Solvent Evaporation-induced Self-assembly Research Articles

Combustion and mechanical properties enhancement strategy based on stearic acid surface activated boron powders

Boric acid and other impurities on the surface of boron (B) particles can interact with hydroxyl-terminated polybutadiene (HTPB), weakening the mechanical properties and energy release efficiency of boron-based solid rocket propellants. SA@B composite particles were created by coating stearic acid (SA) on the surface of B particles through solvent evaporation-induced self-assembly. The study investigated the impact of SA coating on the combustion performance of B particles and the mechanical properties of HTPB matrix composites. The results showed that the SA coating enhanced the oxidation efficiency of B particles in air. The combustion heat of SA@B composite particles is 30.29 MJ/g, about 50% higher than that of B particles. During the combustion of SA@B composite particles, fewer molten solid particles surround the flame, which enhances the stability of the combustion process of the B particles. Furthermore, the SA coating effectively enhanced the dispersion of B particles in HTPB. At a stretching speed of 100 mm/min, the tensile strength of the SA@B/HTPB composite materials is higher than that of the B/HTPB composite materials. Moreover, when the mass loading of the SA@B composite particles reaches 50 wt%, the tensile strength of SA@B/HTPB composite materials is 2.46 MPa. Activating the surface of boron particles with SA can significantly improve their compatibility with HTPB, which is crucial for the stable storage of boron-based solid rocket propellants.

Construction of Molecularly Dispersed Polyoxometalate-Alumina Hybrid Hollow Nanoflowers via Water-Induced Kirkendall Effect.

Hybrid nanomaterials with controllable structures and diverting components have attracted significant interest in the functional materials field. Here, we develop a solvent evaporation-induced self-assembly (EISA) strategy to synthesize nanosheet-assembled phosphomolybdic acid (H3PMo)-alumina hybrid hollow spheres. The resulting nanoflowers display a high surface area (up to 697 m2 g-1), adjustable diameter, high chemical/thermal stability, and especially molecularly dispersed H3PMo species. By employing various microscopic and spectroscopic techniques, the formation mechanism is elucidated, revealing the simultaneous control of the morphology by heteropoly acids and water through the water-induced Kirkendall effect. The versatility of the synthesis method is demonstrated by varying surfactants, heteropoly acids, and metal oxide precursors for the facile synthesis of hybrid metal oxides. Spherical hybrid alumina serves as an attractive support material for constructing metal-acid bifunctional catalysts owing to its advantageous surface area, acidity, and mesoporous microenvironment. Pt-loaded hollow flowers exhibit excellent catalytic performance and exceptional stability in the hydrodeoxygenation of vanillin with recyclability for up to 10 cycles. This research presents an innovative strategy for the controllable synthesis of hybrid metal oxide nanospheres and hollow nanoflowers, providing a multifunctional platform for diverse applications.

Self-Assembly of Multiwalled Carbon Nanotubes on a Silicone Rubber Foam Skeleton for Durable Piezoresistive Sensors.

Conductive nanomaterial/flexible polymer composite foams are of great interest in the field of flexible and wearable piezoresistive pressure sensors. However, the existing composite foam sensors are faced with stability issues from conductive nanomaterials, which tends to decrease their long-term durability. Herein, we developed a solvent evaporation-induced self-assembly strategy, which could significantly improve the stability of multiwalled carbon nanotubes (MWCNTs) on a silicone rubber foam skeleton. The process for self-assembly of MWCNTs was straightforward. Aqueous MWCNT dispersion droplets were first hierarchically enclosed in silicone rubber via water-in-oil (W/O) Pickering high internal phase emulsions (HIPEs). Then, the high pressure generated by fast evaporation of the solvent from the droplets could break the thinnest pore walls to form interconnected pores. As a result, very dense and firm MWCNT layers were self-assembled on the pore wall surface. Due to the excellent stability of MWCNTs and tetramodal interconnected porosity, our MWCNTs/silicone rubber composite foam showed the following "super" properties: low density of 0.26 g/mL, high porosity of 76%, and excellent mechanical strength (the maximum stress loss of 8.3% at 80% strain after 100 compression cycles). In addition, excellent piezoresistive performance, including superior discernibility for different amplitudes of compressive strain (up to 80%), rapid response time (150 ms), and high sensitivity (gauge factor of 1.44), was demonstrated for such foams, together with prominent durability (39,000 compression cycles at 60% strain in air) and excellent stability of resistance response in water and organic solvents (5000 compression cycles at 30% strain in water and ethanol). Regarding its application, a wearable piezoresistive sensor, which was assembled from the as-prepared conductive silicone rubber composite foam, could capture various movements from tiptoeing and finger bending to small deformations resulting from human pulse.

