基于玻璃毛细管制备用于生物检测的纳米孔（英文）

利用玻璃毛细管,发明了一种新型用于生物检测纳米孔的制备方法.实验表明,在玻璃毛细管内壁包埋石蜡层,通过加热玻璃微管的局部,可以拉制形成直径约50 nm的纳米孔.研究表明,制备玻璃纳米孔的关键步骤是控制吸附在内壁上的石蜡层的厚度,这直接影响纳米孔的直径.利用制备的纳米孔,我们已经成功地在实验中检测出生物分子,表明此种方法制作的玻璃纳米孔可以进行生物检测.通过这种方法可快速廉价地制作玻璃纳米孔,提供了一种替代硅技术制作纳米孔的技术.     

Contactless Electrofunctionalization of a Single Pore

Customized pores are smart components that find challenging applications in a variety of fields including purification membranes and biosensing systems. The incorporation of recognition probes within pores is therefore a challenge, due to the technical difficulty of delimiting the area functionalized and obtaining the localized, specific chemical modification of pore walls. An innovative approach, named contactless electrofunctionalization (CLEF), is presented to overcome this problem. CLEF allows easy, one‐step modification of the inner surface of a pore etched in a dielectric membrane. The pore wall is coated under the influence of an electric field created by the application of a voltage between two electrodes, located near but not in contact with the pore openings. This specific localization of the deposited material within the pore is extremely rapid. Coatings were reliably and reproducibly obtained using polypyrrole co‐polymers bearing oligonucleotides, demonstrating that this technology has a promising future in the design of biosensors. Moreover, the versatility of this process allows the deposition of various electroactive entities such as iridium oxide and therefore indicates a strong potential for diverse applications involving porous materials.     

Wetting‐Controlled Localized Placement of Surface Functionalities within Nanopores

In the context of sensing and transport control, nanopores play an essential role. Designing multifunctional nanopores and placing multiple surface functionalities with nanoscale precision remains challenging. Interface effects together with a combination of different materials are used to obtain local multifunctionalization of nanoscale pores within a model pore system prepared by colloidal templating. Silica inverse colloidal monolayers are first functionalized with a gold layer to create a hybrid porous architecture with two distinct gold nanostructures on the top surface as well as at the pore bottom. Using orthogonal silane‐ and thiol‐based chemistry together with a control of the wetting state allows individual addressing of the different locations within each pore resulting in nanoscale localized functional placement of three different functional units. Ring‐opening metathesis polymerization is used for inner silica‐pore wall functionalization. The hydrophobized pores create a Cassie–Baxter wetting state with aqueous solutions of thiols, which enables an exclusive functionalization of the outer gold structures. In a third step, an ethanolic solution able to wet the pores is used to self‐assemble a thiol‐containing initiator at the pore bottom. Subsequent controlled radical polymerization provides functionalization of the pore bottom. It is demonstrated that the combination of orthogonal surface chemistry and controlled wetting states can be used for the localized functionalization of porous materials.     

Electrochemically induced maskless metal deposition on micropore wall

By applying an external electric field across a micropore via an electrolyte, metal ions in the electrolyte can be reduced locally onto the inner wall of the micropore, which was fabricated in a silica-covered silicon membrane. This maskless metal deposition on the silica surface is a result of the pore membrane polarization in the electric field.     

Cover Picture: Localized Functionalization of Single Nanopores (Adv. Mater. 4/2006)

Single nanopores can be fabricated using a combination of focused‐ion‐beam drilling and local ion‐beam‐assisted oxide deposition. On p. 427, Letant and co‐workers show how a silicon oxide ring can be grown around a single nanopore and how it can be functionalized with single‐stranded DNA using thiol‐terminated linkers. Current–voltage measurements demonstrate the presence of DNA on the pore wall and the open nature of the pore. Future applications include specific detection of whole organisms, ranging in size from bacteria to viruses.     

