Layer Assembly Research Articles

Assembly of ionic liquid molecule layers on metal–organic framework-808 for CO2 capture

Ionic liquid molecule layers (ILMLs) were assembled on MOF-808 with high porosity for gas adsorption. ILMLs, as a result of better affinity to CO2, perform like an adhesive layer to trap CO2 and MOF-808 performs as a gas reservoir. Deliberately controlling the thickness of ILMLs from 1.7 to 18 nm, we strike a balance of capacity, selectivity and cycling performances for CO2 capture. The optimal composite adsorbs substantial amount of CO2 at ambient conditions (3.00 mmol g−1), which is 2.6 times of that on MOF-808 (1.15 mmol g−1). CO2/N2 selectivity towards mimic combustion flue gas in industry, was 372 (towards 15 mol.% of CO2 in N2) and 478 (towards 5 mol.% of CO2 in N2), near one-order magnitude higher than MOF-808 and exceeding most benchmark materials. Notably, by overcoming the gas–liquid interface limitation, CO2 capacity on each gram of ILMLs was 1000 times higher than that of the bulk liquid. The composite presents cycling separation performances with great energy efficiency for mimic flus gas, as a complete regeneration can be freely achieved at ambient temperature.

Ordered Nanostructures in Thin Films of Precise Ion-Containing Multiblock Copolymers.

We demonstrate that ionic functionality in a multiblock architecture produces highly ordered and sub-3 nm nanostructures in thin films, including bicontinuous double gyroids. At 40 °C, precise ion-containing multiblock copolymers of poly(ethylene-b-lithium sulfosuccinate ester)n (PESxLi, x = 12 or 18) exhibit layered ionic assemblies parallel to the substrate. These ionic layers are separated by crystalline polyethylene blocks with the polymer backbones perpendicular to the substrate. Notably, above the melting temperature (Tm) of the polyethylene blocks, layered PES18Li thin films transform into a highly oriented double-gyroid morphology with the (211) plane (d211 = 2.5 nm) aligned parallel to the substrate. The cubic lattice parameter (agyr) of the double gyroid is 6.1 nm. Upon heating further above Tm, the double-gyroid morphology in PES18Li transitions into hexagonally packed cylinders with cylinders parallel to the substrate. These layered, double-gyroid, and cylinder nanostructures form epitaxially and spontaneously without secondary treatment, such as interfacial layers and solvent vapor annealing. When the film thickness is less than ∼3agyr, double gyroids and cylinders coexist due to the increased confinement. For PES12Li above Tm, the layered ionic assemblies simply transform into disordered morphology. Given the chemical tunability of ion-functionalized multiblock copolymers, this study reveals a versatile pathway to fabricating ordered nanostructures in thin films.

Electrodeposited MnS@Ni(OH)2 core-shell hybrids as an efficient electrode materials for symmetric supercapacitor applications

The usage of composites with chalcogenides and hydroxides are fascinated prodigious consideration for supercapacitor application. In this work, the layer by layer assembly of MnS@Ni(OH)2 core-shell hybrids were prepared by facile electrodeposition method and utilized as a binder-free electrode material for symmetric supercapacitor application. Systematic analyses have been done to confirms the formation and morphological features of MnS@Ni(OH)2 core-shell hybrids. The core-shell hybrids of MnS@Ni(OH)2 exhibits the redox behavior and delivered a high specific capacity of 2612 F g­1 at a current density of 1 A g­1 with excellent cycle stability of 88% capacity retention over 5000th cycle in 3 M KOH electrolyte. The delivered specific capacity is the highest among MnS and Ni(OH) based supercapacitors and also higher than various types of other metal oxide-based supercapacitors. Moreover, a sandwich-like solid-state symmetric supercapacitor was fabricated using MnS@Ni(OH)2 core-shell hybrid, and thus provided the specific capacity of 168.75 F g­1 at a current density of 1 A g­1 with the energy and power density of 60 Wh kg−1 and 800 W kg−1, respectively. The attained results recommended that the MnS@Ni(OH)2 core-shell hybrid has the probability to be applied as a novel, robust, and low-cost electrode material for supercapacitor energy storage devices.

