Room Temperature Growth of Ultrathin Au Nanowires with High Areal

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Room temperature growth of ultrathin Au nanowires with high areal density over large areas by in-situ functionalization of substrate Subhajit Kundu, A Leelavathi, Giridhar Madras, and Narayanan Ravishankar Langmuir, Just Accepted Manuscript • DOI: 10.1021/la502899x • Publication Date (Web): 03 Oct 2014 Downloaded from http://pubs.acs.org on October 5, 2014

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Room temperature growth of ultrathin Au nanowires with high areal density over large areas by in-situ functionalization of substrate Subhajit Kundu,# Annamalai Leelavathi,$ Giridhar Madras$ and N. Ravishankar#,*

#

Materials Research Centre, Indian Institute of Science, C.V. Raman Avenue, Bangalore, India

560012. $

Centre for Nanoscience and Engineering, Indian Institute of Science, C.V. Raman Avenue,

Bangalore, India 560012. KEYWORDS : Au, nanowire, functionalization, catalysis, sensing

ABSTRACT: Although ultrathin Au nanowires (~ 2 nm diameter) are expected to demonstrate several interesting properties, their extreme fragility has hampered their use in potential applications. One way to improve the stability is to grow them on substrates; however there is no general method to grow these wires over large areas. The existing methods suffer from poor coverage and associated formation of larger nanoparticles on the

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substrate. Herein, we demonstrate a room temperature method for growth of these nanowires with high coverage over large areas by in-situ functionalization of the substrate. Using control experiments, we demonstrate that an in-situ functionalization of the substrate is the key step in controlling the areal density of the wires on the substrate. We show that this strategy works for a variety of substrates ranging like graphene, borosil glass, kapton and oxide supports. We present initial results on catalysis using the wires grown on alumina and silica beads and also extend the method to lithography-free device fabrication. This method is general and may be extended to grow ultrathin Au nanowires on a variety of substrates for other applications.

█ INTRODUCTION Ultrathin Au nanowires (~2 nm in diameter)

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are potential candidates for sensing, catalysis,

plasmonic and biological applications.8-17 The chemical stability, biocompatibility and ligand binding ability of gold makes it an ideal candidate for such applications. Despite the wide range of potential applications, practical demonstration of these applications has been very limited5, 1820

due to the inability of the nanowires to withstand rigorous cleaning. Therefore, there is a need

for a general method of obtaining capping-free, robust nanowires on different substrates with high areal density over large areas. A growth method independent of the substrate topography, rigidity and nature/composition would be ideal. Several reports on dense growth of nanowire onto substrate exists21, 22 but the nanowires in those cases are thicker and/or polycrystalline in nature. For some cases, pre-functionalization of the substrate was also required. However there are some reports of growth of single crystalline ultrathin nanowires23-26 but it suffered from poor coverage and associated formation of particles which was an impediment for many applications.


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Also the nanowire growth was by nucleation of Au nanoparticles on the substrate and subsequent growth by the oriented attachment mechanism and hence this protocol was limited to substrates on which nucleation of Au was favorable. Here, we demonstrate a more general, room temperature method for the growth of dense, particle-free ultrathin nanowires over large areas by in-situ amine functionalization of the substrate. We exploit the binding ability of oleylamine on various substrates that plays the crucial role of anchoring nanowires to substrates making the synthetic protocol general. We demonstrate growth of dense nanowires on a range of substrates with different topography, nature of bonding and rigidity/flexibility making the method very powerful for realizing various applications using ultrathin Au nanowires.

█ EXPERIMENTAL SECTION Growth of Au nanowires on substrates. Au nanowire has been grown on different substrates by dipping them in the Au nanowire growth solution. In a typical experiment 6 mg of HAuCl4 was dispersed in 5 ml of n-hexane containing 200 µL of oleylamine (OA) by sonication for about a minute. 300 µL of Triisopropylsilane (TP) was added to it which is the reducing agent5 in this case. Then the substrate was dipped into the solution and the vial was capped. The solution was aged for a day (turns from yellow to purple) at room temperature (26oC - 30 oC). The substrate was taken out and dipped in n-hexane to remove the excess oleylamine and the loose nanowires that might have landed by chance. Then to further clean the nanowires the substrate was dipped in

ethanol,

water

and

acetone

in

the

given

order.

