Membrane doping

Soon after the initial development of the heparin sensor, an electrode for the detection of the polycation protamine was proposed [38] based on a polymeric membrane doped with the cation exchanger tetrakis-(4-chlorophenyl)borate. Protamine is a polypeptide and usually administered as a heparin antidote. Protamine is a polycation with an average charge of +20 and is rich in arginine (Fig. 4.8). The response function of protamine-selective electrodes is similar to the heparin response function (Fig. 4.9b). 

The fourth type of mediator-based cation optical sensing is using potential sensitive dye and a cation selective ionophore doped in polymer membrane. Strong fluorophores, e.g. Rhodamine-B C-18 ester exhibits differences in fluorescence intensity because of the concentration redistribution in membranes. PVC membranes doped with a potassium ionophore, can selectively extract potassium into the membrane, and therefore produce a potential at the membrane/solu-tion interface. This potential will cause the fluorescent dye to redistribute within the membrane and therefore changes its fluorescence intensity. Here, the ionophore and the fluorescence have no interaction, therefore it can be applied to develop other cation sensors with a selective neutral ionophore. 

The anion optical sensor can also be fabricated with metalloporphyr-ins. For example, polymeric membranes doped with indium porphyrins and a lipophilic dichlorofluorescein derivative were shown to be very selective to chloride and acetate anions. The response mechanism is based on extraction of anions into the bulk organic film by indium porphyrins and a simultaneous coextraction of hydrogen ions. This results in protonation of the pH chromophore, and hence a change in the optical absorbance of the polymeric film. 

Figure 4. Flux and refection of cellulose diacetate membranes doped with organo-philic bentonite as a function of bentonite concentration...

Fig. 2 Different orange-red luminescent layers for O2 sensing, a Indicator layer containing the tris(4,7-diphenyl-l,10-phenanthroline)ruthenium(II) dye adsorbed on CPG particles embedded in a poly(dimethylsiloxane) film [8]. b Perfluorinated (Nation) ionomer membrane doped with the same cationic dye. Although the former appears as a homogeneous material, even under the optical microscope, the luminescent indicator is actually sitting down in various domains as evidenced by its emission kinetics profile [9]...

Staiti, P. et ah. Hybrid Nation-silica membranes doped with heteropolyacids for application in direct methanol fuel cells. Solid State Ionics, 145, 101, 2001. 

Similarly, impervious yttria-stabilized zirconia membranes doped with titania have been prepared by the electrochemical vapor deposition method [Hazbun, 1988]. Zirconium, yttrium and titanium chlorides in vapor form react with oxygen on the heated surface of a porous support tube in a reaction chamber at 1,100 to 1,300 C under controlled conditions. Membranes with a thickness of 2 to 60 pm have been made this way. The dopant, titania, is added to increase electron How of the resultant membrane and can be tailored to achieve the desired balance between ionic and electronic conductivity. Brinkman and Burggraaf [1995] also used electrochemical vapor deposition to grow thin, dense layers of zirconia/yttria/terbia membranes on porous ceramic supports. Depending on the deposition temperature, the growth of the membrane layer is limited by the bulk electrochemical transport or pore diffusion. 

Photoinduced electron transfer across planar bilayer membranes doped with discrete cofacially stacked porphyrin trimers and tetramers has been demonstrated... 

Polypyrrole membrane doped with hexafluorophosphate (I) and p-toluenesulfonate (II)... 

Sotomayor, M. D. P. T. Tanaka, A. A. Kubota, L. T., Development of an amperometric sensor for phenol compounds using a Nafion (R) membrane doped with copper dipyridyl complex as a biomimetic catalyst,./. Electroanal. Chem. 2002, 536, 71-81... 

It was much later, and after the aforementioned work of Rosaro and Kunin, in which it was proven that various synthetic membranes doped with different species could function as ion exchangers, and that these systems were used for quantitative work. Indeed, the properties of these membranes were of... 

The diffusion of TMR/POPE molecules in the membrane was investigated by sequentially recording images from the sample. Figure 14 shows such a sequence taken at 10-ms intervals from a 12.2 x 9.5-fim2 area of a POPC membrane doped with TRM/POP at 10 8mol-mol 1. The migra-... 

A polypyrrole membrane doped with anions of high molecular weight during electrochemical polymerization changes in anion permselectivity or cation perm-... 

Potassium ions are assayed with a selective membrane electrode employing a poly(vinyl-chloride)-membrane doped with a specific ionophore. The classical carrier is the antibiotic valinomycin. Active research is going on at many places to develop synthetic ionophores for both cations, sodium and potassium. 

H. Suda, K. Haraya. Gas transport properties of carbon molecular sieve membranes doped with nano particles in Proceedings of the 8th International Conference on Inorganic Membranes, Jul. 18-22, 2004, Gincinnati, OH, Adams Press, Chicago, IL. 

Tanaka M, Yonezawa Y, Sato T. 1996b. Photochemical control of DC current across planar bilayer lipid membranes doped with azobenzene derivative. Thin Solid Films 284/ 285 833 835. 

M. Li, H. Zhang, and Z.-G. Shao. Quatemized poly(phthalazinone ether sulfone ketone) membrane doped with H3PO4 for high-temperature PEMFC operation. Electrochem. Solid-State Lett., 9 A60-A63, 2006. 

Fig. 19 Left) Schematic representation of the proposed mechanism for topological changes in dioleoyl phosphoethanolamine (DOPE) based liposomal membranes upon ultrasound irradiation. Right) (a) Giant DOPE-based unilamellar vesicle, before sonication, which shows an inhomogeneous membrane DOPE-rich domains of negative curvature are marked in red, embedded in zones rich in dioleoyl phosphocholine (DOPC) of zero mean curvature, (b) Illustration of shape changes upon ultrasound stimuli. Reproduced with permission from [99]. Copyright 2014 The Royal Society of Chemistry...

Ulewicz, M., Sadowska, K., and Biemat, J. F. 2007. Facilitated transport of Zn(II), Cd(II) and Pb(II) across polymer inclusion membranes doped with imidazole azocrown ethers. Desalination 214 352-364. 

Zheng and coworkers have employed a similar methodology and have demonstrated that PVC membranes doped with indium tetraphenylporphyrin show high relative sensitivity to nitrite ions.- Manganese and indium porphyrins immobilized in silicone by Paeng et al. have been used for the potentiometric analysis of serum chloride levels." ... 

The potentiometric response of membranes doped with metalloporphyrins involves the direct interaction of the anion as an axial ligand. So, changes in the porphyrin structure, both in terms of initial ligation as well as substitution on the porphyrin ring, can influence the ability of given anions to bind as axial ligands and thereby alter the potentiometric anion selectivity. When a relatively simple... 

S.M.. Zaidi, S. D. Mikhailenko, S. Kaliaguine, Electrical properties of sulfonated poly ether ketone/polyether-imide blend membranes doped with inorganic acids. Journal of Polymer Science Part B Polymer Physics 38 (2000) 1386-1395. 

I. Honma, Y. Takeda, J.M. Bab, Protonic conducting properties of sol-gel derived organic/inorganic nanocomposite membranes doped with acidic... 

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