arXiv subjects

Laurynas Dagys

Publications and source records attributed to Laurynas Dagys.

7 recordsLinked to original sources

arXiv2026

Robust nuclear hyperpolarization of small molecules through intermolecular transfer of parahydrogen-derived polarization

The recent advent of hyperpolarization techniques, which can enhance NMR signals by several orders of magnitude relative to thermally polarized samples, has enabled applications traditionally out of reach due to the inherently low sensitivity of NMR techniques. However, a high barrier to entry remains, as most hyperpolarization approaches either require complex instrumentation or are applicable only to a relatively small set of molecules. Here we introduce PHIPNOE, a platform that directly addresses both limitations. PHIPNOE is based on parahydrogen-induced polarization (PHIP), which is well-established as a scalable route to hyperpolarization requiring minimal instrumentation, but has been mostly restricted to molecules that undergo specific chemical reactions. We overcome this barrier by tailoring PHIP to create highly polarized, highly concentrated solutions of one specific molecule, which acts as an intermediate source of polarization. This 'source molecule' then distributes polarization to a broad range of target molecules mixed into the solution, via the spin polarization-induced nuclear Overhauser effect (SPINOE). We investigate chemical influences on PHIPNOE, and develop a predictive model to estimate enhancement based on molecular mass and T1 relaxation times. A complete run from PHIP hyperpolarization to PHIPNOE polarization transfer and signal detection takes less than one minute, the approach does not require any modifications to the NMR spectrometer, and enhancements are repeatable across molecular classes. PHIPNOE thus enables applications including single-shot multidimensional NMR, real-time monitoring of dynamic processes, and, with 300-fold signal amplification demonstrated on a benchtop spectrometer, practical low-field NMR, where we show enhanced sensitivity in detecting per- and polyfluoroalkyl substances (PFAS).

physics.chem-ph↗

arXiv2026

Improved SABRE hyperpolarisation using pulse sequences to reduce effective coupling

Hyperpolarisation using Signal Amplification By Reversible Exchange (SABRE) is a convenient method for high repeatability studies. The core of this technique is polarisation transfer to the target substrate during an on-going chemical exchange process. Typically, polarisation transfer is achieved as fast as possible. In this study we employ NMR sequences that on contrary slow down the polarisation transfer and yet demonstrate improved performance. Simulations confirm that such methods can lead to high polarisation yield in SABRE system that exhibit higher magnetic inequivalence and lower chemical exchange rate.

physics.chem-ph↗

arXiv2024

Robust Parahydrogen-Induced Polarization at High Concentrations

Parahydrogen-Induced Polarization (PHIP) is a potent technique for generating target molecules with high nuclear spin polarization. The PHIP process involves a chemical reaction between parahydrogen and a target molecule, followed by the transformation of nuclear singlet spin order into magnetization of a designated nucleus through magnetic field manipulations. Although the singlet-to-magnetization polarization transfer process works effectively at moderate concentrations, it is observed to become much less efficient at high molar polarization, defined as the product of polarization and concentration. This strong dependence on the molar polarization is attributed to interference from the field produced by the sample's magnetization during polarization transfer, which leads to complex dynamics and can severely impact the scalability of the technique. We address this challenge with a pulse sequence that negates the influence of the distant dipolar field, while simultaneously achieving singlet-to-magnetization polarization transfer to the desired target spins, free from restrictions on the molar polarization.

physics.chem-ph↗

arXiv2023

Towards a unified picture of polarization transfer -- pulsed DNP and chemically equivalent PHIP

Nuclear spin hyperpolarization techniques, such as dynamic nuclear polarization (DNP) and parahydrogen-induced polarization (PHIP), have revolutionized nuclear magnetic resonance and magnetic resonance imaging. In these methods, a readily available source of high spin order, either electron spins in DNP or singlet states in hydrogen for PHIP, is brought into close proximity with nuclear spin targets, enabling efficient transfer of spin order under external quantum control. Despite vast disparities in energy scales and interaction mechanisms between electron spins in DNP and nuclear singlet states in PHIP, a pseudo-spin formalism allows us to establish an intriguing equivalence. As a result, the important low-field polarization transfer regime of PHIP can be mapped onto an analogous system equivalent to pulsed-DNP. This establishes a correspondence between key polarization transfer sequences in PHIP and DNP, facilitating the transfer of sequence development concepts. This promises fresh insights and significant cross-pollination between DNP and PHIP polarization sequence developers.

quant-ph↗

arXiv2022

Hyperpolarization read-out through rapidly rotating fields in the zero- and low-field regime

An integral part of para-hydrogen induced polarization (PHIP) methods is the conversion of nuclear singlet order into observable magnetization. In this study polarisation transfer to a heteronucleus is achieved through a selective rotation of the proton singlet-triplet states driven by a combination of a rotating magnetic field and a weak bias field. Surprisingly we find that efficient polarisation transfer driven by a STORM (Singlet-Triplet Oscillations through Rotating Magnetic fields) pulse in the presence of $μ$T bias fields requires rotation frequencies on the order of several kHz. The rotation frequencies therefore greatly exceed any of the internal frequencies of typical zero- to ultralow field experiments. We further show that the rotational direction of the rotating field is not arbitrary and greatly influences the final transfer efficiency. Some of these aspects are demonstrated experimentally by considering hyperpolarised (1-$^{13}$C)fumarate. In addition, we provide numerical simulations highlighting the resilience of the STORM pulse against disruptive quadrupolar coupling partners. In contrast to most of the existing methods, the STORM procedure therefore represents a promising candidate for quadrupolar decoupled polarisation transfer in PHIP experiments.

quant-ph↗

arXiv2022

Direct Production of A Hyperpolarized Metabolite on a Microfluidic Chip

Microfluidic systems hold great potential for the study of live microscopic cultures of cells, tissue samples, and small organisms. Integration of hyperpolarisation would enable quantitative studies of metabolism in such volume limited systems by high-resolution NMR spectroscopy. We demonstrate, for the first time, the integrated generation and detection of a hyperpolarised metabolite on a microfluidic chip. The metabolite 1-$^{13}$C-fumarate is produced in a nuclear hyperpolarised form by (i) introducing para-enriched hydrogen into the solution by diffusion through a polymer membrane, (ii) reaction with a substrate in the presence of a ruthenium-based catalyst, and (iii) conversion of the singlet-polarised reaction product into a magnetised form by the application of a radiofrequency pulse sequence, all on the same microfluidic chip. The microfluidic device delivers a continuous flow of hyperpolarised material at the 2.5 $μ\text{L}/\text{min}$ scale, with a polarisation level of 4%. We demonstrate two methods for mitigating singlet-triplet mixing effects which otherwise reduce the achieved polarisation level.

physics.chem-ph↗

arXiv2021

Low-Frequency Excitation of Singlet-Triplet Transitions. Application to Nuclear Hyperpolarization

Coupled pairs of nuclear spins-1/2 support one singlet state and three triplet states. Transitions between the singlet state and one of the triplet states may be driven by an oscillating low-frequency magnetic field, in the presence of couplings to a third nuclear spin, and a weak bias magnetic field.This phenomenon allows the generation of strong nuclear hyperpolarization of ${}^{13}\mathrm{C}$ nuclei, starting from the nuclear singlet polarization of a ${}^{1}\mathrm{H}$ spin pair, associated with the enriched para spin isomer of hydrogen gas. Hyperpolarization is demonstrated for two molecular system.

quant-ph↗