Solvation forces between molecularly rough surfaces

Surface heterogeneity affects significantly wetting and adhesion properties. However, most of the theories and simulation methods of calculating solid-fluid interactions assume a standard thermodynamic model of the Gibbs' dividing solid-fluid interface, which is molecularly smooth. This assumption gives rise to a layering of the fluid phase near the surface that is displayed in oscillating density profiles in any theories and simulation models, which account for the hard core intermolecular repulsion. This layering brings about oscillations of the solvation (or disjoining) pressure as a function of the gap distance, which are rarely observed in experiments, except for ideal monocrystal surfaces. We present a detailed study of the effects of surface roughness on the solvation pressure of Lennard-Jones (LJ) fluids confined by LJ walls based on the quenched solid density functional theory (QSDFT). In QSDFT, the surface roughness is quantified by the roughness parameter, which represents the thickness of the surface "corona" - the region of varying solid density. We show that the surface roughness of the amplitude comparable with the fluid molecular diameter effectively damps the oscillations of solvation pressure that would be observed for molecularly smooth surfaces. The calculations were done for the LJ model of nitrogen sorption at 74.4 K in slit-shaped carbon nanopores to provide an opportunity of comparing with standard adsorption experiments. In addition to a better understanding of the fundamentals of fluid adsorption on heterogeneous surfaces and inter-particle interactions, an important practical outcome is envisioned in modeling of adsorption-induced deformation of compliant porous substrates.     

Effect of organo‐modified montmorillonite on flame retardant poly(1,4‐butylene terephthalate) composites

In this paper, the effect of organo‐modified montmorillonite (OMMT) on a novel intumescent flame retardant (IFR) system was studied in poly(1,4‐butylene terephthalate) (PBT) composites containing microencapsulated ammonium polyphosphate (MAPP) and melamine cyanurate (MC). Nanocomposite morphology was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal decomposition analysis was studied via thermogravimetric analysis (TGA). Combustion behavior was investigated by microcombustion calorimeter (MCC), limited oxygen index (LOI), and UL‐94 test. Residues obtained after samples treated in muffle furnace at 500°C under air condition for 10 min were analyzed through X‐ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the addition of OMMT improved the flame retardancy of PBT/IFR composites significantly. A mass of microcomposite structure particles formed in the heating or combustion process of PBT/IFR/OMMT nanocomposites were found for the first time in the SEM images, which is strong evidence to confirm the migration or accumulation of montmorillonite and carbonaceous‐silicate materials during the heating or combustion process. Copyright © 2010 John Wiley & Sons, Ltd.     

DESIGN AND CONTROL OF SOAP-FREE HYDROPHILIC-HYDROPHOBIC CORE-SHELL LATEX PARTICLES WITH HIGH CARBOXYL CONTENT IN THE CORE OF THE PARTICLES

Soap-free hydrophilic-hydrophobic core-shell latex particles with high carboxyl content in the core of the particles were synthesized via the seeded emulsion polymerization using methyl methacrylate(MMA),butyl acrylate(BA), methacrylic acid(MAA),styrene(St)and ethylene glycol dimethacrylate(EGDMA)as monomers,and the influences of MMA content used in the core preparation on polymerization,particle size and morphology were investigated by transmission electron microscopy,dynamic light scattering and conductometric titration.The results showed that the seeded emulsion polymerization could be carried out smoothly using "starved monomer feeding process" when MAA content in the core preparation was equal to or less than 24 wt%,and the encapsulating efficiency of the hydrophilic P(MMA-BA-MAAEGDMA) core with the hydrophobic PSt shell decreased with the increase in MAA content.When an interlayer of P(MMAMAA -St)with moderate polarity was inserted between the P(MMA-BA-MAA-EGDMA)core and the PSt shell,well designed soap-free hydrophilic-hydrophobic core-shell latex particles with 24 wt%MAA content in the core preparation were obtained.     

Blue and green upconversion luminescence modification of Tb<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript> co-doped Ca<Subscript>5</Subscript>(PO<Subscript>4</Subscript>)<Subscript>3</Subscript>F inverse opal

Tb³⁺–Yb³⁺ co-doped Ca₅(PO₄)₃F inverse opal photonic crystals were prepared by a self-assembly technique in combination with a sol–gel method. Upconversion luminescence characteristics of the inverse opals were investigated. The results indicate that photonic band gap has a significant effect on upconversion luminescence of Tb³⁺–Yb³⁺ co-doped Ca₅(PO₄)₃F inverse opal. Significant inhibition of the green or blue upconversion luminescence was inspected if the photonic band gap overlapped with the emission band of Tb³⁺ ions.     