(Digital Presentation) Large-Scale Synthesis of Nanoporous Tungsten Oxide for Supercapacitor Application

The development of materials delivering high specific capacitance and energy density is a major challenge for supercapacitors. Due to high redox activity, several metal oxides like RuO2, MnO2, MoO3, Fe3O4, WO3 and CoOx have been broadly utilized as the active material for pseudo-capacitors. Among these, tungsten oxide (WO3), being less toxic, chemically stable, and abundantly available, has become a potential candidate and is widely investigated for pseudo-capacitors. However, some modifications are required to bring its performance to a commercial scale. Various approaches like composites with carbon and other oxides, doping, confinement, and porosity improvement are followed to improve their performances. But there is a need to find the potential of solely WO3 for supercapacitors. Looking forward to it, we have synthesized highly porous pure WO3 using the solution-based nanoprecipitation method. Our approach offers the possibility of large-scale production of porous materials with tunable pore sizes and structures compared to the traditionally used solvent evaporation-induced self-assembly (EISA) method. Herein, we used PS-b-PAA block copolymer as pore creating agent, which was removed after giving thermal treatment. The prepared material was analyzed using Brunauer-Emmett-Teller (BET) and exhibited a high specific surface area of 55.5 m2 g-1 with an average pore diameter of 3.7 nm. A detailed crystallographic and morphological analysis of these materials was carried out to check the feasibility of our material for energy storage applications. Furthermore, electrochemical investigations were carried out in 3E and 2E device configurations. The electrochemical studies demonstrate that porous WO3 has achieved a specific capacitance of 555 F g-1 at 10 mV s-1 scan rate. Figure 1

Synthesis and Application of Mesoporous Materials: Process Status, Technical Problems, and Development Prospects: A Mini-Review

The world today is witnessing a new technological revolution, particularly in the area of new materials. Different types of materials often have different characteristics and uses. Mesoporous materials have a large specific surface area, easily modifiable inner and outer surfaces, tunable pore size and pore channels, and good biocompatibility and thermodynamic stability, thus emerging as a new candidate material in the chemical research community. The presence of mesopores facilitates the rapid diffusion of macromolecules, reduces resistance to mass transfer, and provides different properties depending on the pore size, making mesoporous materials a potential candidate for a wide range of applications. This paper reviews the recent methods used to synthesize mesoporous materials, including hydrothermal synthesis, microwave synthesis, the sol–gel method, the phase conversion method, and the templating method. The soft templating method is introduced in detail, including bulk self-assembly, solvent evaporation-induced self-assembly, solution-based nanoprecipitation, interfacial self-assembly in a solution, and emulsion template self-assembly. The current status of the processes related to mesoporous materials in the fields of biomedicine, environmental and energy, electrochemical energy storage, and gas separation is elaborated. Finally, the technical issues and future directions in the synthesis and application of mesoporous materials are briefly discussed.

