Professor Jenny Clark

School of Mathematical and Physical Sciences

Professor of Materials Physics

Jenny Clark
Profile picture of Jenny Clark
jenny.clark@sheffield.ac.uk
+44 114 222 3526

Full contact details

Professor Jenny Clark
School of Mathematical and Physical Sciences
D16
Hicks Building
Hounsfield Road
91直播
S3 7RH
Profile

My research interests involve understanding the photophysics of carbon-based materials such as biological materials, organic semiconductors and graphene.

I do this using a variety of spectroscopic techniques. For more information see my  or contact me.

Research Experience

  • 2009-2013 Royal Society Dorothy Hodgkin Fellow, Cambridge University, UK.
  • 2009 Visiting Scholar, Hyderabad University, India.
  • 2007-2009 Postdoctoral Research Fellow, Politecnico di Milano, Italy.
    Supervisor: Prof. Guglielmo Lanzani

Fellowships and Awards

  • 2014 University of 91直播 Vice-Chancellor's Fellowship (5 years).
  • 2010 Charles and Catherine Darwin Research Fellowship (3 years).
  • 2009 Royal Society Dorothy Hodgkin Fellowship (4 years).
  • 2004 European Materials Research Society (E-MRS) student award.
  • 2003 EPSRC PhD studentship and Industrial Case Award (Seiko Epson UK, 3 years).

Career Breaks

  • 2012 Maternity leave (9 months)
  • 2013 Maternity leave (13 months)
Qualifications
  • 2003-2007 PhD in Physics, Cambridge University, UK. Supervisor: Prof. C. Silva.
  • 1999-2003 MSci in Physics with a Year in Europe, Imperial College, London, UK. (First Class Degree)
Research interests

New laser facility at 91直播 university

91直播 has a new laser facility that I help run. The facility is currently being built and will have several spectroscopy stations including:

  • Pump-probe spectroscopy in the UV/VIs-NIR with 10fs resolution, capable of tracking excited-state dynamics up to 1ms.
  • Time-resolved IR spectroscopy and 2D IR spectroscopy
  • Time-resolved Raman
  • Photoluminescence Up-Conversion

Ultrafast spectroscopy of carbon-based materials

To study organic semiconductors and biological samples, we mainly use transient absorption spectroscopy.

This technique uses laser pulses as short as 7 femtoseconds (7 millionths of a billionth of a second) to take snapshots of the electronic and vibrational state of the molecules after they have absorbed light. 

By delaying the time at which the 'probe' pulse arrives to take a snapshot of the molecule, we can track the dynamics of the electrons in the molecule as a function of time.

Publications

Show: Featured publications All publications

Journal articles

  • Bossanyi DG, Sasaki Y, Wang S, Chekulaev D, Kimizuka N, Yanai N & Clark J (2021) . JACS Au, 1(12), 2188-2201. RIS download Bibtex download
  • Bossanyi DG, Matthiesen M, Wang S, Smith JA, Kilbride RC, Shipp JD, Chekulaev D, Holland E, Anthony JE, Zaumseil J , Musser AJ et al (2021) . Nature Chemistry, 13(2), 163-171. RIS download Bibtex download
  • Polak D, Jayaprakash R, Lyons TP, Mart铆nez-Mart铆nez L脕, Leventis A, Fallon KJ, Coulthard H, Bossanyi DG, Georgiou K, Petty, II AJ , Anthony J et al (2020) . Chemical Science, 11(2), 343-354. RIS download Bibtex download
  • Musser AJ & Clark J (2019) . Annual Review of Physical Chemistry, 70(1), 323-351. RIS download Bibtex download
  • Musser AJ, Maiuri M, Brida D, Cerullo G, Friend RH & Clark J (2015) . Journal of the American Chemical Society, 137(15), 5130-5139. RIS download Bibtex download
  • Poletayev AD, Clark J, Wilson MWB, Rao A, Makino Y, Hotta S & Friend RH (2014) . Advanced Materials, 26(6), 919-924. RIS download Bibtex download
  • Gelinas S, Rao A, Kumar A, Smith SL, Chin AW, Clark J, van der Poll TS, Bazan GC & Friend RH (2014) . Science, 343(6170), 512-516. RIS download Bibtex download

