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Topological insulators (TIs) are widely recognized as a new state of quantum matter with semiconductor‐like or insulator‐like bulk states (BSs) and Dirac‐like surface states (SSs). Herein, the terahertz (THz) properties of the SSs and BSs in Bi2Te3‐based TIs, as well as the effects of temperature on them, are examined. By using THz time–domain spectroscopy, the optical conductance of Bi2Te3 is obtained for TI thickness of about 10 and 20 nm. It is shown that the THz responses of the SSs and BSs can be distinguished by purely optical means in a wide temperature range (80–280 K). A Drude formula, which includes two terms corresponding to the SSs and BSs, is applied to describe the behavior of the optical conductance. Moreover, the evidence of bulk‐to‐surface scattering and additional electron injection from the BSs to the SSs is also observed without the help of electric measurement. These results are helpful to gain an in‐depth understanding of the THz properties of TIs and to explore new applications in topologically protected plasmonic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

In the exploration of three-dimensional quaternary topological insulators, understanding surface states has become pivotal for unraveling the underlying physics and tapping into potential applications. Our study delves into the temperature and magnetic field-angle dependence of universal conductance fluctuations (UCF) and weak anti-localization (WAL) effects in a Bi1.9Sb0.1Te2Se topological insulator-based mesoscopic device. Conventionally, other low-temperature transport phenomena in probing surface states may inevitably face interference from three-dimensional bulk conductance. However, we experimentally demonstrate that, at low temperatures, UCF reflects the properties of two-dimensional topological surface states more accurately, thereby providing a more reliable and distinct way to confirm their existence. Moreover, we carefully analyze the temperature-dependent WAL using the Hikami–Larkin–Nagaoka model, proposing a crucial role for charge puddles associated with electrostatic fluctuations in the electron dephasing process. Our findings not only emphasize the key role of UCF in unveiling the underlying behavior of topological surface states but also offer a deeper understanding of phase-coherent transport in quaternary topological insulators. [ABSTRACT FROM AUTHOR]

A physics‐based threshold voltage and drain–source current model based on double‐channel AlxGa1−xN/GaN/AlyGa1−yN/GaN high‐electron‐mobility transistors (HEMTs) is proposed in this article. Electrons limited in the potential well are derived from ionized donor‐like surface states of the AlxGa1−xN layer. Accumulated 2D electron gases (2DEGs) and positive charges left are equivalent to planar plate capacitors and further form electric fields, weakening the polarization fields in barrier layers. The physical properties of the dual‐channel HEMT are considered holistically rather than two separate and independent single heterojunctions. The effect of the charges and 2DEGs distributed in lower layers on the upper channel is contained in our model as well. Subsequently, a drain–source current model is proposed through coupling the critical electric field with the threshold voltage (VTH). The influence of channel length modulation, short channel effect, self‐heating effect, and kink effect is involved in this model. The accuracy of the proposed models is verified by comparison with technology computer‐aided design simulations and the experimental results. Proposed models can greatly describe the output characteristics, the transmission characteristics, and the relationship between VTH and device parameters of double‐channel AlGaN/GaN HEMTs. [ABSTRACT FROM AUTHOR]

The AA7075-T6 material is widely used in aerospace applications due to its favourable strength-to-weight ratio and cost-effectiveness. The material undergoes a process of cold rolling and subsequent stretching to form metal sheets. This process generates residual compressive stresses on the surface of the material. Surface changes in the material are observed at low stress levels, resulting in variations in residual stresses and surface roughness. This article presents an approach to monitor the surface state changes of AA7075-T6 material during dynamic loading using Fiber Bragg Grating (FBG) sensor. Numerical Finite Element Method (FEM) simulations analyse the transfer of deformations from the damaged surface through the adhesive layer to FBG with different cladding thicknesses. Loading induces microcrack-related intensity changes in the FBG optical spectrum and deformation response. The magnitude of the response is greater, when the cladding thickness of the optical fibre is thinner. Experimental results show that the FBG optical spectrum response varies with cumulative number of dynamic cycles. [ABSTRACT FROM AUTHOR]

Laser-induced removal of non-destructive substrates is a continuous pursuit for practical applications. Herein, a strategy of scanning cycle's large adjustment combined with laser energy density's fine tuning was established to achieve precise removal of FeCo-based wave-absorbing coatings. First and foremost, no coating residue was observed on the surface and cross-section of optimized sample E5 with a laser energy density of 61.1 J/cm2 (scanning cycles were seven). CIE LAB color analysis indicated that the surface of sample E5 had the highest coating's removal degree. Through numerical simulation and experimental examination, the oxide layer of the aluminum alloy did not present any damage such as cracking and peeling. In addition, the surface roughness remained unchanged, which verifies the possibility of laser removal towards non-destructive substrates. The multi-perspective evaluations of surface states illustrated that Barite (BaSO4), FeCo and other coating's characteristic substances had disappeared, ensuring the subsequent serviceability of the surface after removal. Furthermore, the vaporization removal mechanism of the wave-absorbing coatings was demonstrated by the plasma captured by a high-speed camera. Notably, the substrate's damage mechanism in laser removal was revealed. The remarkable different thermal expansion behavior of oxide layer and alloy induced extreme stress concentrations at the interface, which led to oxide layer's cracks and exfoliation. In summary, substrate's damage suppression can be achieved through simulation and experimental optimization. The presented research not only benefits the strategy design of laser removal for multilayer materials, but also expands the application potential of laser removal in non-destructive substrates.

A flat band structure in momentum space is considered key for the realization of novel phenomena. A topological flat band, also known as a drumhead state, is an ideal platform to drive new exotic topological quantum phases. Using angle-resolved photoemission spectroscopy experiments, we reveal the emergence of a highly localized surface state in a topological semimetal BaAl4 and provide its full energy and momentum space topology. We find that the observed surface state is localized in momentum, inside a square-shaped bulk Dirac nodal loop, and in energy, leading to a flat band and a peak in the density of state. These results imply this class of materials as an experimental realization of drumhead surface states and provide an important reference for future studies of the fundamental physics of correlated quantum effects in topological materials.

