ZnO Core Shell Nanoparticles Research Articles

Effect of High-Purity Ag@ ZnO Core Shell Nanoparticles Synthesized by Pulse Laser Ablation Technique: Evaluation of Skin Cancer Cells

Effect of High-Purity Ag@ ZnO Core Shell Nanoparticles Synthesized by Pulse Laser Ablation Technique: Evaluation of Skin Cancer Cells

Synthesis of core–shell ZnO nanoparticles and their effect on mechanical and antibacterial properties for PLLA/ZnO nanocomposites

AbstractTo overcome the inherent brittleness of renewable poly(l‐lactide) acid (PLLA) and enable it for use in a wide application, we successfully synthesized the toughening agent of ZnO nanoparticles grafted by poly(caprolactone‐co‐d‐lactide) (ZnO‐g‐PCLDLA) via sequential open‐loop polymerization. First, ZnO was silanized to produce hydroxyl groups on the surface of the nanoparticles. Initiated by hydroxyl groups on the ZnO core, the rubbery PCLDLA composed of caprolactone‐d‐lactide co‐polymeric segments and d‐lactide homo‐polymeric segments was successively polymerized, forming ZnO core–shell nanoparticles. PLLA/ZnO‐g‐PCLDLA nanocomposites were prepared by solution blending. The nanocomposites with 10 wt% ZnO‐g‐PCLDLA exhibited superior ductility, whose elongation at break was about 54 times higher than that of neat PLLA. This considerable increment of toughness was attributed to the rubbery shell of PCLDLA and the enhanced interfacial interaction from the interfacial stereocomplex crystallites, formed by co‐crystallization of the PLLA matrix and d‐lactide homo‐polymeric segments of the PCLDLA shell on ZnO. The PLLA/ZnO‐g‐ PCLDLA nanocomposite films possessed outstanding antimicrobial properties against Staphylococcus aureus and Escherichia coli. Positive ZnO produces an electrostatic force to interact with the negatively charged membrane of bacteria, thereby damaging the cell membrane and achieving significant antibacterial effects.Highlights ZnO‐g‐PCLDLA core–shell nanoparticles were constructed by sequential ROP. The ZnO core provided high rigidity and antimicrobial properties. The rubbery PCLDLA shell provided high elasticity and ductility. Interfacial interaction was greatly enhanced by the SC crystallites. The PLLA nanocomposite films exhibited outstanding antimicrobial activity.

Ultrasensitive and stable SERS detection by defect engineering constructed Ag@Ga-doped ZnO core-shell nanoparticles

There has been increasing interest in evolution of semiconductor-based SERS-active substrates to achieve ultrasensitive detection of trace analyte molecules. This work presents a simple solvothermal method and further defect engineering technology to obtain Ag@Ga-doped ZnO core-shell nanoparticles (Ag@n%Ga-ZnO CSNPs), which have both local electromagnetic enhancement from Ag-core and efficient charge transfer enhancement due to the plasmon and photo-induced electrons and numerous deficiency sites after Ga-doping, for achieving ultrahigh detection sensitivity, stability and repeatability. Specifically, the unique Ag@2.6%Ga-ZnO CSNPs exhibited good linearity in the range from 10−6 to 10−12 M for the typical dye analyte rhodamine 6G (R6G), and the limit of detection could be down to 10−12 M. The Raman signal intensity of the Ga-doped core-shell structure was stable after 60 days of storage at room temperature. Moreover, the as-prepared Ag@2.6%Ga-ZnO CSNPs shows excellent signal repeatability as SERS substrate, and the relative standard deviation (RSD) is calculated to be about 9.71%. To illustrate the usefulness for detection of hazardous substance, we showed that such substrate can detect a pesticide, thiram, at a concentration as low as 10−9 M, which is far lower than the national standard. In addition, due to the construction of the core-shell structure and the introduction of Ga-doping, the photoelectric properties of the material have also been greatly improved. Under the irradiation of xenon lamp, the Ag@2.6%Ga-ZnO CSNPs can complete catalytic degradation of organic dye molecule R6G and pesticide molecule thiram within 40 to 50 min. This study demonstrated that the Ag@Ga-doped ZnO core-shell nanoparticles could serve as an effective and versatile SERS platform for reproducible, fast and in-field detection of organic analytes at trace levels.

