Lab profile: Fang Xie, Imperial College London

The ability of some functional materials to manipulate light is vital to applications in solar energy harvesting and nanobiotechnology, including biosensing and optical imaging in the near infrared region.

Fang Xie is the Principal Investigator of the Functional Materials for Light Management Group at Imperial College London, where her group’s research focuses on synthesis and fabrication of such functional nanomaterials including plasmonic materials, semiconducting materials, up-conversion/down-conversion nanoparticles, and dielectric materials.

She received a B.Eng. from Xi'an Jiaotong University in China and an M.Eng from the National University of Singapore. After three years working in the biotech-industry in Singapore, Xie undertook a PhD at Macquarie University in Australia. She received the Award for Postgraduate Excellence from the Australian Institute of Physics in 2006 and the Macquarie University Postgraduate Innovation Award in 2007.

Fang Xie talked to Materials Today about her current research and future plans.

How long has your group been running?

I joined the Department of Materials, Imperial College London as a post-doctoral research associate (PDRA) in 2008, immediately after my PhD study. I won an Imperial College Research Fellowship in 2011 to establish my own group with one PhD student. The Functional Materials for Light Management Group was established in 2013, when I was appointed as a lecturer in the Department.

How many staff currently makes up your group?

Currently, there are 16 researchers in my group, consisting of materials scientists, physicists, chemists, and biologists. Among the researchers in my group are two PDRAs, 10 PhD students, and four Masters students. Since 2011, my group has seen the graduation of four postdoctoral fellows, four PhD students, and over 20 Masters students.

What are the major themes of research in your group?

The underpinning theme in my group is to design and develop functional materials that have interesting optical properties when interacting with light. Our aim is to understand light-matter interactions under a theoretical framework and develop light technologies for solar energy harvesting and biomedical applications including biosensing and bioimaging.

For example, we use plasmonic nanomaterials in solar cell and solar fuel systems to boost photoelectrode performance by enhancing light absorption, electron-hole pair generation and separation. In biomedical applications, a metal-enhanced fluorescence (MEF) platform has been established for fluorescence-based biosensing and bioimaging. This ranges from the UV to the visible NIR I and NIR II regions. We hope to apply this to the detection of multiple biomarkers simultaneously.

How and why did you come to work in these areas?

I originally trained as a chemical engineer with no background in materials or nanotechnology. But I was fortunate in being engaged with photonic materials research during my PhD and was fascinated by manipulating nanostructure-optical properties of materials. 

Photonics is one of the most impactful technologies of the 21^st century. After my PhD, my passion about research naturally focused on light and light-based technologies in diverse applications including imaging, sensing, and solar energy harvesting. I established my team in this area when I started my academic career at Imperial College London.

What facilities and equipment does your lab have?

In our lab, we have a wide range of optical characterization equipment including a modular spectrofluorometer (300-2500 nm and equipped with TCSPC for life time measurement) and a UV-visible-NIR spectrometer. We also have facilities for photoelectrode performance assessment such as incident photon-to-current conversion efficiency (IPCE) and photoelectrochemical cells (PEC). 

Our laboratory also benefits from excellent shared facilities at the Imperial College London Centre for Nanotechnology and the London Institute for Advanced Light Technologies. We routinely use advanced characterization tools including spectroscopy and electron microscopy to understand the features of our functional nanomaterials. Some of the techniques that we use include scanning electron microscopy (SEM) and transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and x-ray diffraction (XRD).

Do you have a favorite piece of kit or equipment?

High-resolution transmission electron microscopy (HRTEM) – because it gets right down to the atomic scale!

What do you think has been your most influential work to date?

Fluorescence imaging could potentially be a powerful tool in disease prognosis, diagnosis, and therapy, with resolution down to the single cell level. The limitation, however, is the penetration depth of current technology. By shifting the imaging wavelength from visible/NIR I range (500-800 nm) to NIR II (1000-1700 nm), the penetration depth could drastically be improved, from micrometers up to a few centimeters.

We recently developed a groundbreaking nano-platform based on Au nanostars that enables naturally low quantum yield NIR-II fluorophores to shine brightly.  Combining the advantage of the great penetration depth of fluorescence imaging in NIR II, this extremely bright probe could be a new star of early cancer diagnosis.

What is the key to running a successful group?

The key for a successful research group lies in two parallel pillars: a panoramic vision of the research field and coherent underpinning research themes. The group leader should be more than just a scientific leader; he or she should also be an excellent mentor for group members. If the group is innovative, hardworking, and self-motivated with a collaborative group culture, it will inevitably be very successful!

