DDAC LB膜的电学性质研究（II）—电荷衰变

在DDAC单分子层在气—液界面上的各种性质以及多分子层电导率随相对湿度的非线性变化[1-3]的基础上,介绍单分子层及多分子层在不同湿度条件下静电电荷随时间横向衰变的情况。使用半导体（或晶体）电荷渗透的理论来解释多分子层电荷衰变的非线性变化与相对湿度的关系。实验数据表明,电荷衰变可以分成两个阶段,即开始时的迅速衰变和随后的缓慢衰变过程。尽管DDAC是绝缘材料,可是它有良好的向空间吸附水分的能力,因而,其导电能力和驱除静电的能力比聚脂材料要好得多。DDAC不仅是一种良好的纤维软化剂而且在一定的相对湿度条件下具有较高的疏电导电能力。     

硅表面化学镀银晶籽层生长过程的研究

室温下在HF+AgNO₃溶液中于硅表面制备了银晶籽层。利用开路电位时间曲线（OCP-t）、阳极溶出伏安法（ASV）以及扫描隧道显微镜（STM）等方法研究了硅表面银晶籽层的形成过程，解释了银晶核长大的过程。提出了银晶籽在硅表面的生长机理是：首先是在硅表面没有被完全覆盖的情况下，单层银晶籽生长的同时伴随有多层的生长，此后单层逐渐形成连续的薄膜，在单层晶籽层上多层薄膜逐渐增厚，并伴随有部分银原子向硅中的扩散。     

锇—聚乙烯吡啶复合物与辣根过氧化物酶分子多层膜的制备及其电化学性质研究

基于分子间静电相互作用力，将锇－聚乙烯吡啶复合物（PVP－OS）与辣根过氧化物酶（HRP）交替沉积于固体基质表面，制得了包含生物成分的分子多层膜，膜层间的聚合物分子起到了粘接与导电的双重作用，用紫外－可见光谱法跟踪了石英基片上的组装过程，研究了多层膜电极对过氧化氢的电催化还原性能，并描述了多层膜电化学行为。     

聚苯胺/苯乙烯-丁二烯-苯乙烯复合材料伸长过程中的导电性变化

以简化物理模型为基础，用实测电流与理论电流之比来研究导电橡胶伸长中电导率的变化，并建立相应测试方法．聚苯胺（ＰＡｎ）／苯乙烯 丁二烯 苯乙烯三嵌段共聚物的复合物用现场乳液聚合法制备．此复合物可熔融加工（ＭＰ）和溶液加工（ＳＰ）．ＳＳＰ样为ＳＰ样用间甲酚二次掺杂处理制得．对ＰＡｎ质量分数为１１０％的复合物进行电导率随伸长变化测试结果表明：ＭＰ样随伸长增加其电导率显著提高，在伸长率为４５０％时，其电导率是初始值（σ０）的１５６倍；ＳＰ样在伸长过程中电导率随伸长而增加，在伸长率为５００％时，其电导率是σ０的５２倍；而ＳＳＰ样在整个伸长过程中电导率变化较小，σ０＜σ＜２σ０．可从复合物的聚集态结构解释以上现象．ＳＳＰ样在导电组分的含量接近逾渗域值时电导率随伸长迅速下降．而当导电组分含量高于逾渗域值时电导率随伸长表现出小的变化并具规律性，此规律性可用σσ０＝１＋ｋａ＋ｂｋ２经验公式来表达（ａ，ｂ为与含量相关的常数）．此结果是由于ＳＳＰ样中导电组分在二次掺杂过程中分子链间存在弱相互作用而自行组成导电网络     

