However, dislocations, disinclinations, and symmetry-breaking instabilities can frequently prompt the formations of defects and grain boundaries in the synthesis processes [15,16] and crystal growth rate of the 2D nanostructure is very slow. [17,18] In nature system, organic-inorganic hybrid nanostructures with high-crystallinity and diverse morphologies can be constructed by biomineralization process. [19,20] This natural process can efficiently induce the molecular rearrangement for high complexity [21] and many functionalities. [22,23] Therefore, these unique biological phenomena have been applied in synthesis method to control the crystallinity and morphology of 2D nanostructures with superior material properties. Here, we show a solution-based ultrafast 2D growth method for large-scale and high-quality silver nanosheets on air/gel interface. The biological hydrogel polymer forms a multilayered structure by a solvent-induced phase separation process at air/gel interface with trapped silver (Ag) salts between the layers. [24] Furthermore, the trapped Ag salts between each biological hydrogel layers can efficiently reduce into large-scale 2D Ag nanosheets during the annealing process.The mixture of the Ag salts and hydrogel solution is a transparent, light yellow color at room temperature with reduced viscosity as compared with pure gelatin solution (Figure S1a, Supporting Information), while its nominal phase-change temperature is 154 °C based on the thermal gravimetric analysis (TGA) analysis results ( Figure S1b, Supporting Information). The viscosity of the hydrogel mixture decreases further at above 40 °C as the hydrogen bond in the triple-helix gelatin chain [25] degrades by the intercalation of Ag ions between various functional side chains (e.g., amine, carboxyl, hydroxyl, and thiolate groups). [26] Adding methyl alcohol and Ag salts in the solution can partially neutralize and condense the hydrogel polymer chains [24,27] to form large and continuous multilayer membranes via the salting-out effect ( Figure S2, Supporting Information). Conceptually, Ag ions are coordinated on the randomly coiled gelatin chains, which are rapidly accumulated under elevated temperature to form a multi layered structure (Figure 1a). [28] The neutralization and condensation process occurs, and the Ag ions are trapped between the layers of the hydrogel scaffold (Figure 1b). A reducing agent, dopamine, is used to promote the conversion of Ag ions to atoms while large, multilayered gelatin scaffolds constrain the crystallization process laterally to increase the The growth of large and high-quality 2D nanomaterials is challenging due to the formation of defects from dislocations, disinclinations, and symmetrybreaking instabilities. In this study it is demonstrated that biological template can be utilized to align the molecular orientation for large grain size in the synthesis of the high-quality 2D silver nanostructure. The solvent assisted multilayering phenomenon of hydrogel forms biological template at the air/ gel interface...

No abstract

No abstract

No abstract

Although self-assembly of various peptides has been widely applied, it is challenging to obtain single-crystalline and layer-by-layered nanostructures in a two-dimensional system. Here, we report a method for controlling the morphology and crystal growth at room temperature by a redox-active peptide template that can specifically co-assemble with metal ions. During the crystal growth, a silver ioncoordinated α-helical peptide (+3HN-YYACAYY-COO-) induces long-range atomic ordering at the air/water interface, which leads to multilayered single-crystalline silver nanosheets without an additional annealing process. Furthermore, this peptide template can facilitate efficient electron transfer between the independent metal nanosheets to improve electrochemical properties. We expect that this peptide templatebased single-crystal growth method can be extended to synthesize other materials.

A novel thin-film coating technique using a gelatin-based GDC precursor solution was developed for dense and smooth 2D layers achieving excellent chemical stability.

A coffee-ring pattern can be yielded on the three-phase contact line following evaporation of sessile droplets with suspended insoluble solutes, such as particles, DNA molecules, and mammalian cells. The formation of such coffee-ring, together with their suppression has been applied in printing and coating technologies. We present here an experimental study on the assembly of silver nanowires inside an evaporating droplet of a colloidal suspension. The effects of nanowire length and concentration on coffee-ring formation of the colloidal suspension were investigated. Several sizes of NWs with an aspect ratio between 50 and 1000 were systematically investigated to fabricate coffee-ring patterns. Larger droplets containing shorter nanowires formed clearer ring deposits after evaporation. An order-to-disorder transition of the nanowires’ alignment was found inside the rings. A printing technique with the evaporation process enabled fabrication of arrays of silver nanowire rings. We could manipulate the patterns silver nanowire rings, which might be applied to the transparent and flexible electrode.

and its change of properties by various experimental conditions are essential to explain the assembly process.Nanoparticles assembly process and behaviors inside the drying droplet were highly affected by the role of internal flow. Deegan et al. reported the coffeering effect that particles assembled by capillary and Marangoni flow inside the drying droplet. [13] Self-assembled structures like the coffee-ring structure using evaporation could be applied to various research and industrial areas, such as transparent electrodes [14,15] and printing technologies. [16] To control the particles, it is an important issue that understand and physics of Marangoni flow. Therefore, there were different parametric researches to control the Marangoni flow with controlling temperature, [16,17] droplet size, [18] particle size, [19] and shape. [20] These internal flows did not only make the internal assemblies but also make the interfacial assemblies of particles. Im et al. have reported the self-ordered structure of nanoparticles was made from the strong convective flow. [21] Film assembly at the interface was highly affected by internal flow and its characteristics. However, there were more studies needed to apply to functional materials and polymer films assembly.In this research, we investigated the hydrogel assembly to interface film affect by internal flow change with evaporation temperature using a gelatin solution. Changing the evaporation temperature, the morphology of assembled final hydrogel films after droplet evaporation was measured using a profiler and scanning electron microscopy (SEM). Also, its mechanical properties were measured using nanoindenter. From the increasing internal flow, film assembly was enhanced and morphology changed. And film hardness was increased with faster evaporation. We analyze its change in characteristic and visualization of its nanostructures. Results and Discussion Film Morphology Change with Evaporation TemperatureTo evaluate the hydrogel film assembly changing with evaporation temperature, we observed the final film morphology with the temperature change. Figure 1a shows the final film Recently, thin-film assembly at the liquid-air interface has been widely studied. These film scaffolds have high potential to control the crystallization process and fabricate single crystals. However, there have been limitations in understanding and controlling the behavior of polymer chains form into films. This study investigates thin-film assembly at the hydrogel droplet interface with internal flow and its role. During the hydrogel film formation, the internal flow of the droplet is visualized using micro-particle image velocimetry technique at various temperatures. From the droplet evaporation, convection flow induced by heat cause buoyancy effect and pressure on the interface film from evaporation flux affect the film morphology and its mechanical characteristics. Therefore, more dense assembled film is generated on the droplet interface. It is expected that the investigations could give bette...