Advancements in polyol synthesis: expanding chemical horizons and Néel temperature tuning of CoO nanoparticles

The polyol synthesis of CoO nanoparticles (NPs) is typically conducted by dissolving and heating cobalt acetate tetrahydrate and water in diethylene glycol (DEG). This process yields aggregates of approximately 100 nm made of partially aligned primary crystals. However, the synthesis demands careful temperature control to allow the nucleation of CoO while simultaneously preventing reduction, caused by the activity of DEG. This restriction hinders the flexibility to freely adjust synthesis conditions, impeding the ability to obtain particles with varied morpho-structural properties, which, in turn, directly impact chemical and physical attributes. In this context, the growth of CoO NPs in polyol was studied focusing on the effect of the polyol chain length and the synthesis temperature at two different water/cations ratios. During this investigation, we found that longer polyol chains remove the previous limits of the method, allowing the tuning of aggregate size (20-150 nm), shape (spherical-octahedral), and crystalline length (8-35 nm). Regarding the characterization, our focus revolved around investigating the magnetic properties inherent in the synthesized products. From this point of view, two pivotal findings emerged. Firstly, we identified small quantities of a layered hydroxide ferromagnetic intermediate, which acted as interference in our measurements. This intermediate exhibited magnetic properties consistent with features observed in other publications on CoO produced in systems compatible with the intermediate formation. Optimal synthetic conditions that prevent the impurity from forming were found. This resolution clarifies several ambiguities existing in literature about CoO low-temperature magnetic behavior. Secondly, a regular relationship of the NPs' TN with their crystallite size was found, allowing us to regulate TN over ~ 80 K. For the first time, a branching was found in this structure-dependent magnetic feature, with samples of spheroidal morphology consistently having lower magnetic temperatures, when compared to samples with faceted/octahedral shape, providing compelling evidence for a novel physical parameter influencing the TN of a material. These two findings contribute to the understanding of the fundamental properties of CoO and antiferromagnetic materials.

Eggshell membranes coated chitosan decorated with metal nanoparticles for the catalytic reduction of organic contaminates

This study focusses on the effect of chitosan coating with eggshell membranes for the reduction of different organic pollutants. Chickens eggs were collected from the local market and utilized to extract the enrich eggshell membranes (ESM). The chicken eggshell membranes are abundant waste material which is inexpensive and illustrates remarkable physiognomies for many possible applications. Fresh fibers/strips coated by chitosan (CS) were prepared by mixing the eggshell membranes with CS solution (2 wt%/v) in different proportions i.e., 10 %, 30 %, 50 %, 60 %, 70 %, 80 %, and 90 %. These strips were then templated with copper and iron metal nanoparticles by putting them in their metal ions aqueous solution to adsorb the metals ions and were then reduced to zero-valent metal nanoparticles (MNPS) by using NaBH₄ aqueous solution. These prepared materials (MNPS@ESM-CS) were characterized by using XRD, XPS, FE-SEM, and EDS to confirm the successful preparation of MNPs over the surface of ESM coated with CS. Afterwards, these prepared materials were investigated as a catalyst for the reduction of different organic pollutants, such as 4-nitroaniline (4-NA), 4-nitrophenol (4-NP) and methylene blue (MB) dye. The catalytic efficiency of ESM was enhanced 5.7-fold by adding only 20 % CS solution. It was observed that Cu@ESM-CS-80 % took 7 min for reduction of 4-NA, 6 min for 4-NP, and 7 min for MB dye. The reusability of the catalytic strip was also investigated for four cycles and found efficient and can be easily recovered by simply pulling it from the reaction mixture.

Thermally induced structural metamorphosis of ZnO:Rb nanostructures for antibacterial impacts

In this work, we report on the synthesis of pure and Rb doped ZnO (ZnO:Rb) nanoparticles by a simple combustion technique followed by thermal treatment in an open-air atmosphere. The prepared samples were characterized using UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), photoluminescence, Raman spectroscopy and scanning electron microscopy. The wurtzite hexagonal phase structure of ZnO and a secondary phase of Rb₂ZnO₂ was observed after doping ZnO with Rb. FTIR and DSC confirmed the functional groups and the thermal stability of the ZnO samples. Field emission scanning electron microscope showed an irregular shaped agglomerated morphology for the ZnO:Rb samples. The chemical states of the undoped and Rb doped samples were identified using X-ray photoelectron spectroscopy for both pure and ZnO:Rb samples. In addition, ZnO:Rb samples exhibit good antimicrobial activities against Bacillus subtilis with a change in antibacterial behaviour as compared to pure ZnO structures indicating their multifunctional applications.

