Qingdao University of Science and Technology

Fog/edge computing has been proposed to be integrated with Internet of Things (IoT) to enable computing services devices deployed at network edge, aiming to improve the user's experience and resilience of the services in case of failures. With the advantage of distributed architecture and close to end-users, fog/edge computing can provide faster response and greater quality of service for IoT applications. Thus, fog/edge computing-based IoT becomes future infrastructure on IoT development. To develop fog/edge computing-based IoT infrastructure, the architecture, enabling techniques, and issues related to IoT should be investigated first, and then the integration of fog/edge computing and IoT should be explored. To this end, this paper conducts a comprehensive overview of IoT with respect to system architecture, enabling technologies, security and privacy issues, and present the integration of fog/edge computing and IoT, and applications. Particularly, this paper first explores the relationship between cyber-physical systems and IoT, both of which play important roles in realizing an intelligent cyber-physical world. Then, existing architectures, enabling technologies, and security and privacy issues in IoT are presented to enhance the understanding of the state of the art IoT development. To investigate the fog/edge computing-based IoT, this paper also investigate the relationship between IoT and fog/edge computing, and discuss issues in fog/edge computing-based IoT. Finally, several applications, including the smart grid, smart transportation, and smart cities, are presented to demonstrate how fog/edge computing-based IoT to be implemented in real-world applications.

Antibiotics and organic explosives are among the main organic pollutants in wastewater; their detection and removal are quite important but challenging. As a new class of porous materials, metal-organic frameworks (MOFs) are considered as a promising platform for the sensing and adsorption applications. In this work, guided by a topological design approach, two stable isostructural Zr(IV)-based MOFs, Zr6O4(OH)8(H2O)4(CTTA)8/3 (BUT-12, H3CTTA = 5'-(4-carboxyphenyl)-2',4',6'-trimethyl-[1,1':3',1″-terphenyl]-4,4″-dicarboxylic acid) and Zr6O4(OH)8(H2O)4(TTNA)8/3 (BUT-13, H3TTNA = 6,6',6″-(2,4,6-trimethylbenzene-1,3,5-triyl)tris(2-naphthoic acid)) with the the-a topological structure constructed by D4h 8-connected Zr6 clusters and D3h 3-connected linkers were designed and synthesized. The two MOFs are highly porous with the Brunauer-Emmett-Teller surface area of 3387 and 3948 m(2) g(-1), respectively. Particularly, BUT-13 features one of the most porous water-stable MOFs reported so far. Interestingly, these MOFs represent excellent fluorescent properties, which can be efficiently quenched by trace amounts of nitrofurazone (NZF) and nitrofurantoin (NFT) antibiotics as well as 2,4,6-trinitrophenol (TNP) and 4-nitrophenol (4-NP) organic explosives in water solution. They are responsive to NZF and TNP at parts per billion (ppb) levels, which are among the best performing luminescent MOF-based sensing materials. Simultaneously, both MOFs also display high adsorption abilities toward these organic molecules. It was demonstrated that the adsorption plays an important role in the preconcentration of analytes, which can further increase the fluorescent quenching efficiency. These results indicate that BUT-12 and -13 are favorable materials for the simultaneous selective detection and removal of specific antibiotics and organic explosives from water, being potentially useful in monitoring water quality and treating wastewater.

Audio pattern recognition is an important research topic in the machine learning area, and includes several tasks such as audio tagging, acoustic scene classification, music classification, speech emotion classification and sound event detection. Recently, neural networks have been applied to tackle audio pattern recognition problems. However, previous systems are built on specific datasets with limited durations. Recently, in computer vision and natural language processing, systems pretrained on large-scale datasets have generalized well to several tasks. However, there is limited research on pretraining systems on large-scale datasets for audio pattern recognition. In this paper, we propose pretrained audio neural networks (PANNs) trained on the large-scale AudioSet dataset. These PANNs are transferred to other audio related tasks. We investigate the performance and computational complexity of PANNs modeled by a variety of convolutional neural networks. We propose an architecture called Wavegram-Logmel-CNN using both log-mel spectrogram and waveform as input feature. Our best PANN system achieves a state-of-the-art mean average precision (mAP) of 0.439 on AudioSet tagging, outperforming the best previous system of 0.392. We transfer PANNs to six audio pattern recognition tasks, and demonstrate state-of-the-art performance in several of those tasks. We have released the source code and pretrained models of PANNs: <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://github.com/qiuqiangkong/audioset_tagging_cnn</uri> .