Thermally controlled permeation of ionic molecules through synthetic nanopores functionalized with amine-terminated polymer brushes

We present temperature-dependent ionic transport through an array of nanopores (cylindrical and conical) and a single conical nanopore functionalized with amine-terminated poly(N-isopropylacrylamide) [PNIPAAM-NH(2)] brushes. For this purpose, nanopores are fabricated in heavy ion irradiated polyethylene terephthlate (PET) membranes by a controlled chemical track-etching technique, which leads to the generation of carboxyl (COOH) groups on the pore surface. End-functionalized polymer chains are immobilized onto the inner pore walls via a 'grafting-to' approach through the covalent linkage of surface COOH moieties with the terminal amine groups of the PNIPAAM molecules by using carbodiimide coupling chemistry. The success of the chemical modification reaction is corroborated by measuring the permeation flux of charged analytes across the multipore membranes in an aqueous solution, and for the case of single conical pore by measuring the current-voltage (I-V) characteristics, which are dictated by the electrostatic interaction of the charged pore surface with the mobile ions in an electrolyte solution. The effective nanopore diameter is tuned by manipulating the environmental temperature due to the swelling/shrinking behaviour of polymer brushes attached to the inner nanopore walls, leading to a decrease/increase in the ionic transport across the membrane. This process should permit the thermal gating and controlled release of ionic drug molecules through the nanopores modified with thermoresponsive polymer chains across the membrane.     

Fouling study of silicon oxide pores exposed to tap water

We report on the fouling of Focused Ion Beam (FIB)-fabricated silicon oxide nanopores after exposure to tap water for two weeks. Pore clogging was monitored by Scanning Electron Microscopy (SEM) on both bare silicon oxide and chemically functionalized nanopores. While fouling occurred on hydrophilic silicon oxide pore walls, the hydrophobic nature of alkane chains prevented clogging on the chemically functionalized pore walls. These results have implications for nanopore sensing platform design.     

Functionalization control of porous silicon optical structures using reflectance spectra modeling for biosensing applications

Modeling and experimental reflectance spectra of porous silicon single layers at different steps of functionalization and protein grafting process are adjusted in order to determine the volume fraction of the biomolecules attached to the internal pore surface. This method is applied in order to control the efficiency of the chemical functionalization process of porous silicon single layers. Using results from single porous silicon layer study, theoretical microcavity is simulated at each step of the functionalization process. The calculated reflectance spectrum is in good agreement to the experimental one. Therefore the single layers study can be applied to multilayer structures and can be adapted for other optical structures such as waveguides, interferometers for biosensing applications.     

Fabrication of nanopores for biomacromolecule detection

Nanopores embedded in a thin membrane with diameter below 10 nm are suitable for the biomacromolecule detection. For such purpose, in this study, we developed a technique of how to obtain small nanopores in silicon nitride films using a focused-ion-beam (FIB) system. By changing the process parameters, such as the beam current, the film thickness of the membrane and the ion beam exposure time, the diameter of the nanopore can be tuned. Under an optimized condition, high quality nanopores with diameter as low as 6 nm was fabricated on a 7 nm thick membrane. Our result suggests that FIB direct writing technique might be a suitable approach for biomacromolecule detector fabrication.     

Polymeric nanopore membranes for hydrophobicity-based separations by conformal initiated chemical vapor deposition

High-aspect ratio hydrophobic, cylindrical nanopores having diameters as low as 5 nm are rapidly fabricated using conformal vapor deposition of fluorinated polymeric layers into porous track-etched polycarbonate membranes. The resultant selectivity of these membranes for pairs of small molecules of similar size, but of different hydrophobicity, arises from solute-pore wall interactions emphasized by confinement. Increasing selectivity was observed as pore diameter decreased and as the surface of the pore became more hydrophobic. Cylindrical pores provided higher selectivity than bottleneck-shaped pores having the same minimum diameter. A maximum selectivity of 234 was achieved between mesitylene and phloroglucinol by the best performing membrane. Membranes with small fluorinated pores exhibited an effective cutoff based on the polar surface area of the molecules, with limited correlation with solute size. This technology could lead to a new generation of membrane separations based on specific interactions.     

Large apparent electric size of solid-state nanopores due to spatially extended surface conduction

Ion transport through nanopores drilled in thin membranes is central to numerous applications, including biosensing and ion selective membranes. This paper reports experiments, numerical calculations, and theoretical predictions demonstrating an unexpectedly large ionic conduction in solid-state nanopores, taking its origin in anomalous entrance effects. In contrast to naive expectations based on analogies with electric circuits, the surface conductance inside the nanopore is shown to perturb the three-dimensional electric current streamlines far outside the nanopore in order to meet charge conservation at the pore entrance. This unexpected contribution to the ionic conductance can be interpreted in terms of an apparent electric size of the solid-state nanopore, which is much larger than its geometric counterpart whenever the number of charges carried by the nanopore surface exceeds its bulk counterpart. This apparent electric size, which can reach hundreds of nanometers, can have a major impact on the electrical detection of translocation events through nanopores, as well as for ionic transport in biological nanopores.     

