On-off Characteristics Research Articles

Approaching Tryptophan-Derived Polynorbornene Fluorescent Chemosensors: Synthesis, Characterization, and Sensing Ability for Biomedical Applications as Biomarkers for Detecting Fe2+ Ions.

We present a novel group of tryptophan (Trp)-based fluorescent polymeric probes synthesized via ring-opening metathesis polymerization (ROMP) of Trp-derived norbornene monomers. These probes, in mono- and disubstituted forms, incorporate amide and ester anchoring groups. The quantity of Trp substituents did not affect fluorescence selectivity but influenced quenching percentage. Poly-diamide-Trp, Poly-monoamide-Trp, Poly-diester-Trp, and Poly-monoester-Trp probes displayed selective detection of Fe2+ and Fe3+ ions with fluorescence on-off characteristics. Poly-diamide-Trp and Poly-monoamide-Trp exhibited a limit of detection (LOD) for Fe2+ and Fe3+ ions of 0.86-11.32 μM, while Poly-diester-Trp and Poly-monoester-Trp showed higher LODs (21.8-108.7 μM). These probes exhibited high selectivity over Fe2+, a crucial metal ion in the body known for its redox properties causing oxidative stress and cell damage. Cell cytotoxicity tests in various cell types confirmed biocompatibility. Additionally, Poly-diamide-Trp displayed excellent cell permeability and iron ion detection in EA.hy926 cells, suggesting potential for bioimaging and clinical applications.

High-Performance Flexible Broadband Photoelectrochemical Photodetector Based on Molybdenum Telluride.

Flexible broadband photodetectors are desired but challenging to be fabricated for next-generation wearable intelligent optoelectronic devices. Considering the narrow bandgap and strong light absorption, molybdenum telluride (MoTe2) based photoelectrochemical photodetectors are successfully assembled by liquid phase exfoliation accompanied with the electrophoretic deposited method. This MoTe2-based photodetector shows a broadband detection in ultraviolet-near-infrared band, long-term stability within 18000s, and fast response in millisecond-level (response time≈19ms, recovery time≈26ms). More importantly, even though the MoTe2 photodetector is bent and twisted at a high degree for several hundred times, it still shows excellent flexibility with stable on-off switching characteristics. Additionally, this photodetector displays a good response for rotation angles in the range from 0° to 360°, and the extracted Iph maintain almost the same value approximately 0.97µAcm-2, suggesting an omnidirectional detection capability. This work demonstrates the proposed flexible photoanode shows a great potential in future broadband omnidirectional detection systems.

Suppression of crosstalk in row–column actuator array using regulation of ferroelectric polarization

This article presents a method for suppressing electrical crosstalk in a ferroelectric row-column (RC) actuator array. In high-density two-dimensional (2D) arrays, the RC addressing scheme has advantages over the conventional method of fully addressing the array, primarily due to its requirement for fewer interconnections to drive the elements. However, electrical crosstalk is an undesirable side effect that restricts the practical use of RC arrays for sensing and actuation. To mitigate this crosstalk between elements and allow activation of the target element, an addressing method using orthogonal biasing is investigated for the RC array. Due to the voltage-dependent polarization state of the ferroelectric film, each element exhibits bias-sensitive activity. Applying a coercive voltage bias to the electrically coupled elements via row electrodes to minimize the net polarization and piezoelectric activity reduces electrical crosstalk, leaving only acoustic crosstalk in the array. The method using coercive voltage bias reduces crosstalk between the elements by 6.25 dB compared to the conventional method. Furthermore, applying a negative bias of 7 V to the target element enhances its activity and increases its dynamic displacement by 33%, thus alleviating the crosstalk by 7.25 dB. The on-off switching characteristics of the biasing method are examined to investigate the feasibility of adopting such biasing in area scanning techniques for potential applications, such as ultrasonic imaging. By adjusting the magnitude of the DC bias, on-off switching operation is demonstrated at 5 kHz while achieving a 3 dB on-off ratio.

