Shape‐directing syntheses have been extensively studied in metallic nanoparticle (NP) systems and yielded corresponding shape‐dependent optoelectronic and catalytic NP properties. As doped‐semiconductor nanostructures gain traction as complementary plasmonic nanomaterials, methods to create anisotropic varieties may offer analogous optoelectronic tunability. Here, we study the roles of both appended and free ligands on the emergent shapes of doped copper selenide (Cu 2– x Se) NPs using representative common ligands including negatively and positively charged small molecules (sodium dodecyl sulfate and cetyltrimethylammonium bromide) as well as a polymer capping agent (poly(vinyl pyrrolidone)). We do not observe platonic shapes for any conditions tested but do observe measurable changes in particle anisotropy. To describe, track, and quantify these changes, we employ the Power's scale of roundness and the Wadell roundness index. Importantly, we find that particle anisotropy arises almost exclusively during the conversion of Se seeds into Cu 2– x Se via Cu ion infiltration. We analyze the impact of the resulting shapes on their corresponding optoelectronic properties by isolating shape and ligand contributions to localized surface plasmon resonances distinct from changes in NP charge carrier densities. Taken together, these results present routes to enhance Cu 2– x Se NP angularity using ligand chemistry, ultimately providing an expanded platform of plasmonically active doped‐semiconductor nanostructures.

The rate at which reducing electrons are generated is a powerful handle for controlling nanoparticle formation, determining how reduced metal incorporates into nanoparticles, and as a result, key aspects of the resulting structures, such as their size. Here, we leverage the high tunability of photocatalytically generated reducing agents to modulate the production of reducing electrons by (1) adjusting photosensitizer concentration (the species that carries the electron used to reduce metal ions) to control the number of reducing electrons available for metal ion reduction and subsequent nanoparticle formation at a given time, (2) modulating PS excited state quenching, and (3) directly controlling relative irradiance delivered to the reaction milieu using a series of increasingly absorptive filters. In each case, nanoparticle formation is followed over time and nanoparticle formation rate constants, kNP, are extracted. We observe a consistent relationship between the instantaneous reducing electron concentration and the average size of the resulting particles, where lower concentrations lead to larger nanoparticles in all cases. By combining the conditions that produce the slowest NP formation kinetics, we design a synthesis that expands the accessible particle size window from ∼4 to 26 nm. These results introduce a framework for controlling size in metal nanoparticle formation pathways, such as continuous nucleation, that diverge from classic metal nanoparticle syntheses and their associated strategies for particle morphology control such as seeding and metal ion to reducing agent ratios.

In the summer of 2023, a group of 35 researchers from across the discipline of nanochemistry gathered to discuss challenges and opportunities that will define the next 10 years of cutting edge nanochemical discovery. Over 2 days, researchers identified four areas with rich possibilities to accelerate the science and translation of nanostructures into society-enhancing tools for technology, health, and sustainability. In this Nano Focus, we summarize highlights from these discussions. A full report from the workshop is provided as Supporting Information.

Significant advances in science and engineering often emerge at the intersections of disciplines. Nanoscience and nanotechnology are inherently interdisciplinary, uniting researchers from chemistry, physics, biology, medicine, materials science, and engineering. This convergence has fostered novel ways of thinking and enabled the development of materials, tools, and technologies that have transformed both basic and applied research, as well as how we address critical societal challenges. In this Nano Focus, we pose and explore 33 questions whose answers could profoundly impact fields such as energy, electronics, the environment, optics, and medicine. These questions highlight the need for deeper foundational understanding, improved tools and techniques, and innovative applications─each with significant societal relevance. Together, they represent a global call-to-action for the scientific community.

Managing drinking water-associated pathogens that can cause infections in immunocompromised individuals is a persistent challenge, particularly for healthcare facilities where occupant exposures carry a substantial health risk.

