Novel conjugates of nanoparticles are provided and have particular utility in the detection of latent fingerprints by their ability to bind to a fingerprint residue. The conjugate comprises a nanoparticle attached to a linker group having a terminal reactive moiety, wherein said nanoparticle comprises a core of a first semiconductor material having a first luminescence and a shell of a second material which at least partially surrounds the core. The conjugated nanoparticle can bind to the fingerprint residue and can be detected using fluorescence.