Optical Properties (optical + property)

Distribution by Scientific Domains

Kinds of Optical Properties

  • good optical property
  • linear optical property
  • nonlinear optical property
  • second-order nonlinear optical property
  • third-order nonlinear optical property
  • unique optical property

  • Selected Abstracts


    JOURNAL OF PHYCOLOGY, Issue 3 2008
    Sébastien Mas
    Diel variations of cellular optical properties were examined for cultures of the haptophyte Imantonia rotunda N. Reynolds and the diatom Thalassiosira pseudonana (Hust.) Hasle et Heimdal grown under a 14:10 light:dark (L:D) cycle and transferred from 100 ,mol photons · m,2 · s,1 to higher irradiances of 250 and 500 ,mol photons · m,2 · s,1. Cell volume and abundance, phytoplankton absorption coefficients, flow-cytometric light scattering and chl fluorescence, and pigment composition were measured every 2 h over a 24 h period. Results showed that cell division was more synchronous for I. rotunda than for T. pseudonana. Several variables exhibited diel variability with an amplitude >100%, notably mean cell volume for the haptophyte and photoprotective carotenoids for both species, while optical properties such as flow-cytometric scattering and chl a,specific phytoplankton absorption generally showed <50% diel variability. Increased irradiance induced changes in pigments (both species) and mean cell volume (for the diatom) and amplified diel variability for most variables. This increase in amplitude is larger for pigments (factor of 2 or more, notably for cellular photoprotective carotenoid content in I. rotunda and for photosynthetic pigments in T. pseudonana) than for optical properties (a factor of 1.5 for chl a,specific absorption, at 440 nm, in I. rotunda and a factor of 2 for the absorption cross-section and the chl a,specific scattering in T. pseudonana). Consequently, diel changes in optical properties and pigmentation associated with the L:D cycle and amplified by concurrent changes in irradiance likely contribute significantly to the variability in optical properties observed in biooptical field studies. [source]


    JOURNAL OF PHYCOLOGY, Issue 6 2002
    Michele D. DuRand
    Micromonas pusilla (Butcher) Manton et Parke, a marine prasinophyte, was used to investigate how cell growth and division affect optical properties of phytoplankton over the light:dark cycle. Measurements were made of cell size and concentration, attenuation and absorption coefficients, flow cytometric forward and side light scattering and chl fluorescence, and chl and carbon content. The refractive index was derived from observations and Mie scattering theory. Diel variations occurred, with cells increasing in size, light scattering, and carbon content during daytime photosynthesis and decreasing during nighttime division. Cells averaged 1.6 ,m in diameter and exhibited phased division, with 1.3 divisions per day. Scattering changes resulted primarily from changes in cell size and not refractive index; absorption changes were consistent with a negligible package effect. Measurements over the diel cycle suggest that in M. pusilla carbon-specific attenuation varies with cell size, and this relationship appears to extend to other phytoplankton species. Because M. pusilla is one of the smallest eukaryotic phytoplankton and belongs to a common marine genus, these results will be useful for interpreting in situ light scattering variation. The relationship between forward light scattering (FLS) and volume over the diel cycle for M. pusilla was similar to that determined for a variety of phytoplankton species over a large size range. We propose a method to estimate cellular carbon content directly from FLS, which will improve our estimates of the contribution of different phytoplankton groups to productivity and total carbon content in the oceans. [source]

    Reactions of [Et4N][Tp*W(,3 -S)(,-S)2­(CuSCN)2] with Nitrogen Donor Ligands: Syntheses, Structures, and Third-Order Nonlinear Optical Properties

