Showing papers by "Zhen Li published in 2006"
TL;DR: Aggregation in poor solvents and complexation with calf thymus DNA and bovine serum albumin turn "on" the fluorescence of tetraphenylethylene derivatives, due to the restriction of intra-molecular rotations of the dyes in the aggregates and complexes.
490 citations
TL;DR: In this article, the authors demonstrated that the as-prepared Fe3O4 nanocrystals can potentially be used as effective magnetic resonance imaging (MRI) contrast agents for cancer diagnosis.
Abstract: Biocompatible Fe3O4 magnetic nanocrystals with reactive moieties on the surface can be prepared via a "one-pot" reaction and used straightforwardly in cancer detection by being coupled with a specific cancer-targeting antibody. It is demonstrated that the as-prepared Fe3O4 nanocrystals can potentially be used as effective magnetic resonance imaging (MRI) contrast agents for cancer diagnosis (see figure).
411 citations
TL;DR: In this paper, two series of polyurethanes (P1−P10) containing NLO chromophores as side chains were prepared, in which the size of isolation groups was changed from small atoms to much larger groups such as carbazolyl groups.
Abstract: Two series of polyurethanes (P1−P10) containing NLO chromophores as side chains were prepared, in which the size of isolation groups was changed from small atoms to much larger groups such as carbazolyl groups. The polymers were well characterized. The tested NLO properties of the polymers demonstrate that the NLO values and the poling efficiency of the polymers are not always improved with increasing of the size of isolation spacer, and for a given chromophore moiety, there is a suitable isolation group present to boost its microscopic β value to possibly higher macroscopic NLO property efficiently.
145 citations
TL;DR: In this article, a shallow ice core from Muztagata, in the eastern Pamirs, allows for a detailed comparison of annual δ18O variation with local meteorological data as well as with global air temperature variations.
Abstract: [1] Many have made efforts to clarify the climatic significance of stable isotopic variations in ice cores around central Asia through the study of stable isotopes in present-day precipitation. A new shallow ice core from Muztagata, in the eastern Pamirs, allows for a detailed comparison of annual δ18O variation with local meteorological data as well as with global air temperature variations. On the basis of a comparison of seasonal fluctuations of δ18O in the local precipitation, the 41.6-m ice core drilled at 7010 m provides a record of about one-half century. The annual fluctuations of δ18O in this ice core are in good agreement (correlation coefficient of 0.67) with the annual air temperature changes at the nearby meteorological station Taxkorgen, indicating that the isotopic record from this ice core is a reliable temperature trend indicator. The most important discovery from the δ18O variation of this ice core is a rapid warming trend in the 1990s, which is consistent with a general global warming trend over this time period. This recent rapid warming at higher elevations in this area has led to the quick retreat of alpine glaciers.
105 citations
TL;DR: It is shown that the development of exocrine pancreas is Islet-1 dependent and Hedgehog signaling is required for exocrine morphogenesis but not for cell differentiation, and the new transgenic line provided a useful experimental tool in analyzing exocrine pancakes development.
87 citations
84 citations
TL;DR: Single-walled carbon nanotubes are covalently functionalized by conjugated polyacetylenes through their cyclization reactions with poly(1-phenyl-1-alkyne) and poly(diphenylacetylene) derivatives carrying azido functional groups at the ends of their alkyl pendants.
Abstract: Single-walled carbon nanotubes are covalently functionalized by conjugated polyacetylenes through their cyclization reactions with poly(1-phenyl-1-alkyne) (3) and poly(diphenylacetylene) derivatives (6) carrying azido functional groups at the ends of their alkyl pendants. The resultant polyene nanotube addends (7 and 8) are soluble in common solvents, emit intense visible lights and strongly attenuate the power of harsh laser pulses.
68 citations
TL;DR: In this paper, three hyperbranched polymers (P1, P3 ) containing second-order nonlinear optical chromophores were synthesized by copolymerization of aromatic dialdehydes (carbazole, triphenylamine or benzene moieties).
66 citations
TL;DR: Experimental measurements of the second-order nonlinear optical response demonstrated that the chromophores exhibit similar or superior optical nonlinearity compared with their analogues with an aniline moiety as the donor group, but the indole-based Chromophores display blue-shifted absorption, even up to 30 nm.
