Unraveling the excited-state vibrational cooling dynamics of chlorophyll-a using femtosecond broadband fluorescence spectroscopy.

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.

Incoherent ultrafast energy transfer in phycocyanin 620 from Thermosynechococcus vulcanus revealed by polarization-controlled two dimensional electronic spectroscopy.

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-ß84 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 ß84 has a lifetime constant of 400 fs, from ß155 to ß84 of 6-8 ps, and from ß155 to α84 of 66 ps, fully conforming to the Förster resonance energy transfer mechanism. The circular dichroism spectrum also reveals that the α84-ß84 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-ß84 excitonic dimer in contrast to allophycocyanin.

Photocatalytic Upgrading of Polylactic Acid Waste into Alanine under Mild Conditions.

Polylactic acid (PLA) has attracted increasing interest as a sustainable plastic because it can be degraded into CO2 and H2O in nature. However, this process is sluggish, and even worse, it is a CO2-emitting and carbon resource waste process. Therefore, it is highly urgent to develop a novel strategy for recycling post-consumer PLA to achieve a circular plastic economy. Herein, we report a one-pot photoreforming route for the efficient and selective amination of PLA waste into value-added alanine using CoP/CdS catalysts under mild conditions. Results show the alanine production rate can reach up to 2.4 mmol gcat -1 h-1, with a high selectivity (>75 %) and excellent stability. Time-resolved transient absorption spectra (TAS) reveal that CoP can rapidly extract photogenerated electrons from CdS to accelerate proton reduction, favoring hole-dominated PLA oxidation to coproduce alanine. This study offers an appealing way for upcycling PLA waste and creates new opportunities for green synthesis of amino acids.

Interfullerene Electronic Interactions and Excited-State Dynamics in Fullerene Dumbbell Conjugates.

Several dumbbell conjugates featuring M3N@Ih-C80 (M = Sc, Y) and C60 were prepared to systematically investigate interfullerene electronic interactions and excited state dynamics. From electrochemical investigations, we concluded that the redox potentials of our M3N@Ih-C80 (M = Sc, Y) dumbbells depend largely on the interfullerene electronic interactions. Assisted by DFT calculation, the unique role of metal atoms was highlighted. Most importantly, ultrafast spectroscopy experiments revealed symmetry-breaking charge separation in Sc3N@C80-dumbbell to yield an unprecedented (Sc3N@C80)•+-(Sc3N@C80)•- charge separated state. This is, to the best of our knowledge, the first time that symmetry-breaking charge separation following photoexcitation is corroborated in a fullerene system. As such, our work shed light on the significance of interfullerene electronic interactions and their uniqueness for modulating excited state properties.

Surface Ru-H Bipyridine Complexes-Grafted TiO2 Nanohybrids for Efficient Photocatalytic CO2 Methanation.

A series of novel surface Ru-H bipyridine complexes-grafted TiO2 nanohybrids were for the first time prepared by a combined procedure of surface organometallic chemistry with post-synthetic ligand exchange for photocatalytic conversion of CO2 to CH4 with H2 as electron and proton donors under visible light irradiation. The selectivity toward CH4 increased to 93.4% by the ligand exchange of 4,4'-dimethyl-2,2'-bipyridine (4,4'-bpy) with the surface cyclopentadienyl (Cp)-RuH complex and the CO2 methanation activity was enhanced by 4.4-fold. An impressive rate of 241.2 µL·g-1·h-1 for CH4 production was achieved over the optimal photocatalyst. The femtosecond transient IR absorption results demonstrated that the hot electrons were fast injected in 0.9 ps from the photoexcited surface 4,4'-bpy-RuH complex into the conduction band of TiO2 nanoparticles to form a charge-separated state with an average lifetime of ca. 50.0 ns responsible for the CO2 methanation. The spectral characterizations indicated clearly that the formation of CO2•- radicals by single electron reduction of CO2 molecules adsorbed on surface oxygen vacancies of TiO2 nanoparticles was the most critical step for the methanation. Such radical intermediates were inserted into the explored Ru-H bond to generate Ru-OOCH species and finally CH4 and H2O in the presence of H2.

