Multiscale Periodic Assembly of Striped Nanocrystal ...drl.ee.ucla.edu/wp-content/uploads/2017/08/...Nanoparticle-Superlatti… · 12.01.2011 · superlattice thin ﬁlms are emerging

Published: January 12, 2011

r 2011 American Chemical Society 841 dx.doi.org/10.1021/nl104208x |Nano Lett. 2011, 11, 841–846

LETTER

pubs.acs.org/NanoLett

Multiscale Periodic Assembly of Striped Nanocrystal SuperlatticeFilms on a Liquid SurfaceAngang Dong,*,†,||,z Jun Chen,‡,z Soong Ju Oh,‡ Weon-kyu Koh,† Faxian Xiu,^ Xingchen Ye,†

Dong-Kyun Ko,‡ Kang L. Wang,^ Cherie R. Kagan,†,‡,§ and Christopher B. Murray*,†,‡

†Department of Chemistry, ‡Department ofMaterials Science and Engineering, and §Department of Electrical and Systems Engineering,University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States

)The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States^Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, California 90095,United States

bS Supporting Information

ABSTRACT: Self-assembly of nanocrystals (NCs) into periodicallyordered structures on multiple length scales and over large areas iscrucial to the manufacture of NC-based devices. Here, we report anunusual yet universal approach to rapidly assembling hierarchicallyorganized NC films that display highly periodic, tunable microscalestripe patterns over square centimeter areas while preserving the localsuperlattice structure. Our approach is based on a drying-drivendynamic assembly process occurring on a liquid surface with the stripepattern formed by a new type of contact-line instability. Periodicordering of NCs is realized on microscopic and nanoscopic scalessimultaneously without the need of any specialized equipment or the application of external fields. The striped NC superlattice filmsobtained can be readily transferred to arbitrary substrates for device fabrication. The periodic structure imparts interestingmodulation and anisotropy to the properties of such striped NC assemblies. This assembly approach is applicable to NCs with avariety of compositions, sizes, and shapes, offering a robust, inexpensive route for large-scale periodic patterning of NCs.

KEYWORDS: Self-assembly, stripe pattern, nanocrystal superlattice, contact line instability, periodic patterning

Many structural patterns in nature form spontaneously viaself-organization accompanied by energy dissipation in

nonequilibrium processes.1 The formation of patterned surfacesthrough self-assembly of molecules,2,3 polymers,4 and micro-meter-sized colloids5,6 has been intensively pursued in the pastdecade, both for fundamental scientific interest and for manytechnological applications.7-9 Recent developments in colloidalsynthesis allow the growth of metallic, semiconductor, andmagnetic nanocrystals (NCs) monodisperse in size, shape, and sur-face functionalization.10 These uniform nanoscale building blocksenable the construction of ordered NC arrays (superlattices),which exhibit many properties that differ from their dispersedconstituents or disordered counterparts.10-17 In particular, NCsuperlattice thin films are emerging as an important class ofmaterials for the fabrication of electronic and optoelectronicdevices.10,18-20 Simple methods to rapidly (<1 min) grow large-scale (∼cm2) NC superlattice films on arbitrary substratesrepresent significant advances in device fabrication.21 Anothermajor challenge is developing inexpensive, lithography-free ap-proaches to control the arrangement of NCs on multiple lengthscales.22-27 Prior studies have mainly focused on the patternformation during the drying of NC dispersions on solid sub-strates and a wealth of dissipative patterns such as fractal aggre-gates,28 rings,29 and cellular networks30 have been observed. Such

nonequilibrium drying processes have also been reported to yieldwell-aligned stripes of randomly packed NCs, providing modula-tion on the microscale without periodicity on the nanoscale.31,32

However, far fewer studies have explored the spontaneousmicro-scale pattern formation upon drying NCs on a liquid surface,33

although liquid-air interfacial assembly such as Langmuir-Blodgett (LB) techniques are widely employed to prepareordered NC monolayers.34-38

