Evoking Photothermy by Capturing Intramolecular Bond Stretching Vibration-Induced Dark-State Energy

Abstract

Development of highly effective approaches to desirable photothermal conversion agents is particularly valuable. Herein, we report a concept, namely, bond stretching vibration-induced photothermy, that serves as a mechanism to construct advanced photothermal conversion agents. As a proof-of-concept, two compounds (DCP-TPA and DCP-PTPA) with donor–acceptor (D–A) structures were synthesized. The bond stretching vibration of the pyrazine-containing unit in these molecules is vigorous and insensitive to the external environmental restraint, which efficiently transforms the absorbed photons to dark-state heat energy. The nanoparticles (NPs) of DCP-TPA and DCP-PTPA show rather high photothermal conversion efficiency (52% and 59%) and stronger photoacoustic (PA) signal than commercial methylene blue and reported high-performance semiconducting polymer nanoparticles. The DCP-PTPA NPs perform better than DCP-TPA NPs in terms of photothermal conversion, PA signal production, and in vivo PA tumor imaging because of the increased bond stretching vibration in the former molecule.

Charge Transfer Metal‐Organic Framework Containing Redox‐Active TTF/NDI Units for Highly Efficient Near‐Infrared Photothermal Conversion

“…The near‐infrared (NIR) photothermal effect has attracted a great deal of interest owing to various applications such as night‐vision technologies [7] . Benefitting from NIR light's typical biological tissue penetration, low photodamage, and low optical scattering, NIR photothermal materials could also be useful in photothermal therapy, [8] diagnosis, [9] and photothermal imaging [10] .…”

“…[6] The near-infrared (NIR) photothermal effect has attracted a great deal of interest owing to various applications such as night-vision technologies. [7] Benefitting from NIR light's typical biological tissue penetration, low photodamage, and low optical scattering, NIR photothermal materials could also be useful in photothermal therapy, [8] diagnosis, [9] and photothermal imaging. [10] In order to pursue high-performance NIR photothermal conversion materials, extensive efforts were made from two aspects: one is to enhance infrared absorption [11] by linking electron donors and acceptors covalently or expanding molecular conjugation length; [12] the other is to restrain the radiative transition process through increasing the concentration of free radicals or enhancing the quenching effect.…”

An All‐Round Athlete on the Track of Phototheranostics: Subtly Regulating the Balance between Radiative and Nonradiative Decays for Multimodal Imaging‐Guided Synergistic Therapy

“…On the other hand, the intramolecular bond stretching vibration as another high-frequency molecular motion is less susceptive to the external environmental constraints compared with the intramolecular rotation, making it extremely advantageous in boosting the heat production inside NPs. [39][40] Based on this consideration, two malononitrile-modified indane was chosen as electronic acceptor, not only because of its extreme electron deficiency, but also mainly regarding the vigorous stretching vibrations of CN bonds in the structure, which is decidedly conducive to the intramolecular motion in aggregate state and highly promising to serve as a forceful supplementary to the intramolecular rotation for guaranteeing favorable PTT-PTI-PAI efficiency within NPs. Evidently, these aforementioned structural features would endow these compounds with AIE characteristics and equip the resulting AIE NPs with prominent versatility as well as longer emission wavelength.…”

Gathering brings strength: How organic aggregates boost disease phototheranostics

“…PA imaging is an emerging noninvasive and nonionized biomedical imaging modality that has attracted considerable interest as it could provide high penetration depth, spatial resolution, and 3D images 134,135 . And, the penetration depths of PA imaging in NIR‐I and NIR‐II region are as high as 5 cm and 11 cm 136–138 .…”