Prospects for graphene-nanoparticle-based hybrid sensors

Nanomaterials for Plant Disease Diagnosis and Treatment: A Review

Currently, the excessive use of pesticides has generated environmental pollution and harmful effects on human health. The controlled release of active ingredients through the use of nanomaterials (NMs) appears to reduce human exposure and ecosystem alteration. Although the use of NMs can offer an alternative to traditional methods of disease diagnosis and control, it is necessary to review the current approach to the application of these NMs. This review describes the most recent and significant advances in using NMs for diagnosing and treating plant diseases (bacteria, phytopathogenic fungi, viruses, and phytopathogenic nematodes) in cultivated plants. Most studies have focused on reducing, delaying, or eliminating bacteria, fungi, viruses, and nematodes in plants. Both metallic (including metal oxides) and organic nanoparticles (NPs) and composites are widely used in diagnosing and controlling plant diseases due to their biocompatibility and ease of synthesis. Few studies have been carried out with regard to carbon-based NPs due to their toxicity, so future studies should address the development of detection tools, ecological and economic impacts, and human health. The synergistic effect of NMs as fertilizers and pesticides opens new areas of knowledge on the mechanisms of action (plant-pathogen-NMs interaction), the interaction of NMs with nutrients, the effects on plant metabolism, and the traceability of NMs to implement sustainable approaches. More studies are needed involving in vivo models under international regulations to ensure their safety. There is still controversy in the release of NMs into the environment because they could threaten the stability and functioning of biological systems, so research in this area needs to be improved.

Graphene-based metal/metal oxide nanocomposites as potential antibacterial agents: a mini-review

Antimicrobial resistance (AMR) is a rising issue worldwide, which is increasing prolonged illness and mortality rates in the population. Similarly, bacteria have generated multidrug resistance (MDR) by developing various mechanisms to cope with existing antibiotics and therefore, there is a need to develop new antibacterial and antimicrobial agents. Biocompatible nanomaterials like graphene and its derivatives, graphene oxide (GO), and reduced graphene oxide (rGO) loaded with metal/metal oxide nanoparticles have been explored as potential antibacterial agents. It is observed that nanocomposites of GO/rGO and metal/metal oxide nanoparticles can result in the synthesis of less toxic, more stable, controlled size, uniformly distributed, and cost-effective nanomaterials compared to pure metal nanoparticles. Antibacterial studies of these nanocomposites show their considerable potential as antibacterial and antimicrobial agents, however, issues like the mechanism of antimicrobial action and their cytotoxicity need to be explored in detail. This review highlights a comparative analysis of graphene-based metal and metal oxide nanoparticles as potential antibacterial agents against AMR and MDR.

Chemiresistive Gas Sensing using Graphene-Metal Oxide Hybrids

Chemiresistive sensing lies in its ability to provide fast, accurate, and reliable detection of various gases in a cost-effective and non-invasive manner. In this context, graphene-functionalized metal oxides play crucial role in hydrogen gas sensing. However, a cost-effective, defect-free, and large production schemes of graphene-based sensors are required for industrial applications. This review focuses on graphene-functionalized metal oxide nanostructures designed for gaseous molecules detection, mainly hydrogen gas sensing applications. For the convenience of the reader and to understand the role of graphene-metal oxide hybrids (GMOH) in gas sensing activities, a brief overview of the properties and synthesis routes of graphene and GMOH have been reported in this paper. Metal oxides play an essential role in the GMOH construct for hydrogen gas sensing. Therefore, various metal oxides-decorated GMOH constructs are detailed in this review as gas sensing platforms, particularly for hydrogen detection. Finally, specific directions for future research works and challenges ahead in designing highly selective and sensitive hydrogen gas sensors have been highlighted. As illustrated in this review, understanding of the metal oxides-decorated GMOH constructs is expected to guide ones in developing emerging hybrid nanomaterials that are suitable for hydrogen gas sensing applications.

