Fast response speed of mechanically exfoliated MoS2 modified by PbS in detecting NO2

MoS2,acting as a promising gas sensing material,has shown huge potential in monitoring of toxic and harmful gases at room temperature.However,MoS2-based gas sensors still suffer from poor gas sensing performance such as poor sensitivity,long response time.Constructing the hete ro structure is an effective approach to improve gas-sensing performance of MoS2.Herein,PbS@MoS2 composites synthesized by mechanical exfoliation combining with wet-chemical precipitation are used to investigate its performance in detecting NO2 at room temperature.The response value of PbS@MoS2 gas sensor against NO2 is significantly improved compared with the pure MoS2 gas sensor.At the same time,the modification with PbS also accelerates the response speed of MoS2,and the response time is almost reduced by two orders of magnitude,from hundreds of seconds to less than ten seconds.The enhanced response value and fast response time are mainly benefited from the modulation effect of NO2 to PbS@MoS2 heterostructure and the mechanically exfoliated MoS2 surface with few defects.This work can be expected to provide useful guidance for designing composite materials with excellent gas sensing properties.

UV soaking for enhancing the photocurrent and response speed of Cs_(2)AgBiBr_(6)-based all-inorganic perovskite photodetectors

The response speed of the reported Cs_(2)AgBiBr_(6)-based photodetectors exhibits a wide variation ranging from microseconds to nanoseconds,while the reason is still unclear.Apart from the conventional approaches such as reducing effective area,new regulating approaches for response speed improvement have rarely been reported.On the other hand,it is generally believed that ultraviolet(UV)light has negative impact on perovskite devices resulting in performance degradation.In this work,we demonstrated that the response speed of the photodetector with FTO/Cs_(2)AgBiBr_(6)/Au structure can be effectively regulated by utilizing UV light-soaking effect without reducing the device area.Particularly,the decay time is efficiently modulated from 30.1μs to 340 ns.In addition,the−3 dB bandwidth of the device is extended from 5 to 20 kHz.It is worth mentioning that the light current is remarkably boosted by 15 times instead of any attenuation.Furthermore,we prove the universality of UV soaking treatment on Cs_(2)AgBiBr_(6)-based photodetectors with other all-inorganic structures,i.e.,FTO/TiO_(2)/Cs_(2)AgBiBr_(6)/Au,FTO/Cs_(2)AgBiBr_(6)/TiO_(2)/Au and FTO/TiO_(2)/Cs_(2)AgBiBr_(6)/CuSCN/Au.Our results demonstrate a new method to improve the response speed and light current of Cs_(2)AgBiBr_(6)-based perovskite all-inorganic photodetectors.

Development of a Novel Parallel-spool Pilot Operated High-pressure Solenoid Valve with High Flow Rate and High Speed

High-pressure solenoid valve with high flow rate and high speed is a key component in an underwater driving system.However,traditional single spool pilot operated valve cannot meet the demands of both high flow rate and high speed simultaneously.A new structure for a high pressure solenoid valve is needed to meet the demand of the underwater driving system.A novel parallel-spool pilot operated high-pressure solenoid valve is proposed to overcome the drawback of the current single spool design.Mathematical models of the opening process and flow rate of the valve are established.Opening response time of the valve is subdivided into 4 parts to analyze the properties of the opening response.Corresponding formulas to solve 4 parts of the response time are derived.Key factors that influence the opening response time are analyzed.According to the mathematical model of the valve,a simulation of the opening process is carried out by MATLAB.Parameters are chosen based on theoretical analysis to design the test prototype of the new type of valve.Opening response time of the designed valve is tested by verifying response of the current in the coil and displacement of the main valve spool.The experimental results are in agreement with the simulated results,therefore the validity of the theoretical analysis is verified.Experimental opening response time of the valve is 48.3 ms at working pressure of 10 MPa.The flow capacity test shows that the largest effective area is 126 mm2 and the largest air flow rate is 2320 L/s.According to the result of the load driving test,the valve can meet the demands of the driving system.The proposed valve with parallel spools provides a new method for the design of a high-pressure valve with fast response and large flow rate.

Recent research process on perovskite photodetectors:A review for photodetector——materials,physics,and applications

The perovskite photodetectors can be used for image sensing, environmental monitoring, optical communication, and chemical/biological detection. In the recent five years, the perovskite photoelectric detectors with various devices are welldesigned and have made unprecedented progress of light detection. It is necessary to emphasize the most interesting works and summarize them to provide researchers with systematic information. In this review, we report the recent progress in perovskite photodetectors, including highly sensitive, ultrafast response speed, high gain, low noise, flexibility, and narrowband, concentrating on the photodetection performance of versatile halide perovskites(organic–inorganic hybrid and all inorganic compositions). Currently, organic–inorganic hybrid and all-inorganic halide microcrystals with polycrystalline film, nanoparticle/wire/chip, and block monocrystalline morphology control show important performance in response rate,decomposition rate, noise equivalent power, linear dynamic range, and response speed. It is expected that a comprehensive compendium of the research status of perovskite photodetectors will contribute to the development of this area.

Cascade adaptive control of uncertain unified chaotic systems

The chaos control of uncertain unified chaotic systems is considered. Cascade adaptive control approach with only one control input is presented to stabilize states of the uncertain unified chaotic system at the zero equilibrium point. Since an adaptive controller based on dynamic compensation mechanism is employed, the exact model of the unified chaotic system is not necessarily required. By choosing appropriate controller parameters, chaotic phenomenon can be suppressed and the response speed is tunable. Sufficient condition for the asymptotic stability of the approach is derived. Numerical simulation results confirm that the cascade adaptive control approach with only one control signal is valid in chaos control of uncertain unified chaotic systems.

