Synthesis of Ni@Au Core-shell Nanoparticles and Its Applications in Ullmann Reaction as a Synergistic Catalyst

The Ni@Au core-shell nanoparticles had been successfully synthesized from aqueous solution by one-step route at room temperature. The Ni@Au nanoparticles can be an excellent catalyst for Ullmann reaction. The advantage of Ni@Au is that the catalyst does not need additional reducing agents. The Au shell can effectively protect the Ni core from oxidation. The Ni core and Au shell have both composited in structure and cooperated in function.

Synthesis and Characterization of Poly (Methyl Methacrylate)/Polyethylenimine Grafting Core-Shell Nanoparticles for CO2 Adsorption Using Soap-Free Emulsion Copolymerization

Unlike previous emulsion polymerization, we used grafting reactions in soap-free emulsion systems. In this study, we synthesized grafted PMMA/PEI core-shell nanoparticles by varying the MMA/PEI content and molecular weight of PEI (Mn = 600, 8000, and 10,000). The size and morphology of the core-shell nanoparticles were characterized by a particle size analyzer and scanning electron microscopy. The nanoparticles were 178 - 408 nm in diameter and swelled in water or methanol by 30 - 75 nm. The size of the nanoparticles increased with MMA contents, whereas the size distribution progressively became homogeneous with increasing molecular weight of PEI. Lastly, we measured CO2 adsorption capacity of the grafted PMMA/PEI core-shell nanoparticles, and we found the capacity to be limited at a level of 0.69 mg, which occurred for nanoparticles prepared from emulsions at a pH value of 11.

Manufacturing of Surface Nanostructured Fibers Featuring an Antibacterial Effect by Magnetic Field Transportation of Magnetite@Silver Core-Shell Nanoparticles

Magnetic core-shell nanoparticles of type Fe3O4@Ag were synthesized in gram scale following a combined co-precipitation phase-transfer method and afterwards, processed to nanoparticle polymer (polypropylene and polyamide) composites. These composites were used as sheath material for the fabrication of core-sheath fibers. During the melt spinning process, a magnetic field was applied around the roving, whereby the particles move in the still liquid sheath polymer towards the surface. The produced fiber materials were investigated by AFM showing a nanostructuring of the surface, which was indirectly confirmed by determination of a slight surface tension lowering. Nanoparticle movement was shown by cross-section SEM and EDX measurements. The antibacterial activity of the spun fibers was proven by contacting them with Escherichia coli. A long-term stability of this effect was observable by carrying out a standard washability test. In contrast to previous works this new approach uses no deposition technique to introduce surface changes. It rather applies a magnetic force to move appropriately equipped nanoparticles from the inside of the fiber to the surface. This leads in only one step to a strong superficial anchoring of the particles resulting in a unique combination of long-term stable antibacterial and improved anti-soiling effects.

Folate-chitosan-gemcitabine core-shell nanoparticles targeted to pancreatic cancer

Objective：Human pancreatic cancer is one of the most common clinical malignancies.The effect of comprehensive treatment based on surgery is general.The effects of chemotherapy were not obvious mainly because of lack of targeting and chemoresistance in pancreatic cancer.This study aimed to investigate the effects of folate receptor （FR）-mediated gemcitabine FA-Chi-Gem nanoparticles with a core-shell structure by electrostatic spray on pancreatic cancer.Methods：In this study,the levels of expression of FR in six human pancreatic cancer cell lines were studied by immunohistochemical analysis.The uptake rate of isothiocyanate-labeled FA-Chi nanoparticles in FR high expression cell line COLO357 was assessed by fluorescence microscope and the inhibition rate of FA-Chi-Gem nanoparticles on COLO357 cells was evaluated by MTT assay.Moreover,the biodistribution of PEG-FA-ICGDER02-Chi in the orthotopic pancreatic tumor model was observed using near-infrared imaging and the human pancreatic cancer orthotopic xenografts were treated with different nanoparticles and normal saline control.Results：The expression of FR in COLO357 was the highest among the six pancreatic cancer cell lines.The FR mainly distributed on cell membrane and fewer in the cytoplasm in pancreatic cancer.Moreover,the absorption rate of the FA-Chi-Gem nanoparticles was more than the Chi nanoparticles without FA modified.The proliferation of COLO357 was significantly inhibited by FA-Chi-Gem nanoparticles.The PEG-FA-ICGDER02-Chi nanoparticles were enriched in tumor tissue in human pancreatic cancer xenografts,while non-targeted nanoparticles were mainly in normal liver tissue.PEG-FA-Gem-Chi significantly inhibited the growth of human pancreatic cancer xenografts （PEG-FA-Gem-Chi vs.Gem,t=22.950,P=0.000）.Conclusions：PEG-FA-FITC-Chi nanoparticles might be an effective targeted drug for treating human FR-positive pancreatic cancer.

