Vibrational Energy Research Articles

Conformational Stability and Vibrational Relaxation as a Function of Halogen Substitution in Benzene sulfonamides: A Theoretical Study

AbstractStudying the vibrational energy flow within molecules can help us better understand their reactivity and facilitate the design of novel functional groups for potential drug candidates. This study examined the conformation of benzene sulfonamide in solvents and vacuum. Potential energy surfaces were computed for the two possible conformations, showing that the conformers’ stability varied with the medium. Additionally, the vibrational energy redistribution of halogen‐substituted benzene sulfonamide conformers was studied in solvents and vacuums. The lifetimes of the halogen stretching mode C−X (where X=F, Cl, or Br) in the substituted benzene sulfonamides were calculated and compared. The solvent and vacuum media lifetimes followed the order: C−Cl>C−Br>C−F. However, the degree of delocalization of vibrational energy was found to vary between them.

A comparative study of analytical representations of potential energy curves for CO in its ground electronic state

AbstractIn this work, a comparative study of four functional forms used to represent potential energy curves (PECs) is presented. The starting point is the Hulburt‐Hirschfelder, followed by the Extended Rydberg potential function, ending with two of the most recent potentials presented in the literature for diatomic systems: the Araújo‐Ballester potential and the Improved Extended Lennard‐Jones potential. The chosen potentials have in common the fact that all their parameters are algebraically calculated, without any fitting procedure, and all of them have direct dependence on Dunham's parameters. The mathematical behavior of these functions for the short‐ and long‐range regions is discussed. As study case, the diatomic system in its ground electronic state was selected. To quantify the accuracy of the potential energy functions, the least‐squares Z‐test method, proposed by Murrell and Sorbie, is used. Furthermore, the main spectroscopic constants and vibrational energy levels are calculated and compared for all potentials.

A pendulum based frequency-up conversion mechanism for vibrational energy harvesting in low-speed rotary structures

Motivated to run a self-powering monitoring sensor on a wind turbine blade, this paper proposes a pendulum based frequency-up converter that effectively captures a low-speed mechanical rotation into high-frequency vibration of a piezoelectric cantilever beam. A system of governing equations for the proposed concept is developed to describe the motion of the pendulum, the vibration of the beam, and the voltage output of the harvester. Design optimization is performed to improve the power generation performance, and the simulation results are verified experimentally. We demonstrate the improved power density from the proposed concept compared to the disk driven frequency-up converters.

Unraveling the excited-state vibrational cooling dynamics of chlorophyll-a using femtosecond broadband fluorescence spectroscopy.

Understanding the dynamics of excited-state vibrational energy relaxation in photosynthetic pigments is crucial for elucidating the mechanisms underlying energy transfer processes in light-harvesting complexes. Utilizing advanced femtosecond broadband transient fluorescence (TF) spectroscopy, we explored the excited-state vibrational dynamics of Chlorophyll-a (Chl-a) both in solution and within the light-harvesting complex II (LHCII). We discovered a vibrational cooling (VC) process occurring over ∼6ps in Chl-a in ethanol solution following Soret band excitation, marked by a notable ultrafast TF blueshift and spectral narrowing. This VC process, crucial for regulating the vibronic lifetimes, was further elucidated through the direct observation of the population dynamics of higher vibrational states within the Qy electronic state. Notably, Chl-a within LHCII demonstrated significantly faster VC dynamics, unfolding within a few hundred femtoseconds and aligning with the ultrafast energy transfer processes observed within the complex. Our findings shed light on the complex interaction between electronic and vibrational states in photosynthetic pigments, underscoring the pivotal role of vibrational dynamics in enabling efficient energy transfer within light-harvesting complexes.

