LB Film Structure of Nanometer‐Scale PEEKK Macrocyclic Oligomers

A rigid macrocyclic oligomer (RCO), cyclic poly(aryl ether ketone), was synthesized and used to produce Langmuir‐Blodgett (LB) films. The isotherm of surface pressure versus surface area showed that the RCO molecules form a stable monolayer on the water subphase with an area per molecule of about 1.7 nm². The structure of the LB film was confirmed by means of atomic force microscope, and two‐dimensionally ordered cavities of nanometer scale were observed in the LB film.     

Structures of palmitoyl-L and DL-lysine monolayers at the air-water interface--polarization modulation infrared reflection absorption spectroscopic study

Polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) was applied to measure the IR spectra of palmitoyl-DL-lysine (L-PL) and palmitoyl-DL-lysine (DL-PL) at the air-water interface. The spectra in the amide I and II regions were simulated by using the extinction coefficients of the amide I and II bands of L-PL and DL-PL determined by the analyses of the IR external reflection spectra of the Langmuir-Blodget (LB) films prepared on a Ge plate (Yasukawa et al. J. Mol. Struct. 2005, 735-736, 53), indicating the angle between the plane of the secondary amide group (the amide plane) and the surface normal in the L-PL monolayer to be about 20 degrees and the angle in the DL-PL monolayer to be about 37 degrees. Comparison of the tilt angles with the corresponding angles in the LB films (about 20 degrees for the LB film of L-PL; about 49 degrees for the LB film of DL-PL) indicated that, upon being transferred to the solid substrate from the air-water interface, the L-PL monolayer keeps the orientation of the amide plane virtually unchanged, while the DL-PL monolayer changes the orientation appreciably to a horizontal direction. The orientation change of the amide plane was interpreted as due to the accommodation of irregularly oriented palmitoyl groups into the LB films of DL-PL on the solid substrate.     

Chiral molecular assemblies from a novel achiral amphiphilic 2-(heptadecyl) naphtha[2,3]imidazole through interfacial coordination

A novel amphiphilic compound 2-(heptadecyl) naphtha[2,3]imidazole (NpImC17) was synthesized, and its coordination with AgNO(3) in situ in the monolayer at the air/water interface and ex situ in the Langmuir-Blodgett (LB) film on solid substrate has been investigated. It has been found that interfacial coordination between NpImC17 and Ag(I) ion occurred both in the monolayer and in the LB film. It is interesting to note that the Ag(I)-coordinated ultrathin film became chiral although the ligand itself is achiral. It was suggested that the chirality of the Ag(I)-coordinated LB film was developed due to the formation of a helical coordination polymer through the interfacial coordination. To the best of our knowledge, this is the first report on the formation of chiral monolayer and LB films from an achiral molecule through interfacial coordination.     

Langmuir-Blodgett films and chiroptical switch of an azobenzene-containing dendron regulated by the in situ host-guest reaction at the air/water interface

An amphiphilic dendron containing an azobenzene ring at the focal point and the l-glutamate peripheral groups was designed. Its monolayer formation and host-guest reaction with cyclodextrins at the air/water interface and the properties of the transferred Langmuir-Blodgett (LB) films were investigated. The individual dendron, although without any long alkyl chains, could still form a stable monolayer at the air/water interface because of the good balance between hydrophilic and hydrophobic parts within the molecule. When cyclodextrin (CyD) was added to the subphase, a host-guest reaction occurred in situ at the air/water interface. The inclusion of the focal azobenzene moiety into the cavity of cyclodextrin decreased the packing of the aromatic ring and also led to the diminishment of the molecular area. Both the films formed at the surface of pure water and aqueous cyclodextrins were transferred onto solid substrates. Nanofiber structures were obtained for the film from the water surface as a result of the packing of the azobenzene groups, and circular domains were obtained for the film transferred from the aqueous CyD phases. The film transferred from the water surface showed an exciton couplet in the absorption band of azobenzene, whereas a negative Cotton effect was obtained for the film from CyD subphases. It was found that the supramolecular chirality in the LB film transferred from water was due to the transfer of the molecular chirality to the assemblies whereas that from the CyD subphase was due to the inclusion of azobenzene into the chiral cavity. Interestingly, the film from the water surface was photoinactive, whereas a reversible optical and chiroptical switch could be obtained for the film from the α-CyD subphase. The work provided a way to regulate the assembly and functions of organized molecular films by taking advantage of the interfacial host-guest reaction.     

