Jumbo 'nanotube' existence confirmed at Sandia/LANL nanotech center

Published on 18 December 2008, 08:10 Last Update: 55 minute(s) ago by Insciences

Tags: Nano Materials Nanotechnology Physics

ALBUQUERQUE, N.M. — A jumbo nanotube, like a jumbo shrimp, sounds contradictory.

A giant lightweight carbon nanotube with good strength and electrical properties is desirable, all right. A micron-sized carbon tube is easier to exploit commercially than any (so to speak) littler nanocousin.

But is it still a nanotube?

Jianyu Huang at the joint Sandia and Los Alamos national laboratories Center for Integrated Nanotechnologies (CINT), with colleagues elsewhere, got around this problem by naming their new creation “colossal carbon tubes” in a paper published in a recent issue of Physical Review Letters.

“The structures are remarkable because they are very light, possess good electrical conductivity, and mechanical properties similar to carbon fibers,” Huang says.

Among possibilities of use are so-called textile electronics and body armor.

Because of their strange, surprising sponginess — walls of graphite-like carbon kept apart by hollow, rectangular compartments — the colossal fibrous tubes are 20 times less dense than carbon fibers, yet about the same length — in the centimeter range. And they appear to be slightly stronger — a very desirable, and until now unheard-of property in large carbon tubes.

The new form of carbon surprised leading nanotechnology researchers. MIT’s carbon technology specialist Mildred Dresselhaus was quoted in an online news article in the journal Nature: “This is a new form of carbon that was unexpected to me.”

Huang, who did the microstructure analysis confirming that the walls of such tubes consist of graphitic structure, describes the new creation as “a porous, giant, carbon fiber-like tubular structure” of diameters ranging from 40 to 100 microns. Conventional carbon nanotubes are about 10 nanometer diameter.

The material was made at Los Alamos National Laboratory. Researchers there led by Yuntian Zhu and Huisheng Peng found that heating ethylene and paraffin oil produced a carbon vapor that condensed into tubes of pure carbon tens of microns wide and up to several centimeters long. Zhu now is at North Carolina State University, and Huisheng Peng is at Tongji University in Shanghai.

JUMBO TUBES -- a scanning electron microscope image (left) of a huge carbon tube. Images at right depict cross-sectional view of the tube, with rectangular pore tunnels visible in its wall. (photo by Sandi/LANL Center for Integrated Nanotechnologies)
Download 300dpi 1.11MB JPEG image

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Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin company, for the U.S. Department of Energy’s National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies, and economic competitiveness.

Contact: Neal Singer, nsinger@sandia.gov, (505) 845-7078

Source: Sandia

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Seventh-grader shines with solar cell research

William Yuan won a $25,000 scholarship for his graduate level work

By Christina Lent

The Beaverton Valley Times, Sep 11, 2008, Updated Sep 16, 2008

Jaime Valdez / The Beaverton Valley Times

William Yuan, 12, will be recognized Sept. 24 for his invention of a highly-efficient, three-dimensional nanotube solar cell for visible and ultraviolet light.

William Yuan’s bright idea to create a new, more efficient solar cell earned him top honors as Oregon’s only 2008 Davidson Fellow.

As part of the honor, the 12-year-old Bethany boy will be flown to Washington, D.C., for a reception Sept. 24 at the Library of Congress where he will receive his award and a $25,000 scholarship from the Davidson Institute for Talent Development.

“William’s work was evaluated by university professors and environmental scientists,” said Tacie Moessner, Davidson Fellows program manager in a call from Reno, Nev. “They look for the project’s potential to benefit society and make sure it is socially relevant. Generally, the projects need to be at the graduate level.”

Yuan worked on his project for the past two years with the encouragement of his science teacher Susan Duncan; support of his parents Gang Yuan and Zhiming Mei; and counsel of professional mentors Professor Chunfei Li of Portland State University’s Center for Nanofabrication and Electron Microscopy, Fred Li of Applied Materials Inc. and Professor Shaofan Li of the Department of Civil Engineering at the University of California – Berkeley.

“He is our youngest fellow in science that we’ve ever had,” Moessner said. “He is really spectacular.