Preparation and characterization of CdO-ZnO core shell nano particles: Prepared by two step wet chemical method

CdO–ZnO core-shell nanoparticles (CSN) were successfully synthesized by two step assisted chemical sol gel method. The structural properties of synthesized CSN have been analyze by X-ray diffraction (XRD) method, XRD pattern shows a uniform, homogenous phase formation of nano crystals. Microstructural properties of prepared CSN have been analyze by FESEM and HRTEM methods, Surface morphology of the CSN was investigated using FESEM, which shows dense growth and thin layer of ZnO shell over CdO core where as crystallinity of the CSN have been observed from HRTEM images, HRTEM reassures the particle size as obtained from XRD analysis. The optical properties and optical band gap of CSN is obtained from UV–Visible spectroscopy. Raman modes obtained from Raman spectroscopy distinctly identify the CdO and ZnO phonon vibrational modes. The electrical properties have been investigated by temperature dependent dielectric measurement. Moreover, the impedance behavior at different temperature has been investigated by impedance spectroscopy.

Nano-ZnO decorated on gold nanoparticles as a core-shell via pulse laser ablation in liquid

In this study, prepared Au:ZnO core-shell nanoparticles (CSNPs) by pulse laser ablation in liquid (PLAL), and succeed to control of growth the ZnO NPs and play a role as a shell decorated on surface of Au NPs as a core. The structure, morphology and visual qualities were examined. The XRD result explained the phase of ZnO NPs was wurtzite structure, and for Au NPs as a cubic crystal. The morphology of structures illuminates the agglomerated and adherent ZnO NPs on Au NPs. TEM image is clearly show the spherical particles for Au NPs with mean size 12 ± 1 nm, and the mean size for ZnO NPs is 29 ± 2 nm, while, its clearly show increased for size of Au:ZnO CSNPs to 45 ± 2 nm.

Enhanced acetone sensing properties of Pt@Al-doped ZnO core-shell nanoparticles

Core-shell Pt@Al-doped ZnO nanoparticles were synthesized and assembled into sensor as sensitive materials, Pt@Al-doped ZnO nanoparticles with 4 mol% Al dosage in ZnO shell layers present excellent sensitivity towards acetone. The response values of the Pt@Al-ZnO-4 % based sensor to 1 and 100 ppm acetone is as high as 9.26 and 128, and the detect limit towards acetone is as low as 20 ppb. Besides, the Pt@Al-ZnO-4 % based sensor demonstrates high selectivity and stability when exposed to acetone at relatively low concentration range. Appropriate amount of Al doping not only induces crystallinity deterioration of ZnO shells which creates more adsorption site, and also leads to a high proportion of oxygen adsorbed on the surface of ZnO shells. The synergistic effect between metal-ZnO hetero-interfaces and Al doping greatly improves the acetone sensing properties of Al doped Pt@ZnO based sensor.

Fast and Efficient Sun Light Photocatalytic Activity of Au_ZnO Core-Shell Nanoparticles Prepared by a One-Pot Synthesis.

Gold nanostructures absorb visible light and show localized surface plasmon resonance bands in the visible region. Semiconducting ZnO nanostructures are excellent for ultraviolet detection, thanks to their wide band gap, large free exciton binding energy, and high electron mobility. Therefore, the coupling of gold and ZnO nanostructures represents the best-suited way to boost photodetection. With the above perspective, we report on the high photocatalytic activity of some Au_ZnO core–shell nanoparticles (NPs) recently prepared by a one-pot synthesis in which a [zinc citrate]− complex acted as the ZnO precursor, a reducing agent for Au3+, and a capping anion for the obtained Au NPs. The overall nanostructures proved to be Au(111) NPs surrounded by a thin layer of [zinc citrate]− that evolved to Au_ZnO core–shell nanostructures. Worthy of note, with this photocatalyst, sun light efficiently decomposes a standard methylene blue solution according to ISO 10678:2010. We rationalized photodetection, reaction rate, and quantum efficiency.

Fe3O4–ZnO Core–Shell Nanoparticles Fabricated by Ultra-Thin Atomic Layer Deposition Technique as a Drug Delivery Vehicle

Fe3O4–ZnO nanoparticles with core–shell structures were successfully fabricated by an atomic layer deposition method. The core–shell NPs consisted of superparamagnetic Fe3O4 cores of 100 nm average size and conformal ZnO shells of 10 nm thickness. The NPs showed a saturation magnetization of ~ 23 emu/g, which is suitable for magnetic delivery of the particles. Cytotoxicity testing revealed that the Fe3O4–ZnO NPs have high cell viability (over 90%) after 24 h culture. Also, they exhibited a high ibuprofen-loading capacity (640 μg per mg of the particles) and good release ability (> 90% after 72 h in simulated body fluid). As a result, the Fe3O4–ZnO nanoparticles with conformal ultra-thin ZnO shell layers are anticipated as promising drug delivery vehicles with acceptable cell viability and high drug loading-release abilities.