All publications

Journal articles

  • Sutherland GA, Pidgeon JP, Lee HKH, Proctor MS, Hitchcock A, Wang S, Chekulaev D, Tsoi WC, Johnson MP, Hunter CN & Clark J (2023) . J Phys Chem Lett, 6135-6142. RIS download Bibtex download
  • Bossanyi DG, Sasaki Y, Wang S, Chekulaev D, Kimizuka N, Yanai N & Clark J (2021) . JACS Au, 1(12), 2188-2201. RIS download Bibtex download
  • Bossanyi DG, Sasaki Y, Wang S, Chekulaev D, Kimizuka N, Yanai N & Clark J (2021) . Journal of Materials Chemistry C. RIS download Bibtex download
  • Bossanyi DG, Matthiesen M, Wang S, Smith JA, Kilbride RC, Shipp JD, Chekulaev D, Holland E, Anthony JE, Zaumseil J , Musser AJ et al (2021) . Nature Chemistry, 13(2), 163-171. RIS download Bibtex download
  • Bossanyi DG, Matthiesen M, Wang S, Smith JA, Kilbride RC, Shipp JD, Chekulaev D, Holland E, Anthony JE, Zaumseil J , Musser AJ et al (2020) . Nature Chemistry. RIS download Bibtex download
  • Sutherland GA, Polak D, Swainsbury DJK, Wang S, Spano FC, Auman DB, Bossanyi DG, Pidgeon JP, Hitchcock A, Musser AJ , Anthony JE et al (2020) . Journal of the American Chemical Society, 142(32), 13898-13907. RIS download Bibtex download
  • Sasitharan K, Bossanyi DG, Vaenas N, Parnell AJ, Clark J, Iraqi A, Lidzey DG & Foster JA (2020) . Journal of Materials Chemistry A. RIS download Bibtex download
  • Polak D, Jayaprakash R, Lyons TP, Mart铆nez-Mart铆nez L脕, Leventis A, Fallon KJ, Coulthard H, Bossanyi DG, Georgiou K, Petty, II AJ , Anthony J et al (2020) . Chemical Science, 11(2), 343-354. RIS download Bibtex download
  • Jayaprakash R, Georgiou K, Coulthard H, Askitopoulos A, Rajendran SK, Coles DM, Musser AJ, Clark J, Samuel IDW, Turnbull GA , Lagoudakis PG et al (2019) . Light: Science & Applications, 8(1). RIS download Bibtex download
  • Musser AJ, Al-Hashimi M, Heeney M & Clark J (2019) . The Journal of Chemical Physics, 151(4). RIS download Bibtex download
  • Musser AJ & Clark J (2019) . Annual Review of Physical Chemistry, 70(1), 323-351. RIS download Bibtex download
  • Grant RT, Jayaprakash R, Coles DM, Musser A, Liberato SDE, Samuel IDW, Turnbull GA, Clark J & Lidzey DG (2018) . Optics Express, 26(3), 3320-3327. RIS download Bibtex download
  • Yong CK, Musser AJ, Bayliss SL, Lukman S, Tamura H, Bubnova O, Hallani RK, Meneau A, Resel R, Maruyama M , Hotta S et al (2017) . Nature Communications, 8. RIS download Bibtex download
  • Musser AJ, Rajendran SK, Georgiou K, Gai L, Grant RT, Shen Z, Cavazzini M, Ruseckas A, Turnbull GA, Samuel IDW , Clark J et al (2017) . Journal of Materials Chemistry C, 5, 8380-8389. RIS download Bibtex download
  • Grant RT, Michetti P, Musser AJ, Gregoire P, Virgili T, Vella E, Cavazzini M, Georgiou K, Galeotti F, Clark C , Clark J et al (2016) . Advanced Optical Materials, 4(10), 1615-1623. RIS download Bibtex download
  • Grant RT, Michetti P, Musser AJ, Gregoire P, Virgili T, Vella E, Cavazzini M, Georgiou K, Galeotti F, Clark C , Clark J et al (2016) . Advanced Optical Materials, 4(10), 1614-1614. RIS download Bibtex download
  • Musser AJ, Maiuri M, Brida D, Cerullo G, Friend RH & Clark J (2015) . Journal of the American Chemical Society, 137(15), 5130-5139. RIS download Bibtex download
  • Tahir M, Sayyad MH, Clark J, Wahab F, Aziz F, Shahid M, Munawar MA & Chaudry JA (2014) . Sensors and Actuators B: Chemical, 192, 565-571. RIS download Bibtex download
  • Poletayev AD, Clark J, Wilson MWB, Rao A, Makino Y, Hotta S & Friend RH (2014) . Advanced Materials, 26(6), 919-924. RIS download Bibtex download
  • Gelinas S, Rao A, Kumar A, Smith SL, Chin AW, Clark J, van der Poll TS, Bazan GC & Friend RH (2014) . Science, 343(6170), 512-516. RIS download Bibtex download
  • Wilson MWB, Rao A, Johnson K, G茅linas S, di Pietro R, Clark J & Friend RH (2013) . Journal of the American Chemical Society, 135(44), 16680-16688. RIS download Bibtex download
  • Musser AJ, Al-Hashimi M, Maiuri M, Brida D, Heeney M, Cerullo G, Friend RH & Clark J (2013) . Journal of the American Chemical Society, 135(34), 12747-12754. RIS download Bibtex download
