We gratefully acknowledge the financial support from National Natural Science Foundation of China (21703104), Jiangsu Science and Technology Plan (SBK2017041514) Nanjing Tech University (39837131), and SICAM Fellowship from Jiangsu National Synergetic Innovation Center for Advanced Materials.

Caution: Please check the material safety data sheets (MSDS) of the chemicals for detailed handling and storage instruction. Please be careful while handling the nanomaterials, as there may be unidentified risk. Please perform the experiments in a fume hood and wear appropriate personal protective equipment.
1. Synthesis of Seed Nanoparticles
Note: To avoid failure caused by the premature nucleation during the nanoparticle synthesis, wash the glassware and stir bar us...

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The mechanism of this active surface growth governed nanowire synthesis has been discussed comprehensively in previous work19. In addition, the effects of seed sizes and types as well as the effect of ligand types and sizes have also been investigated20,21. Generally. the nanowire growth is very different from previous reported routes. No template is required, and the asymmetric growth is induced by the differences between the ligand-cappe...

Typical of one dimensional nanomaterials, nanowires possess both the bulk-related properties and the unique properties originated from the quantum effects of the nanoscale structure. As a bridge between the nanoscale and the bulk scale materials, they have been widely applied in various fields of catalysis, sensing, and nanoelectronic devices, etc.1,2,3.
However, the synthesis of nanowires has long been a great challenge, as it usually requires breaking the intrinsic symmetry in the crystals. Traditionally, a template is employed to regulate the deposition of materials. For instance, template-electrodeposition has been used for the formation of various types of nanowires like Ag nanowires and CdS nanowires4,5,6,7,8,9,10. Another common approach is vapor-liquid-solid (VLS) growth, which employs a molten catalyst to induce the anisotropic growth on the substrate at an elevated temperature11. Common strategies for the synthesis of metal nanowires are the polyol methods for Ag nanowires and the oleylamine-assisted ultrathin Au nanowires12,13,14,15. Both approaches are material-specific, and the nanowire parameters are not readily tuned during the synthesis. In addition, metal nanowires can also be formed by the pressure-driven method, where the assembled metal nanoparticles are mechanically compressed and fused into nanowires16,17,18.
Recently, we reported a distinctive method to synthesis Au nanowires19. With the assist of a thiolated small molecule ligand, the nanowires could grow and form a vertically aligned array on the bulk Si wafer substrate at ambient conditions. It was found that the ligands play an important role in the symmetry-breaking growth. It binds to the surface of the substrate-adsorbed Au seeds strongly, forcing the Au to deposit selectively at the ligand-deficient interface between seeds and substrate. The interface between the newly deposited Au and the substrate remains ligand deficient, therefore, the active surface exists throughout the whole growth. By tuning the ligand concentration, the seed type and concentration as well as several other parameters, a series of Au nanowire-based nanostructures could be synthesized.
In this work, we will provide a detailed protocol for this convenient Au nanowires synthesis. The derived synthesis is also presented, including the synthesis of Au nanowires with hydrophobic surface property, Au nanowires on other substrates, tapered Au nanowires by mixing two ligands and the nanowire-based Au nanostructures formed by tuning the growth conditions.

<table border="0" cellpadding="0" cellspacing="0" width="846">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Trisodium citrate dihydrate</td>
			<td style="width:209px;">Alfa Aesar</td>
			<td style="width:179px;">LoT: 5008F14U</td>
			<td style="width:203px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium borohydride</td>
			<td style="width:209px;">Fluka</td>
			<td style="width:179px;">LoT: STBG0330V</td>
			<td>NaBH4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hydrogen tetrachloroaurate(III) trihydrate</td>
			<td style="width:209px;">Alfa Aesar</td>
			<td style="width:179px;">LoT: T19C006</td>
			<td style="width:203px;">HAuCl4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-aminopropyltriethoxysilane</td>
			<td style="width:209px;">J&#38;K Scientific</td>
			<td style="width:179px;">LoT: LT20Q102</td>
			<td style="width:203px;">APTES</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">L-ascorbic acid&#160;</td>
			<td>Sigma-Aldrich</td>
			<td style="width:179px;">LoT: SLBL9227V</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-mercaptobenzoic acid</td>
			<td>Sigma-Aldrich</td>
			<td style="width:179px;">LoT: MKBV5048V</td>
			<td style="width:203px;">4-MBA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">2-Naphthalenethiol</td>
			<td>Sigma-Aldrich</td>
			<td style="width:179px;">LoT: BCBP4238V</td>
			<td>2-NpSH</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">4-Mercaptophenylacetic acid</td>
			<td style="width:209px;">Alfa Aesar</td>
			<td style="width:179px;">LoT: 10199160</td>
			<td>4-MPAA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-mercaptobenzoic acid</td>
			<td style="width:209px;">Aladdin</td>
			<td style="width:179px;">LoT: G1213027</td>
			<td>3-MBA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3-Mercaptopropionic acid</td>
			<td style="width:209px;">Aladdin</td>
			<td style="width:179px;">LoT: E1618095</td>
			<td>3-MPA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">absolute ethanol</td>
			<td style="width:209px;">Sinopharm chemical Reagent</td>
			<td style="width:179px;">20170802</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Silicon wafer</td>
			<td style="width:209px;">Zhe Jiang lijing</td>
			<td style="width:179px;">P</td>
			<td>Si</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scanning Electron Microscope</td>
			<td style="width:209px;">Quanta FEG 250</td>
			<td style="width:179px;"></td>
			<td>SEM</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge&#160;</td>
			<td style="width:209px;">Eppendorf</td>
			<td style="width:179px;">5424</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic cleaner&#160;</td>
			<td style="width:209px;">Kun Shan hechuang</td>
			<td style="width:179px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Ultra-pure water system</td>
			<td style="width:209px;">NanJing qianyan</td>
			<td style="width:179px;">UP6682-10-11</td>
			<td>for deionized water</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:256px;">Plasma cleaner</td>
			<td style="width:209px;">Harrick Plasma</td>
			<td style="width:179px;">PDC-002</td>
			<td>for oxygen plasma</td>
		</tr>
	</tbody>
</table>

