Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles

Plasma Synthesis and Self-Assembly of Magnetic Nanoparticles
Author: Sebastian Ekeroth
Publisher: Linköping University Electronic Press
Total Pages: 58
Release: 2019-11-08
Genre:
ISBN: 9176850099

Nanomaterials are important tools for enabling technological progress as they can provide dramatically different properties as compared to the bulk counterparts. The field of nanoparticles is one of the most investigated within nanomaterials, thanks to the existing, relatively simple, means of manufacturing. In this thesis, high-power pulsed hollow cathode sputtering is used to nucleate and grow magnetic nanoparticles in a plasma. This sputtering technique provides a high degree of ionization of the sputtered material, which has previously been shown to aid in the growth of the nanoparticles. The magnetic properties of the particles are utilized and makes it possible for the grown particles to act as building blocks for self-assembly into more sophisticated nano structures, particularly when an external magnetic field is applied. These structures created are termed “nanowires” or “nanotrusses”, depending on the level of branching and inter-linking that occurs. Several different elements have been investigated in this thesis. In a novel approach, it is shown how nanoparticles with more advanced structures, and containing material from two hollow cathodes, can be fabricated using high-power pulses. The dual-element particles are achieved by using two distinct and individual elemental cathodes, and a pulse process that allows tuning of individual pulses separately to them. Nanoparticles grown and investigated are Fe, Ni, Pt, Fe-Ni and Ni-Pt. Alternatively, the addition of oxygen to the process allows the formation of oxide or hybrid metal oxide – metal particles. For all nanoparticles containing several elements, it is demonstrated that the stoichiometry can be easily varied, either by the amount of reactive gas let into the process or by tuning the amount of sputtered material through adjusting the electric power supplied to the different cathodes. One aim of the presented work is to find a suitable material for the use as a catalyst in the production of H2 gas through the process of water splitting. H2 is a good candidate to replace fossil fuels as an energy carrier. However, rare elements (such as Ir or Pt) needs to be used as the catalyst, otherwise a high overpotential is required for the splitting to occur, leading to a low efficiency. This work demonstrates a possible route to avoid this, by using nanomaterials to increase the surface-to-volume ratio, as well as optimizing the elemental ratio between different materials to lower the amount of noble elements required.

Magnetic Nanoparticle Field Directed Self-assembly

Magnetic Nanoparticle Field Directed Self-assembly
Author: Ryan Michael Schmidt
Publisher:
Total Pages: 153
Release: 2011
Genre: Block copolymers
ISBN:

Directed self-assembly of nanomaterials via external fields is an attractive processing tool for industry as it is inherently inexpensive and flexible. The self-assembly of magnetic nanoparticles in particular has gained much recent interest for applications ranging from biomedical imaging and targeted cancer therapy to ferrofluid mechanical damping devices, that rely on the state of aggregation and alignment of the nanoparticles. We utilize an oil-water platform to directly observe directed self-assembly of magnetic nanoparticles that are field ordered into two-dimensional mesostructures through the fossilized liquid assembly method. Our system consisted of polymer-coated iron-oxide nanoparticles which were assembled at the interface between a crosslinkable hydrophobic monomer oil, and water through the use of external magnetic fields, and then cured with UV light. In this study, entire magnetic flux field lines in various geometrical configurations were successfully modeled and mapped out by the magnetic nanoparticles, both in-plane and in perpendicular orientations utilizing FLA. As the microscopic behavior of magnetic nanoparticles is known through this first study, further work can then be conducted through the assembly of block copolymer/magnetic nanoparticle nanocomposites. The morphology of neat self-assembled block copolymers have been extensively studied and it has been proven that the molecular weight, volume fraction of the components, and the degree of segment incompatibility are the three independent parameters used to determine equilibrium morphologies. The assembled orientations of lamellar and cylindrical morphologies in particular develop specific directionalities depending on the natural interactions of the blocks with the substrate and surface. It has been shown that treatments such as UV-Ozone treatment of the substrate, mechanical shear, or electrical fields can force this directionality to be altered, however few methods have been developed to readily alter preferential morphologies through the use of magnetic fields. In order to provide preliminary results toward the validity of a magnetically driven reorientation process, systems of polystyrene-b-poly(methylmethacrylate) with varying molecular weights were loaded with up to 1% polystyrene coated cobalt nanoparticles. This study successfully showed that the particles can be loaded into the block copolymers without disrupting the morphology of the block copolymers, and also provided initial results that this method is plausible.

