Colloidal Self-Assembly Approaches to Smart Nanostructured Materials

3D Self-Assembly of a Bilayer Nanoparticle Metasurface for Surface-Enhanced Raman Scattering (SERS) Sensing

Controllable periodic nanoparticle (NP) metasurfaces exhibit unique optical responses, which are crucial for applications in plasmonic sensing, photocatalysis, and nanoscale optical manipulation. Compared with monolayer NPs, bilayer NPs generate additional electromagnetic field localization effects between the layers, exhibiting enhanced light absorption and scattering. Here, we propose a novel method that assembles the monolayer NPs at a three-dimensional liquid-liquid interface (3D-LLI) into large-area two-dimensional bilayer NPs. This method not only allows for the construction of independent bilayer structures for fundamental research on metasurfaces but also enables the formation of "sandwich"-type interlayer structures for in situ SERS detection of both microparticle analytes such as polystyrene (PS), polyethylene terephthalate (PET), and poly(methyl methacrylate) (PMMA) and small molecules such as melamine, cysteine (Cys), and iminothiourazole (AMT).

Chemically active colloidal superstructures

Mimicking biological systems, artificial active colloidal motors that continuously dissipate energy can dynamically self-assemble to form active colloidal superstructures with specific spatial configurations and complex functionalities, which offers a promising pathway for developing new active soft matter materials with adaptability, self-repair, and reconfigurability. Beyond merely propelling their own motion, chemically driven colloidal motors can also induce phoretic effects and osmotic flows to affect the motion of neighboring colloidal motors through local fluid fields generated by chemical reactions, thereby achieving spontaneous chemical communication and promoting dynamic self-assembly between motors. This review summarizes the latest progress in the dynamic self-assembly of chemically driven colloidal motors, ranging from single chemically driven colloidal motors to chemically driven colloidal motors with passive colloidal particles and then to different chemically driven colloidal motors, ultimately forming active colloidal superstructures with complex dynamic behaviors. Not only are the interactions between chemically driven colloidal motors with different self-propulsion mechanisms and passive colloidal particles focused on, but also the communication behaviors between chemically driven colloidal motors are explored. We explain the fundamental physicochemical mechanisms that regulate the assembly behavior of chemically driven colloidal motors, propose general strategies for the controlled construction of active colloidal superstructures, and discuss the potential applications that may emerge from the directed dynamic self-assembly of these superstructures.

Pushing the Frontiers: Artificial Intelligence (AI)-Guided Programmable Concepts in Binary Self-Assembly of Colloidal Nanoparticles

Colloidal nanoparticle self-assembly is a key area in nanomaterials science, renowned for its ability to design metamaterials with tailored functionalities through a bottom-up approach. Over the past three decades, advancements in nanoparticle synthesis and assembly control methods have propelled the transition from single-component to binary assemblies. While binary assembly has been recognized as a significant concept in materials design, its potential for intelligent and customized assembly has often been overlooked. It is argued that the future trend in the assembly of binary nanocrystalline superlattices (BNLSs) can be analogous to the '0s' and '1s' in computer programming, and customizing their assembly through precise control of these basic units could significantly expand their application scope. This review briefly recaps the developmental trajectory of nanoparticle assembly, tracing its evolution from simple single-component assemblies to complex binary co-assemblies and the unique property changes they induce. Of particular significance, this review explores the future prospects of binary co-assembly, viewed through the lens of 'AI-guided programmable assembly'. Such an approach has the potential to shift the paradigm from passive assembly to active, intelligent design, leading to the creation of new materials with disruptive properties and functionalities and driving profound changes across multiple high-tech fields.

Dielectrophoretic Assembly of Customized Colloidal Trimers

The controlled assembly of colloidal trimers with both shape and surface anisotropy remains a challenge. In this work, polymeric dielectric colloidal trimers selectively functionalized with gold nanoparticles are used to create four distinct particles. The shape and surface anisotropy provided by the metallodielectric particles allows for directive assembly in a dielectrophoretic field. When subjected to varied frequencies and media permittivities, the particles assemble with different packing densities and orientations. On-demand assembly and disassembly of the particles are achieved by switching on or off the applied voltage. These multicomponent colloidal particles and their subsequent assemblies presented here provide a promising platform for engineering complex structures with versatile functionalities.

Single-Step Production and Self-Assembly of Magnetic Nanostructures for Magneto-Responsive Soft Films

Magneto-responsive soft films constitute a fascinating class of smart materials and devices capable of performing various tasks, such as micromanipulation or transport, noninvasive surgery, and sensing. These components are fabricated by incorporating magnetic materials into flexible substrates. In this context, arranging magnetic particles into elongated chains exhibiting shape anisotropy has shown great potential. Here, we introduce a novel technique for fabricating magnetically responsive films using continuous single-step production and self-assembly of magnetic nanoparticles from a carrier gas at atmospheric pressure into anisotropic magnetic structures directly onto flexible polymer layers. We show that the resulting magnetic soft films exhibit significant residual magnetization and a large response to external magnetic fields. Furthermore, we investigate the magnetic properties of the nanoparticle assemblies and show that interparticle interactions play a critical role in determining the final magnetic properties of the nanostructures. Moreover, we provide experimental evidence that fusing the nanoparticles via post-annealing results in a transition from magnetostatic to exchange interactions with an ≈50% increase in the coercivity.

Development of Iron Oxide Nanochains as a Sensitive Magnetic Particle Imaging Tracer for Cancer Detection

The advancement of imaging technologies plays a crucial role in improving the diagnosis and monitoring of diseases, including cancer. This study introduces a new design of iron oxide-based nanoparticles specifically developed for magnetic particle imaging (MPI), aimed at tracking and diagnosing breast cancer more effectively. By precisely controlling the size, shape, and magnetic properties of these nanoparticles, we enhance the responsiveness of MPI, resulting in an increased signal. In our research, we established a novel synthetic route for fabricating iron oxide nanochains (FeONCs) characterized by their uniform shape and size, which contribute to high magnetic properties suitable for MPI applications. Initial results indicate these FeONCs exhibit superior magnetic properties compared to conventional spherical superparamagnetic iron oxide nanoparticles, nanocubes, and reported nanoworm-type structures. Magnetic relaxometry studies revealed that FeONCs provide higher sensitivity than the commonly used VivoTrax Synomag D50 and D70 in MPI. Further, the size and shape of FeONCs significantly influence cellular uptake. In vivo experiments using orthotopic breast cancer mouse models allow us to assess the biocompatibility and magnetic characteristics of the nanoparticles, confirming their imaging efficacy. Furthermore, by conjugating these nanoparticles with the RGD peptide, we enhance their ability to specifically target breast cancer, establishing them as promising tracers for in vivo MPI applications characterized by high sensitivity. Thus, our findings highlight that FeONCs significantly improve imaging quality, facilitating the early detection and accurate monitoring of breast cancer. This paves the way for innovative diagnostic strategies and personalized treatment options. Future research will focus on fine-tuning the surface chemistry of these nanoparticles to further enhance the targeting efficiency and optimization of their practice in clinical applications, particularly for MPI-based hyperthermia therapy.

