Optimized Anti-pathogenic Agents Based on Core/Shell Nanostructures and 2-((4-Ethylphenoxy)ethyl)-N-(substituted-phenylcarbamothioyl)-benzamides

The purpose of this study was to design a new nanosystem for catheter surface functionalization with an improved resistance to Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853 colonization and subsequent biofilm development. New 2-((4-ethylphenoxy)methyl)-N-(substituted-phenylcarbamothioyl)-benzamides were synthesized and used for coating a core/shell nanostructure. Their chemical structures were elucidated by NMR, IR and elemental analysis, being in agreement with the proposed ones. Fe₃O₄/C₁₂ of up to 5 nm size had been synthesized with lauric acid as a coating agent and characterized by XRD, FT-IR, TGA, TEM and biological assays. The catheter pieces were coated with the fabricated nanofluid in magnetic field. The microbial adherence ability was investigated in 6 multiwell plates by using culture based methods and Scanning Electron Microscopy (SEM). The nanoparticles coated with the obtained compounds 1a–c inhibited the adherence and biofilm development ability of the S. aureus and P. aeruginosa tested strains on the catheter functionalized surface, as shown by the reduction of viable cell counts and SEM examination of the biofilm architecture. Using the novel core/shell/adsorption-shell to inhibit the microbial adherence could be of a great interest for the biomedical field, opening new directions for the design of film-coated surfaces with improved anti-biofilm properties.     

Hybrid nanostructured coating for increased resistance of prosthetic devices to staphylococcal colonization

Prosthetic medical device-associated infections are responsible for significant morbidity and mortality rates. Novel improved materials and surfaces exhibiting inappropriate conditions for microbial development are urgently required in the medical environment. This study reveals the benefit of using natural Mentha piperita essential oil, combined with a 5 nm core/shell nanosystem-improved surface exhibiting anti-adherence and antibiofilm properties. This strategy reveals a dual role of the nano-oil system; on one hand, inhibiting bacterial adherence and, on the other hand, exhibiting bactericidal effect, the core/shell nanosystem is acting as a controlled releasing machine for the essential oil. Our results demonstrate that this dual nanobiosystem is very efficient also for inhibiting biofilm formation, being a good candidate for the design of novel material surfaces used for prosthetic devices.     

Biohybrid Nanostructured Iron Oxide Nanoparticles and Satureja hortensis to Prevent Fungal Biofilm Development

Cutaneous wounds are often superinfected during the healing process and this leads to prolonged convalescence and discomfort. Usage of suitable wound dressings is very important for an appropriate wound care leading to a correct healing. The aim of this study was to demonstrate the influence of a nano-coated wound dressing (WD) on Candida albicans colonization rate and biofilm formation. The modified WD was achieved by submerging the dressing pieces into a nanofluid composed of functionalized magnetite nanoparticles and Satureja hortensis (SO) essential oil (EO). Chemical composition of the EO was established by GC-MS. The fabricated nanostructure was characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Differential Thermal Analysis (DTA) and Fourier Transform-Infrared Spectroscopy (FT-IR). The analysis of the colonized surfaces using (Scanning Electron Microscopy) SEM revealed that C. albicans adherence and subsequent biofilm development are strongly inhibited on the surface of wound dressing fibers coated with the obtained nanofluid, comparing with regular uncoated materials. The results were also confirmed by the assay of the viable fungal cells embedded in the biofilm. Our data demonstrate that the obtained phytonanocoating improve the resistance of wound dressing surface to C. albicans colonization, which is often an etiological cause of local infections, impairing the appropriate wound healing.     

