Low-Temperature Thermal Transport Characteristics in Epitaxial Bilayer Graphene Microbridges.

In this paper, we present a study of the thermal transport of epitaxial bilayer graphene microbridges. The thermal conductance of three graphene microbridges with different lengths was measured at different temperatures using Johnson noise thermometry. We find that with the decrease of the temperature, the thermal transport in the graphene microbridges switches from electron-phonon coupling to electron diffusion, and the switching temperature is dependent on the length of the microbridge, which is in good agreement with the simulation based on a distributed hot-spot model. Moreover, the electron-phonon thermal conductance has a temperature power law of T3 as predicted for pristine graphene and the electron-phonon coupling coefficient σep is found to be approximately 0.18 W/(m2 K4), corresponding to a deformation potential D of 55 eV. In addition, the electron diffusion in the graphene microbridges adheres to the Wiedemann-Franz law, requiring no corrections to the Lorentz number.

Direct Comparative Studies Revealing the Contribution of TADF Activity of Organic Emitters Towards Efficient Electrochemiluminescence.

Electrochemiluminescence (ECL) featuring thermally activated delayed fluorescence (TADF) properties has attracted considerable interest, showcasing their potential for 100 % exciton harvesting, which marks a significant advancement in the realm of organic ECL. However, the challenge of elucidating the precise contribution of TADF to the enhanced ECL efficiency arises due to the lack of comparative studies of organic compounds with or without efficient TADF properties. In this study, we present four carbazole-benzonitrile molecules possessing similar chemical structures and comparable exchange energy (ΔEST). Despite their comparable properties, these compounds exhibited varying TADF efficiencies, warranting a closer examination of their underlying structural and electronic characteristics governing the optical properties. Consequently, intense ECL emission was only observed from 4CzBN with a remarkable TADF efficiency, underscoring the substantial difference in the ECL signal among molecules with comparable ΔEST and similar spectral properties but varying TADF activity.

Photoluminescence Enhancement in Silica-Confined Ligand-Free Perovskite Nanocrystals by Suppression of Silanol-Induced Traps and Phase Impurities.

The detriments of intrinsic silanol groups in mesoporous silica to the photoluminescence (PL) of lead halide perovskite nanocrystals (LHP NCs) confined in the template have never been determined and clearly elucidated. Here, we disclose that silanol-induced Cs+ and Br- deficiencies prompt the generation of traps and CsPb2Br5 impurities. The temperature-dependent PL spectra verify the higher energetic barrier of trap states in CsPbBr3 NCs confined in silanol-rich mesoporous silica. Femtosecond transient absorption spectra reveal the trapped state mediates a broadband photoinduced absorption and long-lived decay pathway of CsPbBr3 NCs in silanol-rich templates. A remarkable improvement (up to 160-fold) in PL quantum yields is realized by simple silanol elimination. This work demonstrates the detrimental effects of silanol sites on the PL properties of LHP NCs impregnated in mesoporous silica and provides a new perspective for the ligand-free synthesis of high-quality LHP NCs in mesoporous templates by facile impregnation for practical applications.

Fluorescence wavelength shifts combined with light scattering for ratiometric sensing of chloride in the serum based on CsPbBr3@SiO2 perovskite nanocrystal composite halide exchanges.

A traditional fluorescence-scattering intensity based ratiometric sensing system utilizes both inherent scattering and fluorescence intensity and has drawn extensive attention owing to its simplicity and self-calibration properties. In this work, we propose a novel ratiometric fluorescence sensing system that combines a fluorescence wavelength shift and scattering in a single window, using second-order scattering (SOS) as the representative scattering signal based on the halide exchange of CsPbBr3@SiO2 perovskite nanocrystal composites. We observe a fast halide exchange within 10 seconds, resulting in an identifiable fluorescence wavelength blue shift, while the scattering wavelength remains relatively constant for self-correction. This system could be applied for ratiometric sensing of Cl- in the serum without any sample treatment. The established wavelength-based ratiometric system demonstrates high reliability and reproducibility, paving a new way for fluorescence sensing.

