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NiO–SnO2 composite nanofibers are synthesized by electrospinning of a poly(vinyl pyrroridone) (PVP)/SnCl2·2H2O/NiCl2 solution. Indirect-heated sensors are fabricated by coating the nanofibers on ceramic tubes with signal electrodes. The obtained nanofibers are analyzed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The sensors are tested at different temperatures to various gases. High toluene sensing properties are observed at 330 °C, and the corresponding response value (Ra/Rg), response time, and recovery time are about 11.2 s, and 4 s to 50 ppm toluene at this condition. Good selectivity and excellent stability are also observed based on the sensors at this temperature. These high sensor performances are explained by the sensing enhancement brought about by NiO addition and the one-dimensional nanostructure of nanofibers.

We studied the growth process of nanocrystalline ZnO which grown in amorphous ZnO by photoluminescence (PL). In this process, we found a new visible emission band, the visible emission intensity increased quickly at first, then decreased exponentially, while the peaks energy has a red shift from 583nm to 615nm along with the increasing reaction temperature. The results indicate this visible emission band correlate with the nanocrystalline ZnO/amorphous ZnO interface. The interface was polarized by the activated amorphous ZnO acts with the nanocrystalline ZnO surface, thus charge carrier was self-trapped on the nanocrystalline ZnO surface and emitted visible PL by recombination. We studied the changes rule of the nanocrystalline ZnO / amorphous ZnO interface by the characteristic of visible emission.

Algebraic immunity (AI) is a new cryptographic criterion proposed against algebraic attacks. Extended algebraic immunity (EAI) extends the concept of algebraic immunity, whose point is that a Boolean function f may be replaced by another Boolean function f c called the algebraic complement of f In this paper, we investigate EAI of Boolean functions. Firstly, we present a sufficient and necessary condition to judge AI of a Boolean function equals to its EAI. Secondly, we prove that two classes of Boolean functions with maximum AI also have optimal EAI. Finally, we analyze that the structure of the annihilators of Boolean functions with the algebraic complement.