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Background: Natural and living systems are dynamical systems that demonstrate complex behavior, which appears to be deterministic chaotic, characterized and governed by entropy increase and loss of information throughout their entire lifespan. Lipidic nanoparticles, such as liposomes, as artificial biomembranes, have long been considered appropriate models for studying various membrane phenomena that cell systems exhibit. By utilizing these models, we can better comprehend cellular functions, stability, as well as factors that might alter the cell physiology, leading to severe disease states. In addition, liposomes are well-established drug and vaccine delivery nanosystems, which are present in the market, playing a significant role; therefore, due to their importance, issues concerning their effectiveness and stability are research topics that are constantly investigated and updated. Methods: In this study, the emergent deterministic chaotic behavior of liposomes is described, while evaluation in accordance to their colloidal physical stability, by utilizing established nonlinear dynamics tools, is presented. Two liposomes of different composition and physical stability were developed and a chaotic evaluation on the time series of their size and polydispersity was conducted. Results: The utilized models revealed instability, loss of information and order loss for both liposomes in due time, with important differentiations. An initial interpretation of the results is apposed, whereas the foundations for further investigating possible exploitation of the demonstrated nonlinearity and adaptability of artificial biomembranes is laid, with projection on biosystems. Conclusion: The present approach is expected to impact the application of lipidic nanoparticles and liposomes in various crucial fields, such as drug and vaccine delivery, providing useful information for both the academia and industry.

With the increased demand for controlled deterministic growth of III–V semiconductors at the nanoscale, the impact and interest of understanding defect formation and crystal structure switching becomes increasingly important. Vapor–liquid–solid (VLS) growth of semiconductor nanocrystals is an important mechanism for controlling and studying the formation of individual crystal layers and stacking defects. Using in situ studies, combining atomic resolution of transmission electron microscopy and controlled VLS crystal growth using metal organic chemical vapor deposition, we investigate the simplest achievable change in atomic layer stacking–single twinned layers formed in GaAs. Using Au-assisted GaAs nanowires of various diameters, we study the formation of individual layers with atomic resolution to reveal the growth difference in forming a twin defect. We determine that the formation of a twinned layer occurs significantly more slowly than that of a normal crystal layer. To understand this, we conduct thermodynamic modeling and determine that the propagation of a twin is limited by the energy cost of forming the twin interface. Finally, we determine that the slower propagation of twinned layers increases the probability of additional layers nucleating, such that multiple layers grow simultaneously. This observation challenges the current understanding that continuous uniform epitaxial growth, especially in the case of liquid-metal assisted nanowires, proceeds one single layer at a time and that its progression is limited by the nucleation rate.

Coffee-ring patterns are typical phenomena in evaporation-driven nanoparticles suspended (NPs-laden) droplet. However, NPs motion in droplet fails to exhibit characteristic patterns such as coffee-ring formation in lattice Boltzmann (LB) framework. With features of density diffuse interface, new interfacial schemes composed of density gradient force and interfacial force are proposed and coupled in LB-LE model. They offer a solution to well modulate the NPs dynamics in liquid-vapor interface as droplet deforms and evaporates. In the following simulations of one droplet and multi-droplets evaporation, typical coffee-ring pattern is obtained for one droplet evaporation with hysteresis window 5°

Controlling the drop impact behaviors plays an important role in both designing surface functional materials and improving industrial techniques. Here, the impact dynamics of nanodroplets on "V-shaped" substrates is studied, which is manifested as asymmetrical spreading and retraction behaviors that could be weakened by increasing the angles of the "V" shape, accompanied by the evolution of the shape from leaf-like, stripe-like, to dumbbell-like at v = 20 A/ps. When v increases to 40 A/ps, the previously deposited nanodroplets could be transformed to a rebound one at α = 60 and 90°, which is ascribed to the combined effect of the confinement conditions and the extrusion force. Furthermore, an impact behavior map as a function of impact velocity and angle is depicted, which suggests that a decrease in angles or an increase in the impact velocity is likely to cause the nanodroplets to rebound. More importantly, the results give visible evidence that compared to the flat substrates, the V-shaped structure is advantageous for achieving a fast-rebound behavior even at a low speed of impact, which should be good news for practical applications in many multidisciplinary fields, such as self-cleaning, anti-icing/fogging, pollution prevention, energy storage, and so forth.