Finite element analysis of endodontically treated premolars without ferrule restored with one-piece glass fiber post and core in combination with different inner shoulder retention form systems.

OBJECTIVE: The current study was performed to explore the impact of post materials as well as the inner shoulder retention form (ISRF) design on the biomechanical behavior of endodontically treated premolars without ferrule restoration using a method of mathematical three-dimensional (3D) finite element analysis (FEA). METHODS: Based on the tooth anatomy and our previous research, eight mandibular second premolar FEA models representing different restorative situations were built: teeth with (a) 2.0 mm height ferrule (DF), (b) no ferrule (NF), (c) 0.5 mm width and 0.5 mm depth ISRF (ISRFW0.5D0.5), (d) 0.5 mm width and 1.0 mm depth ISRF (ISRFW0.5D1.0), (e) 0.5 mm width and 1.5 mm depth ISRF (ISRFW0.5D1.5), (f) 1.0 mm width and 0.5 mm depth ISRF (ISRFW1.0D0.5), (g) 1.0 mm width and 1.0 mm depth ISRF (ISRFW1.0D1.0), (h) 1.0 mm width and 1.5 mm depth ISRF (ISRFW1.0D1.5). All groups were restored with prefabricated glass fiber post and resin composite core (PGF), one-piece glass fiber post-and-core (OGF) and cast Co-Cr alloy (Co-Cr) respectively, and the zirconia crown was restored. Load (180N) was subjected to the buccal cusp at 45° to the tooth's long axis. Stress pattern, maximum principal stress values (MPS), and maximum displacement values on root, post and core, cement layer were calculated for each model. RESULTS: Stress distributions were similar while the values were different among groups. Regardless of restorative approaches, roots restored with PGF showed the highest MPS values, followed by OGF and Co-Cr groups. Regardless of post materials, NF groups resulted in the highest MPS values and maximum displacement values, while ISRF and DF groups exhibited similar results. Compared with PGF groups in association with ISRF, except for OGF with ISRFW0.5D0.5, the remaining OGF groups with ISRF and all Co-Cr groups in association with ISRF presented lower values than that of DF groups. And among different ISRF systems, roots restored with ISRFW1.0D1.0 presented the lowest stress (PGF: 32.96 MPa, OGF: 31.69 MPa, Co-Cr: 29.66 MPa). CONCLUSIONS: For endodontically treated premolars without ferrule, restored with OGF in combination with ISRF preparation could effectively enhanced its load-bearing capacity. Furthermore, the ISRF with a depth and width of 1.0 mm is recommended.

Traffic light-type ratiometric fluorescence visual sensing of Cs+ in soybean oil based on dimension regulation of 2D perovskite nanosheets.

Determination of cesium ion in soybean oil is of high importance since the increasing risk from releasing of main component of nuclear waste cesium 137. The complex composition and high viscosity of soybean oil make it necessary to convert it into water phase by nitration before detection, so developing a simple, accurate and sensitive method for on-site sensing of Cs+ in soybean oil is still a big challenge. In this work, we report a traffic light-type ratiometric fluorescence strategy for the visual sensing of Cs+ in soybean oil based on dimensional regulation of two dimensional (PEA)2PbI4 perovskite nanosheets (NSs). The PEA+ in (PEA)2PbI4 NSs exchanged with Cs+ and lead to dimension of partial (PEA)2PbI4 NSs progressively increase from 2D to 3D CsPbI3 NCs. Resultantly, the fluorescence of (PEA)2PbI4 NSs decreases with a concomitant fluorescence enhancement of CsPbI3 NCs upon increasing the concentrations of Cs+, and the emission accordingly change from green, yellow to red with a high fluorescence colorimetric resolution up to 5.0 µM, make it successful to achieve on-site sensing of Cs+ in soybean oil just with naked eye in 5 min without any nitration, demonstrating a bright application future for determination of Cs+ in the soybean oil.

Memory matching features bias the ensemble perception of facial identity.

