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Full-Text Articles in Nanoscience and Nanotechnology

Liquid Crystals Formed By Short Dna Oligomers And The Origin Of Life, Gregory Patrick Smith Jan 2018

Liquid Crystals Formed By Short Dna Oligomers And The Origin Of Life, Gregory Patrick Smith

Physics Graduate Theses & Dissertations

When dissolved in water, base paired DNA oligomers form double helices with sufficient structural rigidity that, if they are at high enough concentration, can undergo a phase transition into chiral nematic or hexagonal columnar liquid crystalline (LC) order. Within these LC phases, constrained orientation allows these rods to stack more efficiently by hydrophobic forces than they would otherwise, building them into long double helical aggregates that can be chemically glued together (ligated) to further increase their lengths. Even in absence of chemical ligation, this stacking effect is strong enough that short DNA oligomers, which are otherwise too short to form ...


Revealing The Nanoscale Structure And Properties Of The Twist-Bend Nematic Liquid Crystal Phase, Michael Ryan Tuchband Jan 2018

Revealing The Nanoscale Structure And Properties Of The Twist-Bend Nematic Liquid Crystal Phase, Michael Ryan Tuchband

Physics Graduate Theses & Dissertations

The nematic phases of liquid crystals have been the most thoroughly investigated since the founding of the liquid crystal field in the early 1900’s. The resulting technologies, most notably the liquid crystal display, have changed our world and spawned an entire industry. Consequently, the recent identification of a new type of nematic – the twist-bend nematic – was met with as much surprise as excitement, as it melds the fluid properties and environmental responsiveness of conventional nematics with the intrinsic polarization and complex ordering of bent-core liquid crystals. I summarize the history of the twist-bend nematic phase, charting the development of ...


Quantum Measurement Backaction And Upconverting Microwave Signals With Mechanical Resonators, Robert William Peterson Jan 2017

Quantum Measurement Backaction And Upconverting Microwave Signals With Mechanical Resonators, Robert William Peterson

Physics Graduate Theses & Dissertations

The limits of optical measurement and control of mechanical motion are set by the quantum nature of light. The familiar shot noise limit can be avoided by increasing the optical power, but at high enough powers, the backaction of the randomly-arriving photons' radiation pressure can grow to become the dominant force on the system. This thesis will describe an experiment showing how backaction limits the laser cooling of macroscopic drumhead membranes, as well as work on how these membranes can be used to upconvert microwave signals to optical frequencies, potentially preserving the fragile quantum state of the upconverted signal.


Nanoscale And Ultrafast Imaging And Spectroscopy To Probe Heterogeneity Of Novel Materials And Coherence Of Thermal Near-Fields, Brian Thomas O'Callahan Jan 2017

Nanoscale And Ultrafast Imaging And Spectroscopy To Probe Heterogeneity Of Novel Materials And Coherence Of Thermal Near-Fields, Brian Thomas O'Callahan

Physics Graduate Theses & Dissertations

Novel optical phenomena emerge on nanometer length scales which determine the macroscopic material response. By bringing a sharp atomic force microscopy tip close to a surface and illuminating with either a laser, a broadband light source, or the intrinsic thermal fields of the material itself, we can probe near-field optical properties with spatial resolution only limited by the apex radius of the tip. These properties include the spectral, spatial, and coherence properties of the thermal near-fields that emerge at sub-wavelength distances from any matter at non-zero temperature that affect thermal emission and nanoscale heat transfer. I also apply near-field imaging ...


Uncovering New Thermal And Elastic Properties Of Nanostructured Materials Using Coherent Euv Light, Jorge Nicolás Hernández Charpak Jan 2017

Uncovering New Thermal And Elastic Properties Of Nanostructured Materials Using Coherent Euv Light, Jorge Nicolás Hernández Charpak

Physics Graduate Theses & Dissertations

Advances in nanofabrication have pushed the characteristic dimensions of nanosystems well below 100nm, where physical properties are often significantly different from their bulk counterparts, and accurate models are lacking. Critical technologies such as thermoelectrics for energy harvesting, nanoparticle-mediated thermal therapy, nano-enhanced photovoltaics, and efficient thermal management in integrated circuits depend on our increased understanding of the nanoscale. However, traditional microscopic characterization tools face fundamental limits at the nanoscale. Theoretical efforts to build a fundamental picture of nanoscale thermal dynamics lack experimental validation and still struggle to account for newly reported behaviors. Moreover, precise characterization of the elastic behavior of nanostructured ...


