Bifunctional catalysts that are highly active toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are attractive for efficient electrochemical water splitting. ...Herein, we report a bifunctional FeCoOOH nanosheet catalyst for highly efficient electrochemical water splitting in an alkaline electrolyte. The FeCoOOH nanosheet arrays were grown directly on the surface of a porous Ni foam by using a simple hydrothermal method. Because of their binary oxyhydroxide structure and high electrical conductivity intrinsic to direct growth, these FeCoOOH nanosheets exhibited excellent activities toward both the HER and OER. With the use of this bifunctional FeCoOOH catalyst, an alkaline water electrolyzer in a two‐electrode configuration achieved 10 mA cm−2 only at a cell voltage of 1.62 V without iR compensation in 1 m KOH, which outperformed that based on the combination of commercial IrO2 and Pt/C catalysts.
FeCoOOH nanosheet arrays were grown directly on the surface of a porous Ni foam by using a simple hydrothermal method. The FeCoOOH nanosheets exhibited excellent activities toward both the HER and OER. The water electrolyzer based on the FeCoOOH nanosheet catalyst outperformed one based on the combination of the commercial IrO2 and Pt/C catalysts.
In this study, GaP QDs were synthesized by a facile hot injection method. The optical properties such as absorption and PL emission were investigated and finely controlled by varying synthetic ...parameters such as surfactant loading, precursor composition, and fatty acid. The obtained GaP QDs were applied as a color conversion material on LED based devices.
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Group III–Ⅴ quantum dots (QDs) are preferred over Group Ⅱ–Ⅵ materials because of their relatively mild toxicity. In this study, a facile synthetic method to obtain gallium phosphide (GaP) QDs with color conversion performance is reported. Colloidal GaP QDs were produced via a hot-injection method using an optimized combination of precursors. The products showed controllable emissions from 400 to 520 nm, depending on the band gap. High photoluminescence (PL) quantum yields of 35–40% with a full width at half maximum (FWHM) of 75 nm were achieved in the green emission region. In addition, the green-emission GaP QDs were applied as a color-conversion material for optical devices with UV and blue LED chips. An average color conversion efficiency of 15% was achieved. This study demonstrates the possibility of using GaP QDs as a competitive color-conversion material.
In this article, nitrogen (N) doped porous carbon nanofibers (N-PCNF) were prepared by carbonization of polymer-silica nanocomposite precursor, and its application for heavy metal ion removal was ...demonstrated. Carbon–silica composite nanofibers were obtained by carbonization of electrospun polyacrylonitrile (PAN)-silica nanofiber composites. Subsequent selective etching of silica porogen produced porous carbon nanofibers (PCNF). It was revealed by surface characterization with X-ray photoelectron spectroscopy (XPS) that the surface of the PCNF was nitrogen-doped because N atom from cyanide group in PAN chains remained in the hexagonal carbon structure. The use of the obtained N-PCNF for heavy metal ion (Hg2+) removal was demonstrated using a simple adsorption test apparatus and 5, 10, 15, 20-tetraphenylporphine tetrasulfonic acid (TPPS) as an indicator. The N-PCNF showed a removal efficiency of 96 and 99% in 10 and 120 min, respectively, indicating a maximum heavy metal ion adsorption capacity at pH 7.0. In addition, heavy metal ion adsorption behavior was also analyzed using common adsorption isotherms. This article provides important information for future research activities regarding control over hazardous substances.
In this study, ultrasensitive and precise detection of a representative brain hormone, dopamine (DA), was demonstrated using functional conducting polymer nanotubes modified with aptamers. A ...high-performance aptasensor was composed of interdigitated microelectrodes (IMEs), carboxylated polypyrrole nanotubes (CPNTs) and DA-specific aptamers. The biosensors were constructed by sequential conjugation of CPNTs and aptamer molecules on the IMEs, and the substrate was integrated into a liquid-ion gating system surrounded by pH 7.4 buffer as an electrolyte. To confirm DA exocytosis based on aptasensors, DA sensitivity and selectivity were monitored using liquid-ion gated field-effect transistors (FETs). The minimum detection level (MDL; 100 pM) of the aptasensors was determined, and their MDL was optimized by controlling the diameter of the CPNTs owing to their different capacities for aptamer introduction. The MDL of CPNT aptasensors is sufficient for discriminating between healthy and unhealthy individuals because the total DA concentration in the blood of normal person is generally determined to be ca. 0.5 to 6.2 ng/mL (3.9 to 40.5 nM) by high-performance liquid chromatography (HPLC) (this information was obtained from a guidebook "Evidence-Based Medicine 2018 SCL " which was published by Seoul Clinical Laboratory). The CPNTs with the smaller diameters (CPNT2: ca. 120 nm) showed 100 times higher sensitivity and selectivity than the wider CPNTs (CPNT1: ca. 200 nm). Moreover, the aptasensors based on CPNTs had excellent DA discrimination in the presence of various neurotransmitters. Based on the excellent sensing properties of these aptasensors, the DA levels of exogeneous DA samples that were prepared from PC12 cells by a DA release assay were successfully measured by DA kits, and the aptasensor sensing properties were compared to those of standard DA reagents. Finally, the real-time response values to the various exogeneous DA release levels were similar to those of a standard DA aptasensor. Therefore, CPNT-based aptasensors provide efficient and rapid DA screening for neuron-mediated genetic diseases such as Parkinson's disease.
