This work was supported by the Ministry of Science and Technology, Taiwan, under contract numbers MOST 105-2221-E-492-003-MY2 and MOST 107-2622-E-239-002-CC3.

1.&#160;Sample preparation
<ol>
	<li>TiN substrate preparation using a high-power impulse magnetron sputtering system
	<ol>
		<li>Cut a 4 inch n-type silicon wafer into 2 cm x 2 cm samples.</li>
		<li>Wash the samples using acetone, isopropanol, and deionized water.</li>
		<li>Dry them using an N2 spray for 5 min.</li>
		<li>Place the washed Si samples in a sample holder and place the sample holder into a high-power impulse magnetron sputtering (HiPIMS) chamber.</li>
		<li>Place a titanium target with a diameter of 4 inches on a sputtering cathode.</li>
		<li>Reduce the chamber pressure to less than 8 x 10-6 Torr by using a mechanical pump and cryopump.</li>
		<li>Use HiPIMS to deposit a Ti layer on a silicon wafer and deposit a TiN layer on the Ti layer. See Table 1 for the deposition parameters of Ti and TiN layers in HiPIMS.</li>
	</ol>
	</li>
	<li>Au DNF preparation on TiN/Si substrates
	<ol>
		<li>Place 24 mL of a reactant solution comprising 10 mM chloroauric acid (HAuCl4) and buffered oxide etchant solution comprising 11.4% NH4F and 2.3% HF into a Teflon container measuring 5 cm x 5 cm x 5 cm.</li>
		<li>Dip the substrates into the mixture solution for 3 min.</li>
		<li>Remove the sample and wash it using deionized water.</li>
		<li>Dry the sample using the N2 spray and then incubate it at 120 &#176;C for 5 min to obtain Au DNFs/TiN/Si samples.</li>
		<li>Repeat the Au DNF preparation 10x.</li>
	</ol>
	</li>
</ol>
2.&#160;Sample examination
<ol>
	<li>Scanning electron microscopy analyses
	<ol>
		<li>Cut the sample into 0.4 cm x 0.8 cm with a tungsten pen, and clean it using the N2 spray.</li>
		<li>Coat a thin Pt film on the sample by an ion sputter coater for 50 s.</li>
		<li>Place the prepared sample into a scanning electron microscopy (SEM) instrument.</li>
		<li>Obtain SEM images by the scanning electron microscope and conduct element analysis21,22.</li>
	</ol>
	</li>
	<li>X-ray diffraction analyses
	<ol>
		<li>Place the sample into an X-ray diffraction (XRD) instrument.</li>
		<li>Obtain XRD patterns21,22.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Nehl, C. L., Hafner, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shape-dependent+plasmon+resonances+of+gold+nanoparticles.">Shape-dependent plasmon resonances of gold nanoparticles.</a> Journal of Materials Chemistry. 18 (21), 2415-2419 (2008).</li><li>Augui&#233;, B., Barnes, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Collective+resonances+in+gold+nanoparticle+arrays.">Collective resonances in gold nanoparticle arrays.</a> Physical Review Letters. 101 (14), 143902 (2008).</li><li>Sakai, N., Fujiwara, Y., Arai, M., Yu, K., Tatsuma, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrodeposition+of+gold+nanoparticles+on+ITO:+Control+of+morphology+and+plasmon+resonance-based+absorption+and+scattering.">Electrodeposition of gold nanoparticles on ITO: Control of morphology and plasmon resonance-based absorption and scattering.</a> Journal of Electroanalytical Chemistry. 628 (1-2), 7-15 (2009).</li><li>Shiao, M. H., Lai, C. P., Liao, B. H., Lin, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+photoillumination+on+gold-nanoparticle-assisted+chemical+etching+of+silicon.">Effect of photoillumination on gold-nanoparticle-assisted chemical etching of silicon.</a> Journal of Nanomaterials. 2018, 5479605 (2018).</li><li>Ayati, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photocatalytic+degradation+of+nitrobenzene+by+gold+nanoparticles+decorated+polyoxometalate+immobilized+TiO2+nanotubes.">Photocatalytic degradation of nitrobenzene by gold nanoparticles decorated polyoxometalate immobilized TiO2 nanotubes.</a> Separation and Purification Technology. 171, 62-68 (2016).</li><li>Huang, T., Meng, F., Qi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+synthesis+of+dendritic+gold+nanostructures+assisted+by+supramolecular+complexes+of+surfactant+with+cyclodextrin.">Controlled synthesis of dendritic gold nanostructures assisted by supramolecular complexes of surfactant with cyclodextrin.</a> Langmuir. 26 (10), 7582-7589 (2009).</li><li>Lahiri, A., Wen, R., Kuimalee, S., Kobayashi, S. I., Park, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-step+growth+of+needle+and+dendritic+gold+nanostructures+on+silicon+for+surface+enhanced+Raman+scattering.">One-step growth of needle and dendritic gold nanostructures on silicon for surface enhanced Raman scattering.</a> CrystEngComm. 14 (4), 1241-1246 (2012).</li><li>Lahiri, A., Wen, R., Kobayashi, S. I., Wang, P., Fang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unique+and+unusual+pattern+demonstrating+the+crystal+growth+through+bubble+formation.">Unique and unusual pattern demonstrating the crystal growth through bubble formation.</a> Crystal Growth &#38; Design. 12 (3), 1666-1670 (2012).