Extreme high apspect ratio nanotubes in polymer membranes produced by catalytic ALD

German scientists from Darmstadt and Hamburg has shown that the combination of ion-track technology and ALD provides unique opportunities for highly homogeneous and conformal coatings of extremely long nanochannels. The results clearly demonstrate successful conformal coating of cylindrical 30 μm long nanochannels with initial diameter between 55 and 18 nm by three different inorganic materials (TiO2, SiO2, and Al2O3). The ALD process was carefully adjusted to temperatures low enough to avoid damage to the ion-track etched polymer membranes.

 

(a) Flexible SiO₂ nanotubes exhibiting an outer diameter of ~50 nm and a wall thickness of ~20 nm. (b) Al₂O₃ nanotubes (outer diameter ~50 nm, wall thickness ~15 nm), which are broken due to their rather high brittleness. They are attached to the flat Al₂O₃-film deposited on the polycarbonate surface. (c) TiO₂ nanotubes (outer diameter ~100 nm due to 240 s of etching time, wall thickness ~10 nm) with a length corresponding to the template thickness.

Interestingly they have used the pyridine catalyzed process for H2O low temperature SiO2 (SiCl4) and for TiO2 (titanium isopropoxide). I have never seen it used for other than SiCl4 and HCDS for growing SiO2. This got me curious to know if there is any work done with other metal chlorides - you know the usual suspects - Zr, Hf, Ta, ...

Check out all the details and the experimental part especially in the OPEN ACCESS paper below!

TiO2, SiO2, and Al2O3 coated nanopores and nanotubes produced by ALD in etched ion-track membranes for transport measurements [OPEN ACCESS]

Anne Spende, Nicolas Sobel, Manuela Lukas, Robert Zierold, Jesse C Riedl, Leonard Gura, Ina Schubert, Josep M Montero Moreno, Kornelius Nielsch, Bernd Stühn, Christian Hess, Christina Trautmann and Maria E Toimil-Molares

Published 30 July 2015 • © 2015 IOP Publishing Ltd, Nanotechnology, Volume 26, Number 33

Scheme of fabrication of TiO₂, SiO₂, and Al₂O₃ coated track-etched membranes. (a) Polycarbonate foils are irradiated with high-energy heavy ions; each projectile creates an individual ion track; (b) chemical etching converts ion tracks into cylindrical nanochannels of well-defined diameter; (c) ALD of TiO₂, SiO₂, and Al₂O₃ produces conformal homogeneous coatings.

Low-temperature atomic layer deposition (ALD) of TiO2, SiO2, and Al2O3 was applied to modify the surface and to tailor the diameter of nanochannels in etched ion-track polycarbonate membranes. The homogeneity, conformity, and composition of the coating inside the nanochannels are investigated for different channel diameters (18–55 nm) and film thicknesses (5–22 nm). Small angle x-ray scattering before and after ALD demonstrates conformal coating along the full channel length. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy provide evidence of nearly stoichiometric composition of the different coatings. By wet-chemical methods, the ALD-deposited film is released from the supporting polymer templates providing 30 μm long self-supporting nanotubes with walls as thin as 5 nm. Electrolytic ion-conductivity measurements provide proof-of-concept that combining ALD coating with ion-track nanotechnology offers promising perspectives for single-pore applications by controlled shrinking of an oversized pore to a preferred smaller diameter and fine-tuning of the chemical and physical nature of the inner channel surface.

Peking University demonstrate a ALD modified nanochannels for protein sensing

Peking University demonstrate a new type of nanopore device based on ALD Al2O3 modified track-etched conical nanochannels for protein sensing. The conformal Al2O3 film on the conical nanochannels was performed in a homemade flow-through ALD system with TMA and H2O as the precursors at a low deposition temperature of 120 °C to prevent thermal damage to the polymer PET.

