Composite LB Research Articles

Facile preparation and study of supramolecular architecture of an efficient nanocomposite LB film AHSM/SA based on azo-functionalized hockey stick-shaped mesogen at air-water and air-solid interface

Hockey stick-shaped mesogens are fascinating thermotropic liquid crystal systems owing to their exceptional supramolecular assembly properties and shape anisotropy compared to conventional rod-and bent-shaped mesogens. In this article, we present an investigation of the supramolecular organization of a new azo-functionalized hockey stick-shaped mesogen with stearic acid at the air-water interface and air-solid interfaces by applying the Langmuir-Blodgett film deposition method. The incorporation of stearic acid can change the molecular organization of azo-functionalized hockey stick-shaped mesogen at an aqueous interface through hydrophobic-hydrophobic interactions and form a supramolecular nanostructure at the solid interface. The interfacial nature of the Langmuir monolayer was studied by recording the isotherm (surface pressure area, π–A), which was further analyzed by using Brewster angle microscopy. The significant reduction in molecular area, increased surface pressure, and lower isotherm slope of the AHSM/SA composite mixture indicate the hybrid AHSM/SA monolayer's greater stability compared to pure AHSM. BAM images of the AHSM/SA composite signify nanostructure aggregates formed by the interaction of AHSM and SA molecules at the air-water interface. Field emission scanning electron microscopic analysis of composite films revealed the formation of supramolecular domains. The impact of changing the surface pressure and the number of depositions on the morphology of the composite film surface was monitored using field emission scanning electron microscopy. The supramolecular H-type aggregation of azo-functionalized hockey stick-shaped mesogen and stearic acid molecules in the composite LB film was characterized using UV–visible absorption and steady-state fluorescence spectroscopy. The adsorption of stearic acid onto azo-functionalized hockey stick-shaped mesogen via hydrophobic interactions was confirmed by Fourier transform infrared spectroscopy of the composite Langmuir Blodgett film. Further, Raman spectroscopy of the LB films of the AHSM/SA composites is distinct from the pristine film components due to the merging of signals at similar wave numbers for both SA and AHSM with a lack of typical packing pattern further supported by PXRD studies of the films.

Influence of Inlays/Onlays and Their Material on Stress Distribution in Mandibular Molars: Finite Element Analysis

Background: This study aimed to evaluate the influence of inlays/onlays and their material on stress distribution in mandibular molars with large cavities, using finite element analysis (FEA). Methods: 3D models of the first mandibular molar were created. Then, a mesio-occluso-distal cavity was created, and cusps were reduced (1.5 mm for buccal cusps and 1 mm for lingual cusps). The restorations were: inlay, onlay that covered buccal cusps (B models), and onlay that covered all cusps (LB models). Inlays and onlays were represented by two materials: nanofill composite resin and polymer-infiltrated ceramic network (PICN). Vertical load of 600 N was applied and von Mises stresses were calculated. Results: Inlay models showed higher stress concentration in tooth structures than onlay models. Composite resin inlays and onlays transmitted most of the stress to adjacent structures. On the other hand, PICN inlays/onlays absorbed most of stress and transmitted less stress to dental structures than composite resin restorations. Moreover, stress concentrations in PICN onlay models (B-buccal cusps and LB-all cusps) were similar, while composite resin LB onlay showed higher stress concentration in dental structures than composite resin B onlay. Conclusions: Onlays showed better stress distribution than inlays. PICN might be a suitable choice as a restorative material of inlay/onlay for large cavities in molars, while the composite resin is unfavorable material for such restorations in terms of stress redistribution in dental structures.

Remediation Effects of Different Composite Materials on Cadmium-Contaminated Farmland Soil

A pot experiment was conducted to study the application effects of three composite materials, namely SC (lime:organic compound fertilizer=2:3), LS (ferrous sulfate:lime=1:1) and LB (ferrous sulfate:biochar in combinations of 1:1, 1:2, 1:3, 1:4 and 1:5), on soil Cd bioavailability, Cd cumulative distribution in different wheat organs, and wheat yield. The results indicated that:① Addition of composite materials all significantly decreased the soil available Cd content by 50.2%-81.8% (SC), 29.4%-48.1% (LS), and 18.7%-42.2% (LB). Composite materials significantly increased soil pH by 1.37-2.28 (SC), 0.41-0.86 (LS), and 0.14-0.17 (LB) units. ② The Cd cumulative distribution in different wheat organs were in the order of root > leaf > stem > glume > grain. The translocation abilities of Cd in different organs were in the order of root > glume > stem and leaf. ③ Compared with the control, 0.67% SC addition and 0.67% LS addition significantly increased the wheat yields by 56.4% and 51.2%; LB addition significantly increased wheat yield by 39.6% to 51.2%. ④ The correlation analysis showed that soil pH was significantly negatively correlated with soil available Cd and Cd contents in different wheat organs. There were significant positive correlations between soil available Cd and Cd contents in different wheat organs, and the correlation coefficients were 0.711 (grain), 0.817 (glume), 0.593 (stem), 0.630 (leaf) and 0.622 (root). Meanwhile, there is also a significant positive correlation between Cd content in different wheat organs. ⑤ Comprehensively, the addition of 0.93% SC increased soil pH by a maximum of 2.28 units, and the soil available cadmium content was decreased by a maximum of 81.8%. Therefore, adding 0.93% SC was the most suitable treatment for repairing and controlling the Cd pollution in farmland soil.

