Cane Molasses Derived N-Doped Graphene Quantum Dots: Dynamic Quenching Synergistically Photoinduced Electron Transfer for the Instant Detection of Nitrofuran Antibiotics.

The development of a highly selective, simple, and rapid detection method for nitrofuran antibiotics (NFs) is of great significance for food safety, environmental protection, and human health. To meet these needs, in this work, cyan-color highly fluorescent N-doped graphene quantum dots (N-GQDs) were synthesized using cane molasses as the carbon source and ethylenediamine as the nitrogen source. The synthesized N-GQDs have an average particle size of 6 nm, a high fluorescence intensity with 9 times that of undoped GQDs, and a high quantum yield (24.4%) which is more than 6 times that of GQDs (3.9%). A fluorescence sensor based on N-GQDs for the detection of NFs was established. The sensor shows advantages of fast detection, high selectivity, and sensitivity. The limit of detection for furazolidone (FRZ) was 0.29 µM, the limit of quantification (LOQ) was 0.97 µM, and the detection range was 5-130 µM. The fluorescence quenching mechanism of the sensor was explored by fluorescence spectroscopy, UV-vis absorption spectroscopy, Stern-Volmer quenching constant, Zeta potential, UV-vis diffuse reflectance spectroscopy, and cyclic voltammetry. A fluorescence quenching mechanism of dynamic quenching synergized with photoinduced electron transfer was revealed. The developed sensor was also successfully applied for detecting FRZ in various real samples, and the results were satisfactory.

Electrode Materials, Structural Design, and Storage Mechanisms in Hybrid Supercapacitors.

Currently, energy storage systems are of great importance in daily life due to our dependence on portable electronic devices and hybrid electric vehicles. Among these energy storage systems, hybrid supercapacitor devices, constructed from a battery-type positive electrode and a capacitor-type negative electrode, have attracted widespread interest due to their potential applications. In general, they have a high energy density, a long cycling life, high safety, and environmental friendliness. This review first addresses the recent developments in state-of-the-art electrode materials, the structural design of electrodes, and the optimization of electrode performance. Then we summarize the possible classification of hybrid supercapacitor devices, and their potential applications. Finally, the fundamental theoretical aspects, charge-storage mechanism, and future developing trends are discussed. This review is intended to provide future research directions for the next generation of high-performance energy storage devices.

Hybrid Structures of Sisal Fiber Derived Interconnected Carbon Nanosheets/MoS2/Polyaniline as Advanced Electrode Materials in Lithium-Ion Batteries.

In this work, we designed and successfully synthesized an interconnected carbon nanosheet/MoS2/polyaniline hybrid (ICN/MoS2/PANI) by combining the hydrothermal method and in situ chemical oxidative polymerization. The as-synthesized ICNs/MoS2/PANI hybrid showed a "caramel treat-like" architecture in which the sisal fiber derived ICNs were used as hosts to grow "follower-like" MoS2 nanostructures, and the PANI film was controllably grown on the surface of ICNs and MoS2. As a LIBs anode material, the ICN/MoS2/PANI electrode possesses excellent cycling performance, superior rate capability, and high reversible capacity. The reversible capacity retains 583 mA h/g after 400 cycles at a high current density of 2 A/g. The standout electrochemical performance of the ICN/MoS2/PANI electrode can be attributed to the synergistic effects of ICNs, MoS2 nanostructures, and PANI. The ICN framework can buffer the volume change of MoS2, facilitate electron transfer, and supply more lithium inset sites. The MoS2 nanostructures provide superior rate capability and reversible capacity, and the PANI coating can further buffer the volume change and facilitate electron transfer.

[Luminescence Mechanism of Near-Infrared Quantum Dots].

Near-infrared quantum dots have unique optical properties, such as high fluorescence quantum yield, long fluorescent life, tunable fluorescence emission wavelength, half peak width and large stokes shift, resisting light bleaching etc. The advantage of "near infrared biological window" gives them great potential application value in biological fluorescent tags, solar cells, quantization calculation, photocatalysis, chemical analysis, food detection, vivo imaging and other fields. At present, the luminescence mechanism research of near-infrared quantum dots is still not comprehensive enough. In this paper, the luminescent principle of three different types of near-infrared quantum dots is summarized, including core/shell structure quantum dots (CdTe/CdSe, CdSe/CdTe/ZnSe, etc), ternary quantum dots (Cu-In-Se, CuInS2, etc) and doped quantum dots (Cu∶InP, etc). The luminescence mechanism of Type Ⅱ core/shell structure is most likely to attribute to the interband recombination luminescence, the ternary structure of quantum dots light emitting mechanism is considered to be due to the intrinsic structure defects, and the luminescence mechanism of doped quantum dots is deemed to result from the impurity defects. The existing problems of near-infrared luminescent principle of quantum dots are also discussed and their development tendency is explored t in this review. A systematic study of luminescence mechanism of near-infrared quantum dots will not only help to understand the luminescent properties of near infrared quantum dots, but also contribute to improve the synthesis methods of quantum dots with similarly high quality.

Facile Synthesis to Porous TiO2 Nanostructures at Low Temperature for Efficient Visible-Light Degradation of Tetracycline.

