Search

Like protein phosphorylation, O-GlcNAcylation is a common post-translational protein modification. We already reported that O-GlcNAcylation of amyloid precursor protein (APP) in response to insulin signaling reduces neurotoxic amyloid-β (Aβ) production via inhibition of APP endocytosis. Internalized APP is delivered to endosomes and lysosomes where Aβ is produced. However, the molecular mechanism involved in the effect of APP O-GlcNAcylation on APP trafficking remains unknown. To investigate the relationship between APP O-GlcNAcylation and APP endocytosis, we tested the effects of insulin on neuroblastoma SH-SY5Y cells overexpressing APP and BACE1, and cultured rat hippocampal neurons. The present study showed that APP O-GlcNAcylation translocated APP from lipid raft to non-raft microdomains in the plasma membrane by using immunocytochemistry and discontinuous sucrose gradients method. By using the biotinylation method, we also found that APP preferentially underwent endocytosis from lipid rafts and that the amount of internalized APP from lipid rafts was specifically reduced by O-GlcNAcylation. These results indicate that O-GlcNAcylation can regulate lipid raft-dependent APP endocytosis via translocation of APP into non-raft microdomains. Our findings showed a new functional role of O-GlcNAcylation for the regulation of APP trafficking, offering new mechanistic insight for Aβ production. [ABSTRACT FROM AUTHOR]

This study explores the optimal morphology of photochemical hydrogen evolution catalysts in a one‐dimensional system. Systematic engineering of metal tips on precisely defined CdSe@CdS dot‐in‐rods is conducted to exert control over morphology, composition, and both factors. The outcome yields an optimized configuration, a Au−Pt core‐shell structure with a rough Pt surface (Au@r‐Pt), which exhibits a remarkable fivefold increase in quantum efficiency, reaching 86 % at 455 nm and superior hydrogen evolution rates under visible and AM1.5 G irradiation conditions with prolonged stability. Kinetic investigations using photoelectrochemical and time‐resolved measurements demonstrate a greater extent and extended lifetime of the charge‐separated state on the tips as well as rapid water reduction kinetics on high‐energy surfaces. This approach sheds light on the critical role of cocatalysts in hybrid photocatalytic systems for achieving high performance. [ABSTRACT FROM AUTHOR]

Reusing or recycling waste into new useful materials is essential for environmental protection. Herein, we used discarded polystyrene (PS) and fly-ash (FA) particles and a fabricated fly-ash incorporated polystyrene fiber (FA/PS fiber) composite. The electrospinning process produced continuous PS fibers with a good distribution of FA particles. The prepared nanofibers were characterized by state-of-the-art techniques. The performances of the composite nanofibers were tested for fire-retardant applications. We observed that the incorporation of FA particles into the PS fibers led to an improvement in the performance of the composite as compared to the pristine PS fibers. This study showed an important strategy in using waste materials to produce functional nanofibers through an economical procedure. We believe that the strategy presented in this paper can be extended to other waste materials for obtaining nanofiber membranes for various environmental applications. [ABSTRACT FROM AUTHOR]

The key to current Alzheimer's disease (AD) therapy is the early diagnosis for prompt intervention, since available treatments only slow the disease progression. Therefore, this lack of promising therapies has called for diagnostic screening tests to identify those likely to develop full-blown AD. Recent AD diagnosis guidelines incorporated core biomarker analyses into criteria, including amyloid-β (Aβ), total-tau (T-tau), and phosphorylated tau (P-tau). Though effective, the accessibility of screening tests involving conventional cerebrospinal fluid (CSF)- and blood-based analyses is often hindered by the invasiveness and high cost. In an attempt to overcome these shortcomings, biomarker profiling research using non-invasive body fluid has shown the potential to capture the pathological changes in the patients' bodies. These novel non-invasive body fluid biomarkers for AD have emerged as diagnostic and pathological targets. Here, we review the potential peripheral biomarkers, including non-invasive peripheral body fluids of nasal discharge, tear, saliva, and urine for AD. [ABSTRACT FROM AUTHOR]

