Organic molecules having emission in the NIR(II) region are emergent and receiving enormous attention. Unfortunately, attaining accountable organic emission intensity around the NIR(II) region is hampered by the dominant internal conversion operated by the energy gap law, where the emission energy gap and the associated internal reorganization energy λ int play key roles. Up to the current stage, the majority of the reported organic NIR(II) emitters belong to those polymethines terminated by two symmetric chromophores. Such a design has proved to have a small λ int that greatly suppresses the internal conversion. However, the imposition of symmetric chromophores is stringent, limiting further development of organic NIR(II) dyes in diversity and versatility. Here, we propose a new concept where as far as the emissive state of the any asymmetric polymethines contains more or less equally transition density between two terminated chromophores, λ int can be as small as that of the symmetric polymethines. To prove the concept, we synthesize a series of new polymethines terminated by xanthen-9-yl-benzoic acid and 2,4-diphenylthiopyrylium derivatives, yielding AJBF1112 and AEBF1119 that reveal emission peak wavelength at 1112 and 1119 nm, respectively. The quantum yield is higher than all synthesized symmetric polymethines of 2,4-diphenylthiopyrylium derivatives (SC1162, 1182(SC1162, , 1185(SC1162, , and 1230) in this study. λ int were calculated to be as small as 6.2 and 7.3 kcal/mol for AJBF1112 and AEBF1119, respectively, proving the concept. AEBF1119 was further prepared as a polymer dot to demonstrate its in vitro specific cellular imaging and in vivo tumor/bone targeting in the NIR(II) region.

A series of NIR-II fluorescent TADF-incorporated polymer dots were successfully synthesized. The function of the TADF moiety was fully studied and the bio-applications of these polymer dots including bone imaging were also demonstrated.

Near-infrared-II (NIR-II, 1000–1700 nm) fluorescence imaging boasts high spatial resolution and deep tissue penetration due to low light scattering, reduced photon absorption, and low tissue autofluorescence. NIR-II biological imaging is applied mainly in the noninvasive visualization of blood vessels and tumors in deep tissue. In the study, a stereo NIR-II fluorescence imaging system was developed for acquiring three-dimension (3D) images on tumor vasculature in real-time, on top of the development of fluorescent semiconducting polymer dots (IR-TPE Pdots) with ultra-bright NIR-II fluorescence (1000–1400 nm) and high stability to perform long-term fluorescence imaging. The NIR-II imaging system only consists of one InGaAs camera and a moving stage to simulate left-eye view and right-eye view for the construction of 3D in-depth blood vessel images. The system was validated with blood vessel phantom of tumor-bearing mice and was applied successfully in obtaining 3D blood vessel images with 0.6 mm- and 5 mm-depth resolution and 0.15 mm spatial resolution. The NIR-II stereo vision provides precise 3D information on the tumor microenvironment and blood vessel path.

Creating infection resistant polymer brushes possessing antiadhesive, bactericidal and cell-compatible features can be regarded as a promising approach to prevent biomaterial-associated infections.

Herein, a new π‐electron‐delocalized building block (ProPh‐4CHO) is reported for the construction of a π‐electron‐extended porphyrin/pyrene‐linked covalent organic framework (ProPh‐PyTA‐COF) for use as a saturable absorber (SA) in a Q‐switched all‐solid‐state laser. Employing a mode‐locked fiber laser operated with 130‐fs pulses at 1030 nm and a repetition rate of 28 MHz, ProPh‐PyTA‐COF exhibits remarkable optical nonlinear absorptions: two saturable absorptions with saturation intensities of 92 MW cm−2 and 1 kW cm−2. This material is used to fabricate the first pulsed Q‐switched all‐solid‐state laser incorporating a COF as an absorber. The laser incorporating this COF‐SA exhibited a pump power of 6.5 W with a pulse duration of 1.2 μs, corresponding to a pulse repetition rate of 94.4 kHz. This study not only reveals the possibility of using saturation absorption to pulse a solid‐state laser but also opens up a new path toward optical nonlinearity through the engineering of π‐bond delocalization.