Platinum metal shadowing

Carbon replicas [427] are formed by the evaporation of a thin layer of carbon in a vacuum evaporator. Metal shadowing, at an angle of 20 to 45° to the specimen surface is performed while the specimen is in the evaporator. The highest resolution direct replica material is carbon/platinum (C/Pt). After evap-... 

Ghadially EN, Lock CJL, Lalonde JMA, Ghadially R. Platinosomes produced in synovial membrane by platinum coordination complexes. Virchows Arch., B, Cell Pathol. 1981 35 123-131. Beretta GL, Righetti SC, Lombardi L, Zunino F, Perego P. Electron microscopy analysis of early localization of cisplatin in ovarian carcinoma cells. Ultrastruct. Pathol. 2002 26 331-334. Ruben GC. Ultrathin (Inm) vertically shadowed platinum-carbon replicas for imaging individual molecules in freeze-etched biological DNA and material science metal and plastic specimens. J. Electron. Microsc. Tech. 1989 13 335-354. 

A more reliable and rapid technique for evaporating both shadowing metals and carbon is via electron beam bombardment. This method makes use of a focused flux of high-energy electrons to provide the necessary power for the evaporation of a small metal or carbon source. Generally, this is used to form thin films of Pt/C, W/Ta, and pure C. The platinum films contain some carbon (usually <596) due to the presence of the carbon support rod. The electron beam gun evaporation approach greatly improves throughput and consistency compared to the other approaches. 

An alternative method for the visualization of small structures is shadowing with heavy metals (platinum, tungsten, etc.). Rotary shadowing in combination with the surface spreading technique of Kleinsmidt [7] appeared to be very powerful. In this method macromolecules are decorated with platinum grains of about 40 A which indirectly visualize the shape of these molecules. Double-stranded and even single-... 

C-Pt. Platinum is the most difficult metal to evaporate, but it provides the finest grained shadow. Chromium is quite coarse and useful for very low magnification studies. Aluminium is used for optical microscopy. 

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