The surfaces of strongly correlated materials can exhibit exotic properties that differ substantially from the bulk. Investigation of these surface effects requires both high quality surfaces, and an experimental technique capable of disentangling surface and underneath layers or bulk. Herein, we overcome these two challenges, using newly developed grazing-incident-angle resonant soft x-ray and magnetic scattering techniques to study ultrathin films of Spin(S) = 1/2 La2CuO4, the parent compound of high-critical-temperature (high-Tc) superconductor. We observe emergent surface magnetic ordering and surface-like electronic dipole layers at room temperature. As a function of temperature, intrinsic holes from Cu2+ and O2- ions are mitigated from the surface into subsurface layers and back into the surface. The intrinsic hole and oxygen ion mitigation have different rates, yielding strong temperature hysteresis. Supported with theoretical calculations, these surface orderings consist of a mixture of Cu2+ 3d9 (S = 1/2) and Cu1+ 3d10-like (S = 0) with strong magneto-electronic coupling through the many-body upper Hubbard band. Our results highlight intrinsic holes and oxygen ion mitigations, yielding surface-like electronic dipole and magnetic orderings and the potential of grazing-incident-angle resonant soft X-ray and magnetic scattering to elucidate, layer-by-layer, magnetic and electronic structures."

The emergence of two-dimensional (2D) semiconductors, particularly transition metal dichalcogenides (TMDs), shows great potential in revolution of the development of electronics. However, challenges in contact engineering, such as Fermi-level pinning and metal-induced gap states (MIGS) and disorders greatly hinder the high-performance devices based on 2D materials. Here, we propose a novel strategy to establish quasi-one-dimensional tunneling contacts through locally modulating the electronic properties of monolayer MoS2 beneath the metal electrode by high-electron-affinity transition metal oxides (TMOs). MoO3 is introduced to induce strong charge-transfer anti-doping in the contact region, effectively depleting free carriers and rendering the underlying MoS2 electrically insulating and behaving as the tunneling layer. The Au/MoO3-contacted monolayer-MoS2 field-effect transistors exhibit near-ideal ohmic characteristics with an exceptionally low Schottky barrier height (SBH) of 1.6 meV, nearing the theoretical limit. The field effect mobility reaches 559.5 cm2/V∙s at 10 K. Moreover, we demonstrate that substitution of MoO3 with V2O5 provides a means to tune the SBH, underscoring the versatility of this device fabrication strategy. This study presents a promising pathway for achieving efficient tunneling contacts in 2D electronics, paving the way for the advancement of next-generation high-performance devices.

Magnetic fields typically suppress superconductivity through Pauli and orbital limiting effects. However, there are rare instances of magnetic-field-induced superconductivity, as observed in Chevrel-phase compounds, organic conductors, uranium-based heavy-fermion systems, and moiré graphene-although these materials possess inherently low superconducting transition temperatures (Tc). Here, we demonstrate high-field-stabilized superconductivity in a class of materials recently shown to have significantly higher Tc values (up to 40 K): the infinite-layer nickelates. We show that both the low-field and high-field superconducting states can be understood in terms of a field-compensation mechanism, better known as the Jaccarino-Peter effect. These findings demonstrate the possibility of achieving substantially enhanced upper critical fields in high-temperature superconductors.

Ferroelectric and antiferroelectric materials play a critical role in electrical, optical, and thermal devices due to their electric field-controlled polarization switching capability. Controlling phase formation during thin film growth is essential for the design of these devices. In this study, we separately stabilized pure ferroelectric rhombohedral (N phase) and pure antiferroelectric orthorhombic (P phase) structures by precisely controlling the growth conditions of 70 nm-thick NaNbO3 (NNO) thin films on (111)-oriented Nb-doped SrTiO3 substrates. Through reciprocal space mappings and quarter-order diffraction measurements, a twinning structure within the NNO P-phase film is resolved. An antiferroelectric-to-ferroelectric phase transition, accompanied by a substantial enhancement in the electromechanical coupling response, is observed in the NNO P-phase film. Importantly, a phase diagram is constructed to delineate the growth window for each phase. This work provides a framework for synthesizing NNO thin films with controlled phases and offers a strategy for designing functional ferroelectric and antiferroelectric devices.