Incorporating passive radiative cooling structures into personal thermal management technologies could effectively defend humans against intensifying global climate change. We show that large-scale woven metafabrics can provide high emissivity (94.5%) in the atmospheric window and high reflectivity (92.4%) in the solar spectrum because of the hierarchical-morphology design of the randomly dispersed scatterers throughout the metafabric. Through scalable industrial textile manufacturing routes, our metafabrics exhibit desirable mechanical strength, waterproofness, and breathability for commercial clothing while maintaining efficient radiative cooling ability. Practical application tests demonstrated that a human body covered by our metafabric could be cooled ~4.8°C lower than one covered by commercial cotton fabric. The cost-effectiveness and high performance of our metafabrics present substantial advantages for intelligent garments, smart textiles, and passive radiative cooling applications.

Abstract Construction of Z-scheme heterostructure is of great significance for realizing efficient photocatalytic water splitting. However, the conscious modulation of Z-scheme charge transfer is still a great challenge. Herein, interfacial Mo-S bond and internal electric field modulated Z-scheme heterostructure composed by sulfur vacancies-rich ZnIn 2 S 4 and MoSe 2 was rationally fabricated for efficient photocatalytic hydrogen evolution. Systematic investigations reveal that Mo-S bond and internal electric field induce the Z-scheme charge transfer mechanism as confirmed by the surface photovoltage spectra, DMPO spin-trapping electron paramagnetic resonance spectra and density functional theory calculations. Under the intense synergy among the Mo-S bond, internal electric field and S-vacancies, the optimized photocatalyst exhibits high hydrogen evolution rate of 63.21 mmol∙g −1 ·h −1 with an apparent quantum yield of 76.48% at 420 nm monochromatic light, which is about 18.8-fold of the pristine ZIS. This work affords a useful inspiration on consciously modulating Z-scheme charge transfer by atomic-level interface control and internal electric field to signally promote the photocatalytic performance.

Abstract Electrochemical water splitting plays a crucial role in the development of clean and renewable energy production and conversion, which is a promising pathway to reduce social dependence on fossil fuels. Thus, highly active, cost‐efficient, and robust catalysts must be developed to reduce the reaction overpotential and increase electrocatalytic efficiency. In this review, recent research efforts toward developing advanced electrocatalysts based on noble metals with outstanding performance for water splitting catalysis, which is mainly dependent on their structure engineering, are summarized. First, a simple description of the water‐splitting mechanism and some promising structure engineering strategies are given, including heteroatom incorporation, strain engineering, interface/hybrid engineering, and single atomic construction. Then, the underlying relationship between noble metal electronic/geometric structure and performance for water splitting is discussed with the assistance of theoretical simulation. Finally, a personal perspective is provided in order to highlight the challenges and opportunities for developing novel electrocatalysts suitable for a wide range of commercial uses in water splitting for structural engineering applications.

Abstract Hydrogels of conducting polymers, particularly poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), provide a promising electrical interface with biological tissues for sensing and stimulation, owing to their favorable electrical and mechanical properties. While existing methods mostly blend PEDOT:PSS with other compositions such as non-conductive polymers, the blending can compromise resultant hydrogels’ mechanical and/or electrical properties. Here, we show that designing interconnected networks of PEDOT:PSS nanofibrils via a simple method can yield high-performance pure PEDOT:PSS hydrogels. The method involves mixing volatile additive dimethyl sulfoxide (DMSO) into aqueous PEDOT:PSS solutions followed by controlled dry-annealing and rehydration. The resultant hydrogels exhibit a set of properties highly desirable for bioelectronic applications, including high electrical conductivity (~20 S cm −1 in PBS, ~40 S cm −1 in deionized water), high stretchability (&gt; 35% strain), low Young’s modulus (~2 MPa), superior mechanical, electrical and electrochemical stability, and tunable isotropic/anisotropic swelling in wet physiological environments.

Water is vital for plant growth and development. Water-deficit stress, permanent or temporary, limits the growth and the distribution of natural vegetation and the performance of cultivated plants more than any other environmental factors do. Although research and practices aimed at improving water-stress resistance and water-use efficiency have been carried out for many years, the mechanism involved is still not clear. Further understanding and manipulating plant-water relations and water-stress tolerance at the scale of physiology and molecular biology can significantly improve plant productivity and environmental quality. Currently, post-genomics and metabolomics are very important to explore anti-drought gene resource in different life forms, but modern agricultural sustainable development must be combined with plant physiological measures in the field, on the basis of which post-genomics and metabolomics will have further a practical prospect. In this review, we discussed the anatomical changes and drought-tolerance strategies under drought condition in higher plants.

