Fabricating Nanostructures via Organic Molecular Templates

4 Fabricating Nanostructures via Organic Molecular Templates Yunshen Zhou and Bing Wang 4.1 Introduction In the rapid growth of nanoscience and technology, organic compounds occupy a prominent position and play comprehensive roles as stabilizers [1–5], protective masks [6], templates [7–9], surface modifiers [10], position indicators [11], functional units and building blocks [12–17], and molecular “ink” [18–21], etc. Further more, organic compounds are key components in the design and fabrication of nanomachines and nanodevices. Utilization of organic molecules has allowed prototypes of nanomachines and nanodevices, such as molecular motors [22–26], conductors [27–30], logic gates [31], memories [32], rectifiers [33–36], negative differential resistance devices [37], single electron tunneling devices [38], and gears [39–41], to be developed [42]. Using organic compounds as templates to transfer the desirable and controllable patterned structures into mechanically and chemically stable, durable, and processable nanostructures has received tremendous attention for decades [43–47]. In general, template materials require some characteristics [48]: 1. Have featured structures for the final materials 2. Be stiff and durable enough to maintain their structures during the templating processes 3. Be easily removed without disrupting the final materials, if the final materials do not require the templates Templating nanostructures includes several steps: firstly, organic templates with featured structures are fabricated by advanced techniques; secondly, the organic templates are brought into contact with precursors or preformed building units (the procedure generally occurs in solution, but can also occur in the gas phase), then the template-directed formation of nanostructures results in hybrid structural materials; finally, the organic templates may be removed if necessary by heat treatment [49], or washed with organic solvents [50] to produce the isolated structural materials. Easy removal of organic templates is one of the advantages of using organic templates instead of inorganic templates [51, 52]. Organic templates include any templates consisting of organic species [53]. Organic molecular templates, polymer templates, carbon nanotubes, and 124 Y. Zhou and B. Wang biological templates are a broad subject for discussion. Organic templates as polymer templates [54–64], carbon nanotubes [65–70], and biological templates [71–80] will not be included in this chapter. This chapter focuses on the templating of nanostructures based on organic molecular templates, which we refer to as organic templates consisting of organic molecules. According to the fabricating methods, organic molecular templates can be classified into several groups as surfactant mesophases, Langmuir–Blodgett (LB) monolayers, self-assembled monolayers (SAMs), and self-organized structures, which will be introduced in the following sections: Sect. 4.2, 0-D nanostructures; Sect. 4.3, 1-D nanostructures; Sect. 4.4, 2-D nanostructures. 4.2 0-D Nanostructures 0-D nanostructures are important for their intrinsic properties, as ideal models for fundamental researches, and as building units for fabricating more complicated nanostructures [81–85]. Particle size, composition, and configuration of nanoparticles are of significant importance for researches and applications, and are of eternal pursuit for nano scientists. However, bare metal and semiconductor nanoparticles are unstable owing to their huge surface-to-volume ratio. They intend to agglomerate in order to reduce the surface-to-volume ratio and reach an energetically stable situation. They are oxidized more easily when exposed to air, and are more reactive compared with their macro counterparts. The instability of metal and semiconductor 0-D nanostructures is a major obstacle for researches and applications. Organic molecules have been successfully applied to stabilize nanoparticles and prevent oxidation [1, 86]. Meanwhile, organic molecules also provide versatile templates for size and shape control of nanoparticles [87–91]. Coatings of organic molecules can significantly influence the properties of the nanoparticles, such as hydrophilicity, hydrophobicity, photoactive behavior, and electroactive behavior [53]. Surfactant mesophases, such as microemulsion systems, reverse micelles, and lamellar bilayers [81], have been proved to be applicable and versatile soft templates [81, 87, 88, 90, 92]. Reverse micelles and microemulsion systems with spherical, cylindrical, or bicontinuous aqueous phases have been used for synthesis of nanoparticles and nanowires [88]. Owing to the hydrophobic and hydrophilic head groups of surfactant molecules, surfactant molecules can readily form vesicular structures encapsulating an aqueous core, as displayed in Fig. 4.1. More complicated multilamellar vesicles composed of several concentric surfactant bilayers surrounding an aqueous core can also be elaborately prepared [88], as displayed in Fig. 4.1. The as-prepared vesicles are excellent templates for preparing organic and inorganic nanoparticles, as displayed in Fig. 4.2. One prominent application is fabricating 0-D polymer nanostructures via vesicle templating [88]. By introducing a hydrophobic monomer, which swells the surfactant bilayer, the surfactant vesicle is used as 4 Fabricating Nanostructures via Organic Molecular Templates 125 tv (a) several µm’s ~25-250 nm (b) Fig. 4.1. Vesicle architectures: (a) unilamellar vesicle, typical radii range from 25 to 250 nm, bilayer thicknesses are about 2–4 nm; (b) multilamellar vesicle, composed of several concentric surfactant bilayers surrounding an aqueous core [88] (a) 1. Vesicle (b) 1. Vesicle 2. ‘‘Fixed’’ Vesicle 2. Monomer Swollen 3. Hollow Polymer Sphere with Surfactant Vesicle Fig. 4.2. Templating vesicles: (a) vesicle-forming polymerizable surfactants are fixed into place by polymerization; (b) a hydrophobic monomer swells the interior of a vesicle bilayer and is subsequently polymerized to form a hollow polymer shell [88] a template directing the polymerization process and produces a hollow polymer shell, and surfactant molecules themselves are not incorporated in the polymerization. The polymer shells can be easily isolated from the templating surfactant vesicles for further applications. By choosing suitable monomers, polymer shells with different properties can be easily obtained. Other structures, such as parachutes, matrioshka structures, and necklaces, have also been reported by using surfactant vesicle templates in polymerization [88]. Templated polymer synthesis within vesicular solutions and microemulsions provides ways to fabricate hollow nanospheres and nanoparticles. Fabricating inorganic nanoparticles is another important application of vesicle templates, in which surfactant molecules provide nucleating sites, 126 Y. Zhou and B. Wang shape control, and stabilization of particles. The strong affinity between the metal salts and the polar head groups of amphiphilic molecules and the anisotropic structure of the microemulsion systems plays important roles in the anisotropic growth. Schmid et al. [93] reported the synthesis of ligand-stabilized gold nanoparticles, Au55 (PPh3 )12 Cl6 , in 1981. Then, in 1994, Brust et al. [1] reported the synthesis of thiol-stabilized gold nanoparticles, the method reached its golden era. In general, surfactant vesicles in microemulsion reactions can be used to produce spherical nanoparticles, such as Fe [94, 95], Pt [96], Cd [97], Pd [98, 99], Ag [100], Au [101], Cu [102], ZnS [103, 104], BaSO4 [105–107] particles, Au/Pd [108, 109], Pd/Pt [110], Au/Pt [111], Au/Ag [112–114] bimetallic particles, and Au/CdSe core–shell structures [115]. Nonspherical inorganic nanoparticles can be produced using the similar methods. Pinna et al. [116] reported the synthesis of triangular CdS nanocrystals in a Cd(AOT)2 /isooctane/water system, where AOT is sodium bis(2-ethylhexyl) sulfosuccinate. The group of Pileni [117–121] studied the Cu(AOT)2 /isooctane/water system and obtained spherical, rodshaped, and irregularly shaped Cu particles by adjusting system compositions. Johnson et al. [122] and Jana et al. [123] reported the transformation from gold nanoparticles to nanorods with controllable aspect ratios by adding cetyltrimethylammonium bromide (CTAB) to the system. Summers et al. [107] used polymerizable surfactants to modify the interfacial curvature of reverse micelles, and obtained spherical BaSO4 nanoparticles in the unpolymerized case as well as cylindrical BaSO4 nanoparticles when the polymerization changed the micellar curvature. Hubert et al. [124, 125] described using unilamellar vesicles as templates for transcription into silica. Vesicle-templated structures of more complex morphologies could be obtained by other methods. Silica spheres containing pillarlike structures have been synthesized by controlling the acidification rate of a solution of sodium silicate, butanol, and myristyltrimethylammonium