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.

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).