Russian and foreign scientists have developed a new method of stabilizing two-dimensional macene materials (MXenes) in one stage. The approach proposed by the doctors could improve the properties of macene – adhesion and chemical stability, which are important for the use of manufacturing materials, for example in electric heaters and breathing sensors. The research, supported by the Russian Science Foundation, was published in the journal ACS Applied Materials & Interfaces, the press service of Tomsk Polytechnic University reported.
Macsenes are a family of nanomaterials discovered about ten years ago. These are two-dimensional materials composed of transition metals, carbon and/or nitrogen, and surface functional groups. Maxene has very high electrical conductivity, a large surface area, and is an excellent candidate for uses, such as as a material for supercapacitors and chemical sensors. However, the practical application of macene is seriously hindered by poor adhesion to hydrophobic substrates, such as some commonly used polymers, as well as low chemical stability, leading to deterioration of electrical and mechanical properties under environmental conditions.
Traditional macene stabilization methods, e.g., pre-treatment of the substrate surface with plasma, addition of surfactants, post-treatment using antioxidants, thermal annealing, often reduce the electrical conductivity of the material, are not suitable for all substrates, and also involve complex, multi-stage technological processes.
Russian and Chinese scientists have proposed a new method to stabilize macene – a one-step laser transfer process.
“Laser processing is currently revolutionizing the modification of nanomaterials, offering a one-step solution to the problems of low adhesion and stability. There are some studies using laser processing to form structures for supercapacitors or create samples of different shapes, but usually irradiation does not lead to improved stability or, even worse, leads to oxidation of the structures. In this work, we consider laser processing as an interface design strategy aimed at improving improves the adhesion of macene to both rigid (glass) and flexible (thermoplastic polyurethane) materials. This method ensures reliable “fixation” of maxene on substrates and prolongs the life of devices based on them. The proposed method does not require pre- or post-treatment and is applicable even to old macene films synthesized more than a year ago,” said Evgenia Sheremet, professor at the University's Research School of Chemical and Biomedical Technology. Tomsk Polytechnic said.
To solve the problem, scientists used a so-called “sandwich” configuration, which effectively reduces the risk of oxidation during processing by creating a self-contained hypoxic microenvironment without the need for an inert or vacuum environment, significantly reducing costs and simplifying the process. They used the most widely used titanium carbide-based macene, synthesized by chemical wet etching. The substrate is glassy polyurethane and thermoplastic. Maxene in dispersion form was applied to a thermoplastic polyurethane substrate and air-dried. Next, the system is placed between two transparent glass panels. Laser treatment passes through the top layer of glass, then the “sandwich” structure is separated, due to which macenes are transferred to both contact surfaces, forming strong interfaces with them.
“This configuration allows macenes to adhere to the top glass through reverse transfer and simultaneously to the TPU substrate through direct transfer. Furthermore, the adhesion resulting from laser treatment turned out to be much better than standard plasma treatment of the substrate,” explains Anna Lipovka, associate professor at the Research School of Chemical and Biomedical Technology of Tomsk Polytechnic University.
Analysis of the surfaces showed that the scientists' method preserved the original structure of macene while effectively minimizing further oxidation of the material on both substrates thanks to the carbon-rich protective layer. The result is durable conductive surfaces that retain their properties under prolonged exposure to high humidity and high temperatures.
“To demonstrate the versatility of the method and its practical potential, we created models of thermoelectric heaters and breath sensors based on the obtained interfaces. Heaters are becoming increasingly popular in creating smart windows, fog lights, producing environmentally friendly building materials, etc. Here, we used a maxen glass interface. For the breath sensor, we replaced thermoplastic polyurethane with polyethylene terephthalate, maintaining all other conditions. Evgenia Sheremet concludes: macene-based electronics and sensors in real-world applications.