Simultaneously controlling both stoichiometry and atom arrangement during the synthesis of multimetallic nanoparticles is often challenging, especially when the desired metal precursors exhibit large differences in their intrinsic reduction kinetics. In such cases, traditional synthetic methods often lead to the formation of exclusively phase-segregated structures. In this study, we demonstrate that the relative reduction kinetics of the metal precursors can be manipulated independently of their intrinsic differences in reduction rates by modulating the instantaneous concentrations of the metal cation precursors. We achieve this control by adjusting the precursor addition rate, which decouples chemical ordering outcomes from differences in precursor reduction kinetics. To guide these experiments, we describe a quantitative model to determine how metal ion reduction rates evolve with variations in the precursor addition rate and thereby predict optimal conditions for the synthesis of multimetallic nanoparticles with precise structural and compositional outcomes. We demonstrate the efficacy of this model experimentally by synthesizing both core@shell and alloyed nanoparticles with stoichiometric control using the same metal ion precursors in two different bimetallic systems (Au-Pd and Au-Pt) as well as in a quinary metal system (Co, Ni, Cu, Pd, and Pt). This approach enables the design of nanoparticle architectures independent of intrinsic differences in metal ion reduction potentials of the constituent metals while maintaining both stoichiometric and structural control.

The use of nanoparticle surface chemistry to direct metal deposition has been well-studied in the modification of metal nanoparticle substrates but is not yet well-established for metal chalcogenide particle substrates, although integration of these particles into nanoheterostructures is of high interest. In this report, we investigate the effect of Cu2-xSe surface chemistry on the morphology of metal deposition on these plasmonic semiconductor nanoparticles. Specifically, we functionalize Cu2-xSe nanoparticles with a suite of 12 different ligands and investigate how different aspects of the ligand structure do or do not impact the morphology and extent of subsequent metal deposition on the Cu2-xSe surface. Surprisingly, our results indicate that the morphology of the resulting metal deposits and the extent of metal deposition onto the existing Cu2-xSe particle substrate are indistinguishable for the majority of ligands tested. An exception to these findings is observed for particles functionalized by quaternary alkylammonium bromides, which exhibit statistically distinct metal deposition patterns compared to all other ligands tested. We hypothesize that this unique behavior is due to a cooperative binding mechanism of the quaternary alkylammonium bromides to the surface of copper selenide. Taken together, these results yield both new strategies for controlling postsynthetic modification of copper selenide nanoparticles and also reveal limitations of surface chemistry-based approaches for this system.

Trace palladium in synthetic materials can be rapidly and inexpensively semiquantified by a catalysis-based fluorometric method that converts resorufin allyl ether to resorufin. However, whether sulfur compounds would interfere with this method has not been systematically studied. Herein, we show that although thiourea in solution interferes with quantification, sulfide, thiol, and thiocarbamate do not. The fluorometric method can also detect palladium bound to sulfur-based scavenger resin and outperform inductively coupled plasma mass spectrometry for detecting trace palladium in ibuprofen.

The incidence of waterborne disease outbreaks in the United States attributed to drinking water-associated pathogens that can cause infections in the immunocompromised DWPIs (e.g., Legionella pneumophila, nontuberculous mycobacteria (NTM), and Pseudomonas aeruginosa, among others) appears to be increasing. An emerging technology adopted to reduce DWPIs are point-of-use devices, such as showerheads that contain silver, a known antimicrobial material. In this study, we evaluate the effect of silver-containing showerheads on DWPI density and the broader microbiome in shower water under real-use conditions in a full-scale shower system, considering three different silver-modified showerhead designs: (i) silver mesh within the showerhead, (ii) silver-coated copper mesh in the head and hose, and (iii) silver-embedded polymer composite compared to conventional plastic and metal showerheads. We found no significant difference in targeted DWPI transcriptional activity in collected water across silver and nonsilver shower head designs. Yet, the presence of silver and how it was incorporated in the showerhead influenced the metal concentrations, microbial rare taxa, and microbiome functionality. Microbial dynamics were also influenced by the showerhead age (i.e., time after installation). The results of this study provide valuable information for consumers and building managers to consider when choosing a showerhead meant to reduce microorganisms in shower water.

