Excess Charge Research Articles

The resistivity of rare earth impurities diluted in Lanthanum, Part I

We study the temperature-independent resistivity of rare-earth magnetic impurities (Gd, Tb, Dy) and the non-magnetic impurity (Lu) diluted in double hexagonal close-packed (dhcp) lanthanum. We model the system as a two-band system, where s-electrons perform conduction while d-electrons entirely screen the charge differences induced by impurities. Using the T-matrix formalism derived from the Dyson equation, we obtain an expression for resistivity. Since electronic properties are highly sensitive to band structure, we examine two types: a simplified “parabolic” band structure and a more realistic one obtained through first-principles calculations using VASP. Our results indicate that the exchange parameters, represented as cross products, significantly influence the magnitude of the spin resistivity term. Furthermore, we find that the role of band structure in resonant scattering and the formation of virtual bound states depends on the specific band structure employed. Additionally, our study addresses the effects of translational symmetry breaking and the excess charge introduced by rare-earth impurities on resistivity.

Features of the Defect Structure of LiNbO3:Mg:B Crystals of Different Composition and Genesis.

We proposed and investigated a refinement of technology for obtaining Mg-doped LiNbO3 (LN) crystals by co-doping it with B. LN:Mg (5.0 mol%) is now the most widely used material based on bulk lithium niobate. It is suitable for light modulation and transformation. We found that non-metal boron decreases threshold concentrations of the target dopant in many ways. In addition, we earlier determined that the method of boron introduction into the LN charge strongly affects the LN:B crystal structure. So we investigated the point structural defects of two series of LN:Mg:B crystals obtained by different doping methods, in which the stage of dopant introduction was different. We investigated the features of boron cation localization in LN:Mg:B single crystals. We conducted the study using XRD (X-ray diffraction) analysis. We have confirmed that the homogeneous doping method introduces an additional defect (MgV) into the structure of LN:Mg:B single crystals. Vacancies in niobium positions (VNb) are formed as a compensator for the excess positive charge of point structural defects. According to model calculations, boron is localized in most cases in the tetrahedron face common with the vacant niobium octahedron from the first layer (VNbIO6). The energy of the Coulomb interaction is minimal in the LN:Mg:B crystal (2.57 mol% MgO and 0.42 × 10-4 wt% B in the crystal); it was obtained using the solid-phase doping technology. The solid-phase doping technology is better suited for obtaining boron-containing crystals with properties characteristic of double-doped crystals (LN:Mg:B).

Study of the pH effects on water-oil-illite interfaces by molecular dynamics.

Illite mineral is present in shale rocks, and its wettability behavior is significant for the oil and gas industry. In this work, the pH effects on the affinity between the (001) and (010) crystallographic planes of illite K2(Si7Al)(Al3Mg)O20(OH)4 and direct and inverse emulsions were studied using molecular dynamics simulations. To develop the simulations, an atomistic model of illite was constructed following Löwenstein's rule. The oily phase was modeled using heptane, toluene, and mixtures of heptane/heptanoic acid, heptane/heptanoate, heptane/hexylamine and heptane/hexylammonium. For the heptane/heptanoate and heptane/hexylammonium mixtures, Na+ and Cl- ions were used to neutralize the excess electrical charge of the droplets, respectively. The affinity of the mineral surface to the oil models was estimated by the contact angle for systems where it was possible. However, for systems where the droplets did not adhere to the mineral, a methodology based on the height of the droplet on the surface was proposed. The results showed that, in general, for the inverse emulsions, water exhibited a high affinity for both illite surfaces, with its contact angle remaining below 45° regardless of pH. However, the heptane/heptanoic acid inverse emulsions on the edge surface were an exception to this behavior. Specifically, the contact angles calculated for the water droplets revealed mixed wettability due to hydrogen bonds between the carboxylic functional groups (pH ≪ 4.4) and the surface silanols and aluminols. Oil droplets suspended in water, on the other hand, did not adhere to the illite surfaces, and contact angles were not measurable. Nevertheless, the heptane/heptanoic acid droplets (pH ≪ 4.4) showed heights of approximately 2 Å and 4 Å above the basal and edge surfaces, respectively. This behavior was attributed to the hydrogen bonds formed between the carboxylic functional groups and the water molecules located on the mineral surfaces. Finally, the heptane/heptanoate (pH ≫ 4.4) and heptane/hexylammonium (pH ≪ 10.64) droplets were localized at distances greater than 8 Å from the surface, presumably due to a charge repulsion between the mineral surface and the surface of the droplets.

