To enhance PCE, researchers constructed various structural BODIPYs, which are often involved in intramolecular charge transfer (ICT), photoinduced electron transfer (PET), rotating segments and so forth. For instance, Ma
et al. showed a BODIPY-based PTA, enhanced phototherapeutic performance of which is resulted from the reduction of radiation transition by ICT [
34]. Based on PET to quench the fluorescence, Huang
et al. reported dimethylamino-substituted aza-BODIPY with a moderate PCE (
η = 35%) [
35]. Especially, the low-barrier rotation strategy of a bulky group (such as –CF
3, –
tBu) is employed to directly promote non-radiative decay. In 2017, our group prepared NIR-absorbing
meso-CF
3-BODIPYs by one-pot synthesis for the first time and reveal the property of non-fluorescent emission [
36]. In 2019, Xi
et al. successfully discovered the highest PCE (
η = 88.3%) of this
meso-CF
3-BODIPY [
37]. Very recently, our group successfully synthesized 1,7-di
-tert-butyl-substituted aza-BODIPY for the first time [
38]. Although the low-barrier rotation of the distal –
tBu groups in aza-BODIPY results in low quantum yield, the PCE (
η = 48%) is remarkably enhanced [
38]. Thereby, by restricting fluorescence and ISC, the enhancement of PCE could be achieved by high-efficiency non-radiative decay [
39]. Herein, to understand the influence of the –CF
3 rotation effect on non-radiation attenuation profoundly, 1,7-diphenyl-substituted
meso-CF
3-BODIPY (namely
meso–CF3-BDP) was designed (
Fig. 1a). The crystal structure showed obvious slip-stacked alignment (
θ = 24°), and the dye nanoparticles constituted by self-assembly emerged obvious bathochromic-shift (λ
abs = 746 nm) due to
J-aggregates. In addition, the low-barrier rotation of the –CF
3 group can directly promote non-radiative decay. Self-assembled
meso–CF3-BDP 1 nanoparticles (namely
1-NPs) showed excellent PCE (
η = 82%), which is highly desirable for an effective and potential tumor PTA. Although the photothermal radiation with different photon intensity is acquainted by trigger cell death through either necrosis or apoptosis [
40], PTT is usually engaged in necrosis mechanism. In contrast, PTT caused by apoptosis pathway is rarely reported [
40,
41]. Furthermore, based on American National Standard for Safe Use of Lasers Outdoors, the maximum permissible exposure (MPE) for skin exposure is 0.2 W/cm
2 at the 635 nm laser. Hence, the safe PTT at low power laser density should be advocated and could be involved in the apoptosis mechanism. In this work,
1-NPs fabricated by
J-aggregates could induce the cancer cells death at low laser power density by triggering the apoptosis mechanism, which is fascinating since apoptosis discourages an inflammatory response (
Fig. 1b). As a result, this study proposes an alternate molecular design platform by
J-aggregates to enhance PCE through the insertion of rotating segment (–CF
3) and trigger the cancer cells apoptosis in PTT under low power laser irradiation.