XGLiu

Multifunctional block copolymers are valuable candidates for the simultaneous solubilization of hydrophobic and ionic compounds. This study details the synthesis and characterization of the PEG peptide–based macromolecules as well as the morphological analysis of the self‐assembled nanoparticles. The focus is on the polymers' ability to solubilize hardly soluble mineral calcium phosphates and hydrophobic molecules from different environments.

Abstract

The solubilization of targeted compounds represents key criteria in the sophisticated field of medical chemistry but also in technical applications like scale removal. Especially, the simultaneous dissolution of two chemically different compounds remains challenging. Herein, macromolecular solubilizers are introduced for the simultaneous dissolution and encapsulation of poorly water‐soluble cholesterol and hydroxyapatite. The peptide‐based, amphiphilic block copolymers possess physicochemically disparate segments combined in one polymer chain as binding sites for hydrophobic as well as ionic materials. Small polymer libraries are synthesized and screened for structure–property relationships. Complementary analytical techniques suggest polymeric self‐assembly into spherical adaptive nanoparticles with the fundamental ability to passively absorb significant amounts of hydrophobic cholesterol up to 33 wt%. Furthermore, the additional incorporation of acidic domains enables the simultaneous dissolution of hydrophobic compounds and mineral phases such as hydroxyapatite. Ultimately, those nontoxic block copolymers can be used to solubilize and absorb other lipophilic and ionic compounds such as Sudan III dye and calcium ions. Such multifunctional nanomaterials have a wide range of direct application for simultaneous dissolution or delivery of hydrophobic molecules and cations resp. minerals for instance in the field of atherosclerosis.

Hot rods: Copper nanorods (CuNRs) with tunable aspect ratios were grown in the confined space of preformed rod‐shaped polymer nanocapsules, thereby avoiding the challenges involved in the conventional synthesis. The obtained CuNRs have a strong plasmon resonance to incident light and efficiently convert the light to heat, making them suitable active components for constructing light‐responsive actuators and microrobots.

Abstract

Herein, we show that copper nanostructures, if made anisotropic, can exhibit strong surface plasmon resonance comparable to that of gold and silver counterparts in the near‐infrared spectrum. Further, we demonstrate that a robust confined seeded growth strategy allows the production of high‐quality samples with excellent control over their size, morphology, and plasmon resonance frequency. As an example, copper nanorods (CuNRs) are successfully grown in a limited space of preformed rod‐shaped polymer nanocapsules, thereby avoiding the complex nucleation kinetics involved in the conventional synthesis. The method is unique in that it enables the flexible control and fine‐tuning of the aspect ratio and the plasmonic resonance. We also show the high efficiency and stability of the as‐synthesized CuNRs in photothermal conversion and demonstrate their incorporation into nanocomposite polymer films that can be used as active components for constructing light‐responsive actuators and microrobots.

Recent progresses of in situ synchrotron X‐ray techniques for studying nucleation and growth kinetics of forming colloidal nanoparticles are reviewed. The time‐resolved parameters of growing nanoparticles provide unique information to help better understand the intrinsic kinetic parameters of synthesis reactions, benefiting the synthesis of colloidal nanoparticles with desirable properties in a rational manner.

Abstract

Rational synthesis of colloidal nanoparticles with desirable properties relies on precise control over the nucleation and growth kinetics, which is still not well understood. The recent development of in situ high energy synchrotron X‐ray techniques offers an excellent opportunity to quantitatively monitor the growth trajectories of colloidal nanoparticles in real time under real reaction conditions. The time‐resolved, quantitative data of the growing colloidal nanoparticles are unique to reveal the mechanism of nanoparticle formation and determine the corresponding intrinsic kinetic parameters. This review discusses the kinetics of major steps of forming colloidal nanoparticles and the capability of in situ synchrotron X‐ray techniques in studying the corresponding kinetics.

Time‐resolved self‐assembly of colloidal PbS nanocrystals upon controlled solvent evaporation is studied using in situ synchrotron small‐angle X‐ray scattering and X‐ray cross correlation analysis. PbS nanocrystals first form a highly ordered hexagonal closed‐packed superlattice in a solvent vapor saturated atmosphere, followed by a transition into the final body‐centered cubic superlattice upon complete evaporation of the solvent.