High performance Pt-anchored MoS2based chemiresistive ascorbic acid sensor

Ascorbic acid (AA), known as vitamin C, is a vital bioactive compound that plays a crucial role in several metabolic processes, including the synthesis of collagen and neurotransmitters, the removal of harmful free radicals, and the uptake of iron by cells in the human intestines. As a result, there is an absolute need for a highly selective, sensitive, and economically viable sensing platform for AA detection. Herein, we demonstrate a Pt-decorated MoS2for efficient detection of an AA biosensor. MoS2hollow rectangular structures were synthesized using an easy and inexpensive chemical vapor deposition approach to meet the increasing need for a reliable detection platform. The synthesized MoS2hollow rectangular structures are characterized through field effect scanning electron microscopy (FESEM), energy-dispersive spectroscopy elemental mapping, Raman spectroscopy, and x-ray photoelectron spectroscopy. We fabricate a chemiresistive biosensor based on Pt-decorated MoS2that measures AA with great precision and high sensitivity. The experiments were designed to evaluate the response of the Pt-decorated MoS2biosensor in the presence and absence of AA, and selectivity was evaluated for a variety of biomolecules, and it was observed to be very selective towards AA. The Pt-MoS2device had a higher response of 125% against 1 mM concentration of AA biomolecules, when compared to that of all other devices and 2.2 times higher than that of the pristine MoS2device. The outcomes of this study demonstrate the efficacy of Pt-decorated MoS2as a promising material for AA detection. This research contributes to the ongoing efforts to enhance our capabilities in monitoring and detecting AA, fostering advancements in environmental, biomedical, and industrial applications.

Biomedical applications of graphene-based nanomaterials: recent progress, challenges, and prospects in highly sensitive biosensors

Graphene-based nanomaterials (graphene, graphene oxide, reduced graphene oxide, graphene quantum dots, graphene-based nanocomposites, etc.) are emerging as an extremely important class of nanomaterials primarily because of their unique and advantageous physical, chemical, biological, and optoelectronic aspects. These features have resulted in uses across diverse areas of scientific research. Among all other applications, they are found to be particularly useful in designing highly sensitive biosensors. Numerous studies have established their efficacy in sensing pathogens and other biomolecules allowing for the rapid diagnosis of various diseases. Considering the growing importance and popularity of graphene-based materials for biosensing applications, this review aims to provide the readers with a summary of the recent progress in the concerned domain and highlights the challenges associated with the synthesis and application of these multifunctional materials.

Field effect transistor based wearable biosensors for healthcare monitoring

The rapid advancement of wearable biosensors has revolutionized healthcare monitoring by screening in a non-invasive and continuous manner. Among various sensing techniques, field-effect transistor (FET)-based wearable biosensors attract increasing attention due to their advantages such as label-free detection, fast response, easy operation, and capability of integration. This review explores the innovative developments and applications of FET-based wearable biosensors for healthcare monitoring. Beginning with an introduction to the significance of wearable biosensors, the paper gives an overview of structural and operational principles of FETs, providing insights into their diverse classifications. Next, the paper discusses the fabrication methods, semiconductor surface modification techniques and gate surface functionalization strategies. This background lays the foundation for exploring specific FET-based biosensor designs, including enzyme, antibody and nanobody, aptamer, as well as ion-sensitive membrane sensors. Subsequently, the paper investigates the incorporation of FET-based biosensors in monitoring biomarkers present in physiological fluids such as sweat, tears, saliva, and skin interstitial fluid (ISF). Finally, we address challenges, technical issues, and opportunities related to FET-based biosensor applications. This comprehensive review underscores the transformative potential of FET-based wearable biosensors in healthcare monitoring. By offering a multidimensional perspective on device design, fabrication, functionalization and applications, this paper aims to serve as a valuable resource for researchers in the field of biosensing technology and personalized healthcare.

Gold nanoparticles aggregation on graphene using Reactive force field: A molecular dynamic study

We examine the aggregation behavior of AuNPs of different sizes on graphene as function of temperature using molecular dynamic simulations with Reax Force Field. In addition, the consequences of such aggregation on the morphology of AuNPs and the charge transfer behavior of AuNP-Graphene hybrid structure are analyzed. The aggregation of AuNPs on graphene is confirmed from the center of mass distance calculation. The simulation results indicate that the size of AuNPs and temperature significantly affect the aggregation behavior of AuNPs on graphene. The strain calculation showed that shape of AuNPs changes due to the aggregation and the smaller size AuNPs on graphene exhibit more shape changes than larger AuNPs at all the temperatures studies in this work. The charge transfer calculation reveals that, the magnitude of charge transfer is higher for larger AuNPs-graphene composite when compared with smaller AuNPs-graphene composite. The charge transfer trend and the trends seen in the number of Au atoms directly in touch with graphene are identical. Hence, our results conclude that, quantity of Au atoms directly in contact with graphene during aggregation is primarily facilitates charge transfer between AuNPs and graphene. Our results on the size dependent strain and charge transfer characteristics of AuNPs will aid in the development of AuNPs-graphene composites for sensor applications.

