Simple Route to Gradient Concentric Metal and Metal Oxide Rings

Hong, Suck Won; Giri, Supratim; Lin, Victor S.-Y.; Lin, Zhiqun

doi:10.1021/cm0618805

Cited by 42 publications

(45 citation statements)

References 23 publications

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“…The axially symmetric sphere-on-flat geometry provides a unique environment (i.e., a bound solution) for controlling the flow within an evaporating droplet, which in turn regulates the structure formation. [35][36][37][38][39][40][41] Thus, in sharp contrast to the irregular concentric rings formed due to stochastic ''stick-slip'' cycles of the contact line when a droplet evaporates from a single surface (i.e., an unbound solution), [44,45,47,48] highly ordered, gradient concentric rings of MEH-PPV are produced using the sphere-on-flat geometry.…”

Section: Resultsmentioning

confidence: 99%

“…[35][36][37][38][39][40][41][42][43] Rather than allowing the solvent to evaporate over the entire droplet area as in copious past work, in which droplets evaporated from a single surface, [44][45][46] the evaporation was restricted at the droplet edges. [35,36] Concentric rings were formed by controlled, repetitive pinning and depinning of the contact line (i.e., ''stick-slip'' motion).…”

Section: Introductionmentioning

confidence: 99%

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Directed Self‐Assembly of Gradient Concentric Carbon Nanotube Rings

Hong

Jeong

et al. 2008

Adv Funct Materials

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Hundreds of gradient concentric rings of linear conjugated polymer, (poly[2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐ phenylenevinylene], i.e., MEH‐PPV) with remarkable regularity over large areas were produced by controlled “stick‐slip” motions of the contact line in a confined geometry consisting of a sphere on a flat substrate (i.e., sphere‐on‐flat geometry). Subsequently, MEH‐PPV rings were exploited as a template to direct the formation of gradient concentric rings of multiwalled carbon nanotubes (MWNTs) with controlled density. This method is simple, cost effective, and robust, combining two consecutive self‐assembly processes, namely, evaporation‐induced self‐assembly of polymers in a sphere‐on‐flat geometry, followed by subsequent directed self‐assembly of MWNTs on the polymer‐templated surfaces.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Directed Self‐Assembly of Gradient Concentric Carbon Nanotube Rings

Hong

Jeong

et al. 2008

Adv Funct Materials

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“…20 As depicted in Figure 2c, PMMA rings were formed at the surface of Au-coated ITO. The sample was then treated with the KI/I 2 DI water solution to selectively dissolve Au between PMMA rings.…”

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confidence: 90%

Template-Assisted Formation of Gradient Concentric Gold Rings

Hong

Lin

2006

Nano Lett.

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Gradient concentric rings of polymers, including (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(methyl methacrylate) (PMMA), with unprecedented regularity were formed by repeated "stick-slip" motion of the contact line in a sphere-on-flat geometry. Subsequently, polymer rings served as templates to direct the formation of concentric Au rings. Three methods were described. The first two methods made use of either UV (i.e., on MEH-PPV) or thermal treatment (i.e., on PMMA) on Au-sputtered polymer rings, followed by ultrasonication. The last method, however, was much more simple and robust, involving selective removal of Au and polymer (i.e., PMMA) consecutively.Introduction. Two-dimensional (2D) periodic structures are attractive for a wide range of applications in optics, 1,2 optoelectronics, 3,4 photonics, 5 electronics, 6 magnetic materials, 7 and biotechnology.8 A variety of self-assembled systems have been utilized as templates to produce well-ordered 2D structures with no need of lithography, including microphaseseparated block copolymers, 7,9 hexagonally ordered arrays (i.e., breath figures) made by the condensation of micronsize water droplets on the surface of a polymer solution, 10 self-assembly of colloidal crystals, 11 and self-organized mesoporous silica. 12 Dynamic self-assembly of dispersions through irreversible solvent evaporation of a drop from a solid substrate is widely recognized as a nonlithography route for one-step creation of complex, large-scale structures. [13][14][15] The flow instabilities within the evaporating droplet, however, often result in nonequilibrium and irregular dissipative structures, 16 e.g., convection patterns, fingering instabilities, and so on. Therefore, to fully utilize evaporation as a simple tool for achieving well-ordered 2D structures, it requires delicate control over flow instabilities and evaporation process. Recently, self-organized gradient concentric ring patterns have been produced by constraining a drop of polymer solution in a restricted geometry composed of either two cylindrical mica surfaces placed at a right angle to one another or a sphere on a flat surface (i.e., two surfaces). [17][18][19] The unprecedented regularity makes these polymer rings intriguing templates for producing concentric metal rings. Here, we report on fabrications of gradient concentric gold (Au) rings with nanometers in height and microns in width, replicated from templates of polymer rings. The gradient

