基于Fe(Ⅲ)和邻苯二胺显色反应快速检测硫化物

比较了不同金属离子(Fe²⁺、Fe³⁺、Cu²⁺、Zn²⁺、Al³⁺、Na⁺、Ca²⁺、Mg²⁺、K⁺、Ag⁺、Cr³⁺)对邻苯二胺(OPD)的氧化能力，基于Fe³⁺能直接氧化OPD产生黄色发荧光的产物而构建了Fe³⁺-OPD显色体系。结合硫化物的还原性以及对金属离子较强的亲和性，开发了一种通过比色法选择性检测硫化物的方法。结果表明，在pH 4.0Na Ac-HAc缓冲液中，Fe³⁺-OPD显色体系的吸光度和荧光强度与NaHS的浓度分别在10～200μmol/L和5～150μmol/L范围内呈线性关系，荧光法的检出限可达0.1μmol/L，体系内其他还原性物质及硫醇对Na HS的检测无干扰。将Fe³⁺-OPD显色体系结合纸芯片构建的纸基比色体系蓝色分析色道值(B...     

基于二苯甲酮Schiff碱Fe3+荧光分子探针

以2,4-二羟基二苯甲酮（UV-0）和邻苯二胺合成了Schiff碱L荧光分子探针,采用FT-IR、HNMR和MS对其结构进行了表征。在V(EtOH):V(HEPES)=95:5 （pH=7.2）缓冲溶液中,L能够通过on-off荧光响应选择性识别Fe3+,且几乎不受其他金属离子的干扰。在Fe3+（0～7.0  10-5 mol/L）浓度范围内,溶液荧光强度与Fe3+浓度呈现良好的线性关系。L对Fe3+检出限为1.9410-7 mol/L,二者的结合常数为2.0104 (mol/L)-1。     

碘化钾-Cd(Ⅱ)-罗丹明B离子缔合分光光度法测定土壤中微量镉

将0. 5 g土壤进行消解,采用碘化钾-Cd(Ⅱ)-罗丹明B离子缔合分光光度法测定土壤中微量镉,最佳反应条件:加入2 m L浓度1 mol/L H2SO4,20%碘化钾-抗坏血酸溶液3 m L,显色40 min,在波长588 nm处测定离子缔合物吸光度。结果表明,Cd(Ⅱ)浓度在0. 25～2. 0μg/m L范围内符合郎伯-比尔定律。本方法测定结果相对标准偏差小于2%,方法检出限2. 1μg/kg,加标回收率98. 90%～100. 60%。实验表明,校园内土壤镉含量0. 035～0. 050 mg/kg范围内,几乎无金属镉污染。     

荧光桃红光度分析法测定药物制剂中盐酸氯丙嗪

在酸性介质中,盐酸氯丙嗪与荧光桃红反应,使荧光桃红溶液颜色发生明显改变,据此建立了一种研究测定盐酸氯丙嗪的新方法.最大吸收波长为540 nm,表观摩尔吸光系数为1.49×10(4)L/(mol·cm),盐酸氯丙嗪的浓度在0.5～3.0 μg/mL范围内呈良好的线性关系,检测限为0.34 μg/mL,相对标准偏差为1.2...     

Fe（Ⅲ）-EDTA和酚三元络合物光度法测定工业废水中痕量酚

探讨用深色稳定的Fe（Ⅲ）-EDTA络合物测定苯酚时的条件选择和确定。实验结果表明：苯酚在标准曲线线性范围内,加入0.1mol/L,pH值约8～9的Fe（Ⅲ）-EDTA溶液6.0mL,常温下显色25min后,于波长500nm处进行比色,有色络合物在2h内吸光度无变化。在上述条件下,吸光度与浓度有着很好的线性关系,其相关系数γ=0.9999,E=108,平行测定SD=0.001.RSD=0.26%。该法简单、快速、精密度高。     

一种Hg~(2+)离子探针的合成及表征

设计并合成了一个Hg2+离子选择性化学传感器化合物EBHN,该化合物含有偶氮基团,其结构得到了1HNMR、ESIMS和元素分析的确认。实验结果表明,在混合的水溶液体系中,p H 5~9范围内,该化合物对Hg2+离子表现出高选择性和高灵敏度的显色传感,体系的发光伴随着汞离子的加入,溶液颜色由橙色变成黄色。Hg2+离子浓度在0.5~5μmol/L范围内时,线性相关系数R=0.998 7,最低检出限为0.12μmol/L(n=6)。     

