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We present a comprehensive computational study describing the excited state dynamics and consequent photostability of amino-cyclohexenone (ACyO), the central template of mycosporine systems, widely recognized for their photoprotection of aquatic species. Photoexcitation to the first excited electronic state (S1, 1nπ*) of ACyO is considered an optically dark transition, while photoexcitation to the second excited electronic state (S21ππ*) is an optically bright 1ππ* transition and largely responsible for UV absorption properties of this molecule. We show that following initial photoexcitation to S2, ACyO relaxes via two competing deactivation mechanisms, each mediated by an S1/S0 conical intersection, which directs the excited state population to the electronic ground state (S0). Our ab initio computational results are supported with nonadiabatic dynamics simulation results, yielding an excited state lifetime of ∼280 fs for this system in vacuo. These results explain the inherent photostability of this core structure, commonplace in a wide range of microorganisms. [ABSTRACT FROM AUTHOR]

In response to a community prediction challenge, we simulate the nonadiabatic dynamics of cyclobutanone using the mapping approach to surface hopping (MASH). We consider the first 500 fs of relaxation following photoexcitation to the S2 state and predict the corresponding time-resolved electron-diffraction signal that will be measured by the planned experiment. 397 ab initio trajectories were obtained on the fly with state-averaged complete active space self-consistent field using a (12,11) active space. To obtain an estimate of the potential systematic error, 198 of the trajectories were calculated using an aug-cc-pVDZ basis set and 199 with a 6-31+G* basis set. MASH is a recently proposed independent trajectory method for simulating nonadiabatic dynamics, originally derived for two-state problems. As there are three relevant electronic states in this system, we used a newly developed multi-state generalization of MASH for the simulation: the uncoupled spheres multi-state MASH method (unSMASH). This study, therefore, serves both as an investigation of the photodissociation dynamics of cyclobutanone, and also as a demonstration of the applicability of unSMASH to ab initio simulations. In line with previous experimental studies, we observe that the simulated dynamics is dominated by three sets of dissociation products, C3H6 + CO, C2H4 + C2H2O, and C2H4 + CH2 + CO, and we interpret our predicted electron-diffraction signal in terms of the key features of the associated dissociation pathways. [ABSTRACT FROM AUTHOR]

In order to develop an efficient metal-free solar energy harvester, we herein performed the electronic structure calculation, followed by the hot carrier relaxation dynamics of two dimensional (2D) aza-covalent organic framework by time domain density functional calculations in conjunction with non-adiabatic molecular dynamics (NAMD) simulation. The electronic structure calculation shows that the aza-covalent organic framework (COF) is a direct bandgap semiconductor with acute charge separation and effective optical absorption in the UV-visible region. Our study of non-adiabatic molecular dynamics simulation predicts the sufficiently prolonged electron–hole recombination process (6.8 nanoseconds) and the comparatively faster electron (22.48 ps) and hole relaxation (0.51 ps) dynamics in this two-dimensional aza-COF. According to our theoretical analysis, strong electron–phonon coupling is responsible for the rapid charge relaxation, whereas the electron–hole recombination process is slowed down by relatively weak electron–phonon coupling, relatively lower non-adiabatic coupling, and quick decoherence time. We do hope that our results of NAMD simulation on exciton relaxation dynamics will be helpful for designing photovoltaic devices based on this two dimensional aza-COF. [ABSTRACT FROM AUTHOR]

The photoexcitation dynamics of molecular materials on the 10–100 nm length scale depend on complex interactions between electronic and vibrational degrees of freedom, rendering exact calculations difficult or intractable. The adaptive Hierarchy of Pure States (adHOPS) is a formally exact method that leverages the locality imposed by interactions between thermal environments and electronic excitations to achieve size-invariant scaling calculations for single-excitation processes in systems described by a Frenkel–Holstein Hamiltonian. Here, we extend adHOPS to account for arbitrary couplings between thermal environments and vertical excitation energies, enabling formally exact, size-invariant calculations that involve multiple excitations or states with shared thermal environments. In addition, we introduce a low-temperature correction and an effective integration of the noise to reduce the computational expense of including ultrafast vibrational relaxation in Hierarchy of Pure States (HOPS) simulations. We present these advances in the latest version of the open-source MesoHOPS library and use MesoHOPS to characterize charge separation at a one-dimensional organic heterojunction when both the electron and hole are mobile. [ABSTRACT FROM AUTHOR]

The N–H photodissociation dynamics of the pyridinyl radical upon continuous excitation to the optically bright, first excited ππ* electronic state by an ultra-violet (UV) laser pulse has been investigated within the mathematical framework of optimal control theory. The genetic algorithm (GA) is employed as the optimization protocol. We considered a three-state and three-mode model Hamiltonian, which includes the reaction coordinate, R (a1 symmetry); the coupling coordinates (namely, out-of-plane bending coordinate of the hydrogen atom of azine group), Θ (b1 symmetry); and the wagging mode, Q9 (a2 symmetry). The three electronic states are the ground, ππ*, and πσ* states. The πσ* state crosses both the ground state and the ππ* state, and it is a repulsive state on which N–H dissociation occurs upon photoexcitation. Different vibrational wave functions along the coupling coordinates, Θ and Q9, of the ground electronic state are used as the initial condition for solving the time-dependent Schrödinger equation. The optimal UV laser pulse is designed by applying the GA, which maximizes the dissociation yield. We obtained over 95% dissociation yield through the πσ* asymptote using the optimal pulse of a time duration of ∼30 000 a.u. (∼725.66 fs). [ABSTRACT FROM AUTHOR]

The manipulation of the ultrafast quantum dynamics of a molecular system can be achieved through the application of tailored light fields. This has been done in many ways in the past. In our present investigation, we show that it is possible to exert specific control over the nonadiabatic dynamics of a generic model system describing ultrafast charge-transfer within a condensed dissipative environment by using frequency-chirped pulses. By adjusting the external photoexcitation conditions, such as the chirp parameter, we show that the final population of the excitonic and charge-transfer states can be significantly altered, thereby influencing the elementary steps controlling the transfer process. In addition, we introduce an excitation scheme based on double-pump time-resolved fluorescence spectroscopy using chirped-pulse excitations. Here, our findings reveal that chirped excitations enhance the vibrational system dynamics as evidenced by the simulated spectra, where a substantial signal intensity dependence on the chirp is observed. Our simulations show that chirped pulses are a promising tool for steering the dynamics of the charge-transfer process toward a desired target outcome. [ABSTRACT FROM AUTHOR]