Ionic-Liquid-Assisted One-Step Synthesis of CoO Nanosheets as Electrocatalysts for Oxygen Evolution Reaction

The sluggish oxygen evolution reaction (OER) hinders the development of electrocatalytic water splitting for energy conversion and storage. Therefore, it is imperative to explore the cost-effective and highly efficient noble-metal-free electrocatalysts for OER. Herein, we are introducing such OER electrocatalyst based on Co, fabricated through an ionic-liquid-assisted one-step synthesis, where ionic liquid played a dual role as solvent cum structure-directing agent. Besides possessing large-accessible surface area and numerous active sites, the as-prepared stable CoO nanosheets exhibited excellent electrochemical activity through establishing an extensive contact with the electrolyte. Under alkaline conditions, the overpotential to achieve a current density of 10 mA cm^-2 is only 320 mV, and the Tafel slope is as small as 70 mV dec^-1. Thus, our work provides a new pathway for designing and engineering the highly efficient non-noble metal OER electrocatalysts by using ionic liquids.

Hierarchically Grown NiO-Decorated Polyaniline-Reduced Graphene Oxide Composite for Ultrafast Sunlight-Driven Photocatalysis

Polymers and transition-metal oxides have gained great interest as a photocatalyst in environmental remediation. They could be modified with each other in order to improve their activity. Here, a sunlight-responsive hierarchically structured ternary composite of nickel oxide, polyaniline, and reduced graphene oxide (NiO@PANI/RGO) has been synthesized and employed as a catalyst for dye [methylene blue (MB)] degradation. PANI/GO synthesized by interfacial polymerization acts as a matrix for the growth of NiO using a microemulsion solvothermal method, ensuing an in situ reduction of graphene oxide during the formation of a hierarchical NiO@PANI/RGO composite. Morphological studies of the as-synthesized NiO@PANI/RGO composite reveal fine NiO (10 nm) nanoparticles intercalated between the uniformly grown PANI spines (50-60 nm) over the RGO surface. The optical band gap of ∼1.9 eV calculated from the UV-vis spectrum illustrates the extended light absorption range for the NiO@PANI/RGO photocatalyst. The efficiency of 98% MB degradation within 11 min with the degradation rate constant 0.086 min-1 for NiO@PANI/RGO has surpassed any other report on metal oxide/graphene-based ternary composites. Overall, this work could pave the way for the fabrication of futuristic hierarchical structured ternary nanocomposites as an efficient photocatalyst and facilitate their application in the environmental protection issues.

Chitosan coated cotton cloth supported zero-valent nanoparticles: Simple but economically viable, efficient and easily retrievable catalysts

A simple, economically viable and fast method has been utilized for the preparation of highly active metal nanoparticles (MNPs) in coating layer of chitosan (CH) over cellulose microfibers of cotton cloth (CC). 2 wt% of CH solution was used for the coating of CC strips (CC-CH), and were kept in aqueous solutions of metal salts to adsorb metal ions. The CC-CH templated with metal ions were then treated with aqueous solution of NaBH₄ to reduce the metal ions into zero-valent metal nanoparticles (M⁰). The CC-CH strips loaded with M⁰ were characterized by XRD, XPS, ATR-FTIR, FE-SEM and TGA, which indicates the successful synthesis of MNPs by this method. The M⁰/CC-CH strips were used as an efficient catalyst for the model reduction reaction of nitrophenol and toxic organic dyes. Among all the prepaped samples, Fe/CC-CH showed good catalytic activity for 4-NP and Rh-B dye reduction in the presence of NaBH₄ with rate constants of 0.2937 min^-1 and 0.3804 min^-1, respectively. Moreover Fe/CC-CH has good catalytic reduction ability for MO and MB having rate constants equal to 0.1698 and 0.2802 min^-1, respectively. Beside the good catalytic ability, it could be easily recoverable as compared to other available techniques. The recovery was completed by simply pulling the strip from the reaction matrix after completion of the reaction and can be used several times.

