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Phycocyanin 620 (PC620) is the outermost light-harvesting complex in phycobilisome of cyanobacteria, engaged in light collection and energy transfer to the core antenna, allophycocyanin. Recently, long-lived exciton–vibrational coherences have been observed in allophycocyanin, accounting for the coherent energy transfer [Zhu et al., Nat. Commun. 15, 3171 (2024)]. PC620 has a nearly identical spatial location of three α84–β84 phycocyanobilin pigment pairs to those in allophycocyanin, inferring an existence of possible coherent energy transfer pathways. However, whether PC620 undergoes coherent or incoherent energy transfer remains debated. Furthermore, accurate determination of energy transfer rates in PC620 is still necessary owing to the spectral overlap and broadening in conventional time-resolved spectroscopic measurements. In this work, the energy transfer process within PC620 was directly resolved by polarization-controlled two dimensional electronic spectroscopy (2DES) and global analysis. The results show that the energy transfer from α84 to the adjacent β84 has a lifetime constant of 400 fs, from β155 to β84 of 6–8 ps, and from β155 to α84 of 66 ps, fully conforming to the Förster resonance energy transfer mechanism. The circular dichroism spectrum also reveals that the α84–β84 pigment pair does not form excitonic dimer, and the observed oscillatory signals are confirmed to be vibrational coherence, excluding the exciton–vibrational coupling. Nodal line slope analysis of 2DES further reveals that all the vibrational modes participate in the energy dissipation of the excited states. Our results consolidate that the ultrafast energy transfer process in PC620 is incoherent, where the twisted conformation of α84 is suggested as the main cause for preventing the formation of α84–β84 excitonic dimer in contrast to allophycocyanin. [ABSTRACT FROM AUTHOR]

Understanding the dynamics of excited-state vibrational energy relaxation in photosynthetic pigments is crucial for elucidating the mechanisms underlying energy transfer processes in light-harvesting complexes. Utilizing advanced femtosecond broadband transient fluorescence (TF) spectroscopy, we explored the excited-state vibrational dynamics of Chlorophyll-a (Chl-a) both in solution and within the light-harvesting complex II (LHCII). We discovered a vibrational cooling (VC) process occurring over ∼6 ps in Chl-a in ethanol solution following Soret band excitation, marked by a notable ultrafast TF blueshift and spectral narrowing. This VC process, crucial for regulating the vibronic lifetimes, was further elucidated through the direct observation of the population dynamics of higher vibrational states within the Qy electronic state. Notably, Chl-a within LHCII demonstrated significantly faster VC dynamics, unfolding within a few hundred femtoseconds and aligning with the ultrafast energy transfer processes observed within the complex. Our findings shed light on the complex interaction between electronic and vibrational states in photosynthetic pigments, underscoring the pivotal role of vibrational dynamics in enabling efficient energy transfer within light-harvesting complexes. [ABSTRACT FROM AUTHOR]

With the rapid development of the e-commerce industry, RMFS is prevalent in the modern logistic center. As for this advanced system, robots can apply two following strategies: all-time following and non-following in a task. Alltime following strategy means that robot follows the picking rack until the task is completed, and non-following strategy refers to that robot will leave the rack to perform other tasks when the rack is queued at the workstation, and the robot will be dispatched when the rack needs to be moved. For the robot scheduling problem under two kinds of following strategies, aiming at the shortest total time for the robot to complete the wave tasks, the robot scheduling models under two kinds of following strategies are designed. The simulation experimental platform under two kinds of following strategies are designed based on genetic algorithm, and the system performance of all-time following strategy and non- following strategy is compared through simulation experiments. The decision-making curve of the following strategy based on the shortest total time is obtained, and it is proved that selecting the appropriate following strategy, which is combined with the specific working conditions, can effectively improve the operation efficiency of the picking system. The application following strategy curve can help enterprises to choose robot following strategy. [ABSTRACT FROM AUTHOR]