Superconductivity in infinite-layer nickelates has drawn wide interest as a cuprate analogue, yet how the electronic structure evolves with hole doping remains unsettled. Here we map the doping- and temperature-dependent unoccupied states of the La-based infinite-layer nickelate La1-xCaxNiO2 using O K-edge and Ni L-edge x-ray absorption spectroscopy. Superconductivity occurs for 0.18<=x<=0.27. Near x 0.20-0.23, low-energy spectral weight redistributes: Ni3d-dominated states decrease while O2p-hybridized states increase, indicating an orbital-selective crossover in Ni-O covalency. This crossover coincides with a sign reversal of the Hall coefficient and precedes the reduction of the superconducting critical temperature at higher doping. By directly linking transport anomalies and the superconducting dome to a measurable Ni-O orbital reorganization, our results provide a key step toward a unified, orbital-resolved phase diagram for infinite-layer nickelates and a practical route to engineer superconductivity via hybridization control.

High-temperature superconductivity in cuprate materials remains a major challenge in physics due to the complexity of their strongly correlated electronic states. Interfacial strain is a powerful lever for tuning electronic correlations in complex oxides, offering new pathways to control emergent quantum phases. Here, we report the discovery of interfacial strain-modulated correlated plasmons observed exclusively in superconducting La1.85Sr0.15CuO4 (LSCO) through spectroscopic ellipsometry. This form of plasmons is absent in the non-superconducting LSCO counterparts. Detailed analysis reveals that these correlated plasmons, arising from the collective excitations within Mott-correlated bands, are driven by long-range electronic correlations in the Cu & horbar;O planes. Furthermore, long-range electronic correlations, intricately modulated by interfacial strain, may play a crucial role in the emergence of superconductivity and in tuning the transition temperature. Dynamical cluster approximation (DCA) with quantum Monte Carlo (QMC) calculations of the extended Hubbard model suggest that long-range Coulomb interactions play an important role in LSCO, showing good agreement with our experimental findings. The collective evidence from both the experimental results and theoretical findings provides new insights into the nature of collective excitations and their pivotal role in the emergence of high-temperature superconductivity.

Understanding the electronic properties of doped copper-oxygen planes remains a significant challenge in condensed matter physics and is crucial to unraveling the mechanisms behind high-temperature superconductivity in cuprates. Recently, the observation of charge transfer and interfacial polarons in a superconducting interface has aroused extensive research interest. However, experimental data to investigate charge transfer on the CuO2 plane and the presence of polarons are still missing. Here we conduct extensive research on the optical and electronic properties of 2D materials supported on copper-based superconductors. Unlike monolayer-WSe2 on other substrates, monolayer-WSe2 on La1.85Sr0.15CuO4 (WSe2/LSCO) produces a special band structure. Using high-resolution spectroscopic ellipsometry and density functional theory calculation methods, the special electronic structure can be attributed to the formation of the interfacial small polaron at the WSe2/LSCO interface which is driven by charge transfer between the CuO2 plane of the cuprate superconductor and WSe2. In addition, the structural phase transition of the LSCO substrate was observed to reduce the e-h interaction of WSe2. These findings may spur future investigations on the effect of the interfacial polaron on the superconductivity of cuprates and highlight the significant influence of interface effects on the electronic structure of WSe2 films. It provides an effective method to further explore the intrinsic relationship between interfacial polarons and superconductivity.