Atomic Layer Deposition Modified Track-Etched Conical Nanochannels for Protein Sensing

Ceming Wang, Qibin Fu, Xinwei Wang, Delin Kong, Qian Sheng, Yugang Wang, Qiang Chen, and Jianming Xue

Anal. Chem., Article ASAP
DOI: 10.1021/acs.analchem.5b01501

 

Nanopore-based devices have recently become popular tools to detect biomolecules at the single-molecule level. Unlike the long-chain nucleic acids, protein molecules are still quite challenging to detect, since the protein molecules are much smaller in size and usually travel too fast through the nanopore with poor signal-to-noise ratio of the induced transport signals. In this work, we demonstrate a new type of nanopore device based on atomic layer deposition (ALD) Al2O3 modified track-etched conical nanochannels for protein sensing. These devices show very promising properties of high protein (bovine serum albumin) capture rate with well time-resolved transport signals and excellent signal-to-noise ratio for the transport events. Also, a special mechanism involving transient process of ion redistribution inside the nanochannel is proposed to explain the unusual biphasic waveshapes of the current change induced by the protein transport.

Plasmonic nanostructures for color filtering and nano printing technologies

This is pretty cool technology coming out of Missouri University of Science and Technology and Sandia National Laboratories. Structural color filtering and printing technologies employing plasmonic nanostructures have recently been recognized as an important and beneficial complement to the traditional colorant-based pigmentation. In this demonstration a PVD stack of 100 nm silver / 45 nm SiO2 / 25 nm silver is used. The complete stack is deposited on a Kurt J. Lesker PVD tool and final protection by thin oxide. 

Check out Prof. Xiaodong Yang, at Department of Mechanical and Aerospace Engineering Missouri University of Science and Technology for more interesting nano structures like Photonic crystals and photonic crystal cavities

Structural color printing based on plasmonic metasurfaces of perfect light absorption (Open Access)

Fei Cheng, Jie Gao, Ting S. Luk & Xiaodong Yang

Scientific Reports 5, Article number: 11045 doi:10.1038/srep11045 

Published 05 June 2015

(a) Schematic view of four unit cells for triangular-lattice circular hole arrays fabricated on the silver-silica-silver three layer structure. (b) An example of SEM cross-section image of the metasurface structure with period (P) of 320 nm and hole radius (r) of 100 nm. (c–e) SEM images of three metasurfaces with different lattice geometrical parameters (c: P = 130 nm, r = 35 nm; d: P = 200 nm, r = 50 nm; e: P = 260 nm, r = 65 nm). Insets: Optical reflection microscopy images of the entire 20 × 20 μm2 circular hole arrays of triangular lattice. Scale bars: 500 nm.

Abstract

Subwavelength structural color filtering and printing technologies employing plasmonic nanostructures have recently been recognized as an important and beneficial complement to the traditional colorant-based pigmentation. However, the color saturation, brightness and incident angle tolerance of structural color printing need to be improved to meet the application requirement. Here we demonstrate a structural color printing method based on plasmonic metasurfaces of perfect light absorption to improve color performances such as saturation and brightness. Thin-layer perfect absorbers with periodic hole arrays are designed at visible frequencies and the absorption peaks are tuned by simply adjusting the hole size and periodicity. Near perfect light absorption with high quality factors are obtained to realize high-resolution, angle-insensitive plasmonic color printing with high color saturation and brightness. Moreover, the fabricated metasurfaces can be protected with a protective coating for ambient use without degrading performances. The demonstrated structural color printing platform offers great potential for applications ranging from security marking to information storage.

(a) The original athletics mark image adapted with permission from The Curators of the University of Missouri. (b) SEM image of the fabricated pattern containing six different triangular lattices and corresponding colors shown in panel e. (c) SEM image of the area outlined in panel f. (d) Optical microscopy image of a plasmonic reproduction of the original mark image shown in panel e, containing only yellow and green colors. (e) Optical microscopy image of the plasmonic print presenting another four distinct colors (symbol ‘&’: orange, character ‘S, T’: magenta, pickaxe shape: cyan and word ‘MISSOURI’: navy blue) besides two original colors shown in panel d. Scale bars: 10 μm (b, d and e); 2 μm (c).

