Name: preparation of zno nanorod/graphene/zno nanorod epitaxial double heterostructure for piezoelectrical nanogenerator by using preheating hydrothermal
Uploaded: 2016-01-15T15:00:00
Description: Watch this Scientific Journal Video about Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal at JoVE.co

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...

<ol>
	<li>Lee, S., Lee, Y., Park, J., Choi, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stitchable+organic+photovoltaic+cells+with+textile+electrodes.">Stitchable organic photovoltaic cells with textile electrodes.</a> Nano Energy. 9, 88-93 (2014).</li><li>Pan, 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=Wearable+solar+cells+by+stacking+textile+electrodes.">Wearable solar cells by stacking textile electrodes.</a> Angew. Chem.-Int. Edit. 53, 6110-6114 (2014).</li><li>Yang, 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=Pyroelectric+nanogenerators+for+harvesting+thermoelectric+energy.">Pyroelectric nanogenerators for harvesting thermoelectric energy.</a> Nano Lett. 12, 2833-2838 (2012).</li><li>Lee, J. 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=Highly+stretchable+piezoelectric-pyroelectric+hybrid+nanogenerator.">Highly stretchable piezoelectric-pyroelectric hybrid nanogenerator.</a> Adv. Mater. 26, 765-769 (2014).</li><li>Zhong, 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=Finger+typing+driven+triboelectric+nanogenerator+and+its+use+for+instantaneously+lighting+up+LEDs.">Finger typing driven triboelectric nanogenerator and its use for instantaneously lighting up LEDs.</a> Nano Energy. 2, 491-497 (2013).</li><li>Tang, W., Han, C. B., Zhang, C., Wang, Z. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cover-sheet-based+nanogenerator+for+charging+mobile+electronics+using+low-frequency+body+motion/vibration.">Cover-sheet-based nanogenerator for charging mobile electronics using low-frequency body motion/vibration.</a> Nano Energy. 9, 121-127 (2014).</li><li>Li, S., Yuan, J., Lipson, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ambient+wind+energy+harvesting+using+cross-flow+fluttering.">Ambient wind energy harvesting using cross-flow fluttering.</a> J. Appl. Phys. 109, 026104 (2011).</li><li>Cha, S. 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=Sound-driven+piezoelectric+nanowire-based+nanogenerators.">Sound-driven piezoelectric nanowire-based nanogenerators.</a> Adv. Mater. 22, 4726-4730 (2010).</li><li>Bai, 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=Integrated+multilayered+triboelectric+nanogenerator+for+harvesting+biomechanical+energy+from+human+motions.">Integrated multilayered triboelectric nanogenerator for harvesting biomechanical energy from human motions.</a> ACS Nano. 7, 3713-3719 (2013).</li><li>Xu, S., Wang, Z. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-dimensional+ZnO+nanostructures:+Solution+growth+and+functional+properties.">One-dimensional ZnO nanostructures: Solution growth and functional properties.</a> Nano Res. 4, 1013-1098 (2011).</li><li>Zhao, M. -. H., Wang, Z. -. L., Mao, S. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Piezoelectric+characterization+of+individual+zinc+oxide+nanobelt+probed+by+piezoresponse+force+microscope.">Piezoelectric characterization of individual zinc oxide nanobelt probed by piezoresponse force microscope.</a> Nano Lett. 4, 587-590 (2004).</li><li>Nam, G. -. H., Baek, S. -. H., Cho, C. -. H., Park, I. -. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+flexible+and+transparent+graphene/ZnO+nanorod+hybrid+structure+fabricated+by+exfoliating+a+graphite+substrate.">A flexible and transparent graphene/ZnO nanorod hybrid structure fabricated by exfoliating a graphite substrate.</a> Nanoscale. 6, 11653-11658 (2014).</li><li>Zou, X., Fan, H., Tian, Y., Yan, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+hydrothermal+synthesis+of+large+scale+ZnO+nanorod+arrays+and+their+growth+mechanism.">Facile hydrothermal synthesis of large scale ZnO nanorod arrays and their growth mechanism.</a> Mater. Lett. 107, 269-272 (2013).</li><li>Qiu, 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=Single-crystalline+twinned+ZnO+nanoleaf+structure+via+a+facile+hydrothermal+process.">Single-crystalline twinned ZnO nanoleaf structure via a facile hydrothermal process.</a> J. Nanosci. Nanotechnol. 11, 2175-2184 (2011).</li><li>Qiu, 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=Synthesis+and+characterization+of+flower-like+bundles+of+ZnO+nanosheets+by+a+surfactant-free+hydrothermal+process.">Synthesis and characterization of flower-like bundles of ZnO nanosheets by a surfactant-free hydrothermal process.</a> J. Nanomater. 2014, 281461 (2014).</li><li>Sun, Y., Riley, D. J., Ashfold, M. N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+ZnO+nanotube+growth+by+hydrothermal+methods+on+ZnO+Film-coated+Si+substrates.">Mechanism of ZnO nanotube growth by hydrothermal methods on ZnO Film-coated Si substrates.</a> J. Phys. Chem. B. 110, 15186-15192 (2006).</li><li>Qiu, 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=The+growth+mechanism+and+optical+properties+of+ultralong+ZnO+nanorod+arrays+with+a+high+aspect+ratio+by+a+preheating+hydrothermal+method.">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><li>Qiu, 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=Solution-derived+40+&#181;m+vertically+aligned+ZnO+nanowire+arrays+as+photoelectrodes+in+dye-sensitized+solar+cells.">Solution-derived 40 &#181;m vertically aligned ZnO nanowire arrays as photoelectrodes in dye-sensitized solar cells.</a> Nanotechnology. 21, 195602 (2010).</li><li>Shin, D. -. M., 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=Freestanding+ZnO+nanorod/graphene/ZnO+nanorod+epitaxial+double+heterostructure+for+improved+piezoelectric+nanogenerators.">Freestanding ZnO nanorod/graphene/ZnO nanorod epitaxial double heterostructure for improved piezoelectric nanogenerators.</a> Nano Energy. 12, 268-277 (2015).</li></ol>

