Deqing Zhang

Self-assembly of gold nanoparticles to carbon nanotubes using a thiol-terminated pyrene as interlinker

Gold nanoparticles were self-assembled onto the surface of solubilized carbon nanotubes through an interlinker of bi-functionalized molecule (PHT) terminated with pyrenyl unit at one end and thiol group at the other end. While the fluorescence of PHT is quenched moderately by the carbon nanotubes, the fluorescence is almost totally quenched by the further binding of gold nanoparticles. The enhancement of the Raman responses of nanotubes by the gold nanoparticles is also observed. These results imply there are charge transfer interactions between nanotubes and gold nanoparticles.

Third- and fifth-order optical nonlinearities in a new stilbazolium derivative

The third- and fifth-order optical nonlinear properties of a new stilbazolium derivative, trans-1-[p-(p-dimethylaminobenzyl-azo)-benzyl]-2-(N-methyl-4-pyridinium)-ethene iodide (DABAZO-PEI), were investigated with a Q-switched and mode-locked pulse laser with a duration of 35 ps at 1064 nm. Its linear optical properties were also discussed. DABAZO-PEI exhibits two-photon absorption and strong excited-state absorption induced by two-photon absorption. A positive third-order nonlinear refraction caused by bound electrons and negative excited-state refraction caused by the two-photon absorption-generated excited states were also observed. The magnitude and the sign of the real (refractive) and the imaginary (two-photon absorption) parts of the molecular third-order polarizability, and the excited-state absorption and refraction cross sections, were measured. A feature worth noting is the values of excited-state absorption and refraction cross sections. They are all as high as 10-17xa0cm2. Based on the excited-state absorption induced by the two-photon-absorption mechanism, a highly efficient optical-limiting behavior for incident fluence in the range of 0–10 J/cm2 was demonstrated in a 1-cm-path quartz cell containing DABAZO-PEI solution in dimethyl sulfoxide. The optical-limiting threshold was estimated to be as low as 5 mJ/cm2.

Donor-acceptor-donor triads incorporating tetrathiafulvalene and perylene diimide units: synthesis, electrochemical and spectroscopic studies

Abstract Three donor–acceptor–donor triads 1–3 consisting of tetrathiafulvalene units attached to perylene diimides by flexible and rigid spacers were synthesized and characterized. UV/vis spectroscopic and cyclic voltammetric results indicate that they all show negligible intramolecular charge transfer interaction in their ground states. As compared to the reference compound 21 , triads 1–3 display reduced fluorescence and their fluorescence lifetimes are shortened, which is probably owing to the photoinduced electron transfer interactions between the PI units and TTF units. The different photophysical behaviors between 1 and 2 (and 3 ) might be due to their difference in the spatial separation of TTF and PI units. It is preliminarily found that the steric hindrance of the groups attached to TTF units can affect their photostability.

Synthesis, Crystal Structure and Third‐Order Nonlinear Optical Behavior of a Novel Dimeric Mixed‐Ligand Zinc(II) Complex of 1,3‐Dithiole‐2‐thione‐4,5‐dithiolate

Metal bis-dithiolene complexes have aroused more and more interest over the past decades due to their potential applications as precursors for electrical conductors and superconductors;[1] the optical properties of these compounds are also very interesting. For example, in 1972 Drexhage and co-workers discovered that transition metal dithiolene complexes are very stable to intense irradiation in the nearinfrared region and are particularly suitable for Q-switching lasers.[2,3] Recently, more and more symmetrical bis-dithiolene complexes with third-order optical nonlinearity or optical limiting effects have been explored.[4] Because of the large values of their third-order nonlinear susceptibility χ(3) [1a,5] and negative molecular first hyperpolarizability(β),[1a,6] unsymmetrical dithiolene complexes have also become promising candidates for nonlinear optical materials. Herein we report the synthesis, crystal structure and thirdorder nonlinear optical behavior of a novel dimeric mixedligand zinc(II) complex of 1,3-dithiole-2-thione-4,5-dithiolate (dmit) [Zn(dmit)(2,2 -bpy)]2 (1). To the best of our knowledge, this is the first example of a dimeric mixed-ligand complex of dmit.

