Metal oxide(TiO2or Co3O4)doped activated carbon nanofbers(ACNFs)were prepared by electrospinning.These nanofbers were characterized by X-ray difraction(XRD),scanning electron microscopy(SEM),and BrunnerEmmett-Teller method(BET).The results show that the average diameters of ACNFs were within the range of 200-500nm,and the lengths were several tens of micrometers.The specifc surface areas were 1146.7 m2/g for TiO2-doped ACNFs and 1238.5 m2/g for Co3O4-doped ACNFs,respectively.The electrospun nanofbers were used for adsorption of low concentration sulfur dioxide(SO2).The results showed that the adsorption rates of these ACNFs increased with an increase in SO2concentration.When the SO2concentration was 1.0μg/mL,the adsorption rates of TiO2-doped ACNFs and Co3O4-doped ACNFs were 66.2%and 67.1%,respectively.The adsorption rate also increased as the adsorption time increased.When the adsorption time was 40 min,the adsorption rates were 67.6%and 69.0%for TiO2-doped ACNFs and Co3O4-doped ACNFs,respectively.The adsorption rate decreased as the adsorption temperature increased below 60 C,while it increased as the adsorption temperature increased to more than 60 C.
Ho3+ doped glasses with various compositions xGeO2-(80-x)TeO2-9.5ZnF2-10NaF-0.5Ho2O3(x=0,10,20,30,40,50,60,70 and80) were prepared by a melt-quenching technique.The composition-dependent optical transition properties of Ho3+ were investigated in theframework of Judd-Ofelt theory.The emission cross sections for 5I7→5I8 transition of Ho3+ in these glasses were calculated according toMcCumber theory,and their compositional dependence was discussed.A simple method was proposed in calculating the emission cross sections of 5I7→5I8 transition,and the calculation results were compared with those derived from McCumber theory.Finally,the optical gain coefficient spectra for 5I7→5I8 transition were also analyzed.
Laser crystals of LiYF4 (LYF) singly doped with Er3+ in 2.0% and co-doped with Er3+/Yb3+ in about 2.0%/1.0% molar fraction in the raw composition are grown by a vertical Bridgman method. X-ray diffraction (XRD), absorption spectra, fluorescence spectra and decay curves are measured to investigate the structural and luminescent properties of the crystals. Compared with the Er3+ singly doped sample, obviously enhanced emission at 1.5 μm wavelength and green and red up-conversion emissions from Er3+/Yb3+ co-doped crystal are observed under the excitation of 980 nm laser diode. Meanwhile, the emission at 2.7 μm wavelength from Er3+ singly doped crystal is reduced. The fluorescence decay time ranging from 18.60 ms for Er3+ singly doped crystal to 23.01 ms for Er3+/Yb3+ co-doped crystal depends on the ionic concentration. The luminescent mechanisms for the Er3+/Yb3+ co-doped crystals are analyzed, and the possible energy transfer processes from Yb3+ to Er3+ are proposed.
Eu3+-doped binary borate glasses with different metal oxide components RO (R=Ca, Sr, Ba, Zn or Pb) were prepared by meltquenching technique. The fluorescent spectral properties of Eu3+in these glasses were experimentally studied. The analysis on the phonon sidebands (PSBs) indicated that RO component did not cause obvious change of the electron-phonon coupling constant (EPC). By inspecting the optical absorption edges it was found that RO could greatly affect the band gap energy, and the glass with PbO component revealed the smallest band gap energy, the glasses with ZnO, BaO and SrO showed similar band gap energy. The optical transition intensity parameters of Eu3+in all studied glasses were calculated, it was found that for each sample its value of2 was larger than that of 4 and 6, and the sample with PbO component exhibited the smallest2, but the λ values for ZBE, CBE, BBE and SBE were very similar. These results might be helpful for the design of borate glasses.
