| 1. |
- Amin, Sidra, et al.
(författare)
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A practical non-enzymatic urea sensor based on NiCo2O4 nanoneedles
- 2019
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 9:25, s. 14443-14451
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Tidskriftsartikel (refereegranskat)abstract
- We propose a new facile electrochemical sensing platform for determination of urea, based on a glassy carbon electrode (GCE) modified with nickel cobalt oxide (NiCo2O4) nanoneedles. These nanoneedles are used for the first time for highly sensitive determination of urea with the lowest detection limit (1 mu M) ever reported for the non-enzymatic approach. The nanoneedles were grown through a simple and low-temperature aqueous chemical method. We characterized the structural and morphological properties of the NiCo2O4 nanoneedles by TEM, SEM, XPS and XRD. The bimetallic nickel cobalt oxide exhibits nanoneedle morphology, which results from the self-assembly of nanoparticles. The NiCo2O4 nanoneedles are exclusively composed of Ni, Co, and O and exhibit a cubic crystalline phase. Cyclic voltammetry was used to study the enhanced electrochemical properties of a NiCo2O4 nanoneedle-modified GCE by overcoming the typical poor conductivity of bare NiO and Co3O4. The GCE-modified electrode is highly sensitive towards urea, with a linear response (R-2 = 0.99) over the concentration range 0.01-5 mM and with a detection limit of 1.0 mu M. The proposed non-enzymatic urea sensor is highly selective even in the presence of common interferents such as glucose, uric acid, and ascorbic acid. This new urea sensor has good viability for urea analysis in urine samples and can represent a significant advancement in the field, owing to the simple and cost-effective fabrication of electrodes, which can be used as a promising analytical tool for urea estimation.
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| 2. |
- Amin, Sidra, et al.
(författare)
-
A practical non-enzymatic urea sensor based on NiCo2O4 nanoneedles
- 2019
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 9:25, s. 14443-14451
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a new facile electrochemical sensing platform for determination of urea, based on a glassy carbon electrode (GCE) modified with nickel cobalt oxide (NiCo2O4) nanoneedles. These nanoneedles are used for the first time for highly sensitive determination of urea with the lowest detection limit (1 μM) ever reported for the non-enzymatic approach. The nanoneedles were grown through a simple and low-temperature aqueous chemical method. We characterized the structural and morphological properties of the NiCo2O4 nanoneedles by TEM, SEM, XPS and XRD. The bimetallic nickel cobalt oxide exhibits nanoneedle morphology, which results from the self-assembly of nanoparticles. The NiCo2O4 nanoneedles are exclusively composed of Ni, Co, and O and exhibit a cubic crystalline phase. Cyclic voltammetry was used to study the enhanced electrochemical properties of a NiCo2O4 nanoneedle-modified GCE by overcoming the typical poor conductivity of bare NiO and Co3O4. The GCE-modified electrode is highly sensitive towards urea, with a linear response (R2 = 0.99) over the concentration range 0.01–5 mM and with a detection limit of 1.0 μM. The proposed non-enzymatic urea sensor is highly selective even in the presence of common interferents such as glucose, uric acid, and ascorbic acid. This new urea sensor has good viability for urea analysis in urine samples and can represent a significant advancement in the field, owing to the simple and cost-effective fabrication of electrodes, which can be used as a promising analytical tool for urea estimation.
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| 3. |
- Belmonte, J.C., et al.
(författare)
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Micromachined twin gas sensor for CO and O2 quantification based on catalytically modified nano-SnO2
- 2006
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 114:2, s. 881-892
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present a micromachined twin sensor that can distinguish between carbon monoxide (CO) and O2 gas taking advantage of the high sensitivity of SnO2 to these gases. The SnO2 nanoparticles of both sensors are catalytically modified with different Pd loadings that act as active filters. In this way, one sensor response is turned to present a higher sensitivity to CO than to O2, whereas the other sensor is mainly turned for detecting O2 variations. The twin sensor has two membranes in the same die of micromachined silicon. Each membrane works independently from the other without any cross talk of temperature. The resistance data obtained from this twin sensor as a function of CO and O 2 concentrations is parametrized. Then, two functions are calculated for the quantification of CO/O2 gas mixtures. A comparison with commercial gas sensors is shown. © 2005 Elsevier B.V. All rights reserved.
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| 4. |
- Heiss, M., et al.
