Quantum Leap for Diamond Nanoparticles Thanks to TV-Inspired Coating

Inserting highly sensitive quantum sensors into living cells offers a promising approach for monitoring cell growth and detecting diseases—including cancer—at early stages.

Diamond Nanocrystals as Quantum Biosensors: Integration Challenges

Many of the most advanced and powerful quantum sensors can be built using tiny pieces of diamond, but this presents a challenge: inserting diamond into a cell and making it function properly isn’t easy.

“You need to study many essential cellular processes at the molecular level, which means you can’t use large devices—you have to work inside the cell. That’s where nanoparticles come in,” explained Uri Zvi, a Ph.D. candidate at the University of Chicago’s Pritzker School of Molecular Engineering. Researchers have used diamond nanocrystals as biosensors before, but they consistently found their performance fell short of expectations. In fact, significantly so.

Zvi is the lead author of a paper published in Proceedings of the National Academy of Sciences that addresses this problem. Collaborating with researchers from UChicago PME and the University of Iowa, Zvi combined knowledge from cell biology,  quantum science, traditional semiconductor technology, and even HDTV displays to develop a groundbreaking new quantum biosensor. In the process, the team also helped solve a long-standing puzzle in the field of quantum materials.

The researchers developed a quantum biosensor suited for use inside living cells by coating a diamond nanoparticle with a custom-designed shell—a method inspired by the technology behind QLED televisions. This approach not only enabled the creation of an effective sensor but also revealed new understanding of how altering a material’s surface can boost its quantum properties.

“It was already among the most sensitive tools available, and now they’ve discovered a way to further enhance its performance across various environments,” said Prof. Aaron Esser-Kahn of UChicago’s Pritzker School of Molecular Engineering, Zvi’s principal investigator and a co-author of the study.

A Cell Filled With Diamond Particles

Diamond nanocrystals embed qubits that retain their quantum coherence even when living cells absorb the tiny particles—imagine the cell swallowing and breaking them down without spitting them out. However, as the diamond particles get smaller, the strength of the quantum signal diminishes.

These quantum sensors sparked excitement because researchers can introduce them into living cells, and they can potentially serve as effective sensors. “But while quantum sensors in large bulk diamond pieces have excellent quantum properties, those properties significantly weaken when the sensors are in nanodiamonds.”

To address this, Zvi drew inspiration from an unexpected source: quantum dot LED (QLED) televisions. QLED TVs use bright, fluorescent quantum dots to produce vivid, rich colors. Early on, these colors were bright but unstable and could suddenly flicker off.

“Researchers discovered that encasing quantum dots with specially designed shells reduces harmful surface effects and boosts their emission,” Zvi explained. “Now, those once unstable quantum dots are integral parts of modern TVs.”

A Collaborative Approach to Improving Quantum Dots and Nanodiamonds

Collaborating with UChicago PME and Chemistry Department quantum dot specialist Prof. Dmitri Talapin, a co-author of the study, Zvi hypothesized that since both problems—the weak fluorescence of quantum dots and the reduced quantum signal in nanodiamonds—stemmed from issues with their surfaces, a similar solution might be effective.

However, because the sensor is designed to operate inside living organisms, not every type of coating suits it. With the help of immunoengineering expert Esser-Kahn, they developed a silicon-oxygen (siloxane) shell that enhances the quantum properties while avoiding detection by the immune system.

“The surface of most materials tends to be sticky and irregular, which makes immune cells recognize them as foreign,” Esser-Kahn explained. “But siloxane-coated particles appear like a large, smooth water droplet, so the body is much more willing to engulf and process them.”

Previous attempts to improve diamond nanocrystals’ quantum properties through surface modification had yielded only limited success. Because of this, the team expected only minor improvements. Instead, they observed up to a fourfold increase in spin coherence.

This significant boost, along with a 1.8-fold rise in fluorescence and notable gains in charge stability, was both surprising and fascinating to the researchers.

Read the original article on: Phys.Org

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