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

Graphene Amination towards Its Grafting by Antibodies for Biosensing Applications

The facile synthesis of biografted 2D derivatives complemented by a nuanced understanding of their properties are keystones for advancements in biosensing technologies. Herein, we thoroughly examine the feasibility of aminated graphene as a platform for the covalent conjugation of monoclonal antibodies towards human IgG immunoglobulins. Applying core level spectroscopy methods, namely X ray photoelectron and absorption spectroscopies, we delve into the chemistry and its effect on the electronic structure of the aminated graphene prior to and after the immobilization of monoclonal antibodies. Furthermore, the alterations in the morphology of the graphene layers upon the applied derivatization protocols are assessed by electron microscopy techniques. Chemiresistive biosensors composed of the aerosol deposited layers of the aminated graphene with the conjugated antibodies are fabricated and tested, demonstrating a selective response towards IgM immunoglobulins with a limit of detection as low as 10 pg mL. Taken together, these findings advance and outline graphene derivatives application in biosensing as well as hint at the features of the alterations of graphene morphology and physics upon its functionalization and further covalent grafting by biomolecule

Toward On Chip Multisensor Arrays for Selective Methanol and Ethanol Detection at Room Temperature Capitalizing the Graphene Carbonylation

The artificial olfaction units or e noses capable of room temperature operation are highly demanded to meet the requests of society in numerous vital applications and developing Internet of Things. Derivatized 2D crystals are considered as sensing elements of choice in this regard, unlocking the potential of the advanced e nose technologies limited by the current semiconductor technologies. Herein, we consider fabrication and gas sensing properties of On chip multisensor arrays based on a hole matrixed carbonylated C ny graphene film with a gradually changed thickness and concentration of ketone groups of up to 12.5 at. . The enhanced chemiresistive response of C ny graphene toward methanol and ethanol, of hundred ppm concentration when mixing with air to match permissible exposure OSHA limits, at room temperature operation is signified. Following thorough characterization via core level techniques and density functional theory, the predominant role of the C ny graphene perforated structure and abundance of ketone groups in advancing the chemiresistive effect is established. Advancing practice applications, selective discrimination of the studied alcohols is approached by linear discriminant analysis employing a multisensor array s vector signal, and the fabricated chip s long term performance is show

Guiding graphene derivatization for covalent immobilization of aptamers

Derivatization of 2D materials for bioapplications is at the forefront of nanomaterials research nowadays. Facile synthesis of the biografted 2D derivatives and insight into the conformation of the conjugated biomolecules are two pillars, promoting advances in the field of biosensing, drug delivery and regeneration techniques. This work is devoted to the synthesis and conjugation of carboxylated reduced graphene oxide C xyrGO by aptamers followed by theoretical analysis of their conformation in the immobilized state. Employing the developed method, the hole matrixed graphene with up to 11.1 at. reactive carboxyl groups was synthesized and thoroughly examined via core level spectroscopy. The mechanism of the performed carboxylation with conversion of graphene oxide into carboxylated graphene is proposed, unveiling commonly disregarded impact of ether like components to the fingerprints of the carboxyl groups. We show successful covalent immobilization of the AO 01 aptamer against Hepatitis B protein on the synthesized C xyrGO and for the first time reveal its conformation both in free and immobilized forms via a combination of density functional tight binding DFTB calculations and molecular dynamic MD modeling. Taken together, these results advance the application of graphene derivatives grafted with the biomolecules in the field of biosensin