Design and synthesis of high performance multifunctional ultrathin hematite nanoribbons

1D porous ultrathin nanoribbons of hematite (α-Fe2O3) were prepared by controlled annealing of different oxides and hydroxides of iron obtained from a solvothermal synthesis method. It is found that calcination at a temperature of 500 °C for 150 min decomposes these iron hydroxides into their most stable oxide form, i.e., α-Fe2O3. Driven by different attractive forces, these porous α-Fe2O3 nanoparticles get aggregated in an ordered fashion to form an ultrathin 1D nanoribbon structure, as observed by detailed time dependent TEM and HRTEM analysis. It has been found that the high aspect ratio and porous surface morphology of these nanoribbons have significantly improved their electronic and spintronic properties as manifested by their photocatalysis, gas sensing, electrochemical, and magnetic behaviors. These hematite nanoribbons exhibit a weak ferromagnetic behavior due to surface spin disorder and shape anisotropy. Lateral confinement of electrons increases the band gap of the nanoribbons, as evident from the UV absorption analysis, which in turn improves their photocatalytic degradation efficiency (rate constant ∼0.95 h(-1)) by delaying the electron-hole recombination process. However, their liquid petroleum gas sensing properties have been found to be mainly governed by the improved (porous) surface of the hematite nanoribbons that provides huge interaction sites for the analyte gas. Most of all, these hematite nanoribbons show a significantly enhanced pseudocapacitive performance exhibited by their high specific capacitance of about 145 F g(-1) at a current density of 1 A g(-1), high rate capability, and also long cycle stability (nearly 96% of capacity retention after 1600 charging/discharging cycles).