Writing with Nanoparticles
Novel properties of a material appear when particle size approaches the nanometer scale. ™is makes nanotechnology a new šeld of research, and motivates scientists and technologists to utilize new properties of nanoparticles for a wide range of applications. For example, semiconducting materials exhibit optical absorption and emission properties similar to that of atoms/molecules, that can be used in medical diagnosis, nanoelectronics, and optics. As the size of platinum particles reduces to a few nanometer, the particles start acting as a catalyst for hydrogenation. Gold changes its optical absorption properties and colors depending on its particle-size. Technologies are being developed with gold nanoparticles for biodiagnostics, cancer treatment, and memory devices. Gold nanoparticles have been used for long-lasting coloring of stain glasses long before the arrival of nanotechnology. Novel properties of these nanoparticles were not utilized primarily because of insuÀcient understanding of their properties and absence of mechanisms of directing them to the desired locations. Creating features on a surface needs a specišc tool or a pen to direct the ink to specišc locations. Before human civilization started to use symbols, engraved features on stones and walls were the main method of communication, and the tools that were used for hunting were used as the pen for writing these features on large chunk of stones. A pen with a sharp metal or bone as stylus and iron salt as ink, similar to the fountain pen used today, existed in ancient Greece. In today’s context, we know more about the properties of nanoparticles than we knew 20 years ago; however, writing with nanoparticles is still a challenge, especially for industrial applications. In other words, we need a suitable “pen” to put these particles where we wish to create the features. A few examples of applications that require nanoparticles as ink are nanoelectronics , nano-biosensors , and nanoscopic light sources .