The effect of some color centers on the coloration of natural and synthetic diamonds

Mechanisms of the formation of diamond coloration caused by the light absorption by basic impurity defects, which are optically active in the visible region, have been studied. The analytical relationships between the relative concentration of each defect and the diamond main color tone and saturation have been derived. The influence of the centers under study on the diamond coloration has been compared.     

EPR,optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

Antimony phosphate glasses (SbPO) doped with 3 and 6 mol% of Cr³⁺ were studied by Electron Paramagnetic Resonance (EPR), UV–VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr³⁺-doped glasses showed two principal resonance signals with effective g values at g = 5.11 and g = 1.97. UV–VIS optical absorption spectra of SbPO:Cr³⁺ presented four characteristics bands at 457, 641, 675, and 705 nm related to the transitions from ⁴A₂(F) to ⁴T₁(F), ⁴T₂(F), ²T₁(G), and ²E(G), respectively, of Cr³⁺ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr³⁺ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B = 2.48 indicates that Cr³⁺ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr³⁺ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr³⁺-doped glasses excited with 350 nm revealed weak emission bands from 400 to 600 nm due to the ³P₁ → ¹S₀ electronic transition from Sb³⁺ ions. Cr³⁺-doped glasses excited with 415 nm presented Cr³⁺ characteristic luminescence spectra composed by two broad bands, one band centered at 645 nm (²E → ⁴A₂) and another intense band from 700 to 850 nm (⁴T₂ → ⁴A₂).     

EPR and vibrational studies of YVO4:Tm, Yb single crystal

A well oriented YVO₄ single crystal, with 5% Yb³⁺ and 2% Tm³⁺ nominal doping, was investigated using the Raman and EPR techniques.The EPR measurements suggest that Yb³⁺ ions occupy eight-coordinated Y³⁺ sites forming bisdisphenoids of the D_2d symmetry. An inhomogeneous distribution of rare-earth ions leads to a significant distortion of the local point symmetry (C₁). It seems that strong dipole–dipole interactions between Yb³⁺ ions are responsible for the distortion. As a result, two types of ytterbium magnetic centers appear. They correspond to paired magnetic centers and distorted isolated paramagnetic centers that are strongly sensitive to the magnetic field directions and some imperfections of the crystal. Pair centers can be recorded through the rotation around the c-crystal axis, whereas isolated centers can be measured when the crystal is rotated around the a-crystal axis. With the increasing temperature, the ytterbium signal disappeared at about 23 K and a group of narrow lines became visible. These lines, observed in the range of 240–550 mT, correspond to the Gd³⁺ (S = 7/2) ions, doped to the structure unintentionally from the basic materials.     

TL,EPR and optical absorption studies on natural alexandrite compared to natural chrysoberyl

The TL, optical absorption (OA) and EPR properties of natural Brazilian alexandrite and chrysoberyl have been investigated. The TL measurements for natural alexandrite show five peaks between 100 and 450 degrees C, with their emission spectrum having 370 and/or 570 nm components. The intensity of the 320 degrees C TL peak was found to be enhanced with pre-annealing treatment, more prominently above 600 degrees C. The OA and EPR measurements showed that this kind of heat treatment induces the Fe2+ --> Fe3+ conversion in the natural sample. Chrysoberyl samples exhibited the TL peaks at the same temperatures as alexandrite samples, but the glow curves were more than 200 times less intense than alexandrite ones.     