Low-temperature synthesis of SrTiO3 nanoassemblies on DNA scaffolds and their applications in dye-sensitized solar cells and supercapacitors

Aggregated SrTiO₃ nanoassemblies on DNA scaffolds have been synthesized at ambient conditions and utilized as anode material both in dye-sensitized solar cells (DSSCs) and in supercapacitors.

Controlling structural and magnetic properties of IONPs by aqueous synthesis for improved hyperthermia

Introducing a hydrothermal step after coprecipitation leads to iron oxide nanoparticles with higher vacancy ordering, saturation magnetization and specific absorption rate.

Highly efficient noble metal free copper nickel oxysulfide nanoparticles for catalytic reduction of 4-nitrophenol, methyl blue, and rhodamine-B organic pollutants

Novel and noble metal-free copper nickel oxysulfide nanoparticles have been successfully fabricated by using a simple, cost-effective, and eco-friendly solution-based approach, with copper oxysulfide as a comparative.

A combined self-assembly and calcination method for preparation of nanoparticles-assembled cobalt oxide nanosheets using graphene oxide as template and their application for non-enzymatic glucose biosensing

Cobalt oxide (Co₃O₄)-based materials have been extensively investigated as efficient electrocatalysts for non-enzymatic glucose biosensing. The proper tuning the structure of Co₃O₄-based materials could improve sensing performances for glucose detection. Herein, we have developed a combined self-assembly and calcination method to prepare nanoparticles-assembled Co₃O₄ nanosheets, which exhibit good sensing performances for glucose biosensing. The Co₃O₄ nanosheets were prepared by the following three steps: (i) the Co²⁺ modified graphene oxide (GO) was prepared by the self-assembly of Co²⁺ and GO in aqueous solution firstly, and then Co²⁺ modified GO film was obtained by vacuum filtration method; (ii) after calcination of Co²⁺ modified GO film in N₂ atmosphere, Co₃O₄ nanoparticles modified reduced GO (RGO) was obtained; (iii) finally, nanoparticles-assembled Co₃O₄ nanosheets were obtained by calcination of Co₃O₄ modified RGO in air to remove RGO template. Most importantly, Co₃O₄ nanosheets exhibit good electrocatalytic activity for oxidation of glucose, leading to high-performance glucose sensor. The detection limit and linear range of Co₃O₄ nanosheets-based glucose sensor in the present work are 0.15μM, and 1-50μM, respectively. Furthermore, such sensor also shows excellent selectivity for glucose detection, compared to the commonly interfering species including dopamine, and uric acid.

Grass-like Co2P superstructures: direct synthesis between elements, forming mechanism and catalytic properties

Grass-like Co₂P superstructures with good catalytic performances were successfully prepared through a direct reaction between elements route.

Shape-selective synthesis of Sn(MoO4)2 nanomaterials for catalysis and supercapacitor applications

Size and shape-selective Sn(MoO₄)₂ nanomaterials were synthesized for the first time using hydrothermal route. Needle-like and flake-like nanomaterials were used for two applications, the photocatalytic reduction of nitroarenes and in electrochemical supercapacitors.

Template-free syntheses of hierarchical PbS microstructures using a new sulphur source and their time-dependent morphological evolution and photocatalytic properties

Template-free PbS microstructures composed of nanocrystals exhibiting time-dependent morphological evolution from cubes to dendrites were synthesised by one-pot solvothermal route using DBDS as a new temperature controlled in situ source of S²⁻ ions.

Microwave assisted fast formation of Sn(MoO4)2 nano-assemblies on DNA scaffold for application in lithium-ion batteries

Self-assembled aggregated Sn(MoO₄)₂ nanomaterials on DNA scaffolds exhibit enhanced capability as anode materials in lithium-ion battery (LIB) applications.