Lignin from sugar cane bagasse: extraction, fabrication of nanostructured films, and application

Four lignin samples were extracted from sugar cane bagasse using four different alcohols (methanol, ethanol, n-propanol, and 1-butanol) via the organosolv-CO2 supercritical pulping process. Langmuir films were characterized by surface pressure vs mean molecular area (Pi-A) isotherms to exploit information at the molecular level carrying out stability tests, cycles of compression/expansion (hysteresis), subphase temperature variations, and metallic ions dissolved into the water subphase at different concentrations. Briefly, it was observed that these lignins are relatively stable on the water surface when compared to those obtained via different extraction processes. Besides, the Pi-A isotherms are shifted to smaller molecular areas at higher subphase temperatures and to larger molecular areas when the metallic ions are dissolved into the subphase. The results are related to the formation of stable aggregates (domains) onto the water subphase by these lignins, as shown in the Pi-A isotherms. It was found as well that the most stable lignin monolayer onto the water subphase is that extracted with 1-butanol. Homogeneous Langmuir-Blodgett (LB) films of this lignin could be produced as confirmed by UV-vis absorption spectroscopy and the cumulative transfer parameter. In addition, FTIR analysis showed that this lignin LB film is structured in a way that the phenyl groups are organized preferentially parallel to the substrate surface. Further, these LB films were deposited onto gold interdigitated electrodes and ITO and applied in studies involving the detection of Cd+2 ions in aqueous solutions at low concentration levels through impedance spectroscopy and electrochemical measurements. FTIR spectroscopy was carried out before and after soaking the thin films into Cd+2 aqueous solutions, revealing a possible physical interaction between the lignin phenyl groups and the heavy metal ions. The importance of using nanostructured systems is demonstrated as well by comparing both LB and cast films.     

组份可控的钌螯合物功能单分子膜

用作“表面离子”的钌螯合物Ru(dpphen)32+与脂肪酸类成膜分子以1:2混合时能够得到稳定的混合单分子膜.以十八烷基三氯硅烷（octadecayl trichloro silane, OTS）分子部分取代Ru(dpphen)32+,得到功能分子组份可控的混合单分子膜.研究表明,OTS分子在纯水表面上可以形成交联网状单分子膜结构,混入硬脂酸（SA）分子后,网状结构逐渐被破坏.SA含量增加,破坏的程度就增大,直至SA/OTS为3:1时,完全没有网状交联结构,形成可以用来沉积LB膜的均匀致密的单分子膜.表面离子Ru(dpphen)32+与OTS和SA一起构成三组份混合单分子膜,OTS和Ru(dpphen)32+为表面离子.单分子膜中混有Ru(dpphen)32+分子,可以有效地阻止OTS的交联发生,同时Ru(dpphen)32+/SA基团与OTS/SA基团是均匀共混的.改变Ru(dpphen)32+/SA基团与OTS/SA基团的混合比,即可以做到Ru(dpphen)32+的组份精确可控,得到可用来沉积LB膜的均一、稳定的单分子膜.     

Langmuir-Blodgett films of octadecanethiol--properties and potential applications

Octadecanethiol (ODT) is known to form self-assembled monolayer on noble metal surfaces which has potential technological applications. Langmuir-Blodgett (LB) technique is another useful method of obtaining highly ordered assembly of molecules. It is of interest to find whether ODT molecules can also form a stable Langmuir monolayer which facilitates the preparation of LB films. In literature, it has been reported that ODT molecules form an unstable Langmuir monolayer. We have studied the stability of the monolayer of the ODT molecules at air-water interface using surface manometry and microscopy techniques. We find the monolayer to be stable on ultrapure water of resistivity greater than 18MOmega cm. However, the behavior changes in the presence of even small amount of additives like NaOH or CdCl2 in the subphase. Our AFM studies on the LB films of ODT deposited from ion-free ultrapure water showed streak-like bilayer domains. The LB films of ODT deposited from CdCl2 containing aqueous subphase yield dendritic domains of the complexed unit grown over ODT monolayer. These nanostructures on surfaces may have potential applications in molecular electronics.     

