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Chemical Imaging of Agrochemical Active Ingredient Uptake using Cryo-Electron and Ion Beam Microscopy

PGR-P-1873

Key facts

Type of research degree
PhD
Application deadline
Monday 29 April 2024
Project start date
Tuesday 1 October 2024
Country eligibility
UK only
Funding
Competition funded
Source of funding
Doctoral training partnership
Supervisors
Professor Andy Brown and Professor Rik Drummond-Brydson
Additional supervisors
Jean-Yves Mugnier, Syngenta
Schools
School of Chemical and Process Engineering
<h2 class="heading hide-accessible">Summary</h2>

The optimised and efficient delivery of Agrochemicals and plant nutrients is key to delivering the second United Nations' development goal: to end hunger, achieve food security and improved nutrition and promote sustainable agriculture. Different plant species and varieties have varying levels of uptake depending on a combination of factors which influence their leaf physiology including wettability, cuticular wax composition, wax crystal morphology, cuticle porosity and cuticle thickness. This studentship which is collaboration with Syngenta aims to evaluate the potential of Cryo-Electron and Focused Ion Beam Microscopy in the characterisation of sectioned leaf surfaces and their corresponding chemical and elemental composition. The project will collect a wide range of information across species of interest, varieties and growing conditions which will feed models to better support predictive tools for leaf surface uptake. The project will include the use of a very high-resolution Cryo-3D Volume Electron Microscope with additional in-situ attachments for chemical analysis (Imaging Mass Spectrometry, ToF-SIMS) and compositional analysis (Energy Dispersive Spectroscopy). This project will investigate the effect of varied-level Active Ingredients (AIs) applications on the leaf surface and the potential uptake impact through the cuticle layers. The main aspiration of the project is to provide ultra-structural 3D information at the sub-cellular level with direct 3D chemical and compositional mapping and give a further dimension to the absorption mechanism through the leaf cuticular barrier into the underlying tissue. This would essentially support the understanding of some AIs activity and ultimately define critical factors that would affect leaf uptake and their role in the formulation design i.e., the selection of adjuvants or other formulation optimisation.

<h2 class="heading hide-accessible">Full description</h2>

<p style="margin-bottom:11px"><strong>Background:</strong> The Materials Characterisation Group in the School of Chemical &amp; Process Engineering at the University of Leeds is centred around the Leeds Electron Microscopy &amp; Spectroscopy (LEMAS) facility which comprises 9 instruments and &nbsp;five academics (Brown, Hondow, Collins, Piazolo &amp; Brydson), complemented by 5 FTE permanent research technical professional (RTP) staff, with a track record, the expertise &amp; vision for delivering analytical microscopy-based research. We have more than 18 years&rsquo; experience of Transmission EM (TEM) &amp; Focused Ion beam scanning electron microscopy (FIBSEM) of both hard &amp; soft matter, including mineral&ndash;organic interfacial interactions (see e.g. Bonneville et al. Geology 2009 10.1130/G25699A ), nanoparticle dispersions in biological media &amp; interaction with cells &amp;, following EPSRC awards of a cryo-enabled TEM &amp; cryo-FIBSEM, organic solids including pharmaceuticals, nanoparticle coatings, &amp; emulsions (see e.g. Ilett et al. Phil Trans A 2020 10.1098/rsta.2019.0601). Our instrument suite has recently been strengthened by addition of a cryo-plasma-FIBSEM with time-of-flight secondary ion mass spectrometry (ToFSIMS) &amp;, via a &pound;1.75M collaboration with Project Partner TESCAN , a new dedicated scanning TEM (STEM) with scanning diffraction capability (4D-STEM). The group is a key member of the Bragg Centre for Materials Research, a major part of a recent &pound;100M Faculty investment at Leeds, opened in 2022 &amp; encompassing 315 interdisciplinary members across campus, where all instrumentation is being housed in a purpose-built analytical facility. The proposed Ph.D project will be supervised by Brydson (lead), Collins and Brown, with further input from Hondow and the team of experienced RTPs as required. We will seek a student with a background in Materials, Chemistry, Physics or Biology. The project is co-funded by Syngenta and there will be a strong link with Industrial Supervisors at the company.</p> <p><strong>Methodology:</strong> Large area (ca. 100 micron diameter) cross-sections across different leaf surface &amp; sub-surface regions (as advised by Syngenta) will be cut using plasma FIB from cryogenically frozen samples; we will investigate different freezing methods including high pressure freezing. Results will also be compared against samples prepared by fixation &amp; resin embedding &amp;FIB sectioning (see Bhawana et al. doi: 10.3732/apps.1300090). We will use a combination of secondary electron &amp; backscattered imaging, combined with Secondary Ion Mass Spectrometry (SIMS) mapping at 50 nm spatial resolution &amp; Energy Dispersive X-ray (EDX) analysis at ca. micron resolution. We will use 100 nm thick serial sectioning methods using the ion beam to create a three dimensional picture of the location of active ingredients (AIs - using elemental or mass fragment signatures) in the surface &amp; sub-surface leaf micro-/ultra-structure following model AI uptake studies. In discussion with Syngenta - we will vary the crystallinity, polymorphic form &amp; loading of the AI, as well as investigate model formulations. For higher resolution information we will perform depth profiling SIMS using plan-view samples &amp; also cut thin lamellae using the ion beam &amp; perform in-situ cryo liftout with cryo-transfer to the cryo-TEM where we can perform higher resolution annular dark field STEM imaging &amp; EDX (for heavy element detection), as well as electron energy loss spectroscopy (EELS) which may offer advantage for light element detection. This may also provide information on the exact form of the AI following uptake.</p> <p><strong>Outcomes: </strong>1. An optimised protocol for the faithful preparation of large area leaf cross-sections using 3D cryo-plasma FIBSEM &amp; benchmarking against conventional fixation &amp; embedding sample preparation methods. 2. An understanding of the key parameters which affect the uptake of model AIs into leaf surface &amp; sub-surface micro-/ultra-structure and the development of predictive tools.</p> <p><strong>Risk Management:</strong> All instrumentation is under service contract which will minimise equipment downtime. We will correlate data from different sample preparation methods &amp; also different chemical spectroscopies (including in-situ depth profiling SIMS &amp; ex-situ depth profiling XPS at near ambient pressures) to ensure a full &amp; accurate picture of AI uptake is obtained.</p>

