| 1. |
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- 2017
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Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 96:2
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Tidskriftsartikel (refereegranskat)
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| 2. |
- Zhang, Miao, 1985-, et al.
(författare)
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Super-resolved Optical Mapping of Reactive Sulfur-Vacancies in Two-Dimensional Transition Metal Dichalcogenides
- 2021
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 15:4, s. 7168-7178
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Tidskriftsartikel (refereegranskat)abstract
- Transition metal dichalcogenides (TMDs) represent a class of semiconducting two-dimensional (2D) materials with exciting properties. In particular, defects in 2D-TMDs and their molecular interactions with the environment can crucially affect their physical and chemical properties. However, mapping the spatial distribution and chemical reactivity of defects in liquid remains a challenge. Here, we demonstrate large area mapping of reactive sulfur-deficient defects in 2D-TMDs in aqueous solutions by coupling single-molecule localization microscopy with fluorescence labeling using thiol chemistry. Our method, reminiscent of PAINT strategies, relies on the specific binding of fluorescent probes hosting a thiol group to sulfur vacancies, allowing localization of the defects with an uncertainty down to 15 nm. Tuning the distance between the fluorophore and the docking thiol site allows us to control Foster resonance energy transfer (FRET) process and reveal grain boundaries and line defects due to the local irregular lattice structure. We further characterize the binding kinetics over a large range of pH conditions, evidencing the reversible adsorption of the thiol probes to the defects with a subsequent transitioning to irreversible binding in basic conditions. Our methodology provides a simple and fast alternative for large-scale mapping of nonradiative defects in 2D materials and can be used for in situ and spatially resolved monitoring of the interaction between chemical agents and defects in 2D materials that has general implications for defect engineering in aqueous condition.
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| 3. |
- Cheng, Dan-Chen, et al.
(författare)
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Improving Si solar cell performance using Mn:ZnSe quantum dot-doped PLMA thin film
- 2013
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Ingår i: Nanoscale Research Letters. - : SPRINGER. - 1931-7573 .- 1556-276X. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Poly(lauryl methacrylate) (PLMA) thin film doped with Mn:ZnSe quantum dots (QDs) was spin-deposited on the front surface of Si solar cell for enhancing the solar cell efficiency via photoluminescence (PL) conversion. Significant solar cell efficiency enhancements (approximately 5% to 10%) under all-solar-spectrum (AM0) condition were observed after QD-doped PLMA coatings. Furthermore, the real contribution of the PL conversion was precisely assessed by investigating the photovoltaic responses of the QD-doped PLMA to monochromatic and AM0 light sources as functions of QD concentration, combined with reflectance and external quantum efficiency measurements. At a QD concentration of 1.6 mg/ml for example, among the efficiency enhancement of 5.96%, about 1.04% was due to the PL conversion, and the rest came from antireflection. Our work indicates that for the practical use of PL conversion in solar cell performance improvement, cautions are to be taken, as the achieved efficiency enhancement might not be wholly due to the PL conversion.
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| 4. |
- Chung, Nguyen Xuan, et al.
(författare)
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Optimized electrochemical breakdown etching using temporal voltage variation for formation of nanopores in a silicon membrane
- 2021
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 331
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Tidskriftsartikel (refereegranskat)abstract
- Dielectric breakdown etching is a well-known method of making nanopores on thin (similar to 50 nm) dielectric membranes. However, voltage driven translocation of biomolecules through such nanopores becomes extremely fast. For improved detection, for instance by the current blockage, a high-aspect-ratio nanopore could be beneficial for slowing down the translocation. High-aspect-ratio nanopore on silicon fabrication requires a well-controlled process and is dependent on specific crystal orientation, dopant type and resistivity of substrate. Therefore, an optimized method of processing high-aspect-ratio nanopores is necessary considering the advantage of a silicon membrane being able to be integrated with standard CMOS processing. Here, we present an optimized fabrication method for mass-producing a single and an array of nanopores on a thick (2 mu m) silicon device layer based on a silicon-on-insulator (SOI) wafer. A method of temporal voltage variation is exploited to optimize the etching parameters for the nanopore formation during electrochemical breakdown etching, diameters of nanopores around 12 nm have been achieved. Besides, the correlation between the parameters of etching and nanopore diameter is deduced. The processed high-aspect-ratio nanopore enables applications in single-molecule sensing such as DNA, exosomes, viruses, and protein markers. The developed process is inexpensive, fast and can be batch fabricated.
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| 5. |
- Gatty, Hithesh K., et al.