Piezoelectric catalytic activity of strontium titanate/nickel butadione oxime composites

Vibration energy can be seen everywhere in our daily life, such as walking, noise and car engines. If all this energy could be captured and harnessed, it would be an interesting breakthrough in energy. This has been made possible by the discovery of piezoelectric materials, which can convert vibrational energy into electricity by sensing positive and negative charges. In this paper, nickel butadione oxime Ni(dmgH)2 and strontium titanate (SrTiO3) were successfully combined together to form the composite material of nickel butadione oxime/strontium titanate SrTiO3/Ni(dmgH)2 by hydrothermal method. The morphology and composition of the sample were analyzed by XRD, SEM and XPS characterization methods. Strontium titanate and nickel butadione oxime were successfully combined with good crystallinity. According to the degradation results of HTC solution, the piezoelectric catalytic performance of the dye can be significantly improved in a specific time, and the degradation efficiency of HTC solution reaches about 91 %. Compared with the pure Ni(dmgH)2, the composite sample shows better piezoelectric catalytic activity under ultrasonic vibration.

Tuning ZnO-based piezoelectric nanogenerator efficiency through n-ZnO/p-NiO bulk interfacing

ZnO based piezoelectric nanogenerators (PENG) hold immense potential for harvesting ambient vibrational mechanical energy into electrical energy, offering sustainable solutions in the field of self-powered sensors, wearable electronics, human–machine interactions etc. In this study, we have developed flexible ZnO-based PENGs by incorporating ZnO microparticles into PDMS matrix, with ZnO concentration ranging from 5 to 25 wt%. Among these, the PENG containing 15 wt% ZnO exhibited the best performance with an open-circuit output voltage/short-circuit current of ~ 42.4 V/2.4 µA. To further enhance the output performance of PENG, p-type NiO was interfaced with ZnO in a bulk hetero-junction geometry. The concentration of NiO was varied from 5 to 20 wt% with respect to ZnO and incorporated into the PDMS matrix to fabricate the PENGs. The PENG containing 10 wt% NiO exhibits the best performance with an open-circuit output voltage/short-circuit current of ~ 65 V/4.1 µA under loading conditions of 30 N and 4 Hz. The PENG exhibiting the best performance demonstrates a maximum instantaneous output power density ~ 37.9 µW/cm2 across a load resistance of 20 MΩ under loading conditions of 30 N and 4 Hz, with a power density per unit force and Hertz of about ~ 0.32 µW/cm2·N·Hz. The enhanced output performance of the PENG is attributed to the reduction in free electron concentration, which suppresses the internal screening effect of the piezopotential. To assess the practical utility of the optimized PENG, we tested the powering capability by charging various commercial capacitors and used the stored energy to illuminate 10 LEDs and to power a stopwatch displays. This work not only presents a straightforward, cost-effective, and scalable technique for enhancing the output performance of ZnO-based PENGs but also sheds light on its underlying mechanism.

Numerical investigation of thermochemical non-equilibrium effects in Mach 10 scramjet nozzle

Abstract High-temperature non-equilibrium effects are prominent in scramjet nozzle flows at high Mach numbers. Hence, the thermochemical non-equilibrium gas model incorporating the vibrational relaxation process of molecules in the hydrocarbon-air reaction is developed to numerically simulate the flow of a hydrocarbon fuel scramjet nozzle at Mach 10. Besides, the results computed by the models of the thermally perfect gas, chemically non-equilibrium gas, and thermally non-equilibrium chemically frozen gas are applied for comparative studies. Results indicate that chemical non-equilibrium effects are more significant for the flow-field structure and parameters compared to thermal non-equilibrium effects. Meanwhile, vibrational relaxation and chemical reactions interact in the flow-field. The heat released from the chemical reactions in the flow-field of the thermochemical non-equilibrium gas model makes the thermal non-equilibrium effects weaker compared to the thermally non-equilibrium chemically frozen gas model; the chemical reactions in the thermochemical non-equilibrium gas model are more intense than in the chemically non-equilibrium gas model. Due to the slow relaxation of vibrational energy, the thermal non-equilibrium models predicted nozzle thrust lower than the thermal equilibrium models by approximately 1.11% to 1.33%; when considering the chemical reactions, the chemical non-equilibrium models predicted nozzle thrust higher than the chemical frozen models by approximately 7.30% to 7.54%. Hence, the structural design and performance study of the high Mach numbers scramjet nozzle must consider thermochemical non-equilibrium effects.