Transmutation of long-lived fission products in an advanced nuclear energy system

Disposal of long-lived fission products (LLFPs) produced in reactors has been paid a lot attention for sustainable and clean nuclear energy. Although a few transmutation means have been proposed to address this issue, there are still scientific and/or engineering challenges to achieve efficient transmutation of LLFPs. In this study, we propose a novel concept of advanced nuclear energy system (ANES) for transmuting LLFPs efficiently without isotopic separation. The ANES comprises intense photoneutron source (PNS) and subcritical reactor, which consist of lead–bismuth (Pb-Bi) layer, beryllium (Be) layer, and fuel, LLFPs and shield assemblies. The PNS is produced by bombarding radioactive cesium and iodine target with a laser-Compton scattering (LCS) γ-ray beam. We investigate the effect of the ANES system layout on transmutation efficiency by Monte Carlo simulations. It is found that a proper combination of the Pb-Bi layer and the Be layer can increase the utilization efficiency of the PNS by a factor of ~ 10, which helps to decrease by almost the same factor the LCS γ-beam intensity required for driving the ANES. Supposing that the ANES operates over 20 years at a normal thermal power of 500 MWt, five LLFPs including 99Tc, 129I, 107Pd, 137Cs and 79Se could be transmuted by more than 30%. Their effective half-lives thus decrease drastically from ~ 106 to less than 102 years. It is suggested that this successful implementation of the ANES paves the avenue towards practical transmutation of LLFPs without isotopic separation.

Kelvin Probe Microscopy Investigation of Poly-Octylthiophene Aggregates.

Conductive polymers have fundamental relevance as well as novel technological applications in the organic optoelectronics field. Their photophysical and transport properties strongly depend on the molecular arrangement, and nanoscale characterization is needed to fully understand the optoelectronic processes taking place in organic devices. In this work, we study the electrostatic properties of poly-3-octylthiophene isolated structures: disordered low-packed polymer chains and crystalline layered lamellar assemblies. We characterize the electronic ground state using Kelvin probe microscopy. This allows us to resolve a rich variety of surface potential regions that emerge over the different polymer structures. These SP regions are correlated with different molecular aggregates.

Towards high rate and high areal capacity Zn ion hybrid supercapacitor: Fluffy graphene architecture anchored with ultrathin redox-active molecule

Zn ion hybrid supercapacitor (ZHS) with both high energy density and high power density is a pursuing goal. Coupling high capacity molecule with graphene is recognized as an effective way. However, the common physical integration techniques cannot ensure molecular-level uniformity for electrodes, hence leading to inferior synergetic effects, especially in high mass loading situation. To address this dilemma, here we integrate cost-effective and redox-active phenanthraquinone (PQ) with graphene through two self-assemblies, which are the assembly of PQ layers on GO (graphene oxide) sheets in solvent and assembly of GO sheets into fluffy graphene hydrogel (FGH) architecture, at molecular-scale to prepare highly uniform PQ-FGH. Attributed to the molecular-level adsorption and fluffy morphology, PQ-FGH electrode ensures rapid electron transfer speed between PQ and graphene sheets as well as fast ions transportation. As a result, PQ-FGHs with either low or high mass loading (∼1 or 11.4 mg cm−2) exhibit high capacity and superior rate capability. Correspondingly, the areal energy density of the ZHS at 0.81 ∼ 32.6 mW cm−2 achieves 1.31 ∼ 0.81 mWh cm−2, which is closed to the level of commercial Li-ion batteries. This strategy can be easily extended to other materials to prepare high performance supercapacitors or batteries.

Layered and orthogonal assembly of hydrophilic drugs and hydrophobic photosensitizers for enhanced cancer therapy

