Our students have been involved in new and exciting interdisciplinary research and have published in leading high impact journals including Nature Chemistry, Nature Communications, JACS, Angewandte Chemie, Applied Physics Letters, ACS Nano, Nano Letters, Advanced Materials, Nature Protocols, PloS one, and many others.
A full list of the work published by our NanoDTC Students, Associates and others, acknowledging the NanoDTC grants EP/G037221, EP/L015978 and EP/S022953/1 is below. If you want to view the papers on google scholar, see here.
Some papers published by our students are also featured below with some additional contextual information.
Last updated: Mar 2021
Looking inside lithium-ion batteries
Spectroscopy and Electrocatalysis for a Sustainable Future
From waste to fuel: quantifying sustainability
Novel spin states discovered in silicon-based artificial atoms
A step forward in efficient artificial photosynthesis
Self-assembling hydrogels on microfluidic droplets that respond to light or chemical stimuli by disassembling
2015
72.
Price, Michael B; Butkus, Justinas; Jellicoe, Tom C; Sadhanala, Aditya; Briane, Anouk; Halpert, Jonathan E; Broch, Katharina; Hodgkiss, Justin M; Friend, Richard H; Deschler, Felix
Hot-carrier cooling and photoinduced refractive index changes in organic--inorganic lead halide perovskites Journal Article
In: Nature communications, vol. 6, no. 1, pp. 1–8, 2015.
@article{price2015hot,
title = {Hot-carrier cooling and photoinduced refractive index changes in organic--inorganic lead halide perovskites},
author = {Michael B Price and Justinas Butkus and Tom C Jellicoe and Aditya Sadhanala and Anouk Briane and Jonathan E Halpert and Katharina Broch and Justin M Hodgkiss and Richard H Friend and Felix Deschler},
url = {https://www.nature.com/articles/ncomms9420},
year = {2015},
date = {2015-01-01},
journal = {Nature communications},
volume = {6},
number = {1},
pages = {1--8},
publisher = {Nature Publishing Group},
abstract = {Metal-halide perovskites are at the frontier of optoelectronic research due to solution processability and excellent semiconductor properties. Here we use transient absorption spectroscopy to study hot-carrier distributions in CH3NH3PbI3 and quantify key semiconductor parameters. Above bandgap, non-resonant excitation creates quasi-thermalized carrier distributions within 100 fs. During carrier cooling, a sub-bandgap transient absorption signal arises at ∼1.6 eV, which is explained by the interplay of bandgap renormalization and hot-carrier distributions. At higher excitation densities, a ‘phonon bottleneck’ substantially slows carrier cooling. This effect indicates a low contribution from inelastic carrier-impurity or phonon–impurity scattering in these polycrystalline materials, which supports high charge-carrier mobilities. Photoinduced reflectivity changes distort the shape of transient absorption spectra and must be included to extract physical constants. Using a simple band-filling model that accounts for these changes, we determine a small effective mass of mr=0.14 mo, which agrees with band structure calculations and high photovoltaic performance.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Metal-halide perovskites are at the frontier of optoelectronic research due to solution processability and excellent semiconductor properties. Here we use transient absorption spectroscopy to study hot-carrier distributions in CH3NH3PbI3 and quantify key semiconductor parameters. Above bandgap, non-resonant excitation creates quasi-thermalized carrier distributions within 100 fs. During carrier cooling, a sub-bandgap transient absorption signal arises at ∼1.6 eV, which is explained by the interplay of bandgap renormalization and hot-carrier distributions. At higher excitation densities, a ‘phonon bottleneck’ substantially slows carrier cooling. This effect indicates a low contribution from inelastic carrier-impurity or phonon–impurity scattering in these polycrystalline materials, which supports high charge-carrier mobilities. Photoinduced reflectivity changes distort the shape of transient absorption spectra and must be included to extract physical constants. Using a simple band-filling model that accounts for these changes, we determine a small effective mass of mr=0.14 mo, which agrees with band structure calculations and high photovoltaic performance.
71.
Bernardo, Angelo Di; Salman, Zaher; Wang, Xiaolei; Amado, Mario; Egilmez, Mehmet; Flokstra, Machiel; Suter, Andreas; Lee, Steve; Zhao, Jianhua; Prokscha, Thomas; others,
Research data supporting "Muon spectroscopy data on Au/Ho/Nb thin films" Journal Article
In: 2015.
@article{di2015researchb,
title = {Research data supporting "Muon spectroscopy data on Au/Ho/Nb thin films"},
author = {Angelo Di Bernardo and Zaher Salman and Xiaolei Wang and Mario Amado and Mehmet Egilmez and Machiel Flokstra and Andreas Suter and Steve Lee and Jianhua Zhao and Thomas Prokscha and others},
url = {https://www.repository.cam.ac.uk/handle/1810/251382},
year = {2015},
date = {2015-01-01},
publisher = {University of Cambridge},
abstract = {Measurements data collected at Paul Scherrer Institute showing a paramagnetic Meissner effect due to odd-frequency superconductivity. The data were collected at Paul Scherrer Insitute by performing low-energy spectroscopy on Au/Ho/Nb thin film samples.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Measurements data collected at Paul Scherrer Institute showing a paramagnetic Meissner effect due to odd-frequency superconductivity. The data were collected at Paul Scherrer Insitute by performing low-energy spectroscopy on Au/Ho/Nb thin film samples.
70.
Di, Bernardo A; Salman, Z; Wang, XL; Amado, M; Egilmez, M; Flokstra, MG; Suter, A; Lee, SL; Zhao, JH; Prokscha, T; others,
Intrinsic Paramagnetic Meissner Effect due to S-wave Odd Frequency Superconductivity Journal Article
In: 2015.
