Diffusion with reversible chemical reaction in heterogeneous media.

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1973.Number 138 used twice in paging.Bibliography: leaves 500-514.Sc.D

Asymmetric nanopore rectification for ion pumping, electrical power generation, and information processing applications

Single-track, asymmetric nanopores can currently be functionalised with a spatially inhomogeneous distribution of fixed charges and a variety of pore tip shapes. Optimising the asymmetric nanopore characteristics is crucial for practical applications in nanofluidics. We have addressed here this question for three cases based on different input/output chemical and electrical signals: (i) ion pumping up a concentration gradient by means of a periodic, time-dependent bias potential, (ii) information processing with a single nanopore acting as the nanofluidic diode of a logic gate, and (iii) electrical energy harvesting using a nanopore that separates two solutions of different salt concentrations. The results show the nanopore characteristics (size, shape, and charge distribution) that should be optimised for each application. In particular, the control of the pore tip size and charge appears to be crucial in all cases because it is in this narrow region where the interaction of the ions and the pore surface occurs, and this will eventually determine the nanodevice performance. © 2011 Elsevier Ltd. All rights reserved.We acknowledge the financial support from the Ministry of Science and Innovation of Spain and FEDER, Programme of Materials (project No. MAT2009-07747).Cervera, J.; Ramirez Hoyos, P.; Mafé, S.; Stroeve, P. (2011). Asymmetric nanopore rectification for ion pumping, electrical power generation, and information processing applications. Electrochimica Acta. 56(12):4504-4511. https://doi.org/10.1016/j.electacta.2011.02.056S45044511561

Toxicity of nanomaterials

Nanoscience has matured significantly during the last decade as it has transitioned from bench top science to applied technology. Presently, nanomaterials are used in a wide variety of commercial products such as electronic components, sports equipment, sun creams and biomedical applications. There are few studies of the long-term consequences of nanoparticles on human health, but governmental agencies, including the United States National Institute for Occupational Safety and Health and Japan’s Ministry of Health, have recently raised the question of whether seemingly innocuous materials such as carbon-based nanotubes should be treated with the same caution afforded known carcinogens such as asbestos. Since nanomaterials are increasing a part of everyday consumer products, manufacturing processes, and medical products, it is imperative that both workers and end-users be protected from inhalation of potentially toxic NPs. It also suggests that NPs may need to be sequestered into products so that the NPs are not released into the atmosphere during the product’s life or during recycling. Further, non-inhalation routes of NP absorption, including dermal and medical injectables, must be studied in order to understand possible toxic effects. Fewer studies to date have addressed whether the body can eventually eliminate nanomaterials to prevent particle build-up in tissues or organs. This critical review discusses the biophysicochemical properties of various nanomaterials with emphasis on currently available toxicology data and methodologies for evaluating nanoparticle toxicity

Multipore membranes with nanofluidic diodes allowing multifunctional rectification and logical responses

[EN] We have arranged two multipore membranes with conical nanopores in a three-compartment electrochemical cell. The membranes act as tunable nanofluidic diodes whose functionality is entirely based on the pH-reversed ion current rectification and does not require specific surface functionalizations. This electrochemical arrangement can display different electrical behaviors (quasi-linear ohmic response and inward/outward rectifications) as a function of the electrolyte concentration in the external solutions and the applied voltage at the pore tips. The multifunctional response permits to implement different logical responses including NOR and INHIBIT functions.Support from the Ministry of Economic Affairs and Competitiveness and FEDER (Project No. MAT2015-65011-P) and the Generalitat Valenciana (Project Prometeo/GV/0069 for Groups of Excellence) is gratefully acknowledged. M.A., S.N., and W.E. acknowledge the funding from the Hessen State Ministry of Higher Education, Research and the Arts, Germany, in the frame of LOEWE Project iNAPO.Cervera, J.; Ramirez Hoyos, P.; Gómez Lozano, V.; Nasir, S.; Ali, M.; Ensinger, W.; Stroeve, P.... (2016). Multipore membranes with nanofluidic diodes allowing multifunctional rectification and logical responses. Applied Physics Letters. 108:253701-1-253701-5. https://doi.org/10.1063/1.4954764S253701-1253701-510

