Distinct Vibrational Modes Research Articles

Structural Refinement and Optoelectrical Properties of Nd2Ru2O7 and Gd2Ru2O7 Pyrochlore Oxides for Photovoltaic Applications.

High-performance photovoltaic devices require active photoanodes with superior optoelectric properties. In this study, we synthesized neodymium ruthenate, Nd2Ru2O7 (NRO), and gadolinium ruthenate pyrochlore oxides, Gd2Ru2O7 (GRO), via the solid-state reaction technique, showcasing their potential as promising candidates for photoanode absorbers to enhance the efficiency of dye-sensitized solar cells. A structural analysis revealed predominantly cubic symmetry phases for both materials within the Fd-3m space group, along with residual orthorhombic symmetry phases (Nd3RuO7 and Gd3RuO7, respectively) refined in the Pnma space group. Raman spectroscopy further confirmed these phases, identifying distinct active modes of vibration in the predominant pyrochlore oxides. Additionally, a scanning electron microscopy (SEM) analysis coupled with energy-dispersive X-ray spectroscopy (EDX) elucidated the morphology and chemical composition of the compounds. The average grain size was determined to be approximately 0.5 µm for GRO and 1 µm for NRO. Electrical characterization via I-V measurements revealed that these pyrochlore oxides exhibit n-type semiconductor behavior, with conductivity estimated at 1.5 (Ohm·cm)-1 for GRO and 4.5 (Ohm·cm)-1 for NRO. Collectively, these findings position these metallic oxides as promising absorber materials for solar panels.

Effect of hydrogen flow rate on properties of silicon oxycarbide thin films via hot wire chemical vapor deposition

AbstractThis study explores the impact of hydrogen flow as a carrier gas on silicon oxycarbide thin films produced via hot wire chemical vapor deposition (HWCVD) using tetraethyl orthosilicate as a precursor. Systematically varying the hydrogen flow rates, the influence on thin film composition, microstructure, and optical properties is investigated. Employing diverse characterization techniques, such as X‐ray diffraction, field‐emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy, Fourier‐transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), ellipsometry, and photoluminescence (PL) spectroscopy, it is revealed that there is a correlation between hydrogen flow rate and thin film elemental composition. Higher hydrogen flow rates result in increased silicon content and reduced contributions of oxygen and carbon. FE‐SEM images show agglomerates with improved homogeneity at higher flow rates. FTIR spectra highlight distinctive vibrational modes, including Si–H bonds. XPS confirms the emergence of Si–H bonds at elevated hydrogen flow rates. Ellipsometry indicates increased thickness and refractive index. PL spectra exhibit a broadband across the visible spectrum, influenced by hydrogen‐related defects and electronic transitions. This study provides findings for optimizing HWCVD parameters to tailor thin films for specific applications, emphasizing the important role of hydrogen flow as a carrier gas.

Exploring the Molecular-Scale Structures at Solid/Liquid Interfaces of Li-Ion Battery Materials: A Force Spectroscopy Analysis with Sparse Modeling.

In this study, we clarify the liquid structure formed at the interface between LiCoO2 (LCO), the cathode material of Li-ion batteries, and propylene carbonate (PC), which is used as a solvent in the electrolyte, on a molecular scale. We apply sparse modeling-based modal analysis to force spectroscopy data measured by frequency modulation atomic force microscopy (FM-AFM) and show that each component in the FM-AFM force curve, such as oscillatory solvation force, background, and noise, can be automatically decomposed. Moreover, by combining detailed force curve analysis with solid/liquid interface simulations based on first-principles calculation, we have identified that there are distinct damped vibrational modes in the force curves at the LCO/PC interface with a period of about 0.57 nm and those with shorter periods, which likely correspond to the solvation forces associated with bulk-state PC molecules and those with PC molecules in "lying down" orientations.