“His project will really make a difference in advancing the technology of solar cells. You would never know he’s 12 looking at the quality of his work.”

Young talent

William Yuan is a seventh-grader in Meadow Park Middle School’s Summa options program.

He is an active member of the school’s Math Engineering Science Achievement (MESA) Club, First Lego League team and participant in the Science Bowl and MathCounts programs. He is also a two-time, second-place chess champion for the state.

Recognizing his interest in science, math and engineering, Yuan’s science teacher encouraged him to tackle a challenging engineering project for the Northwest Science Expo after introducing him to nanotechnology and renewable energy research.

“We learned about some great energy and environmental issues,” Yuan said. “To try to help, I researched the application of nanotechnology and renewable energy.

“I felt they would best complement my background knowledge and experience. After extensive research and community outreach, I wanted to work on a project to find a solution for some of the problems of the world.”

Yuan decided to focus his project on finding the most efficient way to harness the sun’s energy.

“I felt solar energy had large potential but it was underused,” he explained. “Fossil fuels like oil, coal and natural gas are only finite and are slated to run out by 2050.

“We need to make solar energy more cost effective and efficient.”

With that thought in mind, Yuan got to work.

“Current solar cells are flat and can only absorb visible light,” he said. “I came up with an innovative solar cell that absorbs both visible and UV light. My project focused on finding the optimum solar cell to further increase the light absorption and efficiency and design a nanotube for light-electricity conversion efficiency.”

Yuan invested countless hours in his research, seeking out new resources in the field to find a workable real-world solution.

“He has worked very hard in the past couple years,” his father Gang Yuan said. “We’re grateful that he had great mentors and teachers to guide him.

“When he started on his research, he had great curiosity and wanted to dig into it more. As his parents, we looked for experiences to help him.”

Watching his dedication impressed William’s parents.

“This generation’s sense of urgency is much stronger than my generation’s,” his father said. “They are thinking about the future and want to know how environmental issues will impact their generation.”

Promising future

Tapping into that talent and giving gifted youth the opportunity to excel is what the Davidson Institute is all about.

The national nonprofit organization recognized 20 students this year for their achievements.

Yuan admitted he submitted his project for review as a learning experience.

“This was a test run — I wasn’t expected anything,” he said. “I thought it would help when I entered another program when I was older.”

His work on developing his three-dimensional solar cell is far from complete.

“My next step is to talk to manufacturers to see if they will build a working prototype,” Yuan said. “If the design works in a real test stage, I want to find a company to manufacture and market it.”

The Davidson Institute scholarship will help Yuan further his research and his career in science and technology.

He plans to use the money to “attend one of the best universities in the country” and study nanotechnology, biotechnology or medicine.

“I’d like to work in technology at Google, Applied Materials or some other company that starts up between now and then,” Yuan said. “I’ve always liked math and science and engineering.

“If used properly, they can help solve the problems of the world. They can also be used to explore the world around us.”

Moessner has no doubt that Yuan will achieve great things in his future and looks forward to meeting him later this month.

“All of the fellows are really focused and driven but still humble,” she said. “They are also creative and brilliant.”

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FWIW, this is the closest document I could find involving nanotubes, solar cells and ultraviolet, visible and infrared light:

United States Patent Application	20070240757
Kind Code	A1
Ren; Zhifeng ; et al.	October 18, 2007

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Solar cells using arrays of optical rectennas

Abstract

The present invention discloses a solar cell comprising a nanostructure array capable of accepting energy and producing electricity. In an embodiment, the solar cell comprises an at least one optical antenna having a geometric morphology capable of accepting energy. In addition, the cell comprises a rectifier having the optical antenna at a first end and engaging a substrate at a second end wherein the rectifier comprises the optical antenna engaged to a rectifying material (such as, a semiconductor). In addition, an embodiment of the solar cell comprises a metal layer wherein the metal layer surrounds a length of the rectifier, wherein the optical antenna accepts energy and converts the energy from AC to DC along the rectifier. Further, the invention provides various methods of efficiently and reliably producing such solar cells.

