| 1. |
- Li, Chen, et al.
(författare)
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Rapid Four-Point Sweeping Method to Investigate Hysteresis of MoS2 FET
- 2020
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Ingår i: IEEE Electron Device Letters. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0741-3106 .- 1558-0563. ; 41:9, s. 1356-1359
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Tidskriftsartikel (refereegranskat)abstract
- Hysteresis is a frequently observed phenomenon in the transfer characteristics of thin film transistors. Charge trapping/de-trapping processes of gate oxide and gate-channel interface are commonly known to be the origin of hysteresis and correlated to low frequency noise (LFN) properties of the devices. In this letter, a rapid four-point sweeping method (RFSM) is proposed to reveal the dependence of hysteresis, as well as the distribution of effective trap density on sweeping rate and gate bias range. Based on the RFSM, the hysteresis properties of four-layer MoS2 FETs are studied in detail. The experimental results demonstrate that the hysteresis and trap density at different frequencies and gate voltages, which could further roughly map the traps with different time constants and energy depths, can be obtained by the simple RFSM. Trap density estimated by RFSM shows a comparable range with that extracted from LFN, indicating that the traps inducing the hysteresis may also cause LFN.
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| 2. |
- Hu, Qitao, et al.
(författare)
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Current gain and low-frequency noise of symmetric lateral bipolar junction transistors on SOI
- 2018
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Ingår i: 2018 48th European Solid-State Device Research Conference (ESSDERC). - 9781538654019 - 9781538654002 - 9781538654026 ; , s. 258-261
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Konferensbidrag (refereegranskat)abstract
- This paper presents a comprehensive study of symmetric lateral bipolar junction transistors (LBJTs) fabricated on SOI substrate using a CMOS-compatible process; LBJTs find many applications including being a local signal amplifier for silicon-nanowire sensors. Our LBJTs are characterized by a peak gain (β) over 50 and low-frequency noise two orders of magnitude lower than what typically is of the SiO 2 /Si interface for a MOSFET. β is found to decrease at low base current due to recombination in the space charge region at the emitter-base junction and at the surrounding SiO 2 /Si interfaces. This decrease can be mitigated by properly biasing the substrate.
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| 3. |
- Li, Shiyu, et al.
(författare)
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Docking and Activity of DNA Polymerase on Solid-State Nanopores
- 2022
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Ingår i: ACS Sensors. - : American Chemical Society (ACS). - 2379-3694. ; 7:5, s. 1476-1483
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Tidskriftsartikel (refereegranskat)abstract
- Integration of motor enzymes with biological nanopores has enabled commercial DNA sequencing technology; yet studies of the similar principle applying to solid-state nanopores are limited. Here, we demonstrate the real-life monitoring of phi29 DNA polymerase (DNAP) docking onto truncated-pyramidal nanopore (TPP) arrays through both electrical and optical readout. To achieve effective docking, atomic layer deposition of hafnium oxide is employed to reduce the narrowest pore opening size of original silicon (Si) TPPs to sub-10 nm. On a single TPP with pore opening size comparable to DNAP, ionic current measurements show that a polymerase-DNA complex can temporally dock onto the TPP with a certain docking orientation, while the majority become translocation events. On 5-by-5 TPP arrays, a label-free optical detection method using Ca2+ sensitive dye, are employed to detect the docking dynamics of DNAP. The results show that this label-free detection strategy is capable of accessing the docking events of DNAP on TPP arrays. Finally, we examine the activity of docked DNAP by performing on-site rolling circle amplification to synthesize single-stranded DNA (ssDNA), which serves as a proof-of-concept demonstration of utilizing this docking scheme for emerging nanopore sensing applications.
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| 4. |
- Li, Shiyu, et al.
