Preparation and stability of nanocrystalline (C6H5C2H4NH3)2PbI4-doped PMMA films

Preparation and stability of nanocrystalline (C₆H₅C₂H₄NH₃)₂PbI₄-doped PMMA films were investigated. By using spin-coating and subsequent annealing technique, nanometer-sized (C₆H₅C₂H₄NH₃)₂PbI₄ precipitates were successfully formed into a PMMA matrix. These films showed clear exciton absorption and free exciton emission at room temperature. Comparing with (C₆H₅C₂H₄NH₃)₂PbI₄ film, marked improvement of thermal- and photo-stability was observed for nanocrystalline (C₆H₅C₂H₄NH₃)₂PbI₄-doped PMMA films. The thermal-stability of these films correlates with the decomposition of the organic part. As for photo-stability, photo-irradiation induced oxidation is one of the possible reasons for the degradation of the films.     

有机/无机层状类钙钛矿(C12 H25 NH3)2 PbI4晶体及薄膜的制备与结构表征

介绍了有机/无机类钙钛矿(C12H25NH3)2PbI4的晶体和薄膜的制备,并采用了XRD、SEM、AFM和PL表征材料的结构、形貌及光学特性等.XRD实验表明制备的(C12 H25NH3)2PbI4晶体结晶度高.探索旋涂法制备工艺参数对薄膜结构的影响,在薄膜XRD中几乎只能观察到(0021)晶面的衍射峰,表明有机/无机类钙钛矿层沿平行与基片方向择优生长,SEM和AFM表明薄膜致密性较好,表面粗糙度较小.     

Crystal Structure of Double Co(NH3)6 3 + Np(V) Malonates Co(NH3)6(NpO2C3H2O4)2A·H2O (A = OH and NO3)

X-ray diffraction analysis of Co(NH₃)₆(NpO₂C₃H₂O₄)₂NO₃·H₂O (I) and Co(NH₃)₆(NpO₂· C₃H₂O₄)₂OH·H₂O (II) showed that they consist of [NpO₂C₃H₂O₄] _n ^{n -} infinite anionic chains, [Co(NH₃)₆]^{3 +} cations, NO₃ ^- (I) and OH^- (II) anions, and molecules of crystallization water. The anionic chain structure is similar to that in the known compound Co(NH₃)₆(NpO₂C₃H₂O₄)₂C₃H₃O₄. Neptunium(V) atoms occur in hexagonal-bipyramidal environment. The coordination capacity of malonate anions is 6, and they simultaneously coordinate three neptunyl(V) cations NpO₂ ⁺ in the chain.     

有机/无机杂化钙钛矿(C4H9NH3)2ZnCl4的制备与表征

合成了新型的有机/无机杂化钙钛矿（C4H9NH3）2ZnCl4,采用元素分析、红外光谱和X射线衍射对其结构进行了表征,结果表明这种材料具有规则的层状结构,有序性高,热分析结果表明（C4H9NH3）2ZnCl4在170℃的高温处存在一个固-固相转变。     

非线性光学晶体MnHg(SCN)4(C2H6SO)2的热学和光学性质的测定

制备了一种新型非线性光学晶体二甲亚砜合硫氰酸汞锰(分子式MnHg(SCN)4(C2H6SO)2,简称MMTD).用热重法、差热分析法、差示扫描量热法、热机械分析法、分光光度法和红外光谱研究了它的热学和光学性质.MMTD晶体具有较好的物理化学稳定性.在27℃时,它的比热为699.5 J/mol·℃.晶体的热膨胀系数为α1=5.33×10-5/℃,α2=4.51×10-5/℃,α3=3.10×10-5/℃.MMTD晶体的截止波长为375nm;透光波段为375-2560 nm.MMTD晶体在标准紫光波长404nm的透过率为44.18%,高于硫氰酸汞锰(MMTC)晶体.     

