Anhui Polytechnic University

Metal oxide gas sensors are predominant solid-state gas detecting devices for domestic, commercial and industrial applications, which have many advantages such as low cost, easy production, and compact size. However, the performance of such sensors is significantly influenced by the morphology and structure of sensing materials, resulting in a great obstacle for gas sensors based on bulk materials or dense films to achieve highly-sensitive properties. Lots of metal oxide nanostructures have been developed to improve the gas sensing properties such as sensitivity, selectivity, response speed, and so on. Here, we provide a brief overview of metal oxide nanostructures and their gas sensing properties from the aspects of particle size, morphology and doping. When the particle size of metal oxide is close to or less than double thickness of the space-charge layer, the sensitivity of the sensor will increase remarkably, which would be called "small size effect", yet small size of metal oxide nanoparticles will be compactly sintered together during the film coating process which is disadvantage for gas diffusion in them. In view of those reasons, nanostructures with many kinds of shapes such as porous nanotubes, porous nanospheres and so on have been investigated, that not only possessed large surface area and relatively mass reactive sites, but also formed relatively loose film structures which is an advantage for gas diffusion. Besides, doping is also an effective method to decrease particle size and improve gas sensing properties. Therefore, the gas sensing properties of metal oxide nanostructures assembled by nanoparticles are reviewed in this article. The effect of doping is also summarized and finally the perspectives of metal oxide gas sensor are given.

Single-crystalline Zn(2)GeO(4) nanobelts with lengths of hundreds of micrometers, thicknesses as small as ∼7 nm, and aspect ratios of up to 10,000 were synthesized in a binary ethylenediamine/water solvent system using a solvothermal route. The ultralong and ultrathin geometry of the Zn(2)GeO(4) nanoribbon proves to greatly promote the photocatalytic activity toward reduction of CO(2) into renewable hydrocarbon fuel (CH(4)) in the presence of water vapor.

Abstract Robust hollow spheres consisting of molecular‐scale alternating titania (Ti 0.91 O 2 ) nanosheets and graphene (G) nanosheets are successfully fabricated by a layer‐by‐layer assembly technique with polymer beads as sacrificial templates using a microwave irradiation technique to simultaneously remove the template and reduce graphene oxide into graphene. The molecular scale, 2D contact of Ti 0.91 O 2 nanosheets and G nanosheets in the hollow spheres is distinctly different from the prevenient G‐based TiO 2 nanocomposites prepared by simple integration of TiO 2 and G nanosheets. The nine times increase of the photocatalytic activity of G‐Ti 0.91 O 2 hollow spheres relative to commercial P25 TiO 2 is confirmed with photoreduction of CO 2 into renewable fuels (CO and CH 4 ). The large enhancement in the photocatalytic activity benefits from: 1) the ultrathin nature of Ti 0.91 O 2 nanosheets allowing charge carriers to move rapidly onto the surface to participate in the photoreduction reaction; 2) the sufficiently compact stacking of ultrathin Ti 0.91 O 2 nanosheets with G nanosheets allowing the photogenerated electron to transfer fast from the Ti 0.91 O 2 nanosheets to G to enhance lifetime of the charge carriers; and 3) the hollow structure potentially acting as a photon trap‐well to allow the multiscattering of incident light for the enhancement of light absorption.

Abstract Selective reduction of ketone/aldehydes to alcohols is of great importance in green chemistry and chemical engineering. Highly efficient catalysts are still demanded to work under mild conditions, especially at room temperature. Here we present a synergistic function of single-atom palladium (Pd 1 ) and nanoparticles (Pd NPs ) on TiO 2 for highly efficient ketone/aldehydes hydrogenation to alcohols at room temperature. Compared to simple but inferior Pd 1 /TiO 2 and Pd NPs /TiO 2 catalysts, more than twice activity enhancement is achieved with the Pd 1+NPs /TiO 2 catalyst that integrates both Pd 1 and Pd NPs on mesoporous TiO 2 supports, obtained by a simple but large-scaled spray pyrolysis route. The synergistic function of Pd 1 and Pd NPs is assigned so that the partial Pd 1 dispersion contributes enough sites for the activation of C=O group while Pd NPs site boosts the dissociation of H 2 molecules to H atoms. This work not only contributes a superior catalyst for ketone/aldehydes hydrogenation, but also deepens the knowledge on their hydrogenation mechanism and guides people to engineer the catalytic behaviors as needed.

