ACS Nanoscience Au最新文献

Colloidal synthesis of multielement nanocrystals demands precise control over precursor reactivity and compatibility. These challenges are amplified when combining elements that span the periodic table, which has limited the complexity of crystal structures and compositions that are readily accessible in solution. Intergrowth structures, which feature alternating layers with distinct compositions and crystallographic motifs, have proven particularly challenging to access in nanocrystalline forms. Here, we present a direct, solution-phase synthesis of LnCuOSe intergrowth nanocrystals incorporating six different lanthanide cations (Ln = La, Ce, Pr, Nd, Sm, and Eu). These nanocrystals exhibit a consistent anisotropic nanoflower morphology, reflecting the layered crystal structure of alternating Cu-Se and Ln-O planes. The synthesis leverages a preformed lanthanide-selenium interaction in a coordination complex precursor that thermally decomposes to yield the quaternary product. Formation proceeds via a crystalline Cu₂Se intermediate that templates the final structure. The resulting nanocrystalline samples are stable in solution up to 350 °C but are unstable at higher temperatures out of solution, showing evidence for anisotropic thermal expansion upon traditional annealing that is not observed in bulk samples of the same material. The nanoflowers are semiconductors with wide band gaps that show evidence of possible quantum confinement and structural defects.

We prepared rutile-type TiNbO₄ by a sol-gel method to investigate the relationship between the calcination temperature in the synthesis and its nanostructure and evaluated the influence of the nanostructure on the electrode properties as a Na-ion battery anode. The crystallite size of TiNbO₄ and the size of the diffusion path along its c-axis were increased with increasing calcination temperature. We revealed that the TiNbO₄ was comprised of aggregated single-crystalline primary nanoparticles to form mesoporous secondary particles of spherical marimo shape. At a high current rate of 5C, the electrode of TiNbO₄ calcined at 700 °C exhibited the highest reversible capacity of 170 mA h g^-1. It is suggested that TiNbO₄ at 700 °C has a relatively wide diffusion path to allow high-speed Na⁺ insertion-extraction and that its smaller crystallite size improves the utilization rate of the active material.

Introducing exogenous biomolecules into individual cells with precise control over space, time, and dosage is crucial for both fundamental and applied biological research. Glass nanopipettes have long been employed to deliver biomolecules into individual cells; yet, their reliance on the electrical charge of the target molecule and the need for penetrating the cellular membrane pose significant limitations. We demonstrate that voltage pulses applied through a glass nanopipette in proximity to the cell membrane induce localized electroporation and generate directional flow, enabling controlled delivery of both charged and neutral biomolecules into subcellular compartments, e.g., the nucleus, without the need for penetrating the cellular membrane. This approach minimizes cell damage and preserves cell viability, even after multiple rounds of injection. Our findings will serve as a reference for the design of novel nanopipette methods, contributing to the newly established field of spatiotemporal analysis of live cells.

Solar energy, as an alternative source to catalyze chemical reactions, has been rapidly utilized and developed over the past few decades, particularly with TiO₂-based semiconductor photocatalysts. Regulating the carrier dynamics under photoexcitation and controlling the interfacial reaction kinetics have been emphasized as fundamental approaches to increase the quantum yield of photocatalytic systems. Transition-metal-ion doping is a promising strategy to address these issues, although the precise roles and optimal spatial distribution of dopants remain unclear. In this systematic study, we designed surface-only, bulk-only, and surface-bulk-doped brookite TiO₂ nanoparticles using Ni²⁺ as dopants and evaluated the photocatalytic performance of these doped samples based on the apparent reaction rate constants. It is demonstrated that the crystal structure, morphology, and surface composition did not change significantly after doping, and the observed enhancement in photocatalysis can be correlated to the doping positions. Continuous doping from the bulk to surface, forming the trap-to-transfer centers to mediate interfacial electron transfer, proves to be the most effective pathway. This proof-of-concept work offers a unique perspective on the transition-metal-ion-induced photocatalysis mechanism of brookite TiO₂ nanoparticles and will help us design more efficient photocatalytic systems.