bromide [126]. In order to improve the nonlinear optical response and catalytic properties of materials, nanometer-sized composite particles containing a core–shell structure, including inorganic–inorganic, inorganic–organic, organic–organic, organic–inorganic, and inorganic–biomolecule nanoparticles, were designed and synthesized in reverse-micelle systems templated by surfactant molecules, and have been systematically reviewed by Adair et al., [81] and Kickelbick and Liz-Marzan [127]. Surfactant monolayers have been well established as templates for nucleating and growing nanoparticles, in which geometrical and stereochemical matching of the monolayers and crystal lattices can result in epitaxial crystal growth [53, 92, 128, 129]. Among various surfactant monolayers, LB monolayers have been demonstrated to be excellent templates for growing nanocrystallites with morphology and orientation control. In 1985, Landau et al. [130] first introduced growing crystals based on the LB films of amphiphilic molecules as artificial templates for the promotion of crystal nucleation. Since the packing of the polar head groups can determine the 4 Fabricating Nanostructures via Organic Molecular Templates 127 nucleation rate and the degree of orientation of the attached growing crystals, adjustment of polar terminating groups of the amphiphilic molecules or dilution of the monolayers with other amphiphiles allows the the packing arrangements of the head groups and the domain sizes of the films to be adjusted and restricted, thus influencing the crystallization process in a controlled manner. The lattice-matching between the functional head groups in the monolayer and the nanocrystals will result in epitaxial growth of corresponding nanocrystallites on a monolayer [7, 131–138]. Yang et al. [129, 139, 140] have carried out fruitful work on this subject, and demonstrated the close relationship between the nucleation faces and the monolayer structures. By floating arachidic acid (AA) monolayers as templates on aqueous lead nitrate and cadmium chloride solutions, Fendler et al. obtained epitaxially grown lead sulfide (PbS), lead selenide (PbSe), and cadmium sulfide (CdS) semiconductor nanocrystallites. In order to investigate the monolayer-directed epitaxy control of nanocrystallites, Fendler et al. performed experiments on growing PbS nanocrystallites under mixed monolayers of AA and octadecylamine (ODA). By adjusting the AA-to-ODA ratio, PbS nanocrystallites with different symmetry and orientations were obtained. The experimental results clearly exhibited excellent monolayer-directed orientational control of nano-crystallite growth. Li et al. [141] carried our a similar experiment on growing CdS nanoparticles using AA and ODA mixed LB films as templates. An ordered array of CdS particles with a particle separation of 4.2 nm was obtained in the absence of ODA. Mixing ODA disturbed the crystalline structure of the AA film, and resulted in randomly distributed particles with average particle size reduced from 4 to 1 nm when the amount of ODA was increased. No CdS particles were produced when AA was absent. The experimental results demonstrated the close relation between the template structure and the growth of nanoparticles. Kmetko et al. [142] reported work on in situ synchrotron X-ray diffraction studies of the nucleation of barium fluoride at fatty acid monolayer templates, and revealed the commensurate relationship between the interfacial lattices of the organic molecules and the inorganic atoms. Although Langmuir monolayers are excellent templates for synthesizing nanoparticles, most surface structures of Langmuir monolayers are difficult to manipulate and characterize, which causes instability in particles size and shape control. Highly ordered structures of SAMs [12, 143, 144], especially alkanethiolates on a gold/silver surface [145], have been extensively studied and abundant structural information has been accumulated, such as surface lattice spacing and the tilting angle of the molecules. So, compared with Langmuir monolayers, SAMs would be more favorable for use as templates for controllable nucleation and growth of nanoparticles. From another point of view, SAMs are more controllable and could be easily patterned with featured structures, which promise SAMs as versatile and controllable templates for fabricating nanostructures. 128 Y. Zhou and B. Wang The synthetic growth of nanocrystallites can be guided by molecular recognition at an interface using patterned SAMs as templates [7, 146, 147]. By the microcontact printing (CP) technique, Whitesides and coworkers patterned metal substrates with SAMs having areas of different terminating groups (such as arrays of acid-terminated regions separated by methylterminated regions), which exhibited different nucleating activity, and immersed the patterned substrate in salt solution. After being taken out from the solution, the liquid droplets were retained in the polar region on the substrate, where the rate of nucleation was fastest but the growth of crystals was confined by the droplets and a suitable choice of array spacing, as displayed in Fig. 4.3. By controlling pattern density and feature sizes of the patterned substrates, terminal functional groups of the SAMs, and the concentration of crystallizing solutions, they could control key parameters of the crystallization process, including the location and density of nucleating regions on the substrate, the density of crystallites nucleated within each regions, and the crystallographic orientation of the crystals. Successful examples were demonstrated by growing oriented calcite nanoparticles by using patterned SAMs of ω-terminated alkanethiols [HS(CH2 )n X}, in which − − + X is CO− 2 , SO3 , PO3 , OH, N(CH3 ) , and CH3 , on metal substrates as templates [146]. Compared with bare metal substrates, SAMs terminated − − with CO− 2 , SO3 , PO3 , and OH groups were more active in inducing nucleation, whereas SAMs terminated with N(CH3 )+ and CH3 groups inhibited nucleation. The orientation of the crystallization of the calcite particles on each substrate was unique and highly homogeneous, but distinct on different substrates, such as SAMs of CO− 2 /Au, which resulted in face-selective nucleation of calcite from the (015) crystallographic planes, and CO− 2 /Ag (012), − /Ag (107), respec/Au (1012), and SO OH/Au (104), OH/Ag (103), SO− 3 3 tively. Whitesides and coworkers demonstrated a promising approach for the templated growth of nanoparticles in a controllable manner. By patterning SAMs with different structural features, similar processes produce 1-D and 2-D nanostructures, which will be introduced in the next sections. The group of Sagiv [8,148–151] developed an all-chemical strategy for the bottom-up fabrication and spatial fixation of nanoparticles and nanowires electrically connected to patterned electrodes. The approach included two processes, surface self-assembly and “constructive nanolithography”, a chemical patterning process utilizing electrical pulses delivered by a conductive atomic force microscope (AFM) tip for the nondestructive nanometer-scale inscription of chemical information on the top surfaces of certain highly ordered long-tail organosilane SAMs on silicon, as displayed in Fig. 4.4. One of the most attractive applications of the method is to produce patterned organic thin films as templates for the precisely controlled assembly of metal and semiconductor nanoparticles. Several successful examples were demonstrated. By tip-induced oxidation of surface-exposed vinyl (–CH=CH2 ) and methyl (CH3 ) groups to carboxyl (–COOH) and mercapto (–SH) groups, which would act as efficient binding sites for cations, they produced 4 Fabricating Nanostructures via Organic Molecular Templates 129 (a) (b) (c) Fig. 4.3. Experimental design of crystallization on patterned self-assembled monolayers (SAMs). (a) Relief structure of the patterned poly(dimethylsiloxane) (PDMS ) stamps used for microcontact printing. (b) The experimental steps. (c) Scanning electron micrograph of the sample patterned surface-printed circles of HS(CH2 )15 CO2 H in a background of HS(CH2 )15 CH3 supported on Ag(111) overgrown with calcite crystals. The images on the right illustrate the wide distribution of the sizes of the crystals formed on the nonpatterned SAMs. To prepare substrates, silicon wafers (test grade, n or p type, Silicon Sense, Nashua, NH, USA) were coated with 2.5 nm of Cr, to promote adhesion, and then coated with metal (Ag, Au, Pd; typically, 50 nm) using an electron-beam evaporator (base pressure 10−7 Torr). The stamps were prepared by casting and curing (PDMS) against rigid masters bearing a photoresist pattern formed using conventional lithographic techniques [7] 130 Y. Zhou and B. Wang Self-assembled Silver Island Conducting Tip (AFM) Nanoelectrochemical Reduction (+) o (-) o Ag o Ag Ag S-Ag S-Ag SH SH S-Ag S-Ag SH S-Ag S-Ag SH S-Ag S-Ag Development T FS M SH SH SH SH - Si - O - Si - O - Si - O - Si - O - Si - O - Si - - Si - O - Si - O - Si - O - Si - O - Si - O - Si - Si Si Ag+ SH SH - Si - O - Si - O - Si - O - Si - O - Si - O - Si - S-Ag S-Ag S-Ag S-Ag S-Ag S-Ag Self-assembled Silver Film - Si - O - Si - O - Si - O - Si - O - Si - O - Si - Si Si o o (NaBH4) Chemical Reduction o o Ag Ag Ag SH SH SH o o Ag o Ag Ag Ag SH SH SH Development SH SH SH SH SH SH - Si - O - Si - O - Si - O - Si - O - Si - O - Si - - Si - O - Si - O - Si - O - Si - O - Si - O - Si - Si Si Fig. 4.4. The site-defined self-assembly of silver metal on a thiol-top-functionalized silane monolayer (TFSM ) preassembled on silicon. The silver thiolate (S-Ag) template surface obtained by the chemisorption of Ag+ ions on the TFSM surface (left) is nondestructively patterned using either a wet chemical reduction process (lower path) or a nanoelectrochemical process (upper path) involving the application of a DC voltage to a conducting atomic force microscope (AFM ) tip. Further development of the macropatterns and nanopatterns of reduced silver particles imprinted on the Ag+ –TFSM template is shown to result in a thicker self-assembled silver film (lower path), or self-assembled silver islands selectively grown at tip-defined sites (upper path) [151] site-selectively patterned substrates with precise spatial control. After treatment with a solution containing Cd+ ions, the substrates were exposed to gaseous H2 S and generated template-controlled arrays of CdS nanoparticles [148]. Similar processes could be applied in fabricating template-controlled arrays of other metal and semiconductor nanoparticles [8,149–151]. The procedure can also be applied in fabricating more complex structures, which will be introduced in the following part of this chapter. Piner et al. [18] presented another important technique for patterning SAMs, named “dip-pen” nanolithography (DPN). By using an AFM tip as a “pen” and organic molecules (especially alkanethiols) as “ink”, they transferred molecules to a solid substrate of interest via capillary transport in an ambient atmosphere, as displayed in Fig. 4.5. The general process began with fabricating a pattern on a solid substrate consisting of arrays of “molecular ink” dots, which would act as binding and nucleating sites for nanoparticle growth. The patterned substrates were then treated with suitable solutions and consequent processes to obtain nanoparticles, 1-D wires, and 2-D arrays, such as growing functionalized gold nanoparticles on a gold substrate patterned with 16-mercaptohexadecanoic acid (MHA). 4 Fabricating Nanostructures via Organic Molecular Templates 131 Fig. 4.5. Dip-pen nanolithography (DPN ). A water meniscus forms between the AFM tip coated with n-octadecanethiol (ODT) and the Au substrate. The size of the meniscus, which is controlled by relative humidity, affects the ODT transport rate, the effective tip–substrate contact area, and DPN resolution [18] Chen and Lin [5] fabricated cubic cadmium sulfide (CdS) nanoparticles using patterned SAMs as templates. By using CP, they fabricated patterned SAMs of alkanethiolates on gold. The patterned SAMs were then immersed sequentially into cadmium and sulfide ion solutions; each drop of the solution remaining on the hydrophilic regions was regarded as tiny vessel. The CdS particles growth was restricted in each droplet. So the crystal sizes might be controlled by the amount and concentration of the ion solutions. Then, a narrow size distribution and uniform morphology were obtained. The average particles sizes could be adjusted by using different solvents in the synthesis. Adjusting patterned SAMs with different terminating groups resulted in the formation of nanoparticles with different crystallographic directions. Woo et al. [152] fabricated tellurium nanoclusters at Au(111) electrodes modified with thiolated β-cyclodextrin molecular templates. Besides the aforementioned techniques for patterning SAMs, Hayes and Shannon [153] reported growth of polyaniline nanostructures on gold electrodes using a two-component SAM consisting 4-aminothiophenol (4-ATP) and n-octadecanethiol (ODT) as a template, in which 4-ATP served as a nucleating site. 4.3 1-D Nanostructures 1-D nanostructures have become the focus of intensive research interest owing to their unique application in mesoscopic physics and fabrication of nanodevices [57, 154–162]. 1-D nanostructures provide an ideal system for investigating the dependence of electrical and thermal transport, as well as mechanical properties on dimensionality and quantum confinement [154]. 132 Y. Zhou and B. Wang 1-D nanostructures are potential interconnects and building units in fabricating nanodevices. Fabrication of 1-D nanostructures can be realized by several advanced nanolithographic techniques, such as template-directed synthesis, chain polymerization, focused ion beam lithography, electron-beam lithography, photolithography applying X-ray and extreme UV, scanningprobe lithography, vapor–liquid–solid method, solution–liquid–solid method, solvothermal method, vapor-phase method, and self-assembly [6,13–15]. One of the most successful examples of 1-D nanostructures is carbon nanotubes [163]. Synthesis of inorganic nanowires/nanotubes/nanobelts/nanorods has been extensively investigated and reviewed [164–176]. Organic species also play important roles in fabricating 1-D nanostructures. In this section we will introduce organic molecular templated 1-D nanostructure fabrication. By adsorbing a C90 H98 molecule, named as the Lander, on a clean Cu(110) surface, Rosei et al. [177] found that a single Lander molecule could act as a template inducing the formation of metallic nanostructures at step edges two Cu atoms wide and eight Cu atoms long, namely, 0.75-nm wide and 1.85-nm long, which were adapted to the dimension of the Lander molecule, as displayed in Fig. 4.6. Assembling behaviors of bis(N -α-amido-glycylglycine)-1,7-heptane dicarboxylate, one of the bolaamphiphiles, exhibit pH sensitivity [178]. In an acidic solution, the heptane bolaamphiphile forms a crystalline tubule with average size of 700 nm in diameter and 10 m in length [179]. The non-hydrogen-bonded amide groups in the assembled heptane bolaamphiphile nanotubes show strong affinity to metal ions such as Pt, Pd, Cu, and Ni, which can act as organic–inorganic junctions. So the heptane bolaamphiphile nanotubes have the potential to be excellent templates for inorganic and metallic nanowires. Matsui et al. [179] reported work on fabrication of Ni and Cu nanowires by electroless metallization of the heptane bolaamphiphile nanotubes in Ni and Cu baths with reducing agents, in which metal ions were coordinated between non-hydrogen-bonded amide groups of neighboring bolaamphiphile molecules. The results indicate a possible way to attach metallic nanowires onto nanoelectrodes by self-assembling the heptane bolaamphiphile nanotubes onto the electrodes by carboxylic acid–thiol self-assembly monolayers. Vesicular structures formed by surfactant molecules also provide versatile templates for fabricating 1-D nanostructures. Simmons et al. [180] reported the synthesis of high-aspect-ratio CdS nanorods in reverse micelles of AOT and phosphatidylcholine. Hopwood and Mann [181] reported the fabrication of highly elongated BaSO4 crystalline filaments in BaNaAOT microemulsions with length up to 100 m and aspect ratio of 1000. Chen et al. [182] reported the synthesis of vanadium oxide nanotubes by hydrothermal selfasembly from NH4 VO3 and using organic molecules as structure-directing templates. Organic molecules including primary amines (C2 H2n−1 NH2 ), α,ωdiamines [H2 N(CH2 )n NH2 ], and quaternary ammonium salt (CTAB) were demonstrated as suitable structure-directing templates for the formation 4 Fabricating Nanostructures via Organic Molecular Templates 133 [110] [001] (a) (b) (c) (d) (e) (f) 4 2 (g) 0.6 nm 0.5 nm ∆z [nm] ∆ z [nm] 0.85 nm 0.45 nm 4 2 0 0 (h) (i) Fig. 4.6. (a)–(d) Manipulation sequence of the Lander molecules from a step edge on Cu(110). The arrows show which molecule is being pushed aside; the circles mark the toothlike structures that are visible on the step where the molecule was docked. All image dimensions are 13 nm by 13 nm. Tunneling parameters for the imaging are It = −0.47 nA; Vt = −1.77 V; tunneling parameters for manipulation are It = −1.05 nA; Vt = −55 mV. (e) Zoom-in smooth-filtered scanning tunneling microscope (STM ) image showing the characteristic two-row width of the toothlike structure (right corner ) after removal of a single Lander molecule from the step edge. The Cu rows are also visible. The arrows show the directions on the surface. It = −0.75 nA; Vt = −1.77 V. Image dimensions are 5.5 nm by 2.5 nm. (f )–(i) Details of the conformation of the Lander molecule on the tooth. (f ) Molecular structure, extracted from a comparison between experimental and calculated STM scans, showing that the board is parallel to the tooth. (g) Calculated constantcurrent 3-D STM image. (h) Cross section of the tooth. (i) Cross section on a terrace. Tunneling parameters are It = −0.47nA; Vt = −1.77 V [177] of nanotubes. They also suggested a rolling