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A deep understanding of the dynamics of photogenerated charge carriers is extremely important for promoting their germination in semiconductors to enhance the efficiency of solar energy conversion. In contrast to that of organic molecular heterojunctions (which are widely employed in organic solar cells), the charge transfer dynamics of purely inorganic molecular heterojunctions remains unexplored. Herein, we reveal the dynamics of charge transfer between inorganic semiconductor molecular heteroclusters by selecting a group of open-framework metal chalcogenides as unique structure models constructed from supertetrahedral T3-InS ([In10S20]) and T4-MInS ([M4In16S35], M = Mn or Fe) clusters. The staggered band gap alignment in T3-T4-MInS molecular heterojunctions enables the photogenerated charge carriers to be directionally transferred from T3-InS clusters to adjacent T4-MInS clusters upon irradiation or application of an external electric field. The simultaneous independence of and interactions between such two heteroclusters are investigated by theoretical calculations, steady- and transient-state absorption/photoluminescence spectroscopy, and surface photovoltage analysis. Moreover, the dynamics of cluster-to-cluster-to-dopant photogenerated charge transfer is deliberately elucidated. Thus, this work demonstrates the direct observation of charge transfer between molecular heterojunctions based on purely inorganic semiconductor clusters and is expected to promote the development of cluster-based semiconductors for solar cells.

We report the existence of a short-lived triplet electronic state of 2,6-ANS (2-anilinonaphthalene-6-sulfonic acid), which, together with nonplanar (NP) and planar [charge-transfer (CT)] states, is produced following photoexcitation; these results are based on nanosecond transient absorption and time-resolved decays. The short-lived triplet state has a lifetime of ∼126 ns and is observed via triplet-triplet (T-T) transitions after exciting 2,6-ANS with a pump laser pulse of 355 nm (probe wavelength range of 360-500 nm). Moreover, the CT state, which is very close to the NP state produced from the locally excited state/NP state, emits active fluorescence with a lifetime of ∼11 ns. The solvent plays a major role in the rotation of the phenylamino group during the conversion of the NP state to the CT state, and vice versa. Intersystem crossing occurs from the CT state. Thus, investigating the triplet state together with the CT/NP states of 2,6-ANS, a commonly used probe for sensing proteins and other biomolecules, is highly relevant and helps reveal its photoexcitation dynamics.

Lead‐free metal halide double perovskites have emerged as promising scintillators owing to their superior optoelectronic properties, low‐cost and solution processability. However, it is still challenging to develop high‐performance flexible X‐ray scintillators based on the B(I)‐site alkali metal modulation in lead‐free double perovskite nanocrystals (NCs). Herein, a series of novel Cs2B(I)GdCl6 (B: Li, Na, K) of double perovskite A2B(I)M(III)X6 NCs structures are successfully synthesized, the optical and scintillator properties of which are significantly sensitive to the B(I)‐site alkali metals with the doping of Sb3+. They showed efficient self‐trapped exciton (STE) emission with high photoluminescence quantum yield (PLQY) and exhibited the highest X‐ray detection limit (86 nGyair s−1) and excellent spatial resolutions (>15 lp mm−1). The femtosecond transient absorption measurement and theoretical analysis further revealed that the B(I)‐site alkali metal fundamentally balanced the exciton–phonon coupling with appropriate STEs formation energy barrier and the electron localization and thus improved the optical and scintillator properties. This B(I)‐site alkali metal engineering offers a strategy to develop bright luminescent double perovskite NCs for X‐ray detection and imaging devices. [ABSTRACT FROM AUTHOR]

The collision time is an important quantity of an elementary chemical reaction and describes the speed of the collision process in a collision reaction. In this study, we present a generalized method to calculate the collision time of a triatomic reaction in which the collision time is defined by the sum of the incoming time, the intermediate complex time, and the outgoing time. Two variables including the total distance [R.sub.total] and [R.sub.avg], the average value of [R.sub.total] over time, are used to compute the three components of the collision time. We compute three triatomic reactions including Ca + HCl [right arrow] CaCl + H, O + HCl [right arrow] OH + Cl/OCl + H, and O + HF [right arrow] OH + F at different collision energies and initial diatomic vibrational levels using the quasi-classical trajectory method to confirm that the method could be reliable and reasonable. The time evolutions of [R.sub.total] could efficiently classify the direct and indirect reactive mechanisms and reveal a distinct discrepancy of the two mechanisms. As the collision energy and initial diatomic vibrational level increase, the percentage of direct reaction trajectories increases. At the same time, the average and maximal values of collision time decrease. Comparing the maximal collision time and the reactive probability distributions of the products, it could be found that most reactive trajectories' collision time is less than 2 ps. Moreover, the present calculations indicate that the method could be applicable to estimate the lifetime of the intermediate complex for the reaction systems with deep potential wells and the collision time of the reactions with a direct abstraction mechanism. Key words: collision time, total distance, reactive probability distribution, direct and indirect reaction. Le temps de collision est une mesure quantitative importante d'une reaction chimique elementaire et temoigne de la vitesse du processus de collision lors de collisions reactionnelles. Dans la presente etude, nous presentons une methode generalisee pour le calcul du temps de collision d'une reaction triatomique dans laquelle le temps de collision correspond a la somme du temps d'approche, de la duree de vie du complexe intermediaire et du temps de retrait. Nous avons utilise deux variables: la distance totale [R.sub.total]e et la valeur moyenne [R.sub.moy] de la distance totale dans le temps pour calculer les trios composantes du temps de collision. Au moyen de la methode des trajectoires quasi classiques, nous avons effectue les calculs pour trois reactions triatomiques (Ca + HCl [right arrow] CaCl + H, O + HCl [right arrow] OH + Cl/OCl + H et O + HF [right arrow] OH + F) a differentes energies de collision et differents niveaux vibrationnels diatomiques afin de confirmer que la methode pouvait etre fiable et convenable. L'evolution de la [R.sub.total] dans le temps permettait de classifier efficacement les mecanismes de reaction directe et indirecte et revelait un ecart distinct entre les deux mecanismes. Le pourcentage des trajectoires de reaction directe augmente en fonction de l'energie de collision et du niveau vibrationnel diatomique initial, tandis que les valeurs moyennes et maximales de temps de collision diminuent. En comparant le temps de collision maximal avec les distributions de probabilite reactionnelle des produits, nous pouvions observer que pour les trajectoires les plus reactives, le temps de collision etait inferieur a 2 ps. En outre, les presents calculs indiquent que la methode pourrait etre appliquee a l'estimation de la duree de vie du complexe intermediaire dans des systemes reactionnels presentant des puits de potentiel profonds et du temps de collision de reactions dont le mecanisme d'arrachement est direct. [Traduit par la Redaction] Mots-cles: temps de collision, distance totale, distribution de probabilite reactionnelle, reaction directe et indirecte., Introduction In elementary chemical reaction research, the model A + BC is widely used. (1) Generally, three reaction channels are mostly concerned by researchers, which are (1) [MATHEMATICAL EXPRESSION NOT [...]