    Zhen-Hong Wei
    Abstract Reactions of the preformed cluster [Et4N][Tp*W(,3 -S)(,-S)2(CuSCN)2] (1) with pyridine (py), 4,4,-bipyridine (4,4,-bipy), or 1,3-bis(4-pyridyl)propane (bpp) led to the formation of three neutral [Tp*W(,3 -S)(,-S)2Cu2]-based compounds [Tp*W(,3 -S)(,-S)2Cu2(SCN)(py)2] (2), [{Tp*W(,3 -S)(,-S)2Cu2(SCN)}2(4,4,-bipy)]·3.5H2O (3·3.5H2O), and [Tp*W(,3 -S)(,-S)2Cu2(SCN)(bpp)]2 (4), respectively. Compounds 2,4 were characterized by elemental analysis, IR spectra, UV/Vis spectra, 1H NMR, and X-ray analysis. There are two linkage isomers [Tp*W(,3 -S)(,-S)2Cu2(SCN)(py)2] and [Tp*W(,3 -S)(,-S)2Cu2(NCS)(py)2], each of which has its own enantiomeric pair in the crystal of 2. Compound 3 has a double butterfly-shaped structure in which two [Tp*W(,3 -S)(,-S)2Cu2(SCN)] fragments are linked with a single 4,4,-bipy bridge. For 4, the two butterfly-shaped [Tp*W(,3 -S)(,-S)2Cu2(SCN)] fragments are interconnected by a pair of bpp bridges. The third-order nonlinear optical (NLO) performances of 2,4 in DMF were also investigated by Z -scan techniques.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Synthesis, Structure, Conductivity, and Calculated Nonlinear Optical Properties of Two Novel Bis(triphenylphosphane)copper(I) Dithiocarbamates,

    Abhinav Kumar
    Abstract A centrosymmetric binuclear [{Cu(PPh3)2}2(piperzdtc)] (1) [piperzdtc2, = piperazinebis(dithiocarbamate)] and another mononuclear [{Cu(PPh3)2}(BzMedtc)] (2) (BzMedtc, = N -benzyl- N -methyldithiocarbamate) complex have been synthesized and characterized by elemental analyses, IR, 1H, 13C, and 31P NMR spectroscopy and by X-ray crystallography. The nonlinear optical properties of 2 have been investigated by density functional theory and its electronic absorption bands have been assigned by time-dependent density functional theory (TD-DFT). Both complexes are weakly conducting (,rt , 10,8 S,cm,1) because of the absence of M···S/S···S intermolecular stacking and exhibit semiconductivity with band gaps of 0.94 and 1.24 eV, respectively.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Synthesis, Characterisation and Optical Properties of Silica Nanoparticles Coated with Anthracene Fluorophore and Thiourea Hydrogen-Bonding Subunits

    Pilar Calero
    Abstract Bifunctionalised hybrid silica nanoparticles have been synthesised and characterised, and their optical emission properties in the presence of certain anions in acetonitrile solutions have been studied. The alkoxysilane derivatives N -butyl- N, -[3-(trimethoxysilyl)propyl]thiourea (1), N -phenyl- N, -[3-(trimethoxysilyl)propyl]thiourea (2) and 3-[(anthracen-10-yl)methylthio]propyltriethoxysilane (3) were prepared and used to functionalise uncoated LUDOX silica nanoparticles with a mean diameter of 18,±,2 nm. The functionalisation of the nanoparticle surfaces was carried out by two different approaches. The first approach relies on the consecutive grafting of the two subunits. In this protocol, the nanoparticles were first functionalised with anthracene derivative 3 (solid NA), and then treated with the corresponding binding sites 1 or 2 to result in the NA-Pt3 and NA-Bt3 solids. The second approach deals with the simultaneous grafting of 1 or 2 and the signalling subunit 3 in different ratios. This method was used for the preparation of the NA1Pt1, NA1Bt1, NA1Pt3 and NA1Bt3 nanoparticles. The bifunctionalised silica nanoparticles were characterised by using standard techniques. Acetonitrile suspensions of NA nanoparticles (5 mg in 20 mL) showed anthracene bands centred at ca. 350, 370 and 390 nm. Upon excitation at 365 nm, a typical emission band with fine structure in the 390,450 nm range was observed. Similar absorption and emission spectra were found for the bifunctionalised nanoparticles. The work is completed with a prospective study of the fluorescence of the prepared nanoparticles in the presence of organic (acetate, benzoate) and inorganic (F,, Cl,, Br,, CN,, HSO4, and H2PO4,) anions. The apparent binding constants (adsorption constants) for the interaction of NA-Pt3 with anions in acetonitrile were determined by performing a Langmuir-type analysis of fluorescence titration data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    How Do the Different Defect Structures and Element Substitutions Affect the Nonlinear Optical Properties of Lacunary Keggin Polyoxometalates?

