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Thermally activated delayed fluorescence (TADF) molecules with through-space charge transfer (TSCT) have attracted much attention in recent years because of their ability to simultaneously reduce the energy difference (ΔEST) and enlarge the spin–orbit coupling (SOC). In this paper, 40 molecules are theoretically designed by changing the different substitution positions of the donors and acceptors, and systematically investigated based on the first-principles calculations and excited-state dynamics study. It is found that the emission wavelengths of v-shaped molecules with intramolecular TSCT are larger than those of the molecules without TSCT. Therefore, the intramolecular TSCT can induce the red-shift of the emission and realize the deep-red/near-infrared emission. Besides intramolecular TSCT can simultaneously increase the SOC as well as the oscillator strength and reduce the ΔEST. In addition, PXZ or PTZ can also favor the realization of smaller ΔEST and red-shift emission. Our calculations suggest that intramolecular TSCT and suitable donors (-PXZ or -PTZ) are an effective strategy for the design of efficient deep red/near-infrared TADF emitters. [ABSTRACT FROM AUTHOR]

The interaction of exciton-plasmon coupling and the conversion of exciton-plasmon-photon have been widely investigated experimentally and theoretically. In this review, we introduce the exciton-plasmon interaction from basic principle to applications. There are two kinds of exciton-plasmon coupling, which demonstrate different optical properties. The strong exciton-plasmon coupling results in two new mixed states of light and matter separated energetically by a Rabi splitting that exhibits a characteristic anticrossing behavior of the exciton-LSP energy tuning. Compared to strong coupling, such as surface-enhanced Raman scattering, surface plasmon (SP)-enhanced absorption, enhanced fluorescence, or fluorescence quenching, there is no perturbation between wave functions; the interaction here is called the weak coupling. SP resonance (SPR) arises from the collective oscillation induced by the electromagnetic field of light and can be used for investigating the interaction between light and matter beyond the diffraction limit. The study on the interaction between SPR and exaction has drawn wide attention since its discovery not only due to its contribution in deepening and broadening the understanding of SPR but also its contribution to its application in light-emitting diodes, solar cells, low threshold laser, biomedical detection, quantum information processing, and so on.

Applying pesticides to crops is one of the causes of water pollution by surface runoff, and chlorpyrifos, trifluralin and chlorothalonil are used respectively as insecticide, herbicide and fungicide for crop plants widely. To explore effects of three pesticides on aquatic organisms, superoxide dismutase (SOD) and glutathione S-transferase (GST) activities were determined after 24 h and 48 h exposure of D. magna with ages of 6–24 h to several low concentrations of chlorpyrifos (0.36, 0.72, 1.43, 2.86, 5.72 μg∙L−1), trifluralin (0.17, 0.33, 0.66, 1.33, 2.65 mg∙L−1) and chlorothalonil (0.09, 0.18, 0.36, 0.72, 1.43 mg∙L−1) respectively. Main reproductive parameters including first pregnancy time, first brood time, the number of first brood and total fecundity after 21 d exposures at the same concentrations of pesticides as described above were also measured. The results showed that the activities of GST increased in lower concentrations and decreased in higher concentrations after 24 h exposure to three pesticides, respectively. The activities of SOD showed the same changes after 48 h exposure. With the time prolonged, the activities of GST decreased while the activities of SOD increased. After 21 d exposure, the first pregnancy time and first brood time were delayed, while the number of the first brood and total fecundity per female decreased with increasing concentrations. These results corroborated that GST activity was more sensitive to those pesticides than SOD activity, and there was a significant relationship between total fecundity and pesticides-dose(r>0.94, n=6), GST activity after 48 h exposure and total fecundity after 21 d exposure (r>0.92, n=6).