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 border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Cu foil</td>
			<td style="width:71px;">Alfa Aesar</td>
			<td align="right" style="width:119px;">13382</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">poly(methyl methacrylate) (PMMA)</td>
			<td style="width:71px;">Aldrich</td>
			<td align="right" style="width:119px;">182230</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">zinc nitrate hexahydrate</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">228732</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">hexamethylenetetramine (HMT)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">398160</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">polyethylenimine (PEI)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">408719</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">indium tin oxide (ITO) coated PET</td>
			<td style="width:71px;">Aldrich</td>
			<td align="right" style="width:119px;">639303</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Silicone Elastomer Kit</td>
			<td style="width:71px;">Dow Corning</td>
			<td style="width:119px;">Sylgard 184 a, b</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Nickel Etchant Type1</td>
			<td style="width:71px;">Transene Company</td>
			<td align="right" style="width:119px;">41212</td>
			<td></td>
		</tr>
	</tbody>
</table>

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...

Watch this Scientific Journal Video about Preparation of ZnO Nanorod/Graphene/ZnO Nanorod Epitaxial Double Heterostructure for Piezoelectrical Nanogenerator by Using Preheating Hydrothermal at JoVE.co

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

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

Research

JoVE Journal

Engineering

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 &#181;m were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min&#160;of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Procedures are outlined to prepare segmented and coaxial nanowires via templated electrodeposition in nanopores. As examples, segmented nanowires consisting of Ag and ZnO segments, and coaxial nanowires consisting of a TiO2 shell and a Ag core were made. The nanowires were used in photocatalytic hydrogen formation experiments.

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 oC. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 oC. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance.
For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 oC by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application.

We offered a method to directly synthesize high c-axis (0002) ZnO thin film by plasma enhanced chemical vapor deposition. The as-synthesized ZnO thin film combined with Pt interdigitated electrode was used as sensing layer for ultraviolet photodetector, showing a high performance through a combination of its good responsivity and reliability.

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto ...

Subsurface Defect Localization by Structured Heating Using Laser Projected Photothermal Thermography

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering thermal wave fields that are disturbed by the defect. This effect is measured and used to locate the defect. We form the destructively interfering wave fields by using a modified projector. The original light engine of the projector is replaced with a fiber-coupled high-power diode laser. Its beam is shaped and aligned to the projector&#39;s spatial light modulator and optimized for optimal optical throughput and homogeneous projection by first characterizing the beam profile, and, second, correcting it mechanically and numerically. A high-performance infrared (IR) camera is set up according to the tight geometrical situation (including corrections of the geometrical image distortions) and the requirement to detect weak temperature oscillations at the sample surface. Data acquisition can be performed once a synchronization between the individual thermal wave field sources, the scanning stage, and the IR camera is established by using a dedicated experimental setup which needs to be tuned to the specific material being investigated. During data post-processing, the relevant information on the presence of a defect below the surface of the sample is extracted. It is retrieved from the oscillating part of the acquired thermal radiation coming from the so-called depletion line of the sample surface. The exact location of the defect is deduced from the analysis of the spatial-temporal shape of these oscillations in a final step. The method is reference-free and very sensitive to changes within the thermal wave field. So far, the method has been tested with steel samples but is applicable to different materials as well, in particular to temperature sensitive materials.