Effect of heavy Dy3+ doping on the magnetic, structural, morphological, and optical characteristics of CuDyxFe2-xO4 nanoparticles

The present study explored the impacts of dysprosium (Dy³⁺) doping on the structure, optical, and magnetic characteristics of CuDyxFe2-xO4 nanospinel ferrites synthesized via a hydrothermal method. X-ray diffraction revealed a tetragonal spinel matrix with increasing Dy³⁺ content, accompanied by a secondary Dy2O3 phase at higher dopant levels for x ≥ 0.1. Crystallite size and microstrain increased with doping, while infrared spectroscopy confirmed the spinel structure and distinct vibrational modes. Interestingly, saturation magnetization displayed a non-monotonic trend, first rising due to spin polarization and cation redistribution, then decreasing with higher Dy³⁺ content attributable to the Dy2O3 phase and larger grains. Coercivity exhibited a maximum at x = 0.2, reflecting the interplay between magnetocrystalline anisotropy, canting angles, and domain wall pinning. These findings highlight the complex interplay between Dy³⁺ doping and the resulting properties, paving the way for tailored CuDyxFe2-xO4 nanospinel ferrites functionalities. . Further research involving advanced techniques and targeted dopant levels holds promise for optimizing properties for diverse technological applications such as magnetic storage, microwave devices, sensors, and hyperthermia treatment.

Unveiling Multiquantum Excitonic Correlations in Push-Pull Polymer Semiconductors.

Bound and unbound Frenkel-exciton pairs are essential transient precursors for a variety of photophysical and biochemical processes. In this work, we identify bound and unbound Frenkel-exciton complexes in an electron push-pull polymer semiconductor using coherent two-dimensional spectroscopy. We find that the dominant A0-1 peak of the absorption vibronic progression is accompanied by a subpeak, each dressed by distinct vibrational modes. By considering the Liouville pathways within a two-exciton model, the imbalanced cross-peaks in one-quantum rephasing and nonrephasing spectra can be accounted for by the presence of pure biexcitons. The two-quantum nonrephasing spectra provide direct evidence for unbound exciton pairs and biexcitons with dominantly attractive force. In addition, the spectral features of unbound exciton pairs show mixed absorptive and dispersive character, implying many-body interactions within the correlated Frenkel-exciton pairs. Our work offers novel perspectives on the Frenkel-exciton complexes in semiconductor polymers.

Role of atypical temperature-responsive lattice thermal transport on the thermoelectric properties of antiperovskites Mg3XN (X = P, As, Sb, Bi)

Antiperovskite materials have garnered significant attention due to their rich array of physical properties. In this study, we undertake a theoretical exploration into the phase stabilities, and the thermal and electronic transport properties of magnesium-based antiperovskite Mg3XN (X = P, As, Sb, and Bi) based on density functional theory (DFT) calculations, aiming at designing promising thermoelectric materials. The Mg3PN and Mg3AsN possess potential lattice distortion and strong quartic anharmonicity associated with the tilting displacement of Mg6N octahedra. After phonon renormalization, the thermal conductivity of Mg3PN and Mg3AsN exhibits relatively subdued temperature responsiveness with T−0.47 and T−0.62, respectively. Of note, the thermal conductivity of Mg3BiN drops the lowest at 900 K because of its distinctive rattle-dominated flat vibrational modes and strong temperature responsiveness with T−0.96, despite having a high initial value. Moreover, the combination of multiple degeneracy pockets and lighter dispersion band edges in Mg3XN ensures high Seebeck coefficient and impressive electronic conductivity, respectively. Ultimately, Mg3BiN achieves the optimal power factor, which also guarantees its excellent thermoelectric performance with the ZT values of 1.03 and 1.01 for n-type and p-type at 900 K, respectively. Our findings shed light on the significant impact of unconventional temperature-responsive lattice thermal conductivity on thermoelectric materials for high-temperature applications.

