Papers by Keyword: Core-Shell

Abstract: Ag@TiO₂ core-shell nanoparticles (NPs) were synthesized through an environmentally benign, two-step method utilizing Aloe vera extract as a natural reducing and capping agent. Structural and morphological characterization via X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) confirmed the successful formation of spherical core-shell structures with a size range of 10-40 nm. Optical analysis revealed a wide bandgap of 4.8 eV, indicative of quantum confinement effects. While electrokinetic measurements suggested moderate colloidal stability (zeta potential near 0 mV), the nanoparticles exhibited potent, strain-dependent antimicrobial activity. Notably, they demonstrated superior efficacy against Gram-positive Staphylococcus epidermidis (32 mm inhibition zone) compared to Gram-negative Escherichia coli (21 mm inhibition zone). This green synthesis route presents a sustainable strategy for producing antibacterial nanoparticles with enhanced activity against Gram-positive pathogens.

Abstract: The present research explores the tunable thermoplasmonic response of spherical core-shell nanostructures through theoretical analysis based on the Mie theory. The study examines the effects of gold (Au) and silver (Ag) shell thickness on mercury (Hg) nanoparticles in a water media (n = 1.33), with systematically varying core sizes between the range 5 nm to 20 nm and shell thicknesses 2 nm to 20 nm for sensing, photonic, and photothermal applications. The optical and thermoplasmonic characteristics are investigated for various core-shell ratio at different localized surface plasmon resonance (LSPR) wavelengths, covering a spectrum from 250 nm to 850 nm. It is observed that the absorption peak spectra are found between 502 nm-537 nm and 345 nm-456 nm wavelengths with Au and Ag shell on Hg-core. Maximum values of absorption cross-section spectra is revealed at 1.80E-14 m² and 1.57E-14 m² of wavelengths 536 nm and 380 nm. Also, 𝐽₀max is calculated 22 and 31.5 for Au and Ag shell thickness of 02 nm on 20 nm Hg-core and maximum temperature rise at 5.91°C of 20 nm Au shell thickness as compared to Ag shell under 1_*10⁴ W/cm² laser irradiation. The results indicate that the temperature generated by these core-shell nanoparticles can be modulated by material’s nature, core radius, gold/silver shell thickness, and the surrounding medium. Further, the examined core-shell nanoparticles show potential as effective heat sources in various applications, including photothermal cancer therapy, cell optoporation, and sterilization and disinfection of medical equipment.

Abstract: Silica-coating is one of simple methods to colloidally stabilize particles. The present work proposed a method for fabricating silica-coated ruby particles having a particle size of ca. 1 µm (ruby/SiO₂) by a process based on a Stöber method. Two systems were examined, which were the systems using sodium hydroxide (NaOH) and aqueous ammonia (NH₄OH) as base catalysts for a sol-gel reaction. In the NaOH system, not only the ruby/SiO₂ particles with silica shells with a thickness of ca. 61 nm but also core-free SiO₂ particles were produced by adding tetraethyl orthosilicate/ethanol solution and NaOH aqueous solution to ethanol dispersing the ruby particle powder. In the NH₄OH system, it was demonstrated that it was possible to increase the shell thickness to 132 nm by repeating addition of TEOS and NH₄OH to a mixture of ruby particles, water, and ethanol, which meant that it was found to vary the shell thickness. The ruby particles emitted luminescence even after the silica-coating, which found that the silica-coating did not deteriorate luminescence property of ruby particles.

Abstract: The photocatalytic activity of NiZnFe₂O₄/TiO₂ core-shell gg nanocrystalline was carried out. The NiZnFe₂O₄/TiO₂ core-shell was synthesized using co-precipitation method with various concentrations 1:0, 1:1, 1:2, 1:3, 1:4, and 1:5. X-ray diffraction spectra pattern showed crystallite size at various concentrations 1:0, 1:1, and 1:3, which of 5.00 nm, 4.90 nm, and 10.81 nm, respectively. The morphology of NiZnFe₂O₄ nanocrystalline was characterized by transmission electron microscopy which confirmed that the sample undergoes agglomeration with not uniform particle shape. The average particle size of the nanocrystalline was 10.26 nm. Fourier transform infra-red showed functional groups such as Ti-O-Ti, M-O_tetra, and M-O_octa at 1473.62, 563 - 586, and 401- 424 cm^-1. In addition, the presence of Ti-O-Ti and M-O functional groups indicates NiZnFe₂O₄/TiO₂ core-shell has been formed. The absorbance spectrum of the NiZnFe₂O₄/TiO₂ core-shell has an energy band gap in the range of 2.1 – 3.3 eV. The results of the Vibrating sample magnetometer showed saturation magnetization and coercivity values ​​in the range of 12.4 – 22.9 emu/gr and 47 - 55 Oe, which were correlated as soft magnetic properties. NiZnFe₂O₄/TiO₂ was successfully degraded Methylene Blue that reach 99.8% under UV light irradiation. The addition of TiO₂ increases degradation, TiO₂ acts as a trapping state that inhibits electron-hole recombination which can prolong the reaction time between free electrons and MB solution molecules. This study revealed the high potential of NiZnFe₂O₄/TiO₂ core-shell nanocrystalline in photocatalytic application.

