Synthesis of organically templated nanoporous tin (II/IV) phosphate for radionuclide and metal sequestration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wellman, Dawn M.; Mattigod, Shas V.; Parker, Kent E.

2006-03-20

Nanoporous tin (II/IV) phosphate materials, with spherical morphology, have been synthesized using cetyltrimethylammonium chloride (CH3(CH2)15N(CH3)3Cl) as the surfactant. The structure of the material is stable at 500°C; however, partial oxidation of the material occurs with redox conversion of Sn2+ to Sn4+, resulting in a mixed Sn(II)/ Sn(IV) material. Preliminary batch contact studies were conducted to assess the effectiveness of nanoporous tin phosphate, NP-SnPO, in sequestering redox sensitive metals and radionuclides, technetium(VII), neptunium(V), thorium(IV), and a toxic metal, chromium(VI), from aqueous matrices. Results indicate tin (II) phosphate removed > 95% of all contaminants investigated from solution.

Porous graphene-based membranes for water purification from metal ions at low differential pressures.

PubMed

Park, Jaewoo; Bazylewski, Paul; Fanchini, Giovanni

2016-05-14

A new generation of membranes for water purification based on weakly oxidized and nanoporous few-layer graphene is here introduced. These membranes dramatically decrease the high energy requirements of water purification by reverse osmosis. They combine the advantages of porous and non-oxidized single-layer graphene, offering energy-efficient water filtration at relatively low differential pressures, and highly oxidized graphene oxide, exhibiting high performance in terms of impurity adsorption. In the reported fabrication process, leaks between juxtaposed few-layer graphene flakes are sealed by thermally annealed colloidal silica, in a treatment that precedes the opening of (sub)nanometre-size pores in graphene. This process, explored for the first time in this work, results in nanoporous graphene flakes that are water-tight at the edges without occluding the (sub)nanopores. With this method, removal of impurities from water occurs through a combination of size-based pore rejection and pore-edge adsorption. Thinness of graphene flakes allows these membranes to achieve water purification from metal ions in concentrations of few parts-per-million at differential pressures as low as 30 kPa, outperforming existing graphene or graphene oxide purification systems with comparable flow rates.

Porous graphene-based membranes for water purification from metal ions at low differential pressures

NASA Astrophysics Data System (ADS)

Park, Jaewoo; Bazylewski, Paul; Fanchini, Giovanni

2016-05-01

A new generation of membranes for water purification based on weakly oxidized and nanoporous few-layer graphene is here introduced. These membranes dramatically decrease the high energy requirements of water purification by reverse osmosis. They combine the advantages of porous and non-oxidized single-layer graphene, offering energy-efficient water filtration at relatively low differential pressures, and highly oxidized graphene oxide, exhibiting high performance in terms of impurity adsorption. In the reported fabrication process, leaks between juxtaposed few-layer graphene flakes are sealed by thermally annealed colloidal silica, in a treatment that precedes the opening of (sub)nanometre-size pores in graphene. This process, explored for the first time in this work, results in nanoporous graphene flakes that are water-tight at the edges without occluding the (sub)nanopores. With this method, removal of impurities from water occurs through a combination of size-based pore rejection and pore-edge adsorption. Thinness of graphene flakes allows these membranes to achieve water purification from metal ions in concentrations of few parts-per-million at differential pressures as low as 30 kPa, outperforming existing graphene or graphene oxide purification systems with comparable flow rates.

Interfacial Engineering of Nanoporous Architectures in Ga2O3 Film toward Self-Aligned Tubular Nanostructure with an Enhanced Photocatalytic Activity on Water Splitting.

PubMed

Shrestha, Nabeen K; Bui, Hoa Thi; Lee, Taegweon; Noh, Yong-Young

2018-04-17

The present work demonstrates the formation of self-aligned nanoporous architecture of gallium oxide by anodization of gallium metal film controlled at -15 °C in aqueous electrolyte consisting of phosphoric acid. SEM examination of the anodized film reveals that by adding ethylene glycol to the electrolyte and optimizing the ratio of phosphoric acid and water, chemical etching at the oxide/electrolyte interfaces can be controlled, leading to the formation of aligned nanotubular oxide structures with closed bottom. XPS analysis confirms the chemical composition of the oxide film as Ga 2 O 3 . Further, XRD and SAED examination reveals that the as-synthesized nanotubular structure is amorphous, and can be crystallized to β-Ga 2 O 3 phase by annealing the film at 600 °C. The nanotubular structured film, when used as photoanode for photoelectrochemical splitting of water, achieved a higher photocurrent of about two folds than that of the nanoporous film, demonstrating the rewarding effect of the nanotubular structure. In addition, the work also demonstrates the formation of highly organized nonporous Ga 2 O 3 structure on a nonconducting glass substrate coated with thin film of Ga-metal, highlighting that the current approach can be extended for the formation of self-organized nanoporous Ga 2 O 3 thin film even on nonconducting flexible substrates.

Highly ordered gold nanotubes using thiols at a cleavable block copolymer interface.

PubMed

Ryu, Ja-Hyoung; Park, Soojin; Kim, Bokyung; Klaikherd, Akamol; Russell, Thomas P; Thayumanavan, S

2009-07-29

We have prepared functionalized nanoporous thin films from a polystyrene-block-polyethylene oxide block copolymer, which was made cleavable due to the intervening disulfide bond. The cleavage reaction of the disulfide bond leaves behind free thiol groups inside the nanopores of polystyrene thin film. This nanoporous thin film can be used as a template for generating gold nanoring structures. This strategy can provide a facile method to form a highly ordered array of biopolymer or metal-polymer composite structures.

Oxidation and reduction under cover: Chemistry at the confined space between ultra-thin nanoporous silicates and Ru(0001)

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. Anibal Boscoboinik; Zhong, Jian -Qiang; Kestell, John

2016-03-23

The oxidation and reduction of Ru(0001) surfaces at the confined space between two-dimensional nanoporous silica frameworks and Ru(0001) have been investigated using synchrotron-based ambient pressure X-ray photoelectron spectroscopy (AP-XPS). The porous nature of the frameworks and the weak interaction between the silica and the ruthenium substrate allow oxygen and hydrogen molecules to go through the nanopores and react with the metal at the interface between the silica framework and the metal surface. In this work, three types of two-dimensional silica frameworks have been used to study their influence in the oxidation and reduction of the ruthenium surface at elevated pressuresmore » and temperatures. These frameworks are bilayer silica (0.5 nm thick), bilayer aluminosilicate (0.5 nm thick), and zeolite MFI nanosheets (3 nm thick). It is found that the silica frameworks stay essentially intact under these conditions, but they strongly affect the oxidation of ruthenium, with the 0.5 nm thick aluminosilicate bilayer completely inhibiting the oxidation. Furthermore, the latter is believed to be related to the lower chemisorbed oxygen content arising from electrostatic interactions between the negatively charged aluminosilicate framework and the Ru(0001) substrate.« less

Engineering the internal surfaces of three-dimensional nanoporous catalysts by surfactant-modified dealloying.

PubMed

Wang, Zhili; Liu, Pan; Han, Jiuhui; Cheng, Chun; Ning, Shoucong; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2017-10-20

Tuning surface structures by bottom-up synthesis has been demonstrated as an effective strategy to improve the catalytic performances of nanoparticle catalysts. Nevertheless, the surface modification of three-dimensional nanoporous metals, fabricated by a top-down dealloying approach, has not been achieved despite great efforts devoted to improving the catalytic performance of three-dimensional nanoporous catalysts. Here we report a surfactant-modified dealloying method to tailor the surface structure of nanoporous gold for amplified electrocatalysis toward methanol oxidation and oxygen reduction reactions. With the assistance of surfactants, {111} or {100} faceted internal surfaces of nanoporous gold can be realized in a controllable manner by optimizing dealloying conditions. The surface modified nanoporous gold exhibits significantly enhanced electrocatalytic activities in comparison with conventional nanoporous gold. This study paves the way to develop high-performance three-dimensional nanoporous catalysts with a tunable surface structure by top-down dealloying for efficient chemical and electrochemical reactions.

Overall Water Splitting with Room-Temperature Synthesized NiFe Oxyfluoride Nanoporous Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Kun; Guo, Limin; Marcus, Kyle

Freestanding and lightweight thin-films were rationally designed to serve as robust electrodes for renewable energy applications. A facile and scalable nanomanufacturing process was developed to fabricate these transformative thin-film electrodes (iron group mixed oxides) that exhibit a nanoporous structure and controllable composition. More specifically, electrodeposition and anodic treatments were employed to produce freestanding and lightweight metal oxides nanoporous layers (NPL). These NPL can be directly used as flexible and additive-free electrodes for renewable energy generation (water splitting) and storage (supercapacitor) applications without requiring binders and current collector and other additives. Significantly enhanced electrochemical performance was achieved due to the uniquemore » merits of the NPL: i) highly porous structure considerably increases the electrode/electrolyte interface, which facilitate electrochemical reactions; ii) NPL substantially increase the number of active sites that are favorable in electrochemical reactions; iii) residual metal network within the NPL forms a conductive framework, drastically improving electrode strength, flexibility and conductivity.« less

A novel input-parasitic compensation technique for a nanopore-based CMOS DNA detection sensor

NASA Astrophysics Data System (ADS)

Kim, Jungsuk

2016-12-01

This paper presents a novel input-parasitic compensation (IPC) technique for a nanopore-based complementary metal-oxide-semiconductor (CMOS) DNA detection sensor. A resistive-feedback transimpedance amplifier is typically adopted as the headstage of a DNA detection sensor to amplify the minute ionic currents generated from a nanopore and convert them to a readable voltage range for digitization. But, parasitic capacitances arising from the headstage input and the nanopore often cause headstage saturation during nanopore sensing, thereby resulting in significant DNA data loss. To compensate for the unwanted saturation, in this work, we propose an area-efficient and automated IPC technique, customized for a low-noise DNA detection sensor, fabricated using a 0.35- μm CMOS process; we demonstrated this prototype in a benchtop test using an α-hemolysin ( α-HL) protein nanopore.

Prototyping Energy Storage Components for Hybrid Power Source

DTIC Science & Technology

2009-12-11

from suitable nanoporous ceramic ( anodized aluminum oxide – AAO ) and polymer (polycarbonate - PC, polyethylene terephtalate - PET) membranes . Metal...of NUC technology: a) sketch of structure, b) SEM image of membrane . The alumina membranes can be easily and inexpensively fabricated via anodization ...of aluminum foil. The pores are formed by self-assembly via pitting and reprecipation of metal oxide . Motivation The work is motivated by the

Confining metal-halide perovskites in nanoporous thin films

PubMed Central

Demchyshyn, Stepan; Roemer, Janina Melanie; Groiß, Heiko; Heilbrunner, Herwig; Ulbricht, Christoph; Apaydin, Dogukan; Böhm, Anton; Rütt, Uta; Bertram, Florian; Hesser, Günter; Scharber, Markus Clark; Sariciftci, Niyazi Serdar; Nickel, Bert; Bauer, Siegfried; Głowacki, Eric Daniel; Kaltenbrunner, Martin

2017-01-01

Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates for the growth of perovskite nanocrystallites directly within device-relevant architectures without the use of colloidal stabilization. We find significantly blue-shifted photoluminescence emission by reducing the pore size; normally infrared-emitting materials become visibly red, and green-emitting materials become cyan and blue. Confining perovskite nanocrystals within porous oxide thin films drastically increases photoluminescence stability because the templates auspiciously serve as encapsulation. We quantify the template-induced size of the perovskite crystals in nanoporous silicon with microfocus high-energy x-ray depth profiling in transmission geometry, verifying the growth of perovskite nanocrystals throughout the entire thickness of the nanoporous films. Low-voltage electroluminescent diodes with narrow, blue-shifted emission fabricated from nanocrystalline perovskites grown in embedded nanoporous alumina thin films substantiate our general concept for next-generation photonic devices. PMID:28798959

Nanoporous Pirani sensor based on anodic aluminum oxide

NASA Astrophysics Data System (ADS)

Jeon, Gwang-Jae; Kim, Woo Young; Shim, Hyun Bin; Lee, Hee Chul

2016-09-01

A nanoporous Pirani sensor based on anodic aluminum oxide (AAO) is proposed, and the quantitative relationship between the performance of the sensor and the porosity of the AAO membrane is characterized with a theoretical model. The proposed Pirani sensor is composed of a metallic resistor on a suspended nanoporous membrane, which simultaneously serves as the sensing area and the supporting structure. The AAO membrane has numerous vertically-tufted nanopores, resulting in a lower measurable pressure limit due to both the increased effective sensing area and the decreased effective thermal loss through the supporting structure. Additionally, the suspended AAO membrane structure, with its outer periphery anchored to the substrate, known as a closed-type design, is demonstrated using nanopores of AAO as an etch hole without a bulk micromachining process used on the substrate. In a CMOS-compatible process, a 200 μm × 200 μm nanoporous Pirani sensor with porosity of 25% was capable of measuring the pressure from 0.1 mTorr to 760 Torr. With adjustment of the porosity of the AAO, the measurable range could be extended toward lower pressures of more than one decade compared to a non-porous membrane with an identical footprint.

Tuning ligament shape in dealloyed nanoporous tin and the impact of nanoscale morphology on its applications in Na-ion alloy battery anodes

NASA Astrophysics Data System (ADS)

Detsi, Eric; Petrissans, Xavier; Yan, Yan; Cook, John B.; Deng, Ziling; Liang, Yu-Lun; Dunn, Bruce; Tolbert, Sarah H.

2018-05-01

Control over the morphology of nanostructured materials is of primary importance in structure-property relationship studies. Although the size of ligaments and pores in dealloyed nanoporous metals can be controlled by thermal and/or (electro)chemical treatments, tuning the shape of those ligaments is much harder. In the present work, we use corroding media with different reactivity to effectively tailor the ligament shape in nanoporous tin (NP-Sn) during dealloying by free corrosion. NP-Sn architectures with nanowire and granular ligament shapes were made by controlling the pH of the corroding solution, and thus the rate of Sn oxidation relative to the etching rate of the sacrificial component. The standard nanowire structure was formed under acidic conditions where oxidation was slow, but a hierarchical granular structure was formed when fusion of the Sn nanocrystals was inhibited by surface oxidation. To demonstrate the advantages of this architectural control, these two materials systems were investigated as electrodes for Na-ion battery anodes. Similar initial Na storage capacities of ˜500 and 550 mAh/g were achieved in the nanowire and granular materials, respectively, but the cycle life of the two materials was quite different. NP-Sn with a granular ligament shape showed enhanced stability with a capacity retention of ˜55 % over 95 cycles at a specific current of 40 mA/g. By contrast, NP-Sn with a nanowire ligament shape showed very fast capacity fading within the first 10 cycles. This work thus demonstrates the dramatic impact of the nanoscale morphology on the electrochemical performance of nanoporous materials and highlights the need for both shape and size control in dealloyed nanoporous metals.

Balancing activity, stability and conductivity of nanoporous core-shell iridium/iridium oxide oxygen evolution catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Yong-Tae; Lopes, Pietro Papa; Park, Shin-Ae

The selection of oxide materials for catalyzing the Oxygen Evolution Reaction in acid-based electrolyzers must be guided by the proper balance between activity, stability and conductivity – a challenging mission of great importance for delivering affordable and environmentally friendly hydrogen. Here we report that the highly conductive nanoporous architecture of an iridium oxide shell on a metallic iridium core, formed through the fast dealloying of osmium from an Ir25Os75 alloy, exhibits an exceptional balance between oxygen evolution activity and stability as quantified by the Activity-Stability FactorASF. Based on this metric, the nanoporous Ir/IrO2 morphology of dealloyed Ir25Os75 shows a factormore » of ~30 improvement ASFrelative to conventional Ir-based oxide materials and a ~8 times improvement over dealloyed Ir25Os75 nanoparticles due to optimized stability and conductivity, respectively. We propose that the Activity-Stability FactorASF is the key “metric” for determining the technological relevance of oxide-based anodic water electrolyzer catalysts.« less

Formation of crack-free nanoporous tin oxide layers via simple one-step anodic oxidation in NaOH at low applied voltages

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Gilek, Dominika; Gawlak, Karolina; Jaskuła, Marian; Sulka, Grzegorz D.

2016-12-01

A simple anodic oxidation of metallic tin in fluoride-free alkaline electrolyte at low potentials was proposed as a new and effective strategy for fabrication of crack-free nanoporous tin oxide layers. A low-purity Sn foil (98.8%) was used as a starting material, and a series of anodizations were performed in 1 M NaOH at different conditions such as anodizing potential, and duration of the process. It was proved for the first time that nanostructured tin oxides with ultra-small nanochannels having diameters of <15 nm can be synthesized by simple anodization of metallic tin at a potential of 2 V in 1 M NaOH electrolyte. Increasing anodizing potential to 3 and 4 V allowed for formation of tin oxide layers with much larger pores (40-50 nm in diameter) which were still free from internal cracks and transversal pores. Applying such low potentials significantly reduces the oxide growth rate and suppresses vigorous oxygen evolution at the anode. As a result mechanical deterioration of the oxide structure is prevented while strongly alkaline electrolyte is responsible for formation of the porous layer with completely open pores even at such low potentials. On the contrary, when anodization was carried out at potentials of 5 and 6 V, much faster formation of anodic layer, accompanied by vigorous oxygen gas formation, was observed. In consequence, as grown oxide layers exhibited typical cracked or even stacked internal structure. Finally, we demonstrated for the first time that nanoporous tin oxide layers with segments of different channel sizes can be successfully obtained by simple altering potential during anodization.

Nanoporous metal-carbon composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Worsley, Marcus A.; Satcher, Joe; Kucheyev, Sergei

Described here is a metal-carbon composite, comprising (a) a porous three-dimensional scaffold comprising one or more of carbon nanotubes, graphene and graphene oxide, and (b) metal nanoparticles disposed on said porous scaffold, wherein the metal-carbon composite has a density of 1 g/cm.sup.3 or less, and wherein the metal nanoparticles account for 1 wt. % or more of the metal-carbon composite. Also described are methods for making the metal-carbon composite.

Color filters based on a nanoporous Al-AAO resonator featuring structure tolerant color saturation.

PubMed

Yue, Wenjing; Li, Yang; Wang, Cong; Yao, Zhao; Lee, Sang-Shin; Kim, Nam-Young

2015-10-19

Reflection type subtractive tri-color filters, enabling metal-thickness tolerant high color saturation, were proposed and demonstrated capitalizing on a nanoporous metal-dielectric-metal (MDM) resonant structure, which comprises a cavity made of self-assembled nanoporous anodic aluminum oxide (AAO), sandwiched between an Al film of the same nanoporous configuration and a highly reflective aluminum (Al) substrate. For the proposed filter, the output color was easily determined by controlling the resonance wavelength via the thickness of the porous AAO cavity. In particular, the spectral response was deemed to exhibit a near-zero resonant dip, thereby achieving enhanced color saturation, which was stably maintained irrespective of the thickness of the porous Al film, due to its reduced effective refractive index. In order to manufacture the proposed color filters on a large scale, a porous Al film of hexagonal lattice configuration was integrated with an identically porous self-assembled AAO layer, which has been grown on an Al substrate. For the realized tri-color filters for cyan, magenta, and yellow (CMY), having a 15-nm Al film, near-zero reflection dips were observed to be centered at the wavelengths of 436, 500, and 600 nm, respectively. The resulting enhanced color saturation was stably maintained even though the variations were as large as 10 nm in the metal thickness.

Measurement of DNA translocation dynamics in a solid-state nanopore at 100-ns temporal resolution

PubMed Central

Shekar, Siddharth; Niedzwiecki, David J.; Chien, Chen-Chi; Ong, Peijie; Fleischer, Daniel A.; Lin, Jianxun; Rosenstein, Jacob K.; Drndic, Marija; Shepard, Kenneth L.

2017-01-01

Despite the potential for nanopores to be a platform for high-bandwidth study of single-molecule systems, ionic current measurements through nanopores have been limited in their temporal resolution by noise arising from poorly optimized measurement electronics and large parasitic capacitances in the nanopore membranes. Here, we present a complementary metal-oxide-semiconductor (CMOS) nanopore (CNP) amplifier capable of low noise recordings at an unprecedented 10 MHz bandwidth. When integrated with state-of-the-art solid-state nanopores in silicon nitride membranes, we achieve an SNR of greater than 10 for ssDNA translocations at a measurement bandwidth of 5 MHz, which represents the fastest ion current recordings through nanopores reported to date. We observe transient features in ssDNA translocation events that are as short as 200 ns, which are hidden even at bandwidths as high as 1 MHz. These features offer further insights into the translocation kinetics of molecules entering and exiting the pore. This platform highlights the advantages of high-bandwidth translocation measurements made possible by integrating nanopores and custom-designed electronics. PMID:27332998

Integrated nanopore sensing platform with sub-microsecond temporal resolution

PubMed Central

Rosenstein, Jacob K; Wanunu, Meni; Merchant, Christopher A; Drndic, Marija; Shepard, Kenneth L

2012-01-01

Nanopore sensors have attracted considerable interest for high-throughput sensing of individual nucleic acids and proteins without the need for chemical labels or complex optics. A prevailing problem in nanopore applications is that the transport kinetics of single biomolecules are often faster than the measurement time resolution. Methods to slow down biomolecular transport can be troublesome and are at odds with the natural goal of high-throughput sensing. Here we introduce a low-noise measurement platform that integrates a complementary metal-oxide semiconductor (CMOS) preamplifier with solid-state nanopores in thin silicon nitride membranes. With this platform we achieved a signal-to-noise ratio exceeding five at a bandwidth of 1 MHz, which to our knowledge is the highest bandwidth nanopore recording to date. We demonstrate transient signals as brief as 1 μs from short DNA molecules as well as current signatures during molecular passage events that shed light on submolecular DNA configurations in small nanopores. PMID:22426489

Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Lang, Xingyou; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2011-04-01

Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes, but their energy storage density is too low for many important applications. Pseudocapacitive transition-metal oxides such as MnO2 could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment. However, the poor conductivity of MnO2 (10-5-10-6 S cm-1) limits the charge/discharge rate for high-power applications. Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO2 have enhanced conductivity, resulting in a specific capacitance of the constituent MnO2 (~1,145 F g-1) that is close to the theoretical value. The nanoporous gold allows electron transport through the MnO2, and facilitates fast ion diffusion between the MnO2 and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery.

Nanoporous metal/oxide hybrid electrodes for electrochemical supercapacitors.

PubMed

Lang, Xingyou; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2011-04-01

Electrochemical supercapacitors can deliver high levels of electrical power and offer long operating lifetimes, but their energy storage density is too low for many important applications. Pseudocapacitive transition-metal oxides such as MnO(2) could be used to make electrodes in such supercapacitors, because they are predicted to have a high capacitance for storing electrical charge while also being inexpensive and not harmful to the environment. However, the poor conductivity of MnO(2) (10(-5)-10(-6) S cm(-1)) limits the charge/discharge rate for high-power applications. Here, we show that hybrid structures made of nanoporous gold and nanocrystalline MnO(2) have enhanced conductivity, resulting in a specific capacitance of the constituent MnO(2) (~1,145 F g(-1)) that is close to the theoretical value. The nanoporous gold allows electron transport through the MnO(2), and facilitates fast ion diffusion between the MnO(2) and the electrolytes while also acting as a double-layer capacitor. The high specific capacitances and charge/discharge rates offered by such hybrid structures make them promising candidates as electrodes in supercapacitors, combining high-energy storage densities with high levels of power delivery.

Pseudocapacitive and hierarchically ordered porous electrode materials supercapacitors

NASA Astrophysics Data System (ADS)

Saruhan, B.; Gönüllü, Y.; Arndt, B.

2013-05-01

Commercially available double layer capacitors store energy in an electrostatic field. This forms in the form of a double layer by charged particles arranged on two electrodes consisting mostly of active carbon. Such double layer capacitors exhibit a low energy density, so that components with large capacity according to large electrode areas are required. Our research focuses on the development of new electrode materials to realize the production of electrical energy storage systems with high energy density and high power density. Metal oxide based electrodes increase the energy density and the capacitance by addition of pseudo capacitance to the static capacitance present by the double layer super-capacitor electrodes. The so-called hybrid asymmetric cell capacitors combine both types of energy storage in a single component. In this work, the production routes followed in our laboratories for synthesis of nano-porous and aligned metal oxide electrodes using the electrochemical and sputter deposition as well as anodization methods will be described. Our characterisation studies concentrate on electrodes having redox metal-oxides (e.g. MnOx and WOx) and hierarchically aligned nano-porous Li-doped TiO2-NTs. The material specific and electrochemical properties achieved with these electrodes will be presented.

Development of Ordered, Porous (Sub-25 nm Dimensions) Surface Membrane Structures Using a Block Copolymer Approach.

PubMed

Ghoshal, Tandra; Holmes, Justin D; Morris, Michael A

2018-05-08

In an effort to develop block copolymer lithography to create high aspect vertical pore arrangements in a substrate surface we have used a microphase separated poly(ethylene oxide) -b- polystyrene (PEO-b-PS) block copolymer (BCP) thin film where (and most unusually) PS not PEO is the cylinder forming phase and PEO is the majority block. Compared to previous work, we can amplify etch contrast by inclusion of hard mask material into the matrix block allowing the cylinder polymer to be removed and the exposed substrate subject to deep etching thereby generating uniform, arranged, sub-25 nm cylindrical nanopore arrays. Briefly, selective metal ion inclusion into the PEO matrix and subsequent processing (etch/modification) was applied for creating iron oxide nanohole arrays. The oxide nanoholes (22 nm diameter) were cylindrical, uniform diameter and mimics the original BCP nanopatterns. The oxide nanohole network is demonstrated as a resistant mask to fabricate ultra dense, well ordered, good sidewall profile silicon nanopore arrays on substrate surface through the pattern transfer approach. The Si nanopores have uniform diameter and smooth sidewalls throughout their depth. The depth of the porous structure can be controlled via the etch process.

Highly Reversible Water Oxidation at Ordered Nanoporous Iridium Electrodes Based on an Original Atomic Layer Deposition.

PubMed

Schlicht, Stefanie; Haschke, Sandra; Mikhailovskii, Vladimir; Manshina, Alina; Bachmann, Julien

2018-05-01

Nanoporous iridium electrodes are prepared and electrochemically investigated towards the water oxidation (oxygen evolution) reaction. The preparation is based on 'anodic' aluminum oxide templates, which provide straight, cylindrical nanopores. Their walls are coated using atomic layer deposition (ALD) with a newly developed reaction which results in a metallic iridium layer. The ALD film growth is quantified by spectroscopic ellipsometry and X-ray reflectometry. The morphology and composition of the electrodes are characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Their catalytic activity is quantified for various pore geometries by cyclic voltammetry, steady-state electrolysis, and electrochemical impedance spectroscopy. With an optimal pore length of L ≈17-20 μm, we achieve current densities of J =0.28 mA cm -2 at pH 5 and J =2.4 mA cm -2 at pH 1. This platform is particularly competitive for achieving moderate current densities at very low overpotentials, that is, for a high degree of reversibility in energy storage.

Highly active thermally stable nanoporous gold catalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biener, Juergen; Wittstock, Arne; Biener, Monika M.

In one embodiment, a system includes a nanoporous gold structure and a plurality of oxide particles deposited on the nanoporous gold structure; the oxide particles are characterized by a crystalline phase. In another embodiment, a method includes depositing oxide nanoparticles on a nanoporous gold support to form an active structure and functionalizing the deposited oxide nanoparticles.

Hierarchical nanoporous metals as a path toward the ultimate three-dimensional functionality.

PubMed

Fujita, Takeshi

2017-01-01

Nanoporous metals prepared via dealloying or selective leaching of solid solution alloys and compounds represent an emerging class of materials. They possess a three-dimensional (3D) structure of randomly interpenetrating ligaments/nanopores with sizes between 5 nm and several tens of micrometers, which can be tuned by varying their preparation conditions (such as dealloying time and temperature) or additional thermal coarsening. As compared to other nanostructured materials, nanoporous metals have many advantages, including their bicontinuous structure, tunable pore sizes, bulk form, good electrical conductivity, and high structural stability. Therefore, nanoporous metals represent ideal 3D materials with versatile functionality, which can be utilized in various fields. In this review, we describe the recent applications of nanoporous metals in molecular detection, catalysis, 3D graphene synthesis, hierarchical pore formation, and additive manufacturing (3D printing) together with our own achievements in these areas. Finally, we discuss possible ways of realizing the ultimate 3D functionality beyond the scope of nanoporous metals.

Hierarchical nanoporous metals as a path toward the ultimate three-dimensional functionality

PubMed Central

Fujita, Takeshi

2017-01-01

Abstract Nanoporous metals prepared via dealloying or selective leaching of solid solution alloys and compounds represent an emerging class of materials. They possess a three-dimensional (3D) structure of randomly interpenetrating ligaments/nanopores with sizes between 5 nm and several tens of micrometers, which can be tuned by varying their preparation conditions (such as dealloying time and temperature) or additional thermal coarsening. As compared to other nanostructured materials, nanoporous metals have many advantages, including their bicontinuous structure, tunable pore sizes, bulk form, good electrical conductivity, and high structural stability. Therefore, nanoporous metals represent ideal 3D materials with versatile functionality, which can be utilized in various fields. In this review, we describe the recent applications of nanoporous metals in molecular detection, catalysis, 3D graphene synthesis, hierarchical pore formation, and additive manufacturing (3D printing) together with our own achievements in these areas. Finally, we discuss possible ways of realizing the ultimate 3D functionality beyond the scope of nanoporous metals. PMID:29057026

Hierarchical nanoporous metals as a path toward the ultimate three-dimensional functionality

NASA Astrophysics Data System (ADS)

Fujita, Takeshi

2017-12-01

Nanoporous metals prepared via dealloying or selective leaching of solid solution alloys and compounds represent an emerging class of materials. They possess a three-dimensional (3D) structure of randomly interpenetrating ligaments/nanopores with sizes between 5 nm and several tens of micrometers, which can be tuned by varying their preparation conditions (such as dealloying time and temperature) or additional thermal coarsening. As compared to other nanostructured materials, nanoporous metals have many advantages, including their bicontinuous structure, tunable pore sizes, bulk form, good electrical conductivity, and high structural stability. Therefore, nanoporous metals represent ideal 3D materials with versatile functionality, which can be utilized in various fields. In this review, we describe the recent applications of nanoporous metals in molecular detection, catalysis, 3D graphene synthesis, hierarchical pore formation, and additive manufacturing (3D printing) together with our own achievements in these areas. Finally, we discuss possible ways of realizing the ultimate 3D functionality beyond the scope of nanoporous metals.

Ultrathin gas permeable oxide membranes for chemical sensing: Nanoporous Ta 2O 5 test study

DOE PAGES

Imbault, Alexander; Wang, Yue; Kruse, Peter; ...

2015-09-25

Conductometric gas sensors made of gas permeable metal oxide ultrathin membranes can combine the functions of a selective filter, preconcentrator, and sensing element and thus can be particularly promising for the active sampling of diluted analytes. Here we report a case study of the electron transport and gas sensing properties of such a membrane made of nanoporous Ta 2O 5. These membranes demonstrated a noticeable chemical sensitivity toward ammonia, ethanol, and acetone at high temperatures above 400 °C. Furthermore, different from traditional thin films, such gas permeable, ultrathin gas sensing elements can be made suspended enabling advanced architectures of ultrasensitivemore » analytical systems operating at high temperatures and in harsh environments.« less

Anode catalysts for direct ethanol fuel cells utilizing directly solar light illumination.

PubMed

Chu, Daobao; Wang, Shuxi; Zheng, Peng; Wang, Jian; Zha, Longwu; Hou, Yuanyuan; He, Jianguo; Xiao, Ying; Lin, Huashui; Tian, Zhaowu

2009-01-01

Shine a light: A PtNiRu/TiO(2) anode catalyst for direct ethanol fuel cells shows photocatalytic activity. The peak current density for ethanol oxidation under solar light illumination is 2-3 times greater than that in the absence of solar light. Ethanol is oxidized by light-generated holes, and the electrons are collected by the TiO(2) support to generate the oxidation current.Novel PtNiRu/TiO(2) anode catalysts for direct ethanol fuel cells (DEFCs) were prepared from PtNiRu nanoparticles (1:1:1 atomic ratios) and a nanoporous TiO(2) film by a sol-gel and electrodeposition method. The performances of the catalysts for ethanol oxidation were investigated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results indicate a remarkable enhancement of activity for ethanol oxidation under solar light illumination. Under solar light illumination, the generated oxidation peak current density is 24.6 mA cm(-2), which is about 2.5 times higher than that observed without solar light (9.9 mA cm(-2)). The high catalytic activity of the PtNiRu/TiO(2) complex catalyst for the electrooxidation of ethanol may be attributed to the modified metal/nanoporous TiO(2) film, and the enhanced electrooxidation of ethanol under solar light may be due to the photogeneration of holes in the modified nanoporous TiO(2) film.

Probing Interactions at the Nanoscale by Ion Current through Nanopores and Nanovoids

NASA Astrophysics Data System (ADS)

Gamble, Trevor Patrick

Polymer nanopores offer themselves as excellent test beds for study of phenomena that occur on the nano-scale, such as Debye layer formation, surface charge modulation, current saturation, and rectification. Studying ions interactions within the Debye layer, for example, is not possible on the micro-scale, where the pore diameter can be 100 times the size of the zone where interactions of interest occur. However, in our nanopores with an opening diameter less than 10 nm, a slight change of the Debye length can lead to drastic changes of the recorded ion current. Here we present our nanopores' use as a tool to study geometrical and electrochemical properties of porous manganese oxide. There is great value in studying nano-scale properties of this material because of its importance in lithium ion batteries and newly developed nano-architectures within supercapacitors. We electrodeposited manganese oxide wires into our cylindrical nanopores, filling them completely. In this use, nanopores became a template to probe properties of the embedded material such as surface charge, ion selectivity, and porosity. This information was then reported to the Energy Frontier Research Center (EFRC) collaboration, so that other groups can incorporate these recently discovered characteristics into future their nano-architecture design. Additionally, we constructed conical nanopores to study interactions between the surface charges found on the walls and alkali metal ions. In particular we looked at lithium, as it is the electrochemically active ion during charge cycling in EFRC energy storage devices. We attempted to reveal lithium ion's affinity to bind to surface charges. We found this binding led to lowering of the effective surface charge of the pore walls, while also decreasing lithium's ability to move through channels or voids that have charged walls. In connection to manganese oxide, a porous, charged material with voids, information on lithium's interaction with these charges is paramount.

TEMPO-oxidized cellulose hydrogel as a high-capacity and reusable heavy metal ion adsorbent.

PubMed

Isobe, Noriyuki; Chen, Xiaoxia; Kim, Ung-Jin; Kimura, Satoshi; Wada, Masahisa; Saito, Tsuguyuki; Isogai, Akira

2013-09-15

Nitroxy radical catalyzed oxidation with hypochlorite/bromide (TEMPO-mediated oxidation) was performed on a cellulose hydrogel prepared using LiOH/urea solvent. TEMPO oxidation successfully introduced carboxyl groups onto the surface of the cellulose hydrogel with retention of the gel structure and its nanoporous property. The equilibrium measurement of Cu(2+) adsorption showed favorable interaction with Cu(2+) and high maximum adsorption capacity. In addition, over 98% of the adsorbed Cu(2+) was recovered using acid treatment, and the subsequent washing allowed the TEMPO-oxidized gels to be used repeatedly. Furthermore, the TEMPO-oxidized cellulose hydrogel showed high adsorption capacity for other toxic metal ions such as Zn(2+), Fe(3+), Cd(2+), and Cs(+). Copyright © 2013 Elsevier B.V. All rights reserved.

Fabrication and characterisation of embedded metal nanostructures by ion implantation with nanoporous anodic alumina masks

NASA Astrophysics Data System (ADS)

Guan, Wei; Peng, Nianhua; Jeynes, Christopher; Ghatak, Jay; Peng, Yong; Ross, Ian M.; Bhatta, Umananda M.; Inkson, Beverley J.; Möbus, Günter

2013-07-01

Lateral ordered Co, Pt and Co/Pt nanostructures were fabricated in SiO2 and Si3N4 substrates by high fluence metal ion implantation through periodic nanochannel membrane masks based on anodic aluminium oxides (AAO). The quality of nanopatterning transfer defined by various AAO masks in different substrates was examined by transmission electron microscopy (TEM) in both imaging and spectroscopy modes.

Design and characterization of a nanopore-coupled polymerase for single-molecule DNA sequencing by synthesis on an electrode array

PubMed Central

Stranges, P. Benjamin; Palla, Mirkó; Kalachikov, Sergey; Nivala, Jeff; Dorwart, Michael; Trans, Andrew; Kumar, Shiv; Porel, Mintu; Chien, Minchen; Tao, Chuanjuan; Morozova, Irina; Li, Zengmin; Shi, Shundi; Aberra, Aman; Arnold, Cleoma; Yang, Alexander; Aguirre, Anne; Harada, Eric T.; Korenblum, Daniel; Pollard, James; Bhat, Ashwini; Gremyachinskiy, Dmitriy; Bibillo, Arek; Chen, Roger; Davis, Randy; Russo, James J.; Fuller, Carl W.; Roever, Stefan; Ju, Jingyue; Church, George M.

2016-01-01

Scalable, high-throughput DNA sequencing is a prerequisite for precision medicine and biomedical research. Recently, we presented a nanopore-based sequencing-by-synthesis (Nanopore-SBS) approach, which used a set of nucleotides with polymer tags that allow discrimination of the nucleotides in a biological nanopore. Here, we designed and covalently coupled a DNA polymerase to an α-hemolysin (αHL) heptamer using the SpyCatcher/SpyTag conjugation approach. These porin–polymerase conjugates were inserted into lipid bilayers on a complementary metal oxide semiconductor (CMOS)-based electrode array for high-throughput electrical recording of DNA synthesis. The designed nanopore construct successfully detected the capture of tagged nucleotides complementary to a DNA base on a provided template. We measured over 200 tagged-nucleotide signals for each of the four bases and developed a classification method to uniquely distinguish them from each other and background signals. The probability of falsely identifying a background event as a true capture event was less than 1.2%. In the presence of all four tagged nucleotides, we observed sequential additions in real time during polymerase-catalyzed DNA synthesis. Single-polymerase coupling to a nanopore, in combination with the Nanopore-SBS approach, can provide the foundation for a low-cost, single-molecule, electronic DNA-sequencing platform. PMID:27729524

Preparation of nanoporous metal foam from high nitrogen transition metal complexes

DOEpatents

Tappan, Bryce C.; Huynh, My Hang V.; Hiskey, Michael A.; Son, Steven F.; Oschwald, David M.; Chavez, David E.; Naud, Darren L.

2006-11-28

Nanoporous metal foams are prepared by ignition of high nitrogen transition metal complexes. The ammonium salts of iron(III) tris[bi(tetrazolato)-amine], cobalt(III) tris(bi(tetrazolato)amine), and high nitrogen compounds of copper and silver were prepared as loose powders, pressed into pellets and wafers, and ignited under an inert atmosphere to form nanoporous metal foam monoliths having very high surface area and very low density.

Ultrafast and scalable laser liquid synthesis of tin oxide nanotubes and its application in lithium ion batteries

NASA Astrophysics Data System (ADS)

Liu, Zhikun; Cao, Zeyuan; Deng, Biwei; Wang, Yuefeng; Shao, Jiayi; Kumar, Prashant; Liu, C. Richard; Wei, Bingqing; Cheng, Gary J.

2014-05-01

Laser-induced photo-chemical synthesis of SnO2 nanotubes has been demonstrated by employing a nanoporous polycarbonate membrane as a template. The SnO2 nanotube diameter can be controlled by the nanoporous template while the nanotube length can be tuned by laser parameters and reaction duration. The microstructure characterization of the nanotubes indicates that they consist of mesoporous structures with sub 5 nm size nanocrystals connected by the twinning structure. The application of SnO2 nanotubes as an anode material in lithium ion batteries has also been explored, and they exhibited high capacity and excellent cyclic stability. The laser based emerging technique for scalable production of crystalline metal oxide nanotubes in a matter of seconds is remarkable. The compliance of the laser based technique with the existing technologies would lead to mass production of novel nanomaterials that would be suitable for several emerging applications.Laser-induced photo-chemical synthesis of SnO2 nanotubes has been demonstrated by employing a nanoporous polycarbonate membrane as a template. The SnO2 nanotube diameter can be controlled by the nanoporous template while the nanotube length can be tuned by laser parameters and reaction duration. The microstructure characterization of the nanotubes indicates that they consist of mesoporous structures with sub 5 nm size nanocrystals connected by the twinning structure. The application of SnO2 nanotubes as an anode material in lithium ion batteries has also been explored, and they exhibited high capacity and excellent cyclic stability. The laser based emerging technique for scalable production of crystalline metal oxide nanotubes in a matter of seconds is remarkable. The compliance of the laser based technique with the existing technologies would lead to mass production of novel nanomaterials that would be suitable for several emerging applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr06444a

Development of a 3D origami multiplex electrochemical immunodevice using a nanoporous silver-paper electrode and metal ion functionalized nanoporous gold-chitosan.

PubMed

Li, Weiping; Li, Long; Li, Meng; Yu, Jinghua; Ge, Shenguang; Yan, Mei; Song, Xianrang

2013-10-25

A simple and sensitive 3D microfluidic origami multiplex electrochemical immunodevice was developed for the first time using a novel nanoporous silver modified paper working electrode as a sensor platform and different metal ion functionalized nanoporous gold-chitosan as a tracer.

Infiltration of methylammonium metal halide in highly porous membranes using sol-gel-derived coating method

NASA Astrophysics Data System (ADS)

Kwon, Seung Lee; Jin, Young Un; Kim, Byeong Jo; Han, Man Hyung; Han, Gill Sang; Shin, Seunghak; Lee, Sangwook; Jung, Hyun Suk

2017-09-01

Organic-inorganic halide perovskites (OIHPs) has emerged as promising optoelectronic materials for solar cells and light-emitting diodes. OIHPs are usually coated on a flat surface or mesoporous scaffold for the applications. Herein, we report a facile sol-gel-derived solution route for coating methylammonium lead iodide (MAPbI3) perovskite layers onto various nanoporous structures. We found that lead-acetate solution has superior infiltration property onto surface of oxide membranes, and it can easily be converted to MAPbI3 by sequential transform to PbO, PbI2, and finally MAPbI3. Excellent pore-filling and full coverage of the nanostructures with the final MAPbI3 perovskite material are demonstrated via this sol-gel-derived solution route, using mesoporous TiO2, TiO2 nanorods, and high-aspect ratio nanopores in anodic aluminum oxide membranes. Given that this sol-gel-based method fills nanopores better than other conventional coating methods for OIHPs, this method may find wide applications in nanostructured OIHPs-based optoelectronic systems.

Integrated Solid/Nanoporous Copper/Oxide Hybrid Bulk Electrodes for High-performance Lithium-Ion Batteries

PubMed Central

Hou, Chao; Lang, Xing-You; Han, Gao-Feng; Li, Ying-Qi; Zhao, Lei; Wen, Zi; Zhu, Yong-Fu; Zhao, Ming; Li, Jian-Chen; Lian, Jian-She; Jiang, Qing

2013-01-01

Nanoarchitectured electroactive materials can boost rates of Li insertion/extraction, showing genuine potential to increase power output of Li-ion batteries. However, electrodes assembled with low-dimensional nanostructured transition metal oxides by conventional approach suffer from dramatic reductions in energy capacities owing to sluggish ion and electron transport kinetics. Here we report that flexible bulk electrodes, made of three-dimensional bicontinuous nanoporous Cu/MnO2 hybrid and seamlessly integrated with Cu solid current collector, substantially optimizes Li storage behavior of the constituent MnO2. As a result of the unique integration of solid/nanoporous hybrid architecture that simultaneously enhances the electron transport of MnO2, facilitates fast ion diffusion and accommodates large volume changes on Li insertion/extraction of MnO2, the supported MnO2 exhibits a stable capacity of as high as ~1100 mA h g−1 for 1000 cycles, and ultrahigh charge/discharge rates. It makes the environmentally friendly and low-cost electrode as a promising anode for high-performance Li-ion battery applications. PMID:24096928

Development of porous metal oxide thin films by co-evaporation

NASA Astrophysics Data System (ADS)

Tesfamichael, T.; Motta, Nunzio; Bostrom, Thor; Bell, J. M.

2007-03-01

This paper focuses on the development of mixed metal oxide thin films and physical characterization of the films. The films were produced by co-evaporation of titanium oxide and tungsten oxide powders. This allowed the development of titanium oxide-tungsten oxide films as analyzed using XPS. Examination in the SEM and AFM showed that the films were nanoporous with the pore size and pore orientation varying as a function of the deposition angle. UV-vis spectra of the films show an increase of transmittance with increasing deposition angle which is attributed to the structure and porosity of the films. Raman analysis indicated that the as-deposited films have broad and weak Raman characteristics, attributed to the nanocrystal nature of the films and the presence of defects, and the peak broadening deceases after annealing the film, as expected.

Membranes with highly ordered straight nanopores by selective swelling of fast perpendicularly aligned block copolymers.

PubMed

Yin, Jun; Yao, Xueping; Liou, Jiun-You; Sun, Wei; Sun, Ya-Sen; Wang, Yong

2013-11-26

Membranes with uniform, straight nanopores have important applications in diverse fields, but their application is limited by the lack of efficient producing methods with high controllability. In this work, we reported on an extremely simple and efficient strategy to produce such well-defined membranes. We demonstrated that neutral solvents were capable of annealing amphiphilic block copolymer (BCP) films of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) with thicknesses up to 600 nm to the perpendicular orientation within 1 min. Annealing in neutral solvents was also effective to the perpendicular alignment of block copolymers with very high molecular weights, e.g., 362 000 Da. Remarkably, simply by immersing the annealed BCP films in hot ethanol followed by drying in air, the originally dense BCP films were nondestructively converted into porous membranes containing highly ordered, straight nanopores traversing the entire thickness of the membrane (up to 1.1 μm). Grazing incident small-angle X-ray spectroscopy confirmed the hexagonal ordering of the nanopores over large areas. We found that the overflow of P2VP chains from their reservoir P2VP cylinders and the deformation of the PS matrix in the swelling process contributed to the transformation of the solid P2VP cylinders to empty straight pores. The pore diameters can be tuned by either changing the swelling temperatures or depositing thin layers of metal oxides on the preformed membranes via atomic layer deposition with a subnanometer accuracy. To demonstrate the application of the obtained porous membranes, we used them as templates and produced centimeter-scale arrays of aligned nanotubes of metal oxides with finely tunable wall thicknesses.

Template-Free Synthesis of Nanoporous Nickel and Alloys as Binder-Free Current Collectors of Li Ion Batteries.

PubMed

Lu, Liqiang; Andela, Paul; De Hosson, Jeff Th M; Pei, Yutao

2018-05-25

This paper reports a versatile template-free method based on the hydrogen reduction of metallic salts for the synthesis of nanoporous Ni and alloys. The approach involves thermal decomposition and reduction of metallic precursors followed with metal cluster nucleation and ligament growth. Topological disordered porous architectures of metals with a controllable distribution of pore size and ligament size ranging from tens of nanometers to micrometers are synthesized. The reduction processes are scrutinized through X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The formation mechanism of the nanoporous metal is qualitatively explained. The as-prepared nanoporous Ni was tested as binder-free current collectors for nickel oxalate anodes of lithium ion batteries. The nanoporous Ni electrodes deliver enhanced reversible capacities and cyclic performances compared with commercial Ni foam. It is confirmed that this synthesis method has versatility not only because it is suitable for different types of metallic salts precursors but also for various other metals and alloys.

Template-Free Synthesis of Nanoporous Nickel and Alloys as Binder-Free Current Collectors of Li Ion Batteries

PubMed Central

2018-01-01

This paper reports a versatile template-free method based on the hydrogen reduction of metallic salts for the synthesis of nanoporous Ni and alloys. The approach involves thermal decomposition and reduction of metallic precursors followed with metal cluster nucleation and ligament growth. Topological disordered porous architectures of metals with a controllable distribution of pore size and ligament size ranging from tens of nanometers to micrometers are synthesized. The reduction processes are scrutinized through X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The formation mechanism of the nanoporous metal is qualitatively explained. The as-prepared nanoporous Ni was tested as binder-free current collectors for nickel oxalate anodes of lithium ion batteries. The nanoporous Ni electrodes deliver enhanced reversible capacities and cyclic performances compared with commercial Ni foam. It is confirmed that this synthesis method has versatility not only because it is suitable for different types of metallic salts precursors but also for various other metals and alloys. PMID:29911687

Novel structure formation at the bottom surface of porous anodic alumina fabricated by single step anodization process.

PubMed

Ali, Ghafar; Ahmad, Maqsood; Akhter, Javed Iqbal; Maqbool, Muhammad; Cho, Sung Oh

2010-08-01

A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time. (c) 2010 Elsevier Ltd. All rights reserved.

Long-Term Outdoor Reliability Assessment of a Wireless Unit for Air-Quality Monitoring Based on Nanostructured Films Integrated on Micromachined Platforms

PubMed Central

Leccardi, Matteo; Decarli, Massimiliano; Lorenzelli, Leandro; Milani, Paolo; Mettala, Petteri; Orava, Risto; Barborini, Emanuele

2012-01-01

We have fabricated and tested in long-term field operating conditions a wireless unit for outdoor air quality monitoring. The unit is equipped with two multiparametric sensors, one miniaturized thermo-hygrometer, front-end analogical and digital electronics, and an IEEE 802.15.4 based module for wireless data transmission. Micromachined platforms were functionalized with nanoporous metal-oxides to obtain multiparametric sensors, hosting gas-sensitive, anemometric and temperature transducers. Nanoporous metal-oxide layer was directly deposited on gas sensing regions of micromachined platform batches by hard-mask patterned supersonic cluster beam deposition. An outdoor, roadside experiment was arranged in downtown Milan (Italy), where one wireless sensing unit was continuously operated side by side with standard gas chromatographic instrumentation for air quality measurements. By means of a router PC, data from sensing unit and other instrumentation were collected, merged, and sent to a remote data storage server, through an UMTS device. The whole-system robustness as well as sensor dataset characteristics were continuously characterized over a run-time period of 18 months. PMID:22969394

Fast-Response, Sensitivitive and Low-Powered Chemosensors by Fusing Nanostructured Porous Thin Film and IDEs-Microheater Chip

PubMed Central

Dai, Zhengfei; Xu, Lei; Duan, Guotao; Li, Tie; Zhang, Hongwen; Li, Yue; Wang, Yi; Wang, Yuelin; Cai, Weiping

2013-01-01

The chemiresistive thin film gas sensors with fast response, high sensitivity, low power consumption and mass-produced potency, have been expected for practical application. It requires both sensitive materials, especially exquisite nanomaterials, and efficient substrate chip for heating and electrical addressing. However, it is challenging to achieve repeatable microstructures across the films and low power consumption of substrate chip. Here we presented a new sensor structure via the fusion of metal-oxide nanoporous films and micro-electro-mechanical systems (MEMS)-based sensing chip. An interdigital-electrodes (IDEs) and microheater integrated MEMS structure is designed and employed as substrate chip to in-situ fabricate colloidal monolayer template-induced metal-oxide (egg. SnO2) nanoporous sensing films. This fused sensor demonstrates mW-level low power, ultrafast response (~1 s), and parts-per-billion lever detection for ethanol gas. Due to the controllable template strategy and mass-production potential, such micro/nano fused high-performance gas sensors will be next-generation key miniaturized/integrated devices for advanced practical applications. PMID:23591580

Structurally Engineered Nanoporous Ta2O5-x Selector-Less Memristor for High Uniformity and Low Power Consumption.

PubMed

Kwon, Soonbang; Kim, Tae-Wook; Jang, Seonghoon; Lee, Jae-Hwang; Kim, Nam Dong; Ji, Yongsung; Lee, Chul-Ho; Tour, James M; Wang, Gunuk

2017-10-04

A memristor architecture based on metal-oxide materials would have great promise in achieving exceptional energy efficiency and higher scalability in next-generation electronic memory systems. Here, we propose a facile method for fabricating selector-less memristor arrays using an engineered nanoporous Ta 2 O 5-x architecture. The device was fabricated in the form of crossbar arrays, and it functions as a switchable rectifier with a self-embedded nonlinear switching behavior and ultralow power consumption (∼2.7 × 10 -6 W), which results in effective suppression of crosstalk interference. In addition, we determined that the essential switching elements, such as the programming power, the sneak current, the nonlinearity value, and the device-to-device uniformity, could be enhanced by in-depth structural engineering of the pores in the Ta 2 O 5-x layer. Our results, on the basis of the structural engineering of metal-oxide materials, could provide an attractive approach for fabricating simple and cost-efficient memristor arrays with acceptable device uniformity and low power consumption without the need for additional addressing selectors.

Understanding and Enhancing the Photostability of Nanoporous Metal Oxide Thin Films for Solar Hydrogen Generation

NASA Astrophysics Data System (ADS)

Chitrada, Kalyan Chakravarthi

Solar water splitting is an environmentally benign process which has received wide attention in the recent years as an alternate method for a clean and safe production of hydrogen. This process employs a semiconductor based photocatalyst, water, and sunlight to produce hydrogen. Metal-oxide based semiconductors are considered to be ideal photocatalytic materials because of their stability against photo-corrosion combined with relatively narrow energy band-gap, appropriately placed band edge positions with reference to oxygen and hydrogen energy levels, less scattering of charges due to wider valence band, high dielectric constant, natural abundance, and non-toxicity. In this dissertation, two metal oxide based semiconductors viz., iron (III) oxide and bismuth (III) oxide were investigated to understand and enhance their photo activity as photoanodes for solar water splitting application. Iron (III) oxide has a well suited band gap to capture solar spectrum but it suffers from inappropriately positioned band edges, recombination losses due to low electron mobility, and a small minority carrier diffusion length. However, it was hypothesized that the Iron (III) oxide might show interesting photoelectrochemical properties by alloying with 4f elements and shifting the conduction band minimum of the iron oxide favorably to more negative potentials. In the present study, a nanoporous iron oxide layer incorporated with Nd3+ and B3+ was synthesized by electrochemical anodization of a FeNdB alloy. The photoelectrochemical behavior of this oxide was compared with thermally oxidized FeNdB alloy and the iron oxides obtained by anodization and thermal oxidation of pure iron foil. Incorporation of Nd3+ and B3+ in the iron oxide showed a direct bandgap of 2.05 eV, an indirect bandgap of 1.9 eV and shifted the flatband potentials to --0.8 VAg/AgCl in 1 M KOH solution. The FeNdB oxide showed marginally better catalytic activity for the oxygen evolution reaction than pure iron oxide under dark conditions. The binary bismuth (III) oxide, in spite being a good photocatalytic material, did not receive as much attention as other bismuth based ternary oxides for photoelectrochemical water splitting application. In this present study, large surface area nanoporous bismuth oxide thin films were synthesized by the electrochemical anodization. These anodic oxides exhibited a dual layered structure having a planar inner oxide and nanoporous outer oxide. Effect of the nanoscale dimensions of the oxides on the photoelectrochemical behavior was studied to understand the charge transport, charge recombination behavior, and long term stability of the material. A maximum photo current density of 0.97 mA/cm2 was observed for the sample anodized at 10 V at 1.53 VRHE. The nanoporous anodic oxides showed a charge carrier density in the range of 1.2 x 1017 -- 4.8 x 1018 cm-3 without illumination and about 60% increase in the charge carrier density upon illumination. However a decay in photo current was observed for the bismuth oxide samples was due to accumulation of holes on the electrode surface. This hole-accumulation was mitigated by the addition of hole scavengers. Addition of hydrogen peroxide as hole scavenger increased the photo current density by about 4 times in 0.5 M Na2SO 4 (pH: 5.8) electrolyte. Addition of H2O2 in 1 M KOH (pH: 13.7) showed an increase-decrease behavior and high photo current density of ~10 mA/cm2 at a bias potential of 0.65 VRHE . The high photo activity observed in this electrolyte was attributed to the in-situ formation of Bi2O4-x phase by the photo-conversion of the beta-Bi2O3 at the surface. The photo-converted Bi2O4-x has a smaller band gap (1.4 eV) and therefore harvested more light in the visible region. This in-situ formation of low band gap phases in the presence of H2O2 during solar water splitting is an interesting observation which has been reported for the first time and this will help design material with very high photo-activity.

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties.

PubMed

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-03-24

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA.

Modeling electrochemical deposition inside nanotubes to obtain metal-semiconductor multiscale nanocables or conical nanopores.

PubMed

Lebedev, Konstantin; Mafé, Salvador; Stroeve, Pieter

2005-08-04

Nanocables with a radial metal-semiconductor heterostructure have recently been prepared by electrochemical deposition inside metal nanotubes. First, a bare nanoporous polycarbonate track-etched membrane is coated uniformly with a metal film by electroless deposition. The film forms a working electrode for further deposition of a semiconductor layer that grows radially inside the nanopore when the deposition rate is slow. We propose a new physical model for the nanocable synthesis and study the effects of the deposited species concentration, potential-dependent reaction rate, and nanopore dimensions on the electrochemical deposition. The problem involves both axial diffusion through the nanopore and radial transport to the nanopore surface, with a surface reaction rate that depends on the axial position and the time. This is so because the radial potential drop across the deposited semiconductor layer changes with the layer thickness through the nanopore. Since axially uniform nanocables are needed for most applications, we consider the relative role of reaction and axial diffusion rates on the deposition process. However, in those cases where partial, empty-core deposition should be desirable (e.g., for producing conical nanopores to be used in single nanoparticle detection), we give conditions where asymmetric geometries can be experimentally realized.

In situ heavy ion irradiation studies of nanopore shrinkage and enhanced radiation tolerance of nanoporous Au

DOE PAGES

Li, Jin; Fan, Cuncai; Ding, Jie; ...

2017-01-03

High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. We show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studiesmore » show dose-rate-dependent diffusivity of defect clusters. Our study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications.« less

Thermally oxidized titania nanotubes enhance the corrosion resistance of Ti6Al4V.

PubMed

Grotberg, John; Hamlekhan, Azhang; Butt, Arman; Patel, Sweetu; Royhman, Dmitry; Shokuhfar, Tolou; Sukotjo, Cortino; Takoudis, Christos; Mathew, Mathew T

2016-02-01

The negative impact of in vivo corrosion of metallic biomedical implants remains a complex problem in the medical field. We aimed to determine the effects of electrochemical anodization (60V, 2h) and thermal oxidation (600°C) on the corrosive behavior of Ti-6Al-4V, with serum proteins, at physiological temperature. Anodization produced a mixture of anatase and amorphous TiO2 nanopores and nanotubes, while the annealing process yielded an anatase/rutile mixture of TiO2 nanopores and nanotubes. The surface area was analyzed by the Brunauer-Emmett-Teller method and was estimated to be 3 orders of magnitude higher than that of polished control samples. Corrosion resistance was evaluated on the parameters of open circuit potential, corrosion potential, corrosion current density, passivation current density, polarization resistance and equivalent circuit modeling. Samples both anodized and thermally oxidized exhibited shifts of open circuit potential and corrosion potential in the noble direction, indicating a more stable nanoporous/nanotube layer, as well as lower corrosion current densities and passivation current densities than the smooth control. They also showed increased polarization resistance and diffusion limited charge transfer within the bulk oxide layer. The treatment groups studied can be ordered from greatest corrosion resistance to least as Anodized+Thermally Oxidized > Anodized > Smooth > Thermally Oxidized for the conditions investigated. This study concludes that anodized surface has a potential to prevent long term implant failure due to corrosion in a complex in-vivo environment. Copyright © 2015 Elsevier B.V. All rights reserved.

Integration of solid-state nanopores in a 0.5 μm cmos foundry process

PubMed Central

Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

2013-01-01

High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor’s 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the N+ polysilicon/SiO2/N+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3 which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3. PMID:23519330

Oxidation of Cyclohexene Catalyzed by Nanoporous Au(Ag) in Liquid Phase

DOE PAGES

Dou, Jian; Tang, Yu; Nguyen, Luan; ...

2016-12-22

Nanoporous gold with minor silver content has been identified as a new type of gold based catalyst for selective oxidation of cyclohexene with molecular oxygen in liquid. By oxidation of the leached nanoporous gold foils in ozone, the minor silver content was oxidized in this paper to form silver oxide nanoclusters on the surface of nanoporous gold. With further treatment in methanol, the surface silver oxide was reduced and surface alloy was formed on gold ligaments. Both nanoporous gold treated with ozone only and the one with ozone and then methanol are very active for selective oxidation of cyclohexene withmore » molecular oxygen in liquid of cyclohexene with a turn-over-frequency (TOF) of 0.55–0.99 molecules per surface Au atom per second under a solvent-free and initiator- free condition. The total selectivity for production of 2-cyclohexene-1-one, 2-cyclohexene-1-ol, and cyclohexene oxide was increased from 57.5 % to 80.8 % by an additional treatment of nanoporous gold in methanol after activation in zone. Finally, the correlation of catalytic selectivity for the production of the three products and corresponding surface chemistry of ligament suggests that (1) the formed Au–Ag alloy surface is favorable for the formation of 2-cyclohexen-1-one, 2-cyclohexene-1-ol, and cyclohexene oxide and (2) the surface silver oxide is favorable for the production of cyclohexenyl hydroperoxide.« less

Oxidation of Cyclohexene Catalyzed by Nanoporous Au(Ag) in Liquid Phase

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dou, Jian; Tang, Yu; Nguyen, Luan

Nanoporous gold with minor silver content has been identified as a new type of gold based catalyst for selective oxidation of cyclohexene with molecular oxygen in liquid. By oxidation of the leached nanoporous gold foils in ozone, the minor silver content was oxidized in this paper to form silver oxide nanoclusters on the surface of nanoporous gold. With further treatment in methanol, the surface silver oxide was reduced and surface alloy was formed on gold ligaments. Both nanoporous gold treated with ozone only and the one with ozone and then methanol are very active for selective oxidation of cyclohexene withmore » molecular oxygen in liquid of cyclohexene with a turn-over-frequency (TOF) of 0.55–0.99 molecules per surface Au atom per second under a solvent-free and initiator- free condition. The total selectivity for production of 2-cyclohexene-1-one, 2-cyclohexene-1-ol, and cyclohexene oxide was increased from 57.5 % to 80.8 % by an additional treatment of nanoporous gold in methanol after activation in zone. Finally, the correlation of catalytic selectivity for the production of the three products and corresponding surface chemistry of ligament suggests that (1) the formed Au–Ag alloy surface is favorable for the formation of 2-cyclohexen-1-one, 2-cyclohexene-1-ol, and cyclohexene oxide and (2) the surface silver oxide is favorable for the production of cyclohexenyl hydroperoxide.« less

Nanoscale Probing of Electrical Signals in Biological Systems

DTIC Science & Technology

2012-03-18

Membranes Anodized aluminum oxide ( AAO ) is an ideal prototype substrate for studying ion transport through nanoporous membranes . For optimal...electrochemical microscopy, scanning ion conductance microscopy, nanoporous membranes , anodized aluminum oxide , atomic layer deposition, focused ion beam...capacity. This approach utilizes atomic layer deposition (ALD) of a thin conformal Ir film into a nanoporous anodized aluminum oxide (

Building Nanoporous Metal-Organic Frameworks "Armor" on Fibers for High-Performance Composite Materials.

PubMed

Yang, Xiaobin; Jiang, Xu; Huang, Yudong; Guo, Zhanhu; Shao, Lu

2017-02-15

The nanoporous metal-organic frameworks (MOFs) "armor" is in situ intergrown onto the surfaces of carbon fibers (CFs) by nitric acid oxidization to supply nucleation sites and serves as a novel interfacial linker between the fiber and polymer matrix and a smart cushion to release interior and exterior applied forces. Simultaneous enhancements of the interfacial and interlaminar shear strength as well as the tensile strength of CFs were achieved. With the aid of an ultrasonic "cleaning" process, the optimized surface energy and tensile strength of CFs with a MOF "armor" are 83.79 mN m -1 and 5.09 GPa, for an increase of 102% and 11.6%, respectively. Our work finds that the template-induced nucleation of 3D MOF onto 1D fibers is a general and promising approach toward advanced composite materials for diverse applications to meet scientific and technical demands.

Nanoporous adsorption effect on altering Li+ diffusion pathway by a highly ordered porous electrolyte additive for high rate all-solid-state lithium metal batteries.

PubMed

Li, Wenwen; Zhang, Sanpei; Wang, Bangrun; Gu, Sui; Xu, Dong; Wang, Jianing; Chen, Chunhua; Wen, Zhaoyin

2018-06-19

Solid polymer electrolytes (SPEs) have shown extraordinary promise for all-solid-state lithium metal batteries with high energy density and flexibility but are mainly limited by the low ionic conductivity and their poor stability with lithium metal anode. In this work, we propose a highly ordered porous electrolyte additive derived from SSZ-13 for high-rate all-solid-state lithium metal batteries. The nanoporous adsorption effect provided by the highly ordered porous nanoparticles in the poly (ethylene oxide) (PEO) electrolyte are found to significantly improve the Li + conductivity (1.91×10 -3 S cm -1 at 60°C, 4.43×10 -5 S cm -1 at 20°C) and widen the electrochemical stability window to 4.7 V vs Li + /Li. Meanwhile, the designed PEO-based electrolyte demonstrates enhanced stability with the lithium metal anode. Through systematically increasing Li + diffusion, widening the electrochemical stability window and enhancing the stability of the SSZ-CPE electrolyte, the LiFePO4/SSZ-CPE/Li cell is optimized to deliver high-rate capability and stable cycling performance, which demonstrates great potential for all-solid-state energy storage application.

