A narrative review of the synthesis, characterization, and applications of iron oxide nanoparticles.

The significance of green synthesized nanomaterials with a uniform shape, reduced sizes, superior mechanical capabilities, phase microstructure, magnetic behavior, and superior performance cannot be overemphasized. Iron oxide nanoparticles (IONPs) are found within the size range of 1-100 nm in nanomaterials and have a diverse range of applications in fields such as biomedicine, wastewater purification, and environmental remediation. Nevertheless, the understanding of their fundamental material composition, chemical reactions, toxicological properties, and research methodologies is constrained and extensively elucidated during their practical implementation. The importance of producing IONPs using advanced nanofabrication techniques that exhibit strong potential for disease therapy, microbial pathogen control, and elimination of cancer cells is underscored by the adoption of the green synthesis approach. These IONPs can serve as viable alternatives for soil remediation and the elimination of environmental contaminants. Therefore, this paper presents a comprehensive analysis of the research conducted on different types of IONPs and IONP composite-based materials. It examines the synthesis methods and characterization techniques employed in these studies and also addresses the obstacles encountered in prior investigations with comparable objectives. A green engineering strategy was proposed for the synthesis, characterization, and application of IONPs and their composites with reduced environmental impact. Additionally, the influence of their phase structure, magnetic properties, biocompatibility, toxicity, milling time, nanoparticle size, and shape was also discussed. The study proposes the use of biological and physicochemical methods as a more viable alternative nanofabrication strategy that can mitigate the limitations imposed by the conventional methods of IONP synthesis.

Effects of polyethylene oxide particles on the photo-physical properties and stability of FA-rich perovskite solar cells.

In this paper, we use Polyethylene Oxide (PEO) particles to control the morphology of Formamidinium (FA)-rich perovskite films and achieve large grains with improved optoelectronic properties. Consequently, a planar perovskite solar cell (PSC) is fabricated with additions of 5 wt% of PEO, and the highest PCE of 18.03% was obtained. This solar cell is also shown to retain up to 80% of its initial PCE after about 140 h of storage under the ambient conditions (average relative humidity of 62.5 ± 3.25%) in an unencapsulated state. Furthermore, the steady-state PCE of the PEO-modified PSC device remained stable for long (over 2500 s) under continuous illumination. This addition of PEO particles is shown to enable the tuning of the optoelectronic properties of perovskite films, improvements in the overall photophysical properties of PSCs, and an increase in resistance to the degradation of PSCs.

Tuning the Nanoporous Structure of Carbons Derived from the Composite of Cross-Linked Polymers for Charge Storage Applications.

Controlling the porosity of carbon-based electrodes is key toward performance improvement of charge storage devices, e.g., supercapacitors, which deliver high power via fast charge/discharge of ions at the electrical double layer (EDL). Here, eco-friendly preparation of carbons with adaptable nanopores from polymers obtained via microwave-assisted cross-linking of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) is reported. The polymeric hydrogels possess porous and foam-like structures, giving excellent control of porosity at the precursor level, which are then subjected to activation at high temperatures of 700-900 °C to prepare carbons with a surface area of 1846 m2 g-1 and uniform distribution of micro-, meso-, and macropores. Then, graphene as an additive to hydrogel precursor improves the surface characteristics and elaborates porous texture, giving composite materials with a surface area of 3107 m2 g-1. These carbons show an interconnected porous structure and bimodal pore size distribution suitable for facile ionic transport. When implemented in symmetric supercapacitor configuration with aqueous 5 mol L-1 NaNO3 electrolyte, a capacitance of 163 F g-1 (per average mass of one electrode) and stable evolution of capacitance, coulombic, and energy efficiency during 10 000 galvanostatic charge/discharge up to 1.6 V at 1.0 A g-1 have been achieved.

Modified Activation Process for Supercapacitor Electrode Materials from African Maize Cob.

In this work, African maize cobs (AMC) were used as a rich biomass precursor to synthesize carbon material through a chemical activation process for application in electrochemical energy storage devices. The carbonization and activation were carried out with concentrated Sulphuric acid at three different temperatures of 600, 700 and 800 °C, respectively. The activated carbon exhibited excellent microporous and mesoporous structure with a specific surface area that ranges between 30 and 254 m2·g-1 as measured by BET analysis. The morphology and structure of the produced materials are analyzed through Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Boehm titration, X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. X-ray photoelectron spectroscopy indicates that a considerable amount of oxygen is present in the materials. The functional groups in the activated carbon enhanced the electrochemical performance and improved the material's double-layer capacitance. The carbonized composite activated at 700 °C exhibited excellent capacitance of 456 F g-1 at a specific current of 0.25 A g-1 in 6 M KOH electrolyte and showed excellent stability after 10,000 cycles. Besides being a low cost, the produced materials offer good stability and electrochemical properties, making them suitable for supercapacitor applications.

