K is an application-specific coefficient and w the full width at half maximum of the scattering peak. We used 𝐾 = 0.91 for Lc from the (002) peak and 𝐾 = 1.84 for La from the (10) peak as defined by Warren . The Scherrer equation has been shown to be valid for graphitic materials with crystallite sizes above 2 nm . The interlayer spacing was computed from the (002) peak position using Bragg's law in the reciprocal space, i.e. 𝑑 002 = 2𝜋 𝑞 ⁄ .