Controlled motion of artificial nanomotors in biological environments, such as blood, can lead to fascinating biomedical applications, ranging from targeted drug delivery to microsurgery and many more. In spite of the various strategies used in fabricating and actuating nanomotors, practical issues related to fuel requirement, corrosion, and liquid viscosity have limited the motion of nanomotors to model systems such as water, serum, or biofluids diluted with toxic chemical fuels, such as hydrogen peroxide. As we demonstrate here, integrating conformal ferrite coatings with magnetic nanohelices offer a promising combination of functionalities for having controlled motion in practical biological fluids, such as chemical stability, cytocompatibility, and the generated thrust. These coatings were found to be stable in various biofluids, including human blood, even after overnight incubation, and did not have significant influence on the propulsion efficiency of the magnetically driven nanohelices, thereby facilitating the first successful "voyage" of artificial nanomotors in human blood. The motion of the "nanovoyager" was found to show interesting stick-slip dynamics, an effect originating in the colloidal jamming of blood cells in the plasma. The system of magnetic "nanovoyagers" was found to be cytocompatible with C2C12 mouse myoblast cells, as confirmed using MTT assay and fluorescence microscopy observations of cell morphology. Taken together, the results presented in this work establish the suitability of the "nanovoyager" with conformal ferrite coatings toward biomedical applications.

One-pot synthesis of amorphous iron oxide nanoparticles with two different dimensions (<5 nm and 60 nm) has been achieved using the reverse micelle method, with <5 nm nanoparticles separated from the stable colloid by exploiting their magnetic behaviour. The transformation of the as-prepared amorphous powders into Fe 3 O 4 and Fe 2 O 3 phases (g and a) is achieved by carrying out controlled annealing at elevated temperatures under different optimized conditions. The as-prepared samples resulting from micellar synthesis and the corresponding annealed ones are thoroughly characterized by powder X-ray diffraction, transmission electron microscopy (TEM), and by Raman and X-ray photoelectron spectroscopies. Expectedly, the magnetic characteristics of Fe 3 O 4 and Fe 2 O 3 phase (g and a)nanoparticles are found to have strong dependence on their phase, dimension, and morphology. The coercivity of Fe 3 O 4 and Fe 2 O 3 (g and a) nanoparticles is reasonably high, even though high resolution TEM studies bring out that these nanoparticles are single crystalline. This is in contrast with previous reports wherein poly-crystallinity of iron oxides nanoparticles has been regarded as a prerequisite for high coercivity.

Layered transition metal dichalcogenides (TMDs), such as MoS2, are candidate materials for next generation 2-D electronic and optoelectronic devices. The ability to grow uniform, crystalline, atomic layers over large areas is the key to developing such technology. We report a chemical vapor deposition (CVD) technique which yields n-layered MoS2 on a variety of substrates. A generic approach suitable to all TMDs, involving thermodynamic modeling to identify the appropriate CVD process window, and quantitative control of the vapor phase supersaturation, is demonstrated. All reactant sources in our method are outside the growth chamber, a significant improvement over vapor-based methods for atomic layers reported to date. The as-deposited layers are p-type, due to Mo deficiency, with field effect and Hall hole mobilities of up to 2.4 cm(2) V(-1) s(-1) and 44 cm(2) V(-1) s(-1) respectively. These are among the best reported yet for CVD MoS2.

Nearly all transparent conducting oxides (TCOs) exhibit only n-type conductivity, restricting them to passive applications as transparent electrodes and as coatings for IR reflection. The development of optoelectronic devices using TCOs would be furthered if, for example, it were possible to fabricate p±n junctions with such materials. This entails the development of p-type TCOs with properties comparable with their n-type counterparts. Recently, compounds of the type CuMO 2 (where M is a trivalent cation), of the delafossite structure, have been reported to exhibit intrinsic p-type conductivity, [1±6] albeit that both the transmittance and conductivity of such materials are quite low compared to the n-type TCOs such as indium tin oxide (ITO). The oxide with the highest p-type conductivity reported to date is CuCrO 2 :Mg (where Mg is the dopant) in thin film form.[6]A conductivity of 220 S cm ±1 and transmittance of about 30±40 % in the visible range have been measured in a film of this material, of thickness 270 nm, deposited by on-axis RF sputtering on fused quartz substrates. In this paper, we report the preparation of p-type CuCrO 2 thin films by low-pressure metal±organic (LP-MO)CVD using copper acetylacetonate [Cu(acac) 2 ] and chromium acetylacetonate [Cr(acac) 3 ] as copper and chromium precursors, respectively, and discuss the conductivity and optical properties of these films. Due to the inherent nature of the MOCVD process, the CuCrO 2 films could be grown successfully on glass substrates at temperatures significantly lower than those reported earlier for the growth of thin films of TCOs of the delafossite structure by techniques such as sputtering, [6] pulsed laser deposition, [1,3] etc.Metal±organic complexes, especially the acetylacetonates, are generally quite stable in air. Though such complexes are usually less volatile than organometallics and alkoxides, they sublime at reasonably low temperatures (100± 230 C). [7] Additionally, they have the advantage of being relatively non-toxic crystalline solids, which makes the handling of these precursors easier. Successful deposition of delafossite-type CuCrO 2 films by MOCVD using the respective acetylacetonates as precursors, as has been accomplished in this work, suggests that the technique may be

Here we report a ‘one-step’ synthetic approach to prepare both transparent (∼7 nm) and scattering particles (∼100–400 nm) of TiO2 from a single precursor for their application as a photoanode in dye-sensitized solar cells (DSCs).

Magnetic nanomotors with integrated theranostic capabilities can revolutionize biomedicine of the future. Typically, these nanomotors contain ferromagnetic materials, such that small magnetic fields can be used to maneuver and localize them in fluidic or gel-like environments. Motors with large permanent magnetic moments tend to agglomerate, which limits the scalability of this otherwise promising technology. Here, we demonstrate the application of a microwave-synthesized ferrite layer to reduce the agglomeration of helical ferromagnetic nanomotors by an order of magnitude, which allows them to be stored in a colloidal suspension for longer than six months and subsequently be manoeuvred with undiminished performance. The ferrite layer also rendered the nanomotors suitable as magnetic hyperthermia agents, as demonstrated by their cytotoxic effects on cancer cells. The two functionalities were inter-related since higher hyperthermia efficiency required a denser suspension, both of which were achieved in a single microwave-synthesized ferrite coating.

A detailed thermodynamic analysis of the solid and gas phases of the Mo-S-C-O-H system used for large area chemical vapor deposition (CVD) of MoS2 is presented and compared with experimental results. Given the multivariable nature of the problem, excellent agreement is observed. Deviations, observed from thermodynamic predictions, mainly at low temperatures and high flow rates have been highlighted and discussed. CVD phase diagrams which predict parameter windows in which pure MoS2 can be synthesized have been provided for important gas phase chemistries. Pure H2 as a carrier gas is shown to facilitate the largest contamination free process window. CO presence is shown to significantly reduce the nucleation rate and enable large island sizes but at the cost of carbon contamination. Oxygen leaks are shown to result in sulphur contamination. The absence of H2S during cooling is shown to yield Mo due to the reduction of MoS2 by hydrogen. Oxidation of Mo causes oxide contamination.

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