Layer by layer composite film of dimyristoyl-phosphatidylcoline and bacteriorhodopsin fabricated by multilayer molecular thin film method using fatty acid and lipid

A composite film of dimyristoyl-phosphatidylcoline (DMPC) and bacteriorhodopsin (BR) was fabricated by multilayer molecular thin film method using fatty acid and lipid on a quartz substrate or a hydrogenated amorphous silicon thin film. FTIR reflection absorption spectrums and UV absorption spectrums of the films were characterized on the detail of surface structure of the films. The spectroscopic data exhibited a specific layer by layer interaction of BR and environmental molecule DMPC above fatty acid. Especially, 4 layer composite LB films DMPC and BR exhibited an entirely different feature of IR reflection absorption spectrum depend on fatty acid species.

Assembly of gold composite thin films by spontaneous reduction of subphase chloroaurate anions beneath vitamin E Langmuir monolayers

Gold composite thin films were generated by the spontaneous reduction of chloroaurate (AuCl 4 −) ions beneath vitamin E (VE) Langmuir monolayer. The monolayer and gold nanocomposite LB films were then characterized by surface pressure–area ( π– A) isotherms, ultraviolet–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD), respectively. The results showed that the limiting area/VE molecule on the HAuCl 4 solution subphase was larger than that on the pure water subphase, and it increased with reaction time. The morphologies of Au particles such as spherical-like, triangular and multiply-twinned particles (MTPs) could be observed. The XRD pattern indicated that the gold particles in LB films were face-centered cubic (fcc) polycrystalline. The plasmon absorption intensities of gold composite LB films increased with the film thickness, which suggested that the monolayer containing gold particles could be transferred successfully onto the substrates.

Tribological behaviour of Langmuir—Blodgett films of polymerised 22‐tricosenoic acid and 22‐tricosenoic acid/CdS nanoparticles

AbstractLangmuir—Blodgett (LB) films of 22‐tricosenoic acid and of 22‐tricosenoic acid polymerised in the presence of an electron beam, and in situ composite LB films of 22‐tricosenoic acid/CdS were prepared. The friction and wear behaviour of the LB films were investigated with a ball‐on‐block one‐way reciprocating friction tester. The structures and morphologies of the LB films were analysed and observed using atomic force microscopy. The wear resistance of the LB films was increased after polymerisation of the acid, and the composite LB film of 22‐tricosenoic acid/CdS showed better wear resistance because the inorganic nanocores of CdS acted to resist wear and to carry load. The LB film of the acid experienced structural changes during the friction process.

X-ray and neutron reflectometry investigation of Langmuir-Blodgett films of cellulose ethers.

Langmuir-Blodgett films of a series of cellulose ethers are investigated by X-ray and neutron reflectometry. Two types of samples are considered: simple alkyl ethers of cellulose and derivatives obtained by the alkylation of (2-hydroxypropyl)cellulose (HPC). All of the cellulose ethers form stable monolayers at the air-water interface. Significant differences are, however, found in the surface pressure-area compression isotherms. Ethers prepared from HPC typically exhibit larger limiting molecular areas and higher surface pressures than the corresponding simple cellulose ethers. The ease of monolayer transfer to hydrophobic silicon substrates differs greatly from one type of molecule to another. Successful transfer conditions are found only for ethers that form stable monolayers at sufficiently high surface pressures. Surprisingly, deuterated HPC ethers, prepared for neutron reflectivity measurements, exhibit monolayer properties significantly different from those of their hydrogenated analogues. Although essentially identical limiting molecular areas are found, the surface pressure corresponding to a characteristic plateau transition in the compression isotherm is found to decrease by about 8-10 mN m(-1) upon side chain deuteration. X-ray reflectivity results show a linear increase of film thickness with the number of deposited layers, indicating a regular and reproducible transfer. Observed average layer spacings are, however, significantly smaller than the calculated length of fully extended side chains. Neutron reflectivity curves recorded for composite LB films composed of both deuterated and hydrogenated polymers exhibit regular Keissig fringes, but no Bragg peak. This result indicates that these LB films do not possess an internal periodic structure and the initial layer-by-layer organization is lost by large interlayer diffusion.

Composite LB films of copper octabutoxy phthalocyanine and polyimide

Composite LB films of copper octabutoxy phthalocyanine (Cu-obo-Pc) and polyimide from polyamic acid alkyl amine salt have been deposited. The multilayers were formed from mixed Langmuir films and by alternate layer deposition. Analyses were by polarised UV–visible spectroscopy and X-ray diffraction. The phthalocyanine component retained its order in the matrix even after the composite was thermally imidised. The orientations of the chromophore in the alternating films were similar to that of the pure phthalocyanine films. However, in the mixed films, the macrocyclic ring changed its position from an almost flat orientation on the substrate surface to one with a smaller inclination to the substrate surface normal. It is suggested that the change in orientation is due to stresses induced by thermal imidisation which is accompanied by loss of the alkyl amine chain from polyamic acid alkyl amine salt.

