6 research outputs found
Self-Assembly of a Diblock Copolymer with Pendant Disulfide Bonds and Chromophore Groups: A New Platform for Fast Release
An amphiphilic block copolymer comprising polyÂ(ethylene
glycol)
(PEG) and polyÂ(2-(methacryloyl)Âoxyethyl-2′-hydroxyethyl disulfide)
(PMAOHD) blocks was synthesized by atom transfer radical polymerization
(ATRP). Pyrenebutyric acid was conjugated to the block copolymer by
esterification, and a block copolymer with pendant disulfide bonds
and pyrenyl groups (PEG-<i>b</i>-PÂ(MAOHD-<i>g</i>-Py)) was obtained. <sup>1</sup>H NMR and gel permeation chromatography
(GPC) results demonstrated the successful synthesis of the block copolymer.
The cleavage of the disulfide bonds and the degrafting of the pyrenyl
groups were investigated in THF and a THF/methanol mixture. Fluorescence
spectroscopy, GPC, and <sup>1</sup>H NMR results demonstrated fast
cleavage of the disulfide bonds by Bu<sub>3</sub>P in THF. Fluorescence
results showed the ratio of the intensity of the excimer peak to the
monomer peak decreased rapidly within 20 min. GPC traces of the block
copolymer moved to a long retention time region after addition of
Bu<sub>3</sub>P, indicating the cleavage of the disulfide bonds and
the degrafting of the pyrenyl groups. PEG-<i>b</i>-PÂ(MAOHD-<i>g</i>-Py) can self-assemble into micelles with polyÂ(MAOHD-<i>g</i>-Py) cores and PEG coronae in a mixture of methanol and
THF (9:1 by volume). The dissociation of the micelles in the presence
of Bu<sub>3</sub>P was investigated. After cleavage of the disulfide
bonds in the micellar cores, a pyrene-containing small molecular compound
and a block copolymer with pendant thiol groups were produced. Transmission
electron microscopy (TEM), dynamic light scattering (DLS), and <sup>1</sup>H NMR were employed to track the dissociation of the polymeric
micelles. All the techniques demonstrated the dissociation of the
micelles and the fast release of pyrenyl groups from the micelles
Stimuli-Responsive Polypropylene for the Sustained Delivery of TPGS and Interaction with Erythrocytes
Hemocompatibility and oxidative stress are significant for blood-contacting
devices. In this study, <i>N</i>-isopropylacrylamide (NIPAAm)
and <i>N</i>-(3-aminopropyl)Âmethacrylamide hydrochloride
(APMA) were cografted on polypropylene (PP) membrane using ultraviolet
grafting to load antioxidative d-α-tocopheryl polyethylene
glycol 1000 succinate (TPGS) and control the release of TPGS. The
immobilization of NIPAAm and APMA onto PP membrane was confirmed by
attenuated total reflectance Fourier-transform infrared spectroscopy
and X-ray photoelectron spectroscopy. Combined with data from platelet
adhesion, red blood cell (RBC) attachment, and hemolysis rate, the
hemocompatibility of PP was significantly improved. An in-depth characterization
using hemolysis rate test, scanning electron microscopy, atomic force
microscopy, and confocal laser scanning microscopy was conducted to
confirm that the mechanism of the release of TPGS interacted with
RBCs was different at different stages. The release of TPGS from the
loading PP membranes affected hemolysis at different stages. At the
early stage of release, TPGS maintained the tiny (nanometer-sized)
tubers on the membrane surface and enhanced the membrane permeabilization
by generating nanosized pores on the cell membranes. Afterward, the
incorporated TPGS slowed the lipid peroxidation of erythrocytes and
filled in the lipid bilayer of erythrocyte to prevent hemolysis. Thus,
the approach implemented to graft NIPAAm and APMA and load TPGS was
suitable to develop medical device with excellent hemocompatibility
and antioxidative property
Fabrication of a Detection Platform with Boronic-Acid-Containing Zwitterionic Polymer Brush
Development of technologies for biomedical
detection platform is critical to meet the global challenges of various
disease diagnoses, especially for point-of-use applications. Because
of its natural simplicity, effectiveness, and easy repeatability,
random covalent-binding technique is widely adopted in antibody immobilization.
However, its antigen-binding capacity is relatively low when compared
to site-specific immobilization of antibody. Herein, we report that
a detection platform modified with boronic acid (BA)-containing sulfobetaine-based
polymer brush. Mainly because of the advantage of oriented immobilization
of antibody endowed with BA-containing three-dimensional polymer brush
architecture, the platform had a high antigen-binding capacity. Notably,
nonspecific protein adsorption was also suppressed by the zwitterionic
pendants, thus greatly enhanced signal-to-noise (S/N) values for antigen
recognition. Furthermore, antibodies captured by BA pendants could
be released in dissociation media. This new platform is promising
for potential applications in immunoassays
Effect of a Long Alkyl Group on Cyclopentadithiophene as a Conjugated Bridge for D–A−π–A Organic Sensitizers: IPCE, Electron Diffusion Length, and Charge Recombination
The
option of using conjugated π-linkers is critical for rational
molecular design toward an energy-level strategy for organic sensitizers.