Research on the Fast Charging Strategy of Power Lithium-Ion Batteries Based on the High Environmental Temperature in Southeast Asia

To address the problem of excessive charging time for electric vehicles (EVs) in the high ambient temperature regions of Southeast Asia, this article proposes a rapid charging strategy based on battery state of charge (SOC) and temperature adjustment. The maximum charging capacity of the cell is exerted within different SOCs and temperature ranges. Taking a power lithium-ion battery (LIB) with a capacity of 120 Ah as the research object, a rapid charging model of the battery module was established. The battery module was cooled by means of a liquid cooling system. The combination of the fast charging strategy and the cooling strategy was employed to comprehensively analyze the restrictions of the fast charging rate imposed by the battery SOC and temperature. The results indicate that when the coolant flow rate was 12 L/min and the inlet coolant temperature was 22 °C, the liquid cooling system possessed the optimal heat exchange capacity and the lowest energy consumption. The maximum temperature (Tmax) of the battery during the charging process was 50.04 °C, and the charging time was 2634 s. To lower the Tmax of the battery during the charging process, a charging rate limit was imposed on the temperature range above 48 °C based on the original fast charging strategy. The Tmax decreased by 0.85 °C when charging with the optimized fast charging strategy.

TCAD Simulation of Two Photon Absorption-Transient Current Technique Measurements on Silicon Detectors and LGADs.

Device simulation plays a crucial role in complementing experimental device characterisation by enabling deeper understanding of internal physical processes. However, for simulations to be trusted, experimental validation is essential to confirm the accuracy of the conclusions drawn. In the framework of semiconductor detector characterisation, one powerful tool for such validation is the Two Photon Absorption-Transient Current Technique (TPA-TCT), which allows for highly precise, three-dimensional spatially-resolved characterisation of semiconductor detectors. In this work, the TCAD framework Synopsys Sentaurus is used to simulate depth-resolved TPA-TCT data for both p-type pad detectors (PINs) and Low Gain Avalanche Detectors (LGADs). The simulated data are compared against experimentally measured TPA-TCT results. Through this comparison, it is demonstrated that TCAD simulations can reproduce the TPA-TCT measurements, providing valuable insights into the TPA-TCT itself. Another significant outcome of this study is the successful simulation of the gain reduction mechanism, which can be observed in LGADs with increasing densities of excess charge carriers. This effect is demonstrated in an p-type LGAD with a thickness of approximately 286 µm. The results confirm the ability of TCAD to model the complex interaction between carrier dynamics and device gain.

The Effect of Electric Fields on Oxidization Processes at the Air-Water Interface.

At the air-water interface, many reactions are accelerated, sometimes by several orders of magnitude. This phenomenon has proved to be particularly important in water microdroplets, where the spontaneous oxidation of many species stable in bulk has been experimentally demonstrated. Different theories have been proposed to explain this finding, but it is currently believed that the role of interfacial electric fields is key. In this work, we have carried out a quantum chemistry study aimed at shedding some light on this question. We have studied two prototypical processes in which a hydroxide anion transfers its excess electron to either the water environment or a dioxygen molecule. To model the interface, we use a cluster of 21 water molecules immersed in an electric field, and we examine the energetics of the studied reactions as a function of field magnitude. Our results reveal that electric fields close to those estimated for the neat air-water interface (∼0.15 V ⋅ Å-1) have a moderate effect on the reaction energetics and that much stronger fields (>1 V ⋅ Å-1) are required to get spontaneous electron transfer. Therefore, the study suggests that additional factors such as an excess charge in microdroplets need to be considered for explaining the experimental observations.

