Molecular Motion Research Articles

Molecular motion in supramolecular ionic crystal of Swiss cheese structure

Abstract In most molecular crystals, crystal structure collapses when solvent molecules are removed. We report the crystal of (isobutylammonium+)(dibenzo[18]crown-6)[Ni(dmit)2]−•0.4CH3CN with Swiss cheese–like structure, in which 60% of the CH3CN sites are voids. The motion of isobutylammonium+ adjacent to the void sites maintains the single crystallinity, which occupy an apparently larger volume than in the static state. This study opens up the possibility of developing novel relaxor dielectrics based on molecular motion in the crystal of partially occupied voids.

Multistimuli-Responsive Soft Actuators with Controllable Bionic Motions.

Soft actuators with biomimetic self-regulatory intelligence have garnered significant scientific interest due to their potential applications in robotics and advanced functional devices. We present a multistimuli-responsive actuator made from a carbon nitride/carbon nanotube (CN/CNTs) composite film. This film features a molecular switch based on reversible hydrogen bonds, whose asymmetric distribution endows the film with the ability to absorb water unevenly and convert molecular motion into macroscopic movement. By incorporating carboxylated CNTs, the film demonstrates improved mechanical properties and actuation performance. Under ambient humidity stimuli, the actuator can autonomously generate walking and tumbling motions. The CN/CNTs composite film's actuating behaviors are programmable, enabling diverse deformation modes and complex biomimetic movements. Additionally, the film exhibits excellent photothermal conversion efficiency (74.10 °C/s), allowing for temperature and light-responsive actuation, which can be remotely controlled in real time. These features have enabled the creation of soft robots capable of complex biomimetic actions such as jumping, directional movement, and transporting objects. This research broadens the potential applications of CN-based actuators and paves the way for the development of intelligent soft robots.

Crystal structure, structural geometry, and molecular motion of organic–inorganic perovskite [N(CH3)4]2MnCl4 crystals at phases I, II, and III

Various aspects of the new development of organic-inorganic hybrid [N(CH3)4]2MnCl4 single crystals have been discussed. The phase transition temperatures were determined to be 268 K (TC2) and 291 K (TC1), and the thermodynamic stability was maintained at temperatures up to 669 K. The crystal structures at 250 K (phase III), 275 K (phase II), and 300 K (phase I) are monoclinic, orthorhombic, and orthorhombic, respectively. Notably, while the 1H and 13C chemical shifts gradually changed near TC1 and TC2, the 14N resonance frequency exhibited a split in the number of signals near TC1. Furthermore, the shorter spin-lattice relaxation time T1ρ of 1H than that of 13C suggests facile energy transfer for1H. Additionally, analysing the temperature dependencies of T1ρ for 13C revealed that the activation energy Ea in phase I is approximately five times greater than those in phases III and II. The high Ea observed in phase I primarily stems from the collective motion of the N(CH3)4 group, which contrasts with the considerable freedom observed for the CH3 group in phases III and II. These distinctive physical properties suggest potential applications for [N(CH3)4]2MnCl4 as an organic‒inorganic hybrid material.

Physics Models and Machine Learning in Molecular Dynamics

Abstract. Tackling the complexity of particle interactions, this investigation introduces a unified computational methodology employing Moldy, Gnuplot, and Visual Molecular Dynamics (VMD). Inspired by the n-body problem's persistent intrigue, specifically the three-body dynamics within molecular systems, we leverage Molecular Dynamics (MD) simulations to forecast and scrutinize the nuanced behavior of atomic and molecular entities. Moldy, a flexible MD software, facilitated the simulation of particle trajectories and interactions across diverse scenarios, with meticulous documentation of the resulting data. For visual analytics and insight extraction, Gnuplot crafted detailed plots depicting kinetic and potential energies alongside other thermodynamic metrics over temporal scales. The integration of VMD culminated in our analysis by vividly portraying the molecular motions, enhancing comprehension of emergent patterns. This study not only endorses Moldy's precision in MD simulations but also highlights the potent alliance among simulation, analysis, and visualization in elucidating intricate particle interactions. In summary, our work underscores the efficacy of the Moldy-Gnuplot-VMD triad as a formidable resource for scientists engaged in molecular motion prediction and analysis, paving fresh paths in computational physics and chemistry research.

