The Nanostructure Problem

Nanostructures can pose big measurement problems:
While many methods exist for probing the atomic structure on the nanoscale, no single technique can provide a unique structural solution. This paper calls for a coordinated effort by researchers to develop a coherent strategy for a comprehensive solution of the “nanostructure problem” using inputs from multiple experimental methods and theory.

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* S.J.L. Billinge and I. Levin. The problem with determining atomic structure at the nanoscale. Science, 316: 5823, April 27, 2007.

Today's Updates

Researchers 'see' catalyst molecules at work: Researchers have for the first time 'watched' in real time single molecules of catalyst participating in a reaction at a solid-liquid interface

Instant insight: Nanocrystals as sensors: This article address the paradox around quantum dots... the properties of the quantum dots for imaging and labeling applications are achieved by making the quantum dot impervious to its environment. How can quantum dots be sensitive to their environment if they are encased within the cocoon of a passivating overcoat?

Nanoscale scales: Scientists at the Massachusetts Institute of Technology (MIT) in the US have designed a device able to accurately weigh to within one femtogram (one thousandth of a millionth of a millionth or 10-15 of a gram) single nanoparticles within a liquid.

Water's surface is acidic: Pure, neutral water has an acid skin. This striking notion has now been confirmed by calculations and tests.The finding could be significant for a number of disciplines. In atmospheric chemistry, many important chemical reactions between trace gases take place at the surface of water droplets in clouds where pH is an essential factor and low pH could also affect the rates of carbon dioxide absorption at the ocean surface. In molecular biology the effect might be reproduced where water comes into contact with water-repelling (hydrophobic) parts of proteins, changing the acid-base chemistry.

Determination of Size and Concentration of Gold Nanoparticles from UV-Vis Spectra: Work by Wolfgang Haiss et al. provide a simple and fast method to determine size and concentration of nanoparticles. Their work, published in Analytical Chemistry describe the theoretical analysis on the dependence of the optical properties of spherical gold nanoparticles on particle size and wavelength using multipole scattering theory, where the complex refractive index of gold was corrected for the effect of a reduced mean free path of the conduction electrons in small particles. The theoretical results were compared to experimental data; gold nanoparticles in the size range of 5 to 100 nm were synthesized and characterized with TEM and UV-vis. Excellent agreement was found, showing that the data produced here can be used to determine both size and concentration of gold nanoparticles directly from UV-Vis spectra. Equations for this purpose are derived, and the precision of various methods is discussed.

NMR Tutorial

Nuclear Magnetic Resonance (NMR) is a powerful chemical analysis tool and is related to Magnetic Resonance Imaging (MRI) by is basis in the same fundemental physical phenomena. I recently came across an intersting tutorial site on the web for NMR. Check it out here

Scanning magnetoresistance microscopy

Scanning magnetoresistance microscopy of atom chips
Results highlight the use of scanning MR microscopy as a convenient and powerful technique for precisely characterizing the magnetic fields produced near the surface of atom chips.

News: IBM researchers push MRI imaging to nanoscale

Researchers at IBM’s Almaden Research Center have developed magnetic resonance imaging (MRI) techniques to visualize nanoscale objects. The new techniques are a major milestone in the quest to build a microscope that could "see" individual atoms in three dimensions.

Click here to go to the IBM news website

Analytical Sciences Digital Library

The Analytical Sciences Digital Libary (ASDL) is supported by the NSDL program of the National Science Foundation and represents a searchable topical library with a large selection of links on A-Z topics relating to analytical chemistry and measurement science. I have already checked out a couple of the links there and have been impressed. Included are links to tutorials, amination, and resources on a whole array of techniques and methodologies. I cretainly recommend that you check it out.

Sorting Out Lead Levels

Concern over the presence of the lead in various sources of drinking water result in an analytical chemistry challenge, because of the need to avoid contamination of the vessels and apparatus. Inadequate attention to this problem has resulted in conflicting reports of the lead concentrations measured in bottled waters. One solution is described by Shotyk and Krachler and applies clean-room procedures and high-sensitivity detection technology that was developed to gauge the nanogram-per-liter concentrations of lead present in polar ice to the measurement of lead levels in commercially available bottled waters from across the world and artesian flow sources in southern Ontario, Canada. The measured concentrations were below the 10microgram/liter level considered hazardous. However, glass bottles appeared to leach lead over time, roughly doubling concentrations from ~100 to ~200 ng/liter in water stored in them over 6 months. Concentrations measured in plastic bottles ranged from <1 to 761 ng/liter. However, other organic materials unanalyzed in this study may be leaching out of the plastic. The artesian sources exhibited a narrowly ranged lead concentration having a median of 5.1 ng/liter.