Fabrication and Characterization of a Poly(3,4-ethylenedioxythiophene)@Tungsten Trioxide-Graphene Oxide Hybrid Electrode Nanocomposite for Supercapacitor Applications

With the rapid development of nanotechnology, the study of nanocomposites as electrode materials has significantly enhanced the scope of research towards energy storage applications. Exploring electrode materials with superior electrochemical properties is still a challenge for high-performance supercapacitors. In the present research article, we prepared a novel nanocomposite of tungsten trioxide nanoparticles grown over supported graphene oxide sheets and embedded with a poly(3,4-ethylenedioxythiophene) matrix to maximize its electrical double layer capacitance. The extensive characterization shows that the poly(3,4-ethylenedioxythiophene) matrix was homogeneously dispersed throughout the surface of the tungsten trioxide-graphene oxide. The poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide exhibits a higher specific capacitance of 478.3 F·g-1 at 10 mV·s-1 as compared to tungsten trioxide-graphene oxide (345.3 F·g-1). The retention capacity of 92.1% up to 5000 cycles at 0.1 A·g-1 shows that this ternary nanocomposite electrode also exhibits good cycling stability. The poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide energy density and power densities are observed to be 54.2 Wh·kg-1 and 971 W·kg-1. The poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide has been shown to be a superior anode material in supercapacitors because of the synergistic interaction of the poly(3,4-ethylenedioxythiophene) matrix and the tungsten trioxide-graphene oxide surface. These advantages reveal that the poly(3,4-ethylenedioxythiophene)@tungsten trioxide-graphene oxide electrode can be a promising electroactive material for supercapacitor applications.

Innovations in the synthesis of graphene nanostructures for bio and gas sensors

Sensors play a significant role in modern technologies and devices used in industries, hospitals, healthcare, nanotechnology, astronomy, and meteorology. Sensors based upon nanostructured materials have gained special attention due to their high sensitivity, precision accuracy, and feasibility. This review discusses the fabrication of graphene-based biosensors and gas sensors, which have highly efficient performance. Significant developments in the synthesis routes to fabricate graphene-based materials with improved structural and surface properties have boosted their utilization in sensing applications. The higher surface area, better conductivity, tunable structure, and atom-thick morphology of these hybrid materials have made them highly desirable for the fabrication of flexible and stable sensors. Many publications have reported various modification approaches to improve the selectivity of these materials. In the current work, a compact and informative review focusing on the most recent developments in graphene-based biosensors and gas sensors has been designed and delivered. The research community has provided a complete critical analysis of the most robust case studies from the latest fabrication routes to the most complex challenges. Some significant ideas and solutions have been proposed to overcome the limitations regarding the field of biosensors and hazardous gas sensors.

Laser-Induced Graphene Electrodes Modified with a Molecularly Imprinted Polymer for Detection of Tetracycline in Milk and Meat

Tetracycline (TC) is a widely known antibiotic used worldwide to treat animals. Its residues in animal-origin foods cause adverse health effects to consumers. Low-cost and real-time measuring systems of TC in food samples are, therefore, extremely needed. In this work, a three-electrode sensitive and label-free sensor was developed to detect TC residues from milk and meat extract samples, using CO₂ laser-induced graphene (LIG) electrodes modified with gold nanoparticles (AuNPs) and a molecularly imprinted polymer (MIP) used as a synthetic biorecognition element. LIG was patterned on a polyimide (PI) substrate, reaching a minimum sheet resistance (R_sh) of 17.27 ± 1.04 Ω/sq. The o-phenylenediamine (oPD) monomer and TC template were electropolymerized on the surface of the LIG working electrode to form the MIP. Surface morphology and electrochemical techniques were used to characterize the formation of LIG and to confirm each modification step. The sensitivity of the sensor was evaluated by differential pulse voltammetry (DPV), leading to a limit of detection (LOD) of 0.32 nM, 0.85 nM, and 0.80 nM in buffer, milk, and meat extract samples, respectively, with a working range of 5 nM to 500 nM and a linear response range between 10 nM to 300 nM. The sensor showed good LOD (0.32 nM), reproducibility, and stability, and it can be used as an alternative system to detect TC from animal-origin food products.