The Effect of Electric Fields on Oxidization Processes at the Air‐Water Interface

AbstractAt the air–water interface, many reactions are accelerated, sometimes by several orders of magnitude. This phenomenon has proved to be particularly important in water microdroplets, where the spontaneous oxidation of many species stable in bulk has been experimentally demonstrated. Different theories have been proposed to explain this finding, but it is currently believed that the role of interfacial electric fields is key. In this work, we have carried out a quantum chemistry study aimed at shedding some light on this question. We have studied two prototypical processes in which a hydroxide anion transfers its excess electron to either the water environment or a dioxygen molecule. To model the interface, we use a cluster of 21 water molecules immersed in an electric field, and we examine the energetics of the studied reactions as a function of field magnitude. Our results reveal that electric fields close to those estimated for the neat air–water interface (∼0.15 V ⋅ Å−1) have a moderate effect on the reaction energetics and that much stronger fields (>1 V ⋅ Å−1) are required to get spontaneous electron transfer. Therefore, the study suggests that additional factors such as an excess charge in microdroplets need to be considered for explaining the experimental observations.

Investigation into the impedance, dielectric behavior, and conductivity within p-silicon/n-nanocrystalline iron disilicide heterojunctions and equivalent circuit model in relation to temperature

The p-Si/n-nanocrystalline FeSi2 heterojunctions constructed through facing-targets sputtering were characterized for impedance under various frequencies and temperatures of between 160−400 K. Imaginary and real impedance plots for all temperatures demonstrated single semicircular arc with negative temperature dependency. From the arc, a circuit model equivalent to electrode resistance serially connected to several loops, each consisting of a parallel circuit comprising a resistance//constant phase element (Q), corresponding to the crystallite, crystallite boundary, and interface. All resistances increased with decreasing temperatures, while the Q values decreased but behaved as ideal capacitors for all temperatures. The dielectric constants versus increasing temperature demonstrated a linear increase. At 300 K and 1 MHz, the dielectric constant was 24.5 with 0.1 loss tangent, denoting its possible usage for filtration and storage. The alternating-current conductivities disclosed that direct-current conductivities increased as the temperature increased. The exponents from Jonscher's fit were 1 or less around 180 K and the values beyond 1 at higher temperatures, indicating the shift from long transitional transport to localized hopping transport. The activation energy based on conductivities was higher than the one based on relaxation times, implying that excess charge led to more energy requirements for transportation.

Development of an advanced current mode charging control strategy system for electric vehicle batteries

Electric vehicles (EVs) face customer hesitancy due to challenges in locating fast charging stations, lengthy recharging times, and incompatible charging ports. This research addresses these issues by proposing a novel current mode control strategy for EV battery charging. Traditional charging methods often result in suboptimal rates, battery degradation, and safety risks. The primary objective is to enhance charging efficiency, safety, and battery lifespan by optimizing parameters such as voltage and current. Control mode charging offers significant advantages over plug-in charging by minimizing stress factors that contribute to degradation, such as high temperatures and excessive charging cycles. This approach aims to extend the lifespan of EV batteries while ensuring safe, efficient, and fast charging. The control system offers three charging modes: slow (0.49 A, 6.31 W, 264 mins), medium (2.74 A, 34.85 W, 50 mins), and fast (4.62 A, 50.80 W, 30 mins) using a 12 V single-phase supply. This advanced strategy significantly improves EV charging system efficiency, with fast charging achieving 80% higher efficiency than slow charging in both simulations and experimental testing. The key contribution of this research is the development of a tailored current mode charging strategy that optimizes charging efficiency while ensuring battery longevity and safety.

Revisiting Band Tails and Localized States in Amorphous Semiconductors

Amorphous semiconductors, such as hydrogenated amorphous silicon (a-Si:H) and amorphous indium gallium zinc oxide (a-IGZO) have been central to the development of thin film transistors (TFTs) for large-area electronic applications such as displays. This is a result of the exceptional material uniformity that can be achieved when depositing over very large areas (~10 m2). This means that all TFTs are essentially identical over an entire large display panel. However, there is a technological price to pay – the carrier mobility is generally less in amorphous semiconductors compared to their crystalline equivalent.The origin of this reduced carrier mobility is a result of a key difference in the density of states between crystalline semiconductors and their amorphous counterparts. The long-range order of a crystalline lattice means that all carrier states in the conduction and valence bands exist over long distances. These ‘extended states’ are associated with generally high mobility carriers. However, there is no long-range order in amorphous semiconductors, but only short-range order over one to two bond lengths associated with local atomic coordination requirements (and to some degree a medium-range order over a few bond lengths). The result is that the bottom of the conduction band and top of the valence band gain ‘tail’ states which are localized in nature.Not only do these localized states frequently dominate (or at least significantly affect) conduction in amorphous semiconductors and hence the switching characteristics of TFTs, but they also have a role to play in other important processes such as hysteresis and bias stress instability. But what are these localized band tail states, how should we think about them in the context of conduction and how do they relate to extended states?These questions are revisited from the starting point that there is a perturbation in the delocalized charge concentration with position in an amorphous semiconductor compared to its crystalline counterpart, and this can be quantified as a spatially varying excess charge concentration (where a deficit is just a negative excess). The rate of spatial variation is long relative to the rate of change in the electron wavefunction, and reflects the short- and medium-range order distances. Charge conservation means that that this excess charge concentration will have a mean of zero and a Gaussian probability distribution is assumed. A model using this as a starting point has been created which reproduces band tails and which provides new insights into their physics which are discussed.