Bio-synthesized ZnO nanoparticles from Aegle marmelos assisted by microwave method for enhanced photocatalytic and antibacterial applications

Microwave-assisted green method was successfully used to synthesize ZnO nanoparticles in Nanoscale range by varying the Aegle marmelos leaf extract concentration. The existence of functional groups on the nanoparticle surface was confirmed by the FTIR spectra, which displayed distinctive vibrational modes. The nanoparticles size, shape, and surface features were discovered through morphological and structural research utilizing HRTEM, and SEM. The average particle size was found to be in the range of 18–28 nm. Under UV light irradiation, the ZnO NPs exhibited promising photocatalytic activity in the breakdown of methylene blue dye. The synthesized ZnO NPs are excellent in degrading dye to 80 % only in one hour. Furthermore, both Gram-positive and Gram-negative bacterial strains were effectively inhibited by the synthesized ZnO NPs' high antibacterial activity. Thus, characterization and promising photocatalytic and antibacterial properties point to the potential of these ZnO NPs for use in a range of environmental and biological applications.

Paroxysmal impulse vibration analysis of an aero-engine dual-rotor system with a defective inner ring for the inter-shaft bearing

Inter-shaft bearings play a central role in connecting high-pressure (HP) and low-pressure (LP) rotors within aero-engines. Local defects in these bearings can lead to two distinct and complex vibration modes—paroxysmal or continuous impulse vibrations, which arise from the unique installation positions. This study offers a comprehensive exploration of the dynamic phenomena, the underlying physical mechanism, and the analytical conditions for the occurrence of paroxysmal impulse vibrations. The local defects of the inner ring are found to induce paroxysmal impulse vibrations when specific rotational speed ratios between HP and LP rotors are achieved. The dynamic differences and connections between paroxysmal and continuous impulse vibrations are contrasted. Three analytic and explicit prediction formulas are derived, enabling the direct calculation of the operating conditions for paroxysmal impulse vibrations. A summarized prediction flow for paroxysmal impulse vibrations is established. In addition, the proposed prediction formulas and flow allow for the prediction of the precise frequency components of paroxysmal impulse vibrations. In the validation of the simulation results, three experimental cases involving inter-shaft bearings with inner ring defects are conducted, confirming the existence of paroxysmal dynamic phenomena and validating the effectiveness of the proposed prediction formulas and prediction flow for paroxysmal impulse vibrations. Hence, this study offers a novel approach to understanding inter-bearing vibration fault mechanisms.

From molecular salt to layered network: cation-driven tuning of band gap, structure, and charge transport in A3Bi2I9 (A = Cs, Rb) perovskites.

The increasing demand for eco-friendly and stable optoelectronic materials has led to interest in all-inorganic lead-free halide perovskites. This study reports the synthesis of A3Bi2I9 (A = Cs, Rb) perovskites via a solvothermal technique. The materials crystallize in hexagonal and monoclinic structures, with micrometer-sized particles. Optical investigations reveal direct band-gaps of 2.03 eV for Cs3Bi2I9 and 1.90 eV for Rb3Bi2I9. Raman spectroscopy highlights distinct vibrational modes, influenced by their structural differences. Space charge limited current (SCLC) measurements indicate varying threshold voltages and trap densities. Impedance spectroscopy and Jonscher's power law analysis reveal different polaron tunneling mechanisms in each compound. Ultrafast transient absorption spectroscopy shows the formation of self-trapped states upon photoexcitation, linked to lattice distortion and the formation of small polarons, which affect electrical conductivity.

Comparative investigation of low and high pelletize pressure for (Ag)x/CuTl-1223 nanoparticles-superconductor composites

