Advances in contemporary nanosphere lithographic techniques.

Nanosphere lithography (NSL) is an inexpensive, high throughput, materials general nanofabrication technique capable of producing a large variety of nanoscale structures including well-ordered 2 dimensional nanoparticle arrays. In this review, we will summarize the most recent advances in the fabrication of size-tunable nanoparticles using NSL. Four examples of new NSL-derived materials will be described: (1) The development of a method to release NSL nanoparticles from the substrate for applications in solution environments, (2) the fabrication of triangular nanoholes with reactive ion etching, (3) the electrochemical fine tuning of the structure of a silver nanoparticle and the wavelength of its localized surface plasmon resonance (LSPR), and (4) the growth of ultra thin protective dielectric layers on NSL-fabricated Ag nanotriangles using atomic layer deposition (ALD).

Plasmonic properties of film over nanowell surfaces fabricated by nanosphere lithography.

In this work, a detailed and systematic study of the plasmonic properties of a novel film over nanowell surface is investigated. These nanostructures are fabricated using nanosphere lithography and reactive ion etching and structurally characterized by AFM and SEM. The resulting structures show remarkably narrow plasmon bands in reflectance spectra (as little as 0.

Second harmonic excitation spectroscopy of silver nanoparticle arrays.

Frequency-scanned excitation profiles of coherent second harmonic generation (SHG) were measured for silver nanoparticle arrays prepared by nanosphere lithography. The frequency of the fundamental beam did not coincide with the localized surface plasmon resonance (LSPR) of the nanoparticles and was tuned so that the coherent second harmonic (SH) emission was in the region of the LSPR at 720-750 nm. The SH emission from the arrays was compared with a smooth silver film to identify an enhancement of SH emission efficiency that peaks near approximately 650 nm for nanoparticles 50 nm in height.

Electrochemical tuning of silver nanoparticles fabricated by nanosphere lithography.

An electrochemical method is developed to quantitatively modify and spectroscopically monitor the size and shape of Ag nanotriangles fabricated by nanosphere lithography (NSL) on an indium tin oxide (ITO) electrode surface. AFM and SEM results demonstrate that the preferential order of electrochemical oxidation for a nanotriangle is, surprisingly, bottom edges first, then triangular tips, then out-of-plane height.

Controlling plasmon line shapes through diffractive coupling in linear arrays of cylindrical nanoparticles fabricated by electron beam lithography.

The effect of diffractive coupling on the collective plasmon line shape of linear arrays of Ag nanoparticles fabricated by electron beam lithography has been investigated using Rayleigh scattering spectroscopy. The array spectra exhibit an intricate multi-peak structure, including a narrow mode that gains strength for interparticle distances that are close to the single particle resonance wavelength. A version of the discrete dipole approximation method provides an excellent qualitative description of the observed behavior.

Progesterone increases blood pressure in spontaneous gestational hypertension in rats.

Background: Gestational hypertensive disorders are a leading cause of maternal mortality in the US, accounting for up to 10% of these deaths. During pregnancy, a new rat model (SHHF rat) has been shown to develop spontaneous hypertension with increases of more than 40 mm Hg systolic blood pressure (BP), which resolves after delivery, and which lead us to ask whether the hypertension may be triggered by increased levels of progesterone in these rats.

Methods: To test this hypothesis, groups of SHHF rats were treated with progesterone (PROG), estrogen (EST), or progesterone and estrogen (PROG+EST) that correspond to levels that occur during pregnancy.

Nanosphere lithography: fabrication of large-area Ag nanoparticle arrays by convective self-assembly and their characterization by scanning UV-visible extinction spectroscopy.

This work employs UV-visible extinction spectroscopy as a new spectral mapping technique to characterize self-assembled polystyrene microsphere samples produced by convective self-assembly (CSA). This spectroscopic technique was successfully used to analyze the periodic particle arrays produced by the polystyrene template, yielding a detailed characterization of each sample. The CSA-prepared samples proved to be more uniform across a sample as well as more reproducible than previous sample preparation techniques.