Combinatorial tumor therapy including chemotherapy and photodynamic therapy (PDT) can compensate for the limitations of each other and significantly increase the therapeutic effect. However, considering the differences of water-soluble characteristics between chemotherapeutic drugs and photosensitizers for photodynamic therapy, simply loading these substances into the same cavities of nanocarriers is rather difficult, leading to the reduced drug loading efficiency. Here, we reported a layered and orthogonal assembly of hydrophilic drugs doxorubicin (Dox) and hydrophobic photosensitizers Chlorin e6 (Ce6) for enhancing the effect of synergistic therapeutics. The assembly was based on polydopamine (PDA) modified with β-cyclodextrin (β-CD) through the addition reaction of -HS in HS-β-CD and-C=C in PDA, then DOX and Ce6 were loaded on the PDA and in the hydrophobic cavities of β-CDs respectively with superior drug loading efficiencies (38.8 ± 0.8% and 5.4 ± 0.3% for DOX and Ce6). PDA was hydrolyzed completely under the lysosomal acidic condition, leading to the controlled release of DOX. Under NIR irradiations, DOX-based chemotherapy was successfully integrated with PDA-based photothermal and Ce6-based photodynamic therapy. Tumor specific aptamer AS1411-modified assembly provides ideal antitumor effects in vitro and in vivo with excellent biocompatibility. Collectively, this layered and orthogonal assembly offers a generalizable solution for delivering matters with distinct aqueous solubility would find broad applications not only in drug delivery but also in bio-nanotechnology.

PH-Controlled assembly of polyelectrolyte layers on silica nanoparticles in concentrated suspension

HypothesisPreparation of suspensions of nanoparticles (>1 wt%) coated with a polyelectrolyte multilayers is a challenging task because of the risk of flocculation when a polyelectrolyte is added to a suspension of oppositely charged nanoparticles. This situation can be avoided if the charge density of the polymers and particles is controlled during mixing so as to separate mixing and adsorption events. ExperimentsThe cationic polyethylenimine (PEI) and the anionic carboxymethylcellulose (CMC) were used as weak polyelectrolytes. Polyelectrolyte multilayers build-up was conducted by reducing the charge of one of the components during the addition of the next component. Charge density was controlled by tuning pH. Analysis of the suspension of coated nanoparticles was done by means of dynamic light scattering, electrophoresis and small angle x-ray scattering measurements, while quartz crystal microbalance was used to study the build-up process on flat silica surfaces. FindingsCharge density, controlled through pH, can be used as a tool to avoid flocculation during layer-by-layer deposition of polyelectrolytes on 20 nm silica particles at high concentration (∼40 wt%). When added to silica at pH 3, PEI did not induce flocculation. Adsorption was triggered by raising the pH to 11, pH at which CMC could be added. The pH was then lowered to 3. The process was repeated, and up to five polyelectrolyte layers were deposited on concentrated silica nanoparticles while inducing minimal aggregation.

An Atomistic Model Describing the Structure and Morphology of Cu-Doped C-S-H Hardening Accelerator Nanoparticles.

Calcium silicate hydrate (C-S-H) is the main binding phase in Portland cement. The addition of C-S-H nanoparticles as nucleation seeds has successfully been used to accelerate the hydration process and the precipitation of binding phases either in conventional Portland cement or in alternative binders. Indeed, the modulation of the hydration kinetics during the early-stage dissolution-precipitation reactions, by acting on the nucleation and growth of binding phases, improves the early strength development. The fine-tuning of concrete properties in terms of compressive strength and durability by designed structural modifications can be achieved through the detailed description of the reaction products at the atomic scale. The nano-sized, chemically complex and structurally disordered nature of these phases hamper their thorough structural characterization. To this aim, we implement a novel multi-scale approach by combining forefront small-angle X-ray scattering (SAXS) and synchrotron wide-angle X-ray total scattering (WAXTS) analyses for the characterization of Cu-doped C-S-H nanoparticles dispersed in a colloidal suspension, used as hardening accelerator. SAXS and WAXTS data were analyzed under a unified modeling approach by developing suitable atomistic models for C-S-H nanoparticles to be used to simulate the experimental X-ray scattering pattern through the Debye scattering equation. The optimization of atomistic models against the experimental pattern, together with complementary information on the structural local order from 29Si solid-state nuclear magnetic resonance and X-ray absorption spectroscopy, provided a comprehensive description of the structure, size and morphology of C-S-H nanoparticles from the atomic to the nanometer scale. C-S-H nanoparticles were modeled as an assembly of layers composed of 7-fold coordinated Ca atoms and decorated by silicate dimers and chains. The structural layers are a few tens of nanometers in length and width, with a crystal structure resembling that of a defective tobermorite, but lacking any ordering between stacking layers.

