Silica nanoparticles containing a rhodamine dye and multiple gold nanorods

Silica shells are grown around colloidally synthesized gold nanorods (AuNRs) to form core–shell particles (AuNR@SiO₂) of variable occupancy, defined as the number of AuNRs per silica particle. Multiple AuNR occupancy within the silica shell, confirmed with high-resolution electron microscopy, is reflected in a redshift of the longitudinal plasmon mode of the nanorods due to multipolar coupling between AuNRs of a favored end–end orientation. In addition to the plasmon resonance that dominates their absorbance spectra, FL-AuNR@SiO₂, core–shell particles incorporating a lipid probe (rhodamine-DOPE), can be monitored by their fluorescence and Raman signals. Optical and scanning electron microscopy (SEM) images are compared directly, enabling the correlation of spectroscopic characteristics with particle morphology. Raman and SEM images show that the most intense Raman signals come from aggregates of AuNRs trapped within the silica matrix. Biexponential fits to fluorescence decays indicate that competing mechanisms of quenching and fluorescence enhancement contribute to a reduced fluorescence lifetime of rhodamine-DOPE located near the AuNRs.     

Estimating quantitative features of nanoparticles using multiple derivatives of scattering profiles

Characterization of nanoparticles on surfaces is a challenging inverse problem whose solution has many practical applications. This article proposes a method, suitable for in situ characterization systems, for estimating quantitative features of nanoparticles on surfaces from scattering profiles and their derivatives. Our method enjoys a number of advantages over competing approaches to this inverse problem. One such advantage is that only a partial solution is required for the companion direct problem. For example, estimating the average diameter of nanoparticles to be 53 nm is possible even when a researcher's existing scattering data pertain to nanoparticles whose average diameters are in multiples of 5 nm. Two numerical studies illustrate the implementation and performance of our method for inferring nanoparticle diameters and agglomeration levels respectively.     

Competitive adsorption of multiple proteins to nanoparticles: the Vroman effect revisited

ABSTRACT

Proteins adsorbed from the blood plasma change nanoparticles interactions with the surrounding biological environment. In general, the adsorption of multiple proteins has a non-monotonic time dependence, that is, proteins adsorbed at first may slowly be replaced by others. This ‘Vroman effect’ leads to a highly dynamic protein corona on nanoparticles that profoundly influences the immune response of the body. Thus, the temporal evolution of the corona must be taken into account when considering applications of nanocarriers in, e.g., nanomedicine or drug delivery. Up to now, the Vroman effect is explained solely in terms of diffusion: Smaller proteins which diffuse faster are adsorbed first, while larger ones, having a stronger interaction with the surface, are preferred at equilibrium. Here we use dynamic density functional theory (DDFT) including steric and electrostatic interactions to provide a full model for the temporal evolution of the protein corona. In particular, we demonstrate that proper consideration of all interactions leads to Vroman-like adsorption signatures in widely different scenarios. Moreover, consideration of energetic terms predicts both competitive as well as cooperative adsorption. In this way, DDFT provides a reacher picture of the evolution of the dynamic protein corona.     

Hydrogen bonds of anti-HIV active aminophenols

Analysis of IR-Fourier spectra from solutions and crystals of antiviral sulfo-containing aminophenols has shown that various types of intramolecular and intermolecular interactions can occur in molecules of these compounds. Three types of intramolecular hydrogen bonds (O–H⋅⋅⋅N, O–H⋅⋅⋅O=S=O, and N–H⋅⋅⋅O=S=O) are formed in CCl₄ solutions of the sulfo-containing aminophenols. The formation of intermolecular H-bonds involving the NH- and OH-groups and the preservation of the intramolecular O–H⋅⋅⋅O=S=O H-bond are characteristic of the anti-HIV active aminophenol crystals. Spectral attributes are determined in order to distinguish between the anti-HIV active and inactive sulfo-containing aminophenols.     

Energy losses from fast structured heavy ions in multiple collisions with molecules and nanoparticles

A nonperturbative method is developed to calculate the energy losses from fast, highly charged, heavy ions in collisions with complex molecules and nanoparticles. All possible processes of excitation and ionization of both projectile and target are taken into account. The contributions to energy losses due to multiple collisions are calculated, and the effect of target orientation with respect to the direction of projectile motion is examined. As examples, the energy losses in collisions with the XeF₄ molecule and a C₃₀₀ nanotube are determined. It is shown that the effect of multiple collisions leads to significant change in energy loss with target orientation, being insignificant for randomly oriented targets.     

