We propose a new concept exploiting thermally activated delayed fluorescence (TADF) molecules as photosensitizers, storage units and signal transducers to harness solar thermal energy. Molecular ...composites based on the TADF core phenoxazine-triphenyltriazine (PXZ-TRZ) anchored with norbornadiene (NBD) were synthesized, yielding compounds PZDN and PZTN with two and four NBD units, respectively. Upon visible-light excitation, energy transfer to the triplet state of NBD occurred, followed by NBD → quadricyclane (QC) conversion, which can be monitored by changes in steady-state or time-resolved spectra. The small S
-T
energy gap was found to be advantageous in optimizing the solar excitation wavelength. Upon tuning the molecule's triplet state energy lower than that of NBD (61 kcal/mol), as achieved by another composite PZQN, the efficiency of the NBD → QC conversion decreased drastically. Upon catalysis, the reverse QC → NBD reaction occurred at room temperature, converting the stored chemical energy back to heat with excellent reversibility.
1,8-Dihydroxy-2-naphthaldehyde (DHNA), having doubly intramolecular hydrogen bonds, was strategically designed and synthesized in an aim to probe a long-standing fundamental issue regarding ...synchronous versus asynchronous double-proton transfer in the excited state. In cyclohexane, DHNA shows the lowest lying S0 →S1 (π–π*) absorption at ∼400 nm. Upon excitation, two large Stokes shifted emission bands maximized at 520 and 650 nm are resolved, which are ascribed to the tautomer emission resulting from the first and second proton-transfer products, denoted by TA* and TB*, respectively. The first proton transfer (DHNA* → TA*) is ultrafast (< system response of 150 fs), whereas the second proton transfer is reversible, for which the rates of forward (TA* → TB*) and backward (TA* ← TB*) proton transfer were determined to be (1.7 ps)−1 and (3.6 ps)−1, respectively. The fast equilibrium leads to identical population lifetimes of ∼54 ps for both TA* and TB* tautomers. Similar excited-state double-proton transfer takes place for DHNA in a single crystal, resulting in TA* (560 nm) and TB* (650 nm) dual-tautomer emission. A comprehensive 2D plot of reaction potential energy surface further proves that the sequential two-step proton motion is along the minimum energetic pathway firmly supporting the experimental results. Using DHNA as a paradigm, we thus demonstrate unambiguously a stepwise, proton-relay type of intramolecular double-proton transfer reaction in the excited state, which should gain fundamental understanding of the multiple proton transfer reactions.
We report unusual photophysical properties observed on two newly designed 3-hydroxychromone derivatives exhibiting the excited-state intramolecular proton transfer (ESIPT) reaction. The efficiency of ...ESIPT reaction is greatly enhanced upon excitation with high energy quanta to S
(
> 1) levels in low-polarity solvents. Based on detailed analyses of excitation and emission spectra as well as time-resolved emission kinetics we derive that conditions, in which this phenomenon contradicting Kasha's rule is observed, are quite different from that for observation of anti-Kasha emission.
We report the design strategy and synthesis of a structurally locked GFP core chromophore p -LHBDI, its ortho-derivative, o -LHBDI, and H2BDI possessing both para- and ortho-hydroxyl groups such that ...the inherent rotational motion of the titled compounds has been partially restricted. o -LHBDI possesses a doubly locked configuration, i.e., the seven-membered ring hydrogen bond and five-membered ring C(4-5-10-13-14) cyclization, from which the excited-state intramolecular proton transfer takes place, rendering a record high tautomer emission yield (0.18 in toluene) and the generation of amplified spontaneous emission. Compared with their unlocked counterparts, a substantial increase in the emission yield is also observed for p -LHBDI and H2BDI in anionic forms in water, and accordingly the structure versus luminescence relationship is fully discussed based on their chemistry and spectroscopy aspect. In solid, o -LHBDI exhibits an H-aggregate-like molecular packing, offers narrow-bandwidth emission, and has been successfully applied to fabricate a yellow organic light emitting diodes (λmax = 568 nm, ηext = 1.9%) with an emission full width at half-maximum as narrow as 70 nm.
The compound 6‐azaindole undergoes self‐assembly by formation of N(1)−H⋅⋅⋅N(6) hydrogen bonds (H bonds), forming a cyclic, triply H‐bonded trimer. The formation phenomenon is visualized by scanning ...tunneling microscopy. Remarkably, the H‐bonded trimer undergoes excited‐state triple proton transfer (ESTPT), resulting in a proton‐transfer tautomer emission maximized at 435 nm (325 nm of the normal emission) in cyclohexane. Computational approaches affirm the thermodynamically favorable H‐bonded trimer formation and the associated ESTPT reaction. Thus, nearly half a century after Michael Kasha discovered the double H‐bonded dimer of 7‐azaindole and its associated excited‐state double‐proton‐transfer reaction, the triply H‐bonded trimer formation of 6‐azaindole and its ESTPT reaction are demonstrated.
Trinity Roots: 6‐azaindole undergoes self‐assembly by formation of N(1)−H⋅⋅⋅N(6) hydrogen bonds (H bonds), to form a cyclic, triply H‐bonded trimer. The H‐bonded trimer undergoes excited‐state triple proton transfer (ESTPT), resulting in a proton‐transfer tautomer emission maximized at 435 nm.
The trade‐off between high‐quality images and cellular health in optical bioimaging is a crucial problem. We demonstrated a deep‐learning‐based power‐enhancement (PE) model in a harmonic generation ...microscope (HGM), including second harmonic generation (SHG) and third harmonic generation (THG). Our model can predict high‐power HGM images from low‐power images, greatly reducing the risk of phototoxicity and photodamage. Furthermore, the PE model trained only on normal skin data can also be used to predict abnormal skin data, enabling the dermatopathologist to successfully identify and label cancer cells. The PE model shows potential for in‐vivo and ex‐vivo HGM imaging.
