6 research outputs found
Rhodium-Catalyzed Oxygenative [2 + 2] Cycloaddition of Terminal Alkynes and Imines for the Synthesis of β‑Lactams
A rhodium-catalyzed
oxygenative [2 + 2] cycloaddition of terminal alkynes and imines has
been developed, which gives β-lactams as products with high <i>trans</i> diastereoselectivity. In the presence of a RhÂ(I) catalyst
and 4-picoline <i>N</i>-oxide, a terminal alkyne is converted
to a rhodium ketene species via oxidation of a vinylidene complex
and subsequently undergoes a [2 + 2] cycloaddition with an imine to
give rise to the 2-azetidinone ring system. Mechanistic studies suggest
that the reaction proceeds through a metalloketene rather than free
ketene intermediate. The new method taking advantage of catalytic
generation of a ketene species directly from a terminal alkyne provides
a novel and efficient entry to the Staudinger synthesis of β-lactams
under mild conditions
Genetically Programmed Clusters of Gold Nanoparticles for Cancer Cell-Targeted Photothermal Therapy
Interpretations
of the interactions of nanocarriers with biological
cells are often complicated by complex synthesis of materials, broad
size distribution, and heterogeneous surface chemistry. Herein, the
major capsid proteins of an icosahedral T7 phage (55 nm in diameter)
are genetically engineered to display a gold-binding peptide and a
prostate cancer cell-binding peptide in a tandem sequence. The genetically
modified phage attracts gold nanoparticles (AuNPs) to form a cluster
of gold nanoparticles (about 70 nanoparticles per phage). The cluster
of AuNPs maintains cell-targeting functionality and exhibits excellent
dispersion stability in serum. Under a very low light irradiation
(60 mW cm<sup>–2</sup>), only targeted AuNP clusters kill the
prostate cancer cells in minutes (not in other cell types), whereas
neither nontargeted AuNP clusters nor citrate-stabilized AuNPs cause
any significant cell death. The result suggests that the prostate
cancer cell-targeted clusters of AuNPs are targeted to only prostate
cancer cells and, when illuminated, generate local heating to more
efficiently and selectively kill the targeted cancer cells. Our strategy
can be generalized to target other types of cells and assemble other
kinds of nanoparticles for a broad range of applications
Bioinspired Design of an Immobilization Interface for Highly Stable, Recyclable Nanosized Catalysts
Immobilization
of nanometer-sized metal catalysts into porous substrates
can stabilize the catalysts and allow their recycled uses, while immobilization
often sacrifices the active surface of catalysts and degenerates the
local microenvironments, resulting in the reduction of the catalytic
activity. To maintain a high activity of immobilized nanocatalysts,
it is critically important to design an interface that minimizes the
contact area and favors reaction chemistry. Here we report on the
application of mussel-inspired adhesion chemistry to the formation
of catalytic metal nanocrystal–polydopamine hybrid materials
that exhibit a high catalytic efficiency during recycled uses. Electrospun
polymer nanofibers are used as a template for in situ formation and
immobilization of gold nanoparticles via polydopamine-induced reduction
of ionic precursors. The prepared hybrid nanostructures exhibit a
recyclable catalytic activity for the reduction of 4-nitrophenol with
a turnover frequency of 3.2–5.1 μmol g<sup>–1</sup> min<sup>–1</sup>. Repeated uses of the hybrid nanostructures
do not significantly alter their morphology, indicating the excellent
structural stability of the hybrid nanostructures. We expect that
the polydopamine chemistry combined with the on-surface synthesis
of catalytic nanocrystals is a promising route to the immobilization
of various colloidal nanosized catalysts on supporting substrates
for long-term catalysis without the physical instability problem
Virus-Directed Design of a Flexible BaTiO<sub>3</sub> Nanogenerator
Biotemplated synthesis of functional nanomaterials has received increasing attention for applications in energy, catalysis, bioimaging, and other technologies. This approach is justified by the unique abilities of biological systems to guide sophisticated assembly and organization of molecules and materials into distinctive nanoscale morphologies that exhibit physicochemical properties highly desirable for specific purposes. Here, we present a high-performance, flexible nanogenerator using anisotropic BaTiO<sub>3</sub> (BTO) nanocrystals synthesized on an M13 viral template through the genetically programmed self-assembly of metal ion precursors. The filamentous viral template realizes the formation of a highly entangled, well-dispersed network of anisotropic BTO nanostructures with high crystallinity and piezoelectricity. Even without the use of additional structural stabilizers, our virus-enabled flexible nanogenerator exhibits a high electrical output up to ∼300 nA and ∼6 V, indicating the importance of nanoscale structures for device performances. This study shows the biotemplating approach as a facile method to design and fabricate nanoscale materials particularly suitable for flexible energy harvesting applications
Virus-Directed Design of a Flexible BaTiO<sub>3</sub> Nanogenerator
Biotemplated synthesis of functional nanomaterials has received increasing attention for applications in energy, catalysis, bioimaging, and other technologies. This approach is justified by the unique abilities of biological systems to guide sophisticated assembly and organization of molecules and materials into distinctive nanoscale morphologies that exhibit physicochemical properties highly desirable for specific purposes. Here, we present a high-performance, flexible nanogenerator using anisotropic BaTiO<sub>3</sub> (BTO) nanocrystals synthesized on an M13 viral template through the genetically programmed self-assembly of metal ion precursors. The filamentous viral template realizes the formation of a highly entangled, well-dispersed network of anisotropic BTO nanostructures with high crystallinity and piezoelectricity. Even without the use of additional structural stabilizers, our virus-enabled flexible nanogenerator exhibits a high electrical output up to ∼300 nA and ∼6 V, indicating the importance of nanoscale structures for device performances. This study shows the biotemplating approach as a facile method to design and fabricate nanoscale materials particularly suitable for flexible energy harvesting applications
Virus-Directed Design of a Flexible BaTiO<sub>3</sub> Nanogenerator
Biotemplated synthesis of functional nanomaterials has received increasing attention for applications in energy, catalysis, bioimaging, and other technologies. This approach is justified by the unique abilities of biological systems to guide sophisticated assembly and organization of molecules and materials into distinctive nanoscale morphologies that exhibit physicochemical properties highly desirable for specific purposes. Here, we present a high-performance, flexible nanogenerator using anisotropic BaTiO<sub>3</sub> (BTO) nanocrystals synthesized on an M13 viral template through the genetically programmed self-assembly of metal ion precursors. The filamentous viral template realizes the formation of a highly entangled, well-dispersed network of anisotropic BTO nanostructures with high crystallinity and piezoelectricity. Even without the use of additional structural stabilizers, our virus-enabled flexible nanogenerator exhibits a high electrical output up to ∼300 nA and ∼6 V, indicating the importance of nanoscale structures for device performances. This study shows the biotemplating approach as a facile method to design and fabricate nanoscale materials particularly suitable for flexible energy harvesting applications