Recent advances in one-dimensional assembly of nanoparticles

Oriented Linear Self-Assembly of Colloidal Nanocrystals through Regioselective Formation of Hydrogen-Bonded Supramolecular Bridges

The linear assembly of nanocrystals (NCs) with orientational order presents a significant challenge in the field of colloidal assembly. This study presents an efficient strategy for assembling oleic acid (OAH)-capped, faceted rare earth NCs─such as nanorods, nanoplates, and nanodumbbells─into flexible chain-like superstructures. Remarkably, these NC chains exhibit a high degree of particle orientation even with an interparticle distance reaching up to 15 nm. Central to this oriented assembly method is the facet-selective adsorption of low-molecular-weight polyethylene glycol (PEG), such as PEG-400 (Mn = 400), onto specific facets of NCs. This regioselectivity is achieved by exploiting the lower binding affinity of OAH ligands on the (100) facets of rare earth NCs, enabling facet-specific ligand displacement and subsequent PEG attachment. By adjusting the solvent polarity, the linear assembly of NCs is induced by the solvophobic effect, which simultaneously promotes the formation of hydrogen-bonded PEG supramolecular bridges. These supramolecular bridges effectively connect NCs and exhibit sufficient robustness to maintain the structural integrity of the chains, despite the large interparticle spacing. Notably, even when coassembling different types of NCs, the resulting multicomponent chains still feature highly selective facet-to-facet connections. This work not only introduces a versatile method for fabricating well-aligned linear superstructures but also provides valuable insights into the fundamental principles governing the facet-selective assembly of NCs in solution.

Template-free generation and integration of functional 1D magnetic nanostructures

The direct integration of 1D magnetic nanostructures into electronic circuits is crucial for realizing their great potential as components in magnetic storage, logical devices, and spintronic applications. Here, we present a novel template-free technique for producing magnetic nanochains and nanowires using directed self-assembly of gas-phase-generated metallic nanoparticles. The 1D nanostructures can be self-assembled along most substrate surfaces and can be freely suspended over micrometer distances, allowing for direct incorporation into different device architectures. The latter is demonstrated by a one-step integration of nanochains onto a pre-patterned Si chip and the fabrication of devices exhibiting magnetoresistance. Moreover, fusing the nanochains into nanowires by post-annealing significantly enhances the magnetic properties, with a 35% increase in the coercivity. Using magnetometry, X-ray microscopy, and micromagnetic simulations, we demonstrate how variations in the orientation of the magnetocrystalline anisotropy and the presence of larger multi-domain particles along the nanochains play a key role in the domain formation and magnetization reversal. Furthermore, it is shown that the increased coercivity in the nanowires can be attributed to the formation of a uniform magnetocrystalline anisotropy along the wires and the onset of exchange interactions.

Precision nanoengineering for functional self-assemblies across length scales

As nanotechnology continues to push the boundaries across disciplines, there is an increasing need for engineering nanomaterials with atomic-level precision for self-assembly across length scales, i.e., from the nanoscale to the macroscale. Although molecular self-assembly allows atomic precision, extending it beyond certain length scales presents a challenge. Therefore, the attention has turned to size and shape-controlled metal nanoparticles as building blocks for multifunctional colloidal self-assemblies. However, traditionally, metal nanoparticles suffer from polydispersity, uncontrolled aggregation, and inhomogeneous ligand distribution, resulting in heterogeneous end products. In this feature article, I will discuss how virus capsids provide clues for designing subunit-based, precise, efficient, and error-free self-assembly of colloidal molecules. The atomically precise nanoscale proteinic subunits of capsids display rigidity (conformational and structural) and patchy distribution of interacting sites. Recent experimental evidence suggests that atomically precise noble metal nanoclusters display an anisotropic distribution of ligands and patchy ligand bundles. This enables symmetry breaking, consequently offering a facile route for two-dimensional colloidal crystals, bilayers, and elastic monolayer membranes. Furthermore, inter-nanocluster interactions mediated via the ligand functional groups are versatile, offering routes for discrete supracolloidal capsids, composite cages, toroids, and macroscopic hierarchically porous frameworks. Therefore, engineered nanoparticles with atomically precise structures have the potential to overcome the limitations of molecular self-assembly and large colloidal particles. Self-assembly allows the emergence of new optical properties, mechanical strength, photothermal stability, catalytic efficiency, quantum yield, and biological properties. The self-assembled structures allow reproducible optoelectronic properties, mechanical performance, and accurate sensing. More importantly, the intrinsic properties of individual nanoclusters are retained across length scales. The atomically precise nanoparticles offer enormous potential for next-generation functional materials, optoelectronics, precision sensors, and photonic devices.