Fabrication of Cu(II) oxide-hydroxide nanostructures onto graphene paper by laser and thermal processes for sensitive nano-electrochemical sensing of glucose

Glucose electrochemical sensors based on nanostructures of CuO/Cu(OH)₂onto graphene paper were prepared by thermal (solid) and nanosecond pulsed laser (molten phase) dewetting of a CuO layer 6 nm thin deposited by sputtering. Dewetted systems, obtained without the use of any binder, act as array of nanoelectrodes. Solid state and molten phase dewetting produce nanostructures of copper oxide-hydroxide with different average size, shape and surface composition. Molten phase dewetting originates particles with size below 100 nm, while solid state dewetting produces particles with average size of about 200 nm. Moreover, molten phase dewetting produce drop-shaped nanostructures, conversely nanostructures derived from solid state dewetting are multifaceted. X-ray photoelectron spectroscopy (XPS) characterization revealed that the surface of nanostructures is formed by a copper(II) species CuO and Cu(OH)₂. Shape of anodic branch of the cyclic voltammograms of glucose in alkali solution evidenced a convergent diffusion mechanism. Analytical performances in amperometric mode are as good as or better than other sensors based on copper oxide. Amperometric detection of glucose was done at potential as low as 0.4 V versus saturated calomel electrode by both types of electrodes. Linear range from 50μM to 10 mM, sensitivity ranging from 7 to 43μA cm^-2mM^-1and detection limit of 7μM was obtained. Good analytical performances were obtained by laser dewetted electrodes with a low copper content up to 1.2 by atoms percentage of the surface. Analytical performance of the proposed electrodes is compliant for the determination of glucose both in blood serum, saliva or tear.

Ammonia Gas Sensing Characteristic of P3HT-rGO-MWCNT Composite Films

In this work, the P3HT:rGO:MWCNTs (PGC) nanocomposite film applied to the ammonia gas sensor was successfully fabricated by a drop-casting technique. The results demonstrated that the optimum weight ratio of the PGC nanocomposite gas sensor is 20%:60%:20% as the weight ratio of P3HT:rGO:MWCNTs (called PGC-60). This weight ratio leads to the formation of nanostructured composites, causing the efficient adsorption/desorption of ammonia gas in/out of the film surface. The sensor based on PGC-60 possessed a response time of 30 s, sensitivity up to 3.6% at ammonia gas concentration of 10 ppm, and relative sensitivity of 0.031%/ppm. These results could be attributed to excellent electron transportation of rGO, the main adsorption activator to NH3 gas of P3HT, and holes move from P3HT to the cathodes, which works as charge “nano-bridges” carriers of Multi-Walled Carbon Nanotubes (MWCNTs). In general, these three components of PGC sensors have significantly contributed to the improvement of both the sensitivity and response time in the NH3 gas sensor.

Gr/3D-ZnO Nanocomposites as Humidity Sensors with Enhanced Sensing Response

This work introduces a novel humidity sensor based on a nanocomposite material comprising graphene decorated with three-dimensional flower-like structures of zinc oxide (Gr/3D–ZnO) fabricated via a hydrothermal method with various weight percentages of graphene. The surface structure and morphology of the Gr/3D–ZnO nanocomposite were analyzed using XRD, EDS, SEM, TEM, and Raman spectroscopy. The influence of humidity on the electrical properties of the nanocomposite was also investigated. Experiment results revealed that the nanocomposite with 70 wt% of graphene provided high sensitivity (S = 446) with rapid response times (120 s) and recovery times (160 s). These results demonstrate the excellent potential of the proposed Gr/3D–ZnO nanocomposite in monitoring atmospheric humidity. A discussion on the mechanism underlying the effects of humidity on the Gr/3D–ZnO nanocomposite is also provided.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

Raman and Fluorescence Enhancement Approaches in Graphene-Based Platforms for Optical Sensing and Imaging

The search for novel platforms and metamaterials for the enhancement of optical and particularly Raman signals is still an objective since optical techniques offer affordable, noninvasive methods with high spatial resolution and penetration depth adequate to detect and image a large variety of systems, from 2D materials to molecules in complex media and tissues. Definitely, plasmonic materials produce the most efficient enhancement through the surface-enhanced Raman scattering (SERS) process, allowing single-molecule detection, and are the most studied ones. Here we focus on less explored aspects of SERS such as the role of the inter-nanoparticle (NP) distance and the ultra-small NP size limit (down to a few nm) and on novel approaches involving graphene and graphene-related materials. The issues on reproducibility and homogeneity for the quantification of the probe molecules will also be discussed. Other light enhancement mechanisms, in particular resonant and interference Raman scatterings, as well as the platforms that allow combining several of them, are presented in this review with a special focus on the possibilities that graphene offers for the design and fabrication of novel architectures. Recent fluorescence enhancement platforms and strategies, so important for bio-detection and imaging, are reviewed as well as the relevance of graphene oxide and graphene/carbon nanodots in the field.