Abstract: Push−pull indole-containing nonlinear optical chromophores with different acceptor and π-conjugated moieties have been synthesized and characterized Experimental measurements of the second-order nonlinear optical response demonstrated that the chromophores exhibit similar or superior optical nonlinearity compared with their analogues with an aniline moiety as the donor group, but the indole-based chromophores display blue-shifted absorption, even up to 30 nm
61 citations
41 citations
TL;DR: The emissions of P9 and P9/H12 were enhanced and weakened, respectively, proving that the inorganic perovskite framework works as a photocatalyst for accelerating the bleaching process of the conjugated PA chains.
Abstract: A highly photoresponsive perovskite hybrid containing an electroactive organic component (H1) was fabricated. A disubstituted polyacetylene (PA) with a hidden amino functionality (P3) was synthesized, hydrolysis and quaternization of which afforded the desired PA ammonium salt (P5). Mixing P5 with lead bromide readily yielded H1, which was stable, soluble, and film-forming. The inorganic framework induced the polymer chains to align in an ordered fashion, which helped to populate the chain segments with long conjugation lengths. The hybrid emitted a blue light (457 nm) in a high quantum yield (62%), thanks to the enhanced electronic conjugation, the weakened interaction between the layer-segregated chains, and the efficient energy transfer from the inorganic sheets to the organic layers. P3 exhibited a half-discharge time as short as ∼0.7 s, representing the first example of an efficient photoconductive disubstituted PA. While stable to normal light illumination, H1 was rapidly bleached upon exposure to h...
TL;DR: In this article, the first time series for these metals from central Asia was provided, spanning the mid-1950s to 2000, by analyzing 101 sections using a sector-field double-focusing inductively coupled plasma mass spectrometer (ICP-MS) instrument.
Abstract: Al, Mn, Rb, Sr, Ba, Cs, Bi and Sb were measured at various depth intervals of a 41.6 m firn/ ice core drilled at an elevation of 7010 m near the top of Muztagh Ata glacier, east Pamirs (38817 0 N, 75806 0 E), central Asia. These data, spanning the mid-1950s to 2000, were obtained by analyzing 101 sections using a sector-field double-focusing inductively coupled plasma mass spectrometer (ICP-MS) instrument. This study provides the first time series for these metals from central Asia. Concentrations are 11.7-329 ng mL -1 for Al, 0.33-42.7 ng mL -1 for Mn, 0.42-17.8 ng mL -1 for Sr, 0.04-1.4 ng mL -1 for Rb, 0.18-10.4 ng mL -1 for Ba, 2-167 pg mL -1 for Cs, 2-51 pg mL -1 for Sb and 1-31 pg mL -1 for Bi. Large variations in metal concentrations were found during the study period. Pronounced increases in concentrations were observed for Sb and Bi from the mid-1960s to the beginning of the 1990s, suggesting increased anthropogenic sources of Sb and Bi in central Asia during the same period. However, the decrease of Sb and Bi concentrations during the mid- to late 1990s reflects a reduction in anthropogenic activities in central Asia.
TL;DR: In this article, a disubstituted polyacetylene with indolylazo moieties in its side chains was synthesized by a post functionalization strategy, which was difficult, or perhaps impossible, to obtain from the direct polymerization of its corresponding monomer.
Abstract: A new disubstituted polyacetylene with indolylazo moieties in its side chains (9) was synthesized by a post functionalization strategy, which was difficult, or perhaps impossible, to obtain from the direct polymerization of its corresponding monomer. The polymer is soluble in common solvents and thermally stable. The polymer shows good optical transparency with an absorption maximum at 393 nm and a band edge at ∼530 nm. Its poled film exhibits a resonant d33 value of 17.9 pm/V and its optical nonlinearity is resistant to thermal decay at up to 147 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5672–5681, 2006
TL;DR: In this article, copolycyclotrimerization of [(E/Z)-2-(1-ferrocenyl)vinyl]-m/p-phenylacetylene with 1,8-nonadiyne (I) was studied.