蓝色荧光碳点的制备及检测、防伪应用

以柠檬酸钠为碳源、氨水为氮源,采用一步水热法制备了氮掺杂碳点(NCDs),对其制备条件进行了优化.采用荧光光谱仪、TEM、AFM、XPS及FTIR对制备的NCDs进行了表征,并探索了NCDs在Fe3+检测及荧光防伪中的应用.结果表明,NCDs的最优制备条件为柠檬酸钠浓度为0.1 mol/L、氨水浓度为1.8 mol/L、反应温度为200℃、反应时间6 h、装载体积25 mL.在最优条件下制备的NCDs的荧光为典型的非激发波长依赖型,最佳激发波长为343 nm,最佳发射波长为443 nm,荧光量子产率可达54.9％.NCDs为球形结构,平均粒径为4.96 nm,碳核为类石墨烯结构且其表面含有—NH2、—OH及—COOH.NCDs的荧光可被Fe3+选择性猝灭,且荧光猝灭程度与Fe3+浓度在0.1～87.5μmol/L范围内线性关系良好,检测限为50 nmol/L.此外,将NCDs配制成荧光墨水,利用喷墨打印机打印出的图案整体饱满、边缘细节清晰具有很强的可识别性.     

基于罗丹明衍生物的Fe(Ⅲ)荧光探针的合成及其性能研究

设计并合成了两种罗丹明类Fe3+荧光分子探针L1、L2,并用核磁和质谱对其结构进行了表征,同时对目标探针进行了荧光光谱性能测试。研究表明:当体系为V(DMF)∶V(H2O)=1∶1时,这两种探针对Fe3+均具有较好的选择性,且基本不受其他离子的干扰;当Fe3+浓度在60~120μmol/L和40~300μmol/L范围内时,L1和L2荧光强度均与之呈现良好的线性关系;通过Job's曲线发现探针与Fe3+的配合比为1∶2。     

新荧光试剂双[3-(3,5-二溴吡啶)重氮氨基]-联苯的合成及其分析应用

合成了新荧光试剂双[3-(3,5-二溴吡啶)重氮氨基]-联苯(BBPDDP)。其结构经元素分析、红外光谱证实。研究表明,在碱性介质中,该试剂在λex/λem=248 nm/304 nm处产生荧光,且能与Fe3+配合并使BBPDDP的荧光猝灭。据此建立了BBPDDP对Fe3+的新荧光分析法。该方法的线性范围为4.5×10-9~9.0×10-7 mol/L,检测限为8.4×10-9 mol/L。将其应用于香蕉中Fe3+的测定,结果满意。     

一种新型比率型次氯酸根荧光探针的合成及性能研究

以4-二苯氨基苯甲醛为原料,与水合肼进行缩合反应,设计合成一种识别0C1_的比率型荧光探针.通过光谱分析,加入oCl-,荧光发射强度明显升高,溶液颜色由黄色变为无色,实现裸眼识别;加入其他分析物,荧光强度无明显变化.在0.5～1 μmol/L的浓度范围内,荧光强度与次氯酸根浓度呈良好的线性关系,最低检出限为0.44pm...     

Effect of carbonation on the hydro-mechanical properties of Portland cements

We evaluate experimentally the effect of carbonation on the hydro-mechanical properties of Portland cement. Samples were carbonated at 90 °C and 28 MPa under wet supercritical CO₂. Two types of carbonation features were achieved, either the samples were homogeneously carbonated or they displayed sharp carbonation fronts. Using a tri-axial apparatus, the static elastic moduli and the mechanical strength were measured at in-situ pressure conditions (28 MPa) and showed a degradation of the mechanical properties of the samples where a carbonation front prevailed. Water and gas permeabilities were measured and showed that the samples with a carbonation front exhibit a stress sensitive permeability. P and S elastic wave velocities were measured to evaluate dynamic (ultrasonic range, 1 MHz) elastic moduli. The use of an effective medium theory approach enabled us to characterize the density and distribution of cracks within the samples. This approach outlines that the samples which developed a carbonation front were damaged.     

