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Herein, we synthesized 1D bimetallic hydrogen phosphate [CoxNix(HPO4)] nanorods by using a simple and effective chemical bath deposition method for supercapacitor applications. The prepared CoxNix(HPO4) was analyzed by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) pattern. The surface morphology was envisaged by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) methods. The porous nature and surface area of the materials were characterized by nitrogen sorption isotherm and a high specific surface area of 153 m2 g-1 was found to be for Co0.75Ni0.25(HPO4). The Co0.75Ni0.25(HPO4) displays a maximum specific capacity of 475 mA h g-1 at 1 A g-1 in a three-electrode configuration using 3 M KOH as the electrolyte. Co0.75Ni0.25(HPO4) exhibits almost 94.8% of its initial specific capacity over 5000 GCD cycles at 10 A g-1. Furthermore, the fabricated asymmetric supercapacitor (ASC) with Co0.75Ni0.25(HPO4) and activated carbon (AC) showed a high specific capacitance of 182.5 F g-1 at 0.5 A g-1. The ASC device delivered a maximum energy density of 64.88 Wh kg-1 at a power density of 800 W kg-1.

Cost-effective and sustainable high-performance supercapacitor material was successfully prepared from cellulosic waste (Sapindus trifoliatus nut shells) biomass-derived activated carbon (CBAC) by physical activation method. The CBAC displays nanofiber morphology, high specific surface area (786 m2/g), large pore volume (0.212 cm3 g−1) which are evaluated using FESEM, BET and possessed excellent electrochemical behavior analyzed through various electrochemical methods. Moreover, the assembled symmetric CBAC//CBAC device exhibits high specific capacitance of 240.8 F g−1 with current density of 0.2 A g−1 and it is maintained to 65.6 F g−1 at high current density of 2.0 A g−1. In addition, the symmetric device delivers an excellent specific energy maximum of over 30 Wh kg−1 at 400 W kg−1 of specific power and excellent cycling stability in long term over 5000 cycles. The operation of the device was tested by light-emitting diode. Hence, CBAC-based materials pave way for developing large-scale, low-cost materials for energy storage device applications.

Energy crisis and environmental pollution have been one of the major global issues. In this regard, the search for new energy storage materials is cheap, flexible and high-performance supercapacitors electrode which has become intensive. Also, reducing the amount of organic dyes polluting in water is a great significance. Herein, one-step electropolymerization of methylene blue on carbon fiber and the resulting films were applied to the supercapacitor. The high performance is associated to the outstanding conductivity, electrochemical stability and superior mechanical flexibility of carbon fiber. A new flexible electrode for supercapacitors was successfully fabricated by demonstrating with a good electrochemical performance and a promising alternative to reduce the water pollution.

A simple, low-cost, and green route for the preparation of lotus carbon (LC) materials using lotus parts including leaves, flowers, fruits (seed pods), and stems as a renewable precursor is reported. Different porous carbons, leaf-carbon (LF-carbon), flower-carbon (FL-carbon), fruit-carbon (FR-carbon), and stem-carbon (ST-carbon) were synthesized from different parts of the lotus plant by simple carbonization method. The as-synthesized LC materials were well-characterized by many techniques such as electron microscopy and spectroscopy techniques, X-ray diffraction, and BET-surface area analysis. These techniques confirmed the porous structure of LC materials and the existence of heteroatoms in the prepared LC materials. The mesoporous structure of LC materials suggested employing it for the supercapacitor applications. The obtained FR-Carbon exhibits a high specific capacitance of 160 F/g in a three-electrode system in an aqueous 1 M H

In the present study, nanoporous graphene based amperometric detection of folic acid using nanoporous graphene modified electrode was carried out. The preparation of nanoporous graphene, in otherwords reduced graphene oxide (RGO) was done via fast reduction of chemically prepared graphene oxide in an acidic solution using an (Mg/Zn) bimetal strips. Structural, morphological and chemical characteristics of the prepared RGO (Mg/Zn) were determined using Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Transmission electron microscopy and X-ray diffraction. The successful formation of the RGO was corroborated using FT-IR and XPS results, which showed significant reduction in the oxygen functionalities. The prepared nanoporous graphene was used for the preparation of constructed modified electrode (CME), which subsequently used for electrochemical sensing of folic acid analyte. Owing to its excellent electrocatalytic activity, CME showed enhanced electrochemical response in the neutral solution of folic acid analyte, when compared to the conventional electrodes. From the differential pulse voltammetry, the peak current (0.75 V) for the folic acid analyte in CME electrode was observed to be linear and concentration range of 0.902–8.52 μM with the lower detection limit of 0.025 μM (S/N = 3). The prepared sensor was successfully implemented for real samples with tolerable limits.