Nanoantennas for selectively switching on and off under different input phase distributions and wavelengths

Optical nanoantennas, as devices connecting free-space light and on-chip light, are important components of integrated photonic circuits. They are often used as optical couplers, and in optical routine of intermediate layers of IC chips. To have more degrees of freedom to manipulate the light scattering, we design a novel optical nanoantenna composed of subwavelength silicon pillars. The antenna can exhibit on and off scattering states under different input optical modes and exhibit opposite on-off characteristics at different wavelengths. The antenna is small in size and flexible in design, and has the potential to build a more flexible 3D optical link for photonic integrated circuits.

Flexible bidirectional self-powered photodetector with significantly reduced volume and accelerated response speed based on hydrogel and lift-off GaN-based nanowires

Due to the wide range of potential applications for next-generation multi-functional devices, the flexible self-powered photodetector (PD) with polarity-switchable behavior is essential but very challenging to be realized. Herein, a wearable bidirectional self-powered PD based on detached (Al,Ga)N and (In,Ga)N nanowires has been proposed and demonstrated successfully. Arising from the photovoltage-competing dynamics across (Al,Ga)N and (In,Ga)N nanowire photoelectrodes, such PD can generate the positive (33.3 mA W−1) and negative (-0.019 mA W−1) photo-responsivity under ultraviolet (UV) and visible illumination, respectively, leading to the bidirectional photocurrent behavior. Thanks to the introduction of quasi solid-state hydrogel, the PD can work without the liquid-electrolyte, thus remarkably reducing the volume from about 482 cm3 to only 0.18 cm3. Furthermore, the use of hydrogel is found to enhance response speed in the UV range by reducing the response time for more than 95%, which is mainly attributed to the increased open circuit potential and reduced ion transport distance. As the GaN connecting segment is pretty thin, the piezoelectric charges generated by stress are proposed to have only a limited effect on the photocurrent density. Therefore, both the stable on-off switching characteristics and photocurrent densities can still be achieved after being bent 400 times. With an excellent flexibility, this work creates opportunities for technological applications of bidirectional photocurrent PDs in flexible optoelectronic devices, e.g., wearable intelligent sensors.

Flexible Single-Chain-Heteropolymer-Derived Transmembrane Ion Channels with High K+ Selectivity and Tunable pH-Gated Characteristics.

A series of single-chain random heteropolymer (RHP)-derived artificial ion channels with both high K+ selectivity and controllable pH-gated behaviors were fabricated by a facile "one-pot" polymerization method. The benzo-18-crown-6 moieties appended on lateral chains of RHPs can form ion-permeable nanopores and transport K+ over Na+ through the lipid bilayers. The ion permeation selectivity was significantly enhanced by incorporating a cholesterol group to serve as a membrane anchor. Interestingly, similar to natural gated protein channels, on-off switchable characteristics were also realized by integrating an additional acid-sensitive alkylamine group into the RHP-derived channel. The unique design strategies have endowed the RHP-derived ion channels with facile synthetic procedures, desirable membrane compatibility, high K+ selectivity, and tunable pH-gated properties. This work provides an entry point for future design of novel functional nanochannels.

Multi-stimuli-responsive fluorescence switching from a novel organic polymorphic benzoimido-benzamide derivative

A novel organic polymorphic luminogen, (Z)-N-((benzoylimino) (4-(diphenylamino)phenyl)methyl)-N-(4-fluorophenyl)benzamide (DPA-PYZ-F), has been designed and synthesized successfully by a green photo-oxidation reaction. Two polymorphs (FB and FG) based on DPA-PYZ-F with different conformations display blue and green fluorescence, respectively. The emission of the newly obtained polymorphic molecule can be switched through the response to a mechanical force, thermal stimulus and protonic acid. The photophysical property tests and single crystal structural analysis disclosed that the mechanical force stimuli-responsive behavior of the FB and FG samples originate from the change of molecular arrangement. More significantly, FT-IR spectroscopy confirmed that the conformation transition from the FG to the FB could be achieved by thermal stimulus at 430 K. Additionally, protonation−deprotonation of the benzoylimino moieties in DPA-PYZ-F induced a remarkable fluorescence on-off characteristics upon protonic acid and thermal stimulus. The multi-stimuli response performance endows the new kind of molecule with the potential as a candidate for applications in mechanical force, thermal and protonic acid sensing.

