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The detection of human body temperature is one of the important indicators to reflect the physical condition. In order to accurately judge the state of the human body, a high-performance temperature sensor with fast response, high sensitivity, and good linearity characteristics is urgently needed. In this paper, the positive temperature characteristics of graphene–polydimethylsiloxane (PDMS) composite with high sensitivity were studied. Besides, doping polyaniline (PANI) with special negative temperature characteristics as the temperature compensation of the composite finally creatively solved the problem of sensor nonlinearity from the material level. Thus, the PANI:graphene and PDMS hybrid temperature sensor with extraordinary linearity and high sensitivity is realized by establishing the space-gap model and mathematical theoretical analysis. The prepared sensor exhibits high sensitivity (1.60%/°C), linearity (R2= 0.99), accuracy (0.3 °C), and time response (0.7 s) in the temperature sensing range of 25–40 °C. Based on this, the fabricated temperature sensor can combine with the read-out circuit and filter circuit with a high-precision analog digital converter (ADC) to monitor real-time skin temperature, ambient temperature, and respiratory rate, et al. This high-performance temperature sensor reveals its great potential in electronic skin, disease diagnosis, medical monitoring, and other fields.

Norepinephrine (NE) is an important neurotransmitter in the body, and stress or injury of neurons in the locus ceruleus (LC) results in the change of NE level in the body. In this work, we developed a micro-needle electrode for real-time monitoring of NE release in rat brain LC and investigating the effects of alpha 2-adrenoceptors on norepinephrine release upon LC stimulation by different drugs. The micro-needle electrode was prepared by modified both Au nanotubes (AuNTs) and carbon nanotubes (CNTs) on the substrate of the acupuncture needle (AN). Due to excellent electrochemical performance and biocompatibility of the nanostructures, highly sensitive detection of NE was realized. The results had shown that the CNTs/AuNTs/AN micro-needle was capable of real-time monitoring NE in the linear range from 0.75 μM to 25 μM with the limit of detection of 0.26 μM in the cell culture medium. Moreover, the stainless steel acupuncture needle was easy to be inserted into the tissue for in vivo monitoring NE release in rat brain with minimal damage compared to other electrode materials. The results also demonstrated that alpha 2-adrenoceptors regulated the release of NE in the brain's locus ceruleus. This stable and sensitive micro-needle sensor had the potential application in studying neural signal transmission, which could potentially provide important new insights into the deep brain study as well as the mechanism underlying neurological disease of the nervous system.

Single-crystal (SC) perovskite is currently a promising material due to its high quantum efficiency and long diffusion length. However, the reported perovskite photodetection range (<800 nm) and response time (>10 μs) are still limited. Here, to promote the development of perovskite-integrated optoelectronic devices, this work demonstrates wider photodetection range and shorter response time perovskite photodetector by integrating the SC CH3NH3PbBr3(MAPbBr3) perovskite on silicon (Si). The Si/MAPbBr3heterojunction photodetector with an improved interface exhibits high-speed, broad-spectrum, and long-term stability performances. To the best of our knowledge, the measured detectable spectrum (405–1064 nm) largely expands the widest response range reported in previous perovskite-based photodetectors. In addition, the rise time is as fast as 520 ns, which is comparable to that of commercial germanium photodetectors. Moreover, the Si/MAPbBr3device can maintain excellent photocurrent performance for up to 3 months. Furthermore, typical gray scale face imaging is realized by scanning the Si/MAPbBr3single-pixel photodetector. This work using an ultrafast photodetector by directly integrating perovskite on Si can promote advances in next-generation integrated optoelectronic technology.

Two-dimensional (2D) hybrid perovskite sandwiched between two long-chain organic layers is an emerging class of low-cost semiconductor materials with unique optical properties and improved moisture stability. Unlike conventional semiconductors, ion migration in perovskite is a unique phenomenon possibly responsible for long carrier lifetime, current–voltage hysteresis, and low-frequency giant dielectric response. While there are many studies of ion migration in bulk hybrid perovskite, not much is known for its 2D counterparts, especially for ion migration induced by light excitation. Here, we construct an exfoliated 2D perovskite/carbon nanotube (CNT) heterostructure field effect transistor (FET), not only to demonstrate its potential in photomemory applications, but also to study the light induced ion migration mechanisms. We show that the FET I–Vcharacteristic curve can be regulated by light and shows two opposite trends under different CNT oxygen doping conditions. Our temperature-dependent study indicates that the change in the I–Vcurve is probably caused by ion redistribution in the 2D hybrid perovskite. The first principle calculation shows the reduction of the migration barrier of I vacancy under light excitation. The device simulation shows that the increase of 2D hybrid perovskite dielectric constant (enabled by the increased ion migration) can change the I–Vcurve in the trends observed experimentally. Finally, the so synthesized FET shows the multilevel photomemory function. Our work shows that not only we could understand the unique ion migration behavior in 2D hybrid perovskite, it might also be used for many future memory function related applications not realizable in traditional semiconductors.