Abstract

Self‐assembled nanocrystal superlattices have attracted large scientific attention due to their potential technological applications. However, the nucleation and growth mechanisms of superlattice assemblies remain largely unresolved due to experimental difficulties to monitor intermediate states. Here, the self‐assembly of colloidal PbS nanocrystals is studied in real time by a combination of controlled solvent evaporation from the bulk solution and in situ small‐angle X‐ray scattering (SAXS) in transmission geometry. For the first time for the investigated system a hexagonal closed‐packed (hcp) superlattice formed in a solvent vapor saturated atmosphere is observed during slow solvent evaporation from a colloidal suspension. The highly ordered hcp superlattice is followed by a transition into the final body‐centered cubic superlattice upon complete drying. Additionally, X‐ray cross‐correlation analysis of Bragg reflections is applied to access information on precursor structures in the assembly process, which is not evident from conventional SAXS analysis. The detailed evolution of the crystal structure with time provides key results for understanding the assembly mechanism and the role of ligand–solvent interactions, which is important both for fundamental research and for fabrication of superlattices with desired properties.

DNA nanostructures perform a wide array of functions from drug delivery to molecular circuits. Their applications in in vitro and in vivo circumstances require special thought in developing a molecular hero suit. This suit equips specialized DNA nanostructures with cell targeting agents, encapsulating therapeutic cargo, and a body armor to protect them from degradation.

Abstract

Precise control of DNA base pairing has rapidly developed into a field full of diverse nanoscale structures and devices that are capable of automation, performing molecular analyses, mimicking enzymatic cascades, biosensing, and delivering drugs. This DNA‐based platform has shown the potential of offering novel therapeutics and biomolecular analysis but will ultimately require clever modification to enrich or achieve the needed “properties” and make it whole. These modifications total what are categorized as the molecular hero suit of DNA nanotechnology. Like a hero, DNA nanostructures have the ability to put on a suit equipped with honing mechanisms, molecular flares, encapsulated cargoes, a protective body armor, and an evasive stealth mode.

Amorphous materials with dangling bonds and band tails could lead the energy of the system to a metastable state and thus facilitate surface electron escape and transfer. The as‐synthesized amorphous Mn₃O₄ octahedral nanocages are dispersed in a nematic liquid crystal matrix E7, and a markedly decreased threshold voltage and saturation voltage, a higher contrast, and a faster response time are achieved.

Abstract

Improving electro‐optic properties is essential for fabricating high‐quality liquid crystal displays. Herein, by doping amorphous Mn₃O₄ octahedral nanocages (a‐Mn₃O₄ ONCs) into a nematic liquid crystal (NLC) matrix E7, outstanding electro‐optic properties of the blend are successfully obtained. At a doping concentration of 0.03 wt%, the maximum decreases of threshold voltage (V _th) and saturation voltage (V _sat) are 34% and 31%, respectively, and the increase of contrast (C _on) is 160%. This remarkable electro‐optic activity can be attributed to high‐efficiency charge transfer within the a‐Mn₃O₄ ONCs NLC system, caused by metastable electronic states of a‐Mn₃O₄ ONCs. To the best of our knowledge, such remarkable decreased electro‐optic activity is observed for the first time from doping amorphous semiconductors, which could provide a new pathway to develop excellent energy‐saving amorphous materials and improve their potential applications in electro‐optical devices.

Nanomaterials are critical components in the Earth system’s past, present, and future characteristics and behavior. They have been present since Earth’s origin in great abundance. Life, from the earliest cells to modern humans, has evolved in intimate association with naturally occurring nanomaterials. This synergy began to shift considerably with human industrialization. Particularly since the Industrial Revolution some two-and-a-half centuries ago, incidental nanomaterials (produced unintentionally by human activity) have been continuously produced and distributed worldwide. In some areas, they now rival the amount of naturally occurring nanomaterials. In the past half-century, engineered nanomaterials have been produced in very small amounts relative to the other two types of nanomaterials, but still in large enough quantities to make them a consequential component of the planet. All nanomaterials, regardless of their origin, have distinct chemical and physical properties throughout their size range, clearly setting them apart from their macroscopic equivalents and necessitating careful study. Following major advances in experimental, computational, analytical, and field approaches, it is becoming possible to better assess and understand all types and origins of nanomaterials in the Earth system. It is also now possible to frame their immediate and long-term impact on environmental and human health at local, regional, and global scales.

Measuring the mechanical properties of atomically thin materials results in a big technical challenge. A method to determine the Young's modulus of thin polymeric films is revisited. The method is demonstrated to be applicable in the field of 2D materials.

