质界面和循环的稳定性.     

聚-4-乙基苯酚抗氧剂对聚丙烯结晶行为的影响

通过差示扫描量热仪(DSC)和X射线粉末衍射仪(XRD)研究了聚-4-乙基苯酚抗氧剂对聚丙烯结晶行为的影响。 分别用Jeziorny法和Mo法处理非等温结晶动力学。 同时用Friedman法和Kissinger法计算其结晶活化能。 最后由结晶活化能与结晶温度的变化曲线求得Hoffman-Lauritzen参数成核速率常数(K_g)和迁移活化能(U^*)值,进而求得折叠链端表面自由能(σ_e)和分子链段折叠功(q)。 结果表明,抗氧剂的加入,使聚丙烯的结晶峰温度向低温区移动,结晶半峰宽变大,半结晶时间(t_1/2)增大,Jeziorny法所得的结晶速率常数(Z)降低,Mo法所得反映结晶速率快慢的参数F(T)提高,在相同结晶转化率下,结晶活化能负值变小。 Hoffman-Lauritzen参数K_g、U^*、σ_e和q值均增大。 所有变化均表明聚-4-乙基苯酚抗氧剂对PP的结晶有抑制作用。     

A monolayer study on three binary mixed systems of dipalmitoyl phosphatidyl choline with cholesterol, cholestanol and stigmasterol

The monolayer behavior of three mixed systems of dipalmitoyl phosphatidyl choline (DPPC) with sterols; cholesterol (Ch), stigmasterol (Stig), and cholestanol (Chsta) formed at the interface of air/water (phosphate buffer solution at 7.4 with addition of NaCl) was investigated in terms of surface pressure (π) and molecular occupation surface area (A) relation. A series of π–A curves at every 0.1 mol fraction of each sterol for the three combinations of mixed systems were obtained at 25.0 °C.

On the basis of the π–A curves, the additivity rule in regard to A versus sterol mole fraction (X_st) was examined at discrete surface pressures such as 5, 10, 15, 20, 25, 30 mN m⁻¹, and then from the obtained A–X_st curves the partial molecular areas (PMA) were determined. The A–X_st relation exhibited a marked negative deviation from ideal mixing in the pressure range below 10 mN m⁻¹, i.e. in the expanded liquid film region (below the transition pressure of DPPC).

The PMA of Ch at π=5 mN m⁻¹, for example, was found to be conspicuously negative in the range of X_Ch=0–0.2 (about −0.4 nm² per molecule) and slightly positive (ca. 0.1 nm² per molecule) in the range X_Ch=0.2 to 0.4. Above X_Ch=0.5, Ch’s PMA was almost the same as the surface area of pure Ch, while DPPC’s PMA was reduced to 60% of that of the pure system.

Excess Gibbs energy (ΔG_(ex)) as a function of X_st was estimated at different pressures. Applying the regular solution theory to thermodynamic analysis of ΔG_(ex), the activity coefficients (f₁ and f₂) of DPPC and the respective sterols as well as the interaction parameter (I_p) in the mixed film phase were evaluated; the results showed a marked dependence on X_st.

Compressibility C_s and elasticity C_s⁻¹ were also examined. These physical parameters directly reflected the mechanical strength of formed monolayer film.

Phase diagrams plotting the collapse pressure (π_c) against X_st were constructed, and the π_c versus X_st curves were examined for the respective mixed systems in comparison with the simulated curves of ideal mixing based on the Joos equation.

Comparing the monolayer behavior of the three mixed systems, little remarkable difference was found in regard to various aspects. In common among the three combinations, the mole fraction dependence in monolayer properties was classified into three ranges: 0<X_st<0.2, 0.2<X_st<0.4 and 0.5<X_st<1. How the difference in the chemical structure of the sterols influenced the properties was examined in detail.     

The effect of terminal chain modifications on the mesomorphic properties of 4,4'-disubstituted diphenyldiacetylenes

A variety of terminal chain modifications (Y) were made on the diacetylenes in which X=C_nH_2n+1, C₁₂H₂₅O and F, and Y=CH₂CH(Me)C₂H₅, COCH₃, C≡CC₅H₁₁, C_nF_2n+1C_nH_2n+1 and CH=CHCO₂C₃H₇. Mesomorphic properties were determined by hot stage polarizing microscopy and DSC. These were compared with those for the dialkyl analogues (X=C_mH_2m+1, Y=C_nH_2n+1) and a series of 1- and 2-olefins (Y=CH=CHC_nH_2n+1 and CH₂CH=CHC_nH_2n+1). The 1-olefin series showed wider range nematics than the dialkyl compounds, whereas the above modifications showed either narrow range nematic phases, no mesophase or higher melting temperatures. New transition temperature and enthalpy data are provided for some of the dialkyl and F-alkyl compounds previously reported, for comparisons. Preliminary birefringence data are also included along with the results of some heat and UV stability studies.     

Predicted radiolysis yield in a Fricke solution irradiated with various heavy ions

Experimental data on the spatial distribution of the energy deposited around an energetic heavy ion, from 1 MeV proton to 5.9 MeV/n uranium ion, which have been reported in the literature were documented to obtain a scaled radial dose distribution; (β/Z*)² D(Z*, β,t)=200 (for t=0–1), 200/t² (for t=1t_c), and 200 t_c/t³ (for t>t_c) where Z* and β are the effective charge and velocity relative to c, the velocity of light, of the incident ion, respectively, D the dose in unit of Gy, t the radial distance in unit of nm, t_c the critical distance empirically determined.

Then, if we know the yield of any chemical reaction as a function of dose from the results of experiments using γ-radiations or fast electrons or theoretical calculations, we can calculate the probability for the yield of the chemical reaction in the system bombarded with a heavy ion of the effective charge Z* and velocity β. The results of the present calculation of the LET-values and of G(Fe³⁺) in the ferrous sulfate acidic solution are presented and compared with reported experimental results.     

Ab initio structural trends and torsional sensitivity in n-hexane and comparisons with crystallographic structural results

The molecular structures of n-hexane were determined by RHF/4-21G ab initio geometry optimization at 30° grid points in its three-dimensional τ₁(C11–C8–C5–C1), τ₂(C14–C11–C8–C5), τ₃(C17–C14–C11–C8) conformational space. Of the resulting 12×12×12=1728 grid structures, 468 are symmetrically non-equivalent and were optimized constraining the torsions τ₁, τ₂, and τ₃ to the respective grid points, while all other structural parameters were relaxed without any constraints. From the results, complete parameter surfaces were constructed using natural cubic spline functions, which make it possible to calculate parameter gradients, |P|=[(∂P/∂τ_i)²+(∂P/∂τ_j)²]^1/2, where P is a C–C bond length or C–C–C angle. The parameter gradients provide an effective measure of the torsional sensitivity of the system and indicate that dynamic activities in one part of the molecule can significantly affect the density of states, and thus the contributions to vibrational entropy, in another part. This opens the possibility of dynamic entropic conformational steering in complex molecules; i.e. the generation of free energy contributions from dynamic effects of one part of a molecule on another. When the conformational trends in the calculated C–C bond lengths and C–C–C angles are compared with average parameters taken from some 900 crystallographic structures containing n-hexyl fragments or longer C–C bond sequences, some correlation between calculated and experimental trends in angles is found, in contrast to the bond lengths for which the two sets of data are in complete disagreement. The results confirm experiences often made in crystallography. That is, effects of temperature, crystal structure and packing, and molecular volume effects are manifested more clearly in bond lengths than bond angles which depend mainly on intramolecular properties. Frequency analyses of the τ₁, τ₂ and τ₃ torsional angles in the crystal structures show conformational steering in the sense that, if τ₁ is trans peri-planar (170°≤τ₁≤180°; −180°≤τ₁≤−170°), the values of τ₂ and τ₃ are clustered closely around the ideal gauche (±60°) and trans (±180°) positions. In contrast, when τ₁ is in the region (50°≤τ₁≤70°), there is a definite increase in the populations of τ₂ and τ₃ at −90 and −150°.