Surface decoration of amine-rich carbon nitride with iron nanoparticles for arsenite (As(III)) uptake: The evolution of the Fe-phases under ambient conditions.

A novel hybrid material (gC3N4-rFe) consisting of amine-rich graphitic carbon nitride (gC3N4), decorated with reduced iron nanoparticles (rFe) is presented. XRD and TEM show that gC3N4-rFe bears aggregation-free Fe-nanoparticles (10nm) uniformly dispersed over the gC3N4 surface. In contrast, non-supported iron nanoparticles are strongly aggregated, with non-uniform size distribution (20-100nm). (57)Fe-Mössbauer spectroscopy, dual-mode electron paramagnetic resonance (EPR) and magnetization measurements, allow a detailed mapping of the evolution of the Fe-phases after exposure to ambient O2. The as-prepared gC3N4-rFe bears Fe(2+) and Fe° phases, however only after long exposure to ambient O2, a Fe-oxide layer is formed around the Fe° core. In this [Fe°/Fe-oxide] core-shell configuration, the gC3N4-rFe hybrid shows enhanced As(III) uptake capacity of 76.5mgg(-1), i.e., ca 90% higher than the unmodified carbonaceous support, and 300% higher than the non-supported Fe-nanoparticles. gC3N4-rFe is a superior As(III) sorbent i.e., compared to its single counterparts or vs. graphite/graphite oxide or activated carbon analogues (11-36mgg(-1)). The present results demonstrate that the gC3N4 matrix is not simply a net that holds the particles, but rather an active component that determines particle formation dynamics and ultimately their redox profile, size and surface dispersion homogeneity.

Quaternized carbon dot-modified graphene oxide for selective cell labelling--controlled nucleus and cytoplasm imaging.

Cationic quaternized carbon dots (QCDs) and anionic graphene oxide sheets (GO) are combined via non-covalent interactions following a self-assembly pathway to form highly biocompatible and fluorescent hybrid materials. These hybrids act as selective probes with controlled labelling of the cell nucleus or cytoplasm depending on the QCD loading.

Fluoro-graphene: nonlinear optical properties.

In the present work, we report on the investigation of the third-order nonlinear optical response of graphene fluoride dispersed in DMF and also of fluorosurfactant-stabilized graphene fluoride dispersed in water under visible (532 nm) and infrared (1064 nm), picosecond and nanosecond laser excitation. Both graphene derivatives were found to exhibit large nonlinear optical response, while significant differences on their nonlinear optical response have been observed (e.g. different sign of nonlinear refraction and absorption). These findings highlight the important role of the degree of fluorination of the graphene sheets on their optical and electronic properties. Furthermore, DMF dispersed graphene fluoride was found to exhibit important broadband optical limiting action under nanosecond laser excitation, making it promising candidate for optical limiting applications.

Large-scale synthesis, size control, and anisotropic growth of gamma-Fe2O3 nanoparticles: organosols and hydrosols.

Monodispersed, spherical gamma-Fe2O3 nanoparticles with controllable size in large-scale were prepared by thermolytic decomposition of FeCl3.6H2O in aliphatic amines. The nanoparticles gave very stable colloidal solution in organic solvents and can be easily converted to water-soluble by a very simple route. Their characterisation was based on TEM microscopy, XRD, Mössbauer, and magnetic measurements. Furthermore, a small amount of Pt can lead to the formation of anisotropic gamma-Fe2O3 nanostructures.

Magnetic resonance in nanoparticles: between ferro- and paramagnetism.

Magnetic nanoparticles of γ-Fe(2)O(3) coated with organic molecules and suspended in liquid and solid matrices, as well as non-diluted magnetic fluid, have been studied by electron magnetic resonance (EMR) at 77-380 K. Slightly asymmetric spectra observed at room temperature become much broader and symmetric, and shift to lower fields upon cooling. An additional narrow spectral component (with a line-width of 30 G) is found in diluted samples; its magnitude obeys the Arrhenius law with an activation temperature of about 850 K. The longitudinal spin-relaxation time, T(1)≈10 ns, is determined by a specially developed modulation method. The angular dependence of the EMR signal position in field-freezing samples points to substantial alignment, suggesting the formation of dipolar-coupled aggregates. The shift and broadening of the spectrum upon cooling are assigned to the effect of the surface-related anisotropy. To describe the overall spectral shape, the 'quantization' model is used which includes summation of resonance transitions over the whole energy spectrum of a nanoparticle considered as a giant exchange cluster. This approach, supplemented with some phenomenological assumptions, provides satisfactory agreement with the experimental data.

NMR and spin relaxation in systems with magnetic nanoparticles.

The ¹H NMR spectra and spin dynamics of the host systems have been studied in liquid and solid suspensions of γ-Fe2O3 nanoparticles. Significant broadening of ¹H NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T1/T2 depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of T1 upon the nanoparticle concentration. We explain the experimental results taking into account the predomination of self-diffusion as a source of the relaxation in liquid suspensions, and estimate effective parameters of relaxation in the systems under study.

Surface-functionalized nanoparticles with liquid-like behavior: the role of the constituent components.

Ionically modified silica nanoparticles with large counter anions (sulfonate, isostearate) at two silica volume fractions (13 and 27%) form a viscous fluid and a glass but not crystalline solids. Dielectric spectroscopy, Brillouin scattering and shear rheometry were employed to investigate these new nanoparticle-based fluids. The glass transition temperature and hence the local dynamics are governed by the large counter anions, whereas the flow properties can be controlled by the spatial correlation between the nanoparticles, e.g. by tuning the volume fraction of hard cores and local interactions between segments in the soft corona. Liquid-like ordering of the cores was revealed by X-ray scattering and found to influence significantly the macroscopic flow properties of these salts.

Shape fabrication of millimeter-sized metal-containing carboxymethyl cellulose hollow capsules.

Dropwise addition of an aqueous carboxymethyl cellulose solution to a solution of a copper or iron salt in n-butanol, leads to self-assembled, permeable millimeter sized metal-ion derivatized carboxymethyl cellulose hollow capsules of uniform dimensions and different morphologies.