Effect of carbon shell thickness on the microwave absorption of magnetite-carbon core-shell nanoparticles

Carbon coated magnetite nanoparticles with two different shell thicknesses were synthesized by a facile two-step method using glucose as a source of carbon. At first, hematite nanoparticles were synthesized by hydrothermal process. Carbon shells were coated on hematite nanoparticles by hydrothermal carbonization process, and the carbon coat thickness on particles was controlled by the amount of glucose in the second step. The hematite-carbon core-shell nanoparticles were then heat treated under argon gas flow in order to produce magnetite-carbon nanocapsules. Phase transformation during the heat treatment was studied by X-ray diffraction (XRD). The existence of carbon shell on nanoparticles was investigated by transmission electron microscopy (TEM) and Raman spectroscopy. The effect of carbon shell thickness variation on the relative complex permittivity (ε_r=ε′+iε″) and permeability (μ_r=μ′+iμ″) was studied in a frequency range of 1–18 GHz. The effect of carbon shell thickness on the Fe₃O₄-C nanoparticles reflection loss was also studied. The results showed that the microwave properties of the carbon coated magnetite nanoparticles can be controlled effectively by adjusting carbon shell thickness.     

Core–shell superparamagnetic iron oxide nanoparticle (SPION) clusters: TEM micrograph analysis,particle design and shape analysis

For the first time, particle shape analysis of silica coated iron oxide (maghemite/magnetite) nanoparticle clusters (core–shell nanostructures) is discussed using computational methods. We analyzed three samples of core–shell nanostructures synthesized with different thickness of the silica shell. A new computational method is presented and successfully applied to the segmentation of the core–shell nanoparticles, as one of the main problems in image analysis of the TEM micrographs. We have introduced the “circularity coefficient”, marked with k_circ and defined as the ratio of circularity measure C₂(S) of nanoparticles core and circularity measure core–shell nanoparticles in order to answer the question how the shell affects the overall shape of the final core–shell structure, with respect to circularity. More precisely, the “circularity coefficient” determines whether the circularity of the core–shell nanoparticle is higher, lower or equal to the circularity of the core. We have also determined the shell's share in the overall area of the core–shell nanoparticle. The core–shell nanoparticle clusters here investigated exhibit superparamagnetic properties at room temperature, thus emphasizing their potential for use in practical applications such as in biomedical and particle separation. We show that the saturation magnetization strength can be easily adjusted by controlling the thickness of the silica shell.     

Synthesis, magnetic and optical properties of core/shell Co1-xZnxFe2O4/SiO2 nanoparticles

The optical properties of multi-functionalized cobalt ferrite (CoFe₂O₄), cobalt zinc ferrite (Co_0.5Zn_0.5Fe₂O₄), and zinc ferrite (ZnFe₂O₄) nanoparticles have been enhanced by coating them with silica shell using a modified Stöber method. The ferrites nanoparticles were prepared by a modified citrate gel technique. These core/shell ferrites nanoparticles have been fired at temperatures: 400°C, 600°C and 800°C, respectively, for 2 h. The composition, phase, and morphology of the prepared core/shell ferrites nanoparticles were determined by X-ray diffraction and transmission electron microscopy, respectively. The diffuse reflectance and magnetic properties of the core/shell ferrites nanoparticles at room temperature were investigated using UV/VIS double-beam spectrophotometer and vibrating sample magnetometer, respectively. It was found that, by increasing the firing temperature from 400°C to 800°C, the average crystallite size of the core/shell ferrites nanoparticles increases. The cobalt ferrite nanoparticles fired at temperature 800°C; show the highest saturation magnetization while the zinc ferrite nanoparticles coated with silica shell shows the highest diffuse reflectance. On the other hand, core/shell zinc ferrite/silica nanoparticles fired at 400°C show a ferromagnetic behavior and high diffuse reflectance when compared with all the uncoated or coated ferrites nanoparticles. These characteristics of core/shell zinc ferrite/silica nanostructures make them promising candidates for magneto-optical nanodevice applications.     

Core–shell structured Cu@m-SiO2 and Cu/ZnO@m-SiO2 catalysts for methanol synthesis from CO2 hydrogenation

The core–shell catalysts with Cu and Cu/ZnO nanoparticles coated by mesoporous silica shells are prepared for CO₂ hydrogenation to methanol. With the confined effect of silica shell, the size of Cu nanoparticles is only about 5.0 nm, which results in high activity for CO₂ conversion. The CH₃OH selectivity is enhanced significantly with the introduction of ZnO. The core–shell structured catalysts endow the Cu nanoparticles trapped inside with excellent anti-aggregation and no deactivation is observed with time-on-stream. Therefore, the core–shell Cu/ZnO@m-SiO₂ catalyst exhibits the maximum CH₃OH yield with high stability.     

