Layers Of Stearic Acid Research Articles

Registration of the immunological reaction in bionanocomposite Langmuir-Schaefer films

Bionanocomposite Langmuir-Schaefer films containing single-wall carbon nanotubes noncovalently bound to immunoglobulin G are prepared. The possibility of using such films for the registration of antigen-antibody reactions is demonstrated. The interaction is recorded by means of surface plasmon resonance (SPR) and an Agilent 86140B spectrum analyzer. The concentration of the specific antigen studied, bovine serum albumin, ranges within 10−8–10−12 M. Application of several layers of stearic acid between the gold layer and the bionanocomposite layer increases of the sensitivity of the system (SPR method) to the antigen by a factor of 2 to 7.3.

Ordered Monomolecular Layers as a Template for the Regular Arrangement of Gold Nanoparticles

Ordered arrays of metal nanoparticles are important for nanoelectronic and nanophotonic applications. Here, we report the formation of self-assembled arrays of gold nanoparticles on molecular layers of diacetylene compounds on a MoS2(0001) substrate. The arrangement of gold nanoparticles is observed using scanning tunneling microscopy. When gold is deposited on a self-assembled monolayer of 10,12-nonacosadiynoic acid or 10,12-octadecadiynoic acid on a MoS2(0001) substrate, the ordered array of diacetylene moieties in the molecular layer serves as a template for the formation of ordered arrays of gold nanoparticles. In contrast, when gold is deposited on a pristine MoS2(0001) surface or on a molecular layer of stearic acid, the gold nanoparticles are randomly distributed on the surface. It is found that the arrangement of gold nanoparticles is largely determined by the deposition rate; faster deposition results in more ordered arrays of gold nanoparticles. Our observations confirm the role of unsaturated π systems in molecules acting as a template for the regular arrangement of gold nanoparticles; this work will open up new possibilities for interfacial nanoarchitectonics.

Evaluation of potential sewage contamination by fecal sterol biomarkers adsorbed in natural biofilms

The use of biofilms for adsorption of sterols was investigated for the first time to evaluate sewage contamination in the Barigüi River, Curitiba (Brazil). The characteristics of a biofilm that favor its use in monitoring include the relatively rapid development of biofilms and their capacity to sorb hydrophobic compounds. Some fecal sterols considered to be biomarkers for human and animal feces have relatively high octanol-water partitioning coefficients (log KOW); thus, sterols were expected to be readily sorbed in the biofilms. The biofilms were developed on glass plates (0.48 m(2)) previously coated with a fine layer of stearic acid and supported by a PVC tube that was submersed in the river 20 cm above the river bottom. After a certain period of incubation time, the biofilm growth was scraped from the plates and analyzed for the following fecal steroids: coprostanol (5β-cholestan-3β-ol), epicoprostanol (5β-cholestan-3α-ol), cholesterol (5,6-cholesten-3β-ol), cholestanol (5α-cholestan-3β-ol), stigmastanol (24β-ethyl-5α-cholestan-3β-ol) and coprostanone (5β-cholestan-3-one). Six samples were collected between March 2012 and June 2012. All analyzed compounds were detected, and in general, cholesterol was present in high amounts (23 160-41.9 ng g(-1) dry biofilm). Variation among campaigns was observed in the distribution of sterols, with cholestanol showing the least variation among the samples. Sterol ratios that are commonly used for evaluating sewage contamination were calculated; these ratios indicated some periods of potential sewage influence. However, these sterol ratios are intended to be applied primarily for sediments and not for biological compartments; thus, the results must be carefully interpreted. Biofilms developed under natural conditions can be a tool for monitoring some important sterols that are used as biomarkers of fecal pollution.

Real Time Study of Detergent Concentration Influence on Solid Fatty Acid Film Removal Processes

AbstractCleaning in an aqueous solution is a complex mechanism which depends on several parameters. The quartz crystal microbalance (QCM) technique was used to investigate the detachment, using an anionic and a nonionic detergents, of stearic acid (C18H36O2) films deposited on gold‐coated quartz surfaces. The cleaning mechanism was observed in real time by measuring the frequency of a quartz crystal during the fatty acid film removal. These observations reveal two successive phenomena: firstly, adsorption and absorption of water and detergent on the stearic acid layer and, secondly, the detachment of the fatty acid layer. A relationship between removal time and detergent concentration was highlighted: fatty acid removal time decreases as detergent concentration increases until an asymptotic value is reached. Initial contamination greatly influences cleaning duration. Increased sample contamination actually leads to increased removal time. However, no real correlation between the two parameters can be established. As a result, optimal parameters can be determined for each detergent, thus the QCM technique appears to be of great interest in monitoring and optimising cleaning protocol.

