2D Materials: Chemistry and Applications (Part 1)

Material science has gone through several evolutionary stages; especially the discovery of graphene has added one of the most defining chapters in this journey. Owing to the enormous potential of this material in various applications, a tremendous pace can be seen in the development of graphene-derived materials and technologies. The 2D revolution in material science can be marked by the shift from the bulk form of materials to their intelligent and efficient two-dimensional (2D) analogs and their use in developing innovative contrivances. Various forms of 2D graphene have recently evolved, including mainly monolayer graphene, bilayer graphene, graphene oxide, graphene nanoribbons, and graphene quantum dots. These materials have shown great potential to revolutionize various aspects of human life, from electronics and actuation to healthcare and energy.

Its exceptional properties make it an ideal candidate for various applications. Continuing explorations and epistemological pieces of evidence will likely reveal even more prospective applications. The book chapter deals with a concise overview of the structural aspects of graphene, the presence of defects, methods of synthesis, and functionalization. The chapter will help develop an essential understanding of the critical aspects of science and recent developments around it. This chapter aims to provide a quick and easily understandable summary of various complex aspects of it by reducing irrelevant or extraneous information. 

Recently, nanoparticle-functionalized graphene materials have been in the spotlight due to their exceptional properties. A pristine graphene sheet is an attractive candidate for the dispersion of nanoparticles due to its large active surface area compared to other carbon allotropes. Moreover, pristine graphene possesses electrical and mechanical strength, which gives it a unique architecture. The chemical functionalization of graphene intends to revamp its properties and elevate its use in multiple applications by incorporating different functional groups. There are two main approaches to the functionalization process, either based on covalent or noncovalent. This chapter elaborates on the major strategies employed for the nanoparticles functionalized graphene. The precursors of nanoparticles are metal salts which are reduced in the solvent of the desired substrate. The strategies above involve the deposition of metal nanoparticles, metal oxide nanoparticles, and quantum dots on graphene substrate. The functionalization of graphene improves its dispersion capacity and sets forth new properties, which broadens its scope of applications. Furthermore, we aim to focus on the potential of materials derived from nanoparticle functionalization in various applications such as wastewater management, biomedical devices, photocatalysis, food additives detection, supercapacitors, electrochemical gas sensors, and energy storage, flexible electronics, photonics, photovoltaic systems, and catalysts. We aspire that the readers will learn the synthetic strategies for the functionalization of graphene along with guidance and inspiration on the emerging trends towards applications of interest. This chapter surveys various properties and applications of nanoparticle-functionalized graphene.

Due to the distinctive 2D lattice structure, graphene, and its derivatives have received much interest in recent years to advance technology into the era of stretchable, bendable, and flexible technology. Graphene has advantageous features that create diversely effective devices when combined with other materials to create composites. Compared to graphene, its composites exhibit improved features such as excellent mechanical strength, tunable electrical and thermal conductivity, and optical properties. Graphene composites utilize graphene fillers, films, or nanosheets with several other organic and inorganic groups, such as polymers, metal oxides, metal nanowires and nanoparticles, quantum dots, ceramics, and cement through covalent or noncovalent interactions. Numerous factors help tune the characteristics of the composites, such as graphene concentration, filler dispersion, chemical bonding, and others. The chapter discusses various methods for synthesizing graphene-based composites, including melt intercalation, in-situ polymerization, solution processing, etc. It also discusses factors that affect the composite's mechanical, electrical, thermal, photonic, and photocatalytic properties and its wide range of uses in electronics, sensors, transistors, energy storage, and environmental remediation. In addition, the problems and obstacles encountered in the manufacture of composites have been highlighted.

Recent progress in the nanotechnology sector has abetted to mitigate the drawbacks associated with conventional therapies' limited effectiveness and medication efficacy after the in vivo drug delivery. In this regard, graphene; a 2D nanomaterial; has emerged as one of the wonder materials in medication delivery systems. Since the discovery of its capabilities in a biological system in 2008, numerous improvements and developments have been made till now in the therapeutic application of graphenebased materials. Additionally, it has been imparted with specific biological activities by both covalent and non-covalent surface revamping which further improves their biocompatibility and colloidal stability. Due to their hexagonal lattice and high surface area, they possess the astounding ability to provide high drug loading capacity via simple preparation methods, which makes them a more fecund material in comparison with other drug delivery systems. The present chapter outlines the exclusive drug and gene delivery applications of graphene-based materials and discusses their up-to-date advances. The chapter also discusses in detail how the integration of graphene and polymers makes them ideal as a delivery system in tissue engineering and nanomedicine for therapeutic approaches. The outlook presented here may help invoke deep insights into the nanotechnology-based drug delivery system for future research.

Graphene-based materials (GMs) are the most promising materials in this era of antimicrobial and antiviral materials. Their excellent physicochemical properties and biocompatibility have opened new doors in this field. Graphene has good mechanical properties, a large surface area, high barrier mobility, excellent electronic transport performance, and resistance to degradation. Antimicrobial and antiviral materials have been used in the health sector for many years to fight off pathogens. Antibiotics, metal ions, and quaternary ammonium hydroxide are used for bacteria, while metals and organic materials are effective against viruses. Although metals are effective against viruses, their toxicity, high cost, and unintended leaching restrict their use as antivirals. Viral strains are progressively mutating, emerging as new threats to our species' survival. Bacterial resistance has developed as a result of the excessive use of antibiotics. The antimicrobial materials used so far have a high cost, cause environmental pollution, and are complex to process. To overcome these challenges, graphene-based materials have been in the limelight for antiviral and antibacterial abilities against pathogens. The combined properties of graphene alongside metals, polymers, metal oxides, and many other materials enable the perfect tool to protect human health. Their efficacy and broad-spectrum activities against gram-positive and gram-negative bacteria can potentially improve the quality of life. This chapter examines the detailed application of graphene-based materials towards wound healing, antibacterial coatings, biosensors, bioimaging, antibacterial sutures, anti-bio films, photocatalytic degradation of bacteria, and antibacterial packaging. 

