In-Between

Save one penny. Save a second, and a third, until you've accrued enough to buy a 1,000-acre property. This is one metaphor for picturing the way molecule-upon-molecule, when combined, will a crystal of solid material make.

In reality, it would take a mighty long time to amass enough pennies for a parcel of land. Similarly, joining molecules together in this incremental fashion could take a lifetime of work and wait.

Profs. Meir Lahav and Leslie Leiserowitz, research student Shouwu Guo in collaboration with Dr. Ronit Popovitch-Biro, Dr. Gary Hodes and Dr. Hagai Cohen of the Materials and Interfaces Department, are literally looking into the matter. As molecular "behaviorists," they're exploring the ways in which different molecules can be collected, and how they behave.

A crystal of solid material is characterized by its latticework structure; the molecules or atoms which compose the crystal are organized in a kind of a set frame which repeats itself, with fixed distances between them. From this description, it would seem that adding molecules together isn't sufficient to create a solid crystal.

To break it down even further, let's go back a step. What exactly is a group of molecules? It's neither a material in a macro-molecular state, nor is it a crystal of solid matter. It's in a kind of interim phase between two types of arrangements, between two physical worlds.

Scientists have a term for this in-between molecular material state: a quantum particle. This is a collection, or quantity, of a few molecules that still hasn't arrived at a solid material stage. That's where the Weizmann researchers are looking for answers.

Recently, they succeeded in arranging several quantum particles of a semiconductor on a substrate of organic material. Here, the quantum "points" were arranged in a kind of matrix reminiscent of the organized structure of a crystal lattice. Interestingly, such a crystal is characterized by different optical and physical properties from those of a crystal composed of atoms or molecules.

Due to their properties, the crystals may one day find a variety of market applications, for example, as electrooptical apparatus.

Thanks to the Weizmann Institute scientists, there's no more need to collect pennies nor to break open the molecular piggybank. As part of their "savings" plan, they're now collecting points.