Fluorinated graphene oxide for enhanced S and X-band microwave absorption

Here we report the microwave absorbing properties of three graphene derivatives, namely, graphene oxide (GO), fluorinated GO (FGO, containing 5.6 at. % Fluorine (F)), and highly FGO (HFGO, containing 23 at. % F). FGO is known to be exhibiting improved electrochemical and electronic properties when compared to GO. Fluorination modifies the dielectric properties of GO and hence thought of as a good microwave absorber. The dielectric permittivities of GO, FGO, and HFGO were estimated in the S (2 GHz to 4 GHz) and X (8 GHz to 12 GHz) bands by employing cavity perturbation technique. For this, suspensions containing GO/FGO/HFGO were made in N-Methyl Pyrrolidone (NMP) and were subjected to cavity perturbation. The reflection loss was then estimated and it was found that −37 dB (at 3.2 GHz with 6.5 mm thickness) and −31 dB (at 2.8 GHz with 6 mm thickness) in the S band and a reflection loss of −18 dB (at 8.4 GHz with 2.5 mm thickness) and −10 dB (at 11 GHz with 2 mm thickness) in the X band were achieved for 0.01 wt. % of FGO and HFGO in NMP, respectively, suggesting that these materials can serve as efficient microwave absorbers even at low concentrations

Low-density Three-dimensional Foam Using Self-reinforced Hybrid Two-dimensional Atomic Layers

Low-density nanostructured foams are often limited in applications due to their low mechanical and thermal stabilities. Here we report an approach of building the structural units of three-dimensional (3D) foams using hybrid two-dimensional (2D) atomic layers made of stacked graphene oxide layers reinforced with conformal hexagonal boron nitride (h-BN) platelets. The ultra-low density (1/400 times density of graphite) 3D porous structures are scalably synthesized using solution processing method. A layered 3D foam structure forms due to presence of h-BN and significant improvements in the mechanical properties are observed for the hybrid foam structures, over a range of temperatures, compared with pristine graphene oxide or reduced graphene oxide foams. 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Modelling Effects of Tariff Liberalisation on India’s Key Export Sectors: Analysis of the EU–India Free Trade Agreement

Trade agreements are increasingly being negotiated between developed and emerging economy partners. An example is the EU–India Free Trade Agreement (FTA) for which negotiations began in 2007. There has been a debate on the potential effects of the proposed FTA and how this can impact on India’s key export sectors. Our study addresses this aspect from a global computable general equilibrium (CGE) modelling perspective. Using the Global Trade Analysis Project (GTAP) framework, we analyse trade and welfare impacts of the proposed FTA between the EU and India. Two scenarios are modelled: first, complete and immediate elimination of tariff on all goods traded and second, selective tariff elimination on textiles, wearing apparel and leather goods—products in which India has a comparative advantage. Results under both scenarios show that India enjoys positive welfare effects though there is a possibility of trade diversion. Under scenario 1, India loses due to a negative terms of trade (ToT) effect. Under scenario 2, with selective sectoral liberalisation, gains are mainly concentrated in the textiles, wearing apparel and leather sectors. There is a positive output effect from change in demand for factors of production, suggesting that the proposed FTA could lead to relocation of labour-intensive production to India

Immune checkpoint blockade reprograms systemic immune landscape and tumor microenvironment in obesity-associated breast cancer

Immune checkpoint blockade (ICB) has improved outcomes in some cancers. A major limitation of ICB is that most patients fail to respond, which is partly attributable to immunosuppression. Obesity appears to improve immune checkpoint therapies in some cancers, but impacts on breast cancer (BC) remain unknown. In lean and obese mice, tumor progression and immune reprogramming were quantified in BC tumors treated with anti-programmed death-1 (PD-1) or control. Obesity augments tumor incidence and progression. Anti-PD-1 induces regression in lean mice and potently abrogates progression in obese mice. BC primes systemic immunity to be highly responsive to obesity, leading to greater immunosuppression, which may explain greater anti-PD-1 efficacy. Anti-PD-1 significantly reinvigorates antitumor immunity despite persistent obesity. Laminin subunit beta-2 (Lamb2), downregulated by anti-PD-1, significantly predicts patient survival. Lastly, a microbial signature associated with anti-PD-1 efficacy is identified. Thus, anti-PD-1 is highly efficacious in obese mice by reinvigorating durable antitumor immunity

Improved heterogeneous electron transfer kinetics of fluorinated graphene derivatives

Though graphitic carbons are commercially available for various electrochemical processes, their performance is limited in terms of various electrochemical activities. Recent experiments on layered carbon materials, such as graphene, demonstrated an augmented performance of these systems in all electrochemical activities due to their unique electronic properties, enhanced surface area, structure and chemical stabilities. Moreover, flexibility in controlling electronic, as well as electrochemical activities by heteroatom doping brings further leverage in their practical use. Here, we study the electron transfer kinetics of fluorinated graphene derivatives, known as fluorinated graphene oxide (FGO) and its reduced form, RFGO. Enhanced electron transfer kinetics (heterogeneous electron transfer (HET)) is observed from these fluorinated systems in comparison to their undoped systems such as graphene oxide (GO) and reduced GO. A detailed study has been conducted using standard redox probes and biomolecules revealing the enhanced electro-catalytic activities of FGO and RFGO, and electron transfer rates are simulated theoretically. This study reveals that fluorine not only induces defects in graphitic lattice leading to an enhanced HET process but also can modify the electronic structure of graphene surfac