    A DFT Study
    Abstract Systematic DFT calculations have been carried out on the lacunary ,-Keggin polyoxometalate derivatives [PW11O39]7,, [XW9O34]n, (X = AlIII, SiIV, GeIV, PV, AsV, and SbV), [XW9M2O39]n,, and [XW9M3O40]n, (X = PV and SiIV, M = MoVI, VV, NbV, and TaV) to investigate the geometric structure and element substitution effects on the molecular nonlinear optical response. Analysis of the computed static second-order polarizability (,0) predicts that the molecular nonlinear optical activity of lacunary Keggin polyoxometalate derivatives can be modified by replacing the central heteroatom and the addenda metal atom. Substitution of the central Al atom or the addenda V atom causes significant enhancement in the molecular nonlinearity. Moreover, the ,0 values are substantially dependent on the defect structures. This class of inorganic complexes possesses remarkably large molecular optical nonlinearity, especially for the partial substitution complex [SiW9Nb2O39]10, (IIIc), which has a computed ,0 value of 2071.0 a.u. Thus, lacunary Keggin polyoxometalates could become excellent candidates in the field of second-order NLO. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Synthesis, Crystal Structure, and Second-Order Nonlinear Optical Properties of Ruthenium(II) Complexes with Substituted Bipyridine and Phenylpyridine Ligands

    Laurence Labat
    Abstract Two new ruthenium(II) complexes of formula [Ru(bpy)2(L1)][PF6] and [Ru(bpy)2(L2)][PF6]2 are reported. HL1 is a (nitrophenyl)ethenyl-substituted phenylpyridine ligand, and L2 is the bipyridine analogue of HL1. The X-ray crystal structure of [Ru(bpy)2(L1)][PF6] has been solved, and the compound is found to crystallize in the monoclinic C2/c space group. The electronic spectrum of the cyclometalated derivative [Ru(bpy)2(L1)][PF6] exhibits a low-lying transition that is red-shifted from 454 to 546 nm relative to that of the parent bipyridine-based complex, which reveals an important charge-transfer character. To support this assumption, the nonlinear optical properties were investigated by the hyper-Rayleigh scattering technique and indicate a molecular static hyperpolarizability (,0) equal to 230,×,10,30 cm5,esu,1. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    A Crystalline Phase Transition and Optical Properties in a CoIICuII Oxamato-Bridged Ferrimagnetic Chain

    Cynthia L. M. Pereira
    Abstract The compound [CoCu(opba)(DMSO)3] (1) [opba = ortho -phenylenebis(oxamato)] has been synthesized and characterized. Its crystal structure has been analyzed by X-ray diffraction techniques at 100 and 298 K. A structural phase-transition has been detected at around 150 K. An orthorhombic crystalline system is found at both temperatures, with very similar unit-cell dimensions. At room temperature 1 crystallizes in the Pnam space group (, -1 phase), with a = 7.6712(2), b = 14.8003(3), c = 21.0028(5) Å, and Z = 4, whereas at low temperature it crystallizes in the Pna21 space group (, -1 phase), with a = 7.3530(2), b = 14.5928(4), c = 21.0510(7) Å, and Z = 4. Both crystalline phases consist of linearly ordered bimetallic chains with the [Cu(opba)]2, units tied by CoII ions to form a one-dimensional system. The DMSO molecules in , -1, which are coordinated to either CuII or CoII, are disordered. At low temperature, a small reorganization of the CuII and CoII environments is observed. The origin of this phase transition, which is completely reversible, is the modification of the crystalline packing with the temperature. Linear birefringence measurements were done on single crystals in the 100,300 K temperature range. Around 150 K, the linear birefringence curve shows an inflexion that is interpreted as being related to the conversion of ,-1 into , -1. Both dc and ac magnetic measurements were performed on the polycrystalline sample. The results reveal a one-dimensional ferrimagnetic behavior. Single crystal optical characterization at room temperature shows that 1 presents a very strong dichroism superposed on the linear birefringence. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Synthesis, Crystal Structure, and Optical Properties of a New Molecular Complex of C60 with a Covalently Linked (FeIIITPP)2O Dimer