This article experimentally investigates the impact of silver (Ag) nano-particles inclusion and high pelletized pressure on the structural, morphological, and electrical properties of Cu0.5Tl0.5Ba2Ca2Cu3O10−δ (noted CuTl-1223) bulk system. The nano-(Ag) x /CuTl-1223 composites were synthesized using a two-step solid-state reaction process with added amount of Ag nano-particles ranging from 0 to 2.0 wt% of the total mass. These nano-composites were produced at both low and high pelletize pressure of 0.202 GPa. All prepared samples were characterized using valuable techniques such as X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and dc-resistivity measurement at low as well as high pelletized pressure, respectively. The structural investigation via the XRD technique indicated that Ag NPs did not affect the CuTl-1223 tetragonal structure, confirmed that Ag nano-particles were settled across the grain boundaries. SEM examination revealed a fine distribution of nano-sized silver (Ag) NPs among the CuTl-1223 grains, as well as improved weak-links and density of void/pores. The position of distinct vibrational oxygen modes in FTIR spectra showed no substantial alteration, indicating that the structural nature of the host CuTl-1223 phase was preserved. The electrical properties were studied using the four-point probe technique, and the activation energy were determined using Arrhenius law. The results of measurements showed that pelletization pressure of 0.202 GPa have an impact on the critical temperature of (Ag) x /CuTl-1223 composites. The superconducting critical temperature was enhanced from 99 K to 107 K at high-pressure of pelletization (0.202 GPa) as compared to low pressure, with = 0 ∼ 2.0 wt nano-particles addition to the host CuTl-1223 phase.

Molecular docking and dynamic simulations of 2-phenoxyaniline and quantum computational, spectroscopic, DFT/TDDFT investigation of electronic states in various solvents

2-phenoxyanline was thoroughly examined using several spectroscopy nuclear magnetic resonance, IR, UV–vis, and quantum mechanical methodologies. D F T with basis set is employed to determine structural optimization and distinct vibration modes. The optimum binding parameters agree closely with the observed binding characteristics. VEDA performed the duties relating to potential energy distribution (PED) satisfactorily. The G I A O approach was adopted to compute chemical shifts in the 13C, 1H- N.M.R and the outcomes were compared to experimental spectra. TD-DFT with PCM model was used to calculate UV–vis with different solvents that, when assessed against observational spectra. The FMO energy provides sufficient proof of such. Molecular docking and dynamic simulations gave a better idea of the interaction of ligands with receptors.

Luminescence investigations of hydrothermally synthesized terbium doped zirconium tungstate nanorods

Rare-earth based phosphors play a key role in enhancing the quality of the phosphor converted LEDs (pc-LEDs). But the creation of phosphors with high thermal stability is still a task. This work aims to investigate the luminescence properties of ZrW2O8, which is known to have a negative or almost zero coefficient of thermal expansion. ZrW2O8 doped with Tb3+ is optimized by the conventional hydrothermal method in acidic medium. The PXRD analysis confirms the crystallization of the material into high purity cubic phase to the P213 space group. The tungstate group's distinctive vibrational modes were identified by FTIR analysis. TGA analysis demonstrates the remarkable thermal stability of the material over a wide temperature range. The preferential growth along one direction to form distinct nanorods was investigated using TEM. The optical band gap is found to increase after doping. The high and broad charge transfer band at 284 nm in the excitation spectra is an indication of the efficient energy transfer from the host to Tb3+ ions and the possibility of NUV excitation. The characteristic green emission peak of the Tb3+ at 543 nm and the values of the CCT and CP obtained using the colorimetry study suggest that the obtained material can be used as a green component to produce cold white LEDs.

Enhanced linearity through high-order antisymmetric vibration for MEMS DC power sensor

We present an electric power meter that capitalizes on the interaction of electrothermal strain and mechanical vibration in a micro-electro-mechanical systems (MEMS) beam undergoing the antisymmetric mode of vibration. This is achieved by using a resonant bridge driven with an electrothermal modulation technique. The change in electrical power is monitored through the alteration in the mechanical stiffness of the structure, which is tracked electrostatically. The observed deflection profile of the beam under the influence of electrothermal effects shows that the deflection geometry due to buckling exhibits similar trends as the first symmetric vibrational mode, in contrast to the antisymmetric mode. Therefore, we compare two distinct vibrational modes, converting the compressive thermal stress generated by the input electrical power via Joule heating into a shift in the resonance frequency. By employing antisymmetric vibrational mode, the output of our device is consistently monotonic to the input electrical power, even when the microbeam is experiencing buckling deflections. In addition, the sensing operation based on antisymmetric modes yields only a 1.5% nonlinear error in the response curve, which is ten times lower than that of symmetric modes. The observed deformation shape of the resonator agrees with the results obtained from multi-physics finite simulations. Finally, this approach has the potential to be extended to other frequency-shift-based sensors, allowing for higher linearity.

