R-3 Repository :: Browsing by Author "Hafner, Jason H."

Browsing by Author "Hafner, Jason H."

Now showing 1 - 20 of 74

A single molecule immunoassay by localized surface plasmon resonance
(IOP Publishing, 2010) Mayer, Kathryn M.; Hao, Feng; Lee, Seunghyun; Nordlander, Peter; Hafner, Jason H.
Array of fullerene nanotubes
(2009-12-15) Smalley, Richard E.; Colbert, Daniel T.; Dai, Hongjie; Liu, Jie; Rinzler, Andrew G.; Hafner, Jason H.; Smith, Kenneth A.; Guo, Ting; Nikolaev, Pavel; Thess, Andreas; Rice University; United States Patent and Trademark Office
This invention relates generally to forming an array of fullerene nanotubes. In one embodiment, a macroscopic molecular array is provided comprising at least about 106 fullerene nanotubes in generally parallel orientation and having substantially similar lengths in the range of from about 5 to about 500 nanometers.
Array of single-wall carbon nanotubes
(2006-07-04) Smalley, Richard E.; Colbert, Daniel T.; Dai, Hongjie; Liu, Jie; Rinzler, Andrew G.; Hafner, Jason H.; Smith, Kenneth A.; Guo, Ting; Nikolaev, Pavel; Thess, Andreas; Rice University; United States Patent and Trademark Office
This invention relates generally to forming an array of single-wall carbon nanotubes (SWNT). In one embodiment, a macroscopic molecular array is provided comprising at least about 106 single-wall carbon nanotubes in generally parallel orientation and having substantially similar lengths in the range of from about 5 to about 500 nanometers.
Attack on single Escherichia coli spheroplast by antimicrobial peptides
(2015-08-13) Sun, Tzu-Lin; Huang, Huey W.; Hafner, Jason H.; McNew, James A.
Studies of the molecular mechanisms of antimicrobial peptides (AMPs) have mostly been performed with lipid bilayers, as a substitute for cell membrane. Hence, there is a persistent question as to whether the action of AMPs on bacterial membranes can be reproduced on lipid bilayers. Valuable information was obtained recently from observing the actions of AMPs on E. coli and Bacillus subtilis by time-lapse fluorescence microscopy. The goal of my dissertation is to study the direct action of AMPs on the cytoplasmic membranes by using E. coli spheroplasts, the cell form from which the outer membranes have been removed. The key question is how to reveal the response of the spheroplast to AMPs. In our previous work, the aspiration method on giant unilamellar vesicle (GUV) has been demonstrated as very effective for researching membrane effects induced by peptides. This method is able to measure the membrane expansion due to peptide binding and simultaneously monitor membrane permeability by using dye indicators. In this work, a spray method was developed for introducing AMPs and customized the experimental procedures for performing the experiments of E. coli spheroplasts. The living state of cytoplasmic membrane makes it difficult to deduce the molecular events from the response of live cells. Hence, the physical methods which have been developed for researching peptide activity on lipid bilayers were practiced first. These methods include X-ray diffraction (XRD), oriented circular dichroism (OCD) and GUV aspiration. These methods were practiced by studying the question as to why a hydrocarbon-stapled peptide NYAD-1 drug was reported to have membrane permeating property. Melittin was selected as the representative of AMPs for the E. coli spheroplast experiments. To better understand the characteristics of melittin, the melittin activity on model lipid membrane was examined before advancing to the spehroplast experiment. The melittin transmembrane was proposed by correlating melittin binding on a lipid vesicle (aspirated GUV imaging) with structural studies in multilayers (XRD and OCD). This behavior was further determined by using fluorescence indicator to track the melittin distribution. The toroidal structure of melittin pore was also detected by grazing-angle X-ray anomalous diffraction. In the studies of NAYD-1 and melittin on a model membrane, our discovery of AMP's transmembrane enables us to clarify the pore-formation mechanism which has been disputed for decades. In addition, our past work on the physical property of E. coli spheroplast cytoplasmic membrane has indicated the existence of a lipid reservoir. The lipid reservoir dominates the surface tension by balancing the membrane folds. Finally, we used the aspiration method to hold a spheroplast so as to measure the change of the spheroplast membrane area in response to the AMPs' binding. Further, a fluorescence indicator which is able to associate with AMPs was used to monitor the peptide distribution and another fluorescence dye to monitor the molecule leakage. The spheroplast study shows that there are similarities and differences between the responses of spheroplasts and GUVs. The recent findings on the unique properties of spheroplast membranes are the key for understanding these results. Our work of understanding the AMPs activity on membrane is potentially applicable in improving peptide drug design and delivery for disease treatment.
