Material: Two-dimensional materials seem to have a staying power in various technical news magazines. The US Department of Energy released a report on efforts involving the Lawrence Berkeley National Laboratory work on molybdenum disulfide (MoS2). [Ref. 1] Granted that the quantity production of this or any other 2-D material is difficult. Research is ongoing to determine the properties of the various 2-D materials with the knowledge that when some material exhibits characteristics that are very important for device development, someone will develop a means of producing the material in sufficient quantity. The researchers measured the bandgap of the material and found it to be 30% higher than theoretically predicted. The fact that they are able to develop a means of accurately measuring the bandgap holds promise for evaluating other materials. The researchers also found a relation between electron density and the bandgap. There findings indicate a possible application in sensors where optical or electrical effects can produce the complimentary effect.
There was a caution that the molybdenum disulfide is extremely sensitive to its local environment. This is not different from the impact of exposure of graphene to the atmosphere. Considering that 2-D materials are one atom think, it means that 100% of the atoms are on the surface and able to react with the environment. Contamination by external factors ends up reducing the properties of the basic material. This fact makes some of the planned applications challenging.
Nano-scale motion: Researchers at CalTech have made measurements of spherical gold nanoparticles moving in in water using a technique called liquid-cell 4D electron microscopy. [Ref. 2] A key element in observing the motion was the application of femtosecond laser pulses. Their efforts were of a liquid, a few hundreds of nanometers thick, captured between parallel plates. The particles appear to be driven by steam nanobubbles near the particles surface. This provides the initial action and then the resultant motion is a random motion as particles bounce of other particles. The hope is that the knowledge gained from this work will provide knowledge to develop both micro and nano actuated transport mechanisms.
Light induced crystal shape changes: Work by scientists at KAUST demonstrated photostriction in Perovskite crystals. In particular the researchers focused on MAPbBr3. When illuminated by light, the material’s photostriction changes the internal strain in the material. Their technique which employs in-situ Raman spectroscopy with confocal microscopy was able to measure intrinsic photoinduced lattice deformation. The researchers demonstrated that only a part of the change was due to the photovoltaic effect. They theorize that the generation of positive and negative charges due to the light polarizes the material which creates a change in the material structure. The researchers think that understanding the mechanisms behind the structural changes could provide a significant benefit in developing greater efficiency solar cells. Other possible applications include optoelectronic devices.
Thoughts: The tools for working in the nano-realm are improving. The discovery of different properties that could be applied to new devices are increasing. The “nano” revolution has been around for a number of years. There are application of nanomaterials being applied to commercial products for increased performance. Medicine is using the nano-sized carriers to combat diseases. But, are we missing something basic? Are we really using the properties of the nano-scale? More on this line of thinking later.
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