Major Advance in Manufacture of El-Mul’s Nanotube-Based Field Emitter

WEBWIRE – Thursday, May 29, 2008

Contact Information

Bob Rosenbaum

Marketing Director

El-Mul Technologies Ltd

+972 8-943-4184

bob.rosenbaum@el-mul.com

Achievement details to be presented at 2008 Conference
of the Nanoscience and Technology Institute in Boston.

YAVNE, ISRAEL (29 May 2008) – El-Mul Technologies announced today that it has gained critical knowledge that will allow commercial manufacture of its proprietary carbon nanotube (CNT) based field emission device. This achievement enables development of the device for a variety of industrial applications, including production of E-beam sources to be used primarily in analytical instruments and semiconductor tools.

Details of the achievement will be presented on June 3 at the 2008 Conference of the Nanoscience and Technology Institute (NSTI) to be held in Boston, by Mr. Sagi Daren, El-Mul’s Nano Electron Source (NES) project manager.

“Today we are offering a working industrial process to manufacture complex CNT-based electron sources with outstanding performance for real life applications,” Dr. Armin Schon, CEO of El-Mul Technologies, announced. “We can now custom design and produce sources for various applications and we will expand our offerings in the near future, both in our home markets and elsewhere.”

The company is focusing on design and manufacture of E-beam sources in two areas: well-characterized fine beam applications based on single CNT emitters, and high-current broad beam applications based on multi-beam CNT emitter arrays. Marketed as the E-Beam On-a-Chip™ platform, El-Mul’s first product is currently undergoing testing with a European partner.

Schon noted that early stages of El-Mul’s CNT electron source project were greeted with skepticism. “I heard many critical comments about the technological difficulties of such an endeavor. Today we can show that we have overcome the biggest challenge of all – high yield manufacturing.” Schon also praised the project team members. “We’ve been successful because we’ve harnessed the best properties of Israel’s high tech culture: highly qualified and motivated team members with very high tolerance for risk and disappointment, working alongside management that has the long-term vision to guide a very challenging process through to its resolution.”

El-Mul’s initial electron source device is targeted primarily for next generation scanning electron microscope (SEM) and transmission electron microscope (TEM) systems. The new device is expected to result in 30 percent higher resolution, a four-fold increase in scanning speeds, and a significant cost reduction in both manufacturing and maintenance of SEM and TEM systems.

El-Mul’s patented approach creates a MEMS-based electron source that results in superior beam brightness, narrower energy spread and smaller source size than conventional electron emitter devices. To manufacture the new device, El Mul has also developed a proprietary chemical vapor deposition (CVD) process that grows single CNT emitters inside cathode wells 4 microns deep.

Among potential application markets for the E-Beam On-a-Chip™ platform are: sub 40 nm E beam lithography, metrology and inspection tools (for semiconductor manufacturing); X ray and mass spectrometry tools (for medical and life sciences); and field emission displays.

CNT-based electron source device R&D has been funded through strategic partnerships and by the Office of the Chief Scientist in Israel’s Ministry of Industry and Trade. El Mul holds US and international patents for its R&D in this area.

El-Mul Technologies has over 16 years experience in the design and manufacture of electron and ion detectors for a wide variety of industries and research environments, and is recognized today as a leading solutions provider for nanotechnology toolmakers. El-Mul has pioneered nanoscale devices since 1999.

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29 May 2008

E-Beam On-a-Chip™ Device Achievements Announced

El-Mul to present major advances in the manufacture of it's patented carbon nanotube-based electron beam source platform at the NSTI 2008 conference in Boston.

Download Press Release (PDF, 152 KB)

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Source

El-Mul US patent reference:

United States Patent	6,512,235
Eitan , et al.	January 28, 2003

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Nanotube-based electron emission device and systems using the same

Abstract

A device that produces an electron beam with high optical quality for processing a sample, is presented. The optical quality is manifested by very high brightness and low energy spread. The device includes an electron source device comprising an electrode in the form of a shaped first layer, preferably in the form of a conducting crater carrying at least one nanotube, and an extracting electrode, which is formed with at least one aperture and is insulated from the firs layer. The source can be used in any column that requires such properties. The column according to the invention may be a full size or a miniature electron microscope, a lithography tool, a tool used for direct writing of wafers or a field emission display.

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Inventors:	Eitan; Guy (Menorah, IL), Zik; Ory (Tel Aviv, IL), Rosenblatt; David (Philadelphia, PA)
Assignee:	El-Mul Technologies Ltd. (Yavne, IL)
Appl. No.:	09/561,958
Filed:	May 1, 2000

Extract:
Since the electron source device that is based on fiber(s), e.g., nanotube(s), in a conducting crater emits with sufficient brightness to be used in electron microscopy, it is evident that a matrix of craters is suitable for a field emission display, where each beamlet correspond to a pixel. Thus, the current invention is also suitable for flat panel displays.

The advantages of the present invention are thus self-evident The electron source device according to the invention enables to solve various constructional and operational problems of electron source device based systems, such as electron microscopes, lithography tools and flat displays. Due to the small size of the nanotube-based electron source device and relaxed vacuum requirements, the entire system can have a desirably small footprint, and can allow for assembling a multiple-column arrangement to be advantageously used in various applications. Due to the elevated optical performance of the electron gun and reduced chromatic and spherical aberrations of the associated electron beam, the performance of the system is significantly improved. In fact, the invention allows to the useful utilization of nanotubes in an electron gun. The use of "patterned" cathode-electrode, and preferably by means of the same anode-electrode, the construction and operation of a lithography tool utilizing such an electron source device is significantly improved.

Source

WO/2001/084130 (PCT equivalent)

Nanoparticles assemble by millions to encase oil drops

05/29/2008

CONTACT: Jade Boyd
PHONE: 713-348-6778
E-MAIL: jadeboyd@rice.edu

Designer 'nanobatons' could be used to trap oil, deliver drugs

In a development that could lead to new technologies for cleaning up oil spills and polluted groundwater, scientists at Rice University have shown how tiny, stick-shaped particles of metal and carbon can trap oil droplets in water by spontaneously assembling into bag-like sacs.

The tiny particles were found to assemble spontaneously by the tens of millions into spherical sacs as large as BB pellets around droplets of oil in water. In addition, the scientists found that ultraviolet light and magnetic fields could be used to flip the nanoparticles, causing the bags to instantly turn inside out and release their cargo -- a feature that could ultimately be handy for delivering drugs.

"The core of the nanotechnology revolution lies in designing inorganic nanoparticles that can self-assemble into larger structures like a 'smart dust' that performs different functions in the world – for example, cleaning up pollution," said lead research Pulickel Ajayan, Rice's Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science. "Our approach brings the concept of self-assembling, functional nanomaterials one step closer to reality."

The research was published online today by the American Chemical Society's journal Nano Letters.