Nickel Nanoparticle-Decorated Porous Carbons for Highly Active Catalytic Reduction of Organic Dyes and Sensitive Detection of Hg(II) Ions

High surface area carbon porous materials (CPMs) synthesized by the direct template method via self-assembly of polymerized phloroglucinol-formaldehyde resol around a triblock copolymer template were used as supports for nickel nanoparticles (Ni NPs). The Ni/CPM materials fabricated through a microwave-assisted heating procedure have been characterized by various analytical and spectroscopic techniques, such as X-ray diffraction, field emission transmission electron microscopy, vibrating sample magnetometry, gas physisorption/chemisorption, thermogravimetric analysis, and Raman, Fourier-transform infrared, and X-ray photon spectroscopies. Results obtained from ultraviolet-visible (UV-vis) spectroscopy demonstrated that the supported Ni/CPM catalysts exhibit superior activity for catalytic reduction of organic dyes, such as methylene blue (MB) and rhodamine B (RhB). Further electrochemical measurements by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) also revealed that the Ni/CPM-modified electrodes showed excellent sensitivity (59.6 μA μM(-1) cm(-2)) and a relatively low detection limit (2.1 nM) toward the detection of Hg(II) ion. The system has also been successfully applied for the detection of mercuric ion in real sea fish samples. The Ni/CPM nanocomposite represents a robust, user-friendly, and highly effective system with prospective practical applications for catalytic reduction of organic dyes as well as trace level detection of heavy metals.

High-value utilization of egg shell to synthesize Silver and Gold-Silver core shell nanoparticles and their application for the degradation of hazardous dyes from aqueous phase-A green approach

The common household material, egg shell of Anas platyrhynchos is utilized for the synthesis of Silver and Gold-Silver core shell nanoparticles using greener, environment friendly and economic way. The egg shell extracts were acting as a stabilizing and reducing agents. This method avoids the use of external reducing and stabilizing agents, templates and solvents. The effects of various reaction parameters, such as reaction temperature, concentration in the formation of nanoparticles have also been investigated. The compositional abundance of gelatin may be envisaged for the effective reductive as well as stabilizing potency. The mechanisms for the formation of NPs have also been presented. The synthesized Ag NPs formed were predominantly spherical in nature with an average size of particles in the range of 6-26 nm. While, Au-Ag core shell nanoparticles formed were spherical and oval shaped, within a narrow size spectrum of 9-18 nm. Both the Ag NPs Au-and Ag core shell nanoparticles showed characteristic Bragg's reflection planes of fcc structure and surface plasmon resonance at 430 nm and 365 nm, respectively. The NPs were utilized for the removal of toxic and hazardous dyes, such as Rose Bengal, Methyl Violet 6 B and Methylene Blue from aqueous phase. Approximately 98.2%, 98.4% and 97% degradations of Rose Bengal, Methyl Violet 6 B, and Methylene Blue were observed with Ag NPs, while the percentage degradation of these dyes was 97.3%, 97.6% and 96% with Au-Ag NPs, respectively. Therefore, the present study has opened up an innovative way for synthesizing Ag NPs and Au-Ag bimetallic nanostructures of different morphologies and sizes involving the utilization of egg shell extract. The high efficiency of the NPs as photocatalysts has opened a promising application for the removal of hazardous dyes from the industrial effluents.

Low temperature, shape-selective formation of Sb2Te3 nanomaterials and their thermoelectric applications

Thermoelectric properties of shape-selective Sb₂Te₃ nanomaterials which synthesized at a low temperature within a short reaction time have been reported.

Alanine based coordinating ligand mediated hydrothermal synthesis of CuS nano/microstructures and morphology dependent photocatalysis

Coordinating ligand controlled CuS nano/microstructures and morphology dependent photocatalysis.

One-pot, template-free syntheses of spherical ZnS nanocrystals using a new S2−source and their photocatalytic study

A facile, one-pot solvothermal method for the syntheses of template-free ZnS NCs (~3–6 nm) using (C₇H₇)S₂as a newin situsource of S²⁻ions without and with the use of MCE-capping agent has been demonstrated. Photocatalytic investigation of the NCs revealed very good activity for degradation of MO under UV light irradiation.

Controllable synthesis of Ni nanotube arrays and their structure-dependent catalytic activity toward dye degradation

Ni nanotube (nanorod) arrays are controllably fabricated by a one-step approach, the GDDATG and DDCG growth mechanisms are introduced. The Ni nanostructures present higher catalytic activities for dye degradation, the relationship between structures and catalytic properties is also studied.