  • Johnson K, Huang Y-S, Huettner S, Sommer M, Brinkmann M, Mulherin R, Niedzialek D, Beljonne D, Clark J, Huck WTS & Friend RH (2013) . Journal of the American Chemical Society, 135(13), 5074-5083. RIS download Bibtex download
  • Clark J, Nelson T, Tretiak S, Cirmi G & Lanzani G (2012) . Nature Physics, 8(3), 225-231. RIS download Bibtex download
  • Lim G-K, Chen Z-L, Clark J, Goh RGS, Ng W-H, Tan H-W, Friend RH, Ho PKH & Chua L-L (2011) . Nature Photonics, 5(9), 554-560. RIS download Bibtex download
  • Wilson MWB, Rao A, Clark J, Kumar RSS, Brida D, Cerullo G & Friend RH (2011) . Journal of the American Chemical Society, 133(31), 11830-11833. RIS download Bibtex download
  • Scotognella F, Puzzo DP, Zavelani-Rossi M, Clark J, Sebastian M, Ozin GA & Lanzani G (2011) . Chemistry of Materials, 23(3), 805-809. RIS download Bibtex download
  • Charas A, Mendon莽a AL, Clark J, Bazzana L, Nocivelli A, Lanzani G & Morgado J (2011) . Journal of Polymer Science Part B: Polymer Physics, 49(1), 52-61. RIS download Bibtex download
  • Clark J & Lanzani G (2010) . Nature Photonics, 4(7), 438-446. RIS download Bibtex download
  • Charas A, Mendon莽a AL, Clark J, Cabanillas-Gonzalez J, Bazzana L, Nocivelli A, Lanzani G & Morgado J (2010) . Frontiers of Optoelectronics in China, 3(1), 45-53. RIS download Bibtex download
  • Chaitanya Vishnubhatla K, Clark J, Lanzani G, Ramponi R, Osellame R & Virgili T (2009) . Applied Optics, 48(31), G114-G114. RIS download Bibtex download
  • Clark J, Chang J-F, Spano FC, Friend RH & Silva C (2009) . Applied Physics Letters, 94(16), 163306-163306. RIS download Bibtex download
  • Spano FC, Clark J, Silva C & Friend RH (2009) . The Journal of Chemical Physics, 130(7), 074904-074904. RIS download Bibtex download
  • Vishnubhatla KC, Clark J, Lanzani G, Ramponi R, Osellame R & Virgili T (2009) . Applied Physics Letters, 94(4), 041123-041123. RIS download Bibtex download
  • Clark J, Archer R, Redding T, Foden C, Tant J, Geerts Y, Friend RH & Silva C (2008) . Journal of Applied Physics, 103(12), 124510-124510. RIS download Bibtex download
  • Bazzana L (2008) . Journal of Nanophotonics, 2(1), 023504-023504. RIS download Bibtex download
  • Ishii W, Fuki M, Bu Ali EM, Sato S, Parmar B, Yamauchi A, Mulyadi CH, Uji M, Medina Rivero S, Watanabe G , Clark J et al () . Journal of the American Chemical Society. RIS download Bibtex download
  • Sasaki Y, Georgiou K, Wang S, Bossanyi DG, Jayaprakash R, Yanai N, Kimizuka N, Lidzey DG, Musser AJ & Clark J () . Physical Chemistry Chemical Physics. RIS download Bibtex download
  • Franca LG, Bossanyi DG, Clark J & dos Santos PL () . ACS Applied Optical Materials. RIS download Bibtex download
  • Aitchison CM, Albrecht K, Awaga K, Bergmann K, Calbo J, Cameron J, Clark J, Collins M, Data P, dos Santos P , Fujigaya T et al () . Faraday Discussions. RIS download Bibtex download
  • Polak DW, Andrews I, Farrow G, Musser AJ, Auty A, Chekulaev D, Weinstein JA, Heeney M & Clark J () . Physical Chemistry Chemical Physics. RIS download Bibtex download
  • Bossanyi DG, Matthiesen M, Jayaprakash R, Bhattacharya S, Zaumseil J & Clark J () . Faraday Discussions. RIS download Bibtex download
  • Sasitharan K, Kilbride RC, Spooner ELK, Clark J, Iraqi A, Lidzey DG & Foster JA () . Advanced Science, 2200366-2200366. RIS download Bibtex download
  • Virgili T, Clark J, Cabanillas-Gonzalez J, Bazzana L, Vishnubhatla KC, Osellame R, Ramponi R & Lanzani G () . J. Mater. Chem., 20(3), 519-523. RIS download Bibtex download
  • Clark J, Silva C, Friend RH & Spano FC () . Physical Review Letters, 98(20). RIS download Bibtex download
  • Chang J-F, Clark J, Zhao N, Sirringhaus H, Breiby DW, Andreasen JW, Nielsen MM, Giles M, Heeney M & McCulloch I () . Physical Review B, 74(11). RIS download Bibtex download
  • Clark J, Bossanyi D, Sasaki Y, Chekulaev D, Kimizuka N & Yanai N () . RIS download Bibtex download