To further optimize photovoltaic performance, methyl- and octyl-substituted
4<i>H</i>-cyclopentaÂ[2,1-<i>b</i>:3,4-<i>b</i>′]Âdithiophene (CPDT) are introduced into D–A−π–A
featured sensitizers. Along with CPDT, instead of thiophene as conjugated
bridge, <b>WS-39</b> and <b>WS-43</b> exhibit an extended
spectral response due to the excellent conjugation and coplanarity
of CPDT. Specifically, we focused on the critical effect of length
of the alkyl group linked to the bridging carbon atoms of CPDT on
the photovoltaic performances. Octyl-substituted <b>WS-39</b> shows a broader IPCE onset with an enhanced photovoltage relative
to the analogue <b>WS-5</b>. In contrast, <b>WS-43</b>, with methyl substituted on the CPDT moiety, presents a relatively
low quantum conversion efficiency within the whole spectral response
region, along with low photocurrent density. <b>WS-43</b> displays
a distinctly low IPCE platform, predominately arising from the short
electron diffusion length with significant electron loss during the
electron transport. The relative movement of the conduction band edge
(<i>E</i><sub>CB</sub>) and charge transfer resistance as
well as lifetime of injected electrons are studied in detail. Under
standard AM 1.5 conditions, <b>WS-39</b>-based solar cells show
a promising photovoltaic efficiency of 9.07% (<i>J</i><sub>SC</sub> = 16.61 mA cm<sup>–2</sup>, <i>V</i><sub>OC</sub> = 770 mV, FF = 0.71). The octyl chains attached on CPDT
can provide <i>dual protection</i> and exhibit a high propensity
to prevent binding of the iodide–triiodide redox couple, producing
an efficient shielding effect to retard the charge recombination and
resulting in improvement of <i>V</i><sub>OC</sub>. Our research
paves the way to explore more efficient sensitizers through ingenious
molecular engineering
Porphyrin Cosensitization for a Photovoltaic Efficiency of 11.5%: A Record for Non-Ruthenium Solar Cells Based on Iodine Electrolyte
Dye-sensitized
solar cells (DSSCs) are promising for utilizing
solar energy. To achieve high efficiencies, it is vital to synergistically
improve the photocurrent (<i>J</i><sub>sc</sub>) and the
photovoltage (<i>V</i><sub>oc</sub>). In this respect, conjugation
framework extension and cosensitization are effective for improving
the absorption and the <i>J</i><sub>sc</sub>, which, however,
is usually accompanied by undesirably decreased <i>V</i><sub>oc</sub>. Herein, based on a rationally optimized porphyrin
dye, we develop a targeted coadsorption/cosensitization approach for
systematically improving the <i>V</i><sub>oc</sub> from
645 to 727, 746, and 760 mV, with synergistical <i>J</i><sub>sc</sub> enhancement from 18.83 to 20.33 mA cm<sup>–2</sup>. Thus, the efficiency has been dramatically enhanced to 11.5%, which
keeps the record for nonruthenium DSSCs using the I<sub>2</sub>/I<sub>3</sub><sup>–</sup> electrolyte. These results compose an
alternative approach for developing highly efficient DSSCs with relatively
high <i>V</i><sub>oc</sub> using traditional iodine electrolyte
Rational Molecular Engineering of Indoline-Based D‑A-π‑A Organic Sensitizers for Long-Wavelength-Responsive Dye-Sensitized Solar Cells
Indoline-based
D-A-Ï€-A organic sensitizers are promising candidates for highly
efficient and long-term stable dye-sensitized solar cells (DSSCs).
In order to further broaden the spectral response of the known indoline
dye <b>WS-2</b>, we rationally engineer the molecular structure
through enhancing the electron donor and extending the π-bridge,
resulting in two novel indoline-based D-A-Ï€-A organic sensitizers <b>WS-92</b> and <b>WS-95</b>. By replacing the 4-methylphenyl
group on the indoline donor of <b>WS-2</b> with a more electron-rich
carbazole unit, the intramolecular charge transfer (ICT) absorption
band of dye <b>WS-92</b> is slightly red-shifted from 550 nm
(<b>WS-2</b>) to 554 nm (<b>WS-92</b>). In comparison,
the incorporation of a larger π-bridge of cyclopentadithiophene
(CPDT) unit in dye <b>WS-95</b> not only greatly bathochromatically
tunes the absorption band to 574 nm but also largely enhances the
molar extinction coefficients (ε), thus dramatically improving
the light-harvesting capability. Under the standard global AM 1.5
solar light condition, the photovoltaic performances of both organic
dyes have been evaluated in DSSCs on the basis of the iodide/triiodide
electrolyte without any coadsorbent or cosensitizer. The DSSCs based
on <b>WS-95</b> display better device performance with power
conversion efficiency (η) of 7.69%. The additional coadsorbent
in the dye bath of <b>WS-95</b> does not improve the photovoltaic
performance, indicative of its negligible dye aggregation, which can
be rationalized by the grafted dioctyl chains on the CPDT unit. The
cosensitization of <b>WS-95</b> with a short absorption wavelength
dye <b>S2</b> enhances the IPCE and improves the η to
9.18%. Our results indicate that extending the π-spacer is more
rational than enhancing the electron donor in terms of broadening
the spectral response of indoline-based D-A-Ï€-A organic sensitizers