Toward Polarization-Switched Molecular Pumps

Microfluidics and Nanofluidics

Analytical Chemistry, 2014

Parahydrogen-induced polarization (PHIP) was used to demonstrate the concept that highly polarized, catalyst-free fluids can be obtained in a catalysisfree regime using a chemical reaction with molecular addition of parahydrogen to a water-soluble Rh(I) complex carrying a payload of compound with unsaturated (C C) bonds. Hydrogenation of norbornadiene leads to formation of norbornene, which is eliminated from the Rh(I) complex and, therefore, leaves the aqueous phase and becomes a gaseous hyperpolarized molecule. The Rh(I) metal complex resides in the original liquid phase, while the product of hydrogen addition is found exclusively in the gaseous phase based on the affinity. Hyperpolarized norbornene 1 H NMR signals observed in situ were enhanced by a factor of approximately 10 000 at a static field of 47.5 mT. High-resolution 1 H NMR at a field of 9.4 T was used for ex situ detection of hyperpolarized norbornene in the gaseous phase, where a signal enhancement factor of approximately 160 was observed. This concept of stoichiometric as opposed to purely catalytic use of PHIP-available complexes with an unsaturated payload precursor molecule can be extended to other contrast agents for both homogeneous and heterogeneous PHIP. The Rh(I) complex was employed in aqueous medium suitable for production of hyperpolarized contrast agents for biomedical use. Detection of PHIP hyperpolarized gas by low-field NMR is demonstrated here for the first time.

The Journal of chemical physics, 2004

We present a method to search low energy configurations of polar molecules in the complex potential energy surfaces associated with dense fluids. The search is done in the configurational space of the translational and rotational degrees of freedom of the molecule, combining steepest-descent and Newton-Raphson steps which embed information on the average sizes of the potential energy wells obtained from prior inspection of the liquid structure. We perform a molecular dynamics simulation of a liquid water shell which demonstrates that the method enables fast and energy-controlled water molecule insertion in aqueous environments. The algorithm finds low energy configurations of incoming water molecules around three orders of magnitude faster than direct random insertion. This method represents an important step towards dynamic simulations of open systems and it may also prove useful for energy-biased ensemble average calculations of the chemical potential.

Physical Review Letters, 2009

We present a method which delivers a continuous, high-density beam of slow and internally cold polar molecules. In our source, warm molecules are first cooled by collisions with a cryogenic helium buffer gas. Cold molecules are then extracted by means of an electrostatic quadrupole guide. For ND3 the source produces fluxes up to (7± 7 4 ) × 10 10 molecules/s with peak densities up to (1.0± 1.0 0.6 ) × 10 9 molecules/cm 3 . For H2CO the population of rovibrational states is monitored by depletion spectroscopy, resulting in single-state populations up to (82 ± 10)%.

2021

The sorption of species from solution into and onto solids, surfaces, crystals, gels and other matrices, underpins the sequestering of waste and pollutants, the recovery of precious metals, heterogeneous catalysis, many forms of chemical and biological analysis and separation science, and numerous other technologies. 1-3 In such cases the transfer of the substrate between phases tends to proceed spontaneously, in the direction of equilibrium. Molecular ratchet mechanisms, 4-7 where kinetic gating 8-12 selectively inhibits or accelerates particular steps in a process, makes it possible to drive dynamic systems 13-16 out of equilibrium 17-22. Here we report on a small-molecule pump 23 immobilised on and near the surface 24-26 of polymer beads, that uses an energy ratchet mechanism 18-22,27-31 to actively transport substrates from solution onto the beads away from equilibrium. One complete cycle of the pump occurs with each pulse of a chemical fuel, 20,32-36 synchronizing the ratchet dynamics so that the immobilised molecular machines all act in unison. Upon addition of the trichloroacetic acid (CCl3CO2H) fuel, 20,35,37,38 micrometre-diameter polystyrene beads functionalised with an average of ~8×10 10 molecular pumps per bead, 39 sequester from solution crown ethers appended with a fluorescent tag (Fig. 1). Following consumption of the fuel, the rings are mechanically trapped in a higher energy, out-of-equilibrium, state on the beads and cannot be removed by dilution nor by switching the binding interactions off. This differs from dissipative assembled materials that require a continuous supply of energy to persist. 13-16 Addition of a second pulse of fuel causes the uptake of more macrocycles, which can be labelled with a different fluorescent tag. This drives the system progressively further away from equilibrium and also confers sequence information 40 on the deposited structure. The polymer-bound substrates (and the stored energy) can subsequently be released back to the bulk on demand, 41-43 either emptying one compartment at a time or all at once. Non-equilibrium 44 sorption by using immobilised artificial molecular machines 45-51 to pump substrates from solution onto and into materials 52 , offers potential 53,54 for the transduction of energy from chemical fuels for the storage and release of energy and information.

Beilstein journal of nanotechnology, 2015

The realization of artificial molecular motors capable of converting energy into mechanical work is a fascinating challenge of nanotechnology and requires reactive systems that can operate away from chemical equilibrium. This article describes the design and construction of a simple, supramolecular ensemble in which light irradiation causes the directional transit of a macrocycle along a nonsymmetric molecular axle, thus forming the basis for the development of artificial molecular pumps.

Energy Procedia, 2013

A new solvent-based CO 2 capture process couples the unique attributes of non-aqueous, CO 2 -binding organic liquids (CO 2 BOLs) with the newly discovered polarity-swing-assisted regeneration (PSAR) process that is unique to switchable ionic liquids. Laboratory measurements with PSAR indicate the ability to achieve a regeneration effect at 7 compared to a temperature of using thermal regeneration only. Initial measurements also indicate the kinetic behavior of CO 2 release is also improved with PSAR.

Theoretical Chemistry Accounts, 2009

The thermodynamic features of a synthetic molecular thread, recently proposed acting as an electrochemically-driven two-states molecular device, have been systematically investigated by means of nanoseconds timescale classical molecular dynamics (MD) simulations and basic statistical mechanics relations. Results clearly suggest that the accessible conformational space of such a potential molecular switch shows a strong environmental dependence: the reversible molecular switching mechanism observed in liquid solution is effectively suppressed when the synthetic thread is hypothesized working in vacuo. Such a result has been related to a subtle energetic/ entropic balance experienced by the whole system (solute and solvent) during the intramolecular conformational transition of the molecular thread, in presence and in absence of the solvent.

Physical review. E, Statistical, nonlinear, and soft matter physics, 2015

A numerical investigation is performed into the characteristics of an electro-osmotic pump consisting of a negatively charged conical nanopore. It is shown that the dependence of the flow rectification effect on the bias direction is the reverse of that of the ion current rectification effect. Moreover, the nozzle mode (i.e., the bias is applied from the base side of the nanopore to the tip side) has a higher flow rate compared to the diffuser mode (i.e., the bias is applied from the tip side of the nanopore to the base side). The results showed that the ion-concentration polarization effect occurred inside the conical nanopore, resulting in surface conduction dominating in the ionic current. The ions inside the nanopore are depleted and enriched under the nozzle mode and the diffuser mode, respectively. As a result, the electro-osmotic pump yields a greater pumping pressure, flow rate, and energy conversion efficiency when operating in the nozzle mode. In addition, we also investig...

Small, 2004