Search

A novel SrSn(OH)6 photocatalyst with large plate and particle size were synthesized via a facile chemical precipitation method. The photocatalytic activity of the SrSn(OH)6 was evaluated by the removal of NO at ppb level under UV light irradiation. Based on the ESR measurements, SrSn(OH)6 photocatalyst was found to have the ability to generate the main active species of O2•−, •OH, and 1O2 during the photocatalytic process. Moreover, SrSn(OH)6 photocatalyst not only exhibits high photocatalytic activity for NO removal (79.6%), but also has good stability after five cycles. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the NOx transfer pathway and the intermediate products distribution during the adsorption and photocatalytic NO oxidation process. The present work not only provides an efficient material for air pollutants purification at room temperature but also in-depth understanding of the mechanism involved in the photocatalytic NO removal process.

Realizing efficient photocatalytic hydrogen production of graphitic carbon nitride (g-C3N4) in the absence of precious metals is one of the urgent research topics for industrial application. In this work, efficient p-n heterojunction of iron(III) hydroxide and graphitic carbon nitride (Fe(OH)3/g-C3N4) for hydrogen production were successfully constructed using the electrostatic attraction self-assembly method. The Fe(OH)3/g-C3N4 heterojunction could harvest more visible light, suppress recombination and boost transmission rate of the carriers. As expected, without participation of any precious metal, the highest hydrogen production rate (733 μmol h−1 g−1) was 51.2 folds higher than the unmodified g-C3N4 at λ > 400 nm, which is superior to many previous results. Additionally, a possible reaction mechanism was proposed according to energy band analysis as well as the experimental photocatalytic activity results. To the energy and environmental studies fields, this work suggests a novel approach to design high efficiency photocatalysts using abundant and inexpensive metals instead of precious metals.

Differentiated crystal structures generally affect the surface physicochemical properties of catalysts, causing variety in catalytic activity between polymorphs. However, the underlying mechanism has not been completely revealed, especially the influence of surface physicochemical properties on photocatalytic redox activity and the reaction mechanism. In this work, we reveal the mechanism of surface redox properties on different crystal forms of gallium oxide from a molecular level. α-Ga2O3 and β-Ga2O3 exhibit a slight difference in catalytic oxidation of organic pollutants due to comprehensive influencing factors, including their valence band position, reactive oxygen species, and pore structure properties related to the adsorption-reaction-desorption process. But the catalytic reduction ability of CO2 is obviously different due to the large differences of interaction between the surface of crystal structures and CO2 molecules, which are critical to determine the catalytic performance and reaction pathways. The enhanced adsorption and activation of CO2 on the α-Ga2O3 surface could promote the reduction reaction efficiency. Moreover, the large energy barrier of CH2* formation on β-Ga2O3 makes the formation of methane (CH4) relatively difficult compared to that on α-Ga2O3. The yield rate of CH4 (1.8 μmol·g-1·h-1) on α-Ga2O3 is three times better than that on β-Ga2O3 (CH4: 0.6 μmol·g-1·h-1). The current findings can offer novel insights into the understanding of crystal-structure-dependent photocatalytic performances and the design of new catalysts applied in energy conversion and environmental purification by crystal structure-tuning.

At present, more and more flexible pressure sensors are used in wearable devices. The improvement of the adsorbability of nanomaterials on sponge flexible pressure sensors is an urgent problem to be solved. Here, using conductive carbon black with good dispersibility and small particle size as the conductive filler filled in the middle of the sponge can improve the absorbability of the sponge. A simple method of soaking a sponge with different thicknesses in conductive carbon black dispersion is used to obtain flexible pressure sensors based on conductive carbon black/sponge. We compare and analyze the differences in initial resistance and sensitivity of sponge pressure sensors with different thicknesses and select the sensor with higher sensitivity (0.194 kPa−1) for response time, recovery time, and stability tests. The sensor is used in the neck, wrist, knee, and other body parts for motion recognition. The two conductive carbon black/sponge sensors are placed orthogonally on the back to identify nod, tilt head, and placed on the elbow to test the angle of arm bending. Conductive carbon black/sponge flexible pressure sensor shows good application prospects in the wearable field.

During underwater acoustic detection, the positioning accuracy of the bionic cilia MEMS vector hydrophone is affected by its own sensitivity. MEMS vector hydrophone operate in different temperature environments, so studies on the environmental temperature and the sensitivity of the MEMS vector hydrophone are of great significance. In this paper, based on the sensitivity of the MEMS vector hydrophone at room temperature (22°C), its sensitivity variation is studied within the temperature range of 0–40°C. The relationship between the temperature and the piezoresistor in the MEMS vector hydrophone is theoretically analyzed, and it is concluded that the sensitivity change is within ±0.6dB. The sensitivity change of MEMS vector hydrophone is proved to be within ±0.3 dB via COMSOL 5.4 simulation software, and the MEMS vector hydrophone is verified experimentally by the hydrophone temperature characteristic testing system. The results show that the variation of the sensitivity is within ±0.5 dB, which is basically consistent with the theoretical analysis results and simulation results. It can be said that under normal non-extreme ambient temperature, the operating temperature has little effect on the sensitivity of the MEMS vector hydrophone.

In this paper, a 3D cone-beam ultrasonic transmission tomography method for capacitive micromachined ultrasonic transducer (CMUT) cylindrical phased array was proposed. The performance of the proposed method was evaluated by numerical simulation experiments. After beam focusing of the transmitting array, the deviation of reconstructed sound attenuation distribution and sound speed distribution were respectively reduced by at least 71.4% and 46.4%. The research results in this paper will provide a good theoretical and practical foundation for the realization of ultrasonic imaging based on CMUT cylindrical array in the future.

