The essence of this study is to apply the Langmuir-Blodgett (LB) technique for assembling asymmetric membranes. Accordingly, Langmuir films of a (further) polymerizable polymer, 1,2-polybutadiene (1,2-pbd), were studied and transferred onto different solid supports, such as gold, indium tin oxide (ITO), and silicon. The layers were characterized both at the air/water interface as well as on different substrates using numerous methods including cyclic voltammetry, impedance spectroscopy, spectroscopic ellipsometry, atomic force microscopy, X-ray photoelectron spectroscopy, and reflection-absorption Fourier transform infrared spectroscopy. The Langmuir films were stable at the air-water interface as long as they were not exposed to UV irradiation. The LB films formed disorganized layers, which gradually blocked the permeation of different species with increasing the number of deposited layers. The thickness was ca. 4-7 Å per layer. Irradiating the Langmuir films caused their cross-linking at the air-water interface. Furthermore, we took advantage of the reactivity of the double bond of the LB films on the solid supports and graft polymerized acrylic acid on top of the 1,2-pbd layers. This approach is the basis of the formation of an asymmetric membrane that requires different porosity on both of its sides.[on SciFinder (R)]

The essence of this study is to apply the Langmuir-Blodgett (LB) technique for assembling asym. membranes. Accordingly, Langmuir films of a (further) polymerizable polymer, 1,2-polybutadiene (1,2-pbd), were studied and transferred onto different solid supports, such as Au, In Sn oxide (ITO), and Si. The layers were characterized both at the air/H2O interface as well as on different substrates using numerous methods including cyclic voltammetry, impedance spectroscopy, spectroscopic ellipsometry, at. force microscopy, XPS, and reflection-absorption FTIR spectroscopy. The Langmuir films were stable at the air-H2O interface as long as they were not exposed to UV irradn. The LB films formed disorganized layers, which gradually blocked the permeation of different species with increasing the no. of deposited layers. The thickness was \~4-7 Å per layer. Irradiating the Langmuir films caused their crosslinking at the air-H2O interface. Also, the authors took advantage of the reactivity of the double bond of the LB films on the solid supports and graft polymd. acrylic acid on top of the 1,2-pbd layers. This approach is the basis of the formation of an asym. membrane that requires different porosity on both of its sides. [on SciFinder(R)]

A review. The past, present, and future of the application of self-assembled monolayers (SAMs) in electroanal. chem. is reviewed. SAMs for electroanal. applications were introduced in the early 1990s and since then were exploited for the detection of different species ranging from metal ions to biomols. and microorganisms. This review describes the different types of monolayers, surfaces on which they were assembled, the various analytes, which were detd., and the various electrochem. techniques employed. The prospective and perspectives of this topic are discussed. [on SciFinder(R)]

The local deposition of Ag nanoparticles (NPs) on ω-mercaptoalkanoic acid, HS(CH2)nCO2H, (n = 2, 10) self-assembled monolayers (SAMs) by scanning electrochem. microscopy (SECM) is reported. We found that the presence of a SAM had a pronounced effect on Ag deposition. Expts. were conducted by applying different potentials to an Au(1 1 1) substrate either in the presence of a const. concn. of Ag+ ions in soln. (bulk deposition) or by generating a flux of Ag+ from an Ag microelectrode that was positioned close to the Au(1 1 1) substrate (SECM deposition). SECM was used for generating a controlled flux of silver ions by anodic dissoln. of an Ag microelectrode close to the SAMs modified Au(1 1 1). We found that the shape of the NPs was affected by the length of the carbon-chain of the SAM. Tetrahedral NPs were obtained on bare Au(1 1 1) surfaces while rod like and cubic Ag NPs were deposited onto 3-mercaptopropanoic acid (MPA) and 11-mercaptoundecanoic acid (MUA) SAMs, resp. The size and shape of the deposited NPs were influenced by the deposition potential. We conclude that the shape and distribution of locally deposited Ag NPs on Au(1 1 1) can be controlled by modification of the substrate with a SAM and through controlling the Ag+ flux generated by SECM. [on SciFinder(R)]

The Langmuir-Blodgett (LB) method was used for depositing cubic polyhedral oligomeric silsesquioxanes (T8POSS) onto Au, indium tin oxide (ITO) and mica supports. Three different T8POSS were examd.; two were amphiphilic and aggregated upon transfer to a solid support, while the highly sym. POSS (termed MP8) gave stable and reproducible Langmuir films as studied by surface pressure and transfer ratio measurements. This was attributed to the eight identical alkanethiol groups located on each of the eight corners of the cubic like skeleton. The LB films were studied by RA-FTIR, XPS, contact angle and cyclic voltammetry. These techniques revealed the formation of a permeable, yet, stable layer. The sym. MP8 was utilized as a bridging building block between the support and Au nanoparticles (Au-NPs). This assembly was examd. by means of AFM, SEM and anodic oxidn. of the nanoparticles. An av. d. of 1.45 × 109 nanoparticles cm-2 was obtained for the deposited Au-NPs on the MP8 layer. Furthermore, anodic stripping voltammetry was used for studying the extn. of Hg2+ by the MP8 LB film. [on SciFinder(R)]