Nanofabrication for Nanophotonics

Nanofabrication, a pivotal technology at the intersection of nanoscale engineering and high-resolution patterning, has substantially advanced over recent decades. This technology enables the creation of nanopatterns on substrates crucial for developing nanophotonic devices and other applications in diverse fields including electronics and biosciences. Here, this mega-review comprehensively explores various facets of nanofabrication focusing on its application in nanophotonics. It delves into high-resolution techniques like focused ion beam and electron beam lithography, methods for 3D complex structure fabrication, scalable manufacturing approaches, and material compatibility considerations. Special attention is given to emerging trends such as the utilization of two-photon lithography for 3D structures and advanced materials like phase change substances and 2D materials with excitonic properties. By highlighting these advancements, the review aims to provide insights into the ongoing evolution of nanofabrication, encouraging further research and application in creating functional nanostructures. This work encapsulates critical developments and future perspectives, offering a detailed narrative on the state-of-the-art in nanofabrication tailored for both new researchers and seasoned experts in the field.

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.

Direct device integration of single 1D nanoparticle assemblies; a magnetization reversal and magnetotransport study

Nanochains (NCs) made up of a one-dimensional arrangement of magnetic nanoparticles (NPs) exhibit anisotropic properties with potential for various applications. Herein, using a novel self-assembly method we directly integrate single NCs onto desired substrates including devices. We present a nanoscopic analysis of magnetization reversal in 1D linear NP arrays by combining x-ray microscopy, magnetoresistance (MR), and micromagnetic simulations. Imaging the local magnetization along individual NCs by scanning transmission x-ray microscopy and x-ray magnetic circular dichroism under varyingin situmagnetic fields shows that each structure undergoes distinct non-homogeneous magnetization reversal processes. The experimental observations are complemented by micromagnetic simulations, revealing that morphological inhomogeneities critically influence the reversal process where regions with parallel chains or larger multi-domain particles act as nucleation centers for the magnetization switching and smaller particles provide pinning sites for the domain propagation. Magnetotransport through single NCs reveals distinct MR behavior that is correlated with the unique magnetization reversal processes dictated by the morphology of the structures. This study provides new insights into the complex magnetization reversal mechanism inherent to one-dimensional particle assemblies and the effective parameters that govern the process.

Probing the Self-Assembly dynamics of cellulose nanocrystals by X-ray photon correlation spectroscopy

HYPOTHESIS

Charge-stabilized colloidal cellulose nanocrystals (CNCs) can self-assemble into higher-ordered chiral nematic structures by varying the volume fraction. The assembly process exhibits distinct dynamics during the isotropic to liquid crystal phase transition, which can be elucidated using X-ray photon correlation spectroscopy (XPCS).

EXPERIMENTS

Anionic CNCs were dispersed in propylene glycol (PG) and water spanning a range of volume fractions, encompassing several phase transitions. Coupled with traditional characterization techniques, XPCS was conducted to monitor the dynamic evolution of the different phases. Additionally, simulated XPCS results were obtained using colloidal rods and compared with the experimental data, offering additional insights into the dynamic behavior of the system.

FINDINGS

The results indicate that the particle dynamics of CNCs undergo a stepped decay in three stages during the self-assembly process in PG, coinciding with the observed phases. The phase transitions are associated with a total drop of Brownian diffusion rates by four orders of magnitude, a decrease of more than a thousand times slower than expected in an ideal system of repulsive Brownian rods. Given the similarity in the phase behaviors in CNCs dispersed in PG and in water, we hypothesize that these dynamic behaviors can be extrapolated to other polar solvent environments. Importantly, these findings represent the direct measurement of CNC dynamics using XPCS, underscoring the feasibility of directly assessing the dynamic behavior of other rod-like colloidal suspensions.

Scalable fabrication of Chip-integrated 3D-nanostructured electronic devices via DNA-programmable assembly

DNA-based self-assembly methods have demonstrated powerful and unique capabilities to encode nanomaterial structures through the prescribed placement of inorganic and biological nanocomponents. However, the challenge of selectively growing DNA superlattices on specific locations of surfaces and their integration with conventional nanofabrication has hindered the fabrication of three-dimensional (3D) DNA-assembled functional devices. Here, we present a scalable nanofabrication technique that combines bottom-up and top-down approaches for selective growth of 3D DNA superlattices on gold microarrays. This approach allows for the fabrication of self-assembled 3D-nanostructured electronic devices. DNA strands are bound onto the gold arrays, which anchor DNA origami frames and promote ordered framework growth on the specific areas of the surface, enabling control of the lateral placement and orientation of superlattices. DNA frameworks selectively grown on the pads are subsequently templated to nanoscale silica and tin oxide (SnOx) that follow the architecture, as confirmed by structural and chemical characterizations. The fabricated SnOx superlattices are integrated into devices that demonstrate photocurrent response.

Recent Advances in Nanostructured Perovskite Oxide Synthesis and Application for Electrocatalysis

Nanostructured materials have garnered significant attention for their unique properties, such as the high surface area and enhanced reactivity, making them ideal for electrocatalysis. Among these, perovskite oxides, with compositional and structural flexibility, stand out for their remarkable catalytic performance in energy conversion and storage technologies. Their diverse composition and tunable electronic structures make them promising candidates for key electrochemical reactions, including the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and carbon dioxide reduction (CO2RR). Nanostructured perovskites offer advantages such as high intrinsic activity and enhanced mass/charge transport, which are crucial for improving electrocatalytic performance. In view of the rapid development of nanostructured perovskites over past few decades, this review aims to provide a detailed evaluation of their synthesis methods, including the templating (soft, hard, colloidal), hydrothermal treatments, electrospinning, and deposition approaches. In addition, in-depth evaluations of the fundamentals, synthetic strategies, and applications of nanostructured perovskite oxides for OER, HER, and CO2RR are highlighted. While progress has been made, further research is needed to expand the synthetic methods to create more complex perovskite structures and improve the mass-specific activity and stability. This review offers insights into the potential of nanostructured perovskite oxides in electrocatalysis and provides potential perspectives for the ongoing research endeavor on the nanostructural engineering of perovskites.

Self-assembled inorganic nanomaterials for biomedical applications

Controlled self-assembly of inorganic nanoparticles has the potential to generate complex nanostructures with distinctive properties. The advancement of more precise techniques empowers researchers in constructing and assembling diverse building blocks, marking a pivotal evolution in nanotechnology and biomedicine. This progress enables the creation of customizable biomaterials with unique characteristics and functions. This comprehensive review takes an innovative approach to explore the current state-of-the-art self-assembly methods and the key interactions driving the self-assembly processes and provides a range of examples of biomedical and therapeutic applications involving inorganic or hybrid nanoparticles and structures. Self-assembly methods applied to bionanomaterials are presented, ranging from commonly used methods in cancer phototherapy and drug delivery to emerging techniques in bioimaging and tissue engineering. The most promising in vitro and in vivo experimental results achieved thus far are presented. Additionally, the review engages in a discourse on safety and biocompatibility concerns related to inorganic self-assembled nanomaterials. Finally, opinions on future challenges and prospects anticipated in this evolving field are provided.