Two-dimensional molybdenum disulfide (MoS2) has been proved to be a good candidate in photodetectors, and MoS2/graphene (MoS2/G) heterostructure has been widely used to expand the optical response wavelength of MoS2. To clarify the carrier transfer dynamics in the MoS2/G heterostructure, time-resolved transient absorption and two-color pump–probe measurements are performed. By comparing the carrier dynamics in MoS2 and MoS2/G under different pump wavelengths, we find that interfacial excitons are formed in the heterostructure, and fast hot carriers transfer (<200 fs) from graphene to MoS2 are observed. The results indicate that the formed heterostructure with graphene can not only expand the optical response wavelength of MoS2 but also improve the response time of the device in the near-infrared region. [ABSTRACT FROM AUTHOR]

Absorption spectra of the solvatochromic dye 2,6-diphenyl-4-2,4,6-triphenyl-1-pyridinophenolate (B30) were measured in seven solvents of varying polarity over temperature ranging from each solvent's freezing point to 300 K. The excitation energies and their variances allowed calculations of the solvent reorganization energies, reorganization free energies and reorganization entropies as functions of temperature. The entropies of solvent packing around the chromophore are found to make major contributions to the reorganization free energies. The variances of the excitation energies depend only weakly on temperature, in disagreement with an expression that is often used for solvent reorganization free energies. Polar solvents reduce the transition dipole strength of B30's long-wavelength absorption band, probably because interactions with the solvent enhance the charge-transfer character of the transition. The dipole strength drops further at low temperatures. [ABSTRACT FROM AUTHOR]

We discuss the possibility of using circularly polarized luminescence (CPL) as a tool to probe individual triplet spin sublevels that are populated nonadiabatically following photoexcitation. This study is motivated by a mechanism proposed for chirality-induced spin selectivity in which coupled electronic-nuclear dynamics may lead to a non-statistical population of the three triplet sublevels in chiral systems. We find that low-temperature CPL should aid in quantifying the exact spin state/s populated through coupled electronic-nuclear motion in chiral molecules. [ABSTRACT FROM AUTHOR]

Ion time-of-flight velocity-map imaging was used to measure the kinetic-energy distributions of the I2 ion-pair fragments formed after photoexcitation of Ar⋯I2 complexes to intermolecular vibrational levels bound within the Ar + I2 (E, vE = 0–2) potential energy surfaces. The kinetic-energy distributions of the I2 products indicate that complexes in the Ar⋯I2 (E, vE) levels preferentially dissociate into I2 in the D and β ion-pair states with no change in I2 vibrational excitation. The energetics of the levels prepared suggest that there is a non-adiabatic coupling of the initially prepared levels with the continuum of states lying above the Ar + I2 (D, vD = vE) and Ar + I2 (β, vβ = vE) dissociation limits. The angular anisotropies of the I2 product signals collected for many of the Ar⋯I2 (E, vE) levels have maxima parallel to the laser polarization axis. This contradicts expectations for the prompt dissociation of complexes with T-shaped geometries, which would result in images with maxima perpendicular to the polarization axis. These anisotropies suggest that there is a perturbation of the transition moment in these clusters or there are additional intermolecular interactions, likely those sampled while traversing above the attractive wells of the lower-energy potentials during dissociation. I2 (D′, vD′) products are also identified when preparing several of the low-lying levels localized in the T-shaped well of the Ar + I2 (E, vE = 0–2) potentials, and they are formed in multiple νD′ vibrational levels spanning energy ranges up to 500 cm−1. [ABSTRACT FROM AUTHOR]

In this study, we explored the use of Mes‐Acr‐MeClO4 as a visible light photocatalyst for multicomponent reactions involving quinoxalin‐2(1H)‐ones with CBrCl3 and styrene. The method showcases regioselective functionalization of quinoxalin‐2(1H)‐ones in a three‐component system, forming two C─C bonds in one pot. Mechanistic investigations suggest a radical‐mediated pathway, initiated by the photoexcitation of Mes‐Acr‐MeClO4, followed by halogen atom abstraction from CBrCl3. This approach provides a versatile and sustainable route for quinoxalin‐2(1H)‐one functionalization, with Mes‐Acr‐MeClO4 effectively facilitating the photocatalyzed multicomponent reaction under mild conditions and visible light irradiation, yielding high selectivity and efficiency. [ABSTRACT FROM AUTHOR]

The donor–acceptor (D–A) dye 4‐(bis‐4‐(5‐(2,2‐dicyano‐vinyl)‐thiophene‐2‐yl)‐phenyl‐amino)‐benzoic acid (P1) has been frequently used to functionalize NiO photocathodes and induce photoelectrochemical reduction of protons when coupled to a suitable catalyst. Photoinduced twisting of the P1 dye is steered on NiO by co‐adsorption of tetradecanoic acid (C14, myristic acid (MA)). Density Functional Theory and time‐resolved photoluminescence studies confirm that twisting lowers the energy levels of the photoexcited D–A dye. The apolar environment provided by the MA suppresses photoinduced D–A twisting, retards charge recombination following photoinduced charge separation between P1 and NiO, and provides a larger electrochemical potential increasing the photocurrent. Very interestingly, co‐adsorption of MA induces H2 evolution upon photoexcitation without the presence of an H2 evolution catalyst. Based on prior art, the formation of H2 is assigned to the dissolution of Ni2+, followed by reduction and re‐deposition of Ni nanoparticles acting as the catalytically active site. It propose that only excited P1 with suppressed twisting provides the sufficient electrochemical potential to induce deposition of Ni nanoparticles. The work illustrates the importance of understanding the effects of photoinduced intramolecular twisting and highlights the promise of designing twisting‐limited D–A dyes to create efficient solar fuel devices. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) light that penetrates our atmosphere initiates various photochemical and photobiological processes. However, the absence of extremely short UV pulses has so far hindered our ability to fully capture the mechanisms at the very early stages of such processes. This is important because the concerted motion of electrons and nuclei in the first few femtoseconds often determines molecular reactivity. Here we investigate the dissociative dynamics of iodomethane following UV photoexcitation, utilizing mass spectrometry with a 5 fs time resolution. The short duration of the UV pump pulse (4.2 fs) allows the ultrafast dynamics to be investigated in the absence of any external field, from well before any significant vibrational displacement occurs until dissociation has taken place. The experimental results combined with semi-classical trajectory calculations provide the identification of the main dissociation channels and indirectly reveal the signature of a conical intersection in the time-dependent yield of the iodine ion. Furthermore, we demonstrate that the UV-induced breakage of the C-I bond can be prevented when the molecule is ionized by the probe pulse within 5 fs after the UV excitation, showcasing an ultrafast stabilization scheme against dissociation. The authors investigate the ultrafast dissociative dynamics of iodomethane induced by sudden ultraviolet photoexcitation. They showcase how subsequent ionization within a 5-femtosecond window can stabilize the molecule and prevent fragmentation. [ABSTRACT FROM AUTHOR]

