A significant advance in rate and precision of identifying the co-surfactant concentrations leading to differential extraction of specific single-wall carbon nanotube (SWCNT) species in aqueous two-polymer phase extraction experiments is reported. These gains are achieved through continuous titration of co-surfactant and other solution components during automated fluorescence measurements on SWCNT dispersions. The resulting fluorescence concentration curves display intensity and wavelength shift transitions traceable to the nature of the adsorbed surfactant layer on specific SWCNT structures at the (,) species and enantiomer level at high resolution. The increased precision and speed of the titration method resolve previously invisible complexity in the SWCNT fluorescence during the transition from one surfactant dominating the SWCNT interface to the other, offering insight into the fine details of the competitive exchange process. For the first time, we additionally demonstrate that the competitive process of the surfactant switch is direction independent (reversible) and hysteresis-free; the latter data effectively specifies an upper bound for the time scale of the exchange process. Titration curves are compared to literature results and initial advanced parameter variation is conducted for previously unreasonable to investigate solution conditions.

This study examines a perovskite-based graphene field effect transistor (P-GFET) device for X-ray detection. The device architecture consisted of a commercially available GFET-S20 chip, produced by Graphenea, with a layer of methylammonium lead iodide (MAPbI) perovskite spin coated onto the top of it. This device was exposed to the field of a molybdenum target X-ray tube with beam settings between 20-60 kVp (X-ray tube voltage) and 30-300 uA (X-ray tube current). Dose measurements were taken with an ion-chamber and thermo-luminescent dosimeters and used to determine the sensitivity of the device as a function of the X-ray tube voltage and current, as well as source-drain voltage. The X-ray tube was also simulated in this work with GEANT4 and MCNP to determine the dose rate and power incident on the device during irradiation. These simulations were then used to determine the responsivity as a function of the X-ray tube voltage and current, as well as the source-drain voltage. Overall, a strong positive correlation between sensitivity and source-drain voltage was found. Conversely, the sensitivity was found to decrease - roughly exponentially - as a function of both the X-ray tube current and energy. Similar trends were seen with responsivity. We report the models used for the study as well as address the feasibility of the device as a low-energy (< 70 keV) X-ray photon detector.

The Coronavirus Disease 2019 (COVID-19) pandemic has led to collaboration between nanotechnology scientists, industry stakeholders, and clinicians to develop solutions for diagnostics, prevention, and treatment of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections. Nanomaterials, including carbon-based materials (CBM) such as graphene and carbon nanotubes, have been studied for their potential in viral research. CBM unique effects on microorganisms, immune interaction, and sensitivity in diagnostics have made them a promising subject of SARS-CoV-2 research. This review discusses the interaction of CBM with SARS-CoV-2 and their applicability, including CBM physical and chemical properties, the known interactions between CBM and viral components, and the proposed prevention, treatment, and diagnostics uses.

Modern nanotechnology provides efficient and cost-effective nanomaterials (NMs). The increasing usage of NMs arises great concerns regarding nanotoxicity in humans. Traditional animal testing of nanotoxicity is expensive and time-consuming. Modeling studies using machine learning (ML) approaches are promising alternatives to direct evaluation of nanotoxicity based on nanostructure features. However, NMs, including two-dimensional nanomaterials (2DNMs) such as graphenes, have complex structures making them difficult to annotate and quantify the nanostructures for modeling purposes. To address this issue, we constructed a virtual graphenes library using nanostructure annotation techniques. The irregular graphene structures were generated by modifying virtual nanosheets. The nanostructures were digitalized from the annotated graphenes. Based on the annotated nanostructures, geometrical nanodescriptors were computed using Delaunay tessellation approach for ML modeling. The partial least square regression (PLSR) models for the graphenes were built and validated using a leave-one-out cross-validation (LOOCV) procedure. The resulted models showed good predictivity in four toxicity-related endpoints with the coefficient of determination (R) ranging from 0.558 to 0.822. This study provides a novel nanostructure annotation strategy that can be applied to generate high-quality nanodescriptors for ML model developments, which can be widely applied to nanoinformatics studies of graphenes and other NMs.