Parametric superfluorescence (PSF), which originated from the optical amplification of vacuum quantum noise, is the primary noise source of femtosecond fluorescence non-collinear optical parametric amplification spectroscopy (FNOPAS). It severely affects the detection limit of FNOPAS to collect the femtosecond time-resolved spectra of extremely weak fluorescence. Here, we report the development of femtosecond fluorescence conical optical parametric amplification spectroscopy (FCOPAS), aimed at effectively suppressing the noise fluctuation from the PSF background. In contrast to traditional FNOPAS configurations utilizing lateral fluorescence collection and dot-like parametric amplification, FCOPAS employs an innovative conical fluorescence collection and ring-like amplification setup. This design enables effective cancellation of noise fluctuation across the entire PSF ring, resulting in an approximate order of magnitude reduction in PSF noise compared to prior FNOPAS outcomes. This advancement enables the resolution of transient fluorescence spectra of 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) dye molecules in ethanol, even at an optically dilute concentration of 10−6 mol/l, with significantly enhanced signal-to-noise ratios. This improvement will be significant for extremely weak fluorescence detection on the femtosecond time scale. [ABSTRACT FROM AUTHOR]

Solar hydrogen production at a high efficiency holds the significant importance in the age of energy crisis, while the micro‐environment manipulation of active sites on photocatalysts plays a profound role in enhancing the catalytic performance. In this work, a series of well‐defined single‐site Ni‐grafted TiO2 photocatalysts with unique and specific coordination environments, 2,2′‐bipyridine‐Ni−O−TiO2 (T−Ni Bpy) and 2‐Phenylpyridine‐Ni−O−TiO2 (T−Ni Phpy), were constructed with the methods of surface organometallic chemistry combined with surface ligand exchange for visible‐light‐induced photocatalytic hydrogen evolution reaction (HER). A prominent rate of 33.82 μmol ⋅ g−1 ⋅ h−1 and a turnover frequency of 0.451 h−1 for Ni are achieved over the optimal catalyst T−Ni Bpy for HER, 260‐fold higher than those of Ni−O−TiO2. Fewer electrons trapped oxygen vacancies and a larger portion of long‐lived photogenerated electrons (>3 ns, ~52.9 %), which were demonstrated by the electron paramagnetic resonance and femtosecond transient IR absorption, correspond to the photocatalytic HER activity over the T−Ni Bpy. The number of long‐lived free electrons injected from the Ni photoabsorber to the conduction band of TiO2 is one of the determining factors for achieving the excellent HER activity. [ABSTRACT FROM AUTHOR]

The presence of quantum coherence in light-harvesting complex II (LHCII) as a mechanism to understand the efficiency of the light-harvesting function in natural photosynthetic systems is still debated due to its structural complexity and weak-amplitude coherent oscillations. Here, we revisit the coherent dynamics and clarify different types of coherences in the energy transfer processes of LHCII using a joint method of the high-S/N transient grating and two-dimensional electronic spectroscopy. We find that the electronic coherence decays completely within 50 fs at room temperature. The vibrational coherences of chlorophyll a dominate over oscillations within 1 ps, whereas a low-frequency mode of 340 cm−1 with a vibronic mixing character may participate in vibrationally assisted energy transfer between chlorophylls a. Our results may suggest that vibronic mixing is relevant for rapid energy transfer processes among chlorophylls in LHCII. [ABSTRACT FROM AUTHOR]

In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe2 flakes from the high-quality single crystals with self-intercalated Ti atoms are investigated by femtosecond transient absorption spectroscopy. The observed coherent acoustic and optical phonon oscillations after ultrafast photoexcitation reveal the strong electron–phonon coupling in 1T-TiSe2. The ultrafast carrier dynamics probed in both visible and mid-infrared regions indicate that some photogenerated carriers localize near the intercalated Ti atoms and form small polarons rapidly within several picoseconds after photoexcitation due to the strong and short-range electron–phonon coupling. The formation of polarons leads to a reduction of carrier mobility and a long-time relaxation process of photoexcited carriers for several nanoseconds. The formation and dissociation rates of the photoinduced polarons are dependent on both the pump fluence and the thickness of TiSe2 sample. This work offers new insights into the photogenerated carrier dynamics of 1T-TiSe2, and emphasizes the effects of intercalated atoms on the electron and lattice dynamics after photoexcitation. [ABSTRACT FROM AUTHOR]