    Aleksey L. Litvinov
    Abstract A new molecular complex of C60 with covalently linked ,-oxo dimer (FeIIITPP)2O are (TPP = tetraphenylporphyrin) was obtained. The complex has a neutral ground state and is formed mainly by van der Waals forces. The X-ray analysis of the crystal structure of the complex showed it to have isolated packing of fullerenes in which each fullerene molecule is embraced in a pocket built by porphyrins. Optical properties and EPR behavior of the complex are described. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Second-Order Nonlinear Optical Properties of Tetraaza-Coordinated Nickel(II) Complexes

    Santo Di Bella
    Abstract In this contribution, we report the design and theoretical analysis, using the INDO/SCI-SOS quantum chemical formalism, of novel molecular architectures based on planar [N4]-, (2-aminobenzylideneiminato)- and tetraazamacrocycle-coordinated nickel(II) complexes, having second-order nonlinear optical (NLO) properties. Calculations indicate that these molecules possess comparable, or even larger, second-order nonlinearity to the bis(salicylaldiminato)NiII Schiff-base analogues. The nonlinearity of substituted complexes is dominated by the nature and position of substituents on the tribenzo[b,f,l] and/or cyclotetradecine rings, and is determined by the relative directions of the ground- and excited-state dipole moments. Moreover, substitution with acceptor groups in the dibenzo[b,l] rings involves a significant octupolar contribution to optical nonlinearity. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Photochromic Properties of a Spirooxazine and a Spiropyran in Alcoholic Solutions of Zirconium and Aluminium Alkoxides: Influence of the Ethyl Acetoacetate Chelating Agent on the Optical Properties

    Aurélie Lafuma
    Abstract The photochromism of two spiro compounds, a spiropyran and a spirooxazine, dissolved in alcoholic solutions of metal alkoxides M(OR)n (M = Zr, Al) has been studied. In the case of the aluminium alkoxide Al(OsBu)3, special photochromic behaviour is observed characteristic of complexation between the coloured form of the dyes and the aluminium. This chemical interaction induces a considerable shift in the absorption spectra and a significant retardation rate in the dark. Addition of ethyl acetoacetate, a bidentate chelate of aluminium, leads to the disappearance of this particular photochromic behaviour. (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003) [source]

    Synthesis, Optical Properties, and Crystal Structure of 1,4-Dipropyltetracene

    Chitoshi Kitamura
    Abstract We synthesized 1,4-dipropyltetracene on a 200-mg scale, the key step of which involved a Diels,Alder reaction between alkyl-substituted o -quinodimethane, generated in situ, and 1,4-naphthoquinone. The product was obtained as an orange solid, which was soluble in organic solvents including hexane. The optical properties of the product in solution showed no marked differences from those of other 1,4,7,10-tetraalkyltetracenes. Solid-state absorption and fluorescence spectra exhibited 20,30 nm blueshifts compared with those of 1,4,7,10-tetrapropyltetracene. X-ray analysis revealed that two propyl groups were coplanar with the tetracene ring, that there was no , overlap along the stacking direction, and that the molecules formed a herringbone structure. The peripheral alkyl chains were found to be important for controlling the molecular packing and optical properties in the solid state. [source]

    Complexation Behavior of a Supramolecular Organic Fluorophore Prepared by Solid-State Co-Grinding Crystallization Using 2-Anthracenecarboxylic Acid and (R)-1-(2-Naphthyl)ethylamine and Its Optical Properties

    Yoshitane Imai
    Abstract A novel crystalline supramolecular organic fluorophorehaving a 21 -helical columnar structure has been prepared by solid-state co-grinding crystallization using crystals of 2-anthracenecarboxylic acid and (R)-1-(2-naphthyl)ethylamine. Although many organic fluorophores lose their fluorescence in the solid state, this supramolecular organic fluorophore exhibits fluorescence even in the solid state.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    One-Pot Synthesis of Core-Modified Rubyrin, Octaphyrin, and Dodecaphyrin: Characterization and Nonlinear Optical Properties

