• Advances in materials Research
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• v.1 no.4
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• pp.311-347
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• 2012

Infections are caused due to the infiltration of tissue or organ space by infectious bacterial agents, among which Staphylococcus aureus bacteria are clinically most relevant. While current treatment modalities are in general quite effective, several bacterial strains exhibit high resistance to them, leading to complications and additional surgeries, thereby increasing the patient morbidity rates. Titanium dioxide is a celebrated photoactive material and has been utilized extensively in antibacterial functions, making it a leading infection mitigating agent. In view of the property amelioration in materials via nanofication, free-standing titania nanofibers (pure and nominally doped) and nanocoatings (on Ti and Ti6Al4V implants) were fabricated and evaluated to assess their efficacy to mitigate the viability and growth of S. aureus upon brief (30 s) activation by a portable hand-held infrared laser. In order to gauge the effect of exposure and its correlation with the antibacterial activities, both isolated (only titania substrate) and simultaneous (substrate submerged in the bacterial suspension) activations were performed. The bactericidal efficacy of the IR-activated $TiO_2$ nanocoatings was also tested against E. coli biofilms. Toxicity study was conducted to assess any potential harm to the tissue cells in the presence of photoactivated materials. These investigations showed that the photoactivated titania nanofibers caused greater than 97% bacterial necrosis of S. aureus. In the case of titania-coated Ti-implant surrogates, the bactericidal efficacy exceeded 90% in the case of pre-activation and was 100% in the case of simultaneous-activation. In addition to their high bactericidal efficacy against S. aureus, the benignity of titania nanofibers and nanocoatings towards tissue cells during in-vivo exposure was also demonstrated, making them safe for use in implant devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.495-495
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• 2011

Miniaturized sensors capable of both sensitive and selective real-time monitoring of target analytes are tremendously valuable for various applications ranging from hazard detection to medical diagnostics. The wide-spread use of such sensors is currently limited due to insufficient selectivity for target molecules. We developed selective nanocoatings by combining trinitrotoluene (TNT) receptors bound to conjugated polydiacetylene (PDA) with single-walled carbon nanotube-field effect transistors (SWNT-FET). Selective binding events between TNT molecules and phage display derived TNT receptors were effectively transduced to sensitive SWNT-FET conductance sensors through the PDA coating. The resulting sensors exhibited unprecedented 1 fM sensitivity toward TNT in real time, with excellent selectivity over various similar aromatic compounds. Our biomimetic receptor coating approach may be useful for the development of sensitive and selective micro and nanoelectronic sensor devices for various other target analytes.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.6.2-6.2
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• 2009

Nanostructured materials arecurrently receiving much attention because of their unique structural andphysical properties. Research has been stimulated by the envisagedapplications for this new class of materials in electronics, optics, catalysisand magnetic storage since the properties derived from nanometer-scalematerials are not present in either isolated molecules or micrometer-scalesolids. This study presents the experimental results derived fromthe various functional materials processed in nano-scale using pulsed laserablation, since those materials exhibit new physical phenomena caused by thereduction dimensionality. This presentation consists of three mainparts to consider in pulsed laser ablation (PLA) technique; first nanocrystallinefilms, second, nanocolloidal particles in liquid, and third, nanocoating fororganic/inorganic hybridization. Firstly, nanocrystalline films weresynthesized by pulsed laser deposition at various Ar gas pressures withoutsubstrate heating and/or post annealing treatments. From the controlof processng parameters, nanocystalline films of complex oxides and non-oxidematerials have been successfully fabricated. The excellentcapability of pulsed laser ablation for reactive deposition and its ability totransfer the original stoichiometry of the bulk target to the deposited filmsmakes it suitable for the fabrication of various functionalmaterials. Then, pulsed laser ablation in liquid has attracted muchattention as a new technique to prepare nanocolloidal particles. Inthis work, we represent a novel synthetic approach to directly producehighly-dispersed fluorescent colloidal nanoparticles using the PLA from ceramicbulk target in liquid phase without any surfactant. Furthermore, novel methodbased on simultaneous motion tracking of several individual nanoparticles isproposed for the convenient determination of nanoparticle sizedistributions. Finally, we report that the GaAs nanocrystals issynthesized successfully on the surface of PMMA (polymethylmethacrylate)microspheres by modified PLD technique using a particle fluidizationunit. The characteristics of the laser deposited GaAs nanocrytalswere then investigated. It should be noted that this is the first successfultrial to apply the PLD process nanocrystals on spherical polymermatrices. The present process is found to be a promising method fororganic/inorganic hybridization.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.196-205
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• 2019

Ni-rich layered oxides $Li(Ni_xCo_yMn_z)O_2$ (x + y + z = 1) have been extensively studied in recent times owing to their high capacity and low cost and can possibly replace $LiCoO_2$ in the near future. However, these layered oxides suffer from problems related to the capacity fading, thermal stability, and safety at high voltages. In this study, we use surface coating as a strategy to improve the thermal stability at higher voltages. The uniform and conformal $Al_2O_3$ coating on prefabricated electrodes using atomic layer deposition significantly prevented surface degradation over prolonged cycling. Initial capacity of 190, 199, 188 and $166mAh\;g^{-1}$ is obtained for pristine, 2, 5 and 10 cycles of ALD coated samples at 0.2C and maintains 145, 158, 151 and $130mAh\;g^{-1}$ for high current rate of 2C in room temperature. The two-cycle $Al_2O_3$ modified cathode retained 75% of its capacity after 500 cycles at 5C with 0.05% capacity decay per cycle, compared with 46.5% retention for a pristine electrode, at an elevated temperature. Despite the insulating nature of the $Al_2O_3$ coating, a thin layer is sufficient to improve the capacity retention at a high temperature. The $Al_2O_3$ coating can prevent the detrimental surface reactions at a high temperature. Thus, the morphology of the active material is well-maintained even after extensive cycling, whereas the bare electrode undergoes severe degradation.