Effect of sugar alcohol on colloidal stabilization of magnetic nanoparticles for hyperthermia and drug delivery applications

We have successfully introduced sugar alcohol (mannitol) onto the surface of iron oxide magnetic nanoparticles and investigated its role on their colloidal stabilization. The mannitol functionalized magnetic nanoparticles (MMNPs) were prepared through co-precipitation of Fe+2 and Fe3+ ions in basic medium under N-2 atmosphere followed by in-situ coating of D-mannitol. The formation of iron oxide nanoparticles is evident from XRD and TEM analysis. The coating of nanoparticles with mannitol is analyzed by FTIR, TGA, DLS and zeta-potential measurements. It has been observed that the presence of mannitol on the surface of nanoparticles strongly affect their surface potential and colloidal stability. They show room temperature superparamagnetism with optimal magnetization of 60.5 emu/g at 20 kOe and protein resistant behaviour in physiological medium. These MMNPs were employed as drug delivery carrier using anticancer drug, doxorubicin hydrochloride (DOX). The drug molecules were loaded onto the surface of nanoparticles through electrostatic interactions between positively charged DOX and negatively charged MMNPs. A loading efficiency of 60% has been observed at DOX to MMNPs ratio (w/w) of 1: 10 and the loaded drug showed pH dependent sustained release characteristics. Further, MMNPs exhibited good self-heating ability under applied AC magnetic field, thus they can be used as efficient heating source for hyperthermia therapy. (C) 2017 Elsevier B.V. All rights reserved

Surface and bulk electronic properties of low temperature synthesized InN microcrystals

Structural and electronic properties of IaN microcrystals, which are synthesized by nitridation of LiInO2 with NaNH2 in a Teflon-lined autoclave at temperatures ranging between 170 and 240 degrees C. are studied as a function of the growth temperature using x-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), photo-absorption, Raman spectroscopy and x-ray photo-emission spectroscopy (XPS) techniques. Our study shows the formation of wurtzite InN crystals with an average size of 100 nm even at 170 degrees C. The study, furthermore, suggests an enhancement of electron concentration and a reduction of electron mobility in the crystal as the synthesis temperature (T-s) decreases. The density of certain defects lying very close to the band edge is also found to increase with the reduction of T-s. These defects are expected to act as donors, which can explain the enhancement of carrier concentration as the growth temperature decreases. (C) 2015 Elsevier B.V. All rights reserved

Catalyst free growth of highly crystalline ZnO nanopillars on c-GaN/sapphire templates by chemical vapor deposition technique

The catalyst free growth of a large density of highly oriented ZnO nanopillars on c-GaN/sapphire templates has been demonstrated through a chemical vapor deposition route. The pillars are found to have a narrow distribution of height and diameter. It has been observed that the morphology of the growth can be varied from entirely continuous epitaxial layer to oriented nanopillars by controlling the growth temperature and growth duration. These parameters can also be adjusted to control the average diameter and height of these pillars. The authors attribute the formation of nanopillars to a two dimension to three dimension transition of the growth mode as a result of an abrupt change of Zn to oxygen flux ratio upon the closure of oxygen flow into the reactor at the end of the growth. (C) 2017 American Vacuum Society

Structural and electronic properties of InN epitaxial layer grown on c-plane sapphire by chemical vapor deposition technique

Growth of InN epilayers on c-plane sapphire substrate by chemical vapor deposition technique using pure indium metal and ammonia as precursors has been systematically explored. It has been found that [0001] oriented indium nitride epitaxial layers with smooth surface morphology can be grown on c-plane sapphire substrates by optimizing the growth conditions. Bandgap of the film is observed to be Burstein-Moss shifted likely to be due to high background electron concentration. It has been found that the concentration of this unintentional doping decreases with the increase in the growth temperature and the ammonia flux. Epitaxial quality on the other hand deteriorates as the growth temperature increases. Moreover, the morphology of the deposited layer has been found to change from flat top islands to faceted mounds as the flow rate of ammonia increases. This phenomenon is expected to be related to the difference in surface termination character at low and high ammonia flow rates. (C) 2016 American Vacuum Society

pH sensitive surfactant-stabilized Fe3O4 magnetic nanocarriers for dual drug delivery