Fabrication of Chitosan/MXene multilayered film based on layer-by-layer assembly: Toward enhanced electromagnetic interference shielding and thermal management capacity

Polymeric composites that feature both highly efficient EMI shielding and rapid heat dissipation have long been attractive, but it remains a significant challenge to fulfill such goals by virtue of lower film thickness and less filler. Inspired by the electrostatic interaction between oppositely charged chitosan (CS) solution and transition metal carbide (MXene) slurry, here we report a series of CS/MXene alternating layered films by taking advantage of layer by layer assembly strategy. The resultant 35-μm thick CS/MXene multilayer film presents a maximum EMI SE of 40.8 dB, a high specific EMI SE (SSEt) of 10, 650 dB cm2 g−1, together with superior thermal conductivity (6.3 W m−1 K−1) and excellent Joule heating capacity. Thus, this research opens up a new horizon for achieving satisfying EMI shielding and heat dissipation capacity, which will further benefit the development of MXene‑based composite materials in next-generation electrical devices.

Waste gelatin based layer by layer assembly for sustainable solution to cotton fabrics flame retardancy

Cotton fabrics are the main textile material in the daily life, but they may threaten people's lives and property when encountering flame due to its flammability. However, traditional halogen-containing flame retardancy strategies were considered owning health risks for human and perceived environmental concerns. In this work, bio-based gelatin extracted from scrap skin in leather processing, which is the component of the carbon source, was utilized for layer-by-layer assembly constructing intumescent flame-retardant coating onto cotton fabrics surface. The flame retardancy of the treated cotton fabrics was significantly improved, as showed by the limited oxygen index values of 28.5 for the cotton fabrics sample with 6 bilayer gelatin/ammonium polyphosphate (GL/APP) coating. Simultaneously, vertical burning test illustrated that the GL/APP coated fabrics exhibited excellent self-extinguishing behavior, and resulting in 63% maximum reduction in peak heat release rate obtained from Micro-scale Combustion Calorimeter tests for C200-6BL sample. These LbL-assembled cotton fabrics also presented excellent breathability and hygroscopicity, and would maintain good perspiration absorption and moisture removal properties in the practical application. Considering their healthy, eco-friendliness, low cost, and excellent flame retardant efficiency, GL/APP coatings can be considered as promising sustainable flame retardant strategy for cotton fabrics.

Advancing bone tissue engineering one layer at a time: a layer-by-layer assembly approach to 3D bone scaffold materials.

The layer-by-layer (LbL) assembly technique has shown excellent potential in tissue engineering applications. The technique is mainly based on electrostatic attraction and involves the sequential adsorption of oppositely charged electrolyte complexes onto a substrate, resulting in uniform single layers that can be rapidly deposited to form nanolayer films. LbL has attracted significant attention as a coating technique due to it being a convenient and affordable fabrication method capable of achieving a wide range of biomaterial coatings while keeping the main biofunctionality of the substrate materials. One promising application is the use of nanolayer films fabricated by LbL assembly in the development of 3-dimensional (3D) bone scaffolds for bone repair and regeneration. Due to their versatility, nanoscale films offer an exciting opportunity for tailoring surface and bulk property modification of implants for osseous defect therapies. This review article discusses the state of the art of the LbL assembly technique, and the properties and functions of LbL-assembled films for engineered bone scaffold application, combination of multilayers for multifunctional coatings and recent advancements in the application of LbL assembly in bone tissue engineering. The recent decade has seen tremendous advances in the promising developments of LbL film systems and their impact on cell interaction and tissue repair. A deep understanding of the cell behaviour and biomaterial interaction for the further development of new generations of LbL films for tissue engineering are the most important targets for biomaterial research in the field. While there is still much to learn about the biological and physicochemical interactions at the interface of nano-surface coated scaffolds and biological systems, we provide a conceptual review to further progress in the LbL approach to 3D bone scaffold materials and inform the future of LbL development in bone tissue engineering.