An overview of surface-enhanced Raman scattering substrates by pulsed laser deposition technique: fundamentals and applications

Metallic nanoparticles (NPs), as an efficient substrate for surface-enhanced Raman scattering (SERS), attract much interests because of their various shapes and sizes. The appropriate size and morphology of metallic NPs are critical to serve as the substrate for achieving an efficient SERS. Pulsed laser deposition (PLD) is one of the feasible physical methods employed to synthesize metallic NPs with controllable sizes and surface characteristics. It has been recognized to be a successful tool for the deposition of SERS substrates due to its good controllability and high reproducibility in the manufacture of metallic NPs. This review provides an overview about the recent advances for the preparation of SERS substrates by PLD technique. The influences of parameters on the sizes and morphologies of metallic NPs during the deposition processes in PLD technique including laser output parameters, gas medium, liquid medium, substrate temperature, and properties of 3D substrate are presented. The applications of SERS substrates produced by PLD in the environmental monitoring and biomedical analysis are summarized. This knowledge could serve as a guideline for the researchers in exploring further applications of PLD technique in the production of SERS substrate.

Detection of food spoilage and adulteration by novel nanomaterial-based sensors

Food industry is always looking for more innovative and accurate ways to monitor the food safety and quality control of final products. Current detection techniques of analytes are costly and time-consuming, and occasionally require professional experts and specialized tools. The usage of nanomaterials in sensory systems has eliminated not only these drawbacks but also has advantages such as higher sensitivity and selectivity. This article first presents a general overview of the current studies conducted on the detection of spoilage and adulteration in foods from 2015 to 2020. Then, the sensory properties of nanomaterials including metal and magnetic nanoparticles, carbon nanostructures (nanotubes, graphene and its derivatives, and nanofibers), nanowires, and electrospun nanofibers are presented. The latest investigations and advancements in the application of nanomaterial-based sensors in detecting spoilage (food spoilage pathogens, toxins, pH changes, and gases) and adulterants (food additives, glucose, melamine, and urea) have also been discussed in the following sections. To conclude, these sensors can be applied in the smart packaging of food products to meet the demand of consumers in the new era.

Graphene-Wrapped Copper Nanoparticles: An Antimicrobial and Biocompatible Nanomaterial with Valuable Properties for Medical Uses

The great demand for antibacterial, biocompatible, and easily manufactured nanostructures has led to the design and development of graphene-wrapped copper nanoparticles (CuNPs) supported on Si wafers. In this study, we investigated the antibacterial properties of graphene/CuNPs nanostructures against Gram-positive and Gram-negative bacteria. Additional experiments regarding graphene/CuNPs nanostructures behavior against mouse fibroblast cell line L929 indicated their biocompatibility and consequently render them as model biomaterials for medical uses. Biofunctionalization of graphene/CuNPs nanostructures with a high-molecular-weight protein (green fluorescent protein), which retains its functionality after a "tight binding" on the nanostructure's surface, opens the way for attaching and other proteins, or biomolecules of great biological interest, to prepare novel biomaterials.

Surface-Directed Disparity in Self-Assembled Structures of Small-Peptide l-Glutathione on Gold and Silver Nanoparticles

Despite the key roles of l-glutathiones (GSHs) inbiology and nano-biotechnology, understanding their labile structures and hydrogen bond interactions with nanoparticles has posed a critical challenge to the scientific community. The structural conformation of GSH as a capping layer on gold nanoparticle (AuNP) and silver nanoparticle (AgNP) surfaces is investigated. In this report, we attempt to explore the material-dependent interaction of GSH with different spherical nanoparticle surfaces by employing Fourier transform infrared (FTIR) spectroscopy. The infrared signal of amide I of GSH is studied as a function of different materials' spherical nanoparticles with comparable size. We revealed the β-sheet secondary structure of GSH on AgNPs and the random structure on AuNPs even though both the nanoparticles have comparable shapes and sizes and belong to the same group of the periodic table. The GSH is firmly anchored on the gold and silver surface via the thiol of the cys part. However, our experimental data designate a further interaction with the AgNP surface via the carboxylic acid group of the gly- and glu- end of the molecule. It is observed that enhancement of IR absorption of amide I of GSH is pronounced by a factor of 10 on AuNP but, in contrast, on the same-sized AgNP, the suppression is perceived by a factor of 2, even though both are plasmonic materials with respect to free GSH. This study can be used as a point of reference for understanding the structural conformation of the capping layer on nanoparticle surfaces as well as surface enhancement of the IR absorption of amide I. We would like to emphasize that molecular self-assembly on the nanoparticle surfaces is definitely of very broad interest for chemists working in nearly any subdiscipline, spanning from the nanoparticle-based medicine to surface-enhanced spectroscopy to heterogeneous catalysis, etc.