Here we present an unusual dynamic assembly process in-duced by the rapid drying of a NC dispersion in alkanes (hexaneor pentane) on the surface of an immiscible polar organic sub-phase (acetonitrile, ethylene glycol, or diethylene glycol) underambient conditions, enabling centimeter-scale, periodically stripedNC superlattice films within 15 s. This facile multiscale assemblyprocess is general for magnetic, metallic, semiconductor, anddielectric NCs and is compatible with heterogeneous integrationprocesses. Different from the traditional LB technique where theordered NC structure is formed by compression through theapplied external forces,37 both the ordered NC superlatticestructure and the periodic microscale stripe pattern form

Received: December 2, 2010Revised: January 5, 2011

842 dx.doi.org/10.1021/nl104208x |Nano Lett. 2011, 11, 841–846

Nano Letters LETTER

spontaneously in our approach without the use of any specializedequipment or the application of external forces.

Monodisperse NCs used for assembly are synthesized accord-ing to literature methods and are dissolved in hexane (or pentane)to form stable colloidal dispersions (see Methods in SupportingInformation). The assembly process observed upon drop-castinga NC dispersion on the surface of acetonitrile confined in aTeflon well (∼2 � 2 � 2 cm3) is depicted in Figure 1. An NCmonolayer forms immediately upon spreading the NC disper-sion, while the remaining dispersion flows rapidly around theperimeter where the subphase surface contacts the Teflon wall(indicated by red arrows in Figure 1ii). The complete wetting ofthe subphase perimeter by the flowing dispersion initiates NCcrystallization as hexane evaporates and a striped film grows fromthe subphase edge where the two dispersion streams converge(Figure 1iii). Once growth is triggered, the striped film keepsexpanding across the subphase as NCs continuously crystallizefrom the dispersion reservoir pinned at the perimeter. This filmgrowth is macroscopically manifested in the rapid sliding motionof the striped film on the subphase surface as it pushes the initiallyformed monolayer forward (Figure 1iii,iv). Upon reaching theopposite side of the well, the solid film front is redissolved in thedispersion reservoir. The striped film keeps growing and slidingunidirectionally until the evaporation of hexane is complete(typically <15 s) (Figure 1v). The resulting striped film can be

transferred from the subphase surface to any substrate previouslyimmersed in the subphase (Figure 1).

Striped NC superlattice films are also obtained upon thedynamic assembly of NCs on the surface of acetonitrile confinedin rectangular or circular Teflon wells or even on an acetonitriledroplet (∼2 cm in diameter) deposited on a flat Teflon plate.This latter assembly process is captured in Supporting Informa-tion Movie S1, where the solid film's unidirectional slidingmotion can be readily observed. These results indicate that thesubphase shape and curvature have no significant influence onthe dynamic assembly of NCs. The complete wetting of the sub-phase perimeter by the NC dispersion, regardless of the subphasegeometry, is however a prerequisite to induce the striped filmformation, with stripes oriented parallel to the contact line in allcases. It is noteworthy that the overall stripe orientations may bevaried by controlling the subphase geometry and/or the locationat which the drop of the NC dispersion is added (SupportingInformation Figure S1), as the striped film typically starts to growfrom the point of the Teflon well where the two dispersionstreams converge and expands toward the point at which the NCdispersion has been added, as depicted in Figure 1.

Figure 2a shows a photograph of a SiO2/Si wafer (∼1 � 1.5cm2) coated with a striped film self-assembled from 10 nmFe3O4

NCs (Figure 2b, inset). Optical microscopy reveals a pattern ofparallel stripes with exceptional regularity at micrometer scale(Figure 2b), which accounts for the strong iridescent colors(structural color) as seen in Figure 2a. The diffraction of a laserbeam (beam size = ∼1 mm2) by a striped NC film further

Figure 1. Schematic of self-assembly and transfer of striped NC films.The right column (i-v) illustrates the detailed stripe formation processfrom the top view. The first- and second-formed stripes are labeled by“1” and “2”, respectively, to show the film sliding motion (indicated byblue arrows) in (iii) and (iv). The dashed oval in (iii) shows the subphaseedge where the striped film grows.