This method aims at locating vertical subsurface defects. Here, we couple a laser with a spatial light modulator and trigger its video input to heat a sample surface deterministically with two anti-phased modulated lines while acquiring highly resolved thermal images. The defect position is retrieved from evaluating thermal wave interference minima.

The presented method is used to locate subsurface defects oriented perpendicularly to the surface. To achieve this, we create destructively interfering ...

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

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

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%.

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...

Additive Manufacturing of Functionally Graded Ceramic Materials by Stereolithography

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light processing/stereolithography, is developed within the scope of the CerAMfacturing European research project. A three-dimensional (3-D) hemi-maxillary bone-like structure is 3-D printed using custom aluminum oxide polymeric mixtures. The powders and mixtures are fully analyzed in terms of rheological behavior in order to ensure proper material handling during the printing process. The possibility to print functionally graded materials using the Admaflex technology is explained in this document. Field-emission scanning electron microscopy (FESEM) show that the sintered aluminum oxide ceramic part has a porosity lower than 1% and no remainder of the original layered structure is found after analysis.

This manuscript describes the processing of single multifunctional ceramic components (e.g., combinations of dense-porous structures) additively manufactured by stereolithography.

An additive manufacturing technology is applied to obtain functionally graded ceramic parts. This technology, based on digital light ...

Construction and Operation of a Light-driven Gold Nanorod Rotary Motor System

The possibility to generate and measure rotation and torque at the nanoscale is of fundamental interest to the study and application of biological and artificial nanomotors and may provide new routes towards single cell analysis, studies of non-equilibrium thermodynamics, and mechanical actuation of nanoscale systems. A facile way to drive rotation is to use focused circularly polarized laser light in optical tweezers. Using this approach, metallic nanoparticles can be operated as highly efficient scattering-driven rotary motors spinning at unprecedented rotation frequencies in water.
In this protocol, we outline the construction and operation of circularly-polarized optical tweezers for nanoparticle rotation and describe the instrumentation needed for recording the Brownian dynamics and Rayleigh scattering of the trapped particle. The rotational motion and the scattering spectra provides independent information on the properties of the nanoparticle and its immediate environment. The experimental platform has proven useful as a nanoscopic gauge of viscosity and local temperature, for tracking morphological changes of nanorods and molecular coatings, and as a transducer and probe of photothermal and thermodynamic processes.

Plasmonic gold nanorods can be trapped in liquids and rotated at kHz frequencies using circularly-polarized optical tweezers. Introducing tools for Brownian dynamics analysis and light scatteringspectroscopy leads to a powerful system for research and application in numerous fields of science.

The possibility to generate and measure rotation and torque at the nanoscale is of fundamental interest to the study and application of biological and ...

An Efficient Method for Selective Desalination of Radioactive Iodine Anions by Using Gold Nanoparticles-Embedded Membrane Filter

Here, we demonstrate a detail protocol for the preparation of nanomaterials-embedded composite membranes and its application to the efficient and ion-selective removal of radioactive iodines. By using citrate-stabilized gold nanoparticles (mean diameter: 13 nm) and cellulose acetate membranes, gold nanoparticle-embedded cellulose acetate membranes (Au-CAM) have easily been fabricated. The nano-adsorbents on Au-CAM were highly stable in the presence of high concentration of inorganic salts and organic molecules. The iodide ions in aqueous solutions could rapidly be captured by this engineered membrane. Through a filtration process using an Au-CAM containing filter unit, excellent removal efficiency (&gt;99%) as well as ion-selective desalination result was achieved in a short time. Moreover, Au-CAM provided good reusability without significant decrease of its performances. These results suggested that the present technology using the engineered hybrid membrane will be a promising process for the large-scale decontamination of radioactive iodine from liquid wastes.

An efficient method for the rapid and ion-selective desalination of radioactive iodine in several aqueous solutions is described by using gold nanoparticles-immobilized cellulose acetate membrane filters.