Amyloid precursor protein (APP) at the plasma membrane is internalized via endocytosis and delivered to endo/lysosomes, where neurotoxic amyloid-β (Aβ) is produced via β-, γ-secretases. Hence, endocytosis plays a key role in the processing of APP and subsequent Aβ generation. β-, γ-secretases as well as APP are localized in cholesterol-enriched lipid raft microdomains. However, it is still unclear whether lipid rafts are the site where APP undergoes endocytosis and whether cholesterol levels affect this process. In this study, we found that localization of APP in lipid rafts was increased by elevated cholesterol level. We also showed that increasing or decreasing cholesterol levels increased or decreased APP endocytosis, respectively. When we labeled cell surface APP, APP localized in lipid rafts preferentially underwent endocytosis compared to nonraft-localized APP. In addition, APP endocytosis from lipid rafts was regulated by cholesterol levels. Our results demonstrate for the first time that cholesterol levels regulate the localization of APP in lipid rafts affecting raft-dependent APP endocytosis. Thus, regulating the microdomain localization of APP could offer a new therapeutic strategy for Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Herein, we prepared a novel photocatalytic ZnO-TiO2 loaded carbon nanofibers composites (ZnO-TiO2-CNFs) via electrospinning technique followed by a hydrothermal process. At first, the electrospun TiO2 NP-embedded carbon nanofibers (TiO2-CNFs) were achieved using electrospinning and a carbonization process. Next, the ZnO particles were grown into the TiO2-CNFs via hydrothermal treatment. The morphology, structure, and chemical compositions were studied using state-of-the-art techniques. The photocatalytic performance of the ZnO-TiO2-CNFs composite was studied using degrading methylene blue (MB) under UV-light irradiation for three successive cycles. It was noticed that the ZnO-TiO2-CNFs nanocomposite showed better MB removal properties than that of other formulations, which might be due to the synergistic effects of carbon nanofibers and utilized metal oxides (ZnO and TiO2). The adsorption characteristic of carbon fibers and matched band potentials of ZnO and TiO2 combinedly help to boost the overall photocatalytic performance of the ZnO-TiO2-CNFs composite. The obtained results from this study indicated that it can be an economical and environmentally friendly photocatalyst. [ABSTRACT FROM AUTHOR]

The excited‐state proton transfer (ESPT) of the strong photoacid, N‐methyl‐7‐hydroxyquinolium (NM7HQ+), was studied in the presence of N‐methylbenzamide (NMB) as a base in the aprotic polar solvent, acetonitrile. According to the Benesi–Hildebrand relation, it was revealed that the hydrogen (H)‐bonded complex of NM7HQ+ and NMB exists in the ground state in a 1:1 stoichiometry with the association constant of 22.2 ± 1.7 M−1. The fluorescence quenching of the 1:1 complex was observed to follow the Stern–Volmer relation with the molecularity of one for NMB indicating that the ESPT of NM7HQ+ occurs with the H‐bonded chain of two NMB molecules. Our study highlights the cooperative nature of H‐bonding in the chemical reactivity of amide in acid–base reactions as has already been reported for alcohol. [ABSTRACT FROM AUTHOR]

This study developed and verified a travel speed prediction model based on the travel speed and work zone statistics collected from the advanced traffic management system (ATMS) real-time data in Daegu, South Korea. A clustered K-nearest neighbors (CKNN) algorithm was used to predict travel speed, resulting in a 6.9% average mean absolute percentage error (MAPE) using the data from 1,815 work zones. Furthermore, road network impact due to road work was calculated by comparing the travel speed prediction results obtained from the historical speed data. The predicted travel speed data in a work zone generated from this study is expected to allow drivers to select optimized paths and use them for traffic management strategies to operate in a work zone efficiently. [ABSTRACT FROM AUTHOR]

There has been extensive research on the sensing of explosive nitroaromatic compounds (NACs) using fluorescent metal-organic frameworks (MOFs). However, ambiguity in the sensing mechanism has hampered the development of efficient explosive sensors. Here we report the synthesis of a hydroxyl-functionalized MOF for rapid and efficient sensing of NACs and examine in detail its fluorescence quenching mechanisms. In chloroform, quenching takes place primarily by exciton migration to the ground-state complex formed between the MOF and the analytes. A combination of hydrogen-bonding interactions and π–π stacking interactions are responsible for fluorescence quenching, and this observation is supported by single-crystal structures. In water, the quenching mechanism shifts toward resonance energy transfer and photo-induced electron transfer, after exciton migration as in chloroform. This study provides insight into florescence-quenching mechanisms for the selective sensing of NACs and reduces the ambiguity regarding the nature of interactions between the MOF and NACs. Metal-organic frameworks are commonly proposed as potential sensors for explosive compounds but the precise sensing mechanism remains unclear. Here, the authors experimentally assess the fluorescence-quenching mechanisms of a hydroxyl-functionalized MOF, as it interacts with nitroaromatics. [ABSTRACT FROM AUTHOR]

Water molecules in the immediate vicinity of biomacromolecules and biomimetic organized assemblies often exhibit a markedly distinct behavior from that of their bulk counterparts. The overall sluggish behavior of biological water substantially affects the stability and integrity of biomolecules, as well as the successful execution of various crucial water‐mediated biochemical phenomena. In this Minireview, insights are provided into the features of truncated hydrogen‐bond networks that grant biological water its unique characteristics. In particular, experimental results and theoretical investigations, based on chemical kinetics, are presented that have shed light on the dynamics and energetics governing such characteristics. It is emphasized how such details help us to understand the energetics of biological water, an aspect relatively less explored than its dynamics. For instance, when biological water at hydrophilic or charged protein surfaces was explored, the free energy of H‐bond breakage was found to be of the order of 0.4 kcal mol−1 higher than that of bulk water. [ABSTRACT FROM AUTHOR]

