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Measurement of Forces between Supported Cationic Bilayers by Colloid Probe Atomic Force Microscopy: Electrolyte Concentration and Composition
摘要： The interactions between supported cationic surfactant bilayers were measured by colloidal probe atomic force spectroscopy, and the effect of different halide salts was investigated. Di(alkylisopropylester)dimethylammonium methylsulfate (DIPEDMAMS) bilayers were fabricated by the vesicle fusion technique on muscovite mica. The interactions between the bilayers were measured in increasing concentrations of NaCl, NaBr, NaI, and CaCl2. In NaCl, the bilayer interactions were repulsive at all concentrations investigated, and the Debye length and surface potential were observed to decrease with increasing concentration. The interactions were found to follow the electrical double layer (EDL) component of DLVO theory well. However, van der Waals forces were not detected; instead, a strong hydration repulsion was observed at short separations. CaCl2 had a similar effect on the interactions as NaCl. NaBr and NaI were observed to be more efficient at decreasing surface potential than the chloride salts, with the efficacy increasing with the ionic radius.
关键词： supported bilayers,DLVO theory,Debye length,surface potential,halide salts,colloidal probe atomic force spectroscopy
更新于2025-09-23 15:23:52
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Gramicidin Lateral Distribution in Phospholipid Membranes: Fluorescence Phasor Plots and Statistical Mechanical Model
摘要： When using small mole fraction increments to study gramicidins in phospholipid membranes, we found that the phasor dots of intrinsic ?uorescence of gramicidin D and gramicidin A in dimyristoyl-sn-glycero-3-phosphocholine (DMPC) unilamellar and multilamellar vesicles exhibit a biphasic change with peptide content at 0.143 gramicidin mole fraction. To understand this phenomenon, we developed a statistical mechanical model of gramicidin/DMPC mixtures. Our model assumes a sludge-like mixture of ?uid phase and aggregates of rigid clusters. In the ?uid phase, gramicidin monomers are randomly distributed. A rigid cluster is formed by a gramicidin dimer and DMPC molecules that are condensed to the dimer, following particular stoichiometries (critical gramicidin mole fractions, Xcr including 0.143). Rigid clusters form aggregates in which gramicidin dimers are regularly distributed, in some cases, even to superlattices. At Xcr, the size of cluster aggregates and regular distributions reach a local maximum. Before a similar model was developed for cholesterol/DMPC mixtures (Sugar and Chong (2012) J. Am. Chem. Soc. 134, 1164–1171) and here the similarities and differences are discussed between these two models.
关键词： lipid bilayers,membrane organization,gramicidins,statistical mechanics,?uorescence spectroscopy,peptide-lipid interactions
更新于2025-09-23 15:21:21
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Opportunities and challenges of interlayer exciton control and manipulation
摘要： Advances in van der Waals heterostructures allow the control of interlayer excitons by electrical and other means, promising exciting opportunities for high-temperature exciton condensation and valley–spin optoelectronics.
关键词： TMD bilayers,exciton condensation,van der Waals heterostructures,valley–spin optoelectronics,interlayer excitons
更新于2025-09-23 15:21:01
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Giant Stark effect in coupled quantum wells: Analytical model
摘要： Coupled quantum wells have been proposed as candidates for highly polarizable structures due to their near-degenerate and dipole-coupled electronic states. Hence, many interesting applications in linear and nonlinear optics can be envisioned. We analyze this proposal considering a simple structure with a delta-function barrier separating the wells. While very substantial Stark shifts are certainly predicted for this geometry, perturbative estimates based on polarizabilities (and hyperpolarizabilities) fail beyond a critical ?eld strength that depends inversely on the barrier. Hence, a giant Stark effect due to near-degenerate states is invariably limited by a small critical ?eld. Our analytical (hyper) polarizability expressions are applied to ?nd quantitative Stark shifts for GaAs quantum wells and transition-metal dichalcogenide bilayers. The predicted Stark shifts and critical ?elds agree with the ?eld dependence observed in a range of available experiments.
关键词： Stark effect,hyperpolarizability,GaAs,transition-metal dichalcogenide bilayers,polarizability,coupled quantum wells
更新于2025-09-23 15:19:57
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Out-of-Plane Nanoscale Reorganization of Lipid Molecules and Nanoparticles Revealed by Plasmonic Spectroscopy
摘要： Lipid bilayers assembled on solid substrates have been extensively studied with single-molecule resolution as the molecules diffuse in 2D, however the out-of-plane motion is typically ignored. Here we present sub-nanometer out-of-plane diffusion of nanoparticles attached to hybrid lipid bilayers (HBLs) assembled on metal surfaces. The nanoscale cavity formed between Au nanoparticle and Au film provides strongly-enhanced optical fields capable of locally probing HBLs assembled in the gaps. This allows us to spectroscopically resolve the nanoparticles assembled on bilayers, near edges, and in membrane defects, showing the strong influence of charged lipid rafts. Nanoparticles sitting on the edges of the HBL are observed to flip onto and off the bilayer, with flip energies of 10 meV showing how thermal energies dynamically modify lipid arrangements around a nanoparticle. We further resolve the movement of individual lipid molecules by doping the HBL with low concentrations of Texas-red (TxR) dye-labeled lipids.