Preparation and Characterization of Nano-Sized (Mg_(x)Fe_(1–x)O/SiO₂) (x = 0.1) Core-Shell Nanoparticles by Chemical Precipitation Method

Magnetic core-shell nanoparticles have been widely studied because of their excellent and convenient magnetic and electrical properties.In this present work core-shell magneticnanoparticles (MNPs) were synthesized by simple chemical precipitation method. Firstly Mg(x)Fe(1–x)O (magnesiwuestite) nano powder samples were synthesised by low temperature chemical combustion method. Secondly the as synthesised Mg(x)Fe(1–x)O nanoparticles are used to synthesis magnetic core-shell Nano particles byusing 2-propanol, poly ethylene glycol (PEG), ammonia solution 30 wt%, tetraethyl orthosilicate (TEOS). Separation of the core-shell magnetic nanoparticles from the aqueous suspension using a centrifuge. The synthesised MNPs and core shell MNP were characterized by X-ray diffraction (XRD), Thermal gravimetric-differential thermal analyzer (TG-DTA), Transmission electron microscopy (TEM), scanning electron microscopy (SEM), (EDAX) for structural, thermal and morphological respectively. It is observed that the particle size of spherical sampleis 32.5 nm.

Shell-driven Fine Structure Transition of Core Materials in Co@Au Core-shell Nanoparticles

Co@Au core shell nanoparticles(NPs) of different shell thicknesses were fabricated by a combination of the displacement process and the reduction-deposition process in a microfluidic reactor. The effect of the shell thickness on the fine structures(local atom arrangement) of core materials was investigated by X-ray Absorption Near Edge Structure(XANES) and Extended X-ray Absorption Fine Structure(EXAFS).The results indicate that the shell thickness affects the fine structure of the core materials by causing atomic re-arrangement between the hexagonal close pack(hcp) and the face centered cubic(fcc) structure, and forming Co-Au bonds in the core-shell interface.

Synthesis of Core-Shell Nanoparticles of Cu-Ag for Application in Electrohydrodynamic Printing Technique

Core-shell nanoparticles of Cu-Ag (Cu core and Ag shell) were synthesized using chemical method. Polyvinyl pyrrolidone (PVP) was used as a surfactant, and ascorbic acid (C6H8O6) and sodium borohydride (NaBH4) were used as reducing agents to reduce the metal complexes [Cu(NH3)4]^2+ and [Ag(NH3)2]^+. The results of transmission electron microscope (TEM) analysis, ultraviolet-visible spectroscopic (UV-Vis) analysis, X-ray diffraction (XRD) analysis showed that the core-shell nanoparticles of Cu-Ag were successfully synthersized. The average particle size was 32 nm. The dispersion of the nanoparticles was still good after 80 days without the formation of the oxides of Cu and Ag. The properties of the nanoparticles suggested that they were suitable to be used as an electrically conductive material for conductive ink-jet printing inks.