Studies on fabricating α-Fe 2O 3 ultrafine particles by LB film technology

The α-Fe 2O 3 ultrafine particles were dispersed in the solutions of stearic acid/ n-hexane/chloroform by the ultrasonic method, and fabricated by the Langmuir–Blodgett film technology. α-Fe 2O 3 ultrafine particles/stearic acid composite LB films were characteried by π–A curve, UV-visible absorption spectrum, IR spectrum, small angle X-ray diffraction, TEM and electron diffraction. The results showed the following: the αFe 2O 3 ultrafine particles were uniformly dispersed in organic solvents; the film-forming characterization of the α-Fe 2O 3 ultrafine particles/stearic acid monolayer was fine, the α-Fe 2O 3 ultrafine particles in the composite film had a small orientation; the α-Fe 2O 3 ultrafine particles/stearic acid composite film had a lamellar structure.

Study on the self-packing of SnO 2 nanoparticles at the air–hydrosol interface and its composite LB films with arachidic acid

SnO 2 nanoparticles were found to self-pack at the air–hydrosol interface and form a nanoparticulate film. The self-packed films were observed under a Brewster angle microscope, and investigated by recording the time evolution of surface pressure and π– A isotherms. The results show that SnO 2 nanoparticles take 3 h to form a complete film at the air–hydrosol interface. Composite monolayers of SnO 2 and arachidic acid were obtained by spreading arachidic acid onto a fresh hydrosol surface. Composite Y-type LB films were transferred from the air–hydrosol interface onto substrates, and characterized by FTIR, UV-vis, X-ray diffraction spectroscopy and TEM techniques. The results show that the composite films have good structure, with SnO 2 nanoparticles uniformly and compactly distributed in the arachidate matrix.

Characteristic Analysis of Molecular Photodiode Using Conducting Polymer (PANI) as an Electrode

Molecular photodiode consisted of an electron acceptor(A), a sensitizer(S) and an electron donor(D) is fabricated by mimicking photo induced electron transfer system in the biological photosynthesis. Polyaniline(PANI)-stearic acid(SA) composite LB films used as an electrode was deposited onto hetero-LB films of A/S/D stacked on ITO glass. The PANI-SA composite LB films exhibited high electrical conductivity of 10−1 ∼ 10−2 S/cm upon with HCl or I2 doping Especially, iodine is found to be the most promising dopant, since it gives a remarkable stability for the molecular photodiode system. The rectifying characteristic and photoswitching function of the proposed molecular photodiode is introduced.

Study on Ordered Assembly of SnO<sub>2</sub> Nanoparticles-Arachidic Acid Composite LB Films

The hydrosol of SnO2 nanoparticles (NP) have been prepared by colloid chemistry method. The composite LB monolayer and multilayer of SnO2 NP-AA have been obtained by LB technique at the gas-liquid interface of the hydrosol subphase. The structures of the monolayer and multilayer were characterized by IR, UV-Vis, small angle X-ray diffraction spectroscopy and TEM technique, The results indicate that the coverage of SnO2 NP at the composite monolayer's surface is high and the sites of SnO2 NP are similar. The multilayer has good periodic structure.

Preparation and properties of conducting arachidic acid/polypyrrole composite Langmuir-Blodgett films

Electrically conducting arachidic acid/polypyrrole (PPy) composite films were prepared by exposing the arachidic acid LB films containing ferric chloride to pyrrole vapor. The optimum conditions to deposit matrix LB film were the subphase temperature of 23–25°C, pH of 6.0 and ferric chloride concentration of 5.0 × 10−5 M. The formation of PPy in the arachidic acid matrix LB films was confirmed by UV-visible spectra, FTIR spectra, and scanning electron micrographs. The average thickness of the composite LB films prepared at 0°C was 1525 Å. The composite films prepared at lower temperatures have more uniform surface and exhibit higher electrical conductivity than the films prepared at higher temperatures do. The in-plain conductivity and the transverse conductivity of the composite film were 10−3−10−2 S/cm and 10−6S/cm, respectively, and, thus, the conductivity anisotropy was about 103 © 1996 John Wiley & Sons, Inc.

Structural Study on 5-(Dodecyloxy)-1-((6-Trimethylammonio)Hexyl)oxy)Naphthalene—Sodium Dextran Sulfate Langmuir-Blodgett Film Through Fourier Transform Infrared Spectroscopy

Abstract The Fourier transform infrared transmission (FTIR-T) and attenuated total reflection (ATR) spectra of the 5-(dodecyloxy)-1-((6-(trimethylammonio)hexyl)oxy)naphthalene — sodium dextran sulfate composite LB films deposited under the surface pressure of 30 mN/m have been recorded and spectral assignments made. By means of polarization techniques and with the application of the uniaxial and biaxial orientation models, the orientation characteristics of the long hydrocarbon chains and the = C-O linkage in the LB films have been investigated, giving rise to the detailed information of the arrangement of molecular fragments in the 1-SDS composite LB films.