Abstract The surface chemistry of solid electrolyte interphase is one of the critical factors that govern the cycling life of rechargeable batteries. However, this chemistry is less explored for zinc anodes, owing to their relatively high redox potential and limited choices in electrolyte. Here, we report the observation of a zinc fluoride-rich organic/inorganic hybrid solid electrolyte interphase on zinc anode, based on an acetamide-Zn(TFSI) 2 eutectic electrolyte. A combination of experimental and modeling investigations reveals that the presence of anion-complexing zinc species with markedly lowered decomposition energies contributes to the in situ formation of an interphase. The as-protected anode enables reversible (~100% Coulombic efficiency) and dendrite-free zinc plating/stripping even at high areal capacities (&gt;2.5 mAh cm ‒2 ), endowed by the fast ion migration coupled with high mechanical strength of the protective interphase. With this interphasial design the assembled zinc batteries exhibit excellent cycling stability with negligible capacity loss at both low and high rates.

Environment-related parameters, including viscosity, polarity, temperature, hypoxia, and pH, play pivotal roles in controlling the physical or chemical behaviors of local molecules. In particular, in a biological environment, such factors predominantly determine the biological properties of the local environment or reflect corresponding status alterations. Abnormal changes in these factors would cause cellular malfunction or become a hallmark of the occurrence of severe diseases. Therefore, in recent years, they have increasingly attracted research interest from the fields of chemistry and biological chemistry. With the emergence of fluorescence sensing and imaging technology, several fluorescent chemosensors have been designed to respond to such parameters and to further map their distributions and variations in vitro/in vivo. In this work, we have reviewed a number of various environment-responsive chemosensors related to fluorescent recognition of viscosity, polarity, temperature, hypoxia, and pH that have been reported thus far.

MXenes refer to a family of 2D transition metal carbides/nitrides that are rich in chemistry. The first member of the family, Ti3C2Tx, was reported in 2011. Since then MXenes have opened up an exciting new field in 2D inorganic functional materials by virtue of their intrinsic electronic conductivity, superior hydrophilicity, rich surface chemistry and layered structure, as evidenced by the fact that the number of papers on MXenes has increased exponentially. The unique properties and ease of processing have positioned them as promising materials for a variety of applications including energy storage, especially for supercapacitors. In this review, we aim to summarize the current advances in MXene research on supercapacitors. We begin by reviewing various fabrication routes and their influence on the structure and surface chemistry of MXenes. The structure, properties, stability, and species of layered MXenes are then introduced. The focus then turns to the capacitive energy-storage mechanisms and the factors determining the electrochemical behavior and performance in supercapacitors. Besides, various types of MXene-based supercapacitors are summarized to highlight the significance of MXenes in constructing energy storage devices. Finally, challenges and prospects in this booming field are proposed to promote further development of MXenes in supercapacitors.

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

Abstract Exploration of high‐efficiency, economical, and ultrastable electrocatalysts for the oxygen reduction reaction (ORR) to substitute precious Pt is of great significance in electrochemical energy conversion devices. Single‐atom catalysts (SACs) have sparked tremendous interest for their maximum atom‐utilization efficiency and fascinating properties. Therefore, the development of effective synthetic methodology toward SACs becomes highly imperative yet still remains greatly challenging. Herein, a reliable SiO 2 ‐templated strategy is elaborately designed to synthesize atomically dispersed Fe atoms anchored on N‐doped carbon nanospheres (denoted as Fe–N–C HNSs) using the cheap and sustainable biomaterial of histidine (His) as the N and C precursor. By virtue of the numerous atomically dispersed Fe–N 4 moieties and unique spherical hollow architecture, the as‐fabricated Fe–N–C HNSs exhibit excellent ORR performance in alkaline medium with outstanding activity, high long‐term stability, and superior tolerance to methanol crossover, exceeding the commercial Pt/C catalyst and most previously reported non‐precious‐metal catalysts. This present synthetic strategy will provide new inspiration to the fabrication of various high‐efficiency single‐atom catalysts for diverse applications.