Automated Enrichment of Single-Walled Carbon Nanotubes with Optical Studies of Enriched Samples
(2013-05-13) Canning, Griffin; Weisman, R. Bruce; Hafner, Jason H.; Kono, Junichiro
The design and performance of an instrument is presented whose purpose is the extraction of samples highly enriched in one species of single-walled carbon nanotubes from density gradient ultracentrifugation. This instrument extracts high purity samples which are characterized by various optical studies. The samples are found to be enriched in just a few species of nanotubes, with the major limitation to enrichment being the separation, rather than extraction. The samples are then used in optical and microscopic studies which attempt to determine the first absorption coefficient (S1) of the (6,5) species of nanotube. Initial experiments give a value of 9.2 ± 2.6 cm2 C atom-1. Future work is proposed to improve upon the experiment in an attempt to reduce possible errors
Biomedical applications of plasmon resonant metal nanoparticles
(Future Medicine Ltd, 2006) Liao, Hongwei; Nehl, Colleen L.; Hafner, Jason H.
Carbon fibers formed from single-wall carbon nanotubes
(2004-01-27) Smalley, Richard E.; Colbert, Daniel T.; Dai, Hongjie; Liu, Jie; Rinzler, Andrew G.; Hafner, Jason H.; Smith, Kenneth A.; Guo, Ting; Nikolaev, Pavel; Thess, Andreas; Rice University; United States Patent and Trademark Office
A method for purifying a mixture comprising single-wall carbon nanotubes and amorphous carbon contaminate is disclosed. The method includes the steps of heating the mixture under oxidizing conditions sufficient to remove the amorphous carbon, followed by recovering a product comprising at least about 80% by weight of single-wall carbon nanotubes. A method for producing tubular carbon molecules of about 5 to 500 nm in length is also disclosed. The method includes the steps of cutting single-wall nanotube containing-material to form a mixture of tubular carbon molecules having lengths in the range of 5-500 nm and isolating a fraction of the molecules having substantially equal lengths. The nanotubes may be used, singularly or in multiples, in power transmission cables, in solar cells, in batteries, as antennas, as molecular electronics, as probes and manipulators, and in composites.
Catalytic growth of single- and double-wall carbon nanotubes from metal particles
(2006-10-24) Smalley, Richard E.; Hafner, Jason H.; Colbert, Daniel T.; Smith, Kenneth A.; Rice University; United States Patent and Trademark Office
Single-walled carbon nanotubes have been synthesized by the catalytic decomposition of both carbon monoxide and ethylene over a supported metal catalyst known to produce larger multi-walled nanotubes. Under certain conditions, there is no termination of nanotube growth, and production appears to be limited only by the diffusion of reactant gas through the product nanotube mat that covers the catalyst. The present invention concerns a catalyst-substrate system which promotes the growth of nanotubes that are predominantly single-walled tubes in a specific size range, rather than the large irregular-sized multi-walled carbon fibrils that are known to grow from supported catalysts. With development of the supported catalyst system to provide an effective means for production of single-wall nanotubes, and further development of the catalyst geometry to overcome the diffusion limitation, the present invention will allow bulk catalytic production of predominantly single-wall carbon nanotubes from metal catalysts located on a catalyst supporting surface.
Catalytic growth of single-and double-wall carbon nanotubes from metal particles
(2007-04-10) Smalley, Richard E.; Hafner, Jason H.; Colbert, Daniel T.; Smith, Kenneth A.; Rice University; United States Patent and Trademark Office
The present invention concerns a method for growing carbon nanotubes using a catalyst system that preferentially promotes the growth of single- and double-wall carbon nanotubes, rather than larger multi-walled carbon nanotubes. Ropes of the carbon nanotubes are formed that comprise single-wall and/or double-wall carbon nanotubes.