Momentum relaxation effects in 2D-Xene field effect device structures

We analyze the electric field driven topological field effect transition on 2D-xene materials with the addition of momentum relaxation effects, in order to account for dephasing processes. The topological field effect transition between the quantum spin Hall phase and the quantum valley Hall phase is analyzed in detail using the Keldysh non-equilibrium Green’s function technique with the inclusion of momentum and phase relaxation, within the self-consistent Born approximation. Details of the transition with applied electric field are elucidated for the ON–OFF characteristics with emphasis on the transport properties along with the tomography of the current carrying edge states. We note that for moderate momentum relaxation, the current carrying quantum spin Hall edge states are still pristine and show moderate decay with propagation. To facilitate our analysis, we introduce two metrics in our calculations, the coherent transmission and the effective transmission. In elucidating the physics clearly, we show that the effective transmission, which is derived rigorously from the quantum mechanical current operator is indeed the right quantity to analyze topological stability against dephasing. Exploring further, we show that the insulating quantum valley Hall phase, as a result of dephasing carries band-tails which potentially activates parasitic OFF currents, thereby degrading the ON–OFF ratios. Our analysis sets the stage for realistic modeling of topological field effect devices for various applications, with the inclusion of scattering effects and analyzing their role in the optimization of the device performance.

Long-Time Memory and Ternary Logic Gate Using a Multistable Cavity Magnonic System.

Multistability is an extraordinary nonlinear property of dynamical systems and can be explored to implement memory and switches. Here we experimentally realize the tristability in a three-mode cavity magnonic system with Kerr nonlinearity. The three stable states in the tristable region correspond to the stable solutions of the frequency shift of the cavity magnon polariton under specific driving conditions. We find that the system staying in which stable state depends on the history experienced by the system, and this state can be harnessed to store the history information. In our experiment, the memory time can reach as long as 5.11s. Moreover, we demonstrate the ternary logic gate with good on-off characteristics using this multistable hybrid system. Our new findings pave a way towards cavity magnonics-based information storage and processing.

A turn-on fluorescent ion-imprinted polymer for selective and reliable optosensing of lead in real water samples

A new fluorescent Pb(II) imprinted polymer (Pb(II)–IIP) was synthesized for the selective detection of this contaminant in natural water. To play the sensing role, a fluorescent probe specific to Pb(II), based on anthracene coupled to 5-amino-8-hydroxyquinoline and a styrene moiety, was used as a functional monomer. It was associated with ethylene glycol dimethacrylate as cross-linker (EGDMA) to prepare microbeads of IIP and NIP (corresponding non-imprinted polymer) via precipitation polymerisation in DMSO-2-methoxyethanol (1:1, v/v) mixture. Solid-state 13C NMR spectroscopy was used to analyse the structure of the polymers and attest the integration of the fluorescent monomer in the polymer matrix. The morphology of the prepared materials was analysed by scanning electron microscopy and nitrogen adsorption/desorption. Results showed high mesoporous materials with important surface areas of 346 and 232 m2·g−1 for IIP and NIP, respectively. Polymers fluorescence properties revealed that the obtained IIP showed remarkably selective fluorescent on-off characteristics towards Pb(II) compared to NIP, emphasizing an imprinting effect. IIP fluorescent calibration curve exhibited a linear range from 7.1–60 μg·L−1 in pure water with a low limit of detection of 2.1 μg·L−1. The synthesized IIP was successfully applied to the determination of Pb(II) in tap water, mineral water and seawater samples.

Percolation-Limited Dual Charge Transport in Vertical p-n Heterojunction Schottky Barrier Transistors.