(författare)
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Wafer-level fabrication of individual solid-state nanopores for sensing single DNAs
- 2020
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 31:35
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Tidskriftsartikel (refereegranskat)abstract
- For biomolecule sensing purposes a solid-state nanopore platform based on silicon has certain advantages as compared to nanopores on other substrates such as graphene, silicon nitride, silicon oxide etc Capitalizing on the developed CMOS technology, nanopores on silicon are scalable without any requirement for additional processing, the devices are low cost and the process can be repeatable with a high yield. One of the essential requirements in biomolecule sensing is the ability of the nanopore to interact with the analyte. In this work, we present a method for processing high aspect ratio, single nanopores in the range of 10-30 nm in diameter and approximately 700 nm in length on a silicon-on-insulator (SOI) wafer. The presented method of manufacturing the high aspect ratio individual nanopores combines optical lithography and anisotropic KOH etching with a final electrochemical etching step to form the nanopores and is repeatable and can be processed in batches. We demonstrate electrical detection of dsDNA translocation, where the characteristic time of the process is in the millisecond range. We also analyse the translocation parameters and correlate the enhanced length of the nanopore to a longer translocation time as compared to other substrates.
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| 6. |
- Sychugov, Ilya, et al.
(författare)
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Non-stationary analysis of molecule capture and translocation in nanopore arrays
- 2019
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 150:8
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Tidskriftsartikel (refereegranskat)abstract
- Analytical formulas for the ON- and OFF-time distributions as well as for the autocorrelation function were derived for the case of single molecule translocation through nanopore arrays. The obtained time-dependent expressions describe very well experimentally recorded statistics of DNA translocations through an array of solid state nanopores, which allows us to extract molecule and system related physical parameters from the experimental traces. The necessity of non-stationary analysis as opposite to the steady-state approximation has been vindicated for the molecule capture process, where different time-dependent regimes were identified. A long tail in the distribution of translocation times has been rationalized invoking Markov jumps, where a possible sequential ordering of events was elucidated through autocorrelation function analysis.
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| 7. |
- Yue, Weipeng, et al.
(författare)
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Picea schrenkiana tree ring blue intensity reveal recent glacier mass loss in High Mountain Asia is unprecedented within the last four centuries
- 2023
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Ingår i: Global and Planetary Change. - 0921-8181. ; 228
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Tidskriftsartikel (refereegranskat)abstract
- Studies on long-term fluctuations in glacier volume and mass are crucial for understanding past climate change. In this paper, we utilized Picea schrenkiana to develop a 525-year chronology of latewood blue intensity (LWBI) in the Tianshan Mountains. Relying on temperature as the main controlling factor for tree growth and glacier mass balance (GMB) variations, the LWBI chronology was used to reconstruct the summer temperature (JJA, R2adj = 47%) and the annual glacier mass balance (annual GMB, R2adj = 39%) in the Tianshan Mountains over the past 400 years. The reconstruction results show that the rapid warming since 1974 has caused the Tianshan No.1 glacier (TS No.1) to experience an unprecedented melting trend within the last four centuries. It is disturbing that the glacier still remain in an ablation state for the next 80 years under both representative concentration paths (RCP) 4.5 and 8.5 scenarios, which will exacerbate the adverse environmental impacts of glacial hazards. Our study provides a continuous record for glacier research in high mountains Asian and contributes to a more detailed assessment of glacier and climate change in this region.
