Molecular Motion Research Articles

The Interaction and Rheological Behavior of Preformed Gel Particles with Surfactants

Heterogeneous combination flooding systems are composed of surfactant and viscoelastic preformed gel particles (PGP) that can migrate in the pores. The interactions between PGP and surfactants have an important impact on the system. In our research described here heterogeneous aqueous suspensions of PGP and an anionic surfactant (sodium dodecyl benzene sulfonate, SDBS) or a nonionic surfactant coconut oil alkanolamide, (CDEA) were prepared. The effects of SDBS and CDEA on the swelling and rheological properties of the PGP was investigated. In addition, the influence of SDBS and CDEA on the thermal effects of PGP was studied. The results showed that the swelling ratio, apparent viscosity and storage modulus of the PGP decreased with the increase of SDBS concentration. On the contrary, the CDEA increased the swelling ratio and the rheological properties of PGP. The specific heat capacity ( C p ) of PGP increased with the SDBS concentration and decreased with the CDEA concentration. Similar to the rheological behavior, the influence of interactions on the PGP molecular thermal motion was related to the concentration of the surfactants. Therefore, studying the variation of C p with concentration can provide reference for the reasonable dosage of surfactants in heterogeneous oil displacement systems and a new perspective for investigating the interaction between surfactant and PGP or other polymers.

Multitarget Ensemble Docking of Potent Anticancer and Antioxidant Active Compounds from the Acacia auriculiformis and Acacia crassicarpa

Bioactive chemicals derived from Acacia auriculiformis and A. crassicarpa have the potential to be developed as sources of anti-cancer raw materials and antioxidants, given that these plants are fast-growing species with medicinal capability. The in silico method was successful in identifying these bioactive chemicals for the preliminary study. Using an in silico approach, this work aimed to identify the most potent compounds as inhibitors of six cancer and stress oxidative therapy-targeted proteins from these two distinct Acacia species. Seventeen out of the 37 compounds examined exhibited low affinity and satisfied the drug-likeness criterion. Five active chemicals were identified by redocking analysis: auriculoside, 3-(3,4-dihydroxybenzyl)-7-hydroxychroman-4-one, kaempferol 7-O-glucoside, quercetin 7-O-glucoside, and keto-teracacidin. According to simulations of molecular dynamics, molecular motion occurs with a root mean square deviation of less than four and generates at least eleven receptor conformations for 0 to 100 ns. Auriculoside showed the lowest average binding energy against four receptors in colorectal and breast cancer, as determined by ensemble docking, followed by 3-(3,4-dihydroxybenzyl)-7-hydroxychroman-4-one, quercetin 7-O-glucoside, and kaempferol 7-O-glucoside. Auriculoside shown multitarget inhibitory effect against colorectal cancer by inhibiting cyclin dependent kinase-6 and breast cancer by inhibiting epidermal growth factor receptor and mammalian target of rapamycin. Auriculoside has the powerful ability to inhibit glycogen synthase kinase-3 beta, hence regulating oxidative stress. Kaempferol 7-O-glucoside and quercetin 7-O-glucoside also exhibited a possible single protein targeting method against breast cancer. These findings are essential for future research targeted at developing these plants as potent natural therapeutic raw materials and for isolating or synthesizing compounds with anticancer and oxidative stress-regulating antioxidant properties.

Electrochemical Synthesis of Sound: Hearing the Electrochemical Double Layer.

Electrochemical double layers (EDLs) govern the operation of batteries, fuel cells, electrochemical sensors, and electrolyzers. However, their invisible nature makes their properties and function difficult to conceptualize, creating an impediment to the broader understanding of double-layer function required for future technologies in energy storage and chemical synthesis. To render the behavior of electrochemical interfaces more intuitive, we made the rearrangement of interfacial components audible by employing the EDL as a variable element in a relaxation oscillator circuit. Connecting the circuit to a speaker generated an audible output corresponding to the change in potential resulting from EDL rearrangement. Variations in the applied voltage, electrolyte concentration and identity, as well as in the electrode material, yielded audible frequency variations that provide an intuitive understanding of EDL behavior. We expect that hearing the trends in behavior will provide a helpful and alternative method for understanding molecular movement at the electrochemical interface.