Self-Assembled Metal Complexes in Biomedical Research

Cisplatin is widely used in clinical cancer treatment; however, its application is often hindered by severe side effects, particularly inherent or acquired resistance of target cells. To address these challenges, an effective strategy is to modify the metal core of the complex and introduce alternative coordination modes or valence states, leading to the development of a series of metal complexes, such as platinum (IV) prodrugs and cyclometalated complexes. Recent advances in nanotechnology have facilitated the development of multifunctional nanomaterials that can selectively deliver drugs to tumor cells, thereby overcoming the pharmacological limitations of metal-based drugs. This review first explores the self-assembly of metal complexes into spherical, linear, and irregular nanoparticles in the context of biomedical applications. The mechanisms underlying the self-assembly of metal complexes into nanoparticles are subsequently analyzed, followed by a discussion of their applications in biomedical fields, including detection, imaging, and antitumor research.

Granular Interfaces in TENGs: The Role of Close-Packed Polymer Bead Monolayers for Energy Harvesters

Over the last decade, triboelectric nanogenerators (TENGs) are proposed as a viable alternative to address the impetus for affordable and clean energy. Here, a novel, cost-effective granular-based TENG comprising two electrodes covered with HCP monolayers of monodisperse polymer (PMMA, PS, and MF-resin) beads with diameters ranging between 0.5 and 10 µm is proposed. These monolayers are attained in <20 s by employing a solvent-free particle rubbing assembly technique on fluorocarbon-coated substrates. The performance of the proposed granular-based TENG is characterized using contact-separation (CS) experiments by changing the bead sizes (topography effects) and the polymer material (mechanical properties). These findings show that when identical polymer material is utilized, large beads charged negatively, and the small beads positively, coinciding with bulk polymer film reports. In addition, the MF particles always charge positively and show the highest charging due to their relatively higher Young's modulus. The results elucidate that a specific pair's surface charge density is enhanced when one of the electrodes is covered with the smaller bead with the highest Young's modulus, highlighting that mechanical properties dominate and that a substantial difference in size benefits the output. The stable performance of the TENG devices after 10 000 cycles corroborates its robustness.

Mediation of Colloidal Encounter Dynamics by Surface Roughness

Rigorous understanding of assembly in colloidal systems is crucial to the development of tailored nanostructured materials. Despite extensive studies, a mechanistic understanding of the dynamics governing encounters of colloidal particles remains an ongoing challenge. We study colloidal encounter dynamics by inducing assembly through optical tweezers that impose an external attractive field for cubic-phase sodium yttrium fluoride nanocrystals. We show that surface roughness of the nanocrystals is a decisive factor for contact leading to assembly between the nanocrystals, manifested by the roughness-dependent hydrodynamic resistivity. This provides direct evidence that dynamics are equally important to energetics in understanding assembly.

Hydrophobized Metal-Organic Frameworks as Versatile Building Blocks for Tailored Nanocrystal Superlattices

This study introduces an effective strategy for hydrophobizing metal-organic frameworks (MOFs) using oleyl phosphate (OP) ligands. This modification makes MOF particles dispersible in nonpolar solvents and provides them with colloidal stability akin to traditional colloidal nanocrystals (NCs). The resulting OP-capped MOF particles can then be employed as building blocks for constructing various two-dimensional (2D) and 3D superlattices through self-assembly methods typically used for NCs. Additionally, binary superlattices with tailored structures can be achieved by coassembling OP-capped MOF particles with different NCs. This robust surface hydrophobization approach is adaptable to various MOFs, facilitating the rational design and creation of complex MOF-based superstructures.

Using Gas Molecules to Assemble Value-Added Materials through Dynamic Gas-Bridged Bond

The conversion and utilization of greenhouse gases and other polluting gases in a green way represents a crucial strategy for developing C1 chemistry and mitigating the dual crises of energy scarcity and the greenhouse effect. As a class of polyatomic molecules with a relatively simple structure, gas molecules are directly involved in the assembled process as the building blocks, converting them into polymer assemblies under mild and low energy consumption, and constructing recyclable functional assembled materials, which is of great significance to enrich the building block of assembly and promote the sustainable value-added of gas. The dynamic gas bridge is a new way of combining gas with other molecules, it provides the possibility for gas conversion and dynamic assembly. This perspective systematically introduces the formation mechanism and unique physicochemical properties of the dynamic gas bridge, and discusses the latest research progress of dynamic gas-bridged chemistry with a particular focus on three key aspects: gas-regulated assembled system, gas-constructed assembled materials, and green and efficient catalysis. Finally, a perspective on critical challenges and future directions of assembled materials based on dynamic gas bridge chemistry are also highlighted.

Programmable Self-Assembly from Two-Dimensional Nanosheets to Spiral, Twisted and Branched Nanostructures

Self-assembly of nanomaterials into hierarchical structure is of great interest to fabricate functional materials. However, programmable design of the assembled structures remains a great challenge. Herein, we reported a programmable self-assembly strategy to customize the assembled structure. The self-assembly strategy is designed to orderly transform the two-dimensional (2D) Ca ions assembled F127 nanosheets (Ca-F127 NSs) into spiral nanosheet structures (S-Ca-F127 NSs), branched nanosheet structures (B-Ca-F127 NSs), branched-spiral nanosheet structures (B-S-Ca-F127 NSs), and twisted-branched structures (T-Ca-F127 NBs). Wide-angle X-ray scattering (WAXS) and X-ray absorption spectroscopy (XAS) indicate that these different structures maintain the same orthorhombic phase and Ca-O octahedral coordination structure. Selected area electron diffraction (SAED) in the double-tilt liquid nitrogen cooling holder identifies the Eshelby twist in the twisted structures, demonstrating the spiral structure are formed by screw dislocation growth. Cryo-electron microscopy (cryo-EM) proves the oriented epitaxial growth in the B-Ca-F127 NSs. Furthermore, the formation mechanisms of spiral structure and branched structure can be recombined to form complex hierarchical structures. The epitaxial growth along screw dislocation can lead to the formation of B-S-Ca-F127 NSs, while the twisted epitaxial growth in the screw dislocation can lead to the formation of T-Ca F127 NBs.

Innovative applications of advanced nanomaterials in cerebrovascular imaging

Cerebrovascular imaging is essential for the diagnosis, treatment, and prognosis of cerebrovascular disease, including stroke, aneurysms, and vascular malformations. Conventional imaging techniques such as MRI, CT, DSA and ultrasound have their own strengths and limitations, particularly in terms of resolution, contrast and safety. Recent advances in nanotechnology offer new opportunities for improved cerebrovascular imaging. Nanomaterials, including metallic nanoparticles, magnetic nanoparticles, quantum dots, carbon-based nanomaterials, and polymer nanoparticles, show great potential due to their unique physical, chemical, and biological properties. This review summarizes recent advances in advanced nanomaterials for cerebrovascular imaging and their applications in various imaging techniques, and discusses challenges and future research directions. The aim is to provide valuable insights for researchers to facilitate the development and clinical application of these innovative nanomaterials in cerebrovascular imaging.

4D-Printed Magnetic Responsive Bilayer Hydrogel

Despite its widespread application in targeted drug delivery, soft robotics, and smart screens, magnetic hydrogel still faces challenges from lagging mechanical performance to sluggish response times. In this paper, a methodology of in situ generation of magnetic hydrogel based on 3D printing of poly-N-isopropylacrylamide (PNIPAM) is presented. A temperature-responsive PNIPAM hydrogel was prepared by 3D printing, and Fe2O3 magnetic particles were generated in situ within the PNIPAM network to generate the magnetic hydrogel. By forming uniformly distributed magnetic particles in situ within the polymer network, 3D printing of customized magnetic hydrogel materials was successfully achieved. The bilayer hydrogel structure was designed according to the different swelling ratios of temperature-sensitive hydrogel and magnetic hydrogel. Combined with the excellent mechanical properties of PNIPAM and printable magnetic hydrogel, 4D-printed remote magnetic field triggered shape morphing of bilayers of five-petal flower-shaped hydrogels was presented, and the deformation process was finished within 300 s.

Non-Reciprocity, Metastability, and Dynamic Reconfiguration in Co-Assembly of Active and Passive Particles

Living organisms often exhibit non-reciprocal interactions where the forces acting on the objects are not equal in magnitude or opposite in direction. The combination of reciprocal and non-reciprocal interactions between synthetic building blocks remains largely unexplored. Here, out-of-equilibrium assemblies of non-motile isotropic passive and metal-patched motile active particles are formed by overlapping bulk interactions with directed self-propulsion. An external alternating current (AC) electric field generates concurrent dipolar and induced-charge electrophoretic forces between the particles which are evaluated using microscopy. The interaction force measurements allow to determine the degree of reciprocity in interactions, which is tunable by designing the active particle and its trajectory. While linearly-propelled active particles evade assembly with passive particles, helically propelled active particles form active-passive clusters with dynamic reconfiguration and long-lived metastability. Large clusters display programmable fluctuations and reconfigurability by controlling the fraction of active particles. The study establishes principles of integrating reciprocal and non-reciprocal interactions in guided colloidal assembly of reconfigurable metastable structures.

Navigating the Landscape of Dry Assembling Ordered Particle Structures: Can Solvents Become Obsolete?

A spur on miniaturized devices led scientists to unravel the fundamental aspects of micro- and nanoparticle assembly to engineer large structures. Primarily, attention is given to wet assembly methods, whereas assembly approaches in which solvents are avoided are scarce. The "dry assembly" strategies can overcome the intrinsic disadvantages that are associated with wet assembly, e.g., the lack of versatility and scalability. This review uniquely summarizes the recent progress made to create highly ordered particle arrays without using a wet environment. Before delving into these methods, the surface interactions (e.g., van der Waals, contact mechanics, capillary, and electrostatics) are elaborated, as a profound understanding and balancing these are a critical aspect of dry assembly. To manipulate these interactions, strategies involving different forces, e.g., mechanical-based, electrical-based, or laser-induced, sometimes in conjunction with pre-templated substrates, are employed to attain ordered colloidal structures. The utilization of the ordered structures obtained without solvents is accompanied by specific examples. Dry assembly methods can aid us in achieving more sustainable assembly processes. Overall, this Review aims to provide an easily accessible resource and inspire researchers, including novices, to broaden dry assembly horizons significantly and close the remaining knowledge gap in the physical phenomena involved in this area.

Siamese neural network improves the performance of a convolutional neural network in colloidal self-assembly state classification

Identifying the state of the colloidal self-assembly process is critical to monitoring and controlling the system into desired configurations. Recent application of convolutional neural networks with unsupervised clustering has shown a comparable performance to conventional approaches, in representing and classifying the states of a simulated 2D colloidal batch assembly system. Despite the early success, capturing the subtle differences among similar configurations still presents a challenge. To address this issue, we leverage a Siamese neural network to improve the accuracy of the state classification. Results from a Brownian dynamics-simulated electric field-mediated colloidal self-assembly system and a magnetic field-mediated colloidal self-assembly system demonstrate significant improvement from the original convolutional neural network-based approach. We anticipate the proposed improvement to further pave the way for automated monitoring and control of colloidal self-assembly processes in real time and real space.

Amorphous Photonic Structure Patterns with Thin Film Interference Effects for Multilevel Anticounterfeiting

Colloidal photonic structures with the ability to control and manipulate light propagation offer long-term color stability, low optical loss, and angle-dependent color properties, while combinations of different photonic structures across multiple scales provide an extensive color range and enhanced optical functionalities, presenting significant potential for advanced anticounterfeiting applications. However, the proper design or manufacture of such complex structures is still challenging. In this study, amorphous photonic structures (APSs) with thin film interference (TFI) effects were fabricated for multilevel anticounterfeiting. The APSs inherit the isotropic resonant scattering and render partial TFI effects, resulting in unprecedented dynamic specular and diffuse color-shifting features as the viewing or incident direction shifts. Additionally, incorporating a certain concentration of fluorescent microspheres into the colloidal ink adds a third layer of fluorescent anticounterfeiting mode to the APSs. Enabled by infiltration-assisted (IFAST) colloidal assembly technologies, the sophisticated color distributions and randomly arranged fluorescent microspheres on the microscale of APSs grant unique and inherent fingerprint features. The unique and unpredictable optical and structural characteristics of APSs provide physical unclonable functions (PUFs) to prevent replication and tampering, demonstrating their potential as optical PUF security labels for anticounterfeiting applications through artificial intelligence (AI) reading and authentication.

Rapid fabrication of tunable structural color patterns by spray-coating

Structural color, a color generated based on physical principles, has broad applications such as displays, optical sensors, and anti-counterfeiting. Traditional methods for producing structural colors are often complex and time-consuming, whereas spray-coating colloidal self-assembly offers a simple and controllable alternative. However, due to the high-pressure atomization process, colloidal inks often form amorphous photonic structures (APSs), making it challenging to precisely control the assembly of colloidal particles on substrates to achieve ordered structures. By rationally designing the composition of colloidal mixed solutions, controlling particle concentration, and adjusting evaporation temperatures, it is possible to effectively regulate the assembly of colloidal particles and obtain angle-dependent iridescent colors. This work proposes a simple spray-coating process that enables the control of both ordered and disordered structures, with tunable optical properties, suitable for colloidal patterning on various substrates. This method not only simplifies the fabrication of photonic crystals (PCs) but also has broad potential, particularly in anti-counterfeiting, where it enables the creation of hard-to-replicate structured patterns with enhanced security.

