Search

Lithium-ion batteries with aqueous electrolytes have substantial safety and cost benefits over the flammable, expensive and moisture sensitive organic electrolytes used in current batteries. However aqueous batteries suffer in terms of a reduced electrochemical stability window and offer much lower energy and power densities relative to batteries with organic electrolytes. Here we report that the use of niobium tungsten oxide anodes in conjunction with lithium manganese oxide cathodes and water-in-salt electrolytes, enables aqueous lithium-ion batteries with outstanding volumetric capacity and rate capability. Our battery could be cycled stably with high coulombic efficiency and a volumetric capacity of ~200 Ah l−1 was observed at 1C rate, which is much higher than state-of-art graphite (50–110 Ah l−1). Moreover, the battery could be cycled at high rates – increasing the charge/discharge rate by an order of magnitude (0.5C–5C) resulted in only about 25% reduction in capacity. The volumetric energy and power density of our full-cell device is far superior to what was been reported for “aqueous” lithium-ion batteries and is attributed to the dense-packing of micron size niobium tungsten oxide particles in the anode, as well as the abundance of tunnels within the particles that allow fast diffusion of lithium ions. The facile synthesis, ease of handling, safety (non-flammable nature) and high-performance, makes aqueous lithium-ion batteries with niobium tungsten oxide anodes an attractive alternative to traditional batteries, especially in applications where high volumetric energy and power density are desired.

Hotspot engineering has the potential to transform the field of surface-enhanced Raman spectroscopy (SERS) by enabling ultrasensitive and reproducible detection of analytes. However, the ability to controllably generate SERS hotspots, with desired location and geometry, over large-area substrates, has remained elusive. In this study, we sculpt artificial edges in monolayer molybdenum disulfide (MoS2) by low-power focused laser-cutting. We find that when gold nanoparticles (AuNPs) are deposited on MoS2 by drop-casting, the AuNPs tend to accumulate predominantly along the artificial edges. First-principles density functional theory (DFT) calculations indicate strong binding of AuNPs with the artificial edges due to dangling bonds that are ubiquitous on the unpassivated (laser-cut) edges. The dense accumulation of AuNPs along the artificial edges intensifies plasmonic effects in these regions, creating hotspots exclusively along the artificial edges. DFT further indicates that adsorption of AuNPs along the artificial edges prompts a transition from semiconducting to metallic behavior, which can further intensify the plasmonic effect along the artificial edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS2 surface (away from the cut edges) or along the natural (passivated) edges of the MoS2 sheet. To demonstrate the practical utility of this concept, we use our substrate to detect Rhodamine B (RhB) with a large SERS enhancement (∼104) at the hotspots for RhB concentrations as low as ∼10-10 M. The single-step laser-etching process reported here can be used to controllably generate arrays of SERS hotspots. As such, this concept offers several advantages over previously reported SERS substrates that rely on electrochemical deposition, e-beam lithography, nanoimprinting, or photolithography. Whereas we have focused our study on MoS2, this concept could, in principle, be extended to a variety of 2D material platforms.

Exploring efficient electrocatalysts for lithium-sulfur (Li-S) batteries is of great significance for the sulfur/polysulfide/sulfide multiphase conversion. Herein, we report nickel-iron intermetallic (Ni3Fe) as a novel electrocatalyst to trigger the highly efficient polysulfide-involving surface reactions. The incorporation of iron into the cubic nickel phase can induce strong electronic interaction and lattice distortion, thereby activating the inferior Ni phase to catalytically active Ni3Fe phase. Kinetics investigations reveal that the Ni3Fe phase promotes the redox kinetics of the multiphase conversion of Li-S electrochemistry. As a result, the Li-S cells assembled with a 70 wt % sulfur cathode and a Ni3Fe-modified separator deliver initial capacities of 1310.3 mA h g-1 at 0.1 C and 598 mA h g-1 at 4 C with excellent rate capability and a long cycle life of 1000 cycles at 1 C with a low capacity fading rate of ∼0.034 per cycle. More impressively, the Ni3Fe-catalyzed cells exhibit outstanding performance even at harsh working conditions, such as high sulfur loading (7.7 mg cm-2) or lean electrolyte/sulfur ratio (∼6 μL mg-1). This work provides a new concept on exploring advanced intermetallic catalysts for high-rate and long-life Li-S batteries.

Iron-based alloys that are ubiquitously used in industrialized societies are prone to corrosion which results in large maintenance and repair costs. Here we design maleic-anhydride-functionalized graphene nanofillers to enhance corrosion resistance of epoxy coating (MAGE) on mild steel surfaces, with a corrosion protection efficiency of 99.9%. A mechanochemical approach based on Diels-Alder reaction was used to synthesize graphene nanofillers and functionalize them with difunctional bisphenol A/epichlorohydrin epoxy. The MAGE coating increased corrosion resistance of steel by 9–10 orders of magnitude compared to bare metal in both abiotic (3.5% NaCl) and aggressive microbial (sulfate-reducing bacteria, SRB) environments. Compared to unfunctionalized graphene nanoplatelets, the MAGE coating offered four orders of magnitude lower corrosion resistance against planktonic SRB cells, 80% lower against sessile SRB cells, and 19-fold lower against 3.5% NaCl. The unique functional groups in maleic-anhydride-graphene adducts enabled their dispersion in epoxy coating and enhanced its mechanical properties. The high corrosion resistance of MAGE in diverse environments is attributed its outstanding ability to block the intercalation of corrosive species.

Solar-driven water evaporation has been proposed as a renewable and sustainable strategy for the generation of clean water from seawater or wastewater. To enable such technologies, development of photothermal materials that enable efficient solar steam generation is essential. The current challenge is to manufacture such photothermal materials cost-effectively and at scale. Furthermore, the photothermal materials should be strongly hydrophilic and environmentally stable. Herein, we demonstrate facile and scalable fabrication of carbon nanotube (CNT)-based photothermal nanocomposite foam by igniting an ethanol solution of ferric acetylacetonate [Fe(acac)3] absorbed within nickel (Ni) foam under ambient conditions. The Fe(acac)3 precursor provides carbon and the zero-valent iron catalyst for growing CNTs on the Ni foam, while ethanol facilitates the dispersion of Fe(acac)3 on the Ni foam and supplies heat energy for the growth of CNTs by its burning. A forest of dense and uniform CNTs decorated with Fe2O3 nanoparticles is generated within seconds. The resultant Fe2O3/CNT/Ni nanocomposite foam exhibits "superhydrophilicity" and high light absorption capacity, ensuring rapid transport and fast evaporation of water within the entire foam. Efficient light-to-heat conversion causes the surface temperature of the foam to reach ∼83.1 °C under 1 sun irradiation. The average water evaporation rates of such foam are as high as ∼1.48 and ∼4.27 kg m-2 h-1 with light-to-heat conversion efficiencies of ∼81.3 and ∼93.8% under 1 sun and 3 sun irradiation, respectively. Moreover, the versatile and scalable combustion synthesis strategy presented here can be realized on various substrates, exhibiting high adaptability for different applications.

