Regioselective surface encoding of nanoparticles for programmable self-assembly

Convergence of DNA nanotechnology and polymer chemistry to 'synthesize' nanopolymers with branching architectures: a computational perspective

Polymer-like superstructures termed nanopolymers from the self-assembly of atom-like nanoparticles are an emerging class of structured metamaterials with enhanced functionalities, but the controllable 'synthesis' of nanopolymers with non-linear architecture and spatially defined dimensions remains a challenge. Inspired by synthetic concepts of branched polymers, we propose a hierarchical polymerization-like protocol for the programmable coassembly of DNA-based multicomponent mixtures into non-linear nanopolymers with well-defined branching architecture and predictable spatial dimensions. By employing computational simulations, it is theoretically demonstrated that the synergy of sequence-designed DNA motifs and the proposed protocol enables the precise control over the assembly kinetics of atom-like nanoparticles and the branching architectures of nanopolymers, in agreement with the predictions of the generalized polymerization kinetics model. Furthermore, it is demonstrated that the fundamental correlations between the spatial dimension and branching architecture of nanopolymers satisfy the scaling law acquired in polymer science. These findings will facilitate the programmable coassembly of DNA supramolecules into structured metamaterials with architectural complexity observed in nature.

Prescribing DNA Origami Barrel-Directed Subtractive Patterning of Nanoparticles for Crystalline Superstructure Assembly

Long-range ordered lattices formed by the directed arrangement of colloidal particles hold significant promise for applications such as photonic crystals, plasmonic metamaterials, and semiconductor electronics. Harnessing regioselective interactions through DNA-mediated assembly is a promising approach to advancing colloidal assembly. Despite efforts to engineer microscale patchy particles using sequence-specific binding properties of DNA, the control of patch formation on nanoscale isotropic spherical nanoparticles remains challenging. We demonstrate a subtractive patterning strategy using barrel-shaped DNA origami (DNA barrel) to selectively block surfaces of DNA-coated gold nanospheres and create regiospecific patches. By designing binding positions and geometric parameters of DNA barrels, we can achieve controlled accessibility to nanosphere surfaces, forming patchy nanoparticles with tunable patch numbers and sizes. This strategy enables the construction of multidimensional superstructures with well-defined stereo relationships, represented by an unprecedented graphane-like bilayered superlattice. Furthermore, we developed a geometrical model that accounts for anisotropic particle bonding and steric hindrance, elucidating the relationship between architectural outcomes and the structural parameters of DNA-barrel-directed patchy nanoparticles, and enabling reverse engineering designs of potential assembly symmetries. This approach opens new avenues for generating nanoparticle assemblies with distinct symmetries and properties.

Directional Self-Assembly of Programmable Atom-like Nanoparticles into Colloidal Molecules

Colloidal molecules, novel nanoparticle clusters with molecular-like structures, can enhance material performance and broaden applications in nanotechnology and materials science. However, constructing them with a precise, controllable architecture remains challenging. Inspired by the concepts of chemical reaction, we theoretically design a novel type of nanoparticles bifunctionalized by DNA strands and polymer chains and propose a stepwise strategy to hierarchically program the assembly of bifunctionalized nanoparticles into well-defined colloidal molecules by virtue of coarse-grained molecular dynamics simulations. This method leverages the synergistic effects of polymers and DNA to create programmable atom-like nanoparticles with various valence domains. By carefully designing strands, these nanoparticles are programmed to coassemble into various colloidal molecules with distinct symmetries and coordination numbers, which can be finely tuned by the molecular design of nanoparticles as well as the composition design of the coassembly system. Our strategy provides a novel protocol for the controlled coassembly of nanoparticles into customized colloidal molecules, expanding nanomaterial manufacturing techniques.

On-Demand Assembly of Nanocrystals into a Superstructure Library in Co(OH)2 Single-Walled Nanotubes

The hierarchical self-assembly of colloidal particles facilitates the bottom-up manufacturing of metamaterials with synergistically integrated functionalities. Here, we define a modular assembly methodology that enables multinary co-assembly of nanoparticles in one-dimensional confined space. A series of isotropic and anisotropic nanocrystals such as plasmonic, metallic, visible, and near-infrared responsive nanoparticles as well as transition-metal phosphides can be selectively assembled within the single-walled Co(OH)2 nanotubes to achieve various increasingly sophisticated assembly systems, including unary, binary, ternary, and quaternary superstructures. Moreover, the selective assembly of distinct functional nanoparticles produces different integrated functional superstructures. This generalizable methodology provides predictable pathways to complex architectures with structural programming and customization that are otherwise inaccessible.

DNA‑Directed Assembly of Photonic Nanomaterials for Diagnostic and Therapeutic Applications

DNA-directed assembly has emerged as a versatile and powerful approach for constructing complex structured materials. By leveraging the programmability of DNA nanotechnology, highly organized photonic systems can be developed to optimize light-matter interactions for improved diagnostics and therapeutic outcomes. These systems enable precise spatial arrangement of photonic components, minimizing material usage, and simplifying fabrication processes. DNA nanostructures, such as DNA origami, provide a robust platform for building multifunctional photonic devices with tailored optical properties. This review highlights recent progress in DNA-directed assembly of photonic nanomaterials, focusing on their applications in diagnostics and therapeutics. It provides an overview of the latest advancements in the field, discussing the principles of DNA-directed assembly, strategies for functionalizing photonic building blocks, innovations in assembly design, and the resulting optical effects that drive these developments. The review also explores how these photonic architectures contribute to diagnostic and therapeutic applications, emphasizing their potential to create efficient and effective photonic systems tailored to specific healthcare needs.

High-Curvature Features on Branched Nanoconstructs Circumvent Protein Corona Interference

This paper reports how the local nanoscale curvature on nanoparticle constructs determines the protein corona distribution in biological conditions. Using transmission electron microscopy, we found that DNA-gold nanostar nanoconstructs (DNA-AuNS) having positive-curvature tips <5 nm in radius showed less dense and less uniform protein corona layers compared to 50 nm gold nanospheres (DNA-50NPs). Statistical analysis based on type of curvature on AuNS revealed that the protein layer thickness on the tips was lower than that on the neutral and negative curvature regions. Since protein coronas screen ligands on nanoparticles, we used DNA hybridization to evaluate whether local ligand functionality was preserved after adsorption of proteins. DNA-AuNS nanoconstructs with less dense protein coronas hybridized more 5 nm gold nanosphere probes (5NPs) compared to DNA-50NPs. Without the protein corona layer, the two classes of nanoconstructs hybridized higher numbers of 5NPs, and differences due to NP shape were minimal. Notably, we found that the tips of DNA-AuNS nanoconstructs exhibited higher percentages of hybridization compared to neutral and negative curvature regions; this trend was independent of DNA sequence. Our work demonstrates the importance of nanoconstruct curvature in mitigating local protein adsorption and preserving ligand functionality at the single-particle level.