Development of silane grafted ZnO core shell nanoparticles loaded diglycidyl epoxy nanocomposites film for antimicrobial applications

In this article a series of epoxy nanocomposites film were developed using amine functionalized (ZnO-APTES) core shell nanoparticles as the dispersed phase and a commercially available epoxy resin as the matrix phase. The functional group of the samples was characterized using FT-IR spectra. The most prominent peaks of epoxy resin were found in bare epoxy and in all the functionalized ZnO dispersed epoxy nanocomposites (ZnO-APTES-DGEBA). The XRD analysis of all the samples exhibits considerable shift in 2θ, intensity and d-spacing values but the best and optimum concentration is found to be 3% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposites supported by FT-IR results. From TGA measurements, 100wt% residue is obtained in bare ZnO nanoparticles whereas in ZnO core shell nanoparticles grafted DGEBA residue percentages are 37, 41, 45, 46 and 52% for 0, 1, 3, 5 and 7% ZnO-APTES-DGEBA respectively, which is confirmed with ICP-OES analysis. From antimicrobial activity test, it was notable that antimicrobial activity of 7% ZnO-APTES core shell nanoparticles loaded epoxy nanocomposite film has best inhibition zone effect against all pathogens under study.

ZnO coated CoFe2O4 nanoparticles for multimodal bio-imaging

The potential of CoFe2O4–ZnO core–shell nanoparticles for fluorescence optical imaging and as a contrast agent for magnetic resonance imaging (MRI) is demonstrated.

Study of Structural and Magnetic Properties of Superparamagnetic Fe3O4–ZnO Core–Shell Nanoparticles

In this work, Fe3O4–ZnO core–shell nanoparticles have been successfully synthesized using a simple two-step co-precipitation method. In this regard, Fe3O4 (magnetite) and ZnO (zincite) nanoparticles (NPs) were synthesized separately. Then, the surface of the Fe3O4 NPs was modified with trisodium citrate in order to improve the attachment of ZnO NPs to the surface of Fe3O4 NPs. Afterwards, the modified magnetite NPs were coated with ZnO NPs. Moreover, the influence of the core to shell molar ratio on the structural and magnetic properties of the core–shell NPs has been investigated. The prepared nanoparticles have been characterized utilizing transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM). The results of XRD indicate that Fe3O4 NPs with inverse spinel phase were formed. The results of VSM imply that the Fe3O4–ZnO core–shell NPs are superparamagnetic. The saturation magnetization of prepared Fe3O4 NPs is 54.24 emu/g and it decreases intensively down to 29.88, 10.51 and 5.75 emu/g, after ZnO coating with various ratios of core to shell as 1:1, 1:10 and 1:20, respectively. This reduction is attributed to core–shell interface effects and shielding. TEM images and XRD results imply that ZnO-coated magnetite NPs are formed. According to the TEM images, the estimated average size for most of core–shell NPs is about 12 nm.

Fluorescence enhancement and quenching of Eu3+ ions by Au–ZnO core-shell and Au nanoparticles

We investigate the enhancement and quenching of Eu3+ emission in presence of Au–ZnO core-shell nanoparticles and Au nanoparticles. The quenching of Eu3+-emission in presence of Au nanoparticles is caused by change of nonradiative rate due to energy transfer. However, the enhancement of Eu3+-emission in presence of Au–ZnO core-shell nanoparticles is due to local field, which modifies the radiative and nonradiative rate. Enhancement and quenching of Eu3+ emission reflect the change in environment of Eu3+ from Au nanoparticles to Au–ZnO core-shell nanoparticles which is confirmed by the Judd–Ofelt parameter (Ω2) analysis.

Violet photoluminescence from shell layer of Zn∕ZnO core-shell nanoparticles induced by laser ablation

A strong violet photoluminescence (PL) band at 425nm (2.92eV) was observed from the ZnO shell layer of the Zn∕ZnO core-shell nanoparticles prepared by laser ablation in liquid media. Such violet PL decreases with increase of the shell thickness or annealing temperature, showing good controllability. Based on the electron paramagnetic resonance measurements, the violet emission is attributed to the electronic transition from the defect level, corresponding to high-concentration zinc interstitials, to the valence band. This study is in favor to clarify the defect-related emissions and to extend the optical and electronic applications of nanostructured ZnO.