***********************************************

ASAP Nano Lett., ASAP Article, 10.1021/nl080407i
Web Release Date: May 29, 2008

Copyright © 2008 American Chemical Society

Controlled Manipulation of Giant Hybrid Inorganic Nanowire Assemblies

Fung Suong Ou,^†‡ Manikoth M. Shaijumon,^‡§ and Pulickel M. Ajayan^*‡§

Department of Applied Physics, Rice University, Houston, Texas 77005, Department of Mechanical Engineering and Materials Science, Rice University, Houston, Texas 77005, and Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180

Received February 11, 2008

Revised April 28, 2008

Abstract:

The ultimate goal of nanotechnology is the design and fabrication of nanosize building blocks with multiple functionalities and their assembly into large-scale functional structures that can be controllably manipulated. Here we show that hybrid inorganic multisegmented nanowires, with hydrophobic carbon nanotube tails and hydrophilic metal nanowire heads, allow the assembly and manipulation of massive ordered structures in solution, reminiscent of the organic molecular micellar assembly. Further, properly designed assemblies can be manipulated using external stimuli such as magnetic field and light. The hybrid nanowires can have multiple segments including magnetic components, allowing the assembly to be manipulated by external magnetic field. The assembled structures can also be manipulated by modifying the hydrophobicity of the respective components via chemical functionalization and optical irradiation. This approach brings the concept of environment sensitive self-assembling nanomaterials closer to reality.

Download the full text: PDF | HTML

Source

**********************************************

The multisegmented nanowires, akin to "nanoscale batons," were made by connecting two nanomaterials with different properties, much like an eraser is attached to the end of a wooden pencil. In the study, the researchers started with carbon nanotubes -- hollow tubes of pure carbon. Atop the nanotubes, they added short segments of gold. Ajayan said that by adding various other segments -- like sections of nickel or other materials -- the researchers can create truly multifunctional nanostructures.

The tendency of these nanobatons to assemble in water-oil mixtures derives from basic chemistry. The gold end of the wire is water-loving, or hydrophilic, while the carbon end is water-averse, or hydrophobic. The thin, water-tight sacs that surround all living cells are formed by interlocking arrangements of hydrophilic and hydrophobic chemicals, and the sac-like structures created in the study are very similar.

Ajayan, graduate student Fung Suong Ou and postdoctoral researcher Shaijumon Manikoth demonstrated that oil droplets suspended in water became encapsulated because of the structures' tendency to align their carbon ends facing the oil. By reversing the conditions -- suspending water droplets in oil – the team was able to coax the gold ends to face inward and encase the water.

"For oil droplets suspended in water, the spheres give off a light yellow color because of the exposed gold ends," Ou said. "With water droplets, we observe a dark sphere due to the protruding black nanotubes."

The team is next preparing to test whether chemical modifications to the "nanobatons" could result in spheres that can both capture and break down oily chemicals. For example, they hope to attach catalysts to the water-hating ends of the nanowires that will cause compounds like trichloroethene, or TCE, to break into nontoxic constituents. Another option would be to attach drugs whose release can be controlled with an external stimulus.

"The idea is to go beyond just capturing the compound and initiate a process that will make it less toxic," Ajayan said. "We want to build upon the method of self assembly and start adding functionality so these particles can carry out tasks in the real world."

The research was supported by Rice University, Applied Materials Inc. and the New York State Foundation for Science, Technology and Innovation.

Source

Quantum Solar Power Corp., Inc.

I am talking my head off here and elsewhere trying to get NNPP or anybody else to get interested in this rectenna development by NNPP's grandpa, a guy named Howard K. Schmidt.

Look here for the rectenna stuff so far:
http://donpatent.blogspot.com/2008/05/inventor-schmidt-howard-k.html

I think rectenna empowered solar could bury oil but what company will develop it is unknown - that's why I would like to see NNPP participate and use either Ren (Boston College) or Schmidt's developments or both to cover all the bases.

Re QVQV:
From : http://investing.businessweek.com/research/stocks/snapshot/snapshot.asp?capId=11817017

QV, Quantum Ventures Enters into Agreement with Canadian Integrated Optics International to Manufacture & Market CIOI's Patent Pending Solar Technology
04/16/2008

QV Quantum Ventures Inc. announced that the company has entered into a License agreement with Canadian Integrated Optics International Ltd. of Douglas, Isle of Man (CIOI), to manufacture and market CIOI's patent pending solar technology based on an optical rectenna. Closing of this agreement will occur on or about May 16, 2008 and is subject to certain terms and conditions. The Purchase Price for the license shall be paid in shares of the Company's common stock and a royalty.

I got this out of the 8K: http://sec.edgar-online.com/2008/04/16/0001096350-08-000061/Section6.asp

"Patent Rights" means issued patents and pending patent applications in any country in respect of an invention owned by the Licensor relating to the Technology, including provisionals, continuations-in-part, continuations, divisionals, re-issues and extensions of those issued patents and pending patent applications, including inventions described in the specifications of United States Patent Application Numbers 60/911,847, 60/911,815, 60/911,823 and 60/911,837 filed on April 13, 2007.

I searched and found nothing - they are not yet published. '60' signifies an early incomplete informal filing to get an early filing date - they have a year to get a proper application filed and to maintain that early filing date.

Rectenna. Remember it - it will change the world.

Goodbye oil and coal, hello rectenna solar.

What is a rectenna? It is an antenna which receives electromagnetic waves from the sun, for example, and converts them into rectified direct electric current.

Quantm Ventures - shortly (June 16, 2008) to be renamed - Quantum Solar Power Corp., Inc.
http://knobias.10kwizard.com/filing.php?param=&ipage=5683950&DSEQ=1&SEQ=&SQDESC=SECTION_BODY&exp=

Imation ships compact Nano Flash Drives

Wednesday, May 28th

Veteran storage manufacturers Imation today announced details of their new line of portable USB flash drives, the Nano Flashes. The drives are available in storage capacities of 1, 2, 4 and 8GB; the design is an evolution of previous USB drives offered by the company, but is only 1.7 inches long, 0.6 inches wide, and 0.4 inches deep. It also focuses on an integrated 360-degree swivel cap, which protects the connector when the drive is not in use, and allows for attachment to keychains, lanyards and even mobile phones.

The Nano is compatible on a basic level with Linux and Mac OS 9 or later, but full compatibility is reserved for Windows 98, 2000, XP and Vista, which support password protection and drive partitioning. Vista additionally supports ReadyBoost funcationality.

Nano Flashes are shipping immediately in the US, at prices ranging between $15 and $90. No information as to when or if the drives will be available worldwide has been released by Imation at the time of writing.

*********************************
Some patent background:
Ref:
WO 2004 075171
DATA RECORDING USING CARBON NANOTUBE ELECTRON SOURCES
OAKLEY, William, S. [LOTS Technology or Imation Corp.]
http://tinyurl.com/62oxg8

The written opinion of the ISA
(See p3 - no invention in view of USP 6,312,303, Yaniv, et al.)

