Langmuir and Langmuir-Blodgett films containing a porphyrin-ruthenium complex

The fabrication of supramolecular structures from the tetraruthenated porphyrin-containing phosphines, {TPyP[RuCl3(dppb)]4}, RuTPyP, is demonstrated with Langmuir and Langmuir-Blodgett films. The surface pressure-molecular area isotherms (pi-A) point to an edge-on arrangement for the RuTPyP molecules in the condensed state. Weak aggregation in the Langmuir films was indicated by non-zero surface potentials at large areas per molecule and a slight red shift in the ultraviolet-visible absorption spectrum in comparison to the spectrum in solution. Further aggregation occurs in the Z-type Langmuir-Blodgett films, which was confirmed with ultraviolet-visible spectroscopy of the deposited films. Fourier transform infrared and Raman spectroscopic data for powder and Langmuir-Blodgett films indicate that the RuTPyP molecules are chemically stable in Langmuir-Blodgett films regardless of the contact with water during film fabrication. The nanostructured nature of the Langmuir-Blodgett films was manifested in cyclic voltammetry due to the high sensitivity of the metallic centers in RuTPyP. Electrodes modified with Langmuir-Blodgett films exhibit an anodic peak at 100 mV and a cathodic peak at 7 mV, which is assigned to RuIII/RuII redox processes. Furthermore, Langmuir-Blodgett films from RuTPyP showed electrocatalytic activity for oxidation of benzyl alcohol, illustrated by a large shift of 100 mV in the anodic peak at 400 mV, while electropolymerized and cast films of the same compound displayed smaller and no activities, respectively.     

Langmuir-Blodgett films made from C60 fullerene with grafted macromolecules

Langmuir-Blodgett films made from C₆₀ fullerene with grafted polymer chains —polystyrene and polyethylene oxide — are obtained for the first time. The Langmuir-Blodgett films are obtained by the transfer of Langmuir films onto substrates of single-crystal silicon. The Langmuir films and the single-layer Langmuir-Blodgett films of C₆₀ with grafted polystyrene are nonuniform over their thickness and form a network consisting of aggregates with a size of ≤6 μm. The Langmuir films of C₆₀ with grafted polyethylene oxide are much more uniform. They can easily be used to obtain Langmuir-Blodgett films containing up to 20 layers and having a surface that appears smooth under an optical microscope. Pis’ma Zh. Tekh. Fiz. 24, 88–94 (June 26, 1998)     

Langmuir-Blodgett法制备b-轴取向MFI型分子筛膜

实验利用Langmuir-Blodgett(LB)技术大面积有序组装分子筛晶粒, 进而制备连续致密且高度b-轴取向MFI型分子筛膜。首先, 采用LB技术在表面性质不同的不锈钢载体和铂电极载体上实现了b-轴取向MFI分子筛晶粒的高度有序组装; 其次, 采用合成液预处理法对LB法制备的高度b-轴取向的MFI晶种层进行二次合成。XRD和SEM表征结果显示: 采用合成液预处理法可以有效抑制分子筛晶粒在二次生长过程中生成孪晶, 进而获得高度b-轴取向MFI分子筛膜; 最后, 电化学测试结果证实采用LB技术制备的b-轴取向MFI分子筛膜致密, 无缺陷。     

Mid-IR biosensor: detection and fingerprinting of pathogens on gold island functionalized chalcogenide films

Antibody (human IgG, anti-E. coli O157:H7, and anti-Salmonella) complexes on the surface of IR-transparent Ge-containing chalcogenide glass films were formed via thiol chemistry on 20-nm-thick gold islands. As a first step, the protocol was validated by monitoring fluorescently tagged targets to validate binding. FT-IR spectroscopy confirmed that the coating of the films with 20-nm gold did not have a significant effect on the propagation and penetration of IR evanescent waves through the film. The films functionalized with anti-E. coli O157:H7 and anti-Salmonella antibodies were used to detect E. coli O157:H7 and S. enteriditis through label-free IR fingerprinting. Highly selective detection of bacterial targets was achieved at both the species (E. coli vs. S. enteriditis) and strain level (E. coli O157:H7 vs E. coli K12). A mid-infrared approach could thus be used as a biosensor as well as a molecular fingerprinting tool.     

