Double J-Coupling Strategy for Near Infrared Emitters.

Fluorophores emitting in the near-infrared (NIR) are highly desired for various applications, but increasing nonradiative rates cause severe fluorescence quenching for wavelengths beyond 800 nm. Here, a bis(squaraine) dye is reported that bears two NIR dyes in a head-to-tail chromophore arrangement. This arrangement leads to intramolecular J-type exciton coupling, resulting in an absorption maximum at 961 nm and a fluorescence peak at 971 nm with a quantum yield of 0.33% in chloroform. In less polar toluene, the bis(squaraine) self-assembles into nanofibers, affording another bathochromic shift with an absorption maximum at 1095 nm and a fluorescence peak at 1116 nm originating from intermolecular J-type coupling.

Polymorphism in Squaraine Dye Aggregates by Self-Assembly Pathway Differentiation: Panchromatic Tubular Dye Nanorods versus J-Aggregate Nanosheets.

A bis(squaraine) dye equipped with alkyl and oligoethyleneglycol chains was synthesized by connecting two dicyanomethylene substituted squaraine dyes with a phenylene spacer unit. The aggregation behavior of this bis(squaraine) was investigated in non-polar toluene/tetrachloroethane (98:2) solvent mixture, which revealed competing cooperative self-assembly pathways into two supramolecular polymorphs with entirely different packing structures and UV/Vis/NIR absorption properties. The self-assembly pathway can be controlled by the cooling rate from a heated solution of the monomers. For both polymorphs, quasi-equilibrium conditions between monomers and the respective aggregates can be established to derive thermodynamic parameters and insights into the self-assembly mechanisms. AFM measurements revealed a nanosheet structure with a height of 2 nm for the thermodynamically more stable polymorph and a tubular nanorod structure with a helical pitch of 13 nm and a diameter of 5 nm for the kinetically favored polymorph. Together with wide angle X-ray scattering measurements, packing models were derived: the thermodynamic polymorph consists of brick-work type nanosheets that exhibit red-shifted absorption bands as typical for J-aggregates, while the nanorod polymorph consists of eight supramolecular polymer strands of the bis(squaraine) intertwined to form a chimney-type tubular structure. The absorption of this aggregate covers a large spectral range from 550 to 875 nm, which cannot be rationalized by the conventional exciton theory. By applying the Essential States Model and considering intermolecular charge transfer, the aggregate spectrum was adequately reproduced, revealing that the broad absorption spectrum is due to pronounced donor-acceptor overlap within the bis(squaraine) nanorods. The latter is also responsible for the pronounced bathochromic shift observed for the nanosheet structure as a result of the slip-stacked arranged squaraine chromophores.

NIR-emitting squaraine J-aggregate nanosheets.

Click chemistry and Yamamoto coupling afforded an S-shaped π-scaffold composed of two directly connected dicyanomethylene-substituted squaraine dyes. This bis(squaraine) self-assembles into nanosheets in a cooperative self-assembly process, affording an absorption maximum at 886 nm and a fluorescence peak at 904 nm due to strong J-type exciton coupling.

Enamel defects in permanent teeth of patients with cleft lip and palate: a cross-sectional study.

OBJECTIVE: This study investigated the prevalence, type, and location of enamel defects in the permanent teeth of patients with complete unilateral or bilateral cleft lip and palate (CLP), and compared the prevalence and characteristics of defects between CLP patients and non-CLP individuals. METHODS: We examined completely erupted permanent dentition, except for third molars, of CLP patients and non-CLP individuals of both sexes, 9-36 years of age, and analyzed corresponding panoramic radiographs. Two independent examiners performed clinical examinations in accordance with the Modified Developmental Defects of Enamel index. RESULTS: A total of 210 (87.9%) CLP patients and 194 (41.4%) non-CLP individuals had at least one enamel defect; these were more prevalent in the CLP group than in the non-CLP group. Upper teeth were primarily affected by enamel defects associated with the cleft; defects were most prevalent on the cleft side in CLP patients, followed by the non-cleft side in CLP patients, and then by non-CLP individuals. CONCLUSION: Enamel defects were more common in CLP patients than in non-CLP individuals. Among CLP patients, enamel defects were more prevalent in the cleft side of the maxilla; the central incisor was the most commonly affected tooth in this quadrant.

Selective parallel G-quadruplex recognition by a NIR-to-NIR two-photon squaraine.

Fluorescence imaging probes for specific G-quadruplex (G4) conformations are of considerable interest in biomedical research. Herein, we present the synthesis and the binding properties of a new water-soluble near-infrared (NIR) amphiphilic squaraine dye (CAS-C1) which is capable of selective detection of parallel over non-parallel and non G4 topologies. The striking changes in its linear optical response upon binding to parallel G4s give rise to high fluorescence quantum yields (Φ f ≈ 0.7) and one-photon molecular brightness in the far-red-NIR region. The outstanding recognition process of CAS-C1 for parallel G4s via end-stacking provides binding constants in the nanomolar regime (K b = 107 to 108 M-1) awarding it as one of the most potent parallel G4 binders currently available. Moreover, the CAS-C1-parallel G4 system exhibits large two-photon absorption (TPA) cross-sections and molecular brightness in the second NIR biological transparency window (λ ≈ 1275 nm), making it an ideal candidate for NIR-to-NIR ultrasensitive two-photon procedures.