Protoporphyrin IX iron(II) revisited. An overview of the Mössbauer spectroscopic parameters of low-spin porphyrin iron(II) complexes.

Mössbauer parameters of low-spin six-coordinate [Fe(II)(Por)L] complexes (where Por is a synthetic porphyrin; L is a nitrogenous aliphatic, an aromatic base or a heterocyclic ligand, a P-bonding ligand, CO or CN) and low-spin [Fe(Por)LX] complexes (where L and X are different ligands) are reported. A known point charge calculation approach was extended to investigate how the axial ligands and the four porphyrinato-N atoms generate the observed quadrupole splittings (ΔE) for the complexes. Partial quadrupole splitting (p.

Studies on the binding of CO to low-spin [Fe(II)(Por)L] complexes: an aid to understanding the binding of CO to haemoglobin and myoglobin.

The visible and Mössbauer spectra of [Fe(II)(Por)L] and [Fe(II)(Por)L(CO)] complexes (where Por = protoporphyrin IX (PPIX) or tetra(p-sulfophenyl)porphyrin (TPPS) and L = an aliphatic or aromatic nitrogenous base) are reported and discussed. The results are compared to those of previously reported [Fe(II)(Por)L(CO)] complexes (where Por = PPIX, TPPS, PMXPP, TPP, OMTBP and OEP; L = a nitrogenous aromatic ligand) and HbCO (where Hb = haemoglobin) and MyCO (where My = myoglobin). A new approach, to extracting information from the Mössbauer parameters has been developed by plotting those of the [Fe(II)(Por)L] complexes against those of [Fe(II)(Por)L(CO)] complexes for the same ligands, has yielded a series of trend lines that show a significant dependence on both the nature of the porphyrin and also of the nitrogenous ligand.

Studies on the binding of nitrogenous bases to protoporphyrin IX iron(II) in aqueous solution at high pH values.

Studies are reported on the formation of low-spin six-coordinate [Fe(PPIX)L] complexes from iron(II) protoporphyrin where L is one of a series of nitrogenous ligands (aliphatic, aromatic or heterocyclic). The bonding constants have been determined by titration of the metal complex with these ligands and are compared in relation to previous studies. The adduct formation was monitored utilising optical spectroscopy.

Numerical analysis of the notional area in cold field electron emission from arrays.

The notional area of field emission is an important parameter to correlate characteristic current density to the emission current, linking field emission theories to experimental observations. Recently, it has been reported that the notional area of emission contributes to the high brightness of large diameter emitters. Thus, it is necessary to understand how the notional area of emission depends on physical and geometrical parameters.

New Developments in Cathodoluminescence Spectroscopy for the Study of Luminescent Materials.

Herein, we describe three advanced techniques for cathodoluminescence (CL) spectroscopy that have recently been developed in our laboratories. The first is a new method to accurately determine the CL-efficiency of thin layers of phosphor powders. When a wide band phosphor with a band gap (E > 5 eV) is bombarded with electrons, charging of the phosphor particles will occur, which eventually leads to erroneous results in the determination of the luminous efficacy.

Structure and luminescence analyses of simultaneously synthesised (LuGd)OS:Tb and (LuGd)O:Tb.

Herein we describe the synthesis and luminescence of nanosized (LuGd)OS:Tb and (LuGd)O:Tb phosphors with y = 0.1 mol% Tb and y = 2 mol% Tb and x ranging between 0 and 1. The concentration of Gd (x) was varied in steps of 0.

Contrast and decay of cathodoluminescence from phosphor particles in a scanning electron microscope.

Cathodoluminescence (CL) studies are reported on phosphors in a field emission scanning electron microscope (FESEM). ZnO: Zn and other luminescent powders manifest a bright ring around the periphery of the particles: this ring enhances the contrast. Additionally, particles resting on top of others are substantially brighter than underlying ones.

Field emission from non-uniform carbon nanotube arrays.

Regular arrays of carbon nanotubes (CNTs) are frequently used in studies on field emission. However, non-uniformities are always present like dispersions in height, radius, and position. In this report, we describe the effect of these non-uniformities in the overall emission current by simulation.

Ultrahigh-current field emission from sandwich-grown well-aligned uniform multi-walled carbon nanotube arrays with high adherence strength.

We describe a new method to grow multi-walled carbon nanotube (MWCNT) arrays, which enable very high and stable macroscopic emission current density of 3.55 A cm(-2) along with a scalable total emission current of more than 710 mA. A sandwich-growth technology was employed to synthesize vertically well-aligned MWCNT arrays in large areas and patterned uniformly by using microwave plasma chemical vapour deposition.