Synthesis of Octylmethoxycinamate-silica Core-shell Nanoparticles with Self-templating Method

t A self-templating method was employed to synthesize core-shell nanoparticles with octylmethoxycinamate（OMC）, a well-known organic UV absorber, as core and nanosilica particles as shell. The characteristic of this method is that the whole process requires neither surface treatment for nanosilica particles nor additional surfactant or stabilizer, and all the reactions could be finished in one-pot, which exempts removing template and reduces reaction steps compared to the conventional process. The morphology, structure, particle size distribution, chemical composition and optical property of OMC-SiO2 nanoparticles were characterized by scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, dynamic light scattering（DLS）, FTIR spectrometry and UV absorption spectrometry, respectively. Experiment results indicate that the resulting OMC-SiO2 nanoparticles were perfectly spherical with smooth particle surfaces, and had clear core-shell structures. The particle size could be tuned by altering reaction conditions. In addition, the mechanism of the self-templating method for forming core-shell nanoparticles was discussed.

Preparation and Characterization of Silica and Clay-Silica Core-Shell Nanoparticles Using Sol-Gel Method

Silica and montmorillonite-supported silica nanoparticles were prepared via an acid one step sol-gel process. The synthesized solids were characterized using XRD, FTIR, TEM and N2 adsorption. The effect of preparing temperatures on the structure and properties of the silica nanoparticles were studied. The results show that the increase of annealing temperature from 25 to 200℃, don’t change amorphous state of silica. While for montmorillonite-supported silica the clay platelets are delaminated during the sol-gel process. TEM results showed that the average particle size of silica is increased by increasing temperature due to the particle sintering and the clay-silica nanoparticles possessed core–shell morphology with diameter of 29 nm. The surface area measurements showed that by increasing annealing temperature the surface area was decreased due to aggregation of particle. The clay-silica sample showed lower average pore width than that of the silica prepared at 200℃ indicating that it has a macropores structure. The adsorption efficiency of the prepared samples was tested by adsorption of protoporphyrin IX. The highest adsorption efficiency was found for SiO2 prepared at 200℃. Temkin model describe the equilibrium of adsorption of protoporphyrin IX on caly-silica nanoparticles under different conditions.

Synthesis and Characterization of Bimetallic Gold-Silver Core-Shell Nanoparticles: A Green Approach

Bimetallic gold-silver core-shell nanoparticles were prepared by chemical reduction in aqueous solution, following a method that was friendly to the environment, allowing us to use this for medicinal purposes. Gold nanoparticles were synthesized, and silver cations were then reduced on the nanoparticles. Using the optical properties of metallic nanoparticles, surface plasmon resonance was determined by UV-Vis spectroscopy, and the values obtained for gold and silver were approximately 520 nm and 400 nm in wavelength, respectively. The absorption peaks of the surface plasmon band show a clear red-shift due to size effect in the case of the silver surface, and a plasmon coupling effect, in the case of gold. To obtain a better understanding of the coating conditions, high resolution transmission electron microscopy was used. The average hydrodynamic size and the size distribution of the synthesized nanoparticles were obtained by dynamic light scattering. The development of this process, which is benign for the environment, opens the possibility for many applications in the areas of renewable energy, medicine and biology.

PREPARATION AND FLUORESCENT PROPERTIES OF Eu^(3+)-CONTAINING CORE-SHELL NANOPARTICLES

By using a two-stage soapless emulsion polymerization, four kinds of core-shell nanoparticles have been prepared,which are composed of a polystyrene core having an average diameter of 256 nm and a poly(methyl methacrylate-co-acrylicacid) shell. The transmission electron microscopy (TEM) micrographs and the atomic force microscopy (AFM) imagesevidenced the presence of a core-shell structure. In the infrared spectra, the shift of v_(COOH) to lower wavenumber withincreasing Eu^(3+) ion content indicates that coordination between the oxygen of the carboxylic group and Eu^(3+) has occurred.The fluorescence intensity of ~5D_0-~7F_2 transition was observed to reach its maximum with a carboxyl group molar percentageof 40% in the shell and an Eu^(3+)/--COO^- molar ratio of 1:3. The fluorescence intensity ratio of ~5D_0-~7F_2 to ~5D_0-~7F_1 transition reached its maximum with an Eu^(3+)/--COO^- molar ratio of 1:3 for all the four series.

