Intermolecular hydrogen bonding delineates the stability of non-canonical adenine base pairs: a first-principles study
Non-canonical nucleobase pairs differ from canonical Watson-Crick (WC) pairs in their hydrogen bonding patterns. This study uses density functional theory with empirical dispersion correction to examine the stability and electronic properties of free adenine dimers stabilized by hydrogen bonds along the WC, Sugar (S), and Hoogsteen (H) edges. Dispersion correction is crucial for accurate interaction energy evaluation. The most stable adenine dimer is stabilized by N-H⋯N hydrogen bonds in gas and solvent phases. Binding energy decreases by ∼10.2 kcal mol for dimers with both C-H⋯N and N-H⋯N bonds, increasing the donor-acceptor distance. However, with a sugar-phosphate backbone, dimers with C-H⋯N and N-H⋯N bonds have higher binding energy in an implicit solvent, emphasizing the role of C-H⋯N interactions in stability and nucleic acid folding dynamics. This study highlights noncovalent interactions, such as hydrogen bonding and π-π stacking, within adenine pairs with potential applications in biosensing and DNA-based self-assembly on nanomaterial interfaces.
Theoretical insights into the vibrational spectra and chemical bonding of Ln(III) complexes with a tripodal NO ligand along the lanthanide series
This study provides new theoretical insights into the vibrational spectra of Ln(III) complexes, along the lanthanide series by utilizing the LModeAGen protocol and integrating cutting-edge topological ideas. It provides a quantitative interpretation of the vibrational spectra of [Ln(trensal)] complexes at the B3LYP/MWB(Ln)/6-311++G** ( from 46 (La) to 60 (Lu)) level using the characterization of normal modes from the local vibrational mode theory. This involves decomposing normal vibrational modes related to the complex formation, distortions in the coordination sphere, and C-H vibrations into local mode contributions, offering particularly promising results aimed at the design of highly luminescent lanthanide complexes. This study also delivers key theoretical insights into the chemical bonding of the coordination sphere of [Ln(trensal)] by combining the local vibrational mode theory and the bond overlap model to achieve relationships between bond properties, including those of the Badger-type. Altogether, we present the theoretical framework necessary to quantitatively interpret the vibrational spectra of [Ln(trensal)] complexes along the lanthanide series and gain a better understanding of the lanthanide-ligand chemical bonds, thereby enhancing our understanding of their chemistry and guiding future design efforts.
Nonadiabatic chemical reaction dynamics for the photoisomerization reaction of 3,5-dimethylisoxazole the S electronic state
Nonadiabatic molecular dynamics simulations were performed to explore the photoisomerization pathway from isoxazole (iso-OXA) to oxazole (OXA), considering four electronic states. The XMS-CASPT2 and SA4-CASSCF theories were employed to describe these electronic structures, which were caused by 12 electrons in 11 orbitals with the cc-pVDZ + sp diffuse basis set; the Gaussian s- and p-type diffuse functions were extracted from Dunning's aug-cc-pVDZ function. The potential energy and its gradient at each time step were computed on-the-fly at these levels in the time evolution of the classical trajectory. When the two electronic states were close to each other, the trajectory surface hopping (TSH) judgment between the two adjacent states was carried out by the anteater procedure based on the Zhu-Nakamura formula (ZN-TSH). The two different excited state lifetimes were found to exist in the first electronic state (S), estimated at 10.77 and 119.81 fs. Upon photoexcitation, the N-O bond breaks and energetically relaxes to the ground state (S). In the pathway leading to the main product, azirine formation, the 5-membered ring retains a planar structure while undergoing a non-adiabatic transition with an increasing N-O bond distance. Furthermore, it was verified that a 1,2-shift takes place in the pathway that results in the production of ketenimine, causing a nonadiabatic transition.
