Assembly Of Metal Nanoparticles Research Articles

Analysis on the Propagation and Assembly of Metallic Nanoparticles through Subwavelength Apertures with Overlapping Electrical Double Layers

Analysis on the Propagation and Assembly of Metallic Nanoparticles through Subwavelength Apertures with Overlapping Electrical Double Layers

Hierarchical Assembly of High-Nuclearity Copper(I) Alkynide Nanoclusters: Highly Effective CO2 Electroreduction Catalyst toward Hydrocarbons.

The pursuit of precision in the engineering of metal nanoparticle assemblies has long fascinated scientists, but achieving atomic-level accuracy continues to pose a significant challenge. This research sheds light on the hierarchical assembly processes of two high-nuclearity Cu(I) nanoclusters (NCs). By employing a multiligand cooperative stabilization strategy, we have isolated a series of thiacalix[4]arene (TC4A)/alkynyl coprotected Cu(I) NCs (Cux, where x = 9, 13, 17, 22). These NCs are intricately coassembled from the fundamental building units of {Cu4(TC4A)} and alkynyl-stabilized Cu5L6 in various ratios. By capturing active anion templates such as O2-, Cl-, or C22- that are generated in situ, we have further explored the secondary structural self-assembly of these clusters. Cu13 serves as a secondary assembly module for constructing Cu38 and Cu43, which exhibit the highest nuclearity reported to date among Cu(I) NCs encased in macrocyclic ligands. Notably, Cu38 demonstrates an impressive Faradaic efficiency of 62.01% for hydrocarbons at -1.57 V vs RHE during CO2 electroreduction, with 34.03% for C2H4 and 27.98% for CH4. This performance establishes it as an exceptionally rare, large, atomically precise metal NC (nuclearity >30) capable of catalyzing the formation of highly electro-reduced hydrocarbon products. Our research has introduced a new approach for constructing high-nuclearity Cu(I) NCs through a hierarchical assembly method and investigating their potential in the electrocatalytic transformation of CO2 into hydrocarbons.

Templated silver nanoparticle deposition on laser-induced periodic surface structures for SERS sensing

Organized assemblies of metal nanoparticles exhibit unique optical properties and can be used as platforms for surface-enhanced Raman scattering (SERS) to detect small amounts of analyte molecules. In this work, we demonstrate that using Yb:KGW femtosecond laser structuring of silicon wafer we can modify surface properties by creating laser-induced quasi periodic surface structures (LIPSS) of 850 ± 43 nm periodicity. We show that silicon with LIPSS is a suitable surface for direct nanoparticle deposition because of its superhydrophilic properties and the nanoparticle density affects the density of the hot spots contributing in the Raman enhancement. We have analyzed the influence of the silver nanoparticle deposition on the structured silicon surface conditions on their density and coverage. 101±8 nm size silver nanoparticles were deposited by two methods, namely drop casting colloidal solution at three different temperatures (4 °C, 21 °C, 35 °C) and their SERS enhancements were compared with the monolayers deposited by liquid-liquid interface. It was found that monolayer deposition on a structured surface was the best approach in the sense of even silver nanoparticles coverage which exhibited best SERS performance reaching a limit of detection of 10−7 M for 2-naphthalenethiol. The obtained LoD is comparable with that of commercial substrates available in the market.

Gold nanoshells with varying morphologies through templated surfactant‐assisted seed‐growth method

AbstractPlasmonic nanoparticles exhibit dramatic changes in optical properties depending on their spatial organization. Therefore, the ability to precisely control their assembly structure is important for both fundamental understanding and practical applications. In this personal account, we describe a templated surfactant‐assisted seed‐growth method to synthesize core–shell‐type gold nanoparticle assemblies with controllable surface morphologies and optical properties. This approach provides a simple procedure for simultaneous growth and assembly of metal nanoparticles on polymer templates, producing well‐defined nanostructures such as spiky nanoshells and raspberry‐like metamolecules with useful and interesting optical properties, such as strong and uniform surface‐enhanced Raman scattering and metamaterial properties. We discuss the factors that control the morphology and collective properties, describe the design rules acquired from the system, and suggest future directions of this research area.

