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Core-shell magnetic nanoparticles have received significant attention recently and are actively investigated owing to their large potential for a variety of applications. Here, the synthesis and characterization of bimetallic nanoparticles containing a magnetic core and a gold shell are discussed. The gold shell facilitates, for example, the conjugation of thiolated biological molecules to the surface of the nanoparticles. The composite nanoparticles were produced by the reduction of a gold salt on the surface of pre-formed cobalt or magnetite nanoparticles. The synthesized nanoparticles were characterized using ultraviolet-visible absorption spectroscopy, transmission electron microscopy, energy dispersion X-ray spectroscopy, X-ray diffraction and super-conducting quantum interference device magnetometry. The spectrographic data revealed the simultaneous presence of cobalt and gold in 5.6±0.8 nm alloy nanoparticles, and demonstrated the presence of distinct magnetite and gold phases in 9.2±1.3 nm core-shell magnetic nanoparticles. The cobalt-gold nanoparticles were of similar size to the cobalt seed, while the magnetite-gold nanoparticles were significantly larger than the magnetic seeds, indicating that different processes are responsible for the addition of the gold shell. The effect on the magnetic properties by adding a layer of gold to the cobalt and magnetite nanoparticles was studied. The functionalization of the magnetic nanoparticles is demonstrated through the conjugation of thiolated DNA to the gold shell.

Magnetic nanocarriers have attracted increasing attention for multimodal cancer therapy due to the possibility to deliver heat and drugs locally. The present study reports the development of magnetic nanocomposites (MNCs) made of an iron oxide core and a pH- and thermo-responsive polymer shell, that can be used as both hyperthermic agent and drug carrier. The conjugation of anticancer drug doxorubicin (DOX) to the pH- and thermo-responsive MNCs via acid-cleavable imine linker provides advanced features for the targeted delivery of DOX molecules via the combination of magnetic targeting, and dual pH- and thermo-responsive behaviour which offers spatial and temporal control over the release of DOX. The iron oxide cores exhibit a superparamagnetic behaviour with a saturation magnetization around 70 emu g(-1). The MNCs contained 8.1 wt% of polymer and exhibit good heating properties in an alternating magnetic field. The drug release experiments confirmed that only a small amount of DOX was released at room temperature and physiological pH, while the highest drug release of 85.2% was obtained after 48 h at acidic tumour pH under hyperthermia conditions (50 °C). The drug release kinetic followed Korsmeyer-Peppas model and displayed Fickian diffusion mechanism. From the results obtained it can be concluded that this smart magnetic nanocarrier is promising for applications in multi-modal cancer therapy, to target and efficiently deliver heat and drug specifically to the tumour.

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We report on photoinduced fluorescence enhancement (PFE) in a thin film of CdSe/ZnS core/shell quantum dots (QDs) sandwiched between a glass substrate and a silicon oxide layer and the dependence on the degree of proximity between the QDs. CdSe/ZnS QDs capped with tri-n-octylphosphine oxide (TOPO) were colloidchemically synthesized, and the QD thin films of various thicknesses were then fabricated on glass substrates using a spin-coating technique. A SiO x protective layer was subsequently sputtered on the QD thin film to prevent photoadsorption of water molecules and photooxidation. The fluorescence intensity monotonically increased under continuous excitation except for the case of the thinnest sample which exhibited intensity decay. Interestingly, the increasing rate of fluorescence intensity increases as a function of the number of QD layers, θ, to the extent of θ e 3.2 and then decreases at θ g 3.2. Fluorescence lifetime measurements indicate that the band-edge radiative relaxation probability becomes relatively higher as the fluorescence intensity is enhanced. Considering the experimental results with respect to QD submonolayers (θ e 1), and in accordance with the theoretical model, PFE is elucidated by the charging effect of trapped electrons.

The first study on the growth process of an array comprising colloidal semiconductor nanoparticles (quantum dots) is presented. Two types of particles, CdS and CdSe/CdS (core/shell), suspended in pyridine and water, respectively, have been used. A liquid drop containing the particles is placed on a solid substrate, and the solvent is allowed to evaporate in a nitrogen atmosphere. As the result, a ring-shaped multilayer forms at the drop periphery, with the ring width depending on the particle volume fraction. The kinetics of ring growth is described by a theoretical model which accounts for the effect of experimental parameters. The reported study can serve as background for the preparation of more sophisticated and ordered arrays of semiconductor nanoparticles whose optical properties can be utilized in light-emitting and -converting devices.

In our present work, magnetic cobalt ferrite (CoFe2O4) nanoparticles have been successfully synthesised by thermal decomposition of Fe(III) and Co(II) acetylacetonate compounds in organic solvents in the presence of oleic acid (OA)/ oleylamine (OLA) as surfactants and 1,2-hexadecanediol (HDD) or octadecanol (OCD-ol) as an accelerating agent. As a result, CoFe2O4 nanoparticles of different shapes were tightly controlled in size (range of 4-30 nm) and monodispersity (standard deviation only at ca. 5%). Experimental parameters, such as reaction time, temperature, surfactant concentration, solvent, precursor ratio, and accelerating agent, in particular, the role of HDD, OCD-ol, and OA/OLA have been intensively investigated in detail to discover the best conditions for the synthesis of the above magnetic nanoparticles. The obtained nanoparticles have been successfully applied for producing oriented carbon nanotubes (CNTs), and they have potential to be used in biomedical applications.