A comprehensive study on the electronic structure,dielectric and optical properties of alkali-earth metals and transition metal hydroxides M(OH)2

In the present work, the physical properties of alkali-earth metal and transition metal hydroxides are comprehensively investigated using the density functional theory. Here, the alkali-earth metals Ca, Mg, and transition metals Cd, Zn are considered from the II-A and II-B groups in the periodic table of elements. The first principle electronic structure calculations show that these bulk hydroxide materials are direct band gap material. Ca(OH)₂ and Mg(OH)₂ exhibit an insulating behavior with a very large band gap. However, Cd(OH)₂ and Zn(OH)₂ are found to be wide band gap semiconductors. The dielectric and optical studies reveal that these materials have a high degree of anisotropy. Hence, the light propagation in these materials behaves differently in the direction perpendicular and parallel to the optical axis, and exhibits birefringence. Therefore, these materials may be useful for optical communication. The calculated electron energy loss suggests that these materials can also be used for unwanted signal noise suppression. The wide band gap makes them useful for high-power applications. Moreover, Ca(OH)₂ and Mg(OH)₂ are found to be suitable for dielectric medium.     

Electronic,transport, magnetic,and optical properties of graphene nanoribbons and their optical sensing applications: A comprehensive review

Low dimensional materials have attracted great research interest from both theoretical and experimental point of views. These materials exhibit novel physical and chemical properties due to the confinement effect in low dimensions. The experimental observations of graphene open a new platform to study the physical properties of materials restricted to two dimensions. This featured article provides a review on the novel properties of quasi one-dimensional (1D) material known as graphene nanoribbon. Graphene nanoribbons can be obtained by unzipping carbon nanotubes (CNT) or cutting the graphene sheet. Alternatively, it is also called the finite termination of graphene edges. It gives rise to different edge geometries, namely zigzag and armchair, among others. There are various physical and chemical techniques to realize these materials. Depending on the edge type termination, these are called the zigzag and armchair graphene nanoribbons (ZGNR and AGNR). These edges play an important role in controlling the properties of graphene nanoribbons. The present review article provides an overview of the electronic, transport, optical, and magnetic properties of graphene nanoribbons. However, there are different ways to tune these properties for device applications. Here, some of them, such as external perturbations and chemical modifications, are highlighted. Few applications of graphene nanoribbon have also been briefly discussed.     

On prediction of optical properties of two- and multiphase nanocomposites for nanomedicine

The theory of optical properties of nanoparticles is considered with the aid of dispersion relations, which are based on the Kramers-Kronig analysis. It is shown that one can utilize rather general dispersion relations, which hold for liquid matrices that contain nanoparticles. Wiener bounds incorporating the Kramers-Kronig analysis are utilized in assessment of the complex permittivity of a nanoparticle.     

多尺度植物色彩表征及其与人体响应的关系

色彩是人们对植物外观的第一印象,与植物视觉特征和人体响应关系密切,因此,对森林美景度提升和公众适宜性契合具有重要作用。结合色彩学形成的历史关键节点和1个世纪以来植物色彩的研究动态,将植物色彩研究的发展历程划分为萌芽、形成、发展和繁荣等4个阶段,并简介了各阶段的主要特点。同时,从植物器官、植物个体、植物群体(涵盖种群和群落)、整体景观等4个视觉尺度以及审美、生理与心理等3个影响层面,阐述与评价了植物色彩传达机制与人体响应关系的相关研究。在此基础上,围绕植物色彩特征提取中存在的色彩要素定量、特征因子选取、色彩量化方法等方面的不足之处,对未来研究方向进行展望,提出植物色彩尺度与公众响应关系剖析、较大尺度色彩评价因子的深入挖掘、色彩量化方法的多学科融入、公众对植物色彩响应关系综合比对、森林景观美景度提升实践等5个方向的发展趋势,以期为全面地了解植物色彩的传达机制与影响、科学地开展不同精度和尺度下的植物色彩研究提供参考。     