Grating Harmony of Orderly-Banded Spherulites of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Tunable Structures

A detailed investigation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blended with poly(vinyl phenol) (PVPh) at a 90/10 weight ratio reveals the significant impact of PVPh on crystallization and spherulite morphology. Because PVPh remains in a rigid, glassy state during PHBV crystallization, it restricts molecular movement, leading to a more controlled and organized morphology of the PHBV lamellae. Advanced microscopic analysis highlights the morphological sensitivity to crystallization conditions, with SEM images showing cracks and diverse lamellae orientations. Etching and fracturing expose the interior 3D lamellae architecture, revealing distinct ridge and valley regions where vertically oriented lamellae beneath ridges transition to horizontal lamellae in valleys, resulting in double ring-banded spherulites. Advanced synchrotron-radiation microbeam X-ray techniques provide additional insights into the polymorphic forms and self-assembly behavior of lamellae. The investigation also examines order-induced photonic phenomena by considering that the orderly-banded spherulites can exhibit iridescence. This comprehensive study enhances our understanding of PHBV crystal assembly, underscoring the sophistication of polymer self-assembly at the microscopic level.

Encasing Triaryltriazine with a Bulky Chiral Cap: Luminescent Chiral Crystalline Molecular Rotors with Modulation of Solid-State Chiroptical Properties Mediated by Molecular Rotation.

A novel structural motif for luminescent chiral crystalline molecular rotors with chiroptical properties correlated with the rotational motion in crystalline media is presented. This scaffold incorporates bulky chiral caps consisting of a homochiral binaphthyl moiety with a triisopropylsilyl (TIPS) group into triaryltriazine, as confirmed by single-crystal X-ray diffraction (XRD) analysis. Variable-temperature solid-state 2H NMR studies revealed a 4-fold rotation of the phenylenes occurred in the rotor crystal between 263 and 333 K, while a steric rotor analogue shows no rotational motion. Notably, a reduction in the dihedral angle of the binaphthyl moiety upon heating was observed in the chiral rotors, and a corresponding alteration of the circular dichroism (CD) signal was detected in the solid-state, while those of the steric rotors showed no alteration by the temperature change. We propose that the fast rotation of the phenyl rings affects the motion of neighboring isopropyl groups, leading to steric repulsion with the binaphthyl moieties and thereby inducing its conformational change. Furthermore, the chiral rotors exhibited circularly polarized phosphorescence in the solid-state at low temperature, originating from rotational displacement of the phenylene on triphenyltriazine during structural relaxation in the excited state. Meanwhile, the steric rotors showed significant circularly polarized fluorescence induced by the suppressed molecular motion via a sterically hindered lattice environment in the excited state. These results indicate that the bulky chiral cap introduced into the triaryltriazines, acting as a luminescent chiral crystalline molecular rotor, can be a useful scaffold for the modulation of solid-state chiroptical properties via molecular rotational motions.

Photoluminescence of Tetra(benzimidazole)phenylethene Derivatives and Their Carbene Metallacycles in Aggregates and Langmuir-Blodgett Films.

Molecular structure, external stimuli, and environmental factors all have a strong effect on the internal molecular rotation and vibration of aggregate-induced emission (AIE) luminogens. Here, we report the AIE effect for several newly synthesized amphiphilic tetra(benzimidazole)phenylethene (TBiPE) derivatives and their binuclear N-heterocyclic carbene silver (NHC-Ag) metallacycles in solutions, aggregates, and Langmuir-Blodgett (LB) films. Monolayer behaviors and microscopic images indicate that introducing alkyl chains and binuclear NHC-Ag metallacycles can facilitate the formation of a well-defined insoluble monomolecular layer at the air-water interface. Absorption and luminescence spectral features suggest that both the TBiPEs' cyclization structure and binuclear NHC-Ag metallacycles can provide additional driving forces to restrict the internal molecular motion of the tetraphenylethene (TPE) unit, thus enhancing the AIE effects. Further, external stimuli and environmental factors such as poor solvent addition and LB film deposition also play important roles in the photoluminescent intensity, maximum wavelength, and lifetime. These internal and external factors can result in around 30-40 nm blue-shift for the maximum luminescence wavelength and 2-3 times shorter for the luminescent lifetime. These phenomena can be attributed to the reason that the nonradiative energy transfer efficiency is weakened because of the enhanced hydrophobic interaction and metal-carbene coordination as well as the closely packed arrangement of AIEgens in the LB films; consequently, the radiation energy transfer efficiency increased.

