Tag Archives: Tokyo Tech

Metallic NanoParticles 50 Times More Effective As Catalysts

Scientists at Tokyo Institute of Technology produced subnano-sized metallic particles that are very effective as catalysts for the oxidation of hydrocarbons. These catalysts can be as much as 50 times more effective than well-known Au-Pd bimetallic nanocatalysts.
The oxidation of aromatic hydrocarbons is critically important for producing a great variety of useful organic compounds that are used throughout all types of industries. These oxidation processes require the use of catalysts and solvents, which are usually environmentally hazardous. Thus, finding a solvent-free oxidation process using nanosized catalytic particles has attracted considerable attention. Interestingly, sub-nanoscale catalytic particles (subnanocatalysts, or SNCs) composed of noble metals are even better at their job because their increased surface area and unique electronic state results in favorable effects for oxidizing hydrocarbons and also prevents them from getting oxidized themselves. This makes them cost-effective because the amount of metal required for SNCs is lower than for nano-sized catalysts.

A team including Dr. Miftakhul Huda, Keigo Minamisawa, Dr. Takamasa Tsukamoto, and Dr. Makoto Tanabe at Tokyo Institute of Technology (Tokyo Tech), led by Prof. Kimihisa Yamamoto, created multiple types of SNCs by using dendrimers, which are tree-like spherical molecules that can be used as a template to contain the desired catalysts. “Dendrimer is expected to provide internal nanospaces that could be suitable for catalytic conversion in the presence of metal particles,” explains Yamamoto . The scientists created various catalysts of different sizes, depending on the noble metal used and the number of atoms of each catalytic particle.

Each dendrimer molecule hosts a subnano-sized metallic particle that allows for the oxidation of aromatic hydrocarbons, such as toluene (left), to produce useful organic compounds, such as benzoic acid (right). Oxygen molecules are represented in red.

They compared their performance to find the best noble metal for making SNCs and then tried to determine the mechanism behind their high catalytic activity. Smaller SNCs were found to be better, while less oxophilic metals (such as platinum) were superior. The team postulated that the surface of platinum SNCs does not oxidize easily, which makes them reusable and results in the highest catalytic performance of the Pt19 SNC that can be as high as 50 times more effective than the common Au-Pd nanocatalysts. The team will continue working to shed light on these catalytic phenomena. “The development of a more detailed mechanism including theoretical considerations is currently in progress,” says Tanabe. The applications of such catalysts could greatly contribute for reducing pollution and enhancing our effective use of Earth’s metal resources.

Source: https://www.titech.ac.jp/

Non-toxic Virus Quickly Dissipate Heat From Electronic Devices

The researcher team of Tokyo Tech discovered that the film constructed by assembling a nontoxic filamentous virus functions as a heat dissipation material, and that can be simply prepared by drying the virus aqueous solution at room temperature. This discovery is expected to elucidate the mechanism of new heat transport in electronics.

Organic polymeric materials generally have low thermal conductivity and are not suitable for rapid heat dissipation of electric and electronic equipment in the past. In order to improve its thermal conductivity, it has been considered effective to heat transfer through a covalent bond by “orientation processing” in which molecules are aligned in the same direction, or to composite with an inorganic material.

A research team led by Assistant Professor Toshiki Sawada and Professor Takeshi Serizawa is focusing on the capability to form regularly assembled structures in a wide scale from nano to macro (so called hierarchical assembly) observed in the natural systems and the hierarchically assembled structures prepared in this way, the phenomenon where molecules accumulate around the perimeter as an aqueous solution in which molecules are dissolved evaporates (coffee ring effect) was utilized to assemble a filamentous virus for the film preparation. As a result, it was found that the thermal diffusivity at the edge of the film drastically enhanced to a value comparable to that of inorganic glass, and that facilitates the utilization of the hierarchically assembled biomacromolecule. This helps future development of electric and electronic devices composed of not only viruses but also various naturally derived molecules.

(a) Phage and (b) hexagonally assembled structures of the phages in the film.

Until now, orientation processing and compositing with inorganic materials have been considered effective for the high thermal conductivity of organic polymeric materials. However, since this virus film can be prepared by evaporating an aqueous solution of a filamentous virus at room temperature, it is expected to lead to the establishment of a method for easily constructing heat dissipation materials under mild conditions that do not require special operations.

Source: https://www.titech.ac.jp/