Correlation between the sidewall surface states and off-state breakdown voltage of AlGaN/GaN heterojunction field effect transistors (HFETs) is investigated for the first time. HFETs explored in this work were realized on a variety of isolation features including conventional mesa, non-slanted fin, and slanted fin. The output and transfer characteristics of the devices from all categories of the fabricated AlGaN/GaN HFETs were studied, and a link between the separation of isolation feature sidewalls in the drain access region and the breakdown voltage was observed. Simulation results showed that by shrinking the width of the isolation feature geometry, the peak of the electric field at the drain edge of the gate is reduced as a result of tailoring its profile when a more resistive path is imposed on the drain access region. While HFETs realized on fins of smaller width benefit more from the depleting effect of acceptor sidewall surface states and consequently a higher off-state breakdown voltage, they suffer from a lower current density in the on-state. The slanted fin isolation feature geometry that we proposed here, while maintaining high breakdown voltage in the off-state, reduces the resistance in the on-state, which is represented by its highest Baliga's figure of merit among the three categories of isolation feature geometries. The proposed solution for achieving an improvement to the off-state breakdown voltage of AlGaN/GaN HFETs relies on a technology that has already been explored as a successful alternative for the realization of enhancement-mode transistors (i.e., with positive threshold voltage). [ABSTRACT FROM AUTHOR]

In this paper, the occupancy of sidewall surface states having a clear signature in the performance of AlGaN/GaN-based self-switching diodes (SSDs) is analyzed using a semi-classical Monte Carlo (MC) simulator in a wide temperature (T) range, from 100 to 300 K. Experimental I – V curves show an unusual current decrease at low temperature attributed to surface trapping. The dependence on T of the negative surface charge density σ at the etched sidewalls of the SSDs is essential to explain the measurements. Two devices with different widths (80 and 150 nm) have been characterized and simulated in detail paying especial attention to the modeling of the surface states. At room temperature, MC simulations with a position-independent value of σ are able to qualitatively reproduce the I – V curves. However, a more complex approach is required to correctly replicate the values and shape of the DC experimental curves at low temperature, below 220 K. An algorithm where σ depends not only on T but also on the applied bias V is proposed to successfully fit the current values at every bias point. The model is able to explain the physics of the unexpected dependence of the resistance with the channel width and the sign change in the bowing coefficient, the parameters that govern the detection capabilities of the diodes. [ABSTRACT FROM AUTHOR]

A hallmark signature of the three-dimensional (3D) topological insulator (TI) is that the spin-momentum locked massless Dirac fermions populate its surface states, where the carrier spins are locked to their momentum. Here, we report on the magnetic-field induced helicity dependent photogalvanic effect (MHPGE) of 3D TI thin films Bi 2 Te 3 or (Bi x Sb 1 − x ) 2 Te 3 of different thicknesses excited by near-infrared (1064 nm) under an in-plane magnetic field. It is found that the MHPGE current J c x under the longitudinal geometry, i.e., J c x ∥ B x , is induced by the Larmor procession, while that under the transverse geometry, i.e., J c x ∥ B y , is mainly introduced by the hexagonal warping, which can be enhanced by the in-plane magnetic field. Our work demonstrates the possibility to tune the spin-polarized photocurrent of the surface states in 3D TIs via a magnetic field, which may be utilized to design new kinds of opto-spintronic devices. [ABSTRACT FROM AUTHOR]

A hallmark signature of the three-dimensional (3D) topological insulator (TI) is that the spin-momentum locked massless Dirac fermions populate its surface states, where the carrier spins are locked to their momentum. Here, we report on the magnetic-field induced helicity dependent photogalvanic effect (MHPGE) of 3D TI thin films Bi 2 Te 3 or (Bi x Sb 1 − x ) 2 Te 3 of different thicknesses excited by near-infrared (1064 nm) under an in-plane magnetic field. It is found that the MHPGE current J c x under the longitudinal geometry, i.e., J c x ∥ B x , is induced by the Larmor procession, while that under the transverse geometry, i.e., J c x ∥ B y , is mainly introduced by the hexagonal warping, which can be enhanced by the in-plane magnetic field. Our work demonstrates the possibility to tune the spin-polarized photocurrent of the surface states in 3D TIs via a magnetic field, which may be utilized to design new kinds of opto-spintronic devices. [ABSTRACT FROM AUTHOR]

The formation and destruction of O3 within the Chapman cycle occurs as a result of inelastic collisions with a third body. Since N2 is the most abundant atmospheric molecule, it can be considered as the most typical candidate when modeling energy-transfer dynamics. We report a new ab initio potential energy surface (PES) of the O3–N2 van der Waals complex. The interaction energies were calculated using the explicitly correlated single- and double-excitation coupled cluster method with a perturbative treatment of triple excitations [CCSD(T)-F12a] with the augmented correlation-consistent triple-zeta aug-cc-pVTZ basis set. The five-dimensional PES was analytically represented by an expansion in spherical harmonics up to eighth order inclusive. Along with the global minimum of the complex (De = 348.88 cm−1), with N2 being perpendicular to the O3 plane, six stable configurations were found with a smaller binding energy. This PES was employed to calculate the bound states of the O3–N2 complex with both ortho- and para-N2 for total angular momentum J = 0 and 1, as well as dipole transition probabilities. The nature of the bound states of the O3–oN2 and O3–pN2 species is discussed based on their rovibrational wave functions. [ABSTRACT FROM AUTHOR]

Developing bifunctional water‐splitting photocatalysts is meaningful, but challenged by the harsh requirements of specific‐facet single crystals with spatially separated reactive sites and anisotropic charge transfer paths contributed by well‐built charge driving force. Herein, tunable ferroelectric polarization is introduced in Bi4NbO8Cl single crystal nanosheets to strengthen the orthogonal charge transfer channels. By manipulating the in‐plane polarization from octahedral off‐centering of Nb5+ and out‐of‐plane polarization from lone pair electron effect of anisotropic Bi3+, both the fast charge recombination in bulk catalyst and the process of charge trapping into surface states can be effectively modulated. Collaborating with modest polarization electric field and facet junction induced built‐in electric field, cooperative charge tractive force is constructed, which reinforces the spatial separation and migration of photogenerated electrons and holes to {110} reductive site facet and {001} oxidation site facet, respectively. While excessive polarization charges impair the facet‐selective charge separation characteristics and conversely promote charge recombination on the surface. As a result, polarity‐optimized Bi4NbO8Cl shows an excellent H2 and O2 evolution rate of 54.21 and 36.08 μmol ⋅ h−1 in the presence of sacrificial reagents under visible light irradiation. This work unveils the function of ferroelectric polarization in tuning the intrinsic facet‐selective charge transfer process of photocatalysts. [ABSTRACT FROM AUTHOR]