We construct a segmental scale force level theory for the center-of-mass diffusion constant and corresponding relaxation time for globally compact unconcatenated ring polymer solutions and melts (degree of polymerization

The control of coalescence and motion of droplets play a significant role in advanced technology and our daily life, and one of the most important approaches is surface design. Here, the microtextured surfaces decorated with wrinkled substrates are designed and studied for coalescence behaviors. The simulation results show that the coalescence speed would be slower on such surfaces due to the downward movement of the droplets induced by the penetration of atoms into the grooves that delays their movement along the coalescence direction, which is considered as a restriction effect. With the increase of the angles and the interval distance of wrinkled structures, the coalescence time becomes longer and the coalescing process becomes unfavorable, resulting from the enhanced restriction effect. More importantly, a composite substrate possessing the original and sub-wrinkled structures has been designed to tune the coalescence dynamics. The results of this work may not only help shed light on understanding the coalescence behaviors on the wrinkled substrates but also propose a feasible method for controlling the liquid coalescence behavior, which is expected to provide some useful implications for practical applications.

The dynamics of complex topological defects in ferroelectric materials is explored using automated experimentation in piezoresponse force microscopy. Specifically, a complex trigger system (i.e., "FerroBot") is employed to study metastable domain-wall dynamics in Pb0.6Sr0.4TiO3 thin films. Several regimes of superdomain wall dynamics have been identified, including smooth domain-wall motion and significant reconfiguration of the domain structures. We have further demonstrated that microscopic mechanisms of the domain-wall dynamics can be identified; i.e., domain-wall bending can be separated from irreversible domain reconfiguration regimes. In conjunction, phase-field modeling was used to corroborate the observed mechanisms. As such, the observed superdomain dynamics can provide a model system for classical ferroelectric dynamics, much like how colloidal crystals provide a model system for atomic and molecular systems.

Branching channels are commonly emerged in a considerable variety of engineering applications, in which most of the fluids present non Newtonian behavior, such as in chemical processes. It is noted that in the material forming process, when one suspends nanoparticles in a basic non Newtonian fluid, a completely new non Newtonian fluid is formed with different rheological characteristics from the former ones. In our present numerical research, considering the side branches inclined at varying angles, we focus on the fluid flow and heat transfer of the laminar power-law nanofluid in a rectangular branching channel under the influences of generalized Reynolds number. Both the consistency coefficient and power-law index of the non Newtonian nanofluid, different from those of the base fluid, are described by empirical formula, dependent on the nanoparticle quantity. Finite element method is applied in the research. It is found that a smaller branch angle α can cause a larger fluctuation in pressure near the branched region. Furthermore, negative pressures exist both in the main and side branch with some certain inclination angle. Above all, the new extensive results of velocity contours, temperature, concentration contours along with pressure drop of the changing rheological models provide detailed information for studies on non Newtonian nanofluids in many intricate industrial applications.

The motion of valence electrons dictates the course of several physical transformations and chemical reactions of great importance in biology and for technological applications. Direct observation ...

