ACS Nanoscience Au最新文献

Amino acid-based nanostructures represent an emerging class of biomolecular building blocks for next-generation biomaterials. Unlike native amino acids that lack structural complexity and mechanical integrity, their nanostructured forms, such as nanoparticles, nanofibers, nanotubes, hydrogels, peptides, and protein-based self-assemblies, offer a multifunctional scaffold design that actively participates in autonomous tissue repair. This perspective delves into the polar and nonpolar amino acid nanostructures and their roles in autonomous tissue repair through dynamic interactions with the cellular microenvironment, therapeutic delivery, and stimuli-responsiveness. The potential of advanced amino acid nanostructures, such as hydrogels and protein assemblies, is also discussed, as hydrogels provide hydrated, bioactive networks that mimic extracellular matrix functions, while protein nanostructures bring structural precision and inherent bioactivity to regenerative systems. Importantly, in our perspective, we highlight that amino acid nanostructures represent a dual closed-loop framework comprising a functional loop where these materials demonstrate adaptive response by sensing microenvironmental cues as well as a life cycle loop wherein green fabrication methods and biodegradation support sustainability. We believe that this dual functionality positions amino acid nanostructures as state-of-the-art regenerative platforms that integrate biological intelligence with sustainability, hence bridging the gap between material design and clinically translatable therapeutics.

We explored the oxidation of solid gold nanoparticles under ambient conditions by X-ray nanodiffraction at a synchrotron radiation source. A droplet of carbohydrate-ligand-functionalized gold nanoclusters was evaporated on a superhydrophobic surface. The resulting layer of core-shell nanoparticles with minimum substrate interactions was repeatedly raster-scanned through a nanoscale X-ray focal spot. We observed radiation-induced liberation of ∼1.3 nm diameter disordered nanoparticles, composed of, on average, 71 gold atoms, and their transformation into ∼2.1 nm diameter face-centered cubic gold nanocrystallites by a nucleation/growth process. Lattice metrology and previously reported simulations supported the formation of a disordered gold oxide surface layer, transforming with increasing particle size into epitaxially stabilized Au₂O nanocrystallites with the theoretically predicted cuprite lattice structure. The nonstoichiometric phase showed lattice expansion, which was attributed to oxygen uptake from the interface. Lattice expansion continued beyond the stoichiometry limit, associated with a loss in crystallinity and the emergence of short-range order.

A series of three symmetric, hollow spherical, and shape-persistent molecular organic cages analogous to C₂₀ and C₆₀ were examined by computational modeling, analyzing structural elements, strain indicators, and physical properties relevant for potential applications. The compounds are covalent aromatic cages based on 1,3,5-substituted benzene nodes linked by para-phenylene or para-pyrenylene-connectors, with diameters varying from 2.3 to 4.2 nm. The apertures in the cage interior are varied by virtue of the cage type (C₂₀- or C₆₀-type cage) and the linear connectors placed between the C₆H₃-units. NBO and MESP analyses indicate the presence of electrophilic and nucleophilic sites in the molecular skeleton. In the cages with the phenylene-connectors, the HOMO-LUMO gaps are close to 4.0 eV. In the cage coated with an enlarged polyaromatic spacer (pyrene-unit), the gap is reduced by approximately 0.4 eV.

Cell-free biosensors combine in vitro bacterial transcription-translation systems with operons to detect analytes, such as heavy-metal ions. These sensors are highly desirable due to their easy portability and long shelf life. Typically, the expression of a fluorescent RNA aptamer or protein tied to the presence of an analyte is used as an optical readout for detection in such biosensors. While these readouts have demonstrated tremendous success in testing water potability, the readout is limited by how many different RNA aptamers and proteins can be used simultaneously. The quantum yield of these biological fluorescent molecules is low as well. Recently, we demonstrated a semiconductor quantum dot (QD)-based reporter system that is fully compatible with cell-free transcription-translation systems. Our reporter, abbreviated as QD-PDD (Peptide-PNA DNA Dye), uses nucleic acid specificity to trigger a change in Förster resonance energy transfer (FRET) between the QD and its acceptor fluorophore (Cy3) when a restriction enzyme (BamHI) is expressed. Given the high specificity of nucleic acids and the quantum yield of QDs, the question remained whether QD-PDD reporters could be plugged downstream of heavy-metal cell-free biosensors. Herein, we connected an operon sensitive to cadmium ions to the cell-free expression of BamHI, which triggered a FRET change in the QD-PDD reporter. The operon system can successfully detect cadmium in water-based cadmium chloride solutions. This system serves as a proof of concept showing that QD-PDD can enable the departure of fluorescent biomolecules (aptamers and proteins) in cell-free biosensors.