For reducing density of nanowires (for the AFM study), the reaction has been carried out at 30oC for 3 h in a water bath shaker to maintain the desired temperature. Such maintenance of specific temperature is done only to obtain controlled density of nanowires with repeatability.


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Temperature dependent growth was also performed in water bath shaker at a temperature of 30oC and 55oC for 3.5 h each. The glass substrate was placed nearly vertical during the growth to avoid any landing of Au nanoparticles due to settlement. Au nucleation experiment. Au nucleation was tried on bare, OA+TP functionalized and OA functionalized substrates. Functionalization of the substrates was done by dipping the substrates in OA+TP (200 µL + 300 µL) and OA (200 µL) solution of n-hexane (5 ml). It was subsequently cleaned with n-hexane to remove the excess linkers and dried before Au nucleation tests. 5 mg of HAuCl4 and 5 mg of tri-sodium citrate was dissolved in 50 ml of de-ionized water and substrate dipped in it. 1.5 ml of NaBH4 solution ( 5.5 mg in 1.5 ml ) was added to it and kept for few minutes. Then the substrates were washed several times with D.I. water, ethanol, acetone and dried. SEM was done to study Au nucleation. Functionalization experiment. For studying the binding of OA and TP molecules on the substrates deliberate ageing of the substrates in the nanowire growth solution without HAuCl4 has been done. In the first set, the substrates had been dipped in OA+TP (in same amount/ratio as the actual experiment) solution of hexane for 5-6 hours at room temperature. Then the substrate was cleaned with hexane rigorously to get rid of the excess linkers and dried. XPS, contact angle measurement and FTIR of the substrates have been done to check the binding of linkers. In the second set the ageing experiment was repeated without adding TP, everything else remaining same. Contact angle measurement was done.


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In the third set the ageing experiment was done without adding OA, everything else remaining same as that of the first set. Contact angle measurement was done. Characterization. SEM images were obtained using Ultra-55, Zeiss field-emission scanning electron microscope. TEM imaging was done at 200 kV/300 kV using Technai T20/F30. XPS spectra were obtained using AXIS UltraDLD by Kratos Analytical. Bruker and Agilent AFM systems were used for AFM imaging. UV-visible absorbance spectra (for monitoring reduction of 4-nitrophenol) was obtained using Perkin Elmer UV-visible absorbance spectrophotometer. IV measurement for Au nanowire devices was done using Agilent probe station.

█ RESULTS AND DISCUSSION

Figure 1. Electron micrographs showing dense growth of ultrathin nanowires on a variety of substrates; (a) Graphitic carbon paper, (b) graphene, (c) borosil glass, (d) glass slide, (e) kapton


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sheet, (f) PET substrate. Nanowires appear to be thicker in SEM images (a) and (c) - (f) but TEM analysis (b) on graphene grid show that the nanowires are ~2 nm in diameter.

Figure 1 shows dense arrays of Au nanowires grown on different types of carbon, glassy and polymeric substrates. The wires were cleaned with n-hexane, ethanol, water and acetone in the given order. The nanowires could not be dislodged from the substrate by rigorous cleaning indicating that they are tightly anchored with the substrate. Also, these ultrafine nanowires on substrates retain their morphology on cleaning with polar solvents and do not disintegrate into particles. One possible mechanism for the growth of such dense assembly of wires could be by direct nucleation of Au nanoparticles and subsequent growth by oriented attachment of more such particles as was reported earlier.23-26 However, in the present case, an effort to nucleate Au nanoparticles by citrate method shows that Au nucleates very sparsely on the substrates used here (Supporting Information, Figure S2). In literature, it is well known that Au does not nucleate on carbon or glass-based substrates due to their high interfacial energy with Au. Functionalization with oxidizing acid treatment and use of molecular linkers are common approaches to improve Au-wettability and hence allow nucleation27-31. We found that pretreating the substrates with a mixture of OA and TP in n-hexane or just OA in hexane in the same proportion as that used for wire growth leads to a dramatic increase in nucleation of Au nanoparticles grown by citrate method. This indicates that OA plays a key role in the functionalization the substrate and enabling the nucleation of Au on such substrates leading to dense nanowire formation.


