Choi Seung-Hoon, Ankonina Guy, Youn Doo-Young, Oh Seong-Geun, Hong Jae-Min, Rothschild Avner, Kim Il-Doo
Center for Energy Materials Research, Korea Institute of Science and Technology, PO Box 131, Cheongryang, Seoul, Republic of Korea.
ACS Nano. 2009 Sep 22;3(9):2623-31. doi: 10.1021/nn900126k.
Thin (0.5 to 1 microm) layers of nonaligned or quasi-aligned hollow ZnO fibers were prepared by sputtering ZnO onto sacrificial templates comprising polyvinyl-acetate (PVAc) fibers deposited by electrospinning on silicon or alumina substrates. Subsequently, the ZnO/PVAc composite fibers were calcined to remove the organic components and crystallize the ZnO overlayer, resulting in hollow fibers comprising nanocrystalline ZnO shells with an average grain size of 23 nm. The inner diameter of the hollow fibers ranged between 100 and 400 nm and their wall thickness varied from 100 to 40 nm from top to bottom. The electronic transport and gas sensing properties were examined using DC conductivity and AC impedance spectroscopy measurements under exposure to residual concentrations (2-10 ppm) of NO(2) in air at elevated temperatures (200-400 degrees C). The inner and outer surface regions of the hollow ZnO fibers were depleted of mobile charge carriers, presumably due to electron localization at O(-) adions, constricting the current to flow through their less resistive cores. The overall impedance comprised interfacial and bulk contributions. Both contributions increased upon exposure to electronegative gases such as NO(2) but the bulk contribution was more sensitive than the interfacial one. The hollow ZnO fibers were much more sensitive compared to reference ZnO thin film specimens, displaying even larger sensitivity enhancement than the 2-fold increase in their surface to volume ratio. The quasi-aligned fibers were more sensitive than their nonaligned counterparts.
通过将氧化锌溅射在牺牲模板上制备了厚度为0.5至1微米的非对齐或准对齐空心氧化锌纤维，该牺牲模板由通过静电纺丝沉积在硅或氧化铝基板上的聚醋酸乙烯酯（PVAc）纤维组成。随后，对氧化锌/PVAc复合纤维进行煅烧以去除有机成分并使氧化锌覆盖层结晶，从而得到具有平均晶粒尺寸为23纳米的纳米晶氧化锌壳的空心纤维。空心纤维的内径在100至400纳米之间，其壁厚从上到下从100纳米变化到40纳米。在高温（200至400摄氏度）下暴露于空气中残余浓度（2至10 ppm）的二氧化氮时，使用直流电导率和交流阻抗谱测量来研究电子传输和气体传感特性。空心氧化锌纤维的内表面和外表面区域耗尽了可移动电荷载流子，这可能是由于电子在氧负离子处的局域化，从而限制电流流过其电阻较小的芯部。总阻抗包括界面和体相贡献。暴露于诸如二氧化氮等电负性气体时，这两种贡献都会增加，但体相贡献比界面贡献更敏感。与参考氧化锌薄膜样品相比，空心氧化锌纤维更敏感，其灵敏度增强甚至比其表面积与体积比增加两倍还要大。准对齐纤维比未对齐的纤维更敏感。
