Utilizing nanotechnology to boost the reliability and determine the vertical load capacity of pile assemblies

Because of their high electrocatalytic activity, sensitivity, selectivity, and long-term stability in electrochemical sensors and biosensors, numerous nanomaterials are being used as suitable electrode materials thanks to developments in nanotechnology. Electrochemical sensors and biosensors are two areas where two-dimensional layered materials (2DLMs) are finding increasing utility due to their unusual structure and physicochemical features. Nanosensors, by their unprecedented sensitivity and minute scale, can probe deeper into the structural integrity of piles, capturing intricacies that traditional tools overlook. These advanced devices detect anomalies, voids, and minute defects in the pile structure with unparalleled granularity. Their effectiveness lies in detection and their capacity to provide real-time feedback on pile health, heralding a shift from reactive to proactive maintenance methodologies. Harvesting data from these nanosensors, data was incorporated into a probabilistic model, executing the reliability index calculations through Monte Carlo simulations. Preliminary outcomes show a commendable enhancement in the predictability of vertical bearing capacity, with the coefficient of variation dwindling by up to 12%. The introduction of nanosensors facilitates instantaneous monitoring and fortifies the long-term stability of pile foundations. This study accentuates the transformative potential of nanosensors in geotechnical engineering.

Memory effect and coexistence of negative and positive photoconductivity in black phosphorus field effect transistor for neuromorphic vision sensors

Black phosphorus (BP) field-effect transistors with ultrathin channels exhibit unipolar p-type electrical conduction over a wide range of temperatures and pressures. Herein, we study a device that exhibits mobility up to 100 cm2 V-1 s-1 and a memory window up to 1.3 μA. Exposure to a supercontinuum white light source reveals that negative photoconductivity (NPC) and positive photoconductivity (PPC) coexist in the same device. Such behavior is attributed to the chemisorbed O2 molecules, with a minor role of physisorbed H2O molecules. The coexistence of NPC and PPC can be exploited in neuromorphic vision sensors, requiring the human eye retina to process the optical signals through alerting and protection (NPC), adaptation (PPC), followed by imaging and processing. Our results open new avenues for the use of BP and other two-dimentional (2D) semiconducting materials in transistors, memories, and neuromorphic vision sensors for advanced applications in robotics, self-driving cars, etc.

Molecular dynamics simulation-based study to analyse the properties of entrapped water between gold and graphene 2D interfaces

Heterostructures based on graphene and other 2D materials have received significant attention in recent years. However, it is challenging to fabricate them with an ultra-clean interface due to unwanted foreign molecules, which usually get introduced during their transfer to a desired substrate. Clean nanofabrication is critical for the utilization of these materials in 2D nanoelectronics devices and circuits, and therefore, it is important to understand the influence of the "non-ideal" interface. Inspired by the wet-transfer process of the CVD-grown graphene, herein, we present an atomistic simulation of the graphene-Au interface, where water molecules often get trapped during the transfer process. By using molecular dynamics (MD) simulations, we investigated the structural variations of the trapped water and the traction-separation curve derived from the graphene-Au interface at 300 K. We observed the formation of an ice-like structure with square-ice patterns when the thickness of the water film was <5 Å. This could cause undesirable strain in the graphene layer and hence affect the performance of devices developed from it. We also observed that at higher thicknesses the water film is predominantly present in the liquid state. The traction separation curve showed that the adhesion of graphene is better in the presence of an ice-like structure. This study explains the behaviour of water confined at the nanoscale region and advances our understanding of the graphene-Au interface in 2D nanoelectronics devices and circuits.

Electrochemical and Electrical Biosensors for Wearable and Implantable Electronics Based on Conducting Polymers and Carbon-Based Materials

Bioelectronic devices are designed to translate biological information into electrical signals and vice versa, thereby bridging the gap between the living biological world and electronic systems. Among different types of bioelectronics devices, wearable and implantable biosensors are particularly important as they offer access to the physiological and biochemical activities of tissues and organs, which is significant in diagnosing and researching various medical conditions. Organic conducting and semiconducting materials, including conducting polymers (CPs) and graphene and carbon nanotubes (CNTs), are some of the most promising candidates for wearable and implantable biosensors. Their unique electrical, electrochemical, and mechanical properties bring new possibilities to bioelectronics that could not be realized by utilizing metals- or silicon-based analogues. The use of organic- and carbon-based conductors in the development of wearable and implantable biosensors has emerged as a rapidly growing research field, with remarkable progress being made in recent years. The use of such materials addresses the issue of mismatched properties between biological tissues and electronic devices, as well as the improvement in the accuracy and fidelity of the transferred information. In this review, we highlight the most recent advances in this field and provide insights into organic and carbon-based (semi)conducting materials' properties and relate these to their applications in wearable/implantable biosensors. We also provide a perspective on the promising potential and exciting future developments of wearable/implantable biosensors.