Recent studies have centered on the potential for effectively controlling the topology state of iso-frequency surfaces in artificial photonic structures using external fields. This paper delves into the topological transitions and singularity states of the isofrequency surface of a highly anisotropic superlattice. This superlattice is composed of alternating layers of ferrite-dielectric and semiconductor-dielectric metamaterials. The superlattice is placed in an external magnetic field in the Voigt geometry that is parallel to the boundaries of the structure layers and perpendicular to the periodicity axis. Material properties of both constituent metamaterials are described in terms of effective components of permittivity and permeability in the long-wave approximation. An external magnetic field influences the properties of transverse electric (TE) waves in the ferrite-dielectric metamaterial, and the properties of transverse magnetic (TM) waves in the semiconductor-dielectric metamaterial. This results in the iso-frequency surface transition from a closed ellipsoid to an open hyperboloid for both TE and TM waves in various configurations. Furthermore, the superlattice can be identified as a hypercrystal under certain conditions, specifically when the constituent metamaterials possess a hyperbolic isofrequency surface state. This research demonstrates that the isofrequency surface properties of the studied hypercrystal can be effectively controlled by altering the external magnetic field, the fill factors of metamaterials, and frequency. Special attention is devoted to investigating the topological singularities that take place when iso-frequency surfaces of TE and TM polarized waves intersect. This intersection leads to the degeneracy of the hypercrystal's isofrequency surface and the potential observation of unique phenomena such as conical refraction or the existence of surface states. [ABSTRACT FROM AUTHOR]

We investigate the photonic topological phases in chiral metamaterials characterized by the magnetoelectric tensors with diagonal chirality components. The underlying medium is considered a photonic analogue of the topological semimetal featured with a Weyl cone and a cylindrical surface in the frequency-wave vector space. As the 'spin'-degenerate condition is satisfied, the photonic system can be rearranged as two hybrid modes that are completely decoupled. By introducing the pseudospin states as the basis for the hybrid modes, the photonic system is described by two subsystems in the form of spin-orbit Hamiltonians of spin 1, which result in nonzero spin Chern numbers that determine the topological properties. Surface modes at the interface between vacuum and the chiral metamaterial exist in their common gap in the wave vector space, which are analytically formulated by algebraic equations. In particular, the surface modes form a pair of spiral surface sheets wrapping around the Weyl cone, resembling the helicoid surface states that occur in topological semimetals. At the Weyl frequency, the surface modes contain two Fermi arc-like states that concatenate to yield a straight line segment. [ABSTRACT FROM AUTHOR]

With the use of Li-ion batteries, Li-ion batteries will experience unavoidable aging, which can cause battery safety issues, performance degradation, and inaccurate SOC estimation, so it is necessary to predict the state of health (SOH) of Li-ion batteries. Existing methods for Li-ion battery state of health assessment mainly focus on parameters such as constant voltage charging time, constant current charging time, and discharging time, with little consideration of the impact of changes in Li-ion battery temperature on the state of health of Li-ion batteries. In this paper, a new prediction method for Li-ion battery health state based on the surface difference temperature (DT), incremental capacity analysis (ICA), and differential voltage analysis (DVA) is proposed. Five health factors are extracted from each of the three curves as input features to the model, respectively, and the weights, thresholds, and number of hidden layers of the Elman neural network are optimized using the Whale of a Whale Algorithm (WOA), which results in an average decrease of 43%, 49%, and 46% in MAE, RMSE, and MAPE compared to the Elman neural network. For the problem where the three predictions depend on different sources, the features of the three curves are fused using the weighted average method and predicted using the WOA–Elman neural network, whose MAE, RMSE, and MAPE are 0.00054, 0.0007897, and 0.06547% on average. The results show that the proposed method has an overall error of less than 2% in SOH prediction, improves the accuracy and robustness of the overall SOH estimation, and reduces the computational burden to some extent. [ABSTRACT FROM AUTHOR]

Exploring highly efficient and stable photoelectrode material is essential for high-performance photoelectrochemical (PEC) water-splitting applications. III-nitride semiconductors, particularly InGaN, have been considered as prospective materials for PEC hydrogen evolution. However, their surface states and other recombination centers, which enhance the charge recombination kinetics, are bottlenecks for the high PEC performance. In this work, we report the construction of type-II heterojunction by sputter depositing SnO2 on InGaN nanorods (NRs) to promote interfacial carrier transport and thereby enhance PEC performance. The energy band offsets at the SnO2/InGaN NRs interface were analyzed by x-ray photoelectron spectroscopy. Type-II heterojunction was defined at the SnO2/InGaN NRs interface with a valence band offset of 0.77 eV and conduction band offset of 0.25 eV. The photocurrent density of the SnO2/InGaN NRs photoanode is 7.09 mA/cm2 at 0.77 V vs Ag/AgCl electrode with 80 nm SnO2 thickness, which is ∼14-fold higher than that of the pristine InGaN NRs photoanode. Furthermore, the applied bias photo-to-current efficiency of SnO2/InGaN NRs photoanode records 3.36% at 0.77 V vs Ag/AgCl electrode. The enhanced PEC performance is mainly ascribed to the formation of high-quality SnO2/InGaN NRs heterojunction that enforces the directional charge transfer and substantially boosts the separation of photogenerated electron–hole pairs at the interface of InGaN NRs and SnO2. Overall, this work sheds light on the promising strategy to design and fabricate III-nitride nanostructures-based photoelectrodes for feasible PEC water-splitting applications. [ABSTRACT FROM AUTHOR]

The spin-to-charge conversion phenomenon is investigated in a trilayer structure consisting of Co(12 nm)/Sb(t)/Py(12 nm), where the thickness t of the antimony layer is varied. Using the spin-pumping technique, a pure spin current is injected from both FM layers into the middle layer, the DC voltage is then measured. We observe a spin-to-charge mechanism in the Sb layer that exhibits striking similarities to the inverse Rashba–Edelstein effect (IREE), driven by surface states. [ABSTRACT FROM AUTHOR]

To date, it has become more and more important to design and synthesize energetic materials that have a good balance between energy and safety. In this study, a new nitrogen-rich energetic compound with high energy and low sensitivity is designed and synthesized. The target compound dihydrazinium 3,3′-azo-5,5′-diazido-1,2,4-triazol (DHADAT) shows a very high nitrogen content (81.27%) and high enthalpy of formation (1405 kJ mol−1). Furthermore, DHADAT not only exhibits a detonation velocity (D = 9122 m s−1) comparable to HMX, but also has a much lower impact sensitivity (IS = 23 J) than HMX (D = 9144 m s−1, IS = 7.4 J). Additionally, a calculation based on dispersion-corrected density functional theory (DFT-D) has been performed to examine the electronic and mechanical properties of DHADAT. And the analysis of the density of states and the Hirshfeld surface indicates that the N–H⋯N hydrogen bonding interaction plays a vital role in stabilizing the whole system. And it is discovered through the analysis of the mechanical properties that this compound exhibits a better ductility, resistance to deformation and stiffness than HMX. The systematic research on DHADAT by combining experiment and theory ensures that DHADAT could be an extremely promising insensitive high-energy material. [ABSTRACT FROM AUTHOR]

In this article, a method based on sliding mode control, named adaptive slope sliding mode control is proposed to increase the response speed of the system outputs. In this method, the difference between the surface and the state is maintained at its minimum value by constantly changing the slope of the surface, making the states converge faster. Compared to fixed slope methods, it can be said that by changing the slope of the system, not only the response speed of the system is increased, but also the output accuracy increases as well. To evaluate the effects of adding a variable slope to sliding mode controllers, the proposed controller is applied to the grid synchronization of a wind turbine system. [ABSTRACT FROM AUTHOR]

An effective interpretation of the complex reliability theory will promote its application in engineering practice. Based on an algorithm for solving the geometric reliability index for cases involving two or three random variables in the original physical space, an advanced algorithm for multivariate random variables is further developed by using a hypersphere model and inverse Nataf transformation. The main components of the algorithm include the definition of limit state surface, the construction of a hypersphere model, the determination of probability density iso‐contour points, the identification of limit state of these points, and the definition of an actual reliability index. Several typical practical problems associated with two to five variables are analyzed, and the results are compared with those obtained using the first‐order reliability method (FORM) and the copula‐based sampling method (CBSM), thus validating the accuracy of the proposed algorithm. With the help of the powerful and open‐source R language platform, the visualization of a reliability index in low dimensions and the solvability in high dimensions are implemented, which makes the interpretation of reliability theory more intuitive. [ABSTRACT FROM AUTHOR]

Plate tectonics is a tectonic style thought to be the hallmark of habitable planets, and yet the inherent complexities of plate tectonic convection have clouded the establishment of simple scaling laws with which to model convective behavior and thermal evolution. We have recently developed a scaling approach for mixed heated convection, based upon several simple physical principles. Here, we generalize our scaling approach to mixed heated convection with pseudoplastic rheology, which gives rise to the plate tectonic mode of convection. We then apply our scaling results to the so‐called bistability of tectonic mode. By illustrating common pitfalls regarding heating mode and nondimensionalization, we demonstrate that tectonic mode is unique with respect to key planetary properties, and that a convective regime diagram for terrestrial planets is within reach. Plain Language Summary: Convection within planetary mantles (the rocky layer bounded by a thin crust and a metallic core) is driven by heating from within and from below, and it is largely dependent on rheology—how mantle rocks deform. We generalize convection scaling laws to the rheology and heating mode appropriate for planetary mantles. These scaling laws describe convective properties of plate tectonic convection, in which the surface layer of the mantle is weak enough to participate in convection, as well as stagnant lid convection, in which the surface layer is strong and immobile. We show that the state of the surface layer (the so‐called tectonic mode) is unique for a given rheological scenario. This restores confidence in the prospect of predicting tectonic mode from first‐order planetary properties, a crucial task given the connection between tectonic mode and habitability. Key Points: Mantle convection scaling laws are generalized for the heating mode and rheology appropriate for planetary mantlesConvective properties may be accurately predicted for both the plate tectonic and stagnant lid modes of convectionTectonic mode is unique for a given rheological scenario, despite the apparent bistability of numerical simulations [ABSTRACT FROM AUTHOR]

Realistic initialization of the land surface is important to produce accurate NWP forecasts. Therefore, making use of available observations is essential when estimating the surface state. In this work, sequential land surface data assimilation of soil variables is replaced with an offline cycling method. To obtain the best possible initial state for the lower boundary of the NWP system, the land surface model is rerun between forecasts with an analyzed atmospheric forcing. We found a relative reduction of 2-m temperature root-mean-square errors and mean errors of 6% and 12%, respectively, and 4.5% and 11% for 2-m specific humidity. During a convective event, the system was able to produce useful (fractions skill score greater than the uniform forecast) forecasts [above 30 mm (12 h)−1] down to a 100-km length scale where the reference failed to do so below 200 km. The different precipitation forcing caused differences in soil moisture fields that persisted for several weeks and consequently impacted the surface fluxes of heat and moisture and the forecasts of screen level parameters. The experiments also indicate diurnal- and weather-dependent variations of the forecast errors that give valuable insight on the role of initial land surface conditions and the land–atmosphere interactions in southern Scandinavia. [ABSTRACT FROM AUTHOR]

We doped carbon into a TiZrN coating to reduce hydrogen permeability, and investigated the phase formation, bonding state, microstructure, and surface roughness of the carbon-doped TiZrN. The laser output for laser carburization was limited to a range of 20–50%. The grain size of the TiZrN coatings decreased from 26.49 nm before carburization to 18.31 nm after carburization. For XPS analysis, the sp2/sp3 ratio was 1.23 at 20% laser output, but it showed 2.64 at 40% laser output, which means that amorphous carbon was formed. As the grain size decreased with the formation of amorphous carbon, the surface microstructure of the carbon-doped TiZrN coatings transitioned to an intergranular structure, indicating the creation of amorphous carbon-embedded (Ti, Zr)(C, N) in the coating. The surface roughness (Ra) of the carbon-doped TiZrN coating was decreased to a maximum of 7.12 nm, and the hydrogen permeability correspondingly decreased by 78% at 573 K. [ABSTRACT FROM AUTHOR]

The surface states of scintillator will affect its scintillation performance such as fluorescence emission intensity and spatial resolution, and then affect the test results of radiation detection system. By means of theoretical simulation and experimental research, this paper systematically explored the spatial distribution of fluorescence intensity of LYSO : Ce scintillator under four surface states ( two sides polished, exit side polished only, inlet side polished only and two sides unpolished) when excited by radiation, and the influence of scintillator thickness on its spatial resolution. The results show that the relative fluorescence intensity of the four states at 0° normal direction is 0. 49:0. 64:0. 89:1, and the fluorescence intensity gradually decreases with the emission angle increase. As the surface polished degree decreases, the spatial distribution of fluorescence emitted from scintillators becomes uniformly. When the thicknesses of the scintillator are 0. 3, 1. 0 and 5. 0 mm, the spatial resolutions of two sides polished are 1. 70, 1. 36 and 1. 12 lp / mm, respectively. The spatial resolutions of exit side polished are 1. 5, 1. 2 and 1. 0 lp / mm, respectively. The spatial resolution decreases with the scintillator thickness increases, and the spatial resolution of two sides polished is improved by about 12% compared to exit side polished only. [ABSTRACT FROM AUTHOR]

