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The conversion of nitrogen to ammonia offers a sustainable and environmentally friendly approach for producing precursors for fertilizers and efficient energy carriers. Owing to the large energy density and significant gravimetric hydrogen content, NH

Two-dimensional (2D) conducting metal-organic frameworks (MOFs) is an emerging family of porous materials that have attracted a great attention due to their outstanding inherent properties such as hierarchical porosity, diverse architectures with high surface area and excellent electrical conductivity. These unique features make them ideal candidates for electrochemical energy storage technologies. This review highlights the key innovations on 2D conducting MOFs with emphasis on the design and synthesis strategies, and their potential applications in energy storage systems. Several recent breakthrough examples of 2D conducting MOFs with enhanced electrochemical performances are outlined. The review further extends the discussion on the significance of Nuclear Magnetic Resonance Spectroscopy (NMR) to understand the charge storage kinetics and their impact on structural implications of the materials. The elucidation of structure-property-performance relationship will further guide the development of new architectures of 2D conducting MOFs for the high-performance energy storage devices.

Lightweight computing technologies such as the Internet of Things and flexible wearable systems have penetrated our everyday lives exponentially in recent years. Without a question, the running of such electronic devices is a major energy problem. Generally, these devices need power within the range of microwatts and operate mostly indoors. Thus, it is appropriate to have a self-sustainable power source, such as the photovoltaic (PV) cell, which can harvest indoor light. Among other PV cells, the dye-sensitized solar cell (DSSC) has immense capacity to satisfy the energy demands of most indoor electronics, making it a very attractive power candidates because of its many benefits such as readily available materials, relatively cheap manufacturing methods, roll-to-roll compatibility, easy processing capabilities on flexible substrates and exceptional diffuse/low-light performance. This review discusses the recent developments in DSSC materials for its indoor applications. Ultimately, the perspective on this topic is presented after summing up the current progress of the research. Graphic abstract

3D chitosan scaffolds treated with alkali showed enhanced mechanical properties and stability in aqueous conditions. Chitosan is a preferred polymer for biomedical applications due to its antimicrobial, antioxidant and wound healing properties. Chitosan has been made into films, fibers, micro and nanoparticles and electrospun membranes for tissue engineering, drug delivery and other medical applications. However, materials made from chitosan have poor strength and stability. Compared to other forms, 3D scaffolds are more suitable for tissue engineering and other applications but are relatively easily susceptible to moisture and have poor strength due to their porous structure. Several physical and chemical approaches have been used to increase the strength and stability of chitosan biomaterials. In this study, we demonstrate that a simple treatment with alkali will substantially improve the strength and stability of freeze-dried 3D chitosan scaffolds. Three different concentrations of chitosan were lyophilized and made into scaffolds with varying properties. These scaffolds were alkali treated and tested for their increase in strength, resistance to water and other properties. Up to 50% increase in strength was possible when higher concentrations of chitosan and alkali treatment were used. The scaffolds have good activity against both gram positive and gram negative bacteria with the highest percentage of inhibition being 97%. Scaffolds also showed the ability to generate hydroxyapatite when incubated in phosphate buffered saline (PBS) for 7 days. This study provides a novel approach to obtain 3D chitosan scaffolds with properties suitable for medical, food and other applications.

In the recent times, global interest on plant-based research has increased significantly. Through this article, a simple heat treatment method to synthesize Centella asiatica (CA) powder has been suggested. The synthesized samples have been subjected to various structural and morphological characterizations, in addition to electrochemical studies. Although the medicinal value of Centella asiatica is well known, its use in other applications is hardly explored. Hence, by combining the cyclic nature of CA and the layered structures of carbonaceous materials, composites of Centella asiatica with graphite powder, GO and rGO have been prepared for the first time and their photocatalytic and electrochemical properties have been investigated. In spite of some agglomeration and flake like structures, the nanosize (14 nm) of the prepared CA sample contributes largely to the aforementioned applications. One of the phenomenal aspects of the synthesized sample is that the low energy gap and high conductivity makes it an excellent photocatalytic material which is also evident from its ability to decolorize AO 8 dye under UV light to a great extent. Among the composites of CA-carbonaceous materials prepared, Centella asiatica-rGO exhibited superior electrochemical properties with high capacitance and low charge transfer resistance.