There is always a temperature difference of more than 10 degrees between the human body, as a sustainable heat source, and the ambient temperature. Converting body heat into electricity that in turn is used to drive personal medical electronics is of significance in smart wearable medicine. To avoid the frangibility and complex preparation of traditional thermoelectric materials, we fabricated a gel electrolyte-based thermogalvanic generator with Fe3+/Fe2+ as a redox pair, which presents not only moderate thermoelectric performance but also excellent flexibility. With a micropore-widespread polyvinylidene fluoride diaphragm implanted in the gel, a thermal barrier was created between the two halves, effectively improving the Seebeck coefficient by reducing its thermal conductivity. Considering the superior temperature response of the gel, a self-powered body temperature monitoring system was established by conformally affixing it to the forehead. Meanwhile, the gel patch with a high specific heat capacity can effectively cool down fever patients. This work may offer a new train of thought for exploiting self-powered wearable medical electronics by scavenging low-grade body heat.

Dispersibility and magnetic response characteristics of magnetic nanoparticles is crucial to the sensitivity and stability of flexible magnetic field sensors. To improve the performance of magnetic nanoparticles, this paper reported a preparation method of the fullerene-coated ferric oxide (C60@Fe3O4) magnetic nanocomposites. The TEM results showed that the C60@Fe3O4 has uniform dispersion and consistent particle size, and C60 particles are distributed on the surface of Fe3O4, forming a coating structure. The X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersion spectroscopy results further proved that the compositions of the nanomaterials are Fe3O4 and C60. The VSM hysteresis loop of the nanocomposites showed good performance in magnetic response. Then, styrene ethylene butylene Styrene (SEBS), the C60@Fe3O4 magnetic nanoparticles, and CNTs, which were used as flexible substrate, magnetic sensitive unit, and conductive networks, respectively, composed the flexible magnetic field sensor. The measurement results of the flexible magnetic field sensor showed its high sensitivity (2.1 T−1) and good stability. The mechanism of the sensor was explored at last.

The integral panel is significant structure of modern advanced aircraft. Stability is one of the most important problems of aircraft structure design. This paper focused on the compression properties of the material 7B50-T7751 and 7150-T7751. According to the engineering algorithm, we got the compression result of the wing integral panel. By the experimental study, we can obtain the load-strain curves of the two integral panel forms. The comparison of the compression properties provides a basis to the choice of integral panel. Keywords: Integral panel, Stability, Compression, 7B50-T7751, 7150-T7751

To obtain profiles with sound weld seams, the effects of extrusion parameters and heat treatment on microstructures and mechanical properties of the weld seam were revealed. It was found that the high extrusion speed increases the mechanical properties and welding quality of the welding area. The micro-voids formed in low temperature and low extrusion speed could hinder the grains from growing through the welding interface during heat treatment, which caused weak bonding of the weld seam. Lots of strengthening phases precipitated during aging treatment, which leads to the disappearance of the softened welding area and the improvement of tensile strength. However, the fine grains of welding area translated to coarse grains quickly during solution treatment, and the precipitated phases coarsened and the precipitation free zone (PFZ) widened when the aging time is excessive, above reasons result in the layered fracture of welding area and poor elongation. Tensile strength and elongation were improved simultaneously because of the fine grain boundary precipitates, narrow PFZ and fine homogeneous T1 phases formed in under-aged (UA) treatment. The weld seam obtained by high extrusion speed shows a fine combination of ultimate tensile strength (UTS) and elongation after UA treatment.

In this paper, an ultrahigh sensitive hydrazine electrochemical sensor based on gold nanoparticles integrated into a reduced graphene oxide/nickel foam (AuNPs-rGO@NF) hybrid structure was synthesized using a facile coating and electrochemical deposition method. The morphology and elemental composition of the as-synthesized AuNPs-rGO@NF structure was comprehensively investigated. Both cyclic voltammetry and potential amperometry results show the optimum AuNPs-rGO@NF sensor exhibits excellent electrochemical performances including higher sensitivity (14.635 μA μM−1 cm−2), lower limit of detection (0.056 μM; S/N = 3), wider linear detection range (0.2–200 μM), good selectivity and long-term stability. Meanwhile, the results of real sample analysis indicate the AuNPs-rGO@NF sensor has great potential for practical electrochemical hydrazine sensing applications.

Clustered indium oxide/copper oxide (In2O3/CuO) nanospheres with different CuO amounts were successfully synthesized as sensing materials for the carbon monoxide (CO) detection. Component and morphological characterizations were performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Sensing performance for CO of the clustered In2O3 and In2O3/CuO nanospheres were investigated under different temperatures and humidity conditions. The results show that the sensors based on 2 mol % In2O3/CuO (InCu2) exhibit about threefold improvement in response to CO compared to that of In2O3 with quick response and recovery time, wide linearity, and low detection limit at 200 °C under 25% relative humidity (RH). Moreover, it shows tiny resistance and response declines despite the wide range of humidity variation from 25 to 95% RH. Meanwhile, the mechanism of enhanced gas-sensing performances and antihumidity properties of InCu2 were systematically investigated. We speculated that most of the water-driven species are predominantly adsorbed by CuO due to its high affinity to the hydroxyl group, which suppresses the interaction between moisture and In2O3. InCu2 is a new and promising material to sense CO in a highly sensitive and fast manner with negligible interference from ambient humidity.

Organic electrochemical transistors (OECTs) exhibit the advantages of high gain, low operation voltage, and compatibility with flexible substrates as well as with biocompatible materials. These unique characteristics promote the application of OECTs in biosensing and electrophysiological monitoring. Low-cost OECTs can be manufactured by electrochemical polymerization, and the functionality of semiconducting polymers can be tailored in a straightforward manner. Fabrication with electrochemical polymerization produces one device per process cycle, and such low-yield hinders further application in dense-array devices. In the current work, OECT arrays were prepared by bipolar electrodeposition, which was carried out three times in total. Five PEDOT:PSS films could be prepared simultaneously in each fabrication cycle. Experimental results illustrate that both the film profile and the device performance exhibited satisfactory repeatability. This research also evidenced that the resulting film properties can be tailored by meticulously tuning alternating current (AC) parameters. By constructing equivalent circuits, we demonstrate the property-tuning mechanism qualitatively based on the electrochemical impedance spectroscopy analyses. Tuning the AC frequency has proven to be more efficient than modifying the voltage amplitude for device engineering. The best AC parameters were found to be 16 Vp–p and 50 Hz. The as-prepared 15 OECTs exhibited a maximum transconductance of 0.77 ± 0.01 mS and an on/off current ratio of 182 ± 5. Time constants for switching on and switching off were 73 ± 4 ms and 217 ± 4 ms, respectively.

