Del Mar Photonics - Carbon Nanotube News

Carbon-nanotubes as Ultrafast Photodetectors

Carbon nanotubes are promising elements for optoelectronic components. However so far there were no electronic methods to analyze the ultra fast optoelectronic dynamics of the nanotubes. A team of physicists headed by Professor Alexander Holleitner from the Technische Universitaet Muenchen (TUM) has now come up with a new method to directly measure the dynamics of photo-excited electrons in nanoscale photodetectors.

Carbon nanotubes bridging two gold electrodes

Carbon nanotubes have a multitude of unusual properties which make them promising candidates for optoelectronic components. However, so far it has proven extremely difficult to analyze or influence their optic and electronic properties.

A team of researchers headed by Professor Alexander Holleitner, a physicist at the Technische Universitaet Muenchen and member of the Cluster of Excellence Nanosystems Munich (NIM), has now succeeded in developing a measurement method allowing a time-based resolution of the so-called photocurrent in photodetectors with picosecond precision.

Single-walled carbon nanotubes are promising building blocks for future optoelectronic devices. With this measurement set-up physicists led by Professor Alexander Holleitner (Technische Universitaet Muenchen) can resolve the ultra fast optoelectronic dynamics of carbon-nanotubes. A first laser exites electrons in the carbon-nanotubes spanning the gap between two gold electrodes while a second laser measures the resulting photo-current.

"A picosecond is a very small time interval," explains Alexander Holleitner. "If electrons traveled at the speed of light, they would make it almost all the way to the moon in one second. In a picosecond they would only cover about a third of a millimeter."

This new measurement technique is about a hundred times faster than any existing method. It allowed the scientists headed by Professor Alexander Holleitner to measure the precise speed of electrons. In the carbon nanotubes the electrons only cover a distance of about 8 ten-thousandths of a millimeter or 800 nanometers in one picosecond.

At the heart of the photodetectors in question are carbon tubes with a diameter of about one nanometer spanning a tiny gap between two gold detectors. The physicists measured the speed of the electrons by means of a special time-resolved laser spectroscopy process the pump-probe technique. It works by exciting electrons in the carbon nanotube by means of a laser pulse and observing the dynamics of the process using a second laser.

The insights and analytic opportunities made possible by the presented technique are relevant to a whole range of applications. These include, most notably, the further development of optoelectronic components such as nanoscale photodetectors, photo-switches and solar cells.

The studies were funded by the German Research Foundation (Cluster of Excellence Nanosystems Initiative Munich, NIM) and the Center for NanoScience (CeNS) at Ludwig-Maximilians-Universitaet Muenchen. Further contributions to the publication came from physicists of the University of Regensburg (Germany) and the Swiss Federal Institute of Technology, Zurich.

TUM press release - Photocurrent measurement techniques

Citation: Time-Resolved Picosecond Photocurrents in Contacted Carbon Nanotubes, Leonhard Prechtel, Li Song, Stephan Manus, Dieter Schuh, Werner Wegscheider, Alexander W. Holleitner, Nano Letters 2011, 11 (1), pp 269, DOI: 10.1021/nl1036897

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Femtosecond Transient Absorption Measurements system Hatteras Femtosecond Transient Absorption Measurements system Hatteras.
Future nanostructures and biological nanosystems will take advantage not only of the small dimensions of the objects but of the specific way of interaction between nano-objects. The interactions of building blocks within these nanosystems will be studied and optimized on the femtosecond time scale - says Sergey Egorov, President and CEO of Del Mar Photonics, Inc. Thus we put a lot of our efforts and resources into the development of new Ultrafast Dynamics Tools such as our Femtosecond Transient Absorption Measurements system Hatteras. Whether you want to create a new photovoltaic system that will efficiently convert photon energy in charge separation, or build a molecular complex that will dump photon energy into local heat to kill cancer cells, or create a new fluorescent probe for FRET microscopy, understanding of internal dynamics on femtosecond time scale is utterly important and requires advanced measurement techniques.

