| 1. |
- Man, Zhang, et al.
(författare)
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Facile one-step synthesis and enhanced photocatalytic activity of WC/ferroelectric nanocomposite
- 2021
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 9:40, s. 22861-22870
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Tidskriftsartikel (refereegranskat)abstract
- The development of noble-metal-free co-catalysts is seen as a viable strategy for improving the performance of semiconductor photocatalysts. Although the photocatalytic efficiency of ferroelectrics is typically low, it can be enhanced through the incorporation of a co-catalyst into nanocomposites. Here, we demonstrate the influence of ferroelectricity on the decolorization of rhodamine B under simulated solar light using RbBi2Ti2NbO10 and compared the performance with that of non-ferroelectric RbBi2Nb5O16. The decolorization rate for RbBi2Ti2NbO10 was 5 times greater than that of RbBi2Nb5O16. This behaviour can be explained in terms of ferroelectric polarization, which drives the separation of charge carriers. The photocatalytic activity of RbBi2Ti2NbO10 was further enhanced to over 30 times upon preparing a nanocomposite with tungsten carbide (WC) through high energy ball milling. This enhancement was attributed not only to the increased specific surface area, but also to the incorporated WC co-catalyst, which also serves as a source of plasmonic hot electrons and extends the photocatalytic activity into the visible light range. The WC/RbBi2Ti2NbO10 nanocomposite shows interesting water oxidation properties and evolves O-2 with a rate of 68.5 mu mol h(-1) g(-1) and a quantum yield of 3% at 420 nm. This work demonstrates a simple route for preparing WC containing nano-ferroelectric composites for solar energy conversion applications.
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| 2. |
- Hinnemo, Malkolm, 1986-, et al.
(författare)
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Protein sensing beyond the Debye Length Using Graphene Field-effect Transistors
- 2018
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Ingår i: IEEE Sensors Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1530-437X .- 1558-1748. ; 18:16, s. 6497-6503
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Tidskriftsartikel (refereegranskat)abstract
- Sensing biomolecules in electrolytes of high ionic strength has been a difficult challenge for field-effect transistor-based sensors. Here, we present a graphene-based transistor sensor that is capable of detection of antibodies against protein p53 in electrolytes of physiological ionic strength without dilution. As these molecules are much larger than the Debye screening length at physiological ionic strengths, this paper proves the concept of detection beyond the Debye length. The measured signal associated with the expected specific binding of the antibodies to p53 is concluded to result from resistance changes at the graphene-electrolyte interface, since a sensor responding to resistance changes rather than charge variations is not limited by Debye screening. The conclusion with changes in interface resistance as the underlying phenomena that lead to the observed signal is validated by impedance spectroscopy, which indeed shows an increase of the total impedance in proportion to the amounts of bound antibodies. This finding opens up a new route for electrical detection of large-size and even neutral biomolecules for biomedical detection applications with miniaturized sensors.
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| 3. |
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| 4. |
- Wang, Yaqiong, et al.
(författare)
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Domain Wall Free Polar Structure Enhanced Photodegradation Activity in Nanoscale Ferroelectric BaxSr1-xTiO3
- 2020
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Ingår i: Advanced Energy Materials. - : WILEY-V C H VERLAG GMBH. - 1614-6832 .- 1614-6840. ; 10:38
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Tidskriftsartikel (refereegranskat)abstract
- Ferroelectric materials exhibit anomalous behavior due to the presence of domains and domain walls which are related to the spontaneous polarization inherent in the crystal structure. Control of ferroelectric domains and domain walls has been used to enhance device performances in ultrasound, pyroelectric detectors, and photovoltaic systems with renewed interest in nanostructuring for energy applications. It is also known that ferroelectrics including domain walls can double photocatalytic rate and increase carrier lifetime from microsecond to millisecond. However, there remains a lack of understanding on the different contributions of the domain and domain walls to photocatalytic activities. Herein it is found, by comparing samples of nanostructured Ba(x)Sr(1-)(x)TiO(3)with and without a polar domain, that the material with polar domains has a faster reaction rate (k= 0.18 min(-1)) than the nonpolar one (k= 0.11 min(-1)). It is further revealed that the observed enhanced photoactivity of perovskite ferroelectric materials stems from the inherent polarization of the domain instead of domain walls. Here, the new understanding of the underlying physics of materials with a spontaneous dipole opens a door to enhance the performance of light induced energy harvesting systems.
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| 5. |
- Zhang, Da, et al.
(författare)
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An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface
- 2018
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 254, s. 363-369
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the dynamics of hydrogen ion reactivity at the solid/liquid interface is of paramount importance for applications involving ion sensing in electrolytes. However, the correlation of this interfacial process to noise generation is poorly characterized. Here, the relationship is unveiled by characterizing the interfacial process with impedance spectroscopy assisted by a dedicated electrochemical impedance model. The model incorporates both thermodynamic and kinetic properties of the amphoteric hydrogen ion site-binding reactions with the surface OH groups. It further takes into consideration the distributed nature of the characteristic energy of the binding sites. The simulated impedance matches the experimental data better with an energy distribution of the kinetic parameters than with that of the thermodynamic ones. Since the potentiometric low-frequency noise (LFN) originating from the solid/liquid interface correlates excellently with the real part of its electrochemical impedance spectrum, this work establishes a method for evaluating sensing surface quality aimed at mitigating LFN.