Coherent Femtosecond Spectroscopy And Nonlinear Optical Imaging On The Nanoscale, Vasily Kravtsov Jan 2017

Coherent Femtosecond Spectroscopy And Nonlinear Optical Imaging On The Nanoscale, Vasily Kravtsov

Physics Graduate Theses & Dissertations

Optical properties of many materials and macroscopic systems are defined by ultrafast dynamics of electronic, vibrational, and spin excitations localized on the nanoscale. Harnessing these excitations for material engineering, optical computing, and control of chemical reactions has been a long-standing goal in science and technology. However, it is challenging due to the lack of spectroscopic techniques that can resolve processes simultaneously on the nanometer spatial and femtosecond temporal scales. This thesis describes the fundamental principles, implementation, and experimental demonstration of a novel type of ultrafast microscopy based on the concept of adiabatic plasmonic nanofocusing. Simultaneous spatio-temporal resolution on a nanometer-femtosecond ...


Scattering-Scanning Near-Field Optical Microscopy With Femtosecond Laser Pulses, Peter B. Van Blerkom Jan 2016

Scattering-Scanning Near-Field Optical Microscopy With Femtosecond Laser Pulses, Peter B. Van Blerkom

Physics Graduate Theses & Dissertations

The macroscopic properties of materials we observe emerge from the collective structural configuration and dynamical behavior of the atomic or molecular constituents. Therefore, in order to fully characterize and understand these properties, it is necessary to develop measurement techniques capable of probing at these scales. Such a technique is that of combining scattering scanning near-field optical microscopy with ultrafast spectroscopy. Traditional, far-field microscopy is limited by diffraction, making it impossible to resolve details smaller than approximately half the wavelength of the illuminating light. However, the electromagnetic field that is produced when an object is illuminated is not simply characterized by ...


Uncovering New Thermal And Mechanical Behavior At The Nanoscale Using Coherent Extreme Ultraviolet Light, Kathleen Marie Hoogeboom-Pot Jan 2015

Uncovering New Thermal And Mechanical Behavior At The Nanoscale Using Coherent Extreme Ultraviolet Light, Kathleen Marie Hoogeboom-Pot

Physics Graduate Theses & Dissertations

Tremendous recent progress in nanofabrication capabilities has made high-quality single-atomic layers and nanostructures with dimensions well below 50 nm commonplace, enabling unprecedented access to materials at the nanoscale. However, tools and techniques capable of characterizing the properties and function of nanosystems are still quite limited, leaving much of the fundamental physics that dominates material behavior in the deep nano-regime still unknown. Further understanding gained by studying nanoscale materials is critical both to fundamental science and to continued technological development. This thesis applies coherent extreme ultraviolet (EUV) light from tabletop high harmonic generation to study nanoscale systems on their intrinsic length ...


Novel Concepts In Near-Field Optics: From Magnetic Near-Field To Optical Forces, Honghua Yang Jan 2015

Novel Concepts In Near-Field Optics: From Magnetic Near-Field To Optical Forces, Honghua Yang

Physics Graduate Theses & Dissertations

Driven by the progress in nanotechnology, imaging and spectroscopy tools with nanometer spatial resolution are needed for in situ material characterizations. Near-field optics provides a unique way to selectively excite and detect elementary electronic and vibrational interactions at the nanometer scale, through interactions of light with matter in the near-field region. This dissertation discusses the development and applications of near-field optical imaging techniques, including plasmonic material characterization, optical spectral nano-imaging and magnetic field detection using scattering-type scanning near-field optical microscopy (s-SNOM), and exploring new modalities of optical spectroscopy based on optical gradient force detection.

Firstly, the optical dielectric functions ...


Investigating Charge Generation And Mobility In Type-Separated Single-Walled Carbon Nanotube Ensembles For Solar Photovoltaics, Kevin S. Mistry Jul 2014

Investigating Charge Generation And Mobility In Type-Separated Single-Walled Carbon Nanotube Ensembles For Solar Photovoltaics, Kevin S. Mistry

Physics Graduate Theses & Dissertations

Single-walled carbon nanotubes (SWCNTs) have a number of unique and remarkable properties, including high electrical conductivity and tunable optical absorption. Due to their optoelectronic properties, considerable interest has been expressed in incorporating them into organic photovoltaic devices. Several challenges, as well as opportunities, have arisen in recent years as SWCNTs have been investigated for photovoltaic applications. This dissertation covers both main roles for SWCNTs in solar cells: as charge collecting transparent electrodes and as charge generating light absorbers in the active layer.