Regulating transport efficiency through the nuclear pore complex: The role of binding affinity with FG-Nups.

Macromolecules are transported through the nuclear pore complex (NPC) via a series of transient binding and unbinding events with FG-Nups, which are intrinsically disordered proteins anchored to the pore's inner wall. Prior studies suggest that the weak and transient nature of this binding is crucial for maintaining the transported molecules' diffusivity. In this study, we explored the relationship between binding kinetics and transport efficiency using Brownian dynamics simulations. Our results indicate that the duration of binding is a critical factor in regulating transport efficiency. Specifically, excessively short binding durations insufficiently facilitate transport, while overly long durations impede molecular movement. We calculated the optimal binding duration for efficient molecular transport and found that it aligns with other theoretical predictions. Additionally, the calculated value is comparable to experimental measurements of the association timescale between nuclear transport receptors and FG-Nups at a single binding site. Our study provides a quantitative framework that bridges local molecular interactions with overall transport dynamics through the NPC, offering valuable insights into the mechanisms governing selective molecular transport.

Controlling Guest Diffusion by Local Dynamic Motion in Soft Porous Crystals to Separate Water Isotopologues and Similar Gases.

ConspectusThe precise and effective separation of similar mixtures is one of the fundamental issues and essential tasks in chemical research. In the field of gas/vapor separation, the size difference among the molecular pairs/isomers of light hydrocarbons and aromatic compounds is generally 0.3-0.5 Å, and the boiling-point difference is generally 6-15 K. These are necessary industrial raw materials and have great separation demands. Still, their separation mainly relies on energy-intensive distillation technology. On the other hand, remarkably similar substances such as oxygen/argon and isotopologues usually exhibit size differences of only 0-0.07 Å and boiling-point differences of only 1-3 K. Although their industrial separation can be realized, their efficiency is considerably low. Therefore, effectively separating remarkably similar mixtures is crucial in fundamental chemistry and industry, but it remains a significant challenge. Porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) are emerging materials platforms for designing adsorbents for separating similar mixtures. However, the reported PCPs did not work well for separating remarkably similar substances. The framework structures of the mainstream PCPs remain unchanged (rigid) or significantly change (globally flexible) upon adsorption. However, rigid and globally flexible PCPs find controlling the pore aperture in subangstrom precision challenging, a prerequisite for distinguishing remarkably similar substances. Thus, novel mechanisms and materials design principles are urgently needed to realize PCPs-based adsorptive separation of remarkably similar mixtures.To confront the obstacles in separating remarkably similar mixtures, our group started contributing to this field in 2017. We employed locally flexible PCPs as the materials designing platform, whose local motions of the side substituent groups potentially regulate the pore apertures to design and control the gas/vapor diffusion in PCPs. Specifically, we encoded dynamic flipping molecular motions into the diffusion-regulatory gate functionality. The ligands were designed by integrating carboxylic coordination groups with nonplanar fused-ring moieties, with the latter moieties exhibiting flipping motion around their equilibrium positions with small energy increases. Such local motions of ligands lead to the dynamic opening and blocking of PCP channels, thus termed flipping dynamic crystals (FDCs). FDCs feature distinctive temperature-responsive adsorption behaviors due to the competition of thermodynamics and kinetics under diffusion regulation, enabling differentiation of remarkably similar mixtures by each gate-admission temperature much higher than the boiling-point temperature of each component. Even when the molecular sizes are the same in the water isotopologue mixtures, FDCs can separate each isotopologue by amplifying their diffusion-rate differences. Finally, by combining the thermodynamic and kinetic factors, FDCs achieve temperature-switched recognition of CO2/C2H2 and diffusion-rate sieving of C3H6/C3H8. Therefore, our work provides a platform for designing locally flexible PCPs by introducing subangstrom precision in flexibility. This opens up the feasibility of separating remarkably similar mixtures on scientific principles. In this Account, we summarize our above ongoing research contributions, including (i) the design of flipping ligands and FDCs, (ii) the characterization of flipping motions, (iii) the gas/isotopologue sorption behaviors, and (iv) the separation of gases and isotopologues. Overall, our studies offer a new aspect of soft porous crystals and provide future opportunities for relevant researchers in this field.