Abstract: Copolycyclotrimerizations of [(E/Z)-2-(1-ferrocenyl)vinyl]-m/p-phenylacetylene [(E/Z)-1(m/p)] with 1,8-nonadiyne (I) were studied. The conformation of the vinyl unit of 1 affected the polycyclotrimerization reaction dramatically: while (Z)-1 failed to give any polymeric products, its E isomer underwent polymerization smoothly, producing hyperbranched copolymers hb-P1/I in good to high yields (up to 100 wt %). The hyperbranched copolymers are soluble in common organic solvents and are thermally stable, losing little of their weights when heated to high temperatures (up to 466 °C). The incorporation of the ferrocenyl moiety endowed the copolymers with redox activity.
TL;DR: Disc repositioning in the treatment of traumatogenic TMJ ankylosis proves to be a feasible and effective method of preventing recurrence of this condition.
TL;DR: In this article, three hyperbranched polymers (P1, P3 ) were prepared by copolymerization of tribromoaryl moieties (triphenylamine, carbazole and fluorene moieties) with 9,9-dihexylfluorene-2,7-bis(trimethyleneborate) from the Suzuki polycondensation reaction.
TL;DR: In this article, a new pyran (1) was synthesized, which is practically non-emissive when molecularly dissolved in acetone and when added to water induces it to cluster into nanoaggregates, which turns its emission "on" and boosts its luminescence efficiency dramatically.
Abstract: A new pyran (1) is synthesized. When molecularly dissolved in acetone, 1 is practically nonemissive. Addition of water induces it to cluster into nanoaggregates, which turns its emission "on" and boosts its luminescence efficiency dramatically. The color of its emission changes from green to red upon aggregation.
Journal Article•
TL;DR: In this article, NH3-enriched near-critical water (NCW) has been used to accelerate base-catalyzed reactions by the addition of NH3 to NCW, such as hydrolysis of cinnamaldehyde and aldol condensation of benzaldehyde with acetaldehyde.
Abstract: Near-critical water (NCW) has drawn increasing attention as an environmentally benign medium for organic chemical reactions, especially acid/base catalysis without added acid or base. However, problems such as low reaction rates and poor selectivity exist for organic syntheses in NCW that greatly hinder the application of this attractive technique in industrially interesting processes. We have developed a novel solvent system to accelerate base-catalyzed reactions by the addition of NH3 to NCW. The reactions demonstrated include hydrolysis of cinnamaldehyde and aldol condensation of benzaldehyde with acetaldehyde. The reaction kinetics of the two reactions were determined. The effects of the NH3 concentration and temperature on the reactions were also investigated. The pOH of NH3-enriched NCW was estimated. The results demonstrate the feasibility of using NH3-enriched NCW as a sustainable reaction medium for the acceleration of base-catalyzed reactions.
TL;DR: In this article, three donor-acceptor conjugated polymers P1, P2 and P3 derived from 3,5-dicyano-2,4,6-tristyrylpyridine (PY) have been synthesized through the Knoevenagel reaction.
Abstract: Three donor–acceptor conjugated polymers P1–P3 derived from 3,5-dicyano-2,4,6-tristyrylpyridine (PY) have been synthesized through the Knoevenagel reaction. The polymers are characterized by 1H NMR, FTIR, UV–vis and elemental analysis. P1 and P2 have high molecular weight up to 2.3 × 105 and 29.5 × 105 and show excellent solubility in common solvents such as THF, CH2Cl2, CHCl3 and DMF. They all have relatively good thermal stability with the 5% weight loss temperature at 402, 264 and 364 °C in argon, respectively. The fluorescence spectrum of P1 displayed the maximum at 588 nm in chloroform solution and at 596 nm in thin film. Two bilayer light-emitting diodes, with 5% or 10% of P1 fabricated in poly (N-vinylcarbazole) (PVK), emitted light at 549 or 552 nm, respectively, and with the increasing content of P1, the electroluminescence efficiencies of the blend devices increased. The optical limiting performance of P1 had been measured at 532 nm with nanosecond pulse, the limiting threshold of P1 was 728 mJ/cm2, and the throughput of P1 was limited to 344 mJ/cm2 for incident fluence as high as 1.1 J/cm2. The preliminary electroluminescent results and optical limiting effect of P1 suggested that P1 may be promising as light-emitting polymer and optical limiting material.
18 Dec 2006
TL;DR: A new data hiding method for 3D triangle meshes is presented that embeds data in the predictive vector quantization (PVQ) compressed domain by modifying the prediction mechanism during the compression process.