Preparation of novel core-shell nanoparticles by electrochemical synthesis

Nanostructural gold/polyaniline core/shell composite particles on conducting electrode ITO were successfully prepared via electrochemical polymerization of aniline based on 4-aminothiophenol (4-ATP) capped Au nanoparticles. The new approach to the fabrication included three steps: preparation of gold nanoparticles as core by pulse electrodeposition; formation of ATP monolayer on the gold particle surface, which served as a binder and an initiator; polymerization of aniline monomer initiated by ATP molecules under controlled voltage lower than the voltammetric threshold of aniline polymerization, which assured the formation of polyaniline shell film occurred on gold particles selectively. Topographic images were also studied by AFM, which indicated the diameter of gold nanoparticles were around 250 nm. Coulometry characterization confirmed the shell thickness of polyaniline film was about 30 nm. A possible formation mechanism of the Au/polyaniline core-shell nanocomposites was also proposed. The novel as-prepared core-shell nanoparticles have potential application in constructing biosensor when bioactive enzymes are absorbed or embedded in polyaniline shell film.

Preparation of Ni/PZT Core-shell Nanoparticles and Their Electromagnetic Properties

The Ni nanoparticles coated with Pb（Zr,Ti）O3（PZT） were synthesized by a sol-gel method and in situ reaction. And their structure, oxidation resistance, and electromagnetic properties were investigated. The X-ray diffraction patterns（XRD） exhibited that a small amount of impure phase characterized to Ni（OH）2 was detected from the ammonia-treated Ni nanoparticles and the ammonia-treated Ni nanoparticles coated with PZT. After being pre-treated with aqueous ammonia, the PZT coating layer was more uniform and about 10 nm in thickness. The oxidation resistance of the ammonia-treated Ni nanoparticles coated with PZT, compared with that of the non-treated ones, was improved by about 66 ℃. The PZT shell layer prepared by in-situ reaction can greatly reduce the dielectric constant and improve the natural resonance loss at high frequency, so as to obtain the optimal impedance matching performance of the electromagnetic wave transmission.

Structural and thermal stabilities of Au@Ag core-shell nanoparticles and their arrays:A molecular dynamics simulation

Thermal stability of core-shell nanoparticles(CSNPs)is crucial to their fabrication processes,chemical and physical properties,and applications.Here we systematically investigate the structural and thermal stabilities of single Au@Ag CSNPs with different sizes and their arrays by means of all-atom molecular dynamics simulations.The formation energies of all Au@Ag CSNPs we reported are all negative,indicating that Au@Ag CSNPs are energetically favorable to be formed.For Au@Ag CSNPs with the same core size,their melting points increase with increasing shell thickness.If we keep the shell thickness unchanged,the melting points increase as the core sizes increase except for the CSNP with the smallest core size and a bilayer Ag shell.The melting points of Au@Ag CSNPs show a feature of non-monotonicity with increasing core size at a fixed NP size.Further simulations on the Au@Ag CSNP arrays with 923 atoms reveal that their melting points decrease dramatically compared with single Au@Ag CSNPs.We find that the premelting processes start from the surface region for both the single NPs and their arrays.

Synthesis and characterization of reporter molecules embedded core-shell nanoparticles as SERS nanotags

