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Kinetics of ozone destruction due to the recombination of oxygen atoms produced by pulsed 266 nm laser photolysis of O3/M (M = CO2 and/or N2) mixtures was studied using the absorption and emission spectroscopy to follow time evolutions of O3 and electronically excited molecules O2* formed in the recombination process 2O(3P) + M → O2* + M. An unexpected high ozone destruction rate was observed when O2* was present in the system. The kinetic model developed for the oxygen nightglow on the terrestrial planets was adapted to interpret the detected temporal profiles of the ozone number density and the O2* emission intensities. It was deduced that the vibrationally excited singlet delta oxygen molecule O2(a1Δ, υ) formed in the secondary processes reacts efficiently with ozone in the process O2(a1Δ, υ ≥ 3) + O3 → 2O2 + O, and the rate constant of this process was estimated to be 3 × 10−11 cm3 s−1. Ab initio calculations at the CASPT2(14, 12)/cc-pVTZ/UωB97XD/cc-pVTZ level of theory were applied to find the reaction pathway from the reactants to products on the O5 potential energy surface. These calculations revealed that the O2(a1Δ) + O3 reaction is likely to proceed via singlet–triplet intersystem crossing exhibiting an energy barrier of 9.6 kcal/mol, which lies between two and three quanta of vibrational excitation of O2(a1Δ), and hence, O2(a1Δ, υ) with υ ≥ 3 could rapidly react with ozone. [ABSTRACT FROM AUTHOR]

Excited state dynamics of molecules at interfaces can be studied using second-order non-linear spectroscopic methods such as time-resolved electronic sum-frequency generation (SFG). However, as such measurements inherently generate very small signals, they are often overwhelmed by signals originating from fluorescence. Here, this limitation is overcome by optical Kerr gating of the SFG signal to discriminate against fluorescence. The new approach is demonstrated on the excited state dynamics of malachite green at the water/air interface, in the presence of a highly fluorescent coumarin dye, and on the photo-oxidation of the phenolate anion at the water/air interface. The generality of the use of optical Kerr gating to SFG measurements is discussed. [ABSTRACT FROM AUTHOR]

This work reports results on the simultaneous spectroscopy of the specific heat and thermal expansivity of glycerol by making use of a wideband time-resolved thermal lens (TL) technique. An analytical model is presented which describes TL transients in a relaxing system subjected to impulsive laser heating. Experimentally, a set of TL waveforms, from 1 ns to 20 ms, has been recorded for a glycerol sample upon supercooling, from 300 to 200 K. The satisfactory fitting of the TL signals to the model allows the assessment of relaxation strength and relaxation frequency of the two quantities up to sub-100 MHz, extending the specific heat and thermal expansion spectroscopy by nearly three and eight decades, respectively. Fragility values, extracted from the relaxation behavior of the specific heat and the thermal expansion coefficient, are found to be similar, despite a substantial difference in relaxation strength. [ABSTRACT FROM AUTHOR]

Recent advances in techniques for generating quantum light have stimulated research on novel spectroscopic measurements using quantum entangled photons. One such spectroscopy technique utilizes non-classical correlations among entangled photons to enable measurements with enhanced sensitivity and selectivity. Here, we investigate the spectroscopic measurement utilizing entangled three photons. In this measurement, time-resolved entangled photon spectroscopy with monochromatic pumping [A. Ishizaki, J. Chem. Phys. 153, 051102 (2020)] is integrated with the frequency-dispersed two-photon counting technique, which suppresses undesired accidental photon counts in the detector and thus allows one to separate the weak desired signal. This time-resolved frequency-dispersed two-photon counting signal, which is a function of two frequencies, is shown to provide the same information as that of coherent two-dimensional optical spectra. The spectral distribution of the phase-matching function works as a frequency filter to selectively resolve a specific region of the two-dimensional spectra, whereas the excited-state dynamics under investigation are temporally resolved in the time region longer than the entanglement time. The signal is not subject to Fourier limitations on the joint temporal and spectral resolution, and therefore, it is expected to be useful for investigating complex molecular systems in which multiple electronic states are present within a narrow energy range. [ABSTRACT FROM AUTHOR]

Funneling dynamics in conjugated dendrimers has raised great interest in the context of artificial light-harvesting processes. Photoinduced relaxation has been explored by time-resolved spectroscopy and simulations, mainly by semiclassical approaches or referring to open quantum systems methods, within the Redfield approximation. Here, we take the benefit of an ab initio investigation of a phenylacetylene trimer, and in the spirit of a divide-and-conquer approach, we focus on the early dynamics of the hierarchy of interactions. We build a simplified but realistic model by retaining only bright electronic states and selecting the vibrational domain expected to play the dominant role for timescales shorter than 500 fs. We specifically analyze the role of the in-plane high-frequency skeletal vibrational modes involving the triple bonds. Open quantum system non-adiabatic dynamics involving conical intersections is conducted by separating the electronic subsystem from the high-frequency tuning and coupling vibrational baths. This partition is implemented within a robust non-perturbative and non-Markovian method, here the hierarchical equations of motion. We will more precisely analyze the coherent preparation of donor states or of their superposition by short laser pulses with different polarizations. In particular, we extend the π-pulse strategy for the creation of a superposition to a V-type system. We study the relaxation induced by the high-frequency vibrational collective modes and the transitory dissymmetry, which results from the creation of a superposition of electronic donor states. [ABSTRACT FROM AUTHOR]

Benefitting from the capability of recording scalar (J) couplings and bonding information, 2D J-resolved NMR spectroscopy constitutes an important tool for molecular structure analysis and mixture component identification. Unfortunately, conventional 2D J-resolved experiments generally encounter challenges of insufficient spectral resolution and strong coupling artifacts. In this study, a general NMR approach is exploited to record absorption-mode artifact-free 2D J-resolved spectra. This proposal adopts the advanced triple-spin-echo pure shift yielded by chirp excitation element to eliminate J coupling splittings and preserve chemical shifts along the F2 dimension, and it additionally utilizes the echo-train J acquisition to reveal the multiplet structure along the F1 dimension in accelerated experimental acquisition. Thus, it permits one to extract multiplet structure information from crowded spectral regions in one-shot experiments, with considerable resolution advantage resulting from completely decoupling F2 dimension and absorption-mode presentation, thus facilitating analysis on complex samples. More importantly, this method grants the superior performance on suppressing strong coupling artifacts, which have been affirmed by experiments on a series of chemical samples. As a consequence, this proposed method serves as a useful tool for J coupling measurements and multiplet structure analyses on complex samples that contain crowded NMR resonances and strong coupling spin systems, and it may exhibit broad application potentials in fields of physics, chemistry, and medical science, among others. [ABSTRACT FROM AUTHOR]