Makes me wonder does all this.

You?

HEWLETT-PACKARD CNT Memory Data Storage

Data storage device including nanotube electron sources
HEWLETT-PACKARD
Priority date July 6, 2001

United States Patent Application 20030007443
Kind Code A1
Nickel, Janice H. January 9, 2003

Matured to USP 6,928,042
What is claimed is:
1. A data storage device comprising an array of nanotubes as electron sources; and a phase-change storage layer proximate tips of the electron sources.

And USP 7,295,503

What is claimed is:

1. A data storage device comprising an array of nanotubes as electron sources.

2. The device of claim 1, wherein the nanotubes are carbon-based.

3. The device of claim 1, wherein the nanotubes are boron nitride-based.

4. The device of claim 1, further comprising a phase-change storage layer proximate tips of the electron sources.

5. The device of claim 1, wherein each nanotube electron source is elongated.

6. The device of claim 5, wherein the nanotubes have an aspect ratio greater than 10:1.

7. The device of claim 1, further comprising word and bit lines for addressing the nanotubes.

8. The device of claim 1, further comprising a micromover for positioning the array.

9. A data storage device comprising: an array of carbon-based nanotubes; and a phase-change storage layer proximate tips of the nanotubes.

10. A data storage device comprising: an array of boron nitride-based nanotubes; and a phase-change storage layer proximate tips of the nanotubes.

11. An electron beam source for a data storage device, the source comprising an array of nanotubes.

12. The electron beam source of claim 11, wherein the nanotubes are carbon nanotubes.

13. The electron beam source of claim 11, wherein the nanotubes are boron nitride nanotubes.

14. The source of claim 11, wherein the nanotubes have an aspect ratio greater than 10:1.

15. The source of claim 11, further comprising word and bit lines for addressing the nanotubes.

16. The device of claim 11, further comprising a micromover for positioning the array.
--------------------------------------------------------------------------------

Description

--------------------------------------------------------------------------------


BACKGROUND

[0001] The present invention relates generally to electron sources. The present invention also relates to data storage devices.

[0002] For decades researchers have been working to increase storage density and reduce storage cost of data storage devices such as magnetic hard-drives, optical drives, and semiconductor random access memory. However, increasing the storage density is becoming increasingly difficult because conventional technologies appear to be approaching fundamental limits on storage density. For instance, information storage based on conventional magnetic recording is rapidly approaching fundamental physical limits such as the superparamagnetic limit, below which magnetic bits are not stable at room temperature.

[0003] Storage devices that do not face these fundamental limits are being researched. An example of such an information storage device is described in Gibson et al. U.S. Pat. No. 5,557,596. The device includes multiple electron sources having electron emission surfaces that are proximate a storage medium. During write operations, the electron sources bombard the storage medium with relatively high intensity electron beams. During read operations, the electron sources bombard the storage medium with relatively low intensity electron beams.

[0004] Size of storage bits in such a device may be reduced by decreasing the electron beam diameter. Reducing the storage bit size increases storage density and capacity, and it decreases storage cost.

[0005] "Spindt" emitters could be used for generating focused electron beams in such a device. A Spindt emitter has a conical shape and emits an electron beam at the tip of its cone. The cone tip is made as sharp as possible to reduce operating voltage and achieve a small electron beam diameter.

[0006] However, certain problems arise with Spindt emitters. One problem is that the Spindt emitters are sensitive to impact. The tips of the Spindt emitters are only a few nanometers from the storage medium. If a tip makes contact with the storage medium, it could be damaged. Another problem is directionality of the electron beams emitted from the Spindt emitters. Sometimes an electron beam can come off the side of the cone rather than the tip. Yet another problem is a loss of material from the tips due to energy being greater than the workfunction. The loss of material reduces the effectiveness of the tips.

SUMMARY

[0007] According to one aspect of the present invention, a data storage device includes nanotubes as electron sources. Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the present invention.

LINK

This filing looks like the dominant one - earliest priority date - July 6, 2001.

These are all noted here:
http://www.geocities.com/mr_module/NanoDataRecorders.html?1094841052781

Method of fabricating memory device utilizing carbon nanotubes

United States Patent 7,378,328 Choi, et al., May 27, 2008

Abstract

A fast, reliable, highly integrated memory device formed of a carbon nanotube memory device and a method for forming the same, in which the carbon nanotube memory device includes a substrate, a source electrode, a drain electrode, a carbon nanotube having high electrical and thermal conductivity, a memory cell having excellent charge storage capability, and a gate electrode. The source electrode and drain electrode are arranged with a predetermined interval between them on the substrate and are subjected to a voltage. The carbon nanotube connects the source electrode to the drain electrode and serves as a channel for charge movement. The memory cell is located over the carbon nanotube and stores charges from the carbon nanotube. The gate electrode is formed in contact with the upper surface of the memory cell and controls the amount of charge flowing from the carbon nanotube into the memory cell.

Inventors: Choi; Won-bong (Yongin, KR), Yoo; In-kyeong (Suwon, KR), Chu; Jae-uk (Gwangmyeong, KR)

Assignee: Samsung Electronics Co., Ltd. (Suwon, Kyungki-do, KR)

http://tinyurl.com/56r5a3

I'm all for it - the more the merrier - Keesmann agrees, I hope.

Phase changeable memory devices including carbon nano tubes

United States Patent 7,378,701 Hideki May 27, 2008, Samsung

Abstract

An integrated circuit phase changeable memory device includes an integrated circuit substrate, a first electrode on the integrated circuit substrate, and a second electrode on the integrated circuit substrate and spaced apart from the first electrode. A carbon nano tube and a phase changeable layer are serially disposed between the first and second electrodes. An insulating layer can include a contact hole and the carbon nano tube may be provided in the contact hole. Moreover, the phase changeable layer also may be provided at least partially in the contact hole. A layer also may be provided at least partially surrounding the carbon nano tube in the contact hole. Related fabrication methods also are provided.

Inventors: Hideki; Horii (Seoul, KR)

Assignee: Samsung Electronics Co., Ltd. (KR)

http://tinyurl.com/4t5yd4

Not sure if this is coincidental, but here it is - same issue day as UMK's offering and very similar. I think the USPTO lets them slug it out together outside the patent office as to who owns what. UMK's was magnetic while this one is phase change so that could be the distinction.

Large-capacity magnetic memory using carbon nano-tube

United States Patent 7,379,326 Ushida,et al., May 27, 2008

[[Note - Is this CNT emitting? If it is Keesmann applies! It could be big!!!]]

