Development of grafting strategies for the polymer functionalisation of graphene

Graphene is well-known for its exceptional mechanical, electrical, and thermal properties, but its potential is yet to be fully realised in bulk applications due to difficulties in obtaining a large yield of high-quality individually-dispersed graphene sheets. In this thesis, reductive exfoliation of bulk graphite is demonstrated as a promising and versatile method which allows the isolation of single- and few-layer graphenes; the production of reduced graphene, or ‘graphenide’, solutions shows varying efficiency in different solvents. Subsequent functionalisation of graphenide dispersions with various electrophiles, including 1-bromododecane, anionic monomers such as methyl methacrylate, and bromine, results in increased solubility in organic solvents, without damage to the graphene basal plane. Exact characterisation and quantification of grafting is complicated by the presence of solvent remaining between graphene layers, a phenomenon which is not significant in other carbon nanomaterials. Reductive alkylation was carried out on five different graphitic starting materials including two types of natural flake graphite, shear-exfoliated graphite platelets, graphite nanofibres, and few-layer graphene. The study reveals pronounced differences in the obtained grafted species with respect to the degree of functionalisation and residual solvent, exfoliation efficiency and product homogeneity. These results are shown to be dependent on the size and nature of the starting material, with few-layer graphene showing the highest grafting ratios. Few-layer graphene was also functionalised with various molecular weight poly(methyl methacrylate) (PMMA) polymers by grafting-to and grafting-from approaches; the grafting ratios were higher for the grafting-from approach and the products showed a far greater dispersibility in acetone (up to 920 µg/mL). In parallel with these direct polymer-grafting strategies on few-layer graphene, the reduction method was used to dissolve and brominate few-layer graphene sheets, achieving direct covalent attachment of bromine to the graphene framework. The brominated few-layer graphenes provide a convenient, stable, liquid-phase precursor, suitable for the synthesis of a variety of directly functionalised graphenes. As an example, the brominated species was used to initiate atom transfer radical polymerisation, to obtain PMMA-grafted graphene, which was six times more dispersible in acetone than controls. In addition, brominated graphene is active for nucleophilic substitution reactions, as illustrated by the preparation of methoxypolyethylene glycol- and hydroxyl-substituted derivatives. Grafting ratios for these polymer-functionalised materials varied between 6 and 25% and all graphene derivatives showed increased solubility in organic solvents, highlighting the potential of this route for preparing large quantities of dispersed graphene with minimal damage to the carbon framework.Open Acces

1st Place Contest Entry: Psychogenic Non-epileptic Seizures Disorder: Treatment after the Diagnostic Odyssey

This is Heather Andrini, Ashley Okhovat, and Sydni Au Hoy\u27s submission for the 2021 Kevin and Tam Ross Undergraduate Research Prize, which won first place. It contains thier essay on using library resources, a summary of their research project on psychogenic non-epileptic seizures (PNES) disorder, and their works cited list. Heather, Ashley, and Sydni are juniors at Chapman University, majoring in Biological Sciences. Their faculty mentor is Dr. Gregory Goldsmith

Critical appraisal of trastuzumab in treatment of advanced stomach cancer

Advanced or metastatic gastric cancer constitutes the majority of patients in clinical practice. In North America, about 70% of cases are advanced or metastatic when diagnosed, which is higher than the 50% reported in Japan. This difference in presentation is reflected in 5-year overall survival, which is about 20% in North America and 40%–60% in Japan. Despite numerous efforts of randomized studies on advanced gastric cancer, no globally accepted standard regimen has yet been established. Systemic chemotherapy provides palliation and prolongs survival, but the prognosis remains poor. Several monotherapies and combined regimens are currently available and vary around the world. Additionally, several molecular targeting agents are under evaluation in international randomized studies. Human epidermal growth factor receptor-2 (HER-2) is overexpressed or amplified in approximately 22% of patients with gastric cancer. Trastuzumab, a recombinant humanized anti-HER-2 monoclonal antibody, is the first biological therapy that has showed a survival improvement by nearly three months (reduced risk of death by 26%). Therefore, trastuzumab in combination with cisplatin is a reasonable treatment option for patients with advanced gastric cancer who are HER-2 positive. This paper will focus on trastuzumab, its chemical and pharmacological characteristics, and the relevant efficacy, safety, and tolerability studies

Functional Seizures: The Patient’s Perspective of a Diagnostic and Treatment Odyssey

Functional seizures can be challenging to properly diagnose, often leading to delays in treatment. The etiology of functional seizures is multifactorial, with psychological factors identified in many, but not all cases. Misdiagnosis may occur due to clinical features mimicking other medical conditions. Once a correct diagnosis is reached, delivery of definitive, evidence-based treatment may be challenging due to limited availability of specialized resources. Research shows psychological education and cognitive behavioral therapy (CBT) have the greatest efficacy. However, individual differences, including acceptance of the diagnosis, therapeutic alliance, duration of symptoms, comorbidities, and access to care may influence outcomes. There is a critical need for reports that can help identify barriers to effective diagnosis and treatment. We present the diagnosis and treatment of a woman who visited the emergency room after an attack of predominant left-sided paralysis, speech dysfunction and altered awareness. Following multiple daily episodes and visits to multiple medical practitioners, testing led to a diagnosis of functional seizures. While the patient was recommended to undergo a variety of therapeutic interventions, including CBT, she ultimately terminated treatment. In a subsequent interview, the patient revealed her personal experience with perceived limitations of acute management strategies. We explore the complexities of diagnosing and treating individuals with functional seizures