Fabrication of ZnO Nanowires Arrays by Anodization and High-Vacuum Die Casting Technique, and Their Piezoelectric Properties

PubMed Central

Kuo, Chin-Guo; Chang, Ho; Wang, Jian-Hao

2016-01-01

In this investigation, anodic aluminum oxide (AAO) with arrayed and regularly arranged nanopores is used as a template in the high-vacuum die casting of molten zinc metal (Zn) into the nanopores. The proposed technique yields arrayed Zn nanowires with an aspect ratio of over 600. After annealing, arrayed zinc oxide (ZnO) nanowires are obtained. Varying the anodizing time yields AAO templates with thicknesses of approximately 50 μm, 60 μm, and 70 μm that can be used in the fabrication of nanowires of three lengths with high aspect ratios. Experimental results reveal that a longer nanowire generates a greater measured piezoelectric current. The ZnO nanowires that are fabricated using an alumina template are anodized for 7 h and produce higher piezoelectric current of up to 69 pA. PMID:27023546

Direct N2H4/H2O2 Fuel Cells Powered by Nanoporous Gold Leaves

PubMed Central

Yan, Xiuling; Meng, Fanhui; Xie, Yun; Liu, Jianguo; Ding, Yi

2012-01-01

Dealloyed nanoporous gold leaves (NPGLs) are found to exhibit high electrocatalytic properties toward both hydrazine (N2H4) oxidation and hydrogen peroxide (H2O2) reduction. This observation allows the implementation of a direct hydrazine-hydrogen peroxide fuel cell (DHHPFC) based on these novel porous membrane catalysts. The effects of fuel and oxidizer flow rate, concentration and cell temperature on the performance of DHHPFC are systematically investigated. With a loading of ~0.1 mg cm−2 Au on each side, an open circuit voltage (OCV) of 1.2 V is obtained at 80°C with a maximum power density 195 mW cm−2, which is 22 times higher than that of commercial Pt/C electrocatalyst at the same noble metal loading. NPGLs thus hold great potential as effective and stable electrocatalysts for DHHPFCs. PMID:23230507

Ion transport by gating voltage to nanopores produced via metal-assisted chemical etching method

NASA Astrophysics Data System (ADS)

Van Toan, Nguyen; Inomata, Naoki; Toda, Masaya; Ono, Takahito

2018-05-01

In this work, we report a simple and low-cost way to create nanopores that can be employed for various applications in nanofluidics. Nano sized Ag particles in the range from 1 to 20 nm are formed on a silicon substrate with a de-wetting method. Then the silicon nanopores with an approximate 15 nm average diameter and 200 μm height are successfully produced by the metal-assisted chemical etching method. In addition, electrically driven ion transport in the nanopores is demonstrated for nanofluidic applications. Ion transport through the nanopores is observed and could be controlled by an application of a gating voltage to the nanopores.

Ion transport by gating voltage to nanopores produced via metal-assisted chemical etching method.

PubMed

Van Toan, Nguyen; Inomata, Naoki; Toda, Masaya; Ono, Takahito

2018-05-11

In this work, we report a simple and low-cost way to create nanopores that can be employed for various applications in nanofluidics. Nano sized Ag particles in the range from 1 to 20 nm are formed on a silicon substrate with a de-wetting method. Then the silicon nanopores with an approximate 15 nm average diameter and 200 μm height are successfully produced by the metal-assisted chemical etching method. In addition, electrically driven ion transport in the nanopores is demonstrated for nanofluidic applications. Ion transport through the nanopores is observed and could be controlled by an application of a gating voltage to the nanopores.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Jin; Fan, Cuncai; Ding, Jie

High energy particle radiations induce severe microstructural damage in metallic materials. Nanoporous materials with a giant surface-to-volume ratio may alleviate radiation damage in irradiated metallic materials as free surface are defect sinks. We show, by using in situ Kr ion irradiation in a transmission electron microscope at room temperature, that nanoporous Au indeed has significantly improved radiation tolerance comparing with coarse-grained, fully dense Au. In situ studies show that nanopores can absorb and eliminate a large number of radiation-induced defect clusters. Meanwhile, nanopores shrink (self-heal) during radiation, and their shrinkage rate is pore size dependent. Furthermore, the in situ studiesmore » show dose-rate-dependent diffusivity of defect clusters. Our study sheds light on the design of radiation-tolerant nanoporous metallic materials for advanced nuclear reactor applications.« less

Nanostructure-directed physisorption vs chemisorption at semiconductor interfaces: the inverse of the HSAB concept.

PubMed

Gole, James L; Ozdemir, Serdar

2010-08-23

A concept, complementary to that of hard and soft acid-base interactions (HSAB-dominant chemisorption) and consistent with dominant physisorption to a semiconductor interface, is presented. We create a matrix of sensitivities and interactions with several basic gases. The concept, based on the reversible interaction of hard-acid surfaces with soft bases, hard-base surfaces with soft acids, or vice versa, corresponds 1) to the inverse of the HSAB concept and 2) to the selection of a combination of semiconductor interface and analyte materials, which can be used to direct a physisorbed vs chemisorbed interaction. The technology, implemented on nanopore coated porous silicon micropores, results in the coupling of acid-base chemistry with the depletion or enhancement of majority carriers in an extrinsic semiconductor. Using the inverse-HSAB (IHSAB) concept, significant and predictable changes in interface sensitivity for a variety of gases can be implemented. Nanostructured metal oxide particle depositions provide selectivity and complement a highly efficient electrical contact to a porous silicon nanopore covered microporous interface. The application of small quantities (much less than a monolayer) of nanostructured metals, metal oxides, and catalysts which focus the physisorbtive and chemisorbtive interactions of the interface, can be made to create a range of notably higher sensitivities for reversible physisorption. This is exemplified by an approach to reversible, sensitive, and selective interface responses. Nanostructured metal oxides developed from electroless gold (Au(x)O), tin (SnO(2)), copper (Cu(x)O), and nickel (NiO) depositions, nanoalumina, and nanotitania are used to demonstrate the IHSAB concept and provide for the detection of gases, including NH(3), PH(3), CO, NO, and H(2)S, in an array-based format to the sub-ppm level.

Selective Separation of Metal Ions via Monolayer Nanoporous Graphene with Carboxyl Groups.

PubMed

Li, Zhan; Liu, Yanqi; Zhao, Yang; Zhang, Xin; Qian, Lijuan; Tian, Longlong; Bai, Jing; Qi, Wei; Yao, Huijun; Gao, Bin; Liu, Jie; Wu, Wangsuo; Qiu, Hongdeng

2016-10-18

Graphene-coated plastic substrates, such as polyethylene terephthalate (PET), are regularly used in flexible electronic devices. Here we demonstrate a new application of the graphene-coated nanoporous PET membrane for the selective separation of metal ions in an ion exchange manner. Irradiation with swift heavy ions is used to perforate graphene and PET substrate. This process could create graphene nanopores with carboxyl groups, thus forming conical holes in the PET after chemical etching to support graphene nanopores. Therefore, a monolayer nanoporous graphene membrane with a PET substrate is constructed successfully to investigate its ionic selective separation. We find that the permeation ratio of ions strongly depends on the temperature and H + concentration in the driving solution. An electric field can increase the permeation ratio of ions through the graphene nanopores, but it inhibits the ion selective separation. Moreover, the structure of the graphene nanopore with carboxyl groups is resolved at the density functional theory level. The results show the asymmetric structure of the nanopore with carboxyl groups, and the analysis indicates that the ionic permeation can be attributed to the ion exchange between metal ions and protons on the two sides of graphene nanopores. These results would be beneficial to the design of membrane separation materials made from graphene with efficient online and offline bulk separation.

Electrochemical annealing of nanoporous gold by application of cyclic potential sweeps

PubMed Central

Sharma, Abeera; Bhattarai, Jay K.; Alla, Allan J.; Demchenko, Alexei V.; Stine, Keith J.

2015-01-01

An electrochemical method for annealing the pore sizes of nanoporous gold is reported. The pore sizes of nanoporous gold can be increased by electrochemical cycling with the upper potential limit being just at the onset of gold oxide formation. This study has been performed in electrolyte solutions including potassium chloride, sodium nitrate and sodium perchlorate. Scanning electron microscopy images have been used for ligament and pore size analysis. We examine the modifications of nanoporous gold due to annealing using electrochemical impedance spectroscopy, and cyclic voltammetry and offer a comparison of the surface coverage using the gold oxide stripping method as well as the method in which electrochemically accessible surface area is determined by using a diffusing redox probe. The effect of additives adsorbed on the nanoporous gold surface when subjected to annealing in different electrolytes as well as the subsequent structural changes in nanoporous gold are also reported. The effect of the annealing process on the application of nanoporous gold as a substrate for glucose electro-oxidation is briefly examined. PMID:25649027

Nanoporous materials for reducing the over potential of creating hydrogen by water electrolysis

DOEpatents

Anderson, Marc A.; Leonard, Kevin C.

2016-06-14

Disclosed is an electrolyzer including an electrode including a nanoporous oxide-coated conducting material. Also disclosed is a method of producing a gas through electrolysis by contacting an aqueous solution with an electrode connected to an electrical power source, wherein the electrode includes a nanoporous oxide-coated conducting material.

Novel Integrated System Architecture for an Autonomous Jumping Micro-Robot

DTIC Science & Technology

2010-01-01

traces Figure 45 Solder joints made directly to FET and capacitor before assembling circuit on hexapod Figure 46 Metal pads attached to...energetic chip using Loctite Figure 47 Circuit connected to oxidized nanoporous Si by soldering to pads on the substrate Figure 48 Capacitor discharge...thermal, shape memory alloy (SMA), piezoelectric , magnetic, etc. Each actuator has a unique set of characteristics, which include operating

Multichannel detection of ionic currents through two nanopores fabricated on integrated Si3N4 membranes.

PubMed

Yanagi, Itaru; Akahori, Rena; Aoki, Mayu; Harada, Kunio; Takeda, Ken-Ichi

2016-08-16

Integration of solid-state nanopores and multichannel detection of signals from each nanopore are effective measures for realizing high-throughput nanopore sensors. In the present study, we demonstrated fabrication of Si3N4 membrane arrays and the simultaneous measurement of ionic currents through two nanopores formed in two adjacent membranes. Membranes with thicknesses as low as 6.4 nm and small nanopores with diameters of less than 2 nm could be fabricated using the poly-Si sacrificial-layer process and multilevel pulse-voltage injection. Using the fabricated nanopore membranes, we successfully achieved simultaneous detection of clear ionic-current blockades when single-stranded short homopolymers (poly(dA)60) passed through two nanopores. In addition, we investigated the signal crosstalk and leakage current among separated chambers. When two nanopores were isolated on the front surface of the membrane, there was no signal crosstalk or leakage current between the chambers. However, when two nanopores were isolated on the backside of the Si substrate, signal crosstalk and leakage current were observed owing to high-capacitance coupling between the chambers and electrolysis of water on the surface of the Si substrate. The signal crosstalk and leakage current could be suppressed by oxidizing the exposed Si surface in the membrane chip. Finally, the observed ionic-current blockade when poly(dA)60 passed through the nanopore in the oxidized chip was approximately half of that observed in the non-oxidized chip.

Air-Impregnated Nanoporous Anodic Aluminum Oxide Layers for Enhancing the Corrosion Resistance of Aluminum.

PubMed

Jeong, Chanyoung; Lee, Junghoon; Sheppard, Keith; Choi, Chang-Hwan

2015-10-13

Nanoporous anodic aluminum oxide layers were fabricated on aluminum substrates with systematically varied pore diameters (20-80 nm) and oxide thicknesses (150-500 nm) by controlling the anodizing voltage and time and subsequent pore-widening process conditions. The porous nanostructures were then coated with a thin (only a couple of nanometers thick) Teflon film to make the surface hydrophobic and trap air in the pores. The corrosion resistance of the aluminum substrate was evaluated by a potentiodynamic polarization measurement in 3.5 wt % NaCl solution (saltwater). Results showed that the hydrophobic nanoporous anodic aluminum oxide layer significantly enhanced the corrosion resistance of the aluminum substrate compared to a hydrophilic oxide layer of the same nanostructures, to bare (nonanodized) aluminum with only a natural oxide layer on top, and to the latter coated with a thin Teflon film. The hydrophobic nanoporous anodic aluminum oxide layer with the largest pore diameter and the thickest oxide layer (i.e., the maximized air fraction) resulted in the best corrosion resistance with a corrosion inhibition efficiency of up to 99% for up to 7 days. The results demonstrate that the air impregnating the hydrophobic nanopores can effectively inhibit the penetration of corrosive media into the pores, leading to a significant improvement in corrosion resistance.

Integration of solid-state nanopores in a 0.5 μm CMOS foundry process.

PubMed

Uddin, A; Yemenicioglu, S; Chen, C-H; Corigliano, E; Milaninia, K; Theogarajan, L

2013-04-19

High-bandwidth and low-noise nanopore sensor and detection electronics are crucial in achieving single-DNA-base resolution. A potential way to accomplish this goal is to integrate solid-state nanopores within a CMOS platform, in close proximity to the biasing electrodes and custom-designed amplifier electronics. Here we report the integration of solid-state nanopore devices in a commercial complementary metal-oxide-semiconductor (CMOS) potentiostat chip implemented in On-Semiconductor's 0.5 μm technology. Nanopore membranes incorporating electrodes are fabricated by post-CMOS micromachining utilizing the n+ polysilicon/SiO2/n+ polysilicon capacitor structure available in the aforementioned process. Nanopores are created in the CMOS process by drilling in a transmission electron microscope and shrinking by atomic layer deposition. We also describe a batch fabrication method to process a large of number of electrode-embedded nanopores with sub-10 nm diameter across CMOS-compatible wafers by electron beam lithography and atomic layer deposition. The CMOS-compatibility of our fabrication process is verified by testing the electrical functionality of on-chip circuitry. We observe high current leakage with the CMOS nanopore devices due to the ionic diffusion through the SiO2 membrane. To prevent this leakage, we coat the membrane with Al2O3, which acts as an efficient diffusion barrier against alkali ions. The resulting nanopore devices also exhibit higher robustness and lower 1/f noise as compared to SiO2 and SiNx. Furthermore, we propose a theoretical model for our low-capacitance CMOS nanopore devices, showing good agreement with the experimental value. In addition, experiments and theoretical models of translocation studies are presented using 48.5 kbp λ-DNA in order to prove the functionality of on-chip pores coated with Al2O3.

EDITORIAL: Nanopores—the 'Holey Grail' in nanotechnology research Nanopores—the 'Holey Grail' in nanotechnology research

NASA Astrophysics Data System (ADS)

Demming, Anna

2012-06-01

'Negative space' may be as important in the development of nanomaterials as it is in creating works of art. The term refers to the space around and between objects, an important aspect in artistic composition. In nanotechnology, while nanoposts and nanowires have been assiduously studied and exploited for enhancing the performance of solar cells [1], real-time chemical sensors [2], UV emitters [3] and many other applications, nanopore structures have also yielded important advances in a wide range of fields. In this issue Melnikov, Leburton and Gracheva report on the electrostatic properties of nanopores in a layered semiconductor, and show how they allow a more accurate characterization of DNA than pores in other membranes [4]. Nanoporous materials have been applied to a diverse range of technological challenges. In recognition of its potential in high-efficiency solar cells, Prakasam and colleagues in the US reported the first ever synthesis of self-aligned nanoporous haematite [5]. Haematite is abundant, stable, non-toxic and has a band gap in the visible region and, as their work demonstrates, the photoresponse of nanoporous haematite is very promising for energy harvesting applications. Nanoporous aluminum oxide has also proved to be a particularly valuable material in applications ranging from liquid display panels to biosensor microchips. A collaboration of researchers in Taiwan demonstrated that porous aluminum oxide on an indium tin oxide surface could act as an alignment layer in liquid crystal display panels that have a transmittance of 60-80%, and switch from black to bright with a response time of 62.5 ms [6]. In Korea, Chung, Son and Min investigated the effect of nanostructural parameters of porous aluminum oxide on cell adhesion and proliferation for cell-based microchips [7]. While aluminum oxide without any modifications is not favourable for adherent cell culture, the proliferation of cells dramatically increased in porous aluminum oxide, particularly when the aspect ratio of the nanopore was near unity. In the mid 1990s a collaboration of researchers in the US demonstrated that nanopores could be used to characterize DNA [8]. They showed that as an electric field drove DNA molecules through a pore in a lipid bilayer membrane, the decrease in ionic current due to the partially blocked channel allowed measurement of the polynucleotide length. 'With further improvements, the method could in principle provide direct, high-speed detection of the sequence of bases in single molecules of DNA or RNA', suggested the authors. The idea inspired a catalogue of further research. Gracheva and colleagues in Illinois described a modified approach to detecting DNA using a nanopore in a membrane fabricated from a metal-oxide-semiconductor (MOS) capacitor [9]. The use of semiconductor materials allows the direct integration of high-sensitivity nanoscale MOS amplifiers on the nanopore layer structure to improve the signal. Researchers in the Netherlands have investigated ways of refining geometrical control of nanopores in SiN membranes for more accurate molecular characterization [10]. They reported the fabrication of nanopores using transmission electron microscope beams of different sizes. They found that the stability of small nanopores is related to their geometry, which could be controlled by the size of the beam used in fabrication. One challenge for accurate DNA characterization has been the speed of translocation through the pore. In a collaboration between the University of Illinois and the University of Notre-Dame in Indiana, researchers used a time-varying electric field to slow down the molecule's passage in the pore [11]. In this issue, researchers in Illinois have studied the translocation and stretching of DNA in a pore in a semiconductor membrane consisting of doped p- and n-layers of Si forming a p-n-junction [4]. Control over the stretching of the DNA is important, as is controlling the speed of translocation. Interference between the secondary structure of the probed molecule can interfere with the recorded signal, muddling measurements of the molecule's charge. According to Gracheva and her colleagues, 'the results indicate that the tunable local electric field inside the membrane can effectively control dynamics of a DNA in the channel to either momentarily trap, slow down or allow the biomolecule to translocate at will'. The fertility of research based on nanopores complements well the interest in nanowires and nanoposts. This may largely be a symptom of the comprehensive rigour in scientific enquiry which encourages the investigation of all approaches to a solution. It was once suggested that 'art and science have their meeting point in method' [12]. One might also argue that the creative and inspired ingenuity that is evident in the application of nanopores to such wide-ranging technological challenges demonstrates how the development of scientific methods is in itself a fine art. References [1] Qiu J et al 2010 Solution-derived 40 μm vertically aligned ZnO nanowire arrays as photoelectrodes in dye-sensitized solar cells Nanotechnology 21 195602 [2] Park I, Li Z, Pisano A P and Williams R S 2010 Top-down fabricated silicon nanowire sensors for real-time chemical detection Nanotechnology 21 015501 [3] Gao J et al 2011 UV light emitting transparent conducting tin-doped indium oxide (ITO) nanowires Nanotechnology 22 195706 [4] Melnikov D V, Leburton J-P and Gracheva M E 2012 Slowing down and stretching DNA with an electrically tunable nanopore in a p-n semiconductor membrane Nanotechnology 23 255501 [5] Prakasam H E, Varghese O K, Paulose M, Mor G K and Grimes C A 2006 Synthesis and photoelectrochemical properties of nanoporous iron (III) oxide by potentiostatic anodization Nanotechnology 17 4285-91 [6] Hong C, Tang T-T, Hung C-Y, Pan R-P and Fang W 2010 Liquid crystal alignment in nanoporous anodic aluminum oxide layer for LCD panel applications Nanotechnology 21 285201 [7] Chung S H, Son S J and Min J 2010 The nanostructure effect on the adhesion and growth rates of epithelial cells with well-defined nanoporous alumina s substrates Nanotechnology 21 125104 [8] Kasianowicz J J, Brandin E, Branton D and Deamer D W 1996 Characterization of individual polynucleotide molecules using a membrane channel Proc. Natl Acad. Sci. 93 13770-3 [9] Gracheva M E, Xiong A, Aksimentiev A, Schulten K, Timp G and Leburton J-P 2006 Simulation of the electric response of DNA translocation through a semiconductor nanopore-capacitor Nanotechnology 17 622-33 [10] Van Den Hout M, Hall A R, Wu M Y, Zandbergen H W, Dekker C and Dekker N H 2010 Controlling nanopore size, shape and stability Nanotechnology 21 115304 [11] Mirsaidov U, Comer J, Dimitrov V, Aksimentiev A and Timp G 2010 Slowing the translocation of double-stranded DNA using a nanopore smaller than the double helix Nanotechnology 21 395501 [12] Baron E and Bulwer L L 1864 Caxtoniana vol 2 (Leipzig: Bernard Tauchnits) p 122

Reaching the Ionic Current Detection Limit in Silicon-Based Nanopores

NASA Astrophysics Data System (ADS)

Puster, Matthew; Rodriguez-Manzo, Julio Alejandro; Nicolai, Adrien; Meunier, Vincent; Drndic, Marija

2015-03-01

Solid-state nanopores act as single-molecule sensors whereby passage of an individual molecule in aqueous electrolyte through a nanopore is registered as a change in ionic conductance (ΔG). Future nanopore applications such as DNA sequencing at high bandwidth require high ΔG for optimal signal-to-noise ratio. Reducing the nanopore diameter and thickness increase ΔG. Molecule size limits the diameter, thus efforts concentrate on minimizing the thickness by thinning oxide/nitride films or using 2D materials. Weighted by electrolyte conductivity the highest ΔG reported to date for DNA translocations were obtained with nanopores made in oxide/nitride films. We present a controlled electron irradiation technique to thin such films to the limit of their stability, producing nanopores tailored to molecule size in amorphous Si with thicknesses less than 2 nm. We compare ΔG values with results found in the literature for DNA translocation through these nanopores, where access resistance becomes comparable to the resistance through the nanopore itself.

Single-step direct fabrication of pillar-on-pore hybrid nanostructures in anodizing aluminum for superior superhydrophobic efficiency.

PubMed

Jeong, Chanyoung; Choi, Chang-Hwan

2012-02-01

Conventional electrochemical anodizing processes of metals such as aluminum typically produce planar and homogeneous nanopore structures. If hydrophobically treated, such 2D planar and interconnected pore structures typically result in lower contact angle and larger contact angle hysteresis than 3D disconnected pillar structures and, hence, exhibit inferior superhydrophobic efficiency. In this study, we demonstrate for the first time that the anodizing parameters can be engineered to design novel pillar-on-pore (POP) hybrid nanostructures directly in a simple one-step fabrication process so that superior surface superhydrophobicity can also be realized effectively from the electrochemical anodization process. On the basis of the characteristic of forming a self-ordered porous morphology in a hexagonal array, the modulation of anodizing voltage and duration enabled the formulation of the hybrid-type nanostructures having controlled pillar morphology on top of a porous layer in both mild and hard anodization modes. The hybrid nanostructures of the anodized metal oxide layer initially enhanced the surface hydrophilicity significantly (i.e., superhydrophilic). However, after a hydrophobic monolayer coating, such hybrid nanostructures then showed superior superhydrophobic nonwetting properties not attainable by the plain nanoporous surfaces produced by conventional anodization conditions. The well-regulated anodization process suggests that electrochemical anodizing can expand its usefulness and efficacy to render various metallic substrates with great superhydrophilicity or -hydrophobicity by directly realizing pillar-like structures on top of a self-ordered nanoporous array through a simple one-step fabrication procedure.

The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots

NASA Astrophysics Data System (ADS)

Yoo, Hana; Park, Soojin

2010-06-01

We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm × 5 cm.

The fabrication of highly ordered block copolymer micellar arrays: control of the separation distances of silicon oxide dots.

PubMed

Yoo, Hana; Park, Soojin

2010-06-18

We demonstrate the fabrication of highly ordered silicon oxide dotted arrays prepared from polydimethylsiloxane (PDMS) filled nanoporous block copolymer (BCP) films and the preparation of nanoporous, flexible Teflon or polyimide films. Polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) films were annealed in toluene vapor to enhance the lateral order of micellar arrays and were subsequently immersed in alcohol to produce nano-sized pores, which can be used as templates for filling a thin layer of PDMS. When a thin layer of PDMS was spin-coated onto nanoporous BCP films and thermally annealed at a certain temperature, the PDMS was drawn into the pores by capillary action. PDMS filled BCP templates were exposed to oxygen plasma environments in order to fabricate silicon oxide dotted arrays. By addition of PS homopolymer to PS-b-P2VP copolymer, the separation distances of micellar arrays were tuned. As-prepared silicon oxide dotted arrays were used as a hard master for fabricating nanoporous Teflon or polyimide films by spin-coating polymer precursor solutions onto silicon patterns and peeling off. This simple process enables us to fabricate highly ordered nanoporous BCP templates, silicon oxide dots, and flexible nanoporous polymer patterns with feature size of sub-20 nm over 5 cm x 5 cm.

Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers

PubMed Central

Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

2017-01-01

Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I–V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later. PMID:28252106

Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers

NASA Astrophysics Data System (ADS)

Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

2017-03-01

Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I-V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later.

Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers.

PubMed

Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

2017-03-02

Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO 2 /nanoporous-Si and the TiO 2 /nanoporous-Si by I-V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO 2 /nanoporous Si are lower than that of the HfO 2 /nanoporous Si, the former is more stable than the later.

Selective Metallization of Well Aligned PS-b-P2VP Block Copolymers in Thin Films and in Confined Geometries

NASA Astrophysics Data System (ADS)

Sievert, James D.; Watkins, James J.; Russell, Thomas P.

2006-03-01

Well aligned, microphase-separated structures of styrene-2-vinylpyridine block copolymers are being used as templates for macromolecule-metal nanocomposites. These composites are either prepared as thin films or confined in nanoporous aluminum oxide membranes. Under optimal conditions, templates are prepared as thin films or confined nanorods and metallized without disturbing the ordered structure. We have developed a procedure that deposits metal within the polymer using supercritical carbon dioxide-soluble metal precursors. The use of supercritical carbon dioxide allows for selective metallization of the polymer at or below the glass transition, without disrupting the morphology. In addition, similar procedures have been investigated using metal salts and acids. Using these techniques, metals and metal-sulfides including silver, gold, platinum and zinc sulfide have been selectively deposited.

A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

NASA Astrophysics Data System (ADS)

Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

2015-12-01

Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes.

PubMed

Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

2015-12-01

Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

Catalytic activity of nanostructured Au: Scale effects versus bimetallic/bifunctional effects in low-temperature CO oxidation on nanoporous Au

PubMed Central

Wang, Lu-Cun; Zhong, Yi; Jin, Haijun; Widmann, Daniel; Weissmüller, Jörg

2013-01-01

Summary The catalytic properties of nanostructured Au and their physical origin were investigated by using the low-temperature CO oxidation as a test reaction. In order to distinguish between structural effects (structure–activity correlations) and bimetallic/bifunctional effects, unsupported nanoporous gold (NPG) samples prepared from different Au alloys (AuAg, AuCu) by selective leaching of a less noble metal (Ag, Cu) were employed, whose structure (surface area, ligament size) as well as their residual amount of the second metal were systematically varied by applying different potentials for dealloying. The structural and chemical properties before and after 1000 min reaction were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic behavior was evaluated by kinetic measurements in a conventional microreactor and by dynamic measurements in a temporal analysis of products (TAP) reactor. The data reveal a clear influence of the surface contents of residual Ag and Cu species on both O2 activation and catalytic activity, while correlations between activity and structural parameters such as surface area or ligament/crystallite size are less evident. Consequences for the mechanistic understanding and the role of the nanostructure in these NPG catalysts are discussed. PMID:23503603

Electrochemical Generation of a Hydrogen Bubble at a Recessed Platinum Nanopore Electrode.

PubMed

Chen, Qianjin; Luo, Long; White, Henry S

2015-04-21

We report the electrochemical generation of a single hydrogen bubble within the cavity of a recessed Pt nanopore electrode. The recessed Pt electrode is a conical pore in glass that contains a micrometer-scale Pt disk (1-10 μm radius) at the nanopore base and a nanometer-scale orifice (10-100 nm radius) that restricts diffusion of electroactive molecules and dissolved gas between the nanopore cavity and bulk solution. The formation of a H2 bubble at the Pt disk electrode in voltammetric experiments results from the reduction of H(+) in a 0.25 M H2SO4 solution; the liquid-to-gas phase transformation is indicated in the voltammetric response by a precipitous decrease in the cathodic current due to rapid bubble nucleation and growth within the nanopore cavity. Finite element simulations of the concentration distribution of dissolved H2 within the nanopore cavity, as a function of the H(+) reduction current, indicate that H2 bubble nucleation at the recessed Pt electrode surface occurs at a critical supersaturation concentration of ∼0.22 M, in agreement with the value previously obtained at (nonrecessed) Pt disk electrodes (∼0.25 M). Because the nanopore orifice limits the diffusion of H2 out of the nanopore cavity, an anodic peak corresponding to the oxidation of gaseous and dissolved H2 trapped in the recessed cavity is readily observed on the reverse voltammetric scan. Integration of the charge associated with the H2 oxidation peak is found to approach that of the H(+) reduction peak at high scan rates, confirming the assignment of the anodic peak to H2 oxidation. Preliminary results for the electrochemical generation of O2 bubbles from water oxidation at a recessed nanopore electrode are consistent with the electrogeneration of H2 bubbles.

Robust and Recyclable Substrate Template with an Ultrathin Nanoporous Counter Electrode for Organic-Hole-Conductor-Free Monolithic Perovskite Solar Cells.

PubMed

Li, Ming-Hsien; Yang, Yu-Syuan; Wang, Kuo-Chin; Chiang, Yu-Hsien; Shen, Po-Shen; Lai, Wei-Chih; Guo, Tzung-Fang; Chen, Peter

2017-12-06

A robust and recyclable monolithic substrate applying all-inorganic metal-oxide selective contact with a nanoporous (np) Au:NiO x counter electrode is successfully demonstrated for efficient perovskite solar cells, of which the perovskite active layer is deposited in the final step for device fabrication. Through annealing of the Ni/Au bilayer, the nanoporous NiO/Au electrode is formed in virtue of interconnected Au network embedded in oxidized Ni. By optimizing the annealing parameters and tuning the mesoscopic layer thickness (mp-TiO 2 and mp-Al 2 O 3 ), a decent power conversion efficiency (PCE) of 10.25% is delivered. With mp-TiO 2 /mp-Al 2 O 3 /np-Au:NiO x as a template, the original perovskite solar cell with 8.52% PCE can be rejuvenated by rinsing off the perovskite material with dimethylformamide and refilling with newly deposited perovskite. A renewed device using the recycled substrate once and twice, respectively, achieved a PCE of 8.17 and 7.72% that are comparable to original performance. This demonstrates that the novel device architecture is possible to recycle the expensive transparent conducting glass substrates together with all the electrode constituents. Deposition of stable multicomponent perovskite materials in the template also achieves an efficiency of 8.54%, which shows its versatility for various perovskite materials. The application of such a novel NiO/Au nanoporous electrode has promising potential for commercializing cost-effective, large scale, and robust perovskite solar cells.

Operation of Thin-Film Electrolyte Metal-Supported Solid Oxide Fuel Cells in Lightweight and Stationary Stacks: Material and Microstructural Aspects

PubMed Central

Roehrens, Daniel; Packbier, Ute; Fang, Qingping; Blum, Ludger; Sebold, Doris; Bram, Martin; Menzler, Norbert

2016-01-01

In this study we report on the development and operational data of a metal-supported solid oxide fuel cell with a thin film electrolyte under varying conditions. The metal-ceramic structure was developed for a mobile auxiliary power unit and offers power densities of 1 W/cm2 at 800 °C, as well as robustness under mechanical, thermal and chemical stresses. A dense and thin yttria-doped zirconia layer was applied to a nanoporous nickel/zirconia anode using a scalable adapted gas-flow sputter process, which allowed the homogeneous coating of areas up to 100 cm2. The cell performance is presented for single cells and for stack operation, both in lightweight and stationary stack designs. The results from short-term operation indicate that this cell technology may be a very suitable alternative for mobile applications. PMID:28773883

Rapid ultrasensitive single particle surface-enhanced Raman spectroscopy using metallic nanopores.

PubMed

Cecchini, Michael P; Wiener, Aeneas; Turek, Vladimir A; Chon, Hyangh; Lee, Sangyeop; Ivanov, Aleksandar P; McComb, David W; Choo, Jaebum; Albrecht, Tim; Maier, Stefan A; Edel, Joshua B

2013-10-09

Nanopore sensors embedded within thin dielectric membranes have been gaining significant interest due to their single molecule sensitivity and compatibility of detecting a large range of analytes, from DNA and proteins, to small molecules and particles. Building on this concept we utilize a metallic Au solid-state membrane to translocate and rapidly detect single Au nanoparticles (NPs) functionalized with 589 dye molecules using surface-enhanced resonance Raman spectroscopy (SERRS). We show that, due to the plasmonic coupling between the Au metallic nanopore surface and the NP, signal intensities are enhanced when probing analyte molecules bound to the NP surface. Although not single molecule, this nanopore sensing scheme benefits from the ability of SERRS to provide rich vibrational information on the analyte, improving on current nanopore-based electrical and optical detection techniques. We show that the full vibrational spectrum of the analyte can be detected with ultrahigh spectral sensitivity and a rapid temporal resolution of 880 μs.

An Innovative Metal Ions Sensitive “Test Paper” Based on Virgin Nanoporous Silicon Wafer: Highly Selective to Copper(II)

NASA Astrophysics Data System (ADS)

Li, Shaoyuan; Chen, Xiuhua; Ma, Wenhui; Ding, Zhao; Zhang, Cong; Chen, Zhengjie; He, Xiao; Shang, Yudong; Zou, Yuxin

2016-11-01

Developing an innovative “Test Paper” based on virgin nanoporous silicon (NPSi) which shows intense visible emission and excellent fluorescence stability. The visual fluorescence quenching “Test Paper” was highly selective and sensitive recognizing Cu2+ at μmol/L level. Within the concentration range of 5 × 10-7 ~50 × 10-7mol/L, the linear regression equation of IPL = 1226.3-13.6[CCu2+] (R = 0.99) was established for Cu2+ quantitative detection. And finally, Cu2+ fluorescence quenching mechanism of NPSi prober was proposed by studying the surface chemistry change of NPSi and metal ions immersed-NPSi using XPS characterization. The results indicate that SiHx species obviously contribute to the PL emission of NPSi, and the introduce of oxidization state and the nonradiative recombination center are responsible for the PL quenching. These results demonstrate how virgin NPSi wafer can serve as Cu2+ sensor. This work is of great significant to promote the development of simple instruments that could realize rapid, visible and real-time detection of various toxic metal ions.

The Integration of Nanoscale Techniques for an Improved Battery Technology

DTIC Science & Technology

2012-06-08

anodized aluminum oxide ( AAO ) membranes that were 13...nanoporous anodized aluminum oxide ( AAO ) substrate [13]. During sputtering, thickened columnar growths form around the pores of the substrate...investigates an interpenetrating network structure where ―tubes‖ of polymer electrolyte are placed in the nanopores of anodic aluminum oxide ( AAO

ATOMIC LAYER DEPOSITION OF TITANIUM OXIDE THIN FILMS ONNANOPOROUS ALUMINA TEMPLATES FOR MEDICAL APPLICATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brigmon, R.

2009-05-05

Nanostructured materials may play a significant role in controlled release of pharmacologic agents for treatment of cancer. Many nanoporous polymer materials are inadequate for use in drug delivery. Nanoporous alumina provides several advantages over other materials for use in controlled drug delivery and other medical applications. Atomic layer deposition was used to coat all the surfaces of the nanoporous alumina membrane in order to reduce the pore size in a controlled manner. Both the 20 nm and 100 nm titanium oxide-coated nanoporous alumina membranes did not exhibit statistically lower viability compared to the uncoated nanoporous alumina membrane control materials. Inmore » addition, 20 nm pore size titanium oxide-coated nanoporous alumina membranes exposed to ultraviolet light demonstrated activity against Escherichia coli and Staphylococcus aureus bacteria. Nanostructured materials prepared using atomic layer deposition may be useful for delivering a pharmacologic agent at a precise rate to a specific location in the body. These materials may serve as the basis for 'smart' drug delivery devices, orthopedic implants, or self-sterilizing medical devices.« less

Synthesis of nanoporous TiO2 materials using a doubly surfactant system and applying them as useful adsorbents

NASA Astrophysics Data System (ADS)

Anbia, Mansoor; Khosravi, Faezeh

Hydrothermal and non-hydrothermal nanoporous TiO2 materials were synthesized via a doubly surfactant route by using cationic cetyltrimethylammonium bromide and anionic sodium dodecyl sulfate surfactants as the molecular template/structure directing agent. Hydrothermal treatment was performed for comparison. The bulk chemical and phase compositions, crystalline structures, particle morphologies, thermal stabilities and surface texturing were determined by means of X-ray powder analysis, SEM and N2 sorptiometry. The nanoporous TiO2 materials were found to have a spherical morphology with a diameter range of 50-200 nm and a high surface area (390 m2 g-1). Hydrothermal and non-hydrothermal nanoporous TiO2 materials were applied for adsorption of heavy metal cations and the toxic organic compound, copper phthalocyanine, from water for evaluation of their adsorption properties. Both nanoporous TiO2 materials were found to have similar adsorption capacities toward heavy metal cations and CuPc. Both hydrothermal and non-hydrothermal TiO2 nanoporous materials were found to have very good potential for application as a new adsorbent especially for adsorbing heavy metal cations from wastewaters.

Inorganic metal oxide/organic polymer nanocomposites and method thereof

DOEpatents

Gash, Alexander E.; Satcher, Joe H.; Simpson, Randy

2004-03-30

A synthetic method for preparation of hybrid inorganic/organic energetic nanocomposites is disclosed herein. The method employs the use of stable metal inorganic salts and organic solvents as well as an organic polymer with good solubility in the solvent system to produce novel nanocomposite energetic materials. In addition, fuel metal powders (particularly those that are oxophillic) can be incorporated into composition. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N.sub.2 adsoprtion/desorption methods, and Fourier-Transform (FT-IR) spectroscopy. According to these characterization methods the organic polymer phase fills the nanopores of the composite material, providing superb mixing of the component phases in the energetic nanocomposite.

Inorganic Metal Oxide/Organic Polymer Nanocomposites And Method Thereof

DOEpatents

Gash, Alexander E.; Satcher, Joe H.; Simpson, Randy

2004-11-16

A synthetic method for preparation of hybrid inorganic/organic energetic nanocomposites is disclosed herein. The method employs the use of stable metal in organic salts and organic solvents as well as an organic polymer with good solubility in the solvent system to produce novel nanocomposite energetic materials. In addition, fuel metal powders (particularly those that are oxophilic) can be incorporated into composition. This material has been characterized by thermal methods, energy-filtered transmission electron microscopy (EFTEM), N.sub.2 adsoprtion/desorption methods, and Fourier-Transform (FT-IR) spectroscopy. According to these characterization methods the organic polymer phase fills the nanopores of the material, providing superb mixing of the component phases in the energetic nanocomposite.

Planar Solid-Oxide Fuel Cell System Demonstration at UT SimCenter

DTIC Science & Technology

2015-12-09

including metals, carbon, and zeolites , have been proposed for sulfur adsorption performances [9-13]. Nickel and copper supported on activated carbon and... zeolite exhibited effective desulfurization effects for jet fuels [14,15]. Muzic et al. [16] examined the adsorptive desulfurization of three...sulfur by using a nanoporous Ni loaded, Y-type zeolite at ambient conditions. The adsorption capacity of Ni-Y zeolite was 0.84 and 2.31 mg S/g

Enhanced electrocatalytic activity of the Au-electrodeposited Pt nanoparticles-coated conducting oxide for the quantum dot-sensitized solar cells

NASA Astrophysics Data System (ADS)

Yoon, Yeung-Pil; Kim, Jae-Hong; Kang, Soon-Hyung; Kim, Hyunsoo; Choi, Chel-Jong; Kim, Kyong-Kook; Ahn, Kwang-Soon

2014-08-01

Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO2 (FTO/Pt) substrates. For comparison, Au-electrodeposited FTO (FTO/Au) and Au-uncoated FTO/Pt were prepared. FTO/Au showed large-sized Au clusters dispersed sparsely over FTO, which resulted in lower electrocatalytic activity than FTO/Pt. In contrast, FTO/Pt exhibited poor stability unlike FTO/Au due to poisoning by the adsorption of sulfur species. The Au-electrodeposited FTO/Pt (FTO/Pt/Au) consisted of small Au clusters deposited over the entire area of Pt due to the effective Au nucleation provided by nanoporous metallic Pt. FTO/Pt/Au exhibited enhanced electrocatalytic activity and excellent stability because the small Au particles well-dispersed over the nanoporous metallic Pt network provided numerous electrochemical reaction sites, and the Pt surface was not exposed to the electrolyte. When FTO/Pt/Au was used as the counter electrode (CE) of a quantum dot-sensitized solar cell, the significantly enhanced electrocatalytic activity of the FTO/Pt/Au CE facilitated the reduction reaction of Sn2- + 2e- (CE) → Sn-12- + S2- at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, Sn2- + 2e- (TiO2 in the photoanode) → Sn-12- + S2-, and significantly improved overall energy conversion efficiency.

Three-Dimensional Morphological and Chemical Evolution of Nanoporous Stainless Steel by Liquid Metal Dealloying [3D Morphological and Chemical Evolution of Nanoporous Stainless Steel by Liquid Metal Dealloying

DOE PAGES

Zhao, Chonghang; Wada, Takeshi; De Andrade, Vincent; ...

2017-09-04

Nanoporous materials, especially those fabricated by liquid metal dealloying processes, possess great potential in a wide range of applications due to their high surface area, bicontinuous structure with both open pores for transport and solid phase for conductivity or support, and low material cost. Here, we used X-ray nanotomography and X-ray fluorescence microscopy to reveal the three-dimensional (3D) morphology and elemental distribution within materials. Focusing on nanoporous stainless steel, we evaluated the 3D morphology of the dealloying front and established a quantitative processing-structure-property relationship at a later stage of dealloying. The morphological differences of samples created by liquid metal dealloyingmore » and aqueous dealloying methods were also discussed. Here, we concluded that it is particularly important to consider the dealloying, coarsening, and densification mechanisms in influencing the performance-determining, critical 3D parameters, such as tortuosity, pore size, porosity, curvature, and interfacial shape.« less

Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nanoporous Carbons

PubMed Central

Tang, Jing; Salunkhe, Rahul R.; Zhang, Huabin; Malgras, Victor; Ahamad, Tansir; Alshehri, Saad M.; Kobayashi, Naoya; Tominaka, Satoshi; Ide, Yusuke; Kim, Jung Ho; Yamauchi, Yusuke

2016-01-01

Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e., bimetallic MOFs). The organic linkers that coordinate with cobalt ions tend to yield graphitic carbons after carbonization, unlike those bridging with zinc ions, due to the controlled catalytic graphitization by the cobalt nanoparticles. In this work, we demonstrate a feasible method to achieve nanoporous carbon materials with tailored properties, including specific surface area, pore size distribution, degree of graphitization, and content of heteroatoms. The bimetallic-MOF-derived nanoporous carbon are systematically characterized, highlighting the importance of precisely controlling the properties of the carbon materials. This can be done by finely tuning the components in the bimetallic MOF precursors, and thus designing optimal carbon materials for specific applications. PMID:27471193

Three-Dimensional Morphological and Chemical Evolution of Nanoporous Stainless Steel by Liquid Metal Dealloying [3D Morphological and Chemical Evolution of Nanoporous Stainless Steel by Liquid Metal Dealloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Chonghang; Wada, Takeshi; De Andrade, Vincent

Nanoporous materials, especially those fabricated by liquid metal dealloying processes, possess great potential in a wide range of applications due to their high surface area, bicontinuous structure with both open pores for transport and solid phase for conductivity or support, and low material cost. Here, we used X-ray nanotomography and X-ray fluorescence microscopy to reveal the three-dimensional (3D) morphology and elemental distribution within materials. Focusing on nanoporous stainless steel, we evaluated the 3D morphology of the dealloying front and established a quantitative processing-structure-property relationship at a later stage of dealloying. The morphological differences of samples created by liquid metal dealloyingmore » and aqueous dealloying methods were also discussed. Here, we concluded that it is particularly important to consider the dealloying, coarsening, and densification mechanisms in influencing the performance-determining, critical 3D parameters, such as tortuosity, pore size, porosity, curvature, and interfacial shape.« less

Atomic layer deposition-based functionalization of materials for medical and environmental health applications

PubMed Central

Narayan, Roger J.; Adiga, Shashishekar P.; Pellin, Michael J.; Curtiss, Larry A.; Hryn, Alexander J.; Stafslien, Shane; Chisholm, Bret; Shih, Chun-Che; Shih, Chun-Ming; Lin, Shing-Jong; Su, Yea-Yang; Jin, Chunming; Zhang, Junping; Monteiro-Riviere, Nancy A.; Elam, Jeffrey W.

2010-01-01

Nanoporous alumina membranes exhibit high pore densities, well-controlled and uniform pore sizes, as well as straight pores. Owing to these unusual properties, nanoporous alumina membranes are currently being considered for use in implantable sensor membranes and water purification membranes. Atomic layer deposition is a thin-film growth process that may be used to modify the pore size in a nanoporous alumina membrane while retaining a narrow pore distribution. In addition, films deposited by means of atomic layer deposition may impart improved biological functionality to nanoporous alumina membranes. In this study, zinc oxide coatings and platinum coatings were deposited on nanoporous alumina membranes by means of atomic layer deposition. PEGylated nanoporous alumina membranes were prepared by self-assembly of 1-mercaptoundec-11-yl hexa(ethylene glycol) on platinum-coated nanoporous alumina membranes. The pores of the PEGylated nanoporous alumina membranes remained free of fouling after exposure to human platelet-rich plasma; protein adsorption, fibrin networks and platelet aggregation were not observed on the coated membrane surface. Zinc oxide-coated nanoporous alumina membranes demonstrated activity against two waterborne pathogens, Escherichia coli and Staphylococcus aureus. The results of this work indicate that nanoporous alumina membranes may be modified using atomic layer deposition for use in a variety of medical and environmental health applications. PMID:20308114

Electrochemical fabrication of nanoporous copper films in choline chloride-urea deep eutectic solvent.

PubMed

Zhang, Q B; Abbott, Andrew P; Yang, C

2015-06-14

Nanoporous copper films were fabricated by a facile electrochemical alloying/dealloying process without the need of a template. A deep eutectic solvent made from choline chloride (ChCl) and urea was used with zinc oxide as the metal salt. Cyclic voltammetry was used to characterise the electrochemical reduction of zinc and follow Cu-Zn alloy formation on the copper substrate at elevated temperatures from 353 to 393 K. The alloy formation was confirmed by X-ray diffraction spectra. 3D, open and bicontinuous nanoporous copper films were obtained by in situ electrochemically etching (dealloying) of the zinc component in the Cu-Zn surface alloys at an appropriate potential (-0.4 V vs. Ag). This dealloying process was found to be highly temperature dependent and surface diffusion controlled, which involved the self-assembly of copper atoms at the alloy/electrolyte interface. Additionally, the effects of the deposition parameters, including deposition temperature, current density as well as total charge density on resulting the microstructure were investigated by scanning electron microscopy, and atomic force microscope.

The formation of nanopores in metal materials after irradiation by beams of Ar+ with energy of 30 keV

NASA Astrophysics Data System (ADS)

Ivchenko, V. A.

2017-01-01

In this paper are the results of direction observations of nanopores in the subsurface volume of metals materials Pt and Pd(CuAg) using field-ion microscopy (FIM). Radiation of tip specimens was carried out with ions having an energy ˜ 25-30 keV in the fluency range of 1016 - 1018 ions/cm2, the current density lying within 150- 340 µA/cm2. Nanopores have been observed immediately after removal of the first atomic layers from the irradiated surface. It was established that, the threshold for ion-implanted platinum corresponds to fluence F = 1017 ions/cm2. For Pd(CuAg) it was revealed that nanopores have been down to 80 nm deep with current density 340 µA/cm2. Their dimensions and volume fractions were determined. The obtained results can be used for prediction of radiation stability of materials based on fcc metals.

Metal-Organic Framework-Derived Nanoporous Metal Oxides toward Supercapacitor Applications: Progress and Prospects.

PubMed

Salunkhe, Rahul R; Kaneti, Yusuf V; Yamauchi, Yusuke

2017-06-27

Transition metal oxides (TMOs) have attracted significant attention for energy storage applications such as supercapacitors due to their good electrical conductivity, high electrochemical response (by providing Faradaic reactions), low manufacturing costs, and easy processability. Despite exhibiting these attractive characteristics, the practical applications of TMOs for supercapacitors are still relatively limited. This is largely due to their continuous Faradaic reactions, which can lead to major changes or destruction of their structure as well phase changes (in some cases) during cycling, leading to the degradation in their capacitive performance over time. Hence, there is an immediate need to develop new synthesis methods, which will readily provide stable porous architectures, controlled phase, as well as useful control over dimensions (1-D, 2-D, and 3-D) of the metal oxides for improving their performance in supercapacitor applications. Since its discovery in late 1990s, metal-organic frameworks (MOFs) have influenced many fields of material science. In recent years, they have gained significant attention as precursors or templates for the derivation of porous metal oxide nanostructures and nanocomposites for next-generation supercapacitor applications. Even though these materials have widespread applications and have been widely studied in terms of their structural features and synthesis, it is still not clear how these materials will play an important role in the development of the supercapacitor field. In this review, we will summarize the recent developments in the field of MOF-derived porous metal oxide nanostructures and nanocomposites for supercapacitor applications. Furthermore, the current challenges along with the future trends and prospects in the application of these materials for supercapacitors will also be discussed.

Slow DNA Transport through Nanopores in Hafnium Oxide Membranes

PubMed Central

Bell, David C.; Cohen-Karni, Tzahi; Rosenstein, Jacob K.; Wanunu, Meni

2016-01-01

We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2–7 nm thick) free-standing hafnium oxide (HfO2) membranes. The high chemical stability of ultrathin HfO2 enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50 000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO2 nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore. PMID:24083444

Ultrahigh-Power Pseudocapacitors Based on Ordered Porous Heterostructures of Electron-Correlated Oxides.

PubMed

Lang, Xing-You; Liu, Bo-Tian; Shi, Xiang-Mei; Li, Ying-Qi; Wen, Zi; Jiang, Qing

2016-05-01

Nanostructured transition-metal oxides can store high-density energy in fast surface redox reactions, but their poor conductivity causes remarkable reductions in the energy storage of most pseudocapacitors at high power delivery (fast charge/discharge rates). Here it is shown that electron-correlated oxide hybrid electrodes made of nanocrystalline vanadium sesquioxide and manganese dioxide with 3D and bicontinuous nanoporous architecture (NP V 2 O 3 /MnO 2 ) have enhanced conductivity because of metallization of electron-correlated V 2 O 3 skeleton via insulator-to-metal transition. The conductive V 2 O 3 skeleton at ambient temperature enables fast electron and ion transports in the entire electrode and facilitates charge transfer at abundant V 2 O 3 /MnO 2 interface. These merits significantly improve the pseudocapacitive behavior and rate capability of the constituent MnO 2 . Symmetric pseudocapacitors assembled with binder-free NP V 2 O 3 /MnO 2 electrodes deliver ultrahigh electrical powers (up to ≈422 W cm 23 ) while maintaining the high volumetric energy of thin-film lithium battery with excellent stability.

Dispersion of Cobalt Nanoparticles on Nanowires Grown on Silicon Carbide-Alumina Nanocomposites.

PubMed

Kim, Inho; Seo, Kyeong Won; Ahn, Byoung Sung; Moon, Dong Ju; Kim, Sang Woo

2017-04-01

Silicon carbide-alumina nanocomposite supports including a nanowire architecture for a high dispersion of cobalt nanocatalysts were fabricated using a modified sol–gel process and paste extrusion process to form cylindrical shape beads, followed by thermal treatment. Well-developed aluminosilicate nanowires were formed on a nanoporous support, which are grown from a catalytic metal seed at the nanowire growth tips during heat treatment at 1,100 °C for 1 h under nitrogen gas flow. Cobalt oxide precursors were highly dispersed on the nanowires grown on the surface of the nanoporous bodies through a supercritical carbon dioxide fluid-assisted wet-impregnation process. The highly-dispersed Co nanoparticles with size of less than 10 nm were finally obtained on the nanowires via phase transitions from Co₃O₄ to CoO and from CoO to Co during the thermal reduction.

Warming up human body by nanoporous metallized polyethylene textile.

PubMed

Cai, Lili; Song, Alex Y; Wu, Peilin; Hsu, Po-Chun; Peng, Yucan; Chen, Jun; Liu, Chong; Catrysse, Peter B; Liu, Yayuan; Yang, Ankun; Zhou, Chenxing; Zhou, Chenyu; Fan, Shanhui; Cui, Yi

2017-09-19

Space heating accounts for the largest energy end-use of buildings that imposes significant burden on the society. The energy wasted for heating the empty space of the entire building can be saved by passively heating the immediate environment around the human body. Here, we demonstrate a nanophotonic structure textile with tailored infrared (IR) property for passive personal heating using nanoporous metallized polyethylene. By constructing an IR-reflective layer on an IR-transparent layer with embedded nanopores, the nanoporous metallized polyethylene textile achieves a minimal IR emissivity (10.1%) on the outer surface that effectively suppresses heat radiation loss without sacrificing wearing comfort. This enables 7.1 °C decrease of the set-point compared to normal textile, greatly outperforming other radiative heating textiles by more than 3 °C. This large set-point expansion can save more than 35% of building heating energy in a cost-effective way, and ultimately contribute to the relief of global energy and climate issues.Energy wasted for heating the empty space of the entire building can be saved by passively heating the immediate environment around the human body. Here, the authors show a nanophotonic structure textile with tailored infrared property for passive personal heating using nanoporous metallized polyethylene.

Symposium P: Three-Dimensional Architectures for Energy Generation and Storage

DTIC Science & Technology

2010-09-02

anodic oxidation of aluminum to produce anodic aluminum oxide ( AAO ). The nanopores have diameters 15-100nm and depths 1-30um... aluminum oxide ( AAO ) template which can be successfully applied for fabrication of vertically aligned SiNWs. Then, we have investigated the electrical...performed in quiescent and rotating disc electrode (RDE) experiments. PSJfl Lateral Growth of Deep Nanopores in Anodic Aluminum Oxide as a Platform

Molecular simulations for energy, environmental and pharmaceutical applications of nanoporous materials: from zeolites, metal-organic frameworks to protein crystals.

PubMed

Jiang, Jianwen; Babarao, Ravichandar; Hu, Zhongqiao

2011-07-01

Nanoporous materials have widespread applications in chemical industry, but the pathway from laboratory synthesis and testing to practical utilization of nanoporous materials is substantially challenging and requires fundamental understanding from the bottom up. With ever-growing computational resources, molecular simulations have become an indispensable tool for material characterization, screening and design. This tutorial review summarizes the recent simulation studies in zeolites, metal-organic frameworks and protein crystals, and provides a molecular overview for energy, environmental and pharmaceutical applications of nanoporous materials with increasing degree of complexity in building blocks. It is demonstrated that molecular-level studies can bridge the gap between physical and engineering sciences, unravel microscopic insights that are otherwise experimentally inaccessible, and assist in the rational design of new materials. The review is concluded with major challenges in future simulation exploration of novel nanoporous materials for emerging applications.

Ammonia Adsorption and Co-adsorption with Water in HKUST-1: Spectroscopic Evidence for Cooperative Interactions

DOE PAGES

Nijem, Nour; Fürsich, Katrin; Bluhm, Hendrik; ...

2015-10-09

Ammonia interactions and competition with water at the interface of nanoporous metal organic framework thin films of HKUST-1 (Cu 3Btc 2 , Btc = 1,3,5-benzenedicarboxylate) are investigated with ambient pressure X-ray photoelectron spectroscopy (APXPS). In the absence of water, ammonia adsorption at the Cu 2+ metal center weakens the metal-linker bond of the framework. In the presence of water, due to the higher binding energy (adsorption strength) of ammonia compared to water, ammonia replaces water at the unsaturated Cu 2+ metal centers. The water molecules remaining in the pores are stabilized by hydrogen bonding to ammonia. Hydrogen bonding between themore » water and ammonia strengthens the metal-ammonia interaction due to cooperative interactions. Cooperative interactions result in a reduction in the metal center oxidation state facilitating linker replacement by other species explaining the previously reported structure degradation.« less

Ammonia Adsorption and Co-adsorption with Water in HKUST-1: Spectroscopic Evidence for Cooperative Interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nijem, Nour; Fürsich, Katrin; Bluhm, Hendrik

Ammonia interactions and competition with water at the interface of nanoporous metal organic framework thin films of HKUST-1 (Cu 3Btc 2 , Btc = 1,3,5-benzenedicarboxylate) are investigated with ambient pressure X-ray photoelectron spectroscopy (APXPS). In the absence of water, ammonia adsorption at the Cu 2+ metal center weakens the metal-linker bond of the framework. In the presence of water, due to the higher binding energy (adsorption strength) of ammonia compared to water, ammonia replaces water at the unsaturated Cu 2+ metal centers. The water molecules remaining in the pores are stabilized by hydrogen bonding to ammonia. Hydrogen bonding between themore » water and ammonia strengthens the metal-ammonia interaction due to cooperative interactions. Cooperative interactions result in a reduction in the metal center oxidation state facilitating linker replacement by other species explaining the previously reported structure degradation.« less

Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries.

PubMed

Li, M M; Yang, C C; Wang, C C; Wen, Z; Zhu, Y F; Zhao, M; Li, J C; Zheng, W T; Lian, J S; Jiang, Q

2016-06-07

Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world's dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials-hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g(-1), which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles.

Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries

PubMed Central

Li, M. M.; Yang, C. C.; Wang, C. C.; Wen, Z.; Zhu, Y. F.; Zhao, M.; Li, J. C.; Zheng, W. T.; Lian, J. S.; Jiang, Q.

2016-01-01

Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world’s dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials—hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g−1, which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles. PMID:27270184

Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries

NASA Astrophysics Data System (ADS)

Li, M. M.; Yang, C. C.; Wang, C. C.; Wen, Z.; Zhu, Y. F.; Zhao, M.; Li, J. C.; Zheng, W. T.; Lian, J. S.; Jiang, Q.

2016-06-01

Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world’s dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials—hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g-1, which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles.

Ion-sculpting of nanopores in amorphous metals, semiconductors, and insulators

DOE Office of Scientific and Technical Information (OSTI.GOV)

George, H. Bola; Madi, Charbel S.; Aziz, Michael J.

2010-06-28

We report the closure of nanopores to single-digit nanometer dimensions by ion sculpting in a range of amorphous materials including insulators (SiO{sub 2} and SiN), semiconductors (a-Si), and metallic glasses (Pd{sub 80}Si{sub 20})--the building blocks of a single-digit nanometer electronic device. Ion irradiation of nanopores in crystalline materials (Pt and Ag) does not cause nanopore closure. Ion irradiation of c-Si pores below 100 deg. C and above 600 deg. C, straddling the amorphous-crystalline dynamic transition temperature, yields closure at the lower temperature but no mass transport at the higher temperature. Ion beam nanosculpting appears to be restricted to materials thatmore » either are or become amorphous during ion irradiation.« less

Water flow in carbon-based nanoporous membranes impacted by interactions between hydrated ions and aromatic rings.

PubMed

Liu, Jian; Shi, Guosheng; Fang, Haiping

2017-02-24

Carbon-based nanoporous membranes, such as carbon nanotubes (CNTs), graphene/graphene oxide and graphyne, have shown great potential in water desalination and purification, gas and ion separation, biosensors, and lithium-based batteries, etc. A deep understanding of the interaction between hydrated ions in an aqueous solution and the graphitic surface in systems composed of water, ions and a graphitic surface is essential for applications with carbon-based nanoporous membrane platforms. In this review, we describe the recent progress of the interaction between hydrated ions and aromatic ring structures on the carbon-based surface and its applications in the water flow in a carbon nanotube. We expect that these works can be extended to the understanding of water flow in other nanoporous membranes, such as nanoporous graphene, graphyne and stacked sheets of graphene oxide.

A transparent electrochromic metal-insulator switching device with three-terminal transistor geometry

NASA Astrophysics Data System (ADS)

Katase, Takayoshi; Onozato, Takaki; Hirono, Misako; Mizuno, Taku; Ohta, Hiromichi

2016-05-01

Proton and hydroxyl ion play an essential role for tuning functionality of oxides because their electronic state can be controlled by modifying oxygen off-stoichiometry and/or protonation. Tungsten trioxide (WO3), a well-known electrochromic (EC) material for smart window, is a wide bandgap insulator, whereas it becomes a metallic conductor HxWO3 by protonation. Although one can utilize electrochromism together with metal-insulator (MI) switching for one device, such EC-MI switching cannot be utilized in current EC devices because of their two-terminal structure with parallel-plate configuration. Here we demonstrate a transparent EC-MI switchable device with three-terminal TFT-type structure using amorphous (a-) WO3 channel layer, which was fabricated on glass substrate at room temperature. We used water-infiltrated nano-porous glass, CAN (calcium aluminate with nano-pores), as a liquid-leakage-free solid gate insulator. At virgin state, the device was fully transparent in the visible-light region. For positive gate voltage, the active channel became dark blue, and electrical resistivity of the a-WO3 layer drastically decreased with protonation. For negative gate voltage, deprotonation occurred and the active channel returned to transparent insulator. Good cycleability of the present transparent EC-MI switching device would have potential for the development of advanced smart windows.

Design of Zeolitic Imidazolate Framework Derived Nitrogen-Doped Nanoporous Carbons Containing Metal Species for Carbon Dioxide Fixation Reactions.

PubMed

Toyao, Takashi; Fujiwaki, Mika; Miyahara, Kenta; Kim, Tae-Ho; Horiuchi, Yu; Matsuoka, Masaya

2015-11-01

Various N-doped nanoporous carbons containing metal species were prepared by direct thermal conversion of zeolitic imidazolate frameworks (ZIFs; ZIF-7, -8, -9, and -67) at different temperatures (600, 800, and 1000 °C). These materials were utilized as bifunctional acid-base catalysts to promote the reaction of CO2 with epoxides to form cyclic carbonates under 0.6 MPa of CO2 at 80 °C. The catalyst generated by thermal conversion of ZIF-9 at 600 °C (C600-ZIF-9) was found to exhibit a higher catalytic activity than the other ZIFs, other conventional catalysts, and other metal-organic framework catalysts. The results of various characterization techniques including elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and transmission electron microscopy show that C600-ZIF-9 contains partly oxidized Co nanoparticles and N species. Temperature-programmed desorption measurements by using CO2 and NH3 as probe molecules revealed that C600-ZIF-9 has both Lewis acid and Lewis base catalytic sites. Finally, the substrate scope was extended to seven other kinds of epoxides. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Redox behavior of uranium at the nanoporous aluminum oxide-water interface: implications for uranium remediation.

PubMed

Jung, Hun Bok; Boyanov, Maxim I; Konishi, Hiromi; Sun, Yubing; Mishra, Bhoopesh; Kemner, Kenneth M; Roden, Eric E; Xu, Huifang

2012-07-03

Sorption-desorption experiments show that the majority (ca. 80-90%) of U(VI) presorbed to mesoporous and nanoporous alumina could not be released by extended (2 week) extraction with 50 mM NaHCO(3) in contrast with non-nanoporous α alumina. The extent of reduction of U(VI) presorbed to aluminum oxides was semiquantitatively estimated by comparing the percentages of uranium desorbed by anoxic sodium bicarbonate between AH(2)DS-reacted and unreacted control samples. X-ray absorption spectroscopy confirmed that U(VI) presorbed to non-nanoporous alumina was rapidly and completely reduced to nanoparticulate uraninite by AH(2)DS, whereas reduction of U(VI) presorbed to nanoporous alumina was slow and incomplete (<5% reduction after 1 week). The observed nanopore size-dependent redox behavior of U has important implications in developing efficient remediation techniques for the subsurface uranium contamination because the efficiency of in situ bioremediation depends on how effectively and rapidly U(VI) bound to sediment or soil can be converted to an immobile phase.

Adsorption of Heavy Metals by Graphene Oxide/Cellulose Hydrogel Prepared from NaOH/Urea Aqueous Solution

PubMed Central

Chen, Xiong; Zhou, Sukun; Zhang, Liming; You, Tingting; Xu, Feng

2016-01-01

By taking advantage of cellulose, graphene oxide (GO), and the process for crosslinking using epichlorohydrin (ECH), we propose a simple and novel method to prepare GO/cellulose hydrogel with good potential to adsorb metal ions. GO nanosheets containing carboxyl and hydroxyl groups were introduced into the surface of the cellulose hydrogel with retention of the gel structure and its nanoporous property. Due to the introduction of GO, the GO/cellulose composite hydrogels exhibited good compressive strength. Adsorption capacity of Cu2+ significantly increases with an increase in the GO/cellulose ratio and GO/cellulose hydrogel showed high adsorption rates. The calculated adsorption capacities at equilibrium (qecal) for GO/cellulose hydrogel (GO:cellulose = 20:100 in weight) was up to 94.34 mg·g−1, which was much higher than that of the pristine cellulose hydrogels. Furthermore, GO/cellulose hydrogel exhibited high efficient regeneration and metal ion recovery, and high adsorption capacity for Zn2+, Fe3+, and Pb2+. PMID:28773705

15N and 31P solid-state NMR study of transmembrane domain alignment of M2 protein of influenza A virus in hydrated cylindrical lipid bilayers confined to anodic aluminum oxide nanopores.

PubMed

Chekmenev, Eduard Y; Hu, Jun; Gor'kov, Peter L; Brey, William W; Cross, Timothy A; Ruuge, Andres; Smirnov, Alex I

2005-04-01

This communication reports the first example of a high resolution solid-state 15N 2D PISEMA NMR spectrum of a transmembrane peptide aligned using hydrated cylindrical lipid bilayers formed inside nanoporous anodic aluminum oxide (AAO) substrates. The transmembrane domain SSDPLVVA(A-15N)SIIGILHLILWILDRL of M2 protein from influenza A virus was reconstituted in hydrated 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine bilayers that were macroscopically aligned by a conventional micro slide glass support or by the AAO nanoporous substrate. 15N and 31P NMR spectra demonstrate that both the phospholipids and the protein transmembrane domain are uniformly aligned in the nanopores. Importantly, nanoporous AAO substrates may offer several advantages for membrane protein alignment in solid-state NMR studies compared to conventional methods. Specifically, higher thermal conductivity of aluminum oxide is expected to suppress thermal gradients associated with inhomogeneous radio frequency heating. Another important advantage of the nanoporous AAO substrate is its excellent accessibility to the bilayer surface for exposure to solute molecules. Such high accessibility achieved through the substrate nanochannel network could facilitate a wide range of structure-function studies of membrane proteins by solid-state NMR.

WS2 nanopores for molecule analysis

NASA Astrophysics Data System (ADS)

Danda, Gopinath; Masih Das, Paul; Chou, Yung-Chien; Mlack, Jerome; Naylor, Carl; Perea-Lopez, Nestor; Lin, Zhong; Fulton, Laura Beth; Terrones, Mauricio; Johnson, A. T. Charlie; Drndic, Marija

Atomically thin 2D materials like graphene and transition metal dichalcogenides (TMDs) are interesting as membranes in solid state nanopore sensors for DNA analysis as they may facilitate single base resolution sequencing. These materials also exhibit unique optical and electronic properties which may be exploited to enhance the functionality of nanopore sensors. Here, we report WS2 nanopores, fabricated using a focused TEM beam. We also report their controlled laser-induced expansion in ionic solution. This study demonstrates the possibility of dynamic control of nanopore characteristics optically. NIH Grant R21HG007856, NSF EFRI-1542707.

Photophysics and energy transfer studies of Alq3 confined in the voids of nanoporous anodic alumina.