Two-dimensional electronic–vibrational spectroscopy (2DEVS) is an emerging spectroscopic technique which exploits two different frequency ranges for the excitation (visible) and detection (infrared) axes of a 2D spectrum. In contrast to degenerate 2D techniques, such as 2D electronic or 2D infrared spectroscopy, the spectral features of a 2DEV spectrum report cross correlations between fluctuating electronic and vibrational energy gaps rather than autocorrelations as in the degenerate spectroscopies. The center line slope of the spectral features reports on this cross correlation function directly and can reveal specific electronic–vibrational couplings and rapid changes in the electronic structure, for example. The involvement of the two types of transition moments, visible and infrared, makes 2DEVS very sensitive to electronic and vibronic mixing. 2DEV spectra also feature improved spectral resolution, making the method valuable for unraveling the highly congested spectra of molecular complexes. The unique features of 2DEVS are illustrated in this paper with specific examples and their origin described at an intuitive level with references to formal derivations provided. Although early in its development and far from fully explored, 2DEVS has already proven to be a valuable addition to the tool box of ultrafast nonlinear optical spectroscopy and is of promising potential in future efforts to explore the intricate connection between electronic and vibrational nuclear degrees of freedom in energy and charge transport applications. [ABSTRACT FROM AUTHOR]

A method has been proposed to reconstruct at arbitrary time the spectral–temporal characteristics of a 14.4‑keV single-photon wave packet that is emitted by a 57Co source and is resonantly absorbed in the medium of 57Fe nuclei. The method is based on the frequency separation of the field emitted by the source and resonance nuclear polarization induced by this field by means of delayed acoustically induced transparency of the absorber, which appears after the activation of oscillations of the absorber at the corresponding frequency and amplitude. The proposed method has been compared to the known quantum-optical memory methods and methods of nuclear polarization control in the gamma-ray range. Experimental conditions have been proposed to implement the method. It has been shown that this method allows the implementation of the time-resolved Mössbauer spectroscopy of various media. [ABSTRACT FROM AUTHOR]

In the presented study, a novel approach for thermal atomic layer deposition (ALD) of Al2O3 thin films using plasma-activated water (PAW) as a co-reactant, replacing traditionally employed deionized (DI) water, is introduced. Utilizing ex situ PAW achieves up to a 16.4% increase in the growth per cycle (GPC) of Al2O3 films, consistent with results from plasma-enhanced atomic layer deposition (PEALD). Time-resolved mass spectrometry (TRMS) revealed disparities in CH4 partial pressures between TMA reactions with DI water and PAW, with PAW demonstrating enhanced reactivity. Reactive oxygen species (ROS), namely H2O2 and O3, are posited to activate Si(100) substrate sites, thereby improving GPC and film quality. Specifically, Al2O3 films grown with PAW pH = 3.1 displayed optimal stoichiometry, reduced carbon content, and an expanded bandgap. This study thus establishes "PAW-ALD" as a descriptor for this ALD variation and highlights the significance of comprehensive assessments of PAW in ALD processes. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) with mobile charges have attracted significant attention due to their potential applications in photoelectric devices, chemical resistance sensors, and catalysis. However, fundamental understanding of the charge transport pathway within the framework and the key properties that determine the performance of conductive MOFs in photoelectric devices remain underexplored. Herein, we report the mechanisms of photoinduced charge transport and electron dynamics in the conductive 2D M−HHTP (M=Cu, Zn or Cu/Zn mixed; HHTP=2,3,6,7,10,11‐hexahydroxytriphenylene) MOFs and their correlation with photoconductivity using the combination of time‐resolved terahertz spectroscopy, optical transient absorption spectroscopy, X‐ray transient absorption spectroscopy, and density functional theory (DFT) calculations. We identify the through‐space hole transport mechanism through the interlayer sheet π–π interaction, where photoinduced hole state resides in HHTP ligand and electronic state is localized at the metal center. Moreover, the photoconductivity of the Cu−HHTP MOF is found to be 65.5 S m−1, which represents the record high photoconductivity for porous MOF materials based on catecholate ligands. [ABSTRACT FROM AUTHOR]

The optical filament-based radioxenon sensing can potentially overcome the constraints of conventional detection techniques that are relevant for nuclear security applications. This study investigates the spectral signatures of pure xenon (Xe) when excited by ultrafast laser filaments at near-atmosphericpressure and in short and loose-focusing conditions. The two focusing conditions lead to laser intensity differences of several orders of magnitude and different plasma transient behavior. The gaseous sample was excited at atmospheric pressure using ∼7 mJ pulses with a 35 fs pulse duration at 800 nm wavelength. The optical signatures were studied by time-resolved spectrometry and imaging in orthogonal light collection configurations in the ∼400 nm (VIS) and ∼800 nm (NIR) spectral regions. The most prominent spectral lines of atomic Xe are observable in both focusing conditions. An on-axis light collection from an atmospheric air–Xe plasma mixture demonstrates the potential of femtosecond filamentation for the remote sensing of noble gases. [ABSTRACT FROM AUTHOR]

Step‐scan Fourier‐transform infrared spectroscopy (ssFTIR) simultaneously provides the spectroscopic and kinetic information of a given reaction. ssFTIR has been extensively employed to acquire the transient absorption and emission spectra in gas phase for identifying unstable species, for example, various Criegee intermediates, and elucidating the dynamics and kinetics of the reaction, such as the molecular elimination dynamics of haloalkenes and the bimolecular reactions involving chlorine atoms and singlet oxygen atoms. In addition to gaseous studies, ssFTIR has been also utilized to record the time‐resolved difference spectra of the photochemical reactions in condensed phases, such as the photolysis of metal–ligand complexes, photocycles of the retinal proteins, coordination capability of solvents to unstable transient species, chemical reactions of atmosphere‐related molecules in aqua, and the exciplex dynamics of organic light emitting materials. Moreover, my group has pioneered the recording of the transient thermal infrared emission of gold nanostructures upon photoexcitation. The experimental setups and the working principles for probing the time‐resolved infrared absorption and emission in condensed phases will be revealed and a number of studies on chemical, biological, and materials systems will be described. These reported results demonstrate that ssFTIR is a versatile tool for exploring the properties of novel materials and photoreactions in condensed phases. [ABSTRACT FROM AUTHOR]

We present X-ray observations of the recent outburst of 2022 from the neutron star low-mass X-ray binary source 1A 1744−361. Spectral properties of the source have been analysed using joint Nuclear Spectroscopic Telescope Array and Neutron Star Interior Composition Explorer observations. During our observations, the source happens to be in the banana state (soft state) of the hardness–intensity diagram. In addition to a power law with a high-energy cut-off, the spectrum is found to exhibit broad iron Kα emission along with distinct absorption features. A prominent absorption feature observed at 6.92 keV may be interpreted as Kα absorption line from hydrogen-like iron. The absorption feature observed at 7.98 keV may be interpreted as a blend of Fe xxv and Ni xxvii transitions. We have summarized the evidence of variability of the spectral features observed in the X-ray continuum by time-resolved spectroscopy. [ABSTRACT FROM AUTHOR]

