CuO/WO3 Hybrid Nanocubes for High‐Responsivity and Fast‐Recovery H2S Sensors Operated at Low Temperature
CuO/WO3 Hybrid Nanocubes for High‐Responsivity and Fast‐Recovery H2S Sensors Operated at Low Temperature
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DOI：
10.1002/ppsc.201500178
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发表时间：
2016-01
影响因子：
2.7
通讯作者：
Weiwei Yu;Yan Sun;Yan Sun;Tianning Zhang;Kenan Zhang;Shuxia Wang;Xin Chen;N. Dai;N. Dai
中科院分区：
文献类型：
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作者：
Weiwei Yu;Yan Sun;Yan Sun;Tianning Zhang;Kenan Zhang;Shuxia Wang;Xin Chen;N. Dai;N. Dai
纯WO 3 颗粒，其形状为立方体或准立方体，表面平坦光滑，尺寸范围为80-150 nm。图1b、c中的HR-TEM图像表明纯WO 3 纳米粒子是高度结晶的；晶格条纹0.365 nm的间距对应于单斜WO 3 (200)面的d间距。从 SEM 和 TEM 图像中可以看出，当掺入 CuO 后，表面变得粗糙且不规则（图 1 d-f 和图 S1，支持信息）。当通过添加更多的 CuO 前驱体来增加 Cu:W 的摩尔比时，不规则形态变得更加明显。 CuO纳米粒子在WO 3 立方体的表面形成粗糙层。 CuO纳米颗粒壳为气体分子吸附提供了更多的缺陷和化学活性位点。提出(CH 3 COO) 2 Cu前驱体物理吸附在WO 3 纳米立方体的表面，然后在水热过程中醇解成Cu(OH) 2 ，最终在500℃退火过程中分解成CuO。 O、W 和 Cu 分布的元素图（图 1 g-i）证实了 WO 3 纳米立方体表面 CuO 纳米团簇的改性。使用 X 射线衍射 (XRD) 和 X 射线光电子能谱 (XPS) 进一步表征物相和组成。图S2（支持信息）中纯WO 3 纳米立方体的XRD 图案可以索引到单斜晶WO 3 （JCPDS 卡编号43-1035），与TEM 结果一致。随着Cu:W的摩尔比增加到1:5，出现了与CuO对应的XRD峰（用绿色方块标记，JCPDS卡编号48-1548）。然而，当 Cu:W 摩尔比低于 1:20 时，在 XRD 曲线中几乎看不到 CuO 的存在。因此，XPS 被进一步用于检查 Cu:W = 1:20 样品的表面化学成分（见图 2；和图 S3，支持信息）。 933.8 eV 和 953.5 eV 的结合能分别归因于 Cu 2p 3/2 和 Cu 2p 1/2 。 963.4 和 942.5 eV 处的两个卫星峰可能与 Cu 2+ 的存在有关。 [24-26] 在图2b中观察到W 4f 的结合能为37.8 eV (W 4f 5/2 )和35.7 eV (W 4f 7/2 )，证实了WO 3 中W离子(W 6+ )的状态。所有结果都证明了 O、W 和 Cu 元素的存在。我们使用生长的CuO/WO 3 混合纳米粒子来制造用于检测H 2 S的气体传感器。我们首先通过比较一系列样品来确定最佳成分。图 3a 显示了由不同 Cu/W 摩尔比制成的器件对 4 ppm H 2 S 的温度依赖性响应。摩尔比为 1:20 的传感器在 55 °C 时的响应约为 270 000，远远高于其他 Cu/W 比的传感器。工作温度时 W. Yu、Y. Sun、T. Zhang、K. Zhang、Prof. S. Wang、Prof. X. Chen、Prof. N. Dai 红外物理国家实验室 中国科学院上海技术物理研究所 上海 200083 E-mail: sunny@mail.sitp.ac.cn； xinchen@mail.sitp.ac.cn 孙宇教授、戴宁教授 中国科学技术大学量子信息与量子物理协同创新中心 安徽 合肥 230026 E-mail: ndai@mail.sitp.ac.cn
pure WO 3 particles, which have a cubic or quasi-cubic shape with fl at and smooth surfaces and size range of 80–150 nm. The HR-TEM images in Figure 1 b,c suggest that the pure WO 3 nanoparticles are highly crystalline; the space of lattice fringe 0.365 nm corresponds to the d -spacing of monoclinic WO 3 (200) planes. When the CuO was incorporated, it is found that the faces become rough and irregular, as seen from the SEM and TEM images (Figure 1 d–f and Figure S1, Supporting Information). The irregular morphology becomes more apparent when the molar ratio of Cu:W was increased by adding more CuO precursor. The CuO nanoparticles form a coarse layer on the surface of WO 3 cubes. The CuO nanoparticle shell provides more defects and chemical active sites for the gas molecule adsorption. It is proposed that the (CH 3 COO) 2 Cu precursor is physically adsorbed on the surfaces of WO 3 nanocubes and then alcoholysis into Cu(OH) 2 during the hydrothermal process, which fi nally decomposes into CuO during annealing at 500 °C. The elemental mapping of O, W, and Cu distributions (Figure 1 g–i) confi rmed the modifi cation of CuO nanoclusters on the surface of WO 3 nanocubes. Further characterization of the phase and composition was conducted using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD patterns of the pure WO 3 nanocubes in Figure S2 (Supporting Information) can be indexed to the monoclinic WO 3 (JCPDS card no.43-1035), in agreement with the TEM result. With the molar ratio of Cu:W increasing to 1:5, the XRD peaks corresponding to CuO appeared (marked with a green square, JCPDS card no.48-1548). However, the presence of CuO was barely visible in the XRD curve when the molar ratio of Cu:W was below 1:20. Thus, XPS was further exploited to examine the surface chemical composition of the Cu:W = 1:20 sample (see Figure 2 ; and Figure S3, Supporting Information). The binding energies at 933.8 and 953.5 eV are attributed to Cu 2p 3/2 and Cu 2p 1/2 , respectively. Two satellite peaks at 963.4 and 942.5 eV might be related to the presence of Cu 2+ . [ 24–26 ] The binding energy of W 4f is observed at 37.8 eV (W 4f 5/2 ) and 35.7 eV (W 4f 7/2 ) in Figure 2 b, confi rming the state of W ion (W 6+ ) in WO 3 . All the results evidence the presence of O, W, and Cu elements. We employed the as-grown CuO/WO 3 hybrid nanoparticles to fabricate gas sensors for detecting H 2 S. We fi rst identifi ed the optimum composition by comparing a series of samples. Figure 3 a exhibits the temperature-dependent response on 4 ppm H 2 S of the devices made from different Cu/W molar ratios. The response of the sensor with 1:20 molar ratio is ≈270 000 at 55 °C, which is drastically higher than the devices with other Cu/W ratios. When the operating temperature W. Yu, Y. Sun, T. Zhang, K. Zhang, Prof. S. Wang, Prof. X. Chen, Prof. N. Dai National Laboratory for Infrared Physics Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai 200083 , China E-mail: sunny@mail.sitp.ac.cn; xinchen@mail.sitp.ac.cn Prof. Y. Sun, Prof. N. Dai Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei , Anhui 230026 , China E-mail: ndai@mail.sitp.ac.cn