Photon upconversion is of great interest for improving the efficiency of silicon photovoltaic cells, for biological imaging, and for thermal management strategies. Currently, the vast majority of materials being developed for solar upconversion are composed of rare and expensive elemental compounds. Moving forward, the development of earth abundant, non-toxic materials that efficiently convert near infrared light into visible light would be ideal. Copper selenide-based materials meet these criteria, and are of great interest due to their unique thermoelectric and plasmonic properties. In particular, doped copper selenides (Cu2−xSe) have tunable near infrared localized surface plasmon resonances, large Seebeck coefficients, and low thermal conductivity, with a range of chemical and thermoelectric applications. Here, we observe another interesting application of this material in the upconversion of near infrared light from a silica xerogel film containing degenerately doped Cu2−xSe nanocrystals, with an onset flux of ∼ 1.96 ± 0.29 kW/cm^2 and at least 1% quantum yield. Our investigations suggest a plasmon-driven thermal mechanism likely plays a role in this upconversion process.

Design criteria for controlling engineered nanomaterial (ENM) antimicrobial performance will enable advances in medical, food production, processing and preservation, and water treatment applications. In pursuit of this goal, better resolution of how specific ENM properties, such as nanoparticle shape, influence antimicrobial activity is needed. This study probes the antimicrobial activity toward a model Gram-negative bacterium, Escherichia coli (E. coli), that results from interfacial interactions with differently shaped silver nanoparticles (AgNPs): cube-, disc-, and pseudospherical-AgNPs. The EC50 value (i.e., the concentration of AgNPs that inactivates 50% of the microbial population) for each shape is identified and presented as a function of mass, surface area, and particle number. Further, shifts in relative potency are identified from the associated dose-response curves (e.g., shifts left, to lower concentrations, indicate greater potency). When using a mass-based dose metric, the disc-AgNPs present the highest antimicrobial activity of the three shapes (EC50: 2.39 ± 0.26 μg/mL for discs, 2.99 ± 0.96 μg/mL for cubes, 116.33 ± 6.43 μg/mL for pseudospheres). When surface area and particle number are used as dose metrics, the cube-AgNPs possess the highest antimicrobial activity (EC50-surface area: 4.70 × 10-5 ± 1.51 × 10-5 m2/mL, EC50-particle: 5.97 × 109 ± 1.92 × 109 particles/mL), such that the relative trend in potency becomes cubes > discs > pseudospheres and cubes ≫ discs ⩾ pseudospheres, respectively. The results reveal that the antimicrobial potency of disc-AgNPs is sensitive to the dose metric, significantly decreasing in potency (∼5-30×) upon conversion from a mass-based concentration to surface area and particle number and influencing the conclusions drawn. The shift in relative particle potency highlights the importance of investigating various dose metrics within the experimental design and signals different particle parameters influencing shape-based antimicrobial activity. To probe shape-dependent behavior, we use a unique empirical approach where the physical and chemical properties (ligand chemistry, surface charge) of the AgNP shapes are carefully controlled, and total available surface area is equivalent across shapes as made through modifications to particle size and concentration. The results herein suggest that surface area alone does not drive antimicrobial activity as the different AgNP shapes at equivalent particle surface area yield significantly different magnitudes of antimicrobial activity (i.e., 100% inactivation for cube-AgNPs, <25% inactivation for disc- and pseudospherical-AgNPs). Further, the particle shapes studied possess different crystal facets, illuminating their potential influence on differentiating interactions between the particle surface and the microbe. Whereas surface area may partly contribute to antimicrobial activity in certain ENM shapes (i.e., disc-AgNPs in relation to the pseudospherical-AgNPs), the different magnitudes of antimicrobial activity across shape provide insight into the likely role of other particle-specific factors, such as crystal facets, driving the antimicrobial activity of other shapes (i.e., cube-AgNPs).