Observation of photoinduced polarons in semimetal 1T-TiSe2.

In this work, ultrafast carrier dynamics of mechanically exfoliated 1T-TiSe2flakes 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 TiSe2sample. 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.

Analysis of Intensive Care Unit Nursing Clinical Judgment and Selection of Nursing Diagnosis for Cerebral Hemorrhage.

Few nursing informatics studies focus on selecting nursing diagnoses for critical patients. The absence of data about nursing clinical judgment in the care of patients with cerebral hemorrhage greatly hinders research progress in evidence-based care. A stratified, retrospective study analyzed 115 electronic "intelligent" nursing information system nurse assessments and nursing diagnoses. Data were documented from April 2019 to November 2020 for critically ill patients admitted with cerebral hemorrhage in a 10-bed medical ICU at a 1500-bed tertiary facility, Henan Honliv Hospital, in Henan Province, China. In the selection of nursing diagnoses among nurses of stratified competencies (novice to expert), novice and experienced nurses were found to have significant variances in selecting nursing diagnoses for critically ill patients with cerebral hemorrhage. Novice nurses more frequently selected the Activity Intolerance Risk diagnosis as an initial diagnosis ( P = .025). Experienced nurses selected the Fluid Volume Excess Risk diagnosis more frequently ( P = .003). Consequently, nursing information systems are important in evaluating professional practice. The access to structured, standardized nursing data for the complete nursing process enables nurse managers to comprehensively analyze the nursing care given to patients, the distribution of patient nursing diagnoses, and the status of patient care risks.

Mimicking Photosynthesis: A Natural Z-Scheme Photocatalyst Constructed from Red Mud Bauxite Waste for Overall Water Splitting.

All-solid-state Z-Scheme photocatalysts have attracted significant attention due to their great potential for solar fuel production. However, delicately coupling two individual semiconductors with a charge shuttle by a material strategy remains a challenge. Herein, we demonstrate a new protocol of natural Z-Scheme heterostructures by strategically engineering the component and interfacial structure of red mud bauxite waste. Advanced characterizations elucidated that the hydrogen-induced formation of metallic Fe enabled the effective Z-Scheme electron transfer from γ-Fe2 O3 to TiO2 , leading to the significantly boosted spatial separation of photo-generated carriers for overall water splitting. To the best of our knowledge, it is the first Z-Scheme heterojunction based on natural minerals for solar fuel production. Thus our work provides a new avenue toward the utilization of natural minerals for advanced catalysis applications.

Excited-state dynamics of all-trans protonated retinal Schiff base in CRABPII-based rhodopsin mimics.

The rhodopsin mimic is a chemically synthetized complex with retinyl Schiff base (RSB) formed between protein and the retinal chromophore that can mimic the natural rhodopsin-like protein. The artificial rhodopsin mimic is more stable and designable than the natural protein and hence has wider uses in photon detection devices. The mimic structure RSB, like the case in the actual rhodopsin-like protein, undergoes isomerization and protonation throughout the photoreaction process. As a result, understanding the dynamics of the RSB in the photoreaction process is critical. In this study, the ultrafast transient absorption spectra of three mutants of the cellular retinoic acid-binding protein II-based rhodopsin mimic at acidic environment were recorded, from which the related excited-state dynamics of the all-trans protonated RSB (AT-PRSB) were investigated. The transient fluorescence spectra measurements are used to validate some of the dynamic features. We find that the excited-state dynamics of AT-PRSB in three mutants share a similar pattern that differs significantly from the dynamics of 15-cis PRSB of the rhodopsin mimic in neutral solution. By comparing the dynamics across the three mutants, we discovered that the aromatic residues near the ß-ionone ring structure of the retinal may help stabilize the AT-PRSB and hence slow down its isomerization rate. The experimental results provide implications on designing a rhodopsin-like protein with significant infrared fluorescence, which can be particularly useful in the applications in biosensing or bioimaging in deeper tissues.

Application of Endoprosthetic Replacement in Old Patients with Isolated Proximal Femoral Bone Metastases.