Incorporation of the trimethoxyphenyl group at position 7 of flavin can drastically change the photophysical properties of flavin. We show unique fast singlet 1(π,π*) excited state deactivation pathway through nonadiabatic transition to the 1(n,π*) excited- state, and subsequent deactivation to the ground electronic state (S0), closing the photocycle. This mechanism explains the exceptionally weak fluorescence and the short excited–state lifetime for the flavin trimethoxyphenyl derivative and the lack of excited triplet T1 state formation. Full recovery of flavin in its ground state takes place within a 15 ps time window after photoexcitation in a polar solvent such as acetonitrile. According to quantum chemical calculations, the C(2)-O distance elongates by 0.16 Å in the 1(n,π*) state, with respect to the ground state. Intermediate–state structures are predicted by theoretical ab initio calculations and their dynamics are investigated using broadband vis-NIR time-resolved transient absorption and fluorescence up-conversion techniques. [ABSTRACT FROM AUTHOR]

Excited-state intramolecular proton transfer (ESIPT) reactions are crucial in photoresponsive materials and fluorescent markers. The fluorescent compound 4-aminophthalimide (4-AP) has been reported to exhibit solvent-assisted ESIPT in protic solvents, such as methanol, wherein the solvent interacts with 4-AP to form a six-membered hydrogen-bonded ring that is strengthened upon excitation. Although the controversial observation of ESIPT in 4-AP has been extensively studied, the molecular mechanism has yet to be fully explored. In this study, femtosecond infrared spectroscopy was used to investigate the dynamics of 4-AP in methanol and acetonitrile after excitation at 350 and 300 nm, which promoted 4-AP to the S1 and S2 states, respectively. The excited 4-AP in the S1 state relaxed to the ground state, while 4-AP in the S2 state relaxed via the S1 state without the occurrence of ESIPT. The enol form of 4-AP (Enol 4-AP) in the S1 state was calculated to be ~10 kcal/mol higher in energy than the keto form in the S1 state, indicating that keto-to-enol tautomerization was endergonic, ultimately resulting in no observable ESIPT for 4-AP in the S1 state. Upon the excitation of 4-AP to the S2 state, the transition to Enol-4-AP in the S1 state was found to be exergonic; however, ESIPT must compete with an internal conversion from the S2 to the S1 state. The internal S2 → S1 conversion was significantly faster than the solvent-assisted ESIPT, resulting in a negligible ESIPT for the 4-AP excited to the S2 state. The detailed excitation dynamics of 4-AP clearly reveal the molecular mechanism underlying its negligible ESIPT, despite the fact that it forms a favorable structure for solvent-assisted ESIPT. [ABSTRACT FROM AUTHOR]

As the simplest nitroaromatic compound, nitrobenzene is an interesting model system to explore the rich photochemistry of nitroaromatic compounds. Previous investigations of nitrobenzene's photochemical dynamics have probed structural and electronic properties. These investigations paint, at times, a convoluted and sometimes contradictory description of the photochemical landscape. We investigate the ultrafast dynamics of nitrobenzene triggered by photoexcitation at 267 nm for the first time using a structural probe with femtosecond time resolution. Our probe complements previous measurements of nitrobenzene's electronic structure evolution and aids in determining the photochemical dynamics with less ambiguity. We employ megaelectronvolt ultrafast electron diffraction to follow nitrobenzene's structural evolution within the first 5 ps after photoexcitation. We observe ground state recovery within 160 ± 60 fs through nonadiabatic dynamics. Based on comparisons of the experimental signal with molecular dynamics simulations, we exclude a significant population of the triplet manifold. Furthermore, we do not observe fragmentation of nitrobenzene within the investigated time window, which indicates that previously observed photofragmentation reactions take place in the vibrationally 'hot' ground state on timescales considerably beyond 5 ps. [ABSTRACT FROM AUTHOR]

The ultrafast processes caused by photoexcitation of (n-Bu4N)2[Pt(NO3)6] complex in acetonitrile were studied by means of transient absorption (TA) pump-probe spectroscopy and verified by quantum chemical calculations. The primary photochemical process was found to be an inner-sphere electron transfer followed by an escape of an •NO3 radical to the bulk solution. The reaction occurs via the dissociative triplet excited LMCT state of the initial complex. Based on the experimental data and quantum chemical calculations, the mechanism of ultrafast photophysical and photochemical processes is proposed. [ABSTRACT FROM AUTHOR]

Regioregular poly(3-hexylthiophene-2,5-diyl)-modified C60–ethylenediamine adduct microparticles film and corresponding references were fabricated using a combination of liquid/liquid interfacial precipitation and spin-coating. The photoexcitation properties of these composite films were evaluated through fluorescence spectra, which suggest that the C60–ethylenediamine adduct microparticles film enhance the fluorescence of poly(3-hexylthiophene-2,5-diyl). Larger photocurrents were observed when using the composite film of poly(3-hexylthiophene-2,5-diyl) and C60–ethylenediamine adduct microparticles film compared to those obtained using poly(3-hexylthiophene-2,5-diyl) alone. [ABSTRACT FROM AUTHOR]

Layered ternary type‐II Weyl semimetals demonstrate promising applications in high‐performance and broadband optoelectronics, therefore it is crucial to gain insights into their photocarriers’ dynamics. In this work, the probing polarization dependence of non‐equilibrium dynamics in NbIrTe4 is investigated by using transient reflectivity spectroscopy. Following photoexcitation at 3.18 eV, the dynamical response of 1.59 eV probe pulse exhibits a strong dependence on probe polarization. The relaxation comprises two components: a rapid recovery of ≈0.6 ps attributed to the electron–phonon scattering, and an anomalous slow recovery spanning hundreds of picoseconds attributed to the photoinduced quasi‐particle. The polarization dependence of rapid relaxation time τ is indicative of the in‐plane anisotropy of electron–phonon coupling in NbIrTe4. The slow relaxation modulated by a latest reported 16 cm−1 coherent phonon also shows strong probing polarization dependence, further revealing the anisotropic nature of electron–phonon coupling and the possibility of anisotropic lattice distortion, as well as photoinduced polaron, under ultrafast photoexcitation in NbIrTe4. The dynamical anisotropy in NbIrTe4 has provided valuable guidance for the application of NbIrTe4 in polarization‐sensitive nonlinear optics or optoelectronic devices and offers insights into the unique carrier transport as well as phonon transport properties of this newly established topological material. [ABSTRACT FROM AUTHOR]

