Dynamics, Control and Energy Transfer at Terahertz Frequencies.

Lead Research Organisation: University of Leeds
Department Name: Sch of Chemistry

Abstract

Chemical and biological reactions are governed by the coupling of ultrafast chemical events to dynamics on much slower timescales. These ultrafast chemical events often occur at THz frequencies and there is a range of indirect experimental and theoretical evidence to suggest that the coupling of vibrational motion at these frequencies governs the dynamics of a range of reactions across chemistry and biology. In this proposal, enabled by recent technological developments, I will develop a THz multidimensional spectrometer that will be able to measure directly the coupling between these modes on an ultrafast timescale. This will enable me to measure energy transfer between THz frequency modes and the timescales involved therein. Once demonstrated this will be a new, powerful analytical technique with many possible applications. Initial measurements will be performed on two very different material types, the first being energetic materials, and the second, materials that show a dramatic structural change upon illumination by light (a photo-induced phase transition or PIPT). In both materials there is strong indirect experimental and theoretical evidence that the coupling between THz frequency vibrations governs the reaction pathways in these materials. THz multidimensional spectroscopic measurements of these materials will provide the first direct experimental evidence that the coupling between these THz vibrations directly governs the pathway, and dynamics, of a reaction. Once this has been demonstrated, in these two diverse sets of materials, this new analytical technique can be applied to many chemical or biological questions, providing an understanding of reaction dynamics on ultrafast timescales - essentially enabling us to watch chemistry happen. This underlying understanding of reactions dynamics will also underpin the future rational design of materials with tailored physical and chemical properties.
Following on from measuring the coupling between THz modes using THz multidimensional spectroscopy, specifically designed intense THz pulses will then be used to interact directly with this vibrational motion, essentially controlling and steering the chemical dynamics. This control, coupled with the understanding of reaction dynamics and the associated timescales provided directly by THz multidimensional spectroscopy, leads to a method where reactions can be steered and controlled - with huge potential applications. This fellowship will concentrate on three possible applications for THz-driven dynamics, namely (a) the control of enzymatic reactions, (b) the control of solid state phase transformations (concentrating of pharmaceutically relevant polymorphs) and (c) the control of catalytic reactions.

Planned Impact

Beneficiaries of this work over the short term (3-5 years) will be mainly academic in nature, which is a necessary step in moving towards non-academic beneficiaries. In particular, the new spectroscopic techniques that I will develop will have a significant impact on the terahertz (THz) and wider ultrafast/multidimensional spectroscopy communities, which are particularly strong within the UK. As the fellowship progresses, the techniques developed and the associated results will be relevant to a cross-disciplinary selection of fields including analytical chemistry, biophysics, reaction dynamics, and free electron laser science. The aim of my impact activities throughout this fellowship will therefore be to disseminate my results to the widest possible audience. To do this the main dissemination route for this proposal will be publication in primary refereed journals with a significant cross-disciplinary readership and by presentations at conferences and workshops that are well attended by a range of academics, SMEs, large companies and government employees.
Industrial beneficiaries in the medium term (5-10 years) will include companies that are interested in the understanding of the initiation and dynamics of reactions involving energetic materials such as the Atomic Weapons Establishment (AWE). In particular the results gained from this fellowship will directly influence the future rational design of more stable, safe energetic materials through control of energy transfer in these materials. I have a track record of working closely with government agencies who are major stakeholders in AWE and would be well placed to increase my impact in this area.
In the longer term (10-25 years), the technology and understanding I will develop as part of this fellowship, and continue to develop beyond the tenure of this programme, has the potential to provide a paradigm shift in the understanding of reaction dynamics in chemistry and biology. Three important areas that I have identified are:
(a) The control and understanding of catalytic reactions;
(b) The control of the formation of pharmaceutical polymorphs;
(c) The development of smart materials.
The areas I have identified are diverse, but a greater understanding of the dynamics of these reactions, coupled with the ability to control them directly, will provide the experimental data needed to design the next generation of such materials. The beneficiaries of such impact would be very broad. It is thought that as much as 90% of all commercially produced chemical products involve catalysts at some stage in the process of their manufacture, thus any information that leads to more efficient, specific catalysts has the potential to improve production and reduce energy consumption across the entire chemical processing industry. In the pharmaceutical industry the development of novel polymorphs and co-crystals is now crucial to the development of new pharmaceutics with the patent landscape of pharmaceutical co-crystals developing rapidly over the previous decade. The potential for new drug discovery by companies such as AstraZeneca and GSK would be significantly increased by the demonstration of control of polymorph formation. Finally, the development of smart materials whose properties can be significantly altered by external stimuli is crucial to the development of new technologies that are interactable, with companies such as Apple, Google and Samsung, along with small technology focussed SMEs all looking for the next technique that provides them with the designing edge in this competitive market.
These are certainly not the only areas where this new technology has the potential to have an impact, however, the connections with academics and industry that I will develop via the network meetings and conferences that I will attend will help me to confirm and develop these areas, while also allowing me to evaluate other high potential and high likelihood impact areas.