Stimuli-responsive self-regulating assembly of chiral colloids for robust size and shape control

Most synthetic self-assemblies grow indefinitely into size-unlimited structures, whereas some biological self-assemblies autonomously regulate their size and shape. One mechanism of such self-regulation arises from the chirality of building blocks, inducing their mutual twisting that is incompatible with their long-range ordered packing and thus halts the assembly's growth at a certain stage. This self-regulation occurs robustly in thermodynamic equilibrium rather than kinetic trapping, and therefore is attractive yet elusive. Until now, studies of self-regulating assemblies have focused on non-responsive systems, whose equilibrium point and corresponding size and shape are hardly changeable. Here, we demonstrate a stimuli-responsive, self-regulating assembly. This assembly consists of chiral and magnetically orientable nanorods, where the effective chirality can be changed by balancing chirality-induced twisting and magnet-induced flattening between nanorods. Consequently, the strength of self-regulation in the assembly is modulable by magnetic field intensity, allowing robust, tunable, and reversible control of its size and shape. Our strategy would provide more biomimetic materials with precision and responsiveness.

β-Hydroxybutyrate dehydrogenase functionalized two-dimensional photonic crystals for quantitative and visual sensing of ketone bodies

β-Hydroxybutyrate (BHB) is a substantial physiological ketone body. Its elevated concentration causes ketoacidosis, which is a disorder with a high mortality rate. Therefore, there is an urgent need to develop a simple method for the in-situ monitoring of BHB in urine. In this study, a photonic crystal hydrogel (PCH) sensing material for the detection of urinary ketones was prepared by embedding a two-dimensional polystyrene photonic crystal array (PCA) in a hydrogel functionalized with β-hydroxybutyrate dehydrogenase (BHBDH). BHBDH catalyzes the interconversion between β-hydroxybutyrate and acetoacetic acid and relies on the cofactor nicotinamide adenine dinucleotide (NAD+) to participate in the reaction process. The catalytic cycle of converting β-hydroxybutyrate to acetoacetate generates H+, which reduces the electrostatic repulsion between the carboxyl groups in the hydrogel network, ultimately leading to the shrinkage of the hydrogel volume. The hydrogel volume change was detected by measuring the diameter of the Debye diffraction ring, thus reflecting the concentration of BHB. When the concentration of BHB was increased from 0 to 10 mM, the reflection spectrum of PCH shifted for 117 nm within 60 min, consequently, the structural color of PCH changed from red to green and finally to blue. The material was used for quantitative detection of BHB with a detection limit of 48.94 μM. Then it was used for detection in artificial urine samples. While, this smart and reusable sensing material could provide a more convenient and efficient strategy for the ketone body detection in clinical diagnosis and point-of-care monitoring.

Kinetically blocked self-assembly of colloidal strings with tunable interactions in magnetic fields

Tunable self-assembly driven by external electric or magnetic fields is of significant interest in modern soft matter physics. While extensively studied in two-dimensional systems, it remains insufficiently explored in three-dimensional systems. In this study, we investigated the formation of vertical strings from an initial monolayer system of particles deposited on a horizontal substrate under the influence of an external magnetic field using experiments, computer simulations, and theoretical frameworks. We demonstrated that the main mechanism of string self-assembly is merging, driven by the interplay between gravity and induced tunable interparticle interactions. During this process, the system has to overcome a saddle point on the energy landscape, whose height increases with the string height. At a certain point, further self-assembly becomes kinetically blocked in a metastable state, far from equilibrium. This contrasts sharply with the typical scenario for tunable self-assembly in two dimensions, where the resulting structures usually correspond to the equilibrium state. Therefore, this finding opens up opportunities for more detailed control of three-dimensional tunable self-assembly by designing and tuning various potential barriers along the kinetic pathways.

Scalable Macroscopic Engineering from Polymer-Based Nanoscale Building Blocks: Existing Challenges and Emerging Opportunities

Natural materials exhibit exceptional properties due to their hierarchical structures spanning from the nano- to the macroscale. Replicating these intricate spatial arrangements in synthetic materials presents a significant challenge as it requires precise control of nanometric features within large-scale structures. Addressing this challenge depends on developing methods that integrate assembly techniques across multiple length scales to construct multiscale-structured synthetic materials in practical, bulk forms. Polymers and polymer-hybrid nanoparticles, with their tunable composition and structural versatility, are promising candidates for creating hierarchically organized materials. This review highlights advances in scalable techniques for nanoscale organization of polymer-based building blocks within macroscopic structures, including block copolymer self-assembly with additive manufacturing, polymer brush nanoparticles capable of self-assembling into larger, ordered structures, and direct-write colloidal assembly. These techniques offer promising pathways toward the scalable fabrication of materials with emergent properties suited for advanced applications such as bioelectronic interfaces, artificial muscles, and other biomaterials.

Multiplex Evaluation of Biointerface-Targeting Abilities and Affinity of Synthetized Nanoparticles-A Step Towards Improved Nanoplatforms for Biomedical Applications

To obtain versatile nanoplatforms comparable for various bio-applications, synthesis and functionalization of two inorganic nanoparticles (NPs), i.e., gold (AuNPs) and iron oxide (SPIONs), are described for different NP diameters. Chosen ligands have adapted chemical function to graft to the surfaces of the NPs (thiols and phosphonates, respectively) and the identical frequently used external carboxyl group for comparison of the NPs' material effect on their final behavior. To further evaluate molecular length effect, AuNPs are functionalized by different ligands. Numerous characterizations highlight the colloidal stability when grafting organic molecules on NPs. The potentiality of the functionalized NPs to react efficiently with a protein monolayer is finally evaluated by grafting them on a protein covered chip, characterized by atomic force microscopy. Comparison of the NPs' surface densities and measured heights enable observation of different NPs' reactivity and infer the influence of the inorganic core material, as well as the NPs' size and ligand length. AuNPs have higher affinities to biomolecules, especially when covered by shorter ligands. NP ligands should be chosen not only based on their length but also on their chemical chain, which affects proteic layer interactions. This original multiplex comparison method using AFM is of great interest to screen the effects of used NP materials and functionalization when developing theranostic nanoplatforms.

Bi-magnetic Mn3O4@Ni core-shell binary superparticles: Self-assembly preparation and magnetic behaviors

Binary superparticles formed by self-assembling two different types of nanoparticles may utilize the synergistic interactions and create advanced multifunctional materials. Bi-magnetic superparticles with a core-shell structure have unique properties due to their specific spatial configurations. Herein, we built Mn3O4@Ni core-shell binary superparticles via an emulsion self-assembly technique. The superparticles are generated with a spherical morphology, and have a typical average size of about 240 nm. By altering the ratio of the two magnetic nanoparticles, the thickness of Ni shells can be adjusted. Oleic acid ligands are crucial for the formation of core-shell structure. Magnetic analysis suggests that core-shell superparticles display dual-phase magnetic interactions, contrasting with the single-phase magnetic behaviors of commonly core-shell magnetic nanoparticles. The calculation on the effective magnetic anisotropy constants indicates that the presence of Ni shell layers reduces the dipole interactions among the Mn3O4 core particles. Due to the presence of Ni nanoparticle shells, the blocking temperature of Mn3O4 is reduced, while the Curie temperature of Mn3O4 is independent on Ni content. Tunable magnetic properties can be achieved by modulating the Ni nanoparticle shell thickness. This study offers insights for the development of core-shell superparticles with varied magnetic characteristics.

