Name: Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal (Video) | JoVE Journal
Uploaded: 2016-01-15T15:00:00.000+00:00
Duration: 10 min 39 s
Description: Learn hydrothermal synthesis of ZnO nanorod/graphene double heterostructures for piezoelectric nanogenerators. This method enhances electrical output performance through improved nanostructure coverage.

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5 minutes

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No.2014R1A2A1A11051146). This work was also supported by National Research Foundation of Korea Grant funded by the Korean Government (NRF-2014R1A1A2058350).

1. Chemical Vapor Deposition (CVD) Growth of Single Layered Graphene
Note: The graphene used in this study was grown on copper (Cu) foil using the thermal chemical vapor deposition (CVD) technique (Figure 1A). Growth is uniform over an area of 2 cm x 10 cm for this system.
<ol>
	<li>Wash the Cu foil (2 cm x 10 cm) with mild flow of acetone, isopropyl alcohol (IPA) and distilled water, respectively.</li>
	<li>Place the cleaned Cu foil in a 2 in. quartz tube (Figure 1B), and then purge the chamber with vacuum (approximately 1 mTorr) for 10 min by using rotary pump.</li>
	<li>Configure the temperature of digitalized furnace and ramp up the furnace to 995 &#176;C, while maintaining the desired flow rates (100 sccm for Argon and 50 sccm for hydrogen) (Figure 1C).</li>
	<li>Introduce the 20 sccm of methane (CH4) for 10 min to grow the single layered graphene. Maintain the 80 sccm of Argon and 20 sccm of hydrogen throughput the process.</li>
	<li>Allow the furnace to cool down to RT&#160;within 5 min with the flow rates specified in the step 1.4. Purge the chamber again with Argon at 100 sccm.</li>
</ol>
2. Preparation of Graphene/Polyethylene Terephthalate (PET) Substrate
<ol>
	<li>Place the graphene grown Cu foil (1.5 cm x 2 cm) on the glass slide, and fix the edges by commercial tape (Figure 2A).</li>
	<li>Spin coat a layer of poly(methyl methacrylate) (PMMA) at 500 rpm for 5 sec and then 3,000 rpm for 30 sec (Figure2B). Then, bake the PMMA-coated Cu foil substrate at 60 &#176;C for 2 min to remove solvent residue.</li>
	<li>Dice the PMMA coated Cu foil into smaller piece 1 cm x 1.5 using razor blade.</li>
	<li>Immerse PMMA coated Cu foil into Ni etchant reservoir (more than 500 ml) by placing the Cu foil face down for 30 min. This leaves the floating PMMA/graphene layer on etchant solution (Figure 2C). A piece of PMMA-coated Cu foil is enough for the experiment forward.</li>
	<li>Scoop PMMA/graphene layer up on slide glass, and then immerse PMMA/graphene layer into DI water reservoir. Repeat twice. Finally, scoop PMMA/graphene layer up on PET substrate (Figure 2D), and then bake the substrate at 105 &#176;C for 2 min to remove water residue.</li>
	<li>Remove the PMMA layer by dipping in warm acetone (60 &#176;C) for 10 min.</li>
</ol>
3. Synthesis of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure
<ol>
	<li>Begin with heating the precursor solution with 40 mM zinc nitrate hexahydrate, 40 mM hexamethylenetetramine (HMT) and 9 mM polyethylenimine (PEI) in DI water for 60 min at 95 &#176;C in convection oven (Figure 3A). Namely, preheating process.</li>
	<li>While preheating process, fully cover the solution with 5 mM zinc acetate in ethanol on the substrate and spin coat a layer of zinc acetate on the graphene/PET substrate at 500 rpm for 5 sec and then 2,000 rpm for 60 sec (Figure 3B and Figure 3C).Then, bake the substrate at 200 &#176;C for 30 min. Repeat twice. The thickness of layer is approximately 30 nm.</li>
	<li>Immerse the seed-coated graphene/PET substrate into preheated solution by placing the substrate face down at 95 &#176;C (Figure 3D). Determine the heating time for the desired nanostructure; i.e., single heterostructure (t &#60; 12 hr, Figure 3E) and double heterostructure (t &#62; 12 hr, Figure 3F).</li>
	<li>Carefully spray ethanol on the substrate and dry it at RT for 1 hr. 
	Note : For scanning electron microscopy (SEM), dice the sample into smaller piece 5 mm x 5 mm using razor blade and mount the sample on SEM stage.</li>
</ol>
4. Fabrication of Piezoelectric Nanogenerator
Note: Piezoelectric nanogenerator in this study has the three electrodes (top, middle, bottom). Use the indium tin oxide (ITO) coated PET as the bottom electrode (Figure 4A).
<ol>
	<li>Spin coat a layer of polydimethylsiloxane (PDMS) at 500 rpm for 5 sec and then 6,000 rpm for 60 sec to form the insulating layer between ITO and ZnO nanorod (Figure 4B). The thickness of layer is approximately 3 &#181;m.</li>
	<li>Fully cure the substrate at 80 &#176;C for 2 hr in convection oven.</li>
	<li>Transfer the graphene to PDMS coated ITO/PET substrate by using the method in Section 2 (Figure 4C).</li>
	<li>Synthesize the double heterostructure on the substrate by using the method in Section 3 (Figure 4D).</li>
	<li>Spin coat a layer of PDMS at 500 rpm for 5 sec and then 5,000 rpm for 60 sec to improve the robustness and durability of the ZnO nanorod, and then fully cure it at 80 &#176;C for 2 hr (Figure 4E). The thickness of layer is approximately 8 &#181;m.</li>
	<li>Cover the substrate with ITO-coated PET as the top electrode (Figure 4F).</li>
</ol>
5. Electrical Performance Measurement Setup
Note: We set up custom-made equipment for electrical performance characterization using linear motor, commercial scale and oscilloscope. Build the frame for vertically supporting the linear motor and place the commercial scale under the linear motor as shown in Figure 5A. The scale should be sensitive to small weight (0.02 kg - 20 kg).
<ol>
	<li>Place the nanogenerator on a scale, and then connect the electrodes of nanogenerator to sensing probes of oscilloscope (Figure 5A and 5B).</li>
	<li>Set up the initial and final positions and speed of linear motor while carefully monitoring the weight in the scale. 
	Tip : Configure the initial position where nanogenerator is slightly contacted with measurement setup. Speed of linear motor determines the strain rate.</li>
	<li>Start the linear motor and monitor the voltage signal with time. Save the time-dependent voltage signal in flash memory. Strain rate: 100 mm/sec and applied load: 50 N.</li>
</ol>