Publications

10 25 50

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Swithenbank M (2017) On-Chip Terahertz-Frequency Measurements of Liquids. in Analytical chemistry

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Kendrick J (2019) Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate in Journal of Infrared, Millimeter, and Terahertz Waves

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Appleby M (2022) Optical excitation processes: general discussion in Faraday Discussions

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Alías-Rodríguez M (2022) Theory of out of equilibrium light-induced phenomena: general discussion. in Faraday discussions

 
Description Work has concentrated on the development of the best combination of high-field THz sources and detection schemes to develop a practical spectrometer. This means having a range of schemes that are easily inter-changed that provide a range of THz fields and bandwidths depending on the properties of the material under test. As such we have developed a range of THz sources including photoconductive arrays, air plasma and Electro-optic sources that produce fields > 300 KV/cm with bandwidths in excess of 20 THz with the development of this instrument continuing through additional funding.

We have for the first time demonstrated a 2D-THz signal on an instrument in the UK noting that a 2D-THz instrument had not been demonstrated before the grant was submitted. The instrument will now be used for a range of different samples which will aid its future development

Our work in this area has led to us being involved in both national and international discussions to combined these THz sources with X-ray free electron lasers to explore the control of materials through phononics.
Exploitation Route The main outcome of this fellowship is the UK's first 2D-THz spectrometer. This technique has the potential to provide a new insight into the dynamics of a range of range of materials from photovoltaics through to pharmaceuticals and energetic materials.
Sectors Aerospace, Defence and Marine,Chemicals,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

 
Description Contributions to the Science Case for a UKFEL as part of the chemical sciences team - the Science Case was positively endorsed by the expert Review Committee in November 2020
Geographic Reach National 
Policy Influence Type Contribution to a national consultation/review
URL https://www.clf.stfc.ac.uk/Pages/UK-XFEL-science-case.aspx
 
Description Applications of 1-D and 2-D Spectroscopy at THz and IR Frequencies
Amount £54,000 (GBP)
Funding ID 2107312 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 09/2018 
End 03/2022
 
Description CEOI THz Facilities Upgrade
Amount £172,123 (GBP)
Organisation National Centre for Earth Observation 
Sector Academic/University
Country United Kingdom
Start 01/2023 
End 03/2023
 
Description Capital Award Support for Early Career Researchers at the University of Leeds
Amount £225,000 (GBP)
Funding ID EP/S01764X/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 11/2018 
End 04/2020
 
Description Functional Hydrogen-Bonded Self-Sorting Networks
Amount £454,258 (GBP)
Funding ID EP/T011726/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2020 
End 02/2023
 
Description Spin-Crossover Lattice Effects
Amount £371,315 (GBP)
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2022 
End 09/2026
 
Description Terahertz calibration targets
Amount £47,917 (GBP)
Funding ID RS04299 
Organisation ESA - ESTEC 
Sector Public
Country Netherlands
Start 03/2022 
End 06/2023
 
Description Understanding complex materials using THz spectral measurements
Amount £6,000 (GBP)
Funding ID IES\R1\201157 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 07/2020 
End 12/2021
 
