Phenoxy acid herbicides are widely used herbicides that play an important role in improving the yield and quality of crops. However, some research has shown that this kind of herbicide is poisonous ...to human and animals. In this study, a rapid and sensitive method was developed for the detection of seven phenoxy acid herbicides in water samples based on magnetic solid‐phase extraction followed by liquid chromatography and tandem mass spectrometry. Magnetic amino‐functionalized multiwalled carbon nanotubes were prepared by mixing bare magnetic Fe3O4 nanoparticles with commercial amino‐functionalized multiwalled carbon nanotubes in water. Then the amino‐functionalized multiwalled carbon nanotubes were used to enrich phenoxy acid herbicides from water samples based on hydrophobic and ionic interactions. The effects of experimental variables on the extraction efficiency have been studied in detail. Under the optimized conditions, the method validation was performed. Good linearities for seven phenoxy acid herbicides were obtained with squared regression coefficients ranging from 0.9971 to 0.9989. The limits of detection ranged from 0.01 to 0.02 μg/L. The method recoveries of seven phenoxy acid herbicides spiked at three concentration levels in a blank sample were from 92.3 to 103.2%, with inter‐ and intraday relative standard deviations less than 12.6%.
Carbon nanotube field-effect transistor (CNT FET) has been considered as a promising candidate for future high-performance and low-power integrated circuits (ICs) applications owing to its ballistic ...transport and excellent immunity to short channel effects (SCEs). Still, it easily suffers from the ambipolar property, and severe leakage current at off-state originated from gate-induced drain leakage (GIDL) in CNT FETs with small bandgap. Although some modifications on device structure have been experimentally demonstrated to suppress the leakage current in CNT FETs, there is still a lack of the structure with excellent scalability, which will hamper the development of CNT FETs toward a competitive technology node. Here, we explore how the device geometry design affects the leakage current in CNT FETs, and then propose the possible device structures to suppress off-state current and check their availability through the two-dimensional (2D) TCAD simulations. Among all the proposed structures, the L-shaped-spacer CNT FET exhibits significantly suppressed leakage current and excellent scalability down to sub-50 nm with a simple self-aligned gate process. According to the simulation results, the 50 nm gate-length L-shaped-spacer CNT FET exhibits an off-state current as low as approximately 1 nA/µm and an on-current as high as about 2.1 mA/µm at a supply voltage of −1 V and then can be extended as a universal device structure to suppress leakage current for all the narrow-bandgap semiconductors based FETs.
Top-gated p-type field-effect transistors (FETs) have been fabricated in batch based on carbon nanotube (CNT) network thin films prepared from CNT solution and present high yield and highly uniform ...performance with small threshold voltage distribution with standard deviation of 34 mV. According to the property of FETs, various logical and arithmetical gates, shifters, and d-latch circuits were designed and demonstrated with rail-to-rail output. In particular, a 4-bit adder consisting of 140 p-type CNT FETs was demonstrated with higher packing density and lower supply voltage than other published integrated circuits based on CNT films, which indicates that CNT based integrated circuits can reach to medium scale. In addition, a 2-bit multiplier has been realized for the first time. Benefitted from the high uniformity and suitable threshold voltage of CNT FETs, all of the fabricated circuits based on CNT FETs can be driven by a single voltage as small as 2 V.
Abstract
High-speed flexible circuits are required in flexible systems to realize real-time information analysis or to construct wireless communication modules for emerging applications. Here, we ...present scaled carbon nanotube-based thin film transistors (CNT-TFTs) with channel lengths down to 450 nm on 2-μm-thick parylene substrates, achieving state-of-the-art performances of high on-state current (187.6 μA μm
−1
) and large transconductance (123.3 μS μm
−1
). Scaling behavior analyses reveal that the enhanced performance introduced by scaling is attributed to channel resistance reduction while the contact resistance (180 ± 50 kΩ per tube) remains unchanged, which is comparable to that achieved in devices on rigid substrates, indicating great potential in ultimate scaled flexible CNT-TFTs with high performance comparable to their counterparts on rigid substrates where contact resistance dominates the performance. Five-stage flexible ring oscillators are built to benchmark the speed of scaled devices, demonstrating a 281 ps stage delay at a low supply voltage of 2.6 V.