An electrodeposition process is provided for depositing a film of org. nanoparticles from liq. dispersion on conductive surfaces. A special feature of the nanoparticles is their ability to aggregate as a response to pH change. The diffusing phase was formed by polylactic acid (43.9 mg) dissoln. in acetone (7.5 mL) and this phase was added dropwise to the dispersing phase of water (TDW, 20 mL) contg. Na oleate (22.2 mg) and NaOH (0.3 mg) while applying continuous moderate stirring to give a dispersion of polylactic acid nanoparticles (av. diam. 153 nm). [on SciFinder(R)]

The electrochemically assisted codeposition of sol-gel thin films on stainless steel is described. Specifically, electrodeposition of films based on aminopropyltriethoxysilane (APTS), and its codeposition with propyltrimethoxysilane (PrTMOS) and phenyltrimethoxysilane (PhTMOS) has been accomplished by applying negative potentials. The latter increases the concentration of hydroxyl ions on the stainless steel surface and thus catalyzes the condensation and deposition of the sol-gel films. The films were characterized by profilometry, electrochemical impedance spectroscopy (EIS), alternating current voltammetry (ACV), goniometry, atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM and SEM analysis of codeposited APTS:PrTMOS films disclosed the structural changes induced by altering the deposition solution composition and the applied potential. Codeposited APTS:PhTMOS did not show any structural differences from their electrodeposited homopolymers, while Nano Scratch Test clearly revealed the changes in the elastic and adhesion properties, suggesting the formation of an APTS:PhTMOS composite. EIS of the films showed good resistance towards penetration of hydrophilic species, such as hexacyanoferrate. ACV measurements of the homo and codeposits showed the decrease of the interfacial capacity as a result of the electrochemical deposition. In essence, controllable sol-gel films with tunable chemical and physical properties based on controlling the combination of the precursors, pH and electrochemical properties can be electrodeposited on conducting surfaces. The application of this approach has been demonstrated by coating a stainless steel coronary stent.[on SciFinder (R)]

The electrochem. assisted codeposition of sol-gel thin films on stainless steel is described. Specifically, electrodeposition of films based on aminopropyltriethoxysilane (APTS), and its codeposition with propyltrimethoxysilane (PrTMOS) and phenyltrimethoxysilane (PhTMOS) has been accomplished by applying neg. potentials. The latter increases the concn. of hydroxyl ions on the stainless steel surface and thus catalyzes the condensation and deposition of the sol-gel films. The films were characterized by profilometry, electrochem. impedance spectroscopy (EIS), a.c. voltammetry (ACV), goniometry, at. force microscopy (AFM) and SEM. AFM and SEM anal. of codeposited APTS:PrTMOS films disclosed the structural changes induced by altering the deposition soln. compn. and the applied potential. Codeposited APTS:PhTMOS did not show any structural differences from their electrodeposited homopolymers, while Nano Scratch Test clearly revealed the changes in the elastic and adhesion properties, suggesting the formation of an APTS:PhTMOS composite. EIS of the films showed good resistance towards penetration of hydrophilic species, such as hexacyanoferrate. ACV measurements of the homo and codeposits showed the decrease of the interfacial capacity as a result of the electrochem. deposition. In essence, controllable sol-gel films with tunable chem. and phys. properties based on controlling the combination of the precursors, pH and electrochem. properties can be electrodeposited on conducting surfaces. The application of this approach has been demonstrated by coating a stainless steel coronary stent. [on SciFinder(R)]

The authors present a new method for deposition of thin nanocomposite films made of sol-gel-based Au nanoparticles using a single electrochem. step. Applying a neg. potential to an electrode (indium Sn oxide or stainless steel) immersed in a soln. of Au nanoparticles stabilized with N-[3-(trimethoxysilyl)propyl]ethylenediamine (EDAS) caused the redn. of the protic solvent, which altered the pH and therefore catalyzed the deposition. The nanocomposite thin films were characterized by various techniques: the morphol. and structure of the layers were examd. by high-resoln. SEM and at. force microscopy; their thickness was detd. by profilometry; and the permeability of the films was studied by electrochem. Homogeneous defect-free layers could be deposited only upon adding tetramethoxysilane (TMOS) to the deposition soln. Also, the applied potential, the ratio between the TMOS and the Au nanoparticles, and the type of the substrate significantly affected the aggregation and d. of the Au nanoparticles in the nanocomposite. Finally, by applying a pos. potential to the nanocomposite films the authors succeeded to electrochem. dissolve the embedded Au nanoparticles, forming holes and channels. The oxidn. treatment had a remarkable effect on the permeability of the film and exposed the electrode to faradic activity. This method seems to be of general applicability in templating of nanometer-sized objects in thin films. [on SciFinder(R)]