Magnetism and Mössbauer study of formation of multi-core γ-Fe2O3 nanoparticles

A systematic investigation of magnetic nanoparticles and the formation of a core-shell structure, consisting of multiple maghemite (γ-Fe2O3) nanoparticles as the core and silica as the shell, has been performed using various techniques. High-resolution transmission electron microscopy clearly shows isolated maghemite nanoparticles with an average diameter of 13?nm and the formation of a core-shell structure. Low temperature Mössbauer spectroscopy reveals the presence of pure maghemite nanoparticles with all vacancies at the B-sites. Isothermal magnetization and zero-field-cooled and field-cooled measurements are used for investigating the magnetic properties of the nanoparticles. The magnetization results are in good accordance with the contents of the magnetic core and the non-magnetic shell. The multiple-core γ-Fe2O3 nanoparticles show similar behavior to isolated particles of the same size.We thank the assistance by Dr. Peter Klavins at the Department of Physics, the University of California Davis, in performing the magnetization measurements. This research was partially supported by the Department of Energy, Office of Nuclear Energy, Nuclear Energy Program, under Grant No. DE-NE000070

Biophysical properties of membrane lipids of anammox bacteria:I. Ladderane phospholipids form highly organized fluid membranes

AbstractAnammox bacteria that are capable of anaerobically oxidizing ammonium (anammox) with nitrite to nitrogen gas produce unique membrane phospholipids that comprise hydrocarbon chains with three or five linearly condensed cyclobutane rings. To gain insight into the biophysical properties of these ‘ladderane’ lipids, we have isolated a ladderane phosphatidylcholine and a mixed ladderane phosphatidylethanolamine/phosphatidylglycerol lipid fraction and reconstituted these lipids in different membrane environments. Langmuir monolayer experiments demonstrated that the purified ladderane phospholipids form fluid films with a relatively high lipid packing density. Fluid-like behavior was also observed for ladderane lipids in bilayer systems as monitored by cryo-electron microscopy on large unilamellar vesicles (LUVs) and epi-fluorescence microscopy on giant unilamellar vesicles (GUVs). Analysis of the LUVs by fluorescence depolarization revealed a relatively high acyl chain ordering in the hydrophobic region of the ladderane phospholipids. Micropipette aspiration experiments were applied to study the mechanical properties of ladderane containing lipid bilayers and showed a relatively high apparent area compressibility modulus for ladderane containing GUVs, thereby confirming the fluid and acyl chain ordered characteristics of these lipids. The biophysical findings in this study support the previous postulation that dense membranes in anammox cells protect these microbes against the highly toxic and volatile anammox metabolites

Triggered release in lipid bilayer-capped mesoporous silica nanoparticles containing SPION using an alternating magnetic field