太湖梅梁湾沿岸带水体生物学与光学特性

基于 1998～ 1999年周年 4季原位水下光场观测资料及中国科学院太湖湖泊生态系统研究站 1992～ 2 0 0 1年悬浮物、叶绿素 a、透明度长期历史观测资料分析了太湖梅梁湾沿岸带第 2号站点水体的生物学与光学特性 ,探讨了水下光合有效辐射(PAR)总量的日变化、垂直分布 ;光衰减系数的季节变化及光谱分布 ;影响光衰减系数的主要水色因子。结果表明 ,无论是 PAR还是光谱衰减系数其值都很高 ,其中 PAR衰减系数在 1.4 0～ 5 .30 / m间变化 ,均值为 2 .4 3± 0 .5 5 / m,秋季最大、夏季最小 ,真光层深度在 0 .87～ 3.2 9m间变化 ,均值为 1.98± 0 .4 1m;水下光谱在蓝光波段衰减最强烈 ,其次是红光、绿光 ,随着深度增加光谱成分出现绿移和红移现象 ,绿红光占得比例越来越大 ;光谱衰减系数随着波长的增加大致呈下降趋势 ,但在 6 70 nm附近有个峰值 ;基于线性相关分析发现在混浊的沿岸带水体中影响光衰减主要因子为水体中的悬浮物和有色可溶性有机物 ,叶绿素 a对 PAR衰减系数的贡献率只占到 1.5 9%～ 14 .2 1%。     

Synthesis,phase evolution and optical properties of Tb3+‐doped KF–YbF3 system materials

KF–YbF₃ system materials have been synthesized by a hydrothermal method without any surfactant or template. By controlling the reactant ratios of KF:Yb³⁺, the hydrothermal temperature and the pH of the prepared solutions, the final products can evolve among the orthorhombic phase of YbF₃, the cubic phase of KYb₃F₁₀ and the cubic phase of KYbF₄. The X‐ray diffraction (XRD) patterns of the samples prove the phase evolution of the final products. The morphologies of the samples were characterized using field emission scanning electron microscopy (FE‐SEM) images and the evolution of the morphology is consistent with that of the crystalline phases. The optical properties of Tb³⁺ in the samples were characterized by PL excitation and emission spectra, as well as luminescent decay curves. Copyright © 2014 John Wiley & Sons, Ltd.     

Daily variations in the optical properties of a small lake

1. The major components of the underwater light field (ULF: vertical attenuation, absorption, scattering and suspensoids including plankton fractions) of Las Madres Lake, a small wind‐sheltered, oligohumic lake in Central Spain, were investigated daily over a period of 3 months at the onset of vernal circulation. 2. Gilvin, arising mostly from the decomposition of reeds in the littoral in autumn, was the main component of vertical attenuation, and its variability explained the highest fraction of absorption variability. Tripton appeared to be the main factor responsible for scattering, and might have resulted from dust deposition from the surrounding mining land. The plankton community played a minor role in attenuation, absorption or scattering throughout the investigation period. 3. Vertical and horizontal mixing dynamics may control the ULF to a certain extent, as most optical properties changed within different mixing periods and poor advective exchanges may have resulted in uneven distribution of water colour in this small lake. 4. Time series analysis showed that most autocorrelations were shorter than a week, inherent properties (absorption, scattering) being delayed longer than apparent properties (attenuation, transparency) as a result of their lower dependence on solar irradiance. A 2‐day lag was observed in cross‐correlations between either gilvin and absorption or tripton and scattering. When different mixing periods at early circulation were considered, however, ULF components changed their relationships and delays with suspensoids and dissolved substances over such periods, probably tracking the dynamics of their controlling factors. 5. Our study, and others at daily, weekly, seasonal, interannual and long‐term scales, demonstrates that ULF is a system upon which different processes are operating at different time scales. Contrary to expectations, however, the variability in the ULF does not increase with time scale and depends partly upon the trophic status of lakes.     

Measurement of optical properties of pig esophagus by using a modified spectrometer set‐up

Optical properties (μ_a, μ_s and g) of certain human tissue types such as skin and blood have been very well investigated. However until today, for internal body organs such as the esophagus they are not well characterized. For ex‐vivo measurements “Inverse Adding Doubling” (IAD) and Inverse Monte‐Carlo‐Simulation (IMCS) are state of the art. Both methods need the measurement of the collimated transmission. Current methods lack a proper way of measuring the collimated transmission. Hence, this measurement of the g‐factor has a systematic error. Therefore, for the measurement of the collimated transmission, a new approach has been developed and evaluated with intralipid. Finally, the optical properties of mucosa, sub mucosa, muscularis and adventitia of pig esophagus tissue are calculated with IAD. The results are promising and in agreement with published literature.