Solution-processed, high-speed, and polarity-selective organic vertical Schottky barrier (SB) transistors and logic gates are presented. The organic layer, which is a bulk heterojunction (BHJ) composed of PBDB-T and PC71BM, is employed to simultaneously realize vertical electron and hole transports through the separate p-channel and n-channel. The gate-modulated graphene work functions enable broad modulation of SB heights at both the graphene-PBDB-T and graphene-PC71BM heterointerfaces. Interestingly, the fine-tuned energy-level alignment enables an exclusive injection of holes or electrons unlike conventional BHJ-based ambipolar transistors, leading to a clear transition between p-channel and n-channel single-carrier-like transistor characteristics. Furthermore, the improved percolation-limited dual charge transport in vertical architecture results in high charge carrier density and high-speed on-off switching characteristics, providing a high on-off current ratio exceeding 105 and an operation speed of 100 kHz. Solution-based on-substrate fabrications of low-power complementary logic gates such as NOT, NOR, and NAND are also successfully performed.

Insight into (alkyl)methacrylate-based copolymer/sepiolite nanocomposite cryogels containing amino and sulfonic acid groups: Optimization of network properties and elasticity via cryogelation process

(Alkyl)methacrylate-based copolymer/sepiolite nanocomposite gels containing amino and sulfonic acid groups have been prepared via (cryo) gelation of N,N-dimethylaminoethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-propanosulfonic acid (AMPS) in the presence of fibrous clay mineral sepiolite (SEP). The morphology, thermal stability, compression performance, and swelling behavior of nanocomposite gels were systematically studied with various SEP contents. X-ray diffractometry results indicated that SEP had been participated in (cryo)gelation, and the resulting thermal stability and surface morphology were improved by the addition of inorganic clay SEP. Owing to dispersion of SEP, the prepared nanocomposite cryogels exhibited dramatic improvements on their elasticity while low water absorption capacity was maintained. The presence of low amount of SEP significantly enhanced the mechanical strength and the cross-link density of DMAEMA-based nanocomposite gels due to its fibrous morphology and crystalline structure acting as cross-links. Addition of 0.4% (w/v) SEP led to five-fold increase in the compressive modulus of nanocomposite cryogels. As SEP concentration in the feed was increased from 0 to 2.40% (w/v), the effective cross-link density in the nanocomposite matrix increased continuously from 2.84 to 22.9 × 103 mol/m3. The prepared nanocomposite gels showed enhanced swelling response and on-off switching characteristics in aqueous KBr solutions. The parameters of equilibrium swelling, initial swelling rate, diffusional exponent, and diffusion coefficient were evaluated and the swelling kinetics of the nanocomposite gels in aqueous KBr solution followed the pseudo second order model. Since DMAEMA and inorganic clay SEP were effectively combined in a nanocomposite network, the obtained results would expand the range of responsive properties and related industrial applications available to DMAEMA and SEP individually.

P(VDF-TrFE-CFE)를 이용한 초소형 압전 적층형 진동 출력 소자의 제작

P(VDF-TrFE-CFE) (Poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), which exhibits a high electrostriction of about 7%, can transmit tactile output as vibration or displacement. In this study, we investigated the applicability of P(VDF-TrFE-CFE) to wearable piezoelectric actuators. The P(VDF-TrFE-CFE) layers were deposited through spin-coating, and interspaced with patterned Ag electrodes to fabricate a two-layer 3.5 mm × 3.5 mm device. This layered structure was designed and fabricated to increase the output and displacement of the actuator at low driving voltages. In addition, a laser vibrometer and piezoelectric force microscope were used to analyze the device’s vibration characteristics over the range of ~200~4,200 Hz. The on-off characteristics were confirmed at a frequency of 40 Hz.

Design and molecular dynamics of multifunctional sulfonated poly(dimethylaminoethyl methacrylate)/mica hybrid cryogels through freezing-induced gelation.