杂化钙钛矿(HOC2H4NH3)2CuCl4的制备与表征

采用低温溶液法合成了新型层状有序的含有羟基的有机/无机杂化钙钛矿材料(HOC₂H₄NH₃)₂CuCl₄, 采用元素分析、红外光谱、紫外-可见光吸收光谱、X射线衍射和X射线吸收精细结构等手段对其结构与性能进行了表征。结果表明:该材料通过无机框架诱导有机组分有序排列, 形成了规则的层状结构, 有序性高。该杂化钙钛矿材料的分解温度为212℃, 电阻率为2.86×10⁶ Ω·cm, 比不含羟基杂化钙钛矿的电阻率低两个数量级。紫外-可见光吸收光谱显示285 nm左右有一归因于电子从Cl(3p)价带顶跃迁到Cu(4s)导带底而产生的吸收峰。X射线吸收精细结构谱图表明: 二维层状杂化钙钛矿晶体中的Cu²⁺与6个Cl^-形成八面体配位, Cu-Cl键长为0.191 nm, 层间距为1.099 nm。     

Synthesis and crystal structures of a new (2,3-(CH3)2C6H3NH3)H2XO4 (X=P,As)

The aim of encapsulation of 2,3-dimethylanilinium cation in (H₂XO₄)_n polymeric anion chains is to build acentric frameworks that are efficient for non-linear optical (NLO) applications. The synthesis and structures of two new inorganic–organic NLO crystals with general formula (2,3-(CH₃)₂C₆H₃NH₃)H₂XO₄ (X=P, As) are reported. The magnitude of their second harmonic generations (SHG) responses was found to be between the KDP and urea. They crystallize with monoclinic unit-cells and are isotopic. We have determined the structure of phosphoric salt. The following unit-cell parameters were found: a=8.866(3) Å, b=5.909(6) Å, c=10.644(5) Å, β=112.44(1)°, V=515.5(5) Å³ and D_X=1.412 g cm⁻³. The space group is P2₁ with Z=2. The structure was refined with R=0.041 (R_w=0.057) for 1652 reflections with I≥3σ(I). It exhibits infinite (H₂PO₄)_nⁿ⁻ chains. The organic groups (2,3-(CH₃)₂C₆H₃NH₃)⁺ are anchored between adjacent polyanions through multiple hydrogen bonds. Chemical preparation, crystal structure, calorimetric and spectroscopic investigation are described.     

Nucleation studies in supersaturated aqueous solutions of (NH4)H2PO4 doped with (NH4)2C2O4·H2O

Induction periods were measured for various supersaturated aqueous solutions of ammonium dihydrogen orthophosphate doped with ammounium oxalate monohydrate by the direct vision method. Various critical nucleation parameters were calculated based on classical theory for homogeneous crystal nucleation and the results reported and discussed. The critical nucleation parameters increased with increase in doping concentration.     

Preparation and blue–white luminescence properties of Bi3+-doped Ba5SiO4Cl6

The Ba₅SiO₄Cl₆:Bi³⁺ phosphor was synthesized by high-temperature solid-state reaction and its luminescence property was investigated. The results showed that the Bi³⁺-doped Ba₅SiO₄Cl₆ phosphors exhibited an intense blue–white light emission located at 480 nm and a broad excitation band from 230 to 340 nm. The Bi³⁺-doped Ba₅SiO₄Cl₆ phosphors can be efficiently excited by the incident light of 220–340 nm, and the emission properties of the Bi³⁺-doped Ba₅SiO₄Cl₆ samples are strongly dependent on the excitation wavelength. The emission color tunability can be obtained by changing the excitation wavelength. The visible region emission characteristics of Ba₅SiO₄Cl₆:Bi³⁺ indicates that it can potentially be used as a new efficient blue–white luminescent material.     

Analysis of C2H4 in C2H6 and C2H5D with VUV absorption spectroscopy and a method to remove C2H4 from C2H6 and C2H5D

The photoabsorption cross section of C2H4 was measured in the spectral region 107-183 nm and those of C2H6 and C2H5D were accurately determined in the spectral region 107-162 nm using radiation from a synchrotron as source of VUV light. Typically, C2H4 present as a minor impurity in samples of C2H6 and C2H5D distorted the absorption cross section in curves of C2H6 and C2H5D in the onset region. We completely eliminated C2H4 from C2H6 and C2H5D using adsorption on activated Pd/charcoal at 195 K. By this means, we detected no C2H4 in samples of C2H6 and C2H5D according to their absorption spectra. The detection limit of C2H4 in C2H6 and C2H5D is less than 0.03 ppm with VUV absorption spectroscopy.     