Abstract The oxygen evolution reaction (OER) is a key reaction for many electrochemical devices. To date, many OER electrocatalysts function well in alkaline media, but exhibit poor performances in neutral and acidic media, especially the acidic stability. Herein, sodium‐decorated amorphous/crystalline RuO 2 with rich oxygen vacancies (a/c‐RuO 2 ) was developed as a pH‐universal OER electrocatalyst. The a/c‐RuO 2 shows remarkable resistance to acid corrosion and oxidation during OER, which leads to an extremely high catalytic stability, as confirmed by a negligible overpotential increase after continuously catalyzing OER for 60 h at pH=1. Besides, a/c‐RuO 2 also exhibits superior OER activities to commercial RuO 2 and most reported OER catalysts under all pH conditions. Theoretical calculations indicated that the introduction of Na dopant and oxygen vacancy in RuO 2 weakens the adsorption strength of the OER intermediates by engineering the d ‐band center, thereby lowering the energy barrier for OER.

Abstract Designing electrocatalysts with high-performance for both reduction and oxidation reactions faces severe challenges. Here, the uniform and ultrasmall (~3.4 nm) high-entropy alloys (HEAs) Pt 18 Ni 26 Fe 15 Co 14 Cu 27 nanoparticles are synthesized by a simple low-temperature oil phase strategy at atmospheric pressure. The Pt 18 Ni 26 Fe 15 Co 14 Cu 27 /C catalyst exhibits excellent electrocatalytic performance for hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). The catalyst shows ultrasmall overpotential of 11 mV at the current density of 10 mA cm −2 , excellent activity (10.96 A mg −1 Pt at −0.07 V vs. reversible hydrogen electrode) and stability in the alkaline medium. Furthermore, it is also the efficient catalyst (15.04 A mg −1 Pt ) ever reported for MOR in alkaline solution. Periodic DFT calculations confirm the multi-active sites for both HER and MOR on the HEA surface as the key factor for both proton and intermediate transformation. Meanwhile, the construction of HEA surfaces supplies the fast site-to-site electron transfer for both reduction and oxidation processes.

An integrated preparation of safety‐reinforced poly(propylene carbonate)‐based all‐solid polymer electrolyte is shown to be applicable to ambient‐temperature solid polymer lithium batteries. In contrast to pristine poly(ethylene oxide) solid polymer electrolyte, this solid polymer electrolyte exhibits higher ionic conductivity, wider electrochemical window, better mechanical strength, and superior rate performance at 20 °C. Moreover, lithium iron phosphate/lithium cell using such solid polymer electrolyte can charge and discharge even at 120 °C. It is also noted that the solid‐state soft‐package lithium cells assembled with this solid polymer electrolyte can still power a red light‐emitting diode lamp without suffering from internal short‐circuit failures even after cutting off one part of the battery. Considering the aspects mentioned above, the solid polymer electrolyte is eligible for practical lithium battery applications with improved reliability and safety. Just as important, a new perspective that the degree of amorphous state of polymer is also as critical as its low glass transition temperature for the exploration of room temperature solid polymer electrolyte is illustrated. In all, this study opens up a kind of new avenue that could be a milestone to the development of high‐voltage and ambient‐temperature all‐solid‐state polymer electrolytes.

Abstract Electrochemical conversion of nitrate to ammonia offers an efficient approach to reducing nitrate pollutants and a potential technology for low-temperature and low-pressure ammonia synthesis. However, the process is limited by multiple competing reactions and NO 3 − adsorption on cathode surfaces. Here, we report a Fe/Cu diatomic catalyst on holey nitrogen-doped graphene which exhibits high catalytic activities and selectivity for ammonia production. The catalyst enables a maximum ammonia Faradaic efficiency of 92.51% (−0.3 V(RHE)) and a high NH 3 yield rate of 1.08 mmol h −1 mg −1 (at − 0.5 V(RHE)). Computational and theoretical analysis reveals that a relatively strong interaction between NO 3 − and Fe/Cu promotes the adsorption and discharge of NO 3 − anions. Nitrogen-oxygen bonds are also shown to be weakened due to the existence of hetero-atomic dual sites which lowers the overall reaction barriers. The dual-site and hetero-atom strategy in this work provides a flexible design for further catalyst development and expands the electrocatalytic techniques for nitrate reduction and ammonia synthesis.

