Two-photon Excited Fluorescence of Bithiophene Derivatives

Two new bithiophene derivatives named as 5, 5-bis(p-N,N-dimethylaminostyryl)-2, 2 -bithiophene (BMSBT), and 5, 5-bis(p-N,N-diethylaminostyryl)-2, 2-bithiophene (BESBT) have been synthesized. Both compounds can emit strong single-photon excited fluorescence (SPEF) and two-photon excited fluorescence (TPEF) with the emission peaks around ~560 nm and with the lifetime of ~1ns.

Morphology, Growth Process and Symmetry of {0001} Face on Yb:YAl_3(BO_3)_4 Crystal

The {0001} face develops on the habit of self-frequency doubling laser crystal Yb: YAI3(B03)4 (YbYAB) only under high growth rate condition, and its morphology is rough. To study the growth mechanism of {0001} face, we have observed the growth morphology on {0001} polishing section by atomic force microscopy (AFM). A series of AFM images captured in different growth durations on the {0001} polishing section reflect the crystal growth process. It is shown that the growth morphology on the {0001} polishing section was rough with many hillocks at the first growth stage, and it can become smooth finally, although the growth morphology on the {0001} face developed naturally on YbYAB crystal habit is always rough. On the smooth {0001} surface formed at the last growth stage, there are some triangular pits. This fact is different from that of hillocks in most crystal growth morphologies. AFM can easily distinguish the pits or hillocks on the surface, but differential interfere contrast microscopy (DIC) can not do. The orientation of the triangular pits is just the opposite to the triangular {0001} faces. The chemical etching pattern is also composed of this kind of triangular pits. These growth morphology and etching pattern of the {0001} faces show 3m symmetry, but the point group of YbYAB crystal is 32. The symmetric contradiction between morphology and point group does not exist for quartz, although which has the same point group as YbYAB. From quartz {0001} surface morphology we can distinguish the right form or left form of the crystal, but from YbYAB {0001} surface morphology we can not do. The reason for the symmetric contradiction between YbYAB {0001} surface morphology and its point group is not known yet.

Growth of Yb∶YAB Crystal and Its Laser Performance

Single crystal of Yb x Y 1- x Al 3(BO 3) 4 (Yb∶YAB) was grown by using flux method based on the potassium trimolybdate. 160 mW efficient continuous wave green output was obtained from a fibre coupled 976 nm laser diode. The conversion efficiency is larger than 11 3%, and the electrical input green conversion efficiency is 3 9%. Tunable green output from 513 0 to 545 8 nm is also demonstrated with a quartz birefringent filter. By enhancing the incident pump power, 1 1 W cw green output can be reached.

Synthesis and Nonlinear Optical Properties of New Quadrupolar Chromophores

Two new symmetric chromophores: 2, 8-bis-[(2-4′-ethoxy phenyl-5-4′-styryl)-1, 3, 4- oxadiazole] didibenzothiophene (abbreviated as SO-G1) and 2, 8-bis-[(2-4′-ethoxy phenyl-5-4′- styryl)-1, 3, 4-oxadiazole]-N-ethyl carbazole (abbreviated as NO-G1) have been synthesized and characterized. Both chromophores exhibit strong two-photon absorption (TPA) with the cross-sections of 2.99×10-48 and 3.48×10-48 cm4?s?photon-1 in THF and large up-conversion emission, when pumped by Ti:sapphire femto-second laser at 720 nm.

Synthesis of New Multibranch Chromophores with Strong Light-emitting in Solution and in PMMA Film

Three new chromophores with triphenylamine as molecular focal point bearing one, two, or three 4-(n-butyloxystyryl) group(s) at the periphery respectively, (named as T1, T2, and T3) have been synthesized and characterized. It is interesting to find that the fluorescence quantum yield increases from T1 (0.489), to T3 (0.535), and to T2 (0.628) in cyclohexane, meanwhile the lifetime for T3 is shorter than T1 and T2, which is an important characteristic for applications in light emitting diode. Also PMMA (polymethyl methacrylate) film doped with T3 gives stronger fluorescence than T1, and T2. Cyclic voltammetry showed that T3 exhibited lowest oxidation potential of 0.52 V vs SCE, suggesting its better hole-transport property.