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Figure 2. (a) N1s core-level XPS spectra showing two different species of N confirming the role of OA in functionalization. (b) Contact angle of water on bare and functionalized glass slide further confirming the role of OA in functionalization. (c) AFM line scan of hexane cleaned Au nanowire show no dip across the length of the nanowire indicating that the nanowire nucleates and grows on OA bilayer. (d) Histogram of height of the nanowire shows that hexane cleaned nanowires ( hc ) have a height of ~6-7 nm where as additional cleaning with polar solvents ( ac ) removes the OA from above the nanowire leading to a height of ~4-5 nm. Schematic alongside demonstrates the same.


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X-ray Photoelectron Spectroscopy (XPS) survey spectra (Supporting information, Figure S3) of the functionalized (OA+TP) carbon and polymer based substrates do not show any prominent peak around 100 eV corresponding to Si indicating that Si has negligible role (if any) in functionalization. The presence of peak around 400 eV (with slight variations depending on the substrate) for N1s confirms the role OA in functionalization of substrates. High resolution scans around the N1s peak (Figure-2a and supporting information, Figure S4) show the presence of two different types of N, possibly due to the presence of free amine and amine bound to substrate due to formation of OA bilayer. Such OA bilayer formation is common under similar synthesis conditions.26, 32 The peak due to free amine (higher intensity peak) is observed around 399 eV 33 for slide, borosil and PET whereas it is slightly shifted towards high binding energy for the case of graphitic carbon. This is possibly due to the strong interaction between the hydrogen atoms of the neighboring OA molecules due to dense coverage. The peak for bound amine is observed around 402 eV for graphitic carbon, slide, borosil that indicates that the moieties bind to more electropositive neighbors like carbon in graphitic carbon and silicon in the glass-based substrates. However, for the case of PET that has oxygen terminated end groups, the peak shifts to lower binding energy due to its vicinity to a higher electronegative entity. The XPS survey spectra (Supporting Information, Figure S5) of the nanowires grown on various substrates and cleaned with hexane and then polar solvents (ethanol, water, acetone) show the presence of significant amount of N due to OA. Presence of N1s peak even after polar solvent cleaning indicates that the excess OA lies underneath the nanowires.26 High-resolution scan around the Au4f peak (Supporting Information, Figure-S6) shows the presence of Au+1 peak along with Au0 peak due to OA binding.


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To further confirm the role of OA in functionalization, contact angle measurement has been carried out. Glass slide has been chosen for this study as it is hydrophilic and therefore would show a prominent change on surface modification with hydrophobic OA molecules. Figure 2b shows the contact angle of water on bare and functionalized glass slide. Photograph of a 3 µL water droplet drop casted by a syringe on glass slide is also shown along side for each case. Bare and TP functionalized glass shows a contact angle of around 30o whereas OA and OA/TP functionalized glass shows a contact angle around 50o-60o that indicates that OA plays the key role in functionalization. FTIR study of the OA/TP functionalized glass also points towards the same (Supporting Information, Figure-S7). We have carried out detailed AFM studies of nanowires grown on C-based substrates that were subsequently cleaned using hexane (Au nw-hc). AFM line scans (Figure 2c) along individual nanowires show a nearly uniform height for the wires grown on the substrate. This is contrast to earlier studies on wires grown at higher temperatures (~ 90oC) 26 where there were depressions in the heights of the wire at the points where the particle nucleation took place directly on the substrate. Since the height of the wires from the substrate is remarkably uniform in the present case, we conclude that there is no direct nucleation of Au particles on the substrate. The histogram for the height of the nanowires (Figure 2d) show a major peak around 6-7 nm which is probably due to the combined heights of the wires and the amine bilayers below and above the wire. A small peak around 2-3 nm is due to amine bilayer binding to the substrate without any Au on it. Polar solvent cleaning (Au nw-ac) leads to the removal of the amine layer from above the wire resulting in consequent reduction of the height to ~ 4 nm as indicated by the histogram. This is also visually evident from the AFM 3D plots (Supporting Information, Figure S8) which show a spiky topography for the sample cleaned with hexane Au due to the presence of OA


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above the nanowires. However, the polar solvent cleaned wires show a very smooth topography due to the removal of this top layer of amine from the wire surface.