Surface-enhanced Raman scattering(SERS)spectroscopy is presented as a sensitive and spe-cific molecular tool for clinical diagnosis and prognosis monitoring of various diseases including cancer.In order for clinical application of SERS technique,an ideal method of bulk synthesis of SERS nanoparticles is necessary to obtain sensitive,stable and highly reproducible Raman signals.In this contribution,we determined the ideal conditions for bulk synthesis of Raman reporter(Ra)molecules embedded silver-gold core-shell nanoparticles(Au@Ra@AgNPs)using hydroquinone as reducing agent of silver nitrate.By using UV-Vis spectroscopy,Raman spectroscopy and transmission electron microscopy(TEM),we found that a 2∶1 ratio of silver nitrate to hydroquinone is ideal for a uniform silver coating with a strong and stable Raman signal.Through stability testing of the optimized Au@Ra@AgNPs over a two-week period,these SERS nanotags were found to be stable with minimal signal change occurred.The sta-bility of antibody linked SERS nanotags is also crucial for cancer and disease diagnosis,thus,we further conjugated the as-prepared SERS nanotags with anti-EpCAM antibody,in which the stability of bioconjugated SERS nanotags was tested over eight days.Both UV-Vis and SERS spectroscopy showed stable absorption and Raman signals on the anti-EpCAM conju-gated SERS nanotags,indicating the great potential of the synthesized SERS nanotags for future applications which require large,reproducible and uniform quantities in order for cancer biomarker diagnosis and monitoring.

Core-shell nanoparticle enhanced Raman spectroscopy in situ probing the composition and evolution of interfacial species on PtCo surfaces

The composition and evolution of interfacial species play a key role during electrocatalytic process.Unveiling the structural evolution and intermediate during catalytic process by in situ characterization can shed new light on the electrocatalytic reaction mechanism and develop highly efficient catalyst.However,directly probing the interfacial species is extremely difficult for most spectroscopic techniques due to complicated interfacial environment and ultra-low surface concentration.Herein,electrochemical core-shell nanoparticle enhanced Raman spectroscopy is utilized to probe the composition and evolution processes of interfacial species on Au@Pt,Au@Co,and Au@PtCo core-shell nanoparticle surfaces.The spectral evidences of interfacial intermediates including hydroxide radical(OH*),superoxide ion(O_(2)^(−)),as well as metal oxide species are directly captured by in situ Raman spectroscopy,which are further confirmed by the both isotopic experiment and density functional theory calculation.These results provide a mechanistic guideline for the rational design of highly efficient electrocatalysts.

Fe-N_(x) sites coupled with core-shell FeS@C nanoparticles to boost the oxygen catalysis for rechargeable Zn-air batteries

The development of efficient single-atom catalysts(SACs) for the oxygen reduction reaction(ORR)remains a formidable challenge,primarily due to the symmetric charge distribution of metal singleatom sites(M-N_(4)).To address such issue,herein,Fe-N_(x) sites coupled synergistic catalysts fabrication strategy is presented to break the uniform electronic distribution,thus enhancing the intrinsic catalytic activity.Precisely,atomically dispersed Fe-N_(x) sites supported on N/S-doped mesoporous carbon(NSC)coupled with FeS@C core-shell nanoparticles(FAS-NSC@950) is synthesized by a facile hydrothermal reaction and subsequent pyrolysis.Due to the presence of an in situ-grown conductive graphitic layer(shell),the FeS nanoparticles(core) effectively adjust the electronic structure of single-atom Fe sites and facilitate the ORR kinetics via short/long-range coupling interactions.Consequently,FAS-NSC@950displays a more positive half-wave potential(E_(1/2)) of 0.871 V with a significantly boosted ORR kinetics(Tafel slope=52.2 mV dec^(-1)),outpacing the commercial Pt/C(E_(1/2)=0.84 V and Tafel slope=54.6 mV dec^(-1)).As a bifunctional electrocatalyst,it displays a smaller bifunctional activity parameter(ΔE) of 0.673 V,surpassing the Pt/C-RuO_(2) combination(ΔE=0.724 V).Besides,the FAS-NSC@950-based zincair battery(ZAB) displays superior power density,specific capacity,and long-term cycling performance to the Pt/C-Ir/C-based ZAB.This work significantly contributes to the field by offering a promising strategy to enhance the catalytic activity of SACs for ORR,with potential implications for energy conversion and storage technologies.