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Carbon nanotubes form ultrasensitive biosensor to detect proteins

Sunday, June 27, 2010

A cluster of carbon nanotubes coated with a thin layer of protein-recognizing polymer form a biosensor capable of using electrochemical signals to detect minute amounts of proteins, which could provide a crucial new diagnostic tool for the detection of a range of illnesses, a team of Boston College researchers report in the journal Nature Nanotechnology.

The nanotube biosensor proved capable of detecting human ferritin, the primary iron-storing protein of cells, and E7 oncoprotein derived from human papillomavirus. Further tests using calmodulin showed the sensor could discriminate between varieties of the protein that take different shapes, according to the multi-disciplinary team of biologists, chemists and physicists.

Molecular imprinting techniques have shown that polymer structures can be used in the development of sensors capable of recognizing certain organic compounds, but recognizing proteins has presented a difficult set of challenges. The BC team used arrays of wire-like nanotubes approximately one 300th the size of a human hair coated with a non-conducting polymer coating capable of recognizing proteins with subpicogram per liter sensitivity.

Central to the function of the sensor are imprints of the protein molecules within the non-conducting polymer coating. Because the imprints reduce the thickness of the coating, these regions of the polymer register a lower level of impedance than the rest of the polymer insulator when contacted by the charges inherent to the proteins and an ionized saline solution. When a protein molecule drops into its mirror image, it fills the void in the insulator, allowing the nanotubes to register a corresponding change in impedance, signaling the presence of the protein, according to co-author Dong Cai, an associate research professor of Biology at BC.

The detection can be read in real time, instead of after days or weeks of laboratory analysis, meaning the nanotube molecular imprinting technique could pave the way for biosensors capable of detecting human papillomavirus or other viruses weeks sooner than available diagnostic techniques currently allow. As opposed to searching for the HPV antibody or cell-mediated immine responses after initial infection, the nanotube sensor can track the HPV protein directly. In addition, no chemical marker is required by the lebel-free electrochemical detection methods.

"In the case of some diseases, no one can be sure why someone is ill," said Cai. "All that may be known is that it might be a virus. At that time, the patient may not have detectable serum antibodies. So at a time when it is critical to obtain a diagnosis, there may not be any traces of the virus. You've basically lost your chance. Now we can detect surface proteins of the virus itself through molecular imprinting and do the analysis."

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Del Mar Photonics

Del Mar Photonics featured customer Bruce Weisman. Professor Weisman ordered Trestles Ti:Sapphire laser with built-in DPSS pump laser.

Professor Weisman wrote: Our applications are for carbon nanotube excitation, mostly with a cw beam but in some experiments with mode-locked pulses.

Del Mar Photonics offered Trestles Ti:Sapphire model with both CW and femtosecond modes of operation.
Detailed laser specifications are as follows (request a quote):

Trestles Ti:Sapphire laser with built-in DPSS pump laser
Ti:Sapphire oscillator having a tuning range of 710-920 nm;
Output power: 30mW (@3W pump, in the whole range);
Spatial mode: TEMoo;
Polarization: linear horizontal;
Repetition rate: 80 MHz;
Pulse duration: <100 fs
Electronic starter with TTL output for mode-locked mode
observation. Output mirrors included.
USB-controlled tuning slit for wavelength tuning

3BRF-TM 3-plate BRF for CW lasers (step motor controlled tuning)
Provides CW tuning and 40 GHz linewidth of the Trestles fs
lasers in CW mode; output power @700 nm - >50 mW (3W pump)

3 W pump DPSS laser with control and power supply unit
Power: 3 W
Wavelength: 532 nm
Beam size: 2.0 mm
Spatial mode: TEM00
Bandwidth: 30 GHz
Divergence: 0.4 mrad
M squared: < 1.1
Power stability: < 0.4 % RMS
Noise: < 0.4% RMS
Noise bandwidth: 1 Hz - 6 MHz
Pointing stability: < 2 microrads/C
Polarization ratio: 100:1
Polarization direction: horizontal
Coherence length: < 1 cm
Beam angle: < 1 mrad
Umbilical length: 1.5 m
Warm-up time: 10 min