The improved electrochemical performance of cross-linked 3D graphene nanoribbon monolith electrodes

Technical advancement in the field of ultra-small sensors and devices demands the development of novel micro- or nano-based architectures. Here we report the design and assembly of cross-linked three dimensional graphene nanoribbons (3D GNRs) using solution based covalent binding of individual 2D GNRs and demonstrate its electrochemical application as a 3D electrode. The enhanced performance of 3D GNRs over individual 2D GNRs is established using standard redox probes – [Ru(NH3)6]3+/2+, [Fe(CN)6]3−/4− and important bio-analytes – dopamine and ascorbic acid. 3D GNRs are found to have high double layer capacitance (2482 μF cm−2) and faster electron transfer kinetics; their exceptional electrocatalytic activity towards the oxygen reduction reaction is indicative of their potential over a wide range of electrochemical applications. Moreover, this study opens a new platform for the design of novel point-of-care devices and electrodes for energy device

Electric field induced transformation of carbon nanotube to graphene nanoribbons using Nafion as a solid polymer electrolyte

We report a remarkable transformation of multiwalled carbon nanotubes (MWCNTs, average diameter 40 nm) to graphene nanoribbons (GNRs) in response to a field gradient of 25 V/cm, in a sandwich configuration using a solid state proton conducting polymer electrolyte like a thin perfluorosulphonated membrane, Nafion. In response to the application of a constant voltage for a sustained period of about 24 h at both room temperature and elevated temperatures, an interesting transformation of MWCNTs to GNRs has been observed with reasonable yield. GNRs prepared by this way are believed to be better for energy storage applications due to their enhanced surface area with more active smooth edge planes. Moreover, possible morphological changes in CNTs under electric field can impact on the performance and long term stability of devices that use CNTs in their electronic circuitr

Above 170 degree water contact angle and oleophobicity of fluorinated graphene oxide based transparent polymeric films

Understanding and tuning the wettability of the surfaces are highly intriguing for various applications. The development of stable and transparent coatings over aluminium alloys and glass substrates for making them superhydrophobic and extended oleophobic (lower to the surface tension of 33.4 mN/m (coconut oil)) using a scalable and simple spray painting technique is demonstrated. Fluorinated graphene oxide (FGO, fluorine content of 34.4 atomic weight %), an atomically layered material, modified Polydimethylsiloxane (PDMS) polymer composite is used as the paint for the coatings. The coated filmswere studied for their surface and compositional features. A water contact angle (CA) of 173.7 degree (close to the highest ever reported water CA, 175degree) is achieved with 60 wt% FGO in PDMS, and the same showing a CA of 94.9degree with coconut oil, in conjunction with a low contact angle hysteresis (4degree). The work of adhesion with the amount of FGO is studied and the surface energy of FGO containing paints is calculated and compared with the bare paints using Zisman plot analysi

Selective and efficient electrochemical biosensing of ultrathin molybdenum disulfide sheets

Atomically thin molybdenum disulfide (MoS2) sheets were synthesized and isolated via solventassisted chemical exfoliation. The charge-dependent electrochemical activities of these MoS2 sheets were studied using positively charged hexamine ruthenium (III) chloride and negatively charged ferricyanide/ferrocyanide redox probes. Ultrathin MoS2 sheet-based electrodes were employed for the electrochemical detection of an important neurotransmitter, namely dopamine (DA), in the presence of ascorbic acid (AA). MoS2 electrodes were identified as being capable of distinguishing the coexistence of the DA and the AA with an excellent stability. Moreover, the enzymatic detection of the glucose was studied by immobilizing glucose oxidase on the MoS2. This study opens enzymatic and non-enzymatic electrochemical biosensing applications of atomic MoS2 sheets, which will supplement their established electronic application

Molecular Motions Aided Thermally Responsive Biocompatible Textile Pads

Development of smart and intelligent textiles (fabrics) is sought after for tremendous applications ranging from textile industries to robotic engineering. [1–5] Synergy of textile chemistry and polymer engineering can leads to the development of such smart and functional composite materials. Moreover, such a synergy can also bring mechanical fl exibility, strength and thermal stability to the designed fabrics. Thermally responsive polymer (TRP) composites are one such class of materials where the polymers can respond to external thermal stimuli causing molecular level global or local dimensional changes. Different types of TRPs in the forms of solution (liquid), fi bres, foams, and fi lms were demonstrated in the recent past. [6–8] Dimensional changes happening in these TRPs can be incorporated to the fabrics for making smart woven and nonwoven textiles