BACKGROUND: Due to radical resection, endoprosthetic reconstruction (EPR) is more invasive and increases the risk of dislocation. Therefore, the suitability of EPR for elderly patients with metastatic tumor needs further investigation. METHODS: Seventy-one adult patients with isolated proximal femoral bone metastases who underwent EPR were retrospectively analyzed and stratified into two groups: elderly age group (≥60 years, n = 31) and younger age group (<60 years, n = 40). The effect of age on prognosis was analyzed to determine whether EPR is beneficial in elderly patients with proximal femoral metastatic tumor. Cox regression modeling was used to evaluate the effect of different factors on postoperative survival outcomes. RESULTS: Ten (32.26%) and 9 (22.50%) cases of perioperative complications were recorded in the elderly and younger age groups, respectively, with median survival times of 22.00 ± 4.61 months and 23.00 ± 2.85 months, respectively; a log-rank test showed that the difference was not statistically significant (p = 0.657). A Cox regression model was established with patient age as the covariable to evaluate whether it affected postoperative survival. The risk of death due to age was not significant (p = 0.649), but malignancy and femoral metastasis type were significantly associated with postoperative survival (p = 0.001 and p = 0.019). CONCLUSION: Although older patients have a slightly higher incidence of postoperative complications than younger patients, they do not experience severe adverse consequences. With rigorous selection and careful preparation, EPR is appropriate for the treatment of proximal femoral metastases in older patients, including those with Harrington type I-II acetabular invasion.

Semiconductor saturable absorber mirror in the 3-5†µm mid-infrared region.

Semiconductor saturable absorber mirrors (SESAMs) have been regarded as a revolutionary technology for ultrafast mode-locked lasers, producing numerous landmark laser breakthroughs. However, the operating wavelength of existing SESAMs is limited to less than 3 µm. In this study, we create a 3-5 µm mid-infrared (MIR) SESAM by engineering an InAs/GaSb type-II superlattice. Bandgap engineering and the strong coupling between potential wells in a superlattice enable a broadband response of saturable absorption in the 3-5 µm spectral range. Using the fabricated SESAM, we realize a SESAM mode-locked Er:ZBLAN fiber laser at 3.5 µm, which delivers MIR ultrashort pulses with high long-term stability. The breakthrough of SESAM fabrication in the MIR will promote the development of MIR ultrafast coherent sources and related application fields.

Vibrational and vibronic coherences in the energy transfer process of light-harvesting complex II revealed by two-dimensional electronic spectroscopy.

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.

Study on the biological mechanism of urolithin a on nasopharyngeal carcinoma in vitro.

CONTEXT: Urolithin A (UroA) can inhibit the growth of many human cancer cells, but it has not be reported if UroA inhibits nasopharyngeal carcinoma (NPC) cells. OBJECTIVE: To explore the inhibitory effect of UroA on NPC and potential mechanism in vitro. MATERIALS AND METHODS: RNA-sequencing-based mechanistic prediction was conducted by comparing KEGG enrichment of 40 µM UroA-treated for 24 h with untreated CNE2 cells. The untreated cells were selected as control. After NPC cells were treated with 20-60 µM UroA, proliferation, migration and invasion of were measured by colony formation, wound healing and transwell experiments. Apoptosis, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) were measured by flow cytometry, Hoechst 33342, Rhodamine 123, JC-1 staining and ROS assay methods, respectively. Gene and protein expression were measured by RT-qPCR and Western blotting assay. RESULTS: RNA-sequencing and KEGG enrichment revealed UroA mainly altered the ECM receptor interaction pathway. UroA inhibited cells proliferation, epithelial-mesenchymal-transition pathway, migration and invasion with IC50 values of 34.72 µM and 44.91 µM, induced apoptosis, MMP depolarization and increase ROS content at a concentration of 40 µM. UroA up-regulated E-cadherin, Bax/Bcl-2, c-caspase-3 and PARP proteins, while inhibiting COL4A1, MMP2, MMP9, N-cadherin, Vimentin and Snail proteins at 20-60 µM. Moreover, co-treatment of UroA (40 µM) and NAC (5 mM) could reverse the effect of UroA on apoptosis-related proteins. DISCUSSION AND CONCLUSIONS: RNA-sequencing technology based on bioinformatic analyses may be applicable for studiying the mechanism of drugs for tumour treatment.