Abstract

Measuring the mechanical properties of 2D materials is a formidable task. While regular electrical and optical probing techniques are suitable even for atomically thin materials, conventional mechanical tests cannot be directly applied. Therefore, new mechanical testing techniques need to be developed. Up to now, the most widespread approaches require micro‐fabrication to create freely suspended membranes, rendering their implementation complex and costly. Here, a simple yet powerful technique is revisited to measure the mechanical properties of thin films. The buckling metrology method, that does not require the fabrication of freely suspended structures, is used to determine the Young's modulus of several transition metal dichalcogenides (MoS₂, MoSe₂, WS₂, and WSe₂) with thicknesses ranging from 2 to 10 layers. The obtained values for the Young's modulus and their uncertainty are critically compared with previously published results, finding that this simple technique provides results which are in good agreement with those reported using other highly sophisticated testing methods. By comparing the cost, complexity, and time required for the different methods reported in the literature, the buckling metrology method presents certain advantages that make it an interesting mechanical test tool for 2D materials.

Liquid cell transmission electron microscopy reveals a new nanocrystallization pathway. The nanoparticle crystallization is mediated by an important intermediate phase of condensed atomic cluster aggregates, which is defined as a cluster‐cloud. Specifically, it follows three fundamental steps: formation of the cluster‐cloud through the aggregation of clusters; condensation of the cluster‐cloud to a poorly crystallized nanoparticle; and multiple out‐and‐in relaxations toward a single crystal via order–disorder phase separation.

Abstract

Elucidating the early stages of crystallization from supersaturated solutions is of critical importance, but remains a great challenge. An in situ liquid cell transmission electron microscopy study reveals an intermediate state of condensed atomic clusters during Pd and Au crystallizations, which is named a “cluster‐cloud.” It is found that nucleation is initiated by the collapse of a cluster‐cloud, first forming a nanoparticle. The subsequent particle maturation proceeds via multiple out‐and‐in relaxations of the cluster‐cloud to improve crystallinity: from a poorly crystallized phase, the particle evolves into a well‐defined single‐crystal phase. Both experimental investigations and atomistic simulations suggest that the cluster‐cloud‐mediated nanocrystallization involves an order–disorder phase separation and reconstruction, which is energetically favored compared to local rearrangements within the particle. This finding grants new insights into nanocrystallization mechanisms, and provides useful information for the improvement of synthesis pathways of nanocrystals.

A hierarchical hexagonal design of nano resonators is used to realize a near infrared metamaterial absorber, inspired by the hierarchical design of diatom frustule pores. With an additional degree of freedom (hierarchy) in the design of metamaterial resonators, a widened high‐absorption band in the spectrum has been demonstrated by the measurements from experiments and from numerical and analytical calculations.

Abstract

Diatoms are photosynthetic algae that exist ubiquitously throughout the planet in water environments. Over the preceding decades, the diatom exoskeletons, termed frustules, featuring abundant micro‐ and nanopores, have served as the source material and inspiration for myriad research efforts. In this work, it is demonstrated that frustule‐inspired hierarchical nanostructure designs may be utilized in the fabrication of metamaterial absorbers, thereby realizing a broadband infrared (IR) absorber with excellent performance in terms of absorption. In an effort to investigate the origin of this absorption characteristic, numerical models are developed to study these structures, revealing that the hierarchical organization of the constituent nanoparticulate metamaterial unit cells introduce an additional resonance mode to the device, broadening the absorption spectrum. It is further demonstrated that the resonant peaks shift linearly as a function of inter‐unit‐cell spacing in the metamaterial, which is attributed to the induced collective dipole mode by the nanoparticles. Ultimately, the work herein represents an innovative perspective in terms of the design and fabrication of IR absorbers inspired by naturally occurring biomaterials, offering the potential to lead to advances in metamaterial absorber technology.

This special issue covers a broad range of carbon nanomaterials research, including controlled growth, scalable synthesis, and multifunctional applications. In the past 25 years, the Center for Nanochemistry (CNC) at Peking University has produced numerous achievements on graphene and other carbon nanomaterials. This special issue focuses on these carbon nanomaterials, while commemorating the 25th anniversary of CNC and the foundation of the Beijing Graphene Institute.

The cheaply available CaO can simultaneously transform renewable alcohols into pure hydrogen (≈99%) and high‐value graphene at a temperature as low as 500 °C. The concept on the comprehensive utilization of biomass with a carbon‐negative cycle offers a new way to mitigate global warning and the energy demands.

Abstract

The direct conversion of biorenewable alcohols into value‐added graphene and pure hydrogen (H₂) at benign conditions is an important challenge, especially, considering the open carbon‐reduced cycle. In this study, it is demonstrated that inexpensive calcium oxide (CaO, from eggshells) can transform alcohols into bulky nanoporous graphene and pure hydrogen (≈99%) with robust selectivity at the temperature as low as 500 °C. Consequently, the growth of graphene can follow the direction of alcohol flow and uniformly penetrate into bulky nanoporous CaO platelets longer than 1 m without clogging. The experimental results and density functional theory calculations demonstrate that alcohol molecules can be catalytically carbonized on the surface of CaO at low temperature. The concept of the comprehensive utilization of biomass‐derived alcohols offers a carbon‐negative cycle for mitigating global warming and the energy demand.

