Effective photocatalysts and their surface engineering are essential for the efficient conversion of solar energy into chemical energy in photocatalyzed organic transformations. Herein, we report an ...effective approach for structuring Pd nanoparticles (NPs) on exfoliated 2H-WS2 nanosheets (WS2/PdNPs), resulting in hybrids with extraordinary photocatalytic activity in Suzuki reactions under visible light. Pd NPs of different sizes and densities, which can modulate the photocatalytic activity of the as-prepared WS2/PdNPs, were effectively structured on the basal plane of 2H-WS2 nanosheets via a sonic wave-assisted nucleation method without any reductants at room temperature. As the size of Pd NPs on WS2/PdNPs increased, their photocatalytic activity in Suzuki reactions at room temperature increased substantially. In addition, it was found that protic organic solvents play a crucial role in activating WS2/PdNPs catalysts in photocatalyzed Suzuki reactions, although these solvents are generally considered much less effective than polar aprotic ones in the conventional Suzuki reactions promoted by heterogeneous Pd catalysts. A mechanistic investigation suggested that photogenerated holes are transferred to protic organic solvents, whereas photogenerated electrons are transferred to Pd NPs. This transfer makes the Pd NPs electron-rich and accelerates the rate-determining step, i.e., the oxidative addition of aryl halides under visible light. WS2/PdNPs showed the highest turnover frequency (1244 h–1) for photocatalyzed Suzuki reactions among previously reported photocatalysts.
Designing artificial nanomaterials capable of selectively detecting targets without the use of expensive and fragile antibodies is of great interest in the applications of nanomedicine. Here, we show ...that the photoluminescence (PL) of graphene oxide (GO) was chemically modulated for the selective detection of a neurotransmitter without the use of antibodies. GO was functionalized with nitrotriacetic acid (NTA) on which four different metal ions were chelated (M-NTA-GO), which led to its different PL responses to neurotransmitters. In particular, the Cu-NTA-GO hybrid was able to selectively detect norepinephrine at nanomolar concentrations in a simple manner via its “turn-on” PL. Moreover, it was successfully applied to the selective detection of norepinephrine secreted from living PC-12 cells.
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Engineering of physical parameters such as shape and texture of microparticle can provide solutions to overcome limitations of conventional microparticles. We demonstrate the ...fabrication of uniform half-moon-shaped microparticles using synthesized poly(d,l-lactide) via a tube-type microfluidic approach. A true half-moon appearance, which comprises of dimple patterns on a round surface and a plain flat surface, is obtained by the optimization of fabrication conditions and a new self-rupturing mechanism. A new pop out mechanism allows for the one-pot synthesis of microparticles with complicated structures. The microparticles can have promising applications such as suspension cell culture, injectable cell carrier, and inhalable particulate drug delivery system because of their excellent cell adhesion, low weight resulting from an internal porous structure, and biodegradable character.
Semiconducting WS2 nanohybrids with different sizes of silver nanoparticles are designed via amine-assisted in situ reduction and growth of Ag(+) ions. These nanohybrids exhibit characteristic ...photocatalytic activity for the reduction of 4-nitrophenol as a function of their structure.
Supporting Pd on a metal oxide is an effective way to modulate its electronic structure to enhance its electrocatalytic activity in the oxygen reduction reaction (ORR). However, strong coupling ...between Pd and metal oxides typically requires high-temperature synthesis or annealing. Here, we report a mild and effective approach for synthesis of PdO nanoclusters coupled to WO3 nanosheets (PdO@WO3Sx) via direct conversion of metallic 1T-WS2 nanosheets into WO3 by spontaneous deposition of PdO onto the nanosheets in H2O at 50 °C for 1 h. Strong coupling in as-prepared PdO@WO3Sx was confirmed by observing shifts in binding energy compared to those of pure PdO and WO3. 1T-MoS2 nanosheets were partially converted into MoO3 in an analogous reaction to produce the hybrid MoSxO3 but in low yield due to preferential dissolution forming aqueous MoO42−. The hybrid PdO@WO3Sx exhibited higher half-wave potential (0.89 V vs. RHE) and limiting current density (−6.24 mA cm−2) in the ORR than both PdO@MoSxO3 and commercial Pt/C. In addition to its higher electrocatalytic activity, PdO@WO3Sx showed greater durability compared to Pt/C in the electrocatalytic activity during the continuous ORR. Computational simulations based on d-band center theory reveal that the d-band center of Pd in PdO@WO3Sx was upshifted to −2.57 eV, very close to that of Pt. This Pt-like d-band center of PdO@WO3Sx enabled its excellent electrocatalytic activity in the ORR. This work presents a facile approach to the synthesis of PdO hybrid catalysts and provides fundamental insight into their enhanced electrocatalytic activity for the ORR.