The automated enforcement systems (AESs), which detect speeding vehicles or vehicles that violate traffic signals, are installed and operated on urban arterial roadways to prevent traffic collisions and reduce injury severity in case of a traffic collision. As it is expensive to install the AES, it will be installed at a site where it is expected to have a great effect. However, as there are no specific guidelines on where it should be installed, it has been installed arbitrarily in high collision concentration locations (HCCLs). The objective of this study is to contribute to the improvement in the efficiency of system operation and budget execution by identifying sites where the enforcement effect of the AES is high, and providing a road manager with the basis of decision-making on system installation. This study classified road sections into clusters based on road environment characteristics and spatial collision occurrence pattern, respectively, and compared collisions statistics and occurrence pattern before and after AES installation to analyze the effect of AES installation. As a result, the study verified that the number of collisions tends to decrease at HCCLs past enforcement sites, while the number of collisions tends to increase at sites where not only red light running but also speeding is enforced after AES installation. In addition, from the perspective of collision severity, it was observed that the severity of collisions was alleviated in most clusters after AES installation. This may be viewed as a positive effect caused by the decrease in vehicle speed due to speeding enforcement. [ABSTRACT FROM AUTHOR]

The identification and quantification of hydrogen (H)‐bonded complexes form the cornerstone of reaction‐mechanism analysis in ultrafast proton‐transfer reactions. Traditionally, the Benesi–Hildebrand method has been employed to obtain the formation constants of H‐bonded complexes, given that H‐bonding additives induce an alteration in spectral features exclusively through H‐bond formation. However, if the additive introduction impacts the bulk polarity of the solution, inducing a spectral shift, the spectroscopic method's accuracy in analyzing the H‐bond formation becomes compromised. In this study, we scrutinize H‐bond formation under the influence of an H‐bond accepting solute in an aprotic solvent. This is achieved by quantifying the fractions of two concurrent pathways involved in the excited‐state proton transfer (ESPT) of a super‐photoacid: the ultrafast ESPT of an H‐bonded complex versus the diffusion‐controlled ESPT of the free acid. Our method offers improved accuracy compared to conventional steady‐state spectroscopic techniques, by directly quantifying the H‐bonded complexes using the time‐resolved spectroscopic method, thereby circumventing the aforementioned limitation. [ABSTRACT FROM AUTHOR]

The phase transition of crystalline ordering is a general phenomenon, but its evolution in space and time requires microscopic probes for visualization. Here we report direct imaging of the transformation of amorphous titanium dioxide nanofilm, from the liquid state, passing through the nucleation step and finally to the ordered crystal phase. Single-pulse transient diffraction profiles at different times provide the structural transformation and the specific degree of crystallinity (η) in the evolution process. It is found that the temporal behaviour of η exhibits unique 'two-step' dynamics, with a robust 'plateau' that extends over a microsecond; the rate constants vary by two orders of magnitude. Such behaviour reflects the presence of intermediate structure(s) that are the precursor of the ordered crystal state. Theoretically, we extend the well-known Johnson-Mehl-Avrami-Kolmogorov equation, which describes the isothermal process with a stretched-exponential function, but here over the range of times covering the melt-to-crystal transformation. [ABSTRACT FROM AUTHOR]

Power conversion efficiencies (PCEs) of glove‐box (GB) processed, two‐component, single‐junction organic solar cells (OSCs) have recently exceeded 18%. However, their mass‐scale manufacture using roll‐to‐roll (R2R) coating techniques is impracticable if they must be fabricated in an air‐free environment. From a commercialization perspective, efficient air‐processed OSCs are of much greater interest than GB‐processed devices since the vast majority of R2R‐manufacturing infrastructure is designed to operate in the air. Herein, it is reported that controlling the crystallinity of non‐fullerene acceptors plays a key role in determining the properties of blend films. Notably, Y6‐hu (a Y6‐derivative) is shown to exhibits a higher degree of crystallinity when processed in air. Air‐processed OSCs show an outstanding PCE of 17.38%, which, to the best of the authors' knowledge, is the highest PCE yet reported for two‐component‐based OSCs processed in air using halogen‐free solvents. Moreover, opaque large‐area OSC sub‐modules with PCEs of 12.44%, and red‐green‐blue colored semi‐transparent OSC sub‐modules with PCEs of >10% are demonstrated. By understanding how morphological features relate to the charge‐generation dynamics of air‐processed OSCs, a new window is opened for the fabrication of efficient and stable air‐processable organic electronics. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) is a very promising carbide material with various applications such as electrochemical supercapacitors, photocatalysis, microwave absorption, field-effect transistors, and sensors. Due to its enticing advantages of high thermal stability, outstanding chemical stability, high thermal conductivity, and excellent mechanical behavior, it is used as a potential candidate in various fields such as supercapacitors, water-splitting, photocatalysis, biomedical, sensors, and so on. This review mainly describes the various synthesis techniques of nanostructured SiC (0D, 1D, 2D, and 3D) and its properties. Thereafter, the ongoing research trends in electrochemical supercapacitor electrodes are fully excavated. Finally, the outlook of future research directions, key obstacles, and possible solutions are emphasized. [ABSTRACT FROM AUTHOR]