Figure 2. (a) Photograph of a SiO2/Si wafer coated with a 10 nm Fe3O4

NC film, showing the strong iridescent colors from the supported film.(b) Optical micrograph of the supported film, showing the highlyperiodic stripe pattern persisting over a large area. Inset shows theTEM image of the 10 nm Fe3O4 NCs. (c) Diffraction of a laser beam(wavelength = 532 nm) by a striped film transferred to a glass slide.(d-g) Optical micrographs of striped films self-assembled from FePtNCs (6 nm), PbTe NCs (7 nm), NaYF4 nanorods (20 nm � 45 nm),and PbS nanocubes (10 nm), respectively. Insets show the TEM imagesof the correspondingNCs used for assembly. Arbitrary colors are appliedin optical micrographs to distinguish different NCs.


Nano Letters LETTER

confirms the periodic structure persisting over at least mm2 areas(Figure 2c). The stripe periodicity is tunable from a few micro-meters to tens of micrometers by changing the concentration ofNC dispersions. In general, the interstripe spacing becomes nar-rower as the NC concentration increases (Supporting Informa-tion Figure S2).More significantly, the stripe formation is generalin that it is independent of NC compositions, sizes, and shapes.Striped films are obtained upon the dynamic assembly of NCswith a broad range of compositions including metal oxides(10 nm Fe3O4, Figure 2b), metals (6 nm FePt, Figure 2d), andsemiconductors (7 nm PbTe, Figure 2e). Self-assembly of non-spherical NCs such as nanorods (20 nm � 45 nm NaYF4,Figure 2f) and nanocubes (10 nm PbS, Figure 2g) also leads tostriped films.

Atomic force microscopy (AFM) establishes that the stripesare of uniform height and pitch (Figure 3a-c), while scanningelectron microscopy (SEM) reveals the detailed ridge structureof the stripes (Figure 3d-f) as well as the ordered nature of theunderlying film (valley) (Figure 3g). Each ridge consists ofterraced NC superlattices, the thickness of which typically rangesbetween 2 and 10 NC layers (depending on the concentrationand volume of the NC dispersion applied), with the layer widthgradually decreasing from bottom (∼1-2μm) to top (∼100 nm),as seen in Figure 3f and illustrated in Figure 3h. The underlying

film can be adjusted frommonolayer tomultilayer also by varyingthe NC concentration (Supporting Information Figure S3). Ofparticular significance is that long-range-ordered NC superlatticestructure is preserved despite the dynamic, far-from-equilibriumassembly process, as evidenced by high-resolution SEM (HRSEM)(Figure 3g) and transmission electron microscopy (TEM) (Sup-porting Information Figure S4).

The striped film formation appears to be governed by acombination of NC self-assembly and other drying-mediatedphysical events occurring at the three-phase (air-solvent-sub-phase) contact line. A characteristic feature of the assemblyprocess is the unidirectional motion of the growing film upon thecomplete wetting of the subphase perimeter by the NC disper-sion. A detailed mechanism for this motion is yet to be deter-mined and may be rather complex, as the driving force may resultfrom the interplay of many parameters such as the surface tensionand wetting properties of two liquid layers. However, ourobservations indicate that the film motion is closely related tothe solvent evaporation rate as well as the subphase viscosity.When the Teflon well is covered with a glass slide during thesolvent evaporation, the film sliding motion is suppressed,yielding an unstriped but well crystallized NC superlattice film(Supporting Information Figure S5). This suggests that the rapidevaporation of hexane (or pentane) plays a key role in driving thedynamic assembly of NCs, which is further supported by the factthat no film motion or stripe formation are observed if higherboiling solvents such as heptane or octane are used. When asubphase of high viscosity such as ethylene glycol is used, the filmsliding rate is reduced, resulting in stripes having uniform heightbut less uniform interstripe spacing (Supporting InformationFigure S6). This result indicates that the lower viscosity ofsubphases like acetonitrile enables rapid motion of the growingfilm, which is important for the formation of highly periodicstripes. Although efforts are made to find conditions for stripeformation on an aqueous subphase, only unstriped monolayersor multilayers are obtained, consistent with earlier studies.34-36

Previous studies of drying-induced pattern formation on solidsubstrates have demonstrated that stripes can form by two distinctmechanisms of the three-phase (air-solvent-substrate) contactline: (I) the stick-slip motion, where the stripes are parallel tothe contact line,2-4,23,32 and (II) a fingering instability, where thestripes are perpendicular to the contact line.5,31 Monitoring thesubphase edge where the striped film nucleates (indicated by thedashed oval in Figure 1iii) allows us to visualize in situ patternformation by optical microscopy. Ethylene glycol is chosen as thesubphase on which the growing film slides relatively slowly,allowing better observation of the contact-line behavior, althoughthe resulting stripes are less uniform in periodicity.

