Zwitterionic Ligands Bound to Cdse/Zns Quantum Dots Prevent Adhesion to Mammalian Cells

<div><p></p><p>Zwitterionic materials are useful tools in material science and biology as they provide high water solubility while preventing nonspecific interactions. Quantum dots (QDs) functionalized with zwitterionic and quaternary ammonium ligands were synthesized to investigate their interactions with the outer membrane of HeLa cells. Quaternary ammonium functionalized quantum dots adhered strongly to the cell surface while zwitterionic QDs had no cell adhesion. These results demonstrate that future noninteracting nanoparticles based on this design are possible.</p></div

High-Performance All-Solid-State Na–S Battery Enabled by Casting–Annealing Technology

Room-temperature all-solid-state Na–S batteries (ASNSBs) using sulfide solid electrolytes are a promising next-generation battery technology due to the high energy, enhanced safety, and earth abundant resources of both sodium and sulfur. Currently, the sulfide electrolyte ASNSBs are fabricated by a simple cold-pressing process leaving with high residential stress. Even worse, the large volume change of S/Na₂S during charge/discharge cycles induces additional stress, seriously weakening the less-contacted interfaces among the solid electrolyte, active materials, and the electron conductive agent that are formed in the cold-pressing process. The high and continuous increase of the interface resistance hindered its practical application. Herein, we significantly reduce the interface resistance and eliminate the residential stress in Na₂S cathodes by fabricating Na₂S-Na₃PS₄-CMK-3 nanocomposites using melting-casting followed by stress-release annealing-precipitation process. The casting–annealing process guarantees the close contact between the Na₃PS₄ solid electrolyte and the CMK-3 mesoporous carbon in mixed ionic/electronic conductive matrix, while the <i>in situ</i> precipitated Na₂S active species from the solid electrolyte during the annealing process guarantees the interfacial contact among these three subcomponents without residential stress, which greatly reduces the interfacial resistance and enhances the electrochemical performance. The <i>in situ</i> synthesized Na₂S-Na₃PS₄-CMK-3 composite cathode delivers a stable and highly reversible capacity of 810 mAh/g at 50 mA/g for 50 cycles at 60 °C. The present casting–annealing strategy should provide opportunities for the advancement of mechanically robust and high-performance next-generation ASNSBs

Self-Templated Formation of P2-type K_0.6CoO₂ Microspheres for High Reversible Potassium-Ion Batteries

Layered metal oxides have been widely used as the best cathode materials for commercial lithium-ion batteries and are being intensively explored for sodium-ion batteries. However, their application to potassium-ion batteries (PIBs) is hampered because of the poor cycling stability and low rate capability due to the larger ionic size of K⁺ than of Li⁺ or Na⁺. Herein, a facile self-templated strategy was used to synthesize unique P2-type K_0.6CoO₂ microspheres that consist of aggregated primary nanoplates as PIB cathodes. The unique K_0.6CoO₂ microspheres with aggregated structure significantly enhanced the kinetics of the K⁺ intercalation/deintercation and also minimized the parasitic reactions between the electrolyte and K_0.6CoO₂. The P2-K_0.6CoO₂ microspheres demonstrated a high reversible capacity of 82 mAh g^–1 at 10 mA g^–1, high rate capability of 65 mAh g^–1 at 100 mA g^–1, and long cycle life (87% capacity retention over 300 cycles). The high reversibility of the P2-K_0.6CoO₂ full cell paired with a hard carbon anode further demonstrated the feasibility of PIBs. This work not only successfully demonstrates exceptional performance of P2-type K_0.6CoO₂ cathodes and microspheres K_0.6CoO₂∥hard carbon full cells, but also provides new insights into the exploration of other layered metal oxides for PIBs

Fully Zwitterionic Nanoparticle Antimicrobial Agents through Tuning of Core Size and Ligand Structure