Abstract: In this paper, we present a new data hiding method for 3D triangle meshes. While most of the existing data hiding schemes introduce some small amount of nonreversible distortion to the cover mesh, the new method is reversible and enables the cover mesh data to be completely restored when the payload is removed from the stego mesh. A noticeable difference between our method and others is that we embed data in the predictive vector quantization (PVQ) compressed domain by modifying the prediction mechanism during the compression process. Experimental results demonstrate the effectiveness of the proposed scheme.
TL;DR: In this article, a new heterocycle-based quadrupolar molecule containing 2,5-diphenyl-1,3,4-oxadiazole as the π-centre and two carbazoles as end units has been synthesized.
Abstract: A new heterocycle-based quadrupolar molecule containing 2,5-diphenyl-1,3,4-oxadiazole as the π-centre and two carbazoles as end units has been synthesized. It exhibits two-photon induced blue emission, and its two-photon absorption cross section in the femtosecond region is measured to be 239 × 10−50 cm4 s photon−1 at a wavelength of 788 nm.
TL;DR: A series of new linear and cyclic polyenes including siloles, butadienes, cyclcobutenes, fulvenes, and 4H-pyrans are designed and synthesized.
Abstract: A series of new linear and cyclic polyenes including siloles, butadienes, cyclcobutenes, fulvenes, and 4H-pyrans are designed and synthesized. When molecularly dissolved in common organic solvents, all the polyenes are practically nonemissive. Addition of poor solvents induces the polyenes to cluster into nanoaggregates, which turns the emission of the polyenes “on” and boosts their luminescence efficiencies dramatically (hence “aggregation-induced emission” or AIE). The emission color ranges from blue to red, depending on the chromophoric structures. Polyene nanoparticles on TLC plates show bright blue fluorescence which switches off reversibly in an atmosphere of volatile organic compounds. Addition of poor solvents to solution of cyclic polyenes bearing cholsteryl moieties leads to polarized green and anisotropic red emissions dependant on the solvent ratios. The different emissions may be caused by different packing patterns of the polyene crystals under different conditions.
TL;DR: In this paper, a poly(1-pentyne)s containing biphenyl and phthalimido pendant groups with different spacer lengths was synthesized in satisfactory yields by WCl 6 -Ph 4 Sn catalyst in toluene at elevated temperatures.
Abstract: Poly(1-pentyne)s containing biphenyl and phthalimido pendant groups with different spacer lengths {P1(m); -[HC=C(CH 2 ) 3 O-Biph-OCO(CH 2 ) m N(CO) 2 C 6 H 4 ] n -, Biph=4,4'-biphenylyl; m = 7, 10) are synthesized in satisfactory yields by WCl 6 -Ph 4 Sn catalyst in toluene at elevated temperatures. The structures and properties of the polymers are characterized and evaluated by IR, NMR, TGA, DSC, POM, and XRD analyses. Both of the polymers are thermally stable (T d ≥ 300 C) and exhibit nematicity at high temperatures. Their phthalimido groups are converted into amino groups by hydrolysis, which can, after acidification, complex with lead(II) bromide to furnish polyacetylene-perovskite hybrids in high yields. The organic components contribute good solubility to the hybrids, while the perovskite framework induces the polyacetylene chains to align within the inorganic sheets. The hybrids emit a strong UV light of 374 nm upon photoexcitation, whose quantum yield increases with an increase in the spacer length.
TL;DR: In this paper, a light-emitting devices (LEDs) device based on tetraphenyletheneare (TPE) was fabricated, which emitted a blue light of 447 nm with a low turn-on voltage of 2.9 V.
Abstract: New chromophoric molecules of 1,1-di(thiophen-2-yl)-2,3,4,5-tetraphenyl-silole (T2TPS), 9-(diphenylmethylene)-9H-fluorene (DPMF), and tetraphenyletheneare (TPE) are designed and synthesized. When molecularly dissolved in common organic solvents, the molecules are practically nonemissive. Addition of poor solvents induces the molecules to aggregate, which turns the emission "on" and boosts their luminescence efficiencies dramatically ("aggregation-induced emission" or AIE). The photoluminescence (PL) of T2TPS and TPE layers adsorbed on the TLC plates can be turned "off" and "on" continuously and reversibly by solvent exposure and evaporation. Transformation from amorphous phase to crystalline structure blue-shifts the PL spectrum of T2TPS and enhances its intensity. A light-emitting devices (LEDs) device based on TPE is fabricated, which emits a blue light of 447 nm with a low turn-on voltage of 2.9 V.