Abstract

A high-capacity magnetic memory capable of writing and reading a magnetic record in/from a magnetic recording film according to a perpendicular magnetic recording system at a high speed in a purely-electrically random access manner. In the magnetic memory, a writing-magnetic-field generating means 62 and a writing word line 43 are disposed relative to a perpendicular magnetic recording film 50, and a reading/writing bit-line conductor 41, a magnetoresistive-effect element 20 and a reading word lead conductor 42 are laminated in order on a probe substrate opposed to the perpendicular magnetic recording film 50. A magnetic probe 30 composed of a carbon nanotube containing a soft magnetic material is disposed relative to the magnetoresistive-effect element 20 in a standing manner, and electrically connected to the reading/writing bit-line conductor. During a writing operation, a micro-discharge is generated in a micro-gap G between the edge of the magnetic probe and the magnetic recording film under a writing magnetic field to allow a writing current to flow through the micro-gap G so as to heat a micro-region of the magnetic recording film in such a manner that it goes through its Curie point to thereby become magnetized in the direction of the recording magnetic field to form a magnetic record therein. During a reading operation, the magnetic record is read out through the magnetic probe in accordance with a current variation in the magnetoresistive-effect element.

Inventors: Ushida; Takashi (Furukawa, JP), Mori; Nobuyuki (Furukawa, JP), Kamijo; Yoshimi (Furukawa, JP), Okazaki; Akihiro (Furukawa, JP), Mitsuzuka; Akira (Furukawa, JP), Hatakeyama; Rikizou (Furukawa, JP), Ido; Hideaki (Furukawa, JP), Nakajima; Ko (Furukawa, JP), Takoshima; Takehiro (Furukawa, JP)

Assignee: UMK Technologies Co., Ltd. (Furukawa-shi, JP)

The nano-magnetic probe 30 is disposed in opposed relation to the perpendicular magnetization film 50 through a micro-gap G, and the space S therebetween is sealed in a vacuum or depressurized state. If the conditions for generating a micro-discharge are satisfied, the space may be maintained under an inert atmosphere instead of the depressurized state. [[Sounds like electron emission is present!]]

http://tinyurl.com/4t5yd4

If this is as big as I think it is or could/will be, it could be worth a pretty penny to us and Keesmann. Don't ya think? Then again it might just be another disappointment - we can handle those!!!!!! We are used to it. ;-)

Refs:
http://www.wipo.int/pctdb/en/wo.jsp?wo=2004001851
http://www.freepatentsonline.com/EP1533846.html

'Avalanche Effect' In Solar Cells Demonstrated

ScienceDaily (May 27, 2008) — Researchers at TU Delft and the FOM Foundation for Fundamental Research on Matter have found irrefutable proof that the so-called avalanche effect by electrons occurs in specific, very small semiconducting crystals. This physical effect could pave the way for cheap, high-output solar cells. The findings are to be published in scientific journal Nano Letters.

Solar cells provide great opportunities for future large-scale electricity generation. However, there are currently significant limitations, such as the relatively low output of most solar cells (typically fifteen percent) and high manufacturing costs.

One possible improvement could derive from a new type of solar cell made of semiconducting nanocrystals (crystals with dimensions in the nanometre size range). In conventional solar cells, one photon (light particle) can release precisely one electron. The creation of these free electrons ensures that the solar cell works and can provide power. The more electrons released, the higher the output of the solar cell.

In some semiconducting nanocrystals, however, one photon can release two or three electrons, hence the term avalanche effect. This could theoretically lead to a maximum output of 44 percent in a solar cell comprising the correct semiconducting nanocrystals. Moreover, these solar cells can be manufactured relatively cheaply.

The avalanche effect was first measured by researchers at the Los Alamos National Laboratories in 2004. Since then, the scientific world has raised doubts about the value of these measurements. Does the avalanche effect really exist or not?

Within the Joint Solar Programme TU Delft's Prof. Laurens Siebbeles has now demonstrated that the avalanche effect does indeed occur in lead selenide (PbSe) nanocrystals. It has been established, however, that the effect in this material is smaller than previously assumed. Siebbeles' results are more reliable than those of other scientists thanks to more careful and more detailed measurement using ultra-fast laser methods.

Siebbeles believes that this research paves the way for further unravelling the secrets of the avalanche effect.

http://www.sciencedaily.com/releases/2008/05/080527091942.htm

Inventor: SCHMIDT, Howard K.

Hello!! Isn't this NNPP(Nano-Proprietary, now Applied Nanotech - APNT)'s grandpa?

Inventor: SCHMIDT, Howard K.

(WO/2008/060640) NANOPARTICLE / NANOTUBE-BASED NANOELECTRONIC DEVICES AND CHEMICALLY-DIRECTED ASSEMBLY THEREOF

Pub. No.: WO/2008/060640 International Application No.: PCT/US2007/061563
Publication Date: 22.05.2008 International Filing Date: 02.02.2007
IPC: G02B 6/12 (2006.01)

Applicants: WILLIAM MARSH RICE UNIVERSITY [US/US]; 6100 Main Street, Houston, TX 77005 (US) (All Except US).
SCHMIDT, Howard K. [US/US]; 20702 Bradford Creek Ct, Cypress, TX 77433 (US) (US Only).

Inventor: SCHMIDT, Howard K. [US/US]; 20702 Bradford Creek Ct, Cypress, TX 77433 (US).

Agent: SHADDOX, Robert C.; Winstead Sechrest & Minick P.c., P.O. Box 50784, Dallas, TX 75201 (US).
Priority Data:
60/764,636 02.02.2006 US

Title: NANOPARTICLE / NANOTUBE-BASED NANOELECTRONIC DEVICES AND CHEMICALLY-DIRECTED ASSEMBLY THEREOF

Abstract:
According to some embodiments, the present invention provides a nanoelectronic device based on a nanostructure that may include a nanotube with first and second ends, a metallic nanoparticle attached to the first end, and an insulating nanoparticle attached to the second end. The nanoelectronic device may include additional nanostructures so a to form a plurality of nanostructures comprising the first nanostructure and the additional nanostructures. The plurality of nanostructures may arranged in a network comprising a plurality of edges and a plurality of vertices, wherein each edge comprises a nanotube and each vertex comprises at least one insulating nanoparticle and at least one metallic nanoparticle adjacent the insulating nanoparticle. The combination of at least one edge and at least one vertex comprises a diode. The device may be an optical rectenna.

[0005] An attraction for rectenna technology is its high theoretical conversion efficiency - roughly 95%. The greatest conversion efficiency ever recorded by a rectenna element occurred in 1977 by Brown, Raytheon Company. Using a GaAs-Pt Schottky barrier diode, a 90.6% conversion efficiency was recorded with an input microwave-power level of 8W. Conversion efficiencies in the range of 80% are typical, with representative circuits shown below.