Size-Dependent, Topology-Regulated, pH-Change-Tolerable, and Reversible Self-Assembly of Ultrasmall Nanoparticles

The multiscale ordering of colloidal nanoparticles (NPs) endows materials with diverse functions and performances. The controllable and predictable assembly of NPs is essential for the new generation of materials science. This study presents a topology-regulated self-assembly approach in an aqueous environment, utilizing polysorbate 20 (Tween-20) and ultrasmall gold nanoparticles (2, 4, and 8 nm AuNPs). The self-assembly process was governed by polyvalent hydrogen bonding interactions between the amphiphilic Tween-20 and tiopronin-capped NPs, with the amphipathic nature of Tween-20 primarily dictating the transformation from 1D to 3D structures. Notably, the NP size influences the assembly process, with the 2 nm particles demonstrating a well-regulated, pH-stable, and reversible assembly capability. Our findings provide a straightforward approach for controlling the assembly of simple nanoparticles and molecules into higher dimensional nano/microstructures, and close the knowledge gap in how NP size affects interactions within the assembly dynamics.

Easy reversible clustering of gold nanoparticles via pH-Induced assembly of PVP-b-PAA copolymer

The growing demand of novel hybrid organic/inorganic systems with exciting properties has contributed to an increasing need for simplifying production strategies. Here, we report a simple method to obtain controlled three-dimensional hybrid architectures, in particular hybrid supracolloids (hSC), formed by gold nanoparticles and a double hydrophilic block copolymer, specifically the poly(acrylic acid)-block-poly(N-vinyl-2-pyrrolidone) (PAA-b-PVP), directly in aqueous medium. The ubiquitous pH-sensitive poly(acrylic acid) (PAA) block initiates the assembly through pH changes, while the poly(N-vinyl-2-pyrrolidone) block assures the close affinity with the AuNPs. We demonstrate that the formation of hybrid supracolloids (hSC) is the result of the synergetic behavior of the two specific polymeric blocks. Additionally, the entire process shows spontaneous and fast switchability. The nanostructured copolymer behaves like a highly swollen hydrogel and displays a disordered internal structure. The driving force for the association of the copolymer chains is induced by the synergetic effects of the decrease in solubility of the poly(acrylic acid) block and the formation of inter and intra chains hydrogen bonds. These were demonstrated by using small angle X-ray scattering (SAXS), quartz crystal microbalance with dissipation monitoring (QCM-D) and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy (STEM-EDX). In turn, the AuNPs are randomly spread all over the polymeric matrix, as demonstrated by field emission gun - scanning electron microscopy (FEG-SEM). A correlation analysis reveals the hSC density depends mostly on the initial concentration of AuNPs. These results can inspire the fabrication of more complex structures with multicomponent composition.

Spontaneous Catalytic Reaction of a Surfactant in the Interfacial Microenvironment of Colloidal Gold Nanoparticles

The performance of nanomaterials is significantly determined by the interfacial microenvironment, in which a surfactant plays an essential role as the adsorbent, but its involvement in the interfacial reaction is often overlooked. Here, it was discovered that citrate and ascorbic acid, the two primarily used surfactants for colloidal gold nanoparticles (Au NPs), can spontaneously undergo catalytic reaction with trace-level nitrogenous residue under ambient environment to form oxime, which is subsequently cleaved to generate CN- or a compound containing the -CN group. Such a catalytic reaction shows wide universality in both reactants, including various carbonaceous and nitrogenous sources, and metal catalysts, including Au, Ag, Fe, Cu, Ni, Pt, and Pd NPs. Furthermore, with the removal of this reaction, adsorbed CO with diverse adsorption configurations was observed via surface-enhanced Raman spectroscopy under ambient conditions without an applied potential. Our work highlights the non-negligible significance of surfactants in interfacial microenvironments and provides crucial insights into the fundamental understanding of interfacial chemical reactions.

Surface Modification of Gold Nanorods: Multifunctional Strategies and Application Prospects

Gold nanorods (AuNRs), as an important type of gold nanomaterials, have attracted much attention in the nano field. Compared with gold nanoparticls, AuNRs have broader application potential due to their tunable localized surface plasmon resonance properties and anisotropic shapes. Yet, conventional synthesis methods using surfactants have limited the use of AuNRs in a variety of fields such as biomedical applications, plasma-enhanced fluorescence, optics and optoelectronic devices. To solve this problem and improve the stability and biocompatibility of AuNRs, researchers in recent years have used surface modification and functionalization to modify AuNRs, among which the introduction of organic ligands to prepare organic/gold hybrid nanorods has become an effective strategy. Organic materials have better toughness and easy processing, and by introducing organic ligands into the surface of AuNRs, the molecular-level composite of organic and inorganic materials can be realized, thus obtaining hybrid nanorods with excellent properties. This paper reviews the research progress of hybrid nanocomposites, and introducing the synthesis methods of AuNRs and the development of surface ligand modification, then summarises the applications of a wide variety of ligands. Also, the advantages and disadvantages of different ligands and their roles in further self-assembly processes are discussed.

Acoustofluidic manipulation for submicron to nanoparticles

Particles, ranging from submicron to nanometer scale, can be broadly categorized into biological and non-biological types. Submicron-to-nanoscale bioparticles include various bacteria, viruses, liposomes, and exosomes. Non-biological particles cover various inorganic, metallic, and carbon-based particles. The effective manipulation of these submicron to nanoparticles, including their separation, sorting, enrichment, assembly, trapping, and transport, is a fundamental requirement for different applications. Acoustofluidics, owing to their distinct advantages, have emerged as a potent tool for nanoparticle manipulation over the past decade. Although recent literature reviews have encapsulated the evolution of acoustofluidic technology, there is a paucity of reports specifically addressing the acoustical manipulation of submicron to nanoparticles. This article endeavors to provide a comprehensive study of this topic, delving into the principles, apparatus, and merits of acoustofluidic manipulation of submicron to nanoparticles, and discussing the state-of-the-art developments in this technology. The discourse commences with an introduction to the fundamental theory of acoustofluidic control and the forces involved in nanoparticle manipulation. Subsequently, the working mechanism of acoustofluidic manipulation of submicron to nanoparticles is dissected into two parts, dominated by the acoustic wave field and the acoustic streaming field. A critical analysis of the advantages and limitations of different acoustofluidic platforms in nanoparticles control is presented. The article concludes with a summary of the challenges acoustofluidics face in the realm of nanoparticle manipulation and analysis, and a forecast of future development prospects.

Evaluating the Accuracy of the COMSOL-Based Finite-Element Method for Simulating Plasmon-Modified Fluorescence

Accurately modeling plasmon-modified fluorescence is important for understanding and guiding the design of experimental nanostructures that reliably enhance fluorescence. They are of particular interest due to their potential to allow localized "hot spots" of high fluorescence enhancement in a reproducible manner. Given the increasingly prevalent use of the COMSOL Multiphysics software package for simulating these phenomena, we investigate its accuracy using an analytically tractable model consisting of a gold nanosphere interacting with either a plane wave or a radiating point dipole. COMSOL simulation results were compared with a formally exact analytical theory. It was found that simulation parameters commonly used for plane-wave scattering do not necessarily produce accurate results for the nanoparticle-plasmon-coupled dipole emission case. Instead, user-input adaptive meshing parameters were found to be helpful in achieving quantitative agreements between COMSOL and analytical theory results for plasmon-modified fluorescence. Our studies suggest convergence to analytically calculated values when a minimum of two additional user-input mesh elements separate the point-dipole position and the nanoparticle surface. This practical insight is expected to aid in the application of COMSOL simulations to planning and interpreting fluorescence modification experiments.