@article{di2015intrinsicb,
title = {Intrinsic Paramagnetic Meissner Effect due to S-wave Odd Frequency Superconductivity},
author = {Bernardo A Di and Z Salman and XL Wang and M Amado and M Egilmez and MG Flokstra and A Suter and SL Lee and JH Zhao and T Prokscha and others},
url = {https://journals.aps.org/prx/abstract/10.1103/PhysRevX.5.041021},
year = {2015},
date = {2015-01-01},
publisher = {APS Publishing},
abstract = {In 1933, Meissner and Ochsenfeld reported the expulsion of magnetic flux—the diamagnetic Meissner effect—from the interior of superconducting lead. This discovery was crucial in formulating the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity. In exotic superconducting systems BCS theory does not strictly apply. A classical example is a superconductor-magnet hybrid system where magnetic ordering breaks time-reversal symmetry of the superconducting condensate and results in the stabilization of an odd-frequency superconducting state. It has been predicted that under appropriate conditions, odd-frequency superconductivity should manifest in the Meissner state as fluctuations in the sign of the magnetic susceptibility, meaning that the superconductivity can either repel (diamagnetic) or attract (paramagnetic) external magnetic flux. Here, we report local probe measurements of faint magnetic fields in a Au/Ho/Nb
trilayer system using low-energy muons, where antiferromagnetic Ho (4.5 nm) breaks time-reversal symmetry of the proximity-induced pair correlations in Au. From depth-resolved measurements below the superconducting transition of Nb, we observe a local enhancement of the magnetic field in Au that exceeds the externally applied field, thus proving the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In 1933, Meissner and Ochsenfeld reported the expulsion of magnetic flux—the diamagnetic Meissner effect—from the interior of superconducting lead. This discovery was crucial in formulating the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity. In exotic superconducting systems BCS theory does not strictly apply. A classical example is a superconductor-magnet hybrid system where magnetic ordering breaks time-reversal symmetry of the superconducting condensate and results in the stabilization of an odd-frequency superconducting state. It has been predicted that under appropriate conditions, odd-frequency superconductivity should manifest in the Meissner state as fluctuations in the sign of the magnetic susceptibility, meaning that the superconductivity can either repel (diamagnetic) or attract (paramagnetic) external magnetic flux. Here, we report local probe measurements of faint magnetic fields in a Au/Ho/Nb
trilayer system using low-energy muons, where antiferromagnetic Ho (4.5 nm) breaks time-reversal symmetry of the proximity-induced pair correlations in Au. From depth-resolved measurements below the superconducting transition of Nb, we observe a local enhancement of the magnetic field in Au that exceeds the externally applied field, thus proving the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state.
trilayer system using low-energy muons, where antiferromagnetic Ho (4.5 nm) breaks time-reversal symmetry of the proximity-induced pair correlations in Au. From depth-resolved measurements below the superconducting transition of Nb, we observe a local enhancement of the magnetic field in Au that exceeds the externally applied field, thus proving the existence of an intrinsic paramagnetic Meissner effect arising from an odd-frequency superconducting state.
69.
Howe, Richard CT; Hu, Guohua; Yang, Zongyin; Hasan, Tawfique
Functional inks of graphene, metal dichalcogenides and black phosphorus for photonics and (opto) electronics Proceedings Article
In: Low-Dimensional Materials and Devices, pp. 95530R, International Society for Optics and Photonics 2015.
@inproceedings{howe2015functional,
title = {Functional inks of graphene, metal dichalcogenides and black phosphorus for photonics and (opto) electronics},
author = {Richard CT Howe and Guohua Hu and Zongyin Yang and Tawfique Hasan},
url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/9553/95530R/Functional-inks-of-graphene-metal-dichalcogenides-and-black-phosphorus-for/10.1117/12.2190415.short?SSO=1},
year = {2015},
date = {2015-01-01},
booktitle = {Low-Dimensional Materials and Devices},
volume = {9553},
pages = {95530R},
organization = {International Society for Optics and Photonics},
abstract = {We discuss the emerging role of solution processing and functional ink formulation in the fabrication of devices based on two dimensional (2d) materials. By drawing on examples from our research, we show that these inks allow 2d materials to be exploited in a wide variety of applications, including in photonics and (opto)electronics.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
We discuss the emerging role of solution processing and functional ink formulation in the fabrication of devices based on two dimensional (2d) materials. By drawing on examples from our research, we show that these inks allow 2d materials to be exploited in a wide variety of applications, including in photonics and (opto)electronics.
2014
68.
Badhwar, Shruti
Laterally confined THz sources and graphene based THz optics PhD Thesis
2014.
