Monolayers deposition

Silver monolayer deposited on foreign metal single crystal. 

Dominguez, D.D.,Mowery, R. L., and Turner, N. H., Friction and Durabilities of Well-Ordered, Close Packed Carboxylic Acid Monolayers Deposited on Glass and Steel Surfaces by the Langmuir-Blodgett Technique, Tribal. Trans., yi. No. 1, 1994, pp. 59-66. 

The floating monolayer can be transferred onto the surface of solid supports. Two main techniques are usually considered for the monolayer deposition, namely, Lang-... 

FIG. 10 Current-voltage characteristics of polyanihiies LS films of 40 monolayers deposited on interdigitated electrodes (1) PANI, (2) POT, (3) POAS, (4) PEOA. 

Figure 9.14 Kinetic current density (squares) at 0.8 V for O2 reduction on the Pt monolayer deposited on various metal single-crystal surfaces in a 0.1 M HCIO4 solution, and calculated binding energies (circles) of atomic oxygen (BEq), as a function of calculated d-band center (relative to the Fermi level, ej — sp) of the respective surfaces. The data for Pt(lll) were obtained from [Markovic et al., 1999] and are included for comparison. Key 1, PIml/ Ru(OOOl) 2, PtML/Ir(lll) 3, PtML/Rh(lH) 4, PtML/Au(lll) 5, Pt(lll) 6, PIml/ Pd(lll). (Reproduced with permission from Zhang et al. [2005a].)...

Similarly to the Pt monolayer catalysts, a series of Pd monolayers deposited on different metal single crystals were tested for ORR activity. The results are shown in Fig. 9.22. The ORR activity increases in the order PdML/Ru(0001) < PdML/fr(lll) < PdMi,/ Rh(lll)[Pg.299]

Pd ternary alloys, including Pd-Co-Au [Fernandez et al., 2005a, b] and Pd-Co-Mo [Raghuveer et al., 2005] have been developed to further improve the stability of the catalyst. The addition of 10% Au to the Pd-Mo mixture improved catalyst stability. Another promising way to improve the activity and durability of Pd-M alloys is to deposit a Pt monolayer on them. Recently, a Pt monolayer deposited on PdsFe/C was found to possess higher activity than that of Pt/C [Shao et al., 2007b]. 

Brankovic SR, Wang JX, Adzic RR. 2001a. Metal monolayer deposition by replacement of metal adlayers on electrode surfaces. Surf Sci 474 L173-L179. 

FIG. 30 Schematic (not to scale) of the arrangement for SECM measurements of proton transport at a stearic acid monolayer deposited at the air-water interface. The UME typically had a diameter, 2a, in the range 10-25 pm and the tip-interface distance, d < la. 

Figure 2. Schematic of the Langmuir Blodgett film balance and monolayer deposition at the air-water interphase.

Deposition of the mixed monolayer. Deposition solutions were prepared by dissolving octadecylmercaptan [ClsSH] and the respective bipyridinium in a mixture of chloroform and methanol. The electrode was cleaned by heating it in a gas-air flame. After cooling, the electrode was immersed in the deposition solution for 15 - 30 minutes, withdrawn, and rinsed in clean methanol or chloroform. Qualitatively the most reproducible surface redox waves and lowest charging currents during cyclic voltammetry were obtained with a freshly-prepared deposition solution containing 50 mM CiaSH and 10 mM of the bipyridinium in a 1 1 volume ratio of chloroform and methanol. 

The first two entries refer to mixed monolayers deposited prior to the electrochemical measurements the last two entries refer to bipyridinium monolayers adsorbed from the electrolyte. J is the peak current in the cathodic and anodic directions for the first redox wave of the bipyridiniums T is the coverage found by integration of the respective cathodic and anodic peaks. The other headings have been defined in the preceding text. Data is omitted where the surface wave is not well-defined relative to the background current. 

Figure 7.2. Dependence of the film conductivity on the number of LB monolayers deposited onto an AI microelectrode array with a 0.1-mm distance between fingers.