Unveiling the contemporary progress of graphene-based nanomaterials with a particular focus on the removal of contaminants from water: a comprehensive review

Water scarcity and pollution pose significant challenges to global environmental sustainability and public health. As these concerns intensify, the quest for innovative and efficient water treatment technologies becomes paramount. In recent years, graphene-based nanomaterials have emerged as frontrunners in this pursuit, showcasing exceptional properties that hold immense promise for addressing water contamination issues. Graphene, a single layer of carbon atoms arranged in a hexagonal lattice, exhibits extraordinary mechanical, electrical, and chemical properties. These inherent characteristics have led to a surge of interest in leveraging graphene derivatives, such as graphene oxide (GO), reduced graphene oxide and functionalized graphene, for water treatment applications. The ability of graphene-based nanomaterials to adsorb, catalyze, and photocatalyze contaminants makes them highly versatile in addressing diverse pollutants present in water sources. This review will delve into the synthesis methods employed for graphene-based nanomaterials and explore the structural modifications and functionalization strategies implemented to increase their pollutant removal performance in water treatment. By offering a critical analysis of existing literature and highlighting recent innovations, it will guide future research toward the rational design and optimization of graphene-based nanomaterials for water decontamination. The exploration of interdisciplinary approaches and cutting-edge technologies underscores the evolving landscape of graphene-based water treatment, fostering a path toward sustainable and scalable solutions. Overall, the authors believe that this review will serve as a valuable resource for researchers, engineers, and policymakers working toward sustainable and effective solutions for water purification.

Utility of structural engineering on the monitoring of acrolein by aluminum nitride nano tube

CONTEXT

The study delves into the adsorption process of acrolein (AC) onto both an untainted and a titanium-doped aluminum nitride nanotube (AlNNT) using computations based on density functional theory. As AC approaches the pure AlNNT, it exhibits a calculated adsorption energy (Ead) of -5.3 kcal/mol, underscoring the feeble nature of the adsorption. Furthermore, there has been very little change to the AlNNT's natural electrical characteristics. On the contrary, the introduction of titanium (Ti) enhances the performance of AlNNT, rendering it more susceptible and reactive to AC signals. Analyzing the conventional Gibbs free energy of formation computationally, we ascertain that replacing a nitrogen (N) atom with a titanium (Ti) atom within the aluminum nitride nanotube (AlNNT) structure presents a more advantageous prospect. Notably, there is a substantial alteration in the energy of adsorption (Ead) for AC as a Ti atom is incorporated onto the AlNNT surface, resulting in a shift from -5.3 to -24.6 kcal/mol.

METHODS

Energy calculations and geometric optimizations were conducted utilizing the dispersion-augmented B3LYP method, known as B3LYP-D. In this approach, Grimme's dispersion term, referred to as the "D" term, was employed to account for dispersion forces. The basis set adopted was 6-31 +  + G** (d), and all computational procedures were executed using the GAMESS software program. Following the incorporation of titanium (Ti), this adjustment leads to a substantial enhancement in sensing capability, reaching a value of 93.7. This indicates an improved electrical conductivity of the aluminum nitride nanotube (AlNNT). Remarkably, the Ti-doped AlNNT demonstrates the ability to detect AC distinctly, even in the presence of HCN, formaldehyde, ethanol, toluene, and acetone. The swift recovery process becomes evident as AC desorbs from the surface of Ti-doped AlNNT, with a calculated recovery time of 14.0 s.

A Short Overview on Graphene and Graphene-Related Materials for Electrochemical Gas Sensing

The development of new and high-performing electrode materials for sensing applications is one of the most intriguing and challenging research fields. There are several ways to approach this matter, but the use of nanostructured surfaces is among the most promising and highest performing. Graphene and graphene-related materials have contributed to spreading nanoscience across several fields in which the combination of morphological and electronic properties exploit their outstanding electrochemical properties. In this review, we discuss the use of graphene and graphene-like materials to produce gas sensors, highlighting the most relevant and new advancements in the field, with a particular focus on the interaction between the gases and the materials.