R. Bruce Weisman Professor of Chemistry

Research Statement
Dr. R. Bruce Weisman and his group investigate the spectroscopy and photophysics of fullerenes and carbon nanotubes. All of these are closed nanoscopic structures formed from carbon atoms. Fullerenes, such as C60, C70, and their chemical derivatives, have unusual molecular properties that cause interesting behaviors following the absorption of light. Time-resolved absorption and emission methods are used to study radiationless decay, photochemical reactions, and energy transfer in fullerenes. Another major research topic is single-walled carbon nanotube spectroscopy. Following the discovery in Weisman?s lab of near-infrared nanotube fluorescence, the group has measured and unraveled the absorption and emission spectra of more than 30 semiconducting nanotube species. Follow-up projects include detailed elucidation of nanotube electronic structure, as well as applications in non-invasive biomedical imaging and analytical nanotechnology.

Selected Publications
R. Bruce Weisman and Shekhar Subramoney "Carbon Nanotubes." Interface (Summer, 2006): 42-46.

J. P. Casey, S. M. Bachilo, C. H. Moran, and R. B. Weisman "Chirality-Resolved Length Analysis of Single-Walled Carbon Nanotube Samples through Shear-Aligned Photoluminescence Anisotropy." ACS Nano, 2 (2008): 1738-1746.

J. P. Casey, S. M. Bachilo, and R. B. Weisman "Efficient Photosensitized Energy Transfer and Near-IR Fluorescence from Porphyrin/SWNT Complexes." J. Mater. Chem., 18 (2008): 1510-1516.

R. B. Weisman "Optical Spectroscopy of Single-Walled Carbon Nanotubes." Contemporary Concepts of Condensed Matter Science. Carbon Nanotubes: Quantum Cylinders of Graphene, 3 (2008): 109-133.

D. A. Tsyboulski, E. L. Bakota, L. S. Witus, J.-D. R. Rocha, J. D. Hartgerink, and R. B. Weisman "Self-Assembling Peptide Coatings Designed for Highly Luminescent Suspension of Single-Walled Carbon Nanotubes." J. Am. Chem. Soc., 130 (2008): 17134-117140.

C. D. Doyle, J.-D. R. Rocha, R. B. Weisman, and J. M. Tour "Structure-dependent Reactivity of Semiconducting Single-Walled Carbon Nanotubes with Benzene Diazonium Salts." J. Am. Chem. Soc., 130 (2008): 6795-6800.

D. A. Tsyboulski, S. M. Bachilo, A. B. Kolomeisky, and R. B. Weisman "Translational and Rotational Dynamics of Individual Single-Walled Carbon Nanotubes in Aqueous Suspension." ACS Nano, 2 (2008): 1770-1776.

Robert F. Curl and R. Bruce Weisman "Biography of Richard Errett Smalley." J. Phys. Chem. C, 111 (2007): 17653-17655.

Christopher J. Gannon, Paul Cherukuri, Boris I. Yakobson, Laurent Cognet, John S. Kanzius, Carter Kittrell, R. Bruce Weisman, Matteo Pasquali, Howard K. Schmidt, Richard E. Smalley, and Steven A. Curley "Carbon Nanotube-enhanced Thermal Destruction of Cancer Cells in a Noninvasive Radiofrequency Field." Cancer, 110 (2007): 2654-2665.

Laurent Cognet, Dmitri A. Tsyboulski, John-David R. Rocha, Condell D. Doyle, James M. Tour and R. Bruce Weisman "Stepwise Quenching of Exciton Fluorescence in Carbon Nanotubes by Single Molecule Reactions." Science, 316 (2007): 1465-1468.