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“…Hence, the ability to precisely control the capillary flow and convective flux in drying‐mediated self‐assembly to create spatially well‐defined surface structures has received considerable attention. To date, a few elegant studies have demonstrated intriguing means based on the controlled evaporation in confined geometries (i.e., bound solution) to delicately tailor the evaporative self‐organization process, thereby yielding highly ordered structures 4–23. For example, by rationally designing the upper curved surface in curve‐on‐flat geometries to accommodate different shapes, a wide range of complex surface patterns with unprecedented regularity were readily produced during the course of solvent evaporation by controlled, repetitive pinning–depinning cycles of the three‐phase contact line of the droplet constrained in curve‐on‐flat geometries 24.…”

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Guided Organization of λ‐DNA into Microring Arrays from Liquid Capillary Bridges

Byun

Han

et al. 2011

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A drying droplet on a solid surface (i.e., unbound solution) often leads to the formation of irregular structures, including coffee rings, [ 1 ] fi ngering instabilities, [ 2 ] and polygonal networks, [ 3 ] owing to the capillary fl ow induced by nonuniform evaporation fl ux or temperature-gradient-induced Marangoni convection. Hence, the ability to precisely control the capillary fl ow and convective fl ux in dryingmediated self-assembly to create spatially well-defi ned surface structures has received considerable attention. To date, a few elegant studies have demonstrated intriguing means based on the controlled evaporation in confi ned geometries (i.e., bound solution) to delicately tailor the evaporative self-organization process, thereby yielding highly ordered structures. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] For example, by rationally designing the upper curved surface in curve-on-fl at geometries to accommodate different shapes, a wide range of complex surface patterns with unprecedented regularity were readily produced during the course of solvent evaporation by controlled, repetitive pinning-depinning cycles of the three-phase contact line of the droplet constrained in curve-on-fl at geometries. [ 24 ] Recently, chemically patterned surface- [25][26][27] and stamp-assisted deposition methods [28][29][30][31][32][33][34][35] have been exploited for evaporative self-assembly of nonvolatile solutes (e.g., nanoparticles and biomolecules). The use of patterned surfaces or polydimethylsiloxane (PDMS) stamps minimizes uncontrolled droplet shape and possible structural instabilities that may otherwise result in a lack of control over the local dewetting dynamics, and thus produces highly regular surface structures. In a typical capillary-force-induced micromolding process, a micropatterned PDMS mold is in contact with a lower stationary substrate where an evaporating droplet is trapped, covering the lower hydrophobic surface and fi lling up the space between adjacent PDMS patterns by either one of two capillary motions: the upward capillary rising induced by wetting between the nonpolar solvent and the hydrophobic surface of the PDMS mold, [ 36 , 37 ] or the downward capillary depression induced by dewetting between the polar solvent and the PDMS mold. [ 38 ] The former capillary motion has been extensively studied and proven to be more successful. [ 36 , 37 ] In contrast, the latter (i.e., the polar solvent/hydrophobic PDMS system, which is recognized as edge-transfer lithography [ 38 ] ) has rarely been utilized due to diffi cult control over the dewetting of the solution. The capillary action of the solution constrained in the confi ned geometry can be signifi cantly infl uenced by the shape and curvature of the molds, thereby providing new opportunities for controlling the local dewetting dynamics to form ordered structures. [ 24 ] Herein, we demonstrate a facile route to creating λ -DNA microring arrays via dewetting-induced self-assembly guided by liquid capillary m...

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Simple Route to Gradient Concentric Metal and Metal Oxide Rings

Cited by 42 publications

References 23 publications

Directed Self‐Assembly of Gradient Concentric Carbon Nanotube Rings

Directed Self‐Assembly of Gradient Concentric Carbon Nanotube Rings

Template-Assisted Formation of Gradient Concentric Gold Rings

Guided Organization of λ‐DNA into Microring Arrays from Liquid Capillary Bridges

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