Adsorption character for removal Cu(II) by magnetic Cu(II) ion imprinted composite adsorbent

A novel magnetic Cu(II) ion imprinted composite adsorbent (Cu(II)-MICA) was synthesized, characterized and applied for the selective removal Cu(II) from aqueous solution in the batch system. The adsorption-desorption and selectivity characteristics were investigated. The maximum adsorption occurred at pH 5-6. The equilibrium time was 6.0h, and a pseudo-second-order model could best describe adsorption kinetics. The adsorption equilibrium data fit Langmuir isotherm equation well with a maximum adsorption capacity of 46.25mg/g and Langmuir adsorption equilibrium constant of 0.0956L/mg at 298K. Thermodynamic parameters analysis predicted an exothermic nature of adsorption and a spontaneous and favourable process that could be mainly governed by physisorption mechanism. The relative selectivity coefficients of Cu(II)-MICA for Cu(II)/Zn(II) and Cu(II)/Ni(II) were 2.31, 2.66 times greater than the magnetic non-imprinted composite adsorbent (MNICA). Results suggested that Cu(II)-MICA was a material of efficient, low-cost, convenient separation under magnetic field and could be reused five times with about 14% regeneration loss.     

Biosorption of Cu(II) ions onto the litter of natural trembling poplar forest

The litter of natural trembling poplar (Populus tremula) forest (LNTPF) was used for the biosorption of Cu(II) ions in a batch adsorption experiments. The sorption capacity of LNTPF was investigated as a function of pH, particle size, agitating speed, initial Cu(II) concentration, adsorbent concentration and temperature. The efficiency of copper uptake by the used LNTPF increases with a rise of solution pH, adsorbent concentration, agitating speed, temperature, and with a decline of particle size and initial Cu(II) concentration. The biosorption process was very fast; 94% of Cu(II) removal occurred within 5 min and equilibrium was reached at around 30 min. Batch adsorption models, based on the assumption of the pseudo-first order, pseudo-second order mechanism were applied to examine the adsorption kinetics. The pseudo-second order model was found to best fit the kinetic data. EPR studies combined with FTIR spectroscopy were used to represent the biosorption mechanism. Thermodynamic parameters such as DeltaH degrees, DeltaS degrees and DeltaG degrees were calculated. The adsorption process was found to be endothermic and spontaneous. Equilibrium data fitted well to Langmuir adsorption model. This study proved that the LNTPF can be used as an effective, cheap and abundant adsorbent for the treatment of Cu(II) containing wastewaters.     

Synthesis,structure, vibrational spectral,nonlinear optical and electron-behavioral studies of N-(5-chloro-2-hydroxyphenyl)-(3-hydroxyphenyl)-methalimine

In recent years, the imine-bridged organics has been one of the hot spots in the field of photo-responsive materials. Herein, N-(5-chloro-2-hydroxyphenyl)-(3-hydroxyphenyl)-methalimine (CHPHPMI) was synthesized by a condensation reaction of 3-hydroxybenzaldehyde and 2-amino-4-chlorophen with formic acid as catalyst in ethanol solvent, and characterized by the single crystal X-ray diffraction and FT-IR measurement techniques as well as theoretical calculations. The studied molecule adopts trans configuration about the central CN bond, in which a five-numbered ring is formed by an intramolecular hydrogen bonding OH⋯N. The adjacent molecules are linked by three kinds of intermolecular hydrogen bonds to form a one-dimensional columnar supermolecular structure along b axis in the monoclinic crystal system with space group P2₁. The spectral bands were assigned to the molecular structure in details with the aid of the theoretical calculation. Furthermore, the physical parameters of thermodynamics, NLO, atomic charges, natural bond orbitals and frontier molecular orbitals were presented by the theoretical analysis for the studied molecule. The first-order hyperpolarizability of CHPHPMI is 30 times that of urea. The studied molecule presents the molecular battery characteristics connected by six directional batteries in a parallel–series mode to transport electrons in a long range. The HOMO and LUMO orbitals with an energy gap 3.632 eV are responsible for the nonlinear optical and electron-transfer properties. The electron-behavioral characteristics of the studied molecule indicate the studied compound will be an excellent molecular semiconductor candidate of photovoltaic materials.     