@phdthesis{Badhwar2014,
title = {Laterally confined THz sources and graphene based THz optics},
author = {Shruti Badhwar},
url = {https://www.repository.cam.ac.uk/handle/1810/246259},
year = {2014},
date = {2014-10-07},
abstract = {The region between the infrared and microwave region in the electromagnetic spectrum, the Terahertz (THz) gap, provides an exciting opportunity for future wireless communications as this band has been under utilised. This doctoral work takes a two-pronged approach into closing the THz gap with low-dimensional materials. The first attempt addresses the need for a compact THz source that can operate at room temperature. The second approach addresses the need to build optical elements such as filters and modulators in the THz spectrum. Terahertz quantum cascade lasers (THz QCLs) are one of the most compact, powerful sources of coherent radiation that bridge the terahertz gap. However, their cryogenic requirements for operation limit the scope of the applications. This is because of the electron-electron scattering and heating of the 2-dimensional free electron gas which leads to significant optical phonon scattering of the hot electrons. Theoretical studies in laterally confined QCL structures have predicted enhanced lifetime of the upper state through suppression of the non-radiative intersubband relaxation of carriers, which leads to lower threshold, and higher temperature performance. Lithographically defined vertical nanopillar arrays with electrostatic radius less than tens of nm offer a possible route to achieve lateral confinement, which can be integrated into QCL structures. A typical gain medium in a QCL consists of at least 100 repeat periods, with a thickness of 6-14 micron. For practical implementation of the top-down approach, restrictions are imposed by aspect ratios that can be achieved in present dry-etching systems. Typically, for sub-200 nm radius pillars, the thickness ranges from 1-3.5 micron. It is therefore necessary to work with THz QCLs based on 3-4 quantum well active regions, so as to maximise the number of repeat periods (hence gain) within an ultra-thin active region. After an introductory chapter, Chapter 2 presents a theoretical treatise on the realistic electrostatic potential in a lithographically defined nanopillar by scaling from a single quantum well (resonant tunnelling diode) to a THz QCL. Chapter 2 also discusses, the effect of lateral confinement on the intersubband states and the plasmonic mode in a THz QCL. One of the key experimental challenges in scaling down from QCLs to quantum-dot cascade lasers is the electrical injection into the nanopillars. This involves insulation and planarisation of the high aspect-ratio nanopillar arrays. Furthermore, the choice of the planarising layer is critical since it determines the loss of any optical mode. This experimental challenge is solved in Chapter 3. Chapter 4 presents the electro-optic performance of low-repeat period QCLs with an active region thickness that is less than 3.5 micron. Another topic of recent interest in the THz optics community is plasmonics in graphene. This is because the bound electromagnetic modes (plasmons) are tightly confined to the surface and can also be tuned with carrier concentration. Plasmonic resonance at terahertz frequencies can be achieved by gating graphene grown via chemical vapour deposition (CVD) to a high carrier concentration. THz time domain spectroscopy of such gated monolayer graphene shows resonance features around 1.6 THz superimposed on the Drude-like frequency response of graphene which may be related to the inherent poly-crystallinity of CVD graphene. Chapter 5 discusses these results, as an understanding of these features is necessary for the development of future THz optical elements based on CVD graphene. Chapter 5 finally describes how the gate tunability of THz transmission through graphene can be exploited to indirectly modulate a THz QCL. Chapter 6 presents ideas from this doctoral work, which can be developed in future to address the issues of enhanced temperature performance of THz QCLs and to realise realistic THz devices based on graphene.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
The region between the infrared and microwave region in the electromagnetic spectrum, the Terahertz (THz) gap, provides an exciting opportunity for future wireless communications as this band has been under utilised. This doctoral work takes a two-pronged approach into closing the THz gap with low-dimensional materials. The first attempt addresses the need for a compact THz source that can operate at room temperature. The second approach addresses the need to build optical elements such as filters and modulators in the THz spectrum. Terahertz quantum cascade lasers (THz QCLs) are one of the most compact, powerful sources of coherent radiation that bridge the terahertz gap. However, their cryogenic requirements for operation limit the scope of the applications. This is because of the electron-electron scattering and heating of the 2-dimensional free electron gas which leads to significant optical phonon scattering of the hot electrons. Theoretical studies in laterally confined QCL structures have predicted enhanced lifetime of the upper state through suppression of the non-radiative intersubband relaxation of carriers, which leads to lower threshold, and higher temperature performance. Lithographically defined vertical nanopillar arrays with electrostatic radius less than tens of nm offer a possible route to achieve lateral confinement, which can be integrated into QCL structures. A typical gain medium in a QCL consists of at least 100 repeat periods, with a thickness of 6-14 micron. For practical implementation of the top-down approach, restrictions are imposed by aspect ratios that can be achieved in present dry-etching systems. Typically, for sub-200 nm radius pillars, the thickness ranges from 1-3.5 micron. It is therefore necessary to work with THz QCLs based on 3-4 quantum well active regions, so as to maximise the number of repeat periods (hence gain) within an ultra-thin active region. After an introductory chapter, Chapter 2 presents a theoretical treatise on the realistic electrostatic potential in a lithographically defined nanopillar by scaling from a single quantum well (resonant tunnelling diode) to a THz QCL. Chapter 2 also discusses, the effect of lateral confinement on the intersubband states and the plasmonic mode in a THz QCL. One of the key experimental challenges in scaling down from QCLs to quantum-dot cascade lasers is the electrical injection into the nanopillars. This involves insulation and planarisation of the high aspect-ratio nanopillar arrays. Furthermore, the choice of the planarising layer is critical since it determines the loss of any optical mode. This experimental challenge is solved in Chapter 3. Chapter 4 presents the electro-optic performance of low-repeat period QCLs with an active region thickness that is less than 3.5 micron. Another topic of recent interest in the THz optics community is plasmonics in graphene. This is because the bound electromagnetic modes (plasmons) are tightly confined to the surface and can also be tuned with carrier concentration. Plasmonic resonance at terahertz frequencies can be achieved by gating graphene grown via chemical vapour deposition (CVD) to a high carrier concentration. THz time domain spectroscopy of such gated monolayer graphene shows resonance features around 1.6 THz superimposed on the Drude-like frequency response of graphene which may be related to the inherent poly-crystallinity of CVD graphene. Chapter 5 discusses these results, as an understanding of these features is necessary for the development of future THz optical elements based on CVD graphene. Chapter 5 finally describes how the gate tunability of THz transmission through graphene can be exploited to indirectly modulate a THz QCL. Chapter 6 presents ideas from this doctoral work, which can be developed in future to address the issues of enhanced temperature performance of THz QCLs and to realise realistic THz devices based on graphene.
67.
Bell, Nicholas AW; Keyser, Ulrich F
Nanopores formed by DNA origami: A review Journal Article
In: FEBS letters, vol. 588, no. 19, pp. 3564–3570, 2014.
@article{bell2014nanopores,
title = {Nanopores formed by DNA origami: A review},
author = {Nicholas AW Bell and Ulrich F Keyser},
url = {https://www.sciencedirect.com/science/article/pii/S0014579314004700},
year = {2014},
date = {2014-01-01},
journal = {FEBS letters},
volume = {588},
number = {19},
pages = {3564--3570},
publisher = {No longer published by Elsevier},
abstract = {Nanopores have emerged over the past two decades to become an important technique in single molecule experimental physics and biomolecule sensing. Recently DNA nanotechnology, in particular DNA origami, has been used for the formation of nanopores in insulating materials. DNA origami is a very attractive technique for the formation of nanopores since it enables the construction of 3D shapes with precise control over geometry and surface functionality. DNA origami has been applied to nanopore research by forming hybrid architectures with solid state nanopores and by direct insertion into lipid bilayers. This review discusses recent experimental work in this area and provides an outlook for future avenues and challenges.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nanopores have emerged over the past two decades to become an important technique in single molecule experimental physics and biomolecule sensing. Recently DNA nanotechnology, in particular DNA origami, has been used for the formation of nanopores in insulating materials. DNA origami is a very attractive technique for the formation of nanopores since it enables the construction of 3D shapes with precise control over geometry and surface functionality. DNA origami has been applied to nanopore research by forming hybrid architectures with solid state nanopores and by direct insertion into lipid bilayers. This review discusses recent experimental work in this area and provides an outlook for future avenues and challenges.