An ultrathin, single-crystal WO3 nanosheet of ∼4-5 nm in thickness, corresponding to six repeating unit cells of monoclinic WO3 along the c axis, was synthesized with laterally oriented attachment of tiny WO3 nanocrystals formed using a solid-liquid phase arc discharge route in an aqueous solution. Size-quantization effects in this ultrathin nanostructure alter the WO3 band gap to enable the nanosheet to exhibit enhanced performance for photocatalytic reduction of CO2 in the presence of water in hydrocarbon fuels that do not exist in its bulk form.

A Zn(II)-based fluorescent metal-organic framework (MOF) was synthesized and applied as a highly sensitive and quickly responsive chemical sensor for antibiotic detection in simulated wastewater. The fluorescent chemical sensor, denoted FCS-1, exhibited enhanced fluorescence derived from its highly ordered, 3D MOF structure as well as excellent water stability in the practical pH range of simulated antibiotic wastewater (pH = 3.0-9.0). Remarkably, FCS-1 was able to effectively detect a series of sulfonamide antibiotics via photoinduced electron transfer that caused detectable fluorescence quenching, with fairly low detection limits. Two influences impacting measurements related to wastewater treatment and water quality monitoring, the presence of heavy-metal ions and the pH of solutions, were studied in terms of fluorescence quenching, which was nearly unaffected in sulfonamide-antibiotic detection. Additionally, the effective detection of sulfonamide antibiotics was rationalized by the theoretical computation of the energy bands of sulfonamide antibiotics, which revealed a good match between the energy bands of FCS-1 and sulfonamide antibiotics, in connection with fluorescence quenching in this system.

Abstract Photochemical conversion of CO 2 into high-value C 2+ products is difficult to achieve due to the energetic and mechanistic challenges in forming multiple C-C bonds. Herein, an efficient photocatalyst for the conversion of CO 2 into C 3 H 8 is prepared by implanting Cu single atoms on Ti 0.91 O 2 atomically-thin single layers. Cu single atoms promote the formation of neighbouring oxygen vacancies (V O s) in Ti 0.91 O 2 matrix. These oxygen vacancies modulate the electronic coupling interaction between Cu atoms and adjacent Ti atoms to form a unique Cu-Ti-V O unit in Ti 0.91 O 2 matrix. A high electron-based selectivity of 64.8% for C 3 H 8 (product-based selectivity of 32.4%), and 86.2% for total C 2+ hydrocarbons (product-based selectivity of 50.2%) are achieved. Theoretical calculations suggest that Cu-Ti-V O unit may stabilize the key *CHOCO and *CH 2 OCOCO intermediates and reduce their energy levels, tuning both C 1 -C 1 and C 1 -C 2 couplings into thermodynamically-favourable exothermal processes. Tandem catalysis mechanism and potential reaction pathway are tentatively proposed for C 3 H 8 formation, involving an overall ( 20 e − – 20 H + ) reduction and coupling of three CO 2 molecules at room temperature.

The photoreduction of CO2 on inorganic semiconductors has been researched for several decades, but the conversion efficiency is still low due to the recombination of photo-generated electron–hole pairs, low utilization efficiency of solar energy and weak adsorption of CO2. Here we for the first time demonstrate that metal–organic frameworks such as ZIF-8 can effectively adsorb CO2 dissolved in water, and promote photocatalytic activity of a semiconductor catalyst in CO2 reduction into liquid fuels in an aqueous medium. In particular, Zn2GeO4/ZIF-8 hybrid nanorods were successfully synthesized by growing ZIF-8 nanoparticles on Zn2GeO4 nanorods. The Zn2GeO4/ZIF-8 nanocomposite inherits both high CO2 adsorption capacity of ZIF-8 nanoparticles and high crystallinity of Zn2GeO4 nanorods. The Zn2GeO4/ZIF-8 hybrid nanorods containing 25 wt% ZIF-8 exhibit 3.8 times higher dissolved CO2 adsorption capacity than the bare Zn2GeO4 nanorods, resulting in a 62% enhancement in photocatalytic conversion of CO2 into liquid CH3OH fuel. The strategy reported here is promising for developing more active photocatalysts for improving CO2 conversion efficiency by taking advantage of excellent adsorption property of metal–organic frameworks in aqueous media.

