A blueprint for the synthesis and characterization of thiolated graphene

Graphene derivatization to either engineer its physical and chemical properties or overcome the problem of the facile synthesis of nanographenes is a subject of significant attention in the nanomaterials research community. In this paper, we propose a facile and scalable method for the synthesis of thiolated graphene via a two step liquid phase treatment of graphene oxide GO . Employing the core level methods, the introduction of up to 5.1 at. of thiols is indicated with the simultaneous rise of the C O ratio to 16.8. The crumpling of the graphene layer upon thiolation without its perforation is pointed out by microscopic and Raman studies. The conductance of thiolated graphene is revealed to be driven by the Mott hopping mechanism with the sheet resistance values of 2.15 k amp; 937; sq and dependable on the environment. The preliminary results on the chemiresistive effect of these films upon exposure to ethanol vapors in the mix with dry and humid air are shown. Finally, the work function value and valence band structure of thiolated graphene are analyzed. Taken together, the developed method and findings of the morphology and physics of the thiolated graphene guide the further application of this derivative in energy storage, sensing devices, and smart material

From graphene oxide towards aminated graphene facile synthesis, its structure and electronic properties

In this paper we present a facile method for the synthesis of aminated graphene derivative through simultaneous reduction and amination of graphene oxide via two-step liquid phase treatment with hydrobromic acid and ammonia solution in mild conditions. The amination degree of the obtained aminated reduced graphene oxide is of about 4 at.%, whereas C/O ratio is up to 8.8 as determined by means of X-ray photoelectron spectroscopy. The chemical reactivity of the introduced amine groups is further verified by successful test covalent bonding of the obtained aminated graphene with 3-Chlorobenzoyl chloride. The morphological features and electronic properties, namely conductivity, valence band structure and work function are studied as well, illustrating the influence of amine groups on graphene structure and physical properties. Particularly, the increase of the electrical conductivity, reduction of the work function value and tendency to form wrinkled and corrugated graphene layers are observed in the aminated graphene derivative compared to the pristine reduced graphene oxide. As obtained aminated graphene could be used for photovoltaic, biosensing and catalysis application as well as a starting material for further chemical modifications

Manifesting Epoxide and Hydroxyl Groups in XPS Spectra and Valence Band of Graphene Derivatives

The derivatization of graphene to engineer its band structure is a subject of significant attention nowadays, extending the frames of graphene material applications in the fields of catalysis, sensing, and energy harvesting. Yet, the accurate identification of a certain group and its effect on graphene s electronic structure is an intricate question. Herein, we propose the advanced fingerprinting of the epoxide and hydroxyl groups on the graphene layers via core level methods and reveal the modification of their valence band VB upon the introduction of these oxygen functionalities. The distinctive contribution of epoxide and hydroxyl groups to the C 1s X ray photoelectron spectra was indicated experimentally, allowing the quantitative characterization of each group, not just their sum. The appearance of a set of localized states in graphene s VB related to the molecular orbitals of the introduced functionalities was signified both experimentally and theoretically. Applying the density functional theory calculations, the impact of the localized states corresponding to the molecular orbitals of the hydroxyl and epoxide groups was decomposed. Altogether, these findings unveiled the particular contribution of the epoxide and hydroxyl groups to the core level spectra and band structure of graphene derivatives, advancing graphene functionalization as a tool to engineer its physical propertie

Valence Band Structure Engineering in Graphene Derivatives

Engineering of the 2D materials electronic structure is at the forefront of nanomaterials research nowadays, giving an advance in the development of next generation photonic devices, e sensing technologies, and smart materials. Herein, employing core level spectroscopy methods combined with density functional theory DFT modeling, the modification of the graphenes valence band VB upon its derivatization by carboxyls and ketones is revealed. The appearance of a set of localized states in the VB of graphene related to molecular orbitals of the introduced functionalities is signified both experimentally and theoretically. Applying the DFT calculations of the density of states projected on the functional groups, their contributions to the VB structure are decomposed. An empirical approach, allowing one to analyze and predict the impact of a certain functional group on the graphenes electronic structure in terms of examination of the model molecules, mimicking the introduced functionality, is proposed and validated. The interpretation of the arising states origin is made and their designation, pointing out their symmetry type, is proposed. Taken together, these results guide the band structure engineering of graphene derivatives and give a hint on the mechanisms underlying the alteration of the VB structure of 2D materials upon their derivatizatio

Guiding Graphene Derivatization for the On Chip Multisensor Arrays From the Synthesis to the Theoretical Background

Engineering the physics and chemistry of 2D materials is a key to unlock the potential of the advanced e nose technologies limited by the current semiconductor technologies. Herein, the adjustment of the graphene s morphology, physics, and gas sensing properties upon its carboxylation via the developed photochemical method is demonstrated. Formation of matrices of nanoscale holes yet with the retention of the lamellar structure of the graphene layer is signified upon the introduction of up to 9.5 at of carboxyl groups. The impact of the applied carboxylation on the conduction mechanism and electronic structure is demonstrated. The appearance of a set of the localized states in the valence band is revealed, originating from the molecular orbitals of carboxyls as is signified by the proposed approach for the identification of electronic states in graphene chemical derivatives. Given holey structure, predominance of highly affine carboxyls, and lateral inhomogeneity, the enhanced detection and discrimination of various alcohols, acetone, and ammonia vapors at room temperature is demonstrated. The opposite chemiresistive response toward ammonia in the humid air is also experimentally revealed and justified by the performed density functional theory modeling on the effect of ammonia, water, and their mix on electronic structure, and resistivity of the carboxylated graphen