A simple and sensitive electrochemical determination of l-vanillin (VA), a powerful anti-microbial agent and a commonly employed food preservative was investigated using copper hexacyanoferrate (CuHCF) film modified on 2-mercaptoethylamine functionalized colloidal gold nanoparticles (colloid-Au) graphite-wax composite electrode. As achieved surface modification was characterized using confocal Raman spectroscopy studies which gave rise to peaks at 351, 493, 807 and 2048 cm−1 that corresponds to the characteristics vibrational modes of ν(Fe–C ≡N–Cu), ν(Cu–N), ν(Fe–C) and ν(–C≡N) for the CuHCF film. Further, the elemental analysis investigated using X-ray photoelectron spectroscopy confirms the presence of 2p peaks of Cu (II), Fe(II) and 1 s edge peaks of N for the CuHCF film modified electrode. The modified electrode exhibited a high sensitivity of 0.1817 μA μM−1 at a lower detection potential of 0.68 V towards the VA determination and the limit of detection was observed to be 2.53 × 10−7 M (S/N = 3). The VA content in commercial roasted coffee beans was also examined with the proposed sensor and the results were found to be satisfactory.

To accomplish high-performance flexible energy storage devices, a new class of flexible electrodes with prosperous constructions bearing exceptional electrical conductivity, exclusive porosity, and outstanding mechanical stability is extremely needed. Here, we have successfully fabricated a highly flexible electrode with nanocomposite of polyaniline/manganese hexacyanoferrate PANI/MnHCF nanocomposite (PANI/MnHCF) on highly conductive carbon fiber (FCF). The nanocomposite exhibits an ultra-high specific capacitance of 730 F g−1 at a current density of 1 A g−1 with exceptional rate capability (350 F g−1 capacitance retention at a current density of 20 A g−1), and outstanding cycling performance (capacitance retention of ∼85% after 1000 cycles). The PANI/MnHCF/FCF electrode shows better electrochemical performance due to their exclusive properties such as excellent electrical conductivity, unique porous network and outstanding mechanical flexibility. Furthermore, the higher surface area of PANI/MnHCF nanocomposite facilitates the transport of electrons and electrolyte ions during rapid charge/discharge process. This present work offers a simple, scalable and cost-effective method for fabrication of other PANI/MnHCF nanocomposite based electrode, which is applicable for providing energy in practical flexible portable devices.

Herein, Sargassum coreanum (marine algae)-mediated silver nanoparticles (AgNPs) were successfully synthesized by a simple reduction method. The synthesized AgNPs were characterized using ultraviolet-visible spectroscopy, attenuated total reflection Fourier transformed infrared spectroscopy, X-ray diffractometry, field emission scanning electron microscopy (FESEM) with energy-dispersive X-ray (EDX) spectroscopy, and high-resolution transmission electron microscopy (HR-TEM) analysis. The acquired colloidal AgNPs were strongly absorbed around 420 nm and displayed brown color under visible light. The XRD pattern of AgNPs exposed their face-centered cubic geometry along with crystalline nature. The HRTEM images of synthesized AgNPs confirmed the mean particle size of 19 nm with a distorted spherical shape, and the calculated interlayer distance (d-spacing value) was about 0.24 nm. Further, the catalytic degradation of methylene blue using sodium borohydride and AgNPs was monitored using UV–vis spectroscopy. The result revealed that AgNPs performed as a superior catalyst, which completely degraded MB in 20 min. The rate constant for MB degradation was calculated to be 0.106 min−1, demonstrating that the marine algae-mediated AgNPs had outstanding catalytic activity. This approach is easy and environmentally benign, which can be applied for environmental-based applications such as dye degradation and pollutant detoxification.

In the present study, pores enriched high surface area of carbon electrode obtained from hypercross-linked polymer of poly(divinylbenzene-co-vinylbenzyl chloride) [P(DVB:VBC)] for supercapacitor application. First, hypercross-linking reaction was carried out in [P(DVB:VBC)] via. simple Friedel-Crafts alkylation method (HCP) followed by pyrolysis at 800 °C (HCP-800). The surface morphology of the synthesized HCP and HCP-800 materials was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) technique. HCP-800 showed a remarkable surface area of 1027 m2 g−1 with the abundance of micropores. In addition, the oxidation state of the porous carbon was assessed by x-ray photo electron spectroscopy (XPS). In a three-electrode and symmetric two-electrode configurations, electrodes exhibited a supreme specific capacitance of 272 and 145 F g−1 in aqueous electrolyte, respectively. Specific energy of 39.47 Wh kg−1 at specific power of 699.96 W kg−1 is yielded from the symmetric supercapacitor device (SSCD). Furthermore, SSCD retains more than 94% of its residual capacitance after 5000 GCD cycles at a current density of 5 A g−1 suggests a good cyclic stability.