A radical trapping method based on an SH2' homolytic substitution reaction was applied to study the mechanism of a photochemical spirocyclisation of indole‐ynones in the presence of thiols. Starting material, products and a range of trapped radical intermediates were simultaneously detected in reaction mixtures by mass spectrometry (MS). The trapped intermediates included both initiating and main chain propagating radicals. These data made it possible to propose a self‐initiation mechanism consistent with the originally postulated photoexcitation of an intramolecular electron donor‐acceptor complex of the substrate. The effect of thiol structure on the MS peak intensity of the reaction components was rationalised in terms of the relative stability of the radical intermediates. The results were compared to a simpler related reaction, a photochemical thiol‐ene addition where reagents, products and trapped intermediate radicals were also detected by MS. Relative MS peak intensities were again explained by a combination of electronic and steric effects on the stability of intermediate radicals. Overall, SH2' radical trapping was demonstrated to be a powerful experimental technique for providing mechanistic evidence on photochemical and other organic radical reactions. [ABSTRACT FROM AUTHOR]

Effective selective recycling of spent lithium‐ion batteries (S‐LIBs) and giving recycled products a “second life” are crucial for advancing energy supply circularity, environmental and economic sustainability development. However, separating metal compounds with similar charge differences requires substantial energy, water, and chemical inputs. Herein, an innovative strategy is present for selective recycling S‐LIBs by photoexcitation inspired by the Hard Soft Acid Base (HSAB) principle. Theoretical calculations and experimental results show that photoexcitation drives charge transfer and modulates subtle charge density differences among metal components, thereby enhancing their solubility disparity and facilitating metal separation. Remarkably, the photoexcitation‐induced metal separation factor reaches 46900 and the metal recovery efficiency approaches 100%, representing a significant improvement over non‐photoexcitation separation with a separation factor of non‐photoexcitation of merely 2.7. Through techno‐economic analysis, the viability of photoexcitation selective recycling technology has been confirmed as an eco‐friendly and economical approach for battery recycling. Furthermore, high‐value reuse of recovered Mn components is implemented. The Recycled Mn components are treated by calcination to obtain porous, defect‐rich Mn2O3, which showed a specific capacity of 613 mAh g−1 at 0.1 A g−1) in aqueous Zn‐ion batteries (AZIBs). This work provides fresh insight into recycling S‐LIBs and moving toward more sustainable storage technologies. [ABSTRACT FROM AUTHOR]

Direct interband and intragap photoexcitation by intense mid-infrared (4.0 and 4.7 μm) femtosecond (fs) laser pulses was explored in ultrapure chemical-vapor deposited (CVD) diamond via acquisition of characteristic ultraviolet photoluminescence of free excitons and A-band photoluminescence of electrons anchored at deep donor–acceptor or dislocation-related traps, respectively. At lower laser intensities (<10 TW/cm2) the excitonic photoluminescence yields exhibit highly nonlinear dependences with Iλ2-scaling and power slopes N ≈ 17 (4.0 μm) and 14 (4.7 μm), still insufficient to cross over the direct bandgap (≥6.5 eV) by ≈1.2 and 2.8 eV, respectively. Similarly high slope of ≈9 (4.7 μm) for intragap (≥3.5 eV) photo-population of donor–acceptor traps is still insufficient for their direct excitation by ≈1 eV. At the intermediate Iλ2-dependent values of the Keldysh parameter γ ∼ 1 such incomplete multiphoton excitation anticipates the hybrid total "multiphoton + tunneling" photoexcitation generally predicted by the Keldysh theory, but never unambiguously experimentally demonstrated. At higher laser intensities (>10 TW/cm2) both the excitonic and A-band photoluminescence yields exhibit (sub)linear slopes, apparently, indicating formation of more strongly absorbing electron–hole plasma. These findings shed light on the hybrid multiphoton + tunneling character of Keldysh photoexcitation at intermediate values γ and pave the way to defect/impurity band engineering of intragap nonlinear optical properties in bulk dielectrics for their precise fs-laser nanomodification. [ABSTRACT FROM AUTHOR]

A theoretical analysis is presented on the photoexcitation of a macroscopic atomic target by a Hermite–Gaussian (HG) beam within the framework of density matrix theory. Special emphasis is paid to the influence of the incoming HG mode on the population of an excited state and the emitted fluorescence radiation. In particular, a general expression for the alignment parameter of the excited state is derived, which depends on the beam parameters of the HG mode. Although the developed theory can be applied to any atomic system, here the electric dipole transition 3s2S1/2→3p2P3/2$3s\; {}^{2}S_{1/2}\nobreakspace \rightarrow \nobreakspace 3p \; {}^{2}P_{3/2}$ in neutral sodium atoms is investigated when driven by three HG10${\rm HG}_{10}$, HG01,${\rm HG}_{01,}$ and HG11${\rm HG}_{11}$ modes. For this optical (valence‐shell) excitation, it is demonstrated that the population of the excited state is sensitive to the beam waist and the mode index of the HG beam. Furthermore, the influence of beam parameters on the angular distribution and linear polarization of the emitted fluorescence radiation is discussed. [ABSTRACT FROM AUTHOR]

We develop a theory of singlet fission in carotenoid dimers. Following photoexcitation of the "bright" state (i.e., a singlet electron–hole pair) in a single carotenoid, the first step in the singlet fission process is ultrafast intramolecular conversion into the highly correlated "dark" (or 2Ag) state. This state has both entangled singlet triplet-pair and charge-transfer character. Our theory is predicated on the assumption that it is the singlet triplet-pair component of the "dark" state that undergoes bimolecular singlet fission. We use valence bond theory to develop a minimal two-chain model of the triplet-pair states. The single and double chain triplet-pair spectra are described, as this helps explain the dynamics and the equilibrated populations. We simulate the dynamics of the initial entangled pair state using the quantum Liouville equation, including both spin-conserving and spin-nonconserving dephasing processes. By computing the intrachain and interchain singlet, triplet, and quintet triplet-pair populations, we show that singlet fission critically depends on the interchain coupling and the driving potential (that determines endothermic vs exothermic fission). [ABSTRACT FROM AUTHOR]