Gd@C_(82) Langmuir-Blodgett纳米薄膜的表面微观结构

采用Langmuir-Blodgett(LB)技术在新解理的云母和氧化铟锡(ITO)基片上成功地制备出富勒烯金属包合物Gd@C82/SA的单层及多层Langmuir-Blodgett分子薄膜,采用原子力显微镜(AFM)和X射线光电子能谱(XPS)对所制备纳米超分子薄膜的表面形貌和表面元素组成进行了系统研究,结果表明,与纯的Gd@C82 Langmuir薄膜相比,以硬脂酸(SA)为辅助成膜材料所得到的Gd@C82/SA复合Langmuir薄膜能更好地转移到云母和ITO基片表面,其镀膜转移比接近1,当硬脂酸(SA)与Gd@C82的摩尔比达到4:1时,所对应的Gd@C82/SA LB薄膜表现出良好的均一性和理想的层状结构。     

Annealing temperature and ultraviolet irradiation effect on the ferroelectric properties of Bi(3.25)La(0.75)Ti3O12 thin films

Bi(3.25)La(0.75)Ti3O12 thin films were prepared on Pt/Ti/SiO2/Si substrates by the metal organic decomposition method. The structural characterizations and the surface morphology observations were carried out applying X-ray diffraction and atomic force microscope, respectively. The annealing temperature and the ultraviolet irradiation effect on the ferroelectric properties were studied. It was found that the remnant polarization (Pr) and the coercive field (Ec) increased with the increase of the applied electric field (E) for all films. With the annealing temperature increasing from 670 degrees C to 750 degrees C, the increase tendency of Pr(E) and Ec (E) got enhanced from 670 degrees C to 720 degrees C, followed by weakened from 720 degrees C at 750 degrees C. These phenomena could be well explained by the different internal strain in films. The remnant polarization and the coercive field showed an obvious decrease when the top electrodes of the thin films were illuminated with UV light due to the screening effect of trapped charge carries.     

Surface acoustic wave sensors incorporating Langmuir-Blodgett films

Acoustoelectric devices offer many attractive features for applications as physical and chemical sensors. Surface acoustic wave (SAW) oscillators are of particular importance owing to their high sensitivity. This paper describes the use of Langmuir-Blodgett (LB) films as gas absorbent layers on the surface of SAW devices.

Areal densities of standard LB film forming materials were measured and found to agree with those obtained from pressure-area isotherms. Sensors incorporating ω-tricosenoic acid and docosylamine overlayers were examined and their responses to alkanoic acids reported.

The room temperature chemiresponse of a SAW device coated with monolayers of tetra-4-tert butyl silicon phthalocyanine dichloride showed response and recovery times comparable with those reported for other phthalocyanine-based sensors operated at much higher temperatures. The detection limit of the LB film device was found to be 40 ppb NO₂ in dry air at an operating frequency of 98.6 MHz and an ambient temperature of 22°C. The frequency change was shown to be entirely due to the mass of gas absorbed by the film.     

LB膜及其在气体传感器中的应用（一）

ＬＢ膜技术在近十几年来取得了很大的进展。ＬＢ膜作为传感器的敏感材料，由于其灵敏度高、响应时间快、工作温度低（室温）等优点而受到广泛重视。简要讨论了ＬＢ膜技术的工作原理、ＬＢ膜技术研究的一些进展、ＬＢ膜的表征及其在气体传感器制造中的应用     

A novel highly conducting phosphonium tetracyanoquinodimethane Langmuir-Blodgett film

We describe the properties of pristine and iodine-doped Langmuir-Blodgett films built up from a new semi-amphiphilic tetracyanoquinodimethane (TCNQ) salt, namely trimethyloctadecylphosphonium TCNQ. The films are transferred from a water subphase to a solid substrate. After exposure to diluted iodine vapour, the films become conducting. This behaviour is checked by the IR absorption spectrum. The conductivity estimated from the energy of the maximum of the charge transfer absorption band is about 20–50 Ω^-1 cm^-1.     