Catalytic growth of single-wall carbon nanotubes from metal particles
(2004-02-17) Smalley, Richard E.; Hafner, Jason H.; Colbert, Daniel T.; Smith, Kenneth A.; Rice University; United States Patent and Trademark Office
Single-walled carbon nanotubes have been synthesized by the catalytic decomposition of both carbon monoxide and ethylene over a supported metal catalyst known to produce larger multi-walled nanotubes. Under certain conditions, there is no termination of nanotube growth, and production appears to be limited only by the diffusion of reactant gas through the product nanotube mat that covers the catalyst The present invention concerns a catalyst-substrate system which promotes the growth of nanotubes that are predominantly single-walled tubes in a specific size range, rather than the large irregular-sized multi-walled carbon fibrils that are known to grow from supported catalysts. With development of the supported catalyst system to provide an effective means for production of single-wall nanotubes, and further development of the catalyst geometry to overcome the diffusion limitation, the present invention will allow bulk catalytic production of predominantly single-wall carbon nanotubes from metal catalysts located on a catalyst supporting surface.
Charge regulation in lipid membranes due to lipid mobility
(2010) Wickremasinghe, Yantrawaduge Nissanka Sirimevan; Hafner, Jason H.
Lipid bilayer membranes are ubiquitous in biology and electrostatics play a key role in their functionality. The interfacial electrostatics of lipid bilayers involves interplay between the surface potential and charge regulation in the form of ion binding, protonation and lipid mobility. Mobile lipid charge regulation in particular is unique to lipid interfaces and is thought to be an important factor in charged macromolecule-membrane interactions. We used Atomic Force Microscopy (AFM) for the first nanometer scale experimental demonstration of mobile lipid charge regulation occurring in supported lipid bilayer membranes. By combining finite element computer simulations and experimental AFM data, we showed that mobile lipid charge regulation accounts for the short range deviations from the expected electrostatics over anionic lipids. We also accounted for van der Waal interactions and electrolyte ion binding in our calculations and found the mobility of the lipid to be the dominant factor in the short range deviations. Control experiments on silicon nitride surfaces, whose surface charges are immobile, showed that the short range deviation could be accounted for by the formation of a stem layer due to cation binding. Further evidence for tip-induced mobile lipid charge regulation was presented in the form of clear differences in the short range electrostatics of mobile fluid phase lipids when compared to immobile gel phase lipids. Furthermore, our data confirmed the theoretically predicted differences between surfaces containing mobile versus immobile charges.
Compressive Hyperspectral Microscopy of Scattering and Fluorescence of Nanoparticles
(American Chemical Society, 2022) Xu, Yibo; Lu, Liyang; Giljum, Anthony; Payne, Courtney M.; Hafner, Jason H.; Ringe, Emilie; Kelly, Kevin F.
Hyperspectral imaging in optical microscopy is of importance in the study of various submicron physical and chemical phenomena. However, its practical application is still challenging because the additional spectral dimension increases the number of sampling points to be independently measured compared to two-dimensional (2D) imaging. Here, we present a hyperspectral microscopy system through passive illumination approach based on compressive sensing (CS) using a spectrometer with a one-dimensional (1D) detector array and a digital micromirror device (DMD). The illumination is patterned after the sample rather than on it, making this technique compatible with both dark-field and bright-field imaging. The DMD diffraction issue resulting from this approach has been overcome by a novel striped DMD pattern modulation method. In addition, a split pattern method is developed for increasing the spatial resolution when employing the DMD pattern modulation. The efficacy of the system is demonstrated on nanoparticles using two model systems: extended plasmonic metal nanostructures and fluorescent microspheres. The compressive hyperspectral microscopic system provides a fast, high dynamic range, and enhanced signal-to-noise ratio (SNR) platform that yields a powerful and low-cost spectral analytical system to probe the optical properties of a myriad of nanomaterial systems. The system can also be extended to wavelengths beyond the visible spectrum with greatly reduced expense compared to other approaches that use 2D array detectors.
Continued growth of single-walled carbon nanotubes from open-ended SWNT substrates
(2006) Kim, Myung Jong; Hafner, Jason H.; Smalley, Richard E.