修饰Langmuir-Blodget膜法制备聚(3,4-亚乙基二氧噻吩)薄膜结构和导电性能的研究

采用修饰Langmuir-Blodget(LB)膜法以二十烷酸(AA)LB膜为模板,通过3,4-亚乙基二氧噻吩(EDOT)单体在LB膜亲水基团间聚合,制备了二十烷酸/聚(3,4-亚乙基二氧噻吩)(AA/PEDOT)复合LB膜.UV-Vis、FTIR和XPS分析表明EDOT在多层膜中有效聚合,生成了PEDOT导电聚合物;X射线衍射(XRD)和二次离子质谱(SIMS)分析表明薄膜具有较好的层状有序结构,进一步研究发现EDOT在AA多层膜中的聚合破坏了原有LB膜的有序性,这可能与聚合过程对层状结构产生的破坏作用有关;采用四探针仪及半导体测试仪研究了薄膜导电性能,发现AA/PEDOT多层膜的电导率随处理时间的变化产生突变,这与多层膜中导电通道的"逾渗"有关,在有效导电网络连通后电导率发生了突变.测试结果还表明AA层和PEDOT层之间具有较为明显的界面,PEDOT显示出较好的定域性,薄膜具有很好的层状有序结构.     

石墨烯吸附TiCl4分子的条件控制及光电性能的理论研究

为研究石墨烯吸附TiCl₄分子的影响因素及其光电性能,探索复合物应用于传感器及透明导电薄膜的可能性,采用第一性原理与蒙特卡罗方法研究TiCl₄气体分子在石墨烯表面的吸附条件控制与光电性能。结果表明：(1)石墨烯对TiCl₄气体分子具有较强的物理吸附作用,Cl原子吸附在其附近相距质心位置最远的碳原子顶位最稳定;(2)温度升高不利于TiCl₄气体分子吸附,气体逸度增加有利于吸附,TiCl₄气体分子插入石墨/双层石墨烯/多层石墨烯时宜将温度维持在TiCl₄沸点附近,并增加气体的压力;(3) TiCl₄的吸附对石墨烯的电子结构进行了调控,使费米能级附近的态密度显著提高,赝能隙减小,有效提高了导电性能;(4)在可见光区域,TiCl₄的吸附对体系的吸收性能影响不大,在提升透明导电薄膜导电性的同时未影响薄膜的光学性能。     

修饰LB膜法制备聚3,4-乙烯二氧噻吩薄膜

采用修饰Langmuir-Blodget(LB)膜法以二十烷酸(AA) LB膜为模板, 通过3,4-乙烯二氧噻吩(EDOT)单体在LB膜亲水基团间聚合, 制备了AA/PEDOT复合LB膜. 实验分析表明薄膜具有较好的层状有序结构, 并进一步研究发现EDOT在AA多层膜中的聚合破坏了原有LB膜的有序性, 这与聚合过程对层状结构产生的破坏作用有关; 研究了薄膜导电性能, 发现AA/PEDOT多层膜的电导率随处理时间的变化产生突变, 这与多层膜中导电通道的“渝渗”有关, 在有效导电网络连通后电导率发生了突变. 测试结果还表明AA/PEDOT膜导电性明显优于PEDOT旋涂膜和十八胺-硬脂酸/聚(3,4)乙烯二氧噻吩-聚苯乙烯磺(ODA-SA/PEDOT-PSS)复合膜.     

基于纳米多孔薄膜光学干涉的光学传感器

光学传感器是一种利用光把介质与目标分子的相互作用转换为光信号的装置.光学干涉是光学传感器中常用的技术,具有无需标记、无破坏性、响应迅速等优点.在光学传感器中光的干涉主要源于从单层薄膜上下表面反射的光或者从多层薄膜各个界面处反射的光.由于纳米多孔薄膜具有较高的比表面积,将其应用于传感器中能够提高传感器的灵敏度、降低检测限.常见的薄膜类型主要有单层、双层、多层（光子晶体）等.本文综述了多孔硅、阳极氧化铝、二氧化钛、金属有机骨架等纳米多孔薄膜材料的光学干涉在传感器中的应用,并对其进行了展望.     

纳米银/聚乙烯复合体的太赫兹光谱学性质

测定了纳米银/聚乙烯(nano-Ag/PE)复合体的电导率和太赫兹时域光谱(THz-TDS),研究了其导电性质和在远红外区的反常吸收特性;结合有效介质理论和Drude理论,利用简化的公式对太赫兹时域光谱测量结果进行了分析,并通过对电导率测量结果进行拟合分析得到了纳米Ag及其表层氧化物的电导率信息.结果表明,nano-Ag/PE复合体的逾渗阈值在0.11附近(体积分数),n值接近4.5,偏离"普适性行为".这是由于颗粒表面的氧化层及颗粒隧穿导电效应所致.与此同时,nano-Ag/PE复合体在THz波段的反常吸收性质与表面氧化层有关.     