Understanding Aerobic Nitrogen Photooxidation on Titania through In Situ Time-Resolved Spectroscopy.

Nitrate is an important raw material for chemical fertilizers, but it is industrially manufactured in multiple steps at high temperature and pressure, urgently motivating the design of a green and sustainable strategy for nitrate production. We report the photosynthesis of nitrate from N2 and O2 on commercial TiO2 in a flow reactor under ambient conditions. The TiO2 photocatalyst offered a high nitrate yield of 1.85 µmol h-1 as well as a solar-to-nitrate energy conversion efficiency up to 0.13 %. We combined reactivity and in situ Fourier transform infrared spectroscopy to elucidate the mechanism of nitrate formation and unveil the special role of O2 in N≡N bond dissociation. The mechanistic insight into charge-involved N2 oxidation was further demonstrated by in situ transient absorption spectroscopy and electron paramagnetic resonance. This work exhibits the mechanistic origin of N2 photooxidation and initiates a potential method for triggering inert catalytic reactions.

Sub-3 nm Ultrafine Cu2 O for Visible Light Driven Nitrogen Fixation.

Cu2 O, a low-cost, visible light responsive semiconductor photocatalyst represents an ideal candidate for visible light driven photocatalytic reduction of N2 to NH3 from the viewpoint of thermodynamics, but it remains unexplored. Reported here is the successful synthesis of uniformly sized and ultrafine Cu2 O platelets, with a lateral size of <3 nm, by the in situ topotactic reduction of a CuII -containing layered double hydroxide with ascorbic acid. The supported ultrafine Cu2 O offered excellent performance and stability for the visible light driven photocatalytic reduction of N2 to NH3 (the Cu2 O-mass-normalized rate as high as 4.10 mmol g Cu 2 O -1 h-1 at λ>400 nm), with the origin of the high activity being long-lived photoexcited electrons in trap states, an abundance of exposed active sites, and the underlying support structure. This work guides the future design of ultrafine catalysts for NH3 synthesis and other applications.

[Efficacy and safety of levetiracetam versus phenytoin as second-line drugs for the treatment of children with convulsive status epilepticus: a Meta analysis].

OBJECTIVE: To systematically evaluate the efficacy and safety of levetiracetam (LEV) versus phenytoin (PHT) as second-line drugs for the treatment of convulsive status epilepticus (CSE) in children. METHODS: English and Chinese electronic databases were searched for the randomized controlled trials comparing the efficacy and safety of LEV and PHT as second-line drugs for the treatment of childhood CSE. RevMan 5.3 software was used for data analysis. RESULTS: Seven studies with 1 434 children were included. The Meta analysis showed that compared with the PHT group, the LEV group achieved a significantly higher control rate of CSE (RR=1.12, 95%CI:1.00-1.24, P=0.05), but there was no significant difference between the two groups in the recurrence rate of epilepsy within 24 hours (RR=0.82, 95%CI:0.22-3.11, P=0.77) and the rate of further antiepileptic drug therapy (RR=0.97, 95%CI:0.64-1.45, P=0.87). There was no significant difference in the incidence rate of adverse events between the two groups (RR=0.77, 95%CI:0.55-1.09, P=0.15). CONCLUSIONS: LEV has a better clinical effect than PHT in the treatment of children with CSE and does not increase the incidence rate of adverse events.

In Situ Switching of Photoinduced Electron Transfer Direction by Regulating the Redox State in Fullerene-Based Dyads.

