Theranostic nanoagents that integrate the diagnoses and therapies within a single nanomaterial are compelling in their use for highly precise and efficient antitumor treatments. Herein, polyethylene glycol (PEG)-modified cobalt sulfide nanosheets (CoS-PEG NSs) are synthesized and unitized as a powerful theranostic nanoagent for efficient photothermal conversion and multimodal imaging for the first time. We demonstrate that the obtained CoS-PEG NSs show excellent compatibility and stability in water and various physiological solutions, and can be effectively internalized by cells, but exhibit a low cytotoxicity. The CoS-PEG NSs exhibit an efficient photothermal conversion capacity, benefited from the strong near-infrared (NIR) absorption, high photothermal conversion efficiency (~33.0%), and excellent photothermal stability. Importantly, the highly effective photothermal killing effect on cancer cells after exposure to CoS-PEG NSs plus laser irradiation has been confirmed by both the standard Cell Counting Kit-8 and live-dead cell staining assays, revealing a concentration-dependent photothermal therapeutic effect. Moreover, utilizing the strong NIR absorbance together with the T2-MR contrast ability of the CoS-PEG NSs, a high-contrast triple-modal imaging, i.e., photoacoustic (PA), infrared thermal (IRT), and magnetic resonance (MR) imaging, can be achieved, suggesting a great potential for multimodal imaging to provide comprehensive cancer diagnosis. Our work introduces the first bioapplication of the CoS-PEG nanomaterial as a potential theranostic nanoplatform and may promote further rational design of CoS-based nanostructures for precise/efficient cancer diagnosis and therapy.

Supramolecular self-assembly of the organic semiconductor perylene-3, 4, 9, 10-tetracarboxylic diimide (PTCDI) together with Ni atoms on the inert Au(111) surface has been investigated using high-resolution scanning tunneling microscopy under ultrahigh vacuum conditions. We demonstrate that it is possible by tuning the co-adsorption conditions to synthesize three distinct self-assembled Ni-PTCDI nanostructures from zero-dimensional (0-D) nanodots over one-dimensional (1-D) chains to a two-dimensional (2-D) porous network. The subtle interplay among non-covalent interactions responsible for the formation of the observed structures has been revealed from force-field structural modeling and calculations of partial charges, bond orders and binding energies in the structures. A unifying motif for the 1-D chains and the 2-D network is found to be double N-H…O hydrogen bonds between PTCDI molecules, similar to the situation found in surface structures formed from pure PTCDI. Most interestingly, we find that the role of the Ni atoms in forming the observed structures is not to participate in metal-organic coordination bonding. Rather, the Ni adatoms acquire a negative partial charge through interaction with the substrate and the Ni-PTCDI interaction is entirely electrostatic.