Adsorption of toxic substances is an important research field. In this work, the adsorption dynamics of halogenated and methylated benzenes onto hydroxylated silica upon photoexcitation has been investigated theoretically. The intermolecular interaction between the hydroxy (OH) group and the π electron density at the center of the benzene ring was also a major subject. In the ground state, the order of calculated adsorption energy was consistent with the OH⋅⋅⋅C bond strengths (SiO2–MeBe > SiO2–DimeBe > SiO2–BrBe > SiO2–ClBe > SiO2–FBe > SiO2–Be), implying this bond to be the major contributor to the adsorption. Upon photoexcitation to the first excited (S1) state by adsorbing shortwave-ultraviolet (UV), the OH⋅⋅⋅C bonds in each complex were strengthened with only the order of the bond strengths of SiO2–DimeBe and SiO2–MeBe reversed relative to the order in the ground state. In contrast to OH⋅⋅⋅C bonds, the OH⋅⋅⋅π bonds were all indicated to weaken upon photoexcitation. The results showed that the order of OH⋅⋅⋅π bond strengths in the S1 state to be SiO2–FBe > SiO2–BrBe > SiO2–DimeBe > SiO2–Be > SiO2–ClBe > SiO2–MeBe. However, the change in the corresponding adsorption energy was inconsistent with the order of OH⋅⋅⋅C bond strengths in the S1 state, due to the degree of weakening of the OH⋅⋅⋅π bond being greater than the degree of strengthening of the OH⋅⋅⋅C bonds. These changes were concluded to be induced by local excitation for each of the six complexes. This work has presented the photophysical dynamics of an adsorbent before and after photoexcitation. [ABSTRACT FROM AUTHOR]

The radiation intensity dependence of photothermal (PT) and photocarrier (PC) signals from n-type CdSe single crystals was investigated by modulated infrared radiometry (MIRR) in the mid-IR range (5–11.3 μm) with superbandgap photoexcitation. The influence of dc temperature increase of the sample was avoided by a new step-sine modulation method that combines the advantages of transient and periodical modulation. With increasing laser intensity I, the amplitude of the PC component shows a sub-linear dependence (|SPC| ∝ I0.5), while the PT one has the expected linear dependence (|SPT| ∝ I). As a result, the transition frequency ft between the two components is shifted to higher frequencies, which is explained in the frame of a simple model. The origin of the observed effects is the decrease of the effective photocarrier lifetime τ ∝ I−0.5 over three laser intensity decades. In contrast, previous studies on nonlinear PC response in semiconductors performed in the near-IR range (0.7–1.8 μm) have found supra-linear |SPC| dependence with exponent between 1 and 2. This difference is attributed to the fact that the near-IR radiometric signal features characteristics of a photoluminescence (PL) signal that are different from those of the mid-IR PC signal, as shown in our previous study [J. Appl. Phys. 119, 125108 (2016)] on the same CdSe samples. [ABSTRACT FROM AUTHOR]

Controlling matter at the level of electrons using ultrafast laser sources represents an important challenge for science and technology. Recently, we introduced a general laser control scheme (the Stark control of electrons at interfaces or SCELI) based on the Stark effect that uses the subcycle structure of light to manipulate electron dynamics at semiconductor interfaces [A. Garzón-Ramírez and I. Franco, Phys. Rev. B 98, 121305 (2018)]. Here, we demonstrate that SCELI is also of general applicability in molecule–semiconductor interfaces. We do so by following the quantum dynamics induced by non-resonant few-cycle laser pulses of intermediate intensity (non-perturbative but non-ionizing) across model molecule–semiconductor interfaces of varying level alignments. We show that SCELI induces interfacial charge transfer regardless of the energy level alignment of the interface and even in situations where charge exchange is forbidden via resonant photoexcitation. We further show that the SCELI rate of charge transfer is faster than those offered by resonant photoexcitation routes as it is controlled by the subcycle structure of light. The results underscore the general applicability of SCELI to manipulate electron dynamics at interfaces on ultrafast timescales. [ABSTRACT FROM AUTHOR]

Understanding ultrafast response of a semiconductor is necessary for next-generation optoelectronic device applications. Here, we investigate the ultrafast response of an archetypal semiconductor Ge [111] crystal upon photoexcitation at two pump wavelengths, 800 nm (fundamental) and 400 nm (second harmonic, UV radiation), using time-resolved x-ray diffraction (TXRD). The simulated TXRD profiles using a proposed four-layer model and Takagi–Taupin equations reveal that the strain propagation is primarily due to electron diffusion. Intriguingly, the initial (<100 ps) fast decrease in the induced strain for second harmonic excitation suggests that the strain originates from the deformation potential (DP) effect. The higher photon energy (second harmonic pump) excites the electrons to higher conduction band valleys, resulting in DP-induced strain compared to the fundamental pump, which only generates thermo-elastic strain. The DP strain, estimated from the DP coefficient (simulated via density functional theory-based electronic structure simulations) and electron density (simulated from experimental results), shows an excellent agreement with the observed strain. The strain after ∼100 ps delay for second harmonic excitation and strain from fundamental excitation are attributed to the thermo-elastic effect as confirmed by the density-dependent two-temperature model. Our study reveals the long-lasting DP effect in Ge [111], which provides an opportunity to avoid heating in optoelectronic devices due to the thermo-elastic effect at the initial time scale. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the regulation behaviors of photoexcited nonequilibrium carriers in a GaN piezoelectric semiconductor PN junctions. It is shown that the electromechanical field of the PN junction has a fast response to the illumination intensity. This is attributed to the ultraviolet photoexcited non-equilibrium carriers, which can shield the piezoelectric charges and significantly weaken the built-in barrier height. Furthermore, the electrical transmission characteristics are also regulated. It implies that the electrical behaviors of a nano GaN PN junctions are highly sensitive to ultraviolet light, and such a contactless approach can be applied to control the nano GaN devices. [ABSTRACT FROM AUTHOR]

