On the shape of atomic fluorescence analytical curves with a laser excitation source

The effect of high irradiance levels (approaching saturation) upon the shape of atomic fluorescence analytical curves is considered theoretically for both line and continuum sources. The linear range of the analytical curve may be greatly extended over that obtained with normal (low irradiance) sources, as is experimentally verified using a pulsed dye laser as an excitation source.     

Laser spectroscopy for atmospheric chemistry: selected applications involving the fluorescence technique

The application of laser-based techniques to the study of different problems related to atmospheric chemistry is well established. Among the various laser spectroscopic methods, the focus here is directed towards selected applications of the laser photofragmentation and fluorescence techniques, which are used to investigate the complex chemistry of tropospheric sulphur species, with particular emphasis on the oxidation of dimethyl sulphide (DMS) and the consequent formation of sulphuric acid, and to the possibility of detecting with very high sensitivity and selectivity a particular element (e.g., gold) in size-segregated aerosol particles in view of its possible release as a tracer in the atmosphere. The atomic fluorescence technique is also applied to the real time detection of lead in a miniature air-acetylene flame, in which monodisperse aerosol particle are introduced.     

Atomic fluorescence flame spectrometry using a mercury line source

The possibility of exciting the fluorescence of several elements with the “overlapping” lines of other elements and the effectiveness of exciting the fluorescence of Fe, Mn, Ni, Cr, Tl, Cu and Mg with a 90 W mercury discharge lamp, are discussed. A method of increasing the fluorescence radiation by suitable optics, with a simple adaptation of a Jarrell-Ash AA spectrometer, is described. A two-pass system of the incident radiation into the flame is coupled with a mirror, in the optical axis, which reflects the fluorescence radiation emitted at the opposite side to the monochromator slit. This produces an increase of 168% of the signal. Detection limits for 10 elements are reported.     

High-resolution Fabry–Pérot interferometric emission measurements of the 535.046 nm thallium line in a see-through hollow cathode discharge

A thallium see-through hollow cathode lamp, or galvatron, is investigated for applications as a narrow band atomic line filter. In order to determine the resolving power of this atom reservoir, high resolution emission profile measurements of the 535.046 nm line were obtained by a scanning Fabry–Pérot interferometer coupled to a spectrometer. The resulting spectra are modeled by a two-layer model which takes into account line broadening due to self-absorption and allows the calculation of the Doppler temperature and optical depths of the two layers. The results obtained for the galvatron are compared to a traditional thallium hollow cathode lamp and a thallium electrodeless discharge lamp. The galvatron was found to produce Doppler temperatures from 495 K to 630 K from currents of 10.0 mA to 30.0 mA, respectively, which were lower than the values found from the traditional hollow cathode lamp at similar currents. These results make this atomic reservoir attractive for applications as an atomic line filter. PACS 52.25.Tx; 32.70.Jz; 32.10.Fn     

Photoswitching of bis-spiropyran using near-infrared excited upconverting nanoparticles

Bis-spiropryran molecules were grafted onto the surface of upconverting nanoparticles. Fluorescence resonance energy transfer from the upconverting nanoparticles to the surface bis-spiropyran molecules triggered the transformation of the ring-closed bis-spiropyran to the ring-open bis-merocyanine forms.     

Supramolecular chemistry of halogens: complementary features of inorganic (M-X) and organic (C-X') halogens applied to M-X...X'-C halogen bond formation

Electronic differences between inorganic (M-X) and organic (C-X) halogens in conjunction with the anisotropic charge distribution associated with terminal halogens have been exploited in supramolecular synthesis based upon intermolecular M-X...X'-C halogen bonds. The synthesis and crystal structures of a family of compounds trans-[MCl(2)(NC(5)H(4)X-3)(2)] (M = Pd(II), Pt(II); X = F, Cl, Br, I; NC(5)H(4)X-3 = 3-halopyridine) are reported. With the exception of the fluoropyridine compounds, network structures propagated by M-Cl...X-C halogen bonds are adopted and involve all M-Cl and all C-X groups. M-Cl...X-C interactions show Cl...X separations shorter than van der Waals values, shorter distances being observed for heavier halogens (X). Geometries with near linear Cl...X-C angles (155-172 degrees ) and markedly bent M-Cl...X angles (92-137 degrees ) are consistently observed. DFT calculations on the model dimers {trans-[MCl(2)(NH(3))(NC(5)H(4)X-3)]}(2) show association through M-Cl...X-C (X not equal F) interactions with geometries similar to experimental values. DFT calculations of the electrostatic potential distributions for the compounds trans-[PdCl(2)(NC(5)H(4)X-3)(2)] (X = F, Cl, Br, I) demonstrate the effectiveness of the strategy to activate C-X groups toward halogen bond formation by enhancing their electrophilicity, and explain the absence of M-Cl...F-C interactions. The M-Cl...X-C halogen bonds described here can be viewed unambiguously as nucleophile-electrophile interactions that involve an attractive electrostatic contribution. This contrasts with some types of halogen-halogen interactions previously described and suggests that M-Cl...X-C halogen bonds could provide a valuable new synthon for supramolecular chemists.     

Anomalous spatial distribution of temporal and spectral behaviour within a pulsed dye laser beam

A peculiar effect, probably overlooked in some past laser induced fluorescence (LIF) and laser enhanced ionisation (LEI) experiments, is described. Such an effect has been observed when the temporal profile of an excimer laser-pumped, pulsed dye laser beam was analysed with a microchannel plate photomultiplier detector and a fast digitising signal analyser. Substantially different shapes were found at selected spatial locations, of 1 mm size, within the same laser beam. The overall time profile of the full size beam (~6 mm) can be described by the overlapping of two limiting shapes, that is, a narrow pulse, of about 3 ns full-width-at-half-maximum (FWHM), and a much broader pulse (~7 ns FWHM). The peak intensities of the limiting pulses differ in time by ~10 ns. In addition, it is shown that the two peaks also differ in wavelength by an amount which can be as large as the width of the atomic absorption line in the atomiser. The effect, which occurs in a random manner and is easily observed only with time resolution, is extremely sensitive to the alignment of the oscillator cavity of the dye laser. This was demonstrated experimentally by comparing the laser excitation and fluorescence waveforms of gallium and lead atoms in the inductively coupled argon plasma. The recognition of such anomalous behaviour is essential for a correct interpretation of some time-resolved fluorescence and ionisation experiments.     

The relationship between the electrospray ionization behaviour and biological activity of some phosphino Cu(I) complexes

Electrospray ionization mass spectrometry was usefully employed for the characterization of three phosphino copper(I) complexes of medicinal interest. This technique revealed that the original [CuL₄]⁺ pro‐drugs (L = hydrophilic tertiary phosphine) underwent dissociation with production of coordinative unsaturated [CuL₃]⁺ and [CuL₂]⁺ species, which represented key intermediates for the activation of potential biological properties. The more favoured was the displacement of the ligands from the [CuL₄]⁺ parent complex, the more favoured was in turn the possibility for the metal ion to directly interact with biological substrates, including pharmacological targets related to cancer proliferation. An inverse correlation between the stability and the cytotoxic activity of the three copper(I) complexes investigated has been clearly established. Copyright © 2010 John Wiley & Sons, Ltd.