The spatially resolved characterisation of Egyptian blue, Han blue and Han purple by photo-induced luminescence digital imaging

The photo-induced luminescence properties of Egyptian blue, Han blue and Han purple were investigated by means of near-infrared digital imaging. These pigments emit infrared radiation when excited in the visible range. The emission can be recorded by means of a modified commercial digital camera equipped with suitable glass filters. A variety of visible light sources were investigated to test their ability to excite luminescence in the pigments. Light-emitting diodes, which do not emit stray infrared radiation, proved an excellent source for the excitation of luminescence in all three compounds. In general, the use of visible radiation emitters with low emission in the infrared range allowed the presence of the pigments to be determined and their distribution to be spatially resolved. This qualitative imaging technique can be easily applied in situ for a rapid characterisation of materials. The results were compared to those for Egyptian green and for historical and modern blue pigments. Examples of the application of the technique on polychrome works of art are presented.

Removal of methylene blue by two zeolites prepared from naturally occurring Egyptian kaolin as cost effective technique

The optimum condition as well as adsorption behavior of two zeolite types prepared from Egyptian kaolin (namely, zeolite A and zeolite X) with methylene blue (MB) are demonstrated in this study. This will be a step to remove such dyes from textile as well as dying industries.MB removal was investigated using synthetic solutions at initial concentrations 15 mg/L of MB at constant temperature and pH (25 ± 0.1 °C and 7.5 ± 0.2) respectively. The removal efficiency was determined at different contact times and different zeolite doses.The optimum contact times for the removal of MB were 60 min and 75 min for zeolite X and zeolite A, respectively. 0.6 g was the optimum dose for removal of MB with both zeolite types.The batch method has been employed, using MB concentration in solution ranging from 2 to 25 mg/L. The percentage removal and distribution coefficients (K_d) were determined for the adsorption system as a function of sorbate concentration. The isothermal models investigated in this study show that adsorption ratios of MB on both zeolites match to Langmuir and Freundlich equation adding to that every equation constant has been calculated. According to the equilibrium studies, adsorption of zeolite X in higher concentrations is much better than that of zeolite A. Dublin–Kaganer–Radushkevich (DKR) shows physisorption endothermic adsorption process for both zeolites and also linear correlation of Redlich–Peterson and Tekman isothermal models were proved.These results show that zeolites prepared from naturally abundant Egyptian kaolin hold great potential to remove dying materials such as MB from wastewater. This will encourage using such low cost technique in removal of dyes from industrial wastewater.     

Nondestructive analysis of ancient Egyptian funerary relics by Raman spectroscopic techniques

The non-destructive Raman spectroscopic analysis of a range of ancient Egyptian funerary artefacts has been undertaken with a view to establish the identification of the pigment composition and nature of the interaction with the substrate. The specimens date from the New Kingdom to the Graeco-Roman period, ca. 3900-1800 years b.p. In this study a comparison has also been effected between the near-infrared and red excitation wavelengths for the characterisation of these materials. A particular problem for Raman analysis of these artefacts was found in the application of resin or organic compounds to the surface or substrata, as colourants or to aid adhesion of the pigments, and degradation of the resins with burial environment and exposure has resulted in large fluorescent backgrounds. Nevertheless, useful information has been obtained which assists in the interpretation of the construction of some of the artefacts.     

Electrochemical Characterization of Egyptian Blue Pigment in Wall Paintings Using the Voltammetry of Microparticles Methodology

The solid state voltammetric response of Egypt blue, Han blue and ploss blue pigments upon attachment to graphite electrodes in contact with aqueous phosphate buffer at pH 7.0 is studied by voltammetry of microparticles and scanning electrochemical microscopy. Such voltammetric responses, combined with those for synthetic specimens consisting of binary mixtures of the pigment and SiO₂ or CaCO₃ as well as ternary ones of CaCO₃ and SiO₂ mixtures allow for the identification of the pigment and the support in samples from wall paintings using different electrochemical parameters, in particular upon performing the Tafel and modified Tafel analysis of voltammetric peaks. Identification of Egypt blue in microsamples of murals from a Roman archaeological site in Castulo (Jaén, Spain) is discussed.     

New paramagnetic N-heterocyclic stannylenes: An EPR study

The reactions of N,N′-bis[(2,6-di-iso-propylphenyl)-1,2,3-diazastannole-2-ylidene with some radicals, mercury(II) or silver(I) halides have been investigated. The formation of new paramagnetic stannylene complexes has been shown by EPR spectroscopy.     