Towards Single-component Molecular Conductor[Ni(dmit)2]by Charge Disproportionation:2[Ni(dmit)2]^0.5→[Ni(dmit)2]+[Ni(dmit)2]^-

A new method of synthesizing single-component molecular conductor [Ni(dmit)2] by the reaction 2(Me4N)[Ni(dmit)2]2 [Ni(dmit)2] + (Me4N)[Ni(dmit)2] is reported. [Ni(dmit)2] exhibits a semiconductive behavior above 167 K, while from 167 K down to the measuring limit of 60 K, it exhibits metallic conductivity.

Effect of growth interruption and strain buffer layer on PL performance of AlGaAs/GaAs/InGaAs quantum well for 1065 nm wavelength lasers

Strained InGaAs/GaAs quantum well (QW) was grown by low-pressuremetallorganic chemical vapor deposition (MOCVD). Growth interruption and strain buffer layer wereintroduced to improve the photoluminescence (PL) performance of the InGaAs/GaAs quantum well. GoodPL results were obtained under condition of growth an interruption of 10 s combined with a moderatestrain buffer layer. Wavelength lasers of 1064 nm using the QW were grown and processed intodevices. Broad area lasers (100 μm x 500 μm) show very low threshold current densities (43 A/cm^2)and high slop efficiency (0.34 W/A, per facet).

Synthesis,Structure and Conductivity of(PyH)[Ni(dmit)2]2

A new molecular conductor (PyH)[Ni(dmit)2]2 (dmit = 4, 5-dimercapto-1, 3-dithiole-2-thione) has been prepared and its crystal structure has been determined. Crystallographic parameters for (PyH)[Ni(dmit)2]2: C17H6NNi2S20; triclinic system; P-1 space group; a = 5.9227 (4) , b =8.2279 (6), c = 16.7535 (9) A, a = 90.233 (5) , 0 = 92.107 (6) , y= 104.654 (6) ; V= 789.25 (9) A3; Z = 1; Dc = 2.068 g/cm3; F (000) = 491. The conductivity at one direction on (001) plane at room temperature was measured to be 0.13 ii^-cmf1. The resistivity-temperature curve in the temperature range of 90-290 K shows that this compound behaves as a semiconductor.

Synthesis of New Naphthaline-type Chromophores with Strong Green-emitting or the Blue-emitting in β-Cyclodextrin

Three new naphthaline-type chromophores end-capped with different (p-substituted amino) styryl groups on the both sides (named as BPASN, BHMASN and BMASN) have been synthesized. Under excitation of 380 nm, strong green light-emitting locating at 517 nm with the fluorescence quantum yield of 0.88 in CH2Cl2 has been obtained. In the presence of b-cyclodextrin (b-CD), strong blue-emitting at 456 nm in DMF was also recorded.

Synthesis and Two-photon Absorption Properties of s-Triazine Derivatives

Two new s-triazine derivatives, which belong to linear dipolar type and triangle octupolar type respectively, have been synthesized. The structure of the dipolar compound has been determined by X-ray diffraction. The two-photon absorption cross-section σ, and the two-photon excited fluorescence (TPEF) intensities are increased significantly from dipolar compound to octupolar compound.

New Thiophene Derivatives with Two-photon Excited Fluorescence

Two new compounds involving a thiophene moiety named as 2,5-bis[4-(N,N- diphenyl- amino)styryl]thiophene (BPST) and 2,5-bis[4-(N,N-diethylamino)styryl]thiophene (BEST) have been synthesized. The two-photon absorption cross section of BPST was measured as large as 256 × 10-50 cm4·s/photon, when it was excited by 800 nm femtosecond laser.

Synthesis, Structure and Conductivity of the New Charge-transfer Salt (ET)_2(CH_2=CH-CH_2-SO_3)·H_2O

Electro-oxidation of 3,4,3, 4-bis(ethylenedithio)-2,2,5,5-tetrathiafulvalen (abbr. ET) in the presence of allylsulfonate affords a new charge-transfer salt (ET)2(CH2=CH-CH2-SO3)H2O. The single crystal structure of the title compound is determined to be in orthorhombic crystal system, Pma2 space group. This salt is a semiconductor and its room-temperature conductivity is 0.0489Ω-1m-1.