A rapid and facile method for the detection of hydrogen peroxide (H2O2) in chemical reactions has been reported using molybdenum oxide Nanoparticles (MoO3 NPs) synthesized via an eco-friendly and economical solution combustion route using Centella Asiatica leaf powder. The formation of porous agglomerated NPs has been confirmed by subjecting the synthesized material to various analytical and spectroscopic techniques to understand their size, morphology, and nature. In this study, MoO3 NPs-based electrode has been fabricated and its electrochemical sensing capabilities have been investigated. Electrochemical investigation of hydrogen peroxide exhibits an increase in the peak current response at pH 13. The cyclic voltammetry (CV) results indicate an appreciable reversibility of the electrode reaction. The anodic and cathodic peaks show a greater inclination towards the positive and negative sides with a significant development in the reversibility of the oxidation and reduction states. These findings open up new avenues for the exploration of various other metal oxide based NPs as sensors for the detection of chemically toxic substances.

Textiles are known to be the best substrates for growing a variety of microorganisms efficiently at appropriate temperatures and humidity in contact with the human body. Currently, increasing public concern about hygiene has been driving many investigations about antimicrobial surface modification of textiles. The present research reports on the synthesis and characterization of nanosized copper oxide nanoparticles (CuONPs) and their application on cotton fabric to increase the bactericidal and hydrophobic properties. The synthesized materials have been subjected to spectroscopic and microscopic characterizations to help in understanding their structure, morphology, size, and composition. Further, upon dispersion of the nanoparticles onto the fabric, its hydrophobicity and mechanical properties were evaluated using electron microscopy and universal testing machine. Treated cotton fabric exhibits higher tensile strength (32 MPa) than the untreated one (27 MPa), whereas copper nanoparticle-coated cotton fabric shows a fair hydrophobicity. Moreover, CuONPs-treated and untreated cotton fabrics have been analyzed for bactericidal activity against various gram-negative and gram-positive strains. Finally, the CuONPs-coated cotton fabric displays greater antibacterial activity against E. coli and exhibits superior antimicrobial activity even after 30 cycles of washing, indicating that the CuONPs-coated cotton fabric has a higher potential to be employed as a medical textile to avoid cross-infection within a clinical environment.

A green combustion method using Aloe vera latex as a fuel was employed to synthesize nanocrystalline cupric oxide (CuO). The nanocrystalline nature and phase of CuO was confirmed by powder X-ray diffraction. Applying the Kubelka–Monk function to diffuse reflectance spectra showed the band gap of CuO to be 1.632 eV. Paracetamol and d -glucose in 1 M KOH solution were sensed using a carbon paste electrode modified using CuO nanoparticles (NPs). The cyclic voltammetry results suggest that CuO NPs possess superior electrochemical properties due to a lower value of the difference between oxidation and reduction potential (EO-ER). The proton diffusion coefficient for CuO electrode material was1.5047 × 10−5cm2s−1. Electrochemical impedance and Bode studies confirmed that the charge-transfer resistance value of CuO NPs was on the lower side due to the phase angle (55°) being near to ф = ᴨ/2. The electrochemical behavior indicates that CuO is a promising electrode material for sensing molecules such as paracetamol and glucose.

An economic low-temperature self-ignition solution combustion method was used to synthesize 1–11 mol% chromium ion (Cr3+) doped MgAl2O4 nanoparticles (NPs). The structural, morphological and energy gap variations due to the influence of Cr3+ on the host matrix were evidenced by powder X-ray diffraction (PXRD), Fourier transformed infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). Under visible light irradiation, the as-prepared NPs showed excellent photocatalytic activities (PCA) for the industrial dye Acid Red-88 (AR-88) and pyrocatechol (PY) - an emerging pollutant (EP). The experiments were carried out at room temperature in an aqueous solution at a concentration of 20 ppm. Among others, MgAl2O4:Cr3+(5 mol%) showed 91.38% degradation within 150 min exhibiting zero-order kinetics and 82% degradation in 6 h displaying the first order kinetics for AR-88 dye and PY EP, respectively. In this case, a greater number of hydroxyl (OH.) radicles dominate over other reactive oxygen species (ROS), such as holes and singlet oxygens (1O2) under different pH conditions. Electrochemical studies have yielded the proton diffusion coefficient (D) value as large as 2.145 × 10−4 cm2s−1 for the optimized NP electrode, which is substantially greater than 1.0935 × 10−5 cm2s−1 for the pure MgAl2O4 one owing to the intercalated anions and structurally disordered density of the electrode material. This superior electrochemical behaviour suggests the potential application of the optimized NP material as an anodic electrode for supercapacitors. Published version This work was supported by the Science and Engineering Research Board, Govt. of India under the ASEAN - India Collaborative R&D Scheme (Project Grant No. CRD/2018/000066 M.S.S) of the ASEAN - India S&T Development Fund (AISTDF)