     

Theoretical study of geometrical and nonlinear optical properties of pyridinum N-phenolate betaine dyes

This paper presents an ab initio quantum chemical investigation of the geometrical structures and the non-linear optical properties (NLO) of three structural isomers of pyridinium N-phenolate betaine dye. The ground state geometrical parameters and the first-order hyperpolarizabilities were calculated using the Hartree-Fock (HF) as well as the second-order perturbation Møller-Pleset (MP2) method with the 6–31G, 6–31G(d), 6–31G(d,p), 6–31+G(d), 6–31++G(d,p), 6–311+G(d), aug-cc-PVDZ and the recently developed Z3PolX basis sets. Moreover, the first-order hyperpolarizability was calculated at the coupled cluster singles and doubles (CCSD/6–31+G(d)) level of theory. The analysis of the results of calculations for the investigated isomers indicates that there are important differences in their NLO activities. Additionally, it was shown that Z3PolX basis set works reasonable well for betaine dyes.

Syntheses and structures’ influence on the nonlinear optical properties of o-ferrocenylbenzoate compounds

Two complexes containing o-ferrocenylbenzoate [o-⁻OOCH₄C₆Fc, Fc = (η⁵-C₅H₅)Fe(η⁵-C₅H₄)] components: {[Pb(η²-o-OOCH₄C₆Fc)₂(phen)](NO₃)} (phen = phenanthroline) (1) and {[Zn(η²-o-OOCH₄C₆Fc)₂(bpe)](CH₃OH)}_n (bpe = 1,2-bis(4-pyridyl) ethene) (2) have been synthesized and structurally characterized by single crystal X-ray diffraction. 1 gives a discrete mononuclear framework, 2 features an infinite 1-D chain structure constructed by the bpe linking two adjacent zinc (II) ions. The third-order nonlinear optical (NLO) properties of complexes 1, 2 and the reactant o-NaOOCH₄C₆Fc were determined by Z-scan techniques in DMF solution. The results show that the structures of complexes have great impact on NLO properties. Complex 1 and o-NaOOCH₄C₆Fc display self-defocusing behaviors, while complex 2 exhibits strong self-focusing effect. The solution-state differential pulse voltammograms of complexes 1, 2 and o-NaOOCH₄C₆Fc were investigated as well. The results reveal that the half-wave potential of the ferrocenyl moieties is strongly influenced by the Pb(II) or Zn(II) ions in complexes 1 and 2.     

生物被膜的物理特性及其表征

生物被膜涉及到人类生产生活的方方面面。生物被膜的形成有时是有益的,可用于生物降解、生物催化等;但同时也造成了诸多不利的影响,医疗领域中的感染性疾病、工业生产中的生物污损等均与生物被膜的形成有关。生物被膜形成过程中的物理性质决定着生物被膜的形态结构以及机械稳定性,对它在应对外界环境刺激并得以生存具有重要的意义。本文介绍了生物被膜形成初期和发展过程中的物理性质以及相应的表征手段。其中,细菌的表面粘附由细菌的近界面运动行为及细菌与表面的相互作用决定,并对生物被膜的初期形成起关键的作用。此外,机械性能测试发现成熟的生物被膜可看作具备粘弹性的聚合物。     

Synthesis, crystal structure and magnetic properties of a novel iron(III) 18-azametallacrown-6 compound

A novel macrocyclic hexanuclear iron(III) 18-azametallacrown-6 compound, [Fe₆(C₉H₇N₂O₃)₆(CH₃OH)₆]·8CH₃OH·2H₂O, has been prepared using a trianionic pentadentate ligand N-acetylsalicylhydrazide (ashz³⁻) and characterized by X-ray diffraction. Due to the meridional coordination of the ligand to the Fe³⁺ ion, the ligand enforces the stereochemistry of the Fe³⁺ ions as a propeller configuration with alternating Λ/Δ forms. The disc-shaped hexanuclear ring shows about 6.20 Å in diameter at entrance, about 9.31 Å at its largest diameter at the center of the cavity, respectively. There are many kinds of intramolecular and intermolecular hydrogen bonds in the title compound. The OH?O hydrogen bond distances range from 2.609(5)-2.901(5) Å. The magnetic susceptibility (4-275K) study indicates antiferromagnetic exchange interactions between the adjacent Fe³⁺ ions around the ring.     

