13 research outputs found
Entrapment and condensation of DNA in neutral reverse micelles.
DNA condensation and compaction is induced by a variety of condensing agents such as polycations. The present study analyzed the structure of plasmid DNA (DNA) in the small inner space of reverse micelles formed from nonionic surfactants (isotropic phase). Spectroscopic studies indicated that DNA was dissolved in an organic solvent in the presence of a neutral detergent. Fluorescent quenching of ethidium bromide and of rhodamine covalently attached to DNA suggested that the DNA within neutral, reverse micelles was condensed. Circular dichroism indicated that the DNA structure was C form (member of B family) and not the dehydrated A form. Concordantly, NMR experiments indicated that the reverse micelles contained a pool of free water, even at a ratio of water to surfactant (Wo) of 3.75. Electron microscopic analysis also indicated that the DNA was in a ring-like structure, probably toroids. Atomic force microscopic images also revealed small, compact particles after the condensed DNA structures were preserved using an innovative cross-linking strategy. In the lamellar phase, the DNA was configured in long strands that were 20 nm in diameter. Interestingly, such DNA structures, reminiscent of "nanowires," have apparently not been previously observed
Rapidly Reversible Hydrophobization: An Approach to High First-Pass Drug Extraction
SummaryWe have investigated a rapidly reversible hydrophobization of therapeutic agents for improving first-pass uptake in locoregional drug therapy. This approach involves the attachment of a hydrophobic moiety to the drug by highly labile chemical linkages that rapidly hydrolyze upon injection. Hydrophobization drastically enhances cell-membrane association of the prodrug and, consequently, drug uptake, while the rapid lability protects nontargeted tissues from exposure to the highly active agent. Using the membrane-impermeable DNA intercalator propidium iodide, and melphalan, we report results from in vitro cellular internalization and toxicity studies. Additionally, we report in vivo results after a single liver arterial bolus injection, demonstrating both tumor targeting and increased survival in a mouse tumor model
Thermoactivated Electrical Conductivity in Perylene Diimide Nanofiber Materials
Thermoactivated
electrical conductivity has been studied on nanofibers
fabricated from the derivatives of perylene tetracarboxylic diimide
(PTCDI) both in the dark and under visible light illumination. The
activation energy obtained for the nanofibers fabricated from donor–acceptor
(D–A) PTCDIs are higher than that for symmetric <i>n</i>-dodecyl substituted PTCDI. Such difference originates from the strong
dependence of thermoactivated charge hopping on material disorder,
which herein is dominated by the D–A charge-transfer and dipole–dipole
interactions between stacked molecules. When the nanofibers were heated
above the first phase transition temperature (around 85 °C),
the activation energy was significantly increased because of the thermally
enhanced polaronic effect. Moreover, charge carrier density can be
increased in the D–A nanofibers under visible light illumination.
Consistent with the theoretical models in the literature, the increased
charge carrier density did cause decrease in the activation energy
due to the up-shifting of Fermi level closer to the conduction band
edge
Donor–Acceptor Supramolecular Organic Nanofibers as Visible-Light Photoelectrocatalysts for Hydrogen Production
Perylene
tetracarboxylic diimide (PTCDI) derivatives have been extensively
studied for one-dimensional (1D) self-assembled systems and for applications
in photocatalysis. Herein, we constructed a PTCDI-based donor–acceptor
(D–A) supramolecular system via in situ self-assembly on an
indium tin oxide conductive glass surface. The self-assembled PTCDI
nanostructures exhibit well-defined nanofibril morphologies and strong
photocurrents. Interestingly, a strong and reversible electrochromic
color change was observed during cyclic voltammetry. The color of
the nanofibers changed from red to blue and then to violet as the
reduction progressed to the radical anion and then to the dianion.
This series of one-electron reductions was confirmed by UV absorption,
electron paramagnetic resonance spectroscopy, and hydrazine reduction.
