NanoBlog

Making good electrical connections to devices has always been important but may be even more important with organic semiconductors. The high simplified figure below shows a hypothetical single organic molecule (polyacetylene) based FET with metal contacts at each end. According the the article Molecular electronics with single molecules in solid-state devices by Kasper Moth-Poulsen & Thomas Bjørnholm, the molecular-electrode coupling strength strongly effects the electronic state of the entire device. The conduction of the electrons through the device can range from hopping to tunneling as the molecule-electrode contact goes from weak to strong.

Thermo Fisher Scientific held a well attended symposium on the latest technique in spectroscopy in Princeton, NJ on March 18. There were six talks presented of which I could only attend the first four. Presently, I lack enough knowledge in spectroscopy to be dangerous so I was treading water while most people appeared to be swimming comfortably with the subject matter.

I was excited to learn that there is a type of spectroscopy called Energy Dispersive X-ray Spectroscopy (EDS) that allows you to identify material composition of a sample from the X-ray spectrum emitted by the material when it is excited by an electron beam. When EDS is combined with an Scanning Electron Microscopy, you can image a sample such as a nanowire and determine the chemical composition of any spot on the nanowire. It was cool to see an images of a sample like a cross section of a CIGS solar cell and see the chemical composition of the structures within the cell at the same time.

The talks included:

• Microanalysis of Micron-Sized Features in Solar Energy Conversion Devices, by Breno Leite, Ph.D, Thermo Scientific.
• Coupling AFM with FR-IP: Opportunities and Challenges, Christopher M Yip, Ph.D, University of Toronto.
• Combat Wounds: Gaining insight with Vibrational Spectroscopy, Nicole J. Crane, Ph.D, Naval Medical Research Center.
• Applications of IR and Raman in Art Fraud and Authentication, James Martin, Orion Analytical, LLC.
• Infrared and Raman Analysis of Photovoltaic Materials, Jeffrey Hirsch, Ph.D, Thermo Fisher Scientific.
• Deep Ultraviolet Raman spectroscopy combined with advanced statistics is a powerful tool for structual characterization of protein aggregates, Igor K. Lednev, Ph.d, University of Albany, SUNY.

I missed part of it but you can check out the replay of I Know I Can, But Should I? The first presentation describes a nanoindenter and their advantage over using an AFM. This talk references the application note Imaging and Indenting: The Pros and Cons of Stretching Functionality. The second talk is an introduction to AFM.

A typical biosensor as shown in the figure below1 contains three main elements: a bioreceptor, a transducer, and a signal-processing element. The bioreceptor is sensitive to a particular analyte of target molecule of interest. The transducer detects that the bioreceptor has changed due to an interaction with the analyte. The signal processing elements buffers, amplifies or filters the detected signal.



There are two very good papers on biosensors in the IEEE Transactions on Nanotechnology.

• Real-Time, Label-Free Detection of Biological Entities Using Nanowire-Based FETs, by Curreli, M. Rui Zhang Ishikawa, F.N. Hsiao-Kang Chang Cote, R.J. Chongwu Zhou Thompson, M.E. Dept. of Chem., Univ. of Southern California, Los Angeles, CA
  • The biosensors in this paper are based on FET transducers, and many linker molecules and bioreceptors are described.
• Chemical Sensors and Electronic Noses Based on 1-D Metal Oxide Nanostructures by Po-Chiang Chen Guozhen Shen Chongwu Zhou Ming-Hsieh Dept. of Electr. Eng., Univ. of Southern California, Los Angeles, CA
  • The biosensors in this paper are primarily chemoresistors for gas sensing using many different metal oxide nanostructures.

The following links will take you to sites where you can download tools to draw chemical and molecules. Chemsketch is easy to use and can output standard form molecules and chemicals. It also as a database of molecules to simplify the drawing of a chemical. The Symyx tools are on my list to evaluate.

• Chemsketch (free for non commercial use).
• Symyx Tools

The figure shows Pentacene drawn using Chemsketch with and without Hydrogen bonds.



Chemskech can then output the chemical symbol in ball and stick form



For other nano related tools and software see our wiki pages on Nano simulation Software and Quick Tools Link.

Researchers at the Israel Institute of Technology built a chemiresistor based sensor array based on functionalized gold nanoparticles to detect volatile organic compound (VOC) associated with lung cancer directly from exhaled breath unconcentrated samples. The article appeared in the October 2009 issue of Nature Nanotechnology (Vol 4, No 10). The article is is titled Diagnosing lung cancer in exhaled breath using gold nanoparticles.

The researchers cataloged 42 different VOCs from both healthy patients and cancer patients to determine which VOCs indicate the presence of lung cancer tumors (i.e. identify biomarkers). The chemiresistor sensor array was then configure with the proper functionalization to detect nine biomarkers selected as the best indicator of a tumor. The sensor proved to a very good selectivity. The paper is a very good read.

Check out these companies in California:

• Bloom Energy
• Nanosolar
• Solyndra

Nature Video Nobel Reactions has seven short videos on various subjects from 2009 Nobel Laureate Meeting in Lindau. I watched the video with Harold Kroto and was interested but mostly annoyed with the video. The video has two students speaking with Dr. kroto about nanotechnology and C60. Not sure how real life type interviews pioneered by MTV fits here. The video is offset in my player so the the right 25% of the video is cut off. At first, I thought that this was a video style but later text appeared and show the problem with the video, player, browser or what. The more interesting bits are clips of his speech to the conference. I saw Dr. Kroto speak at Rutgers University a few years ago and he is a excellent speaker that is very inspiring and informative. Since, I know how good his talks can be, this video disappoints. I would rather see his talk from the conference instead. Anyway, if you get a chance to hear him speak, I recommend going for the extra effort.

• Kroto personal web site
• Kroto on Wikipedia

BTW, The videographers might benefit from seeing films by Errol Morris of Faster, Cheaper, and Out of Controlfame.

I did. Check out the replay at Resolution and Research?

Update
Dr. Song Xu describes techniques to get the best resolution of a sample in an efficient amount of time. Dr. Anil Patri describes the coordinated efforts between the NCI, NIST, and FDA to find treatments for cancer.

Assay Cascade Protocols from the National Cancer Institute
Nanotechnology Characterization Laboratory.

NREL certifies the efficiency of all solar cells and produces this handy reference chart on the efficiencies of all types of solar cell technologies. The measurements are usually made on cells the are a couple of cm square and are the best examples that a particular technology can produce. Production cells are usually less efficient due to imperfections introduced by the manufacturing process. Further loss are introduced when the cells are built into modules. I recommend two excellent books on photovoltaics:

• Clean Electricity from Photovoltaics by Archer and Hill
• The Physics of Solar Cells by Nelson

The chart was created by NREL and captured from the solar cell page on wikipedia.