Employment Growth and Industrial Policy: The Challenge for Indian States.

The nature of and the future potential for economic growth will vary across Indian States because of their differences in the rates of demographic transitions. The growing population of the young in some of the States in the east and north of the country, notably Bihar and Uttar Pradesh, opens up a huge economic opportunity. It is also a serious policy challenge-to create new opportunities that meet the rising expectations of the job aspirants. At the same time, for States such as Kerala and Tamil Nadu, which have an ageing population, there are limits to future growth based on labour-intensive sectors. Across Indian States, during the period between 2005 and 2018, labour absorption into industry, construction and services lagged way behind the increase in the potential supply of workers into these sectors. The mismatch between labour demand and potential labour supply widened after 2012, leading to an increase in unemployment rates and a large-scale withdrawal of women from the labour market. For reviving employment growth, India requires a mix of social, employment and industrial policies. The States should have greater financial and functional autonomy to implement these policies in a way that suit their specific stages of development.

Energized Composites for Electric Vehicles: A Dual Function Energy-Storing Supercapacitor-Based Carbon Fiber Composite for the Body Panels.

The current electric vehicles (EVs) face many challenges like limited charge capacity, low miles/charge, and long charging times. Herein, these issues are addressed by developing a dual-function supercapacitor-based energy-storing carbon fiber reinforced polymer (e-CFRP) that can store electrical energy and function as the structural component for the EV's body shell. This is achieved by developing a unique design, vertically aligned graphene sheets attached to carbon fiber electrodes on which different metal oxides are deposited to obtain high-energy density electrodes. A high-strength multilayer e-CFRP assembly is fabricated using an alternate layer patterning configuration of epoxy and polyacrylamide gel electrolyte. The e-CFRP so developed delivers a high areal energy density of 0.31 mWh cm-2 at 0.3 mm thickness and a high tensile strength of 518 MPa, bending strength of 477 MPa, and impact strength of 2666 J m-1 . To show its application in EVs, a toy car's body panel is fabricated with e-CFRP and the toy car is able to operate using the energy stored in its frame. Moreover, when integrated with a solar cell, this composite powers an Internet of Things device, showing its feasibility in communication satellites.

Perovskite Quantum Dot-Reduced Graphene Oxide Superstructure for Efficient Photodetection.

High-performance photodetectors require efficient photogeneration and charge transport. Perovskite quantum dots (PQDs) have received enormous interest for applications in optoelectronics due to their high photogeneration efficiency. However, they offer meager carrier transport. Reduced graphene oxide (RGO) exhibits inferior photoresponse compared to materials such as quantum dots. An effective synthesis protocol to grow PQDs from the RGO lattice may facilitate direct charge transfers from PQDs to RGO, which could not be accomplished by mixing individual PQDs with RGO or making a bilayer. At ambient condition, the photodetector fabricated with the PQD-RGO superstructure showed high responsivity of 1.07 × 103 A/W, detectivity of 1 × 1013 Jones as well as sharp switching in the visible wavelength. After 3 months in an unencapsulated sample, the photocurrent was decreased ∼10% of its initial value while preserving speed and cycle stability at ambient condition.

Flexible supercapacitor electrodes using metal-organic frameworks.

Advancements in the field of flexible and wearable devices require flexible energy storage devices to cater their power demands. Metal-ion batteries (such as lithium-ion batteries, sodium-ion batteries, etc.) and electrochemical capacitors (also called supercapacitors or ultracapacitors) have achieved great interest in the recent past due to their superior energy storage characteristics like high power density and long cycle life. A major bottleneck of using metal-ion batteries in wearable devices is their lack of flexibility. Low power density, toxicity and flammability due to organic electrolytes inhibit them from safe on-body device applications. On the other hand, supercapacitors can be made with aqueous electrolytes, making them a safer alternative for wearable applications. Metal-organic frameworks (MOFs) are novel candidates as electrode materials due to their salient features such as large surface area, three-dimensional porous architecture, permeability to foreign entities, structural tailorability, etc. Though pristine MOFs suffer from poor intrinsic conductivity, this can be rectified by preparing composites with other electronically conducting materials. MOF-based electrodes are highly promising for flexible and wearable supercapacitors since they exhibit good energy and power densities. This review focuses on the new developments in the field of MOF-based composite electrodes for developing flexible supercapacitors.

New Method for the Synthesis of 2D Vanadium Nitride (MXene) and Its Application as a Supercapacitor Electrode.