Introduction: Humans have the ability to efficiently extract summary statistics (i.e., mean) from a group of similar objects, referred to as ensemble coding. Recent studies have demonstrated that ensemble perception of simple objects is modulated by the visual working memory (VWM) task through matching features in VWM. However, few studies have examined the extending scope of such a matching feature effect and the influence of the organization mode (i.e., the way of combining memory matching features with ensemble properties) on this effect. Two experiments were done to explore these questions. Methods: We used a dual-task paradigm for both experiments, which included a VWM task and a mean estimation task. Participants were required to adjust a test face to the mean identity face and report whether the irregular objects in a memory probe were identical or different to the studied objects. In Experiment 1, using identity faces as ensemble stimuli, we compared participants' performances in trials where a subset color matched that of the studied objects to those of trials without color-matching subsets. In Experiment 2, we combined memory matching colors with ensemble properties in common region cues and compared the effect with that of Experiment 1. Results: Results of Experiments 1 and 2 showed an effect of the VWM task on high-level ensemble perception that was similar to previous studies using a low-level averaging task. However, the combined analysis of Experiments 1 and 2 revealed that memory matching features had less influence on mean estimations when matching features and ensemble properties combined in the common region than when combined as parts of a complete unit. Conclusion: These findings suggest that the impact of memory matching features is not limited by the level of stimulus feature, but can be impacted by the organization between matching features and ensemble target properties.

Green synthesis of highly stable CsPbBr3 perovskite nanocrystals using natural deep eutectic solvents as solvents and surface ligands.

Perovskite nanocrystals (PNCs) have attracted widespread attention as promising materials for the optoelectronic field due to their remarkable photophysical properties and structural tunability. However, their poor stability and the use of toxic organic solvents in the preparation process have severely restricted their practical applications. Herein, a facile, rapid and toxic organic solvent-free synthesis strategy of CsPbBr3 PNCs was developed for the first time via the ligand-assisted reprecipitation (LARP) method using natural deep eutectic solvents (NADESs) as solvents and surface ligands. In this method, the NADESs not only functioned as solvents for green synthesis, but also served simultaneously as surface ligands of CsPbBr3 PNCs to significantly improve their optical properties and stability. The as-synthesized CsPbBr3 PNCs exhibited high photoluminescence quantum yield (PLQY, ∼96.8%), narrow full width at half-maximum (FWHM, ∼18.8 nm) and a high stability that retained 82.9% of PL intensity after 70 days. This work provides a new strategy for the green synthesis of PNCs, which promises feasibility for the industrial large-scale synthesis of high-quality PNCs.

Ratiometric fluorescence sensing of temperature based on perovskite nanocrystals and rhodamine B doped electrospun fibers.

Sensing temperature (T) has gained great attention since T is the most important parameter in daily life, scientific research and industry. A ratiometric fluorescence T sensor is fabricated by doping MAPbBr3 perovskite nanocrystals (PNCs) and rhodamine B (RhB) into a polyacrylonitrile (PAN) matrix and the composite materials are electrospun into optical fibers. The fibers show characteristic emissions at 521 and 587 nm under UV irradiation (λ ex = 365 nm). Both emission intensities gradually increased with elevating T, accompanied with a fluorescence color change from green to yellow. There is a linear relationship between fluorescence intensity ratio (I 521/I 587) and T in the range of 30-45 °C. The T response sensitivity is as high as 4.38% °C-1 at 45 °C.

Ultrasensitive Temperature Sensing Based on Ligand-Free Alloyed CsPbClx Br3-x Perovskite Nanocrystals Confined in Hollow Mesoporous Silica with High Density of Halide Vacancies.

