Synthesis of nanoparticles using vapor-phase decomposition of copper(II) acetylacetonate

Experimental data on the synthesis of crystalline Cu, Cu₂O, and CuO nanoparticles obtained earlier by the vapor-phase decomposition of copper(II) acetylacetonate (Cu(acac)₂) were systematized and generalized. Studies were performed using a laminar flow reactor at atmospheric pressure within the ranges of precursor partial vapor pressure P _prec = 0.06–44 Pa and reactor temperature from 432 to 1216°C. The decomposition of Cu(acac)₂ was studied in an inert nitrogen atmosphere and in the presence of various reagents (water vapors, H₂, O₂, and CO). The composition of synthesized particles varied from pure copper to its oxides (Cu₂O and CuO) depending on experimental conditions and used reagents. A semi-empirical kinetic model was proposed for describing the product dynamics. The hypothesis on the predominant role of copper dimers in a particles growth was stated. It was established that the composition of products is determined by the surface reactions on growing particles and is dependent on the ratio between the concentrations of the gaseous reagents. Calculated phase diagrams of the products of Cu(acac)₂ decomposition in the presence of various reagents were in good agreement with experimental data. The proposed method of construction of the phase diagram of decomposition products can be employed for other systems. It was established that, upon the Cu(acac)₂ decomposition in the presence of CO, carbon nano-onions were formed in addition to copper nanoparticles.Translated from Kolloidnyi Zhurnal, Vol. 67, No. 1, 2005, pp. 5–25.Original Russian Text Copyright © 2005 by Nasibulin, Shurygina, Kauppinen.     

Synthesis of boron nitride multi-walled nanotubes by laser ablation technique

Carbon nanotubes are known as prospective material for the optoelectronics, vacuum electronics, non-linear optics and for the composite material synthesis. Boron nitride nanotubes (BNNTs) were obtained only recently. It is expected that these nanotubes possess the unique properties. BN is much more chemically inert than carbon. Its oxidation temperature is above 1000°C as the graphite is totally oxidized already at 650°C. BNNTs are wide-gap semiconductors with the 6 eV gap. In case of the introducing of the carbon atoms into the BN nanotube wall its bandgap may be varied in wide range. This property is important for the UV optics.     

The ν9 + ν11 − ν11, ν10 + ν11 − ν11 hot band system in allene-d4

The hot band system ν₉ + ν₁₁ ? ν₁₁, ν₁₀ + ν₁₁ ? ν₁₁ in allene-d₄ was studied at a resolution near 0.010 cm^?1. About 1500 partly overlapped hot band rotational lines were assigned and fitted to a model taking into account z-Coriolis resonance between the combination levels ν₉ + ν₁₁ and ν₁₀ + ν₁₁ as well as vibrational l-type resonances within these levels. Upperstate constants have been derived from an analysis in which the constants for the ν₁₁ level were constrained. A detailed study of rotational as well as vibrational l-type doublings occurring in the KΔK = ?1 subband is presented, and the sign of vibrational l-type doubling constants for the ν₁₀ + ν₁₁ level is determined. A localized (x, y)-Coriolis resonance between ν₁₀ + ν₁₁ and ν₄(B₁) + ν₁₁ is discussed and the interaction parameter is obtained as well as some constants for ν₄ + ν₁₁.     

ν7 and ν9 bands of formic acid near 16 μm

The ν₇ and ν₉ fundamental bands of formic acid were studied by Fourier transform spectroscopy with a resolving power of 0.020 cm^?1. Band centers obtained are ν₇ = 626.158 cm^?1 and ν₉ = 640.722 cm^?1. It was possible to determine rotational and centrifugal distortion parameters for both vibrational states v₇ = 1 and v₉ = 1 and also the two first-order Coriolis interaction parameters along z and x axes and the second-order Coriolis parameter along z axis. The stability of rotational and distortion parameters compared to ground state values confirms that a Watson type Hamiltonian is well adapted to such a problem.     