Herein, using the femtosecond absorption spectroscopy method, the dynamics of the nonstationary induced absorption spectra of diflavonoid 3,7-dihydroxy-2,8-di(4-methoxyphenyl)-4H, 6H-pyrano[3,2-g]chromene-4,6-dione (DFV) in solvents of different polarities is studied. It is found that the rapid transformation of the transient absorption spectra of DFV in time is due to the processes of intramolecular protons transfer in excited singlet states. For a nonpolar solvent, two protons are transferred in two stages. Initially, during the sub-picosecond times, a form with a single transferred proton is formed from the Frank-Condon state. From this transition state, in a time range of about 9 ps, the second proton is transferred and the two proton transfer tautomer with a high quantum yield of fluorescence ~0.66 is formed, which has the gain band in the transient absorption spectra. For the polar solvent dimethylformamide only the short-lived form with a single proton transferred is formed also during the subpicosecond times practically the same ones as for the nonpolar solution and has a lifetime of about 20 ps. The polarity of the medium, which affects the formation of a set of the “closed” and “open” forms of DFV in the ground state, differing in relative positions in the space of hydroxyl and carbonyl groups, largely determines the mechanism of the intramolecular proton transfer process in the DFV molecule, which consists in the sequential transfer of two protons in a non-polar solvent to form a fluorescent long-lived tautomer and the transfer of one proton in polar solvents to form a short-lived non-fluorescent form.

Although organic photovoltaics has made significant progress since its appearance decades ago, the underlying physics of charge transport in working cells is still under debate. Carrier mobility, determining the carrier extraction and recombination, is one of the most important but complex and still poorly understood parameters. Low-energy charge carrier states acting as traps play a particularly important role in carrier transport. Occupation of these states under real operation conditions of solar cells induces additional complexity. In this study, we use several transient methods and numerical modeling to address carrier transport under actual working conditions of bulk heterojunction organic solar cells based on fullerene and nonfullerene acceptors. We show that occupation of low-energy states strongly depends on the blend materials and the effective electric field. We define conditions when such occupation increases carrier mobility, making it less time-dependent on the microsecond time scale, and when its influence is only marginal. We also show that the initial mobility, determined by carrier relaxation within the high-energy part of the distributed density of states, strongly decreases with time independently of the low-energy state population. Funding Agencies|Vetenskapsradet, project "OPV2.0"; Carl Zeiss Foundation

Neutron scattering is a powerful tool to elucidate the structure and dynamics of systems that are important to geochemists, including ion association in complex aqueous solutions, solvent-exchange reactions at mineral–water interfaces, and reaction and transport of fluids in nanoporous materials. This article focusses on three techniques: neutron diffraction, which can reveal the atomic-level structure of aqueous solutions and solids; quasi-elastic neutron scattering, which measures the diffusional dynamics at mineral–water interfaces; and small-angle neutron scattering, which can show how properties of nanoporous systems change during gas, liquid, and solute imbibition and reaction. The usefulness and applicability of the experimental results are extended by rigorous comparison to computational simulations.

Polypropylene (PP) is being considered as a suitable alternative to the cross‐linked polyethylene (XLPE) insulation as the latter is prone to the space charge accumulation when subjected to the voltage polarity reversals in line‐commutated converter high voltage direct current transmission. This novel contribution correlates the space charge accumulation with the trap distribution inside XLPE and PP under the polarity reversal condition. The pulse electro‐acoustic and surface potential decay methods are used to measure the space charge and trap distributions, respectively. These measurements are carried at different poling durations (1 and 6 h at each polarity) and cycles of voltage polarity reversal (one and three cycles) at the electric field of 60 kV/mm. The XLPE shows more homo and hetero charge accumulation than PP. Dominant shallow traps in the XLPE are responsible for the space charge accumulation, whereas deep traps with higher trap density inhibit space charge accumulation within the PP. Furthermore, the positive and negative threshold fields for the space charge accumulation are measured. It is observed that the space charge can be easily accumulated under the negative electric field. Interestingly, the space charge decays rapidly inside the XLPE with the increased number of polarity reversal cycle. A valid theoretical model is developed to explain the space charge accumulation inside the XLPE and PP. The field‐assisted ionization plays a key role in the space charge accumulation inside the XLPE.