Abstract The development of highly active and stable oxygen evolution reaction (OER) electrocatalysts is crucial for improving the efficiency of water splitting and metal–air battery devices. Herein, an efficient strategy is demonstrated for making the oxygen vacancies dominated cobalt–nickel sulfide interface porous nanowires (NiS 2 /CoS 2 –O NWs) for boosting OER catalysis through in situ electrochemical reaction of NiS 2 /CoS 2 interface NWs. Because of the abundant oxygen vacancies and interface porous nanowires structure, they can catalyze the OER efficiently with a low overpotential of 235 mV at j = 10 mA cm −2 and remarkable long‐term stability in 1.0 m KOH. The home‐made rechargeable portable Zn–air batteries by using NiS 2 /CoS 2 –O NWs as the air–cathode display a very high open‐circuit voltage of 1.49 V, which can maintain for more than 30 h. Most importantly, a highly efficient self‐driven water splitting device is designed with NiS 2 /CoS 2 –O NWs as both anode and cathode, powered by two‐series‐connected NiS 2 /CoS 2 –O NWs‐based portable Zn–air batteries. The present work opens a new way for designing oxygen vacancies dominated interface nanowires as highly efficient multifunctional electrocatalysts for electrochemical reactions and renewable energy devices.

ConspectusTotal synthesis, where desired organic- and/or biomolecules could be produced from simple precursors at atomic precision and with known step-by-step reactions, has prompted centuries-lasting bloom of organic chemistry since its conceptualization in 1828 (Wöhler synthesis of urea). Such expressive science is also highly desirable in nanoscience, since it represents a decisive step toward atom-by-atom customization of nanomaterials for basic and applied research. Although total synthesis chemistry is less established in nanoscience, recent years have witnessed seminal advances and increasing research efforts devoted into this field. In this Account, we discuss recent progress on introducing and developing total synthesis routes and mechanisms for atomically precise metal nanoclusters (NCs). Due to their molecular-like formula and properties (e.g., HOMO–LUMO transition, strong luminescence and stereochemical activity), atomically precise metal NCs could be regarded as “molecular metals”, holding potential applications in various practical sectors such as biomedicine, energy, catalysis, and many others. More importantly, the molecular-like properties of metal NCs are sensitively dictated by their size and composition, suggesting total synthesis of them as an indispensable basis for reliably realizing their practical applications.Atomically precise thiolate-protected Au, Ag and their alloy NCs are employed as model NCs to exemplify design strategies and governing principles in total synthesis of inorganic nanoparticles. This Account starts with a brief summary of total synthesis methodologies of atomically precise metal NCs. Following the methodological summary is a detailed discussion on the mechanisms governing these synthetic strategies, which is the main focus of this Account. Based on unprecedented precision (at atomic resolution) and ease (ensured by size-dependent properties) of tracking clusters’ size/structure changes, mechanisms driving growth (e.g., reduction growth and seeded growth) and functionalization (e.g., alloying reaction and ligand exchange) of metal NCs have been explored at molecular level. With definitive step-by-step reaction routes, two-electron (2 e–) reduction (driving the growth reactions) and surface motif exchange (SME, prompting alloying and ligand exchange reactions) are discussed in depth and details. In addition to those sub- and/or individual-cluster level understandings, the self-assembly chemistry delivering high orderliness and enhanced materials performance in NC assemblies/supercrystals is also deciphered. This Account is then concluded with our perspectives toward potential development of cluster chemistry. Advances in total synthesis chemistry of metal NCs could not only serve as guidelines for future synthetic practice of NCs, but also provide molecular-level clues for many pending fundamental puzzles in nanochemistry, including nucleation growth, alloying chemistry, surface engineering and evolution of metamaterials.

The ability to fabricate sensory systems capable of highly selective operation in complex fluid will undoubtedly underpin key future developments in healthcare. However, the abundance of (bio)molecules in these samples can significantly impede performance at the transducing interface where nonspecific adsorption (fouling) can both block specific signal (reducing sensitivity) and greatly reduce assay specificity. Herein, we aim to provide a comprehensive review discussing concepts and recent advances in the construction of antifouling sensors that are, through the use of chemical, physical, or biological engineering, capable of operating in complex sample matrix (e.g., serum). We specifically highlight a range of molecular approaches to the construction of solid sensory interfaces (planar and nanoparticulate) and their characterization and performance in diverse in vitro and in vivo analyte (e.g., proteins, nucleic acids, cells, neuronal transmitters) detection applications via derived selective optical or electrochemical strategies. We specifically highlight those sensors that are capable of detection in complex media or those based on novel architectures/approaches. Finally, we provide perspectives on future developments in this rapidly evolving field.