A photovoltaic device fabricated with conventional zincblende materials can use the Type-II quantum well structure, which spatially separates electrons and holes, to reduce their recombination rate. In order to obtain higher power conversion efficiency, it is desirable to preserve more energetic carriers by engineering a phonon "bottleneck," a mismatch between the gaps in the well and barrier phonon structure. Such a mismatch leads to poor phonon transport and therefore prevents energy from leaving the system in the form of heat. In this paper, we perform a superlattice phonon calculation to verify the "bottleneck" effect and build on this a model to predict the steady state of the hot electrons under photoexcitation. We describe the electrons and phonons with a coupled Boltzmann equation system and numerically integrate it to get the steady state. We find that inhibited phonon relaxation does lead to a more out-of-equilibrium electron distribution and discuss how this might be enhanced. We examine the different behaviors obtained for various combinations of recombination and relaxation rates and their experimental signatures. [ABSTRACT FROM AUTHOR]

A resonant system consisting of an excess electron and a closed-shell atom or molecule, as a temporary negative ion, is usually in doublet-spin states that are analogous to bright states of photoexcitation of the neutral. However, anionic higher-spin states, noted as dark states, are scarcely accessed. Here, we report the dissociation dynamics of CO− in dark quartet resonant states that are formed by electron attachments to electronically excited CO (a3Π). Among the dissociations to O−(2P) + C(3P), O−(2P) + C(1D), and O−(2P) + C(1S), the latter two are spin-forbidden in the quartet-spin resonant states of CO−, while the first process is preferred in 4Σ− and 4Π states. The present finding sheds new light on anionic dark states. [ABSTRACT FROM AUTHOR]

Operando time-resolved soft x-ray absorption spectroscopy (TR-SXAS) is an effective method to reveal the photochemical processes of metal complexes in solutions. In this study, we have developed the TR-SXAS measurement system for observing various photochemical reactions in solutions by the combination of laser pump pulses with soft x-ray probe pulses from the synchrotron radiation. For the evaluation of the developed TR-SXAS system, we have measured nitrogen K-edge x-ray absorption spectroscopy (XAS) spectra of aqueous iron phenanthroline solutions during a photoinduced spin transition process. The decay process of the high spin state to the low spin state in the iron complex has been obtained from the ligand side by N K-edge XAS, and the time constant is close to that obtained from the central metal side by time-resolved Fe K-edge XAS in the previous studies. [ABSTRACT FROM AUTHOR]

Perovskite quantum dots (QDs) have shown attractive prospects in the field of visible photocatalysis, especially in the synthesis of high value‐added chemicals. However, under aerobic conditions, the stable operation of QD catalysts has been limited by the reactive oxygen species (ROS) generated by photoexcitation, especially superoxide species O2⋅−. Here, we propose a strategy of Ce3+ doping in perovskite QDs to guide superoxide species for photocatalytic oxidation reactions. In C(sp3)−H bond oxidation of hydrocarbons, superoxide species were rapidly generated and efficiently utilized on the surface of perovskite QDs, which achieves the stable operation of the catalytic system and obtains a high product conversion rate (15.3 mmol/g/h for benzaldehydes). The mechanism studies show that the strong Ce‐oxygen affinity accelerates the relaxation process of photoinduced exciton transfer to superoxide species and inhibits the radiative recombination pathway. This work provides a new idea of utilizing oxygen species on perovskite surface and broadens the design strategy of high‐performance QD photocatalysts. [ABSTRACT FROM AUTHOR]

The interlayer twist angle endows a new degree of freedom to manipulate the spatially separated interlayer excitons in van der Waals (vdWs) heterostructures. Herein, we find that the band-edge Γ-Γ interlayer excitation directly forms interlayer exciton in InSe/Sb heterostructure, different from that of transition metal dichalcogenides (TMDs) heterostructures in two-step processes by intralayer excitation and transfer. By tuning the interlayer coupling and breathing vibrational modes associated with the Γ-Γ photoexcitation, the interlayer twist can significantly adjust the excitation peak position and lifetime of recombination. The interlayer excitation peak in InSe/Sb heterostructure can shift ~400 meV, and the interlayer exciton lifetime varies in hundreds of nanoseconds as a periodic function of the twist angle (0°–60°). This work enriches the understanding of interlayer exciton formation and facilitates the artificial excitonic engineering of vdWs heterostructures. [ABSTRACT FROM AUTHOR]

We present photophysical studies on homoleptic zinc-dipyrrin complexes representing intramolecular donor–acceptor systems. Intramolecular charge transfer depends on ligand variation and intermolecular environmental influences. In particular, we focus on steady-state and transient absorption methods to compare the response of the ligand dynamics with that of the complexes after photoexcitation. For the first time, we successfully tested zinc bis(dipyrrinato) complexes as photocatalysts in two different aerobic photooxidation reactions. Early-time dynamics after 100 fs in dichloromethane and in ethanol can be assigned to charge transfer states, while the subsequent response constitutes broad-band excited state dynamics, most likely of overlapping singlet and triplet states when probed in a relatively wide spectral window from 350 to 1400 nm and up to a delay time of 1.6 ns. In addition, a strong correlation between steady-state and time-resolved experiments makes this experimental approach a versatile tool for future investigations of this class of molecules, especially with respect to photocatalysis. The results of this study underpin the need for further development for quantifying amplitudes of the excited state population of electronically excited singlet and triplet states. [ABSTRACT FROM AUTHOR]

Organic materials with switchable dual circularly polarized luminescence (CPL) are highly desired because they can not only directly radiate tunable circularly polarized light themselves but also induce CPL for guests by providing a chiral environment in self‐assembled structures or serving as the hosts for energy transfer systems. However, most organic molecules only exhibit single CPL and it remains challenging to develop organic molecules with dual CPL. Herein, novel through‐space conjugated chiral foldamers are constructed by attaching two biphenyl arms to the 9,10‐positions of phenanthrene, and switchable dual CPL with opposite signs at different emission wavelengths are successfully realized in the foldamers containing high‐polarizability substitutes (cyano, methylthiol and methylsulfonyl). The combined experimental and computational results demonstrate that the intramolecular through‐space conjugation has significant contributions to stabilizing the folded conformations. Upon photoexcitation in high‐polar solvents, strong interactions between the biphenyl arms substituted with cyano, methylthio or methylsulfonyl and the polar environment induce conformation transformation for the foldamers, resulting in two transformable secondary structures of opposite chirality, accounting for the dual CPL with opposite signs. These findings highlight the important influence of the secondary structures on the chiroptical property of the foldamers and pave a new avenue towards efficient and tunable dual CPL materials. [ABSTRACT FROM AUTHOR]

