Modulated Structure Research Articles

Broad-angle coherent perfect absorption-lasing and collimation in two-dimensional non-Hermitian phononic crystals

Abstract Coherent perfect absorption-lasing and collimation have been extensively studied primarily for normal incidence, leaving broad-angle scenarios relatively unexplored. In this work, we investigate a two-dimensional non-Hermitian phononic crystal, aiming to achieve broad-angle coherent perfect absorption-lasing and collimation. Our approach involves orchestrating a parity-time phase transition in the band structure through a combination of non-symmorphic glide symmetry in the lattice, gain-loss modulation, and engineering of the band structure. In both the real and imaginary parts of the band structure, exceptional points form a slab-like contour with nearly zero dispersion along the boundary of the Brillouin zone. As a result, the range of incidence angles for coherent perfect absorption-lasing and collimation is significantly expanded at the frequency of the exceptional points.

Viscous and turbulent stress measurements above and below laboratory wind waves

Abstract The influence of wind stress, wind drift, and wind-wave (microscale) breaking on the coupled air–sea boundary layer is poorly understood. We performed high-resolution planar and stereo velocity measurements within the first micrometers to centimeters above and below surface gravity waves at the University of Miami’s SUSTAIN air–sea interaction facility. A particle image velocimetry (PIV) system was adapted and installed in the large (18 m long, 6 m wide) wind-wave tunnel at a fetch of approximately 10 m. In addition, wave field properties were captured by laser-induced fluorescence (LIF). Experiments were conducted with wind waves and wind over mechanically generated swell. In this work, we focus on rather smooth, young, wind-generated waves. We present instantaneous velocity and vorticity fields above and below the air–water interface for the same wind-wave conditions. Both instantaneous and phase-averaged fields show strong along-wave modulations in viscous stress. For steeper waves, we observe airflow separation and increased negative turbulent stress below crests, accompanied by sporadic drops in viscous stress below zero. We describe the wave-induced modulations of the airflow structure as well as the wind-induced water dynamics and discuss the importance of the viscous stress for the total momentum budget. Graphic abstract

Enhancing Battery Performance through Solvation Structure Modulation of Iron–Chromium Electrolytes Using Guanidine Hydrochloride

Enhancing Battery Performance through Solvation Structure Modulation of Iron–Chromium Electrolytes Using Guanidine Hydrochloride

Structural Modulation of Nanographenes Enabled by Defects, Size and Doping for Oxygen Reduction Reaction

Nanographenes are among the fastest‐growing materials used for the oxygen reduction reaction (ORR) thanks to their low cost, environmental friendliness, excellent electrical conductivity, and scalable synthesis. The perspective of replacing precious metal‐based electrocatalysts with functionalized graphene is highly desirable for reducing costs in energy conversion and storage systems. Generally, the enhanced ORR activity of the nanographenes is typically deemed to originate from the heteroatom doping effect, size effect, defects effect, and/or their synergistic effect. All these factors can efficiently modify the charge distribution on the sp2‐conjugated carbon framework, bringing about optimized intermediate adsorption and accelerated electron transfer steps during ORR. In this review, the fundamental chemical and physical properties of nanographenes are first discussed about ORR applications. Afterward, the role of doping, size, defects, and their combined influence in boosting nanographenes’ ORR performance is introduced. Finally, significant challenges and essential perspectives of nanographenes as advanced ORR electrocatalysts are highlighted.