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In this work, the coatings obtained by a combined method, including Cr3C2-NiCr coating applied using a multichamber detonation device and subsequent pulse-plasma treatment, were investigated. This paper presents the results of an investigation of the influence of the pulse-plasma treatment (PPT) exposure distance on the structural-phase state of the surface layer of Cr3C2-NiCr-based detonation coatings. It was seen that after the PPT melting and alignment of the structural elements of coatings there were no signs of coating destruction from the impact of plasma pulses. It was established that the microstructure of the coatings was a molten metal–ceramic material based on Cr3C2-NiCr. It was also found that after pulse-plasma treatment, Cr2O3 chromium oxide phases are found on the surface, and the intensity of Cr3C2 peaks increased and new Cr3C2 reflexes appeared. It was further found that after pulse-plasma treatment the microstructure became more homogeneous, which led to the densification of the Cr3C2-NiCr-based detonation coating. It was established that the pulse-plasma treatment (PPT) contributed to increased hardness of the Cr3C2-NiCr coating material, from ~13.4 GPa (before PPT) to ~17.6 GPa (after PPT) and wear resistance twice that of the non-treated coating. The abrasive wear resistance and erosion resistance of Cr3C2-NiCr coatings were improved after pulse-plasma treatment. [ABSTRACT FROM AUTHOR]

Surface states of topological materials provide extreme electronic states for unconventional superconducting states. CaAg1−xPdxP is an ideal candidate for a nodal-line Dirac semimetal with drumhead surface states and no additional bulk bands. Here, we report that CaAg1−xPdxP has surface states that exhibit unconventional superconductivity (SC) around 1.5 K. Extremely sharp magnetoresistance, tuned by surface-sensitive gating, determines the surface origin of the ultrahigh-mobility "electrons." The Pd-doping elevates the Fermi level towards the surface states, and as a result, the critical temperature (Tc) is increased up to 1.7 K from 1.2 K for undoped CaAgP. Furthermore, a soft point-contact study at the surface of Pd-doped CaAgP proved the emergence of unconventional SC on the surface. We observed the bell-shaped conductance spectra, a hallmark of the unconventional SC. Ultrahigh mobility carriers derived from the surface flat bands generate a new class of unconventional SC. CaAg1−xPdxP is a nodal-line Dirac semimetal. Here, using ionic-liquid gated transport and soft point-contact spectroscopy, the authors show that this material realizes surface-confined unconventional superconductivity. [ABSTRACT FROM AUTHOR]

Cemented sands exhibit superior mechanical properties compared to clean sands. Based on this evidence, ground improvement methods are increasingly employed to induce cementing reactions that can bind the solid particles of sands and other soils for the ultimate enhancement of their properties and behavior. Despite increasing ground improvement applications, constitutive models capable of capturing cementation effects on the mechanics of sands remain scarce. This article presents SANISAND-C*: a constitutive model developed in the framework of bounding surface and critical state plasticity to capture cementation effects on the mechanics of sands. In this paper, the mathematical formulation of this model is presented first. Then, a vast amount of experimental data available for different materials (i.e., types of sand), loading conditions (i.e., stress levels and paths), and cementation types (i.e., natural and artificial cementations) is used to validate the model. Based on the comparison between experimental and simulation results, this work finally discusses the capabilities and limitations of the proposed model, highlighting that it can realistically capture key properties of cemented sands: increased strength and stiffness, increased dilatancy, and bond destructuration upon loading. [ABSTRACT FROM AUTHOR]

Weyl semimetals exhibit exotic magnetotransport phenomena such as the chiral anomaly and surface-to-bulk quantum oscillations (Weyl orbits) due to chiral bulk states and topologically protected surface states. Here we report a unique transport property in crystals of the ferromagnetic nodal-line Weyl semimetal Co2MnGa that have been polished to micron thicknesses using a focused ion beam. These thin crystals exhibit a large planar resistance anisotropy (10 ×) with axes that rotate by 90 degrees between opposite faces of the crystal. We use symmetry arguments and electrostatic simulations to show that the observed anisotropy resembles that of an isotropic conductor with surface states that are impeded from hybridization with bulk states. The origin of these states awaits further experiments that can correlate the surface bands with the observed 90° twist. Weyl semimetals exhibit a rich variety of transport phenomena, but it usually takes low temperatures and a strong magnetic field to realize them. Here, Quirk et al. show that when the ferromagnetic Weyl semimetal Co2MnGa is polished to micron thicknesses, it develops a remarkable resistance anisotropy that has opposite directions on opposing crystal faces. They show that this unusual transport property, which is robust at room temperature and in a strong magnetic field, may be generated by distinct conducting states on the surfaces of these thin crystals. [ABSTRACT FROM AUTHOR]

By means of zincophilic regulation and protection of covalent organic framework (COF), uniform Zn ion deposition can be induced to inhibit dendrite growth and prevent chemical corrosion reactions. Moreover, abundant zincophilic sites and excellent zinc ion conduction pathway in the interfacial layer of COF can optimize the zinc ion transfer kinetics between electrolyte and Zn anode, thus inducing uniform Zn ion migration, nucleation, dissolution/plating. To realize the efficient and stable utilization of zinc anode. [Display omitted] Zn-ion energy storage devices will play important roles in the future energy storage field. However, Zn-ion device development suffers significantly from adverse chemical reactions (dendrite formation, corrosion, and deformation) on the Zn anode surface. Zn dendrite formation, hydrogen evolution corrosion, and deformation combine to degrade Zn-ion devices. Zincophile modulation and protection using covalent organic frameworks (COF) inhibited dendritic growth by induced uniform Zn ion deposition, which also prevented chemical corrosion. The Zn@COF anode circulated stably for more than 1800 cycles even at high current density in symmetric cells and maintained a low and stable voltage hysteresis. This work explains the surface state of the Zn anode and provides information for further research. [ABSTRACT FROM AUTHOR]