Polymer nanocomposite films have recently shown superior energy dissipation capability through the micro-projectile impact testing method. However, how stress waves interact with nanointerfaces and the underlying deformation mechanisms have remained largely elusive. This paper investigates the detailed stress wave propagation process and dynamic failure mechanisms of layered poly(methyl methacrylate) (PMMA) - graphene nanocomposite films during piston impact through coarse-grained molecular dynamics simulations. The spatiotemporal contours of stress and local density clearly demonstrate shock front, reflected wave, and release wave. By plotting shock front velocity ( ) against piston velocity ( ), we find that the linear Hugoniot - relationship generally observed for bulk polymer systems also applies to the layered nanocomposite system. When the piston reaches a critical velocity, PMMA crazing can emerge at the location where the major reflected wave and release wave meet. We show that the activation of PMMA crazing significantly enhances the energy dissipation ratio of the nanocomposite films, defined as the ratio between the dissipated energy through irreversible deformation and the input kinetic energy. The ratio maximizes at the critical when the PMMA crazing starts to develop and then decreases as further increases. We also find that a critical PMMA-graphene interfacial strength is required to activate PMMA crazing instead of interfacial separation. Additionally, layer thickness affects the amount of input kinetic energy and dissipated energy of nanocomposite films under impact. This study provides important insights into the detailed dynamic deformation mechanisms and how nanointerfaces/nanostructures affect the energy dissipation capability of layered nanocomposite films.

Additive manufacturing has played a crucial role in the COVID-19 global emergency allowing for rapid production of medical devices, indispensable tools for hospitals, or personal protection equipment. However, medical devices, especially in nosocomial environments, represent high touch surfaces prone to viral infection and currently used filaments for 3D printing can't inhibit transmission of virus [1]. Graphene-family materials are capable of reinforcing mechanical, optical and thermal properties of 3D printed constructs. In particular, graphene can adsorb near-infrared light with high efficiency. Here we demonstrate that the addition of graphene nanoplatelets to PLA filaments (PLA-G) allows the creation of 3D-printed devices that can be sterilized by near-infrared light exposure at power density analog to sunlight. This method has been used to kill SARS-CoV-2 viral particles on the surface of 3D printed PLA-G by 3 min of exposure. 3D-printed PLA-G is highly biocompatible and can represent the ideal material for the production of sterilizable personal protective equipment and daily life objects intended for multiple users.

Due to the numerous failed clinical trials of anti-amyloid drugs, microtubule associated protein tau (MAPT) now stands out as one of the most promising targets for AD therapy. In this study, we report for the first time the structure-dependent MAPT aggregation inhibition of carbon nitride dots (CNDs). CNDs have exhibited great promise as a potential treatment of Alzheimer's disease (AD) by inhibiting the aggregation of MAPT. In order to elucidate its structure-activity relationship, CNDs were separated via column chromatography and five fractions with different structures were obtained that were characterized by multiple spectroscopy methods. The increase of surface hydrophilic functional groups is consistent with the increase of polarity from fraction 1 to 5. Particle sizes (1-2 nm) and zeta potentials (~-20 mV) are similar among five fractions. With the increase of polarity from fraction 1 to 5, their MAPT aggregation inhibition capacity was weakened. This suggests hydrophobic interactions between CNDs and MAPT, validated via molecular dynamics simulations. With a zebrafish blood-brain barrier (BBB) model, CNDs were observed to cross the BBB through passive diffusion. CNDs were also found to inhibit the generation of multiple reactive oxygen species, which is an important contributor to AD pathogenesis.