The detection and intracellular tracking of nanoplastics in human cells remain critical challenges in understanding their biological impact. Here, we demonstrate the use of multimodal vibrational spectroscopy to identify and localize fluorescently labeled polystyrene nanoparticles (PS-NPs) within individual fibroblast and LN-229 glioblastoma cells. While fluorescence microscopy and Raman imaging confirmed the presence of PS-NPs around the nucleus, conventional Fourier-transform infrared (FT-IR) spectroscopy lacked the spatial resolution to detect intracellular nanoplastics. To overcome this limitation, we applied two advanced IR photothermal-based techniques: atomic force microscopy-infrared (AFM-IR) and optical photothermal infrared (O-PTIR) spectroscopy. AFM-IR enabled nanoscale chemical imaging and topographical mapping, while O-PTIR allowed label-free, noncontact detection of PS-NPs with submicron resolution. Both methods successfully identified characteristic spectral signatures of PS-NPs and revealed their perinuclear localization. Comparative analyses highlight O-PTIR's operational simplicity and spectral fidelity, and AFM-IR's superior spatial resolution. Our findings establish AFM-IR and O-PTIR as powerful, complementary tools for visualizing nanoplastics within single cells and lay the foundation for future studies exploring nanoplastic biodistribution and toxicity using vibrational spectroscopy.

Recent advancements in powerful pump optical lasers and X-ray free-electron lasers have reignited interest in vacuum birefringence, a phenomenon predicted by quantum electrodynamics (QED). Detecting this subtle effect requires X-ray photons with exceptionally high linear polarization. To meet this need, several polarimeters employing channel-cut crystal monochromators, designed to deflect only σ-polarization while suppressing π-polarization, have been proposed. In this paper, we utilize the upgraded SHADOW code to perform high-accuracy simulations of the linear polarization of X-ray beams by Brewster deflection. Our results highlight a promising beamline configuration capable of achieving linear polarization purity on the order of 10 −13 . We propose using this setup for single-shot experiments to verify vacuum birefringence, offering a novel avenue for probing linear polarization purity in future experimental investigations.

Cuprate superconductors remain central to condensed matter physics due to their technological relevance and unconventional, incompletely understood electronic behavior. While the canonical phase diagram and low-energy models have been shaped largely by studies of underdoped and moderately doped cuprates, the overdoped regime has received comparatively limited attention.Here, we track the evolution of the electronic structure from optimal to heavy overdoping in La2-xSrxCuO4(LSCO) using broadband optical spectroscopy across x=0.15-0.60. The measured spectral changes–including the redistribution of Zhang-Rice-related spectral weigh–are in qualitative agreement with determinant quantum Monte Carlo simulations of the three-orbital Emery model, which together indicate a pronounced reconstruction of the electronic structure beyond hole concentrations x>0.2. Guided by these observations, we propose a spontaneous checkerboard-type Zhang-Rice electronic configuration that captures the coexistence of itinerant and localized carriers characteristic of the heavily overdoped state. Our results refine the doping-dependent Zhang-Rice-based framework for cuprates, illuminate how correlations persist deep into the overdoped regime, and provide new constraints on microscopic mechanisms of high-temperature superconductivity, with broader implications for correlated transition-metal oxides.

Hydrogen production from water splitting has gained tremendous interest as an alternative to fossil fuels, while the sluggish nature of the four-electron process during oxygen evolution reaction (OER) has impeded its practical applications. Here, we report the ultraviolet (UV) assisted OER enhancement of NiFe Prussian blue analogues (PBAs) by the creation and stabilization of new active sites. UV treatment induces the cleavage of certain M-C/MN (M: Ni or Fe) bonds and the removal of CN groups, thereby increasing the number of active sites. Additionally, due to the breaking of M-C/M-N bonds, OH- functional groups readily bonded to Fe sites, transforming them into active sites that require only three-electrons for the OER process. The optimally treated sample exhibited superior OER performance, with an overpotential of 279 mV, a Tafel slope of 52.0 mV dec-1, a mass activity of 733.33 A g- 1 and a turnover frequency of 2.48 s-1 compared to pristine PBA which showed values of 409 mV, 134.6 mV dec-1, 28.83 A g-, 1 and 0.10 s-1, respectively. Density functional theory (DFT) calculations further confirm lower reaction energy barrier for OER after UV irradiation. Moreover, UV treatment could serve as a universal strategy to enhance the OER performance of other types of metal organic frameworks-based catalysts.