Figure 3. (a) & (b) show Au nanowire grown on near-vertically placed glass slide at 30ºC and 55ºC respectively. (c) Schematic showing that temperature plays a crucial role in in-situ functionalization. At low temperature the OA binding density is high and hence dense nanowires form and vice versa.

An increased nucleation density due to in-situ functionalization of the substrate is the main reason for such dense growth of nanowires on various substrates. We have investigated the role of temperature on the nucleation and growth of the wires. We observe that at low temperature (30oC), the density of nanowires is high but at higher temperature (55oC), it becomes sparse


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(Figure 3a, b). It is known that static binding of ligand with high density is extremely favorable at low temperatures.34 Therefore at low temperature (30oC), high areal density of linkers causes dense Au nanowire formation whereas at higher temperature (55oC), the areal density of linkers becomes poor leading to poor nanowire density. Hence, we conclude that the key difference between the earlier literature reports23-26 and this study is in the temperature of wire growth. Higher temperatures (~90oC) may completely unbind the oleyamine and hence the growth may happen by direct nucleation on the substrate as reported.23-26


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Figure 4. (a), (b) SEM images of Au nanowire grown on alumina and silica beads respectively. Very low magnification SEM image in inset shows the size of the beads for each case. (c) Degradation of 4-nitrophenol with Au nw-alumina catalyst has been shown for different temperatures. Inset shows the activation energy plot. (d) shows the I-V plot for a typical lithography-free Au nanowire device on flexible sheets of kapton. Device photographs have been shown along side.


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Understanding the criterion of dense nanowire growth enabled the extension of the method to grow nanowires on micrometer sized alumina and silica beads (Figure-4a,b). Growth of these otherwise hydrophobic nanowires (due to oleylamine capping when in solution) on hydrophilic support enabled transfer of nanowires to water that extends its utility in various aqueous phase catalysis and biological applications. The growth of nanowires on micrometer-sized support also has the distinct advantage of efficient recovery and hence reusability and the potential for catalysis. We demonstrate the reduction of 4-nitrophenol (4-np) to 4-aminophenol with Au nanowires grown alumina beads (Al2O3-Au nw). The concentration decay for nitrophenolate ion (nph) as a function of time at various temperatures is shown in Figure 4c. The apparent reaction rate coefficient (kapp, min-1) was calculated from the slope of ln(C/C0) with time (Figure 4c) where C is the concentration at a particular time and C0 is the initial concentration. For a similar initial 4-np concentration of 10-4 M, the apparent rate constant of reduction was 0.528 min-1 at 26ºC, which is higher than that reported in the literature35 but comparable to other studies.36-38 The variation of this rate coefficient with temperature is plotted as Arrhenius plot (inset of Figure 4c) and the activation energy determined from the slope of this plot is 18 ± 1.4 kJ/mol, which is lower than the activation energy reported in literature.37, 39-41 In order to determine the surface area of the nanowires in the solution, we have modeled the reaction using the equilibrium and rate parameters, as discussed by Ballauff and co-workers,39, 42, 43 where