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Inventors:	Ren; Zhifeng; (Newton, MA) ; Kempa; Krzysztof; (Billerica, MA) ; Wang; Yang; (Allston, MA)
Assignee Name and Adress:	The Trustees of Boston College

Claims:
17. A method for producing a solar cell, comprising: growing a plurality of vertically-aligned nanotubes on a substrate; depositing a layer of a rectifying material onto the nanotubes; and depositing a layer of metal to cover a length of the nanotubes.

[0052] Aligned MWCNT arrays grown on silicon substrates using PECVD act as optical rectennas, receiving and transmitting light at ultraviolet (UV), visible and infrared (IR) frequencies.

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Researchers Generate Hydrogen Without The Carbon Footprint

ScienceDaily (July 15, 2008) — A greener, less expensive method to produce hydrogen for fuel may eventually be possible with the help of water, solar energy and nanotube diodes that use the entire spectrum of the sun's energy, according to Penn State researchers.

"Other researchers have developed ways to produce hydrogen with mind-boggling efficiency, but their approaches are very high cost," says Craig A. Grimes, professor of electrical engineering. "We are working toward something that is cost effective."

Currently, the steam reforming of natural gas produces most of our hydrogen. As a fuel source, this produces two problems. The process uses natural gas and so does not reduce reliance on fossil fuels; and, because one byproduct is carbon dioxide, the process contributes to the carbon dioxide in the atmosphere, the carbon footprint.

Grimes' process splits water into its two components, hydrogen and oxygen, and collects the products separately using commonly available titanium and copper. Splitting water for hydrogen production is an old and proven method, but in its conventional form, it requires previously generated electricity. Photolysis of water solar splitting of water has also been explored, but is not a commercial method yet.

Grimes and his team produce hydrogen from solar energy, using two different groups of nanotubes in a photoelectrochemical diode. They report in the July issue of Nano Letters that using incident sunlight, "such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 milliampere per centimeter square, at a photoconversion efficiency of 0.30 percent."

"It seems that nanotube geometry is the best geometry for production of hydrogen from photolysis of water," says Grimes.

In Grimes' photoelectrochemical diode, one side is a nanotube array of electron donor material -- n-type material -- titanium dioxide, and the other is a nanotube array that has holes that accept electrons - p-type material -- cuprous oxide titanium dioxide mixture. P and n-type materials are common in the semiconductor industry. Grimes has been making n-type nanotube arrays from titanium by sputtering titanium onto a surface, anodizing the titanium with electricity to form titanium dioxide and then annealing the material to form the nanotubes used in other solar applications. He makes the cuprous oxide titanium dioxide nanotube array in the same way and can alter the proportions of each metal.

While titanium dioxide is very absorbing in the ultraviolet portion of the sun's spectrum, many p-type materials are unstable in sunlight and damaged by ultraviolet light, they photo-corrode. To solve this problem, the researchers made the titanium dioxide side of the diode transparent to visible light by adding iron and exposed this side of the diode to natural sunlight. The titanium dioxide nanotubes soak up the ultraviolet between 300 and 400 nanometers. The light then passes to the copper titanium side of the diode where visible light from 400 to 885 nanometers is used, covering the light spectrum.

The photoelectrochemical diodes function the same way that green leaves do, only not quite as well. They convert the energy from the sun into electrical energy that then breaks up water molecules. The titanium dioxide side of the diode produces oxygen and the copper titanium side produces hydrogen.

Although 0.30 percent efficiency is low, Grimes notes that this is just a first go and that the device can be readily optimized.

"These devices are inexpensive and because they are photo-stable could last for years," says Grimes. "I believe that efficiencies of 5 to 10 percent are reasonable."

Grimes is now working with an electroplating method of manufacturing the nanotubes, which will be faster and easier.

Working with Grimes are Gopal K. Mor, Oomman K. Varghese and Karthik Shankar, research associates; Rudeger H. T. Wilke and Sanjeev Sharma, Ph.D. candidates; Thomas J. Latempa, graduate student, all at Penn State; and Kyoung-Shin Choi, associate professor of chemistry, Purdue University.

The U.S. Department of Energy supported this research.

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