We describe early and recent advances in the fascinating field of combined magnetic and optical properties of inorganic coordination compounds and in particular of 3d–4f single molecule magnets. We cover various applied techniques which allow for the correlation of results obtained in the frequency and time domain in order to highlight the specific properties of these compounds and the future challenges towards multidimensional spectroscopic tools. An important point is to understand the details of the interplay of magnetic and optical properties through performing time‐resolved studies in the presence of external fields especially magnetic ones. This will enable further exploration of this fundamental interactions i. e. the two components of electromagnetic radiation influencing optical properties. [ABSTRACT FROM AUTHOR]

Ammonia, poised as a carbon‐neutral energy carrier, holds immense promise in reshaping the future energy landscape. Despite the enduring importance of the Haber–Bosch process in ammonia production, its substantial carbon emissions and energy demands necessitate more sustainable pathways. Here, an advanced ammonia synthesis route, enhanced by photoexcitation is demonstrated, which fundamentally modifies the activation pathways of N2 molecules. This alteration significantly lowers the reaction activation energy, resulting in remarkably improved reaction efficiency. The impact of light excitation culminates in an unprecedented ammonia synthesis rate of 18 mmol g−1 h−1, surpassing the traditional thermal catalytic process by 2.57‐fold. More importantly, light assistance reduces the thermal energy input by ≈16%, making it comparable to thermal catalysis while substantially improving energy utilization. This work introduces a greener strategy for ammonia synthesis, pushing the century‐old fossil‐fueled Haber–Bosch process to a new frontier. [ABSTRACT FROM AUTHOR]

Urea is believed to have been essential to the synthesis of prebiotic nucleotides and thereby the RNA or DNA of the first lifeforms. Models suggesting that life began in wet‐dry cycles around shallow aquatic ponds imply that reactants such as urea were exposed to deep ultraviolet irradiation from the young sun. Detrimental photodissociation of urea induced by deep UV excitation potentially challenges these models. We here follow the primary deep ultraviolet photochemistry of aqueous urea. The data show that urea is barely excited at 200 nm due to weak ultraviolet absorption. The likelihood of photodissociation is further reduced by strong intra‐molecular coupling of the CN and CO stretch vibrations accompanied by an efficient dissipation of the excitation energy to the surrounding water molecules mitigated by urea‐water hydrogen bonds. We find that 54±5 % of the excited urea molecules dissociate. Reactions between the photoproducts and surrounding solvent molecules form carbamic acid or the carbamate anions within 0.6 ps. The molecules that do not dissociate return to the electronic ground state in 2 ps. Interestingly, the photodissociation processes of urea in the aqueous phase is different from earlier reported reactions observed following the VUV photolysis of urea in noble gas matrices and highlight the potential influence of water on the prebiotic photochemistry. [ABSTRACT FROM AUTHOR]

The achievement of high performance in organic solar cells (OSCs) is highly dependent on efficient exciton dissociation. However, a comprehensive understanding of the exciton dissociation process under photoexcitation in OSCs remains elusive. Herein, a prototypical system of PM6:Y6 is adopted to explore the exciton dissociation process. An organic semiconductor PCz with distinctive photoexcitation signals from PM6 and Y6 is incorporated as the third component. Femtosecond transient absorption spectroscopy demonstrates clear cascade charge transfer processes in ternary PM6:PCz:Y6 system. These cascade channels contribute to enhancing the efficiency of exciton dissociation. Consequently, the nonradiative recombination energy loss is reduced, resulting in an improved power conversion efficiency (PCE) of OSCs. Furthermore, the reduction of energy loss is verified in different OSCs. When PCz is introduced into the D18:L8‐BO system, a low nonradiative recombination energy loss of 0.175 eV is demonstrated, contributing a PCE of over 19%. This work highlights that the insight of efficient exciton dissociation enables low nonradiative recombination losses for efficient OSCs. [ABSTRACT FROM AUTHOR]

Direct reduction of unactivated alkyl halides for C(sp3)-N couplings under mild conditions presents a significant challenge in organic synthesis due to their low reduction potential. Herein, we introduce an in situ formed pyridyl-carbene-ligated copper (I) catalyst that is capable of abstracting halide atom and generating alkyl radicals for general C(sp3)-N couplings under visible light. Control experiments confirmed that the mono-pyridyl-carbene-ligated copper complex is the active species responsible for catalysis. Mechanistic investigations using transient absorption spectroscopy across multiple decades of timescales revealed ultrafast intersystem crossing (260 ps) of the photoexcited copper (I) complexes into their long-lived triplet excited states (>2 μs). The non-Stern-Volmer quenching dynamics of the triplets by unactivated alkyl halides suggests an association between copper (I) complexes and alkyl halides, thereby facilitating the abstraction of halide atoms via inner-sphere single electron transfer (SET), rather than outer-sphere SET, for the formation of alkyl radicals for subsequent cross couplings. Direct reduction of unactivated alkyl halides for C(sp3)-N couplings under mild conditions presents a significant challenge in organic synthesis. Here the authors introduce an in situ formed pyridyl carbene-ligated copper (I) catalyst that is capable of abstracting halide atom and generating alkyl radicals for general C(sp3)-N couplings under visible light. [ABSTRACT FROM AUTHOR]

A circular defect in 2D photonic crystal (CirD) lasers is developed, which has the potential to achieve a target communication density of 10 Pbps cm−2 for intrachip optical communications by vertical current injection. The AlGaOx cladding layer's oxidation width strongly influences the device's light confinement and electronic resistance. Herein, samples with different oxidation widths are fabricated and the relationship between threshold power and oxidation width through photoexcitation is revealed. The optimal range of the oxidation width is found to be 349–439 nm, which can ensure low electronic resistance and low threshold power. [ABSTRACT FROM AUTHOR]

The electron paramagnetic resonance (EPR) spectra of oxygen-deficient rutile TiO2 – δ under photoexcitation at low temperatures in the range of 15–40 K were measured. Excluding the early described Ti3+ centers, concentration of which is independent of photoexcitation, new EPR signals appear at various wavelengths (λ) of photoexcitation taken in the range 400–460 nm. From the analysis of the EPR data we conclude that the observed EPR signals can be attributed to either the positive-charged oxygen vacancies () with S = 1/2 (upon photoexcitation with λ ≤ 420 nm only), or more complex defects such as positively-charged [Ti3+–VO]+ pairs with S = 1/2 and neutral complexes of (Ti3+–VO–Ti3+) with S = 1. The latter is observed upon photoexcitation with a wavelength above 420 nm. [ABSTRACT FROM AUTHOR]