    Rajeev Kumar
    Abstract Modified 26, rubyrin, 36, octaphyrin, and 54, dodecaphyrin systems have been synthesized in moderately good yields through acid-catalyzed condensations of terthiophene diols and tripyrranes. The product distributions are decided both by the acid catalyst concentration and by the nature of the meso substituents. For example, a new isomer of [26]hexaphyrin( (rubyrin) was obtained with 0.3 equiv. of p -toluenesulfonic acid, when the meso substituent was mesityl in at least one of the precursors. A change of the mesityl substituent for a p -methoxy substituent in terthiophene diol resulted in the formation of a [3,+,3,+,3,+,3] condensation product , [54]dodecaphyrin( , in addition to the expected rubyrin. Furthermore, an increase in the acid concentration to 0.6 equiv. resulted in the formation of a new [36]octaphyrin(, in addition to the rubyrin and dodecaphyrin. A single-crystal X-ray analysis of octaphyrin represents the first example of a planar conformation of an octaphyrin with six meso links. In rubyrin 19, one thiophene ring, opposite to the terthiophene subunit, is inverted, while in octaphyrin 30 one pyrrole ring and two thiophene rings are inverted. The various conformational possibilities tested for the unsubstituted dodecaphyrin 28, at semiempirical level, suggest that the most stable conformation is a figure-eight. The final geometry optimization of figure-eight dodecaphyrin was done at the B3LYP/6-31G* level of DFT. Octaphyrins and dodecaphyrins bind trifluoroacetate anion effectively in their diprotonated forms, the binding constants (K) being 638 M,1 for dodecaphyrin 28, and 415 M,1 for octaphyrin 30. Electrochemical data reveal HOMO destabilization with increasing , electron conjugation, consistently with the large red shifts of the absorption bands. Preliminary studies on the use of these expanded porphyrins as third-order NLO materials were followed by measurements of their two-photon absorption (TPA) cross-sections [,(2)]. The ,(2) values increase upon going from the 26, rubyrins to the 54, dodecaphyrins, confirming our earlier observation that increases in ,-conjugated electrons increase the TPA values.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

    Synthesis, Characterisation and Nonlinear Optical Properties of Two-Dimensional Octupolar Systems Based on Phthalocyanine Compounds

    Maurizio Quintiliani
    Abstract Four phthalocyanine-based compounds with pseudo D3h symmetry have been synthesised and fully characterised. Palladium cross-coupling methodologies were employed in order to synthesise 1,3,5-tris[(phthalocyaninyl)ethenyl]benzene (Heck) and 1,3,5-tris[(phthalocyaninyl)ethynyl]benzene (Sonogashira) derivatives. Knoevenagel condensation conditions were then applied to the synthesis of 1,3,5-tris[cyano(phthalocyaninyl)ethenyl]benzene and 2,4,6-tris[(phthalocyaninyl)ethenyl]-1,3,5-triazine. Preliminary second-order nonlinear optical studies, by hyper-Rayleigh scattering measurements, revealed that the compounds containing ethenyl linkers induce a strong octupolar effect while the ethynyl-containing compound does not show any octupolar enhancement. The introduction of a triazine central core does not modify significantly the nonlinear optical behaviour of the compound. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Enhanced Optical Properties and Opaline Self-Assembly of PPV Encapsulated in Mesoporous Silica Spheres

    Timothy L. Kelly
    Abstract A new poly(p -phenylenevinylene) (PPV) composite material has been developed by the incorporation of insoluble PPV polymer chains in the pores of monodisperse mesoporous silica spheres through an ion-exchange and in situ polymerization method. The polymer distribution within the resultant colloidal particles is characterized by electron microscopy, energy dispersive X-ray microanalysis, powder X-ray diffraction, and nitrogen adsorption. It was found that the polymer was selectively incorporated into the mesopores of the silica host and was well distributed throughout the body of the particles. This confinement of the polymer influences the optical properties of the composite; these were examined by UV,vis and fluorescence spectroscopy and time-correlated single-photon counting. The results show a material that exhibits an extremely high fluorescence quantum yield (approaching 85%), and an improved resistance to oxidative photobleaching compared to PPV. These enhanced optical properties are further complemented by the overall processability of the colloidal material. In marked contrast to the insolubility of PPV, the material can be processed as a stable colloidal dispersion, and the individual composite spheres can be self-assembled into opaline films using the vertical deposition method. The bandgap of the opal can be engineered to overlap with the emission band of the polymer, which has significant ramifications for lasing. [source]