Chapters

  • Clark J, Cabanillas-Gonzalez J, Virgili T, Bazzana L & Lanzani G (2009) , Springer Series in Chemical Physics (pp. 463-465). RIS download Bibtex download

Conference proceedings papers

  • Polak D, Coulthard H, Jayaprakash R, Fallon K, Leventis A, Bronstein H, Anthony J, Lidzey DG, Clark J & Musser A (2018) . Physical Chemistry of Semiconductor Materials and Interfaces XVII, 19 August 2018 - 23 August 2018. RIS download Bibtex download
  • Gelinas S, Rao A, Kumar A, Smith SL, Chin AW, Clark J, van der Poll TS, Bazan GC & Friend RH (2014) . 19th International Conference on Ultrafast Phenomena, 2014. RIS download Bibtex download
  • Lu铆sa Mendon莽a A, Charas A, Clark J, Bazzana L, Nocivelli A, Lanzani G & Morgado J (2011) . International Conference on Applications of Optics and Photonics RIS download Bibtex download
  • Sauter W, Kaldor S, Clark J, Laforte S, McCarthy C, Restaino D, Casey J & Questad D (2011) . 2011 IEEE 61st Electronic Components and Technology Conference (ECTC), 31 May 2011 - 3 June 2011. RIS download Bibtex download
  • Carlson A, Bachiraju P, Clark J & Trost D (2010) . Metrology, Inspection, and Process Control for Microlithography XXIV RIS download Bibtex download
  • Grancini G, Polli D, Clark J, Virgili T, Cerullo G & Lanzani G (2010) . MRS Proceedings, Vol. 1270 RIS download Bibtex download
  • Polli D, Grancini G, Virgili T, Clark J, Celebrano M, Lanzani G & Cerullo G (2010) . International Conference on Ultrafast Phenomena, 2010. RIS download Bibtex download
  • Vishnubhatla KC, Crespi A, Bellini N, Clark J, Lanzani G, Ramponi R, Osellame R & Virgili T (2009) . 2009 International Symposium on Optomechatronic Technologies, 21 September 2009 - 23 September 2009. RIS download Bibtex download
  • Polli D, Celebrano M, Clark J, Grancini G, Virgili T, Lanzani G & Cerullo G (2009) (pp 161-165) RIS download Bibtex download
  • Vishnubhatla KC, Clark J, Osellame R, Lanzani G, Virgili T & Ramponi R (2009) . 2009 3rd ICTON Mediterranean Winter Conference (ICTON-MW), 10 December 2009 - 12 December 2009. RIS download Bibtex download
  • Polli D, Clark J, Celebrano M, Grancini G, Lanzani G & Cerullo G (2009) . CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 14 June 2009 - 19 June 2009. RIS download Bibtex download
  • Vishnubhatla KC, Clark J, Lanzani G, Ramponi R, Osellame R & Virgili T (2009) . CLEO/Europe - EQEC 2009 - European Conference on Lasers and Electro-Optics and the European Quantum Electronics Conference, 14 June 2009 - 19 June 2009. RIS download Bibtex download
  • Polli D, Clark J, Celebrano M, Grancini G, Lanzani G & Cerullo G (2009) . Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009. RIS download Bibtex download
  • Polli D, Clark J, Celebrano M, Grancini G, Lanzani G & Cerullo G (2009) Ultrafast confocal microscope for time-resolved imaging of thin films. Optics InfoBase Conference Papers RIS download Bibtex download
  • Vishnubhatla KC, Clark J, Lanzani G, Ramponi R, Osellame R & Virgili T (2009) Microfluidic channels fabricated by femtosecond laser irradiation and chemical etching for optofluidic devices. Optics InfoBase Conference Papers RIS download Bibtex download
  • Vishnubhatla KC, Crespi A, Bellini N, Clark J, Lanzani G, Ramponi R, Osellame R, Virgili T & IEEE (2009) Organic optofluidic devices produced by femtosecond laser micromachining. ISOT: 2009 INTERNATIONAL SYMPOSIUM ON OPTOMECHATRONIC TECHNOLOGIES (pp 404-408) RIS download Bibtex download
  • Morgado J, Mendon莽a AL, Charas A, Clark J, Lanzani G, Bazzana L & Nocivelli A (2008) . Organic Optoelectronics and Photonics III RIS download Bibtex download
  • Lanzani G, Clark J, Virgili T & Cabanillas-Gonzales J (2008) . Frontiers in Optics 2008/Laser Science XXIV/Plasmonics and Metamaterials/Optical Fabrication and Testing, 2008. RIS download Bibtex download
  • Lanzani G, Clark J, Virgili T & Cabanillas-Gonzales J (2008) Ultrafast photonics in polymers. Optics InfoBase Conference Papers RIS download Bibtex download
  • Virgili T, Cabanillas-Gonzalez J, Mroz M, Clark J & Lanzani G (2007) Ultrafast resonant optical switching in organic materials doped in matrix. Materials Research Society Symposium Proceedings, Vol. 1003 (pp 142-146) RIS download Bibtex download
  • Polli D, Grancini G, Clark J, Celebrano M, Virgili T, Cerullo G & Lanzani G () . Advanced Materials, Vol. 22(28) (pp 3048-3051) RIS download Bibtex download

