Structural and Optical Properties of Discrete Dendritic Pt Nanoparticles on Colloidal Au Nanoprisms.

Catalytic and optical properties can be coupled by combining different metals into nanoscale architectures in which both the shape and the composition provide fine-tuning of functionality. Here, discrete, small Pt nanoparticles (diameter = 3-6 nm) were grown in linear arrays on Au nanoprisms, and the resulting structures are shown to retain strong localized surface plasmon resonances. Multidimensional electron microscopy and spectroscopy techniques (energy-dispersive X-ray spectroscopy, electron tomography, and electron energy-loss spectroscopy) were used to unravel their local composition, three-dimensional morphology, growth patterns, and optical properties. The composition and tomographic analyses disclose otherwise ambiguous details of the Pt-decorated Au nanoprisms, revealing that both pseudospherical protrusions and dendritic Pt nanoparticles grow on all faces of the nanoprisms (the faceted or occasionally twisted morphologies of which are also revealed), and shed light on the alignment of the Pt nanoparticles. The electron energy-loss spectroscopy investigations show that the Au nanoprisms support multiple localized surface plasmon resonances despite the presence of pendant Pt nanoparticles. The plasmonic fields at the surface of the nanoprisms indeed extend into the Pt nanoparticles, opening possibilities for combined optical and catalytic applications. These insights pave the way toward comprehensive nanoengineering of multifunctional bimetallic nanostructures, with potential applications in plasmon-enhanced catalysis and in situ monitoring of chemical processes via surface-enhanced spectroscopy.R. K. L. acknowledges support from a Clare College Junior Research Fellowship. S. M. C. acknowledges support from a Gates Cambridge Scholarship. This work has received funding from the European Union Seventh Framework Programme under Grant Agreement 312483-ESTEEM2 (Integrated Infrastructure Initiative-I3), and support from the European Research Council, Reference 291522 3DIMAGE. J. E. M. acknowledges support from the Research Corporation for Science Advancement.This is the author accepted manuscript. The final version is available from the American Chemical Society via http://dx.doi.org/10.1021/acs.jpcc.6b0210

Feature-interaction detection based on feature-based specifications

A Gd3+-coordinated polymerizable analogue of the MRI contrast agent Gd-DOTA was used to prepare amphiphilic block copolymers, with hydrophilic blocks composed entirely of the polymerized contrast agent. The resulting amphiphilic block copolymers assemble into nanoparticles (NPs) of spherical- or fibril-shape, each demonstrating enhanced relaxivity over Gd-DOTA. As an initial examination of their behavior in vivo, intraperitoneal (IP) injection of NPs into live mice was performed, showing long IP residence times, observed by MRI. Extended residence times for particles of well-defined morphology may represent a valuable design paradigm for treatment or diagnosis of peritoneal malignances

Surface Chemistry Controls Magnetism in Cobalt Nanoclusters

Magnetic properties of Co₁₃ and Co₅₅ nanoclusters, passivated by surface ligand shells that exhibit varying electronic interactions with the metal, are studied using density functional theory. The calculations show that the chemical nature of the bond between the ligand and the metal core (X-type or L-type) impacts the total magnetic moment of Co nanoclusters dramatically. Furthermore, the chemical identity of the ligand within each binding motif then provides a fine handle on the exhibited magnetic moment of the cluster. Thus, ligand shell chemistry is predicted to not only stabilize Co nanoclusters, but provide a powerful approach to control their magnetic properties, which combined enable a variety of magnetism-based applications

Seedless Initiation as an Efficient, Sustainable Route to Anisotropic Gold Nanoparticles

Seedless initiation has been used as a simple and sustainable alternative to seed-mediated production of two canonical anisotropic gold nanoparticles: nanorods and nanoprisms. The concentration of reducing agent during the nucleation event was found to influence the resulting product morphology, producing nanorods with lengths from 30 to 630 nm and triangular or hexagonal prisms with vertex-to-vertex lengths ranging from 120 to over 700 nm. The seedless approach is then used to eliminate several chemical reagents and reactions steps from classic particle preparations while achieving almost identical nanoparticle products and product yields. Our results shed light on factors that influence (or do not influence) the evolution of gold nanoparticle shape and present a dramatically more efficient route to obtaining these architectures. Specifically, using these methods reduces the total amount of reagent needed to produce nanorods and nanoprisms by as much as 90 wt % and, to the best of our knowledge, has yielded the first report of spectroscopically discernible, colloidal gold nanoplates synthesized using a seedless methodology

Impact of As-Synthesized Ligands and Low-Oxygen Conditions on Silver Nanoparticle Surface Functionalization

Here, we compare the ligand exchange behaviors of silver nanoparticles synthesized in the presence of two different surface capping agents: poly­(vinyl­pyrrolidone) (MW = 10 or 40 kDa) or trisodium citrate, and under either ambient or low-oxygen conditions. In all cases, we find that the polymer capping agent exhibits features of a weakly bound ligand, producing better ligand exchange efficiencies with an incoming thiolated ligand compared to citrate. The polymer capping agent also generates nanoparticles that are more susceptible to reactions with oxygen during both synthesis and ligand exchange. The influence of the original ligand on the outcome of ligand exchange reactions with an incoming thiolated ligand highlights important aspects of silver nanoparticle surface chemistry, crucial for applications ranging from photocatalysis to antimicrobials

Impacts of Copper Position on the Electronic Structure of [Au_25‑xCu_<i>x</i>(SH)₁₈]⁻ Nanoclusters

Here, we use density functional theory to model the impact of heteroatom position on the optoelectronic properties of mixed metal nanoclusters. First, we consider the well-described [Au₂₅(SH)₁₈]⁻ motif, and substitute Cu atoms at the three geometrically unique positions within the cluster. These clusters are atomically precise and show an electronic structure that is a function of both composition and heteroatom position. We then model clusters containing Cu substitutions at two positions, and demonstrate an additional and significant impact from heteroatom proximity with respect to one another. For each system, we report the formation energy, HOMO–LUMO gap, and energy level structure, and suggest how trends in these parameters may be explained using classic atomic descriptors such as electronegativity, analogous to design principles widely used in the field of organic electronics. Further, we use linear response time-dependent density functional theory to model the absorption behavior of each system in order to correlate these electronic properties with a convenient experimental readout

Plate-Like Colloidal Metal Nanoparticles

This article is part of the Anisotropic Nanomaterials special issue.The pseudo-two-dimensional (2D) morphology of plate-like metal nanoparticles 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.M.R.J. thanks the Robert A. Welch Foundation (grant C-1954), the David and Lucile Packard Foundation (grant 2018-68049), the National Science Foundation for a CAREER award (grant 2145500), and Rice University for financial support. L.S. receives support from the 2020 “la Caixa”Foundation Postdoctoral Junior Leader-Incoming Fellowship (ID 100010434, fellow-ship code LCF/BQ/PI20/11760028), and from a 2022 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation. L.M.L.-M. acknowledges funding from the European Research Council (ERC Advanced grant 787510, 4DbioSERS) and the Spanish Ministerio de Ciencia e Innovación, MCIN/AEI/10.13039/501100011033 (grant PID2020-117779RB-I00). X.Z. acknowledges financial support from the Juan de la Cierva fellowship (FJC2018-036104-I) and CUHK-Shenzhen (UDF01002665). M.S. thanks the Natural Science Foundation of China for their support (grant no. 22202133). J.E.M. thanks Leo and Theresa Wegemer for their generous support.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe