The discovery of gas sensing properties of single-crystalline nanostructures comparable or even better than their polycrystalline counterparts has triggered the attention of the gas sensor research community. To eleborate the sensing mechanisms of single-crystalline and polycrystalline nanostructures, the single-crystalline (SC) NiO hexagonal nanosheet and the nanoparticle self-assembled polycrystalline (PC) NiO nanosheet were prepared for room-temperature NO 2 sensing studies. The gas sensing studies revealed that the SC NiO exhibited a remarkably higher response to NO 2 at room temperaure than the PC NiO. The correlation between the structural features of NiO and the room temperature NO 2 sensing performances was discussed in detail via the grain boundary scattering theroy. It was found that the scattering potential played a vital role in the sensing process. Since the absence of grain boundary in the SC NiO reduced the NO 2 chemisorption-induced carrier scattering at interfaces, the SC NiO performed the largely enhanced sensitivity. Here we hope that this work can help us to further understand the gas sensing mechanism, and open up a new generation of gas sensors.

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Two new prenylflavonoids, morusalbols A and B (1 and 2), were isolated from the branches and leaves of Morus alba, together with three known compounds, kuwanon C (3), morusin (4), morusinol (5). The structures of these two prenylflavonoids were elucidated by extensive analyzes of the spectroscopic data.

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