Interfacial Stability of Ru-Based Li-Rich Layered Oxide Cathode by Guaiacol as an Organic Superoxide Dismutase Mimics

As the battery-based energy storage market develops, the demand for Li-ion batteries (LIBs) with high energy density is increasing, which leads to the development of new electrode materials. Li-rich layered oxides (LLO), Li2MO3 where M represents a transition metal such as Mn, Ru or Ir, are attracting attention as promising cathode materials which deliver high discharge capacities exceed 250 mAh g-1 originated from oxygen redox in addition to typical transition (TM) metal redox. The oxygen redox provides progressive insights for higher energy density cathode, however, the oxygen redox is also the origin of the structural instability. The structural distortion of LLOs evolves along a sequence of lattice TM oxidation, ligand-to-metal charge transfer from lattice oxygen (O2 -) to oxidized TM, peroxo-like species formation and dioxygen de-coordination followed by cationic disordering and stacking faults. The de-coordinated dioxygen is reduced to be a reactive oxygen species (ROS) represented by superoxide radical (O2 •-) by oxidizing carbonate solvent molecules and/or carbon materials in electrodes. Besides, the irreversible superoxo-like species generated during excessive charge aggravate the electrolyte decomposition of its nucleophilicity. The reactive oxygen species deteriorates LLO by a circular chain of superoxide generation – electrolyte decomposition – water-induced HF formation – TM dissolution – structural distortion – superoxide generation.To scavenge superoxide radicals for guaranteeing the interfacial stability of LLO by breaking the LLO-deteriorating chain mechanism, we have noticed the antiaging mechanisms of biological system suffering from ROS issues such as enzymatic and antioxidant mechanisms. Superoxide dismutase (SOD) catalytically transforms superoxide into the less reactive O2 and O2 2-, serving as a reversible catalyst. Conversely, antioxidants undergo oxidation by reacting with superoxide before it induces damage to other cellular constituents. The numerous papers have reported the application of antioxidants in LIBs, despite their consumption nature in scavenging superoxide radicals, whereas the lack of application of SOD in LIBs has been noted. One is the malonic-acid-decorated fullerene (MA-C60) that our group was presented, as the mobile catalyst to disproportionate lithium superoxide (Li2O) to lithium peroxide (Li2O2) for LLO. This class of catalyst was named superoxide dismutase mimic (SODm) as the enzymes responsible for the analogous reaction in aerobic organisms.In this work, we introduce the first organic SODm additive, which inherits the SODm characteristics of the inorganic MA-C60 for antiaging a LLO based on 4d-TM (Li2RuO3, LRO) for LIBs. Among phenolic antioxidants, guaiacol was chosen as the organic SODm, a mono-phenolic compound having two functional groups to grab superoxide for disproportionation by an associative manner. The antioxidizing capacities of phenolic compounds against superoxide have been documented. Both monophenols and polyphenols act as Brønsted acids in aprotic solvents, transferring protons to superoxide radicals. This proton transfer initiates a protonation-facilitated disproportionation reaction, leading to the formation of peroxide anions and dioxygen. However, these protonation-facilitated disproportionation was limited in LIB electrolytes with abundant lithium ions. Instead, we demonstrated that the ability of guaiacol to scavenge superoxide arises from the potential for chelation of a superoxide radical by the two oxygens, one from the hydroxyl group and the other from the methoxy group due to their close proximity. This was verified by comparing guaiacol with phenol through cyclic voltammograms and DFT calculations. Moreover, the phenolic components undergo oxidative polymerization to form cathode-electrolyte interphase (CEI) layers. Such phenol-derived CEI layers were previously reported to improve charge transfer when compared to conventional electrolyte-derived CEI layers.The SODm ability of guaiacol successfully enhance the interfacial stability of cathode. In presence of guaiacol, ruthenium dissolution and structural distortion was significantly reduced. The guaiacol-derived CEI layer exhibited reduced thickness and less pronounced growth over cycling, with the presence of lithium peroxide confirming the SODm activity of guaiacol. Consequently, guaiacol effectively mitigated the collapse of LRO, resulting in a capacity of 150 mAh g-1 after 400 cycles at 1C, twice the capacity in the absence of guaiacol under the same conditions.To improve the electrochemical stability of LRO, most of endeavors were devoted to stabilizing the lattice oxygen redox chemistry by metal co-doping and tunning of local symmetry around the lattice oxygen without focusing on the ROS issue. On the other hand, we tried to find a solution in electrolyte instead of active material itself. This work highlights the importance of deactivating reactive oxygen species in 4d TM-based LLO proposes a simple solution through the application of an additive with antioxidant properties, guaiacol. Figure 1