PubMed

Mohammadpour, Arash; Utkin, Ilya; Bodepudi, Srikrishna Chanakya; Kar, Piyush; Fedosejevs, Robert; Pramanik, Sandipan; Shankar, Karthik

2013-04-01

We report on a hierarchical nanoarchitecture wherein distinct chromophores are deterministically placed at two different types of sites in a nanoporous metal oxide framework. One chromophore, namely Tris(8-hydroxyquinoline)aluminium(III) (Alq3), is embedded in the 1-2 nm sized nanovoids of anodic aluminum oxide (AAO) and another chromophore (carboxyfluorescein or pyrenebutyric acid) is anchored in the form of a monolayer to the surface of the walls of the cylindrical nanopores (- 20 nm in diameter) of AAO. We found the luminescence maximum to occur at 492 nm, blueshifted by at least 18 nm from the value in solutions and thin films. The excited state decay of Alq3 molecules in nanovoids was found to be biexponential with a fast component of 338 ps and a slower component of 2.26 ns, different from Alq3 thin films and solutions. Using a combination of steady state and time-resolved luminescence studies, we found that efficient Forster-type resonance energy transfer (FRET) from Alq3 in the nanovoids to the carboxyfluorescein monolayer could be used to pump the emission of surface-bound chromophores. Conversely, the emission of nanovoid-confined Alq3 could be pumped by energy transfer from a pyrenebutyric acid monolayer. Such intra-nanoarchitecture interactions between chromophores deterministically placed in different spatial locations are important in applications such as organic light emitting diodes, chemical sensors, energy transfer fluorescent labels, light harvesting antennas and organic spintronics.

High rate sodium ion battery anodes from block copolymer templated mesoporous nickel–cobalt carbonates and oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhaway, Sarang M.; Tangvijitsakul, Pattarasai; Lee, Jeongwoo

2015-09-16

Micelle-templated ordered mesoporous nickel–cobalt carbonates and oxides are fabricated using a metal nitrate–citric acid strategy, which avoids the hydrolysis and aging requirements associated with sol–gel chemistry. A series of mesoporous Ni xCo (3-x)(CO 3) y and Ni xCo (3-x)O 4 films with varying Ni–Co compositions and 14 ± 4 nm mesopores are fabricated with the same block copolymer template. AFM and GISAXS analysis indicates that the mesostructure is maintained through the formation of the carbonate and oxide, while GIXD profiles confirm formation of pure spinel phases of semi-crystalline Ni xCo (3-x)O 4. The micelle templated mesopores are interconnected and providemore » transport paths for the electrolyte to minimize the solid-state diffusion requirements associated with battery electrodes. These materials exhibit good performance as sodium ion battery anodes even at high current densities of 4 A g -1. Amongst the mixed-metal oxides, Ni 2CoO 4 exhibits the highest specific capacity of 239 mA h g -1 after galvanostatic cycling at a current density of 1 A g -1 for 10 cycles. We attribute the superior performance of Ni 2CoO 4 at high rates to the high surface area and short ion-diffusion paths of the nanoporous anode architecture, while the higher nickel content in the mixed metal oxide provides enhanced stability during oxide formation along with enhanced electronic conductivity, leading to improved cycling stability of the anode. This micelle template metal nitrate–citric acid method enables new possibilities for fabricating variety of ordered mesoporous mixed-metal carbonates and oxides that could be used in a wide range of applications.« less

Boosting infrared energy transfer in 3D nanoporous gold antennas.

PubMed

Garoli, D; Calandrini, E; Bozzola, A; Ortolani, M; Cattarin, S; Barison, S; Toma, A; De Angelis, F

2017-01-05

The applications of plasmonics to energy transfer from free-space radiation to molecules are currently limited to the visible region of the electromagnetic spectrum due to the intrinsic optical properties of bulk noble metals that support strong electromagnetic field confinement only close to their plasma frequency in the visible/ultraviolet range. In this work, we show that nanoporous gold can be exploited as a plasmonic material for the mid-infrared region to obtain strong electromagnetic field confinement, co-localized with target molecules into the nanopores and resonant with their vibrational frequency. The effective optical response of the nanoporous metal enables the penetration of optical fields deep into the nanopores, where molecules can be loaded thus achieving a more efficient light-matter coupling if compared to bulk gold. In order to realize plasmonic resonators made of nanoporous gold, we develop a nanofabrication method based on polymeric templates for metal deposition and we obtain antenna arrays resonating at mid-infrared wavelengths selected by design. We then coat the antennas with a thin (3 nm) silica layer acting as the target dielectric layer for optical energy transfer. We study the strength of the light-matter coupling at the vibrational absorption frequency of silica at 1240 cm -1 through the analysis of the experimental Fano lineshape that is benchmarked against identical structures made of bulk gold. The boost in the optical energy transfer from free-space mid-infrared radiation to molecular vibrations in nanoporous 3D nanoantenna arrays can open new application routes for plasmon-enhanced physical-chemical reactions.

Study on Locally Confined Deposition of Si Nanocrystals in High-Aspect-Ratio Si Nano-Pillar Arrays for Nano-Electronic and Nano-Photonic Applications II

DTIC Science & Technology

2010-12-03

photoluminescence characteristics of equivalent-size controlled silicon quantum dots by employing a nano-porous aluminum oxide membrane as the template for growing...synthesis of Si quantum dots (Si-QDs) embedded in low-temperature (500oC) annealed Si-rich SiOx nano-rod deposited in nano-porous anodic aluminum oxide ...characteristics of the equivalent-size controlled Si-QDs by employing the nano-porous AAO membrane as the template for growing Si-rich SiOx nano-rods

Recent Advances in Nanoporous Membranes for Water Purification

PubMed Central

Wang, Zhuqing; Colombi Ciacchi, Lucio

2018-01-01

Nanoporous materials exhibit wide applications in the fields of electrocatalysis, nanodevice fabrication, energy, and environmental science, as well as analytical science. In this review, we present a summary of recent studies on nanoporous membranes for water purification application. The types and fabrication strategies of various nanoporous membranes are first introduced, and then the fabricated nanoporous membranes for removing various water pollutants, such as salt, metallic ions, anions, nanoparticles, organic chemicals, and biological substrates, are demonstrated and discussed. This work will be valuable for readers to understand the design and fabrication of various nanoporous membranes, and their potential purification mechanisms towards different water pollutants. In addition, it will be helpful for developing new nanoporous materials for quick, economic, and high-performance water purification. PMID:29370128

Nanoporous cerium oxide thin film for glucose biosensor.

PubMed

Saha, Shibu; Arya, Sunil K; Singh, S P; Sreenivas, K; Malhotra, B D; Gupta, Vinay

2009-03-15

Nanoporous cerium oxide (CeO(2)) thin film deposited onto platinum (Pt) coated glass plate using pulsed laser deposition (PLD) has been utilized for immobilization of glucose oxidase (GOx). Atomic force microscopy studies reveal the formation of nanoporous surface morphology of CeO(2) thin film. Response studies carried out using differential pulsed voltammetry (DPV) and optical measurements show that the GOx/CeO(2)/Pt bio-electrode shows linearity in the range of 25-300 mg/dl of glucose concentration. The low value of Michaelis-Menten constant (1.01 mM) indicates enhanced enzyme affinity of GOx to glucose. The observed results show promising application of the nanoporous CeO(2) thin film for glucose sensing application without any surface functionalization or mediator.

Directing Reaction Pathways through Controlled Reactant Binding at Pd-TiO2 Interfaces.

PubMed

Zhang, Jing; Wang, Bingwen; Nikolla, Eranda; Medlin, J Will

2017-06-01

Recent efforts to design selective catalysts for multi-step reactions, such as hydrodeoxygenation (HDO), have emphasized the preparation of active sites at the interface between two materials having different properties. However, achieving precise control over interfacial properties, and thus reaction selectivity, has remained a challenge. Here, we encapsulated Pd nanoparticles (NPs) with TiO 2 films of regulated porosity to gain a new level of control over catalyst performance, resulting in essentially 100 % HDO selectivity for two biomass-derived alcohols. This catalyst also showed exceptional reaction specificity in HDO of furfural and m-cresol. In addition to improving HDO activity by maximizing the interfacial contact between the metal and metal oxide sites, encapsulation by the nanoporous oxide film provided a significant selectivity boost by restricting the accessible conformations of aromatics on the surface. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Quantitative Phase Composition of TiO 2-Coated Nanoporous-Au Monoliths by X-ray Absorption Spectroscopy and Correlations to Catalytic

DOE PAGES

Bagge-Hansen, Michael; Wichmann, Andre; Wittstock, Arne; ...

2014-02-03

Porous titania/metal composite materials have many potential applications in the fields of green catalysis, energy harvesting, and storage in which both the overall morphology of the nanoporous host material and the crystallographic phase of the titania (TiO 2) guest determine the material’s performance. New insights into the structure–function relationships of these materials were obtained by near-edge X-ray absorption fine structure (NEXAFS) spectroscopy that, for example, provides quantitative crystallographic phase composition from ultrathin, nanostructured titania films, including sensitivity to amorphous components. We demonstrate that crystallographic phase, morphology, and catalytic activity of TiO 2-functionalized nanoporous gold (np-Au) can be controlled by amore » simple annealing procedure (T < 1300 K). The material was prepared by atomic layer deposition of ~2 nm thick TiO 2 on millimeter-sized samples of np-Au (40–50 nm mean ligament size) and catalytically investigated with respect to aerobic CO oxidation. Moreover, the annealing-induced changes in catalytic activity are correlated with concurrent morphology and phase changes as provided by cross-sectional scanning electron microscopy, transmission electron microscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.« less

A New Approach to the Computer Modeling of Amorphous Nanoporous Structures of Semiconducting and Metallic Materials: A Review

PubMed Central

Romero, Cristina; Noyola, Juan C.; Santiago, Ulises; Valladares, Renela M.; Valladares, Alexander; Valladares, Ariel A.

2010-01-01

We review our approach to the generation of nanoporous materials, both semiconducting and metallic, which leads to the existence of nanopores within the bulk structure. This method, which we have named as the expanding lattice method, is a novel transferable approach which consists first of constructing crystalline supercells with a large number of atoms and a density close to the real value and then lowering the density by increasing the volume. The resulting supercells are subjected to either ab initio or parameterized—Tersoff-based—molecular dynamics processes at various temperatures, all below the corresponding bulk melting points, followed by geometry relaxations. The resulting samples are essentially amorphous and display pores along some of the “crystallographic” directions without the need of incorporating ad hoc semiconducting atomic structural elements such as graphene-like sheets and/or chain-like patterns (reconstructive simulations) or of reproducing the experimental processes (mimetic simulations). We report radial (pair) distribution functions, nanoporous structures of C and Si, and some computational predictions for their vibrational density of states. We present numerical estimates and discuss possible applications of semiconducting materials for hydrogen storage in potential fuel tanks. Nanopore structures for metallic elements like Al and Au also obtained through the expanding lattice method are reported.

Nanopore thin film enabled optical platform for drug loading and release.

PubMed

Song, Chao; Che, Xiangchen; Que, Long

2017-08-07

In this paper, a drug loading and release device fabricated using nanopore thin film and layer-by-layer (LbL) nanoassembly is reported. The nanopore thin film is a layer of anodic aluminum oxide (AAO), consisting of honeycomb-shape nanopores. Using the LbL nanoassembly process, the drug, using gentamicin sulfate (GS) as the model, can be loaded into the nanopores and the stacked layers on the nanopore thin film surface. The drug release from the device is achieved by immersing it into flowing DI water. Both the loading and release processes can be monitored optically. The effect of the nanopore size/volume on drug loading and release has also been evaluated. Further, the neuron cells have been cultured and can grow normally on the nanopore thin film, verifying its bio-compatibility. The successful fabrication of nanopore thin film device on silicon membrane render it as a potential implantable controlled drug release device.

Design and fabrication of Ni nanowires having periodically hollow nanostructures

NASA Astrophysics Data System (ADS)

Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2014-09-01

We propose a concept for the design and fabrication of metal nanowires having periodically hollow nanostructures inside the pores of an anodic aluminum oxide (AAO) membrane using a sacrificial metal. In this study, nickel (Ni) and silver (Ag) were used as the base metal and the sacrificial metal, respectively. Alternating an applied potential between -0.4 and -1.0 V provided alternatively deposited Ni and Ag segments in a Ni-Ag `barcode' nanowire with a diameter of 18 or 35 nm. After etching away the Ag segments, we fabricated Ni nanowires with nanopores of 12 +/- 5.3 nm. Such nanostructure formation is explained by the formation of a Ni shell layer over the surface of the Ag segments due to the strong affinity of Ni2+ for the interior surfaces of AAO. The Ni shell layer allows the Ni segments to remain even after dissolution of the Ag segments. Because the electroplating conditions can be easily controlled, we could carefully adjust the size and pitch of the periodically hollow nanospaces. We also describe a method for the fabrication of Ni nanorods by forming an Ag shell instead of a Ni shell on the Ni-Ag barcode nanowire, in which the interior of the AAO surfaces was modified with a compound bearing a thiol group prior to electroplating.We propose a concept for the design and fabrication of metal nanowires having periodically hollow nanostructures inside the pores of an anodic aluminum oxide (AAO) membrane using a sacrificial metal. In this study, nickel (Ni) and silver (Ag) were used as the base metal and the sacrificial metal, respectively. Alternating an applied potential between -0.4 and -1.0 V provided alternatively deposited Ni and Ag segments in a Ni-Ag `barcode' nanowire with a diameter of 18 or 35 nm. After etching away the Ag segments, we fabricated Ni nanowires with nanopores of 12 +/- 5.3 nm. Such nanostructure formation is explained by the formation of a Ni shell layer over the surface of the Ag segments due to the strong affinity of Ni2+ for the interior surfaces of AAO. The Ni shell layer allows the Ni segments to remain even after dissolution of the Ag segments. Because the electroplating conditions can be easily controlled, we could carefully adjust the size and pitch of the periodically hollow nanospaces. We also describe a method for the fabrication of Ni nanorods by forming an Ag shell instead of a Ni shell on the Ni-Ag barcode nanowire, in which the interior of the AAO surfaces was modified with a compound bearing a thiol group prior to electroplating. Electronic supplementary information (ESI) available: Information on the current profile during pulsed-electroplating, the histogram for the Ni and nanopores, and STEM images of obtained nanowires. See DOI: 10.1039/c4nr02625j

Simultaneous Size Control of Microcapsule and Its Nanopores Using Polymer Concentration

NASA Astrophysics Data System (ADS)

Cha, Jemyung; Jeong, Eun Ho; Takahiro, Arakawa; Kim, Kyung Chun; Shoji, Shuich; Go, Jeung Sang

2010-03-01

Polymeric microcapsules with nanopores are produced using the droplet-based self-assembly of a block copolymer in the microfluidic channel. Differently from the conventional wise, the sizes of the microcapsule and its nanopores are controlled by changing the concentration of the block copolymer dissolved in an organic solvent. The increase in the polymer concentration shows the increase in the size of the microcapsule and the decrease of the size and number of the nanopores. Also, to obtain the optimal morphology of the nanopores in the microcapsule, the removal process of a surfactant is newly developed by using a microporous metal mesh.

Synthesis of copper oxide nanowires and nanoporous copper via environmentally friendly transformation of bulk copper-calcium alloys.

PubMed

Zhang, X; Turcheniuk, K; Zusmann, B; Benson, J; Nelson, S; Luo, S; Magasinski, A; Yushin, G

2018-05-24

In this work, we report a novel, one-step, inexpensive and environmentally friendly synthesis of Cu nanostructures by means of chemical de-alloying of bulk Cu-Ca alloys in aqueous solutions. By controlling the synthesis conditions, we tune the morphology of the nanostructured Cu from nanoporous Cu to copper oxide nanowires.

Nanoporous frameworks exhibiting multiple stimuli responsiveness

NASA Astrophysics Data System (ADS)

Kundu, Pintu K.; Olsen, Gregory L.; Kiss, Vladimir; Klajn, Rafal

2014-04-01

Nanoporous frameworks are polymeric materials built from rigid molecules, which give rise to their nanoporous structures with applications in gas sorption and storage, catalysis and others. Conceptually new applications could emerge, should these beneficial properties be manipulated by external stimuli in a reversible manner. One approach to render nanoporous frameworks responsive to external signals would be to immobilize molecular switches within their nanopores. Although the majority of molecular switches require conformational freedom to isomerize, and switching in the solid state is prohibited, the nanopores may provide enough room for the switches to efficiently isomerize. Here we describe two families of nanoporous materials incorporating the spiropyran molecular switch. These materials exhibit a variety of interesting properties, including reversible photochromism and acidochromism under solvent-free conditions, light-controlled capture and release of metal ions, as well reversible chromism induced by solvation/desolvation.

Photoswitchable nanoporous films by loading azobenzene in metal-organic frameworks of type HKUST-1.

PubMed

Müller, Kai; Wadhwa, Jasmine; Singh Malhi, Jasleen; Schöttner, Ludger; Welle, Alexander; Schwartz, Heidi; Hermann, Daniela; Ruschewitz, Uwe; Heinke, Lars

2017-07-13

Photoswitchable metal-organic frameworks (MOFs) enable the dynamic remote control of their key properties. Here, a readily producible approach is presented where photochromic molecules, i.e. azobenzene (AB) and o-tetrafluoroazobenzene (tfAB), are loaded in MOF films of type HKUST-1. These nanoporous films, which can be reversibly switched with UV/visible or only visible light, have remote-controllable guest uptake properties.

Single Molecule Sensing by Nanopores and Nanopore Devices

PubMed Central

Gu, Li-Qun; Shim, Ji Wook

2010-01-01

Molecular-scale pore structures, called nanopores, can be assembled by protein ion channels through genetic engineering or be artificially fabricated on solid substrates using fashion nanotechnology. When target molecules interact with the functionalized lumen of a nanopore, they characteristically block the ion pathway. The resulting conductance changes allow for identification of single molecules and quantification of target species in the mixture. In this review, we first overview nanopore-based sensory techniques that have been created for the detection of myriad biomedical targets, from metal ions, drug compounds, and cellular second messengers to proteins and DNA. Then we introduce our recent discoveries in nanopore single molecule detection: (1) using the protein nanopore to study folding/unfolding of the G-quadruplex aptamer; (2) creating a portable and durable biochip that is integrated with a single-protein pore sensor (this chip is compared with recently developed protein pore sensors based on stabilized bilayers on glass nanopore membranes and droplet interface bilayer); and (3) creating a glass nanopore-terminated probe for single-molecule DNA detection, chiral enantiomer discrimination, and identification of the bioterrorist agent ricin with an aptamer-encoded nanopore. PMID:20174694

Use of steric encumbrance to develop conjugated nanoporous polymers for metal-free catalytic hydrogenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Chengcheng; Zhu, Xiang; Abney, Carter W.

The design and synthesis of metal-free heterogeneous catalysts for efficient hydrogenation remains a great challenge. Here we report a novel approach to create conjugated nanoporous polymers with efficient hydrogenation activities toward unsaturated ketones by leveraging the innate steric encumbrance. The steric bulk of the framework as well as the local sterics of the Lewis basic sites within the polymeric skeleton result in the generation of the putative catalyst. This approach opens up new possibilities for the development of innovative metal-free heterogeneous catalysts.

Use of steric encumbrance to develop conjugated nanoporous polymers for metal-free catalytic hydrogenation

DOE PAGES

Tian, Chengcheng; Zhu, Xiang; Abney, Carter W.; ...

2016-09-08

The design and synthesis of metal-free heterogeneous catalysts for efficient hydrogenation remains a great challenge. Here we report a novel approach to create conjugated nanoporous polymers with efficient hydrogenation activities toward unsaturated ketones by leveraging the innate steric encumbrance. The steric bulk of the framework as well as the local sterics of the Lewis basic sites within the polymeric skeleton result in the generation of the putative catalyst. Lastly, this approach opens up new possibilities for the development of innovative metal-free heterogeneous catalysts.

Use of steric encumbrance to develop conjugated nanoporous polymers for metal-free catalytic hydrogenation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Chengcheng; Zhu, Xiang; Abney, Carter W.

The design and synthesis of metal-free heterogeneous catalysts for efficient hydrogenation remains a great challenge. Here we report a novel approach to create conjugated nanoporous polymers with efficient hydrogenation activities toward unsaturated ketones by leveraging the innate steric encumbrance. The steric bulk of the framework as well as the local sterics of the Lewis basic sites within the polymeric skeleton result in the generation of the putative catalyst. Lastly, this approach opens up new possibilities for the development of innovative metal-free heterogeneous catalysts.

Helium in inert matrix dispersion fuels

NASA Astrophysics Data System (ADS)

van Veen, A.; Konings, R. J. M.; Fedorov, A. V.

2003-07-01

The behaviour of helium, an important decay product in the transmutation chains of actinides, in dispersion-type inert matrix fuels is discussed. A phenomenological description of its accumulation and release in CERCER and CERMET fuel is given. A summary of recent He-implantation studies with inert matrix metal oxides (ZrO 2, MgAl 2O 4, MgO and Al 2O 3) is presented. A general picture is that for high helium concentrations helium and vacancy defects form helium clusters which convert into over-pressurized bubbles. At elevated temperature helium is released from the bubbles. On some occasions thermal stable nano-cavities or nano-pores remain. On the basis of these results the consequences for helium induced swelling and helium storage in oxide matrices kept at 800-1000 °C will be discussed. In addition, results of He-implantation studies for metal matrices (W, Mo, Nb and V alloys) will be presented. Introduction of helium in metals at elevated temperatures leads to clustering of helium to bubbles. When operational temperatures are higher than 0.5 melting temperature, swelling and helium embrittlement might occur.

High performance SERS on nanoporous gold substrates synthesized by chemical de-alloying a Au-based metallic glass

NASA Astrophysics Data System (ADS)

Xue, Yanpeng; Scaglione, Federico; Rizzi, Paola; Battezzati, Livio

2017-12-01

A Au20Cu48Ag7Pd5Si20 metallic glass precursor has been used to synthesize nanoporous gold by chemical de-alloying in a mixture of HNO3 and HF. Gold ligaments of size ranging from 45 to 100 nm were obtained as a function of HNO3 concentration, electrolyte temperature and de-alloying time. The as-prepared nanoporous gold exhibited strong surface enhanced Raman scattering (SERS) effect using 4,4‧-bi-pyridine as probe molecule. For application in melamine sensing, the detection limit of 10-6 M was achieved, which indicated that this biocompatible material has great potential as SERS active substrate.

Photoluminescence emission of nanoporous anodic aluminum oxide films prepared in phosphoric acid

PubMed Central

2012-01-01

The photoluminescence emission of nanoporous anodic aluminum oxide films formed in phosphoric acid is studied in order to explore their defect-based subband electronic structure. Different excitation wavelengths are used to identify most of the details of the subband states. The films are produced under different anodizing conditions to optimize their emission in the visible range. Scanning electron microscopy investigations confirm pore formation in the produced layers. Gaussian analysis of the emission data indicates that subband states change with anodizing parameters, and various point defects can be formed both in the bulk and on the surface of these nanoporous layers during anodizing. PMID:23272786

High-volumetric performance aligned nano-porous microwave exfoliated graphite oxide-based electrochemical capacitors.

PubMed

Ghaffari, Mehdi; Zhou, Yue; Xu, Haiping; Lin, Minren; Kim, Tae Young; Ruoff, Rodney S; Zhang, Q M

2013-09-20

Ultra-high volumetric performance electrochemical double layer capacitors based on high density aligned nano-porous microwave exfoliated graphite oxide have been studied. Elimination of macro-, meso-, and larger micro-pores from electrodes and controlling the nano-morphology results in very high volumetric capacitance, energy, and power density values. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-grown oxy-hydroxide@ nanoporous metal electrode for high-performance supercapacitors.

PubMed

Kang, JianLi; Hirata, Akihiko; Qiu, H-J; Chen, LuYang; Ge, XingBo; Fujita, Takeshi; Chen, MingWei

2014-01-15

A binder-free self-grown oxy-hydroxide@nanoporous Ni-Mn hybrid electrode with high capacitance and cyclic stability is fabricated by electrochemical polarization of a dealloyed nanoporous Ni-Mn alloy. Combined with the low material costs, high electrochemical stability, and environmentally friendly nature, this novel electrode holds great promise for applications in high-capacity commercial supercapacitors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultrafine nanoporous palladium-aluminum film fabricated by citric acid-assisted hot-water-treatment of aluminum-palladium alloy film

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harumoto, Takashi; Tamura, Yohei; Ishiguro, Takashi, E-mail: ishiguro@rs.noda.tus.ac.jp

Hot-water-treatment has been adapted to fabricate ultrafine nanoporous palladium-aluminum film from aluminum-palladium alloy film. Using citric acid as a chelating agent, a precipitation of boehmite (aluminum oxide hydroxide, AlOOH) on the nanoporous palladium-aluminum film was suppressed. According to cross-sectional scanning transmission electron microscopy observations, the ligament/pore sizes of the prepared nanoporous film were considerably small (on the order of 10 nm). Since this fabrication method only requires aluminum alloy film and hot-water with chelating agent, the ultrafine nanoporous film can be prepared simply and environmentally friendly.

Fabrication of nano-engineered transparent conducting oxides by pulsed laser deposition.

PubMed

Gondoni, Paolo; Ghidelli, Matteo; Di Fonzo, Fabio; Li Bassi, Andrea; Casari, Carlo S

2013-02-27

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O₂ pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (>80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO₂, Al₂O₃, WO₃ and Ag₄O₄.

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

PubMed Central

Gondoni, Paolo; Ghidelli, Matteo; Di Fonzo, Fabio; Li Bassi, Andrea; Casari, Carlo S.

2013-01-01

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (>80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4. PMID:23486076

Nanotubular surface modification of metallic implants via electrochemical anodization technique.

PubMed

Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

2014-01-01

Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility.

Nanotubular surface modification of metallic implants via electrochemical anodization technique

PubMed Central

Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

2014-01-01

Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility. PMID:25258532

Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism.

PubMed

Ali, Mubarak; Ramirez, Patricio; Duznovic, Ivana; Nasir, Saima; Mafe, Salvador; Ensinger, Wolfgang

2017-02-01

We design and characterize a nanofluidic device for the label-free specific detection of histamine neurotransmitter based on a metal ion displacement mechanism. The sensor consists of an asymmetric polymer nanopore fabricated via ion track-etching technique. The nanopore sensor surface having metal-nitrilotriacetic (NTA-Ni 2+ ) chelates is obtained by covalent coupling of native carboxylic acid groups with N α ,N α -bis(carboxymethyl)-l-lysine (BCML), followed by exposure to Ni 2+ ion solution. The BCML immobilization and subsequent Ni 2+ ion complexation with NTA moieties change the surface charge concentration, which has a significant impact on the current-voltage (I-V) curve after chemical modification of the nanopore. The sensing mechanism is based on the displacement of the metal ion from the NTA-Ni 2+ chelates. When the modified pore is exposed to histamine solution, the Ni 2+ ion in NTA-Ni 2+ chelate recognizes histamine through a metal ion coordination displacement process and formation of stable Ni-histamine complexes, leading to the regeneration of metal-free NTA groups on the pore surface, as shown in the current-voltage characteristics. Nanomolar concentrations of the histamine in the working electrolyte can be detected. On the contrary, other neurotransmitters such as glycine, serotonin, gamma-aminobutyric acid, and dopamine do not provoke significant changes in the nanopore electronic signal due to their inability to displace the metal ion and form a stable complex with Ni 2+ ion. The nanofluidic sensor exhibits high sensitivity, specificity and reusability towards histamine detection and can then be used to monitor the concentration of biological important neurotransmitters. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of 3D nanoporous copper-supported cuprous oxide for high-performance lithium ion battery anodes.

PubMed

Liu, Dequan; Yang, Zhibo; Wang, Peng; Li, Fei; Wang, Desheng; He, Deyan

2013-03-07

Three-dimensional (3D) nanoporous architectures can provide efficient and rapid pathways for Li-ion and electron transport as well as short solid-state diffusion lengths in lithium ion batteries (LIBs). In this work, 3D nanoporous copper-supported cuprous oxide was successfully fabricated by low-cost selective etching of an electron-beam melted Cu(50)Al(50) alloy and subsequent in situ thermal oxidation. The architecture was used as an anode in lithium ion batteries. In the first cycle, the sample delivered an extremely high lithium storage capacity of about 2.35 mA h cm(-2). A high reversible capacity of 1.45 mA h cm(-2) was achieved after 120 cycles. This work develops a promising approach to building reliable 3D nanostructured electrodes for high-performance lithium ion batteries.

Extremely durable biofouling-resistant metallic surfaces based on electrodeposited nanoporous tungstite films on steel

PubMed Central

Tesler, Alexander B.; Kim, Philseok; Kolle, Stefan; Howell, Caitlin; Ahanotu, Onye; Aizenberg, Joanna

2015-01-01

Formation of unwanted deposits on steels during their interaction with liquids is an inherent problem that often leads to corrosion, biofouling and results in reduction in durability and function. Here we report a new route to form anti-fouling steel surfaces by electrodeposition of nanoporous tungsten oxide (TO) films. TO-modified steels are as mechanically durable as bare steel and highly tolerant to compressive and tensile stresses due to chemical bonding to the substrate and island-like morphology. When inherently superhydrophilic TO coatings are converted to superhydrophobic, they remain non-wetting even after impingement with yttria-stabilized-zirconia particles, or exposure to ultraviolet light and extreme temperatures. Upon lubrication, these surfaces display omniphobicity against highly contaminating media retaining hitherto unseen mechanical durability. To illustrate the applicability of such a durable coating in biofouling conditions, we modified naval construction steels and surgical instruments and demonstrated significantly reduced marine algal film adhesion, Escherichia coli attachment and blood staining. PMID:26482559

Preparation of Mesoporous Ceramics from Polymer Nanotubes

NASA Astrophysics Data System (ADS)

Chen, Dian; Park, Soojin; Chen, Jiun-Tai; Redston, Emily; Russell, Thomas

2009-03-01

Poly(styrene-b-4-vinylpyridine) (PS-b-P4VP) nanotubes were prepared by placing polymer solution into the cylindrical nanopores of an anodic aluminum oxide (AAO) membrane. The PS-b-P4VP nanotubes within the AAO membranes were exposed to tetrahydrofuran vapor to produce uniform spherical micelles along the tube. The tubes were removed from the membranes, then suspended in ethylene glycol, a preferential solvent for P4VP. At 95^ oC, near the glass transition temperature (Tg) of PS, nanotubes with uniform nanopores were obtained by a reconstruction of the nanotubes. As the temperature was increased, mesoporous polymer structures were obtained. Tetraethyl orthosilicate or titanium tetraethoxide, ceramic precursors, were introduced into the 4VP microdomains. After exposure to an oxygen plasma or high temperature, the copolymer was removed and the precursor converted to a mesoporous ceramic. This process offers a simple route for the fabrication of tunable mesoporous ceramic or metallic structures by changing molecular weight of copolymers.

Extremely durable biofouling-resistant metallic surfaces based on electrodeposited nanoporous tungstite films on steel

NASA Astrophysics Data System (ADS)

Tesler, Alexander B.; Kim, Philseok; Kolle, Stefan; Howell, Caitlin; Ahanotu, Onye; Aizenberg, Joanna

2015-10-01

Formation of unwanted deposits on steels during their interaction with liquids is an inherent problem that often leads to corrosion, biofouling and results in reduction in durability and function. Here we report a new route to form anti-fouling steel surfaces by electrodeposition of nanoporous tungsten oxide (TO) films. TO-modified steels are as mechanically durable as bare steel and highly tolerant to compressive and tensile stresses due to chemical bonding to the substrate and island-like morphology. When inherently superhydrophilic TO coatings are converted to superhydrophobic, they remain non-wetting even after impingement with yttria-stabilized-zirconia particles, or exposure to ultraviolet light and extreme temperatures. Upon lubrication, these surfaces display omniphobicity against highly contaminating media retaining hitherto unseen mechanical durability. To illustrate the applicability of such a durable coating in biofouling conditions, we modified naval construction steels and surgical instruments and demonstrated significantly reduced marine algal film adhesion, Escherichia coli attachment and blood staining.

Extremely durable biofouling-resistant metallic surfaces based on electrodeposited nanoporous tungstite films on steel

DOE PAGES

Tesler, Alexander B.; Kim, Philseok; Kolle, Stefan; ...

2015-10-20

Formation of unwanted deposits on steels during their interaction with liquids is an inherent problem that often leads to corrosion, biofouling and results in reduction in durability and function. Here we report a new route to form anti-fouling steel surfaces by electrodeposition of nanoporous tungsten oxide (TO) films. TO-modified steels are as mechanically durable as bare steel and highly tolerant to compressive and tensile stresses due to chemical bonding to the substrate and island-like morphology. When inherently superhydrophilic TO coatings are converted to superhydrophobic, they remain non-wetting even after impingement with yttria-stabilized-zirconia particles, or exposure to ultraviolet light and extrememore » temperatures. Upon lubrication, these surfaces display omniphobicity against highly contaminating media retaining hitherto unseen mechanical durability. Furthermore, to illustrate the applicability of such a durable coating in biofouling conditions, we modified naval construction steels and surgical instruments and demonstrated significantly reduced marine algal film adhesion, Escherichia coli attachment and blood staining.« less

Periodically Ordered Nanoporous Perovskite Photoelectrode for Efficient Photoelectrochemical Water Splitting.

PubMed

Shi, Li; Zhou, Wei; Li, Zhao; Koul, Supriya; Kushima, Akihiro; Yang, Yang

2018-06-18

Nonmetallic materials with localized surface plasmon resonance (LSPR) have a great potential for solar energy harvesting applications. Exploring nonmetallic plasmonic materials is desirable yet challenging. Herein, an efficient nonmetallic plasmonic perovskite photoelectrode, namely, SrTiO 3 , with a periodically ordered nanoporous structure showing an intense LSPR in the visible light region is reported. The crystalline-core@amorphous-shell structure of the SrTiO 3 photoelectrode enables a strong LSPR due to the high charge carrier density induced by oxygen vacancies in the amorphous shell. The reversible tunability in LSPR of the SrTiO 3 photoelectrode was observed by oxidation/reduction treatment and incident angle adjusting. Such a nonmetallic plasmonic SrTiO 3 photoelectrode displays a dramatic plasmon-enhanced photoelectrochemical water splitting performance with a photocurrent density of 170.0 μA cm -2 under visible light illumination and a maximum incident photon-to-current-conversion efficiency of 4.0% in the visible light region, which are comparable to the state-of-the-art plasmonic noble metal sensitized photoelectrodes.

Nanoporous Ni(OH)2 thin film on 3D Ultrathin-graphite foam for asymmetric supercapacitor.

PubMed

Ji, Junyi; Zhang, Li Li; Ji, Hengxing; Li, Yang; Zhao, Xin; Bai, Xin; Fan, Xiaobin; Zhang, Fengbao; Ruoff, Rodney S

2013-07-23

Nanoporous nickel hydroxide (Ni(OH)2) thin film was grown on the surface of ultrathin-graphite foam (UGF) via a hydrothermal reaction. The resulting free-standing Ni(OH)2/UGF composite was used as the electrode in a supercapacitor without the need for addition of either binder or metal-based current collector. The highly conductive 3D UGF network facilitates electron transport and the porous Ni(OH)2 thin film structure shortens ion diffusion paths and facilitates the rapid migration of electrolyte ions. An asymmetric supercapacitor was also made and studied with Ni(OH)2/UGF as the positive electrode and activated microwave exfoliated graphite oxide ('a-MEGO') as the negative electrode. The highest power density of the fully packaged asymmetric cell (44.0 kW/kg) was much higher (2-27 times higher), while the energy density was comparable to or higher, than high-end commercially available supercapacitors. This asymmetric supercapacitor had a capacitance retention of 63.2% after 10,000 cycles.

A nanoporous titanium surface promotes the maturation of focal adhesions and formation of filopodia with distinctive nanoscale protrusions by osteogenic cells.

PubMed

Guadarrama Bello, Dainelys; Fouillen, Aurélien; Badia, Antonella; Nanci, Antonio

2017-09-15

While topography is a key determinant of the cellular response to biomaterials, the mechanisms implicated in the cell-surface interactions are complex and still not fully elucidated. In this context, we have examined the effect of nanoscale topography on the formation of filopodia, focal adhesions, and gene expression of proteins associated with cell adhesion and sensing. Commercially pure titanium discs were treated by oxidative nanopatterning with a solution of H 2 SO 4 /H 2 O 2 50:50 (v/v). Scanning electron microscopy and atomic force microscopy characterizations showed that this facile chemical treatment efficiently creates a unique nanoporous surface with a root-mean-square roughness of 11.5nm and pore diameter of 20±5nm. Osteogenic cells were cultured on polished (control) and nanotextured discs for periods of 6, 24, and 72h. Immunofluorescence analysis revealed increases in the adhesion formation per cell area, focal adhesion length, and maturity on the nanoporous surface. Gene expression for various focal adhesion markers, including paxillin and talin, and different integrins (e.g. α1, β1, and α5) was also significantly increased. Scanning electron microscopy revealed the presence of more filopodia on cells grown on the nanoporous surface. These cell extensions displayed abundant and distinctive nanoscale lateral protrusions of 10-15nm diameter that molded the nanopore walls. Together the increase in the focal adhesions and abundance of filopodia and associated protrusions could contribute to strengthening the adhesive interaction of cells with the surface, and thereby, alter the nanoscale biomechanical relationships that trigger cellular cascades that regulate cell behavior. Oxidative patterning was exploited to create a unique three-dimensional network of nanopores on titanium surfaces. Our study illustrates how a facile chemical treatment can be advantageously used to modulate cellular behavior. The nanoscale lateral protrusions on filopodia elicited by this surface are novel adhesive structures. Altogether, the increases in focal adhesion, length, maturity, and filopodia with distinctive lateral protrusions could substantially increase the contact area and adhesion strength of cells, thereby promoting the activation of cellular signaling cascades that may explain the positive osteogenic outcomes previously achieved with this surface. Such physicochemical cueing offers a simple attractive alternative to the use of bioactive agents for guiding tissue repair/regeneration around implantable metals. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Formation, Characteristics and Electrocatalytic Properties of Nanoporous Metals Formed by Dealloying of Ternary-Noble Alloys

NASA Astrophysics Data System (ADS)

Vega Zuniga, Adrian A.

Nanoporous metals formed by electrochemical dealloying of silver from Ag-Au-Pt alloys, with 77 at.% silver and platinum contents of 1, 2 and 3 at.%, have been studied. The presence of platinum, which is immobile relative to gold, refine the ligament size and stabilized the nanostructure against coarsening, even under experimental conditions that would be expected to promote coarsening (e.g., exposure to high temperature, longer dealloying times). By adding only 1 at.% Pt to the alloy precursor, the ligament/pore size was reduced by 50% with respect to that in nanoporous gold (NPG), which was formed on a Ag-Au alloy with the same silver content as ternary alloys. A further decrease in the ligament size was observed by increasing the platinum content of the precursor; however, most of the improvement occurred with 1 at.% Pt. The adsorbate-induced surface segregation of platinum was also investigated for these nanoporous metals. By exposing freshly-dealloyed nanostructures to moderate temperatures in the presence of air, platinum segregated to the ligament surface; in contrast, in an inert atmosphere (Ar-H 2), platinum mostly reverted to the bulk of the ligaments. This thermally activated process was thermodynamically driven by the interaction between platinum and oxygen; however, at the desorption temperature of oxygen, platinum de-segregated from the surface. Moreover, the co-segregation of platinum and oxygen hindered the thermal coarsening of the ligaments. Finally, the electrocatalytic abilities of these nanostructures were studied towards methanol and ethanol electro-oxidation, in alkaline and acidic media, showing significantly improved response in comparison to that observed in NPG. The synergistic effect between gold and platinum atoms and the smaller feature size of the nanostructures were directly associated with this behaviour. In alkaline electrolyte, the nanostructure formed on the alloy with 1 at.% Pt showed higher catalytic response than the other two ternary nanostructures, which could be associated with the platinum/gold ratio on the surface of the structure. In acidic electrolyte, the nanostructure with the highest platinum content displayed the highest electrocatalytic response. Furthermore, the presence of platinum changed the selectivity of both reactions: the concentrations of carbonate produced increased by increasing the platinum content in the alloy precursor.

Nanoporous nickel microspheres: synthesis and application for the electrocatalytic oxidation and determination of acyclovir.

PubMed

Heli, Hossein; Pourbahman, Fatemeh; Sattarahmady, Naghmeh

2012-01-01

Nickel microspheres were synthesized via a water-in-oil reverse nanoemulsion system using nickel nitrate as the nickel precursor and hydrazine hydrate as the reducing agent. The nanoemulsion was a triton X-100/cyclohexane/water ternary system. The surface morphology of the nickel microspheres was studied by scanning electron microscopy, which indicated that the microspheres had a nanoporous structure. The electrochemical behavior of the nanoporous nickel microspheres were studied in alkaline solution and were then employed to fabricate a modified carbon paste electrode in order to investigate the electrocatalytic oxidation of the drug acyclovir. The oxidation process involved, and its kinetics were investigated using cyclic voltammetry and chronoamperometry. The rate constant of the catalytic oxidation of acyclovir and the electron-transfer coefficient are reported. A sensitive, simple and time-saving amperometric procedure was developed for the analysis of acyclovir. The proposed amperometric method was also applied to determine acyclovir in tablets and topical cream.

Surface Modifications of Materials by Electrochemical Methods to Improve the Properties for Industrial and Medical Applications

NASA Astrophysics Data System (ADS)

Benea, Lidia

2018-06-01

There are two applied electrochemical methods in our group in order to obtain advanced functional surfaces on materials: (i) direct electrochemical synthesis by electro-codeposition process and (ii) anodization of materials to form nanoporous oxide layers followed by electrodeposition of hydroxyapatite or other bioactive molecules and compounds into porous film. Electrodeposition is a process of low energy consumption, and therefore very convenient for the surface modification of various types of materials. Electrodeposition is a powerful method compared with other methods, which led her to be adopted and spread rapidly in nanotechnology to obtain nanostructured layers and films. Nanoporous thin oxide layers on titanum alloys as support for hydroxyapatite or other biomolecules electrodeposition in view of biomedical applications could be obtained by electrochemical methods. For surface modification of titanium or titanium alloys to improve the biocompatibility or osseointegration, the two steps must be fulfilled; the first is controlled growth of oxide layer followed by second being biomolecule electrodeposition into nanoporous formed titanium oxide layer.

Biomimetic novel nanoporous niobium oxide coating for orthopaedic applications

NASA Astrophysics Data System (ADS)

Pauline, S. Anne; Rajendran, N.

2014-01-01

Niobium oxide was synthesized by sol-gel methodology and a crystalline, nanoporous and adherent coating of Nb2O5 was deposited on 316L SS using the spin coating technique and heat treatment. The synthesis conditions were optimized to obtain a nanoporous morphology. The coating was characterized using attenuated total reflectance-Infrared spectroscopy (ATR-IR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), atomic force microscopy (AFM) and transmission electron microscopy (TEM) and the formation of crystalline Nb2O5 coating with nanoporous morphology was confirmed. Mechanical studies confirmed that the coating has excellent adherence to the substrate and the hardness value of the coating was excellent. Contact angle analysis showed increased hydrophilicity for the coated substrate. In vitro bioactivity test confirmed that the Nb2O5 coating with nanoporous morphology facilitated the growth of hydroxyapatite (HAp). This was further confirmed by the solution analysis test where increased uptake of calcium and phosphorous ions from simulated body fluid (SBF) was observed. Electrochemical evaluation of the coating confirmed that the crystalline coating is insulative and protective in nature and offered excellent corrosion protection to 316L SS. Thus, this study confirmed that the nanoporous crystalline Nb2O5 coating conferred bioactivity and enhanced corrosion resistance on 316L SS.

Aptamer-Encoded Nanopore for Ultrasensitive Detection of Bioterrorist Agent Ricin at Single-Molecule Resolution

PubMed Central

Gu, Li-Qun; Ding, Shu; Gao, Changlu

2011-01-01

The molecular-scale pore structure, called nanopore, can be formed from protein ion channels by genetic engineering or fabricated on solid substrates using fashion nanotechnology. Target molecules in interaction with the functionalized lumen of nanopore, can produce characteristic changes in the pore conductance, which act as fingerprints, allowing us to identify single molecules and simultaneously quantify each target species in the mixture. Nanopore sensors have been created for tremendous biomedical detections, with targets ranging from metal ions, drug compounds and cellular second messengers, to proteins and DNAs. Here we will review our recent discoveries with a lab-in-hand glass nanopore: single-molecule discrimination of chiral enantiomers with a trapped cyclodextrin, and sensing of bioterrorist agent ricin. PMID:19964179

Integrating Sub-3 nm Plasmonic Gaps into Solid-State Nanopores.

PubMed

Shi, Xin; Verschueren, Daniel; Pud, Sergii; Dekker, Cees

2018-05-01

Plasmonic nanopores combine the advantages of nanopore sensing and surface plasmon resonances by introducing confined electromagnetic fields to a solid-state nanopore. Ultrasmall nanogaps between metallic nanoantennas can generate the extremely enhanced localized electromagnetic fields necessary for single-molecule optical sensing and manipulation. Challenges in fabrication, however, hamper the integration of such nanogaps into nanopores. Here, a top-down approach for integrating a plasmonic antenna with an ultrasmall nanogap into a solid-state nanopore is reported. Employing a two-step e-beam lithography process, the reproducible fabrication of nanogaps down to a sub-1 nm scale is demonstrated. Subsequently, nanopores are drilled through the 20 nm SiN membrane at the center of the nanogap using focused-electron-beam sculpting with a transmission electron microscope, at the expense of a slight gap expansion for the smallest gaps. Using this approach, sub-3 nm nanogaps can be readily fabricated on solid-state nanopores. The functionality of these plasmonic nanopores for single-molecule detection is shown by performing DNA translocations. These integrated devices can generate intense electromagnetic fields at the entrance of the nanopore and can be expected to find applications in nanopore-based single-molecule trapping and optical sensing. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrochemical pore filling strategy for controlled growth of magnetic and metallic nanowire arrays with large area uniformity

NASA Astrophysics Data System (ADS)

Arefpour, M.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

2016-07-01

While a variety of template-based strategies have been developed in the fabrication of nanowires (NWs), a uniform pore filling across the template still poses a major challenge. Here, we present a large area controlled pore filling strategy in the reproducible fabrication of various magnetic and metallic NW arrays, embedded inside anodic aluminum oxide templates. Using a diffusive pulsed electrodeposition (DPED) technique, this versatile strategy relies on the optimized filling of branched nanopores at the bottom of templates with Cu. Serving the Cu filled nanopores as appropriate nucleation sites, the DPED is followed by a uniform and homogeneous deposition of magnetic (Ni and Fe) and metallic (Cu and Zn) NWs at a current density of 50 mA cm-2 for an optimal thickness of alumina barrier layer (˜18 nm). Our strategy provides large area uniformity (exceeding 400 μm2) in the fabrication of 16 μm long free-standing NW arrays. Using hysteresis loop measurements and scanning electron microscopy images, the electrodeposition efficiency (EE) and pore filling percentage (F p) are evaluated, leading to maximum EE and F p values of 91% and 95% for Ni and Zn, respectively. Moreover, the resulting NW arrays are found to be highly crystalline. Accordingly, the DPED technique is capable of cheaply and efficiently controlling NW growth over a large area, providing a tool for various nanoscale applications including biomedical devices, electronics, photonics, magnetic storage medium and nanomagnet computing.

Electrochemical pore filling strategy for controlled growth of magnetic and metallic nanowire arrays with large area uniformity.

PubMed

Arefpour, M; Kashi, M Almasi; Ramazani, A; Montazer, A H

2016-06-01

While a variety of template-based strategies have been developed in the fabrication of nanowires (NWs), a uniform pore filling across the template still poses a major challenge. Here, we present a large area controlled pore filling strategy in the reproducible fabrication of various magnetic and metallic NW arrays, embedded inside anodic aluminum oxide templates. Using a diffusive pulsed electrodeposition (DPED) technique, this versatile strategy relies on the optimized filling of branched nanopores at the bottom of templates with Cu. Serving the Cu filled nanopores as appropriate nucleation sites, the DPED is followed by a uniform and homogeneous deposition of magnetic (Ni and Fe) and metallic (Cu and Zn) NWs at a current density of 50 mA cm -2 for an optimal thickness of alumina barrier layer (∼18 nm). Our strategy provides large area uniformity (exceeding 400 μm 2 ) in the fabrication of 16 μm long free-standing NW arrays. Using hysteresis loop measurements and scanning electron microscopy images, the electrodeposition efficiency (EE) and pore filling percentage (F p ) are evaluated, leading to maximum EE and F p values of 91% and 95% for Ni and Zn, respectively. Moreover, the resulting NW arrays are found to be highly crystalline. Accordingly, the DPED technique is capable of cheaply and efficiently controlling NW growth over a large area, providing a tool for various nanoscale applications including biomedical devices, electronics, photonics, magnetic storage medium and nanomagnet computing.

Laser Hybrid Fabrication of Nanoporous Structures on Metallic Material Surface

DTIC Science & Technology

2009-06-01

Research Center, Department of Mechanical Engineering,Beijing, 100084&# 65292 ;China, 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING...rials, 2005, 15: 989-994. [9]Jia F, Yu C, Ai Z, et al. Fabrication of nanoporous gold film electrodes with ultrahigh surface area and electro

One-step synthesis of zero-dimensional hollow nanoporous gold nanoparticles with enhanced methanol electrooxidation performance.

PubMed

Pedireddy, Srikanth; Lee, Hiang Kwee; Tjiu, Weng Weei; Phang, In Yee; Tan, Hui Ru; Chua, Shu Quan; Troadec, Cedric; Ling, Xing Yi

2014-09-17

Nanoporous gold with networks of interconnected ligaments and highly porous structure holds stimulating technological implications in fuel cell catalysis. Current syntheses of nanoporous gold mainly revolve around de-alloying approaches that are generally limited by stringent and harsh multistep protocols. Here we develop a one-step solution phase synthesis of zero-dimensional hollow nanoporous gold nanoparticles with tunable particle size (150-1,000 nm) and ligament thickness (21-54 nm). With faster mass diffusivity, excellent specific electroactive surface area and large density of highly active surface sites, our zero-dimensional nanoporous gold nanoparticles exhibit ~1.4 times enhanced catalytic activity and improved tolerance towards carbonaceous species, demonstrating their superiority over conventional nanoporous gold sheets. Detailed mechanistic study also reveals the crucial heteroepitaxial growth of gold on the surface of silver chloride templates, implying that our synthetic protocol is generic and may be extended to the synthesis of other nanoporous metals via different templates.

One-step synthesis of zero-dimensional hollow nanoporous gold nanoparticles with enhanced methanol electrooxidation performance

NASA Astrophysics Data System (ADS)

Pedireddy, Srikanth; Lee, Hiang Kwee; Tjiu, Weng Weei; Phang, In Yee; Tan, Hui Ru; Chua, Shu Quan; Troadec, Cedric; Ling, Xing Yi

2014-09-01

Nanoporous gold with networks of interconnected ligaments and highly porous structure holds stimulating technological implications in fuel cell catalysis. Current syntheses of nanoporous gold mainly revolve around de-alloying approaches that are generally limited by stringent and harsh multistep protocols. Here we develop a one-step solution phase synthesis of zero-dimensional hollow nanoporous gold nanoparticles with tunable particle size (150-1,000 nm) and ligament thickness (21-54 nm). With faster mass diffusivity, excellent specific electroactive surface area and large density of highly active surface sites, our zero-dimensional nanoporous gold nanoparticles exhibit ~1.4 times enhanced catalytic activity and improved tolerance towards carbonaceous species, demonstrating their superiority over conventional nanoporous gold sheets. Detailed mechanistic study also reveals the crucial heteroepitaxial growth of gold on the surface of silver chloride templates, implying that our synthetic protocol is generic and may be extended to the synthesis of other nanoporous metals via different templates.

Nanoporous Ni with High Surface Area for Potential Hydrogen Storage Application.

PubMed

Zhou, Xiaocao; Zhao, Haibo; Fu, Zhibing; Qu, Jing; Zhong, Minglong; Yang, Xi; Yi, Yong; Wang, Chaoyang

2018-06-01

Nanoporous metals with considerable specific surface areas and hierarchical pore structures exhibit promising applications in the field of hydrogen storage, electrocatalysis, and fuel cells. In this manuscript, a facile method is demonstrated for fabricating nanoporous Ni with a high surface area by using SiO₂ aerogel as a template, i.e., electroless plating of Ni into an SiO₂ aerogel template followed by removal of the template at moderate conditions. The effects of the prepared conditions, including the electroless plating time, temperature of the structure, and the magnetism of nanoporous Ni are investigated in detail. The resultant optimum nanoporous Ni with a special 3D flower-like structure exhibited a high specific surface area of about 120.5 m²/g. The special nanoporous Ni exhibited a promising prospect in the field of hydrogen storage, with a hydrogen capacity of 0.45 wt % on 4.5 MPa at room temperature.

Leakage conduction behavior in electron-beam-cured nanoporous silicate films

NASA Astrophysics Data System (ADS)

Liu, Po-Tsun; Tsai, T. M.; Chang, T. C.

2005-05-01

This letter explores the application of electron-beam curing on nanoporous silicate films. The electrical conduction mechanism for the nanoporous silicate film cured by electron-beam radiation has been studied with metal-insulator-semiconductor capacitors. Electrical analyses over a varying temperature range from room temperature to 150°C provide evidence for space-charge-limited conduction in the electron-beam-cured thin film, while Schottky-emission-type leaky behavior is seen in the counterpart typically cured by a thermal furnace. A physical model consistent with electrical analyses is also proposed to deduce the origin of conduction behavior in the nanoporous silicate thin film.

The mystery of gold's chemical activity: local bonding, morphology and reactivity of atomic oxygen.

PubMed

Baker, Thomas A; Liu, Xiaoying; Friend, Cynthia M

2011-01-07

Recently, gold has been intensely studied as a catalyst for key synthetic reactions. Gold is an attractive catalyst because, surprisingly, it is highly active and very selective for partial oxidation processes suggesting promise for energy-efficient "green" chemistry. The underlying origin of the high activity of Au is a controversial subject since metallic gold is commonly thought to be inert. Herein, we establish that one origin of the high activity for gold catalysis is the extremely reactive nature of atomic oxygen bound in 3-fold coordination sites on metallic gold. This is the predominant form of O at low concentrations on the surface, which is a strong indication that it is most relevant to catalytic conditions. Atomic oxygen bound to metallic Au in 3-fold sites has high activity for CO oxidation, oxidation of olefins, and oxidative transformations of alcohols and amines. Among the factors identified as important in Au-O interaction are the morphology of the surface, the local binding site of oxygen, and the degree of order of the oxygen overlayer. In this Perspective, we present an overview of both theory and experiments that identify the reactive forms of O and their associated charge density distributions and bond strengths. We also analyze and model the release of Au atoms induced by O binding to the surface. This rough surface also has the potential for O(2) dissociation, which is a critical step if Au is to be activated catalytically. We further show the strong parallels between product distributions and reactivity for O-covered Au at low pressure (ultrahigh vacuum) and for nanoporous Au catalysts operating at atmospheric pressure as evidence that atomic O is the active species under working catalytic conditions when metallic Au is present. We briefly discuss the possible contributions of oxidants that may contain intact O-O bonds and of the Au-metal oxide support interface in Au catalysis. Finally, the challenges and future directions for fully understanding the activity of gold are considered.

Atomic Layer Deposition for the Conformal Coating of Nanoporous Materials

DOE PAGES

Elam, Jeffrey W.; Xiong, Guang; Han, Catherine Y.; ...

2006-01-01

Amore » tomic layer deposition ( LD ) is ideal for applying precise and conformal coatings over nanoporous materials. We have recently used LD to coat two nanoporous solids: anodic aluminum oxide ( O ) and silica aerogels. O possesses hexagonally ordered pores with diameters d ∼ 40 nm and pore length L ∼ 70 microns. The O membranes were coated by LD to fabricate catalytic membranes that demonstrate remarkable selectivity in the oxidative dehydrogenation of cyclohexane. dditional O membranes coated with LD Pd films show promise as hydrogen sensors. Silica aerogels have the lowest density and highest surface area of any solid material. Consequently, these materials serve as an excellent substrate to fabricate novel catalytic materials and gas sensors by LD .« less

Contrast enhancement of biological nanoporous materials with zinc oxide infiltration for electron and X-ray nanoscale microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ocola, L. E.; Sampathkumar, V.; Kasthuri, N.

Here, we show that using infiltration of ZnO metal oxide can be useful for high resolution imaging of biological samples in electron and X-ray microscopy. This method is compatible with standard fixation techniques that leave the sample dry, such as finishing with super critical CO 2 drying, or simple vacuum drying at 95°C. We demonstrate this technique can be applied on tooth and brain tissue samples. We also show that high resolution X-ray tomography can be performed on biological systems using Zn K edge (1s) absorption to enhance internal structures, and obtained the first nanoscale 10 KeV X-ray absorption imagesmore » of the interior regions of a tooth.« less

Contrast enhancement of biological nanoporous materials with zinc oxide infiltration for electron and X-ray nanoscale microscopy

DOE PAGES

Ocola, L. E.; Sampathkumar, V.; Kasthuri, N.; ...

2017-07-19

Here, we show that using infiltration of ZnO metal oxide can be useful for high resolution imaging of biological samples in electron and X-ray microscopy. This method is compatible with standard fixation techniques that leave the sample dry, such as finishing with super critical CO 2 drying, or simple vacuum drying at 95°C. We demonstrate this technique can be applied on tooth and brain tissue samples. We also show that high resolution X-ray tomography can be performed on biological systems using Zn K edge (1s) absorption to enhance internal structures, and obtained the first nanoscale 10 KeV X-ray absorption imagesmore » of the interior regions of a tooth.« less

Responsive nanoporous metals: recoverable modulations on strength and shape by watering

NASA Astrophysics Data System (ADS)

Ye, Xing-Long; Liu, Ling-Zhi; Jin, Hai-Jun

2016-08-01

Many biological materials can readily modulate their mechanical properties and shape by interacting with water in the surrounding environment, which is essential to their high performance in application. In contrast, typical inorganic materials (such as the metals) cannot change their strength and shape without involving thermal/mechanical treatments. By introducing nano-scale porous structure and exploiting a simple physical concept—the water-capillarity in nanopores, here we report that a ‘dead’ metal can be transformed into a ‘smart’ material with water-responsive properties. We demonstrate that the apparent strength, volume and shape of nanoporous Au and Au(Pt) can be modulated in situ, dramatically and recoverably, in response to water-dipping and partial-drying. The amplitude of strength-modulation reaches 20 MPa, which is nearly 50% of the yield strength at initial state. This approach also leads to reversible length change up to 1.3% in nanoporous Au and a large reversible bending motion of a bi-layer strip with tip displacement of ˜20 mm, which may be used for actuation. This method is simple and effective, occurring in situ under ambient conditions and requiring no external power, analogous to biological materials. The findings may open up novel applications in many areas such as micro-robotics and bio-medical devices.

Pd-Metalated Conjugated Nanoporous Polycarbazoles for Additive-Free Cyanation of Aryl Halides: Boosting Catalytic Efficiency through Spatial Modulation

DOE PAGES

Ding, Shunmin; Tian, Chengcheng; Zhu, Xiang; ...

2017-03-23

Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed in this paper to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. Finally, the catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.

Capture and alignment of phi29 viral particles in sub-40 nanometer porous alumina membranes.

PubMed

Moon, Jeong-Mi; Akin, Demir; Xuan, Yi; Ye, Peide D; Guo, Peixuan; Bashir, Rashid

2009-02-01

Bacteriophage phi29 virus nanoparticles and its associated DNA packaging nanomotor can provide for novel possibilities towards the development of hybrid bio-nano structures. Towards the goal of interfacing the phi29 viruses and nanomotors with artificial micro and nanostructures, we fabricated nanoporous Anodic Aluminum Oxide (AAO) membranes with pore size of 70 nm and shrunk the pores to sub 40 nm diameter using atomic layer deposition (ALD) of Aluminum Oxide. We were able to capture and align particles in the anodized nanopores using two methods. Firstly, a functionalization and polishing process to chemically attach the particles in the inner surface of the pores was developed. Secondly, centrifugation of the particles was utilized to align them in the pores of the nanoporous membranes. In addition, when a mixture of empty capsids and packaged particles was centrifuged at specific speeds, it was found that the empty capsids deform and pass through 40 nm diameter pores whereas the particles packaged with DNA were mainly retained at the top surface of the nanoporous membranes. Fluorescence microscopy was used to verify the selective filtration of empty capsids through the nanoporous membranes.

Hierarchical Nanoporous Gold-Platinum with Heterogeneous Interfaces for Methanol Electrooxidation

PubMed Central

Xiao, Shuang; Xiao, Fei; Hu, Yuan; Yuan, Songliu; Wang, Shuai; Qian, Lihua; Liu, Yunqi

2014-01-01

The electrocatalysts utilized as the prospective electrodes in fuel cells and high efficient energy conversion devices require both the interconnected channels for efficient electrolyte transportation and the superior catalytic activity with long service life. In this work, nanoporous gold with the rigid skeletons in three dimensions is partially decorated by porous platinum shell containing nanoscale interstitials, aiming to create the heterogeneous gold-platinum interfaces and facilitate the electrolyte transportation as well. In comparison with no catalytic activity of bare nanoporous gold, the catalytic activity of hierarchical nanoporous gold-platinum towards electrochemical oxidation of methanol increases with the loading level of platinum shells, resulting in the highest electrochemical area of 70.4 m2·g−1 after the normalization by the mass of platinum. Heterogeneous gold-platinum interfaces affect the tolerance of the absorbed intermediate species because of the oxidization by the oxygenated species absorbed on the gold surface and the enhanced ion transportation within the porous platinum shell. PMID:24621809

Application of 1-(2-pyridylazo)-2-naphthol-modified nanoporous silica as a technique in simultaneous trace monitoring and removal of toxic heavy metals in food and water samples.

PubMed

Abolhasani, Jafar; Behbahani, Mohammad

2015-01-01

Solid-phase extraction is one the most useful and efficient techniques for sample preparation, purification, cleanup, preconcentration, and determination of heavy metals at trace levels. In this paper, functionalized MCM-48 nanoporous silica with 1-(2-pyridylazo)-2-naphthol was applied for trace determination of copper, lead, cadmium, and nickel in water and seafood samples. The experimental conditions such as pH, sample and eluent flow rate, type, concentration and volume of the eluent, breakthrough volume, and effect of coexisting ions were optimized for efficient solid-phase extraction of trace heavy metals in different water and seafood samples. The content of solutions containing the mentioned heavy metals was determined by flame atomic absorption spectrometry (FAAS), and the limits of detection were 0.3, 0.4, 0.6, and 0.9 ng mL(-1) for cadmium, copper, nickel, and lead, respectively. Recoveries and precisions were >98.0 and <4%, respectively. The adsorption capacity of the modified nanoporous silica was 178 mg g(-1) for cadmium, 110 mg g(-1) for copper, 98 mg g(-1) for nickel, and 210 mg g(-1) for lead, respectively. The functionalized MCM-48 nanoporous silica with 1-(2-pyridylazo)-2-naphthol was characterized by thermogravimetry analysis (TGA), differential thermal analysis (DTA), transmission electron microscopy (TEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), elemental analysis (CHN), and N2 adsorption surface area measurement.

Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane.

PubMed

Liu, L; Lee, W; Huang, Z; Scholz, R; Gösele, U

2008-08-20

The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.

3-D simulation of nanopore structure for DNA sequencing.

PubMed

Park, Jun-Mo; Pak, Y Eugene; Chun, Honggu; Lee, Jong-Ho

2012-07-01

In this paper, we propose a method for simulating nanopore structure by using conventional 3-D simulation tool to mimic the I-V behavior of the nanopore structure. In the simulation, we use lightly doped silicon for ionic solution where some parameters like electron affinity and dielectric constant are fitted to consider the ionic solution. By using this method, we can simulate the I-V behavior of nanopore structure depending on the location and the size of the sphere shaped silicon oxide which is considered to be an indicator of a DNA base. In addition, we simulate an Ionic Field Effect Transistor (IFET) which has basically the nanopore structure, and show that the simulated curves follow sufficiently the I-V behavior of the measurement data. Therefore, we think it is reasonable to apply parameter modeling mentioned above to simulate nanopore structure. The key idea is to modify electron affinity of silicon which is used to mimic the KCl solution to avoid band bending and depletion inside the nanopore. We could efficiently utilize conventional 3-D simulation tool to simulate the I-V behavior of nanopore structures.

A Generalizable Top-Down Nanostructuring Method of Bulk Oxides: Sequential Oxygen-Nitrogen Exchange Reaction.

PubMed

Lee, Lanlee; Kang, Byungwuk; Han, Suyoung; Kim, Hee-Eun; Lee, Moo Dong; Bang, Jin Ho

2018-05-27

A thermal reaction route that induces grain fracture instead of grain growth is devised and developed as a top-down approach to prepare nanostructured oxides from bulk solids. This novel synthesis approach, referred to as the sequential oxygen-nitrogen exchange (SONE) reaction, exploits the reversible anion exchange between oxygen and nitrogen in oxides that is driven by a simple two-step thermal treatment in ammonia and air. Internal stress developed by significant structural rearrangement via the formation of (oxy)nitride and the creation of oxygen vacancies and their subsequent combination into nanopores transforms bulk solid oxides into nanostructured oxides. The SONE reaction can be applicable to most transition metal oxides, and when utilized in a lithium-ion battery, the produced nanostructured materials are superior to their bulk counterparts and even comparable to those produced by conventional bottom-up approaches. Given its simplicity and scalability, this synthesis method could open a new avenue to the development of high-performance nanostructured electrode materials that can meet the industrial demand of cost-effectiveness for mass production. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Influence of Pore Size on the Indentation Behavior of Metallic Nanoporous Materials: A Molecular Dynamics Study

PubMed Central

Esqué-de los Ojos, Daniel; Pellicer, Eva; Sort, Jordi

2016-01-01

In general, the influence of pore size is not considered when determining the Young’s modulus of nanoporous materials. Here, we demonstrate that the pore size needs to be taken into account to properly assess the mechanical properties of these materials. Molecular dynamics simulations of spherical indentation experiments on single crystalline nanoporous Cu have been undertaken in systems with: (i) a constant degree of porosity and variable pore diameter; and (ii) a constant pore diameter and variable porosity degree. The classical Gibson and Ashby expression relating Young’s modulus with the relative density of the nanoporous metal is modified to include the influence of the pore size. The simulations reveal that, for a fixed porosity degree, the mechanical behavior of materials with smaller pores differs more significantly from the behavior of the bulk, fully dense counterpart. This effect is ascribed to the increase of the overall surface area as the pore size is reduced, together with the reduced coordination number of the atoms located at the pores edges. PMID:28773476

Formation and photopatterning of nanoporous titania thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Oun-Ho; Cheng, Joy Y.; Kim, Hyun Suk

2007-06-04

Photopatternable nanoporous titania thin films were generated from mixtures of an organic diblock copolymer, poly(styrene-b-ethylene oxide) (PS-b-PEO), and an oligomeric titanate (OT) prepared from a chelated titanium isopropoxide. The PS-b-PEO templates well-defined microdomains in thin films of the mixtures, which upon thermal treatment at 450 deg. C, become nanopores in titania. Average pore size and porosity are controlled by the molecular weight and loading level of the PS-b-PEO, respectively. Patterns of nanoporous titania were created by selectively exposing UV light on the mixture films. The UV irradiation destroys the chelating bond and induces the cross-linking reaction of the OT. Subsequentmore » wet development followed by thermal treatment gives patterned nanoporous films of anatase phase titania.« less

Review of Fabrication Methods, Physical Properties, and Applications of Nanostructured Copper Oxides Formed via Electrochemical Oxidation.

