Visualizing the valence states of europium ions in Eu-doped BaAl2O4 using X-ray nanoprobe mapping.

This study develops and successfully demonstrates visualization methods for the characterization of europium (Eu)-doped BaAl2O4 phosphors using X-ray nanoprobe techniques. X-ray fluorescence (XRF) mapping not only gives information on the elemental distributions but also clearly reveals the valence state distributions of the Eu2+ and Eu3+ ions. The accuracy of the estimated valence state distributions was examined by performing X-ray absorption spectroscopy (XAS) across the Eu L3-edge (6.977 keV). The X-ray excited optical luminescence (XEOL) spectra exhibit different emission lines in the selected local areas. Their corresponding emission distributions can be obtained via XEOL mapping. The emission properties can be understood through correlation analysis. The results demonstrate that the main contribution to the luminescence intensity of the Eu-doped BaAl2O4 comes from the Eu2+ activator and the emission intensity will not be influenced by the concentration of Eu2+ or Eu3+ ions. It is anticipated that X-ray nanoprobes will open new avenues with significant characterization ability for unravelling the emission mechanisms of phosphor materials.

Silver-decorated hierarchical cuprous oxide micro/nanospheres as highly effective surface-enhanced Raman scattering substrates.

A facile and simple route to manufacture active surface-enhanced Raman scattering (SERS) substrate based on Ag-decorated Cu2O micro/nanospheres on Cu foil was systematically investigated. Hierarchical Cu2O micro/nanostructure transfers from CuO nanosheets and Cu(OH)2 nanowires by means of thermally reducing the oxides from Cu2+ to Cu1+ at temperature of 500 °Cunder nitrogen atmosphere. The subsequent decoration of Ag on Cu2O nanostructural substrate was carried out by means of thermal evaporator deposition. Using 4-aminothiophenol (4-ATP) as probing molecules, the SERS experiments showed that the Ag-decorated Cu2O micro/nanospheres exhibit excellent detecting performance, which could be used as effective SERS substrate for ultrasensitive detection. Additionally, these novel hierarchical SERS substrates showed good reproducibility and a linear dependence between analyte concentrations and intensities, revealing the advantage of this method for easily scale-up production.

The open container-used microfluidic chip using IrO(x) ultramicroelectrodes for the in situ measurement of extracellular acidification.

The measurement of metabolic activity based on the extracellular acidification rate has attracted wide interests in the field of biochemical detection. In the study, the chip comprising a microfluid-controlled open container and iridium oxide (IrO(x)) pH ultramicroelectrodes (UMEs) was constructed for the purpose of in situ measurement of extracellular acidification rate. The feasible anodic depositing parameters of IrO(x) film were in the range of +0.53 to +0.8 V by means of exploring the electrochemical properties of alkaline Ir(IV) deposition solution. The IrO(x) pH UMEs electrodeposited for 300 cycles between 0 V and +0.6 V exhibited the near-super-Nernstian sensitivity of -68 to -76 mV/pH and the good stability with potential drifting of 11.7 mV within 24h. The design of the open container connected with a position-raised microchannel improved the sensing stability of IrO(x) pH UMEs, with the potential deviation of as low as 0.1 mV under the flow rate of 20 µl/min. The acidification rate of HeLa cells (2160 cells/mm(2)) repeatedly measured 5 times in the microfluidic chip showed the good reproducibility of 0.021±0.002 pH/min. Moreover, the chip can decrease the acidosis occurrence, a decrease of only 0.13-0.17 pH unit in 8 min interval, during the measurement of cellular metabolic activity.