Radial-Position-Controlled Doping in CdS/ZnS Core/Shell Nanocrystals

A nice new paper just out in JACS by Cao's group down at the Univ. of Florida. They controlled the position of the Mn dopant atoms within the CdS/ZnS core/shell nanocrystal and then studies what affect the radial position had on the photoluminescence properties of the nanocrystals. They also studied how the concentration of Mn dopant atoms affected the photoluminescence (PL) quantum yield (QY).

One question the authors failed to answer: why does the Mn emision peak blue-shift as the radial position of the Mn dopant atoms increases?

Also, one questions their quantum efficiency measurements since they use quinine sulfate as the PL standard which as an extremely broad emission peak and therefore can introduce error in the measurments.

Besides these two points, the science in this paper is definitely good. The idea is simple, but worth exploring even further. More studies must be done on how the Mn dopants diffuse within the nanocrystals and how that influences the Mn emission qualities.

ALL YOUR BASE ARE BELONG TO US

Those who know will get this joke!
But seriously ....

nano-Peas in a nano-Pod

Entrapping of Exohedral Metallofullerenes in Carbon Nanotubes: (CsC₆₀)_n@SWNT Nano-Peapods

Bao-Yun Sun, Yuta Sato, Kazutomo Suenaga, Toshiya Okazaki, Naoki Kishi, Toshiki Sugai, Shunji Bandow, Sumio Iijima, and Hisanori Shinohara*

Abstract:

Exohedral C₆₀-based metallofullerenes, CsC₆₀, have been synthesized and successfully encapsulated into single-wall carbon nanotubes (SWNTs) in high yield by reducing C₆₀ molecules into anions. High-resolution transmission electron microscopy (HRTEM) images and in situ electron energy loss spectroscopy (EELS) indicate that Cs atoms and C₆₀ molecules align within SWNTs as CsC₆₀ exohedral metallofullerenes, and that the formal charge state of encaged CsC₆₀ is expressed as Cs⁺¹C₆₀^-1. The present peapods with the exohedral metallofullerenes provide a new insight and the possibility to fine-tune the electronic and transport properties of carbon nanotubes.

J. Am. Chem. Soc., 127 (51), 17972 -17973, 2005.

We wonder if any real applications of this will be practical, but the idea is very interesting nonetheless. The C60 is a soccer ball molecule of 60 carbon atoms, called buckyball or fullerene after the architect Buckminster Fullerene, who designed buildings with this structure. Carbon nanotubes are simply buckyballs extended in one dimension to form long tubes. These tubes are nano-sized in width, but can extend over much larger than nano distances in legth. They can be used to improve the strength of certain materials when embedded in them. Also, they can be conductive, acting as nanowires for nano-sized electronic circuits. In this case, these scientists use single-wall carbon nanotubes (SWNTs) which have only one wall as the name suggests.

C60 molecules and carbon nanotubes are fundamentally a kind of soot. Surprisingly, we have been creating C60 molecules for ages without realizing it or understanding what to do with them!

3D Solar Cell using nanocomposite interpenetrating network of TiO2 and CuInS2

M. Nanu, J. Schoonman, and A. Goosens, "Nanocomposite Three-Dimensional Solar Cells Obtained by Chemical Spray Deposition", Nano Letters 5, 1716 (2005).

Abstract:

The present study is focused on low-cost preparation of thin film TiO2CuInS2 nanocomposite three-dimensional (3D) solar cells. With the aid of a simple spray deposition method, we have been able to obtain 3D solar cells, with a remarkable energy conversion efficiency of 5%. The new 3D solar cell design has the potential to breakdown the price barrier and to open up new production technologies for low-cost photovoltaic solar cells.

We selected this paper since it provides a clear demonstration of the way solar cells need to go in the future: three-dimensional interpenetrating networks of all-organic, all-inorganic, and hybrid organic-inorganic heterojunctions. The major advantages of this type of design are :

1. Increased p-n junction surface area.
2. Defect tolerance.
3. Reduced loss from recombination before charge separation.

We hope to highlight more of these types of nano-structured solar cells in the future.

THIS FIRST

We're going to require all you readers (zero at the moment) to watch these Feynman Lectures before we really get on with this blog. Remember, we are scientists. We appreciate good science and good science should be explained in simple terms so all can understand. Let us approach from this perspective.

Here it is: http://www.vega.org.uk/video/subseries/8