Two-dimensional metal oxide nanoflower-like architectures: a general growth method and their applications in energy storage and as model materials for nanofabrication

Nanoflower-like architectures represent a unique type of nanomaterials in which thin 2D nanosheets are self-organised into interconnected structures. Lack of restacking between nanosheets and significant internal porosity are the particular advantages of such nanoscale architectures. A general method for the preparation of nanoflowers of a range of oxides (e.g., FeTiO 3 , TiO 2 , Mn 2 O 3 ) through a two-step procedure of ball milling and subsequent hydrothermal treatment is outlined. Importantly, the synthetic method is valid not only for a single oxide, but is extendable to a family of oxide materials. It is established that the formation of the nanoflowers from ball-milled powders follows a dissolution–precipitation mechanism; this is confirmed by inductively coupled plasma time of flight mass spectrometry measurements. Additional information on the X-ray photoelectron spectroscopy characterisation and intermediate stage of growth of the nanostructures is included. Furthermore, two applications of Mn 2 O 3 nanostructures are briefly investigated. Firstly, their properties for energy storage in the electrodes of electrochemical supercapacitors are presented. A capacitive response in the potential window of −0.1–0.9 V versus an Ag/AgCl reference electrode is observed, with an associated increase of the capacitance values over cycling. Secondly, the use of Mn 2 O 3 nanoflowers as model systems for the development of novel nanofabrication techniques (such as nanopatterning with a He + beam) is investigated.