[0006] The concept is arbitrarily scaleable, and the optical rectenna is a direct extension to shorter wavelengths. Some of recent work in the area was performed by ITN energy systems [[For background see below!]] under DOE and DARPA sponsorship "BROADBAND OPTICAL RECTENNA FOR ENERGY HARVESTING", CECOM ENERGY HARVESTING PROGRAM Slides, April 14, 2000 ). Such micro- and nano-scale rectenna devices can convert ambient electromagnetic radiation (i.e. solar spectrum, blackbody radiators, active emitters) to DC electric power. The potential is to convert over 85% of the sun's energy to useable power compared to ~30% now achievable with conventional semiconductor based photovoltaics. Such devices may also be applicable to uncooled infrared detectors.

[0007] While the concept has been proven in principal, useful power conversion in the optical frequency range is prevented by the low frequency response of the planar diodes employed.

[0008] Thus there remains a need for optical rectennas having desirable frequency response and power conversion.

BRIEF DESCRIPTION OF THE INVENTION

[0009] These and other features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of various embodiments, taken together with the accompanying figures and claims, in which:

[0010] According to some embodiments, the present invention provides a nanoelectronic device based on a nanostructure that may include a nanotube with first and second ends, a metallic nanoparticle attached to the first end, and an insulating nanoparticle attached to the second end.

[0011] The nanotube may be conducting. Thus, it may be any one of conducting, semiconducting, and semi-metallic. Further, the nanotube may be a single walled nanotube or a multi-walled nanotube. The nanotube may be primarily carbon.

[0012] The nanotube may absorb light. Yet further, the nanotube may be an antenna.

The length between the first and second ends is about half a wavelength of the light. The light may include at least one of visible and infrared radiation.

[0013] The insulating nanoparticle may be formed of a metal oxide. The metallic nanoparticle may be formed of elemental metal.

WHAT IS CLAIMED IS:

1. A nanoelectronic device, comprising: a first nanostructure, comprising: a nanotube having first and second opposing ends; a metallic nanoparticle attached to the first end; and an insulating nanoparticle attached to the second end.

2. The nanoelectronic device according to claim 1, wherein the nanotube is conducting.

3. The nanoelectronic device according to claim 1, wherein the nanotube absorbs light.

4. The nanoelectronic device according to claim 3, wherein the nanotube comprises an antenna.

5. The nanolectronic device according to claim 4, wherein the length between the first and second ends is about half a wavelength of the light.

6. The nanolectronic device according to claim 5, wherein the light comprises at least one of visible and infrared radiation.

7. The nanolectronic device according to claim 1, wherein the insulating nanoparticle comprises a metal oxide.

8. The nanolectronic device according to claim 1, wherein the metallic nanoparticle comprises elemental metal.

9. The nanolectronic device according to claim 1, wherein the nanoelectronic device further comprises additional nanostructures so a to form a plurality of nanostructures comprising the first nanostructure and the additional nanostructures.

10. The nanoelectronic device according to claim 9, wherein the plurality of nanostructures is arranged in a network comprising a plurality of edges and a plurality of vertices, wherein each edge comprises a nanotube and each vertex comprises at least one insulating nanoparticle and at least one metallic nanoparticle adjacent the insulating nanoparticle.

11. The nanolectronic device according to claim 10, wherein the combination of at least one edge and at least one vertex comprises a diode.

12. The nanolectronic device according to claim 9, wherein the device is an optical rectenna.

13. A nanoelectronic device comprising an optical rectenna comprising a plurality of nanostructures arranged so as to form a plurality of nanoscale diodes with integrated antennas, wherein each nanostructure comprises: a conducting nanotube having first and second opposing ends; a metallic nanoparticle attached to the first end, wherein the first nanoparticle comprises elemental metal; and an insulating nanoparticle attached to the second end, wherein the insulating nanoparticle comprises a metal oxide.

14. The nanoelectronic device according to claim 13, wherein the conducting nanotube is metallic.

15. The nanoelectronic device according to claim 13, wherein the conducting nanotube is semi-metallic.

16. The nanoelectronic device according to claim 13, wherein the conducting nanotube is semi-conducting.

17. The nanoelectronic device according to claim 13, wherein the conducting nanotube is a single-walled nanotube.

18. The nanoelectronic device according to claim 13, wherein the conducting nanotube is a multi-walled nanotube.

19. A method of making a nanoelectronic device, comprising: making a plurality of asymmetric nanostructures, wherein making the plurality of nanostructures comprises: providing a plurality of nanotubes, each having a first end functionalized with at least one functionalizing moiety and a second end having a linker molecule attached thereto; attaching a metallic nanoparticle to the linker molecule; and attaching an insulating nanoparticle to the functionalizing moiety.

20. The method according to claim 17, comprising: aligning the plurality of nanostructures so as to form an oriented network.

Source:
http://tinyurl.com/68f82h

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BACKGROUND - ITN Energy Systems:

http://www.itnes.com/about_itn/itn_team.html

Photovoltaic Technologies Beyond the Horizon
Optical Rectenna Solar Cell

1. Background on ITN Energy Systems’ Optical Rectenna Technology
1.1. Motivation for Next-Generation, High-Efficiency Solar Cells

Worldwide energy demands have increased by 40% over the last 20 years.1 Although the deleterious effects of hydrocarbon-based power are becoming increasingly apparent, more than 85% of the world’s power is still generated by combustion of fossil fuels.1 Clean renewable alternative energy sources are required to meet the demands, with direct solar-conversion devices as leading candidates. The worldwide market for conventional photovoltaics (PV) has increased at an annual rate of 20% over the last five years, and industry estimates suggest as much as 18 billion watts per year could ship by 2020.1 To meet the increased demands for solar-conversion technologies, dramatic improvements are required in state-of-the-art PV technologies. Efficiency improvements and cost/complexity reduction are the main issues that need to be addressed to meet these goals.

Traditional p-n junction solar cells are the most mature of the solar-energy-harvesting technologies. Although great improvements have been made in the last 20 years, energy absorption, carrier generation, and collection are all a function of the materials chemistry and corresponding electronic properties (i.e., bandgap). As a quantum device, the efficiency of PV is a function of, and therefore, ultimately fundamentally limited by, the bandgap and the match of the bandgap to the solar spectrum. For single-junction cells, this sets an upper efficiency limit of ~30%.2 Even with complex multi-junction designs, the theoretical efficiency plateaus around 55% without excessive concentration of the incident radiation.3 Current state-of-the-art solar cells are ~20% efficient for single cells and ~30% efficient for multijunction systems.4 In the long term, the PV industry will require newer, higher efficiency technologies to improve performance and to meet the increasing demands of the solar power market.

As an alternative, ITN Energy Systems is developing next-generation solar cells based on the concepts of an optical rectenna (see Figure 1). ITN’s optical rectenna consists of two key elements: 1) an optical antenna to efficiently absorb the incident solar radiation, and 2) a highfrequency metal-insulator-metal (MIM) tunneling diode that rectifies the AC field across the antenna, providing DC power to an external load. The combination of a rectifying diode at the feedpoints of a receiving antenna is often referred to as a rectenna. Rectennas were originally proposed in the 1960s for power transmission by radio waves for remote powering of aircraft for surveillance or communications platforms.5 Conversion efficiencies greater than 85% have been demonstrated at radio frequencies (efficiency defined as DC power generated divided by RF power incident on the device). Later, concepts were proposed to extend the rectennas into the infrared (IR) and optical region of the electromagnetic spectrum for use as energy collection devices (optical rectennas).6
http://www.nrel.gov/docs/fy03osti/33263.pdf

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BACKGROUND: Boston College - Ren; Zhifeng

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.