Two-color interferometric scattering (iSCAT) microscopy reveals structural dynamics in discrete plasmonic molecules.

Plasmonic molecules are discrete assemblies of noble metal nanoparticles (NPs) that are of interest as transducers in optical nanosensors. So far, NPs with diameters of ∼40 nm have been the preferred building blocks for plasmonic molecules intended as optical single molecule sensors due to difficulties associated with detecting smaller NPs through elastic scattering in conventional darkfield microscopy. Here, we apply 405 nm, 445 nm two-color interferometric scattering (iSCAT) microscopy to characterize polyethylene glycol (PEG) tethered dimers of 10 nm and 20 nm Ag NPs and their monomers. Dimers of both NP sizes can be discerned from their respective monomers through changes in the average iSCAT contrast. In the case of 20 nm Ag NPs, dimer formation induces a change in the sign of the iSCAT contrast, providing a characteristic signal for detecting binding events. 20 nm Ag NP dimers with 0.4 kDa and 3.4 kDa polyethylene glycol (PEG) spacers show iSCAT contrast distributions with significantly different averages on both wavelength channels. The iSCAT contrast measured for individual PEG-tethered 10 nm or 20 nm NP dimers as a function of time shows contrast fluctuations indicative of a rich structural dynamics in the assembled plasmonic molecules, which provides an additional metric to discern dimers from monomers and paves the path to a new class of interferometric plasmon rulers.

A cerebral cortex-like structured metallized elastomer for high-performance triboelectric nanogenerator

The advancement of wearable electronics, particularly triboelectric nanogenerators (TENGs), relies on the development of flexible, stretchable, and compressible electrodes that possess a large active surface area, high electrical conductivity, and excellent mechanical stability and deformability. However, existing elastomeric electrodes face challenges in meeting all of these requirements. Herein, we present a novel approach to address these limitations and create electrodes with elastomeric properties, stable metal-like electrical conductivity, and an expanded active surface area. For this goal, we perform an assembly of metal nanoparticles (NPs) in toluene and amine-functionalized organic linkers in alcohol onto the thiol-functionalized, embossed-structured elastomer. Particularly, the assembly process involves ligand exchange reaction-mediated metal NPs and subjecting them to solvent-swelling/deswelling of the embossed PDMS. This process induces the formation of cerebral cortex-like structured elastomer electrode, which is subsequently electroplated with Ni. The resulting electrodes exhibit metal-like electrical conductivity, elastomer-like flexibility, and cerebral cortex-like structure with substantially large surface area and high stress relieving properties. When combined with an intaglio-structured dielectric PDMS electrode, the device exhibits impressive TENG performance, surpassing the performance of conventional TENGs. This approach provides a basis for developing and designing a variety of high-performance flexible electronics, including TENGs.

In Situ Insights into the Nucleation and Growth Mechanisms of Gold Nanoparticles on Tobacco Mosaic Virus.

Biotemplated syntheses have emerged as an efficient strategy to control the assembly of metal nanoparticles (NPs) and generate promising plasmonic properties for sensing or biomedical applications. However, understanding the nucleation and growth mechanisms of metallic nanostructures on biotemplate is an essential prerequisite to developing well-controlled nanotechnologies. Here, we used liquid cell Transmission Electron Microscopy (TEM) to reveal how the formation kinetics of gold NPs affects their size and density on Tobacco Mosaic Virus (TMV). These in situ insights are used as a guideline to optimize bench-scale synthesis with the possibility to homogenize the coverage and tune the density of gold NPs on TMV. In line with in situ TEM observations, fluorescence spectroscopy confirms that the nucleation of NPs occurs on the virus capsid rather than in solution. The proximity of gold NPs on TMV allows shifting the plasmonic resonance of the assembly in the biological window.

Molecular Engineering of Noble Metal Aerogels Boosting Electrocatalytic Oxygen Reduction

AbstractDeveloping robust oxygen reduction reaction (ORR) electrocatalysts with high activity and durability remains great challenging while noble metal aerogels (NMAs) hold great potential because of their hierarchically porous morphology, excellent activity, and self‐supported characteristic. Herein, a general molecular engineering strategy to synthesize molecule‐noble metal aerogels (M‐NMAs) via 3D assembly of metal nanoparticles (e.g., Pt, Pd, Au, Ag, and PtPd NPs) induced by metalloporphyrin as cross‐linkers is reported. Due to the well synergy of NMAs and porphyrin molecule in creating the facile reaction pathway for ORR catalysis, these M‐NMAs demonstrate boosted ORR activity and durability in different electrolytes. Particularly, the best PtPd‐based M‐NMA delivers 1.47 A mgPt−1 and 2.13 mA cm−2 in mass and specific activities, which are 11.3 and 14.2 times higher than those of the commercial Pt/C catalyst, respectively. Thus, this work not only provides a simple and universal functional engineering approach of NMAs with catalytic molecules, but also opens an avenue of the rational design for superior ORR electrocatalysts.

Micro/nano‐wrinkled elastomeric electrodes enabling high energy storage performance and various form factors

AbstractStretchable elastomer‐based electrodes are considered promising energy storage electrodes for next‐generation wearable/flexible electronics requiring various shape designs. However, these elastomeric electrodes suffer from the limited electrical conductivity of current collectors, low charge storage capacities, poor interfacial interactions between elastomers and conductive/active materials, and lack of shape controllability. In this study, we report hierarchically micro/nano‐wrinkle‐structured elastomeric electrodes with notably high energy storage performance and good mechanical/electrochemical stabilities, simultaneously allowing various form factors. For this study, a swelling/deswelling‐involved metal nanoparticle (NP) assembly is first performed on thiol‐functionalized polydimethylsiloxane (PDMS) elastomers, generating a micro‐wrinkled structure and a conductive seed layer for subsequent electrodeposition. After the assembly of metal NPs, the conformal electrodeposition of Ni and NiCo layered double hydroxides layers with a homogeneous nanostructure on the micro‐wrinkled PDMS induces the formation of a micro/nano‐wrinkled surface morphology with a large active surface area and high electrical conductivity. Based on this unique approach, the formed elastomeric electrodes show higher areal capacity and superior rate capability than conventional elastomeric electrodes while maintaining their electrical/electrochemical properties under external mechanical deformation. This notable mechanical/electrochemical performance can be further enhanced by using spiral‐structured PDMS (stretchability of ~500%) and porous‐structured PDMS (areal capacity of ~280 μAh cm−2).

A Strategy for the Determination of Alkaline Phosphatase Based on the Self-Triggered Degradation of Metal-Organic Frameworks by Phosphate.

Alkaline phosphatase (ALP) is widely present in the human body and is an important biomarker. Numerous ALP detection studies have been carried out, and ascorbic acid (AA) is often used as the reducing component in the sensors to monitor ALP levels since it can be produced from ascorbic acid 2-phosphate (AA2P) hydrolysis in the presence of ALP. However, it is well-known that AA is a strong reducing agent and can be easily oxidized. The disproportion between oxidized AA and reduced AA reactions results in the generation of AA free radicals with single electrons that may lead to inaccurate results in assays. To solve this problem, we synthesized a core-shell metal-organic framework sensor (PATP-Au@ZIF-8 NP) and used it as a sensitive and accurate ALP detection sensor with self-triggered control of phosphate ions (Pi) to avoid the potential inaccuracy of the method that uses AA as the reducing component. By establishing a physical shell on the surface of the gold nanoparticles (Au NPs), the sensor not only can eliminate the random assembly of metal nanoparticles caused by plasma exposure but also can generate self-triggering of Pi caused by ALP. Pi can decompose ZIF-8 through coordination with Zn2+ and thus can destroy the ZIF-8 shell structure of the prepared PAZ NPs. Au NPs are released and then become aggregated, in turn causing the SERS "hot spot" area to increase. The enhancement of the SERS signals was found to be directly associated with the level of Pi released from ALP-triggered hydrolysis. The response of the strategy was linear at ALP concentrations ranging from 0.1 to 150 mU/mL (r = 0.996) with a detection limit of 0.03 mU/mL. Lastly, the developed strategy was employed in the evaluation of ALP inhibitors, and the possibility to implement the developed SERS strategy for rapid and selective analysis of ALP in human serum was demonstrated.

