The preparation is described of a novel highly emissive ytterbium complex with a proposed unusual structure obtained
by reaction of tricyanovinylbenzene (TCNVB) with bis(indenyl)ytterbium(II) in THF. The reaction occurs under
extremely mild conditions, the tetraphenyltetracyanoporphyrazine macrocycle being assembled in high yield from
TCNVB building-blocks by Yb3+-template synthesis. The analytical, spectral and electrochemical investigations of the
obtained ytterbium complex indicate its existence in the form of a binuclear adduct with Yb(TCNVB)3 species in which a
one doubly reduced TCNVB molecule bridges two Yb3+ cations. The formation of a disordered polynuclear coordination
polymer network including a macrocyclic structure and metal cations bridged through the nitrile nitrogen atoms is
proposed. The complex is readily soluble and is compatible with a variety of polymeric matrices giving doped polymeric
glasses and films which are highly luminescent in the biologically relevant optical window covering the visible and near
infrared range (640-1000 nm). In addition, doped polymeric glasses and films highly emissive at the telecommunication
wavelength (1540 nm) including the novel ytterbium complex and originally not luminescent erbium chelate in an
equimolar ratio have been obtained. The compound is found to be an extraordinarily strong sensitizer of near-IR Er3+
emission. Use of the Yb complex as a fluorescent marker for biomedical in vitro investigations has been demonstrated.
William Douglas, Larissa Klapshina, Ilya Grigoryev, Tatyana Lopatina, Vladimir Semenov, Georgy Domrachev, Boris Bushuk, Sergei Bushuk, Andrey Lukianov, Andrey Afanas'ev, Robert Benfield, Alexey Korytin
Novel nonlinear optical polymeric film-producing nanocomposites based on bis(arene)chromium complexes incorporated into a CN-containing matrix have been developed. Polymer-precursors were prepared by the reaction of Cr(EtnC6H6?n)2 mixtures (n = 1,2,3) with CN-containing vinyl monomers (acrylonitrile, crotononitrile and ethylcyanoacrylate). The nonlinear-optical measurements in the absence of external electrical fields showed a "natural" anisotropy resulting from self-organization taking place during the film formation process. Measurements by the spectrally-resolved two-beam coupling method confirmed that the test composites exhibited a significant cubic nonlinear optical susceptibility of the ultra-fast electronic type.
The paper presents the results of a study of the spatial structure of Si-containing [poly(ethynediyl-arylene-ethynediyl-silylene)] composites in the nanometer scale, as well as of an optical study of photorefractive effects in the visible and near-infrared ranges in these composites. The compositions have been examined using transmission/diffraction electron microscopy. The results suggest the existence of an extraordinary self-organisation in conjugated silicon organometallic polymers (nano-structured layers with a spatial period of several nanometers and the length of more than 100 nm). The most probable mechanism of the structure formation is π-stacking of the aromatic groups with the poly(phenylsilsesquioxane) matrix as a template. The observed self-organisation is very important for the understanding of the infrared photorefractive effect in the organometallic polymer compositions. Two-wave mixings in the Raman-Nath and Bragg modes were used to study non-linear optical properties in the visible (632 nm) and near-infrared (1500 nm) spectral ranges. Both local and non-local types of refractive index gratings have been observed.
Novel unique organometallic nanomaterials with high nonlinearities of various types (nonresonant, resonant, photorefractive) have been prepared. Two main kinds of nanomaterials actualizing the different nonlinear-optical processes have been created: 1) polymeric photorefractive nanocomposites with very low glass transition temperatures (ca. 8 deg C) based on poly[ethynediyl-arylene-ethynediyl-silylene]s and sensitive in the visible (633 nm) and near-infrared region (1000-1500 nm) have been developed. The TEM investigations of the composite thin films have revealed self-oganized lamellar structures. The red shift of the absorption spectra and the appearance of a long absorption tail in the near IR region in the case of the films (unlike the solutions) confirm the essentially pi-stacking mechanism in the formation of the supramolecular assembly. The mechanism of self-organization into lamellar phases is discussed. 2) chromium-containing polymeric nanocomposites of high optical and mechanical quality have been prepared. They contain bis-arenechromium complexes covalently bonded to polyacrylonitrile macrochains. The conditions of film-casting give rise to the formation of conjugated polynaphthyridine-type structures inside the polymeric matrix as a result of cyclization of the acrylonitrile units. In addition, the TEM investigations of the films showed that nanosize particles (20-30 nm), containing chromium are formed in the material. These materials exhibit record Kerr-type cubic nonlinearities (chi3 = -2.5×10-10 esu) suggesting a pi-stacking mechanism giving rise to self-organized supramolecular structures. Our theoretical calculations show that the level of nonresonant optical nonlinearity should in principle allow actualizion of fast optical switching with speeds suitable for modern optical connection systems (100 Gbit/s).