Temperature sensing based on fluorescent semiconductor nanocrystals has recently received immense attention. Enhancing the trap-facilitated thermal quenching of the fluorescence should be an effective approach to achieve high sensitivity for temperature sensing. Compared with conventional semiconductor nanocrystals, the defect-tolerant feature of lead halide perovskite nanocrystals (LHP NCs) endows them with high density of defects. Here, hollow mesoporous silica (h-SiO2 ) template-assisted ligand-free synthesis and halogen manipulation (chloride-importing) are proposed to fabricate highly defective yet fluorescent CsPbCl1.2 Br1.8 NCs confined in h-SiO2 (CsPbCl1.2 Br1.8 NCs@h-SiO2 ) for ultrasensitive temperature sensing. The trap barrier heights, exciton-phonon scattering, and trap state filling process in the CsPbCl1.2 Br1.8 NCs@h-SiO2 and CsPbBr3 NCs@h-SiO2 are studied to illustrate the higher temperature sensitivity of CsPbCl1.2 Br1.8 NCs@h-SiO2 at physiological temperature range. By integrating the thermal-sensitive CsPbCl1.2 Br1.8 NCs@h-SiO2 and thermal-insensitive K2 SiF6 :Mn4+ phosphor into the flexible ethylene-vinyl acetate polymer matrix, ratiometric temperature sensing from 30.0 °C to 45.0 °C is demonstrated with a relative temperature sensitivity up to 13.44% °C-1 at 37.0 °C. The composite film shows high potential as a thermometer for monitoring the body temperature. This work demonstrates the unparalleled temperature sensing performance of LHP NCs and provides new inspiration on switching the defects into advantages in sensing applications.

The Varying Coherences of Implied Motion Modulates the Subjective Time Perception.

Previous research has demonstrated that duration of implied motion (IM) was dilated, whereas hMT+ activity related to perceptual processes on IM stimuli could be modulated by their motion coherence. Based on these findings, the present study aimed to examine whether subjective time perception of IM stimuli would be influenced by varying coherence levels. A temporal bisection task was used to measure the subjective experience of time, in which photographic stimuli showing a human moving in four directions (left, right, toward, or away from the viewer) were presented as probe stimuli. The varying coherence of these IM stimuli was manipulated by changing the percentage of pictures implying movement in one direction. Participants were required to judge whether the duration of probe stimulus was more similar to the long or short pre-presented standard duration. As predicted, the point of subjective equality was significantly modulated by the varying coherence of the IM stimuli, but not for no-IM stimuli. This finding suggests that coherence level might be a key mediating factor for perceived duration of IM images, and top-down perceptual stream from inferred motion could influence subjective experience of time perception.

Colorimetric sensing of chloride in sweat based on fluorescence wavelength shift via halide exchange of CsPbBr3 perovskite nanocrystals.

Considering the high importance of the rapid detection of chloride ion (Cl-) in sweat for the diagnosis of fibrotic cysts, we have investigated the heterogeneous halide exchange between CsPbBr3 perovskite nanocrystals (PNCs) in n-hexane and Cl- in aqueous solution. The results show that CsPbBr3 PNCs could achieve fast halide exchange with Cl- in the aqueous phase under magnetic stirring at pH = 1, accompanied by a significant wavelength blue shift and vivid fluorescence color changes from green to blue. Therefore, a fluorescence wavelength shift-based colorimetric sensing of Cl- based on the halide exchange of CsPbBr3 PNCs has been developed to realize the rapid detection of Cl- in sweat. Compared with the conventional fluorescence intensity-based method, this method is of high convenience since the whole procedure could be achieved within 5 min without any sample pretreatment (even no dilution), demonstrating promising application prospects. Graphical Abstract Fluorescence wavelength-shift based colorimetric sensing of chloride in sweat via halide exchange of CsPbBr3 perovskite nanocrystals.

Dual-Mode of Fluorescence Turn-On and Wavelength-Shift for Methylamine Gas Sensing Based on Space-Confined Growth of Methylammonium Lead Tribromide Perovskite Nanocrystals.