Most importantly, these PTCDI nanofibers exhibit efficient photoelectrocatalytic
hydrogen production with remarkable stability under xenon lamp illumination
(λ ≥ 420 nm). Among the three nanofibers prepared, the
fibers assembled from PTCDI molecule <b>2</b> were found to
be the most effective catalyst with 30% Faradaic efficiency. In addition,
the nanofibers produced hydrogen at a steady-state for more than 8
h and produced repeatable results in 3 consecutive testing cycles,
giving them great potential for practical industrial applications.
Under an applied bias voltage, the 1D intermolecular stacking along
the long axis of the nanofibers affords efficient separation and migration
of photogenerated charge carriers, which play a crucial role in the
photoelectrocatalytic process. As a proof-of-concept, the D–A-structured
PTCDI nanofibers presented herein may guide future research on photoelectrocatalysis
based on self-assembled supramolecular systems by providing more options
for material design of the catalysts to achieve greater efficiencies
Donor–Acceptor Supramolecular Organic Nanofibers as Visible-Light Photoelectrocatalysts for Hydrogen Production
Perylene
tetracarboxylic diimide (PTCDI) derivatives have been extensively
studied for one-dimensional (1D) self-assembled systems and for applications
in photocatalysis. Herein, we constructed a PTCDI-based donor–acceptor
(D–A) supramolecular system via in situ self-assembly on an
indium tin oxide conductive glass surface. The self-assembled PTCDI
nanostructures exhibit well-defined nanofibril morphologies and strong
photocurrents. Interestingly, a strong and reversible electrochromic
color change was observed during cyclic voltammetry. The color of
the nanofibers changed from red to blue and then to violet as the
reduction progressed to the radical anion and then to the dianion.
This series of one-electron reductions was confirmed by UV absorption,
electron paramagnetic resonance spectroscopy, and hydrazine reduction.
Most importantly, these PTCDI nanofibers exhibit efficient photoelectrocatalytic
hydrogen production with remarkable stability under xenon lamp illumination
(λ ≥ 420 nm). Among the three nanofibers prepared, the
fibers assembled from PTCDI molecule <b>2</b> were found to
be the most effective catalyst with 30% Faradaic efficiency. In addition,
the nanofibers produced hydrogen at a steady-state for more than 8
h and produced repeatable results in 3 consecutive testing cycles,
giving them great potential for practical industrial applications.
Under an applied bias voltage, the 1D intermolecular stacking along
the long axis of the nanofibers affords efficient separation and migration
of photogenerated charge carriers, which play a crucial role in the
photoelectrocatalytic process. As a proof-of-concept, the D–A-structured
PTCDI nanofibers presented herein may guide future research on photoelectrocatalysis
based on self-assembled supramolecular systems by providing more options
for material design of the catalysts to achieve greater efficiencies
Donor–Acceptor Supramolecular Organic Nanofibers as Visible-Light Photoelectrocatalysts for Hydrogen Production
Perylene
tetracarboxylic diimide (PTCDI) derivatives have been extensively
studied for one-dimensional (1D) self-assembled systems and for applications
in photocatalysis. Herein, we constructed a PTCDI-based donor–acceptor
(D–A) supramolecular system via in situ self-assembly on an
indium tin oxide conductive glass surface. The self-assembled PTCDI
nanostructures exhibit well-defined nanofibril morphologies and strong
photocurrents. Interestingly, a strong and reversible electrochromic
color change was observed during cyclic voltammetry. The color of
the nanofibers changed from red to blue and then to violet as the
reduction progressed to the radical anion and then to the dianion.
This series of one-electron reductions was confirmed by UV absorption,
electron paramagnetic resonance spectroscopy, and hydrazine reduction.