PubMed

Stepniowski, Wojciech J; Misiolek, Wojciech Z

2018-05-29

Typically, anodic oxidation of metals results in the formation of hexagonally arranged nanoporous or nanotubular oxide, with a specific oxidation state of the transition metal. Recently, the majority of transition metals have been anodized; however, the formation of copper oxides by electrochemical oxidation is yet unexplored and offers numerous, unique properties and applications. Nanowires formed by copper electrochemical oxidation are crystalline and composed of cuprous (CuO) or cupric oxide (Cu₂O), bringing varied physical and chemical properties to the nanostructured morphology and different band gaps: 1.44 and 2.22 eV, respectively. According to its Pourbaix (potential-pH) diagram, the passivity of copper occurs at ambient and alkaline pH. In order to grow oxide nanostructures on copper, alkaline electrolytes like NaOH and KOH are used. To date, no systemic study has yet been reported on the influence of the operating conditions, such as the type of electrolyte, its temperature, and applied potential, on the morphology of the grown nanostructures. However, the numerous reports gathered in this paper will provide a certain view on the matter. After passivation, the formed nanostructures can be also post-treated. Post-treatments employ calcinations or chemical reactions, including the chemical reduction of the grown oxides. Nanostructures made of CuO or Cu₂O have a broad range of potential applications. On one hand, with the use of surface morphology, the wetting contact angle is tuned. On the other hand, the chemical composition (pure Cu₂O) and high surface area make such materials attractive for renewable energy harvesting, including water splitting. While compared to other fabrication techniques, self-organized anodization is a facile, easy to scale-up, time-efficient approach, providing high-aspect ratio one-dimensional (1D) nanostructures. Despite these advantages, there are still numerous challenges that have to be faced, including the strict control of the chemical composition and morphology of the grown nanostructures, their uniformity, and understanding the mechanism of their growth.

Electrochemical Protection of Thin Film Electrodes in Solid State Nanopores

PubMed Central

Harrer, Stefan; Waggoner, Philip S.; Luan, Binquan; Afzali-Ardakani, Ali; Goldfarb, Dario L.; Peng, Hongbo; Martyna, Glenn; Rossnagel, Stephen M.; Stolovitzky, Gustavo A.

2011-01-01

We have eliminated electrochemical surface oxidation and reduction as well as water decomposition inside sub-5-nm wide nanopores in conducting TiN membranes using a surface passivation technique. Nanopore ionic conductances, and therefore pore diameters, were unchanged in passivated pores after applying potentials of ±4.5 V for as long as 24 h. Water decomposition was eliminated by using aqueous 90% glycerol solvent. The use of a protective self-assembled monolayer of hexadecylphosphonic acid was also investigated. PMID:21597142

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J [Naperville, IL; Hryn, John N [Naperville, IL; Elam, Jeffrey W [Elmhurst, IL

2009-12-01

A nanoporous catalytic membrane which displays several unique features including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity.

Nanopore reactive adsorbents for the high-efficiency removal of waste species

DOEpatents

Yang, Arthur Jing-Min; Zhang, Yuehua

2005-01-04

A nanoporous reactive adsorbent incorporates a relatively small number of relatively larger reactant, e.g., metal, enzyme, etc., particles (10) forming a discontinuous or continuous phase interspersed among and surrounded by a continuous phase of smaller adsorbent particles (12) and connected interstitial pores (14) therebetween. The reactive adsorbent can effectively remove inorganic or organic impurities in a liquid by causing the liquid to flow through the adsorbent. For example, silver ions may be adsorbed by the adsorbent particles (12) and reduced to metallic silver by reducing metal, such as ions, as the reactant particles (10). The column can be regenerated by backwashing with the liquid effluent containing, for example, acetic acid.

Promising applications of graphene and graphene-based nanostructures

NASA Astrophysics Data System (ADS)

Nguyen, Bich Ha; Hieu Nguyen, Van

2016-06-01

The present article is a review of research works on promising applications of graphene and graphene-based nanostructures. It contains five main scientific subjects. The first one is the research on graphene-based transparent and flexible conductive films for displays and electrodes: efficient method ensuring uniform and controllable deposition of reduced graphene oxide thin films over large areas, large-scale pattern growth of graphene films for stretchble transparent electrodes, utilization of graphene-based transparent conducting films and graphene oxide-based ones in many photonic and optoelectronic devices and equipments such as the window electrodes of inorganic, organic and dye-sensitized solar cells, organic light-emitting diodes, light-emitting electrochemical cells, touch screens, flexible smart windows, graphene-based saturated absorbers in laser cavities for ultrafast generations, graphene-based flexible, transparent heaters in automobile defogging/deicing systems, heatable smart windows, graphene electrodes for high-performance organic field-effect transistors, flexible and transparent acoustic actuators and nanogenerators etc. The second scientific subject is the research on conductive inks for printed electronics to revolutionize the electronic industry by producing cost-effective electronic circuits and sensors in very large quantities: preparing high mobility printable semiconductors, low sintering temperature conducting inks, graphene-based ink by liquid phase exfoliation of graphite in organic solutions, and developing inkjet printing technique for mass production of high-quality graphene patterns with high resolution and for fabricating a variety of good-performance electronic devices, including transparent conductors, embedded resistors, thin-film transistors and micro supercapacitors. The third scientific subject is the research on graphene-based separation membranes: molecular dynamics simulation study on the mechanisms of the transport of molecules, vapors and gases through nanopores in graphene membranes, experimental works investigating selective transport of different molecules through nanopores in single-layer graphene and graphene-based membranes toward the water desalination, chemical mixture separation and gas control. Various applications of graphene in bio-medicine are the contents of the fourth scientific subject of the review. They include the DNA translocations through nanopores in graphene membranes toward the fabrication of devices for genomic screening, in particular DNA sequencing; subnanometre trans-electrode membranes with potential applications to the fabrication of very high resolution, high throughput nanopore-based single-molecule detectors; antibacterial activity of graphene, graphite oxide, graphene oxide and reduced graphene oxide; nanopore sensors for nucleic acid analysis; utilization of graphene multilayers as the gates for sequential release of proteins from surface; utilization of graphene-based electroresponsive scaffolds as implants for on-demand drug delivery etc. The fifth scientific subject of the review is the research on the utilization of graphene in energy storage devices: ternary self-assembly of ordered metal oxide-graphene nanocomposites for electrochemical energy storage; self-assembled graphene/carbon nanotube hybrid films for supercapacitors; carbon-based supercapacitors fabricated by activation of graphene; functionalized graphene sheet-sulfure nanocomposite for using as cathode material in rechargeable lithium batteries; tunable three-dimensional pillared carbon nanotube-graphene networks for high-performance capacitance; fabrications of electrochemical micro-capacitors using thin films of carbon nanotubes and chemically reduced graphenes; laser scribing of high-performance and flexible graphene-based electrochemical capacitors; emergence of next-generation safe batteries featuring graphene-supported Li metal anode with exceptionally high energy or power densities; fabrication of anodes for lithium ion batteries from crumpled graphene-encapsulated Si nanoparticles; liquid-mediated dense integration of graphene materials for compact capacitive energy storage; scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage; superior micro-supercapacitors based on graphene quantum dots; all-graphene core-sheat microfibres for all-solid-state, stretchable fibriform supercapacitors and wearable electronic textiles; micro-supercapacitors with high electrochemical performance based on three-dimensional graphene-carbon nanotube carpets; macroscopic nitrogen-doped graphene hydrogels for ultrafast capacitors; manufacture of scalable ultra-thin and high power density graphene electrochemical capacitor electrodes by aqueous exfoliation and spray deposition; scalable synthesis of hierarchically structured carbon nanotube-graphene fibers for capacitive energy storage; phosphorene-graphene hybrid material as a high-capacity anode material for sodium-ion batteries. Beside above-presented promising applications of graphene and graphene-based nanostructures, other less widespread, but perhaps not less important, applications of graphene and graphene-based nanomaterials, are also briefly discussed.

Surface-Directed Synthesis of Erbium-Doped Yttrium Oxide Nanoparticles within Organosilane Zeptoliter Containers

PubMed Central

2015-01-01

We introduce an approach to synthesize rare earth oxide nanoparticles using high temperature without aggregation of the nanoparticles. The dispersity of the nanoparticles is controlled at the nanoscale by using small organosilane molds as reaction containers. Zeptoliter reaction vessels prepared from organosilane self-assembled monolayers (SAMs) were used for the surface-directed synthesis of rare earth oxide (REO) nanoparticles. Nanopores of octadecyltrichlorosilane were prepared on Si(111) using particle lithography with immersion steps. The nanopores were filled with a precursor solution of erbium and yttrium salts to confine the crystallization step to occur within individual zeptoliter-sized organosilane reaction vessels. Areas between the nanopores were separated by a matrix film of octadecyltrichlorosilane. With heating, the organosilane template was removed by calcination to generate a surface array of erbium-doped yttria nanoparticles. Nanoparticles synthesized by the surface-directed approach retain the periodic arrangement of the nanopores formed from mesoparticle masks. While bulk rare earth oxides can be readily prepared by solid state methods at high temperature (>900 °C), approaches for preparing REO nanoparticles are limited. Conventional wet chemistry methods are limited to low temperatures according to the boiling points of the solvents used for synthesis. To achieve crystallinity of REO nanoparticles requires steps for high-temperature processing of samples, which can cause self-aggregation and dispersity in sample diameters. The facile steps for particle lithography address the problems of aggregation and the requirement for high-temperature synthesis. PMID:25163977

Synthesis of Three-Dimensional Nanoporous Li-Rich Layered Cathode Oxides for High Volumetric and Power Energy Density Lithium-Ion Batteries.

PubMed

Qiu, Bao; Yin, Chong; Xia, Yonggao; Liu, Zhaoping

2017-02-01

As rechargeable Li-ion batteries have expanded their applications into on-board energy storage for electric vehicles, the energy and power must be increased to meet the new demands. Li-rich layered oxides are one of the most promising candidate materials; however, it is very difficult to make them compatible with high volumetric energy density and power density. Here, we develop an innovative approach to synthesize three-dimensional (3D) nanoporous Li-rich layered oxides Li[Li 0.144 Ni 0.136 Co 0.136 Mn 0.544 ]O 2 , directly occurring at deep chemical delithiation with carbon dioxide. It is found that the as-prepared material presents a micrometer-sized spherical structure that is typically composed of interconnected nanosized subunits with narrow distributed pores at 3.6 nm. As a result, this unique 3D micro-/nanostructure not only has a high tap density over 2.20 g cm -3 but also exhibits excellent rate capability (197.6 mA h g -1 at 1250 mA g -1 ) as an electrode. The excellent electrochemical performance is ascribed to the unique nanoporous micro-nanostructures, which facilitates the Li + diffusion and enhances the structural stability of the Li-rich layered cathode materials. Our work offers a comprehensive designing strategy to construct 3D nanoporous Li-rich layered oxides for both high volumetric energy density and power density in Li-ion batteries.

Self-ordered, controlled structure nanoporous membranes using constant current anodization.

PubMed

Lee, Kwan; Tang, Yun; Ouyang, Min

2008-12-01

We report a constant current (CC) based anodization technique to fabricate and control structure of mechanically stable anodic aluminum oxide (AAO) membranes with a long-range ordered hexagonal nanopore pattern. For the first time we show that interpore distance (Dint) of a self-ordered nanopore feature can be continuously tuned over a broad range with CC anodization and is uniquely defined by the conductivity of sulfuric acid as electrolyte. We further demonstrate that this technique can offer new degrees of freedom for engineering planar nanopore structures by fine tailoring the CC based anodization process. Our results not only facilitate further understanding of self-ordering mechanism of alumina membranes but also provide a fast, simple (without requirement of prepatterning or preoxide layer), and flexible methodology for controlling complex nanoporous structures, thus offering promising practical applications in nanotechnology.

Engineering of highly ordered TiO2 nanopore arrays by anodization

NASA Astrophysics Data System (ADS)

Wang, Huijie; Huang, Zhennan; Zhang, Li; Ding, Jie; Ma, Zhaoxia; Liu, Yong; Kou, Shengzhong; Yang, Hangsheng

2016-07-01

Finite element analysis was used to simulate the current density distributions in the TiO2 barrier layer formed at the initial stage of Ti anodization. The morphology modification of the barrier layer was found to induce current density distribution change. By starting the anodization with proper TiO2 barrier layer morphology, the current density distribution can be adjusted to favor the formation of either nanotube arrays or nanopore arrays of anodic TiO2. We also found that the addition of sodium acetate into the electrolyte suppressed both the field-assisted chemical dissolution of TiO2 and the TiF62- hydrolysis induced TiO2 deposition during anodization, and thus further favored the nanopore formation. Accordingly, highly ordered anodic TiO2 nanopore arrays, similar to anodic aluminum oxide nanopore arrays, were successfully prepared.

Nanoporous Hybrid Electrolytes for High-Energy Batteries Based on Reactive Metal Anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tu, Zhengyuan; Zachman, Michael J.; Choudhury, Snehashis

2017-01-06

Successful strategies for stabilizing electrodeposition of reactive metals, including lithium, sodium, and aluminum are a requirement for safe, high-energy electrochemical storage technologies that utilize these metals as anodes. Unstable deposition produces high-surface area dendritic structures at the anode/electrolyte interface, which causes premature cell failure by complex physical and chemical processes that have presented formidable barriers to progress. Here, it is reported that hybrid electrolytes created by infusing conventional liquid electrolytes into nanoporous membranes provide exceptional ability to stabilize Li. Electrochemical cells based on γ-Al2O3 ceramics with pore diameters below a cut-off value above 200 nm exhibit long-term stability even atmore » a current density of 3 mA cm-2. The effect is not limited to ceramics; similar large enhancements in stability are observed for polypropylene membranes with less monodisperse pores below 450 nm. These findings are critically assessed using theories for ion rectification and electrodeposition reactions in porous solids and show that the source of stable electrodeposition in nanoporous electrolytes is fundamental.« less

Microwave-aided synthesis and applications of gold and nickel nanoporous metal foams

NASA Astrophysics Data System (ADS)

Lu, Zhifeng

In the field of nanoscience, nanoporous metal foams are a representative type of nanostructured materials, representing the ultimate form factor of a metal. They possess the hybrid properties of metal and nanoarchitectures, including the following properties such as good electrical and thermal conductivity, catalytic activity and high surface area, ultralow density, high strength-to-weight ratio. The outstanding properties bring the nanoporous metal foams to a wide range of applications, especially in the field of sensor system, energy storage and chemical catalyst. A new method of synthesis developed recently is presented for nanoporous metal foams of gold and nickel. The goal of this study is for the synthesis process of NMFs of and some applications in research and realistic life. Gold NMFs were produced by mixing gold chloride with ethylene glycol, ethanol, and reducing agent, and heating at 150 °C for 5 min with a CEM microwave. Both hydrazine and sodium borohydride were applied as the reducing agent for this redox reaction. Nickel NMFs were produced through the similar procedure with a little difference in the heating condition of 50 W, instead of 150 °C, with either hydrazine or sodium borohydride as the reducing agent. Gold NMFs were applied in surface-enhanced Raman spectroscopy (SERS) as a substrate. It is presented that with the presence of gold NMFs, the detection of the rhodamine 6G (R6G), a model analyte, can be enhanced significantly. The limit of detection for rhodamine 6G was found to be 5.2 x 10 -7 M in this research. Nickel NMFs was applied to degrade methyl orange (MO). An aqueous MO solution will turn nearly colorless after only 10 h of mixing with 0.025 g of nickel NMFs at room temperature under dark condition. In order to study the kinetics of the degradation reaction, MO solution with different initial concentration were used. This application of Ni NMFs is applicable as waste treatment of industrial water and to protect the environment.

Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping

NASA Astrophysics Data System (ADS)

Freedman, Kevin J.; Otto, Lauren M.; Ivanov, Aleksandar P.; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B.

2016-01-01

Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 108-1010 times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 103 reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput.

Analysis of nanopore arrangement of porous alumina layers formed by anodizing in oxalic acid at relatively high temperatures

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Stępniowski, Wojciech J.; Jaskuła, Marian; Sulka, Grzegorz D.

2014-06-01

Anodic aluminum oxide (AAO) layers were formed by a simple two-step anodization in 0.3 M oxalic acid at relatively high temperatures (20-30 °C) and various anodizing potentials (30-65 V). The effect of anodizing conditions on structural features of as-obtained oxides was carefully investigated. A linear and exponential relationships between cell diameter, pore density and anodizing potential were confirmed, respectively. On the other hand, no effect of temperature and duration of anodization on pore spacing and pore density was found. Detailed quantitative and qualitative analyses of hexagonal arrangement of nanopore arrays were performed for all studied samples. The nanopore arrangement was evaluated using various methods based on the fast Fourier transform (FFT) images, Delaunay triangulations (defect maps), pair distribution functions (PDF), and angular distribution functions (ADF). It was found that for short anodizations performed at relatively high temperatures, the optimal anodizing potential that results in formation of nanostructures with the highest degree of pore order is 45 V. No direct effect of temperature and time of anodization on the nanopore arrangement was observed.

Nanoporous Metallic Networks: Fabrication, Optical Properties, and Applications.

PubMed

Ron, Racheli; Haleva, Emir; Salomon, Adi

2018-05-17

Nanoporous metallic networks are a group of porous materials made of solid metals with suboptical wavelength sizes of both particles and voids. They are characterized by unique optical properties, as well as high surface area and permeability of guest materials. As such, they attract a great focus as novel materials for photonics, catalysis, sensing, and renewable energy. Their properties together with the ability for scaling-up evoke an increased interest also in the industrial field. Here, fabrication techniques of large-scale metallic networks are discussed, and their interesting optical properties as well as their applications are considered. In particular, the focus is on disordered systems, which may facilitate the fabrication technique, yet, endow the three-dimensional (3D) network with distinct optical properties. These metallic networks bridge the nanoworld into the macroscopic world, and therefore pave the way to the fabrication of innovative materials with unique optoelectronic properties. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Sulfur-Doping Templated Synthesis of Nanoporous Graphitic Nanocages and Its Supported Catalysts for Efficient Methanol Oxidation.

PubMed

Sheng, Zhao Min; Hong, Cheng Yang; Dai, Xian You; Chang, Cheng Kang; Chen, Jian Bin; Liu, Yan

2015-04-01

We demonstrate a new sulfur (S)-doping templated approach to fabricate highly nanoporous graphitic nanocages (GNCs) by air-oxidizing the templates in the graphitic shells to create nanopores. Sulfur can be introduced, when Fe@C core-shell nanoparticles are prepared and then S-doped GNCs can be obtained by removing their ferrous cores. Due to removing S-template, both the specific surface area (from 540 to 850 m2 g(-1)) and the mesopore volume (from 0.44 to 0.9 cm3 g(-1)) of the graphitic nanocages have sharply risen. Its high specific surface area improves catalyst loading to provide more reaction electro-active sites while its high mesopore volume pro- motes molecule diffusion across the nanocages, making it an excellent material to support Pt/Ru catalysts for direct methanol fuel cells.

Synthesis of nanoporous CuO/TiO2/Pd-NiO composite catalysts by chemical dealloying and their performance for methanol and ethanol electro-oxidation

NASA Astrophysics Data System (ADS)

Niu, Mengying; Xu, Wence; Zhu, Shengli; Liang, Yanqin; Cui, Zhenduo; Yang, Xianjin; Inoue, Akihisa

2017-09-01

Nanoporous CuO/TiO2/Pd-NiO-x (x = 0, 1, 3, 5, 7 at%) catalysts have been synthesized by dealloying Cu-Ti-Pd-Ni alloy ribbons in acid solution. The nanoporous structure and chemical composition of the catalysts distribute uniformly. Based on the electrochemical active area (EASA), electrocatalytic activity and stability, the np-CuO/TiO2/Pd-NiO-3 catalyst possesses the best performance for methanol and ethanol electro-oxidation. For methanol and ethanol electro-oxidation, the anodic current densities in forward scan of the np-CuO/TiO2/Pd-NiO-3 catalyst are about 5.6 times and 2.1 times larger than that of the np-CuO/TiO2/Pd catalyst, respectively. The introduction of NiO provides more electrochemical active sites due to the improved geometrical and bifunctional mechanism. NiO promotes the adsorption of oxygen-containing species (OHads) on the catalyst surface, and electron effect between Pd and Ni is favorable for charge transfer. This accelerates the removal of intermediate products during the oxidation process. The electrocatalytic processes of methanol and ethanol oxidation in alkaline solution are controlled by both charge transfer and diffusion.

Rapid, conformal gas-phase formation of silica (SiO2) nanotubes from water condensates

NASA Astrophysics Data System (ADS)

Bae, Changdeuck; Kim, Hyunchul; Yang, Yunjeong; Yoo, Hyunjun; Montero Moreno, Josep M.; Bachmann, Julien; Nielsch, Kornelius; Shin, Hyunjung

2013-06-01

An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications.An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications. Electronic supplementary information (ESI) available: TEM gallery of silica NTs under different experimental conditions, detailed calculation of estimating the thickness of condensed water and Hamaker constants, and a comparison of processing times. See DOI: 10.1039/c3nr00906h

Self-induced redox cycling coupled luminescence on nanopore recessed disk-multiscale bipolar electrodes

DOE PAGES

Ma, Chaoxiong; Zaino III, Lawrence P.; Bohn, Paul W.

2015-03-25

Self-induced redox cycling at nanopore ring-disk electrodes is coupled, through a bipolar electrode, to a remote fluorigenic reporter reaction. We present a new configuration for coupling fluorescence microscopy and voltammetry using self-induced redox cycling for ultrasensitive electrochemical measurements. An array of nanopores, each supporting a recessed disk electrode separated by 100 nm in depth from a planar multiscale bipolar top electrode, was fabricated using multilayer deposition, nanosphere lithography, and reactive-ion etching. Self-induced redox cycling was induced on the disk electrode producing ~30× current amplification, which was independently confirmed by measuring induced electrogenerated chemiluminescence from Ru(bpy) 3 2/3+/tri-n-propylamine on the floatingmore » bipolar electrode. In this design, redox cycling occurs between the recessed disk and the top planar portion of a macroscopic thin film bipolar electrode in each nanopore. Electron transfer also occurs on a remote (mm-distance) portion of the planar bipolar electrode to maintain electroneutrality. This couples the electrochemical reactions of the target redox pair in the nanopore array with a reporter, such as a potential-switchable fluorescent indicator, in the cell at the distal end of the bipolar electrode. Oxidation or reduction of reversible analytes on the disk electrodes were accompanied by reduction or oxidation, respectively, on the nanopore portion of the bipolar electrode and then monitored by the accompanying oxidation of dihydroresorufin or reduction of resorufin at the remote end of the bipolar electrode, respectively. In both cases, changes in fluorescence intensity were triggered by the reaction of the target couple on the disk electrode, while recovery was largely governed by diffusion of the fluorescent indicator. Reduction of 1 nM of Ru(NH 3) 6 3+ on the nanoelectrode array was detected by monitoring the fluorescence intensity of resorufin, demonstrating high sensitivity fluorescence-mediated electrochemical sensing coupled to self-induced redox cycling.« less

Self-induced redox cycling coupled luminescence on nanopore recessed disk-multiscale bipolar electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Chaoxiong; Zaino III, Lawrence P.; Bohn, Paul W.

Self-induced redox cycling at nanopore ring-disk electrodes is coupled, through a bipolar electrode, to a remote fluorigenic reporter reaction. We present a new configuration for coupling fluorescence microscopy and voltammetry using self-induced redox cycling for ultrasensitive electrochemical measurements. An array of nanopores, each supporting a recessed disk electrode separated by 100 nm in depth from a planar multiscale bipolar top electrode, was fabricated using multilayer deposition, nanosphere lithography, and reactive-ion etching. Self-induced redox cycling was induced on the disk electrode producing ~30× current amplification, which was independently confirmed by measuring induced electrogenerated chemiluminescence from Ru(bpy) 3 2/3+/tri-n-propylamine on the floatingmore » bipolar electrode. In this design, redox cycling occurs between the recessed disk and the top planar portion of a macroscopic thin film bipolar electrode in each nanopore. Electron transfer also occurs on a remote (mm-distance) portion of the planar bipolar electrode to maintain electroneutrality. This couples the electrochemical reactions of the target redox pair in the nanopore array with a reporter, such as a potential-switchable fluorescent indicator, in the cell at the distal end of the bipolar electrode. Oxidation or reduction of reversible analytes on the disk electrodes were accompanied by reduction or oxidation, respectively, on the nanopore portion of the bipolar electrode and then monitored by the accompanying oxidation of dihydroresorufin or reduction of resorufin at the remote end of the bipolar electrode, respectively. In both cases, changes in fluorescence intensity were triggered by the reaction of the target couple on the disk electrode, while recovery was largely governed by diffusion of the fluorescent indicator. Reduction of 1 nM of Ru(NH 3) 6 3+ on the nanoelectrode array was detected by monitoring the fluorescence intensity of resorufin, demonstrating high sensitivity fluorescence-mediated electrochemical sensing coupled to self-induced redox cycling.« less

Highly effective hydrogen isotope separation in nanoporous metal-organic frameworks with open metal sites: direct measurement and theoretical analysis.

PubMed

Oh, Hyunchul; Savchenko, Ievgeniia; Mavrandonakis, Andreas; Heine, Thomas; Hirscher, Michael

2014-01-28

Separating gaseous mixtures that consist of very similar size is one of the critical issues in modern separation technology. Especially, the separation of the isotopes hydrogen and deuterium requires special efforts, even though these isotopes show a very large mass ratio. Conventionally, H/D separation can be realized through cryogenic distillation of the molecular species or the Girdler-sulfide process, which are among the most energy-intensive separation techniques in the chemical industry. However, costs can be significantly reduced by using highly mass-selective nanoporous sorbents. Here, we describe a hydrogen isotope separation strategy exploiting the strongly attractive open metal sites present in nanoporous metal-organic frameworks of the CPO-27 family (also referred to as MOF-74). A theoretical analysis predicts an outstanding hydrogen isotopologue separation at open metal sites due to isotopal effects, which has been directly observed through cryogenic thermal desorption spectroscopy. For H2/D2 separation of an equimolar mixture at 60 K, the selectivity of 12 is the highest value ever measured, and this methodology shows extremely high separation efficiencies even above 77 K. Our theoretical results imply also a high selectivity for HD/H2 separation at similar temperatures, and together with catalytically active sites, we propose a mechanism to produce D2 from HD/H2 mixtures with natural or enriched deuterium content.

Nanoporous Gold: Fabrication, Characterization, and Applications

PubMed Central

Seker, Erkin; Reed, Michael L.; Begley, Matthew R.

2009-01-01

Nanoporous gold (np-Au) has intriguing material properties that offer potential benefits for many applications due to its high specific surface area, well-characterized thiol-gold surface chemistry, high electrical conductivity, and reduced stiffness. The research on np-Au has taken place on various fronts, including advanced microfabrication and characterization techniques to probe unusual nanoscale properties and applications spanning from fuel cells to electrochemical sensors. Here, we provide a review of the recent advances in np-Au research, with special emphasis on microfabrication and characterization techniques. We conclude the paper with a brief outline of challenges to overcome in the study of nanoporous metals.

Lithium-coated polymeric matrix as a minimum volume-change and dendrite-free lithium metal anode

PubMed Central

Liu, Yayuan; Lin, Dingchang; Liang, Zheng; Zhao, Jie; Yan, Kai; Cui, Yi

2016-01-01

Lithium metal is the ideal anode for the next generation of high-energy-density batteries. Nevertheless, dendrite growth, side reactions and infinite relative volume change have prevented it from practical applications. Here, we demonstrate a promising metallic lithium anode design by infusing molten lithium into a polymeric matrix. The electrospun polyimide employed is stable against highly reactive molten lithium and, via a conformal layer of zinc oxide coating to render the surface lithiophilic, molten lithium can be drawn into the matrix, affording a nano-porous lithium electrode. Importantly, the polymeric backbone enables uniform lithium stripping/plating, which successfully confines lithium within the matrix, realizing minimum volume change and effective dendrite suppression. The porous electrode reduces the effective current density; thus, flat voltage profiles and stable cycling of more than 100 cycles is achieved even at a high current density of 5 mA cm−2 in both carbonate and ether electrolyte. The advantages of the porous, polymeric matrix provide important insights into the design principles of lithium metal anodes. PMID:26987481

Lithium-coated polymeric matrix as a minimum volume-change and dendrite-free lithium metal anode

DOE PAGES

Liu, Yayuan; Lin, Dingchang; Liang, Zheng; ...

2016-03-18

Lithium metal is the ideal anode for the next generation of high-energy-density batteries. Nevertheless, dendrite growth, side reactions and infinite relative volume change have prevented it from practical applications. Here, we demonstrate a promising metallic lithium anode design by infusing molten lithium into a polymeric matrix. The electrospun polyimide employed is stable against highly reactive molten lithium and, via a conformal layer of zinc oxide coating to render the surface lithiophilic, molten lithium can be drawn into the matrix, affording a nano-porous lithium electrode. Importantly, the polymeric backbone enables uniform lithium stripping/plating, which successfully confines lithium within the matrix, realizingmore » minimum volume change and effective dendrite suppression. The porous electrode reduces the effective current density; thus, flat voltage profiles and stable cycling of more than 100 cycles is achieved even at a high current density of 5 mA cm -2 in both carbonate and ether electrolyte. Furthermore, the advantages of the porous, polymeric matrix provide important insights into the design principles of lithium metal anodes.« less

Lithium-coated polymeric matrix as a minimum volume-change and dendrite-free lithium metal anode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yayuan; Lin, Dingchang; Liang, Zheng

Lithium metal is the ideal anode for the next generation of high-energy-density batteries. Nevertheless, dendrite growth, side reactions and infinite relative volume change have prevented it from practical applications. Here, we demonstrate a promising metallic lithium anode design by infusing molten lithium into a polymeric matrix. The electrospun polyimide employed is stable against highly reactive molten lithium and, via a conformal layer of zinc oxide coating to render the surface lithiophilic, molten lithium can be drawn into the matrix, affording a nano-porous lithium electrode. Importantly, the polymeric backbone enables uniform lithium stripping/plating, which successfully confines lithium within the matrix, realizingmore » minimum volume change and effective dendrite suppression. The porous electrode reduces the effective current density; thus, flat voltage profiles and stable cycling of more than 100 cycles is achieved even at a high current density of 5 mA cm -2 in both carbonate and ether electrolyte. Furthermore, the advantages of the porous, polymeric matrix provide important insights into the design principles of lithium metal anodes.« less

Interconnected V2O5 nanoporous network for high-performance supercapacitors.

PubMed

Saravanakumar, B; Purushothaman, Kamatchi K; Muralidharan, G

2012-09-26

Vanadium pentoxide (V(2)O(5)) has attracted attention for supercapcitor applications because of its extensive multifunctional properties. In the present study, V(2)O(5) nanoporous network was synthesized via simple capping-agent-assisted precipitation technique and it is further annealed at different temperatures. The effect of annealing temperature on the morphology, electrochemical and structural properties, and stability upon oxidation-reduction cycling has been analyzed for supercapacitor application. We achieved highest specific capacitance of 316 F g(-1) for interconnected V(2)O(5) nanoporous network. This interconnected nanoporous network creates facile nanochannels for ion diffusion and facilitates the easy accessibility of ions. Moreover, after six hundred consecutive cycling processes the specific capacitance has changed only by 24%. A simple cost-effective preparation technique of V(2)O(5) nanoporous network with excellent capacitive behavior, energy density, and stability encourages its possible commercial exploitation for the development of high-performance supercapacitors.

Nanoporous Metals with Structural Hierarchy: A Review

DOE PAGES

Juarez, Theresa; Biener, Juergen; Weissmüller, Jörg; ...

2017-08-09

Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. Here, this review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, wemore » focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Lastly, we conclude with a discussion about future opportunities for the advancement and application of np metals.« less

Nanoporous Metals with Structural Hierarchy: A Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Juarez, Theresa; Biener, Juergen; Weissmüller, Jörg

Nanoporous (np) metals have generated much interest since they combine several desirable material characteristics, such as high surface area, mechanical size effects, and high conductivity. Most of the research has been focused on np Au due to its relatively straightforward synthesis, chemical stability, and many promising applications in the fields of catalysis and actuation. Other materials, such as np-Cu, Ag, and Pd have also been studied. Here, this review discusses recent advances in the field of np metals, focusing on new research areas that implement and leverage structural hierarchy while using np metals as their base structural constituents. First, wemore » focus on single-element porous metals that are made of np metals at the fundamental level, but synthesized with additional levels of porosity. Second, we discuss the fabrication of composite structures, which use auxiliary materials to enhance the properties of np metals. Important applications of these hierarchical materials, especially in the fields of catalysis and electrochemistry, are also reviewed. Lastly, we conclude with a discussion about future opportunities for the advancement and application of np metals.« less

An embryo of protocells: The capsule of graphene with selective ion channels

PubMed Central

Li, Zhan; Wang, Chunmei; Tian, Longlong; Bai, Jing; Yao, Huijun; Zhao, Yang; Zhang, Xin; Cao, Shiwei; Qi, Wei; Wang, Suomin; Shi, Keliang; Xu, Youwen; Mingliang, Zhang; Liu, Bo; Qiu, Hongdeng; Liu, Jie; Wu, Wangsuo; Wang, Xiaoli; Wenzhen, An

2015-01-01

The synthesis of artificial cell is a route for searching the origin of protocell. Here, we create a novel cell model of graphene capsules with selective ion channels, indicating that graphene might be an embryo of protocell membrane. Firstly, we found that the highly oxidized graphene and phospholipid-graphene oxide composite would curl into capsules under a strongly acidic saturated solution of heavy metallic salt solution at low temperature. Secondly, L-amino acids exhibited higher reactivity than D-amino acids on graphene oxides to form peptides, and the formed peptides in the influence of graphene would be transformed into a secondary structure, promoting the formation of left-handed proteins. Lastly, monolayer nanoporous graphene, prepared by unfocused 84Kr25+, has a high selectivity for permeation of the monovalent metal ions ( Rb+ > K+ > Cs+ > Na+ > Li+, based on permeation concentration), but does not allow Cl- go through. It is similar to K+ channels, which would cause an influx of K+ into capsule of graphene with the increase of pH in the primitive ocean, creating a suitable inner condition for the origin of life. Therefore, we built a model cell of graphene, which would provide a route for reproducing the origin of life. PMID:25989440

An embryo of protocells: The capsule of graphene with selective ion channels

DOE PAGES

Li, Zhan; Wang, Chunmei; Tian, Longlong; ...

2015-05-19

In this study, the synthesis of artificial cell is a route for searching the origin of protocell. Here, we create a novel cell model of graphene capsules with selective ion channels, indicating that graphene might be an embryo of protocell membrane. Firstly, we found that the highly oxidized graphene and phospholipid-graphene oxide composite would curl into capsules under a strongly acidic saturated solution of heavy metallic salt solution at low temperature. Secondly, L-amino acids exhibited higher reactivity than D-amino acids on graphene oxides to form peptides, and the formed peptides in the influence of graphene would be transformed into amore » secondary structure, promoting the formation of left-handed proteins. Lastly, monolayer nanoporous graphene, prepared by unfocused 84Kr 25+, has a high selectivity for permeation of the monovalent metal ions ( Rb + > K + > Cs + > Na + > Li +, based on permeation concentration), but does not allow Cl- go through. It is similar to K+ channels, which would cause an influx of K + into capsule of graphene with the increase of pH in the primitive ocean, creating a suitable inner condition for the origin of life. Therefore, we built a model cell of graphene, which would provide a route for reproducing the origin of life.« less

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

2013-08-27

A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

Planarized arrays of aligned, untangled multiwall carbon nanotubes with Ohmic back contacts

DOE PAGES

Rochford, C.; Limmer, S. J.; Howell, S. W.; ...

2014-11-26

Vertically aligned, untangled planarized arrays of multiwall carbon nanotubes (MWNTs) with Ohmic back contacts were grown in nanopore templates on arbitrary substrates. The templates were prepared by sputter depositing Nd-doped Al films onto W-coated substrates, followed by anodization to form an aluminum oxide nanopore array. The W underlayer helps eliminate the aluminum oxide barrier that typically occurs at the nanopore bottoms by instead forming a thin WO 3 layer. The WO 3 can be selectively etched to enable electrodeposition of Co catalysts with control over the Co site density. This led to control of the site density of MWNTs grownmore » by thermal chemical vapor deposition, with the W also serving as a back electrical contact. As a result, Ohmic contact to MWNTs was confirmed, even following ultrasonic cutting of the entire array to a uniform height.« less

Effects of nanoporous anodic titanium oxide on human adipose derived stem cells.

PubMed

Malec, Katarzyna; Góralska, Joanna; Hubalewska-Mazgaj, Magdalena; Głowacz, Paulina; Jarosz, Magdalena; Brzewski, Pawel; Sulka, Grzegorz D; Jaskuła, Marian; Wybrańska, Iwona

The aim of current bone biomaterials research is to design implants that induce controlled, guided, successful, and rapid healing. Titanium implants are widely used in dental, orthopedic, and reconstructive surgery. A series of studies has indicated that cells can respond not only to the chemical properties of the biomaterial, but also, in particular, to the changes in surface topography. Nanoporous materials remain in focus of scientific queries due to their exclusive properties and broad applications. One such material is nanostructured titanium oxide with highly ordered, mutually perpendicular nanopores. Nanoporous anodic titanium dioxide (TiO 2 ) films were fabricated by a three-step anodization process in propan-1,2,3-triol-based electrolyte containing fluoride ions. Adipose-derived stem cells offer many interesting opportunities for regenerative medicine. The important goal of tissue engineering is to direct stem cell differentiation into a desired cell lineage. The influence of nanoporous TiO 2 with pore diameters of 80 and 108 nm on cell response, growth, viability, and ability to differentiate into osteoblastic lineage of human adipose-derived progenitors was explored. Cells were harvested from the subcutaneous abdominal fat tissue by a simple, minimally invasive, and inexpensive method. Our results indicate that anodic nanostructured TiO 2 is a safe and nontoxic biomaterial. In vitro studies demonstrated that the nanotopography induced and enhanced osteodifferentiation of human adipose-derived stem cells from the abdominal subcutaneous fat tissue.

Applying graphene oxide nano-film over a polycarbonate nanoporous membrane to monitor E. coli by infrared spectroscopy

NASA Astrophysics Data System (ADS)

Singh, Krishna Pal; Dhek, Neeraj Singh; Nehra, Anuj; Ahlawat, Sweeti; Puri, Anu

2017-01-01

Nano-biosensors are excellent monitoring tools for rapid, specific, sensitive, inexpensive, in-field, on-line, and/or real-time detection of pathogens in foods, soil, air, and water samples. A variety of nano-materials (metallic, polymeric, and/or carbon-based) were employed to enhance the efficacy, efficiency, and sensitivity of these nano-biosensors, including graphene-based materials, especially graphene oxide (GO)-based materials. GO bears many oxygen-bearing groups, enabling ligand conjugation at the high density critical for sensitive detection. We have fabricated GO-modified nano-porous polycarbonate track-etched (PCTE) membranes that were conjugated to an Escherichia coli-specific antibody (Ab) and used to detect E. coli. The random distribution of nanopores on the PCTE membrane surface and the bright coating of the GO onto the membrane were confirmed by scanning electron microscope. Anti-E. coli β-gal Abs were conjugated to the GO surface via 1-ethyl-3,3-dimethylaminopropyl carbodiimide hydrochloride-N-hydroxysuccinimide chemistry; antibody coating was confirmed by the presence of a characteristic IR peak near 1600 cm- 1. A non-corresponding Ab (anti-Pseudomonas) was used as a negative control under identical conditions. When E. coli interacted anti-E.coli β-gal with Ab-coated GO-nano-biosensor units, we observed a clear shift in the IR peak from 3373.14 to 3315 cm- 1; in contrast, we did not observe any shift in IR peaks when the GO unit was coated with the non-corresponding Ab (anti-Pseudomonas). Therefore, the detection of E. coli using the described GO-nano-sensor unit is highly specific, is highly selective and can be applied for real-time monitoring of E. coli with a detection limit between 100 μg/mL and 10 μg/mL, similar to existing detection systems.

Applying graphene oxide nano-film over a polycarbonate nanoporous membrane to monitor E. coli by infrared spectroscopy.

PubMed

Singh, Krishna Pal; Dhek, Neeraj Singh; Nehra, Anuj; Ahlawat, Sweeti; Puri, Anu

2017-01-05

Nano-biosensors are excellent monitoring tools for rapid, specific, sensitive, inexpensive, in-field, on-line, and/or real-time detection of pathogens in foods, soil, air, and water samples. A variety of nano-materials (metallic, polymeric, and/or carbon-based) were employed to enhance the efficacy, efficiency, and sensitivity of these nano-biosensors, including graphene-based materials, especially graphene oxide (GO)-based materials. GO bears many oxygen-bearing groups, enabling ligand conjugation at the high density critical for sensitive detection. We have fabricated GO-modified nano-porous polycarbonate track-etched (PCTE) membranes that were conjugated to an Escherichia coli-specific antibody (Ab) and used to detect E. coli. The random distribution of nanopores on the PCTE membrane surface and the bright coating of the GO onto the membrane were confirmed by scanning electron microscope. Anti-E. coli β-gal Abs were conjugated to the GO surface via 1-ethyl-3,3-dimethylaminopropyl carbodiimide hydrochloride-N-hydroxysuccinimide chemistry; antibody coating was confirmed by the presence of a characteristic IR peak near 1600cm(-1). A non-corresponding Ab (anti-Pseudomonas) was used as a negative control under identical conditions. When E. coli interacted anti-E.coli β-gal with Ab-coated GO-nano-biosensor units, we observed a clear shift in the IR peak from 3373.14 to 3315cm(-1); in contrast, we did not observe any shift in IR peaks when the GO unit was coated with the non-corresponding Ab (anti-Pseudomonas). Therefore, the detection of E. coli using the described GO-nano-sensor unit is highly specific, is highly selective and can be applied for real-time monitoring of E. coli with a detection limit between 100μg/mL and 10μg/mL, similar to existing detection systems. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanopore sensing at ultra-low concentrations using single-molecule dielectrophoretic trapping

PubMed Central

Freedman, Kevin J.; Otto, Lauren M.; Ivanov, Aleksandar P.; Barik, Avijit; Oh, Sang-Hyun; Edel, Joshua B.

2016-01-01

Single-molecule techniques are being developed with the exciting prospect of revolutionizing the healthcare industry by generating vast amounts of genetic and proteomic data. One exceptionally promising route is in the use of nanopore sensors. However, a well-known complexity is that detection and capture is predominantly diffusion limited. This problem is compounded when taking into account the capture volume of a nanopore, typically 108–1010 times smaller than the sample volume. To rectify this disproportionate ratio, we demonstrate a simple, yet powerful, method based on coupling single-molecule dielectrophoretic trapping to nanopore sensing. We show that DNA can be captured from a controllable, but typically much larger, volume and concentrated at the tip of a metallic nanopore. This enables the detection of single molecules at concentrations as low as 5 fM, which is approximately a 103 reduction in the limit of detection compared with existing methods, while still maintaining efficient throughput. PMID:26732171

Analysis of effect of nanoporous alumina substrate coated with polypyrrole nanowire on cell morphology based on AFM topography.

PubMed

El-Said, Waleed Ahmed; Yea, Cheol-Heon; Jung, Mi; Kim, Hyuncheol; Choi, Jeong-Woo

2010-05-01

In this study, in situ electrochemical synthesis of polypyrrole nanowires with nanoporous alumina template was described. The formation of highly ordered porous alumina substrate was demonstrated with Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). In addition, Fourier transform infrared analysis confirmed that polypyrrole (PP) nanowires were synthesized by direct electrochemical oxidation of pyrrole. HeLa cancer cells and HMCF normal cells were immobilized on the polypyrrole nanowires/nanoporous alumina substrates to determine the effects of the substrate on the cell morphology, adhesion and proliferation as well as the biocompatibility of the substrate. Cell adhesion and proliferation were characterized using a standard MTT assay. The effects of the polypyrrole nanowires/nanoporous alumina substrate on the cell morphology were studied by AFM. The nanoporous alumina coated with polypyrrole nanowires was found to exhibit better cell adhesion and proliferation than polystyrene petridish, aluminum foil, 1st anodized and uncoated 2nd anodized alumina substrate. This study showed the potential of the polypyrrole nanowires/nanoporous alumina substrate as biocompatibility electroactive polymer substrate for both healthy and cancer cell cultures applications.

Molecular Simulation Evaluation of Macromolecular Transport through Nanofiltration Membranes

NASA Astrophysics Data System (ADS)

Almodovar Arbelo, Noelia; Boudouris, Bryan; Corti, David

A hybrid Monte Carlo and Molecular Dynamics simulation technique was implemented to elucidate the equilibrium behavior and transport properties of a model macromolecule as it navigated across a nanoporous polymer thin film (i.e., a nanofiltration membrane). The model linear homopolymer chosen was one that had interactions that were representative of poly(ethylene oxide) (PEO) due to the known interactions of PEO with solution molecules when a PEO chain is dissolved in an aqueous environment. The structural rearrangements of the PEO chain as it passes through the nanopore under an imposed chemical potential gradient was quantified as a function of solvent quality, polymer chain length, nanopore diameter and shape, and PEO-nanopore wall interactions. Thus, these computational studies provide a more detailed picture of the underlying physical mechanisms that drive macromolecular transport through nanopores, and, in particular, how dimensionally-large macromolecules (i.e., with large radii of gyration) enter and move through dimensionally-small pores (i.e., small radii nanopores). The insights gained from these studies will aid in the development of more cost-effective water purification systems in separation technologies for myriad industrial applications.

Advanced Nanoporous Materials for Micro-Gravimetric Sensing to Trace-Level Bio/Chemical Molecules

PubMed Central

Xu, Pengcheng; Li, Xinxin; Yu, Haitao; Xu, Tiegang

2014-01-01

Functionalized nanoporous materials have been developed recently as bio/chemical sensing materials. Due to the huge specific surface of the nano-materials for molecular adsorption, high hopes have been placed on gravimetric detection with micro/nano resonant cantilevers for ultra-sensitive sensing of low-concentration bio/chemical substances. In order to enhance selectivity of the gravimetric resonant sensors to the target molecules, it is crucial to modify specific groups onto the pore-surface of the nano-materials. By loading the nanoporous sensing material onto the desired region of the mass-type transducers like resonant cantilevers, the micro-gravimetric bio/chemical sensors can be formed. Recently, such micro-gravimetric bio/chemical sensors have been successfully applied for rapid or on-the-spot detection of various bio/chemical molecules at the trace-concentration level. The applicable nanoporous sensing materials include mesoporous silica, zeolite, nanoporous graphene oxide (GO) and so on. This review article focuses on the recent achievements in design, preparation, functionalization and characterization of advanced nanoporous sensing materials for micro-gravimetric bio/chemical sensing. PMID:25313499

Hydrothermally formed three-dimensional nanoporous Ni(OH)2 thin-film supercapacitors.

PubMed

Yang, Yang; Li, Lei; Ruan, Gedeng; Fei, Huilong; Xiang, Changsheng; Fan, Xiujun; Tour, James M

2014-09-23

A three-dimensional nanoporous Ni(OH)2 thin-film was hydrothermally converted from an anodically formed porous layer of nickel fluoride/oxide. The nanoporous Ni(OH)2 thin-films can be used as additive-free electrodes for energy storage. The nanoporous layer delivers a high capacitance of 1765 F g(-1) under three electrode testing. After assembly with porous activated carbon in asymmetric supercapacitor configurations, the devices deliver superior supercapacitive performances with capacitance of 192 F g(-1), energy density of 68 Wh kg(-1), and power density of 44 kW kg(-1). The wide working potential window (up to 1.6 V in 6 M aq KOH) and stable cyclability (∼90% capacitance retention over 10,000 cycles) make the thin-film ideal for practical supercapacitor devices.

Nanoporous metal organic frameworks as hybrid polymer-metal composites for drug delivery and biomedical applications.

PubMed

Beg, Sarwar; Rahman, Mahfoozur; Jain, Atul; Saini, Sumant; Midoux, Patrick; Pichon, Chantal; Ahmad, Farhan Jalees; Akhter, Sohail

2017-04-01

Metal organic frameworks (MOFs), porous hybrid polymer-metal composites at the nanoscale, are recent innovations in the field of chemistry; they are novel polymeric materials with diverse biomedical applications. MOFs are nanoporous materials, consisting of metal ions linked together by organic bridging ligands. The unique physical and chemical characteristics of MOFs have attracted wider attention from the scientific community, exploring their utility in the field of material science, biology, nanotechnology and drug delivery. The practical feasibility of MOFs is possible owing to their abilities for biodegradability, excellent porosity, high loading capacity, ease of surface modification, among others. In this regard, this review provides an account of various types of MOFs, their physiochemical characteristics and use in diverse disciplines of biomedical sciences - with special emphasis on drug delivery and theranostics. Moreover, this review also highlights the stability and toxicity issues of MOFs, along with their market potential for biomedical applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Facile fabrication of nanofluidic diode membranes using anodic aluminium oxide

NASA Astrophysics Data System (ADS)

Wu, Songmei; Wildhaber, Fabien; Vazquez-Mena, Oscar; Bertsch, Arnaud; Brugger, Juergen; Renaud, Philippe

2012-08-01

Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al2O3/SiO2 (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al2O3 (positive) and SiO2 (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion.Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al2O3/SiO2 (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al2O3 (positive) and SiO2 (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion. Electronic supplementary information (ESI) available: Pattern transfer of local AAO mask into Si layers of different thickness; characterization of the Ag/AgCl electrodes and the cell constant; control experiments of mono-charged nanopore membranes; and simulation of ionic transport in nanofluidic diodes. See DOI: 10.1039/c2nr31243c

Cu@C nanoporous composites containing little copper oxides derived from dimethyl imidazole modified MOF199 as electrocatalysts for hydrogen evolution reaction

NASA Astrophysics Data System (ADS)

Wei, Xuedong; Li, Na; Zhang, Xianming

2017-12-01

It remains a huge challenge to develop non precious electrocatalysts with high activity to substitute commercial Pt catalysts for hydrogen evolution reactions (HER). Here, the C-Cu-DI and C-Cu materials with the copper based nanoporous carbon structures were synthesized by carbonizing MOF199 and DI-MOF199. The composite structure and HER electrocatalytic properties of the C-Cu-DI and C-Cu materials are studied. The results show that C-Cu-DI and C-Cu samples exhibit good catalytic activity. And C-Cu-DI sample through the addition of Dimethyl imidazole(DI) in the DI-MOF199 precursor has higher electrocatalytic activity than the C-Cu sample. The superior catalytic activity is attributed to the special composite structure of nanoscale deposition particles on the framework with plenty of nano pores and nano copper and few copper oxidation particles distributed or wrapped into the amorphous porous carbon phase. The nano copper and few copper oxidation particles in the C-Cu and C-Cu-DI catalysts maybe provide the more effective catalytic activity sites. The C-Cu-DI composite with large size spherical hollow deposition particles has higher conductivity, better BET surface area and reasonable micro-meso-macro porous distribution, so the overpotentials at the current density of 1 mA cm-2 and 10 mA cm-2 are respectively 270 mV and 390 mV vs. RHE. Although the HER activity has a big gap with commercial platinum catalyst, this study can provide an important experimental exploration for the design of copper based non noble metal/nano porous carbon composite HER electrocatalyst.

Polyelectrolyte layer-by-layer deposition in cylindrical nanopores.

PubMed

Lazzara, Thomas D; Lau, K H Aaron; Abou-Kandil, Ahmed I; Caminade, Anne-Marie; Majoral, Jean-Pierre; Knoll, Wolfgang

2010-07-27

Layer-by-layer (LbL) deposition of polyelectrolytes within nanopores in terms of the pore size and the ionic strength was experimentally studied. Anodic aluminum oxide (AAO) membranes, which have aligned, cylindrical, nonintersecting pores, were used as a model nanoporous system. Furthermore, the AAO membranes were also employed as planar optical waveguides to enable in situ monitoring of the LbL process within the nanopores by optical waveguide spectroscopy (OWS). Structurally well-defined N,N-disubstituted hydrazine phosphorus-containing dendrimers of the fourth generation, with peripherally charged groups and diameters of approximately 7 nm, were used as the model polyelectrolytes. The pore diameter of the AAO was varied between 30-116 nm and the ionic strength was varied over 3 orders of magnitude. The dependence of the deposited layer thickness on ionic strength within the nanopores is found to be significantly stronger than LbL deposition on a planar surface. Furthermore, deposition within the nanopores can become inhibited even if the pore diameter is much larger than the diameter of the G4-polyelectrolyte, or if the screening length is insignificant relative to the dendrimer diameter at high ionic strengths. Our results will aid in the template preparation of polyelectrolyte multilayer nanotubes, and our experimental approach may be useful for investigating theories regarding the partitioning of nano-objects within nanopores where electrostatic interactions are dominant. Furthermore, we show that the enhanced ionic strength dependence of polyelectrolyte transport within the nanopores can be used to selectively deposit a LbL multilayer atop a nanoporous substrate.

Propylene/propane permeation properties of ethyl cellulose (EC) mixed matrix membranes fabricated by incorporation of nanoporous graphene nanosheets

PubMed Central

Yuan, Bingbing; Sun, Haixiang; Wang, Tao; Xu, Yanyan; Li, Peng; Kong, Ying; Niu, Q. Jason

2016-01-01

Nanopore containing graphene nanosheets were synthesized by graphene oxide and a reducing agent using a facile hydrothermal treatment in sodium hydroxide media. The as-prepared nanoporous graphene was incorporated into ethyl cellulose (EC) to prepare the mixed matrix membranes (MMMs) for C3H6/C3H8 separation. Transmission electron microscopy (TEM) photograph and X-ray photoelectron spectroscopy (XPS) analysis of nanoporous graphene nanosheets indicated that the structure of nano-pore was irregular and the oxygen-containing groups in the surface were limited. More importantly, the as-prepared MMMs presented better separation performance than that of pristine EC membrane due to simultaneous enhancement of C3H6 permeability and ideal selectivity. The ideal selectivity of the MMMs with 1.125 wt‰ nanoporous graphene content for C3H6/C3H8 increased from 3.45 to 10.42 and the permeability of C3H6 increased from 57.9 Barrer to 89.95 Barrer as compared with the pristine membrane. The presumed facilitated mechanism was that the high specific surface area of nanoporous graphene in polymer matrix increased the length of the tortuous pathway formed by nanopores for the gas diffusion as compared with the pristine graphene nanosheets, and generated a rigidified interface between the EC chains and fillers, thus enhanced the diffusivity selectivity. Therefore, it is expected that nanoporous graphene would be effective material for the C3H6/C3H8 separation. PMID:27352851

Towards molecular electronics with large-area molecular junctions.

PubMed

Akkerman, Hylke B; Blom, Paul W M; de Leeuw, Dago M; de Boer, Bert

2006-05-04

Electronic transport through single molecules has been studied extensively by academic and industrial research groups. Discrete tunnel junctions, or molecular diodes, have been reported using scanning probes, break junctions, metallic crossbars and nanopores. For technological applications, molecular tunnel junctions must be reliable, stable and reproducible. The conductance per molecule, however, typically varies by many orders of magnitude. Self-assembled monolayers (SAMs) may offer a promising route to the fabrication of reliable devices, and charge transport through SAMs of alkanethiols within nanopores is well understood, with non-resonant tunnelling dominating the transport mechanism. Unfortunately, electrical shorts in SAMs are often formed upon vapour deposition of the top electrode, which limits the diameter of the nanopore diodes to about 45 nm. Here we demonstrate a method to manufacture molecular junctions with diameters up to 100 microm with high yields (> 95 per cent). The junctions show excellent stability and reproducibility, and the conductance per unit area is similar to that obtained for benchmark nanopore diodes. Our technique involves processing the molecular junctions in the holes of a lithographically patterned photoresist, and then inserting a conducting polymer interlayer between the SAM and the metal top electrode. This simple approach is potentially low-cost and could pave the way for practical molecular electronics.

FITC-modified PPy nanotubes embedded in nanoporous AAO membrane can detect trace PCB20 via fluorescence ratiometric measurement.

PubMed

Wang, Meiling; Meng, Guowen; Huang, Qing; Xu, Qiaoling; Chu, Zhaoqin; Zhu, Chuhong

2011-04-07

A highly sensitive and selective fluorescence ratiometric sensor membrane for 2,3,3'-trichlorobiphenyl has been achieved, via depositing polypyrrole nanotubes (PPyNTs, the fluorescence indicator) in nano-porous anodic aluminium oxide (NPAAO) template and subsequently immobilizing fluorescein isothiocyanate (as an internal reference) onto the inner walls of the PPyNTs embedded in the NPAAO.

Fabrication of complete titania nanoporous structures via electrochemical anodization of Ti

PubMed Central

2011-01-01

We present a novel method to fabricate complete and highly oriented anodic titanium oxide (ATO) nano-porous structures with uniform and parallel nanochannels. ATO nano-porous structures are fabricated by anodizing a Ti-foil in two different organic viscous electrolytes at room temperature using a two-step anodizing method. TiO2 nanotubes covered with a few nanometer thin nano-porous layer is produced when the first and the second anodization are carried out in the same electrolyte. However, a complete titania nano-porous (TNP) structures are obtained when the second anodization is conducted in a viscous electrolyte when compared to the first one. TNP structure was attributed to the suppression of F-rich layer dissolution between the cell boundaries in the viscous electrolyte. The structural morphologies were examined by field emission scanning electron microscope. The average pore diameter is approximately 70 nm, while the average inter-pore distance is approximately 130 nm. These TNP structures are useful to fabricate other nanostructure materials and nanodevices. PMID:21711844

Removal of heavy metals from aqueous systems with thiol functionalized superparamagnetic nanoparticles.

PubMed

Yantasee, Wassana; Warner, Cynthia L; Sangvanich, Thanapon; Addleman, R Shane; Carter, Timothy G; Wiacek, Robert J; Fryxell, Glen E; Timchalk, Charles; Warner, Marvin G

2007-07-15

We have shown that superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) are an effective sorbent material for toxic soft metals such as Hg, Ag, Pb, Cd, and Tl, which effectively bind to the DMSA ligands and for As, which binds to the iron oxide lattices. The nanoparticles are highly dispersible and stable in solutions, have a large surface area (114 m2/g), and have a high functional group content (1.8 mmol thiols/g). They are attracted to a magnetic field and can be separated from solution within a minute with a 1.2 T magnet. The chemical affinity, capacity, kinetics, and stability of the magnetic nanoparticles were compared to those of conventional resin based sorbents (GT-73), activated carbon, and nanoporous silica (SAMMS) of similar surface chemistries in river water, groundwater, seawater, and human blood and plasma. DMSA-Fe3O4 had a capacity of 227 mg of Hg/g, a 30-fold larger value than GT-73. The nanoparticles removed 99 wt% of 1 mg/L Pb within a minute, while it took over 10 and 120 min for Chelex-100 and GT-73 to remove 96% of Pb.

Preparation and electrochemical performances of nanoporous/cracked cobalt oxide layer for supercapacitors

NASA Astrophysics Data System (ADS)

Gobal, Fereydoon; Faraji, Masoud

2014-12-01

Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc-cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic voltammetry, galvanostatic charge-discharge studies and electrochemical impedance spectroscopy in 1 M NaOH solution. The electrochemical data demonstrated that the electrodes display good capacitive behavior with a specific capacitance of 430 F g-1 at a current density of 1.0 A g-1 and specific capacitance retention of ca. 80 % after 10 days of being used in electrochemical experiments, indicating to be promising electroactive materials for supercapacitors. Furthermore, in comparison with electrodes prepared by simple cathodic deposition of cobalt onto TiO2 nanotubes(without dealloying procedure), the impedance studies showed improved performances likely due to nanoporous/cracked structures of electrodes fabricated by dealloying of zinc, which provide fast ion and electron transfer routes and large reaction surface area with the ensued fast reaction kinetics.

Stable catalyst layers for hydrogen permeable composite membranes

DOEpatents

Way, J. Douglas; Wolden, Colin A

2014-01-07

The present invention provides a hydrogen separation membrane based on nanoporous, composite metal carbide or metal sulfide coated membranes capable of high flux and permselectivity for hydrogen without platinum group metals. The present invention is capable of being operated over a broad temperature range, including at elevated temperatures, while maintaining hydrogen selectivity.

Boron Nitride Nanoporous Membranes with High Surface Charge by Atomic Layer Deposition.

PubMed

Weber, Matthieu; Koonkaew, Boonprakrong; Balme, Sebastien; Utke, Ivo; Picaud, Fabien; Iatsunskyi, Igor; Coy, Emerson; Miele, Philippe; Bechelany, Mikhael

2017-05-17

In this work, we report the design and the fine-tuning of boron nitride single nanopore and nanoporous membranes by atomic layer deposition (ALD). First, we developed an ALD process based on the use of BBr 3 and NH 3 as precursors in order to synthesize BN thin films. The deposited films were characterized in terms of thickness, composition, and microstructure. Next, we used the newly developed process to grow BN films on anodic aluminum oxide nanoporous templates, demonstrating the conformality benefit of BN prepared by ALD, and its scalability for the manufacturing of membranes. For the first time, the ALD process was then used to tune the diameter of fabricated single transmembrane nanopores by adjusting the BN thickness and to enable studies of the fundamental aspects of ionic transport on a single nanopore. At pH = 7, we estimated a surface charge density of 0.16 C·m -2 without slip and 0.07 C·m -2 considering a reasonable slip length of 3 nm. Molecular dynamics simulations performed with experimental conditions confirmed the conductivities and the sign of surface charges measured. The high ion transport results obtained and the ability to fine-tune nanoporous membranes by such a scalable method pave the way toward applications such as ionic separation, energy harvesting, and ultrafiltration devices.

Dealloying of gold–copper alloy nanowires: From hillocks to ring-shaped nanopores

PubMed Central

Chauvin, Adrien; Delacôte, Cyril; Boujtita, Mohammed; Angleraud, Benoit; Ding, Junjun; Choi, Chang-Hwan; Tessier, Pierre-Yves

2016-01-01

Summary We report on a novel fabrication approach of metal nanowires with complex surface. Taking advantage of nodular growth triggered by the presence of surface defects created intentionally on the substrate as well as the high tilt angle between the magnetron source axis and the normal to the substrate, metal nanowires containing hillocks emerging out of the surface can be created. The approach is demonstrated for several metals and alloys including gold, copper, silver, gold–copper and gold–silver. We demonstrate that applying an electrochemical dealloying process to the gold–copper alloy nanowire arrays allows for transforming the hillocks into ring-like shaped nanopores. The resulting porous gold nanowires exhibit a very high roughness and high specific surface making of them a promising candidate for the development of SERS-based sensors. PMID:27826510

Self bleaching photoelectrochemical-electrochromic device

DOEpatents

Bechinger, Clemens S.; Gregg, Brian A.

2002-04-09

A photoelectrochemical-electrochromic device comprising a first transparent electrode and a second transparent electrode in parallel, spaced relation to each other. The first transparent electrode is electrically connected to the second transparent electrode. An electrochromic material is applied to the first transparent electrode and a nanoporous semiconductor film having a dye adsorbed therein is applied to the second transparent electrode. An electrolyte layer contacts the electrochromic material and the nanoporous semiconductor film. The electrolyte layer has a redox couple whereby upon application of light, the nanoporous semiconductor layer dye absorbs the light and the redox couple oxidizes producing an electric field across the device modulating the effective light transmittance through the device.

Synthesis and characterization of nanoporous anodic oxide film on aluminum in H3PO4 + KMnO4 electrolyte mixture at different anodization conditions

NASA Astrophysics Data System (ADS)

Verma, Naveen; Jindal, Jitender; Singh, Krishan Chander; Mari, Bernabe

2016-04-01

The micro structural properties of nanoporous anodic oxide film formed in H3PO4 were highly influenced by addition of a low concentration of KMnO4 (0.0005 M) in 1 M H3PO4 solution. The KMnO4 as additive enhanced the growth rate of oxide film formation as well as thickness of pore walls. Furthermore the growth rate was found increased with increase in applied current density. The increase in temperature and lack of stirring during anodization causes the thinness of pore wall which leads to increase in pore volume. With the decrease in concentration of H3PO4 in anodizing electrolyte from 1M to 0.3 M, keeping all other conditions constant, the decrease in porosity was observed. This might be due to the dissolution of aluminium oxide film in highly concentrated acidic solution.

Nanoporous niobium nitride (Nb2N) with enhanced electrocatalytic performance for hydrogen evolution

NASA Astrophysics Data System (ADS)

Li, Yan; Zhang, Jianli; Qian, Xingyue; Zhang, Yue; Wang, Yining; Hu, Rudan; Yao, Chao; Zhu, Junwu

2018-01-01

The transition metal nitrides (TMNs) with nanoporous structure have shown great promise as potential electrocatalysts for the hydrogen evolution reaction (HER). Herein, self-organized nanoporous Nb2N was first successfully synthesized through the anodization of niobium in mixed oxalic acid/HF electrolyte, followed by a simple annealing treatment in the ammonia atmosphere. Due to the highly ordered nanoporous structure with abundant active sites and the enhanced electrical conductivity, the Nb2N exhibits a high catalytic current (326.3 mA cm-2) and low onset potential (96.3 mV), which is almost 3.9 times and 4.2 times better than that of Nb2O5, respectively. Meanwhile, the Nb2N also presents low Tafel slope (92 mV dec-1), and excellent cycling durability. More importantly, this study will provide more opportunities for designing and fabricating niobium compounds as an innovative HER catalysts.

Evaluation of elastic properties of nanoporous silicon oxide thin films by picosecond laser ultrasonics

NASA Astrophysics Data System (ADS)

Mechri, C.; Ruello, P.; Gusev, V.; Breteau, J. M.; Mounier, D.; Henderson, M.; Gibaud, A.; Dourdain, S.