</li><li>Lahiri, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Photo-assisted+control+of+gold+and+silver+nanostructures+on+silicon+and+its+SERRS+effect.">Photo-assisted control of gold and silver nanostructures on silicon and its SERRS effect.</a> Journal of Physics D: Applied Physics. 46 (27), 275303 (2013).</li><li>Lv, Z. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+and+controlled+electrochemical+route+to+three-dimensional+hierarchical+dendritic+gold+nanostructures.">Facile and controlled electrochemical route to three-dimensional hierarchical dendritic gold nanostructures.</a> Electrochimica Acta. 109, 136-144 (2013).</li><li>Dutta, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mesoporous+gold+and+palladium+nanoleaves+from+liquid&#8211;liquid+interface:+enhanced+catalytic+activity+of+the+palladium+analogue+toward+hydrazine-assisted+room-temperature+4-nitrophenol+reduction.">Mesoporous gold and palladium nanoleaves from liquid&#8211;liquid interface: enhanced catalytic activity of the palladium analogue toward hydrazine-assisted room-temperature 4-nitrophenol reduction.</a> ACS Applied Materials &#38; Interfaces. 6 (12), 9134-9143 (2014).</li><li>Lin, C. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+fabrication+of+three-dimensional+gold+dendritic+nanoforests+for+visible+light-enhanced+methanol+oxidation.">Rapid fabrication of three-dimensional gold dendritic nanoforests for visible light-enhanced methanol oxidation.</a> Electrochimica Acta. 192, 15-21 (2016).</li><li>Lahiri, A., Kobayashi, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroless+deposition+of+gold+on+silicon+and+its+potential+applications.">Electroless deposition of gold on silicon and its potential applications.</a> Surface Engineering. 32 (5), 321-337 (2016).</li><li>White, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface/interface+analysis+and+optical+properties+of+RF+sputter-deposited+nanocrystalline+titanium+nitride+thin+films.">Surface/interface analysis and optical properties of RF sputter-deposited nanocrystalline titanium nitride thin films.</a> Applied Surface Science. 292, 74-85 (2014).</li><li>Zhao, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+enhanced+Raman+scattering+substrates+based+on+titanium+nitride+nanorods.">Surface enhanced Raman scattering substrates based on titanium nitride nanorods.</a> Optical Materials. 47, 219-224 (2015).</li><li>Lorite, I., Serrano, A., Schwartzberg, A., Bueno, J., Costa-Kr&#228;mer, J. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+enhanced+Raman+spectroscopy+by+titanium+nitride+non-continuous+thin+films.">Surface enhanced Raman spectroscopy by titanium nitride non-continuous thin films.</a> Thin Solid Films. 531, 144-146 (2013).</li><li>O&#8217;Kelly, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Room+temperature+electroless+plating+copper+seed+layer+process+for+damascene+interlevel+metal+structures.">Room temperature electroless plating copper seed layer process for damascene interlevel metal structures.</a> Microelectronic Engineering. 50 (1), 473-479 (2000).</li><li>Cesiulis, H., Ziomek-Moroz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrocrystallization+and+electrodeposition+of+silver+on+titanium+nitride.">Electrocrystallization and electrodeposition of silver on titanium nitride.</a> Journal of Applied Electrochemistry. 30 (11), 1261-1268 (2000).</li><li>Wu, Y., Chen, W. C., Fong, H. P., Wan, C. C., Wang, Y. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Displacement+reactions+between+metal+ions+and+nitride+barrier+layer/silicon+substrate.">Displacement reactions between metal ions and nitride barrier layer/silicon substrate.</a> Journal of the Electrochemical Society. 149 (5), G309-G317 (2002).</li><li>Koo, H. C., Ahn, E. J., Kim, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct-electroplating+of+Ag+on+pretreated+TiN+surfaces.">Direct-electroplating of Ag on pretreated TiN surfaces.</a> Journal of the Electrochemical Society. 155 (1), D10-D13 (2008).</li><li>Shiao, M. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+gold+dendritic+nanoflowers+deposited+on+titanium+nitride+for+photoelectrochemical+cells.">Novel gold dendritic nanoflowers deposited on titanium nitride for photoelectrochemical cells.</a> Journal of Solid State Electrochemistry. 22 (10), 3077-3084 (2018).</li><li>Shiao, M. H., Lin, C. T., Zeng, J. J., Lin, Y. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+gold+dendritic+nanoforests+combined+with+titanium+nitride+for+visible-light-enhanced+chemical+degradation.">Novel gold dendritic nanoforests combined with titanium nitride for visible-light-enhanced chemical degradation.</a> Nanomaterials. 8 (5), 282 (2018).</li><li>Carraro, C., Maboudian, R., Magagnin, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metallization+and+nanostructuring+of+semiconductor+surfaces+by+galvanic+displacement+processes.">Metallization and nanostructuring of semiconductor surfaces by galvanic displacement processes.</a> Surface Science Reports. 62 (12), 499-525 (2007).</li></ol>