Base treatment and metal doping were evaluated as means of enhancing the photocatalytic activity of ZrO2 nanoparticles (NPs) via the generation of oxygen vacancies (OvS), and the sites responsible for this enhancement were identified and characterized by spectroscopic and microscopic techniques. We confirmed that OvS produced by base treatment engaged in photocatalytic activity for organic pollutant degradation, whereas surface defects introduced by Cr-ion doping engaged in oxidative catalysis of molecules. Moreover, we verified that base-treated ZrO2 NPs outperformed their Cr-ion doped counterparts as photocatalysts using in situ X-ray photoelectron spectroscopy and scanning transmission electron microscopy coupled with electron energy loss spectroscopy (STEM-EELS). Thus, our study provides valuable information on the origin of the enhanced photocatalytic activity of modified ZrO2 NPs and demonstrates the practicality of in situ spectroscopy and STEM-EELS for the evaluation of highly efficient metal oxide photocatalysts. [ABSTRACT FROM AUTHOR]

Abstract: Electron energy loss spectroscopy (EELS) is a powerful tool in the study of valency, bonding and structure of solids. Previously, EEL spectra were either time-integrated or at best time-resolved on the millisecond to seconds scale, being limited by video rates and detector responses. Here, using our 4D electron microscope, we report ultrafast EELS, taking the time resolution in the energy–time space into the femtosecond regime, a 10 order of magnitude increase, and for a table-top apparatus. It is shown that the energy–time–amplitude space of graphite is selective to changes, especially in the electron density of the π+σ plasmon of the collective oscillation of the four electrons of carbon. [Copyright &y& Elsevier]

A major difficulty in the polymer solar cell (PSC) community is discovering a methodology capable of accessing polymeric photovoltaic materials with controllable/predictable molecular weights. Effective mathematical equations that enable the reproduction of polymer batches with precisely controlled molecular weight, by mixing as‐synthesized polymer batches with the ones that have different molecular weights, are formulated in this study. The properties of both the as‐synthesized and mixed‐different‐molecular weight PM6 polymer series are systematically investigated to determine the effect of molecular weight on the performance of related PSCs. The power conversion efficiencies (PCEs) improve monotonically with an increase in weight average molecular weight (Mw) up to 120 kDa, but a further increase in Mw results in a sharp decline in PCE. This trend in PCEs is correlated with the charge‐separation efficacy as a function of the balance between the counteracting domain size and packing in the blends. Further, decreasing the polydispersity index in the optimal‐molecular weight PM6 sample produces a small but noticeable positive effect on device performance, yielding the best PCE of 16.5%. This viable mixing approach is useful in producing desirable molecular weight polymers, facilitating the development of high‐quality, high‐reproducibility photovoltaic polymers. [ABSTRACT FROM AUTHOR]

Abstract: In four-dimensional (4D) ultrafast electron microscopy (UEM), timed-pulse electron imaging and selected-area diffraction are used to study structural dynamics with space- and time-resolutions that allow direct observation of transformations affecting the fundamental properties of materials. Only recently, the UEM studies have begun to reveal a variety of dynamic responses of nanoscale specimens to material excitation, on ultrafast time scales and up to microseconds. Here, we give an account of some of these results, including imaging and diffraction dynamics of gold and graphite single crystal films, revealing atomic motions and morphology change in the former and two forms of acoustic resonance in the latter. We also report, for the first time, dynamic changes upon lattice excitation of moiré fringes in graphite, recorded in bright- and dark-field images. Oscillations that are seen in moiré fringe spacing and other selected-area image properties have the same temporal period as observed in Bragg spot changes in diffraction patterns from the same specimen areas. This period is shown to vary linearly with the local thickness of the specimen, thus establishing that the oscillations are due to excitation of a resonant elastic modulation of the film thickness and allowing derivation of a value of the Young''s modulus (c 33) of 36GPa for the c-axis strain. The second form of resonance dynamics observed in graphite, on much longer time scales, corresponds to an out-of-plane drumming vibration of the film consistent with a 0.94TPa elastic modulus for in-plane (a-axis) stretching. For the latter, the nanoscale membrane motion appears complicated (“chaotic”) at early time and builds up to a resonance at longer times. Finally, electron energy loss spectroscopy (EELS) in the UEM provides a unique domain of study of chemical bonding on the time scale of change (femtoseconds), and its application to graphite is discussed. [Copyright &y& Elsevier]