Ordered mesoporous Ni-La2O3/Al2O3 catalysts towards efficient plasma-assisted dry reforming of methane

Plasma-assisted dry reforming of methane reaction provides a promising way to produce syngas with unity H2/CO ratio as one important chemical feedstock. Aiming to establish a match between CH4 and CO2 activation rates to suppress carbon deposition under combining plasma and catalyst, the design of reasonable and efficient catalytic materials is great of importance. Herein, we reported that the addition of La enhanced the reducibility of Ni2+ species and promoted Ni dispersion over the highly ordered mesoporous 10Ni5LaAl-one pot catalyst. In comparison to 10Ni5La/Al prepared by the incipient wetness impregnation (IWI) method and 10NiAl-one pot prepared by one pot solvent evaporation-induced self-assembly (EISA) method, the 10Ni5LaAl-one pot catalyst exhibited the highest catalytic activity for syngas production (H2/CO ratio of 0.98) and the strongest coke-resistance ability in the plasma-assisted DRM reaction. Meanwhile, excellent stability performance was obtained within 90 h for the catalyst owing to the higher discharge power, efficient capacitance and lower apparent activation energy of CO2 under plasma condition. And possible reaction mechanism of the10Ni5LaAl-one pot was proposed during plasma-catalytic DRM process.

Colloidal crystals of monodisperse fluoro-nanoparticles by aqueous polymerization-induced self-assembly.

Here, we prepared monodisperse fluorinated nanospheres with the diameter regulated from 100 to 200 nm and PDI of the diameter lower than 0.05 via polymerization-induced self-assembly (PISA). Mono/multilayered 2D and large-scale ordered 3D lattices were formed by solvent evaporation-induced colloidal self-assembly. This work shows the promising application of PISA in colloidal self-assembly.

Tannin-Derived Ordered Mesoporous Carbon Cathode for Zn-Ion Hybrid Supercapacitor with Remarkable Energy Density

Zn-ion hybrid supercapacitors (ZHSCs) have been considered as a promising candidate for energy storage systems because of the merits they inherited from both supercapacitors and rechargeable batteries. Herein, we show the eco-friendly modified solvent evaporation-induced self-assembly (EISA) synthesis of newly engineered plant polyphenol tannin-derived ordered mesoporous carbons (TOMCs) and employ them as cathode material for high-performance ZHSCs to promote the diffusion dynamics of Zn2+ ions for the first time. The optimized TOMC-700 possesses a high Brunauer–Emmett–Teller (BET) surface area of 967 m2 g–1, narrow mesopores centered at ∼3.5 nm, and rich heteroatoms. Profiting from the synergy of enhanced kinetics and electroactivity, the aqueous TOMC-700-based ZHSC exhibits intriguing Zn-storage capabilities, including a superior energy density of 148.9 Wh kg–1 at 180 W kg–1 in a broad potential range of 0–1.8 V and long-term cycling stability. Moreover, the quasi-solid TOMC-700-based ZHSC also delivers an outstanding energy density of 121.3 Wh kg–1 at 180 W kg–1. These results highlight the facile fabrication of a natural carbohydrate-derived ordered mesoporous carbon as cathode material, notably boosting the development of Zn-based hybrid energy storage systems.

Synthesis of wrinkle silica nanospheres by solvent evaporation-induced self-assembly method for hydrogenation reaction

Wrinkle silica nanoparticles (WSNs) possess the typical characteristics in their short diffusion path and central-radial pore structure, which are favorable to use in a wide range of practical application. In this research, a solvent evaporation-induced self-assembly strategy was adopted for the preparation of WSN materials to give an insight into the formation mechanism of the WSNs. Through one-step temperature-controlled method, it was found that the WSNs could be successfully synthesized under the temperature of 60 °C, while the pore sizes and particle sizes were both gradually decreased as the synthesis temperature continued to increase. Comparably, a two-step temperature-controlled method was employed through modulating the stirring time length in order to synthesize silica nanospheres with large pore size and small particle size. The results showed that Ni2P/WSNs-8+16 catalyst performed the highest naphthalene hydrogenation activity (almost 100% conversion at 300 °C) when the stirring time in the first stage and the second stage was 8 h and 16 h, respectively.