MoS_(2)core-shell nanoparticles prepared through liquid-phase ablation and light exfoliation of femtosecond laser for chemical sensing

Molybdenum disulfide(MoS_(2))-based nanostructures are highly desirable for applications such as chemical and biological sensing,photo/electrochemical catalysis,and energy storage due to their unique physical and chemical properties.In this work,MoS_(2)core-shell nanoparticles were first prepared through the liquid-phase processing of bulk MoS2by a femtosecond laser.The core of prepared nanoparticles was incompletely and weakly crystalline MoS_(2);the shell of prepared nanoparticles was highly crystalline MoS_(2),which wrapped around the core layer by layer.The femtosecond laser simultaneously achieved liquid-phase ablation and light exfoliation.The formation mechanism of the core-shell nanoparticles is to prepare the nanonuclei first by laser liquid-phase ablation and then the nanosheets by light exfoliation;the nanosheets will wrap the nanonuclei layer by layer through van der Waals forces to form core-shell nanoparticles.The MoS_(2)core-shell nanoparticles,because of Mo-S bond breakage and recombination,have high chemical activity for chemical catalysis.Afterward,the nanoparticles were used as a reducing agent to directly prepare three-dimensional(3D)Au-MoS_(2)micro/nanostructures,which were applied as surface-enhanced Raman spectroscopy(SERS)substrates to explore chemical sensing activity.The ultrahigh enhancement factor(1.06×10^(11)),ultralow detection limit(10-13M),and good SERS adaptability demonstrate highly sensitive SERS activity,great ability of ultralow concentration detection,and ability to detect diverse analytes,respectively.This work reveals the tremendous potential of 3D Au-MoS_(2)composite structures as excellent SERS substrates for chemical and biological sensing.

Upconversion nanoparticles@AgBiS_(2) core-shell nanoparticles with cancer-cell-specific cytotoxicity for combined photothermal and photodynamic therapy of cancers

UCNPs@AgBiS_(2) core-shell nanoparticles that AgBiS_(2) coated on the surface of upconversion nanoparticles (UCNPs) was successfully prepared through an ion exchange reaction. The photothermal conversion efficiency of AgBiS_(2) can be improved from 14.7% to 45% due to the cross relaxation between Nd ions and AgBiS_(2). The doping concentration of Nd ions played a critical role in the production of reactive oxygen species (ROS) and enhanced the photothermal conversion efficiency. The NaYF4:Yb/Er/Nd@NaYF4:Nd nanoparticles endows strong upcon-version emissions when the doped concentration of Nd ions is 1% in the inner core, which excites the AgBiS_(2) shell to produce ROS for photodynamic therapy (PDT) of cancer cells. As a result, the as-prepared NaYF4:Yb/Er/ Nd@NaYF4:Nd@AgBiS_(2) core-shell nanoparticles showed combined photothermal/photodynamic therapy (PTT/ PDT) against malignant tumors. This work provides an alternative near-infrared light-active multimodal nano-structures for applications such as fighting against cancers.

Targeted core-shell nanoparticles for precise CTCF gene insert in treatment of metastatic breast cancer

Clustered regularly interspaced short palindromic repeats(CRISPR)technology emerges a remarkable potential for cure of refractory cancer like metastatic breast cancer.However,how to efficiently deliver the CRISPR system with non-viral carrier remains a major issue to be solved.Here,we report a kind of targeted core-shell nanoparticles(NPs)carrying dual plasmids(pHR-pCas9)for precise CCCTC-binding factor(CTCF)gene insert to circumvent metastatic breast cancer.The targeted core-shell NPs carrying pHR-pCas9 can accomplishγGTP-mediated cellular uptake and endosomal escape,facilitate the precise insert and stable expression of CTCF gene,inhibit the migration,metastasis,and colonization of metastatic breast cancer cells.Besides,the finding further reveals that the inhibitory mechanism of metastasis could be associated with up-regulating CTCF protein,followed by down-regulating stomatin(STOM)protein.The study offers a universal nanostrategy enabling the robust non-viral delivery of gene-editing system for treatment of severe illness.