A sustainable generated hydrochar from pomegranate residues for remediation of process water contaminated with Cu(II) ions

An eco-friendly, flexible and sustainable valorization of pomegranate residue (PR) was studied by hydrothermal technology. PR was used as a feedstock for producing hydrochar (PRHC) and the effects of treatment temperature (TT; 180, 200, 220 °C) and treatment time (Tt; 6, 12, 24 h) on the elemental composition, yield, higher heating value (HHV) and energy density (D_E) parameters were examined. The most suitable production conditions were recommended as TT of 220 °C and Tt of 12 h with a HHV of 23.23 MJ/kg and D_E of 1.22 GJ/m³. A broad spectral survey including FTIR, SEM/EDX, XPS, XRD, Raman and ¹³C MAS-NMR techniques were performed to define its physicochemical characteristics. PRHC was applied as an adsorbent for removal of Cu(II) ions from water and adsorption kinetics indicated well-suitability of the data to the pseudo second order model while the Langmuir model best described the equilibrium data with a 113.64 mg/g. Thermodynamics evaluation displayed the spontaneous, feasible and endothermic adsorption of Cu(II) ions. In addition, regeneration studies have shown efficiently usage of PRHC for multiple times in wastewater treatment.     

Crystal structure and EPR study of Mn-doped β-tricalcium phosphate

Mn-doped β-tricalcium phosphate was prepared by solid state reaction at 1100 °C. The crystal structure of Ca_2.85Mn_0.15(PO₄)₂, was determined by single crystal X-ray diffraction and found to be rhombohedral, R3c. Unit cell parameters are: a = 10.3419(3); c = 37.025(3) Å (hexagonal setting), Z = 21. Structure refinement data show that from the five Ca positions the Ca(4) site is only half filled and that the Mn²⁺ ions occupy the hexacoordinated Ca(5) site solely. EPR spectroscopy reveals that manganese in solid solutions Ca_3−xMn_x(PO₄)₂ (x = 0.1; 0.28; 0.6) is divalent and supports the structure refinement results that Mn occupies the Ca(5) site with a geometry very near to a regular octahedron.     

Functionalized cotton via surface-initiated atom transfer radical polymerization for enhanced sorption of Cu(II) and Pb(II)

The surface-initiated atom transfer radical polymerization (ATRP) was used to successfully prepare the aminated cotton and polyacrylic acid sodium (P(AA-Na))-grafted cotton for the efficient removal of Cu(II) and Pb(II) from aqueous solution in this study. The modified cotton surfaces were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The grafted long polymers with high density of amine and carboxyl groups on the cotton surfaces were responsible for the enhanced adsorption of heavy metals. The sorption behaviors including sorption kinetics, isotherms and pH effect were investigated. The sorption equilibrium of Cu(II) and Pb(II) was achieved within 1 h on the P(AA-Na)-grafted cotton, much faster than 8 h on the aminated cotton. According to the Langmuir fitting, the maximum sorption capacities of Cu(II) and Pb(II) on the P(AA-Na)-grafted cotton were 2.45 and 2.44 mmol/g, respectively, higher than many adsorbents reported in the literature. The P(AA-Na)-grafted cotton had better adsorption behaviors for Cu(II) and Pb(II) than the aminated cotton.     

理论研究ZnO掺杂Al;Ga;In电子结构与光学属性(英文)

计算了Ga、Al、In掺杂对ZnO体系电子结构和光学性质的影响.所有计算都是基于密度泛函理论(DFT)框架下的第一原理平面波超软赝势方法.计算结果表明:Ga、AI、In掺杂在ZnO中占据了Zn位置,为n型浅施主掺杂,导带底引入了大量由掺杂原子贡献的导电载流子,明显提高了体系的电导率.同时,光学带隙展宽,且向低能方向漂移,可作为优良的透明导电薄膜材料.同时,计算结果为我们制备基于ZnO透明导电材料的设计与大规模应用提供了理论依据,也为监测和控制ZnO透明导电材料的生长过程提供了可能性.     