66.
Satoshi Tominaka Patrick J Beldon, P Singh; Cheetham, Anthony
Layered structures and nanosheets of pyrimidinethiolate coordination polymers Journal Article
In: Chemical Communications, vol. 50, no. 30, pp. 3955–3957, 2014.
@article{beldon2014layered,
title = {Layered structures and nanosheets of pyrimidinethiolate coordination polymers},
author = {Patrick J Beldon, Satoshi Tominaka, P Singh, Saha T Dasgupta, Erica Bithell and Anthony Cheetham},
url = {https://pubs.rsc.org/lv/content/articlelanding/2014/cc/c4cc00771a/unauth#!divAbstract},
year = {2014},
date = {2014-01-01},
journal = {Chemical Communications},
volume = {50},
number = {30},
pages = {3955--3957},
publisher = {Royal Society of Chemistry},
abstract = {We report the synthesis, crystal structure and exfoliation of a new member of an important family of layered compounds: lamellar pyrimidinethiolate coordination polymers. Conductivity measurements and DFT calculations of iron(II) pyrimidine-2-thiolate show that this material and a related compound are insulators.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report the synthesis, crystal structure and exfoliation of a new member of an important family of layered compounds: lamellar pyrimidinethiolate coordination polymers. Conductivity measurements and DFT calculations of iron(II) pyrimidine-2-thiolate show that this material and a related compound are insulators.
65.
Sam Crossley, RA Whiter; Kar-Narayan, Sohini
Polymer-based nanopiezoelectric generators for energy harvesting applications Journal Article
In: Materials Science and Technology, vol. 30, no. 13, pp. 1613–1624, 2014.
@article{crossley2014polymer,
title = {Polymer-based nanopiezoelectric generators for energy harvesting applications},
author = {Sam Crossley, RA Whiter and Sohini Kar-Narayan},
url = {https://www.tandfonline.com/doi/abs/10.1179/1743284714Y.0000000605@yema20.2014.9.issue-3},
year = {2014},
date = {2014-01-01},
journal = {Materials Science and Technology},
volume = {30},
number = {13},
pages = {1613--1624},
publisher = {Taylor & Francis},
abstract = {Energy harvesting from ambient vibrations originating from sources such as moving parts of machines, fluid flow and even body movement, has enormous potential for small power applications, such as wireless sensors, flexible, portable and wearable electronics, and bio-medical implants, to name a few. Nanoscale piezoelectric energy harvesters, also known as nanogenerators (NGs), can directly convert small scale ambient vibrations into electrical energy. Scavenging power from ubiquitous vibrations in this way offers an attractive route to provide power to small devices, which would otherwise require direct or indirect connection to electrical power infrastructure. Ceramics such as lead zirconium titanate and semiconductors such as zinc oxide are the most widely used piezoelectric energy harvesting materials. This review focuses on a different class of piezoelectric materials, namely, ferroelectric polymers, such as polyvinlyidene fluoride (PVDF) and its copolymers. These are potentially superior energy harvesting materials as they are flexible, robust, lightweight, easy and cheap to fabricate, as well as being lead free and biocompatible. We review some of the theoretical and experimental aspects of piezoelectric energy recovery using Polymer-based NGs with a novel emphasis on coupling to mechanical resonance, which is relevant for efficient energy harvesting from typically low frequency (<1 kHz) ambient vibrations. The realisation of highly efficient and low cost piezoelectric polymer NGs with reliable energy harvesting performance could lead to wide ranging energy solutions for the next generation of autonomous electronic and wireless devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Energy harvesting from ambient vibrations originating from sources such as moving parts of machines, fluid flow and even body movement, has enormous potential for small power applications, such as wireless sensors, flexible, portable and wearable electronics, and bio-medical implants, to name a few. Nanoscale piezoelectric energy harvesters, also known as nanogenerators (NGs), can directly convert small scale ambient vibrations into electrical energy. Scavenging power from ubiquitous vibrations in this way offers an attractive route to provide power to small devices, which would otherwise require direct or indirect connection to electrical power infrastructure. Ceramics such as lead zirconium titanate and semiconductors such as zinc oxide are the most widely used piezoelectric energy harvesting materials. This review focuses on a different class of piezoelectric materials, namely, ferroelectric polymers, such as polyvinlyidene fluoride (PVDF) and its copolymers. These are potentially superior energy harvesting materials as they are flexible, robust, lightweight, easy and cheap to fabricate, as well as being lead free and biocompatible. We review some of the theoretical and experimental aspects of piezoelectric energy recovery using Polymer-based NGs with a novel emphasis on coupling to mechanical resonance, which is relevant for efficient energy harvesting from typically low frequency (<1 kHz) ambient vibrations. The realisation of highly efficient and low cost piezoelectric polymer NGs with reliable energy harvesting performance could lead to wide ranging energy solutions for the next generation of autonomous electronic and wireless devices.
64.
Michele, Lorenzo Di; Fiocco, D; Varrato, F; Sastry, Srikanth; Eiser, Erika; Foffi, Giuseppe
Aggregation dynamics, structure, and mechanical properties of bigels Journal Article
In: Soft matter, vol. 10, no. 20, pp. 3633–3648, 2014.
