Drastic modification of graphene oxide properties by incorporation of nickel: a simple inorganic chemistry approach

Strong increase in electrical conductivity of graphene oxide (GO) (I ≈ 10⁻⁹ A) is found by addition of Ni nanoparticles (Ni_NPs) preliminarily solved by HCl (Ni_sol) (I ≈ 10⁻⁴ A) or powder (Ni_pow) obtained from this solution (I ≈ 10⁻⁶ A), while simply mixing GO with Ni_NPs an insulator similar to pure GO is obtained. Thus, Ni_sol and Ni_pow can be used to transform GO from insulator to semiconductor. One of the transformation mechanisms is Ni as spillover. At the same time, different kinds of the magnetic response are obtained on GO and reduced GO (rGO) samples with and without Ni. Weak paramagnetic response is detected in pure GO. Stronger paramagnetic behavior is observed for GO and rGO mixed with Ni_sol or Ni_pow. Pure rGO sample shows weak ferromagnetism represented by slim but visible hysteresis with remnant magnetization M _r of 0.05 emu/g. GO with Ni_NPs presents clear hysteresis with M _r of 2.8 emu/g, while sample prepared by addition of Ni_NPs to rGO presents the largest hysteresis with M _r as high as 11.8 emu/g. Thus, the optimal procedure to obtain the magnetic response requested for particular application can be chosen.