<h2 class="heading">How to apply</h2>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="https://www.leeds.ac.uk/research-applying/doc/applying-research-degrees">University&#39;s website</a>. Please state clearly in the Planned Course of Study section that you are applying for <em><strong>EPSRC DTP Engineering &amp; Physical Sciences</strong></em> (if you do not apply to this programme code, your application will not be considered) and in the research information section&nbsp;that the research degree you wish to be considered for is&nbsp;<em><strong>Chemical Imaging of Agrochemical Active Ingredient Uptake using Cryo-Electron and Ion Beam Microscopy</strong></em><strong>&nbsp;</strong>as well as&nbsp;<a href="https://eps.leeds.ac.uk/chemical-engineering/staff/155/professor-rik-drummond-brydson">Prof. Rik Drummond-Brydson</a> as your proposed supervisor. Please state in the Finance section that the funding source you are applying for is <em><strong>EPSRC Doctoral Training Partnership 2024/25:&nbsp; Chemical &amp; Process Engineering</strong></em>.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p class="MsoNoSpacing">Applications will be considered after the closing date. &nbsp;Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application. &nbsp;We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p>Please note that you must provide the following documents in support of your application by the closing date of 29 April 2024:</p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul>

<h2 class="heading heading--sm">Entry requirements</h2>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

<h2 class="heading heading--sm">English language requirements</h2>

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<h2 class="heading">Funding on offer</h2>

<p class="MsoNoSpacing">A highly competitive EPSRC Doctoral Training Partnership Studentship offering the award of fees, together with a tax-free maintenance grant (currently &pound;18,622 for academic session 2023/24) for 3.5 years.&nbsp; Training and support will also be provided. <strong>This funding is supported by a 50% contribution from the Syngenta and there will be substantial opportunities to interact with the company.</strong></p> <p>This opportunity is open to UK applicants only.&nbsp; All candidates will be placed into the EPSRC Doctoral Training Partnership Studentship Competition and selection is based on academic merit.</p> <p>Please refer to the&nbsp;<a href="https://www.ukcisa.org.uk/">UKCISA</a>&nbsp;website for&nbsp;information regarding Fee Status for Non-UK Nationals.</p>

<h2 class="heading">Contact details</h2>

<p>For further information about this project, please contact Professor Rik Drummond-Brydson by email to&nbsp;<a href="mailto:R.M.Drummond-Brydson@leeds.ac.uk">R.M.Drummond-Brydson@leeds.ac.uk</a>&nbsp;</p> <p>For further information about your application, please contact Doctoral College Admissions by email to&nbsp;<a href="mailto:phd@engineering.leeds.ac.uk">phd@engineering.leeds.ac.uk</a></p>


<h3 class="heading heading--sm">Linked funding opportunities</h3>
<h3 class="heading heading--sm">Linked research areas</h3>