Engineering Anisotropy into Organized Nanoscale Matter

Programming the organization of discrete building blocks into periodic and quasi-periodic arrays is challenging. Methods for organizing materials are particularly important at the nanoscale, where the time required for organization processes is practically manageable in experiments, and the resulting structures are of interest for applications spanning catalysis, optics, and plasmonics. While the assembly of isotropic nanoscale objects has been extensively studied and described by empirical design rules, recent synthetic advances have allowed anisotropy to be programmed into macroscopic assemblies made from nanoscale building blocks, opening new opportunities to engineer periodic materials and even quasicrystals with unnatural properties. In this review, we define guidelines for leveraging anisotropy of individual building blocks to direct the organization of nanoscale matter. First, the nature and spatial distribution of local interactions are considered and three design rules that guide particle organization are derived. Subsequently, recent examples from the literature are examined in the context of these design rules. Within the discussion of each rule, we delineate the examples according to the dimensionality (0D-3D) of the building blocks. Finally, we use geometric considerations to propose a general inverse design-based construction strategy that will enable the engineering of colloidal crystals with unprecedented structural control.

Surface Orthogonal Patterning and Bidirectional Self-Assembly of Nanoparticles Tethered by V-Shaped Diblock Copolymers

We investigated the surface orthogonal patterning and bidirectional self-assembly of binary hairy nanoparticles (NPs) constructed by uniformly tethering a single NP with multiple V-shaped AB diblock copolymers using Brownian dynamics simulations in a poor solvent. At low concentration, the chain collapse and microphase separation of binary polymer brushes can lead to the patterning of the NP surface into A- and B-type orthogonal patches with various numbers of domains (valency), n = 1-6, that adopt spherical, linear, triangular, tetrahedral, square pyramidal, and pentagonal pyramidal configurations. There is a linear relationship between the valency and the average ratio of NP diameter to the polymers' unperturbed root-mean-square end-to-end distance for the corresponding valency. The linear slope depends on the grafting density and is independent of the interaction parameters between polymers. At high concentration, the orthogonal patch NPs serve as building blocks and exhibit directional attractions by overlapping the same type of domains, resulting in self-assembly into a series of fascinating architectures depending on the valency and polymer length. Notably, the 2-valent orthogonal patch NPs have the bidirectional bonding ability to form the two-dimensional (2D) square NP arrays by two distinct pathways. Simultaneously patching A and B blocks enables the one-step formation of 2D square arrays via bidirectional growth, whereas step-by-step patching causes the directional formation of 1D chains followed by 2D square arrays. Moreover, the gap between NPs in the 2D square arrays is related to the polymer length but independent of the NP diameter. These 2D square NP arrays are of significant value in practical applications such as integrated circuit manufacturing and nanotechnology.

Enhanced Prostate-specific Membrane Antigen Targeting by Precision Control of DNA Scaffolded Nanoparticle Ligand Presentation

Targeted nanoparticles have been extensively explored for their ability to deliver their payload to a selective cell population while reducing off-target side effects. The design of actively targeted nanoparticles requires the grafting of a ligand that specifically binds to a highly expressed receptor on the surface of the targeted cell population. Optimizing the interactions between the targeting ligand and the receptor can maximize the cellular uptake of the nanoparticles and subsequently improve their activity. Here, we evaluated how the density and presentation of the targeting ligands dictate the cellular uptake of nanoparticles. To do so, we used a DNA-scaffolded PLGA nanoparticle system to achieve efficient and tunable ligand conjugation. A prostate-specific membrane antigen (PSMA) expressing a prostate cancer cell line was used as a model. The density and presentation of PSMA targeting ligand ACUPA were precisely tuned on the DNA-scaffolded nanoparticle surface, and their impact on cellular uptake was evaluated. It was found that matching the ligand density with the cell receptor density achieved the maximum cellular uptake and specificity. Furthermore, DNA hybridization-mediated targeting chain rigidity of the DNA-scaffolded nanoparticle offered ∼3 times higher cellular uptake compared to the ACUPA-terminated PLGA nanoparticle. Our findings also indicated a ∼ 3.7-fold reduction in the cellular uptake for the DNA hybridization of the non-targeting chain. We showed that nanoparticle uptake is energy-dependent and follows a clathrin-mediated pathway. Finally, we validated the preferential tumor targeting of the nanoparticles in a bilateral tumor xenograft model. Our results provide a rational guideline for designing actively targeted nanoparticles and highlight the application of DNA-scaffolded nanoparticles as an efficient active targeting platform.

Symmetry-Breaking of Nanoparticle Surface Function Via Conformal DNA Design

Asymmetric surface functionalization of complex nanoparticles to control their directional self-assembly remains a considerable challenge. Here, we demonstrated a conformal DNA design strategy for flexible remodeling of the surface of complex nanoparticles, taking Au nanobipyramids (AuNBPs) as a model. We sheathed one or both tips of AuNBPs into conformal DNA origami with an exceptionally accurate orientation control. Such asymmetrically and symmetrically distributed surface patches possess regioselective, sequence, and site-specific DNA binding capabilities. As a result, we realized a series of prototypical multicomponent "colloidal molecules" made of AuNBPs and Au nanospheres (AuNSs) with defined directionality and number of "bonding valence" as well as 1D and 3D hierarchical assemblies, e.g., inverse core-satellites of AuNBPs and AuNSs, side-by-side and tip-to-tip linear assemblies of AuNBPs, and 3D helical superstructures of AuNBPs with tunable twists. These findings inspire new opportunities for nanoparticle surface engineering and the high-order self-assembly of nanoarchitectures with higher complexity and broadened functionalities.

Programmable Colloids with Analogous Hypercoordination Complex Architectures

Colloidal molecule clusters (CMCs) are promising building blocks with molecule-like symmetry, offering exceptional synergistic properties for applications in plasmonics and catalysis. Traditional CMC fabrication has been limited to simple molecule-like structures utilizing isotropic particles. Here, we employ molecular dynamics simulation to investigate the co-assembly of anisotropic nanorods (NRs) and the stimulus-responsive polymer (SRP) via reversible adsorption. The results of the simulation show that it is possible to fabricate hypercoordination complex structures with high symmetry from the co-assembly of NRs and the SRP, even in analogy to the Th(BH4)4 structure. The coordination number of these CMCs can be precisely programmed by adjusting the shape and size of the ends of the NRs and the SRP cohesion energy. Furthermore, a finite-difference time-domain simulation indicates these hypercoordination structures exhibit significantly enhanced optical activity and plasmonic coupling effects. These findings introduce a new design approach for complex molecule-like structures utilizing anisotropic nanoparticles and may expand the applications of CMCs in photonics.