In this study, the insertion of different monodentate co-ligands on Pt(II) complexes bearing a monoanionic C^N*N luminophore as a tridentate chelator was achieved beyond the previously reported chlorido- ([PtCl(L)]) and cyanido-decorated ([PtCN(L)]) analogues. To investigate the impact of the auxiliary ligand on the photophysical properties, we introduced a neutral carbonyl-ligand and observed a lower photoluminescence quantum yield (ΦL) than with a cyanido moiety. However, the direct substitution of the chlorido co-ligand by a NO-related derivative was not successful. Interestingly, the attempted reduction of the successfully inserted nitrito-N-ligand in [PtNO2(L)] resulted in the oxidation of the Pt(II)-center to Pt(IV), as demonstrated by X-ray diffractometry. For comparison, the trifluoroacetato Pt(II) and chlorido Pt(IV) complexes ([PtTFA(L)] and [PtCl3(L)], respectively) were also synthesized. The photophysical characterization revealed similar photoluminescence profiles for all complexes, indicating a weak effect of the co-ligand on the excited state; in fact, all complexes display emission from metal-perturbed ligand-centered states (even the Pt(IV) species). Nonetheless, longer excited state lifetimes (τav) suggest a reduced thermally-activated radiationless deactivation via metal-centered states upon exchange of the chlorido units for other monodentate entities, yet without significantly improving the overall ΦL at room temperature. The irreversible oxidation waves (measured via cyclic voltammetry) mostly stem from the Pt(II)-center; the co-ligand-related drop of these potentials correlates with the increasing σ-donating capacities of the ancillary ligand. In summary, an enhanced π-acceptor capacity does not necessarily improve the ΦL and can even impair radiative rates by compromising the perturbative participation of the metal center on the emissive triplet state; in addition, strong σ-donor abilities improve the phosphorescence efficiencies by hampering the thermal population of dissociative electronic configurations related to the participation of antibonding d*-orbitals at the metal center. [ABSTRACT FROM AUTHOR]

Femtosecond double optical pulse experiments with nanosecond time delay were conducted in air. Terahertz pulses were generated from laser plasmas produced by the irradiation with the main pulses on shockwave excited by the pre‐pulse illumination. Intensity of the terahertz pulses depends on the time difference Δt and relative position Δy between the pre‐ and main pulses. We found a characteristic dependence of the intensity of the terahertz pulses on Δy at a longer time delay, Δt = 14.7 ns, which has two maxima while only one maximum was observed when delay times were at and shorter than 9.7 ns. The results are discussed taking into account air density distribution of the shockwave. The terahertz emission spectroscopy shown here can be a useful technique for investigating density structure and its time variation of shockwave with high temporal resolution. [ABSTRACT FROM AUTHOR]

The properties of a conjugated copolymer (CP), poly[(9,9-Dioctyl-2,7-divinylenefluorenylene)-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene) (PDVF-co-MEH-PV), were investigated in the presence of graphene oxide (GO) and reduced graphene oxide (rGO) using absorption, fluorescence, laser, and time-resolved spectroscopy. CPs are usually dissolved in low-polar solvents. Although GO does not dissolve well, rGO and PDVF-co-MEH-PV dissolve in chloroform due to their oxygen acceptor sites. Hence, we studied rGO/PDVF-co-MEH-PV (CP/rGO), performing all experiments and simulations in chloroform. We performed simulations on PDVF-co-MEH-PV, approximate GO, and rGO using time-dependent density-functional theory calculations to comprehend the molecular dynamics and interactions at the molecular level. The simulation polymer used a tail-truncated oligomer model with up to three monomer units. The simulation and experimental results were in agreement. Further, the PDVF-co-MEH-PV exhibited fluorescence, laser quenching, rGO-mediated laser blinking, and spectral broadening effects when GO and rGO concentrations increased. The experimental and simulation results were compared to provide a plausible mechanism of interaction between PDVF-co-MEH-PV and rGO. We observed that for lower concentrations of rGO, the interaction did not considerably decrease the amplified spontaneous emissions of PDVF-co-MEH-PV. However, the fluorescence of PDVF-co-MEH-PV was considerably quenched at higher concentrations of rGO. These results could be helpful for future applications, such as in sensors, solar cells, and optoelectronic device design. To demonstrate the sensor capability of these composites, a paper-based sensor was designed to detect ethanol and nitrotoluene. An instrumentation setup was proposed that is cheap, reusable, and multifunctional. [ABSTRACT FROM AUTHOR]

Ephrin type-A receptor 2 (EphA2) is a receptor tyrosine kinase that initiates both ligand-dependent tumor-suppressive and ligand-independent oncogenic signaling. We used time-resolved, live-cell fluorescence spectroscopy to show that the ligand-free EphA2 assembles into multimers driven by two types of intermolecular interactions in the ectodomain. The first type entails extended symmetric interactions required for ligand-induced receptor clustering and tumor-suppressive signaling that inhibits activity of the oncogenic extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) protein kinases and suppresses cell migration. The second type is an asymmetric interaction between the amino terminus and the membrane proximal domain of the neighboring receptors, which supports oncogenic signaling and promotes migration in vitro and tumor invasiveness in vivo. Our results identify the molecular interactions that drive the formation of the EphA2 multimeric signaling clusters and reveal the pivotal role of EphA2 assembly in dictating its opposing functions in oncogenesis. [ABSTRACT FROM AUTHOR]

Purpose: It has been reported that cerebral oxygen saturation (rSO2) measured by near infrared spectroscopy is low in dialysis patients. We compared the rSO2 values of dialysis patients before living donor kidney transplantation and their donors as controls by using three spectroscopes that utilize different principals, the INVOS 5100C (spatially resolved spectroscopy), FORE-SIGHT ELITE (modified Beer–Lambert law) and tNIRS-1 (time-resolved spectroscopy). Methods: Before induction of anesthesia, the sensors of one of the three spectroscopes were placed on the forehead and rSO2 values were recorded followed by the same measurement using the other two spectroscopes. The primary objective was to compare the rSO2 values of the dialysis patients and controls using the three spectroscopes by the unpaired t test. Then we compared the rSO2 values among the spectroscopes in both dialysis patients and controls by one-way ANOVA. Finally, we examined the relations between the rSO2 values and the physiological values by using the Pearson correlation coefficient. Results: Fifteen pairs of dialysis patients and controls were studied. With the INVOS 5100 C, the values of the dialysis patients (59.7 ± 9.7% (mean ± standard deviation) were 13% lower than those of the controls (73.3 ± 6.9%) (P < 0.01). With the tNIRS-1, the values were 57.8 ± 4.8% in the dialysis patients and 63.3 ± 3.5% in the controls (P < 0.01). Almost no differences were observed with the FORE-SIGHT ELITE (71.6 ± 4.9% [dialysis patients] vs. 70.8 ± 4.3% [Controls]) (P = 0.62). Among the spectroscopes, the values were significantly different in both dialysis patients and controls. For the INVOS 5100C and tNIRS-1, correlation coefficients between rSO2 values and blood Hb and serum Alb were more than 0.5. Conclusions: The rSO2 values for comparisons between the dialysis patients and the controls were different according to differences of the principles of the near infrared spectroscopes. In the INVOS 5100C and tNIRS-1, rSO2 values may be related to blood Hb and serum Alb. [ABSTRACT FROM AUTHOR]

