Volume 83, Issue 11

The International Conference on Nanomaterials and Nanotechnology (NANO-2010) was organized by the Center for Nanoscience and Technology (CNST), K.S. Rangasamy College of Technology, in association with the Department of Nanobio Materials and Electronics (DNE), World Class University (WCU), Gwangju Institute of Science and Technology (GIST), South Korea, and the Technische Unversität Kaiserslautern, Germany, from 13 to 16 December 2010. The interdisciplinary conference was held at the KSRCT, Tiruchengode, Tamil Nadu, India, and included a series of scientific lectures, an exhibition, and a panel discussion with funding agencies such as the DST, Defense Research and Development Organization (DRDO), DAE, and the Council for Scientific and Industrial Research (CSIR). In addition, a special session for DRDO was arranged, including a benefit for the delegates to explore potential areas of collaboration with the DRDO laboratories. This special session on the “Application of Nanotechnology for National Security” was held 14 December 2010. Also, 13 companies exhibited their products in the exhibition hall. Distinguished persons from various funding agencies participated in the panel discussion to identify the road map for nanotechnology in India. The conference was enlightened by three plenary lectures, which included one given by Prof. Dr. Richard Ernst, Nobel laureate. In addition, 39 invited lectures and more than 560 contributed papers from over 24 countries were presented. We would like to thank IUPAC for coming forward to publish the invited papers in Pure and Applied Chemistry . Out of 39 invited lectures, 12 papers were accepted after peer review for publication. We also thank IUPAC for sponsoring this event. Our special thanks are due to the reviewers for their help with critical reviews and detailed comments on the manuscripts and also to the speakers for considering the reviewers’ comments. V. Rajendran, Burkard Hillbrands, and Kurt E. Geckeler Conference Editors

Bi-substituted iron garnet (Bi:IG) compounds synthesized in thin film form are the best semi-transparent magneto-optical (MO) materials for applications in magnetic recording, optical sensors, and photonics. These materials can possess attractive magnetic properties and the highest specific Faraday rotation in the visible and near-infrared spectral regions, if the deposited layers contain a high volumetric fraction of the garnet phase and possess high-quality surfaces and microstructure. In this paper, we study the effects of various deposition and annealing process parameters on the properties of Bi:IG and garnet-oxide nanocomposite films of several composition types fabricated using radio-frequency (RF) sputtering deposition followed by high-temperature isothermal crystallization. We also investigate the kinetics of garnet phase formation within a garnet-Bi-oxide nanocomposite material.

The successful conjunction of the ultimate spatial resolution capability of the scanning tunneling microscope (STM) with the sensitivity to the spin of the tunneling electrons has opened the door to investigations of magnetism at the nanoscale where the fundamental interactions responsible for magnetic order can be studied. Spin-polarized (SP) STM allows insight into a fascinating world with surprisingly rich magnetic phenomena. Ferromagnetic structures with magnetic domains are found at nanometer length scales, or 2D antiferromagnetically ordered monolayers (MLs) where the magnetization is reversed from one atom to the next. Such collinearly ordered states may be modified by the Dzyaloshinsky–Moriya (DM) interaction which can induce a small canting angle between neighboring atomic moments, thus giving rise to novel non-collinear spin spiral ground states. DM interaction is a result of electron scattering in a crystal environment with broken inversion symmetry. Spin spirals were observed in a variety of systems, like ultrathin Fe films, or MLs of Mn atoms on the (110) and (001) faces of a W crystal. Using a magnetically sensitive probe tip, individual Co atoms were assembled to form chains on top of a spin spiral. The magnetization orientation of each individual atom can be manipulated by repositioning it along the spin spiral.

Spin-wave (SW) modes are addressed which are confined in thin individual Ni 80 Fe 20 nanowires with widths ranging from 220 to 360 nm. In periodic arrays with an edge-to-edge separation of down to 100 nm, confined modes of neighboring nanowires are found to couple coherently and form allowed minibands and forbidden frequency gaps. This gives rise to a one-dimensional magnonic crystal. We present all-electrical SW spectroscopy data and micromagnetic simulations. We find that the nanowire arrays allow us to reprogram the relevant magnonic band structure via the magnetic history. A forbidden frequency gap of up to about 1 GHz is controlled by an in-plane magnetic field being as small as a few mT.