Title Data associated with 'Increasing the sensitivity of terahertz split ring resonator metamaterials for dielectric sensing by localized substrate etching' 
Description Data relevant to the design and measurement of split ring resonator metamaterials for dielectric sensing 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact none currently 
URL https://doi.org/10.5518/546
 
Title Data associated with Exploring the Reliability of DFT Calculations of the Infrared and Terahertz Spectra of Sodium Peroxodisulfate. 
Description The data included in this dataset has been generated by A number of DFT programs with various combinations of pseudo-potentials and van der Waals' dispersive corrections have been used to optimize the structure of sodium peroxodisulfate and to calculate the infra-red, attenuated total reflectance and terahertz absorption spectra of the powdered crystal. Comparison of the results from the different methods highlights the problems of calculating the absorption spectrum reliably. In particular the low frequency phonon modes are especially sensitive to the choice of grids to represent the wavefunction or the charge distribution, k-point integration grid and the energy cutoff. A comparison is made between the Maxwell-Garnett (MG) and Bruggeman effective medium methods used to account for the effect of crystal shape on the predicted spectrum. Possible scattering of light by air inclusions in the sample and by larger particles sodium peroxodisulfate of is also considered using the Mie method. The results of the calculations are compared with experimental measurements of the transmission and attenuated total reflection spectra. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
Impact Only recently been released 
URL https://doi.org/10.5518/606
 
Title Data to Support Photoconductive Arrays on Insulating Substrates for High-Field Terahertz Generation 
Description The data included in this repository supports our work on the design, fabrication and characterisation of large-area photoconductive THz array structures, consisting of a thin LT-GaAs active region transferred to an insulating substrate using a wafer-scale bonding process. The electrically insulating, transparent substrate reduces the parasitic currents in the devices, allowing peak THz-fields as high as 140 kV cm-1 to be generated over a bandwidth >5 THz. These results are achieved using lower pulse energies than demanded by conventional photoconductive arrays and other popular methods of generating high-field THz radiation. Two device sizes are fully characterised and the emission properties are compared to generation by optical rectification in ZnTe. The device can be operated in an optically saturated regime in order to suppress laser noise. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL http://archive.researchdata.leeds.ac.uk/682/
 
Title Dataset associated with "All-electronic phase-resolved THz microscopy using the self-mixing effect in a semiconductor laser" 
Description This dataset relates to data presented in the work, "All-electronic phase-resolved THz microscopy using the self-mixing effect in a semiconductor laser". In this work we report all-electronic coherent scattering-type scanning near-field microscopy (s-SNOM) using a terahertz-frequency quantum cascade laser. By exploiting the coherent self-mixing effect in these lasers, in conjunction with electronic frequency tuning of the laser, we demonstrate spatial mapping of both the amplitude and phase of the scattered field with deeply sub-wavelength resolution. We apply our technique for coherent microscopy of a phonon-resonant crystal. The extracted amplitude and phase parameters reveal clear contrast when compared to both metallic and non-resonant dielectric materials, and show excellent agreement with those calculated using a finite-dipole model of the near-field interaction between the s-SNOM tip and the resonant sample in the Reststrahlen band. 
Type Of Material Database/Collection of data 
Year Produced 2021 
Provided To Others? Yes  
URL http://archive.researchdata.leeds.ac.uk/835/
 