<ol><li>Lee, S., Lee, Y., Park, J., Choi, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Stitchable+organic+photovoltaic+cells+with+textile+electrodes%5BTitle%5D)+AND+%22Nano+Energy%22%5BJournal%5D)">Stitchable organic photovoltaic cells with textile electrodes.</a> Nano Energy. 9, 88-93 (2014).</li>
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<li>Qiu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+growth+mechanism+and+optical+properties+of+ultralong+ZnO+nanorod+arrays+with+a+high+aspect+ratio+by+a+preheating+hydrothermal+method%5BTitle%5D)+AND+%22Nanotechnology%22%5BJournal%5D)">The growth mechanism and optical properties of ultralong ZnO nanorod arrays with a high aspect ratio by a preheating hydrothermal method.</a> Nanotechnology. 20, 155603(2009).</li>
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The authors declare that they have no competing financial interests.

Please note that the high quality (&#62;99.8%, annealed) of Cu foil should be considered as a substrate for successful growth of single layer graphene. Otherwise, the single layer graphene is not uniformly grown over the Cu foil, leading to dramatically decrease in conductivity of graphene. A 1 hr annealing at high temperature would help the improvement of the Cu foil crystallinity as well as removal of any contaminants from the Cu foil.
The growth of ZnO nanorod depends on the conditions for ...