Nanoporous metallic networks: Growth process and optical properties

Nanoporous metallic systems exhibit a new generation of advanced materials with potential in a wide variety of technological fields among them catalysis, photonics, optoelectronics and sensors.Their high surface-to-volume ratio, multimodal nanoscale moieties, ability to host guest materials, and inhomogeneous surface at the submicron scale distinct them from both bulk metals and conventional plasmonic materials as well as meta-surfaces. Those structures can be prepared through different fabrication and synthesis strategies including chemical dealloying, assembly of pre-synthesized metallic nanoparticles, and via templating. In a sharp contrast with these preparation strategies, we have demonstrated one can fabricate a macroscopic nanopourus metallic networks by using physical vapor deposition in a short single-step process. These materials are highly pure, and they show very unique linear and non-linear optical properties, among them high Second-Harmonic-generation response. Herein, we will discuss their growth process mechanism, and utilize it for more complex 3d structure which behave as SHG reflectors.

A general method for precise chain assembly of noble metal nanoparticles

We report a general method for obtaining precise chain aggregates of noble metal nanoparticles, which could be generally applied to AuNPs, AgNPs and PtNPs of various sizes, giving single long chains.

High-performance electrified hydrogel actuators based on wrinkled nanomembrane electrodes for untethered insect-scale soft aquabots.

Hydrogels have diverse chemical properties and can exhibit reversibly large mechanical deformations in response to external stimuli; these characteristics suggest that hydrogels are promising materials for soft robots. However, reported actuators based on hydrogels generally suffer from slow response speed and/or poor controllability due to intrinsic material limitations and electrode fabrication technologies. Here, we report a hydrogel actuator that operates at low voltages (<3 volts) with high performance (strain > 50%, energy density>7×105 joules per cubic meter, and power density>3×104 watts per cubic meter), surpassing existing hydrogel actuators and other types of electroactive soft actuators. The enhanced performance of our actuator is due to the formation of wrinkled nanomembrane electrodes that exhibit high conductivity and excellent mechanical deformation through capillary-assisted assembly of metal nanoparticles and deswelling-induced wrinkled structures. By applying an electric potential through the wrinkled nanomembrane electrodes that sandwich the hydrogel, we were able to trigger a reversible and substantial electroosmotic water flow inside a hydrogel film, which drove the controlled swelling of the hydrogel. The high energy efficiency and power density of our wrinkled nanomembrane electrode-induced actuator enabled the fabrication of an untethered insect-scale aquabot integrated with an on-board control unit demonstrating maneuverability with fast locomotion speed (1.02 body length per second), which occupies only 2% of the total mass of the robot.

