Novel NiO nanoparticles via phytosynthesis method: Structural, morphological and optical properties

New porous amine-functionalized biochar-based desiccated coconut waste as efficient CO2 adsorbents

Climate change caused by the greenhouse gases CO2 remains a topic of global concern. To mitigate the excessive levels of anthrophonic CO2 in the atmosphere, CO2 capture methods have been developed and among these, adsorption is an especially promising method. This paper presents a series of amine functionalized biochar obtained from desiccated coconut waste (amine-biochar@DCW) for use as CO2 adsorbent. They are ethylenediamine-functionalized biochar@DCW (EDA-biochar@DCW), diethylenetriamine-functionalized biochar@DCW (DETA-biochar@DCW), triethylenetetramine-functionalized biochar@DCW (TETA-biochar@DCW), tetraethylenepentamine-functionalized biochar@DCW (TEPA-biochar@DCW), and pentaethylenehexamine-functionalized biochar@DCW (PEHA-biochar@DCW). The adsorbents were obtained through amine functionalization of biochar and they are characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Brunauer-Emmett-Teller (BET), and thermogravimetric analysis (TGA). The CO2 adsorption study was conducted isothermally and using a thermogravimetric analyzer. From the results of the characterization analyses, a series of amine-biochar@DCW adsorbents had larger specific surface area in the range of 16.2 m2/g-37.1 m2/g as compare to surface area of pristine DCW (1.34 m2/g). Furthermore, the results showed an increase in C and N contents as well as the appearance of NH stretching, NH bending, CN stretching, and CN bending, suggesting the presence of amine on the surface of biochar@DCW. The CO2 adsorption experiment shows that among the amine modified biochar adsorbents, TETA-biochar@DCW has the highest CO2 adsorption capacity (61.78 mg/g) when using a mass ratio (m:m) of biochar@DCW:TETA (1:2). The adsorption kinetics on the TETA-biochar@DCW was best fitted by the pseudo-second model (R2 = 0.9998), suggesting the adsorption process occurs through chemisorption. Additionally, TETA-biochar@DCW was found to have high selectivity toward CO2 gas and good reusability even after five CO2 adsorption-desorption cycles. The results demonstrate the potential of novel CO2 adsorbents based on amine functionalized on desiccated coconut waste biochar.

Phytoassisted synthesis of CuO and Ag-CuO nanocomposite, characterization, chemical sensing of ammonia, degradation of methylene blue

The elimination of hazardous industrial pollutants from aqueous solutions is an emerging area of scientific research and a worldwide problem. An efficient catalyst, Ag-CuO was synthesized for the degradation of methylene blue, the chemical sensing of ammonia. A simple novel synthetic method was reported in which new plant material Capparis decidua was used for the reduction and stabilization of the synthesized nanocatalyst. A Varying amount of Ag was doped into CuO to optimize the best catalyst that met the required objectives. Through this, the Ag-CuO nanocomposite was characterized by XRD, SEM, HR-TEM, EDX, and FTIR techniques. The mechanism of increased catalytic activity with Ag doping involves the formation of charge sink and suppression of drop back probability of charge from conduction to valance band. Herein, 2.7 mol % Ag-CuO exhibited better catalytic activities and it was used through subsequent catalytic experiments. The experimental conditions such as pH, catalyst dose, analyte initial concentration, and contact time were optimized. The as-synthesized nanocomposite demonstrates an excellent degradation efficacy of MB which is 97% at pH 9. More interestingly, the as-synthesized catalyst was successfully applied for the chemical sensing of ammonia even at very low concentrations. The lower limit of detection (LLOD) also called analytic sensitivity was calculated for ammonia sensing and found to be 1.37 ppm.

Chitosan Nanoparticles Modified by Anredera cordifolia (Ten.) Steenis Leaf Extract for Enhancement of Azithromycin Encapsulation Efficiency and Loading Capacity: In vitro Drug Release Study

The encapsulation efficiency and the loading capacity of azithromycin (AZI) were succesfully enhanced by modifying chitosan nanoparticle (NCh) with Anredera cordifolia leaf extract (ACLE), as demonstrated in this study. The prominent secondary metabolites in ACLE could establish a new chemical bonds with NCh's amino groups and partly improved the hydrophobicity of NCh, which leads to excellent AZI encapsulation efficiency and loading capacity of 95.24 ± 1.30% and 55.74 ± 1.03%, respectively. TEM characterization demonstrated that the AZI-loaded ACLE-NCh nanoparticles were uniformly distributed with a particle size of 24.6 ± 2.9 nm. According to the result of in vitro drug release studies, AZI-loaded ACLE-NCh releases 1.12 ± 0.33% at a pH of 1.6 for 2 h, 82.05 ± 2.26% at a pH of 6.8 for 6 h, and 93.44 ± 1.94% at a pH of 7.4 for 24 h. It is remarkable that the encapsulation activityu of AZI-loaded ACLE-NCh is more effective due to the better interaction between NCh and AZI resulting from the increased hydrophobicity of modified NCh. Moreover, this work provides novel findings on the significant contribution of NCh modified by plant extracts, which has the potential as a carrier for azithromycin.