Hydrothermal synthesis of manganese phosphate/graphene foam composite for electrochemical supercapacitor applications.

Manganese phosphate (Mn3(PO4)2 hexagonal micro-rods and (Mn3(PO4)2 with different graphene foam (GF) mass loading up to 150mg were prepared by facile hydrothermal method. The characterization of the as-prepared samples proved the successful synthesis of Mn3(PO4)2 hexagonal micro-rods and Mn3(PO4)2/GF composites. It was observed that the specific capacitance of Mn3(PO4)2/GF composites with different GF mass loading increases with mass loading up to 100mg, and then decreases with increasing mass loading up to 150mg. The specific capacitance of Mn3(PO4)2/100mg GF electrode was calculated to be 270Fg-1 as compared to 41Fg-1 of the pristine sample at a current density of 0.5Ag-1 in a three-electrode cell configuration using 6M KOH. Furthermore, the electrochemical performance of the Mn3(PO4)2/100mg GF electrode was evaluated in a two-electrode asymmetric cell device where Mn3(PO4)2/100mg GF electrode was used as a positive electrode and activated carbon (AC) from coconut shell as a negative electrode. AC//Mn3(PO4)2/100mg GF asymmetric cell device was tested within the potential window of 0.0-1.4V, and showed excellent cycling stability with 96% capacitance retention over 10,000 galvanostatic charge-discharge cycles at a current density of 2Ag-1.

High performance asymmetric supercapacitor based on molybdenum disulphide/graphene foam and activated carbon from expanded graphite.

Molybdenum disulphide which has a graphene-like single layer structure has excellent mechanical and electrical properties and unique morphology, which might be used with graphene foam as composite in supercapacitor applications. In this work, Molybdenum disulphide (MoS2)/graphene foam (GF) composites with different graphene foam loading were synthesized by the hydrothermal process to improve on specific capacitance of the composites. Asymmetric supercapacitor device was fabricated using the best performing MoS2/GF composite and activated carbon derived from expanded graphite (AEG) as positive and negative electrodes, respectively, in 6M KOH electrolyte. The asymmetric MoS2/GF//AEG device exhibited a maximum specific capacitance of 59Fg-1 at a current density of 1Ag-1 with maximum energy and power densities of 16Whkg-1 and 758Wkg-1, respectively. The supercapacitor also exhibited a good cyclic stability with 95% capacitance retention over 2000 constant charge-discharge cycles. The results obtained demonstrate the potential of MoS2/GF//AEG as a promising material for electrochemical energy storage application.

High electrochemical performance of hybrid cobalt oxyhydroxide/nickel foam graphene.

In this study, we report the in-situ hydrothermal synthesis of mesoporous nanosheets of cobalt oxyhydroxide (CoOOH) on nickel foam graphene (Ni-FG) substrate, obtained via atmospheric pressure chemical vapour deposition (AP-CVD). The produced composite were closely interlinked with Ni-FG, which enhances the synergistic effect between graphene and the metal hydroxide, CoOOH. It is motivating that the synthesized CoOOH on the Ni-FG substrate showed a homogenous coating of well-ordered intersected nanosheets with porous structure. The electrochemical properties of the material as electrode showed a maximum specific capacity of 199mAhg-1 with a capacity retention of 98% after 1000 cycling in a three electrode measurements.

Silicene and transition metal based materials: prediction of a two-dimensional piezomagnet.

We use first-principles density functional theory based calculations to determine the stability and properties of silicene, a graphene-like structure made from silicon, and explore the possibilities of modifying its structure and properties through incorporation of transition metal ions (M: Ti, Nb, Ta, Cr, Mo and W) in its lattice, forming MSi(2). While pure silicene is stable in a distorted honeycomb lattice structure obtained by opposite out-of-plane displacements of the two Si sub-lattices, its electronic structure still exhibits linear dispersion with the Dirac conical feature similar to graphene. We show that incorporation of transition metal ions in its lattice results in a rich set of properties with a clear dependence on the structural changes, and that CrSi(2) forms a two-dimensional magnet exhibiting a strong piezomagnetic coupling.