It is well established that the biomolecular corona affects the biological behavior of nanomaterials, including cellular uptake, toxicity, and biodistribution. However, the unique physicochemical properties of advanced materials, such as graphene oxide, challenge the effectiveness of standard protocols for biomolecular corona characterization, which may lead to incomplete biomolecule recovery and biased experimental results. Protein analysis is one of the broadest techniques in the characterization of the biomolecular corona, providing important information about the composition and behavior of proteins adsorbed onto nanomaterial surfaces. Two widely accepted protein analysis methods include SDS-PAGE and mass spectrometry, and both require the complete elution of the proteins from the nanoparticle surface during denaturation steps. In this work, limitations of widely used SDS-based elution methods with GO were identified, and an improved protocol using chaotropic agents (urea and thiourea) was developed. The stepwise extraction allowed for near-complete protein desorption. Under the modified protocol, strongly bound proteins that are more hydrophobic have been proved to be underestimated using the standard method. This further reiterates the necessity for the development of methodologies tailored to the specific materials under study which accurately characterize the protein corona. Our results highlight the need for standardization and optimization of protocols to ensure reproducibility and reliability in nanosafety studies, hence promoting the safe and sustainable use of advanced materials in biological and environmental systems.

The complex chemical nature of metal nanoparticle synthesis presents obstacles for the mechanistic understanding of nanoparticle growth and predictive synthesis design, despite significant progress in this area. Real-time characterization of the chemical processes that take place throughout nanoparticle growth will enable progress toward addressing outstanding challenges in metal nanoparticle synthesis, such as mitigating synthetic reproducibility issues, defining chemical mechanisms that direct nanoparticle growth, and designing synthetic conditions for previously unachievable combinations of nanoparticle shape and composition. In this Perspective, we present open-circuit potential (OCP) measurements as an in situ, real-time method for characterizing chemical changes during nanoparticle growth and discuss the method’s strengths in comparison to and in combination with other characterization techniques. We propose the use of OCP measurements as benchmarks for troubleshooting irreproducibility and streamlining synthetic optimization. Finally, we explore possibilities for using the increased parameter space accessible by electrodeposition to accelerate the development of shape-selective nanoparticle syntheses.

Metal nanocrystals (NCs) show utility in a variety of applications due to their unique structure-dependent properties. Isolating these structure–property relationships is crucial for NC design, but heterogeneities present in NC ensembles as well as limitations in NC characterization strategies complicate this goal. Herein, we describe the various types of intraparticle and interparticle heterogeneities common to NC ensembles and then provide a detailed description and comparison of single-particle techniques that can be used to characterize these different heterogeneities. Case studies then showcase the use of multimodal characterization approaches, where multiple, primarily single-NC techniques are used in tandem to provide new insights into metal NC structure–property relationships. We conclude with a critique of single-NC techniques that motivates the development of new high-throughput and high-resolution single-NC characterization approaches as well as computational tools, with a proposed workflow outlined to accelerate NC design and discovery.

Superconductors are characterized by macroscopic phase coherence and have enabled cryogenic electronics and quantum technologies. Recent advances in 3D nanofabrication now offer possibilities for tuning functional properties relevant for on-chip 3D integration of superconductors. However, nonequilibrium phenomena in 3D nanostructures exposed to transport currents remain largeley unexplored. Here, we employ numerical simulations to investigate phase slipsdiscrete 2π jumps in the phase of the superconducting order parameterin a tubular Nb superconductor with a central constriction, which is subjected to both direct current (DC) and alternating current (AC) transport currents. We find that under DC drive, the system stabilizes periodic phase slips, resulting in GHz voltage oscillations. Introducing an additional AC frequency modulation generates microwave frequency combs which depend characteristically on the interaction between moving vortices and phase slips. Our findings open avenues for developing on-chip frequency comb generators in 3D cryoelectronics.