First principles study of photocatalytic activity in ZnO-Janus van der Waals heterostructures
The design of type-II van der Waals (vdW) heterostructures is regarded as a promising route to produce green hydrogen photocatalytic water splitting. To this aim, we propose novel vertically stacked vdW heterostructures based on ZnO and Janus VXY (X = Br, Cl, Y = Se, and Te) phases, and investigate their optoelectronic properties and photocatalytic performance by means of density functional theory simulations. The thermal stability of the heterostructures is confirmed by molecular dynamics simulations at 300 K. The HSE06 calculated band structures show that a specific stacking of ZnO-VBrSe and ZnO-VClSe exhibits an indirect band gap with type-II band alignment, while all other stackings exhibit a direct band gap with type-I band alignment. The type-II band alignment, along with the difference in the work function and the electrostatic potential between the ZnO and VXY monolayer, will result in a built-in electric field direct from the ZnO monolayer to the VXY monolayer which is crucial for photogenerated charge separation, and prevents the charge recombinations. The optical absorption coefficient of all the considered ZnO-VXY heterostructures displays the first excitonic peak in the energy range required for photocatalysis applications. Based on the band edge potential analysis, all the studied systems are capable of starting an oxygen evolution reaction spontaneously, while some external stimuli will be required to initiate the hydrogen evolution reaction. The reported results suggest that the proposed ZnO-VXY vdW heterostructures have great potential for photocatalysis and optoelectronic device applications.
Capturing ultrafast energy flow of a heme protein in crowded milieu
Energy flow in biomolecules is a dynamic process vital for understanding health, disease, and applications in biotechnology and medicine. In crowded environments, where biomolecular functions are modulated, comprehending energy flow becomes crucial for accurately understanding cellular processes like signaling and subsequent functions. This study employs ultrafast transient absorption spectroscopy to demonstrate energy funneling from the photoexcited heme of bovine heart cytochrome to the protein exterior, in the presence of common synthetic (Dextran 40, Ficoll 70, PEG 8 and Dextran 70) and protein-based (BSA and β-LG) crowders. The through-space energy transfer mode for ferric and the methionine rebinding mode for ferrous cytochrome show the strongest solvent coupling. The heterogeneous behaviour of crowders, influenced by crowder-protein interactions and caging effects at certain higher concentrations, reveal diverse trends. Notably, protein crowders perturb all transport routes of vibrational energy transfer, causing delays in energy transfer processes. These findings provide significant insights into the basic tenets of energy flow, one of the most fundamental processes, in crowded cellular environments.
Evaluation and optimization of polycarbonate track-etched (PCTE) membranes for direct methanol fuel cells
Direct methanol fuel cells (DMFCs) offer a promising power source by utilizing liquid-state methanol as fuel, providing easy storage and transportability. Currently, DMFCs commonly employ perfluorosulfonic acid membranes, such as the well-known Nafion membrane, as proton exchange membranes. However, perfluorosulfonic acid membranes have significant drawbacks in DMFCs, including a high crossover rate, substantial swelling, poor thermal stability, and elevated costs. The crossover of methanol fuel to the cathode side is particularly detrimental as it can poison the precious Pt catalyst, leading to damage in the fuel cell system. In this manuscript, we propose a non-ionic proton exchange membrane based on the polycarbonate track etched (PCTE) membrane. The aligned nanopores in pristine PCTE, with a regular diameter, facilitate proton passage while mitigating the crossover of methanol molecules. This results in satisfactory proton conductivity and selectivity comparable to that of the commercial Gore membrane. By adding a layer of graphene treated with oxygen plasma for 10 seconds, methanol permeation can be reduced by 16.44%, while achieving a 42.11% increase in proton conductivity compared to the commercial Gore membrane. Furthermore, PCTE material offers a more cost-effective alternative to Gore membrane, with a 18.37% lower swelling ratio and significantly higher stability. These characteristics make PCTE a promising choice for DMFCs, offering potential improvements in performance and cost-effectiveness.