Large‐scale FET‐type graphene micropatten (GM) nano‐biohybrid‐based immunosensor (GMNS) is fabricated in a controlled fashion to detect human immunodeficiency virus 2 antibody. Flexible GMNS shows a ...highly sensitive response and excellent mechanical bendability. The flexible GMNS in fluidic systems also has a stable response. This is the first experimental demonstration of a large‐scale flexible fluidic FET‐type immunoassay based on GM nano‐biohybrids.
Fluorouracil (5-FU) has been the most widely used chemotherapy agent since its clinical introduction in 1957, and it continues to form the basis of treatment for various cancers. However, due to the ...side effects of an antimetabolite, a strategy fulfilling stringent requirements placed on a 5-FU delivery system requires controlled and extended release of 5-FU in a localized manner. Here, an in-situ gel-forming method for the preparation of micropatterned, α-chymotrypsin-degradable hydrogel (PHcd) for controlled release of 5-FU is introduced. More specifically, methacrylated hyaluronic acid (HA) and polyethylene glycol diacrylate (PEGDA), known for their excellent moisture retention capacity, are chosen for skin therapy. They are crosslinked with CYKC peptide through a thiol-ene click reaction. The synthesis of the CYKC peptide and its cleavage by α-chymotrypsin were confirmed using high-performance liquid chromatography (HPLC). Additionally, the in vitro release behavior was accurately monitored using the micropatterning method, demonstrating the stable immobilization and successful sustained release of 5-FU upon the addition of α-chymotrypsin in micropatterned PHcd hydrogel. Consequently, this micropatterned PHcd hydrogel can be considered a promising scaffold for localized and sustained delivery of cytotoxic drugs for skin cancer treatment.
A polymer-based nanofiber membrane with a high specific surface area, high porosity and abundant adsorption sites is demonstrated for selective trapping of radionuclides. The Prussian blue ...(PB)/poly(methyl methacrylate) (PMMA) nanofiber composites were successfully prepared through a one-step, single-nozzle electrospinning method. Various analytical techniques were used to examine the physical and chemical properties of PB nanoparticles and electrospun nanofibers. It is possible to enhance binding affinity and selectivity to radionuclide targets by incorporation of the PB nanoparticles into the polymer matrix. It is noteworthy that the maximum
Cs adsorption capacity of hte PB/PMMA nanofiber filter is approximately 28 times higher than that of bulk PB, and the removal efficiency is measured to be 95% at 1 ppm of
Cs. In addition, adsorption kinetics shows that the PB/PMMA nanofiber has a homogenous surface for adsorption, and all sites on the surface have equal adsorption energies in terms of ion-exchange between cyano groups of the introduced PB nanoparticles and radionuclides.
The influence of various nanoparticles with different dimension, density, dielectric constant, and surface property on electrohydrodynamic (EHD) instabilities of polymer/nanoparticle nanocomposite ...thin films was examined as a function of nanoparticle concentration. Transmission electron microscopy (TEM) images of polystyrene (PS)/nanoparticles (NPs) thin films demonstrated that all the nanoparticles were uniformly distributed in polymer matrix and the homogeneous dispersions of nanoparticles were not affected by thermal annealing above glass transition temperature. Optical microscopy (OM) observations indicated that thin films of polystyrene containing silica (SiO
2), gold (Au), cadmium selenide (CdSe), and titania (TiO
2) nanoparticles showed electrohydrodynamic instability patterns similar to those seen in pure polystyrene, up to 3
vol% nanoparticles. The presence of nanoparticles changed the dielectric constant of the thin films, which led to systematic variations in the wavelengths of the surface instabilities, which were consistent with calculated values. Cross-sectional transmission electron microscopy (TEM) images showed that migration or aggregation of the nanoparticles occurred only for silica contrary to other nanoparticles. This work points to a simple route to reduce the scale of final well-ordered columnar structures.
As the control over radioactive species becomes critical for the contemporary human life, the development of functional materials for decontamination of radioactive substances has also become ...important. In this work, a three-dimensional (3D) porous carbon monolith functionalized with Prussian blue particles was prepared through removal of colloidal silica particles from exfoliated graphene/silica composite precursors. The colloidal silica particles with a narrow size distribution were used to act a role of hard template and provide a sufficient surface area that could accommodate potentially hazardous radioactive substances by adsorption. The unique surface and pore structure of the functionalized porous carbon monolith was examined using electron microscopy and energy-dispersive X-ray analysis (EDS). The effective incorporation of PB nanoparticles was confirmed using diverse instrumentations such as X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). A nitrogen adsorption/desorption study showed that surface area and pore volume increased significantly compared with the starting precursor. Adsorption tests were performed with
Cs ions to examine adsorption isotherms using both Langmuir and Freundlich isotherms. In addition, adsorption kinetics were also investigated and parameters were calculated. The functionalized porous carbon monolith showed a relatively higher adsorption capacity than that of pristine porous carbon monolith and the bulk PB to most radioactive ions such as
Cs,
Rb,
Ba,
Sr,
Ce, and
Tl. This material can be used for decontamination in expanded application fields.
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