As revealed by optical microscopy (Supporting InformationMovie S2), the striped film continuously grows from the NCdispersion front at the subphase edge, propagating like a waveacross the subphase, with stripes parallel to the contact line. Asnapshot of Supporting Information Movie S2 is given inFigure 4a. These findings suggest our stripe formation processis analogous to the contact-line stick-slip motion, while furtherobservation reveals that these stripes are formed by a new type ofcontact-line oscillating instability that has not been observedpreviously. Figure 4b schematically illustrates the pattern forma-tion mechanism that is proposed based on the observation of thecontact-line motion. We surmise that, as the film is sliding on thesubphase, the film or the accompanied subphase flow stretchesthe NC dispersion front (meniscus) until a critical contact angle

Figure 3. (a) AFM height image of a striped film consisting of 10 nmFe3O4 NCs (scan size = 45� 45 μm2). (b) Height analysis of the profileas indicated in (a). (c) Three dimensional AFM image of the film. (d,e)SEM images of a striped Fe3O4 NC film at low and high magnifications,respectively. (f) HRSEM image of a single ridge as indicated in (e). (g)HRSEM image of the underlying film as indicated in (e). (h) Schematicof the striped NC superlattice film.


Nano Letters LETTER

is reached. This leads to the pinning of the contact line for a finiteperiod of time (on the order of milliseconds estimated fromSupporting Information Movie S2) (Figure 4bii). The greatersolvent evaporation rate near the dispersion front drives NCs topile up at the pinned contact line.4,7,32 The subsequent nuclea-tion of NCs as a ridge relaxes the pinning force, enabling thecontact line to recede, depositing a smooth layer of NCs until thenext pinning event (Figure 4biii). Because of the continuous filmmotion as well as the steady NC supply from the dispersionreservoir, the contact line keeps moving back and forth (oscillat-ing) at the subphase edge, resulting in a periodically striped filmthat is seen to be continuously extruded from the dispersionfront. This type of contact-line instability is distinct from theconventional stick-slip process on a solid surface where thecontact line keeps receding during the drying process.4,32 Inter-estingly, another type of fingerlike stripes, which are perpendi-cular to the stripes as described above, can also be observed insome cases, especially when the NC concentration is high(Supporting Information Figure S7). This type of pattern resultsfrom a fingering instability, induced by convective flow in the NCdispersion.5,31 The simultaneous occurrence of these two in-stabilities produces ladderlike patterns (Supporting InformationFigure S7c).4

The periodic structure is found to impart property modulationto NC films, which will expand the NC applicability in solid statedevices. To demonstrate this, we incorporate striped PbSe NCfilms onto quartz substrates prepatterned with Au electrodes and

measure the spatially resolved photoconductivity (see Methodsin Supporting Information). The film is treated with hydrazine toenhance the conductivity.18 Despite some aggregates arisingfrom hydrazine treatment, the stripe pattern is preserved asrevealed by optical microscopy (Figure 4c, top). An oscillatorybehavior in photocurrent is observed as the film is scanned underthe laser excitation (Figure 4c, bottom), which correlates wellwith the stripe's periodic structure. The 2D photocurrent map-ping over a large area (20 � 20 μm2) provides a detailed exami-nation of the spatially resolved photoconductivity (SupportingInformation Figure S8), confirming the higher photoconductiv-ity exhibited by the ridges. We note these ridged thin films areideal architectures for photovoltaic applications, as corrugatedstructures have been reported to significantly enhance deviceperformance due to the high interfacial area between the donorand acceptor components.39,40 In addition to the modulated pro-perties, such striped NC films also display interesting in-planeanisotropic properties. The electrical transport measurementsshow the conductivity along the stripe direction is 20 times largerthan that in the direction perpendicular to stripes (Figure 4d).Furthermore, cracks are found to propagate preferentially alongthe ridges in fractured NC films (Supporting InformationFigure S9), suggesting anisotropy in mechanical properties.