Theory and simulation of ligand functionalized nanoparticles - a pedagogical overview

Synthesizing reconfigurable nanoscale synthons with predictive control over shape, size, and interparticle interactions is a holy grail of bottom-up self-assembly. Grand challenges in their rational design, however, lie in both the large space of experimental synthetic parameters and proper understanding of the molecular mechanisms governing their formation. As such, computational and theoretical tools for predicting and modeling building block interactions have grown to become integral in modern day self-assembly research. In this review, we provide an in-depth discussion of the current state-of-the-art strategies available for modeling ligand functionalized nanoparticles. We focus on the critical role of how ligand interactions and surface distributions impact the emergent, pre-programmed behaviors between neighboring particles. To help build insights into the underlying physics, we first define an "ideal" limit - the short ligand, "hard" sphere approximation - and discuss all experimental handles through the lens of perturbations about this reference point. Finally, we identify theories that are capable of bridging interparticle interactions to nanoscale self-assembly and conclude by discussing exciting new directions for this field.

Hierarchically Responsive Alternating Nano-Copolymers with Tailored Interparticle Bonds

Self-assembly of inorganic nanoparticles (NPs) is an essential tool for constructing structured materials with a wide range of applications. However, achieving ordered assembly structures with externally programmable properties in binary NP systems remains challenging. In this work, we assemble binary inorganic NPs into hierarchically pH-responsive alternating copolymer-like nanostructures in an aqueous medium by engineering the interparticle electrostatic interactions. The polymer-grafted NPs bearing opposite charges are viewed as nanoscale monomers ("nanomers"), and copolymerized into alternating nano-copolymers (ANCPs) driven by the formation of interparticle "bonds" between nanomers. The resulting ANCPs exhibit reversibly responsive "bond" length (i.e., the distance between nanomers) in response to the variation of pH in a range of ~7-10, allowing precise control over the surface plasmon resonance of ANCPs. Moreover, specific interparticle "bonds" can break up at pH≥11, leading to the dis-assembly of ANCPs into molecule-like dimers and trimers. These dimeric and trimeric structures can reassemble to form ANCPs owing to the resuming of interparticle "bonds", when the pH value of the solution changes from 11 to 7. The hierarchically responsive nanostructures may find applications in such as biosensing, optical waveguide, and electronic devices.

Tuning the dimensional order in self-assembled magnetic nanostructures: theory, simulations, and experiments

A major obstacle to building nanoscale magnetic devices or even experimentally studying novel nanomagnetic spin textures is the present lack of a simple and robust method to fabricate various nano-structured alloys. Here, theoretical and experimental investigations were conducted to understand the underlying physical mechanisms of magnetic particle self-assembly in zero applied magnetic field. By changing the amount of NaOH added during the synthesis, we demonstrate that the resulting morphology of the assembled FeCo structure can be tuned from zero-dimensional (0D) nanoparticles to one-dimensional (1D) chains, and even three-dimensional (3D) networks. Two numerical simulations were developed to predict aspects of nanostructure formation by accounting for the magnetic interactions between individual magnetic nanoparticles. The first utilized the Boltzmann distribution to determine the equilibrium structure of a nanochain, iteratively predicting the local deviation angle θ of each particle as it attaches to a forming chain. The second simulation illustrates the differences in nanostructure arrangement and dimensionality (0D, 1D, or 3D) that arise from random interactions at various nanoparticle densities. The simulation results closely match the experimental findings, as seen from SEM images, demonstrating their ability to capture the system's structural properties. In addition, magnetic hysteresis measurements of the samples were performed along two orthogonal directions to show the influence of dimensional order on the magnetic behavior. The normalized remanence (MR/MS||) of the FeCo alloys increases as the dimensions of nanostructures are increased. Of the three cases, the FeCo 3D network structures exhibit the highest normalized nanostructure remanence of 0.33 and an increased coercivity to above 200 Oe at 300 K. This combined numerical and experimental investigation aims to shed light on the preparation of FeCo nanostructures with tailorable dimensional order and it opens new avenues for exploring the complex spin textures and coercive behavior of these multi-dimensional nanomagnetic structures.

Photo-Induced Self-assembly of Copolymer-Capped Nanoparticles into Colloidal Molecules

Colloidal molecules (CMs) are precisely defined assemblies of nanoparticles (NPs) that mimic the structure of real molecules, but externally programming the precise self-assembly of CMs is still challenging. In this work, we show that the photo-induced self-assembly of complementary copolymer-capped binary NPs can be precisely controlled to form clustered ABx or linear (AB)y CMs at high yield (x is the coordination number of NP-Bs, and y is the repeating unit number of AB clusters). Under UV light irradiation, photolabile p-methoxyphenacyl groups of copolymers on NP-A*s are converted to carboxyl groups (NP-A), which react with tertiary amines of copolymers on NP-B to trigger the directional NP bonding. The x value of ABx can be precisely controlled between 1 and 3 by varying the irradiation duration and hence the amount of carboxyl groups generated on NP-As. Moreover, when NP-A* and NP-B are irradiated after mixing, the assembly process generates AB clusters or linear (AB)y structures with alternating sequence of the binary NPs. This assembly approach offers a simple yet non-invasive way to externally regulate the formation of various CMs on demand without the need of redesigning the surface chemistry of NPs for use in drug delivery, diagnostics, optoelectronics, and plasmonic devices.

Regulating phase behavior of nanoparticle assemblies through engineering of DNA-mediated isotropic interactions

Self-assembly of isotropically interacting particles into desired crystal structures could allow for creating designed functional materials via simple synthetic means. However, the ability to use isotropic particles to assemble different crystal types remains challenging, especially for generating low-coordinated crystal structures. Here, we demonstrate that isotropic pairwise interparticle interactions can be rationally tuned through the design of DNA shells in a range that allows transition from common, high-coordinated FCC-CuAu and BCC-CsCl lattices, to more exotic symmetries for spherical particles such as the SC-NaCl lattice and to low-coordinated crystal structures (i.e., cubic diamond, open honeycomb). The combination of computational and experimental approaches reveals such a design strategy using DNA-functionalized nanoparticles and successfully demonstrates the realization of BCC-CsCl, SC-NaCl, and a weakly ordered cubic diamond phase. The study reveals the phase behavior of isotropic nanoparticles for DNA-shell tunable interaction, which, due to the ease of synthesis is promising for the practical realization of non-close-packed lattices.