All-Cellulose-Based Quasi-Solid-State Sodium-Ion Hybrid Capacitors Enabled by Structural Hierarchy

Na-ion hybrid capacitors consisting of battery-type anodes and capacitor-style cathodes are attracting increasing attention on account of the abundance of sodium-based resources as well as the potential to bridge the gap between batteries (high energy) and supercapacitors (high power). Herein, hierarchically structured carbon materials inspired by multiscale building units of cellulose from nature are assembled with cellulose-based gel electrolytes into Na-ion capacitors. Nonporous hard carbon anodes are obtained through the direct thermal pyrolysis of cellulose nanocrystals. Nitrogen-doped carbon cathodes with a coral-like hierarchically porous architecture are prepared via hydrothermal carbonization and activation of cellulose microfibrils. The reversible charge capacity of the anode is 256.9 mAh g−1 when operating at 0.1 A g−1 from 0 to 1.5 V versus Na+/Na, and the discharge capacitance of cathodes tested within 1.5 to 4.2 V versus Na+/Na is 212.4 F g−1 at 0.1 A g−1. Utilizing Na+ and ClO4− as charge carriers, the energy density of the full Na-ion capacitor with two asymmetric carbon electrodes can reach 181 Wh kg−1 at 250 W kg−1, which is one of the highest energy devices reported until now. Combined with macrocellulose-based gel electrolytes, all-cellulose-based quasi-solid-state devices are demonstrated possessing additional advantages in terms of overall sustainability

Poxviruses and paramyxoviruses use a conserved mechanism of STAT1 antagonism to inhibit interferon signaling.

The induction of interferon (IFN)-stimulated genes by STATs is a critical host defense mechanism against virus infection. Here, we report that a highly expressed poxvirus protein, 018, inhibits IFN-induced signaling by binding to the SH2 domain of STAT1, thereby preventing the association of STAT1 with an activated IFN receptor. Despite encoding other inhibitors of IFN-induced signaling, a poxvirus mutant lacking 018 was attenuated in mice. The 2.0 Å crystal structure of the 018:STAT1 complex reveals a phosphotyrosine-independent mode of 018 binding to the SH2 domain of STAT1. Moreover, the STAT1-binding motif of 018 shows similarity to the STAT1-binding proteins from Nipah virus, which, similar to 018, block the association of STAT1 with an IFN receptor. Overall, these results uncover a conserved mechanism of STAT1 antagonism that is employed independently by distinct virus families

<i>Grafting from</i> versus <i>Grafting to</i> Approaches for the Functionalization of Graphene Nanoplatelets with Poly(methyl methacrylate)

Graphene nanoplatelets (GNP) were exfoliated using a nondestructive chemical reduction method and subsequently decorated with polymers using two different approaches: <i>grafting from</i> and <i>grafting to</i>. Poly­(methyl methacrylate) (PMMA) with varying molecular weights was covalently attached to the GNP layers using both methods. The grafting ratios were higher (44.6% to 126.5%) for the <i>grafting from</i> approach compared to the <i>grafting to</i> approach (12.6% to 20.3%). The products were characterized using thermogravimetric analysis–mass spectrometry (TGA-MS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The g<i>rafting from</i> products showed an increase in the grafting ratio and dispersibility in acetone with increasing monomer supply; on the other hand, due to steric effects, the <i>grafting to</i> products showed lower absolute grafting ratios and a decreasing trend with increasing polymer molecular weight. The excellent dispersibility of the <i>grafting from</i> functionalized graphene, 900 μg/mL in acetone, indicates an increased compatibility with the solvent and the potential to increase graphene reinforcement performance in nanocomposite applications

Operando visualisation of battery chemistry in a sodium-ion battery by 23Na magnetic resonance imaging

© 2020, The Author(s). Sodium-ion batteries are a promising battery technology for their cost and sustainability. This has led to increasing interest in the development of new sodium-ion batteries and new analytical methods to non-invasively, directly visualise battery chemistry. Here we report operando 1H and 23Na nuclear magnetic resonance spectroscopy and imaging experiments to observe the speciation and distribution of sodium in the electrode and electrolyte during sodiation and desodiation of hard carbon in a sodium metal cell and a sodium-ion full-cell configuration. The evolution of the hard carbon sodiation and subsequent formation and evolution of sodium dendrites, upon over-sodiation of the hard carbon, are observed and mapped by 23Na nuclear magnetic resonance spectroscopy and imaging, and their three-dimensional microstructure visualised by 1H magnetic resonance imaging. We also observe, for the first time, the formation of metallic sodium species on hard carbon upon first charge (formation) in a full-cell configuration

Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes

Graphene-related materials are promising supports for electrocatalysts due to their stability and high surface area. Their innate surface chemistries can be controlled and tuned via functionalisation to improve the stability of both the carbon support and the metal catalyst. Functionalised graphenes were prepared using either aryl diazonium functionalisation or non-destructive chemical reduction, to provide groups adapted for platinum deposition. XPS and TGA-MS measurements confirmed the presence of polyethyleneglycol and sulfur-containing functional groups, and provided consistent values for the extent of the reactions. The deposited platinum nanoparticles obtained were consistently around 2 nm via reductive chemistry and around 4 nm via the diazonium route. Although these graphene-supported electrocatalysts provided a lower electrochemical surface area (ECSA), functionalised samples showed enhanced specific activity compared to a commercial platinum/carbon black system. Accelerated stress testing (AST) showed improved durability for the functionalised graphenes compared to the non-functionalised materials, attributed to edge passivation and catalyst particle anchoring