To systematically add functionality to nanoscale polymer switches, an understanding of their responsive behavior is crucial. Herein, solvent vapor stimuli are applied to thin films of a diblock ...copolymer consisting of a short poly(methyl methacrylate) (PMMA) block and a long poly(N‐isopropylmethacrylamide) (PNIPMAM) block for realizing ternary nanoswitches. Three significantly distinct film states are successfully implemented by the combination of amphiphilicity and co‐nonsolvency effect. The exposure of the thin films to nitrogen, pure water vapor, and mixed water/acetone (90 vol%/10 vol%) vapor switches the films from a dried to a hydrated (solvated and swollen) and a water/acetone‐exchanged (solvated and contracted) equilibrium state. These three states have distinctly different film thicknesses and solvent contents, which act as switch positions “off,” “on,” and “standby.” For understanding the switching process, time‐of‐flight neutron reflectometry (ToF‐NR) and spectral reflectance (SR) studies of the swelling and dehydration process are complemented by information on the local solvation of functional groups probed with Fourier‐transform infrared (FTIR) spectroscopy. An accelerated responsive behavior beyond a minimum hydration/solvation level is attributed to the fast build‐up and depletion of the hydration shell of PNIPMAM, caused by its hydrophobic moieties promoting a cooperative hydration character.
Ternary nanoswitches are realized using PMMA‐b‐PNIPMAM diblock copolymer thin films. Three distinct film states (off, on, and standby) are successfully prepared by the combination of amphiphilicity and co‐nonsolvency effect. The exposure to N2, pure water vapor, and mixed 90 vol% water/10 vol% acetone vapor switches the films between dried, hydrated (solvated, swollen) and water/acetone exchanged (solvated, contracted) states.
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Unravelling the structural diversity of cellular membranes is a paramount challenge in life sciences. In particular, lipid composition affects the membrane collective behaviour, and ...its interactions with other biological molecules.
Here, the relationship between membrane composition and resultant structural features was investigated by surface pressure-area isotherms, Brewster angle microscopy and neutron reflectometry on in vitro membrane models of the mammalian plasma and endoplasmic-reticulum-Golgi intermediate compartment membranes in the form of Langmuir monolayers. Natural extracted yeast lipids were used because, unlike synthetic lipids, the acyl chain saturation pattern of yeast and mammalian lipids are similar.
The structure of the model membranes, orthogonal to the plane of the membrane, as well as their lateral packing, were found to depend strongly on their specific composition, with cholesterol having a major influence on the in-plane morphology, yielding a coexistence of liquid-order and liquid-disorder phases.
A variety of emergent phenomena have been enabled by interface engineering in complex oxides. The existence of an intrinsic interfacial layer has often been found at oxide heterointerfaces. However, ...the role of such an interlayerin controlling functionalities is not fully explored. Here, we report the control of the exchange bias (EB) in single-phase manganite thin films with nominallyuniform chemical composition across the interfaces. The sign of EB depends on the magnitude of the cooling field. A pinned layer, confirmed by polarized neutron reflectometry, provides the source of unidirectional anisotropy. The origin of the exchange bias coupling is discussed in terms of magnetic interactions between the interfacial ferromagnetically reduced layer and the bulk ferromagnetic region. The sign of EB is related to the frustration of antiferromagnetic coupling between the ferromagnetic region and the pinned layer. Our results shed new light on using oxide interfaces to design functional spintronic devices.
In article number 2001324, the authors report the achievement of strong ferromagnetism in atomically thin cobaltite by local structural modification, where a surprisingly large magnetic moment and ...Curie temperature are observed. Thus, a strategy for creating functional quantum heterostructures by exploiting atomic interface engineering is demonstrated.
The vacancy distribution of oxygen and its dynamics directly affect the functional response of complex oxides and their potential applications. Dynamic control of the oxygen composition may provide ...the possibility to deterministically tune the physical properties and establish a comprehensive understanding of the structure–property relationship in such systems. Here, an oxygen‐vacancy‐induced topotactic transition from perovskite to brownmillerite and vice versa in epitaxial La0.7Sr0.3MnO3−δ thin films is identified by real‐time X‐ray diffraction. A novel intermediate phase with a noncentered crystal structure is observed for the first time during the topotactic phase conversion which indicates a distinctive transition route. Polarized neutron reflectometry confirms an oxygen‐deficient interfacial layer with drastically reduced nuclear scattering length density, further enabling a quantitative determination of the oxygen stoichiometry (La0.7Sr0.3MnO2.65) for the intermediate state. Associated physical properties of distinct topotactic phases (i.e., ferromagnetic metal and antiferromagnetic insulator) can be reversibly switched by an oxygen desorption/absorption cycling process. Importantly, a significant lowering of necessary conditions (temperatures below 100 °C and conversion time less than 30 min) for the oxygen reloading process is found. These results demonstrate the potential applications of defect engineering in the design of perovskite‐based functional materials.
