Precipitation and recrystallization of uniform CuCl particles formed by aggregation of nanosize precursors

Uniform, spherical CuCl particles were obtained by mixing aqueous solutions of CuCl ₂ and ascorbic acid in the presence of polyvinylpyrrolidone (PVP) as dispersing agent. The size and the uniformity of the resulting particles depended on the volume ratio of the reactant solutions, their concentrations, the distribution of the stabilizers, and the mixing method. The single jet precipitation yielded large spheres of broad size distributions, while the particles obtained by the double jet technique were rather uniform in size. The final colloidal CuCl particles were formed by the aggregation of nanocrystals, initially generated in the system. Depending on the pH of the reaction mixture, these particles slowly change to large CuCl crystals on aging in the mother liquor.     

ALD resist formed by vapor-deposited self-assembled monolayers

A new process of applying molecular resists to block HfO2 and Pt atomic layer deposition has been investigated. Monolayer films are formed from octadecyltrichlorosilane (ODTS) or tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS) and water vapor on native silicon oxide surfaces and from 1-octadecene on hydrogen-passivated silicon surfaces through a low-pressure chemical vapor deposition process. X-ray photoelectron spectroscopy data indicates that surfaces blocked by these monolayer resists can prevent atomic layer deposition of both HfO2 and Pt successfully. Time-dependent studies show that the ODTS monolayers continue to improve in blocking ability for as long as 48 h of formation time, and infrared spectroscopy measurements confirm an evolution of packing order over these time scales.     

Synthesis of nanosize europium oxide particles by using W/O microemulsion

Europium hydroxide particles with an average diameter of 10 run and a BET surface area of 127 m2 /g have been prepared by controlled precipitation in the polyoxyethylene octylphenol (Triton X-100) (hex-anol)/cyclohexane/water microemulsion system. After calcination in air at 750℃, the obtained europium hydroxide particles were readily converted to the nanosize Eu2O3 particles with an average size of 30 nm and a high BET surface area of 36.5 m2/g.     

Phase transformations of the nanosize zinc hydroxide and oxide particles

The structure and properties of zinc hydroxide and oxide nanoparticles obtained by chemical and combined means were studied by transmission electron microscopy, X-ray phase, thermal analysis, and atomic emission spectroscopy. The effect of the synthesis conditions on the formation structure and morphology of nanoparticles was studied. It was shown that the electric field effect on a solution allows us to obtain almost single-phase systems with a narrower range of the particle sizes than in the case of chemical deposition.     

Thermodynamics of monolayers formed by mixtures of phosphatidylcholine/phosphatidylserine

In this work we obtain the thermodynamic properties of mixed (1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine) PC and (1-stearoyl-2-oleoyl-sn-glycero-3-phospho-l-serine (sodium salt)) PS monolayers. Measurements of compressibility (isotherms, bulk modulus, and excess area per molecule) and surface potential show that the properties of monolayers at the air-water interface depend on the concentration of ions (Na(+) and K(+)) and the proportion of PS in the mixture. The dependence on PS arises because the molecule is originally bound to a Na(+) counterion; by increasing the concentration of ions the entropy changes, creating a favorable system for the bound counterions of PS to join the bulk, leaving a negatively charged molecule. This change leads to an increase in electrostatic repulsions which is reflected by the increase in area per molecule versus surface pressure and a higher surface potential. The results lead to the conclusion that this mixture of phospholipids follows a non ideal behavior and can help to understand the thermodynamic behavior of membranes made of binary mixtures of a zwitterionic and an anionic phospholipid with a bound counterion.     

Synthesis of nanosize metallic and alloyed particles in ordered phases

Functionalized reverse micelles have been used to synthesize Copper and Cobalt nanoparticles differing by their size and shape. They can be also used to synthesize Fe–Cu alloy (at 30% Fe) and composite (at 70% Fe) particles. In the case of Fe–Cu system, the magnetic properties are presented.     

Pressure versus length isotherms of homogenous and mixed one-dimensional dipolar monolayers

We demonstrate a novel method for compressing and expanding microscopic one-dimensional monolayers consisting of a finite number of aligned magnetic dipoles using a pair of microscopic magnetic barriers. By measuring the interaction between the beads and the barriers, we are able to determine the pressure of the dipolar monolayers. Our sensor can measure one-dimensional pressure in the femto and piconewton regime and is used to probe both homogeneous and mixed monolayers consisting of magnetic beads with diameters 1.0 microm and 2.8 microm. The larger beads appear to be well-described by a formalism taking into account magnetic dipolar interactions, whereas for smaller beads, such a simple picture does not hold. Upon compressing the monolayer above a certain density, it forms a bilayer. This process is governed by steric interactions or dipolar interactions, depending on the applied magnetic field. We also found odd-even effects, where the number of beads in the monolayer determines the initial structure of the bilayer.     

