Several Ir/IrO2 pH electrodes were prepared by a cyclic thermal oxidation process via dip-coating in a concentrated solution of NaOH. A hydrothermal hydration treatment at 220 °C for 24 h was used to address the problematic potential drift that is common in Ir/IrO2 pH electrodes. The electrodes that were treated by the hydrothermal method exhibited good stability and high sensitivity compared to those that were hydrated at room temperature. The reasons for this improvement were investigated by Raman spectroscopy, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy. The results suggested that the hydrothermally treated electrode had a more orderly crystal arrangement and a higher content of OH− groups, which drove improvements in the performance of electrode by modification of the Ir/IrO2 structure. The relationship between the electrode structure and performance was investigated and discussed in detail herein.

Ultrafine-structure La0.65Sr0.35MnO3 (LSM) powders synthesized by self-propagating combustion method have been used to fabricate sensing electrodes (SEs) for NO2 mixed-potential sensors based on yttria-stabilized zirconia (YSZ). This type of sensor was found to provide better NO2 sensitivity at 500 °C than sensors with LSM powders synthesized by traditional solid-state methods. The response values of the sensor have good linear relationship (sensitivity 36.6 mV/decade and linear fit 0.99) with the logarithm of NO2 concentration varying from 30 to 500 ppm. The influence of sintering temperature (1000, 1100, 1200, and 1300 °C) on sensor response was also examined and was found to have a significant effect on the morphology of LSM-SEs. Moreover, in the presence of NO, CO2, CO, and NO2, the sensor exhibited good NO2 selectivity.

Layered-structure Bi2W2O9 powders synthesized by conventional solid-state reaction and treated by ball milling have been used to create an electrode for a mixed-potential-type NO2 sensor with yttria-stabilized zirconia as an oxygen ion conductor. This sensor was found to provide good sensitivity to NO2 at 500 °C, thanks to the grain refinement induced by ball milling. The electromotive force generated was linear to the logarithm of NO2 concentration in the range of 30–500 ppm, with analysis of the impedance spectroscopy revealing a similar linear correlation between the conductance of the electrode and the logarithm of NO2 concentration. The influence of CO2 was also examined and found to have little effect on the sensitivity of the sensor.

A novel luminescent inorganic/organic hybrid nanosheet [Y2(1−x)Eu2x(OH)5(TTA)n]+ was successfully synthesized. The photoluminescence of the hybrid nanosheet was significantly different from that of the unmodified nanosheet. The main charge transfer band Eu–O of the nanosheet was replaced by the more efficient π–π* electron transition band of the organic ligands in the hybrid. The emission bands of the 5D0–7F2 electric dipole transition in the hybrid were enhanced greatly. We also prepared a novel transparent thin film of the luminescent inorganic/organic hybrid on FTO glass by electrophoretic deposition. On being excited by ultraviolet radiation, the thin films show strong red emission.

Novel single-layer rare-earth oxide nanosheets were obtained by the exfoliation of Y(1−X)REXOBr (RE = Eu/Tb) layer. First, the Br− ions in Y(1−X)REXOBr were exchanged by benzoate ions under microwave conditions. The interlayer benzoate can chelate RE ions in the oxide layer, and change the structure and luminescence properties of the new layer compound. Then, a colloid of yttrium oxide nanosheets was obtained in n-butanol after the ultrasonic treatment of the benzoate-inserted layer for 30 min. The size and thickness of the yttrium oxide nanosheets were ∼800 nm and 0.8 nm, as measured by transmission electron and atomic force microscopies, respectively. A transparent thin film of the yttrium oxide nanosheets on indium tin oxide glass was prepared by electrophoretic deposition. The thin film showed strong red or green emission upon UV-light excitation based on Eu3+ and Tb3+ ions, respectively.

Novel ZnS quantum dots (QDs) and ZnS quantum flakes (QFs) were successfully prepared with graphene nanosheets (GNs) as a special template, and two unique heterostructures of ZnS/GNs were also obtained. Due to the structure-directing template effect of GNs, the as-synthesized ZnS with different morphologies, dots or flakes, were uniformly distributed on the surface of GNs by controlling nucleation and growth. The two different heterostructures of ZnS/GNs exhibited obvious photovoltaic response, and ZnS/GN QFs-on-sheet heterostructures show higher photovoltage than that of ZnS/GN QDs-on-sheet.

Lamellar aggregates of the semiconductor nanosheets accommodating rare earth ions of Tb3+ or Eu3+ have been fabricated by flocculation of colloidal TiTaO5− nanosheet. The as-obtained composites were analyzed by a range of methods including powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) with energy dispersive X-ray spectrometer (EDS). The results indicated that the re-stacking of the nanosheets could form a uniform layered structure. Meanwhile, the RE ions could be attached to the flocculated samples. The photoluminescence (PL) spectra were also employed to explore the optical property of the hybrid. The characteristic emission from the composites either by exciting the nanosheet host with UV light or by directly exciting RE at a longer wavelength has been investigated in detail. At the same time, the energy transfer between nanosheet and RE ions could be discussed systemically.

ZnO quantum dots (QDs) are anchored on multi-walled carbon nanotubes (MWCNTs) by a wet chemical self-assembling technique. The structure and properties of QDs/MWCNTs are also studied in detail. First, MWCNTs are functionalized with thiol by a series of chemical reactions. Fourier transform infrared spectroscopy is used to verify changes of chemical bonds on MWCNTs. At one time, quantum dots of ZnO alcogel are prepared by a sol–gel process. Finally, the functionalized MWCNTs (f-MWCNTs) are added into ZnO alcogels under ultrasonic condition or being magnetically stirred, and ZnO QDs/f-MWCNT composite is obtained by a self-assembling technique. A typical transmission electron microscopy image of the as-received ZnO QDs/f-MWCNT composite reveals that monodispersed ZnO QDs are anchored stably on functionalized MWCNTs. Moreover, photoluminescence spectrum and current–voltage curves display the special optoelectronic properties of this ZnO QDs/f-MWCNT hybrid.