The bombardment of the surface of a solid by energetic ions often results in pronounced surface modifications, leading to characteristic topographical features. In this report, the development of specific morphological nanostructures on surfaces under ion irradiation is discussed. The following aspects will be emphasized: (i) on an atomic scale, the generation of isolated defects such as adatoms and surface vacancies due to single-ion impacts, and their possible clustering; (ii) the transition from such individual defects toward extended morphological features on the surface and suitable scaling relations to describe them; (iii) the formation of highly periodic structures with nanoscale dimensions such as nanodots and “ripple”-like features, and the dependence of these nanostructcures on various ion-irradiation parameters and substrate materials; (iv) the theoretical concepts proposed to model the observed patterns which are thought to be related to (and caused by) the interplay between ion erosion and diffusion of adatoms (vacancies), thus inducing a surface reorganization.

In this study, tamoxifen citrate-loaded chitosan nanoparticles (tamoxcL-ChtNPs) and tamoxifen citrate-free chitosan nanoparticles (tamoxcF-ChtNPs) were prepared by an ionic gelation (IG) method. The physicochemical properties of the nanoparticles were analyzed for particle size, zeta (ζ) potential, and other characteristics using photon correlation spectroscopy (PCS), zeta phase analysis light scattering (PALS), scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and differential scanning calorimetry (DSC). The variation in particle size was assessed by changing the concentration of chitosan, pentasodium tripolyphosphate (TPP), and the pH of the solution. The optimized tamoxcL-ChtNPs showed mean diameter of 187 nm, polydispersity of 0.125, and ζ-potential of +19.1 mV. The encapsulation efficiency (EE) of tamoxifen citrate (tamoxc) increased at higher concentrations, and release of tamoxc from the chitosan matrix displayed controlled biphasic behavior. Those tamoxcL-ChtNPs tested for chemosensitivity showed dose- and time-dependent antiproliferative activity of tamoxc. Further, tamoxcL-ChtNPs were found to be hemocompatible with human red blood cells (RBCs) and safe by in vitro cytotoxicity tests, suggesting that they offer promise as drug delivery systems in therapy.

Metal nanoparticles encapsulated by silicate sol-gel matrix find numerous applications particularly in electrocatalysis and sensors. In our previous reports, we have reported the mono- and bi-metal gold, silver, and core/shell gold/silver nanoparticles embedded in functionalized silicate sol-gel matrices. Modified electrodes were fabricated using mono- and bi-metallic gold, silver, and core/shell gold/silver nanoparticles embedded in silicate sol-gel, and they were used for the electrocatalysis and sensing of H 2 O 2 and simultaneous detection of hydrazine, sulfite, and nitrite. We have prepared the gold nanoparticles encapsulated by amine-functionalized silicate sol-gel matrix in a single step without using any external reducing agents. The gold nanoparticles were also synthesized by using amine-functionalized silane monomer in the presence of β-cyclodextrin (β-CD), resulting in metal/polymer core/shell nanostructures. This nanocomposite material showed a synergistic stabilizing effect when compared to either silicate sol-gel matrix or β-CD alone as stabilizer. The synthesized gold nanoparticles were characterized using UV–vis spectroscopy and high-resolution transmission electron microscopy. Modified electrodes were prepared by using the gold nanoparticles embedded in silicate sol-gel matrix, and their electrochemical characteristics were studied.

The interactions of gold nanoparticles (AuNPs) with human serum albumin (HSA) greatly influence their in vivo characteristics. It is important to develop conjugates that can serve as ideal structural models to understand the interaction of AuNPs with HSA. We report the synthesis and stabilization of AuNPs in HSA matrix with no additional ligands on the surface of the NPs. The hydrodynamic size of the AuNP–HSA conjugate is 22 nm, and transmission electron microscopy (TEM) measurement shows the core size as 8–13 nm. We have performed strip assay to establish that the biological activity of HSA is retained even after conjugation. Our cellular toxicity evaluation studies show that AuNP–HSA conjugates are nontoxic and biocompatible.

