Evaporation-induced Self-assembly Research Articles

Multilayered structural design of flexible films for smart thermal management

Intelligent materials have the ability to sense the environment and respond to their surrounding accordingly. Herein, the thermally conductive hybrid films were intellectualized by using activated shape memory composite as matrix, which endows hybrid films with active heat dissipation behavior. The obtained hybrid films not only visualize the temperature of the device by the change of shape, but also further improve thermal management abilities through the increase of contact area of the films with air in the shape changing process. The hybrid films also show high thermal conductivity because the multilayered structure was designed and constructed through the method of evaporation-induced self-assembly followed by hot-pressing technology. With the same content of graphene nanosheets, thermal conductivities of hybrid films are increased with the increase of layers. Five layered hybrid film shows the highest thermal management abilities and achieves the thermal conductivity as high as 19.37 W·m−1·K−1, which is 79.4% higher than single layered hybrid film. The structure design of hybrid films and their intellectualization opens up a new direction to improve thermal management effect of soft polymeric materials.

Assembly of Cellulose Nanocrystal-Lysozyme Composite Films with Varied Lysozyme Morphology.

In modern society, there is a constant need for developing reliable, sustainable, and cost-effective antibacterial materials. Here, we investigate the preparation of cellulose nanocrystal (CNC)-lysozyme composite films via the well-established method of evaporation-induced self-assembly. We consider the effects of lysozyme concentration and aggregation state (native lysozyme, lysozyme amyloid fibers, and sonicated lysozyme amyloid fibers) on suspension aggregation and film-forming ability. Although at higher lysozyme loading levels (ca. 10 wt %), composite films lost their characteristic chiral nematic structuring, these films demonstrated improved mechanical properties and antibacterial activity with respect to CNC-only films, regardless of lysozyme aggregation state. We anticipate that the results presented herein could also contribute to the preparation of other CNC-protein-based materials, including films, hydrogels, and aerogels, with improved mechanical performance and antibacterial activity.

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.

Spray drying as an efficient route for synthesis of silica nanoparticles-sodium alginate biohybrid drug carrier of doxorubicin

Biohybrids (a combination of biological material and inorganic nanoparticles) offer a number of advantages like improved functionality over conventional materials.Thus, to understand the practical application of biohybrids as drug carriers, a biohybrid drug carrier of colloidal silica nanoparticles (NP)-sodium alginate loaded with doxorubicin (Dox-biohybrid) was synthesized by evaporation induced self-assembly (EISA) using spray drying technique. Further, the morphology, size and interactions between various components of the biohybrid were studied through SEM, DLS and FTIR techniques. The drug loading efficiency, release profile, cellular uptake and cytotoxicity of Dox-biohybrid was investigated and compared with free Dox. The drug loading efficiencies of Dox-biohybrid, Dox-silica NP and Dox-sodium alginate were 93.7 %, 96.4 % and 88.3 % respectively. In vitro release study showed a slow release of entrapped Dox from Dox-biohybrid as compared to other carriers. This release was also pH-responsive with significantly higher cumulative drug release at pH 5.5 (cancer microenvironment) in comparison to pH 7.4 (physiological conditions). The empty biohybrid carrier did not show cytotoxicity to normal mouse lymphocytes upto a concentration of 25 μg/mL which was used further. The uptake of Dox from Dox-biohybrid by A549 cells was more than 2fold as compared to uptake from free Dox. in vitro viability assay revealed that treatment of lung carcinoma A549 cells with Dox-biohybrid resulted in 50 % loss of cell viability at 500 nM, compared to only 12 % loss with free Dox. Thus, we report the synthesis of a novel biohybrid drug delivery system by means of spray drying process that has promising applications in cancer treatment.