We electrically characterized melt-quenched amorphized Ge2Sb2Te5 (GST) phase-change memory cells of 20 nm thickness, ∼66–124 nm width, and ∼100–600 nm length with and without photoexcitation in the 80–275 K temperature range. The cells show distinctly different current–voltage characteristics in the low-field (≲19 MV/m), with a clear response to optical excitation by red light, and high-field (≳19 MV/m) regimes, with a very weak response to optical excitation. The reduction in carrier activation energy with photoexcitation in the low-field regime increases from ∼10 meV at 80 K to ∼50 meV at 150 K (highest sensitivity) and decreases again to 5 meV at 275 K. The heterojunctions at the amorphous–crystalline GST interfaces at the two sides of the amorphous region lead to formation of a potential well for holes and a potential barrier for electrons with activation energies in the order of 0.7 eV at room temperature. The alignment of the steady state energy bands suggests the formation of tunnel junctions at the interfaces for electrons and an overall electronic conduction by electrons. When photoexcited, the photo-generated holes are expected to be stored in the amorphous region, leading to positive charging of the amorphous region, reducing the barrier for electrons at the junctions and hence the device resistance in the low-field regime. Holes accumulated in the amorphous region are drained under a high electric field. Hence, the potential barrier cannot be modulated by photogenerated holes, and the photo-response is significantly reduced. These results support the electronic origin of resistance drift in amorphous GST. [ABSTRACT FROM AUTHOR]

Self‐inclusion complexes consisting of host‐guest conjugates are one of the unique supramolecular structures because they form in‐state and out‐state depending on the external stimuli. Despite many reports of the stimuli‐responsive self‐inclusion complex formation, study of the structural relaxation from out‐state to in‐state by photoexcitation has been unexplored. Herein, we report that an electron‐donating host and an electron‐accepting guest conjugate exhibits the structural relaxation from out‐state to in‐state by photoexcitation. Formation of the in‐state in the excited state resulted in exciplex emission along with the locally excited emission from the out‐state. Moreover, this structural relaxation by photoexcitation was suppressed not only by temperature, but also by the presence of guest molecules, resulting in changes in the ratio of the dual emission intensities. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) technology offers new opportunities for pushing the renewable energy‐driven ammonia synthesis toward a practical level, while still facing unsatisfactory efficiency due to the obstacle of dissociating inert nitrogen triple‐bonds. Herein, a novel donor‐site‐acceptor system is constructed in covalent organic frameworks to tackle this challenge for highly efficient PEC ammonia synthesis. Highly active boron site is elaborately embedded between the donor and acceptor units, which can be effectively activated with continuous electron flow upon photoexcitation. With the assistance of solar irradiation, the stubborn nitrogen dissociation is successfully changed from a passive endothermic reaction to a spontaneous exothermic process, completely eliminating the energy barrier of the rate‐determining step and facilitating the overall reaction kinetics. The proof‐of‐concept system achieved an excellent PEC NRR performance with a remarkable Faradaic efficiency of 91.6%, reaching the target set by the U.S. Department of Energy (90%). [ABSTRACT FROM AUTHOR]

Photocatalytic hydrogen production has garnered considerable attention as a latent solution to various energy challenges. Because of their distinct optical characteristics, persistent luminescence nanoparticles (PLNPs) can emit light long after illumination ends, making them highly advantageous for round-the-clock photocatalysis. However, photocatalytic activity is currently restricted owing to the low specific surface area and the high number of photogenerated electron–hole pairs. In this study, PLNP (ZnGa5Si5O18)/sulfur-doped carbon nitride (SCN) was synthesized via a solvothermal method and calcination. Under irradiation with a xenon lamp, the resulting PLNPs/SCN (1 : 1) composite exhibited excellent photocatalytic hydrogen evolution activity, with a hydrogen evolution rate of 3963.80 μmol g−1 h−1, which was 15 times and 1.4 times higher than that of PLNPs (307.1 μmol g−1 h−1) and SCN (2800.80 μmol g−1 h−1), respectively. The formation of a stable type II heterojunction is responsible for the high photocatalytic activity. This heterojunction effectively suppressed the electron–hole complexation generated during photoexcitation and enhanced the carrier flexibility. In addition, the PLNPs/SCN (1 : 1) composite had a larger specific surface area than the PLNPs. The synthesis of this novel composite heterojunction under mild conditions not only provides a new strategy for preparing PLNP-based composite catalysts but also holds significant potential for enabling round-the-clock photocatalysis. [ABSTRACT FROM AUTHOR]

Various selective excitation methods for molecular vibrations have been developed based on the characteristics of the applied lasers. In the present work, we coherently and selectively excited molecular vibrations up to 3000 cm−1 by irradiation with a sub-10-fs laser pulse. The spectral shaping of this laser pulse enabled us to selectively excite only the target vibrational frequency range (of the model compounds acetonitrile and benzene). Furthermore, the coherent molecular vibrational dynamics were compared between selective and nonselective excitation. The coherence of the molecular vibration persisted until 2–3 ps after photoexcitation, with the lifetime of this coherence being independent of whether the coherent molecular vibration was selective or nonselective excitation. [ABSTRACT FROM AUTHOR]

Hydrotalcite/bismuth solid solution (2D/2D CoAl-LDH/BiO(OH)XI1−X) heterojunction photocatalysts were fabricated through a hydrothermal route. Because of their identical layered structure and interlayer hydroxides, CoAl-LDH(2D) and BiO(OH)XI1−X(2D) form a tightly bonded heterojunction, resulting in efficient light absorption, excitation, and carrier migration conversion. At the same time, the large specific surface area and abundant hydroxyl groups of the layered structure make the heterojunction catalyst exhibit excellent performance in the photocatalytic degradation of organic pollutants. Under visible light irradiation and in the presence of 1 g/L of the catalyst, 10 mg/L of methyl orange (MO) in water could be completely degraded within 20 min, and the degradation rate of tetracycline (TC) reached 99.23% within 5 min. CoAl-LDH/BiO(OH)XI1−X still maintained good photocatalytic degradation activity of tetracycline after five cycles, and the structure of the catalyst did not change. The reaction mechanism related to the degradation of TC by photocatalytic reactions was explored in detail, and the photoexcitation of the semiconductor heterojunction, as well as the subsequent free radical reaction process and the degradation pathway of TC were clarified. This work provides a promising strategy for the preparation of efficient photocatalytic materials and the development of water purification technology. [ABSTRACT FROM AUTHOR]

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