mechanism for the formation of nanotubes from lamellar structures. Niederberger et al. [183] reported synthesis of vanadium oxide nanotubes by novel non-alkoxide routes by using 134 Y. Zhou and B. Wang either vanadium(V) oxytrichloride or vanadkum(V) pentoxide as a vanadium source and primary amines as templates, respectively. Qi et al. [184] synthesized BaCO3 crystal nanowires with lengths up to 100 m and diameters of 10–30 nm in a barium ions/carbonate ions/tetraethylene glycol monododecyl ether)/cyclohexane reverse-micelle system. CTAB is a cationic surfactant which can form a CH3 –CH3 –CH3 –N structure and induce sphere–rod micelle structures in aqueous solution when some salts such as NaCl and Na2 SO4 are added [185]; therefore, CTAB can be used as a soft template for synthesizing materials with special morphologies [123, 186]. Using Ag seeds for the growth of silver in solution, Jana et al. [187] obtained silver nanorods and nanowires from AgNO3 /ascorbic acid/CTAB/NaOH solution with a rodlike micelle as a template. Silver nanorods of controllable aspect ratio of 2.5–15 (10–15-nm short axes) and nanowires of 1–4-m length and 12–18-nm short axes were produced and effectively separated. Liu et al. [188] synthesized single crystalline SnS nanowires with average diameter of 30 nm and length of hundreds of microns in a SnC12 /Na2 S/CTAB/oxalic acid system with CTAB as a soft template. Yao et al. [189] reported the synthesis of a hydroxyapatite nanostructure using CTAB as a template. Perez-Juste et al. [190] reported the synthesis of Au nanorods with controllable aspect ratio in aqueous surfactant solutions in the presence of CTAB, to which gold ions were attached. From the experiments, it was demonstrated that the size and the aspect ratio of the gold nanorods could be controlled through the use of different sized seed particles with length tuned from 25 to 170 nm, while the width remained almost constant at 22–25 nm. The presence of CTAB and lower temperature are favored. The addition of chloride ions or the use of dodecyltrimethylammonium bromide caused shorter-aspect rods. Synthesis of Cu and Cu2 O nanwith hydrazine hydrate and otubes were reported by reducing Cu(OH)2− 4 glucose in the presence of CTAB as a structure-directing template [191]. Yu et al. [192] reported the synthesis of porous Cu2 O nanowhiskers with shape control by using CTAB as a template. The porous nanowhiskers exhibit a well-crystallized 1-D structure of more than 200 nm in length and a diameter of 15–30 nm, growing mainly along the <111> direction. The 1-D structures cannot be obtained when poly(ethylene glycol), glucose and sodium dodecyl benzenesulfonate are used as templates. From transmission electron microscopy studies, it was found that the role of CTAB was to interact with tiny Cu(OH)2 , which could bind OH− and be negatively charged, to disperse the tiny Cu(OH)2 solid and induce the growth of Cu2 O along the 1-D direction. When Cu2+ was used as a precursor, no nanowhiskers were obtained, which demonstrated the importance of the ion character of the precursor [Cu(OH)2 ·OH− or Cu2+ ] in the formation of 1-D nanostructures. Huang et al. [193, 194] used lyotropic reverse hexagonal liquid-crystalline phases as templates, which contained 1-D aqueous channels for fabricating nanowires such as those of Cu2 O and Ag. Cu2 O nanowires growing from anionic surfactant AOT reverse hexagonal liquid-crystalline phases could 4 Fabricating Nanostructures via Organic Molecular Templates 135 reach tens of micrometers in length and 25–100 nm in diameter. High-aspectratio crystalline silver nanowires with a uniform wire diameter of 20–30 nm were obtained from a similar system. Huang et al. [193–195] and Luo et al. [196,197] demonstrated the potential of lyotropic liquid-crystalline phases used as soft templates for fabricating inorganic nanostructures. Li et al. [198] reported direct formation of 1-D and more complex structures by combining nanoparticle synthesis with self-assembly. The experiments were carried out by adding Ba(AOT)2 reverse micelles into Na2 CrO4 containing NaAOT microemulsion droplets. By adjusting the reactant molar ratio and the water content, they obtained different structures, such as linear chains, rectangular superlattices, and long filaments. The difference was ascribed to the interfacial activity of reverse micelles and microemulsions arising from the interdigitation of surfactant molecules attached to specific nanoparticle crystal faces. SAMs are another kind of important technique for templated fabrication of 1-D nanostructures. Cheung et al. [199] demonstrated the fabrication of virus arrays consisting of 1-D virus nanowires by a multistep approach combining scanning probe nanolithography with chemoselective deposition of a virus onto functionalized SAMs. Choi and Park [200] developed an approach using SAMs as molecular templates to grow nano-sized conducting polymer wires and rings tens of nanometer thick and a few micrometers long. The surface patterning technique, combining surface self-assembly with “constructive nanolithography,” developed by Sagiv and coworkers [8, 148, 201], as displayed in Fig. 4.4, can also be used in fabricating 1-D nanostructures by inscribing 1-D patterns on corresponding SAMs using conductive AFM tips. 1-D gold wires inscribed on smooth silicon surfaces were produced by selectively assembling gold clusters on a purpose-designed organic template via a hierarchical layer-by-layer self-assembly strategy with lateral confinement produced by constructive nanolithography. The all-chemical technique provides attractive options for the nanofabrication in different dimensionalities, and might have real impact on future nanofabricating applications. The DPN technique developed by Piner et al. [18] also provides a promising approach for future nanofabrication. By combining DPN and wet chemical etching, Zhang et al. [202] reported the synthesis of a class of openended cylindrical Au–Ag alloy nanostructrues on a Si/SiOx substrate. Ag dots with average diameter of 585 ± 60 nm were firstly prepared by etching MHA-patterned Ag/Si film. The average height of the Ag dots was 48±3 nm, which is consistent with the thickness of the Ag film. Then, the as-prepared Ag nanodot pattern was transferred into aqueous HAuCl4 (a known redox etchant for Ag) for 5 min, and the solid Ag nanodots were transformed into open-ended hollow cylindrical nanostructures with average diameter of 570 ± 80 nm and height of 83 ± 6 nm. 136 Y. Zhou and B. Wang Annealing treatments of alkanethiol SAMs have been extensively studied [203–206]. By carefully controlling the annealing treatment, condensed alkanethiol SAMs could be converted to periodic concave–convex striped structures. The striped structures provide excellent spatial confinement in nanoscale, and could be applied as templates for fabricating 1-D nanostructures. Zeng et al. [9] have successfully utilized annealed alkanethiol SAMs for growing 1-D C60 molecular chains. By annealing decanethiol SAMs in vacuum, they achieved alkanethiol templates with a mixed striped phase, as displayed in Fig. 4.7. Three kinds of typical grooves were observed, with widths of about 3.3, 1.9, and 1.0 nm, respectively. The grooves provided lateral confinement for growing 1-D C60 molecular chains, since their widths were about integer multiples of the C60 bulk spacing. By depositing C60 onto the annealed templates, they observed only bimolecular C60 chains with maximal length up to 20 nm grown along grooves of 1.9 nm in width, as displayed in Fig. 4.8. C60 molecules were preferentially located at the S terminus sites of the flat-lying decanethiols, and only the grooves of 1.9 nm in width had S terminuses in the middle of the groove, so only C60 molecular chains were observed in this kind of groove. During the process of annealing treatment, it was noted that C–S bonds were easily broken in the SAMs of alkanethiols on Au(111), with alkane chains desorbing from the surfaces and S atoms aggregating and being confined by the striped structures to form 1-D atomic chains under well-controlled annealing condition, as displayed in Fig. 4.9. After the annealing treatment, flat-lying striped structures were √ observed similar to the well-defined (11.5 × 3) phase [204]. Bright chains between adjacent stripe pairs were observed as indicated by arrows with a spacing of about 5 Å along the stripes and were attributed to S atom chains. D' D (b) Height (nm) (a) 0.3 0.2 0.1 0.0 A B C 2 4 6 8 10 12 14 Distance (nm) 10 nm (c) A B C Fig. 4.7. (a) STM image of the striped template with furrowlike structures obtained by annealing decanethiol SAMs. (b) Height profile along line DD′ in (a). Three furrows with different widths are marked as A, B, and C, respectively. (c) Corresponding structural model for the furrow structures along line DD′ in (a). Open circles represent Au atoms, shaded gray circles C atoms, shaded white circles H atoms, and light gray circles S atoms [9] 4 Fabricating Nanostructures via Organic Molecular Templates (a) 137 (b) 5 nm Fig. 4.8. (a) STM