Band alignment in CdS-α-Te van der Waals heterostructures for photocatalytic applications: influence of biaxial strain and electric field
We present a comprehensive theoretical analysis of the structural and electronic properties of a van der Waals heterostructure composed of CdS and α-Te single layers (SLs). The investigation includes an in-depth study of fundamental structural, electronic, and optical properties with a focus on their implications for photocatalytic applications. The findings reveal that the α-Te SL significantly influences the electronic properties of the heterostructure. Specifically, the optical properties of the heterostructure are notably dominated by the contribution of α-Te. The layer-resolved density of states analyses indicate that the valence and conduction bands near the Fermi level are mainly determined by the α-Te SL. Band edge analyses demonstrate a type-I band alignment in the heterostructure, causing charge carriers (electrons and holes) to localize within α-Te. The electronic properties can be further modulated by external strain and electric fields. Remarkably, the CdS-α-Te heterostructure undergoes a transition from type-I to type-II band alignment when subjected to biaxial strain and an external electric field. This may be interesting for the application of the heterostructure for photocatalysis.
A comprehensive guide for accurate conformational energies of microsolvated Li clusters with organic carbonates
Organic carbonates and their mixtures are frequently used in electrolyte solutions in lithium-ion batteries. Rationalization and tuning of the related Li solvation processes are rooted in the proper identification of the representative low-energy spatial structures of the microsolvated Li(S) clusters. In this study, we introduce an automatically generated database of conformational energies (CEs), LICARBCONF806, comprising 806 diverse conformers of Li clusters with 7 common organic carbonates. A number of standard and composite density functional theory (DFT) approaches and fast semi-empirical methods are examined to reproduce the reference CEs obtained at the RI-SCS-MP2/CBS level of theory. A hybrid PBE0-D4 functional paired with the def2-QZVP basis set is the most robust in reproducing the reference values while composite B97-3c demonstrates the best cost-benefit ratio. Contemporary tight-binding semi-empirical methods GFNn-xTB can be used for the filtering of high-energy structures, but their performance worsens significantly when the limited number of low-energy (CE < 3 kcal mol) conformers are to be sorted. Thermal corrections used to convert electronic energies to respective Gibbs free energies and especially corrections imposed by a continuum solvation model can significantly influence both the conformer ranking and the width of the CE distribution. These should be appropriately taken into account to identify lowest energy conformers in solution and at non-zero temperatures. The almost black-box conformation generation workflow used in this work successfully predicts representitative low-energy four-coordinated conformers of Li clusters with cyclic carbonates and unravels the complex conformational nature of the clusters with flexible linear carbonates.
The quantum anomalous Hall effect and strong robustness in two-dimensional p-state Dirac half-metals YX (Y = Li, Na; X = Se, Te)
Based on first-principles calculations, we have predicted a novel group of 2D p-state Dirac half-metal (DHM) materials, YX (Y = Li, Na; X = Se, Te) monolayers. All the monolayers exhibit intrinsic ferromagnetism. Among them, LiTe and NaSe open topologically nontrivial band gaps of 4.0 meV and 5.0 meV considering spin-orbit coupling (SOC), respectively. The Curie temperature of LiTe is 355 K. The non-zero Chern number and the presence of edge states further confirm that the LiTe monolayer is a room-temperature ferromagnetic material and a quantum anomalous Hall (QAH) insulator. Additionally, it is found that YX (Y = Li, Na; X = Se, Te) monolayers exhibit strong robustness against strain and electric fields. Finally, we have proposed the growth of YX (Y = Li, Na; X = Se, Te) monolayers on h-BN substrates, which shows promise for experimental synthesis. Our research indicates that YX (Y = Li, Na; X = Se, Te) monolayers exhibit strong robustness as DHMs, showcasing significant potential for realizing the intrinsic quantum anomalous Hall effect (QAHE).
