Synthesis Of Core-shell Nanoparticles Research Articles

Mitigation of erosion and corrosion of steel using nano-composite coating: Polyurethane reinforced with SiO2-ZnO core-shell nanoparticles

In the present study, we developed a multifunctional surface coating with silica-ZnO (SiO2-ZnO) core-shell nanoparticles. The idea behind the synthesis of core-shell nanoparticles was to utilize the mechanical strength of silica and the hydrophobicity of ZnO together in a single coating structure. Coating formulations were developed with solvent-based polyurethane binder containing silica-ZnO core-shell nanoparticles at various concentrations (1–4 wt%) on the steel substrate. These nanoparticles were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) etc. Further, developed coatings were characterized for their surface wettability through measuring water contact angle. The erosion behaviour of the developed coatings has been analyzed through an air-jet solid particle erosion tester. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization study are used to analyze the corrosion response of the substrate and the coatings. The coatings exhibited lesser Vickers and scratch hardness values then the substrate. The best erosion and corrosion resistant, and nearly superhydrophobic surface was achieved by nanocoating developed with 4 % (wt.) of silica-ZnO core-shell nanoparticles on the substrate material. The erosion performance was significantly improved in this coating as compared to the uncoated substrate (at 30° impact angle, erosion reduction ≈ 98 % and at impact angle 90°, erosion reduction ≈ 96 %). Lowest current density and the highest corrosion potential in polarization tests, and the highest impedance in EIS studies were also observed in the nanocoating developed with 4 % (wt.) SiO2-ZnO core-shell nanoparticles. Based on the coatings' performance evaluation, they can be used as protective layers for structural marine components.

A novel method for ZnO@NiO core–shell nanoparticle synthesis using pulse laser ablation in liquid and plasma jet techniques

Given their versatile nature and wide range of possible applications, core–shell nanoparticles (NPs) have received considerable attention. This paper proposes a novel method for synthesizing ZnO@NiO core–shell nanoparticles using a hybrid technique. The characterization demonstrates the successful formation of ZnO@NiO core–shell nanoparticles, which have an average crystal size of 13.059 nm. The results indicate that the prepared NPs have excellent antibacterial activity against both Gram-negative and Gram-positive bacteria. This behavior is primarily caused by the accumulation of ZnO@NiO NPs on the bacteria's surface, which results in cytotoxic bacteria and a relatively increased ZnO, resulting in cell death. Moreover, the use of a ZnO@NiO core–shell material will prevent the bacteria from nourishing themselves in the culture medium, among many other reasons. Finally, the PLAL is an easily scalable, cost-effective, and environmentally friendly method for the synthesis of NPs, and the prepared core–shell NPs could be used in other biological applications such as drug delivery, cancer treatment, and further biomedical functionalization.

Synthesis of Core-Shell Nanoparticles (Cu:Se) by Plasma Jet for Parasitic Leishmaniasis Treatment

Cu:Se core-shell nanomaterials were created using atmospheric cold plasma in order to treat parasite leishmaniasis. In this investigation, leishmania parasite treatment was examined experimentally (<i>Leishmania tropica</i>). Specifically, a 1mm diameter high-voltage electrode was used to produce atmospheric pressure non-thermal plasma. Cu:Se nanoparticles (NPs) were made using copper and selenium salts in aqueous solution as a precursor. The NPs were examined using X-ray diffraction, ultraviolet spectroscopy, and field emission scanning electron microscopy (FESEM). The ideal concentration (3:7) yields grains with a diameter of 17 nm. Morphology of the Cu:Se NPs was studied with FESEM. Observations show that the synthesized NPs were spherical (cluster) in shape with diameters of 15-50 nm, the samller size the samller size of NPs was the best for treatment of NPs was the best for treatment of parasitic leishmaniasis were created. After 48 h of exposure, the percentage of <i>L. tropica</i> parasites for the parasites at a molar concentration of 3:7, 30 min of Cu salt exposure, and 10 min of Se salt exposure, was equal to 78.8%. The core-shell NPs are a viable method for treating the parasite leishmaniasis that threatens people all over the world, according to the results.