The Pyramidalization of sp2 Centers in 3/2‐Systems Is a “Structural Breathing” Independent of Energy

AbstractIn 3/2‐systems, such as the acetate anion H3CαC′OO−, an sp3 center and an sp2 center are connected by a covalent bond. The interaction of threefold and twofold symmetry results in the pyramidalization of the sp2 center during rotation about bond Esp3−Esp2. Rotation angles ψ=0°, ±60°, ±120°, and ±180° account for conformations with a symmetry plane containing the planar sp2 center CαC′OO. However, in all conformations with rotation angles ψ≠0°, ±60°, ±120°, and ±180° this symmetry plane is lost and pyramidalization must occur with maxima at rotation angles ψ=±30°, ±90°, and ±150°, because the two sides of the sp2 center CαC′OO are different. Inevitably, this leads to a pyramidalization/rotation profile θ/ψ with three maxima, three minima, and six zero‐crossings. Thus, myriads of 3/2‐compounds pyramidalize their sp2 centers each moment to the order of about 2° in a coupled pyramidalization/rotation molecular motion independent of energy.

Post-Transition State Bifurcation Controls Torsional Selectivity in Radical Addition of Allenes.

Post-transition state bifurcation (PTSB) has received wide attention in the field of reaction mechanism research due to its role in producing nonstatistical reaction selectivity, which cannot be solely explained by transition state theory. Particularly, even subtle molecular motions such as bond torsion can precipitate PTSB, thereby significantly complicating the quantitative understanding of dynamic selectivity. In this work, we found that the radical addition of allenes is an elementary transformation that generally exhibits PTSB stereoselectivity, where a single radical addition transition state can lead to both Z- and E-allylic radicals via the post-transition state allylic single bond torsion. Interestingly, dynamic Z/E-selectivity favors the Z-allylic radicals, which contrasts the thermodynamic preference. Based on the dynamics study of twenty-five radical additions of mono-substituted allenes with diverse electronic and steric effects, we have identified that this dynamic stereoselectivity is synergistically controlled by the transition state structure and the differential trends within specific dimensions of the bifurcating reaction coordinates, which also holds true for di-substituted allene substrates. This study refines the mechanism of radical addition of allenes and underscores the importance of the differential trend of the reaction coordinates in controlling dynamic selectivity, offering a deeper insight into PTSB selectivity factors.

Characterization of myocardial ischemia-reperfusion injury in a pig model with novel CW T1r and RAFF2 MRI methods in 1.5T

Abstract Introduction Myocardial ischemia-reperfusion injury (IRI) occurs after myocardial infarction when reperfusion aggravates the initial damage in myocardium by vast infiltration of inflammatory cells and elevated oxidative stress in myocardium that may lead to cardiac remodeling, heart failure and even death [1]. Magnetic resonance imaging (MRI) can accurately determine the anatomy of the heart and to characterize myocardial tissue. Novel endogenous rotating frame MRI methods, including continuous wave (CW) T1r and relaxation along a fictitious field with rank 2 (RAFF2), have been shown to characterize MI and other CVD in mouse and human myocardium with high sensitivity and specificity [2,3]. CW T1r and RAFF2 contrasts are occurring during radio frequency (RF) pulse (in kHz range) making them to be sensitive to slow molecular motions [2]. Comparing to conventional endogenous T1 and T2 methods, these are occurring after the RF pulse (in Larmor frequency (MHz) range) and therefore, these are non-selectively sensitive to different correlation times [4]. Golden standard to image MI is to use contrast agent (CA) in late gadolinium enhancement (LGE) method [2,4]. Using CA has drawbacks and therefore, there is an urgent need for optimizing the endogenous MRI methods in clinical practice. Purpose To characterize myocardial IRI in a pig model and to determine the sensitivity of both novel and conventional cardiac MRI methods. Methods IRI operation was done in 7 pig (30-35 kg) by occluding the LAD with a balloon catheter for 50 minutes. Imaging was done with 1.5T (MAGNETOM Aera) at 3 days and 28 days after the operation. Pig hearts were imaged with conventional native T1, T2, LGE, and with novel CW T1r and RAFF2 methods in both time points. These were imaged before CA injection and LGE was done 25 minutes after CA injection. Relaxation time mappings were done in a pixel-by-pixel manner with monoexponentially fitting. Region-of-interest (ROI) analysis was done to determine the relaxation times in IRI and remote areas. LGE was used to confirm the IRI areas in the myocardium. Relative relaxation time difference (RRTD)-values were calculated with the function of (((Relaxation Time of IRI area) – (Relaxation Time of Remote Area))/ (Relaxation Time of Remote Area)) to determine the contrast difference between IRI and remote areas. Results Relaxation times were elevated in IRI areas compared to remote areas (Figure 1A). Novel rotating frame RRTD-values were significantly higher than RRTD-values in conventional methods. This means that novel methods have larger contrast difference between IRI and remote areas compared to conventional methods, which indicates that novel methods are sensitive to characterize IRI area (Figure 1B). The location of MI areas was similar in both novel rotating frame and conventional methods compared to LGE (Figure 2). Conclusion Novel rotating frame relaxation time methods are sensitive to characterize the IRI area in pig model.Relaxation times, RRTD-valuesRelaxation times maps and LGE

