Chemistry Meets Quantum Sensing: Towards Atomic Architectures Tailored for Diamond Probes

Project Information

ChemiQS

Grant agreement ID: 101038045

DOI

10.3030/101038045

Project closed

EC signature date 12 April 2021

Start date 1 April 2022

End date 31 March 2024

Funded under

• SPREADING EXCELLENCE AND WIDENING PARTICIPATION

Total cost

€ 144 980,64

EU contribution

€ 144 980,64

Coordinated by

USTAV ORGANICKE CHEMIE A BIOCHEMIE, AV CR, V.V.I.
Czechia

Periodic Reporting for period 1 - ChemiQS (Chemistry Meets Quantum Sensing: Towards Atomic Architectures Tailored for Diamond Probes)

Reporting period: 2022-04-01 to 2024-03-31

Summary of the context and overall objectives of the project

The rise of quantum sensing brings the opportunity to develop sensors that can be substantially more sensitive, scalable and faster than the classical ones, thus affecting many scientific and industrial disciplines, including chemistry, biochemistry, biology and medicine. Although different sensing principles and nanoprobes have been studied, they are still limited mainly in sensitivity and spatiotemporal resolution. For instance, nanodiamond particles with qubits can act as optical probes and have enormous potential e.g. for intracellular localized detection, but the sensitivity is limited by short coherence times of the qubits due to subsurface defects and unsaturated bonds. Moreover, the sensor specificity and colloidal stability in the biological liquids need to be addressed. The project aims to tackle these problems by exploring surface chemistry, polymer coating and chemical linking strategies to develop a new generation of nanodiamond-based quantum sensing probes. Specifically, novel chemical approach will be tested to annihilate the dangling bonds and subsurface defects by controlled surface removal using radical etching in the gas phase. The nanodiamond probes will be then stabilized colloidally by developing ultrathin polymer coatings and the probe specificity will be ensured by novel linking strategies. Finally, the qubit spin properties will be monitored optically to detect paramagnetic ions and nucleic acids in biologically relevant conditions with unprecedented sensitivity.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Months 1-3
WP1: Prototype of non-thermal plasma (NTP) generator in gas phase for direct ND etching in solution.
WP3: Relaxometry upgrade including addition of AOM for laser pulsing, APD, counter and delay generator (Fig1).
WP4-6: Safety training, Career Development Plan, project communication plan, seminar about the NV photo-physics, project-dedicated accounts facebook.com/ChemiQS twitter.com/QsChemi chemiqs.webnode.cz/

Months 4-6
WP1: Initial ND-modification experiments with NTP (Fig2) with varying diamond sample, various set of conditions, and different ambient gases.
WP3: Setup fully upgraded, instructions were demonstrated to the relevant IOCB employees
WP4-6: Progress meeting, training, eMRS Fall Meeting - invited speaker

Months 7-9
WP1: Following the NTP surface modification using FTIR (Fig3) and zeta potential.
WP2: Poly-glycerol for creation of the covalent ultrathin coatings of the ND probes.
WP4-6: Training, presentation at CEITEC, paper writing

Months 10-12
WP1: This WP has been successfully finished. NDs show longer T1 and T2 times, the NTP reaction is time-dependent and can be well controlled (Fig4).
WP2: Optimization of the ultrathin polymer coating of NDs. RAFT polymerization of NDs with responsive polymers.
WP4-6: Progress meeting, training, presentation at SBDD XXVII Hasselt

Months 13-15
WP2: ND polymer coating of 3-4 nm achieved. Synthesis of Cu-binding ligands. Modification of polymers with Gd3+ chelates (Fig5).
WP3: T1 measurement optimization.
WP4-6: Progress meeting, supervision of high school student, manuscript preparation

Months 16-18
WP2: Fusion of silica-coated-NDs with DOPC liposomes. ND azidation.
WP3: Effect of polymer on the T1 time. T1 measurements inside cells (Fig6).
WP4-6: Progress meeting, presentations at GRC Quantum Sensing conference and 75th Chemists Convention

Months 19-21
WP2: Preparation of the NDs with molecular beacons for sensing of nucleic acids.
WP3: Calibrated polymer-based probes (Fig7).
WP4-6: Student supervision, manuscript preparation

Months 22-24
WP3: Anchoring mechanism of NDs to substrate for colloidal T1 measurements. Calibration of probes for miRNA sensing (Fig8).
WP4-6: Progress meeting, project finalization

Overview:
The T1 setup was developed and was used to measure and calibrate the developed probes. The surface modification of NDs using NTP was carried out successfully resulting in prolongation of T1 and T2 times. A methodology to create minimal 2-4 nm polymer coating of NDs was established. Such probes show excellent colloidal stability and further enhanced spin properties. They were used to create series of specific sensors for metal ions, temperature and miRNA detection based on T1 relaxometry. The project resulted in 10 publications (3 published, 1 submitted, and 6 in preparation). The outcomes were further presented at several international conferences: eMRS, SBDD Hasselt, GRC Quantum Sensing, 75th Chemists Convention (NDNC and NPO Workshop in future), at IOCB seminar, in CEITEC as an invited talk. The work was further disseminated online via project dedicated webpage and social media channels, and on the NanoChem website.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Development of quantum sensing is part of the European Commission’s Quantum Flagship aiming at detecting individual atomistic events in real-time. Diamond sensors are in the center of the focus, however, currently limited by significantly shorter coherence times of the shallow (nitrogen-vacancy) NV centers. The problem of shorter NV coherence times near surface is commonly tackled either by surface termination or by creating ultra-pure CVD diamond. However, these methods are either not sufficient (termination) or not applicable (CVD) especially for small luminescent nanodiamond (ND) crystals. This project will explore a different approach, by controllably removing the surface diamond layers by radical etching, eliminating thus subsurface point-defects that are spin-active and otherwise inaccessible. In addition, thanks to the possibility to control the reaction coordinate by temperature, the omnipresent radical pool in gaseous phase can recombine with potentially exposed radical defects, creating thus densely terminated diamond surface without sp2 reconstructions. The proposed radical etching procedure thus aims to solve this issue and can be applied to larger diamond crystal as well, bringing a solution to a long-standing problem.

Regarding intracellular applications, embedding NDs into different kinds of shells and coatings has been shown recently as a viable approach to improve colloidal stability. This project will innovate the current polymer coating methods by two-fold: 1) producing soluble probes even when additional ligands are attached, while simultaneously 2) keeping the distance from the probed spin as low as possible. Such approach is entirely unexplored. Selective detection and quantification: the use of established ion-selective ligands merged with ND probes for sensitive detection of paramagnetic ions is entirely new concept. Similarly, distance-dependent actuation of paramagnetic through molecular beacon is a new idea, which has not been applied to NDs and will bring original way to locally detect nucleic acids. The development of the selective detection of transition metals and small nucleotides will advance further the cell biology research and, additionally, the sensing concept can be then transferred to larger diamond crystal for the purpose of selective nanoscale-NMR, which is a highly-researched area of NV sensing.

Even though luminescent NDs are highly researched topic, this project brings novelty in terms of interdisciplinary approach, based on produce-test-repeat practice, which will give access to detection of potentially individual probed spins. Overall, the project aims to develop complex ND probes, that can be then modified for different sensing purposes and used as a versatile tool for localized live-cell quantum sensing.

Quantum sensing in cells

Development of relaxometry update

Detection of miRNA

Development of NTP functionalization

Time-dependency control of ND surface

T1 calibration of ND probes

Translating physical quantity into T1-detectable signal

FTIR results of NTP functionalization