Here, we reported a strategy-based plasmonic enzyme-linked immunosorbent assay (ELISA) using alcohol dehydrogenase-catalyzed gold nanoparticle seed-mediated growth to serve as a colorimetric signal ...generation method for detecting disease biomarkers with the naked eye. This system possesses the advantages of outstanding robustness, sensitivity, and universality. By using this strategy, we investigated the hepatitis B surface antigen (HBsAg) and α-fetoprotein (AFP) with the lowest concentration of naked-eye detection down to 1.0 × 10–12 g mL–1. Experiments with real serum samples from HBsAg-infected patients are presented, demonstrating the potential for clinical analysis. Our method eliminates the need for sophisticated instruments and high detection expenses, making it possible to be a reliable alternative in resource-constrained regions.
Single material-based monolithic optoelectronic integration with complementary metal oxide semiconductor-compatible signal processing circuits is one of the most pursued approaches in the post-Moore ...era to realize rapid data communication and functional diversification in a limited three-dimensional space. Here, we report an electrically driven carbon nanotube-based on-chip three-dimensional optoelectronic integrated circuit. We demonstrate that photovoltaic receivers, electrically driven transmitters and on-chip electronic circuits can all be fabricated using carbon nanotubes via a complementary metal oxide semiconductor-compatible low-temperature process, providing a seamless integration platform for realizing monolithic three-dimensional optoelectronic integrated circuits with diversified functionality such as the heterogeneous AND gates. These circuits can be vertically scaled down to sub-30 nm and operates in photovoltaic mode at room temperature. Parallel optical communication between functional layers, for example, bottom-layer digital circuits and top-layer memory, has been demonstrated by mapping data using a 2 × 2 transmitter/receiver array, which could be extended as the next generation energy-efficient signal processing paradigm.
Graphene nanoribbons (GNRs) are promising in nanoelectronics for their quasi‐1D structures with tunable bandgaps. The methods for controllable fabrication of high‐quality GNRs are still limited. Here ...a way to generate sub‐5‐nm GNRs by annealing single‐walled carbon nanotubes (SWCNTs) on Cu(111) is demonstrated. The structural evolution process is characterized by low‐temperature scanning tunneling microscopy. Substrate‐dependent measurements on Au(111) and Ru(0001) reveal that the intermediate strong SWCNT‐surface interaction plays a pivotal role in the formation of GNRs.
A novel approach is reported to facilely prepare graphene nanoribbons (GNRs) through the simple annealing of single‐walled carbon nanotubes (SWCNTs) on Cu(111). The surface‐catalyzed unzipping of SWCNTs occurs along a longitudinal line which directly contacts with Cu(111), affording straight GNRs. The structural evolution process is characterized by low‐temperature scanning tunneling microscopy with atom resolution.
Learning to Beamform for Minimum Outage Shi, Yunmei; Konar, Aritra; Sidiropoulos, Nicholas D. ...
IEEE transactions on signal processing,
10/2018, Letnik:
66, Številka:
19
Journal Article
Recenzirano
Acquiring channel state information (CSI) at the base station (BS) is a critical requirement for successfully employing transmit beamforming in multiantenna systems. In practice, channel ...estimation/quantization errors, feedback delays, and fast fading can make it difficult to obtain accurate CSI at the BS. In this paper, we consider an outage-based approach for transmit beamforming in order to deal with the channel uncertainty at the BS. Our formulation is applicable to both point-to-point transmit beamforming as well as single-group multicasting scenarios. A key difference from prior works is that we do not assume knowledge of the underlying channel distribution; instead, stochastic approximation is used for computing approximate solutions of a nonconvex stochastic optimization problem via simple first-order methods (FOMs). We evaluate the performance of our FOMs in two settings: First) where we design a beamformer at the BS based on historical channel realizations collected over a relatively long time window before deployment, and second) in a post-deployment phase where we perform incremental updates of our beamformer based on intermittent, delayed, or peer feedback. Simulation results reveal the effectiveness of FOMs for our problem compared to other alternatives.
Field-effect transistors (FETs) based on moderate or large diameter carbon nanotubes (CNTs) usually suffer from ambipolar behavior, large off-state current and small current on/off ratio, which are ...highly undesirable for digital electronics. To overcome these problems, a feedback-gate (FBG) FET structure is designed and tested. This FBG FET differs from normal top-gate FET by an extra feedback-gate, which is connected directly to the drain electrode of the FET. It is demonstrated that a FBG FET based on a semiconducting CNT with a diameter of 1.5 nm may exhibit low off-state current of about 1 × 10–13 A, high current on/off ratio of larger than 1 × 108, negligible drain-induced off-state leakage current, and good subthreshold swing of 75 mV/DEC even at large source-drain bias and room temperature. The FBG structure is promising for CNT FETs to meet the standard for low-static-power logic electronics applications, and could also be utilized for building FETs using other small band gap semiconductors to suppress leakage current.
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