Oxygen vacancy dynamics and ordering in La0.7Sr0.3MnO3−δ epitaxial films are identified by real‐time X‐ray diffraction. A novel intermediate phase with a noncentered crystal structure is observed. Huge changes of the physical properties (i.e., ferromagnetic metal and antiferromagnetic insulator) are found just by altering the oxygen content. Reverse switching among distinct topotactic phases is achieved at remarkably reduced temperatures.
The calculation of neutron reflectivity from raw time‐of‐flight data including instrumental corrections and an improved resolution calculation is presented. The theoretical calculations are compared ...with experimental data measured on the vertical sample plane reflectometer D17 and the horizontal sample plane reflectometer FIGARO at the Institut Laue–Langevin (ILL), Grenoble, France. This article comprises the mathematical body of the time‐of‐flight reflectivity data‐reduction software COSMOS which is used on D17 and FIGARO.
The mathematical body of the time‐of‐flight reflectometry data‐reduction software COSMOS is described. COSMOS is used on the reflectometers D17 and FIGARO at the Institut Laue–Langevin in Grenoble, France.
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It is known that nanoparticles (NPs) in a biological fluid are immediately coated by a protein corona (PC), composed of a hard (strongly bounded) and a soft (loosely associated) ...layers, which represents the real nano-interface interacting with the cellular membrane in vivo. In this regard, supported lipid bilayers (SLB) have extensively been used as relevant model systems for elucidating the interaction between biomembranes and NPs. Herein we show how the presence of a PC on the NP surface changes the interaction between NPs and lipid bilayers with particular care on the effects induced by the NPs on the bilayer structure.
In the present work we combined Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) and Neutron Reflectometry (NR) experimental techniques to elucidate how the NP-membrane interaction is modulated by the presence of proteins in the environment and their effect on the lipid bilayer.
Our study showed that the NP-membrane interaction is significantly affected by the presence of proteins and in particular we observed an important role of the soft corona in this phenomenon.
Accurate, cost-efficient, and safe hydrogen sensors will play a key role in the future hydrogen economy. Optical hydrogen sensors based on metal hydrides are attractive owing to their small size and ...costs and the fact that they are intrinsically safe. These sensors rely on suitable sensing materials, of which the optical properties change when they absorb hydrogen if they are in contact with a hydrogen-containing environment. Here, we illustrate how we can use alloying to tune the properties of hydrogen-sensing materials by considering thin films consisting of tantalum doped with ruthenium. Using a combination of optical transmission measurements, ex situ and in situ X-ray diffraction, and neutron and X-ray reflectometry, we show that introducing Ru in Ta results in a solid solution of Ta and Ru up to at least 30% Ru. The alloying has two major effects: the compression of the unit cell with increasing Ru doping modifies the enthalpy of hydrogenation and thereby shifts the pressure window in which the material absorbs hydrogen to higher hydrogen concentrations, and it reduces the amount of hydrogen absorbed by the material. This allows one to tune the pressure/concentration window of the sensor and its sensitivity and makes Ta1–y Ru y an ideal hysteresis-free tunable hydrogen-sensing material with a sensing range of >7 orders of magnitude in pressure. In a more general perspective, these results demonstrate that one can rationally tune the properties of metal hydride optical hydrogen-sensing layers by appropriate alloying.
Sensors that can quickly measure the lipase activity from biological samples are useful in enzyme production and medical diagnostics. However, current lipase sensors have limitations such as ...requiring fluorescent labels, pH control of buffer vehicles, or lengthy assay preparation. We introduce a sparsely tethered triglyceride substrate anchored off of a gold electrode for the impedance sensing of real-time lipase activity. The tethered substrate is self-assembled using a rapid solvent exchange technique and can form an anchored bilayer 1 nm off the gold electrode. This allows for an aqueous reservoir region, providing access to ions transported through membrane defects caused by triglyceride enzymatic hydrolysis. Electrical impedance spectroscopy techniques can readily detect the decrease in resistance caused by enzymatically induced defects. This rapid and reliable lipase detection method can have potential applications in disease studies, monitoring of lipase production, and as point-of-care diagnostic devices.
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