Leishmania is an obligate intracellular protozoan parasite, which resides in human macrophage vacuoles that are referred to as parasitophorus vacuoles. Amphotericin B (AmB) is the first-line drug with 99% cure rates; however, overdose-induced toxic side effects are a major limitation. To improve the efficacy at lower dose and subsequently to avoid toxicity and to further investigate the role of charge dynamics on the efficacy, a graphene oxide (GO)-based composite of AmB was developed with native negatively charged GO and amine-conjugated positively charged AGO. The AGO composite resulted in enhanced uptake as confirmed by confocal and FACS analysis. Thus, AGO caused a strong inhibition of amastigotes, with IC50 values 5-fold lower than free AmB. The parasitophorus vacuoles harbour a hydrolytic and acidic environment, which is favourable for the parasites, as they don't attenuate this condition. AGO–AmB was able to modify the intracellular pH of the Leishmania donovani-infected macrophages, generating unfavourable conditions for the amastigote, and thus improving its efficacy.

The field of chemical (gas) sensing has witnessed an unprecedented increase in device sensitivity with single molecule detection now becoming a reality. In contrast to this, the ability to distinguish or discriminate between gas species has lagged behind. This is problematic and results in a high rate of false alarms. Here, we demonstrate a short period sinusoidal thermal modulation strategy to quantitatively and rapidly identify two industrially relevant gases (hydrogen sulfide (H2S) and sulfur dioxide (SO2)) by using a single semiconducting metal oxide sensor device. By applying sinusoidal heating voltages with a fixed short period, we were able to simultaneously obtain distinct patterns of dynamic responses. These characteristic patterns were adopted to build and validate a gas recognition library. Our approach does not rely on large-scale sensor arrays and complex algorithms and is amenable for real-time and low-power gas monitoring.

High specific capacity materials that can store potassium (K) are essential for next-generation K-ion batteries. One such candidate material is phosphorene (the 2D allotrope of phosphorus (P)), but the potassiation capability of phosphorene has not yet been established. Here we systematically investigate the alloying of few-layer phosphorene (FLP) with K. Unlike lithium (Li) and sodium (Na), which form Li3P and Na3P, FLP alloys with K to form K4P3, which was confirmed by ex situ X-ray characterization as well as density functional theory calculations. The formation of K4P3 results in high specific capacity (∼1200 mAh g-1) but poor cyclic stability (only ∼9% capacity retention in subsequent cycles). We show that this capacity fade can be successfully mitigated by the use of reduced graphene oxide (rGO) as buffer layers to suppress the pulverization of FLP. We studied the performance of rGO and single-walled carbon nanotubes (sCNTs) as buffer materials and found that rGO being a 2D material can better encapsulate and protect FLP relative to 1D sCNTs. The half-cell performance of FLP/rGO could also be successfully reproduced in a full-cell configuration, indicating the possibility of high-performance K-ion batteries that could offer a sustainable and low-cost alternative to Li-ion technology.

Silicon shows potential as an anode material in lithium ion batteries due to its high specific capacity, yet its considerable volume expansion during lithiation leads to fracture and pulverization. Unfortunately, neither the atomic-level structural evolution, nor the mechanical behavior of the anode during lithiation and delithiation cycles is well understood. Interestingly, the lithiation process of a-Si provides an interesting continuum from open-structured network glass to densely-packed atomic glass, which could be used to obtain useful insights regarding commonalities in glasses. Here atomic level simulation has been used to investigate one cycle of lithiation and delithiation of amorphous silicon electrode, using Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The atomic level structural transformation and damage accumulation of the anode during cycling has been systematically analyzed, as well as their mechanical responses in compact tension tests. There appears to be a ductile-brittle-ductile transition for the amorphous silicon anode during both the lithiation and delithiation cycle. In other words, amorphous silicon is particularly vulnerable at intermediate lithiation. The fracture behavior of lithiated silicon was found to correlate to the Poisson's ratio, due to variations in bond covalency and structural disorder.

Over the past few decades, lithium ion batteries (LIBs) have dominated the rechargeable battery landscape. These LIBs are based on the rocking chair concept, where Lithium (Li) - ions shuttle between electrodes that behave as hosts for the ions during charge and discharge. Lithium metal, with a theoretical specific capacity of 3860 mAh g−1 is the ideal choice for the anode in a Li battery. However, the utilization of Li metal as the anode has been plagued by the inevitable formation of dendrites on electrochemical cycling (i.e., plating/stripping of Li). These dendrites are associated with a number of problems including irreversible capacity loss, reduced columbic efficiency, drying and degradation of the electrolyte as well as electrical shorting and thermal runaway of the battery. Here, we show that Li dendrites can be healed in situ in a Li-metal battery with a lithium iron phosphate based cathode and a Li metal anode. The healing is triggered by current-controlled, self-heating of the battery, which causes migration of surface atoms away from the dendrite tips, thereby smoothening the dendritic surface. Computational thermal modelling in conjunction with first principles density functional theory calculations are used in this study to understand the diffusion characteristics of Li atoms on the dendrite surface. Such in situ healing of Li dendrites could eliminate the risk of short circuiting and enable the safe deployment of Li-metal batteries for the next generation of high performance energy storage devices.

Unlike the vast majority of transition metal dichalcogenides which are semiconductors, vanadium disulfide is metallic and conductive. This makes it particularly promising as an electrode material in lithium-ion batteries. However, vanadium disulfide exhibits poor stability due to large Peierls distortion during cycling. Here we report that vanadium disulfide flakes can be rendered stable in the electrochemical environment of a lithium-ion battery by conformally coating them with a ~2.5 nm thick titanium disulfide layer. Density functional theory calculations indicate that the titanium disulfide coating is far less susceptible to Peierls distortion during the lithiation-delithiation process, enabling it to stabilize the underlying vanadium disulfide material. The titanium disulfide coated vanadium disulfide cathode exhibits an operating voltage of ~2 V, high specific capacity (~180 mAh g−1 @200 mA g−1 current density) and rate capability (~70 mAh g−1 @1000 mA g−1), while achieving capacity retention close to 100% after 400 charge−discharge steps., VS2 is a promising cathode material for lithium-ion batteries, but is susceptible to Peierls distortion during (de)lithiation. Here the authors show that VS2 cathodes can be stabilized by conformally coating them with a nanoscale TiS2 protective layer, leading to impressive electrochemical performance.