The authors have nothing to disclose.

In this study, Au DNFs with multiple branch sizes were decorated on the surface of TiN/Si by using FAGRR. The deposition of the Au DNFs could be directly identified by a significant change in color. The thickness of the Au DNFs on TiN/Si increased to 5.10 &#177; 0.20 &#181;m within 15 min, and this increase in thickness can be expressed using the following linear equation: y = 0.296t + 0.649, where the time varied from 1 to 15 min.
In FAGRR, the metal deposition is affected b...

Gold nanoparticles have characteristic optical properties and localized surface plasmon resonances (LSPRs), depending on the size and shape of the nanoparticles1,2,3,4. Moreover, gold nanoparticles can significantly enhance plasmonic photocatalytic reactions5. Dendritic nanoforests stacked using gold nanoparticles have received considerable attention because of their noteworthy specific surface areas and robust LSPR enhancement6,7,8,9,10,11,12,13.
TiN is an extremely hard ceramic material and has remarkable thermal, chemical, and mechanical stability. TiN has distinctive optical properties and can be used for plasmonic applications with visible-to-near-infrared light14,15. Research has demonstrated that TiN can produce electromagnetic field enhancements, similar to Au nanostructures16. The deposition of copper17 or silver18,19,20 on TiN substrates for applications has been demonstrated. However, few studies have been performed on Au/TiN composite materials for applications. Shiao et al. have recently demonstrated potential applications of Au DNFs/TiN composites for photoelectrochemical cells21 and chemical degradation22.
Au can be synthesized on a TiN substrate by using a FAGRR23. The deposition condition of Au DNFs on TiN is crucial in the performance of applications. This study examines the growth of Au DNFs on a TiN-coated Si substrate.