While cationic surfactants such as hexadecyltrimethylammonium bromide (CTAB) are ubiquitous in the synthesis of noble metal nanocrystals, anionic surfactants are rarely used. This work explores the addition of sodium alkyl sulfonates with chain lengths ranging from one to eight carbons to a silver nanoplatelet reaction. Short-chain sulfonates comprised of one to four carbons show little effect on the nanocrystal synthesis, but alkyl sulfonates comprised of five or more carbons at concentrations above 1 mM have a pronounced effect on the absorbance of the nanocrystals, causing a blue-shift in the wavelength of maximum absorbance (λ_max) from approximately 800 to 400 nm as the sulfonate concentration is increased to 7 mM. Higher concentrations of sulfonate result in a subsequent red-shift of the peak. Investigation into the possible formation mechanisms responsible for this synthetic control revealed the absence of sulfonate micelles under the reaction conditions. Instead, we hypothesize that sulfonate bilayers are nucleated around the silver nanocrystals at concentrations below the critical micelle concentration and interact with either the citrate ligands or the silver surface to influence nanocrystal morphology, and thus absorbance. Strikingly, the addition of long-chain alkyl sulfonates to already-synthesized nanocrystals results in similar changes to the nanocrystal absorbance that occur within seconds, providing further support for the proposal that these effects are related to the surface chemistry of the nanocrystals, which appear to be highly dynamic.

Materials combining graphitic carbon with metal oxide nanoparticles are critical for applications in water treatment, catalysis, and energy storage. These composites leverage carbon's electrical conductivity and chemical resilience to enhance the catalytic, electronic, and magnetic properties of metal oxide nanoparticles. Previous approaches to synthesizing such materials have relied on high-temperature (>600 °C) pyrolysis of powders, a process that can alter nanoparticle size, composition, and morphology. Alternative lower-temperature routes in solution yield amorphous carbon, which lacks the conductivity and chemical resistance of graphitized carbon. This study presents a route to form graphitic carbon coatings on iron, manganese, and cobalt oxide nanoparticles at temperatures below 400 °C. The synthetic process exploits the thermal decomposition of metal carboxylates, which generates carbon monoxide (CO) within the reaction environment that further disproportionates to elemental carbon on the nanoparticle surface. Gas chromatography confirms CO evolution, and electron microscopy reveals the formation of core-shell structures with graphitic coatings of varying thickness. Iron oxide nanoparticles coated via this method exhibit exceptional chemical resistance, remaining intact in strong acids while maintaining their magnetic properties. This advancement enables the production of size-tunable nanoparticle-graphite suspensions via conventional solution-phase chemistry. These findings suggest a scalable approach for producing graphitized carbon-metal oxide composites without the need for extreme temperatures, broadening the potential applications of these materials in energy storage and environmental remediation.

Direct ink writing (DIW) of nanomaterial dispersions enables the production of structures and devices that combine the benefits of the nanomaterial properties with use-specific manufacturing designs. However, printing nanomaterial inks requires the ability to produce stable dispersions at concentrations high enough to meet the rheological criteria for DIW. Herein, we report on DIW of one-dimensional lepidocrocite (1DL) nanofilament, NF, dispersions at concentrations of 150 g/L, which are much greater than previously achieved concentrations. Moreover, the resulting birefringent, binder-free nematic gel can be printed into standard test patterns with outstanding dimensional accuracy, structural integrity, and shape fidelity. Both the ability to directly produce higher concentrations and the ability to print them open new opportunities for the production of functional 1DL materials and devices.

We present the design principles and assembly route for a reconfigurable DNA-scaffolded nanomachine comprising a fluorophore and two gold nanoparticles (AuNPs) operated by DNA strand displacement. The mechanism confines the fluorophore in the proximity of one or simultaneously two DNA-tethered 15 nm AuNPs, resulting in discrete emission levels associated with the system state. Bi- and single-molecule DNA scaffolds were compared as alternative building blocks, aiming at the optimal structure in terms of reversibility, response to molecular triggers, and signal-to-noise ratio. Upon comparison, single-molecule DNA scaffold (i.e., nano-bolas), devoid of intrastructural equilibria, was only minimally affected by cross-talk interferences and stood out for its highly reversible transitions, lower noise, and better kinetics. Distance-dependent responses and kinetics were fully in harmony with theoretical modeling, well illustrating the nano-bolas interconversion between a linear and a quasi-ring geometry. The nano-bolas actuator could find application as an ultrasensitive, reversible, and small-volume plasmonic reporter for single-strand nucleic acid analytes.

Metal-organic frameworks (MOFs) have proven to be versatile platforms for anchoring individual metal atoms, which can act as single-atom catalysts. Due to their well-defined geometric and electronic structure, high porosity, and adjustable pore size, MOFs can modulate the catalytic performance of anchored individual atoms. In this work, we explored the surface-assisted synthesis of 2D surface metal-organic networks (SMONs) of 1,3,5-tris-[4-(pyridine)-[1,1'-biphenyl]-benzene] (TPyPPB) coordinated with Pt atoms on Ag(111) by using scanning tunneling microscopy at room temperature. The Pt deposition was performed in two routes: (i) by using the dichloro-(1,10-phenanthroline)-platinum-(II) (Cl₂PhPt) or (ii) by direct deposition of Pt atoms. Using Cl₂PhPt as a Pt source and applying various annealing sequences at a temperature of 400 K, a long-range hexagonal SMONs is obtained. After the dechlorination of the Cl₂PhPt molecule, individual Pt atoms establish quadruple coordination with two N atoms at the pyridyl end groups of the TPyPPB molecule and two Cl atoms. These pores have efficiently induced the formation of large molecules that behave like rotors. Such a system has the potential to open new frontiers and shed light on a better understanding of the physical-chemistry mechanisms involved in "host-guest" chemistry.