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| 6. |
- Zhang, Da, et al.
(författare)
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Correlation of Low-Frequency Noise to the Dynamic Properties of the Sensing Surface in Electrolytes
- 2017
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 2:8, s. 1160-1166
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Tidskriftsartikel (refereegranskat)abstract
- Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/debinding dynamic properties. Here, we employ impedance spectroscopy to systematically characterize this specific noise component for its correlation to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen debinding) processes. This correlation is facilitated by applying our recently developed interfacial impedance model to ultrathin TiO2 layers grown by means of atomic layer deposition (ALD) on a TiN metallic electrode. With an excellent fitting of the measured noise power density spectra by the model for the studied TiO2 layers, we are able to extract several characteristic dynamic parameters for the TiO2 sensing surface. The observed increase of noise with TiO2 ALD cycles can be well accounted for with an increased average binding site density. This study provides insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.
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| 7. |
- Zhang, Da, et al.
(författare)
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Low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface of ion sensors
- 2018
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Konferensbidrag (refereegranskat)abstract
- Low-frequency noise (LFN) is of significant implications in ion sensing. As a primary component of LFN for ion sensing in electrolytes, the solid/liquid interfacial noise remains poorly explored especially regarding its relation to the surface binding/de-binding dynamic properties. In this talk, the solid/liquid interfacial noise will first be characterized by direct electrical measurements. It will then be correlated to the dynamic properties of surface protonation (i.e., hydrogen binding) and deprotonation (i.e., hydrogen de-binding) processes using an impedance spectroscopy. Finally we will provide insights into how detailed surface properties may affect the noise performance of an ion sensor operating in electrolytes.
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| 8. |
- Botvinik-Nezer, Rotem, et al.
(författare)
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Variability in the analysis of a single neuroimaging dataset by many teams
- 2020
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 582, s. 84-88
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Tidskriftsartikel (refereegranskat)abstract
- Data analysis workflows in many scientific domains have become increasingly complex and flexible. Here we assess the effect of this flexibility on the results of functional magnetic resonance imaging by asking 70 independent teams to analyse the same dataset, testing the same 9 ex-ante hypotheses(1). The flexibility of analytical approaches is exemplified by the fact that no two teams chose identical workflows to analyse the data. This flexibility resulted in sizeable variation in the results of hypothesis tests, even for teams whose statistical maps were highly correlated at intermediate stages of the analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Notably, a meta-analytical approach that aggregated information across teams yielded a significant consensus in activated regions. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset(2-5). Our findings show that analytical flexibility can have substantial effects on scientific conclusions, and identify factors that may be related to variability in the analysis of functional magnetic resonance imaging. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for performing and reporting multiple analyses of the same data. Potential approaches that could be used to mitigate issues related to analytical variability are discussed. The results obtained by seventy different teams analysing the same functional magnetic resonance imaging dataset show substantial variation, highlighting the influence of analytical choices and the importance of sharing workflows publicly and performing multiple analyses.
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| 9. |
- Chen, Si, 1982-, et al.
(författare)
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Current gain enhancement for silicon-on-insulator lateral bipolar junction transistors operating at liquid-helium temperature
- 2020
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 41:6, s. 800-803
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Tidskriftsartikel (refereegranskat)abstract
- Conventional homojunction bipolar junction transistors (BJTs) are not suitable for cryogenic operation due to heavy doping-induced emitter band-gap narrowing and strong degradation in current gain (β) at low temperature. In this letter, we show that, on lateral version of the BJTs (LBJTs) fabricated on silicon-on-insulator (SOI) substrate, such β degradation can be mitigated by applying a substrate bias (V sub ), and a β over unity is achieved in a base current (I B ) range over 5 orders of magnitudes at 4.2 K, with a peak β ~ 100 demonstrated. The β improvement is explained by the enhanced electron tunneling through base region as a result of base barrier lowering and thinning by a positive Vsub, which leads to dramatic increase of collector current (IC) while IB is negligibly affected.
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| 10. |
- Chen, Xi, et al.
(författare)
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Device noise reduction for Silicon nanowire field-effect-transistor based sensors by using a Schottky junction gate
- 2019
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 4:2, s. 427-433
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Tidskriftsartikel (refereegranskat)abstract
- The sensitivity of metal-oxide-semiconductor field-effect transistor (MOSFET) based nanoscale sensors is ultimately limited by noise induced by carrier trapping/detrapping processes at the gate oxide/semiconductor interfaces. We have designed a Schottky junction gated silicon nanowire field-effect transistor (SiNW-SJGFET) sensor, where the Schottky junction replaces the noisy oxide/semiconductor interface. Our sensor exhibits significantly reduced noise, 2.1×10-9 V2µm2/Hz at 1 Hz, compared to reference devices with the oxide/semiconductor interface operated at both inversion and depletion modes. Further improvement can be anticipated by wrapping the nanowire by such a Schottky junction thereby eliminating all oxide/semiconductor interfaces. Hence, a combination of the low-noise SiNW-SJGFET sensor device with a sensing surface of the Nernstian response limit holds promises for future high signal-to-noise ratio sensor applications.
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