Block copolymer (BCP) phase separation dynamics can be expected to differ significantly from that of the polymer blends due to the constraint of chain connectivity. BCP phase separation dynamics has been studied theoretically, but there has been little experimental evidence to confirm the BCP domain growth scaling laws put forward theoretically. Here, we investigate the dynamics of late-stage lamellar BCP domain coarsening and find that the scaling exponent for lamellar domain growth is ≈1/6 (0.17), irrespective of the annealing temperature, a value close to the scaling exponent of 0.2 predicted by theoretical studies. Furthermore, we show that the prefactors in the domain coarsening equation show Arrhenius dependence on temperature, indicating that the BCP domain growth dynamics is Arrhenius over the temperature range investigated.

We report the study of supramolecular assembling from both experimental and theoretical points of view. A scanning tunneling microscope (STM) and the Johnson–Mehl–Avrami (JMA) equation were, respec...

The review describes the application of nuclear magnetic resonance (NMR) spectroscopy to study kinetics of folding, refolding and aggregation of proteins, RNA and DNA. Time-resolved NMR experiments can be conducted in a reversible or an irreversible manner. In particular, irreversible folding experiments pose large requirements for (i) signal-to-noise due to the time limitations and (ii) synchronising of the refolding steps. Thus, this contribution discusses the application of methods for signal-to-noise increases, including dynamic nuclear polarisation, hyperpolarisation and photo-CIDNP for the study of time-resolved NMR studies. Further, methods are reviewed ranging from pressure and temperature jump, light induction to rapid mixing to induce rapidly non-equilibrium conditions required to initiate folding.

Metal–semiconductor heterostructures are believed to improve hot-electron injection efficiency and influence the photocatalytic performance. Understanding the carrier dynamics at the heterostructur...

Intermolecular interactions in J- and H-aggregates of π-conjugated molecules provide fascinating incentives for excitonic pathways. Investigation regarding exciton dynamics in aggregates of tricarb...

It is now generally agreed that the most dramatic influence of a free surface on local relaxation dynamics occurs over the first 10 nm from the surface. Using the cooperative free volume (CFV) rate...

The effects of the application of constant electric fields on the dynamics of a confined water droplet between two different surfaces are investigated, by using a molecular dynamics method. It is found that the water molecules responded to the electric field, which partially depends on the wettability of the different surfaces. The results reveal that the application of external electric fields causes to create extra pressure on the surfaces, which are theoretically justified. The induced pressure could be experienced by multilayer nano-filters, which are used in desalination processes, with the aid of an external electric field, and may reduce the water filters shelf life.

Although experimental evidence for shear-banding flows in concentrated polymer solutions has accumulated over the last 20 years, the origin of such shear-banding flows is still under heated debate....

The function of proteins depends on their structural flexibility and conformational change. By utilizing silicon-nanowire-based single-molecule electrical circuits, here we present a label-free real-time measurement method that can directly monitor conformational changes of a photosynthetic LH1-RC complex, reaching the ultimate goal of analytic chemistry. These results manifest that the conformation of the LH1-RC complex vibrates among four conformations with strong temperature dependence. At the optimal temperature, States 2 and 3 occupy the main conformations of the LH1-RC complex, and its conformational variation mostly emerges as anharmonic vibration modes, which contributes to photon acquisition and heat transmission. The influence of light activation on occurrence percentage is observed, resulting from light-driven quivering of pigments. Therefore, this avenue proves to be an efficient platform for revealing the fundamental mechanisms of various biological processes in vitro.

How tethered probes report dynamics of host polymers near the glass transition was investigated by changing the length of the flexible linkers and the number of tethering points via imaging rotational fluorescence correlation microscopy and compared with free probes of different sizes. The results show that tethering did not alter the temperature-dependence of polymer dynamics and the shape of the correlation decay reported by the probe; however, the rotation slowed down up to ≈1 decade when both ends of the probe were restricted with short alkyl chain linkers. Upon comparison with the bigger free probe, the mechanism of the slowdown was attributed to the restricted motion upon tethering for tethered probes compared to averaging over different regions of the dynamic heterogeneity for the bigger probe. If the size of the probe was comparable to that of the dynamic heterogeneity of the system, tethered probes accurately report dynamics relevant to glass transition, regardless of tethering conditions.