Three-Dimensional Coffee-Ring Effect Induced Deposition on Foam Surface for Enhanced Photothermal Conversion

Uniformly depositing a thin layer of functional constituents on porous foam is attractive to realize their concentrated interfacial application. Here, a simple but robust polyvinyl alcohol (PVA)-mediated evaporation drying strategy to achieve uniform surface deposition on melamine foam (MF) is introduced. Solutes can be accumulated homogeneously to the surface periphery of MF due to the enhanced coffee-ring effect of PVA and its stabilizing effect on various functional constituents, including molecules and colloidal particles. The deposition thickness is positively correlated with the feeding amounts of PVA but seems to be independent of drying temperature. 3D outward capillary flow driven by the combination of contact surface pinning and continual interfacial evaporation induces the forming of core-shell foams. The enhanced interfacial photothermal effect and solar desalination performance using PVA/polypyrrole-coated MF as a Janus solar evaporator are demonstrated.

Periodic Assembly of Diblock Pt-Au Heteronanowires for the Methanol Oxidation Reaction

Periodic assembly of heterogeneous nanoparticles provides a strategy for integrating distinct nanocatalyst blocks where their synergic effects can be explored for diverse applications. To achieve the synergistic enhancement, an intimate clean interface is preferred which however is usually plagued by the bulky surfactant molecules used in the synthesis and assembly process. Herein, we showed the creation of one-dimensional Pt-Au nanowires (NWs) with periodic alternating Pt and Au nanoblocks, by assembling Pt-Au Janus nanoparticles with the assistance of peptide T7 (Ac-TLTTLTN-CONH₂). It is demonstrated that the Pt-Au NWs showed much-improved performance in the methanol oxidation reaction (MOR), exhibiting 5.3 times higher specific activity and 2.5 times higher mass activity than the current state-of-the-art commercial Pt/C catalyst. In addition, the periodic heterostructure also improves the stability of Pt-Au NWs in the MOR, where the Pt-Au NWs retained 93.9% of their initial mass activity much higher than commercial Pt/C (30.6%).

Reversible assembly of nanoparticles: theory, strategies and computational simulations

The significant advances in synthesis and functionalization have enabled the preparation of high-quality nanoparticles that have found a plethora of successful applications. The unique physicochemical properties of nanoparticles can be manipulated through the control of size, shape, composition, and surface chemistry, but their technological application possibilities can be further expanded by exploiting the properties that emerge from their assembly. The ability to control the assembly of nanoparticles not only is required for many real technological applications, but allows the combination of the intrinsic properties of nanoparticles and opens the way to the exploitation of their complex interplay, giving access to collective properties. Significant advances and knowledge gained over the past few decades on nanoparticle assembly have made it possible to implement a growing number of strategies for reversible assembly of nanoparticles. In addition to being of interest for basic studies, such advances further broaden the range of applications and the possibility of developing innovative devices using nanoparticles. This review focuses on the reversible assembly of nanoparticles and includes the theoretical aspects related to the concept of reversibility, an up-to-date assessment of the experimental approaches applied to this field and the advanced computational schemes that offer key insights into the assembly mechanisms. We aim to provide readers with a comprehensive guide to address the challenges in assembling reversible nanoparticles and promote their applications.

Nanoscale thermoplasmonic welding

Establishing direct, close contact between individual nano-objects is crucial to fabricating hierarchical and multifunctional nanostructures. Nanowelding is a technical prerequisite for successfully manufacturing such structures. In this paper, we review the nanoscale thermoplasmonic welding with a focus on its physical mechanisms, key influencing factor, and emerging applications. The basic mechanisms are firstly described from the photothermal conversion to self-limited heating physics. Key aspects related to the welding process including material scrutinization, nanoparticle geometric and spatial configuration, heating scheme and performance characterization are then discussed in terms of the distinctive properties of plasmonic welding. Based on the characteristics of high precision and flexible platform of thermoplasmonic welding, the potential applications are further highlighted from electronics and optics to additive manufacturing. Finally, the future challenges and prospects are outlined for future prospects of this dynamic field. This work summarizes these innovative concepts and works on thermoplasmonic welding, which is significant to establish a common link between nanoscale welding and additive manufacturing communities.

