Templated photonic crystal fabrication of stoichiometrically complex nanoparticles for resonance raman solid cross section determinations

Development of methods to fabricate nanoparticles is of great interest for many applications. In this paper, we developed a facile method to fabricate complex stoichiometrically defined nanoparticles by ultilizing the defined volume interstices of close-packed photonic crystals. Fabrication of small defined size nanoparticles enables measurements of resonance Raman cross sections of solid materials. We successfully ultilized this method to fabricate mixed NaNO3/Na2SO4 nanoparticles with a defined stoichiometry on the surface of the photonic crystal spherical particles. We used these stoichiometrically defined NaNO3/Na2SO 4 nanoparticles to determine the solid UV resonance Raman cross section of the NO31 symmetric stretching band (229 nm excitation wavelength) by monitoring the Raman spectrum of Na2SO4 as an internal standard. These are the first resonance Raman cross section measurements of solids that avoid the biasing of self-absorption. These NaNO3/Na2SO4 nanoparticles appear to show a more facile photolysis than is observed for normal solid NaNO3 samples. This templated photonic crystal fabrication of complex nanoparticle method will be important for many applications. © 2011 American Chemical Society

Nanoparticles of Polyethylene Sebacate: A New Biodegradable Polymer

The present study demonstrates feasibility of preparation of nanoparticles using a novel polymer, polyethylene sebacate (PES), and its application in the design of drug-loaded nanocarriers. Silymarin was selected as a model hydrophobic drug for the present study. Two methods of preparation, viz., nanoprecipitation and emulsion solvent diffusion, were evaluated for preparation of nanoparticles. Effect of surfactants polyvinyl alcohol (PVA), lutrol F 68, and Tween 80 on the preparation of blank and silymarin-loaded PES nanoparticles was evaluated. Nanoprecipitation resulted in the formation of nanoparticles with all the surfactants (<450 nm). Increase in surfactant concentration resulted in decrease in entrapment efficiency and particle size except with PVA. The type and concentration of surfactant was critical to achieve low size and adequate drug entrapment. While increase in concentration of PES resulted in larger nanoparticles, inclusion of acetone in the organic phase resulted in particles of smaller size. In case of emulsion solvent diffusion, nanoparticles were obtained only with lutrol F 68 as surfactant and high surfactant concentration. The study revealed nanoprecipitation as a more versatile method for preparation of PES nanoparticles. Scanning electron microscopy studies revealed spherical shape of nanoparticles. Freeze-dried nanoparticles exhibited ease of redispersion, with a marginal increase in size. Differential scanning calorimetry and X-ray diffraction analysis revealed amorphous nature of the drug. The study demonstrates successful design of PES nanoparticles as drug carriers