2008-01-01

Picosecond laser ultrasonics uses femtosecond laser pulses for the generation and detection of acoustic pulses with a typical duration between few picoseconds and few hundreds of pico seconds. The shorter the duration of the acoustic pulse is, the more precisely could be made the measurements of the film thickness [C. Thomsen et al., Phys. Rev. B 34, 4129 (1986)] and the elastic modulus by pulse-echo method or through Brillouin scattering detection. In this short communication we report the results of the evaluation of the properties of nanoporous silicon oxide thin films which present potential low-k and thermal barrier properties and are also of great interest for the microelectronic industry to replace the traditional silicate glass films in order to decrease the resistance-capacitance transition delay in the VLSI circuits. Most of the studies that have been carried so far have treated the optical properties of such structures. We report the results of the evaluation of acoustic properties of nanoporous thin films.

Facile fabrication of nanofluidic diode membranes using anodic aluminium oxide.

PubMed

Wu, Songmei; Wildhaber, Fabien; Vazquez-Mena, Oscar; Bertsch, Arnaud; Brugger, Juergen; Renaud, Philippe

2012-09-21

Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al(2)O(3)/SiO(2) (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al(2)O(3) (positive) and SiO(2) (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion.

Influences of Au ion radiation on microstructure and surface-enhanced Raman scattering of nanoporous copper

NASA Astrophysics Data System (ADS)

Wang, Jing; Hu, Zhaoyi; Li, Rui; Liu, Xiongjun; Xu, Chuan; Wang, Hui; Wu, Yuan; Fu, Engang; Lu, Zhaoping

2018-05-01

In this work, effects of Au ion irradiation on microstructure and surface-enhanced Raman scattering (SERS) performance of nanoporous copper (NPC) were investigated. It is found that the microstructure of NPC could be tailored by the ion irradiation dose, i.e., the pore size decreases while the ligament size significantly coarsens with the increase of the irradiation dose. In addition, the SERS enhancement for rhodamine 6G molecules was improved by Au ions irradiation at an appropriate dose. The underlying mechanism of the increase of SERS enhancement resulted from ion irradiation was discussed. Our findings could provide a new way to tune nanoporosity of nanoporous metals and improve their SERS performance.

Influences of Au ion radiation on microstructure and surface-enhanced Raman scattering of nanoporous copper.

PubMed

Wang, Jing; Hu, Zhaoyi; Li, Rui; Liu, Xiongjun; Xu, Chuan; Wang, Hui; Wu, Yuan; Fu, Engang; Lu, Zhaoping

2018-05-04

In this work, effects of Au ion irradiation on microstructure and surface-enhanced Raman scattering (SERS) performance of nanoporous copper (NPC) were investigated. It is found that the microstructure of NPC could be tailored by the ion irradiation dose, i.e., the pore size decreases while the ligament size significantly coarsens with the increase of the irradiation dose. In addition, the SERS enhancement for rhodamine 6G molecules was improved by Au ions irradiation at an appropriate dose. The underlying mechanism of the increase of SERS enhancement resulted from ion irradiation was discussed. Our findings could provide a new way to tune nanoporosity of nanoporous metals and improve their SERS performance.

Photochemistry of nanoporous carbons: Perspectives in energy conversion and environmental remediation.

PubMed

Gomis-Berenguer, Alicia; Velasco, Leticia F; Velo-Gala, Inmaculada; Ania, Conchi O

2017-03-15

The interest in the use of nanoporous carbon materials in applications related to energy conversion and storage, either as catalysts or additives, has grown over recent decades in various disciplines. Since the early studies reporting the benefits of the use of nanoporous carbons as inert supports of semiconductors and as electron acceptors that enhance the splitting of the photogenerated excitons, many researchers have investigated the key role of carbon matrices coupled to all types of photoactive materials. More recently, our group has demonstrated the ability of semiconductor-free nanoporous carbons to convert the absorbed photons into chemical reactions (i.e. oxidation of pollutants, water splitting, reduction of surface groups) opening new opportunities beyond conventional applications in light energy conversion. The aim of this paper is to review the recent progress on the application of nanoporous carbons in photochemistry using varied illumination conditions (UV, simulated solar light) and covering their role as additives to semiconductors as well as their use as photocatalysts in various fields, describing the photochemical quantum yield of nanoporous carbons for different reactions, and discussing the mechanisms postulated for the carbon/light interactions in confined pore spaces. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Three-dimensional block copolymer nanostructures by the solvent-annealing-induced wetting in anodic aluminum oxide templates.

PubMed

Chu, Chiang-Jui; Chung, Pei-Yun; Chi, Mu-Huan; Kao, Yi-Huei; Chen, Jiun-Tai

2014-09-01

Block copolymers have been extensively studied over the last few decades because they can self-assemble into well-ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this work, the fabrication and morphologies of three-dimensional polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanostructures confined in the nanopores of anodic aluminum oxide (AAO) templates are studied. It is discovered that the block copolymers can wet the nanopores using a novel solvent-annealing-induced nanowetting in templates (SAINT) method. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS-b-PDMS nanostructures can be controlled by changing the wetting conditions. Different solvents are used as the annealing solvent, including toluene, hexane, and a co-solvent of toluene and hexane. When the block copolymer wets the nanopores in toluene vapors, a perpendicular morphology is observed. When the block copolymer wets the nanopores in co-solvent vapors (toluene/hexane = 3:2), unusual circular and helical morphologies are obtained. These three-dimensional nanostructures can serve as naontemplates for refilling with other functional materials, such as Au, Ag, ZnO, and TiO2 . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Synthesis of Coral-Like Tantalum Oxide Films via Anodization in Mixed Organic-Inorganic Electrolytes

PubMed Central

Yu, Hongbin; Zhu, Suiyi; Yang, Xia; Wang, Xinhong; Sun, Hongwei; Huo, Mingxin

2013-01-01

We report a simple method to fabricate nano-porous tantalum oxide films via anodization with Ta foils as the anode at room temperature. A mixture of ethylene glycol, phosphoric acid, NH4F and H2O was used as the electrolyte where the nano-porous tantalum oxide could be synthesized by anodizing a tantalum foil for 1 h at 20 V in a two–electrode configuration. The as-prepared porous film exhibited a continuous, uniform and coral-like morphology. The diameters of pores ranged from 30 nm to 50 nm. The pores interlaced each other and the depth was about 150 nm. After calcination, the as-synthesized amorphous tantalum oxide could be crystallized to the orthorhombic crystal system. As observed in photocatalytic experiments, the coral-like tantalum oxide exhibited a higher photocatalytic activity for the degradation of phenol than that with a compact surface morphology, and the elimination rate of phenol increased by 66.7%. PMID:23799106

Electrolysis-induced protonation of VO2 thin film transistor for the metal-insulator phase modulation

NASA Astrophysics Data System (ADS)

Katase, Takayoshi; Endo, Kenji; Ohta, Hiromichi

2016-02-01

Compared to state-of-the-art modulation techniques, protonation is the most ideal to control the electrical and optical properties of transition metal oxides (TMOs) due to its intrinsic non-volatile operation. However, the protonation of TMOs is not typically utilized for solid-state devices because of imperative high-temperature annealing treatment in hydrogen source. Although one solution for room temperature (RT) protonation of TMOs is liquid-phase electrochemistry, it is unsuited for practical purposes due to liquid-leakage problem. Herein we demonstrate solid-state RT-protonation of vanadium dioxide (VO2), which is a well-known thermochromic TMO. We fabricated the three terminal thin-film-transistor structure on an insulating VO2 film using a water-infiltrated nanoporous glass, which serves as a solid electrolyte. For gate voltage application, water electrolysis and protonation/deprotonation of VO2 film surface occurred, leading to reversible metal-insulator phase conversion of ~11-nm-thick VO2 layer. The protonation was clearly accompanied by the structural change from an insulating monoclinic to a metallic tetragonal phase. Present results offer a new route for the development of electro-optically active solid-state devices with TMO materials by engineering RT protonation.

Determination by Small-angle X-ray Scattering of Pore Size Distribution in Nanoporous Track-etched Polycarbonate Membranes

NASA Astrophysics Data System (ADS)

Jonas, A. M.; Legras, R.; Ferain, E.

1998-03-01

Nanoporous track-etched membranes with narrow pore size distributions and average pore size diameters tunable from 100 to 1000 Åare produced by the chemical etching of latent tracks in polymer films after irradiation by a beam of accelerated heavy ions. Nanoporous membranes are used for highly demanding filtration purposes, or as templates to obtain metallic or polymeric nanowires (L. Piraux et al., Nucl. Instr. Meth. Phys. Res. 1997, B131, 357). Such applications call for developments in nanopore size characterization techniques. In this respect, we report on the characterization by small-angle X-ray scattering (SAXS) of nanopore size distribution (nPSD) in polycarbonate track-etched membranes. The obtention of nPSD requires inverting an ill-conditioned inhomogeneous equation. We present different numerical routes to overcome the amplification of experimental errors in the resulting solutions, including a regularization technique allowing to obtain the nPSD without a priori knowledge of its shape. The effect of deviations from cylindrical pore shape on the resulting distributions are analyzed. Finally, SAXS results are compared to results obtained by electron microscopy and conductometry.

Modified secondary lithium metal batteries with the polyaniline-carbon nanotube composite buffer layer.

PubMed

Zhang, Ding; Yin, Yanli; Liu, Changhong; Fan, Shoushan

2015-01-07

A modified secondary lithium metal battery inserted with a polyaniline-carbon nanotube nanoporous composite buffer layer was fabricated. This unique and simple design of battery has the great potential to decrease the safety risk of the secondary Li metal battery in cycles of recharging processes and improve its cycle life in the future.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devkota, Jagannath; Kim, Ki-Joong; Ohodnicki, Paul R.

The integration of nanoporous materials such as metal organic frameworks (MOFs) with sensitive transducers can result in robust sensing platforms for monitoring gases and chemical vapors for a range of applications.

Facile Synthesis of Nanoporous Pt-Y alloy with Enhanced Electrocatalytic Activity and Durability

NASA Astrophysics Data System (ADS)

Cui, Rongjing; Mei, Ling; Han, Guangjie; Chen, Jiyun; Zhang, Genhua; Quan, Ying; Gu, Ning; Zhang, Lei; Fang, Yong; Qian, Bin; Jiang, Xuefan; Han, Zhida

2017-02-01

Recently, Pt-Y alloy has displayed an excellent electrocatalytic activity for oxygen reduction reaction (ORR), and is regarded as a promising cathode catalyst for fuel cells. However, the bulk production of nanoscaled Pt-Y alloy with outstanding catalytic performance remains a great challenge. Here, we address the challenge through a simple dealloying method to synthesize nanoporous Pt-Y alloy (NP-PtY) with a typical ligament size of ~5 nm. By combining the intrinsic superior electrocatalytic activity of Pt-Y alloy with the special nanoporous structure, the NP-PtY bimetallic catalyst presents higher activity for ORR and ethanol oxidation reaction, and better electrocatalytic stability than the commercial Pt/C catalyst and nanoporous Pt alloy. The as-made NP-PtY holds great application potential as a promising electrocatalyst in proton exchange membrane fuel cells due to the advantages of facile preparation and excellent catalytic performance.

Over-limiting Current and Control of Dendritic Growth by Surface Conduction in Nanopores

PubMed Central

Han, Ji-Hyung; Khoo, Edwin; Bai, Peng; Bazant, Martin Z.

2014-01-01

Understanding over-limiting current (faster than diffusion) is a long-standing challenge in electrochemistry with applications in desalination and energy storage. Known mechanisms involve either chemical or hydrodynamic instabilities in unconfined electrolytes. Here, it is shown that over-limiting current can be sustained by surface conduction in nanopores, without any such instabilities, and used to control dendritic growth during electrodeposition. Copper electrodeposits are grown in anodized aluminum oxide membranes with polyelectrolyte coatings to modify the surface charge. At low currents, uniform electroplating occurs, unaffected by surface modification due to thin electric double layers, but the morphology changes dramatically above the limiting current. With negative surface charge, growth is enhanced along the nanopore surfaces, forming surface dendrites and nanotubes behind a deionization shock. With positive surface charge, dendrites avoid the surfaces and are either guided along the nanopore centers or blocked from penetrating the membrane. PMID:25394685

Nanoporous Gallium Nitride Through Anisotropic Metal-Assisted Electroless Photochemical Wet Etching Technique

NASA Astrophysics Data System (ADS)

Perumal, R.; Hassan, Z.

2016-12-01

Nanoporous gallium nitride (GaN) has many potential applications in light-emitting diodes (LEDs), photovoltaics, templates and chemical sensors. This article reports the porosification of GaN through UV enhanced metal-assisted electroless photochemical wet etching technique using three different acid-based etchants and platinum served as catalyst for porosification. The etching process was conducted at room temperature for a duration of 90min. The morphological, structural, spectral and optical features of the developed porous GaN were studied with appropriate characterization techniques and the obtained results were presented. Field emission scanning electron micrographs exhibited the porosity nature along with excellent porous network of the etched samples. Structural studies confirmed the mono crystalline quality of the porous nanostructures. Raman spectral analyzes inferred the presenting phonon modes such as E2 (TO) and A1 (LO) in fabricated nanoporous structures. The resulted porous nanostructures hold the substantially enhanced photoluminescence intensity compared with the pristine GaN epitaxial film that is interesting and desirable for several advances in the applications of Nano-optoelectronic devices.

3D architecture constructed via the confined growth of MoS2 nanosheets in nanoporous carbon derived from metal-organic frameworks for efficient hydrogen production.

PubMed

Liu, Yun; Zhou, Xiaoli; Ding, Tao; Wang, Chunde; Yang, Qing

2015-11-21

The design and synthesis of robust, high-performance and low-cost three-dimensional (3D) hierarchical structured materials for the electrochemical reduction of water to generate hydrogen is of great significance for practical water splitting applications. In this study, we develop an in situ space-confined method to synthesize an MoS2-based 3D hierarchical structure, in which the MoS2 nanosheets grow in the confined nanopores of metal-organic frameworks (MOFs)-derived 3D carbons as electrocatalysts for efficient hydrogen production. Benefiting from its unique structure, which has more exposed active sites and enhanced conductivity, the as-prepared MoS2/3D nanoporous carbon (3D-NPC) composite exhibits remarkable electrocatalytic activity for the hydrogen evolution reaction (HER) with a small onset overpotential of ∼0.16 V, large cathodic currents, small Tafel slope of 51 mV per decade and good durability. We anticipate that this in situ confined growth provides new insights into the construction of high performance catalysts for energy storage and conversion.

3D nanoporous graphene films converted from liquid-crystalline holey graphene oxide for thin and high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Wang, Bin; Liu, Jinzhang; Zhao, Yi; Zheng, Dezhi; Li, Yan; Sha, Jiangbo

2018-01-01

Holey graphene oxide (HGO) is prepared and its liquid crystal (LC) formation in water is investigated. The blade-coated LC-HGO hydrogel is hydrothermally reduced to form 3D nanoporous films used as supercapacitor electrodes. Holey graphene sheets are rumpled and interconnected to form a cellular structure with pore size around 100 nm during the reduction process. Reduced HGO films with different thicknesses are integrated into solid-state symmetric supercapacitors and their electrochemical performances are studied. High specific capacitance up to 304 F g-1 and high volumetric capacitance around 400 F cm-3 are achieved from our thin and flexible devices.

Novel spider-web-like nanoporous networks based on jute cellulose nanowhiskers.

PubMed

Cao, Xinwang; Wang, Xianfeng; Ding, Bin; Yu, Jianyong; Sun, Gang

2013-02-15

Cellulose nanowhiskers as a kind of renewable and biocompatible nanomaterials evoke much interest because of its versatility in various applications. Herein, for the first time, a novel controllable fabrication of spider-web-like nanoporous networks based on jute cellulose nanowhiskers (JCNs) deposited on the electrospun (ES) nanofibrous membrane by simple directly immersion-drying method is reported. Jute cellulose nanowhiskers were extracted from jute fibers with a high yield (over 80%) via a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/NaBr/NaClO system selective oxidization combined with mechanical homogenization. The morphology of JCNs nanoporous networks/ES nanofibrous membrane architecture, including coverage rate, pore-width and layer-by-layer packing structure of the nanoporous networks, can be finely controlled by regulating the JCNs dispersions properties and drying conditions. The versatile nanoporous network composites based on jute cellulose nanowhiskers with ultrathin diameters (3-10 nm) and nanofibrous membrane supports with diameters of 100-300 nm, would be particularly useful for filter applications. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.

Rapid, conformal gas-phase formation of silica (SiO2) nanotubes from water condensates.

PubMed

Bae, Changdeuck; Kim, Hyunchul; Yang, Yunjeong; Yoo, Hyunjun; Montero Moreno, Josep M; Bachmann, Julien; Nielsch, Kornelius; Shin, Hyunjung

2013-07-07

An innovative atomic layer deposition (ALD) concept, with which nanostructures of water condensates with high aspect ratio at equilibrium in cylindrical nanopores can be transformed uniformly into silica (SiO2) at near room temperature and ambient pressure, has been demonstrated for the first time. As a challenging model system, we first prove the conversion of cylindrical water condensates in porous alumina membranes to silica nanotubes (NTs) by introducing SiCl4 as a metal reactant without involving any catalytic reaction. Surprisingly, the water NTs reproducibly transformed into silica NTs, where the wall thickness of the silica NTs deposited per cycle was found to be limited by the amount of condensed water, and it was on the orders of ten nanometers per cycle (i.e., over 50 times faster than that of conventional ALD). More remarkably, the reactions only took place for 10-20 minutes or less without vacuum-related equipment. The thickness of initially adsorbed water layers in cylindrical nanopores was indirectly estimated from the thickness of formed SiO2 layers. With systematic experimental designs, we tackle the classical Kelvin equation in the nanosized pores, and the role of van der Waals forces in the nanoscale wetting phenomena, which is a long-standing issue lacking experimental insight. Moreover, we show that the present strategy is likely generalized to other oxide systems such as TiO2. Our approach opens up a new avenue for ultra-simple preparation of porous oxides and allows for the room temperature formation of dielectric layers toward organic electronic and photovoltaic applications.

A facile one-pot oxidation-assisted dealloying protocol to massively synthesize monolithic core-shell architectured nanoporous copper@cuprous oxide nanonetworks for photodegradation of methyl orange

PubMed Central

Liu, Wenbo; Chen, Long; Dong, Xin; Yan, Jiazhen; Li, Ning; Shi, Sanqiang; Zhang, Shichao

2016-01-01

In this report, a facile and effective one-pot oxidation-assisted dealloying protocol has been developed to massively synthesize monolithic core-shell architectured nanoporous copper@cuprous oxide nanonetworks (C-S NPC@Cu2O NNs) by chemical dealloying of melt-spun Al 37 at.% Cu alloy in an oxygen-rich alkaline solution at room temperature, which possesses superior photocatalytic activity towards photodegradation of methyl orange (MO). The experimental results show that the as-prepared nanocomposite exhibits an open, bicontinuous interpenetrating ligament-pore structure with length scales of 20 ± 5 nm, in which the ligaments comprising Cu and Cu2O are typical of core-shell architecture with uniform shell thickness of ca. 3.5 nm. The photodegradation experiments of C-S NPC@Cu2O NNs show their superior photocatalytic activities for the MO degradation under visible light irradiation with degradation rate as high as 6.67 mg min−1 gcat−1, which is a diffusion-controlled kinetic process in essence in light of the good linear correlation between photodegradation ratio and square root of irradiation time. The excellent photocatalytic activity can be ascribed to the synergistic effects between unique core-shell architecture and 3D nanoporous network with high specific surface area and fast mass transfer channel, indicating that the C-S NPC@Cu2O NNs will be a promising candidate for photocatalysts of MO degradation. PMID:27830720

A facile one-pot oxidation-assisted dealloying protocol to massively synthesize monolithic core-shell architectured nanoporous copper@cuprous oxide nanonetworks for photodegradation of methyl orange

NASA Astrophysics Data System (ADS)

Liu, Wenbo; Chen, Long; Dong, Xin; Yan, Jiazhen; Li, Ning; Shi, Sanqiang; Zhang, Shichao

2016-11-01

In this report, a facile and effective one-pot oxidation-assisted dealloying protocol has been developed to massively synthesize monolithic core-shell architectured nanoporous copper@cuprous oxide nanonetworks (C-S NPC@Cu2O NNs) by chemical dealloying of melt-spun Al 37 at.% Cu alloy in an oxygen-rich alkaline solution at room temperature, which possesses superior photocatalytic activity towards photodegradation of methyl orange (MO). The experimental results show that the as-prepared nanocomposite exhibits an open, bicontinuous interpenetrating ligament-pore structure with length scales of 20 ± 5 nm, in which the ligaments comprising Cu and Cu2O are typical of core-shell architecture with uniform shell thickness of ca. 3.5 nm. The photodegradation experiments of C-S NPC@Cu2O NNs show their superior photocatalytic activities for the MO degradation under visible light irradiation with degradation rate as high as 6.67 mg min-1 gcat-1, which is a diffusion-controlled kinetic process in essence in light of the good linear correlation between photodegradation ratio and square root of irradiation time. The excellent photocatalytic activity can be ascribed to the synergistic effects between unique core-shell architecture and 3D nanoporous network with high specific surface area and fast mass transfer channel, indicating that the C-S NPC@Cu2O NNs will be a promising candidate for photocatalysts of MO degradation.

Investigation of nanoporous platinum thin films fabricated by reactive sputtering: Application as micro-SOFC electrode

NASA Astrophysics Data System (ADS)

Jung, WooChul; Kim, Jae Jin; Tuller, Harry L.

2015-02-01

Highly porous Pt thin films, with nano-scale porosity, were fabricated by reactive sputtering. The strategy involved deposition of thin film PtOx at room temperature, followed by the subsequent decomposition of the oxide by rapid heat treatment. The resulting films exhibited percolating Pt networks infiltrated with interconnected nanosized pores, critical for superior solid oxide fuel cell cathode performance. This approach is particularly attractive for micro-fabricated solid oxide fuel cells, since it enables fabrication of the entire cell stack (anode/electrolyte/cathode) within the sputtering chamber, without breaking vacuum. In this work, the morphological, crystallographic and chemical properties of the porous electrode were systematically varied by control of deposition conditions. Oxygen reduction reaction kinetics were investigated by means of electrochemical impedance spectroscopy, demonstrating the critical role of nano-pores in achieving satisfactory micro-SOFC cathode performance.

Piezoelectric and dielectric properties of nanoporous polyvinylidence fluoride (PVDF) films

NASA Astrophysics Data System (ADS)

Zhao, Ping; Wang, Shifa; Kadlec, Alec

2016-04-01

A nanoporous polyvinylidene Fluoride (PVDF) thin film was developed for applications in energy harvesting, medical surgeries, and industrial robotics. This sponge-like nanoporous PVDF structure dramatically enhanced the piezoelectric effect because it yielded considerably large deformation under a small force. A casting-etching method was adopted to make films, which is effective to control the porosity, flexibility, and thickness of the film. The films with various Zinc Oxide (ZnO) mass fractions ranging from 10 to 50% were fabricated to investigate the porosity effect. The piezoelectric coefficient d33 as well as dielectric constant and loss of the films were characterized. The results were analyzed and the optimal design of the film with the right amount of ZnO nanoparticles was determined.

Nano-assembly and Controlled Release Kinetics of Nanoelements from Nanoporous Templates

NASA Astrophysics Data System (ADS)

Gultepe, E.; Nagesha, D.; McNulty, J.; Sridhar, S.

2008-03-01

Nanotemplates and nanoparticles have potential for use in the area of nanomanufacturing and biomedical applications. We are using highly ordered nanoporous alumina as a template for drug delivery and to assemble nanoelements such as latex beads and single wall carbon nanotubes (SWNT) by the means of electrophoresis and/or dielectrophoresis. The results of 100% assembly of latex beads and controlled elution of drugs from nanoporous templates will be discussed. Vertically assembled SWNT and with the I-V characteristic as 3D interconnects, will also be presented. We have developed a variety of platforms incorporating superparamagnetic iron oxide nanoparticles for targeted delivery, magnetic hyperthermia and as a contrast agent for magnetic resonance imaging. The results of cell studies on these platforms will be discussed.

Enhanced piezoelectric output of NiO/nanoporous GaN by suppression of internal carrier screening

NASA Astrophysics Data System (ADS)

Waseem, Aadil; Jeong, Dae Kyung; Johar, Muhammad Ali; Kang, Jin-Ho; Ha, Jun-Seok; Key Lee, June; Ryu, Sang-Wan

2018-06-01

The efficiency of piezoelectric nanogenerators (PNGs) significantly depends on the free carrier concentration of semiconductors. In the presence of a mechanical stress, piezoelectric charges are generated at both ends of the PNG, which are rapidly screened by the free carriers. The screening effect rapidly decreases the piezoelectric output within fractions of a second. In this study, the piezoelectric outputs of bulk- and nanoporous GaN-based heterojunction PNGs are compared. GaN thin films were epitaxially grown on sapphire substrates using metal organic chemical vapor deposition. Nanoporous GaN was fabricated using electrochemical etching, depleted of free carriers owing to the surface Fermi-level pinning. A highly resistive NiO thin film was deposited on bulk- and nanoporous GaN using radio frequency magnetron sputter. The NiO/nanoporous GaN PNG (NPNG) under a periodic compressive stress of 4 MPa exhibited an output voltage and current of 0.32 V and 1.48 μA cm‑2, respectively. The output voltage and current of the NiO/thin film-GaN PNG (TPNG) were three and five times smaller than those of the NPNG, respectively. Therefore, the high-resistivity of NiO and nanoporous GaN depleted by the Fermi-level pinning are advantageous and provide a better piezoelectric performance of the NPNG, compared with that of the TPNG.

Localization Transport in Granular and Nanoporous Carbon Systems.

NASA Astrophysics Data System (ADS)

Fung, Alex Weng Pui

Porous carbon materials have long since been used in industry to make capacitors and adsorption agents because of their high specific surface area. Although their adsorption properties have been extensively studied, we have not seen the same vigor in the investigation of their physical properties, which are important not only for providing complementary characterization methods, but also for understanding the physics which underlies the manufacturing process and motivates intelligent design of these materials. The study of the new physics in these novel nanoporous materials also straddles the scientific forefronts of nanodimensional and disordered systems. In this thesis, we study the structural and electrical properties of two nanoporous carbons, namely activated carbon fibers and carbon aerogels. Specifically, we perform Raman scattering, x-ray diffraction, magnetic susceptibility, electrical transport and magnetotransport experiments. Results from other experiments reported in the literature or communicated to us by our collaborators, such as porosity and surface area measurements by adsorption methods, electron spin resonance, transmission electron microscopy, mechanical properties measurements and so on, are also frequently used in this thesis for additional characterization information. By correlating all the relevant results, we obtain the structure -property relationships in these nanoporous materials. This study shows that the transport properties of these porous materials can be used on one hand for sensitive characterization of complex materials, and on the other hand, for observing interesting and unusual physical phenomena. For example, as-prepared nanoporous carbon systems, exhibit in their low-temperature electrical conductivity a universal temperature dependence which is characteristic of a granular metallic system, despite their morphological differences. By studying further the magnetoresistance in these carbon materials, it is found that the variable-range hopping mechanism cannot be totally disregarded in the understanding of the low-temperature conduction process in some granular metals having a similar morphology. In the transport study of the heat-treated activated carbon fibers, the surprising observation of a negative magnetoresistance at room temperature has also provided some insight into the weak localization phenomenon in the percolation limit. In particular, the effects of anomalous diffusion in a percolating system is now included in the calculations of the weak-localization corrections to the conductivity and magnetoresistance, yielding a new temperature dependence of the dephasing distance. These localization phenomena in the nanoporous carbon structures studied here are mostly understandable in terms of the existing theories for disordered systems, but their detailed interpretations often indicate problems and shortcomings in some of these theories, at times because the physical properties of the nanoporous carbon materials studied here are unique among disordered materials. Hence, nanoporous carbons belong to a distinct class of disordered systems in their own rights. In the field of transport in disordered systems, porous media also seem to have been an oversight of the general research community, although theoretical percolation studies have often touched upon systems with similar morphologies. This thesis presents a study of the transport behavior in nanoporous carbons over the full spectrum of disorder, controlled by heat treatment, starting from the strong localization regime, then crossing the metal-insulator transition, and finally to the weak localization limit. In each regime of disorder, the existing theories are either adapted, and when necessary, extended to explain the observed transport behavior in these fascinating materials. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-1690.).

Comprehensive study of thin film evaporation from nanoporous membranes for enhanced thermal management

NASA Astrophysics Data System (ADS)

Wilke, Kyle; Barabadi, Banafsheh; Lu, Zhengmao; Zhang, Tiejun; Wang, Evelyn

Performance of emerging electronics is often dictated by the ability to dissipate heat generated in the device. Thin film evaporation from nanopores promises enhanced thermal management by reducing the thermal transport resistance across the liquid film while providing capillary pumping. We present a study of the dependence of evaporation from nanopores on a variety of geometric parameters. Anodic aluminum oxide membranes were used as an experimental template. A biphilic treatment was also used to create a hydrophobic section of the pore to control meniscus location. We demonstrated different heat transfer regimes and observed more than an order of magnitude increase in dissipated heat flux by confining fluid within the nanopore. Pore diameter had little effect on evaporation performance at pore radii of this length scale due to the negligible conduction resistance from the pore wall to the evaporating interface. The dissipated heat flux scaled linearly with porosity as the evaporative area increased. Furthermore, it was demonstrated that moving the meniscus as little as 1 μm into the pore could decrease performance significantly. The results provide a better understanding of evaporation from nanopores and provide guidance in future device design.

Metal-assisted electroless fabrication of nanoporous p-GaN for increasing the light extraction efficiency of light emitting diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Ruijun; Liu Duo; Zuo Zhiyuan

2012-03-15

We report metal-assisted electroless fabrication of nanoporous p-GaN to improve the light extraction efficiency of GaN-based light emitting diodes (LEDs). Although it has long been believed that p-GaN cannot be etched at room temperature, in this study we find that Ag nanocrystals (NCs) on the p-GaN surface enable effective etching of p-GaN in a mixture of HF and K{sub 2}S{sub 2}O{sub 8} under ultraviolet (UV) irradiation. It is further shown that the roughened GaN/air interface enables strong scattering of photons emitted from the multiple quantum wells (MQWs). The light output power measurements indicate that the nanoporous LEDs obtained after 10more » min etching show a 32.7% enhancement in light-output relative to the conventional LEDs at an injection current of 20 mA without significant increase of the operating voltage. In contrast, the samples etched for 20 min show performance degradation when compared with those etched for 10 min, this is attributed to the current crowding effect and increased surface recombination rate.« less

Design and fabrication of Ni nanowires having periodically hollow nanostructures.

PubMed

Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2014-10-07

We propose a concept for the design and fabrication of metal nanowires having periodically hollow nanostructures inside the pores of an anodic aluminum oxide (AAO) membrane using a sacrificial metal. In this study, nickel (Ni) and silver (Ag) were used as the base metal and the sacrificial metal, respectively. Alternating an applied potential between -0.4 and -1.0 V provided alternatively deposited Ni and Ag segments in a Ni-Ag 'barcode' nanowire with a diameter of 18 or 35 nm. After etching away the Ag segments, we fabricated Ni nanowires with nanopores of 12 ± 5.3 nm. Such nanostructure formation is explained by the formation of a Ni shell layer over the surface of the Ag segments due to the strong affinity of Ni(2+) for the interior surfaces of AAO. The Ni shell layer allows the Ni segments to remain even after dissolution of the Ag segments. Because the electroplating conditions can be easily controlled, we could carefully adjust the size and pitch of the periodically hollow nanospaces. We also describe a method for the fabrication of Ni nanorods by forming an Ag shell instead of a Ni shell on the Ni-Ag barcode nanowire, in which the interior of the AAO surfaces was modified with a compound bearing a thiol group prior to electroplating.

Electrostatic Assembly of Nanomaterials for Hybrid Electrodes and Supercapacitors

NASA Astrophysics Data System (ADS)

Hammond, Paula

2015-03-01

Electrostatic assembly methods have been used to generate a range of new materials systems of interest for electrochemical energy and storage applications. Over the past several years, it has been demonstrated that carbon nanotubes, metals, metal oxides, polymeric nanomaterials, and biotemplated materials systems can be incorporated into ultrathin films to generate supercapacitors and battery electrodes that illustrate significant energy density and power. The unique ability to control the incorporation of such a broad range of materials at the nanometer length scale allows tailoring of the final properties of these unique composite systems, as well as the capability of creating complex micron-scale to nanoporous morphologies based on the scale of the nanomaterial that is absorbed within the structure, or the conditions of self-assembly. Recently we have expanded these capabilities to achieve new electrodes that are templated atop electrospun polmer fiber scaffolds, in which the polymer can be selectively removed to achieve highly porous materials. Spray-layer-by-layer and filtration methods of functionalized multiwall carbon nanotubes and polyaniline nanofibers enable the generation of electrode systems with unusually high surface. Incorporation of psuedocapacitive nanoparticles can enhance capacitive properties, and other catalytic or metallic nanoparticles can be implemented to enhance electrochemical or catalytic function.

Nanoporous films: From conventional to the conformal

DOE PAGES

Allendorf, Mark D.; Stavila, Vitalie

2015-12-14

Here, thin and continuous films of porous metal-organic frameworks can now be conformally deposited on various substrates using a vapor-phase synthesis approach that departs from conventional solution-based routes.

A facile route towards large area self-assembled nanoscale silver film morphologies and their applications towards metal enhanced fluorescence

DOE PAGES

Hohenberger, Erik; Freitag, Nathan; Rosenmann, Daniel; ...

2017-04-19

Here, we present a facile method for fabricating nanostructured silver films containing a high density of nanoscopic gap features through a surface directed phenomenon utilizing nanoporous scaffolds rather than through traditional lithographic patterning processes. This method enables tunability of the silver film growth by simply adjusting the formulation and processing conditions of the nanoporous film prior to metallization. We further demonstrate that this process can produce nanoscopic gaps in thick (100 nm) silver films supporting localized surface plasmon resonance with large field amplification within the gaps while enabling launching of propagating surface plasmons within the silver grains. These enhanced fieldsmore » provide metal enhanced fluorescence with enhancement factors as high as 21 times compared to glass, as well as enable visualization of single fluorophore emission. This work provides a low-cost rapid approach for producing novel nanostructures capable of broadband fluorescence amplification, with potential applications including plasmonic and fluorescence based optical sensing and imaging applications.« less

Ion-beam-induced planarization, densification, and exfoliation of low-density nanoporous silica

NASA Astrophysics Data System (ADS)

Kucheyev, S. O.; Shin, S. J.

2017-09-01

Planarization of low-density nanoporous solids is challenging. Here, we demonstrate that ion bombardment to doses of ˜1015 cm-2 results in significant smoothing of silica aerogels, yielding mirror-like surfaces after metallization. The surface smoothing efficiency scales with the ion energy loss component leading to local lattice heating. Planarization is accompanied by sub-surface monolith densification, resulting in surface exfoliation with increasing ion dose. These findings have implications for the fabrication of graded-density nanofoams, aerogel-based lightweight optical components, and meso-origami.

Heterobimetallic Metal–Organic Framework as a Precursor to Prepare a Nickel/Nanoporous Carbon Composite Catalyst for 4-Nitrophenol Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ying; Zhang, Ying; Sun, Cheng Jun

2014-11-01

Nickel/nanoporous carbon (Ni/NPC) composites are facilely prepared by direct pyrolysis of nonporous heterobimetallic zinc-nickel-terephthalate frameworks (Zn1-xNixMOF, x approximate to 0-1, MOF= metal-organic framework) at 1223 K in situ. Tailoring the Ni/Zn ratio creates densely populated and small Ni nanocrystals (Ni NCs) while maintaining sufficient porosity and surface area in the final product, which exhibits the largest activity factor (9.2 s(-1)g(-1)) and excellent stability toward 4-nitrophenol reduction.

One-Step to Prepare Self-Organized Nanoporous NiO/TiO2 Layers and its Use in Non-Enzymatic Glucose Sensing

PubMed Central

Gao, Zhi-Da; Han, Yuyao; Wang, Yongmei; Xu, Jingwen; Song, Yan-Yan

2013-01-01

A highly ordered nanoporous NiTi oxide layers were fabricated on Ti alloys with high Ni contents (50.6 at.%) by a combination of self-organizing anodization at 0°C and subsequent selective etching in H2O2. The key for successful formation of such layers is to sufficiently suppress the dissolve of NiO by applying lower temperature during anodization. The resulting nanoporous structure is connected and well-adhered, which exhibits a much higher electrochemical cycling stability in 0.1 M NaOH. Without further surface modification or the use of polymer binders, the layers can be behave as a low-cost, stable and sensitive platform in non-enzymatic glucose sensing. PMID:24270125

Spatially confined synthesis of SiOx nano-rod with size-controlled Si quantum dots in nano-porous anodic aluminum oxide membrane.

PubMed

Pai, Yi-Hao; Lin, Gong-Ru

2011-01-17

By depositing Si-rich SiOx nano-rod in nano-porous anodic aluminum oxide (AAO) membrane using PECVD, the spatially confined synthesis of Si quantum-dots (Si-QDs) with ultra-bright photoluminescence spectra are demonstrated after low-temperature annealing. Spatially confined SiOx nano-rod in nano-porous AAO membrane greatly increases the density of nucleated positions for Si-QD precursors, which essentially impedes the route of thermally diffused Si atoms and confines the degree of atomic self-aggregation. The diffusion controlled growth mechanism is employed to determine the activation energy of 6.284 kJ mole(-1) and diffusion length of 2.84 nm for SiO1.5 nano-rod in nano-porous AAO membrane. HRTEM results verify that the reduced geometric dimension of the SiOx host matrix effectively constrain the buried Si-QD size at even lower annealing temperature. The spatially confined synthesis of Si-QD essentially contributes the intense PL with its spectral linewidth shrinking from 210 to 140 nm and its peak intensity enhancing by two orders of magnitude, corresponding to the reduction on both the average Si-QD size and its standard deviation from 2.6 to 2.0 nm and from 25% to 12.5%, respectively. The red-shifted PL wavelength of the Si-QD reveals an inverse exponential trend with increasing temperature of annealing, which is in good agree with the Si-QD size simulation via the atomic diffusion theory.

Dehydration, Dehydrogenation, and Condensation of Alcohols on Supported Oxide Catalysts Based on Cyclic (WO3)3 and (MoO3)3 Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousseau, Roger J.; Dixon, David A.; Kay, Bruce D.

2014-01-01

Supported early transition metal oxides have important applications in numerous catalytic reactions. In this article we review preparation and activity of well-defined model WO3 and MoO3 catalysts prepared via deposition of cyclic gas-phase (WO3)3 and (MoO3)3 clusters generated by sublimation of WO3 and MoO3 powders. Conversion of small aliphatic alcohols to alkenes, aldehydes/ketons, and ethers is employed to probe the structure-activity relationships on model WO3 and MoO3 catalysts ranging from unsupported (WO3)3 and (MoO3)3 clusters embedded in alcohol matrices, to (WO3)3 clusters supported on surfaces of other oxides, and epitaxial and nanoporous WO3 films. Detailed theoretical calculations reveal the underlyingmore » reaction mechanisms and provide insight into the origin of the differences in the WO3 and MoO3 reactivity. For the range of interrogated (WO3)3 they further shed light into the role structure and binding of (WO3)3 clusters with the support play in determining their catalytic activity.« less

Giant increase in the metal-enhanced fluorescence of organic molecules in nanoporous alumina templates and large molecule-specific red/blue-shift of the fluorescence peak.

PubMed

Sarkar, S; Kanchibotla, B; Nelson, J D; Edwards, J D; Anderson, J; Tepper, G C; Bandyopadhyay, S

2014-10-08

The fluorescence of organic fluorophore molecules is enhanced when they are placed in contact with certain metals (Al, Ag, Cu, Au, etc.) whose surface plasmon waves couple into the radiative modes of the molecules and increase the radiative efficiency. Here, we report a hitherto unknown size dependence of this metal-enhanced fluorescence (MEF) effect in the nanoscale. When the molecules are deposited in nanoporous anodic alumina films with exposed aluminum at the bottom of the pores, they form organic nanowires standing on aluminum nanoparticles whose plasmon waves have much larger amplitudes. This increases the MEF strongly, resulting in several orders of magnitude increase in the fluorescence intensity of the organic fluorophores. The increase in intensity shows an inverse superlinear dependence on nanowire diameter because the nanowires also act as plasmonic "waveguides" that concentrate the plasmons and increase the coupling of the plasmons with the radiative modes of the molecules. Furthermore, if the nanoporous template housing the nanowires has built-in electric fields due to space charges, a strong molecule-specific red- or blue-shift is induced in the fluorescence peak owing to a renormalization of the dipole moment of the molecule. This can be exploited to detect minute amounts of target molecules in a mixture using their optical signature (fluorescence) despite the presence of confounding background signals. It can result in a unique new technology for biosensing and chemical sensing.

Resizing metal-coated nanopores using a scanning electron microscope.

PubMed

Chansin, Guillaume A T; Hong, Jongin; Dusting, Jonathan; deMello, Andrew J; Albrecht, Tim; Edel, Joshua B

2011-10-04

Electron beam-induced shrinkage provides a convenient way of resizing solid-state nanopores in Si(3) N(4) membranes. Here, a scanning electron microscope (SEM) has been used to resize a range of different focussed ion beam-milled nanopores in Al-coated Si(3) N(4) membranes. Energy-dispersive X-ray spectra and SEM images acquired during resizing highlight that a time-variant carbon deposition process is the dominant mechanism of pore shrinkage, although granular structures on the membrane surface in the vicinity of the pores suggest that competing processes may occur. Shrinkage is observed on the Al side of the pore as well as on the Si(3) N(4) side, while the shrinkage rate is observed to be dependent on a variety of factors. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

In Situ Fabrication of PtCo Alloy Embedded in Nitrogen-Doped Graphene Nanopores as Synergistic Catalyst for Oxygen Reduction Reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhong, Xing; Wang, Lei; Zhou, Hu

A novel PtCo alloy in situ etched and embedded in graphene nanopores (PtCo/NPG) as a high-performance catalyst for ORR was reported. Graphene nanopores were fabricated in situ while forming PtCo nanoparticles that were uniformly embedded in the graphene nanopores. Given the synergistic effect between PtCo alloy and nanopores, PtCo/NPG exhibited 11.5 times higher mass activity than that of the commercial Pt/C cathode electrocatalyst. DFT calculations indicated that the nanopores in NPG cannot only stabilize PtCo nanoparticles but can also definitely change the electronic structures, thereby change its adsorption abilities. This enhancement can lead to a favorable reaction pathway on PtCo/NPGmore » for ORR. This study showed that PtCo/NPG is a potential candidate for the next generation of Pt-based catalysts in fuel cells. This study also offered a promising alternative strategy and enabled the fabrication of various kinds of metal/graphene nanopore nanohybrids with potential applications in catalysts and potential use for other technological devices. The authors acknowledge the financial support from the National Basic Research Program (973 program, No. 2013CB733501), Zhejiang Provincial Education Department Research Program (Y201326554) and the National Natural Science Foundation of China (No. 21306169, 21101137, 21136001, 21176221 and 91334013). D. Mei acknowledges the support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) and by the National Energy Research Scientific Computing Center (NERSC).« less

Nanoporous, Metal Carbide, Surface Diffusion Membranes for High Temperature Hydrogen Separations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Way, J. Douglas; Wolden, Colin A.

2013-09-30

Colorado School of Mines (CSM) developed high temperature, hydrogen permeable membranes that contain no platinum group metals with the goal of separating hydrogen from gas mixtures representative of gasification of carbon feedstocks such as coal or biomass in order to meet DOE NETL 2015 hydrogen membrane performance targets. We employed a dual synthesis strategy centered on transition metal carbides. In the first approach, novel, high temperature, surface diffusion membranes based on nanoporous Mo 2C were fabricated on ceramic supports. These were produced in a two step process that consisted of molybdenum oxide deposition followed by thermal carburization. Our best Momore » 2C surface diffusion membrane achieved a pure hydrogen flux of 367 SCFH/ft 2 at a feed pressure of only 20 psig. The highest H 2/N 2 selectivity obtained with this approach was 4.9. A transport model using “dusty gas” theory was derived to describe the hydrogen transport in the Mo 2C coated, surface diffusion membranes. The second class of membranes developed were dense metal foils of BCC metals such as vanadium coated with thin (< 60 nm) Mo 2C catalyst layers. We have fabricated a Mo 2C/V composite membrane that in pure gas testing delivered a H 2 flux of 238 SCFH/ft 2 at 600 °C and 100 psig, with no detectable He permeance. This exceeds the 2010 DOE Target flux. This flux is 2.8 times that of pure Pd at the same membrane thickness and test conditions and over 79% of the 2015 flux target. In mixed gas testing we achieved a permeate purity of ≥99.99%, satisfying the permeate purity milestone, but the hydrogen permeance was low, ~0.2 SCFH/ft 2.psi. However, during testing of a Mo 2C coated Pd alloy membrane with DOE 1 feed gas mixture a hydrogen permeance of >2 SCFH/ft 2.psi was obtained which was stable during the entire test, meeting the permeance associated with the 2010 DOE target flux. Lastly, the Mo 2C/V composite membranes were shown to be stable for at least 168 hours = one week, including cycling at high temperature and alternating He/H 2 exposure.« less

Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes

NASA Astrophysics Data System (ADS)

Hevia, Samuel; Homm, Pía; Cortes, Andrea; Núñez, Verónica; Contreras, Claudia; Vera, Jenniffer; Segura, Rodrigo

2012-06-01

Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors.

Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes.

PubMed

Hevia, Samuel; Homm, Pía; Cortes, Andrea; Núñez, Verónica; Contreras, Claudia; Vera, Jenniffer; Segura, Rodrigo

2012-06-25

Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors.

Optical characterization of nanoporous AAO sensor substrate

NASA Astrophysics Data System (ADS)

Kassu, Aschalew; Farley, Carlton W.; Sharma, Anup

2014-05-01

Nanoporous anodic aluminum oxide (AAO) has been investigated as an ideal and cost-effective chemical and biosensing platform. In this paper, we report the optical properties of periodic 100 micron thick nanoporous anodic alumina membranes with uniform and high density cylindrical pores penetrating the entire thickness of the substrate, ranging in size from 18 nm to 150 nm in diameter and pore periods from 44 nm to 243 nm. The surface geometry of the top and bottom surface of each membrane is studied using atomic force microscopy. The optical properties including transmittance, reflectance, and absorbance spectra on both sides of each substrate are studied and found to be symmetrical. It is observed that, as the pore size increases, the peak resonance intensity in transmittance decreases and in absorbance increases. The effects of the pore sizes on the optical properties of the bare nanoporous membranes and the benefit of using arrays of nanohole arrays with varying hole size and periodicity as a chemical sensing platform is also discussed. To characterize the optical sensing technique, transmittance and reflectance measurements of various concentrations of a standard chemical adsorbed on the bare nanoporous substrates are investigated. The preliminary results presented here show variation in transmittance and reflectance spectra with the concentration of the chemical used or the amount of the material adsorbed on the surface of the substrate.

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

PubMed Central

Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S. D.; Vukovic, Zorica; de Hosson, Jeff Th. M.; ten Brinke, Gerrit; Loos, Katja

2014-01-01

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology. PMID:24797367

Gyroid nickel nanostructures from diblock copolymer supramolecules.

PubMed

Vukovic, Ivana; Punzhin, Sergey; Voet, Vincent S D; Vukovic, Zorica; de Hosson, Jeff Th M; ten Brinke, Gerrit; Loos, Katja

2014-04-28

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template's channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

Impedimetric DNA biosensor based on a nanoporous alumina membrane for the detection of the specific oligonucleotide sequence of dengue virus.

PubMed

Deng, Jiajia; Toh, Chee-Seng

2013-06-17

A novel and integrated membrane sensing platform for DNA detection is developed based on an anodic aluminum oxide (AAO) membrane. Platinum electrodes (~50-100 nm thick) are coated directly on both sides of the alumina membrane to eliminate the solution resistance outside the nanopores. The electrochemical impedance technique is employed to monitor the impedance changes within the nanopores upon DNA binding. Pore resistance (Rp) linearly increases in response towards the increasing concentration of the target DNA in the range of 1 × 10⁻¹² to 1 × 10⁻⁶ M. Moreover, the biosensor selectively differentiates the complementary sequence from single base mismatched (MM-1) strands and non-complementary strands. This study reveals a simple, selective and sensitive method to fabricate a label-free DNA biosensor.

Nanoporous polymeric nanofibers based on selectively etched PS-b-PDMS block copolymers.

PubMed

Demirel, Gokcen B; Buyukserin, Fatih; Morris, Michael A; Demirel, Gokhan

2012-01-01

One-dimensional nanoporous polymeric nanofibers have been fabricated within an anodic aluminum oxide (AAO) membrane by a facile approach based on selective etching of poly(dimethylsiloxane) (PDMS) domains in polystyrene-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymers that had been formed within the AAO template. It was observed that prior to etching, the well-ordered PS-b-PDMS nanofibers are solid and do not have any porosity. The postetched PS nanofibers, on the other hand, had a highly porous structure having about 20-50 nm pore size. The nanoporous polymeric fibers were also employed as a drug carrier for the native, continuous, and pulsatile drug release using Rhodamine B (RB) as a model drug. These studies showed that enhanced drug release and tunable drug dosage can be achieved by using ultrasound irradiation. © 2011 American Chemical Society

Tailoring uniform gold nanoparticle arrays and nanoporous films for next-generation optoelectronic devices

NASA Astrophysics Data System (ADS)

Farid, Sidra; Kuljic, Rade; Poduri, Shripriya; Dutta, Mitra; Darling, Seth B.

2018-06-01

High-density arrays of gold nanodots and nanoholes on indium tin oxide (ITO)-coated glass surfaces are fabricated using a nanoporous template fabricated by the self-assembly of diblock copolymers of poly (styrene-block-methyl methacrylate) (PS-b-PMMA) structures. By balancing the interfacial interactions between the polymer blocks and the substrate using random copolymer, cylindrical block copolymer microdomains oriented perpendicular to the plane of the substrate have been obtained. Nanoporous PS films are created by selectively etching PMMA cylinders, a straightforward route to form highly ordered nanoscale porous films. Deposition of gold on the template followed by lift off and sonication leaves a highly dense array of gold nanodots. These materials can serve as templates for the vapor-liquid-solid (VLS) growth of semiconductor nanorod arrays for next generation hybrid optoelectronic applications.

Effect of nanoscale flows on the surface structure of nanoporous catalysts.

PubMed

Montemore, Matthew M; Montessori, Andrea; Succi, Sauro; Barroo, Cédric; Falcucci, Giacomo; Bell, David C; Kaxiras, Efthimios

2017-06-07

The surface structure and composition of a multi-component catalyst are critical factors in determining its catalytic performance. The surface composition can depend on the local pressure of the reacting species, leading to the possibility that the flow through a nanoporous catalyst can affect its structure and reactivity. Here, we explore this possibility for oxidation reactions on nanoporous gold, an AgAu bimetallic catalyst. We use microscopy and digital reconstruction to obtain the morphology of a two-dimensional slice of a nanoporous gold sample. Using lattice Boltzmann fluid dynamics simulations along with thermodynamic models based on first-principles total-energy calculations, we show that some sections of this sample have low local O 2 partial pressures when exposed to reaction conditions, which leads to a pure Au surface in these regions, instead of the active bimetallic AgAu phase. We also explore the effect of temperature on the surface structure and find that moderate temperatures (≈300-450 K) should result in the highest intrinsic catalytic performance, in apparent agreement with experimental results.

2D nanostructures for water purification: graphene and beyond.

PubMed

Dervin, Saoirse; Dionysiou, Dionysios D; Pillai, Suresh C

2016-08-18

Owing to their atomically thin structure, large surface area and mechanical strength, 2D nanoporous materials are considered to be suitable alternatives for existing desalination and water purification membrane materials. Recent progress in the development of nanoporous graphene based materials has generated enormous potential for water purification technologies. Progress in the development of nanoporous graphene and graphene oxide (GO) membranes, the mechanism of graphene molecular sieve action, structural design, hydrophilic nature, mechanical strength and antifouling properties and the principal challenges associated with nanopore generation are discussed in detail. Subsequently, the recent applications and performance of newly developed 2D materials such as 2D boron nitride (BN) nanosheets, graphyne, molybdenum disulfide (MoS2), tungsten chalcogenides (WS2) and titanium carbide (Ti3C2Tx) are highlighted. In addition, the challenges affecting 2D nanostructures for water purification are highlighted and their applications in the water purification industry are discussed. Though only a few 2D materials have been explored so far for water treatment applications, this emerging field of research is set to attract a great deal of attention in the near future.

Facile Fabrication of Cu2O Nanobelts in Ethanol on Nanoporous Cu and Their Photodegradation of Methyl Orange

PubMed Central

Yang, Yulin; Qin, Fengxiang; Wang, Hao; Chang, Hui

2018-01-01

Thin cupric oxide (Cu2O) nanobelts with width of few tens of nanometers to few hundreds of nanometers were fabricated in anhydrous ethanol on nanoporous copper templates that was prepared via dealloying amorphous Ti40Cu60 ribbons in hydrofluoric acid solutions at 348 K. The Cu2O octahedral particles preferentially form in the water, and nanobelts readily undergo the growth along the lengthwise and widthwise in the anhydrous ethanol. The ethanol molecules serve as stabilizing or capping reagents, and play a key role of the formation of two-dimensional Cu2O nanobelts. Cu atoms at weak sites (i.e., twin boundary) on the nanoporous Cu ligaments are ionized to form Cu2+ cations, and then react with OH− to form Cu2O and H2O. The two-dimensional growth of Cu2O nanostructure is preferred in anhydrous ethanol due to the suppression of random growth of Cu2O nanoarchitectures by ethanol. Cu2O nanobelts have superior photodegradation performance of methyl orange, three times higher than nanoporous Cu. PMID:29562692

Oxygen Reduction at Very Low Overpotential on Nanoporous Ag Catalysts

DOE PAGES

Zhou, Yang; Lu, Qi; Zhuang, Zhongbin; ...

2015-05-07

Here we report a monolithic nanoporous Ag (np-Ag) material, synthesized using the dealloying method, as high-performance catalysts for ORR in alkaline media. As shown in Scheme 1, when there is insufficient potential input, the O 2 molecules are more likely to rebound off from a planar electrode surface (i.e. bulk polycrystalline metal, films made from nanoparticles or nanowires) before they could be reduced. In contrast, they are more likely to be trapped inside the monolithic nanoporous structure, contacting with catalytic surface for multiple time, which greatly enhances the chance for them to be fully reduced. As a result, the np-Agmore » catalyst is able to achieve an equivalent or better ORR performance than the state-of the-art Pt/C catalyst at low overpotentials, which is most desired in electrochemical energy applications for maximizing efficiency.« less

Sponge-like nanoporous single crystals of gold

PubMed Central

Khristosov, Maria Koifman; Bloch, Leonid; Burghammer, Manfred; Kauffmann, Yaron; Katsman, Alex; Pokroy, Boaz

2015-01-01

Single crystals in nature often demonstrate fascinating intricate porous morphologies rather than classical faceted surfaces. We attempt to grow such crystals, drawing inspiration from biogenic porous single crystals. Here we show that nanoporous single crystals of gold can be grown with no need for any elaborate fabrication steps. These crystals are found to grow following solidification of a eutectic composition melt that forms as a result of the dewetting of nanometric thin films. We also present a kinetic model that shows how this nano-porous single-crystalline structure can be obtained, and which allows the potential size of the porous single crystal to be predicted. Retaining their single-crystalline nature is due to the fact that the full crystallization process is faster than the average period between two subsequent nucleation events. Our findings clearly demonstrate that it is possible to form single-crystalline nano porous metal crystals in a controlled manner. PMID:26554856

Optimized nanoporous materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Braun, Paul V.; Langham, Mary Elizabeth; Jacobs, Benjamin W.

2009-09-01

Nanoporous materials have maximum practical surface areas for electrical charge storage; every point in an electrode is within a few atoms of an interface at which charge can be stored. Metal-electrolyte interfaces make best use of surface area in porous materials. However, ion transport through long, narrow pores is slow. We seek to understand and optimize the tradeoff between capacity and transport. Modeling and measurements of nanoporous gold electrodes has allowed us to determine design principles, including the fact that these materials can deplete salt from the electrolyte, increasing resistance. We have developed fabrication techniques to demonstrate architectures inspired bymore » these principles that may overcome identified obstacles. A key concept is that electrodes should be as close together as possible; this is likely to involve an interpenetrating pore structure. However, this may prove extremely challenging to fabricate at the finest scales; a hierarchically porous structure can be a worthy compromise.« less

Dewetting of polymer thin films on modified curved surfaces: preparation of polymer nanoparticles with asymmetric shapes by anodic aluminum oxide templates.

PubMed

Liu, Chih-Ting; Tsai, Chia-Chan; Chu, Chien-Wei; Chi, Mu-Huan; Chung, Pei-Yun; Chen, Jiun-Tai

2018-04-18

We study the dewetting behaviors of poly(methyl methacrylate) (PMMA) thin films coated in the cylindrical nanopores of anodic aluminum oxide (AAO) templates by thermal annealing. Self-assembled monolayers (SAMs) of n-octadecyltrichlorosilane (ODTS) are introduced to modify the pore surfaces of the AAO templates to induce the dewetting process. By using scanning electron microscopy (SEM), the dewetting-induced morphology transformation from the PMMA thin films to PMMA nanoparticles with asymmetric shapes can be observed. The sizes of the PMMA nanoparticles can be controlled by the original PMMA solution concentrations. The dewetting phenomena on the modified nanopores are explained by taking into account the excess intermolecular interaction free energy (ΔG). This work opens a new possibility for creating polymer nanoparticles with asymmetric shapes in confined geometries.

Nanoporous palladium anode for direct ethanol solid oxide fuel cells with nanoscale proton-conducting ceramic electrolyte

NASA Astrophysics Data System (ADS)

Li, Yong; Wong, Lai Mun; Xie, Hanlin; Wang, Shijie; Su, Pei-Chen

2017-02-01

In this work, we demonstrate the operation of micro-solid oxide fuel cells (μ-SOFCs) with nanoscale proton-conducting Y-BaZrO3 (BZY) electrolyte to avoid the fuel crossover problem for direct ethanol fuel cells (DEFCs). The μ-SOFCs are operated with the direct utilisation of ethanol vapour as a fuel and Pd as anode at the temperature range of 300-400 °C. The nanoporous Pd anode is achieved by DC sputtering at high Ar pressure of 80 mTorr. The Pd-anode/BYZ-electrolyte/Pt-cathode cell show peak power densities of 72.4 mW/cm2 using hydrogen and 15.3 mW/cm2 using ethanol at 400 °C. No obvious carbon deposition is seen from XPS analysis after fuel cell test with ethanol fuel.

Preparation of Nanocomposite Plasmonic Films Made from Cellulose Nanocrystals or Mesoporous Silica Decorated with Unidirectionally Aligned Gold Nanorods.

PubMed

Campbell, Michael G; Liu, Qingkun; Sanders, Aric; Evans, Julian S; Smalyukh, Ivan I

2014-04-11

Using liquid crystalline self-assembly of cellulose nanocrystals, we achieve long-range alignment of anisotropic metal nanoparticles in colloidal nanocrystal dispersions that are then used to deposit thin structured films with ordering features highly dependent on the deposition method. These hybrid films are comprised of gold nanorods unidirectionally aligned in a matrix that can be made of ordered cellulose nanocrystals or silica nanostructures obtained by using cellulose-based nanostructures as a replica. The ensuing long-range alignment of gold nanorods in both cellulose-based and nanoporous silica films results in a polarization-sensitive surface plasmon resonance. The demonstrated device-scale bulk nanoparticle alignment may enable engineering of new material properties arising from combining the orientational ordering of host nanostructures and properties of the anisotropic plasmonic metal nanoparticles. Our approach may also allow for scalable fabrication of plasmonic polarizers and nanoporous silica structures with orientationally ordered anisotropic plasmonic nanoinclusions.

Trapping guests within a nanoporous metal-organic framework through pressure-induced amorphization.

PubMed

Chapman, Karena W; Sava, Dorina F; Halder, Gregory J; Chupas, Peter J; Nenoff, Tina M

2011-11-23

The release of guest species from within a nanoporous metal-organic framework (MOF) has been inhibited by amorphization of the guest-loaded framework structure under applied pressure. Thermogravimetric analyses have shown that by amorphizing ZIF-8 following sorption of molecular I(2), a hazardous radiological byproduct of nuclear energy production, the pore apertures in the framework are sufficiently distorted to kinetically trap I(2) and improve I(2) retention. Pair distribution function (PDF) analysis indicates that the local structure of the captive I(2) remains essentially unchanged upon amorphization of the framework, with the amorphization occurring under the same conditions for the vacant and guest-loaded framework. The low, accessible pressure range needed to effect this change in desorption is much lower than in tradition sorbents such as zeolites, opening the possibility for new molecular capture, interim storage, or controlled release applications.

High-performance supercapacitors using a nanoporous current collector made from super-aligned carbon nanotubes.

PubMed

Zhou, Ruifeng; Meng, Chuizhou; Zhu, Feng; Li, Qunqing; Liu, Changhong; Fan, Shoushan; Jiang, Kaili

2010-08-27

Nanoporous current collectors for supercapacitors have been fabricated by cross-stacking super-aligned carbon nanotube (SACNT) films as a replacement for heavy conventional metallic current collectors. The CNT-film current collectors have good conductivity, extremely low density (27 microg cm(-2)), high specific surface area, excellent flexibility and good electrochemical stability. Nanosized active materials such as NiO, Co(3)O(4) or Mn(2)O(3) nanoparticles can be directly synthesized on the SACNT films by a straightforward one-step, in situ decomposition strategy that is both efficient and environmentally friendly. These composite films can be integrated into a pseudo-capacitor that does not use metallic current collectors, but nevertheless shows very good performance, including high specific capacitance (approximately 500 F g(-1), including the current collector mass), reliable electrochemical stability (<4.5% degradation in 2500 cycles) and a very high rate capability (245 F g(-1) at 155 A g(-1)).

High-performance supercapacitors using a nanoporous current collector made from super-aligned carbon nanotubes

NASA Astrophysics Data System (ADS)

Zhou, Ruifeng; Meng, Chuizhou; Zhu, Feng; Li, Qunqing; Liu, Changhong; Fan, Shoushan; Jiang, Kaili

2010-08-01

Nanoporous current collectors for supercapacitors have been fabricated by cross-stacking super-aligned carbon nanotube (SACNT) films as a replacement for heavy conventional metallic current collectors. The CNT-film current collectors have good conductivity, extremely low density (27 µg cm - 2), high specific surface area, excellent flexibility and good electrochemical stability. Nanosized active materials such as NiO, Co3O4 or Mn2O3 nanoparticles can be directly synthesized on the SACNT films by a straightforward one-step, in situ decomposition strategy that is both efficient and environmentally friendly. These composite films can be integrated into a pseudo-capacitor that does not use metallic current collectors, but nevertheless shows very good performance, including high specific capacitance (~500 F g - 1, including the current collector mass), reliable electrochemical stability (<4.5% degradation in 2500 cycles) and a very high rate capability (245 F g - 1 at 155 A g - 1).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hohenberger, Erik; Freitag, Nathan; Rosenmann, Daniel

Here, we present a facile method for fabricating nanostructured silver films containing a high density of nanoscopic gap features through a surface directed phenomenon utilizing nanoporous scaffolds rather than through traditional lithographic patterning processes. This method enables tunability of the silver film growth by simply adjusting the formulation and processing conditions of the nanoporous film prior to metallization. We further demonstrate that this process can produce nanoscopic gaps in thick (100 nm) silver films supporting localized surface plasmon resonance with large field amplification within the gaps while enabling launching of propagating surface plasmons within the silver grains. These enhanced fieldsmore » provide metal enhanced fluorescence with enhancement factors as high as 21 times compared to glass, as well as enable visualization of single fluorophore emission. This work provides a low-cost rapid approach for producing novel nanostructures capable of broadband fluorescence amplification, with potential applications including plasmonic and fluorescence based optical sensing and imaging applications.« less

A template-free solvent-mediated synthesis of high surface area boron nitride nanosheets for aerobic oxidative desulfurization.

PubMed

Wu, Peiwen; Zhu, Wenshuai; Chao, Yanhong; Zhang, Jinshui; Zhang, Pengfei; Zhu, Huiyuan; Li, Changfeng; Chen, Zhigang; Li, Huaming; Dai, Sheng

2016-01-04

Hexagonal boron nitride nanosheets (h-BNNs) with rather high specific surface area (SSA) are important two-dimensional layer-structured materials. Here, a solvent-mediated synthesis of h-BNNs revealed a template-free lattice plane control strategy that induced high SSA nanoporous structured h-BNNs with outstanding aerobic oxidative desulfurization performance.

Hybrid micro/nanostructural surface offering improved stress distribution and enhanced osseointegration properties of the biomedical titanium implant.

PubMed

Hou, Ping-Jen; Ou, Keng-Liang; Wang, Chin-Chieh; Huang, Chiung-Fang; Ruslin, Muhammad; Sugiatno, Erwan; Yang, Tzu-Sen; Chou, Hsin-Hua

2018-03-01

The aim of the present study was to investigate the surface characteristic, biomechanical behavior, hemocompatibility, bone tissue response and osseointegration of the optimal micro-arc oxidation surface-treated titanium (MST-Ti) dental implant. The surface characteristic, biomechanical behavior and hemocompatibility of the MST-Ti dental implant were performed using scanning electron microscope, finite element method, blood dripping and immersion tests. The mini-pig model was utilized to evaluate the bone tissue response and osseointegration of the MST-Ti dental implant in vivo. Data were analyzed by analysis of variance using the Student's t-test (P ≤ 0.05). The hybrid volcano-like micro/nanoporous structure was formed on the surface of the MST-Ti dental implant. The hybrid volcano-like micro/nanoporous surface played an important role to improve the stress transfer between fixture, cortical bone and cancellous bone for the MST-Ti dental implant. Moreover, the MST-Ti implant was considered to have the outstanding hemocompatibility. In vivo testing results showed that the bone-to-implant contact (BIC) ratio significantly altered as the implant with micro/nanoporous surface. After 12 weeks of implantation, the MST-Ti dental implant group exhibited significantly higher BIC ratio than the untreated dental implant group. In addition, the MST-Ti dental implant group also presented an enhancing osseointegration, particularly in the early stages of bone healing. It can be concluded that the micro-arc oxidation approach induced the formation of micro/nanoporous surface is a promising and reliable alternative surface modification for Ti dental implant applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

[Effects of different annealing conditions on the photoluminescence of nanoporous alumina film].