关键词： Purcell factor,Plasmonics,Single-molecule,Nano-assembly,Nanocavities,Lipid bilayers
更新于2025-09-23 15:19:57
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Plasmonica??Assisted Graphene Oxide Films with Enhanced Photothermal Actuation for Soft Robots
摘要： Carbon-based materials are widely used as light-driven soft actuators relying on their thermal desorption or expansion. However, applying a passive layer in such film construction greatly limits the actuating efficiency, e.g., bending amplitude and speed. In this work, a dual active layer strengthened bilayer composite film made of graphene oxide (GO)–polydopamine (PDA)–gold nanoparticles (Au NPs)/polydimethylsiloxane (PDMS) is developed. In this film, the conventional passive layer is replaced by another AuNPs-enhanced thermal responsive layer. When applying NIR light exposure, the whole film deforms controllably resulting from the water loss in the GO–PDA–Au NPs layer and thermal expansion in the PDMS layer. Benefiting from the dual active bilayer mechanism, the thin film’s actuating efficiency is dramatically improved compared with that of conventional methods. Specifically, the bending amplitude is enhanced up to 173%, and the actuating speed is improved to 3.5-fold. The soft actuator can act as an artificial arm with high actuating strength and can be used as a wireless gripper. Moreover, the film can be designed as soft robots with various locomotion modes including linear, rolling, and steering motions. The developed composite film offers new opportunities for biomimetic soft robotics as well as future applications.
关键词： plasmonic-enhanced effects,soft manipulators,carbon-based materials,soft robotics,dual active bilayers
更新于2025-09-23 15:19:57
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Formation of lipid bilayers on the pore walls of macroporous silicon
摘要： Electron paramagnetic resonance (EPR) spectroscopy was used to study the pore filling of macroporous silicon with lipid vesicles (liposomes), added with a spin label. Different EPR spectra were obtained with the magnetic field parallel and perpendicular to the macroporous silicon sample surface. These spectra could be well simulated with an admixture of the isotropic spectrum of liposomes, plus a simulated spectrum corresponding to a cylindrical distribution of lipid bilayers. This means that a portion of the liposomes were disrupted, and supported lipid bilayers were formed covering the inner surface of the pores. Diverse protocols can be explored in order to optimize the lipid covering of the pore walls, and to achieve an adequate lipid hydration. This system can be used as a platform to study lipid phase transitions in a confined environment, and to characterize membrane proteins.
关键词： Liposomes,Electron paramagnetic resonance/electron spin resonance,Supported lipid bilayers,Porous silicon,Spin labels
更新于2025-09-19 17:15:36
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Enhancing Quantum Yield in Strained MoS2 Bilayers by Morphology-controlled Plasmonic Nanostructures towards Superior Photodetectors
摘要： Recently, extracting hot electrons from plasmonic nanostructures and utilizing them to enhance the optical quantum yield of 2D transition-metal dichalcogenides (TMDs) have been topics of interest in the field of optoelectronic device applications, such as solar cells, light emitting diodes, photodetectors and so on. The coupling of plasmonic nanostructures with nanolayers of TMDs depends on the optical properties of the plasmonic materials, including radiation pattern, resonance strength, and hot electron injection efficiency. Herein, we demonstrate the augmented photodetection of a large-scale, transfer-free bilayer MoS2, by decorating this TMD with four different morphology-controlled plasmonic nanoparticles. This approach allows engineering the bandgap of the bilayer MoS2 due to localized strain that stems up from plasmonic nanoparticles. In particular, the plasmonic strain blue shifts the band gap of bilayer MoS2 with 32 times enhanced photoresponse demonstrating immense hot electron injection. Besides, we observed the varied photoresponse of MoS2 bilayer hybridized with different morphology controlled plasmonic nanostructures. Although, hot electron injection was a substantial factor for photocurrent enhancement in hybrid plasmonic-semiconductor devices, our investigations further show that other key factors such as highly directional plasmonic modes, high aspect-ratio plasmonic nanostructures and plasmonic strain induced beneficial band-structure modifications were crucial parameters for effective coupling of plasmons with excitons. As a result, our study sheds light on designing highly tailorable plasmonic nanoparticles integrated transition metal dichalcogenide-based optoelectronic devices.
关键词： Plasmonic Nanostructures,Strained MoS2 Bilayers,Quantum Yield,Photodetectors
更新于2025-09-16 10:30:52
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CdS Quantum Dots‐Organometallic Halide Perovskites Bilayer Electrodes Structures for Supercapacitor Applications
摘要： Supercapacitors are attracting great attention because of their fast charging?discharging ability as well as high power density. The current research in this area focuses mainly on exploring novel low-cost electrode materials with higher energy and power densities. In this work, thin film electrochemical capacitors were fabricated using layers of self-synthesized cadmium sulfide quantum dots and organometallic halide perovskite materials as active electrodes. Organometallic halide perovskites exhibit interesting ionic responses besides its extraordinary electronic property. These properties are exploited in fabricating the electrochemical capacitors, and the devices showed excellent cycling ability with stable capacitances output beyond 4000 cycles. Impedance spectroscopy measurements revealed that perovskites do not only serve as active electrodes but also as solid electrolytes thereby enhancing capacitance of the devices and hence energy densities. The layers provide high surface areas for electrolytes to access the electrode materials; reasonably low charge transfer resistance and small relaxation time were also observed. This work opens new opportunities for developing thin film supercapacitors using low-cost electrode materials and employing a facile, inexpensive solution process coating.
关键词： Perovskites,CdS,quantum dots,supercapacitor,bilayers
更新于2025-09-12 10:27:22
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Beyond DPPH: Use of Fluorescence-Enabled Inhibited Autoxidation to Predict Oxidative Cell Death Rescue
摘要： Shah et al. develop a fluorescence-enabled inhibited autoxidation (FENIX) approach that permits accurate quantitation of radical-trapping antioxidant activity in phospholipid bilayers. The methodology is far superior to existing assays (e.g., DPPH) and enables reliable prediction of the anti-ferroptotic potency of redox-active compounds. The approach is easily amenable to high-throughput screening.
关键词： anti-ferroptotic potency,high-throughput screening,radical-trapping antioxidant activity,DPPH assay,phospholipid bilayers,FENIX
更新于2025-09-12 10:27:22