[EN] We report here the on-command cargo controlled delivery using an alternating magnetic field (AMF) from magnetic silica mesoporous supports capped with a lipid bilayer. © 2012 The Royal Society of Chemistry.Financial support from the Spanish Government (projects MAT2009-14564-C04-01 and CTQ2008-00690) and the Generalitat Valenciana (project PROMETEO/2009/016) is gratefully acknowledged. E. B. thanks the Spanish Ministry of Education (MEC) for his Jose Castillejo fellowship (JC2010-0090).Bringas, E.; Köysüren, Ö.; Quach, DV.; Mahmoudi, M.; Aznar Gimeno, E.; Roehling, JD.; Marcos Martínez, MD.... (2012). Triggered release in lipid bilayer-capped mesoporous silica nanoparticles containing SPION using an alternating magnetic field. Chemical Communications. 48:5647-5649. https://doi.org/10.1039/C2CC31563GS5647564948Aznar, E., Martínez-Máñez, R., & Sancenón, F. (2009). Controlled release using mesoporous materials containing gate-like scaffoldings. Expert Opinion on Drug Delivery, 6(6), 643-655. doi:10.1517/17425240902895980Cotí, K. K., Belowich, M. E., Liong, M., Ambrogio, M. W., Lau, Y. A., Khatib, H. A., … Stoddart, J. F. (2009). Mechanised nanoparticles for drug delivery. Nanoscale, 1(1), 16. doi:10.1039/b9nr00162jLai, C.-Y., Trewyn, B. G., Jeftinija, D. M., Jeftinija, K., Xu, S., Jeftinija, S., & Lin, V. S.-Y. (2003). A Mesoporous Silica Nanosphere-Based Carrier System with Chemically Removable CdS Nanoparticle Caps for Stimuli-Responsive Controlled Release of Neurotransmitters and Drug Molecules. Journal of the American Chemical Society, 125(15), 4451-4459. doi:10.1021/ja028650lPark, C., Oh, K., Lee, S. C., & Kim, C. (2007). Controlled Release of Guest Molecules from Mesoporous Silica Particles Based on a pH-Responsive Polypseudorotaxane Motif. Angewandte Chemie International Edition, 46(9), 1455-1457. doi:10.1002/anie.200603404Casasús, R., Climent, E., Marcos, M. D., Martínez-Máñez, R., Sancenón, F., Soto, J., … Ruiz, E. (2008). Dual Aperture Control on pH- and Anion-Driven Supramolecular Nanoscopic Hybrid Gate-like Ensembles. Journal of the American Chemical Society, 130(6), 1903-1917. doi:10.1021/ja0756772Liu, R., Liao, P., Liu, J., & Feng, P. (2011). Responsive Polymer-Coated Mesoporous Silica as a pH-Sensitive Nanocarrier for Controlled Release. Langmuir, 27(6), 3095-3099. doi:10.1021/la104973jCliment, E., Martínez-Máñez, R., Sancenón, F., Marcos, M. D., Soto, J., Maquieira, A., & Amorós, P. (2010). Controlled Delivery Using Oligonucleotide-Capped Mesoporous Silica Nanoparticles. Angewandte Chemie International Edition, 49(40), 7281-7283. doi:10.1002/anie.201001847Mal, N. K., Fujiwara, M., & Tanaka, Y. (2003). Photocontrolled reversible release of guest molecules from coumarin-modified mesoporous silica. Nature, 421(6921), 350-353. doi:10.1038/nature01362Aznar, E., Marcos, M. D., Martínez-Máñez, R., Sancenón, F., Soto, J., Amorós, P., & Guillem, C. (2009). pH- and Photo-Switched Release of Guest Molecules from Mesoporous Silica Supports. Journal of the American Chemical Society, 131(19), 6833-6843. doi:10.1021/ja810011pFu, Q., Rao, G. V. R., Ista, L. K., Wu, Y., Andrzejewski, B. P., Sklar, L. A., … López, G. P. (2003). Control of Molecular Transport Through Stimuli-Responsive Ordered Mesoporous Materials. Advanced Materials, 15(15), 1262-1266. doi:10.1002/adma.200305165Thomas, C. R., Ferris, D. P., Lee, J.-H., Choi, E., Cho, M. H., Kim, E. S., … Zink, J. I. (2010). Noninvasive Remote-Controlled Release of Drug Molecules in Vitro Using Magnetic Actuation of Mechanized Nanoparticles. Journal of the American Chemical Society, 132(31), 10623-10625. doi:10.1021/ja1022267Ruiz-Hernández, E., Baeza, A., & Vallet-Regí, M. (2011). Smart Drug Delivery through DNA/Magnetic Nanoparticle Gates. ACS Nano, 5(2), 1259-1266. doi:10.1021/nn1029229Aznar, E., Mondragón, L., Ros-Lis, J. V., Sancenón, F., Marcos, M. D., Martínez-Máñez, R., … Amorós, P. (2011). Finely Tuned Temperature-Controlled Cargo Release Using Paraffin-Capped Mesoporous Silica Nanoparticles. Angewandte Chemie International Edition, 50(47), 11172-11175. doi:10.1002/anie.201102756Bruce, I. J., Taylor, J., Todd, M., Davies, M. J., Borioni, E., Sangregorio, C., & Sen, T. (2004). Synthesis, characterisation and application of silica-magnetite nanocomposites. Journal of Magnetism and Magnetic Materials, 284, 145-160. doi:10.1016/j.jmmm.2004.06.032Sen, T., Magdassi, S., Nizri, G., & Bruce, I. J. (2006). Dispersion of magnetic nanoparticles in suspension. Micro & Nano Letters, 1(1), 39. doi:10.1049/mnl:20065033Zhang, L., Longo, M. L., & Stroeve, P. (2000). Mobile Phospholipid Bilayers Supported on a Polyion/Alkylthiol Layer Pair. Langmuir, 16(11), 5093-5099. doi:10.1021/la9913405Liu, J., Stace-Naughton, A., Jiang, X., & Brinker, C. J. (2009). Porous Nanoparticle Supported Lipid Bilayers (Protocells) as Delivery Vehicles. Journal of the American Chemical Society, 131(4), 1354-1355. doi:10.1021/ja808018yLiu, J., Jiang, X., Ashley, C., & Brinker, C. J. (2009). Electrostatically Mediated Liposome Fusion and Lipid Exchange with a Nanoparticle-Supported Bilayer for Control of Surface Charge, Drug Containment, and Delivery. Journal of the American Chemical Society, 131(22), 7567-7569. doi:10.1021/ja902039yAshley, C. E., Carnes, E. C., Phillips, G. K., Padilla, D., Durfee, P. N., Brown, P. A., … Brinker, C. J. (2011). The targeted delivery of multicomponent cargos to cancer cells by nanoporous particle-supported lipid bilayers. Nature Materials, 10(5), 389-397. doi:10.1038/nmat2992Hoare, T., Timko, B. P., Santamaria, J., Goya, G. F., Irusta, S., Lau, S., … Kohane, D. S. (2011). Magnetically Triggered Nanocomposite Membranes: A Versatile Platform for Triggered Drug Release. Nano Letters, 11(3), 1395-1400. doi:10.1021/nl200494tNappini, S., Bonini, M., Bombelli, F. B., Pineider, F., Sangregorio, C., Baglioni, P., & Nordèn, B. (2011). Controlled drug release under a low frequency magnetic field: effect of the citrate coating on magnetoliposomes stability. Soft Matter, 7(3), 1025-1037. doi:10.1039/c0sm00789gMalam, Y., Loizidou, M., & Seifalian, A. M. (2009). Liposomes and nanoparticles: nanosized vehicles for drug delivery in cancer. Trends in Pharmacological Sciences, 30(11), 592-599. doi:10.1016/j.tips.2009.08.004Mahmoudi, M., Laurent, S., Shokrgozar, M. A., & Hosseinkhani, M. (2011). Toxicity Evaluations of Superparamagnetic Iron Oxide Nanoparticles: Cell «Vision» versus Physicochemical Properties of Nanoparticles. ACS Nano, 5(9), 7263-7276. doi:10.1021/nn2021088Mahmoudi, M., Azadmanesh, K., Shokrgozar, M. A., Journeay, W. S., & Laurent, S. (2011). Effect of Nanoparticles on the Cell Life Cycle. Chemical Reviews, 111(5), 3407-3432. doi:10.1021/cr100316