The Inorganic-free Organic Conductor α'-(ET)_2C_6H_4(SO_3)_2 : Its Synthesis, Structure, and Conductivity

A new ET based cation radical salt, a-(ET)2C6H4(SO3)2 (ET = bis(ethylenedithio) tetrathiafulvalene) has been synthesized by oxidative electro-crystallization and the crystal structure determined to be in monoclinic system, P2/n space group. Its resistivity-temperature curve shows a semi-conductive behavior with a discontinuation at about 150K.

Key factors dominating luminescent properties of a GaP nanocomposite material

A GaP/morin nanocomposite material was prepared, and the key factorsaffecting the luminescent properties of the material were investigated. Intense luminescence wasobserved after the composite reaction between GaP nanocrystals and morin. The luminescence of theGaP/morin composite material is intensified remarkably with the ratio of morin to GaP nanocrystalsincreasing, but the peak wavelength remains unchanged. With the size of GaP particles decreasing,the luminescent intensity of the composite increases and the peak wavelength blue-shifts. Thepossible reason for this phenomenon was discussed.

One—and Two—photon Excited Fluorescence of Zinc（Ⅱ）,Cadmium（Ⅱ）Complexes Containing Phenothiazine Ligand

A new ligand, 10ethylphenothiazinyl 3 yl methylene thiosemicarbazon (HL) and its complexes ML2 (M=Zn2+, Cd2+), which exhibit intensive two-photon excited (TPE) fluorescence at 800 nm laser pulses in femtosecond regime, were synthesized and characterized. The measured power dependence of the fluorescence signals provided direct evidence for TPE. All of them exhibited a large two-photon absorptive cross section and, more importantly from the application point of view, high photochemical/photothermal stability.

Synthesis and Crystal Structure of E,E-1,4-Bis[4'-(N,N-di-n-butylamino)- styryl]-2,5-dimenthoxybenzene

The title compound E,E-1,4-bis[4?-(N,N-di-n-butylamino)styryl]-2,5-dimen- thoxybenzene (abbreviated to DBMB) has been synthesized by the wittig reaction of [(2,5- dimethoxy-1,4-phenylene)]bis(methylene)]bistriphenylphosphonium dichloride with 4-(N,N-di-n- butylamino)benzaldehyde. Its crystal structure was determined by a four-circle diffractometer. Crystal data: C40H56N2O2, Mr = 596.87, triclinic, space group P1, a = 0.9303(2), b = 0.9625(2), c = 1.0442(2) nm, α = 81.493(12), β = 78.387(12), γ = 87.876(11)o, V = 0.9057(4) nm3, Z = 1, Dc = 1.094 g/cm3, F(000) = 326, μ(MoKa) = 0.066 mm-1, the final R = 0.0925 and wR = 0.2092. The results reveal that the molecule is a completely reverse structure with fine symmetry and a conju- gated system.

Magnetic and Magnetoresistance Properties in (La_(0.67)Ca_(0.33)MnO_3)_x / (ZrO_2 )_(1-x) Composite System

La_(0.67)Ca_(0.33)MnO_3)_x /(ZrO_2)_(1-x) (x is the volume fraction ratio) percolated composites were fabricated by combining La_(0.67)Ca_(0.33)MnO_3 (LCMO) powders with ZrO_2 particles, where LCMO powders were prepared by sol-gel process. Low field magnetoresistance ( LFMR ) is greatly enhanced at low temperature when the system is close to the metallic percolation threshold of x=0.4. The magnetoresistance ratio of ( LCMO)_(0.4) /( ZrO_2 )_(0.6) in a 10 mT magnetic field at 77 K is 7.8 %, about 7.12 times larger than that of pure LCMO compound. The enhancement of spin-dependent tunneling of electrons at the interfaces between LCMO and ZrO_2 grains is responsible for the enhanced LFMR. With increasing ZrO_2 addition, Curie temperature T_C decreases firstly and then remains constant at about 220 K when (x<60%), showing limited substitution effect of Zr ions on B sites.

Growth,defects,and properties of GdCa4O（BO3）3 and Nd：GdCa4O（BO3）3 crystals

Pure and neodymium-doped gadolinium calcium oxoborate crystals of high quality were grown by the Czochralski method.The orientation of crystal was precisely determined,and the samples for measurements were prepared.Through synchrotron x-ray topography and high-resolution x-ray diffractometry,the twin structure was discovered.Some properties such as the figure of merit value,and dielectric,piezoelectric,and elastic constants were meausured along with a discussion of the anisotropy of the laser properties.