Shikang Wu

Colorimetric test kit for Cu2+ detection.

A coumarin-based colorimetric chemosensor 1 was designed and synthesized. It exhibits good sensitivity and selectivity for the copper cation over other cations such as Zn(2+), Cd(2+), Pb(2+), Co(2+), Fe(2+), Ni(2+), Ag(+), and alkali and alkaline earth metal cations both in aqueous solution and on paper-made test kits. The change in color is very easily observed by the naked eye in the presence of Cu(2+) cation, whereas other metal cations do not induce such a change. The quantitative detection of Cu(2+) was preliminarily examined.

The fabrication and optical properties of highly crystalline ultra-long Cu-doped ZnO nanowires

We demonstrate the bulk synthesis of single crystalline Cu-doped ZnO nanowires using (CuI+ZnI2) powders at 600 °C. These mass nanowires are characterized through x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction, and high-resolution TEM; they have uniform diameters of about 65 nm and are several tens of microns in length. The growth of ZnCuO nanowires is suggested for self-catalyzed vapour–liquid–solid. In particular, the PL spectra of these nanowires show emission peaks that strongly shift to long wavelength with increasing Cu, and the doping quantity is found to be responsible for the different characteristics; the PL mechanism is explained in detail.

Spectroscopy and photophysics of bridged enone derivatives: effect of molecular structure and solvent

Abstract The spectroscopy and photophysics of several substituted enones with different bridged structures were studied in a variety of solvents. Results show that, in all cases, the non-radiative and radiative decay processes of the excited states are strongly influenced by the molecular structure and the solvent polarity. The “negative solvatokinetic effect” and “positive solvatokinetic effect” are observed for all four compounds. Compounds 3 and 4, with bridged double bond structures, have high fluorescence quantum yields and (especially compound 4 with a rigid structure even in non-polar solvents (cyclohexane, Φf=0.5)), indicating that radiative decay is predominant during the decay of the excited states of these compounds. In contrast, the enone compounds with a free double bond have very low fluorescence quantum yields, indicating that non-radiative decay is important for these compounds.

Triplet-triplet absorption of 2-(2′-hydroxyphenyl) benzoxazole (HBO) in polar solvents

Abstract The transient TT absorption spectra of 2-(2′-hydroxyphenyl) benzoxazole (HBO) have been measured in liquid polar solvents and in polymethylthacrylate. In non-protonic polar solvents the main TT absorption is from the keto form of the compound ( 3 K ∗ ). With a triplet sensitizer the compound just gives a TT absorption of its enol from ( 3 E ∗ ) after triplet energy transfer from the sensitizer to HBO. The excited state intramolecular proton transfer (ESIPT) from the enol form to keto form occurs just in the singlet state. The protonic solvent can break the intramolecular hydrogen bond of HBO and decrease the ESIPT process. In solid solution both 3 E ∗ and 3 K ∗ can be formed and the TT absorptions were detected because of the inhibition of the rotational conformation transfer.

A nonpolymeric highly emissive ESIPT organogelator with neither dendritic structures nor long alkyl/alkoxy chains

A highly fluorescent excited state intramolecular proton transfer (ESIPT) small molecular organic gelator based on 2-(2′-hydroxy)phenylbenzoxazole, N,N′-bis(4-(benzo[d]oxazol-2-yl)-3-hydroxyphenyl)-5-tert-butylisophthalamide, is developed in the present study. The ESIPT organogelator does not have a dendritic structure or long alkyl chains, but has a specific bent molecular structure. The intermolecular H-bonding (N–H⋯OC) between the J-aggregated dimers is the main driving force in the formation of the subsequent long-range one-dimensional assemblies in gel. The ESIPT gelator shows characteristics of aggregation-induced enhanced emission (AIEE). With its AIEE characteristics, ESIPT properties, simple and scalable fabrication of elongated nanobelts, as well as easy synthetic procedures, the versatile multifunctional fluorescent gelator has good prospects for future application in photoelectrical nanodevices.

A study on the spectroscopy and photophysical behaviour of chalcone derivatives

Abstract Several chalcone derivatives, containing a strong electron donor moiety and groups with various electron withdrawing abilities, were synthesized. The spectra and photophysical properties of these compounds were studied. The luminescence behaviour of these compounds depends on the character of the substituents, the solvent polarity and the temperature. From a correlation of the fluorescence quantum yield with the solvent polarity, a clear maximum was observed.

Formation of ZnS/SiO2 nanocables

Nanometer-sized coaxial cables with a single-crystal ZnS core and a thin amorphous SiO2 shell were synthesized by simple thermal evaporation in vacuum. As-fabricated ZnS/SiO2 nanocables were studied using scanning electron microscopy, x-ray diffraction and transmission electron microscopy. The ZnS/SiO2 nanocables have diameters of ∼50nm, lengths of several tens of micrometers, and shell thickness of ∼4nm. The core of the nanocable has a wurtzite structure with a growth direction along [001]. The nanocables show strong photoluminescence with two peaks related to band gap and defect-related emission.

Study of the temperature-dependent luminescence behaviour of 4′-N,N-dimethylaminoflavone derivatives

Abstract In this work, several 4′- N,N -dimethylaminoflavone derivatives with different structures were synthesized. The spectroscopic and photophysical properties of these compounds under different conditions were studied. Results show that the spectroscopic properties of compounds in polar solvents are different from those in non-polar solvents. In polar solvents, fluorescence emissions at different wavelengths were observed at room temperature and 77 K , corresponding to different conformations of the compounds. In non-polar solvents, the compounds form dimers and aggregates (microcrystals) at low temperature. The tendency to form dimers or aggregates (microcrystals) was different for compounds with different structures. A preliminary discussion of the results is given.

Morphology-controllable preparation of 1D poly(vinyl pyrrolidone) nanostructured arrays

Morphology-controlled, ordered poly(vinyl pyrrolidone) (PVP) nanotubes and nanowires have been prepared on porous alumina templates with hydrophilic or hydrophobic pore surfaces. The nanostructures were about 270 nm in diameter with a narrow size distribution and up to 10 µm in length. The fluorescence spectrum was used to characterize the pore surface of AAO templates with different polarities. The mechanism of the formation of PVP nanotubes or nanowires was discussed.

Rotational relaxation of pyrazoline compounds in solution

Abstract The photophysical behaviour of pyrazoline derivatives was studied in this work. The fluorescence quantum yields of these compounds were measured in various media with identical polarity but different viscosity. In accordance with microviscosity theory, a linear relationship was observed between the product of the non-radiative decay rate constant and solvent viscosity and η x . It is suggested that the process of non-radiative decay occurs via rotation of the phenyl group which is connected to the N-1 position in the diphenyl pyrazoline molecule.