(författare)
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Self-assembled quantum dots in a nanowire system for quantum photonics
- 2013
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Ingår i: Nature Materials. - 1476-4660. ; 12:5, s. 439-444
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Tidskriftsartikel (refereegranskat)abstract
- Quantum dots embedded within nanowires represent one of the most promising technologies for applications in quantum photonics. Whereas the top-down fabrication of such structures remains a technological challenge, their bottom-up fabrication through self-assembly is a potentially more powerful strategy. However, present approaches often yield quantum dots with large optical linewidths, making reproducibility of their physical properties difficult. We present a versatile quantum-dot-innanowire system that reproducibly self-assembles in core-shell GaAs/AlGaAs nanowires. The quantum dots form at the apex of a GaAs/AlGaAs interface, are highly stable, and can be positioned with nanometre precision relative to the nanowire centre. Unusually, their emission is blue-shifted relative to the lowest energy continuum states of the GaAs core. Large-scale electronic structure calculations show that the origin of the optical transitions lies in quantum confinement due to Al-rich barriers. By emitting in the red and self-assembling on silicon substrates, these quantum dots could therefore become building blocks for solid-state lighting devices and third-generation solar cells.
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| 6. |
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| 7. |
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| 8. |
- Pellegrino, P., et al.
(författare)
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Time-resolved analysis of the white photoluminescence from SiO2 films after Si and C coimplantation
- 2004
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:1, s. 25-27
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Tidskriftsartikel (refereegranskat)abstract
- The analysis of the white photoluminescence (PL) from Si+ and C+ coimplanted SiO2 is reported as a function of the implanted dose. By both steady and time-resolved measurements, the presence of several components in the emission between 2 and 3.3 eV has been resolved. The decays of the PL transients are characterized by short lifetimes, below 2 ns. For the emission at 2.1-2.3 eV, photoluminescence decay transients have been measured, obtaining a fast relaxation component of about 50-70 ps, followed by a slower component of the order of 1 ns. These values contrast with the very slow behavior, characteristic for the light emission from Si nanocrystals, and make carbon-related emitting centers interesting for optoelectronic applications where fast switching behavior is important.
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| 9. |
- Romano-Rodriguez, A., et al.
(författare)
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Epitaxial growth of beta-SiC on ion-beam synthesized beta-SiC : Structural characterization
- 2000
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Ingår i: Silicon Carbide and Related Materials - 1999 Pts, 1 & 2. - : Trans Tech Publications Inc.. ; , s. 309-312
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Konferensbidrag (refereegranskat)abstract
- In this work we present for the first time, to our knowledge, the CVD epitaxial growth of β-SiC using an ion beam synthesized (IBS) β-SiC layer as seed, which has been formed by multiple implantation into Si wafers at 500 °C. The ion beam synthesized continuous layer is constituted by β-SiC nanocrystals that are well oriented relative to the silicon substrate. Comparison of the epitaxial growth on these samples with that on silicon test samples, both on and off-axis, is performed. The results show that the epitaxial growth can be achieved on the IBS samples without the need of the carbonization step and that the structural quality of the CVD layer is comparable to that obtained on a carbonized silicon sample. Improvement of the quality of the deposited layer is proposed.
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| 10. |
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| 11. |
- Spirkoska, D., et al.
(författare)
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Structural and optical properties of high quality zinc-blende/wurtzite GaAs nanowire heterostructures
- 2009
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 80:24
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Tidskriftsartikel (refereegranskat)abstract
- The structural and optical properties of three different kinds of GaAs nanowires with 100% zinc-blende structure and with an average of 30% and 70% wurtzite are presented. A variety of shorter and longer segments of zinc-blende or wurtzite crystal phases are observed by transmission electron microscopy in the nanowires. Sharp photoluminescence lines are observed with emission energies tuned from 1.515 eV down to 1.43 eV when the percentage of wurtzite is increased. The downward shift of the emission peaks can be understood by carrier confinement at the interfaces, in quantum wells and in random short period superlattices existent in these nanowires, assuming a staggered band offset between wurtzite and zinc-blende GaAs. The latter is confirmed also by time-resolved measurements. The extremely local nature of these optical transitions is evidenced also by cathodoluminescence measurements. Raman spectroscopy on single wires shows different strain conditions, depending on the wurtzite content which affects also the band alignments. Finally, the occurrence of the two crystallographic phases is discussed in thermodynamic terms.
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