This article addresses various strategies that have been explored to design sulfonated poly(dimethylaminoethyl methacrylate)/mica hybrid-gels with optimized network parameters and mechanical/swelling properties. A series of hybrid cryogels and hydrogels containing amino and sulfonic acid groups were prepared from N,N-dimethylaminoethyl methacrylate (DMAEMA) and 2-acrylamido-2-methyl-1-propane sulfonic acid in the presence of inorganic additive mica via a cryogelation process and conventional in situ copolymerization. Cryogelation was used to fine-tune the mechanical properties of the PDMAEMA-based hybrid gels. The effects of pH, temperature and mica content on the network parameters, mechanical properties and swelling behavior were discussed. X-ray diffractometry and Fourier transform infrared spectroscopy confirmed that mica particles had participated in (cryo)polymerization, and the thermal stability and surface morphologies were improved by the addition of mica. The profile of water loss, decomposition of amine groups and breakdown of PDMAEMA chains of the resulting hybrid gels were determined by thermogravimetric analysis. A critical mica concentration was found for the hybrid hydrogels where the degree of swelling attains a maximum value. Below 0.50% (w/v) of mica, the ionic nature of mica dominates its crosslinker effect. The hybrid cryogels were tough and able to recover at room temperature after compression testing. The prepared hybrid-gels showed an enhanced swelling response and on-off switching swelling characteristics in water and in aqueous NaCl solutions. The parameters of equilibrium swelling, the initial swelling rate, the diffusional exponent, and the diffusion coefficient were evaluated and the swelling kinetics of the hybrid hydrogels and cryogels in water followed the pseudo second order model. All the prepared hybrid hydrogel and cryogel materials with tunable mechanical stability and elasticity can be excellent candidates for designing smart materials.

Switching Control Strategy for Greenhouse Temperature-Humidity System Based on Prediction Modeling: A Simulation Study

It is difficult to achieve coordination control of multiple facilities that are driven by on-off actuators in a greenhouse, especially when there is more than one indoor environmental factor to consider at the same time. With the consideration of indoor air temperature and relative humidity, we propose a switching control strategy based on prediction modeling. The operation of the greenhouse system was divided into several modes according to the on-off control characteristics of the available facilities. Then, a switching diagram was designed according to the relationship between the indoor air temperature and humidity and their setting ranges. When the two indoor environmental factors reach their upper or lower limits, IARX models are used to predict them over a specified horizon for each optional mode respectively. Mode switching is carried out based on prediction results. The switching control strategy was simulated based on a mechanistic model of the greenhouse microclimate. The results show that the facilities can be coordinated very well by the proposed control strategy and it is easy to implement. The control strategy is still applicative when more facilities or more indoor environmental factors need to be taken into account.

Designing 4H-SiC P-shielding trench gate MOSFET to optimize on-off electrical characteristics

In order to enhance specific on-resistance (Ron,sp), the trench gate structure was also introduced into 4H-SiC MOSFET as Si MOSFET. But the 4H-SiC trench gate has worse off-state characteristics than the Si trench gate due to the incomplete gate oxidation process (Šimonka et al., 2017). In order to overcome this problem, P-shielding trench gate MOSFET (TMOS) was proposed and researched in previous studies. But P-shielding has to be designed with minimum design rule in order to protect gate oxide effectively. P-shielding TMOS also has the drawback of on-state characteristics degradation corresponding to off state improvement for minimum design rule. Therefore optimized design is needed to satisfy both on and off characteristics.In this paper, the design parameters were analyzed and optimized so that the 4H-SiC P-shielding TMOS satisfies both on and off characteristics. Design limitations were proposed such that P-shielding is able to defend the gate oxide.The P-shielding layer should have the proper junction depth and concentration to defend the electric field to gate oxide during the off-state. However, overmuch P-shielding junction depth disturbs the on-state current flow, a problem which can be solved by increasing the trench depth. As trench depth increases, however, the breakdown voltage decreases. Therefore, trench depth should be designed with due consideration for on-off characteristics. For this, design conditions and modeling were proposed which allow P-shielding to operate without degradation of on-state characteristics.Based on this proposed model, the 1200 V 4H-SiC P-shielding trench gate MOSFET was designed and optimized.

