Silver Nanowires Coated Nitrocellulose Paper for High-Efficiency Electromagnetic Interference Shielding.

A thin and conductive coating on an environmentally friendly polymer is imperative for protecting sensitive electronic devices. In this regard, a series of silver nanowires (AgNWs) coated nitrocellulose (NC) papers are fabricated by a simple and fast processed vacuum-assisted filtration method by varying filtrate volume to address electromagnetic interference. Their structural and EMI shielding performance is analyzed. The submicron thick and the lighter paper reveal the conductive AgNWs interwoven on the rough NC surface, making a 2D in-planar structure. Due to a strongly interconnected network, the coated paper displays an exceptional electrical conductivity of 8603 S/m. Despite having a minimum AgNW coating thickness of ∼0.69 µm and an area density of 0.041 mg/cm2, an ultrahigh EMI shielding effectiveness (SE) of about 69.4 dB (a specific EMI SE (SE/t) of 1005797 dB/cm) in the entire X-band (8-12 GHz) region is achieved. The effective material parameters, extracted using plane-wave theory, indicate that AgNWs form closed current loops resulting in magnetic losses. These AgNWs coated NC papers synthesized by a simple procedure are promising EMI shielding materials for current emerging electronic devices.

A flexible, ceramic-rich solid electrolyte for room-temperature sodium-sulfur batteries.

A sodium superionic conductor, Na3Zr2Si2PO12 (NZSP) ceramic, is a promising solid electrolyte (SE) and holds the potential to solve the safety and energy density problems of several sodium-based batteries. In particular, in room temperature sodium-sulfur (RT Na/S) batteries, the use of SEs can solve polysulfide shuttle effects. A significant challenge in the commercialization of NZSP is producing the ceramic in a thin and flexible form. Herein, we report a method to produce a thin (<250 µm thickness) and flexible "polymer in ceramic" type sodium ion conductor film from the erstwhile brittle ceramic film and demonstrate its application in RT Na/S batteries.

Graphitic Carbon Nitride Causes Widespread Global Molecular Changes in Epithelial and Fibroblast Cells.

For scaffold and imaging applications, nanomaterials such as graphene and its derivatives have been widely used. Graphitic carbon nitride (g-C3N4) is among one such derivative of graphenes, which draws strong consideration due to its physicochemical properties and photocatalytic activity. To use g-C3N4 for biological applications, such as molecular imaging or drug delivery, it must interact with the epithelium, cross the epithelial barrier, and then come in contact with the extracellular matrix of the fibroblast cells. Thus, it becomes essential to understand its molecular mechanism of action. Hence, in this study, to understand the molecular reprogramming associated with g-C3N4, global gene expression using DNA microarrays and proteomics using tandem mass tag (TMT) labeling and mass spectrometry were performed in epithelial and fibroblast cells, respectively. Our results showed that g-C3N4 can cross the epithelial barrier by regulating the adherens junction proteins. Further, using g-C3N4-PDMS scaffolds as a mimic of the extracellular matrix for fibroblast cells, the common signaling pathways were identified between the epithelium and fibroblast cells. These pathways include Wnt signaling, integrin signaling, TGF-ß signaling, cadherin signaling, oxidative stress response, ubiquitin proteasome pathway, and EGF receptor signaling pathways. These altered signature pathways identified could play a prominent role in g-C3N4-mediated cellular interactions in both epithelial and fibroblast cells. Additionally, ß catenin, EGFR, and MAP2K2 protein-protein interaction networks could play a prominent role in fibroblast cell proliferation. The findings could further our knowledge on g-C3N4-mediated alterations in cellular molecular signatures, enabling the potential use of these materials for biological applications such as molecular imaging and drug delivery.

Retracting interphasial stored Li+ ions by transition metal/metal carbide nanoparticles for enhanced Li+ ion storage capacity.