In this work we demonstrate the potential of using an automated cell viability analyzer for developing high-throughput screening of orthopedic bioactive materials. We used a biomaterial of carbon nanotubes (CNTs)-based composite integrated with hydroxyapatite/polymethyl methacrylate (HA/PMMA) with controlled physical and chemical properties to evaluate the usefulness of morphometric analysis in conjunction with trypan blue dye exclusion assays in MG63 cell cultures. The MG63 cell line, derived from human bone osteo-sarcoma, is often used as a model for studying osteoblast-like cellular response to bioactive materials for orthopedic surgery. The viability analyzer, Vi-CELL TM XR, Beckman Coulter, was used with trypan blue dye exclusion method in cell suspensions obtained after trypsinization along with determining the distribution plots of cell diameter and circularity, which are critical cellular characteristics. In addition, the activity of alkaline phosphatase (ALP), a typical representation of osteogenic activity of osteoblasts, was also measured spectro-photometrically using p -nitrophenol phosphate as the substrate. Comparative analysis of the frequency histogram of average cell diameter and circularity allowed for the analyses of significant alterations in cell morphology not only over time in control cultures (spherical vs. a flat morphology) but also with respect to PMMA and HA nanocomposites. After cell exposure to HA/PMMA/CNTs, a shift toward loss of cell circularity was observed. The appearances of more differentiated morphologic features were well correlated with the increase of secreted ALP activity. In conclusion, the evaluation of material-induced changes of cell morphology could represent a valuable prescreening test for bioactive properties.

The off-stoichiometric Ni 2 MnGa ferromagnetic alloys are one of the active materials that are of great interest when they are ball milled into nanopowder. These powders are prospective materials for nanosystem applications. However, the properties of the nano-crystalline Ni–Mn–Ga alloys depend strongly on their structure and internal stress, which develop during the milling process. Ni–Mn–Ga nanoparticles were prepared by ball-milling method, and characterized by X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) techniques. The powders are found to be a disordered mixture structure of austenite and martensite. We calculated that an average internal stress is 0.28 to 2.05 MPa stored in the distorted lattice due to milling. Reduction in particle sizes is accompanied by increase of the lattice strain level when the milling time increases. The VSM reveals that magnetic saturation and coercivity decrease with increase of the milling duration. This phenomenon causes deterioration in the hard magnetic properties.

The main process medium in the reprocessing industry is highly oxidizing nitric acid ranging from dilute to concentrated solutions containing fission products and from room temperature to boiling conditions. Corrosion resistance of materials chosen for reprocessing plants is of prime importance for uninterrupted operation. Surface modification and coatings can significantly improve the corrosion resistance of materials. A number of surface modification and coating development works such as double oxide coating on Ti for reconditioning (DOCTOR); mixed oxide coated Ti anodes (MOCTAs); nanostructured Ti, TiO 2 , TiN, and ZrN; bulk metallic glasses (BMGs); and superhydrophobic (SHB) coatings for corrosion protection are being pursued in our laboratory. Nanostructured coatings developed on Ti-like DOCTOR and MOCTAs showed improved corrosion resistance and longer life. Nanostructured Ti, TiO 2 , and ZrN coatings deposited on type 304L stainless steel (SS) by magnetron sputtering technique and Zr-based bulk metallic Zr 59 Ti 3 Cu 20 Al 10 Ni 8 alloy deposited on type 304L SS by pulsed laser deposition (PLD) technique showed improved corrosion resistance in nitric acid. SHB coating on 9Cr-1Mo and Ti lead to improved corrosion resistance and biofouling resistance of Ti. The surface modification and coating development carried out in our laboratory for corrosion protection in reprocessing plants are briefly highlighted.

We review the recent literature on carbon catalyst layers for dye-sensitized solar cells (DSCs), and then report an improved fabrication method for screen-printed carbon counter electrodes. The carbon-printing ink was prepared by mixing carbon black, TiO 2 nanoparticles, α-terpineol, and ethyl cellulose using a mortar, an ultrasonic homogenizer, and a rotary evaporator. Scanning electron microscopy (SEM) showed that the resulting screen-printed carbon layers were flatter and smoother at nano- and micro-scales than a carbon layer prepared using water-based ink. The photovoltaic performance of the screen-printed catalyst layers was similar to the photoenergy conversion of platinum counter electrodes. The highest cell efficiency with a carbon counter electrode was 7.11 % at a light intensity of 100 mW cm -2 .

We discuss the light absorption enhancement factor dependence on the design of nanogratings inscribed into metal-semiconductor-metal photodetector (MSM-PD) structures. These devices are optimized geometrically, leading to light absorption improvement through plasmon-assisted effects. Finite-difference time-domain (FDTD) simulation results show ~50 times light absorption enhancement for 850 nm light due to improved optical signal propagation through the nanogratings. Also, we show that the light absorption enhancement is strongly dependent on the nanograting shapes in MSM-PDs.