Highly homogeneous monomeric AuNP and AgNP arrays are fabricated through ultrasonication‐induced self‐assembly into anodized aluminum oxide nanopores. The dimensions of AuNPs and interparticle distances can be controlled to exhibit asymmetric line shapes due to Fano‐like plasmon resonances. The AgNP array can be utilized as a highly functional photocatalytic substrate for plasmon‐driven 4‐nitrobenzenethiol reduction and bacterial annihilation.

Abstract

Monomeric gold (Au) and silver (Ag) nanoparticle (NP) arrays are self‐assembled uniformly into anodized aluminium oxide (AAO) nanopores with a high homogeneity of greater than 95%, using ultrasonication. The monomeric metal NP array exhibits asymmetric plasmonic absorption due to Fano‐like resonance as interpreted by finite‐difference time‐domain (FDTD) simulation for the numbers up to 127 AuNPs. To examine gap distance‐dependent collective‐plasmonic resonance, the different dimensions of S, M, and L arrays of the AuNP diameters/the gap distances of ≈36 nm/≈66 nm, ≈45 nm/≈56 nm, and ≈77 nm/≈12 nm, respectively, are prepared. Metal NP arrays with an invariable nanogap of ≈50 nm can provide consistent surface‐enhanced Raman scattering (SERS) intensities for Rhodamine 6G (Rh6G) with a relative standard deviation (RSD) of 3.8–5.4%. Monomeric arrays can provide an effective platform for 2D hot‐electron excitation, as evidenced by the SERS peak‐changes of 4‐nitrobenzenethiol (4‐NBT) adsorbed on AgNP arrays with a power density of ≈0.25 mW µm^‐2 at 514 and 633 nm. For practical purposes, the bacteria captured by 4‐mercaptophenylboronic acid are found to be easily destroyed under visible laser excitation at 514 nm with a power density of ≈14 mW µm^‐2 for 60 min using Ag due to efficient plasmonic‐electron transfer.

A new method for preparing silica‐passivated perovskite nanocrystals that are precipitable by polar solvents without destroying their surface chemistry or losing quantum yield, and can also be encapsulated into non‐crosslinked polystyrene microspheres for long‐term storage against moisture and reusage.

Abstract

Perovskite nanocrystals (PNCs) are emerging luminescent materials due to their fascinating physic‐optical properties. However, their sensitive surface chemistry with organic polar solvents, oxygen, and moisture greatly hinders their developments towards practical applications. Herein we promote silica‐passivated PNCs (SP‐PNCs) by in situ hydrolyzing the surface ligands of (3‐aminopropyl) triethoxysilane. The resultant SP‐PNCs possesses a high quantum yield (QY) of 80 % and are precipitable by polar solvents, such as ethanol and acetone, without destroying their surface chemistry or losing QY, which offers an eco‐friendly and efficient method for separation, purification, and phase transfer of PNCs. Moreover, we further promoted a swelling–deswelling encapsulation process to incorporate the as‐made SP‐PNCs into non‐crosslinked polystyrene microspheres (PMs), which can largely increase the stability of the SP‐PNCs against moisture for long‐term storage.

Measuring the mechanical properties of atomically thin materials results in a big technical challenge. A method to determine the Young's modulus of thin polymeric films is revisited. The method is demonstrated to be applicable in the field of 2D materials.

Abstract

Measuring the mechanical properties of 2D materials is a formidable task. While regular electrical and optical probing techniques are suitable even for atomically thin materials, conventional mechanical tests cannot be directly applied. Therefore, new mechanical testing techniques need to be developed. Up to now, the most widespread approaches require micro‐fabrication to create freely suspended membranes, rendering their implementation complex and costly. Here, a simple yet powerful technique is revisited to measure the mechanical properties of thin films. The buckling metrology method, that does not require the fabrication of freely suspended structures, is used to determine the Young's modulus of several transition metal dichalcogenides (MoS₂, MoSe₂, WS₂, and WSe₂) with thicknesses ranging from 2 to 10 layers. The obtained values for the Young's modulus and their uncertainty are critically compared with previously published results, finding that this simple technique provides results which are in good agreement with those reported using other highly sophisticated testing methods. By comparing the cost, complexity, and time required for the different methods reported in the literature, the buckling metrology method presents certain advantages that make it an interesting mechanical test tool for 2D materials.