TL;DR: Azo-functionalized hyperbranched polymers 1 and 2, and linear polyacetylene 3 are synthesized by palladium-catalyzed coupling of triiodoarenes with a diethynylazobenzene, and post functionalization, respectively as mentioned in this paper.
Abstract: Azo-functionalized hyperbranched polymers 1 and 2, and linear polyacetylene 3 are synthesized by palladium-catalyzed coupling of triiodoarenes with a diethynylazobenzene, and post functionalization, respectively. These polymers are soluble, film-forming, and morphologically stable (T g > 180 qC). The poled polymer films of 1 and 2 exhibit high second-harmonic genera tion coefficients (d 33 up to 177 pm/V), thanks to the ch romophore-separation and site-isolation effects of hyperbranched architectural structure of the polymers in the three-dimensional space. The poled film of polymer 3 shows the trade-off of nonlinearity-transparency-orientation thermal stability. The poled films are all orientationally and thermally stable due to the facile cross-linking of the multiple acetylenic triple bonds in the hyperbranched polymer and the rigid backbone in the linear polyacetylene, respectively. Keywords: Second-order nonlinear optics, linear and hyperbranche d polymers, orientation thermal stability, trade-off.
Patent•
19 Jul 2006
TL;DR: The related hyperbranched second-order nonlinear optical macromolecule has structural formula as I (R for nitro, sulfuryl or other electron-attacting groups; n=10-120 as mentioned in this paper.
Abstract: The related new hyperbranched second-order nonlinear optical macromolecule has structural formula as I (R for nitro, sulfuryl or other electron-attacting groups; n=10-120, can be prepared with composed second-order nonlinear optical chromophore and triphenylaminotrialdehyde, and has practical application in remote communication, data storage and conversion, etc.
Patent•
01 Mar 2006
TL;DR: In this article, a second order non-linear optical chromophore containing indolyl radical with indole, alkyl halide, electron-drawing acceptor and other reagents as materials and through serial chemical reactions is presented.
Abstract: The present invention relates to second order non-linear optical chromophore containing indolyl radical with the general expression as shown. The present invention prepares the second order non-linear optical chromophore containing indolyl radical with indole, alkyl halide, electron-drawing acceptor and other reagents as materials and through serial chemical reactions. The second order non-linear optical chromophore containing indolyl radica as one kind of second order non-linear material may find its practical application in remote communication, data storing, phase conjugation and other fields.
01 Jan 2006
01 Oct 2006
TL;DR: The assessing parameter system is proposed and it is testified in real application comparing to assessment result of the geometric tolerance theory, and statistical parameters of this assessing system can reveal the impact of spatial straightness error on the accessory function more roundly.
Abstract: In order to assess spatial straightness error matched new generation Dimensional Geometrical Product Specification and Verification (GPS), the theory of spatial straightness error assessing is proposed and its advantages are analyzed based on metrology and statistics in this paper. Then, the assessing parameter system is proposed and it is testified in real application comparing to assessment result of the geometric tolerance theory. Statistical parameters of this assessing system post the different characteristics of spatial straightness error, and can reveal the impact of spatial straightness error on the accessory function more roundly to complement the single assessing parameter of geometrical tolerance for straightness error. The statistical spatial straightness tolerance and statistical spatial straightness error proposed in this paper is possible to be applied in evaluation of other error of form, orientation, location and run-out.
01 Jul 2006
TL;DR: A new two-scale model is proposed for bistatic scattering from a composite surface that holds the potential to bridge the gap between the regions of validity of the Kirchhoff approximation and the small perturbation model.
Abstract: A new two-scale model is proposed for bistatic scattering from a composite surface. For the large scale surface roughness, we use the newly developed statistical integral equation model; for the small scale surface roughness, we adopt the second-order small slope approximation. It holds the potential to bridge the gap between the regions of validity of the Kirchhoff approximation and the small perturbation model. Keywords-two scale model; statistical integral equation mode;, small slope approximation; bistatic scattering