(författare)
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Dynamics of DNA Clogging in Hafnium Oxide Nanopores
- 2020
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 124:51, s. 11573-11583
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Tidskriftsartikel (refereegranskat)abstract
- Interfacing solid-state nanopores with biological systems has been exploited as a versatile analytical platform for analysis of individual biomolecules. Although clogging of solid-state nanopores due to nonspecific interactions between analytes and pore walls poses a persistent challenge in attaining the anticipated sensing efficacy, insufficient studies focus on elucidating the clogging dynamics. Herein, we investigate the DNA clogging behavior by passing double-stranded (ds) DNA molecules of different lengths through hafnium oxide(HfO2)-coated silicon (Si) nanopore arrays, at different bias voltages and electrolyte pH values. Employing stable and photoluminescent-free HfO2/Si nanopore arrays permits a parallelized visualization of DNA clogging with confocal fluorescence microscopy. We find that the probability of pore clogging increases with both DNA length and bias voltage. Two types of clogging are discerned: persistent and temporary. In the time-resolved analysis, temporary clogging events exhibit a shorter lifetime at higher bias voltage. Furthermore, we show that the surface charge density has a prominent effect on the clogging probability because of electrostatic attraction between the dsDNA and the HfO2 pore walls. An analytical model based on examining the energy landscape along the DNA translocation trajectory is developed to qualitatively evaluate the DNA–pore interaction. Both experimental and theoretical results indicate that the occurrence of clogging is strongly dependent on the configuration of translocating DNA molecules and the electrostatic interaction between DNA and charged pore surface. These findings provide a detailed account of the DNA clogging phenomenon and are of practical interest for DNA sensing based on solid-state nanopores.
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| 5. |
- Li, Shiyu, et al.
(författare)
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Label-Free Optical Detection of DNA Polymerase Docking on Solid-State Nanopore Arrays
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Integration of motor enzymes with biological nanopores has enabled commercial DNA sequencing, yet studies of the similar principle applying to solid-state nanopores are limited. Here, we demonstrate the label-free optical detection of phi29 DNA polymerase (DNAP) docking onto truncated-pyramidal nanopores (TPP). Atomic layer deposition of hafnium oxide is employed to shrink the pore opening size of original silicon (Si) TPP to sub-10 nm. Ionic current measurements of single TPP of an opening size comparable to DNAP show that polymerase-DNA complexes can temporally dock onto the TPP with a certain docking orientation, while the majority are translocation events. A label-free optical detection method using Ca2+ sensitive dye is employed to detect the docking of DNAP on 5-by-5 nanopore arrays. The results of the proof-of-concept experiment show that this label-free detection strategy is capable of accessing the docking events of DNAP on solid-state nanopore arrays.
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| 6. |
- Li, Shiyu, et al.
(författare)
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Nanoarrays on Passivated Aluminum Surface for Site-Specific Immobilization of Biomolecules
- 2018
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Ingår i: ACS Applied Bio Materials. - : American Chemical Society (ACS). - 2576-6422. ; 1:1, s. 125-135
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Tidskriftsartikel (refereegranskat)abstract
- The rapid development of biosensing platforms for highly sensitive and specific detection raises the desire of precise localization of biomolecules onto various material surfaces. Aluminum has been strategically employed in the biosensor system due to its compatibility with CMOS technology and its optical and electrical properties such as prominent propagation of surface plasmons. Herein, we present an adaptable method for preparation of carbon nanoarrays on aluminum surface passivated with poly(vinylphosphonic acid) (PVPA). The carbon nanoarrays were defined by means of electron beam induced deposition (EBID) and they were employed to realize site-specific immobilization of target biomolecules. To demonstrate the concept, selective streptavidin/neutravidin immobilization on the carbon nanoarrays was achieved through protein physisorption with a significantly high contrast of the carbon domains over the surrounding PVPA-modified aluminum surface. By adjusting the fabrication parameters, local protein densities could be varied on similarly sized nanodomains in a parallel process. Moreover, localization of single 40 nm biotinylated beads was achieved by loading them on the neutravidin-decorated nanoarrays. As a further demonstration, DNA polymerase with a streptavidin tag was bound to the biotin-beads that were immobilized on the nanoarrays and in situ rolling circle amplification (RCA) was subsequently performed. The observation of organized DNA arrays synthesized by RCA verified the nanoscale localization of the enzyme with retained biological activity. Hence, the presented approach could provide a flexible and universal avenue to precise localizing various biomolecules on aluminum surface for potential biosensor and bioelectronic applications.
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| 7. |
- Li, Shiyu, et al.