Most importantly, these PTCDI nanofibers exhibit efficient photoelectrocatalytic
hydrogen production with remarkable stability under xenon lamp illumination
(λ ≥ 420 nm). Among the three nanofibers prepared, the
fibers assembled from PTCDI molecule <b>2</b> were found to
be the most effective catalyst with 30% Faradaic efficiency. In addition,
the nanofibers produced hydrogen at a steady-state for more than 8
h and produced repeatable results in 3 consecutive testing cycles,
giving them great potential for practical industrial applications.
Under an applied bias voltage, the 1D intermolecular stacking along
the long axis of the nanofibers affords efficient separation and migration
of photogenerated charge carriers, which play a crucial role in the
photoelectrocatalytic process. As a proof-of-concept, the D–A-structured
PTCDI nanofibers presented herein may guide future research on photoelectrocatalysis
based on self-assembled supramolecular systems by providing more options
for material design of the catalysts to achieve greater efficiencies
Chemical Self-Doping of Organic Nanoribbons for High Conductivity and Potential Application as Chemiresistive Sensor
Intrinsically low electrical conductivity
of organic semiconductors hinders their further development into practical
electronic devices. Herein, we report on an efficient chemical self-doping
to increase the conductivity through one-dimensional stacking arrangement
of electron donor–acceptor (D–A) molecules. The D–A
molecule employed was a 1-methylpiperidine-substituted perylene tetracarboxylic
diimide (MP-PTCDI), of which the methylpiperidine moiety is a strong
electron donor, and can form a charge transfer complex with PTCDI
(acting as the acceptor), generating anionic radical of PTCDI as evidenced
in molecular solutions. Upon self-assembling into nanoribbons through
columnar π–π stacking, the intermolecular charge
transfer interaction between methylpiperidine and PTCDI would be enhanced,
and the electrons generated are delocalized along the π–π
stacking of PTCDIs, leading to enhancement in conductivity. The conductive
fiber materials thus produced can potentially be used as chemiresistive
sensor for vapor detection of electron deficient chemicals such as
hydrogen peroxide, taking advantage of the large surface area of nanofibers.
As a major component of improvised explosives, hydrogen peroxide remains
a critical signature chemical for public safety screening and monitoring
Donor–Acceptor Supramolecular Organic Nanofibers as Visible-Light Photoelectrocatalysts for Hydrogen Production
Perylene
tetracarboxylic diimide (PTCDI) derivatives have been extensively
studied for one-dimensional (1D) self-assembled systems and for applications
in photocatalysis. Herein, we constructed a PTCDI-based donor–acceptor
(D–A) supramolecular system via in situ self-assembly on an
indium tin oxide conductive glass surface. The self-assembled PTCDI
nanostructures exhibit well-defined nanofibril morphologies and strong
photocurrents. Interestingly, a strong and reversible electrochromic
color change was observed during cyclic voltammetry. The color of
the nanofibers changed from red to blue and then to violet as the
reduction progressed to the radical anion and then to the dianion.
This series of one-electron reductions was confirmed by UV absorption,
electron paramagnetic resonance spectroscopy, and hydrazine reduction.
Most importantly, these PTCDI nanofibers exhibit efficient photoelectrocatalytic
hydrogen production with remarkable stability under xenon lamp illumination
(λ ≥ 420 nm). Among the three nanofibers prepared, the
fibers assembled from PTCDI molecule <b>2</b> were found to
be the most effective catalyst with 30% Faradaic efficiency. In addition,
the nanofibers produced hydrogen at a steady-state for more than 8
h and produced repeatable results in 3 consecutive testing cycles,
giving them great potential for practical industrial applications.
Under an applied bias voltage, the 1D intermolecular stacking along
the long axis of the nanofibers affords efficient separation and migration
of photogenerated charge carriers, which play a crucial role in the
photoelectrocatalytic process. As a proof-of-concept, the D–A-structured
PTCDI nanofibers presented herein may guide future research on photoelectrocatalysis
based on self-assembled supramolecular systems by providing more options
for material design of the catalysts to achieve greater efficiencies