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Nano‐ and microcrystals of diamond are attractive for optical thermometry applications and possess unique optical properties as well as high chemical stability and biocompatibility. For biological application, there are interests of diamonds with color centers that emit in the biological transparency window. One such defect is nickel‐related color centers that radiate in the near‐infrared range (1.4 eV Ni centers), but have not yet been sufficiently investigated. In this study, the optical characteristics of high‐pressure high‐temperature (HPHT) diamond microcrystals with average sizes of 4 and 30 μm containing 1.4 eV Ni centers are reported. The temperature dependence of the spectral and temporal properties of Ni center emissions in the range from room temperature to 85 °C is demonstrated and thereby the possibility of appliance these centers as temperature sensors. The relative temperature sensitivities of luminescence peak intensity and lifetime for Ni centers are found to be 1.3% K−1 and 0.42% K−1, respectively. Moreover, the temperature determination accuracy reaches better than 1 K. [ABSTRACT FROM AUTHOR]

We present a comprehensive optical spectroscopic study on air-suspended single-walled carbon nanotubes (SWNTs) with diameters ranging from 1.7 nm to 3.4 nm and at higher-order optical transitions, a previously inaccessible regime. We establish an atlas of resonant radial breathing modes (RBMs) for more than 100 new SWNTs in this unknown regime, thus significantly extending the RBM dataset in Kataura plot and enhancing our knowledge of SWNTs. Additionally, we develop an innovative transfer technique for manipulating individual SWNTs of known chiralities (determined by optical spectroscopies) by integrating a polarization imaging technique with the conventional van der Waals (vdW) dry transfer. The unprecedented spatial and structural control of this technique enables a deterministic fabrication and integration of a variety of novel mixed-dimensional vdW heterostructures that were considered unachievable before. Our work significantly extends RBM dataset of SWNT Kataura plot and represents a huge advancement towards controlled fabrication and integration of mixed-dimensional vdW heterostructures encompassing one-dimensional vdW materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Here we report on the non-hydrothermal aqueous synthesis and characterization of nanocrystalline lithium aluminum iodate, LiAl(IO3)4. Morphological and compositional analyses were carried out by using scanning electron microscopy (SEM) and energy-dispersive X-ray measurements (EDX). The optical and vibrational properties of LiAl(IO3)4 have been studied by UV-Vis and IR spectroscopy. LiAl(IO3)4 is found to crystallize in the non-centrosymmetric, monoclinic P21 space group, contrary to what was reported previously. Theoretical simulations and Rietveld refinements of crystal structure support this finding, together with the relatively high Second Harmonic Generation (SGH) response that was observed. Electronic band structure calculations show that LiAl(IO3)4 crystal has an indirect band gap Egap=3.68 eV, in agreement with the experimental optical band gap Egap=3.433 eV. The complex relative permittivity and the refraction index of LiAl(IO3)4 have also been calculated as a function of energy, as well as its elastic constants and mechanical parameters. LiAl(IO3)4 is found to be a very compressible and ductile material. Our findings imply that LiAl(IO3)4 is a promising material for optoelectronic and non -linear optical applications.

A new bioactive material of cobalt(II) with 5,10,15,20-tetrakis[4 (benzoyloxy)phenyl] porphyrin (TPBP) and bpy ligands ([CoII(TPBP)(bpy) 2 ] 1) has been synthesized and characterized by Single-crystal X-ray diffraction (SCXRD), spectroscopic methods and quantum-chemistry calculations. In the crystalline structures of six coordinated Co(II) [CoII(TPBP)(bpy) 2 ] 1 , linear 1D polymeric chains were observed in which all the porphyrin units are aligned parallel to each other. The crystal packing is stabilized by inter-and intramolecular C–H⋯O and C–H⋯N hydrogen bonds, and by weak C–H⋯Cg π interactions. Interestingly, NBO–Second-order perturbation theory analysis, carried out at the UB3LYP/6-31G(d)/SDD DFT level of theory, demonstrated that a two-center bond between the nitrogen atoms and the cobalt ions (Co) was not found, the Co–N py/bp interactions are coming from an electronic delocalization between the N py /N bp filled orbitals to the anti-bonding LP*(4) and LP*(5) metal NBOs. Mass spectroscopy, and elemental analysis were also investigated to confirm the molecular structure. The downfield shift and the peak broadening of the axial ligand resonances observed in the 1H NMR indicated the contiguity to the paramagnetic Co(II) center. Additionally, the photophysical properties have been evaluated by UV–visible absorption, and fluorescence emission spectroscopies. Finally, bioactivity investigations revealed that free porphyrin TPBP, CoIITPBP and complex 1 could be used as potential antioxidant agents. [ABSTRACT FROM AUTHOR]