Ben Ofori-Okai

Ben Ofori-Okai, a spectroscopist at the SLAC National Accelerator Laboratory, has some big questions about what’s happening at the center of planets. The secret lives of high-pressure and high-temperature environments hold the key to scientists’ long-standing questions about the evolution of our universe and even the elusive chemistry within nuclear reactors. To explore these exotic conditions, Ofori-Okai is taking spectroscopy to the extreme. Ofori-Okai specializes in a field called terahertz spectroscopy, which measures the vibrational energy of molecules as they interact with and emit terahertz radiation. This region of the electromagnetic spectrum, which lies roughly between infrared and microwave wavelengths, captures distinct vibrational modes of molecules that other spectroscopic measurements miss. For example, chemists can use terahertz spectra to reveal the chemical composition of molecular mixtures that might be indistinguishable by nuclear magnetic resonance or infrared spectroscopy, Ofori-Okai says. Yet chemists have been slow to adopt terahertz spectroscopy because “it’s

A Review on Silver Nanoparticles

Nanoparticles are defined as particulate dispersions or solid particles with a size between 10 and 1000 nm. A one billionth of a metre scale is the simplest unit of measurement for nanotechnology. Silver nanoparticles superiority over silver in bulk forms is primarily due to the size, shape, composition, crystallinity, and structure of AgNPs. Silver nanoparticles synthesis can be achieved by physical, chemical and green methods. Evaporation-condensation and laser ablation processes are used in the physical synthesis of silver nanoparticle. Evaporation-condensation has been used to create a number of metal nanoparticles in the past, including fullerene, lead sulphide, cadmium sulphide, gold, and silver. Chemical reduction, photo-induced reduction, micro-emulsion, microwave-assisted synthesis, UV-initiated photo-reduction, electrochemical synthetic technique, and irradiation procedures are some of the chemical processes utilised to create nanoparticles. The temperature, pH, concentration, type of precursor, reducing and stabilising agents, and the molar ratio of surfactant and precursor are some of the reaction parameters that control how NPs form and grow in the chemical method. Utilizing biological organisms like bacteria, mould, algae, and plants allows for one-step synthesis. Proteins and enzymes found in plants and microbes are used in the reduction process to create nanoparticles. Silver nanoparticles function as nanoscale antennas at the plasmon resonant wavelength, boosting the strength of a nearby electromagnetic field. Raman spectroscopy, which uses molecules distinctive vibrational modes to identify them, is one spectroscopic method that benefits from the strengthened electromagnetic field. The plasmonic Au/Ag hollow-shelled NIR SERS probes were put together on silica nanospheres, which showed a redshift in the plasmonic extinction band in the NIR optical window region (700–900 nm). Animal tissues that were 8 mm deep showed a measurable signal in the NIR-SERS nanoprobe signals for single particle detection. Silver nanoparticles size-tunable absorption spectra can be used to multiplex optical attributes for point-of-care diagnostics. Silver nanoparticles have antimicrobial, anti-neoplastic, antioxidant, and antidiabetic activity. Silver nanoparticles also shows some kind of toxicity like Oral toxicity, Immunotoxicity, Neurotoxicity, Environmental toxicity, Reproductive toxicity etc.

Anisotropic coupling of individual vibrational modes to a Cu(110) substrate.

