Syntheses, crystal structures and optical spectroscopy of Ln2(SO4)3·8H2O (Ln=Ho, Tm) and Pr2(SO4)3·4H2O

The lanthanide sulphate octahydrates Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) and the respective tetrahydrate Pr₂(SO₄)₃·4H₂O were obtained by evaporation of aqueous reaction mixtures of trivalent rare earth oxides and sulphuric acid at 300 K. Ln₂(SO₄)₃·8H₂O (Ln=Ho, Tm) crystallise in space group C2/c (Z=4, a_Ho=13.4421(4) Å, b_Ho=6.6745(2) Å, c_Ho=18.1642(5) Å, β_Ho=102.006(1) Å³ and a_Tm=13.4118(14) Å, b_Tm=6.6402(6) Å, c_Tm=18.1040(16) Å, β_Tm=101.980(8) Å³), Pr₂(SO₄)₃·4H₂O adopts space group P2₁/n (a=13.051(3) Å, b=7.2047(14) Å, c=13.316(3) Å, β=92.55(3) Å³). The vibrational and optical spectra of Ho₂(SO₄)₃·8H₂O and Pr₂(SO₄)₃·4H₂O are also reported.     

Synthesis and characterizations of novel spindle-like terphenyl-type chromophores for non-linear optical materials

A series of novel spindle-like terphenyl-type chromophores, based on 2,5-diphenyl-1,4-distyrylbenzene π-conjugating bridge, N,N-dimethyl and triphenyl amino donors, and Tricyanovinyldihydrofuran(TCF), 1,3,3-trimethyl-5-dicyanovinyl-1-cyclohexene (TDC) acceptors, have been synthesized successfully for the first time. And the non-linear optical properties were evaluated by using the finite-field (FF) method. The results show that, the first-order hyperpolarizability of the chromophores increase with the increase of the withdraw ability of the substituent group on the π-conjugating bridge.     

Influence of acidification on the optical properties and molecular composition of dissolved organic matter

Acidification is a common method for preserving dissolved organic matter (DOM) in natural water samples until sophisticated laboratory analyses can be performed. However, little is known about the effects of this practice on the composition and optical properties of DOM. In this study, the effects of acidification on DOM in porewater samples collected from the RL IV bog system of the Glacial Lake Agassiz Peatlands in northern Minnesota were characterized. Molecular composition was determined by ultrahigh resolution mass spectrometry and optical properties by UV absorption and three-dimensional fluorescence spectroscopy. Excitation–emission matrix fluorescence spectroscopy results indicate that the fluorescence properties of the peatland porewater DOM were sensitive to pH and that the observed changes were fluorophore dependent. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry revealed the appearance of newly formed, oxygen-rich compounds upon acidification. The extent to which these oxygen-rich compounds were formed was also dependent on the composition of the DOM.     

一维有机微纳米光功能材料研究进展

近年来,一维有机小分子微纳材料因为其新颖的光学性能和在未来小型化器件中的广泛应用,受到了人们越来越多的关注.相比于传统无机半导体材料,有机小分子材料具有结构多样性、功能可设计性、易大量制备、易机械加工等显著优势.本文将从一维有机小分子纳米材料的制备方法、形貌调控、光学性能(如光波导、受激发射、电致发光等),及其在光学器件上的应用出发,对近十年来的相关研究进展及成果进行总结和介绍.     

Morphology and physical properties of poly(ethylene oxide) loaded graphene nanocomposites prepared by two different techniques

Organic–inorganic hybrids are artificially created structures presenting novel properties not exhibited by either of the component materials alone. In this contribution one addresses processing, morphology and properties of polymer nanocomposites reinforced graphene. First, synthesis routes to graphite oxide (GO) and foliated graphene sheets (FGS) are illustrated. Physical characterization of these graphene sheets were conducted using atomic force microscopy and X-ray diffraction techniques. Processing, structure and properties of graphene/poly(ethylene oxide) (PEO) nanocomposites are discussed. FGS was dispersed into PEO via two different composite manufacturing techniques: melt compounding and solvent mixing. Morphology of dispersed graphene and properties from different blending routes are compared. TEM showed that graphene distributed parallel to the composite surface using solvent method, while distributed randomly in melt blended method. Optical measurements indicated that the transparency of PEO/graphene prepared by solvent method is higher than that of melt blended method in the visible region. Electrical conductivity measurements are employed to evaluate threshold concentration for rigidity and connectivity percolation. The percolation concentration of the composites prepared by solvent method is less than those of melt blended method. The mechanical performance of the composites prepared by solvent method is higher than melt blended. Halpin–Tsai model has been used to confirm the distribution of the graphene into PEO by the two different processing techniques.     