Encapsulated boron-based energetic spherical composites with improved reaction efficiency and combustion performance

The low energy release efficiency seriously hinders the application of Boron (B) powder as metal fuel in solid propellants. To overcome this issue, a series of B-based spherical composites were produced by encapsulating B-based metastable intermixed composites (MICs) with ammonium perchlorate (AP) by a solvent evaporation-induced self-assembly (EISA) method in this work. A self-developed combustion system containing an ignition pool, indicator light, and high-speed camera to precisely monitor ignition delay and burning times was utilized. The EISA-prepared B/Bi2O3/AP spherical composites showed higher combustion temperature (1435 °C) and shorter ignition delay time (379 ± 25 ms) than the physically mixed sample (1264 °C and 1035 ± 63 ms). The isolated reaction units of spherical B/Bi2O3/AP composite accelerated heat transfer and accumulation and reduced sintering and agglomeration, thus promoting the combustion efficiency of B powder. This study presents a promising strategy by doping and encapsulating process to increase the combustion performance of B-based metal fuel.

Strong Bacterial Cellulose-Based Films with Natural Laminar Alignment for Highly Sensitive Humidity Sensors.

Humidity sensors have been widely used for humidity monitoring in industry and agriculture fields. However, the rigid structure, nondegradability, and large dimension of traditional humidity sensors significantly restrict their applications in wearable fields. In this study, a flexible, strong, and eco-friendly bacterial cellulose-based humidity sensor (BPS) was fabricated using a two-step method, involving solvent evaporation-induced self-assembly and electrolyte permeation. Rapid evaporation of organic solvent induces the formation of nanopores of the bacterial cellulose (BC) surface and promotes structural densification. Furthermore, the successful embedding of potassium hydroxide into the sophisticated network of BC effectively enhanced the sensing performance of BPS. The BPS exhibits an excellent humidity sensing response of more than 103 within the relative humidity ranging from 36.4 to 93% and strong (66.4 MPa) and high flexibility properties owing to the ultrafine fiber network and abundant hydrophilic functional groups of BC. Besides being strong and thin, BPS is also highly flexible, biodegradable, and humidity-sensitive, making it a potential candidate in wearable electronics, human health monitoring, and noncontact switching.

High-index planes T-Nb2O5 using self-assembly strategy for aerobic oxidative desulfurization in fuels

High-index planes viewed as reactive facets are possessed of the high-density, low-coordination atoms, which are distributed at catalytic sites with high activity, such as steps, edges and kink sites. Herein, the orthorhombic niobium pentoxide (T-Nb2O5) is synthesized, with the elevated ratio of high-index planes, first for aerobic oxidative desulfurization (ODS) of the refractory aromatic sulfides. Through a solvent evaporation-induced self-assembly strategy, mesoporous structure Nb2O5 with three different crystal phases, amorphous, pseudo-hexagonal and orthorhombic, are prepared using the calcination method. The proportion of high-index facets increases, as raising the calcination temperature, which contributes to the faster production of the superoxide free radical (•O2–) intermediate using molecular oxygen as the green oxidant. Under optimal conditions, a 100% sulfur removal rate is obtained using 650 °C-T-Nb2O5 within 7 h, showing its excellent catalytic performance. The cycle experiments confirm the stability of the prepared 650 °C-T-Nb2O5 after 8 times regeneration process, showing a promising prospect of NbOx-based materials for ODS under mild conditions.

A Gold Nanocluster Constructed Mixed-Metal Metal-Organic Network Film for Combating Implant-Associated Infections.