image after deposition of 0.1 monolayers of C60 onto the striped thiol template. C60 bimolecular chains are observed in furrow B. Arrows indicate the flanges of furrow B. (b) Proposed structural model for a C60 chain in furrow B in top view (upper ) and side view (lower ), respectively. C60 molecules are located at the sites of S terminuses of the flat-lying decanethiols [9] (a) (b) Fig. 4.9. (a) STM image of the S atomic chains (indicated by the arrows) formed between adjacent flat-lying decanethiol stripe pairs on the Au(111) surface. (b) Corresponding structural model for a S atomic chain in top view (upper ) and side view (lower ), respectively. Shaded black circles represent individual S atoms. The S atoms in the atomic chains are located at the threefold Au(111) hollow sites [9] They ascribed the existence of spatial confinement of the decanethiol stripes as the key element in the formation of S atomic chains. Self-organized molecular assemblies provide a direction for templated fabrication of nanostructures. Baral and Schoen [207] reported the synthesis of hollow submicron-diameter silica cylinders by using a self-organized molecular assembly, an aqueous dispersion of phospholipid tubules, as a template for silica film deposition by the sol–gel method. The silica film coated phospholipid tubules were then treated with freeze-drying following heating at 600◦ C and resulted in hollow silica cylinders. Hoeppener et al. [201] reported the formation of linearly arranged Au55 clusters on a molecular template at the solid–liquid interface. The strategy utilized the incorporation of chemically modified Au55 clusters into highly oriented molecular templates by 138 Y. Zhou and B. Wang substitution of individual molecules of the template. The organic templates required were formed spontaneously at the solid–liquid interface of highly oriented pyrolytic graphite (HOPG) by self-organization of a fatty acid or a linear alkane. By adjusting the length of the linear alkyl molecule, they could control the distance between gold cluster rows. 4.4 2-D Nanostructures 2-D nanostructures, including monolayers and arrays, exhibit unique topological ordering and surface-bound characteristics, which promise the importance of 2-D nanostructures in fundamental research and technological application [208]. 2-D nanostructures also provide an ideal platform for study of surface chemistry, friction and lubrication, molecular biological behavior, wettability, corrosion resistance, nanobioelectronics, and functional devices, and will help us extend our investigations to nano and quantum worlds [27, 42, 128, 143, 168, 209]. 0-D and 1-D nanostructures are more likely to act as potential functional devices, building units, and interconnectors, but 2-D nanostructures are intended to be integrated and more applicable systems [42,168]. Intensive exploration has been carried out aimed at achieving 2-D nanostructures with controllable structures and desired properties, which have several requirements: stability, orderliness, orientation of adsorbates, composition, morphology, symmetry, and location of active functional units. Among the numerous methods explored, SAMs play important roles in fabricating and patterning 2-D nanostructures [42, 128, 143, 168, 209–211]. Structures, stability, and characteristics of SAMs have been widely studied and reviewed [12, 144, 145], and will not be discussed here. The main theme of this section focuses on the formation of 2-D nanostructures using SAMs as templates. Using functionalized SAMs as templates for the controlled formation of thin films from aqueous solutions has been demonstrated as an effective technique, such as for growing lead lanthanum zirconate titanate thin films using silane/quartz SAMs as templates [212], TiO2 films growing on octadecyltrichlorosilane (OTS)/SiO2 SAMs using the sol–gel method [213], γ-FeO(OH) films growing on alkylthiols/Au(111) SAMs using a soft-chemical method [214], and magnetic CoNiFe films growing on thiol/Cu SAMs using electrodeposition [215]. K. Koumoto et al. [216] demonstrated the formation of ordered 2-D structures consisting -CN terminated silica spheres using a patterned silane SAMs as template, in which SiO2 spheres were selectively attached to silanol surfaces via ester bonds. Cao et al. reported the fabrication of SrTiO3 thin films on patterned silane SAMs by liquid-phase deposition, in which SrTiO3 films were selectively deposited in the silanol regions [217]. By annealing at 500◦ C for 2 h in air, the amorphous SrTiO3 films obtained were crystallized. 4 Fabricating Nanostructures via Organic Molecular Templates 139 The DPN technique developed by the group of Mirkin [18, 218–222] provides a powerful tool for patterning 2-D monolayers and surfaces. Using MHA as molecular ink, the AFM tip as a pen, positively charged protonated amine- or amidine-modified polystyrene (PS) spheres as building units, they used a gold surface patterned with negatively charged carboxyl terminating groups as a template for growing PS particle arrays [222]. Different 2-D nanostructures, such as a DNA pattern [221] and an Fe3 O4 nanoparticle pattern [220], could be obtained by adjusting building units while using similar templates. By using a binary ink, consisting of 11-mercaptoundecylpenta(ethylene glycol) disulfide and a mixed disulfide substituted with one maleimide group, they patterned a gold surface with nanoscale features presenting functional terminal groups for the chemospecific immobilization of biomolecular particles [219]. Ordered 2-D cysteine mutant cowpea mosaic virus capsid particle arrays with well-defined spatial restriction were prepared via the procedure. Functionalized organic monolayers with patterning features are promissing candidates for preparing templates with selectable surface chemical properties. Qin et al. [147] introduced a combinatorial method including CP of SAMs, surface-templated self-assembly, and confined crystallization or precipitation for fabricating ordered 2-D arrays of microparticles or nanoparticles on solid substrates. The gold surface was patterned by CP into grids of hydrophobic (CH3 -terminated) and hydrophilic (COOH-terminated) SAMs of alkanethiolates. The patterned substrate was then transferred into aqueous solution for site-selective deposition. The size and shape of the pattern and the contact angle of the liquid determined the volume of the liquid droplet absorbed on the surface. The particle arrays were obtained by evaporating solvents. The distribution of particles in hydrophilic regions could be adjusted by withdrawing the substrate from the solution with different orientations of the pattern relative to the direction of shear on the liquid film. The size of the particles could be controlled by several factors, such as the concentration and compositions of the solution, the shape and area of the hydrophilic region, and the parameters influencing the volume of the droplets deposited on the hydrophilic region. Tien et al. [223] produced 2-D nanoparticle arrays by electrostatic self-assembly on gold substrates with patterned surface charge. The whole process included preparation of a charged surface, fabrication of charged particles, and assembly of the charged particles onto the charged surface. The charged surface was prepared by modifying a gold surface with different terminal groups, –NH3 Cl− , N(CH3 )2 , N(CH3 )3 Br− , and C(NH2 )2 Cl− yielded a positively charged surface, while –COOH and PO3 H2 yielded a negatively charged surface. Gold particles covered with ionized SAMs were prepared by immersing SAM-covered gold particles in corresponding solutions; the process also prevented the particle aggregation. The ionized particles were then assembled onto charged substrates through electrostatic self-assembly and formed 2-D structures. Sagiv et al. reported fabrication of spatially defined self-assembly of nanostructures through a 140 Y. Zhou and B. Wang (a) (c) (b) (d) Fig. 4.10. (a) The native cage structure of C60 molecules. STM image (35 Å×35 Å) of a C60 lattice taken at −268◦ C with −2.0 V sample bias. Detailed internal features of the C60 molecule are evident that closely resemble the C60 cage structure and match the theoretical simulation shown in the inset. (b) Top view (left) and side view (right) of a stick model outlining the C60 orientations obtained by simulation. The c-axis points out of the image. (c) Domain boundary of a 2-D C60 array. STM image (100 Å×100 Å) of two molecular orientational domains and the domain boundaries. Both the positional order and the bond-orientational order are fully preserved and no defect exists along the domain boundaries. (d) The two molecular orientations derived by comparison with the theoretically simulated images [226] nanoelectrochemically patterned monolayer based on nondestructive patterning techniques. Being extensively studied and well understood, alkanethiol SAMs are promising candidate for use as molecular templates [53, 92, 128, 143, 144, 168, 224]. The use of alkanethiol SAMs as templates has demonstrated