Size effect on thermodynamic parameters for the peanut-like CaMoO4 micro/nano reaction systems

Peanut-like CaMoO₄ micro/nano structures with three different sizes were harvested by a simple reverse-microemulsion method at room temperature. Employing synthesized micro/nano CaMoO₄ and HCl as reaction systems, thermodynamic parameters such as standard molar enthalpy of reaction Δ_r H _m ^θ , standard molar Gibbs free energy of activation Δ _r ^≠ G _m ^θ , standard molar enthalpy of activation Δ _r ^≠ H _m ^θ , and standard molar entropy of activation Δ _r ^≠ S _m ^θ were successfully acquired for the first time by in situ microcalorimetry. Furthermore, change regularities of the thermodynamic parameters for the micro/nano reaction systems were obtained and discussed. It demonstrated that size effect has significant influence on thermodynamic parameters of micro/nano material reaction systems.     

Dielectrophoresis for manipulation of micro/nano particles in microfluidic systems

Dielectrophoretic (DEP) force is exerted when a neutral particle is polarized in a non-uniform electric field, and depends on the dielectric properties of the particle and the suspending medium. The integration of DEP and microfluidic systems offers numerous applications for the separation, trapping, assembling, transportation, and characterization of micro/nano particles. This article reviews the applications of DEP forces in microfluidic systems. It presents the theory of dielectrophoresis, different configurations, and the applications of such systems for particle manipulation and device fabrication.     

不同粒度八面体纳米钼酸镉的表面热力学性质

室温条件下,采用反相微乳液法制备了一系列不同粒度的八面体纳米CdMoO4,并对其组成、结构及形貌进行了表征.基于纳米CdMoO4与块体CdMoO4热力学性质的本质差异,结合化学热力学基本理论与热动力学原理,导出了获取纳米CdMoO4表面热力学性质的关系式;在此基础上,利用原位微量热技术成功获得了所制备的不同粒度八面体纳米CdMoO4的表面热力学函数,如比表面Gibbs自由能、比表面焓和比表面熵.本文为获取纳米材料表面热力学函数提供了一种有效而普适的新方法.     

Luminescence properties of Eu3+ doped CaMoO4 nanoparticles

When Eu(3+) ions occupy Ca(2+) sites of CaMoO(4), which has a body centered tetragonal structure with inversion symmetry, only the magnetic dipole transition ((5)D(0)→(7)F(1)) should be allowed according to Judd-Ofelt theory. Even if there are a few distortions in the Eu(3+) environment, its intensity should be more than that of the electric dipole transition ((5)D(0)→(7)F(2)). We report here the opposite effect experimentally and ascribe this to the polarizability effect of the MoO(4) tetrahedron, which is neighboring to EuO(8) (symmetric environment). The contribution of the energy transfer process from the Mo-O charge transfer band to Eu(3+) and the role of Eu(3+) over the surface of the particle could be distinguished when luminescence decay processes were measured at two different excitations (250 and 398 nm). Further, the luminescence intensities and lifetimes increase significantly with increasing heat-treatment temperature of the doped samples. This is attributed to the reduction of H(2)O from the surface of the particles and a non-radiative process after heat treatment.     

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term “nano” is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms “nano” and “enantiomer separation” on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.     

Dielectric effect on thermodynamic properties in vinblastine by DFT/Onsager modelling

We know that vinblastine, as one of the vinca alkaloids, has played a major role in cancer chemotherapy by inhibiting the polymerisation of tubulin into microtubules. We present an in-depth investigation of the structural, infrared (IR) spectra of vinblastine. The structure of vinblastine is theoretically investigated using the density functional theory and Hartree–Fock levels of theory with the standard 6-31g* and 6-31g** basis sets. The vibrational spectral data obtained from IR spectra are assigned modes based on the results of the theoretical calculations as intensity and frequency curves. The fundamental vibrational modes were characterised depending on the stability of vinblastine in different dielectric constants. Thermodynamic analysis of data demonstrates good correlation of vinblastine at various media by SCRF–Onsager model with linear coefficient (R ²). Thus, the goal of this article is to evaluate and quantify the molecular basis for vinblastine structure in variant positions.     