Title Dataset associated with "Terahertz Dielectric Property Characterization of Photopolymers for Additive Manufacturing" 
Description Figures and source data for the paper '0.2 - 1.4-THz Dielectric Property Characterization of Photopolymers for Additive Manufacturing': In this paper, resin-based photocurable polymer materials for stereolithography (SLA), digital-light-processing (DLP) and polymer-jetting (PolyJet) additive manufacturing techniques were characterized from 0.2 - 1.4 terahertz (THz) for their comprehensive dielectric properties, e.g. reflective index, absorption coefficient, dielectric constant and loss tangent, by using laser-based time-domain spectroscopy (TDS). Fourteen photocurable 3D-printing polymers were chosen due to their suitability, in terms of printing resolution, material characteristics and etc., for millimeter-wave (mm-wave) and THz applications. The propagation loss mechanism and other electrical/optical properties of the chosen photopolymers for terahertz radiation were determined by correlating absorption coefficients and loss tangents obtained from the measurements. To demonstrate the utilization of the selected photopolymers at THz spectrum, an asymptotically quasi-single-mode Bragg fiber microfabricated by DLP micromanufacturing technique using HTM140-V2 photopolymer was prototyped and characterized at the nominal frequencies from 0.246 to 0.276 THz. The measurement results show that the average propagation loss of the asymptotically single-mode THz Bragg fiber is less than 5dB/m for the whole band, which is the lowest propagation loss reported to date for asymptotically single-mode all-dielectric fiber at this frequency band. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
Impact Data will be useful when designing and developing new microwave/terahertz devices based on Additive Manufacturing techniques 
URL https://doi.org/10.5518/440
 
Title Dataset associated with "Tunable broadband terahertz polarizer using graphene-metal hybrid metasurface" 
Description An electrically tunable polarizer for terahertz frequency electromagnetic waves formed from a hybrid graphene-metal metasurface is demonstrated. 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? Yes  
 
Title Dataset associated with Effects of Structural Ordering on IR Active Vibrations Within Bi2(Te?1???Se?)3 
Description This is the dataset associated with the materials study performed on the IR active E1u phonon within the Bi2(Te?1???Se?)3 alloy system. It contains THz and DC conductivity data that show the change in phonon dynamics over a wide range of temperatures and stoichiometries. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
Impact This dataset includes spectral measurements of a range TI materials along with supporting DFT based calculations. In particular the calculated data can be sued by other research groups to further there understanding of these materials without wasting time and energy performing the same calculations again 
URL https://archive.researchdata.leeds.ac.uk/1047/
 
Description P2D - Polarised 2D spectroscopy for probing spin systems 
Organisation University of Hamburg
Country Germany 
Sector Academic/University 
PI Contribution This project is jointly funded through the University of Leeds and University of Hamburg's joint call as part of a new strategic partnership. From the Leeds side we will produce topological insulator samples and develop THz/IR measurement systems in Hamburg for characterisation of these samples. We will also provide THz training to Hamburg staff
Collaborator Contribution Hamburg will host Visits from Leeds researchers and provide guidance in the setup of the IR side of the instrument. We will also jointly host a THz workshop in Hamburg. Hamburg Staff will also visit Leeds to perform THz measurements on there own samples
Impact This is a multi-disciplinary collaboration across, chemistry, physics and biology to develop instrumentation for a range of applications across both sites and is currently ongoing
Start Year 2022
 
Title PDielec (v6.4.5) 
Description The Python package, PDielec calculates the infrared absorption characteristics of a crystalline material supported in a non absorbing medium by post processesing the output of solid state quantum mechanical and molecular mechanical calculations of the phonons or dielectric response of the crystalline material. The package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. In this release significant changes were made to the GUI including fixing issues with displaying molecules and adding a supercell functionality. The package now includes a modified version of the VibAnalysis module based on the work of filipe teixeira (https://github.com/teixeirafilipe/vibAnalysis) which can now be applied to solid-sate calculations 
Type Of Technology Software 
Year Produced 2021 
Open Source License? Yes  
Impact regularly used by a number of groups across Chemistry/Physics and Earth sciences. 
URL https://github.com/JohnKendrick/PDielec
 
