Strong coupling between light and matter leads to the spontaneous formation of hybrid light–matter states, having different energies than the uncoupled states. This opens up for new ways of modifying the energy landscape of molecules without changing their atoms or structure. Heavy metal-free organic light emitting diodes (OLED) use reversed intersystem crossing (RISC) to harvest light from excited triplet states. This is a slow process, thus increasing the rate of RISC could potentially enhance OLED performance. Here we demonstrate selective coupling of the excited singlet state of Erythrosine B without perturbing the energy level of a nearby triplet state. The coupling reduces the triplet–singlet energy gap, leading to a four-time enhancement of the triplet decay rate, most likely due to an enhanced rate of RISC. Furthermore, we anticipate that strong coupling can be used to create energy-inverted molecular systems having a singlet ground and lowest excited state.
Photoswitchable molecules are able to isomerize between two metastable forms through light stimuli. Originally being studied by photochemists, this type of molecule has now found a wide range of applications within physics, chemistry and biology. The extensive usage of photochromic molecules is due to the two isomers having fundamentally different physical and chemical properties. The most important attribute of a photoswitch is the photoisomerization quantum yield, which defines the efficiency of the photoisomerization event. Here we show how to determine the photoisomerization quantum yield in the solid state and in solution when taking thermal processes into account. The described method together with provided software allows for rapid and accurate determination of the isomerization process for this important class of molecules.
Chemically converted graphene (CCG) covalently linked with porphyrins has been prepared by a Suzuki coupling reaction between iodophenyl-functionalized CCG and porphyrin boronic ester. The covalently linked CCG-porphyrin composite was designed to possess a short, rigid phenylene spacer between the porphyrin and the CCG. The composite material formed stable dispersions in DMF and the structure was characterized by spectroscopic, thermal, and microscopic measurements. In steady-state photoluminescence spectra, the emission from the porphyrin linked to the CCG was quenched strongly relative to that of the porphyrin reference. Fluorescence lifetime and femtosecond transient absorption measurements of the porphyrin-linked CCG revealed a short-lived porphyrin singlet excited state (38 ps) without yielding the porphyrin radical cation, thereby substantiating the occurrence of energy transfer from the porphyrin excited state to the CCG and subsequent rapid decay of the CCG excited state to the ground state. Consistently, the photocurrent action spectrum of a photoelectrochemical device with a SnO(2) electrode coated with the porphyrin-linked CCG exhibited no photocurrent response from the porphyrin absorption. The results obtained here provide deep insight into the interaction between graphenes and π-conjugated systems in the excited and ground states.
Altered lipid metabolism and extensive lipid storage in cells have been associated with various medical disorders, including cancer. The development of fluorescent probes that specifically accumulate in lipid deposits is therefore of great interest in order to study pathological processes that are linked to dysregulated lipogenesis. In the present study, we present a small fluorescent benzothiadiazole dye that specifically stains lipid droplets in living and fixated cells. The photophysical characterization of the probe revealed strong solvatochromic behavior, large Stokes shifts, and high fluorescent quantum yields in hydrophobic solvents. In addition, the fluorophore exhibits a nontoxic profile and a high signal-to-noise ratio in cells (i.e., lipid droplets vs cytosol), which make it an excellent candidate for studying lipid biology using confocal fluorescent microscopy.
Three new perylene diimide (PDI)-based ligands have been synthesized by the covalent attachment of dipyrido[a,c]phenazine moiety to one of the bay-positions of PDI, while the second position has been substituted with either a 4-tert-butylphenoxy or a pyrrolidinyl group to obtain two types of chromophores, Ph-PDI and Py-PDI, respectively, with distinct properties. In the case of Py-PDI, the resultant 1,7- and 1,6-regioisomers have been successfully separated by column chromatography and characterized by (1)H NMR spectroscopy. The ligands have been employed to prepare donor-acceptor-based ensembles incorporating the covalently linked PDI and Ru(II) polypyridine complex as the acting chromophores. A comprehensive study of the excited-state photodynamics of the ensembles has been performed by means of electrochemical and steady state and time-resolved spectroscopic methods. Although, in all the three ensembles, the photoexcitation of either chromophore resulted in a long-lived triplet excited state of PDI ((3)PDI) as the final excited state, the photochemical reactions leading to the triplet states were found to be essentially different for the two types of the ensembles. In the case of the Ph-PDI-based ensemble, the excitation of either chromophore leads to the electron transfer from the Ru(II) complex to Ph-PDI, whereas for the Py-PDI-based ensembles, the electron transfer is observed in the opposite direction and only when the Ru(II) complex is excited. The difference in the behavior was rationalized based on electrochemical study of the compounds, which has shown that the Ph-PDI chromophore is a better electron acceptor and the Py-PDI chromophores are relatively better electron donors. This study shows a chemical approach to control the photoreactions in PDI-based dichromophoric ensembles including the possibility to switch the direction of the photoinduced electron transfer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.