MXenes are the class of two-dimensional transition metal carbides and nitrides that exhibit unique properties and are used in a multitude of applications such as biosensors, water purification, electromagnetic interference shielding, electrocatalysis, supercapacitors, and so forth. Carbide-based MXenes are being widely explored, whereas investigations on nitride-based ones are seldom. Among the nitride-based MXenes obtained from their MAX phases, only Ti4N3 and Ti2N are reported so far. Herein, we report a novel synthesis of V2NT x (T x is the surface termination) obtained by the selective removal of "Al" from V2AlN by immersing powders of V2AlN in the LiF-HCl mixture (salt-acid etching) followed by sonication to obtain V2NT x (T x = -F, -O) MXene which is then delaminated using the dimethyl sulfoxide solvent. The V2NT x MXene is characterized by X-ray diffraction studies, field emission scanning electron microscope imaging, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope imaging. Supercapacitor electrodes are prepared using V2NT x MXenes and their electrochemical performances are examined by cyclic voltammetry, galvanostatic charge/discharge measurement, and electrochemical impedance spectroscopy. The V2NT x MXene electrode exhibits a specific capacitance of 112.8 F/g at a current density of 1.85 mA/cm2 with an energy and power density of 15.66 W h/kg and 3748.4 W/kg, respectively, in 3.5 M KOH aqueous electrolyte. The electrode exhibits an excellent capacitance retention of 96% even after 10,000 charge/discharge cycles. An asymmetric supercapacitor fabricated with V2NT x as a negative electrode and Mn3O4 nanowalls as a positive electrode helps obtain a cell voltage of 1.8 V in aqueous KOH electrolyte.

High-performance flexible asymmetric supercapacitor based on rGO anode and WO3/WS2 core/shell nanowire cathode.

Flexible smart electronics require their energy storage device to be flexible in nature. Developing high-performance flexible energy storage devices require direct integration of electrode active materials on current collectors to satisfy the high electronic/ionic conductivity and long-term durability requirements. Herein, we develop a flexible all-solid-state asymmetric supercapacitor comprised of reduced graphene oxide (rGO) and core/shell tungsten trioxide/tungsten disulfide (WO3/WS2) nanowire based electrodes. The electrodes synthesized via electrochemical deposition and chemical vapor deposition avoided the necessity to use non-conductive binders and offered excellent cyclic stability. The structural integrity provided by the rGO and WO3/WS2 electrodes facilitated excellent electrochemical stability with capacitance retention of 90% and 100% after 10 000 charge-discharge cycles, respectively. An all-solid-state device provides a voltage window of 1.5 V and more than 70% capacitance retention after 10 000 charge-discharge cycles. Providing 97% capacitance retention upon mechanical bending reveals its potential to be used as an energy storage devices in flexible electronics.

Synthesis of air-stable two-dimensional nanoplatelets of Ruddlesden-Popper organic-inorganic hybrid perovskites.

We present a simple and facile method to synthesize nanoplatelets of 2D Ruddlesden-Popper (RP) perovskites of the type (CH3(CH2)3NH3)2(CH3NH3)Pb2I7 where n = 2. The 2D RP nanoplatelets are synthesized from bulk 2D RP crystals via a reflux pre-treatment mediated-ultrasonication method. The as-synthesized 2D RP nanoplatelets are highly air-stable even after two months of storage under an ambient atmosphere. The bulk 2D RP crystals and 2D RP nanoplatelets are characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Kelvin probe force microscopy, UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence, time correlated single photon counting measurement, etc. A significant blue shift in the ultraviolet-visible absorption spectrum, high photoluminescence in the UV region, and the modified work function of the nanoplatelets indicate a strong quantum confinement effect. The quantum confinement in the nanoplatelets is further confirmed using XPS. A photodetector fabricated using these 2D RP nanoplatelets exhibits a high photodetectivity of 3.09 × 1010 Jones.

Ultrasensitive and ultrathin phototransistors and photonic synapses using perovskite quantum dots grown from graphene lattice.

