This is a truly unique molecule that can crosslink NPs upon light stimulus. When the nanoparticles are stabilized by surfactants (e.g., dodecylamine, DDA) and this dithiol is added, spontaneous nanoparticle crosslinking is entropically unfavorable. When, however, the sample is exposed to UV light, the central azobenzene group isomerizes into the so-called cis-form characterized by the presence of electric dipole (ca. 4 debye). The dipole-dipole forces between dithiols on different NPs bring these nanoparticles close together and allow the terminal thiolate groups to crosslink the NPs into either supraspheres (Science2007, 316, 261-264) or into crystalline aggregates (Proc. Natl. Acad. Sci. U.S.A.2007, 104, 10305-10309). In this way, light stimulus effectively controls and directs nanoscale self-assembly. A very unique compound, indeed!