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| 8. |
- Zhang, Miao, 1985-
(författare)
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Silicon Nanopore Arrays : Fabrication and Applications for DNA Sensing
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanopore biomolecule sensing and sequencing has emerged as a simple but powerful tool for single molecule studies over the past two decades. By elec- trophoretically driving single molecules through a nanometer-sized pore, often sitting in an insulating membrane that separates two buffer solutions, ionic current blockades can be detected to reveal rich information of the molecules, such as DNA length, protein size and conformation, even nucleic acid se- quence. Biological protein pores, as well as solid-state nanopores have been used, but both suffer from relatively low throughput due to the lack of abil- ity to scale up to a large array. In this thesis, we tackled the throughput issue from the fabrication aspect as well as from the detection aspect, aim- ing at a parallel optical single molecule sensing on an array of well-separated nanopores.From the fabrication aspect, several lithography-based self-regulating meth- ods were tested to obtain nanopore arrays in silicon membranes, including anisotropic KOH etching, thermal oxidation-induced pore shrinkage, metal- assisted etching and electrochemical etching. Among those, the most success- ful method was the electrochemical etching of silicon. By electron-beam or photo lithography, the positions of the pores were defined on a silicon mem- brane. Followed by anisotropic KOH etching, inverted pyramids were formed as etching pits. The nanopores were then formed by anodic etching of silicon in HF. Using this concept, the size of the pores does not depend on the lithog- raphy step; only the positions of pores were defined by lithography. In this way, an array of ∼ 900 pores with an average entrance diameter of 18 ± 4 nm was fabricated on a 120 μm × 120 μm membrane.From the detection aspect, parallel readout of fluorescence signals from the labelled DNA molecules while translocating through an array of nanopores was performed using a wide-field microscope with a relatively fast CMOS camera recording at 1 KHz frame rate. Statistics of duration and frequency of the translocation events were extracted and studied. It was found that the event duration decreases with rising excitation laser power. This can be attributed to a laser-induced heating effect. Simulation suggested that a sig- nificant thermal gradient was generated at the pore vicinity by the excitation laser due to photon absorption by the silicon membrane. Such temperature rise affects all mass transport in a solution via a viscosity change. The ther- mal effect has also been proven by that conductance of an array of nanopores scales with the laser power. The thermal effect on the translocation frequency has been studied systematically as well. Due to thermophoresis of DNA in a thermal gradient, the thermophoretic force serves as a repulsion force, op- posing the electrophoretic force at the pore vicinity, depleting molecules away from the pore. Because of the molecule-size-dependent thermal depletion, a size-dependent translocation frequency was observed. This can be potentially used for a high throughput molecule sorting by adjusting the balance between the thermophoretic force and the electrophoretic force.
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| 9. |
- Zhao, Yadong, 1985-, et al.
(författare)
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Cellulose nanofibrils-stabilized food-grade Pickering emulsions : Clarifying surface charge's contribution and advancing stabilization mechanism understanding
- 2024
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 152
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Tidskriftsartikel (refereegranskat)abstract
- Pickering emulsions stabilized by cellulose nanofibrils (CN) have sparked significant attention, however the fundamental mechanisms underpinning the stabilization process remain insufficiently elucidated. Focusing on an academic debate of surface charge's contribution to stabilization, this study first explored how the varying carboxyl group contents of TEMPO-oxidized CN (TCNs) impacted Pickering emulsions' formation and stability. TCNs with 662 μmol/g carboxyl groups exhibited distinctive attributes, including larger particle sizes (322 nm in length), improved thermal stability (maximum decomposition temperature of 317 °C), and increased viscosity (1.57 Paִִ⋅s) compared to their counterparts with 963–1011 μmol/g charge density. Notably, the former one, with a larger three-phase contact angle (51.5°), higher interfacial tension, and greater detachment energy (21.69 × 10−18 J), resulted in a homogeneous dispersion of spherical oil droplets and super-stable Pickering emulsions with a consistent emulsifying index of 100% over 30 days. These findings clearly clarified that TCNs with a lower charge density exhibit superior emulsifying properties. In addition, for the first time, a distinct oil droplet-decorated fibrillar structure was observed, probably suggesting that TCNs might be able to serve as anchoring matrixes to guide the distribution of oil droplets. These structures seemed to impeded the migration and accumulation of the oil droplets, consequently enhancing the stability of the resulting Pickering emulsions. To sum, this study clearly elucidated the role of surface charge in stabilizing cellulose-based Pickering emulsions and proposed a new model to expound the cellulose-oil interaction mechanisms, thus providing new theoretical and practical insights on utilization of CN as highly effective emulsifier for super-stable food-grade Pickering emulsions.
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| 10. |
- Zhao, Yadong, 1985-, et al.
(författare)
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Enhancement of surimi gel properties through the synergetic effect of fucoidan and oligochitosan
- 2023
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 140
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, two common marine-derived dietary fibres (MDFs), fucoidan (FU) and oligochitosan (OCS), were introduced as textural and nutritional enhancers in hairtail surimi gels. The MDFs could assist with inhabiting the endogenous proteolytic enzyme activity, unfolding the myosin to expose more reactive domains, inducing favorable protein conformational transition, and thus, promoting gelation. The highly hydrophilic MDFs rich in -OH groups can bind water molecules via strong hydrogen bonds, facilitating water redistribution within the gel network. Driven by the enhanced chemical forces, a stable protein-FU-OCS gel is obtained, which improves the hardness by almost 100% and the water holding capacity from 86.25% to 92.25%. Collectively, this study demonstrates that MDFs are a group of effective additives to improve gel characteristics and nutritional profiles of surimi-based seafood products. The proposed MDF-protein interaction model would guide the application of MDFs as novel additives in the food industry.
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