PubMed

Xie, Ning; Ma, Kai-Di; Shen, Yi-Fan; Wang, Qian

2013-12-01

The nanoporous alumina films were prepared by two-step anodic oxidation in 0.5 mol L-1 oxalic acid electrolyte at 40 V. Photoluminescence (PL) of nanoporous alumina films was investigated under different annealing atmosphere and different temperature. The authors got three results about the PL measurements. In the same annealing atmosphere, when the annealling temperature T< or =600 degreeC, the intensity of the PL peak increases with elevated annealing temperature and reaches a maximum value at 500 degreeC, but the intensity decreases with a further increase in the annealing temperature, and the PL peak intensity of samples increases with the increase in the annealing temperature when the annealling temperature T> or =800 degreeC. In the different annealling atmosphere, the change in the photoluminescence peak position for nanoporous alumina films with the increase in the annealing temperature is different: With the increase in the annealling temperature, the PL peak position for the samples annealed in air atmosphere is blue shifted, while the PL peak position for the samples annealed in vacuum atmosphere will not change. The PL spectra of nanoporous alumina films annealed at 1100 degreeC in air atmosphere can be de-convoluted by three Gaussian components at an excitation wavelength of 350 nm, with bands centered at 387, 410 and 439 nm, respectively. These results suggest that there might be three luminescence centers for the PL of annealed alumina films. At the same annealling temperature, the PL peak intensity of samples annealed in air atmosphere is stronger than that annealed in the vacuum. Based on the experimental results and the X-ray dispersive energy spectrum (EDS) combined with infrared reflect spectra, the luminescence mechanisms of nanoporous alumina films are discussed. There are three luminescence centers in the annealed nanoporous alumina films, which originate from the F center, F+ center and the center associated with the oxalic impurities. The effects of different annealing conditions on the photoluminescence of nanoporous alumina film are reasonably explained.

Nanoporous Au structures by dealloying Au/Ag thermal- or laser-dewetted bilayers on surfaces

NASA Astrophysics Data System (ADS)

Ruffino, F.; Torrisi, V.; Grillo, R.; Cacciato, G.; Zimbone, M.; Piccitto, G.; Grimaldi, M. G.

2017-03-01

Nanoporous Au attracts great technological interest and it is a promising candidate for optical and electrochemical sensors. In addition to nanoporous Au leafs and films, recently, interest was focused on nanoporous Au micro- and nano-structures on surfaces. In this work we report on the study of the characteristics of nanoporous Au structures produced on surfaces. We developed the following procedures to fabricate the nanoporous Au structures: we deposited thin Au/Ag bilayers on SiO2 or FTO (fluorine-doped tin oxide) substrates with thickness xAu and xAg of the Au and Ag layers; we induced the alloying and dewetting processes of the bilayers by furnace annealing processes of the bilayers deposited on SiO2 and by laser irradiations of the bilayers deposited on FTO; the alloying and dewetting processes result in the formation of AuxAgy alloy sub-micron particles being x and y tunable by xAu and xAg. These particles are dealloyed in HNO3 solution to remove the Ag atoms. We obtain, so, nanoporous sub-micron Au particles on the substrates. Analyzing the characteristics of these particles we find that: a) the size and shape of the particles depend on the nature of the dewetting process (solid-state dewetting on SiO2, molten-state dewetting on FTO); b) the porosity fraction of the particles depends on how the alloying process is reached: about 32% of porosity for the particles fabricated by the furnace annealing at 900 °C, about 45% of porosity for the particles fabricated by the laser irradiation at 0.5 J/cm2, in both cases independently on the Ag concentration in the alloy; c) After the dealloying process the mean volume of the Au particles shrinks of about 39%; d) After an annealing at 400 °C the nanoporous Au particles reprise their initial volume while the porosity fraction is reduced. Arguments to justify these behaviors are presented.

Renewable Wood Pulp Paper Reactor with Hierarchical Micro/Nanopores for Continuous-Flow Nanocatalysis.

PubMed

Koga, Hirotaka; Namba, Naoko; Takahashi, Tsukasa; Nogi, Masaya; Nishina, Yuta

2017-06-22

Continuous-flow nanocatalysis based on metal nanoparticle catalyst-anchored flow reactors has recently provided an excellent platform for effective chemical manufacturing. However, there has been limited progress in porous structure design and recycling systems for metal nanoparticle-anchored flow reactors to create more efficient and sustainable catalytic processes. In this study, traditional paper is used for a highly efficient, recyclable, and even renewable flow reactor by tailoring the ultrastructures of wood pulp. The "paper reactor" offers hierarchically interconnected micro- and nanoscale pores, which can act as convective-flow and rapid-diffusion channels, respectively, for efficient access of reactants to metal nanoparticle catalysts. In continuous-flow, aqueous, room-temperature catalytic reduction of 4-nitrophenol to 4-aminophenol, a gold nanoparticle (AuNP)-anchored paper reactor with hierarchical micro/nanopores provided higher reaction efficiency than state-of-the-art AuNP-anchored flow reactors. Inspired by traditional paper materials, successful recycling and renewal of AuNP-anchored paper reactors were also demonstrated while high reaction efficiency was maintained. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Plasmonic response in nanoporous metal: dependence on network topology

NASA Astrophysics Data System (ADS)

Galí, Marc A.; Tai, Matthew C.; Arnold, Matthew D.; Cortie, Michael B.; Gentle, Angus R.; Smith, Geoffrey B.

2015-12-01

The optical and electrical responses of open, nanoscale, metal networks are of interest in a variety of technologies including transparent conducting electrodes, charge storage, and surfaces with controlled spectral selectivity. The properties of such nanoporous structures depend on the shape and extent of individual voids and the associated hyper-dimensional connectivity and density of the metal filaments. Unfortunately, a quantitative understanding of this dependence is at present only poorly developed. Here we address this problem using numerical simulations applied to a systematically designed series of prototypical sponges. The sponges are produced by a Monte Carlo simulation of the dealloying of Ag-Al alloys containing from 60% to 85% Al. The result is a series of Ag sponges of realistic morphology. The optical properties of the sponges are then calculated by the discrete dipole approximation and the results used to construct an 'effective medium' model for each sponge. We show how the resulting effective medium can be correlated with the associated morphological characteristics of each target and how the optical properties are primarily controlled by the density of the sponge and its state of percolation.

Renewable Wood Pulp Paper Reactor with Hierarchical Micro/Nanopores for Continuous‐Flow Nanocatalysis

PubMed Central

Namba, Naoko; Takahashi, Tsukasa; Nogi, Masaya; Nishina, Yuta

2017-01-01

Abstract Continuous‐flow nanocatalysis based on metal nanoparticle catalyst‐anchored flow reactors has recently provided an excellent platform for effective chemical manufacturing. However, there has been limited progress in porous structure design and recycling systems for metal nanoparticle‐anchored flow reactors to create more efficient and sustainable catalytic processes. In this study, traditional paper is used for a highly efficient, recyclable, and even renewable flow reactor by tailoring the ultrastructures of wood pulp. The “paper reactor” offers hierarchically interconnected micro‐ and nanoscale pores, which can act as convective‐flow and rapid‐diffusion channels, respectively, for efficient access of reactants to metal nanoparticle catalysts. In continuous‐flow, aqueous, room‐temperature catalytic reduction of 4‐nitrophenol to 4‐aminophenol, a gold nanoparticle (AuNP)‐anchored paper reactor with hierarchical micro/nanopores provided higher reaction efficiency than state‐of‐the‐art AuNP‐anchored flow reactors. Inspired by traditional paper materials, successful recycling and renewal of AuNP‐anchored paper reactors were also demonstrated while high reaction efficiency was maintained. PMID:28394501

Template-Growth of Highly Ordered Carbon Nanotube Arrays on Silicon POSTPRINT

DTIC Science & Technology

2006-09-01

packed uni- form CNTs that are spatially isolated from each other is to use a growth template. Highly ordered anodic aluminum oxide ( AAO ) template can...process for evaporating thick aluminum of high quality and good adhesion. 15. SUBJECT TERMS Anodic Aluminum Oxide Template, Carbon Nanotubes (CNTs...within the highly ordered nanopores of an alumina oxide template, which is in turn formed on silicon through anodization of aluminum of unprecedented

Zeolitic imidazolate framework-coated acoustic sensors for room temperature detection of carbon dioxide and methane

DOE PAGES

Devkota, Jagannath; Kim, Ki-Joong; Ohodnicki, Paul R.; ...

2018-01-01

The integration of nanoporous materials such as metal organic frameworks (MOFs) with sensitive transducers can result in robust sensing platforms for monitoring gases and chemical vapors for a range of applications.

A tunable sub-100 nm silicon nanopore array with an AAO membrane mask: reducing unwanted surface etching by introducing a PMMA interlayer

NASA Astrophysics Data System (ADS)

Lim, Namsoo; Pak, Yusin; Kim, Jin Tae; Hwang, Youngkyu; Lee, Ryeri; Kumaresan, Yogeenth; Myoung, Nosoung; Ko, Heung Cho; Jung, Gun Young

2015-08-01

Highly ordered silicon (Si) nanopores with a tunable sub-100 nm diameter were fabricated by a CF4 plasma etching process using an anodic aluminum oxide (AAO) membrane as an etching mask. To enhance the conformal contact of the AAO membrane mask to the underlying Si substrate, poly(methyl methacrylate) (PMMA) was spin-coated on top of the Si substrate prior to the transfer of the AAO membrane. The AAO membrane mask was fabricated by two-step anodization and subsequent removal of the aluminum support and the barrier layer, which was then transferred to the PMMA-coated Si substrate. Contact printing was performed on the sample with a pressure of 50 psi and a temperature of 120 °C to make a conformal contact of the AAO membrane mask to the Si substrate. The CF4 plasma etching was conducted to transfer nanopores onto the Si substrate through the PMMA interlayer. The introduced PMMA interlayer prevented unwanted surface etching of the Si substrate by eliminating the etching ions and radicals bouncing at the gap between the mask and the substrate, resulting in a smooth Si nanopore array.Highly ordered silicon (Si) nanopores with a tunable sub-100 nm diameter were fabricated by a CF4 plasma etching process using an anodic aluminum oxide (AAO) membrane as an etching mask. To enhance the conformal contact of the AAO membrane mask to the underlying Si substrate, poly(methyl methacrylate) (PMMA) was spin-coated on top of the Si substrate prior to the transfer of the AAO membrane. The AAO membrane mask was fabricated by two-step anodization and subsequent removal of the aluminum support and the barrier layer, which was then transferred to the PMMA-coated Si substrate. Contact printing was performed on the sample with a pressure of 50 psi and a temperature of 120 °C to make a conformal contact of the AAO membrane mask to the Si substrate. The CF4 plasma etching was conducted to transfer nanopores onto the Si substrate through the PMMA interlayer. The introduced PMMA interlayer prevented unwanted surface etching of the Si substrate by eliminating the etching ions and radicals bouncing at the gap between the mask and the substrate, resulting in a smooth Si nanopore array. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02786a

Facile Synthesis of Highly Aligned Multiwalled Carbon Nanotubes from Polymer Precursors

DOE PAGES

Han, Catherine Y.; Xiao, Zhi-Li; Wang, H. Hau; ...

2009-01-01

We report a facile one-step approach which involves no flammable gas, no catalyst, and no in situ polymerization for the preparation of well-aligned carbon nanotube array. A polymer precursor is placed on top of an anodized aluminum oxide (AAO) membrane containing regular nanopore arrays, and slow heating under Ar flow allows the molten polymer to wet the template through adhesive force. The polymer spread into the nanopores of the template to form polymer nanotubes. Upon carbonization the resulting multi-walled carbon nanotubes duplicate the nanopores morphology precisely. The process is demonstrated for 230, 50, and 20 nm pore membranes. The synthesized carbonmore » nanotubes are characterized with scanning/transmission electron microscopies, Raman spectroscopy, and resistive measurements. Convenient functionalization of the nanotubes with this method is demonstrated through premixing CoPt nanoparticles in the polymer precursors.« less

Carbon membranes for efficient water-ethanol separation.

PubMed

Gravelle, Simon; Yoshida, Hiroaki; Joly, Laurent; Ybert, Christophe; Bocquet, Lydéric

2016-09-28

We demonstrate, on the basis of molecular dynamics simulations, the possibility of an efficient water-ethanol separation using nanoporous carbon membranes, namely, carbon nanotube membranes, nanoporous graphene sheets, and multilayer graphene membranes. While these carbon membranes are in general permeable to both pure liquids, they exhibit a counter-intuitive "self-semi-permeability" to water in the presence of water-ethanol mixtures. This originates in a preferred ethanol adsorption in nanoconfinement that prevents water molecules from entering the carbon nanopores. An osmotic pressure is accordingly expressed across the carbon membranes for the water-ethanol mixture, which agrees with the classic van't Hoff type expression. This suggests a robust and versatile membrane-based separation, built on a pressure-driven reverse-osmosis process across these carbon-based membranes. In particular, the recent development of large-scale "graphene-oxide" like membranes then opens an avenue for a versatile and efficient ethanol dehydration using this separation process, with possible application for bio-ethanol fabrication.

Carbon membranes for efficient water-ethanol separation

NASA Astrophysics Data System (ADS)

Gravelle, Simon; Yoshida, Hiroaki; Joly, Laurent; Ybert, Christophe; Bocquet, Lydéric

2016-09-01

We demonstrate, on the basis of molecular dynamics simulations, the possibility of an efficient water-ethanol separation using nanoporous carbon membranes, namely, carbon nanotube membranes, nanoporous graphene sheets, and multilayer graphene membranes. While these carbon membranes are in general permeable to both pure liquids, they exhibit a counter-intuitive "self-semi-permeability" to water in the presence of water-ethanol mixtures. This originates in a preferred ethanol adsorption in nanoconfinement that prevents water molecules from entering the carbon nanopores. An osmotic pressure is accordingly expressed across the carbon membranes for the water-ethanol mixture, which agrees with the classic van't Hoff type expression. This suggests a robust and versatile membrane-based separation, built on a pressure-driven reverse-osmosis process across these carbon-based membranes. In particular, the recent development of large-scale "graphene-oxide" like membranes then opens an avenue for a versatile and efficient ethanol dehydration using this separation process, with possible application for bio-ethanol fabrication.

Preparing nano-hole arrays by using porous anodic aluminum oxide nano-structural masks for the enhanced emission from InGaN/GaN blue light-emitting diodes

NASA Astrophysics Data System (ADS)

Nguyen, Hoang-Duy; Nguyen, Hieu Pham Trung; Lee, Jae-jin; Mho, Sun-Il

2012-12-01

We report on the achievement of the enhanced cathodoluminescence (CL) from InGaN/GaN light-emitting diodes (LEDs) by using roughening surface. Nanoporous anodic aluminum oxide (AAO) mask was utilized to form nano-hole arrays on the surface of InGaN/GaN LEDs. AAO membranes with ordered hexagonal structures were fabricated from aluminum foils by a two-step anodization method. The average pore densities of ˜1.0 × 1010 cm-2 and 3.0 × 1010 cm-2 were fabricated with the constant anodization voltages of 25 and 40 V, respectively. Anodic porous alumina film with a thickness of ˜600 nm has been used as a mask for the induced couple plasma etching process to fabricate nano-hole arrays on the LED surface. Diameter and depth of nano-holes can be controlled by varying the etching duration and/or the diameter of AAO membranes. Due to the reduction of total internal reflection obtained in the patterned samples, we have observed that the cathodoluminescence intensity of LEDs with nanoporous structures is increased up to eight times compared to that of samples without using nanoporous structure.

Fabrication and characterization of conductive anodic aluminum oxide substrates

NASA Astrophysics Data System (ADS)

Altuntas, Sevde; Buyukserin, Fatih

2014-11-01

Biomaterials that allow the utilization of electrical, chemical and topographic cues for improved neuron-material interaction and neural regeneration hold great promise for nerve tissue engineering applications. The nature of anodic aluminum oxide (AAO) membranes intrinsically provides delicate control over topographic and chemical cues for enhanced cell interaction; however their use in nerve regeneration is still very limited. Herein, we report the fabrication and characterization of conductive AAO (CAAO) surfaces for the ultimate goal of integrating electrical cues for improved nerve tissue behavior on the nanoporous substrate material. Parafilm was used as a protecting polymer film, for the first time, in order to obtain large area (50 cm2) free-standing AAO membranes. Carbon (C) was then deposited on the AAO surface via sputtering. Morphological characterization of the CAAO surfaces revealed that the pores remain open after the deposition process. The presence of C on the material surface and inside the nanopores was confirmed by XPS and EDX studies. Furthermore, I-V curves of the surface were used to extract surface resistance values and conductive AFM demonstrated that current signals can only be achieved where conductive C layer is present. Finally, novel nanoporous C films with controllable pore diameters and one dimensional (1-D) C nanostructures were obtained by the dissolution of the template AAO substrate.

In situ monitoring of PTHLH secretion in neuroblastoma cells cultured onto nanoporous membranes.

PubMed

de la Escosura-Muñiz, Alfredo; Espinoza-Castañeda, Marisol; Chamorro-García, Alejandro; Rodríguez-Hernández, Carlos J; de Torres, Carmen; Merkoçi, Arben

2018-06-01

In this work, we propose for the first time the use of anodic aluminum oxide (AAO) nanoporous membranes for in situ monitoring of parathyroid hormone-like hormone (PTHLH) secretion in cultured human cells. The biosensing system is based on the nanochannels blockage upon immunocomplex formation, which is electrically monitored through the voltammetric oxidation of Prussian blue nanoparticles (PBNPs). Models evaluated include a neuroblastoma cell line (SK-N-AS) and immortalized keratinocytes (HaCaT) as a control of high PTHLH production. The effect of total number of seeded cells and incubation time on the secreted PTHLH levels is assessed, finding that secreted PTHLH levels range from approximately 60 to 400 ng/mL. Moreover, our methodology is also applied to analyse PTHLH production following PTHLH gene knockdown upon transient cell transfection with a specific silencing RNA (siRNA). Given that inhibition of PTHLH secretion reduces cell proliferation, survival and invasiveness in a number of tumors, our system provides a powerful tool for the preclinical evaluation of therapies that regulate PTHLH production. This nanoporous membrane - based sensing technology might be useful to monitor the active secretion of other proteins as well, thus contributing to characterize their regulation and function. Copyright © 2018 Elsevier B.V. All rights reserved.

Improving the performance of water desalination through ultra-permeable functionalized nanoporous graphene oxide membrane

NASA Astrophysics Data System (ADS)

Hosseini, Mostafa; Azamat, Jafar; Erfan-Niya, Hamid

2018-01-01

Molecular dynamics simulations were performed to investigate the water desalination performance of nanoporous graphene oxide (NPGO) membranes. The simulated systems consist of a NPGO as a membrane with a functionalized pore in its center immersed in an aqueous ionic solution and a graphene sheet as a barrier. The considered NPGO membranes are involved four types of pore with different size and chemistry. The results indicated that the NPGO membrane has effective efficiency in salt rejection as well as high performance in water flux. For all types of pore with the radius size of 2.9-4.5 Å, the NPGO shows salt rejection of >89%. Functional groups on the surface and edge of pores have a great effect on water flux. To precisely understand the effect of functional groups on the surface of nanostructured membranes, nanoporous graphene was simulated under the same condition for comparison. Hydrophilic groups on the surface make the NPGO as an ultra-permeable membrane. As a result, the obtained water flux for NPGO was about 77% greater than graphene. Also, it was found that the water flux of NPGO is 2-5 orders of magnitude greater than other existing reverse osmosis membranes. Therefore, the investigated systems can be recommended as a model for the water desalination.

Synthesis of Nanoporous Activated Iridium Oxide Films by Anodized Aluminum Oxide Templated Atomic Layer Deposition

DTIC Science & Technology

2010-11-01

number of deposition strategies, including sputtering [10–12] and electrodeposition [13,14]. With all synthesis strategies, control of the film...to 10% ozone in 400 sccm O2 for 10 min. A 20 Å Al2O3 film was then deposited as a nucleation layer by iterative exposures of trimethyla- luminum and

A template-free solvent-mediated synthesis of high surface area boron nitride nanosheets for aerobic oxidative desulfurization

DOE PAGES

Wu, Peiwen; Zhu, Wenshuai; Chao, Yanhong; ...

2015-10-16

Hexagonal boron nitride nanosheets (h-BNNs) with rather high specific surface area (SSA) are important two-dimensional layer-structured materials. Here in this study, a solvent-mediated synthesis of h-BNNs revealed a template-free lattice plane control strategy that induced high SSA nanoporous structured h-BNNs with outstanding aerobic oxidative desulfurization performance.

Chemical synthesis of oriented ferromagnetic LaSr-2 × 4 manganese oxide molecular sieve nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carretero-Genevrier, Adrián; Gazquez, Jaume; Magen, Cesar

2012-04-25

Here we report a chemical solution based method using nanoporous track-etched polymer templates for producing long and oriented LaSr-2 × 4 manganese oxide molecular sieve nanowires. Scanning transmission electron microscopy and electron energy loss spectroscopy analyses show that the nanowires are ferromagnetic at room temperature, single crystalline, epitaxially grown and self-aligned.

Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis.

PubMed

Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

2013-12-07

Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis

NASA Astrophysics Data System (ADS)

Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

2013-11-01

Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

Selective growth of palladium and titanium dioxide nanostructures inside carbon nanotube membranes

PubMed Central

2012-01-01

Hybrid nanostructured arrays based on carbon nanotubes (CNT) and palladium or titanium dioxide materials have been synthesized using self-supported and silicon-supported anodized aluminum oxide (AAO) as nanoporous template. It is well demonstrated that carbon nanotubes can be grown using these membranes and hydrocarbon precursors that decompose at temperatures closer to 600°C without the use of a metal catalyst. In this process, carbonic fragments condensate to form stacked graphitic sheets, which adopt the shape of the pores, yielding from these moulds' multi-walled carbon nanotubes. After this process, the ends of the tubes remain open and accessible to other substances, whereas the outer walls are protected by the alumina. Taking advantage of this fact, we have performed the synthesis of palladium and titanium dioxide nanostructures selectively inside carbon nanotubes using these CNT-AAO membranes as nanoreactors. PMID:22731888

Sulfur containing nanoporous materials, nanoparticles, methods and applications

DOEpatents

Archer, Lynden A.; Navaneedhakrishnan, Jayaprakash

2018-01-30

Sulfur containing nanoparticles that may be used within cathode electrodes within lithium ion batteries include in a first instance porous carbon shape materials (i.e., either nanoparticle shapes or "bulk" shapes that are subsequently ground to nanoparticle shapes) that are infused with a sulfur material. A synthetic route to these carbon and sulfur containing nanoparticles may use a template nanoparticle to form a hollow carbon shape shell, and subsequent dissolution of the template nanoparticle prior to infusion of the hollow carbon shape shell with a sulfur material. Sulfur infusion into other porous carbon shapes that are not hollow is also contemplated. A second type of sulfur containing nanoparticle includes a metal oxide material core upon which is located a shell layer that includes a vulcanized polymultiene polymer material and ion conducting polymer material. The foregoing sulfur containing nanoparticle materials provide the electrodes and lithium ion batteries with enhanced performance.

Nanocontainers made of Various Materials with Tunable Shape and Size

NASA Astrophysics Data System (ADS)

Zhao, Xianglong; Meng, Guowen; Han, Fangming; Li, Xiangdong; Chen, Bensong; Xu, Qiaoling; Zhu, Xiaoguang; Chu, Zhaoqin; Kong, Mingguang; Huang, Qing

2013-07-01

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications.

Removal of nano and microparticles by granular filter media coated with nanoporous aluminium oxide.

PubMed

Lau, B L T; Harrington, G W; Anderson, M A; Tejedor, I

2004-01-01

Conventional filtration was designed to achieve high levels of particle and pathogen removal. Previous studies have examined the possibility of modifying filtration media to improve their ability to remove microorganisms and viruses. Although these studies have evaluated filter media coatings for this purpose, none have evaluated nanoscale particle suspensions as coating materials. The overall goal of this paper is to describe the preliminary test results of nanoporous aluminium oxide coated media that can be used to enhance filtration of nano and microparticles. Filtration tests were carried out using columns packed with uncoated and coated forms of granular anthracite or granular activated carbon. A positive correlation between isoelectric pH of filter media and particle removal was observed. The modified filter media with a higher isoelectric pH facilitated better removal of bacteriophage MS2 and 3 microm latex microspheres, possibly due to increased favorable electrostatic interactions.

Rapid antibiotic efficacy screening with aluminum oxide nanoporous membrane filter-chip and optical detection system.

PubMed

Tsou, Pei-Hsiang; Sreenivasappa, Harini; Hong, Sungmin; Yasuike, Masayuki; Miyamoto, Hiroshi; Nakano, Keiyo; Misawa, Takeyuki; Kameoka, Jun

2010-09-15

We have developed a filter-chip and optical detection system for rapid antibiotic efficacy screening. The filter-chip consisted of a 1-mL reservoir and an anodic aluminum oxide (AAO) nanoporous membrane. Sample solution with liquid growth media, bacteria, and antibiotics was incubated in the reservoir for a specific period of time. The number of live bacteria on the surface of membrane was counted after the incubation with antibiotics and filtration. Using this biosensing system, we have demonstrated a 1-h antibiotic screening for patients' clinical samples, significantly faster than the conventional antibiotic susceptibility tests that typically take more than 24h. This rapid screening nature makes the filter-chip and detection system ideal for tailoring antibiotic treatment to individual patients by reducing the microbial antibiotic resistance, and improving the survival rate for patients suffering from postoperative infections. Published by Elsevier B.V.

Nanocontainers made of Various Materials with Tunable Shape and Size

PubMed Central

Zhao, Xianglong; Meng, Guowen; Han, Fangming; Li, Xiangdong; Chen, Bensong; Xu, Qiaoling; Zhu, Xiaoguang; Chu, Zhaoqin; Kong, Mingguang; Huang, Qing

2013-01-01

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications. PMID:23867836

Study the effect of striping in two-step anodizing process on pore arrangement of nano-porous alumina

NASA Astrophysics Data System (ADS)

Rahimi, M. H.; Saramad, S.; Tabaian, S. H.; Marashi, S. P.; Zolfaghari, A.; Mohammadalinezhad, M.

2009-10-01

Two-step anodic oxidation of aluminum is generally employed to produce the ordered porous anodized alumina (PAA). Dissolving away (striping) the oxide film after the first anodizing step plays a key role in the final arrangement of nano-pores. In this work, different striping durations between 1 and 6 h were applied to the sample that was initially anodized at a constant voltage of 40 V at 17 °C for 15 h. The striping duration of 3 h was realized as the optimum time for achieving the best ordering degree for the pores. Scanning electron microscopy (SEM) was used during and at the end of the process to examine the cross section and finishing surface of the specimens. Linear-angular fast Fourier transform (LA-FFT), an in-house technique based on MATLAB software, was employed to assess the ordering degree of the anodized samples.

Nanoporous Block Polymer Thin Films Functionalized with Bio-Inspired Ligands for the Efficient Capture of Heavy Metal Ions from Water.

PubMed

Weidman, Jacob L; Mulvenna, Ryan A; Boudouris, Bryan W; Phillip, William A

2017-06-07

Heavy metal contamination of water supplies poses a serious threat to public health, prompting the development of novel and sustainable treatment technologies. One promising approach is to molecularly engineer the chemical affinity of a material for the targeted removal of specific molecules from solution. In this work, nanoporous polymer thin films generated from tailor-made block polymers were functionalized with the bio-inspired moieties glutathione and cysteamine for the removal of heavy metal ions, including lead and cadmium, from aqueous solutions. In a single equilibrium stage, the films achieved removal rates of the ions in excess of 95%, which was consistent with predictions based on the engineered material properties. In a flow-through configuration, the thin films achieved an even greater removal rate of the metal ions. Furthermore, in mixed ion solutions the capacity of the thin films, and corresponding removal rates, did not demonstrate any reduction due to competitive adsorption effects. After such experiments the material was repeatedly regenerated quickly with no observed loss in capacity. Thus, these membranes provide a sustainable platform for the efficient purification of lead- and cadmium-contaminated water sources to safe levels. Moreover, their straightforward chemical modifications suggest that they could be engineered to treat sources containing other recalcitrant environmental contaminants as well.

Nano-porous electrode systems by colloidal lithography for sensitive electrochemical detection: fabrication technology and properties

NASA Astrophysics Data System (ADS)

Lohmüller, Theobald; Müller, Ulrich; Breisch, Stefanie; Nisch, Wilfried; Rudorf, Ralf; Schuhmann, Wolfgang; Neugebauer, Sebastian; Kaczor, Markus; Linke, Stephan; Lechner, Sebastian; Spatz, Joachim; Stelzle, Martin

2008-11-01

A porous metal-insulator-metal sensor system was developed with the ultimate goal of enhancing the sensitivity of electrochemical sensors by taking advantage of redox cycling of electro active molecules between closely spaced electrodes. The novel fabrication technology is based on thin film deposition in combination with colloidal self-assembly and reactive ion etching to create micro- or nanopores. This cost effective approach is advantageous compared to common interdigitated electrode arrays (IDA) since it does not require high definition lithography technology. Spin-coating and random particle deposition, combined with a new sublimation process are discussed as competing strategies to generate monolayers of colloidal spheres. Metal-insulator-metal layer systems with low leakage currents < 10 pA and an insulator thickness as low as 100 nm were obtained at high yield (typically > 90%). We also discuss possible causes of sensor failure with respect to critical fabrication processes. Short circuits which could occur during or as a result of the pore etching process were investigated in detail. Infrared microscopy in combination with focused ion beam etching/SEM were used to reveal a defect mechanism creating interconnects and increased leakage current between the top and bottom electrodes. Redox cycling provides for amplification factors of >100. A general applicability for electrochemical diagnostic assays is therefore anticipated.

Using X-ray Microscopy To Understand How Nanoporous Materials Can Be Used To Reduce the Large Volume Change in Alloy Anodes

DOE PAGES

Cook, John B.; Lin, Terri C.; Detsi, Eric; ...

2017-01-05

Tin metal is an attractive negative electrode material to replace graphite in Li-ion batteries due to its high energy density. However, tin undergoes a large volume change upon alloying with Li, which pulverizes the particles, and ultimately leads to short cycling lifetimes. Nevertheless, nanoporous materials have been shown to extend battery life well past what is observed in nonporous material. Despite the exciting potential of porous alloying anodes to significantly increase the energy density in Li-ion batteries, the fundamental physics of how nanoscale architectures accommodate the electrochemically induced volume changes are poorly understood. Here, operando transmission X-ray microscopy has beenmore » used to develop an understanding of the mechanisms that govern the enhanced cycling stability in nanoporous tin. We found that in comparison to dense tin, nanoporous tin undergoes a 6-fold smaller areal expansion after lithiation, as a result of the internal porosity and unique nanoscale architecture. The expansion is also more gradual in nanoporous tin compared to the dense material. The nanoscale resolution of the microscope used in this study is ~30 nm, which allowed us to directly observe the pore structure during lithiation and delithiation. We found that nanoporous tin remains porous during the first insertion and desinsertion cycle. This observation is key, as fully closed pores could lead to mechanical instability, electrolyte inaccessibility, and short lifetimes. Here, while tin was chosen for this study because of its high X-ray contrast, the results of this work should be general to other alloy-type systems, such as Si, that also suffer from volume change based cycling degradation.« less

Using X-ray Microscopy To Understand How Nanoporous Materials Can Be Used To Reduce the Large Volume Change in Alloy Anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, John B.; Lin, Terri C.; Detsi, Eric

Tin metal is an attractive negative electrode material to replace graphite in Li-ion batteries due to its high energy density. However, tin undergoes a large volume change upon alloying with Li, which pulverizes the particles, and ultimately leads to short cycling lifetimes. Nevertheless, nanoporous materials have been shown to extend battery life well past what is observed in nonporous material. Despite the exciting potential of porous alloying anodes to significantly increase the energy density in Li-ion batteries, the fundamental physics of how nanoscale architectures accommodate the electrochemically induced volume changes are poorly understood. Here, operando transmission X-ray microscopy has beenmore » used to develop an understanding of the mechanisms that govern the enhanced cycling stability in nanoporous tin. We found that in comparison to dense tin, nanoporous tin undergoes a 6-fold smaller areal expansion after lithiation, as a result of the internal porosity and unique nanoscale architecture. The expansion is also more gradual in nanoporous tin compared to the dense material. The nanoscale resolution of the microscope used in this study is ~30 nm, which allowed us to directly observe the pore structure during lithiation and delithiation. We found that nanoporous tin remains porous during the first insertion and desinsertion cycle. This observation is key, as fully closed pores could lead to mechanical instability, electrolyte inaccessibility, and short lifetimes. Here, while tin was chosen for this study because of its high X-ray contrast, the results of this work should be general to other alloy-type systems, such as Si, that also suffer from volume change based cycling degradation.« less

A tunable sub-100 nm silicon nanopore array with an AAO membrane mask: reducing unwanted surface etching by introducing a PMMA interlayer.

PubMed

Lim, Namsoo; Pak, Yusin; Kim, Jin Tae; Hwang, Youngkyu; Lee, Ryeri; Kumaresan, Yogeenth; Myoung, NoSoung; Ko, Heung Cho; Jung, Gun Young

2015-08-28

Highly ordered silicon (Si) nanopores with a tunable sub-100 nm diameter were fabricated by a CF4 plasma etching process using an anodic aluminum oxide (AAO) membrane as an etching mask. To enhance the conformal contact of the AAO membrane mask to the underlying Si substrate, poly(methyl methacrylate) (PMMA) was spin-coated on top of the Si substrate prior to the transfer of the AAO membrane. The AAO membrane mask was fabricated by two-step anodization and subsequent removal of the aluminum support and the barrier layer, which was then transferred to the PMMA-coated Si substrate. Contact printing was performed on the sample with a pressure of 50 psi and a temperature of 120 °C to make a conformal contact of the AAO membrane mask to the Si substrate. The CF4 plasma etching was conducted to transfer nanopores onto the Si substrate through the PMMA interlayer. The introduced PMMA interlayer prevented unwanted surface etching of the Si substrate by eliminating the etching ions and radicals bouncing at the gap between the mask and the substrate, resulting in a smooth Si nanopore array.

Wettability transition induced transformation and entrapment of polymer nanostructures in cylindrical nanopores.

PubMed

Feng, Xunda; Mei, Shilin; Jin, Zhaoxia

2011-12-06

We apply the concept of wettability transition to manipulate the morphology and entrapment of polymer nanostructures inside cylindrical nanopores of anodic aluminum oxide (AAO) membranes. When AAO/polystyrene (PS) hybrids, i.e., AAO/PS nanorods or AAO/PS nanotubes, are immersed into a polyethylene glycol (PEG) reservoir above the glass transition temperature of PS, a wettability transition from wetting to nonwetting of PS can be triggered due to the invasion of the more wettable PEG melt. The wettability transition enables us to develop a nondestructive method to entrap hemispherically capped nanorods inside nanopores. Moreover, we can obtain single nanorods with the desired aspect ratio by further dissolving the AAO template, in contrast to the drawbacks of nonuniformity or destructiveness from the conventional ultrasonication method. In the case of AAO/PS nanotubes, the wettability transition induced dewetting of PS nanotube walls results in the disconnection and entrapment of nonwetting PS domains (i.e., nanospheres, nanocapsules, or capped nanorods). Moreover, PEG is then washed to recover the pristine wettability of PS on the alumina surface; further annealing of the PS nanospheres inside AAO nanopores under vacuum can generate some unique nanostructures, particularly semicylindrical nanorods. © 2011 American Chemical Society

Nanoporous structures on ZnO thin films

NASA Astrophysics Data System (ADS)

Gür, Emre; Kılıç, Bayram; Coşkun, C.; Tüzemen, S.; Bayrakçeken, Fatma

2010-01-01

Porous structures were formed on ZnO thin films which were grown by an electrochemical deposition (ECD) method. The growth processes were carried out in a solution of dimethylsulfoxide (DMSO) zinc perchlorate, Zn(ClO 4) 2, at 120 ∘C on indium tin oxide (ITO) substrates. Optical and structural characterizations of electrochemically grown ZnO thin films have shown that the films possess high (0002) c-axis orientation, high nucleation, high intensity and low FWHM of UV emission at the band edge region and a sharp UV absorption edge. Nanoporous structures were formed via self-assembled monolayers (SAMs) of hexanethiol (C 6SH) and dodecanethiol (C 12SH). Scanning electron microscope (SEM) measurements showed that while a nanoporous structure (pore radius 20 nm) is formed on the ZnO thin films by hexanathiol solution, a macroporous structure (pore radius 360 nm) is formed by dodecanethiol solution. No significant variation is observed in X-ray diffraction (XRD) measurements on the ZnO thin films after pore formation. However, photoluminescence (PL) measurements showed that green emission is observed as the dominant emission for the macroporous structures, while no variation is observed for the thin film nanoporous ZnO sample.

Controllable Switching Filaments Prepared via Tunable and Well-Defined Single Truncated Conical Nanopore Structures for Fast and Scalable SiOx Memory.

PubMed

Kwon, Soonbang; Jang, Seonghoon; Choi, Jae-Wan; Choi, Sanghyeon; Jang, Sukjae; Kim, Tae-Wook; Wang, Gunuk

2017-12-13

The controllability of switching conductive filaments is one of the central issues in the development of reliable metal-oxide resistive memory because the random dynamic nature and formation of the filaments pose an obstacle to desirable switching performance. Here, we introduce a simple and novel approach to control and form a single silicon nanocrystal (Si-NC) filament for use in SiO x memory devices. The filament is formed with a confined vertical nanoscale gap by using a well-defined single vertical truncated conical nanopore (StcNP) structure. The physical dimensions of the Si-NC filaments such as number, size, and length, which have a significant influence on the switching properties, can be simply engineered by the breakdown of an Au wire through different StcNP structures. In particular, we demonstrate that the designed SiO x memory junction with a StcNP of pore depth of ∼75 nm and a bottom diameter of ∼10 nm exhibited a switching speed of up to 6 ns for both set and reset process, significantly faster than reported SiO x memory devices. The device also exhibited a high ON-OFF ratio, multistate storage ability, acceptable endurance, and retention stability. The influence of the physical dimensions of the StcNP on the switching features is discussed based on the simulated temperature profiles of the Au wire and the nanogap size generated inside the StcNP structure during electromigration.

d -zero magnetism in nanoporous amorphous alumina membranes

NASA Astrophysics Data System (ADS)

Esmaeily, Amir Sajad; Venkatesan, M.; Sen, S.; Coey, J. M. D.

2018-05-01

Nanoporous alumina membranes produced by mild or hard anodization have a controllable pore surface area up to 400 times that of the membrane itself. They exhibit a temperature-independent and almost anhysteretic saturating response to a magnetic field up to temperatures of 300 K or more. The magnetism, which cannot be explained by the ˜1 ppm of transition-metal impurities present in the membranes, increases with the area of the open nanopores, reaching values of 0.6 Bohr magnetons per square nanometer for mild anodization and 8 Bohr magnetons per square nanometer for the faster hard anodization process. Crystallization of the membrane or treatment with salicylic acid can destroy 90% of the magnetism. The effect is therefore linked with the surfaces of the open pores in the amorphous A l2O3 . Possible explanations in terms of electrons associated with oxygen vacancies (F or F+ centers) are considered. It is concluded that the phenomenon involved is likely to be saturating giant orbital paramagnetism, rather than any sort of collective ferromagnetic spin order.

Two-step fabrication of nanoporous copper films with tunable morphology for SERS application

NASA Astrophysics Data System (ADS)

Diao, Fangyuan; Xiao, Xinxin; Luo, Bing; Sun, Hui; Ding, Fei; Ci, Lijie; Si, Pengchao

2018-01-01

It is important to design and fabricate nanoporous metals (NPMs) with optimized microstructures for specific applications. In this contribution, nanoporous coppers (NPCs) with controllable thicknesses and pore sizes were fabricated via the combination of a co-sputtering of Cu/Ti with a subsequent dealloying process. The effect of dealloying time on porous morphology and the corresponding surface enhanced Raman scattering (SERS) behaviors were systematically investigated. Transmission electron microscopy (TEM) identified the presences of the gaps formed between ligaments and also the nanobumps on the nanoparticle-aggregated ligament surface, which were likely to contribute as the ;hot spots; for electromagnetic enhancement. The optimal NPC film exhibited excellent SERS performance towards Rhodamine 6G (R6G) with a low limiting detection (10-9 M), along with good uniformity and reproducibility. The calculated enhancement factor of ca. 4.71 × 107 was over Au substrates and comparable to Ag systems, promising the proposed NPC as a cheap candidate for high-performance SERS substrate.

Role of the electric field in selective ion filtration in nanostructures.

PubMed

Park, Yong; Kim, Sueon; Jang, In Hyuk; Nam, Young Suk; Hong, Hiki; Choi, Dukhyun; Lee, Won Gu

2016-02-21

Nafion has received great attention as a proton conductor that can block negative ions. Here, we report the effect of a Nafion coating on an anodic aluminium oxide (AAO) nanoporous membrane on its function of ion rejection and filtering depending on the electric field. In our experiments, Nafion, once coated, was used to repel the negative ions (anions) from the coated surface, and then selectively allowed positive ions (cations) to pass through the nanopores in the presence of an electric field. To demonstrate the proof-of-concept validation, we coated Nafion solution onto the surface of AAO membranes with 20 nm nanopores average diameter at different solution concentration levels. Vacuum filtration methods for Nafion coating were vertically applied to the plane of an AAO membrane. An electric field was then applied to the upper surface of the Nafion-coated AAO membrane to investigate if ion rejection and filtering was affected by the presence of the electric field. Both anions and cations could pass through the AAO nanopores without an electric field applied. However, only cations could well pass through the AAO nanopores under an electric field, thus effectively blocking anions from passing through the nanopores. This result shows that ion filtration of electrons has been selectively performed while the system also works as a vital catalyst in reactivating Nafion via electrolysis. A saturated viscosity ratio of Nafion solution for the coating was also determined. We believe that this approach is potentially beneficial for better understanding the fundamentals of selective ion filtration in nanostructures and for promoting the use of nanostructures in potential applications such as ion-based water purification and desalination system at the nanoscale in a massively electrically integrated format.

Physiological and hydrological controls on mineral redox cycling by long-range electron transport by bacteria in anaerobic sediments

NASA Astrophysics Data System (ADS)

Michelson, K.; Werth, C. J.; Sanford, R. A.; Valocchi, A. J.

2016-12-01

The cycling of iron and manganese oxides plays a critical role in the bioavailability of trace elements and macronutrients, the flux of carbon across terrestrial and atmospheric ecosystems, and the remediation of groundwater contaminated by toxic metals and radionuclides. Bacteria control one half of the redox cycle as the primary drivers of iron and manganese reduction in anaerobic soils and sediments. However, Fe(III) and Mn(IV) are almost exclusively present under anaerobic conditions as insoluble oxides, the reduction of which are facilitated by extracellular electron transport via conductive `nanowires', electron shuttling, and direct contact with outer membrane cytochromes. Our research focus is on the relative contribution of nanowires and electron shuttles under different physiological and hydrological conditions, which remains unexplored. We present a novel microfluidic platform that allows us to directly observe these phenomena under a controlled environment representative of groundwater conditions, monitor the metabolic activity and redox state of bacteria, and determine the presence of reduced products in-situ using Raman spectroscopy. Using Geobacter sulfurreducens and Shewanella oneidensis as model metal-reducing bacteria, and insoluble manganese dioxide (i.e. birnessite) as an electron acceptor, we show that 1) electron shuttling is more effective under static conditions 2) the presence of exogenous shuttles allows efficient electron transport under all flow regimes 3) redox potential of the bulk medium exerts significant control over reduction by both nanowires and electron shuttles 4) shuttling is amplified by orders of magnitude in nanopores.

Rainfall observations using dual-polarization radar coupled with a drop motion and evaporation model

NASA Astrophysics Data System (ADS)

Pallardy, Quinn

In the field of nanoscience, nanoporous metal foams are a representative type of nanostructured materials, representing the ultimate form factor of a metal. They possess the hybrid properties of metal and nanoarchitectures, including the following properties such as good electrical and thermal conductivity, catalytic activity and high surface area, ultralow density, high strength-to-weight ratio. The outstanding properties bring the nanoporous metal foams to a wide range of applications, especially in the field of sensor system, energy storage and chemical catalyst. A new method of synthesis developed recently is presented for nanoporous metal foams of gold and nickel. The goal of this study is for the synthesis process of NMFs of and some applications in research and realistic life. Gold NMFs were produced by mixing gold chloride with ethylene glycol, ethanol, and reducing agent, and heating at 150 °C for 5 min with a CEM microwave. Both hydrazine and sodium borohydride were applied as the reducing agent for this redox reaction. Nickel NMFs were produced through the similar procedure with a little difference in the heating condition of 50 W, instead of 150 °C, with either hydrazine or sodium borohydride as the reducing agent. Gold NMFs were applied in surface-enhanced Raman spectroscopy (SERS) as a substrate. It is presented that with the presence of gold NMFs, the detection of the rhodamine 6G (R6G), a model analyte, can be enhanced significantly. The limit of detection for rhodamine 6G was found to be 5.2 x 10 -7 M in this research. Nickel NMFs was applied to degrade methyl orange (MO). An aqueous MO solution will turn nearly colorless after only 10 h of mixing with 0.025 g of nickel NMFs at room temperature under dark condition. In order to study the kinetics of the degradation reaction, MO solution with different initial concentration were used. This application of Ni NMFs is applicable as waste treatment of industrial water and to protect the environment.

Nanoporous gold membranes: From morphological control to fuel cell catalysis

NASA Astrophysics Data System (ADS)

Ding, Yi

Porous noble metals are particularly attractive for scientific research and industrial applications such as catalysis, sensing, and filtration. In this thesis, I will discuss the fabrication, characterization, and application of a new class of porous metals, called nanoporous metals (NPM). NPM is made during selective dissolution (also called dealloying) of reactive components (e.g., silver) from multi-component alloys (e.g., Ag/Au alloy). Commercially available white gold leaf (Ag65Au35) can, for example, be etched into nanoporous gold (NPG) membrane by simply floating the leaf on concentrated nitric acid for periods of a few minutes. NPG leaf adopts a single crystal porous structure within individual grains. The microstructure of NPG, such as the pore size, is tunable between a few nanometers to sub-micron length scale by either thermal annealing or post-treatment in nitric acid for extended period of time. A new gas-liquid-solid interface electroless plating technique is developed to uniformly cover the NPG surface with other metals, such as silver and platinum. This technique allows new opportunities of making functionalized nanostructures. We show that a combination of silver plating and dealloying can be used to make multimodal porous metals, which are expected to have application in sensing field. Electroless platinum plating onto NPG shows very usual growth mode. TEM observation indicates that the platinum layer on NPG surface takes a novel form of layer-islanding growth (Stranski-Krastanov growth). Annealing the Pt/NPG composite smoothens the Pt islands and forms a 1 nm coherent Pt layer on the NPG backbone, possibly with dislocation formation at the Pt/Au interface. Furthermore, it was found that we could dissolve the gold away in aqueous gold etchant, leaving behind the 1 nm-thick Pt shell, a structure we call nanotubular mesoporous platinum (NMP). Pt plated NPG has a series of unique structural properties, such as high active surface area, thermally stable, low Pt usage, and better tolerance to CO poisoning. We incorporated it as a membrane electrode into a working proton exchange membrane fuel cells (PEMFC). Preliminary results show that Pt/NPG has very good fuel cell performance at a very low platinum loading.

Sn Nanoparticles Encapsulated in 3D Nanoporous Carbon Derived from a Metal-Organic Framework for Anode Material in Lithium-Ion Batteries.

PubMed

Guo, Yuanyuan; Zeng, Xiaoqiao; Zhang, Yu; Dai, Zhengfei; Fan, Haosen; Huang, Ying; Zhang, Weina; Zhang, Hua; Lu, Jun; Huo, Fengwei; Yan, Qingyu

2017-05-24

Three-dimensional nanoporous carbon frameworks encapsulated Sn nanoparticles (Sn@3D-NPC) are developed by a facile method as an improved lithium ion battery anode. The Sn@3D-NPC delivers a reversible capacity of 740 mAh g -1 after 200 cycles at a current density of 200 mA g -1 , corresponding to a capacity retention of 85% (against the second capacity) and high rate capability (300 mAh g -1 at 5 A g -1 ). Compared to the Sn nanoparticles (SnNPs), such improvements are attributed to the 3D porous and conductive framework. The whole structure can provide not only the high electrical conductivity that facilities the electron transfer but also the elasticity that will suppress the volume expansion and aggregation of SnNPs during the charge and discharge process. This work opens a new application of metal-organic frameworks in energy storage.

Encapsulated heterogeneous base catalysts onto SBA-15 nanoporous material as highly active catalysts in the transesterification of sunflower oil to biodiesel

NASA Astrophysics Data System (ADS)

Albayati, Talib M.; Doyle, Aidan M.

2015-02-01

Alkali metals and their hydroxides, Na, NaOH, Li, and LiOH, were encapsulated onto SBA-15 nanoporous material as highly active catalysts for the production of biodiesel fuel from sunflower oil. The incipient wetness impregnation method was adopted for the prepared catalysts. The characterization properties of the catalysts and unmodified SBA-15 were determined using X-ray diffraction, scanning electron microscopy, EDAX, nitrogen adsorption-desorption porosimetry (Brunauer-Emmett-Teller), Fourier-transform infrared spectroscopy, and transmission electron microscopy. Transesterification was conducted in a batch reactor at atmospheric pressure and 65 °C. The catalysts were highly active with yields of fatty acid methyl ester (FAME) in the range 96-99 %. Na/SBA-15 catalyst was reused for seven consecutive cycles under the same reaction conditions; the yield to FAME on the final cycle was 96 %. This study shows that the alkali metals and their hydroxides supported on SBA-15-based catalyst are excellent catalysts for the biodiesel reaction.

Thermal conversion of an Fe₃O₄@metal-organic framework: a new method for an efficient Fe-Co/nanoporous carbon microwave absorbing material.

PubMed

Zhang, Xingmiao; Ji, Guangbin; Liu, Wei; Quan, Bin; Liang, Xiaohui; Shang, Chaomei; Cheng, Yan; Du, Youwei

2015-08-14

A novel FeCo nanoparticle embedded nanoporous carbon composite (Fe-Co/NPC) was synthesized via in situ carbonization of dehydro-ascorbic acid (DHAA) coated Fe3O4 nanoparticles encapsulated in a metal-organic framework (zeolitic imidazolate framework-67, ZIF-67). The molar ratio of Fe/Co significantly depends on the encapsulated content of Fe3O4 in ZIF-67. The composites filled with 50 wt% of the Fe-Co/NPC-2.0 samples in paraffin show a maximum reflection loss (RL) of -21.7 dB at a thickness of 1.2 mm; in addition, a broad absorption bandwidth for RL < -10 dB which covers from 12.2 to 18 GHz can be obtained, and its minimum reflection loss and bandwidth (RL values exceeding -10 dB) are far greater than those of commercial carbonyl iron powder under a very low thickness (1-1.5 mm). This study not only provides a good reference for future preparation of carbon-based lightweight microwave absorbing materials but also broadens the application of such kinds of metal-organic frameworks.

Modification of structure and magnetic anisotropy of epitaxial CoFe₂O₄ films by hydrogen reduction

DOE PAGES

Chen, Aiping; Poudyal, Narayan; Xiong, Jie; ...

2015-03-16

Heteroepitaxial CoFe₂O₄ (CFO) thin films with different thicknesses were deposited on MgO (001) substrates. The as-deposited CFO films show a clear switching of magnetic anisotropy with increasing film thickness. The thinner films (<100 nm) show a perpendicular magnetic anisotropy due to the out-of-plane compressive strain. The thicker films exhibit an in-plane easy axis owing to the dominating shape anisotropy effect. The magnetostriction coefficient of CFO films is estimated to be λ[001] =-188 × 10⁻⁶. Metallic CoFe₂ films were obtained by annealing the as-deposited CFO films in forming gas (Ar 93% + H₂ 7%) at 450 °C. XRD shows that CoFe₂more » films are textured out-of-plane and aligned in-plane, owing to lattice matching between CoFe₂ and MgO substrate. TEM results indicate that as-deposited films are continuous while the annealed films exhibit a nanopore mushroom structure. The magnetic anisotropy of CoFe₂ films is dominated by the shape effect. The results demonstrate that hydrogen reduction can be effectively used to modify microstructures and physical properties of complex metal oxide materials.« less

Surface modification of nanoporous alumina layers by deposition of Ag nanoparticles. Effect of alumina pore diameter on the morphology of silver deposit and its influence on SERS activity

NASA Astrophysics Data System (ADS)

Pisarek, Marcin; Nowakowski, Robert; Kudelski, Andrzej; Holdynski, Marcin; Roguska, Agata; Janik-Czachor, Maria; Kurowska-Tabor, Elżbieta; Sulka, Grzegorz D.

2015-12-01

Self-organized Al2O3 nanoporous/nanotubular (Al2O3-NP) oxide layers decorated with silver nanoparticles (Ag-NPs) exhibiting specific properties may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as stable platforms for detecting various organic compounds. This article presents the influence of the size of the alumina nanopores with a deposit of silver nanoparticles obtained by the magnetron sputtering technique on the morphology of silver film. Moreover, the effect of pore diameter on the intensity of SERS spectra in Ag-NPs/Al2O3-NP/Al composites has also been estimated. For such investigations we used pyridine as a probe molecule, since it has a large cross-section for Raman scattering. To characterize the morphology of the composite oxide layer Ag-NPs/Al2O3-NP/Al, before and after deposition of Ag-NPs by PVD methods (Physical Vapor Deposition), we used scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface analytical technique of surface-enhanced Raman spectroscopy (SERS) was used to investigate the surface activity of the composite. The results obtained show that, for a carefully controlled amount of Ag (0.020 mg/cm2 - deposited on the top of alumina nanopores whose average size varies from ∼86 nm up to ∼320 nm) in the composites investigated, pore size significantly affects SERS enhancement. We obtained distinctly higher intensities of SERS spectra for substrates with an Ag-NPs deposit having a larger diameter of the alumina nanopores. AFM results suggest that both the lateral and perpendicular distribution of Ag-NPs within and on the top of the largest pores is responsible for the highest SERS activity of the resulting Ag-NPs/Al2O3-NP/Al composite layer, since it produces a variety of cavities and slits which function as resonators for the adsorbed molecules. The Ag-NPs/MeOx-NP/Me composite layers obtained ensure a good reproducibility of the SERS measurements.

Immobilization of glucose oxidase into a nanoporous TiO₂ film layered on metallophthalocyanine modified vertically-aligned carbon nanotubes for efficient direct electron transfer.

PubMed

Cui, Hui-Fang; Zhang, Kuan; Zhang, Yong-Fang; Sun, Yu-Long; Wang, Jia; Zhang, Wei-De; Luong, John H T

2013-08-15

Glucose oxidase (GOD) was adsorbed into a nanoporous TiO₂ film layered on the surface of an iron phthalocyanine (FePc) vertically-aligned carbon nanotube (CNT) modified electrode. A Nafion film was then dropcast on the electrode's surface to improve operational and storage stabilities of the GOD-based electrode. Scanning electron microscopy (SEM) micrographs revealed the formation of FePc and nanoporous TiO₂ nanoparticles along the sidewall and the tip of CNTs. Cyclic voltammograms of the GOD electrode in neutral PBS exhibited a pair of well-defined redox peaks, attesting the direct electron transfer of GOD (FAD/FADH₂) with the underlying electrode. The potential of glucose electro-oxidation under nitrogen was ∼+0.12 V with an oxidation current density of 65.3 μA cm(-2) at +0.77 V. Voltammetric and amperometric responses were virtually unaffected by oxygen, illustrating an efficient and fast direct electron transfer. The modification of the CNT surface with FePc resulted in a biosensor with remarkable detection sensitivity with an oxygen-independent bioelectrocatalysis. In deaerated PBS, the biosensor displayed average response time of 12 s, linearity from 50 μM to 4 mM, and a detection limit of 30 μM (S/N=3) for glucose. Copyright © 2013 Elsevier B.V. All rights reserved.

Mechanical stability of heat-treated nanoporous anodic alumina subjected to repetitive mechanical deformation

NASA Astrophysics Data System (ADS)

Bankova, A.; Videkov, V.; Tzaneva, B.; Mitov, M.

2018-03-01

We report studies on the mechanical response and deformation behavior of heat-treated nanoporous anodic alumina using a micro-balance test and experimental test equipment especially designed for this purpose. AAO samples were characterized mechanically by a three-point bending test using a micro-analytical balance. The deformation behavior was studied by repetitive mechanical bending of the AAO membranes using an electronically controlled system. The nanoporous AAO structures were prepared electrochemically from Al sheet substrates using a two-step anodizing technique in oxalic acid followed by heat treatment at 700 °C in air. The morphological study of the aluminum oxide layer after the mechanical tests and mechanical deformation was conducted using scanning electron and optical microscopy, respectively. The experimental results showed that the techniques proposed are simple and accurate; they could, therefore, be combined to constitute a method for mechanical stability assessment of nanostructured AAO films, which are important structural components in the design of MEMS devices and sensors.

Fabrication of cobalt-nickel binary nanowires in a highly ordered alumina template via AC electrodeposition

PubMed Central

2013-01-01

Cobalt-nickel (Co-Ni) binary alloy nanowires of different compositions were co-deposited in the nanopores of highly ordered anodic aluminum oxide (AAO) templates from a single sulfate bath using alternating current (AC) electrodeposition. AC electrodeposition was accomplished without modifying or removing the barrier layer. Field emission scanning electron microscope was used to study the morphology of templates and alloy nanowires. Energy-dispersive X-ray analysis confirmed the deposition of Co-Ni alloy nanowires in the AAO templates. Average diameter of the alloy nanowires was approximately 40 nm which is equal to the diameter of nanopore. X-ray diffraction analysis showed that the alloy nanowires consisted of both hexagonal close-packed and face-centered cubic phases. Magnetic measurements showed that the easy x-axis of magnetization is parallel to the nanowires with coercivity of approximately 706 Oe. AC electrodeposition is very simple, fast, and is useful for the homogenous deposition of various secondary nanostuctured materials into the nanopores of AAO. PMID:23941234

Controlled release of astaxanthin from nanoporous silicified-phospholipids assembled boron nitride complex for cosmetic applications

NASA Astrophysics Data System (ADS)

Lee, Hye Sun; Sung, Dae Kyung; Kim, Sung Hyun; Choi, Won Il; Hwang, Ee Tag; Choi, Doo Jin; Chang, Jeong Ho

2017-12-01

Nanoporous silicified-phospholipids assembled boron nitride (nSPLs@BN) powder was prepared and demonstrated for use in controlled release of anti-oxidant astaxanthin (AX) as a cosmetic application. The nanoporous silicified phospholipids (nSPLs) were obtained by the silicification with tetraethyl orthosilicate (TEOS) of the hydrophilic region of phospholipid bilayers. This process involved the co-assembly of chemically active phospholipid bilayers within the porous silica matrix. In addition, nSPLs@BN was characterized using several analytical techniques and tested to assess their efficiency as drug delivery systems. We calculated the maximum release amounts as a function of time and various pH. The release rate of AX from the nSPLs@BN for the initial 24 h was 10.7 μmol/(h mg) at pH 7.4. Furthermore, we determined the antioxidant activity (KD) for the released AX with DPPH (1,1-diphenyl-2-picryl-hydrazyl) radical and the result was 34.6%.

Nanoair-bridged lateral overgrowth of GaN on ordered nanoporous GaN template

NASA Astrophysics Data System (ADS)

Wang, Y. D.; Zang, K. Y.; Chua, S. J.; Tripathy, S.; Chen, P.; Fonstad, C. G.

2005-12-01

We report the growth of high-quality GaN epilayers on an ordered nanoporous GaN template by metalorganic chemical vapor deposition. The nanopores in GaN template were created by inductively coupled plasma etching using anodic aluminum oxide film as an etch mask. The average pore diameter and interpore distance is about 65 and 110nm, respectively. Subsequent overgrowth of GaN first begins at the GaN crystallite surface between the pores, and then air-bridge-mediated lateral overgrowth leads to the formation of the continuous layer. Microphotoluminescence and micro-Raman measurements show improved optical properties and significant strain relaxation in the overgrown layer when compared to GaN layer of same thickness simultaneously grown on sapphire without any template. Similar to conventional epitaxial lateral overgrown GaN, such overgrown GaN on a nanopatterned surface would also serve as a template for the growth of ultraviolet-visible light-emitting III-nitride devices.

Fabrication of very high aspect ratio metal nanowires by a self-propulsion mechanism.

PubMed

Sharabani, Rona; Reuveni, Saada; Noy, Gilad; Shapira, Eyal; Sadeh, Shira; Selzer, Yoram

2008-04-01

A novel synthesis method of very high aspect ratio metal nanowires is described. The synthesis utilizes a nanoporous membrane as a template and self-electrophoresis as a directed force that continuously push formed nanowires out of the pores in a rate that is identical to the rate of their elongation. As a result, while the pores of membranes are only 6 microm long, the formed nanowires could be more than 100 microm long.

Peptide assembly-driven metal-organic framework (MOF) motors for micro electric generators.

PubMed

Ikezoe, Yasuhiro; Fang, Justin; Wasik, Tomasz L; Uemura, Takashi; Zheng, Yongtai; Kitagawa, Susumu; Matsui, Hiroshi

2015-01-14

Peptide-metal-organic framework (Pep-MOF) motors, whose motions are driven by anisotropic surface tension gradients created via peptide self-assembly around frameworks, can rotate microscopic rotors and magnets fast enough to generate an electric power of 0.1 μW. A new rigid Pep-MOF motor can be recycled by refilling the peptide fuel into the nanopores of the MOF. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Analysis of nanopore arrangement and structural features of anodic alumina layers formed by two-step anodizing in oxalic acid using the dedicated executable software

NASA Astrophysics Data System (ADS)

Zaraska, Leszek; Stępniowski, Wojciech J.; Sulka, Grzegorz D.; Ciepiela, Eryk; Jaskuła, Marian

2014-02-01

Anodic porous alumina layers were fabricated by a two-step self-organized anodization in 0.3 M oxalic acid under various anodizing potentials ranging from 30 to 60 V at two different temperatures (10 and 17 ∘C). The effect of anodizing conditions on structural features and pore arrangement of AAO was investigated in detail by using the dedicated executable publication combined with ImageJ software. With increasing anodizing potential, a linear increase of the average pore diameter, interpore distance, wall thickness and barrier layer thickness, as well as a decrease of the pore density, were observed. In addition, the higher pore diameter and porosity values were obtained for samples anodized at the elevated temperature, independently of the anodizing potential. A degree of pore order was investigated on the basis of Delaunay triangulations (defect maps) and calculation of pair distribution or angle distribution functions (PDF or ADF), respectively. All methods confirmed that in order to obtain nanoporous alumina with the best, hexagonal pore arrangement, the potential of 40 V should be applied during anodization. It was confirmed that the dedicated executable publication can be used to a fast and complex analysis of nanopore arrangement and structural features of nanoporous oxide layers.

A Nanoporous Carbon/Exfoliated Graphite Composite For Supercapacitor Electrodes

NASA Astrophysics Data System (ADS)

Rosi, Memoria; Ekaputra, Muhamad P.; Iskandar, Ferry; Abdullah, Mikrajuddin; Khairurrijal

2010-12-01

Nanoporous carbon was prepared from coconut shells using a simple heating method. The nanoporous carbon is subjected to different treatments: without activation, activation with polyethylene glycol (PEG), and activation with sodium hydroxide (NaOH)-PEG. The exfoliated graphite was synthesized from graphite powder oxidized with zinc acetate (ZnAc) and intercalated with polyvinyl alcohol (PVA) and NaOH. A composite was made by mixing the nanoporous carbon with NaOH-PEG activation, the exfoliated graphite and a binder of PVA solution, grinding the mixture, and annealing it using ultrasonic bath for 1 hour. All of as-synthesized materials were characterized by employing a scanning electron microscope (SEM), a MATLAB's image processing toolbox, and an x-ray diffractometer (XRD). It was confirmed that the composite is crystalline with (002) and (004) orientations. In addition, it was also found that the composite has a high surface area, a high distribution of pore sizes less than 40 nm, and a high porosity (67%). Noting that the pore sizes less than 20 nm are significant for ionic species storage and those in the range of 20 to 40 nm are very accessible for ionic clusters mobility across the pores, the composite is a promising material for the application as supercapacitor electrodes.

Recent advances in functionalized micro and mesoporous carbon materials: synthesis and applications.

PubMed

Benzigar, Mercy R; Talapaneni, Siddulu Naidu; Joseph, Stalin; Ramadass, Kavitha; Singh, Gurwinder; Scaranto, Jessica; Ravon, Ugo; Al-Bahily, Khalid; Vinu, Ajayan

2018-04-23

Functionalized nanoporous carbon materials have attracted the colossal interest of the materials science fraternity owing to their intriguing physical and chemical properties including a well-ordered porous structure, exemplary high specific surface areas, electronic and ionic conductivity, excellent accessibility to active sites, and enhanced mass transport and diffusion. These properties make them a special and unique choice for various applications in divergent fields such as energy storage batteries, supercapacitors, energy conversion fuel cells, adsorption/separation of bulky molecules, heterogeneous catalysts, catalyst supports, photocatalysis, carbon capture, gas storage, biomolecule detection, vapour sensing and drug delivery. Because of the anisotropic and synergistic effects arising from the heteroatom doping at the nanoscale, these novel materials show high potential especially in electrochemical applications such as batteries, supercapacitors and electrocatalysts for fuel cell applications and water electrolysis. In order to gain the optimal benefit, it is necessary to implement tailor made functionalities in the porous carbon surfaces as well as in the carbon skeleton through the comprehensive experimentation. These most appealing nanoporous carbon materials can be synthesized through the carbonization of high carbon containing molecular precursors by using soft or hard templating or non-templating pathways. This review encompasses the approaches and the wide range of methodologies that have been employed over the last five years in the preparation and functionalisation of nanoporous carbon materials via incorporation of metals, non-metal heteroatoms, multiple heteroatoms, and various surface functional groups that mostly dictate their place in a wide range of practical applications.

Fabrication of Pd Micro-Membrane Supported on Nano-Porous Anodized Aluminum Oxide for Hydrogen Separation.