The process of monolayer deposition of metal ions in underpotential deposition is strongly affected by anion-specific adsorption, and the two processes at the electrode interface must be elucidated if one is to understand underpotential deposition phenomena in a unified way. 

The solid-state Si SPE NMR spectra of SBA-15 and the titania surface-coated SBA-15 (Ti-SBA-15) are in accord with this expectation. The spectrum of SBA-15 displays a broad as)mimetric peak at 109 ppm (Q" sites) with shoulders at —101 ppm (Q sites) and 90 ppm(Q sites) in the area ratio 79 19 2. The NMR spectrum of Ti-SBA-15 (one layer) shows a reduction of the band intensity relative to the intensity. The normalized Q Q Q site populations become 85 13 2. No asymmetry is observed in the Q site band. Repetition of the monolayer deposition to form a double layer of titania on silica yields a material whose Si NMR spectrum is indistinguishable from that of the Ti-SBA-15 with a monolayer coverage. As expected, the titania-insulated silica resonances are unperturbed by the second titania layer. 

Substrates DME = dropping mercury electrode FTO = fluorine-doped tin oxide G = graphite GC = glassy carbon GrC = graphic carbon ITO = indium tin oxide-coated glass SC = single crystals SS = stainless steel TCO = transparent conducting oxide VC = vitrious carbon. Miscellaneous ECALE = electrochemical atomic layer epitaxy ED = electrodeposition ML = monolayer RT = room temperature SMD = sequential monolayer deposition V = vacuum. 

The quantity and quality of the deposited monolayer on a solid support is measured by a so-called transfer ratio, tr. This is defined as the ratio between the decrease in monolayer area during a deposition stroke, Al, and the area of the substrate, As. For ideal transfer, the magnitude of tr is equal to 1. Depending on the behavior of the molecule, the solid substrate can be dipped through the film until the desired thickness of the film is achieved. Different kinds of LB multilayers can be produced and/or obtained by successive deposition of monolayers on the same substrate (see Figure 4.11). The most common one is the Y-type multilayer, which is produced when the monolayer deposits on the solid substrate in both up and down directions. When the monolayer deposits only in the up or down direction, the multilayer structure is called either Z-type or X-type. Intermediate structures are sometimes observed for some LB multilayers, and they are often referred to be XY-type multilayers. 

Fig. 9. Pt Lj-edge SEXAFS data obtained with TEY detection for Pt monolayers deposited at room temperature onto Si(l 11)7x7 substrates (base pressure 1 x 10" Pa)...

Surfactants provide several types of well-organized self-assembhes, which can be used to control the physical parameters of synthesized nanoparticles, such as size, geometry and stability within liquid media. Estabhshed surfactant assembles that are commonly employed for nanoparticie fabrication are aqueous micelles, reversed micelles, microemulsions, vesicles [15,16], polymerized vesicles, monolayers, deposited organized multilayers (Langmuir-Blodgett (LB) films) [17,18] and bilayer Upid membranes [19](Fig. 2). 

Adsorption and kinetics of electroreduction of safranine T in self-assembled phospholipid monolayer deposited on mercury have also been studied [157]. 

Thin-liquid-film stability. The effect of surfactants on film and foam stability. Surface elasticity. Froth flotation. The Langmuir trough and monolayer deposition. Laboratory project on the flotation of powdered silica. 

Variations on the vertical dipping technique have been utilized to construct films containing divalent metal ions. For example, the quartz crystal microbalance (QCM) has been used to evaluate the horizontal lifting method of CdSt LB Film construction (26). In this method, the QCM quartz plate was touched to monolayers compressed on a subphase and lifted horizontally. Y-type transfer (transfer ratio of 1) was demonstrated with two centrosymmetric monolayers deposited for each cycle. A combination of the vertical and horizontal dipping techniques has been utilized to prepare multilayer films from an amphiphilic porphyrin compound (27). 

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