Inversion of circularly polarized luminescence by electric current flow during transition
The development of chiral compounds exhibiting circularly polarized luminescence (CPL) has advanced remarkably in recent years. Designing CPL-active compounds requires an understanding of the electric transition dipole moment () and the magnetic transition dipole moment () in the excited state. However, while the direction and magnitude of can, to some extent, be visually inferred from chemical structures, remains elusive, posing challenges for direct predictions based on structural information. This study utilized binaphthol, a prominent chiral scaffold, and achieved CPL-sign inversion by strategically varying the substitution positions of phenylethynyl (PE) groups on the binaphthyl backbone, while maintaining consistent axial chirality. Theoretical investigation revealed that the substitution position of PE groups significantly affects the orientation of in the excited state, leading to CPL-sign inversion. Furthermore, we propose that this CPL-sign inversion results from a reversal in the rotation of instantaneous current flow during the S → S transition, which in turn alters the orientation of . The current flow can be predicted from the chemical structure, allowing anticipation of the properties of and, consequently, the characteristics of CPL. This insight provides a new perspective in designing CPL-active compounds, particularly for -symmetric molecules where the S → S transition predominantly involves LUMO → HOMO transitions. If represents the directionality of electron movement during transitions, , the "difference" in electron locations before and after transitions, then could be represented as the "path" of electron movement based on the current flow during the transition.
Conformational dynamics of the pyrene excimer
The conformational dynamics of the pyrene excimer play a critical role in its unique fluorescence properties. Yet, the influence of multiple local minima on its excited-state behavior remains underexplored. Using a combination of time-dependent density functional theory (TD-DFT) and unsupervised machine learning analysis, we have identified and characterized a diverse set of stable excimer geometries in the first excited state. Our analysis reveals that rapid structural reorganization towards the most stable stacked-twisted conformer dominates the excimer's photophysics, outcompeting radiative relaxation. This conformer, which is primarily responsible for the characteristic red-shifted, structureless fluorescence emission, reconciles experimental observations of long fluorescence lifetimes and emission profiles. These findings provide new insights into the excited-state dynamics of excimers. They may inform the design of excimer-based materials in fields ranging from organic electronics to molecular sensing.
Investigation of oxidation-reduction processes of nickel hydroxide precipitation and their carbothermical reduction
Most of the known methods for the chemical production of nickel nano- and microparticles, nickel oxides and hydroxides use various reducing agents and solvents, which are often toxic to the environment. As a rule, these methods are energy-consuming, lengthy and multi-stage, requiring complex equipment. Therefore, the development of a simple and "green" process for the synthesis of nickel-containing particles, including those with magnetic properties, remains one of the priority tasks. In this paper, a new physicochemical method for oxidation-reduction contact deposition of nickel(II) hydroxide nano-microparticles on the surface of magnesium particles from aqueous solutions of nickel-containing electrolyte is proposed. This method is based on the local corrosion of microgalvanic cells' formation with predominant hydrogen depolarization. The proposed method was used to obtain nickel(II) hydroxide samples and study their morphology using SEM, as well as their phase composition using XRD analysis. It has been proven that the shape and structure of the resulting Ni(OH) particles depend on the contact deposition conditions: depending on the surface state of the magnesium particles as a reducing agent, it is possible to obtain both plate-shaped α/β-Ni(OH) particles and three-dimensional β-Ni(OH) "flowers" with different degrees of crystallinity.
A first principles study on the stability and electronic and optical properties of 2D SbXY (X = Se/Te and Y = I/Br) Janus layers
Motivated by the exceptional optoelectronic properties of 2D Janus layers (JLs), we explore the properties of group Va antimony-based JLs SbXY (X = Se/Te and Y = I/Br). Using Bader charges, the electric dipole moment in the out-of-plane direction of all the JLs is studied and the largest dipole moment is found to be in the SbSeI JL. Our results on the formation energy, phonon spectra, elastic constants, and molecular dynamics (AIMD) simulation provide insights into the energetic, vibrational, mechanical, and thermal stability of JLs. After confirming the stability, the three-dimensional phase diagram is investigated to propose the experimental conditions required to fabricate the predicted JLs. Then, the electronic band structure is calculated using different levels of theory, namely, the generalized gradient approximation (GGA), GGA + spin-orbit coupling (GGA + SOC), hybrid Heyd-Scuseria-Ernzerhof (HSE) functional, and many-body perturbation theory-based Green's function method (GW). According to the HSE results, JLs show band gaps between 1.653 and 1.852 eV. The GGA + SOC calculations reveal Rashba spin splitting in these JLs. The calculated carrier mobility using deformation potential theory shows that the electrons have exceptionally high mobility compared to holes, which assists the spatial separation of both charge carriers. The optical spectra are determined using GGA, HSE, and GW methods. With respect to GGA results, HSE and GW optical spectra show a blue shift. More accurate calculations using the GW-Bethe Salpeter equation (BSE) yield optical absorption spectra that are dominated by strong excitonic effects with the excitonic binding energy (BE) in the range of 550-800 meV. Compared to the GW-BSE method, the Mott-Wannier (MW) model predicts a lower BE. A strong e-h coupling is observed for dispersions along K-M in the Brillouin zone from the fat band analysis. Our study suggests that the SbSeI JL is a potential candidate for photocatalytic and photovoltaic applications due to its largest dipole moment and low excitonic binding energy.
