Size Of Core-shell Nanoparticles Research Articles

Synthesis of tertiary amine functionalized Multi-Stimuli-Responsive latex nanoparticles by semicontinuous emulsion Polymerization: Investigation of responsivities and antimicrobial activity

Stimuli-responsive core–shell nanoparticles (CSNPs) are an important class of smart polymers, which their physical and chemical properties could be changed in response to induced external stimuli. In this study, the amphiphilic CSNPs were synthesized via semi-continuous seeded emulsion polymerization using dimethylamino ethyl methacrylate (DMAEMA) as a hydrophilic monomer, and styrene as a hydrophobic monomer. Developed CSNPs were obtained in two series, poly(N, N-dimethylamino ethyl methacrylate) (PDMAEMA)-polystyrene (PS) core–shell particles and PS-PDMAEMA core–shell particles. The PDMAEMA chains exhibited different responsivities towards temperature rising, pH change, and CO2-gas, which their smart behaviors were investigated by dynamic light scattering (DLS) analysis. The temperature-responsivity of CSNPs was confirmed by observed particle size variation in the case of PDMAEMA-PS (increase) and PS-PDMAEMA (decrease) core–shell latex particles, when temperature increased to 70 °C, above the lower critical solution temperature (LCST) of PDMAEMA. Protonation of tertiary amine functional groups in the presence of CO2 bubbling led to an increase in the size of CSNPs as a result of water swelling of PDMAEMA chains. On the other hand, the size of CSNPs was changed in acidic (pH = 4) and basic (pH = 10) media by swelling and deswelling of PDMAEMA located in the core or shell. Obtained results indicated that maximum antimicrobial activity was observed for PS-PDMAEMA CSNPs compared to PDMAEMA-PS, which is probably due to presence of the PDMAEMA on the surface and increase of positive charge related to amine groups in this sample. The developed antimicrobial latexes have potential applications for using as antibacterial additives in water-based coatings and adhesives.

Synthesis of Fe3O4@Y2O3:Eu3+ core–shell multifunctional nanoparticles and their magnetic and luminescence properties

A simple wet chemical route has been employed to synthesize multifunctional core–shell nanoparticles of Fe3O4@Y2O3:Eu3+ showing an interesting combination of magnetic and luminescent properties having potential for medical applications. The core–shell nanoparticles were synthesized in a two-step process wherein first step, the Fe3O4 nanoparticles were synthesized and subsequently they are coated with Y2O3:Eu3+. XRD and magnetization curves were successfully used to retrieve the particle size of Fe3O4 nanoparticles. Particle size (∼10nm) extracted from XRD and magnetization curves have been found to be consistent with the measured size from AFM and TEM. Further, the XRD analysis reveals formation of pure cubic phases of magnetite as well as of Y2O3:Eu3+. It has been shown here that through simple chemistry it is possible to change the thickness of Y2O3:Eu3+ shell. From SEM and TEM studies, the size of core shell nanoparticles seen as ∼30nm. In addition to bright red (612nm) emission, these materials also show superparamagnetic behavior at room temperature. Emission intensity has been found to significantly increase with increase in annealing temperature. The synthesized materials have extensive for applications in the area of drug delivery and bio-imaging.

Fabrication of a tunable glucose biosensor based on zinc oxide/chitosan-graft-poly(vinyl alcohol) core-shell nanocomposite

A potentiometrically tuned-glucose biosensor was fabricated using core-shell nanocomposite based on zinc oxide encapsulated chitosan-graft-poly(vinyl alcohol) (ZnO/CHIT-g-PVAL). In a typical experiment, ZnO/CHIT-g-PVAL core-shell nanocomposite containing <20nm ZnO nanoparticles was synthesized using wet-chemical method. The glucose responsive bio-electrode, i.e., glucose oxidase/ZnO/chitosan-graft-poly(vinyl alcohol) (GOD/ZnO/CHIT-g-PVAL/ITO) was obtained by immobilization of glucose oxidase (GOD) onto the electrode made of resulting ZnO core-shell nanocomposite coated on the indium-tin oxide (ITO) glass substrate. The ZnO/CHIT-g-PVAL/ITO and GOD/ZnO/CHIT-g-PVAL electrodes were characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), whereas ZnO/CHIT-g-PVAL size of core-shell nanoparticles were measured using transmission electron microscopy (TEM). The electrostatic interaction between GOD and ZnO/CHIT-g-PVAL provided the resulting tuned enzyme electrode with a high degree of enzyme immobilization and excellent lifetime stability. The response studies were carried out as a function of glucose concentration with potentiometric measurement. The GOD/ZnO/CHIT-g-PVAL/ITO bioelectrode has showed a linear potential response to the glucose concentration ranging from 2μM to 1.2mM. The glucose biosensor exhibited a fast surface-controlled redox biochemistry with a detection limit of 0.2μM, a sensitivity of >0.04V/μM and a response time of three sec. ZnO/CHIT-g-PVAL core-shell nanocomposite could be a promising nanomaterials for a range of enzymic biosensors.

Core-shell Nanoparticles Reinforced Polystyrene with no Effect on its Transparency

Bisvinyl-A and styrene core-shell copolymer nanoparticles with different particle size were synthesized through the composite emulsion polymerization. The PS (polystyrene) blends with different concentration and particle size of core-shell nanoparticles were prepared. The impact strength and the transparency were studied which indicated that the best condition for reinforced the PS was that the particle size was above 100nm and the concentration of the particles in PS blends was roughly within the range of 2 ∼ 5% weight percent, which improved the strength of PS near to two times while the PS transparency was not affected.