Chemistry Division, ‡Technical Physics Division, and §Solid State Physics Division, Bhabha Atomic Research Centre , Mumbai 400085, India.
ACS Appl Mater Interfaces. 2016 Jul 6;8(26):16997-7003. doi: 10.1021/acsami.6b04120. Epub 2016 Jun 24.
Nanoparticulate thin films of PdO were prepared using the Langmuir-Blodgett (LB) technique by thermal decomposition of a multilayer film of octadecylamine (ODA)-chloropalladate complex. The stable complex formation of ODA with chloropalladate ions (present in subphase) at the air-water interface was confirmed by the surface pressure-area isotherm and Brewster angle microscopy. The formation of nanocrystalline PdO thin film after thermal decomposition of as-deposited LB film was confirmed by X-ray diffraction and Raman spectroscopy. Nanocrystalline PdO thin films were further characterized by using UV-vis and X-ray photoelectron spectroscopic (XPS) measurements. The XPS study revealed the presence of prominent Pd(2+) with a small quantity (18%) of reduced PdO (Pd(0)) in nanocrystalline PdO thin film. From the absorption spectroscopic measurement, the band gap energy of PdO was estimated to be 2 eV, which was very close to that obtained from specular reflectance measurements. Surface morphology studies of these films using atomic force microscopy and field-emission scanning electron microscopy indicated formation of nanoparticles of size 20-30 nm. These PdO film when employed as a chemiresistive sensor showed H2 sensitivity in the range of 30-4000 ppm at room temperature. In addition, PdO films showed photosensitivity with increase in current upon shining of visible light.
采用 LB 技术，通过十八胺（ODA）-氯钯酸络合物多层膜的热分解，制备了 PdO 纳米颗粒薄膜。在空气-水界面，ODA 与亚相中的氯钯酸离子（present in subphase）稳定络合，这可以通过表面压-面积等温线和偏光显微镜得到证实。热分解沉积的 LB 膜后形成的纳米晶 PdO 薄膜通过 X 射线衍射和拉曼光谱得到确认。纳米晶 PdO 薄膜进一步通过紫外-可见和 X 射线光电子能谱（XPS）测量进行了表征。XPS 研究表明，纳米晶 PdO 薄膜中存在大量的 Pd(2+)和少量（18%）还原的 PdO（Pd(0)）。从吸收光谱测量可以估算出 PdO 的带隙能约为 2 eV，这非常接近镜面反射测量得到的值。原子力显微镜和场发射扫描电子显微镜的表面形貌研究表明，这些薄膜形成了 20-30nm 大小的纳米颗粒。当这些 PdO 薄膜用作化学电阻式传感器时，在室温下，其对 30-4000ppm 的 H2 具有敏感性。此外，PdO 薄膜在可见光照射时电流增加，表现出光敏性。