Fabrication of heterogeneous bimetallic nanochains through photochemical welding for promoting the electrocatalytic hydrogen evolution reaction

Heterogeneous bimetallic nanochains (NCs) have gained significant attention in the field of catalysis due to their abundant active sites, multi-component synergistic catalytic, and exotic electronic structures. Here, we present a novel approach to synthesize one-dimensional heterogeneous bimetallic nanochains using a local surface plasmon resonance (LSPR) based strategy of liquid-phase photochemical welding method containing self-assembly and subsequent welding processes. Initially, we introduce additives that facilitate the self-assembly and alignment of Au nanoparticles (NPs) into orderly lines. Subsequently, the LSPR effect of the Au NPs is stimulated by light, enabling the second metal precursor to overcome the energy barrier and undergo photodeposition in the gap between the arranged Au NPs, thereby connecting the nano-metal particles. This strategy can be extended to the photochemical welding of Au NPs-Ag and Au NRs. Using electrocatalytic hydrogen evolution reaction (HER) as a proof-of-concept application, the obtained one-dimensional structure of Au5Pt1 NCs exhibit promoted HER performances, where the mass activity of the Au5Pt1 nanochains is found to be 4.8 times higher than that of Au5Pt1 NPs and 10.4 times higher than that of commercial 20 wt% Pt/C catalysts. The promoted HER performance is benefited from the electron conduction ability and abundant active sites.

A Spatially Programmable DNA Nanorobot Arm to Modulate Anisotropic Gold Nanoparticle Assembly by Enzymatic Excision

Programmable assembly of gold nanoparticle superstructures with precise spatial arrangement has drawn much attention for their unique characteristics in plasmonics and biomedicine. Bio-inspired methods have already provided programmable, molecular approaches to direct AuNP assemblies using biopolymers. The existing methods, however, predominantly use DNA as scaffolds to directly guide the AuNP interactions to produce intended superstructures. New paradigms for regulating AuNP assembly will greatly enrich the toolbox for DNA-directed AuNP manipulation and fabrication. Here, we developed a strategy of using a spatially programmable enzymatic nanorobot arm to modulate anisotropic DNA surface modifications and assembly of AuNPs. Through spatial controls of the proximity of the reactants, the locations of the modifications were precisely regulated. We demonstrated the control of the modifications on a single 15 nm AuNP, as well as on a rectangular DNA origami platform, to direct unique anisotropic AuNP assemblies. This method adds an alternative enzymatic manipulation to DNA-directed AuNP superstructure assembly.

Composite ligand shells on gold nanoprisms - an ensemble and single particle study

The attachment of thiolated molecules onto gold surfaces is one of the most extensively used and robust ligand exchange approaches to exploit the nanooptical features of nanoscale and nanostructured plasmonic materials. In this work, the impact of thiol adsorption on the optical properties of wet-chemically synthesized gold nanoprisms is studied both at the ensemble and single particle level to investigate the build-up of more complex ligand layers. Two prototypical ligands with different lengths have been investigated ((16-mercaptohexadecyl)trimethylammonium bromide - MTAB and thiolated polyethylene glycol - mPEG-SH). From ensemble experiments it is found that composite ligand layers are obtained by the sequential addition of the two thiols, and an island-like surface accumulation of the molecules can be anticipated. The single particle experiment derived chemical interface damping and resonance energy changes further support this and show additionally that when the two thiols are used simultaneously, a higher density, intermixed layer is formed. Hence, when working with more than a single type of ligand during surface modification, sequential adsorption is preferred for the combination of accessible essential surface functionalities, whereas for high overall loading the simultaneous use of the different ligand types is favourable.

Programmable Self-Assembly of Nanoplates into Bicontinuous Nanostructures

Self-assembly is the process by which individual components arrange themselves into an ordered structure by changing the shapes, components, and interactions. It has enabled us to construct an extensive range of geometric forms on many length scales. Nevertheless, the potential of two-dimensional polygonal nanoplates to self-assemble into extended three-dimensional structures with compartments and corridors has remained unexplored. In this paper, we show coarse-grained Monte Carlo simulations demonstrating self-assembly of hexagonal/triangular nanoplates via complementary interactions into faceted, sponge-like "bicontinuous polyhedra" (or infinite polyhedra) whose flat walls partition space into a pair of mutually interpenetrating labyrinths. Two bicontinuous polyhedra can be self-assembled: the regular (or Platonic) Petrie-Coxeter infinite polyhedron (denoted {6,4|4}) and the semi-regular Hart "gyrangle". The latter structure is chiral, with both left- and right-handed versions. We show that the Petrie-Coxeter assembly is constructed from two complementary populations of hexagonal nanoplates. Furthermore, we find that the 3D chiral Hart gyrangle can be assembled from identical achiral triangular nanoplates decorated with regioselective complementary interaction sites. The assembled Petrie-Coxeter and Hart polyhedra are faceted versions of two of the simplest triply periodic minimal surfaces, namely, Schwarz's primitive and Schoen's gyroid surfaces, respectively, offering alternative routes to those bicontinuous nanostructures, which are widespread in synthetic and biological materials.

The design of highly conductive and stretchable polymer conductors with low-load nanoparticles

Highly conductive and stretchable polymer conductors fabricated from conductive fillers and stretchable polymers are urgently needed in flexible electronics, implants, soft robotics, etc. However, polymer conductors encounter the conductivity-stretchability dilemma, in which high-load fillers needed for high conductivity always result in the stiffness of materials. Herein, we propose a new design of highly conductive and stretchable polymer conductors with low-load nanoparticles (NPs). The design is achieved by the self-assembly of surface-modified NPs to efficiently form robust conductive pathways. We employ computer simulations to elucidate the self-assembly of the NPs in the polymer matrices under equilibrium and tensile states. The conductive pathways retain 100% percolation probability even though the loading of the NPs is lowered to ∼2% volume. When the tensile strain reaches 400%, the percolation probability of the ∼2% NP system is still greater than 25%. The theoretical prediction suggests a way for advancing flexible conductive materials.

DNA-mediated regioselective encoding of colloids for programmable self-assembly

How far we can push chemical self-assembly is one of the most important scientific questions of the century. Colloidal self-assembly is a bottom-up technique for the rational design of functional materials with desirable collective properties. Due to the programmability of DNA base pairing, surface modification of colloidal particles with DNA has become fundamental for programmable material self-assembly. However, there remains an ever-lasting demand for surface regioselective encoding to realize assemblies that require specific, directional, and orthogonal interactions. Recent advances in surface chemistry have enabled regioselective control over the formation of DNA bonds on the particle surface. In particular, the structural DNA nanotechnology provides a simple yet powerful design strategy with unique regioselective addressability, bringing the complexity of colloidal self-assembly to an unprecedented level. In this review, we summarize the state-of-art advances in DNA-mediated regioselective surface encoding of colloids, with a focus on how the regioselective encoding is introduced and how the regioselective DNA recognition plays a crucial role in the self-assembly of colloidal structures. This review highlights the advantages of DNA-based regioselective modification in improving the complexity of colloidal assembly, and outlines the challenges and opportunities for the construction of more complex architectures with tailored functionalities.

Dynamic interfaces for contact-time control of colloidal interactions

Understanding pairwise interactions between colloidal particles out of equilibrium has a profound impact on dynamical processes such as colloidal self assembly. However, traditional colloidal interactions are effectively quasi-static on colloidal timescales and cannot be modulated out of equilibrium. A mechanism to dynamically tune the interactions during colloidal contacts can provide new avenues for self assembly and material design. In this work, we develop a framework based on polymer-coated colloids and demonstrate that in-plane surface mobility and mechanical relaxation of polymers at colloidal contact interfaces enable an effective, dynamic interaction. Combining analytical theory, simulations, and optical tweezer experiments, we demonstrate precise control of dynamic pair interactions over a range of pico-Newton forces and seconds timescales. Our model helps further the general understanding of out-of-equilibrium colloidal assemblies while providing extensive design freedom via interface modulation and nonequilibrium processing.

