Publications
120 results found
Carey T, Cacovich S, Divitini G, et al., 2017, Fully inkjet printed 2d material field effect heterostructures for wearable and textile electronics, Nature Communications
Fully-printed electronics based on two-dimensional (2d) material heterostructures, such as field effect transistors, require robust and reproducible printed multi-layer stacks consisting of active channel, dielectric and conductive contact layers. Solution processing of graphite and other layered materials provides low-cost inks enabling printed electronic devices, for example by inkjet printing. However, the limited quality of the 2d material inks, the complexity of the layered arrangement for fully inkjet printed field effect heterostructures operating at room temperature and pressure, and the lack of a suitable dielectric 2d ink has impeded the fabrication of active field effect devices with fullyprinted 2d heterostructures. Moreover, electronic devices on textile (i.e. textile electronics) operate over a long time at room temperature, under strain and after several washing cycles. Exploiting the properties of inkjet printed electronics based on 2d materials for wearable and textile electronics requires robust, stable and washable printed devices. Here we demonstrate fully inkjet printed 2d material active heterostructures using graphene and hexagonal-boron nitride (h-BN) inks, and use them to fabricate all inkjet printed flexible and washable field effect transistors (FETs) on textile, reaching a field effect mobility of μ ~ 91 ± 29 cm2 V-1 s -1 on polyester fabric, at low operating voltages (< 5 V). The devices maintained their performance even under ∼ 4% strain and showed stable operation for periods up to 2 years, indicating the two-fold role of the h-BN layer as a flexible dielectric and encapsulant. Our graphene/h-BN FETs are washable up to 20 cycles, which is ideal for textile electronics. The viability of our process for printed and textile electronics is demonstrated by fully inkjet printing electronic circuits, such as reprogrammable volatile memory cells, complementary inverters, and OR logic gates with graphene/h-BN FETs.
Bianchi V, Carey T, Viti L, et al., 2017, Terahertz saturable absorbers from liquid phase exfoliation of graphite, Nature Communications, Vol: 8, ISSN: 2041-1723
Saturable absorbers (SA) operating at terahertz (THz) frequencies can open new frontiers in the development of passively mode-locked THz micro-sources. Here we report the fabrication of THz SAs by transfer coating and inkjet printing single and few-layer graphene films prepared by liquid phase exfoliation of graphite. Open-aperture z-scan measurements with a 3.5 THz quantum cascade laser show a transparency modulation ∼80%, almost one order of magnitude larger than that reported to date at THz frequencies. Fourier-transform infrared spectroscopy provides evidence of intraband-controlled absorption bleaching. These results pave the way to the integration of graphene-based SA with electrically pumped THz semiconductor micro-sources, with prospects for applications where excitation of specific transitions on short time scales is essential, such as time-of-flight tomography, coherent manipulation of quantum systems, time-resolved spectroscopy of gases, complex molecules and cold samples and ultra-high speed communications, providing unprecedented compactness and resolution.
Popa D, Jiang Z, Bonacchini GE, et al., 2017, A stable, power scaling, graphene-mode-locked all-fiber oscillator, Applied Physics Letters, Vol: 110, ISSN: 1077-3118
We report power tunability in a fiber laser mode-locked with a solution-processed filtered graphene film on a fiber connector. ∼370 fs pulses are generated with output power continuously tunable from ∼4 up to ∼52 mW. This is a simple, low-cost, compact, portable, all-fiber ultrafast source for applications requiring environmentally stable, portable sources, such as imaging.
Karagiannidis PG, Hodge SA, Lombardi L, et al., 2017, Microfluidization of graphite and formulation of graphene-based conductive inks, ACS Nano, Vol: 11, Pages: 2742-2755, ISSN: 1936-0851
We report the exfoliation of graphite in aqueous solutions under high shear rate [∼ 108 s-1] turbulent flow conditions, with a 100% exfoliation yield. The material is stabilized without centrifugation at concentrations up to 100 g/L using carboxymethylcellulose sodium salt to formulate conductive printable inks. The sheet resistance of blade coated films is below ∼2Ω/□. This is a simple and scalable production route for conductive inks for large-area printing in flexible electronics.