Synthesis, structure and optic properties of 2-methylimidazolium and 2-phenylimidazolium uranyl acetates

Two new salts based on heterocyclic organic cations and uranyl triacetate anion were obtained via reaction of zinc uranyl acetate with 2-substituted imidazoles in presence of an excess of acetic acid. Uranyl triacetate anion in [2-MeImH]⁺ [UO₂(CH₃COO)₃]⁻ and [2-PhImH]⁺ [UO₂(CH₃COO)₃]⁻ H₂O has an expected bipyramidal structure with linear uranyl group and three acetate groups laying in equatorial plane. [2-MeImH]⁺ [UO₂(CH₃COO)₃]⁻ structure analysis reveals H-bonded 1D chains connected through N-H···O hydrogen bonds. 2-phenylimidazolium in [2-PhImH]⁺ [UO₂(CH₃COO)₃]⁻ H₂O demonstrate planar geometry without any rotation of its rings, which was not registered before. H-bonds and π-π interactions of phenyl groups in this system lead to complicate 2D “sandwich” layer formation. The main features of IR- and luminescence spectrum of both compounds are also discussed.     

An azomethin-zinc complex for organic electroluminescence: Crystal structure, thermal stability and optoelectronic properties

An azomethin-zinc complex, bis[salicylidene(4-dimethylamino)aniline]zinc(II) (Zn(sada)₂) was synthesized and structurally characterized by single-crystal X-ray crystallography. Crystal data for Zn(C₁₅H₁₅N₂O)₂ was determined as follows: space group, triclinic, ; a = 10.2791(9) Å, b = 16.5008(14) Å, c = 17.5984(15) Å, α = 114.830(2)°, β = 96.579(2)°, γ = 97.674(2)°, Z = 4. Through thermal analysis characterization and FT-IR spectra, this complex was proved to have good thermal stability. The vapor-deposited films exhibited uniform and environment-stable morphology. The light emission and charge transporting performance of Zn(sada)₂ in organic light emitting diodes (OLEDs) were investigated preliminarily, and the results indicated the superior electron transporting property of this complex. Compared with the typical bilayer device of N,N′-diphenyl-N,N′-bis(1-naphthyl)-benzidine (NPB)/tris-(8-hydroxyquinoline)aluminum (Alq₃), the device with Zn(sada)₂ as the electron transporting layer exhibited a much lower turn-on voltage of 2.5 V (it is usually 3.5 V for an NPB/Alq₃ device).     

Two cobalt(II) one-dimensional ribbon of rings polymers: Syntheses, structures and non-linear optical properties

Two cobalt(II) coordination polymers {[Co(SCN)₂(3-bpit)₂] · 2CH₃OH}_n (1) (3-bpit = N,N′-bis(3-pyridylformyl)imidazolidine-2-thione) and {[Co(SCN)₂(4-bpit)₂] · CH₃OH · CH₃CN}_n (2) (4-bpit = N,N′-bis(4-pyridylformyl)imidazolidine-2-thione) have been synthesized for study of the third-order non-linear properties. X-ray crystal structural analyses reveal that the two polymers show the same topological motif: a ribbon of rings. Their third-order non-linear optical (NLO) properties in DMF solution have been studied by Z-scan techniques with a linearly polarized laser light (λ = 532 nm; pulse widths = 7 ns). Both of them exhibit strong self-focusing effect. The third-order NLO susceptibility χ⁽³⁾ values are calculated to be 2.61 × 10⁻¹¹ esu (1) and 2.76 × 10⁻¹¹ esu (2), respectively. The values are comparable to those of the reported good NLO materials.     

Algorithm independent properties of RNA secondary structure predictions

Algorithms predicting RNA secondary structures based on different folding criteria – minimum free energies (mfe), kinetic folding (kin), maximum matching (mm) – and different parameter sets are studied systematically. Two base pairing alphabets were used: the binary GC and the natural four-letter AUGC alphabet. Computed structures and free energies depend strongly on both the algorithm and the parameter set. Statistical properties, such as mean number of base pairs, mean numbers of stacks, mean loop sizes, etc., are much less sensitive to the choice of parameter set and even of algorithm. Some features of RNA secondary structures, such as structure correlation functions, shape space covering and neutral networks, seem to depend only on the base pairing logic (GC or AUGC alphabet). Received: 16 May 1996 / Accepted: 10 July 1996     

Measuring local properties inside a cell‐mimicking structure using rotating optical tweezers

Exploring the rheological properties of intracellular materials is essential for understanding cellular and subcellular processes. Optical traps have been widely used for physical manipulation of micro and nano objects within fluids enabling studies of biological systems. However, experiments remain challenging as it is unclear how the probe particle's mobility is influenced by the nearby membranes and organelles. We use liposomes (unilamellar lipid vesicles) as a simple biomimetic model of living cells, together with a trapped particle rotated by optical tweezers to study mechanical and rheological properties inside a liposome both theoretically and experimentally. Here, we demonstrate that this system has the capacity to predict the hydrodynamic interaction between three‐dimensional spatial membranes and internal probe particles within submicron distances, and it has the potential to aid in the design of high resolution optical micro/nanorheology techniques to be used inside living cells.      