Ferromagnetic FeCo nanoparticles for biotechnology

Calculated magnetophoretic mobility of a variety of magnetic compounds has identified FeCo to be an alternative for magnetite in in vitro biological cell separations. The synthesis of FeCo nanoparticles and the resulting microstructure is discussed as a function of the particle size. Their synthesis kinetics is modeled using a consecutive decomposition and growth model and is compared to experimental data.     

Synthesis of multiple shapes of gold nanoparticles with controlled sizes in aqueous solution using ultrasound

Effects of concentration of stabilizer (sodium dodecylsulfate: SDS) and ultrasonic irradiation power on the formation of gold nanoparticles (Au-NPs) were investigated. Au-NPs with multiple shapes and size were synthesized by controlling the concentration of stabilizer and ultrasonic irradiation power. The shapes and size of Au-NPs were controlled by changing either the ratio of Au(III) ion/SDS or the power of ultrasonic irradiation. The multiple shapes and size distribution of Au-NPs are dependent on not only the ratio of Au(III) ion/SDS but also ultrasonic irradiation power. The sonochemically synthesized Au-NPs were characterized by TEM and UV-vis spectroscopy.     

Electronic structure and spectroscopic properties of anti-HIV active aminophenols

We have measured the absorption and fluorescence spectra and fluorescence quantum yields of sulphone-containing anti-HIV active o-aminophenol molecules in an inert solvent, hexane, and in a polar solvent, acetonitrile. We have studied IR Fourier-transform spectra and examined structural features of o-aminophenols with different substituents in solutions and crystals. Functional groups of molecules that are involved in the formation of hydrogen bonds have been revealed. Proton acceptor properties of o-aminophenol molecules have been theoretically evaluated using the method of molecular electrostatic potential. Using quantum chemistry methods, we have calculated and interpreted absorption and fluorescence spectra of o-aminophenols. Calculation data are compared with experimental results. We have determined the main channels and mechanisms of photophysical relaxation processes in o-aminophenols.     

Extended embedded-atom method for platinum nanoparticles

We present a new technique to extend the embedded-atom method (EAM) for the simulations of non-bulk systems down to the atomic cluster level. To overcome the limitation of the traditional bulk-fit EAM interatomic potentials, bond characteristics from first-principles calculations are systematically included by introducing a local structure dependent prefactor with three additional parameters to the conventional EAM many-body term. The additional parameters improve the local potential landscape virtually for the entire range of atomic configuration space in a quantitative sense. The proposed scheme is applied to two different EAM function sets and validated for both bulk and non-bulk environments in elemental platinum. The obtained material properties, including the binding energies of Pt particles and the Pt adatom diffusion barrier on the Pt(1 1 1) surface, show a significant improvement over the conventional EAM formalism.     

Ferrimagnetic nanoparticles for self-controlled magnetic hyperthermia

Based on the Heisenberg model including single-site uniaxial anisotropy and using aGreen’s function technique we studied the influence of size and composition effects on theCurie temperature T _C , saturationmagnetization M _S and coercivityH _C of spherical nanoparticles with astructural formulaM e _1?x Zn _x Fe₂O₄,Me = Ni, Cu, Co, Mn. It is shown that for x = 0.4–0.5and d = 10–20 nm these nanoparticles have aT _C  = 315 K and are suitable for aself-controlled magnetic hyperthermia.     

Ratiometric fluorescent nanoparticles for sensing temperature

A ratiometric type of fluorescent nanoparticle was prepared via an encapsulation–reprecipitation method. By introducing an alkoxysilanized dye as a reference, the nanoparticles (NPs) give both a green and a red fluorescence under one single-wavelength excitation. The resulted ratiometric fluorescence is found to be highly temperature-dependent in the physiological range (25–45 °C), with an intensity temperature sensitivity of ?4.0%/°C. Given the small size (20–30 nm in diameter) and biocompatible nature (silica out layer), such kind of NPs were very promising as temperature nanosensors for cellular sensing and imaging.     

MnZnFe nanoparticles for self-controlled magnetic hyperthermia

Manganese zinc iron magnetic nanoparticles were synthesized by a co-precipitation method for application as hyperthermia inducing agents. The structure, morphology and magnetic properties of the nanoparticles are characterized using scanning electron microscopy, X-ray diffraction, and a superconducting quantum interference device. The magnetic properties being investigated include Curie temperature, saturation magnetization, remnant magnetization, coercive field, and hysteresis. The study showed that adjusting the Mn contribution to the particles contributed to the adjustment of all magnetic properties of the complex.     