2D materials in electrochemical sensors for in vitro or in vivo use

Individual cells and cell populations are at the present time investigated with a myriad of analytical tools. While most of them are commercially available, some of these analytical tools are just emerging from research laboratories and are in the developmental phase. Electrochemical sensors which allow the monitoring of low molecular weight compounds released (and / or uptaken) by cells are among these emerging tools. Such sensors are increasingly built using 2D materials (e.g. graphene-based materials, transition metal dichalcogenides, etc.) with the aim of conferring better analytical performances to these devices. The present work critically reviews studies published during the last 10 years describing electrochemical sensors made with 2D materials and exploited to monitor small compounds (e.g. H₂O₂, ·NO, glucose, etc.) in living biological systems. It also discusses the very few 2D material-based electrochemical sensors which are wearable or usable in vivo. Finally, the present work includes a specific section about 2D material biocompatibility, a fundamental requirement for 2D material-based sensor applications in vitro and in vivo. As such, the review provides a critical view on the state of the art of electrochemical sensors made with 2D materials and used at cellular level and it evaluates the possibility that such sensors will be used on / in the human body on a wider scale.

Two dimensional carbon based nanocomposites as multimodal therapeutic and diagnostic platform: A biomedical and toxicological perspective

Graphene based nanocomposites have revolutionized cancer treatment, diagnosis and imaging owing to its good compatibility, elegant flexibility, high surface area, low mass density along with excellent combined additive effect of graphene with other nanomaterials. This review inculcates the type of graphene based nanocomposites and their fabrication techniques to improve its properties as photothermal and theranostic platform. With decades' efforts, many significant breakthroughs in the method of synthesis and characterization in addition to various functionalization options of graphene based nanocomposite have paved a solid foundation for their potential applications in the cancer therapy. This work intends to provide a thorough, up-to-date holistic discussion on correlation of breakthroughs with their biomedical applications and illustrate how to utilize these breakthroughs to address long-standing challenges in the clinical translation of nanomedicines. This review also emphasizes on graphene based nanocomposites based toxicity concerns pertaining to delivery platforms.

Vapour sensing properties of graphene-covered gold nanoparticles

We investigated the vapour sensing properties of different graphene-gold hybrid nanostructures. We observed the shifts in the optical spectra near the local surface plasmon resonance of the gold nanoparticles by changing the concentration and nature of the analytes (ethanol, 2-propanol, and toluene). The smaller, dome-like gold nanoparticles proved to be more sensitive to these vapours compared to slightly larger, flat nanoparticles. We investigated how the optical response of the gold nanoparticles can be tuned with a corrugated graphene overlayer. We showed that the presence of graphene increased the sensitivity to ethanol and 2-propanol, while it decreased it towards toluene exposure (at concentrations ≥ 30%). The slope changes observed on the optical response curves were discussed in the framework of capillary condensation. These results can have potential impact on the development of new sensors based on graphene-gold hybrids.

Is small smarter? Nanomaterial-based detection and elimination of circulating tumor cells: current knowledge and perspectives

Circulating tumor cells (CTCs) are disseminated cancer cells. The occurrence and circulation of CTCs seem key for metastasis, still the major cause of cancer-associated deaths. As such, CTCs are investigated as predictive biomarkers. However, due to their rarity and heterogeneous biology, CTCs’ practical use has not made it into the clinical routine. Clearly, methods for the effective isolation and reliable detection of CTCs are urgently needed. With the development of nanotechnology, various nanosystems for CTC isolation and enrichment and CTC-targeted cancer therapy have been designed. Here, we summarize the relationship between CTCs and tumor metastasis, and describe CTCs’ unique properties hampering their effective enrichment. We comment on nanotechnology-based systems for CTC isolation and recent achievements in microfluidics and lab-on-a-chip technologies. We discuss recent advances in CTC-targeted cancer therapy exploiting the unique properties of nanomaterials. We conclude by introducing developments in CTC-directed nanosystems and other advanced technologies currently in (pre)clinical research.