Abstract Relaxor ferroelectric (FE) ceramic capacitors have attracted increasing attention for their excellent energy‐storage performance. However, it is extremely difficult to achieve desirable comprehensive energy‐storage features required for industrial applications. In this work, very high recoverable energy density W rec ≈ 8.73 J cm –3 , high efficiency η ≈ 80.1%, ultrafast discharge rate of <85 ns, and temperature‐insensitive high W rec and η ( W rec ≈ 5.73 ± 4% J cm –3 , η ≈ 75 ± 6%, 25–200 °C) are simultaneously obtained in 0.68NaNbO 3 ‐0.32(Bi 0.5 Li 0.5 )TiO 3 relaxor FE ceramics by introducing various polarization configurations in combination with microstructure modification. The structure mechanism for the excellent energy‐storage performance is disclosed by analyzing in situ structure evolution on multiple scales during loading/unloading by means of transmission electron microscopy and Raman spectroscopy. Both local regions consisting of different‐scale polar nanodomains and a nonpolar matrix, and local orthorhombic symmetry remaining with electric fields ensure a linear‐like polarization response within a wide field and temperature range owing to significantly delayed polarization saturation. The stabilization of orthorhombic FE phases rather than antiferroelectric orthorhombic phases in NaNbO 3 after adding (Bi 0.5 Li 0.5 )TiO 3 is also explored by means of X‐ray diffraction, dielectric properties, and selected area electron diffraction. In comparison with antiferroelectric ceramics, NaNbO 3 ‐based relaxor FE ceramics provide a new solution to successfully design next‐generation pulsed power capacitors.

In the framework of the networked control systems (NCSs), the components are connected with each other over a shared band-limited network. The merits of NCSs include easy extensibility, resource sharing, high reliability and so forth. However, the insertion of the communication network brings many challenges, such as network-induced phenomena and cyber-security, which should be handled properly. On the other hand, the sliding mode control (SMC) has become an effective scheme for the synthesis of NCSs due to its strong robustness and SMC has wide applications in NCSs. In this paper, some recent advances on SMC for NCSs are reviewed. In particular, some new SMC schemes for NCSs subject to time-delay, packet losses, quantisation and uncertainty/disturbance are summarised firstly. Subsequently, the problem of SMC for NCSs under scheduling protocols is discussed, where different communication protocols are introduced for the energy saving purpose during the synthesis of NCSs. Next, some recent results on SMC for NCSs with actuator/sensor fault and cyber-attack are recalled. Finally, the conclusion is provided and the potential research challenges on SMC for NCSs are pointed out.

The complex detection background and lesion features make the automatic detection of dermoscopy image lesions face many challenges. The previous solutions mainly focus on using larger and more complex models to improve the accuracy of detection, there is a lack of research on significant intra-class differences and inter-class similarity of lesion features. At the same time, the larger model size also brings challenges to further algorithm application; In this paper, we proposed a lightweight skin cancer recognition model with feature discrimination based on fine-grained classification principle. The propose model includes two common feature extraction modules of lesion classification network and a feature discrimination network. Firstly, two sets of training samples (positive and negative sample pairs) are input into the feature extraction module (Lightweight CNN) of the recognition model. Then, two sets of feature vectors output from the feature extraction module are used to train the two classification networks and feature discrimination networks of the recognition model at the same time, and the model fusion strategy is applied to further improve the performance of the model, the proposed recognition method can extract more discriminative lesion features and improve the recognition performance of the model in a small amount of model parameters; In addition, based on the feature extraction module of the proposed recognition model, U-Net architecture, and migration training strategy, we build a lightweight semantic segmentation model of lesion area of dermoscopy image, which can achieve high precision lesion area segmentation end-to-end without complicated image preprocessing operation; The performance of our approach was appraised through widespread experiments comparative and feature visualization analysis, the outcome indicates that the proposed method has better performance than the start-of-the-art deep learning-based approach on the ISBI 2016 skin lesion analysis towards melanoma detection challenge dataset.