血红素在有序分子膜中的行为研究

本文研究了血红素(Heme)在硬脂酸(SA)单分子膜和Langmuir-B1odgett(LB)膜中的行为。Heme及其与SA的混合物均能在纯水亚相形成稳定的单分子膜。当摩尔分数x     

液晶聚合物的单层与Langmuir-Blodgett膜

系统研究了手性液晶聚硅氧烷和光致变色液晶聚硅氧烷两个毓的侧链液晶聚合物在空气/水界面的单层行为和Langmuir-Blodgett(LB)膜沉积特性,对LB膜结构与存在的聚集现象进行了系统的表征,并初步探讨了LB膜中液晶聚合物表现的功能性。     

Fabrication and properties of fullerodendron thin films

Thin films of fullerodendron (C(60)(Gn-COOMe) (n = 0.5, 1.5, 2.5)), which was synthesized from fullerene and anthracenyl poly(amido amine) dendron with methyl ester terminals and different generations (G), were fabricated by the Langmuir-Blodgett (LB) and adsorption techniques. It was characterized by X-ray reflectometry that the LB films possessed well-ordered structure, although the adsorption method led to random orientation of molecules. As to C(60)(G0.5-COOMe) and C(60)(G1.5-COOMe), the LB films took a four-layer structure consisting of a double layer of molecules, and fullerene moieties exist in the interior of the LB films. On the other hand, C(60)(G2.5-COOMe) led to a two-layer structure in which the fullerene moieties were at the air side and the dendron moieties were at the substrate side. With increasing generation of dendron, the monolayer formation ability at the air/water interface as amphiphilic molecule strengthens and the amphiphilic property becomes superior to the fullerene-fullerene attractive interaction that prevents the monolayer formation. Furthermore, in the case of C(60)(G0.5-COOMe) and C(60)(G1.5-COOMe), the reduction peak in cyclic voltammetry of the LB film remained even after UV light irradiation. On the contrary, the peak of the C(60)(G2.5-COOMe) LB film disappeared, indicating that molecular arrangement in the films affects electrochemical properties.     

Chiral assemblies of achiral rigid-flexible molecules at the air/water interface induced by silver(I) coordination

Chiral films are obtained from achiral rigid-flexible molecules. Due to hydrogen bonding and steric constraints, these molecules can self-assemble into chiral assemblies at the air/water interface upon compression. When the molecules are spread on a subphase containing AgNO(3), they form a stable monolayer through coordination with Ag(I) ions, as confirmed by surface pressure-area isotherms, UV/Vis and FTIR spectroscopy, and AFM. More interestingly, macroscopic chirality was detected in the Ag(I)-coordinated films by circular dichroism measurements. The formation mechanisms of the two kinds of chiral films are briefly discussed.     

Acidichromism in the Mixed Langmuir—Blodgett Films of Stearic Acid with a Carbazole—containing Schiff Base

ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｖｅｒｓｉｂｌｅｃｏｌｏｒｃｈａｎｇｅｓｕｐｏｎｅｘｔｅｒｎａｌｏｒｉｎｔｅｒｎａｌｓｔｉｍｕｌａｔｉｏｎｓｈａｖｅｂｅｅｎａｔｔｒａｃｔｉｎｇｍｕｃｈａｔｔｅｎｔｉｏｎｄｕｅｔｏｔｈｅｉｒｕｔｉｌｉｔｙａｓｆｕｎｃｔｉｏｎａｌｍａｔｅｒｉａｌｓ .Ｆｏｒｅｘａｍｐｌｅ ,ｐｈｏ ｔｏｃｈｒｏｍｉｓｍｄｅｓｃｒｉｂｅｓｔｈｅｃｏｌｏｒｃｈａｎｇｅｓｉｎｄｕｃｅｄｂｙｐｈｏ ｔｏｉｒｒａｄｉａｔｉｏｎａｎｄｃａｎｂｅｕｓｅｄａｓｐｈｏｔｏ ｒｅｃｏｒｄｉｎｇｍａｔｅｒｉ ａｌｓ…     

Electron transfer studies on cholesterol LB films assembled on thiophenol and 2-naphthalenethiol self-assembled monolayers

We have formed the cholesterol monolayer and multilayer LB films on the self-assembled monolayers of 2-naphthalenethiol (2-NT) and thiophenol (TP) and studied the electrochemical barrier properties of these composite films using cyclic voltammetry and electrochemical impedance spectroscopy. We have also characterized the cholesterol monolayer film using grazing angle FTIR, scanning tunneling microscopy (STM) and atomic force microscopy (AFM). Cholesterol has a long hydrophobic steroid chain, which makes it a suitable candidate to assemble on the hydrophobic surfaces. We find that the highly hydrophobic surface formed by the self-assembled monolayers (SAM) of 2-NT and TP act as effective platforms for the fabrication of cholesterol monolayer and multilayer films. The STM studies show that the cholesterol monolayer films on 2-NT form striped patterns with a separation of 1.0 nm between them. The area per cholesterol molecule is observed to be 0.64 nm2 with a tilt angle of about 28.96 degrees from the surface normal. The electrochemical studies show a large increase in charge transfer resistance and lowering of interfacial capacitance due to the formation of the LB film of cholesterol. We have compared the behavior of this system with that of cholesterol monolayer and multilayers formed on the self-assembled monolayer of thiophenol.     