Quantitative determination of the effects of surfactant chemistry and polymer chain length on the concentration conditions necessary to yield extraction of specific single-wall carbon nanotube (SWNCT) species in an aqueous two-polymer phase extraction (ATPE) separation are reported. In particular, the effects of polyethylene glycol (PEG) chain length, surfactant ratios, and systematic structural variations of alkyl surfactants and bile salts on the surfactant ratios necessary for extraction were investigated using a recently reported fluorescence-based method. Alkyl surfactant tail length was observed to strongly affect the amount of surfactant necessary to cause PEG-phase extraction of nanotube species in ATPE, while variation in the anionic sulfate/sulfonate head group chemistry has less impact on the concentration necessary for extraction. Substitution of different bile salts results in different surfactant packings on the SWCNTs, with substitution greatly affecting the alkyl surfactant concentrations required for () extraction. Finally, distinct alkyl-to-bile surfactant ratios were found to extract specific () SWCNTs across the whole effective window of absolute concentrations, supporting the hypothesized competitive adsorption mechanism model of SWCNT sorting. Altogether, these results provide valuable insights into the underlying mechanisms behind ATPE-based SWCNT separations, towards further development and optimization of the ATPE method for SWCNT chirality and handedness sorting.

Fabrication of heteroatom-doped graphene electrodes remains a challenging endeavor, especially on flexible substrates. Precise chemical and morphological control is even more challenging for patterned microelectrodes. We herein demonstrate a scalable process for directly generating micropatterns of heteroatom-doped porous graphene on polyimide with different backbones using a continuous-wave infrared laser. Conventional two-step polycondensation of 4,4'-oxydianiline with three different tetracarboxylic dianhydrides enabled the fabrication of fully aromatic polyimides with various internal linkages such as phenylene, trifluoromethyl or sulfone groups. Accordingly, we leverage this laser-induced polymer-to-doped-graphene conversion for fabricating electrically conductive microelectrodes with efficient utilization of heteroatoms (N-doped, F-doped, and S-doped). Tuning laser fluence enabled achieving electrical resistivity lower than ~13 Ω sq for F-doped and N-doped graphene. Finally, our microelectrodes exhibit superior performance for electrochemical sensing of dopamine, one of the important neurotransmitters in the brain. Compared with carbon fiber microelectrodes, the gold standard in electrochemical dopamine sensing, our F-doped high surface area graphene microelectrodes demonstrated 3 order of magnitude higher sensitivity per unit area, detecting dopamine concentrations as low as 10 nM with excellent reproducibility. Hence, our approach is promising for facile fabrication of microelectrodes with superior capabilities for various electrochemical and sensing applications including early diagnosis of neurological disorders.

Due to weak light-matter interaction, standard chemical vapor deposition (CVD)/exfoliated single-layer graphene-based photodetectors show low photoresponsivity (on the order of mA/W). However, epitaxial graphene (EG) offers a more viable approach for obtaining devices with good photoresponsivity. EG on 4H-SiC also hosts an interfacial buffer layer (IBL), which is the source of electron carriers applicable to quantum optoelectronic devices. We utilize these properties to demonstrate a gate-free, planar EG/4H-SiC-based device that enables us to observe the positive photoresponse for (405-532) nm and negative photoresponse for (632-980) nm laser excitation. The broadband binary photoresponse mainly originates from the energy band alignment of the IBL/EG interface and the highly sensitive work function of the EG. We find that the photoresponsivity of the device is > 10 A/W under 405 nm of power density 7.96 mW/cm at 1 V applied bias, which is three orders of magnitude greater than the obtained values of CVD/exfoliated graphene and higher than the required value for practical applications. These results path the way for selective light-triggered logic devices based on EG and can open a new window for broadband photodetection.

Multilayer graphene sheets (MLGSs) are promising nano-reinforcements that can effectively enhance the properties of polymer matrices. Despite many studies on MLGSs-reinforced polymer nanocomposites, the effect of wrinkles formed in MLGSs on the reinforcement effect and the viscoelastic properties of polymer nanocomposites has remained unknown. In this study, building upon previously developed coarse-grained models of MLGSs and poly(methyl methacrylate) coupled with molecular dynamics simulations, we have systematically investigated nanocomposites with different numbers of graphene layers and various wrinkle configurations. We find that with decreasing degree of waviness and increasing numbers of layers, the elastic modulus of the nanocomposites increases. Interestingly, we observe a sudden stress drop during shear deformation of certain wrinkled MLGSs-reinforced nanocomposites. We further conduct small amplitude oscillatory shear simulations on these nanocomposites and find that the nanocomposites with these specific wrinkle configurations also show peculiarly large loss tangents, indicating an increasing capability of energy dissipation. These behaviors are attributed to the activation of the interlayer sliding among these wrinkled MLGSs, as their interlayer shear strengths are indeed lower than flat MLGSs measured by steered molecular dynamics technique. Our study demonstrates that the viscoelastic properties and deformation mechanisms of polymer nanocomposites can be tuned through MLGS wrinkle engineering.

Pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) causes inflammation and fibrosis. Our previous work has shown that industrially produced MWCNTs trigger specific changes in gene expression in the lungs of exposed animals. To elucidate whether epigenetic effects play a role for these gene expression changes, we performed whole genome bisulphite sequencing to assess DNA methylation patterns in the lungs 56 days after exposure to MWCNTs. Lung tissues were also evaluated with respect to histopathological changes and cytokine profiling of bronchoalveolar lavage (BAL) fluid was conducted using a multi-plex array. Integrated analysis of transcriptomics data and DNA methylation data revealed concordant changes in gene expression. Functional analysis showed that the muscle contraction, immune system/inflammation, and extracellular matrix pathways were the most affected pathways. Taken together, the present study revealed that MWCNTs exert epigenetic effects in the lungs of exposed animals, potentially driving the subsequent gene expression changes.

We propose a novel method to exploit chirality of highly sensitive graphene plasmonic metasurfaces to characterize complex refractive indexes (RI) of viruses by detecting the polarization state of the reflected electric fields in the THz spectrum. A dispersive graphene metasurface is designed to produce chiral surface currents to couple linearly polarized incident fields to circularly polarized reflected fields. The metasurface sensing sensitivity is the result of surface plasmon currents that flow in a chiral fashion with strong intensity due to the underlying geometrical resonance. Consequently, unique polarization states are observed in the far-field with the ellipticity values that change rapidly with the analyte's RI. The determination of bimolecular RI is treated as an inverse problem in which the polarization states of the virus is compared with a pre-calculated calibration model that is obtained by full-wave electromagnetic simulations. We demonstrate the polarization selective sensing method by RI discrimination of three different types of Avian Influenza (AI) viruses including H1N1, H5N2, and H9N2 is possible. Since the proposed virus characterization method only requires determination of the polarization ellipses including its orientation at monochromatic frequency, the required instrumentation is simpler compared to traditional spectroscopic methods which need a broadband frequency scan.

Thermal exfoliation is an efficient and scalable method for the production of graphene nanosheets or nanoplatelets, which are typically re-assembled or blended to form new macroscopic "graphene-based materials". Thermal exfoliation can be applied to these macroscopic graphene-based materials after casting to create internal porosity, but this process variant has not been widely studied, and can easily lead to destruction of the physical form of the original cast body. Here we explore how the partial thermal exfoliation of graphene oxide (GO) multilayer nanosheet films can be used to control pore structure and electrical conductivity of planar, textured, and confined GO films. The GO films are shown to exfoliate explosively when the instrument-set heating rates are 100 K/min and above leading to complete destruction of the film geometry. Textured films with engineered micro-wrinkling and crumpling show similar thermal behavior to planar films. Here, we also demonstrate a novel method to produce fairly large size intact rGO films of high electrical conductivity and microporosity based on confinement. Sandwiching GO precursor films between inert plates during partial exfoliation at 250°C produces high conductivity and porosity material in the form of a flexible film that preserves the macroscopic structure of the original cast body.