X-Ray and Neutron Reflectivity: Principles and Applications

X-Ray and Neutron Reflectivity: Principles and Applications
Author: Jean Daillant
Publisher: Springer Science & Business Media
Total Pages: 347
Release: 2003-07-01
Genre: Science
ISBN: 3540486968

The reflection of and neutrons from surfaces has existed as an x-rays exp- imental for almost it is in the last technique fifty Nevertheless, only years. decade that these methods have become as of enormously popular probes This the surfaces and interfaces. to be due to of several appears convergence of intense different circumstances. These include the more n- availability be measured orders tron and sources that can over (so reflectivity x-ray many of and the much weaker surface diffuse can now also be magnitude scattering of thin films and studied in some the detail); growing importance multil- basic the realization of the ers in both and technology research; important which in the of surfaces and and role roughness plays properties interfaces; the of statistical models to characterize the of finally development topology its and its characterization from on roughness, dependence growth processes The of and to surface scattering experiments. ability x-rays neutro4s study four five orders of in scale of surfaces over to magnitude length regardless their and also their to ability probe environment, temperature, pressure, etc. , makes these the choice for buried interfaces often probes preferred obtaining information about the microstructure of often in statistical a global surfaces, the local This is manner to complementary imaging microscopy techniques, of such studies in the literature witnessed the veritable by explosion published the last few Thus these lectures will useful for over a resource years.

Magnetic Nanoparticles

Magnetic Nanoparticles
Author: Sergey P. Gubin
Publisher: John Wiley & Sons
Total Pages: 484
Release: 2009-11-18
Genre: Science
ISBN: 352762757X

This interdisciplinary approach to the topic brings together reviews of the physics, chemistry, fabrication and application of magnetic nanoparticles and nanostructures within a single cover. With its discussion of the basics as well as the most recent developments, and featuring many examples of practical applications, the result is both a clear and concise introduction to the topic for beginners and a guide to relevant comprehensive physical phenomena and essential technological applications for experienced researchers.

Magnetic Nanoparticles in Biosensing and Medicine

Magnetic Nanoparticles in Biosensing and Medicine
Author: Nicholas J. Darton
Publisher: Cambridge University Press
Total Pages: 317
Release: 2019-02-14
Genre: Medical
ISBN: 1107031095

Drawing together topics from a wide range of disciplines, and featuring up-to-date examples of clinical usage and research applications, this text provides a comprehensive insight into the fundamentals of magnetic biosensors and the applications of magnetic nanoparticles in medicine.

Self-Assembly of Nano- and Micro-structured Materials Using Colloidal Engineering

Self-Assembly of Nano- and Micro-structured Materials Using Colloidal Engineering
Author: Dwaipayan Chakrabarti
Publisher: Elsevier
Total Pages: 184
Release: 2019-04-25
Genre: Science
ISBN: 0081023030

Self-assembly of Nano- and Micro-structured Materials Using Colloidal Engineering, Volume 12, covers the recent breakthroughs in the design and manufacture of functional colloids at the micro- and nanoscale level. In addition, it provides analyses on how these functionalities can be exploited to develop self-assembly pathways towards nano- and micro-structured materials. As we seek increasingly complex functions for colloidal superstructures, in silico design will play a critical role in guiding experimental fabrication by reducing the element of trial-and-error that would otherwise be involved. In addition to novel experimental approaches, recent developments in computational modelling are also presented, along with an overview of the arsenal of designing tools that are available to the modern materials scientist. Focuses on promoting feedback between experiment, theory and computation in this cross-disciplinary research area Shows how colloid science plays a crucial role in the bottom-up fabrication of nanostructured materials Presents recent developments in computational modelling