Ren J, Wang C, Zhang X, et al., 2017, Environmentally-friendly conductive cotton fabric as flexible strain sensor based on hot press reduced graphene oxide, Carbon, Vol: 111, Pages: 622-630, ISSN: 0008-6223
A flexible conductive cotton fabric was demonstrated by formulation and deposition of a graphene oxide (GO) dispersion onto a cotton fabric by vacuum filtration. The deposited GO amount was controlled by the concentration and volume of the GO dispersion. The GO was reduced by a hot press method at 180 °C for 60 min, and no chemical reductant was needed in both the deposition and reduction processes. The carbon-oxygen ratio increased from 1.77 to 3.72 after the hot press reduction. The as-prepared flexible conductive cotton fabric showed a sheet resistance as low as 0.9 kΩ/sq. The sheet resistance of the conductive cotton fabric only increased from ∼0.9 kΩ/sq to ∼1.2 kΩ/sq after 10 washing cycles, exhibiting good washability. The conductive cotton fabric showed viability as a strain sensor even after 400 bending cycles, in which the stable change in the electrical resistance went from ∼3500 kΩ under tensile strain to ∼10 kΩ under compressive strain. This cost-effective and environmentally-friendly method can be easily extended to scalable production of reduced GO based flexible conductive cotton fabrics.
Capelli E, Torrisi F, Venturini L, et al., 2017, Low-Frequency Pulsed Electromagnetic Field Is Able to Modulate miRNAs in an Experimental Cell Model of Alzheimer's Disease, JOURNAL OF HEALTHCARE ENGINEERING, Vol: 2017, ISSN: 2040-2295
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Torrisi F, Popa D, Milana S, et al., 2016, Stable, surfactant-free graphene–styrene methylmethacrylate composite for ultrafast lasers, Advanced Optical Materials, Vol: 4, Pages: 1088-1097, ISSN: 2195-1071
Graphene–polymer composites play an increasing role in photonic and optoelectronic applications, from ultrafast pulse generation to solar cells. The fabrication of an optical quality surfactant-free graphene-styrene methyl methacrylate composite, stable to large humidity and temperature ranges is reported. The composite is tailored for photonic applications showing wavelength-independent linear absorption in the visible and near-infrared. When tested in a mode-locked laser, it allows the generation of stable ≈326 fs mode-locked pulses at 1550 nm, unperturbed by environmental conditions. The composite continues to operate as a saturable absorber even under complete water immersion at 60 °C. This confirms its stability against high-temperature and humidity.
Fabbro A, Scaini D, León V, et al., 2016, Graphene-Based Interfaces Do Not Alter Target Nerve Cells., ACS Nano, Vol: 10, Pages: 615-623, ISSN: 1936-086X
Neural-interfaces rely on the ability of electrodes to transduce stimuli into electrical patterns delivered to the brain. In addition to sensitivity to the stimuli, stability in the operating conditions and efficient charge transfer to neurons, the electrodes should not alter the physiological properties of the target tissue. Graphene is emerging as a promising material for neuro-interfacing applications, given its outstanding physico-chemical properties. Here, we use graphene-based substrates (GBSs) to interface neuronal growth. We test our GBSs on brain cell cultures by measuring functional and synaptic integrity of the emerging neuronal networks. We show that GBSs are permissive interfaces, even when uncoated by cell adhesion layers, retaining unaltered neuronal signaling properties, thus being suitable for carbon-based neural prosthetic devices.
Woodward RI, Howe RCT, Runcorn TH, et al., 2015, Wideband saturable absorption in few-layer molybdenum diselenide (MoSe₂) for Q-switching Yb-, Er- and Tm-doped fiber lasers., Opt Express, Vol: 23, Pages: 20051-20061, ISSN: 1094-4087
We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices.
Purdie DG, Popa D, Wittwer VJ, et al., 2015, Few-cycle pulses from a graphene mode-locked all-fiber laser, Applied Physics Letters, Vol: 106, ISSN: 0003-6951
© 2015 AIP Publishing LLC. We combine a graphene mode-locked oscillator with an external compressor and achieve ∼29-fs pulses with ∼52-mW average power. This is a simple, low-cost, and robust setup, entirely fiber based, with no free-space optics, for applications requiring high temporal resolution.
Zhang M, Howe RCT, Woodward RI, et al., 2015, Solution processed MoS2-PVA composite for sub-bandgap mode-locking of a wideband tunable ultrafast Er:fiber laser, Nano Research, Vol: 8, Pages: 1522-1534, ISSN: 1998-0000
We fabricate a free-standing few-layer molybdenum disulfide (MoS2)-polymer composite by liquid phase exfoliation of chemically pristine MoS2 crystals and use this to demonstrate a wideband tunable, ultrafast mode-locked fiber laser. Stable, picosecond pulses, tunable from 1,535 nm to 1,565 nm, are generated, corresponding to photon energies below the MoS2 material bandgap. These results contribute to the growing body of work studying the nonlinear optical properties of transition metal dichalcogenides that present new opportunities for ultrafast photonic applications.