In-plane orientational motions of the functional groups of molecules at the air/water interface by time-resolved vibrational sum frequency generation.

The movements of molecules at interfaces and surfaces are restricted by their asymmetric environments, leading to anisotropic orientational motions. In this work, in-plane orientational motions of the -C=O and -CF3 groups of coumarin 153 (C153) at the air/water interface were measured using time-resolved (TR) vibrational sum frequency generation (SFG). The in-plane orientational time constants of the -C=O and -CF3 groups of C153 are found to be 41.5 ± 8.2 and 36.0 ± 4.5ps. These values are over five-times faster than that of 198 ± 15ps for the permanent dipole of the whole C153molecule at the interface, which may indicate that the two groups experience different interfacial friction in the plane. These differences could also be the result of the permanent dipole of C153 being almost five times those of the -C=O and -CF3 groups. The difference in orientational motions reveals the microscopic heterogeneous environment that molecules experience at the interface. While the interfacial dynamics of the two functional groups are similar, our TR-SFG experiments allowed the quantification of the in-plane dynamics of individual functional groups for the first time. Our experimental findings about the interfacial molecular motion have implications for molecular rotations, energy transfer, and charge transfer at material interfaces, photocatalysis interfaces, and biological cell/membrane aqueous interfaces.

Investigating Different Dynamic pHP1α States in Their KCl-Mediated Liquid-Liquid Phase Separation (LLPS) Using Solid-State NMR (SSNMR) and Molecular Dynamic (MD) Simulations.

Chromatin phase separation is dynamically regulated by many factors, such as post-translational modifications and effector proteins, and plays a critical role in genomic activities. The liquid-liquid phase separation (LLPS) of chromatin and/or effector proteins has been observed both in vitro and in vivo. However, the underlying mechanisms are largely unknown, and elucidating the physicochemical properties of the phase-separated complexes remains technically challenging. In this study, we detected dynamic, viscous, and intermediate components within the phosphorylated heterochromatin protein 1α (pHP1α) phase-separated system by using modified solid-state NMR (SSNMR) pulse sequences. The basis of these sequences relies on the different time scale of motion detected by heteronuclear Overhauser effect (hetNOE), scalar coupling-based, and dipolar coupling-based transfer schemes in NMR. In comparison to commonly utilized scalar coupling-based methods for studying the dynamic components in phase-separated systems, hetNOE offers more direct insight into molecular dynamics. NMR signals from the three different states in the protein gel were selectively excited and individually studied. Combined with molecular dynamics (MD) simulations, our findings indicate that at low KCl concentration (30 mM), the protein gel displays reduced molecular motion. Conversely, an increase in molecular motion was observed at a high KCl concentration (150 mM), which we attribute to the resultant intermolecular electrostatic interactions regulated by KCl.

Fluorescent Dye-Based Chiral Crystalline Organic Salt Networks for Circularly Polarized Luminescence.

A facile and general strategy is developed herein for the construction of circularly polarized luminescence (CPL) materials with simultaneously high fluorescence quantum efficiency (Φ) and large luminescence dissymmetry factor (glum). The self-assembly of fluorescent dye, disodium 4,4'-bis(2-sulfonatostyryl)biphenyl (CBS), with chiral diamines such as (R,R)/(S,S)-1,2-diaminocyclohexane (R/S-DACH) and R/S-1,2-diaminopropane (R/S-DAP), produces four chiral crystalline organic salt networks (COSNs). These as-synthesized organic salts emit strong blue-color CPL upon excitation, with both high Φ and glum values of up to 79% and 0.022. The well-defined molecular structures and arrangements of CBS are directly observed through single crystal X-ray analysis, offering crucial information regarding the origins of high-efficiency CPL performance. The chirality of amine is effectively transferred to CBS and further amplified to the supramolecular structure by multiple hydrogen bonding and π-π stacking interactions, giving rise to the large glum factors; meanwhile, the fixation and the ordered arrangement of CBS by these multiple interactions empower efficient suppression of molecular motions, facilitating strong fluorescence. This work can inspire the assembly of CPL organic materials with high Φ and glum via charge-assisted hydrogen bonds between fluorescent dyes and chiral inducers. It also offers important insight into the structural origins of supramolecular chirality and CPL performance.