From Simple Probe to Smart Composites: Water-Soluble Pincer Complex With Multi-Stimuli-Responsive Luminescent Behaviors

Water-soluble smart materials with multi-stimuli-responsiveness and ultra-long room-temperature phosphorescence (RTP) have garnered broad attention. Herein, a water-soluble terpyridine zinc complex (MeO-Tpy-Zn-OAc), featuring a simple donor-π-acceptor (D-π-A) structure is presented, which responds to a variety of stimuli, including changes in solvents, pH, temperature, and the addition of amino acids. Notably, MeO-Tpy-Zn-OAc functions as a fluorescence probe, capable of visually and selectively discriminating aspartate or histidine among other common amino acids in water. Additionally, when incorporated into polyvinyl alcohol (PVA) to form the composite MeO-Tpy-Zn-OAc@PVA, the material exhibits reversible writing, photochromism, and a prolonged RTP with a 14 s afterglow. These unique properties enable the composite to be utilized in potential applications such as secure data encryption and inkless printing.

Cellulose-Templated Nanomaterials for Nanogenerators and Self-Powered Sensors

Energy crisis inspires the development of renewable and clean energy sources, along with related applications such as nanogenerators and self-powered devices. Balancing high performance and environmental sustainability in advanced material innovation is a challenging task. Addressing the global challenges of sustainable development and carbon neutrality lead to increased interest in biopolymer research. Nanocellulose materials, derived from biopolymers, demonstrate potential as template candidates for advanced materials, due to their unique properties, including high strength, high surface area, controllable pore structures and high-water retention. In recent years, cellulose-templated nanomaterials enable delicate nano-/microscale structural construction, thus promoting developments in the field of nanogenerators and self-powered sensors. However, there is still a limited number of reviews focused on cellulose-templated nanomaterials for applications in nanogenerators and self-powered sensors. This review aims to fill this research gap by introducing various cellulose-templated nanomaterials and providing a detailed analysis of their fashionable applications in nanogenerators and self-powered sensors. The goal is to present cellulose-templated nanomaterials as highly promising template and guest materials for templating technologies, offering sustainable nano-/microscale control over advanced materials for the foreseeable future. This potential is promising for new applications in the fields of nanogenerators and self-powered sensors.

Robo-Matter towards reconfigurable multifunctional smart materials

Maximizing materials utilization efficiency via enhancing their reconfigurability and multifunctionality offers a promising avenue in addressing the global challenges in sustainability. To this end, significant efforts have been made in developing reconfigurable multifunctional smart materials, which can exhibit remarkable behaviors such as morphing and self-healing. However, the difficulty in efficiently manipulating and controlling matter at the building block level with manageable cost and complexity, which is crucial to achieving superior responsiveness to environmental clues and stimuli, has significantly hindered the further development of such smart materials. Here we introduce a concept of Robo-Matter, which can be activated and controlled through external information exchange at the building block level, to enable a high-level of controllability, mutability and versatility for reconfigurable multifunctional smart materials. Using specially designed micro-robot building blocks with symmetry-breaking active motion modes, tunable anisotropic interactions, and interactive coupling with a programmable spatial-temporal dynamic light field, we demonstrate an emergent Robot-Matter duality, which enables a spectrum of desirable behaviors spanning from matter-like properties such as ultra-fast self-assembly and adaptivity, to robot-like properties including active force output, smart healing, smart morphing and infiltration. Our work demonstrates a promising direction for designing next-generation smart materials and large-scale robotic swarms.

Aligned colloidal clusters in an alternating rotating magnetic field elucidated by magnetic relaxation

Precise control at the colloidal scale is one of the most promising bottom-up approaches to fabricating new materials and devices with tunable and precisely engineered properties. Magnetically driven colloidal assembly offers great versatility because of the ability to externally tune particle-particle interactions and to construct a host of particle arrangements. However, despite previous efforts to probe the parameter space, global orientational control in conjunction with two-dimensional microstructural control has remained out of reach. Furthermore, the magnetic relaxation time of superparamagnetic beads has been largely overlooked despite being a key feature of the magnetic response. Here, we take advantage of the magnetic relaxation time of superparamagnetic beads in an alternating rotating magnetic field and show how harnessing this feature facilitates the formation of oriented clusters. The orientation of these clusters can be controlled by field parameters. Using experiments, simulations, and theory, we probe a two-particle system (dimer) under this alternating rotating magnetic field and use its dynamics to provide insights into the collective response that forms clusters. We find that the type of field has significant implications for the dipolar interactions between the colloids because of the nonnegligible magnetic relaxation. Moreover, we find that the competing time scales of the magnetic relaxation and the alternating field generate an anisotropic interaction potential that drives cluster alignment. By exploiting the magnetic relaxation time of magnetic systems, we can tailor new types of interparticle interactions, thereby expanding the capabilities of colloidal assembly in engineering unique materials and devices.

Exerting pulling forces in fluids by directional disassembly of microcrystalline fibres

Biomolecular polymerization motors are biochemical systems that use supramolecular (de-)polymerization to convert chemical potential into useful mechanical work. With the intent to explore new chemomechanical transduction strategies, here we show a synthetic molecular system that can generate forces via the controlled disassembly of self-organized molecules in a crystal lattice, as they are freely suspended in a fluid. An amphiphilic monomer self-assembles into rigid, high-aspect-ratio microcrystalline fibres. The assembly process is regulated by a coumarin-based pH switching motif. The microfibre crystal morphology determines the monomer reactivity at the interface, resulting in anisotropic etching. This effect exerts a directional pulling force on microscopic beads adsorbed on the crystal surface through weak multivalent interactions. We use optical-tweezers-based force spectroscopy to extract mechanistic insights into this process, quantifying a stall force of 2.3 pN (±0.1 pN) exerted by the ratcheting mechanism produced by the disassembly of the microfibres.

Active Assembly of CsPbBr3 Nanorods into Microcolumns by Electric Field in Nonpolar Solvent

High-precision, controllable, mass-producible assembly of nanoparticles into complex structures or devices holds immense importance in the application across various fields but it remains challenging. Here a highly controllable and reversible active assembly of colloidal CsPbBr3 nanorods, driven by an external electric field is achieved. This approach enables the nanorods dynamically orient themselves, assemble into chains, aggregate into columns, and eventually form an ordered column array, with the electric field intensity varying from 0 to 50 V µm-1 at 100 kHz. The nanorods inside the columns align parallel to the electric field, leading to a well-ordered structure. With the analysis of the interactions among the nanorods, a quantitative interpretation of the assembly is proposed. Monte Carlo calculation is also introduced to simulate the assembly process and the results prove to be in great agreement with the experimental observations. This electric field-driven assembly presents an exciting opportunity to pave the way for next-generation sensors and photonic devices based on well-developed colloidal nanoparticles.