@article{di2014aggregation,
title = {Aggregation dynamics, structure, and mechanical properties of bigels},
author = {Lorenzo Di Michele and D Fiocco and F Varrato and Srikanth Sastry and Erika Eiser and Giuseppe Foffi},
url = {https://pubs.rsc.org/lv/content/articlelanding/2014/sm/c3sm52558a/unauth#!divAbstract},
year = {2014},
date = {2014-01-01},
journal = {Soft matter},
volume = {10},
number = {20},
pages = {3633--3648},
publisher = {Royal Society of Chemistry},
abstract = {Recently we have introduced bigels, inter-penetrating gels made of two different colloidal species. Even if particles with simple short-range isotropic potential are employed, the selective interactions enable the tunability of the self-assembly, leading to the formation of complex structures. In the present paper, we explore the non-equilibrium dynamics and the phenomenology underlying the kinetic arrest under quench and the formation of bigels. We demonstrate that the peculiar bigel kinetics can be described through an arrested spinodal decomposition driven by demixing of the colloidal species. The role played by the presence of a second colloidal species on the phase diagram, as expanded to account for the increased number of parameters, is clarified both via extensive numerical simulations and experiments. We provide details on the realisation of bigels, by means of DNA-coated colloids (DNACCs), and the consequent imaging techniques. Moreover we evidence, by comparison with the usual one-component gel formation, the emergence of controllable timescales in the aggregation of the bigels, whose final stages are also experimentally studied to provide morphological details. Finally, we use numerical models to simulate the bigel response to mechanical strain, highlighting how such a new material can bear significantly higher stress compared to the usual one-component gel. We conclude by discussing possible technological uses and by providing insights on the viable research steps to undertake for more complex and yet tuneable multi-component colloidal systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently we have introduced bigels, inter-penetrating gels made of two different colloidal species. Even if particles with simple short-range isotropic potential are employed, the selective interactions enable the tunability of the self-assembly, leading to the formation of complex structures. In the present paper, we explore the non-equilibrium dynamics and the phenomenology underlying the kinetic arrest under quench and the formation of bigels. We demonstrate that the peculiar bigel kinetics can be described through an arrested spinodal decomposition driven by demixing of the colloidal species. The role played by the presence of a second colloidal species on the phase diagram, as expanded to account for the increased number of parameters, is clarified both via extensive numerical simulations and experiments. We provide details on the realisation of bigels, by means of DNA-coated colloids (DNACCs), and the consequent imaging techniques. Moreover we evidence, by comparison with the usual one-component gel formation, the emergence of controllable timescales in the aggregation of the bigels, whose final stages are also experimentally studied to provide morphological details. Finally, we use numerical models to simulate the bigel response to mechanical strain, highlighting how such a new material can bear significantly higher stress compared to the usual one-component gel. We conclude by discussing possible technological uses and by providing insights on the viable research steps to undertake for more complex and yet tuneable multi-component colloidal systems.
63.
Whiter, Richard A; Narayan, Vijay; Kar-Narayan, Sohini
A scalable nanogenerator based on self-poled piezoelectric polymer nanowires with high energy conversion efficiency Journal Article
In: Advanced Energy Materials, vol. 4, no. 18, pp. 1400519, 2014.
@article{whiter2014scalable,
title = {A scalable nanogenerator based on self-poled piezoelectric polymer nanowires with high energy conversion efficiency},
author = {Richard A Whiter and Vijay Narayan and Sohini Kar-Narayan},
url = {https://onlinelibrary.wiley.com/doi/full/10.1002/aenm.201400519},
year = {2014},
date = {2014-01-01},
journal = {Advanced Energy Materials},
volume = {4},
number = {18},
pages = {1400519},
abstract = {Energy harvesting from vibrations is demonstrated using a nanogenerator composed of piezoelectric polymer nanowires with high energy conversion efficiency. Nanowires of poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) grown using a simple, scalable, and cost‐effective template‐wetting technique are shown to be successfully exploited in high‐performance nanogenerators without the need for electrical poling.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Energy harvesting from vibrations is demonstrated using a nanogenerator composed of piezoelectric polymer nanowires with high energy conversion efficiency. Nanowires of poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) grown using a simple, scalable, and cost‐effective template‐wetting technique are shown to be successfully exploited in high‐performance nanogenerators without the need for electrical poling.
62.
Janas, Dawid; Koziol, Krzysztof K
Improved performance of ultra-fast carbon nanotube film heaters Journal Article
In: Journal of Automation and Control Engineering Vol, vol. 2, no. 2, 2014.
@article{janas2014improved,
title = {Improved performance of ultra-fast carbon nanotube film heaters},
author = {Dawid Janas and Krzysztof K Koziol},
url = {http://www.joace.org/uploadfile/2013/1015/20131015051332456.pdf},
year = {2014},
date = {2014-01-01},
journal = {Journal of Automation and Control Engineering Vol},
volume = {2},
number = {2},
abstract = {With current level of development, mankind is about to face many energy-related problems unless we find ways for more efficient power generation and transmission. In this paper, we depicted the operation of highperformance carbon nanotube film heaters, which show a clear advantage over traditionally employed materials. The material was synthesized by a facile one-step method and used as resistive heating element. The results have shown very effective conversion of electric power into heat. To improve the homogeneity of the heaters electrical resistance, we explored a selection of volatile solvents. Such a pretreatment step prior to heaters use caused densification of the material and favorable changes to the electrothermal behavior. },
keywords = {},
pubstate = {published},
tppubtype = {article}
}
With current level of development, mankind is about to face many energy-related problems unless we find ways for more efficient power generation and transmission. In this paper, we depicted the operation of highperformance carbon nanotube film heaters, which show a clear advantage over traditionally employed materials. The material was synthesized by a facile one-step method and used as resistive heating element. The results have shown very effective conversion of electric power into heat. To improve the homogeneity of the heaters electrical resistance, we explored a selection of volatile solvents. Such a pretreatment step prior to heaters use caused densification of the material and favorable changes to the electrothermal behavior.
61.
Müller, Karin H; Motskin, Michael; Philpott, Alistair J; Routh, Alexander F; Shanahan, Catherine M; Duer, Melinda J; Skepper, Jeremy N
In: Biomaterials, vol. 35, no. 3, pp. 1074–1088, 2014.