New photoactive mesoporous Ce-modified TiO2 for simultaneous wastewater treatment and electric power generation

In the present paper is presented an efficient strategy for synthesis of mesoporous TiO2 modified with different Ce concentrations through a sol–gel process in the presence of triblock Pluronic P123 as structure directing agent, integrated with evaporation-induced self- assembly (EISA) approach. The nanocomposite consisted mostly of small crystallite of anatase. The presence of a new crystal phase corresponding to cerium titanate was evidenced in Ce-modified powder samples. All materials were characterized by SEM and TEM microscopies, UV–vis, XPS and N2 adsorption-desorption isotherms in order to examine the textural and structural characteristics and the chemical nature of their surface. Furthermore, the photoelectrochemical characterization evidenced the effect of the TiO2 mesoporous structure, the amount of cerium and the oxidation state of Ti and Ce in the new photocatalysts on the enhanced photovoltaic performance. The photocatalytic activity of the as-synthesized materials was evaluated for phenol photodegradation in aqueous media and the reactive species involved in photocatalytic process were established by using some radical scavengers in the photodegradation experiments. Based on the obtained results, these new Ce-modified mesoporous TiO2 photocatalysts could be considered for degradation of organic compounds from wastewaters by advanced oxidation processes or for photoanodes construction for efficient photoelectrochemical fuel cell (PFC) systems.

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.

Synthesis and Characterization of Hierarchical Mesoporous-Macroporous TiO2-ZrO2 Nanocomposite Scaffolds for Cancellous Bone Tissue Engineering Applications

Bone tissue engineering has been introduced several decades ago as a substitute for traditional grafting techniques to treat bone defects using engineered materials. The main goal in bone tissue engineering is to introduce materials and structures which can mimic the function of bone to restore the damaged tissue and promote cell restoration and proliferation. Titania and zirconia are well-known bioceramics which have been widely used in tissue engineering applications due to their unsurpassed characteristics. In this study, hierarchical meso/macroporous titania-zirconia (TiO2-ZrO2) nanocomposite scaffolds have been synthesized and evaluated for bone tissue engineering applications. The scaffolds were produced using the evaporation-induced self-assembly (EISA) technique along with the foamy method. To characterize the samples, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), simultaneous thermal analysis (STA), and Brunauer-Emmett-Teller (BET) analysis were performed. The results showed that TiO2-ZrO2 scaffolds can be produced after sintering the samples at 550°C for 2 h. Among samples with different weight percentages of zirconia and titania, the sample containing 13 wt.% zirconia was considered as the optimum sample due to its structural integrity. This scaffold had pore size, pore wall size, and mesopores in the range of 185±66 μm, 15±4 μm, and 7-13 nm, respectively. The specific surface area obtained from the BET theory, total volume, and mean diameter of pores of this sample was 13.627 m2g1-, 0.03788 cm3g-1, and 11 nm, respectively. The results showed that the produced scaffolds can be considered as the promising candidates for cancellous bone regeneration.

Photocatalytic degradation of antibiotic and hydrogen production using diatom-templated 3D WO3-x@mesoporous carbon nanohybrid under visible light irradiation

Synthesis of highly efficient 3D photocatalysts offers unique abilities for hydrogen production and chemical conversion to find a solution for energy shortage and environmental pollution issues. However, current strategies for production of ordered nanohybrid photocatalysts usually involve complex procedures and the use of expensive templates, which limit their practical applications. In this work, 3D WO3-x@mesoporous carbon photocatalyst was fabricated through one-pot evaporation-induced self-assembly (EISA) process using Cyclotella sp. as natural template. During heat-treatment, the precursor of carbon could partially reduce tungsten oxide under N2 atmosphere leading to the embedding of WO3-x in conductive mesoporous carbon structure. The diatom templated WO3-x@mesoporous carbon (DT-WO3-x@MC) nanohybrid exhibited high surface area (195.37 m2 g−1) and narrowed band gap (2.67 eV). Integration of tungsten oxide with mesoporous carbon and formation of oxygen vacancies enhanced the absorption of visible light using DT-WO3-x@MC and limited the recombination of electron-hole pairs. 98.7% of cefazolin (CFZ) degradation efficiency and 85.5% of total organic carbon (TOC) removal efficiency were observed within 90 and 180 min under visible light irradiation, respectively. Scavenger quenching tests and electron spin resonance (ESR) analysis demonstrated thatO2•− played a main role in photocatalysis. CFZ degradation pathway was proposed via identification of conversion intermediates using GC-MS analysis. Photocatalytic hydrogen production rates of the pure WO3 and the DT-WO3-x@MC nanohybrid were determined as 746 and 1851 μmol g−1 h−1, respectively. This study presented a way to develop a high-performance and stable photocatalyst using diatom frustules as natural template which works under practical conditions for environmental remediation and energy production.

