Morphology controlled uranium oxide hydroxide hydrate for catalysis, luminescence and SERS studies

Abstract

Here we report a modified hydrothermal (MHT) reaction to substantiate the nucleation, growth and reversible dehydration of a well defined uranium oxide hydroxide hydrate (UOHH) species, (UO₂)₈O₂(OH)₁₂(H₂O)₁₂ to fabricate a morphologically different array of well defined nanoplates. The reaction between uranyl acetate (UA) and triethylamine (TEA) from an aqueous phase has revealed a new role of TEA for alternation of shapes, aspect ratio and columnar stacking of the nanoplates. Interesting morphology alternation of (UO₂)₈O₂(OH)₁₂(H₂O)₁₂ nanoplates and furthermore, their secondary growth have been highlighted by manipulating the ratio of UA to TEA and reaction time. Then we found citrate as a capping agent for selective planes of the nanoplates as a result of which nanoplates assembled to the flowery structures or columnar stacking, depending on the citrate concentration. The structure and morphology of all the products have been characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). It has also been reported that upon calcination at ∼700 °C the nanoplates are converted to U₃O₈ but with the retaintion of their morphology. Furthermore, in situsilver nanoparticles loading in the UOHH nanoplates has been described for the first time using photochemical technique to make the nanoplates SERS active. Fluorescence property (λ_em = 520 nm) and finally very high catalytic activity of the UOHH nanoplates over U₃O₈ towards benzyl alcohol oxidation has been discussed.