<table><tbody><tr><td>Acetone</td><td>Dinhaw Enterprise Co. Ltd.,Taipei, Taiwan</td><td></td><td></td></tr><tr><td>Isopropanol</td><td>Echo Chemical Co. Ltd., Miaoli, Taiwan</td><td>TG-078-000000-75NL</td><td></td></tr><tr><td>Buffered Oxide Etch</td><td>Uni-onward Corp., Hsinchu, Taiwan&amp;nbsp;</td><td>UR-BOE-1EA</td><td></td></tr><tr><td>Chloroauric Acid</td><td>Alfa Aesar., Heysham, United Kingdom</td><td>36400.03</td><td></td></tr><tr><td>N-Type Silicon Wafer</td><td>Summit-Tech Company, Hsinchu, Taiwan</td><td></td><td></td></tr><tr><td>High-Power Impulse Magnetron Sputtering System (HiPIMS)</td><td>Melec GmbH, Germany</td><td></td><td>SPIK2000A&amp;nbsp;</td></tr><tr><td>Scanning Electron Microscope (SEM)</td><td>JEOL, Japan</td><td></td><td>JSM-7800F</td></tr><tr><td>Ion Sputter Coater</td><td>Hitachi, Japan</td><td></td><td>E-1030</td></tr><tr><td>X-Ray Diffractometer (XRD)</td><td>PANalytical, The Netherlands</td><td></td><td>X&#039;Pert PRO MRD</td></tr></tbody></table>

growth of gold dendritic nanoforests on titanium nitride-coated silicon substrates

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a fluoride-assisted galvanic replacement reaction (FAGRR) is employed for the rapid and easy deposition of gold dendritic nanoforests (Au DNFs) on the TiN/Si substrates. Scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy patterns of TiN/Si and Au DNFs/TiN/Si samples validate that the synthesis process is accurately controlled. Under the reaction conditions in this study, the thickness of the Au DNFs increases linearly to 5.10 &#177; 0.20 &#181;m within 15 min of the reaction. Therefore, the employed synthesis procedure is a simple and rapid approach for preparing Au DNFs/TiN/Si composites.

Figure 1 depicts images of the Au DNFs/TiN/Si sample preparations. The silicon wafer was silvery white (Figure 1a). TiN/Si was golden yellow and had a homogeneous surface (Figure 1b), which indicated the uniform TiN coating on the silicon wafer. Au DNFs/TiN/Si was yellowish brown and less homogeneous on the surface (Figure 1c) because of the random distribution of Au DNF...

Watch this Scientific Journal Video about Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates at JoVE.com

Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

This study presents a feasible procedure for synthesizing gold dendritic nanoforests on titanium nitride/silicon substrates. The thickness of gold dendritic nanoforests increases linearly within 15 min of a synthesis reaction.

In this study, a high-power impulse magnetron sputtering system is used to coat a flat and firm titanium nitride (TiN) film on silicon (Si) wafers, and a ...

growth-gold-dendritic-nanoforests-on-titanium-nitride-coated-silicon

Research

JoVE Journal

Chemistry

6.4K Views.  National Applied Research Laboratories. Dit protocol is een eenvoudige, snelle, elektrolyses depositie methode voor de voorbereiding van goud dendritische nanobossen op een titanium nitride-gecoate silicium substraat. De belangrijkste voordelen van deze techniek zijn de eenvoud en de snelheid. Gouden dendritische nanobossen kunnen plasmonische hotspots opwekken en de reactie op de plasmonische fotokatalytische versterken.Men kan deze procedure ook gebruiken om de dendritische nanobossen van legeringsmetalen zoals zilver voor...

Video: Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

Fabricating Nanogaps by Nanoskiving

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two electrodes-and generating them in practical quantities-is still challenging. The preparation of nanogap electrodes using nanoskiving, which is a form of edge lithography, is a fast, simple and powerful technique. This method is an entirely mechanical process which does not include any photo- or electron-beam lithographic steps and does not require any special equipment or infrastructure such as clean rooms. Nanoskiving is used to fabricate electrically addressable nanogaps with control over all three dimensions; the smallest dimension of these structures is defined by the thickness of the sacrificial layer (Al or Ag) or self-assembled monolayers. These wires can be manually positioned by transporting them on drops of water and are directly electrically-addressable; no further lithography is required to connect them to an electrometer.

