Silver layers spacers

The data for the same fluorophores embedded in structure II are illustrated in Figure 19.7C. We observe enhancement but veiy little dependence on spacer thickness. Since the silver layer has thickness of the same order as the largest spacer, the variation of average chromophore distance from the silver is relatively mild. The small enhancement is also easy to understand since the chromophores will not be placed in the interstices betweoi silver particles when films are assembled with silver on top. 

Magenta dye developer layer Green - sensitive silver halide layer Spacer... 

Figure 2.105 Optically transparent thin layer electrochemical (OTTLE) cell. A = PTFE cell body, B = 13 x 2 mm window, (C and E) = PTFE spacers, D = gold minigrid electrode, F = 25 mm window, G = pressure plate, H = gold working electrode contact, 1 = reference electrode compartment, J = silver wire, K = auxiliary electrode and L = solution presaturator. From Ranjith...

Figure 9.9 Assembly of sandwich-type optically transparent thin-layer electrochemical cell, a, Glass or quartz plates b, adhesive Teflon tape spacers c, minigrid working electrode d, metal thin-film working electrode, which may be used in place of (c) e, platinum wire auxiliary electrode f, silver-silver chloride reference electrode g, sample solution h, sample cup. [Adapted with permission from T.P. DeAngelis and W.R. Heineman, J. Chem. Educ. 53 594 (1976), Copyright 1976 American Chemical Society.]...

Here, the specific and strong chelating interaction between 6 x Histidine and the tetradentate nitrilotriacetic acid (NTA) mediated by Ni2+ [43] was used for the immobilization of a reconstituted LHCII mutant, whose c-terminus was extended by 6 x Histidine residues via genetic engineering (cf. Fig. 13(A)). NTA terminated thiols and OEG (spacer) thiols were used to built up a mixed SAM (X = 0.4) on a substrate coated by 23 nm silver and 5 nm Au (the gold layer was used to protect the silver film from being oxidized). 

Silver island film using SiOx spacer layers Basic ftichsin 200 14]... 

Silver island film with 15 nm fatty acid spacer layer Phthalocyanine 400 15]... 

Figure 6.15 Relative fluorescence enhancement of Ru-PEL dye deposited over silver NPs (circles), alloy NPs (square) and gold NPs (triangles), as a function of thickness of intermediate PEL spacer layer.

Figure 19.7A reports the fluorescent enhancement of the conjugated polymer emitter for structure I when it is deposited on top of various thicknesses of polyelectrolyte spacers for silver treated versus untreated substrates. The fluorescence increases nearly 40 fold for 2 bilayers (roughly 4-6 nm) and then drops though it remains dramatically enhanced even for as much as 13 bi layers (25 nm). 

Amperometric detection included a BAS (Bioanalytical Systems, Inc.) LC-4B amperometric detector, a BAS TL-3 thin-layer amperometric flow cell (5 mil spacer), and an RC-2A reference compartment. The flow cell contained a carbon paste-paraffin oil working electrode, a silver/silver chloride reference electrode (RE-1), and a stainless steel auxiliary electrode. A BAS RYT strip-chart recorder was used. 

Figure 14.9 Thin layer cell for temperature controlled specular reflectance spectroelectrochem-istry. (1) Tightening brass cap (threaded inside). (2) Teflon or brass washer required to tighten the cell. (3) Working electrode (a brass rod with platinum foil soldered to the base. (4) Auxiliary electrode platinum wire with the tip made flush to the Teflon base of the cell. (5) Pseudo-reference electrode silver wire, also made flush to the Teflon. (6, 7) Luer lock type injection ports. (8) Cell body, top part aluminum, lower part Teflon. (9) Teflon spacer which determines the path length of the cell. (10) Calcium fluoride window. (11) Rubber gasket. (12) Hollow brass cell body. (13) Two mirror reflectance accessory (Nicolet FT-30). (14, 15) Mirrors. Reproduced from reference (35) with permission from Elsevier.

In the context of this study both, SHG [49] and enhanced Raman scattering [50], from multilayer samples have been studied. These substrates, which consist of a silver island film separated from a silver mirror by a dielectric spacer layer, excel by remarkable reflectivity and absorption properties that have been accoimted for by appropriate modelling [51]. 

In 1988, the distance dependence of surface-enhanced fluorescence was studied for Langmuir-Blodgett monolayers deposited on silver island films. This study was inspired in part by two earlier reports that examined the distance dependence of SERS of LB films on metal surfaces. Varying numbers of spacer layers of arachidic acid were employed in order to probe the competition between EM enhancement and radiationless energy transfer for a phthalocyanine monolayer. In direct contact with the metal surface, a broadened, enhanced, and red-shifted fluorescence spectrum was observed. These spectral changes can be attributed to a drastic decrease in the fluorescence lifetime of the molecule when it is placed in contact with the metal surface. However, an enhanced version of the unperturbed spectrum was observed when intervening spacer layers were introduced. It was found at enhancements on the order of about 400 could be realized when S monolayers were placed between the Ag island film and the phthalocyanine monolayer. 

Figure 14. Surface-enhanced fluorescence spectra of OD-PTCO LB fllm on glass, LB on 6 nm silver island film, and LB film on 6 nm Ag film coaled with one spacer layer of arachidic acid. Reprinted from Spectrochimca Acta Part A Molecular A Biomolecular Spectroscopy, 53, J. DeSaja-Gonzalez, R. Aroca, Y. Nagao, J. A. DeSaja, Surface-enhanced fluorescence and SERRS spectra of Af-octadecyl-3,4 9,10-perylenetetracarboxylic monoanhydride on silver island films, 173-181, 1997, with permission from Elsevier.

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