Zinc oxide (ZnO) is a technologically important material because of its multi-functional properties, with applications ranging from piezoelectric transducers and varistors to wide-bandgap semiconductor for UV emitters and detectors. In addition to polycrystalline ceramic powders and epitaxial thin films, recent advances in ZnO have been in vapor and solution phase growth of complex nanostructures. For these nanostructures to be useful, a means to place them strategically on the surface is needed. Here we will describe using micro-contact printing to pattern self-assembled monolayer (SAM) molecules that locally inhibit crystal growth on surfaces. These chemically patterned surfaces are then used as templates for ZnO nanorod growth in aqueous solutions. We demonstrate good control of crystal placement
with feature size down to 1 µm. In addition, we find that restricting active nucleation regions results in a marked increase in nucleation density. These results are the first demonstration of combining soft lithography and bio-inspired crystal growth to make nanostructures of ZnO. The success illustrated here indicates that such a combination may be applicable to a much broader range of materials systems than previously envisioned.
Recent interest in colloidal gold focuses on understanding the tunability of the longitudinal and transverse plasma resonance. It was reported that the reduction of HAuCl4 by Na2S produces gold nanoparticles with an optical absorption in the near infrared. This absorption blue shifts during the course of the reaction. X-ray photoemission spectroscopy (XPS) measurements on this system indicated that there was little sulfur present in the system. A small angle x-ray scattering (SAX) experiment was used to monitor the reaction while simultaneously the UV-VIS spectrum was measured. During the reaction the fractal dimension decreased from 4.154 ± 0.850 to 0.624 ± 0.146. The decrease in fractal dimension coincided with the blue shift in the longitudinal plasma resonance from the near IR to the visible. This suggests a change from reaction limited colloid aggregation (RLCA) to diffusion limited colloid aggregation (DLCA), caused the shift in the plasma resonance.
We describe the development and performance of microchips that interface capillary electrophoresis (CE) with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The chip contains an open channel where CE is performed. The open channel functions as the CE column and is used to separate the mixture. Once separation occurs, the solvent is evaporated and the chip placed in the ionization source of a Fourier transform mass spectrometer. To perform the MALDI, a buffer will be used in the CE that will also function as matrix once the solvent is evaporated. Preliminary results will be described showing: (1) the design and construction of a new ionization source for an external source FTMS that will handle the microchip, (2) the feasibility of the CE on an open channel and (3) the feasibility of MALDI on an open channel. Two chips made of glass with groves cut on the surface have been fabricated for these experiments. The rates of evaporation of different solvent mixtures indicate that evaporation will not be a problem during the CE analysis. The rates of evaporation are considerably slower than the speed of the separation. To determine the feasibility of CE, a colored dye was placed on a 2 cm long column and high voltages attached to the two ends. Movement of a colored dye on the chip was observed under an electric field correspond to about 500 V/cm. This experiment indicates that CE can be performed on an open channel. The first experiments with MALDI of biomolecules, in this case oligosaccharides have been performed. (beta) -Cyclodextrin, a seven-membered cyclic oligosaccharide, was mixed with 3,5-dihydroxybenzoic acid (matrix) on an open channel. Striking the grove with a 337 nm beam from a N2 laser produces the mass spectrum of the compound with excellent resolution and high signal-to-noise.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.