The extremely large optical extinction coefficient of gold nanorods (Au-NRs) enables their use in a diverse array of technologies, rnging from plasmonic imaging, therapeutics and sensors, to large area coatings, filters, and optical attenuators. Development of the latter technologies has been hindered by the lack of cost-effective, large volume production. This is due in part to the low reactant concentration required for symmetry breaking in conventional seed-mediated synthesis. Direct scale up of laboratory procedures has limited viability because of excessive solvent volume, exhaustive postsynthesis purification processes, and the generation of large amounts of waste (e.g., hexadecyltrimethylammonium bromide(CTAB)). Following recent insights into the growth mechanism of Au-NRs and the role of seed development, we modify the classic seed-mediated synthesis via temporal control of seed and reactant concentration to demonstrate production of Au-NRs at more than 100-times the conventional concentration, while maintaining independent control and narrow distribution of nanoparticle dimensions, aspect ratio, and volume. Thus, gram scale synthesis of Au-NRs with prescribed aspect ratio and volume is feasible in a 100 mL reactor with 1/100th of organic waste relative to conventional approaches. Such scale-up techniques are crucial to cost-effectively meet the increased demand for large quantities of Au-NRs in emerging applications.
The stability of polymer thin films is crucial to a broad range of technologies, including sensors, energy storage, filtration, and lithography. Recently, the demonstration of rapid deposition on solid substrates of ordered monolayers of polymer grafted nanoparticles (PGN) has increased potential for inks to additively manufacture such components. Herein, enhanced stability against dewetting of these self-assembled PGN films (gold nanoparticle functionalized with polystyrene (AuNP-PS)) is discussed in context to linear polystyrene (PS) analogues using high throughput surface gradients: surface energy (20−45 mN/m) and temperature (90−160 °C). PGNs exhibit a lower surface (γ p ) and interfacial (γ sp ) energy relative to linear polymers, which results in increased thermal and energetic stability by 10−25 °C and 5−15 mN/m, respectively. This enhanced wetting−dewetting transition is qualitatively consistent with the behavior of star macromolecules and depends on the architecture of the polymer canopy. Increased film stability through canopy architecture expands the manufacturability of thin film hybrids and refines postprocessing conditions to maximize local PGN order.
Solution-based printing of anisotropic nanostructures is foundational to many emerging technologies, such as energy storage devices, photonic elements, and sensors. Methods to rapidly (>mm/s) manufacture large area assemblies (≫cm2) with simultaneous control of thickness (<10 nm), nanoparticle spacing (<5 nm), surface roughness (<5 nm), and global and local orientational order are still lacking. Herein, we demonstrate such capability using flow-coating to fabricate robust, self-supporting mono- and bilayer films of polystyrene-grafted gold nanorods (PS-AuNRs) onto solid substrates. The relationship among solvent evaporation, deposition speed, substrate surface energy, concentration, and film thickness for solutions of such hairy hybrid nanoparticles spans the Landau–Levich and evaporative film formation regimes. In the Landau–Levich regime, solvent evaporation rapidly concentrates the PS-AuNRs, leading to the formation of thin films with distinct, randomized side-by-side domains. Alternatively, processing at slower velocities in the evaporative regime results in the global alignment of PS-AuNRs. Processing speed and substrate surface energy afford tuning of the film’s optical extinction of a given PS-AuNR via fine control of inter-rod distance and subsequent plasmonic coupling between neighboring nanorods. Because the concept of the polymer-grafted nanorod can be expanded to a variety of different polymer canopies, shapes, and core materials, the processing–structure relationships established in this work will have important implications on the future development of anisotropic nanostructure-based applications.
Controlling the surface chemistry of nanoparticles is crucial and affects everything from performance to synthesis, processability, and toxicity. Many times, however, stability requirements during synthesis, processing, and integration are contradictory and necessitate phase transfer methods and surface modifications that lead to waste and limit functionalization options. Herein, we demonstrate that the solvation of colloidal gold nanorods (AuNRs) can be tuned from water to aprotic organic solvents by thermodynamically tuning the morphology of its ligand bilayer assembly (cetyltrimethylammonium bromide, CTAB), performing as an alchemical alkahest canopy. As CTAB concentration decreases below the critical micelle concentration (CMC), the bilayer is depleted due to an equilibrium between surfactant molecules in solution and on the AuNR surface. These aqueous stable AuNRs with a depleted ligand stabilization layer directly transfer to aprotic polar organic solvents. This behavior is consistent with a structural inversion of the weakly coordinating, defective CTAB bilayer in response to the polarity of the solvent medium. This process also affords the creation of anhydrous dispersions and enables the formulation of dispersions in nonpolar organic solvents. The utility of these organically stable AuNR dispersions is demonstrated by substantially increasing the effectiveness of grafting-to reactions of thiolated apolar polymers and the formation of Au−C bonds via anhydrous Grignard surface reactions.
Objective The combination of opioids and ethanol can synergistically depress breathing and the acute ventilatory response to hypoxia. Multiple studies have shown that the underlying mechanisms for this may involve calcium channel inhibition in central neurons. But we have previously identified opioid receptors in the carotid bodies and shown that their activation inhibits calcium influx into the chemosensitive cells. Given that the carotid bodies contribute to the drive to breathe and underpin the acute hypoxic ventilatory response, we hypothesized that ethanol and opioids may act synergistically in these peripheral sensory organs to further inhibit calcium influx and therefore inhibit ventilation. Methods Carotid bodies were removed from 56 Sprague–Dawley rats (1021 days old) and then enzymatically dissociated to allow calcium imaging of isolated chemosensitive type I cells. Cells were stimulated with high K + in the presence and absence of the µ-opioid agonist [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO) (10 µM), a maximal sublethal concentration of ethanol (3 g L -1 , 65.1 mM) or a combination of both. Results DAMGO alone significantly inhibited Ca 2+ influx but this effect was not potentiated by the high concentration of ethanol. Conclusion These results indicate for the first time that while opioids may suppress breathing via an action at the level of the carotid bodies, ethanol is unlikely to potentiate inhibition via this pathway. Thus, the synergistic effects of ethanol and opioids on ventilatory parameters are likely mediated by central rather than peripheral actions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.