The complexation of the styryl dyes 1-ethyl-4-{(E)-2-[4-(methylthio)phenyl]vinyl}pyridinium perchlorate (1) and 1-ethyl-4-[(E)-2-(4-methoxyphenyl)vinyl]pyridinium perchlorate (2) with cucurbit[6]uril (CB[6]) in aqueous solutions has been studied using steady-state and time-resolved fluorescence spectroscopy. The binding constant of the 1 : 1 inclusion complex of 1 and CB[6] is logK = 6.28, with fluorescence increasing threefold, and the 1 : 1 complex of 2 and CB[6] has logK = 5.99, with fluorescence increasing by four times. The fluorescence decay of the dyes and their complexes has two characteristic times, the short one of ~2–3 ps and the long one on the order of ten picoseconds. In inclusion complexes, the latter is greater than in the free dyes. The mechanism of photobleaching of the studied dyes and their complexes with cucurbit[6]uril is considered. [ABSTRACT FROM AUTHOR]

The nature of the photoprocess for a Ni(Se2P(C6H5)2)2 = Ni(dsepi)2 complex in CCl4 and CH3CN has been determined by the EPR, steady-state and time-resolved optical spectroscopy methods. In both cases, the ultrafast relaxation of the excited state of Ni(dsepi)2 molecules are observed; however, the occurrence of a photochemical reaction, in addition to the above process, has been detected in CCl4 solutions. The photolysis mechanism of Ni(dsepi)2 includes the ClNi(dsepi)(•dsepi) species formation stage initiated by electron transfer from the photoexcited complex to the halocarbon and subsequent fast reactions involving these intermediates. The final products of the photoreaction are the ((C6H5)2PSe)Se2 diselenide and the NiCl2 salt. [ABSTRACT FROM AUTHOR]

We investigate the ablation of silicon as a function of laser pulse length at a constant fluence using time-resolved x-ray spectroscopy data obtained from OMEGA EP experiments at the University of Rochester's Laboratory for Laser Energetics. Our targets consisted of three-layer planar structures composed of Si (50 μm), Cu (25 μm), and SiO2 (500 μm) layers. The Si layer was irradiated by a 351-nm laser with varying pulse widths of 250 ps, 500 ps, 1 ns, and 10 ns while maintaining a constant fluence of ∼27.9 kJ/cm2. Electron temperatures and densities of the ablated plasma were determined by analyzing the time-resolved x-ray spectroscopy data through a comparison of experimental measurements with synthetic results obtained from Si atomic calculations in a steady state and non-local thermodynamic equilibrium. These calculations were computed using PrismSPECT [MacFarlane et al., High Energy Density Phys. 3, 181 (2007)]. Additionally, radiation-hydrodynamics simulations with FLASH are used to generate simulated plasma-density and plasma-temperature profiles, which are then compared with the experimental measurements. Our analyses reveal that increasing the laser pulse length at a constant fluence results in a decrease in electron temperatures and densities. Furthermore, the longer pulses with lower intensities lead to deeper ablation regions before reaching the peak ablation but lower ionization balances in the silicon layer. These findings emphasize the critical role of laser pulse length in plasma ablation and shock generation for laser-impulse studies. [ABSTRACT FROM AUTHOR]

Time-resolved reflectance spectroscopy (TRS), a nondestructive technique, can help the industry to provide high-quality fruit to encourage pear consumption. The absorption coefficient measured by TRS at 670 nm (μa670) represents a maturity index for pear fruit, with less mature pears high μa670 and more mature low μa670. The aim of this work was to study the quality characteristics, the sensory profiles and the ethylene production of 'Abate Fetel' pears sorted at harvest in different TRS maturity classes and stored in different atmospheres. At harvest, 540 pears were measured by TRS for μa670, ranked by μa670 in three maturity classes (less-LeM, medium-MeM and more-MoM mature) and randomized in nine samples according to 1-MCP treatment (treated, control), storage time (4–6 months) and atmosphere (air-NA; CA: 8–12 kPa O2, 1 kPa CO2). Fruits were examined at harvest and after 7 days of poststorage shelf life for skin color, firmness, soluble solids, acidity and ethylene production and were submitted to sensory analysis. At harvest and after storage, MoM pears were less green and showed a higher SSC content than LeM ones. After storage, MoM pears produced less ethylene and were perceived to be firmer (especially in 1-MCP-treated pears), more astringent and less juicy (when stored for 6 months) than LeM ones. [ABSTRACT FROM AUTHOR]

Photo-induced carrier dynamics were measured in the organic Dirac electron candidate  α -(BETS) 2 I 3  to investigate why resistivity increases below  T MI  = 50 K. We found a change in carrier dynamics due to an insulating gap formation below  T ′  = 50 K. On the other hand, the relaxation time and polarization anisotropy of the observed dynamics differ from those in the charge-ordering (CO) state of the isostructural salt  α -(ET) 2 I 3 . Based on the difference, it can be concluded that the insulating phase has a different origin than the CO state. [ABSTRACT FROM AUTHOR]

The nature of the photoprocess for a Ni(Se2P(C6H5)2)2 = Ni(dsepi)2 complex in CCl4 and CH3CN has been determined by the EPR, steady-state and time-resolved optical spectroscopy methods. In both cases, the ultrafast relaxation of the excited state of Ni(dsepi)2 molecules are observed; however, the occurrence of a photochemical reaction, in addition to the above process, has been detected in CCl4 solutions. The photolysis mechanism of Ni(dsepi)2 includes the ClNi(dsepi)(•dsepi) species formation stage initiated by electron transfer from the photoexcited complex to the halocarbon and subsequent fast reactions involving these intermediates. The final products of the photoreaction are the ((C6H5)2PSe)Se2 diselenide and the NiCl2 salt. [ABSTRACT FROM AUTHOR]

Both semiconductor nanocrystals and organic molecules are important photofunctional materials for an array of applications. It is interesting to examine the intermediate regime between these two families, which can be interpreted as the strong-confinement limit of the nanocrystals or alternatively as the large-size limit of molecules. Here, we choose Cd3P2 magic-size clusters (MSCs) as a unique platform and apply time-resolved spectroscopy to investigate their spectral and dynamic properties. We find that these small clusters display molecular-like vibronic progression on their absorption and emission spectra and a large Stokes shift, which leads to well-separated transient absorption bleach and stimulated emission signals distinct from typical nanocrystals. On the other hand, such small size MSCs can still accommodate biexciton states, and the strongly enhanced Coulombic interactions lead to very fast dephasing of the biexciton resonance as well as rapid biexciton Auger annihilation (1.5 ps). Further, temperature-dependent measurements provide evidence for the transformation of band-edge excitons to localized excitons, with the localization likely driven by the softened lattice in these small-size clusters. These collective results demonstrate that strongly-confined nanoclusters indeed bridge the gap between nanocrystals and molecules, and can be a unique library to search for exotic excited state properties. [ABSTRACT FROM AUTHOR]

Metastable phases present a promising route to expand the functionality of complex materials. Of particular interest are light-induced metastable phases that are inaccessible under equilibrium conditions, as they often host new, emergent properties switchable on ultrafast timescales. However, the processes governing the trajectories to such hidden phases remain largely unexplored. Here, using time- and angle-resolved photoemission spectroscopy, we investigate the ultrafast dynamics of the formation of a hidden quantum state in the layered dichalcogenide 1T-TaS2 upon photoexcitation. Our results reveal the nonthermal character of the transition governed by a collective charge-density-wave excitation. Using a double-pulse excitation of the structural mode, we show vibrational coherent control of the phase-transition efficiency. Our demonstration of exceptional control, switching speed, and stability of the hidden state are key for device applications at the nexus of electronics and photonics. [ABSTRACT FROM AUTHOR]

Triplet state modification in organic phosphorescence molecules for a desired color and quantum yield is typically pursued by chemical modification. A facile methodology is introduced to tune the triplet state dynamics of a phosphorescent molecule by changing the host‐matrix parameters. An organic phosphor, Br2PmDI (2–Bromo pyromellitic diimide), dispersed at dilute levels (1.5 wt.%) in a semicrystalline high‐κ relaxer ferroelectric host matrix emit room‐temperature phosphorescence accompanied by a delayed fluorescence component. The host relaxer ferroelectric polymer film can be engineered to form a photonic matrix with a regular micropore structure of refractive index contrast ≈0.6 that can increase the density of optical states and introduce photonic coupling. The phosphorescence quantum yield of Br2PmDI in this photonic matrix increases by ≈2.3 fold, and the lifetime reduces by a factor of three. The coupled quantum states are investigated by time‐resolved spectroscopy at different temperatures and pump intensities. [ABSTRACT FROM AUTHOR]

Visible and near-infrared spectroscopy has been well studied for characterizing the organic compounds in fruit and vegetables from pre-harvest to late harvest. However, due to the challenge of decoupling of optical properties, the relationship between the collected samples' spectral data and their properties, especially their mechanical properties (e.g., firmness, hardness, and resilience) is hard to understand. This study developed a time-resolved transmittance spectroscopic method to validate the light scattering changing characteristics in kiwifruit during shelf-life and in cold storage conditions. The experimental results demonstrated that the reduced scattering coefficient ( μ s ′ ) of 846 nm inside kiwifruit decreased steadily during postharvest storage and is more evident under shelf-life than in cold storage conditions. Moreover, the correlation between the μ s ′ and the storage time was confirmed to be much higher than that using the external color indexes measured using a conventional colorimeter. Furthermore, employing time-resolved profiles at this single wavelength, an efficacious mathematical model has been successfully formulated to classify the stages of kiwifruit softening, specifically early, mid-, and late stages. Notably, classification accuracies of 84% and 78% were achieved for the shelf-life and cold storage conditions, respectively. [ABSTRACT FROM AUTHOR]

Ultra-hot Jupiters are perfect targets for transmission spectroscopy. However, their atmospheres feature strong spatial variations in temperature, chemistry, dynamics, cloud coverage, and scale height. This makes transit observations at high spectral resolution challenging to interpret. In this work, we model the cross-correlation signal of five chemical species – Fe, CO, H2O, OH, and TiO – on WASP-76b, a benchmark ultra-hot Jupiter. We compute phase-dependent high-resolution transmission spectra of three-dimensional (3D) SPARC/MITgcm models. The spectra are obtained with gCMCRT, a 3D Monte-Carlo radiative-transfer code. We find that, on top of atmospheric dynamics, the phase-dependent Doppler shift of the absorption lines in the planetary rest frame is shaped by the combined effect of planetary rotation and the unique 3D spatial distribution of chemical species. For species probing the dayside (e.g. refractories or molecules like CO and OH), the two effects act in tandem, leading to increasing blueshifts with orbital phase. For species that are depleted on the dayside (e.g. H2O and TiO), the two effects act in an opposite manner, and could lead to increasing redshifts during the transit. This behaviour yields species-dependent offsets from a planet's expected K p value that can be much larger than planetary wind speeds. The offsets are usually negative for refractory species. We provide an analytical formula to estimate the size of a planet's K p offsets, which can serve as a prior for atmospheric retrievals. We conclude that observing the phase-resolved absorption signal of multiple species is key to constraining the 3D thermochemical structure and dynamics of ultra-hot Jupiters. [ABSTRACT FROM AUTHOR]

Square‐planar NiII complexes are interesting as cheaper and more sustainable alternatives to PtII luminophores widely used in lighting and photocatalysis. We investigated the excited‐state behavior of two NiII complexes, which are isostructural with two luminescent PtII complexes. The initially excited singlet metal‐to‐ligand charge transfer (1MLCT) excited states in the NiII complexes decay to metal‐centered (3MC) excited states within less than 1 picosecond, followed by non‐radiative relaxation of the 3MC states to the electronic ground state within 9–21 ps. This contrasts with the population of an emissive triplet ligand‐centered (3LC) excited state upon excitation of the PtII analogues. Structural distortions of the NiII complexes are responsible for this discrepant behavior and lead to dark 3MC states far lower in energy than the luminescent 3LC states of PtII compounds. Our findings suggest that if these structural distortions could be restricted by more rigid coordination environments and stronger ligand fields, the excited‐state relaxation in four‐coordinate NiII complexes could be decelerated such that luminescent 3LC or 3MLCT excited states become accessible. These insights are relevant to make NiII fit for photophysical and photochemical applications that relied on PtII until now. [ABSTRACT FROM AUTHOR]

Structurally defined graphene nanoribbons (GNRs) have emerged as promising candidates for nanoelectronic devices. Low band gap (<1 eV) GNRs are particularly important when considering the Schottky barrier in device performance. Here, we demonstrate the first solution synthesis of 8‐AGNRs through a carefully designed arylated polynaphthalene precursor. The efficiency of the oxidative cyclodehydrogenation of the tailor‐made polymer precursor into 8‐AGNRs was validated by FT‐IR, Raman, and UV/Vis‐near‐infrared (NIR) absorption spectroscopy, and further supported by the synthesis of naphtho[1,2,3,4‐ghi]perylene derivatives (1 and 2) as subunits of 8‐AGNR, with a width of 0.86 nm as suggested by the X‐ray single crystal analysis. Low‐temperature scanning tunneling microscopy (STM) and solid‐state NMR analyses provided further structural support for 8‐AGNR. The resulting 8‐AGNR exhibited a remarkable NIR absorption extending up to ∼2400 nm, corresponding to an optical band gap as low as ∼0.52 eV. Moreover, optical‐pump TeraHertz‐probe spectroscopy revealed charge‐carrier mobility in the dc limit of ∼270 cm2 V−1 s−1 for the 8‐AGNR. [ABSTRACT FROM AUTHOR]

KY3F10, a fluoride compound with two polymorphs (α and δ), has been a subject of study due to its unique properties. Obtaining the metastable δ-phase has been challenging, but this study presents an enhanced synthetic methodology using coprecipitation to isolate specific crystal phases. Varying the reaction temperature and time allows for the modulation of polymorph formation. The structural analysis of the synthesized powders reveals the influence of kinetic and thermodynamic control. The morphology of the particles is also affected by these factors, with different reaction conditions leading to distinct particle shapes. The luminescent response of Eu3+-doped powders helps understand the structural stability. It is demonstrated that time-resolved fluorescence spectroscopy is a sensitive and direct measurement to follow the observed changes. Overall, this study demonstrates the interplay between thermodynamics and kinetics in materials synthesis and the impact on crystal phase formation and properties. [ABSTRACT FROM AUTHOR]

Time-resolved infrared spectroscopy reveals the flow of electron density through coenzyme B12 in the light-activated, bacterial transcriptional regulator, CarH. The protein stabilises a series of charge transfer states that result in a photoresponse that avoids reactive, and potentially damaging, radical photoproducts. [ABSTRACT FROM AUTHOR]

Nanosecond time‐resolved X‐ray (tr‐XAS) and optical transient absorption spectroscopy (OTA) are applied to study 3 multimolecular photocatalytic systems with [Ru(bpy)3]2+photoabsorber, ascorbic acid electron donor and Co catalysts with methylene (1), hydroxomethylene (2) and methyl (3) amine substituents in pure water. OTA and tr‐XAS of 1 and 2 show that the favored catalytic pathway involves reductive quenching of the excited photosensitizer and electron transfer to the catalyst to form a CoII square pyramidal intermediate with a bonded aqua molecule followed by a CoI square planar derivative that decays within ≈8 μs. By contrast, a CoI square pyramidal intermediate with a longer decay lifetime of ≈35 μs is formed from an analogous CoII geometry for 3 in H2O. These results highlight the protonation of CoI to form the elusive hydride species to be the rate limiting step and show that the catalytic rate can be enhanced through hydrogen containing pendant amines that act as H−H bond formation proton relays. [ABSTRACT FROM AUTHOR]

Bodipy (BDP)‐perylenebisimide (PBI) donor–acceptor dyads/triad were prepared to study the spin–orbit charge‐transfer intersystem crossing (SOCT‐ISC). For BDP‐PBI‐3, in which BDP was attached at the imide position of PBI, higher singlet oxygen quantum yield (ΦΔ=85 %) was observed than the bay‐substituted derivative BDP‐PBI‐1 (ΦΔ=30 %). Femtosecond transient absorption spectra indicate slow Förster resonance energy transfer (FRET; 40.4 ps) and charge separation (CS; 1.55 ns) in BDP‐PBI‐3, while for BDP‐PBI‐1, CS takes 2.8 ps. For triad BDP‐PBI‐2, ultrafast FRET (149 fs) and CS (4.7 ps) process were observed, the subsequent charge recombination (CR) takes 5.8 ns and long‐lived 3PBI* (179.8 μs) state is populated. Nanosecond transient absorption spectra of BDP‐PBI‐3 show that the CR gives upper triplet excited state (3BDP*) and subsequently, via a slow intramolecular triplet energy transfer (14.5 μs), the 3PBI* state is finally populated, indicating that upper triplet state is involved in SOCT‐ISC. Time‐resolved electron paramagnetic resonance spectroscopy revealed that both radical pair ISC (RP ISC) and SOCT‐ISC contribute to the ISC. A rare electron spin polarization of (e, e, e, e, e, e) was observed for the triplet state formed via the RP ISC mechanism, due to the S−T+1/T0 states mixing. [ABSTRACT FROM AUTHOR]

The tetrahedral shape‐persistent molecule 14+, containing four identical pyridyl pyridinium units connected via a sp3 hybridized carbon atom, has been investigated in detail by means of steady‐state and time resolved spectroscopy. Remarkable photophysical properties are observed, particularly in comparison with protonated and methylated analogues (1H48+, 1Me48+), which exhibit substantially shorter excited state lifetimes and lower emission quantum yields. Theoretical studies have rationalized the behavior of the tetrameric molecules relative to the monomers, with DFT and TD‐DFT calculations corroborating steady‐state (absorption and emission) and transient absorption spectra. The behavior of the monomeric compounds (each consisting in one of the four identical subunits of the tetramers, i. e. 2+, 2H2+ and 2Me2+) considerably differs from that of the tetramers, indicating a strong electronic interaction between the subunits in the tetrameric species, likely promoted by the homoconjugation through the connecting sp3 C atom. 2+ is characterized by a peculiar S1‐S2 excited state inversion, whereas the short‐lived emitting S1 state of 2H2+ and 2Me2+ exhibits a partial charge‐transfer character, as substantiated by spectro‐electrochemical studies. Among the six investigated systems, only 14+ is a sizeable luminophore (Φem=0.15), which is related to the peculiar features of its singlet state. [ABSTRACT FROM AUTHOR]

Understanding the effects of X‐rays on halide perovskite thin films is critical for accurate and reliable characterization of this class of materials, as well as their use in detection systems. In this study, advanced optical imaging techniques are employed, both spectrally and temporally resolved, coupled with chemical characterizations to obtain a comprehensive picture of the degradation mechanism occurring in the material during photoemission spectroscopy measurements. Two main degradation pathways are identified through the use of local correlative physico‐chemical analysis. The first one, at low X‐Ray fluence, shows minor changes of the surface chemistry and composition associated with the formation of electronic defects. Moreover, a second degradation route occurring at higher fluence leads to the evaporation of the organic cations and the formation of an iodine‐poor perovskite. Based on the local variation of the optoelectronic properties, a kinetic model describing the different mechanisms is proposed. These findings provide valuable insight on the impact of X‐rays on the perovskite layers during investigations using X‐ray based techniques. More generally, a deep understanding of the interaction mechanism of X‐rays with perovskite thin films is essential for the development of perovskite‐based X‐ray detectors and solar for space applications. [ABSTRACT FROM AUTHOR]

This work examines the influence of applied external voltage in bulk electrolysis on the excited‐state properties of 8′‐apo‐β‐carotenal in acetonitrile by steady‐state and ultrafast time‐resolved absorption spectroscopy. The data collected under bulk electrolysis were compared with those taken without applied voltage. The steady‐state measurements showed that although intensity of the S0‐S2 absorption band varies with the applied voltage, the spectral position remain nearly constant. Comparison of transient absorption spectra shows that the magnitude of the ICT‐like band decreases during the experiment under applied voltage condition, and is associated with a prolongation of the S1/ICT‐like lifetime from 8 ps to 13 ps. Furthermore, switching off the applied voltage resulted in returning to no‐voltage data within about 30 min. Our results show that the amplitude of the signal associated with the ICT state can be tuned by applying an external voltage. [ABSTRACT FROM AUTHOR]