Preprints

  • Sutherland GA, Pidgeon JP, Lee HKH, Proctor MS, Hitchcock A, Wang S, Chekulaev D, Tsoi WC, Johnson MP, Hunter CN & Clark J (2022) , arXiv. RIS download Bibtex download
  • Polak DW, Musser AJ, Sutherland GA, Auty A, Branchi F, Dzurnak B, Chidgey J, Cerullo G, Hunter CN & Clark J (2019) Band-edge Excitation of Carotenoids Removes S* Revealing Triplet-pair Contributions to the S1 Absorption Spectrum. RIS download Bibtex download
  • Polak D, Jayaprakash R, Leventis A, Fallon KJ, Coulthard H, Petty AJ, Anthony J, Bronstein H, Lidzey DG, Clark J & Musser AJ (2018) , arXiv. RIS download Bibtex download
  • Bossanyi D, Sasaki Y, Chekulaev D, Kimizuka N, Yanai N & Clark J () , American Chemical Society (ACS). RIS download Bibtex download
Research group

Research highlights
  •  

In organic solar cells, absorption of light typically creates a tightly bound electron-hole pair. To collect the charges and produce current, the e-h pair must separate.

This happens at a junction between an electron accepting and an electron donating material. By directly tracking the separation of the charges, we showed that they separate to 4nm within 40fs thereby overcoming the electronic Coulomb potential between the electron and hole.

This fast separation occurs due to the wavelike nature of electrons which are governed by fundamental laws of quantum mechanics.

We were able to track the electron-hole separation using the electric field generated between them as they separate.

This electric field perturbs the spectra of the surrounding material and leads to an electro-absorption feature.

Measuring the evolution of the electroabsorption using transient absorption spectroscopy allowed us to track the charge separation in a polymer: PCBM blend and a small molecule: PCBM blend.

A single photon can alter the shape of a molecule. In the eye for example, a photon drives the cis-trans isomerisation which allows us to see.

Using a pump-push-probe technique, we showed that quantum effects can play an important role in this change leading to conformation relaxation rates hundreds of times faster than previously expected.