Nanoparticles with absorbances in the near-infrared window (NIR, 700–1300 nm) are ideal contrast agents for in vivo imaging of deep tissue with high signal-to-noise ratios. By using CTAB and L(+)-ascorbic acid (AA) as ligands to effectively balance particle nucleation and growth, PEGylated Au nanorods (NRs) with broad absorption bands (from 650 to 1100 nm) in the first NIR window could be successfully realized. The morphologies, crystal structures, absorption and biotoxicities of the samples were determined by TEM, TGA, UV-vis and MTT assay. The results indicated that the presence of a thin poly(ethylene glycol) (PEG) shell could greatly improve the biocompatibility of the Au NRs (1.7 times that of non-PEGylated Au NRs), making them harmless to living cells. Moreover, the prepared PEGylated Au NRs displayed the highest image contrast and SNR values (1.1–1.5 times that of commercial Au nanospheres and NRs), with excitation lasers of 532, 680 and 828 nm, showing their great potential for use in multicolor photoacoustic imaging in vivo. With the prepared PEGylated Au NRs, a functional image of oxygen saturation was constructed in a single step without changing the contrast agent.

In this paper, a series of Co3O4–Ag photocatalysts with different Ag loadings were synthesized by facile hydrothermal and in situ photoreduction methods and fully characterized by XRD, SEM, TEM, FTIR spectroscopy, XPS, UV-vis and PL techniques. The catalysts were used for the degradation of methyl orange (MO). Compared with the pure Co3O4 catalyst, the Co3O4–Ag catalysts showed better activity; among these, the Co3O4–Ag-0.3 catalyst demonstrated the most efficient activity with 96.4% degradation efficiency after 30 h UV light irradiation and high degradation efficiency of 99.1% after 6 h visible light irradiation. According to the corresponding dynamics study under UV light irradiation, the photocatalytic efficiency of Co3O4–Ag-0.3 was 2.72 times higher than that of Co3O4 under identical reaction conditions. The excellent photocatalytic activity of Co3O4–Ag can be attributed to the synergistic effect of strong absorption under UV and visible light, reduced photoelectron and hole recombination rate, and decreased band gap due to Ag doping. Additionally, a possible reaction mechanism over the Co3O4–Ag photocatalysts was proposed and explained.

In this paper, highly sensitive air-filled substrate integrated waveguide (SIW) resonators integrated wireless passive slot-antenna are designed and fabricated for confined environmental detection. The models of SIW sensors were established by using the software of HFSS to optimize the performance of the sensor for the 802.11 WLAN application. Due to the symmetry and the ideal-wall characteristic of the SIW, the SIW sensor can be designed into a half-mode substrate integrated waveguide (HMSIW) to reduce the size of the sensor. The SIW and HMSIW sensor were fabricated and measured experimentally. The sensitivities of HMSIW sensor for humidity detection without humidity sensitivity materials using the dielectric perturbation method were 187.67 kHz/%RH and 0.233 dB/%RH and 211.5 kHz/%RH and 0.33 dB/%RH for SIW sensor. Meanwhile, the SIW sensor can also realize the detection of ammonia filled with polyaniline material into the air-filled hole array of sensor. The slot-antenna integrated wireless passive air-filled SIW resonators with the low-cost advantage provide a new method for the detection of confined environments.

Soft-strain-based sensors are being increasingly used across various fields, including wearable sensing, behavior monitoring, and electrophysiological diagnostics. However, throughout all applications, the function of these sensors is limited because of high sensitivity, high-dynamic range, and low-power consumption. In this paper, we focus on improving the sensitivity and strain range of the soft-strain-based sensor through structure, surface, and sensitive unit treatment. Nanosilver (Ag)-coated hydroxyl-functionalized multi-walled carbon nanotubes (OH-f MWCNTs) were explored for highly acute sensing. With stretching and depositing methods, Ag@OH-f MWCNTs and polydimethylsiloxane (PDMS) are fabricated into a wrinkled and sandwich structure for a soft-strain-based sensor. The electronic properties were characterized in that the gauge factor (GF) = ΔR/R0 was 412.32, and the strain range was 42.2%. Moreover, our soft-strain-based sensor exhibits features including flexibility, ultra-lightweight and a highly comfortable experience in terms of wearability. Finally, some physiological and behavioral features can be sampled by testing the exceptional resistance change, including the detection of breath, as well as facial and hand movement recognition. The experiment exhibits its superiority in terms of being highly sensitive and having an extensive range of sensing.

Solar water splitting by photoelectrochemical (PEC) reactions is promising for hydrogen production. The gold nanoparticles (AuNPs) are often applied to promote the visible response of wideband photocatalysts. However, in a typical TiO2/AuNPs structure, the opposite transfer direction of excited electrons between AuNPs and TiO2 under visible light and UV light severely limits the solar PEC performance. Here we present a unique Pt/TiO2/Cu2O/NiO/AuNPs photocathode, in which the NiO hole transport layer (HTL) is inserted between AuNPs and Cu2O to achieve unidirectional transport of charge carriers and prominent plasmon-induced resonance energy transfer (PIRET) between AuNPs and Cu2O. The measured applied bias photon-to-current efficiency and the hydrogen production rate under AM 1.5G illumination can reach 1.5% and 16.4 μmol·cm-2·h-1, respectively. This work is original in using the NiO film as the PIRET spacer and provides a promising photoelectrode for energy-efficient solar water splitting.

Silicon nano-film is essential for the rapidly developing fields of nanoscience and flexible electronics, due to its compatibility with the CMOS process. Viscoelastic PDMS material can adhere to Si, SiO2, and other materials via intermolecular force and play a key role in flexible electronic devices. Researchers have studied many methods of transfer printing silicon nano-films based on PDMS stamps with pyramid microstructures. However, only large-scale transfer printing processes of silicon nano-films with line widths above 20 μm have been reported, mainly because the distribution of pyramid microstructures proposes a request on the size of silicon nano-films. In this paper, The PDMS base to the curing agent ratio affects the adhesion to silicon and enables the transfer, without the need for secondary alignment photolithography, and a flat stamp has been used during the transfer printing, with no requirement for the attaching pressure and detaching speed. Transfer printing of 20 μm wide structures has been realized, while the success rate is 99.3%. The progress is promising in the development of miniature flexible sensors, especially flexible hydrophone.