Molecular Engineering of Colloidal Atoms

Creation of architectures with exquisite hierarchies actuates the germination of revolutionized functions and applications across a wide range of fields. Hierarchical self-assembly of colloidal particles holds the promise for materialized realization of structural programing and customizing. This review outlines the general approaches to organize atom-like micro- and nanoparticles into prescribed colloidal analogs of molecules by exploiting diverse interparticle driving motifs involving confining templates, interactive surface ligands, and flexible shape/surface anisotropy. Furthermore, the self-regulated/adaptive co-assembly of simple unvarnished building blocks is discussed to inspire new designs of colloidal assembly strategies.

DNA-Patched Nanoparticles for the Self-Assembly of Colloidal Metamaterials

Colloidal metamaterials are highly desired artificial materials that recapitulate the structure of simple molecules. They exhibit exceptional functionalities conferred by the organization of and specific interaction among constituent elements. Harvesting such exquisite attributes for potential applications necessitates establishing precise control over their structural configuration with high precision. Yet, creating molecule-like small clusters of colloidal metamaterials remains profoundly challenging, as a lack of regioselectively encoded surface chemical heterogeneity prevents specific recognition interactions. Herein, we report a new strategy by harnessing magnetic-bead-assisted DNA cluster transferring to create discretely DNA cluster-patched nanoparticles for the self-assembly of colloidal metamaterials. This strategy affords broad generalizability and scalability for robustly patching DNA clusters on nanoparticles unconstrained by geometrical, dimensional, and compositional complexities commonly encountered in colloidal materials at the nano- and microscale. We direct judiciously patched nanoparticles into a wide variety of nanoassemblies and present a case study demonstrating the distinct metamaterial properties in enhancing the spontaneous emission of diamond nanoparticles. This newly invented strategy is readily implementable and extendable to construct a palette of structurally sophisticated and functionality-explicit architecture, paving the way for nanoscale manipulation of colloidal material functionalities with wide-ranging applications for biological sensing, optical engineering, and catalytic chemistry.

DNA-scaffolded multivalent vaccine against SARS-CoV-2

Short peptides are poor immunogens. One way to increase their immune responses is by arraying immunogens in multivalency. Simple and efficient scaffolds for spatial controlling the inter-antigen distance and enhancing immune activation are required. Here, we report a molecular vaccine design principle that maximally drives potent SARS-CoV-2 RBD subunit vaccine on DNA duplex to induce robust and efficacious immune responses in vivo. We expect that the DNA-peptide epitope platform represents a facile and generalizable strategy to enhance the immune response. STATEMENT OF SIGNIFICANCE: DNA scaffolds offer a biocompatible and convenient platform for arraying immunogens in multivalency antigenic peptides, and spatially control the inter-antigen distance. This can effectively enhance immune response. Peptide (instead of entire protein) vaccines are highly attractive. However, short peptides are poor immunogens. Our DNA scaffolded multivalent peptide immunogen system induced robust and efficacious immune response in vivo as demonstrated by the antigenic peptide against SAR-CoV-2. The present strategy could be readily generalized and adapted to prepare multivalent vaccines against other viruses or disease. Particularly, the different antigens could be integrated into one single vaccine and lead to super-vaccines that can protect the host from multiple different viruses or multiple variants of the same virus.

Engineering the Au-Cu2 O Crystalline Interfaces for Structural and Catalytic Integration

Precise structural control has attracted tremendous interest in pursuit of the tailoring of physical properties. Here, this work shows that through strong ligand-mediated interfacial energy control, Au-Cu₂ O dumbbell structures where both the Au nanorod (AuNR) and the partially encapsulating Cu₂ O domains are highly crystalline. The synthetic advance allows physical separation of the Au and Cu₂ O domains, in addition to the use of long nanorods with tunable absorption wavelength, and the crystalline Cu₂ O domain with well-defined facets. The interplay of plasmon and Schottky effects boosts the photocatalytic performance in the model photodegradation of methyl orange, showing superior catalytic efficiency than the AuNR@Cu₂ O core-shell structures. In addition, compared to the typical core-shell structures, the AuNR-Cu₂ O dumbbells can effectively electrochemically catalyze the CO₂ to C₂₊ products (ethanol and ethylene) via a cascade reaction pathway. The excellent dual function of both photo- and electrocatalysis can be attributed to the fine physical separation of the crystalline Au and Cu₂ O domains.

Surface engineering of colloidal nanoparticles

Synthesis of engineered colloidal nanoparticles (NPs) with delicate surface characteristics leads to well-defined physicochemical properties and contributes to multifunctional applications. Surface engineering of colloidal NPs can improve their stability in diverse solvents by inhibiting the interparticle attractive forces, thus providing a prerequisite for further particle manipulation, fabrication of the following materials and biological applications. During the last decades, surface engineering methods for colloidal NPs have been well-developed by numerous researchers. However, accurate control of surface properties is still an important topic. The emerging DNA/protein nanotechnology offers additional possibility of surface modification of NPs and programmable particle self-assembly. Here, we first briefly review the recent progress in surface engineering of colloidal NPs, focusing on the improved stability by grafting suitable small molecules, polymers or biological macromolecules. We then present the practical strategies for nucleic acid surface encoding of NPs and subsequent programmable assembly. Various exciting applications of these unique materials are summarized with a specific focus on the cellular uptake, bio-toxicity, imaging and diagnosis of colloidal NPs in vivo. With the growing interest in colloidal NPs in nano-biological research, we expect that this review can play an instructive role in engineering the surface properties for desired applications.

Self-Assembled Tetratic Crystals by Orthogonal Colloidal Force

Bonding simple building blocks to create crystalline materials with design has been sophisticated in the molecular world, but this is still very challenging for anisotropic nanoparticles or colloids, because the particle arrangements, including position and orientation, cannot be manipulated as expected. Here biconcave polystyrene (PS) discs to present a shape self-recognition route are used, which can control both the position and orientation of particles during self-assembly by directional colloidal forces. An unusual but very challenging two-dimensional (2D) open superstructure-tetratic crystal (TC)-is achieved. The optical properties of the 2D TCs are studied by the finite difference time domain method, showing that the PS/Ag binary TC can be used to modulate the polarization state of the incident light, for example, converting the linearly polarized light into left-handed or right-handed circularly polarized light. This work paves an important way for self-assembling many unprecedented crystalline materials.