(författare)
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Nanoparticle Localization on Solid-State Nanopores Via Electrophoretic Force
- 2019
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Ingår i: 2019 20TH INTERNATIONAL CONFERENCE ON SOLID-STATE SENSORS, ACTUATORS AND MICROSYSTEMS & EUROSENSORS XXXIII (TRANSDUCERS & EUROSENSORS XXXIII). - : IEEE. - 9781728120072 ; , s. 2372-2375
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Konferensbidrag (refereegranskat)abstract
- This work presents a versatile and facile method for precise localization of nanoparticles on solid-state nanopores surface-functionalized with carbon via electron beam induced deposition (EBID). For the first time, EBID of carbon is demonstrated to enable nanoparticle localization on solid-state nanopores. To avoid non-specific adsorption of nanoparticles on the surface, an atomic layer deposited Al2O3 layer in combination with phosphonate passivation is used. By tuning the electron dose in the EBID process, the loading fraction of nanoparticles on carbon nanoarrays can be varied on similarly sized domains. Nanoparticle loading driven by electrophoresis can achieve an efficiency that is orders of magnitude higher than that driven by diffusion.
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| 8. |
- Li, Shiyu, et al.
(författare)
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Visualization of DNA Translocation and Clogging Using Photoluminescent-Free Silicon Nanopore Arrays
- 2020
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Ingår i: 2020 IEEE 20th International Conference on Nanotechnology (IEEE-NANO). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781728182643 ; , s. 193-197
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Konferensbidrag (refereegranskat)abstract
- Solid-state nanopore arrays hold promises for high-throughput optical analysis of single molecules. However, the high photoluminescence (PL) background emanating from the commonly used silicon nitride (SiNx) membrane for nanopore fabrication and the nonspecific adsorption of analyte on the pore sidewalls have plagued the high sensing sensitivity and efficiency offered by optical sensing. Here, the present work demonstrates an optical monitoring system using a truncated pyramidal nanopore array on a silicon membrane coated with a lipid bilayer for visualization of DNA translocation events. The silicon membrane produces essentially no PL under blue-green laser illumination, which enables more clear identification of DNA translocation and clogging events than using SiNx-based devices. The lipid bilayer coating based on small unilamellar vesicles (SUVs) minimizes the nonspecific adsorption of DNA. With confocal microscopy, the fluorescent labeled DNA translocation motion is visualized in three dimensions. The statistical results show that the percentage of DNA clogged pores is significantly reduced for the lipid bilayer coated nanopores as compared to the uncoated nanopores.
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| 9. |
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Optical monitoring of single nanoparticle capture in solid-state nanopore array
- 2019
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Proceedings (redaktörskap) (refereegranskat)abstract
- Solid-state nanopore arrays hold promises for high-throughput optical or electrical analysis of nanoscale entities. Here, we demonstrate an optical monitoring system for investigation of the capture process of single nanoparticles driven by electrophoretic force in a nanopore array. Over 50% of the single nanoparticle capture events are achieved by controlling the applied voltage across the nanopore membrane with a tailored nanopore size. We find that at a certain voltage bias, the capture of single nanoparticles is a self-termination process.
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| 10. |
- Palomar, Quentin, 1991-, et al.
(författare)
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Detection of gingipain activity using solid state nanopore sensors
- 2022
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier. - 0925-4005 .- 1873-3077. ; 368
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Tidskriftsartikel (refereegranskat)abstract
- Accurate, robust, and rapid diagnostics is the basis for all well-functioning healthcare. There is a large need in point-of-care biosensors to facilitate diagnosis and reduce the need for cumbersome laboratory equipment. Proteases are key virulence factors in periodontitis. Periodontal disease is very common and characterized by inflammation and infection in the tooth-supporting structures and is linked to many systemic diseases such as cardiovascular disease, diabetes, and Alzheimer's disease. Proteases present in periodontal disease, gingipains, are highly responsible for the disease onset and progression and are therefore a promising biomarker. Here we show a novel nanopore-based biosensor strategy for protease activity monitoring. Solid-state nanopores were modified with a proteolytic substrate, restricting the ionic current through the apertures of the nanopores. Protease can digest the proteolytic substrate thus enlarge the aperture and the ionic current. Trypsin was used as an initial model protease to investigate the performance of the sensor. We show that the solid-state nanoporebiosensor can detect trypsin with a limit of detection (LOD) of 0.005 ng/mL (0.2 pM). The detection system developed for the model enzyme was then applied to the detection of gingipains. The LOD for detection of gingipains was 1 ng/mL (0.02 nM), with a 27% recovery of the signal at 0.1 mu g/mL, indicating that the sensitivity and dynamic range are relevant for the clinical diagnosis of periodontitis. The generic detection of protease activity and high sensitivity make this a promising sensor technology for both diagnosis of periodontal disease and monitoring of other disease-related proteases.
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