Ren Y, Brown G, Mary R, et al., 2015, 7.8-GHz Graphene-Based 2-μm Monolithic Waveguide Laser, IEEE Journal on Selected Topics in Quantum Electronics, Vol: 21, ISSN: 1077-260X
© 1995-2012 IEEE. We report a pulsed waveguide laser working at 1944 nm, mode-locked with a saturable absorber consisting of a graphene film deposited on an output coupler mirror. The waveguide is created into a ceramic Thulium-doped Yttrium Aluminium Garnet by ultrafast laser inscription. Q-switched mode-locking is achieved, with 6.5 mW average output power and ∼7.8 GHz pulse rate. This is a convenient, compact, high repetition rate laser for various applications, such as medical diagnostics and spectroscopy.
Woodward RI, Howe RCT, Hu G, et al., 2015, Few-layer MoS<inf>2</inf> saturable absorbers for short-pulse laser technology: Current status and future perspectives [Invited], Photonics Research, Vol: 3, Pages: A30-A41, ISSN: 2327-9125
© 2015 Chinese Laser Press. Few-layer molybdenum disulfide (MoS2) is emerging as a promising quasi-two-dimensional material for photonics and optoelectronics, further extending the library of suitable layered nanomaterials with exceptional optical properties for use in saturable absorber devices that enable short-pulse generation in laser systems. In this work, we catalog and review the nonlinear optical properties of few-layer MoS2, summarize recent progress in processing and integration into saturable absorber devices, and comment on the current status and future perspectives of MoS2-based pulsed lasers.
Woodward RI, Kelleher EJR, Howe RCT, et al., 2014, Tunable Q-switched fiber laser based on saturable edge-state absorption in few-layer molybdenum disulfide (MoS₂), Opt Express, Vol: 22, Pages: 31113-31122, ISSN: 1094-4087
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.
Torrisi F, Coleman JN, 2014, Electrifying inks with 2D materials., Nat Nanotechnol, Vol: 9, Pages: 738-739, ISSN: 1748-3395
Hasan T, Sun Z, Tan P, et al., 2014, Double-wall carbon nanotubes for wide-band, ultrafast pulse generation., ACS Nano, Vol: 8, Pages: 4836-4847, ISSN: 1936-086X
We demonstrate wide-band ultrafast optical pulse generation at 1, 1.5, and 2 μm using a single-polymer composite saturable absorber based on double-wall carbon nanotubes (DWNTs). The freestanding optical quality polymer composite is prepared from nanotubes dispersed in water with poly(vinyl alcohol) as the host matrix. The composite is then integrated into ytterbium-, erbium-, and thulium-doped fiber laser cavities. Using this single DWNT-polymer composite, we achieve 4.85 ps, 532 fs, and 1.6 ps mode-locked pulses at 1066, 1559, and 1883 nm, respectively, highlighting the potential of DWNTs for wide-band ultrafast photonics.
Purdie D, Popa D, Wittwer VJ, et al., 2014, Sub-50 fs compressed pulses from a graphene-mode locked fiber laser, Optics InfoBase Conference Papers, ISSN: 2162-2701
We demonstrate a graphene mode-locked fiber laser system generating 42 fs pulses with 53mW output power, ideal for high temporal resolution applications. © 2014 Optical Society of America.
Woodward RI, Kelleher EJR, Runcorn TH, et al., 2014, Q-switched fiber laser with MoS<inf>2</inf> saturable absorber
A MoS2-based saturable absorber is fabricated using wet chemistry techniques. We use it to passively Q-switch a fiber laser at 1068 nm. © 2014 Optical Society of America.
Thomas S, Cole M, De Luca A, et al., 2014, Graphene-coated Rayleigh SAW resonators for NO <inf>2</inf> detection, Pages: 999-1002, ISSN: 1877-7058
© 2014 Published by Elsevier Ltd. This paper describes the development of a novel low-cost Rayleigh Surface Acoustic Wave Resonator (SAWR) device coated with a graphene layer that is capable of detecting PPM levels of NO 2 in air. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh SAWRs arranged in a dual oscillator configuration; where one resonator is coated with gas-sensitive graphene, and the other left uncoated to act as a reference. An array of NMP-dispersed exfoliated reduced graphene oxide dots was deposited in the active area inside the SAWR IDTs by a non-contacting, micro ink-jet printing system. An automated Mass Flow Controller system has been developed that delivers gases to the SAWR sensors with circuitry for excitation, amplification, buffering and signal read-out. This SAW-based graphene sensor has sensitivity to NO 2 of ca. 25 Hz/ppm and could be implemented in a low-power low-cost gas sensor.