that 2-D C60 monolayers/domains on SAMs of alkanethiol can exhibit molecular orientational domains at low temperature [225, 226], as displayed in Fig. 4.10. Unlike strong binding between C60 and metal/semiconductor substrates, which freeze molecular rotation of C60 at room temperature, C60 molecules adsorbed on the SAMs of alkanethiol rotate freely and display smooth hemispherical protuberance. C60 molecules can detach readily and diffuse easily on the templates at room temperature. At −196◦ C, C60 molecules display a hemisphere consistent with a rotating pattern around a fixed axis. When the sample was cooled down to −268◦ C, well-known C60 cage structures were observed experimentally with novel orientationally ordered domains. An abrupt boundary separating two distinguishable domains with different orientations is clearly observed. No positional defect at the domain boundary is observed and centers of C60 maintain perfect translation symmetry. The topological orders observed in 2-D C60 are significantly different from those in 3-D cases and it is concluded that this is an intrinsic property of a 2-D system. The corresponding theoretical explanation points out that the reduced dimensionality allows the molecules a greater degree of freedom in adjusting mutual 4 Fabricating Nanostructures via Organic Molecular Templates 141 orientations. Although the 2-D orientations have lower symmetry than those of the 3-D counterparts, the presence of the SAMs adequately minimizes the system energy and the domain boundary energies and leads to a novel uniorientational molecular order for 2-D C60 and a new topological order for the orientational domains. Phase-separated ultrathin organic films can serve as surface templates for the selective and patterned deposition of functional units on 2-D nanostructures [58, 153, 227–230]. The selective deposition is governed by the chemical differences in the domains or domain boundaries generated by phase separation. Fang and Knobler [231] reported the generation of phase-separated organosilane monolayers using OTS and 1H, 1H, 2H, 2H -perflurodecyltrichlorosilane (FTS) as building units with well-defined distribution of two terminal groups by combining LB deposition with self-assembly. The as-prepared phase-separated OTS/FTS monolayers can be easily adjusted by controlling the deposition condition, and used effectively as templates for selective deposition of proteins. Hayes and Shannon [153] reported templatedirected growth of polyaniline nanostructrues on patterned surfaces of twocomponentSAMs consisting of 4-ATP and ODT, in which 4-ATP served as a nucleation site for the deposition of polyaniline. The coverage of the polyaniline nanostructrues is closely related to the monolayer composition. Moraille and Badia [232] reported the application of a chemically homogeneous surface with coexisting solid/fluid phase as templates for spatially directed adsorption. The system studied consisted of nanoscale parallel strips generated by the LB deposition composing of l-α-dipalmitoylphosphatidylcholine (DPPC) and l-α-dilauroylphosphatidylcholine (DLPC) in different phases. Generations of novel protein and Au nanoparticle/protein patterns from the selective deposition of human serum albumin and human γ-globulin to the DPPC/DLPC monolayers were observed. More complex structures, such as superlattices of metal–metal or metal– semiconductor quantum dots can be readily prepared through layer-by-layer deposition of nanoparticle arrays on prepared self-assembled templates. Brust et al. [233] reported growth of multilayer thin films with alternating layers of 6-nm Au nanoparticles and α,ω-dithiols on –SH functionalized glass slides. Sarathy et al. [234] also reported similar experiments of growing a Au–Pt superlattice consisting of alternating layers of Au and Pt nanoparticles, and Pt–CdS heterostructures consisting of alternating layers of Pt and CdS nanoparticles using dithiol-modified Au substrates as templates. Noncovalently connected self-organized structures provide another group of templates for fabricating nanostructures. Lei et al. [235] reported assembly of phthalocyanine (Pc) single molecular arrays using 2-D alkane lamellar structures on HOPG as templates, as displayed in Figs. 4.11 and 4.12. Linear alkanes adsorbed from nonpolar solutions could form close-packed monolayers through 2-D crystallization of alkane parts on a graphite surface with polar groups paired together, which were used as molecular templates for assembling ordered Pc arrays. Linear C18 X (X is Cl, Br, I, CN, and SH) molecules 142 Y. Zhou and B. Wang phase I phase II 25 nm (a) 25 nm (b) phase III phase II 20 nm (c) Fig. 4.11. (a) A large-scale image of the uniform assembly of phthalocyanine (Pc) with C18 SH when the molar ratio was been adapted to 1:3 (667 mV, 1.019 nA). (b) Coexistence of phase I (domain of pure thiol) and phase II (uniform assembly) when the molar ratio was below 1:3 (−431 mV, 677 pA). (c) Coexistence of phase II and phase III (pure Pc domain) when the molar ratio was above 1:3 (715 mV, 1.136 nA). The insert shows a high-resolution image obtained of the Pc domain [235] 12.5 10.0 7.5 l 5.0 2.5 4.0 nm 0 0 (a) 2.5 5.0 7.5 10.0 12.5 nm (b) Fig. 4.12. (a) High-resolution image of the uniform assembly of Pc with C18 SH (560 mV, 1.019 nA). (b) High-resolution image of the uniform assembly of Pc with C18 I (−828 mV, 1.168 nA) [235] 4 Fabricating Nanostructures via Organic Molecular Templates 143 were chosen for fabricating molecular templates. By adjusting the molar ratio of Pc to C18X to about 1:3, they obtained uniform assemblies of Pc molecules on C18 X templates. The formation of the as-observed structures was ascribed to the interaction between Pc and the end group of the alkane derivative as well as the interaction between functional groups of the alkane derivative. Byrd et al. [236, 237] demonstrated that an organized organic monolayer could be used as a template for assembling an inorganic lattice by combining LB and self-assembly techniques. A LB monolayer of octadecylphosphonic acid formed on an octadecyltrichlorosilane-covered substrate was used as a template for growing Zr2+ ions from solution. A capping octadecylphosphonic acid LB monolayer was added to complete the thin film structure. 4.5 Summary In this chapter, a comprehensive review on examples of organic molecular templates and methods for the fabrication of nanostructrues in different dimensionalities has been presented. Organic molecular templates can be divided into several groups, reverse-micelle and microemulsion system, LB monolayers, SAMs (including versatile patterned SAMs), and self-organized structures, in which SAMs occupy a prominent and unparalleled position owing to their excellent stability, orderliness, and versatile structures. SAMs provide not only techniques for fabricating nanostructures, but also methods of integrating systems for future applications. The fabrication and the applications of organic molecular templates have been investigated for decades and obtained fruitful results. It is believed that in the era of nanoscience and technology, organic molecular templates (especially SAMs) will play important roles for exploration and application of the amazing nano and quantum world. References 1. M. Brust, M. Walker, D. Bethell, D.J. Schiffrin, R. Whyman: J. Chem. Soc. Chem. Commun., 801 (1994) 2. G. Carotenuto, L. Pasquini, E. Milella, M. Pentimalli, R. Lamanna, L. Nicolais: Eur. Phys. J. B. 31, 545 (2003) 3. M. Aslam, G. Gopakumar, T.L. Shoba, I.S. Mulla, K. Vijayamohanan, S.K. Kulkarni, J. Urban, W. Vogel: J. Colloid Interface Sci. 255, 79 (2002) 4. I. Quiros, M. Yamada, K. Kubo, J. Mizutani, M. Kurihara, H. Nishihara: Langmuir 18, 1413 (2002) 5. C.C. Chen, J.J. Lin: Adv. Mater. 13, 136 (2001) 6. Y.N. Xia, J.A. Rogers, K.E. Paul, G.M. Whitesides: Chem. Rev. 99, 1823 (1999) 7. J. Aizenberg, A.J. Black, G.M. Whitesides: Nature 398, 495 (1999) 8. S.T. Liu, R. Maoz, G. Schmid, J. Sagiv: Nano Lett. 2, 1055 (2002) 9. C.G. Zeng, B. Wang, B. Li, H.Q. Wang, J.G. Hou: Appl. Phys. Lett. 79, 1685 (2001) 144 Y. Zhou and B. Wang 10. B. Xu, S.X. Yin, C. Wang, X.H. Qiu, Q.D. Zeng, C.L. Bai: J. Phys. Chem. B. 104, 10502 (2000) 11. S.L. Dawson, J. Elman, D.E. Margevich, W. McKenna, D.A. Tirrell, A. Ulman: In: Hydrogels and Biodegradable Polymers for Bioapplications (ACS Symposium Series 627), ed by R. Ottenbrite, S. Hwang, K. Park, (American Chemical Society, Washington, DC, 1996), pp 187–196 12. A. Ulman: Chem. Rev. 96, 1533 (1996) 13. Y. Okawa, M. Aono: J. Chem. Phys. 115, 2317 (2001) 14. Y. Okawa, M. Aono: Nature 409, 683 (2001) 15. A. Miura, S. De Feyter, M.M.S. Abdel-Mottaleb, A. Gesquiere, P.C.M. Grim, G. Moessner, M. Sieffert, M. Klapper, K. Mullen, F.C. De Schryver: Langmuir 19, 6474 (2003) 16. J. Zak, H.P. Yuan, M.Ho, L.K. Woo, M.D. Porter: Langmuir 9, 2772 (1993) 17. T.A. Postlethwaite, J.E. Hutchison, K.W. Hathcock, R.W. Murray: Langmuir 11, 4109 (1995) 18. R.D. Piner, J. Zhu, F. Xu, S.H. Hong, C.A. Mirkin: Science 283, 661 (1999) 19. Y.N. Xia, J.J. McClelland, R. Gupta, D. Qin, X.M. Zhao, L.L. Sohn, R.J. Celotta, G.M. Whitesides: Adv. Mater. 