Conventional single-component quantum dots (QDs) suffer from low recombination rates of photogenerated electrons and holes, which hinders their ability to meet the requirements for LED and laser applications. Therefore, it is urgent to design multicomponent heterojunction nanocrystals with these properties. Herein, we used CdSe quantum dot nanocrystals as a typical model, which were synthesized by means of a colloidal chemistry method at high temperatures. Then, CdS with a wide band gap was used to encapsulate the CdSe QDs, forming a CdSe@CdS core@shell heterojunction. Finally, the CdSe@CdS core@shell was modified through the growth of the ZnS shell to obtain CdSe@CdS@ZnS heterojunction nanocrystal hybrids. The morphologies, phases, structures and performance characteristics of CdSe@CdS@ZnS were evaluated using various analytical techniques, including transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy, fluorescence spectroscopy and time-resolved transient photoluminescence spectroscopy. The results show that the energy band structure is transformed from type II to type I after the ZnS growth. The photoluminescence lifetime increases from 41.4 ns to 88.8 ns and the photoluminescence quantum efficiency reaches 17.05% compared with that of pristine CdSe QDs. This paper provides a fundamental study and a new route for studying light-emitting devices and biological imaging based on multicomponent QDs. [ABSTRACT FROM AUTHOR]

A series of four regioisomeric Pt(II) complexes (PtLa-n and PtLb-n) bearing tetradentate luminophores as dianionic ligands were synthesized. Hence, both classes of cyclometallating chelators were decorated with three n-hexyl (n = 6) or n-dodecyl (n = 12) chains. The new compounds were unambiguously characterized by means of multiple NMR spectroscopies and mass spectrometry. Steady-state and time-resolved photoluminescence spectroscopy as well quantum chemical calculations show that the effect of the regioisomerism on the emission colour and on the deactivation rate constants can be correlated with the participation of the Pt atom on the excited state. The thermal properties of the complexes were studied by DSC, POM and temperature-dependent steady-state photoluminescence spectroscopy. Three of the four complexes (PtLa-12, PtLb-6 and PtLb-12) present an intriguing thermochromism resulting from the responsive metal–metal interactions involving adjacent monomeric units. Each material has different transition temperatures and memory capabilities, which can be tuned at the intermolecular level. Hence, dipole–dipole interactions between the luminophores and disruption of the crystalline packing by the alkyl groups are responsible for the final properties of the resulting materials. [ABSTRACT FROM AUTHOR]

Lead halide‐based salts exhibit good photoelectric properties; however, the use, leakage, and recovery of toxic lead require careful consideration. Therefore, developing a lead‐free optoelectronic material conveniently and quickly is very important. Moreover, there is relatively little research on the salts of bismuth halides. In this study, we synthesized [PEA]3[Bi2I9] single crystals (SC) by volatilizing N,N‐dimethylformamide (DMF) solvent at 70°C. The crystal system and spatial group of [PEA]3[Bi2I9] are monoclinic and P21/n, respectively. The Tauc plot reveals the optical band gap of the [PEA]3[Bi2I9] SC at 2.048 eV. The carrier mobility of [PEA]3[Bi2I9] SC is 47.4 cm2 V−1 s−1. Steady‐state fluorescence and time‐resolved fluorescence spectrum indicate that there are four fluorescence peaks and about 7 μs lifetime, respectively. The photodetector based on [PEA]3[Bi2I9] SC under different voltages (0.5, 1, 1.5, 2, and 2.5 V) exhibits stability and regularity with turning‐on/off of the light. In addition, thermogravimetric analysis (TGA) tests indicate that [PEA]3[Bi2I9] SC has considerable thermal stability at temperatures up to 260°C, showing promise for becoming a high temperature resistant and nontoxic sensor with good application prospects. [ABSTRACT FROM AUTHOR]

Even though the excited state lifetimes can be found out experimentally using well-known time-resolved spectroscopy but low signal to noise ratio leading to lack of data points on the hyperbolic curves makes it difficult to clearly reproduce the individual exponentials simply by fitting to further analyse the decay curves. Keeping these things in mind, in this work, time-resolved photoluminescent emission decay curves were simulated for aluminium doped zinc oxide [ZnO:Al (0.1–3.0%)] nanophosphors and europium doped cadmium-zinc sulphide [Cd1−xZnxS:Eu (0.01–10.00%, x = 0–0.5)] nanocomposite phosphor using FORTRAN-77 subroutines for three different lifetimes. Excited state lifetime is the most important parameter of nanophosphors to investigate for the purpose of opto-electronic applications, among emission intensity and wavelength. Experimentally obtained excited state lifetimes were used as the primary input to study the effect of various parameters like cut-off intensity, dopant concentration and nanocomposite composition on the decay nature of emission intensities from individual excited states, and the decay nature of total emission intensity. Decay curves generated for the ZnO:Al (0.1–3.0%) nanophosphors displayed the lifetime shortening and enhanced emission due to increasing Al-doping at all simulated arbitrary intensities for all excited state lifetimes. Decay curves generated for the Cd1−xZnxS:Eu (0.01–10.00%, x = 0–0.5) nanocomposite phosphors similarly displayed the trend of lifetime shortening with increasing Zn-concentration and Eu-doping for every individually simulated exponential. [ABSTRACT FROM AUTHOR]

Cooking oil is a critical component of human food and its main component, lipid, is influential to health, but assessing its authenticity and quality can be challenging due to its complex chemical composition. In this study, we introduce a novel application of time-resolved coherent anti-Stokes Raman scattering (T-CARS) spectroscopy for detecting adulteration and understanding the mechanisms of lipid oxidation in various cooking oils. Our research surpasses the limitations of conventional spontaneous Raman spectroscopy, demonstrating that intra-molecular interactions from unsaturated bonds in triglycerides significantly influence vibrational dephasing time. We observed that these dephasing times, although diverse initially, converge to a similar value after heating cycles. Notably, a longer vibrational dephasing of the CH2 symmetric stretching mode was found to correlate with a higher lipid oxidation rate. These findings underscore the potential of T-CARS in identifying and characterizing subtle molecular interactions, offering a transformative approach to understanding molecular dynamics. This research paves the way for broader applications of T-CARS across fields such as chemistry, biomedicine, and material science, marking a significant advancement in the development of innovative analytical techniques. [ABSTRACT FROM AUTHOR]

Lead halide‐based salts exhibit good photoelectric properties; however, the use, leakage, and recovery of toxic lead require careful consideration. Therefore, developing a lead‐free optoelectronic material conveniently and quickly is very important. Moreover, there is relatively little research on the salts of bismuth halides. In this study, we synthesized [PEA]3[Bi2I9] single crystals (SC) by volatilizing N,N‐dimethylformamide (DMF) solvent at 70°C. The crystal system and spatial group of [PEA]3[Bi2I9] are monoclinic and P21/n, respectively. The Tauc plot reveals the optical band gap of the [PEA]3[Bi2I9] SC at 2.048 eV. The carrier mobility of [PEA]3[Bi2I9] SC is 47.4 cm2 V−1 s−1. Steady‐state fluorescence and time‐resolved fluorescence spectrum indicate that there are four fluorescence peaks and about 7 μs lifetime, respectively. The photodetector based on [PEA]3[Bi2I9] SC under different voltages (0.5, 1, 1.5, 2, and 2.5 V) exhibits stability and regularity with turning‐on/off of the light. In addition, thermogravimetric analysis (TGA) tests indicate that [PEA]3[Bi2I9] SC has considerable thermal stability at temperatures up to 260°C, showing promise for becoming a high temperature resistant and nontoxic sensor with good application prospects. [ABSTRACT FROM AUTHOR]

