A nanocrystal shines on and off indefinitely

New York, NY—May 31, 2023—In 2021, lanthanide-doped nanoparticles made waves—or rather, an avalanche—when Changwan Lee, then a PhD student in Jim Schuck’s lab at Columbia Engineering, set off an extreme light-producing chain reaction from ultrasmall crystals developed at the Molecular Foundry at Berkeley Lab. Those same crystals are back again with a blink that can now be deliberately and indefinitely controlled.

“We’ve found the first fully photostable, fully photoswitchable nanoparticle—a holy grail of nanoprobe design,” said Schuck, associate professor of mechanical engineering.

This unique material was synthesized in the laboratories of Emory Chan and Bruce Cohen at the Molecular Foundry, Lawrence Berkeley National Laboratory as well as in a national lab in South Korea. The research team also included Yung Doug Suh’s lab at Ulsan National Institute of Science and Technology (UNIST).

The Holy Grail: A Simple, Stable Light Switch

Existing organic dyes and fluorescent proteins used in applications like optical memory, nanopatterning, and bioimaging have yielded years of breakthroughs (and garnered a Nobel Prize in Chemistry in 2014), but these molecules have limited lifespans. Upon illumination, most will begin blinking randomly and ultimately will go dark permanently, or “photobleach.”

In contrast, lanthanide-doped nanoparticles show remarkable photostability. In over 15 years of working with them in his lab, Schuck noted they’ve never seen one die. Until one random day in 2018 when Lee and PhD student Emma Xu observed a crystal go dark, and then turn back on again. Lee dug into the literature and found 30-year-old mentions of lanthanide optical fibers that could be “photodarkened” and “photobrightened”—suggesting the blinking behavior could be controlled. 

In a new paper published today in Nature, the team does just that. Using near-infrared light, they darkened and brightened their nanoparticles over a thousand times in different ambient and aqueous environments with no signs of degradation.

“We can turn these particles, which don’t otherwise photobleach, off with one wavelength of light and back on with another, simply using common lasers,” Lee said. Notably, near-infrared light can penetrate deeply into both inorganic materials and biological tissue with minimal scattering or phototoxicity.

Weird Results Brighten Future Applications

Looking towards potential applications, the team demonstrated how the particles can be used to write—and rewrite—patterns onto 3D substrates, which could one day improve high-density optical data storage and computer memory.

"This indefinite, bidirectional photoswitching nanocrystal could yield an all-optical quantum memory device for storing the vast amount of data produced by quantum computers—think of CD-ROMs and CD-RWs, but faster and much more precise,” Suh said.

The particles also offer potentially infinite resolving power, which depends on the number of photons produced by a probe under a super-resolution nanoscope. Using equipment in Suh’s lab, Lee reached sub-Àngstrom precision in only a few hours.

The team believes that photoswitching observed in the current work ultimately results from atomic crystal defects too small to be visualized even with the most advanced electron microscopes. These defects shift the particle’s avalanche threshold up or down and can be toggled by different wavelengths of light to make the signal dimmer or brighter.

In addition to pursuing potential applications in optical memory, super-resolution microscopy, and bioimaging and biosensing, the team is using nanoparticle synthesis robots at the Molecular Foundry, advanced computational models, and machine learning to improve the current crystals further and explore whether they can synthesize other kinds of nanoparticles with similar photoswitchable properties.

This entire study was a surprise, said Cohen. “We had been saying since our 2009 paper that this class of nanoparticles doesn't switch on and off, and yet that's exactly what we're studying here. One of the things we've found with these nanoparticles is to embrace weird results.”

About the Study

Journal: Nature

The study is titled “Indefinite and Bidirectional Near Infrared Nanocrystal Photoswitching.”

Authors are: Changhwan Lee¹, Emma Z. Xu¹, Kevin W. C. Kwock², Ayelet Teitelboim³, Yawei Liu^3,4, Hye Sun Park⁵, Benedikt Ursprung¹, Mark E. Ziffer⁶, Yuzuka Karube⁷, Natalie Fardian-Melamed¹, Cassio C. S. Pedroso³, Jongwoo Kim⁸, Stefanie D. Pritzl^9,10, Sang Hwan Nam⁸, Theobald Lohmueller⁹, Jonathan S. Owen⁷, Peter Ercius³, Yung Doug Suh^{11, 8,12,13,}*, Bruce E Cohen^3,14,*, Emory M Chan^3,*, P. James Schuck^1,*

¹Department of Mechanical Engineering, Columbia University, New York, NY, United States

²Department of Electrical Engineering, Columbia University, New York, NY, United States

³The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.

⁴State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China

⁵Research Center for Bioconvergence Analysis, Korea Basic Science Institute (KBSI), Cheongju, South Korea

⁶Department of Physics, Columbia University, New York, NY, United States

⁷Department of Chemistry, Columbia University, New York, NY, United States

⁸Laboratory for Advanced Molecular Probing (LAMP), Korea Research Institute of Chemical Technology (KRICT), Daejeon, South Korea

⁹Chair for Photonics and Optoelectronics, Nano-Institute Munich, Ludwig-Maximilians Universität München, Germany

¹⁰Department of Physics and Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands 

¹¹Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea

¹²School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea

¹³Center for Multidimensional Carbon Materials(CMCM), Institute for Basic Science(IBS), Ulsan, South Korea

¹⁴Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

The study was supported by the Global Research Laboratory (GRL) Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (number 2016911815), and KRICT (KK2261-12, SKO1930-20); the Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under contract number DE-AC02-05CH11231; the Defense Advanced Research Project Agency (DARPA) Enhanced Night Vision in Eyeglass Form (ENVision) program (number HR00112220006); the National Science Foundation under Grant No. DMR-2019444; the NSF Graduate Research Fellowship Program; the DOE NNSA Laboratory Residency Graduate Fellowship program (No. DE-NA0003960); Programmable Quantum Materials, an Energy Frontier Research Center funded by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award DE-SC0019443IBS-R019-D1; 2022 UNIST Research Fund (1.220108.01); seed funding support from Columbia University's Research Initiatives in Science & Engineering competition; the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No 893439; the Fulbright Scholarship Program; the Zuckerman-CHE STEM Leadership Program; and the ISEF Foundation;  the National Science Foundation under Grant No. CHE-2203510. S.D.P; the German Research Foundation (DFG) through the Collaborative Research Center 1032, Project no. 201269156, A8).

The authors declare no financial or other conflicts of interest.

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LINKS:

Paper: https://www.nature.com/articles/s41586-023-06076-7
DOI:  10.1038/s41586-023-06076-7

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