1D Colloidal chains: recent progress from formation to emergent properties and applications

Integrating nanoscale building blocks of low dimensionality (0D; i.e., spheres) into higher dimensional structures endows them and their corresponding materials with emergent properties non-existent or only weakly existent in the individual building blocks. Constructing 1D chains, 2D arrays and 3D superlattices using nanoparticles and colloids therefore continues to be one of the grand goals in colloid and nanomaterial science. Amongst these higher order structures, 1D colloidal chains are of particular interest, as they possess unique anisotropic properties. In recent years, the most relevant advances in 1D colloidal chain research have been made in novel synthetic methodologies and applications. In this review, we first address a comprehensive description of the research progress concerning various synthetic strategies developed to construct 1D colloidal chains. Following this, we highlight the amplified and emergent properties of the resulting materials, originating from the assembly of the individual building blocks and their collective behavior, and discuss relevant applications in advanced materials. In the discussion of synthetic strategies, properties, and applications, particular attention will be paid to overarching concepts, fresh trends, and potential areas of future research. We believe that this comprehensive review will be a driver to guide the interdisciplinary field of 1D colloidal chains, where nanomaterial synthesis, self-assembly, physical property studies, and material applications meet, to a higher level, and open up new research opportunities at the interface of classical disciplines.

Stoichiometric Ratio Controlled Dimension Transition and Supramolecular Chirality Enhancement in a Two-Component Assembly System

To control the dimension of the supramolecular system was of great significance. We construct a two component self-assembly system, in which the gelator LHC18 and achiral azobenzene carboxylic acid could co-assembly and form gels. By modulating the stoichiometric ratio of the two components, not only the morphology could be transformed from 1D nanaotube to 0D nanospheres but also the supramolecualr chirality could be tuned. This work could provide some insights to the control of dimension and the supramolecular chirality in the two-component systems by simply modulating the stoichiometric ratio.

From dynamic self-organization to avalanching instabilities in soft-granular threads

We study the dynamics of threads of monodisperse droplets, including droplet chains and multi-chains, in which the droplets are interconnected by capillary bridges of another immiscible liquid phase. This system represents wet soft-granular matter - a class of granular materials in which the grains are soft and wetted by thin fluid films-with other examples including wet granular hydrogels or foams. In contrast to wet granular matter with rigid grains (e.g., wet sand), studied previously, the deformability of the grains raises the number of available metastable states and facilitates rearrangements which allow for reorganization and self-assembly of the system under external drive, e.g., applied via viscous forces. We use a co-flow configuration to generate a variety of unique low-dimensional regular granular patterns, intermediate between 1D and 2D, ranging from linear chains and chains with periodically occurring folds to multi-chains and segmented structures including chains of finite length. In particular, we observe that the partially folded chains self-organize via limit cycle of displacements and rearrangements occurring at a frequency self-adapted to the rate of build-up of compressive strain in the chain induced by the viscous forces. Upon weakening of the capillary arrest of the droplets, we observe spontaneous fluidization of the quasi-solid structures and avalanches of rearrangements. We identify two types of fluidization-induced instabilities and rationalize them in terms of a competition between advection and propagation. While we use aqueous droplets as the grains we demonstrate that the reported mechanisms of adaptive self-assembly apply to other types of soft granular systems including foams and microgels. We discuss possible application of the reported quasi-1D compartmentalized structures in tissue engineering, bioprinting and materials science.

Shaping in the Third Direction; Synthesis of Patterned Colloidal Crystals by Polyester Fabric-Guided Self-Assembly

