George Robert Fern

Mössbauer parameters of low spin six coordinate [Fe(II)(Por)L ₂ ] and [Fe(II)(Por)LX] complexes (where Por is PPIX or a synthetic porphyrin; L is OH ⁻ , H ₂ O, a nitrogenous base, CCl ₂ , CO or CN ⁻ and X is a different ligand to L) are discussed. Our point charge calculation approach is extended to investigate how the axial ligands and the four porphyrinato-N atoms generate the observed quadrupole splittings (ΔE _Q ). Partial quadrupole splitting (p.q.s.) and partial centre shift (p.c.s.) values are derived and discussed for all the axial ligands studied herein. It is shown that when the D _4h symmetry breaks down due to porphyrin ring ruffling, the point charge calculations no longer apply. This happens for many synthetic porphyrins but not for the uniquely important [Fe(II)(PPIX)] moiety, (which is ubiquitous in nature). Thus, synthetic porphyrins (like TPP) cannot always act as perfect proxies for natural haem proteins. In all the haem proteins containing [Fe(II)(PPIX)] moieties the haem is planar. Calculations indicate that if H ₂ O were bound to the [Fe(II)(PPIX))] present in deoxyhaemoglobin or deoxy myoglobin, then these Fe(II) atoms would be low spin. In contrast for synthetic and natural haem proteins containing haem b (where the haem is connected to the protein backbone via two cysteine residues) the haem plane is ruffled (probably because of the methionine linkages transferring force and controlling the stereochemistry of the haem plane, and thereby its chemistry). For the [Fe(II)(TPP)(CN) ₂ ] and [Fe(II)(TPP)(1-MeIm)(CN)] the calculated CN ⁻ ligand p.q.s values are suspect and probably show that the lattice charge is affecting them.

Off-notes in plant-based sources of protein are mainly formed via the lipid oxidation of unsaturated fatty acids. During gas chromatography-olfactometry analysis of pea protein isolate, previously uncharacterized old soap odors were detected. These were found to arise from a family of α,β-unsaturated aldehydes formed from the aldol condensation of pentanal and hexanal during the protein extraction process. These compounds were synthesized, and it was confirmed that they are highly odor-active and contribute to the old soap odor in pea protein isolates at very low concentrations. Comparison with rice, soy, and hemp protein isolates showed that they all contained at least one such aldol condensate, whereas they were not detected in whey protein. We suggest that the main factor determining the formation of these compounds is the manufacturing process used to isolate and dry the pea protein biomass.

Mössbauer parameters of low-spin six-coordinate [Fe(II)(Por)L₂] 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_Q) for the complexes. Partial quadrupole splitting (p.q.s.) and partial chemical shifts (p.c.s.) values were derived for all the axial ligands, and porphyrins reported in the literature. The values for each porphyrin are different emphasising the importance/uniqueness of the [Fe(PPIX)] moiety, (which is ubiquitous in nature). This new analysis enabled the construction of figures relating p.c.s and p.q.s values. The relationships presented in the figures indicates that strong field ligands such as CO can, and do change the sign of the electric field gradient in the [Fe(II)(Por)L₂] complexes. The limiting p.q.s. value a ligand can have and still form a six-coordinate low-spin [Fe(II)(Por)L₂] complex is established. It is shown that the control the porphyrin ligands exert on the low-spin Fe(II) atom limits its bonding to a defined range of axial ligands; outside this range the spin state of the iron is unstable and five-coordinate high-spin complexes are favoured. Amongst many conclusions, it was found that oxygen cannot form a stable low-spin [Fe(II)(Por)L(O₂)] complex and that oxy-haemoglobin is best described as an [Fe(III)(Por)L(O₂⁻)] complex, the iron is ferric bound to the superoxide molecule. Graphical abstract

Y₃Al₅O₁₂ (YAG) and Lu₃Al₅O₁₂ (LuAG) doped with rare earth elements are widely used as scintillators, solid state lasers, and phosphors in white light emitting diodes (LEDs). Additionally, (Gd,La)B₃O₆:Bi has found application as a UV-B emitting phosphor in fluorsecent lamps a long time ago. This paper reports both the photoluminescence (PL) and cathodoluminescence (CL) of Pr³⁺ or Gd³⁺ substituted YAG and LuAG in comparison to the widely applied UV-B phosphor (Gd,La)B₃O₆:Bi under vacuum ultra violet (VUV) and cathode ray excitation, respectively. The powder diffraction pattern, emission, excitation, and reflection spectra and a comparison of the luminescence efficiency are shown and discussed. It turned out that all investigated phosphors show efficient luminescence in the UV-B spectral range. Moreover, it is found that LuAG:Gd has the highest efficiency upon VUV and upon CL excitation too.

Here, we report the synthesis and spectral properties of ultrathin nanodiscs (NDs) of Y2O3:Eu3+. It was found that the NDs of Y2O3:Eu3+ with a thickness of about 1 nm can be fabricated in a reproducible, facile and self-assembling process, which does not depend on the Eu3+ concentration. The thickness and morphology of these NDs were determined with small angle x-ray scattering and transmission electron microscopy. We found that the crystal field in these nanoparticles deviates from both the cubic and monoclinic characteristics, albeit the shape of the 5D0 → 7F J (J = 0, 1, 2) transitions shows some similarity with the transitions in the monoclinic material. The Raman spectra of the non-annealed NDs manifest various vibration modes of the oleic acid molecules, which are used to stabilise the NDs. The annealed NDs show two very weak Raman lines, which may be assigned to vibrational modes of Y2O3 NDs. The concentration quenching of the Eu3+ luminescence of the NDs before annealing is largely suppressed and might be explained in terms of a reduction of the phonon density of states.

The cathodoluminescence (CL) spectra of nanocrystalline Y₂O₃:Tb³⁺ (0.3%), Y₂O₃:Er³⁺ (1%), Y₂O₃:Tm³⁺ (2%) and Y₂O₃:Bi³⁺ (1%) were recorded in a transmission electron microscope at 200 keV, low current density and various temperatures.

Zn_1-xCd_x:Cu_0.03%,Cl (where x = 0.5–0.9) infrared emitting phosphors have been synthesized by an aqueous thermal decomposition method. The aim was to developing infrared emitting phosphors for coding, marking, and identification applications. The phosphors were characterized by, X-ray powder diffraction, scanning electron microscopy and photoluminescence spectroscopy. The emission band at 1000 nm was sufficiently far into the infrared region that visible emission was minimized. Co-doping Zn_1-xCd_xS:Cu_0.03% with Al³⁺ increased the infrared emission intensity to over twice that of the equivalent Zn_0.3Cd_0.7S:Cu_0.03% phosphor (with no Al³⁺ ion co-doping), with the highest intensity being found for the phosphor composition Zn_0.1Cd_0.9S:Cu_0.03%, Al_0.03%. It is shown herein that the inclusion of Al³⁺ into the phosphors causes the formation of cells with smaller cell volume, and it is suggested that this is the prerequisite for the improved photoluminescent properties. Finally we have shown herein that these infrared emitting powder phosphors are thus able to meet marking and coding requirements, especially in low light and poor visibility.