The defect-tolerant nature of lead halide perovskites renders outstanding luminescence by simple space-confined growth in nanopores. The fluorescence turn-on and wavelength-shift phenomena could be found in the formation of methylammonium lead tribromide (MAPbBr3) nanocrystals in hollow SiO2 nanospheres triggered by the reaction between methylamine (MA) gas and HPbBr3/PbBr2@SiO2 nanospheres. The enhanced fluorescence intensity is linear with the MA concentration in the range of 1.0-95 ppm with a limit of detection (LOD) of 70 ppb (S/N = 3). In addition, the maximum emission wavelength is consistently red-shifted from 478.7 to 510.6 nm as the MA concentration increases from 1.0 to 95 ppm, imparting the potential for colorimetric sensing. By combining the fluorescence turn-on and colorimetric sensing modes, the flexible method meets the demands for visual discrimination and point-of-care determination with portable devices.

Theta band behavioral fluctuations synchronized interpersonally during cooperation.

Human behavior fluctuates. A growing body of evidence has demonstrated that behavioral performance in perception fluctuates rhythmically, with dynamics closely resembling spectral features of neural oscillations. However, it is unclear whether the behavioral fluctuations in a complex cooperation context can also express similar rhythmic features, and, more importantly, whether these behavioral rhythms are synchronized among co-actors in a neurophysiologically relevant manner. To answer these questions, we applied a time-resolved approach, previously used for probing individual-level behavioral oscillations in perception, in a complex social interaction context, and further probed dyad-level behavioral synchrony. Twenty pairs of male participants completed, in dyad, joint-action tasks with cooperation or competition demand. We extracted behavioral rhythms from ongoing cooperative performance and measured behavioral synchrony by computing the phase coherence of these behavioral rhythms between dyad members. Despite the absence of significant behavioral oscillations in individuals' amplitude spectrum, we observed enhanced theta-band phase coherence between co-actors' behavioral rhythms during cooperation compared to competition conditions. These results indicate that cooperative behaviors of co-actors fluctuated synchronously within the theta band, providing a behavioral counterpart of theta-band interbrain synchrony in cooperation reported in previous hyperscanning studies. Furthermore, the observed behavioral synchrony could be used as a sensitive predictor of cooperation pattern, as evidenced by its significant correlation with leader-follower relationship during cooperation.

Frontal Theta Oscillation as a Mechanism for Implicit Gender Stereotype Control: Electrophysiological Evidence From an Extrinsic Affective Simon Task.

Previous research has indicated that frontal midline theta (FMθ) reflects a domain-general cognitive control mechanism of the prefrontal cortex. Brain imaging studies have shown that the inhibition of implicit stereotypes was dependent on this domain-general cognitive control mechanism. Based on this knowledge, the present study investigated the neural oscillatory correlates of implicit gender stereotype control in an extrinsic affective Simon task (EAST) using electrophysiological methods. Participants in this task conducted verification to white gender names and colored gender traits, and their behavioral response and electroencephalogram (EEG) were recorded during their performances. As predicted, stereotype-inconsistent trials resulted in reduced response accuracies and slower response times than stereotype-consistent trials. For the event-related potential (ERP) results, the enhanced performance of stereotype-inconsistent trials was accompanied by an enhanced N400 amplitude but an attenuated late positive potential amplitude. In contrast, early attentional components such as P2 and N2 as well as their amplitudes were impacted by the experimental manipulations and individual differences in gender factors. In addition, based on time-frequency (TF) analysis, we found that the enhanced performance of stereotype-inconsistent trials was also accompanied by an event-related synchronization on the frontal theta oscillation. This frontal theta appeared at a late processing stage and persisted across a time window from N400 to late positive potential. Additionally, this enhanced frontal theta effect was not modulated by the experimental manipulations and individual differences in gender factors. Based on these findings, the feature of frontal theta oscillation in the implicit gender stereotype control process was discussed.

Fluorometric sensing of oxygen using manganese(II)-doped zinc sulfide nanocrystals.