In this report, we investigate the addition of two metal cations, simultaneously and sequentially to Cu2-xSe nanoparticles. The metal combinations (Ag-Au, Ag-Pt, Hg-Au and Hg-Pt) are chosen such that one metal adds to the structure via cation exchange and the other adds to the structure via metal deposition when added individually to Cu2-xSe nanoparticles. Surprisingly, we find that for each metal combination, across all three synthesis routes, cation exchange and metal deposition products are obtained without deviation from the outcomes seen in the binary metal systems. However, within those outcomes the data show several types of heterogeneities in the morphologies formed including extent and composition of cation exchange products as well as the extent and composition of the metal deposited products. Taken together, these results suggest a hierarchical control for nanoheterostructure morphologies where the pathways of cation exchange or metal deposition in post-synthetic modification of Cu2-xSe exhibit relatively general outcomes as a function of metal, regardless of synthetic approach or metal combination. However, the detailed composition and interface populations of the resulting materials are more sensitive to both metal identities and synthetic procedure (e.g. order of reagent addition), suggesting that certain principles of metal chalcogenide post-synthetic modification are excitingly robust, while also revealing new avenues for both mechanistic discovery and structural control.

The diffusion coefficients of poly(ethylene glycol) methyl ether thiol (PEGSH)-functionalized gold nanoparticles (NPs) with different effective grafting densities were measured in polyacrylamide hydrogels. The NP core size was held constant, and the NPs were functionalized with mixtures of short oligomeric ligands (254 Da PEGSH) and longer (either 1 or 2 kDa PEGSH) ligands. The ratio of short and long ligands was varied such that the grafting density of the high-molecular-weight (MW) ligand ranged from approximately 1 to 100 high-MW ligands/NP. The diffusion coefficients of the NPs were then measured in gels with varying average mesh sizes. The measured diffusion coefficients decreased with higher MW ligand density. Interestingly, the diffusion coefficients for NPs with high effective grafting densities were well-predicted by their hydrodynamic diameters, but the diffusion coefficients for NPs with low effective grafting densities were higher than expected from their hydrodynamic diameters. These results suggest that crowding in the NP ligand shell influences the mechanism of diffusion, with lower grafting densities allowing ligand chain relaxations that facilitate movement through the gel. This work brings new insights into the factors that dictate how NPs move through hydrogels and will inform the development of models for applications such as drug delivery in complex viscoelastic biological materials.

The pseudo-two-dimensional (2D) morphology of plate-like metal nano -particles makes them one of the most anisotropic, mechanistically understood, and tunable structures available. Although well-known for their superior plasmonic properties, recent progress in the 2D growth of various other materials has led to an increasingly diverse family of plate-like metal nanoparticles, giving rise to numerous appealing properties and applications. In this review, we summarize recent progress on the solution-phase growth of colloidal plate-like metal nanoparticles, including plasmonic and other metals, with an emphasis on mechanistic insights for different synthetic strategies, the crystallographic habits of different metals, and the use of nanoplates as scaffolds for the synthesis of other derivative structures. We additionally highlight representative self-assembly techniques and provide a brief overview on the attractive properties and unique versatility benefiting from the 2D morphology. Finally, we share our opinions on the existing challenges and future perspectives for plate-like metal nanomaterials.

Here, we report thesynthesis of multinary, heterostructured, andoctahedral nanoshells with tunable structures. The synthesis leveragesa unique combination of widely used post-synthetic modifications,including galvanic replacement, facet selective growth and etching,as well as cation exchange (CE) reactions. We start by using octahedralAu nanoparticles, converting these to PtAu nanoframes, and then depositingSe windows onto that framework. The subsequent reaction of Se withCu(+/2+) ions yields a hollow, metal-semiconductorhybrid PtAu@Cu2-x Se structure withobservable plasmonic features from the Cu2-x Se component. We then show that these Cu2-x Se domains can undergo CE and metal deposition reactionsusing Ag and Pd to yield both quinary and senary nanoshells with controlover the identity, composition, and spatial arrangement of the domains.Taken together, these experiments yield a new class of complex, hollow,metal-semiconductor hybrid particles. More broadly, these resultsdemonstrate remarkable modularity of the constituent reactions andindicate that these structures, as well as even more diverse and complexstructures, are likely accessible by retrosynthetic design.