Structural Modulation of Nanographenes Enabled by Defects, Size and Doping for Oxygen Reduction Reaction

Nanographenes are among the fastest‐growing materials used for the oxygen reduction reaction (ORR) thanks to their low cost, environmental friendliness, excellent electrical conductivity, and scalable synthesis. The perspective of replacing precious metal‐based electrocatalysts with functionalized graphene is highly desirable for reducing costs in energy conversion and storage systems. Generally, the enhanced ORR activity of the nanographenes is typically deemed to originate from the heteroatom doping effect, size effect, defects effect, and/or their synergistic effect. All these factors can efficiently modify the charge distribution on the sp2‐conjugated carbon framework, bringing about optimized intermediate adsorption and accelerated electron transfer steps during ORR. In this review, the fundamental chemical and physical properties of nanographenes are first discussed about ORR applications. Afterward, the role of doping, size, defects, and their combined influence in boosting nanographenes’ ORR performance is introduced. Finally, significant challenges and essential perspectives of nanographenes as advanced ORR electrocatalysts are highlighted.

Synergetic Modulation of Electronic Properties of Cobalt Oxide via “Tb” Single Atom for Uphill Urea and Water Electrolysis

AbstractExploring single‐atom (SA) catalysts in hybrid urea‐assisted water electrolysis offers a viable alternative to both Hydrogen (H2) generation and polluted water treatment. However, the unfavorable electronic stabilization, low SA content, intrinsically slow kinetics, and imbalanced adsorption‐desorption steps are the bottleneck for its scale‐up implementation. Herein, a rare‐earth Terbium single atom (TbSA) is topologically stabilized on defect‐rich Co3O4 (TbSA@d‐Co3O4) by Tb─O co‐ordination for urea oxidation reaction (UOR) and H2 evolution reaction (HER). Benefitting from the strong TbSA interaction with the d‐Co3O4, the TbSA@d‐Co3O4 achieves a 10 mA cm−2 current density at 1.27 V and −35 mV for UOR and HER, respectively. Remarkably, when TbSA@d‐Co3O4 is applied as a bi‐functional catalyst in a two‐electrode system, it merely requires 1.22 V to acquire 10 mA cm−2 with excellent operational stability for 100 h. The hybrid electrolyzer can be successfully empowered by the triboelectric nanogenerator, AA battery, and solar panel with a nominal potential of 1.5 V. The mechanistic investigation predicts “TbSA” insertion in d‐Co3O4 lowered the potential determining step, attributed to balanced reaction energetics for adsorption‐desorption of intermediates and favorable charge transfer characteristics for UOR. This work offers a new paradigm to explore the catalytic properties of rare‐earth “f‐block” elements to create advanced electrocatalysts via structural modulation.

Photovoltaic response promoted via intramolecular charge transfer in triphenylpyridine core with small acceptors: A DFT/TD-DFT study

Currently, A−π−A configured molecules (TTP1-TTP6) were designed from the reference compound (TPPR) by modifying the terminal acceptors for photovoltaic materials. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using the M06/6-311G(d,p) functional were employed to analyze the photonic and electronic properties of the newly designed derivatives. Various analyses; frontier molecular orbitals (FMOs), density of states (DOS), absorption spectra (λmax), transition density matrix (TDM), binding energy (Eb), hole-electron and open circuit voltage (Voc) were performed to explore the photovoltaic properties of triphenylpyridine based compounds. The structural modulation with acceptor moieties significantly tuned their HOMO and LUMO levels, resulting in reduced band gaps (2.833–3.037 eV). They also exhibited broader absorption spectra (λmax) ranging from 482.560 to 514.756 nm as compared to the reference compound (486.289 nm). Notably, TPP3 showed the good photovoltaic response as it displayed the least energy gap (2.833 eV) with lower binding energy (0.415 eV) and bathochromic shift (512.798 nm) in absorption spectra as compared to all other derivatives. Beside this, a comparative study with spiro-OMeTAD and P3HT standard hole transport materials illustrated that these materials can also be utilized as effective photovoltaic materials.

Preparation and characterization of Tobacco polysaccharides and its modulation on hyperlipidemia in high-fat-diet-induced mice.

This study aimed to investigate the structural properties of tobacco polysaccharide (TP) and its mechanism of modulating hyperlipidemia in high-fat diet-induced mice. The structural properties of TP were characterized by FT-IR, 1HNMR, SEM, AFM and thermogravimetric analysis. And the regulatory mechanism of TP on lipid metabolism was investigated in hyperlipidemia mice. These results showed that TP had a high composition of reducing monosaccharide and the glycosidic bond type was α-glycosidic bond. The intervention by TP resulted in a significant reduction of body weight and improvement in lipid accumulation. And the modulation mechanism by which TP ameliorated the abnormalities of lipid metabolism was associated with the expression levels of lipid metabolism-related genes and serum exosomes miRNA-128-3p, as well as the modulation of structure and abundance of the gut microbiota in mice. In addition, TP treatment significantly increased the content of short-chain fatty acids (SCFAs) in mice feces. The results of molecular docking and dual-luciferase assay exhibited a good interaction between propionic acid and PPAR-α, and it was hypothesized that the interaction might further ameliorate the hyperlipidemia. Therefore, TP can regulate the expression levels of lipid metabolism-related genes through miRNAs from serum exosomes and SCFAs from gut microbiota.

Regulating the electronic modulation configuration of MnxFeCoNiCu high entropy alloy for reliable sulfur redox kinetics

Current research on sulfur redox catalysis primarily focuses on the adsorption and catalytic conversion of lithium polysulfides (LiPSs). However, it often neglecting the modulation of the catalysts' electronic structure, which includes charge transfer and orbital interactions that significantly affect adsorption and catalytic properties. In this work, multi-channel carbon nanotubes modified with high entropy alloy nanoparticles (MnxFeCoNiCu/MCCFs) are elaborately synthesized as hosts to reveal the relationship between the catalytic activity and surface electronic configuration for reliable sulfur electrochemistry. Combining density functional theory (DFT) calculations with detailed experimental investigations, we demonstrate that modulating the electron consumption center of this intrinsic electron transfer-replenishment mechanism, the surface charge distribution is reestablished, thereby improving the performance of multi-electron reactions. Achieving a balance between adsorption and desorption significantly enhance the catalytic efficiency for LiPSs conversion. Consequently, the as-prepared Mn1.00/MCCFs with an optimized electronic structure as sulfur host can deliver a high capacity of 938 mAh g−1, corresponding to an ultralow capacity decay of 0.013 % per cycle over 500 cycles at 1.0 C.

Exploring advanced microwave strategy for the synthesis of two-dimensional energy materials

The rapid pace of technology and increasing energy demands underscore the urgent need for eco-friendly materials with exceptional energy conversion and storage capabilities. Two-dimensional (2D) energy materials, characterized by unique physicochemical properties, hold great promise in renewable energy conversion, catalysis, and electronics. Nevertheless, conventional synthesis methods often falter in balancing high quality, high yield, and cost-effectiveness, presenting substantial obstacles to their large-scale application. Microwave-assisted synthesis, characterized by its rapid and efficient process, emerges as a promising approach to surmount these limitations. This review meticulously examines the pivotal role of microwave-assisted synthesis in the preparation of 2D materials, highlighting its profound impact on enhancing material quality and production efficiency. By scrutinizing the unique physical properties of microwaves and their applications in material synthesis, the review elucidates the innovative contributions of microwave technology to materials science. Furthermore, it delves into the intricate influence of microwave parameter control on the synthesis process and resultant material properties, offering insight into the potential of microwave technology for the precise modulation of material structure and functionality. This comprehensive analysis underscores microwave-assisted synthesis as a viable solution for overcoming current challenges, thereby advancing the development of high-performance 2D energy materials.