Zwitterionic nanoparticles are generally considered nontoxic and noninteracting. Here, we report effective and selective antimicrobial activity of zwitterionic gold nanoparticles (AuNP) through modulation NP size and surface charge orientation. Using a set of 2, 4, and 6 nm core AuNPs, increasing particle size increased antimicrobial efficiency through bacterial membrane disruption. Further improvement was observed through control of the ligand structure, generating antimicrobial particles with low hemolytic activity and demonstrating the importance of size and surface structure in dictating the bioactivity properties of nanomaterials

The Interplay of Size and Surface Functionality on the Cellular Uptake of Sub-10 nm Gold Nanoparticles

Correlation of the surface physicochemical properties of nanoparticles with their interactions with biosystems provides key foundational data for nanomedicine. We report here the systematic synthesis of 2, 4, and 6 nm core gold nanoparticles (AuNP) featuring neutral (zwitterionic), anionic, and cationic headgroups. The cellular internalization of these AuNPs was quantified, providing a parametric evaluation of charge and size effects. Contrasting behavior was observed with these systems: with zwitterionic and anionic particles, uptake <i>decreased</i> with increasing AuNP size, whereas with cationic particles, uptake <i>increased</i> with increasing particle size. Through mechanistic studies of the uptake process, we can attribute these opposing trends to a surface-dictated shift in uptake pathways. Zwitterionic NPs are primarily internalized through passive diffusion, while the internalization of cationic and anionic NPs is dominated by multiple endocytic pathways. Our study demonstrates that size and surface charge interact in an interrelated fashion to modulate nanoparticle uptake into cells, providing an engineering tool for designing nanomaterials for specific biological applications

Existence of Solid Electrolyte Interphase in Mg Batteries: Mg/S Chemistry as an Example

Magnesium redox chemistry is a very appealing “beyond Li ion chemistry” for realizing high energy density batteries due to the high capacity, low reduction potential, and most importantly, highly reversible and dendrite-free Mg metal anode. However, the progress of rechargeable Mg batteries has been greatly hindered by shortage of electrolytes with wide stability window, high ionic conductivity, and good compatibility with cathode materials. Unlike solid electrolyte interphase on Li metal anode, surface film formed by electrolyte decomposition in Mg batteries was considered to block Mg ion transport and passivate Mg electrode. For this reason, the attention of the community has been mainly focusing on surface layer free electrolytes, while reductively unstable salts/solvents are barely considered, despite many of them possessing all the necessary properties for good electrolytes. Here, for the first time, we demonstrate that the surface film formed by electrolyte decomposition can function as a solid electrolyte interphase (SEI). Using Mg/S chemistry as a model system, the SEI formation mechanism on Mg metal anode was thoroughly examined using electrochemical methods and surface chemistry characterization techniques such as EDX and XPS. On the basis of these results, a comprehensive view of the Mg/electrolyte interface that unifies both the SEI mechanism and the passivation layer mechanism is proposed. This new picture of surface layer on Mg metal anode in Mg batteries not only revolutionizes current understanding of Mg/electrolyte interface but also opens new avenues for electrolyte development by uncovering the potential of those reductively unstable candidates through interface design

Zn/MnO₂ Battery Chemistry With H⁺ and Zn²⁺ Coinsertion

Rechargeable aqueous Zn/MnO₂ battery chemistry in a neutral or mildly acidic electrolyte has attracted extensive attention recently because all the components (anode, cathode, and electrolyte) in a Zn/MnO₂ battery are safe, abundant, and sustainable. However, the reaction mechanism of the MnO₂ cathode remains a topic of discussion. Herein, we design a highly reversible aqueous Zn/MnO₂ battery where the binder-free MnO₂ cathode was fabricated by in situ electrodeposition of MnO₂ on carbon fiber paper in mild acidic ZnSO₄+MnSO₄ electrolyte. Electrochemical and structural analysis identify that the MnO₂ cathode experience a consequent H⁺ and Zn²⁺ insertion/extraction process with high reversibility and cycling stability. To our best knowledge, it is the first report on rechargeable aqueous batteries with a consequent ion-insertion reaction mechanism