Pathological Mutations D169G and P112H Electrostatically Aggravate the Amyloidogenicity of the Functional Domain of TDP-43.

Aggregation of TDP-43 is linked to the pathogenesis of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Notably, electrostatic point mutations such as D169G and P112H, located within the highly conserved functional tandem RNA recognition motif (RRM) domains of the TDP-43 protein (TDP-43tRRM), have been identified in diseased patients as well. In this study, we address how the electrostatic mutations alter both the native state stability and aggregation propensity of TDP-43tRRM. The mutants D169G and P112H show increased chemical stability compared to the TDP-43tRRM at physiological pH. However, at low pH, both the mutants undergo a conformational change to form amyloid-like fibrils, though with variable rates─the P112H mutant being substantially faster than the other two sequences (TDP-43tRRM and D169G mutant) showing comparable rates. Moreover, among the three sequences, only the P112H mutant undergoes a strong ionic strength-dependent aggregability trend. These observations signify the substantial contribution of the excess charge of the P112H mutant to its unique aggregation process. Complementary simulated observables with atomistic resolution assign the experimentally observed sequence-, pH-, and ionic strength-dependent aggregability pattern to the degree of thermal lability of the mutation site-containing RRM1 domain and its extent of dynamical anticorrelation with the RRM2 domain whose combination eventually dictate the extent of generation of aggregation-prone partially unfolded conformational ensembles. Our choice of a specific charge-modulated pathogenic mutation-based experiment-simulation-combination approach unravels the otherwise hidden residue-wise contribution to the individual steps of this extremely complicated multistep aggregation process.

A Piezocatalysis Strategy to Enable Efficient Redox in Solid‐State Battery

AbstractPiezocatalysis is considered to be a favorable catalytic technology by utilizing external mechanical stimulation to promote the specific redox reactions. The application of piezocatalysis in batteries is promising but faces formidable challenges. Herein, the operation principles of piezocatalysis were successfully demonstrated by constructing solid‐state Li−Se and Li−S battery models with interfacial stress accumulation. Lead zirconate titanate with an ultra‐high piezoelectric coefficient was applied as the piezoelectric catalyst. The uniformity of the dipole orientation in materials was essential for achieving piezocatalysis in batteries. The accumulated high‐stress converts to piezopotential for catalyzing most reaction processes in batteries, while the rapid stress change prevents the internal charge reorganization, ensuring continuous efficient catalysis. The internal stress change alters the internal polarisation strength, driving excess screening charge to participate in the electrochemical reaction. Under piezocatalysis, solid‐state Li−Se batteries exhibited a initial discharge capacity of 670.9 mAh g−1 (99.4 % of the theoretical value) at 0.1 C, and Li−S batteries showed a capacity of 1463 mAh g−1 at 0.2 C, which was still maintained up to 1084 mAh g−1 at an elevated rate of 0.5 C. This piezocatalysis strategy provides a strong theoretical basis and design specification for enhancing Li−Se and Li−S battery reaction kinetics.