In order to meet the requirements of having a small structure, a wide frequency band, and high sensitivity for acoustic signal measurement, an acoustic sensor based on a silicon-based grooved microring resonator is proposed. In this paper, the effective refractive index method and the finite element method are used to analyze the optical characteristics of a grooved microring resonator, and the size of the sensor is optimized. The theoretical analysis results show that, when the bending radius reaches 10 μm, the theoretical quality factor is about 106, the sensitivity is 3.14 mV/Pa, and the 3 dB bandwidth is 430 MHz, which is three orders of magnitude larger based on the sensitivity of the silicon-based cascaded resonator acoustic sensor. The sensor exhibits high sensitivity and can be used in hydrophones. The small size of the sensor also shows its potential application in the field of array integration.

Paper based flexible pressure sensors have received extensive attention due to their recoverability and accessibility. In this paper, we proposed graphical pressure sensors array with multilayered structure. A simple writing method was adopted to achieve the adsorption of sensitive materials on the fiber structure of cellulose paper. Pressure sensors with 1, 3, 5 and 7 stacked layers were fabricated and compared, respectively. The results show that the 7layers sensor combined high sensitivity (44 kPa-1) and fast time response (150 ms). The highly sensitive stacked paper-based sensor array realizes the pressure detection of objects and special-shaped surfaces. A pressure sensor base on commercial corrugated box was also fabricated to compare. The corrugated carton array was made to switch reminder devices for its convenience and accessibility. Since there are many scenarios that require a safe distance, especially under the influence of the COVID-19, the writable paper-based sensor array was used to realize graphical distance perception and warning.

A hemispherical resonator consists of a hemispherical shell and the surrounding circular electrodes. The asymmetry of a hemispherical shell has influence on the vibrating mode and quality factor. The gap distance from shell to electrode is critical for the capacitance and sensitivity of a hemispherical resonator. To realize a symmetric shell and a small gap, a kind of micro-hemispherical resonator (μHR) structure including sandwich-shaped stacks and eave-shaped electrodes has been developed using a glassblowing process. The blowing process could bring favorable surface roughness and symmetry. The locations of the hemispherical shell and surrounding electrodes can be precisely controlled by the designs of sandwich-shaped stacks and eave-shaped electrodes, making it feasible to realize uniform and small gaps. In addition, electrical insulation between the hemispherical shell and eave-shaped electrodes can be guaranteed owing to eave-shaped structure. The fabrication process and results are demonstrated in detail. Furthermore, an estimation method of shell thickness in a nondestructive manner is proposed, with deviation below 5%. Taking asymmetry, surface roughness, and gap into consideration, these results preliminarily indicate this structure with a hemispherical shell and surrounding eave-shaped electrodes is promising in hemispherical resonator applications.

Capacitive micromachined ultrasonic transducer (CMUT) is an ultrasonic transducer based on the microelectromechanical system (MEMS). CMUT elements are easily made into a high-density array, which will increase the hardware complexity. In order to reduce the number of active channels, this paper studies the grating lobes generated by CMUT periodic sparse array (PSA) pairs. Through the design of active element positions in the transmitting and receiving processes, the simulation results of effective aperture and beam patterns show that the common grating lobes (CGLs) generated by the transmit and receive array are eliminated. On the basis of point targets imaging, a CMUT linear array with 256 elements is used to carry out the PSA pairs experiment. Under the same sparse factor (SF), the optimal sparse array configuration can be selected to reduce the imaging artifacts. This conclusion is of great significance for the application of CMUT in three-dimensional ultrasound imaging.

The advantages of the capacitive micromachined ultrasound transducer (CMUT) technology have provided revolutionary advances in ultrasound imaging. Extensive research on CMUT devices for high-frequency medical imaging applications has been conducted because of strong demands and fabrication realization by using standard silicon IC fabrication technology. However, CMUT devices for low-frequency underwater imaging applications have been rarely researched because it is difficult to fabricate thick membrane structures through depositing processes using standard IC fabrication technology due to stress-related problems. To address this shortcoming, in this paper, a CMUT device with a 2.83-μm thick silicon membrane is proposed and fabricated. The CMUT device is fabricated using silicon fusion wafer-bonding technology. A 5-μm thick Parylene-C is conformally deposited on the device for immersion measurement. The results show that the fabricated CMUT can transmit an ultrasound wave, receive an ultrasound wave, and have pulse-echo measurement capability. The ability of the device to emit and receive ultrasonic waves increases with the bias voltage but does not depend on the voltage polarity. The results demonstrate the viability of the fabricated CMUT in low-frequency applications from the perspectives of the device structure, fabrication, and characterization. This study presents the potential of the CMUT for underwater ultrasound imaging applications.

Due to the complicated deformation of the billet in roll forming process and the lack of the theoretical understanding, there are still no unified methods to design and optimize roll profiles. Theoretical analysis of the deformation in roll forming process based on mathematical method is efficient and necessary. A qualified roll profile optimization method should be based on the accurate calculation of the spatial configuration of the billet. However, the existing models for calculating the spatial configuration of the billet in roll forming process cannot calculate the springback of the billet. In this paper, according to the mathematical model established by the author for calculating the spatial configuration of the billet, a roll profile optimization method for high-strength V channel roll forming process was proposed by taking the maximum edge membrane longitudinal strain as constraint conditions. After optimization, the number of roll stands required for final V channels was reduced from 8 to 5. Through analyzing and comparing the deformation of the billet in simulation results of bending and roll forming process, it is found that bending tests can also be used to verify the feasibility of the roll profile optimization method proposed in this paper. The bending tests were carried out using the original and optimized process parameters, respectively. The results show that the shape of the V channel obtained by the optimized process parameters is much closer to that of the designed V channel.