Abstract: We report highly fluorescent oxadiazole-based excited-state intramolecular proton-transfer (ESIPT) material, 2,5-bis-[5-(4-tert-butyl-phenyl)-[1,3,4]oxadiazol-2-yl]-phenol (SOX) in solid state film (Φ f =0.47) as well as in solution (Φ f =0.40). From the single crystal X-ray crystallography, a molecular geometry of SOX was found to be nearly planar due to the strong intramolecular hydrogen-bond between the hydroxyl and oxadiazole groups to give rise to the virtually single keto fluorescence. In view of the molecular arrangement, a specific dimer interaction caused by a Coulomb attraction in the SOX crystal was most likely associated with a sliding-away stacking, which contributed to the intense solid-state fluorescence. On the other hand, 2,5-bis-[5-(4-tert-butyl-phenyl)-[1,3,4]oxadiazol-2-yl]-benzene-1,4-diol (DOX) with dual ESIPT sites but otherwise the same as SOX showed a significantly red-shifted orange emission (λ em =573nm) of keto tautomer relative to the bluish-green emission (λ em =486nm) of SOX in chloroform. Similarly, the fluorescence emission of DOX in solid-state film (Φ f =0.13) was highly enhanced from that in solution (Φ f =0.02). Interestingly, SOX and DOX showed well-defined room-temperature phosphorescence. Kinetic studies on the ESIPT keto fluorescence as well as the phosphorescence were investigated using picosecond laser experiments. [Copyright &y& Elsevier]

The excited-state proton transfer (ESPT) of a cationic super-photoacid, N -methyl-7-hydroxyquinolium, has been studied within the water pool of an aerosol-OT reverse micelle (RM). Time-resolved emission spectra were obtained and analyzed to reveal the effect of environmental heterogeneity on the ESPT process. The ESPT was found to involve two main emissive species, namely the excited cationic and keto forms of the photoacid and was facilitated by scenarios that expose them to an abundance of water molecules. The dynamic charge-state transition (from positive to neutral) induced by the ESPT dictated the location and diffusion of the probe with the modulation of the Coulombic interaction between the probe and anionic interface of the RM. The non-exponential behavior of the ESPT was observed using time-resolved intensity profiles and rationalized in terms of the heterogeneity along the reaction coordinates involving the hydrogen-bond network, polarity, and viscosity of the confined water pool within the RM. It was found that the disruption of the hydrogen-bond network in the vicinity of the interface resulted in the decrease of polarity that retarded the overall ESPT by modulating the energetics of the reactant and the product in the ESPT. Solvation dynamics was also considered and found to occur on timescales faster than the ESPT process, profoundly for larger water pools. • Using time-resolved spectroscopy proton transfer in a reverse micelle was studied. • The excited-state proton transfer of the photoacid was dependent on its location. • The proton transfer was not solvation-governed, but activation-controlled. • The polarity gradient within the reverse micelle modulated the proton transfer. [ABSTRACT FROM AUTHOR]

We investigated the hydration dynamics in the nanosized water pool of an Aerosol-OT (AOT) reverse micelle (RM) using a prototropic (proton-donating) fluorescent dye, N -methyl-7-hydroxyquinolinium (NM7HQ+), as the probe. NM7HQ+ is a photoacid, and the deprotonation of its excited-state cationic form (C*) gives rise to a neutral keto species (K*). In the present study, the residence sites of C* and K* in water pools of various sizes were determined by monitoring their time-resolved fluorescence anisotropy. Additionally, the evolutions of the C* and K* bands in the time-resolved fluorescence spectra were analyzed by fitting the spectra to the sum of two lognormal peak functions. The time-dependent spectral shifts of the species with different formal charges revealed the characteristic hydration behavior at the interface of the anionic AOT headgroups and the bound water region, as well as the rotational and translational diffusion of the probe within the RM. • Time-resolved fluorescence was used to study the behavior of an ionic/neutral probe in a reverse micelle. • The location-dependent hydration dynamics and anisotropy decay of the probes were determined. • The effect of photo-induced proton transfer and the charge state on the solvation dynamics of the probe was investigated. [ABSTRACT FROM AUTHOR]

Photoinduced excited-state processes have been platforms for understanding the molecular mechanisms of many chemical and biological reactions. To elucidate associated chemical kinetics, time-resolved spectroscopic experiments have been performed tracking how the populations of reactants and products change during the reactions while reaction conditions such as the concentration of a reactant, temperature, and solvent properties change. Here, we simulate the lifetimes of a reactant and a product, and construct their lifetime-associated spectra with the various combinations of rate constants based on the analytical solutions of differential rate equations. Depending on the combinations of the rate constants, the results diverge, which has often been overlooked in previous works. To demonstrate the validity of our approach, the results are compared with the experimental results on diffusion-controlled excited-state proton transfer. The presented global analysis simulation can generally be applied to other excited two-state reactions.

Nanothermometry in in situ transmission electron microscopy (TEM) is useful for comprehending the functioning mechanisms of the heterogeneous matter through real-time observations. Herein, we introduce a Boltzmann-distribution-driven cathodoluminescence (CL) nanothermometry for in situ local temperature probing in TEM. The population distribution across the close-lying Stark sublevels of dysprosium ions in an yttrium vanadate matrix follows the Boltzmann distribution, enabling the use of the CL-intensity ratio as a thermometry over a wide temperature range of 103-435 K with a relative sensitivity exceeding 3% K -1 and precision of ±2%. Superior to other CL-based thermometries, the present approach is independent of electron-beam parameters and dopant concentration, extending the robustness and applicability of CL-based nanothermometry in electron microscopy. We further demonstrate the real-time mapping of the temperature distribution across a TEM grid under laser irradiation.