Highly thermally conductive yet mechanically robust composites with nacre-mimetic structure prepared by evaporation-induced self-assembly approach

Highly thermally conductive and mechanically strong nanocomposites for efficient thermal management have received wide attention because of the rapid development of modern electronics. Boron nitride nanosheet (BNNS) with combined benefits of high thermal conductivity (TC) and good electrical insulation has been considered a promising filler to fabricate thermally conductive nanocomposites. Herein, inspired by biological systems, large-scale and high-performance artificial nacre-like composite composed of BNNS and oxidized cellulose nanocrystal (OCNC) is fabricated through simple evaporation-induced self-assembly (EISA) approach for the first time. Thanks to the template effect of OCNC host, BNNS and OCNC are self-assembled to form an artificial layer-by-layer nacre structure, where OCNC combined with the epoxy-based adhesive agent (AA) serves as the mortar to form a stiff and dense structure. The resulting BNNS-OCNC-AA composite at a relative low BNNS loading of 11.6 vol% exhibits a high in-plane thermal conductivity of 10.9 W/mK as well as the excellent tensile strength of 197.3 MPa, which are prominent compared to other composites fabricated via the various currently established methods under higher filler loadings (13.4 ~ 95 vol%). From the characterization results, we could attribute the multiple properties to the construction of the unique nacre-like structure and the robust interfacial interaction. The artificial nacre-like BNNS composite with excellent thermal and mechanical properties simultaneously has significant potential application for thermal management in flexible and wearable electronics fields.

Pd/Mo2N-TiO2 as efficient catalysts for promoted selective hydrogenation of 4-nitrophenol: A green bio-reducing preparation method

The addition of a suitable co-catalyst is an encouraging way to enhance the catalytic performance of Pd based catalyst with low content. Herein, we describe an easy synthesis of Mo2N-TiO2 with well-dispersed Mo2N nanoparticles through one pot evaporation-induced self-assembly and nitridation treatment method. Moreover, a green bio-reductive approach with Catalpa Fruit (CF) extract was adopted to fabricate Pd/Mo2N-TiO2 catalysts for promoting selective hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) as model reaction. Among these Pd/Mo2N-TiO2 catalysts, 0.8 wt%Pd/Mo2N-TiO2 exhibits significantly high catalytic activity for selective hydrogenation of various nitrophenols and cinnmaldehyde. Importantly, the catalytic activity of the catalyst prepared by the reduction method of the CF extract is higher than that prepared by the reduction method of NaBH4. A serials of characterization, including XRD, N2 adsorption–desorption, TEM, XPS, CO chemisorption and CO-FTIR etc., was carried out to investigate the influence of the prepared method on the surface Pd species and activity. The high performance can be attributed to the specific nanostructure characteristics of the catalyst and the good synergistic effect between Pd and Mo2N, improving the dispersion of Pd nanoparticles atoms and the exposure of more active Pd atoms (surface Pd0 species) on 0.8 wt%Pd/Mo2N-TiO2 due to the CF extract as reductant.