CeO2/CuO/NiO hybrid nanostructures loaded on N-doped reduced graphene oxide nanosheets as an efficient electrocatalyst for water oxidation and non-enzymatic glucose detection

In this work, the three-component heterostructure of CeO₂/CuO/NiO was synthesized by a co-precipitation procedure and heating at a temperature of 750 °C. Then, CeO₂/CuO/NiO nanoparticles were successfully supported on N-doped reduced graphene oxide (N-rGO) by a hydrothermal method. The obtained nanomaterials were used as effective electrocatalysts for the oxygen evolution reaction and glucose sensing in an alkaline medium. The results indicated that when CeO₂/CuO/NiO is anchored on N-rGO nanosheets, active catalytic sites increase. On the other hand, N-doped rGO enhances electrical conductivity and electron transfer for water or glucose oxidation. CeO₂/CuO/NiO@N-rGO has a large electrochemically active surface area and more active catalytic positions, and thus exhibits high activity for the OER with a low overpotential of 290 mV, a suitable Tafel slope of 110 mV dec^-1, and superior stability and durability for at least 10 hours. CeO₂/CuO/NiO@N-rGO can also detect glucose with a high sensitivity of 912.7 μA mM^-1 cm^-2, a low detection limit of 0.053 μM, a wide linear range between 0.001 and 24 mM, and a short response time of about 2.9 s. Moreover, the high selectivity and stability of this electrode for glucose sensing show its potential for clinical applications.

Electrochemical activity of glassy carbon electrode modified with ZnO nanoparticles prepared Via Senna Alata L. leaf extract towards antiretroviral drug

The phytosynthesis method was used to prepare ZnO nanoparticles (ZnO NPs) via Senna alata L. leaf extract (SALE) by involving alkaloids, which play an essential role as a source of weak bases during the formation reaction of NPs. ZnO NPs on glassy carbon electrodes (GCE/ZnO NP) have been introduced to investigate its electrochemical activity towards the antiretroviral drug, lamivudine (3TC). Several characterization techniques, such as Fourier Transform Infra-Red (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), and Dynamic Light Scattering (DLS) techniques were employed to analyze the properties of GCE/ZnO NPs. As a result, ZnO NPs in spherical shape showed a high purity crystalline hexagonal wurtzite structure with a particle diameter of 40–60 nm. A Cyclic Voltammetry (CV) measurement confirmed that the electrochemical reduction of 3TC on GCE/ZnO NPs exhibited an excellent linear range of 10–300 µM with a detection limit of 1.902 µM, quantitation limit of 6.330 µM, and sensitivity of 0.0278 µA/µM. Thus, this research suggests a facile method for the preparation of material-based ZnO NPs as a promising antiretroviral drug sensors due to their excellent electrochemical properties.

NiO-Based Electronic Flexible Devices

Personal, portable, and wearable electronics have become items of extensive use in daily life. Their fabrication requires flexible electronic components with high storage capability or with continuous power supplies (such as solar cells). In addition, formerly rigid tools such as electrochromic windows find new utilizations if they are fabricated with flexible characteristics. Flexibility and performances are determined by the material composition and fabrication procedures. In this regard, low-cost, easy-to-handle materials and processes are an asset in the overall production processes and items fruition. In the present mini-review, the most recent approaches are described in the production of flexible electronic devices based on NiO as low-cost material enhancing the overall performances. In particular, flexible NiO-based all-solid-state supercapacitors, electrodes electrochromic devices, temperature devices, and ReRAM are discussed, thus showing the potential of NiO as material for future developments in opto-electronic devices.

Removal mechanism of Sb(III) by a hybrid rGO-Fe/Ni composite prepared by green synthesis via a one-step method

The annual influx of antimony (Sb) into the environment due to the widespread use of Sb compounds in industry and agriculture has become of global concern. Herein, a functional nanomaterial composite based on loading bimetallic iron/nickel nanoparticles on reduced graphene oxide (rGO-Fe/Ni) was initially prepared in a one-step phytogenic synthesis using a green tea extract. Subsequently, when applied for Sb(III) removal, the removal efficiency of rGO-Fe/Ni reached 69.7% within 3 h at an initial Sb concentration of 1.0 mg·L^-1. Advanced materials characterization via scanning electron microscopy-energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy revealed that Sb(III) was initially adsorbed onto the surface of rGO and then oxidized to Sb(V). This result was also supported by adsorption isotherm, kinetics, and thermodynamic analysis. These studies revealed that the adsorption was spontaneous and endothermic, following a Langmuir adsorption model with pseudo-second-order kinetics and allowed a Sb(III) removal mechanism based on adsorption and catalytic oxidation to be proposed. Furthermore, when rGO-Fe/Ni was practically used to remove Sb(III) in groundwater a 95.7% removal efficiency was obtained at 1 mg·L^-1 Sb(III), thus successfully demonstrating that rGO-Fe/Ni has significant potential for the practical remediation of Sb contaminated groundwater.

Electrospun highly corrosion-resistant polystyrene–nickel oxide superhydrophobic nanocomposite coating

A key challenge in producing superhydrophobic coatings (SHC) is to tailor the surface morphology on the micro-nanometer scale. In this work, a feasible and straightforward route was employed to manufacture polystyrene/nickel oxide (PSN) nanocomposite superhydrophobic coatings on aluminum alloys to mitigate their corrosion in a saline environment. Different techniques were employed to explore the influence of the addition of NiO nanoparticles to the as-prepared coatings. PSN-2 composite with ~ 4.3 wt% of NiO exhibited the highest water contact angle (WCA) of 155° ± 2 and contact angle hysteresis (CAH) of 5°.

Graphic abstract

EIS Nyquist plots of 3 g of electrospun polystyrene coatings (a) without and with (b) 0.1, (c) 0.15, and (d) 0.2 g of NiO.