Permselective Ion Transport Across the Nanoscopic Liquid/Liquid Interface Array

Abstract

Free-standing silica nanochannel membrane (SNM) with perforated channels was utilized to create arrays of nanoscale interfaces between two immiscible electrolyte solutions (nano-ITIES), at which permselective ion transfer and detection were achieved. The SNM consisted of a high density of straight nanochannels with a diameter of 2-3 nm and a length of 70 nm. The silicon wafer coated by 150 nm-thick porous silicon nitride film (p-SiNF) with pores of 5 μm-in-diameter was used to support the SNM in a form of nanochannel-on-micropore. Considering the material surface lipophilicity, the nano-ITIES array was formed at the boundary between SNM and p-SiNF, with a diffusion geometry equivalent to two back-to-back inlaid microdisc interfaces. Thus, the transfer of tetraethylammonium (TEA(+)) across the nano-ITIES array yielded symmetric sigmoidal current responses. In addition, because of the ultrasmall size and negatively charged surface of silica nanochannels, the nano-ITIES displayed obvious size and charge permselectivities. Transfer of ions with a size comparable with or larger than the nanochannel was sterically blocked. Also that of anions with a size smaller than the nanochannels encountered the strong electrostatic repulsion from channel walls, showing obvious dependence on the ionic strength of aqueous solution. The present approach is facile and inexpensive for building a nano-ITIES array with potential applications in ion detection and separation.

Ion transfer at polarised liquid-liquid interfaces modified with adsorbed silica nanoparticles

“…Micro-ITIES arrays were also modified with mesoporous silica channels prepared ex-situ by a Stöber-like method [36]. The vertically aligned channels obtained have demonstrated their potential for analytical applications [37][38][39][40]. We investigated here the adsorption of silica nanoparticles onto the ITIES and their impact on the electrochemical transfer behaviour of ions (e.g.…”

Unraveling the Phase‐Transfer Catalysis Mechanism of Oxygen Reduction Catalyzed by Iron(III) meso‐tetra‐(4‐N‐Methyl‐pyridyl) Porphine at the Liquid/Liquid Interface

“…In this case, aU -tube glass cell in at wo-electrode configurationw as used (see Scheme 1b). As we have reported recently, [15] owing to the uniform size of silica nanochannels (approximately 2-3nm), transfer of ions with as izec omparable to or larger than the nanochannelsi ss terically blocked. Figure 5a shows the CV resultso btained at the nano-ITIES array in four different cases that are similart ot hose at the macro-ITIES (namely Figure 1a).…”

“…[16] Free-standing SNM supported by porous silicon nitride film (p-SiNF), designated as SNM/p-SiNF,w as prepared as reported previously. [15] Electrochemical Measurements at the Micro-and Nano-ITIES…”

Decorating soft electrified interfaces: From molecular assemblies to nano-objects

“…Ex-situ prepared silica isoporous film supported on micropatterned SiN-coated silicon wafers were used to study ion transfer reactions across electrified water -DCE interface [198][199][200].…”

“…This can be achieved with inorganic materials in a form of a membrane e.g. mesoporous silica [42,196,198,199] or zeolite [190,192] materials that can affect size and charge screening properties of the ITIES. For the former the ionic transport is affected by the confined size of the pores within the membrane framework whereas for the latter it is the membrane surface charge governed by ionisable functionalities that can electrostatically interact with transferring ions.…”