Researchers pursuing advanced photoelectric devices have discovered near room-temperature metal-insulator transitions (MIT) in non-volatile VO2. Despite theoretical investigations suggesting that polaron dynamics mediate the MIT, direct experimental evidence remains scarce. In this study, we present direct evidence of the polaron state in insulating VO2 through high-resolution spectroscopic ellipsometry measurements and first-principles calculations. We illustrate the complementary role of polaron dynamics in facilitating Peierls and Mott transitions, thereby contributing to the MIT processes. Furthermore, our observations and characterizations of conventional metallic and correlated plasmons in the respective phases of the VO2 film offer valuable insights into their electron structures. This investigation enhances comprehension of the MIT mechanism in correlated systems and underscores the roles of polarons, lattice distortions, and electron correlations in facilitating phase transition processes in strongly-correlated systems. Additionally, the detailed detection of small polarons and plasmons serves as inspiration for the development of new device functionalities.

Phase engineering strategies in two-dimensional transition metal dichalcogenides (2D-TMDs) have garnered significant attention due to their potential applications in electronics, optoelectronics, and energy storage. Various methods, including direct synthesis, pressure control, and chemical doping, have been employed to manipulate structural transitions in 2D-TMDs. Metal intercalation emerges as an effective technique to modulate phase transition dynamics by inserting external atoms or ions between the layers of 2D-TMDs, altering their electronic structure and physical properties. Here, we investigate the significant structural phase transitions in Pb(Ta1+xSe2)2 single crystals induced by Ta intercalation using a combination of Raman spectroscopy and first-principles calculations. The results highlight the pivotal role of Ta atoms in driving these transitions and elucidate the interplay between intercalation, phase transitions, and resulting electronic and vibrational properties in 2D-TMDs. By focusing on Pb(Ta1+xSe2)2 as an ideal case study and investigating like metal intercalation, this study advances understanding in the field and paves the way for the development of novel applications for 2D-TMDs, offering insights into the potential of these materials for future technological advancements.

The development of advanced electronic devices is contingent upon sustainable material development and pioneering research breakthroughs. Traditional semiconductor-based electronic technology faces constraints in material thickness scaling and energy efficiency. Atomically thin two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising candidates for next-generation nanoelectronics and optoelectronic applications, boasting high electron mobility, mechanical strength, and a customizable band gap. Despite these merits, the Fermi level pinning effect introduces uncontrollable Schottky barriers at metal–2D-TMD contacts, challenging prediction through the Schottky-Mott rule. These barriers fundamentally lead to elevated contact resistance and limited current-delivery capability, impeding the enhancement of 2D-TMD transistor and integrated circuit properties. In this review, we succinctly outline the Fermi level pinning effect mechanism and peculiar contact resistance behavior at metal/2D-TMD interfaces. Subsequently, highlights on the recent advances in overcoming contact resistance in 2D-TMDs devices, encompassing interface interaction and hybridization, van der Waals (vdW) contacts, prefabricated metal transfer and charge-transfer doping will be addressed. Finally, the discussion extends to challenges and offers insights into future developmental prospects.

