Breakthrough! Tsinghua Develops New 3D Nanoprinting Technology Based on Semiconductor Quantum Dots
Recently, researchers from Tsinghua University and Jilin University have collaborated to develop a new 3D nanoprinting technique using semiconductor quantum dots (QDs). The related paper was published in the journal Science under the title "3D nanoprinting of semiconductor quantum dots by photoexcitation-induced chemical bonding" [1].
01Aggregation-independent laser writing technology: Light excitation induces chemical bonding
Over the past decade, the use of 3D printing technology to make 3D objects has expanded greatly, leading to new products and faster ways to create exemplary objects. But, as the researchers of this new work point out: 3D printers primarily use polymer-based materials, limiting the types of products that can be made. Numerous manufacturers have said they would buy 3D printers capable of printing products with optical or electronic properties; in this new effort, the Chinese researchers have taken a big step in that direction.
The new approach involves the use of semiconductor quantum dots - nanocrystals made of cadmium selenide (CdSe), covered with zinc sulfide, with a cap made of 3-mercaptopropionic acid formulation - as additions to the printing material. These "dots" are activated with a laser: photons from the laser are absorbed by the nanocrystals, leading to chemical changes that cause binding between the quantum dots; this process is called two-photon absorption. In their setup, the absorption of protons is only possible where the light intensity is highest. Therefore, this experiment allowed the creation of chemical bonds at wavelengths smaller than those of light.
Working principle of photoexcitation-induced chemical bonding (PEB). (A) 3D nanoprinting of 3-mercaptopropionic acid (MPA)-covered CdSe/ZnS quantum dots (QDs) using PEB. (B) The basic mechanism of PEB. (C) Fourier transform infrared (FTIR) spectra of drop-cast (drop-cast) QDs and printed structures.
Schematic diagram of the two-photon nanoprinting device. The intense beam of an infrared femtosecond laser induces the simultaneous absorption of two photons in a very small volume to trigger a photochemical reaction on the surface of a nanocrystal.
In this experiment, the scientists developed a direct laser writing technique that is not related to polymerization - the photoexcitation-induced chemical bonding technique. In the absence of any additives, excited holes inside semiconductor quantum dots are transferred to the nanocrystal surface and improve its chemical reactivity, leading to inter-particle chemical bonding. As a proof of concept, arbitrary 3D quantum dot architectures were experimentally printed at a resolution exceeding the diffraction limit. The researchers note that their technique preserves the optoelectronic properties of quantum dots, which means that 3D products printed with inks made from quantum dots can be used in optoelectronic devices.
02Promising market applications will revolutionize prototyping, small-scale manufacturing processes
In the same issue, Jia-Ahn Pan and Dmitri Talapin of the University of Chicago provided an article on more versatile 3D printing devices and for this new work by the Tsinghua team: "3D Printing Nanocrystals with Light" [2]. In the past, nanocrystals had many functional properties, but their integration with 3D printing was limited: it relied mainly on the use of polymeric materials as scaffolding (scaffolding), the article says. "Nanocrystals can be connected to form complex 3D structures by two-photon lithography, and in this experiment, the Chinese team demonstrated a 'two-photon lithography' approach to 3D printing nanocrystals. This ability to create custom 3D objects on demand will revolutionize prototyping and small-scale manufacturing processes."
Reference link：
[1]https://www.science.org/doi/10.1126/science.abo5345
[2]https://www.science.org/doi/10.1126/science.add8382
[3]https://phys.org/news/2022-09-3d-nanoprinting-semiconductor-quantum-dots.html