CdSe and CdSe/CdS core–shell QDs: New approach for synthesis,investigating optical properties and application in pollutant degradation

In this work, CdSe quantum dots (QDs) were synthesized by a simple and rapid microwave activated approach using CdSO₄, Na₂SeO₃ as precursors and thioglycolic acid (TGA) as capping agent molecule. A novel photochemical approach was introduced for the growth of CdS QDs and this approach was used to grow a CdS shell around CdSe cores for the formation of a CdSe/CdS core–shell structure. The core–shells were structurally verified using X‐ray diffraction, transmission electron microscopy and FTIR (Fourier‐transform infrared (FTIR)) spectroscopy. The optical properties of the samples were examined by means of UV–Vis and photoluminescence (PL) spectroscopy. It was found that CdS QDs emit a broad band white luminescence between 400 to 700 nm with a peak located at about 510 nm. CdSe QDs emission contained a broad band resulting from trap states between 450 to 800 nm with a peak located at 600 nm. After CdS shell growth, trap states emission was considerably quenched and a near band edge emission was appeared about 480 nm. Optical studies revealed that the core–shell QDs possess strong ultraviolet (UV) ? visible light photocatalytic activity. CdSe/CdS core–shell QDs, showed an enhancement in photodegradation of Methyl orange (MO) compared with CdSe QDs.     

Preparation, structure and properties of triphenylphosphine rhodium aryloxides

The reaction of Wilkinson's catalyst with NaOAr in toluene cleanly affords the corresponding aryloxide complexes Rh(PPh₃)₃OAr (1). In solution, 1 exists in equilibrium with PPh₃ and the corresponding Rh(PPh₃)₂(π-ArO) (2). The addition of HOAr shifts the equilibrium completely toward the corresponding adducts 2·2HOAr, due to hydrogen bonding between the oxygen atom of the π-coordinated OAr ligand and two molecules of HOAr. Heating of 1a-d in toluene at 60–80°C leads to the elimination of HOAr with concomitant cyclometallation of a phenyl ring of one PPh₃ ligand, affording mixtures of 1,2·2HOAr, a cyclometallated Rh complex and PPh₃. At room temperature, a reverse reaction slowly occurs to give equilibrium mixtures of 1, 2 and PPh₃. Complexes 1 readily with water, CO and H₂, affording Rh₂(PPh₃)₄(μ-OH)₂, Rh(PPh₃)₂(CO)OAr (3) and HRh(PPh₃)₃, respectively. The latter complex was also obtained when complexes 1 were treated with methanol. The structures of the phenoxide complexes 1 and 2·2PhOH and of p-nitrophenoxide complex 3 were established by X-ray diffraction.     

Preparation and optical properties of alloyed ZnxCd1‐xS/alginate core/shell nanoparticles

Zn_xCd_1‐xS/alginate core/shell nanoparticles were synthesized via a colloidal route by reacting zinc and cadmium ions with sulfide ions, followed by coating with alginate. The crystal structure, morphology, size and optical properties of the core/shell nanoparticles were characterized by X‐ray diffraction, transmission electron microscopy, UV/vis and photoluminescent spectra, respectively. The Zn_xCd_1‐xS nanoparticles are spherical and have a cubic structure with a mean crystalline size of 2–4 nm. The band gap of Zn_xCd_1‐xS/alginate core/shell nanoparticles increases with increasing Zn/Cd molar ratio, and the UV/vis absorption blue‐shifts correspondingly. Two emissions related to zinc and sulfide ion vacancies were observed for the Zn_xCd_1‐xS/alginate core/shell nanoparticles due to the surface changes from the alginate coating. A cadmium‐related emission was observed for both the uncovered Zn_xCd_1‐xS and Zn_xCd_1‐xS/alginate core/shell nanoparticles, which has a significant blue‐shift with increasing Zn/Cd molar ratio. Copyright © 2014 John Wiley & Sons, Ltd.