The composite of gold and PDMS hold remarkable potential for surface stress-based biosensor applicaitons. However, the gold and PDMS in composite suffers from poor compatibility with each other and suppresses the performance of the biosensor. Here, we conduct two-step synthesis of the composite of gold and PDMS by in-situ reduction and glucose reduction of HAuCl4. The composite shows stable conductive gold nanoparticle network (SC-AuNW). In in-situ reduction, Au-seeds are embedded in PDMS surface. Furthermore, AuNPs are also generated inside the PDMS and enhance conductivity. The SC-AuNW plays a crucial role in tunneling conductivity of composite film and exhibits an excellent sensitivity to surface stress. We construct SC-AuNW-PDMS biosensors based on surface stress for glucose detection with a detection limit of 0.021 mM, high repeatability and specificity. Our research can promote the application of flexible conductive films in biosensors for disease diagnosis.

In this paper, a method for transmitting LC sensor signals in a multi-dimensional rotating environment with dual-inductor resonators (DIR) has been proposed. The DIR is fabricated on printed circuit boards whose characteristics are studied via experiment and simulation. The LC pressure sensor, based on high-temperature co-fired ceramics and platinum conductor was fabricated, which showed a frequency variation of 1.185 MHz in a range of 0˜3 bar, and was measured in a rotating environment via DIR selected according to examination and simulations. The test results showed two signal peaks due to frequency splitting. The left signal peak drift with pressure was 1.05 MHz at a range of 0˜3 bar while the variation of the right signal was significantly lower at 0.175 MHz. Meanwhile, the left signal peak in atmosphere at 41.325 MHz was particularly close to the sensor frequency of 42.1175 MHz. Finally, the variation in the right signal was ignored, and the left signal peak was used to reflect the changes in the frequency of the sensor with pressure in multi-dimensional rotating environment.

Black silicon is a kind of micro-/nanostructure formed on the surface of silicon, which can greatly reduce light reflection. In this review, five main fabrication techniques of black silicon are introduced and these techniques can change the morphology of the surface of crystalline silicon to a certain extent, thus making the preparation of black silicon more feasible and convenient. The utilization of black silicon is then reviewed. Black silicon has originally been used as a bactericidal to eradicate bacteria such as Pseudomonas aeruginosa. It is bound to have more novel applications in the field of sterilization. Black silicon is like a sponge that absorbs light. It can capture almost all sunlight, both visible and infrared light. It also reduces the amount of silicon used in optical sensors, making products cheaper, smaller, and lighter. Due to the above characteristics, black silicon is widely used in Surface Enhanced Raman Scattering detection, biomedical sensing, and infrared device manufacturing. It also has the potential to improve the performance of solar cells. This review is intended to serve as a useful introduction to this novel material and its properties, and provide a general overview of recent progress in its main applications.

The photocatalysis process follows two fundamental sequences: reactant adsorption and surface photocatalysis. In this work, Bi metal-deposited Bi2GeO5 (Bi@BiGeO) is prepared as a model photocatalyst to understand the adsorption and activation mechanisms of the reactants and the photocatalytic oxidation of NO under visible light irradiation. Density functional theory and analytical approaches are employed to reveal the electronic structure and photo-induced carrier transfer processes. The introduction of Bi metal and the generation of oxygen vacancies (OVs) in BiGeO were achieved simultaneously via a facile method. The Bi metal served as a visible light antenna and as an electron sink and promoted the carrier separation and transfer. The OVs promote reactant (H2O and O2) activation, thereby reinforcing the generation of reactive oxygen species (ROS). The NO molecules are actively adsorbed at the coordinative unsaturated sites on Bi@BiGeO and get activated via electron exchange. The photocatalytic NO oxidation mechanism on Bi@BiGeO is revealed based on the reaction intermediates and final products monitored using in-situ FTIR. This work highlights the importance of reactant activation as a new strategy for the design of highly efficient photocatalysts to overcome the bottlenecks in environmental applications.

Pure WO3 sensors and Mn3O4/WO3 composite sensors with different Mn concentrations (1 atom %, 3 atom % and 5 atom %) were successfully prepared through a facile hydrothermal method. As gas sensing materials, their sensing performance at different temperatures was systematically investigated for gas detection. The devices displayed different sensing responses toward different gases at specific temperatures. The gas sensing performance of Mn3O4/WO3 composites (especially at 3 atom % Mn) were far improved compared to sensors based on pure WO3, where the improvement is related to the heterojunction formed between the two metal oxides. The sensor based on the Mn3O4/WO3 composite with 3 atom % Mn showed a high selective response to hydrogen sulfide (H2S), ammonia (NH3) and carbon monoxide (CO) at working temperatures of 90 °C, 150 °C and 210 °C, respectively. The demonstrated superior selectivity opens the door for potential applications in gas recognition and detection.

Surface plasmon resonance (SPR) of metals may provide a way to improve light absorption and utilization of semiconductors, achieving better solar light conversion and photocatalysis efficiency. This study uses the advantages of SPR in metallic Bi and artificial defects to cooperatively enhance the photocatalytic performance of BiOI. The catalysts were prepared by partial reduction of BiOI to form Bi@defective BiOI, which showed highly enhanced visible photocatalytic activity for NOx removal. The effects of reductant quantity on the photocatalytic performance of Bi@defective BiOI were investigated. The as-prepared photocatalyst (Bi/BiOI-2) using 2 mmol of reductant NaBH4 showed the most efficient visible light photocatalytic activity. This enhanced activity can be ascribed to the synergistic effects of metallic Bi and oxygen vacancies. The electrons from the valence band tend to accumulate at vacancy states; therefore, the increased charge density would cause the adsorbed oxygen to transform more easily into superoxide radicals and, further, into hydroxyl radicals. These radicals are the main active species that oxidize NO into final products. The SPR effect of elemental Bi enables the improvement of visible light absorption efficiency and the promotion of charge carrier separation, which are crucial factors in boosting photocatalysis. NO adsorption and reaction processes on Bi/BiOI-2 were dynamically monitored by in situ infrared spectroscopy (FT-IR). The Bi/BiOI photocatalysis mechanism co-mediated by elemental Bi and oxygen vacancies was proposed based on the analysis of intermediate products and DFT calculations. This present work could provide new insights into the design of high-performance photocatalysts and understanding of the photocatalysis reaction mechanism for air-purification applications.