How do you plan to develop your group in the future?

My group will continue to drive innovations in the field of light-responsive materials and their applications in various fields, aiming to have an impact in biomedical as well as clean energy applications.

Key publications

1. J.S. Pang, I.G. Theodorou, A. Centeno, P.K. Petrov, N.M. Alford, M.P. Ryan, F. Xie. Tunable Three-Dimensional Plasmonic Arrays for Large Near-Infrared Fluorescence Enhancement. ACS Appl. Mater. Interfaces 11 (2019) 23083-23092. https://doi.org/10.1021/acsami.9b08802
2. P. Ruenraroengsak, D. Kiryushko, I.G. Theodorou, M.M. Klosowski, E.R. Taylor, T. Niriella, C. Palmieri, E. Yagüe, M.P. Ryan, R.C. Coombes, F. Xie, A.E. Porter. Frizzled-7-targeted delivery of zinc oxide nanoparticles to drug-resistant breast cancer cells. Nanoscale 11 (2019) 12858-12870. https://doi.org/10.1039/C9NR01277J
3. I.G. Theodorou, P. Ruenraroengsak, D.A. Gonzalez-Carter, Q. Jiang, E. Yague, E.O. Aboagye, R.C. Coombes, A.E. Porter, M.P. Ryan, F. Xie. Towards multiplexed near-infrared cellular imaging using gold nanostar arrays with tunable fluorescence enhancement. Nanoscale, 11 (2019) 2079 – 2088. https://doi.org/10.1039/C8NR09409H
4. Q. Jiang, C. Ji, D.J. Riley, F. Xie. Boosting the Efficiency of Photoelectrolysis by the Addition of Non-Noble Plasmonic Metals: Al & Cu. Nanomaterials 9 (2019) 1. https://doi.org/10.3390/nano9010001
5. S. Fothergill, C. Joyce, F. Xie. Metal Enhanced Fluorescence Biosensing: From Ultra-Violet towards Second Near-Infrared Window. Nanoscale 10 (2018) 20914-20929. https://doi.org/10.1039/C8NR06156D
6. I. Theodorou, Q. Jiang, L. Malms, X. Xie, R.C. Coombes, E. Aboagye, A.E. Porter, M.P. Ryan, F. Xie. Fluorescence enhancement from single gold nanostars: towards ultra-bright emission in the first and second near-infrared biological windows. Nanoscale 10 (2018) 15854-15864. https://doi.org/10.1039/C8NR04567D
7. Z.A.R. Jawad, I. Theodorou, L.R. Jiao, F. Xie. Highly Sensitive Plasmonic Detection of the Pancreatic Cancer Biomarker CA 19-9. Scientific Reports 7 (2017) 14309. https://doi.org/10.1038/s41598-017-14688-z
8. H. Qin, A.E. Shamso, A. Centeno, L.G. Theodorou, A.P. Mihai, M.P. Ryan, F. Xie. Enhancement of the upconversion photoluminescence of hexagonal phase NaYF₄:Yb³⁺,Er³⁺ nanoparticles by mesoporous gold film. Phys. Chem. Chem. Phys. 19 (2017) 19159-19167. https://doi.org/10.1039/C7CP01959A
9. I.G. Theodorou, Z.A.R. Jawad, Q. Jiang, E.O. Aboagye, A.E. Porter, M.P. Ryan, F. Xie. Gold Nanostar Substrates for Metal-Enhanced Fluorescence through the First and Second Near-Infrared Windows. Chem. Mater. 29 (2017) 6916-6926. https://doi.org/10.1021/acs.chemmater.7b02313
10. I.G. Theodorou, Z. Jawad, H. Qin, E.O. Aboagye, A. Porter, M. Ryan, F. Xie. Significant metal enhanced fluorescence of Ag₂S quantum dots in the second near-infrared window. Nanoscale 8 (2016) 12869-12873. https://doi.org/10.1039/C6NR03220F
11. X. Wu, A. Centeno, X. Zhang, D. Darvill, M. Ryan, D.J. Riley, N.M. Alford, F. Xie. Broadband plasmon photocurrent generation from Au nanoparticles/mesoporous TiO₂ nanotube electrodes. Solar Energy Mater. Solar Cells 138 (2015) 80–85. https://doi.org/10.1016/j.solmat.2015.02.021