Dumbbell-like Au0.5Cu0.5@Fe3O4 Nanocrystals: Synthesis, Characterization, and Catalytic Activity in CO Oxidation

Synthetic Approaches to Colloidal Nanocrystal Heterostructures Based on Metal and Metal-Oxide Materials

Composite inorganic nanoarchitectures, based on combinations of distinct materials, represent advanced solid-state constructs, where coexistence and synergistic interactions among nonhomologous optical, magnetic, chemical, and catalytic properties lay a basis for the engineering of enhanced or even unconventional functionalities. Such systems thus hold relevance for both theoretical and applied nanotechnology-based research in diverse areas, spanning optics, electronics, energy management, (photo)catalysis, biomedicine, and environmental remediation. Wet-chemical colloidal synthetic techniques have now been refined to the point of allowing the fabrication of solution free-standing and easily processable multicomponent nanocrystals with sophisticated modular heterostructure, built upon a programmed spatial distribution of the crystal phase, composition, and anchored surface moieties. Such last-generation breeds of nanocrystals are thus composed of nanoscale domains of different materials, assembled controllably into core/shell or heteromer-type configurations through bonding epitaxial heterojunctions. This review offers a critical overview of achievements made in the design and synthetic elaboration of colloidal nanocrystal heterostructures based on diverse associations of transition metals (with emphasis on plasmonic metals) and transition-metal oxides. Synthetic strategies, all leveraging on the basic seed-mediated approach, are described and discussed with reference to the most credited mechanisms underpinning regioselective heteroepitaxial deposition. The unique properties and advanced applications allowed by such brand-new nanomaterials are also mentioned.

Batoko plum (Flacourtia inermis) peel extract attenuates deteriorative oxidation of selected edible oils

The oxidation of oils has an adverse effect on the organoleptic properties and shelf-life of stored oils. Flacourtia inermis is one of the underutilized fruits grown in Sri Lanka with promising antioxidant properties. F. inermis peel extract (FIPE) was used to retard rancidity in edible oils. The efficacy of added FIPE (500, 1000, 2000 ppm) on sunflower oil (SO) and virgin coconut oil (VCO) was monitored at 3-day intervals at 65 ± 5 °C against a positive control (α-tocopherol at 500 ppm level) using Free Fatty Acid (FFA) and Peroxide Value (PV). Oils without FIPE were used as the control. Antioxidant efficacy (IC50) and Total Phenol Content (TPC) of FIPE were determined by DPPH assay and the Folin-Ciocalteu method. Fourier transform infrared spectroscopy was used to monitor the oxidative stability. The IC50 value and TPC of FIPE were 227.14 ± 4.12 µg·mL-1 and 4.87 ± 0.01 mg GAE/g extract, respectively. After 21 days, VCO (control) sample exhibited significantly (p < 0.05) higher FFA and PV than the treatments. FIPE exhibited comparable results with α-tocopherol. Conclusively, FIPE had strong antioxidant properties and thus, could be used as an alternative to α-tocopherol to improve the oxidative stability of virgin coconut oil and sunflower oil. However, only minor differences in the FTIR spectra were detected in treated and untreated virgin coconut and sunflower oil samples after 21 days storage at 65 ± 5 °C.

Magnetic-Plasmonic Heterodimer Nanoparticles: Designing Contemporarily Features for Emerging Biomedical Diagnosis and Treatments

Magnetic-plasmonic heterodimer nanostructures synergistically present excellent magnetic and plasmonic characteristics in a unique platform as a multipurpose medium for recently invented biomedical applications, such as magnetic hyperthermia, photothermal therapy, drug delivery, bioimaging, and biosensing. In this review, we briefly outline the less-known aspects of heterodimers, including electronic composition, interfacial morphology, critical properties, and present concrete examples of recent progress in synthesis and applications. With a focus on emerging features and performance of heterodimers in biomedical applications, this review provides a comprehensive perspective of novel achievements and suggests a fruitful framework for future research.

Dually responsive gold-iron oxide heterodimers: merging stimuli-responsive surface properties with intrinsic inorganic material features

We demonstrate a versatile approach for the preparation of dually responsive smart inorganic heterostructures (HSs) with the potential for exploitation in nanomedicine. We utilize Au-Fe_xO_y dimers as templates for generating smart inorganic HSs with a pH-responsive coating and a thermo-responsive coating attached to iron oxide and gold nanoparticles (NPs), respectively. First, a thiol-modified thermo-responsive (PNIPAAM-co-PEGA) polymer could be selectively attached to the gold domain by ligand exchange. The sequential attachment of a catechol-modified initiator to the iron oxide surface enables the in situ polymerization of a pH-responsive (PDMAEA) polymer. As hereby shown, the presence of the two distinct polymer domains on each NP subdomain enables each side of the HS to be loaded with different agents. Indeed, by a gel electrophoresis experiment we demonstrate the loading of siRNA on the pH-responsive polymer and the loading of Nile Blue dye, used as a drug model molecule, on the thermo-responsive polymer. The smart HSs exhibited good biocompatibility and downregulated GFP production when loaded with anti-GFP siRNA molecules. In addition, an investigation of the magnetic relaxivity times revealed that the high R2 relaxivity values of the HSs suggest their potential as contrast agents in magnetic resonance imaging (MRI) applications.

Manipulating the morphology of the nano oxide domain in AuCu–iron oxide dumbbell-like nanocomposites as a tool to modify magnetic properties

We highlighted the effects of oleic acid on the structural and magnetic properties of colloidal nanodumbbells.

Shape-Controlled Synthesis of Dumbbell-like Pt-Fe3O4-MnO x Nanoparticles by Governing the Reaction Kinetics

The production of shape-controlled heterometallic nanoparticles (NPs) consisting of Pt and nonprecious metal oxides is crucial to demonstrate the composition-property relationship of NPs. Herein, we report a facile one-pot approach for the controlled synthesis of dumbbell-like Pt-Fe₃O₄-MnO _x and dendritic Pt-MnO _x NPs. The key to the success of this synthesis is in changing the quantity of Fe(CO)₅ additive to control the reaction kinetics. In the absence of Fe(CO)₅, dendritic Pt-MnO _x NPs were synthesized through the assembly of small seed NPs. On the other hand, dumbbell-like Pt-Fe₃O₄-MnO _x NPs were obtained in the presence of Fe(CO)₅ through controlling the nucleation and growth of Fe and Mn on the Pt NPs, followed by air oxidation. Compared to a Pt/graphene oxide (GO) catalyst, dumbbell-like Pt-Fe₃O₄-MnO _x NPs on GO showed an enhancement of specific activity toward the oxygen reduction reaction owing to the compressive-strain effect exerted on the Pt lattice.