The high fifth-order nonlinearity in a new stilbazolium derivative: trans-1-[p-(p-dimethylaminobenzyl-azo)-benzyl]-2-(N-methyl-4-pyridinium)-ethene iodide

The third- and fifth-order optical nonlinearities from the titled molecule were investigated using Z-scan technique. The titled molecule exhibits two-photon absorption (2PA) and 2PA-generated excited-state absorption (ESA). A very interesting feature is that the titled molecule shows a high fifth-order nonlinearity, being about one-order of magnitude larger than the reported organic molecules. Due to this strong ESA, a highly efficient optical limiting effect was observed.

Three-photon absorption from six stilbazolium derivatives: application for optical limiting

Abstract Three-photon absorption (3PA) and subsequently induced optical limiting behavior of several stilbazolium derivatives were investigated by using a mode-locked/Q-switched Nd:YAG pulse with a duration of 35 ps and a repetition of 10 Hz at 1064 nm. The measured molecular 3PA cross-sections are in the order 10 −78 –10 −76 cm 6 s 2 at the intensity levels of 0–55 GW / cm 2 . It is observed that the 3PA cross-section as well as the optical limiting effect can be enhanced by increasing strength of electron-acceptor units of stilbazolium derivatives.

Carboxylic acid-dependent assembly of neodymium–organic frameworks with attractive topologies and second-order nonlinear optical and/or magnetic properties

Four new neodymium(III) coordination polymers, Nd(HL)2(CH3COO) (1), Nd(HL)2(CH3COO) (1′), Nd(HL)2(C2H5COO) (2) and Nd(HL)3(H2O) · 4H2O (3) were prepared by the hydrothermal reactions of Nd2O3 with 1,6-dihydro-6-oxopyridine-3-carboxylic acid (H2L) using the modulation roles of different carboxylic acids (acetic acid, malonic acid, propionic acid and formic acid for 1, 1′, 2 and 3, respectively). Complexes 1 and 1′ are conformational polymorphs: 1 crystallizes in an acentric space group Cmc2(1) and shows a new 3D {3,6} topology (63)2(4261083), while 1′ crystallizes in the centrosymmetric space groupPbcn, exhibiting the rutile topology. Complex 2 possesses the same space group and topology as 1′. Complex 3 exhibits a new 2D three-node network topology with the Schlafli symbol of (83). Complex 1 is a second-order nonlinear optical molecular material, and magnet measurements indicated the magnetic coupling interaction between Nd3+ ions in these four complexes is weak.

Reversible modulation of the fluorescence of pyrenemethylamine hydrochloride by light in the presence of spiropyran: signal communication between two molecular switches through proton transfer

The fluorescence of pyrenemethylamine hydrochloride was reversibly modulated by light in the presence of spiropyran. The results demonstrated the signal communication through proton transfer between one three-state molecular switch based on spiropyran and one fluorescence molecular switch.

An Hg2+-gated chiral molecular switch created by using binaphthalene molecules with two anthracene units and two 1,3-dithiole-2-thione (1,3-dithiole-2-one) units.

By integrating the features of anthracene, 1,3-dithiole-2-thione, and binaphthalene units, (S)-1 and its analogue (S)-2, which contains two 1,3-dithiole-2-one units instead of 1,3-dithiole-2-thione, were studied for creating a new molecular regulation system and building a gated chiral molecular switch. The results show that the photodimerization is controlled by the remote functional-group transformation of C=S into C=O, thus providing an elegant example of molecular regulation. The photodimerization of two anthracene units induces circular dichroism (CD) spectral variation. Overall, the CD spectrum can be remotely modulated by Hg2+ in (S)-1, which leads to an Hg2+-gated chiral molecular switch.

Novel magnetic properties of complex TTFxC60Bry

The complex TTFxC60Bry was prepared and characterized. Its magnetic properties were measured as a function of temperature and external field respectively. The results indicated that this complex showed novel magnetic properties.