A polyester fabric with rectangular openings was used as a sacrificial template for the guiding of a sub-micron sphere (polystyrene (PS) and silica) aqueous colloid self-assembly process during evaporation as a patterned colloidal crystal (PCC). This simple process is also a robust one, being less sensitive to external parameters (ambient pressure, temperature, humidity, vibrations). The most interesting feature of the concave-shape-pattern unit cell (350 μm × 400 μm × 3 μm) of this crystal is the presence of triangular prisms at its border, each prism having a one-dimensional sphere array at its top edge. The high-quality ordered single layer found inside of each unit cell presents the super-prism effect and left-handed behavior. Wider yet elongated deposits with ordered walls and disordered top surfaces were formed under the fabric knots. Rectangular patterning was obtained even for 20 μm PS spheres. Polyester fabrics with other opening geometries and sizes (~300–1000 μm) or with higher fiber elasticity also allowed the formation of similar PCCs, some having curved prismatic walls. A higher colloid concentration (10–20%) induces the formation of thicker walls with fiber-negative replica morphology. Additionally, thick-wall PCCs (~100 μm) with semi-cylindrical morphology were obtained using SiO₂ sub-microspheres and a wavy fabric. The colloidal pattern was used as a lithographic mask for natural lithography and as a template for the synthesis of triangular-prism-shaped inverted opals.

3D Printing-Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications

3D printing (additive manufacturing (AM)) has enormous potential for rapid tooling and mass production due to its design flexibility and significant reduction of the timeline from design to manufacturing. The current state-of-the-art in 3D printing focuses on material manufacturability and engineering applications. However, there still exists the bottleneck of low printing resolution and processing rates, especially when nanomaterials need tailorable orders at different scales. An interesting phenomenon is the preferential alignment of nanoparticles that enhance material properties. Therefore, this review emphasizes the landscape of nanoparticle alignment in the context of 3D printing. Herein, a brief overview of 3D printing is provided, followed by a comprehensive summary of the 3D printing-enabled nanoparticle alignment in well-established and in-house customized 3D printing mechanisms that can lead to selective deposition and preferential orientation of nanoparticles. Subsequently, it is listed that typical applications that utilized the properties of ordered nanoparticles (e.g., structural composites, heat conductors, chemo-resistive sensors, engineered surfaces, tissue scaffolds, and actuators based on structural and functional property improvement). This review's emphasis is on the particle alignment methodology and the performance of composites incorporating aligned nanoparticles. In the end, significant limitations of current 3D printing techniques are identified together with future perspectives.

One-dimensional necklace-like assemblies of inorganic nanoparticles: Recent advances in design, preparation and applications

One-dimensional (1D) necklace-like assembly of inorganic nanoparticles exhibits unique collective properties, which are critical to open up new and remarkable opportunities in the field of nanotechnology. This review focuses on the recent advances in the production of these types of assemblies employing two strategies: colloidal synthesis and self-assembly procedures. After a brief description of the forces guiding nanoparticles towards the assembly, the main features of both strategies are discussed. Examples of approaches, typically involved in colloidal synthesis, are highlighted. The peculiar properties of 1D nanostructures are strictly associated with the nanoparticle arrangement in the form of highly ordered assemblies, which are attained during the synthesis both in the solution and using a template, as well as under the action of an external force. The various 1D necklace-like structures, created through nanoparticle self-assembly, demonstrate aligned, oriented nanoparticle organization. Diverse nature, size and shape of preformed particles as building blocks, along with utilizing different linkers, templates or external field lead to fabrication of 1D chain nanostructures with properties responsible for their wide applications. The unique structure-property relationship, both in colloidal synthesis, and self-assembly, offers broad spectrum of 1D necklace-like nanostructure implementations, illustrated by their use in photonics, electronics, electrocatalysis, magnetics.

Porous self-supporting film of semi-flexible supracolloidal chains of diblock copolymer micelles

Patchy micelles of diblock copolymers can be polymerized into a linear supracolloidal chain. We measure the persistence and contour lengths of supracolloidal chains coated on a solid substrate to evaluate their flexibility. Based on the analysis, the chain is semi-flexible, and the conformation is suitably explained by the worm-like chain model. In addition, utilizing a spin-coating technique with the semi-flexible nature of the chains, we produce a self-supporting film of supracolloidal chains having nanoscale pores essentially from colloidal constituents that tend to form dense packing if there is no prior organization of them into a semi-flexible chain.