Morphological transformation of gold nanoparticles on graphene oxide: effects of capping ligands and surface interactions

This article presents the influence of capping ligand and surface interaction types on the coarsening or reshaping behavior of surface-immobilized gold nanoparticles with different core size and shape. The morphological transformation of gold nanoparticles and nanorods on graphene oxide upon heating at temperatures ranging from 50 to 200 °C was investigated. The aggregation and coarsening behaviors of spherical nanoparticles on graphene oxide were slightly affected by the core size of nanoparticles (~ 1, 3, and 10 nm). The comparison of two different surface ligands revealed that glutathione ligands provide much better protection than cetyltrimethylammonium bromide ligands against the morphological transformation of nanoparticles. In addition, the evaluation of surface binding interactions indicated that the attachment of nanoparticles and nanorods onto graphene oxide with additional thiol functional groups could improve the immobilization of particles and therefore decelerate coarsening and reshaping of nanoparticle and nanorods.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

The correlation between electrical conductivity and second-order Raman modes of laser-reduced graphene oxide

Second-order Raman modes correlate with the electrical properties of reduced graphene oxide measured at the nanoscale by atomic force microscopy.

Graphene and Graphene-Based Nanomaterials for DNA Detection: A Review

DNA detection with high sensitivity and specificity has tremendous potential as molecular diagnostic agents. Graphene and graphene-based nanomaterials, such as graphene nanopore, graphene nanoribbon, graphene oxide, and reduced graphene oxide, graphene-nanoparticle composites, were demonstrated to have unique properties, which have attracted increasing interest towards the application of DNA detection with improved performance. This article comprehensively reviews the most recent trends in DNA detection based on graphene and graphene-related nanomaterials. Based on the current understanding, this review attempts to identify the future directions in which the field is likely to thrive, and stimulate more significant research in this subject.

Advancement of Ag-Graphene Based Nanocomposites: An Overview of Synthesis and Its Applications

Graphene has been employed as an excellent support for metal nanomaterials because of its unique structural and physicochemical properties. Silver nanoparticles (AgNPs) with exceptional properties have received considerable attention in various fields; however, particle aggregation limits its application. Therefore, the combination of AgNPs and graphene based nanocomposites (Ag-graphene based nanocomposites) has been widely explored to improve their properties and applications. Excitingly, enhanced antimicrobial, catalytic, and surface enhanced Raman scattering properties are obtained after their combination. In order to have a comprehensive knowledge of these nanocomposites, this Review highlights the chemical and biological synthesis of Ag-graphene nanocomposites. In particular, their applications as antimicrobial agents, catalysts, and sensors in biomedicine, agricultural protection, and environmental remediation and detection are covered. Meanwhile, the factors that influence the synthesis and applications are also briefly discussed. Furthermore, several important issues on the challenges and new directions are also provided for further development of these nanocomposites.

Simulation Studies on the Interaction of Graphene and Gold Nanoparticle

In this computational study, the interaction between a single layer graphene sheet and a gold nanoparticle is investigated employing molecular dynamics (MD) simulation at room temperature. The interactions between the graphene and gold nanoparticle were explored for three different types of gold nanoparticle, namely, bare gold nanoparticle, methyl terminated alkane thiol-coated gold nanoparticle and hydroxy terminated alkane thiol-coated gold nanoparticle. The interactions between the graphene and gold nanoparticle have resulted in the adsorption of gold nanoparticle on the surface of graphene. The structural properties of the graphene–gold hybrid nanostructures were found to be influenced by the capping layer of the gold nanoparticle.

Nanostructured Electrochemical Biosensors for Label-Free Detection of Water- and Food-Borne Pathogens

The emergence of nanostructured materials has opened new horizons in the development of next generation biosensors. Being able to control the design of the electrode interface at the nanoscale combined with the intrinsic characteristics of the nanomaterials engenders novel biosensing platforms with improved capabilities. The purpose of this review is to provide a comprehensive and critical overview of the latest trends in emerging nanostructured electrochemical biosensors. A detailed description and discussion of recent approaches to construct label-free electrochemical nanostructured electrodes is given with special focus on pathogen detection for environmental monitoring and food safety. This includes the use of nanoscale materials such as nanotubes, nanowires, nanoparticles, and nanosheets as well as porous nanostructured materials including nanoporous anodic alumina, mesoporous silica, porous silicon, and polystyrene nanochannels. These platforms may pave the way toward the development of point-of-care portable electronic devices for applications ranging from environmental analysis to biomedical diagnostics.

