pH dependent microstructural changes of α-Ni(OH) 2 hollow-sphere nanostructure thin films

In this work, we report the microstructural changes and variation in the properties of α-Ni(OH) 2 nanostructure thin films synthesized via dip coating. The cleaned glass substrate was immersed alternatively in the aqueous solution of nickel nitrate hexahydrate (Ni(NO 3 ) 2 ·6H 2 O) and sodium hydroxide (NaOH). The molarity of the precursor NaOH was varied. The no. of dip and molarity of Ni(NO 3 ) 2 ·6H 2 O were kept constant at 20 and 0.2 M, respectively. The synthesized nanostructured thin films were characterized by using FESEM, XRD, FTIR and UV–Vis spectroscopy techniques. From FESEM images, interestingly the microstructure was changed from hollow-sphere nanostructure to small nanoparticles with increase in NaOH molarity. The change in NaOH molarity produced a pH change in the reactant solution. Accordingly, with increase in pH the crystallite size of synthesized Ni(OH) 2 decreased and the bandgap of nanostructure thin films was increased. The change and detailed analysis of formation of nanostructure of thin film was explained in respect of nucleation and growth of the nanocrystallites that was affected by the degree of supersaturation of the reactant solution on the glass substrate. Lastly, the importance of these results in terms of bandgap engineering of microstructurally tuned NHTFs development for prospective futuristic industrial application in energy storage and energy harvesting devices are highlighted.