Preparation and thermal decomposition of hexa-ammonium tetraphosphate dihydrate(NH4)6P4O13·2H2O

Hexa-ammonium tetraphosphate dihydrate, (NH4)6P4O13·2H2O (HATP), was prepared by the hydrolysis of sodium cyclo-tetraphosphate with sodium hydroxide solution, followed by ion-exchange with ammonium. Thermal decomposition in static air was first carried out dynamically, at a heating rate of 5 K min-1 as used in thermal analysis (thermogravimetric-differential thermal analysis), and also isothermally. To examine the effect of humidity on the thermal decomposition, HATP was heated isothermally in streams of dry and humid air. The products were characterized by X-ray diffraction analysis and high-performance liquid chromatography–flow injection analysis. At 100°C, HATP was decomposed to mono- and triphosphates and to 2 mol diphosphate, and this was accelerated by humidity. Further degradation of the triphosphate to mono- and diphosphates took place slowly. The 2 mol diphosphate also decomposed slowly to 4 mol monophosphate. At temperatures above 150°C, the form I of ammonium polyphosphate (I-APP) was produced. I-APP was further hydrolysed by humidity to shorter-chain phosphates, such as mono-, di- and triphosphates. This revised version was published online in November 2006 with corrections to the Cover Date.     

DC electrical conductivity of CoSiF6·6H2O and (NH4)2SO4

D.C. electrical conductivity of single crystals of (NH₄)₂SO₄ and CoSiF₆·6H₂O have shown conductivity jump near their respective structural transition temperature. Activation energy of (NH₄)₂SO₄ has been found to be consistent with the earlier data. However, CoSiF₆·6H₂O has given prolonged aging effect due to dipolar relaxation and formation of space charge polarisation.σ _true andP _max have been measured.P _max has shown a negative maximum at the transition point. Activation energy of ZnSiF₆·6H₂O has been found to be comparable with CoSiF₆·6H₂O.     

Synthesis and characterization of a new p-phenylenediammonium dihydrogenmonophosphate [p-NH3C6H4NH3][H2PO4]2

Chemical preparation, crystal structure and NMR spectroscopy of a new organic cation p-phenylenediammonium monophosphate [p-NH₃C₆H₄NH₃][H₂PO₄]₂ are presented. This new compound crystallizes in the orthorhombic system, with the space group Pnma and the following parameters: a = 7.970 (2) Å; b = 22.770 (7) Å; c = 7.000 (7) Å, V = 1270.3 (11) Å³, Z = 4 and D_x = 1.590 g cm⁻³. The crystal structure has been determined and refined to R = 0.043 and R_(w) = 0.057 using 2623 independent reflections. The structural arrangement can be described as inorganic layers of (H₈P₄O₁₆)⁴⁻ units, parallel to (a, c) planes. The organic groups (p-H₃NC₆H₄NH₃)²⁺are anchored between the phosphoric layers to form a three-dimensional infinite network. This compound is also investigated by IR and solid-state ¹H, ¹³C and ³¹P MAS NMR spectroscopies. The ab initio method is used in the calculation of chemical shifts.     

Dielectric properties of K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3

Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static dielectric constant at room temperature are 7.67 and 4.80 for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K₂Zn₂(SO₄)₃ and (NH₄)₂ Mg₂(SO₄)₃ respectively.     

Preparation of SiO2 films from Si(OC2H5)4-C2H5OH-H2O solutions without catalysts

Thin and homogeneous SiO₂ films were prepared on aluminium plates from Si(OC₂H₅)₄-C₂H₅OH-H₂O solutions which had controlled compositions and did not contain any acid as a catalyst. Aluminium with the coatings showed good corrosion resistance. However, SiO₂ films prepared from alkoxide solutions with HCI contained Cl^– ions. Aluminium with coatings including Cl^– ions corroded in a corrosion test. Alkoxide solutions without acids were necessary for use in the coating of aluminium. The transformation of gels prepared from solutions without acids to amorphous SiO₂ was investigated.     

APCVD法制备掺氮二氧化钛薄膜及其性能研究

采用常压化学气相沉积(APCVD)法,以四氯化钛(TiCl4)、氧气(O2)氨气(NH3)作为先驱体,成功制备了掺氮二氧化钛(TiO2)薄膜.通过对其进行扫描电镜(SEM)、X射线衍射(XRD)、紫外可见透过光谱(UV-VIS)研究后发现,氮掺杂后在二氧化钛薄膜中引入Ti4O7相,抑制了锐钛矿相向金红石相的转变,光吸收限发生红移,相应从365.8nm红移到了402.6nm,提高了薄膜在可见光照射下的光催化效率,并改善了薄膜表面的亲水性能.