The infrared band ν6 of CD3I

The lowest perpendicular fundamental ν₆ of CD₃I around 650 cm^?1 is studied at a resolution of 0.015 cm^?1. More than 2000 rotational transitions are identified and they are used to get the molecular constants of the level v₆ = 1, including, e.g., the η constants.     

Infrared spectrum of CO2 in the region of the bending fundamental ν2

The infrared spectrum of CO₂ in the region 540–830 cm^?1 has been studied with a Fourier spectrometer at a resolution of 0.010 cm^?1. In addition to the fundamental ν₂, more than 10 “hot” band transitions of ¹²C¹⁶O₂ have been identified. The rotational constants involved have been derived. Special care has been taken in obtaining accurate constants for the level 01¹0. The ν₂ fundamentals of the isotopic molecules ¹³C¹⁶O₂, ¹⁶O¹²C¹⁸O, and ¹⁶O¹²C¹⁷O have also been observed in a natural sample.     

Preparation of amino acid nanoparticles at varying saturation conditions in an aerosol flow reactor

In this article, we describe the synthesis of new and ion-selective nanofiltration (NF) membranes using polyvinylidene fluoride (PVDF) nanofibers and hyperbranched polyethylenimine (PEI) as building blocks. These new nanofibrous composite (NFC) membranes consist of crosslinked hyperbranched PEI networks supported by PVDF nanofibrous scaffolds that are electrospun onto commercial PVDF microfiltration (MF) membranes. A major objective of our study was to fabricate positively charged NF membranes that can be operated at low pressure with high water flux and improved rejection for monovalent cations. To achieve this, we investigated the effects of crosslinker chemistry on membrane properties (morphology, composition, hydrophobicity, and zeta potential) and membrane performance (salt rejection and permeate flux) in aqueous solutions (2,000?mg/L) of four salts (NaCl, MgCl₂, Na₂SO₄, and MgSO₄) at pH 4, 6, and 8. We found that an NFC?CPVDF membrane with a network of PEI macromolecules crosslinked with trimesoyl chloride has a high water flux (~30?L?m^?2?h^?1) and high rejections for MgCl₂ (~88 %) and NaCl (~65 %) at pH 6 using a pressure of 7?bar. The overall results of our study suggest that PVDF nanofibers and hyperbranched PEI are promising building blocks for the fabrication of high performance NF membranes for water purification.     

Micromechanically tuned ring resonator in silicon on insulator

We demonstrate a monolithically integrated micromechano-optical device where the resonance wavelength of a silicon ring resonator is tuned by perturbing the evanescent field with an electrostatically actuated silicon nitride microcantilever. The resonance wavelength can be tuned over 125 pm.     

Dispersion of cerebral on-resonanceT 1 in the rotating frame (T 1ρ) in global ischaemia

T ₁ in the rotating frame (T _1ρ) has been recently shown to be an early magnetic resonance imaging index of ongoing pathology in vivo. Dispersion ofT _1ρ at aB ₁ range from 620 to 160500 rad/s was quantified in the rat brain to study the effects of ischaemia onT _1ρ relaxation and to elude the role of physico-chemical mechanisms underlying the relaxation changes. The results show a biphasic effect of the dispersion ofR _1ρ (1/T _1ρ) in ischaemic brain. In the lowB ₁ region (less than 5000 rad/s), an increase was detected, while at the highB ₁ end of the experiments,R _1ρ was reduced. This was accompanied by a change in the fitted values describing the dispersion characteristics. Injection of a superparamagnetic contrast agent, AMI-227, before ischaemia shifted theR _1ρ curve upwards by 4% but showed no effect on the shape of theR _1ρ dispersion curve. The present results argue for a specific effect of endogenous susceptibility on cerebralR _1ρ in the early moments of ischaemia due to a relaxation enhancement in the blood pool. Our results confirm that quantitativeR _1ρ dispersion nuclear magnetic resonance (NMR) improves the sensitivity ofR _1ρ NMR to detect ischaemia in vivo. Simple empirical linear or exponential fits proved to be efficient ways to describe dispersion data in the limitedB ₁ range, as more detailed models may not offer additional information in a physically relevant manner for complex systems, such as the brain.