A Piezocatalysis Strategy to Enable Efficient Redox in Solid-State Battery.

Piezocatalysis is considered to be a favorable catalytic technology by utilizing external mechanical stimulation to promote the specific redox reactions. The application of piezocatalysis in batteries is promising but faces formidable challenges. Herein, the operation principles of piezocatalysis were successfully demonstrated by constructing solid-state Li-Se and Li-S battery models with interfacial stress accumulation. Lead zirconate titanate with an ultra-high piezoelectric coefficient was applied as the piezoelectric catalyst. The uniformity of the dipole orientation in materials was essential for achieving piezocatalysis in batteries. The accumulated high-stress converts to piezopotential for catalyzing most reaction processes in batteries, while the rapid stress change prevents the internal charge reorganization, ensuring continuous efficient catalysis. The internal stress change alters the internal polarisation strength, driving excess screening charge to participate in the electrochemical reaction. Under piezocatalysis, solid-state Li-Se batteries exhibited a initial discharge capacity of 670.9 mAh g-1 (99.4 % of the theoretical value) at 0.1 C, and Li-S batteries showed a capacity of 1463 mAh g-1 at 0.2 C, which was still maintained up to 1084 mAh g-1 at an elevated rate of 0.5 C. This piezocatalysis strategy provides a strong theoretical basis and design specification for enhancing Li-Se and Li-S battery reaction kinetics.

Interface Energy‐Level Reorganization for Efficient Perovskite γ‐Ray Detectors

AbstractMetal halide perovskites are promising candidates for gamma‐ray (γ‐ray) spectrum detectors. However, achieving high‐resolution energy spectra in single‐photon pulse‐height analysis mode remains challenging, due to the inevitable leakage currents degrade the recognizable fingerprint energies which is critical for resolving γ‐ray spectroscopy. We demonstrate under high bias voltage, a deficient contact barrier can lead to excessive surface charge injection, thereby increasing leakage current from electrodes to perovskites. Hence, we conceive to employ surface ligand engineering on perovskite single crystals to manipulate energy levels to suppress leakage current. In particular, anchoring a strong dipole ligand onto the perovskite induced surface charge‐density displacement, leading to a downward band bending and heightened the corresponding contact barrier. Consequently, the strategy minimized the detectors’ leakage current by an order of magnitude, to as low as 44 nA cm−2 at −100 V. The resulting detectors show a significant improvement in energy resolution, 3.9 % for 22Na 511 keV γ‐rays has been achieved at room temperature. The resulting detector further resolves each fingerprint energy for 152Eu γ‐spectrum, representing one of the best γ‐rays perovskite detectors reported to date. Moreover, the detectors exhibited stabilized energy resolution without any degradation under a continuous electric field (1,000 V cm−1) for over 300 minutes, representing the longest longevity reported to date.

Carbon nanotube intermediate layer intercalation and its influence on surface charge of thin film composite membrane

The surface charge of a separation membrane is a critical factor affecting its performance in ion separation and fouling resistance. Thin-film composite (TFC) polyamide (PA) membrane, commonly used in water treatment, often suffer from excessive surface negative charges, which significantly limits their application and fouling resistance. To address this issue, this work introduces a carbon nanotubes (CNT) intermediate layer to adjust the surface charge of TFC PA membranes, aiming to achieve a PA layer with neutral properties. Novel grazing-incidence wide-angle x-ray scattering (GIWAXS) measurements were employed to elucidate the effect of CNT on the molecular chain stacking of PA. The CNT intermediate layer was found to influence the PA cross-linking, which is related to surface negative charge, by controlling the storage and release of the m-phenylenediamine monomer during interfacial polymerization. The neutral CNT-TFC membrane demonstrated improved NH4+ retention and increased resistance to fouling by protein, surfactant, and E. coli. However, other surface properties, such as roughness and hydrophilicity, could counteract the antifouling benefits of a neutral surface. This work provides insights into additional advantages of CNT intermediate layer intercalation in TFC PA membranes, such as enhanced cross-linking and surface charge control.

Interface Energy-Level Reorganization for Efficient Perovskite γ-Ray Detectors.