@article{muller2014effect,
title = {The effect of particle agglomeration on the formation of a surface-connected compartment induced by hydroxyapatite nanoparticles in human monocyte-derived macrophages},
author = {Karin H Müller and Michael Motskin and Alistair J Philpott and Alexander F Routh and Catherine M Shanahan and Melinda J Duer and Jeremy N Skepper},
url = {https://www.sciencedirect.com/science/article/pii/S0142961213012714},
year = {2014},
date = {2014-01-01},
journal = {Biomaterials},
volume = {35},
number = {3},
pages = {1074--1088},
publisher = {Elsevier},
abstract = {Agglomeration dramatically affects many aspects of nanoparticle–cell interactions. Here we show that hydroxyapatite nanoparticles formed large agglomerates in biological medium resulting in extensive particle uptake and dose-dependent cytotoxicity in human macrophages. Particle citration and/or the addition of the dispersant Darvan 7 dramatically reduced mean agglomerate sizes, the amount of particle uptake and concomitantly cytotoxicity. More surprisingly, agglomeration governed the mode of particle uptake. Agglomerates were sequestered within an extensive, interconnected membrane labyrinth open to the extracellular space. In spite of not being truly intracellular, imaging studies suggest particle degradation occurred within this surface-connected compartment (SCC). Agglomerate dispersion prevented the SCC from forming, but did not completely inhibit nanoparticle uptake by other mechanisms. The results of this study could be relevant to understanding particle–cell interactions during developmental mineral deposition, in ectopic calcification in disease, and during application of hydroxyapatite nanoparticle vectors in biomedicine.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Agglomeration dramatically affects many aspects of nanoparticle–cell interactions. Here we show that hydroxyapatite nanoparticles formed large agglomerates in biological medium resulting in extensive particle uptake and dose-dependent cytotoxicity in human macrophages. Particle citration and/or the addition of the dispersant Darvan 7 dramatically reduced mean agglomerate sizes, the amount of particle uptake and concomitantly cytotoxicity. More surprisingly, agglomeration governed the mode of particle uptake. Agglomerates were sequestered within an extensive, interconnected membrane labyrinth open to the extracellular space. In spite of not being truly intracellular, imaging studies suggest particle degradation occurred within this surface-connected compartment (SCC). Agglomerate dispersion prevented the SCC from forming, but did not completely inhibit nanoparticle uptake by other mechanisms. The results of this study could be relevant to understanding particle–cell interactions during developmental mineral deposition, in ectopic calcification in disease, and during application of hydroxyapatite nanoparticle vectors in biomedicine.
60.
Ogata, Ken; Salager, E; Kerr, CJ; Fraser, AE; Ducati, Caterina; Morris, Andrew James; Hofmann, Stephan; Grey, Clare Philomena
Revealing lithium--silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy Journal Article
In: Nature communications, vol. 5, no. 1, pp. 1–11, 2014.
@article{ogata2014revealing,
title = {Revealing lithium--silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy},
author = {Ken Ogata and E Salager and CJ Kerr and AE Fraser and Caterina Ducati and Andrew James Morris and Stephan Hofmann and Clare Philomena Grey},
url = {https://www.nature.com/articles/ncomms4217?originu003dppub},
year = {2014},
date = {2014-01-01},
journal = {Nature communications},
volume = {5},
number = {1},
pages = {1--11},
publisher = {Nature Publishing Group},
abstract = {Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by 7Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium–silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by 7Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium–silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.
59.
Parker, Miles; Acland, Andrew; Armstrong, Harry J; Bellingham, Jim R; Bland, Jessica; Bodmer, Helen C; Burall, Simon; Castell, Sarah; Chilvers, Jason; Cleevely, David D; others,
Identifying the science and technology dimensions of emerging public policy issues through horizon scanning Journal Article
In: PloS one, vol. 9, no. 5, pp. e96480, 2014.
@article{parker2014identifying,
title = {Identifying the science and technology dimensions of emerging public policy issues through horizon scanning},
author = {Miles Parker and Andrew Acland and Harry J Armstrong and Jim R Bellingham and Jessica Bland and Helen C Bodmer and Simon Burall and Sarah Castell and Jason Chilvers and David D Cleevely and others},
url = {https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096480},
year = {2014},
date = {2014-01-01},
journal = {PloS one},
volume = {9},
number = {5},
pages = {e96480},
publisher = {Public Library of Science},
abstract = {Public policy requires public support, which in turn implies a need to enable the public not just to understand policy but also to be engaged in its development. Where complex science and technology issues are involved in policy making, this takes time, so it is important to identify emerging issues of this type and prepare engagement plans. In our horizon scanning exercise, we used a modified Delphi technique [1]. A wide group of people with interests in the science and policy interface (drawn from policy makers, policy adviser, practitioners, the private sector and academics) elicited a long list of emergent policy issues in which science and technology would feature strongly and which would also necessitate public engagement as policies are developed. This was then refined to a short list of top priorities for policy makers. Thirty issues were identified within broad areas of business and technology; energy and environment; government, politics and education; health, healthcare, population and aging; information, communication, infrastructure and transport; and public safety and national security.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Public policy requires public support, which in turn implies a need to enable the public not just to understand policy but also to be engaged in its development. Where complex science and technology issues are involved in policy making, this takes time, so it is important to identify emerging issues of this type and prepare engagement plans. In our horizon scanning exercise, we used a modified Delphi technique [1]. A wide group of people with interests in the science and policy interface (drawn from policy makers, policy adviser, practitioners, the private sector and academics) elicited a long list of emergent policy issues in which science and technology would feature strongly and which would also necessitate public engagement as policies are developed. This was then refined to a short list of top priorities for policy makers. Thirty issues were identified within broad areas of business and technology; energy and environment; government, politics and education; health, healthcare, population and aging; information, communication, infrastructure and transport; and public safety and national security.
58.