The fabrication of electrically addressable, high-aspect-ratio (> 1000:1) metal nanowires separated by gaps of single nanometers using either sacrificial layers of aluminum and silver or self-assembled monolayers as templates is described. These nanogap structures are fabricated without a clean room or any photo- or electron-beam lithographic processes by a form of edge lithography known as nanoskiving.

There are several methods of fabricating nanogaps with controlled spacings, but the precise control over the sub-nanometer spacing between two ...

Synthesis and Functionalization of Nitrogen-doped Carbon Nanotube Cups with Gold Nanoparticles as Cork Stoppers

Nitrogen-doped carbon nanotubes consist of many cup-shaped graphitic compartments termed as nitrogen-doped carbon nanotube cups (NCNCs). These as-synthesized graphitic nanocups from chemical vapor deposition (CVD) method were stacked in a head-to-tail fashion held only through noncovalent interactions. Individual NCNCs can be isolated out of their stacking structure through a series of chemical and physical separation processes. First, as-synthesized NCNCs were oxidized in a mixture of strong acids to introduce oxygen-containing defects on the graphitic walls. The oxidized NCNCs were then processed using high-intensity probe-tip sonication which effectively separated the stacked NCNCs into individual graphitic nanocups. Owing to their abundant oxygen and nitrogen surface functionalities, the resulted individual NCNCs are highly hydrophilic and can be effectively functionalized with gold nanoparticles (GNPs), which preferentially fit in the opening of the cups as cork stoppers. These graphitic nanocups corked with GNPs may find promising applications as nanoscale containers and drug carriers.

We discussed the synthesis of individual graphitic nanocups using a series of techniques including chemical vapor deposition, acid oxidation and probe-tip sonication. By citrate reduction of HAuCl4, the graphitic nanocups were effectively corked with gold nanoparticles due to the chemically reactive edges of the cups.

Nitrogen-doped carbon  nanotubes consist of many cup-shaped graphitic compartments termed as  nitrogen-doped carbon nanotube cups (NCNCs).  These ...

Engineering

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

Gold Nanostar Synthesis with a Silver Seed Mediated Growth Method

The physical, chemical and optical properties of nano-scale colloids depend on their material composition, size and shape 1-5. There is a great interest in using nano-colloids for photo-thermal ablation, drug delivery and many other biomedical applications 6. Gold is particularly used because of its low toxicity 7-9. A property of metal nano-colloids is that they can have a strong surface plasmon resonance 10. The peak of the surface plasmon resonance mode depends on the structure and composition of the metal nano-colloids. Since the surface plasmon resonance mode is stimulated with light there is a need to have the peak absorbance in the near infrared where biological tissue transmissivity is maximal 11, 12.
We present a method to synthesize star shaped colloidal gold, also known as star shaped nanoparticles 13-15 or nanostars 16. This method is based on a solution containing silver seeds that are used as the nucleating agent for anisotropic growth of gold colloids 17-22. Scanning electron microscopy (SEM) analysis of the resulting gold colloid showed that 70 % of the nanostructures were nanostars. The other 30 % of the particles were amorphous clusters of decahedra and rhomboids. The absorbance peak of the nanostars was detected to be in the near infrared (840 nm). Thus, our method produces gold nanostars suitable for biomedical applications, particularly for photo-thermal ablation.

We synthesized star shaped gold nanostars using a silver seed mediated growth method. The diameter of the nanostars ranges from 200 to 300 nm and the number of tips vary from 7 to 10. The nanoparticles have a broad surface plasmon resonance mode centered in the near infrared.

The physical, chemical and optical properties of nano-scale colloids depend on their material composition, size and shape 1-5. There is a great interest ...