Fabrication of solid-state nanopores with single-nanometre precision

Single nanometre-sized pores (nanopores) embedded in an insulating membrane are an exciting new class of nanosensors for rapid electrical detection and characterization of biomolecules. Notable examples include alpha-hemolysin protein nanopores in lipid membranes and solid-state nanopores in Si3N4. Here we report a new technique for fabricating silicon oxide nanopores with single-nanometre precision and direct visual feedback, using state-of-the-art silicon technology and transmission electron microscopy. First, a pore of 20 nm is opened in a silicon membrane by using electron-beam lithography and anisotropic etching. After thermal oxidation, the pore can be reduced to a single-nanometre when it is exposed to a high-energy electron beam. This fluidizes the silicon oxide leading to a shrinking of the small hole due to surface tension. When the electron beam is switched off, the material quenches and retains its shape. This technique dramatically increases the level of control in the fabrication of a wide range of nanodevices.     

静电纺PVDF/SiO_2原位复合隔膜的研究

采用原位复合溶胶-凝胶法配制复合纺丝液,通过高压静电纺丝制备出PVDF/SiO2复合纳米纤维膜。通过SEM表征了PVDF/SiO2复合纳米纤维的纺丝效果,同时对比了使用两种方法添加6%SiO2制得的PVDF静电纺复合纳米纤维的表面形貌及力学性能。研究了原位纳米SiO2的加入对膜的孔径变化以及力学性能的影响。结果表明,原位硅的加入,增加了纤维的表面粗糙度;降低了复合膜内的微孔直径,并使得微孔直径分布更加集中;改善了膜的力学性能,添加6%原位硅时效果最佳。在SiO2含量为6%时,与直接添加相比,原位复合法制得的复合膜力学性能更佳。     

Electrochemical Fabrication of Metallic Nanowires and Metal Oxide Nanopores

A nuclear track etched polycarbonate membrane filter with numerous cylindrical nanopores was applied as a nanoporous template for growing metallic nanowires. Nickel, cobalt, and iron nanowires were electrodeposited into the cylindrical nanopores. Cathodic polarization curves were measured to determine an optimum condition for growing nanowires. The shape of nanowires was observed using scanning electron microscope (SEM) and the crystal structure was analyzed using transmission electron microscopy (TEM). Diameter and length of nanowires corresponded to those of nanopores and each nanowire was composed of a single crystal. Anodized aluminum oxide films were also fabricated as a novel nanoporous template. The pore length and diameter was controlled changing anodizing conditions. Ordering behavior of nanopores array in an anodized aluminum oxide film was also investigated to make a novel nanoporous template with a highly ordered honeycomb array of nanopores.     

Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements

We reconstruct the profile of asymmetric ion track nanopores from an algorithm developed for conductometric measurements of symmetric nanopores. The validity of the reconstruction is supported by FESEM observations. Our analysis reveals that asymmetric pores fabricated by one-sided etching are funnel-like and not conical. The analysis provides the constriction diameter and the pore profile as a function of etching time. The reconstruction of the pore profile defines the starting conditions of asymmetric nanopores at breakthrough. The deviation from the conical shape is most pronounced at the pore tip. This critical zone dominates transport properties relevant to ion conductance, selectivity, current rectification, resistive pulse sensing and biosensors. The classical cone approximation used until now underestimates the tip diameter by a factor of two. As transport processes in nanopores depend in a highly nonlinear way on the constriction diameter the presented reconstruction must be taken into account when studying ionic and molecular transport processes in asymmetric pores.     

Nanoparticles of Mesoporous SO3H‐Functionalized Si‐MCM‐41 with Superior Proton Conductivity

Nanometer‐sized mesoporous silica particles of around 100‐nm diameter functionalized with a large amount of sulfonic acid groups are prepared using a simple and fast in situ co‐condensation procedure. A highly ordered hexagonal pore structure is established by applying a pre‐hydrolysis step in a high‐dilution synthesis approach, followed by adding the functionalization agent to the reaction mixture. The high‐dilution approach is advantageous for the in situ functionalization since no secondary reagents for an effective particle and framework formation are needed. Structural data are determined via electron microscopy, nitrogen adsorption, and X‐ray diffraction, proton conductivity values of the functionalized samples are measured via impedance spectroscopy. The obtained mesoporous SO₃H‐MCM‐41 nanoparticles demonstrate superior proton conductivity than their equally loaded micrometer‐sized counterparts, up to 5 × 10^?2 S cm^?1. The mesoporosity of the particles turns out to be very important for effective proton transport since non‐porous silica nanoparticles exhibit worse efficient proton transport, and the obtained particle size dependence might open up a new route in rational design of highly proton conductive materials.     