Ultralong Room-Temperature Phosphorescence in Ca(II) Metal-Organic Frameworks Based on Nicotinic Acid Ligands.

In recent years, metal-organic framework (MOF) materials with long persistent luminescence (LPL) have inspired extensive attention and presented various applications in security systems, information anticounterfeiting, and biological imaging fields. However, obtaining LPL materials with ultralong lifetime remains challenging. Halogen atoms, as nonmetallic elements existing in the frameworks, can not only induce the heavy-atom effect, effectively enhancing spin-orbit coupling and promoting intersystem crossing (ISC) processes, but also suppress non-radiative transition of the triplet states through the intra- and intermolecular interactions. Specifically, fluorine atoms with the strongest electronegativity may form intermolecular aggregate interlockings through halogen-bonding interactions that restrict molecular motions and vibrations, thereby improving phosphorescent lifetime. With the aforementioned considerations, two distinct types of MOFs with/without fluorine atoms (namely, Ca-MOF and 5FCa-MOF) were synthesized. Notably, by introducing fluorine atoms into MOFs, fluorine-induced intermolecular aggregate interlockings effectively enhanced the phosphorescent lifetime of 5FCa-MOF exceeding 264 ms compared to that of Ca-MOF (103.94 ms). Remarkably, both MOFs displayed bright LPL to the naked eye after removal of the irradiation source, especially 5FCa-MOF which can last for about 2 s. By introducing fluorine atoms, 5FCa-MOF exhibits greatly enhanced ISC with a rate constant up to 4.1 × 106 s-1 and suppressed non-radiative decay down to 3.73 s-1, thereby extending the LPL time. The thus obtained LPL provides potential in information encryption, security systems, optical anticounterfeiting, and so on.

Full‐Color Tunability Room Temperature Phosphorescence from Inorganic Crystal Frameworks

AbstractRoom temperature afterglow (RTA) materials have aroused prodigious research interests owing to their unique long‐life luminescent properties. However, it is rare for RTA materials to be reported with full‐color afterglow emission. Herein, a universal strategy is designed to activate full‐color tunability RTA based on phenylboronic acid derivatives (BOH) and boric acid (BA) via an ingenious solvent‐free solid‐phase heating. As the conjugation degrees of aromatic groups of the guest molecule expanded, the BOH/BA composites showed tunable afterglow colors ranging from blue to red after ultraviolet (UV) irradiation. This strategy is to firmly anchor the guest molecule in a rigid framework of the inorganic metaboric acid matrix by abundant hydrogen‐bonding interactions between the host and guest, suppressing molecular motion and promoting the intersystem crossing (ISC) rate between the singlet and triplet excited states for enhanced afterglow emission. In addition, through mixing in multiple guest molecules into BA simultaneously, the obtained composite can be modulated in a wide excitation range from blue to red. This fascinating study provides a simple and universal method to fabricate full‐color tunability RTA composites, making them a promising candidate for applications in advanced information security and multi‐level encryption.

Visualizing dynamic alterations of vitreous viscosity during elevated intraocular pressure in glaucoma with a Near-infrared/Magnetic resonance imaging dual-modal nanoprobe

