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Limited By:	Author = Lovera, Pierre;

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Diffusion profile simulations and enhanced iron sensing in generator-collector mode at interdigitated nanowire electrode arrays (2018)

Wahl, Amélie J. C.; Seymour, Ian P.; Moore, Micheal; Lovera, Pierre; O'Riordan, Al...

Diffusion profile simulations and enhanced iron sensing in generator-collector mode at interdigitated nanowire electrode arrays (2018)

Wahl, Amélie J. C.; Seymour, Ian P.; Moore, Micheal; Lovera, Pierre; O'Riordan, Alan; Rohan, James F.

Abstract:

Gold interdigitated nanowire electrode arrays (INEAs) (∼100 nm wide, ∼50 nm high, ∼45 μm long and ∼500 nm spacing) on a Si/SiO2 chip substrate were fabricated and characterised. Arrays were employed in both non-generator-collector (non-GC) mode (one array electrically connected) and in generator-collector (GC) mode (both arrays electrically connected). In non-GC mode, the individual arrays were confirmed to behave as microelectrodes arising from linear diffusion to the total area of the array. By contrast, in GC-mode, arrays displayed steady-state electrochemical behaviour arising from enhanced diffusion to the nanowires and redox cycling (RC) between adjacent electrodes. Finite element simulations were investigated to explore the effect of altering connected and non-connected electrodes on the diffusional behaviour of the arrays with 500 nm separations. They correlated well with the experimental observations for the influence of the collector electrode potential on redox reactions ...

http://hdl.handle.net/10468/6101

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Electrochemical detection of free-chlorine in Water samples facilitated by in-situ pH control using interdigitated microelectrodes (2020)

Seymour, Ian P.; O'Sullivan, Benjamin; Lovera, Pierre; Rohan, James F.; O'Rio...

Electrochemical detection of free-chlorine in Water samples facilitated by in-situ pH control using interdigitated microelectrodes (2020)

Seymour, Ian P.; O'Sullivan, Benjamin; Lovera, Pierre; Rohan, James F.; O'Riordan, Alan

Abstract:

Residual free-chlorine concentration in water supplies is a key metric studied to ensure disinfection. High residual chlorine concentrations lead to unpleasant odours and tastes, while low concentrations may lead to inadequate disinfection. The concentration is most commonly monitored using colorimetric techniques which require additional reagents. Electrochemical analysis offers the possibility for in-line analysis without the need for additional reagents. Electrochemical-based detection of chlorine is influenced by the solution pH, which defines the particular chlorine ionic species present in solution. As such, controlling the pH is essential to enable electrochemical based detection of residual chlorine in water. To this end, we explore the application of solid state interdigitated electrodes to tailor the in-situ pH of a solution while simultaneously detecting free-chlorine. Finite element simulations and subsequent electrochemical characterization, using gold interdigitated mi...

http://hdl.handle.net/10468/10541

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Lasing in nanoimprinted two-dimensional photonic crystal band-edge lasers (2013)

Reboud, V.; Romero-Vivas, J.; Lovera, Pierre; Kehagias, Nikolaos; Kehoe, Timothy; Redmo...

Lasing in nanoimprinted two-dimensional photonic crystal band-edge lasers (2013)

Reboud, V.; Romero-Vivas, J.; Lovera, Pierre; Kehagias, Nikolaos; Kehoe, Timothy; Redmond, Gareth; Sotomayor Torres, Clivia M.