Yb:NaY(WO4)2晶体生长及性能研究

本文首次采用提拉法生长出了四方晶系白钨矿结构的Yb:NaY(WO4)2晶体,通过TG-DTA分析得到晶体的熔点为1211℃,测试了该晶体的红外光谱、拉曼光谱和吸收光谱.结果表明,该晶体在848nm、968nm附近有较强、较宽的吸收峰,适合于LD泵浦.     

Synthesis and application of chloromethylated polystyrene modified with 1-phenyl-1,2-propanedione-2-oxime thiosemicarbazone (PPDOT) as a new sorbent for the on-line preconcentration and determination of copper in water, soil, and food samples by FAAS

In this paper, we report a simple and sensitive on-line solid phase extraction system for the preconcentration and determination of Cu(II) by flame atomic absorption spectrometry (FAAS). This method is based upon the on-line retention of copper at pH 5.0 on a minicolumn packed with chloromethylated polystyrene modified by 1-phenyl-1,2-propanedione-2-oxime thiosemicarbazone (PPDOT) as a new solid-phase extraction (SPE) sorbent. The retained Cu(II) ions were eluted with 1.0 M HNO₃, and transported directly to FAAS for determination. Several chemical and flow variables were studied and optimized for a quantitative preconcentration and determination of copper(II). At the optimized conditions, for preconcentration of 10.0 mL of a sample solution, a linear calibration graph was obtained over the concentration range of 3.00-120.0 μg L⁻¹ for Cu(II). The limit of detection (3σ), limit of quantification (10σ), and enrichment factor are 0.56 μg L⁻¹, 2.0 μg L⁻¹ and 41, respectively. The relative standard deviation (n = 6) at 20 μg L⁻¹ of Cu(II) is 2.0%. This method could be applied for determination of trace amounts of Cu(II) in water, soil, and food samples with satisfactory results.     

Cloud point extraction and flame atomic absorption spectrometry combination for copper(II) ion in environmental and biological samples

A cloud point extraction procedure was presented for the preconcentration of copper(II) ion in various samples. After complexation by 4-(phenyl diazenyl) benzene-1,3-diamine (PDBDM) (chrysoidine), copper(II) ions were quantitatively recovered in Triton X-114 after centrifugation. 0.5 ml of methanol acidified with 1.0 mol L⁻¹ HNO₃ was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry (FAAS). The influence of analytical parameters including ligand, Triton X-114 and HNO₃ concentrations, bath temperature, heating time, centrifuge rate and time were optimized. The effect of the matrix ions on the recovery of copper(II) ions was investigated. The detection limit (3S.D._b/m, n = 10) of 0.6 ng mL⁻¹ along with preconcentration factor of 30 and enrichment factor of 41.1 with R.S.D. of 1.0% for Cu was achieved. The proposed procedure was applied to the analysis of various environmental and biological samples.     

EPR and SQUID studies on magnetic properties of SiO2-doped Ni–Zn ferrite nanocomposites

Effects of the silica content and temperature on the magnetic properties of Ni_0.5Zn_0.5Fe₂O₄/SiO₂ nanocomposites have been studied by electron paramagnetic resonance (EPR) and superconducting quantum interference device (SQUID) technique. The content of TEOS in the starting solution affects the interaction between NiZn ferrite and silica, and then determines the particle size and the EPR properties. In addition, the SQUID properties of the composites were sensitive to particle size. It was observed that the saturation magnetization (M_s), remnant magnetization (M_r) and initial susceptibility (χ_i) decreased with increasing SiO₂ content.     