The development of modular strategies for programming self-assembled supramolecular architectures with distinct structural and functional features is of immense scientific interest. We reported on the intrinsic antibacterial capability of anionic amphiphilic gold nanoclusters (GNCs) capped by para-mercaptobenzoic acid, which was closely related to the protonation level of terminal carboxylate groups. By using of the metal-ligand coordination-driven and solvent evaporation-induced self-assembly, we constructed GNCs-based mixed-metal metal-organic network (MM-MON) films on titanium disks as antibacterial nanocoatings. Taking the reasonable utilization of tetravalent metal ions M4+ (Ti, Zr, Hf; hard Lewis acid) and bactericidal divalent metal ions M2+ (Cu, Zn; borderline acid) co-incorporated metal-carboxylate coordination bonds, the MM-MON films exhibited superior stability due to the robust M4+-O bonds and M2+ releasing behavior resulting from the labile M2+-O coordinating. Together, the MM-MON films integrated the bacteria-responsive character of GNCs, exceptional chemical stability, and greatly enhanced antibacterial activity, ultimately killing adherent bacteria and initiating a self-defensive function. In a rat model for subcutaneous implant-associated infection, the MM-MON nanocoating showed an approximately 2 and 1 log lower multidrug-resistant Staphylococcus aureus implant and tissue colonization, respectively. The generalizable modular strategy of the GNC-metal networks is amenable to facilitate the functionalization of metal surfaces for combating implant-associated infections.

Ordered Bicontinuous Mesoporous Polymeric Semiconductor Photocatalyst.

Owning triply periodic minimal surfaces and three-dimensional (3D) interconnected pores, bicontinuous porous materials have drawn enormous attention due to their great academic interest and potential applications in many fields including energy and catalysis. However, their synthesis has remained a great challenge. Here, we demonstrate the synthesis of a bicontinuous porous organic semiconductor photocatalyst, which involves the preparation of SiO2 with a shifted double diamond (DD) structure through solvent evaporation-induced self-assembly of a polystyrene-block-poly(ethylene oxide) diblock copolymer and tetraethyl orthosilicate, followed by SiO2-templated self-condensation of melamine monomers in a vacuum. Strikingly, the resultant DD-structured graphitic carbon nitride (g-CN) possesses two sets of 3D continuous mesopores with a mean diameter of 14 nm, which afford a high specific surface area of 131 m2 g-1 and an optical band gap of 2.8 eV. Being a visible-light-driven photocatalyst, the bicontinuous mesoporous g-CN exhibits high catalytic activity for water splitting to generate H2 (6831 μmol g-1 h-1) with excellent cycling stability. This study provides a protocol for the construction of ordered mesoporous materials containing 3D continuous channels, which holds promise for catalysis applications.

Micro-scale 2D quasi-nanosheets formed by 0D nanocrystals: from single to multicomponent building blocks

Self-assembly of colloidal nanocrystals (NCs) into large-scale superlattices with complex and controllable structures has attracted extensive attention due to their collective properties and promising device applications. Plasmonic NCs are very popular for long-range ordered superstructures by virtue of their collective nanogaps for electromagnetic field enhancement, in particular bulk-scale single-layer assembly. Large-area two-dimensional (2D) quasinanosheets (QNSs) composed of mono-component Au NCs or multi-component Au@ZnS core-shell hetero-nanocrystals (HNCs) were successfully prepared, via careful solvent evaporation-induced interfacial self-assembly. The entire self-assembly process was carried out on the liquid-air surface and mediated simply by tuning the operating temperatures and concentrations of the NCs. Specifically, monolayer and double-layer 2D QNSs in tens of micrometers scale with different stacking models were fabricated by precisely controlling the solvent evaporation rate and colloidal concentration.

Chemically Tailored Multifunctional Asymmetric Isoporous Triblock Terpolymer Membranes for Selective Transport.

Membrane-based separation of organic molecules with 1-2 nm lateral dimensions is a demanding but rather underdeveloped technology. The major challenge is to fabricate membranes having distinct nanochannels with desired functionality. Here, a bottom-up strategy to produce such a membrane using a tailor-made triblock terpolymer featuring miscible end blocks with two different functional groups is demonstrated. A scalable multifunctional integral asymmetric isoporous membrane is fabricated by the solvent evaporation-induced self-assembly of the block copolymer combined with nonsolvent-induced phase separation. The membrane nanopores are readily functionalized using positively and negatively charged moieties by two straightforward gas-solid reactions. The pores of the post-functionalized membranes act as target-specific functional soft nanochannels due to swelling of the polyelectrolyte blocks in a hydrated state. The membranes show unprecedented separation selectivity of small molecules based on size and/or charge which demonstrates the potential of the proposed strategy to prepare next-generation nanofiltration membranes.