In model-free sliding mode control (MFSMC) of permanent magnet synchronous motor (PMSM), the first-order sliding mode surface convergence state is asymptotic convergence, and the dithering of the first-order sliding mode surface causes the motor control performance to degrade when the motor parameters change. To save the problem, a model-free fast non-singular terminal sliding mode control (MFFNTSMC) strategy is proposed. Firstly, considering the perturbation of motor parameters, a mathematical model of embedded permanent magnet synchronous motor is established, and the ultra-local model of the speed link is summarized. Then, according to the defined fast non-singular terminal sliding mode surface and the new reaching law, a new mode-free sliding mode controller based on the speed link is designed, which weakens the jitter by eliminating the high-gain switching by the high-order sliding surface, and at the same time makes the system state converge to zero in a limited time. In order to more accurately track the speed tracking effect, an extended sliding mode observer (ESMO) is used to observe the unknown disturbance of the system in real time. Finally, simulation and experiment comparisons with PI control as well as MFSMC control confirm that the method proposed in this paper has better steady state and transient performance for PMSM. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs), as an important carbon-based nanomaterial, have been widely used in fluorescence (FL) detection, bioimaging, photocatalysis, light-emitting devices (LEDs) and many other fields, owing to their excellent optical properties. Regulating the fluorescent properties of carbon dots (CDs) in a controlled manner has been a fundamental research goal. Herein, solvent-dependent CDs (N-CDs) are synthesized through the solvothermal reaction of o -phenylenediamine (OPD) in ethanol. When N-CDs are dispersed in solvents of different polarities, the emission wavelength only turned 39 nm red-shift. While, the O-CDs are obtained by modifying the surface of N-CDs with 1,2,4-benzenetricarboxylic acid (TMA). O-CDs show four obvious FL emission peaks in the yellow, orange and red regions at 554 nm, 604 nm, 650 nm and 712 nm with a tail extending to 750 nm, even entering into near-infrared-I (NIR-I) region. Thus, according to the special structure of CDs, this work provides a novel donor- π -acceptor (D- π -A) strategy for preparing long wavelength emissive CDs. Finally, the N-CDs and O-CDs are successfully applied to cellular imaging. Solvent-dependent CDs (N-CDs) are synthesized through the solvothermal reaction of o-phenylenediamine (OPD) in ethanol. While the O-CDs are obtained by modifying the surface of N-CDs with 1,2,4-benzenetricarboxylic acid (TMA), O-CDs show four obvious FL emission peaks in the yellow, orange and red regions at 554, 604, 650 and 712 nm with a tail extending to 750 nm, even enter into near-infrared-I (NIR-I) region. [ABSTRACT FROM AUTHOR]

Due to the long coherence time and efficient manipulation, the surface electron (SE) provides a perfect 2D platform for quantum computation and quantum simulation. In this work, a theoretical scheme to realize the controlled‐NOT gate is proposed, where the two‐qubit system is encoded on the four‐level Rydberg structure of SE. The state transfer is achieved by a three‐level structure with an intermediate level. By simultaneously driving the SE with two external electromagnetic fields, the dark state in the electromagnetically induced transparency effect is exploited to suppress the population of the most dissipative state and increase the robustness against dissipation. The fidelity of the scheme is 0.9989 with experimentally achievable parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe 2 TiO 5 /NiCo-LDH composite photoelectrode exhibits dual role as heterojunction and co-catalyst. • The effect of surface state on charge transfer is systematically discussed. • Fe 2 TiO 5 /NiCo-LDH photoelectrode expands application in photoelectrochemistry for sulfide oxidation reaction. The Fe 2 TiO 5 photoelectrode is limited in photoelectrochemical field (PEC) due to the slow charge transfer kinetics, short carrier diffusion distances and low separation efficiency. Hence, the Fe 2 TiO 5 /NiCo-LDH photoelectrodes with dual roles of co-catalyst and heterojunction are constructed, in which the photogenerated carriers are effectively separated and the conductivity is enhanced. At the same time, the surface state of the Fe 2 TiO 5 -based photoanode is modulated by the co-catalyst, which drives charge transfer into the electrolyte. With the synergistic effect of inhibiting photogenerated carrier complexation and accelerating charge transfer, the OER photocurrent density of Fe 2 TiO 5 /NiCo-LDH photoelectrode is enhanced to 2.42 mA/cm2, which is 3.4 folds higher than that of pristine Fe 2 TiO 5. Specifically, Fe 2 TiO 5 /NiCo-LDH photoanode exhibits good stability and photoelectrochemical performance in hydrogen sulfide oxidation reaction (SOR). Similar to the OER, the sulphur oxidation photocurrent density of Fe 2 TiO 5 /NiCo-LDH photoelectrodes is enhanced to 0.21 mA/cm2, which is 2 folds higher than that of pristine Fe 2 TiO 5. This work provides a new idea for the modification of Fe 2 TiO 5 photoanodes and also explores a pioneering demonstration for the photoelectrochemical decomposition of hydrogen sulfide. [ABSTRACT FROM AUTHOR]

Enhancing computability of cerebral recordings and connections made with human/non-human brain have been on track and are expected to propel in our current era. An effective contribution towards said ends is improving accuracy of attempts at discerning intricate phenomena taking place within human brain. Here and in two different capacities of experiments, we attempt to distinguish cerebral perceptions shaped and affective states surfaced during observation of samples of media incorporating distinct audio–visual and emotional contents, through employing electroencephalograph/EEG recorded sessions of two reputable datasets of DEAP and SEED. Here we introduce AltSpec(E3) the inceptive form of CollectiveNet intelligent computational architectures employing collective and concurrent multi-spec analysis to exploit complex patterns in complex data-structures. This processing technique uses a full array of diversification protocols with multifarious parts enabling surgical levels of optimization while integrating a holistic analysis of patterns. Data-structures designed here contain multi-electrode neuroinformatic and neurocognitive features studying emotion reactions and attentive patterns. These spatially and temporally featured 2D/3D constructs of domain-augmented data are eventually AI-processed and outputs are defragmented forming one definitive judgement. The media-perception tracing is arguably first of its kind, at least when implemented on mentioned datasets. Backed by this multi-directional approach and in subject-independent configurations for perception-tracing on 5-media-class basis, mean accuracies of 81.00% and 68.93% were obtained on DEAP and SEED, respectively. We also managed to classify emotions with accuracies of 61.59% and 66.21% in cross-dataset validation followed by 81.47% and 88.12% in cross-subject validation settings trained on DEAP and SEED, consecutively. [ABSTRACT FROM AUTHOR]

As a layered topological nodal line semimetals hosting a quasi-one-dimensional (quasi-1D) crystalline structure, TaNiTe5 has attracted intensive attention. In this research, we analyze the low temperature (low-T) transport properties in single crystals of TaNiTe5. The high anisotropic transport behaviors confirm the anisotropic electronic structure in quasi-1D TaNiTe5. The resistivity shows a magnetic field-induced resistivity upturn followed by a plateau at low temperatures when current is parallel to the c axis and magnetic field is parallel to the b axis. An extremely large magnetoresistance of 1000% has been observed at 2 K and 13 T. Such a magnetic field-induced phenomenon can be generally explained using the topological theory, but we find that the behaviors are well accounted with the classical Kohler's rule. The analysis of the Hall resistivity points to carrier compensation in TaNiTe5, fully justifying Kohler's rule. Our findings imply that analogous magnetic field-induced low-T properties in nodal line semimetals TaNiTe5 can be understood in the framework of classical magnetoresistance theories that do not require to invoke the topological surface states. [ABSTRACT FROM AUTHOR]