Extraction mechanism of phenolic compounds by a choline chloride/glycerol solvent: DFT and molecular dynamics studies
The mechanism of a solvent consisting of choline chloride and glycerol (ChCl/GLY) for extracting phenolic compounds from coal tar was theoretically studied using density functional theory calculations and molecular dynamics simulations. The thermodynamic properties, interaction essence, and molecular dynamics properties of the extraction system were investigated, as well as the influence of ChCl/GLY on the vibration spectra of phenolic compounds. The results show that the solvation free energy of phenolic compounds in ChCl/GLY is more negative than that in coal tar, leading to the spontaneous transfer of phenolic compounds from coal tar to ChCl/GLY. The electrostatic and dispersion interactions between phenolic compounds and ChCl/GLY have similar significance in the extraction process, with interaction energies ranging from -46 to -53 kJ mol. The mixing of phenolic compounds with ChCl/GLY has minimal impact on their internal molecular structure, however, it does reduce the diffusion coefficients of each component in ChCl/GLY and shortens the lifetime of hydrogen bonds in both phenolic compounds and ChCl/GLY. The first shell of each phenolic compound is surrounded by 1.15 chloride ions. Following dissolving in ChCl/GLY, the stretching vibration peaks of phenolic compounds, namely the -OH and C-H/-CH regions, undergo a shift. The results enhance comprehension of the extraction process of phenolic compounds by DES.
Effects of surface oxygen vacancy on CO adsorption and its activation towards CH using metal (Cu, Pd, CuPd) cluster-loaded TiO catalysts: a first principles study
The conversion of the highly selective CO reduction reaction (CORR) into desired value-added multicarbon compounds, like CH, is crucial, but it is mainly constrained by the high energy barrier for C-C coupling and the multi-electron transfer process. Herein, M/TiO and M/TiO-V (M = Cu, Pd, CuPd, and V refers to the surface oxygen vacancy) catalysts were designed to study the CORR towards CH by using density functional theory (DFT). We found that the surface oxygen vacancy enhances the adsorption ability of studied catalysts. The CO molecule is strongly adsorbed at the metal-surface interfaces of Cu/TiO-V, Pd/TiO-V and CuPd/TiO-V catalysts with adsorption energies of -1.79, -1.75 and -1.71 eV, respectively. Furthermore, the C-C coupling reaction does not occur on the Cu and PdCu cluster sites of the M/TiO-V catalysts, indicating the inactivity of these sites for C products. However, Pd/TiO, CuPd/TiO and M/TiO-V interfaces favor the C-C coupling reaction and therefore have the potential to reduce CO to C products. Additionally, the Gibbs free energy calculations reveal that the surface oxygen vacancy improves the OCCO hydrogenation to CH at the CuPd/TiO-V interface.