Study on the Effect of Cations on the Surface Energy of Nano-SiO2 Particles for Oil/Gas Exploration and Development Based on the Density Functional Theory.

Although nano SiO2 exhibits excellent application potential in the field of oil and gas exploration and development, such as drilling fluid, enhanced oil/gas recovery, etc., it is prone to agglomeration and loses its effectiveness due to the action of cations in saline environments of oil and gas reservoirs. Therefore, it is crucial to study the mechanism of the change in energy between nano SiO2 and cations for its industrial application. In this paper, the effect of cations (Na+, K+, Ca2+, and Mg2+) on the surface energy of nano SiO2 particles is investigated from the perspective of molecular motion and electronic change by density functional theory. The results are as follows: Due to the electrostatic interactions, cations can migrate towards the surface of nano SiO2 particles. During the migration process, monovalent cations are almost unaffected by water molecules, and they can be directly adsorbed on the surface by nano SiO2 particles. However, when divalent cations migrate from a distance to the surface of nano SiO2 particles, they can combine with water molecules to create an energy barrier, which can prevent them from moving forward. When divalent cations break through the energy barrier, the electronic kinetic energy between them and nano SiO2 particles changes more strongly, and the electrons carried by them are more likely to break through the edge of the atomic nucleus and undergo charge exchange with nano SiO2 particles. The change in interaction energy is more intense, which can further disrupt the configuration stability of nano SiO2. The interaction energy between cations and nano SiO2 particles mainly comes from electrostatic energy, followed by Van der Waals energy. From the degree of influence of four cations on nano SiO2 particles, the order from small to large is as follows: K+ < Na+ < Mg2+ < Ca2+. The research results can provide a theoretical understanding of the interaction between nano SiO2 particles and cations during the application of nano SiO2 in the field of oil and gas exploration and development.

Pyrene-Based Deep-Blue Fluorophores with Narrow-Band Emission.

High-efficiency narrow-band luminescent materials have attracted intense interest, resulting in their great colorimetric purity. This has led to a variety of high-tech applications in high-definition displays, spectral analysis, and biomedicine. In this study, a rigid pyrene core was employed as the molecular backbone, and four narrow-band pyrene-based blue emitters were synthesized using various synthetic methods (such as Lewis-acid catalyzed cyclization domino reactions, Pd-catalyzed coupling reactions like Suzuki-Miyaura and Sonogashira). Due to the steric effect of the hydroxy group at the 2-position, the target compounds exhibit deep blue emission (<429 nm, CIEy < 0.08) with full width at half-maximum (FWHM) less than 33 nm both in solution and when solidified. The experimental and theoretical results indicated that the substituents at the 1- and 3-positions afford a large dihedral angle with the pyrene core, and the molecular motion is almost fixed by multiple intra- and intermolecular hydrogen bonding interactions in the crystallized state, leading to a suppression of the vibrational relaxation of the molecular structure. Moreover, we observed that the suppression of the vibrational relaxation in the molecular structures and the construction of rigid conjugated structures can help develop narrow-band organic light-emitting materials.

Exploring Efficient Dual-Phase Emissive Fluorophores with High Mobility by Integrating a Rigid Donor and Flexible Acceptor.