Herein, we report the synthesis of metal/metal carbide (Co, Ni, and Fe3C) nanoparticles (NPs) encapsulated nitrogen-doped carbon nanotubes (NCNT) and its application as the anode materials for lithium-ion battery (LIB). The electron microscopy images confirm the encapsulation of metal NPs inside the carbon nanotubes, which can inhibit the NPs aggregations and offer long cycle life for LIB. The metal/metal carbide encapsulated NCNT as anode material exhibits higher specific capacity than pure NCNT. The cyclic voltammetry studies reveal that Co, Ni, and Fe3C NPs can oxidize and reduce the solid electrolyte interphase (SEI) layer components of the anode. This offers the extra specific capacity to Fe3C/NCNT, Co/NCNT, and Ni/NCNT anodes by retracting the interphasial stored Li+ ions. Moreover, in this study, the catalytic activity of Co, Ni, and Fe3C NPs for tailoring the SEI components are compared for the first time, and it shows Fe3C/NCNT anode has the highest catalytic activity than Co/NCNT and Ni/NCNT. Co/NCNT and Fe3C/NCNT also exhibit good cycle life up to 1300 cycles at a current density of 1 A g-1. Overall, this work demonstrates an effective strategy to improve the performance of LIB anode by retracting the interphasial stored Li+ ions.

Synergy between Interconnected Porous Carbon-Sulfur Cathode and Metallic MgB2 Interlayer as a Lithium Polysulfide Immobilizer for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are the potential candidates for developing high-energy-density electric vehicles. However, poor electrical conductivity of sulfur/discharged products, low active material utilization, shuttle mechanism, and poor cycle life remain the major challenges for the development of Li-S batteries. Herein, we report the nitrogen-doped highly porous carbon (NC) with interconnected pores as the sulfur host (NC-S), which is synthesized by a facile one-step process without using any template and activation agents. The highly interconnected porous structure of NC can accommodate a high amount of sulfur loading and provide space for sulfur volume expansion during redox reactions. Besides, to mitigate the lithium polysulfide dissolution and shuttle mechanism, metallic and polar magnesium diboride (MgB2) is used as an interlayer. Consequently, the NC-S/MgB2 cathode delivers higher specific capacity, rate capability, and excellent cyclic stability than the NC-S cathode and bulk sulfur cathode with MgB2 interlayer. The lithium polysulfide (LPS) adsorption test shows that MgB2 has strong chemisorption toward lithium polysulfides, which can inhibit the dissolution of LPS into the electrolyte and minimizes the shuttle effect. The dynamic electrochemical impedance spectroscopy analysis investigates the electrochemical reaction kinetics of the NC-S/MgB2 cathode during the charging and discharging processes. Overall, this work demonstrates that the synergy between the nitrogen-doped porous carbon-sulfur host and polar metallic MgB2 improves the performance of the Li-S battery, which is beneficial for the development of high-energy-density batteries for the future.

Waterproof Flexible Polymer-Functionalized Graphene-Based Piezoresistive Strain Sensor for Structural Health Monitoring and Wearable Devices.

In recent times, flexible piezoresistive polymer nanocomposite-based strain sensors are in high demand in wearable devices and various new age applications. In the polymer nanocomposite-based strain sensor, the dispersion of conductive nanofiller remains challenging due to the competing requirements of homogenized dispersion of nanofillers in the polymer matrix and retaining of the inherent characteristics of nanofillers. In the present work, waterproof and flexible poly(vinylidene difluoride) (PVDF) with a polymer-functionalized hydrogen-exfoliated graphene (HEG)-based piezoresistive strain sensor is developed and demonstrated. The novelty of the work is the incorporation of polystyrene sulfonate sodium salt (PSS) polymer-functionalized HEG in a PVDF-based flexible piezoresistive strain sensor. The PSS-HEG provides stable dispersion in the hydrophobic PVDF polymer matrix without sacrificing its inherent characteristics. The electrical conductivity of the PVDF/PSS-HEG-based strain sensor is 0.3 S cm-1, which is two orders of magnitude higher than the PVDF/HEG-based strain sensor. Besides, near the percolation region, the PVDF/PSS-HEG shows a maximum gauge factor of 10, which is about two times higher than the PVDF/HEG-based flexible strain sensor and 5-fold higher than the commercially available metallic strain gauge. The enhancement in the gauge factor is due to the stable dispersion of PSS-HEG in the PVDF matrix and electron conjugation caused by the adherence of negatively charged sulfonate functional groups on the HEG. The developed waterproof flexible strain sensor is demonstrated using portable wireless interfacing device for various applications. This work shows that the waterproof flexible PVDF/PSS-HEG-based strain sensor can be a potential alternative to the commercially available metallic strain gauge.