synthesis of substrate-bound au nanowires via an active surface growth mechanism

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a challenge, as it requires asymmetric growth of symmetric crystals. Here, we report a distinctive synthesis of substrate-bound Au nanowires. This template-free synthesis employs thiolated ligands and substrate adsorption to achieve the continuous asymmetric deposition of Au in solution at ambient conditions. The thiolated ligand prevented the Au deposition on the exposed surface of the seeds, so the Au deposition only occurs at the interface between the Au seeds and the substrate. The side of the newly deposited Au nanowires is immediately covered with the thiolated ligand, while the bottom facing the substrate remains ligand-free and active for the next round of Au deposition. We further demonstrate that this Au nanowire growth can be induced on various substrates, and different thiolated ligands can be used to regulate the surface chemistry of the nanowires. The diameter of the nanowires can also be controlled with mixed ligands, in which another &#34;bad&#34; ligand could turn on the lateral growth. With the understanding of the mechanism, Au nanowire-based nanostructures can be designed and synthesized.

The Au nanoparticle seeds, substrate-bound Au nanowires and Au nanowire-based derivative nanostructures are characterized with SEM. Figure 1 shows the representative SEM images of the 3-5 nm Au nanoparticles, 15 nm Au Nanoparticles and 40 nm Au nanoparticles adsorbed on the Si wafer, confirming their sizes, adsorption and distribution. The Au nanowires grown from the respective seeds on the Si wafer substrate are also presented. The representative SEM images ...

Watch this Scientific Journal Video about Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism at JoVE.com

Synthesis of Substrate-Bound Au Nanowires Via an Active Surface Growth Mechanism

We report a solution-based method to synthesize substrate-bound Au nanowires. By tuning the molecular ligands used during the synthesis, the Au nanowires can be grown from various substrates with different surface properties. Au nanowire-based nanostructures can also be synthesized by adjusting the reaction parameters.

Advancing synthetic capabilities is important for the development of nanoscience and nanotechnology. The synthesis of nanowires has always been a ...