Uncovering strong π-metal interactions on Ag and Au nanosurfaces under ambient conditions via in-situ surface-enhanced Raman spectroscopy

Uncovering strong π-metal interactions on Ag and Au nanosurfaces under ambient conditions via in-situ surface-enhanced Raman spectroscopy

Grain‐Boundary‐Rich Noble Metal Nanoparticle Assemblies: Synthesis, Characterization, and Reactivity

AbstractHere, a comprehensive study on the synthesis, characterization, and reactivity of grain‐boundary (GB)‐rich noble metal nanoparticle (NP) assemblies is presented. A facile and scalable synthesis of Pt, Pd, Au, Ag, and Rh NP assemblies is developed, in which NPs are predominantly connected via Σ3 (111) twin GBs, forming a network. Driven by water electrolysis, the random collisions and oriented attachment of colloidal NPs in solution lead to the formation of Σ3 (111) twin boundaries and some highly mismatched GBs. This synthetic method also provides convenient control over the GB density without altering the crystallite size or GB type by varying the NP collision frequency. The structural characterization reveals the presence of localized tensile strain at the GB sites. The ultrahigh activity of GB‐rich Pt NP assembly toward catalytic hydrogen oxidation in air is demonstrated, enabling room‐temperature catalytic hydrogen sensing for the first time. Finally, density functional theory calculations reveal that the strained Σ3(111) twin boundary facilitates oxygen dissociation, drastically enhancing the hydrogen oxidation rate via the dissociative pathway. This reported large‐scale synthesis of the Σ3 (111) twin GB‐rich structures enables the development of a broad range of high‐performance GB‐rich catalysts.

Colloidal Multiscale Assembly via Photothermally Driven Convective Flow for Sensitive In-Solution Plasmonic Detections.

The assembly of metal nanoparticles and targets to be detected in a small light probe volume is essential for achieving sensitive in-solution surface-enhanced Raman spectroscopy (SERS). Such assemblies generally require either chemical linkers or templates to overcome the random diffusion of the colloids unless the aqueous sample is dried. Here, a facile method is reported to produce 3D multiscale assemblies of various colloids ranging from molecules and nanoparticles to microparticles for sensitive in-solution SERS detection without chemical linkers and templates by exploiting photothermally driven convective flow. The simulations suggest that colloids sub 100nm in diameter can be assembled by photothermally driven convective flow regardless of density; the assembly of larger colloids up to several micrometers by convective flow is significant only if their density is close to that of water. Consistent with the simulation results,the authors confirm that the photothermally driven convective flow is mainly responsible for the observed coassembly of plasmonic gold nanorods with either smaller molecules or larger microparticles. It is further found that the coassembly with the plasmonic nanoantennae leads to dramatic Raman enhancements of molecules, microplastics, and microbes by up to fivefold of magnitude compared to those measured in solution without the coassembly.

Gold nanoparticle arrays organized in mixed patterns through directed self-assembly of ultrathin block copolymer films on topographic substrates

Controlling complexity in assemblies of metal and semiconductor nanoparticles has the potential to expand the utilization of photonic devices into wavelength regimes that are currently inaccessible. Here we show that casting ultrathin films of asymmetric block copolymers on topographically defined substrates affords four types of mixed patterns through fine control of film thickness. Analysis of top-view and cross-sectional images revealed different morphological behavior of the film in the trench and on the plateau, which was explained by the difference in the type of boundary imposed by each topographic feature. Exposed domains were chemically modified and selectively decorated with gold nanoparticles, giving rise to nanoparticle superstructures with mixed patterns in a controlled fashion. We envisage utilization of such hierarchical superstructures as plasmon waveguides and metasurfaces.

Phyto-Assisted Assembly of Metal Nanoparticles in Chitosan Matrix Using S. argel Leaf Extract and Its Application for Catalytic Oxidation of Benzyl Alcohol.