Nanoporous activated carbons derived from bio-waste are gaining consideration due to their exceptional potential for energy storage and CO2 adsorption. Herein, we put forward a straightforward, low-cost method for preparing a highly efficient nanoporous biocarbon from ginger using solid-state activation approach. Ginger was pyrolyzed at various temperatures before activating using different amounts of KOH as an activator to produce nanoporous biocarbon. The prepared samples possess high specific surface areas and large pore volumes. By simply adjusting the pyrolysis temperature, the microporosity and surface oxygen functionalities can be finely tuned. The best sample exhibits a high Brunauer-Emmett-Teller-specific surface area of 2,330 m2/g and a large pore volume of 1.10 cm3/g and offers excellent specific capacitance of 244 and 119 F/g when tested in a three-electrode and two-electrode, at a current density of 0.5 A/g. Additionally, the optimized material demonstrates a high CO2 uptake capacity of 4.87 mmol/g at ambient pressure and 25.8 mmol/g at 0 °C and 30 bar. These interesting adsorption and energy storage performances of the nanoporous biocarbon underscore the potential of converting food waste into high-performance CO2 adsorbents and supercapacitors.

The current advancement in tailoring the morphological states of GaN nanomaterials (GaN-NMs) is highly pursued. However, utilising different types of catalysts during the synthesis could alter the outcome of the electronic response of the GaN-NMs. Herein, we demonstrate the applicability of the element- and surfacesensitive X-ray absorption spectroscopy (XAS) as a tool to distinguish Ga L- and N K-edges features of GaN-NMs synthesised with Ge, Ni, and Ge/Ni catalysts. In particular, we resolved the implication of tuning indirectly the unoccupied 2p states of N atoms corresponding to access the orbital hybridisation mixing at low temperatures. We propose that the type of catalysts playa role in determining the sp3/sp2 ratio of N orbitals, as observed with a deconvolution of XAS spectra. Temperature-dependent XAS exemplified the sp2 hold majority contribution for Ni- and Ge-catalysed GaN-NMs until reaching the inflexion point at 80 K. On the other hand, Ge/Ni catalysed GaN-NMs display a minute-increasing trend of sp3 contribution. We propose that the structure- property correlation can be realised from the XRD and XAS shifts, thus a simplified model of interconversion orbital arrangement of hybrid electronic states is proposed. To investigate the applications for optoelectronic applications based on the different shapes of the nanomaterials, current-voltage measurement reveals that Ge/Ni-catalysed GaN-NMs shows the best photoelectric response as credited to their largest surface area. This work provides an understanding of tailoring the electronic properties of GaN-NMs by morphology control.

Metal-free semiconducting carbon nitride materials with tunable band structure and rich functional groups afford new materials with ground-breaking features and potential applications in various areas. To obtain a mesoporous structure with high surface area and enhanced active sites utilizing templating is an effective strategy to further improve the performance of such functional materials, especially benefitting adsorption and sensing. Herein, hierarchical mesoporous graphitic carbon nitride showing tubular morphology and high nitrogen content were synthesized using economic halloysite nanoclay as the template and aminoguanidine as the CN precursor. Materials characterization and spectrum analysis revealed that the fabricated carbon nitride possessed mesoporous feature with tunable band structure and a C and N stoichiometry of C3N5.36. The optimized sample showed rich nitrogen content with a high specific surface area (214.2 m(2)/g), exhibiting superior adsorption performance for CO2 (27.18 mu mol m(-2 )at 0 degrees C) and sensing over flammable aromatic and volatile aliphatic compounds. Besides, it was demonstrated as a promising sensor, exhibiting high stability and selectivity towards dichloromethane, a class 2 A carcinogen. The excellent performance of CO2 capture and the sensing of toxic vapors is due to the tubular morphology, high surface area, and hydrophilic functionalities with more active sites for the adsorption on the surface of the materials.