We prepared nanoscopically flat open-ended SWNT substrates from SWNT spun fibers by using the microtome cutting technique or the focused ion beam cutting technique followed by various etching and cleaning schemes or alternatively from vertically aligned SWNT film by flipping-over. Deposited catalyst was docked to the open ends of SWNTs, and carbon feedstocks were catalyzed into continued single-walled carbon nanotube growth resembling 1D molecular epitaxy. The data obtained from Raman spectroscopy indicates that the (n, m) structure of the newly grown SWNT was cloned from that of the pre-existing SWNT substrate. Such results lead us to believe that this method will provide us with a means of chirality-controlled SWNTs growth on a macroscopic scale using a fairy general and scalable setup in the future.
Continuous fiber of fullerene nanotubes
(2010-02-02) Smalley, Richard E.; Colbert, Daniel T.; Dai, Hongjie; Liu, Jie; Rinzler, Andrew G.; Hafner, Jason H.; Smith, Kenneth A.; Guo, Ting; Nikolaev, Pavel; Thess, Andreas; Rice University; United States Patent and Trademark Office
This invention relates generally to carbon fiber produced from fullerene nanotube arrays. In one embodiment, the present invention involves a macroscopic carbon fiber comprising at least 106 fullerene nanotubes in generally parallel orientation.
Continuous fiber of single-wall carbon nanotubes
(2006-08-29) Colbert, Daniel T.; Dai, Hongjie; Hafner, Jason H.; Rinzler, Andrew G.; Smalley, Richard E.; Rice University; United States Patent and Trademark Office
This invention relates generally to carbon fiber produced from single-wall carbon nanotube (SWNT) molecular arrays. In one embodiment, the carbon fiber which comprises an aggregation of substantially parallel carbon nanotubes comprises more than one molecular array. Another embodiment of this invention is a large cable-like structure with enhanced tensile properties comprising a number of smaller separate arrays. In another embodiment, a composite structure is disclosed in which a central core array of metallic SWNTs is surrounded by a series of smaller circular non-metallic SWNT arrays.
Continuous fiber of single-wall carbon nanotubes
(2005-12-27) Smalley, Richard E.; Colbert, Daniel T.; Dai, Hongjie; Liu, Jie; Rinzler, Andrew G.; Hafner, Jason H.; Smith, Kenneth A.; Guo, Ting; Nikolaev, Pavel; Thess, Andreas; Rice University; United States Patent and Trademark Office
This invention relates generally to carbon fiber produced from single-wall carbon nanotube (SWNT) molecular arrays. In one embodiment, the present invention involves a macroscopic carbon fiber comprising at least 106 signal-wall carbon nanotubes in generally parallel orientation.
Engineered Plasmonic Nanostructures: Fano Resonance Response, Magnetic Plasmon Resonance for Waveguiding and Hot Electron Induced Photochemistry
(2013-08-05) Mukherjee, Shaunak; Halas, Naomi J.; Nordlander, Peter J.; Hafner, Jason H.
Surface plasmons are collective and coherent oscillations of conduction band electrons in metal nanostructure which enable coupling of photons to electrons at a metal dielectric interface. Plasmonic nanostructures have gained much attention due to their ability to confine, tune and manipulate light for specific applications simply by varying their geometries and local dielectric environment. This thesis will focus on designing and studying fundamental plasmonic properties of Au nanostructures for applications in photothermal cancer therapy, chemical sensing, optical waveguiding, and room temperature gas phase photocatalysis. First, this thesis focuses on spherically concentric nanoparticles, a rudimentary “nanomatryushka”, composed of a silica-coated gold nanosphere surrounded by a gold shell layer. These nanoparticles were synthesized using wet chemistry technique and were found to possess exceptional geometrically tunable optical resonances in a compact, sub-100 nm size. Changing the internal geometry of the nanoparticle not only shifts its resonance frequencies, but can also strongly modifies the relative magnitudes of the absorption and scattering cross sections, independent of nanoparticle size. In addition the inherent asymmetry of each individual Au/SiO2/Au nanomatryushka generate multiple Fano resonances due to the overlapping bright superradiant and dark subradiant plasmon modes. Fano resonances have immense potential for single particle localized surface plasmon sensing applications. Next, this thesis investigates a new class of waveguiding consisting of chains of fused heptamer nanodiscs. This novel waveguiding structure transports electromagnetic energy via magnetic plasmon resonance mode. In this new geometry, heptamer structure serves as a benzene-like subdiffraction limit building blocks which support antiphase magnetic plasmons with “antiferromagnetic” behavior in multiple repeated structures. By repeating the heptamer units, this waveguide enables low-loss magnetic plasmon propagation along linear chains, steering over large-angle bends and splitting. It has numerous potential uses in energy transport, data storage, near-field microscopy, and other nanophotonic applications. Finally, this thesis explores the use of Au-photocatalysts as multifunctional catalysts for enhanced reactivity and efficiency. Au-photocatalysts were used for room temperature dissociation of H2 on Au nanoparticle surface using visible light. Surface plasmons excited in the Au nanoparticle decay into hot electrons which can be transferred into an antibonding resonance of an H2 molecule adsorbed on the Au nanoparticle surface, triggering dissociation. This process is probed by detecting the formation of HD molecules from the dissociations of H2 and D2. The rate of dissociation was also profoundly dependent on of intensity and wavelength of excitation light. This work demonstrates an important application of plasmonics in the field of heterogeneous photocatalysis opening up a new pathway for all optical control of chemical reactions on metallic catalysts.