The excited-state proton transfer (ESPT) dynamical behavior of aloesaponarin I (ASI) was studied using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. Our calculated vertical excitation energies based on TDDFT reproduced the experimental absorption and fluorescence spectra well [Nagaoka et al. J. Phys. Chem. B, 117, 4347 (2013)]. Two intramolecular hydrogen bonds were confirmed to be strengthened in the [S.sub.1] state, which makes ESPT possible. Herein, the ESPT process is more likely to happen, along with one hydrogen bond ([O.sub.1]-[H.sub.2]***[O.sub.3]). Qualitative analyses about charge distribution further demonstrate that the ESPT process could occur because of the intramolecular charge transfer. Our constructed potential energy surfaces of both [S.sub.0] and [S.sub.1] states show that a single proton transfer reactive is more reasonable along with the intramolecular hydrogen bond ([O.sub.1]-[H.sub.2]***[O.sub.3]) rather than [O.sub.4]--[H.sub.5]***[O.sub.6] in the [S.sub.1] stated potential energy surface. Then, ASI-SPT* decays to the ground state with a 640 nm fluorescence; subsequently, the ASI-SPT form shows that reverse ground state single-proton transfer back to the ASI structure occurs. Particularly, dependent on relatively accurate potential energy barriers among these excited-state stable structures, we confirmed the excited-state single proton transfer process rather than using the controversial nodal plane model. Key words: proton transfer, intramolecular hydrogen bond, PES, frontier molecular orbital. Nous avons etudie le comportement dynamique du transfert de proton a l'etat excite (TPEE) de l'aloesaponarine I (ASI) a l'aide des methodes de la theorie de la fonctionnelle de la densite (DFT) et de la DFT dependante du temps (TDDFT). Les energies d'excitation verticales que nous avons obtenues par calculs bases sur la TDDFT concordaient bien avec les spectres d'absorption et de fluorescence experimentaux [Nagaoka et al. J. Phys. Chem. B, 117 (2013) 4347-4353]. Nous avons demontre que les deux liaisons hydrogene intramoleculaires se trouvaient renforcees dans l'etat S1, ce qui indique la possibilite qu'un TPEE reactif puisse se produire. Dans le cadre des presents travaux, nous montrons que le processus de TPEE est plus susceptible de se produire le long d'une des liaisons hydrogene ([O.sub.1]-[H.sub.2]...O3). Des analyses quantitatives de la distribution de charge permettent de demontrer de maniere plus convaincante que le TPEE pourrait se produire par transfert de charge intramoleculaire. D'apres les surfaces d'energie potentielle des etats [S.sub.0] et [S.sub.1] que nous avons elaborees, nous montrons que, sur la surface d'energie potentielle de l'etat S1, le transfert d'un proton reactif unique est plus susceptible de se produire le long de la liaison hydrogene intramoleculaire [O.sub.1]-[H.sub.2]...[O.sub.3] que le long de la liaison [O.sub.4]-[H.sub.5]...[O.sub.6]. Par la suite, la forme excitee de l'ASI* en transfert de proton unique retourne a l'etat fondamental en emettant une bande de fluorescence a 640 nm, puis subit un retrotransfert de proton unique a l'etat fondamental pour reformer la structure de l'ASI. En nous basant sur les barrieres d'energie potentielle relativement exactes entre ces structures stables a l'etat excite, nous avons demontre que le processus de transfert de proton unique a l'etat excite constituait une hypothese plus plausible que le controverse modele de plan nodal. [Traduit par la Redaction] Mots-cles: transfert de proton, liaison hydrogene intramoleculaire, SEP, orbitale moleculaire frontiere., Introduction Proton transfer, a fundamental kind of photochemical and photophysical process, is ubiquitous. (1-5) In general, in chemical and biological acid-base dynamics, proton transfer is very important, resulting from site-specific [...]

To investigate the influence of nitrogen (N) and phosphorus (P) availability on the periphytic algal biomass and assemblage composition (by pigment analysis) in the eutrophic lake, natural littoral intact sediment cores in a subtropical eutrophic lake (Lake Taihu) were collected, and subjected to three levels of water N and P loading (N-P [mg. L−1]: 1.5, 0.075; 2.5, 0.125; 3.5, 0.175) in the tanks, eighteen artificial substances (glass slides) were fixed at three water depths (1, 17, and 33 cm above the surface sediment) for development of periphytic algae in each tank, respectively. The results showed that the biomass of periphytic algae on artificial substance was significantly enhanced with increasing N and P levels in water column and water depth (p < 0.05), while sediment-associated periphytic algae did not significantly increase with increasing N and P levels in water column. The development of sediment-associated periphytic algae changed the phosphorus form, calcium-bound phosphorus and inorganic phosphorus in the sediments decreased slightly, and the total phosphorus and organic phosphorus in the sediments increased. Our results suggest that N and P availability is conducive to the development of periphytic algae in subtropical eutrophic shallow lakes in spring. [ABSTRACT FROM AUTHOR]