Note: The article has been distributed under a Creative Commons CC-BY license (please see the article itself for the license version number). You may reuse this material without obtaining permission from Nature Publishing Group

Eureka moments in Nanochemistry – 2015 Centenary Award, Professor Geoffrey Ozin

Here is a fantastic article on Nanochemistry published in Materials Views - Eureka moments in Nanochemistry – 2015 Centenary Award

This article is an invited piece from Professor Geoffrey Ozin, University of Toronto, on his 2015 RSC Centenary Award for his work in defining, enabling and popularising a chemical approach to nanomaterials for innovative nanotechnology in advanced materials and biomedical science.

"In this Perspective I will look back over my careers work and reminisce, with the help of a few graphical depictions, about the “eureka moments” that led me to imagine and help develop the field of Nanochemistry. "

1, 2, 3, 4, 5, 6, 7 - ALD!

7. Multi-photon direct laser written (DLW) photonic bandgap nanomaterials

"In collaboration with colleagues at the Karlsruhe Institute of Technology, I used this nanofabrication method to invert a DLW polymer template in silica by atomic layer deposition. This enabled a subsequent inversion in silicon by disilane chemical vapor deposition, creating thereby a silicon replica of the original polymer template (Nature Materials 2006). Silicon photonic bandgap nanomaterials created by this inventive ‘double inversion’ method facilitate the development of silicon-based all-optical devices, circuits and chips with utility in optical telecommunication and computer systems. I spearheaded a creative extension of this work with single-step DLW in a high refractive index ‘inorganic’ photo-resist, arsenic sesquisulphide, As2S3. This opened the door to a large variety of new photonic bandgap materials and architectures that can be made by DLW without inversion of a sacrificial polymer template (ChemMater 2008)."

Read the complete article here: http://www.materialsviews.com/eureka-moments-in-nanochemistry-2015-centenary-award/

Tuning the nanopore diameter using ALD

Working on deep deep nano holes and tubes for a long time (DRAM) and for a lab growing nanowires I found this an interesting paper on how ALD can be used to tune the nanopore diameter. Nanopore (NP) technologies have been researched the last 10 years or so. According to the paper "The next major breakthrough" of this technology will depend on :

• the fundamental understanding of the dynamical processes that govern macromolecules translocation through NP
• the availability of methods that allow routine fabrication of nanoscale materials. 

Particles, holes, tubes, wires, pores, ..., transistors etc. - what else could you do nano?

Influence of nanopore surface charge and magnesium ion on polyadenosine translocation

Mathilde Lepoitevin, Pierre Eugène Coulon, Mikhael Bechelany, Julien Cambedouzou, Jean-Marc Janot and Sebastien Balme
Mathilde Lepoitevin et al 2015 Nanotechnology 26 144001
doi:10.1088/0957-4484/26/14/144001

We investigate the influence of a nanopore surface state and the addition of Mg2+ on poly-adenosine translocation. To do so, two kinds of nanopores with a low aspect ratio (diameter ~3–5 nm, length 30 nm) were tailored: the first one with a negative charge surface and the second one uncharged. It was shown that the velocity and the energy barrier strongly depend on the nanopore surface. Typically if the nanopore and polyA exhibit a similar charge, the macromolecule velocity increases and its global energy barrier of entrance in the nanopore decreases, as opposed to the non-charged nanopore. Moreover, the addition of a divalent chelating cation induces an increase of energy barrier of entrance, as expected. However, for a negative nanopore, this effect is counterbalanced by the inversion of the surface charge induced by the adsorption of divalent cations.

Cartoon to illustrate polyA translocation through NP and the electrolyte distribution. (a) Native -NP at NaCl 150 mM (b) native-NP at NaCl 500 mM and (c) TMS-NP at NaCl 150 mM.

Check out The Nanopore Site!