Characterization of aquatic dissolved organic matter by asymmetrical flow field-flow fractionation coupled to UV-Visible diode array and excitation emission matrix fluorescence

Flow field-flow fractionation (FlFFF) with on-line UV/Visible diode array detector (DAD) and excitation emission matrix (EEM) fluorescence detector has been developed for the characterization of optical properties of aquatic dissolved organic matter (DOM) collected in the Otonabee River (Ontario, Canada) and Athabasca River (Alberta, Canada). The molecular weight (MW) distribution of DOM was estimated using a series of organic macromolecules ranging from 479 to 66,000 Da. Both the number-average (M_n) and weight-average (M_w) molecular weights of Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA) determined using these macromolecular standards were comparable to those obtained using polystyrenesulfonate (PSS) standards, suggesting that organic macromolecules can be used to estimate MW of natural organic colloids. The MW of eight river DOM samples determined by this method was found to have an M_n range of 0.8–1.1 kDa, which agrees with available literature estimates. The FlFFF-DAD-EEM system provided insight into the MW components of river DOM including the optical properties by on-line absorbance and fluorescence measurement. A red-shift in emission and excitation wavelength maxima associated with lower spectral slope ratios (S_R = S_275–295:S_350–400) was related to higher MW DOM. However, DOM of different origins at similar MW also showed significant difference in optical properties. A difference of 47 and 40 nm in excitation and emission peak C maxima was found. This supports the hypothesis that river DOM is not uniform in size and optical composition.     

Non-local order in Mott insulators,duality and Wilson loops

It is shown that the Mott insulating and superfluid phases of bosons in an optical lattice may be distinguished by a non-local ‘parity order parameter’ which is directly accessible via single site resolution imaging. In one dimension, the lattice Bose model is dual to a classical interface roughening problem. We use known exact results from the latter to prove that the parity order parameter exhibits long range order in the Mott insulating phase, consistent with recent experiments by Endres et al. [M. Endres, M. Cheneau, T. Fukuhara, C. Weitenberg, P. Schauß, C. Gross, L. Mazza, M.C. Bañuls, L. Pollet, I. Bloch, et al., Science 334 (2011) 200]. In two spatial dimensions, the parity order parameter can be expressed in terms of an equal time Wilson loop of a non-trivial U(1)$U\left(1\right)$ gauge theory in 2+1$2+1$ dimensions which exhibits a transition between a Coulomb and a confining phase. The negative logarithm of the parity order parameter obeys a perimeter law in the Mott insulator and is enhanced by a logarithmic factor in the superfluid.     

Comparison of subwavelength focusing properties of diffraction and Fresnel zone plate plasmonic planar lenses

The subwavelength focusing properties of diffractive plasmonic planar lenses (DPLs) and Fresnel zone plate plasmonic planar lenses (FZPs) have been compared in this paper. To that end, we use the same lens material, incident wavelength, thickness and focal length for comparison. Both DPLs and FZPs consist of central circular slits surrounded by transparent and opaque zones and can get clear focusing performances. By using the rigorous electromagnetic numerical method, the fields in the focal region are analyzed in detail, and our results demonstrate that FZP can generate higher transmission efficiency, and higher peak field intensity at the focal plane. Focusing polarization properties of the lens illuminated by linearly polarized state, are calculated and analyzed also. The numerical results show that both the DPL and the FZP produce asymmetrical focal spot distributions with a low f-number. To the FZP, the full-width at half-maximum (FWHM) varies from 256 nm (along y-axis) to 516 nm(along x-axis) and to the DPL, the FWHM varies from 256 nm(along y-axis) to 580 nm(along x-axis), respectively. But for a high f-number, the asymmetrical performance of the focal spot will be reduced due to complicated electromagnetical field interferences and micro waveguide effect. Otherwise, the DPL can get a higher depolarization effect than the FZP does.     

A novel construction algorithm of the LDPC code for high-speed long-haul optical transmission systems

According to the transmission characteristics of high-speed long-haul optical transmission system, the main construction method of Low-Density Parity-Check (LDPC) code for optical transmission system is presented and a novel construction algorithm of LDPC code is proposed, the theoretical analysis shows that the parity check matrix of the LDPC code constructed by the proposed construction algorithm has no four-girth phenomenon, this is also theoretically proved out. Both the novel LDPC(3969,3720) code with 6.69% redundancy and the novel LDPC(8281,7920) code with 4.56% redundancy for optical transmission systems are constructed by using the presented construction method and proposed construction algorithm. The simulation results show that the net coding gain (NCG) of the two novel LDPC codes at the eighteenth iteration for the BER of 10^?12 are respectively 1.63 dB and 1.49 dB more than that of the RS(255,239) code in ITU-T G.975. Moreover, the decoding of the LDPC code in the hardware can parallel be implemented, so the decoding speed of the two novel LDPC codes are very rapid, the complexities of implementing the two novel LDPC codes, compared with the concatenated codes in ITU-T G.975.1, are relatively lower, furthermore, the hardware overhead and storage space can relatively be saved and the computation complexity can be reduced in implementing the hardware in the future. As a result, the two novel LDPC codes can better be suitable for high-speed long-haul optical transmission systems.     

Measurement of chlorophyll in water based on laser-induced fluorescence spectroscopy: Using spiral-wound unclad optical fiber system and partial least squares regression

The feasibility of laser-induced fluorescence (LIF) method for chlorophyll concentration determination in water was investigated in this study. The chlorophyll fluorescence spectra were received by a spiral-wound unclad optical fiber system. Baseline and smoothing correction methods were studied. Statistical equations were established between reference data and fluorescence spectra by linear regression and partial least squares (PLSs) regression. The PLS regression outperformed linear regression by higher correlation coefficient of 0.9996063 and root mean square error value of 0.0221807. Based on the results, it was concluded that laser-induced fluorescence method with a spiral-wound unclad optical fiber system was suitable for chlorophyll concentration determination in water, and PLS regression was a reliable method for fluorescence spectra analysis.