Mg-coordinated self-assembly of MgO-doped ordered mesoporous carbons for selective recovery of phosphorus from aqueous solutions

MgO-doped ordered mesoporous carbon (OMC-MgO) was synthesized by evaporation-induced self-assembly (EISA) in one-pot with biomass-derived gallic acid instead of phenolics as carbon precursor, metal ion Mg2+ instead of formaldehyde as cross-linking agent and F127 as template. Mg had dual roles as cross-linking agent to coordinate gallic acid-F127 micelle composites, and as promoter of active sites. With the developed protocol, MgO could be uniformly dispersed throughout the carbon skeleton during calcination at 800 °C without agglomeration. As-prepared OMC-MgO-T800 had a specific surface area of 808 m2/g, a perfectly-ordered mesoporous structure centered at (6–8) nm, and exhibited good performance for phosphorus removal from aqueous solutions with a maximum sorption capacity of 107 mg/g. Electrostatic attraction, ligand exchange, and Lewis acid-base interactions are the main phosphate adsorption mechanisms of the developed MgO-doped OMC adsorbents. The as-prepared mesoporous carbon materials are highly selective for phosphorus adsorption from aqueous streams and are reusable and recyclable. This work proposes a green protocol to synthesize OMC-metal oxide composites that is widely applicable to wastewater treatment and technological areas in catalysis and energy storage.

Using cellulose nanocrystals for graphene/hexagonal boron nitride nanosheet films towards efficient thermal management with tunable electrical conductivity

High-efficiency thermal management materials have attracted increasingly more attention in the heat dissipation of electronic chips, LED light and electro-thermal heating. Herein, we judiciously designed and synthesized thermally conductive nanocomposite films with tunable electrical conductivity, by assembly of graphene oxide (GO) and hexagonal boron nitride (h-BN) nanosheets. Specfically, the GO/BN/cellulose nanocrystal (CNC) hybrid dispersions, which were prepared by mixing and stirring GO and BN/CNC dispersions, were converted into macroscopic films through the evaporation-induced self-assembly. Cellulose nanocrystals (CNC) played a key role in the assembly process, becuase they acted as a dispersant for h-BN nanosheets and formed chiral-structured connection between h-BN and GO. The thermal and electrical performance was tuned by different ratios of reduced GO (RGO) to h-BN with an appropriate reduction procedure. When a thermally conductive yet electrically insulating BN/GO/CNC (mass ratio 76/5/19) film was reduced by hydrazine, it showed thermal conductivity of 107.6 W·m−1·K−1 and resistivity over 109 Ω·cm. On the other hand, an RGO/BN/carbonized CNC nanorods (CNR) (mass ratio 7.5/4.0/1.0) film which was annealed at 1500 °C exhibited thermal conductivity of 2037.9 W·m−1·K−1 and electrical conductivity of 1930.5 S·cm−1. These improvements were attributed to the conductive network consisting of RGO, h-BN and CNR. This research would provide a new platform for development of the next-generation thermal management materials.

Highly active and stable Ni dispersed on mesoporous CeO2-Al2O3 catalysts for production of syngas by dry reforming of methane

Ni-based mesoporous mixed CeO2-Al2O3 oxide catalysts prepared by one pot Evaporation Induced Self Assembly (EISA) were tested in dry reforming of methane. The textural, structural and physicochemical properties of the catalysts were studied by N2 adsorption-desorption, TEM-EDS, XRD and elemental analysis. The mobility of oxygen in the structure and the redox properties were investigated by OSCC measurements, TPR and in situ DRIFTS. Finally, the post-reaction samples were analyzed by TGA, RAMAN and TEM. The calcined catalysts prepared by EISA method present mesoporous structures with highly dispersed Ni in the form of NiAl2O4 spinel clusters. After reduction, small size metallic Ni particles are observed (< 5 nm). The presence of Ce in the structure interacting strongly with Al2O3 promotes the oxygen mobility and acts as sites for CO2 adsorption, increasing the activity of the catalyst and promoting the carbon removal mechanism. In absence of Ce in the mesoporous alumina support, the activity for carbon gasification is limited and C filaments accumulate inside the reactor. The same behavior occurs with CeO2-Al2O3 oxide prepared by EISA method when Ni is post-impregnated because of the presence of isolated larger Ni particles which promotes the decomposition of CH4. Therefore, Ni-based CeO2-Al2O3 catalysts prepared by one pot EISA method exhibited high activity and stability for the dry reforming of methane thanks to both properties which are the confinement of Ni particles and the inhibition of carbon deposition.