PubMed

Kim, Taegyu

2015-08-01

In the present study, nano-porous anodized aluminum oxide (AAO) was used as a support of the Pd membrane. The AAO fabrication process consists of an electrochemical polishing, first/second anodizing, barrier layer dissolving and pores widening. The Pd membrane was deposited on the AAO support using an electroless plating with ethylenediaminetetraacetic acid (EDTA) as a plating agent. The AAO had the regular pore structure with the maximum pore diameter of ~100 nm so it had a large opening area but a small free standing area. The 2 µm-thick Pd layer was obtained by the electroless plating for 3 hours. The Pd layer thickness increased with increasing the plating time. However, the thickness was limited to ~5 µm in maximum. The H2 permeation flux was 0.454 mol/m2-s when the pressure difference of 66.36 kPa0.5 was applied at the Pd membrane under 400 °C.

Optical properties of InP/ZnS quantum dots deposited into nanoporous anodic alumina

NASA Astrophysics Data System (ADS)

Savchenko, S. S.; Vokhmintsev, A. S.; Weinstein, I. A.

2016-08-01

Spectral characteristics of InP/ZnS core/shell colloidal quantum dots of two different sizes (QD-1 and QD-2) were investigated. Absorption and luminescence spectra were analyzed for a series of solutions with a concentration range from 0.04 to 40 g/l. Energies of the optical transitions are evaluated. The obtained values of 2.60 eV (QD-1) and 2.38 eV (QD-2) correspond to the InP first excitonic transitions while 4.06 (QD-2) and 4.70 eV (QD-1, QD-2) are assumed to be caused by the ZnS shell absorption. Structures based on nanoporous anodic aluminum oxide (AAO) with the QDs were synthesized via an electrochemical oxidation and ultrasonic-assisted deposition. Chromaticity coordinates and correlated color temperatures for all phosphors under study were calculated. The fabrication possibilities of InP/ZnS@AAO nanostructures with tunable emission color (including the border of white region) were shown.

Fabrication of pH sensitive nanovalves using smart surface coated nanopores

NASA Astrophysics Data System (ADS)

Nieto-Soto, A. M.; Diaz-Maldonado, D. K.; Rios Angarita, F. A.

2017-01-01

A pH sensitive nanovalve was fabricated using different smart surfaces covalently attached to an anodized aluminium oxide membrane (AAO). The smart surfaces were synthesized using a mixture of aliphatic and aminated silanes. Effect on the contact angle of the aliphatic silane chain length was evaluated. The smart surface, in conjunction with a nanoporous membrane, allowed the formation of a hydrophobic plug which controlled the transport of the molecule safranine depending on the pH of the solution. It was demonstrated that mixtures of butyl and methyl-trimethoxysilane with aminopropyl-trimethoxysilane were able to perform as effective nanovalves creating a plug that remained closed at pH>7 and opened up at pH<5.

Synthesis and energy applications of oriented metal oxide nanoporous films

NASA Astrophysics Data System (ADS)

Wu, Qingliu

This dissertation mainly addresses the synthesis of well-ordered mesoporous titania thin films by dip coating with PEO-PPO-PEO triblock copolymer surfactant template P123. Because P123 is composed of poly(ethylene oxide) [PEO] and poly(propylene oxide) [PPO] blocks, concentrations of ingredients are adjusted to tune the films' wall thickness, pore size and mesophase. Structural changes are consistent with partitioning of species among PEO blocks, PPO blocks, and the PEO/PPO interface. Titanates localize near PEO and increase wall thickness (by 5 nm to 7 nm). Depending on aging temperature, PPG either swells the PPO cores (when it is hydrophobic) or introduces large (>200 nm) voids (when it is hydrophilic but phase separates during heating). 1-butanol localizes at the PEO/PPO interface to favor a 3D hexagonal mesostructure. In another approach, anodizing Ti foils yields vertically aligned titania nanotubes arrays with exceptional stabilities as anodes in lithium ion batteries; they maintain capacities of 130-230 mAhg-1 over 200 cycles. No microstructural changes are induced by battery cycling and good electrical contact is maintained. A diffusion induced stress model suggests that thin-walled nanotubes arrays should be stable under testing conditions, and that ordered hexagonal columnar pore arrays should have both high charge/discharge rates and low stress development. KEY WORDS: materials synthesis, porous, thin film, alternative energy, self-assembly

Parametric study of thin film evaporation from nanoporous membranes

NASA Astrophysics Data System (ADS)

Wilke, Kyle L.; Barabadi, Banafsheh; Lu, Zhengmao; Zhang, TieJun; Wang, Evelyn N.

2017-10-01

The performance and lifetime of advanced electronics are often dictated by the ability to dissipate heat generated within the device. Thin film evaporation from nanoporous membranes is a promising thermal management approach, which reduces the thermal transport distance across the liquid film while also providing passive capillary pumping of liquid to the evaporating interface. In this work, we investigated the dependence of thin film evaporation from nanoporous membranes on a variety of geometric parameters. Anodic aluminum oxide membranes were used as experimental templates, where pore radii of 28-75 nm, porosities of 0.1-0.35, and meniscus locations down to 1 μm within the pore were tested. We demonstrated different heat transfer regimes and observed more than an order of magnitude increase in dissipated heat flux by operating in the pore-level evaporation regime. The pore diameter had little effect on pore-level evaporation performance due to the negligible conduction resistance from the pore wall to the evaporating interface. The dissipated heat flux scaled with porosity as the evaporative area increased. Furthermore, moving the meniscus as little as 1 μm into the pore decreased the dissipated heat flux by more than a factor of two due to the added resistance to vapor escaping the pore. The experimental results elucidate thin film evaporation from nanopores and confirm findings of recent modeling efforts. This work also provides guidance for the design of future thin film evaporation devices for advanced thermal management. Furthermore, evaporation from nanopores is relevant to water purification, chemical separations, microfluidics, and natural processes such as transpiration.

Electrically Conductive and Optically Active Porous Silicon Nanowires

PubMed Central

Qu, Yongquan; Liao, Lei; Li, Yujing; Zhang, Hua; Huang, Yu; Duan, Xiangfeng

2009-01-01

We report the synthesis of vertical silicon nanowire array through a two-step metal-assisted chemical etching of highly doped n-type silicon (100) wafers in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of the as-grown silicon nanowires is tunable from solid nonporous nanowires, nonporous/nanoporous core/shell nanowires, and entirely nanoporous nanowires by controlling the hydrogen peroxide concentration in the etching solution. The porous silicon nanowires retain the single crystalline structure and crystallographic orientation of the starting silicon wafer, and are electrically conductive and optically active with visible photoluminescence. The combination of electronic and optical properties in the porous silicon nanowires may provide a platform for the novel optoelectronic devices for energy harvesting, conversion and biosensing. PMID:19807130

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Shunmin; Tian, Chengcheng; Zhu, Xiang

Transition-metal-catalyzed cyanation of aryl halides is a common route to benzonitriles, which are integral to many industrial procedures. However, traditional homogeneous catalysts for such processes are expensive and suffer poor recyclability, so a heterogeneous analogue is highly desired. A novel spatial modulation approach has been developed in this paper to fabricate a heterogeneous Pd-metalated nanoporous polymer, which catalyzes the cyanation of aryl halides without need for ligands. Finally, the catalyst displays high activity in the synthesis of benzonitriles, including high product yields, excellent stability and recycling, and broad functional-group tolerance.

L1(0)-FePd nanocluster wires by template-directed thermal decomposition and subsequent hydrogen reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, BZ; Marinescu, M; Liu, JF

2013-12-14

This paper reports the nanostructure, formation mechanism, and magnetic properties of tetragonal L1(0)-type Fe55Pd45 (at. %) nanocluster wires (NCWs) fabricated by thermal decomposition of metal nitrates and subsequent hydrogen reduction in nanoporous anodized aluminum oxide templates. The as-synthesized NCWs have diameters in the range of 80-300 nm, and lengths in the range of 0.5-10 mu m. The NCWs are composed of roughly round-shaped nanoclusters in the range of 3-30 nm in size and a weighted average size of 10 nm with a mixture of single-crystal and poly-crystalline structures. The obtained intrinsic coercivity H-i(c) of 3.32 kOe at room temperature formore » the tetragonal Fe55Pd45 NCWs is higher than those of electrodeposited Fe-Pd solid nanowires while among the highest values reported so far for L1(0)-type FePd nanoparticles. (C) 2013 AIP Publishing LLC.« less

Photo-electrochemically synthesized light emtting nanoporous silicon based UV photodetector: influence of current density

NASA Astrophysics Data System (ADS)

Thahe, Asad A.; Bidin, Noriah; Hassan, Z.; Bakhtiar, Hazri; Qaeed, M. A.; Bououdina, Mohamed; Ahmed, Naser M.; Talib, Zainal A.; Al-Azawi, Mohammed A.; Alqaraghuli, Hasan; Uday, M. B.; Hamad Ahmed, Omar

2017-11-01

Nanoporous silicon (n-PSi) with diverse morphologies was prepared on silicon (Si) substrate via photo-electrochemical etching technique. The role of changing current density (15, 30 and 45 mA cm-2) on the structure, morphology and optical properties was determined. As-prepared samples were systematically characterized using XRD, FESEM, AFM and photoluminescence measurements. Furthermore, the achieved n-PSi sample was used to make metal-semiconductor-metal (MSM) UV photodetector. The performance of these photodetectors was evaluated upon exposing to visible light of wavelength 530 nm (power density 1.55 mW cm-2), which exhibited very high sensitivity of 150.26 with a low dark current. The achieved internal photoconductive gain was 2.50, the photoresponse peak was 1.23 A W-1 and the response time was 0.49 s and the recovery time was 0.47 s. Excellent attributes of the fabricated photodetectors suggest that the present approach may provide a cost effective and simple way to obtain n-PSi suitable for sundry applications.

Ozone-Activated Nanoporous Gold: A Stable and Storable Material for Catalytic Oxidation

DOE PAGES

Personick, Michelle L.; Zugic, Branko; Biener, Monika M.; ...

2015-05-28

We report a new method for facile and reproducible activation of nanoporous gold (npAu) materials of different forms for the catalytic selective partial oxidation of alcohols under ambient pressure, steady flow conditions. This method, based on the surface cleaning of npAu ingots with ozone to remove carbon documented in ultrahigh vacuum conditions, produces active npAu catalysts from ingots, foils, and shells by flowing an ozone/dioxygen mixture over the catalyst at 150 °C, followed by a temperature ramp from 50 to 150 °C in a flowing stream of 10% methanol and 20% oxygen. With this treatment, all three materials (ingots, foils,more » and shells) can be reproducibly activated, despite potential carbonaceous poisons resulting from their synthesis, and are highly active for the selective oxidation of primary alcohols over prolonged periods of time. The npAu materials activated in this manner exhibit catalytic behavior substantially different from those activated under different conditions previously reported. Once activated in this manner, they can be stored and easily reactivated by flow of reactant gases at 150 °C for a few hours. They possess improved selectivity for the coupling of higher alcohols, such as 1-butanol, and are not active for carbon monoxide oxidation. As a result, this ozone-treated npAu is a functionally new catalytic material.« less

Ozone-Activated Nanoporous Gold: A Stable and Storable Material for Catalytic Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Personick, Michelle L.; Zugic, Branko; Biener, Monika M.

We report a new method for facile and reproducible activation of nanoporous gold (npAu) materials of different forms for the catalytic selective partial oxidation of alcohols under ambient pressure, steady flow conditions. This method, based on the surface cleaning of npAu ingots with ozone to remove carbon documented in ultrahigh vacuum conditions, produces active npAu catalysts from ingots, foils, and shells by flowing an ozone/dioxygen mixture over the catalyst at 150 °C, followed by a temperature ramp from 50 to 150 °C in a flowing stream of 10% methanol and 20% oxygen. With this treatment, all three materials (ingots, foils,more » and shells) can be reproducibly activated, despite potential carbonaceous poisons resulting from their synthesis, and are highly active for the selective oxidation of primary alcohols over prolonged periods of time. The npAu materials activated in this manner exhibit catalytic behavior substantially different from those activated under different conditions previously reported. Once activated in this manner, they can be stored and easily reactivated by flow of reactant gases at 150 °C for a few hours. They possess improved selectivity for the coupling of higher alcohols, such as 1-butanol, and are not active for carbon monoxide oxidation. As a result, this ozone-treated npAu is a functionally new catalytic material.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoon, Yeung-Pil; Kim, Jae-Hong; Ahn, Kwang-Soon, E-mail: kstheory@ynu.ac.kr

Au was electrodeposited potentiostatically at 0.3 V for 5 min on nanoporous Pt nanoparticle-coated F-doped SnO{sub 2} (FTO/Pt) substrates. For comparison, Au-electrodeposited FTO (FTO/Au) and Au-uncoated FTO/Pt were prepared. FTO/Au showed large-sized Au clusters dispersed sparsely over FTO, which resulted in lower electrocatalytic activity than FTO/Pt. In contrast, FTO/Pt exhibited poor stability unlike FTO/Au due to poisoning by the adsorption of sulfur species. The Au-electrodeposited FTO/Pt (FTO/Pt/Au) consisted of small Au clusters deposited over the entire area of Pt due to the effective Au nucleation provided by nanoporous metallic Pt. FTO/Pt/Au exhibited enhanced electrocatalytic activity and excellent stability because the small Aumore » particles well-dispersed over the nanoporous metallic Pt network provided numerous electrochemical reaction sites, and the Pt surface was not exposed to the electrolyte. When FTO/Pt/Au was used as the counter electrode (CE) of a quantum dot-sensitized solar cell, the significantly enhanced electrocatalytic activity of the FTO/Pt/Au CE facilitated the reduction reaction of S{sub n}{sup 2− }+ 2e{sup −} (CE) → S{sub n−1}{sup 2−} + S{sup 2−} at the CE/electrolyte interface, resulting in a significantly hindered recombination reaction, S{sub n}{sup 2− }+ 2e{sup −} (TiO{sub 2} in the photoanode) → S{sub n-1}{sup 2−} + S{sup 2−}, and significantly improved overall energy conversion efficiency.« less

The radiation gas detectors with novel nanoporous converter for medical imaging applications

NASA Astrophysics Data System (ADS)

Zarei, H.; Saramad, S.

2018-02-01

For many reason it is tried to improve the quantum efficiency (QE) of position sensitive gas detectors. For energetic X-rays, the imaging systems usually consist of a bulk converter and gas amplification region. But the bulk converters have their own limitation. For X-rays, the converter thickness should be increased to achieve a greater detection efficiency, however in this case, the chance of escaping the photoelectrons is reduced. To overcome this limitation, a new type of converter, called a nanoporous converter such as Anodizing Aluminum Oxide (AAO) membrane with higher surface to volume ratio is proposed. According to simulation results with GATE code, for this nanoporous converter with the 1 mm thickness and inter pore distance of 627 nm, for 20-100 keV X-ray energies with a reasonable gas pressure and different pore diameters, the QE can be one order of magnitude greater than the bulk ones, which is a new approach for proposing high QE position sensitive gas detectors for medical imaging application and also high energy physics.

Argon-ion-induced formation of nanoporous GaSb layer: Microstructure, infrared luminescence, and vibrational properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datta, D. P.; Som, T., E-mail: tsom@iopb.res.in; Kanjilal, A.

2014-07-21

Room temperature implantation of 60 keV Ar{sup +}-ions in GaSb to the fluences of 7 × 10{sup 16} to 3 × 10{sup 18} ions cm{sup −2} is carried out at two incidence angles, viz 0° and 60°, leading to formation of a nanoporous layer. As the ion fluence increases, patches grow on the porous layer under normal ion implantation, whereas the porous layer gradually becomes embedded under a rough top surface for oblique incidence of ions. Grazing incidence x-ray diffraction and cross-sectional transmission electron microscopy studies reveal the existence of nanocrystallites embedded in the ion-beam amorphized GaSb matrix up to the highest fluence used inmore » our experiment. Oxidation of the nanoporous layers becomes obvious from x-ray photoelectron spectroscopy and Raman mapping. The correlation of ion-beam induced structural modification with photoluminescence signals in the infrared region has further been studied, showing defect induced emission of additional peaks near the band edge of GaSb.« less

Nanoporous Films with Sub-10 nm in Pore Size from Acid-Cleavable Block Copolymers.

PubMed

Li, Yayuan; Xu, Yawei; Cao, Shubo; Zhao, Yongbin; Qu, Ting; Iyoda, Tomokazu; Chen, Aihua

2017-03-01

Nanoporous thin films with pore size of sub-10 nm are fabricated using an acid-cleavable block copolymer (BCP), a benzoic imine junction between poly(ethylene oxide) (PEO) and poly(methacrylate) (PMAAz) bearing an azobenzene side chain (denoted as PEO-bei-PMAAz) as the precursor. After a thermal annealing, the block copolymers are self-assembled to form highly ordered PEO cylinders within a PMAAz matrix normal to the film, even in the case of low BCP molecular weight due to the existing of the liquid crystalline (LC) azobenzene rigid segment. Thus, PMAAz thin films with pore size of ≈7 nm and density of ≈10 12 cm -2 are obtained after removal of the PEO minor phase by breaking the benzoic imine junction under mild acidic conditions. This work enriches the nanoporous polymer films from BCP precursors and introduces the LC property as a functionality which can further enhance the mechanical properties of the films and broaden their applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interfacial microstructure and properties of copper clad steel produced using friction stir welding versus gas metal arc welding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Z.; Chen, Y.; Haghshenas, M., E-mail: mhaghshe@uwaterloo.ca

A preliminary study compares the feasibility and microstructures of pure copper claddings produced on a pressure vessel A516 Gr. 70 steel plate, using friction stir welding versus gas metal arc welding. A combination of optical and scanning electron microscopy is used to characterize the grain structures in both the copper cladding and heat affected zone in the steel near the fusion line. The friction stir welding technique produces copper cladding with a grain size of around 25 μm, and no evidence of liquid copper penetration into the steel. The gas metal arc welding of copper cladding exhibits grain sizes overmore » 1 mm, and with surface microcracks as well as penetration of liquid copper up to 50 μm into the steel substrate. Transmission electron microscopy reveals that metallurgical bonding is produced in both processes. Increased diffusion of Mn and Si into the copper cladding occurs when using gas metal arc welding, although some nano-pores were detected in the FSW joint interface. - Highlights: • Cladding of steel with pure copper is possible using either FSW or GMAW. • The FSW yielded a finer grain structure in the copper, with no evidence of cracking. • The FSW joint contains some evidence of nano-pores at the interface of the steel/copper. • Copper cladding by GMAW contained surface cracks attributed to high thermal stresses. • The steel adjacent to the fusion line maintained a hardness value below 248 HV.« less

Normal-incidence quantum cascade detector coupled by nanopore structure

NASA Astrophysics Data System (ADS)

Liu, Jianqi; Wang, Fengjiao; Zhai, Shenqiang; Zhang, Jinchuan; Liu, Shuman; Liu, Junqi; Wang, Lijun; Liu, Fengqi; Wang, Zhanguo

2018-04-01

A normal-incidence quantum cascade detector coupled by a nanopore array structure (NPS) is demonstrated. The NPS is fabricated on top of an In0.53Ga0.47As contact layer by inductively coupled plasma etching using anodic aluminum oxide as a mask. Because of the nonuniform volume fraction at different areas of the device mesa, the NPS acts as subwavelength random gratings. Normal-incidence light can be scattered into random oblique directions for inter-sub-band transition absorption. With normal incidence, the responsivities of the device reach 24 mA/W at 77 K and 15.7 mA/W at 300 K, which are enhanced 2.23 and 1.96 times, respectively, compared with that of the 45°-edge device.

Calcium silicate-based drug delivery systems.

PubMed

Zhu, Ying-Jie; Guo, Xiao-Xuan; Sham, Tsun-Kong

2017-02-01

Compared with other inorganic materials such as silica, metal oxides, noble metals and carbon, calcium silicate-based materials, especially nanostructured calcium silicate materials, have high biocompatibility, bioactivity and biodegradability, high specific surface area, nanoporous/hollow structure, high drug-loading capacity, pH-responsive drug release behavior and desirable drug release properties, and thus they are promising for the application in drug delivery. Calcium silicate-based drug delivery systems have a long drug-release time, which can significantly prolong the therapeutic effect of drugs. Another advantage of calcium silicate-based drug delivery systems is their pH-responsive drug release property, which can act as an ideal platform for targeted drug delivery. Areas covered: In recent years, studies have been carried out on calcium silicate-based drug delivery systems, and important results and insights have been documented. This article is not intended to offer a comprehensive review on the research on calcium silicate-based drug delivery systems, but presents some examples reported in the literature, and includes new insights obtained by tracking the interactions between drug molecules and calcium silicate carriers on the molecular level using the synchrotron-based X-ray spectroscopy. Expert opinion: Finally, our opinions on calcium silicate-based drug delivery systems are provided, and several research directions for the future studies are proposed.

Highly efficient direct aerobic oxidative esterification of cinnamyl alcohol with alkyl alcohols catalysed by gold nanoparticles incarcerated in a nanoporous polymer matrix: a tool for investigating the role of the polymer host.

PubMed

Buonerba, Antonio; Noschese, Annarita; Grassi, Alfonso

2014-04-25

The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi-block copolymer matrix, which consisted of syndiotactic polystyrene-co-cis-1,4-polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base-catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10-45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol or 1-octanol. The rate constants of the latter reaction are pseudo-zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (Ea) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1-butanol (Ea = 57.8±11.5 and 62.7±16.7 kJ mol(-1) for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2-phenylethanol follows pseudo-first-order kinetics with respect to 2-phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Three-dimensional metal-intercalated covalent organic frameworks for near-ambient energy storage

PubMed Central

Gao, Fei; Ding, Zijing; Meng, Sheng

2013-01-01

A new form of nanoporous material, metal intercalated covalent organic framework (MCOF) is proposed and its energy storage property revealed. Employing density functional and thermodynamical analysis, we find that stable, chemically active, porous materials could form by stacking covalent organic framework (COF) layers with metals as a gluing agent. Metal acts as active sites, while its aggregation is suppressed by a binding energy significantly larger than the corresponding cohesive energy of bulk metals. Two important parameters, metal binding and metal-metal separation, are tuned by selecting suitable building blocks and linkers when constructing COF layers. Systematic searches among a variety of elements and organic molecules identify Ca-intercalated COF with diphenylethyne units as optimal material for H2 storage, reaching a striking gravimetric density ~ 5 wt% at near-ambient conditions (300 K, 20 bar), in comparison to < 0.1 wt% for bare COF-1 under the same condition. PMID:23698018

Closed end regeneration method

DOEpatents

Yang, Arthur Jing-Min; Zhang, Yuehua

2006-06-27

A nanoporous reactive adsorbent incorporates a relatively small number of relatively larger reactant, e.g. metal, enzyme, etc. particles (10) forming a discontinuous or continuous phase interspersed among and surrounded by a continuous phase of smaller adsorbent particles (12) and connected interstitial pores (14) therebetween. The reactive adsorbent can effectively remove inorganic or organic impurities in a liquid by causing the liquid to flow through the adsorbent. For example, silver ions may be adsorbed by the adsorbent particles (12) and reduced to metallic silver by reducing metal, such as irons, as the reactant particles (10). The column can be regenerated by backwashing with the liquid effluent containing, for example, acetic acid.

Synthesis of single-crystal-like nanoporous carbon membranes and their application in overall water splitting

PubMed Central

Wang, Hong; Min, Shixiong; Ma, Chun; Liu, Zhixiong; Zhang, Weiyi; Wang, Qiang; Li, Debao; Li, Yangyang; Turner, Stuart; Han, Yu; Zhu, Haibo; Abou-hamad, Edy; Hedhili, Mohamed Nejib; Pan, Jun; Yu, Weili; Huang, Kuo-Wei; Li, Lain-Jong; Yuan, Jiayin; Antonietti, Markus; Wu, Tom

2017-01-01

Nanoporous graphitic carbon membranes with defined chemical composition and pore architecture are novel nanomaterials that are actively pursued. Compared with easy-to-make porous carbon powders that dominate the porous carbon research and applications in energy generation/conversion and environmental remediation, porous carbon membranes are synthetically more challenging though rather appealing from an application perspective due to their structural integrity, interconnectivity and purity. Here we report a simple bottom–up approach to fabricate large-size, freestanding and porous carbon membranes that feature an unusual single-crystal-like graphitic order and hierarchical pore architecture plus favourable nitrogen doping. When loaded with cobalt nanoparticles, such carbon membranes serve as high-performance carbon-based non-noble metal electrocatalyst for overall water splitting. PMID:28051082

Synthesis of MOF-525 Derived Nanoporous Carbons with Different Particle Sizes for Supercapacitor Application.

PubMed

Chang, Ting-Hsiang; Young, Christine; Lee, Min-Han; Salunkhe, Rahul R; Alshehri, Saad M; Ahamad, Tansir; Islam, Md Tofazzal; Wu, Kevin C-W; Hossain, Md Shahriar A; Yamauchi, Yusuke; Ho, Kuo-Chuan

2017-11-02

Nanoporous carbon (NC) materials have attracted great research interest for supercapacitor applications, because of their excellent electrochemical and mechanical stability, good electrical conductivity, and high surface area. Although there are many reports on metal-organic framework (MOF)-derived carbon materials, previous synthetic studies have been hindered by imperfect control of particle sizes and shapes. Here, we show precise control of the particle sizes of MOF-525 from 100 nm to 750 nm. After conversion of MOF-525 to NC, the effects of variation of the particle size on the electrochemical performance have been carefully investigated. The results demonstrate that our NC is a potential candidate for practical supercapacitor applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Application of Radiation Chemistry to Some Selected Technological Issues Related to the Development of Nuclear Energy.

PubMed

Bobrowski, Krzysztof; Skotnicki, Konrad; Szreder, Tomasz

2016-10-01

The most important contributions of radiation chemistry to some selected technological issues related to water-cooled reactors, reprocessing of spent nuclear fuel and high-level radioactive wastes, and fuel evolution during final radioactive waste disposal are highlighted. Chemical reactions occurring at the operating temperatures and pressures of reactors and involving primary transients and stable products from water radiolysis are presented and discussed in terms of the kinetic parameters and radiation chemical yields. The knowledge of these parameters is essential since they serve as input data to the models of water radiolysis in the primary loop of light water reactors and super critical water reactors. Selected features of water radiolysis in heterogeneous systems, such as aqueous nanoparticle suspensions and slurries, ceramic oxides surfaces, nanoporous, and cement-based materials, are discussed. They are of particular concern in the primary cooling loops in nuclear reactors and long-term storage of nuclear waste in geological repositories. This also includes radiation-induced processes related to corrosion of cladding materials and copper-coated iron canisters, dissolution of spent nuclear fuel, and changes of bentonite clays properties. Radiation-induced processes affecting stability of solvents and solvent extraction ligands as well oxidation states of actinide metal ions during recycling of the spent nuclear fuel are also briefly summarized.

Design and fabrication of asymmetric nanopores using pulsed PECVD

NASA Astrophysics Data System (ADS)

Kelkar, Sanket S.

Manipulating matter at nanometric length scales is important for many electronic, chemical and biological applications. Structures such as nanopores demonstrate a phenomenon known as hindered transport which can be exploited in analytical applications such as DNA sequencing, ionic transistors, and molecular sieving. Precisely controlling the size, geometry and surface characteristics of the nanopores is important for realizing these applications. In this work, we employ relatively large template structures (˜ 100 nm) produced by track-etching or electron beam lithography. The pore size is then reduced to the desired level by deposition of material using pulsed plasma enhanced chemical vapor deposition (PECVD). Pulsed PECVD has been developed as a high throughput alternative to atomic layer deposition (ALD) to deliver self-limiting growth of thin films. The goal of this thesis is to extend the application of pulsed PECVD to fabricate asymmetric nanopores. In contrast to ALD, pulsed PECVD does not result in perfectly conformal deposition profiles, and predicting the final nanostructure is more complicated. A two dimensional feature scale model was developed to predict film profile evolution. The model was built in COMSOL, and is based on a diffusion reaction framework with a spatially varying Knudsen diffusion coefficient to account for the molecular transport inside the features. A scaling analysis was used to account for ALD exposure limitations that commonly occur when coating these extremely high aspect ratio features. The model was verified by cross-section microscopy of deposition profiles on patterned cylinders and trenches. The model shows that it is possible to obtain unique nanopore morphologies in pulsed PECVD that are distinct from either steady state deposition processes such as physical vapor deposition (PVD) or conventional ALD. Polymeric track etched (TE) membrane supports with a nominal size of 100 nm were employed as model template structures to demonstrate the capability of pulsed PECVD for precise pore size reduction of model supports. The efficacy of pulsed PECVD for nanopore fabrication was compared to both ALD and PVD. Flux and solute rejection measurements demonstrate that the pulsed PECVD-modified TE membranes exhibit higher selectivity without compromising on the flux due to their asymmetric structure. For example, the TiO2 modified supports were demonstrated to deliver high retention (˜ 75%) of bovine serum albumin (BSA) protein while maintaining 70% of their initial pure water flux. PVD also forms asymmetric membranes that enable high flux. But due to morphological instabilities, reproducibility and control were poor in the PVD-modified membranes, and it was not possible to optimize the flux and the selectivity of the membranes simultaneously. Excellent agreement between measured flux and model predictions based on feature scale simulations provided further validation of the tool's fidelity. Since surface energetics can often dominate hindered transport, the kinetics and thermodynamics of the octadecyltrichlorosilane (OTS) attachment was investigated in-depth as an approach to convert hydrophilic metal oxides into hydrophobic surfaces. It was shown that a simple ozone treatment was a satisfactory alternative to hazardous acids to create the highly hydroxylated surface required for OTS attachment, and that using heptane as the solvent enabled the process to be conducted under ambient conditions without the need of a glovebox. The kinetics of OTS self-assembled monolayer (SAM) formation and the saturation contact angle (˜100°) on alumina are comparable to what has been observed for OTS attachment on silicon. The OTS SAMs also demonstrated excellent thermal stability, and the modified surface showed a critical surface tension of 21.4 dyne/cm.

Dynamic restructuring drives catalytic activity on nanoporous gold–silver alloy catalysts

DOE PAGES

Zugic, Branko; Wang, Lucun; Heine, Christian; ...

2016-12-19

Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver–gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity. Advanced in situ electron microscopy and X-ray photoelectron spectroscopy are used to demonstrate that major restructuring and compositional changesmore » occur along the path to catalytic function for selective alcohol oxidation. Transient kinetic measurements correlate the restructuring to three types of oxygen on the surface. The direct influence of changes in surface silver concentration and restructuring at the nanoscale on oxidation activity is demonstrated. Finally, our results demonstrate that characterization of these dynamic changes is necessary to unlock the full potential of bimetallic catalytic materials.« less

Revealing the semiconductor–catalyst interface in buried platinum black silicon photocathodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguiar, Jeffery A.; Anderson, Nicholas C.; Neale, Nathan R.

2016-01-01

Nanoporous 'black' silicon semiconductors interfaced with buried platinum nanoparticle catalysts have exhibited stable activity for photoelectrochemical hydrogen evolution even after months of exposure to ambient conditions. The mechanism behind this stability has not been explained in detail, but is thought to involve a Pt/Si interface free from SiOx layer that would adversely affect interfacial charge transfer kinetics. In this paper, we resolve the chemical composition and structure of buried Pt/Si interfaces in black silicon photocathodes from a micron to sub-nanometer level using aberration corrected analytical scanning transmission electron microscopy. Through a controlled electrodeposition of copper on samples aged for onemore » month in ambient conditions, we demonstrate that the main active catalytic sites are the buried Pt nanoparticles located below the 400-800 nm thick nanoporous SiOx layer. Though hydrogen production performance degrades over 100 h under photoelectrochemical operating conditions, this burying strategy preserves an atomically clean catalyst/Si interface free of oxide or other phases under air exposure and provides an example of a potential method for stabilizing silicon photoelectrodes from oxidative degradation in photoelectrochemical applications.« less

Dynamic restructuring drives catalytic activity on nanoporous gold–silver alloy catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zugic, Branko; Wang, Lucun; Heine, Christian

Bimetallic, nanostructured materials hold promise for improving catalyst activity and selectivity, yet little is known about the dynamic compositional and structural changes that these systems undergo during pretreatment that leads to efficient catalyst function. Here we use ozone-activated silver–gold alloys in the form of nanoporous gold as a case study to demonstrate the dynamic behaviour of bimetallic systems during activation to produce a functioning catalyst. We show that it is these dynamic changes that give rise to the observed catalytic activity. Advanced in situ electron microscopy and X-ray photoelectron spectroscopy are used to demonstrate that major restructuring and compositional changesmore » occur along the path to catalytic function for selective alcohol oxidation. Transient kinetic measurements correlate the restructuring to three types of oxygen on the surface. The direct influence of changes in surface silver concentration and restructuring at the nanoscale on oxidation activity is demonstrated. Finally, our results demonstrate that characterization of these dynamic changes is necessary to unlock the full potential of bimetallic catalytic materials.« less

Controlling interferometric properties of nanoporous anodic aluminium oxide

PubMed Central

2012-01-01

A study of reflective interference spectroscopy [RIfS] properties of nanoporous anodic aluminium oxide [AAO] with the aim to develop a reliable substrate for label-free optical biosensing is presented. The influence of structural parameters of AAO including pore diameters, inter-pore distance, pore length, and surface modification by deposition of Au, Ag, Cr, Pt, Ni, and TiO2 on the RIfS signal (Fabry-Perot fringe) was explored. AAO with controlled pore dimensions was prepared by electrochemical anodization of aluminium using 0.3 M oxalic acid at different voltages (30 to 70 V) and anodization times (10 to 60 min). Results show the strong influence of pore structures and surface modifications on the interference signal and indicate the importance of optimisation of AAO pore structures for RIfS sensing. The pore length/pore diameter aspect ratio of AAO was identified as a suitable parameter to tune interferometric properties of AAO. Finally, the application of AAO with optimised pore structures for sensing of a surface binding reaction of alkanethiols (mercaptoundecanoic acid) on gold surface is demonstrated. PMID:22280884

Controlling the orientation of spin-correlated radical pairs by covalent linkage to nanoporous anodic aluminum oxide membranes.

PubMed

Chen, Hsiao-Fan; Gardner, Daniel M; Carmieli, Raanan; Wasielewski, Michael R

2013-10-07

Ordered multi-spin assemblies are required for developing solid-state molecule-based spintronics. A linear donor-chromophore-acceptor (D-C-A) molecule was covalently attached inside the 150 nm diam. nanopores of an anodic aluminum oxide (AAO) membrane. Photoexcitation of D-C-A in a 343 mT magnetic field results in sub-nanosecond, two-step electron transfer to yield the spin-correlated radical ion pair (SCRP) (1)(D(+)˙-C-A(-)˙), which then undergoes radical pair intersystem crossing (RP-ISC) to yield (3)(D(+)˙-C-A(-)˙). RP-ISC results in S-T0 mixing to selectively populate the coherent superposition states |S'> and |T'>. Microwave-induced transitions between these states and the unpopulated |T(+1)> and |T(-1)> states result in spin-polarized time-resolved EPR (TREPR) spectra. The dependence of the electron spin polarization (ESP) phase of the TREPR spectra on the orientation of the AAO membrane pores relative to the externally applied magnetic field is used to determine the overall orientation of the SCRPs within the pores at room temperature.

Nanoporous gold as an active low temperature catalyst toward CO oxidation in hydrogen-rich stream

PubMed Central

Li, Dongwei; Zhu, Ye; Wang, Hui; Ding, Yi

2013-01-01

Preferential CO oxidation (PROX) was investigated by using dealloyed nanoporous gold (NPG) catalyst under ambient conditions. Systematic investigations were carried out to characterize its catalytic performance by varying reaction parameters such as temperature and co-existence of CO2 and H2O, which revealed that NPG was a highly active and selective catalyst for PROX, especially at low temperature. At 20°C, the exit CO concentration could be reduced to less than 2 ppm with a turnover frequency of 4.1 × 10−2 s−1 at a space velocity of 120,000 mL h−1 g−1cat. and its high activity could retain for more than 24 hours. The presence of residual Ag species in the structure did not seem to improve the intrinsic activity of NPG for PROX; however, they contributed to the stabilization of the NPG structure and apparent catalytic activity. These results indicated that NPG might be readily applicable for hydrogen purification in fuel cell applications. PMID:24145317

Osteoblast response to magnesium ion-incorporated nanoporous titanium oxide surfaces.

PubMed

Park, Jin-Woo; Kim, Youn-Jeong; Jang, Je-Hee; Song, Hwangjun

2010-11-01

This study investigated the surface characteristics and in vitro osteoconductivity of a titanium (Ti) surface incorporated with the magnesium ions (Mg) produced by hydrothermal treatment for future application as an endosseous implant surface. Mg-incorporated Ti oxide surfaces were produced by hydrothermal treatment using Mg-containing solution on two different microstructured surfaces--abraded minimally rough (Ma) or grit-blasted moderately rough (RBM) samples. The surface characteristics were evaluated using scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, optical profilometry, and inductively coupled plasma atomic emission spectroscopy (ICP-AES). MC3T3-E1 pre-osteoblast cell attachment, proliferation, alkaline phosphatase (ALP) activity, and quantitative analysis of osteoblastic gene expression on Ma, RBM, Mg-incorporated Ma (Mg), and Mg-incorporated grit-blasted (RBM/Mg) Ti surfaces were evaluated. Hydrothermal treatment produced an Mg-incorporated Ti oxide layer with nanoporous surface structures. Mg-incorporated surfaces showed surface morphologies and surface roughness values almost identical to those of untreated smooth or micro-rough surfaces at the micron scale. ICP-AES analysis showed Mg ions released from treated surfaces into the solution. Mg incorporation significantly increased cellular attachment (P=0 at 0.5 h, P=0.01 at 1 h) on smooth surfaces, but no differences were found on micro-rough surfaces. Mg incorporation further increased ALP activity in cells grown on both smooth and micro-rough surfaces at 7 and 14 days of culture (P=0). Real-time polymerase chain reaction analysis showed higher mRNA expressions of the osteoblast transcription factor gene (Dlx5), various integrins, and the osteoblast phenotype genes (ALP, bone sialoprotein and osteocalcin) in cells grown on micro-rough (RBM) and Mg-incorporated (Mg and RBM/Mg) surfaces than those on Ma surfaces. Mg incorporation further increased the mRNA expressions of key osteoblast genes and integrins (α1, α2, α5, and β1) in cells grown on both the smooth and the micro-rough surfaces. These results indicate that an Mg-incorporated nanoporous Ti oxide surface produced by hydrothermal treatment may improve implant bone healing by enhancing the attachment and differentiation of osteoblastic cells. © 2010 John Wiley & Sons A/S.

High density group IV semiconductor nanowire arrays fabricated in nanoporous alumina templates

NASA Astrophysics Data System (ADS)

Redwing, Joan M.; Dilts, Sarah M.; Lew, Kok-Keong; Cranmer, Alexana E.; Mohney, Suzanne E.

2005-11-01

The fabrication of high density arrays of semiconductor nanowires is of interest for nanoscale electronics, chemical and biological sensing and energy conversion applications. We have investigated the synthesis, intentional doping and electrical characterization of Si and Ge nanowires grown by the vapor-liquid-solid (VLS) method in nanoporous alumina membranes. Nanoporous membranes provide a convenient platform for nanowire growth and processing, enabling control of wire diameter via pore size and the integration of contact metals for electrical testing. For VLS growth in nanoporous materials, reduced pressures and temperatures are required in order to promote the diffusion of reactants into the pore without premature decomposition on the membrane surface or pore walls. The effect of growth conditions on the growth rate of Si and Ge nanowires from SiH 4 and GeH 4 sources, respectively, was investigated and compared. In both cases, the measured activation energies for nanowire growth were substantially lower than activation energies typically reported for Si and Ge thin film deposition under similar growth conditions, suggesting that gold plays a catalytic role in the VLS growth process. Intentionally doped SiNW arrays were also prepared using trimethylboron (TMB) and phosphine (PH 3) as p-type and n-type dopant sources, respectively. Nanowire resistivities were calculated from plots of the array resistance as a function of nanowire length. A decrease in resistivity was observed for both n-type and p-type doped SiNW arrays compared to those grown without the addition of a dopant source.

Characterization of nanoporous shales with gas sorption

NASA Astrophysics Data System (ADS)

Joewondo, N.; Prasad, M.

2017-12-01

The understanding of the fluid flow in porous media requires the knowledge of the pore system involved. Fluid flow in fine grained shales falls under different regime than transport regime in conventional reservoir due to the different average pore sizes in the two materials; the average pore diameter of conventional sandstones is on the micrometer scale, while of shales can be as small as several nanometers. Mercury intrusion porosimetry is normally used to characterize the pores of conventional reservoir, however with increasingly small pores, the injection pressure required to imbibe the pores becomes infinitely large due to surface tension. Characterization of pores can be expressed by a pore size distribution (PSD) plot, which reflects distribution of pore volume or surface area with respect to pore size. For the case of nanoporous materials, the surface area, which serves as the interface between the rock matrix and fluid, becomes increasingly large and important. Physisorption of gas has been extensively studied as a method of nanoporous solid characterization (particularly for the application of catalysis, metal organic frameworks, etc). The PSD is obtained by matching the experimental result to the calculated theoretical result (using Density Functional Theory (DFT), a quantum mechanics based modelling method for molecular scale interactions). We present the challenges and experimental result of Nitrogen and CO2 gas sorption on shales with various mineralogy and the interpreted PSD obtained by DFT method. Our result shows significant surface area contributed by the nanopores of shales, hence the importance of surface area measurements for the characterization of shales.

Magnetic and superconducting nanowires.

PubMed

Piraux, L; Encinas, A; Vila, L; Mátéfi-Tempfli, S; Mátéfi-Tempfli, M; Darques, M; Elhoussine, F; Michotte, S

2005-03-01

This article is focused on the use of electrodeposition and of various nanoporous templates for the fabrication of metallic nanowires made from single metals (Ni, Co, Pb, Sn), alloys (NiFe, CoFe, CoPt), and multilayers (Co/Cu, NiFe/Cu). An overview is given of our recent studies performed on both magnetic and superconducting nanowires. Using different approaches entailing measurements on both single wires and arrays, numerous interesting physical properties have been identified in relation to the nanoscopic dimensions of these materials. Finally, various novel applications of the nanowires are also discussed.

Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes

DOE PAGES

Liu, Wei; Li, Weiyang; Zhuo, Denys; ...

2017-02-08

Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO 2@PMMA) core–shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Lastly, enhanced Coulombic efficiencies during lithium charge/discharge cycles have been achieved at various current densities andmore » areal capacities.« less

Core–Shell Nanoparticle Coating as an Interfacial Layer for Dendrite-Free Lithium Metal Anodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wei; Li, Weiyang; Zhuo, Denys

Lithium metal based batteries represent a major challenge and opportunity in enabling a variety of devices requiring high-energy-density storage. However, dendritic lithium growth has limited the practical application of lithium metal anodes. Here we report a nanoporous, flexible and electrochemically stable coating of silica@poly(methyl methacrylate) (SiO 2@PMMA) core–shell nanospheres as an interfacial layer on lithium metal anode. This interfacial layer is capable of inhibiting Li dendrite growth while sustaining ionic flux through it, which is attributed to the nanoscaled pores formed among the nanospheres. Lastly, enhanced Coulombic efficiencies during lithium charge/discharge cycles have been achieved at various current densities andmore » areal capacities.« less

Metal-in-metal localized surface plasmon resonance

NASA Astrophysics Data System (ADS)

Smith, G. B.; Earp, A. A.

2010-01-01

Anomalous strong resonances in silver and gold nanoporous thin films which conduct are found to arise from isolated metal nano-islands separated from the surrounding percolating metal network by a thin loop of insulator. This observed resonant optical response is modelled. The observed peak position is in agreement with the observed average dimensions of the silver core and insulator shell. As the insulating ring thickness shrinks, the resonance moves to longer wavelengths and strengthens. This structure is the Babinet's principle counterpart of dielectric core-metal shell nanoparticles embedded in dielectric. Like for the latter, tuning of resonant absorption is possible, but here the matrix reflects rather than transmits, and tuning to longer wavelengths is more practical. A new class of metal mirror occurring as a single thin layer is identified using the same resonances in dense metal mirrors. Narrow band deep localized dips in reflectance result.

Impact of the De-Alloying Kinetics and Alloy Microstructure on the Final Morphology of De-Alloyed Meso-Porous Metal Films

PubMed Central

Lin, Bao; Kong, Lingxue; Hodgson, Peter D.; Dumée, Ludovic F.

2014-01-01

Nano-textured porous metal materials present unique surface properties due to their enhanced surface energy with potential applications in sensing, molecular separation and catalysis. In this paper, commercial alloy foils, including brass (Cu85Zn15 and Cu70Zn30) and white gold (Au50Ag50) foils have been chemically de-alloyed to form nano-porous thin films. The impact of the initial alloy micro-structure and number of phases, as well as chemical de-alloying (DA) parameters, including etchant concentration, time and solution temperature on the final nano-porous thin film morphology and properties were investigated by electron microscopy (EM). Furthermore, the penetration depth of the pores across the alloys were evaluated through the preparation of cross sections by focus ion beam (FIB) milling. It is demonstrated that ordered pores ranging between 100 nm and 600 nm in diameter and 2–5 μm in depth can be successfully formed for the range of materials tested. The microstructure of the foils were obtained by electron back-scattered diffraction (EBSD) and linked to development of pits across the material thickness and surface during DA. The role of selective etching of both noble and sacrificial metal phases of the alloy were discussed in light of the competitive surface etching across the range of microstructures and materials tested. PMID:28344253

Current-Voltage Characteristics of Nb2O5 nanoporous via light illumination

NASA Astrophysics Data System (ADS)

Samihah Khairir, Nur; Rani, Rozina Abdul; Fazlida Hanim Abdullah, Wan; Hafiz Mamat, Mohamad; Kadir, Rosmalini Abdul; Rusop, M.; Sabirin Zoolfakar, Ahmad

2018-03-01

This work discussed the effect of light on I-V characteristics of anodized niobium pentoxide (Nb2O5) which formed nanoporous structure film. The structure was synthesized by anodizing niobium foils in glycerol based solution with 10 wt% supplied by two different voltages, 5V and 10V. The anodized foils that contained Nb2O5 film were then annealed to obtain an orthorhombic phase for 30 minutes at 450°C. The metal contact used for I-V testing was platinum (Pt) and it was deposited using thermal evaporator at 30nm thickness. I-V tests were conducted under different condition; dark and illumination to study the effect of light on I-V characteristics of anodized nanoporous Nb2O5. Higher anodization voltage and longer anodization time resulted in higher pore dispersion and larger pore size causing the current to increase. The increase of conductivity in I-V behaviour of Nb2O5 device is also affected by the illumination test as higher light intensity caused space charge region width to increase, thus making it easier for electron transfer between energy band gap.

Hydroxyl-Exchanged Nanoporous Ionic Copolymer toward Low-Temperature Cycloaddition of Atmospheric Carbon Dioxide into Carbonates.

PubMed

Guo, Zengjing; Cai, Xiaochun; Xie, Jingyan; Wang, Xiaochen; Zhou, Yu; Wang, Jun

2016-05-25

An ionic copolymer catalyst with nanopores, large surface area, high ionic density, and superior basicity was prepared via the radical copolymerization of amino-functionalized ionic liquid bromide and divinylbenzene, followed with a hydroxyl exchange for removing bromonium. Evaluated in chemical fixation of CO2 with epoxides into cyclic carbonates in the absence of any solvent and basic additive, the nanoporous copolymer catalyst showed high and stable activity, superior to various control catalysts including the halogen-containing analogue. Further, high yields were obtained over a wide scope of substrates including aliphatic long carbon-chain alkyl epoxides and internal epoxide, even under atmospheric pressure and less than 100 °C for the majority of the substrates. On the basis of in situ Fourier transform infrared (FT-IR) investigation and density functional theory (DFT) calculation for the reaction intermediates, we proposed a possible reaction mechanism accounting for the superior catalytic activity of the ionic copolymer. The specifically prepared ionic copolymer material of this work features highly stable, noncorrosive, and sustainable catalysis and, thus, may be a new possibility for efficient chemical fixation of CO2 since it is an environmentally friendly, metal-free solid catalyst.

Multiscale Morphology of Nanoporous Copper Made from Intermetallic Phases

DOE PAGES

Egle, Tobias; Barroo, Cédric; Janvelyan, Nare; ...

2017-07-11

Many application-relevant properties of nanoporous metals critically depend on their multiscale architecture. For example, the intrinsically high step-edge density of curved surfaces at the nanoscale provides highly reactive sites for catalysis, whereas the macroscale pore and grain morphology determines the macroscopic properties, such as mass transport, electrical conductivity, or mechanical properties. Here, in this work, we systematically study the effects of alloy composition and dealloying conditions on the multiscale morphology of nanoporous copper (np-Cu) made from various commercial Zn–Cu precursor alloys. Using a combination of X-ray diffraction, electron backscatter diffraction, and focused ion beam cross-sectional analysis, our results reveal thatmore » the macroscopic grain structure of the starting alloy surprisingly survives the dealloying process, despite a change in crystal structure from body-centered cubic (Zn–Cu starting alloy) to face-centered cubic (Cu). The nanoscale structure can be controlled by the acid used for dealloying with HCl leading to a larger and more faceted ligament morphology compared to that of H 3PO 4. Finally, anhydrous ethanol dehydrogenation was used as a probe reaction to test the effect of the nanoscale ligament morphology on the apparent activation energy of the reaction.« less

Multiple Approaches to Characterizing Nano-Pore Structure of Barnett Shale

NASA Astrophysics Data System (ADS)

Hu, Q.; Gao, Z.; Ewing, R. P.; Dultz, S.; Kaufmann, J.; Hamamoto, S.; Webber, B.; Ding, M.

2013-12-01

Microscopic characteristics of porous media - pore shape, pore-size distribution, and pore connectivity - control fluid flow and mass transport. This presentation discusses various approaches to investigating nano-pore structure of Barnett shale, with its implications in gas production behavior. The innovative approaches include imbibition, tracer diffusion, edge-accessible porosity, porosimetry (mercury intrusion porosimetry, nitrogen and water vapor sorption isotherms, and nuclear magnetic resonance cyroporometry), and imaging (Wood's metal impregnation followed with laser ablation-inductively coupled plasma-mass spectrometry, focused ion beam/scanning electron microscopy, and small angle neutron scattering). Results show that the shale pores are predominantly in the nm size range, with measured median pore-throat diameters about 5 nm. But small pore size is not the major contributor to low gas recovery; rather, the low mass diffusivity appears to be caused by low pore connectivity of Barnett shale. Chemical diffusion in sparsely-connected pore spaces is not well described by classical Fickian behavior; anomalous behavior is suggested by percolation theory, and confirmed by results of imbibition and diffusion tests. Our evolving complementary approaches, with their several advantages and disadvantages, provide a rich toolbox for tackling the nano-pore structure characteristics of shales and other natural rocks.

Multiscale Morphology of Nanoporous Copper Made from Intermetallic Phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Egle, Tobias; Barroo, Cédric; Janvelyan, Nare

Many application-relevant properties of nanoporous metals critically depend on their multiscale architecture. For example, the intrinsically high step-edge density of curved surfaces at the nanoscale provides highly reactive sites for catalysis, whereas the macroscale pore and grain morphology determines the macroscopic properties, such as mass transport, electrical conductivity, or mechanical properties. Here, in this work, we systematically study the effects of alloy composition and dealloying conditions on the multiscale morphology of nanoporous copper (np-Cu) made from various commercial Zn–Cu precursor alloys. Using a combination of X-ray diffraction, electron backscatter diffraction, and focused ion beam cross-sectional analysis, our results reveal thatmore » the macroscopic grain structure of the starting alloy surprisingly survives the dealloying process, despite a change in crystal structure from body-centered cubic (Zn–Cu starting alloy) to face-centered cubic (Cu). The nanoscale structure can be controlled by the acid used for dealloying with HCl leading to a larger and more faceted ligament morphology compared to that of H 3PO 4. Finally, anhydrous ethanol dehydrogenation was used as a probe reaction to test the effect of the nanoscale ligament morphology on the apparent activation energy of the reaction.« less

Nanoporous Anodic Alumina 3D FDTD Modelling for a Broad Range of Inter-pore Distances

NASA Astrophysics Data System (ADS)

Bertó-Roselló, Francesc; Xifré-Pérez, Elisabet; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluis F.

2016-08-01

The capability of the finite difference time domain (FDTD) method for the numerical modelling of the optical properties of nanoporous anodic alumina (NAA) in a broad range of inter-pore distances is evaluated. FDTD permits taking into account in the same numerical framework all the structural features of NAA, such as the texturization of the interfaces or the incorporation of electrolyte anions in the aluminium oxide host. The evaluation is carried out by comparing reflectance measurements from two samples with two very different inter-pore distances with the simulation results. Results show that considering the texturization is crucial to obtain good agreement with the measurements. On the other hand, including the anionic layer in the model leads to a second-order contribution to the reflectance spectrum.

Solvent-annealing-induced nanowetting in templates: towards tailored polymer nanostructures.

PubMed

Chen, Jiun-Tai; Lee, Chih-Wei; Chi, Mu-Huan; Yao, I-Chun

2013-02-25

We study the solvent-annealing-induced nanowetting in templates using porous anodic aluminum oxide membranes. The morphology of polystyrene and poly(methyl methacrylate) nanostructures can be controlled, depending on whether the swollen polymers are in the partial or complete wetting regimes, which are characterized by the spreading coefficient. When the swollen polymers are in the partial wetting regime, polymers wet the nanopores by capillary action, resulting in the formation of polymer nanorods. When the swollen polymers are in the complete wetting regime, polymers form wetting layers in the nanopores, resulting in the formation of polymer nanotubes. The solubility parameters of polymers and solvents are also used to predict the wetting behavior of swollen polymers in cylindrical geometry. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanoporous Anodic Alumina 3D FDTD Modelling for a Broad Range of Inter-pore Distances.

PubMed

Bertó-Roselló, Francesc; Xifré-Pérez, Elisabet; Ferré-Borrull, Josep; Pallarès, Josep; Marsal, Lluis F

2016-12-01

The capability of the finite difference time domain (FDTD) method for the numerical modelling of the optical properties of nanoporous anodic alumina (NAA) in a broad range of inter-pore distances is evaluated. FDTD permits taking into account in the same numerical framework all the structural features of NAA, such as the texturization of the interfaces or the incorporation of electrolyte anions in the aluminium oxide host. The evaluation is carried out by comparing reflectance measurements from two samples with two very different inter-pore distances with the simulation results. Results show that considering the texturization is crucial to obtain good agreement with the measurements. On the other hand, including the anionic layer in the model leads to a second-order contribution to the reflectance spectrum.

Highly conducting leakage-free electrolyte for SrCoOx-based non-volatile memory device

NASA Astrophysics Data System (ADS)

Katase, Takayoshi; Suzuki, Yuki; Ohta, Hiromichi

2017-10-01

The electrochemical switching of SrCoOx-based non-volatile memory with a thin-film-transistor structure was examined by using liquid-leakage-free electrolytes with different conductivities (σ) as the gate insulator. We first examined leakage-free water, which is incorporated in the amorphous (a-) 12CaO.7Al2O3 film with a nanoporous structure (Calcium Aluminate with Nanopore), but the electrochemical oxidation/reduction of the SrCoOx layer required the application of a high gate voltage (Vg) up to 20 V for a very long current-flowing-time (t) ˜40 min, primarily due to the low σ [2.0 × 10-8 S cm-1 at room temperature (RT)] of leakage-free water. We then controlled the σ of the leakage-free electrolyte, infiltrated in the a-NaxTaO3 film with a nanopillar array structure, from 8.0 × 10-8 S cm-1 to 2.5 × 10-6 S cm-1 at RT by changing the x = 0.01-1.0. As the result, the t, required for the metallization of the SrCoOx layer under small Vg = -3 V, becomes two orders of magnitude shorter with increase of the σ of the a-NaxTaO3 leakage-free electrolyte. These results indicate that the ion migration in the leakage-free electrolyte is the rate-determining step for the electrochemical switching, compared to the other electrochemical process, and the high σ of the leakage-free electrolyte is the key factor for the development of the non-volatile SrCoOx-based electro-magnetic phase switching device.

Flow-through lipid nanotube arrays for structure-function studies of membrane proteins by solid-state NMR spectroscopy.

PubMed

Chekmenev, Eduard Y; Gor'kov, Peter L; Cross, Timothy A; Alaouie, Ali M; Smirnov, Alex I

2006-10-15

A novel method for studying membrane proteins in a native lipid bilayer environment by solid-state NMR spectroscopy is described and tested. Anodic aluminum oxide (AAO) substrates with flow-through 175 nm wide and 60-mum-long nanopores were employed to form macroscopically aligned peptide-containing lipid bilayers that are fluid and highly hydrated. We demonstrate that the surfaces of both leaflets of such bilayers are fully accessible to aqueous solutes. Thus, high hydration levels as well as pH and desirable ion and/or drug concentrations could be easily maintained and modified as desired in a series of experiments with the same sample. The method allows for membrane protein NMR experiments in a broad pH range that could be extended to as low as 1 and as high as 12 units for a period of up to a few hours and temperatures as high as 70 degrees C without losing the lipid alignment or bilayers from the nanopores. We demonstrate the utility of this method by a solid-state 19.6 T (17)O NMR study of reversible binding effects of mono- and divalent ions on the chemical shift properties of the Leu(10) carbonyl oxygen of transmembrane pore-forming peptide gramicidin A (gA). We further compare the (17)O shifts induced by binding metal ions to the binding of protons in the pH range from 1 to 12 and find a significant difference. This unexpected result points to a difference in mechanisms for ion and proton conduction by the gA pore. We believe that a large number of solid-state NMR-based studies, including structure-function, drug screening, proton exchange, pH, and other titration experiments, will benefit significantly from the method described here.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability.

PubMed

Pawar, Rajendra C; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S

2016-08-08

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g(-1)) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g(-1)). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

NASA Astrophysics Data System (ADS)

Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-Ho; Ahn, Sunghoon; Lee, Caroline S.

2016-08-01

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g-1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g-1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective.

Room-temperature synthesis of nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) with highly enhanced photocatalytic activity and stability

PubMed Central

Pawar, Rajendra C.; Kang, Suhee; Park, Jung Hyun; Kim, Jong-ho; Ahn, Sunghoon; Lee, Caroline S.

2016-01-01

A one-dimensional (1D) nanostructure having a porous network is an exceptional photocatalytic material to generate hydrogen (H2) and decontaminate wastewater using solar energy. In this report, we synthesized nanoporous 1D microrods of graphitic carbon nitride (g-C3N4) via a facile and template-free chemical approach at room temperature. The use of concentrated acids induced etching and lift-off because of strong oxidation and protonation. Compared with the bulk g-C3N4, the porous 1D microrod structure showed five times higher photocatalytic degradation performance toward methylene blue dye (MB) under visible light irradiation. The photocatalytic H2 evolution of the 1D nanostructure (34 μmol g−1) was almost 26 times higher than that of the bulk g-C3N4 structure (1.26 μmol g−1). Additionally, the photocurrent stability of this nanoporous 1D morphology over 24 h indicated remarkable photocorrosion resistance. The improved photocatalytic activities were attributed to prolonged carrier lifetime because of its quantum confinement effect, effective separation and transport of charge carriers, and increased number of active sites from interconnected nanopores throughout the microrods. The present 1D nanostructure would be highly suited for photocatalytic water purification as well as water splitting devices. Finally, this facile and room temperature strategy to fabricate the nanostructures is very cost-effective. PMID:27498979

How the guest molecules in nanoporous Zn(II) metal-organic framework can prevent agglomeration of ZnO nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moeinian, Maryam; Akhbari, Kamran, E-mail: akhbari.k@khayam.ut.ac.ir

The host and the apohost framework of [Zn{sub 2}(BDC){sub 2}(H{sub 2}O){sub 2}·(DMF){sub 2}]{sub n} (1·2H{sub 2}O·2DMF), (BDC{sup 2−}=benzene-1,4-dicarboxylate and DMF=N,N-Dimethylformamide), were synthesized and subsequently used for preparation of ZnO nanomaterials. With calcination of the host framework of 1·2H{sub 2}O·2DMF, ZnO nanoparticles were obtained. By the same process on the apohost framework of 1, agglomerated nanoparticles of ZnO were formed. These nano-structures were characterized by X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). These results indicate that with removal of the guest DMF and coordinated H{sub 2}O molecules from the one-dimensional channels of 1·2H{sub 2}O·2DMF, the tendency of nanoparticles tomore » agglomerate increases and the role of this MOF in preparation of ZnO nanoparticles from this precursor was reduced. - Graphical abstract: Nano-porous zinc(II) MOF with guest DMF and coordinated H{sub 2}O molecules has been synthesized and characterized. The host and the apohost framework of it were used for preparation of ZnO nanomaterials. The role of these species in preparation of ZnO nanoparticles from the host framework is probably similar to the role of polymeric stabilizers in formation of nanoparticles. - Highlights: • Nanoparticles of ZnO were fabricated from nanoporous metal-organic framework. • The effect of guest DMF and coordinated H{sub 2}O molecules on this process was studied. • The effect of them in formation nanoparticle is similar to polymeric stabilizers.« less

AMN-2: Second International Conference on Advanced Materials and Nanotechnology

DTIC Science & Technology

2005-02-11

radiography 13:45 Geopolymers : nanoparticulate, nanoporous ceramics fabricated under ambient conditions 14:10 Smartening-up carbon: towards chemically...interpenetrating composites 16.15 Nanoscale surface properties of metals treated by electrochemical and physico- chemical methods 16.30 Atomistic strain...sulfonic acid for quantum dot and its characters 16.15 Characterization of photoluminescent CdTe/CdSe composite nanoparticles synthesized by the

Metal-Organic Framework Thin Film Coated Optical Fiber Sensors: A Novel Waveguide-Based Chemical Sensing Platform.

PubMed

Kim, Ki-Joong; Lu, Ping; Culp, Jeffrey T; Ohodnicki, Paul R

2018-02-23

Integration of optical fiber with sensitive thin films offers great potential for the realization of novel chemical sensing platforms. In this study, we present a simple design strategy and high performance of nanoporous metal-organic framework (MOF) based optical gas sensors, which enables detection of a wide range of concentrations of small molecules based upon extremely small differences in refractive indices as a function of analyte adsorption within the MOF framework. Thin and compact MOF films can be uniformly formed and tightly bound on the surface of etched optical fiber through a simple solution method which is critical for manufacturability of MOF-based sensor devices. The resulting sensors show high sensitivity/selectivity to CO 2 gas relative to other small gases (H 2 , N 2 , O 2 , and CO) with rapid (

Antibacterial Activity of Zinc Oxide-Coated Nanoporous Alumina

DTIC Science & Technology

2012-05-17

microorganisms, including Bacillus subtilis, Enterococcus faecalis, E. coli, methicillin - sensitive S. aureus , methicillin - resistant S. aureus , S... Staphylococcus aureus , and Staphylococcus epidermidis. On the other hand, zinc 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY...alumina membranes against several bacteria found on the skin surface, including Bacillus subtilis, Escherichia coli, Staphylococcus aureus , and

Computational predictions of zinc oxide hollow structures

NASA Astrophysics Data System (ADS)

Tuoc, Vu Ngoc; Huan, Tran Doan; Thao, Nguyen Thi

2018-03-01

Nanoporous materials are emerging as potential candidates for a wide range of technological applications in environment, electronic, and optoelectronics, to name just a few. Within this active research area, experimental works are predominant while theoretical/computational prediction and study of these materials face some intrinsic challenges, one of them is how to predict porous structures. We propose a computationally and technically feasible approach for predicting zinc oxide structures with hollows at the nano scale. The designed zinc oxide hollow structures are studied with computations using the density functional tight binding and conventional density functional theory methods, revealing a variety of promising mechanical and electronic properties, which can potentially find future realistic applications.

Effect of flattened surface morphology of anodized aluminum oxide templates on the magnetic properties of nanoporous Co/Pt and Co/Pd thin multilayered films

NASA Astrophysics Data System (ADS)

Nguyen, T. N. Anh; Fedotova, J.; Kasiuk, J.; Bayev, V.; Kupreeva, O.; Lazarouk, S.; Manh, D. H.; Vu, D. L.; Chung, S.; Åkerman, J.; Altynov, V.; Maximenko, A.

2018-01-01

For the first time, nanoporous Al2O3 templates with smoothed surface relief characterized by flattened interpore areas were used in the fabrication of Co/Pd and Co/Pt multilayers (MLs) with strong perpendicular magnetic anisotropy (PMA). Alternating gradient magnetometry (AGM) revealed perfectly conserved PMA in the Co/Pd and Co/Pt porous MLs (antidot arrays) with a ratio of remanent magnetization (Mr) to saturation magnetization (MS) of about 0.99, anisotropy fields (Ha) of up to 2.6 kOe, and a small deviation angle of 8° between the easy magnetization axis and the normal to the film surface. The sufficient magnetic hardening of the porous MLs with enhanced coercive field HC of up to ∼1.9 kOe for Co/Pd and ∼1.5 kOe for Co/Pt MLs, as compared to the continuous reference samples (∼1.5-2 times), is associated with the pinning of the magnetic moments on the nanopore edges. Application of the Stoner-Wohlfarth model for fitting the experimental M/MS(H) curves yielded clear evidence of the predominantly coherent rotation mechanism of magnetization reversal in the porous films.

Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics.

PubMed

Munje, Rujuta D; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

2015-09-30

An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics

NASA Astrophysics Data System (ADS)

Munje, Rujuta D.; Muthukumar, Sriram; Panneer Selvam, Anjan; Prasad, Shalini

2015-09-01

An ultra-sensitive and highly specific electrical double layer (EDL) modulated biosensor, using nanoporous flexible substrates for wearable diagnostics is demonstrated with the detection of the stress biomarker cortisol in synthetic and human sweat. Zinc oxide thin film was used as active region in contact with the liquid i.e. synthetic and human sweat containing the biomolecules. Cortisol detection in sweat was accomplished by measuring and quantifying impedance changes due to modulation of the double layer capacitance within the electrical double layer through the application of a low orthogonally directed alternating current (AC) electric field. The EDL formed at the liquid-semiconductor interface was amplified in the presence of the nanoporous flexible substrate allowing for measuring the changes in the alternating current impedance signal due to the antibody-hormone interactions at diagnostically relevant concentrations. High sensitivity of detection of 1 pg/mL or 2.75 pmol cortisol in synthetic sweat and 1 ng/mL in human sweat is demonstrated with these novel biosensors. Specificity in synthetic sweat was demonstrated using a cytokine IL-1β. Cortisol detection in human sweat was demonstrated over a concentration range from 10-200 ng/mL.

Citrus-Peel-Derived, Nanoporous Carbon Nanosheets Containing Redox-Active Heteroatoms for Sodium-Ion Storage.