Recently, the portable and wearable electronics devices became an essential element for a comfortable life owing to the nanotechnology development, which results in the tremendous demands for a power source in the range of microwatt to milliwatt. Considerable approaches for the power source of portable and wearable devices have been achieved by the renewable energy, including solar energy 1,2, thermal 3,4 and mechanical source 5,6. Piezoelectric nanogenerator have been intensively studied as one of possible candidate for energy harvesting device from environments, such as rustling the leaf 7, sound wave 8 and movement of human being 9. The primary principle underlying the nanogenerator is the coupling between the piezoelectric potential and dielectric material as a barrier. The piezoelectric potential generated in strained material induces the transient current that flows through the external circuit, which balances the potential at the interface between piezoelectric and dielectric material. The performance of nanogenerator would be improved by using nanostructure of piezoelectric material due to robustness under robustness under high stress and responsiveness to tiny deformation 10.
One-dimensional zinc oxide nanostructure is a promising component for piezoelectric materials in nanogenerator due to its attractive properties, e.g., its high piezoelectricity (26.7 pm/V) 11, optical transparency 12, and facile synthesis by using chemical process 13. Hydrothermal approach for growing the well aligned ZnO nanorod receives a great attention due to low cost, environmental friendly synthesis and potential for easy scaling up. Moreover, the preheating hydrothermal technique is easily controllable in experimental condition, resulting in many kinds of novel nanostructures, such as nanoleaves 14, nanoflowers 15 and nanotubes 16. The novel nanostructures enable a beneficial effect on performance of the electric and optoelectric devices wherever the high specific surface area of material is demanded.
In this protocol, we describe the experimental procedures for synthesis of more novel nanostructure (i.e., freestanding double heterostructure). The growth of ZnO nanorod at interface between graphene and polyethylene terephthalate (PET) substrate leads to the self-elevating the ZnO nanorod/graphene single heterostructure, yielding the freestanding double heterostructure. Furthermore, the feasible application of this unique nanostructure for electronic and optoelectric devices is demonstrated by fabricating a piezoelectric nanogenerator. Freestanding double heterostructure provides not only a high specific surface area but also a high number density of nanorod in a given area. This unique nanostructure has a tremendous potential for applications of electrical and optoelectrical devices, such as pressure sensor, immuno-biosensor and dye-sensitized solar cells.

<table><tbody><tr><td>Cu foil</td><td>Alfa Aesar</td><td>13382</td><td></td></tr><tr><td>poly(methyl methacrylate) (PMMA)</td><td>Aldrich</td><td>182230</td><td></td></tr><tr><td>zinc nitrate hexahydrate</td><td>Sigma-Aldrich</td><td>228732</td><td></td></tr><tr><td>hexamethylenetetramine (HMT)</td><td>Sigma-Aldrich</td><td>398160</td><td></td></tr><tr><td>polyethylenimine (PEI)</td><td>Sigma-Aldrich</td><td>408719</td><td></td></tr><tr><td>indium tin oxide (ITO) coated PET</td><td>Aldrich</td><td>639303</td><td></td></tr><tr><td>Silicone Elastomer Kit</td><td>Dow Corning</td><td>Sylgard 184 a, b</td><td></td></tr><tr><td>Nickel Etchant Type1</td><td>Transene Company</td><td>41212</td><td></td></tr></tbody></table>

preparation of zno nanorod/graphene/zno nanorod epitaxial double heterostructure for piezoelectrical nanogenerator by using preheating hydrothermal

Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal

Well-aligned ZnO nanostructures have been intensively studied over the last decade for remarkable physical properties and enormous applications. Here, we describe a one-step fabrication technique to synthesis freestanding ZnO nanorod/graphene/ZnO nanorod double heterostructure. The preparation of the double heterostructure is performed by using thermal chemical vapor deposition (CVD) and preheating hydrothermal technique. In addition, the morphological properties were characterized by using the scanning electron microscopy (SEM). The utility of freestanding double heterostructure is demonstrated by fabricating the piezoelectric nanogenerator. The electrical output is improved up to 200% compared to that of a single heterostructure owing to the coupling effect of the piezoelectricity between the arrays of ZnO nanorods on the top and bottom of graphene. This unique double heterostructure have a tremendous potential for applications of electrical and optoelectrical devices where the high number density and specific surface area of nanorod are needed, such as pressure sensor, immuno-biosensor and dye-sensitized solar cells.

The scanning electron microscopy (SEM) images shown in Figure 6 present the morphologies of hydrothermally grown ZnO nanorods. The preheating hydrothermal technique can result in two different nanostructures depending on the growth time. Figure 6A shows a typical image of ZnO nanorod on graphene/PET substrate at the growth time of 5 hr. In contrast, the image shown in Figure 6B indicates that the growth of ZnO nanorod at the growth time o...

One-step fabrication method for obtaining freestanding epitaxial double heterostructure is presented. This approach could achieve ZnO coverage with a higher number density than that of the epitaxial single heterostructure, leading to a piezoelectric nanogenerator with an increased output electrical performance.