9, 147 (1997) 20. X.M. Zhao, Y.N. Xia, G.M. Whitesides: J. Mater. Chem. 7, 1069 (1997) 21. X.M. Zhao, Y.N. Xia, D. Qin, G.M. Whitesides: Adv. Mater. 9, 251 (1997) 22. T.R. Kelly: Acc. Chem. Res. 34, 514 (2001) 23. T.R. Kelly, H. De Silva, R.A. Silva: Nature 401, 150 (1999) 24. T.R. Kelly, J.P. Sestelo: In: Molecular Machines and Motors (Structure and Bonding), Series 99, ed by J.-P. Sauvage, (Springer, Berlin Heidelberg New York, 2001), pp 19–53 25. N. Koumura, R.W.J. Zijlstra, R.A. van Delden, N. Harada, B.L. Feringa: Nature 401, 152 (1999) 26. R.K. Soong, G.D. Bachand, H.P. Neves, A.G. Olkhovets, H.G. Craighead, C.D. Montemagno: Science 290, 1555 (2000) 27. L.G. Zhu, S.M. Peng: Chin. J. Inorg. Chem. 18, 117 (2002) 28. R.H. Mitchell, Y.S. Chen: Tetrahedron Lett. 37, 6665 (1996) 29. X. Chi, M.E. Itkis, B.O. Patrick, T.M. Barclay, R.W. Reed, R.T. Oakley, A.W. Cordes, R.C. Haddon: J. Am. Chem. Soc. 121, 10395 (1999) 30. T.M. Barclay, A.W. Cordes, R.C. Haddon, M.E. Itkis, R.T. Oakley, R.W. Reed, H. Zhang: J. Am. Chem. Soc. 121, 969 (1999) 31. C.P. Collier, E.W. Wong, M. Belohradsky, F.M. Raymo, J.F. Stoddart, P.J. Kuekes, R.S. Williams, J.R. Heath: Science 285, 391 (1999) 32. Z.Y. Hua, G.R. Chen, W. Xu, D.Y. Chen: Appl. Surf. Sci. 169, 447 (2001) 33. R.M. Metzger, J.W. Baldwin, W.J. Shumate, I.R. Peterson, P. Mani, G.J. Mankey, T. Morris, G. Szulczewski, S. Bosi, M. Prato, A. Comito, Y. Rubin: J. Phys. Chem. B. 107, 1021 (2003) 34. R.M. Metzger: J. Solid State Chem. 168, 696 (2002) 35. R.M. Metzger, B. Chen, U. Hopfner, M.V. Lakshmikantham, D. Vuillaume, T. Kawai, X.L. Wu, H. Tachibana, T.V. Hughes, H. Sakurai, J.W. Baldwin, C. Hosch, M.P. Cava, L. Brehmer, G.J. Ashwell: J. Am. Chem. Soc. 119, 10455 (1997) 36. B. Chen, R.M. Metzger: J. Phys. Chem. B. 103, 4447 (1999) 37. C.G. Zeng, H.Q. Wang, B. Wang, J.L. Yang, J.G. Hou: Appl. Phys. Lett. 77, 3595 (2000) 4 Fabricating Nanostructures via Organic Molecular Templates 145 38. S.H.M. Persson, L. Olofsson, L. Gunnarsson, E. Olsson: Nanostruct. Mater. 12, 821 (1999) 39. A.M. Stevens, C.J. Richards: Tetrahedron Lett. 38, 7805 (1997) 40. J. Han, A. Globus, R. Jaffe, G. Deardorff: Nanotechnology 8, 95 (1997) 41. J. Clayden, J.H. Pink: Angew. Chem. Int. Ed. Engl. 37, 1937 (1998) 42. D.A. Bonnell: J. Vac. Sci. Technol. A 21, S194 (2003) 43. R.A. Caruso, M. Antonietti: Chem. Mater. 13, 3272 (2001) 44. S.A. Davis, M. Breulmann, K.H. Rhodes, B. Zhang, S. Mann: Chem. Mater. 13, 3218 (2001) 45. L.A. Estrof, A.D. Hamilton: Chem. Mater. 13, 3227 (2001) 46. S. Mann, S.L. Burkett, S.A. Davis, C.E. Fowler, N.H. Mendelson, S.D. Sims, D. Walsh, N.T. Whilton: Chem. Mater. 9, 2300 (1997) 47. N.K. Raman, M.T. Anderson, C.J. Brinker: Chem. Mater. 8, 1682 (1996) 48. R.A. Caruso: Top. Curr. Chem. 226, 91 (2003) 49. N. Kawahashi, E. Matijevic: J. Colloid Interface Sci. 143, 103 (1991) 50. Y. Lu, Y.D. Yin, Y.N. Xia: Adv. Mater. 13, 271 (2001) 51. C. Sanchez, G.J.D.A. Soler-Illia, F. Ribot, T. Lalot, C.R. Mayer, V. Cabuil: Chem. Mater. 13, 3061 (2001) 52. P. Innocenzi, G. Brusatin, Chem. Mater. 13, 3126 (2001) 53. K.J.C. van Bommel, A. Friggeri, S. Shinkai: Angew. Chem. Int. Ed. Engl. 42, 980 (2003) 54. T.P. Lodge: Macromol. Chem. Phys. 204, 265 (2003) 55. K.M. Ryan, N.R.B. Coleman, D.M. Lyons, J.P. Hanrahan, T.R. Spalding, M.A. Morris, D.C. Steytler, R.K. Heenan, J.D. Holmes: Langmuir 18, 4996 (2002) 56. D.B. Zhang, L.M. Qi, J.M. Ma, H.M. Cheng: Chem. Mater. 13, 2753 (2001) 57. C.R. Martin: Chem. Mater. 8, 1739 (1996) 58. M. Goren and R.B. Lennox: Nano Lett. 1, 735 (2001) 59. J.Y. Cheng, A.M. Mayes, C.A. Ross: Nat. Mater. 3, 823 (2004) 60. I.W. Hamley: Nanotechnology 14, R39 (2003) 61. W. Meier: Curr. Opin. Colloid Interface Sci. 4, 6 (1999) 62. H.W. Li, W.T.S. Huck: Curr. Opin. Solid State Mater. Sci. 6, 3 (2002) 63. M.F. Zhang, M. Drechsler, A.H.E. Muller: Chem. Mater. 16, 537 (2004) 64. I.A. Ansari, I.W. Hamley: J. Mater. Chem. 13, 2412 (2003) 65. S. Fullam, D. Cottell, H. Rensmo, D. Fitzmaurice: Adv. Mater. 12, 1430 (2000) 66. Y. Zhang, H.J. Dai: Appl. Phys. Lett. 77, 3015 (2000) 67. L. Hu, Y.X. Li, X.X. Ding, C. Tang, S.R. Qi: Chem. Phys. Lett. 397, 271 (2004) 68. A. Govindaraj, B.C. Satishkumar, M. Nath, C.N.R. Rao: Chem. Mater. 12, 202 (2000) 69. C.N.R. Rao, B.C. Satishkumar, A. Govindaraj, M. Nath: Chem. Phys. Chem. 2, 78 (2001) 70. B.C. Satishkumar, A. Govindaraj, M. Nath, C.N.R. Rao: J. Mater. Chem. 10, 2115 (2000) 71. S.A. Davis, S.L. Burkett, N.H. Mendelson, S. Mann: Nature 385, 420 (1997) 72. E. Braun, Y. Eichen, U. Sivan, G. Ben-Yoseph: Nature 391, 775 (1998) 73. C.J.F. Dupraz, P. Nickels, U. Beierlein, W.U. Huynh, F.C. Simmel: Superlattices Microstruct. 33, 369 (2003) 74. Y. Eichen, E. Braun, U. Sivan, G. Ben-Yoseph: Acta Polym. 49, 663 (1998) 146 Y. Zhou and B. Wang 75. M. Field, C.J. Smith, D.D. Awschalom, N.H. Mendelson, E.L. Mayes, S.A. Davis, S. Mann, Appl. Phys. Lett. 73, 1739 (1998) 76. C.J. Loweth, W.B. Caldwell, X.G. Peng, A.P. Alivisatos, P.G. Schultz: Angew. Chem. Int. Ed. Engl. 38, 1808 (1999) 77. J.E. Meegan, A. Aggeli, N. Boden, R. Brydson, A.P. Brown, L. Carrick, A.R. Brough, A. Hussain, R.J. Ansell: Adv. Funct. Mater. 14, 31 (2004) 78. N.C. Seeman, Trends. Biotechnol. 17, 437 (1999) 79. W. Shenton, D. Pum, U.B. Sleytr, S. Mann: Nature 389, 585 (1997) 80. T. Shimizu: Macromol. Rapid Commun. 23, 311 (2002) 81. J.H. Adair, T. Li, T. Kido, K. Havey, J. Moon, J. Mecholsky, A. Morrone, D.R. Talham, M.H. Ludwig, L. Wang: Mater. Sci. Eng. R 23, 139 (1998) 82. P.M. Mendes, Y. Chen, R.E. Palmer, K. Nikitin, D. Fitzmaurice, J.A. Preece: J. Phys. Condens. Mater. 15, S3047 (2003) 83. A.N. Shipway, E. Katz, I. Willner: Chem. Phys. Chem. 1, 18 (2000) 84. Z.T. Liu, C. Lee, V. Narayanan, G. Pei, E.C. Kan: IEEE Trans. Electron Devices 49, 1606 (2002) 85. C.N.R. Rao, G.U. Kulkarni, P.J. Thomas, P.P. Edwards: Chem. Soc. Rev. 29, 27 (2000) 86. Y.S. Shon, H. Choo: Cr. Chim. 6, 1009 (2003) 87. I. Capek: Adv. Colloid Interface Sci. 110, 49 (2004) 88. H.P. Hentze, C.C. Co, C.A. McKelvey, E.W. Kaler: Top. Curr. Chem. 226, 197 (2003) 89. H.P. Hentze, E.W. Kaler: Curr. Opin. Colloid Interface Sci. 8, 164 (2003) 90. D. Horn, J. Rieger: Angew. Chem. Int. Ed. Engl. 40, 4331 (2001) 91. T.B. Liu, C. Burger, B. Chu: Prog. Polym. Sci. 28, 5 (2003) 92. V.T. John, B. Simmons, G.L. McPherson, A. Bose: Curr. Opin. Colloid Interface Sci. 7, 288 (2002) 93. G. Schmid, R. Boese, R. Pfeil, F. Bandermann, S. Meyer, G. Calis, J. van der Velden: Chem. Ber. 114, 3634 (1981) 94. M.A. Lopezquintela, J. Rivas: J. Colloid Interf. Sci. 158, 446 (1993) 95. N. Lufimpadio, J.B. Nagy, E.G. Derouane: Surfactants in Solution (Plenum, New York, 1984), p 1483 96. H.H. Ingelsten, R. Bagwe, A. Palmqvist, M. Skoglundh, C. Svanberg, K. Holmberg, D.O. Shah: J. Colloid Interface Sci. 241, 104 (2001) 97. A. Henglein: Chem. Rev. 89, 1861 (1989) 98. M. Iida, S. Ohkawa, H. Er, N. Asaoka, H. Yoshikawa: Chem. Lett., 1050 (2002) 99. W. Lu, B. Wang, K.D. Wang, X.P. Wang and J.G. Hou, Langmuir 19, 5887 (2003) 100. A. Manna, B.D. Kulkarni, K. Bandyopadhyay, K. Vijayamohanan: Chem. Mater. 9, 3032 (1997) 101. A.B.R. Mayer, J.E. Mark: Eur. Polym. J. 34, 103 (1998) 102. E.M. Egorova, A.A. Revina: Colloid Surf. A 168, 87 (2000) 103. G.C. De, A.M. Roy, S. Saba, S. Aditya: J. Indian Chem. Soc. 80, 551 (2003) 104. H. Ohde, M. Ohde, F. Bailey, H. Kim, C.M. Wai: Nano Lett. 2, 721 (2002) 105. D. Adityawarman, A. Voigt, P. Veit, K. Sundmacher: Chem. Eng. Sci. 60, 3373 (2005) 106. L.M. Qi, J.M. Ma, H.M. Cheng, Z.G. Zhao: Colloids Surf. A 108, 117 (1996) 107. M. Summers, J. Eastoe, S. Davis: Langmuir 18, 5023 (2002) 108. G. Cardenas, R. Segura: Mater. Res. Bull. 35, 1369 (2000) 4 Fabricating Nanostructures via Organic Molecular Templates 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 147 M.L. Wu, D.H. Chen, T.C. Huang: Langmuir 17, 3877 (2001) M.L. Wu, D.H. Chen, T.C. Huang: J. Colloid Interface Sci. 243, 102 (2001) M.L. Wu, D.H. Chen, T.C. Huang: Chem. Mater. 13, 599 (2001) L. Guczi: Catal. Today 101, 53 (2005) O.M. Wilson, R.W.J. Scott, J.C. Garcia-Martinez, R.M. Crooks: J. Am. Chem. Soc. 127, 1015 (2005) D.H. Chen, C.J. Chen: J. Mater. Chem. 12, 1557 (2002) W. Lu, B. Wang, J. Zeng, X. Wang, S. Zhang, J.G. Hou: Langmuir 21, 3684 (2005) N. Pinna, K. Weiss, H. Sack-Kongehl, W. Vogel, J. Urban, M.P. Pileni: Langmuir 17, 7982 (2001) A. Filankembo, S. Giorgio, I. Lisiecki, M.P. Pileni: J. Phys. Chem. B 107, 7492 (2003) M.P. Pileni, J. Tanori, A. Filankembo: Colloids Surf. A 123, 561 (1997) M.P. Pileni: Langmuir 17, 7476 (2001) I. Lisiecki, M.P. Pileni: J. Am. Chem. Soc. 115, 3887 (1993) J. Tanori, M.P. Pileni: Langmuir 13, 639 (1997) C.J. Johnson, E. Dujardin, S.A. Davis, C.J. Murphy, S. Mann: J. Mater. Chem. 12, 1765 (2002) N.R. Jana, L. Gearheart, C.J. Murphy: J. Phys. Chem. B. 105, 4065 (2001) D.H.W. Hubert, M. Jung, P.M. Frederik, P.H.H. Bomans, J. Meuldijk, A.L. German: Adv. Mater. 12, 1286 (2000) D.H.W. Hubert, M. Jung, A.L. German: Adv. Mater. 12, 1291 (2000) H.P. Lin, Y.R. Cheng, C.Y. Mou: Chem. Mater. 