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Crystallization and Structural Linkages of COFs
Published in Atsushi Nagai, Covalent Organic Frameworks, 2019
Squaric acid and amines are used as building blocks for the synthesis of squaraine-based COFs, which allow strong π conjugation from donor and acceptor interaction into a squaraine bond (Eq. 2.8). Nagai et al. reported a new reaction based on squaraine for the synthesis of a new type of building block to construct a crystalline 2D conjugated COF (CuP-Sq COF) with a tetragonal mesoporous skeleton (Fig. 2.21) [73]. The CuP-Sq COF possesses strong hydrogen bond capabilities that are strengthened by the delocalization of the lone pair of electrons in nitrogen into a four-membered ring to form zwitterionic resonance structures and shows strong π conjugation, as shown in Eq. 2.8. This COF shows a BET surface area of 539 m2/g with a pore size of 2.1 nm. This research expands the types of COFs. Construction of squaraine-based COFs (CuP-SQ COF).
Low Energy Gap, Conducting, and Transparent Polymers
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Arvind Kumar, Yogesh Ner, Gregory A. Sotzing
All the above examples employed high Eg monomers such as thiophene, pyrrole, and their derivatives to prepare LEGPs using the DA approach. Polymers with even lower Eg are expected if lower Eg monomers are used, such as organic dyes, which are known to absorb in visible to NIR region. Squaraine dyes are known to be the best for this purpose, and are obtained by condensation reaction between electron rich aromatic and heterocyclic molecules such as pyrrole, azulenes, phenols, and N,N-dialkylanilines with 3,4-dihydroxy-3-cyclobutene-1,2-dione (squaric acid) [36]. Polysquaraines (46) and polycroconaines (47) of Figure 7.23 were found to have Eg’s in the range of 1.0–1.5 eV, with 47 having the lower Eg due to the stronger donor–acceptor interactions.
Multicolor upconversion luminescence of dye-coordinated Er3+ at the interface of Er2O3 and CaF2 nanoparticles
Published in Science and Technology of Advanced Materials, 2019
Ayumi Ishii, Yuya Adachi, Ayaka Hasegawa, Miyu Komaba, Shuhei Ogata, Miki Hasegawa
Here, the squaraine dye, 2,4-bis[8-hydroxyl-1,1,7,7-tetramethyl-julolidin-9-yl]squaraine (bjSQ), having a metal coordination site, was selected as a photosensitizer to enhance the upconversion emission of Er3+ (Figure 1(a)). Squaraine dyes, with their unique aromatic four-membered ring system derived from squaric acid, are a class of organic dyes that exhibit intense absorption (absorption coefficient: ɛ ≈ 3 × 105 cm−1M−1) and fluorescence bands (luminescence quantum yield: ϕ ≈ 0.65), typically in the red and near-IR regions [18]. Two core nanoparticles with different vibration modes (Er2O3 and CaF2) were selected to construct the interface of the dye-coordinated nanoparticles. In the oxide state, which is the most stable in Ln compounds, the surface conditions may strongly affect the relaxation pathways of Ln3+ since the vibration energy of the hydroxyl group (-OH) in adsorbed (or hydrated) H2O on the surface matches well with some transition energies of Ln3+. On the other hand, CaF2 nanoparticles as the core can suppress the vibration deactivation pathway in the upconversion process due to their low phonon energy, high refractive index, optical transparency, and high chemical and thermal stabilities [19–22].
Dual colorimetric and fluorescent determination of iron (III) using a novel squaraine dye
Published in Instrumentation Science & Technology, 2018
Chen Zhang, Mengyuan Wang, Yuzhe Zhang, Zhongyu Li, Song Xu
Herein, a novel squaraine compound 6-carboxy-2-[[3-[(1,3-dihydro-3,3-dimethyl-1-ethyl-2H-indol-2-ylidene)methyl]-2-hydroxy-4-oxo-2-cyclobuten-1-ylidene]methyl]-3,3-trimethyl-3H-indolium as an on–off fluorescent probe for detecting Fe3+ in CH3CH2OH/H2O (4:1, v/v) is reported. The squaraine dye is much highly selective and sensitive to Fe3+ ions and the corresponding signal is displayed by the change of fluorescence. The optical properties are studied by the fluorescence emission and absorption spectra. Squaraine dye dramatically displays ascendant sensitivity and reversibility for sensing Fe3+.
Shortwave infrared-absorbing squaraine dyes for all-organic optical upconversion devices
Published in Science and Technology of Advanced Materials, 2021
Karen Strassel, Wei-Hsu Hu, Sonja Osbild, Daniele Padula, Daniel Rentsch, Sergii Yakunin, Yevhen Shynkarenko, Maksym Kovalenko, Frank Nüesch, Roland Hany, Michael Bauer
Here, we report the synthesis and OUC device integration of SWIR squaraine dyes. Squaraines are known for their straightforward and scalable synthesis, narrow and intense absorption and emission properties in the NIR [30,31], as well as good thermal- and photostability [30,32,33]. The squaraine family is a large material library suitable for a variety of applications in chemical sensing, optoelectronic devices, photodynamic therapy and bioimaging [30,31,34,35].