Fe−N Co‐Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation

AbstractBismuth vanadate (BVO) ranks among the most promising photoanodes for photoelectrochemical (PEC) water splitting. Nonetheless, slow charge separation and transport, besides the sluggish water oxidation kinetics, are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO photoanodes. We found that, under standard one sun illumination, the Fe−N co‐doped BVO photoanode (Fe−N−BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm−2 at 1.23 V vs RHE after modified a surface co‐catalyst (FeNiOOH), and exhibits an outstanding stability. By contrast, much lower photocurrent density is obtained for the N‐doped, Fe‐doped and Fe/N‐doped BVO photoanode with separated N and Fe precursors. The detailed experimental characterizations show that the high activity of the Fe−N co‐doped BVO photoanode is attributed to the enhanced photo‐induced bulk charge separation, as well as the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe−N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites.

Phyto-mediated synthesis of ZnO/attapulgite nanocomposites using C. limon peel extract for enhancing the resistance against multidrug-resistant bacteria and fungi

ZnO have great potential in combating multidrug-resistant (MDR) bacteria, however, green synthesis and activity regulation still face challenges. In this study, we designed a green bioinspired method mediated by C. limon peel extract to synthesise a series of attapulgite (APT) supported ZnO nanocomposites for enhancing the resistance against MDR pathogenic bacterial and fungal, in which the structure and morphology of ZnO was regulated by APT inducing heterogeneous nucleation of ZnO, thus enhancing the antibacterial activity of the nanocomposites. XRD and TEM analysis demonstrated that ZnO/APT with a unique peg-top-like morphology and well-defined crystal structure was successfully synthesized via the regulation of Zn2+ ions concentration. XPS results confirmed that the oxygen vacancy increased significantly compared with the pure ZnO (has a cubic shape) due to the structural modulation of ZnO induced by APT. The obtained ZnO/APT nanocomposites exhibited excellent biocompatibility and enhanced antibacterial efficacy with a complete inhibition at a concentration of 0.125 mg/mL for MRSA, a high inhibitory rate of 94.68 ± 1.43 % at a concentration of 0.5 mg/mL for ESBLs-E. coli, and the antifungal rate against C. albicans was found to be 95.59 ± 1.08 % at a concentration of 0.25 mg/mL. In addition, the ZnO/APT had a good hemostatic effect and enhanced biocompatibility compared to pure ZnO. The study provides a green way to design efficient ZnO antibacterial nanomaterials with remarkable antimicrobial efficacy and lower cytotoxicity, and the ZnO/APT nanocomposite is potential for clinical applications.

Unique Oxygen-Bridged Nickel Atomic Pairs Efficiently Boost Electrochemical Reduction of Carbon Dioxide.

Benefiting from the synergism between adjacent bimetallic atoms, in comparison with single atom catalysts, the dual atom catalysts have displayed great potential in electrocatalytic CO2 reduction reaction (CO2RR). However, the further modulation of the electronic structure of dual atom sites to enhance CO2RR performance still remains a challenge. Herein, an atomically dispersed oxygen-bridged Ni2N6O/NC catalyst with unique Ni-O-Ni sites is successfully synthesized through the microwave pyrolysis of the supported mixture containing the dinuclear nickel phthalocyanine and glucose on N-doped carbon nanosheets. Experiments and density functional theory calculation reveal that the Ni-O-Ni sites can adsorb H+ from the KHCO3 electrolyte to in situ-form the unique Ni-OH-Ni sites without Ni─Ni bonding interaction, which effectively lowers the energy barrier towards the formation of *COOH from CO2. As a result, the Ni2N6OH/NC catalyst exhibits a 99.4% of CO Faradaic efficiency with a 32.4 mA·cm-2 of CO partial current density at -0.7V versus RHE in H-cell, much superior to the Ni2N6/NC with a Ni-Ni bonding interaction prepared by a similar procedure to that for Ni2N6O/NC but replacing microwave pyrolysis by a traditional heating process.