Flexible pressure sensors still face a great challenge to combine fast frequency response, wide pressure range, multiple detection modes, satisfactory mechanical and environmental stability, and simple fabrication process into a sensor. Herein, flexible piezoresistive pressure sensors are fabricated by treating the backbone of polyurethane (PU) sponge with chitosan (CS) to obtain positively charged CS@PU sponge, followed by dip-coating of negatively charged Ti3C2Tx MXene sheets. The resulting MXene@CS@PU sponge-based sensor provides a versatile sensing platform with potentials for detecting both small and large pressure signals. Due to the highly compressive resilience of the PU sponge and its polar interaction with the MXene sheets, the MXene@CS@PU sensor has high compressibility and stable piezoresistive response for compressive strains of up to 85% with a stress of 245.7 kPa, and it also exhibits a satisfactory reproducibility for 5000 compression-release cycles. Even after washing in water for 1 h, the sensor still shows good performances. With a rapid response time of only 19 ms and a low detection limit of 30 μN corresponding to a pressure of 9 Pa, the MXene sponge sensor is promising for detecting human physiological signals and insect movements. In addition to the contact mode detection, the sponge sensor could detect voices and human breaths by a non-contact detection mode.

Because microbes use carotenoids as an antioxidant for protection, dietary carotenoids could be associated with gut microbiota composition. We aimed to determine associations among reported carotenoid intake, plasma carotenoid concentrations, and fecal bacterial communities in pregnant women. Pregnant women (n = 27) were enrolled in a two-arm study designed to assess feasibility of biospecimen collection and delivery of a practical nutrition intervention. Plasma and fecal samples were collected and women were surveyed with a 24-hr dietary checklist and recalls. Plasma carotenoids were analyzed by HPLC using photodiode array detection. Fecal bacteria were analyzed by 16S rRNA DNA sequencing. Results presented are cross-sectional from the 36-week gestational study visit combined across both study arms due to lack of significant differences between intervention and usual care groups (n = 23 women with complete data). Recent intake of carotenoid-containing foods included carrots, sweet potatoes, mangos, apricots, and/or bell peppers for 48% of women; oranges/orange juice (17%); egg (39%); tomato/tomato-based sauces (52%); fruits (83%); and vegetables (65%). Average plasma carotenoid concentrations were 6.4 µg/dL α-carotene (AC), 17.7 µg/dL β-carotene (BC), 11.4 µg/dL cryptoxanthin, 39.0 µg/dL trans-lycopene, and 29.8 µg/dL zeaxanthin and lutein. AC and BC concentrations were higher in women who recently consumed foods high in carotenoids. CR concentrations were higher in women who consumed oranges/orange juice. Microbiota α-diversity positively correlated with AC and BC. Microbiota β-diversity differed significantly across reported intake of carotenoid containing foods and plasma concentrations of AC. This may reflect an effect of high fiber or improved overall dietary quality, rather than a specific effect of carotenoids. PRACTICAL APPLICATION: Little is known about the association between the gut microbiome and specific dietary microconstituents, such as carotenoids, especially during pregnancy. This research demonstrates that a carotenoid-rich diet during pregnancy supports a diverse microbiota, which could be one mechanism by which carotenoids promote health.

Deficiencies of sulfur cathode including polysulfide shuttling and poor redox kinetics severely limit cycling performance of lithium-sulfur (Li-S) batteries. Herein, we have designed a binary host featuring highly sulfiphilic Ni-Fe bimetallic oxide (NiFe2O4) nanoparticles anchored on carbon nanotubes for Li-S batteries. NiFe2O4 nanoparticles provide highly sulfiphilic sites to confine lithium polysulfides by the formation of Li-O and S-O bonds, and act as an electrocatalyst to promote the conversion of polysulfides. The carbon nanotubes play an important synergistic role by providing efficient electron conduction pathways and preventing agglomeration of the catalyst. As a result, the sulfur cathode enables stable cycling with a very low capacity fade rate (∼0.029% per cycle upon 1000 cycles) at 1.0 C and a reversible capacity of ∼550 mAh g−1 at 5.0 C. Further, the superior cycling stability could be retained even for high sulfur loading of ∼5.0 mg cm−2. The development of such hybrid electrodes comprised of bimetallic oxides supported on carbon nanotubes could help realize long-lasting and stable Li–S batteries.

Background: Urolithiasis is the third common disorder of the urinary system affecting 10–15% of the general population. In recent years, search for new antilithiatic drugs from natural sources has assumed greater importance. Objectives: This study was performed to investigate the anti-urolithiatic activity of methanolic extract of Duranta erecta leaves by in vitro and in vivo analysis. Materials and methods: The study was designed to determine presence of phytochemicals in D. erecta, its yield in percentage, antioxidant activity against 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and anti-microbial property against few bacteria. In vitro analysis was carried out study anti-urolithiatic property of D. erecta by nucleation assay and synthetic urine assay for inhibition of calcium oxalate and calcium oxalate monohydrate crystals formation. An in vivo experiment was performed on Wistar rats for confirmation of anti-urolithiatic property of D. erecta in animal model. Results: D. erecta has the presence of primary and secondary metabolites like glycoside, saponins, sterols, flavonoids, phenols, tannins, alkaloids, carbohydrates and proteins. Methanolic extract of D. erecta gave a very good yield (60%). D. erecta proved its antioxidant potential by 93.51% inhibition of DPPH radical at a concentration of 1000 μg/mL where ascorbic showed 94.71% of DPPH radical at the same concentration. In vitro tests like nucleation assay and synthetic urine assay showed that D. erecta inhibits formation of calcium oxalate and calcium oxalate monohydrate crystals. It also showed the anti-microbial property by formation of zone of inhibition against few bacteria. An in vivo experiment on Wistar rat animal model confirmed the anti-urolithiatic property of D. erecta L. leaves extract. Conclusions: Based on the results, we reported that D. erecta may treat calcium oxalate crystal deposition in the kidney by preventing hyperoxaluria-induced peroxidative damage to the renal tubular membrane surface (lipid peroxidation). It has anti-microbial potential so it may also inhibit the secondary bacterial infection in kidney. Based on the data, it can be concluded that this herb can be used as a potential anti-urolithiasis agent for kidney stone removal. Keywords: Antiurolithitic, Duranta erecta, Sodium oxalate, Antimicrobial, Urolithiasis

Chemiresistive sensor devices using two-dimensional (2D) materials have been extensively studied. However, so far no single material has all the desirable attributes. For example, graphene and MXenes lack a band gap, transition metal dichalcogenides (such as MoS2) lack high sensitivity, while phosphorene exhibits poor air-stability. Here we report that tellurene, a new emergent single-element 2D material, excels as a sensor for NO2 detection. Devices based on tellurene exhibit a detection limit of ∼25 ppb, large detection range (from 25 ppb to 5 ppm), baseline noise as low as ∼0.5%, and excellent “selectivity” to NO2 even in the presence of cross-contaminants such as CO, SO2, H2S, acetone and ethanol. Density functional theory calculations indicate that large adsorption energy and intense charge redistribution are the reasons for the high sensitivity and selectivity of tellurene for NO2 detection. Further, we find that “heat-pulsing” enables fast sensor response and recovery time, without damaging the tellurene sheets. Most importantly, tellurene exhibits outstanding air-stability, making it a promising candidate for next-generation chemical sensors.