Liquid-phase deposition of exfoliated 2D nanosheets is the basis for emerging technologies that include writable electronic inks, molecular barriers, selective membranes, and protective coatings against fouling or corrosion. These nanosheet thin films have complex internal structures that are discontinuous assemblies of irregularly tiled micron-scale sheets held together by van der Waals (vdW) forces. On stiff substrates, nanosheet vdW films are stable to many common stresses, but can fail by internal delamination under shear stress associated with handling or abrasion. This "re-exfoliation" pathway is an intrinsic feature of stacked vdW films and can limit nanosheet-based technologies. Here we investigate the shear stability of graphene oxide and MoSe nanosheet vdW films through lap shear experiments on polymer-nanosheet-polymer laminates. These sandwich laminate structures fail in mixed cohesive and interfacial mode with critical shear forces from 40 - 140 kPa and fracture energies ranging from 0.2 - 6 J/m. Surprisingly these energies are higher than delamination energies reported for smooth peeling of ordered stacks of continuous 2D sheets, which we propose is due to energy dissipation and chaotic crack motion during nanosheet film disassembly at the crack tip. Experiment results also show that film thickness plays a key role in determining critical shear force (maximum load before failure) and dissipated energy for different nanosheet vdW films. Using a mechanical model with an edge crack in the thin nanosheet film, we propose a shear-to-tensile failure mode transition to explain a maximum in critical shear force for graphene oxide films but not MoSe films. This transition reflects a weakening of the substrate confinement effect and increasing rotational deformation near the film edge as the film thickness increases. For graphene oxide, the critical shear force can be increased by electrostatic cross-linking achieved through interlayer incorporation of metal cations. These results have important implications for the stability of functional devices that employ 2D nanosheet coatings.

Development of efficient and cost-effective mass-production techniques for size reduction of high- pressure, high-temperature (HPHT) diamonds with sizes from tens to hundreds of micrometers remains one of the primary goals towards commercial production of fluorescent submicron and nanodiamond (fND). fNDs offer great advantages for many applications, especially in labelling, tracing, and biomedical imaging, owing to their brightness, exceptional photostability, mechanical robustness and intrinsic biocompatibility. This study proposes a novel processing method utilizing explosive fragmentation that can potentially be used for the fabrication of submicron to nanoscale size fluorescent diamond particles. In the proposed method, synthetic HPHT 20 pm and 150 pm microcystalline diamond particles containing color centers are rapidly fragmented in conditions of high explosive detonation. X-ray diffraction and Raman spectroscopy show that the detonation fragmented diamond particles consist of good quality submicron diamonds of ~420-800 nm in size, while fluorescence spectroscopy shows photoluminescence spectra with noticeable changes for large (150 μm) starting microcrystalline diamond particles, and no significant changes in photoluminescence properties for smaller (20 μm) starting microcrystalline diamond particles. The proposed detonation method shows potential as an efficient, cost effective, and industrially scalable alternative to milling for the fragmentation of fluorescent diamond microcrystals into submicron- to nano-size domain.

In this study, the structural properties of soot produced in diffusion flames are analyzed to elucidate the formation of mature aggregates from large young particles. Soot samples are generated in a laminar diffusion inverted gravity flame reactor (IGFR) operated on methane, ethane, and ethylene with Ar dilution to reduce the flame temperature. Soot produced in temperature ranges from 1495K-1568 K contains 100nm-300nm particles with (i) isotropic or (ii) multiple core structures, supporting a soot maturation pathway where one young soot particle evolves into a mature fractal aggregate via an internal nucleation route. During the process, these large amorphous particles can form internal voids as the particle loses mass due to pyrolysis or oxidation. Transmission electron microscopy (TEM) shows that young soot aggregates contain a higher fraction of shorter fringes and highly curved aromatics (11% vs. 23%), which is in agreement with their higher organic carbon content (3.3%-5.4% vs. 12.1%-28.8% wt.). Increasing the flame temperature reduces the curvature of polycyclic aromatic hydrocarbons (PAHs) and allows for more efficient layer stacking as indicated by a higher percent of stacked fringes. For these gaseous fuels, carbonization appears to be primarily a function of the flame temperature and independent of the fuel composition.