10, 3772 (1998) G. Kickelbick, L.M. Liz-Marzan: In: Encyclopedia of Nanoscience and Nanotechnology, Series 10, ed by H.S. Nalwa, (American Scientific, Stevenson Ranch, 2003), pp. 1–22 I. Soten, G.A. Ozin: Curr. Opin. Colloid Interface Sci. 4, 325 (1999) J.P. Yang, F.C. Meldrum, J.H. Fendler: J. Phys. Chem. 99, 5500 (1995) E.M. Landau, M. Levanon, L. Leiserowita, M. Lahav, J. Sagiv: Nature 318, 353 (1985) S. Mann, B.R. Heywook, S. Rajam, J.D. Birchall: Nature 334, 692 (1988) E.M. Landau, S.G. Wolf, M. Levanon, L. Leiserowita, M. Lahav, J. Sagiv: J. Am. Chem. Soc. 111, 1436 (1989) J.H. Fendler, F.C. Meldrum: Adv. Mater. 7, 607 (1995) J.M. Didymus, S. Mann, W.J. Benton, I.R. Collins: Langmuir 11, 3130 (1995) B.R. Heywood, S. Mann: J. Am. Chem. Soc. 114, 4681 (1992) B.R. Heywood, S. Mann: Chem. Mater. 6, 311 (1994) S. Mann, B.R. Heywood, S. Rajam, J.B.A. Walker: J. Phys. D Appl. Phys. 24, 154 (1991) S. Mann, G.A. Ozin: Nature 382, 313 (1996) J.P. Yang, J.H. Fendler: J. Phys. Chem. 99, 5505 (1995) X.K. Zhao, J. Yang, L.D. Mccormick, J.H. Fendler: J. Phys. Chem. 96, 9933 (1992) H.H. Li, G.Z. Mao, K.Y.S. Ng: Thin Solid Films 358, 62 (2000) J. Kmetko, C.J. Yu, G. Evmenenko, S. Kewalramani, P. Dutta: Phys. Rev. Lett. 89, 186102 (2002) J.J. Gooding, F. Mearns, W.R. Yang, J.Q. Liu: Electroanalysis 15, 81 (2003) F. Schreiber: Prog. Surf. Sci. 65, 151 (2000) 148 Y. Zhou and B. Wang 145. G.E. Poirier: Chem. Rev. 97, 1117 (1997) 146. J. Aizenberg, A.J. Black,G.M. Whitesides: J. Am. Chem. Soc. 121, 4500 (1999) 147. D. Qin, Y.N. Xia, B. Xu, H. Yang, C. Zhu, G.M. Whitesides: Adv. Mater. 11, 1433 (1999) 148. S. Hoeppener, R. Maoz, S.R. Cohen, L.F. Chi, H. Fuchs, J. Sagiv: Adv. Mater. 14, 1036 (2002) 149. R. Maoz, S.R. Cohen, J. Sagiv: Adv. Mater. 11, 55 (1999) 150. R. Maoz, E. Frydman, S.R. Cohen, J. Sagiv: Adv. Mater. 12, 725 (2000) 151. R. Maoz, E. Frydman, S.R. Cohen, J. Sagiv: Adv. Mater. 12, 424 (2000) 152. D.H. Woo, S.J. Choi, D.H. Han, H. Kang, S.M. Park: Phys. Chem. Chem. Phys. 3, 3382 (2001) 153. W.A. Hayes, C. Shannon: Langmuir 14, 1099 (1998) 154. N.I. Kovtyukhova, T.E. Mallouk: Chem-Eur. J. 8, 4355 (2002) 155. Z.Y. Tang, N.A. Kotov: Adv. Mater. 17, 951 (2005) 156. S.M. Prokes, K.L. Wang: MRS Bull. 24, 13 (1999) 157. X.F. Duan, Y. Huang, Y. Cui, J.F. Wang, C.M. Lieber: Nature 409, 66 (2001) 158. Y. Huang, X.F. Duan, Y. Cui, L.J. Lauhon, K.H. Kim, C.M. Lieber: Science 294, 1313 (2001) 159. Y. Huang, X.F. Duan, Q.Q. Wei, C.M. Lieber: Science 291, 630 (2001) 160. C.A. Huber, T.E. Huber, M. Sadoqi, J.A. Lubin, S. Manalis, C.B. Prater: Science 263, 800 (1994) 161. T.M. Whitney, J.S. Jiang, P.C. Searson, C.L. Chien: Science 261, 1316 (1993) 162. C.G. Wu, T. Bein: Science 264, 1757 (1994) 163. S. Iijima: Nature 354, 56 (1991) 164. B.T. Mayers, K. Liu, D. Sunderland, Y.N. Xia: Chem. Mater. 15, 3852 (2003) 165. B. Mayers, Y.N. Xia: J. Mater. Chem. 12, 1875 (2002) 166. Z.L. Wang: Annu. Rev. Phys. Chem. 55, 159 (2004) 167. X.D. Wang, Y. Ding, C.J. Summers, Z.L. Wang: J. Phys. Chem. B. 108, 8773 (2004) 168. B.A. Parviz, D. Ryan, G.M. Whitesides: IEEE Trans. Adv. Packaging 26, 233 (2003) 169. P.D. Yang, F. Kim: Abstr. Pap. Am. Chem. Soc. 225, U136 (2003) 170. C.N.R. Rao, G. Gundiah, F.L. Deepak, A. Govindaraj, A.K. Cheetham: J. Mater. Chem. 14, 440 (2004) 171. C.N.R. Rao, F.L. Deepak, G. Gundiah, A. Govindaraj: Prog. Solid State Chem. 31, 5 (2003) 172. C. Qian, F. Kim, L. Ma, F. Tsui, P.D. Yang, J. Liu: J. Am. Chem. Soc. 126, 1195 (2004) 173. S.K. Lee, H.J. Choi, P. Pauzauskie, P.D. Yang, N.K. Cho, H.D. Park, E.K. Suh, K.Y. Lim, H.J. Lee: Phys. Status Solidi B. 241, 2775 (2004) 174. M. Law, J. Goldberger, P.D. Yang: Annu. Rev. Mater Res. 34, 83 (2004) 175. J.R. LaRoche, Y.W. Heo, B.S. Kang, L.C. Tien, Y. Kwon, D.P. Norton, B.P. Gila, F. Ren, S.J. Pearton: J. Electron. Mater. 34, 404 (2005) 176. Y.W. Heo, D.P. Norton, L.C. Tien, Y. Kwon, B.S. Kang, F. Ren, S.J. Pearton, J.R. LaRoche: Mater. Sci. Eng. R 47, 1 (2004) 177. F. Rosei, M. Schunack, P. Jiang, A. Gourdon, E. Laegsgaard, I. Stensgaard, C. Joachim, F. Besenbacher: Science 296, 328 (2002) 178. H. Matsui, B. Gologan: J. Phys. Chem. B. 104, 3383 (2000) 4 Fabricating Nanostructures via Organic Molecular Templates 149 179. H. Matsui, S. Pan, B. Gologan, S.H. Jonas: J. Phys. Chem. B. 104, 9576 (2000) 180. B.A. Simmons, S.C. Li, V.T. John, G.L. McPherson, A. Bose, W.L. Zhou, J.B. He: Nano Lett. 2, 263 (2002) 181. J.D. Hopwood, S. Mann: Chem. Mater. 9, 1819 (1997) 182. X. Chen, X.M. Sun, Y.D. Li: Inorg. Chem. 41, 4524 (2002) 183. M. Niederberger, H.J. Muhr, F. Krumeich, F. Bieri, D. Gunther, R. Nesper: Chem. Mater. 12, 1995 (2000) 184. L.M. Qi, J.M. Ma, H.M. Cheng, Z.G. Zhao: J. Phys. Chem. B. 101, 3460 (1997) 185. L. Yan, Y.D. Li, Z.X. Deng, J. Zhuang, X.M. Sun: Int. J. Inorg. Mater. 3, 633 (2001) 186. N.R. Jana, L. Gearheart, C.J. Murphy: Adv. Mater. 13, 1389 (2001) 187. N.R. Jana, L. Gearheart, C.J. Murphy: Chem. Commun. 617 (2001) 188. Y.K. Liu, D.D. Hou, G.H. Wang: Chem. Phys. Lett. 379, 67 (2003) 189. J. Yao, W. Tjandra, Y.Z. Chen, K.C. Tam, J. Ma, B. Soh: J. Mater. Chem. 13, 3053 (2003) 190. J. Perez-Juste, L.M. Liz-Marzan, S. Carnie, D.Y.C. Chan: Adv. Funct. Mater. 14, 571 (2004) 191. M.H. Cao, C.W. Hu, Y.H. Wang, Y.H. Guo, C.X. Guo, E.B. Wang: Chem. Commun. 1884 (2003) 192. Y. Yu, F.P. Du, J.C. Yu, Y.Y. Zhuang, P.K. Wong: J. Solid State Chem. 177, 4640 (2004) 193. L.M. Huang, H.T. Wang, Z.B. Wang, A. Mitra, K.N. Bozhilov, Y.S. Yan: Adv. Mater. 14, 61 (2002) 194. L.M. Huang, H.T. Wang, Z.B. Wang, A.P. Mitra, D. Zhao, Y.H. Yan: Chem. Mater. 14, 876 (2002) 195. Y.S. Yan, L.M. Huang: Abstr. Pap. Am. Chem. Soc. 221, U629 (2001) 196. H.M. Luo, J.F. Zhang, Y.S. Yan: Chem. Mater. 15, 3769 (2003) 197. H.M. Luo, L. Sun, Y.F. Lu, Y.S. Yan: Langmuir 20, 10218 (2004) 198. M. Li, H. Schnablegger, S. Mann: Nature 402, 393 (1999) 199. C.L. Cheung, J.A. Camarero, B.W. Woods, T.W. Lin, J.E. Johnson, J.J. De Yoreo: J. Am. Chem. Soc. 125, 6848 (2003) 200. S.J. Choi, S.M. Park: Adv. Mater. 12, 1547 (2000) 201. S. Hoeppener, L.F. Chi, H. Fuchs: Nano Lett. 2, 459 (2002) 202. H. Zhang, R.C. Jin, C.A. Mirkin: Nano Lett. 4, 1493 (2004) 203. M. Toerker, R. Staub, T. Fritz, T. Schmitz-Hubsch, F. Sellam, K. Leo: Surf. Sci. 445, 100 (2000) 204. R. Staub, M. Toerker, T. Fritz, T. Schmitz-Hubsch, F. Sellam, K. Leo: Langmuir 14, 6693 (1998) 205. G.E. Poirier: Langmuir 15, 3018 (1999) 206. G.E. Poirier: Langmuir 15, 1167 (1999) 207. S. Baral, P. Schoen: Chem. Mater. 5, 145 (1993) 208. S.K. Sinha: Ordering in Two Dimensions, (Elsevier North Holland, Amsterdam, 1980) 209. J.H. Fendler: Chem. Mater. 13, 3196 (2001) 210. Y.S. Zhou, B. Wang, S.Q. Xiao, S.Q. Xiao, Y.L. Li, J. G. Hou: Appl. Surf. Sci. 252, 2119 (2006) 211. Y.S. Zhou, B. Wang, M.Z. Zhu, J.G. Hou: Chem. Phys. Lett. 403, 140 (2005) 150 Y. Zhou and B. Wang 212. A.K. Grag, A.K. Tripathi, T.C. Goel, M.M.A. Sekar, C.N. Sukenik: Mater. Sci. Eng. 87, 87 (2001) 213. H. Lin, H. Kozuka, T. Yoko: Thin Solid Films 315, 111 (1998) 214. M. Nagtegaal, P. Stroeve, J. Ensling, P. Gutlich, M. Schurrer, H. Voit, J. Flath, J. Kashammer, W. Knoll, W. Tremel: Chem. Eur. J. 5, 1331 (1999) 215. O. Azzaroni, P.L. Schilardi, R.C. Salvarezza: Appl. Phys. Lett. 80, 1061 (2002) 216. Y. Masuda, W.S. Seo, K. Koumoto: Thin Solid Films 382, 183 (2001) 217. Y.F. Gao, Y. Masuda, T. Yonezawa, K. Koumoto: Chem. Mater. 14, 5006 (2002) 218. H. Zhang, Z. Li, C.A. Mirkin: Adv. Mater. 14, 1472 (2002) 219. J.C. Smith, K.B. Lee, Q. Wang, M.G. Finn, J.E. Johnson, M. Mrksich, C.A. Mirkin: Nano Lett. 3, 883 (2003) 220. X.G. Liu, L. Fu, S.H. Hong, V.P. Dravid, C.A. Mirkin: Adv. Mater. 14, 231 (2002) 221. L.M. Demers, S.J. Park, T.A. Taton, Z. Li, C.A. Mirkin: Angew. Chem. Int. Ed. Engl. 40, 3071 (2001) 222. L.M. Demers, C.A. Mirkin: Angew. Chem. Int. Ed. Engl. 40, 3069 (2001) 223. J. Tien, A. Terfort, G.M. Whitesides: Langmuir 13, 5349 (1997) 224. I.W. Hamley: Angew. Chem. Int. Ed. Engl. 42, 1692 (2003) 225. L.F. Yuan, J.L. Yang, H.Q. Wang, C.G. Zeng, Q.X. Li, B. Wang, J.G. Hou, Q.S. Zhu, D.M. Chen: J. Am. Chem. Soc. 125, 169 (2003) 226. J.G. Hou, J.L. Yang, H.Q. Wang, Q.X. Li, C.G. Zeng, L.F. Yuan, B. Wang, D.M. Chen, Q.S. Zhu: Nature 409, 304 (2001) 227. R.W. Zehner, W.A. Lopes, T.L. Morkved, H. Jaeger, L.R. Sita: Langmuir 14, 241 (1998) 228. T. Lee, N. Yao, I.A. Aksay: Langmuir 13, 3866 (1997) 229. J. Frommer, R. Luthi, E. Meyer, D. Anselmetti, M. Dreier, R. Overney, H.J. Guntherodt, M. Fujihira: Nature 364, 198 (1993) 230. J.Y. Fang, C.M. Knobler: Abstr. Pap. Am. Chem. Soc. 214, 1 (1997) 231. J.Y. Fang, C.M. Knobler: Langmuir 12, 1368 (1996) 232. P. Moraille, A. Badia: Angew. Chem. Int. Ed. Engl. 41, 4303 (2002) 233. M. Brust, D. Bethell, C.J. Kiely, D.J. Schiffrin: Langmuir 14, 5425 (1998) 234. K.V. Sarathy, P.J. Thomas, G.U. Kulkarni, C.N.R. Rao: J. Phys. Chem. B. 103, 399 (1999) 235. S.B. Lei, C. Wang, S.X. Yin, C.L. Bai: J. Phys. Chem. B. 105, 12272 (2001) 236. H. Byrd, S. Whipps, J.K. Pike, D.R. Talham: Abstr. Pap. Am. Chem. Soc. 206, 216 (1993) 237. H. Byrd, J.K. Pike, D.R. Talham: Chem. Mater. 5, 709 (1993)