PubMed

Kim, Na Rae; Yun, Young Soo; Song, Min Yeong; Hong, Sung Ju; Kang, Minjee; Leal, Cecilia; Park, Yung Woo; Jin, Hyoung-Joon

2016-02-10

Advanced design of nanostructured functional carbon materials for use in sustainable energy storage systems suffers from complex fabrication procedures and the use of special methods and/or expensive precursors, limiting their practical applications. In this study, nanoporous carbon nanosheets (NP-CNSs) containing numerous redox-active heteroatoms (C/O and C/N ratios of 5.5 and 34.3, respectively) were fabricated from citrus peels by simply heating the peels in the presence of potassium ions. The NP-CNSs had a 2D-like morphology with a high aspect ratio of >100, high specific surface area of 1167 m(2) g(-1), and a large amount of nanopores between 1 and 5 nm. The NP-CNSs also had an electrical conductivity of 2.6 × 10(1) s cm(-1), which is approximately 50 times higher than that of reduced graphene oxide. These unique material properties resulted in superior electrochemical performance with a high specific capacity of 140 mAh g(-1) in the cathodic potential range. In addition, symmetric full-cell devices based on the NP-CNSs showed excellent cyclic performance over 100,000 repetitive cycles.

Layered double hydroxide films on nanoporous anodic aluminum oxide/aluminum wire: a new fiber for rapid analysis of Origanum vulgare essential oils.

PubMed

Piryaei, Marzieh

2018-01-01

Zn/Al layered double hydroxide (LDH) films were fabricated in situ with anodic aluminium oxide aluminium as both the substrate and the sole aluminium source by means of urea hydrolysis. Headspace solid phase microextraction using LDH fibre in combination with capillary GC-MS was utilised as a monitoring technique for the collection and detection of the volatile compounds of Origanum vulgare. Experimental parameters, including the sample weight, microwave power, extraction time and humidity effect, were examined and optimised.

Surface enhanced Raman scattering of biospecies on anodized aluminum oxide films

NASA Astrophysics Data System (ADS)

Zhang, C.; Smirnov, A. I.; Hahn, D.; Grebel, H.

2007-06-01

Traditionally, aluminum and anodized aluminum oxide films (AAO) are not the platforms of choice for surface-enhanced raman scattering (SERS) experiments despite of the aluminum's large negative permittivity value. Here we examine the usefulness of aluminum and nanoporous alumina platforms for detecting soft biospecies ranging from bacterial spores to protein markers. We used these flat platforms to examine SERS of a model protein (cytochrome c from bovine heart tissue) and bacterial cells (spores of Bacillus subtilis ATCC13933 used as Anthrax simulant) and demonstrated clear Raman amplification.

A high-performance nanoporous Si/Al2O3 foam lithium-ion battery anode fabricated by selective chemical etching of the Al-Si alloy and subsequent thermal oxidation.

PubMed

Hwang, Gaeun; Park, Hyungmin; Bok, Taesoo; Choi, Sinho; Lee, Sungjun; Hwang, Inchan; Choi, Nam-Soon; Seo, Kwanyong; Park, Soojin

2015-03-14

Nanostructured micrometer-sized Al-Si particles are synthesized via a facile selective etching process of Al-Si alloy powder. Subsequent thin Al2O3 layers are introduced on the Si foam surface via a selective thermal wet oxidation process of etched Al-Si particles. The resulting Si/Al2O3 foam anodes exhibit outstanding cycling stability (a capacity retention of 78% after 300 cycles at the C/5 rate) and excellent rate capability.

Design of electrolyzer for carbon dioxide conversion to fuels and chemicals

NASA Astrophysics Data System (ADS)

Rosen, Jonathan S.

The stabilization of global atmospheric CO2 levels requires a transition towards a renewable energy based economy as well as methods for handling current CO2 output from fossil fuels. Challenges with renewable energy intermittency have thus far limited the use of these alternative energy sources to only a fraction of the current energy portfolio. To enable more widespread use of renewable energy systems, methods of large scale energy storage must be developed to store excess renewable energy when demand is low and allow for combined use of energy storage and renewable systems when demand is high. To date, no one technique has demonstrated energy storage methods on the gigawatt scale needed for integration with renewable sources; therefore the development of suitable energy storage technologies, such as CO2 electrolysis to fuels is needed. In this work, research efforts have focused on two major thrusts related to electrochemical methods of CO 2 conversion to fuels. The first thrust focuses on the synthesis and design of highly efficient anode and cathode catalysts with emphasis on understanding structure-property relationships. A second thrust focuses on the design of novel electrochemical devices for CO2 conversion and integration of synthesized materials into flow cell systems. On the anode side, the synthesis of highly active catalysts using abundant transition metals is crucial to reducing capital costs and enabling widespread use of electrochemical CO2 conversion devices. Highly active mesoporous Co3O4 and metal-substituted Co3O4 water oxidation catalysts were designed to investigate the role of the spinel structure on water oxidation activity. Further analysis of metal substituted samples reveal the importance of the octahedral sites in the spinel structure, which was later used to design an Mg-Co3O4 sample with improved water oxidation activity. The design of efficient cathode materials which can selectivity reduce CO2 to fuels and chemicals is critical to the widespread use of CO2 electrolysis. A nanoporous Ag material was synthesized through a dealloying technique able to operate with less than 0.5 V overpotential and high selectivity towards CO. CO is a valuable intermediate chemical which can used in Fischer-Tropsch or Gas-to-liquids technologies to produce liquids fuels. A detailed investigation of nanostructured Ag catalysts found stepped sites to be responsible for enhanced CO2 reduction activity due to improved stabilization of the COOH intermediate on the catalyst surface. In addition, an low-cost Zn dendrite electrocatalyst was developed using an electroplating technique. Low coordinated sites formed through electrodeposition demonstrated the suppression of hydrogen evolution while maintaining CO activity. The Zn dendrite electrocatalyst was further examined using a newly developed in situ X-ray absorption technique able to probe catalyst stability and crystalline structure under CO2 reduction operating conditions. A final hurdle in the realization of CO2 electrolysis technologies is the integration of catalysts into working flow cell devices. To address this issue and enable testing in a practical system, a highly efficient and robust CO2 electrolysis flow cell was designed including the scale up of the previous nanoporous Ag synthesis procedure. Using the modified porous Ag catalyst, currents in the Amp regime were demonstrated approaching rates needed for energy storage applications. Stability on the order of days was successfully demonstrated due to use of robust system components and conditions suitable for process scale up.

Effect of electrolyte temperature on the formation of self-organized anodic niobium oxide microcones in hot phosphate-glycerol electrolyte

NASA Astrophysics Data System (ADS)

Yang, S.; Aoki, Y.; Habazaki, H.

2011-07-01

Nanoporous niobium oxide films with microcone-type surface morphology were formed by anodizing at 10 V in glycerol electrolyte containing 0.6 mol dm -3 K 2HPO 4 and 0.2 mol dm -3 K 3PO 4 in a temperature range of 428-453 K. The microcones appeared after prolonged anodizing, but the required time was largely reduced by increasing electrolyte temperature. The anodic oxide was initially amorphous at all temperatures, but crystalline oxide nucleated during anodizing. The anodic oxide microcones, which were crystalline, appeared on surface as a consequence of preferential chemical dissolution of initially formed amorphous oxide. The chemical dissolution of an initially formed amorphous layer was accelerated by increasing the electrolyte temperature, with negligible influence of the temperature on the morphology of microcones up to 448 K.

Expanding the functionality and applications of nanopore sensors

NASA Astrophysics Data System (ADS)

Venta, Kimberly E.

Nanopore sensors have developed into powerful tools for single-molecule studies since their inception two decades ago. Nanopore sensors function as nanoscale Coulter counters, by monitoring ionic current modulations as particles pass through a nanopore. While nanopore sensors can be used to study any nanoscale particle, their most notable application is as a low cost, fast alternative to current DNA sequencing technologies. In recent years, signifcant progress has been made toward the goal of nanopore-based DNA sequencing, which requires an ambitious combination of a low-noise and high-bandwidth nanopore measurement system and spatial resolution. In this dissertation, nanopore sensors in thin membranes are developed to improve dimensional resolution, and these membranes are used in parallel with a high-bandwidth amplfier. Using this nanopore sensor system, the signals of three DNA homopolymers are differentiated for the first time in solid-state nanopores. The nanopore noise is also reduced through the addition of a layer of SU8, a spin-on polymer, to the supporting chip structure. By increasing the temporal and spatial resolution of nanopore sensors, studies of shorter molecules are now possible. Nanopore sensors are beginning to be used for the study and characterization of nanoparticles. Nanoparticles have found many uses from biomedical imaging to next-generation solar cells. However, further insights into the formation and characterization of nanoparticles would aid in developing improved synthesis methods leading to more effective and customizable nanoparticles. This dissertation presents two methods of employing nanopore sensors to benet nanoparticle characterization and fabrication. Nanopores were used to study the formation of individual nanoparticles and serve as nanoparticle growth templates that could be exploited to create custom nanoparticle arrays. Additionally, nanopore sensors were used to characterize the surface charge density of anisotropic nanopores, which previously could not be reliably measured. Current nanopore sensor resolution levels have facilitated innovative research on nanoscale systems, including studies of DNA and nanoparticle characterization. Further nanopore system improvements will enable vastly improved DNA sequencing capabilities and open the door to additional nanopore sensing applications.

Nanoporous anodic aluminum oxide with a long-range order and tunable cell sizes by phosphoric acid anodization on pre-patterned substrates

PubMed Central

Surawathanawises, Krissada; Cheng, Xuanhong

2014-01-01

Nanoporous anodic aluminum oxide (AAO) has been explored for various applications due to its regular cell arrangement and relatively easy fabrication processes. However, conventional two-step anodization based on self-organization only allows the fabrication of a few discrete cell sizes and formation of small domains of hexagonally packed pores. Recent efforts to pre-pattern aluminum followed with anodization significantly improve the regularity and available pore geometries in AAO, while systematic study of the anodization condition, especially the impact of acid composition on pore formation guided by nanoindentation is still lacking. In this work, we pre-patterned aluminium thin films using ordered monolayers of silica beads and formed porous AAO in a single-step anodization in phosphoric acid. Controllable cell sizes ranging from 280 nm to 760 nm were obtained, matching the diameters of the silica nanobead molds used. This range of cell size is significantly greater than what has been reported for AAO formed in phosphoric acid in the literature. In addition, the relationships between the acid concentration, cell size, pore size, anodization voltage and film growth rate were studied quantitatively. The results are consistent with the theory of oxide formation through an electrochemical reaction. Not only does this study provide useful operational conditions of nanoindentation induced anodization in phosphoric acid, it also generates significant information for fundamental understanding of AAO formation. PMID:24535886

Recent advances in experimental basic research on graphene and graphene-based nanostructures

NASA Astrophysics Data System (ADS)

Hieu Nguyen, Van

2016-06-01

The present work is a review of the results achieved in the experimental basic research on following rapidly developing modern topics of nanoscience and nanotechnology related to graphene and graphene-based nanosystems: reduction of graphene oxide and investigation of physical properties of reduced graphene oxide; fabrication and investigation of graphene quantum dots; study of light emission from excited graphene; fabrication and investigation of graphene nanopores; preparation and investigation of graphene oxide-liquid crystals as well as aqueous graphene oxide dispersions. Besides presenting the scientific content of the above-mentioned five topics in detail, we briefly mention promising and interesting works, demonstrating that the area of basic research on graphene and graphene-based nanostructures is still being enlarged.

Fabrication of metallized nanoporous films from the self-assembly of a block copolymer and homopolymer mixture.

PubMed

Li, Xue; Zhao, Shuying; Zhang, Shuxiang; Kim, Dong Ha; Knoll, Wolfgang

2007-06-19

Inorganic compound HAuCl4, which can form a complex with pyridine, is introduced into a poly(styrene-block-2-vinylpyridine) (PS-b-P2VP) block copolymer/poly(methyl methacrylate) (PMMA) homopolymer mixture. The orientation of the cylindrical microdomains formed by the P2VP block, PMMA, and HAuCl4 normal to the substrate surface can be generated via cooperative self-assembly of the mixture. Selective removal of the homopolymer can lead to porous nanostructures containing metal components in P2VP domains, which have a novel photoluminescence property.

Formation of self-ordered porous anodized alumina template for growing tungsten trioxide nanowires

NASA Astrophysics Data System (ADS)

Hussain, Tajamal; Shah, Asma Tufail; Shehzad, Khurram; Mujahid, Adnan; Farooqi, Zahoor Hussain; Raza, Muhammad Hamid; Ahmed, Mirza Nadeem; Nisa, Zaib Un

2015-12-01

Uniform porous anodized aluminum oxide (AAO) membrane has been synthesized by two-step anodization for fabricating tungsten trioxide (WO3) nanowires. Under assayed conditions, uniform porous structure of alumina (Al2O3) membrane with long range ordered hexagonal arrangements of nanopores was achieved. The self-assembled template possesses pores of internal diameter of 50 nm and interpore distance ( d int) of 80 nm with a thickness of about 80 µm, i.e., used for fabrication of nanostructures. WO3 nanowires have been fabricated by simple electroless deposition method inside Al2O3 nanopores. SEM images show tungsten trioxide nanowire with internal diameter of about 50 nm, similar to porous diameter of AAO template. XRD results showed that nanowires exist in cubic crystalline state with minor proportion of monoclinic phase.

Stabilizing Single Ni Adatoms on a Two-Dimensional Porous Titania Overlayer at the SrTiO3(110) Surface

PubMed Central

2014-01-01

Nickel vapor-deposited on the SrTiO3(110) surface was studied using scanning tunneling microscopy, photoemission spectroscopy (PES), and density functional theory calculations. This surface forms a (4 × 1) reconstruction, composed of a 2-D titania structure with periodic six- and ten-membered nanopores. Anchored at these nanopores, Ni single adatoms are stabilized at room temperature. PES measurements show that the Ni adatoms create an in-gap state located at 1.9 eV below the conduction band minimum and induce an upward band bending. Both experimental and theoretical results suggest that Ni adatoms are positively charged. Our study produces well-dispersed single-adatom arrays on a well-characterized oxide support, providing a model system to investigate single-adatom catalytic and magnetic properties. PMID:25177410

Peptide assembly-driven metal-organic framework (MOF) motors for micro electric generators

DOE PAGES

Ikezoe, Yasuhiro; Fang, Justin; Wasik, Tomasz L.; ...

2014-11-22

Peptide–metal–organic framework (Pep-MOF) motors, whose motions are driven by anisotropic surface tension gradients created via peptide self-assembly around frameworks, can rotate microscopic rotors and magnets fast enough to generate an electric power of 0.1 μW. Finally, a new rigid Pep-MOF motor can be recycled by refilling the peptide fuel into the nanopores of the MOF.

Vertical Carbon Nanotube Device in Nanoporous Templates

NASA Technical Reports Server (NTRS)

Sands, Timothy (Inventor); Fisher, Timothy Scott (Inventor); Bashir, Rashid (Inventor); Maschmann, Matthew Ralph (Inventor)

2014-01-01

A modified porous anodic alumina template (PAA) containing a thin CNT catalyst layer directly embedded into the pore walls. CNT synthesis using the template selectively catalyzes SWNTs and DWNTs from the embedded catalyst layer to the top PAA surface, creating a vertical CNT channel within the pores. Subsequent processing allows for easy contact metallization and adaptable functionalization of the CNTs and template for a myriad of applications.

Internal passivation of Al-based microchannel devices by electrochemical anodization

NASA Astrophysics Data System (ADS)

Hymel, Paul J.; Guan, D. S.; Mu, Yang; Meng, W. J.; Meng, Andrew C.

2015-02-01

Metal-based microchannel devices have wide-ranging applications. We report here a method to electrochemically anodize the internal surfaces of Al microchannels, with the purpose of forming a uniform and dense anodic aluminum oxide (AAO) layer on microchannel internal surfaces for chemical passivation and corrosion resistance. A pulsed electrolyte flow was utilized to emulate conventional anodization processes while replenishing depleted ionic species within Al microtubes and microchannels. After anodization, the AAO film was sealed in hot water to close the nanopores. Focused ion beam (FIB) sectioning, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were utilized to characterize the AAO morphology and composition. Potentiodynamic polarization corrosion testing of anodized Al microtube half-sections in a NaCl solution showed an order of magnitude decrease in anodic corrosion current when compared to an unanodized tube. The surface passivation process was repeated for Al-based microchannel heat exchangers. A corrosion testing method based on the anodization process showed higher resistance to ion transport through the anodized specimens than unanodized specimens, thus verifying the internal anodization and sealing process as a viable method for surface passivation of Al microchannel devices.

Template directed synthesis of plasmonic gold nanotubes with tunable IR absorbance.

PubMed

Bridges, Colin R; Schon, Tyler B; DiCarmine, Paul M; Seferos, Dwight S

2013-04-01

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates, as well as a wide range of other fields such as photo-thermal heating, permselective transport, catalysis, microfluidics, and electrochemical sensing. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening.

Amorphisation and recrystallisation study of lithium intercalation into TiO2 nano-architecture.

NASA Astrophysics Data System (ADS)

Matshaba, M. G.; Sayle, D. C.; Sayle, T. X. T.; Ngoepe, P. E.

2017-02-01

Titanium dioxide is playing an increasingly significant role in easing environmental and energy concerns. Its rich variety of polymorphic crystal structures has facilitated a wide range of applications such as photo-catalysis, photo-splitting of water, photoelectrochromic devices, insulators in metal oxide, semiconductors devices, dye sensitized solar cells (DSSCs) (energy conversions), rechargeable lithium batteries (electrochemical storage). The complex structural aspects in nano TiO2, are elucidated by microscopic visualization and quantification of the microstructure for electrode materials, since cell performance and various aging mechanisms depend strongly on the appearance and changes in the microstructure. Recent studies on MnO2 have demonstrated that amorphisation and recrystallisation simulation method can adequately generate various nanostructures, for Li-ion battery compounds. The method was also previously employed to produce nano-TiO2. In the current study, the approach is used to study lithiated nanoporous structure for TiO2 which have been extensively studied experimentally, as mentioned above. Molecular graphic images showing microstructural features, including voids and channels have accommodated lithium’s during lithiation and delithiation. Preliminary lithiation of TiO2 will be considered.

Preparation of electrochemically active silicon nanotubes in highly ordered arrays

PubMed Central

Grünzel, Tobias; Lee, Young Joo; Kuepper, Karsten

2013-01-01

Summary Silicon as the negative electrode material of lithium ion batteries has a very large capacity, the exploitation of which is impeded by the volume changes taking place upon electrochemical cycling. A Si electrode displaying a controlled porosity could circumvent the difficulty. In this perspective, we present a preparative method that yields ordered arrays of electrochemically competent silicon nanotubes. The method is based on the atomic layer deposition of silicon dioxide onto the pore walls of an anodic alumina template, followed by a thermal reduction with lithium vapor. This thermal reduction is quantitative, homogeneous over macroscopic samples, and it yields amorphous silicon and lithium oxide, at the exclusion of any lithium silicides. The reaction is characterized by spectroscopic ellipsometry for thin silica films, and by nuclear magnetic resonance and X-ray photoelectron spectroscopy for nanoporous samples. After removal of the lithium oxide byproduct, the silicon nanotubes can be contacted electrically. In a lithium ion electrolyte, they then display the electrochemical waves also observed for other bulk or nanostructured silicon systems. The method established here paves the way for systematic investigations of how the electrochemical properties (capacity, charge/discharge rates, cyclability) of nanoporous silicon negative lithium ion battery electrode materials depend on the geometry. PMID:24205460

Quantitative differentiation of multiple virus in blood using nanoporous silicon oxide immunosensor and artificial neural network.

PubMed

Chakraborty, W; Ray, R; Samanta, N; RoyChaudhuri, C

2017-12-15

In spite of the rapid developments in various nanosensor technologies, it still remains challenging to realize a reliable ultrasensitive electrical biosensing platform which will be able to detect multiple viruses in blood simultaneously with a fairly high reproducibility without using secondary labels. In this paper, we have reported quantitative differentiation of Hep-B and Hep-C viruses in blood using nanoporous silicon oxide immunosensor array and artificial neural network (ANN). The peak frequency output (f p ) from the steady state sensitivity characteristics and the first cut off frequency (f c ) from the transient characteristics have been considered as inputs to the multilayer ANN. Implementation of several classifier blocks in the ANN architecture and coupling them with both the sensor chips, functionalized with Hep-B and Hep-C antibodies have enabled the quantification of the viruses with an accuracy of around 95% in the range of 0.04fM-1pM and with an accuracy of around 90% beyond 1pM and within 25nM in blood serum. This is the most sensitive report on multiple virus quantification using label free method. Copyright © 2017 Elsevier B.V. All rights reserved.

Highly sensitive surface-enhanced Raman scattering substrate made from superaligned carbon nanotubes.

PubMed

Sun, Yinghui; Liu, Kai; Miao, Jiao; Wang, Zheyao; Tian, Baozhong; Zhang, Lina; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

2010-05-12

Surface-enhanced Raman scattering (SERS) has attracted wide attention because it can enhance normally weak Raman signal by several orders of magnitude and facilitate the sensitive detection of molecules. Conventional SERS substrates are constructed by placing metal nanoparticles on a planar surface. Here we show that, if the planar surface was substituted by a unique nanoporous surface, the enhancement effect can be dramatically improved. The nanoporous surface can be easily fabricated in batches and at low costs by cross stacking superaligned carbon nanotube films. The as-prepared transparent and freestanding SERS substrate is capable of detecting ambient trinitrotoluene vapor, showing much higher Raman enhancement than ordinary planar substrates because of the extremely large surface area and the unique zero-dimensional at one-dimensional nanostructure. These results not only provide a new approach to ultrasensitive SERS substrates, but also are helpful for improving the fundamental understanding of SERS phenomena.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Photosensitivity of nanoporous glasses and polymers doped with Eu(fod)3 molecules

NASA Astrophysics Data System (ADS)

Gerasimova, V. I.; Zavorotnyi, Yu S.; Rybaltovskii, A. O.; Lemenovskii, Dmitrii A.; Timofeeva, V. A.

2006-08-01

The decay kinetics of photoluminescence (PL) of Eu3+ ions (the 5D0→7Fj transition) excited by UV radiation (in particular, by a laser) is studied in a Vycor nanoporous glass and transparent polymers doped with Eu(fod)3 molecules (where fod stands for 6,6,7,7,8,8,8-heptofluor-2,2-dimethyl-3,5-octadionate) using a solution of supercritical CO2. It is found that the decrease in the PL intensity is caused by the photoinduced transformation of the ligand component of the complex (fod), while the decay rate depends significantly on the type of the matrix. Models of mechanisms of photodissociation of the original complex related to excitation to the singlet absorption band of the ligand (S0→S1 transition) in one case and to the ligand—metal charge transfer band in the other case are proposed.

Sensing small neurotransmitter-enzyme interaction with nanoporous gated ion-sensitive field effect transistors.

PubMed

Kisner, Alexandre; Stockmann, Regina; Jansen, Michael; Yegin, Ugur; Offenhäusser, Andreas; Kubota, Lauro Tatsuo; Mourzina, Yulia

2012-01-15

Ion-sensitive field effect transistors with gates having a high density of nanopores were fabricated and employed to sense the neurotransmitter dopamine with high selectivity and detectability at micromolar range. The nanoporous structure of the gates was produced by applying a relatively simple anodizing process, which yielded a porous alumina layer with pores exhibiting a mean diameter ranging from 20 to 35 nm. Gate-source voltages of the transistors demonstrated a pH-dependence that was linear over a wide range and could be understood as changes in surface charges during protonation and deprotonation. The large surface area provided by the pores allowed the physical immobilization of tyrosinase, which is an enzyme that oxidizes dopamine, on the gates of the transistors, and thus, changes the acid-base behavior on their surfaces. Concentration-dependent dopamine interacting with immobilized tyrosinase showed a linear dependence into a physiological range of interest for dopamine concentration in the changes of gate-source voltages. In comparison with previous approaches, a response time relatively fast for detecting dopamine was obtained. Additionally, selectivity assays for other neurotransmitters that are abundantly found in the brain were examined. These results demonstrate that the nanoporous structure of ion-sensitive field effect transistors can easily be used to immobilize specific enzyme that can readily and selectively detect small neurotransmitter molecule based on its acid-base interaction with the receptor. Therefore, it could serve as a technology platform for molecular studies of neurotransmitter-enzyme binding and drugs screening. Copyright © 2011 Elsevier B.V. All rights reserved.

Growth control of carbon nanotubes using by anodic aluminum oxide nano templates.

PubMed

Park, Yong Seob; Choi, Won Seek; Yi, Junsin; Lee, Jaehyeong

2014-05-01

Anodic Aluminum Oxide (AAO) template prepared in acid electrolyte possess regular and highly anisotropic porous structure with pore diameter range from five to several hundred nanometers, and with a density of pores ranging from 10(9) to 10(11) cm(-2). AAO can be used as microfilters and templates for the growth of CNTs and metal or semiconductor nanowires. Varying anodizing conditions such as temperature, electrolyte, applied voltage, anodizing and widening time, one can control the diameter, the length, and the density of pores. In this work, we deposited Al thin film by radio frequency magnetron sputtering method to fabricate AAO nano template and synthesized multi-well carbon nanotubes on a glass substrate by microwave plasma-enhanced chemical vapor deposition (MPECVD). AAO nano-porous templates with various pore sizes and depths were introduced to control the dimension and density of CNT arrays. The AAO nano template was synthesize on glass by two-step anodization technique. The average diameter and interpore distance of AAO nano template are about 65 nm and 82 nm. The pore density and AAO nano template thickness are about 2.1 x 10(10) pores/cm2 and 1 microm, respectively. Aligned CNTs on the AAO nano template were synthesized by MPECVD at 650 degrees C with the Ni catalyst layer. The length and diameter of CNTs were grown 2 microm and 50 nm, respectively.

Influence of Nanopore Shapes on Thermal Conductivity of Two-Dimensional Nanoporous Material.

PubMed

Huang, Cong-Liang; Huang, Zun; Lin, Zi-Zhen; Feng, Yan-Hui; Zhang, Xin-Xin; Wang, Ge

2016-12-01

The influence of nanopore shapes on the electronic thermal conductivity (ETC) was studied in this paper. It turns out that with same porosity, the ETC will be quite different for different nanopore shapes, caused by the different channel width for different nanopore shapes. With same channel width, the influence of different nanopore shapes can be approximately omitted if the nanopore is small enough (smaller than 0.5 times EMFP in this paper). The ETC anisotropy was discovered for triangle nanopores at a large porosity with a large nanopore size, while there is a similar ETC for small pore size. It confirmed that the structure difference for small pore size may not be seen by electrons in their moving.

Micro solid oxide fuel cell fabricated on porous stainless steel: a new strategy for enhanced thermal cycling ability

PubMed Central

Kim, Kun Joong; Park, Byung Hyun; Kim, Sun Jae; Lee, Younki; Bae, Hongyeul; Choi, Gyeong Man

2016-01-01

Miniaturized solid oxide fuel cells (micro-SOFCs) are being extensively studied as a promising alternative to Li batteries for next generation portable power. A new micro-SOFC is designed and fabricated which shows enhanced thermal robustness by employing oxide-based thin-film electrode and porous stainless steel (STS) substrate. To deposit gas-tight thin-film electrolyte on STS, nano-porous composite oxide is proposed and applied as a new contact layer on STS. The micro-SOFC fabricated on composite oxide- STS dual layer substrate shows the peak power density of 560 mW cm−2 at 550 °C and maintains this power density during rapid thermal cycles. This cell may be suitable for portable electronic device that requires high power-density and fast thermal cycling. PMID:26928921

Micro solid oxide fuel cell fabricated on porous stainless steel: a new strategy for enhanced thermal cycling ability.

PubMed

Kim, Kun Joong; Park, Byung Hyun; Kim, Sun Jae; Lee, Younki; Bae, Hongyeul; Choi, Gyeong Man

2016-03-01

Miniaturized solid oxide fuel cells (micro-SOFCs) are being extensively studied as a promising alternative to Li batteries for next generation portable power. A new micro-SOFC is designed and fabricated which shows enhanced thermal robustness by employing oxide-based thin-film electrode and porous stainless steel (STS) substrate. To deposit gas-tight thin-film electrolyte on STS, nano-porous composite oxide is proposed and applied as a new contact layer on STS. The micro-SOFC fabricated on composite oxide- STS dual layer substrate shows the peak power density of 560 mW cm(-2) at 550 °C and maintains this power density during rapid thermal cycles. This cell may be suitable for portable electronic device that requires high power-density and fast thermal cycling.

Introduction of Molecular Building Blocks to Improve the Stability of Metal-Organic Frameworks for Efficient Mercury Removal.

PubMed

Jiang, Shu-Yi; He, Wen-Wen; Li, Shun-Li; Su, Zhong-Min; Lan, Ya-Qian

2018-05-21

With expanding human needs, many heavy metals were mined, smelted, processed, and manufactured for commercialization, which caused serious environmental pollutions. Currently, many adsorption materials are applied in the field of adsorption of heavy metals. Among them, the principle of many mercury adsorbents is based on the interaction between mercury and sulfur. Here, a S-containing metal-organic framework NENU-400 was synthesized for effective mercury extraction. Unfortunately, the skeleton of NENU-400 collapsed easily when exposed to the mercury liquid solution. To improve the stability, a synthetic strategy installing molecular building blocks (MBBs) into the channels was used. Modified by the MBBs, a more stable nanoporous framework was synthesized, which not only exhibits a high capacity of saturation mercury uptake but also shows high selectivity and efficient recyclability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talin, Albert Alec; Jones, Reese E.; Spataru, Dan Catalin

Metal organic frameworks (MOFs) are extended, nanoporous crystalline compounds consisting of metal ions interconnected by organic ligands. Their synthetic versatility suggest a disruptive class of opto - electronic materials with a high degree of electrical tunability and without the property - degrading disorder of organic conductors. In this project we determined the factors controlling charge and energy transport in MOFs and evaluated their potential for thermoelectric energy conversion. Two strategies for a chieving electronic conductivity in MOFs were explored: 1) using redox active 'guest' molecules introduced into the pores to dope the framework via charge - transfer coupling (Guest@MOF), 2)more » metal organic graphene analogs (MOGs) with dispersive band structur es arising from strong electronic overlap between the MOG metal ions and its coordinating linker groups. Inkjet deposition methods were developed to facilitate integration of the guest@MOF and MOG materials into practical devices.« less

Exploiting nanospace for asymmetric catalysis: confinement of immobilized, single-site chiral catalysts enhances enantioselectivity.

PubMed

Thomas, John Meurig; Raja, Robert

2008-06-01

In the mid-1990s, it became possible to prepare high-area silicas having pore diameters controllably adjustable in the range ca. 20-200 Å. Moreover, the inner walls of these nanoporous solids could be functionalized to yield single-site, chiral, catalytically active organometallic centers, the precise structures of which could be determined using in situ X-ray absorption and FTIR and multinuclear magic angle spinning (MAS) NMR spectroscopy. This approach opened up the prospect of performing heterogeneous enantioselective conversions in a novel manner, under the spatial restrictions imposed by the nanocavities within which the reactions occur. In particular, it suggested an alternative method for preparing pharmaceutically and agrochemically useful asymmetric products by capitalizing on the notion, initially tentatively perceived, that spatial confinement of prochiral reactants (and transition states formed at the chiral active center) would provide an altogether new method of boosting the enantioselectivity of the anchored chiral catalyst. Initially, we anchored chiral single-site heterogeneous catalysts to nanopores covalently via a ligand attached to Pd(II) or Rh(I) centers. Later, we employed a more convenient and cheaper electrostatic method, relying in part on strong hydrogen bonding. This Account provides many examples of these processes, encompassing hydrogenations, oxidations, and aminations. Of particular note is the facile synthesis from methyl benzoylformate of methyl mandelate, which is a precursor in the synthesis of pemoline, a stimulant of the central nervous system; our procedure offers several viable methods for reducing ketocarboxylic acids. In addition to relying on earlier (synchrotron-based) in situ techniques for characterizing catalysts, we have constructed experimental procedures involving robotically controlled catalytic reactors that allow the kinetics of conversion and enantioselectivity to be monitored continually, and we have access to sophisticated, high-sensitivity chiral chromatographic facilities and automated high-throughput combinatorial test rigs so as to optimize the reaction conditions (e.g., H(2) pressure, temperature, time on-stream, pH, and choice of ligand and central metal ion) for high enantioselectivity. This Account reports our discoveries of selective hydrogenations and aminations of synthetic, pharmaceutical, and biological significance, and the findings of other researchers who have achieved similar success in oxidations, dehydrations, cyclopropanations, and hydroformylations. Although the practical advantages and broad general principles governing the enhancement of enantioselectivity through spatial confinement are clear, we require a deeper theoretical understanding of the details pertaining to the phenomenology involved, particularly through molecular dynamics simulations. Ample scope exists for the general exploitation of nanospace in asymmetric hydrogenations with transition metal complexes and for its deployment for the formation of C-N, C-C, C-O, C-S, and other bonds.

Mesoporous metal oxides and processes for preparation thereof

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suib, Steven L.; Poyraz, Altug Suleyman

A process for preparing a mesoporous metal oxide, i.e., transition metal oxide. Lanthanide metal oxide, a post-transition metal oxide and metalloid oxide. The process comprises providing an acidic mixture comprising a metal precursor, an interface modifier, a hydrotropic ion precursor, and a surfactant; and heating the acidic mixture at a temperature and for a period of time sufficient to form the mesoporous metal oxide. A mesoporous metal oxide prepared by the above process. A method of controlling nano-sized wall crystallinity and mesoporosity in mesoporous metal oxides. The method comprises providing an acidic mixture comprising a metal precursor, an interface modifier,more » a hydrotropic ion precursor, and a surfactant; and heating the acidic mixture at a temperature and for a period of time sufficient to control nano-sized wall crystallinity and mesoporosity in the mesoporous metal oxides. Mesoporous metal oxides and a method of tuning structural properties of mesoporous metal oxides.« less

Role of solvent in metal-on-metal surface diffusion: A case for rational solvent selection for materials synthesis

NASA Astrophysics Data System (ADS)

Imandi, Venkataramana; Jagannath, Mantha Sai Pavan; Chatterjee, Abhijit

2018-09-01

The effect of solvent on diffusion at metal surfaces is poorly understood despite its importance to morphological evolution during materials processing, corrosion and catalysis. In this article, we probe the metal-solvent interfacial structure, effective nature of interactions and dynamics when a solvent is in contact with a metal using a novel accelerated molecular dynamics simulation technique called temperature programmed molecular dynamics (TPMD). TPMD simulations reveal that surface diffusion of metal-on-metal can be made to vary over orders-of-magnitude by tuning the metal-solvent interaction. Ultimately, the solvent can have an indirect effect on diffusion. As the solvent tugs at the metal surface the separation between the adsorbed metal atom (adatom) and the surface layer can be modulated via metal-solvent interactions. The resulting adatom-surface separation can cause stronger/weaker binding of the adatom to the metal surface, which in turn results in the observed slower/enhanced diffusion in the presence of solvent. We believe this effect is ubiquitous in pure metal and metal alloys and in principle one could rationally select solvent to control the material structural evolution. Implications on materials synthesis are discussed in the context of formation of nanoporous materials.

Engineering of Nanoscale Antifouling and Hydrophobic Surfaces on Naval Structural Steel HY-80 by Anodizing

DTIC Science & Technology

2015-06-01

examination of the morphologies of the nanoporous structures and the evaluation of the anodization parameters such as anodization potential, time... sponges , anemones, tunicates, and hydroids, whilst hard fouling comprises invertebrates such as barnacles, mussels, and tubeworms. The specific...of metals by making them more stable and highly resistant, but also to modify the surface by giving it a desired morphology . Ferrous alloys such as

Nanoporous metals for biodegradable implants: Initial bone mesenchymal stem cell adhesion and degradation behavior.

PubMed

Heiden, Michael; Huang, Sabrina; Nauman, Eric; Johnson, David; Stanciu, Lia

2016-07-01

Nanostructured Fe-Mn and Fe-Mn-Zn metal scaffolds were generated through a well-controlled selective leaching process in order to fulfill the growing demand for adjustable degradation rates and improved cellular response of resorbable materials. Mouse bone marrow mesenchymal stem cells (D1 ORL UVA) were seeded onto eleven, carefully chosen nanoporous surfaces for 24 h in vitro. Using a combination of fluorescence microscopy, scanning electron microscopy (SEM), and an MTS assay, it was discovered that scaffolds with nanoscale roughened surfaces had increased cell attachment by up to 123% compared to polished smooth Fe-Mn surfaces. Significant cell spreading and construction of cell multilayers were also apparent after 24 h, suggesting better adhesion. Additionally, static electrochemical polarization experiments revealed an improvement of up to 26% in the actual rate of biodegradation for Fe-Mn surface-modified materials. However, any residual concentration of zinc after leaching was shown to slightly increase corrosion resistance. The results demonstrate that selectively leached, nanostructured Fe-Mn surfaces have the potential of being tailored to a diverse set of transient implant scenarios, while also effectively boosting overall biocompatibility, initial cell attachment, and degradation rate. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1747-1758, 2016. © 2016 Wiley Periodicals, Inc.

Electrochemical immunoassay for carcinoembryonic antigen based on signal amplification strategy of nanotubular mesoporous PdCu alloy.

PubMed

Cai, Yanyan; Li, He; Li, Yuyang; Zhao, Yanfang; Ma, Hongmin; Zhu, Baocun; Xu, Caixia; Wei, Qin; Wu, Dan; Du, Bin

2012-01-01

Interests in using nanoporous metals for biosensing applications have been increasing. Herein, nanotubular mesoporous PdCu (NM-PdCu) alloy is used to fabricate a novel label-free electrochemical immunosensor for cancer biomarker carcinoembryonic antigen (CEA). It operates through physisorption of anti-CEA on NM-PdCu and the mixture of sulfonated graphene sheets (HSO(3)-GS) and thionine (TH) functionalized glassy carbon electrode interface as the detection platform. In this study, chitosan (CS)-PdCu is bound very strongly to carcinoembryonic antibody (anti-CEA), because of the good electron conductivity, high surface area, and good biocompatibility. CS-PdCu is immobilized on electrodes by electrostatic interactions between the negatively charged sulfo group of HSO(3)-GS and the abundant positively charged amino groups of chitosan. TH acts as the redox probe. Under the optimized conditions, the electrochemical immunosensor exhibits a wide working range from 0.01 to 12 ng/mL with a low detection limit of 4.86 pg/mL. The accuracy, reproducibility, and stability of the immunosensor are acceptable. The assay is evaluated for real serum samples, receiving satisfactory results. The nanoporous metal materials-based immunoassay provides a promising approach in clinical application and thus represents a versatile detection method. Copyright © 2012 Elsevier B.V. All rights reserved.

Thermally stable solids based on endohedrally doped ZnS clusters.

PubMed

Matxain, Jon M; Piris, Mario; Lopez, Xabier; Ugalde, Jesus M

2009-01-01

The existence of inorganic, hollow, fullerene-like ZnS clusters has been theoretically predicted and then recently confirmed experimentally. These clusters were observed to trap alkali metals and halogens because the ionization energies (IE) of alkali metals are very similar to the electron affinities (EA) of halogens. This opens the possibility of forming molecular solids composed of these fullerene building blocks because the energy released due to the difference between the IE and EA would be very small. Herein we have focused on assembling bare Zn(12)S(12) and endohedral X@Zn(12)S(12)-Y@Zn(12)S(12) dimers (X = Na, K; Y = Cl, Br) by considering the square-faces-square orientation of every two adjacent clusters, which leads to a fcc cubic crystal structure in the solid. The structures were fully optimized in all cases, and their thermal stability was confirmed by ab initio thermal molecular dynamics calculations. The optimum lattice parameter of the solids was found to be around 13.8 A, which corresponds to distances of about 2.5 A between monomers, which is typical of covalent Zn-S bonds. The resulting solids are nanoporous materials similar to B(12)N(12). Due to their nanoporous structure, these zeolite-shaped solids could be used in heterogeneous catalysis and as storage materials and molecular sieves.

Device properties of nanopore PN junction Si for photovoltaic application

NASA Astrophysics Data System (ADS)

Jin, Hyunjong; Chang, Te Wei; Liu, Logan Gang

2011-09-01

Improvement of energy conversion efficiency of solar cells has led to innovative approaches, in particular the introduction of nanopillar photovoltaics [1]. Previous work on nanopillar Si photovoltaic has shown broadband reduction in optical reflection and enhancement of absorption [2]. Radial or axial PN junctions [3, 4] have been of high interest for improved photovoltaic devices. However, with the PN junction incorporated as part of the pillar, the discreteness of individual pillar requires additional conductive layer that would electrically short the top of each pillar for efficient carrier extraction. The fragile structure of the surface pillars would also require a protection layer for possible mechanical scratch to prevent pillars from breaking. Any additional layer that is applied, either for electrical contact or for mechanical properties may introduce additional recombination sites and also reduce the actual light absorption by the photovoltaic material. In this paper, nanopore Si photovoltaics that not only provides the advantages but also addresses the challenges of nanopillers is demonstrated. PN junction substrate of 250 nm thick N-type polycrystalline Si on P-type Si wafer is prepared. The nanopore structure is formed by using anodized aluminum oxide (AAO) as an etching mask against deep reactive ionic etching (DRIE). The device consists of semi-ordered pores of ~70 nm diameter.

Methods of producing adsorption media including a metal oxide

DOEpatents

Mann, Nicholas R; Tranter, Troy J

2014-03-04

Methods of producing a metal oxide are disclosed. The method comprises dissolving a metal salt in a reaction solvent to form a metal salt/reaction solvent solution. The metal salt is converted to a metal oxide and a caustic solution is added to the metal oxide/reaction solvent solution to adjust the pH of the metal oxide/reaction solvent solution to less than approximately 7.0. The metal oxide is precipitated and recovered. A method of producing adsorption media including the metal oxide is also disclosed, as is a precursor of an active component including particles of a metal oxide.

Nanostructured diamond layers enhance the infrared spectroscopy of biomolecules.

PubMed

Kozak, Halyna; Babchenko, Oleg; Artemenko, Anna; Ukraintsev, Egor; Remes, Zdenek; Rezek, Bohuslav; Kromka, Alexander

2014-03-04

We report on the fabrication and practical use of high-quality optical elements based on Au mirrors coated with diamond layers with flat, nanocolumnar, and nanoporous morphologies. Diamond layers (100 nm thickness) are grown at low temperatures (about 300 °C) from a methane, carbon dioxide, and hydrogen gas mixture by a pulsed microwave plasma system with linear antennas. Using grazing angle reflectance (GAR) Fourier transform infrared spectroscopy with p-polarized light, we compare the IR spectra of fetal bovine serum proteins adsorbed on diamond layers with oxidized (hydrophilic) surfaces. We show that the nanoporous diamond layers provide IR spectra with a signal gain of about 600% and a significantly improved sensitivity limit. This is attributed to its enhanced internal surface area. The improved sensitivity enabled us to distinguish weak infrared absorption peaks of <10-nm-thick protein layers and thereby to analyze the intimate diamond-molecule interface.

Self-Ordered Nanoporous Alumina Templates Formed by Anodization of Aluminum in Oxalic Acid

NASA Astrophysics Data System (ADS)

Vida-Simiti, Ioan; Nemes, Dorel; Jumate, Nicolaie; Thalmaier, Gyorgy; Sechel, Niculina

2012-10-01

Anodic aluminum oxide (AAO) membranes with highly ordered nanopores serve as ideal templates for the formation of various nanostructured materials. The procedure of the template preparation is based on a two-step self-organized anodization of aluminum. In the current study, AAO templates were fabricated in 0.3 M oxalic acid under the anodizing potential range of 30-60 V at an electrolyte temperature of ~5°C. The AAO templates were analyzed using scanning electron microscopy, x-ray diffraction, Fourier-transform infrared spectroscopy, and differential thermal analysis. The as obtained layers are amorphous; the mean pore size is between 40 nm and 75 nm and increases with the increase of the anodization potential. Well-defined pores across the whole aluminum template, a pore density of ~1010 pores/cm2, and a tendency to form a porous structure with hexagonal symmetry were observed.

Structural transitions and guest/host complexing of liquid crystal helical nanofilaments induced by nanoconfinement.

PubMed

Kim, Hanim; Ryu, Seong Ho; Tuchband, Michael; Shin, Tae Joo; Korblova, Eva; Walba, David M; Clark, Noel A; Yoon, Dong Ki

2017-02-01

A lamellar liquid crystal (LC) phase of certain bent-core mesogenic molecules can be grown in a manner that generates a single chiral helical nanofilament in each of the cylindrical nanopores of an anodic aluminum oxide (AAO) membrane. By introducing guest molecules into the resulting composite chiral nanochannels, we explore the structures and functionality of the ordered guest/host LC complex, verifying the smectic-like positional order of the fluidic nematic LC phase, which is obtained by the combination of the LC organization and the nanoporous AAO superstructure. The guest nematic LC 4'- n -pentyl-4-cyanobiphenyl is found to form a distinctive fluid layered ordered LC complex at the nanofilament/guest interface with the host 1,3-phenylene bis[4-(4-nonyloxyphenyliminomethyl)benzoate], where this interface contacts the AAO cylinder wall. Filament growth form is strongly influenced by mixture parameters and pore dimensions.

Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks.

PubMed

Li, Z P; Xu, Z M; Qu, X P; Wang, S B; Peng, J; Mei, L H

2017-03-03

How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks

NASA Astrophysics Data System (ADS)

Li, Z. P.; Xu, Z. M.; Qu, X. P.; Wang, S. B.; Peng, J.; Mei, L. H.

2017-03-01

How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

Structural transitions and guest/host complexing of liquid crystal helical nanofilaments induced by nanoconfinement

PubMed Central

Kim, Hanim; Ryu, Seong Ho; Tuchband, Michael; Shin, Tae Joo; Korblova, Eva; Walba, David M.; Clark, Noel A.; Yoon, Dong Ki

2017-01-01

A lamellar liquid crystal (LC) phase of certain bent-core mesogenic molecules can be grown in a manner that generates a single chiral helical nanofilament in each of the cylindrical nanopores of an anodic aluminum oxide (AAO) membrane. By introducing guest molecules into the resulting composite chiral nanochannels, we explore the structures and functionality of the ordered guest/host LC complex, verifying the smectic-like positional order of the fluidic nematic LC phase, which is obtained by the combination of the LC organization and the nanoporous AAO superstructure. The guest nematic LC 4′-n-pentyl-4-cyanobiphenyl is found to form a distinctive fluid layered ordered LC complex at the nanofilament/guest interface with the host 1,3-phenylene bis[4-(4-nonyloxyphenyliminomethyl)benzoate], where this interface contacts the AAO cylinder wall. Filament growth form is strongly influenced by mixture parameters and pore dimensions. PMID:28246642

Steady-state generation of hydrogen peroxide: kinetics and stability of alcohol oxidase immobilized on nanoporous alumina.

PubMed

Kjellander, Marcus; Götz, Kathrin; Liljeruhm, Josefine; Boman, Mats; Johansson, Gunnar

2013-04-01

Alcohol oxidase from Pichia pastoris was immobilized on nanoporous aluminium oxide membranes by silanization and activation by carbonyldiimidazole to create a flow-through enzyme reactor. Kinetic analysis of the hydrogen peroxide generation was carried out for a number of alcohols using a subsequent reaction with horseradish peroxidase and ABTS. The activity data for the immobilized enzyme showed a general similarity with literature data in solution, and the reactor could generate 80 mmol H2O2/h per litre reactor volume. Horseradish peroxidase was immobilized by the same technique to construct bienzymatic modular reactors. These were used in both single pass mode and circulating mode. Pulsed injections of methanol resulted in a linear relation between response and concentration, allowing quantitative concentration measurement. The immobilized alcohol oxidase retained 58 % of initial activity after 3 weeks of storage and repeated use.

Effect of film thickness on localized surface plasmon enhanced chemical sensor

NASA Astrophysics Data System (ADS)

Kassu, Aschalew; Farley, Carlton; Sharma, Anup; Kim, Wonkyu; Guo, Junpeng

2014-05-01

A highly-sensitive, reliable, simple and inexpensive chemical detection and identification platform is demonstrated. The sensing technique is based on localized surface plasmon enhanced Raman scattering measurements from gold-coated highly-ordered symmetric nanoporous ceramic membranes fabricated from anodic aluminum oxide. To investigate the effects of the thickness of the sputter-coated gold films on the sensitivity of sensor, and optimize the performance of the substrates, the geometry of the nanopores and the film thicknesses are varied in the range of 30 nm to 120 nm. To characterize the sensing technique and the detection limits, surface enhanced Raman scatterings of low concentrations of a standard chemical adsorbed on the gold coated substrates are collected and analyzed. The morphology of the proposed substrates is characterized by atomic force microscopy and the optical properties including transmittance, reflectance and absorbance of each substrate are also investigated.

Mapping Base Modifications in DNA by Transverse-Current Sequencing

NASA Astrophysics Data System (ADS)

Alvarez, Jose R.; Skachkov, Dmitry; Massey, Steven E.; Kalitsov, Alan; Velev, Julian P.

2018-02-01

Sequencing DNA modifications and lesions, such as methylation of cytosine and oxidation of guanine, is even more important and challenging than sequencing the genome itself. The traditional methods for detecting DNA modifications are either insensitive to these modifications or require additional processing steps to identify a particular type of modification. Transverse-current sequencing in nanopores can potentially identify the canonical bases and base modifications in the same run. In this work, we demonstrate that the most common DNA epigenetic modifications and lesions can be detected with any predefined accuracy based on their tunneling current signature. Our results are based on simulations of the nanopore tunneling current through DNA molecules, calculated using nonequilibrium electron-transport methodology within an effective multiorbital model derived from first-principles calculations, followed by a base-calling algorithm accounting for neighbor current-current correlations. This methodology can be integrated with existing experimental techniques to improve base-calling fidelity.

Microfluidic multiplexing of solid-state nanopores

NASA Astrophysics Data System (ADS)

Jain, Tarun; Rasera, Benjamin C.; Guerrero, Ricardo Jose S.; Lim, Jong-Min; Karnik, Rohit

2017-12-01

Although solid-state nanopores enable electronic analysis of many clinically and biologically relevant molecular structures, there are few existing device architectures that enable high-throughput measurement of solid-state nanopores. Herein, we report a method for microfluidic integration of multiple solid-state nanopores at a high density of one nanopore per (35 µm2). By configuring microfluidic devices with microfluidic valves, the nanopores can be rinsed from a single fluid input while retaining compatibility for multichannel electrical measurements. The microfluidic valves serve the dual purpose of fluidic switching and electric switching, enabling serial multiplexing of the eight nanopores with a single pair of electrodes. Furthermore, the device architecture exhibits low noise and is compatible with electroporation-based in situ nanopore fabrication, providing a scalable platform for automated electronic measurement of a large number of integrated solid-state nanopores.

Threading DNA through nanopores for biosensing applications

NASA Astrophysics Data System (ADS)

Fyta, Maria

2015-07-01

This review outlines the recent achievements in the field of nanopore research. Nanopores are typically used in single-molecule experiments and are believed to have a high potential to realize an ultra-fast and very cheap genome sequencer. Here, the various types of nanopore materials, ranging from biological to 2D nanopores are discussed together with their advantages and disadvantages. These nanopores can utilize different protocols to read out the DNA nucleobases. Although, the first nanopore devices have reached the market, many still have issues which do not allow a full realization of a nanopore sequencer able to sequence the human genome in about a day. Ways to control the DNA, its dynamics and speed as the biomolecule translocates the nanopore in order to increase the signal-to-noise ratio in the reading-out process are examined in this review. Finally, the advantages, as well as the drawbacks in distinguishing the DNA nucleotides, i.e., the genetic information, are presented in view of their importance in the field of nanopore sequencing.

A strontium-incorporated nanoporous titanium implant surface for rapid osseointegration

NASA Astrophysics Data System (ADS)

Zhang, Wenjie; Cao, Huiliang; Zhang, Xiaochen; Li, Guanglong; Chang, Qing; Zhao, Jun; Qiao, Yuqin; Ding, Xun; Yang, Guangzheng; Liu, Xuanyong; Jiang, Xinquan

2016-02-01

Rapid osseointegration of dental implants will shorten the period of treatment and enhance the comfort of patients. Due to the vital role of angiogenesis played during bone development and regeneration, it might be feasible to promote rapid osseointegration by modifying the implant surface to gain a combined angiogenesis/osteogenesis inducing capacity. In this study, a novel coating (MAO-Sr) with strontium-incorporated nanoporous structures on titanium implants was generated via a new micro-arc oxidation, in an attempt to induce angiogenesis and osteogenesis to enhance rapid osseointegration. In vitro, the nanoporous structure significantly enhanced the initial adhesion of canine BMSCs. More importantly, sustained release of strontium ions also displayed a stronger effect on the BMSCs in facilitating their osteogenic differentiation and promoting the angiogenic growth factor secretion to recruit endothelial cells and promote blood vessel formation. Advanced mechanism analyses indicated that MAPK/Erk and PI3K/Akt signaling pathways were involved in these effects of the MAO-Sr coating. Finally, in the canine dental implantation study, the MAO-Sr coating induced faster bone formation within the initial six weeks and the osseointegration effect was comparable to that of the commercially available ITI implants. These results suggest that the MAO-Sr coating has the potential for future use in dental implants.Rapid osseointegration of dental implants will shorten the period of treatment and enhance the comfort of patients. Due to the vital role of angiogenesis played during bone development and regeneration, it might be feasible to promote rapid osseointegration by modifying the implant surface to gain a combined angiogenesis/osteogenesis inducing capacity. In this study, a novel coating (MAO-Sr) with strontium-incorporated nanoporous structures on titanium implants was generated via a new micro-arc oxidation, in an attempt to induce angiogenesis and osteogenesis to enhance rapid osseointegration. In vitro, the nanoporous structure significantly enhanced the initial adhesion of canine BMSCs. More importantly, sustained release of strontium ions also displayed a stronger effect on the BMSCs in facilitating their osteogenic differentiation and promoting the angiogenic growth factor secretion to recruit endothelial cells and promote blood vessel formation. Advanced mechanism analyses indicated that MAPK/Erk and PI3K/Akt signaling pathways were involved in these effects of the MAO-Sr coating. Finally, in the canine dental implantation study, the MAO-Sr coating induced faster bone formation within the initial six weeks and the osseointegration effect was comparable to that of the commercially available ITI implants. These results suggest that the MAO-Sr coating has the potential for future use in dental implants. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08580b

Single-molecule nanopore enzymology

PubMed Central

Wloka, Carsten; Maglia, Giovanni

2017-01-01

Biological nanopores are a class of membrane proteins that open nanoscale water-conduits in biological membranes. When they are reconstituted in artificial membranes and a bias voltage is applied across the membrane, the ionic current passing through individual nanopores can be used to monitor chemical reactions, to recognize individual molecules and, of most interest, to sequence DNA. More recently, proteins and enzymes have started being analysed with nanopores. Monitoring enzymatic reactions with nanopores, i.e. nanopore enzymology, has the unique advantage that it allows long-timescale observations of native proteins at the single-molecule level. Here we describe the approaches and challenges in nanopore enzymology. PMID:28630164

Ion transport in a pH-regulated nanopore.

PubMed

Yeh, Li-Hsien; Zhang, Mingkan; Qian, Shizhi

2013-08-06

Fundamental understanding of ion transport phenomena in nanopores is crucial for designing the next-generation nanofluidic devices. Due to surface reactions of dissociable functional groups on the nanopore wall, the surface charge density highly depends upon the proton concentration on the nanopore wall, which in turn affects the electrokinetic transport of ions, fluid, and particles within the nanopore. Electrokinetic ion transport in a pH-regulated nanopore, taking into account both multiple ionic species and charge regulation on the nanopore wall, is theoretically investigated for the first time. The model is verified by the experimental data of nanopore conductance available in the literature. The results demonstrate that the spatial distribution of the surface charge density at the nanopore wall and the resulting ion transport phenomena, such as ion concentration polarization (ICP), ion selectivity, and conductance, are significantly affected by the background solution properties, such as the pH and salt concentration.

Methods for synthesizing metal oxide nanowires

DOEpatents

Sunkara, Mahendra Kumar; Kumar, Vivekanand; Kim, Jeong H.; Clark, Ezra Lee

2016-08-09

A method of synthesizing a metal oxide nanowire includes the steps of: combining an amount of a transition metal or a transition metal oxide with an amount of an alkali metal compound to produce a mixture; activating a plasma discharge reactor to create a plasma discharge; exposing the mixture to the plasma discharge for a first predetermined time period such that transition metal oxide nanowires are formed; contacting the transition metal oxide nanowires with an acid solution such that an alkali metal ion is exchanged for a hydrogen ion on each of the transition metal oxide nanowires; and exposing the transition metal oxide nanowires to the plasma discharge for a second predetermined time period to thermally anneal the transition metal oxide nanowires. Transition metal oxide nanowires produced using the synthesis methods described herein are also provided.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barroo, Cedric; Janvelyan, Nare; Zugic, Branko

To improve the understanding of catalytic processes, the surface structure and composition of the active materials need to be determined before and after reaction. Morphological changes may occur under reaction conditions and can dramatically influence the reactivity and/or selectivity of a catalyst. Goldbased catalysts with different architectures are currently being developed for selective oxidation reactions at low temperatures. Specifically, nanoporous Au (npAu) with a composition of Au 97-Ag 3 is obtained by dealloying a Ag 70-Au 30 bulk alloy. Recent studies highlight the efficiency of npAu catalysts for methanol oxidation using ozone to activate the catalysts before methanol oxidation. Inmore » this paper, we studied the morphological and compositional changes occurring at the surface of Au-based catalysts in certain conditions.« less

Nanopore Electrochemistry: A Nexus for Molecular Control of Electron Transfer Reactions

PubMed Central

2018-01-01

Pore-based structures occur widely in living organisms. Ion channels embedded in cell membranes, for example, provide pathways, where electron and proton transfer are coupled to the exchange of vital molecules. Learning from mother nature, a recent surge in activity has focused on artificial nanopore architectures to effect electrochemical transformations not accessible in larger structures. Here, we highlight these exciting advances. Starting with a brief overview of nanopore electrodes, including the early history and development of nanopore sensing based on nanopore-confined electrochemistry, we address the core concepts and special characteristics of nanopores in electron transfer. We describe nanopore-based electrochemical sensing and processing, discuss performance limits and challenges, and conclude with an outlook for next-generation nanopore electrode sensing platforms and the opportunities they present. PMID:29392173

A novel adenine-based metal organic framework derived nitrogen-doped nanoporous carbon for flexible solid-state supercapacitor.

PubMed

Li, Haowen; Fu, Dongying; Zhang, Xian-Ming

2018-01-01

In this article, we have synthesized a series of nitrogen-doped nanoporous carbon (NPC) from metal organic framework of UiO-66 with different ratios of adenine and 1,4-benzendicarboxylate (H 2 BDC) coated on carbon nanotube film (CNTF) to obtain a flexible porous electrode (NPC/CNTF). It is worth noting that the introduction of adenine at different ratios did not change the structure of UiO-66. We also investigated the effect of carbonization temperature from 800 to 1000°C on the electrochemical properties of the NPC. The ratio (H 2 BDC:adenine) 9 : 1 and the NPC carbonized at 900°C (denoted as NPC-1-900) exhibits better electrochemical properties. The results show that NPC-1-900/CNTF electrode exhibits an exceptional areal capacitance of 121.5 mF cm -2 compared to that of PC-900/CNTF electrode (22.8 mF cm -2 ) at 5 mV s -1 in a three-electrode system, indicating that the incorporation of nitrogen is beneficial to the electrochemical properties of nanoporous carbon. A symmetric flexible solid-state supercapacitor of NPC-1-900/CNTF has also been assembled and tested. Electrochemical data show that the device exhibited superior areal capacitance (43.2 mF cm -2 ) at the scan rate of 5 mV s -1 ; the volumetric energy density is 57.3 µWh cm -3 and the volumetric power density is 2.4 mW cm -3 at the current density of 0.5 mA cm -2 based on poly(vinyl alcohol)/H 3 PO 4 gel electrolyte. For practical application, we have also studied the bending tests of the device, which show that the device exhibits outstanding mechanical stability under different bending angles. Furthermore, the flexible device shows excellent cyclic stability, which can retain 91.5% of the initial capacitance after 2000 cycles.

A novel adenine-based metal organic framework derived nitrogen-doped nanoporous carbon for flexible solid-state supercapacitor

PubMed Central

Li, Haowen; Zhang, Xian-Ming

2018-01-01

In this article, we have synthesized a series of nitrogen-doped nanoporous carbon (NPC) from metal organic framework of UiO-66 with different ratios of adenine and 1,4-benzendicarboxylate (H2BDC) coated on carbon nanotube film (CNTF) to obtain a flexible porous electrode (NPC/CNTF). It is worth noting that the introduction of adenine at different ratios did not change the structure of UiO-66. We also investigated the effect of carbonization temperature from 800 to 1000°C on the electrochemical properties of the NPC. The ratio (H2BDC:adenine) 9 : 1 and the NPC carbonized at 900°C (denoted as NPC-1-900) exhibits better electrochemical properties. The results show that NPC-1-900/CNTF electrode exhibits an exceptional areal capacitance of 121.5 mF cm−2 compared to that of PC-900/CNTF electrode (22.8 mF cm−2) at 5 mV s−1 in a three-electrode system, indicating that the incorporation of nitrogen is beneficial to the electrochemical properties of nanoporous carbon. A symmetric flexible solid-state supercapacitor of NPC-1-900/CNTF has also been assembled and tested. Electrochemical data show that the device exhibited superior areal capacitance (43.2 mF cm−2) at the scan rate of 5 mV s−1; the volumetric energy density is 57.3 µWh cm−3 and the volumetric power density is 2.4 mW cm−3 at the current density of 0.5 mA cm−2 based on poly(vinyl alcohol)/H3PO4 gel electrolyte. For practical application, we have also studied the bending tests of the device, which show that the device exhibits outstanding mechanical stability under different bending angles. Furthermore, the flexible device shows excellent cyclic stability, which can retain 91.5% of the initial capacitance after 2000 cycles. PMID:29410815

Controlled growth of novel hyper-branched nanostructures in nanoporous alumina membrane.

PubMed

Zhang, Junping; Day, Cynthia S; Carroll, David L

2009-12-07

This paper proposes a novel approach to fabricate hyper-branched anodic aluminium oxide (AAO) nanostructures with different branches on the vertically-aligned trunk and at the trunk terminal. Silver nanowires with different dimensional and multifunctional complexity have been prepared from this hyper-branched AAO template by varying the electrodeposition time. These kinds of novel nanostructure may be used to build blocks for nanoelectronic and nanophotonic devices.

Biosensor based on glucose oxidase-nanoporous gold co-catalysis for glucose detection.

PubMed

Wu, Chao; Sun, Huihui; Li, Yufei; Liu, Xueying; Du, Xiaoyu; Wang, Xia; Xu, Ping

2015-04-15

Promoting the electrocatalytic oxidation of glucose is crucial in glucose biosensor design. In this study, nanoporous gold (NPG) was selected for glucose oxidase (GOx) immobilization and glucose biosensor fabrication because of its open, highly conductive, biocompatible, and interconnected porous structure, which also facilitates the electrocatalytic oxidation of glucose. The electrochemical reaction on the surface of the resulting GOx/NPG/GCE bioelectrode was attributed to the co-catalysis effect of GOx and NPG. A surface-confined reaction in a phosphate buffer solution was observed at the bioelectrode during cyclic voltammetry experiments. Linear responses were observed for large glucose concentrations ranging from 50μM to 10mM, with a high sensitivity of 12.1μAmM(-1)cm(-2) and a low detection limit of 1.02μM. Furthermore, the GOx/NPG/GCE bioelectrode presented strong anti-interference capability against cholesterol, urea, tributyrin, ascorbic acid, and uric acid, along with a long shelf-life. For the detection of glucose in human serum, the data generated by the GOx/NPG/GCE bioelectrode were in good agreement with those produced by an automatic biochemical analyzer. These unique properties make the GOx/NPG/GCE bioelectrode an excellent choice for the construction of a glucose biosensor. Copyright © 2014 Elsevier B.V. All rights reserved.

Fabrication of complex free-standing nanostructures with concave and convex curvature via the layer-by-layer approach.

PubMed

Raoufi, Mohammad; Schönherr, Holger

2014-02-18

We report on the fabrication of unprecedented free-standing complex polymeric nanoobjects, which possess both concave and convex curvatures, by exploiting the layer-by-layer (LBL) deposition of polyelectrolytes. In a combined top-down/bottom-up replication approach pore diameter-modulated anodic aluminum oxide (AAO) templates, fabricated by temperature modulation hard anodization (TMHA), were replicated with multilayers of poly(styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) to yield open nanotubes with diameters in the wide and narrow segments of 210 and 150 nm, respectively. To obtain stable pore diameter-modulated nanopores, which possess segment lengths between 1 and 5 μm and 5 and 10 μm in the narrow and wide pore portion, respectively, conventional hard anodization of aluminum was followed by a subsequent temperature-modulated anodization. After removing the backside aluminum electrode, silanizing the aluminum oxide, and passivating the exposed membrane surface with a thin layer of gold, PSS and PAH were deposited alternatingly to yield LBL multilayers. For optimized LBL multilayer thicknesses and compactness, established in separate experiments on silicon substrates and nanoporous AAO with straight pores, free-standing polymeric nanoobjects with concave and convex curvatures, were obtained. These were stable for wall thickness to pore diameter ratios of ≥0.08.

Nanoporous gold as a solid support for protein immobilization and development of an electrochemical immunoassay for prostate specific antigen and carcinoembryonic antigen

PubMed Central

Pandey, Binod; Demchenko, Alexei V.; Stine, Keith J.

2013-01-01

Nanoporous gold (NPG) was utilized as a support for immobilizing alkaline phosphatase (ALP) conjugated to monoclonal antibodies against either prostate specific antigen (PSA) or carcinoembryonic antigen (CEA). The antibody-ALP conjugates were coupled to self-assembled monolayers of lipoic acid and used in direct kinetic assays. Using the enzyme substrate p-aminophenylphosphate, the product p-aminophenol was detected by its oxidation near 0.1 V (vs. Ag|AgCl) using square wave voltammetry. The difference in peak current arising from oxidation of p-aminophenol before and after incubation with biomarker increased with biomarker concentration. The response to these two biomarkers was linear up to 10 ng mL-1 for CEA and up to 30 ng mL-1 for PSA. The effect of interference on the PSA assay was studied using bovine serum albumin (BSA) as a model albumin protein. The effect of interference from a serum matrix was examined for the PSA assay using newborn calf serum. A competitive version of the immunoassay using antigen immobilized onto the NPG surface was highly sensitive at lower antigen concentration. Estimates of the surface coverage of the antibody-ALP conjugates on the NPG surface are presented. PMID:23935216