6.4.3 Particle Size Analysis

 Size analysis was performed before TMOS addition, and after reaction and dialysis. This

allowed determination of the core diameter and shell thickness for every nanocapsule sample

prepared. All samples were diluted to avoid interparticle aggregation and filtered prior to size

analysis using 0.22 pum pore size filters (Fisher Scientific). DLS was used to follow changes in

particle sizes with a Precision Detectors PDDLS/CoolBatch+90T instrument. The data were

analyzed with the Precision Deconvolve32 Program. Measurements were taken at 20 OC at a 900

scattering angle using a 632 nm laser source. Final sizes were obtained from the average of at

least five reproducible results.

6.4.4 Spectroscopy Measurements

 UV-vi s absorption spectra were recorded on a UV-vi s Varian CARY 500

spectrophotometer, and excitation and fluorescence emission spectra were measured on a SPEX

Fluorolog-3 (Jobin-Yvon). A right-angle configuration was used. The optical density of the

samples was checked to be less than 0.1 to avoid reabsorption artifacts. Iodine and Nile Red are

both commercially available (Aldrich Chemical Co.). The Nile Red stock solution was prepared

by placing 2 mg of Nile Red in 5 mL of methanol, filtering with a 0.22 pum Millipore filter, and

adding the saturated Nile Red methanol solution to 100 mL of acidic water (pH = 1.2).

 UV-vis absorption spectra were recorded after mixing thoroughly 1 mL of a saturated

iodine aqueous solution with reference solutions consisting of 2 mL of water, 2 mL of ethyl

butyrate, 2 mL of water with 1 drop of Tween-80, and 1 mL of water with 1 mL of nanocapsule

solution.

 Fluorescence spectra were recorded on Nile Red after excitation at 595 nm. For the

measurements involving the three aqueous solutions (nanocapsules, Tween-80 aqueous solution,

and acidic water), fluorescence spectra were recorded after mixing 0.5 mL of the Nile Red stock