Novel fullerene-based donor-acceptor (DA) dyads, Sc3N@C80-PTZ and C60-PTZ, have been synthesized and investigated in which the photoinduced electron transfer direction is proved to be switchable by regulating the redox state. In detailed photophysical experiments, reductive electron transfer from the PTZ moiety to Sc3N@C80 is confirmed with transient absorption (TA) spectroscopy in the neutral Sc3N@C80-PTZ dyad. After oxidizing the PTZ moiety to PTZ•+ in a reversible manner, oxidative electron transfer from the Sc3N@C80 moiety to the PTZ•+ radical cation is corroborated experimentally and theoretically, leading to formation of a metastable charge transfer (CT) state (Sc3N@C80)•+-PTZ, which is not observed in the C60-PTZ•+ dyad. To the best of our knowledge, this is the first time in situ tunable molecular photodiode-like behavior is fulfilled utilizing a fullerene dyad. These findings will contribute to the future application of fullerene-based DA conjugates in molecular electronic devices.

Electronic State-Resolved Multimode-Coupled Vibrational Wavepackets in Oxazine 720 by Two-Dimensional Electronic Spectroscopy.

The difference between the excited- and ground-state vibrational wavepackets remains to be fully explored when multiple vibrational modes are coherently excited simultaneously by femtosecond pulses. In this work, we present a series of one- and two-dimensional electronic spectroscopy for studying multimode wavepackets of oxazine 720 in solution. Fourier transform (FT) maps combined with time-frequency transform (TFT) are employed to unambiguously distinguish the origin of low-frequency vibrational wavepackets, that is, an excited-state vibrational wavepacket of 586 cm-1 with a dephasing time of 0.7 ps and a ground-state vibrational wavepacket of 595 cm-1 with a dephasing time of 1.3-1.7 ps. We also found the additional low-frequency vibrational wavepackets resulting from the coupling of the 595 cm-1 mode to a series of high-frequency modes centered at 1150 cm-1 via electronic transitions. The combined use of FT maps and TFT analysis allows us to reveal the potential vibrational coupling of wavepackets and offers the possibility of disentangling the coupling between the electronic and vibrational degrees of freedom in condensed-phase systems.

Correction of spectral distortion in two-dimensional electronic spectroscopy arising from the wedge-based delay line.

Unlike the probe wavelength, which is spectrally resolved by monochromator, the excitation wavelength in two-dimensional electronic spectroscopy is retrieved by means of Fourier transform of the interference signal introduced by the coherence delay time between the first and second excitation laser pulses. Hence, the calibration of delay lines would determine its accuracy. In this work, we showed that an inaccurate calibration factor of wedge-based delay line would result in a global peak shift and asymmetric spectral twists along the excitation axis. Both theoretical analysis and experiments have shown that such spectral distortions can be corrected by an accurately predetermined calibration factor. The relative accuracy of calibration factor reaches 3 × 10-5 in our setup. The dispersion effect of wedges also has been considered for the broadband excitation.

Effect of trap states on photocatalytic properties of boron-doped anatase TiO2 microspheres studied by time-resolved infrared spectroscopy.

The features of the electronic structure of semiconductor photocatalysts are fundamental to understanding the corresponding photocatalytic process. Besides the bandgap and edges, the behavior of photogenerated charge carriers and trap states can also greatly affect the photocatalytic process but it has been less considered during the material design. A previous study (G. Liu, J. Pan, L. Yin et al., Adv. Funct. Mater., 2012, 22, 3233-3238) showed that the interstitial boron on anatase {001} facets can change the photocatalytic preference from reductive H2 evolution to oxidative O2 evolution in the water splitting reaction, interpreted as the change in the band edges. In this work, we employed transient infrared absorption-excitation energy scanning spectroscopy and femtosecond time-resolved mid-infrared spectroscopy to investigate this phenomenon in view of the effect caused by the boron dopant on the photogenerated carrier kinetics and the energy level distribution of the trap states. We found that the surface boron doping eliminates significantly the trap states above the valence band, which improves its photocatalytic oxygen generation. On the other hand, surface boron doping also introduces a substantial amount of electron recombination centers (i.e., Bσ+ in the shell layer). Furthermore, surface boron doping also leads to an inefficient electron transfer from TiO2 to the co-catalyst Pt. Both of these effects give rise to its inferior photocatalytic capability in H2 evolution.