电导滴定法研究阳离子乳胶粒的导电性能及其在棉织物上的吸附

阳离子乳胶粒与棉纤维存在静电作用而发生吸附,研究其导电能力与吸附作用具有重要理论和应用价值。 采用电导滴定法通过测定乳胶粒表面氯离子含量,研究了乳胶粒的导电能力,并探讨了乳胶粒在棉纤维表面的吸附模型。 结果表明,阳离子乳胶粒的浓度(cp)在0.05~0.3×10-8 mol/L 范围内与电导率(Λ)呈良好的线性关系(Λ=8.0913cp+1.8093,R2=0.9986);根据电解质理论计算得出阳离子乳胶粒中胶核的极限摩尔电导率在恒定温度（25 ℃）下随着乳胶粒浓度的增加呈降低趋势;此外,阳离子乳胶粒在棉纤维表面的吸附符合Langmuir型吸附模型。     

Role of deliquescence lowering in enhancing chemical reactivity in physical mixtures

Mixtures of deliquescent solids are susceptible to deliquescence lowering, where water vapor condensation occurs in mixtures at a lower critical relative humidity (RH(0mix)) than individual component critical relative humidities (RH(0)s). The purpose of this study was to evaluate the effect of deliquescence lowering on chemical reactivity. Sucrose, citric acid and their physical mixtures were characterized using vapor sorption analysis to determine RH(0) and RH(0mix). Acid-catalyzed sucrose hydrolysis kinetics was determined using polarimetric analysis. Physical mixtures of sucrose and citric acid crystals were prepared and stored at various relative humidities at 22 degrees C. For these physical mixtures, sucrose hydrolysis was found to occur only when the environmental RH exceeded RH(0mix). Degradation kinetics correlated with the storage RH, being fastest at higher RH. In addition, a lag period was initially observed, which was most prominent for samples stored close to RH(0mix). With exposure to RHs below RH(0mix), no sucrose degradation was detected over the experimental time period. In conclusion, mixtures of deliquescent solids showed increased water sorption at lower RHs, which caused solid dissolution and subsequently led to an increase in the chemical reactivity.     

Physisorbed water layer formation on fully hydroxylated mesoporous silicas

Kinetic adsorption isotherms were obtained by gravimetric determination of water adsorption into fully hydroxylated mesoporous silicas using samples exposed to controlled humidity air at 22+/-2 degrees C. Twenty kinetic isotherms at several relative humidities (11, 33, 43, 51, 75, and 85%) were obtained with 11 different batches of silica using this simple procedure to obtain quantitative information on the formation of H2O adsorbates. The H2O surface concentrations obtained from the plateau data of individual kinetic adsorption isotherms at 43 and 51% RH, typically precise to about +/-1%, show that a complete monolayer is formed with negligible second-layer adsorption at these relative humidities. This monolayer has a surface concentration of 7.68+/-0.30 micromol H2O/m2, which is lower than the quasi-equilibrium concentration at these relative humidities obtained by the conventional equilibrium-isotherm procedure. Comparison with the Kiselev-Zhuravlev concentration of silanol groups on fully hydroxylated silicas (7.6+/-0.8 micromol SiOH/m2) confirms 1:1 H2O:SiOH stoichiometry of this monolayer. The presence of partial-layer structures at 2.85+/-0.1 and 5.7+/-0.1 micromol H2O/m2 is suggested by isotherms at 11 and 33% RH, respectively, while a bilayer at approximately 14+/-1 micromol H2O/m2 is suggested by kinetic isotherms at 75 and 85% RH.     