Confined evaporation-induced self-assembly of colloidal lignin particles for anisotropic adhesion

Colloidal lignin particles out of lignocellulosic biorefineries have gained interest due to their improved properties and wide application range compared to standard lignin. In this work, an application as green adhesive was investigated. Solely a suspension of aqueous colloidal lignin particles was used to achieve anisotropic adhesion between two glass slides. The self-assembly of the colloidal lignin particles into macroscopic structures during drying lead to shear strength 8-times higher the tensile strength. Predefined lignin particles are crucial for the adhesion whereas dissolved lignin leads to no practicable adhesion. The high anisotropy of the adhesion and the fact that solely pure lignin is necessary opens new application and research fields and will propagate the application of colloidal lignin particles even more.

Assessing the potential of xNi-yMg-Al2O3 catalysts prepared by EISA-one-pot synthesis towards CO2 methanation: An overall study

Mesoporous xNi-yMg-Al2O3 catalysts prepared by combined evaporation induced self-assembly (EISA) and one-pot techniques were tested in CO2 methanation reaction. All calcined/reduced materials were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 physisorption, thermogravimetric analysis (TGA), CO2 adsorption, H2 temperature programmed reduction (H2-TPR) and transmission electron microscopy (TEM). The effects of Mg and Ni loadings on the catalysts properties and performances were systematically studied. Higher Mg contents enhanced methanation performances due to more favourable metallic interactions between the Ni, Mg and Al species. In addition, higher Ni contents led to better selectivity to CH4 by enhancing methane formation that involves H2 dissociation on Ni0 sites. The mesoporous 5Ni–Al2O3 catalyst obtained by the EISA-one-pot technique was significantly more active than silica-based catalysts with same 5 wt% Ni content supported on USY zeolite and SBA-15. Moreover, the performances of the most promising 15Ni–7Mg–Al2O3 mesoporous material were similar to those of a commercial 25Ni/γ-Al2O3 catalyst in spite of its reduced nickel content.

Structure-dependence of anti-methicillin-resistant staphylococcus aureus (MRSA) activity on ZnO-containing bioglass

Drug-resistant infection control is an important concern when developing biomedical materials. In this regard, most studies have investigated the effect of metal ions incorporated in bioglass. However, the relevance of bioglass structure and antibacterial activity have received limited attention. In this study, the bioglass of mol% composition 80SiO2–15CaO–5P2O5 (80S) was synthesized by evaporation-induced self-assembly (EISA). We can suppose that the Zn substituted in the 80S glass matrix of the xZnO/80S series) would dilute the total content of Ca, thus decrease the overall antibacterial activity and mineralization of the xZnO/80Sseries. To further support our hypothesis, a series of 80S with ZnO powders (80S + xZnO) was analyzed as well. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) indicated that tetrahedral coordinated Zn2+ was dissolved in the glass as a solid solution. Moreover, in the xZnO/80S series, because of the structure of Zn2+ substituted in the glass, the amount of ZnO being released was limited and no anti-methicillin-resistant staphylococcus aureus (MRSA) activity was detected. In conclusion, this study has confirmed and integrated that the suitable application of the textural-structure properties of ZnO substituted in bioglass for the future allocate.

