Stephanie A Pruzinsky | PubMed Health

PubMed2005

Diffraction response of colloidal crystals: effect of numerical aperture.

We present a quantitative experimental and theoretical study of the effect of numerical aperture (NA) on the Bragg diffraction from a dry polystyrene colloidal crystal. The diffraction peak parameters changed noticeably as the NA was increased from 0.017 to 0.5. The diffraction wavelength blueshifted 1.4% from 584 to 576 nm, and the normalized full width at half-maximum increased from 6.2% to 7.0%. These shifts occurred primarily for NA > 0.3 and agreed qualitatively with results predicted by a layered Korringa-Kohn-Rostoker method. Thus, by using focusing optics with NAs below 0.3, the diffraction response of low-photonic-strength mesostructures may be compared with normal-incidence experimental and theoretical data.

Journal Article↗

PubMed2004

Glucose-sensitive inverse opal hydrogels: analysis of optical diffraction response.

A glucose-sensitive inverse opal hydrogel was synthesized through photopolymerization of 2-hydroxyethyl methacrylate and 3-acrylamidophenylboronic acid within the interstitial space of a dried poly(styrene) colloidal crystal template, followed by template removal. Charged complex formation between the phenylboronic acid functional group and the 1,2-cis-diol glucose resulted in reversible swelling of the inverse opal hydrogel, which was observed through shifts in the optical diffraction wavelength. The hydrogel was sensitive to glucose at physiological concentrations and ionic strength. The effects of phenylboronic acid concentration, ionic strength, and buffer pH on the equilibrium hydrogel swelling were also studied. The kinetics of hydrogel swelling was also examined, and it was found that the rate of diffraction shift matched well with diffusion-limited kinetics. Additionally, the diffraction response was compared with simulations using the scalar wave approximation and transfer matrix method.

Boronic Acids↗