We present a study on the excitation of individual vibrational modes with ballistic charge carriers propagating along the Cu(110) surface. By means of the molecular nanoprobe technique, where the reversible switching of a molecule-in this case tautomerization of porphycene-is utilized to detect excitation events, we reveal anisotropic coupling of two distinct vibrational modes to the substrate. The N-H bending mode, excited below |E| ≈ 376 meV, exhibits maxima perpendicular to the rows of the Cu(110) substrate and minima along the rows. In contrast, the N-H stretching mode, excited above |E| ≈ 376 meV, displays maxima along the rows and is constant otherwise. This inversion of the anisotropy reflects the orthogonality between the N-H bending and stretching mode. Additionally, we observe an energy-dependent asymmetry in the propagation direction of charge carriers injected into the Cu(110) surface state. Hereby, the anisotropic band structure results in a correlation between the group velocity and the tunneling probability into electronic states of the substrate.

A low-frequency multiple-band sound insulator without blocking ventilation along a pipe

It is challenging to insulate sound transmission in low frequency-bands without blocking the air flow in a pipe. In this work, a small and light membrane-based cubic sound insulator is created to block acoustic waves in multiple low frequency-bands from 200 to 800 Hz in pipes. Due to distinct vibration modes of the membrane-type faces of the insulator and co-action of acoustic waves transmitting along different paths, large sound attenuation is achieved in multiple frequency-bands, and the maximum transmission loss reaches 25 dB. Furthermore, because the sound insulator with a deep subwavelength size is smaller than the cross-sectional area of the pipe, it does not block ventilation along the pipe.

Biosynthesis, Physicochemical and Magnetic Properties of Inverse Spinel Nickel Ferrite System

Nanosized Ni ferrite has been prepared by an ecofriendly green synthesis approach based on the self-combustion method. In this route, the egg white as a green fuel was employed with two different amounts (3 and 10 mL). The XRD results display the formation of a stoichiometric NiFe2O4-type inverse spinel structure with a lattice parameter located at 0.8284 nm and 0.8322 nm. Additionally, the nickel ferrites’ typical crystallite size, as synthesized, ranged between 4 and 18 nm. Indicating the development of ferrite material, FTIR analysis shows two distinctive vibrational modes around 600 cm−1 and 400 cm−1. TEM measurements show the formation of nanosized particles with semispherical-type structure and some agglomerations. As the egg white concentration rises, the surface area, total pore volume, and mean pore radius of the material, as prepared, all decrease, and according to the surface area parameters discovered using BET analysis. Based on VSM analysis, the values of saturation magnetization are 6.6589 emu/g and 37.727 emu/g, whereas the coercivity are 159.15 G and 113.74 G. The as-synthesized Ni ferrites fit into the pseudo-single domain predicated by the squareness values (0.1526 and 0.1824). It is mentioned that increasing the egg white content would promote the magnetization of NiFe2O4.

Molybdenum Oxide/Dopamine-Derived Carbon Electrodes with Enhanced Electrochemical Activity in Energy Storage Systems