Nd2Fe14B/FeCo Core–Shell Nanoparticle Synthesis Using Galvanic Substitution Based Electroless Plating

Core–shell structured magnetic nanoparticles combine hard and soft phases to improve energy efficiency. The mutual interaction of the two phases can lead to the exchange spring effect, leading to higher magnetic energy. In this regard, synthesis of Nd2Fe14B-based core–shell-structured powders have proven to be elusive, due to the relatively reactive nature of this phase. In this study, a process has been established for successfully coating the surface of Nd2Fe14B powders with a FeCo layer using the galvanic displacement method. Initially, a binary phase magnetic powder was synthesized containing Nd2Fe14B and Nd2Fe17 phase. Subsequently, the powders were coated using a Co precursor at 303 K. During coating, the metastable Nd2Fe17 phase was dissolved, and the Fe ions were released into the solution. Subsequently, the Fe ions deposited together with the Co ions on the surface of Nd2Fe14B powder to form a FeCo shell. The deposited layer thickness and composition was confirmed using TEM analysis.

Synthesis and Differential Antibacterial Activity of Bioconjugated Bimetallic Nanoparticles

Core-shell nanoparticles are preferable due to their new and/or improved properties over monometallic nanoparticles. Shell metals are present as a film on the surface of a core metal, which leads to an increase in reactivity of the surface. The synthesis of core-shell nanoparticles using biomolecules is an important strategy to get more activity with less toxicity. The present work was intended to prepare bimetallic nanoparticle preparation by green synthetic method. Aqueous extract of Muntingia calabura flowers was used for the preparation of metal core-shell nanoparticles where flower extract acted as both reducing agent and stabilizing agent. Monometallic gold nanoparticles (AuNPs) and silver nanoparticles (AgNP) were prepared using metal precursors chloroauric acid (HAuCl4) and silver nitrate (AgNO3), respectively. For the preparation of bimetallic core-shell nanoparticles, a shell metal precursor (copper acetate) was added. The obtained nanoparticles were characterized by various instrumental methods including UV–Vis spectrophotometry, TEM and SEM techniques, and EDX spectral analysis. Preliminary antibacterial screening of Au@Cu NP and Ag@Cu NP was performed by disk diffusion assay. TEM and SEM images showed that Au@Cu NPs were spherical whereas Ag@Cu NPs had irregular shapes. The EDX analysis revealed that more Cu was deposited in AuCuNPs than in AgCuNPs. The antibacterial activity assay proved that spherical AuCuNPs were more potent than irregular shaped AgCuNPs.

Optimization of Fe@Cu Core–Shell Nanoparticle Synthesis, Characterization, and Application in Dye Removal and Wastewater Treatment

Green synthesis of core–shell nanoparticles is gaining importance nowadays as it is viewed as being environmental friendly and cost effective. The present study aimed to synthesize iron@copper core–shell nanoparticles using a polysaccharide-based bioflocculant from Alcalegenis faecalis and to evaluate its efficiency in dye removal and river water and domestic wastewater treatment. The synthesized samples were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, transmission electron microscopy, and UV-Vis spectroscopy analysis. To optimize the best concentration for core–shell formation, different ratios of iron to copper were prepared. Sample 1 (S1) contained 1:3 iron to copper (Fe 25%–Cu 75%), sample 2 (S2) contained 1:1 iron to copper (Fe 50%–Cu 50%), and the third sample (S3) contained 3:1 iron to copper (Fe 75%–Cu 25%). The flocculation activity (FA) was above 98% at 0.2 mg/mL for all the samples and the samples flocculated well under acidic, alkaline, and neutral pH conditions. Sample 3 was shown to be thermostable, with flocculation activity above 90%, and samples 2 and 1 were also thermostable, but the flocculation decreased to 87 at 100 °C. All three samples revealed some remarkable properties for staining dye removal as the removal efficiency was above 89% for all dyes tested. The synthesized core–shell nanoparticles could remove nutrients such as total nitrogen and phosphate in both domestic wastewater and Mzingazi river water. Furthermore, high removal efficiency for chemical oxygen demand (COD) and biological oxygen demand (BOD) was also observed.

Lattice Strain Mapping of Platinum Nanoparticles on Carbon and SnO2 Supports.

It is extremely important to understand the properties of supported metal nanoparticles at the atomic scale. In particular, visualizing the interaction between nanoparticle and support, as well as the strain distribution within the particle is highly desirable. Lattice strain can affect catalytic activity, and therefore strain engineering via e.g. synthesis of core-shell nanoparticles or compositional segregation has been intensively studied. However, substrate-induced lattice strain has yet to be visualized directly. In this study, platinum nanoparticles decorated on graphitized carbon or tin oxide supports are investigated using spherical aberration-corrected scanning transmission electron microscopy (Cs-corrected STEM) coupled with geometric phase analysis (GPA). Local changes in lattice parameter are observed within the Pt nanoparticles and the strain distribution is mapped. This reveals that Pt nanoparticles on SnO2 are more highly strained than on carbon, especially in the region of atomic steps in the SnO2 lattice. These substrate-induced strain effects are also reproduced in density functional theory simulations, and related to catalytic oxygen reduction reaction activity. This study suggests that tailoring the catalytic activity of electrocatalyst nanoparticles via the strong metal-support interaction (SMSI) is possible. This technique also provides an experimental platform for improving our understanding of nanoparticles at the atomic scale.