Farah, Petros; Demetriadou, Angela; Salvatore, Stefano; Vignolini, Silvia; Stefik, Morgan; Wiesner, Ulrich; Hess, Ortwin; Steiner, Ullrich; Valev, Ventsislav K; Baumberg, Jeremy J
Ultrafast nonlinear response of gold gyroid three-dimensional metamaterials Journal Article
In: Physical Review Applied, vol. 2, no. 4, pp. 044002, 2014.
@article{farah2014ultrafast,
title = {Ultrafast nonlinear response of gold gyroid three-dimensional metamaterials},
author = {Petros Farah and Angela Demetriadou and Stefano Salvatore and Silvia Vignolini and Morgan Stefik and Ulrich Wiesner and Ortwin Hess and Ullrich Steiner and Ventsislav K Valev and Jeremy J Baumberg},
url = {https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.2.044002},
year = {2014},
date = {2014-01-01},
journal = {Physical Review Applied},
volume = {2},
number = {4},
pages = {044002},
publisher = {American Physical Society},
abstract = {We explore the nonlinear optical response of three-dimensional gyroidal metamaterials, which show greater than tenfold enhancements compared to all other metallic nanomaterials as well as bulk gold. A simple analytical model for this metamaterial response shows how the reflectivity spectrum scales with the metal fill fraction and the refractive index of the material that the metallic nanostructure is embedded in. The ultrafast response arising from the interconnected three-dimensional nanostructure can be separated into electronic and lattice contributions with strong spectral dependences on the dielectric filling of the gyroids, which invert the sign of the nonlinear transient reflectivity changes. These metamaterials thus provide a wide variety of tunable nonlinear optical properties, which can be utilized for frequency mixing, optical switching, phase modulators, novel emitters, and enhanced sensing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We explore the nonlinear optical response of three-dimensional gyroidal metamaterials, which show greater than tenfold enhancements compared to all other metallic nanomaterials as well as bulk gold. A simple analytical model for this metamaterial response shows how the reflectivity spectrum scales with the metal fill fraction and the refractive index of the material that the metallic nanostructure is embedded in. The ultrafast response arising from the interconnected three-dimensional nanostructure can be separated into electronic and lattice contributions with strong spectral dependences on the dielectric filling of the gyroids, which invert the sign of the nonlinear transient reflectivity changes. These metamaterials thus provide a wide variety of tunable nonlinear optical properties, which can be utilized for frequency mixing, optical switching, phase modulators, novel emitters, and enhanced sensing.
57.
Butcher, Annabel L; Offeddu, Giovanni S; Oyen, Michelle L
Nanofibrous hydrogel composites as mechanically robust tissue engineering scaffolds Journal Article
In: Trends in biotechnology, vol. 32, no. 11, pp. 564–570, 2014.
@article{butcher2014nanofibrous,
title = {Nanofibrous hydrogel composites as mechanically robust tissue engineering scaffolds},
author = {Annabel L Butcher and Giovanni S Offeddu and Michelle L Oyen},
url = {https://www.sciencedirect.com/science/article/abs/pii/S0167779914001814},
year = {2014},
date = {2014-01-01},
journal = {Trends in biotechnology},
volume = {32},
number = {11},
pages = {564--570},
publisher = {Elsevier Current Trends},
abstract = {Hydrogels closely resemble the extracellular matrix (ECM) and can support cell proliferation while new tissue is formed, making them materials of choice as tissue engineering scaffolds. However, their sometimes-poor mechanical properties can hinder their application. The addition of meshes of nanofibers embedded in their matrix forms a composite that draws from the advantages of both components. Given that these materials are still in the early stages of development, there is a lack of uniformity across methods for characterizing their mechanical properties. Here, we propose a simple metric to enable comparisons between materials. The fibrous constituent improves the mechanical properties of the hydrogel, while the biocompatibility and functionality of the gels are maintained or even improved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hydrogels closely resemble the extracellular matrix (ECM) and can support cell proliferation while new tissue is formed, making them materials of choice as tissue engineering scaffolds. However, their sometimes-poor mechanical properties can hinder their application. The addition of meshes of nanofibers embedded in their matrix forms a composite that draws from the advantages of both components. Given that these materials are still in the early stages of development, there is a lack of uniformity across methods for characterizing their mechanical properties. Here, we propose a simple metric to enable comparisons between materials. The fibrous constituent improves the mechanical properties of the hydrogel, while the biocompatibility and functionality of the gels are maintained or even improved.
56.
Salvatore, Stefano; Vignolini, Silvia; Philpott, Julian; Stefik, Morgan; Wiesner, Ulrich; Baumberg, Jeremy J; Steiner, Ullrich
A high transmission wave-guide wire network made by self-assembly Journal Article
In: Nanoscale, vol. 7, no. 3, pp. 1032–1036, 2014.
@article{salvatore2014high,
title = {A high transmission wave-guide wire network made by self-assembly},
author = {Stefano Salvatore and Silvia Vignolini and Julian Philpott and Morgan Stefik and Ulrich Wiesner and Jeremy J Baumberg and Ullrich Steiner},
url = {https://pubs.rsc.org/en/content/articlelanding/2014/nr/c4nr04485a/unauth#!divAbstract},
year = {2014},
date = {2014-01-01},
journal = {Nanoscale},
volume = {7},
number = {3},
pages = {1032--1036},
publisher = {The Royal Society of Chemistry},
abstract = {Polymer self-assembly of a 3D continuous gyroid morphology was replicated into a network consisting of hollow gold struts. This was achieved by first replicating a gyroid structured film into nickel. The Ni network was employed as an electrode for electrochemical Au deposition, followed by the removal of Ni. The resulting hollow network of plasmonic gold exhibited a substantial optical transmission enhancement by a factor of nearly 3, compared to a network of full Au struts. The overall transmission across the hollow wave-guide morphology depends sensitively on the wall-thickness of the hollow struts down to 1 nm. The dramatic transmission increase arises from an interplay of three mechanisms: (1) the additional number of modes propagating through the wave-guide structure, (2) the increased efficiency of light in-coupling, and (3) a reduction of dissipation by decreasing the Au-volume experienced in plasmon mode propagation.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Polymer self-assembly of a 3D continuous gyroid morphology was replicated into a network consisting of hollow gold struts. This was achieved by first replicating a gyroid structured film into nickel. The Ni network was employed as an electrode for electrochemical Au deposition, followed by the removal of Ni. The resulting hollow network of plasmonic gold exhibited a substantial optical transmission enhancement by a factor of nearly 3, compared to a network of full Au struts. The overall transmission across the hollow wave-guide morphology depends sensitively on the wall-thickness of the hollow struts down to 1 nm. The dramatic transmission increase arises from an interplay of three mechanisms: (1) the additional number of modes propagating through the wave-guide structure, (2) the increased efficiency of light in-coupling, and (3) a reduction of dissipation by decreasing the Au-volume experienced in plasmon mode propagation.