    Synthesis and Optical Properties of KYF4/Yb, Er Nanocrystals, and their Surface Modification with Undoped KYF4,

    Helmut Schäfer
    Abstract KYF4/Yb3+, Er3+ nanocrystals with a mean diameter of approximately 13,nm were synthesized at 200,°C in the high boiling organic solvent N -(2-hydroxyethyl)ethylenediamine (HEEDA). The particles crystallize in the cubic phase known from , -NaYF4 and form transparent colloidal solutions in tetraethylene glycol (TEG) or propanol. Solutions containing 1,wt % of the nanocrystals in TEG display visible upconversion emission upon continuous wave (CW) excitation at 978,nm. Growing undoped KYF4 on the surface of the KYF4/Yb3+, Er3+ nanocrystals increases the upconversion efficiency by more than a factor of 20. The XRD data of these particles, display a slight increase in the mean particle size from 13 to 15.5,nm, indicating that only a part of the subsequently added KYF4 shell material is deposited onto the particle surface. Nevertheless the performed surface modification obviously leads to core/shell structured particles. [source]

    Lattice-Registered Two-Photon Polymerized Features within Colloidal Photonic Crystals and Their Optical Properties,

    Erik C. Nelson
    Abstract In this work we demonstrate a significant advance in the introduction of embedded defects in 3D photonic crystals by means of two-photon polymerization. We have developed the ability to precisely position embedded defects with respect to the lattice of 3D photonic crystals by imaging the structure concurrently with two-photon writing. Defects are written with near-perfect lattice registration and at specifically defined depths within the crystal. The effect of precise defect position on the optical response is investigated for embedded planar cavities written in a photonic crystal. The experimental data are compared to spectra calculated using the Scalar Wave Approximation (SWA). [source]

    Linear and Nonlinear Optical Properties of Ag Nanowire Polarizing Glass,

    Q.-Q. Wang
    Abstract An R2O,B2O3,SiO2 (R,=,Li, Na, K) polarizing glass containing Ag nanorods is prepared by thermal elongation,reduction technology. The transverse and longitudinal plasmon absorption peaks of the embedded Ag nanorods are near 460 and 720,nm, respectively. When the polarization of the laser is parallel to the long axis of the Ag nanorods, the nonlinear absorption coefficient ,,=,0.82,cm,GW,1 and the nonlinear refractive index n2,=,,1.5,×,10,4,cm2,GW,1. When the polarization of light is perpendicular to the long axis of the Ag nanorods ,,=,0.12,cm,GW,1 and n2,=,,7.2,×,10,5,cm2,GW,1 and the appropriate one- and two-photon figures of merit (FOM), W,=,1.6 and T,=,0.16, respectively, are obtained, which satisfies the demand, W,>,1 and T,<,1, for applications in all optical switching, where W is a one-photon FOM, and T is a two-photon FOM. [source]

    Anisotropic Optical Properties of Semitransparent Coatings of Gold Nanocaps,

    J. Liu
    Abstract An ordered array of cap-shaped gold nanoparticles has been prepared by vapor deposition onto polystyrene nanospheres supported on a glass substrate. The method of fabrication used imparts a significant anisotropy to the geometric and optical properties of the coating. The optical-absorption properties of these deposits have been measured using UV-vis spectrometry and simulated using a code based on the discrete dipole approximation. Because the nanocaps are not interconnected, they interact with incident light as individual particles with a plasmon resonance that depends upon wavelength and the polarization vector of the light. The resulting extinction peaks manifest in the upper visible and near-infrared regions of the electromagnetic spectrum. Surprisingly, varying the angle of incidence of the light (for a fixed polarization) has no effect on the optical properties of individual nanocaps. Calculations show that these phenomena may be readily interpreted in terms of dipole resonances excited across the longitudinal, transverse, and short-transverse directions of the nanocaps. Coatings comprised of arrays of these particles have the potential to serve as angularly and spectrally selective filters. [source]

    Synthesis and Optical Properties of Europium-Doped ZnS: Long-Lasting Phosphorescence from Aligned Nanowires,