The current energy situation requires not only enormous energy in a brief period of time but clean energy as well. In this direction, a dye-sensitized solar cell (DSSC)—supercapacitor (SC) integrated energy device has been fabricated. This embedded energy system has a specific advantage such as easy manufacturing, low manufacturing costs, and flexible substrates compatibility. A natural photosensitizer was extracted from readily available beetroots and characterized using ultraviolet (UV)-visible spectroscopy. The zinc oxide semiconductor was synthesized using microwave technique and regarded as the DSSC photoanode material. The ZnO’s phase, purity, and morphology were investigated using X-ray diffraction (XRD) spectroscopy and scanning electron microscope. The iodine-doped cellulose acetate propionate (CAP) biopolymer electrolyte functions as the DSSC and supercapacitor electrolyte. The solid polymer electrolyte conductivity and dielectric studies were performed using electrochemical impedance spectroscopy (EIS). The laser-induced technique was used to synthesize graphene that plays a dual purpose as photocathode in DSSC and supercapacitor electrodes. The embedded energy unit from the DSSC-supercapacitor demonstrates a 6.75% fill factor representing its decent efficiency.

A new nanocomposite has been prepared embedding CuO nanoparticles as an additive into grafted β-nickel hydroxide electrode and their electrochemical performance in KOH electrolyte have been investigated. β-nickel hydroxide (β-Ni(OH)2) has been prepared by a simple precipitation method. Ni(OH)2/NiOOH, the main active materials in the pasted nickel electrode have been prepared using nickel mesh in the form of current collector. A study on the electrochemical performances of the pure β-Ni(OH)2 and CuO added β-Ni(OH)2 electrodes in 6.0 M KOH electrolyte has revealed that CuO embedded β-Ni(OH)2 displays much higher specific capacitance and better cyclability than pure β-Ni(OH)2. In fact, the addition of CuO improves the reversibility of the electrode by reducing the anodic (Epa) and cathodic (Epc) peak potential difference and also increases the separation of the oxygen evolution (EOE) and anodic (Epa) peak potential. Further, CuO nanoparticles grafted β-Ni(OH)2 electrode displays elevated proton diffusion co-efficient (D) and inferior charge transfer resistance. Specifically, CuO embedded β-Ni(OH)2 exhibits 855 F g−1 at 5 Ag-1 and good cycling stability as it maintains more than 90% of its original capacitance even after 3000 cycles. The enhancement may be attributed to the nanosize of CuO and chemical interaction between CuO and β-Ni(OH)2. These results are expected to offer new insight to future researchers who wish to work on the development of novel electrode materials for energy storage applications.

The development of cost-effective and eco-friendly alternatives of energy storage systems is needed to solve the actual energy crisis. Although technologies such as flywheels, supercapacitors, pumped hydropower and compressed air are efficient, they have shortcomings because they require long planning horizons to be cost-effective. Renewable energy storage systems such as redox flow batteries are actually of high interest for grid-level energy storage, in particular iron-based flow batteries. Here we review all-iron redox flow battery alternatives for storing renewable energies. The role of components such as electrolyte, electrode and membranes in the overall functioning of all-iron redox flow batteries is discussed. The effect of iron–ligand chemistry on the performance of battery is highlighted. Additionally, a brief contextual background and fundamentals of redox flow batteries are provided. The design aspects, progress in research, mathematical modeling, cost estimations and future prospects of using all-iron energy systems are discussed in the context of future grid-level energy storage.

The persistence of hollow centre in the carbon obtained from milkweed floss provides exceptional sorption characteristics, not seen in common biomasses or their derivatives. A considerably high sorption of 320mg of lead per gram of milkweed carbon was achieved without any chemical modification to the biomass. In this research, we have carbonized milkweed floss and used the carbon as a sorbent for lead in waste water. A high surface area of 170m2g-1 and pore volume of 1.07cm3g-1 was seen in the carbon. Almost complete removal (>99% efficiency) of lead could be achieved within 5min when the concentration of lead in the solution was 100ppm, close to that prevailing in industrial waste water. SEM images showed that the carbon was hollow and confocal images confirmed that the sorbate could penetrate inside the hollow tube.

