Trapping of micro- and nano-objects in solution is of great scientific interest in various fields. One method of trapping and detecting objects smaller than 100 nm is the combination of ...geometry-induced electrostatic (GIE) trapping devices and interferometric scattering detection (iSCAT). In GIE trapping, charged nano-objects are confined in a nanofluidic system that hosts topographically modified surfaces, resulting in electrostatic potential wells. We observe optical limits of detecting gold nanoparticles smaller than 60 nm because of the high reflection of the strong background signal in current silicon-based GIE trapping chips. The high reflection rapidly leads to overexposure of the camera detector and thus limits the incident laser power. In this work, we introduce new functional geometry-induced electrostatic devices fabricated from glass substrates. Due to the reduced reflection at the water-glass interface compared to the silicon-based devices, higher incident laser power can be used to image the nano-objects resulting in higher contrast as well as signal-to-noise ratios (SNR) of the gold nanoparticles. Using glass-based GIE trapping devices, significant SNR increases are achieved in comparison to that of silicon-based devices. These improvements enable the detection of much smaller nanoparticles and thereby studies on their trapping, as well as further investigation in nanofluidic systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this article, an artificial neural network (ANN)-based large-signal model (LSM) of AlGaN/GaN high electron mobility transistors (HEMTs) with accurate buffer-related trapping effects ...characterization and modeling is proposed. A hybrid small-signal parameter-extraction method for AlGaN/GaN HEMTs is used to acquire the parasitic parameters. To simplify the modeling procedure of the drain-source current <inline-formula> <tex-math notation="LaTeX">I_{\mathrm{ ds}} </tex-math></inline-formula>, an ANN-based model associated with the empirical equations taking into account the trapping effects, self-heating effects, and breakdown issue is developed. The low-frequency dispersions related to the buffer-related trapping effects have been well modeled by using a new empirical equation, which has been verified by small-signal S-parameters. Also, a new thermal factor <inline-formula> <tex-math notation="LaTeX">K_{T} </tex-math></inline-formula> and an improved Shockley diode equation are given in the proposed model as well. The developed LSM has been fully verified by a <inline-formula> <tex-math notation="LaTeX">2\times 100\,\,\mu \text{m} </tex-math></inline-formula> AlGaN/GaN HEMT with the pulsed I-V, small-signal S-parameters, power sweep, and load-pull measurements.
While the use of silicon‐based electrodes can increase the capacity of Li‐ion batteries considerably, their application is associated with significant capacity losses. In this work, the influences of ...solid electrolyte interphase (SEI) formation, volume expansion, and lithium trapping are evaluated for two different electrochemical cycling schemes using lithium‐metal half‐cells containing silicon nanoparticle–based composite electrodes. Lithium trapping, caused by incomplete delithiation, is demonstrated to be the main reason for the capacity loss while SEI formation and dissolution affect the accumulated capacity loss due to a decreased coulombic efficiency. The capacity losses can be explained by the increasing lithium concentration in the electrode causing a decreasing lithiation potential and the lithiation cut‐off limit being reached faster. A lithium‐to‐silicon atomic ratio of 3.28 is found for a silicon electrode after 650 cycles using 1200 mAhg−1 capacity limited cycling. The results further show that the lithiation step is the capacity‐limiting step and that the capacity losses can be minimized by increasing the efficiency of the delithiation step via the inclusion of constant voltage delithiation steps. Lithium trapping due to incomplete delithiation consequently constitutes a very important capacity loss phenomenon for silicon composite electrodes.
Lithium trapping, caused by incomplete delithiation, is identified as the main reason for the capacity loss for silicon‐based half‐cell batteries. While limited capacity cycling can extend the cycle life, the silicon is continuously filled with lithium up to a point when the trapped lithium prevents new lithium from being deposited. The latter yields a rapid capacity decay.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Particle trapping and enrichment into confined volumes can be useful in particle processing and analysis. This review is an evaluation of the methods used to trap and enrich particles into ...constrained volumes in microfluidic and nanofluidic systems. These methods include physical, optical, electrical, magnetic, acoustic, and some hybrid techniques, all capable of locally enhancing nano- and microparticle concentrations on a microscale. Some key qualitative and quantitative comparison points are also explored, illustrating the specific applicability and challenges of each method. A few applications of these types of particle trapping are also discussed, including enhancing biological and chemical sensors, particle washing techniques, and fluid medium exchange systems.
Abstract
In some waveguides, mutually opposing power flows are formed in the core and cladding. They give rise to forward and backward modes whose degeneracy results in the light-trapping mode. When ...the guiding modes become lossy, this mode degeneracy or formation of the light-trapping mode is forbidden if the loss is described as spatial attenuation but is allowed if the loss is described as temporal decay. We show that this is because the guiding modes have only one temporal direction of decay (only forward), while they have two spatial directions of attenuation (both forward and backward).
