Molecular discrimination inside polymer nanotubules

Savariar, Elamprakash N.; Krishnamoorthy, Kothandam; Thayumanavan, S.

doi:10.1038/nnano.2008.6

Cited by 162 publications

(147 citation statements)

References 30 publications

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“…SiN membranes prepared by the ITE technique are therefore useful for separation of molecules by charge, which we tested by performing separation experiments with two oppositely charged fluorescent dyes: rhodamine 123 (MW ϳ 400, charge: ϩ1), and Alexa Fluor 568 (MW ϳ 800, charge: Ϫ3). Due to the negatively charged silanol groups, the negatively charged dye (Alexa Fluor) should be excluded from the pores by electrostatic forces (16,41,42). As a consequence, only the positive dye (rhodamine) was expected to pass through the membrane.…”

Section: Resultsmentioning

confidence: 99%

“…There have been many reports on preparation of membranes with well-defined pore geometry in polymer and inorganic materials (7)(8)(9)(10)(11)(12)(13)(14)(15)(16). There have also been studies on thin membrane platforms containing free standing polymer membranes (17)(18)(19), inverse opals (20) as well as protein (21), and block copolymer membranes (22)(23)(24).…”

mentioning

confidence: 99%

“…The number of heavy ions corresponds to the number of fabricated pores. The technique has been used for membrane production for more than four decades (32); however, most of track-etched membranes are made in polymer films with thicknesses of at least several micrometers (16). In contrast, the ITE SiN membranes reported here have thicknesses of ϳ100 nm, and the pore diameter can be made as small as 1 nm.…”

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confidence: 99%

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Versatile ultrathin nanoporous silicon nitride membranes

Vlassiouk

Apel

Dmitriev

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

157

144

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Single-and multiple-nanopore membranes are both highly interesting for biosensing and separation processes, as well as their ability to mimic biological membranes. The density of pores, their shape, and their surface chemistry are the key factors that determine membrane transport and separation capabilities. Here, we report silicon nitride (SiN) membranes with fully controlled porosity, pore geometry, and pore surface chemistry. An ultrathin freestanding SiN platform is described with conical or doubleconical nanopores of diameters as small as several nanometers, prepared by the track-etching technique. This technique allows the membrane porosity to be tuned from one to billions of pores per square centimeter. We demonstrate the separation capabilities of these membranes by discrimination of dye and protein molecules based on their charge and size. This separation process is based on an electrostatic mechanism and operates in physiological electrolyte conditions. As we have also shown, the separation capabilities can be tuned by chemically modifying the pore walls. Compared with typical membranes with cylindrical pores, the conical and double-conical pores reported here allow for higher fluxes, a critical advantage in separation applications. In addition, the conical pore shape results in a shorter effective length, which gives advantages for single biomolecule detection applications such as nanopore-based DNA analysis.ion track-etching ͉ nanofluidics ͉ filtration ͉ SiN

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Versatile ultrathin nanoporous silicon nitride membranes

Vlassiouk

Apel

Dmitriev

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

157

144

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“…In order to study the effects of these on the final pore structures, a careful characterization of the pores is necessary [99]. Previous techniques to control the size of nanoporous membranes involve coating pores with polymers [109] or metal [110]. While polymer coatings are relatively easy to deposit, they are unable to withstand high temperatures and harsh chemical environments.…”

Section: Methods Of Controlling the Pore Shape Porosity And Size Of mentioning

confidence: 99%

Nanomembrane Materials Based on Polymer Blends

Agboola

Sadiku

Mokrani

2016

Design and Applications of Nanostructured Polymer Blends and Nanocomposite Systems

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“…While we were able to previously demonstrate drastic pore-size changes by using our self-assembling polymers, systematic control over the size of the final nanopores was not demonstrated. [23] We envisaged that dendrimers would provide a significant amount of control over the nanopore dimensions. We tested this possibility by assessing the porediameter change induced by the dendrimer functionalization; this was carried out by using a calibration curve obtained from …”

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confidence: 99%

Functional Group Density and Recognition in Polymer Nanotubes

et al. 2008

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Control of the placement of functional groups within confined nanospaces is of interest because of its potential in applications such as sensing and separations. [1][2][3][4][5][6][7][8][9][10][11][12] For effective recognition of analytes within nanopores, it is necessary that control over two factors-pore size and functional group presentation-be achieved. While pore-size changes in nanopores and their effects upon recognition have been reported, [2,[13][14][15] it is also important to investigate the relative effect of binding-site density upon molecular recognition inside these nanopores. Herein, we report the effect that the density of functional groups within polymeric nanotubes could have upon complementary analyte molecules that pass through membrane nanopores. Since dendrimers are known as a class of artificial macromolecules that can have a high density of functional groups with a significant degree of control, [16][17][18][19][20] we hypothesized that these molecules are ideal candidates for this study. Even though dendrimer-based "testtube-like" nanostructures, where one end of the tube is closed, have been obtained using alumina membranes, the possibility of molecular recognition within such nanotubes has not been investigated. [21,22] Recently, we described a very simple and versatile methodology by which polymer-based functionalities can be incorporated inside nanoporous polycarbonate membranes by using polyvalent interactions.[23] We have utilized this methodology to achieve the formation of dendrimer-functionalized nanotubes.Since polypropyleneimine (PPI) dendrimers [24] are easily accessible, water-soluble, and charged, we used these molecules to test our hypotheses (Scheme 1). Our methodology for functionalization of the membrane nanopores uses electrostatic interactions and the PPI dendrimers are positively charged. Therefore, it is necessary that the predendrimerfunctionalized membrane nanopores be negatively charged. To achieve this, we first incorporated Sn 2+ ions into the pore walls of the membrane by using its poly(vinylpyrrolidone) functionalities. The Sn 2+ ions were used to introduce a layer of an anionic polymer, polyacrylic acid (PAA). We have shown that the vacuum-filtration-based incorporation of polymers is uniform throughout the membrane.[23] This anionic polymerfunctionalized membrane interior was then utilized to incorporate the cationic PPI dendrimers. The schematic illustration of membrane functionalization using PPI dendrimers is shown in Figure 1.Prior to investigating how this functionalization effected recognition of the analytes that passed through the membrane, we needed to characterize the nanotubes formed in this process. We were first interested in assessing the change in pore size of the membranes upon dendrimer functionalization. While we were able to previously demonstrate drastic pore-size changes by using our self-assembling polymers, systematic control over the size of the final nanopores was not demonstrated. [23] We envisaged that dendrimers would provide a ...

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Molecular discrimination inside polymer nanotubules

Cited by 162 publications

References 30 publications

Versatile ultrathin nanoporous silicon nitride membranes

Versatile ultrathin nanoporous silicon nitride membranes

Nanomembrane Materials Based on Polymer Blends

Functional Group Density and Recognition in Polymer Nanotubes

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