Nonconventional Luminescence of Hyperbranched Polysiloxanes for Film Fabrication and Bacterial Imaging

Nonconventional luminescent polymers devoid of extended π-conjugation have drawn considerable attention because of their potential applications and theoretical implications. Herein, hyperbranched polysiloxane with a C═C backbone (HPSi-1) exhibits enhanced and red-shifted emission compared to HPSi-2, bearing a C–C backbone, with a high absolute photoluminescence quantum yield (QY) of 11%. Notably, as HPSi-1 content increased, the excitation/emission wavelength of polyacrylamide (PAAm)/HPSi-1 films red-shifted from 320/390 to 400/466 nm, achieving a QY as high as 29.9%. These results indicate that the aggregation of polymer molecules within the matrix increases with increasing HPSi-1 content, thereby enhancing through-space interactions and restricting molecular motion, which significantly improves the fluorescence performance. The fluorescence of HPSi-1 is stable under various pH conditions and can be selectively quenched by Fe³⁺. Furthermore, HPSi-1 serves as an effective fluorescent probe for imaging Escherichia coli cells. This work provides a strategy to enhance the fluorescence performance of nonconventional luminescent polymers and broaden their application in bioimaging.