---

Inventors:

Ren; Zhifeng; (Newton, MA) ; Kempa; Krzysztof; (Billerica, MA) ; Wang; Yang; (Allston, MA)

Assignee Name and Adress: The Trustees of Boston College

Link

See also:

(WO/2007/086903) APPARATUS AND METHODS FOR SOLAR ENERGY CONVERSION USING NANOCOAX STRUCTURES

[SNIP]

The presently disclosed embodiments generally relate to the use of nano-coaxial transmission lines (NCTL) to fabricate a nano-optics apparatus. The nano-optics apparatus is a multifunctional nano-composite material made of a metallic film having a top surface and a bottom surface and a plurality of cylindrical channels filled with a dielectric material. An array of nanorods penetrate the metallic film through the plurality of cylindrical channels. The array of nanorods has a protruding portion that extends beyond a surface of the metallic film and an embedded portion that is within the metallic film. The protruding portion acts as a nano-antenna and is capable of receiving and transmitting an electromagnetic radiation at a visible frequency. The embedded portion acts as a nano-coaxial transmission line (CTL) and allows for propagation of external radiation with a wavelength exceeding the perpendicular dimensions of the nanorod.

The nano-optics apparatus can concentrate light, and therefore enhance a field up to about 10³ times. The array of optical nano-antennas, with nano-CTL embedded in a metallic film, effectively compresses light into nanoscopic dimensions. The nano-antennas are capable of receiving and transmitting an electromagnetic radiation at the visible frequencies. The extreme compression of light in the nano-CTL leads to an asymmetric tunneling of electrons between the electrodes of the nano-CTL, and thus provides a rectifying action at the light frequencies, and thus conversion of the light into a direct current (DC) voltage. This property leads to a new class of efficient, and low cost rectenna solar cells. The extreme compression of light in the nano-CTL is quick, and is not limited by the usual parasitic capacitances that make the conventional diode rectification inefficient, if not impossible, at the light frequencies.

And these, as well:

Physics Team Sees Potential for 'Perfect' Solar Cell

Solasta Inc.

Abstract

Submitted for the MAR08 Meeting of The American Physical Society

Sorting Category: 16.12.6 (E)
Nanocoax Solar Cells1 M.J. NAUGHTON, K. KEMPA, Z.F. REN, J. RYBCZYNSKI2, T. PAUDEL, Y. GAO, Y. XU, Boston College
A novel architecture for high effciency solar energy conversion, employing separated photo- and -voltaic pathways and antenna-based light collection, is described.

**************************************************************

Dr. Howard K. Schmidt Bio:

Dr. Howard K. Schmidt, Executive Director of the Carbon Nanotechnologies Laboratory

Howard Schmidt is the Executive Director of the Carbon Nanotechnology Laboratory (CNL) at Rice University. He is an expert in the field of carbon nanotechnology and single-wall carbon nanotubes, one of the most versatile materials on the nanotechnology horizon. At the CNL, Dr. Schmidt is responsible for developing and managing key federal and industrial relationships to drive emerging applications for carbon nanotubes. He serves on the Board of Directors of Axion Power Corporation (member of Audit and Technology Committees), and the Advisory Board of Texas Nanotech Ventures (Chairman). He also serves occasionally as an Expert Witness or Technology Advisor in patent litigation.

Schmidt's current research and development projects focus on nanostructured carbon and metallic materials for structural composites, energy storage and solar cells.

Prior to joining the CNL, Schmidt founded or co-launched four technology companies over seventeen years: Ionwerks, SI Diamond Technology (SIDT), EQUEX and Road-Show.Com. Schmidt took SIDT public in 1993; the firm (now called NanoProprietary) is a long-time leader in developing nanotechnology applications.

Schmidt holds a Bachelors' in Electrical Engineering (1980) and a Doctorate in Physical Chemistry (1986), both from Rice University.

http://www.tntventures.com/schmidt.html

Re TNT:
http://www.tntventures.com/board.html
(Note 'Zvi Yaniv')

*****************************************************************
Power Review:

http://cohesion.rice.edu/CentersAndInst/CNST/emplibrary/HTC%20Panel%20040615%20Final.ppt

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You know - when I see this kinda statement --The potential is to convert over 85% of the sun's energy to useable power compared to ~30% now achievable-- I get all tingly with excitement, sell oil short and believe in sugarplum fairies!!

And go talk to grandpa just to say hello....and maybe see what's up, too.

The wallet needs filling!

Did you notice Schmidt and Ren are both using CNTs!!!

;-)

Hello grandpa!!!! Come back to NNPP. Bring Boston College and Ren et al with you!!

Carbon nanotubes mimic asbestos in early study

By BRIAN BERGSTEIN – 3 hours ago [May 20, 2008]

BOSTON (AP) — Strong, versatile little "nanotubes" made out of carbon are considered future stars in nanotechnology research in medicine and industry. Now a study finds that longer threads of the stuff mimic the toxic qualities of asbestos, renewing questions about how carbon nanotubes can be used safely.

Researchers with British institutes and the U.S.-based Project on Emerging Nanotechnologies injected mice with asbestos and with commercial samples of carbon nanotubes of varying sizes. When they examined the lining of the rodents' abdominal cavities, the researchers observed that longer nanotubes behaved like asbestos, provoking inflammation and lesions.

The study was reported Tuesday in Nature Nanotechnology, a scientific journal.

Carbon nanotubes are widely available for sale, but the study's authors and outside experts said they are not certain how extensively the materials have begun to be used in electronic gear, composite metal structures or consumer products. Such uses are expected eventually.

Because of that uncertainty, the researchers hope to pressure companies developing carbon nanotube-based materials to reveal whether they are using longer strands such as the ones that appear to act like asbestos — which was once a wonder material, too, before its cancerous consequences were discovered.

"I think it ups the stakes," said one of the authors, Andrew Maynard of the Project on Emerging Nanotechnologies, a partnership of the Woodrow Wilson International Center for Scholars and the Pew Charitable Trusts. "Up to this point we could talk hypothetically about the risks, but there wasn't enough there to demand action."

Vicki Colvin, a Rice University chemist who directs the National Science Foundation-funded Center for Biological and Environmental Nanotechnology, said carbon nanotubes' potential applications — such as cars that could be 80 percent lighter than today's models, but just as sturdy — are too powerful to ignore. She said the new study drove home the importance of making sure "we know how to handle it." Colvin was not involved in the new research.