The coupled electronic and structural transitions in metal-insulator transition (MIT) hinder ultrafast switching and ultimate endurance. Decoupling these transitions and achieving a zero-strain electronic MIT can overcome the fundamental limitations of MIT in solid materials. Here, this study demonstrates that iso-valent Ti dopants in supercooled VO 2 epitaxial films cause MIT with minimal hysteresis without changing unit-cell volume and crystal symmetry. The Ti dopants in the VO 2 lattice locally alter the configuration of V-V pairs, where the long-range ordering in V-V pairs is disrupted, and the nano-domains of V-V dimers are formed. Strikingly, these local V-V dimers persist even above the electronic transition temperature (T MI ), facilitating the zero-strain electronic MIT with nanoscale structural heterogeneity. The geometrically compatible interface between insulating and metallic phases drastically enhances switching speed and endurance during electrically and optically driven zero-strain MIT. This discovery offers a fresh perspective on the scientific understanding of MIT and the improved functionality in terms of device speed and reliability by decoupling electronic and structural transitions., (© 2024 Wiley‐VCH GmbH.)

The development of the olfactory system is influenced by sensory inputs, and it maintains neuronal generation and plasticity throughout the lifespan. The olfactory bulb contains a higher proportion of interneurons than other brain regions, particularly during the early postnatal period of neurogenesis. Although the relationship between sensory stimulation and olfactory bulb development during the postnatal period has been well studied, the molecular mechanisms have yet to be identified. In this study, we used western blotting and immunohistochemistry to analyze the expression of the transcription factor Npas4, a neuron-specific immediate-early gene that acts as a developmental regulator in many brain regions. We found that Npas4 is highly expressed in olfactory bulb interneurons during the early postnatal stages and gradually decreases toward the late postnatal stages. Npas4 expression was observed in all olfactory bulb layers, including the rostral migratory stream, where newborn neurons are generated and migrate to the olfactory bulb. Under sensory deprivation, the olfactory bulb size and the number of olfactory bulb interneurons were reduced. Furthermore, Npas4 expression and the expression of putative Npas4 downstream molecules were decreased. Collectively, these findings indicate that Npas4 expression induced by sensory input plays a role in the formation of neural circuits with excitatory mitral/tufted cells by regulating the survival of olfactory bulb interneurons during the early stages of postnatal development.

When navigated by the available energy of a system, often provided in the form of heat, physical processes or chemical reactions fleet on a free-energy landscape, thus changing the structure. In in situ transmission electron microscopy (TEM), where material structures are measured and manipulated inside the microscope while being subjected to external stimuli such as electrical fields, laser irradiation, or mechanical stress, it is necessary to precisely determine the local temperature of the specimen to provide a comprehensive understanding of material behavior and to establish the relationship among energy, structure, and properties at the nanoscale. Here, we propose using cathodoluminescence (CL) spectroscopy in TEM for in situ measurement of the local temperature. Gadolinium oxide particles doped with emissive europium ions present an opportunity to utilize them as a temperature probe in CL measurements via a ratiometric approach. We show the thermometric performance of the probe and demonstrate a precision of ±5 K in the temperature range from 113 to 323 K with the spatial resolution limited by the size of the particles, which surpasses other methods for temperature determination. With the CL-based thermometry, we further demonstrate measuring local temperature under laser irradiation.

Harvesting full-spectrum solar energy is a critical issue for developing high-performance photocatalysts. Here, we report a hierarchical heteronanostructure consisting of upconverting, plasmonic, and semiconducting materials as a solar-to-chemical energy conversion platform that can exploit a wide range of sunlight (from ultraviolet (UV) to near-infrared). Lanthanide-doped NaYF 4 nanorod-spherical Au nanocrystals-TiO 2 ternary hybrid nanostructures with a well-controlled configuration and intimate contact between the constituent materials could be synthesized by a wet-chemical method. Notably, the prepared ternary hybrids exhibited high photocatalytic activity for the H 2 evolution reaction under simulated solar and near-infrared light irradiation due to their broadband photoresponsivity and strong optical interaction between the constituents. Through systematic studies on the mechanism of energy transfer during the photocatalysis of the ternary hybrids, we revealed that upconverted photon energy from the upconversion domain transfers to the Au and TiO 2 domains primarily through the Förster resonance energy transfer process, resulting in enhanced photocatalysis.

Assessing the ergodicity of graphene liquid cell electron microscope measurements, we report that loop states of circular DNA interconvert reversibly and that loop numbers follow the Boltzmann distribution expected for this molecule in bulk solution, provided that the electron dose is low (80-keV electron energy and electron dose rate 1-20 e - Å -2 s -1 ). This imaging technique appears to act as a "slow motion" camera that reveals equilibrated distributions by imaging the time average of a few molecules without the need to image a spatial ensemble., Competing Interests: Competing interests statement:The authors declare no competing interest.