Our study presents a deep‐learning‐based power‐enhancement (PE) model for a harmonic generation microscope (HGM) capable of generating high‐quality images from low‐power images, diminishing phototoxicity and photodamage. This PE model, trained only on normal skin data, has effectively predicting abnormal skin data, potentially enhancing cancer detection in dermatopathology.
Surface acoustic wave (SAW) sensors based on reduced graphene oxide/poly (diketopyrrolopyrrolethiophene-thieno 3,2-bthiophene-thiophene) (rGO/DPP2T-TT) composite sensing films for the detection of ...ammonia were investigated at room temperature in this study. The rGO/DPP2T-TT composite films were deposited onto ST-X quartz SAW resonators by a drop-casting method. FESEM, EDS, and XRD characterizations showed that the rGO/DPP2T-TT composite film was successfully synthesized and exhibited numerous wrinkles and a rough structure, which are crucial for gas adsorption. The frequency response to 500–1400 ppb ammonia shown by the prepared SAW sensor coated with rGO/DPP2T-TT composite film increased linearly as the ammonia concentration increased. The sensor based on a rGO/DPP2T-TT composite film exhibited a positive frequency shift of 55 Hz/ppm, and its frequency response to 500 ppb ammonia was 35 Hz. The sensors thus show promising potential in detecting sub-ppm concentration levels of NH3 at room temperature, which opens up possibilities for applications in the noninvasive detection of NH3 in the breath. As a result, the rGO/DPP2T-TT composite sensor can be a good candidate for in situ medical diagnosis and indoor/outdoor environment monitoring.
A series of 2-pyridyl pyrazoles 1a and 1–5 with various functional groups attached to either pyrazole or pyridyl moieties have been strategically designed and synthesized in an aim to probe the ...hydrogen bonding strength in the ground state versus dynamics of excited-state intramolecular proton transfer (ESIPT) reaction. The title compounds all possess a five-membered-ring (pyrazole)N–H···N(pyridine) intramolecular hydrogen bond, in which both the N–H bond and the electron density distribution of the pyridyl nitrogen lone-pair electrons are rather directional, so that the hydrogen bonding strength is relatively weak, which is sensitive to the perturbation of subtle chemical substitution and consequently reflected from the associated ESIPT dynamics. Various approaches such as 1H NMR (N–H proton) to probe the hydrogen bonding strength and absorption titration to assess the acidity-basicity property were made for all the title analogues. The results, together with supplementary support provided by a computational approach, affirm that the increase of acidity (basicity) on the hydrogen bonding donor (acceptor) sites leads to an increase of hydrogen-bonding strength among the title 2-pyridyl pyrazoles. Luminescence results and the associated ESIPT dynamics further reveal an empirical correlation in that the increase of the hydrogen bonding strength leads to an increase of the rate of ESIPT for the title 2-pyridyl pyrazoles, demonstrating an interesting relationship among N–H acidity, hydrogen bonding strength, and the associated ESIPT rate.
Colorectal cancer (CRC) is one of the most common cancers and causes of cancer‐related death. There are several first‐line chemotherapeutic drugs used to treat CRC. Oxaliplatin (OXA) is an alkylating ...cytotoxic agent that is usually combined with other chemotherapeutic drugs to treat stage II and stage III CRC. However, cancer cells commonly acquire multidrug resistance (MDR), which is a major obstruction to cancer treatment. Recent studies have shown that natural components from traditional Chinese medicine or foods that have many biological functions may be new adjuvant therapies in clinical trials. We challenged LoVo CRC cell lines with OXA in a dose‐dependent manner to create an OXA‐resistant model. The expression of ABCG2 was significantly higher, and levels of endoplasmic reticulum (ER) stress markers were lower than those Parental cells. However, Lupeol, which is found in fruits and vegetables, has been shown to have bioactive properties, including anti‐tumor properties that are relevant to many diseases. In our study, Lupeol downregulated cell viability and activated cell apoptosis. Moreover, Lupeol decreased the expression of ABCG2 and activated ER stress to induce OXA‐resistant cell death. Importantly, the anti‐tumor effect of Lupeol in OXA‐resistant cells was higher than that of LoVo Parental cells. In addition, we also confirmed our results with a xenograft animal model, and the tumor size significantly decreased after Lupeol injections. Our findings show that Lupeol served as a strong chemoresistant sensitizer and could be a new adjuvant therapy method for chemoresistant patients.
3-Me-2,6-diazaindole ((2,6-aza)Ind) was strategically designed and synthesized to probe water molecule catalyzed excited-state proton transfer in aqueous solution. Upon electronic excitation (λmax ∼ ...300 nm), (2,6-aza)Ind undergoes N(1)–H to N(6) long-distance proton transfer in neutral H2O, resulting in normal (340 nm) and proton-transfer tautomer (480 nm) emissions with an overall quantum yield of 0.25. The rate of the water-catalyzed proton transfer shows a prominent H/D kinetic isotope effect, which is determined to be 8.3 × 108 s–1 and 4.7 × 108 s–1 in H2O and D2O, respectively. Proton inventory experiments indicate the involvement of two water molecules and three protons, which undergo a relay type of excited-state triple proton transfer (ESTPT) in a concerted, asynchronous manner. The results demonstrate for the first time the fundamental of triple proton transfer in pure water for azaindoles as well as pave a new avenue for 2,6-diazatryptophan, an analogue of tryptophan exhibiting a similar ESTPT property with (2,6-aza)Ind, to probe biowaters in proteins.
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