Editorial

3 pages, 187 KiB

Open AccessEditorial

Advances of Nanoparticles and Thin Films

by Bogdana Borca and Cristina Bartha

Coatings 2022, 12(8), 1138; https://doi.org/10.3390/coatings12081138 - 07 Aug 2022

Cited by 2 | Viewed by 1661

Nanoparticles and thin films are currently among the most active research fields in materials sciences for technological applications [...] Full article

(This article belongs to the Special Issue Advances of Nanoparticles and Thin Films)

Research

Jump to: Editorial, Review

12 pages, 2884 KiB

Open AccessArticle

Highly Coercive L1₀-Phase Dots Obtained through Low Temperature Annealing for Nano-Logic Magnetic Structures

by Ovidiu Crisan, Alina Daniela Crisan, Gabriel Schinteie and Victor Kuncser

Coatings 2023, 13(12), 2068; https://doi.org/10.3390/coatings13122068 - 11 Dec 2023

Viewed by 721

Abstract

Nano-logic magnetic structures are of great interest for spintronic applications. While the methods used for developing arrays of magnetic L1₀-phase dots are, in most cases, based on deposition followed by annealing at high temperatures, usually around 700 °C, we demonstrate here [...] Read more.

Nano-logic magnetic structures are of great interest for spintronic applications. While the methods used for developing arrays of magnetic L1₀-phase dots are, in most cases, based on deposition followed by annealing at high temperatures, usually around 700 °C, we demonstrate here a technique where a much lower annealing temperature (i.e., 400 °C) is needed in order to promote fully the disorder–order phase transformation and achievement of highly coercive L1₀-phase dots. In order to develop building blocks based on arrays of L1₀-phase FePt dots for further spintronic applications, an engraving technique using electron beam lithography is employed. This paper describes the fabrication, as well as the morphological and magnetic characterization, of regularly placed FePt dots of various shapes, as pre-requisites for integration into nano-logic devices. As a proof of concept, regular arrays of FePt circular dots were devised and their structural characterization, using X-ray diffraction (XRD) and transmission electron microscopy (TEM), was performed. It has been shown that annealing at only 400 °C for 30 min proved the occurrence of the tetragonal L1₀ phase. Moreover, structural characterization showed that the disorder–order phase transformation was complete with only the L1₀ phase detected in high resolution TEM. The magnetic characterization provided more insight into the potential of such arrays of magnetic devices with convenient values of magnetic coercivity, remanent and saturation magnetization. These findings show good potential for developing regular arrays of uniformly shaped magnetic entities with encouraging magnetic performances in view of various applications. Full article

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15 pages, 3924 KiB

Open AccessArticle

Synthesis of CoFe₂O₄ through Wet Ferritization Method Using an Aqueous Extract of Eucalyptus Leaves

by Dana Gingasu, Daniela C. Culita, Jose Maria Calderon Moreno, Gabriela Marinescu, Cristina Bartha, Ovidiu Oprea, Silviu Preda, Mariana Carmen Chifiriuc and Marcela Popa

Coatings 2023, 13(7), 1250; https://doi.org/10.3390/coatings13071250 - 14 Jul 2023

Cited by 3 | Viewed by 1028

Abstract

This study explored a new green approach of the wet ferritization method to obtain magnetic cobalt ferrite (CoFe₂O₄) by using eucalyptus leaves aqueous extract as a reducing/chelating/capping agent. The spinel single cubic phases of prepared samples were proved by [...] Read more.