The researchers acknowledged their work had limitations and called for more study.

For one thing, they put nanotubes directly into the abdomens of mice and stopped their experiments after a week — before seeing whether the nanotubes went on to induce mesothelioma, the cancer of the organ lining caused by asbestos exposure.

Mesothelioma is slow to develop; it can take 30 to 40 years in humans. But Vincent Castranova, chief of a pathology research unit at the National Institute for Occupational Safety and Health, said signs of the cancer would have been apparent in the mice after a month or two.

Whether that would have happened in a meaningful way is a vital question.

Castranova noted that earlier research in Japan, similar to Tuesday's paper, found that mice injected with carbon nanotubes did develop mesothelioma. But the doses of carbon nanotubes were so high that Castranova questioned the results.

And in research in his labs, in which mice are not injected with nanotubes but breathe it into their lungs — the way people would presumably be exposed — the animals developed inflammation that peaked within seven days of exposure, and returned to normal within one or two months.

"Whether the material is asbestos-like is still a question to be debated," Castranova said. "Having a panic that you have the next asbestos is a little bit premature in my view."

It's also worth noting that the new study did not find an asbestos-like effect with shorter or more tangled strands of carbon nanotubes. That does not mean smaller carbon nanotubes are necessarily safe. It just means that the asbestos-like effects in this experiment did not come from inherent properties of all carbon nanotubes. Rather, those effects came from stacking nanotubes together into a long, thin, asbestos-like fiber, which the body struggles to process.

Carbon nanotubes basically are minuscule, rolled pipes of graphite. They can be as narrow as one nanometer, or one billionth of a meter. (For comparison, a human hair is more than 80,000 nanometers across.)

Because their structure endows them with powerful physical properties, such as strength greater than that of steel, carbon nanotubes are being explored for a wide range of uses in electronics and medicine. Some potential applications involve coating the nanotubes in other substances, which could blunt any toxic effects.

For example, researchers have explored using nanotubes as the mechanism for delivering tiny, cancer-killing smart bombs to tumors. Stanford University scientists involved in such work found that coated, short carbon nanotubes — unlike the ones at issue in the asbestos study — were safely digested by mice after being injected into their bloodstreams.

Maynard said the combination of that research with his group's new study "shows there are no simple answers here. What type of materials you're using and what you're using them for makes a big difference."

Source

Nanotech makes radioactive sensors obsolete

R. Colin Johnson
EE Times
(05/20/2008 12:26 PM EDT)

PORTLAND, Ore. — "Green" smoke-alarm ionizers using field-emission from nanotubes instead of radioactive isotopes could eliminate a source of dirty-bomb material, according to recipients of a U.S. Small Business Innovation Research (SBIR) contract sponsored by the Homeland Security Advanced Research Projects Agency.

Applied Nanotech Inc. (Austin, Texas) and Sionex Corp. (Bedford, Mass.) now have the funding from Homeland Security to produce a small, safe, high-performance sensor using electron field emission from carbon nanotube arrays instead the ionizing alpha rays from radioactive isotopes.

"We believe that carbon nanotube emitters can replace radioactive materials in consumer devices like smoke detectors, industrial sensors, medical equipment, homeland security applications and elsewhere," said Applied Nanotech scientist Richard Fink.

Many American households have as much as a milligram of radioactive americium-241 in the various smoke alarms and other gas-phase detectors found there. About a fifth of a milligram of americium is used to ionize the air inside a smoke detector. But just one gram of americium is dangerous for people to handle; dekagrams to hectograms are enough for "dirty" bombs, and kilograms could be used to make a nuclear bomb.

Instead of seeding our land-fills with radioactive materials like nickel-63 and americium-241, which have half-lives of 100 and 432 years, respectively, the U.S. Nuclear Regulatory Commission, the National Research Council and the Homeland Security Advanced Research Projects Agency are all investing in "green" alternatives to radioactive isotopes in smoke alarms and medical diagnostic and research equipment.

The Applied Nanotech and Sionix joint-development effort aims to provide a safe, inexpensive, high-performance alternative method of ionizing samples by using carbon nanotube emitters integrated into air-flow passages ahead of a differential mobility spectrometer. Applied Nanotech and Sionex claim to have proven in principle that carbon nanotube emitters can perform all the necessary ionization and identification steps without the use of radioactive materials.

Ionizing gas molecules

Ion mobility spectroscopy works by ionizing gas molecules as they pass through the sensor, then identifying them by their atomic weight. After ionization of the sample, the molecules are electrically attracted through a drift tube, where they spread out according to their atomic weight, allowing the location to reveal their identity to an integrated detector.

Applied Nanotech's carbon nanotube emitters perform the ionization step instead of using radioactive materials, allowing gas particles to be safely separated and detected by Sionex's integrated differential mobility spectroscopy (DMS).

Carbon nanotube emitters perform the ionization step by concentrating electrical fields in a manner similar to a lightning rod, allowing the emission of electrons at room temperature and at atmospheric pressures. As the electrons pass through the air sample they ionize the gas molecules, thus supplying the charge that enables them to be attracted to the sensors and detectors. Carbon nanotube emitters may impart either positive or negative ionization as needed for a particular sensor.

Source

Titania–germanium nanocomposite for photo-thermo-electric application

Sukti Chatterjee 2008 Nanotechnology 19 265701 (9pp) doi: 10.1088/0957-4484/19/26/265701

	PDF (1.72 MB) | References

Sukti Chatterjee¹
Center for Composite Materials, University of Delaware, Newark, DE 19716, USA
¹ Present address: Naval Materials Research Laboratory, Defence Research and Development Organization, Ambernath e 421 506, India
E-mail: Sukti@yahoo.com

Abstract. The introduction of germanium (Ge) into titania (TiO₂) creates an attractive semiconductor. The new semiconductor is named titania–germanium (TiO₂–Ge). Ge dots are dispersed in the distorted TiO₂ matrix of TiO₂–Ge. The quantum Bohr radius of Ge is 24.3 nm, and hence the properties of the Ge dot can be varied by tailoring its size if it is smaller than its Bohr radius due to the quantum confinement effect (QCE). Therefore, simply by changing the Ge concentration, the morphology of TiO₂–Ge can be varied within a wide range. Consequently, the optical, electronic and thermal properties of TiO₂–Ge can be tailored. TiO₂–Ge becomes a promising material for the next generation of photovoltaics as well as thermoelectric devices. It could also be used for photo-thermo-electric applications.

Print publication: Issue 26 (2 July 2008)
Received 14 December 2007, in final form 14 April 2008
Published 20 May 2008

PDF (1.72 MB) | References

Source

By adding graphene, researchers create superior polymer

Posted: May 19, 2008

(Nanowerk News) Researchers at Northwestern University and Princeton University have created a new kind of polymer that, because of its extraordinary thermal and mechanical properties, could be used in everything from airplanes to solar cells.