Sepsis is an aberrant systemic inflammatory response mediated by excessive production of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Developing an efficient antioxidant therapy ...for sepsis via scavenging ROS and RNS remains a big challenge owing to the insufficient activity and sustainability of conventional antioxidants. Herein, biocompatible transition-metal dichalcogenide antioxidants with excellent scavenging activity and sustainability for H2O2, O2 •–, OH•, and nitric oxide are developed for effective sepsis treatment. WS2, MoSe2, and WSe2 nanosheets exfoliated and functionalized with a biocompatible polymer effectively scavenge mitochondrial and intracellular ROS and RNS in inflammatory cells. Among the nanosheets, WS2 most efficiently suppresses the excessive secretion of inflammatory cytokines along with scavenging ROS and RNS without affecting the expression levels of the anti-inflammatory cytokine and ROS-producing enzymes. The WS2 nanosheets significantly improve the survival rate up to 90% for severely septic mice by reducing systemic inflammation. The pharmacokinetics suggests that the WS2 nanosheets can be excreted from mice 3 days after intravenous injection. This work demonstrates the potential of therapeutic nanosheet antioxidants for effective treatment of ROS and RNS-related diseases.
Supporting Pd on a metal oxide is an effective way to modulate its electronic structure to enhance its electrocatalytic activity in the oxygen reduction reaction (ORR). However, strong coupling ...between Pd and metal oxides typically requires high-temperature synthesis or annealing. Here, we report a mild and effective approach for synthesis of PdO nanoclusters coupled to WO
3
nanosheets (PdO@WO
3
S
x
)
via
direct conversion of metallic 1T-WS
2
nanosheets into WO
3
by spontaneous deposition of PdO onto the nanosheets in H
2
O at 50 °C for 1 h. Strong coupling in as-prepared PdO@WO
3
S
x
was confirmed by observing shifts in binding energy compared to those of pure PdO and WO
3
. 1T-MoS
2
nanosheets were partially converted into MoO
3
in an analogous reaction to produce the hybrid MoS
x
O
3
but in low yield due to preferential dissolution forming aqueous MoO
4
2−
. The hybrid PdO@WO
3
S
x
exhibited higher half-wave potential (0.89 V
vs.
RHE) and limiting current density (−6.24 mA cm
−2
) in the ORR than both PdO@MoS
x
O
3
and commercial Pt/C. In addition to its higher electrocatalytic activity, PdO@WO
3
S
x
showed greater durability compared to Pt/C in the electrocatalytic activity during the continuous ORR. Computational simulations based on d-band center theory reveal that the d-band center of Pd in PdO@WO
3
S
x
was upshifted to −2.57 eV, very close to that of Pt. This Pt-like d-band center of PdO@WO
3
S
x
enabled its excellent electrocatalytic activity in the ORR. This work presents a facile approach to the synthesis of PdO hybrid catalysts and provides fundamental insight into their enhanced electrocatalytic activity for the ORR.
The direct conversion of 1T-WS
2
into WO
3
nanosheets by spontaneous deposition of PdO nanoclusters produces a PdO@WO
3
S
x
electrocatalyst for the ORR.
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•PAA-WSe2 and PAA-MoSe2 nanosheets are prepared as narrow-spectrum antibiotics.•PAA-WSe2 exhibits strong bactericidal activity only for gram-positive bacteria.•PAA-MoSe2 exhibits ...species-specific bactericidal activity for S. aureus.•Their narrow-spectrum bactericidal mechanisms have been found.•PAA-WSe2 eradicates S. aureus in mice, showing a great therapeutic efficacy.