The wide applications of X-ray computed tomography (CT) bring low-dose CT (LDCT) into a clinical prerequisite, but reducing the radiation exposure in CT often leads to significantly increased noise and artifacts, which might lower the judgment accuracy of radiologists. In this paper, we put forward a domain progressive 3D residual convolution network (DP-ResNet) for the LDCT imaging procedure that contains three stages: sinogram domain network (SD-net), filtered back projection (FBP), and image domain network (ID-net). Though both are based on the residual network structure, the SD-net and ID-net provide complementary effect on improving the final LDCT quality. The experimental results with both simulated and real projection data show that this domain progressive deep-learning network achieves significantly improved performance by combing the network processing in the two domains.

Recursive filtering for nonlinear systems, one of the core technologies of modern industrial systems, is an ever-increasing research topic from the control and computer communities. Some challenges from communication scheduling, limited bandwidth as well as security vulnerability have to be seriously handled though the applications of communication technologies bring into some conveniences. As such, it is of utmost significance in theory and great importance in applications to establish engineering-feasible recursive filtering algorithms for networked nonlinear systems. This paper focuses on the development of this topic and provides an up-to-date survey of the existing nonlinear filtering techniques. The introduction of three classes of communication protocols is first presented in great detail, and then comprehensive reviews and summaries of the nonlinear recursive filtering problems with Gaussian/non-Gaussian noises are elaborated according to different strategies responding to nonlinear functions or noises. Particularly, the reviews are layout from the extended Kalman filtering, the unscented/cubature Kalman filtering, the set-membership filtering as well as the $ H_\infty $ H∞ filtering. Furthermore, several challenging issues are raised to stimulate further related theoretical research and practical applications in this field.

Abstract Breathable, flexible, and highly sensitive pressure sensors have drawn increasing attention due to their potential in wearable electronics for body‐motion monitoring, human‐machine interfaces, etc. However, current pressure sensors are usually assembled with polymer substrates or encapsulation layers, thus causing discomfort during wearing (i.e., low air/vapor permeability, mechanical mismatch) and restricting their applications. A breathable and flexible pressure sensor is reported with nonwoven fabrics as both the electrode (printed with MXene interdigitated electrode) and sensing (coated with MXene/silver nanowires) layers via a scalable screen‐printing approach. Benefiting from the multi‐layered porous structure, the sensor demonstrates good air permeability with high sensitivity (770.86–1434.89 kPa −1 ), a wide sensing range (0–100 kPa), fast response/recovery time (70/81 ms), and low detection limit (≈1 Pa). Particularly, this sensor can detect full‐scale human motion (i.e., small‐scale pulse beating and large‐scale walking/running) with high sensitivity, excellent cycling stability, and puncture resistance. Additionally, the sensing layer of the pressure sensor also displays superior sensitivity to humidity changes, which is verified by successfully monitoring human breathing and spoken words while wearing a sensor‐embedded mask. Given the outstanding features, this breathable sensor shows promise in the wearable electronic field for body health monitoring, sports activity detection, and disease diagnosis.

Fault detection of networked dynamical systems (NDSs) has attracted ever-increasing attention since it can maintain high-quality products as well as operational safety. Considering the utilisation of communication networks, it is desirable to develop engineering-oriented approaches to NDSs subject to the incompleteness from network-induced phenomena (NIP) and the sparsity from communication scheduling. As such, this paper presents a survey of trends and techniques of fault detection in NDSs. First, some typical fault detection methods are summarised based on the various residual assessment functions. Then, some interesting developments are systematically reviewed from two aspects, that is, fault detection with NIP and fault detection under various communication scheduling schemes. In addition, some frontier topics are extensively discussed on fault detection with communication protocols, cyber-attacks, and its applications. Finally, several future works of fault detection problems are investigated to motivate future research.

The multicomponent reactions (MCRs) consist of two or more synthetic steps which are carried out without isolation of any intermediate thus reducing time, saving money, energy and raw materials. The development of MCRs in the presence of molecular iodine is an efficient approach that meets with the requirements of sustainable chemistry. The aim of this review is to highlight the synergistic effect of the combined use of MCRs and molecular iodine for the development of new eco-compatible methodologies for organic chemistry.

