Treated samples without any purification where subjected PXRD. Structural changes of the Cu 3-x P nanocrystals following the redox reactions were monitored using powder x-ray diffraction (PXRD). In comparison to the pristine samples, these oxidised and reduced samples had weak signals in XRD. Further, many of the expected peaks corresponding to the products following these treatment where either at similar position as those of Cu 3-x P or very weak intensity. The latter could be due to the fact that only surface atoms were undergoing these reactions. Oxidation of Cu 3-x P following the treatment of cerium oxidant showed sign of copper(II) oxide (CuO) (Figure ) and copper(I) oxide (Cu 2 O) (Figure ). The XRD had peaks at 35 ). This confirms that apart from the Cu(II) to Cu (I) conversion, there is also further reduction. Such reductions are feasible in the presence of a strong reducing agent such as LTBH. Apart from Cu, there could be also redox process happening on the surface P atoms. It is well known that the metal phosphide nanocrystals have oxidised phosphate species on their surface. Infact, the surface of nanocrystals under present study also has oxide layer on its surface as reported by shavel et al. However, the effect of redox process on surface phosphorus atom and subsequent influence on the plasmons requires a dedicated study of it own and is not the focus of present manuscript.