MXenes have attracted great attention for their potential applications in electrochemical and electronic devices due to their excellent characteristics. Traditional sound sources based on the thermoacoustic effect demonstrated that a conductor needs to have an extremely low heat capacity and high thermal conductivity. Hence, a thin MXene film with a low heat capacity per unit area (HCPUA) and special layered structure is emerging as a promising candidate to build loudspeakers. However, the use of MXenes in a sound source device has not been explored. Herein, we have successfully prepared sound source devices on an anodic aluminum oxide (AAO) and a flexible polyimide (PI) substrates by using the prepared Ti3C2MXene nanoflakes. Due to the larger interlayer distance of MXene, the MXene-based sound source device has a higher sound pressure level (SPL) than that of graphene of the same thickness. High-quality Ti3C2MXene nanoflakes were fabricated by selectively etching the Ti3AlC2powder. The as-fabricated MXene sound source device on an AAO substrate exhibits a higher SPL of 68.2 dB (f= 15 kHz) and has a very stable sound spectrum output with frequency varying from 100 Hz to 20 kHz. A theoretical model has been built to explain the mechanism of the sound source device on an AAO substrate, matching well with the experimental results. Furthermore, the MXene sound source device based on a flexible PI substrate has been attached to the arms, back of the hand, and fingers, indicating an excellent acoustic wearability. Then, the MXene film is packaged successfully into a commercial earphone case and shows an excellent performance at high frequencies, which is very suitable for human audio equipment.

Exosomes are small membrane-bound nanovesicles with a size of 50–150 nm which contain many functional biomolecules, such as nucleic acids and proteins. Due to their high homology with parental generation, they are of great significance in clinical diagnosis. At present, the quantitative detection of low concentrations of cancer-derived exosomes present in biofluids is still a great challenge. In this study, we develop an electrical and label-free method to directly detect exosomes with high sensitivity based on a reduced graphene oxide (RGO) field effect transistor (FET) biosensor. An RGO FET biosensor modified with specific antibody CD63 in the sensing area was fabricated and was used for electrical and label-free quantification of exosomes. The method achieved a low limit of detection down to 33 particles/μL, which is lower than that of many other available methods. In addition, the FET biosensor was employed to detect exosomes in clinical serum samples, showing significant differences in detecting healthy people and prostate cancer (PCa) patients. Different from other technologies, this study provides a unique technology capable of directly quantifying exosomes without labeling, indicating its potential as a tool for early diagnosis of cancer.

Glutamate, one of the most important central excitatory neurotransmitters, plays crucial roles in nerve signal transduction and is implicated in several neurological disorders. However, no effective means has been developed for specific detection of glutamate released from primary cultured neurons. Here we present a reduced graphene oxide (RGO)-based field effect transistor (FET) biosensor functionalized with synthesized glutamate receptor for real-time monitoring of glutamate release from primary cultured rat hippocampus neurons. Metabotropic glutamate receptors (mGluR) was specifically synthesized and then immobilized on the RGO surface by 1-pyrenebutanoic acid succinimidyl ester (PASE) linker, after which target glutamate (pI = 3.22) could specifically bind to the synthesized mGluR in the neutral buffer, causing the charge density change. After the neurons were cultured on the sensing channel with a self-made liquid reservoir, the FET biosensor could discriminate glutamate in the femtomolar range in complete cell culture medium and generate encouraging results in real-time monitoring of glutamate release from primary rat hippocampus neurons. This work is the first report of specific and direct detection of glutamate molecules released from primary culture of differentiated central neurons, which may further help understand the nature of neuronal communication. Moreover, this work paves a way for the detection of electrochemically inactive small molecules released by cells.

•Various bioelectrochemical sensors have been discussed.•The different properties of various graphene and their derivatives for electrode modification have been discussed.•The latest advances in ion detection have been discussed.•Suggestions for future electrochemical detection have been proposed.