Carbon nanomaterials are used to improve electrodes for neurotransmitter detection, but what properties are important for maximizing those effects? In this work, we compare a newer form of graphene, carbon nanospikes (CNSs), with carbon nanotubes (CNTs) grown on wires and carbon fibers (CFs). CNS electrodes have a short, dense, defect-filled surface that produces remarkable electrochemical properties, much better than CNTs or CFs. The CNS surface roughness is 5.5 times greater than glassy carbon, while CNTs enhance roughness only 1.8-fold. D/G ratios are higher for CNS electrodes than CNT electrodes, an indication of more defect sites. For cyclic voltammetry of dopamine and ferricyanide, CNSs have both higher currents and smaller ΔE values than CNTs and CFs. CNS electrodes also have a very low resistance to charge transfer. With fast-scan cyclic voltammetry (FSCV), CNS electrodes have enhanced current density for dopamine and cationic neurotransmitters due to increased adsorption to edge plane sites. This study establishes that not all carbon nanomaterials are equally advantageous for dopamine electrochemistry, but that short, dense nanomaterials that add defect sites provide improved current and electron transfer. CNSs are simple to mass fabricate on a variety of substrates and thus could be a favorable material for neurotransmitter sensing.

Increasing use of carbon nanotubes (CNTs) in consumer and industrials goods increases their potential release, and subsequent risks to environmental and human health. Therefore, it is becoming ever more important that CNTs are designed to reduce or eliminate hazards and that hazard assessment methodologies are robust. Here, oxygen-functionalized multi-walled CNTs (O-MWCNTs), modified under varying redox conditions, were assessed for toxic potential using the zebrafish () embryo model. Multiple physicochemical properties (e.g., MWCNT aggregate size, morphology, and rate; surface charge and oxygen concentration; and reactive oxygen species (ROS) generation) were characterized and related to zebrafish embryo mortality through the use of multivariate statistical methods. Of these properties, surface charge and aggregate morphology emerged as the greatest predictors of embryo mortality. Interestingly, ROS generation was not significantly correlated to observed mortality, contrary to prior predictions by nanotoxicology researchers. This suggests that the mechanism of MWCNT-induced mortality of embryonic zebrafish is physical, driven by electrostatic and shape effects, both of which are related to nanomaterial aggregation. This raises the importance of rigorously considering aggregation during aqueous-based nanotoxicology assays as nanomaterial aggregation can affect perceived nanomaterial toxicity. As such, future nanotoxicity studies relying on aqueous media must sufficiently consider nanomaterial aggregation.

Carbon nanotubes (CNTs) have emerged as promising drug delivery systems particularly for cancer therapy, due to their abilities to overcome some of the challenges faced by cancer treatment, namely non-specificity, poor permeability into tumour tissues, and poor stability of anticancer drugs. Encapsulation of anticancer agents inside CNTs provides protection from external deactivating agents. However, the open ends of the CNTs leave the encapsulated drugs exposed to the environment and eventually their uncontrolled release before reaching the desired target. In this study, we report the successful encapsulation of cisplatin, a FDA-approved chemotherapeutic drug, into multi-walled carbon nanotubes and the capping at the ends with functionalised gold nanoparticles to achieve a "carbon nanotube bottle" structure. In this proof-of-concept study, these caps did not prevent the encapsulation of drug in the inner space of CNTs; on the contrary, we achieved higher drug loading inside the nanotubes in comparison with data reported in literature. In addition, we demonstrated that encapsulated cisplatin could be delivered in living cells under physiological conditions to exert its pharmacological action.

Monolayer epitaxial graphene (EG) has been shown to have clearly superior properties for the development of quantized Hall resistance (QHR) standards. One major difficulty with QHR devices based on EG is that their electrical properties drift slowly over time if the device is stored in air due to adsorption of atmospheric molecular dopants. The crucial parameter for device stability is the charge carrier density, which helps determine the magnetic flux density required for precise QHR measurements. This work presents one solution to this problem of instability in air by functionalizing the surface of EG devices with chromium tricarbonyl -Cr(CO). Observations of carrier density stability in air over the course of one year are reported, as well as the ability to tune the carrier density by annealing the devices. For low temperature annealing, the presence of Cr(CO) stabilizes the electrical properties and allows for the reversible tuning of the carrier density in millimeter-scale graphene devices close to the Dirac point. Precision measurements in the quantum Hall regime show no detrimental effect on the carrier mobility.