In this work, we demonstrate an LC (inductor-capacitor) wireless passive humidity sensor based on MWCNTs(tungsten disulfide-multiwalled carbon nanotubes)/WS2 nanocomposites. We optimized the sensor structure and subsequently investigated the transmitting distance effect on the sensing performance of the sensor via the HFSS software. Subsequently, we observed the MWCNTs/WS2 nanocomposites by a scanning electron microscope, and the as-designed humidity sensor was fabricated via screen printing technology. In the experiments, we proved that the detectable transmitting distance of the sensor was up to 28 mm, and originally validated the transmitting distance effect on the sensitivity of the as-fabricated humidity. Based on the results, the transmitting distance of 6 mm was chosen to be the desired transmitting distance for further investigation of the humidity sensor. Consequently, the sensing test at the transmitting distance of 6 mm indicates that the resonance frequency of the proposed humidity sensor shifts by approximately 2.562 MHz in 15–95%RH(RT) with a sensitivity of 2201.25Hz/%RH at a low humidity range (15–55%RH) and a sensitivity of up to 70684Hz/%RH at a high humidity range (55–95%RH). The sensor has a response and recovery time of 7.8 s and 19.6 s, respectively, in 15–95%RH, and the repeatability and stability tests indicate the MWCNTs/WS2 nanocomposites applied for humidity sensors are reusable and stable in 15–95%RH. Eventually, the sensing mechanism of the proposed sensor at different transmitting distances is analyzed. Our results show that the humidity sensor is applicable for fast humidity detection in both sealed and open environments.

We report fabrication and photovoltaic properties of flexible dye-sensitized solar cells (FDSSCs) based on stainless steel mesh (SSM)-supported core-shell ZnO/TiO2 nanorods photoanode and Pt nanoparticles- coated SSM counter electrode (Pt/SSM CE). The core-shell ZnO/TiO2 structures were prepared via simple chemical bath deposition, and optimal conversion efficiency of 2.84% was achieved. When aluminum foil membrane was introduced on the back of the FDSSCs as reflecting film (Rf) for improving utilization of sunlight, the conversion efficiency of FDSSCs was increased from 2.84% to 3.12%. The relative improvement of 218% was achieved in conversion efficiency compared with similar device without TiO2 buffer layer and reflecting film (0.98%). Meanwhile, the Pt CE based on SSM possessed of higher catalytic ability and longer stability compared with ITO/PET-based Pt CE.

Bi metal deposited hexagonal BiPO4 with the exposure of {102} facet (Bi-HBPO-102) and Bi metal deposited monoclinic BiPO4 with the exposure of {120} facet (Bi-MBPO-120) were prepared by chemical deposition method and solvothermal approach, respectively. The as-prepared catalysts presented more efficient photocatalytic activity of NOx removal than pure BiPO4 (2.0% for BiPO4, 51.4% for Bi-HBPO-102 and 36.2% for Bi-MBPO-120) under visible light irradiation, which can be attributed to the synergistic effects endowed by the phosphate defect, the surface plasmon resonance (SPR) effect of Bi metal and the facet effect. The existence of phosphate defect was confirmed by the XPS and solid state EPR technique. The DFT calculation revealed the position of phosphate and the phosphate defect induced the formation of an intermediate level within the forbidden band to allow efficient charge transfer from valence band to conduction band. Moreover, the Bi metal would act as the electron contributor and electron conductor which facilitated the charge carriers separation. Therefore, a new charge transfer pathway can be certified on account of the fact that the covalent loop was evidently generated both at the interface and along with the path of [Bi2O2]2+ → Bi metal → PO43− on the Bi@BiPO4. More importantly, the Bi-HBPO-102 with exposure of {102} facet exhibited higher photocatalytic activity than the Bi-MBPO-120 with exposed {120} facet. The {102} facet with the stronger distorted PO4 tetrahedron and the lower potential energy barrier (-17.5eV) contributed to the contacted interface with the more efficient charge transfer, which promoted the generation of active radicals on {102} facet. Additionally, for Bi-HBPO-102, the reaction intermediate NO+ can be observed with in situ DRIFTS, which facilitated the activation of NO via the formation of NO+ to promote the oxidation of NO into final products. Herein, a new strategy for tailoring the charge transfer pathway was developed to enhance the photocatalytic performance and a new photocatalytic reaction mechanism for photocatalytic NOx removal was proposed. This work could provide new insights into the modification of photocatalysts and mechanistic understanding of the gas-phase photocatalytic reaction mechanism.

The BiOCl/Bi12O17Cl2@MoS2 (BOC-MS) composites were successfully synthesized by a facile method at room temperature. The physicochemical properties of the as-obtained samples were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible diffuse reflection spectra (UV–Vis DRS), photoluminescence (PL), Brunauer–Emmett–Teller–Barrett–Joyner–Halenda (BET–BJH), and electron spin resonance (ESR) in detail. Moreover, the in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was applied to elucidate the adsorption and photocatalytic reaction mechanism. The optimized BOC-MS-1.0 composites exhibited excellent visible light photocatalytic capability (51.1%) and photochemical stability for removal of NO. Based on the DMPO-ESR spin trapping, the ·O2− radicals and ·OH radicals were identified as the main active species generated from BOC-MS-1.0 under visible light irradiation. The enhanced photocatalytic performance can be ascribed to the positive synergetic effect of the MoS2 and the effective carrier separation ability.

In this paper, a novel and wireless magnetoelastic (ME) immunosensor for human serum albumin (HSA) detection is presented. Gold nanoparticles layer on the sensor surface can enhance its biocompatibility, stability and sensitivity. The anti-HSA IgG, as a capture probe, was immobilized on the gold-plated ME sensor surface to specifically recognize the target HSA. The binding complex accumulated on the immunosensor surface leads to a decrease in the immunosensor’s resonance frequency, corresponding to the HSA concentrations. The atomic force microscopy, the Raman spectrum and the X-ray electron spectroscopy were used to confirm that the antibody immobilization was successful. Furthermore, to enhance its sensitivity, the working concentration of the antibody was optimized to be 25 µg ml−1. The experimental results demonstrated that the immunosensor exhibited a linear response to the logarithm of HSA concentrations ranging from 0.01 to 100 µg ml−1, with the sensitivity of 9.3 Hz/μg ml−1 and the detection limit of 0.01 µg ml−1, which is significantly lower than the minimum diagnosis limit of urine microalbumin.

