Measurement of dissolved oxygen based on the phosphorescence of lumophore and quantum dots.

摘要

Unsaturated dissolved oxygen can be measured easily using oxygen probes based on electrochemistry. However, supersaturated dissolved oxygen is difficult to measure by traditional methods. A technique to measure supersaturated dissolved oxygen (SSDO) using caged lumophores is introduced. Intense phosphorescence is observed when a molecular "lid" is introduced to aqueous solutions containing 1-bromonaphthalene and beta-cyclodextrin. The phosphorescence enhancement induced by the "lid" is related to its effectiveness in shielding the photo-excited 1-bromonaphthalene from dissolved oxygen. By relating the concentration of oxygen to the intensity and the lifetime of the phosphorescence of 1-bromonaphthalene, the dissolved oxygen concentration can be measured. Currently, this technique using the complex with neopentanol can measure oxygen from 0 mM to 40.2 mM (31,390% saturation). However, the "cap" is connected with cyclodextrin through hydrogen bond.; Four alkyl modified beta-cyclodextrins (CD): 6-O-pentyl-CD, 6-O-hexyl-CD, 6-O-octyl-CD, and 6-neopentyl-CD were synthesized as molecular cages for 1-bromonaphthalene (1-BrNp) to detect SSDO. The luminescence enhancement of the covalently-bound "lids" (i.e. the alkyl groups) was compared to the hydrogen-bound "lids" of alcohol-CD ternary complexes. The alkyl-modified CD gave much larger luminescence intensity than did the alcohol-CD complexes. Because the alcohols are not covalently bound to the CD, they are less efficient at shielding the CD. Among the four different alkyl-modified CD, 1-BrNp in 6-O-neopentyl-CD shows the largest fluorescence and phosphorescence intensity. By relating the concentration of oxygen to the lifetime of the phosphorescence, the dissolved oxygen concentration can be measured.; Semiconductor nanoparticles, "quantum dot", have unique properties unlike the bulk materials, due to quantum size confinement effects. ZnS nanocrystrals are synthesized with zinc stearate and elemental sulfur as the precursors. Spherical ZnS nanoparticles (∼2nm) were obtained and characterized using several different techniques (XRD, SEM, TEM and UV-Vis). The long chain amines were exchanged with 11-mercaptoundecanoic acid, making the ZnS nanoparticles water soluble. Calibrating the fluorescence lifetime of ZnS and different dissolved oxygen concentration, the dissolved oxygen concentration can be measured.