Double perovskites (DPs) are one of the most promising candidates for developing white light‐emitting diodes (WLEDs) owing to their intrinsic broadband emission from self‐trapped excitons (STEs). ...Translation of three‐dimensional (3D) DPs to one‐dimensional (1D) analogues, which could break the octahedral tolerance factor limit, is so far remaining unexplored. Herein, by employing a fluorinated organic cation, we report a series of highly luminescent 1D DP‐inspired materials, (DFPD)2MIInBr6 (DFPD=4,4‐difluoropiperidinium, MI=K+ and Rb+). Highly efficient warm‐white photoluminescence quantum yield of 92 % is achieved by doping 0.3 % Sb3+ in (DFPD)2KInBr6. Furthermore, single‐component warm‐WLEDs fabricated with (DFPD)2KInBr6:Sb yield a luminance of 300 cd/m2, which is one of the best‐performing lead‐free metal‐halides WLEDs reported so far. Our study expands the scope of In‐based metal‐halides from 3D to 1D, which exhibit superior optical performances and broad application prospects.
We report on a new class of 1D double perovskite‐inspired materials (DFPD)2MIInBr6 (DFPD=4,4‐difluoropiperidinium, MI=K+ and Rb+), which exhibit an intrinsic warm‐white light emission. Further enhancement is achieved by 0.3 % Sb3+ doping, which boosts PLQY to ≈92 %. Warm white light‐emitting diodes based on single component (DFPD)2KInBr6:Sb are fabricated.
Herein, the first acceptorless dehydrogenation of tetrahydroquinolines (THQs), indolines, and other related N‐heterocycles, by merging visible‐light photoredox catalysis and cobalt catalysis at ...ambient temperature, is described. The potential applications to organic transformations and hydrogen‐storage materials are demonstrated. Primary mechanistic investigations indicate that the catalytic cycle occurs predominantly by an oxidative quenching pathway.
Cobalt and blue: The titled method is utilized for the reversible dehydrogenation‐hydrogenation protocol at ambient temperature under mild reaction conditions. Primary mechanistic investigations indicate that the catalytic cycle relies predominantly on an oxidative quenching pathway.
Because of its fundamental importance in many branches of science, hydrogen bonding is a subject of intense contemporary research interest. The physical and chemical properties of hydrogen bonds in ...the ground state have been widely studied both experimentally and theoretically by chemists, physicists, and biologists. However, hydrogen bonding in the electronic excited state, which plays an important role in many photophysical processes and photochemical reactions, has scarcely been investigated. Upon electronic excitation of hydrogen-bonded systems by light, the hydrogen donor and acceptor molecules must reorganize in the electronic excited state because of the significant charge distribution difference between the different electronic states. The electronic excited-state hydrogen-bonding dynamics, which are predominantly determined by the vibrational motions of the hydrogen donor and acceptor groups, generally occur on ultrafast time scales of hundreds of femtoseconds. As a result, state-of-the-art femtosecond time-resolved vibrational spectroscopy is used to directly monitor the ultrafast dynamical behavior of hydrogen bonds in the electronic excited state. It is important to note that the excited-state hydrogen-bonding dynamics are coupled to the electronic excitation. Fortunately, the combination of femtosecond time-resolved spectroscopy and accurate quantum chemistry calculations of excited states resolves this issue in laser experiments. Through a comparison of the hydrogen-bonded complex to the separated hydrogen donor or acceptor in ground and electronic excited states, the excited-state hydrogen-bonding structure and dynamics have been obtained. Moreover, we have also demonstrated the importance of hydrogen bonding in many photophysical processes and photochemical reactions. In this Account, we review our recent advances in electronic excited-state hydrogen-bonding dynamics and the significant role of electronic excited-state hydrogen bonding on internal conversion (IC), electronic spectral shifts (ESS), photoinduced electron transfer (PET), fluorescence quenching (FQ), intramolecular charge transfer (ICT), and metal-to-ligand charge transfer (MLCT). The combination of various spectroscopic experiments with theoretical calculations has led to tremendous progress in excited-state hydrogen-bonding research. We first demonstrated that the intermolecular hydrogen bond in the electronic excited state is greatly strengthened for coumarin chromophores and weakened for thiocarbonyl chromophores. We have also clarified that the intermolecular hydrogen-bond strengthening and weakening correspond to red-shifts and blue-shifts, respectively, in the electronic spectra. Moreover, radiationless deactivations (via IC, PET, ICT, MLCT, and so on) can be dramatically influenced through the regulation of electronic states by hydrogen-bonding interactions. Consequently, the fluorescence of chromophores in hydrogen-bonded surroundings is quenched or enhanced by hydrogen bonds. Our research expands our understanding of the nature of hydrogen bonding by delineating the interaction between hydrogen bonds and photons, thereby providing a basis for excited-state hydrogen bonding studies in photophysics, photochemistry, and photobiology.
•An optimal number of indoor plants appears to improve air characteristics.•PM2.5, PM10, and TVOC had lower concentrations close to indoor plants.•CO2 and HCHO had lower concentrations far away from ...indoor plants.•Placing two indoor plants can improve indoor air characteristics.