Ultrahigh-quality graphene resonators by liquid-based strain-engineering

Two-dimensional (2D) material-based nanoelectromechanical (NEM) resonators are expected to be enabling components in hybrid qubits that couple mechanical and electromagnetic degrees of freedom. However, challenges in their sensitivity and coherence time have to be overcome to realize such mechanohybrid quantum systems. We here demonstrate the potential of strain engineering to realize 2D material-based resonators with unprecedented performance. A liquid-based tension process was shown to enhance the resonance frequency and quality factor of graphene resonators six-fold. Spectroscopic and microscopic characterization reveals a surface-energy enhanced wall interaction as the origin of this effect. The response of our tensioned resonators is not limited by external loss factors and exhibits near-ideal internal losses, yielding superior resonance frequencies and quality factors to all previously reported 2D material devices. Our approach represents a powerful method of enhancing 2D NEM resonators for future quantum systems.

Single-sized N-functionality graphene quantum dot in tunable dual-modality near infrared-I/II illumination detection and photodynamic therapy under multiphoton nonlinear excitation

Doping sorted graphene quantum dots (GQDs) with heteroatoms and functionalizing them with amino acid could improve their radiative recombination and two-photon properties-including their excitation-wavelength-independent photoluminescence from the ultraviolet to the near-infrared-I (NIR-I) region, absorption, quantum yield, absolute cross section, lifetime, and radiative-to-nonradiative decay ratio-under two-photon excitation (TPE) at a low excitation energy and short photoexcitation duration, as determined using a self-made optical microscopy system with a femtosecond Ti-sapphire laser. Four types of sorted GQDs were investigated: undoped GQDs, nitrogen-doped GQDs (N-GQDs), amino-functionalized GQDs (amino-GQDs), and N-doped and amino-functionalized GQDs (amino-N-GQDs). Among them, the sorted amino-N-GQDs are effective as a two-photon photosensitizer and generate the highest quantity of reactive oxygen species for the elimination of multidrug-resistant cancer cells through two-photon photodynamic therapy (PDT). Larger amino-N-GQDs result in a greater number of C-N and N-functionalities, leading to a superior photochemical effect and more favorable intrinsic luminescence properties, making the dots effective contrast agents for tracking and localizing cancer cells during in-depth bioimaging in a three-dimensional biological environment under TPE in the NIR-II region. Overall, this study highlights the potential of large amino-N-GQDs as a material for future application to dual-modality two-photon PDT and biomedical imaging.

Liquid-phase photo-induced covalent modification (PICM) of single-layer graphene by short-chain fatty acids

We report an efficient photo-induced covalent modification (PICM) of graphene by short-chain fatty acids (SCFAs) with an alkyl chain at the liquid-solid interface for spatially resolved chemical functionalization of graphene. Light irradiation on monolayer graphene under an aqueous solution of the SCFAs with an alkyl chain efficiently introduces sp³-hybridized defects, where the reaction rates of PICM are significantly higher than those in pure water. Raman and IR spectroscopy revealed that a high density of methyl, methoxy, and acetate groups is covalently attached to the graphene surface while it was partially oxidized by other oxygen-containing functional groups, such as OH and COOH. A greater downshift of the G-band in Raman spectra was observed upon the PICM with longer alkyl chains, suggesting that the charge doping effect can be controlled by the alkyl chain length of the SCFAs. The systematic research and exploration of covalent modification in SCFAs provide new insight and a potentially facile method for bandgap engineering of graphene.

Flexible Tuning of Friction on Atomically Thin Graphene

The tuning of flexible microscale friction is desirable for the reliability of wearable electronic devices, tactile sensors, and flexible gears. Here, the tuning of friction of atomically thin graphene on a flexible polydimethylsiloxane (PDMS) substrate was obtained with the elastic modulus using a 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) self-assembly monolayers (SAMs)-modified microsphere probe with the diameter of 5 μm at the microscale. The friction can be tuned at a large scale with the difference in the elastic modulus of PDMS and thickness of graphene. The hydrophobic property of the FDTS SAMs-modified probe decreased friction by reducing interfacial adhesion and preventing the effect of capillary interaction; thus, the friction decreased with the increase in the elastic modulus of the PDMS substrate due to decreasing indentation depth and thus the interfacial contact area; and also, the enhanced out-of-plane stiffness effectively decreased the interfacial contact quality with the increase of the thickness of graphene. The flexible tuning of friction on graphene was further verified by the theoretical calculation from the aspects of the friction arising from the normal and lateral deformation around the contacting area. This work is meaningful for promoting the design and reliability of flexible micro-devices.

