6 research outputs found
Understanding the Origin of Formation and Active Sites for Thiomolybdate [Mo<sub>3</sub>S<sub>13</sub>]<sup>2â</sup> Clusters as Hydrogen Evolution Catalyst through the Selective Control of Sulfur Atoms
[Mo<sub>3</sub>S<sub>13</sub>]<sup>2â</sup> clusters have
become known as one of the most efficient catalysts for the hydrogen
evolution reaction (HER) because most of the sulfur (S) atoms in the
cluster are exposed, resulting in many active sites. However, the
origin of the cluster formation and active S sites in the cluster
is unknown, hindering the development of efficient catalysts. Herein,
the mechanism of the transition from amorphous MoS<sub>3</sub> to
[Mo<sub>3</sub>S<sub>13</sub>]<sup>2â</sup> clusters is systematically
investigated. In addition, the active S sites have been identified
by the selective removal of S atoms via low-temperature heat treatment.
In summary, we believe that the clusters grow from amorphous MoS<sub>3</sub> with apical S atoms, and bridging S atoms are the active
HER sites in the [Mo<sub>3</sub>S<sub>13</sub>]<sup>2â</sup> clusters. The clusters deposited on carbon nanotubes exhibited good
electrochemical HER activity with a low onset potential of â96
mV, a Tafel slope of 40 mV/decade, and stability for 1000 cycles
Exposed Edge Planes of Cup-Stacked Carbon Nanotubes for an Electrochemical Capacitor
The end sites of graphitic planes and their catalytic, chemical, physical, and electrochemical roles have been a longstanding issue in the surface chemistry of carbon science. In this study, complete exposure of the active edge sites on the outer surface of catalytically grown cup-stacked carbon nanotubes is accomplished using a conventional exfoliation method, and its intrinsic contribution to the improvement of the electrochemical behavior in an electrochemical capacitor is demonstrated. The significant enhancement in the capacitance of the nanotubes after exfoliation, occurring without a distinctive change in pore structure, was confirmed with the exposure of the electrochemically active edge sites thus being able to accumulate more charge. Such active sites make nanotubes useful in the fabrication of high-performance electrochemical capacitors, catalysts, supporting materials for catalysts, and photocurrent generators in photochemical cells
Enhancement of Adsorption Performance for Organic Molecules by Combined Effect of Intermolecular Interaction and Morphology in Porous rGO-Incorporated Hydrogels
In
this study, we developed reduced graphene oxide (rGO)-incorporated
porous agarose (Ar-rGO) composites that were prepared via a âone-potâ
solâgel method involving a mixing and vacuum freeze-drying
process. These composites represent an easy-to-use adsorbent for organic
contaminant removal. Ar-rGOs can efficiently adsorb organic molecules,
especially aromatic organic compounds from wastewater, because of
the synergistic effect between the agarose bundles, which function
as a water absorption site, and the rGO sheets, which function as
active sites for pollutant binding. The pore structures and morphology
of the Ar-rGO composites varied according to the added rGO, resulting
in effective water infiltration into the composites. The main adsorption
mechanism of the aromatic organic compounds onto Ar-rGOs involved ÏâÏ
interactions with the rGO sheets. The surface interaction was more
effective for adsorbing/desorbing the aromatic pollutants than the
electrostatic interaction via the O-containing functional groups.
In addition, we confirmed that Ar-rGO is highly stable over the entire
pH range (1â13) because of the presence of the rGO sheets
Encapsulation and Enhanced Delivery of Topoisomerase I Inhibitors in Functionalized Carbon Nanotubes
The
topoisomerase I inhibitors SN-38 and camptothecin (CPT) have
shown potent anticancer activity, but water insolubility and metabolic
instability limits their clinical application. Utilizing carbon nanotubes
as a protective shell for water-insoluble SN-38 and CPT while maintaining
compatibility with aqueous media via a carboxylic acid-functionalized
surface can thus be a strategy to overcome this limitation. Through
hydrophobicâhydrophobic interactions, SN-38 and CPT were successfully
encapsulated in carboxylic acid functionalized single-walled carbon
nanotubes and dispersed in water. The resulting cell proliferation
inhibition and drug distribution profile inside the cells suggest
that these drug-encapsulated carbon nanotubes can serve as a promising
delivery strategy for water-insoluble anticancer drugs
Solid-Phase Synthesis of Peptide-Conjugated Perylene Diimide Bolaamphiphile and Its Application in Photodynamic Therapy
Here,
we describe a rapid and efficient synthetic method of peptide-conjugated
perylene diimide (P-PDI) using solid-phase peptide synthesis (SPPS).
Due to severe insolubility of perylene dianhydride (PDA) as a starting
material of perylene diimide (PDI), PDA was initially conjugated with
amino acids to obtain soluble PDI derivatives. Target peptides were
synthesized on a 2-chlorotrityl chloride resin using the SPPS method
and then conjugated with the amino acid-appended PDI. Various conditions
such as loading levels, reaction times and solvents were optimized
for introducing the peptides to both sides of the amino acid-appended
PDI. The final P-PDI was obtained with a maximum yield of 80% in 12
h. Its singlet oxygen-derived phototoxicity on cells was confirmed,
which could be applicable to photodynamic therapy
Defect-Assisted Heavily and Substitutionally Boron-Doped Thin Multiwalled Carbon Nanotubes Using High-Temperature Thermal Diffusion
Carbon nanotubes have shown great
potential as conductive fillers in various composites, macro-assembled
fibers, and transparent conductive films due to their superior electrical
conductivity. Here, we present an effective defect engineering strategy
for improving the intrinsic electrical conductivity of nanotube assemblies
by thermally incorporating a large number of boron atoms into substitutional
positions within the hexagonal framework of the tubes. It was confirmed
that the defects introduced after vacuum ultraviolet and nitrogen
plasma treatments facilitate the incorporation of a large number of
boron atoms (ca. 0.496 atomic %) occupying the trigonal sites on the
tube sidewalls during the boron doping process, thus eventually increasing
the electrical conductivity of the carbon nanotube film. Our approach
provides a potential solution for the industrial use of macro-structured
nanotube assemblies, where properties, such as high electrical conductance,
high transparency, and lightweight, are extremely important