The importance of Ni-based batteries in the present context is extremely valuable, as their electrochemical properties are expected to offer significant insights into their application as battery materials. In this direction, Ni(OH) 2 has been prepared using the co-precipitation method by varying the concentrations of zinc additive (2, 4, 6 & 8 wt%) and pH (8, 9, 10 & 11). The results show that the prepared samples exist in β-phase with flake like structure. The electrochemical properties of b-Ni(OH) 2 have been investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements using a paste-type electrode on a nickel mesh as a current collector. The cyclic voltammetry measurements indicate that the reversibility of the electrode reaction increases at pH 10 and 6% Zn additive. Whereas, the EIS measurements reveal that a reduction in the charge transfer resistance increases the double layer capacitance of the nickel electrode.

In this paper, the performance of Fe based redox flow batteries (IRFBs) was dramatically improved by coating N-doped carbon spheres (NDCS) on the graphite felt electrodes. NDCS was synthesized by the single-step hydrothermal method using dextrose and ammonia as a precursor and coated over a graphite felt electrode by electrostatic spraying. The weight of NDCS required for the modification of the electrode to achieve the effective performance of the battery was studied using electrochemical techniques. Cyclic voltammetry (CV) and potentiodynamic polarization study was used to evaluate the kinetic reversibility and linear polarization resistance offered by the electrode towards electrolyte. The characterizing features of the NDCS, untreated graphite felt (UGF) electrode, and optimized modified graphite felt (MGF) electrode were analyzed using SEM, EDAX, XRD, and Raman spectroscopy. The charge-discharge studies were performed for the 132 cm2 IRFB using a 2 mg/cm2 MGF electrode as a positive electrode by varying the current densities from 20 to 60 mA/cm2. The cell resulted in an average coulombic efficiency (CE) of 93%, voltaic efficiency (VE) of 72%, and energy efficiency (EE) of 68% for 15 cycles at the current density of 30 mA/cm2. The improvement in the performance of the IRFB is due to the presence of electrochemically active nitrogen-bearing carbon catalysts. In this paper, the pioneering effort has been made to improve the efficiency of the IRFB with an active area of 132 cm2 using glycine as the ligand.

Dye-sensitized solar cells (DSSCs) are an efficient and versatile method of transforming the clean and most plentiful energy resources available. DSSC is translucent to some extent and relatively inexpensive than the traditional solar cell. Thus, it may be a possible source of electricity for the future. But other things need to be focused on before it is considered a viable commercial product. The review discusses these facets and the numerous changes the DSSC has experienced in the recent years. Photoelectric conversion systems struggle to fulfil the specifications of constant power output owing to the erratic and unstable characteristics of the solar radiation. With the evolution of rechargeable electric energy storage systems (ESSs), the integration of a DSSC and ESSs has developed into a promising approach to solve this issue. Here, we describe the working principle, recent progress of DSSCs, including photoanodes, sensitizers, electrolytes, and counter electrodes, and the use of DSSCs in energy storage, targeting DSSC and supercapacitor (SC) integrated devices. The future prospects for highly effective, reliable DSSC and DSSC-SC development have also been highlighted.

A custom designed DNA probe against cry1 gene of Bacillus thuringiensis has been used to fabricate a DNA biosensor by self-assembled monolayers of mercaptohexanol (MCH) and thiol-linked custom designed probe (ssDNA-thiol), immobilized on a screen printed gold nanostructured electrode. DNA immobilization and hybridization have been characterized by differential pulse voltammetry (DPV) using methylene blue as an electrochemical hybridization indicator. With this approach, the target DNA could be quantified in the range of 1.0 × 10−6 M to 1.0 × 10−12 M, with a detection limit of 0.997 × 10−12 M by 3σ. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) have been performed to characterize the sequentially modified electrode. In addition, a non-complementary DNA sequence of Bacillus cereus has been tested as a non-target, that hardly causes any variation in the reduction current of MB reaffirming that the DNA-based biosensor is high selective to Bacillus thuringiensis. The electrochemical detection methods employed in this work can be extended further to develop DNA-based biosensors for the detection of other microorganisms having applications in agriculture, food industries and medical applications.

