Department of Energy and Material Sciences, Faculty of Engineering Sciences, and ‡Department of Molecular and Material Sciences, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University , Kasuga, Fukuoka 816-8580, Japan.
Langmuir. 2014 Mar 11;30(9):2571-9. doi: 10.1021/la4049105. Epub 2014 Feb 26.
Tungsten trioxide (WO3) is one of the important multifunctional materials used for photocatalytic, photoelectrochemical, battery, and gas sensor applications. Nanostructured WO3 holds great potential for enhancing the performance of these applications. Here, we report highly sensitive NO2 sensors using WO3 nanolamellae and their sensitivity improvement by morphology control using SnO2 nanoparticles. WO3 nanolamellae were synthesized by an acidification method starting from Na2WO4 and H2SO4 and subsequent calcination at 300 °C. The lamellae were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), which clearly showed the formation of single-crystalline nanolamellae with a c-axis orientation. The stacking of each nanolamella to form larger lamellae that were 50-250 nm in lateral size and 15-25 nm in thickness was also revealed. From pore size distribution measurements, we found that introducing monodisperse SnO2 nanoparticles (ca. 4 nm) into WO3 lamella-based films improved their porosity, most likely because of effective insertion of nanoparticles into lamella stacks or in between assemblies of lamella stacks. In contrast, the crystallite size was not significantly changed, even by introducing SnO2. Because of the improvement in porosity, the composites of WO3 nanolamellae and SnO2 nanoparticles displayed enhanced sensitivity (sensor response) to NO2 at dilute concentrations of 20-1000 ppb in air, demonstrating the effectiveness of microstructure control of WO3 lamella-based films for highly sensitive NO2 detection. Electrical sensitization by SnO2 nanoparticles was also considered.
三氧化钨 (WO3) 是一种重要的多功能材料，可用于光催化、光电化学、电池和气体传感器应用。纳米结构的 WO3 在提高这些应用的性能方面具有巨大的潜力。在这里，我们报告了使用 WO3 纳米薄片的高灵敏度 NO2 传感器及其通过使用 SnO2 纳米粒子控制形态来提高灵敏度。WO3 纳米薄片是通过从 Na2WO4 和 H2SO4 开始的酸化方法合成的，随后在 300°C 下煅烧。X 射线衍射 (XRD)、扫描电子显微镜 (SEM) 和透射电子显微镜 (TEM) 对薄片进行了表征，清楚地显示了具有 c 轴取向的单晶纳米薄片的形成。还揭示了每个纳米薄片的堆叠，以形成更大的薄片，其横向尺寸为 50-250nm，厚度为 15-25nm。从孔径分布测量中，我们发现将单分散 SnO2 纳米粒子（约 4nm）引入 WO3 薄片基膜中提高了其孔隙率，这很可能是因为纳米粒子有效地插入了薄片堆叠中或在薄片堆叠的组装之间。相比之下，即使引入 SnO2，结晶度尺寸也没有明显变化。由于孔隙率的提高，WO3 纳米薄片和 SnO2 纳米粒子的复合材料在空气中对 20-1000ppb 的稀浓度 NO2 表现出增强的灵敏度（传感器响应），证明了 WO3 基于薄片的薄膜的微观结构控制对高灵敏度 NO2 检测的有效性。SnO2 纳米粒子的电敏化也被认为是有效的。
