Fluorescence-based biosensing and bioimaging technologies are widely used in research and clinical settings to detect and image various biological species of interest. While fluorescence-based detection and imaging techniques are convenient to use, they suffer from poor sensitivity. For example, when a patient carries low levels of antigens in the blood or urine, the fluorescent signal can be feeble, making visualization and diagnosis difficult. For this reason, fluorescence-based detection is not always preferred when sensitivity is a key requirement.