Use of inverse gas chromatography to characterize cotton fabrics and their interactions with fragrance molecules at controlled relative humidity

The present work focused on the surface characterization and fragrance interactions of a common cotton towel at different relative humidities (RHs) using inverse gas chromatography (IGC) and dynamic vapour sorption. The sigmoidal water sorption isotherms showed a maximum of 16% (w/w) water uptake with limited swelling at 100% RH. This means that water interacts strongly with cotton and might change its initial physico-chemical properties. The same cotton towel was then packed in a glass column and characterized by IGC at different relative humidities, calculating the dispersive and specific surface energy components. The dispersive component of the surface energy decreases slightly as a function of relative humidity (42 mJ/m2 at 0% RH to 36 mJ/m2 at 80% RH) which would be expected from swelling of the humidified cotton. The Gutmann's donor constant Kd increased from 0.28 kJ/mol at 0% RH to 0.42 kJ/mol at 80% RH, indicating that a greater hydrophilic surface exists at 80% RH, which is also as expected. Water, undecane and four fragrance molecules (dimetol, benzyl acetate, decanal and phenylethanol) were used to investigate cotton-fragrance interactions between 0 and 80% RH. The adsorption enthalpies and the Henry's constants were calculated and are discussed. The higher values for the adsorption enthalpies of polar molecules such as dimetol and phenylethanol suggest the presence of hydrogen bonds as the main adsorption mechanism. The Henry's constant of dimetol was also determined by headspace gas chromatography measurements at 20% RH, giving a similar value (230 nmol/Pa g by IGC and 130 nmol/Pa g by headspace GC), supporting the usefulness of IGC for such determinations. This work confirms the usefulness of chromatographic methods to investigate biopolymers such as textiles, starches and hairs.     

Investigations of the hygroscopic properties of ammonium sulfate and mixed ammonium sulfate and glutaric acid micro droplets by means of optical levitation and Raman spectroscopy

In the presented work an optical levitation technique performed by means of a focused laser beam, Mie and Raman spectroscopy have been utilized for measuring hygroscopic growth curves and composition of laboratory generated single ammonium sulfate (AS) and internally mixed ammonium sulfate-glutaric acid (GA) droplets in the micrometer range. The generated particles have been found to immediately supersaturate (above 45wt% for AS) at 297 K after capturing in the laser beam. Further increase of the relative humidity (RH) up to 85% does not dilute the droplets under the saturation point. A spontaneous hygroscopic growth takes place at 73.5-78% RH for pure AS. The particle grows with an average factor of 1.62 at the deliquescence relative humidity (DRH). Efflorescence of AS occurs at 43% RH with a corresponding concentration of more than 85wt%. Independent of the mixing ratios in ranges 25/75, 50/50, 75/25% AS/GA mixed particles don't exist as a metastable supersaturated solution droplets in the 35-85% RH range. Instead of growing with increasing relative humidity internally mixed particles build up a solid crystalline layer on the surface. This crystalline phase is not further influenced by ambient relative humidities.     

Reactive uptake of nitric acid onto sodium chloride aerosols across a wide range of relative humidities

Reactive uptake coefficients for nitric acid onto size-selected (d(ve) = 102 and 233 nm) sodium chloride aerosols are determined for relative humidities (RH) between 85% and 10%. Both pure sodium chloride and sodium chloride mixed with magnesium chloride (X(Mg/Na) = 0.114, typical of sea salt) are studied. The aerosol is equilibrated with a carrier gas stream at the desired RH and then mixed with nitric acid vapor at a concentration of 60 ppb in a laminar flow tube reactor. At the end of the reactor, the particle composition is determined in real time with a laser ablation single particle mass spectrometer. For relative humidities above the efflorescence relative humidity (ERH), the particles exist as liquid droplets and the uptake coefficient ranges from 0.05 at 85% RH to >0.1 near the ERH. The droplet sizes, relative humidity and composition dependencies, are readily predicted by thermodynamics. For relative humidities below the ERH, the particles are nominally "solid" and uptake depends on the amount of surface adsorbed water (SAW). The addition of magnesium chloride to the particle phase (0.114 mole ratio of magnesium to sodium) facilitates uptake by increasing the amount of SAW. In the presence of magnesium chloride, the uptake coefficient remains high (>0.1) down to 10% RH, suggesting that the displacement of chloride by nitrate in fine sea salt particles is efficient over the entire range of conditions in the ambient marine environment. In the marine boundary layer, displacement of chloride by nitrate in fine sea salt particles should be nearly complete within a few hours (faster in polluted areas)-a time scale much shorter than the particle residence time in the atmosphere.     