The solubility of CaMoO4(c) and an aqueous thermodynamic model for Ca2+-MoO 4 2 -ion-interactions

The solubility of powellite [CaMoO₄(c)] was studied in aqueous Na₂MoO₄, CaCl₂ and Ca(NO₃)₂ solutions ranging in concentrations from 1×10^–4M to 1.0M and over equilibration times extending to 36 days. Our experimental data were interpreted using the aqueous ion-interaction model of Pitzer and coworkers. The Ca²⁺–MoO ₄ ^2– ion-interactions were found to be analogous to Ca²⁺–SO ₄ ^2– . The use of Ca²⁺–MoO ₄ ^2– ion-interactions parameters (⁽⁰⁾=0.2, ⁽¹⁾ = 3.1973 and ⁽²⁾) and a logK _sp of –7.93 gave excellent predictions of all of the experimental data. Commonion ternary interaction parameters such as MoO ₄ ^2– –Cl^– or MoO ₄ ^2– –NO ₃ ^– were not required.     

Fabrication of micro reaction cages with tailored properties

Hollow polyelectrolyte capsules in micro- and submicrometer size were prepared. Their interior was functionalized by a "ship in bottle" synthesis of copolymers. While the monomers permeated the capsule wall easily, the formed polymers remained in the capsule cage. The physicochemical properties of the capsule interior such as ion strength, pH, light absorption, and fluorescence could be controlled independently from the surrounding solvent by means of the chemical nature of the captured polymer. In case of polyelectrolytes the osmotic pressure of the counterions led to a swelling of the capsules which can be important for micromechanics. The functionalization with light-sensitive materials allowed selective photoreactions inside the capsules. Synthesis of polyelectrolytes at high concentration resulted in an intertwining of the capsule wall with the polymer. The modified walls behaved like ion exchange membranes and showed selectivity toward adsorption and permeation of organic ions. The modified capsules offer many possibilities for novel applications as containers for controlled precipitation, as nanoreactors for catalyzed reactions, or as sensors.     

银基微纳米半导体光催化应用研究进展

综述了银基微纳米半导体光催化应用研究进展.指出银基微纳米半导体在可见光辐照下表现出良好的光催化性能(光催化降解有机物或光解水制氢制氧),目前的研究主要集中在简单的含银化合物、含银的异质结构、含银的多金属氧化物和含银的固溶体这几类;并从光催化原理和能隙调节手段入手阐述了决定其光催化性能的因素.     

Strategies and opportunities of micro/nano delivery systems for targeted therapy of ulcerative colitis: Focus on underlying mechanisms and future perspectives

Ulcerative colitis(UC) is a common progressive inflammatory disease whose incidence has increased rapidly in recent years, and can develop into colorectal cancer in severe cases. There are currently no adequate or effective treatments for UC due to the fact that some patients have found suboptimal results after repeated administration, while others have experienced adverse effects. With the rapid development of nanotechnology, developing innovative colon-targeting platforms is essential to impro...     

The thermodynamic properties of 4-pentenoic acid

The enthalpy of formation of liquid 4-pentenoic acid was determined by combustion calorimetry. The vapor pressure and enthalpy of vaporization of the compound were measured by the transfer method over the temperature range 289–324 K. Conformational analysis was performed. The equilibrium structure, fundamental vibrations, moments of inertia, and total energy of the stablest acid conformers were calculated by the B3LYP/6-311G(d, p) and G3MP2 quantum-chemical methods. The experimental IR spectrum and calculated vibrational frequencies were used to assign IR bands. The thermodynamic properties of monomeric 4-pentenoic acid in the ideal gas state were calculated over the temperature range 0–1500 K. Additive and quantum-chemical methods were used to estimate the Δ_f H°(g) and Δ_vap H° values. Close agreement between the calculation results and experimental data was obtained. It was shown that additive and quantum-chemical methods could be used for estimating the enthalpies of formation and vaporization of nonconjugated alkenoic acids.     

Superhydrophobic surface based on micro/nano structured ZnO nanosheets for high-efficiency anticorrosion

Journal of Solid State Electrochemistry - There are two key factors in the fabrication of superhydrophobic surfaces. One is to have the appropriate micro/nano structure, and the other is to reduce...     