Recent research has indicated that fluorescent probes have tremendous potential for the selective detection of chemical and biological species. Over the past decade, researchers have proposed a ...series of fluorescence‐based sensing mechanisms of such probes by the calculation of their electronic excited states. Investigations of sensing mechanisms have been based on deep insights into the interactions between probe molecules and their target species, as well as their fluorescence properties. Advances in calculation methods, modeling software, and computational power have enabled researchers to use excited‐state theoretical calculations to reproduce experimental fluorescence phenomena and then provide molecular‐level explanations thereof. In this advanced review, we describe the evolution of theoretical studies on excited‐state sensing mechanisms for fluorescent probes that respond to target species. Focusing on calculation methods that facilitate investigation of the photophysical properties and excited‐state dynamics of probes, we emphasize sensing mechanisms mainly reported by our group. Most of these studies have been supported by theoretical predictions based on time‐dependent density functional theory. For this most popular excited‐state calculation method, vertical excitation energy, excited‐state geometrical optimization and a scan of the excited‐state potential energy surface should be noted in the calculation of electronic and molecular differences between the excited‐state probe and its reaction product with the target analyte. These state‐of‐the‐art calculations are of great importance for unraveling details of fluorescence‐based sensing mechanisms, including photochemical reactions (such as twist intramolecular charge transfer and excited‐state proton transfer) and excited‐state electronic processes (such as intramolecular charge transfer and photoinduced electron transfer). These studies have generated new and inspirational mechanistic proposals and have provided a systematic approach for the development of efficient fluorescent sensors. WIREs Comput Mol Sci 2018, 8:e1351. doi: 10.1002/wcms.1351
This article is categorized under:
Structure and Mechanism > Computational Biochemistry and Biophysics
Theoretical and Physical Chemistry > Spectroscopy
Sensing mechanisms for fluorescent probes that respond to target species can be obtained by excited‐state calculations.
Single‐component emitters with stable and bright warm white‐light emission are highly desirable for high‐efficacy warm white light‐emitting diodes (warm‐WLEDs), however, materials with such ...luminescence properties are extremely rare. Lowdimensional lead (Pb) halide perovskites can achieve warm white photoluminescence (PL), yet they suffer from low stability and PL quantum yield (PLQY). While Pb‐free air‐stable perovskites such as Cs2AgInCl6 emit desirable warm white light, sophisticated doping strategies are typically required to increase their PL intensity. Moreover, the use of rare metal‐bearing compounds along with the typically required vacuum‐based thin‐film processing may greatly increase their production cost. Herein, organic–inorganic hybrid cuprous (Cu+)‐based metal halide MA2CuCl3 (MA = CH3NH3+) that meets the requirements of i) nontoxicity, ii) high PLQY, and iii) dopant‐free is presented. Both single crystals and thin films of MA2CuCl3 can be facilely prepared by a low‐cost solution method, which demonstrate bright warm white‐light emission with intrinsically high PLQYs of 90–97%. Prototype electroluminescence devices and down‐conversion LEDs are fabricated with MA2CuCl3 thin films and single crystals, respectively, which show bright luminescence with decent efficiencies and operational stability. These findings suggest that MA2CuCl3 has a great potential for the single‐component indoor lighting and display applications.
The newly developed hybrid MA2CuCl3 meets the requirements of i) broadband warm white‐light emission, ii) nontoxicity, iii) high photoluminescence quantum yield, iv) dopant‐free, v) low‐cost, and vi) excellent film‐forming ability. Besides, the first successful electroluminescence application of MA2CuCl3 opens a new avenue toward single‐component warm white light‐emitting diodes.
The time-dependent density functional theory (TDDFT) method was carried out to investigate the hydrogen-bonded intramolecular charge-transfer (ICT) excited state of 4-dimethylaminobenzonitrile ...(DMABN) in methanol (MeOH) solvent. We demonstrated that the intermolecular hydrogen bond Cidentical withN···H---O formed between DMABN and MeOH can induce the Cidentical withN stretching mode shift to the blue in both the ground state and the twisted intramolecular charge-transfer (TICT) state of DMABN. Therefore, the two components at 2091 and 2109 cm⁻¹ observed in the time-resolved infrared (TRIR) absorption spectra of DMABN in MeOH solvent were reassigned in this work. The hydrogen-bonded TICT state should correspond to the blue-side component at 2109 cm⁻¹, whereas not the red-side component at 2091 cm⁻¹ designated in the previous study. It was also demonstrated that the intermolecular hydrogen bond Cidentical withN···H---O is significantly strengthened in the TICT state. The intermolecular hydrogen bond strengthening in the TICT state can facilitate the deactivation of the excited state via internal conversion (IC), and thus account for the fluorescence quenching of DMABN in protic solvents. Furthermore, the dynamic equilibrium of these electronically excited states is explained by the hydrogen bond strengthening in the TICT state.
Facial expressions are deeply tied to empathy, which plays an important role during social communication. The eye region is effective at conveying facial expressions, especially fear and sadness ...emotions. Further, it was proved that subliminal stimuli could impact human behavior. This research aimed to explore the effect of subliminal sad, fearful and neutral emotions conveyed by the eye region on a viewer's empathy for pain using event-related potentials (ERP). The experiment used an emotional priming paradigm of 3 (prime: subliminal neutral, sad, fear eye region information) × 2 (target: painful, nonpainful pictures) within-subject design. Participants were told to judge whether the targets were in pain or not. Results showed that the subliminal sad eye stimulus elicited a larger P2 amplitude than the subliminal fearful eye stimulus when assessing pain. For P3 and late positive component (LPC), the amplitude elicited by the painful pictures was larger than the amplitude elicited by the nonpainful pictures. The behavioral results demonstrated that people reacted to targets depicting pain more slowly after the sad emotion priming. Moreover, the subjective ratings of Personal Distress (PD) (one of the dimensions in Chinese version of Interpersonal Reactivity Index scale) predicted the pain effect in empathic neural responses in the N1 and N2 time window. The current study showed that subliminal eye emotion affected the viewer's empathy for pain. Compared with the subliminal fearful eye stimulus, the subliminal sad eye stimulus had a greater impact on empathy for pain. The perceptual level of pain was deeper in the late controlled processing stage.
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