On non‐hydrogen‐atom products of thermal decomposition of benzyl radical: A theoretical investigation by the transition state theory/multi‐well master equation approach

AbstractBenzyl radical (C7H7), one of the resonantly stabilized hydrocarbon radicals, is one of the significant precursors of polycyclic aromatic hydrocarbons in interstellar media and combustion engines. The unimolecular decomposition of benzyl radical is still incompletely understood despite of its importance and relatively small molecular size. The decomposition reactions of benzyl radical were investigated in the present study by using the ab initio transition state theory (TST) and the multi‐well master equation theory. Specifically, all reaction pathways on the potential energy surface of C7H7 was calculated at the level of QCISD(T)/CBS. For the reactions with multireference characters, the CASPT2(9e,7o)/aug‐cc‐pVTZ method was used to calculate the vibrational frequencies and energies of structures along the one‐dimensional reaction coordinate of the breaking bond. The high‐pressure limits of rate constants for all the reactions were obtained by using the TST except those for C7H6 + H and C6H4 + CH3 by the variational TST. The pressure‐dependent rate constants were obtained by using the multi‐well master equation simulations. The calculated rate constants agree well with available experimental and theoretical data in the literature. Moreover, the present results identify the composition of the non‐hydrogen‐atom production observed in previous experiments, which provide new insights into the reactions of aromatic compounds.

Theoretical Insights into the Vibrational Structure of Carbon Dioxide Rare-Gas Complexes.

Two new flexible-monomer two-body ab initio potential energy surfaces (PESs) for the neon and krypton van der Waals complexes with carbon dioxide were developed, extending our previous work on the Ar-CO2 molecule. The accuracy of the PESs was validated by their agreement with the vibrational spectrum of the rare-gas complexes. The intermolecular and intramolecular vibrational excitation energies were computed at the vibrational self-consistent field and vibrational configuration interaction levels of theory. Overall, the agreement between theory and experiment is excellent throughout the vibrational spectra. The observed slight splitting of the bending modes, resulting from their nondegeneracy in the complexes, is confirmed by our computations, and the results qualitatively agree with the experiment. The splitting increases with increasing polarizability of the rare-gas atom. Additionally, we explain a discrepancy in the mode assignment in the intermolecular region of the neon complex with our VCI character assignment.

DNA as a perfect quantum computer based on the quantum physics principles

DNA is a complex multi-resolution molecule whose theoretical study is a challenge. Its intrinsic multiscale nature requires chemistry and quantum physics to understand the structure and quantum informatics to explain its operation as a perfect quantum computer. Here, we present theoretical results of DNA that allow a better description of its structure and the operation process in the transmission, coding, and decoding of genetic information. Aromaticity is explained by the oscillatory resonant quantum state of correlated electron and hole pairs due to the quantized molecular vibrational energy acting as an attractive force. The correlated pairs form a supercurrent in the nitrogenous bases in a single band π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi$$\\end{document}-molecular orbital (π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi$$\\end{document}-MO). The MO wave function (Φ)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\Phi )$$\\end{document} is assumed to be the linear combination of the n constituent atomic orbitals. The central Hydrogen bond between Adenine (A) and Thymine (T) or Guanine (G) and Cytosine (C) functions like an ideal Josephson Junction. The approach of a Josephson Effect between two superconductors is correctly described, as well as the condensation of the nitrogenous bases to obtain the two entangled quantum states that form the qubit. Combining the quantum state of the composite system with the classical information, RNA polymerase teleports one of the four Bell states. DNA is a perfect quantum computer.

The Near-Sightedness of Many-Body Interactions in Anharmonic Vibrational Couplings.

Couplings between vibrational motions are driven by electronic interactions, and these couplings carry special significance in vibrational energy transfer, multidimensional spectroscopy experiments, and simulations of vibrational spectra. In this investigation, the many-body contributions to these couplings are analyzed computationally in the context of clathrate-like alkali metal cation hydrates, including Cs+(H2O)20, Rb+(H2O)20, and K+(H2O)20, using both analytic and quantum-chemistry potential energy surfaces. Although the harmonic spectra and one-dimensional anharmonic spectra depend strongly on these many-body interactions, the mode-pair couplings were, perhaps surprisingly, found to be dominated by one-body effects, even in cases of couplings to low-frequency modes that involved the motion of multiple water molecules. The origin of this effect was traced mainly to geometric distortion within water monomers and cancellation of many-body effects in differential couplings, and the effect was also shown to be agnostic to the identity of the ion. These outcomes provide new understanding of vibrational couplings and suggest the possibility of improved computational methods for the simulation of infrared and Raman spectra.