This work investigates the structural, magnetic and magneto-optical properties of a new zinc phosphate-tellurite glass belonging to the 45ZnO-10Al2O3-40P2O5-5TeO2 system. The glass was prepared by a wet method of processing the starting reagents followed by suitable melting–stirring–quenching–annealing steps. Specific parameters such as density, average molecular mass, molar volume, oxygen packaging density, refractive index, molar refractivity, electronic polarizability, reflection loss, optical transmission, band gap and optical basicity have been reported together with thermal, magnetic and magneto-optical characteristics. Absorption bands appear in the blue and red visible region, while over 600 nm the glass becomes more transparent. FTIR and Raman spectra evidenced phosphate-tellurite vibration modes proving the P2O5 and TeO2 network forming role. Magnetic measurements reveal the diamagnetic character of the Te-doped glass with an additional weak ferromagnetic signal, specific to diluted ferromagnetic oxides. Positive Faraday rotation angle with monotonous decreasing value at increasing wavelength was evidenced from magneto-optical measurements. The final product is a composite material comprising of a non-crystalline vitreous phase and Te-based nanoclusters accompanied by oxygen vacancies. The metallic-like Te colloids are responsible for the dark reddish color of the glass whereas the accompanying oxygen vacancies might be responsible for the weak ferromagnetic signal persisting up to room temperature.

Abstract Basic principles and recent work using probes including Mössbauer, optical, X-ray, and vibrational spectroscopies to follow the transitions in spin crossover complexes are reviewed. X-ray spectroscopy, being a relatively lesser-known probe, is discussed in more detail. X-ray spectroscopic methods have been used in the spin crossover field mostly to elucidate surface phenomena, ultrafast dynamics, and high pressure effects, but recent technical developments provide perspectives for a more widespread use of these powerful techniques in home laboratories. [ABSTRACT FROM AUTHOR]

Advantage is taken of a complete and precise experimental study of the luminescent properties of yttrium aluminium garnet doped with Ce 3+ , previously accomplished by other authors, to confirm the accuracy of the invoked theoretical methods for dealing with the realistic calculation of the electromagnetic spectra of condensed phases. The fluorescent spectra at T = 0 and T = 250 K of YAG:Ce 3+ were calculated with no adjustable parameter, giving complete agreement with experiment. The energy released by the electronic transitions was determined with precision better than 5% the full width at half maximum of the spectral features. It is shown that fitting the experimental features with a lineshape function well grounded in the physics of the emission process can greatly improve the accuracy of the analysis of the spectra. Thermal quenching of the fluorescent yield is discussed and calculated in a less accurate way, but anyway showing good agreement with experiment. The same theoretical framework can be extended to infrared and Raman spectroscopies to improve the accuracy of these analytic techniques. [ABSTRACT FROM AUTHOR]