Graphene- gold based nanocomposites applications in cancer diseases; Efficient detection and therapeutic tools

Early detection and efficient treatment of cancer disease remains a drastic challenge in 21st century. Throughout the bulk of funds, studies, and current therapeutics, cancer seems to aggressively advance with drug resistance strains and recurrence rates. Nevertheless, nanotechnologies have indeed given hope to be the next generation for oncology applications. According to US National cancer institute, it is anticipated to revolutionize the perspectives of cancer diagnosis and therapy. With such success, nano-hybrid strategy creates a marvelous preference. Herein, graphene-gold based composites are being increasingly studied in the field of oncology, for their outstanding performance as robust vehicle of therapeutic agents, built-in optical diagnostic features, and functionality as theranostic system. Additional modes of treatments are also applicable including photothermal, photodynamic, as well as combined therapy. This review aims to demonstrate the various cancer-related applications of graphene-gold based hybrids in terms of detection and therapy, highlighting the major attributes that led to designate such system as a promising ally in the war against cancer.

Synthesis of graphene-transition metal oxide hybrid nanoparticles and their application in various fields

Single layer graphite, known as graphene, is an important material because of its unique two-dimensional structure, high conductivity, excellent electron mobility and high surface area. To explore the more prospective properties of graphene, graphene hybrids have been synthesised, where graphene has been integrated with other important nanoparticles (NPs). These graphene-NP hybrid structures are particularly interesting because after hybridisation they not only display the individual properties of graphene and the NPs, but also they exhibit further synergistic properties. Reduced graphene oxide (rGO), a graphene-like material, can be easily prepared by reduction of graphene oxide (GO) and therefore offers the possibility to fabricate a large variety of graphene-transition metal oxide (TMO) NP hybrids. These hybrid materials are promising alternatives to reduce the drawbacks of using only TMO NPs in various applications, such as anode materials in lithium ion batteries (LIBs), sensors, photocatalysts, removal of organic pollutants, etc. Recent studies have shown that a single graphene sheet (GS) has extraordinary electronic transport properties. One possible route to connecting those properties for application in electronics would be to prepare graphene-wrapped TMO NPs. In this critical review, we discuss the development of graphene-TMO hybrids with the detailed account of their synthesis. In addition, attention is given to the wide range of applications. This review covers the details of graphene-TMO hybrid materials and ends with a summary where an outlook on future perspectives to improve the properties of the hybrid materials in view of applications are outlined.

Fabrication of Graphene Aerogels with Heavily Loaded Metallic Nanoparticles

Natural biomaterials with hierarchical structures that enable extraordinary capability of detecting chemicals have inspired the interest in producing materials that can mimic these natural structures. This study reports the fabrication of hierarchically-structured, reduced graphene oxide (rGO) aerogels with heavily loaded palladium (Pd), platinum (Pt), nickel (Ni), and tin (Sn) metallic nanoparticles. Metal salts chelated with ethylenediaminetetraacetic acid (EDTA) were mixed with graphene oxide (GO) and then freeze-dried. The subsequent reduction produces rGO/metal nanoparticle aerogels. SEM and EDS results indicated that a loading of 59, 67, 39, and 46 wt % of Pd, Pt, Ni, and Sn nanoparticles was achieved. Pd/rGO aerogels of different Pd nanoparticle concentrations were exposed to H₂ gas to monitor the resistance change of the composites. The results suggest that rGO aerogels can achieve a higher nanoparticle loading by using chelation to minimize electrostatic interactions between metal ions and GO. Higher loading of Pd nanoparticles in graphene aerogels lead to improved hydrogen gas sensing performance.

Novel π-conjugated iron oxide/reduced graphene oxide nanocomposites for high performance electrochemical supercapacitors

Nanocomposite of π-conjugated 2-aminoterephthalic acid (ATA) coated iron oxide (Fe₃O₄) nanoparticles and reduced graphene oxide (RGO) provides an enhanced capacitive performance with higher specific capacitance and long term cyclic stability.