Regression Models for Calculating State-to-State Coefficients of the Rate of Vibrational Energy Exchanges

Regression Models for Calculating State-to-State Coefficients of the Rate of Vibrational Energy Exchanges

Vibrational Energy Flow in Molecules Attached to Plasmonic Nanoparticles

Vibrational Energy Flow in Molecules Attached to Plasmonic Nanoparticles

Role of Bi3+ ion substitution on the piezocatalytic degradation performance of lead-free BaTi0·89Sn0·11O3 at low vibrational energy

Harnessing low ultrasonic vibration energy to initiate piezocatalytic-based reactions is increasingly becoming a significant focus due to the current environmental energy crisis. In this study, we report on the potential of heterovalent ion substitution in improving piezocatalytic degradation of Rhodamine B dye (RhB) under the application of low-power ultrasonic vibration. For this purpose, bismuth ions Bi3+ are substituted into the lead-free ferroelectric BaTi0·89Sn0·11O3 (BTSn11-xBi, x = 0, 0.02, 0.04) submicrocubes synthesized using sol-gel method. The structural, morphological, optical and piezocatalytic properties of the prepared materials appear to be significantly influenced by the substituting content. Compared to pure BTSn11 and BTSn11-0.04Bi, BTSn11-0.02Bi exhibits the lowest band gap energy value of 3.22 eV, the smallest particle size value of 283 nm, the strongest piezoelectric current of about 8 μA/cm2, and the lowest required applied field for piezoresponse force microscopy hysteresis loops. The degradation efficiency and the kinetic rate constant are substantially higher for BTSn11-0.02Bi, indicating its enhanced piezocatalytic efficiency. Total organic carbon (TOC) measurements revealed good RhB mineralization using BTSn11-xBi piezocatalysts. Furthermore, the BTSn11-0.02Bi sample demonstrates good reusability and stability by maintaining effective RhB dye degradation for five consecutive cycling tests. These findings suggest that the BTSn11-0.02Bi piezocatalytic system holds significant potential for environmental remediation applications.

Atomic-force-microscopy-based time-domain two-dimensional infrared nanospectroscopy.

For decades, infrared (IR) spectroscopy has advanced on two distinct frontiers: enhancing spatial resolution and broadening spectroscopic information. Although atomic force microscopy (AFM)-based IR microscopy overcomes Abbe's diffraction limit and reaches sub-10 nm spatial resolutions, time-domain two-dimensional IR spectroscopy (2DIR) provides insights into molecular structures, mode coupling and energy transfers. Here we bridge the boundary between these two techniques and develop AFM-2DIR nanospectroscopy. Our method offers the spatial precision of AFM in combination with the rich spectroscopic information provided by 2DIR. This approach mechanically detects the sample's photothermal responses to a tip-enhanced femtosecond IR pulse sequence and extracts spatially resolved spectroscopic information via FFTs. In a proof-of-principle experiment, we elucidate the anharmonicity of a carbonyl vibrational mode. Further, leveraging the near-field photons' high momenta from the tip enhancement for phase matching, we photothermally probe hyperbolic phonon polaritons in isotope-enriched h10BN. Our measurements unveil an energy transfer between phonon polaritons and phonons, as well as among different polariton modes, possibly aided by scattering at interfaces. The AFM-2DIR nanospectroscopy enables the in situ investigations of vibrational anharmonicity, coupling and energy transfers in heterogeneous materials and nanostructures, especially suitable for unravelling the relaxation process in two-dimensional materials at IR frequencies.

Effect of exchange reactions and NO vibrational excitation on shock-heated air component flows

Shock-heated flows of air components are studied using the state-to-state approach taking into account coupled vibrational energy transitions and state-specific chemical reactions. Effects of exchange reactions and vibrational excitation of NO molecules on the fluid-dynamic variables and vibrational distributions are evaluated; the results are compared to experimental data and direct simulations Monte Carlo; satisfactory agreement is obtained. It is shown that the effects are opposite in mixtures with and without initial admixture of NO. Whereas in NO/N2/Ar mixture the effect of NO vibrational excitation is important, in air it is negligible. Exchange reactions in air are more important than in NO/N2/Ar mixture.