High Purity and High Yield Sic Nanowires Synthesis Without Catalyst by Graphite Sheet Layer Assembly and Thermal Evaporation

High Purity and High Yield Sic Nanowires Synthesis Without Catalyst by Graphite Sheet Layer Assembly and Thermal Evaporation

Hydrological Effects of Prefabricated Permeable Pavements on Parking Lots

Permeable pavements can infiltrate and reduce stormwater runoff in parking lots, but issues around long construction periods and proper maintenance still required proper research and further understanding. The application of precast concrete can help to solve this. In this study, precast concrete components were applied to the design of permeable pavements to form prefabricated permeable pavements. The laboratory study is one of the first to examine the hydrological effect of prefabricated pervious pavements in parking lots. Four kinds of permeable pavements were designed and manufactured. These had different materials (natural sand-gravel, medium sand) which comprised the leveling layer or different assembly forms of precast concrete at the base. Three scenarios of rainfall intensity (0.5, 1, and 2 mm/min) and three rainfall intervals (one, three, and seven days) were simulated using rainfall simulators. The initial runoff time, runoff coefficient, and runoff control rate of each permeable pavement were investigated during the process of simulating. Results showed that the initial runoff time was no earlier than 42 min, the maximum runoff coefficient was 0.52, and the minimum runoff control rate was 47.7% within the rainfall intensity of 2 mm/min. The initial runoff time of each permeable pavement was no earlier than 36 min when the rainfall interval was one day, whereas, the maximum runoff coefficient was 0.64, and the average runoff control rate was 41.5%. The leveling layer material had a greater impact on the hydrological effect of permeable pavements, while the assembly form of precast concrete had no significant effect. Compared with natural sand-gravel, when the leveling layer was medium sand, the runoff generation was advanced by 4.5–7.8 min under different rainfall intensities, and 7–10 min under different rainfall intervals. The maximum runoff coefficient increased with about 14.6% when the rainfall interval was one day. Among four kinds of permeable pavements, the type I permeable pavement had the best runoff regulation performance. The results revealed that all prefabricated permeable pavements used in this study had good runoff control performance, and this design idea proved to be an alternative for the future design of permeable pavements.

Janus Photonic Microspheres with Bridged Lamellar Structures via Droplet-Confined Block Copolymer Co-Assembly.

Artificial self-assembly systems typically exhibit limited capability in creating nature-inspired complex materials with advanced functionalities. Here, an effective co-assembly strategy is demonstrated for the facile creation of complex photonic structures with intriguing light reflections. Two different lipophilic and amphiphilic bottlebrush block copolymers (BCPs) are placed within shrinking droplets to enable a cooperative working mechanism of microphase segregation and organized spontaneous emulsification, respectively. Layer assemblies of the lipophilic BCP and uniform water nanodroplets stabilized by the bottlebrush surfactant are both generated, and co-assembled into a bridged lamellar structure with the alternating arrangement of layers and closely packed nanodroplet arrays. Janus microspheres with diverse dual optical characteristics are successfully fabricated, and reflected wavelengths of light are highly tunable simply by changing the formulation or molecular weight of BCP.

Janus Photonic Microspheres with Bridged Lamellar Structures via Droplet‐Confined Block Copolymer Co‐Assembly

AbstractArtificial self‐assembly systems typically exhibit limited capability in creating nature‐inspired complex materials with advanced functionalities. Here, an effective co‐assembly strategy is demonstrated for the facile creation of complex photonic structures with intriguing light reflections. Two different lipophilic and amphiphilic bottlebrush block copolymers (BCPs) are placed within shrinking droplets to enable a cooperative working mechanism of microphase segregation and organized spontaneous emulsification, respectively. Layer assemblies of the lipophilic BCP and uniform water nanodroplets stabilized by the bottlebrush surfactant are both generated, and co‐assembled into a bridged lamellar structure with the alternating arrangement of layers and closely packed nanodroplet arrays. Janus microspheres with diverse dual optical characteristics are successfully fabricated, and reflected wavelengths of light are highly tunable simply by changing the formulation or molecular weight of BCP.