Synthesis of 2-Oxo amide triacylglycerol analogues and study of their inhibition effect on pancreatic and gastric lipases

A general method for the synthesis of chiral 2-oxo amide triacylglycerol analogues, from (R)- or (S)-3-aminopropane-1,2-diol, was developed. These novel inhibitors of digestive lipases are analogues of the triacylglycerol molecule, a natural substrate of lipases, and they were designed to contain the 2-oxo amide functionality in place of the scissile ester bond at the sn-1 or sn-3 position and nonhydrolysable ether bonds instead of ester bonds at the other two remaining positions. The 2-oxo amide derivatives synthesised were tested for their ability to form stable monomolecular films at the air/water interface by recording their surface pressure/molecular area compression isotherms. The inhibition of porcine pancreatic and human gastric lipases by the 2-oxo amides was studied by means of the monolayer technique with mixed films of 1,2-dicaprin and with variable proportions of each inhibitor. The alpha50 values of these triacylglycerol analogues for PPL and HGL varied between 4.4 to 7.0% and 5.6 to 15.9%, respectively. The chirality at the sn-2 position of 2-oxo amide triacylglycerol analogues affected the alpha50 value for HGL, but not for PPL.     

Formation of complex Langmuir and Langmuir-Blodgett films of water soluble rosebengal

This communication reports the formation of complex Langmuir monolayer at the air-water interface by charge transfer types of interaction with the water soluble N-cetyl N,N,N-trimethyl ammonium bromide (CTAB) molecules doped with rosebengal (RB), with the stearic acid (SA) molecules of a preformed SA Langmuir monolayer. The reaction kinetics of the formation of RB-CTAB-SA complex monolayer was monitored by observing the increase in surface pressure with time while the barrier was kept fixed. Completion of interaction kinetics was confirmed by FTIR study. This complex Langmuir films at the air-water interface was transferred onto solid substrates at a desired surface pressure to form multilayered Langmuir-Blodgett films. Spectroscopic characterizations reveal some molecular level interactions as well as formation of microcrystalline aggregates depending upon the molar ratios of CTAB and RB within the complex LB films. Presence of two types of species in the complex LB films was confirmed by fluorescence spectroscopy.     

Structuring of tricarbocyanine dye molecules in Langmuir-Blodgett films

The problems of formation of stable Langmuir monolayers containingN-sulfopropyl substituted thiatricarbocyanine dyes are considered: the effects of the composition of the mixture applied on the surface of an aqueous subphase and of the extent of compression of the monolayer on processes of ordering of molecular structure. Dyes are introduced into complex monolayers at the water-air interface and then are transferred on solid substrates as multilayered Langmuir-Blodgett (LB) films. For the first time the formation of J-aggregates has been observed for two tricarbocyanine dyes. The structure of J-aggregates depends on the composition of the mixture and the value of the constant pressure at which the transfer occurs. LB films of J-aggregated dyes are optically anisotropic, which is related to the fact that they are formed in the monolayer on the surface and there is no interlayer aggregation during the transfer to substrates. Heterodimers are formed in complex monolayers containing oppositely charged ions of dyes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1278–1283, July, 1995.The work was partially financially supported by the Foundation for Basic Research of the State Committee on Science and Technologies of the Ukraine (Project No. 2.2/48 Normal').     

由组分可控的LB膜前驱物法制备Y2O3稳定立方相ZrO2的超薄陶瓷膜

由有机LB膜技术发展了一种制备组分、厚度可控的无机超薄陶瓷膜的方法.以Zr、 Y的β-二酮络合物的作为"表面离子"代替传统的亚相离子,沉积它们与花生酸的混合LB膜.并将它作为前驱物,经臭氧处理和热处理,成功制得了Y2O3稳定的立方相ZrO2超薄膜(YSZ).用X射线衍射(XRD)、 X射线光电子能谱(XPS)等手段研究了YSZ薄膜的相结构和其组成.结果表明,超薄陶瓷膜中Zr与Y的含量比率控制得很好,且形成Y2O3稳定的立方相ZrO2.说明这种方法可以成功地用来制备组分和膜厚均可控的纳米陶瓷膜.     