Glossoscolex paulistus extracellular hemoglobin (HbGp) stability has been monitored in the presence of denaturant agents. 8-Anilino-1-naphtalene-sulfonic acid (ANS) was used, and spectroscopic and hydrodynamic studies were developed. Dodecyltrimethylammonium bromide (DTAB) induces an increase in ANS fluorescence emission intensity, with maximum emission wavelength blue-shifted from 517 to 493 nm. Two transitions are noticed, at 2.50 and 9.50 mmol/L of DTAB, assigned to ANS interaction with pre-micellar aggregates and micelles, respectively. In oxy-HbGp, ANS binds to protein sites less exposed to solvent, as compared to DTAB micelles. In DTAB–HbGp–ANS ternary system, at pH 7.0, protein aggregation, oligomeric dissociation and unfolding were observed, while, at pH 5.0, aggregation is absent. DTAB induced unfolding process displays two transitions, one due to oligomeric dissociation and the second one, probably, to the denaturation of dissociated subunits. Moreover, guanidine hydrochloride and urea concentrations above 1.5 and 4.0 mol/L, respectively, induce the full HbGp denaturation, with reduction of ANS-bound oxy-HbGp hydrophobic patches, as noticed by fluorescence quenching up to 1.0 and 5.0 mol/L of denaturants. Our results show clearly the differences in probe sensitivity to the surfactant, in the presence and absence of protein, and new insights into the denaturant effects on HbGp unfolding. [ABSTRACT FROM AUTHOR]

Abstract: It is shown that different techniques (XRD, TPR, FE-SEM, IR, visible and UV spectroscopies) reveal the presence of bulk NiO particles in NiO/Al2O3 catalyst precursors at different loadings. This is explained considering both the different properties revealed by the different techniques and the likely different effect of particle size, shape and interaction with the support on these properties. Oxide-like supported particles revealed by XRD and FE-SEM in these and maybe similar catalyst systems may have well different electronic and chemical properties with respect to unsupported bulk particles. Different Ni oxide surface species may give rise to different catalytic behaviors in CO2 methanation and steam reforming of ethanol–phenol mixture. [Copyright &y& Elsevier]

Abstract: Polycrystalline YMn1−x In x O3 compounds were obtained by solid state reaction and found to present a blue color for high substitution rate. X-ray diffraction analyses reveal the formation of solid solutions and the increase of cell parameters following Vegard''s law. Far infrared reflectivity and Raman scattering spectra show the presence of random disorder and structural modifications without phase transition. A detailed analysis of some phonon modes allows to explain the structural changes upon doping. It was found that monocaping YO7 antiprisms are almost unaffected by substitution. However, results reveal the existence of two different MO5 (M = In, Mn) trigonal bipyramids. Their apical Mn–O distances are shorter than In–O bonds and both distances increase with the substitution rate, which is consistent with the evolution of the cell parameters. [Copyright &y& Elsevier]

Abstract: Singly doped and Tm3+/Ho3+ co-doped NaY(WO4)2 single crystals were grown successfully by Czochralski method. The room temperature polarized absorption and fluorescence spectra as well as the decay curves were measured. Spectroscopic parameters related to the laser operation around 2.0μm via the 3F4 → 3H6 (Tm3+) and 5I7 → 5I8 (Ho3+) transitions have been evaluated. The energy level scheme and energy transfer processes of Tm3+ and Ho3+ were analyzed. [Copyright &y& Elsevier]

Abstract: The effective refractive index of silica based artificial opals can be strongly modulated through magnesiothermic and wet etching processes. The magnesiothermic reduction of silica spheres assembled in a fcc lattice produces amorphous silicon/magnesia matrix, which can be easily converted in oxidized porous silicon, preserving the ordered structure. These results are verified by electron microscopies and IR/Raman spectroscopies. The optical properties are analyzed in terms of the experimental reflectance spectra. By comparing the measured data to rigorous calculations, the good quality of the opaline replicas is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: A Tm3+-doped Gd3Ga5O12 single crystal with a dimension of Ø 25mm×20mm was grown successfully by Czochralski method. The absorption spectrum was recorded at room temperature and used to calculate the absorption cross-section. Based on the Judd–Ofelt (J–O) theory, we obtained three intensity parameters and a series of spectral parameters, such as the radiative probabilities, radiative lifetimes and branch ratios. Room temperature fluorescence spectra and luminescence decay curve were recorded. The stimulated emission cross-section of the 3F4 → 3H6 IR transition was calculated. The maximum emission cross-section with the peak at 2.0μm is 1.05×10−21 cm2. The potential laser gain for this transition was also investigated. This crystal is promising as a tunable infrared laser crystal at 2.0μm. [Copyright &y& Elsevier]