This paper describes a solvothermal approach to synthesize CuInS2 quantum dots (QDs) and demonstrates their application as a potential electron accepting material for polymer-based hybrid solar cells, for the first time. The CuInS2 QDs with a size of 2–4 nm are synthesized by the solvothermal method with 4-bromothiophenol (HSPh) as both reduction and capping agents, and characterized by XRD, XPS, TEM, FT-IR, cyclic voltammetry (CV), and absorption and photoluminescence spectra. Results reveal that the CuInS2 QDs result from the solvothermal decomposition of a soluble organic sodium salt as an intermediate precursor formed by simple reactions among CuCl2, InCl3, HSPh and Na2S at room temperature; they have an ionization potential (IP) of −5.8 eV and an electron affinity (EA) of −4.0 eV and can quench effectively the luminescence of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV). Due to the favorable IP and EA positions with respect to MEH-PPV, the CuInS2 QDs act as an effective electron acceptor for the hybrid solar cells based on MEH-PPV/CuInS2-QDs blends with a wide spectral response extending from 300 to 900 nm, by allowing the efficient charge separation for neutral excited states produced either on the polymer or on the QDs. The MEH-PPV/CuInS2-QDs solar cells exhibit a promising open circuit voltage (Voc) of 0.62 V under the monochromic illumination of 15.85 mW cm−2 at 470 nm. The charge transfer processes in the solar cells are also described.

Abstract Supercritical relaxor nanograined ferroelectrics are demonstrated for high‐performance dielectric capacitors, showing record‐high overall properties of energy density ≈13.1 J cm −3 and field‐insensitive efficiency ≈90% at ≈74 kV mm −1 and superior charge–discharge performances of high power density ≈700 MW cm −3 , high discharge energy density ≈6.67 J cm −3 , and ultrashort discharge time <40 ns at 55 kV mm −1 . Ex/in situ transmission electron microscopy, Raman spectroscopy, and synchrotron X‐ray diffraction provide clear evidence of the supercritical behavior in (Na,K)(Sb,Nb)O 3 –SrZrO 3 –(Bi 0.5 Na 0.5 )ZrO 3 ceramics, being achieved by engineering the coexistence of multiple local symmetries within the ergodic relaxor zone. The vanished difference between the ground relaxor state and the high‐field supercritical state eliminates polarization hysteresis. The supercritical evolution with electric field enables a highly delayed polarization saturation with continuously increased polarization magnitudes. The results demonstrate that such a design strategy of compositionally induced and field‐manipulated supercritical behavior can be generalizable for developing desirable energy‐storage dielectrics for applications in ceramic/film capacitors.

With the rapid development of information technology and electronics, the traditional textiles hardly fulfill the requirements of wearable electronics. Multifunctional textile-based electronics integrated with energy storage, joule heating, electromagnetic interference (EMI) shielding and sensing has become a favorable solution. Herein, a scalable spray-coating and dip-coating strategy is developed to fabricate the multifunctional reduced graphene oxide/Ti3C2Tx MXenes decorated cotton fabrics. The RGO/MXene modified fabrics show hydrophilic surface, high electrical conductivity, good flexibility and breathability. In addition, the RGO/MXene modified fabrics demonstrate excellent electrochemical performance, and the assembled all-solid-state supercapacitors show one of the highest specific capacitances of 383.3 F g−1 (258 mF cm−2). More importantly, the RGO/MXene fabrics show distinctive negative resistance variation and high sensitivity when they are applied as the strain sensors to detect the human motions including the bending of finger, elbow, knee and swallowing process. Moreover, the RGO/MXene fabrics show good joule heating and EMI shielding performance. This work may shed light on cost-effective but high-performance textile-based strain sensors, EMI shielding and electrochemical energy storage devices, and paves the way for the development of multifunctional wearable electronics.

the world is experiencing a strong rush towards modern technology, while specialized companies are living a terrible rush in the information technology towards the so-called Internet of things IoT or Internet of objects, which is the integration of things with the world of Internet, by adding hardware or/and software to be smart and so be able to communicate with each other and participate effectively in all aspects of daily life, so enabling new forms of communication between people and things, and between things themselves, that’s will change the traditional life into a high style of living. But it won’t be easy, because there are still many challenges and issues that need to be addressed and have to be viewed from various aspects to realize their full potential. The main objective of this review paper will provide the reader with a detailed discussion from a technological and social perspective. The various IoT challenges and issues, definition and architecture were discussed. Furthermore, a description of several sensors and actuators and their smart communication. Also, the most important application areas of IoT were presented. This work will help readers and researchers understand the IoT and its potential application in the real world.