The Jahn–Teller distortion‐induced electronic structure regulation of Mn‐doped Co3O4 for enhanced acetone detection

AbstractThe modulation of the electronic structure of metal oxides is crucial to enhance their gas‐sensing performance. However, there is lacking in profound study on the effect of electronic structure regulation on sensing performance. Herein, we propose an innovative strategy of Jahn–Teller distortion‐induced electronic configuration regulation of Co3O4 to improve acetone sensing performance. After the introduction of Mn3+ into Co3O4 (Mn‐Co3O4), the Jahn–Teller distortion of high‐spin Mn3+ (t2g3eg1) conversed to low‐spin Mn4+ (t2g3eg0), resulting in conversion of Co3+ (t2g6eg0) into Co2+ (t2g6eg1). As expected, Mn‐Co3O4 exhibits a high response value of 46.7 toward 100 ppm acetone, low limit of detection of 0.75 ppb, high selectivity, and high stability, which are overwhelmingly superior to previous Co3O4‐based acetone sensors. The dynamics and thermodynamics analysis demonstrate that the Mn doping improves sensing reaction rate, reduces reaction barrier, and promotes the charge transfer. The theoretical calculations further prove the charge transfer from Mn to Co derived from Jahn–Teller distortion and support promoting the adsorption of acetone on Co3O4 by Mn dopant. Moreover, we demonstrated the substantial potential application of Mn‐Co3O4 sensor as a monitoring gas sensor in pest resistance of Arabidopsis. This work provides a new strategy to design sensing materials from electronic configuration perspective.image

Ammonium-driven modulation of 1T-MoS2 structure and composite with graphene: A pathway to high-performance lithium-ion battery anodes

Ammonium-driven modulation of 1T-MoS2 structure and composite with graphene: A pathway to high-performance lithium-ion battery anodes

Raising the performances of copoly(ether-imide) films by structural design modulation towards energy storage applications

The present study aims to shed light onto the influence of structural design on the overall properties of a series of aliphatic–aromatic CN-based copoly(ether-imide)s, with emphasis on energy storage performance, with the support provided by selected benchmarks. To boost the energy storage capability of the free-standing films made therefrom, three molar ratios of a CN-aromatic hard segment and a Jeffamine-based soft component were used. Thus, through different chemical strategies and their synergism, the films morphology and their physico-chemical properties like wetting, optical, mechanical, thermal, dielectric and, particularly breakdown strength and energy storage were modulated. The results showed high thermal stability, single glass transition temperatures, good mechanical properties, and relative low dielectric constants of the copolymers. The absence of crystallization demonstrated the amorphous nature of the films due to the good interpenetration of soft and hard components, although some phase separations were observed in some copolymers with no clearly defined boundaries. Due to the balanced thermal stability, dielectric behavior, mechanical features, and film processing ability, these copoly(ether-imide)s display potential applications in high-temperature energy storage field, reaching breakdown strength and energy storage density values up to 459 kV/mm and 2.70 J/cm3, respectively.

Electronic structure modulation of yttrium sites with heteroanions coordination enhances the bidirectional catalytic performance of lithium-sulfur batteries

Oxyfluorides exhibit unique properties, including catalytic activity and electrical conductivity. However, to date, there has been minimal application of oxyfluorides in the field of lithium-sulfur (Li-S) batteries. This study synthesizes yttrium oxyfluoride-doped semi-encapsulated porous carbon nanofibers (YOF@PCNFs) using through electrospinning strategy for the separator coating in Li-S batteries. The precisely engineered OF heteroanionic environment surrounding the Y cation can adjust the lattice spacing and electronic density of the catalyst. This enhancement improves interactions between the active sites and the reactants, intermediates, and products, reduces the energy barrier for polysulfide (LiPSs) conversion, and enhances the bidirectional catalytic conversion capability of LiPSs. Furthermore, the semi-encapsulated structure helps inhibit polysulfide shuttle and ensures uniform Li-ion deposition. Improved catalysts and the interconnected special structure can establish a series of polysulfides conversion factories which operate efficiently over the long term through a “confinement-adsorption-catalysis-desorption” process, thereby enhancing battery cycling stability. The assembled Li-S full cell exhibits a high initial capacity of 1013.2 mAh/g at 1 mA cm−2 and maintains steady operation over 1500 cycles, with a minimal capacity decay rate of only 0.039 % per cycle. Even at a high current density of 4 mA cm−2, it operates for 200 cycles with an exceptionally low decay rate of 0.081 % per cycle. The study provides an anion hybrid strategy for typical metal catalysts, offering design guidelines for tailored advanced Li-S catalysts.