Nonprecious Catalyst for Three-Phase Contact in a Proton Exchange Membrane CO2 Conversion Full Cell for Efficient Electrochemical Reduction of Carbon Dioxide.

Development of a cost-effective and highly efficient electrocatalyst is essential but challenging in order to convert carbon dioxide to value-added chemicals at ambient conditions. In the current work, the activity of a full electrochemical cell has been demonstrated, utilizing a proton exchange membrane CO2 conversion cell that can selectively convert carbon dioxide to a value-added chemical (formic acid) at room temperature and pressure. A cost-effective, nonprecious-metal-based electrocatalyst, nitrogen-doped carbon nanotubes encapsulating Fe3C nanoparticles (Fe3C@NCNTs), has been reported to exhibit superior catalytic activity toward the electrochemical CO2 reduction reaction (CO2RR). A facile one-step synthesis procedure has been undertaken to synthesize Fe3C@NCNTs. CO2 adsorption takes place via sharing of charge between the nucleophilic anchoring site (Fe3C) and the electrophilic C site of CO2, as shown by the DFT studies. The porous architecture, unique tubular structure, high graphitization degree, and appropriate doping of the Fe3C-encapsulating NCNTs allow better three-phase contact of CO2 (gas), H2O (liquid), and catalyst (solid), which can enhance the electrocatalytic activity of the cell, as demonstrated by the experimental findings. The cell was tested under a continuous flow of CO2 gas and has been demonstrated to produce a good amount of formic acid (HCOOH). The production of formic acid was examined by utilizing UV-vis spectroscopy and high-performance liquid chromatography (HPLC). A series of designed experiments disclosed that the maximum yield of formic acid was as high as 90% with Fe3C@NCNTs as both anode and cathode catalysts. Technology to scale up the reduction procedure has also been proposed and shown in this particular work. These unique observations open a route for the development of cost-effective and highly active platinum-free electrocatalysts for the CO2RR.

A room temperature multivalent rechargeable iron ion battery with an ether based electrolyte: a new type of post-lithium ion battery.

The feasibility of developing a rechargeable iron ion battery is demonstrated for the first time. A rechargeable iron ion battery using mild steel as the anode and vanadium pentoxide as the cathode is demonstrated to deliver a specific capacity of 207 mA h g-1 at 30 mA g-1. Using ex situ characterisation techniques, reversible intercalation of iron ions into a host structure is confirmed.

High Entropy Oxides-A Cost-Effective Catalyst for the Growth of High Yield Carbon Nanotubes and Their Energy Applications.

This report anticipates a thorough strategy for the utilization of high entropy oxide (HEO) nanoparticles (1) as a cost-effective catalyst for the growth of high yield carbon nanotubes (CNTs), resulting in HEO-CNT nanocomposites, and (2) the implementation of HEO-CNT nanocomposites for energy applications such as electrochemical capacitors (ECs). In the first step, HEO nanoparticles were synthesized by a simple sol-gel autocombustion method and then the as-synthesized HEO nanoparticles were ground and used as the catalyst for the growth of CNTs by chemical vapor deposition technique. The as-grown CNTs (HEO-CNT nanocomposite) exhibited unexpectedly high yield, a superior specific surface area of ∼151 m2 g-1, and encapsulation and diffusion of the catalyst throughout the HEO-CNT nanocomposite, providing remarkably high mechanical strength, which make them a promising candidate for energy applications. To study the electrochemical activity of the HEO-CNT nanocomposite, half-cell and full-cell ECs were assembled in different electrolytes. Stupendously, a complete 100% capacitance retention and a Coulombic efficiency up to 15 000 cycles were realized for the HEO-CNT nanocomposite-based full-cell EC assembled in the polyvinyl alcohol/H2SO4 hydrogel electrolyte. Additionally, a high specific capacitance value of 286.0 F g-1 at a scan rate of 10 mV s-1 for the HEO-CNT nanocomposite-based full-cell EC assembled in the [BMIM][TFSI] electrolyte with a wide potential window of 2.5 V is reported. Also, high energy density and power density of ∼217 W h kg-1 and ∼24 521 W kg-1, respectively, are reported. Furthermore, the HEO-CNT nanocomposite-based full-cell EC assembled in the [BMIM][TFSI] electrolyte can successfully light up a red light-emitting diode, demonstrating great potential of the HEO-CNT nanocomposite in the various energy applications.