This study explored a new green approach of the wet ferritization method to obtain magnetic cobalt ferrite (CoFe₂O₄) by using eucalyptus leaves aqueous extract as a reducing/chelating/capping agent. The spinel single cubic phases of prepared samples were proved by powder X-ray diffraction (XRD), Fourier-Transform Infrared (FTIR) and Raman spectroscopy. The average crystallite size is in the range between 3 and 20 nm. The presence of the functional groups coating the obtained material is confirmed from FTIR and thermal analysis. The scanning electron microscopy (SEM) analysis showed a morphology consisting of nanoparticle aggregates. Raman spectroscopy detects the characteristic bands of spinel-type CoFe₂O₄. Magnetic investigations reveal the formation of ferromagnetic compounds with cubic magnetic anisotropy and a blocking temperature around 140 K, specific for this type of material. The biosynthesized CoFe₂O₄ could be an attractive candidate for biomedical applications, exhibiting promising antimicrobial and antibiofilm activity, particularly against Gram-negative bacteria and fungal strains. Full article

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11 pages, 1534 KiB

Open AccessArticle

Photopolymerised Coatings with Nanopigments Based on Dye Mixtures

by Viktor B. Ivanov, Elena V. Solina and Peter P. Levin

Coatings 2023, 13(2), 300; https://doi.org/10.3390/coatings13020300 - 28 Jan 2023

Viewed by 1132

Abstract

The properties of new coatings with nanopigments (NPs) prepared by the dye mixture treatment of montmorillonite modified with cationic surfactants were investigated. The colorimetric parameters of polymer films with nanopigments were determined. The mutual interference of the dyes in their adsorption on nanoparticles [...] Read more.

The properties of new coatings with nanopigments (NPs) prepared by the dye mixture treatment of montmorillonite modified with cationic surfactants were investigated. The colorimetric parameters of polymer films with nanopigments were determined. The mutual interference of the dyes in their adsorption on nanoparticles and their colourfastness (photostability) to light was analysed. The properties of oligomer/monomer compositions with synthesised nanopigments designed for the printing of non-metallic surfaces were discussed. The structure of nanopigments and polymerised oligomer/monomer compositions was revealed by small-angle X-ray diffraction, UV–Vis spectra, and atomic force microscopy. NPs with a wide colour range were prepared using dye mixtures. One other advantage of these NPs over NPs based on individual dyes is the possibility to increase the total concentration of the colouring components in the NPs and to increase the colourfastness. Full article

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15 pages, 4063 KiB

Open AccessArticle

Structural and Magnetic Specificities of Fe-B Thin Films Obtained by Thermionic Vacuum Arc and Magnetron Sputtering

by Cornel Staicu, Claudiu Locovei, Andrei Alexandru Dinu, Ion Burducea, Paul Dincă, Bogdan Butoi, Oana Gloria Pompilian, Corneliu Porosnicu, Cristian Petrica Lungu and Victor Kuncser

Coatings 2022, 12(10), 1592; https://doi.org/10.3390/coatings12101592 - 20 Oct 2022

Cited by 1 | Viewed by 1196

Abstract

Fe-B based compounds are of high interest due to their special properties and the wide range of involved applications. While B is the element that facilitates the increase in the hardness and the degree of wear resistance, it is also an effective glass [...] Read more.

Fe-B based compounds are of high interest due to their special properties and the wide range of involved applications. While B is the element that facilitates the increase in the hardness and the degree of wear resistance, it is also an effective glass former, controlling the formation of a much-desired amorphous structure with specific magnetic properties. Major difficulties related to the proper engineering of Fe-B thin films lay especially in their preparation under well-defined compositions, which in turn, should be accurately determined. The present study closely analyzes the morpho-structural and magnetic properties of thin coatings of Fe-B of approximately 100 nm thickness and with the nominal B content ranging from 5 at. % to 50 at. %. The comparison between films obtained by two preparation methods, namely, the thermionic vacuum arc and the magnetron sputtering is envisaged. Morpho-structural properties were highlighted using X-ray diffraction supplemented with X-ray reflectometry and scanning electron microscopy, whereas the elemental investigations were performed by X-ray dispersive spectroscopy and Rutherford back-scattering spectroscopy. The magnetic properties of the Fe-B layers were carefully investigated by the vectorial magneto-optic Kerr effect and conversion electron Mössbauer spectroscopy. The high capability of Mössbauer Spectroscopy to provide the phase composition and the B content in the formed Fe-B intermetallic films was proven, in correlation to Rutherford back-scattering techniques, and to explain their magnetic properties, including the magnetic texture of interest in many applications, in correlation with longitudinal magneto-optic-Kerr-effect-based techniques. Full article