The design and synthesis of eco-friendly solid-supported metal nanoparticles with remarkable stability and catalytic performance have gained much attention for both industrial and environmental applications. This study provides a novel, low-cost, simple, and eco-friendly approach for decorating cross-linked chitosan with gold nanoparticles (AuNPs), greenly prepared with Solenostemma argel (S. argel) leaf extract under mild conditions. Glutaraldehyde-modified chitosan beads were used to coordinate with Au(III) ions and act as stabilizing agents, and S. argel leaf extract was used as a cost-effective phyto-reducing agent to reduce gold ions to elemental Au nanoparticles. The successful cross-linking of chitosan with glutaraldehyde, the coordination of Au(III) ions into the chitosan matrix, and the phytochemical reduction of Au(III) to Au nanoparticles were investigated via FT-IR spectroscopy. The obtained Au nanoparticles have a uniform spherical shape and size <10 nm, as confirmed by both X-ray diffraction (XRD) (~8.8 nm) and TEM (6.0 ± 3 nm). The uniformity of the AuNPs’ size was confirmed by Scanning Electron Microscopy (SEM) and Transition Electron Microscopy (TEM). The powder X-ray diffraction technique showed crystalline AuNPs with a face-centered cubic structure. The elemental analysis and the Energy Dispersive Spectroscopy (EDS) analysis both confirmed the successful integration of Au nanoparticles with the chitosan network. The catalytic activity of this highly stable nanocomposite was systematically investigated via the selective oxidation of benzyl alcohol to benzaldehyde. Results showed a remarkable conversion (97%) and excellent selectivity (99%) in the formation of benzaldehyde over other side products.

Silver Nanoparticle-Decorated Personal Protective Equipment for Inhibiting Human Coronavirus Infectivity.

The Coronavirus disease 2019 (COVID-19) global outbreak and its continued growth and mutation into various forms emphasize the need for effective disinfectants to assist in the reduction of the virus’s spread from individual to individuals and community to communities through various modes, including coughing, sneezing, touching of contaminated surfaces, and being in proximity of an unprotected infected person, to mention a few. The rapid development of reliable disinfecting materials or solutions and their incorporation in personal protective equipment is a critical need at the moment that will assist significantly in curbing the spread of the virus SARS-CoV-2, the cause of COVID-19 illness. Here, we present an in situ assembly of antiviral metal nanoparticles on a rigid surface and on commercial face masks made up of nonwoven and woven textiles. The results indicate a very high efficacy of 99.99% against a surrogate virus to SARS-CoV-2. Such a versatile and cost-effective approach using the blade-coating technique can be easily extended to the roll-to-roll manufacturing setting to expedite the efforts and mitigate the rapid spread of the virus.

Supramolecular Chirality from Hierarchical Self-Assembly of Atomically Precise Silver Nanoclusters Induced by Secondary Metal Coordination.

Chiral assembly of metal nanoparticles (NPs) into complex superstructures has been widely studied, but their formation mechanisms still remain mysterious due to the lack of precise structural information from the metal-organic interface to metallic kernel. As "molecular models" of metal NPs, atomically precise metal nanoclusters (NCs) used in the assembly of a macroscale superstructure will provide details of microscopic structure for deep understanding of such highly sophisticated assemblies; however, chiral superstructures have not been realized starting from achiral metal NCs with atomic precision. Herein, we report the supramolecular assembly of a water-soluble silver NC ((NH4)9[Ag9(mba)9], H2mba = 2-mercaptobenzoic acid, abbreviated as Ag9-NCs hereafter) into chiral hydrogels induced by the coordination of secondary metal ions. Single crystal X-ray diffraction reveals the triskelion-like structure of Ag9-NCs with a pseudochiral conformation caused by special arrangement of the peripheral mba2- ligands. The enantioselective orientation of the peripheral carboxyl group facilitates the assembly of Ag9-NCs into nanotubes with a chiral cubic (I*) lattice when coordinating to Ba2+. The nanotubes can further intertwine into one-dimensional chiral nanobraids with a preferred left-handed arrangement. These multiple levels of chirality can be tuned by drying, during which the I* phase is missing but the chiral entanglement of the nanotubes is enhanced. Through the gelation of atomically precise, achiral NCs coordination of secondary metal ions, chiral amplification of superstructures was realized. The origination of the chirality at different length scales was also discussed.