Influence of the nature of aggregates on the behaviour of concrete subjected to elevated temperature

An experimental study is carried out on concretes composed of three different types of aggregates: semi crushed silico-calcareous, crushed calcareous and rolled siliceous. For each aggregate type, two water/cement ratios (W/C), 0.6 and 0.3 are studied. Aggregates and concrete specimens were subjected to 300, 600 and 750 °C heating–cooling cycles. We analyse the evolution of thermal, physical and mechanical properties of concrete in terms of behaviour and physical characteristic evolutions of aggregates with temperature. The study of thermal behaviour of aggregates showed the importance of initial moisture state for the flints. The crystallisation and microstructure of quartz play an important role in the thermal stability of siliceous aggregates. The residual mechanical behaviour of concrete varies depending on the aggregate and the influence of aggregates is also dependent on paste composition. This study allowed to better understand the influence of chemical and mineralogical characteristics of aggregates on the thermomechanical behaviour of concrete.     

Assessment of the long-term stability of cementitious barriers of radioactive waste repositories by using digital-image-based microstructure generation and reactive transport modelling

Cement-based grout plays a significant role in the design and performance of nuclear waste repositories: used correctly, it can enhance their safety. However, the high water-to-binder ratios, which are required to meet the desired workability and injection ability at early age, lead to high porosity that may affect the durability of this material and undermine its long-term geochemical performance.In this paper, a new methodology is presented in order to help the process of mix design which best meets the compromise between these two conflicting requirements. It involves the combined use of the computer programs CEMHYD3D for the generation of digital-image-based microstructures and CrunchFlow, for the reactive transport calculations affecting the materials so simulated. This approach is exemplified with two grout types, namely, the so-called Standard mix 5/5, used in the upper parts of the structure, and the “low-pH” P308B, to be injected at higher depths.The results of the digital reconstruction of the mineralogical composition of the hardened paste are entirely logical, as the microstructures display high degrees of hydration, large porosities and low or nil contents of aluminium compounds.Diffusion of solutes in the pore solution was considered to be the dominant transport process. A single scenario was studied for both mix designs and their performances were compared. The reactive transport model adequately reproduces the process of decalcification of the C-S-H and the precipitation of calcite, which is corroborated by empirical observations. It was found that the evolution of the deterioration process is sensitive to the chemical composition of groundwater, its effects being more severe when grout is set under continuous exposure to poorly mineralized groundwater. Results obtained appear to indicate that a correct conceptualization of the problem was accomplished and support the assumption that, in absence of more reliable empirical data, it might constitute a useful tool to estimate the durability of cement-based structures.     

New method for determination of absorption capacity of internal curing agents

Accurate assessment of absorption capacity (k) of internal curing agents is necessary to properly proportion cement-based mixtures and to measure their effectiveness in mitigating autogenous shrinkage. Standard methods for quantifying absorption capacity, such as those for coarse and fine aggregate, are not appropriate for the highly absorptive, finely divided materials often used for internal curing. Here, it is demonstrated that the absorption capacity of internal curing materials may be determined from early age heat evolution data measured through isothermal calorimetry. An example application, using pulp fibers as internal curing agents, is used to demonstrate the utility of the method.     

Effects of mixing state of composite powders on sintering behavior of cathode for solid oxide fuel cells

For efficient development of high-performance composite electrodes for solid oxide fuel cells (SOFCs), it is crucial to precisely tailor the microstructural features of the electrodes, such as their grain size, phase connectivity, and pore structure. Herein, we report the effects of the mixing state of component powders of a composite cathode composed of Sr-doped LaMnO₃ (LSM) and yttria-stabilized zirconia (YSZ) on its sintering behavior. LSM-YSZ composite powders were synthesized by a particle-dispersed glycine-nitrate process using YSZ particles as inclusions in the LSM precursor solution. The dispersion state of the YSZ particles in the solution was varied from a well-dispersed state to a highly flocculated state through adjustment of the amount of adsorbed polyethylene glycol. The dispersion state of the component powders was found to strongly impact the densification behavior of the composite, which was explained by the formation of a continuous network of the “slow-sintering” inclusion particles. A highly porous structure with phase connectivity and sufficient triple phase boundaries could be achieved by enhancing the mixing homogeneity and optimizing the mixing scale. The proposed concept provides new insights into the microstructural evolution of composites in constrained sintering, and it could potentially enable development of the ideal electrode structure for SOFCs.     

Influence of chemical degradation on mechanical behavior of a petroleum cement paste

Cement paste used in the Oil Industry is generally subjected to chemical degradation due to flow of acid fluids in various situations. The present study focuses on the evolution of thermo-hydro-mechanical (THM) behavior with chemical degradation of petroleum cement paste. Triaxial compression tests with different confining pressures (0, 3, 10 and 20 MPa) are carried out on a standard oil cement paste in sound state and completely degraded state by ammonium nitrate solution under a temperature of 90 °C. The results obtained show that the material in its initial state exhibits a small elastic phase and a strong capacity of compaction. The mechanical behavior depends on the load induced pore water pressure. Because of the increase in porosity caused by chemical degradation, the mechanical strength (cohesion and friction angle) and Young's modulus decrease. The dependence of mechanical strength and Young's modulus on confining pressure is smaller in the chemically degraded cement paste than in the sound one. In fine, the mechanical behavior of the whole material becomes more ductile. As a result, such effects of chemical degradation should be taken into account when modeling such cement paste materials exposed to such chemical degradations.     

Effect of fibre morphology on flocculation of fibre–cement suspensions

The objective of the present research was to evaluate the effect of fibre morphology (e.g., length, width, fibrillation, broken ends, content of fines and number of fibres per gram) on flocculation and drainage properties of fibre–cement suspensions and on physical properties of the fibre–cement composites. Mechanical refining was used to change the morphological properties of Eucalyptus and Pinus pulps. Results show that the mechanical refining increased the size of the formed flocs and decreased the concentration of free small particles (with dimensions between 1 and 20 µm) as a consequence of the increased fibrillation and content of fines, which increased the capacity of the fibres to capture the mineral particles. High levels of refining were necessary for Pinus pulp to obtain cement retention values similar to those obtained by unrefined Eucalyptus pulp. This is due to the higher number of fibres per gram in Eucalyptus pulp than in Pinus pulp. Pulp refining improved the packing of the particles and, although decreased the drainage rate, it contributed to a less porous structure, which improved the microstructure of the composite.     

Modelling of ageing effects on crack-bridging behaviour of AR-glass multifilament yarns embedded in cement-based matrix

This article focus on modelling of ageing effects on crack-bridging behaviour of AR-glass multifilament yarns embedded in cement-based matrix. In the first step, age-dependent changes in the crack-bridging behaviour of AR-glass multifilament yarns were investigated at the meso and micro levels. Two cementitious matrices were considered where the binder contained Portland cement clinker and ground granulated blast furnace slag cement, respectively. Mechanical characteristics of the bond between matrix and multifilament yarns after accelerated ageing were measured by means of double-sided yarn pullout tests. In these tests the multifilament yarns bridged a single crack in the matrix arising in a notched area of the specimen. Losses in performance with increasing age differed widely depending on matrix material composition. The essential cause of such losses was discovered to be the microscopic densification of the fibre-to-matrix interface. This led to increased bond intensity and restricted slip-ability of the filaments. Subsequently, these micro-structural phenomena were related to the mesoscopic material behaviour by means of a phenomenological bond model. This cross-linkage model describes the crack-bridging effect of the entire multifilament yarn at the single filament level. According to the model, each filament possesses a specific deformation length depending on its position in the cross-section of the yarn. This deformation length depends on bond characteristics between single filament and cementitious matrix, which vary with age. Characteristic values of the model were computed from load-crack width curves obtained from the yarn pullout tests. The changes in the microstructure were represented by the characteristic values of the model.     

Resistivity of cementitious materials measured in diaphragm migration cells: The effect of the experimental set-up

Experimental measurements and numerical analysis were carried out to study the effect of the cell geometry in resistivity determinations. The resistance of the diaphragm in cement paste and mortar samples was determined using impedance spectroscopy. Numerical simulations were performed using finite element method (FEM). Several surface ratios (geometrical diaphragm surface to electrolyte-diaphragm surface, S/S′) were investigated. The thickness of the diaphragm, L, was also considered.The experimental results show a significant decrease of the apparent resistivity when the ratio S/S′ increases. Similar trend was observed for increasing values of the L/S′ ratio. The numerical simulations can explain the experimental findings and also allow to formulate a general rule for the design of migration and diffusion experiments in porous materials.     

Effect of maturation time on the fresh and hardened properties of an air lime mortar

The restoration and maintenance of old renders is one of the key aspects of correct rehabilitation practice. The ideal course of action is to replace the damaged material by a material with compatible characteristics. This work aims to analyze the effect of the maturation process on hardened state characteristics of hydrated powder lime mortars. The rheological characterization shows an air lime mortar thickening behaviour with the length of the test. The different mixes were subjected to a maturation process consisting on keeping them in the fresh state, covered with water, isolated from CO₂, during seven days. The specimens and applications were prepared both with the non-matured and the matured mortars. Maturation seems to influence the hardened state characteristics causing a decrease in the capillary values, and an increase on the mechanical strength, which are more evident for mortars with higher binder contents.