Thiocarbonyl compounds possess unusual photophysical properties they fluoresce from S-2 phosphoresce from T-1 only at extremely low concentrations in solution at room temperature have unit quantum yield of intersystem crossing from S-1 to T-1 undergo self-quenching at diffusion-controlled rates and are quenched by ground-state oxygen leading to self-destruction In this article, we are concerned with finding a new method to observe phosphorescence from throketones at room temperature in aqueous solution at high concentrations To achieve this goal, one needs to find ways to eliminate diffusion-limited self-quenching and oxygen quenching We present here a general strategy that has allowed us to record phopshorescence from a number of throketones in aqueous solution at room temperature The method involves encapsulation of throketone molecules within a "closed nanocontainer made up of two cavitand molecules known by its trivial name as octa acid In these supramolecular complexes, despite two throcarbonyl compounds being present in close proximity, no self-quenching occurs within the confined space due to curtailment of their rotational freedom Although phosphorescence could also be observed when these thioketones are included in open containers such as cucurbiturils and cyclodextrines the closed container made up of octa acid is found to be the best medium to observe phosphorescence from throketones whose excited state chemistry is essentially controlled by self-quenching