This paper’s emphasis is on the development of a fluorescent chemosensor for Fe3+ ions in an aqueous solution, using hydrophilic carbon dots (O-CDs). A simple, cost-effective, and environmentally friendly one-step hydrothermal synthesis method was used to synthesize fluorescent hydrophilic O-CDs from Oxalis corniculata (Family; Oxalidaceae). The graphitic structure and size distribution of the O-CDs was verified by X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy studies. The resulting O-CDs had a near-spherical shape and an adequate degree of graphitization at the core, with an average diameter of 4.5 nm. X-ray photoelectron and Fourier transform infrared spectroscopy methods revealed the presence of several hydrophilic groups (carbonyl, amine, carboxyl, and hydroxyl, along with nitrogen and oxygen-rich molecules) on the surface of O-CDs. The synthesized hydrophilic O-CDs with excitation wavelength-dependent emission fluorescence characteristics showed a high quantum yield of about 20%. Besides this, the hydrophilic O-CDs exhibited a bright and controllable fluorescence with prolonged stability and photo-stability. These fluorescent hydrophilic O-CDs were used as a nanoprobe for the fluorometric identification of Fe3+ ions in an aqueous solution, with high sensitivity and selectivity. By quenching the blue emission fluorescence of this nanosensor, a highly sensitive Fe3+ ion in the range of 10–50 µM with a minimum detection limit of 0.73 µM was achieved. In addition, the developed nanosensor can be used to sense intracellular Fe3+ ions with high biocompatibility and cellular imaging capacity, and it has a lot of potential in biomedical applications.

Recently, the use of natural products for the synthesis of carbon dots (CDs) has received much attention. Herein, leftover kiwi (Actinidia Deliciosa) fruit peels were successfully turned into beneficial fluorescent carbon dots (KN-CDs) via the hydrothermal-carbonization route. KN-CDs 1 and KN-CDs 2 were prepared without and with ammonium hydroxide, respectively. KN-CDs 1 and KN-CDs 2 were systematically characterized by various analytical techniques. Synthesized KN-CDs showed spherical-shaped morphology with narrow size distribution and excellent optical properties with excitation-independent behaviors. The quantum yields of KN-CDs 1 and KN-CDs 2 were calculated as 14 and 19%, respectively. Additionally, the KN-CDs possess excellent prolonging and photostability. Because of the excellent optical properties of KN-CDs, they were utilized as fluorescent sensors. The strong fluorescence of the KN-CDs was selectively quenched by Fe3+ ion, and quenching behavior showed a linear correlation with the concentrations of Fe3+ ion. KN-CDs 1 and KN-CDs 2 showed the detection of Fe3+ ions within the concentration range of 5–25 µM with the detection limit of 0.95 and 0.85 µM, respectively. Based on the turn-off sensing by the detection of Fe3+ ions, KN-CDs would be a promising candidate as a selective and sensitive fluorescent sensor.

The growth of industry fulfills our necessity and promotes economic development. However, pollutants from such industries pollute water bodies which pose a high risk for living organisms. Thus, researchers have been urged to develop an efficient method to remove toxic heavy metal ions from water bodies. The adsorption method shows promising results for the removal of heavy metal ions and is easy to operate on a large scale, thus can be applied to practical applications. Numerous adsorbents were developed and reported, among them hydrogels, which attract great attention because of the reusability, ease of preparation, and handling. Hydrogels are generally prepared by the cross-linking of polymers that result in a three-dimensional structure, showing high porosity and high functionality. They are hydrophilic in nature because of the functional groups, and are non-toxic. Thus, this review provides various methods of hydrogel adsorbents preparation and summarizes recent progress in the use of hydrogel adsorbents for the removal of heavy metal ions. Further, the mechanism involved in the removal of heavy metal ions is briefly discussed. The most recent studies about the adsorption method for the treatment of heavy metal ions contaminated water are presented.

