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Optical second harmonic generation (SHG) signals from a cyanine dye during compression of a monolayer in a Langmuir-Blodgett trough were measured to investigate the mean tilt angle of the dye corresponding to the formation of an H-band. The pressure-surface area (π-A) isotherm for 3,3′-dioctadecyloxacarbocyanine molecules spread on an aqueous subphase showed a plateau region after a kink point in the isotherm characteristic, which suggests a phase transition from the liquid expanded (LE) phase to the liquid condensed (LC) phase. SHG signals from the monolayer were obtained as the surface area decreased for the input and output polarization combinations PP, MS, SP, PS, and SS, where the first and second letters denote the input and output polarizations, respectively, and M refers to the polarization midway between S and P. For polarization combination PP, the SHG signal increased steeply during compression, whereas for polarization combination MS, the signal increased gently. The SH field from the monolayer for polarization combination SP in the LC phase was almost inverted to the field in the LE phase. We estimated the mean polar angles from the SHG responses during compression. The angle decreased continuously by almost 5° from 28° with the growth of domains in the LC phase. Visible absorption spectra of monolayers transferred to glass substrates were also obtained. The area intensity of the peak in the spectra attributed to H-aggregates increased compared with that of the monomer as the surface area decreased in the LC phase. The results were consistent with the polar angle reduction in the LC phase observed by in situ SHG. The decrease of the angle in the LC phase probably allowed the cyanine dyes to pack together tightly and align side by side, promoting H-aggregation.

Major aim of this research study is to comprehend the interaction of soft nanoparticle-based vesicles with model lung surfactant monolayer. Vertebrate lung surfactant plays a pivotal role in gaseous exchange plus breathing. As pulmonary lung surfactant is the one which directly comes in contact to inhaled air so it also acts as defensive agent against air-borne pollutants (any foreign particle). In this enquiry, several different types of lipids namely 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-Dimitrystoyl-sn-glycero-3-phosphorylcholine, 1-palmitoyl-2-oleoyl-sn-glyceero-3-phosphocholine are used as lipid monolayer and vesicles in different combinations while using Langmuir-Blodgett trough. The different lipids are treated with chloroform and buffer solution to make vesicles and then extruded. Nanoparticles present in vesicles interact with lipid monolayer when processed in Langmuir-Blodgett trough and mimics the behavior of natural pulmonary lung surfactant system. In Quartz Crystal with gold mounted on it as thin layer, different combinations of lipid bilayer and vesicles are used from the same list of lipids. The results obtained from this investigation are quite informative in depicting the interaction of soft nanoparticle based vesicles with lung surfactant system, also this work would pave the way to explore still more on interaction of soft nanoparticles based vesicles with lung surfactant, as very little work is done on soft nanoparticles. This novelty of this work is to plan to develop some alternatives of lung surfactant because we cannot perform the experiment directly in living souls as some of these has lethal effects.

Developing a clean handling and transfer process, capable of preserving the integrity of two-dimensional materials, is still a challenge. Here, we present a flexible, dynamic, and lipid-based scaffold that clamps graphene at the edges providing a practical, simple, and clean graphene manipulation and transfer method. Lipid films with different surface pressures are deposited at the air/copper-etchant interface immediately after placing the graphene samples. We show that at surface pressures above 30 mN/m, the lateral support prevents graphene movement and cracking during all etching and transfer. The method provides new insights into the handling of graphene and can yield efficient, sensitive, and clean graphene-based devices.

The interface between a nematic liquid crystal phase, 4-cyano-4′-pentylbiphenyl (5CB) and water was examined for protein detection by monitoring the formation of a complex between sodium polystyrene sulfonate (PSSNa) and a positively charged biological species on the 5CB in a transmission electron microscopy (TEM) grid cell coated with a strong anionic polyelectrolyte-containing block copolymer, LCP-b-PSSNa (LCP:poly(4-cyanobiphenyl-4′-oxyundecylacrylate)). This block copolymer was successfully synthesized by reversible addition-fragmentation chain transfer polymerization. A monolayer of LCP-b-PSSNa in a Langmuir Blodgett trough (in which PSSNa and LCP were located in and above water, respectively, in the TEM grid cell) was transferred to the 5CB/water interface in the 5CB-filled TEM grid that was already placed on octadecyltrichlorosilane-coated glass. Model proteins such as bovine serum albumin (BSA), hemoglobin (Hb), α chymotrypsinogen-A (ChTg), and lysozyme (LYZ) having different isoelectric points (pIs) were tested for non-specific protein detection. When the protein solutions were injected into the TEM grid cell, the initial homeotropic orientation of 5CB in the TEM grid cell changed to a planar one below the pIs of the proteins due to electrostatic interactions between PSSNa (- charge) and the proteins (+ charge); this did not occur above the pIs of the tested proteins. The minimum concentrations at which the homeotropic to planar configurational changes (H-P changes) occurred were 0.02, 0.04, 0.04, and 0.08 wt% for BSA, Hb, ChTg, and LYZ, respectively. Therefore, the positively charged biomaterials were visually detected at the PSSNa-coated LC/water interface during an H-P change by using polarized optical microscopy under crossed polarizers. This simple set-up for non-specific biomaterial detection paves a way for the development of efficient and excellent quality biosensors.