Electromagnetic vibrational energy harvester with targeted frequency-tuning capability based on magnetic levitation

Electromagnetic vibrational energy harvester with targeted frequency-tuning capability based on magnetic levitation

Miniaturized and High Volumetric Energy Density Power Supply Device Based on a Broad-Frequency Vibration Driven Triboelectric Nanogenerator.

The widespread vibration is one of the most promising energy sources for IoT and small sensors, and broad-frequency vibration energy harvesting is important. Triboelectric nanogenerators (TENGs) can convert vibration energy into electrical energy through triboelectricity and electrostatic induction, providing an effective solution to the collection of broad-frequency vibration energy. Also, the power supply in constrained and compact spaces has been a long-standing challenge. Here, a miniaturized power supply (MPS) based on a broad-frequency vibration-driven triboelectric nanogenerator (TENG) is developed. The size of the MPS is 38 mm × 26 mm × 20 mm, which can adapt to most space-limited environments. The TENG device is optimized through theoretical mechanical modeling for the external stimuli, it can efficiently harvest vibrational energy in the frequency range of 1-100 Hz and has a high output power density of 134.11 W/cm3. The developed device demonstrates its practical application potential in powering small electronics like LEDs, watches, and timers.

Anthocyanins of Delonix Regia Floral Petals: A Novel Approach on Fluorescence Enhancement, Forster Resonance Energy Transfer Mechanism and Photostability Studies for Optoelectronic Applications.

In this work, we focused on extracting the anthocyanin dye in acetone, butanol, ethanol, and water solvents from Delonix regia flowers by a simple maceration extraction process. The identification of functional group analysis, vibrational studies, energy transfer mechanisms, optoelectronic properties, photostability studies, FRET-assisted potential light emissions and photometric properties of the anthocyanin dyes are successively investigated. FTIR spectroscopy and vibrational studies have confirmed the existence of polyphenolic groups in 2-phenyl chromenylium (anthocyanin) dyes. The optoelectronic results show the least direct bandgap (2.04eV), indirect bandgap (1.55eV), Urbach energy (0.380eV), high refractive index (1.20), dielectric constant (2.794), and high optical conductivity (1.954 × 103 S/m) for the anthocyanin dye extracted found in water solvent. The photoluminescence properties such as Stoke's shift, high quantum yield, and lifetime results show that anthocyanin dyes are promising candidates for red-LEDs and optical materials. The absorption and emission spectra of the anthocyanin dyes follow the mirror image rule and the Franck-Condon factor exists between vibrational energy levels corresponding to all the electronic transitions. The excellent correspondence between the absorption and emission spectra reinforces that the anthocyanins are efficient (46%) FRET probes. Further, photometric properties such as CIE, CRI, CCT and colour purity results of anthocyanins in all studied solvents revealed that this material exhibits orange to red shades (x = 0.48 → 0.54 and y = 0.36 →0.45) and is well suitable for have great potential in the manufacturing of Organic-LEDs and other optoelectronic device applications.

Rainbow energy harvesting using a high-order topological meta-device

We present an innovative rainbow piezoelectric energy harvesting approach that harnesses the untapped potential of the topological meta-device for robust and efficient vibration energy trapping and conversion, from its theoretical rudiments, through design of the device to experimental validation. The rigorously designed meta-device features a series of second-order phononic topological insulators to host topologically protected corner states of different eigenfrequencies. By tailoring and tuning various corner sites, multi-frequency vibrations along a specially engineered channel that supports the edge states spanning these frequencies can be trapped into different corner sites. The vibrational energy is thus converted into electrical energy efficiently using strategically placed piezoelectric harvesters. Experimental results reveal the capability of the device in trapping targeted vibration, in which vibrational energy can be trapped into different corner sites in terms of its frequency, leading to an interesting rainbow energy conversion. This new approach not only implements high-efficiency energy harvesting but also offers enhanced design flexibilities for diverse applications by spatially separating vibrational frequencies.