Janus Mesostructures for Simultaneous Multivariable Gases Sensors

Conventional mesoporous materials-based transducers generally possess symmetrical geometries and are unable to easily distinguish two or more components in mixtures and reject the interferences. In this issue, Zhao et al. develop Janus mesostructures to realize a simultaneous multivariable gases sensor using solvent evaporation-induced self-assembly (EISA) with subsequent surface modifications.

Janus Mesoporous Sensor Devices for Simultaneous Multivariable Gases Detection

Summary Single-gas-phase chemical detections have recently attracted much attention in diverse fields; however, the pathways of composite sensing systems for detection of multiple gases could provoke better substantial potentials, which have not been fully explored due to the deficiency of feasible integrated sensing platforms. Here, we demonstrate a Janus mesoporous sensor device based on multi-response mechanisms, which can simultaneously detect multiple gases. The sensor devices based on Janus mesoporous carbon/silica films with asymmetric mesostructures and disparate active sites (–NH2 and –COOH groups) can be prepared via a solvent evaporation-induced self-assembly and selective functionalization strategy. Such Janus devices have exhibited distinct ultrafast response time under ultralow limit of detection and great selectivity and stability for NH3 and H2S sensing, and each gas concentration can be quantified individually. Theoretical calculation reveals that the distinction of response time is ascribed to the interaction difference to target gases, allowing for distinguished multiple signals.

Facile synthesis of mesoporous WO3@graphene aerogel nanocomposites for low-temperature acetone sensing

Nanocomposites constructed by combining mesoporous metal oxides and graphene have received tremendous attention in wide fields of catalysis, energy storage and conversion, gas sensing and so on. Herein, we present a facile interface-induced co-assembly process to synthesize the mesoporous WO3@graphene aerogel nanocomposites (denoted as mWO3@GA), in which graphene aerogel (GA) was used as a macroporous substrate, mesoporous WO3 was uniformly coated on both sides of graphene sheets through a solvent evaporation-induced self-assembly (EISA) strategy using diblock copolymer poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a template. The resultant mWO3@GA nanocomposites possess well-interconnected macroporous graphene networks covered by mesoporous WO3 layer with a uniform pore size of 19 nm, high surface area of 167 m2/g and large pore volume of 0.26 cm3/g. The gas sensing performance of mWO3@GA nanocomposites toward acetone and other gases was studied, showing a high selectivity and great response to acetone at low temperature of 150 °C, which could be developed as a promising candidate as novel sensors for VOCs detection.

Photostable Iridium(III)-Cyanine Complex Nanoparticles for Photoacoustic Imaging Guided Near-Infrared Photodynamic Therapy in Vivo.

The iridium(III)-cyanine complex (IrCy) was fabricated by conjugating an iridium(III) complex to a cyanine dye with an intense near-infrared (NIR) absorption. IrCy complex nanoparticles (NPs) with high water solubility and photostability were prepared by a solvent evaporation-induced self-assembly strategy. Considering their effective photacoustic (PA) imaging and generation of 1O2 property with 808 nm laser irradiation in aqueous solution, PA imaging guided NIR-driven photodynamic therapy in vivo was effectively conducted in the 4T1 xenograft model. We developed a real-time PA imaging methodology to investigate the pharmacokinetics, tumor targeting, and biodistribution of IrCy NPs. Taking advantage of the analysis of the PA signal of the common iliac vein, the blood circulation half-life of IrCy NPs in mice was calculated to be ∼18 h, and the enhanced permeability and retention effect of IrCy NPs offered the maximum targeting property in the tumor at about 24 h. The obvious change of PA imaging signal in kidney and bladder confirmed IrCy NPs should be excreted partially from the urine system, and the PA signal decreased from 12.5× to 2.8× in the liver, and from 28.8× to 9.4× in the spleen also confirmed the hepatic metabolic pathway.