Synthesis of nanosize particles of cobalt and nickel oxides from solutions

Rounded nanosize particles of Co₃O₄ and NiO were prepared by precipitation with ammonium carbonate from cobalt and nickel nitrate solutions. Cobalt and nickel oxides and their precursors were characterized by thermal and X-ray phase analyses, electron microscopy, and IR spectroscopy.     

Assembly of nanosize metallic particles and molecular wires on electrode surfaces

This article highlights recent developments in the assembly of nanosize materials on electrode surfaces. A brief historical background of the field is given, followed by a selection of topics of particular current interest. We focus especially on the assembly of nanosize metallic particles and molecular wires on gold and silicon electrode surfaces. The fabrication, properties, and characteristics of functional nanostructured biointerfaces on electrode surfaces are also described.     

Characteristics of soot particles formed by diesel pyrolysis

This experiment involving diesel fuel pyrolysis was performed to study the process of soot formation without oxidation. The effects of temperature, residence time, and lubricating oil presence on soot formation were investigated through measurement of particle size distribution, morphology, and C/H ratio as well as through thermal analysis. The results show that the formation of soot during diesel pyrolysis depended strongly on both temperature and residence time. The critical temperature for the creation of soot with a primary particle diameter of 20 nm was about 1100 °C. Greater temperatures and residence times resulted in diesel soot particles that were more mature, i.e., with a higher C/H ratio, larger particle size, and higher ignition temperature. The carbonization of diesel soot through pyrolysis was also weakly affected by the addition of 5% lubricating oil to the diesel fuel. The results of this experiment provide information for modeling the formation of diesel soot without oxidation as well as for developing soot generators for after-treatment systems.     

Structural studies of the monolayers and bilayers formed by a novel cholesterol-phospholipid chimera

Langmuir isotherm, neutron reflectivity, and small angle neutron scattering studies have been conducted to characterize the monolayers and vesicular bilayers formed by a novel chimeric phospholipid, ChemPPC, that incorporates a cholesteryl moeity and a C-16 aliphatic chain, each covalently linked via a glycerol backbone to phosphatidylcholine. The structures of the ChemPPC monolayers and bilayers are compared against those formed from pure dipalmitoylphoshatidylcholine (DPPC) and those formed from a 60:40 mol % mixture of DPPC and cholesterol. In accord with previous findings showing that very similar macroscopic properties were exhibited by ChemPPC and 60:40 mol % DPPC/cholesterol vesicles, it is found here that the chimeric lipid and lipid/sterol mixture have very similar monolayer structures (each having a monolayer thickness of ～26 ?), and they also form vesicles with similar lamellar structure, each having a bilayer thickness of ～50 ? and exhibiting a repeat spacing of ～65 ?. The interfacial area of ChemPPC, however, is around 10 ?(2) greater than that of the combined DPPC/cholesterol unit in the mixed lipid monolayer (viz., 57 ± 1 vs 46 ± 1 ?(2), at 35 mN·m(-1)), and this difference in area is attributed to the succinyl linkage which joins the ChemPPC steroid and glyceryl moieties. The larger area of the ChemPPC is reflected in a slightly thicker monolayer solvent distribution width (9.5 vs 9 ? for the DPPC/cholesterol system) and by a marginal increase in the level of lipid headgroup hydration (16 vs 13 H(2)O per lipid, at 35 mN·m(-1)).     

Electro-oxidation of glucose at self-assembled monolayers incorporated by copper particles

A novel copper incorporated self-assembled monolayers (SAMs) modified gold electrode (Cu/SAMs) for determination of glucose was developed by electrodepositing Cu particles on the SAMs of hexanethiol. The scanning electron microscopic (SEM) images showed that copper formed orbicular particles of nanosizes on the SAMs, which was much different from the fractal-like particles of copper formed at gold electrode. The Cu/SAMs film electrode exhibited high sensitivity to glucose oxidation and depressed responses towards some interferents of glucose in blood like uric acid and ascorbic acid. Under optimal working conditions, the oxidation current of glucose was proportional to the concentration of glucose in the range from 3.0 μM to 10 mM by amperometry with a low detection limit of 0.7 μM glucose (S/N = 3). This electrode was successfully applied to the determination of glucose in rat blood and the results were satisfactory.     

Factors that may influence the micro-emulsion synthesis of nanosize magnetite particles

The influence of experimental conditions on the formation of nanosize magnetite by micro-emulsion method was investigated using Mössbauer and FT-IR spectroscopies, FE SEM/EDS and TEM. It was found that the concentration of starting chemicals (FeCl₃/FeSO₄), aeration/de-aeration, high alkalinity and γ-irradiation influenced this precipitation process. Rod-like goethite particles ～200–300 nm long and up to 10 nm wide were obtained by destabilization of the micro-emulsions aged 5 to 45 days at RT. Si-containing ferrihydrite was also formed and it retarded the formation of goethite by the dissolution/re-precipitation mechanism. A small amount of Si from a glass flask was dissolved. A very strong influence of γ-irradiation on the formation of nanosize magnetite by micro-emulsion method was observed. γ-irradiation created strong reductive conditions in the micro-emulsions. At an ～460 kGy dose, nanosize magnetite particles sized ～5 to 20 nm and very small amounts of goethite particles were obtained. The EDS measurements on the particles suggested the formation of sub-stoichiometric magnetite (Fe_3?x O₄) and not of maghemite. This finding is in line with the strong reductive conditions induced with γ-irradiation.     

