Nowadays, the use of nanostructures in various medical and biological fields such as drug delivery in cancer treatment is increasing. Among the nanostructures, graphene oxide (GO) is an excellent candidate for drug delivery application because of its unique properties. For more stability, GO can bind with various polymers by its carboxyl, hydroxyl and epoxy functional groups. In this study, firstly GO synthesized by the improved Hummers chemical method and then polyethylene glycol polymer was conjugated to it by using EDC/NHS catalyst. Finally, curcumin (Cur) as anti-cancer drug has been loaded onto the PEGylated graphene oxide (GO-PEG). Next, curcumin loaded onto PEGylated graphene oxide (GO-PEG-Cur) were evaluated by using ultraviolet, Fourier transform infrared spectroscopy, differential scanning calorimeter, atomic microscopic force and dynamic light scattering. The amount of loaded drug was calculated about 4.5% with the help of the standard curcumin curve and UV/Vis spectrometer. Also, the result of release shows that maximum drug release rate for this nanocarrier in pH 5.5 and 7.4 was measured 50% and 60%, respectively, after 96 hours. The results showed that the zeta-potential analysis of GO-PEG-Cur was about -13.9 mV that expresses a negative surface charge for produced nanocarrier.
We study the effect of the interfacial transparency on the Josephson current in a diffusive ferromagnetic contact between two superconductors. In contrast to the cases of the fully transparent and the low-transparency interfaces, the current-phase relation is shown to be nonsinusoidal for a finite transparency. It is demonstrated that even for the nearly fully transparent interfaces the small corrections due to weak interfacial disorders contribute a small second-harmonic component in the current-phase relation. For a certain thicknesses of the ferromagnetic contact and the exchange field this can lead to a tiny minimum supercurrent at the crossover between 0 and π states of the junction. Our theory has a satisfactory agreement with the recent experiments in which a finite supercurrent was observed at the transition temperature. We further explain the possibility for observation of a large residual supercurrent if the interfaces have an intermediate transparency.
-We theoretically propose a graphene-based adiabatic quantum pump with intrinsic spin-orbit coupling (SOC) subject to strain where two time-dependent extrinsic spin-orbit coupled barriers drive spin and charge currents. We study three differing operation modes where i) location, ii) chemical potential, and iii) SOC of the two barriers oscillate periodically and out of phase around their equilibrium states. Our results demonstrate that the amplitude of adiabatically pumped currents highly depends on the considered operation mode. We find that such a device operates with highest efficiency and in a broader range of parameters where the barriers' chemical potential drives the quantum pump. Our results also reveal that by introducing strain to the system, one can suppress or enhance the charge and spin currents separately, depending on strain direction.Spintronics is an emerging filed which has aimed at exploiting the spin degree of freedom to construct faster and high performance low-power nanoscale devices [1]. The discovery of isolated graphene monolayer [2,3], a single layer of Carbon atoms, with unique electrical, optical and thermal properties has triggered numerous efforts to achieve graphene-based nanoscale devices [5][6][7][8]. The massless Dirac fermions in ballistic graphene can reflect chirality and linear dispersion relation of graphene around the Dirac points; two inequivalent corners of the first Brillouin zone [4]. Also, the long spin relaxation time of the Dirac fermions in graphene monolayers due to a small intrinsic spin-orbit coupling (SOC) which originates from the intra-atomic spin-orbit coupling of the Carbon atoms has made it an exceptional candidate to the spintronics devices [7].Quite recently, it was experimentally demonstrated that a strong Rashba SOC ∼ 17 meV can be induced into graphene monolayers by means of proximity to a semiconducting tungsten disulphide substrate [8]. This finding is highly appealing in terms of generation and manipulation of spin currents in more controllable platforms. The intrinsic SOC that can be caused by the crystalline potential associated with the band structure respects all the lattice symmetries in graphene and results in a small energy gap at the Dirac points. The extrinsic or Rashba SOC, however, results from the lack of inversion symmetry due to perpendicular electric fields, substrate effects, chemical doping, or curvature of graphene corrugations and can be responsible for inducing a spin polarization in graphene. [9,10] The influences of intrinsic and Rashba SOCs on the transport properties of graphene monolayer systems have extensively been studied in the recent years [5,6,[11][12][13][14]. For instance, it was shown that spin polarization induced by a charge current can reside in the graphene plane and perpendicular to the electric field while its sign changes by varying the Fermi level through an external gate voltage [11]. Also, it was theoretically found that the interplay of massive electrons with SOC or strain in a graphene layer can...
We investigate a graphene quantum pump, adiabatically driven by two thin potential barriers vibrating around their equilibrium positions. For the highly doped leads, the pumped current per mode diverges at the Dirac point due to the more efficient contribution of the evanescent modes in the pumping process. The pumped current shows an oscillatory behavior with an increasing amplitude as a function of the carrier concentration. This effect is in contrast to the decreasing oscillatory behavior of a similar normal pump (i.e. a pump based on a two-dimensional electron gas). The graphene pump driven by two vibrating thin barriers operates more efficiently than the graphene pump driven by two oscillating thin barriers.
We study the Josephson current through a ballistic normal metal layer of thickness D, on which two superconducting electrodes are deposited within a distance L of each other. In the presence of an ͑in-layer͒ magnetic field, we find that the oscillations of the critical current I c ͑⌽͒ with the magnetic flux ⌽ are significantly different from an ordinary magnetic interference pattern. Depending on the ratio L / D and temperature, I c ͑⌽͒ oscillations can have a period smaller than flux quantum ⌽ 0 , nonzero minima, and damping rate much smaller than 1 / ⌽. A similar anomalous magnetic interference pattern was recently observed experimentally.
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