Optical Storage Memory Research Articles

Cooperative and fully reversible color switching activation in hybrid graphene decorated nanocages and copper-TiO2 nanoparticles

Nanostructured systems showing reversible color switching are envisaged to play a significant role in photo-switches, photo-optical sensors, smart windows, displays, optical storage memories. Most of the materials exhibiting reversible color switching are organic molecules. However, their UV-light activation, low thermal and chemical stability, as well as harmful synthesis methods, limit their extensive use. In this research, we have created an inorganic switchable photochromic material exploiting TiO2 ability of creating an exciton upon excitation, copper as the chromophore, and graphene's extraordinarily high electron mobility. Spatially-resolved electron energy-loss spectroscopy and aberration-corrected transmission electron microscopy imaging highlight the high sp2 content of the graphene flakes as well as the presence of few-layers nanocage graphene decorating the surface of the flakes. Our material showed itself to be able to work under visible-light, its photochromic property being three times faster than conventional titania based photochromic materials, reaching a stable change in coloration after only 30 min of visible-light irradiation (vs. > 120 min in conventional Cu–TiO2). With the addition of just 1 wt% graphene, the material exhibited a staggeringly stable photochromic switching over repeated cycles. These results relate to the best previously reported values for any form of TiO2-based photochromic material. This is therefore an excellent candidate for smart-windows, light-sensitive information and energy storage devices, and other chromic devices and applications.

Synergy of Neodymium and Copper for Fast and Reversible Visible-light Promoted Photochromism, and Photocatalysis, in Cu/Nd-TiO2 Nanoparticles

Multifunctional materials working under solely visible-light are expected to play a significant role in photoelectronics, in particular photoswitches, photo-optical sensors, smart windows, displays, optical storage memories, and self-cleaning materials. We have modified the surface of a versatile semiconductor material (TiO2) with a noble metal (copper) and simultaneously doped its structure with a rare-earth element (neodymium). Exploiting the ability of a semiconductor to generate an exciton upon excitation, a multifunctional material working with visible-light and showing photochromic and photocatalytic activity was engineered. A combination of high-resolution (scanning) transmission electron microscopy (including image simulations), spatially resolved electron spectroscopies, and X-ray analyses were used to characterize the structure and local chemical environment of the modified material. We showed that Nd entered the TiO2 structure in a substitutional fashion, and when at 1 mol %, neodymium atoms we...

Anthracene monomer-dimer photochemistry: High density 3D optical storage memory

Ultrafast spectra and kinetics of all spectroscopic states and intermediate species in the photodimerization process of substituted anthracenes have been identified and measured by means of ultrafast spectroscopy. The two forms of this process, monomer and dimer, have been used to construct a 3D optical storage memory device capable of 1013 bits/cm3 density and very large bandwidth. Storage and accessing 3D information is based on non-linear absorption and the different structures of the monomer and dimer. This rather novel 3D memory device and its operation is described in detail.