Highly water-dispersible surfactant-stabilized Fe3O4 magnetic nanocarriers (SMNCs) were prepared by self-assembly of anionic surfactant, sodium dodecyl sulphate (SDS) on hydrophobic (oleic acid coated) nanoparticles and their biomedical applications were investigated. These nanocarriers have an average size of about 10 nm and possess tunable surface charge properties. The formation of an organic coating of SDS was evident from infrared spectroscopy, dynamic light scattering, zeta-potential and thermogravi-metric measurements. These nanocarriers were used for loading of both hydrophilic and hydrophobic anticancer agents such as doxorubicin hydrochloride (DOX) and curcumin (CUR), respectively. DOX was conjugated onto the surface of nanocarriers through electrostatic interaction, whereas CUR was encapsulated into the hydrophobic interlayer between oleic acid and SDS. The toxicity and cellular internalization of drug loaded nanocarriers were investigated against WEHI-164 cancer cell line. Specifically, the drug loading, pH sensitive drug release and cellular internalization studies suggested that these nanocarriers are suitable for dual drug delivery. Furthermore, they show good heating ability under AC magnetic field, thus can be used as effective heating source for hyperthermia treatment of cancer. (C) 2017 Elsevier B.V. All rights reserved

Structural and electronic properties of InN nanowire network grown by vapor-liquid-solid method

Growth of InN nanowires have been carried out on quartz substrates at different temperatures by vapor-liquid-solid (VLS) technique using different thicknesses of Au catalyst layer. It has been found that a narrow window of Au layer thickness and growth temperature leads to multi-nucleation, in which each site acts as the origin of several nanowires. In this multi-nucleation regime, several tens of micrometer long wires with diameter as small as 20 nm are found to grow along [11 (2) over bar0] direction (a-plane) to form a dense network. Structural and electronic properties of these wires are studied. As grown nanowires show degenerate n-type behavior. Furthermore, x-ray photoemission study reveals an accumulation of electrons on the surface of these nanowires. Interestingly, the wire network shows persistence of photoconductivity for several hours after switching off the photoexcitation. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License

Tailoring of defect luminescence in CVD grown monolayer MoS2 film

Optical properties of strictly monolayer MoS2 films, which are grown on c-sapphire substrates using microcavity based CVD route, have been investigated by temperature dependent absorption and temperature as well as excitation intensity dependent photoluminescence (PL) spectroscopy. Our study reveals a high intensity broad luminescence band appearing at similar to 1.7 eV along with the usual free exciton/trion peak (similar to 1.86 eV). The investigation furthermore attributes this broad transition to excitons bound to two types of defects, whose binding energies are found to be similar to 11 and similar to 118 meV. Integrated intensity of this feature decreases with the increase in the impinging sulfur flux during growth and by post-growth annealing in sulfur atmosphere suggesting that these defects must be related to sulfur deficiency. Interestingly, exciton-phonon coupling for these defect bound excitons is found to be much stronger than that is associated with free excitons/trions. (C) 2018 Elsevier B.V. All rights reserved

Network of vertically c-oriented prismatic InN nanowalls grown on c-GaN/sapphire template by chemical vapor deposition technique

Networks of vertically c-oriented prism shaped InN nanowalls, are grown on c-GaN/sapphire templates using a CVD technique, where pure indium and ammonia are used as metal and nitrogen precursors. A systematic study of the growth, structural and electronic properties of these samples shows a preferential growth of the islands along [11 (2) over bar0] and [0 0 0 1] directions leading to the formation of such a network structure, where the vertically [0 0 0 1] oriented tapered walls are laterally align along one of the three [11 (2) over bar0]directions. Inclined facets of these walls are identified as semipolar [11 (2) over bar2]-planes of wurtzite InN. Onset of absorption for these samples is observed to be higher than the band gap of InN suggesting a high background carrier concentration in this material. Study of the valence band edge through XPS indicates the formation of positive depletion regions below the surface of the side facets [(1122)-planes] of the walls. This is in contrast with the observation for c-plane InN epilayers, where electron accumulation is often reported below the top surface. (C) 2018 Elsevier B.V. All rights reserved