Abstract: Quaternary bismuthate glasses containing Li2O, ZnO and B2O3 have been prepared by melt quench technique and studied by density, DSC, IR and Raman spectroscopy. Raman and infrared spectroscopy have been employed to investigate the (75− x)Bi2O3–xLi2O–10ZnO–15B2O3 glasses in order to obtain information about the competitive role of Bi2O3 and B2O3 in the formation of glass network. The increase of Bi2O3 content causes a progressive conversion of three- to four-fold coordinated boron. IR and Raman spectra show that these glasses are made up of [BiO3] pyramidal and [BiO6] octahedral units. The formation of Zn in tetrahedral coordination was observed. [Copyright &y& Elsevier]

Abstract: The present work focuses on the interaction between the zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp). Electronic optical absorption, fluorescence emission and circular dichroism spectroscopy techniques, together with Gel-filtration chromatography, were used in order to evaluate the oligomeric dissociation as well as the autoxidation of HbGp as a function of the interaction with HPS. A peculiar behavior was observed for the HPS–HbGp interaction: a complex ferric species formation equilibrium was promoted, as a consequence of the autoxidation and oligomeric dissociation processes. At pH 7.0, HPS is more effective up to 1mM while at pH 9.0 the surfactant effect is more intense above 1mM. Furthermore, the interaction of HPS with HbGp was clearly less intense than the interaction of this hemoglobin with cationic (CTAC) and anionic (SDS) surfactants. Probably, this lower interaction with HPS is due to two factors: (i) the lower electrostatic attraction between the HPS surfactant and the protein surface ionic sites when compared to the electrostatic interaction between HbGp and cationic and anionic surfactants, and (ii) the low cmc of HPS, which probably reduces the interaction of the surfactant in the monomeric form with the protein. The present work emphasizes the importance of the electrostatic contribution in the interaction between ionic surfactants and HbGp. Furthermore, in the whole HPS concentration range used in this study, no folding and autoxidation decrease induced by this surfactant were observed. This is quite different from the literature data on the interaction between surfactants and tetrameric hemoglobins, that supports the occurrence of this behavior for the intracellular hemoglobins at low surfactant concentration range. Spectroscopic data are discussed and compared with the literature in order to improve the understanding of hemoglobin–surfactant interaction as well as the acid isoelectric point (pI) influence of the giant extracellular hemoglobins on their structure–activity relationship. [Copyright &y& Elsevier]

Abstract: The effects of two ionic surfactants on the oligomeric structure of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy - form have been studied through the use of several spectroscopic techniques such as electronic optical absorption, fluorescence emission, light scattering, and circular dichroism. The use of anionic sodium dodecyl sulphate (SDS) and cationic cethyltrimethyl ammonium chloride (CTAC) has allowed to differentiate the effects of opposite headgroup charges on the oligomeric structure dissociation and hemoglobin autoxidation. At pH 7.0, both surfactants induce the protein dissociation and a significant oxidation. Spectral changes occur at very low CTAC concentrations suggesting a significant electrostatic contribution to the protein–surfactant interaction. At low protein concentration, 0.08 mg/ml, some light scattering within a narrow CTAC concentration range occurs due to protein–surfactant precipitation. Light scattering experiments showed the dissociation of the oligomeric structure by SDS and CTAC, and the effect of precipitation induced by CTAC. At higher protein concentrations, 3.0 mg/ml, a precipitation was observed due to the intense charge neutralization upon formation of ion pair in the protein–surfactant precipitate. The spectral changes are spread over a much wider SDS concentration range, implying a smaller electrostatic contribution to the protein–surfactant interactions. The observed effects are consistent with the acid isoelectric point (pI) of this class of hemoglobins, which favors the intense interaction of HbGp with the cationic surfactant due to the existence of excess acid anionic residues at the protein surface. Protein secondary structure changes are significant for CTAC at low concentrations while they occur at significantly higher concentrations for SDS. In summary, the cationic surfactant seems to interact more strongly with the protein producing more dramatic spectral changes as compared to the anionic one. This is opposite as observed for several other hemoproteins. The surfactants at low concentrations produce the oligomeric dissociation, which facilitates the iron oxidation, an important factor modulating further oligomeric protein dissociation. [Copyright &y& Elsevier]