Nanofibrous Photocatalytic Membranes Based on Tailored Anisotropic Gold/Ceria Nanoparticles

The combination of plasmonic nanoparticles with semiconductor photocatalysts is a good strategy for synthesizing highly efficient photocatalysts. Such binary nanoparticles have demonstrated enhanced catalytic activity in comparison to either plasmonic catalysts or semiconductor catalysts. However, problematic recovery and limited long-term colloidal stability of those nanoparticles in suspension limit their wide use in catalysis. To palliate to such limitations, we embedded binary nanoparticles in polymer fibers to design photocatalytic membranes. First, we used the selective over-growth of crystalline cerium oxide on the gold nanoparticle template with distinct shapes. Gold nanospheres, gold nanorods, and gold nanotriangles were used as the template for the growth of the cerium oxide domains. Then, the resulting nanoparticles were used to catalyze model reactions in suspensions. The gold nanoparticles covered with patches of cerium oxide outperformed the fully covered and naked nanoparticles in terms of catalytic efficiency. Finally, the most efficient binary nanostructures were successfully embedded in nanofibrous membranes by colloidal electrospinning and used in water remediation experiments in a flow-through reactor.

Programmable Self-Assembly of Gold Nanoarrows via Regioselective Adsorption

Programing the self-assembly of colloidal nanoparticles into predetermined superstructures represents an attractive strategy to realize functional assemblies and novel nanodevices, but it remains a challenge. Herein, gold nanoarrows (GNAs) showing a distinct convex-concave structure were employed as unique building blocks for programmable self-assembly involving multiple assembly modes. Regioselective adsorption of 1,10-decanedithiol on the vertexes, edges, and facets of GNAs allowed for programmable self-assembly of GNAs with five distinct assembly modes, and regioselective blocking with 1-dodecanethiol followed by adsorption of 1,10-decanedithiol gave rise to programmable self-assembly with six assembly modes including three novel wing-engaged modes. The assembly mode was essentially determined by regioselective adsorption of the dithiol linker dictated by the local curvature together with the shape complementarity of GNAs. This approach reveals how the geometric morphology of nanoparticles affects their regioselective functionalization and drives their self-assembly.

Unravelling Magnetic Nanochain Formation in Dispersion for In Vivo Applications

Self-assembly of iron oxide nanoparticles (IONPs) into 1D chains is appealing, because of their biocompatibility and higher mobility compared to 2D/3D assemblies while traversing the circulatory passages and blood vessels for in vivo biomedical applications. In this work, parameters such as size, concentration, composition, and magnetic field, responsible for chain formation of IONPs in a dispersion as opposed to spatially confining substrates, are examined. In particular, the monodisperse 27 nm IONPs synthesized by an extended LaMer mechanism are shown to form chains at 4 mT, which are lengthened with applied field reaching 270 nm at 2.2 T. The chain lengths are completely reversible in field. Using a combination of scattering methods and reverse Monte Carlo simulations the formation of chains is directly visualized. The visualization of real-space IONPs assemblies formed in dispersions presents a novel tool for biomedical researchers. This allows for rapid exploration of the behavior of IONPs in solution in a broad parameter space and unambiguous extraction of ​the parameters of the equilibrium structures. Additionally, it can be extended to study novel assemblies formed by more complex geometries of IONPs.

Transition metal sulfides meet electrospinning: versatile synthesis, distinct properties and prospective applications

One-dimensional (1D) electrospun nanomaterials have attracted significant attention due to their unique structures and outstanding chemical and physical properties such as large specific surface area, distinct electronic and mass transport, and mechanical flexibility. Over the past years, the integration of metal sulfides with electrospun nanomaterials has emerged as an exciting research topic owing to the synergistic effects between the two components, leading to novel and interesting properties in energy, optics and catalysis research fields for example. In this review, we focus on the recent development of the preparation of electrospun nanomaterials integrated with functional metal sulfides with distinct nanostructures. These functional materials have been prepared via two efficient strategies, namely direct electrospinning and post-synthesis modification of electrospun nanomaterials. In this review, we systematically present the chemical and physical properties of the electrospun nanomaterials integrated with metal sulfides and their application in electronic and optoelectronic devices, sensing, catalysis, energy conversion and storage, thermal shielding, adsorption and separation, and biomedical technology. Additionally, challenges and further research opportunities in the preparation and application of these novel functional materials are also discussed.