In continuation of our previous studies on Langmuir nanoparticle films we prepared well-ordered bilayer film on the air–water interface in the Langmuir–Blodgett trough. The distance of neighboring nanoparticles was adjustable by shortening the carbon chain length by UV–ozone irradiation. Kinetics of the nanoparticle reassembly in multilayer structure was monitored in time by grazing-incidence small angle X-ray scattering (GISAXS) technique. The interparticle distance determined from the first lateral peak positions decayed exponentially with characteristic time of 102 ± 13 s. The final GISAXS pattern proves nanoparticle multilayer collapse and multilayer agglomeration at the end of the UV exposition.

International audience; This study comprises 3 experiments exploring the possible benefits and mechanism of action of liposomes for chilling (4 degrees C) canine sperm over a period of 4 days. In the first experiment, 20 ejaculates collected from 5 Beagle dogs were chilled in an extender containing 6% low density lipoproteins (LDL) (Control), or one of 7 extenders containing different concentrations (2, 4, 6, 8, 10, 15, 20%) of liposomes (LIPO). These ejaculates were chilled over 4 days and motility was assessed daily using a Hamilton Thorne analyzer (HTM-IVOS, 14.0). The 2% LIPO obtained the best results (p = 0.038) after four days (72.55% motile spermatozoa and 31.4% progressive spermatozoa). In experiment 2, 10 ejaculates were collected from same 5 dogs and chilled in 6% LDL or 2% LIPO-based extenders. Sperm integrity characteristics were assessed prior to refrigeration and every 48 h for four days (DO, D2, and D4). Acrosome integrity was assessed using the FITC-PSA test (Fluorescein IsoThiocyanate-Pisum Sativum Agglutinin), plasma membrane (PM) integrity using both the hypo-osmotic swelling test (HOSt) and SYBR14/Propidium Iodide test (SYBR14/130, and DNA integrity using the Acridine-Orange test (AO). The 2% LIPO extender provided equivalent preservation of sperm integrity parameters to the reference extender (6% LDL). In experiment 3, a Langmuir-Blodgett trough was used to evaluate the mechanistic interactions between LDL, LIPO, prostatic fluid, and the canine spermatozoal membrane during chilling. Results indicate that LDL and LIPO interact differently with the biomimetic membrane. The most likely conclusion of these findings is that LDL and liposomes employ different protective mechanisms during the chilling (4 degrees C) of canine spermatozoa.

A review of Langmuir–Blodgett (LB) trough designs is given. A modular design of Langmuir–Blodgett trough is presented. This trough can be used for monolayer analysis, conventional deposition of LB films, and deposition of alternating LB films by adding different combination of pressure sensors and dipper mechanisms. Research results produced with this trough are referenced.