Controlling the morphology of ceria nanoparticles (CeNPs) has been proven an effective approach to mimic the activities of antioxidant enzymes including catalase (CAT) and superoxide dismutase (SOD). However, the mechanism of the morphology-dependent enzyme-like activities was elusive. Energy-band structure tailoring of NPs through morphologies closely correlates with their catalytic activities. Herein, three kinds of CeNPs with octahedron, cube and rod morphologies were synthesized. Octahedron-CeO2 with exposed {111} facets, cube-shaped CeO2 with {100} facets and rod-shaped CeO2 with {110} and {111} facets were observed. Due to the lower formation energy of oxygen vacancy (VO) for {110} facets, higher VO content was detected for rod-CeO2, which directly correlated with the energy level of surface defect states (ESDS). The ESDS for rod-CeO2 (0.86 V) roughly lied in the middle point of E0 (H2O2, H+/H2O) and E0(O2, H+/H2O2) (0.83 V), which resulted in higher CAT-like activity. Likewise, the ESDS of octahedron-CeO2 (0.48 V) approximately located at the midpoint of two half-reaction potentials in SOD catalytic cycle (0.39 V) which was agreement with its enhanced SOD-like activity. Overall, regulating ESDS towards the midpoint of the half-reaction potentials becomes a feasible approach to achieve enhanced catalytic efficiency. [ABSTRACT FROM AUTHOR]

To explain the effect of joint roughness on joint peak shear strength (JPSS) and investigate the effect of different contact states of joint surface on JPSS, we try to clarify the physical mechanism of the effect of joint cavity percentage (JCP) on JPSS from the perspective of the three-dimensional (3D) distribution characteristics of the actual contact joint surface, and propose a JPSS model considering the JCP. Shear tests for red sandstone joints with three different surface morphologies and three different JCPs were performed under constant normal load condition. Based on test fitting results, the reduction effect of the JCP on JPSS is investigated, and a JPSS model for cavity-containing joints is obtained. However, the above model only considers the influence of JCP by fitting test data, and does not reveal the physical mechanism of JCP affecting the JPSS. Based on the peak dilation angle model for consideration of the actual contact joint morphology, and the influence of JCP on the roughness of the actual contact joint surface, a theoretical model of the JPSS considering the JCP is proposed. The derivation process does not depend on the test fitting, but is entirely based on the joint mechanical law, and its physical significance is clear. It is proposed that the essence of the influence of the JCP on JPSS is that the JCP first affects the normal stress of the actual contact joints, further affects the roughness of actual contact joints, and then affects the shear strength. [ABSTRACT FROM AUTHOR]

Low photoluminescence (PL) quantum yield of molybdenum disulfide (MoS2) quantum dots (QDs) has limited practical application as potential fluorescent materials. Here, we report the intercalation of aluminum ion (Al3+) to enhance the PL of MoS2 QDs and the underlying mechanism. With detailed characterization and exciton dynamics study, we suggest that additional surface states including new emission centers have been effectively introduced to MoS2 QDs by the Al3+ intercalation. The synergy of new radiative pathway for exciton recombination and the passivation of non-radiative surface traps is responsible for the enhanced fluorescence of MoS2 QDs. Our findings demonstrate an efficient strategy to improve the optical properties of MoS2 QDs and are important for understanding the regulation effect of surface states on the emission of two dimensional sulfide QDs. [ABSTRACT FROM AUTHOR]

The National Aeronautics and Space Administration (NASA) has launched a new initiative, the Open-Source Science Initiative (OSSI), to enable and support science towards openness. The OSSI supports open-source software development and dissemination. In this work, we present NASAaccess, which is an open-source software package and web-based environmental modeling application for earth observation data accessing, reformatting, and presenting quantitative data products. The main objective of developing the NASAaccess platform is to facilitate exploration, modeling, and understanding of earth data for scientists, stakeholders, and concerned citizens whose objectives align with the new OSSI goals. The NASAaccess platform is available as software packages (i.e., the R and conda packages) as well as an interactive-format web-based environmental modeling application for earth observation data developed with Tethys Platform. NASAaccess has been envisioned as lowering the technical barriers and simplifying the process of accessing scalable distributed computing resources and leveraging additional software for data and computationally intensive modeling frameworks. Specifically, NASAaccess has been developed to meet the need for seamless earth observation remote-sensing and climate data ingestion into various hydrological modeling frameworks. Moreover, NASAaccess is also contributing to keeping interested parties and stakeholders engaged with environmental modeling, accessing the information available in various remote-sensing products. NASAaccess' current capabilities cover various NASA datasets and products that include the Global Precipitation Measurement (GPM) data products, the Global Land Data Assimilation System (GLDAS) land surface states and fluxes, and the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) Coupled Model Intercomparison Project Phase 5 (CMIP5) and Coupled Model Intercomparison Project Phase 6 (CMIP6) climate change dataset products. [ABSTRACT FROM AUTHOR]

In this work, a Z-scheme LaFeO3/g-C3N4/ZnO heterojunction photocatalyst with large specific surface (68.758 m2/g) and low cost (0.00035 times the cost of per gram of Au) was easily synthesized by glucose-assisted hydrothermal method. The structure, surface morphology, and optical properties of the photocatalyst were investigated. The constructed Z-scheme heterojunction catalysts can enhance the visible light absorption and carrier separation efficiency. Among these photocatalysts, the 10%-LaFeO3/g-C3N4/ZnO composite possesses the premium performance for efficient degrading 97.43% of phenol within 120 min. Even after 5 cycles, it still sustains an excellent photocatalytic stability (92.13% phenol degradation). According to the XPS surface states and the capture of active species on LaFeO3/g-C3N4/ZnO, the electrons would be transferred from ZnO and LaFeO3 to g-C3N4. In addition, ·OH plays an important role in photocatalytic reactions for phenol degradation. Thus, the proposed possible photocatalytic reaction mechanism of Z-scheme LaFeO3/g-C3N4/ZnO can provide a more economical and efficient conception for phenol degradation. [ABSTRACT FROM AUTHOR]

In this work, we have prepared a series of Pd catalysts on a CN x support for the liquid phase decomposition of formic acid. The structured CN x support was obtained through thermal pyrolysis of melamine foam and the pyrolysis conditions were optimized to achieve high surface area. The resulting support contains high amount of nitrogen with a contribution of pyridinic component. Several Pd catalysts were prepared and under optimized conditions, we were able to obtain small (2.7 ± 0.9) nm Pd particles by using the oxidized support in powdery form. The activity of the optimized catalyst was studied under different conditions in the fresh and the used form. The fresh catalyst did not show significant activity. However, we found that the catalyst activated after use. Activation was understood in terms of the variation of surface Pd oxidation states under the effect of formic acid/sodium formate solutions. We found that the best activity is achieved under an optimal proportion of Pd0/PdII surface states according to previous reports. Under the best conditions, the activity of the best catalyst (8.6Pd/CN 0.3) was as high as 9245 h−1, attributable to the small particle size, the Pd0/PdII ratio, the amount of pyridinic nitrogen, and the testing conditions, which included the preadsorption of sodium formate. [Display omitted] • We prepared CN x -supported Pd catalysts for the decomposition of formic acid. • The CN x support was obtained by thermal pyrolysis of melamine foam at 700 °C. • We obtained 2.7nm Pd particles on the oxidized CN 0.3 support under optimized conditions. • The optimized 8.6Pd/CN 0.3 catalyst was not very active but activated upon use. • Activation understood in terms of the variation of surface Pd0/PdII states after use. [ABSTRACT FROM AUTHOR]