The relaxation dynamics of polyisoprene (PI) and nitrile butadiene rubber (NBR) chains at the SiO2 interface were directly probed as a function of distance from the SiO2 surface using time-resolved...

We report a fundamentally new nonlinear dynamic system that couples optical autocatalytic behavior to phase evolution in photoreactive binary polymer blends. Upon exposure to light, the blend undergoes spontaneous patterning into a dense arrangement of microscale polymer filaments. The filaments’ growth in turn induces local spinodal decomposition of the blend along their length, thereby regulating the spatially dynamics of phase separation. This leads to the spontaneous organization of a large-scale binary phase morphology dictated by the filament arrangement. This is a new mechanism for polymer blend organization, which couples nonlinear optical dynamics to chemical phase separation dynamics, and offers a new approach to light-directed patterning and organization of polymer and hybrid blends.

We present molecular dynamics simulations of bead-and-spring polymer chains on chemically heterogeneous, energetically disordered surfaces at near-monolayer coverages. The surfaces consist of random mixtures of weakly (W) and strongly (S) attractive sites. We explore systematically the effect of surface composition on the diffusive dynamics of the chains. The polymer diffusion coefficients have a near-Arrhenius temperature dependence, with activation energies which have a nonmonotonic dependence on the fraction of S sites. In other words, we see a nonmonotonic dependence of the interfacial polymer dynamics on its affinity with the surface, when the latter involves some heterogeneity. The maximum activation energy belongs to the surface containing 75% S and 25% W sites, which combines near-maximum average polymer-surface interactions with near-maximum spread or disorder in these interactions. Our results have interesting implications for polymer adhesion and friction and structure-property relationships in polymer nanocomposites.

The mass and phase transitions among intermediate species are unique dynamics in nonclassical crystallization that are under investigation. In this research, we used a pulsed laser to initiate crys...

Though the strong transformation in mechanical properties of glass-forming materials such as amorphous polymers near the glass transition, Tg, has long been recognized and exploited, efforts to und...

We present the results from an extensive atomistic molecular dynamics simulation study of poly(ethylene oxide) (PEO) doped with various amounts of lithium-bis(trifluoromethane)sulfonimide (LiTFSI) salt under the influence of external electric field strengths up to $1\,$V/nm. The motivation stems from recent experimental reports on the nonlinear response of mobilities to the application of an electric field in such electrolyte systems and arising speculations on field-induced alignment of the polymer chains, creating channel-like structures that facilitate ion passage. Hence, we systematically examine the electric field impact on the lithium coordination environment, polymer structure as well as ionic transport properties and further present a procedure to quantify the susceptibility of both structural and dynamical observables to the external field. Our investigation reveals indeed a coiled-to-stretched transformation of the PEO strands along with a concurrent nonlinear behavior of the dynamic properties. However, from studying the temporal response of the unperturbed electrolyte system to field application we are able to exclude a structurally conditioned enhancement of ion transport and surprisingly observe a slowing down. A microscopic understanding is supplied., Main manuscript comprises 30 pages and 13 figures, supplementary information section comprises 30 pages and 28 figures

Floppy molecules can be defined as molecules performing large amplitude vibrations (LAVs). There are different types of LAVs among which the most common are inversion and internal rotation. Molecules with LAVs have been of great interest for a very long time since their dynamic, geometry and molecular spectra were very often considered as a challenge. In the review, we present an outline of the history and development of various theoretical approaches concerning molecules with LAVs. Different types of LAVs are described with the emphasis on inversion tunneling (wagging) and internal rotation (torsion). Furthermore, strategies for building explicit and effective Hamiltonians are given and explained in detail using a hydrazine molecule, which is an exemplary molecule performing three LAVs—two inversions and one internal rotation. Since floppy molecules play a significant role in numerous areas as chemistry, pharmacy, astrophysics, biology, agriculture etc., we also provide an overview of their applications.