"Quantitative Analysis of Bulk SWCNT Samples using Near-IR Fluorimetry, Focus Session on Development of Purity Evaluation Criteria and Quality Assurance Standards for Carbon Nanotubes,." Materials Research Society Meeting, Boston, Massachusetts. (November 30, 2008)

"Near-infrared Fluorescence of Single-Walled Carbon Nanotubes: a Tool for Developing Medical Applications." Nanomedicine Summit 08, Cleveland, Ohio. (September 25, 2008)

"Single-walled Carbon Nanotubes: Physical Properties and Biomedical Applications." Howard Hughes Medical Institute Summer Lecture Series, Harvey Mudd College, Claremont, California. (July 16, 2008)

"Near-IR Fluorescence of Single-Walled Carbon Nanotubes: A Tool for Developing Medical Applications." Carbon Nanotube Biology, Medicine, and Toxicology Symposium, Montpelier, France. (June 28, 2008)

"Qualitative and Quantitative Analysis of Bulk SWNT Samples using Near-IR Fluorimetry." Workshop on Metrology, Standardization, and Industrial Quality of Nanotubes, Montpelier, France. (June 28, 2008)

Editorial Positions

Associate Editor, Applied Physics A, Springer-Verlag,, (2008).
Paul Cherukuri, Ph.D. "Biomedical Studies of Single-Walled Carbon Nanotubes Using Near-Infrared Fluorescence." (2007).(Thesis or Dissertation Director)

Dmitry Tsyboulski, Ph.D. "Spectroscopic and Optical Imaging Studies of Fullerene Complexes and Single-Walled Carbon Nanotubes." (2006).(Thesis or Dissertation Director)

Eric Booth, PhD. "Photophysical Studies of Selected C84 Isomers, C80 Species, Aqueous C60 Colloid, and a C60-Amino Acid Derivative." (2005).(Thesis or Dissertation Director)

Elected Fellow, American Physical Society. (2008).
Paul Frison Accelator Award for Applied NanoFluorescence, Houston Business Journal. (2007).
Institute of Physics in Ireland Lecturer, . (2005).


Del Mar Photonics - Newsletter Fall 2010 - Newsletter Winter 2010

Del Mar Photonics is involved in research of CNTs, graphene nanoplatelets and graphene materials, develops advanced multifunctional materials for variety of applications as well as research instrumentation for characterization of the above.

We currently we can offer:

1) Graphene nanoplatelets: the stack of multi-layer graphene sheets with high aspect ratio, diameter: 0.5-20 m, thickness: 5-25 nm.
2) Graphene materials: Graphene Powder, Graphene Oxide Powder, Graphene Suspension.
3) Carbon Nanotubes.

Contact our application team to discuss your requirements for high-performance nanocomposite materials, display materials, sensing materials, ultracapacitors, batteries, energy storage and other area to improve electrical, thermal, barrier, or mechanical properties by using low-cost nano-additive.

Graphene nanoplatelets are the stack of multi-layer graphene sheets including platelet morphology, with characteristics as follows:

Physical Properties
Diameter Thickness Specific Surface Area Density Electrical Conductivity Tensile Strength
0.5 - 20 m 5 - 25 nm 40-60 m2/g ~2.25 g/cm3 8000-10000 S/m 5 GPa


Bulk Characteristics
Appearance Carbon content Bulk density Water Content Residual impurities
A black and grey powder >99.5% ~0.30 g/ml <0.5 wt% <0.5 wt%

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The high performance composite additives in PPO, POM, PPS, PC, ABS, PP, PE, PS, Nylon and rubbers.
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Fuel cells: both bi-polar plate and electrode efficiencies can be improved.

Del Mar Photonics develops advanced instrumentation for research of CNTs, graphene nanoplatelets and graphene materials including lasers for broadband spectroscopy, femtosecond transient absorption and fluorescence measurements.

T&D Scan high resolution Laser Spectrometer based on broadly tunable CW laser
CW single-frequency ring Dye laser
Beacon Femtosecond Optically Gated Fluorescence Kinetic Measurement System
New Hatteras femtosecond transient absorption system
Photon Scanning Tunneling Microscope