Short-fragment Na-DNA dilute aqueous solutions: Fundamental length scales and screening

Tomić, Silvia; Babić, Sanja; Ivek, Tomislav; Vuletić, Tomislav; Krča, Sanja; Livolant, Françoise; Podgornik, Rudolf

doi:10.1209/0295-5075/81/68003

Cited by 18 publications

(19 citation statements)

References 18 publications

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“…Saline solutions were used for Tween surfactants and DNA, which denatures below a 100 mM threshold of counterions. 152 High salt concentrations have been shown to initiate SWNT flocculation, and could further impede direct comparison between suspensions produced using the ionic surfactants and Tween or DNA. 71 All tested ionic surfactants and DNA successfully suspended SWNTs, but the nonionic Tween series showed less predictable results.…”

Section: Recommended Swnt Dispersing Agentsmentioning

confidence: 99%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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Single-walled carbon nanotubes (SWNTs) are cylindrical graphitic molecules that have remained at the forefront of nanomaterials research since 1991, largely due to their exceptional and unusual mechanical, electrical, and optical properties. The motivation for understanding how nanotubes interact with light (i.e., SWNT photophysics) is both fundamental and applied. Individual nanotubes may someday be used as superior near-infrared fluorophores, biological tags and sensors, and components for ultrahigh-speed optical communications systems. Establishing an understanding of basic nanotube photophysics is intrinsically significant and should enable the rapid development of such innovations. Unlike conventional molecules, carbon nanotubes are synthesized as heterogeneous samples, composed of molecules with different diameters, chiralities, and lengths. Because a nanotube can be either metallic or semiconducting depending on its particular molecular structure, SWNT samples are also mixtures of conductors and semiconductors. Early progress in understanding the optical characteristics of SWNTs was limited because nanotubes aggregate when synthesized, causing a mixing of the energy states of different nanotube structures. Recently, significant improvements in sample preparation have made it possible to isolate individual nanotubes, enabling many advances in characterizing their optical properties. In this Account, single-molecule confocal microscopy and spectroscopy were implemented to study the fluorescence from individual nanotubes. Single-molecule measurements naturally circumvent the difficulties associated with SWNT sample inhomogeneities. Intrinsic SWNT photoluminescence has a simple narrow Lorentzian line shape and a polarization dependence, as expected for a one-dimensional system. Although the local environment heavily influences the optical transition wavelength and intensity, single nanotubes are exceptionally photostable. In fact, they have the unique characteristic that their single molecule fluorescence intensity remains constant over time; SWNTs do not “blink” or photobleach under ambient conditions. In addition, transient absorption spectroscopy was used to examine the relaxation dynamics of photoexcited nanotubes and to elucidate the nature of the SWNT excited state. For metallic SWNTs, very fast initial recovery times (300–500 fs) corresponded to excited-state relaxation. For semiconducting SWNTs, an additional slower decay component was observed (50–100 ps) that corresponded to electron–hole recombination. As the excitation intensity was increased, multiple electron–hole pairs were generated in the SWNT; however, these e−h pairs annihilated each other completely in under 3 ps. Studying the dynamics of this annihilation process revealed the lifetimes for one, two, and three e−h pairs, which further confirmed that the photoexcitation of SWNTs produces not free electrons but rather one-dimensional bound electron–hole pairs (i.e., excitons). In summary, nanotube photophysics is a rapidly developing area o...

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Section: Recommended Swnt Dispersing Agentsmentioning

confidence: 99%

Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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“…For the particular quantum dynamics of spacetime, for example, its value can be related not only to the Planck length but also, say, to a nonvanishing cosmological constant or to the vacuum energy density [6]. In the simplified context of quantum mechanics this quantity can even be treated as one of phenomenological, experimentally determined characteristics, say, of a condensed-matter system [7]. In parallel, in some more ambitious theoretical studies the introduction of a fundamental length constant is being based on a deeper principle like the stabilization requirement imposed upon relativistic algebra [8].…”

Section: Introductionmentioning

confidence: 99%

Fundamental length in quantum theories withPT-symmetric Hamiltonians

Znojil

2009

Phys. Rev. D

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“…Conductivity at 100 kHz shows a minimal influence from the electrode polarization effects, as well as from the conductivity chamber resonance at 100 MHz. Basically, one has to measure a spectrum [37], to be able to confidently extract conductivity values. Only in this manner, the obtained conductivity may be regarded as dc conductivity, the conductivity related to currents of freely mobile charges (polyions and free counterions) and not due to polarization currents.…”

Section: Conductometrymentioning

confidence: 99%

Manning free counterion fraction for a rodlike polyion: Aqueous solutions of short DNA fragments in presence of very low added salt

et al. 2011

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We quantified the Manning free (uncondensed) counterions fraction θ for dilute aqueous solutions of rodlike polyions: 150 bp DNA fragments, in the presence of a very low concentration of monovalent salt c(salt)<0.05 mM. Conductivity measurements of these solutions for DNA base pair concentration range 0.015≤c≤8 mM were complemented by fluorescence correlation spectroscopy (FCS) measurements of the DNA polyion diffusion coefficient D(p)(c). We observed a crossover in the normalized conductivity σ(c)/c that nearly halved across the c=0.05-1 mM range, while D(p)(c) remained rather constant, as we established by FCS. Analyzing these data we extracted θ(c)=0.30-0.45, and taking the Manning asymmetry field effect on polyelectrolyte conductivity into account we got θ(c)=0.40-0.60. We relate the θ(c) variation to gradual DNA denaturation occurring, in the very low salt environment, with the decrease in DNA concentration itself. The extremes of the experimental θ(c) range occur toward the highest, above 1 mM, and the lowest, below 0.05 mM, DNA concentrations and correspond to the theoretical θ values for dsDNA and ssDNA, respectively. Therefore, we confirmed Manning condensation and conductivity models to be valuable in description of dilute solutions of rodlike polyions.

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Short-fragment Na-DNA dilute aqueous solutions: Fundamental length scales and screening

Cited by 18 publications

References 18 publications

Photophysics of Individual Single-Walled Carbon Nanotubes

Photophysics of Individual Single-Walled Carbon Nanotubes

Fundamental length in quantum theories withPT-symmetric Hamiltonians

Manning free counterion fraction for a rodlike polyion: Aqueous solutions of short DNA fragments in presence of very low added salt

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