The use of potassium (K) metal anodes could result in high-performance K-ion batteries that offer a sustainable and low-cost alternative to lithium (Li)-ion technology. However, formation of dendrites on such K-metal surfaces is inevitable, which prevents their utilization. Here, we report that K dendrites can be healed in situ in a K-metal battery. The healing is triggered by current-controlled, self-heating at the electrolyte/dendrite interface, which causes migration of surface atoms away from the dendrite tips, thereby smoothening the dendritic surface. We discover that this process is strikingly more efficient for K as compared to Li metal. We show that the reason for this is the far greater mobility of surface atoms in K relative to Li metal, which enables dendrite healing to take place at an order-of-magnitude lower current density. We demonstrate that the K-metal anode can be coupled with a potassium cobalt oxide cathode to achieve dendrite healing in a practical full-cell device.

Lithium sulfur (Li-S) batteries are viewed as a promising candidate for next-generation energy storage systems due to their high energy density, low cost and ease of manufacturing. However, rapid capacity decay caused by lithium polysulfide shuttle during charging/discharging processes hinder its practical application. In this work, we demonstrate a cellulose encapsulated carbon/sulfur core-shell structure for advanced Li-S batteries based on electrostatic spinning with coaxial spinnerets. Cellulose serves as an excellent “shell” due to its good ion conductivity, flexible structure to accommodate volumetric expansion of sulfur, and strong capability to prevent sulfur and its intermediate reaction products from dissolving into the electrolyte. CMK-3 mesoporous carbon in the core is helpful to confine sulfur in the pores, and improve the electrical conductivity of the fiber electrode together with the carbon black particles on the outside of the fiber. As a result, the obtained cellulose based flexible sulfur electrode delivers a high initial discharge capacity (>1200 mA h g−1), good electrochemical performance with Coulombic efficiency above 99%, and a low capacity decay rate of ~ 0.12% per cycle over 300 charging/discharging cycles.

Copper nanowires have been synthesized at different pH values through the template assisted electrodeposition technique using polycarbonate track-etch membranes as scaffolds. The effect of pH (0.8–2.8) of the electrolyte on structure, morphology, composition and deposition rate of copper into the pores of the template, while keeping other electrochemical conditions same, was investigated. X-ray diffraction analysis confirmed the face centered cubic phase of synthesized nanowires. With the change in pH, no shift in peaks was observed except the inclusion of an additional peak of copper oxide in nanowires synthesized at pH 2.8. The nanocrystallite size, strain, lattice stress and energy density were evaluated by X-ray analysis. Field emission scanning electron microscopy images revealed that nanowires obtained at pH 0.8, 1.1 and 1.4 showed incomplete deposition in the pores of the membrane whereas, the nanowires obtained at pH 1.7 were densely stacked, vertically aligned and uniform along the diameter and that obtained from pH 2.0–2.8 had overdeposition on their top. An increase in deposition rate was observed with the increase in pH value. The average diameter of Cu nanowires was found to be ~ 105 nm. The electrical conductivity of as-grown nanowires was observed to decrease 13-fold as the transition from bulk values to the nanosystem. Nanowires prepared at pH of 1.7 were characterized for their field-emission properties. A very large field-enhancement factor of ~ 10,855 was obtained indicating that Cu nanowires grown by reported technique shows outstanding potential as efficient field-emitters for flat panel displays.

A monolayer of black phosphorus (BP), also called phosphorene, is an emerging member of the family of two-dimensional (2D) materials. It has sparked a surge of research activities in material science since its first preparation by mechanical exfoliation in 2014. Several reviews have focused on the structure and anisotropic properties of phosphorene as well as its applications in transistors, batteries, and solar cells. Compared to graphene and transition metal dichalcogenides (TMDs), phosphorene possesses higher surface to volume ratio due to its “puckered” lattice structure and has presented some unique advantages in sensing applications. This review aims to summarize recent developments in the sensing applications of phosphorene, including gas sensing, humidity sensing, photo-detection, bio-sensing and ion sensing. The article concludes with the current challenges and future prospects for the production and sensing applications of phosphorene.

The present study aims to demonstrate the application of sugarcane bagasse as an excellent field emitter. Field emission property of as-pyrolyzed sugarcane bagasse (p-SBg) before and after the plasma treatment has been investigated. It has been observed that electronic nature of p-SBg transformed from semiconducting to metallic after plasma treatment. Maximum current and turn-on field defined at 10 μA/cm2 was found to be 800 μA/cm2 and 2.2 V/μm for as-pyrolyzed sugarcane bagasse (p-SBg) and 25 μA/cm2 and 8.4 V/μm for H2-plasma treated p-SBg. These values are found to be better than the reported values for graphene and activated carbon. In this report, pyrolysis of bagasse has been carried in a thermal chemical vapor deposition (Th-CVD) system in inert argon atmosphere. Scanning electron microscopy (SEM), X-ray Diffraction (XRD), High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) have been used to study the structure of both pre and post plasma-treated p-SBg bagasse’s sample. HRTEM study reveals that carbonaceous structures such as 3D-nanographene oxide (3D-NGO), graphite nanodots (GNDs), carbon nanotubes (CNTs), and carbon onions are present in both pre-treated and plasma-treated p-SBg. Hence, we envision that the performed study will be a forwarding step to facilitate the application of p-SBg in display devices.

High specific capacity anode materials such as silicon (Si) are increasingly being explored for next-generation, high performance lithium (Li)-ion batteries. In this context, Si films are advantageous compared to Si nanoparticle based anodes since in films the free volume between nanoparticles is eliminated, resulting in very high volumetric energy density. However, Si undergoes volume expansion (contraction) under lithiation (delithiation) of up to 300%. This large volume expansion leads to stress build-up at the interface between the Si film and the current collector, leading to delamination of Si from the surface of the current collector. To prevent this, adhesion promotors (such as chromium interlayers) are often used to strengthen the interface between the Si and the current collector. Here, we show that such approaches are in fact counter-productive and that far better electrochemical stability can be obtained by engineering a van der Waals "slippery" interface between the Si film and the current collector. This can be accomplished by simply coating the current collector surface with graphene sheets. For such an interface, the Si film slips with respect to the current collector under lithiation/delithiation, while retaining electrical contact with the current collector. Molecular dynamics simulations indicate (i) less stress build-up and (ii) less stress "cycling" on a van der Waals slippery substrate as opposed to a fixed interface. Electrochemical testing confirms more stable performance and much higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) as compared to conventional nickel current collectors.