The facile transfer of the liquid-supported films also allows thecreation of complex, higher-order architectures, as those shownin Figure 5 where bilayer films with tunable stripe orientations areproduced by sequential transfer of striped NC films (Figure 5a,b).Interesting Moir�e patterns arise when the NC superlattices oftwo layers are intentionally misoriented with respect to eachother.41 The pattern symmetry is tunable by changing the mis-orientation angle (Supporting Information Figure S10). In par-ticular, 12-fold quasicrystalline-like symmetry develops when theangle is close to 30� (Figure 5c).41 Furthermore, bilayer films

Figure 4. (a) Snapshot of Supporting Information Movie S2. The redarrow indicates the film sliding direction. (b) Proposed mechanism forpattern formation, showing that the contact-line oscillatory motion atthe subphase edge induces the stripe formation. The first- and second-formed stripes are labeled by “1” and “2”, respectively, to show the filmsliding motion. (c) Spatially resolved photoconductivity measurementof a striped film self-assembled from 7 nm PbSe NCs, showing theoscillatory photocurrent (bottom) which correlates with the film's periodicstructure (top). The dark current is nearly constant (∼1.6 μA). Theyellow arrow indicates the laser scanning direction. (d) Current-vol-tage (I-V) characterization of a 6 nm FePt NC film in parallel orperpendicular directions with respect to stripes, showing anisotropy inelectrical transport.

Figure 5. (a,b) Optical micrographs of bilayer films with meshlikestructures, which are formed by sequential transfer of striped NC (6 nmFePt) films to SiO2/Si wafers. Insets show the corresponding SEMimages. (c) TEM image of the 12-fold quasicrystalline-likeMoir�e patternthat develops upon stacking two layers of 15 nmFe3O4NCs. Inset showsthe small-angle electron diffraction pattern. (d) TEM image of a bilayerfilm consisting one layer of 10 nm Fe3O4 NCs and one layer of 6 nmFePt NCs. Inset shows the magnified view.


Nano Letters LETTER

with different NC compositions are also accessible by sequentialfilm transfer (Figure 5d), providing a simple, efficient way tofabricate multilayer NC superlattice films with arbitrary consti-tuents. Future work can certainly benefit from the ability to formand transfer large-area NC superlattice films.42

In summary, our studies have established a robust approachthat harnesses contact-line oscillatory instabilities to direct rapidassembly of NCs into large-area, periodically striped NC super-lattice films. This far-from-equilibrium assembly process dependslargely on the solvent evaporation rate and on the subphaseviscosity, rather than on the NC composition, size, and shape.Therefore, it is applicable to a variety of colloidal NCs andmay beextendable to other systems such as micrometer-sized colloidsand polymers. The ability to transfer the striped NC superlatticefilms enables the fabrication of devices as well as the rationaldesign of complicated architectures. NC device applications havebeen growing rapidly in recent years and the push to integrateNC films to solid state devices will be accelerated dramatically bythe ability to induce order on both microscopic and nanoscopicscales and the opportunity to harness the intrinsic anisotropies insuch periodically modulated NC assemblies.

’ASSOCIATED CONTENT

bS Supporting Information. Experimental details, additionaloptical, TEM and SEM images, and real-timemovies showing thedynamic assembly of striped NC films and the stripe formationprocess. This material is available free of charge via the Internet athttp://pubs.acs.org.

’AUTHOR INFORMATION

Corresponding Author*E-mail: (A.D.) [email protected]; (C.B.M.) [email protected].

Author ContributionszThese authors contributed equally to this work.