In photocatalysis, metal-semiconductor hybrid structures have been proposed for ideal photocatalytic systems. In this study, we investigate the effect of morphology and surface nature of Pt cocatalysts on photocatalytic hydrogen evolution activity in Pt-tipped CdSe nanorods. Three distinct morphologies of Pt cocatalysts were synthesized and employed as visible light photocatalysts. The rough tips exhibit the highest activity, followed by the round and cubic tips. Kinetic investigations using transient absorption spectroscopy reveal that the cubic tips exhibit lower charge-separated states feasible for reacting with water and water reduction rates due to their defectless surface facets. In contrast, the rough tips show a similar charge-separation value but a two-fold higher surface reaction rate than the round tips, resulting in a significant enhancement of hydrogen evolution. These findings highlight the importance of rational design on metal cocatalysts in addition to the main semiconductor bodies for maximizing photocatalytic activities., Competing Interests: There are no conflicts of interest to declare., (This journal is © The Royal Society of Chemistry.)

The shaping of matter into desired nanometric structures with on-demand functionalities can enhance the miniaturization of devices in nanotechnology. Herein, strong light-matter interaction was used as an optical lithographic tool to tailor two-dimensional (2D) matter into nanoscale architectures. We transformed 2D black phosphorus (BP) into ultrafine, well-defined, beyond-diffraction-limit nanostructures of ten times smaller size and a hundred times smaller spacing than the incident, femtosecond-pulsed light wavelength. Consequently, nanoribbons and nanocubes/cuboids scaling tens of nanometers were formed by the structured ablation along the extremely confined periodic light fields originating from modulation instability, the tailoring process of which was visualized in real time via light-coupled in situ transmission electron microscopy. The current findings on the controllable nanoscale shaping of BP will enable exotic physical phenomena and further advance the optical lithographic techniques for 2D materials.

Low-dimensional Cu(I)-based metal halide materials are gaining attention due to their low toxicity, high stability and unique luminescence mechanism, which is mediated by self-trapped excitons (STEs). Among them, Cs 5 Cu 3 Cl 6 I 2 , which emits blue light, is a promising candidate for applications as a next-generation blue-emitting material. In this article, an optimized colloidal process to synthesize uniform Cs 5 Cu 3 Cl 6 I 2 nanocrystals (NCs) with a superior quantum yield (QY) is proposed. In addition, precise control of the synthesis parameters, enabling anisotropic growth and emission wavelength shifting is demonstrated. The synthesized Cs 5 Cu 3 Cl 6 I 2 NCs have an excellent photoluminescence (PL) retention rate, even at high temperature, and exhibit high stability over multiple heating-cooling cycles under ambient conditions. Moreover, under 850-nm femtosecond laser irradiation, the NCs exhibit three-photon absorption (3PA)-induced PL, highlighting the possibility of utilizing their nonlinear optical properties. Such thermally stable and highly luminescent Cs 5 Cu 3 Cl 6 I 2 NCs with nonlinear optical properties overcome the limitations of conventional blue-emitting nanomaterials. These findings provide insights into the mechanism of the colloidal synthesis of Cs 5 Cu 3 Cl 6 I 2 NCs and a foundation for further research., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Two new Y6 derivatives of symmetrical YBO-2O and asymmetrical YBO-FO nonfullerene acceptors (NFAs) are prepared with a simplified synthetic procedure by incorporating octyl and fluorine substituents onto the terminal 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN) moiety. By moving the alkyl substituents on the Y6 core to the terminal INCN moiety, the lowest unoccupied molecular orbital of the YBO NFAs increases without decreasing solubility, resulting in high open-circuit voltages of the devices. Molecular dynamics simulation shows that YBO-2O/-FO preferentially form core-core and terminal-terminal dimeric interactions, demonstrating their tighter packing structure and higher electron mobility than Y6, which is consistent with 2D grazing incidence X-ray scattering and space charge limited current measurements. In blend films, the hole transfer (HT) from YBO-2O/-FO to the polymer donor PM6 is studied in detail by transient absorption spectroscopy, demonstrating efficient HT from YBO-FO to PM6 with their suitable energy level alignment. Despite the simplified synthesis, YBO-FO demonstrates photovoltaic performance similar to that of Y6, exhibiting a power conversion efficiency of 15.01%. Overall, this design strategy not only simplifies the synthetic procedures but also adjusts the electrical properties by modifying the intermolecular packing and energy level alignment, suggesting a novel simplified molecular design of Y6 derivatives., (© 2022 Wiley-VCH GmbH.)

Using an energy filter in transmission electron microscopy has enabled elemental mapping at the atomic scale and improved the precision of structural determination by gating inelastic and elastic imaging electrons, respectively. Here, we use an energy filter in ultrafast electron microscopy to enhance the temporal resolution toward the domain of atomic motion. Visualizing transient structures with femtosecond temporal precision was achieved by selecting imaging electrons in a narrow energy distribution from dense chirped photoelectron packets with broad longitudinal momentum distributions and thus typically exhibiting picosecond durations. In this study, the heterogeneous ultrafast phase transitions of vanadium dioxide (VO 2 ) nanoparticles, a representative strongly correlated system, were filmed and attributed to the emergence of a transient, low-symmetry metallic phase caused by different local strains. Our approach enables electron microscopy to access the time scale of elementary nuclear motion to visualize the onset of the structural dynamics of matter at the nanoscale.