Fourier-transform microwave spectroscopy of the ClCO radical
Scientists are interested in the CO cycle in the atmosphere of Venus. In order to study the cycle involving the reaction with chlorine, it is necessary to investigate the reaction intermediate, the ClCO radical, which can be used to prove the hypothesis of the CO cycle on Venus. In the present work, we observed the pure rotational transitions of the ClCO radical by FTMW spectroscopy. Due to the large rotational constant , only = 0 a-type transitions were observed. Based on the experimental results of the ClCO radical, it was found that the unpaired electron is mainly located in the in-plane p orbital of the central carbon atom. The distribution of the unpaired electron on the chlorine nucleus does not extend toward the direction of the Cl-C bond, which is different from the case of the FCO radical.
Engineering highly efficient porphyrin sensitizers through metal, ligand and bridge modification: a DFT study
This work presents a systematic investigation of porphyrin sensitizers for application in dye-sensitized solar cells (DSSCs). Density functional theory calculations, including both static and time-dependent methods, were employed to evaluate a series of candidate dyes for their potential to achieve high power conversion efficiency. The well-established SM315 dye, known for its record-breaking PCE of 13%, was adopted as a reference point. A range of metal atoms including alkaline-earth and 3d transition metals were screened, Ca was identified as the most promising metal for light capture and conversion. Ca-porphyrin-based sensitizer was further modified by introducing different axial ligands and four distinct bridging units. The designed dyes exhibit red-shifted absorption spectra and optimal frontier orbital alignment with the semiconductor's conduction band, promoting efficient light capture and charge transfer. In addition to these core parameters, a comprehensive analysis of light harvesting efficiency (LHE), reorganization energy (), short-circuit current density (), exciton binding energy (EBE), open-circuit voltage (), electron transfer rate (), polarization () and hyperpolarization () collectively paint a clear picture of superior light capture, efficient charge transport dynamics, and minimized energy losses within the designed dyes. This ultimately translates to the remarkable power conversion efficiency (PCE) exceeding 27% achieved by the specifically designed dye with the Ca as metal atom, 4,4'-bipyridine as axial ligands and cyclopenta-1,3-diene as bridging unit, surpassing the performance of SM315 dye (13% PCE). This systematic study combines the design of high-performance porphyrin sensitizers through molecular engineering with a comprehensive investigation of their impact on DSSC function using advanced computational methods.
Uniaxial tensile strain impact on 1T-NbS monolayers as cathode material for lithium-sulfur batteries
The application of lithium-sulfur (Li-S) batteries as efficient energy storage systems is hindered by the polysulfide shuttle and expansion effects. To overcome these obstacles, we employed density functional theory (DFT) to explore the 1T-NbS monolayer as a cathode material for Li-S batteries, particularly focusing on the effects of uniaxial tensile strain. Our results indicate that the pristine 1T-NbS monolayer presents a balanced adsorption affinity for LiPSs, thereby mitigating the shuttle effect. The bond formation information is investigated through comprehensive analysis of charge transfer, physical/chemical adsorption, and projected crystal orbital Hamiltonian population (pCOHP). The projected density of states (PDOS) analysis reveals the role of sulfur atoms near the Fermi surface in the lithiation process. Notably, the system keeps superior metallic characteristics, alongside a diminished decomposition energy barrier (0.45 eV), lowered lithium-ion migration energy barrier (0.16 eV), and a diminished positive Gibbs free energy change (0.41 eV) during the sulfur reduction reaction (SSR). The imposition of uniaxial tensile strain on the 1T-NbS monolayer improves its adsorptive capacity for LiPSs and bolsters the retention of lithium-sulfur aggregates. These insights underscore the role of tensile strain in amplifying the efficiency of two-dimensional transition metal dichalcogenides as cathode materials of Li-S batteries.