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10 pages, 3500 KiB

Open AccessArticle

Memory Properties of Zr-Doped ZrO₂ MOS-like Capacitor

by Catalin Palade, Adrian Slav, Ionel Stavarache, Valentin Adrian Maraloiu, Catalin Negrila and Magdalena Lidia Ciurea

Coatings 2022, 12(9), 1369; https://doi.org/10.3390/coatings12091369 - 19 Sep 2022

Cited by 2 | Viewed by 1700

Abstract

The high-k-based MOS-like capacitors are a promising approach for the domain of non-volatile memory devices, which currently is limited by SiO₂ technology and cannot face the rapid downsizing of the electronic device trend. In this paper, we prepare MOS-like trilayer memory structures [...] Read more.

The high-k-based MOS-like capacitors are a promising approach for the domain of non-volatile memory devices, which currently is limited by SiO₂ technology and cannot face the rapid downsizing of the electronic device trend. In this paper, we prepare MOS-like trilayer memory structures based on high-k ZrO₂ by magnetron sputtering, with a 5% and a 10% concentrations of Zr in the Zr–ZrO₂ floating gate layer. For crystallization of the memory structure, rapid thermal annealing at different temperatures between 500 °C and 700 °C was performed. Additionally, Al electrodes were deposited in a top-down configuration. High-resolution transmission electron microscopy reveals that ZrO₂ has a polycrystalline–columnar crystallization and a tetragonal crystalline structure, which was confirmed by X-ray diffraction measurements. It is shown that the tetragonal phase is stabilized during the crystallization by the fast diffusion of oxygen atoms. The capacitance–voltage characteristics show that the widest memory window (ΔV = 2.23 V) was obtained for samples with 10% Zr annealed at 700 °C for 4 min. The charge retention characteristics show a capacitance decrease of 36% after 10 years. Full article

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15 pages, 2918 KiB

Open AccessArticle

Magnetic Properties of Nanosized Fe and FeCo Systems on Trenched Mo Templates

by Anda Elena Stanciu, Gabriel Schinteie, Andrei Cristian Kuncser, Claudiu Locovei, Lucian Trupina, Nicusor Iacob, Aurel Leca, Bogdana Borca and Victor Kuncser

Coatings 2022, 12(9), 1366; https://doi.org/10.3390/coatings12091366 - 19 Sep 2022

Cited by 4 | Viewed by 1724

Abstract

The manipulation of magnetic anisotropy represents the fundamental prerequisite for the application of magnetic materials. Here we present the vectorial magnetic properties of nanostructured systems and thin films of Fe and FeCo prepared on linearly trenched Mo templates with thermally controlled periodicity. The [...] Read more.

The manipulation of magnetic anisotropy represents the fundamental prerequisite for the application of magnetic materials. Here we present the vectorial magnetic properties of nanostructured systems and thin films of Fe and FeCo prepared on linearly trenched Mo templates with thermally controlled periodicity. The magnetic properties of the nanosystems are engineered by tuning the shape, size, thickness, and composition parameters of the thin films. Thus, we control coercivity, magnetization, orientation of the easy axis of magnetization, and the long-range magnetic order of the system in the function of the temperature. We distinguish magnetic components that emerge from the complex morpho-structural features of the undulating Fe or FeCo nanostructured films on trenched Mo templates: (i) assembly of magnetic nanowires and (ii) assembly of magnetic islands/clusters. Uniaxial anisotropy at room temperature was proven, characterized, and explained in the case of all systems. Our work contributes to the understanding of magnetic properties necessary for possible further applications of linear systems and undulated thin films. Full article

