The overproduction of acidic by products is implicated in the development of numerous diseases, and there is currently great interest in developing contrast agents that can image acidic tissue in vivo. Here we report a biodegradable pH-sensing near-infrared (NIB) nanoprobe capable of providing both fluorescence intensity amplification and lifetime information. The pH-sensing NIR nanoprobe is synthesized, in six high yielding and scalable steps, and functions within the tissue transparency window. Both fluorescence intensity and lifetime provided complementary physiological (low pH) and molecular (released fluorophore binding to albumin) information, respectively.