Bismuth sulfide (Bi S ) nanomaterials are emerging as a promising theranostic platform for computed tomography imaging and photothermal therapy of cancer. Herein, the photothermal properties of Bi S nanorods (NRs) were unveiled to intensely correlate to their intrinsic deep-level defects (DLDs) that potentially could work as electron-hole nonradiative recombination centers to promote phonon production, ultimately leading to photothermal performance. Bi S -Au heterojunction NRs were designed to hold more significant DLD properties, exhibiting more potent photothermal performance than Bi S NRs. Under 808 nm laser irradiation, Bi S -Au NRs could trigger higher cellular heat shock protein 70 expression and more apoptotic cells than Bi S NRs, and caused severe cell death and tumor growth inhibition, showing great potential for photothermal therapy of cancer guided by computed tomography imaging.

Gold (Au) core@void@copper sulfide (CuS) shell (Au-CuS) yolk-shell nanoparticles (YSNPs) were prepared in the present study for potential chemo-, photothermal, and photodynamic combination therapy, so-called "chemophototherapy". The resonance energy transfer (RET) process was utilized in Au-CuS YSNPs to achieve both enhanced photothermal and photodynamic performance compared with those of CuS hollow nanoparticles (HNPs). A series of Au nanomaterials as cores that had different localized surface plasmon resonance (LSPR) absorption peaks at 520, 700, 808, 860, and 980 nm were embedded in CuS HNPs to screen the most effective Au-CuS YSNPs according to the RET process. Thermoresponsive polymer was fabricated on these YSNPs' surface to allow for controlled drug release. Au-CuS and Au-CuS YSNPs were found capable of inducing the largest temperature elevation and producing the most significant hydroxyl radicals under 808 and 980 nm laser irradiation, respectively, which could accordingly cause the most severe 4T1 cell injury through oxidative stress mechanism. Moreover, doxorubicin-loaded (Dox-loaded) P(NIPAM-co-AM)-coated Au-CuS (p-Au-CuS@Dox) YSNPs could more efficiently kill cells than unloaded particles upon 980 nm laser irradiation. After intravenous administration to 4T1 tumor-bearing mice, p-Au-CuS YSNPs could significantly accumulate in the tumor and effectively inhibit the tumor growth after 980 nm laser irradiation, and p-Au-CuS@Dox YSNPs could further potentiate the inhibition efficiency and exhibit excellent in vivo biocompatibility. Taken together, this study sheds light on the rational design of Au-CuS YSNPs to offer a promising candidate for chemophototherapy.

Thermoelectric materials can be used to convert waste heat into electrical energy, which is considered to be a cleaner form of energy that reduces carbon dioxide and greenhouse gas emissions.