Persistence Length Control of the Polyelectrolyte Layer-by-Layer Self-Assembly on Carbon Nanotubes

One-dimensional inorganic materials such as carbon nanotubes1 and semiconductor nanowires have been central to important advances in materials science in the last decade. Unique mechanical and electronic properties of these molecular-scale wires enabled a variety of applications ranging from novel composite materials, to electronic circuits, to new sensors. Often, these applications require non-covalent modification of carbon nanotubes with organic compounds, DNA and biomolecules, and polymers to change nanotube properties or to add new functionality. We recently demonstrated a versatile and flexible strategy for non-covalent modification of carbon nanotubes using layer-by-layer self-assembly of polyelectrolytes. Researchers used this technique extensively for modification of flat surfaces, micro-, and nano-particles; however, little is known about the mechanism and the factors influencing layer-by-layer self-assembly in one-dimensional nanostructures. The exact conformation of polyelectrolyte chains deposited on single-walled carbon nanotubes (SWNT) is still unknown. There are two possible configurations: flexible polymers wrapping around the nanotube and stretched, rigid chains stacked parallel to the nanotube axis. Several factors, such as polymer rigidity, surface curvature, and strength of polymer-surface interactions, can determine the nature of assembly. Persistence length of the polymer chain should be one of the critical parameters, since it determines the chain's ability to wrap around the nanotube. Indeed, computer simulations for spherical substrates show that polymer rigidity and substrate surface curvature can influence the deposition process. Computational models also show that the persistence length of the polymer must fall below the threshold values determined by target surface curvature in order to initiate polyelectrolyte deposition process. Although these models described the effects of salt concentration and target surface curvature, they considered only nano-particles with radius 5 nanometer and larger. One-dimensional materials, such as carbon nanotubes, provide an even more interesting template for studying self-assembly mechanisms, since they give us access to even smaller surface curvatures down to 1 nm. We have examined the role of the polymer persistence length in layer-by-layer self-assembly process on carbon nanotubes by observing formation of multilayer polyelectrolyte shells around carbon nanotubes at different ionic strength. Persistence length of polyelectrolytes varies with solution ionic strength, due to screening of the electrostatic repulsion between the polymer Figure 1. TEM images of single-walled carbon nanotubes after polymer deposition for ionic strengths of (A) 0.05M, (B) 0.1M, (C) 0.2M, (D) 0.4M, (E) 0.65M, and (F) 1.05M. Scale bar corresponds to 10 nm. backbone charges; therefore changing ionic strength is a convenient way to alter the configuration of the polymer molecule systematically. We have used the layer-by-layer self-assembly technique to form 5-layer thick coating of the alternating polyallylamine hydrochloride (PAH) and sodium poly(styrenesulfonate) (PSS) layers on the surfaces of the pristine single-wall carbon nanotubes. For our experiments, we grew the nanotubes across copper TEM grid openings using catalytic chemical vapor deposition. The deposition solutions contained different amounts of NaCl to vary the ionic strength. After polymer multilayer formation we examined the resulting coating in high-resolution TEM