This Focus Review describes the emerging class of near-infrared (NIR) organic compounds containing the conjugated polyene, polymethine, and donor-acceptor chromophores and exploration of their NIR-absorbing, NIR-fluorescence, and NIR-photosensitizing properties for potential applications in heat absorbers, solar cells, and NIR light-emitting diodes. Examples of NIR organic compounds are reviewed with emphasis on the molecular design, NIR absorption, and fluorescence and particular emerging applications. The donor-acceptor type of NIR chromophores are particularly introduced owing to some unique features, including the designer-made energy gaps, facile synthesis, good processability, and controllable morphology and properties in the solid state. Future directions in research and development of NIR organic materials and applications are then offered from a personal perspective.

A series of D-π-A-π-D type of near-infrared (NIR) fluorescent compounds based on benzobis(thiadiazole) and its selenium analogues were synthesized and fully characterized by 1 H and 13 C NMR, highresolution mass spectrometry, and elemental analysis. The absorption, fluorescence, and electrochemical properties were also studied. Photoluminescence of these chromophores ranges from 900 to 1600 nm and their band gaps are between 1.19 and 0.56 eV. Replacing the sulfur by selenium can lead to a red shift for emission and reduce the band gaps further. Interestingly, compound 1 exhibits aggregationinduced emission enhancement effect in the solid state. All-organic light-emitting diodes based on M1 and M2 were made and exclusive NIR emissions above 1 µm with external quantum efficiency of 0.05% and maximum radiance of 60 mW Sr -1 m -2 were observed. The longest electroluminescence wavelength reaches 1115 nm.

No abstract

A series of NIR organic chromophores with donor–π–acceptor–π–donor structure are synthesized. Good thermal stability and strong photoluminescence in solid state render them suitable for application in light‐emitting diodes. Exclusive near‐infrared emission at 1080 nm with external quantum efficiency of 0.28% is obtained from the nondoped OLEDs. The longest electroluminescence wavelength is 1220 nm.

[structure: see text] Described here are the synthesis and optical and electrochemical properties of a series of indenofluorenes as new building blocks for electronic and optoelectronic materials.

Small-sized PbSe nanocrystals (NCs) were syn-thesized at low temperature such as 50−80 °C with high reaction yield (up to 100%), high quality, and high synthetic reproducibility, via a noninjection-based one-pot approach. These small-sized PbSe NCs with their first excitonic absorption in wavelength shorter than 1200 nm (corresponding to size < ∼3.7 nm) were developed for photovoltaic applications requiring a large quantity of materials. These colloidal PbSe NCs, also called quantum dots, are high-quality, in terms of narrow size distribution with a typical standard deviation of ∼7−9%, excellent optical properties with high quantum yield of ∼50−90% and small full width at half-maximum of ∼130−150 nm of their band-gap photoemission peaks, and high storage stability. Our synthetic design aimed at promotion of the formation of PbSe monomers for fast and sizable nucleation with the presence of a large number of nuclei at low temperature. For formation of the PbSe monomer, our low-temperature approach suggests the existence of two pathways of Pb−Se (route a) and Pb−P (route b) complexes. Either pathway may dominate, depending on the method used and its experimental conditions. Experimentally, a reducing/nucleation agent, diphenylphosphine, was added to enhance route b. The present study addresses two challenging issues in the NC community, the monomer formation mechanism and the reproducible syntheses of small-sized NCs with high yield and high quality and large-scale capability, bringing insight to the fundamental understanding of optimization of the NC yield and quality via control of the precursor complex reactivity and thus nucleation/growth. Such advances in colloidal science should, in turn, promote the development of next-generation low-cost and high-efficiency solar cells. Schottky-type solar cells using our PbSe NCs as the active material have achieved the highest power conversion efficiency of 2.82%, in comparison with the same type of solar cells using other PbSe NCs, under Air Mass 1.5 global (AM 1.5G) irradiation of 100 mW/cm2.

Liver tumor is one of the most lethal cancers due to its low ratio of surgical resection, high recurrence rate, and invasiveness. Photothermal therapy (PTT) possesses many advantages for cancer therapy because of its noninvasive nature. However, most PTT is conducted in the first near-infrared (NIR-I) window, so second nearinfrared (NIR-II) photosensitizers with higher penetrating ability and clinical prospects are seriously desirable. Herein, a semiconducting polymer with optimized absorption in NIR-I and NIR-II regions is obtained by ternary copolymerization methodology. The prepared nanoparticle (NP) from the semiconducting polymer is used for treatment of orthotopic liver cancer upon laser irradiation. Compared with an 808 nm laser, a 1064 nm laser leads to more effective inhibition toward orthotopic liver cancer in the same conditions. These results thus demonstrate that the NIR-II polymeric NPs may inspire another aspect for highly efficient therapy of various orthotopic cancers.

A green tea polyphenol fraction was evaluated for its ability to inhibit tumor initiation by polycyclic aromatic hydrocarbons and tumor promotion by a phorbol ester in the skin of CD-1 mice. Topical application of the green tea polyphenol fraction inhibited benzo[a]pyrene- and 7,12-dimethylbenz[a]-anthracene-induced tumor initiation as well as 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion. Topical application of the green tea polyphenol fraction also inhibited TPA-induced inflammation, ornithine decarboxylase activity, hyperplasia and hydrogen peroxide formation. Studies with individual polyphenolic compounds in green tea indicated that topical application of (-)-epigallocatechin gallate, (-)-epigallocatechin and (-)-epicatechin gallate inhibited TPA-induced inflammation in mouse epidermis.