The optical reflectivity in the far infrared region (FIR spectra) was measured for five samples of ZnxCd1-xTe in the Zn range 0.056 using the Hg-lamp as well as synchrotron radiation. The analysis of the two bands of FIR phonon spectra with subtle structure was performed on the basis of the five-configuration tetrahedron model of ternary compounds and the seven-axiom statistical strained-tetrahedral model of Robouch et al. [J. Alloys Comp. 340 (2002) 13]. The eight phonon mode oscillator parameters triplets {Sk, ωk, γk}k=1,8 are obtained using the fitting procedure that enables us to determine the three SOP parameters W1, W2, W3. Thus, the real local crystalline structure of ZnCdTe is defined. [Copyright &y& Elsevier]

This paper describes new software—called GranFilm—for computing linear optical coefficients for surfaces and thin layers. The underlying theory relies on the treatment of the electromagnetic boundary conditions at the surface using the notions of integrated electromagnetic excess fields and surface susceptibilities. Any type of Fresnel quantities (reflection, transmission, absorption or ellipsometric coefficients) and dielectric coefficients (energy electron loss cross-section) can be computed by this software for various kinds of surface morphology: thin continuous films, island layers made of truncated spheres or spheroids, or rough surfaces. The only restriction on the morphology is that the thickness of the surface perturbed layer is much smaller than the optical wavelength. GranFilm covers most of the material developed by Bedeaux and Vlieger in the recently published book ‘Optical Properties of Surfaces’ (Imperial College Press, London, 2001). [Copyright &y& Elsevier]

Here we report on the non-hydrothermal aqueous synthesis and characterization of nanocrystalline lithium aluminum iodate, LiAl(IO3)4. Morphological and compositional analyses were carried out by using scanning electron microscopy (SEM) and energy-dispersive X-ray measurements (EDX). The optical and vibrational properties of LiAl(IO3)4 have been studied by UV-Vis and IR spectroscopy. LiAl(IO3)4 is found to crystallize in the non-centrosymmetric, monoclinic P21 space group, contrary to what was reported previously. Theoretical simulations and Rietveld refinements of crystal structure support this finding, together with the relatively high Second Harmonic Generation (SGH) response that was observed. Electronic band structure calculations show that LiAl(IO3)4 crystal has an indirect band gap E gap = 3.68 eV, in agreement with the experimental optical band gap E gap = 3.43 3 eV. The complex relative permittivity and the refraction index of LiAl(IO3)4 have also been calculated as a function of energy, as well as its elastic constants and mechanical parameters. LiAl(IO3)4 is found to be a very compressible and ductile material. Our findings imply that LiAl(IO3)4 is a promising material for optoelectronic and non -linear optical applications. [ABSTRACT FROM AUTHOR]

