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Search Publications by: Ming Zheng (Fed)

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Displaying 26 - 49 of 49

Differentiating Left- and Right-Handed Carbon Nanotubes by DNA

December 28, 2016
Author(s)
Ming Zheng, Geyou Ao, Jason K. Streit, Jeffrey A. Fagan
The emergence of macromolecules of defined structures is a crucial step in the evolution of life. The mechanism by which these structures are selected from astronomical numbers of biopolymer sequences has long been a topic of controversy1,2. Experimenting

Attractive Interactions between DNA-Carbon Nanotube hybrids in Monovalent Salts

June 30, 2016
Author(s)
Ming Zheng, Xiangyun Qiu, Fuyou Ke, Raju Timsina, Constantine Y. Khripin
DNA-carbon nanotube (DNA-CNT) hybrids are nanometer-sized, highly-charged, rod-like molecules with complex surface chemistry, and their behaviors in aqueous solutions are governed by multifactorial interactions with both solvent and co-solutes. We have

Intensity Ratio of Resonant Raman Modes for (n,m) Enriched Semiconducting Carbon Nanotubes

April 29, 2016
Author(s)
Yanmei Piao, Jeffrey R. Simpson, Jason K. Streit, Geyou Ao, Ming Zheng, Angela R. Hight Walker
Relative intensities of resonant Raman spectral features, specifically the radial breathing mode (RBM) and G modes, of eleven chirality-enriched single-wall carbon nanotube (SWCNT) species were established under second-order optical transition excitation

How Large Can We Go? Isolation of > 1 nm Diameter Single-Wall Carbon Nanotubes Species using Aqueous Two Phase Extraction

April 14, 2015
Author(s)
Jeffrey A. Fagan, Erik Haroz, Rachelle Ihly, Hui Gui, Jeffrey Blackburn, Jeffrey R. Simpson, Stephen K. Doorn, Stephanie Lam, Angela R. Hight Walker, Ming Zheng
We demonstrate the effective separation of near-monochiral single-wall carbon nanotube (SWCNT) species with diameters > 1 nm through multi-stage aqueous two phase extraction (ATPE), and report an empirical function for the surfactant concentrations at

Preparation and Separation of DNA-Wrapped Carbon Nanotubes

March 18, 2015
Author(s)
Geyou Ao, Ming Zheng
Purification of single-chirality single-wall carbon nanotubes (SWCNTs)from their synthetic mixture is a prerequisite for many applications. DNA-controlled carbon nanotube (CNT) purification has evolved over a decade along with other separation techniques

Redox sorting of carbon nanotubes

March 17, 2015
Author(s)
Hui Gui, Jason K. Streit, Jeffrey Fagan, Angela R. Hight Walker, Chongwu Zhou, Ming Zheng
This work expands the redox chemistry of single-wall carbon nanotube (SWCNT) by investigating its role in a number of SWCNT sorting processes. Using a polyethylene glycol (PEG)/dextran (DX) aqueous two-phase system, we show that electron-transfer reaction

DNA-Controlled Carbon Nanotube Partition in Polymer Aqueous Two-Phase Systems

June 28, 2014
Author(s)
Geyou Ao, Constantine Y. Khripin, Ming Zheng
Sorting single-wall carbon nanotubes (SWCNTs) of different chiralities is both scientifically interesting and technologically important. Recent studies have shown that polymer aqueous two-phase extraction is a very effective way to achieve nanotube sorting

Hydrodynamic Behavior of Carbon Nanotubes and Characterization of Length Distributions

February 28, 2014
Author(s)
Carlos A. Silvera Batista, Ming Zheng, Constantine Y. Khripin, Xiaomin X. Tu, Jeffrey Fagan
The sedimentation behavior of SWCNTs was studied through analytical ultracentrifugation. SWCNTs were dispersed with the aid of surfactants, doubly sorted by density and length to produce samples with invariant diameter distributions and aspect ratios that

Isolation of Specific Small Diameter Single-Wall Carbon Nanotube Species via Aqueous Two-Phase Extraction

January 21, 2014
Author(s)
Jeffrey A. Fagan, Constantine Y. Khripin, Carlos A. Silvera Batista, Jeffrey R. Simpson, Angela R. Hight Walker, Ming Zheng
Aqueous two-phase extraction (ATPE) is demonstrated to enable isolation of multiple semiconducting and metallic single-wall carbon nanotube species from a small diameter synthetic mixture. Separation by ATPE is rapid and robust, with remarkable tunability

Analyzing Surfactant Structures on Length and Chirality Resolved (6,5) Single-Wall Carbon Nanotubes by Analytical Ultracentrifugation

March 26, 2013
Author(s)
Jeffrey A. Fagan, Ming Zheng, Jeffrey R. Simpson, Vinayak Rastogi, Constantine Y. Khripin, Carlos A. Silvera Batista, Angela R. Hight Walker
The structure and density of the bound interfacial surfactant layer and associated hydration shell were investigated using analytical ultracentrifugation for length and chirality purified (6,5) single-wall carbon nanotubes (SWCNTs) in three different bile

High Resolution Length Fractionation of Surfactant Dispersed Carbon Nanotubes

December 23, 2012
Author(s)
Constantine Y. Khripin, Xiaomin X. Tu, Jeffrey A. Fagan, Ming Zheng
Length fractionation of colloidal carbon nanotube dispersions is required for many studies. Size- exclusion chromatography (SEC) has been reported as a reliable method for high resolution length fractionation of DNA-dispersed single-wall carbon nanotubes

Chirality-controlled cloning of carbon nanotubes

November 13, 2012
Author(s)
Ming Zheng, Xiaomin X. Tu, Jia Liu, Chuan Wang, Chongwu Zhou
Carbon nanotubes possess superior electrical and optical properties and hold great promise for electronic and biomedical applications1-10. The electronic properties of carbon nanotubes strongly depend on their chirality, with 1/3 being metallic1, 2/3 being

Concentration Measurement of Length-Fractionated Colloidal Single-Wall Carbon Nanotubes

September 20, 2012
Author(s)
Constantine Y. Khripin, Xiaomin X. Tu, John Howarter, Jeffrey A. Fagan, Ming Zheng
Determination of the colloid concentration for a given single-wall carbon nanotube (SWCNT) dispersion is a basic requirement for many studies. The commonly used optical absorption based concentration measurement is complicated by the spectral change due to

Measuring Single-Walled Carbon Nanotube Length Distributions from Diffusional Trajectories

August 27, 2012
Author(s)
Jason Streit, Sergei M. Bachilo, Anton V. Naumov, Constantine Y. Khripin, Ming Zheng, R B. Weisman
A new method is demonstrated for measuring the length distributions of dispersed single-walled carbon nanotube (SWCNT) samples by analyzing diffusional motions of many individual nanotubes in parallel. In this method, termed Length Analysis by Nanotube

Chiral Index Dependence of the G+ and G- RamanModes in Semiconducting Carbon Nanotubes

January 24, 2012
Author(s)
Ming Zheng, Xiaomin X. Tu, Hagen Telg, Stephen K. Doorn, Juan Duque
Raman spectroscopy on the radial breathing mode is a common tool to determine the diameter d or chiral indices (n;m) of single walled carbon nanotubes. In this work we presentan alternative technique to determine d and (n;m) based on the high-energy G mode

Violation of the Condon Approximation in Semiconducting Carbon Nanotubes

June 28, 2011
Author(s)
Ming Zheng
A long-held but untested fundamental assumption in Raman spectroscopy of carbon nanotubes is that intensities arising from resonance with incident and scattered photons are equal. We present here the first complete Raman excitation profiles (REPs) for the