For large-scale energy storage, iron-based flow batteries (IRFBs) have been considered as a better choice because of their low-cost and use of environmentally friendly iron-based salts. The development of a IRFBs has been limited by the sluggish kinetics of the reaction, especially at the positive electrode during charging. Therefore, it is very important to look for stable electrolytes and superior electrode materials along with their modifications. Carbon-based electrodes are majorly used in IRFBs and these electrodes are feasible to modify using electrocatalysts. In the current study, nitrogen-doped carbon particles (NICaps) derived from Bermuda grass were used to modify graphite felt electrode. SEM, EDAX, Raman, and XPS analysis were used to characterize the modified graphite felt (MGF) electrode. It was observed that the NICaps MGF electrode had a significant improvement in electrochemical properties. The cathodic and anodic peak currents for the MGF electrode (1.55 and 1.63 mA/cm2 respectively) had a remarkable increase in comparison with the untreated graphite felt electrode (UGF) (0.48 and 0.88 mA/cm2 respectively). The Nyquist plot and the data derived from the equivalent circuit indicated lower charge transfer resistance for MGF. The charge-discharge studies carried out using 132 cm2 cell reveals that the modified electrodes result in higher current uptake of 50 mA/cm2 whereas the current uptake from the UGF electrode was limited to 20 mA/cm2. The battery resulted in an average coulombic efficiency of 95%, the peak power density of 60 mW/cm2, and better stability during multiple cycling.

Polyethylene tetraphthalate (PET) bottles, a major environmental pollutant from the food industry, has been used as an activated carbon source in the current work. The specific surface area of the activated carbon has been analyzed using N2 adsorption/desorption isotherms, at different sonication time periods. A high surface area of 899 m2 g-1 with microporosity has been achieved for 20 h sonication followed by activation at 800 °C. To further enhance the material performance, carbon doped MoS2 (MoS2–C), using conventional hydrothermal technique has been synthesized. Different composite ratios of activated carbon and MoS2-C have been tested using electrochemical impedance spectroscopy and the best ratio owing to lesser charge-transfer resistance has been chosen for supercapacitor and HER analysis. The porous network of the plastic derived activated carbon (PAC) with a few layers of MoS2–C contributes significantly to the increase in the power density (469 W kg-1). By inducing defects on the material surface, there has been a significant enhancement in the electrocatalytic activity on PAC and this facilitates HER on its surface. Subsequently, the HER activity of the PDAC/MoS2–C composite has also been reported. Here, the PDAC defective sites along with the hexagonal MoS2–C’s largely exposed reactive edges indicate a reduction in the overpotential and Tafel values of −195 mV and −82 mVdec−1, suggesting that the material under investigation is a good catalyst for electrochemical HER. Also, this article reports for the first-time, HER activity of defect induced plastic derived activated carbon and its excellent catalytic activity.

A new photocatalytic material sodium iron disulfide (NaFeS2) has been synthesized via a hydrothermal method for the degradation of methylene blue (MB) and indigo carmine (IC). This material has been subjected to various analytical, electrochemical and photocatalytic studies to understand its morphology, crystallinity, band gap, oxidation-reduction potential and ability to catalyse the rate of dye degradation. The material exists as nanorods with a thickness of 30–100 nm and a monoclinic phase with an average crystallite size of 25–30 nm. The energy bandgap of the prepared photocatalyst has been calculated using the Kubelka-Munk function and is found to be 2.01 eV. Using a UV light source, the photocatalytic activity of NaFeS2 has been carried out, where the time of irradiation determined the ability of the catalyst to degrade the dye under investigation. With a degradation efficiency of 97% in 105 min for MB and 99% in 45 min for IC, NaFeS2 appears as an excellent photocatalytic material. The electrochemical studies also act as a testament for NaFeS2’sadmirable photocatalytic property. The photocatalytic and electrochemical activities of NaFeS2 offer an innovative platform for the treatment of various other environmental pollutants as well.

In the recent times, cost-effective and eco-friendly processes of synthesizing nanoparticles (NPs) have emerged as a substitute to conventional synthetic methods. Several research groups in the past have synthesized silver oxide (Ag2O) nanoparticles from various plant extracts and have been extensively reported. A first of its kind facile green combustion method has been adopted here to synthesize Ag2O NPs using Centella asiatica and Tridax plant powder. The unique pentacyclic and triterpene constituents of Centella asiatica and Tridax powder has kindled our curiosity to explore their electrochemical, photocatalytic and biological activities that may contribute to various environmentally benign industrial applications. The cyclic voltammetric studies show that the cathodic and anodic peak potentials for the synthesized Ag2O NPs exhibit hysteresis in the range of 0.3 V to –0.1 V. A high percentage of degradation of acid orange 8 (AO8) dye by the synthesized Ag2O NPs offers new hope on its potential photocatalytic activity. Finally, their anti-bacterial and anti-fungal activities carried out against S. epidermidis and S. aureus and A. fumigates and A. aureus respectively, have shed new light on the ability of the synthesized Ag2O NPs to inhibit the growth of various disease-causing pathogens. Hence, it is believed that this research work will act as a fundamental basis to various researchers and industrialists working in the energy, water and biological fields to carry out advanced studies in the aforementioned domains.