Controllable Self-Assembly of Carbon Nanotubes on Ammonium Polyphosphate as a Game-Changer for Flame Retardancy and Thermal Conductivity in Epoxy Resin

The optimization of flame retardancy and thermal conductivity in epoxy resin (EP), utilized in critical applications such as mechanical components and electronics packaging, is a significant challenge. This study introduces a novel, ultrasound-assisted self-assembly technique to create a dual-functional filler consisting of carbon nanotubes and ammonium polyphosphate (CNTs@APP). This method, leveraging dynamic ligand interactions and strategic solvent selection, allows for precise control over the assembly and distribution of CNTs on APP surfaces, distinguishing it from conventional blending approaches. The integration of 7.5 wt.% CNTs@APP10 into EP nanocomposites results in substantial improvements in flame retardancy, as evidenced by a limiting oxygen index (LOI) value of 31.8% and achievement of the UL-94 V-0 rating. Additionally, critical fire hazard indicators, including total heat release (THR), total smoke release (TSR), and the peak intensity of CO yield (PCOY), are significantly reduced by 45.9% to 77.5%. This method also leads to a remarkable 3.6-fold increase in char yield, demonstrating its game-changing potential over traditional blending techniques. Moreover, despite minimal CNTs addition, thermal conductivity is notably enhanced, showing a 53% increase. This study introduces a novel approach in the development of multifunctional EP nanocomposites, offering potential for wide range of applications.

Functional supraparticles produced by the evaporation of binary colloidal suspensions on superhydrophobic surfaces

Hierarchically structured supraparticles can be produced by drying droplets of colloidal suspensions. Using binary suspensions provides degrees of structural and functional control beyond those possible for single components, while remaining tractable for fundamental mechanistic studies. Here, we implement evaporative co-assembly of two distinct particle types - 'large' polystyrene microparticles and 'small' inorganic oxide nanoparticles (silica, titania, zirconia, or ceria) - dried on superhydrophobic surfaces to produce bowl-shaped supraparticles. We extend this method to raspberry colloid templating, in which the binary suspension consists of titania nanoparticles together with gold-decorated polystyrene colloids. Following removal of the polymer particles, we demonstrate catalytic oxidative coupling of methanol to methyl formate using the resulting mesoporous supraparticles, showcasing their practical application.

Theory and simulations of light-induced self-assembly in colloids with quantum chemistry derived empirical potentials

Light-induced self-assembly (LISA) is a non-invasive method for tuning material properties. Photoresponsive ligands coated on the surfaces of nanoparticles are often used to achieve LISA. We report simulation studies for a photoresponsive ligand, azobenzene dithiol (ADT), which switches from a trans-to-cis configuration on exposure to ultraviolet light, allowing self-assembly in ADT-coated gold nanoparticles (NPs). This is attributed to a higher dipole moment of cis-ADT over trans-ADT which leads to a dipole-dipole attraction facilitating self-assembly. Singh and Jha [Comput. Theor. Chem., 2021, 1206, 113492] used quantum-chemistry calculations to quantify the interaction energy of a pair of ADT ligands in their cis and trans conformations. The interaction energy between ligands was fit to a potential energy function of the Lennard-Jones (LJ) form having distinct exponents for attractive and repulsive contributions. Using this generalized equation for the ligand-ligand interaction energy, we calculated the total effective interaction energy between a pair of cis as well as trans ADT-coated NPs. Specifically, we calculated the effective interaction energies between cis/trans-NPs using discrete as well as continuous approaches. Given the limitations of experiments in probing individual ligand conformations, we also studied the effect of varying the functional ligand length on the interaction energy between NPs and identified the optimal functional ligand length to capture the steric and conformational effects. Finally, using the effective interaction energy, we obtained a generalized potential energy function, which was applied in Langevin dynamics simulations to capture self-assembly in NPs.

π-Diamond: A Diamondoid Superstructure Driven by π-Interactions

Modulating the arrangement of superstructures through noncovalent interactions has a significant impact on macroscopic shape and the expression of unique properties. Constructing π-interaction-driven hierarchical three-dimensional (3D) superstructures poses challenges on account of limited directional control and weak intermolecular interactions. Here we report the construction of a 3D diamondoid superstructure, named π-Diamond, employing a ditopic strained Z-shaped building block comprising a porphyrin unit as bow-limb double-strapped with two m-xylylene units as bowstrings. This superstructure, reminiscent of diamond's tetrahedral carbon composition, is composed of double-walled tetrahedron (DWT) driven solely by π-interactions. Hetero-π-stacking interactions between porphyrin and m-xylylene panels drive the assembly of four building blocks predominantly into a DWT, which undergoes extension to create an adamantane unit and eventually a diamondoid superstructure wherein each porphyrin panel is shared by two neighboring tetrahedra through hetero-π-stacking. π-Diamond exhibits a solid-state fluorescent quantum yield 44 times higher than that of tetraphenylporphyrin along with excellent photocatalytic performance. The precise 3D directionality of π-interactions, achieved through strained multipanel building blocks, revolutionizes the assembly of hierarchical 3D superstructures driven by π-interactions.

Contact Electrification as an Emerging Strategy for Controlling the Performance of Metal Nanoparticle Catalysts

Contact electrification (CE) is an emerging strategy for controlling the performance of metal nanoparticle (NP) catalysts. The underlying physical principle of this control is the sensitivity of the Fermi level to metal-metal contacts. This change in electronic structure has a direct impact on surface properties and chemical reactivity. The concept article briefly introduces the basic theory of CE and its relationship to catalytic performance. We then highlight selected recent examples of advances in the preparation of hybrid metal NP assemblies, experimental techniques for characterizing CE, and finally applications of CE for altering catalytic performance.

Magnetite Nanoparticle Assemblies and Their Biological Applications: A Review

Magnetite nanoparticles (Fe3O4 NPs) have garnered significant attention over the past twenty years, primarily due to their superparamagnetic properties. These properties allow the NPs to respond to external magnetic fields, making them particularly useful in various technological applications. One of the most fascinating aspects of Fe3O4 NPs is their ability to self-assemble into complex structures. Research over this period has focused heavily on how these nanoparticles can be organized into a variety of superstructures, classified by their dimensionality-namely one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) configurations. Despite a wealth of studies, the literature lacks a systematic review that synthesizes these findings. This review aims to fill that gap by providing a thorough overview of the recent progress made in the fabrication and organization of Fe3O4 NP assemblies via a bottom-up self-assembly approach. This methodology enables the controlled construction of assemblies at the nanoscale, which can lead to distinctive functionalities compared to their individual counterparts. Furthermore, the review explores the diverse applications stemming from these nanoparticle assemblies, particularly emphasizing their contributions to important areas such as imaging, drug delivery, and the diagnosis and treatment of cancer.