Efficient Defect Engineering for Solution Combustion Processed In-Zn-O thin films for high performance transistors

The oxygen related defects in the solution combustion-processed InZnO vitally affect the field-effect mobility and on-off characteristics in thin film transistors (TFTs). We use photoelectron spectroscopy to reveal that these defects can be well controlled by adjusting the atmosphere and flow rate during the combustion reaction, but are hardly affected by further post-annealing after the reaction. In device performance, the threshold voltage of the InZnO-TFTs was regulated in a wide range from 3.5 V to 11.0 V. To compromise the high field-effect mobility and good subthreshold properties, we fabricate the TFTs with double active layers of InZnO to achieve vertical gradience in defect distribution. The resulting TFT exhibits much higher field-effect mobility as 17.5 cm2 · V−1 · s−1, a low reversed sub-threshold slope as 0.35 V/decade, and a high on-off ratio as 107. The presented understandings and methods on defect engineering are efficient in improving the device performance of TFTs made from the combustion reaction process.

Energy/Quality-of-Experience TradeOff of Power Saving Modes for Voice Over IP Services

Deploying a power saving mode (PSM) is considered an effective solution for saving energy; however, a key challenge is how to simultaneously save energy and support a required level of quality of experience (QoE) using PSM for voice over IP (VoIP) services. This paper aims at developing a novel Markovian-based evaluation framework that assesses the energy consumption and QoE, achieved by a fixed sleeping time-based PSM. Based on this framework, a novel QoE-aware PSM is developed, which exploits the ON-OFF characteristics of a VoIP session to further improve the energy saving, while accounting for the effect of bursty losses on the QoE. The QoE and energy consumption achieved by the proposed PSM are evaluated via solving a system of linear equations. This facilitates the analytical formulation of the QoE/energy tradeoff that is needed for the successful integration of this QoE-aware PSM within the traffic offloading mechanisms. Numerical results validate the accuracy of the performance evaluation framework and verify the efficacy of the proposed QoE-aware PSM in saving energy while assuring a desired level of QoE. The Pareto-optimal operational regime show that the proposed QoE-aware PSM significantly reduces power consumption at a desired level of QoE compared with its counterparts.

Modeling, Simulation, and Analysis of Novel Threshold Voltage Definition for Nano-MOSFET

Threshold voltage (VTH) is the indispensable vital parameter in MOSFET designing, modeling, and operation. Diverse expounds and extraction methods exist to model the on-off transition characteristics of the device. The governing gauge for efficient threshold voltage definition and extraction method can be itemized as clarity, simplicity, precision, and stability throughout the operating conditions and technology node. The outcomes of extraction methods diverge from the exact values due to various short-channel effects (SCEs) and nonidealities present in the device. A new approach to define and extract the real value of VTH of MOSFET is proposed in the manuscript. The subsequent novel enhanced SCE-independent VTH extraction method named “hybrid extrapolation VTH extraction method” (HEEM) is elaborated, modeled, and compared with few prevalent MOSFET threshold voltage extraction methods for validation of the results. All the results are verified by extensive 2D TCAD simulation and confirmed analytically at various technology nodes.

Dynamic Mechanistic Modeling of Air Temperature and Humidity in the Greenhouses with on-off Actuators

The mechanistic models of greenhouse microclimate can be used as the simulators for designing new control strategies. According to the on-off characteristics of the actuators in greenhouse in China, the operating state of a greenhouse was divided into several sub-states, and new mechanistic models of greenhouse air temperature and humidity were built. In order to validate the new models, the relevant environmental factors under three sub-states were measured in a glass greenhouse. The mean square error of greenhouse air temperature and relative humidity are 0.57°C and 2.8% respectively. These results indicate that the new models are suitable for the development of energy-saving control strategies of greenhouse microclimate in future.