Organic-inorganic halide perovskite quantum dots (PQDs) constitute an attractive class of materials for many optoelectronic applications. However, their charge transport properties are inferior to materials like graphene. On the other hand, the charge generation efficiency of graphene is too low to be used in many optoelectronic applications. Here, we demonstrate the development of ultrathin phototransistors and photonic synapses using a graphene-PQD (G-PQD) superstructure prepared by growing PQDs directly from a graphene lattice. We show that the G-PQDs superstructure synchronizes efficient charge generation and transport on a single platform. G-PQD phototransistors exhibit excellent responsivity of 1.4 × 108 AW-1 and specific detectivity of 4.72 × 1015 Jones at 430 nm. Moreover, the light-assisted memory effect of these superstructures enables photonic synaptic behavior, where neuromorphic computing is demonstrated by facial recognition with the assistance of machine learning. We anticipate that the G-PQD superstructures will bolster new directions in the development of highly efficient optoelectronic devices.

Vertically Aligned Graphene-Carbon Fiber Hybrid Electrodes with Superlong Cycling Stability for Flexible Supercapacitors.

Graphene electrode-based supercapacitors are in high demand due to their superior electrochemical characteristics. A major bottleneck of using the supercapacitors for commercial applications lies in their inferior electrode cycle life. Herein, a simple and facile method to fabricate highly efficient supercapacitor electrodes using pristine graphene sheets vertically stacked and electrically connected to the carbon fibers which can result in vertically aligned graphene-carbon fiber nanostructure is developed. The vertically aligned graphene-carbon fiber electrode prepared by electrophoretic deposition possesses a mesoporous 3D architecture which enabled faster and efficient electrolyte-ion diffusion with a gravimetric capacitance of 333.3 F g-1 and an areal capacitance of 166 mF cm-2 . The electrodes displayed superlong electrochemical cycling stability of more than 100 000 cycles with 100% capacitance retention hence promising for long-lasting supercapacitors. Apart from the electrochemical double layer charge storage, the oxygen-containing surface moieties and α-Ni(OH)2 present on the graphene sheets enhance the charge storage by faradaic reactions. This enables the assembled device to provide an excellent gravimetric energy density of 76 W h kg-1 with a 100% capacitance retention even after 1000 bending cycles. This study opens the door for developing high-performing flexible graphene electrodes for wearable energy storage applications.

Two-Dimensional Mn3O4 Nanowalls Grown on Carbon Fibers as Electrodes for Flexible Supercapacitors.

Emerging flexible and wearable electronic devices necessitates the development of fiber-type energy storage devices to power them. Supercapacitors received great attention for applications in flexible and wearable devices due to their scalability, safety, and miniature size. Herein, we report the fabrication of a flexible supercapacitor using manganese(II,III) oxide (Mn3O4) nanowalls (NWs) grown by electrochemical deposition on carbon fiber (CF) as electrode-active material. Here, CF serves as both a substrate for the growth of Mn3O4 NWs and a current collector for making a lightweight supercapacitor. Two-dimensional Mn3O4 NWs were uniformly grown on CF with high surface coverage. A three-dimensional nanostructured electrode is obtained using these individual two-dimensional Mn3O4 NWs. The Mn3O4 NWs grown on CF are characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy. A symmetric sandwich-type supercapacitor is fabricated using two-dimensional Mn3O4 NW electrodes in an aqueous 1 M Na2SO4 electrolyte. The Mn3O4 NW supercapacitor electrode exhibits a specific capacitance of 300.7 F g-1 at a scan rate of 5 mV s-1. The assembled symmetric sandwich-type supercapacitor displayed high flexibility even at a bending angle of 180° without altering its performance. The Mn3O4 NW supercapacitor also displayed a long cycle life of 7500 cycles with 100% capacitance retention.

Novel mesoporous electrode materials for symmetric, asymmetric and hybrid supercapacitors.

Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due to their potential applications ranging from microelectronic devices to hybrid electric vehicles. Supercapacitors can provide high power densities but their inherently low energy density remains a great challenge. The high-performance supercapacitors utilize large electrode surface area for electrochemical double-layer capacitance and/or pseudocapacitance. To enhance the performance of supercapacitors, various strategies have been adopted such as electrode nanostructuring, hybrid electrode designs using nanocomposite electrodes and hybrid supercapacitor (HSC) configurations. Nanoarchitecturing of electrode-active materials is an effective way of enhancing the performance of supercapacitors as it increases the effective electrode surface area for enhanced electrode/electrolyte interaction. In this review, we focus on the recent developments in the novel electrode materials and various hybrid designs used in supercapacitors for obtaining high specific capacitance and energy density. A family of electrode-active materials including carbon nanomaterials, transition metal-oxides, transition metal-nitrides, transition metal-hydroxides, electronically conducting polymers, and their nanocomposites are discussed in detail. The HSC configurations for attaining enhanced supercapacitor performance as well as strategies to integrate with other microelectronic devices/wearable fabrics are also included.