Amplification of weak ultraviolet signals has always been a challenging issue to design and fabricate high-performance ultraviolet photodetectors. Here, we observe a distinctive microplasma breakdown behavior in AlGaN-based ultraviolet avalanche photodiodes with artificial mesa architecture. At 107 V breakdown voltage, the photocurrent increases sharply whereas dark current intriguingly remains at the extremely low level of 0.1 nA as the applied voltage increases. Simultaneously, a significant blue luminescence phenomenon is observed at the mesa edge of photodiode at breakdown voltage, indicating the occurrence of microplasma breakdown. Ultimately, the microplasma avalanche photodiode achieves a record-high avalanche gain of 3 × 106 with light–dark current ratio readily exceeding 107. Kelvin probe force microscopy was employed to reveal the physical mechanism of localized avalanche breakdown induced by photoelectric effects and elaborate the microplasma discharge process, which is related to surface states. The unprecedented detection mode of photocurrent triggering avalanche events while remaining low dark current is anticipated to effectively shield the background noise and amplify ultraviolet signals. It is worth further research to explore its possibility on high-sensitivity ultraviolet photodetection. [ABSTRACT FROM AUTHOR]

Grooved grinding wheels play an important role in reducing grinding thermal damage. Aluminum oxide grinding wheels of approximately 1 mm slot width and 35% groove ratio were successfully fabricated using a novel reciprocating ultrafast laser scanning mode to improve the grinding stability. Grinding experiments with grooved and non-grooved wheels were conducted on 42CrMo. The cutting mechanisms of grooved structures were analyzed with the established cutting kinematics of the abrasives in the groove edges and the grinding force components model. The decreased grinding forces were observed and analyzed with abrasive cutting mechanisms, indicating that grooved structures can increase the undeformed chip thickness of grains at the slot edges and decrease the specific grinding energy by reducing the specific plowing and sliding energy. The grooved grinding wheels exhibited high performance in inhibiting grinding heat and workpiece burns. The burned workpiece ground with non-grooved wheels experienced a phase transformation and had a high tensile residual stress state on the ground surface and subsurface, while compressive residual stresses were detected on the unburned workpiece surface ground with grooved wheels. Grooved grinding wheels can improve the grinding quality of workpieces due to the lower grinding temperature and residual stress. [ABSTRACT FROM AUTHOR]

Enamel coating has potential application in steel rebar protection due to its high durability, excellent corrosion resistance, and strong coating/concrete interface bond. The newly developed low temperature enamel (LTE) coating has a substantially lower sintering temperature than that of traditional enamel coatings, whereas its adhesion mechanism to the substrate is expected to vary dramatically. In this study, abrasives of various particle sizes were used to blast steel substrates to create various surface states, to investigate the influence of substrate surface roughening on the interfacial properties of LTE coating. The surface roughness of substrates was quantitatively characterized by a 3D optical profiler. The adhesion, impact resistance, and abrasion resistance of LTE coating under different substrate surface states were investigated by pull-off, falling weight impact, and Taber abrasion test, respectively. The results showed that with increasing substrate surface roughness, the adhesion strength and impact resistance of the LTE coating were greatly improved. Within the investigated range, the substrate surface roughness had negligible influence on abrasion resistance. Overall, appropriate substrate surface roughening can provide the LTE coating with sufficient interface adhesion, impact resistance, and abrasion resistance. [ABSTRACT FROM AUTHOR]

Carbon dots (CDs) demonstrate great superiority in optoelectronic devices due to their tunable emission and photobleaching resistance properties. Although the fluorescence of CDs in solution has been extensively studied, their solid‐state fluorescence (SSF) mechanism still remains largely unexplored experimentally. Herein, solid‐state fluorescent CDs with unique clusteroluminescence (CL) generated from clusterization‐triggered emission are designed based on condensation between precursors with carboxyl and amino groups. The CDs demonstrate obvious concentration‐dependent fluorescence and quench‐resistant SSF, which is attributed to the activation of amide (n, π*) transition by the clusterization process. This sub‐luminophore is non‐luminescent at long wavelengths in isolated state, while it induces photoluminescence redshift via through‐space interaction in aggregated state. Besides, the SSF of CDs can be tuned from quenched to quenching‐resistant emission through amide formation, and the dominant fluorescent center of CDs solids is switchable from surface to edge state through amide passivation. Based on their long‐wavelength CL feature, high‐purity red light‐emitting diode devices exhibiting 656‐nm warm light are fabricated with the Commission Internationale de l´Eclairage (CIE) coordinates of (0.66, 0.34) and unchanged wavelength under different driving currents. These findings provide novel insights into the SSF mechanism of CDs and a universal strategy to construct fluorescent materials with tailored properties. [ABSTRACT FROM AUTHOR]

Surface defects cause non‐radiative charge recombination and reduce the photovoltaic performance of perovskite solar cells (PSCs), thus effective passivation of defects has become a crucial method for achieving efficient and stable devices. Organic ammonium halides have been widely used for perovskite surface passivation, due to their simple preparation, lattice matching with perovskite, and high defects passivation ability. Herein, a surface passivator 2,4,6‐trimethylbenzenaminium iodide (TMBAI) is employed as the interfacial layer between the spiro‐OMeTAD and perovskite layer to modify the surface defect states. It is found that TMBAI treatment suppresses the nonradiative charge carrier recombination, resulting in a 60 mV increase of the open‐circuit voltage (Voc) (from 1.11 to 1.17 V) and raises the fill factor from 76.3% to 80.3%. As a result, the TMBAI‐based PSCs device demonstrates a power conversion efficiency (PCE) of 23.7%. Remarkably, PSCs with an aperture area of 1 square centimeter produce a PCE of 21.7% under standard AM1.5 G sunlight. The unencapsulated TMBAI‐modified device retains 92.6% and 90.1% of the initial values after 1000 and 550 h under ambient conditions (humidity 55%–65%) and one‐sun continuous illumination, respectively. [ABSTRACT FROM AUTHOR]