Whether in organic synthesis or solar energy conversion, light can be a powerful reagent in chemical reactions and introduce new opportunities for synthetic control including duration, intensity, interval, and energy of irradiation. Here, we report the use of a molecular photosensitizer as a reducing agent in metallic nanoparticle syntheses. Using this approach, we report three key findings. (1) Nanoparticles produced by photocatalytic reduction form via a continuous nucleation mechanism, as opposed to burst and burst-like nucleation processes typically observed in metal nanoparticle syntheses. (2) Because nucleation is continuous, as long as the solution is irradiated (and there remains excess reagents in solution), nanoparticle nucleation can be turned on and off by controlling the timing and duration of irradiation, with no observable particle growth. (3) This synthetic method extends to the formation of bimetallic nanoparticles, which we show also form via a continuous nucleation pathway, and follow predicted patterns of metal incorporation as a function of the magnitude of the difference between the reduction potentials of the two metals. Taken together, these results establish a versatile synthetic method for the formation of multimetallic nanoparticles using visible light.

ADVERTISEMENT RETURN TO ISSUEPREVEditorialNEXTCelebrating a Nobel Prize to the "Discovery of Quantum Dots, an Essential Milestone in Nanoscience"Luis M. Liz-Marzán*Luis M. Liz-Marzán*Email for L.M.L.-M.: [email protected]More by Luis M. Liz-Marzánhttps://orcid.org/0000-0002-6647-1353, Natalie ArtziNatalie ArtziMore by Natalie Artzihttps://orcid.org/0000-0002-2211-6069, Sara BalsSara BalsMore by Sara Balshttps://orcid.org/0000-0002-4249-8017, Jillian M. BuriakJillian M. BuriakMore by Jillian M. Buriakhttps://orcid.org/0000-0002-9567-4328, Warren C. W. ChanWarren C. W. ChanMore by Warren C. W. Chanhttps://orcid.org/0000-0001-5435-4785, Xiaodong ChenXiaodong ChenMore by Xiaodong Chenhttps://orcid.org/0000-0002-3312-1664, Mark C. HersamMark C. HersamMore by Mark C. Hersamhttps://orcid.org/0000-0003-4120-1426, Il-Doo KimIl-Doo KimMore by Il-Doo Kimhttps://orcid.org/0000-0002-9970-2218, Jill E. MillstoneJill E. MillstoneMore by Jill E. Millstonehttps://orcid.org/0000-0002-9499-5744, Paul MulvaneyPaul MulvaneyMore by Paul Mulvaneyhttps://orcid.org/0000-0002-8007-3247, Wolfgang J. ParakWolfgang J. ParakMore by Wolfgang J. Parakhttps://orcid.org/0000-0003-1672-6650, Andrey RogachAndrey RogachMore by Andrey Rogachhttps://orcid.org/0000-0002-8263-8141, and Raymond E. SchaakRaymond E. SchaakMore by Raymond E. Schaakhttps://orcid.org/0000-0002-7468-8181Cite this: ACS Nano 2023, 17, 20, 19474–19475Publication Date (Web):October 17, 2023Publication History Published online17 October 2023Published inissue 24 October 2023https://pubs.acs.org/doi/10.1021/acsnano.3c09671https://doi.org/10.1021/acsnano.3c09671editorialACS PublicationsCopyright © Published 2023 by American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views3951Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (940 KB) Get e-AlertscloseSUBJECTS:Diagnostic imaging,Diodes,Materials science,Nanoscience,Quantum dots Get e-Alerts

Light driven hydrogen production from the water splitting reaction has the ability to reduce dependence on fossil fuels in a green energy future.