Molecular recognition of cytosine- and guanine-functionalized nucleolipids in the mixed monolayers at the air-water interface and Langmuir-Blodgett films

Molecular recognition of mixed nucleolipids of 1-(2-octadecyloxycarbonylethyl)cytosine and 7-(2-octadecyloxycarbonylethyl)guanine in the monolayers at the air-water interface and Langmuir-Blodgett (LB) films has been investigated in detail using surface pressure/potential-area isotherms, infrared reflection-absorption spectroscopy (IRRAS), and Fourier transform infrared (FTIR) transmission spectroscopy, respectively. Prior to molecular recognition, the cytosine moieties in the monolayer were hydrogen bonded with an almost flat-on orientation, the alkyl chains were uniaxially oriented with respect to the film normal, the guanine moieties in the monolayer were stacked probably through pi-pi interaction with an end-on orientation, and the C-C-C planes of the alkyl chains were preferentially oriented parallel to the water surface. In the monolayer of equimolar mixture, molecular recognition between the cytosine and guanine moieties occurred together with the ring planes of base pairing and the C-C-C planes of the alkyl chains favorably oriented parallel to the water surface. The guanine moieties underwent an orientation change from an end-on mode before molecular recognition to a flat-on one after molecular recognition. The base pairing between the cytosine and guanine moieties in the monolayers was achieved since the N7-substituted guanine derivatives suppressed the formation of guanine tetramers. Both the IRRAS spectra of the monolayers and the FTIR spectra of the LB films presented the exact sites in the cytosine and guanine moieties for the formation of triple hydrogen bonds. The base pairing resulted in a change in molecular orientation and interaction, and the corresponding LB film exhibited a different phase transition behavior from a typical crystal transition for the cytosine-functionalized nucleolipids and an analogous glass transition for the guanine-functionalized nucleolipids. The thermal stability of the mixed LB film was improved in comparison to the LB films of pure components.     

Molecular organization and electrochemical reduction of a Ni(II)Porphyrin complex in LB films

In this work, mixed films of a tetra-cationic porphyrin, Ni(II)TMPyP, and an anionic phospholipid, DMPA, in molar ratio of 1:4, were formed at the air–water interface and transferred onto glass and optically transparent indium tin oxide (ITO) electrodes. Transmission spectroscopy (on glass and ITO) and cyclic voltammetry (on ITO) were used to infer the molecular organization and the electrochemical reduction of these LB films. Likewise, we compare the electrochemical reduction of the Ni(II)TMPyP in water solution with that in LB films. The porphyrin molecules in water solution show three two-electron reduction waves, which are related to the two-electron reduction of the central ring of the porphyrin and to the one-electron reductions of the four methyl–pyridyl groups of the molecule, respectively, while only two reversible one-electron reduction waves are observed in LB films corresponding to the reduction of the central ring of the porphyrin and to the Ni(II) to Ni(I) reduction, respectively.     

Structure and photoelectric properties of LB films of porphyrin bearing pyridinium with long-chain alkyl group

Ｉｎｒｅｃｅｎｔｙｅａｒｓ,ｔｈｅｓｔｕｄｙｏｎｔｈｅｃｏｎｖｅｒｓｉｏｎａｎｄａｐｐｌｉｃａｔｉｏｎｏｆｓｏｌａｒｅｎｅｒｇｙｈａｓｂｅｅｎｏｎｅｏｆｔｈｅｍｏｓｔａｃｔｉｖｅａｓｐｅｃｔｓｉｎｔｈｅｆｉｅｌｄｓｏｆｎｅｗｅｎｅｒｇｅｔｉｃｓｏｕｒｃｅｄｅｖｅｌｏｐｍｅｎｔ,ｔｈｅｆａｂｒｉｃａｔｉｏｎｏｆｎｏｖｅｌｓｏｌａｒｅｎｅｒｇｙｃｅｌｌｓｂｅｃｏｍｅｓｔｈｅｇｏａｌｏｆｐｅｏｐｌｅ’ｓｅｆｆｏｒｔｓ.Ｉｎｏｒｇａｎｉｃｓｅｍｉｃｏｎｄｕｃｔｉｖｅｓｏｌａｒｅｎｅｒｇｙｃｅｌｌｓｈａｖｅ…