Modeling of Growth Morphology of Core–Shell Nanoparticles

We model shell formation of core–shell noble metal nanoparticles. A recently developed kinetic Monte Carlo approach is utilized to reproduce growth morphologies realized in recent experiments on core–shell nanoparticle synthesis, which reported smooth epitaxially grown shells. Specifically, we identify not only growth regimes that yield such smooth shells but also those that lead to the formation of shells made of small clusters. The developed modeling approach allows us to qualitatively study the effects of temperature and supply the shell-metal atoms on the resulting shell morphology, when grown on a presynthesized nanocrystal core.

Productive encounter: molecularly imprinted nanoparticles prepared using magnetic templates.

Synthesis of core-shell nanoparticles by surface initiated reversible addition fragmentation chain transfer polymerization in presence of a chiral template conjugated to magnetic nanoparticles is reported. The approach leads to imprinted nanoparticles featuring enantioselectivity and enhanced affinity compared to nanoparticles prepared using free template.

Nanometer precise adjustment of the silver shell thickness during automated Au–Ag core–shell nanoparticle synthesis in micro fluid segment sequences

In this work, a wet-chemical synthesis method for gold-silver core-shell particles with nanometer precise adjustable silver shell thicknesses is presented. Typically wet-chemical syntheses lead to relatively large diameter size distributions and losses in the yield of the desired particle structure due to thermodynamical effects. With the here explained synthesis method in micro fluidic segment sequences, a combinatorial in situ parameter screening of the reactant concentration ratios by programmed flow rate shifts in conjunction with efficient segment internal mixing conditions is possible. The highly increased mixing rates ensure a homogeneous shell deposition on all presented gold core particles while the amount of available silver ions was adjusted by automated flow rate courses, from which the synthesis conditions for exactly tunable shell thicknesses between 1.1 and 6.1 nm could be derived. The findings according to the homogeneity of size and particle structure were confirmed by differential centrifugal sedimentation (DCS), scanning and transmission electron microscopy (SEM, TEM) and X-ray photoelectron spectroscopy (XPS) measurements. In UV-Vis measurements, a significant contribution of the core metal was found in the shape of the extinction spectra in the case of thin shells. These results were confirmed by theoretical calculations.

In situ growth of Au@CeO2core–shell nanoparticles and CeO2nanotubes from Ce(OH)CO3nanorods

Core–shell (CS) nanoparticles (NPs) have many applications in areas such as catalysis and sensing. The utilization of hollow nanostructured materials as the supports, such as nanotubes (NT), is a growing interest to anchor NPs. Generally, several steps are necessary to prepare CS NP–NT nanocomposites, including: (i) the synthesis of CS NPs; (ii) the preparation of NTs; and (iii) the combination of CS NPs and NTs. Moreover, surface modifications with organic ligands are often involved during the synthesis of CS NPs and/or the step combining CS NPs and supports. Here we report a facile method for in situ growth of Au@CeO2 CS NPs and CeO2 NTs by mixing HAuCl4 and Ce(OH)CO3 nanorods under mild conditions. The formation of Au–CeO2 nanocomposite is due to the interfacial oxidation–reduction reaction between HAuCl4 and Ce(OH)CO3, where Au(III) in HAuCl4 is reduced to Au(0) by Ce(III) in Ce(OH)CO3, while Ce(III) is oxidized into Ce(IV), followed by hydrolysis to generate CeO2. The slow hydrolysis rate of Ce(IV) leads to the coverage of CeO2 on the Au NPs, and on the residual Ce(OH)CO3 surface, developing into Au@CeO2 and Ce(OH)CO3@CeO2 CS structures. Further depletion/dissolution of Ce(OH)CO3 results in Au@CeO2 CS NP–CeO2 NT nanocomposite eventually. The advantages of our synthetic strategy are independent of foreign reducing agents and additional surface modification. And, such CS NP–NT nanocomposite can be obtained in one step, simplifying the synthesis procedures greatly. This method based on interfacial oxidation–reduction may be employed as a unique entry to other nanocomposites.