Transition metal dichalcogenides (TMDs) like Molybdenum disulfide (MoS2) have extra-ordinary physical and chemical peculiarities which can be additionally modified by ion beam irradiation. In the present work, we illustrate the tailoring of MoS2 thin films by employing ion beam irradiation. Silicon ion beam with 100 MeV energy was displayed to have an apparent impact on structural, morphological and optical properties of MoS2 thin films. Sputtered (MoS2) films were irradiated with 100 MeV Si8+ ion beam with a fluence of 1E13 ions/cm2. The XRD (X-ray diffraction) validates the structural analysis of MoS2 films with hexagonal phase and reduction in the crystallinity is observed after irradiation owing to the generation of defects by high energy ion beam irradiation. MoS2 thin films display Raman modes at ⁓378 cm−1 and ⁓411 cm−1 corresponding to the one molybdenum atom and two sulfur atoms of the same layer vibrates in the converse in-plane and out-of-plane direction respectively. Intensity of Raman peaks is reduced after the employment of ion beam irradiation. Slight reduction in transmittance is observed after irradiation. The Intensity of broad PL emission spectra observed at 360 nm showed the enhancement in PL intensity after ion beam irradiation. Rutherford Backscattering Spectroscopy (RBS) substantiated the presence of Mo (Molybdenum) and Sulfur (S) elements and 440 nm thickness of the samples. The Investigation of the thickness and atomic fraction of the specimen was also governed by simulating the RBS spectrum using SIMNRA software. To demonstrate the changes occur in grain size and surface roughness parameters in ion irradiated and pristine MoS2 thin films were analyzed by AFM (Atomic Force microscopy). The alterations of binding energy of Mo 3d and S 2p region of MoS2 pristine and ion irradiated thin films were analyzed by XPS (x-ray photoelectron spectroscopy).

Single-layer rhenium disulfide (ReS2) is a unique material with distinctive, anisotropic electronic, mechanical, and optical properties and has the potential to be used as an anode in alkali-metal-ion batteries. In this work, first principles calculations were performed to systematically evaluate the potential of monolayer pristine and defective ReS2 as anodes in lithium (Li)- and sodium (Na)-ion batteries. Our calculations suggest that there are several potential adsorption sites for Li and Na on pristine ReS2, owing to its low-symmetry structure. Additionally, the adsorption of Li and Na over pristine ReS2 is very strong with adsorption energies of −2.28 and −1.71 eV, respectively. Interestingly, the presence of point defects causes significantly stronger binding of the alkali-metal atoms with adsorption energies in the range −2.98 to −3.17 eV for Li and −2.66 to −2.92 eV for Na. Re single vacancy was found to be the strongest binding defect for Li adsorption, whereas S single vacancy was found to be th...

Red phosphorus (P) shows enormous potential as a high-performance and cost-effective Lithium (Li)-ion anode material. It alloys with Li forming Li3P, which translates to a theoretical capacity of ∼2595 mAh g−1 (∼7 times better than graphite). Further, the cost of bulk P is comparable to battery-grade graphite. However, there are two intrinsic limitations that prevent deployment of P, viz., its low electrical conductivity and its high volume change on cycling that leads to pulverization and loss of electrical contact. Here, we present an approach to concurrently address both limitations. We employ electro-spraying and far-infrared reduction (FIR) to fabricate composites of P and reduced graphene oxide (rGO). The electro-spraying process enables ultra-small P particles (5–10 nm), which suppresses stress-induced pulverization and drastically reduces Li-ion diffusion distances. The low electrical conductivity of P is also not a limitation at such small particle sizes. FIR establishes carbon-phosphorous bonds that prevent surface migration and agglomeration of P, and enable efficient electron transfer between the rGO matrix and P nanoparticles. The P/rGO anode delivers outstanding specific capacity (∼1763 mAh g−1 at current density of ∼0.1 A g−1), extraordinary high-rate capability (up to ∼40 A g−1) and long cycle-life (>1000 cycles with ∼99% coulombic efficiency).

The recovery and repurposing of biomass are critically important and make a significant contribution to environmental preservation. Lignosulfonate, a by-product of the paper manufacturing industry, is an abundant low cost material with unique potential as a sulfur precursor for high performance cathode materials. In this work, we develop a practical green method of using lignosulfonate as both the donor (decomposition of sulfonic groups (–SO3H)) of sulfur and the sulfur acceptor in lignosulfonate derived activated carbon. Through a circulatory pyrolysis process with carbon activation and sulfur capture, a high surface area carbon/sulfur composite was obtained. This material was successfully developed into a cathode for a lithium–sulfur battery, which demonstrates outstanding cycling stability with a capacity decay rate as low as 0.1% per cycle over 200 cycles. When the sulfur loading was further increased to 68 wt%, the capacity still reaches as high as 1100 mA h g−1, suggesting its promising potential for applications in the field of high energy storage devices.

Despite decades of research, metallic corrosion remains a long-standing challenge in many engineering applications. Specifically, designing a material that can resist corrosion both in abiotic as well as biotic environments remains elusive. Here a lightweight sulfur-selenium (S-Se) alloy is designed with high stiffness and ductility that can serve as an excellent corrosion-resistant coating with protection efficiency of ≈99.9% for steel in a wide range of diverse environments. S-Se coated mild steel shows a corrosion rate that is 6-7 orders of magnitude lower than bare metal in abiotic (simulated seawater and sodium sulfate solution) and biotic (sulfate-reducing bacterial medium) environments. The coating is strongly adhesive, mechanically robust, and demonstrates excellent damage/deformation recovery properties, which provide the added advantage of significantly reducing the probability of a defect being generated and sustained in the coating, thus improving its longevity. The high corrosion resistance of the alloy is attributed in diverse environments to its semicrystalline, nonporous, antimicrobial, and viscoelastic nature with superior mechanical performance, enabling it to successfully block a variety of diffusing species.

Hot/cold pressing is a very common process in powder metallurgy and polymer industry, in which powders are compacted at a temperature/pressure high enough to induce sintering and creeping processes, and make the materials much denser and stronger. In this study, we extent this strategy to the synthesis of carbon nanotube (CNT) nanocomposites, yet with the high compressive stress generated naturally during the ultra-filtration process. Employing dead filtration, which is traditionally employed to extract solids from solution in water treatment process, we fabricate CNTs/PVA nanocomposites with high CNTs loading. It was found that this process not only greatly accelerates the filtration, but also generates significant in-situ pressure on the nanocomposites during its formation. Such pressure can compress the nanocomposites in-situ from the very onset of the formation of the nanocomposites and at molecular scale, which makes the nanocomposites densely compacted and eventually translates to very high mechanical properties even at high CNTs concentrations of up to ∼90 vol%. The tensile strength and Young's modulus can be increased by 435% and 859%, respectively, and the toughness is comparable with the nacre at similar content of inorganic constituent.