Jiang Z, Bonacchini GE, Popa D, et al., 2014, Graphene saturable absorber power scaling laser, Optics InfoBase Conference Papers, ISSN: 2162-2701
A solution-processed graphene-film coated on a fiber-based connector is used for stable, mode-locked femtosecond-duration pulses with 16mW average output power. © 2014 OSA.
Jiang Z, Bonacchini GE, Popa D, et al., 2014, Graphene saturable absorber power scaling laser, Optics InfoBase Conference Papers, ISSN: 2162-2701
A solution-processed graphene-film coated on a fiber-based connector is used for stable, mode-locked femtosecond-duration pulses with 16mW average output power. © 2014 Optical Society of America.
Jiang Z, Bonacchini GE, Popa D, et al., 2014, Graphene saturable absorber power scaling laser
© 2014 Optical Society of America. A solution-processed graphene-film coated on a fiber-based connector is used for stable, mode-locked femtosecond-duration pulses with 16 mW average output power.
Jiang Z, Bonacchini GE, Popa D, et al., 2014, Graphene saturable absorber power scaling laser, ISSN: 2162-2701
A solution-processed graphene-film coated on a fiber-based connector is used for stable, mode-locked femtosecond-duration pulses with 16mW average output power. © 2014 Optical Society of America.
Milne WI, Hu G, Howe RCT, et al., 2014, Graphene for Plastic electronics, Pages: 368-369
© 2014 ITE and SID. This paper will begin with a description of the liquid phase exfoliation method of graphene production. The remainder of the talk will concentrate on our work on the application of graphene to plastic electronics, including its use as a transparent conductor for transparent pianos and flexible smart windows.
Zhang M, Kelleher EJR, Runcorn TH, et al., 2014, Synchronously coupled fiber lasers and sum frequency generation using graphene composites
Graphene mode-locked and self-sychronized fiber lasers are used for sum- frequency mixing in a graphene-polymer composite.
Woodward RI, Kelleher EJR, Runcorn TH, et al., 2014, Q-switched fiber laser with MoS<inf>2</inf>saturable absorber
© 2014 Optical Society of America. A MoS2-based saturable absorber is fabricated using wet chemistry techniques. We use it to passively Q-switch a fiber laser at 1068 nm.
Zhang M, Kelleher EJR, Runcorn TH, et al., 2014, Synchronously coupled fiber lasers and sum frequency generation using graphene composites, Optics InfoBase Conference Papers, ISSN: 2162-2701
Graphene mode-locked and self-sychronized fiber lasers are used for sum-frequency mixing in a graphene-polymer composite. © 2014 Optical Society of America.
Purdie D, Popa D, Wittwer VJ, et al., 2014, Sub-50 fs compressed pulses from a graphene-mode locked fiber laser
We demonstrate a graphene mode-locked fiber laser system generating 42 fs pulses with 53 mW output power, ideal for high temporal resolution applications.
Mary R, Brown G, Beecher SJ, et al., 2013, Evanescent-wave coupled right angled buried waveguide: Applications in carbon nanotube mode-locking, Applied Physics Letters, Vol: 103, ISSN: 0003-6951
We present an evanescent-field device based on a right-angled waveguide. This consists of orthogonal waveguides, with their points of intersection lying along an angled facet of the chip. Light guided along one waveguide is incident at the angled dielectric-air facet at an angle exceeding the critical angle, so that the totally internally reflected light is coupled into the second waveguide. By depositing a nanotube film on the angled surface, the chip is then used to mode-lock an Erbium doped fiber ring laser with a repetition rate of 26 MHz, and pulse duration of 800 fs. © 2013 AIP Publishing LLC.
Brown G, Thomson RR, Beecher SJ, et al., 2013, Mode-locking using right-angle waveguide, based nanotube saturable absorber, Pacific Rim Conference on Lasers and Electro-Optics, CLEO - Technical Digest
We report passive mode-locking of an Er-doped fiber laser using carbon nanotubes deposited on the facet of a right-angle optical waveguide. © 2013 IEEE.
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