kapp =

ka S K

Nip

[1 + ( K

n (c

Nip

)n −1 K

c BH 4 BH 4

2 n+K c ] ) Nip Nip BH 4 BH 4

c


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Based on this, a surface area of 1 m2/L was found. This value is comparable to that reported Pd studies.39, 44, 45 Further, ICP-MS analysis suggests that the amount of Au used in the experiment (Au present on 11 mg of alumina beads) in this study is 2.28 µg which is significantly lesser compared to literature report40. Such high activity with nominal amount of Au may be due to extremely fine diameter and exposed high indexed facets46 which has been reported to greatly influence the catalytic activity. It has been shown that growth of ultrafine Au nanowires between pre-defined Au contact pads enables fabrication of device without any problem of contact resistance.24-26 But contact pads separated by few 100 nm could only be bridged by the existing technique. Even with such small spacing between contact pads, the chance of success in device making was poor as the density of nanowire was low. Associated formation of particles further reduced the success rate. Enhanced growth density of nanowires not only enhances the success rate of device fabrication but also enables device making without use of any lithographic technique. Au nanowires grown on flexible kapton sheet could be grown to span across sputtered Au contact pads 0.3 mm apart. The I-V of the device shows a linear response in the voltage range of study as shown in Figure 4d. Inset shows the digital photograph of such a device. Fabrication of more such devices show that even ~1 mm separated contact pads could be bridged consistently. Resistance of some of the devices have been tabulated in supporting information, table S2.


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█ CONCLUSION

In summary, this study reports growth of dense, particle-free ultrafine Au nanowires on various support materials. A new mechanism of anchoring nanowire to substrate at room temperature based on in-situ functionalization of the substrate has been elucidated. High density of nanowire on alumina beads has opened possibility for catalytic applications as shown for the case of reduction of 4-nitrophenol to 4-aminophenol. Lithography free device fabrication on flexible substrate (kapton) has been demonstrated which has potential application in strain sensing, chemical sensing and biomolecule sensing. Direct growth on graphitic carbon electrode has potential for electrochemical sensing and energy harvesting. More importantly, the strategy of in-situ functionalization may be exploited to grow other nanostructures including nanowires on various other substrates for applications.

ASSOCIATED CONTENT AUTHOR INFORMATION Corresponding Author •

Fax: +91 08023607316. Tel: +91 08022933255. E-mail: [email protected].

ACKNOWLEDGMENT The authors acknowledge Department of Science and Technology (DST) for funding. SEM, XPS and Probe station are part of characterization facility in Centre for Nanoscience and Engineering


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(CENSE). SK and NR acknowledge Sindhu and Professor Praveen Ramamurthy for their help with contact angle measurement. Supporting Information. Low magnification SEM images showing Au nanowire over large area and Au nanoparticle nucleation density, XPS spectra, FTIR data, AFM 3D plots, catalysis and device fabrication details. This material is available free of charge via the Internet at http://pubs.acs.org.

ABBREVIATIONS OA, oleylamine; TP, triisopropylsilane; 4-np, 4-nitrophenol. REFERENCES 1. 2.

3. 4.

5.

6.

7.

8.

9. 10.

Halder, A.; Ravishankar, N., Ultrafine Single-Crystalline Gold Nanowire Arrays by Oriented Attachment. Adv. Mater. 2007, 19, (14), 1854-1858. Lu, X.; Yavuz, M. S.; Tuan, H.-Y.; Korgel, B. A.; Xia, Y., Ultrathin Gold Nanowires Can Be Obtained by Reducing Polymeric Strands of Oleylamine-AuCl Complexes Formed via Aurophilic Interaction. J. Am. Chem. Soc. 2008, 130, (28), 8900-8901. Huo, Z.; Tsung, C.-k.; Huang, W.; Zhang, X.; Yang, P., Sub-Two Nanometer Single Crystal Au Nanowires. Nano Lett. 2008, 8, (7), 2041-2044. Pazos-Pérez, N.; Baranov, D.; Irsen, S.; Hilgendorff, M.; Liz-Marzán, L. M.; Giersig, M., Synthesis of Flexible, Ultrathin Gold Nanowires in Organic Media. Langmuir 2008, 24, (17), 9855-9860. Feng, H.; Yang, Y.; You, Y.; Li, G.; Guo, J.; Yu, T.; Shen, Z.; Wu, T.; Xing, B., Simple and rapid synthesis of ultrathin gold nanowires, their self-assembly and application in surface-enhanced Raman scattering. Chem. Commun. 2009, 15, 1984-1986. Morita, C.; Tanuma, H.; Kawai, C.; Ito, Y.; Imura, Y.; Kawai, T., Room-Temperature Synthesis of Two-Dimensional Ultrathin Gold Nanowire Parallel Array with Tunable Spacing. Langmuir 2013, 29, (5), 1669-1675. Roy, A.; Kundu, S.; Müller, K.; Rosenauer, A.; Singh, S.; Pant, P.; Gururajan, M. P.; Kumar, P.; Weissmüller, J.; Singh, A. K.; Ravishankar, N., Wrinkling of Atomic Planes in Ultrathin Au Nanowires. Nano Lett. 2014, 14, (8), 4859-4866. Zhang, X.; Li, D.; Bourgeois, L.; Wang, H.; Webley, P. A., Direct Electrodeposition of Porous Gold Nanowire Arrays for Biosensing Applications. ChemPhysChem 2009, 10, (2), 436-441. Zanolli, Z.; Leghrib, R.; Felten, A.; Pireaux, J.-J.; Llobet, E.; Charlier, J.-C., Gas Sensing with Au-Decorated Carbon Nanotubes. ACS Nano 2011, 5, (6), 4592-4599. Haruta, M., Catalysis: Gold rush. Nature 2005, 437, (7062), 1098-1099.