The abuse and misuse of broad-spectrum antibiotics cause drug resistance in bacteria, which compromises their benefits and thereby increases the demand for new bactericidal mechanisms to reduce the emergence of multidrug-resistant pathogenic bacteria. Herein, ultrathin WSe2 and MoSe2 nanosheets are exfoliated and functionalized with poly(acrylic acid) (PAA) (PAA-WSe2 and PAA-MoSe2) in an aqueous solution as narrow-spectrum or species-specific antibiotics for the treatment of bacterial infections. PAA-WSe2 nanosheets exhibit narrow-spectrum bactericidal activity with low minimum inhibitory concentrations only for gram-positive bacteria, including multidrug-resistant S. aureus, and PAA-MoSe2 displays species-specific antimicrobial activity against S. aureus without external stimuli. Mechanistic studies have revealed that the redox reactions of PAA-WSe2 nanosheets mediated by lipoteichoic acid of gram-positive bacteria to produce a more active element Se4+ are responsible for their narrow-spectrum bactericidal activity against gram-positive bacteria. Finally, the PAA-WSe2 nanosheets effectively eradicate the bacteria in S. aureus-infected mice, leading to excellent therapeutic efficacy in infected wounds. This strategy, based on narrow-spectrum transition metal dichalcogenide antibiotics, can provide an alternative route for the effective treatment of various bacterial infections.
Abstract Single‐walled carbon nanotubes (SWCNTs) are desirable nanoparticles for sensing biological analytes due to their photostability and intrinsic near‐infrared fluorescence. Previous strategies ...for generating SWCNT nanosensors have leveraged nonspecific adsorption of sensing modalities to the hydrophobic SWCNT surface that often require engineering new molecular recognition elements. An attractive alternate strategy is to leverage pre‐existing molecular recognition of proteins for analyte specificity, yet attaching proteins to SWCNT for nanosensor generation remains challenging. Toward this end, a generalizable platform is introduced to generate protein‐SWCNT‐based optical sensors and use this strategy to synthesize a hydrogen peroxide (H 2 O 2 ) nanosensor by covalently attaching horseradish peroxidase (HRP) to the SWCNT surface. A concentration‐dependent response is demonstrated to H 2 O 2 , confirming the nanosensor can image H 2 O 2 in real‐time, and assess the nanosensor's selectivity for H 2 O 2 against a panel of biologically relevant analytes. Taken together, these results demonstrate successful covalent attachment of enzymes to SWCNTs while preserving both intrinsic SWCNT fluorescence and enzyme function. It is anticipated this platform can be adapted to covalently attach other proteins of interest including other enzymes for sensing or antibodies for targeted imaging and cargo delivery.
Modulating the dimensions and phases of transition metal dichalcogenides is of great interest to enhance their intrinsic properties or to create new physicochemical properties. Herein, we report an ...effective approach to synthesize 2H-WS2 quantum dots (QDs) via the dimension and phase engineering of 1T-WS2 nanosheets. The solvothermal reaction of chemically exfoliated 1T-WS2 nanosheets in N-methyl-2-pyrrolidone (NMP) under an N2 atmosphere induced their chopping and phase transition at lower temperature to produce 2H-WS2 QDs with a high quantum yield (5.5 ± 0.3%). Interestingly, this chopping and phase transition process showed strong dependency on solvent; WS2 QDs were not produced in other solvents such as 1,4-dioxane and dimethyl sulfoxide. Mechanistic investigations suggested that NMP radicals played a crucial role in the effective production of 2H-WS2 QDs from 1T-WS2 nanosheets. WS2 QDs were successfully applied for the selective, sensitive, and rapid detection of dopamine in human serum (4 min, as low as 23.8 nM). The intense fluorescence of WS2 QDs was selectively quenched upon the addition of dopamine and Au3+ ions due to fluorescence resonance energy transfer between WS2 QDs and the quickly formed Au nanoparticles. This new sensing principle enabled us to discriminate dopamine from dopamine-derivative neurotransmitters including epinephrine and norepinephrine, as well as other interference compounds.