Sputtering ZnO films on langasite and its SAW properties

C-axis-oriented ZnO films were sputtered on Langasite substrate (LGS, La(3)Ga(5)SiO(14)). The crystalline structure of the films was determined by grazing incident angle X-ray diffraction, the surface microstructure of films was investigated by scanning electron microscopy and atomic force microscopy, the atom composition ratio O/Zn of films was determined by energy dispersive X-ray spectroscopy, and the resistivity of films was determined by the four-point probe instrument. The measurement results showed those films prepared were all polycrystalline hexagonal ZnO films. By analyzing the microstructure of the ZnO films, those prepared at the oxygen flow rate (O(2)/O(2)+Ar) of 20%, the RF power of 200 W, and the substrate temperature of 200 degrees C had the best performance: highly c-axis-oriented microstructures, dense surface morphology, and the atom composition ratio 1.02. The measured scattering parameters of the SAW device fabricated on the composite substrate (ZnO/LGS) with film thickness 1.76 microm showed an average shifted velocity around 2741 m/s at 57.1 MHz and a electromagnetic coupling coefficient greater than 1%.     

Room temperature toluene sensing using phthalocyanine Langmuir-Blodgett films

Organic thin films, produced by the Langmuir-Blodgett (LB) technique were used to sense toluene gas at levels of 5–9 p.p.m.(parts per million). The interaction of the gas with the surface of the thin films led to significant changes in the electrical conductivity of the film. Since surface reaction is vital in these sensors, it is expected that films produced by the LB technique would provide the necessary surface uniformity to improve the performances of these devices. Most thin film sensors are operated at elevated temperatures to obtain higher efficiencies. A major problem associated with the use of LB films at elevated temperatures is the probability of disintegration and distortion of the layered structure. Thin films (thickness 100–120 nm) of specially substituted phthalocyanine molecules were investigated as possible sensors of toluene gas for room-temperature operation. The preliminary results indicated instantaneous response and recovery times, and the saturation value was reached within 2–3 s when the film was exposed to the gas at intervals of 2 min. The results thus offer potential for using such versatile organic materials as microsensors, even at room temperature.     

An optical chemical sensor using a fluorophor- embedded Langmuir-Blodgett film

An optical sensor with a Langmuir-Blodgett (LB) film was developed for simultaneous recognition of amino acids in an aqueous solution. Anthroyloxy- stearate-containing stearate LB films and perylene-containing arachidate LB films were deposited on a quartz glass. The fluorescence of these LB films in an aqueous solution was quenched in response to amino acids. Amino acids were classified into five groups by the pattern of fluorescence quenching of anthroyloxy stearate and perylene LB films.     

C60—聚苯乙烯LB膜摩擦学性能的初步研究

介绍了Ｃ６０－聚苯乙烯（Ｃ６０－Ｐｓｔ）ＬＢ膜的部分研究结果：合成方法、ＬＢ膜制备、用原子力／摩擦力显微镜测试的Ｃ６０－聚苯乙烯ＬＢ膜的表面微观形貌及轻载荷下的摩擦力等微观摩擦学性能。     

Structural change of Langmuir-Blodgett film of tetra-neopentoxy phthalocyanine zinc during heat treatment

Langmuir-Blodgett (LB) films of tetra-neopentaxy phthalocyanine zinc (TNPPcZn) were prepared and annealed at a selected temperature. Their optical spectra and optical constants were measured and the structural changes of the films were studied by X-ray diffraction. The arrangement of molecules in the TNPPcZn LB film is changed from disorder to order due to increase of the dimer when the films are annealed at the temperature range of 363 to 433 K. When the annealing temperature is increased further from 433 K to the 573 K, the film undergoes a reorganization in which the orientation of phthalocyanine rings are transformed formed from perpendicular to the substrate surface into parallel to the substrate surface, because the dimers are destroyed owing to the segregation of the neopentoxy and the monomers are recovered.     