Exploring the Chemical Structures and Phototochemical Properties of Graphene Oxide Derivatives by Laser Desorption/Ionization Time-of-Flight Mass Spectrometry to Develop an Efficient Platform for Mass Spectrometric Analysis

Laser desorption/ionization time-of-flight mass spectrometry (LDI-TOF-MS) analysis is harnessed to investigate the chemical structure and photochemical properties of two distinct graphene oxide (GO) derivatives simultaneously. The GO derivatives are synthesized with modified Brodie's method (BGO) and Hummers' method (HGO) and characterized by LDI-TOF-MS as well as conventional tools. A series of LDI-TOF-MS analyses reveal that BGO provides higher laser energy absorption, photochemical stability, and photothermal conversion property than HGO based on their fragmentation patterns and laser desorption/ionization behavior of a thermometer molecule. Based on these characteristics, BGO exhibits higher efficiency in the LDI-TOF-MS analysis of various small molecules and synthetic polymers than HGO. These different photochemical properties of BGO are derived from its large sp² carbon domains compared to HGO. Based on our findings, the analytical potential of LDI-TOF-MS for GO derivatives is clearly demonstrated, which can be an efficient and unique characterization tool to explore both chemical structures and photochemical properties of various carbon materials.

Water adsorption and dynamics on graphene and other 2D materials: Computational and experimental advances

The interaction of water and surfaces, at molecular level, is of critical importance for understanding processes such as corrosion, friction, catalysis and mass transport. The significant literature on interactions with single crystal metal surfaces should not obscure unknowns in the unique behaviour of ice and the complex relationships between adsorption, diffusion and long-range inter-molecular interactions. Even less is known about the atomic-scale behaviour of water on novel, non-metallic interfaces, in particular on graphene and other 2D materials. In this manuscript, we review recent progress in the characterisation of water adsorption on 2D materials, with a focus on the nano-material graphene and graphitic nanostructures; materials which are of paramount importance for separation technologies, electrochemistry and catalysis, to name a few. The adsorption of water on graphene has also become one of the benchmark systems for modern computational methods, in particular dispersion-corrected density functional theory (DFT). We then review recent experimental and theoretical advances in studying the single-molecular motion of water at surfaces, with a special emphasis on scattering approaches as they allow an unparalleled window of observation to water surface motion, including diffusion, vibration and self-assembly.

Carbon-Based Nanomaterials Thin Film Deposited on a Flexible Substrate for Strain Sensing Application

Hybrid nanomaterial film consisting of multi-walled carbon nanotubes (MWCNT) and graphene nanoplatelet (GNP) were deposited on a highly flexible polyimide (PI) substrate using spray gun. The hybridization between 2-D GNP and 1-D MWCNT reduces stacking among the nanomaterials and produces a thin film with a porous structure. Carbon-based nanomaterials of MWCNT and GNP with high electrical conductivity can be employed to detect the deformation and damage for structural health monitoring. The strain sensing capability of carbon-based hybrid nanomaterial film was evaluated by its piezoresistive behavior, which correlates the change of electrical resistance with the applied strain through a tensile test. The effects of weight ratio between MWCNT and GNP and the total amount of hybrid nanomaterials on the strain sensitivity of the nanomaterial thin film were investigated. Experimental results showed that both the electrical conductivity and strain sensitivity of the hybrid nanomaterial film increased with the increase of the GNP contents. The gauge factor used to characterize the strain sensitivity of the nanomaterial film increased from 7.75 to 24 as the GNP weight ratio increased from 0 wt.% to 100 wt.%. In this work, a simple, low cost, and easy to implement deposition process was proposed to prepare a highly flexible nanomaterial film. A high strain sensitivity with gauge factor of 24 was achieved for the nanomaterial thin film.

