Electrochemically assisted fabrication of size-exclusion films of organically modified silica and application to the voltammetry of phospholipids

Abstract

Modification of electrodes with nm-scale organically modified silica films with pores diameters controlled at 10- and 50-nm is described. An oxidation catalyst, mixed-valence ruthenium oxide with cyano crosslinks or gold nanoparticles protected by dirhodium-substituted phosophomolybdate (AuNP-Rh2PMo11), was immobilized in the pores. These systems comprise size-exclusion films at which the biological compounds, phosphatidylcholine and cardiolipin, were electrocatalytically oxidized without interference from surface-active concomitants such as bovine serum albumin. 10-nm pores were obtained by adding generation-4 poly(amidoamine) dendrimer, G4-PAMAM, to a (CH3)3SiOCH3 sol. 50-nm pores were obtained by modifying a glassy carbon electrode (GC) with a sub-monolayer film of aminopropyltriethoxylsilane, attaching 50-nm diameter poly(styrene sulfonate), PSS, spheres to the protonated amine, transferring this electrode to a (CH3)3SiOCH3 sol, and electrochemically generating hydronium at uncoated GC sites, which catalyzed ormosil growth around the PSS. Voltammetry of Fe(CN)63− and Ru(NH3)63+ demonstrated the absence of residual charge after removal of the templating agents. With the 50-nm system, the pore structure was sufficiently defined to use layer-by-layer electrostatic assembly of AuNP-Rh2PMo11 therein. Flow injection amperometry of phosphatidylcholine and cardiolipin demonstrated analytical utility of these electrodes.

Immobilization of nanobeads on a surface to control the size, shape, and distribution of pores in electrochemically generated sol–gel films

“…We previously demonstrated that modification of glassy carbon with APTES to which 50-nm PSS spheres were attached followed by electrochemically assisted deposition of an ormosil yielded a film with 50-nm pores [27]. The results suggested that the APTES and PSS were removed by soaking the electrode in chloroform.…”

“…After rinsing, PSS was immobilized on the GC | APTES by immersion in a 1:1 dilution of the commercial 20-nm PSS suspension in water for 30 s. The GC | APTES-PSS electrode was rinsed and transferred to an aged (for 60 min) sol that was prepared by mixing 5.0 mL of 0.1 mol dm -3 LiClO 4 in 2-propanol with 2.5 mL H 2 O, adjusting the pH to 5.0 with 0.1 mol dm -3 HCl, and slowly adding 2.0 mL of trimethylmethoxysilane. Based on our previous study [27], a potential of 1.5 V vs. Ag | AgCl was applied for 20 min during which the solution was stirred. Copious evolution of gas was not observed under this condition.…”

“…We fabricated thin films of organically modified silica with 50-nm pores by combining electrochemically assisted sol-gel processing of a trimethylmethoxysilane precursor with modification of a glassy carbon electrode by electrostatic attachment of 50-nm PSS beads to a sub-monolayer of 3-aminopropyltriethoxysilane (APTES) [27]. The PSS and APTES were dissolved from the dried film with chloroform.…”

“…The pore geometry was sufficiently well defined to permit immobilization of electrochemical catalysts within the void volumes using layer-by-layer electrostatic assembly. The resulting modified electrodes were applied to size-exclusion electrocatalytic oxidation of phospholipids in protein-containing media [27]. In contrast to analogous experiments at an electrode without the size-exclusion property, the protein did not passivate the electrode.…”

Poly(dimethylsiloxane) as a pre-coating in layer-by-layer films containing phosphotungstate nanoclusters electrochemically sensitive toward s-triazines

“…34,37,38 The analytes detected included nitrite, bromate, iodate, arsenite, oxalate, hydrogen peroxide and NO. [26][27][28][29]34,[37][38][39][40][41][42][43][44] In this paper, we report on the electrochemical properties of LbL lms containing a Keggin-type POM, the phosphotungstic acid (HPW), deposited onto ITO. Particular emphasis is given to the effect of the PDMS aminopropyl terminated pre-coating layer on the electrochemical response of the LbL lms.…”