Reactivity of some vanadium oxides: An EPR and XRD study

V₂O₅, VO₂ and V₂O₃ fresh samples and at different times after purchase or preparation (aged samples) were investigated by chemical analysis, redox treatments, XRD and EPR. The ageing process through a reaction with water and oxygen slowly oxidize crystalline VO₂ and V₂O₃, leading to a quasi-amorphous phase with bariandite structure (V₁₀O₂₄·12H₂O). The role of water is the progressive demolition of the compact structures and formation of hydrated phase. Kinetic study of VO₂ oxidation by O₂ and O₂+H₂O mixture indicates that increasing the temperature up to 723 K the effect of water becomes less important. The reaction leads to partially oxidized products with decreasing water content: bariandite at room temperature, V₃O₇·H₂O at 383 K and V₃O₇ at 723 K. Kinetic investigation of V₂O₅ reduction by CO at 633-723 K showed that the reduction process proceeds trough the formation of V⁴⁺ and of electrons delocalized in the conduction band.     

An EPR study of thermally and photochemically generated oxygen radicals on hydrated and dehydrated titania surfaces

The formation of a series of oxygen-centred radicals on different TiO₂ samples (P25 and two different rutile materials) under various conditions was investigated using X-band c.w. Electron Paramagnetic Resonance (EPR) spectroscopy. The radicals were formed either on thermally-reduced TiO₂, or by UV irradiation of the oxide under an oxygen atmosphere. The nature and stability of the radicals was also explored as a function of surface hydration. On thermally reduced TiO₂, containing surface and bulk Ti³⁺ centres, oxygen adsorption at 300 K results in the preferential formation and stabilisation of O₂ ^- anions on the P25 surface, but O^- and O₃ ^- anions are generated on the rutile surfaces. Superoxide anions (O^-) and trapped holes (O₂ ^-) were also identified after photo-irradiation of the thoroughly dehydrated TiO₂ samples under oxygen. The O^- anions were only visible at low temperatures under continuous irradiation, while the O₂ ^- anions were stable for days at 300 K. By comparison, on fully hydrated surfaces, no stable oxygen centred radicals could be detected on P25, while O₂ ^- anions were easily observed on the rutile surfaces. On partially hydrated P25, the O^-, O₂ ^- and HO₂ anions were detected after UV irradiation at 77 K; all radicals decayed upon warming to 298 K. On partially hydrated rutile, the O^- and O₂ ^- anions were detected and, unlike the case for P25, were found to be stable for days under the same conditions. The results illustrate the varied formation and stability of the oxygen centred radicals on TiO₂ surfaces depending on the pretreatment conditions.     

水杨醛酪氨酸铜配合物合成和EPR波谱

A new Schiff base derived from tyrosine and salicylidene and its copper(Ⅱ) complex have been synthesized and characterized by elemental analyses,molar conductances,thermal analyses,infrared spectra,electronic spectra and EPR spectra.The composition of the complex is K[CuL(Ac)]•H2O, where L=H13C16NO4. EPR spectra of the copper(Ⅱ) complex were investigated in various solvents at different temperatures.It is found that the linewidth of four hyperfine lines on solution spectra at room temperature is unequal and changes with mⅠ ,this could be satisfactorily explained by the relaxation effect.The relaxation time and the relaxation rate were calculated.By using spectral parameters from solution spectra at low temperature,the bonding parameters of Cu(Ⅱ) complex were calculated.The bonding characterization and stability of the complex were disscussed.The results show that the in plane 螵瞓ond and the in plane 皙瞓ond in the complex all play an important role.     

Synthesis of Large Platelets of Egyptian Blue via Pseudomorphosis after NaRUB-18

A colored platy substrate with appreciable aspect ratio can improve the hiding power while extending the color range of pearlescent pigments. One of the oldest synthetic pigments, Egyptian blue, possesses a layered structure and a platy morphology, making it a promising colored substrate for pearlescent pigments, which derives its blue color from Cu^II. Unfortunately, existing synthesis routes are either not technically benign or lack the natural platy morphology. Here, we introduce a new synthesis route starting with large, square-shaped platelets of a synthetic layered sodium silicate (NaRUB-18). As evidenced by Rietveld refinement and scanning electron microscopy, NaRUB-18 can be converted with conservation of this attractive morphology (pseudomorphosis) into Egyptian blue.     

A convenient one-pot synthesis of ethylene blue

We have developed an efficient one-pot, two-step preparation of ethylene blue by eliminating aqueous work-ups and cumbersome purification techniques. Our procedure generates ethylene blue in good overall yields of 45-56% with approximately 95% purity, which is uncommon for the synthesis of a phenothiazinium salt. Due to its unique properties, ethylene blue has great potential for a broad range of biological applications and, as a result, an efficient procedure for the synthesis of ethylene blue is critical.     