Citric-acid-coated magnetite nanoparticles for biological applications

Water-based magnetic fluids, generally intended for biomedical applications, often have various coating molecules that make them stable and compatible with biological liquids. Magnetic fluids containing iron oxide particles have been prepared by a co-precipitation method, using citric acid as stabilizer. The magnetic particles of the magnetic fluids were obtained by chemical precipitation from ferric ( FeCl₃) and ferrous salts ( FeSO₄ or FeCl₂) in alkali medium (ammonia hydroxide). Citric acid was used to stabilize the magnetic-particle suspension. Physical tests were performed in order to determine various microstructural and rheological features. Transmission electron microscopy was the main investigation method for assessing the magnetic-particle size. The dimensional distribution of the magnetic-particle physical diameter was analyzed using the box-plot statistical method while infrared absorption spectra were used to study the colloidal particle structure. The magnetic-fluid density (picnometric method), viscosity (capillary method) and surface tension (stalagmometric method) were measured using standard methods.     

High-magnetic-moment multifunctional nanoparticles for nanomedicine applications

Multifunctional FeCo nanoparticles with narrow size distribution (less than 8% standard deviation) were fabricated by a novel physical vapor nanoparticle-deposition technique. The size of magnetic nanoparticles was controlled in the range from 3 to 100 nm. The shape of nanoparticles was controlled to be either spherical or cubic. The particles had a high specific magnetization of 226 emu/g at low saturation field, which is much higher than the currently commercialized iron oxide nanoparticles. Core–shell-type Co(Fe)–Au nanoparticles were produced by the same technique. They combined the high moment of the Co(Fe) core with the plasmonic feature of a Au shell.     

Aqueous immune magnetite nanoparticles for immunoassay

Immune magnetite nanoparticles (MNPs) are prepared by four successive reactions, which are MNPs preparation, silica-coating, surface modification with amino group, and conjugation with bio-molecule, respectively. The crystal structure and morphology of intermediate products are characterized by XRD, TEM and AFM. Qualitative and quantitative assays for amino group on the MNPs’ surface are made by FTIR and Organic Element Assay. Ultraviolet–visible absorption spectrum can indirectly illustrate the quantity of bio-molecule conjugated with MNPs. In addition, specific combination and nonspecific combination of immune MNPs are measured by commercial RIA box. The results show that the size of MNPs prepared is 10 ± 5 nm, and silica-coated MNPs with spinel structure have quasi-spherical morphology. Infrared absorption bands of –NH₂ are appeared around 3380–3200 cm⁻¹ and 1650–1510 cm⁻¹, and the amino group content is 0.5 μmol –NH₂ per mg MNPs. The specific immune combination of immune MNPs is up to 75%, and nonspecific combination is under 5%.     

Ferrite nanoparticles for future heart diagnostics

Normally, CoFe₂O₄ has been known as ferromagnetic ferrite with a quite large magnetic moment. However, since we aim to inject the particles into the human body, we are also interested in ZnFe₂O₄ because in the human body, Fe and Zn exist, so that adding ZnFe₂O₄ is safer. In both cases, the nanoparticles are coated by silica in order to get rid of toxicity. Our main purpose is to test whether these nanoparticles affect the contractile function of heart cells. Our results on rat’s heart cells have shown that both Zn and Co ferrites improved the contractility of heart cells. Notably, although both nanoparticles increased contraction and delayed relaxation, Co ferrites induced a greater contraction but with a slower relaxation. We can theoretically argue that the magnetization effects of the quantum dots have a considerable effect on the pulsating properties of the heart cells. Through this effect, the locally applied magnetic field is able to induce as well as turn on/off various regular beating patterns, thus, resetting the heart beatings.     

Metallic cobalt nanoparticles for heating applications

We investigated the properties of metallic cobalt particles which were prepared by metal organic synthesis. By X-ray diffraction we identified the FCC Co phase and obtained a particle size of 6 nm. VSM measurements revealed a specific magnetization of 77.5 Am²/kg which is 46% of the bulk value. From the analysis of the magnetization curve the parameters of the particle size distribution were estimated. In order to assess the suitability of the material for heating applications AC susceptometry as well as calorimetrical measurements of the specific loss power at 400 kHz and 13–25 kA/m were performed. We obtained values from 500 to 1300 W/g.     

Theories for multiple resonances

Two microscope theories for multiple resonances in nuclei are compared, n-particle-hole RPA and quantized Time-Dependent Hartree-Fock (TDHF). The Lipkin-Meshkov-Glick model is used as test case. We find that quantized TDHF is superior in many respects, except for very small systems.