June 6th is International Graphene Day, and the research and application of graphene have always been a hot topic of discussion in the scientific community. Graphene itself exists in nature as a thin sheet formed by a layer of carbon atoms, with a hexagonal ring formed between the atoms and connected to form a honeycomb like plane. It is stacked layer by layer as graphite, with a thickness of 1 millimeter containing approximately 3 million layers of graphene. At the beginning of the 21st century, two scientists from the University of Manchester, England, successfully prepared graphene by mechanical stripping method. They first pasted two sides of the graphite with tape, then ripped off the tape for stripping, and repeated this step until graphene was stripped. They were awarded the Nobel Prize in Physics in 2010, which sparked scholars' attention to this new type of material.
Graphene is the thinnest material in the world, only about 0.34 nanometers thick. Graphene is harder than diamonds and has a strength higher than the best steel in the world
200 times, the maximum pressure that can be withstood at a distance of 100 nanometers actually reaches 2.9 microns, which means that if it is made into a packaging bag, it will be able to withstand approximately two tons of weight. At the same time, it also has good elasticity, and the stretching range can reach 20% of its own size. Graphene has excellent thermal and chemical stability, with a melting point of up to 3850 ℃, and is resistant to harsh environments such as strong acids and bases. When electrons in graphene move in their orbits, they do not scatter or consume energy due to lattice defects or the introduction of foreign atoms. Electrons can migrate extremely efficiently, with a migration rate of only one-third of the speed of light, far higher than their rate in traditional semiconductors and conductors such as silicon and copper. Graphene, due to its unique properties, has high potential application value and broad application prospects in materials science, micro/nano processing, energy, biomedicine, and drug delivery, and is known as "black gold".

Here are some news related to graphene.

Researchers have developed a new nanotube crystal that enables the direct observation of electron transfer in solids

Electron transfer (ET) is a process in which an electron is transferred from one atom or molecule to another. ET is fundamental to electrochemical reactions with applications in many fields. Nanoscale ET, which involves the transfer of electrons in the range of 1-100 nanometers in solids is fundamental to the design of multifunctional materials. However, this process is not yet clearly understood.

Nanotubes, nanomaterials with unique cylindrical nanostructures, offer a variety of ET properties that can be realized through electron and hole (vacant spaces left by electrons) injections into the nanotubes, making them a suitable candidate for studying nanoscale ET. Although carbon-based nanotubes have fascinating ET properties, they are particularly difficult to control in terms of their shape and size due to extreme conditions, such as high temperatures, required for their synthesis. A viable approach for fabricating well-defined tunable nanotubes is bottom-up fabrication of non-covalent nanotubes, which sometimes result in crystalline-form nanotubes. Non-covalent nanotubes are formed through the inherent attractive interactions or non-covalent interactions between atoms, instead of the strong covalent interactions seen in carbon nanotubes. However, they are not strong enough to endure electron and hole injections, which can break their non-covalent interactions and destroy their crystalline structure.

In a recent study, a team of researchers from the Department of Applied Chemistry at Tokyo University of Science, led by Professor Junpei Yuasa and including Dr. Daiji Ogata, Mr. Shota Koide, and Mr. Hiroyuki Kishi, used a novel approach to directly observe solid-state ET. Prof. Yuasa explains, "We have developed crystalline nanotubes with a special double-walled structure. By incorporating electron donor molecules into the pores of these crystalline nanotubes through a solid-state oxidation reaction, we succeeded in directly observing the electron transfer reaction in the solid using X-ray crystal structure analysis." Their findings were published in the journal Nature Communications on May 23, 2024.

The researchers used a novel supramolecular crystallization method, which involves oxidation-based crystallization, to fabricate zinc-based double-walled crystalline nanotubes. This double-walled structure with large windows in the nano-tube walls makes the crystal robust and flexible enough to maintain its crystalline state when subjected to ET oxidation processes. Moreover, this structure allows the crystal to absorb electron donor molecules. The researchers used ferrocene and tetrathiafulvalene as electron donor molecules, which were absorbed through the windows of the nanotube crystals. This allows electrons to be removed from the absorbed electron donors through solid-state ET oxidation reactions, resulting in the accumulation of holes in the donors inside the nanotube. Due to the robustness of the crystals, the researchers were able to observe this ET oxidation process using X-ray crystal structure analysis directly, uncovering key insights.

This novel approach is highly valuable for direct observation of ET in solid nanomaterials. Highlighting the potential applications of this study, Prof. Yuasa says, "Understanding ET can lead to the development of novel functional materials, which in turn can lead to the design of more efficient semiconductors, transistors, and other electronic devices. Optoelectronic devices, such as solar cells, rely heavily on ET. Hence, direct observation of ET can help improve these devices' performance. Additionally, this approach can lead to advancements in energy storage, nanotechnology, and materials science research."

Overall, this study is a striking example of direct observation of solid-state ET, which can be expanded to observe ET and related phenomena in other nanomaterials.