A variety of novel materials has been synthesized including poly(ethynediyl-arylene-ethynediyl-silylene)s (PEAES) containing hypercoordinate silicon, and films of metal- containing polyacrylonitrile materials. The (chi) (3) properties in various matrices have been investigated by various techniques such as DFWM and Z-scan. The (chi) (3) values are outstandingly high; e.g. sol-gel films incorporating 5-14 mass percent PEAES show Re(chi) (3) equals 3-9 X 10-11 esu, and films of Cr-containing polyacrylonitrile materials synthesized by the polycyanoethylation reaction between acrylonitrile and Ar2Cr show (chi) (3) equals -2.5 X 10-10 esu.
Polymeric photorefractive materials have attracted much attention over the past decade due to their potential applications, especially for optical information processing. However, their practical use has until now been limited, the available photosensitizers being efficient only in the visible range. Here, the chemical development and optical investigations of a photorefractive polymeric material active at 1500 nm are described. To our knowledge, this is the first such material to be reported. A conjugated poly[(ethynediyl)(arylene)(ethynediyl)silylene] acts as both an optical chromophore, as well as charge generator and conductor. Its absorption band tails into the near-IR hence providing charge generation at the 1500 nm excitation. The photoconductivity of the composite samples was measured with a dc-method using a 1500 nm diode laser source. The electro-optical coefficient was measured with a simple reflection technique. The photorefractive response was investigated with a two-beam coupling technique. The gain of the probe beam intensity, delivered from the pumping beam, reached 40 cm-1 at the electric field strength of 650 kVcm-1 thus confirming the photorefractive nature of the grating. The gain exceeded the absorption (30 cm-1) that showed a good potential of this material for applications.
We present the results of chemical development and optical investigation of the extraordinarily large photorefractive effect in the new polymer nanocomposites. The composites are composed of poly(ethynylene)arylenesilanes as optical chromophores, poly(9-vinylcarbazole) as photoconductor, N- ethylcarbazole and phenyltrimethoxysilane as plasticizer, and C70 and C60 fullerenes as charge generators. The magnitude of the change in photorefractive index and its origin, and temporal behavior were studied at 633 nm by a variety of nonlinear optical techniques, including nonlinear lens method, four-wave mixing and two-beam coupling. The relaxation time of the photorefractive index changed in a range from a few seconds to tens of minutes at changing beam intensity.
The third-order optical nonlinearities of new conjugated poly[(arylene)(ethynylene)silylene]s, and a variety of chromium, neodymium or cobalt complexes incorporated into polymeric matrices as thin sol-gel or polyacrylonitrile films have been determined by using a single beam Z-scan technique. The samples were pumped by a single ultrashort pulse of a mode-locked Nd-phosphate glass laser (wavelength 1054 nm) with a 5ps pulse duration (full width at half- maximum), the repetition rate of the Gaussian beam being low (0.3Hz) ro avoid thermal effects. The spot radius of the focused pulse was ca. 60micrometers , its beam waist being in the sample (intensity up to 4x1013 Wm-2). Calibration was done with chloroform and benzene, the value of N2 for the latter (2x10-12esu) being similar to that previously reported. A small-aperture Z-scan (S=0.03) was used to measure the magnitude and the sign of the nonlinear refractive index, n2. Very high nonlinear refractive indices were found for a film containing (a) a poly[(arylene)(ethynylene)silylene]s with pentacoordinated silicon (c 5 gl-1) in a sol-gel matrix (N2 = 6 x 10-13 cm2W-1), (b) a film containing a poly[(arylene)(ethynylene)silylene] with tetracoordinated silicon (c 0.5 gl-1) and a very small proportion of fullerene-C70 incorporated into an NH2-containing sol-gel matrix (n2 = 5x10-13 cm2W-1, and (c) a thin polyacrylonitrile film of polycyanoethylate bis-arenechromium(I) hydroxide (n2 = -5 x 10-12 cm(superscript 2W-1.
The third-order optical nonlinearity of a series of new conjugated silicon-ethynylene polymers, poly(aryleneethynylenesilylene)s, have been studied by using the degenerate four-wave mixing technique. The fast nonlinear optical susceptibilities of the polymers containing various groups were determined for the solutions in chloroform, tetrahydrofuran and toluene. The electronic and nuclear contributions of the (chi) (3 susceptibility and the thermal nonlinearity of the solutions were separated. The (chi) (3 susceptibility of the polymer containing tetracoordinate Ph2Si groups was found to be comparable with those of the best polymers.
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