Green synthesis of Au, Pd and Au@Pd core–shell nanoparticles via a tryptophan induced supramolecular interface

A facile, eco-friendly, room-temperature method for rapid one-pot synthesis of Au@Pd bimetallic nanoparticles exhibiting a core–shell morphology (∼60 nm) has been developed based on the successive reduction of Au(III) and Pd(II) precursors with tryptophan (Trp) in an aqueous environment. The unique supramolecular chemistry arising due to the hydrogen bonded indole group layer over the Au core seemed critical in the formation Pd shell. The core–shell morphology and surface analysis of the resulting Au@Pd nanoparticles were confirmed by aberration corrected scanning transmission electron microscopy followed by X-ray photoelectron spectroscopy. The formation of the core (Au) and shell (Pd) was also confirmed by Energy Dispersive X-Ray elemental scanning analysis. The resulting Au, Pd and Au@Pd nanoparticles were also analysed by UV-Vis spectroscopy, X-ray diffraction and Dynamic Light Scattering. Our results suggest a simple coordination mechanism where the pre-stabilized poly-Trp Au core serves as a template to facilitate the subsequent reduction of Pd(II) via active carboxyl groups. This study effectively demonstrates for the first time that core–shell nanoparticle synthesis (reduction and stabilization) can be effectively achieved by simple amino acids like Trp in an aqueous reaction mixture.

Environment Controlled Dewetting of Rh–Pd Bilayers: A Route for Core–Shell Nanostructure Synthesis

Chemical environment plays a significant role on the size, shape, or surface composition of nanostructures. Here, the chemical environment effects are studied in the context of core–shell nanoparticle synthesis. The environment driven dynamics and kinetics of Rh/Pd bilayers is investigated by in situ ambient pressure X-ray photoelectron spectroscopy. Thin Rh (∼1.5 nm)/Pd (∼ 1.5 nm) bilayers were grown on thermally oxidized Si substrates. The films were heated in CO or NO environments or heated in vacuum with a subsequent NO/CO cycling. This study demonstrates that not the initial stacking sequence but the chemical environment plays a crucial role in controlling the surface composition. Heating in CO results in a surface enrichment of Pd at ∼200 °C and is followed by film dewetting at ∼300 °C. Heating in NO results in progressive oxidation of Rh starting at ∼150 °C, which stabilizes the film continuity up to >∼375 °C. The film rupture correlates with the thermal destabilization of the surface oxide. Heatin...

Aerosol copper initiated core–shell nanoparticle synthesis and micropatterning

We report the development of copper–silver core–shell nanoparticles where the aerosol copper nanoparticles served as the seeds for the deposition of silver atoms on their surface. The copper particles were also electrostatically patterned on the substrate to fabricate silver micropatterns.

Size controlled synthesis of semiconductor nanocrystals in a continuous-flow mode microcapillary reactor

A microcapillary reactor with 320 μm inner diameter was utilized for CdSe nanoparticle synthesis. The influence of the reaction temperature and flow rate of precursors on the size and size distribution of prepared CdSe nanoparticles was systematically studied. The as-prepared nanoparticles exhibit sharp excitonic absorption and photoluminescence peak (FWHM 30 nm) with a quantum-yield around 10-40%. The microcapillary reactor was also used for CdSe/ZnS core-shell nanoparticle synthesis in continuous-flow mode. The quantum yield of the core-shell nanoparticles was found to be considerably influenced by the reactor temperature and have a close correlation with the thickness of ZnS shell under growth. An optimized quantum yield up to 70% was obtained for the CdSe/ZnS core-shell nanoparticles.

Synthesis of Core-Shell Nanoparticles Using Organic Surface-Functionalized Gold and Au@SiO<SUB>2</SUB> Nanoparticles as Multifunctional Initiators in Atom Transfer Radical Polymerization

Gold and Au@SiO2 nanoparticles were synthesized and surface-functionalized by initiators for atom transfer radical polymerization (ATRP), either using a thiol or a trialkoxysilane anchor group for the immobilization of the initiating functionality. The thus obtained initiator-capped gold systems were applied in polymerizations of various monomers, such as styrene, methacrylic acid trimethyloxysilyl propylester and isoprene and copolymers thereof. The final inorganic-organic core-shell nanoparticles were characterized applying different techniques such as electron microscopy and light scattering. Kinetic studies of the polymerizations revealed that they were highly controlled and therefore the thickness of the polymer shell could be easily adjusted. The obtained nanoparticles formed stable suspensions in various organic solvents and can therefore be used as building blocks for polymer nanocomposites.