Electron beam radiation effects on UHMWPE: an EPR study

Electron paramagnetic resonance (EPR) technique has been employed to detect and characterise a series of different radical species generated in ultra‐high molecular weight polyethylene (UHMWPE) via electron beam irradiation. Three different radical species have been found and assigned on the basis of their EPR spectra and of the related computer simulations. A secondary alkyl species, the prevalent one, is present immediately after irradiation, an allyl species appears only 24 h after irradiation when the alkyl species disappears.The third species, clearly visible at high microwave power only, has been observed for the first time and assigned to a tertiary alkyl carbon radical, whose formation is strictly connected with a Y‐shape crosslink and a migration of the unpaired electron on a carbon atom localised in an adjacent position. Copyright © 2011 John Wiley & Sons, Ltd.     

Magnetic properties of single crystal alpha-benzoin oxime: An EPR study

The electron paramagnetic resonance (EPR) spectra of gamma irradiated single crystals of alpha-benzoinoxime (ABO) have been examined between 120 and 440 K. Considering the dependence on temperature and the orientation of the spectra of single crystals in the magnetic field, we identified two different radicals formed in irradiated ABO single crystals. To theoretically determine the types of radicals, the most stable structure of ABO was obtained by molecular mechanic and B3LYP/6-31G(d,p) calculations. Four possible radicals were modeled and EPR parameters were calculated for the modeled radicals using the B3LYP method and the TZVP basis set. Calculated values of two modeled radicals were in strong agreement with experimental EPR parameters determined from the spectra. Additional simulated spectra of the modeled radicals, where calculated hyperfine coupling constants were used as starting points for simulations, were well matched with experimental spectra.     

Synthesis and mesomorphic properties of novel tetrafluorinated biphenyl acetylene liquid crystals with a blue phase

Five novel tetrafluorinated biphenyl acetylene molecules containing two chiral centres in the side chain were synthesized. The mesomorphic behaviour of these compounds was characterized by differiential scanning calorimetry (DSC) and optical polarizing microscopy. All these compounds exhibit cholesteric and blue phases.     

High-spin chloro mononuclear MnIII complexes: a multifrequency high-field EPR study.

The isolation, structural characterization, and electronic properties of two six-coordinated chloromanganese (III) complexes, [Mn(terpy)(Cl)3] (1) and [Mn(Phterpy)(Cl)3] (2), are reported (terpy = 2,2':6'2"-terpyridine, Phterpy = 4'-phenyl-2,2':6',2"-terpyridine). These complexes complement a series of mononuclear azide and fluoride Mn(lll) complexes synthesized with neutral N-tridentate ligands, [Mn(L)(X)3] (X = F- or N3 and L = terpy or bpea [N,N-bis(2-pyridylmethyl)-ethylamine)], previously described. Similar to these previous complexes, 1 and 2 exhibit a Jahn-Teller distortion of the octahedron, characteristic of a high-spin Mn(III) complex (S = 2). The analysis of the crystallographic data shows that, in both cases, the manganese ion lies in the center of a distorted octahedron characterized by an elongation along the tetragonal axis. Their electronic properties were investigated by multifrequency EPR (190-475 GHz) performed in the solid state at different temperatures (5-15 K). This study confirms our previous results and further shows that: i) the sign of D is correlated with the nature of the tetragonal distortion; ii) the magnitude of D is not sensitive to the nature of the anions in our series of rhombic complexes, contrary to the porphyrinic systems; iii) the [E/D] values (0.124 for 1 and 0.085 for 2) are smaller compared to those found for the [Mn(L)(X)3] complexes (in the range of 0.146 to 0.234); and iv) the E term increases when the ligand-field strength of the equatorial ligands decreases.     

An optical, EPR and electrical conductivity study of blue barium titanate, BaTiO3−δ

The electronic UV–VIS–NIR absorption spectra of single crystalline BaTiO_3−δ (BTO) are studied in the temperature range of 102–1173 K in pure oxygen and at conditions of moderate and strong reduction of the material. The strongly reduced crystals are of deep blue colour. The optical spectra of blue BTO are characterised by a strong absorption in the NIR region at around 7000 cm⁻¹, which is attributed to polaronic defects associated with the formation of Ti³⁺ in the material. This assumption is supported by fits of the spectra using polaronic line shape functions appropriate for disordered systems and also by the electrical conductivity of blue BTO which, in agreement with results from the optical spectra, exhibits an activation energy of 0.20 eV. The EPR spectra of moderately reduced BTO powders show an anisotropic g-factor, which is compatible with the optical spectrum. The temperature dependence of the band gap energy of BTO was found to be given as dE_g/dT = −7.21 × 10⁻⁴ eV/K.     

