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Although attempts to form gold nitrides have been recorded for the past 20 years, for example, such a compound was recently observed, when low energy nitrogen ions were implanted into a single crystal Au (110) gold surface. Gold nitride can also be made as a thin film by a plasma etching method [1].
In this work atomic force microscopy images of gold nitride surface produced by the plasma method unexpectedly show a striking similarity to the metastable ionized states predicted in theoretical models for the colloidal behaviour in confined systems. The type of nanoclusters observed, which have never been detected in gold films, can be described as a cluster comprising a spheroidal nanoparticle, with a size of the order of 100 nm, surrounded by a group of smaller particles (2 to 6 times smaller in diameter) that aggregate on the large particle surface. This type of cluster could be explained by the attraction between two like-charged colloidal spheres (‘macroions’), a concept known in colloidal science [2]. To the best of our knowledge this is the first such observation in a solid phase.
A Surface Enhanced Raman Spectroscopy (SERS) signal from 0.5 m mol of L- Alanine and Si nanocrystals deposited on plasma treated gold nitride surface has been investigated as a function of the state of aggregation and has been compared with a signal obtained from a commercial available substrate, showing similar levels of signal to noise ratio. The production of gold nitride samples for commercial use is much cheaper since there is no need for the use of e-beam lithography.
1. L. Šiller, N. Peltekis, S. Krishnamurthy, Y. Chao, S. J. Bull and M. R.C. Hunt, Appl. Phys. Lett. 86, 221912 (2005).
2. R. Messina, C. Holm, & K. Kremer, Phys. Rev. Lett. 85, 872-875 (2000).
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