Self-assembly of gold nanorods and polyelectrolytes for superoleophobic coatings
Recently, interest in the fabrication of water-repelling superhydrophobic surfaces has significantly increased, however, there have been fewer studies on superoleophobic surfaces, which prohibit the adhesion of oils. The long nonpolar chains that make up oils are difficult to remove from nonpolar as well as polar surfaces, due to their strong intermolecular forces stemming from London dispersion forces. Nevertheless, superoleophobic surfaces have various desirable applications including use in the cleanup of oil spills, promoting fuel efficient systems, or the inhibition of cholesterol buildup in stents and artificial arteries. The goal of this study is to investigate the contribution of electrostatic chemical interactions and physical surface roughness to superoleophobic surfaces. The surface charges of glass slides are modified by the electrostatic interactions of layer by layer polyelectrolytes assemblies, so that gold nanorods subsequently deposited can position themselves vertically and generate surface roughness. Synthesized gold nanorods are viewed under a transmission electron microscope for size and morphology analysis. The behavior of water and oil on completed films containing alternating layers of polyelectrolytes of opposite charges, are tested by oil contact angle analysis and compared. The findings of this study provide the scientific community with detailed understanding of the role of surface roughness in superoleophobicity and could lead to a better design for superoleophobic surfaces in the future.
Olivia Park & Adam Berry
Synthesis and Characterization of Panax Ginseng-Mediated Gold Nanoparticles
Recently Panax ginseng and gold nanoparticles (AuNPs) have shown promising results in the literature against breast cancer. This research is focused on sonochemically synthesizing Panax ginseng-mediated AuNPs in order to minimize their cost and environmental impact, and provide pathways to investigate a ginsenoside-based drug delivery system as ginsenosides, like phytoestrogens, are expected to inhibit human estrogen receptors. The synthesis protocol entails adding small amounts of sodium tetrachloroaurate(III) dihydrate solution to a 2.0 w/v% Panax ginseng solution and then sonicating the mixture at 100 W for 1 hour at room temperature. UV-visible absorption spectra of both ginseng only and ginseng-AuNPs have similar trends while Fourier Transform Infrared (FTIR) spectroscopy matched bending vibrations of C-C-O or C-COH distinct in ginsenosides (i.e. 1410, 1305 wavenumbers) with ginseng-AuNPs, confirming the existence of ginseng molecules on the surface of AuNPs. The morphology of ginseng-AuNPs was investigated with transmission electron microscopy (TEM) and the size distribution of these nanoparticles was measured by dynamic light scattering (DLS). These ginseng-coated gold nanoparticles may have significant medical applications in the future due to the health benefits of ginsenosides.
Synthesis of Gold Nanotubes for Photothermal Therapy Applications
Gold nanotubes can be used to deliver drugs and act as the sensitizer for photothermal therapy when treating cancer. The purpose of this experiment was to determine the optimal ratio between HAuCl 4 and Silver Nanorods, created through synthesizing of nanoseeds and silver nitrate, in order to maximize the yield of gold nanotubes. The existence and the morphology of structures formed were determined through ultraviolet-visible spectroscopy and transmission electron microscopy. It was determined that 3.075:1 ratio of gold to silver was optimal in producing tubes around 50 nm in length. The extent of effect of this ratio on drugs carrying capacity was numerically inconclusive.
Michael Park & Eugene Han
Effects of Variable Environment on Properties of Gecko-Mimetic Nanostructures
It has been known for many years that the toes of geckoes display adhesive properties due to setae arranged in lamellae that enables attractive van der Waals forces. Many methods of synthesizing faux gecko setae have been manufactured since this initial observation and utilized in order to test the different properties displayed by the setae. Prior to experimentation, an attempt was made to facilitate a method of fabrication for faux gecko setae. However, no structures were discovered under a SEM, which it was hypothesized to be due to the viscosity of PDMS. Upon successful synthesis of faux gecko setae the objective of this project will be to test the adhesive properties of these faux setae in variable environment, such as in vacuum and in aqueous solution.
Low-Temperature Fabrication of Hydroxyapatite-Titanium Nanocomposites for Bone Replacements
Titanium alloys are frequently used as bone replacements due to their high mechanical strength, but titanium-based metals do not closely match the physical properties of bone, causing stress shielding and bone resorption in the long run. In this study, fabrication of hydroxyapatite for coating on porous titanium at low temperature was attempted as a simple model system to understand the behavior of nucleation and crystallization of hydroxyapatite nanocomposites. Preliminary results reveal that the organic-inorganic hybrid sol-gel process resulted in an inconsistent Ca/P ratio, but that the precipitation method from Ca-rich solutions provided a facile synthetic route for crystalline hydroxyapatite at 20 C. Transmission electron imaging confirmed regular rod-shaped nanocrystals about 20 nanometers in length. Hydroxyapatite fabricated via this method was successfully coated on porous titanium substrates but with a low level of penetration. A greater degree of integration was seen with a reverse micelle approach incorporating both hydroxyapatite nanorods and titanium nanoparticles. Future research will focus on extending this work to three-dimensional printing to produce customizable bone replacements via additive manufacturing.
Sol Jay Lim
Carbon Dioxide Capture using Functionalized, Metal-ion doped Carbon Nanotubes
Multi-wall carbon nanotubes (MWCNTs) have quickly become subjects of research interest due to their versatile properties such as high surface area, high electrical conductivity, high mechanical strength and etc. Utilizing their high surface area, it is hypothesized that MWCNTs may become good candidates for carbon dioxide sequestration. Their ability to capture carbon dioxide could be enhanced further by functionalizing MWCNTs with carboxylic ( COOH) groups or amide ( CONH2) and entrapping calcium ions inside MWCNTs. It is anticipated that such manipulations will increase the quantity of carbon dioxide uptake significantly as opposed to uptake by non-functionalized MWCNTs. First, bucky papers containing different MWCNTs samples were prepared from filtering aqueous MWCNTs dispersions stabilized by sodium dodecylbenzene sulfonate and ultrasonification. Calcium chloride concentrations of 0.01 M and 0.005 M will then be filtered through the buckypaper to allow adsorption of calcium ions on to the surface. The resulting buckypaper will be exposed to carbon dioxide and the quantity of calcium carbonate formed will be recorded, providing helpful data in determining the effectiveness of functionalized, metal-ion entrapped MWCNTs for CO2 uptake.