 Graphene possesses exceptional structural, mechanical, electrical, optical, and thermal properties. These properties have provided researchers worldwide with a vast horizon for their application in diverse fields including electronics, energy, sensing, drug/gene delivery, photothermal therapy, and the biomedical field. Moreover, in recent years, we have come across enormous research on graphene and its functional analogs, especially in the biomedical imaging field. Therefore, the present chapter provides impetus on bio-imaging modalities including optical imaging, magnetic resonance imaging, positron emission tomography/single-photon emission computed tomography, Raman imaging, and multimodal imaging. This chapter will provide its readers with deep insights into the advances in bio-imaging using graphene-based materials such as graphene, graphene oxide, and reduced graphene oxide. Finally, a brief discussion on the challenges and prospects of using graphene materials in bioimaging is provided.

The surge in morbidity and death rates among patients suffering from cancer call for innovation towards efficient therapeutic strategies. Conventional therapy fails to treat cancer or to provide prolonged survival rate due to its toxic side effects on normal cells and lack of target specificity. In recent years, 2D materials (graphene and graphene analogues) have gained remarkable attention owing to their intriguing potential for therapeutic and targeted delivery in cancer theranostics. Due to their tunable physicochemical properties, π-π conjugated structure, optical characteristics, modifiable active moieties, strong photothermal effect, high compatibility, and ease of fabrication, graphene-based materials are highly suited for cancer treatment. This book chapter meticulously discusses the synthesis, modifications, and biomedical applications of graphene-based materials, explicitly focusing on graphene oxide (GO) and reduced graphene oxide (rGO). The authors detail the various methods for synthesizing GO and rGO, their physicochemical properties, and how these properties can be tailored for specific applications in drug delivery systems for cancer therapy. Notably, this work highlights the versatility of GO and rGO in enhancing the solubility and efficacy of chemotherapeutic agents, supported by examples such as the improved solubility of doxorubicin and the use of graphene for targeted drug delivery, which leverages the nano-scale properties of graphene for effective cancer treatment. By compiling and synthesizing recent research findings, the chapter is a valuable resource for nanotechnology and biomedical sciences researchers, providing a solid foundation for future studies and technological advancements in using graphene-based materials for cancer therapy. This work underscores the critical advancements in graphene technology and its promising future in medical applications, especially in enhancing the effectiveness and safety of cancer treatments.

 In recent years, there has been a surge in research studies exploring the potential of graphene-based materials for scaffold fabrication, with a particular emphasis on harnessing their exceptional properties such as high mechanical strength and high surface area. Significant advancements in tissue engineering have led to the development of innovative tools for creating artificial biotherapeutics. Among these, graphene-based composites have emerged as a thriving area of research in tissue engineering and regenerative medicine. The exceptional mechanical and cell-oriented properties of graphene have positioned it at the forefront of tissue engineering applications, encompassing various body systems such as nerve connections, the cardiovascular system, the skeletal system, cartilage, skin, and more. This chapter aims to succinctly explore the applications of graphene and its derivatives in tissue engineering, considering tissue engineering as a pinnacle of human-made biotherapeutics with immense therapeutic potential. Additionally, the prospects associated with the utilization of graphene-based composite scaffold materials have been reviewed in depth, providing valuable insights and a broad perspective on their application in tissue engineering.

The extensive range of applications associated with graphene and its derivatives has captivated the attention of nano biotechnologists due to their remarkable versatility. The 2D clan of graphene possesses exceptional physical, chemical, and mechanical characteristics, rendering it an extraordinary material with unparalleled properties. It is an allotrope of carbon which has a 2-dimensional hexagonal lattice structure. It has broad applicability in material science, physics, chemistry, biology, etc. Graphene is advantageous over other materials because (a) it is the finest and toughest material known to date; (b) It has a monolayer of carbon atoms that are transparent and also possess flexibility; (c) it acts as an excellent electrical and thermal conductor. Besides its natural availability, its demand has led to its synthesis using hierarchical and self-assembly methods. Modification of graphene according to various biological systems increases its solubility, selectivity, and compatibility. Graphene is used as a substrate interfacing with different biomolecules and cells as tissue scaffolds and to generate stem cells for regenerative medicines. Graphene and its derivatives are applied in drug delivery, gene delivery, biomolecule recognition, molecular medicine, bioassays, antibacterial compositions, biosensing, energy storage, and catalysis. Graphene derivatives have been recently used as theranostics in cancer because of their intrinsic photoluminescent properties and treatment of several microbial infections. Though graphene has been explored tremendously, studying the toxicity issues and its interaction with the environment and ecosystem is imperative. This chapter will uncover the different forms of graphene and its derivatives; its synthesis approaches, and various applications in biomedicine.