The reconfiguration of DNA‐linked substrate‐supported nanoparticle assemblies in response to ethanol added to the aqueous solution is studied using in situ atomic force microscopy. In situ imaging directly shows the changes to the monolayer superlattice during ethanol‐induced contraction and expansion. A statistical analysis of the interparticle spacings reveals hysteresis in the lattice parameter due to the nanoparticle–substrate DNA bonding.

Abstract

The ability to dynamically reconfigure superlattices in response to external stimuli is an intriguing prospect for programmable DNA‐guided nanoparticle (NP) assemblies, which promises the realization of “smart” materials with dynamically adjustable interparticle spacing and real‐time tunable properties. Existing in situ probes of reconfiguration processes have been limited mostly to reciprocal space methods, which can follow larger ordered ensembles but do not provide access to real‐space pathways and dynamics. Here, in situ atomic force microscopy is used to investigate DNA‐linked NP assemblies and their response to external stimuli, specifically the contraction and expansion of on‐surface self‐assembled monolayer superlattices upon reversible DNA condensation induced by ethanol. In situ microscopy allows observation and quantification of key processes in solution, e.g., lattice parameter changes, defects, and monomer displacements in small groups of NPs. The analysis of imaging data uncovers important boundary conditions due to DNA bonding of NP superlattices to a substrate. Tension in the NP–substrate DNA bonds, which can elastically extend, break, and re‐form during contraction/expansion cycles, counteracts the changes in lattice parameter and causes hysteresis in the response of the system. The results provide insight into the behavior of supported DNA‐linked NP superlattices and establish a foundation for designing and probing tunable nanocrystal‐based materials in solution.

Asymmetric silica: The C_ABCD labeling rule for the judgment of asymmetry in tetrahedral carbon materials is not suitable in the case of silicate materials. The structure of silica based on the accumulation of SiO₄ tetrahedrons is practically asymmetric owing to the formation of irregular tetrahedrons with different bond lengths and bond angles on Si−O, and thus, the protocol of enantioselective synthesis is applicable in the preparation of chiral silica.

Abstract

Silica is abundant in the Earth's crust, and silicate materials are used on the global scale, from industrial products for architecture, vehicles, electronics, and optics to consumption as foods, medicines, supplements, and cosmetics. Silica has become increasingly important in current science and technology, as seen in the components of advanced materials. The characteristic formula of silica is very simply often expressed as SiO₂. However, it is difficult to draw silica precisely owing to its intricate chemical structures. We need to make a greater effort in understanding silica, even though silica chemistry has existed for over 200 years. Similar to the homochirality observed in natural amino acids, natural silica of quartz is chiral, and in some sense, the origin of life with chirality might be partly related to quartz‐like silica chirality. This review focuses on the asymmetry of silica from the view of the formation of irregular tetrahedron structures of SiO₄. Silica is composed of several repeated tetrahedron units of SiO₄, leading to the formation of inorganic polymers with divergently expanded 3D structures. In this large polymeric skeleton, not every unit of SiO₄ can maintain an ideal tetrahedron, and thus, it becomes twisted. The twisting results in an asymmetric point on the Si atom, leading silica to become racemic in the stereochemical sense. Therefore, enantioselective preparation of silica should endow silica with chirality through the silica skeleton. Some recent achievements exhibit that silica is an effective chiral material and has great potential for transferring chirality from silica to other matter.

Single‐molecule imaging of the metal‐ion‐mediated formation of dsDNA in a DNA frame was demonstrated. By using two types of metallo‐base pairs C‐Ag‐C and T‐Hg‐T, formation of dsDNA from two consecutive C and T strands in the presence of metal ions was characterized. The dynamic formation of dsDNA using T‐Hg‐T was directly observed using high‐speed atomic force microscopy.

Abstract

This work demonstrates single‐molecule imaging of metal‐ion induced double‐stranded DNA formation in DNA nanostructures. The formation of the metal ion‐mediated base pairing in a DNA origami frame was examined using C‐Ag‐C and T‐Hg‐T metallo‐base pairs. The target DNA strands containing consecutive C or T were incorporated into the DNA frame, and the binding was controlled by the addition of metal ions. Double‐stranded DNA formation was monitored by observing the structural changes in the incorporated DNA strands using high‐speed atomic force microscopy (AFM). Using the T‐Hg‐T base pair, the dynamic formation of unique dsDNA and its dissociation were observed. The formation of an unusual shape of dsDNA with consecutive T‐Hg‐T base pairs was visualized in the designed nanoscale structure.