Surface Modification Mechanism of Stearic Acid to Zirconia Powders Induced by Ball Milling for Water-Based Injection Molding

In conventional process of ceramic injection molding, wax-based binders could only be removed by thermal or organic solvent debinding. Recently, water solvent debinding has appeared as a good alternative owing to its high efficiency and environmental friendliness. In present work, we have demonstrated the surface modification mechanism of stearic acid (SA) to zirconia powders induced by a prior ball-milling treatment before the blending process. Layers of SA with various thicknesses coated around the zirconia powders have been achieved with different amount of SA after the treatment, agreeing well with the theoretically calculated values. The coating is disclosed to be an esterification occurring between the carboxyl group of SA and hydroxyl group of zirconia surface. It plays an important role in limiting agglomeration of ceramic powders and changing the nature of powder surface from hydrophilicity to hydrophobicity, which decreases the shear viscosity of the feedstock and makes the water-debound compact process-compatible with few phase separation. In addition, a significantly faster water-debinding rate was obtained.

Reversible switching of nanostructured cobalt hydroxide films from superhydrophobic to superhydrophilic state

Superhydrophobic cobalt hydroxide films with flower-like micro-nano structure prepared by chemical-bath deposition undergo a change in wettability from superhydrophobic to superhydrophilic state either by immersion in ethyl acetate or by heat treatment at 200°C and above. The superhydrophobicity of the film can be regained by immersion in an ethanolic solution of stearic acid. The superhydrophobicity is attributed to the combined effect of micro-nano binary surface morphology and the low surface energy of the self-assembled monolayer of stearic acid. It is proposed that switching from superhydrophobicity to superhydrophilicity is caused by removal of the adsorbed layer of stearic acid by solvent or heat treatment.

Luminescent cellulose sheet fabricated by facile self-assembly of cadmium selenide nanoparticles on cellulose nanofibres

A hierarchical luminescent cellulose sheet was fabricated viaself-assembly of cadmium selenide (CdSe) nanoparticles capped with trioctylphosphine oxide (TOPO) and 1-hexadecylamine (HDA) onto ultrathin titania film pre-coated cellulose nanofibres of bulk natural cellulose substance (common commercial filter paper). Each cellulose nanofibre of the filter paper was firstly coated with nanometre-thick titania film by means of the surface sol–gel process, followed by alternative deposition of self-assembled layers of stearic acid (SA) and TOPO/HDA capped CdSe nanoparticles, giving a filter paper/titania/SA/(CdSe/SA) composite luminescent sheet possessing stable and well-defined green fluorescence. SEM and TEM observations showed that the resulting luminescent sheet retained the hierarchical structures and morphologies of the initial cellulose substance; meanwhile, the CdSe nanoparticles were anchored on the nanofibre surfaces within SA thin layers through the hydrophobic interaction between the alkyl chains of the surface ligands of CdSe nanoparticles and SA molecules. UV-vis and photoluminescence spectra indicated that the resulting luminescent sheet showed similar characteristic absorption and emission properties as those of the original CdSe nanoparticles. The current approach provides a facile shortcut to fabricate bulk luminescent materials that inherit the mechanical behaviour of cellulose substances and simultaneously possess designed luminescent properties.

Production of titanium dioxide powders by atmospheric pressure plasma jet

TiO2 powders have been successfully synthesized by atmospheric pressure plasma jet (APPJ), which operates by feeding air between two coaxial electrodes that are driven by a 20.8kHz power source. Tetrachloride titanium is mixed with the effluent of the plasma jet in deferent regions to produce TiO2 powders. The synthesized samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The chlorine contents in the TiO2 powders were determined by the energy dispersive spectroscopy (EDS). Photocatalytic activities of samples were measured by FT-IR spectroscopy based on the destruction of stearic acid layers. And the effects of post-discharge plasma and deposition parameters were studied with respect to the morphology of TiO2 powders. The results show that crystallized TiO2 anatase structure can be obtained at the temperature ranged from 150°C to 250°C.