Unconventional-Phase Crystalline Materials Constructed from Multiscale Building Blocks

Crystal phase, an intrinsic characteristic of crystalline materials, is one of the key parameters to determine their physicochemical properties. Recently, great progress has been made in the synthesis of nanomaterials with unconventional phases that are different from their thermodynamically stable bulk counterparts via various synthetic methods. A nanocrystalline material can also be viewed as an assembly of atoms with long-range order. When larger entities, such as nanoclusters, nanoparticles, and microparticles, are used as building blocks, supercrystalline materials with rich phases are obtained, some of which even have no analogues in the atomic and molecular crystals. The unconventional phases of nanocrystalline and supercrystalline materials endow them with distinctive properties as compared to their conventional counterparts. This Review highlights the state-of-the-art progress of nanocrystalline and supercrystalline materials with unconventional phases constructed from multiscale building blocks, including atoms, nanoclusters, spherical and anisotropic nanoparticles, and microparticles. Emerging strategies for engineering their crystal phases are introduced, with highlights on the governing parameters that are essential for the formation of unconventional phases. Phase-dependent properties and applications of nanocrystalline and supercrystalline materials are summarized. Finally, major challenges and opportunities in future research directions are proposed.

One-dimensional assembly of β-form anhydrous guanine microrods

Biogenic guanine crystals exhibit excellent optical properties owing to their extremely high refractive index. However, there is no report related to the highly-ordered guanine assemblies in the synthetic systems. Herein, β-phase anhydrous guanine (β-AG) microrods were formed in mixed solvents of formamide and water in the presence of small organic molecules such as uric acid, pyrrole (Py), N-methyl-2-pyrrolidone (NMP), N-vinyl-2-pyrrolidone (NVP). The one-dimensional (1D) assembly of β-AG microrods form spontaneously in water, which is the first reported highly ordered 1D assembly of organic micro- or nanocrystals in the solution. The obtained β-AG microrods obtained in Py system can form reversible 1D assembly in water after being treated in organic solvents such as ethanol, acetone and isopropanol, which have high solubility in water. However, no reversible 1D assembly but only dispersed or aggregated guanine microrods formed in water after similar treatment in the other three organic solvents such as n-hexane, dichloroethane and petroleum ether with low solubility in water. Similar reversible assembly features can also be observed in other three systems, standard system, and NVP and NMP systems. The reversible 1D assemblies of guanine microrods in water and organic solvents with high solubility in water indicate that there is a strong interaction between the (100) planes of β-AG microrods in water. The oriented 1D assembly of guanine microrods with long axes perpendicular to the horizontal magnetic field can form in water under magnetic field.

Disturbance of cellular homeostasis as a molecular risk evaluation of human endothelial cells exposed to nanoparticles

Even though application of nanoparticles in medicine seems to provide unique solutions for drug delivery and diagnosis diseases, understanding interactions between nanoscale materials and biological systems is imperative. Therefore, this study determined the effect of different types of nanoparticles (NPs) on human endothelial cells and examined the types of toxicity responses they can induce. Four different types of NPs were tested (PLA/MMT/TRASTUZUMAB, PLA/EDTMP, PLGA/MDP, and Pluronic F127 MICELLES), representing three putative areas of application: anticancer therapy, scintigraphy, and cosmetology. The experiments were performed on immortalized human umbilical vein endothelial cells (HUVEC-STs). Light contrast phase microscopy as well as cell viability assays showed that only Pluronic F127 MICELLES decreased the number of HUVEC-STs in contrast to PLA/MMT/TRASTUZUMAB, PLA/EDTMP, and PLGA/MDP NPs, which altered cell morphology, but not their confluency. The tested NPs induced not only DNA strand-breaks and alkali-labile sites, but also internucleosomal DNA fragmentation, visualized as a DNA ladder pattern typical of apoptosis. Moreover, generation of free radicals and subsequent mitochondrial membrane potential collapse showed the significance of free radical production during interactions between NPs and endothelial cells. High concentrations of NPs had different degrees of toxicity in human endothelial cells and affected cell proliferation, redox homeostasis, and triggered mitochondrial dysfunction.