Developing luminogens with a high emission efficiency in both single-molecule and aggregate states, as well as high mobility, shows promise for advancing the iteration and update of organic optoelectronic materials. However, achieving a delicate balance between the plane configuration of luminophores and the strong exciton interactions of aggregates is a formidable task from the molecular design perspective. This dilemma was overcome by integrating a rigid donor and flexible acceptor to establish donor-acceptor (D-A) type emitters. The π-conjugate-extended donor ensures the substantial planarity of these molecules, allowing strong emission in solution with photoluminescence quantum yield values of 86% and 75%. Furthermore, the restricted molecular motion of the aggregation-induced emission moiety and the formation of J-aggregates reduce the quenching effect, leading to a high emissive efficiency of 85% and 91% in the aggregate state. The mildly distorted D-A geometry builds moderate electrostatic interaction, resulting in high mobility with μM,h of 7.12 × 10-5 and 3.27 × 10-4 cm2/V s. Additionally, an improved synthesized procedure for terminal E-configured acrylonitrile with metal-free and concise reaction conditions is presented. The successful application of the synthesized compounds in organic light-emitting diode devices demonstrates the practicability of the molecular design strategy with connecting a rigid donor and flexible acceptor.

Study of the matrix–particle interactions of polymer nanocomposites in the low‐frequency regime

AbstractIn this study, the dynamic moduli, in a wide frequency scale, of two series of polymer nanocomposites were qualitatively discussed. The dynamic mechanical analysis experimental results of polylactic acid (PLA)/silica nanocomposites, as well as PLA/graphene oxide‐carbon nanotubes hybrid nanocomposites, were employed. The study has been focused on the low‐frequency regime, estimating the terminal incline of the storage and loss modulus. In addition, the relative position of the two dynamic moduli was examined and results about the nanofiller's dispersion quality, as well as their interaction with the matrix were extracted. The consequence of nanofiller kind, loading, and distribution quality on the mechanical enhancement was thoroughly studied. In addition, the storage modulus master curves could be simulated by a model from the literature, considering the topological constraints of an entangled polymer reinforced by nanoparticles. It was shown that by adopting the linear contribution of the free and adsorbed chains to the relaxation function, the details of the master curves could be captured in the entire frequency range, quite effectively. The estimated model parameter values confirmed the analysis of the matrix–particle interactions.Highlights The SiO2 size effect on the terminal zone slope of the dynamic moduli. Successful description of the dynamic moduli by the tube reptation concept. Analysis of the physical meaning of the model parameter values. Relation between SiO2 dispersion quality and molecular motion restriction. Matrix‐particle interactions is the governing mechanism of enhancement.

Boosting Theranostic Performance of AIEgens Using Nanocatalyzer for Robust Cancer Immunotherapy

AbstractHigh‐performance theranostic systems are of paramount importance for achieving precise image‐guided cancer immunotherapy. Here, a novel nanoplatform is presented that integrates aggregation‐induced emission luminogen (AIEgen) with prussian blue (PB) nanocatalyzer for robust cancer immunotherapy. The AIEgen with dimethylamine substitution demonstrates compelling near‐infrared (NIR) light‐induced photothermal conversion and photodynamic therapy (PDT) capabilities. By incorporating AIEgen into porous PBNPs, and further enveloped within M1 macrophage membrane, a tumor‐specific theranostic nanoagent is constructed. This strategic integration effectively constrains the molecular motion of AIEgen, leading to amplified NIR‐II fluorescence brightness and PDT attributes. Moreover, PBNPs can catalyze tumor‐overexpressed H2O2 to generate oxygen to boost PDT efficacy, and PB's NIR absorption also intensifies photoacoustic imaging and photothermal effect. The integration of NIR‐II fluorescence and photoacoustic imaging provides comprehensive information for photoimmunotherapy in orthotopic breast cancer‐bearing mice. Leveraging its potent immunogenic cell death effect, the nanoagent not only significantly inhibits cancer growth, but also generates a whole‐cell therapeutic cancer vaccine to protect mice from tumor rechallenge. In highly malignant post‐surgery breast cancer models, the nanoagent enables both accurate identification of residual tumors and efficient inhibition of postoperative tumor recurrence and pulmonary metastasis. This study will offer valuable insights for creating highly efficacious and multifaceted photoimmunotherapy protocols.

Modulation of Heterotypic and Homotypic Interactions to Visualize the Evolution of Organic Aggregates in a Fluorescence Turn-on Manner.