This work analyzes the organization of thin films of nematic liquid crystals on liquid substrates (water and glycerol). In this situation, the planar anchoring at the liquid interface is stronger than the homeotropic anchorage at the air interface. Below a critical thickness about 0.5-0.6 µm, stripes appear that correspond to a modulation of the nematic orientation. The stripe wavelength is much larger than the film thickness. We have analyzed the specific situation of very thin films and we have shown that a striped phase can exist for thin flat films with thickness down to 20-40 nm. The relevance of the elastic surface-like terms (K24 and K13) in the theoretical analysis is discussed. On water, thin nematic films coexist with a trilayer of molecules which has a special organization directed by very short ranged interactions with the subphase. The thickness gradients which exist at the edge of the films prevent the formation of stripes. Static and dynamic measurements of the energy of film boundary have been performed. It seems then that the nematic film can accommodate a distorted state thanks to the formation of stripes below the critical transition thickness induced by confinement. Finally, a study of the coalescence process driven by line tension enables to identify two dissipation mechanisms: at short times, the dissipation is surface dominated whereas at long times, the dissipation is mainly in the subphase. A scaling approach enables to understand the experimental dynamics., Ce travail de thèse analyse l'organisation des films de cristaux liquides nématiques sur substrats liquides (eau et glycérol). Dans ce cas, l'ancrage planaire au niveau du substrat liquide est plus fort que l'ancrage homéotrope à l'interface libre. En dessous d'une épaisseur critique de l'ordre de 0.5-0.6 µm, des stries qui correspondent à une modulation de l'orientation du directeur, apparaissent. La longueur d'onde de ces stries est largement supérieure à l'épaisseur du film. Nous avons analysé la situation spécifique des films très minces et montré qu'une phase striée existait pour des films plats jusqu'à des épaisseurs de l'ordre de 20-40 nm. La pertinence de l'introduction des termes élastiques dits de surface (K24 et K13) dans l'analyse théorique des stries a été discutée. Sur l'eau, les films nématiques coexistent avec une tricouche de molécules dont l'organisation est régie par des interactions à très courte portée avec le substrat. Les gradients d'épaisseur présents en bord de film empêchent la formation de stries. Des mesures statiques et dynamiques de l'énergie d'un bord de film ont été effectuées. Il semble alors que le film nématique puisse accommoder un état distordu grâce à la formation de stries bien en dessous de l'épaisseur critique de transition de confinement. Enfin, une étude du processus de coalescence contrôlée par la tension de ligne a permis de mettre en évidence deux régimes de dissipation : aux temps courts la dissipation s'effectue en surface alors qu'aux temps longs, la dissipation se fait principalement dans la sous-phase. Une analyse en loi d'échelle permet de rendre compte de la dynamique observée expérimentalement.

A Langmuir-Blodgett (LB) trough has been developed from the ‘diamond design’ previously reported, by fixing two points of the diamond to facilitate a modular construction which could also be conveniently adapted for alternating-layer and Montal-Mueller studies. With biomolecular applications in mind, the trough was deliberately made small; barriers can vary the surface area between 115 cm 2 and 17.5 cm 2 with a low subphase volume of about 550 cm 3 . The surface flow is channelled by shoulders; this produces near-normal flow at an LB substrate, and yields high quality films for both low molecular mass materials and appropriate polymers with a range of surface viscosities.

Some factors important to Langmuir-Blodgett film quality like vibrations generated within the trough, unevenness of motion of the barrier or substrate holder, control of constant pressure during deposition are evaluated. It is shown that the addition of analogue devices to the computer control can greatly improve trough performance. Vibrations in the frequency range from 0 to 100 Hz can be cut down to an acceleration amplitude as low as 0.02 × 10−3 m s−2. A novel translational unit design is presented by which both amplitude and frequency of vibrations can be controlled. The unevenness coefficient strongly depends on the construction of the drive unit and varies from 15 to 50% for different module designs. Integration time below 0.3 s and data acquisition rate above 10 readings per second are recommended for precise surface pressure maintenance.

The monomer, 2-pentadecyl aniline, was spread at air-aqueous interfaces to produce stable monolayer films. Its surface pressure and surface potential isotherms are discussed. Polymerization of 2-pentadecyl aniline confined to a monolayer with a Langmuir trough was also studied. By using the trough itself as an instrument to probe the polymerization, the effects of initiator concentration and subphase acid concentration on the polymerization reaction are discussed.

Design details of a new Langmuir-Blodgett trough are presented. It uses a diamond-shaped barrier which flexes at the corners to alter the area, giving high cleanliness and a constant perimeter. The amplitude of surface waves is of the order of 1 mu m (mostly due to background noise), and the uncertainty in the area of the diamond-shaped barrier is less than 1.5%. Trough performance was evaluated using eicosanoic and tricosanoic acid, both on subphases containing cadmium ions. Good stability of the surface monolayers and sharp phase transitions indicate that high levels of cleanliness are possible. Isotherms show excellent reproducibility. Surface flow patterns during deposition are satisfactory, and film quality is high, as judged from microscopic examination and preliminary optical and electrical studies.

A moving-wall-type Langmuir-Blodgett (LB) trough was constructed to overcome the problems associated with an ordinary LB trough. LB films of a polymer monolayer which does not posses a hydrocarbon chain were deposited using this new deposition system. Methacrylic acid-methylacrylate random copolymer, two-dimensionally cross-linked by lanthanum ions on the water surface, was successively deposited onto a hydrophilic glass substrate as a complete Z-type film. These multilayer films have a sharp, clear X-ray diffraction pattern which shows a layer spacing of 8.43 A.