We report the observations of electronic properties of graphene oxide and reduced graphene oxide, performed with electron paramagnetic resonance technique in a broad temperature range. Both materials were examined in pure form and saturated with air, helium, and heavy water molecules. We show that spin localization strongly depends on the type and amount of molecules adsorbed at the graphene layer edges (and possible in-plane defects). Physical and chemical states of edges play crucial role in electrical transport within graphene-based materials, with hopping as the leading mechanism of charge carrier transport. Presented results are a good basis to understand the electronic properties of other carbon structures made of graphene-like building blocks. Most active carbons show some degree of functionalization and are known of having good adsorptive properties; thus, controlling both phenomena is important for many applications. Sample treatment with temperature, vacuum, and various adsorbents allowed for the observation of a possible metal-insulator transition and sorption pumping effects. The influence of adsorption on the localization phenomena in graphene would be very important if to consider the graphene-based material as possible candidates for the future spintronics that works in ambient conditions.

Analysis of the EPR results for graphite and fullerenes has led to the development of a model for the g-factor in follerene based on the analogy between graphite and fullerene. Pressure dependence of g-factor in C₆₀ powder confirms the validity of this model. ¹³C hyperfine splitting of_a0.36 mT in pristine fullerene is also reported. The g-factors of C₆₀ ⁻¹ and C₆₀ ⁻³ in a solution and in a different K°C₆₀ fullerides are presented. C₆₀ ⁺ⁿ states should be described by the spectroscopic splitting factor larger than that of a free spin.

Mechanisms of spin localization in graphitic nanoparticles of activated carbon fibers (ACFs) are discussed. Electronic properties of ACFs are described by the model which is the fusion of two approaches: Langevin paramagnetism represented by Curie law in electron paramagnetic resonance measurements and granular metal model used to describe conducting properties of separated fibers according to metal-insulator transition. This approach shows the possibility of changing the electronic properties of ACFs by temperature or adsorbed molecules as a main factors.