Superhydrophobic alumina surface based on stearic acid modification

A novel superhydrophobic alumina surface is fabricated by grafting stearic acid layer onto the porous and roughened aluminum film. The chemical and phase structure, morphology, and the chemical state of the atoms at the superhydrophobic surface were investigated by techniques as FTIR, XRD, FE-SEM, and XPS, respectively. Results show that a super water-repellent surface with a contact angle of 154.2° is generated. The superhydrophobic alumina surface takes on an uneven flowerlike structure with many nanometer-scale hollows distribute in the nipple-shaped protrusions, and which is composed of boehmite crystal and γ-Al2O3. Furthermore, the roughened and porous alumina surface is coated with a layer of hydrophobic alkyl chains which come from stearic acid molecules. Therefore, both the roughened structure and the hydrophobic layer endue the alumina surface with the superhydrophobic behavior.

Formation process of a strong water-repellent alumina surface by the sol–gel method

A novel strong water-repellent alumina thin film is fabricated by chemically adsorbing stearic acid (STA) layer onto the porous and roughened aluminum film coated with polyethyleneimine (PEI). The formation process and the structure of the strong water-repellent alumina film are investigated by means of contact angle measurement and atomic force microscope (AFM). Results show that the water contact angles for the alumina films increase with the increase of the immersion time in the boiling water, and meanwhile, the roughness of the alumina films increases with the dissolution of the boehmite in the boiling water. Finally, the strong water-repellent film with a high water contact angle of 139.1° is obtained when the alumina films have distinct roughened morphology with some papillary peaks and porous structure. Moreover, both the roughened structure and the hydrophobic materials of the STA endow the alumina films with the strong water-repellence.

Photocatalytic efficiencies of self-cleaning glasses. Influence of physical factors

Two commercial types of self-cleaning glass (SCG) have been tested to confirm the real photocatalytic nature of their properties. This was done by using four photocatalytic tests: (i) in the gas phase with the total oxidation of acetylene; (ii) in water with the total degradation of malic acid, (iii) in water with the total degradation of methylene blue, and (iv) in the solid phase with the total oxidative degradation of a layer of stearic acid deposited on the self-cleaning glass surface, in contact with the superficial titania coating. The influence of various factors (temperature, humidity, wavelength, radiant flux, presence of inorganic particles stuck at the glass surface) was explained in line with the fundamentals of photocatalysis. The results helped to understand the behaviour of self-cleaning glass.

Effect of Organic Modification Temperature on the Microstructure of Nanoscale Titania

Nanoscale titania aqueous dispersion was prepared firstly,and then nano-titania particles was transfered into methylbenzene in which stearic acid was dissolved from water by distillation so that the surface modification was carried out in organic system.Nanoscale titania was modified with stearic acid at different temperatures.The samples were characterized by Fourier transform infrared spectra(FTIR),X-ray photoelectron spectroscope(XPS),thermogravimetry(TG),derivative thermogravimetry(DTG) and transmission electron microscopye(TEM).The results show that stearic acid is bound on the surface of nanoscale titania by bidentate structure,and even monolayer coverage is obtained.With modification temperature increasing,the crystallite size of nanoscale titania increase,the mass fraction of chemisorbed stearic acid on the surface of nanoscale titania decrease,and the thickness of stearic acid layer changes from 1nm to 2-3nm.The modification temperature has little effect on interactions between stearic acid and titania.

Structure, wettability and photocatalytic activity ofCO2 lasersintered TiO2/multi-walled carbon nanotube coatings

Nanocomposites of titanium dioxide(TiO2) and multi-walled carbon nanotubes (MWNTs) were prepared and depositedby sol–gel spin coating on borosilicate substrates and sintered in air at300 °C for 15 min. Further irradiation of the films with differentCO2 laser intensities(4.3–17 W m−2) was carried outin order to crystallize TiO2 in the anatase form while preserving the MWNT’s structure. The laser irradiation changedthe crystal structure of the coatings and also affected the wettability and photocatalyticactivity of the films. The anatase phase was only observed when a minimum laser intensity of12.5 W m−2 was used. The contact angle decreased with the enhancement of the laserintensity. The photocatalytic activity of the films was determined from thedegradation of a stearic acid layer deposited on the films. It was observed that theaddition of carbon nanotubes themselves increases the photocatalytic activity ofTiO2 films. This efficiency is even improved when highCO2 laser intensities are used during the sintering of the coatings.