Controlling the thermally-driven crystallization of DNA-coated nanoparticles with formamide

DNA-coated nanoparticles, also known as programmable atom equivalents (PAEs), facilitate the construction of materials with nanoscopic precision. Thermal annealing plays a pivotal role by controlling DNA hybridization kinetics and thermodynamics, which ensures the formation of intended structures. While various design handles such as particle size, DNA design, and salt concentration influence the stability of the DNA duplexes linking PAEs in a lattice, their influence on the system's melting temperature (Tm) often follows complicated trends that make rational tuning of self-assembly challenging. In this work, the denaturant formamide is used to precisely tune the thermal response of PAEs. Our results reveal a clear and predictable trend in the PAEs' response to formamide, enabling rational control over the Tm of a diverse set of PAE systems. Unlike adjustments made through alterations to PAE design or solution parameters such as ionic strength, formamide achieves its temperature shift without impacting the kinetics of assembly. As a result, PAEs can be rapidly crystallized at ambient temperatures, producing superlattices with similar quality to PAE crystals assembled through standard protocols that use higher temperatures. This study therefore positions formamide as a useful tool for enhancing the synthesis of complex nanostructures under mild conditions.

Recent Advances in Research from Nanoparticle to Nano-Assembly: A Review

The careful arrangement of nanomaterials (NMs) holds promise for revolutionizing various fields, from electronics and biosensing to medicine and optics. This review delves into the intricacies of nano-assembly (NA) techniques, focusing on oriented-assembly methodologies and stimuli-dependent approaches. The introduction provides a comprehensive overview of the significance and potential applications of NA, setting the stage for review. The oriented-assembly section elucidates methodologies for the precise alignment and organization of NMs, crucial for achieving desired functionalities. The subsequent section delves into stimuli-dependent techniques, categorizing them into chemical and physical stimuli-based approaches. Chemical stimuli-based self-assembly methods, including solvent, acid-base, biomolecule, metal ion, and gas-induced assembly, are discussed in detail by presenting examples. Additionally, physical stimuli such as light, magnetic fields, electric fields, and temperature are examined for their role in driving self-assembly processes. Looking ahead, the review outlines futuristic scopes and perspectives in NA, highlighting emerging trends and potential breakthroughs. Finally, concluding remarks summarize key findings and underscore the significance of NA in shaping future technologies. This comprehensive review serves as a valuable resource for researchers and practitioners, offering insights into the diverse methodologies and potential applications of NA in interdisciplinary research fields.

Dynamic Gas-Bridged Bond: An Opportunity of Fabricating Dynamic Assembled Materials with Gas

Gas molecules, as a family of unique polyatomic building blocks, have long been considered hard to involve in molecular assembly or construct assembled materials due to their structural simplicity yet paucity of defined interacting sites. To solve this non-trivial challenge, a core idea is to break the limit of current ways of bonding gas molecules, endowing them with new modes of interactions that match the basic requirements of molecular assembly. In recent years, a new concept, named the dynamic gas-bridged bond (DGB), has emerged, which allows for gas molecules to constitute a dynamic bridging structure between other building blocks with the aid of frustrated Lewis pairs. This makes it possible to harness gas in a supramolecular or dynamic manner. Herein, this perspective discusses distinct dynamic natures of DGBs and manifests their particular functions in various fields, including the control of molecular/polymeric self-assembly nanostructures, creation of multidimensional assembled materials, and recyclable catalysts. The future research direction and challenges of dynamic gas-bridged chemistry toward gas-programmed self-assembly and gas-constructed adaptive materials are highlighted.

Modeling order-disorder boundaries of colloidal dispersions in organic solvents using interaction force measurements

HYPOTHESIS

The formation of soft colloidal crystals, which are nonclose-packed ordered arrays of colloidal particles suspended in a solvent, is dictated by a single physical factor that yields a fixed threshold at order-disorder boundaries for different experimental conditions such as ion concentration, solvent type, and particle size. Identifying the determinant factor and its threshold value should enable the prediction of the critical concentrations of colloidal particles to form soft colloidal crystals.

EXPERIMENTS

Soft colloidal crystals were fabricated using a series of monohydric alcohols as dispersion media and reflectance spectra were measured to locate order-disorder boundaries. The interaction forces acting between particles were also measured by employing atomic force microscopy.

FINDINGS

The interparticle forces at the order-disorder boundaries exhibited a universal threshold that was independent of the solvent types including alcohols and water. Therefore, the determinant factor for the formation of soft colloidal crystals was determined to be the force acting between the particles. Furthermore, a priori calculation of this critical force and consequently the critical particle concentration in colloidal systems was demonstrated by referring to the pressure at the liquid-to-solid transition in a hard sphere system (Alder transition).

Coassembly of Complementary Polyhedral Metal-Organic Framework Particles into Binary Ordered Superstructures

Here we report the formation of a 3D NaCl-type binary porous superstructure via coassembly of two colloidal polyhedral metal-organic framework (MOF) particles having complementary sizes, shapes, and charges. We employed a polymeric-attenuated Coulombic self-assembly approach, which also facilitated the coassembly of these MOF particles with spherical polystyrene particles to form 2D binary superstructures. Our results pave the way for using MOFs to create sophisticated superstructures comprising particles of various sizes, shapes, porosities, and chemical compositions.

Robust Multifunctional Ultrathin 2 Nanometer Organic Nanofibers

Ultrathin organic nanofibers (UTONFs) represent an emerging class of nanomaterials as they carry a set of favorable attributes, including ultrahigh specific surface area, lightweight, and mechanical flexibility, over inorganic counterparts, for use in biomedicine and nanotechnology. However, precise synthesis of uniform UTONFs (diameter ≤ 2 nm) with tailored functionalities remained challenging. Herein, we report robust multifunctional UTONFs using hydrophobic interaction-driven self-assembly of amphiphilic alternating peptoids containing hydrophobic photoresponsive azobenzene and hydrophilic hydroxyl moieties periodically arranged along the peptoid backbone. Notably, the as-crafted UTONFs are approximately 2 nm in diameter and tens of micrometers in length (an aspect ratio, AR, of ∼10000), exemplifying the UTONFs with the smallest diameter yielded via self-assembly. Intriguingly, UTONFs were disassembled into short-segmented nanofibers and controllably reassembled into UTONFs, resembling "step-growth polymerization". Photoisomerization of azobenzene moieties leads to reversible transformation between UTONFs and spherical micelles. Such meticulously engineered UTONFs demonstrate potential for catalysis, bioimaging, and antibacterial therapeutics. Our study highlights the significance of the rational design of amphiphiles containing alternating hydrophobic and hydrophilic moieties in constructing otherwise unattainable extremely thin UTONFs with ultrahigh AR and stimuli-responsive functionalities for energy and bionanotechnology.