Stability of lipid films formed on gamma-aminopropyl monolayers

The stability of supported lipid membranes (SLMs) deposited on planar substrates derivatized with (gamma-aminopropyl)silane (GAPS) was examined. Ellipsometry, fluorescence microscopy, and atomic force microscopy were used to characterize SLMs exposed to repeated drying and rehydration. Vesicle fusion on GAPS-coated substrates produced SLMs with a thickness significantly greater than that of a single lipid bilayer. Exposure to even one cycle of drying/rehydration significantly decreased the thickness of a SLM on GAPS, and repeated drying/rehydration resulted in near quantitative lipid desorption. Thus SLMs on GAPS do not appear to be significantly more stable than the single bilayer SLM that is formed on bare glass or SiO2 under equivalent conditions.     

Langmuir monolayers of an inclusion complex formed by a new calixarene derivative and fullerene

The design of new molecules with directed interactions to functional molecules as complementary building blocks is one of the main goals of supramolecular chemistry. A new p-tert-butylcalix[6]arene monosubstituted derivative bearing only one alkyl chain with an acid group (C6A3C) has been synthesized. The C6A3C has been successfully used for building Langmuir monolayers at the air-water interface. The C6A3C molecule adopts a flatlike orientation with respect to the air-water interface. The molecular structure gives the molecule amphiphilic character, while allowing the control of both the dissociation degree and the molecular conformation at the air-water interface. The C63AC has been combined with pristine fullerene (C60) to form the supramolecular complex C6A3C:C60 in 2:1 molar ratio (CFC). The CFC complex retains the ability of C6A3C to form Langmuir monolayers at the air/water interface. The interfacial molecular arrangement of the CFC complex has been convincingly described by in situ UV-vis reflection spectroscopy and synchrotron X-ray reflectivity measurements. Computer simulations complement the experimental data, confirming a perpendicular orientation of the calixarene units of CFC with respect to the air-water interface. This orientation is stabilized by the formation of intermolecular H-bonds. The interfacial monolayer of the CFC supramolecular complex is proposed as a useful model for the well-defined self-assembly of recognition and functional building blocks.     

Fine particles of icosahedral quasicrystal formed by gas evaporation technique

Al-T (T=Mn, V, Cr) particles in the icosahedral phase have been prepared by evaporation and condensation of metals in an inactive gas. The particles were spherical in shape, with diameters ranging from 50 to 300 nm, and showed speckled contrast in bright and dark field images. Each particle consisted of fine grains of several nm with small misorientations (less than a few degrees). Patterson functions of the icosahedral Al-Mn were also calculated from electron diffraction data. Among several structure models examined in the present study, a model with an array of two-shell Mackay icosahedra gave the best fit with the Patterson functions.     

Study of the Calix[4]resorcinarene--dopamine interactions in monolayers by measurement of pressure--area isotherms and Maxwell displacement currents

The mechanisms of interactions between calix[4]resorcinarene and dopamine in monolayers formed at the air-water interface were studied by analyzing their mechanical, thermodynamic, and electrical properties evaluated from measurements of pressure-area isotherms and Maxwell displacement currents (MDCs). An increased concentration of dopamine in the water subphase resulted in an increase in the area per calix[4]resorcinarene molecule, an increase in the collapse pressure, and a shift in the monolayer phase transitions from the gaseous to the liquid state and from the liquid to the solid state toward higher molecular areas. A contactless method of recording MDCs enabled the monitoring of changes in the charge state of the monolayer-constituting molecules and the determination of a relationship between the phase state of the monolayer and the structural transitions of calix[4]resorcinarene. The changes of the MDC recordings started already in the gaseous state of the monolayer. On the basis of MDC values, we determined the normal component of the dipole moment of calix[4]resorcinarene, as well as that of its complex with dopamine. The dipole moment reached a maximum value of 1040 mD in the region of the phase transition from the liquid to the solid state of the monolayer. The results obtained suggest that the binding of dopamine with calix[4]resorcinarene depends on the orientation of the calixarene molecules in the monolayer. The calix[4]resorcinarene-dopamine interactions were also quantified in terms of the excess of Gibbs free energy, thereby allowing the evaluation of the energy of the calix [4]resorcinarene-dopamine bond, which was in the range from 1.95 to 8.54 kJ/mol depending on the surface pressure. This value implies weak interactions between these molecules.