Title PDielec V 6.2 
Description The Python package PDielec calculates the infrared absorption characteristics of a crystalline material supported in a non absorbing medium by post processing the output of solid state quantum mechanical and molecular mechanical calculations of the phonons or dielectric response of the crystalline material. The package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. The theory of the approach is about to be submitted for publication. Version 6.2 treats the case of a support matrix with spherical inclusions. The scattering from the inclusions is accounted for by Mie theory. The resulting effective permittivity is used in the calculation of the effective permittivity of the active dielectric in the matrix. In addition the following features have been added; the sign of the imaginary component of the Mie permittivity is now consistent with Bruggeman and Maxwell-Garnett methods a Hodrick-Prescott filter performs a baseline correction to the experimental spectrum in the Fitter tab. saving a script has been modified to improve the scripts robustness various other minor bugs have been fixed Version 6.1 sees the release of new Mie routines which allow a more robust treatment of anisotropic crystals. A few other issues have also been addressed. The mass and volume fractions can be edited more easily. The spreadsheet is now written out at the end of the calculation (on exiting the program). There are several changes to the fitter tab. All the options are now in their own settings tab, which gives more space for listing the frequencies. A new fitting algorithm has been provided, which minimises the root means squared error between the experimental and calculated spectra. 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact This Version of the software is described in detail in 10.1007/s10762-019-00643-8 
URL https://github.com/JohnKendrick/PDielec
 
Title PDielec v5.0 
Description The Python package PDielec calculates the infrared absorption characteristics of a crystalline material supported in a non absorbing medium by post processing the output of solid state quantum mechanical and molecular mechanical calculations of the phonons or dielectric response of the crystalline material. The package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. The theory of the approach is about to be submitted for publication. Version v5.0 sees the removal of the command line interface. All calculations are now performed by PDGui. Calculation of ATR spectra has now been incorporated into the package. 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact Two papers explaining the use of PDielec for IR and THz calculations are currently in preparation and the work has been presented at a castep training workshop by Calum Towler (current PhD student) and was presented by myself at the first Castep User Meeting 
URL https://github.com/JohnKendrick/PDielec
 
Title PDielec(7.1.1) 
Description The Python package PDielec calculates the infrared and terahertz absorption characteristics of crystalline materials by post processing the output of solid state quantum mechanical and molecular mechanical calculations of the phonons or dielectric response of the crystalline material. For crystalline samples (thin films or thick slabs) the program uses a generalized transfer matrix approach to calculate the transmission, absorption and reflection. For powdered systems, the package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. In this particular version large changes have been made to the working of the code, increasing the parallel efficiency and improving the ability to use the scripting system included. There is now additional functionality to calculate the reflected and transmitted radiation from a crystal surface to expand the use of the code to include single crystals. Additionally a new testing suite has been included. 
Type Of Technology Software 
Year Produced 2022 
Open Source License? Yes  
Impact The code is now used by a number of groups across chemistry, physics and earth sciences. The code has been download > 9000 times since we made the code avaliable on conda-forge (https://anaconda.org/conda-forge/pdielec) 
URL https://github.com/JohnKendrick/PDielec
 
Title Pdielec V 6.0 
Description The Python package PDielec calculates the infrared absorption characteristics of a crystalline material supported in a non absorbing medium by post processing the output of solid state quantum mechanical and molecular mechanical calculations of the phonons or dielectric response of the crystalline material. The package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. The theory of the approach is about to be submitted for publication. Version v6.0 adds the ability to alter the Lorentzian widths of the phonon transitions and compare the results interactively with an experimental spectrum. 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact Continued development of a number of publications based on the use of PDielec 
 
Title Pdielec V4.0 
Description The Python package PDielec calculates the infrared absorption characteristics of a crystalline material supported in a non absorbing medium by post processing the output of solid state quantum mechanical and molecular mechanical calculations of the phonons or dielectric response of the crystalline material. The package calculates the internal electric field arising from different particle morphologies and calculates the resulting shift in absorption frequency and intensity arising from the coupling between a phonon and the internal field. The theory of the approach is about to be submitted for publication. Version v4.0 Sees the release of a version of PDielec with a graphical user interface. PDGui allows access to nearly all of the functionality of PDielec. In addition there is a visualiser which allows the normal modes to be shown using an arrow to describe the atomic displacements, or as an animation. There is also the ability to break down each phonon mode into inter and intra-molecular contributions. Included in this release is a Windows compatible installation executable, which installs a version of PDielec/PDGui onto a Windows machine. 
Type Of Technology Software 
Year Produced 2018 
Open Source License? Yes  
Impact none at the moment