Electric, magnetic, and shear field-directed assembly of inorganic nanoparticles

Ordered assemblies of inorganic nanoparticles (NPs) have shown tremendous potential for wide applications due to their unique collective properties, which differ from those of individual NPs. Various assembly methods, such as external field-directed assembly, interfacial assembly, template assembly, biomolecular recognition-mediated assembly, confined assembly, and others, have been employed to generate ordered inorganic NP assemblies with hierarchical structures. Among them, the external field-directed assembly method is particularly fascinating, as it can remotely assemble NPs into well-ordered superstructures. Moreover, external fields (e.g., electric, magnetic, and shear fields) can introduce a local and/or global field intensity gradient, resulting in an additional force on NPs to drive their rotation and/or translation. Therefore, the external field-directed assembly of NPs becomes a robust method to fabricate well-defined functional materials with the desired optical, electronic, and magnetic properties, which have various applications in catalysis, sensing, disease diagnosis, energy conversion/storage, photonics, nano-floating-gate memory, and others. In this review, the effects of an electric field, magnetic field, and shear field on the organization of inorganic NPs are highlighted. The methods for controlling the well-ordered organization of inorganic NPs at different scales and their advantages are reviewed. Finally, future challenges and perspectives in this field are discussed.

Development of Janus Particles as Potential Drug Delivery Systems for Diabetes Treatment and Antimicrobial Applications

Janus particles have emerged as a novel and smart material that could improve pharmaceutical formulation, drug delivery, and theranostics. Janus particles have two distinct compartments that differ in functionality, physicochemical properties, and morphological characteristics, among other conventional particles. Recently, Janus particles have attracted considerable attention as effective particulate drug delivery systems as they can accommodate two opposing pharmaceutical agents that can be engineered at the molecular level to achieve better target affinity, lower drug dosage to achieve a therapeutic effect, and controlled drug release with improved pharmacokinetics and pharmacodynamics. This article discusses the development of Janus particles for tailored and improved delivery of pharmaceutical agents for diabetes treatment and antimicrobial applications. It provides an account of advances in the synthesis of Janus particles from various materials using different approaches. It appraises Janus particles as a promising particulate system with the potential to improve conventional delivery systems, providing a better loading capacity and targeting specificity whilst promoting multi-drugs loading and single-dose-drug administration.

Gold Nanoparticles Synthesized Using Various Reducing Agents and the Effect of Aging for DNA Sensing

Gold nanoparticles (AuNPs) are one of the most commonly used reagents in colloidal science and biosensor technology. In this work, we first compared AuNPs prepared using four different reducing agents including citrate, glucose, ascorbate, and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES). At the same absorbance at the surface plasmon peak of 520-530 nm, citrate-AuNPs and glucose-AuNPs adsorbed more DNA and achieved higher affinity to the adsorbed DNA. In addition, citrate-AuNPs had better sensitivity than glucose-AuNPs for label-free DNA detection. Then, using citrate-AuNPs, the effect of aging was studied by incubation of the AuNPs at 22 °C (room temperature) and at 4 °C for up to 6 months. During aging, the colloidal stability and DNA adsorption efficiency gradually decreased. In addition, the DNA sensing sensitivity using a label-free method also dropped around 4-fold after 6 months. Heating at boiling temperature of the aged citrate-AuNPs could not rejuvenate the sensing performance. This study shows that while citrate-AuNPs are initially better than the other three AuNPs in their colloid properties and sensing properties, this edge in performance might gradually decrease due to constantly changing surface properties caused from the aging effect.

Advances in Colloidal Building Blocks: Toward Patchy Colloidal Clusters

The scalable synthetic route to colloidal atoms has significantly advanced over the past two decades. Recently, colloidal clusters with DNA-coated cores called "patchy colloidal clusters" have been developed, providing a directional bonding with specific angle of rotation due to the shape complementarity between colloidal clusters. Through a DNA-mediated interlocking process, they are directly assembled into low-coordination colloidal structures, such as cubic diamond lattices. Herein, the significant progress in recent years in the synthesis of patchy colloidal clusters and their assembly in experiments and simulations is reviewed. Furthermore, an outlook is given on the emerging approaches to the patchy colloidal clusters and their potential applications in photonic crystals, metamaterials, topological photonic insulators, and separation membranes.

Toward Quantitative Surface-Enhanced Raman Scattering with Plasmonic Nanoparticles: Multiscale View on Heterogeneities in Particle Morphology, Surface Modification, Interface, and Analytical Protocols

Surface-enhanced Raman scattering (SERS) provides significantly enhanced Raman scattering signals from molecules adsorbed on plasmonic nanostructures, as well as the molecules' vibrational fingerprints. Plasmonic nanoparticle systems are particularly powerful for SERS substrates as they provide a wide range of structural features and plasmonic couplings to boost the enhancement, often up to >10⁸-10¹⁰. Nevertheless, nanoparticle-based SERS is not widely utilized as a means for reliable quantitative measurement of molecules largely due to limited controllability, uniformity, and scalability of plasmonic nanoparticles, poor molecular modification chemistry, and a lack of widely used analytical protocols for SERS. Furthermore, multiscale issues with plasmonic nanoparticle systems that range from atomic and molecular scales to assembled nanostructure scale are difficult to simultaneously control, analyze, and address. In this perspective, we introduce and discuss the design principles and key issues in preparing SERS nanoparticle substrates and the recent studies on the uniform and controllable synthesis and newly emerging machine learning-based analysis of plasmonic nanoparticle systems for quantitative SERS. Specifically, the multiscale point of view with plasmonic nanoparticle systems toward quantitative SERS is provided throughout this perspective. Furthermore, issues with correctly estimating and comparing SERS enhancement factors are discussed, and newly emerging statistical and artificial intelligence approaches for analyzing complex SERS systems are introduced and scrutinized to address challenges that cannot be fully resolved through synthetic improvements.

Interfacial-Shear-Mediated Snowball Assembly of Hotspot-Rich Silver Pompon Architectures for Tailored Surface-Enhanced Raman Scattering Responses

To gain superior signal-enhanced performance, metal nanocrystals serving as building blocks can be collectively assembled into a hierarchically ordered structure for creating multiple hotspots. However, the collaborative assembly of anisotropic crystals to form a hotspot-rich structure remains a challenging task. In this study, controllable shear was introduced to a soft liquid-liquid interface to provide a unique environment for the snowball assembly of silver pompon architectures (Ag-PAs). Micrometer-scale 3D plasmonic Ag pompon architectures composed of densely packed nanoparticles (NPs) are fabricated using shear-mediating crystal growth dynamics. The crystal morphology and size are easily controlled by tuning the interfacial shear and diffusion pathways. The hotspot-rich Ag-PAs with high sensitivity (LOD = 1.1 × 10^-13 mol/L) exhibit a superior Raman enhancement performance, which is comparable to some bimetals.

