Su Qingde

Size-dependent optical properties of nanocrystalline CeO2:Er obtained by combustion synthesis

Nanocrystalline Er-doped CeO2 phosphors with an average crystallite size of 18, 38, and 70 nm were prepared by glycine–nitrate solution combustion synthesis. The particle size of the resultant powders is tied up with the combustion flame temperature, which can be controlled by adjusting the ratio of glycine to nitrate. The microstructure and morphology of the CeO2 :Er materials were investigated by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). It is found that nanocrystalline CeO2 :Er is surrounded by amorphous phase, and that the area of the amorphous phase increases with the decrease of the particle size. The photoacoustic spectra (PAS) show the particle-size dependence of the optical properties. With the decrease of the particle size, a blue shift of the PAS absorption peak and an enhancement of the exciton absorption are observed, which result from a quantum size effect. The photoluminescence of the CeO2 :Er materials was measured. When the nanoparticle size decreases, the red-to-green ratio of the Er3+ emission becomes high. This means that there is a stronger interaction and a more efficient energy transfer between the Er3+–Er3+ dopants in smaller CeO2 :Er nanocrystals.

PHOTOACOUSTIC SPECTROSCOPY STUDY ON LANTHANIDE TERNARY COMPLEXES WITH DIBENZOYLMETHIDE AND PHENANTHROLINE

Abstract The photoacoustic (PA) spectra of Eu(Dbm) 3 ·Phen and coprecipitates Eu 0.8 Ln 0.2 (Dbm) 3 ·Phen complexes (Ln 3+ : Nd 3+ , Gd 3+ , Tb 3+ ; Dbm: dibenzoylmethide; Phen: phenanthroline) are reported. The PA intensity in the region of the ligand absorption increases for Eu 0.8 Gd 0.2 (Dbm) 3 ·Phen, Eu 0.8 Tb 0.2 (Dbm) 3 ·Phen, Eu(Dbm) 3 ·Phen and Eu 0.8 Nd 0.2 (Dbm) 3 ·Phen, respectively. It is indicated that additions of the second lanthanide ions change the relaxation processes of the complexes. The changes of fluorescence spectra turn out to be complementary to the PA spectra. The intramolecular energy transfer and intermolecular energy transfer processes in the coprecipitates are discussed.

Rapid Removal of Template from Molecularly Imprinted Polymers by Accelerated Solvent Extraction

A novel extraction method to remove template from molecularly imprinted polymer (MIP) and reduce template bleeding using accelerated solvent extraction (ASE) has been developed. The MIP was synthesized following a noncovalent protocol using nicotine as the template molecule, methacrylic acid as the functional monomer, and ethylene glycol dimethacrylate as the cross-linker. After optimizing the extraction solvent and temperature, the method was carried out to remove template from nicotine MIP at 80°C with 300 ml of methanol-acetic acid (90:10, v/v), and the extraction efficiency of nicotine template from MIP was 94.2%. The extraction procedure was completed in 70 min. After the treatment, the imprinted polymers were packed into solid-phase extraction columns and the bleeding amount of nicotine template was estimated by quantifying the amount of template released in 10 ml of methanol-acetic acid (90:10, v/v). In this case, a bleeding level of 9.8μg l−1 was found. Compared with the traditional template removing methods, soxhlet extraction and ultrasonic assisted extraction, ASE was the more effective method aimed at rapid removal of template from molecularly imprinted polymer.

Study on photoacoustic phase spectrum of rare earth complex: Pr(HFA)3·2H2O

Abstract The β-diketone rare earth complex: Pr(HFA) 3 ·2H 2 O was synthesized and its amplitude and phase photoacoustic spectra in the range of 300–700 nm were reported. It was observed that the phase angle depends variously on the relaxation time τ and the optical absorption coefficient β with the incident light wavelength λ. A model of a homogeneous powder sample containing multiple optical absorption bands based on the Mandelis work was introduced to interpret the phase spectrum. It is shown that this model is very suitable for explaining the phase data associated with the π-π∗ transition and tf-tf transitions of the title complex. The phase angle ψ is mainly related to τ for the π-π∗ transition while it is determined by β for the tf-tf transition at relatively low chopping frequencies. Furthermore, the dependence of amplitude and phase information on the chopping frequency was also investigated.

