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Merits of Selecting Metal-Organic Frameworks as Sensors
Published in Ram K. Gupta, Tahir Rasheed, Tuan Anh Nguyen, Muhammad Bilal, Metal-Organic Frameworks-Based Hybrid Materials for Environmental Sensing and Monitoring, 2022
Harmeet Kaur, Amit L Sharma, Akash Deep
Photoinduced electron transfer (PET) involves the transfer of an electron between excited molecules. The excited state molecules act as a redox system that donates or captures electrons from other molecules. PET is governed by the distance between donor and acceptor molecules as well as the matching of their reduction and oxidation potentials. After, the transfer of an electron from donor to acceptor, the deactivation process is non-radiative. Thus, the PET receptors and excited luminophores are selected according to their redox potentials to maximize luminescence quenching. Excited-state proton transfer (ESPT) is a proton transfer process of photoacids (molecules acting as strong acids or bases in an excited state) to solvents. The emission spectrum of photoacids is dependent upon the solvent and its pH. A few examples of PET-based optical sensors include Zr-MOF-based fluorescent switches and Tb-MOF-based protamine sensors [32, 33].
A Review of Carbon Dots – A Versatile Carbon Nanomaterial
Published in Swamini Chopra, Kavita Pande, Vincent Shantha Kumar, Jitendra A. Sharma, Novel Applications of Carbon Based Nano-Materials, 2023
Jayanta Sarmah Boruah, Ankita Deb, Jahnabi Gogoi, Kabyashree Phukan, Neelam Gogoi, Devasish Chowdhury
Photoinduced Electron Transfer: Photoinduced electron transfer (PET) is an excited state electron transfer process by which an excited electron is transferred from donor to acceptor. CDs can serve as both electron donors and acceptors (Liang et al. 2016). They typically demonstrate fluorescence emission; however, the addition of electron acceptors causes quenching of fluorescence intensity because of photoinduced electron transfer between the CDs and the electron acceptor (Liang et al. 2016). Photoinduced electron transfer is important in CD-sensitized materials and CD-based photocatalysts (Wang et al. 2017).
Synthesis and properties of supramolecular gels based on tetrathiafulvalene and cyanobiphenyl units
Published in Soft Materials, 2021
Lina Ma, Li Wang, Yongqi Bai, Yan Xia, Dongfeng Li, Bingzhu Yin, Ruibin Hou
The self-assembly of covalently linked electron donors (D)-acceptor (A) dyads with total segregation at the molecular level has been extensively investigated owing to their potential candidacy in organic photovoltaics and related fields already recognized. For example, Würthner et al. constructed oligo(p-phenylene vinylene)s (OPVs) as donors and bay-substituted perylene bisimides (PERYs) as acceptor dyes to form supramolecular p-n-heterojunctions through hierarchical co-self-organization of OPV donor and PERY acceptor chromophores .[22] These well-defined coaggregated dyes exhibited photoinduced electron transfer on a subpicosecond timescale. Therefore, these supramolecular entities might serve as valuable nanoscopic functional units. Aida and coworkers reported a coaxial nanotubular object formed by controlled self-assembly of trinitrofluorenone (A)-appended hexabenzocoronene (D) amphiphile molecules. The coaxial nanotubular structure allowed the photochemical generation of spatially separated charge carriers and a quick photoconductive response with a large on/off ratio greater than 104 .[23] Although higher charge carrier mobilities have been observed in such segregated stacking systems, most have been realized in solution or liquid crystalline states .[24] To our knowledge, using D-A molecules as gelators has not been reported previously.
Application of commercially available fluorophores as triplet spin probes in EPR spectroscopy
Published in Molecular Physics, 2019
Kerstin Serrer, Clemens Matt, Monja Sokolov, Sylwia Kacprzak, Erik Schleicher, Stefan Weber
The positive difference absorption at around 560 nm in the transient absorption spectrum of EB is in good agreement with data from a study that was devised to investigate photoinduced electron transfer between EB and duroquinone [45]. Similarly, our data from RB are in accord with previously published values from a laser-flash photolysis examination [46]: a ground-state bleaching between 480 and 580 nm was observed together with three maxima around 390, 470 and 600 nm that were assigned to the excited triplet state. Transient absorption data on AT12 is, to the best of our knowledge, unavailable. When comparing the lifetimes of the three dyes in water (Table 1), it turns out that EB and RB have comparable values of around 5.5 µs, whereas the one of AT12 is roughly three times larger. The former finding can be expected from the similar chemical structures of EB and RB. The triplet-state lifetimes of both EB and RB are decreased by a factor of two when the temperature is increased by about 15 K, see Table 1. Moreover, the triplet-state lifetimes of all three dye molecules strongly depend on the solvent; an overview of previously published data with our own results is presented in Table 4.
Experimental and theoretical studies on structure, bonding and luminescence properties of Eu(III) and Tb(III) complexes of a new macrocyclic based 8HQ ligand
Published in Journal of Coordination Chemistry, 2019
Enterobactin, a natural occurring siderophore (Figure 1), is probably the most prominent example of ligand which has high thermodynamic stability [logK = 49 for Fe(III)] that met the above criteria, that has encouraged the synthesis of a wide range of nonnatural compounds used for the binding of metal ions. This incorporates a highly symmetric (C3) serine unit linked to three catechol units through amide spacers. Many biomimetic siderophores have served as excellent chelators for lanthanide luminescence and coordination [13]. Polyaza-macrocycles have a framework similar to L-serine. Incorporation of 8HQ units to the flexible puckered ring of the macrocyclic 9N3 results in the existence of several rotamers/conformers [14]: this has an additional advantage that can adjust its geometry to minimum energy on coordination with metal ions giving extra stability. The macrocycle offers the ability to fine-tune the properties of metal chelation by varying the cycle’s size and flexibility. Very few macrocycles have been described with 8HQ coordinating groups as shown in Figure 2(a–c) [15, 16]. It may be emphasized here that the position of attachment of 8HQ unit plays a significant role in properties and coordination of metal complexes. There are many examples of poly-8HQ chelates in which the 8HQ ring is attached at positions 2, 3, or 7. Tripods incorporating 8HQ substituted at position 5 are scarce. The coordinating property of –N pyridyl group mainly depends upon substitution position at the C-2, C-3, C-5 and/or C-7 in the 8HQ. In the case, where 8HQ is substituted at the position C-2 or C-7, a photoinduced electron transfer (PET) process leads to fluorescence quenching [17].