Stimulus-responsive organic room temperature phosphorescence (RTP) materials with long lifetimes, high efficiencies and tunable emission properties have broad applications. However, the amounts and species of efficient RTP materials are far from meeting the requirements and the inner stimulus-responsive mechanisms are unclear. Therefore, developing efficient stimulus-responsive RTP materials is highly desired and the relationship between the molecular structures and luminescent properties of RTP materials needs to be clarified. Based on this point, the influences of different substitution sites of Br on the luminescent properties of RTP molecules are studied by the combined quantum mechanics and molecular mechanics (QM/MM) coupled with thermal vibration correlation function (TVCF) theory. Moreover, the hydrostatic pressure effect on the efficiencies and lifetimes is explored and the inner mechanism is illustrated. The results show that, for the exciton conversion process, the o-substitution molecule possesses the largest spin–orbit coupling (SOC) value (〈S1‖Ĥso‖T1〉) in the intersystem crossing (ISC) process and this is conducive to the accumulation of triplet excitons. However, for the energy consumption process, the large SOC value (〈S0‖Ĥso‖T1〉) for the p-substitution molecule brings a fast non-radiative decay rate, and the small SOC value for the m-substitution molecule generates a decreased non-radiative decay rate which is helpful for realizing long lifetime emission. Keeping with this perspective, the conflict between high exciton utilization and long RTP emission needs to be balanced rather than enhancing the SOC effect by simply adding heavy atoms in RTP systems. Through regulating the molecular stacking modes by the hydrostatic pressure effect, the inner stimulus-responsive mechanism is revealed. The data of 〈S1‖Ĥso‖T1〉 in the ISC process remain almost unchanged, while 〈S0‖Ĥso‖T1〉 values and transition dipole moments are sensitive to the hydrostatic pressure. Under 1 GPa, the RTP molecule achieves a maximum efficiency (81.17%) and long lifetime (2.72 ms) with the smallest SOC and decreased non-radiative decay rate. To our knowledge, this is the first time that the hydrostatic pressure responsive mechanism for RTP molecules is revealed from a theoretical perspective, and the relationships between molecular structures and luminescent properties are detected. Our work could facilitate the development of high performance RTP molecules and expand their applications in multilevel information encryption. [ABSTRACT FROM AUTHOR]

With the many-body expansion method, an accurate global potential energy surface (PES) is constructed for Si H 2 + (X2A1) by mapping 4762 ab initio energy points calculated on the multireference configuration interaction level including Davidson corrections with aug-cc-pV6Z Dunning's basis set. The dissociation energies and equilibrium geometries of SiH+(X1Σ+) and H 2 ( X 1 Σ g + ) agree well with the experimental results. The topographical characteristics of all stationary points for the SiH 2 + ( X 2 A 1 ) PES are discussed in detail and compared with other theoretical and experimental results. In order to verify the validity and usability of the present PES, the dynamics calculations based on the Chebyshev quantum wave packet method are performed for the H (S 2 ) + Si H + ( X 1 Σ + ) → S i + (P 2 ) + H 2 ( X 1 Σ g + ) reaction. The probabilities, the total integral cross sections, and the rate constants are computed, and the analogies with the corresponding ones of reaction H (S 2 ) + C H + ( X 1 Σ + ) → C + (P 2 ) + H 2 ( X 1 Σ g + ) are also made. The reasonable dynamical behavior throughout the entire configuration space indicates that the PES is suitable for relevant dynamics investigations and serves as a building block for constructing the PES of larger molecular systems containing Si+/H. [ABSTRACT FROM AUTHOR]

The single-sheeted potential energy surface (PES) of H 2 S + (X 2 A ′ ′ ) is developed based on the ab initio energies calculated by the multi-reference configuration interaction method including the Davidson correction. All the ab initio energies are first calculated using aug-cc-pVQdZ and aug-cc-pV5dZ basis sets, which are then extrapolated to the complete basis set (CBS) limit. A switching function is developed to model the transition of S + D 2 to S + S 4 . The many-body expansion formalism is employed to obtain the H 2 S + (X 2 A ′ ′ ) PES by fitting such CBS energies and the root-mean square derivation is 0.0367 eV. The topographical features of the present PES are examined in detail, which are well consistent with previous studies. The quasiclassical trajectory method is subsequently utilized to study the S + D 2 + H 2 ( X 1 Σ g + ) → S H + (X 3 Σ − ) + H (S 2 ) reaction. The capture time, integral cross sections, and rovibrational distributions are calculated. By examining the capture time, it can be concluded that the title reaction is mainly controlled by the indirect mechanism for lower collision energies, while the direct and indirect mechanisms coexist and the latter plays a dominant role for higher collision energies. [ABSTRACT FROM AUTHOR]