Synthesis of biomass derived microporous activated carbon materials has fascinated attention in the emerging field of energy storage due to its high specific surface area, excellent electrical conductivity, low cost and environmental benevolence. Herein, we report facile and cost-effective method to produce porous activated carbons for the first time by physical activation method using two different biomass sources Syzygium cumini fruit shells (SCFS) and Chrysopogon zizanioides roots (CZR) for fabrication of symmetric supercapacitors. Biomass-derived activated carbon (BAC) materials were obtained via a two-step synthesis: (i) carbonization at 700 °C in N2 atmosphere (ii) CO2 activation at 700 °C in N2 atmosphere. The formation of high surface area and disordered micropores on the carbon by CO2 activation was identified by N2 adsorption-desorption and FE-SEM techniques. SCFS-AC and CZR-AC exhibit enhanced electrochemical performances in three-electrode configuration showing their high specific capacitances with good capacitance retention. These biomass derived activated carbon (BAC) based symmetric supercapacitors deliver energy density maximum of 27.22 W h kg−1 (SCFS-AC) and 16.72 W h kg−1 (CZR-AC) at 200 W kg−1 power density with an outstanding cycling stability over 5000 cycles. This work offers an environmentally safe and innovative approach to control the porosity in BAC for energy storage applications.

In this paper, a facile immobilization of copper hexacyanoferrate nanoparticles (CuHCFNP) on a paraffin wax-impregnated graphite electrode (PIGE) was carried out using the room-temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) as an ionic binder. The characteristics of the CuHCFNP/EMIMBF4 gel-modified electrode were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, and the modified electrode morphology was also characterized using field emission scanning electron microscopy (FESEM). The electrocatalytic behavior of butylated hydroxyl anisole (BHA) at the modified electrode has been investigated in 0.1 M KNO3 in static and dynamic conditions. Under the optimum conditions, the oxidation peak current was proportional to the BHA concentration in the range from 1.5 to 1000 μM with a detection limit of 0.5 μM (S/N = 3). The proposed method was applied to determine BHA content in real samples with satisfactory results.

Integration of materials acts as a bridge between the electronic and biological worlds, which has revolutionized the development of bioelectronic devices. This review highlights the rapidly emerging field of switchable interface and its bioelectronics applications. This review article highlights the role and importance of two-dimensional (2D) materials, especially graphene, in the field of bioelectronics. Because of the excellent electrical, optical, and mechanical properties graphene have promising application in the field of bioelectronics. The easy integration, biocompatibility, mechanical flexibility, and conformity add impact in its use for the fabrication of bioelectronic devices. In addition, the switchable behavior of this material adds an impact on the study of natural biochemical processes. In general, the behavior of the interfacial materials can be tuned with modest changes in the bioelectronics interface systems. It is also believed that switchable behavior of materials responds to a major change at the nanoscale level by regulating the behavior of the stimuli-responsive interface architecture.

Nitrogen rich porous carbon balls are derived from hypercross-linked polymers (HCPs) of anthracene and subsequent carbonization with urea. The obtained materials exhibit combination of abundant microporous and minimal mesoporous property with large surface area (623.27 to 928.44 m2 g − 1). The influence of annealing temperature in nitrogen doped porous HCPs was examined the capacitive performance of the prepared electrode materials using electrochemical techniques. A symmetric device was assembled, and it shows a high specific capacitance of 206.4 F g − 1 at 0.2 A g − 1 with excellent rate capability. Also, the material exhibits excellent durability only 3.5% loss was observed after 5000 cycles (capacitance retention of 96.5%). These outcomes justify that nitrogen anchored porous carbon balls are excellent materials for high-performance symmetric supercapacitors.

A novel enzyme-free modified electrode constructed by electropolymerization of L-cysteine on a graphite electrode, followed by electrodeposition of copper nanoparticles using ionic liquid as a green electrolyte. The modified electrode exhibits an excellent electrocatalytic activity towards the oxidation of hydrogen peroxide (H2O2) and glucose at a reduced overpotential of 0 V and +0.35 V, respectively. The immobilization of copper nanoparticle encapsulated by polycysteine (PC) formed on the electrode was confirmed by Fourier transform infrared (FT-IR) spectroscopy, Raman spectra, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic force microscopy (AFM) studies. The determination of H2O2 and glucose with the modified electrode shows the advantages of ease of preparation, high sensitivity, good selectivity and stability. The practical application of the modified electrode for selective detection of H2O2 and glucose has been evaluated by analyzing the real samples of stain remover solutions and human urine samples to determine H2O2 and glucose, respectively.

An air and moisture stable ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate (EMIMES) was used as an electrolyte for electropolymerization of L-cysteine followed by electrodeposition of nickel nanoparticles (NiNP) on paraffin wax impregnated graphite electrode (PIGE). The electrodeposited NiNP modified electrode showed good redox activity and stability in 0.1M KOH solution. The modified electrode has been characterized using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified electrode was examined for electrocatalytic oxidation of some compounds of biological and clinical importance such as vitamin B6, L-tyrosine, L-tryptophan, vanillin, glucose and hydrogen peroxide by cyclic voltammetry to demonstrate the electrocatalytic activity of the electrodeposited NiNPs.