Optimization of Synthesis Parameters for Mesoporous Shell Formation on Magnetic Nanocores and Their Application as Nanocarriers for Docetaxel Cancer Drug

In this work, Fe₃O₄@SiO₂ nanoparticles were coated with mesoporous silica shell by S⁻N⁺I⁻ pathway by using anionic surfactant (S⁻) and co-structure directing agent (N⁺). The role of co-structure directing agent (CSDA) is to assist the electrostatic interaction between negatively charged silica layers and the negatively charged surfactant molecules. Prior to the mesoporous shell formation step, magnetic cores were coated with a dense silica layer to prevent iron oxide cores from leaching into the mother system under any acidic circumstances. However, it was found that both dense and mesoporous coating parameters affect the textural properties of the produced mesoporous silica shell (i.e., surface area, pore volume and shell thickness). The synthesized Fe₃O₄@SiO₂@m-SiO₂ (MCMSS) nanoparticles have been characterized by low-angle X-ray diffraction, transmission electron microscopy (TEM), and N₂ adsorption-desorption analysis, and magnetic properties. The synthesized particles had dense and mesoporous silica shells of 8–37 nm and 26–50 nm, respectively. Furthermore, MCMSS possessed surface area of ca. 259–621 m²·g⁻¹, and pore volume of ca. 0.216–0.443 cc·g⁻¹. MCMSS showed docetaxcel cancer drug storage capacity of 25–33 w/w% and possessed control release from their mesochannels which suggest them as proper nanocarriers for docetaxcel molecules.     

Synthesis and optical limiting effects in ZrO2 and ZrO2@SiO2 core–shell nanostructures

ZrO₂ nanoparticles were synthesized by the chemical precipitation method and coated with silica through seeded polymerization technique to form core–shell type ZrO₂@SiO₂ nanostructures. The structural, morphological and silica coating formation of the bare and silica coated particles were studied using Transmission electron microscopy, X-ray diffraction and Fourier Transform Infrared Spectroscopy. Thermogravimetric analysis and Zeta potential measurements were performed to check the thermal and dispersion stability of the nanostructures. The optical limiting performance of these nanostructures was studied using open-aperture Z-scan technique in which nanosecond laser pulses at 532 nm have been used for optical excitation. Both bare and silica coated ZrO₂ nanoparticles exhibited good optical limiting behavior due to excited state absorption, arising from effective three photon absorption. It is observed that the optical nonlinearity is enhanced in core shell structures as compared with the bare particles.     

Pt-rich shell coated Ni nanoparticles as catalysts for methanol electro-oxidation in alkaline media

The Pt-rich shell coated Ni nanoparticles in size of 8.9–12.1 nm were synthesized by chemical deposition via successive reduction of NiCl₂ and H₂PtCl₆, respectively, in an ethylene glycol solution and characterized by TEM, XPS, ICP–AES, and XRD techniques. The electrochemical evaluation showed that as-prepared core–shell structural nanoparticles, as a catalyst for methanol electro-oxidation in alkaline media, not only exhibited better catalytic activity and resistance to carbonaceous intermediate poison than pure solid Pt nanoparticles but also decreased wastage of expensive Pt.     

Effect of side chains and solvents on the film surface of linear fluorosilicone pentablock copolymers