’ACKNOWLEDGMENT

We thank D. Lee for useful discussions. A.D., J.C., F.X., and K.L.W. acknowledge the financial support from the U.S. ArmyResearch Office (ARO) under Award No.MURIW911NF-08-1-0364. This work was partially performed at the MolecularFoundry, Lawrence Berkeley National Laboratory and wassupported by the Office of Science, Office of Basic EnergySciences, Scientific User Facilities Division, of the U.S. Depart-ment of Energy under Contract No. DE-AC02-05CH11231. D.K.K. is grateful for support from the NSF MRSEC programunder award number DMR-0520020. S.J.O., C.R.K., X.Y., and C.B.M. acknowledge support from the U.S. Department of Energy,Office of Basic Energy Sciences, Division of Materials Sciencesand Engineering under Award No. DE-SC0002158.

’REFERENCES

(1) Ball, P. The Self-Made Tapestry:Pattern Formation in Nature;Oxford University Press: New York, 1999.(2) van Hameren, R.; Schon, P.; vanBuul, A. M.; Hoogboom, J.;

Lazarenko, S. V.; Gerritsen, J. W.; Engelkamp, H.; Christianen, P. C. M.;Heus, H. A.; Maan, J. C.; Rasing, T.; Speller, S.; Rowan, A. E.; Elemans, J.A. A. W.; Nolte, R. J. M. Science 2006, 314, 1433–1436.(3) Gleiche, M.; Chi, L. F.; Fuchs, H. Nature 2000, 403, 173–175.

(4) Yabu, H.; Shimomura, M. Adv. Funct. Mater. 2005, 15, 575–581.(5) Cai, Y.; Newby, B.M. Z. J. Am. Chem. Soc. 2008, 130, 6076–6077.(6) Velikov, K. P.; Christova, C. G.; Dullens, R. P. A.; van Blaaderen,

A. Science 2002, 296, 106–109.(7) Deegan, R. D.; Bakajin, O.; Dupont, T. F.; Huber, G.; Nagel,

S. R.; Witten, T. A. Nature 1997, 389, 827–829.(8) Kumar, A.; Biebuyck, H. A.; Whitesides, G. M. Langmuir 1994,

10, 1498–1511.(9) Vossen, D. L. J.; Fific, D.; Penninkhof, J.; van Dillen, T.; Polman,

A.; van Blaaderen, A. Nano Lett. 2005, 5, 1175–1179.(10) Talapin, D. V.; Lee, J. S.; Kovalenko, M. V.; Shevchenko, E. V.

Chem. Rev. 2010, 110, 389–458.(11) Korgel, B. A.; Fullam, S.; Connolly, S.; Fitzmaurice, D. J. Phys.

Chem. B 1998, 102, 8379–8388.(12) Lin, X. M.; Jaeger, H. M.; Sorensen, C. M.; Klabunde, K. J.

J. Phys. Chem. B 2001, 105, 3353–3357.(13) Bodnarchuk, M. I.; Kovalenko, M. V.; Pichler, S.; Fritz-Popovs-

ki, G.; Hesser, G.; Heiss, W. ACS Nano 2009, 4, 423–431.(14) Dong, A.; Chen, J.; Vora, P. M.; Kikkawa, J. M.; Murray, C. B.

Nature 2010, 466, 474–477.(15) Zhuang, J.; Wu, H.; Yang, Y.; Cao, Y. C. J. Am. Chem. Soc. 2007,

129, 14166–14167.(16) Noh, H.; Choi, C.; Hung, A. M.; Jin, S.; Cha, J. N. ACS Nano

2010, 4, 5076–5080.(17) Zhang, J.; Kumbhar, A.; He, J. B.; Das, N. C.; Yang, K. K.;Wang,

J. Q.; Wang, H.; Stokes, K. L.; Fang, J. Y. J. Am. Chem. Soc. 2008, 130,15203–15209.

(18) Talapin, D. V.; Murray, C. B. Science 2005, 310, 86–89.(19) Luther, J. M.; Law, M.; Song, Q.; Perkins, C. L.; Beard, M. C.;

Nozik, A. J. ACS Nano 2008, 2, 271–280.(20) Luther, J. M.; Law, M.; Song, Q.; Reese, M. O.; Beard, M. C.;

Ellingson, R. C.; Nozik, A. J. Nano Lett 2008, 8, 3488–3492.(21) Talapin, D. V. ACS Nano 2008, 2, 1097–1100.(22) Cheng, W.; Park, N.; Walter, M. T.; Hartman, M. R.; Luo, D.