STUDY ON CATASTROPHIC MECHANISM FOR ROTOR DROP TRANSIENT VIBRATION FOLLOWING MAGNETIC BEARING FAILURE

The nonlinear and transient vibration of a rotor, which dropped onto back-up bearings when its active magnetic bearings were out of order, was investigated. After strictly deriving its equations of motion and performing numerical simulations, the time-histories of rotating speed of the dropping rotor, and normal force at the rubbing contact point as well as the frequency spectrum of the vibration displacement of back-up bearings are fully analyzed. It is found that the strong and unsteady forced bending vibration of the unbalanced and, damped rotor decelerating through : its first. bending vibtation of the unbalanced and, damped rotor decelerating through its,first critical speed as well as chattering at high frequencies caused by the nonlinearity at the rubbing contact point between, the journal and back-up bearings may lead to the catastrophic damage. of the system.

Research on the Response Characteristics of Solenoid Valve of the Air-jet Loom by Simulation

Solenoid valve is one of the executive parts of weft insertion control system. According to the response characteristics of the solenoid valve, an improved design becomes a necessity. Firstly, the numerical model was established after analyzing the solenoid valve during its start-up and shut-down. Comparing the simulation data with the practical data, it is verified that the numerical simulation model has a high feasibility. Secondly, excitation voltage and spring pre-compression were adjusted respectively, and the response rules after adjusting were investigated. The research of the study shows: the response time tends to be inverse proportional to the excitation voltage during start-up, and it becomes a constant value with the increase of the excitation voltage; the response time is proportional to the spring pre-compression when the solenoid valve starts up, it is inverse proportional to spring pre-compression when the solenoid valve shuts down. And the total response time is a constant value with the increase of the spring pre-compression. Therefore, the value of the excitation voltage and the spring pre-compression should be selected when the curve is becoming flatten. The results of the research can provide the reference to the further development of the solenoid valve.

Fast-response,high-stability,and high-efficiency full-color quantum dot light-emitting diodes with charge storage layer

Recently,solution-processed quantum dot lightemitting diodes(QLEDs)have emerged as a promising candidate for next-generation lighting and display devices.However,when given a constant voltage or current,the QLEDs need a certain working time to reach their maximum brightness.Such positive aging challenge,dramatically reducing the response speed of the device and causing a luminescence delay,is urgent to be investigated and resolved.In the current work,we introduce a charge-storage layer architecture by inserting copper(I)thiocyanate(CuSCN)between the organic holeinjection layer and hole-transport layer.The extracted holes will be released during the next electrical signal stimulation to increase the efficiency of charge transport.As a result,the response speed of the QLEDs is improved by an order of magnitude.In addition,by inserting an inorganic CuSCN layer,the efficiency,lifetime,and environmental stability of red/green/blue full-color QLEDs are enhanced simultaneously.Moreover,this work provides a generic strategy for the fabrication of fast-response and high-efficiency full-color QLEDs without luminescence delay,which plays a critical role in the practical industrialization of QLEDs.

Hole-dominated Fowler–Nordheim tunneling in 2D heterojunctions for infrared imaging

Heterostructures based on diverse two-dimensional(2D)materials are effective for tailoring and further promoting device performance and exhibit considerable potential in photodetection.However,the problem of high-density thermionic carriers can be hardly overcome in most reported heterostructure devices based on type I and type II band alignment,which leads to an unacceptably small Iphoto/Idark and strong temperature dependence that limit the performance of photodetectors.Here,using the MoTe_(2)/h-BN/MoTe_(2)/h-BN heterostructure,we report the hole-dominated Fowler–Nordheim quantum tunneling transport in both on and off states.The state-of-the-art device operating at room temperature shows high detectivity of>10^(8) Jones at a laser power density of<0.3 nW μm^(-2) from the visible to near infrared range.In addition,the fast on–off switching and highly sensitive photodetection properties promise superior imaging capabilities.The tunneling mechanism,in combination with other unique properties of 2D materials,is significant for novel photodetection.

Advances in perovskite photodetectors

Perovskite photodetectors have gradually shown preeminent photoelectric performance due to the unique material properties.In recent years,lots of works have been reported in improving the sensitivity,changing detection spectrum range and enhancing long-term stability.Herein,we summarize the some efficient strategies for performance improvement and synchronously analyze severe issues exposed in that.Furthermore,some reasonable proposals are put forward to solve future predicted troubles.In addition,more prospective assumptions are proposed on the basis of the development trend in photoelectric detection fields.We hope this perspective will allow researchers to have a clearer understanding of recent studies based on perovskite photodetectors and inspire more meaningful work in the future.

Sb_(2)Se_(3) film with grain size over 10μm toward X-ray detection

Direct X-ray detectors are considered as competitive next-generation X-ray detectors because of their high spatial resolution,high sensitivity,and simple device configuration.However,their potential is largely limited by the imperfections of traditional materials,such as the low crystallization temperature of α-Se and the low atomic numbers of α-Si and α-Se.Here,we report the Sb_(2)Se_(3) X-ray thin-film detector with a p-n junction structure,which exhibited a sensitivity of 106.3 μC/(Gyair·cm^(2))and response time of<2.5 ms.This decent performance and the various advantages of Sb_(2)Se_(3),such as the average atomic number of 40.8 and μτ product(μ is the mobility,and τ is the carrier lifetime)of 1.29×1O^(-5) cm^(2)/V,indicate its potential for application in X-ray detection.