A novel approach to fabricate a high performance flexible piezoelectric nanogenerator (PNG) by employing K0.5Na0.5NbO3 (KNN)/PDMS/C composite thin film has been proposed. The formed 12 wt% C doping KNN/PDMS PNG demonstrates a higher relative permittivity (Ɛr, 173.56) and larger remanent polarization (Pr, 1.84 µC/cm2) than pure KNN/PDMS film, thus serving as the possible origins of their comparative piezoelectric activities, which could generate an maximum output voltage of 10.55 V (3.3 times as much as the PNG without C doping). Besides, the PNG is able to light up a commercial green light-emitting diode (LED) through an energy storage capacitor (47 µF), showing its great potential as power of wearable and mobile devices.

Background: With the increasing serious problem of water environment pollution, it is a hot spot to study the high efficient sewage treatment method. Owning to the photosensitization of carbon nanomaterials, carbon doped TiO2 (C-TiO2) has higher photocatalytic activity. Method: Here, we proposed a new method, carbon-assisted method, to prepare C-TiO2 nanomaterials. We first used degreasing cotton as a dispersant to fully absorb the TiCl4 sol. Results: After high-temperature calcination, C-TiO2nanomaterials were obtained. Characterizations results showed that the high specific surface area C-TiO2 nanomaterials in the size of about 50 nm showed a broader light absorption and narrower bandgap spectrum than P25 (commercial TiO2 nanoparticles). Conclusion: The C-TiO2 nanomaterials showed stronger photocatalytic ability than P25.

Strain sensor is widely desired for flexible and wearable electronic devices, such as human motion capturing and electronic skin. In strain sensing, it is a challenge to ensure that the strain sensor based on CNTs–PDMS has both high-performance flexibility and sensitivity. Here, this study reports a flexible strain sensor based on the AuNPs/CNTs/PDMS composite films fabricated by in-situ reduction, which has high sensitivity and wide linear strain range. DFT revealed that the AuNPs effectively improved the conductivity of the composite films, which show high consistency with electrical test. The AuNPs synergistically improved the sensitivity and flexibility of strain sensors with CNTs in PDMS. The flexible strain sensors with 3 wt% CNTs and 16 h AuNPs’ reduction time have the higher gage factor of 366.7 at a linear strain ranging from 0 to 15%. We demonstrated the applicability of our high-performance strain sensors by testing the tiny motion sensing caused by wrist bending, finger bending, wrist raising, neck rotation, and facial muscle movement. The AuNPs/CNTs/PDMS composite film with high sensitivity, flexible, and stability provides a new elastomer nanocomposite as strain sensor for strain-sensing applications.

Nowadays, flexible strain sensors applied in the fields of health care and electronic skin have been widely studied and applied. In fact, the temperature characteristic of flexible strain sensors based on metal nanomaterials is rarely concerned. In this work, the ohmic and tensile properties of the flexible strain sensor based on silver nanowires–polydimethylsiloxane were tested and it was found that the sensor has good ohmic characteristics and a maximum gauge factor of 536.98. In addition, the resistance of the sensor was affected little by temperature when the temperature environment of the sensor was changed, and the resistance temperature coefficient of the flexible strain sensor is −1050 ppm/°C. Furthermore, it was found that the sensor was sensitive to minute strain when the sensors were applied to the two application tests of strain and pulse.

A novel Au-decorated α-Fe2O3 nanocomposite has been successfully prepared using 4-mercaptobenzoic acid as bridging agent via a facile and cost-effective method. The formed 10 mol% Au-decorated α-Fe2O3 (Au/α-Fe2O3) nanocomposite demonstrates a narrower band gap (1.88 eV), 4.3 times larger photocurrent, more hot spots, and stronger electromagnetic coupling effect between gold and iron oxide than pure hematite nanoparticles, thus serving as the possible origins of their comparative photocatalytic activities. In addition, the synthesized Au/α-Fe2O3 exhibits excellent in handling anionic dyes like methyl orange and congo red, remarkably superior to their α-Fe2O3 precursors, and efficiently improves persistent organic pollutants (POPs) treatment.

In this work, multifunctional α-Fe2O3@dopamine core-shell nanocomposites consisting of α-Fe2O3 core surrounded by a thin dopamine (DA) shell have been successfully fabricated. The crystal structure, surface morphology and optical properties of the samples were determined by XRD, SEM, TEM and UV–vis, respectively, indicating that the presence of thin DA shell could affect the optical properties of Fe2O3 nanostructures. When it was incubated with NIH3T3 cells and injected in living body, the concave shape Fe2O3@dopamine nanocomposites exhibited the highest cell viability (94.6% within 16 h), and harmless to the living body. Moreover, the concave shape Fe2O3@dopamine nanocomposites also displayed the highest image contrast and distinguishability (3.74 times of control group, and 1.5 times of purchased Au nanoparticles). Thus, α-Fe2O3@dopamine core-shell structures are promising candidates for precise photoacoustic imaging and therapeutic process.

In this paper, pure ZnO, Co3O4-ZnO, Pd@ZnO and Pd@Co3O4-ZnO composite nanofibers were synthesized by electrospinning method. Multiple characterizations were employed to investigate the crystal structure, composition, morphology, and bonding states of the Pd@Co3O4-ZnO composite nanofibers. The sensing properties of the as-synthesized nanofibers were evaluated toward different volatile organic components (VOCs) including ethanol, acetone, isopropanol and formaldehyde under the various operating temperatures. The obtained results have clearly demonstrated that the Pd@Co3O4-ZnO composite nanofibers exhibits significantly enhanced VOC sensing performance compared with other nanofibers. Specifically, the response of Pd@Co3O4-ZnO composite nanofibers toward 200 ppm ethanol is 59 at 240℃, which is much higher than that of ZnO nanofibers. The enhanced VOC sensing properties of Pd@Co3O4-ZnO composite nanofibers could be attributed to the electronic and chemical sensitizations of Pd and the p-n junction formation at the interface of Co3O4 and ZnO.