Abstract:

We demonstrate optically pumped polymer band-edge lasers based on a two-dimensional photonic crystal slab fabricated by nanoimprint lithography (NIL). Lasing was obtained at the photonic band-edge, where the light exhibits a low group velocity at the C point of the triangular lattice photonic crystal band structure. The active medium was composed of a dye chromophore-loaded polymer matrix directly patterned in a single step by nanoimprint lithography. Plane-wave and finite difference time domain algorithms were used to predict experimental lasing frequencies and the lasing thresholds obtained at different C points. A low laser threshold of 3 mu J/mm(2) was achieved in a defect-free photonic crystal thus showing the suitability of nanoimprint lithography to produce cost-efficient optically pumped lasers. (C) 2013 American Institute of Physics. (http://dx.doi.org/10.1063/1.4790646)

http://hdl.handle.net/10468/4287

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Luminescent optical detection of volatile electron deficient compounds by conjugated polymer nanofibers (2015)

Wade, Aidan; Lovera, Pierre; O'Carroll, Deirdre; Doyle, Hugh; Redmond, Gareth

Luminescent optical detection of volatile electron deficient compounds by conjugated polymer nanofibers (2015)

Wade, Aidan; Lovera, Pierre; O'Carroll, Deirdre; Doyle, Hugh; Redmond, Gareth

Abstract:

Optical detection of volatile electron deficient analytes via fluorescence quenching is demonstrated using ca. 200 nm diameter template-synthesized polyfluorene nanofibers as nanoscale detection elements. Observed trends in analyte quenching effectiveness suggest that, in addition to energetic factors, analyte vapor pressure and polymer/analyte solubility play an important role in the emission quenching process. Individual nanofibers successfully act as luminescent reporters of volatile nitroaromatics at sub-parts per million levels. Geometric factors, relating to the nanocylindrical geometry of the fibers and to low nanofiber substrate coverage, providing a less crowded environment around fibers, appear to play a role in providing access by electron deficient quencher molecules to the excited states within the fibers, thereby facilitating the pronounced fluorescence quenching response.

http://hdl.handle.net/10468/2457

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Nanoimprint lithography-based fabrication of plasmonic array of elliptical nanoholes for dual-wavelength, dual-polarisation refractive index sensing (2018)

Robinson, Caoimhe; Justice, John; Petäjä, Jarno; Karppinen, Mikko; Corbett, Brian M.; O...

Nanoimprint lithography-based fabrication of plasmonic array of elliptical nanoholes for dual-wavelength, dual-polarisation refractive index sensing (2018)

Robinson, Caoimhe; Justice, John; Petäjä, Jarno; Karppinen, Mikko; Corbett, Brian M.; O'Riordan, Alan; Lovera, Pierre

Abstract:

We report on the novel fabrication and characterisation of plasmonic arrays of elliptical nanohole, and their use for refractive index based sensing. The substrates were fabricated using nanoimprint lithography into a chromium hard mask followed by transfer of the patterns into the underlying gold layer by dry etching—a combination of processes amendable to mass manufacturing. 3D-FDTD simulations were undertaken and showed the transmission spectrum was dependant upon the polarisation of the incident light, with a series of minima that can be attributed to plasmonic effects on the gold/water or gold/substrate interfaces. Each polarisation showed two peaks on the gold/water interface, one in the visible and one in the near-infrared part of the spectrum. Simulated electric field profiles showed that the electric field in the infrared propagates deep in the bulk while the one in the visible was more tightly bound to the surface. Experimental transmission spectra of the fabricated sample...

http://hdl.handle.net/10468/7147

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Nonlinear refractive index and three-photon absorption coefficient of poly(9,9-dioctylfluorence) (2009)

Jang, J. I.; Mani, S.; Ketterson, J. B.; Lovera, Pierre; Redmond, Gareth

Nonlinear refractive index and three-photon absorption coefficient of poly(9,9-dioctylfluorence) (2009)

Jang, J. I.; Mani, S.; Ketterson, J. B.; Lovera, Pierre; Redmond, Gareth

Abstract:

We investigate the optical Kerr effect and third harmonic generation (THG) arising from chi((3)) of poly(9,9-dioctylfluorence), which is an emerging organic pi-conjugated polymer from the perspective of diverse optoelectronic applications. The measured nonlinear refractive index, obtained with closed-aperture Z-scan, is n(2)=(2.04 +/- 0.10)x10(-12) esu at lambda=1540 nm. Open-aperture Z-scan yields the three-photon absorption coefficient of gamma=(1.88 +/- 0.26)x10(-3) cm(3)/GW(2) at lambda=1064 nm, arising from chi((5)) response. The wavelength-dependent THG indicates that this semiconducting polymer can be a potentially useful polymer system for nonlinear-optics applications involving high-order optical processes in the mid-IR range. (C) 2009 American Institute of Physics. (doi:10.1063/1.3269588)

http://hdl.handle.net/10468/4349

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Redox cycling at interdigitated nanowire electrode arrays: enhanced electrochemical sensing (2018)