This abstract is based on that presented in the Editor's Choice list of ScienceMag.org: here. Full details were published in Environ. Sci. Technol. 41, 10.1021/es062964h (2007).

Separations Science: Molecular-beam methods and novel electrodes simplify analysis of mixtures

Separations Science
Molecular-beam methods and novel electrodes simplify analysis of mixtures by Mitch Jacoby describes the work of a team that recently developed and tested an advanced-generation GC-MS interface device that transports sample compounds eluting from a GC column to a mass spectrometer by way of a supersonic molecular beam. This methodology promises to circumvent two particularly intractable problems in GC-MS analysis.

1. The relatively small range of volatile and thermally stable compounds that are amenable to analysis; and
2. The relatively weak molecular ion observed from many analytes.

For the entire Chemical and Engineering News article, click here .

The Daily Pennsylvanian - Penn prof, Nobel laureate dies at 79

During my term on the Nichols Medal Jury (a medal honoring chemists that is award by the New York Section of the American Chemical Society), our 2002 awardee was Dr. Alan MacDiarmid. Dr. MacDiarmid had already been awarded the Nobel Prize; however, he was very honored to recieve the Nichols Medal. I remember my meeting him with great fondness. He caried the gold medal Nobel Prize in his pocket and enjoyed offering people the opportunity to hold it saying, "I have created more Nobel Prize holders than any other recipient in history." His passing was in February and I only learned of it today. The news may be late, but to me it is sad. Below is a link to the story...

Emailing Penn prof, Nobel laureate dies at 79 Penn prof, Nobel laureate dies at 79 Chemistry professor Alan MacDiarmid, one of three recipients of the 2000 Nobel Prize in Chemistry, died yesterday afternoon. He was 79. MacDiarmid had been suffering from Myelodysplastic Syndrome, a disease that affects the bone marrow and blood, for the past four years. Read Full Article * The sender's identity has not been verified.

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Diffraction and scattering -- the solution to what's in solution

Researchers at the Department of Energy's Argonne National Laboratory and the University of Notre Dame have successfully applied X-ray scattering techniques to determine how dissolved metal ions interact in solution. Click here for details.
Credit: Argonne National Laboratory

A Peek Inside*

The semiconductor industry routinely fabricates device structures with feature sizes smaller than 100 nm. With millions of components crowded onto each chip and complex circuitry arrayed in three dimensions, methods to test the structures for defects--preferably nondestructively and with high throughput--become challenging. Techniques for imaging the subsurface structures tend to face a tradeoff between resolution and contrast. The probe light must have a relatively long wavelength (usually in the infrared) in order to penetrate through several millimeters of silicon in the wafer and be absorbed by the active layers of the device; however, this wavelength requirement has generally restricted lateral resolution. Ramsay et al. combine immersion lens imaging with two-photon absorption microscopy to improve both the lateral resolution and the absorption contrast, thereby providing a technique for the high-resolution three-dimensional imaging of the subsurface structures in silicon chip circuitry. -- ISO

Appl. Phys. Lett. 90, 131101 (2007).

*the above text is taken directly from - this link: http://www.sciencemag.org/content/vol316/issue5822/twil.dtl?rss=1#316/5822/174b

Raman Probes Shape Up

A method in which a probe pulse is delayed and has its shape optimized so to minimize the nonresonant background contributions may enable many practical applications of Raman spectroscopy previously determined impracticle. Raman spectrscopy is a technique that can provide a wealth of information about molecular vibrations and provide fingerprint-like signatures for identification, but even when signal strength is boosted by coherently exciting the vibrations with laser pulses, a fluctuating background signal hindersin sensing. For details on this new development, click here

Water Identified in Extrasolar Planet Atmosphere

Water has been identified in the atmosphere of an extrasolar planet for the first time using a combination of previously published Hubble Space Telescope measurements and new theoretical models. This result was recently accepted for publication in the Astrophysical Journal (http://lanl.arxiv.org/abs/0704.1114). For the details, click here