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15 pages, 9698 KiB

Open AccessArticle

Effect of a Discontinuous Ag Layer on Optical and Electrical Properties of ZnO/Ag/ZnOStructures

by Petko Vitanov, Tatyana Ivanova, Hristosko Dikov, Penka Terziyska, Maxim Ganchev, Nikolay Petkov, Yordan Georgiev and Asen Asenov

Coatings 2022, 12(9), 1324; https://doi.org/10.3390/coatings12091324 - 11 Sep 2022

Cited by 4 | Viewed by 1932

Abstract

ZnO/Ag/ZnO nanolaminate structures were deposited by consecutive RF sputtering at room temperature.The optical transparency, sheet resistance, and figure of merit are determined in relation to the deposition time of Ag and to the film thickness of the ZnO top layer. An improved transmittance [...] Read more.

ZnO/Ag/ZnO nanolaminate structures were deposited by consecutive RF sputtering at room temperature.The optical transparency, sheet resistance, and figure of merit are determined in relation to the deposition time of Ag and to the film thickness of the ZnO top layer. An improved transmittance has been found in the visible spectral range of the ZnO/Ag/ZnO structure compared to ZnO multilayers without Ag. High transmittance of 98% at 550 nm, sheet resistance of 8 Ω/sq, and figure of merit (FOM) of 111.01 × 10⁻³ Ω⁻¹are achieved for an optimized ZnO/Ag/ZnO nanolaminate structure. It is suggested that the good optical and electrical properties are due to the deposition of the discontinuous Ag layer. The electrical metallic type conductivity is caused by planar located silver metal granules. The deposition of a discrete layer of Ag nano-granules is confirmed by atomic force microscopy (AFM) and cross-section high-resolution transmission electron microscopy (HRTEM) observations. Full article

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Review

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31 pages, 5511 KiB

Open AccessReview

Recent Advances in Surface Functionalization of Magnetic Nanoparticles

by Cezar Comanescu

Coatings 2023, 13(10), 1772; https://doi.org/10.3390/coatings13101772 - 15 Oct 2023

Viewed by 1758

Abstract

In recent years, significant progress has been made in the surface functionalization of magnetic nanoparticles (MNPs), revolutionizing their utility in multimodal imaging, drug delivery, and catalysis. This progression, spanning over the last decade, has unfolded in discernible phases, each marked by distinct advancements [...] Read more.

In recent years, significant progress has been made in the surface functionalization of magnetic nanoparticles (MNPs), revolutionizing their utility in multimodal imaging, drug delivery, and catalysis. This progression, spanning over the last decade, has unfolded in discernible phases, each marked by distinct advancements and paradigm shifts. In the nascent stage, emphasis was placed on foundational techniques, such as ligand exchange and organic coatings, establishing the groundwork for subsequent innovations. This review navigates through the cutting-edge developments in tailoring MNP surfaces, illuminating their pivotal role in advancing these diverse applications. The exploration encompasses an array of innovative strategies such as organic coatings, inorganic encapsulation, ligand engineering, self-assembly, and bioconjugation, elucidating how each approach impacts or augments MNP performance. Notably, surface-functionalized MNPs exhibit increased efficacy in multimodal imaging, demonstrating improved MRI contrast and targeted imaging. The current review underscores the transformative impact of surface modifications on drug delivery systems, enabling controlled release, targeted therapy, and enhanced biocompatibility. With a comprehensive analysis of characterization techniques and future prospects, this review surveys the dynamic landscape of MNP surface functionalization over the past three years (2021–2023). By dissecting the underlying principles and applications, the review provides not only a retrospective analysis but also a forward-looking perspective on the potential of surface-engineered MNPs in shaping the future of science, technology, and medicine. Full article

(This article belongs to the Special Issue Advances of Nanoparticles and Thin Films)

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