How water fosters a remarkable 5-fold increase in low-pressure CO2 uptake within mesoporous MIL-100(Fe)

The uptake and adsorption enthalpy of carbon dioxide at 0.2 bar have been studied in three different topical porous MOF samples, HKUST-1, UiO-66(Zr), and MIL-100(Fe), after having been pre-equilibrated under different relative humidities (3, 10, 20, 40%) of water vapor. If in the case of microporous UiO-66, CO(2) uptake remained similar whatever the relative humidity, and correlations were difficult for microporous HKUST-1 due to its relative instability toward water vapor. In the case of MIL-100(Fe), a remarkable 5-fold increase in CO(2) uptake was observed with increasing RH, up to 105 mg g(-1) CO(2) at 40% RH, in parallel with a large decrease in enthalpy measured. Cycling measurements show slight differences for the initial three cycles and complete reversibility with further cycles. These results suggest an enhanced solubility of CO(2) in the water-filled mesopores of MIL-100(Fe).     

Halogenated polymeric humidity sensors

The limitations of known organic polymer humidity sensors in humidity-sensing applications may be overcome through the use of halogenated organic polymers having pendant groups of both a relatively strong acidic type and a relatively weak acidic type. The combined advantages of halogen in the polymer and the presence of two pendant functional groups provides for a longer sensor life and stability.Thin membrane films of hygroscopic, fluorinated organic polymer having pendant functional groups of sulfonic acid and of carboxylic acid have been investigated for their electrical and thermodynamic characteristics for humidity sensing at high levels of relative humidity and elevated temperatures. Based on the measured conductance data, values of differential thermodynamic functions of enthalpy and entropy are found to be significantly larger than those previously obtained for a sensor system at relative humidities and temperatures above 70% and 50 °C respectively.     

Encapsulation of polyaniline in 3-D interconnected mesopores of silica KIT-6

Composite material PANI/KIT-6, with polyaniline (PANI) chains encapsulated in the 3-D interconnected pore channels of mesoporous silica, KIT-6, has been synthesized via a gas-phase method. The composite formation and the presence of PANI inside the pore channels of KIT-6 were evidenced by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), small-angle X-ray scatter (SAXS), transmission electron microscopy (TEM), and N₂ adsorption–desorption isotherms. The PANI/KIT-6 composite showed good electrical conductivity (2.4 × 10^?3 S/cm) due to the formation of 3-D networks of PANI inside the 3-D interconnected channels of KIT-6. The resistance of PANI/KIT-6 composite at different relative humidities (RH) was investigated. An essentially linear relationship between the relative resistance of the composite and the relative humidity of the environment was found from 11.3% to 97.3% RH.     

Effect of sodium dodecyl sulfate at different hydration conditions on dioleoyl phosphatidylcholine bilayers studied by grazing incidence X-ray diffraction

The effect of the surfactant content and hydration conditions in the phases of dioleoyl phosphatidylcoline (DOPC)/sodium dodecyl sulfate (SDS) mixtures was studied. To this end, surface X-ray diffraction experiments have been performed on bilayers of the mixtures deposited on hydrophobic silicon wafers by dip coating. To investigate the effect of relative humidity (RH) on bilayer organization, a humidity chamber with dry-wet air control was used, and RH values were fixed between 1 and 65%. Our results showed, in addition to the lamellar phase, a rhombohedral phase in mixtures at low hydration conditions (RH < 30%). The d spacing between lamellae increased with the RH and SDS content. This fact could be associated with a swelling effect that is probably due to the localization of water molecules between the polar headgroups of the DOPC and SDS forming the bilayers. The electron-density profiles calculated by Fourier reconstruction of the lamellar stacking for the different samples also confirmed this fact. In addition, the increase in d spacing could be related to the increase in the hydrophilic character of the mixture when the SDS content increases. The rhombohedral phase was more clearly observed in mixtures with high SDS content. Thus, the stalk structure of the rhombohedral phase could be facilitated because of the SDS contribution to inverse structures.