In this work, Ni-doped manganite perovskite oxides (La0.8Sr0.2Mn1–xNixO3, x= 0.2 and 0.4) and undoped La0.8Sr0.2MnO3were synthesized via a general and facile sol–gel route and used as bifunctional catalysts for oxygen cathode in rechargeable lithium–air batteries. The structural and compositional characterization results showed that the obtained La0.8Sr0.2Mn1–xNixO3(x= 0.2 and 0.4) contained more oxygen vacancies than did the undoped La0.8Sr0.2MnO3as well as a certain amount of Ni3+(eg= 1) on their surface. The Ni-doped La0.8Sr0.2Mn1–xNixO3(x= 0.2 and 0.4) was provided with higher bifunctional catalytic activities than that of the undoped La0.8Sr0.2MnO3. In particular, the La0.8Sr0.2Mn0.6Ni0.4O3had a lower total over potential between the oxygen evolution reaction and the oxygen reduction reaction than that of the La0.8Sr0.2MnO3, and the value is even comparable to that of the commercial Pt/C yet is provided with a much reduced cost. In the lithium–air battery, oxygen cathodes containing the La0.8Sr0.2Mn0.6Ni0.4O3catalyst delivered the optimized electrochemical performance in terms of specific capacity and cycle life, and a reasonable reaction mechanism was given to explain the improved performance.

The BaTiO3 precursor was prepared by alkoxide method, in which barium hydroxide octahydrate and butyl titanate were chosen as the Ba and Ti sources, and diethanolamine (DEA) as the polymerizing agent respectively. In order to determine the synthesis parameters of the target product, the phase transition process of the precursor with temperature increasing was investigated by TG-DTA. The effect of calcination temperature, the dosage of DEA and calcination time on the phase compositions and crystal structure of the synthesized samples were investigated by XRD. The results indicate that DEA can promote the formation of tetragonal BaTiO3 effectively, and the high-purity tetragonal BaTiO3 was obtained by heat treatment of the precursor at 1100°C for 3h with 1mL DEA dosage.

This paper introduces the experimental results of long-term carbonization of concrete with machine-made sand (MSC), which is part of the studies on durability of this new concrete. Three strength grades of concrete C30, C40 and C50, and the contents of stone powder in machine-made sand of 5%, 9% and 13% in mass were considered in the mix proportion of concrete with machine-made sand. The ordinary concrete with natural river sand in the same strength grade was tested at the same time for comparison. The test was conducted for 360 days, and the results showed that the carbonization of MSC was similar with that of ordinary concrete, the carbonized depth increased with the increasing carbonization time. The carbonization was rapid at initial before 28 days, and became slowly with the time going by. The content of stone powder in machine-made sand affected the carbonization of MSC in some extent, which should be limited in a reasonable range. Based on the test data, the formulas for forecasting the carbonized depth of MSC are suggested.

Two-dimensional (2D) halide perovskite material is characterized by a mixed conducting behavior that possesses both electronic and ionic conductivity. The study on the influence of the light on ion migration in the 2D perovskite is helpful to improve the performance of perovskite-based optoelectronic devices. Here, we constructed an exfoliated 2D perovskite/carbon nanotubes (CNTs) heterostructure optical synapse, in which CNTs can be used as nanoprobes to qualitatively observe the ion aggregation or dissipation process in 2D perovskite, and found that light significantly changes the memory curve of the reconfigurable optical synapses. Through the molecular dynamic simulation, the dynamic process of ion migration in the heterostructure was simulated and the electrostatic interaction effect of nonequilibrium charge distribution of CNTs on iodide ion was demonstrated. Finally, an effective light-controlled process was realized through the synapses, which in situ regulated the performance of the weight-value discretized BP (WD-BP) neural network. This work lays a foundation for the future development of intelligent nano-optoelectronic devices.

This paper expounds the application of rotary expanding process to manufacture the large-diameter hot-rolled seamless gas cylinder. Through analytic geometry method, an equation is established among the tail roll gap, roll distance and the plug protrusion distance. 3D drawing software CATIA-V5 is applied to build 3d models of steel tube and rolling tools. The rolling process is simulated by MSC.Marc FEA (finite element analysis) software. Marc’s second development function and FORTRAN software’s extracting finite element node coordinates function are applied to calculate the wall thickness uniformity. A novel method to calculate the wall thickness uniformity after finite element analysis is proposed. The wall thickness uniformity of steel tube after rolling is well simulated and compared by MSC.Marc FEA software, which can help the technologist to predict and choose the best rolling parameter. For gas cylinder rolling, the tail roll gap should be set to 17mm. The roller distance and the plug protrusion distance should be set as 342mm and 78mm separately.