Optically Programmable Plateau-Rayleigh Instability for High-Resolution and Scalable Morphology Manipulation of Silver Nanowires for Flexible Optoelectronics

The ability to engineer microscale and nanoscale morphology upon metal nanowires (NWs) has been essential to achieve new electronic and photonic functions. Here, this study reports an optically programmable Plateau-Rayleigh instability (PRI) to demonstrate a facile, scalable, and high-resolution morphology engineering of silver NWs (AgNWs) at temperatures <150 °C within 10 min. This has been accomplished by conjugating a photosensitive diphenyliodonium nitrate with AgNWs to modulate surface-atom diffusion. The conjugation is UV-decomposable and able to form a cladding of molten salt-like compounds, so that the PRI of the AgNWs can be optically programmed and triggered at a much lower temperature than the melting point of AgNWs. This PRI self-assembly technique can yield both various novel nanostructures from single NW and large-area microelectrodes from the NW network on various substrates, such as a nanoscale dot-dash chain and the microelectrode down to 5 μm in line width that is the highest resolution ever fabricated for the AgNW-based electrode. Finally, the patterned AgNWs as flexible transparent electrodes were demonstrated for a wearable CdS NW photodetector. This study provides a new paradigm for engineering metal micro-/nanostructures, which holds great potential in fabrication of various sophisticated devices.

Growth of Porous Ag@AuCu Trimetal Nanoplates Assisted by Self-Assembly

The self-assembly process of metal nanoparticles has aroused wide attention due to its low cost and simplicity. However, most of the recently reported self-assembly systems only involve two or fewer metals. Herein, we first report a successful synthesis of self-assembled Ag@AuCu trimetal nanoplates in aqueous solution. The building blocks of multibranched AuCu alloy nanocrystals were first synthesized by a chemical reduction method. The growth of Ag onto the AuCu nanocrystals in the presence of hexadecyltrimethylammonium chloride (CTAC) induces a self-assembly process and formation of Ag@AuCu trimetal nanoplates. These nanoplates with an average side length of over 2 μm show a porous morphology and a very clear boundary with the branches of the as-prepared AuCu alloy nanocrystals extending out. The shape and density of the Ag@AuCu trimetal nanoplates can be controlled by changing the reaction time and the concentration of silver nitrate. The as-assembled Ag@AuCu nanoplates are expected to have the potential for wide-ranging applications in surface-enhanced Raman scattering (SERS) and catalysis owing to their unique structures.

Construction of a Smart Nanofluidic Sensor through a Redox Reaction Strategy for High-Performance Carbon Monoxide Sensing

Carbon monoxide (CO), an important gas signaling molecule, demonstrated various physiological and pathological functions by regulating the ion flux of biological channels. Herein, inspired by the CO-regulated K⁺ channel in vivo, we propose a smart CO-responsive nanosensor through the redox reaction strategy. Such nanosensor demonstrated an outstanding CO specificity and selectivity with high ion rectification (∼9) as well as excellent stability and recyclability. Therefore, these results will provide a new direction for the design of nanochannel-based sensors for future practical and biological applications.

Microscale Self-Assembly of Upconversion Nanoparticles Driven by Block Copolymer

Lanthanide-based upconversion nanoparticles can convert low-energy excitation to high-energy emission. The self-assembled upconversion nanoparticles with unique structures have considerable promise in sensors and optical devices due to intriguing properties. However, the assembly of isotropic nanocrystals into anisotropic structures is a fundamental challenge caused by the difficulty in controlling interparticle interactions. Herein, we report a novel approach for the preparation of the chain-like assemblies of upconversion nanoparticles at different scales from nano-scale to micro-scale. The dimension of chain-like assembly can be fine-tuned using various incubation times. Our study observed Y-junction aggregate morphology due to the flexible nature of amphiphilic block copolymer. Furthermore, the prepared nanoparticle assemblies of upconversion nanoparticles with lengths up to several micrometers can serve as novel luminescent nanostructure and offer great opportunities in the fields of optical applications.

Intracellular microtubules as nano-scaffolding template self-assembles with conductive carbon nanotubes for biomedical device

Cellular bilayer and its membrane have been mimicked and for decades, e.g., to synthesize amphiphilic carriers for controlled release. Here we report using nanosized cellular microtubules (MT) as scaffolding template and amphiphilic cytomembrane fragment to self-assemble with hydrophobic carbon nanotubes (MWNT). The hybrid was then cross-linked to form a conductive scaffold. Polyaniline (PANI) was finally added to the nanocomposite to enhance conductivity. Being an electrode, the obtained cell-based conductive gel raise interfacial surface area, increase the conductivity of the material, and enhance the energy density and power density of the material with a relatively low MWNTs concentration (less than 4.8 wt%). The cell-based supercapacitor reaches a specific capacitance of 209.2 F/g and thus the fabricated cell-based electrode achieves a conductivity of 38Scm^-1. The cellular electric device exhibits great potential for future implantable bio-device and bio-electronic interface applications.