The linear fluorosilicone pentablock copolymers PDMS-b-(PMMA-b-PFMA)₂ are synthesized via two-step ATRP approaches by dimethylsiloxane (DMS), methyl methacrylate (MMA) and fluorinated methacrylate (FMA). Trifluoroethyl methacrylate (3FMA), hexafluorobutyl methacrylate (6FMA), octafluoropentyl methacrylate (8FMA) and dodecafluoroheptyl methacrylate (12FMA) are used as FMA. The effect of different fluorinated side chains on the surface properties of PDMS-b-(PMMA-b-PFMA)₂ films indicates that 3FMA, 6FMA and 8FMA behave the similar surface properties as lower water contact angles (θ(H₂O) = 105–106°) and higher surface free energy (26.83–27.55 mN/m) than P12FMA (θ(H₂O) = 116°, 19.52 mN/m) due to the competing migration between the PFMA and PDMS chains. Therefore, the effect of chloroform (CHCl₃), tetrahydrofuran (THF), trifluorotoluene (TFT) and CHCl₃–TFT solvents on the self-assembly and surface properties of PDMS-b-(PMMA-b-P12FMA)₂ film is investigated by DLS, TEM, SCA, XPS, SEM, AFM and QCM-D. A typical bimodal distribution with high content of micelles (310 nm, 93%) in CHCl₃ solution and high content of unimers (17 nm, 70%) in CHCl₃–TFT solution are formed, but a special unimodal distribution of unimers (15 nm) in THF solution and micelles (75 nm) in TFT solution are found. The micelles are confirmed by TEM as P12FMA core–PDMS/PMMA shell in CHCl₃ solution, but PDMS core–PMMA/P12FMA shell in TFT and CHCl₃–TFT solutions. The results reveal that the higher content of unimers contributes much to the fluorine-rich surface, higher cetane contact angle, lower surface energy and lower viscoelasticity for the film, but the higher content of micelles promote forming the roughness surface. Therefore, the most hydrophobic surfaces are the films casting from THF and CHCl₃–TFT solution.     

Chemical composition, angiotensin I-converting enzyme inhibitory, antioxidant and antimicrobial activities of essential oil of Tunisian Thymus algeriensis Boiss. et Reut. (Lamiaceae)

The present study describes chemical composition, angiotensin I-converting enzyme (ACE) inhibitory, antioxidant and antimicrobial activities of the essential oil of wild growing Thymus algeriensis Boiss. et Reut. (Lamiaceae), a traditional medicinal plant which is mainly endemic in Tunisia and Algeria. The essential oil from the fresh leaves and flowers of T. algeriensis were extracted by hydrodistillation and analysed by GC and GC/MS. Fifty-seven compounds were identified accounting for 97.71% of the total oil, where oxygenated monoterpenes constituted the main chemical class (44.85%). The oil was dominated by camphor (7.82%), 4-terpineol (7.36%), α-pinene (6.75%), 1,8-cineole (5.54%) and cis-sabinene hydrate (5.29%). The T. algeriensis essential oil was found to possess an interesting inhibitory activity towards ACE with an IC50 value of 150 μg/ml. The obtained results also showed that this oil can act as radical scavengers (IC₅₀ = 0.8 mg/ml) and displayed a lipid peroxidation inhibitory activity (IC₅₀ = 0.5 mg/ml) as evaluated by 2,2-diphenyl-1-picrylhydrazyl and β-carotene bleaching methods, respectively. Furthermore, the oil was tested for antimicrobial activity against six bacterial strains and two fungal strains. The inhibition zones and minimal inhibitory concentration values of microbial strains were in the range of 13.5-64 mm and 1-6 μl/ml, respectively. The oil exhibited remarkable inhibitory activity against fungal and Gram-positive bacteria strains.     

Synthesis of hermetically-sealed graphite-encapsulated metallic cobalt (alloy) core/shell nanostructures

Hermetically-sealed graphite encapsulated cobalt core/shell nanostructures have been prepared by the CO Boudouard reaction using in situ generated cobalt as the catalyst. Only core/shell nanostructures were obtained, rather than a mixture of cobalt nanoparticles with carbon nanotubes or nanofibers. The magnetic cobalt nanoparticles are highly crystallized with a hexagonal-close packed crystal phase (average diameter of ca. 25 nm) and coated with an 8–9 nm thick graphitic shell. The nanostructures have a high saturation magnetization of 85 emu/g and can be easily separated by an external magnet. The creation of the hermetically-sealed graphitic shell not only keeps the magnetic cobalt nanoparticles from reacting with strong mineral acids, but also has biocompatibility and makes further functionalization easy. A pseudo-planar aromatic molecule, xylenol orange, was used as the model molecule because it can be absorbed on the graphitic shell mainly by π–π stacking interaction. This was confirmed by Raman and ultraviolet–visible spectroscopy. Graphite encapsulated Fe₂Co and Fe_0.64Ni_0.36 alloy core/shell nanostructures were also fabricated by this method.     