One of the major challenges in effective cancer chemotherapy is the severe systemic cytotoxicities of anticancer drugs on healthy tissues. The present study reports chemically modified polymeric nanocapsules (NCs) encapsulating combination of chemotherapeutic drugs Docetaxel (DTX) and Quercetin (QU) for its active targeting to prostate cancer (PCa). The active targeting was achieved by conjugating Luteinizing-hormone-releasing hormone (LHRH) ligand to poly-lactide-co-glycolide (PLGA) using polyethylene glycol (PEG) as a spacer. The structure of the conjugates was characterized and confirmed using 1H NMR and ATR-FTIR. The drug encapsulated NCs showed a homogenous size distribution with their size ranging between 120 and 150 nm, and exhibited a negative zeta potential in the range of −20 to −40 mV. The in vitro release studies highlighted the sustained drug release pattern from the respective NCs; while the PEG coating to polymeric NCs provided serum stability to the NCs. The in vitro biological evaluation of the NCs was conducted using PC-3 and LNCaP cell lines. The results of the cellular uptake studies showed a significantly higher untake of the LHRH targeted NCs, while the LHRH-targeted-PEGylated DTX: QU NCs exhibited higher caspase-3 activity. The cell viability assay results showed the enhanced cell inhibition activity of the combinatorial DTX: QU when compared to individual DTX. Further, higher cell cytotoxicity was achieved by LHRH-targeted DTX: QU NCs as compared to their free-form or non-targeted NCs. Finally, the results of in vivo tumor localization and in vivo antitumor activity studies complimented and upheld the in vitro results, demonstrating the beneficial role of PLGA-PEG-LHRH NCs encapsulating combination of DTX and QU in combating prostate cancer (PCa).

A major concern for exposed steel in structural applications is susceptibility to atmospheric corrosion. The International Organization for Standardization classifies atmospheric environments into ...

Graphene oxide (GO) is increasingly used in various applications, and the implications of this nano-sized material entering the natural environment are of great interest. GO is highly soluble in water, and its accumulation in soil could significantly alter the physical and mechanical properties of the soil. In this laboratory study, we mixed GO with a soil (clayey sand, SC) to systematically study the engineering properties and microstructure of the modified soil. The experimental results reveal that the physical and mechanical properties and microstructure of clayey sand can be significantly changed by the addition of a minute quantity of GO. The liquid limit and plasticity index of the soil steadily increased (up to a GO concentration of 0.08 wt%), whereas the plastic limit did not change significantly. The addition of GO (up to 0.08 wt%) into the soil generally decreased the soil's void ratio under a given hydrostatic consolidation pressure, while increasing its undrained shear strength. Such remarkable modifications of soil by minute amounts of GO can be attributed to the extremely high specific surface area of GO and its stable dispersion in water.

Lithium–sulfur (Li S) battery, as a high energy-density storage system, has attracted great attention for next generation rechargeable battery applications. However, the fast capacity decay caused by lithium polysulfides (LiPSs) dissolution impedes its prospect for commercialization. In this work, nitrogen-doped graphene, as a chemical immobilizer, was designed to bind LiPSs and stabilize sulfur in the cathode for high performance Li S batteries. The incorporated nitrogen dopants in the graphene network were found to have a strong binding effect on the LiPSs to improve electrochemical stability and promote fast electrochemical reaction kinetics. As a result, the nitrogen doped graphene-based sulfur electrode could deliver an initial capacity of ∼1200 mAh g−1 at 0.3 A g−1, and exhibit good capacity retention with only 0.05% capacity decay per cycle after 300 cycles at 0.75 A g−1.

Transition-metal dichalcogenide (TMD) nanolayers show potential as high-performance catalysts in energy conversion and storage devices. Synthetic TMDs produced by chemical-vapor deposition (CVD) methods tend to grow parallel to the growth substrate. Here, we show that with the right precursors and appropriate tuning of the CVD growth conditions, ReS2 nanosheets can be made to orient perpendicular to the growth substrate. This accomplishes two important objectives; first, it drastically increases the wetted or exposed surface area of the ReS2 sheets, and second, it exposes the sharp edges and corners of the ReS2 sheets. We show that these structural features of the vertically grown ReS2 sheets can be exploited to significantly improve their performance as polysulfide immobilizers and electrochemical catalysts in lithium-sulfur (Li-S) batteries and in hydrogen evolution reactions (HER). After 300 cycles, the specific capacity of the Li-S battery with vertical ReS2 catalyst is retained above 750 mA h g(-1), with only ∼0.063% capacity decay per cycle, much better than the baseline battery (without ReS2), which shows ∼0.184% capacity decay per cycle under the same test conditions. As a HER catalyst, the vertical ReS2 provides very small onset overpotential (100 mV) and an exceptional exchange-current density (∼67.6 μA/cm(2)), which is vastly superior to the baseline electrode without ReS2.

We report on a novel technique to enhance the thermal conductivity of epoxy nanocomposites using graphene coated poly-methyl-methacrylate (PMMA) balls. PMMA balls with a diameter in the range of 200–300 nm were synthesized using suspension polymerization. These balls were coated with chemically reduced graphene oxide to form a core–shell additive and dispersed in epoxy. Thermal conductivity measurements of bulk samples of graphene-coated PMMA (GPMMA) epoxy nanocomposite were carried out and compared with baseline samples comprised of graphene nanosheets (not in the core–shell form) dispersed in the epoxy resin. Results show that the addition of 1% (by weight) GPMMA balls increases thermal conductivity by 7-fold. By contrast, the addition of 1% (by weight) of graphene nanosheets (not in the core–shell form) only improves thermal conductivity of the nanocomposite by approximately 3-fold. We attribute this improvement in thermal performance to more uniform dispersion and improved phonon conduction pathways for the GPMMA core–shell additive.

2D materials have been extensively studied due to their unique optical and electronic properties. Compositional doping in these materials could further enable useful utilization of these materials in electronics, optoelectronics and energy harvesting. However, scalable one pot synthesis of doped Transition Metal Dichalcogenides (TMDs) has been challenging. Here we develop a facile approach for controlled one step Rhenium (Re) doping in multilayer Molybdenum Disulphide (MoS2) by powder Chemical Vapor Deposition (CVD). Interestingly, we find the morphology of MoS2 is also dependent on the dopant concentrations with a flower like morphology observed at higher doping concentrations. Further we demonstrate a clear correlation between the shift in PL and Raman peaks as a function of Re doping concentrations. A red shift in PL is observed with increased concentration of Re atoms. The ability to controllably dope thin layers of MoS2 could open up unique applications of this material in areas hitherto unexplored.

Utilizing lithium (Li) metal as the anode can enable lithium metal battery (LMB) systems to achieve energy densities of up to 1150 Wh Kg−1, approaching that of gasoline. However, the use of Li metal is plagued with a whole host of problems, the most serious of which is the issue of nucleation of Li metal dendrites. These dendrites grow inexorably on charge–discharge cycling, piercing through the battery separator membrane and eventually electrically shorting the battery. This can result in thermal runaway leading to an unacceptable fire hazard. In this review article, we focus on recent advances in mitigating, suppressing, and healing Li metal dendrites in LMBs with liquid electrolytes. We discuss a whole host of exciting approaches including electrolyte engineering, interface engineering, the use of stable Li hosts, homogenizing Li-ion flux, and the physical healing of dendrites using temperature fields. We discuss the pros and cons of these approaches and provide our perspectives for future research directions. In particular, it is important to consider dendrite mitigation in a full-cell setting and with a realistic form factor such as prismatic or cylindrical cells. Given the multifaceted nature of the dendrite challenge, it is unlikely that there is a single magic solution, making it necessary to explore a combination of strategies to work in synergy to make Li metal anodes viable in commercial systems.