Glaucoma is a chronic progressive disease leading to irreversible visual impairment and blindness. High intraocular pressure (IOP) resulting from abnormally high outflow resistance is a major risk factor for glaucoma development, however, it is unclear how IOP elevation influences the structure and function of the retina and the optic nerve via vitreous humor located between the lens and retina in the eye. To understand vitreous biomechanical and stimulus response toward IOP elevation, we developed a novel near-infrared (NIR)/MRI dual-modal nanoprobe, DTA/P-NCA/17F@Co, which is composed of N, N-dimethyl-4(thien-2-yl)-aniline group (DTA) as NIR fluorophore and the fluorine-based polyamino acid cobalt nanoparticles (P-NCA/17F@Co) as T2 contrast agent. These nanoprobes exhibit good biocompatibility, low surface energy characteristics, and viscosity-responsive NIR emission and T2 relaxation values. The intrinsic viscosity-sensitivemechanismof nanoprobes was ascribed to constrained molecular motion in high-viscosity vitreous chamber, which causes enhanced fluorescence emission and shortened T2 relaxation times. By using its ability for dual-modal visualization of viscosity, we achieved non-invasive in vivo monitoring the changes in vitreous viscosity during elevated IOP in a glaucoma rat model. In vivo experiments validated that vitreous viscosity is very strongly correlated with IOP elevation induced by glaucoma, much earlier than structural and functional change in the retina. Our findings revealed that IOP elevation induced the increase of vitreous viscosity, indicating that monitoring vitreous viscosity is key to the glaucoma model. This study not only provides versatile nanoprobes for dual-modal visualization of biomechanical properties of the vitreous humor in its native environment, but also shows great potential in the early diagnosis of glaucoma.

Optimising Nanoparticle Dispersion Time for Enhanced Thermomechanical Properties in DGEBA-Based Shape Memory Polymer Composites

Shape-memory polymers (SMPs) are smart materials that can change shape upon an external stimulus. This phenomenon is called the shape memory effect (SME), which is caused by entropy change due to rapid molecular motion in the polymer segments. Due to the inherently weak thermomechanical properties, use of SMPs is limited in many engineering applications. Therefore, SMPs are often reinforced with fibres and nanoparticles (NPs). NPs offered greater flexibility due to their superior physical, chemical, electrical, mechanical, and thermal properties. However, the homogeneous distribution of NPs is crucial for composition’s stability and enhancement of the base material’s properties. Among the different techniques used for dispersing NPs, ultrasonic irradiation has shown excellent emulsifying and crushing performance. The sonication process is essential for mitigating agglomerates; however, prolonged sonication time probably increases epoxy temperature, micro-bubbles, cavitation, breaking apart molecules and finally degrading the epoxy resin performances. This paper provides critical insight of nanoparticle dispersion into diglycidyl ether of bisphenol A epoxies (DGEBA). DGEBA epoxy resin was added to TiO2 NPs and sonicated for 60 min with 5 min intervals while the temperature of epoxy was maintained below 60oC by using a water cooling throughout the sonication process. The process parameters such as amplitude, mode, epoxy volume and the weight percentage of NPs were kept constant. After each sonication step, Fourier-transform infrared spectroscopy (FTIR) was performed using Thermo Scientific™ and analysed through OMNIC™ Professional quantitation software. In accordance with FTIR results, until 30 min of the sonication, DGEBA resin was not degraded. In order to confirm the performances and the reinforcing effect of NPs, thermo-mechanical and shape memory properties were compared with the neat specimen. The outcomes of this research have suggested quick guidance to find optimum NP dispersion time for DGEBA resins, which has been hardly studied before.

Au···I coinage bonds: Boosting photoluminescence efficiency and solid‐state molecular motion

AbstractCoinage bonds, a type of noncovalent interaction, occur between group 11 elements (Au, Ag, and Cu) with electron donor groups. Despite theoretical validation, empirical evidence remains limited. In this study, an aggregation‐induced emission (AIE)‐active Au(I) complex, ITCPAu, which exhibits Au···I coinage bonds, was revealed based on the single‐crystal X‐ray diffraction and theoretical calculations. Further examination of the luminescence properties of the ITCPAu revealed multiswitchable behavior, including mechanochromism and thermochromism. Nearly pure white‐light emission was achieved with Commission Internationale de L'Eclairage (CIE) 1931 chromaticity coordinates of (0.30, 0.31) by grinding the green‐emissive ITCPAu monomer crystals. Moreover, visualization and manipulation of solid‐state molecular motion (SSMM) in the yellow‐emissive ITCPAu dimer crystals, driven by the robust Au···I coinage bonds, were revealed through a combination of crystal engineering and luminescent properties. Furthermore, to support the robust Au···I coinage bonds, a versatile carrier for small solvent molecules in crystal lattices was developed for uptake and release. Our findings provide experimental and theoretical evidence for Au···I coinage bonds, highlighting their ability to boost photoluminescence quantum yield (PLQY) and trigger SSMM, emphasizing their potential in developing smart materials with stimuli‐responsive properties.