How do I create a concentrated solution of singlet oxygen (in the dark)?
Potassium ferricyanide (and other ion complexes, like hemoglobin) will decompose hydrogen peroxide into water and (presumably) singlet oxygen. This process is necessary for the luminol reaction. 

$$\ce{2H2O2 \overset{Fe}{-&gt;} 2H2O + ^1O2}$$