Photoactive and antibacterial TiO 2 thin films on stainless steel

This paper describes an innovative method to achieve highly photoactive and antibacterial titania thin films on stainless steel by a novel combination of flame-assisted CVD (FACVD) – to deposit silica, and thermal APCVD – to deposit titania. We compare the chemical and structural characteristics, and photocatalytic activities of thin films of titania deposited onto stainless steel using APCVD from two different precursors. We show that the silica layer acts as a barrier to prevent the deleterious effect on photoactivity of iron and chromium from the substrate, and in particular, we show that the interaction of the precursor chemistry with the steel surface influences the structure of the films. The films were analysed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and secondary neutral mass spectrometry (SNMS). Photocatalytic activity of the coatings was determined by the destruction of stearic acid layers, monitored using FT-IR spectroscopy. Studies show selected films to be effective as antibacterial coatings against Escherichia coli, with antibacterial performance comparable to reported values of TiO 2 on other substrates. The shape-forming capabilities and mechanical robustness of steel make it an ideal substrate for the exploration of new applications of photocatalysis. Applications of this technology include water purification, air cleaning, self-sterilizing and self-cleaning surfaces such as those used in hospitals or food preparation.

Multi-functional self-cleaning thermochromic films by atmospheric pressure chemical vapour deposition

Thin films of titanium dioxide and vanadium dioxide were deposited onto glass using atmospheric pressure chemical vapour deposition (APCVD). The films were investigated as individual layers and as part of multilayer systems to assess their potential to be combined to offer dual functionality, self-cleaning thermochromic films. The multilayer systems were achieved by deposition of vanadium dioxide with subsequent titanium dioxide deposition and vice-versa. XRD revealed that the titanium dioxide existed exclusively in the anatase form and the vanadium oxide either monoclinic VO 2 or mixed vanadium oxides, depending on the position within the multilayer structure. XPS analysis indicated good stoichiometry in the films, and also suggested that the films remained elementally discrete when deposited in the multilayer systems. The multilayered films were active in the destruction of stearic acid layers under UV radiation and showed good thermochromic switching properties. Furthermore, the titania over-layer imparted a significant degree of enhanced durability to the underlying thermochromic film. This combination of enhanced durability and ‘self-cleaning’ property, offers interesting potential for wider potential use of this technology.

The role of SiO2 barrier layers in determining the structure and photocatalytic activity of TiO2 films deposited on stainless steel

Abstract TiO 2 thin films were deposited using two different precursor systems, and their photocatalytic activities studied in the context of the feasibility of self-cleaning added value steel products. SiO 2 layers deposited using flame-assisted CVD were investigated as possible barrier layers to prevent diffusion of substrate components in to the TiO 2 films. The films were characterized by X-ray photoelectron spectroscopy (XPS), sputtered neutral mass spectrometry (SNMS), Raman spectroscopy and scanning electron microscopy (SEM). Photo-activity was characterised by the UV-induced destruction of stearic acid layers. On bare steel growth using titanium tetraisopropoxide yielded anatase, while growth with titanium tetrachloride (with ethyl acetate) yielded rutile. In contrast, on silica coated steels both precursor systems yielded anatase exclusively. The diffusion of components originating from the steel substrates was shown to have a deleterious effect on the photoactivities of the TiO 2 thin films, with this effect being more influential at higher deposition temperatures. However, the presence of the SiO 2 barrier layers significantly reduced ion diffusion into the TiO 2 film and consequently also improved the photocatalytic activity of the samples. While the SiO 2 coated samples gave rise to anatase growth, there is evidence that the thickness of the SiO 2 coating has a direct effect on TiO 2 morphology.