Copper(II)‐containing mordenite (CuMOR) is capable of activation of C−H bonds in C1‐C3 alkanes, albeit there are remarkable differences between the functionalization of ethane and propane compared to methane. The reaction of ethane and propane with CuMOR results in the formation of ethylene and propylene, while the reaction of methane predominantly yields methanol and dimethyl ether. By combining in situ FTIR and MAS NMR spectroscopies as well as time‐resolved Cu K‐edge X‐ray absorption spectroscopy, the reaction mechanism was derived, which differs significantly for each alkane. The formation of ethylene and propylene proceeds via oxidative dehydrogenation of the corresponding alkanes with selectivity above 95 % for ethane and above 85 % for propane. The formation of stable π‐complexes of olefins with CuI sites, formed upon reduction of CuII‐oxo species, protects olefins from further oxidation and/or oligomerization. This is different from methane, the activation of which proceeds via oxidative hydroxylation leading to the formation of surface methoxy species bonded to the zeolite framework. Our findings constitute one of the major steps in the direct conversion of alkanes to important commodities and open a novel research direction aiming at the selective synthesis of olefins. [ABSTRACT FROM AUTHOR]

Amalgamation of green synthesis and nanotechnology is considered as the preponderant forefronts over the past decade. A low-cost, eco-friendly and reproducible plant-mediated synthesis of NPs has been on the focus of interest of researchers. In this work, synthesis of Copper Sulphide (CuS) NPs using Ocimum tenuiflorum (Tulsi) extract as a novel solvent is reported. Tulsi extract contains eugenol as a biocatalyst which acts as a reducing agent during the synthesis process. The NPs were prepared via co-precipitation and hydrothermal method and structural characterization was investigated with X-Ray Diffraction, Field Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission Electron Microscopy (HRTEM). The optical properties were studied utilizing Ultraviolet-Visible absorption, Raman spectroscopy, Photoluminescence spectroscopy and Time-resolved spectroscopy. HRTEM confirms the size of the synthesized CuS nanoparticles ∼ 10 nm. The UV–Visible spectroscopic studies reveal that the bandgap of nanoparticles is in the range of 3.6–3.8 eV. The prominent Raman band obtained at 470 cm−1 and a weak band at 260 cm−1 attributed to S–S stretch and Cu–S stretch mode respectively in the sample. The results of CIE plots demonstrate that the synthesized material can be utilized as an optical sensor to fabricate optical devices. [ABSTRACT FROM AUTHOR]

Diradicals based on the Blatter units and connected by acetylene and alkene spacers have been prepared. All the molecules show sizably large diradical character and low energy singlet‐triplet gaps. Their photo‐physical properties concerning their lowest energy excited state have been studied in detail by steady‐state and time‐resolved absorption spectroscopy. We have fully identified the main optical absorption band and full absence of emission from the lowest energy excited state. A computational study has been also carried out that has helped to identify the presence of a conical intersection between the lowest energy excited state and the ground state which produces a highly efficient light‐to‐heat conversion of the absorbed radiation. Furthermore, an outstanding photo‐thermal conversion 77.23 % has been confirmed, close to the highest in the diradicaloid field. For the first time, stable diradicals are applied to photo‐thermal therapy of tumor cells with good stability and satisfactory performance at near‐infrared region. [ABSTRACT FROM AUTHOR]

Transition‐metal nitrides/nitrenes are highly promising reagents for catalytic nitrogen‐atom‐transfer reactivity. They are typically prepared in situ upon optically induced N2 elimination from azido precursors. A full exploitation of their catalytic potential, however, requires in‐depth knowledge of the primary photo‐induced processes and the structural/electronic factors mediating the N2 loss with birth of the terminal metal‐nitrogen core. Using femtosecond infrared spectroscopy, we elucidate here the primary molecular‐level mechanisms responsible for the formation of a unique platinum(II) nitrene with a triplet ground state from a closed‐shell platinum(II) azide precursor. The spectroscopic data in combination with quantum‐chemical calculations provide compelling evidence that product formation requires the initial occupation of a singlet excited state with an anionic azide diradical ligand that is bound to a low‐spin d8‐configured PtII ion. Subsequent intersystem crossing generates the Pt‐bound triplet azide diradical, which smoothly evolves into the triplet nitrene via N2 loss in a near barrierless adiabatic dissociation. Our data highlight the importance of the productive, N2‐releasing state possessing azide ππ* character as a design principle for accessing efficient N‐atom‐transfer catalysts. [ABSTRACT FROM AUTHOR]

Localized surface plasmon resonance (LSPRs) shown by gold nanorods (AuNRs) has several applications in photocatalysis, sensing, and biomedicine. The combination of AuNRs with Polydopamine (PDA) shells results in a strong photo‐thermal effect, making them appealing nanomaterials for biomedical applications. However, the precise roles and relative contributions of plasmonic effects in gold, and light‐to‐heat conversion in PDA are still debated. Herein, a hybrid nanoplatform made by an AuNR core surrounded by a polydopamine (PDA) shell is synthesized, and its photocatalytic behavior is studied. Synthesis is based on a seed‐mediated growth followed by the further self‐polymerization of dopamine hydrochloride (DA) on the surface of the AuNRs, and the effect of the thickness of the PDA shell on the plasmon response of the composite is the main examined parameter. Photocatalytic performance is tested toward Rhodamine 6G (Rh6G), with the nanocomposites achieving better performance than bare AuNRs and bare PDA nanoparticles. The degradation of 54% of Rh6G initial concentration is achieved within 60 min of irradiation with a catalyst concentration of 7.4 µg mL−1. Photodegradation kinetics, time‐resolved spectroscopy, and finite‐element‐method simulations of plasmons show that AuNRs plasmons, coupled with the low thermal conductivity of PDA, provide slow thermalization, while enhancing the charge carrier transfer. [ABSTRACT FROM AUTHOR]

The aim of this study was to demonstrate the utility of time-resolved fluorescence spectroscopy in the detection of subtle changes in the local microenvironment of a tryptophan chromophore in a confined and crowded medium of AOT reverse micelles, which mimic biological membranes and cell compartmentalization. For this purpose, fluorescence properties of L-tryptophan and several newly synthesized tryptophan-containing peptides in buffer and in an AOT reverse micelle medium were determined. It was shown that insertion of tryptophan and its short di- and tripeptides inside micelles led to evident changes in both the steady-state emission spectra and in fluorescence decay kinetics. The observed differences in spectral characteristics, such as a blue shift in the emission maxima, changes in the average fluorescence lifetime, and the appearance of environmental-dependent fluorescent species, showed the utility of time-resolved fluorescence spectroscopy as a sensitive tool for detecting subtle conformational modifications in tryptophan and its peptides induced by changes in polarity, viscosity, and specific interactions between chromophores and water molecules/polar groups/ions that occur inside reverse micelles. [ABSTRACT FROM AUTHOR]