Nat. Nanotechnol. 2008, 3, 682–690.(23) Huang, J.; Tao, A. R.; Connor, S.; He, R.; Yang, P. Nano Lett.

2006, 6, 524–529.(24) Hung, A. M.; Micheel, C. M.; Bozano, L. D.; Osterbur, L. W.;

Wallraff, G. M.; Cha, J. N. Nat. Nanotechnol. 2010, 5, 121–126.(25) Tang, Z.; Zhang, Z.; Wang, Y.; Glotzer, S. C.; Kotov, N. A.

Science 2006, 314, 274–278.(26) Rasch, M. R.; Rossinyol, E.; Hueso, J. L.; Goodfellow, B. W.;

Arbiol, J.; Korgel, B. A. Nano Lett. 2010, 10, 3733–3739.(27) Kraus, T.; Malaquin, L.; Schmid, H.; Riess, W.; Spencer, N. D.;

Wolf, H. Nat. Nanotechnol. 2007, 2, 570–576.(28) Rabani, E.; Reichman, D. R.; Geissler, P. L.; Brus, L. E. Nature

2003, 426, 271–274.(29) Ohara, P. C.; Heath, J. R.; Gelbart, W. M. Angew. Chem., Int. Ed.

1997, 36, 1078–1080.(30) Martin, C. P.; Blunt, M. O.; Moriarty, P. Nano Lett. 2004, 4,

2389–2392.(31) Huang, J.; Kim, F.; Tao, A. R.; Connor, S.; Yang, P. Nat. Mater.

2005, 4, 896–900.(32) Xu, J.; Xia, J.; Lin, Z. Angew. Chem., Int. Ed. 2007, 46, 1860–

1863.(33) Sear, R. P.; Chung, S.; Markovich, G.; Gelbart, W. M.; Heath,

J. R. Phys. Rev. E 1999, 59, R6255–R6258.(34) Santhanam, V.; Liu, J.; Agarwal, R.; Andres, R. P. Langmuir

2003, 19, 7881–7887.(35) Pang, J. B.; Xiong, S. S.; Jaeckel, F.; Sun, Z. C.; Dunphy, D.;

Brinker, C. J. J. Am. Chem. Soc. 2008, 130, 3284–3285.(36) Bigioni, T. P.; Lin, X. M.; Nguyen, T. T.; Corwin, E. I.; Witten,

T. A.; Jaeger, H. M. Nat. Mater. 2006, 5, 265–270.(37) Tao, A. R.; Huang, J. X.; Yang, P. D. Acc. Chem. Res. 2008, 41,

1662–1673.(38) Aleksandrovic, V.; Greshnykh, D.; Randjelovic, I.; Fromsdorf,

A.; Kornowski, A.; Roth, S. V.; Klinke, C.; Weller, H. ACS Nano 2008, 2,1123–1130.


Nano Letters LETTER

(39) Liedtke, A.; Lei, C.; O'Neill, M.; Dyer, P. E.; Kitney, S. P.; Kelly,S. M. ACS Nano 2010, 4, 3248–3253.(40) Chanyawadee, S.; Harley, R. T.; Henini, M.; Talapin, D. V.;

Lagoudakis, P. G. Phys. Rev. Lett. 2009, 102, No. 077402.(41) Luchnikov, V.; Kondyurin, A.; Formanek, P.; Lichte, H.;

Stamm, M. Nano Lett. 2007, 7, 3628–3632.(42) Gur, I.; Fromer, N. A.; Geier, M. L.; Alivisatos, A. P. Science

2005, 310, 462–465.

Multiscale Periodic Assembly of Striped Nanocrystal ...drl.ee.ucla.edu/wp-content/uploads/2017/08/...Nanoparticle-Superlatti… · 12.01.2011 · superlattice thin ﬁlms are emerging

Documents