This work investigates the long-term stability\ud of suspensions of surfactant-free gold nanostars\ud with mean diameter of 78 ± 13 nm (measured from\ud tip to tip across the nanostar).We monitored the optical\ud and morphological properties of the nanostars over the\ud course of several days after synthesis by observing the\ud changes in the UV–visible absorption spectra and\ud mean radius of curvature of the nanostar tips. An aging\ud process can be observed, evident in the blunting of the\ud nanostar tips, leading to a blue shift in the absorption\ud maximum. Stability is greatly improved by depositing\ud on the nanostars a monolayer of mercaptopropionic\ud acid (MPA), possibly because of the formation of the\ud gold–sulfur (Au–S) bond that limits the mobility of the\ud Au atoms. Capping the nanostars with MPA is an easy\ud additional step for extending the stability of the\ud nanostars in suspension without significan

Very low levels of monoclinic content in zirconia have been determined coupling Raman spectroscopy and principal component analysis.The method can be useful for the characterization of biomaterials based on zirconia

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