Redispersible Reduced Graphene Oxide Prepared in a Gradient Solvent System

We designed a gradient solvent strategy for the reduction of graphene oxide, matching the hydrophilic properties of graphene oxide (GO) and reduced graphene oxide (RGO), respectively. A third solvent was added dropwise to regulate the hydrophilic variation of the continuous gradient system which maintained the whole reduction process without aggregation, and the obtained RGO dispersions could maintain stability for a long time. The separated RGO solid powder can be directly ultrasonically redispersed in N-methyl-pyrrolidone (NMP) with an average particle size as low as 200 nm. Furthermore, RGO with a high C/O ratio of 13.75 was prepared on the basis of the gradient solvent system. Using different structures of dispersants and polymers as representatives, we employed successive solvent rinsing, thermal solvent extraction, and thermal treatment to study adsorption and desorption. It was found that the above measures differed significantly in the removal of surface sorbates. The selected fatty alcohol polyoxyethylene ether (AEO) series achieved a good balance between the system dispersion and surface adsorbate removal. The conductivity was originally 5236 S m^-1, and it increased from 9024 to 18,000 S m^-1 after thermal treatment at 300 and 500 °C, respectively.

Specific and Sensitive Detection of Tartrazine on the Electrochemical Interface of a Molecularly Imprinted Polydopamine-Coated PtCo Nanoalloy on Graphene Oxide

A novel electrochemical sensor designed to recognize and detect tartrazine (TZ) was constructed based on a molecularly imprinted polydopamine (MIPDA)-coated nanocomposite of platinum cobalt (PtCo) nanoalloy-functionalized graphene oxide (GO). The nanocomposites were characterized and the TZ electrochemical detection performance of the sensor and various reference electrodes was investigated. Interestingly, the synergistic effect of the strong electrocatalytic activity of the PtCo nanoalloy-decorated GO and the high TZ recognition ability of the imprinted cavities of the MIPDA coating resulted in a large and specific response to TZ. Under the optimized conditions, the sensor displayed linear response ranges of 0.003–0.180 and 0.180–3.950 µM, and its detection limit was 1.1 nM (S/N = 3). The electrochemical sensor displayed high anti-interference ability, good stability, and adequate reproducibility, and was successfully used to detect TZ in spiked food samples. Comparison of important indexes of this sensor with those of previous electrochemical sensors for TZ revealed that this sensor showed improved performance. This surface-imprinted sensor provides an ultrasensitive, highly specific, effective, and low-cost method for TZ determination in foodstuffs.

Two-Photon-Near Infrared-II Antimicrobial Graphene-Nanoagent for Ultraviolet-Near Infrared Imaging and Photoinactivation

Nitrogen doping and amino group functionalization through chemical modification lead to strong electron donation. Applying these processes to a large π-conjugated system of graphene quantum dot (GQD)-based materials as electron donors increases the charge transfer efficiency of nitrogen-doped amino acid-functionalized GQDs (amino-N-GQDs), resulting in enhanced two-photon absorption, post-two-photon excitation (TPE) stability, TPE cross-sections, and two-photon luminescence through the radiative pathway when the lifetime decreases and the quantum yield increases. Additionally, it leads to the generation of reactive oxygen species through two-photon photodynamic therapy (PDT). The sorted amino-N-GQDs prepared in this study exhibited excitation-wavelength-independent two-photon luminescence in the near-infrared region through TPE in the near-infrared-II region. The increase in size resulted in size-dependent photochemical and electrochemical efficacy, increased photoluminescence quantum yield, and efficient two-photon PDT. Therefore, the sorted amino-N-GQDs can be applicable as two-photon contrast probes to track and localize analytes in in-depth two-photon imaging executed in a biological environment along with two-photon PDT to eliminate infectious or multidrug-resistant microbes.

Graphene-Supported Naphthalene-Based Polyimide Composite as a High-Performance Sodium Storage Cathode

Electroactive acid anhydride with multicarbonyl is highly promising for electrochemical energy storage because of its high specific capacity and environmental benignity. Its low electrical conductivity and high dissolution in organic electrolyte, however, result in poor cycling and rate capabilities. Here, we report a naphthalene polyimide derivative (NPI) synthesized by using anhydride under condensation polymerization conditions, along with its composite with graphene (NPI-G) fabricated via in situ polymerization. The composite delivers a high reversible capacity and outstanding cycling stability and rate capability as a cathode for sodium-ion batteries (SIBs) owing to the formation of a polymer, the improvement in the electrical conductivity brought about by the highly dispersed graphene sheets, and the enhancement of structural stability resulting from the π-π stacking interaction between the phenyl groups of NPI and the six-member carbon rings of graphene. This investigation sheds light on the development, design, and screening of next-generation organic electrode materials with high performance for SIBs.

Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy for Probing Riboflavin on Graphene

Graphene research and technology development requires to reveal adsorption processes and understand how the defects change the physicochemical properties of the graphene-based systems. In this study, shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and graphene-enhanced Raman spectroscopy (GERS) coupled with density functional theory (DFT) modeling were applied for probing the structure of riboflavin adsorbed on single-layer graphene substrate grown on copper. Intense and detailed vibrational signatures of the adsorbed riboflavin were revealed by SHINERS method. Based on DFT modeling and detected downshift of prominent riboflavin band at 1349 cm⁻¹ comparing with the solution Raman spectrum, π-stacking interaction between the adsorbate and graphene was confirmed. Different spectral patterns from graphene-riboflavin surface were revealed by SHINERS and GERS techniques. Contrary to GERS method, SHINERS spectra revealed not only ring stretching bands but also vibrational features associated with ribityl group of riboflavin and D-band of graphene. Based on DFT modeling it was suggested that activation of D-band took place due to riboflavin induced tilt and distortion of graphene plane. The ability to explore local perturbations by the SHINERS method was highlighted. We demonstrated that SHINERS spectroscopy has a great potential to probe adsorbed molecules at graphene.

Graphene-enabled wearable sensors for healthcare monitoring

Wearable sensors in healthcare monitoring have recently found widespread applications in biomedical fields for their non- or minimal-invasive, user-friendly and easy-accessible features. Sensing materials is one of the major challenges to achieve these superiorities of wearable sensors for healthcare monitoring, while graphene-based materials with many favorable properties have shown great efficiency in sensing various biochemical and biophysical signals. In this paper, we review state-of-the-art advances in the development and modification of graphene-based materials (i.e., graphene, graphene oxide and reduced graphene oxide) for fabricating advanced wearable sensors with 1D (fibers), 2D (films) and 3D (foams/aerogels/hydrogels) macroscopic structures. We summarize the structural design guidelines, sensing mechanisms, applications and evolution of the graphene-based materials as wearable sensors for healthcare monitoring of biophysical signals (e.g., mechanical, thermal and electrophysiological signals) and biochemical signals from various body fluids and exhaled gases. Finally, existing challenges and future prospects are presented in this area.

Defects Produced during Wet Transfer Affect the Electrical Properties of Graphene

Graphene has been widely used due to its excellent electrical, mechanical and chemical properties. Defects produced during its transfer process will seriously affect the performance of graphene devices. In this paper, single-layer graphene was transferred onto glass and silicon dioxide (SiO₂) substrates by wet transfer technology, and the square resistances thereof were tested. Due to the different binding forces of the transferred graphene surfaces, there may have been pollutants present. PMMA residues, graphene laminations and other defects that occurred in the wet transfer process were analyzed by X-ray photoelectron spectroscopy and Raman spectroscopy. These defects influenced the square resistance of the produced graphene films, and of these defects, PMMA residue was the most influential; square resistance increased with increasing PMMA residue.

Copper(II)-Bis-Cyclen Intercalated Graphene Oxide as an Efficient Two-Dimensional Nanocomposite Material for Copper-Catalyzed Azide–Alkyne Cycloaddition Reaction

We report stable and heterogeneous graphene oxide (GO)–intercalated copper as an efficient catalyst for the organic transformations in green solvents. The GO-intercalated copper(II) complex of bis(1,4,7,10-tetraazacyclododecane) [Cu(II)-bis-cyclen] was prepared by a facile synthetic approach with a high dilution technique. The as-prepared GO-Cu(II)-bis-cyclen nanocomposite was used as a click catalyst for the 1,3 dipolar Huisgen cycloaddition reaction of terminal alkyne and azide substrates. On directing a great deal of attention toward the feasibility of the rapid electron transfer rate of the catalyst in proliferating the yield of 1,2,3-triazole products, the click catalyst GO-Cu(II)-bis-cyclen nanocomposite was designed and synthesized via non-covalent functionalization. The presence of a higher coordination site in an efficient 2D nanocomposite promotes the stabilization of Cu(I) L-acetylide intermediate during the catalytic cycle initiated by the addition of reductants. From the XRD analysis, the enhancement in the d-interlayer spacing of 1.04 nm was observed due to the intercalation of the Cu(II)-bis-cyclen complex in between the GO basal planes. It was also characterized by XPS, FT-IR, RAMAN, UV, SEM, AFM, and TGA techniques. The recyclability of the heterogeneous catalyst [GO-Cu(II)-cyclen] with the solvent effect has also been studied. This class of GO-Cu(II)-bis-cyclen nanocomposite paves the way for bioconjugation of macromolecules through the click chemistry approach.