Organic-inorganic halide perovskites are intrinsically unstable when exposed to moisture and/or light. Additionally, the presence of lead in many perovskites raises toxicity concerns. Herein is reported a thin film of BaZrS3, a lead-free chalcogenide perovskite. Photoluminescence and X-ray diffraction measurements show that BaZrS3 is far more stable than methylammonium lead iodide (MAPbI3) in moist environments. Moisture- and light-induced degradations in BaZrS3 and MAPbI3 are compared by using simulations and calculations based on density functional theory. The simulations reveal drastically slower degradation in BaZrS3 due to two factors - weak interaction with water, and very low rates of ion migration. BaZrS3 photo-detecting devices with photo-responsivity of ~46.5 mA W-1 are also reported. The devices retain ~60% of their initial photo-response after 4 weeks in ambient conditions. Similar MAPbI3 devices degrade rapidly and show ~95% decrease in photo-responsivity in just 4 days. The findings establish the superior stability of BaZrS3 and strengthen the case for its use in optoelectronics. New possibilities for thermoelectric energy conversion using these materials are also demonstrated.

Graphene oxide (GO) slurries were deposited onto copper foil for use in lithium-ion battery anodes to determine the best deposition method(s) for research or high-volume manufacturing. Four deposition methods were tested: doctor blade, Mayer rod, slot die, and low volume low pressure (LVLP) spray. Analytical models that link tooling and process characteristics to mass flow rate of slurry and the resulting dry deposition height are developed and validated experimentally. While all methods successfully produced functioning batteries, a number of different qualitative and quantitative metrics from experimental results identified the best method for both situations. Observations were recorded on adhesion, deposition consistency, usability, and cleanability. Data on specific discharge capacity were recorded to show performance over the anode lifetime and at different charge/discharge rates. The data indicate that anodes produced using reduced graphene oxide (rGO) deliver a specific charge storage capacity of 50 to 400 mAh/g at charge–discharge rates of 1 C to 0.05 C. Doctor blading proved to be best for laboratory setups because of its adjustability, while the Mayer rod shows promise for high-volume manufacturing due to better performance and the use of nonadjustable, dedicated tooling. All methods, analysis, and metrics are discussed.

Two-dimensional sheets of transition metal dichalcogenides are an emerging class of atomically thin semiconductors that are considered to be "air-stable", similar to graphene. Here we report that, contrary to current understanding, chemical vapor deposited transition metal dichalcogenide monolayers exhibit poor long-term stability in air. After room-temperature exposure to the environment for several months, monolayers of molybdenum disulfide and tungsten disulfide undergo dramatic aging effects including extensive cracking, changes in morphology, and severe quenching of the direct gap photoluminescence. X-ray photoelectron and Auger electron spectroscopy reveal that this effect is related to gradual oxidation along the grain boundaries and the adsorption of organic contaminants. These results highlight important challenges associated with the utilization of transition metal dichalcogenide monolayers in electronic and optoelectronic devices. We also demonstrate a potential solution to this problem, featuring encapsulation of the monolayer sheet by a 10-20 nm thick optically transparent polymer (parylene C). This strategy is shown to successfully prevent the degradation of the monolayer material under accelerated aging (i.e., high-temperature, oxygen-rich) conditions.

High density graphene hybrid aerogels with enhanced thermal conductivity and compressive properties are fabricated by self-assembly of aqueous mixtures of graphene oxide and high-quality graphene nanoplatelets (GNPs) followed by a convenient and cost-effective air drying process. The reduced graphene oxide sheets form an integrated three-dimensional network to accommodate GNPs, while the GNPs act as reinforcements to avoid excessive volume shrinkage of the network during the air drying process. Octadecanol is thus easily impregnated into the porous graphene network to obtain octadecanol/graphene phase change composites (PCCs) with exceptional thermal conductivities. The PCC with 12 wt% graphene exhibits a thermal conductivity of ∼5.92 W m−1 K−1 that is 26-fold higher than that of neat 1-octadecanol while maintaining a high latent heat of fusion (∼202.8 J g−1). Even when compressed by a high weight at ∼70 °C, the PCC still retains shape stability without any leakage. Such abilities to endow PCCs with exceptional shape stability and to boost their thermal conductivity by an order-of-magnitude without incurring a significant loss in the heat of fusion are important attributes in enabling their practical application as latent heat storage/release units for thermal management and thermal protection.

One of the primary challenges in the development of a breakthrough lithium ion battery technology is to identify a composition that can effectively provide high power densities as well as high energy densities. Conventional graphitic anodes are considerably limited in this regard, owing to a limited charge storage capacity and constrained ionic and electrical conductivity. In this work, we report the use of a facile, scalable and low-cost Far Infrared (FIR) reduction strategy for the synthesis of graphene anodes as an alternative to conventional graphitic anodes. FIR irradiation was found to effectively reduce graphene oxide to graphene in under 3 min and displayed exceptional charge/discharge rates and charge storage capacities when used as an anode in lithium ion batteries. The binder-free FIR graphene anodes provided a very high reversible capacity of ~1016 mA h/g at a C-rate of ~1 C. Further, the FIR-reduced graphene anodes displayed impressive rate capabilities, delivering remarkably steady capacities as high as ~181 mA h/g at a C-rate of ~40 C over 1000 charge/discharge cycles, corresponding to an average power density of ~14 kW/kg.

The recent interest and excitement in graphene has also opened up a pandora's box of other two-dimensional (2D) materials and material combinations which are now beginning to come to the fore. One family of these emerging 2D materials is transition metal dichalcogenides (TMDs). So far there is very limited understanding on the wetting behavior of "monolayer" TMD materials. In this study, we synthesized large-area, continuous monolayer tungsten disulfide (WS2) and molybdenum disulfide (MoS2) films on SiO2/Si substrates by the thermal reduction and sulfurization of WO3 and MO3 thin films. The monolayer TMD films displayed an advancing water contact angle of ∼83° as compared to ∼90° for the bulk material. We also prepared bilayer and trilayer WS2 films and studied the transition of the water contact angle with increasing number of layers. The advancing water contact angle increased to ∼85° for the bilayer and then to ∼90° for the trilayer film. Beyond three layers, there was no significant change in the measured water contact angle. This type of wetting transition indicates that water interacts to some extent with the underlying silica substrate through the monolayer TMD sheet. The experimentally observed wetting transition with numbers of TMD layers lies in-between the predictions of one continuum model that considers only van der Waals attractions and another model that considers only dipole-dipole interactions. We also explored wetting as a function of aging. A clean single-layer WS2 film (without airborne contaminants) was shown to be strongly hydrophilic with an advancing water contact angle of ∼70°. However, over time, the sample ages as hydrocarbons and water present in air adsorb onto the clean WS2 sheet. After ∼7 days, the aging process is completed and the advancing water contact angle of the aged single-layer WS2 film stabilizes at ∼83°. These results suggest that clean (i.e., nonaged) monolayer TMDs are hydrophilic materials. We further show that substitution of sulfur atoms by oxygen in the lattice of aged monolayer WS2 and MoS2 films can be used to generate well-defined 'hydrophobic-hydrophilic' patterns that preferentially accumulate and create microdrop arrays on the surface during water condensation and evaporation experiments.