    C. Cheng
    Abstract Quasi-aligned Eu2+ -doped wurtzite ZnS nanowires on Au-coated Si wafers have been successfully synthesized by a vapor deposition method under a weakly reducing atmosphere. Compared with the undoped counterpart, incorporation of the dopant gives a modulated composition and crystal structure, which leads to a preferred growth of the nanowires along the [010] direction and a high density of defects in the nanowire hosts. The ion doping causes intense fluorescence and persistent phosphorescence in ZnS nanowires. The dopant Eu2+ ions form an isoelectronic acceptor level and yield a high density of bound excitons, which contribute to the appearance of the radiative recombination emission of the bound excitons and resonant Raman scattering at higher pumping intensity. Co-dopant Cl, ions can serve not only as donors, producing a donor,acceptor pair transition with the Eu2+ acceptor level, but can also form trap levels together with other defects, capture the photoionization electrons of Eu2+, and yield long-lasting (about 4,min), green phosphorescence. With decreasing synthesis time, the existence of more surface states in the nanowires forms a higher density of trap centers and changes the crystal-field strength around Eu2+. As a result, not only have an enhanced Eu2+ 4f65d1,4f7 intra-ion transition and a prolonged afterglow time been more effectively observed (by decreasing the nanowires' diameters), but also the Eu2+ related emissions are shifted to shorter wavelengths. [source]

    Composition- and Shape-Controlled Synthesis and Optical Properties of ZnxCd1,xS Alloyed Nanocrystals,

    C. Li
    Abstract Composition-tunable ZnxCd1,xS alloyed nanocrystals have been synthesized by a new approach consisting of thermolyzing a mixture of cadmium ethylxanthate (Cd(exan)2) and zinc ethylxanthate (Zn(exan)2) precursors in hot, coordinating solvents at relatively low temperatures (180,210,°C). The composition of the alloyed nanocrystals was accurately adjusted by controlling the molar ratio of Cd(exan)2 to Zn(exan)2 in the mixed reactants. The alloyed ZnxCd1,xS nanocrystals prepared in HDA/TOP (HDA: hexadecylamine; TOP: trioctylphosphine) solution exhibit composition-dependent shape and phase structures as well as composition-dependent optical properties. The shape of the ZnxCd1,xS nanocrystals changed from dot to single-armed rod then to multi-armed rod with a decrease of Zn content in the ternary nanoparticles. The alloying nature of the ZnxCd1,xS nanocrystals was consistently confirmed by the results of high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and UV-vis absorption and photoluminescence (PL) spectroscopy. Further, the shape-controlled synthesis of the ternary alloyed nanocrystals was realized by selecting appropriate solvents. Uniform nanodots in the whole composition range were obtained from TOPO/TOP solution, (TOPO: trioctylphosphine oxide) and uniform nanorods in the whole composition range were prepared from HDA/OA solution (OA: octylamine). The effect of the reaction conditions, such as solvent, reaction temperature, and reaction time, on the PL spectra of the alloyed ZnxCd1,xS nanocrystals was also systematically studied, and the reaction conditions were optimized for improving the PL properties of the nanocrystals. [source]

    Synthesis, Structure, and Optical Properties of Terminally Sulfur-Functionalized Core-Substituted Naphthalene-Bisimide Dyes

    Alfred B, aszczyk
    Abstract The synthesis, characterization, and optical properties of a series of new 2,6-disubstituted naphthalene-bisimide dyes as molecular rods comprising terminal AcS groups is reported. The first series of dyes (1,3), comprising phenylhetero (Ph-X) core substituents, cover a broad range of the VIS spectrum, ranging from yellow (2) over red (3) to blue (1). The second series of dyes contains benzylhetero (Bn-X) core substituents (4,7). For the same heteroatom connecting the substituent to the naphthalene core, both series were found to display comparable colors. For the second series, the colors were blue (4), red (5), and violet (6, 7). The Ph-X-substituted dyes 1,3 are nonfluorescent, in contrast to the Bn-X-substituted compounds 4,7. This rich variety of optical features that can be adjusted by rather small alterations of the core substituents makes these structurally very comparable molecular rods ideal candidates for optically triggered molecular-transport investigations. Also, thanks to the terminal AcS groups, these compounds can be placed between nobel-metal electrodes for optically triggered transport experiments. [source]