The Role of Graphene and Other 2D Materials in Solar Photovoltaics.

2D materials have attracted considerable attention due to their exciting optical and electronic properties, and demonstrate immense potential for next-generation solar cells and other optoelectronic devices. With the scaling trends in photovoltaics moving toward thinner active materials, the atomically thin bodies and high flexibility of 2D materials make them the obvious choice for integration with future-generation photovoltaic technology. Not only can graphene, with its high transparency and conductivity, be used as the electrodes in solar cells, but also its ambipolar electrical transport enables it to serve as both the anode and the cathode. 2D materials beyond graphene, such as transition-metal dichalcogenides, are direct-bandgap semiconductors at the monolayer level, and they can be used as the active layer in ultrathin flexible solar cells. However, since no 2D material has been featured in the roadmap of standard photovoltaic technologies, a proper synergy is still lacking between the recently growing 2D community and the conventional solar community. A comprehensive review on the current state-of-the-art of 2D-materials-based solar photovoltaics is presented here so that the recent advances of 2D materials for solar cells can be employed for formulating the future roadmap of various photovoltaic technologies.

Rapid Nanofabrication of Nanostructured Interdigitated Electrodes (nIDEs) for Long-Term In Vitro Analysis of Human Induced Pluripotent Stem Cell Differentiated Cardiomyocytes.

Adverse cardiac events are a major cause of late-stage drug development withdrawals. Improved in vitro systems for predicting cardiotoxicity are of great interest to prevent these events and to reduce the expenses involved in the introduction of cardiac drugs into the marketplace. Interdigitated electrodes (IDEs) affixed with a culture well provide a simple, suitable solution for in vitro analysis of cells because of their high sensitivity, ease of fabrication, and label-free, nondestructive analysis. Culturing human pluripotent stem cell differentiated cardiomyocytes onto these IDEs allows for the use of the IDE⁻cell combination in predictive toxicity assays. IDEs with smaller interdigitated distances allow for greater sensitivity, but typically require cleanroom fabrication. In this communication, we report the definition of a simple IDE geometry on a printed nanostructured substrate, demonstrate a Cellular Index (CI) increase from 0 to 7.7 for human cardiomyocytes, and a decrease in CI from 2.3 to 1 with increased concentration of the model drug, norepinephrine. The nanostructuring results in an increased sensitivity of our 1 mm pitch IDEs when compared to traditionally fabricated IDEs with a pitch of 10 µm (100 times larger electrode gap). The entire nanostructured IDE (nIDE) is fabricated and assembled in a rapid nanofabrication environment, thus allowing for iterative design changes and robust fabrication of devices.

Fiber-Type Solar Cells, Nanogenerators, Batteries, and Supercapacitors for Wearable Applications.

Wearable electronic devices represent a paradigm change in consumer electronics, on-body sensing, artificial skins, and wearable communication and entertainment. Because all these electronic devices require energy to operate, wearable energy systems are an integral part of wearable devices. Essentially, the electrodes and other components present in these energy devices should be mechanically strong, flexible, lightweight, and comfortable to the user. Presented here is a critical review of those materials and devices developed for energy conversion and storage applications with an objective to be used in wearable devices. The focus is mainly on the advances made in the field of solar cells, triboelectric generators, Li-ion batteries, and supercapacitors for wearable device development. As these devices need to be attached/integrated with the fabric, the discussion is limited to devices made in the form of ribbons, filaments, and fibers. Some of the important challenges and future directions to be pursued are also highlighted.

Asymmetric Supercapacitor Electrodes and Devices.

The world is recently witnessing an explosive development of novel electronic and optoelectronic devices that demand more-reliable power sources that combine higher energy density and longer-term durability. Supercapacitors have become one of the most promising energy-storage systems, as they present multifold advantages of high power density, fast charging-discharging, and long cyclic stability. However, the intrinsically low energy density inherent to traditional supercapacitors severely limits their widespread applications, triggering researchers to explore new types of supercapacitors with improved performance. Asymmetric supercapacitors (ASCs) assembled using two dissimilar electrode materials offer a distinct advantage of wide operational voltage window, and thereby significantly enhance the energy density. Recent progress made in the field of ASCs is critically reviewed, with the main focus on an extensive survey of the materials developed for ASC electrodes, as well as covering the progress made in the fabrication of ASC devices over the last few decades. Current challenges and a future outlook of the field of ASCs are also discussed.

