User:Moira M. Esson/Notebook/CHEM-581/2013/02/13

Objectives

1. Determine the lower and upper limit of detection of Rhodamine 6G on the fluorimeter.
2. Run fluoroscopy of all hydrogel samples that were placed in distilled H₂O to soak on 2013/02/06.
3. Run diffusion test on prepared microspheres(PVOH 146K MW and Lamponite clay in a 90:10 ratio) with Rhodamine 6G dye added.

Notes

• The microspheres prepared on 2013/02/08 did not form microsphere structures. After placing on the lyophilizer for over 48 hours, a large, solid clump of pure white material formed. This indicates that the emulsion that was prepared was not sufficient for the precipitaiton of microsphere structures. A mortar and pestle was used to grind the large PVOH and clay solid in an attempt to create microsphere structures. DSC will be run of these structures.
• The two hydrogels prepared on 2013/02/08 were removed from the freezer to thaw for their last freeze-thaw cycle. During the next lab session, these hydrogels will be placed in distilled H₂O to soak.
• After observation of the hydrogels that were allowed to soak in Rhodamine 6G 1μM solution, it was apparent that the concentration of Rhodamine 6G was enough in the gel. A small, second fraction of 3mL of 1μM Rhodamine 6G was added to the hydrogels. The hydrogels will be allowed to soak until 02/15/13, when diffusion tests will be run on the samples.
• Due to the lack of success with the preparation of PVOH/clay microspheres, a new method for the preparation of microspheres will be used. An aqueous solution of PVOH/clay will be suspended in mineral oil with the necessary amount of DMSO additive. This will be suspended and emulsified for approximately 20 minutes at 90°C. The prepared microspheres will then undergo the freeze thaw method utilized by the hydrogels.

Fluorescence

Rhodamine 6G limit of detection:

• A 1μM solution of Rhodamine 6G in water was prepared by diluting the 92μM Rhodamine 6G solution in DMSO with distilled H₂O.

 (1μM)(5000μL)/(92μM)=54.34μL

• This solution proved to be too concentrated. A 0.5μM solution of Rhodamine 6G in water was prepared by diluting the 92μM Rhodamine 6G solution in DMSO with distilled H₂O.

 (0.5μM)(5000μL)/(92μM)=27.17μL

• This solution was still too concentrated. A 0.25μM solution of Rhodamine 6G in water was prepared by diluting the 0.5μM Rhodamine 6G solution with distilled H₂O.

 (0.25μM)(5000μL)/(0.5μM)=2.5mL

• This solution produced a readable spectra. 0.25μM appears to be the upper limit of detection for Rhodamine 6G. All future data will be collected using a 0.25μM concentration of Rhodamine 6G.

Hydrogel Fluorescence:

• Fluorescence was run on the distilled H₂O that was soaking the hydrogels placed in distilled H₂O on