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24.

25.

Hughes, M. D.; Xu, Y.-J.; Jenkins, P.; McMorn, P.; Landon, P.; Enache, D. I.; Carley, A. F.; Attard, G. A.; Hutchings, G. J.; King, F.; Stitt, E. H.; Johnston, P.; Griffin, K.; Kiely, C. J., Tunable gold catalysts for selective hydrocarbon oxidation under mild conditions. Nature 2005, 437, (7062), 1132-1135. Lu, Y.; Tu, J.-p.; Gu, C.-d.; Xia, X.-h.; Wang, X.-l.; Mao, S. X., Growth of and methanol electro-oxidation by gold nanowires with high density stacking faults. J. Mater. Chem. 2011, 21, (13), 4843-4849. Hashmi, A. S. K.; Hutchings, G. J., Gold Catalysis. Angew. Chem. Int. Ed. 2006, 45, (47), 7896-7936. Wang, T.; Hu, X.; Wang, J.; Dong, S., Surface-enhanced Raman scattering from surfactant-free 3D gold nanowire networks substrates. Talanta 2008, 75, (2), 455-460. Fabris, L.; D.S. Indrasekara, A. S.; Meyers, S.; Shubeita, S.; Feldman, L. C.; Gustafsson, T., Gold Nanostar Substrates for SERS-based Chemical Sensing in the Femtomolar Regime. Nanoscale 2014, 6, (15) 8891-8899. Alkilany, A. M.; Thompson, L. B.; Boulos, S. P.; Sisco, P. N.; Murphy, C. J., Gold nanorods: Their potential for photothermal therapeutics and drug delivery, tempered by the complexity of their biological interactions. Adv. Drug Delivery Rev. 2011, 64, (2), 190199. Giljohann, D. A.; Seferos, D. S.; Daniel, W. L.; Massich, M. D.; Patel, P. C.; Mirkin, C. A., Gold Nanoparticles for Biology and Medicine. Angew. Chem. Int. Ed. 2010, 49, (19), 3280-3294. Sánchez-Iglesias, A.; Rivas-Murias, B.; Grzelczak, M.; Pérez-Juste, J.; Liz-Marzán, L. M.; Rivadulla, F.; Correa-Duarte, M. A., Highly Transparent and Conductive Films of Densely Aligned Ultrathin Au Nanowire Monolayers. Nano Lett. 2012, 12, (12), 6066-6070. Chen, Y.; Ouyang, Z.; Gu, M.; Cheng, W., Mechanically Strong, Optically Transparent, Giant Metal Superlattice Nanomembranes From Ultrathin Gold Nanowires. Adv. Mater. 2013, 25, (1), 80-85. Kisner, A.; Heggen, M.; Mayer, D.; Simon, U.; Offenhausser, A.; Mourzina, Y., Probing the effect of surface chemistry on the electrical properties of ultrathin gold nanowire sensors. Nanoscale 2014, 6, (10), 5146-5155. He, J.; Wang, Y.; Feng, Y.; Qi, X.; Zeng, Z.; Liu, Q.; Teo, W. S.; Gan, C. L.; Zhang, H.; Chen, H., Forest of Gold Nanowires: A New Type of Nanocrystal Growth. ACS Nano 2013, 7, (3), 2733-2740. Chen, Y.-L.; Lee, C.-Y.; Chiu, H.-T., Growth of gold nanowires on flexible substrate for highly sensitive biosensing: detection of thrombin as an example. J. Mater. Chem. B. 2013, 1, (2), 186-193. Kundu, P.; Halder, A.; Viswanath, B.; Kundu, D.; Ramanath, G.; Ravishankar, N., Nanoscale Heterostructures with Molecular-Scale Single-Crystal Metal Wires. J. Am. Chem. Soc. 2010, 132, (1), 20-21. Kundu, P.; Chandni, U.; Ghosh, A.; Ravishankar, N., Pristine, adherent ultrathin gold nanowires on substrates and between pre-defined contacts via a wet chemical route. Nanoscale 2012, 4, (2), 433-437. Chandni, U.; Kundu, P.; Singh, A. K.; Ravishankar, N.; Ghosh, A., Insulating State and Breakdown of Fermi Liquid Description in Molecular-Scale Single-Crystalline Wires of Gold. ACS Nano 2011, 5, (10), 8398-8403.