This time I introduce using for generating one-dimensional nanostructure. The main advantage of this technique is that you can trace nano-wire, a long temperature under mild conditions with simple wet chemistry operations. First in a four-milliliter vial, dissolve 10 milligrams of hydrogen tetrachloroauric trihydrate in one milliliter of deionized water.By PET 0.197 milliliters of this 2.5 millimolar chloroauric acid stock solution into a 50-milliliter round bottom flask equipped with a stir bar. Add 19.7 milliliters of deionized water to the flask and stir to obtain a 0.025-millimolar chloroauric acid solution. Then in another four-milliliter vial, dissolve 10 milligrams of trisodium citrate dihydrate in one milliliter of deionized water.Add 0.147 milliliters of this 0.1-gram-per-milliliter sodium citrate stock solution to the diluted chloroauric acid solution while stirring. Next in a third four-milliliter vial dissolve 2.3 milligrams of sodium borohydride and 0.6 milliliters of deionized water to obtain a 0.1-molar solution which should be used within a few minutes. Ensure that the pale yellow reaction mixture is stirring vigorously.Quickly pipette the sodium borohydride solution into the vigorously stirring mixture which will immediately become bright orange. Continue stirring the mixture for 10 minutes to obtain the gold nanoparticles as indicated by a gradual color change to reddish-orange. The nano articles can be stored for up to a week.To synthesize gold nanowires, first cut a five-milliliter-by-five-milliliter piece from a 0.5 milliliter-thick silicon wafer. Sonicate this substrate for 15 minutes each in deionized water and ethanol in sequence. Wipe off the clean substrate and allow it to dry in air.Then treat the substrate with oxygen plasma at 29.6 watts and 220 volts for 20 minutes. During the plasma treatment, in a 20-milliliter vial, dissolve 11.1 milligrams of APTES in 10 milliliters of a one-to-one by volume mixture of deionized water and ethanol to obtain a 5-millimolar solution. When the plasma treatment has finished, soak the substrate in the APTES solution for 30 minutes.Then thoroughly rinse the substrate with about 20 milliliters each of ethanol and deionized water in sequence. Soak the substrate in the gold nanoparticle solution for two hours to allow the seed nanoparticles to absorb onto its surface. Then prepare 10 milliliters each of a 1.65-millimolar solution of 4-MBA and ethanol.Add 5.10 millimolars solution of chloroauric acid in a one-to-one mixture of deionized water and ethanol Add a 12.3 millimolar solution of L-ascorbic acid in deionized water. Combine 0.5 milliliters each of the chloroauric acid solution and the 4-MBA solution in a 10-milliliter vial. Shake the vial to mix the solutions.Next pick up the seeded substrate with tweezers and wash it with 20 milliliters of deionized water to remove unabsorbed gold nanoparticles. Immerse the seeded substrate in the mixture of chloroauric acid in 4-MBA. Then add 0.5 milliliters of the ascorbic acid solution to the mixture.Gently shake the vial to evenly mix the solutions. Leave the substrate soaking in the mixture undisturbed for 15 minutes. The air ascorbic acid must be added after the mixing of 4-MBA and chloroauric acid otherwise it will cause immediate homogeneous nucleation and the nanowires will not grow.Monitor the formation of bubbles during the growth process. The substrate surface will change from shiny gray to reddish-brown in appearance. Then remove the substrate from the mixture and rinse it with ethanol and deionized water.Allow it to air dry afterwards. The substrate surface will become a golden appearance as it dries. To synthesize gold nanowires with alternating segments of different thicknesses, first seed gold nanoparticles on a silicon substrate as previously described.Also prepare 10 milliliters each of a 1.65-millimolar 4-MBA solution, a 5.10-millimolar chloroauric acid solution, and a 12.3-millimolar ascorbic acid solution as previously described. Then dilute 0.1 milliliters of the 1.6-millimolar 4-MBA solution, 20-fold with ethanol to make two milliliters of a 0.083-millimolar 4-MBA solution. In a 10-milliliter vial, combine 0.5 milliliters each of the 1.65-millimolar solution of 4-MBA, the chloroauric acid solution and the ascorbic solution.Vortex the mixture to form growth solution A.In another 10-milliliter vial, combine 0.5 milliliters each of the 0.083-millimolar solution of 4-MBA, the chloroauric acid, and the ascorbic acid solution. Vortex the mixture to obtain growth solution B.Soak the gold nanoparticle seeded substrate and growth solution B for about one minute. Rapidly transfer the substrate to the container of growth solution A and allow it to soak for two minutes.Repeat the soaking sequence once being careful not to let the substrate dry as it is moved between vials. Finally rinse the substrate with 50 milliliters of ethanol and 50 milliliters of deionized water. Gold nanoparticle with diameters of three to five nanometers, 15 nanometers, and 40 nanometers were all successfully seeded on silicon wafer substrates.Substrate-bound gold nanowires were then grown from these seeds with 4-MBA as the ligand. Gold nanowires were also successfully grown on alumina, strontium titanate, lanthanum aluminate, glass, indium tin oxide, and fluorine-doped tin oxide surfaces. Nanowires with alternating thick-thin segments were grown by alternately immersing the substrate in growth solutions with different ligand concentrations.And nanoflowers were grown by quickly drying the growth solution on the silicon substrate. The nanowire structures could also be changed by varying the ligand. Using 4-MPAA, 2-naphthalenethiol, or 3-MBA as the ligand, yielded ultra-thin nanowires arrays.Using mixtures of 4-MBA and 3-MBA in various proportions yielded tapered nanowires. After watching this video, you should have a good understanding of how to grow growth nanowires from a foreign substrate with at the surface growth mechanism.

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Chemistry

7.6K vistas.  Nanjing Tech University. This time I introduce using for generating one-dimensional nanostructure. The main advantage of this technique is that you can trace nano-wire, a long temperature under mild conditions with simple wet chemistry operations. First in a four-milliliter vial, dissolve 10 milligrams of hydrogen tetrachloroauric trihydrate in one milliliter of deionized water.By PET 0.197 milliliters of this 2.5 millimolar chloroauric acid stock solution into a 50-milliliter round bottom flask equipped with ...