Manganese(II)-doped zinc sulfide nanocrystals (Mn:ZnS NCs) with dual-emission fluorescence (peaks at 445 nm and 590 nm under 330 nm excitation), good water stability and low toxicity were synthesized by hot injection. The fluorescence intensity of both emission bands of the nanocrystals can change rapidly by the content of gaseous and dissolved oxygen. The process is fully reversible. Compared with the maximum intensity of Mn:ZnS sensing film in 100% nitrogen, the emission of the blue emission decreases by 72% in the presence of 100% oxygen, and the yellow emission by 32%. Response is linear in the presence of 3% to 12% of oxygen percentage in gas. For water-dissolved oxygen, the linear response occurs between 0.54 and 11.4 mg·L-1. Graphical abstractMn-doped ZnS NCs with dual-emission fluorescence were synthesized by hot-injection method. The reversible and rapid sensing characteristics of Mn-doped ZnS NCs to oxygen were studied, and the possible sensing mechanism was investigated.

Wavelength-Shift-Based Colorimetric Sensing for Peroxide Number of Edible Oil Using CsPbBr3 Perovskite Nanocrystals.

The peroxide number of edible oil relates to its quality. The classical determination methods for the peroxide number are still unsatisfactory due to their complexity and poor reproducibility in the analytical process and their incapability of field rapid detection. In this study, a novel wavelength-shift-based visual method has been developed for the peroxide number determination of edible oil using halide perovskite nanocrystals (CsPbBr3 NCs). In the analysis, the edible oil sample underwent redox reactions with a part of oleylammonium iodide (OLAM-I) in advance. Then, the halogen exchange occurred between the added CsPbBr3 NCs and the iodide ions from the residual OLAM-I. The resulting wavelength shift of the fluorescence emission reflects the peroxide number in the edible oil sample. Under the ultraviolet light excitation at 365 nm, the apparent color of the photoluminescence could directly be compared with a color chart to determine and qualify the peroxide number. Using the approach, the visual detection of the peroxide number of edible oil samples on site could be realized. The detection process takes only ∼15 min and is convenient and accurate.

Enhancing the Stability of CH3NH3PbBr3 Nanoparticles Using Double Hydrophobic Shells of SiO2 and Poly(vinylidene fluoride).

The instability of lead halide perovskites (LHPs) has tremendously hindered their practical applications. Although some examples on encapsulating LHPs into a SiO2 shell have been reported, these SiO2-coated LHPs still suffer from limited stability. Herein, MAPbBr3 (MA = CH3NH3+) nanoparticles encapsulated in double hydrophobic shells of organic functionalized SiO2 and poly(vinylidene fluoride) (MAPbBr3@SiO2/PVDF) are successfully synthesized by infiltrating the MAPbBr3 precursor solution into hollow siliceous nanospheres and followed by PVDF capping. With the dual protection of SiO2 and PVDF, the MAPbBr3@SiO2/PVDF nanoparticles exhibit drastically improved stability against water and UV-light illumination. A white light-emitting diode with luminous efficiency up to 147.5 lm W-1 and a color gamut encompassing 120% of National Television System Committee in Commission Internationale de L'Eclairage 1931 color space has been demonstrated using the MAPbBr3@SiO2/PVDF nanoparticles as the green light source. This study enlightens new insights into the synthesis of highly stable LHPs-based core-shell-shell architectures toward their practical applications.

Attentional Blink Effects on S-Cone Stimuli.

This study aimed to compare attentional blink (AB) effects on S-cone and on luminance stimuli. Recent research had revealed considerable AB effects not only on high-order visual areas but also on low-order visual areas. Therefore, whether AB formation occurred or not at primary visual cortex must be examined. Previous studies had reported the absence of attention modulation in an early koniocellular pathway driven by S-cone stimuli; therefore, the AB effects on S-cone stimuli would be a strong piece of evidence for late-stage hypothesis at least in the koniocellular pathway. For this study, 12 participants were instructed to identify a centrally presented target (T1) only or to identify either T1 or a peripheral target (T2). The targets were either luminance or S-cone stimuli. As expected, comparable AB effects on S-cone and luminance stimuli were observed. Findings suggested that AB formation through a koniocellular pathway must occur at a later cortical processing stage.