The abnormal evolution of membrane-less organelles into amyloid fibrils is a causative factor in many neurodegenerative diseases. Fundamental research on evolving organic aggregates is thus instructive for understanding the root causes of these diseases. In-situ monitoring of evolving molecular aggregates with built-in fluorescence properties is a reliable approach to reflect their subtle structural variation. To increase the sensitivity of real-time monitoring, we presented organic aggregates assembled by TPAN-2MeO, which is a triphenyl acrylonitrile derivative. TPAN-2MeO showed a morphological evolution with distinct turn-on emission. Upon rapid nanoaggregation, it formed non-emissive spherical aggregates in the kinetically metastable state. Experimental and simulation results revealed that the weak homotypic interactions between the TPAN-2MeO molecules liberated their molecular motion for efficient non-radiative decay, and the strong heterotypic interactions between TPAN-2MeO and water stabilized the molecular geometry favorable for the non-fluorescent state. After ultrasonication, the decreased heterotypic interactions and increased homotypic interactions acted synergistically to allow access to the emissive thermodynamic equilibrium state with a decent photoluminescence quantum yield (PLQY). The spherical aggregates were eventually transformed into micrometer-sized blocklike particles. Under mechanical stirring, the co-assembly of TPAN-2MeO and Pluronic F-127 formed uniform fluorescent platelets, inducing a significant enhancement in PLQY. These results decipher the stimuli-triggered structural variation of organic aggregates with concurrent sensitive fluorescence response and pave the way for a deep understanding of the evolutionary events of biogenic aggregates.

Inside Cover: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. Int. Ed. 9/2024)

Inside Cover: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. Int. Ed. 9/2024)

Innentitelbild: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. 9/2024)

Innentitelbild: Massive Molecular Motion in Crystal Leads to an Unexpected Helical Covalent Polymer in a Solid‐state Polymerization (Angew. Chem. 9/2024)

Refractometry of Pure Water and Normal Saline under the Influence of Taheri Consciousness Fields

A change in the refractive index of light in a medium indicates effective molecular interactions in creating the optical density of that medium. In general, changes in molecular content resulting from the formation of solvent and solute molecular systems lead to changes in the refractive index of a solution. In continuation of studies on the effect of T-Consciousness Fields (TCFs) on water and its well-known solution on Earth's surface with medicinal value, normal saline, this study investigates the impact of TCFs on the refractive index of pure water and normal saline, compared to the control. According to the results, TCFs generally lead to an increase in the refractive index in the samples, indicating changes in molecular motion or, in other words, an increase in the optical density of both water and normal saline samples. In pure water samples, there is no significant difference in the effect of various TCFs, but in normal saline samples, the highest impact belongs to TCF3, followed by TCF 2 and 1. Further investigations into molecular changes in the samples are in the authors' research agenda.

Characterizing ATP processing by the AAA+ protein p97 at the atomic level

The human enzyme p97 regulates various cellular pathways by unfolding hundreds of protein substrates in an ATP-dependent manner, making it an essential component of protein homeostasis and an impactful pharmacological target. The hexameric complex undergoes substantial conformational changes throughout its catalytic cycle. Here we elucidate the molecular motions that occur at the active site in the temporal window immediately before and after ATP hydrolysis by merging cryo-EM, NMR spectroscopy and molecular dynamics simulations. p97 populates a metastable reaction intermediate, the ADP·Pi state, which is poised between hydrolysis and product release. Detailed snapshots reveal that the active site is finely tuned to trap and eventually discharge the cleaved phosphate. Signalling pathways originating at the active site coordinate the action of the hexamer subunits and couple hydrolysis with allosteric conformational changes. Our multidisciplinary approach enables a glimpse into the sophisticated spatial and temporal orchestration of ATP handling by a prototype AAA+ protein.

Single-molecular diffusivity and long jumps of large organic molecules: CoPc on Ag(100).