AgBr@Ag/TiO2 core–shell composite with excellent visible light photocatalytic activity and hydrothermal stability

AgBr@Ag/TiO₂ core–shell photocatalysts were fabricated by a facile green route. TiO₂ was uniformly coated on the surface of cubic AgBr, making AgBr@Ag/TiO₂ core–shell photocatalyst show excellent hydrothermal stability. Beneficial from that Ag nanoparticles and AgBr can respond to visible light and core–shell structure can effectively separate the photogenerated electrons and holes, AgBr@Ag/TiO₂ core–shell composites exhibited outstanding visible light photocatalytic activity for the degradation of acid orange 7. The activity of AgBr@Ag/TiO₂ is related to the thickness of TiO₂ shell, and the optimal shell thickness for obtaining the highest activity is 10 nm.     

Broadband infrared emissivity of Ag@SiO2 nanoparticles due to coupled transverse EM modes

The extension of plasmonic spectra to the Mid-Infrared (MIR) spectral range (2 μm to 14 μm) of Silver coated Silica (Ag@SiO₂) nanoparticles was discussed in this paper. Most of the previous findings in this regard, describe the intrinsic infrared response of individual Ag@SiO₂ particles or dimer and less explanation is available about the effect of electric field coupling over infrared radiation. This work provides detailed analysis about the contribution in the infrared response from the coupling of transverse EM (Electric-Magnetic) modes between the particles in the dimer. The simulated data also suggests a strong dependence of infrared radiation on the coupling of transverse EM which will facilitate the researchers in future to prepare the paint of randomly distributed Ag@SiO₂ nanoparticles for passive radiative cooling. A smooth extra thin shell of Ag were deposited over SiO₂ nanoparticles successfully, by employing wet chemical method. The morphology, qualitative and quantitative analysis were performed by using Transmission Electron spectroscopy (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) respectively. The emissivity of the particles was measured with the Fourier Transform Infrared (FTIR) Spectrometer. The IR response of Ag@SiO₂ nanoparticles was simulated by employing the Finite Element Method (FEM) with the Microwave Studio in Computer Simulation Technology (CST) software. All the simulations and experimental results were found in agreement with slight difference between them. This slight difference has been explained in Modeling and Numerical analysis section.     

Synthesis and characterization of poly(styrene-co-fluorescein O-methacrylate)/poly(N-isopropylacrylamide)-Fe3O4 core/shell composite particles

We demonstrate the synthesis and characteristics of multifunctional poly(styrene-co-fluorescein O-methacrylate)/poly(N-isopropylacrylamide)-Fe₃O₄ [P(St/FMA)/PNIPAAm-Fe₃O₄] core/shell composite particles, in which the core consists of fluorescent materials and the shell consists of magnetic and thermo-responsive components. First, core/shell particles consisting of a fluorescent P(St/FMA) core and thermo-responsive PNIPAAm-rich shell were prepared by two-stage shot-growth emulsion polymerization. Next, Fe₃O₄ nanoparticles were immobilized via electrostatic interactions and then covalently linked to the shell via surface coordinated Aphen by a coupling reaction in order to obtain magnetic properties. The morphology of P(St/FMA)/PNIPAAm-Fe₃O₄ composite particles, confirmed by transmission electron microscopy (TEM), reveals that Fe₃O₄ nanoparticles are located in the PNIPAAm shell. The thermo-sensitivity of composite particles to hydrodynamic diameter was confirmed by using dynamic light scattering (DLS). Photoluminescence (PL) spectra indicate that the fluorescence emission intensity of core/shell particles is highly sensitive to the pH of an aqueous medium. The core/shell composite particles exhibited a combination of fluorescent, magnetic, pH and thermo-responsive behavior.     

Evaluation of the Cytotoxic Behavior of Fungal Extracellular Synthesized Ag Nanoparticles Using Confocal Laser Scanning Microscope

Silver nanoparticles have been synthesized by subjecting a reaction medium to a Fusarium oxysporum biomass at 28 °C for 96 h. The biosynthesized Ag nanoparticles were characterized on the basis of their anticipated peak at 405 nm using UV-Vis-NIR spectroscopy. Structural confirmation was evident from the characteristic X-ray diffraction (XRD) pattern, high-resolution transmission electron Microscopy (HRTEM) and the particle size analyzer. The Ag nanoparticles were of dimension 40 ± 5 nm and spherical in shape. The study mainly focused on using the confocal laser scanning microscope (CLSM) to examine the cytotoxic activities of fungal synthesized Ag nanoparticles on a human breast carcinoma cell line MCF7 cell, which featured remarkable vacuolation, thus indicating a potent cytotoxic activity.     