Ethylene glycol-assisted electrochemical synthesis of CaMoO4 crystallites with different morphology and their luminescent properties

CaMoO₄ crystallites with different morphology were successfully prepared by an electrochemical method with the assistance of ethylene glycol (EG) for the first time. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescent spectra techniques (PL), respectively. The results showed that the crystallization of CaMoO₄ relies on both applied electric current intensity and EG content in the electrolytic solution. With the increase of EG content, CaMoO₄ crystallite sizes decreased, and their morphology gradually changed from a cake-like shape into micro-rods with a higher aspect ratio. Moreover, the higher the applied electric current intensity, the more obvious the above effect was. All samples exhibit a green emission centered at 512 nm with 280 nm excitation wavelength at room temperature, but show different PL intensity.     

Fracture toughness and surface morphology of micro/nano sized fibrils-modified epoxy resin

Two kinds of micro/nano sized fibrils based on cellulose (MFC) and polyvinyl alcohol (PVA) were used as reinforcer for epoxy resin (EP) with different contents in the range from 0 to 0.3 wt %. PVA nanofibers with diameter about 40–80 nm were fabricated by electrospinning technique. The analysis of mechanical properties showed that by both adding MFC and PVA to EP the fracture toughness was increased. The SEM results showed that micro/nano sized fibers dispersed throughout epoxy resin, prevented and changed the path of crack growth.     

The physicochemical properties of micro/mesoporous materials prepared by the recrystallization of zeolite BEA

Micro-mesoporous materials with various ratios between micro- and mesopores were prepared by the recrystallization of zeolite BEA in an alkaline medium in the presence of cetyltrimethylammonium bromide. The materials were characterized by X-ray diffraction, low-temperature nitrogen adsorption, and IR spectroscopy. Recrystallization under mild conditions did not cause substantial changes in the number of acid centers but increased the accessibility of acid centers to large-sized molecules because of the creation of mesopores. An increase in the degree of recrystallization caused first partial and then complete zeolite transformation into MSM-41 mesoporous aluminosilicate, which was accompanied by a decrease in the number of acid centers. The IR spectra were used to determine the diffusion coefficients of cumene in the initial and recrystallized samples. Recrystallization increased the diffusion coefficient by 3–4 times. Original Russian Text ? V.V. Ordomskii, Yu.V. Monakhova, E.E. Knyazeva, N.S. Nesterenko, I.I. Ivanova, 2009, published in Zhurnal Fizicheskoi Khimii, 2009, Vol. 83, No. 6, pp. 1150–1155.     

Synthesis of nano/micro scale ZSM-5 from kaolin and its catalytic performance

Nano/micro scale ZSM-5 zeolites were synthesized by using natural kaolin as raw material. The effect of particle size on the catalytic performance of ZSM-5 zeolite for the methanol to olefins conversion was evaluated in a fixed-bed reactor. The results indicated the crystal size had a significant effect on the catalytic stability and the products distribution. ZSM-5 with nanosize showed better tolerance to coke formation, longer catalytic lifetime, and higher selectivity to propylene. The selectivity to propylene on nanosized ZSM-5 was on average 4.5% higher than on the submicron sample and 10% higher than on microsized ZSM-5. After the reaction was conducted for 20 h the ZSM-5 catalyst synthesized from kaolin showed longer lifetime and higher propylene selectivity than the sample synthesized with chemical materials The reason can be explained by the occurence of such elements as Fe, P, and especially Ti.     

Zeolite 4A: heat capacity and thermodynamic properties

The heat capacity of zeolite 4A (also known as LTA, Linde Type A and sodium zeolite A), in the temperature range from 37 to 311 K, is reported. The heat capacity shows no anomalies in this temperature range. Thermodynamic parameters, H, S and G, relative to their values at T=0 K were derived. From these data, we find that zeolite 4A is stabilized by strong enthalpic interactions. Furthermore, its thermodynamic stability results from the strong Si---O and Al---O bonds in the primary building units, with bond strengths very close to those in other similar materials.     

Thermodynamic properties of epoxy reaction systems

Enthalpy, entropy, and Gibbs free energy of epichlorhydrin, bisphenol A, and epoxy resins from specific heat data obtained experimentally in a DuPont 900 differential thermal analyzer are described. The epoxy resin used has a second-order transition temperature around ?15°C and a chain rigidity of 50.6 cal/g.