Photoacoustic spectra of complexes of tryptophan with Sm(III), Tb(III) and Dy(III)

Abstract Crystals of the complexes of Tryptophan with Sm(III), Tb(III) and Dy(III) were synthesized and the photoacoustic (PA) spectra in the UV–vis region were recorded. The PA intensities of the central lanthanide ions are interpreted in terms of the probability of nonradiative transitions. It is found that the PA intensity of the ligand bears a relation to the intramolecular energy transfer process. For the title complexes, the different PA intensities of the ligand, tryptophan, are interpreted by comparison with the fluorescence spectra. The relaxation process models are also studied based on the PA and fluorescence spectra.

Photoacoustic spectroscopy study on intramolecular energy transfer and relaxation processes of Tb(III) complexes

The photoacoustic (PA) amplitude spectra and luminescence spectra of different Tb(III) complexes (Tb(AA)3.2H2O Na[Tb(AA)4], Tb(AA)3bpy and Tb(AA)3phen) have been measured, and the PA phase shifts of the different complexes calculated. Combined with the luminescence spectra, the PA amplitude spectra reflected the variation of the luminescence efficiency and the PA phase is directly relative to the relaxation processes. According to the variation of the luminescence efficiency and the phase shift, the intramolecular energy transfer and relaxation processes of different Tb(III) complexes were discussed.

Spectral study of the structure of compartmental complexes of europium and copper

Abstract Compartmental complexes [EuH2(fsa)2en]Cl·3H2O and [CuH2(fsa)2en]·0.5H2O have been synthesized and characterized. The compartmental ligand (H4(fsa)2en) is N,N′-bis(3-carboxysalicy- lidene)ethylenediamine. Spectral study indicates that Eu(III) and Cu(II) are coordinated by the O2O2 coordinating atoms (outside) and the N2O2 coordinating atoms (inside), respectively. Since there is a considerable difference in the ligand field strength between the “outside” and “inside” coordination spheres, their different fluorescence properties have been investigated by photoacoustic spectroscopy and fluorescence spectroscopy.

Photoacoustic spectra of Nd(TFA)3 · 2H2O and Nd(HFA)3 · 2H2O

Abstract A new synthesis of trisfluoroacetylactone (TFA) and hexafluoroacetylactone (HFA) Nd complexes: Nd(TFA) 3 · 2H 2 O and Hd(HFA) 3 · 2H 2 O is reported. The photoacoustic (PA) spectra in the 300–800 nm region of the compounds NdCl 3 · 6H 2 O, Nd(TFA) 3 · 2H 2 O and Nd(HFA) 3 · 2H 2 O are reported. The PA absorption bands are assigned and their relative intensities represented by intensity branching vectors are calculated. The perturbation of the ligand on the energy levels of Nd 3+ ion is discussed and a model of the relaxation process of Nd(HFA) 3 · 2H 2 O is proposed based on its PA and absorption spectra.

Optical determination of the thickness of thin films symmetrically deposited on both sides of the substrates

The optical transmission spectra of ceria thin films symmetrically deposited on both sides of the glass slide substrate were modelled to determine the film thickness. Removal of absorption phenomenon of the substrate from the experimental spectra allowed direct examination of ceria thin-film optical characteristics. This technique is applicable to weakly absorbing thin films, especially to those with typical thickness smaller than 100 nm, which is difficult to determine by scanning electron microscopy.

An Overview of The Photoacoustic Phase Spectra of Rare Earth Complexes

Abstract The photoacoustic(PA) amplitude and phase spectra of several kinds of rare earth (RE) complexes are reported and summarized briefly. It is observed that both the amplitude and phase spectra well characterize the different energy levels of the RE complexes. The phase angle of the RE complexes is associated with the relaxation time τ and the optical absorption coefficient β concerning with the π-π∗ transition and the f-f transitions, respectively. After individual detailed discussion of the phase spectra, a reasonable theoretical consideration is given to interpret the results.