55.
Echtermeyer, Tim J; Nene, PS; Trushin, Maxim; Gorbachev, Roman V; Eiden, Anna L; Milana, Silvia; Sun, Zhipei; Schliemann, John; Lidorikis, Elefterios; Novoselov, Konstantin S; others,
Photothermoelectric and photoelectric contributions to light detection in metal--graphene--metal photodetectors Journal Article
In: Nano letters, vol. 14, no. 7, pp. 3733–3742, 2014.
@article{echtermeyer2014photothermoelectric,
title = {Photothermoelectric and photoelectric contributions to light detection in metal--graphene--metal photodetectors},
author = {Tim J Echtermeyer and PS Nene and Maxim Trushin and Roman V Gorbachev and Anna L Eiden and Silvia Milana and Zhipei Sun and John Schliemann and Elefterios Lidorikis and Konstantin S Novoselov and others},
url = {https://pubs.acs.org/doi/abs/10.1021/nl5004762},
year = {2014},
date = {2014-01-01},
journal = {Nano letters},
volume = {14},
number = {7},
pages = {3733--3742},
publisher = {American Chemical Society},
abstract = {Graphene’s high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal–graphene–metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo- and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphene’s high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal–graphene–metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo- and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.
54.
Niu, Wendy; Eiden, Anna; Prakash, G Vijaya; Baumberg, Jeremy J
Exfoliation of self-assembled 2D organic-inorganic perovskite semiconductors Journal Article
In: Applied Physics Letters, vol. 104, no. 17, pp. 171111, 2014.
@article{niu2014exfoliation,
title = {Exfoliation of self-assembled 2D organic-inorganic perovskite semiconductors},
author = {Wendy Niu and Anna Eiden and G Vijaya Prakash and Jeremy J Baumberg},
url = {https://aip.scitation.org/doi/full/10.1063/1.4874846},
year = {2014},
date = {2014-01-01},
journal = {Applied Physics Letters},
volume = {104},
number = {17},
pages = {171111},
publisher = {American Institute of Physics},
abstract = {Ultra-thin flakes of 2D organic-inorganic perovskite (C6H9C2H4NH3)2PbI4 are produced using micromechanical exfoliation. Mono- and few-layer areas are identified using optical and atomic force microscopy, with an interlayer spacing of 1.6 nm. Refractive indices extracted from the optical spectra reveal a sample thickness dependence due to the charge transfer between organic and inorganic layers. These measurements demonstrate a clear difference in the exciton properties between “bulk” (>15 layers) and very thin (<8 layer) regions as a result of the structural rearrangement of organic molecules around the inorganic sheets.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ultra-thin flakes of 2D organic-inorganic perovskite (C6H9C2H4NH3)2PbI4 are produced using micromechanical exfoliation. Mono- and few-layer areas are identified using optical and atomic force microscopy, with an interlayer spacing of 1.6 nm. Refractive indices extracted from the optical spectra reveal a sample thickness dependence due to the charge transfer between organic and inorganic layers. These measurements demonstrate a clear difference in the exciton properties between “bulk” (>15 layers) and very thin (<8 layer) regions as a result of the structural rearrangement of organic molecules around the inorganic sheets.
53.
Edmund Kelleher Robert I. Woodward, Richard Howe; Taylor, John R.
Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoS 2) Journal Article
In: Optics express, vol. 22, no. 25, pp. 31113–31122, 2014.
@article{woodward2014tunable,
title = {Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoS 2)},
author = {Robert I. Woodward, Edmund Kelleher, Richard Howe , Guohua Hu, Felice Torrisi, Tawfique Hasan, Sergey V. Popov and John R. Taylor},
url = {https://www.osapublishing.org/DirectPDFAccess/42C1F0FA-FF4B-42C7-832514D8964EF5BD_306175/oe-22-25-31113.pdf?da=1&id=306175&seq=0&mobile=no},
year = {2014},
date = {2014-01-01},
journal = {Optics express},
volume = {22},
number = {25},
pages = {31113--31122},
publisher = {Optical Society of America},
abstract = {We fabricate a few-layer molybdenum disulfide (MoS2) polymer composite saturable absorber by liquid-phase exfoliation, and use this to passively Q-switch an ytterbium-doped fiber laser, tunable from 1030 to 1070 nm. Self-starting Q-switching generates 2.88 µs pulses at 74 kHz repetition rate, with over 100 nJ pulse energy. We propose a mechanism, based on edge states within the bandgap, responsible for the wideband nonlinear optical absorption exhibited by our few-layer MoS2 sample, despite operating at photon energies lower than the material bandgap.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We fabricate a few-layer molybdenum disulfide (MoS2) polymer composite saturable absorber by liquid-phase exfoliation, and use this to passively Q-switch an ytterbium-doped fiber laser, tunable from 1030 to 1070 nm. Self-starting Q-switching generates 2.88 µs pulses at 74 kHz repetition rate, with over 100 nJ pulse energy. We propose a mechanism, based on edge states within the bandgap, responsible for the wideband nonlinear optical absorption exhibited by our few-layer MoS2 sample, despite operating at photon energies lower than the material bandgap.