Abstract: Advances in radar technology today are experiencing rapid development based on the latest findings that complement each other. BaFe₁₂O₁₉ is a type M hexagonal ferrite material as the best candidate for absorber material applications. Manganese dioxide (MnO₂) is a transition metal that has a high dielectric loss and has the opportunity to increase the absorption of electromagnetic waves. The BaFe₁₂O₁₉@MnO₂ core-shell composite produces the combined characteristics of BaFe₁₂O₁₉ and MnO₂, which can improve performance as radar-absorbing material. The BaFe₁₂O₁₉@MnO₂ core-shell composite is synthesized in two stages: molten salt synthesis in manufacturing BaFe₁₂O₁₉ as a core and hydrothermal synthesis to grow MnO₂ nanoflowers as a shell. The research objective was to produce BaFe₁₂O₁₉@MnO₂ core-shell composite for radar absorbing applications in the x-band with absorption of ~99%. In molten salt synthesis, using two calcination operations at 1000 °C for two hours to create BaFe₁₂O₁₉ as a template, then combining BaFe₁₂O₁₉ template with Fe₂O₃ and BaCl₂.2H₂O for eight hours at 1100 °C prepared for MnO₂ pathways on the BaFe₁₂O₁₉ surface. Hydrothermal synthesis occurs by dissolving BaFe₁₂O₁₉ and KMnO₄ in deionized water with a mass ratio of BaFe₁₂O₁₉ to KMnO₄ is 1:1, followed by hydrothermal synthesis at a holding time of 12 hours with a temperature of 150 °C; 170 °C; 190 °C. Characterization of vector network analysis on a variation of sample thickness (1; 1.5; 2; 2.5; 3) mm were analyzed in the x-band frequency on 8-12 GHz. BaFe₁₂O₁₉@MnO₂ core-shell composite was hydrothermally produced at 170 °C with a particle size of 197.1 nm, a thickness of 2.5 mm, and a reflection loss of -20.31 dB at 8.7 GHz. The absorber material from the combined synthesis of molten salt and hydrothermal synthesis to make BaFe₁₂O₁₉@MnO₂ core-shell composite successfully produced microwave absorption up to 99.06%.

Abstract: Electric vehicles (EVs) have a significant advantage in terms of energy efficiency and environmental friendliness. In lithium-ion batteries, silicon is seeking more attention than graphite-based anodes due to its high storage capacity. However, it faces severe structural degradation due to volume expansion which is responsible for fast capacity degradation. In the present study, the core shell is developed with the core as silicon and titania as shell (Si@TiO₂) and utilized it as an anode in the 2016-coin cell. The material characterization (FE-SEM, TEM, EDS, XRD and XPS) of this developed core-shell material is recorded to confirm its elemental composition and structural validation. The electrochemical performance is measured using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) test. Cyclic voltammetry profiles reveal the stable lithiation and delithiation process. Initial specific capacity of ≈3180 mAh/g is reported, capacity retention of 61% for the developed core-shell while 34% for the bare silicon is noted over 100 cycles. The proposed method (peptization technique) for the development of core-shell nanoparticles is also compared with the sol-gel approach. The result shows an increment of 5% in capacity retention after 100 cycles by following the peptization technique.

Abstract: Magnetic-bead separation or purification serves as a technique for effective isolation of biomolecules. In presented work we prepared and characterized core-shell magnetic nanoparticle samples consisted of Fe₃O₄ core coated with SiO₂ shell. Samples were subsequently coated with ligands MPTMS (3-(mercaptopropyl)trimethoxysilane), CPTMS (3-(chloropropyl)trimethoxysilane) and MMSP (3-(trimethoxysilyl)propyl methacrylate) with aim to increase the number of active centers for specific binding with RNA. Such samples were further investigated for their magnetic properties, size, and morphology. Magnetic properties were studied in DC field up to 5 T in temperature range 5 – 300 K. Size and morphology were determined from SEM micrographs and elemental compositions of the samples were investigated using EDX analysis. Modification of nanoparticle surface with different ligands leads to modification of active centers on the SiO₂ surface on which the DNA and RNA molecules can be bounded. It also causes the change in magnetic and structural properties of nanoparticles.

Abstract: Metal-organic frameworks (MOFs) have exciting properties and promising applications in different fields. In this work, novel zeolitic imidazolate frameworks (ZIFs) have been synthesized by encapsulating N-doped carbon quantum dots (N-CDs) with a blue FL into the zeolitic imidazolate framework materials core-shell structure (ZIF-8@ZIF-67). The functionalized core-shell MOFs maintained their crystal structure, morphology, and enhanced UV-vis absorbance. The properties of these new composites exhibit excellent potential for different applications including sensing, photo-catalysis, and selective adsorption.

Abstract: Integration of low bandgap antimonide based nanowires on Si substrate has been attracting huge attention for opto-electronic applications. In this work we demonstrated InAs/InSb and InAs/GaSb heterostructure nanowires on Si substrate by metal organic chemical vapor deposition. We grew high quality axial InSb heterostructure segment on InAs stem by self-catalyzed growth technique, which paves a way to tune the crystal structure of InSb. In case of InAs-GaSb core-shell architecture, GaSb crystal quality highly depends on InAs core. We successfully demonstrated basic electrical characteristics of InAs-GaSb core-shell nanowire which exhibits negative differential resistance at 0.8 V and peak-to-valley current ratio of 3.84.

Abstract: In this work, germanium nanowires (GeNWs) were fabricated by galvanostatic electrodeposition using In nanoparticles from water solutions at different temperatures. It was found that in the temperature range from 10°C to 60°C there was no significant change in the structure of GeNWs, and the average diameter was about 40 nm. The growth time of GeNWs increases linearly with increasing temperature of the electrolyte solution. However, the structure of GeNW obtained at a solution temperature of 90°C has changed. It was shown that these GeNWs have a core-shell structure: the core is a crystalline Ge phase containing In atoms, and the shell is Ge oxides (hydroxides).