Adsorption performance of VOCs in ordered mesoporous silicas with different pore structures and surface chemistry

Ordered mesoporous silicas with different pore structures, including SBA-15, MCM-41, MCM-48 and KIT-6, were functionalized with phenyltriethoxysilane by a post-synthesis grafting approach. It was found that phenyl groups were covalently anchored onto the surface of mesoporous silicas, and the long-range ordering of the mesoporous channels was well retained after the surface functionalization. The static adsorption of benzene and the dynamic adsorption of single component (benzene) and bicomponent (benzene and cyclohexane) on the original and functionalized materials were investigated. As indicated by the adsorption study, the functionalized silicas exhibit improvement in the surface hydrophobicity and affinity for aromatic compounds as compared with the original silicas. Furthermore, the pore structure and the surface chemistry of materials can significantly influence adsorption performance. A larger pore diameter and cubic pore structure are favorable to surface functionalization and adsorption performance. In particular, the best adsorption performance observed with phenyl-grafted KIT-6 is probably related to the highest degree of surface functionalization, arising from the relatively large mesopores and bi-continuous cubic pore structure which allow great accessibility for the functional groups. In contrast, functionalized MCM-41 exhibits the lowest adsorption efficiency, probably owing to the small size of mesopores and 1D mesoporous channels.     

Ag nanotubes and Ag/AgCl electrodes in nanoporous membranes

Miniaturization of the entire experimental setup is a key requirement for widespread application of nanodevices. For nanopore biosensing, integrating electrodes onto the nanopore membrane and controlling the pore length is important for reducing the complexity and improving the sensitivity of the system. Here we present a method to achieve these goals, which relies on electroless plating to produce Ag nanotubes in track-etched polymer nanopore templates. By plating from one side only, we create a conductive nanotube that does not span the full length of the pore, and thus can act as a nanoelectrode located inside the nanopore. To give optimal electrochemical behavior for sensing, we coat the Ag nanotube with a layer of AgCl. We characterize the behavior of this nanoelectrode by measuring its current-voltage response and find that, in most cases, the response is asymmetric. The plated nanopores have initial diameters between 100 and 300?nm, thus a range suitable for detection of viruses.     

Automated Multi- and Block-Copolymer Writing in Mesoporous Films Using Visible-Light PET-RAFT and a Microscope (Small 16/2023)

For high throughput applications, e.g., in the context of sensing especially when being combined with machine learning, large sample numbers in acceptable production time are required. This needs automated synthesis and material functionalization concepts ideally combined with high precision. To automate sensing relevant mesopore polymer functionalization while being highly precise in polymer placement, polymer amount control, and polymer sequence design, a process for polymer writing in mesoporous silica films with pore diameter in the range of 13 nm is developed. Mesoporous films are functionalized with different polymers in adjustable polymer amount including block-copolymer functionalization in an automated process using a visible-light induced, controlled photo electron/energy transfer-reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization. While transferring this PET-RAFT to a commercially available microscope, direct, automated laser writing of three different polymers, as well as polymer re-initiation is demonstrated. Using a laser diameter of ≈72 µm, significantly smaller polymer spots of ≈7 µm in diameter are realized. Micrometerscale resolved polymer images including block-copolymers are written into mesoporous layers covering millimeter scale areas requiring a writing time in the range of one second per polymer spot.     

Field-effect transistors assembled from functionalized carbon nanotubes

We have fabricated field-effect transistors from carbon nanotubes using a novel selective placement scheme. We use carbon nanotubes that are covalently bound to molecules containing a hydroxamic acid functionality. The functionalized nanotubes bind strongly to basic metal oxide surfaces, but not to silicon dioxide. Upon annealing, the functionalization is removed, restoring the electronic properties of the nanotubes. The devices thus fabricated show excellent electrical characteristics.