Dimension-Tunable Circularly Polarized Luminescent Nanoassemblies with Emerging Selective Chirality and Energy Transfer

The selective interplay between dimensional morphology transition and signal transfer is an important feature for both nanomaterials and biosystems. While most of those reported examples considered either dimensional transition or signal transfer, the integrated interplay or selectivity for these two aspects in single self-assembled system has been rarely studied. Here, we report that a positively charged chiral π-building block could self-assemble into multidimensional nanostructures, which showed tunable circularly polarized luminescence (CPL). Impressively, when these CPL-active multidimensional structures interacted with two achiral dyes (positively charged ThT and negatively charged CNA), 3D nanocubes and 0D nanospheres showed neither chirality transfer nor energy transfer, while 2D nanoplates could successfully trigger a selective chirality or energy transfer depending on the charge type of acceptor dyes, which then emitted an enhanced CPL signal. This work demonstrated rational design of charged π-building block for the construction of dimension controllable and selective signal transfer self-assembly system, which might deepen the understanding the interplay of dimensional structures and signal transfer functions in natural and nano systems.

Writing chemical patterns using electrospun fibers as nanoscale inkpots for directed assembly of colloidal nanocrystals

Applications that range from electronics to biotechnology will greatly benefit from low-cost, scalable and multiplex fabrication of spatially defined arrays of colloidal inorganic nanocrystals. In this work, we present a novel additive patterning approach based on the use of electrospun nanofibers (NFs) as inkpots for end-functional polymers. The localized grafting of end-functional polymers from spatially defined nanofibers results in covalently bound chemical patterns. The main factors that determine the width of the nanopatterns are the diameter of the NF and the extent of spreading during the thermal annealing process. Lowering the surface energy of the substrates via silanization and a proper choice of the grafting conditions enable the fabrication of nanoscale patterns over centimeter length scales. The fabricated patterns of end-grafted polymers serve as the templates for spatially defined assembly of colloidal metal and metal oxide nanocrystals of varying sizes (15 to 100 nm), shapes (spherical, cube, rod), and compositions (Au, Ag, Pt, TiO2), as well as semiconductor quantum dots, including the assembly of semiconductor nanoplatelets.

Halogen bond-assisted self-assembly of gold nanoparticles in solution and on a planar surface

Halogen bonding (XB) has been shown to be a powerful tool for promoting molecular self-assembly in different fields. The use of XB for noncovalent assembly of inorganic nanoparticles (NP) is, instead, quite limited, considering how extensively other interactions (i.e., electrostatic forces, hydrophobic effect, hydrogen bonding, etc.) have been exploited to modulate and program NP self-assembly. Here, we designed and synthesized XB-capable organic ligands that were efficiently used to functionalize the surface of gold NPs (AuNPs). XB-assisted AuNP self-assembly was attained in solution mixing AuNPs bearing XB-donor ligands with ditopic XB-acceptor molecules and AuNPs functionalized with XB-acceptor moieties. Likewise, a preliminary study of XB-driven adsorption of these AuNPs on surface was performed via Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D), used as an in situ tool for measuring mass changes upon XB-driven self-assembly.

Thermoreversible magnetic nanochains

The reversible organization of nanomagnets into highly anisotropic assemblies is of considerable interest for many applications, including theragnostic strategies in vivo. The current preparation strategies lead to structures that are not stable without the permanent presence of an applied magnetic field (MF); otherwise, irreversible assemblies are produced with moderate shape anisotropy at nanoscales. Here, we present a new approach based on the thermoreversible Diels-Alder reaction in the presence of an external MF that enables the assembly of single-domain nanomagnets into narrow chains with lengths of several micrometers. The MF-assisted click chemistry approach included (i) the synthesis of nanoparticles through a modified hydrothermal method, (ii) their functionalization via ligand exchange, (iii) the MF-assisted formation of chains, and (iv) the linkage of the nanomagnets in the presence of the magnetic field. Moreover, the chains can be again disassembled at elevated temperatures through a retro-Diels-Alder reaction. We thus demonstrated for the first time that MF-assisted click chemistry is a convenient method for large-scale preparation of highly anisotropic assemblies of nanosized magnets that can be reversibly decomposed by thermal treatment.