Barium Titanate-Based Porous Ceramic Flexible Membrane as a Separator for Room-Temperature Sodium-Ion Battery.

Sodium-ion batteries (NIBs) are an alternative low-cost battery technology for large-scale energy storage application, and the development of high-performance polymer-based electrolytes is crucial for further advancement of low-cost NIBs. Though electrode materials provide significant contribution to the energy density of the battery, the separator plays a vital role in deciding the safety, duration, and performance of batteries. The glass fiber membrane is considered as the most compatible separator for NIBs because of its high ionic conductivity and reasonable performance. However, the leakage and flammability of the liquid electrolytes while using the glass fiber separator can lead to safety issues. Therefore, herein, we present an alternative approach for the first time to replace the glass fiber separator in NIBs using the porous ceramic membrane (PCM). The polymer blend-based PCM is prepared by a simple solution-casting technique and used as the separator in NIBs. The good thermal stability of the PCM up to 400 °C, high ionic conductivity of about 10-3 S cm-1, high electrolyte uptake, and porous nature make it a better choice over the glass fiber membrane. To demonstrate the applicability of PCM in NIBs, the sodium-ion storage property of hard carbon is evaluated using the PCM as the separator at room temperature. The specific capacity of hard carbon using the PCM-based separator is about 270 mA h g-1 at a current density of 30 mA g-1 which is ∼23% higher than the glass fiber separator (208 mA h g-1) at the same current density. The enhancement in specific capacity is due to the compatibility of the PCM with sodium electrodes, low interfacial resistance, high sodium-ion transference number (0.8), and good electrochemical stability (4.9 V) than the glass fiber separator. This study demonstrates a promising alternative separator to the glass fiber membrane, which can lead to the development of a practical and safe NIB.

Enhanced Sodium Ion Storage in Interlayer Expanded Multiwall Carbon Nanotubes.

We report an effective approach of utilizing multiwalled carbon nanotubes (MWCNTs) as an active anode material in sodium ion batteries by expanding the interlayer distance in a few outer layers of multiwalled carbon nanotubes. The performance enhancement was investigated using a density functional tight binding (DFTB) molecular dynamics simulation. It is found that a sodium atom forms a stable bonding with the partially expanded MWCNT (PECNT) with the binding energy of -1.50 eV based on the density functional theory calculation with van der Waals correction, where a sodium atom is caged between the two carbon hexagons in the two consecutive MWCNTs. Wave function and charge density analyses show that this binding is physisorption in nature. This larger exothermic nature of binding energy favors the stable bonding between the PECNT and a sodium atom, and thereby, it helps to enhance the electrochemical performance. In the experimental works, partial opening of the MWCNT with the expanded interlayer has been designed by the well-known Hummer's method. It has been found that the introduction of functional groups causes a partial opening of the outer few layers of a MWCNT, with the inner core remaining undisturbed. The enhanced performance is due to an expanded interlayer of carbon nanotubes, which provide sufficient active sites for the sodium ions to adsorb as well as to intercalate into the carbon structure. The PECNT shows a high specific capacity of 510 mAh g-1 at a current density of 20 mA g-1, which is about 2.3 times the specific capacity obtained for a pristine MWCNT at the same current density. This specific capacity is higher when compared to other carbon-based materials. The PECNT also shows a satisfactory cyclic stability at a current density of 200 mA g-1 for 100 cycles. Based on our experimental and theoretical results, an alternative perspective for the storage of sodium ions in MWCNTs is proposed.