Physical and Chemical Sensors on the Basis of Laser-Induced Graphene: Mechanisms, Applications, and Perspectives

Laser-induced graphene (LIG) is produced rapidly by directly irradiating carbonaceous precursors, and it naturally exhibits as a three-dimensional porous structure. Due to advantages such as simple preparation, time-saving, environmental friendliness, low cost, and expanding categories of raw materials, LIG and its derivatives have achieved broad applications in sensors. This has been witnessed in various fields such as wearable devices, disease diagnosis, intelligent robots, and pollution detection. However, despite LIG sensors having demonstrated an excellent capability to monitor physical and chemical parameters, the systematic review of synthesis, sensing mechanisms, and applications of them combined with comparison against other preparation approaches of graphene is still lacking. Here, graphene-based sensors for physical, biological, and chemical detection are reviewed first, followed by the introduction of general preparation methods for the laser-induced method to yield graphene. The preparation and advantages of LIG, sensing mechanisms, and the properties of different types of emerging LIG-based sensors are comprehensively reviewed. Finally, possible solutions to the problems and challenges of preparing LIG and LIG-based sensors are proposed. This review may serve as a detailed reference to guide the development of LIG-based sensors that possess properties for future smart sensors in health care, environmental protection, and industrial production.

Robust Superlubric Interface across Nano- and Micro-Scales Enabled by Fluoroalkylsilane Self-Assembled Monolayers and Atomically Thin Graphene

Robust superlubrication across nano- and microscales is highly desirable at the interface with asperities of different sizes in durable micro/nanoelectromechanical systems under a harsh environment. A novel method to fabricate superlubric interfaces across nano- and microscales is developed by combining a batch of surface modification with atomically thin graphene. The robust superlubric interface across nano- and microscales between hydrophobic 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS) self-assembly monolayers (SAMs) and graphene was achieved under high relative humidity, sliding speed, and contact pressure. The superlubric mechanisms at the interface of FDTS/graphene could be attributed to the following at different scales: the hydrophobicity of FDTS SAMs and graphene preventing the capillary interaction of the interfacial friction under high relative humidity; the high elastic modulus of graphene leading to small interfacial contact area; the compressing and orientating of FDTS SAMs decreasing interfacial shear strength under high contact pressure; the surface modification of FDTS molecules reducing the interfacial potential barriers when sliding on the atomically thin graphene. The robust superlubric interface across nano- and microscales reducing the friction at the complicated interfaces with asperities at different scales and improving the performance and durability have great potentials in the field of micro/nano mechanical systems.

Two-Dimensional Polymers and Polymerizations

Synthetic chemists have developed robust methods to synthesize discrete molecules, linear and branched polymers, and disordered cross-linked networks. However, two-dimensional polymers (2DPs) prepared from designed monomers have been long missing from these capabilities, both as objects of chemical synthesis and in nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization of covalently linked macromolecular sheets. Here we review 2DPs and 2D polymerization methods. Three predominant 2D polymerization strategies have emerged to date, which produce 2DPs either as monolayers or multilayer assemblies. We discuss the fundamental understanding and scope of each of these approaches, including: the bond-forming reactions used, the synthetic diversity of 2DPs prepared, their multilayer stacking behaviors, nanoscale and mesoscale structures, and macroscale morphologies. Additionally, we describe the analytical tools currently available to characterize 2DPs in their various isolated forms. Finally, we review emergent 2DP properties and the potential applications of planar macromolecules. Throughout, we highlight achievements in 2D polymerization and identify opportunities for continued study.