Bioengineering

Atomically Traceable Nanostructure Fabrication

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process being used in order to maintain exquisite control over both feature size and feature density. Here, we demonstrate a method for tracking atomically resolved and controlled structures from initial template definition through final nanostructure metrology, opening up a pathway for top-down atomic control over nanofabrication. Hydrogen depassivation lithography is the first step of the nanoscale fabrication process followed by selective atomic layer deposition of up to 2.8 nm of titania to make a nanoscale etch mask. Contrast with the background is shown, indicating different mechanisms for growth on the desired patterns and on the H passivated background. The patterns are then transferred into the bulk using reactive ion etching to form 20 nm tall nanostructures with linewidths down to ~6 nm. To illustrate the limitations of this process, arrays of holes and lines are fabricated. The various nanofabrication process steps are performed at disparate locations, so process integration is discussed. Related issues are discussed including using fiducial marks for finding nanostructures on a macroscopic sample and protecting the chemically reactive patterned Si(100)-H surface against degradation due to atmospheric exposure.

We report a protocol for combining the atomic metrology of the Scanning Tunneling Microscope for surface patterning with selective Atomic Layer Deposition and Reactive Ion Etching. Using a robust process involving numerous atmospheric exposures and transport, 3D nanostructures with atomic metrology are fabricated.

Reducing the scale of etched nanostructures below the 10 nm range eventually will require an atomic scale understanding of the entire fabrication process ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Microfabrication of Nanoporous Gold Patterns for Cell-material Interaction Studies

Nanostructured materials with feature sizes in tens of nanometers have enhanced the performance of several technologies, including fuel cells, biosensors, biomedical device coatings, and drug delivery tools. Nanoporous gold (np-Au), produced by a nano-scale self-assembly process, is a relatively new material that exhibits large effective surface area, high electrical conductivity, and catalytic activity. These properties have made np-Au an attractive material to scientific community. Most studies on np-Au employ macro-scale specimens and focus on fundamental science of the material and its catalytic and sensor applications. The macro-scale specimens limit np-Au's potential in miniaturized systems, including biomedical devices. In order to address these issues, we initially describe two different methods to micropattern np-Au thin films on rigid substrates. The first method employs manually-produced stencil masks for creating millimeter-scale np-Au patterns, while the second method uses lift-off photolithography to pattern sub-millimeter-scale patterns. As the np-Au thin films are obtained by sputter-deposition process, they are compatible with conventional microfabrication techniques, thereby amenable to facile integration into microsystems. These systems include electrically-addressable biosensor platforms that benefit from high effective surface area, electrical conductivity, and gold-thiol-based surface bioconjugation. We describe cell culture, immunostaining, and image processing techniques to quantify np-Au's interaction with mammalian cells, which is an important performance parameter for some biosensors. We expect that the techniques illustrated here will assist the integration of np-Au in platforms at various length-scales and in numerous applications, including biosensors, energy storage systems, and catalysts.

We report on techniques to micropattern nanoporous gold thin films via stencil printing and photolithography, as well as methods to culture cells on the microfabricated patterns. In addition, we describe image analysis methods to characterize morphology of the material and the cultured cells using scanning electron and fluorescence microscopy techniques.

Nanostructured materials with feature sizes in tens of nanometers have enhanced the performance of several technologies, including fuel cells, biosensors, ...

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs ...

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.

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 ...

Large Area Substrate-Based Nanofabrication of Controllable and Customizable Gold Nanoparticles Via Capped Dewetting

Recent scientific advances in the utilization of metallic nanoparticle for enhanced energy conversion efficiency, improved optical device performance, and high-density data storage have demonstrated the potential benefit of their use in industrial applications. These applications require precise control over nanoparticle size, spacing, and sometimes shape. These requirements have resulted in the use of time and cost intensive processing steps to produce nanoparticles, thus making the transition to industrial application unrealistic. This protocol will resolve this issue by providing a scalable and affordable method for the large-area production of nanoparticle films with improved nanoparticle control compared to the current techniques. In this article, the process will be demonstrated with gold, but other metals can also be used.

This protocol details a novel nano-manufacturing technique that can be used to make controllable and customizable nanoparticle films over large areas based on the self-assembly of dewetting of capped metal films.

Recent scientific advances in the utilization of metallic nanoparticle for enhanced energy conversion efficiency, improved optical device performance, and ...

Growth of Gold Dendritic Nanoforests on Titanium Nitride-coated Silicon Substrates

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