Herein, a versatile sol-gel reaction produces new electrode materials consisting of tightly integrated molybdenum oxide and carbon derived from chemically incorporated dopamine molecules, and the materials show enhanced electrochemical activity in nonaqueous Li-ion and aqueous Zn-ion energy storage systems. The novel synthesis entails the oxidation of molybdenum in aqueous solutions of excess and limited dopamine (Dopa) hydrochloride via a hydrogen peroxide-initiated process.The transformation of molybdenum under the condition of Dopa excess (Mo:Dopa molar ratio of 1:1) resulted in the formation of a metastable precipitate of polydopamine (PDopa) spheres encapsulated by Dopa-preintercalated molybdenum oxide, (Dopa)xMoOy@PDopa. Hydrothermal treatment (HT) of (Dopa)xMoOy@PDopa precursor was concomitant with concurrent Dopa carbonization and molybdenum reduction processes, resulting in a formation of spherical matrices of Dopa-derived carbon decorated by MoO2 nanoplatelets (HT-MoO2/C), as determined through FTIR spectroscopy, Raman spectroscopy, and SEM imaging. Annealing (An) of HT-MoO2/C at 600°C under argon atmosphere (AnHT-MoO2/C) led not only to improvements in MoO2 crystallinity, but also to an increased oxidation state of molybdenum and a facilitated interaction between molybdenum-based and Dopa-derived components, resulting in an intimate MoO2/C heterointerface. Consequently, while both HT-MoO2/C and AnHT-MoO2/C showed reversible intercalation-type behavior when evaluated as electrodes versus Li/Li+ in nonaqueous lithium-ion cells, AnHT-MoO2/C demonstrated higher capacities, enhanced capacity retention, better rate capability, and lower charge transfer resistance. The AnHT-MoO2/C electrode showed an initial specific capacity of 260 mAh/g and 67% capacity retention after 50 cycles at 10 mA/g, compared to an initial specific capacity of 235 mAh/g and 47% capacity retention shown by HT-MoO2/C at the same current density. Furthermore, in rate capability experiments, HT-MoO2/C and AnHT-MoO2/C delivered specific capacities of 93 mAh/g and 120 mAh/g respectively at 100 mA/g.When molybdenum was transformed in the presence of Dopa deficit (Mo:Dopa molar ratio of 5:1), a (Dopa)xMoOy powder precursor was isolated, and subsequent hydrothermal treatment of this precursor produced an MoO3 material with carbonized Dopa molecules, HT-MoO3/C. Reference α-MoO3 electrodes (α-MoO3-ref) were synthesized similarly but in the absence of Dopa molecules in the initial sol-gel reaction. The appearance of characteristic D and G bands in the Raman spectra and distinct vibrational modes in the FTIR spectra of HT-MoO3/C confirmed the presence of carbon in its structure. SEM images showed a uniform nanobelt morphology with fragmentation due to interactions between interlayer Dopa and MoO3 layers under the conditions of hydrothermal treatment. HT-MoO3/C delivered a second-cycle capacitance of 141.4 F/g when cycled at 2 mV/s in a -0.25–0.70 V versus Ag/AgCl potential window in 5M ZnCl2 electrolyte, while α-MoO3-ref delivered a nearly two-fold smaller second-cycle capacitance of 76.1 F/g under the same conditions. HT-MoO3/C also showed increased capacitance compared to α-MoO3-ref when cycled at increasing sweep rates up to 20 mV/s. The superior performance of HT-MoO3/C prompted a study of the electrode in an expanded potential window, based on previous reports in which MoO3 showed electrochemical activity at negative potentials versus Ag/AgCl. The HT-MoO3/C electrode exhibited a capacitance of 347.6 F/g on the second cycle when cycled between -0.85–1.00V versus Ag/AgCl at 2 mV/s in 5M ZnCl2 electrolyte.This work demonstrates a new strategy to improve the electrochemical performance of transition metal oxide electrodes for next-generation energy storage systems. Integration of oxides with carbon through the wet chemistry synthesis approaches that involve carbonization of organic molecules can be used to control oxide crystal phase and heterointerfaces leading to improved charge transfer and energy storage properties.

Fabricating Graphene Oxide/h-BN Metal Insulator Semiconductor Diodes by Nanosecond Laser Irradiation.

To employ graphene’s rapid conduction in 2D devices, a heterostructure with a broad bandgap dielectric that is free of traps is required. Within this paradigm, h-BN is a good candidate because of its graphene-like structure and ultrawide bandgap. We show how to make such a heterostructure by irradiating alternating layers of a-C and a-BN film with a nanosecond excimer laser, melting and zone-refining constituent layers in the process. With Raman spectroscopy and ToF-SIMS analyses, we demonstrate this localized zone-refining into phase-pure h-BN and rGO films with distinct Raman vibrational modes and SIMS profile flattening after laser irradiation. Furthermore, in comparing laser-irradiated rGO-Si MS and rGO/h-BN/Si MIS diodes, the MIS diodes exhibit an increased turn-on voltage (4.4 V) and low leakage current. The MIS diode I-V characteristics reveal direct tunneling conduction under low bias and Fowler-Nordheim tunneling in the high-voltage regime, turning the MIS diode ON with improved rectification and current flow. This study sheds light on the nonequilibrium approaches to engineering h-BN and graphene heterostructures for ultrathin field effect transistor device development.