As a promising sustainable power source for intelligent electronics, triboelectric nanogenerator (TENG) has attracted remarkable attention and various strategies have been sought to improve its ...output performance. However, most of these approaches for triboelectric materials optimization only focus on either chemical composition modulation or surface microstructure fabrication. In this work, both aspects are considered and an effective strategy is proposed to construct high performance TENGs based on polyvinylidene fluoride (PVDF) via graphene nanosheets incorporation in conjunction with electrospinning technology. Hence, a 20 × 20 mm2 TENG comprising of PVDF/G nanofibers and polyamide-6 (PA6) films demonstrates superior triboelectric performance with an output voltage of ~1511 V, a short-circuit current density of ~189 mA m−2, and a maximum peak power density of ~130.2 W m−2, nearly eight times higher than that of the PVDF-PA6 TENG. Additionally, under impedance matching condition, the PVDF/G-PA6 TENG can harvest ~74.13 μJ energy per cycle, with a time-averaged output power density of 926.65 mW m−2. Detail investigation reveals that both composition modulation with graphene and nanofiber structure fabricated through electrospinning contribute to the triboelectric performance enhancement of PVDF/G NF films. This work provides an effective strategy of simultaneously optimizing the chemical composition and surface microstructure of triboelectric materials to significantly improve the output performance of TENGs, and to further promote the widespread application of TENGs.
Polyvinylidene fluoride (PVDF)-graphene nanosheet composite nanofibers with much enhanced triboelectric property and charge trapping capability are promising triboelectric materials for fabricating high performance TENGs. The PVDF/G NF-PA6 TENG demonstrated superior triboelectric output with a peak output voltage of ~1511 V, a short-circuit current density of 189 mA m−2, and a maximum peak power density of ~130.2 W m−2, nearly eight times higher than that of the PVDF-PA6 TENG. This work provides an effective strategy of simultaneously optimizing the chemical composition and surface microstructure of triboelectric materials to significantly improve the output performance of TENGs, and to further promote the widespread application of TENGs. Display omitted
•An effective strategy that simultaneously optimizes the chemical composition and surface microstructure of triboelectric materials is proposed to fabricate high performance TENGs.•Flat PVDF/G films and PVDF/G nanofibers have been prepared and investigated as negative triboelectric materials for the first time.•The PVDF/G nanofibers based PVDF/G NF-PA6 TENGs demonstrate much enhanced triboelectric performance and superior stability, achieving a maximum output power density of ~130.2 W m−2.•Both graphene nanosheets addition and micro/nanostructure construction enhance the triboelectric property of PVDF/G composite nanofiber and make it to be a promising negative triboelectric material for energy harvesting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Much of the functionality of multicellular systems arises from the spatial organization and dynamic behaviours within and between cells. Current single-cell genomic methods only provide a ...transcriptional 'snapshot' of individual cells. The real-time analysis and perturbation of living cells would generate a step change in single-cell analysis. Here we describe minimally invasive nanotweezers that can be spatially controlled to extract samples from living cells with single-molecule precision. They consist of two closely spaced electrodes with gaps as small as 10-20 nm, which can be used for the dielectrophoretic trapping of DNA and proteins. Aside from trapping single molecules, we also extract nucleic acids for gene expression analysis from living cells without affecting their viability. Finally, we report on the trapping and extraction of a single mitochondrion. This work bridges the gap between single-molecule/organelle manipulation and cell biology and can ultimately enable a better understanding of living cells.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We investigate the origin of the hysteresis observed in the transfer characteristics of back-gated field-effect transistors with an exfoliated MoS2 channel. We find that the hysteresis is strongly ...enhanced by increasing either gate voltage, pressure, temperature or light intensity. Our measurements reveal a step-like behavior of the hysteresis around room temperature, which we explain as water-facilitated charge trapping at the MoS2/SiO2 interface. We conclude that intrinsic defects in MoS2, such as S vacancies, which result in effective positive charge trapping, play an important role, besides H2O and O2 adsorbates on the unpassivated device surface. We show that the bistability associated to the hysteresis can be exploited in memory devices.
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•A CTAB-assisted polyol method was designed to fabricate BiVO4/BiOBr composites.•BiVO4/BiOBr composite exhibited enhanced photocatalytic activity under visible light irradiation.•The ...formation of p-n junction promoted the separation and migration of photo-generated carriers.•The mechanism of the photo-degradation process was proposed.
BiVO4/BiOBr composites with enhanced photocatalytic activity were fabricated by a CTAB-assisted polyol method through a coprecipitation process. The photocatalytic activities of as-prepared samples were evaluated by the degradation of Rhodamine B under irradiation of 500 W xenon lamp. The highest degradation efficiency could reach 94.4% in 90 min when the molar ratio of V to Br was 1:1, and the apparent degradation rate constant was 0.02998 min−1, which was 54.5 and 2.9 times higher than that of the pure BiVO4 and BiOBr, respectively. The combination of BiVO4 and BiOBr could increase the migration efficiency and inhibit the recombination of photo-generated electron-hole pairs indicated by electrochemical and photoluminescence analysis. Confirmed by the radical trapping experiments, holes (h+) and superoxide radicals (O2−) were the main active species for the degradation of RhB. It was supposed that n-type BiVO4 and p-type BiOBr could form p-n junction at their interface, promoting the transfer of photo-induced carriers by internal electric field. Furthermore, BiVO4/BiOBr composites showed stable photocatalytic performance and structural stability after 7 consecutive recycles for the photo-degradation of RhB.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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