Photoacoustic, EPR and electrical conductivity investigations of three synthetic mineral pigments: hematite, goethite and magnetite

Three iron oxide pigments: hematite, goethite and magnetite, have been synthesized from the copperas by-product produced as a waste material in large quantities in the titanium dioxide plant in Chemical Works “Police,” Poland. These pigments have been characterized by X-ray diffractometry and X-ray fluorescence spectroscopy and it has been found that they are mono-phase systems with only a small addition of other spurious phases. The electrical resistivity measurements reveals that the ion oxide samples are semiconductor materials. Conductivity of magnetite at room temperature is over six orders of magnitude greater than that of the other two materials. Photoacoustic (PA) spectra of hematite and goethite in the visual region of the electromagnetic radiation shows a single intense absorption peak centred at 558 and 480 nm, respectively, while for the magnetite a continuous spectrum of increasing amplitude with increasing wavelength of the measurement is obtained. EPR spectra for the iron(III) complexes have been registered at room temperature which indicate hematite and goethite have only one similar EPR line centred at g∼2 with different linewidths, while magnetite has two very intense overlapping and broad EPR lines centred at low and high magnetic resonance fields. Additional EPR line of Mn²⁺ ions has been also recorded for the hematite sample. Application of these pigments is discussed in terms of economic and environmental advantages.     

Geometric and electronic changes during interface alloy formation in Cu/Pd bimetal layers

This study involves monitoring the interface evolution with increasing annealing temperatures in a Cu-Pd bimetal layer structure. The changes due to interdiffusion and ensuing charge transfer are monitored by extensive X-ray photoelectron spectroscopy (XPS) and glancing angle X-ray diffraction (GAXRD) studies. The Pd and Cu core level fingerprinting and change in lattice parameter provide evidence for alloy formation. The changes in the valence band features indicate the formation of new states that are different from the density of states of individual metal surfaces. The study demonstrates the possibility of tuning interface properties by alloy formation that may have specific applications in catalysis, hydrogen sensing and storage.     

Silver and proton driven fluorescent multiple-mode molecular logic gates employing phthalocyanines

Spectral properties and switch behavior of two alkyl thia units bearing Zn (II) phthalocyanine derivatives (Pc-A and Pc-B) were investigated in solvents and in solid matrix of ethyl cellulose by means of absorption and emission spectroscopy. Fluorescence lifetime and fluorescence quantum yield values of the Zn (II) phthalocyanines were calculated. The employed phthalocyanines demonstrated multiple molecular logic gate functions operated by H⁺ and Ag⁺ ions as chemical inputs. The silver driven fluorescence modulation of the Pc-A arises from reversible variations in emission signal intensity at 717 nm. The Pc-B exhibited a similar decreasing emission response to proton and silver ions and an accompanying increasing peak yielding an isobestic point at 746 nm upon protonation. The phthalocyanine doped thin films selectively responded to silver ions in sub-nano and/or pico molar levels. Observed detection limits were 7.6 × 10⁻¹² and 2.3 × 10⁻¹¹ M for Pc-A and Pc-B, respectively. In immobilized phases the attained reversible relative signal changes of Pc-A and Pc-B were 82 and 90%, respectively.     

Cu含量对TiN-Cu纳米复合膜结构与性能的影响

为研究纳米复合膜超硬机理和促进其商业应用,利用电弧离子镀制备了Ti N-Cu纳米复合膜,并对其表面形貌、晶体结构、能谱、XPS谱和硬度进行研究.结果表明:沉积膜仅含有Ti N相和少量的Ti相,Ti N相晶粒尺寸随薄膜Cu含量的增加而逐渐减小;尽管有的沉积膜中Cu原子数分数高达8.99%,但仍没有发现金属Cu相或Cu的化合物相衍射峰;沉积膜中Cu元素以金属Cu的状态存在,Ti主要以Ti N相存在,少量以金属Ti相存在,但没有Ti2N相;薄膜生长过程中,Cu、Ti和N共沉积,竞争生长,Cu的加入抑制了Ti N晶粒的长大;沉积膜的硬度随Cu含量增加而增加,达到最大值后下降,薄膜硬度随Cu含量变化与薄膜中Ti N相或Cu相尺寸有关.