Here, we firstly report a wireless magnetoelastic (ME) nanobiosensor, based on ME materials and gold nanoparticles (AuNPs), for highly sensitive detection of atrazine employing the competitive immunoassay. In response to a time-varying magnetic field, the ME material longitudinally vibrates at its resonance frequency which can be affected by its mass loading. The layer of AuNPs coating on the ME material contributes to its biocompatibility, stability, and sensitivity. The atrazine antibody was oriented immobilized on the AuNPs-coated ME material surface through protein A, improving the nanobiosensor’s performance. Atomic force microscope (AFM) analysis proved that the immobilization of atrazine antibody was successful. Furthermore, to enhance the sensitivity, atrazine–albumin conjugate (Atr–BSA) was induced to compete with atrazine for binding with atrazine antibody, amplifying the signal response. The resonance frequency shift is inversely and linearly proportional to the logarithm of atrazine concentrations ranging from 1 ng/mL to 100 μg/mL, with the sensitivity of 3.43 Hz/μg mL−1 and the detection limit of 1 ng/mL, which is significantly lower than the standard established by US Environmental Protection Agency (EPA). The experimental results indicated that the ME nanobiosensor displayed strong specificity and stability toward atrazine. This study provides a new convenient method for rapid, selective, and highly sensitive detection of atrazine, which has implications for its applications in water quality monitoring and other environmental detection fields.

There is plenty of exploitable energy in the ambient environments. Triboelectric nanogenerator is an innovative electricity generation technology to convert the wasted mechanical energy into electrical energy. However, the output of conventional triboelectric nanogenerators cannot be employed efficiently because their tremendous internal resistance limits the current of electrons. Inspired by the principle of lightning rods, for the first time we propose the utilization of electrostatic discharge to improve the performance of triboelectric nanogenerators, which is realized by an opposite needles structure enclosed in an inert atmosphere. When this structure is connected in series with a vertical contact-separation triboelectric nanogenerator, the strong electric field near tips of two needles ionizes the gas around them, forming a conductive plasma channel between the tips, and releasing a mass of free charges. As a result, some exciting performances are obtained in triboelectric nanogenerator. The output peak-to-peak voltage is increased from 300 V to 1300 V, and the equivalent impedance of energy harvesting circuit is reduced from 100 MΩ to 10 kΩ. Especially in the optimal conditions, the maximum continuous power can even be significantly improved by 330.76%. Therefore, this work provides a new strategy for the energy conversion technology, which is significant for the advancement and application of triboelectric nanogenerators.

In photoelectrochemical (PEC) water splitting systems, crucial obstacles limiting their performance are poor charge carrier dynamics and high recombination rate of photoexcited electron hole pairs. Here, we report that this issue can be alleviated by engineering a hybrid-junction that is composed of homo- and hetero- junctions. This strategy is performed by facile hand-spraying MoS2 over the surface of a anatase/rutile homo-junction TiO2 film on the Ti substrate to further form a hybrid-junction photocathode. By applying this photocathode into PEC reactor, enhanced catalytic activity is achieved under visible light (AM1.5 illumination of 300 W/m2) with hydrogen evolution reaction (HER) potential of −114 mV versus reversible hydrogen electrode (RHE) at 10 mA/cm2 and long-term stability of more than 10 times improvement comparing to ordinary electrode without the introduciton of hybrid-junction. The hybrid-junction that effectively regulates charge separation and transfer pathways is proven to be responsible for the enhanced activity. As an novel exploration, this hybrid-junction system comprising of low-cost, efficient charge separation and transfer, and visible light responsivity offers a new path for relative materials to boost their PEC performance.

Promoting the detection range, durability, and shapeable manufacturing of flexible strain sensors is essential to broaden their applications. Therefore, in this study, styrene ethylene butylene styrene (SEBS) rubber as a flexible material and a melt-mixing molding method are adopted to design an ultra-flexible strain sensor. Carbon nanotubes (CNTs) are added to form a conductive network, and the effect of Ag flakes on improving the sensor performance is studied. The experiment results exhibit good strain–resistance dependent characteristics of the obtained sensor, which demonstrates an excellent sensing range of about 540% with a gauge factor (GF) of 5.197. The good hydrophobicity (water contact angle ≈120.4°), repeatable characteristics at different rates, strain-dependence and long-term recycling of the sensor are demonstrated as well. Finally, the fabricated round bracelet sensor is applied to detect different cross-sections, the movement of human joints, balloon inflation, bottle cap sealing and numerous other aspects.

Three-dimensional MEMS devices, which provide a mechanical response with high strain deformation, have been widely used in flexible electronics due to their excellent properties. In this paper, we introduce a kind of stretchable flexible buckling crossbeam-cilia Vector shear flow sensor. The transient model of shear flow signal simulation was established through COMSOL Multiphysics soft, a multi-physics coupling simulation software. The voltage signal output ratio of the sensor X channel and Y channel is as high as 0.44%, so it has good directivity, and the velocity sensitivity is as high as $6.4\times 10^{-3}$ Vms2/kg. It has laid a foundation for the manufacture and application of sensors and opened up a new road for ocean exploration.

The bionic application of electronic skin (e-skin) requires a high resolution close to that of human skin, while its long-term attachment to human body or robotic skin requires a porous structure that is air permeable and enables hair growth. To simultaneously meet the requirements of high resolution and porous structure, as well as improve the sensing performance, we propose a fully 3D printed e-skin with high-resolution and air permeable porous structure. The flexible substrate and electrodes are 3D printed by a direct ink writing extrusion printer. The sensitive material is 3D printed by a self-made low-viscosity liquid extrusion 3D print module. This e-skin has a high sensor density of 100/cm2, which is close to the resolution of the human fingertip skin. The piezoresistive sensor units of e-skin exhibit a highly linear resistance response and a relatively performance consistency between devices. Owing to the porous and breathable structure, better human comfort and mechanical heat dissipation are realized. This high-resolution e-skin is successfully applied to identify small-sized objects with complex contours.