Energy dissipation and the transfer rate of adsorbed molecules do not only determine the rates of chemical reactions but are also a key factor that often dictates the growth of organic thin films. Here, we present a study of the surface dynamical motion of cobalt phthalocyanine (CoPc) on Ag(100) in reciprocal space based on the helium spin-echo technique in comparison with previous scanning tunnelling microscopy studies. It is found that the activation energy for lateral diffusion changes from 150meV at 45-50K to ≈100meV at 250-350K, and that the process goes from exclusively single jumps at low temperatures to predominantly long jumps at high temperatures. We thus illustrate that while the general diffusion mechanism remains similar, upon comparing the diffusion process over widely divergent time scales, indeed different jump distributions and a decrease of the effective diffusion barrier are found. Hence a precise molecular-level understanding of dynamical processes and thin film formation requires following the dynamics over the entire temperature scale relevant to the process. Furthermore, we determine the diffusion coefficient and the atomic-scale friction of CoPc and establish that the molecular motion on Ag(100) corresponds to a low friction scenario as a consequence of the additional molecular degrees of freedom.

Coupled Electron-Nuclear Dynamics Induced and Monitored with Femtosecond Soft X-ray Pulses in the Amino Acid Glycine.

The coupling of electronic and nuclear motion in polyatomic molecules is at the heart of attochemistry. The molecular properties, transient structures, and reaction mechanism of these many-body quantum objects are defined on the level of electrons and ions by molecular wave functions and their coherent superposition, respectively. In the present contribution, we monitor nonadiabatic quantum wave packet dynamics during molecular charge motion by reconstructing both the oscillatory charge density distribution and the characteristic time-dependent nuclear configuration coordinate from time-resolved Auger electron spectroscopic data recorded in previous studies on glycine molecules [Schwickert et al. Sci. Adv. 2022, 8, eabn6848]. The electronic and nuclear motion on the femtosecond time scale was induced and probed in kinematically complete soft X-ray experiments at the FLASH free-electron laser facility. The detailed analysis of amplitude, instantaneous phase, and instantaneous frequency of the propagating many-body wave packet during its lifecycle provides unprecedented insight into dynamical processes beyond the Born-Oppenheimer approximation. We are confident that the refined experimental data evaluation helps to develop new theoretical tools to describe time-dependent molecular wave functions in complicated but ubiquitous non-Born-Oppenheimer photochemical conditions.

Constructing [2.2]Paracyclophane‐Based Ultrasensitive Optical Fluorescent‐Phosphorescent Thermometer with Cucurbit[8]uril Supramolecular Assembly

AbstractThe pursuit of developing novel approaches to fully organic and efficient phosphorescent materials is in high demand. The optical activity of such functional, organic phosphorescent/fluorescent materials may exhibit great temperature dependence, allowing their application as advanced, highly sensitive molecular thermometers. In this study, a rational strategy involving host–guest complexation and polymerization of [2.2]paracyclophane (PCP) based molecules with cucurbit[8]uril (CB8) to suppress the molecular motion and promote temperature‐dependent phosphorescence is presented. The rigid cavity of CB8 provides an ideal microenvironment to host PCP molecules 1 and 2, significantly enhancing the photophysical performance after complexation. Co‐polymerizing phosphors 1 and 2 with acrylamide is an efficient method for improving phosphorescence. Incorporating CB8 into the resulting P‐1 and P‐2 polymers enhances phosphorescence performance. Importantly, the obtained materials exhibit a big structure‐dependent spectral shift and change of phosphorescence lifetimes with temperature, allowing novel, phosphorescence‐based, and purely organic optical thermometers to be developed. The practical applications of PCP‐based luminescent materials in temperature sensing via a multi‐parameter approach are showcased, i.e., using fluorescence spectral shift and changes in bandwidth, as well as phosphorescence lifetimes, exhibiting thermal sensitivity of ≈17.7 cm−1 °C−1, 47.8 cm−1 °C, and 5.2% °C−1, respectively.

Symmetry-Breaking Triplet Excited State Enhances Red Afterglow Enabling Ubiquitous Afterglow Readout.