Well-aligned ZnO nanostructures have been intensively studied over the last decade for remarkable physical properties and enormous applications. Here, we ...

The overall goal of this experiment is to synthesize a novel zinc oxide nanostructure on graphene, using hydrothermal technique and demonstrate that it exhibits enhanced piezoelectric performance. This method can help answer key questions in the nanomaterial field for electric and optoelectronic applications, such as photovoltics, biosensors, as well as wearable and implantable electronics. The main advantage of this noble nanostructure is that it could enhance not only the number of nanoload, but also the specifics of this area, in the key-boleez-an, for piezoelectric nanogenerators.Generally, individuals new to this method for graphing transfer, we struggle because it is not easy to place the floating graphene on the giant position of the substrate. I first had an idea that I could apply this noble structure to a nanogenerator for improving the performance when I found that a zinc oxide nanoload can grow on both sides of the graphene. The graphene used in this study is grown on copper foil, using the thermal chemical vapor deposition, or CVD technique.To begin, wash the copper foil with a mild flow of acetone, isopropyl alcohol, and distilled water, respectively. Place the cleaned copper foil in a two inch quartz tube in the furnace, and then purge the furnace chamber with vacuum for ten minutes, by using a rotary pump. Configure the temperature of a digitalized furnace to ramp up the furnace to 995 degrees Celsius, while maintaining the desired flow rates.Introduce the 20 sccm of methane for 10 minutes to grow the single-layered graphene. Maintain the 80 sccm of argon and 20 sccm of hydrogen throughout the process. After allowing the furnace to cool down to room temperature, within five minutes, purge the chamber again with argon at 100 sccm.Place the graphene grown copper foil on a glass slide and fix the edges by commercial tape. Spin coat a layer of polymethylmethacrylate, or PMMA, at 550 rpm for five seconds, and then 3, 000 rpm for 30 seconds. Next, bake the PMMA-coated copper foil substrate at 60 degrees Celsius for two minutes to remove the solvent residue.Dice the PMMA-coated copper foil into a smaller, one centimeter by one point five centimeter piece using a razor blade. Immerse the PMMA-coated copper foil into a nickel etchant reservoir by placing the copper foil facedown for 30 minutes. This leaves the floating PMMA graphene layer on the etchant solution.A piece of PMMA-coated copper foil is enough for the experiment forward. Scoop the PMMA graphene layer up on slide glass, and then immerse the PMMA graphene layer into a deionized water reservoir. After repeating this process twice, scoop the PMMA graphene layer up on the polyethylene terephthalate, or PET, substrate.Then, bake the substrate at 105 degrees Celsius for two minutes, to remove water residue. Finally, move the PMMA layer by dipping the substrate in warm acetone for 10 minutes. Begin synthesis with preheating the precursor solution of 40 millimolar zinc nitrate hexahydrate, 40 millimolar hexamethylene tetramine, and nine millimolar polyethylenimine in deionized water for 60 minutes at 95 degrees Celsius in a convection oven.Meanwhile, fully cover the graphene PET substrate with a five millimolar zinc acetate solution in ethanol. Spin coat a layer of zinc acetate on the substrate at 500 rpm for five seconds, and then 2, 000 rpm for 60 seconds. Then, bake the substrate at 200 degrees Celsius for 30 minutes.After repeating this process twice, the thickness of the layer is approximately 30 nanometers. Next, immerse the seed coated graphene PET substrate into the preheated solution by placing the substrate facedown at 95 degrees Celsius. Determine the heating time for the desired nanostructure.Carefully spray ethanol on the substrate and allow it to dry at room temperature for one hour. The piezoelectric nanogenerator fabricated in this study has three electrodes. The indium tin oxide, or ITO coated PET, is used as the bottom electrode.Spin coat a layer of polydimethylsiloxane, or PDMS, onto the ITO PET substrate at 500 rpm for five seconds, and then 6, 000 rpm for 60 seconds to form the insulating layer between the ITO and the zinc oxide nanorod. The thickness of the layer is approximately three microns. Fully cure the substrate at 80 degrees Celsius for two hours in a convection oven.Then, transfer the graphene to the PDMS-coated ITO PET substrate as done before. Next, synthesize the double heterostructure on the substrate by using the demonstrated method. Spin coat a layer of PDMS at 500 rpm for five seconds, and then 5, 000 rpm for 60 seconds, to improve the robustness and durability of the zinc oxide nanorod.Then, fully cure the nanorod at 80 degrees Celsius for two hours. The thickness of the layer is approximately eight microns. As a final step, cover the substrate with ITO-coated PET as the top electrode.Set up custom-made equipment for electrical performance characterization, using a linear motor, commercial scale, and oscilliscope. Build the frame for vertically supporting the linear motor and place the commercial scale under the linear motor. The scale should be sensitive to small weight.Place the nanogenerator on a scale, and then connect the electrodes of the nanogenerator to the sensing probes of an oscilloscope. Set up the initial and final positions, as well as the speed of the linear motor, while carefully monitoring the weight on the scale. Configure the initial position where the nanogenerator is slightly in contact with the measurement setup.Start the linear motor. The speed of the linear motor determines the strain rate. Here, a strain rate of 100 millimeters per second and an applied load of 50 newtons is used.Monitor the voltage signal with time, saving the time-dependent voltage signal in flash memory. The SCM images shown here present the morphologies of hydrothermally-grown zinc oxide nanorods. The preheating hydrothermal technique can result in two different nanostructures, depending on the growth time.Here is a typical image of the zinc oxide nanorod on a graphene PET substrate at a growth time of five hours. In contrast, the image shown here indicates that the growth of the zinc oxide nanorod at 12 hours is successful on the top and the bottom of the graphene. Both zinc oxide nanorods are vertically aligned to the graphene layer, with average lengths of two point four nine and zero point seven zero microns, respectively.In addition, the length of the zinc oxide nanorod on the bottom of the graphene is increased approximately two times as the growth time increases up to 24 hours. The growth of the zinc oxide nanorod on the bottom of the graphene is carried out over a large scale, and results in the self-elevation of the zinc oxide nanorod graphene construct, thereby forming the freestanding double-hetero structure. The electrical output is originated from the piezoelectric nanogenerator, rather than the measurement system, which is confirmed by polarity switching measurement.The output voltages from the arrays of the zinc oxide nanorod are observed up to zero point five volts on the top of the graphene, and up to zero point three volts on the bottom of the graphene, by applying the periodic compress release loads of 49 newtons. Once mastered, this technique can be done in one or two days if it is performed properly. After watching this video, you should have a good understanding of how to synthesize a noble nanostructure and fabricate the piezoelectric nanogenerator.