Wearable energy-smart ribbons for synchronous energy harvest and storage.

A promising energy source for many current and future applications is a ribbon-like device that could simultaneously harvest and store energy. Due to the high flexibility and weavable property, a fabric/matrix made using these ribbons could be highly beneficial for powering wearable electronics. Unlike the approach of using two separate devices, here we report a ribbon that integrates a solar cell and a supercapacitor. The electrons generated by the solar cell are directly transferred and stored on the reverse side of its electrode which in turn also functions as an electrode for the supercapacitor. When the flexible solar ribbon is illuminated with simulated solar light, the supercapacitor holds an energy density of 1.15 mWh cm-3 and a power density of 243 mW cm-3. Moreover, these ribbons are successfully woven into a fabric form. Our all-solid-state ribbon unveils a highly flexible and portable self-sufficient energy system with potential applications in wearables, drones and electric vehicles.

High-Performance One-Body Core/Shell Nanowire Supercapacitor Enabled by Conformal Growth of Capacitive 2D WS2 Layers.

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have emerged as promising capacitive materials for supercapacitor devices owing to their intrinsically layered structure and large surface areas. Hierarchically integrating 2D TMDs with other functional nanomaterials has recently been pursued to improve electrochemical performances; however, it often suffers from limited cyclic stabilities and capacitance losses due to the poor structural integrity at the interfaces of randomly assembled materials. Here, we report high-performance core/shell nanowire supercapacitors based on an array of one-dimensional (1D) nanowires seamlessly integrated with conformal 2D TMD layers. The 1D and 2D supercapacitor components possess "one-body" geometry with atomically sharp and structurally robust core/shell interfaces, as they were spontaneously converted from identical metal current collectors via sequential oxidation/sulfurization. These hybrid supercapacitors outperform previously developed any stand-alone 2D TMD-based supercapacitors; particularly, exhibiting an exceptional charge-discharge retention over 30,000 cycles owing to their structural robustness, suggesting great potential for unconventional energy storage technologies.

Probing Ternary Solvent Effect in High V(oc) Polymer Solar Cells Using Advanced AFM Techniques.

This work describes a simple method to develop a high V(oc) low band gap PSCs. In addition, two new atomic force microscopy (AFM)-based nanoscale characterization techniques to study the surface morphology and physical properties of the structured active layer are introduced. With the help of ternary solvent processing of the active layer and C60 buffer layer, a bulk heterojunction PSC with V(oc) more than 0.9 V and conversion efficiency 7.5% is developed. In order to understand the fundamental properties of the materials ruling the performance of the PSCs tested, AFM-based nanoscale characterization techniques including Pulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFM (MSAFM) are introduced. Interestingly, MSAFM exhibits high sensitivity for direct visualization of the donor-acceptor phases in the active layer of the PSCs. Finally, conductive-AFM (cAFM) studies reveal local variations in conductivity in the donor and acceptor phases as well as a significant increase in photocurrent in the PTB7:ICBA sample obtained with the ternary solvent processing.

Coil-Type Asymmetric Supercapacitor Electrical Cables.

Cable-shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable-shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable-shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil-type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical-electrochemical stability. The CASECs show excellent charge-discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm(-3)), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets.

Enhanced magnetism in highly ordered magnetite nanoparticle-filled nanohole arrays.

A new approach to develop highly ordered magnetite (Fe3O4) nanoparticle-patterned nanohole arrays with desirable magnetic properties for a variety of technological applications is presented. In this work, the sub-100 nm nanohole arrays are successfully fabricated from a pre-ceramic polymer mold using spin-on nanoprinting (SNAP). These nanoholes a then filled with monodispersed, spherical Fe3O4 nanoparticles of about 10 nm diameter using a novel magnetic drag and drop procedure. The nanohole arrays filled with magnetic nanoparticles a imaged using magnetic force microscopy (MFM). Magnetometry and MFM measurements reveal room temperature ferromagnetism in the Fe3O4-filled nanohole arrays, while the as-synthesized Fe3O4 nanoparticles exhibit superparamagnetic behavior. As revealed by MFM measurements, the enhanced magnetism in the Fe3O4-filled nanohole arrays originates mainly from the enhanced magnetic dipole interactions of Fe3 O4 nanoparticles within the nanoholes and between adjacent nanoholes. Nanoparticle filled nanohole arrays can be highly beneficial in magnetic data storage and other applications such as microwave devices and biosensor arrays that require tunable and anisotropic magnetic properties.