Seymour, Ian P.; Lovera, Pierre; Wahl, Amélie J. C; Rohan, James F.; O'Riordan, Alan

Redox cycling at interdigitated nanowire electrode arrays: enhanced electrochemical sensing (2018)

Seymour, Ian P.; Lovera, Pierre; Wahl, Amélie J. C; Rohan, James F.; O'Riordan, Alan

Abstract:

Interdigitated nanowire arrays can be used to perform generator collector type electrochemical measurements. For this set up, one comb of nanowire arrays are used to perform a standard voltammetric technique while the other comb is biased at a constant potential. This technique gives rise to multiple benefits, most notably enhancement of electrochemical signals due to redox cycling, and reduced diffusional overlap in the electrode arrays. Simulations have been used to optimize the electrode designs and to help understand the processes that occur at the electrode surfaces under these conditions. The combination of experimental and simulation data has led to the optimization of a generator collector system with significant collection efficiencies at a variety of conditions.

http://hdl.handle.net/10468/7665

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Structure, stability and water adsorption on ultra-thin TiO2 supported on TiN (2019)

Gutiérrez Moreno, José Julio; Fronzi, Marco; Lovera, Pierre; O'Riordan, Alan; Ford...

Structure, stability and water adsorption on ultra-thin TiO2 supported on TiN (2019)

Gutiérrez Moreno, José Julio; Fronzi, Marco; Lovera, Pierre; O'Riordan, Alan; Ford, Mike; Li, Wenjin; Nolan, Michael

Abstract:

Stochastic computing (SC) has emerged as a potential alternative to binary computing for a number of low-power embedded systems, DSP, neural networks and communications applications. In this paper, a new method, associated architectures and implementations of complex arithmetic functions, such as exponential, sigmoid and hyperbolic tangent functions are presented. Our approach is based on a combination of piecewise linear (PWL) approximation as well as a polynomial interpolation based (Lagrange interpolation) methods. The proposed method aims at reducing the number of binary to stochastic converters. This is the most power sensitive module in an SC system. The hardware implementation for each complex arithmetic function is then derived using the 65nm CMOS technology node. In terms of accuracy, the proposed approach outperforms other well-known methods by 2 times on average. The power consumption of the implementations based on our method is decreased on average by 40 % comparing to ...

http://hdl.handle.net/10468/8806

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Two-dimensional polymer photonic crystal band-edge lasers fabricated by nanoimprint lithography (2007)

Reboud, Vincent; Lovera, Pierre; Kehagias, Nikolaos; Zelsmann, M.; Schuster, C.; Reuthe...

Two-dimensional polymer photonic crystal band-edge lasers fabricated by nanoimprint lithography (2007)

Reboud, Vincent; Lovera, Pierre; Kehagias, Nikolaos; Zelsmann, M.; Schuster, C.; Reuther, F.; Gruetzner, G.; Redmond, Gareth; Torres, C. M. Sotomayor

Abstract:

We report on the fabrication and characterization of two-dimensional polymer photonic crystal band-edge lasers operating in the visible range. The components have been fabricated in a dye chromophore-loaded polymer matrix by nanoimprint lithography. High-symmetry band-edge modes are used to generate laser emission. The experimental lasing frequencies are in good agreement with those calculated using a two-dimensional plane wave algorithm. These results demonstrate the potential of nanoimprint lithography for the fabrication of two-dimensional planar photonic crystal structures in an active medium in a one-step process.(C) 2007 American Institute of Physics. (DOI:10.1063/1.2798250)

http://hdl.handle.net/10468/4377