Chun-Yun Peng

Near-infrared emission from novel tris(8-hydroxyquinolinate)lanthanide(III) complexes-functionalized mesoporous SBA-15

A novel mesoporous material covalently bonded with 8-hydroxyquinoline (HQ) was synthesized (designated as Q-SBA-15). The 5-formyl-8-hydroxyquinoline grafted to (3-aminopropyl)triethoxysilane, that is, alkoxysilane modified 8-hydroxyquinoline (Q-Si), was used as one of the precursors for the preparation of the Q-SBA-15 material. On the basis of the other function of the Q-Si of coordinating to lanthanide (Ln) ions, for the first time, the LnQ 3 complexes (Ln = Er, Nd, Yb) have been covalently bonded to the SBA-15 materials. The derivative materials, denoted as LnQ 3-SBA-15, were characterized by field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption, and fluorescence spectra. Upon excitation at the ligands absorption bands, all of these materials show the characteristic near-infrared (NIR) luminescence of the corresponding lanthanide ions through the intramolecular energy transfer from the ligands to the lanthanide ions. The NIR luminescence of these mesoporous materials was compared with that of the corresponding pure LnQ 3 complexes and discussed in detail.

Incorporation of luminescent lanthanide complex inside the channels of organically modified mesoporous silica via template-ion exchange method

Luminescent lanthanide complex, Eu(phen)2Cl3·2H2O (Euphen, phen = 1,10-phenanthroline) has been incorporated inside the channels of mesoporous silica MCM-41 with its external surface modified by phenyltriethoxysilane (Ph-Si(OEt)3) via a simple template-ion exchange method. The passivation of active groups such as silanols in the external surface ensures that the ion exchange reaction occurs between the surfactant cations and the lanthanide complex ions inside the channels of the modified MCM-41. The passivation result is confirmed by 29Si MAS NMR spectroscopy. FT-IR demonstrates that the cationic surfactants are completely removed. XRD and N2 adsorption–desorption measurements are employed to characterize the mesostructure of Euphen-Ph-MCM-41. Luminescence and stability studies on the materials of Euphen and Euphen-Ph-MCM-41 show that the resultant hybrid material Euphen-Ph-MCM-41 exhibits the characteristic emission of Eu3+ ions under UV irradiation with higher 5D0 luminescence quantum efficiency, longer lifetime and better thermal stability than the corresponding pure complex Euphen. Moreover, the characterization results show that the local symmetry and the first coordination shell of Eu3+ ions are changed after the complex ions become incorporated into the MCM-41 channels and that a more symmetric environment is occupied by the Eu3+ ions in Euphen-Ph-MCM-41 than in Euphen. There is also a more efficient ligand-to-Eu(III) intramolecular energy transfer process in Euphen-Ph-MCM-41.

Palladium nanowires stabilized by thiol-functionalized ionic liquid: seed-mediated synthesis and heterogeneous catalyst for Sonogashira coupling reaction

With the recent surge of the use of room-temperature ionic liquids in the syntheses of inorganic nanomaterials, we have successfully integrated the advantages of a thiol-functionalized ionic liquid and the seed growth method to generate palladium nanowires at room temperature. Moreover, the as-prepared palladium nanowires show very high catalytic activity and stability for the Sonogashira coupling reaction.

Preparation and luminescence properties of in situ formed lanthanide complexes covalently grafted to a silica network

Lanthanide-doped sol-gel-derived materials are an attractive type of luminescent materials that can be processed at ambient temperatures. However, the solubility of the lanthanide complexes in the matrix is a problem and it is difficult to obtain a uniform distribution of the complexes. Fortunately, these problems can be solved by covalently linking the lanthanide complex to the sol-gel-derived matrix. In this study, luminescent Eu3+ and Tb3+ bipyridine complexes were immobilized on sol-gel-derived silica. FT-IR, DTA-TG and luminescence spectra, as well as luminescence decay analysis, were used to characterize the obtained hybrid materials. The organic groups from the bipyridine-Si moiety were mostly destroyed between 220 and 600 °C. The luminescence properties of lanthanide bipyridine complexes anchored to the backbone of the silica network and the corresponding pure complexes were comparatively investigated, which indicates that the lanthanide bipyridine complex was formed during the hydrolysis and co-condensation of TEOS and modified bipyridine. Excitation at the ligand absorption wavelength (336 nm for the hybrid materials and 350 nm for the pure complexes) resulted in strong emission of the lanthanide ions: Eu3+5D0–7FJ (J = 0, 1, 2, 3, 4) and Tb3+5D4–7FJ (J = 6, 5, 4, 3) emission lines due to efficient energy transfer from the ligands to the lanthanide ions.

Unique gold sponges: biopolymer-assisted hydrothermal synthesis and potential application as surface-enhanced Raman scattering substrates

In this paper we describe a biopolymer-assisted hydrothermal approach to the synthesis of gold sponges. This is carried out by transferring a hyaluronic acid potassium salt/HAuCl4 aqueous solution into a stainless steel autoclave with a Teflon liner and heating in an oven at 180 °C for 6 h. Here, hyaluronic acid potassium salt plays three roles in the synthesis, namely, stabilization, reduction, and as a soft template. Field emission scanning electron microscopy images, energy-dispersive x-ray spectroscopy, and x-ray diffraction reveal that the materials obtained consist of an interconnected framework of face-centred cubic metallic gold filaments, which is approximately 0.6 µm in width and composed of fused micrometre-sized particles that enclose pores 1–4 µm in size. The test of surface-enhanced Raman scattering (SERS) from 4-mercaptobenzoic acid shows that the prepared gold sponges are an active SERS substrate. This is largely because they had an increased number of particle junctions, which are SERS active sites. This route can also be extended to the fabrication of silver sponges, which are composed of fused crystallites with diameters of 200–400 nm that enclosed pores 0.4–2 µm in size. The test of SERS from Rhodamine 6G also reveals that the prepared silver sponges are likewise an excellent SERS substrate.

Dependence of performance of organic light-emitting devices on sheet resistance of indium-tin-oxide anodes

The dependence of the performance of organic light-emitting devices(OLEDs) on the sheet resistance of indium-tin-oxide(ITO) anodes was investigated by measuring the steady state current density brightness voltage characteristics and the electroluminescent spectra. The device with a higher sheet resistance anode shows a lower current density, a lower brightness level, and a higher operation voltage. The electroluminescence(EL) efficiencies of the devices with the same structure but different ITO anodes show more complicated differences. Furthermore, the shift of the light-emitting zone toward the anode was found when an anode with a higher sheet resistance was used. These performance differences are discussed and attributed to the reduction of hole injection and the increase in voltage drop over ITO anode with the increase in sheet resistance.