In general, conformational change occurs on a timescale defined by the energy of the main vibrational mode and the rate of energy dissipation.

Typically, for a conformational change such as a twist around the backbone of a conjugated molecule, this occurs on the tens of picoseconds timescale. However, we demonstrated experimentally that in certain circumstances the molecule, in this case an oligofluorene, can change conformation over two orders of magnitude faster (that is sub-100鈥塮s) in a manner analogous to inertial solvent reorganization demonstrated in the 1990s.

Theoretical simulations demonstrate that non-adiabatic transitions during internal conversion can efficiently convert electronic potential energy into torsional kinetic energy, providing the 鈥榢ick鈥 that prompts sub-100鈥塮s torsional reorganization.

  • Ultrafast triplet formation: two for the price of one [3,4]

In general, photoexcitation leads to an excited state with spin-0 character known as a singlet exciton.

This can convert to a spin-1 excited state (a triplet exciton) through intersystem crossing. In systems made up entirely of Carbon, Nitrogen, Oxygen, Hydrogen or even Sulphur, intersystem crossing generally takes 10s of nanoseconds or more.

However, in certain systems, when the triplet energy is roughly half the singlet energy or less and there is enough space, the singlet can split into two triplet excitons.

The splitting process is known as singlet exciton fission. The ability to generate two excited states from one photon could be used in solar cells to dramatically improve their efficiency.

The fission process is still not fully understood. We have studied a range of materials with the aim of understanding - and one day hopefully controlling - singlet exciton fission.

In [3].

 [4] and in carotenoid aggregates it ranges from 50-100fs depending on aggregate type [5].

Under intense laser excitation, thin films and suspensions of graphite and its nanostructure, including carbon black, nanotubes, few-layer graphenes and graphene oxides, exhibit induced transparency due to saturable absorption.

This switches to optical limiting only at very high fluences when induced breakdown gives rise to microbubbles and microplasmas that causes nonlinear scattering.

Here, we showed that dispersed graphenes, in contrast, can exhibit broadband nonlinear optical absorption at fluences well below this damage threshold with a strong matrix effect.

We obtained, for nanosecond visible and near-infrared pulses, a new benchmark for optical energy-limiting onset of 10 mJ cm鈭2 for a linear transmittance of 70%, with excellent output clamping in both heavy-atom solvents and polymer film matrices.

Nanosecond pump鈥損robe spectroscopy in chlorobenzene reveals that the nanographene domains switch from the usual broadband photo-induced bleaching to a novel reverse saturable absorption mechanism with increasing excitation densities across this threshold.

Strong solvent/matrix effect on the nonlinear optical properties of dispersed sub-GOx. a, Plot of output versus input fluence for a neat film of sub-GOx (T'=0.97), and sub-GOx in PMMA (T'=0.40) and in PC (T'=0.055). T 鈥 is the limiting differential transmittance.

The linear transmittance T is 0.73 for all films. b, Plot of output versus input fluence for sub-GOx dispersed in different solvents compared with C60 in TOL and single-walled CNT in THF, all in cells with 1.0 mm path length. NMP, N-methylpyrrolidinone; THF, tetrahydrofuran; ANS, anisole; MES, mesitylene; DFB, 1,3-difluorobenzene;
BN, benzonitrile; CB, chlorobenzene; BB, bromobenzene; DCB, 1,2-dichlorobenzene; TCB, 1,2,4-trichlorobenzene; TOL, toluene. T is 0.70.

The large non-linear effect is due to the formation of localised exciton-like states which we attribute to triplet excitons due to the heavy-atom effect.

We speculate that the initial electron鈥揾ole gas condenses to triplet-like excitons when promoted by spin鈥搊rbit coupling with heavy atoms.

In contrast, in graphite or multilayer graphenes in which the inner layers are effectively isolated from the environment, the electron鈥揾ole gas cools and recombines rapidly.

  • Ultrafast all-optical switching in plastic optical fibers [7]

The ability to switch light with sub-picosecond time-scales in an optical fiber network is important for improved signal data communication speed and potentially for optical computing.

We made a logical NOT gate using gain switching in isolated conjugated fluorene oligomers. We use the fact that charge absorption overlaps with stimulated emission and generate charges on the oligomers which recombine within a few tens of femtoseconds.

The change from amplification through stimulated emission to loss through charge absorption produces a large switching signal and the recombination allows for ultrafast sub 100fs switching.