Surface Modification of Luminescent LnIII Fluoride Core–Shell Nanoparticles with Acetylsalicylic acid (Aspirin): Synthesis,Spectroscopic and in Vitro Hemocompatibility Studies

Luminescent lanthanide fluoride core–shell (LaF₃:Tb³⁺,Ce³⁺@SiO₂-NH₂) nanoparticles, with acetylsalicylic acid (aspirin) coated on the surface have been obtained. The synthesized products, which combine the potential located in the silica shell with the luminescent activity of the core, were characterized in detail with the use of luminescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and transmission electron microscopy (TEM) methods. The in vitro effects of the modified luminescent nanoparticles on human red blood cell (RBC) membrane permeability, RBC shape, and sedimentation rate were investigated to assess the hemocompatibility of the obtained compounds. This study demonstrates that LaF₃: Tb³⁺ 5 %, Ce³⁺ 10 %@SiO₂-NH₂ nanoparticles with acetylsalicylic acid (aspirin) coated on the surface are very good precursors for multifunctional drug-delivery systems or bio-imaging probes that can be used safely in potential biomedical applications.     

Preparation of VO2/Al-O core-shell structure with enhanced weathering resistance for smart window

VO₂/Al-O core-shell structure (V/AO) was synthesized by a facile method and its application for thermochromic film on smart window was investigated. Comparisons of thermochromic properties and stabilities in different environments between VO₂ and annealed V/AO nanoparticles were made. As a result, VO₂ nanoparticle was easily oxidized and lost thermochromic property. In contrast, with the protection provided by Al-O-based shell, the VO₂ core remained stable at a high temperature (350 °C in air) and in H₂O₂ solution. Especially, thermochromic films made by annealed V/AO nanoparticles almost kept thermochromic performance in damp heating environment (T=60 °C, RH=90%) for 20 days while VO₂ films lost their thermochromic properties after 3 days. Besides, the degradation progress of VO₂ and V/AO nanoparticles in damp heating environment was also explored. Results indicate that Al-O-based shell provides a good protection for the VO₂ core originated from the compact structure of shell, which effectively prevents oxygen and water from eroding VO₂. In summary, the VO₂ nanoparticles coated with Al-O-based shell exhibit a great potential in the application of smart window.     

Influence of Si nanoparticles on the electrochemical behavior of organic coatings on carbon steel in chloride environment

Scanning electrochemical microscopy (SECM) is an excellent technique to detect electrochemical processes with high spatial resolution. In this work, the effect of silicon (Si) nanoparticles on the corrosion protection performance of epoxy-coated steel was examined by electrochemical impedance spectroscopy (EIS) and SECM analysis. The EIS was performed in continuous immersion in 0.1?M NaCl_(aq) solution. The addition of Si nanoparticles increased the coating film resistance (R _f) and the charge transfer resistance (R _ct) of coated steel. SECM mapping and line scan analysis was performed in order to estimate the coating performance with Si nanoparticles in 0.1?M NaCl_(aq) solution. SECM results indicated that the tip current at ?0.70?V was decreased by the addition of Si nanoparticles in epoxy film. These results suggested that the dissolved oxygen (DO) was consumed by anodic dissolution of Si nanoparticles. Surface analysis showed that the Si was enriched at the scratched region of the coated steel after a corrosion test. From these results, Si was dissolved as Si ⁿ⁺ and transferred to the scratched area, and then consumed the DO in the solution. Thus, the anodic dissolution of Fe at the scratched area was suppressed by the Si nanoparticles, which implies the sacrificial effect of Si from the coating against the steel corrosion. Hence, it was concluded that the Si nanoparticles had a beneficial effect on enhancing the corrosion resistance of the coated steel.