Palladium films, ultra-thin

Xu, T., Zach, M.P., Xiao, Z.L., Rosenmann, D., Welp, U., Kwok, W.K. and Crabtree, G.W., Self-assembled monolayer-enhanced hydrogen sensing with ultra thin palladium films, Applied Physics Letters, 86, 203104, 2005. 

Fig. 13.10a. An MNF was coated with an ultra thin palladium film. The operational principle of this sensor was based on the fact that a thin palladium film has the ability to selectively absorb hydrogen. If a palladium film is exposed to hydrogen, its refractive index, and, in particular, absorbance, changes. The change in refractive index causes a change in transmission power of an MNF. The MNF fabricated in Ref. 15 had a palladium film of 4 nm in thickness and 2 mm in length. In Fig. 13.10b, the transmission power of the MNF is shown as a function of time when the sensor was exposed successively to a 3.9% concentration of hydrogen. The response time calculated from the plot was 10 s. This response time is 3 5 times faster than that of other optical hydrogen sensors and about 15 times faster than that of some electrical nano hydrogen sensors. The fast response of the sensor is, presumably, due to the ultra small thickness of the palladium film that is rapidly filled with hydrogen. Figure 13.10c shows the transmission of this sensor as a function of time for...

In comparison to most other methods in surface science, STM offers two important advantages (1) it provides local information on the atomic scale and (2) it does so in situ [50]. As STM operates best on flat surfaces, applications of the technique in catalysis relate to models for catalysts, with the emphasis on metal single crystals. Several reviews have provided excellent overviews of the possibilities [51-54], and many studies of particles on model supports have been reported, such as graphite-supported Pt [55] and Pd [56] model catalysts. In the latter case, Humbert et al. [56] were able to recognize surface facets with (111) structure on palladium particles of 1.5 nm diameter, on an STM image taken in air. The use of ultra-thin oxide films, such as AI2O3 on a NiAl alloy, has enabled STM studies of oxide-supported metal particles to be performed, as reviewed by Freund [57]. 

Some efforts involve supporting ultra-thin (<1 gm) palladium films on various types of engineered porous supports. Perforated supports within modules have been fabricated and coated with thin layers of palladium alloys through micromachining and manufacturing techniques borrowed from the integrated circuit... 

PANI composites with oxides of rhodium, palladium, osmium, iridium, and platinum were rarely investigated, especially in the recent period. Fabrication of methane gas sensor by layer-by-layer self-assembly of PANI/ PdO ultra thin films consisting of a dense network of NFs (Figure 2.23 left) on quartz crystal microbalance was successfully performed by Xie et al. [240] (Figure 2.23 right). 

Kirchner, A., Brown, I.W.M., Bowden, M.E., Kemmitt, T. (2007b). Hydrogen Purification using Ultra-thin Palladium Films supported on Porous Anodic Alumina Membranes, in Functional Nanoscale Ceramics for Energy Systems, ed. E. Ivers-Tiffee and S. Barnett (Mater. Res. Soc. Symp. Proc. 1023E, Warrendale, PA, 2007), Paper 1023-JJ09-02. 

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