The excited-state proton transfer (ESPT) of a cationic superphotoacid, N -methyl-7-hydroxyquinolium, was studied within the water pool of an anionic aerosol-OT (AOT), bis(2-ethylhexyl) sulfosuccinate, reverse micelle (RM). Previously, we had found that the cationic photoacid residing at the anionic AOT interface was conducive to ESPT to the bound water having concentric heterogeneity on the time scale of hundreds of picoseconds to nanoseconds. In our present study, on the time scale of hundreds of femtoseconds to a few tens of picoseconds, the photoacid underwent an ultrafast ESPT influenced by mobile water constituting the core of the RM. The two subpopulations of the core water molecules that determine the ultrafast biphasic deprotonation of the photoacid on time scales differing by an order of magnitude were identified. The core water molecules solvating the counteranion of the photoacid showed a higher basicity than typical water clusters in bulk resulting in ESPT on a subpicosecond time scale. Bare water clusters sensed by the photoacid showed a slower ESPT, over several picoseconds, as typically limited by the rotational motion of water molecules for similar types of the photoacid.

By taking advantage of bulk-heterojunction structures formed by blending conjugated donor polymers and non-fullerene acceptors, organic photovoltaic devices have recently attained promising power conversion efficiencies of above 18%. For optimizing organic photovoltaic devices, it is essential to understand the elementary processes that constitute light harvesters. Utilising femtosecond-resolved spectroscopic techniques that can access the timescales of locally excited (LE) state and charge-transfer (CT)/-separated (CS) states, herein we explored their photophysics in single chains of the top-notch performance donor-acceptor polymer, PM6, which has been widely used as a donor in state-of-the-art non-fullerene organic photovoltaic devices, in a single LE state per chain regime. Our observations revealed the ultrafast formation of a CT state and its equilibrium with the parent LE state. From the chain-length dependence of their lifetimes, the equilibrated states were found to idle until they reach a chain folding. At the chain folding, the CT state transforms into an interchain CT state that bifurcates into forming a CS state or annihilation within a picosecond. The observation of prevalent nonexponential behaviour in the relaxation of the transient species is attributed to the wide chain-length distribution that determines the emergence of the chain foldings in a single chain, thus, the lifetime of a LE and equilibrated CT states. Our findings indicate that the abundance of chain folding, where the generation of the "reactive" CS state is initiated from the interchain CT state, is essential for maximising charge carriers in organic photovoltaic devices based on PM6.

Implementing the modern technologies of light-emitting devices, light harvesting, and quantum information processing requires the understanding of the structure-function relations at spatial scales below the optical diffraction limit and time scales of energy and information flows. Here, we distinctively combine cathodoluminescence (CL) with ultrafast electron microscopy (UEM), termed CL-UEM, because CL and UEM synergetically afford the required spectral and spatiotemporal sensitivities, respectively. For color centers in nanodiamonds, we demonstrate the measurement of CL lifetime with a local sensitivity of 50 nm and a time resolution of 100 ps. It is revealed that the emitting states of the color centers can be populated through charge transfer among the color centers across diamond lattices upon high-energy electron beam excitation. The technical advance achieved in this study will facilitate the specific control over energy conversion at nanoscales, relevant to quantum dots and single-photon sources.

Two kinds of dumbbell-shaped acceptor-donor-acceptor (A-D-A)-type triad single-component (SC) photovoltaic molecules based on a benzodithiophene-rhodanine (BDTRh) core and [6,6]-phenyl-C 61 butyric acid (PC 61 BA) termini, BDTRh-C 2 -PC 61 BA and BDTRh-C 10 -PC 61 BA, were synthesized by modulating the alkyl (C2 and C10) spacer lengths. Both SC photovoltaic structures had similar UV-vis spectra in solution, but BDTRh-C 10 -PC 61 BA showed a significantly higher absorption coefficient as a thin film. In films, a more facile intermolecular photo-induced charge transfer was observed for BDTRh-C 10 -PC 61 BA in the broad-band transient absorption measurements. BDTRh-C 10 -PC 61 BA also exhibited a higher hole mobility (by 25 times) and less bimolecular recombination than BDTRh-C 2 -PC 61 BA. By plotting the normalized external quantum efficiency data, a higher charge-transfer state was measured for BDTRh-C 10 -PC 61 BA, reducing its voltage loss. A higher power conversion efficiency of ∼2% was obtained for BDTRh-C 10 -PC 61 BA, showing higher open-circuit voltage, short-circuit current density, and fill factor than those of BDTRh-C 2 -PC 61 BA devices. The different carrier dynamics, voltage loss, and optical and photoelectrical characteristics depending on the spacer length were interpreted in terms of the film morphology. The longer decyl spacer in BDTRh-C 10 -PC 61 BA afforded a significantly enhanced intermolecular ordering of the p-type core compared to BDTRh-C 2 -PC 61 BA, suggesting that the alkyl spacer length plays a critical role in controlling the intermolecular packing interaction.