Single-hole hollow nanospheres from enantioselective self-assembly of chiral AIE carboxylic acid and amine.

Phenylacrylonitrile tartaric acids have been found to enantioselectively self-assemble with an enantiomer of a chiral amine to form either nanofibers or nanospheres that exhibit aggregation-induced emission (AIE). The nanofibers exhibited stronger emission intensity and longer wavelengths of absorption and emission than the nanospheres because of increased π-π conjugation, an effect previously unseen in AIE. When the solvent consists of a mixture of water and THF rather than water and ethanol, the resultant nanospheres have holes. The holes are the result of the dissolution of defects and a decrease in the bending energy. This is in contrast to hole formation from solvents flowing out of the nanospheres, as previously seen. Through control of the water/THF ratio, the size of the holes in the nanospheres can be tuned. Nanospheres with a single hole displayed both higher uptake capacity and larger release speed of the drug naproxen than closed nanospheres. The ability to adjust fluorescent properties of AIE molecules through the preparation of organic single-hole hollow nanospheres has also been investigated along with the implications of the AIE mechanism.