This work investigates the structural, magnetic and magneto-optical properties of a new zinc phosphate-tellurite glass belonging to the 45ZnO-10Al2O3-40P2O5-5TeO2 system. The glass was prepared by a wet method of processing the starting reagents followed by suitable melting–stirring–quenching–annealing steps. Specific parameters such as density, average molecular mass, molar volume, oxygen packaging density, refractive index, molar refractivity, electronic polarizability, reflection loss, optical transmission, band gap and optical basicity have been reported together with thermal, magnetic and magneto-optical characteristics. Absorption bands appear in the blue and red visible region, while over 600 nm the glass becomes more transparent. FTIR and Raman spectra evidenced phosphate-tellurite vibration modes proving the P2O5 and TeO2 network forming role. Magnetic measurements reveal the diamagnetic character of the Te-doped glass with an additional weak ferromagnetic signal, specific to diluted ferromagnetic oxides. Positive Faraday rotation angle with monotonous decreasing value at increasing wavelength was evidenced from magneto-optical measurements. The final product is a composite material comprising of a non-crystalline vitreous phase and Te-based nanoclusters accompanied by oxygen vacancies. The metallic-like Te colloids are responsible for the dark reddish color of the glass whereas the accompanying oxygen vacancies might be responsible for the weak ferromagnetic signal persisting up to room temperature. [ABSTRACT FROM AUTHOR]

• Synthesis of mononuclear cobalt(II) complex. • Molecular features were described via optical spectroscopic methods. • A non-Debye relaxation phenomenon is observed. • The activation energies were determined from the conductivity and the electrical modulus. In this work, a new 5,10,15,20-tetrakis[4-(benzoyloxy)phenyl]porphyrin (H 2 TPBP)-based cobalt(II) complex involving DABCO ligand [CoII(TPBP)(DABCO) 2 (1), has been prepared and characterized. The single crystal structure of (1) was obtained with a space group of P-1 and this study provides further information about the structure of the octahedral complex. This six-coordinate complex is close to a perfect plane in H 2 TPBP, and the molecules are interconnected through C–H⋯O and C–H⋯ π interactions to form 1D and 3D architectures. Spectroscopic characterizations such as Mass spectroscopy, elemental analysis, infrared, and 1HNMR in solution demonstrate the contiguity of the paramagnetic Co(II) center. The photophysical properties were investigated by UV–visible absorption and emission spectroscopies. The dielectric properties such as dielectric constant (ε ′), dielectric loss (ε ″), conductivity (σ), real (M′) and imaginary part (M″) of dielectric modulus were investigated as a function of temperature and frequency. The impedance analysis was carried out using Cole-Cole plots to elucidate the electrical conduction mechanism. [ABSTRACT FROM AUTHOR]

• Magnetic and optical spectroscopies of melanin doped by 3d-TMS are investigated. • V/Fe-melanin have a half-metallic nature, and the other TMs-melanin are insulators. • The doping effect of TMs on melanin identifies the edge change of the optical spectra. • Emergence of ferromagnetism in melanin doped by 3d-TMs is useful for spintronics. By employing spin-polarized density functional theory calculations, systematic investigations are carried out on the electronic, magnetic and optical features of melanin doped with 3d-transition metals (TMs). Our study aims to seek for a novel appealing nanomaterial that could be applied to spintronic devices. The structural models of isolated monomers of melanin and the electronic spin-polarized properties of these organic molecules doped with 3d-TMs are analyzed. According to our theoretical finding, the Ni-doped melanin has a nonmagnetic state, although a tiny magnetic moment is induced in both Cu- and Zn-doped into melanin. This can be essentially ascribed by the bonding interactions between these 3d-TMs and oxygen atom. Interestingly, the remaining frameworks of isolated monomer structures of melanin doped with 3d-TMs carry a quite significant magnetic moment. Only V- and Fe-doped into melanin are found to exhibit a half-metallic character, albeit the other TMs-melanin have a semiconducting property. For the overall systems, such as the pure melanin and its doping with 3d-TMs, we computed the optical absorption, reflectivity, and X-ray absorption near-K-edge structure spectra to identify the edge alteration of the optical spectra. This scrutiny could pave a new route to acquire the ferromagnetism in the isolated monomers of melanin doped with some selected 3d-TM species. We anticipate that these organic molecules doped with 3d-TMs could be potential candidates for energy storage, catalysts, and molecular electronic and spintronics. [ABSTRACT FROM AUTHOR]