Utilizing cationic vacancies to enhance nickel-cobalt layered double hydroxides for efficient electrocatalytic urea oxidation reaction

Electrocatalytic urea oxidation reaction (UOR) is a promising approach for urea-rich wastewater splitting, which benefits for reducing energy consumption in hydrogen production accompanying environmental protection and sustainable energy development. To address the limitations posed by the self-oxidation of nickel-based catalysts on the activity of UOR, we here developed a NiCo LDH nanosheet catalyst with abundant Ni vacancies to initiate the UOR process prior to nickel oxidation. Electrochemical impedance spectroscopy and In-situ spectroscopic characterizations confirm that the UOR process primarily occurs on the surface of the catalyst, rather than being driven by nickel oxidation products. The favorable electronic structure modulation induced by Ni vacancies makes the catalyst more energetically favorable for the UOR compared to nickel self-oxidation. The catalyst exhibits excellent UOR activity, only requiring 1.27 V vs. RHE at 10 mA cm−2 and 1.34 V vs. RHE at 100 mA cm−2, with no significant decay observed after over 120 h of operation. Furthermore, it can function as a bifunctional catalyst, requiring only 1.66 V to achieve 100 mA cm−2 for the UOR||HER system. This study expands the pathway for the application of cationic vacancies in UOR.

Structural modulation of methyl 4-(2,11-diisopropylbenzopentaphen-5-yl based chromophore with B12N12 nano cage for enhancing the NLO Properties: A DFT study

Currently, key electronic and nonlinear optics (NLO) properties of DPOB chromophore were explored through doping with B12N12 nanocage. Therefore, two complexes I and II were designed by doping nanocage on methoxy and carbonyl group of DPOB at minimum distance. The DFT/TD-DFT approaches at B3LYP-GD3/6-311G(d,p) functional were utilized to accomplished the NLO properties. A band gap: 3.109 and 2.707 eV in complexes I and II, respectively with higher value of softness and least hardness were investigated in doped material than their pure forms (DPOB and B12N12). The hyperpolarizability of studied compounds increases as: B12N12 < DPOB<Complex I<Complex II. Among all investigated compounds, complex II showed the maximum values of dipole moment (15.826 D), linear polarizability (7.04 × 102a.u.) and non-linear polarizability (βtot = 4.13 × 103 and γtot = 6.70 × 105a.u.). These findings illustrated that doping of inorganic nanocages over organic surfaces is an efficient strategy to improve the NLO properties.

Electric field modulation of electronic structure, charge transfer, and nonlinear optical properties of crocetin for dye-sensitized solar cells

Natural sensitizing dyes in solar energy applications have gained attention due to their sustainability, cost-effectiveness, and environmental friendliness. However, enhancing their performance, light-harvesting efficiency, and durability requires a deeper understanding of their structural and electronic properties under solar irradiance. Accordingly, this study explores the electronic structure and nonlinear optical properties of crocetin dye (cis and trans conformers) under varying external electric fields using M06-2X/6-311+G(d,p) model chemistry. The absorption characteristics strongly depend on field intensity, with electron injection efficiency expected to decrease as the field increases. Key nonlinear optical (NLO) parameters, such as dipole moment, polarizability, and hyperpolarizabilities, were calculated at solar irradiance peak frequencies. The NLO properties are wavelength-independent in the infrared region but show significant wavelength dependency in the visible region, increasing substantially near the absorption energy.