We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V ( vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as polyaniline. In addition to impermeability, the insulating nature of SL-hBN suppresses galvanic effects and improves its ability to combat microbial corrosion.

Diamond-based cutting tools are preferred by the manufacturing community to machine high-value, hard-to-cut materials, especially for applications with stringent surface roughness requirements. However, these tools are not an economically viable option to machine any of the transition metals or their alloys. This is due to the extreme rates of tool wear caused by chemical diffusion of carbon from the diamond tool into the transition metal/alloy workpiece. In this paper we report the use of carbon-rich, graphene oxide colloidal suspensions, as a cutting fluid, to address this critical diamond tool wear issue. Our machining tests conducted on a low-carbon steel alloy reveal that the use of graphene oxide colloidal suspension results in a ∼74% reduction in the tool wear over that seen under the dry machining condition. It also results in a ∼50% reduction in the cutting temperatures and a ∼20 to 30% reduction in the cutting forces, when compared against the dry machining condition. The trends seen in the cutting temperatures, cutting forces and the X-ray photoelectron spectroscopy (XPS) data collectively point to the possibility of the graphene oxide platelets serving as a barrier to the carbon diffusion reaction. These findings have the potential to make diamond a cost-effective tool material for machining transition metal-based materials such as ferrous and titanium alloys that have wide-spread engineering applications.

Silicon (Si) shows promise as an anode material in lithium-ion batteries due to its very high specific capacity. However, Si is highly brittle, and in an effort to prevent Si from fracturing, the research community has migrated from the use of Si films to Si nanoparticle based electrodes. However, such a strategy significantly reduces volumetric energy density due to the porosity of Si nanoparticle electrodes. Here we show that contrary to conventional wisdom, Si films can be stabilized by two strategies: (a) anchoring the Si films to a carbon nanotube macrofilm (CNM) current collector and (b) draping the films with a graphene monolayer. After electrochemical cycling, the graphene-coated Si films on CNM resembled a tough mud-cracked surface in which the graphene capping layer suppresses delamination and stabilizes the solid electrolyte interface. The graphene-draped Si films on CNM exhibit long cycle life (>1000 charge/discharge steps) with an average specific capacity of ∼806 mAh g–1. The volumetric capa...

We performed first-principle calculations based on density functional theory (DFT) to investigate adsorption of lithium (Li) on graphene with divacancy and Stone–Wales defects. Our results confirm that lithiation is not possible in pristine graphene. However, enhanced Li adsorption is observed on defective graphene because of the increased charge transfer between adatom and underlying defective sheet. Because of increased adsorption, the specific capacity is also increased with the increase in defect densities. For the maximum possible divacancy defect density, Li storage capacities of up to ∼1675 mAh/g can be achieved. While for Stone–Wales defects, we find that a maximum capacity of up to ∼1100 mAh/g is possible. Our results provide deeper understanding of Li-defect interactions and will help to create better high-capacity anode materials for Li-ion batteries.

Inspired by the structure of a leaf, which is constituted of veins, midribs and laminas, we report the synthesis of aerogels based on nanocarbon complexes that exhibit good electrical conductivity, large internal surface area and stable structural integrity upon cyclic compression. These materials are prepared as monolithic solids from suspensions of unzipped and partially exfoliated multi-walled carbon nanotubes. Under optimized oxidation conditions, all the walls of the multi-walled carbon nanotubes are unzipped but only the outer tubes are exfoliated, creating nanoscale multi-layered graphene oxide sheets attached to inner trench-like structures. The exfoliated parts provide high surface area and functional groups, while the inner trench-like structures remain relatively intact and thus retain their electrical conductivity and mechanical properties, which facilitates charge transport and structural stability for the aerogel. The hydrophilic functional groups on the graphene oxide nanosheets make these structures highly soluble, and as a result, the density and mechanical properties can be adjusted to a large extent without sacrificing the porosity or cell wall uniformity. These nanocarbon aerogel complexes exhibit high damping capability with no significant change in piezoresistive properties after more than 4500 compressive cycles, and its original shape can be recovered quickly after compression release.

We report a novel far-infrared (FIR) thermal reduction process to effectively reduce graphene oxide films for supercapacitor electrode applications. The binder-free graphene oxide films used in this study were produced by electro-spray deposition of a graphene oxide colloidal solution onto stainless steel current collectors. The reduction of graphene oxide was performed using a commercial FIR convection oven that is ubiquitous in homes for cooking and heating food. The reduction process incorporated a simple, one-step FIR irradiation carried out in ambient air. Further, the FIR irradiation process was completed in ∼3 min, wherein neither special atmosphere nor high temperature was employed, resulting in an economic, efficient and simplified processing technique. The as-produced FIR graphene electrode gave a specific capacitance of ∼320 F/g at a current density of ∼0.2 A/g with less than 94% loss in specific capacitance over 10,000 charge/discharge cycles. This is one of the best specific capacitances reported for all-carbon electrodes without any additives. Even at ultrafast charge/discharge rates (current densities as high as ∼100 A/g), the FIR graphene electrode still delivered specific capacitances in excess of 90 F/g. The measured energy and power densities of the FIR supercapacitors were found to be ∼3–6 times higher than commercial (activated carbon) supercapacitor devices. This excellent electrochemical performance of the FIR graphene coupled with its ease of production (in air at low temperatures) using a commercial home-use FIR convection oven indicates the significant potential of this concept for large-scale commercial electrochemical supercapacitor applications.

We report fabrication of a flexible, thorn-like ZnO-multiwalled carbon nanotube (MWCNT) hybrid paper with high aspect ratio for efficient ultraviolet (UV) sensing and photocatalyst applications. The thorn-like ZnO-MWCNT hybrid paper was synthesized via atomic layer deposition (ALD) of a uniform ZnO thin film on the outside surface of the MWCNT followed by hydrothermal growth of ZnO branches. The hybrid paper achieved very high surface to volume ratio, which is favorable for photodetector and photocatalyst applications. A photodetector fabricated from the hybrid paper demonstrates a high sensitivity to UV light with a maximum photoresponsivity of 45.1 A W(-1) at 375 nm, corresponding to an external quantum efficiency as high as 14927%. The rise time and fall time of the UV photodetector are 29 ms and 33 ms, respectively, indicating fast transient response characteristics for the device. The high photoresponsivity and fast transient response are attributed to efficient carrier transport and collection efficiency of the hybrid paper. Besides, the thorn-like ZnO-MWCNT hybrid paper demonstrates excellent photocatalytic performance under UV irradiation, enabling photo-degradation of organic dyes such as Rhodamine B (RhB) within 90 minutes, with good recyclability.