Contrast enhanced photoacoustic (PA) imaging has the potential for deep tissue imaging, but clinically approved exogenous agents, such as indocyanine green (ICG), have poor photostability, low photothermal efficiency and poor blood retention that limit their use in vivo. Additionally, commonly used PA contrast agents have optical extinction peaks in the first near infrared (NIR-I) window, where light attenuation by tissue is high. Plasmonic nanoparticles (NPs) have high tunable localized surface plasmon resonance (LSPR)-induced optical extinction, allowing imaging at NIR-II wavelengths where light penetration is maximized in biological tissues. However, conventional plasmonic NPs, such as gold nanorods (AuNRs) bioaccumulate at sizes needed for NIR-II LSPR. Semiconductor nanocrystals (NCs), such as copper sulfides (CuxS), exhibit NIR-II optical extinction without size modulation. However, compared to AuNRs, typical CuxS have reduced peak LSPR due to lower densities of free charge carriers. Hence, our group is interested in characterizing novel biocompatible and biodegradable NIR-II PA contrast agent capable of translating PA systems for transabdominal imaging.