[Study on the preparation and spectral characteristics of CeO2 nanocrystallines].

Ceria (CeO2) nanoparticles were prepared by precipitation method using cerium nitrate (Ce(NO3)3 x 6H2O) and ammonia (25 Wt%) as raw materials under the reaction for 3 h and ageing for 9 h at 80 degrees C without any surfactants and further calcination. The powder X-ray diffraction (XRD) pattern shows the as-prepared CeO2 crystals belong to the cubic phase and are well crystallized. Transmission electron microscopic (TEM) studies reveal that the appearance of as-prepared CeO2 is hexagonal, which is proposed to be the projection of polyhedral shape. The regular fringes spacing of 0.31 nm is in agreement with the d value of (111) lattice planes of cubic phase CeO2 from high-magnification TEM image. Reaction conditions such as the concentration of precipitant, reaction temperature and ageing duration exert important influence on the purity and morphology of the product. Ce(OH)3 was detected when the reaction was processed at lower pH (< 9) or with ageing duration less than 8 h at 80 degrees C. The size of polyhedral ceria nanoparticles increased with longer ageing time (> 15 h). If the reaction went on at a temperature lower than 40 degrees C, a large quantity of rodlike Ce(OH)3 was produced according to TEM observation. Raman spectra of CeO2 nanocrystallines exhibit a Raman shift at 465 cm(-1), corresponding to a F2g Raman band from the space group Fm3m of a cubic fluorite structure, while the Raman shift at about 600 cm(-1) may be attributed to the second Raman vibration mode of O2- vacancy due to Ce3+ impurity. Photoluminescence spectrum of CeO2 shows an emission at 465 nm at room temperature, which may be explained by charge transition from the 4f band to the valence band of CeO2.

Construction of sandwich-like porous structure of graphene-coated foam composites for ultrasensitive and flexible pressure sensors.

Ultrasensitive and flexible pressure sensors that can perceive and respond to environmental stimuli have attracted considerable attention due to their potential applications in wearable electronics and electronic skin devices. Here, we report a simple and low-cost strategy to fabricate high-performance pressure sensors via constructing a unique conductive/insulating/conductive sandwich-like porous structure (SPS). Interpenetration of the conductive graphene network throughout the porous insulating interlayer produces a highly efficient transition from the non-conductive to the conductive state. Consequently, the SPS sensors exhibit an extreme resistance-switching behavior (resistance change of >105 at 30 kPa), high sensitivity (∼0.67 kPa-1, <1.5 kPa), fast response/recovery time (∼10 and ∼16 ms) and outstanding mechanical stability. Such SPS pressure sensors are applicable for detecting various mechanical deformation modes (press, bend and torsion) and different stress/strain levels (from gait feature, finger/wrist/elbow movement to breathing monitoring and real-time pulse wave), providing a new concept of device design for wearable electronic applications.

Development of a BODIPY-based ratiometric fluorescent probe for hypochlorous acid and its application in living cells.

A BODIPY-based ratiometric fluorescent probe for HOCl has been designed based on the transduction of thioether to sulfoxide function. This probe features a marked absorption and emission blue-shift upon the HOCl-promoted rapid transduction, enabling the highly selective and ratiometric detection. In addition, the probe works excellently within a wide pH range of 4-10, addressing the existing pH dependency issue. Living cells studies demonstrate that the probe is cell membrane permeable and can be employed successfully to image endogenous HOCl generation in macrophage cells.