Three-dimensional real-time tracking of nanoparticles at an oil-water interface

Single-particle tracking with real-time feedback control can be used to study three-dimensional nanoparticle transport dynamics. We apply the method to study the behavior of adsorbed nanoparticles at a silicone oil-water interface in a microemulsion system over a range of particles sizes from 24 nm to 2000 nm. The diffusion coefficient of large particles (>200 nm) scales inversely with particle size, while smaller particles exhibit an unexpected increase in drag force at the interface. The technique can be applied in the future to study three-dimensional dynamics in a range of systems, including complex fluids, gels, biological cells, and geological media.     

Condition optimization of amperometric determination of chemical oxygen demand using boron-doped diamond sensor

The amperometric determination of chemical oxygen demand (COD) reported by Quan Xie??s group (Electrochem Commun 9:2281, 14), was a rapid, green and simple COD evaluation method. This work focused on testing and verifying this method by using a home-made boron-doped diamond (BDD) film as anode and optimizing the experiment conditions. The BDD thin film electrode was employed as anode and the electrochemical process was run with different experimental parameters including counter electrode, electrode gap, applied potential, electrolyte pH, and temperature. Standard samples were determined in the optimum conditions, a linear range of 19.2?C11,600?mg l^?1 COD and a low detection limit of 0.192?mg l^?1 COD were well established with the present approach. The COD value of the simulated organic wastewater determined by this method agreed well with the standard dichromate method, and it showed good accuracy, stability, and reproducibility.     

Glycosylated Star‐Shaped Conjugated Oligomers for Targeted Two‐Photon Fluorescence Imaging

A glucopyranose functionalized star‐shaped oligomer, N‐tris{4,4′,4′′‐[(1E)‐2‐(2‐{(E)‐2‐[4‐(benzo[d]thiazol‐2‐yl)phenyl]vinyl}‐9,9‐bis(6‐2‐amido‐2‐deoxy‐1‐thio‐β‐D ‐glucopyranose‐hexyl)‐9H‐fluoren‐7‐yl)vinyl]phenyl}phenylamine (TVFVBN‐S‐NH₂), is synthesized for two‐photon fluorescence imaging. In water, TVFVBN‐S‐NH₂ self‐assembles into nanoparticles with an average diameter of ～49 nm and shows a fluorescence quantum yield of 0.21. Two‐photon fluorescence measurements reveal that TVFVBN‐S‐NH₂ has a two‐photon absorption cross‐section of ～1100 GM at 780 nm in water. The active amine group on the glucopyranose moiety allows further functionalization of TVFVBN‐S‐NH₂ with folic acid to yield TVFVBN‐S‐NH₂FA with similar optical and physical properties as those for TVFVBN‐S‐NH₂. Cellular imaging studies reveal that TVFVBN‐S‐NH₂FA has increased uptake by MCF‐7 cells relative to that for TVFVBN‐S‐NH₂, due to specific interactions between folic acid and folate receptors on the MCF‐7 cell membrane. This study demonstrates the effectiveness of glycosylation as a molecular engineering strategy to yield water‐soluble materials with a large two‐photon absorption (TPA) cross‐section for targeted cancer‐cell imaging.     

Composition of essential oil and antioxidant capacity of Centaurea drabifolia Sm. subsp. detonsa (Bornm.) Wagenitz, endemic to Turkey

In this study, composition of essential oil and antioxidant capacity of Centaurea drabifolia subsp. detonsa were investigated. The antioxidant capacity of the methanolic extract was evaluated by various methods including measuring the total phenolic content, total antioxidant capacity, free radical scavenging activity (DPPH assay), β-carotene/linoleic acid bleaching assay and ferric and cupric ion reducing power assay. The composition of essential oil was identified by using gas chromatography-mass spectrometry. Totally, 41 compounds were described in the essential oil. Germacrene D (44.829%) was determined as the major compound of the essential oil. The total phenolic content, total antioxidant capacity, inhibition rate of oxidation of linoleic acid, IC(50) (in DPPH assay) and EC(50) (in reducing power) value were found to be 40.454?mg?GAE/g, 100.840?mg?AAE/g, 65.639%, 39.584?μg?mL(-1) and 0.603?mg?mL(-1), respectively. The results indicated that the extract of C. drabifolia subsp. detonsa has strong antioxidant properties and this species can be used as a natural antioxidant in food processing and pharmaceutical industries.