Nanoscopic spontaneous poration as a precursor to protein-based transport in early protocells
Understanding the mechanisms of material transport in protocells before the emergence of proteins is crucial to uncovering the origins of cellular life. While previous research has demonstrated that direct permeation is a feasible transport mechanism for protocells with fatty acid-based membranes, this process becomes less efficient as membranes evolve to include phospholipids-before the advent of protein transport systems. To address this knowledge gap, we investigated fundamental processes that could have facilitated molecular transport in such protein-free systems. In this study, we identify and characterize nanoscopic transient pores spontaneously forming in phospholipid vesicle membranes, likely driven by osmotic imbalances. We for the first time pinpointed individual pore formation events by observing intermittent fluorescence bursts resulting from the brief influx of fluorescent tracers into the vesicular interior. Kinetic analysis of these burst profiles reveals that these membrane pores possess lifespans of about fourteen milliseconds and radii of around twenty nanometers, suggesting that they are sufficiently large and long-lived to enable the transport of essential nutrients and metabolic products. These findings are confirmed by conventional pore-sizing methods using tracers of various sizes and supported by numerical simulations. Importantly, this transient pore formation does not compromise the integrity of the membrane, nor does it require the participation of proteins or peptides. Our results indicate that spontaneous transient poration provides a viable mechanism for molecular transport through the membrane of primitive cellular entities, offering an alternative to simple diffusion or direct permeation. This study sheds light on potential evolutionary strategies employed by pre-protein protocellular entities to facilitate material transport, contributing to our understanding of the early mechanisms that may have driven the origin of life.
The structural and functional impacts of rationally designed cyclic peptides on self-assembly-mediated functionality
Compared with their linear counterparts, cyclic peptides, characterized by their unique topologies, offer superior stability and enhanced functionality. In this review article, the rational design of cyclic peptide primary structures and their significant influence on self-assembly processes and functional capabilities are comprehensively reviewed. We emphasize how strategically modifying amino acid sequences and ring sizes critically dictate the formation and properties of peptide nanotubes (PNTs) and complex assemblies, such as rotaxanes. Adjusting the number of amino acid residues and side chains allows researchers to tailor the diameter, surface properties, and functions of PNTs precisely. In addition, we discuss the complex host-guest chemistry of cyclic peptides and their ability to form rotaxanes, highlighting their potential in the development of mechanically interlocked structures with novel functionalities. Moreover, the critical role of computational methods for accurately predicting the solution structures of cyclic peptides is also highlighted, as it enables the design of novel peptides with tailored properties for a range of applications. These insights set the stage for groundbreaking advances in nanotechnology, drug delivery, and materials science, driven by the strategic design of cyclic peptide primary structures.
Self-healing in dielectric capacitors: a universal method to computationally rate newly introduced energy storage designs
Metalized-film dielectric capacitors provide lump portions of energy on demand. While the capacities of various capacitor designs are comparable in magnitude, their stabilities make a difference. Dielectric breakdowns - micro-discharges - routinely occur in capacitors due to the inevitable presence of localized structure defects. The application of polymeric dielectric materials featuring flexible structures helps obtain more uniform insulating layers. At the modern technological level, it is impossible to completely avoid micro-discharges upon device exploitation. Every micro-discharge results in the formation of a soot channel, which is empirically known to exhibit a semiconductor behavior. Because of its capability to conduct electricity, the emerged soot channels harm the subsequent capacitor performance and decrease the amount of stored energy. The accumulation of the soot throughout a dielectric capacitor ultimately results in irreversible overall failure. We have developed a universal method for predicting the composition and evaluating the properties of the decomposition products obtained after the dielectric breakdown of a metalized film capacitor. This method applies to both existing and newly developed designs of capacitors. In our work, we compared samples based on polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), and Kapton. We found that the decomposition of the PP-based composition yields the greatest number of gaseous products. The corresponding soot has the lowest electrical conductivity compared to other samples. The smallest fraction of gaseous products and the highest conductivity corresponded to the Kapton-based system. According to the electrical conductivity, the obtained soot samples have been ranked in the following order: PP < PET < PC < Kapton. The resulting gas phase content is as follows: PP (12.3 wt%) > PC (6.4 wt%) > PET (6.2 wt%) > Kapton (5.1 wt%). The obtained results are in agreement with the experimental data on the self-healing efficiency of metalized-film capacitors. The novel method qualitatively correctly rates the performances of the known capacitors. The method relies on various electronic-structure simulations and potential landscape explorations. The reported advances open an impressive avenue to computationally probe thousands of hypothetical capacitor designs and boost engineering practices.