Effect of pore texture property of mesoporous alumina on adsorption performance of ammonia gas

We report that the adsorption of ammonia gas on the synthesized mesoporous alumina (MA) with the controlled pore texture properties were measured. The MA adsorbents with controlled pore properties were synthesized by the Evaporation Induced Self Assembly (EISA) method. It was found that the pore size, and surface area could be adjusted by changing the mole ratio of the acid to alumina precursor during the preparation procedure. When the MA materials were used as adsorbents on ammonia gas adsorption, both adsorption kinetics and capacity were highly influenced by the pore texture properties. Pseudo first order that adsorption kinetic constant and the effective diffusivities of alumina adsorbents decreased with decreasing pore size or increasing surface area, while adsorption capacities increased. In order to estimate the adsorption behavior of ammonia gas, the Langmuir, Freundlich, Sips, and Toth isotherm models were employed. Langmuir model-based calculation reveals that mesoporous alumina MA-1.1 adsorbent with a large surface area and a small pore size shows the best performance in terms of the calculated maximum adsorption capacity of ammonia (193.57 mg/g), which is almost double that of other MA adsorbents (MA-3.3, MA-4.4) and 2.89 times that of commercial γ-Al2O3.

Photodegradation Activity of Poly(ethylene oxide-b-ε-caprolactone)-Templated Mesoporous TiO₂ Coated with Au and Pt.

Mesoporous TiO₂ films are synthesized through evaporation-induced self-assembly using poly(ethylene oxide-b-ε-caprolactone) diblock copolymers as a soft-template. Using small-angle X-ray scattering and scanning electron microscopy, we investigate the effect of the TiO₂/PEO-b-PCL ratio on the resulting nanoarchitectonic structure. After sputter-coating Au and Pt layers, these Au/TiO₂ and Pt/TiO₂ nanocomposite films display drastically enhanced photodegradation of rhodamine 6G under ultraviolet irradiation, due to the metal films inhibiting the rapid recombination of photogenerated charge carriers.

Effect of Mg Contents on Catalytic Activity and Coke Formation of Mesoporous Ni/Mg-Aluminate Spinel Catalyst for Steam Methane Reforming

Ni catalysts are most suitable for a steam methane reforming (SMR) reaction considering the activity and the cost, although coke formation remains the main problem. Here, Ni-based spinel catalysts with various Mg contents were developed through the synthesis of mesoporous Mg-aluminate supports by evaporation-induced self-assembly followed by Ni loading via incipient wetness impregnation. The mesoporous Ni/Mg-aluminate spinel catalysts showed high coke resistance under accelerated reaction conditions (0.0014 gcoke/gcat·h for Ni/Mg30, 0.0050 gcoke/gcat·h for a commercial catalyst). The coke resistance of the developed catalyst showed a clear trend: the higher the Mg content, the lower the coke deposition. The Ni catalysts with the lower Mg content showed a higher surface area and smaller Ni particle size, which originated from the difference of the sintering resistance and the exsolution of Ni particles. Despite these advantageous attributes of Ni catalysts, the coke resistance was higher for the catalysts with the higher Mg content while the catalytic activity was dependent on the reaction conditions. This reveals that the enhanced basicity of the catalyst could be the major parameter for the reduction of coke deposition in the SMR reaction.

Formation of Deposition Patterns Induced by the Evaporation of the Restricted Liquid.

Evaporation-induced self-assembly of colloids or suspensions has received increasing attention. Given its critical applications in many fields of science and industry, we report deposition patterns constructed by the evaporation of the restricted aqueous suspension with polystyrene particles at different substrate temperatures and geometric container dimensions. With the temperature increases, the deposition patterns transition from honeycomb to multiring to island, which is attributed to the competition between the particle deposition rate UP and the contact line velocity UCL, and the dimension of the geometric container has an effect on the characteristics of patterns. In this paper, the formation of an ordered multiring pattern is mainly focused on as a result of UP keeping up with UCL such that the entire contact line can be pinned, that is, the periodic stick-slip motion of the contact line and the particle sedimentation. Moreover, based on the Onsager principle, we develop a theoretical model to reveal the physical mechanisms behind the multiring phenomena. The position and spacing of rings are measured, which shows that the theoretical prediction agrees well with experiments. We also find that the ring spacing decays exponentially from center to edge experimentally and theoretically. This may not only help us to understand the formation of the deposition patterns but also assist future design and control in practical applications.