Zonal Intratumoral Delivery of Nanoparticles Guided by Surface Functionalization

Delivery of small molecules and anticancer agents to malignant cells or specific regions within a tumor is limited by penetration depth and poor spatial drug distribution, hindering anticancer efficacy. Herein, we demonstrate control over gold nanoparticle (GNP) penetration and spatial distribution across solid tumors by administering GNPs with different surface chemistries at a constant injection rate via syringe pump. A key finding in this study is the discovery of different zone-specific accumulation patterns of intratumorally injected nanoparticles dependent on surface functionalization. Computed tomography (CT) imaging performed in vivo of C57BL/6 mice harboring Lewis lung carcinoma (LLC) tumors on their flank and gross visualization of excised tumors consistently revealed that intratumorally administered citrate-GNPs accumulate in particle clusters in central areas of the tumor, while GNPs functionalized with thiolated phosphothioethanol (PTE-GNPs) and thiolated polyethylene glycol (PEG-GNPs) regularly accumulate in the tumor periphery. Further, PEG functionalization resulted in larger tumoral surface coverage than PTE, reaching beyond the outer zone of the tumor mass and into the surrounding stroma. To understand the dissimilarities in spatiotemporal evolution across the different GNP surface chemistries, we modeled their intratumoral transport with reaction-diffusion equations. Our results suggest that GNP surface passivation affects nanoparticle reactivity with the tumor microenvironment, leading to differential transport behavior across tumor zones. The present study provides a mechanistic understanding of the factors affecting spatiotemporal distribution of nanoparticles in the tumor. Our proof of concept of zonal delivery within the tumor may prove useful for directing anticancer therapies to regions of biomarker overexpression.

Symmetry-breaking in patch formation on triangular gold nanoparticles by asymmetric polymer grafting

Synthesizing patchy particles with predictive control over patch size, shape, placement and number has been highly sought-after for nanoparticle assembly research, but is fraught with challenges. Here we show that polymers can be designed to selectively adsorb onto nanoparticle surfaces already partially coated by other chains to drive the formation of patchy nanoparticles with broken symmetry. In our model system of triangular gold nanoparticles and polystyrene-b-polyacrylic acid patch, single- and double-patch nanoparticles are produced at high yield. These asymmetric single-patch nanoparticles are shown to assemble into self-limited patch‒patch connected bowties exhibiting intriguing plasmonic properties. To unveil the mechanism of symmetry-breaking patch formation, we develop a theory that accurately predicts our experimental observations at all scales—from patch patterning on nanoparticles, to the size/shape of the patches, to the particle assemblies driven by patch‒patch interactions. Both the experimental strategy and theoretical prediction extend to nanoparticles of other shapes such as octahedra and bipyramids. Our work provides an approach to leverage polymer interactions with nanoscale curved surfaces for asymmetric grafting in nanomaterials engineering.

Steering DNA Condensation on Engineered Nanointerfaces

DNA has received increasing attention in nanotechnology due to its ability to fold into prescribed structures. Different from the commonly adopted base-pairing strategy, an emerging class of amorphous DNA materials are formed by DNA's abiological interactions. Despite the great successes, a lack of nanoscale nucleation/growth control disables more advanced considerations. This work aims at harnessing the heterogeneous nucleation of metal-ion-glued DNA condensates on nanointerfaces. Upon unveiling key orthogonal factors including solution pH, ionic cross-linkers, and surface functionalities, chemically programmable DNA condensation on nanoparticle seeds is achieved, resembling a famous Stöber process for silica coating. The nucleation rules discovered on individual nanoseeds can be passed on to their dimeric assemblies, where broken spherical symmetry and the existence of interparticle gaps help a regiospecific DNA gelation. The steerable DNA condensation, and the multifunctions from DNA, metal ions, and nanocores, hold a great promise in noncanonical DNA nanotechnology toward novel applications.

Kinetically Programming Copolymerization-like Coassembly of Multicomponent Nanoparticles with DNA

Programmable coassembly of multicomponent nanoparticles (NPs) into heterostructures has the capability to build upon nanostructured metamaterials with enhanced complexity and diversity. However, a general understanding of how to manipulate the sequence-defined heterostructures using straightforward concepts and quantitatively predict the coassembly process remains unreached. Drawing inspiration from the synthetic concepts of molecular block copolymers is extremely beneficial to achieve controllable coassembly of NPs and access mesoscale structuring mechanisms. We herein report a general paradigm of kinetic pathway guidance for the controllable coassembly of bivalent DNA-functionalized NPs into regular block-copolymer-like heterostructures via the stepwise polymerization strategy. By quantifying the coassembly kinetics and structural statistics, it is demonstrated that the coassembly of multicomponent NPs, through directing the specific pathways of prepolymer intermediates, follows the step-growth copolymerization mechanism. Meanwhile, a quantitative model is developed to predict the growth kinetics and outcomes of heterostructures, all controlled by the designed elements of the coassembly system. Furthermore, the stepwise polymerization strategy can be generalized to build upon a great variety of regular nanopolymers with complex architectures, such as multiblock terpolymers and ladder copolymers. Our theoretical and simulation results provide fundamental insights on quantitative predictions of the coassembly kinetics and coassembled outcomes, which can aid in realizing a diverse set of supramolecular DNA materials by the rational design of kinetic pathways.

3D Optical Heterostructure Patterning by Spatially Allocating Nanoblocks on a Printed Matrix

Heterostructures have attracted enormous interest due to the properties arising from the coupling and synergizing between multiscale structures and the promising applications in electronics, mechanics, and optics. However, it is challenging for current technologies to precisely integrate cross-scale micro/nanomaterials in three dimensions (3D). Herein, we realize the precise spatial allocation of nanoblocks on micromatrices and programmable 3D optical heterostructure patterning via printing-assisted self-assembly. This bottom-up approach fully exploits the advantages of printing in on-demand patterning, low cost, and mass production, as well as the merits of solution-based colloidal assembly for simple structuring and high-precision regulating, which facilitates the patterned integration of multiscale materials. Importantly, the luminescent nanoparticle assembly can be accurately coupled to the dye-doped polymer matrix by regulating the interface wettability, enabling facile multicolor tuning in a single heterostructure. Thus, the heterostructure can be specially encoded for anticounterfeiting and encryption applications due to the morphology-dependent and interface-coupling-induced luminescence. Moreover, with the capability to achieve single-nanoparticle resolution, these findings have great potential for designing photonic superstructures and advanced optical devices.

Synthesis of Patchy Nanoparticles with Symmetry Resembling Polar Small Molecules

Patchy nanoparticles (NPs) show many important applications, especially for constructing structurally complex colloidal materials, but existing synthetic strategies generate patchy NPs with limited types of symmetry. This article describes a versatile copolymer ligand-based strategy for the scalable synthesis of uniform Au-(SiO₂ )_x patchy NPs (x is the patch number and 1 ≤ x ≤ 5) with unusual symmetry at high yield. The hydrolysis and condensation of tetraethyl orthosilicate on block-random copolymer ligands induces the segregation of copolymers on gold NPs (AuNPs) and hence governs the structure and distribution of silica patches formed on the AuNPs. The resulting patchy NPs possess unique configurations where the silica patches are symmetrically arranged at one side of the core NP, resembling the geometry of polar small molecules. The number, size, and morphology of silica patches, as well as the spacing between the patches and the AuNP can be precisely tuned by tailoring copolymer architectures, grafting density of copolymers, and the size of AuNPs. Furthermore, it is demonstrated that the Au-(SiO₂ )_x patchy NPs can assemble into more complex superstructures through directional interaction between the exposed Au surfaces. This work offers new opportunities of designing next-generation complex patchy NPs for applications in such as biomedicines, self-assembly, and catalysis.