Some observations on electrothermal vaporisation for sample introduction into the inductively coupled plasma

The development and analytical utility of electrothermal vaporisation techniques employing a graphite rod for sample introduction into the inductively coupled plasma (ICP) are assessed. In most instances detection limits are superior to those obtained with nebulisation based systems, and are comparable to those obtained with graphite furnace atomic absorption spectrometry. A model is derived for the sample injection process. Additionally the major interference and alteration of the plasma excitation phenomena ensuing from the sample introduction of a solvent free aerosol are discussed in order to assess the analytical potential of the technique for routine μl volume sample introduction in ICP spectrometry. The capability for simultaneous multi-element analyses is maintained with the electrothermal vaporisation technique.     

The determination of chloride by microwave helium plasma emission spectrometry using a hydrogen chloride generation technique

Hydrogen chloride is generated from aqueous solution from a concentrated sulphuric acid—potassium sulphate mixture and is passed into a microwave-induced atmospheric pressure helium plasma. Measurement at the Cl-(II) 479.5-nm line gives a linear calibration graph over the range 6 ng (detection limit) to 50 μg of chloride. Other halides, and arsenic, do not interfere, but Te and Hg depress the emission.     

The determination of sulphur and phosphorus by cool-flame chemiluminescence emission spectrometry with an electrothermal atomiser for sample introduction

The technique described allows simple and rapid determination of sulphur and phosphorus in solutions of samples and sample digests. A graphite-tube atomisation device is employed for the introduction of microlitre volumes of liquid samples, after desolvation, into a cool argon—hydrogen entrained air flame in which the chemiluminescent emission from S₂ and HPO species is monitored by using a wide band-pass monochromator system.     

Structure of hard-sphere fluid and precursor structures to crystallization

The structural origin of the commonly observed split second peak of the radial distribution function of a supercooled or glassy liquid is examined in this work using the hard-sphere fluid as an example. A novel approach to the analysis of the microscopic structure of a fluid is described, which permits the decomposition of both the radial distribution function and bond-angle distribution function of a system of particles into contributions from a small number of ring structures. The method uses a modified shortest-path definition of rings appropriate to the analysis of the medium-range structure of dense systems. It is shown that the split peak is an indicator of the emergence of precursor structures to crystal formation. The origin of the split peak provides a structural link between fluid and crystalline phases and our results suggest that it is neither a structural feature peculiar to glassy phases nor a smooth structural continuation of the stable-fluid phase. This structural feature of simple glassy systems is more appropriately described as a signifier of the frustration of emerging crystalline order in a fluid.     

On the formation mechanism of the "pancake" decahedron gold nanoparticle

We have studied the thermodynamic and kinetic growth mechanisms behind the formation of the "pancake" decahedron (D(h)) gold nanoparticle using computer simulation. Free energy calculations showed that the full pancake morphology is thermodynamically unstable across all the nanoparticle size ranges studied. However, from observations of growth simulations we discovered that a kinetic transport mechanism plays a significant contributing role in the formation process through a transfer of adatoms from the top and bottom (111) D(h) faces to the side (100) faces. More specifically we observed how diffusing adatoms on the (111) face are at times "pulled" off this face and into the (111)-(100) edge of the D(h), forcing a row of (100) side atoms into a (1x5) hexagonal reconstruction. Subsequently, this row of atoms was observed to buckle and then deconstruct forcing adatoms out onto the (100) side face completing the transfer. This transport mechanism is shown to be the main kinetic driving force behind the growth of the thermodynamically unstable pancake D(h) nanoparticle. The observed mechanism has implications for the nonequilibrium morphologies of nanoparticles involving a (100)-(111) surface boundary, especially for systems with surface reconstructions which increase the density of the surface.     

Discrimination of prostate cancer cells by reflection mode FTIR photoacoustic spectroscopy

In this communication reflection mode Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS) is used to obtain IR spectra of four prostate and prostate cancer cell line types (CaP) allowing their differentiation by principal components analysis.     

Ab initio modelling of dopants in diamond nanowires: Ii

In this study an analysis is presented of the bonding and structural properties of dehydrogenated and hydrogenated doped cylindrical diamond nanowires calculated using the Vienna Ab Initio Simulation Package, employing density functional theory within the generalized-gradient approximation. The dopants studied here have been inserted substitutionally, equidistant along the axis of an infinite (periodic) diamond nanowire. These dopants include aluminium, phosphorus, oxygen and sulphur. The doped nanowires have then been re-relaxed, and properties compared with previously calculated results for undoped, boron-doped and nitrogen-doped structures. Structural properties of relaxed nanowires considered here include an examination bonding via the electron charge density, with the aim of providing a better understanding of the effects of dopants on the stability of diamond nanostructures and nanodevices.     

Thermal lens investigation of the temperature dependence of the refractive index of organo–aqueous solutions

The thermal lens technique has been used to experimentally determine the temperature of maximum refractive index (TMRi) of low molarity aqueous methanol solutions. The well-known decrease in the measured TMRi is observed with increasing concentration of methanol. At the TMRi, the temperature dependence of refractive index (dn/dT) is zero, resulting in the absence of a thermal lens signal. In this work, the observed changes in the TMRi are related to the changes in the expansion coefficient of the water and to a lesser extent, to changes in the polarisability coefficient of the water. It is also seen that the enhancement in the thermal lens parameter upon the addition of methanol to water is related primarily to the change in expansion coefficient of the aqueous solution.     

Sorption of inorganic nanoparticles in woven cellulose fabrics

Titanium dioxide was deposited from aqueous suspension onto cellulosic surfaces.Titania was sourced from Degussa (P25TM,70:30 anatase:rutile).Dry uptake of particles was shown to be rapid and dominant with one-third of the deposition occurring in less than 30 s and over one-half in the first minute.Isotherms were recorded to compare the rate of titanium deposition on dry and pre-wetted cotton.In the dry case uptake reached a maximum in 30 min whereas in the pre-wetted case the uptake was seen to continue beyond 180 min.A broad trend of higher deposition occurring at lower pH was seen,corresponding to the region where surface charges were opposite and thus attractive.Dry pickup was less significant at high pH.The response to varying ionic strength was complex and was attributed to the combined effect of charge screening,particle aggregation and consequent particle entrapment or occlusion.Titania deposition into the interstices of woven cotton sheets resulted in the formation of inorganic,nanoparticulate skeletons which could be isolated by controlled combustion of the cellulose and thus cotton was suggested to have potential for the templated synthesis of high surface area semiconductor materials.