Chemical Vapor Deposition-Grown Nickel-Encapsulated N-Doped Carbon Nanotubes as a Highly Active Oxygen Reduction Reaction Catalyst without Direct Metal-Nitrogen Coordination.

Nickel-encapsulated nitrogen-doped carbon nanotubes (Ni-TiO2-NCNTs) are synthesized via chemical vapor deposition by thermal decomposition of acetylene with acetonitrile vapor at 700 °C on the Ni-TiO2 matrix. TiO2 is used as a dispersant medium for Ni nanoparticles, which assists in higher CNT growth at high temperatures. A reference catalyst is made by following the similar procedure without acetonitrile vapor, which is called a Ni-TiO2-CNT. Acid treatment of these two catalysts dissolved Ni on the surface of CNTs-NCNTs, producing catalysts with enhanced surface area and defects. The transmission electron microscopy-energy-dispersive X-ray spectra analysis of acid-treated version of the catalysts confirmed the presence of encapsulated Ni. Oxygen reduction reaction (ORR) activity of these catalysts was analyzed in 0.1 N KOH solution. Among these, the acid-treated Ni-TiO2-NCNT exhibited highest ORR onset potential of 0.88 V versus reversible hydrogen electrode and a current density of 3.7 mA cm-2 at 170 µg cm-2 of catalyst loading. The stability of the acid-treated Ni-TiO2-NCNT is proved by cyclic voltammetry and chronoamperometry measurements which are done for 800 cycles and 100 h, respectively. Primarily N doping of CNTs is the reason behind the improved ORR activity.

Chemical Simultaneous Synthesis Strategy of Two Nitrogen-Rich Carbon Nanomaterials for All-Solid-State Symmetric Supercapacitor.

Present work demonstrates a single step process for simultaneous synthesis of metal-nanoparticle-encapsulated nitrogen-doped bamboo-shaped carbon nanotubes (M/N-BCNTs) and graphitic carbon nitride (G-C3N3). The synthesis of two different carbon nanostructures in a single step is recognized for the first time. This process involves the use of inexpensive and nontoxic precursors such as melamine as carbon and nitrogen sources for the growth of G-C3N3 and M/N-BCNTs. In this technique, the utilization of unwanted gases such as ammonia and hydrocarbons released during the decomposition of melamine is the key to grow M/N-BCNTs over the catalyst along with the formation of G-C3N4. The implementation of M/N-BCNTs as the electrode material for all-solid-state symmetric supercapacitor results in a maximum specific capacitance of ∼368 F g-1 with excellent electrochemical stability with 97% capacity retention after 10 000 cycles. Furthermore, fabricated symmetric supercapacitor shows maximum high energy and power density up to 10.88 W h kg-1 and 2.06 kW kg-1, respectively. The superior electrochemical activity of M/N-BCNTs can be attributed to its high surface to area volume ratio, unique structural characteristics, ultrahigh electrical conductivity, and carrier mobility.

Investigation of catalytic activity towards oxygen reduction reaction of Pt dispersed on boron doped graphene in acid medium.

Boron doped graphene was prepared by a facile method and platinum (Pt) decoration over boron doped graphene was done in various chemical reduction methods such as sodium borohydride (NaBH4), polyol and modified polyol. X-ray diffraction analysis indicates that the synthesized catalyst particles are present in a nanocrystalline structure and transmission and scanning electron microscopy were employed to investigate the morphology and particle distribution. The electrochemical properties were investigated with the help of the rotating disk electrode (RDE) technique and cyclic voltammetry. The results show that the oxygen reduction reaction (ORR) takes place by a four-electron process. The kinetics of the ORR was evaluated using K-L and Tafel plots. The electrocatalyst obtained in modified polyol reduction method has shown the better catalytic activity compared to other two electrocatalysts.