Graphene Biodevices for Early Disease Diagnosis Based on Biomarker Detection

The early diagnosis of diseases plays a vital role in healthcare and the extension of human life. Graphene-based biosensors have boosted the early diagnosis of diseases by detecting and monitoring related biomarkers, providing a better understanding of various physiological and pathological processes. They have generated tremendous interest, made significant advances, and offered promising application prospects. In this paper, we discuss the background of graphene and biosensors, including the properties and functionalization of graphene and biosensors. Second, the significant technologies adopted by biosensors are discussed, such as field-effect transistors and electrochemical and optical methods. Subsequently, we highlight biosensors for detecting various biomarkers, including ions, small molecules, macromolecules, viruses, bacteria, and living human cells. Finally, the opportunities and challenges of graphene-based biosensors and related broad research interests are discussed.

Promising Graphene-Based Nanomaterials and Their Biomedical Applications and Potential Risks: A Comprehensive Review

Graphene-based nanomaterials (GBNs) have been the subject of research focus in the scientific community because of their excellent physical, chemical, electrical, mechanical, thermal, and optical properties. Several studies have been conducted on GBNs, and they have provided a detailed review and summary of various applications. However, comprehensive comments on biomedical applications and potential risks and strategies to reduce toxicity are limited. In this review, we systematically summarized the following aspects of GBNs in order to fill the gaps: (1) the history, synthesis methods, structural characteristics, and surface modification; (2) the latest advances in biomedical applications (including drug/gene delivery, biosensors, bioimaging, tissue engineering, phototherapy, and antibacterial activity); and (3) biocompatibility, potential risks (toxicity in vivo/vitro and effects on human health and the environment), and strategies to reduce toxicity. Moreover, we have analyzed the challenges to be overcome in order to enhance application of GBNs in the biomedical field.

Synthesis of Single-Crystal Graphene on Copper Foils Using a Low-Nucleation-Density Region in a Quartz Boat

The nucleation of graphene at different locations in the quartz boat was studied, and the lowest nucleation density of graphene in the quartz boat was found. The nucleation density of graphene is the lowest at the bottom of the quartz boat near the gas inlet side. Based on the above results, a simple and reproducible way is proposed to significantly suppress the nucleation density of graphene on the copper foil during the chemical vapor deposition process. Placing the copper foil with an area of 1.3 cm × 1 cm in the middle of the bottom of the quartz boat or further back, and placing two copper pockets in front of the copper foil, an ultra-low nucleation density of ~42 nucleus/cm2 was achieved on the back of the copper foil. Single-crystal monolayer graphene with a lateral size of 800 μm can be grown on the back of copper foils after 60 min of growth. Raman spectroscopy revealed the single-crystal graphene to be in uniform monolayers with a low D-band intensity.

Graphene quantum dots decorated with imatinib for leukemia treatment

The use of graphene quantum dots as biomedical device and drug delivery system has been increasing. This nanoplatform of pure carbon has showed unique properties and showed to be safe for human use. The imatinib is a molecule designed to specifically inhibit the tyrosine kinase, used for leukemia treatment. In this study, we successfully decorated the graphene quantum dots (GQDs@imatinb) by a carbodiimide crosslinking reaction. The GQDs@imatinb were characterized by FTIR and AFM. The nanoparticles' in vitro behaviors were evaluated by cellular trafficking (internalization) assay and cell viability and apoptosis assays in various cancer cell lines, including suspension (leukemia) cells and adherent cancer cells. The results showed that the incorporation of the imatinib on the surface of the graphene quantum dots did not change the nanoparticles' morphology and properties. The GQDs@imatinb could be efficiently internalized and kill cancer cells via the induction of apoptosis. The data indicated that the prepared GQDs@imatinb might be a great drug nano-platform for cancer, particularly leukemia treatments.

Motion of water monomers reveals a kinetic barrier to ice nucleation on graphene

The interfacial behaviour of water remains a central question to fields as diverse as protein folding, friction and ice formation. While the properties of water at interfaces differ from those in the bulk, major gaps in our knowledge limit our understanding at the molecular level. Information concerning the microscopic motion of water comes mostly from computation and, on an atomic scale, is largely unexplored by experiment. Here, we provide a detailed insight into the behaviour of water monomers on a graphene surface. The motion displays remarkably strong signatures of cooperative behaviour due to repulsive forces between the monomers, enhancing the monomer lifetime ( ≈ 3 s at 125 K) in a free-gas phase that precedes the nucleation of ice islands and, in turn, provides the opportunity for our experiments to be performed. Our results give a molecular perspective on a kinetic barrier to ice nucleation, providing routes to understand and control the processes involved in ice formation.