Transition metal carbides, known as MXenes, particularly Ti3C2Tx, have been extensively explored as promising materials for electrochemical reactions. However, transition metal carbonitride MXenes with high nitrogen content for electrochemical reactions are rarely reported. In this work, transition metal carbonitride MXenes incorporated with Pt-based electrocatalysts, ranging from single atoms to sub-nanometer dimensions, are explored for hydrogen evolution reaction (HER). The fabricated Pt clusters/MXene catalyst exhibits superior HER performance compared to the single-atom-incorporated MXene and commercial Pt/C catalyst in both acidic and alkaline electrolytes. The optimized sample shows low overpotentials of 28, 65, and 154 mV at a current densities of 10, 100, and 500 mA cm-2, a small Tafel slope of 29 mV dec-1, a high mass activity of 1203 mA mgPt-1 and an excellent turnover frequency of 6.1 s-1 in the acidic electrolyte. Density functional theory calculations indicate that this high performance can be attributed to the enhanced active sites, increased surface functional groups, faster charge transfer dynamics, and stronger electronic interaction between Pt and MXene, resulting in optimized hydrogen absorption/desorption toward better HER. This work demonstrates that MXenes with a high content of nitrogen may be promising candidates for various catalytic reactions by incorporating single atoms or clusters.

Nanoporous activated biocarbons derived from biomass offer a sustainable alternative to traditional carbon materials in various applications. Even though multiple methods are available to prepare these carbon materials with different biomasses and activating agents, there are still many challenges such as optimizing pore structure, surface functionalization control, and maintaining high electrical conductivity which are critical to achieve high performance in energy storage applications. These challenges can be overcome by choosing the appropriate biomass with different chemical structure and composition. Herein, we use food waste garlic to synthesize nanoporous biocarbon through the activation process using potassium hydroxide (KOH) as an activating agent. The resulting biocarbon exhibited a high specific surface area of 3449.2 m2 g-1 and a pore volume of 1.67 cm3 g-1, together with sulfur and oxygen functionalities. Pyrolysis was employed to fine-tune the pore structure, achieving a balance of microporosity and mesoporosity, which are beneficial for energy storage and carbon capture applications. The nanostructured materials delivered exceptional CO2 adsorption capacity at low (5.25 mmol/g at 1 bar) and high pressure (30.6 and 24.9 mmol/g at 0 and 25 degrees C at 30 bar), making it a promising sorbent for both post-combustion and pre-combustion CO2 capture. The breakthrough studies combined with the dynamic adsorption models like the Yoon-Nelson and Thomas models demonstrated superior CO2 capture and rate constant for practical applications. Furthermore, the biocarbon revealed excellent electrochemical performance as a supercapacitor electrode with a specific capacitance of 262 F/g at 0.5 A g-1 and stability over 10,000 cycles with excellent retention and coulombic efficiency. The presence of oxygen and sulfur functionalities enhanced hydrophilicity and wettability, contributing to the superior electrochemical performance. The study highlights the potential of functionalized nanoporous biocarbon with a tunable porous structure derived from waste biomass as a sustainable and efficient material for CO2 capture and energy storage applications.

Graphitic carbon nitride (g-C3N4) has attracted enormous attention as a photocatalyst due to its appropriate bandgap, high chemical stability, and visible light response. However, it is still challenging to synthesize highly crystalline g-C3N4, favoring the separation of photogenerated electron-hole pairs and promoting improved photocatalytic activity. Herein, we report a novel approach to achieve highly crystalline g-C3N4 by simply pressing sodium chloride and carbon nitride into a pellet followed by heat treatment, which is different from conventional molten salt methods. The resulting g-C3N4 has an optimum band structure that benefits enhanced light absorption and charge separation efficiency. The intimate contact between sodium chloride and carbon nitride in the pressed pellet facilitates the diffusion of sodium ions and increases the material's resistance to high annealing temperatures, leading to improved crystallinity. The photocurrent response of this highly crystalline material under visible light irradiation is approximately four times higher than that of its bulk counterpart, resulting in a hydrogen production rate of up to 650 mu mol g-1 h-1 (10% TEOA). This work paves a new path in designing novel carbon nitrides with enhanced photoelectrochemical and photocatalytic performance.