Mixture deposition method for graphene quantum dots-based dye-sensitized solar cell

Unambiguously layer by layer (LBL) assembly of graphene quantum dots (GQDs), and dye (GQDs/dye) on TiO2 photoanode is the traditional and straightforward approach in the fabrication of graphene quantum dot-cosensitized solar cells (QDSSCs). Unfortunately, limited light absorption and low affinity of GQDs to TiO2 surface shadow the advantages of LBL and constrain its practical application. Herein, a new strategy of mixture configuration (GQDs+dye) was investigated. The experimental results demonstrated that the mixture of GQDs+N719 exhibited the highest efficiency of 3.01%. The increased Jsc (5.075 mA/cm2) and high charge collection efficiency (0.96) in the mixture sample indicated enhanced electron collection at TiO2. The less -OH groups on TiO2 provide a good surface intact of GQDs and N719, thus increasing the affinity between the photoanode and photosensitizers. In addition to that, the high surface potential (33.47 mV) of the premixed sample restricted the photogenerated electrons to go into a deep state, reducing back electron transfer. Therefore, mixture assembly of co-sensitization is an effective approach for light-harvesting in QDSSC.

Growing Hydrogel Organ Mannequins with Interconnected Cavity Structures

AbstractBiomimicking organ mannequins with not only lifelike biological geometries but also virtually constituting connected circulation channels for exchanging substances are critical for in vitro biomedical applications, yet the big challenges remain. This paper reports a big step toward the goal to achieve hydrogel‐based organ mannequins with internal channels and a cavity, gradient structures, and a physiological environment of organs for in vitro purposes via metal ions‐induced interface supramolecular assembly of hydrogel layers on the thermally splitting templates. The templates composed of gelatin and ι‐carrageenan are built through direct ink writing, which are employed as the supports to in situ grow the alginate/Ca2+ hydrogel layers by rapid diffusion‐induced gelation process. Removing the hydrogel templates based on sol–gel conversion can readily yield hydrogel architectures with connected channels, structural integrity, and favorable physicochemical properties. Proof‐of‐concept hydrogel mannequins including the branched vascular replicas, digestive system, distal lung subunit, and glomerulus with mechanical robustness are engineered from replicating the tubular structure to imitate the basic profiles of organs. It is believed that this protocol paves a versatile way to construct hydrogel‐based biomimicking mannequins with cavity structures that can be used for in vitro biomedical training, testing, pharmacology, etc.

Ultrasensitive wearable sensor with novel hybrid structures of silver nanowires and carbon nanotubes in fluoroelastomer: Multi-directional sensing for human health monitoring and stretchable electronics

Today, wearable sensors are being developed for personalized human health monitoring for physical motion detection and physiological signal detection, and well-being. These wearable devices need to be extremely flexible, lightweight, and stretchable to be compatible with the contours of the human body, and mechanically and dynamically stable. Their functionality can be assured by simultaneously increasing conductivity, stretchability, and sensitivity for accurate and fast response. The challenge in fabricating stretchable sensors with these functionalities is embracing current wearable fashion. In this work, for the first time, a new 3D hybrid nanonetwork structures of high aspect ratio silver nanowires (AgNW) and carbon nanotubes (CNT) in fluoroelastomer FKM are developed. An optimized solution mixing (SM) and layer by layer (LBL) assembly technique, and LBL drop-coating process are employed to establish the hierarchical and shell-like nanostructures. The sensor films are ultra-thin and show high conductivity up to 2 × 105 S. m−1, high stretchability of up to 300%, and a maximum sensitivity (gage factor) of up to 2.5 × 107. The multifunctional sensor with hybrid nanonetwork shows high performance in various wearable electronic applications including human motion detection and stretchable light-emitting diode (LED) circuits. These ultra-sensitive materials show capability for multidirectional sensing by special configurations for each human body part movement, and small movements for human heartbeat monitoring.

Oligourea molecular lifter triggered by electric field

We have synthesized an oligourea foldamer containing seven urea residues, with a Cys-like residue introduced near the N-terminus of the helix. This enabled the immobilization of the molecules on gold electrode using gold-sulfur chemistry. Molecular layer was characterized by electrochemical and spectroelectrochemical methods. Electrochemical measurements confirmed the formation of a dielectric layer on the electrode surface and the determined potential of zero free charge proved that the molecules are adsorbed with the positive pole of the dipole pointing to the electrode surface. The measurements with the use of in situ surface-enhanced infrared absorption spectroscopy provided insight into the dynamics of molecules under the influence of the electric field. Namely, helical oligourea molecules undergo reversible potential-induced changes in the orientation of the molecules. Our results show that molecular layers of oligourea helical foldamers can be used as building blocks for assembly of stimuli-responsive molecular layers serving as molecular lifters triggered by electric field.