17

Langmuir

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

26. 27.

28.

29.

30.

31.

32.

33.

34.

35.

36. 37. 38.

39.

40.

41.

Page 18 of 20

Chandni, U.; Kundu, P.; Kundu, S.; Ravishankar, N.; Ghosh, A., Tunability of Electronic States in Ultrathin Gold Nanowires. Adv. Mater. 2013, 25, (17), 2486-2491. Georgakilas, V.; Gournis, D.; Tzitzios, V.; Pasquato, L.; Guldi, D. M.; Prato, M., Decorating carbon nanotubes with metal or semiconductor nanoparticles. J. Mater. Chem. 2007, 17, (26), 2679-2694. Zanella, R.; Basiuk, E. V.; Santiago, P.; Basiuk, V. A.; Mireles, E.; Puente-Lee, I. n.; Saniger, J. M., Deposition of Gold Nanoparticles onto Thiol-Functionalized Multiwalled Carbon Nanotubes. J. Phys. Chem. B. 2005, 109, (34), 16290-16295. Maria Claesson, E.; Philipse, A. P., Thiol-functionalized silica colloids, grains, and membranes for irreversible adsorption of metal(oxide) nanoparticles. Colloids Surf. A 2007, 297, (1-3), 46-54. Phonthammachai, N.; Kah, J. C. Y.; Jun, G.; Sheppard, C. J. R.; Olivo, M. C.; Mhaisalkar, S. G.; White, T. J., Synthesis of Contiguous Silica-Gold Core-Shell Structures: Critical Parameters and Processes. Langmuir 2008, 24, (9), 5109-5112. Pham, T.; Jackson, J. B.; Halas, N. J.; Lee, T. R., Preparation and Characterization of Gold Nanoshells Coated with Self-Assembled Monolayers. Langmuir 2002, 18, (12), 49154920. Borges, J. o.; Ribeiro, J. A.; Pereira, E. M.; Carreira, C. t. A.; Pereira, C. M.; Silva, F., Preparation and characterization of DNA films using oleylamine modified Au surfaces. J. Coll. Inter. Sci. 2011, 358, (2), 626-634. Loubat, A.; Impéror-Clerc, M.; Pansu, B.; Meneau, F.; Raquet, B.; Viau, G.; Lacroix, L.M., Growth and Self-Assembly of Ultrathin Au Nanowires into Expanded Hexagonal Superlattice Studied by in Situ SAXS. Langmuir 2014, 30, (14), 4005-4012. Menagen, G.; Macdonald, J. E.; Shemesh, Y.; Popov, I.; Banin, U., Au Growth on Semiconductor Nanorods: Photoinduced versus Thermal Growth Mechanisms. J. Am. Chem. Soc. 2009, 131, (47), 17406-17411. Choi, Y.; Bae, H. S.; Seo, E.; Jang, S.; Park, K. H.; Kim, B.