preparation-zno-nanorodgraphenezno-nanorod-epitaxial-double

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High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

This manuscript describes how to design and fabricate efficient inverted SMPV1:PC71BM solar cells with ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The well-aligned vertically oriented ZnO NRs exhibit high crystalline properties. The power conversion efficiency of solar cells can reach 6.01%.

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

The article aims to introduce a standard and reliable fabrication procedure for the development of future low dimensional nanoelectronics.

A Standard and Reliable Method to Fabricate Two-Dimensional Nanoelectronics

Attainment of high-quality Schottky contacts is imperative for achieving efficient gate modulation in heterostructure field effect transistors (HFETs). We present the fabrication methodology and characteristics of Schottky diodes on Zn-polar BeMgZnO/ZnO heterostructures with high-density two dimensional electron gas (2DEG), grown by plasma-assisted molecular beam epitaxy on GaN templates.

Fabrication of Schottky Diodes on Zn-polar BeMgZnO/ZnO Heterostructure Grown by Plasma-assisted Molecular Beam Epitaxy

Here, we present a protocol for the fabrication and preparation of a graphene liquid cell for in situ transmission electron microscopy observation, along with a synthesis of electrode materials and electrochemical battery cell tests.

Preparation of Graphene Liquid Cells for the Observation of Lithium-ion Battery Material

Low-grade heat is abundant, but its efficient recovery is still a great challenge. We report an asymmetric thermoelectrochemical cell using graphene oxide as a cathode and polyaniline as an anode with KCl as the electrolyte. This cell works under isothermal heating, exhibiting a high heat-to-electricity conversion efficiency in low-temperature regions.

Asymmetric Thermoelectrochemical Cell for Harvesting Low-grade Heat under Isothermal Operation

Learn hydrothermal synthesis of ZnO nanorod/graphene double heterostructures for piezoelectric nanogenerators. This method enhances electrical output performance through improved nanostructure coverage.

Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal (Video) | JoVE Journal

Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal

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