The intriguing properties of two-dimensional transition metal dichalcogenides (2D TMDCs) have led to a significant body of fundamental research and rapid uptake of these materials in many applications. Specifically, 2D TMDCs have shown great potential in biological systems due to their tunable electronic characteristics, unique optical properties, stability in aqueous environments, large surface area that can be manipulated and functionalized as well as an intercalatable layered structure, and low levels of toxicity. Here, the characteristics and use of 2D TMDCs for biological applications are reviewed and future possibilities for these materials in biological systems are outlined.

Two-Dimensional Transition Metal Dichalcogenides in Biosystems

Manifestation of intermolecular interactions in FTIR spectra of methylene blue molecules

The transport of electrically charged quasiparticles (based on electrons or ions) plays a pivotal role in modern technology as well as in determining the essential functions of biological organisms. In contrast, the transport of magnetic charges has barely been explored experimentally, mainly because magnetic charges, in contrast to electric ones, are generally considered at best to be convenient macroscopic parameters, rather than well-defined quasiparticles. However, it was recently proposed that magnetic charges can exist in certain materials in the form of emergent excitations that manifest like point charges, or magnetic monopoles. Here we address the question of whether such magnetic charges and their associated currents—‘magnetricity’—can be measured directly in experiment, without recourse to any material-specific theory. By mapping the problem onto Onsager's theory of electrolytes, we show that this is indeed possible, and devise an appropriate method for the measurement of magnetic charges and their dynamics. Using muon spin rotation as a suitable local probe, we apply the method to a real material, the ‘spin ice’ Dy2Ti2O7 (refs 5–8). Our experimental measurements prove that magnetic charges exist in this material, interact via a Coulomb potential, and have measurable currents. We further characterize deviations from Ohm's law, and determine the elementary unit of magnetic charge to be 5 μB Å-1, which is equal to that recently predicted using the microscopic theory of spin ice. Our measurement of magnetic charge and magnetic current establishes an instance of a perfect symmetry between electricity and magnetism.

http://absimage.aps.org/image/MAR10/MWS_MAR10-2009-004399.pdf

Measurement of the charge and current of magnetic monopoles in spin ice

The development of visual tumor theranostic nanoparticles has become a great challenge. In this study, D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) was conjugated to acid-sensitive cis-aconitic anhydride-modified doxorubicin (CAD) to obtain pH-sensitive anti-tumor prodrug nanoparticles (TCAD NPs) via self-assembling. Subsequently, the photosensitizer chlorin e6 (Ce6) was loaded into the resulting prodrug nanoparticles to prepare a novel tumor near-infrared fluorescence imaging and chemo–photodynamic combination therapy system (TCAD@Ce6 NPs). An accelerated release of doxorubicin (DOX) and chlorin e6 (Ce6) from the TCAD@Ce6 NPs could be achieved due to the hydrolysis of the acid-sensitive amide linker under mild acidic conditions (pH = 5.5). An in vitro experiment showed that A549 lung cancer cells exhibited a significantly higher uptake of DOX and Ce6 by using our delivery system than the free form of DOX and Ce6. An in vivo experiment showed that TCAD@Ce6 NPs displayed better tumor targeting gathering through the enhanced permeability and retention (EPR) effect than free Ce6, thus improving fluorescence imaging. Moreover, the chemo–photodynamic combination therapy of TCAD@Ce6 NPs combined with near-infrared laser irradiation was confirmed to be capable of inducing high apoptosis and necrosis of tumor cells (A549) in vitro and to display a significantly higher tumor growth suppression in the A549 lung cancer-bearing mice model. Furthermore, compared with exclusive chemotreatment (DOX) or photodynamic treatment (Ce6), our system showed enhanced therapeutic effects both in vitro and in vivo. In conclusion, the high performance TCAD@Ce6 NPs can be used as a promising NIR fluorescence imaging and highly effective chemo–photodynamic system for theranostics of lung cancer, etc. in the near future.

/pdf/ph-sensitive-self-assembling-nanoparticles-for-tumor-near-14ywol29jk.pdf

pH-Sensitive self-assembling nanoparticles for tumor near-infrared fluorescence imaging and chemo–photodynamic combination therapy

Combined toxicity of two crystalline phases (anatase and rutile) of Titania nanoparticles towards freshwater microalgae: Chlorella sp

Oleate-based hydrothermal preparation of CoFe2O4 nanoparticles, and their magnetic properties with respect to particle size and surface coating

The CoCr2O4 nanoparticles were prepared by hydrothermal treatment of chromium and cobalt oleates in a mixture of solvents (water and ethanol or pentanol) at various temperatures. The samples were further annealed at the temperatures from 300 to 500 °C. The obtained nanoparticles were characterized using powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), high-resolution TEM, scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy, and magnetic measurements. The particle size, ranging from 4.4 to 11.5 nm, was determined from the TEM and PXRD methods. The tendency of particles to form the aggregates with the increasing annealing temperature has been observed. The magnetic measurements revealed that the typical features of the CoCr2O4 long-range magnetic order are suppressed in the nanoparticles.

Hydrothermal synthesis, characterization, and magnetic properties of cobalt chromite nanoparticles

コバルトクロマイトナノ粒子の水熱合成,特性化,磁気的性質

The magnetic response of spindle-shaped hematite (α-Fe2O3) nanoparticles was investigated by simultaneous small-angle and wide-angle X-ray scattering (SAXS/WAXS) experiments. The field-dependent magnetic and nematic order parameters of the magnetic single-domain nanospindles in a static magnetic field are fully described by SAXS simulations of an oriented ellipsoid with the implemented Langevin function. The experimental scattering intensities of the spindle-like particles can be modeled simply by using the geometrical (length, radius, size distribution) and magnetic parameters (strength of magnetic field, magnetic moment) obtained from isotropic SAXS and macroscopic magnetization measurements, respectively. Whereas SAXS gives information on the morphological particle orientation in the applied field, WAXS texture analysis elucidates the atomic scale orientation of the magnetic easy direction in the hematite crystal structure. Our results strongly suggest the tendency for uniaxial anisotropy but indicate significant thermal fluctuations of the particle moments within the hematite basal plane.

Morphological and crystallographic orientation of hematite spindles in an applied magnetic field.

Zinc phthalocyanine (ZnPc) thin films were prepared by pulsed laser deposition (PLD) using KrF laser (λ = 248 nm, τ = 5 ns). The effect of laser fluence (in the region from 10 to 100 mJ/cm2) and repetition rate of 50 and 200 Hz to the film growth and its properties was investigated. The growth of ZnPc thin film was in situ monitored using transmission measurement in ultraviolet-visible spectral range. The optical properties in conjunction with density functional theory/time-dependent density functional theory calculations suggested the growth of the film in β-phase. X-ray diffraction also revealed crystalline character of the film. The electrical properties analyzed by van der Pauw method exhibited resistivity ρ ≈ 108–1010 Ω cm. Fourier transform infrared spectroscopy analyses revealed low deterioration of PLD deposited ZnPc films. We demonstrate that, by finely tuning the deposition conditions, PLD is a successful technique for fabrication of ZnPc thin films.

Dominika Zákutná

Papers

Oleate-based hydrothermal preparation of CoFe2O4 nanoparticles, and their magnetic properties with respect to particle size and surface coating

Hydrothermal synthesis, characterization, and magnetic properties of cobalt chromite nanoparticles

コバルトクロマイトナノ粒子の水熱合成,特性化,磁気的性質

Morphological and crystallographic orientation of hematite spindles in an applied magnetic field.

The growth of zinc phthalocyanine thin films by pulsed laser deposition