    Alkali Metal Doped Organic Molecules on Insulators: Charge Impact on the Optical Properties

    ADVANCED MATERIALS, Issue 36 2010
    Thomas Dienel
    Doping-induced absorption changes of organic molecules on an insulating solid are reported. The charge transfer between alkali metal atoms and individual molecules on a surface leads to new electronic transitions identified with optical absorption spectroscopy. Progressive doping allows the discrimination of neutral, monoanionic and dianionic molecules in the solid state through examination of the spectra and rate equation modeling. [source]

    Tailored Synthesis of Superparamagnetic Gold Nanoshells with Tunable Optical Properties

    ADVANCED MATERIALS, Issue 17 2010
    Qiao Zhang
    Multifunctional Au nanoshells with tunable optical properties and fast magnetic response have been fabricated through a sequence of sol,gel, surface-protected etching, and seed-mediated growth processes. The use of a porous silica layer enhances the uniformity of nanoshell growth, the reproducibility of the synthesis, and the structural and optical stability of the products. [source]

    Blue-Gap Poly(p -phenylene vinylene)s with Fluorinated Double Bonds: Interplay Between Supramolecular Organization and Optical Properties in Thin Films

    ADVANCED MATERIALS, Issue 10-11 2009
    Maria Losurdo
    Blue-light-emitting poly(p-phenylene vinylene)s with fluorinated vinylene units are presented. It is demonstrated that self-aggregation governs the strength and polarization of the absorption spectra of thin films of these polymers. This indicates that self-assembly of the polymer chains in the films provides a means of tuning the electronic and optical properties of the , -conjugated systems. [source]

    Exploring Optical Properties of Liquid Crystals for Developing Label-Free and High-Throughput Microfluidic Immunoassays,

    ADVANCED MATERIALS, Issue 2 2009
    Chang-Ying Xue
    The orientational transition of liquid crystals (LCs) is used as a label-free detection mechanism for immunoassays developed in microfluidic systems. LCs only show bright optical textures (visible to the naked eye) in the line-line intersections in which label-free antibodies bind to their surface-immobilized antigens, suggesting the feasibility of using LCs to detect specific antigen-antibody binding events in a high-throughput and multiplexed manner. [source]

    Enhanced Optical Properties of a Photosynthetic System Conjugated with Semiconductor Nanoparticles: The Role of Förster Transfer,

    ADVANCED MATERIALS, Issue 22 2008
    Alexander O. Govorov
    The rate of optical generation of electron--hole pairs inside a photosynthetic system can be greatly increased through conjugation with nanoparticles. The enhancement stems from much larger optical absorption cross section of a semiconductor nanoparticle compared to a photosynthetic system. In the hybrid complex, excitons are transferred via the Förster mechanism to the photosynthetic system, where charge separation takes place. [source]

    Synthesis and Optical Properties of Tetrapod-Like ZnSSe Alloy Nanostructures,

    ADVANCED MATERIALS, Issue 17 2008
    Haiyang Xu
    Tetrapod-like ZnS1,xSex alloy nanostructures (T-ZnS1,xSex) of different compositions (0,,,x,,,1) are synthesized by chemical vapor deposition. Their composition-dependent Raman scattering and cathodoluminescence are studied. The single-crystal T-ZnS1,xSex nanostructures exhibit strong and narrow near-band-edge emissions that can be continuously tuned from 330,459,nm (see figure). [source]

    Nanostructures, Optical Properties, and Imaging Application of Lead-Sulfide Nanocomposite Coatings

    Song Wei Lu
    Lead-sulfide (PbS) nanocrystals were precipitated in nanocomposite coatings after a pre-photo-polymerization followed by a reaction with H2S gas at 25°C for 1 hr. PbS nanocrystalline size and optical absorption increased with decreasing UV energy for pre-photo-polymerization and increasing concentration. The absorption onset has a large blue shift from 0.41 eV of the corresponding bulk crystal, resulting from the quantum confinement effect. As a result, coating color changes significantly from deep brown to light yellow depending on coating processing conditions. Partially masking the coatings during pre-photo-polymerization gives rise to different colors, leading to imaging applications of PbS nanocomposite coatings. [source]