EPR and ab-initio study on the solid state radiolysis of aliphatic and aromatic polyesters

Low temperature matrix EPR spectroscopy was employed to investigate the free radical intermediates in the solid state radiolysis of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(ethylene naphthalate) (PEN), poly(1,4-cyclohexanedimethylene terephthalate-co-ethylene terephthalate) (PCT-co-ET) and poly(ethylene adipate) (PEA). With PEA the species identified is consistent with the formation of carbon centred radicals stemming from electron capture, C–O scissions and H abstractions, the most abundant species at room temperature being the -ester radical, –CH₂–CH–COO–. The radiolysis of PEN is characterized by the predominance of radicals arising from the aromatic section, the preferred reaction being the H atom addition at a position adjacent to the ester unit, leading to the formation of cyclohexadienyl type radicals. In the copolymer, PET and PBT, the role played by the aliphatic and aromatic sections with respect to radical forming processes is of comparable importance. The cyclohexadienyl radicals arising from these latter polymers are reckoned with the prominent H addition at the sites adjacent to the esters groups which are also statistically favoured. The reactivity distribution in the aromatic rings with respect to the formation of cyclohexadienyls was analyzed in greater detail by comparing the experimental results with DFT B3LYP M.O. calculations. The DFT method has also been employed for assessing the EPR properties of the cyclohexadienyl and ion-radicals from PEN and PET models.     

Magnetic properties of poly(propylene imine)-copper dendromesogenic complexes: An EPR study.

Copper(II) complexes formed by coordination of the Cu(II) ion with liquid-crystalline poly(propylene imine) dendrimer ligand (L) of the first (complex 1) and second (complex 2) generations with various Cu(II) contents (x = Cu/L) have been studied by electron paramagnetic resonance (EPR) spectroscopy. The existence of a redox-active blue complex 1 (x = 1.9) and the copper(II) nitrate electron transfer associated with the valence tautomerism are revealed for the first time in copper-based dendrimers. It has been shown that the electronic structure of the blue complex 1 (x = 1.9) is adequately described as a mixed-valence dimer containing d9- and diamagnetic d10-configurated copper ions, and an antiferromagnetically coupled NO3* radical arising on the nitrate-bridged counter ligand. The activation energy value found for the electron transfer is about 0.35 meV, which indicates a low-energy charge dynamic. The ability of the blue and green complexes 1 (x = 1.9) dissolved in isotropic solvents to orient themselves in the magnetic field was revealed by EPR spectroscopy. The degree of orientation of the molecular z axis (S(z)) of these complexes in the magnetic field differs, depending on the type of copper(II)-complexing site in the dendrimer ligand, and can reach 0.76, which is close to S(z) = 1 (completely aligned system). A combination of magnetic and orientational parameters indicates an NO4 environment of the Cu(II) ion in green complex 1 (x = 1.9), and confirms the chain structure with intermolecular Cu(II)-NO3-Cu(II) bridges between Cu(II) centres in columns.     

A noninvasive complementary study of an Egyptian polychrome cartonnage pigments using SEM,EPMA, and Raman spectroscopy

Raman spectroscopy, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA) were used to study pigments on an Egyptian cartonnage from the Ptolemaic period (305–30 bc ). The surface morphology of each color region was examined using backscattering (BS) and secondary electron imaging. SEM X-ray energy dispersive spectrometry and EPMA wavelength dispersive spectroscopy provided semiquantitative chemical analysis of each pigment. Raman spectroscopy was used to identify the minerals associated with the pigments. This technique confirmed the presence of cinnabar (α-HgS) in the red part of the fragments. A mixture of orpiment (As₂S₃) and bonazziite (β-As₄S₄) and/or alacránite (As₈S₉) was detected in the yellow regions of the fragments. The orange pigment was confirmed to be a mixture of orpiment, uzonite (χ-As₄S₅), and pararealgar (As₄S₄). Egyptian blue (CaCuSi₄O₁₀) and Egyptian green ((Cu,Ca)SiO₃) pigments were detected from blue/green dark-colored regions of the fragments.     

An EPR, ENDOR and EIE study of gamma-irradiated poly (lactide-co-glycolide) polymers

Gamma radiation of poly (lactide-co-glycolide) raw polymers and processed microspheres under vacuum and at 77 K results in the formation of a series of free radicals. The resulting powder electron paramagnetic resonance (EPR) spectrum contains a distribution of several different radicals, depending on the annealing temperature, and is therefore difficult to interpret. By utilising the selectivity of the electron nuclear DOuble resonance (ENDOR) and associated ENDOR induced EPR (EIE) techniques, a more direct approach for the deconvolution of the EPR spectrum can be achieved. Using this approach, the radiolytically induced CH3 *CHC(O)R- chain scission radical was identified at 120 K by simulation of the EIE spectrum. At elevated temperatures (250 K), this radical decays considerably and the more stable radicals -O*CHC(O)-, CH3 *C(OR)C(O)- and CH3 *C(OH)C(O)- predominate. This work demonstrates the utility of the EIE approach to supplement and aid the interpretation of powder EPR spectra of radicals in a polymer matrix.