-S., Hybrid gold nanoparticlereduced graphene oxide nanosheets as active catalysts for highly efficient reduction of nitroarenes. J. Mater. Chem. 2011, 21, (39), 15431-15436. Kuroda, K.; Ishida, T.; Haruta, M., Reduction of 4-nitrophenol to 4-aminophenol over Au nanoparticles deposited on PMMA. J. Molecular Catal. A 2009, 298, (1-2), 7-11. Zeng, J.; Zhang, Q.; Chen, J.; Xia, Y., A Comparison Study of the Catalytic Properties of Au-Based Nanocages, Nanoboxes, and Nanoparticles. Nano Lett. 2009, 10, (1), 30-35. Hayakawa, K.; Yoshimura, T.; Esumi, K., Preparation of Gold-Dendrimer Nanocomposites by Laser Irradiation and Their Catalytic Reduction of 4-Nitrophenol. Langmuir 2003, 19, (13), 5517-5521. Wunder, S.; Lu, Y.; Albrecht, M.; Ballauff, M., Catalytic Activity of Faceted Gold Nanoparticles Studied by a Model Reaction: Evidence for Substrate-Induced Surface Restructuring. ACS Catal. 2011, 1, (8), 908-916. Panigrahi, S.; Basu, S.; Praharaj, S.; Pande, S.; Jana, S.; Pal, A.; Ghosh, S. K.; Pal, T., Synthesis and Size-Selective Catalysis by Supported Gold Nanoparticles: Study on Heterogeneous and Homogeneous Catalytic Process. J. Phys. Chem. C. 2007, 111, (12), 4596-4605. Fenger, R.; Fertitta, E.; Kirmse, H.; Thunemann, A. F.; Rademann, K., Size dependent catalysis with CTAB-stabilized gold nanoparticles. Phys. Chem. Chem. Phys. 2012, 14, (26), 9343-9349.


18

Page 19 of 20

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Langmuir

42.

43.

44.

45.

46.

Gu, S.; Wunder, S.; Lu, Y.; Ballauff, M.; Fenger, R.; Rademann, K.; Jaquet, B.; Zaccone, A., Kinetic Analysis of the Catalytic Reduction of 4-Nitrophenol by Metallic Nanoparticles. J. Phys. Chem. C. 2014, 118, (32), 18618-18625. Wunder, S.; Polzer, F.; Lu, Y.; Mei, Y.; Ballauff, M., Kinetic Analysis of Catalytic Reduction of 4-Nitrophenol by Metallic Nanoparticles Immobilized in Spherical Polyelectrolyte Brushes. J. Phys. Chem. C. 2010, 114, (19), 8814-8820. Esumi, K.; Isono, R.; Yoshimura, T., Preparation of PAMAM- and PPI-Metal (Silver, Platinum, and Palladium) Nanocomposites and Their Catalytic Activities for Reduction of 4-Nitrophenol. Langmuir 2003, 20, (1), 237-243. Mei, Y.; Sharma, G.; Lu, Y.; Ballauff, M.; Drechsler, M.; Irrgang, T.; Kempe, R., High Catalytic Activity of Platinum Nanoparticles Immobilized on Spherical Polyelectrolyte Brushes. Langmuir 2005, 21, (26), 12229-12234. Chirea, M.; Freitas, A.; Vasile, B. S.; Ghitulica, C.; Pereira, C. M.; Silva, F., Gold Nanowire Networks: Synthesis, Characterization, and Catalytic Activity. Langmuir 2011, 27, (7), 3906-3913.


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TOC Figure


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Room Temperature Growth of Ultrathin Au Nanowires with High Areal

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