Metal halide perovskites are promising candidates for gamma-ray (γ-ray) spectrum detectors. However, achieving high-resolution energy spectra in single-photon pulse-height analysis mode remains challenging, due to the inevitable leakage currents degrade the recognizable fingerprint energies which is critical for resolving γ-ray spectroscopy. We demonstrate under high bias voltage, a deficient contact barrier can lead to excessive surface charge injection, thereby increasing leakage current from electrodes to perovskites. Hence, we conceive to employ surface ligand engineering on perovskite single crystals to manipulate energy levels to suppress leakage current. In particular, anchoring a strong dipole ligand onto the perovskite induced surface charge-density displacement, leading to a downward band bending and heightened the corresponding contact barrier. Consequently, the strategy minimized the detectors' leakage current by an order of magnitude, to as low as 44 nA cm-2 at -100 V. The resulting detectors show a significant improvement in energy resolution, 3.9 % for 22Na 511 keV γ-rays has been achieved at room temperature. The resulting detector further resolves each fingerprint energy for 152Eu γ-spectrum, representing one of the best γ-rays perovskite detectors reported to date. Moreover, the detectors exhibited stabilized energy resolution without any degradation under a continuous electric field (1,000 V cm-1) for over 300 minutes, representing the longest longevity reported to date.

The Role of Excess Charge Mitigation in Electromagnetic Hygiene: An Integrative review.

The electromagnetic characteristics of many environments have changed significantly in recent decades. This is in large part due to the increased presence of equipment that emits electromagnetic radiation and materials that may often readily gain excess charge. The presence of excess charge can often increase risk of infection from pathogens, and likelihood of individuals experiencing compromised performance, respiratory problems and other adverse health issues from increased uptake of particulate matter. It is proposed that adopting improved electromagnetic hygiene measures, including optimized humidity levels, to reduce the presence of inappropriate levels of electric charge can help reduce the likelihood of ill health, infection and poor performance arising from contaminant inhalation and deposition, plus reduce the likelihood of medical devices and other electronic devices getting damaged and/or having their data compromised. It is suggested that such measures should be more widely adopted within clinical practice guidelines and water, sanitation and hygiene programs.

On a Study of Photoionization of Atoms and Ions from Endohedral Anions

We study the relationship between the results of two qualitatively different semi-empirical models for photoionization cross sections, σnℓ, of neutral atoms (A) and their cations (A+) centrally encapsulated inside a fullerene anion, CNq, where q represents the negative excess charge on the shell. One of the semi-empirical models, broadly employed in previous studies, assumes a uniform excess negative charge distribution over the entire fullerene cage, by analogy with a charged metallic sphere. The other model, presented here, considers the quantum states of the excess electrons on the shell, determined by specific n and ℓ values of their quantum numbers. Remarkably, both models yield similar photoionization cross sections for the encapsulated species. Consequently, we find that the photoionization of the encapsulated atoms or cations inside the CNq anion is influenced only slightly by the quantum states of the excess electrons on the fullerene cage. Furthermore, we demonstrate that the influence decreases even further as the size of the fullerene cage increases. All this holds true at least under the assumption that the encapsulated atom or cation is compact, i.e., its electron density remains primarily within itself rather than being drawn into the fullerene shell. This remarkable finding results from Hartree–Fock calculations combined with a popular modeling of the fullerene shell which is simulated by an attractive spherical annular potential.

Nonlinear Thermoplasmonics in Graphene Nanostructures.

The linear electronic dispersion relation of graphene endows the atomically thin carbon layer with a large intrinsic optical nonlinearity, with regard to both parametric and photothermal processes. While plasmons in graphene nanostructures can further enhance nonlinear optical phenomena, boosting resonances to the technologically relevant mid- and near-infrared (IR) spectral regimes necessitates patterning on ∼10 nm length scales, for which quantum finite-size effects play a crucial role. Here we show that thermoplasmons in narrow graphene nanoribbons can be activated at mid- and near-IR frequencies with moderate absorbed energy density, and furthermore can drive substantial third-harmonic generation and optical Kerr nonlinearities. Our findings suggest that photothermal excitation by ultrashort optical pulses offers a promising approach to enable nonlinear plasmonic phenomena in nanostructured graphene that avoids potentially invasive electrical gating schemes and excessive charge carrier doping levels.