H2S modified atomic layer deposition process for photocatalytic TiO2thin films

H2S modified TiO2 films were grown by atomic layer deposition (ALD) using TiCl4, H2S and water as precursors. The films were characterized by XRD, XPS, TOF-SIMS, SEM and UV-VIS spectrometry. Photocatalytic activities of the films under UV and visible light were determined by the degradation of a thin layer of stearic acid. Light induced superhydrophilicity of the films was also studied. Although the sulfur content of the films was very low, substantial modification of the film properties occurred. All the films prepared at 400 and 500 °C with H2S were photocatalytically active under visible light. Photocatalytic activity under UV irradiation of the H2S modified films was also drastically improved when proper deposition parameters were applied.

An experimental and theoretical study on the concept of dropwise condensation

Hydrophobic coatings have been created through self-assembled mono layers (SAMs) of n-octadecyl mercaptan (SAM-1) and stearic acid (SAM-2) on copper alloy (99.9% Cu, 0.1% P) surfaces to enhance steam condensation through dropwise condensation. When compared to complete filmwise condensation, n-octadecyl mercaptan (SAM-1) coated surface increased the condensation heat transfer rate by a factor of 3 for copper alloy surfaces, under vacuum condition (33.86 kPa) and to about eight times when operated under atmospheric condition (101 kPa). A model using the population balance concept is used to derive a theoretical formula to predict the drop-size distribution of small drops which grow mainly by direct condensation. All the important resistances to heat transfer such as the heat conduction through the drop, vapor–liquid interface are considered in developing this model. By knowing the contact angle of the drop made with the condensing surface and the maximum drop radius the sweeping effect of large falling drops could be calculated which is also incorporated into the model. The effect of interfacial heat transfer coefficient on heat transfer rate is also considered in developing the theoretical model. This is combined with the well known size distribution for large drops proposed by Le Fevre and Rose [E.J. Le Ferve, J.W. Rose, A theory of heat transfer by dropwise condensation, in: Proceedings of 3rd International Heat Transfer Conference, vol. 2, Chicago, 1966, pp. 362–375] which grow mainly by coalescence. There has been a satisfactory agreement between our experimental data and the present theoretical model.

Atomic layer deposition of TiO 2− xN x thin films for photocatalytic applications

Titanium dioxide (TiO 2) is recognized as the most efficient photocatalytic material, but due to its large band gap energy it can only be excited by UV irradiation. Doping TiO 2 with nitrogen is a promising modification method for the utilization of visible light in photocatalysis. In this work, nitrogen-doped TiO 2 films were grown by atomic layer deposition (ALD) using TiCl 4, NH 3 and water as precursors. All growth experiments were done at 500 °C. The films were characterized by XRD, XPS, SEM and UV–vis spectrometry. The influence of nitrogen doping on the photocatalytic activity of the films in the UV and visible light was evaluated by the degradation of a thin layer of stearic acid and by linear sweep voltammetry. Light-induced superhydrophilicity of the films was also studied. It was found that the films could be excited by visible light, but they also suffered from increased recombination.

Protein–lipid interactions at the air/water interface

Surface pressure measurements and external reflection FTIR spectroscopy have been used to probe protein-lipid interactions at the air/water interface. Spread monomolecular layers of stearic acid and phosphocholine were prepared and held at different compressed phase states prior to the introduction of protein to the buffered subphase. Contrasting interfacial behaviour of the proteins, albumin and lysozyme, was observed and revealed the role of both electrostatic and hydrophobic interactions in protein adsorption. The rate of adsorption of lysozyme to the air/water interface increased dramatically in the presence of stearic acid, due to strong electrostatic interactions between the negatively charged stearic acid head group and lysozyme, whose net charge at pH 7 is positive. Introduction of albumin to the subphase resulted in solubilisation of the stearic acid via the formation of an albumin-stearic acid complex and subsequent adsorption of albumin. This observation held for both human and bovine serum albumin. Protein adsorption to a PC layer held at low surface pressure revealed adsorption rates similar to adsorption to the bare air/water interface and suggested very little interaction between the protein and the lipid. For PC layers in their compressed phase state some adsorption of protein occurred after long adsorption times. Structural changes of both lysozyme and albumin were observed during adsorption, but these were dramatically reduced in the presence of a lipid layer compared to that of adsorption to the pure air/water interface.