Molecular vibrations are often factors that deactivate luminescence. However, if there are molecular motion elements that enhance luminescence, it may be possible to utilize molecular movement as a design guideline to enhance luminescence. Here, the authors report a large contribution of symmetry-breaking molecular motion that enhances red persistent room-temperature phosphorescence (RTP) in donor-π-donor conjugated chromophores. The deuterated form of the donor-π-donor chromophore exhibits efficient red persistent RTP with a yield of 21% and a lifetime of 1.6s. A dynamic calculation of the phosphorescence rate constant (kp) indicates that the symmetry-breaking movement has a crucial role in selectively facilitating kp without increasing nonradiative transition from the lowest triplet excited state. Molecules exhibiting efficient red persistent RTP enable long-wavelength excitation, indicating the suitability of observing afterglow readout in a bright indoor environment with a white-light-emitting diode flashlight, greatly expanding the range of anti-counterfeiting applications that use afterglow.

A 3D Phosphorescent Supramolecular Organic Framework in Aqueous Solution

AbstractSupramolecular organic framework (SOF) has recently garnered significant research interest in the field of luminescent materials. However, SOF with room‐temperature phosphorescence emission in solution is very rare due to the quenching of dissolved oxygen and free molecular motions, which would lead to nonradiative deactivation of triplet exciton in liquid state. In this work, a 3D cationic phosphorescent SOF is synthesized through host‐guest interaction between CB[8] and a tetrahedral monomer TBBP, which can rapidly adsorb anionic guests in solution. When anionic dyes are introduced, triplet to singlet Förster resonance energy transfer (TS‐FRET) in solution can be achieved, and delayed fluorescence with large Stokes shift can be realized. Additionally, when anionic drugs are introduced, the phosphorescence of TBBP‐CB[8] can be quenched due to charge transfer, enabling the detection of drugs through phosphorescence signals. Taking advantage of the fast adsorption property of 3D SOF, an INHIBIT logic gate with three inputs and two outputs is constructed. These findings provide a novel method to prepare phosphorescent functional materials and a new pathway to construct TS‐FRET system in solution.

Triplet state photophysics of bis(dimethylphenanthroline)copper(I) might involve volume-changing molecular motion: Ultrafast absorption and emission studies

Study of triplet photophysics has remained a contemporary field for the last eight decades due to its wide-ranging applications. Many recent studies deciphered the influence of molecular vibrations on the electronic coupling for facile intersystem crossing (ISC) in numerous metal complexes. Through a combined analysis of steady-state and time-resolved spectroscopies, we identified the role of environmental rigidity on the triplet photophysics of bis(dimethylphenanthroline)copper(I) chloride ([Cu(dmphen)2]Cl). Our experiments suggest an involvement of volume-changing coordinate in ISC of [Cu(dmphen)2]Cl having an activation energy barrier of 5.9 kJ mol−1. This insight can be useful in the research and development of efficient triplets.

Power-dependent study of the photothermal response of several alcoholic media with femtosecond laser-induced thermal lens.

We explore the photothermal response of methanol, ethylene glycol, and glycerol using the femtosecond laser-induced thermal lens spectroscopy (FTLS) technique. A mode mismatched pump-probe spectroscopic technique was utilized to analyze the influence of localized thermal heating on the photothermal response of solvents. The findings revealed a strong dependence on both the input pump power and the molecular characteristics of the solvents. At significantly high pump power, the excess heat load deposited to the solvent is found to be responsible for the induction of the convection currents in the heat transfer mechanisms. Our results highlight that the influence of pump power on photothermal and thermal lens characteristics is intricately linked to the natural drifting and heat transfer mechanisms of solvent molecules. The molecular motion and existing connective processes were correlated with the molecular characteristics of the samples. The present finding reveals that FTLS is a sensitive probe for comprehending the impact of input laser power, molecular structure, and intermolecular H bonding on the photothermal characteristics and thermo-optical properties of the alcoholic medium.