Engineering Application-Specific Plasmonic Nanoparticles: Quantitative Measurements and Precise Characterization
(2013-09-16) Anderson, Lindsey; Hafner, Jason H.; Halas, Naomi J.; Kelly, Kevin F.
Nobel metal nanoparticles that exhibit plasmon resonances in the visible and near infrared have been of great interest in recent years. Strong light-matter interactions on the nanoscale have a range of interesting properties that may be useful in applications in medicine, sensing, solar energy harvesting and information processing. Depending on the application, particle materials and geometries can be optimized for performance. A novel method of quantifying individual nanoparticle scattering cross-sections by comparing experiments with analytical theory for gold nanospheres is proposed and utilized. Results show that elongated particles scatter very brightly for their volumes. This brightness is due to a strong longitudinal plasmon resonance that occurs in the near infrared – where gold has minimal loss. Elongated particles, such as nanorods, are therefore, ideal for applications that rely on particles scattering brightly in small spaces, such as biological imaging. Next, gold nanobelts are discussed and characterized. These novel structures are akin to nanowires, but with a small, rectangular cross-sectional geometry. Gold nanobelts are shown to exhibit a strong transverse resonance that has never been reported previously in nanowires. The transverse resonance is shown to shift linearly with crosssectional aspect ratio. Other interesting products from the nanobelt synthesis, tapered and split nanobelts, are discussed. Gold nanobelts also support longitudinal propagating plasmons, and have the smallest cross-sectional area of any elongated plasmonic structure that has been reported to do so. By analyzing the output tip signal of propagating plasmons for nanobelts of different lengths, the decay length is measured. Finite Difference Time Domain simulations and polarization measurements show the fundamental, azimuthally symmetric mode is very strong for thin structures such as these, but decays much more quickly than a higher-order mode, which begins to dominate at longer lengths. The cross-sectional mode area is given, illustrating the high confinement of plasmons in these structures. A figure of merit that takes into account both confinement and propagation length is calculated to be 1300 for the higher-order mode, the highest reported for nanoscale plasmonic waveguides. The high figure of merit makes gold nanobelts excellent candidates for studying strong coupling between plasmonic structures and objects that exhibit quantum behavior.
Exploration of Chemical Analysis Techniques for Nanoscale Systems
(2013-09-16) Chang, Albert; Kelly, Kevin F.; Natelson, Douglas; Hafner, Jason H.
As the critical dimensions of many devices, especially electronics, continue to become smaller, the ability to accurately analyze the properties at ever smaller scales becomes necessary. Optical techniques, such as confocal microscopy and various spectroscopies, have produced a wealth of information on larger length scales, above the diffraction limit. Scanning probe techniques, such as scanning tunneling microscopy and atomic force microscopy, provide information with an extremely fine resolution, often on the order of nanometers or angstroms. In this document, plasmon coupling is used to generate large signal increases, with clear future applications toward scanning probe optical spectroscopies. A variation on scanning tunneling microscopy is also used to study the surface structure of environmentally interesting nanoparticles. Traditional Raman spectroscopy is used to examine doped graphene, which is becoming a hot material for future electronic applications.
Fluid Electric Force Microscopy for Charge Density Mapping in Biological Systems
(American Chemical Society, 2003-10-06) Johnson, Amber S.; Nehl, Colleen L.; Mason, Monica G.; Hafner, Jason H.

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