The polymer, a nanocomposite that incorporates functionalized, exfoliated graphene sheets, even conducts electricity, and researchers hope to use that property to eventually create thermally stable, optically transparent conducting polymers.

The results of their research were published May 11 in the online version of Nature Nanotechnology ("Functionalized graphene sheets for polymer nanocomposites"). ******************************** Letter abstract Nature Nanotechnology Published online: 11 May 2008 | doi:10.1038/nnano.2008.96 Functionalized graphene sheets for polymer nanocomposites T. Ramanathan1, A. A. Abdala2,7, S. Stankovich3, D. A. Dikin1, M. Herrera-Alonso2, R. D. Piner1,6, D. H. Adamson4, H. C. Schniepp2, X. Chen1, R. S. Ruoff1,6, S. T. Nguyen3, I. A. Aksay2, R. K. Prud'Homme2 & L. C. Brinson1,5 Abstract Polymer-based composites were heralded in the 1960s as a new paradigm for materials. By dispersing strong, highly stiff fibres in a polymer matrix, high-performance lightweight composites could be developed and tailored to individual applications1. Today we stand at a similar threshold in the realm of polymer nanocomposites with the promise of strong, durable, multifunctional materials with low nanofiller content2, 3, 4, 5, 6, 7, 8, 9, 10, 11. However, the cost of nanoparticles, their availability and the challenges that remain to achieve good dispersion pose significant obstacles to these goals. Here, we report the creation of polymer nanocomposites with functionalized graphene sheets, which overcome these obstacles and provide superb polymer–particle interactions. An unprecedented shift in glass transition temperature of over 40 °C is obtained for poly(acrylonitrile) at 1 wt% functionalized graphene sheet, and with only 0.05 wt% functionalized graphene sheet in poly(methyl methacrylate) there is an improvement of nearly 30 °C. Modulus, ultimate strength and thermal stability follow a similar trend, with values for functionalized graphene sheet– poly(methyl methacrylate) rivaling those for single-walled carbon nanotube–poly(methyl methacrylate) composites. Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08544, USA Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544, USA Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA Present Address: Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712-0292, USA Present Address: Chemical Engineering Program, The Petroleum Institute, Abu Dhabi, United Arab Emirates Correspondence to: L. C. Brinson1,5 e-mail: cbrinson@northwestern.edu *********************************

Researcher at the McCormick School of Engineering originally teamed up with researchers at Princeton several years ago. McCormick researchers had experience working with polymer nanocomposites, and Princeton researchers had developed a way to exfoliate, or split apart, graphite sheets into very thin single layer, surface-functionalized graphene sheets.

Previous use of graphite in polymers did not garner significantly improved properties since researchers could never get the graphite exfoliated. That meant the graphite was rigid with a low surface area and could only minimally impact properties of the polymer.

But when researchers put even a small amount the newly exfoliated graphene sheets — enough to equal only .05 percent of the material — into the polymer, they found the graphene changed the polymer’s thermal stability temperature by 30 degrees. Even adding graphene sheets equal to .01 percent of the material increased stiffness by 33 percent — far beyond what researchers had predicted. The drastic changes in both the thermal stability and the stiffness after adding just a tiny percentage of functionalized graphene indicated that the graphene changes large regions of the polymer radiating out from the nanoparticle surfaces in a percolating network structure.

The new polymer nanocomposite based on graphene also exhibited the same or superior thermal and mechanical properties as using functionalized single-wall nanotubes in polymer — but was much easier and cheaper to create.

“This is the first time people have been able to demonstrate dramatically altered properties like this with really small quantities of graphite-based materials,” says Cate Brinson, Jerome B. Cohen Professor of Mechanical Engineering and corresponding author of the paper.

The graphene sheets also will inherently be able to block moisture and gases from penetrating the material as well as change the thermal stability temperature and improve mechanical properties, making the durable polymer a candidate for use in everything from aircrafts to sports equipment to solar cells

“I think it has enormous potential,” Brinson says. “With the ready availability of graphite and the properties we have demonstrated, this new material will enable significant structural scale use of carbon-based nanocomposites.”

Next researchers are studying the polymer’s electroconductivity, quantifying and optimizing the results with the goal of creating optically transparent conducting polymers that are thermomechanically stable.

Source: Northwestern University

Source

A new artificial virus construction with therapeutic potential

By Yun Xie | Published: May 19, 2008 - 09:06AM CT

For years, scientists have been trying to create artificial viruses that are as proficient as natural ones in delivering materials to cells. Successful, artificial viruses could carry therapeutic agents into human cells to treat a variety of diseases. Unfortunately, synthesizing an artificial virus with the ideal shape and size for maximum delivery efficiency is extremely difficult. A common method for their generation involves polyion coupling, which often leads to aggregates with uncontrollable dimensions.

The Lee research group at Yonsei University in Seoul, Korea found an alternate strategy, one that used pre-organized supramolecular nanostructures to construct, for the first time, a filament-shaped artificial virus. Filamentous shaped nanostructures last longer in vivo, and many natural viruses are filamentous. The process started with the creation of Glu-KW, a β-sheet peptide based supramolecule. Glu-KW's self-assembeled β-sheet contains two linkers: a nucleic acid-binding segment and a carbohydrate ligand. The β-sheet consists of alternating hydrophobic and charged amino acids, assisting the self-assembly. Glu-KW is coated with glucose to shield the charges on the surface of the β ribbon, which increases the chance of cell binding.

Lee's group proposed that the self-assembled virus can bind to therapeutic agents and deliver it into the cell. They tested their idea using small interfering RNA (siRNA), a double stranded RNA that induces specific post-transcriptional gene-silencing. Based on evidence from circular dichroism and transmission electron microscopy, their artificial virus can make a complex with the negatively charged siRNA. To examine the virus' ability as an intracellular siRNA delivery carrier, the chemists compared Glu-KW with Lipofectamine 2000, a commercial compound with high siRNA transfection efficiencies, using a human cervical cancer cell line. In gene knockdown experiments, Glu-KW performed just as well as Lipofectamine 2000.

In addition to delivering nucleic acids like siRNA, the artificial virus can also carry a hydrophobic guest molecule because the β ribbon bilayer forms a hydrophobic space useful for encapsulation. The chemists tested Glu-KW's potential for delivering nile red, a hydrophobic stain, while the virus was complexed with siRNA. Nile red was delivered to the cytoplasm and nucleus of the cells and gene knockdown still occurred, although with less efficiency.

The β ribbon templates are capable of assembling artificial viruses with favorable sizes and shapes. The virus' simultaneous ability to deliver genetic materials and hydrophobic therapeutic reagents are particularly useful, and the researchers' approach is flexible and allows for a variety of structural changes to the virus. Until we study the toxicology of these artificial viruses, however, we cannot judge their full potential for treating diseases.

Angewandte, 2008. DOI: 10.1002/anie.200800266

Source