2024-03-28T18:05:35Z
http://digitalcommons.unl.edu/do/oai/
oai:digitalcommons.unl.edu:chemengmaterials-1000
2006-10-31T17:46:22Z
publication:cbmesaraf
publication:chemicalengineer
publication:cbmefaculty
publication:chemengmaterials
Direct Measurement of Ion Accumulation at the Electrode Electrolyte Interface under an Oscillatory Electric Field
Saraf, Dr.Ravi
The ionic charge accumulation at the metal-electrolyte interface is directly measured by using differential interferometry as a function of magnitude and frequency (2-50 kHz) of extemal electric field. The technique developed probes the ion dynamics confined to the electrical double layer. The amplitude of modulation of the ions is linearly proportional to the amplitude of applied potential. The linearity is observed up to high electrode potentials and salt concentrations. The frequency response of the ion dynamics at the interface is interpreted in terms of the classical RC model.
2006-04-12T07:00:00Z
text
https://digitalcommons.unl.edu/chemengmaterials/1
Papers in Materials Science
DigitalCommons@University of Nebraska - Lincoln
Materials Science and Engineering
oai:digitalcommons.unl.edu:chemengmaterials-1002
2007-01-10T19:20:46Z
publication:cbmesaraf
publication:chemengsingh
publication:chemicalengineer
publication:cbmefaculty
publication:chemengmaterials
publication:chemeng_researchpub
Optical Properties of an Immobilized DNA Monolayer from 255 to 700 nm
Saraf, Dr.Ravi F.
Singh, Gaurav
Elhadj, Selim
The real (n) and imaginary (k) refractive indices of an immobilized monolayer of 27 nucleotide (nt) single stranded DNA (ssDNA) and the corresponding double stranded DNA (dsDNA) are measured in the 255- 700 nm range. Multiple techniques are used to obtain consistent estimation. The coverage is 6.5% with an average interchain distance of tethered ssDNA molecules of 11.8 nm, which is significantly larger than the “footprint” of the chain on the surface. The measured increase in n by 5% between the ssDNA and the dsDNA is 20% smaller than the expected change due to doubling of the molecular weight. The change in k is not significant, indicating that the electron delocalization effect expected in dsDNA due to base pair stacking is not important at optical frequencies.
2004-02-09T08:00:00Z
text
https://digitalcommons.unl.edu/chemengmaterials/3
Papers in Materials Science
DigitalCommons@University of Nebraska - Lincoln
refractive indices
immobilized monolayer
nucleotide
DNA
optical frequencies.
Materials Science and Engineering
oai:digitalcommons.unl.edu:chemengmaterials-1001
2007-01-10T19:11:07Z
publication:cbmesaraf
publication:chemicalengineer
publication:cbmefaculty
publication:chemengmaterials
Near Surface Structure of Solvent-free Processed Polyimide Thin Film
Saraf, Ravi F.
Dimitrakopoulos, Christos
Toney, Michael F.
Kowalczyk, Steven P.
The surface structure of solvent-free processed poly(pyromellitic dianhydride-oxydianiline) PMDAODA is probed using grazing incidence X-ray scattering (GIXS). The films are cured below the (bulk) glass transition temperature of the polyimide. The surface-influenced ordering in the top 10 nm of the film is comparable to that of films which were cast and cured from polymeric precursor solutions in a polar solvent that complexed prior to the conversion to polyimide (PI). This shows that the surface effects are the dominant force to influence the near surface ordering. The crystal orientation closer to the surface has more fiber texture with the b-axis perpendicular to the surface and the a- and c-axes randomly oriented in the film plane. Line shape analysis as a function of X-ray penetration depth and changes in the unit cell dimensions suggests that the distortion is at the ether linkage of theODAunit. The decrease in crystal distortion and amorphous halo peaks relative to crystalline peaks, as penetration depth decreases, shows that both the quality and quantity of the order improves closer to the air/PI interface.
1995-09-27T07:00:00Z
text
https://digitalcommons.unl.edu/chemengmaterials/2
Papers in Materials Science
DigitalCommons@University of Nebraska - Lincoln
X-ray Optics
PMDA-ODA
helix conformation
Materials Science and Engineering