LB膜及其在气体传感器中的应用（二）

ＬＢ膜技术在近十几年来取得了很大的进展。ＬＢ膜作为传感器的敏感材料，由于其灵敏度高、响应时间快、工作温度低（室温）等优点而受到广泛重视。简要讨论了ＬＢ膜技术的工作原理、ＬＢ膜技术研究的一些进展、ＬＢ膜的表征及其在气体传感器制造中的应用。     

Photoisomerization of the azobenzenes included in Langmuir-Blodgett films of cyclodextrins

A new type of photochemical Langmuir-Blodgett (LB) film containing azobenzenes (p-phenylazobenzoic acid (PAB), methyl red (MR) and methyl orange (MO)) without long alkyl chains was prepared by the host-guest interaction with an amphiphilic cyclodextrin derivative. The azobenzenes in the LB film of the host- guest complex exhibited an excellent cis-trans photoisomerization, while trans-to- cis photoisomerization was restricted for LB films of long chain azobenzene derivatives alone. The cavity of cyclodextrin provides a favourable environment for the photochemical reaction leading to an increase in the molecular area in the rigid LB film. The half-life times of cis isomers of PAB, MR and MO in the host-guest complex LB films were 35 h, 55 s and 13 min respectively at 20°C.     

Experimental studies on substituted copper phthalocyanine Langmuir-Blodgett films

Using the Langmuir-Blodgett (LB) technique, novel copper bis(3-hydroxypropyloxy-hexaisopentyloxy)phthalocyanine molecules were deposited on quartz substrates. It is argued on the basis of pressure-area isotherms that films are deposited as monolayers. Optical absorption spectroscopy suggests that the deposited films were uniform. A.c. measurements were performed on LB films in a planar configuration at different temperatures. The power-law dependence of the conductivity on frequency is explained in terms of electronic conduction through hopping over a coulombic barrier 0.66 eV high. The Debye relaxation time is estimated to be of the order 811 µs at room temperature.     

Bleaching of exciton transition in Langmuir-Blodgett films of polydiacetylene

Saturation absorption measurements with laser pulses of a few picosecond duration performed on thin Langmuir-Blodgett films of polydiacetylene blue form at the absorption band are reported and discussed. The measurements give directly the imaginary part of the Kerr susceptibility χ⁽³⁾(-ω;ω,ω,-ω) which is found to be very large (in excess of 10^-8 e.s.u.) with a fast response time. The results are discussed in terms of the phase-space-filling exciton model.     

Semifluorinated TTF derivatives in Langmuir-Blodgett films

New semifluorinated tetrathiafulvalene (TTF) derivatives were prepared and used in Langmuir and Langmuir-Blodgett (LB) films. Transfer onto a solid substrate of such pure monolayers can be easily achieved leading to organized LB films in which the fluorinated chains are tilted with respect to the normal of the substrate as demonstrated by infrared and X-ray experiments. Doping of such films by iodine does not induce change in the layer spacing on the contrary to already published studies concerning alkyl derivatives of TTF. Such structural stability and values of the layer thickness suggest some interdigitation between TTF groups within the LB film. Depending on the exact chemical structure of the TTF moiety, the iodination is stabilized or not. When the doped film is stabilized in a mixed valency state, conductivity of approx. 10⁻² S cm⁻¹ was measured at room temperature.     

Study of electric dipole and space charge characteristics of Al/C12TCNQ/Al by means of thermally stimulated current measurements

Electric dipole and space charge characteristics of Al/2-dodecyl-7, 7, 8, 8-tetracyanoquinodimethane (C₁₂TCNQ)/Al were studied by means of thermally stimulated current (TSC) measurements. The TSC curve of Al/C₁₂TCNQ/Al had two peaks, one at a temperature below 80 °C, which is due to the depolarization of electric dipoles, and the other, at a temperature above 80 °C, which is due to the movement of space charges in the C₁₂TCNQ Langmuir-Blodgett (LB) films. The polarization direction of the electric dipoles in the C₁₂TCNQ LB films was from the hydrophilic group to the hydrophobic group.