Typical SWCNT synthesis methods produce both metallic and semiconducting species with a wide range of diameters, electron affinities ...


Magnetic And Optical Holonomic Manipulation Of Colloids, Structures And Topological Defects In Liquid Crystals For Characterization Of Mesoscale Self-Assembly And Dynamics, Michael Christopher Mason Varney Jan 2014

Magnetic And Optical Holonomic Manipulation Of Colloids, Structures And Topological Defects In Liquid Crystals For Characterization Of Mesoscale Self-Assembly And Dynamics, Michael Christopher Mason Varney

Physics Graduate Theses & Dissertations

Colloidal systems find important applications ranging from fabrication of photonic crystals to direct probing of phenomena encountered in atomic crystals and glasses; topics of great interest for physicists exploring a broad range of scientific, industrial and biomedical fields. The ability to accurately control particles of mesoscale size in various liquid host media is usually accomplished through optical trapping methods, which suffer limitations intrinsic to trap laser intensity and force generation. Other limitations are due to colloid properties, such as optical absorptivity, and host properties, such as viscosity, opacity and structure. Therefore, alternative and/or novel methods of colloidal manipulation are ...


Ultrastable Atomic Force Microscopy For Biophysics, Allison Beth Churnside Jan 2013

Ultrastable Atomic Force Microscopy For Biophysics, Allison Beth Churnside

Physics Graduate Theses & Dissertations

Atomic force microscopy (AFM) is a multifunctional workhorse of nanoscience and molecular biophysics, but instrumental drift remains a critical issue that limits the precision and duration of experiments. We have significantly reduced the two most important types of drift: in position and in force. The first, position drift, is defined as uncontrolled motion between the tip and the sample, which occurs in all three dimensions. By scattering a laser off the apex of a commercial AFM tip, we locally measured and thereby actively controlled its three-dimensional position above a sample surface to <0.4Å(Δf = 0.01-10 Hz) in air at room ...


Dispersion And Self-Assembly Of Anisotropic Plasmonic Nanoparticles In Liquid Crystalline Media, Julian Samuel Goodwin Evans Jan 2013

Dispersion And Self-Assembly Of Anisotropic Plasmonic Nanoparticles In Liquid Crystalline Media, Julian Samuel Goodwin Evans

Physics Graduate Theses & Dissertations

Noble metal nanoparticles possess extraordinary optical properties due to their plasmon modes that make them desirable for inclusion into materials. Non-dipolar plasmon modes are one of the simplest known ways to control the magnetic properties of a material; consequently gold nanoparticles are one of the most promising systems to produce metamaterials. In order to fully utilize the properties of gold nanoparticles for device applications, one needs to control the interparticle spacing, distribution, and orientation of anisotropic gold nanoparticles within a material. Liquid crystalline host materials can allow for alignment and self-assembly of nanoparticles through viscoelastic forces. In this thesis, I ...


Nanostructures Of Liquid Crystal Phases, Dong Chen Jan 2012

Nanostructures Of Liquid Crystal Phases, Dong Chen

Physics Graduate Theses & Dissertations

Bent-core liquid crystals have attracted intense interest in recent years, exhibiting a wide variety of novel structural phenomena involving the interplay of chirality, molecular bend and molecular tilt. Freeze-fracture transmission electron microscopy together with other experimental methods has been used to characterize the nanostructures of bent-core liquid crystal phases in which the molecules undergo complex self-assembly, forming, for example, helical nanofilaments (the B4 phase), disordered focal conics (the DC phase), and layer undulations (the B7 phase) in the bulk. These studies have helped us better understand the complex nature of these and other liquid crystal phases. For example, the investigation ...


Smectic Liquid Crystal Freely Suspended Films: Testing Beds For The Physics In Thin Membranes, Duong Hoang Nguyen Jan 2011

Smectic Liquid Crystal Freely Suspended Films: Testing Beds For The Physics In Thin Membranes, Duong Hoang Nguyen

Physics Graduate Theses & Dissertations

This thesis highlights the unique features of smectic liquid crystal freely suspended films to study surface effects and two-dimensional physics via three experiments: the first confirms the popular Saffman-Delbruck theory of the drag on a small cylinder in a thin membrane, the second measures the surface tension of a freely suspended molecular monolayer, and the third is a high-speed observation of the coalescence of two thin fluid disks. In the first experiment, we measure the diffusion constant of thicker domains (islands) in the film. They are perfectly circular and are readily observed under the microscope, making it possible to track ...