In this study, nanoporous TiO2 with hierarchical micro/nanostructures was synthesized on a large scale by a facile one-step solvothermal method at a low temperature. A series of characterizations was performed and carried out on the as-prepared photocatalysts, which were applied to the degradation of the antibiotic tetracycline (TC). The results demonstrated that nanoporous TiO2 obtained at a solvothermal temperature of 100 °C had a spherical morphology with high crystallinity and a relatively large specific surface area, composed of a large number of nanospheres. The nanoporous TiO2 with hierarchical micro/nanostructures exhibited excellent photocatalytic degradation activity for TC under simulated sunlight. The degradation rate was close to 100% after 30 min of UV light irradiation, and reached 79% only after 60 min of visible light irradiation, which was much better than the photodegradation performance of commercial TiO2 (only 29%). Moreover, the possible intermediates formed during the photocatalytic degradation of TC were explored by the density functional theory calculations and HPLC-MS spectra. Furthermore, two possible degradation routes were proposed, which provided experimental and theoretical support for the photocatalytic degradation of TC. In this study, we provide a new approach for the hierarchical micro/nanostructure of nanoporous TiO2, which can be applied in industrial manufacturing fields.

Boosting the Initial Coulomb Efficiency of Sisal Fiber-Derived Carbon Anode for Sodium Ion Batteries by Microstructure Controlling.

As anode material for sodium ion batteries (SIBs), biomass-derived hard carbon has attracted a great deal of attention from researchers because of its renewable nature and low cost. However, its application is greatly limited due to its low initial Coulomb efficiency (ICE). In this work, we employed a simple two-step method to prepare three different structures of hard carbon materials from sisal fibers and explored the structural effects on the ICE. It was determined that the obtained carbon material, with hollow and tubular structure (TSFC), exhibits the best electrochemical performance, with a high ICE of 76.7%, possessing a large layer spacing, a moderate specific surface area, and a hierarchical porous structure. In order to better understand the sodium storage behavior in this special structural material, exhaustive testing was performed. Combining the experimental and theoretical results, an "adsorption-intercalation" model for the sodium storage mechanism of the TSFC is proposed.

Detection of Microplastics Based on a Liquid-Solid Triboelectric Nanogenerator and a Deep Learning Method.

Microplastics are sub-millimeter-sized fragments of plastics, which have been found in environments to a great extent. They are relatively new pollutants that are difficult to be degraded. They not only cause irreversible adverse effects on microorganisms, animals, and plants but also enter the human body through the food chain and affect human health. However, due to their small size, variety, and differences in physical and chemical properties of microplastics, traditional detection and identification still face challenges. This work provides a method for detecting and classifying microplastics in liquids using a liquid-solid triboelectric nanogenerator (LS-TENG) in combination with a deep learning model. The experiment showed that the type and content of microplastics in the liquid had a great effect on the contact electrification between the liquid and the perfluoroethylene-propylene copolymer. After adding polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and polystyrene microplastics to the liquids, it was found that the type and content of different microplastics have a significant impact on the output voltage signal of the LS-TENG sensor. When the mass fraction of microplastics ranged from 0.025 to 0.25 wt %, the voltage output of the LS-TENG sensor had a linear relationship with the mass fraction of microplastics. Therefore, a method for quantitatively detecting the content of microplastics using the LS-TENG sensor has been established. Based on the LS-TENG output voltage signal, a convolutional neural network deep learning model was used to identify different types of labels, and high recognition accuracy was achieved. These are of great significance for expanding the application prospect of LS-TENG and realizing the detection of microplastics in liquids.

The development and future frontiers of global ecological restoration projects in the twenty-first century: a systematic review based on scientometrics.

Ecological restoration projects are becoming a mainstream of research, and their studies are widely followed by scholars worldwide, yet there is no comprehensive review of this research. Nowadays, bibliometrics has attracted much attention from the scientific community, and its methodological approach allows quantitative and qualitative analysis of research performance in journals or subject areas. This paper provides a systematic and comprehensive description of the progress and hotspots of ecological restoration projects from a bibliometric perspective, based on 1173 articles in the Web of Science Core Collection (WOSCC) database. Research on ecological restoration projects has shown a positive growth trend since the twenty-first century. China and the USA are the most active countries in terms of the number of relevant articles published, and more than half of the top 10 active institutions are from China, but there is less collaboration between different countries/institutions. Research in ecological restoration projects is summarized into three main research areas: the main ecological damage problems, the impact of human beings on ecological damage, and the main methods of ecological restoration. Finally, some challenges and outlooks conducive to the rapid and balanced development of ecological restoration projects are presented, which provide valuable references and help for future researchers.

A Multifunction Freestanding Liquid-Solid Triboelectric Nanogenerator Based on Low-Frequency Mechanical Sloshing.

A simple rectangular-structured freestanding liquid-solid triboelectric nanogenerator (LS-TENG) was fabricated, which used fluorinated ethylene propylene (FEP) films and deionized water (DI) as friction materials. The LS-TENG can effectively convert mechanical energy into electrical energy under the extremely low-frequency shaking of 2 Hz and shows greatly reliable stability. The influence of liquid volume and units on the output performance of the LS-TENG was studied, and the mechanism of the triboelectric electrification process of the LS-TENG was analyzed by COMSOL Multiphysics software. The results show that friction materials, liquid types, and number of units have a great effect on the output performance of the LS-TENG. Under the optimized conditions, the designed array LS-TENG shows high output performance with the open-circuit voltage, short-circuit current, and transferred charge of 120 V, 3.9 µA, and 133 nC, respectively. The LS-TENG can be applied in capacitive storage, AC power, signal acquisition, and self-powered sensor. The multifunctional LS-TENG provides a potentially practical route for harvesting low-frequency mechanical energy in natural environments and enabling multifunctional applications.

Cerebral Regional Homogeneity Alternation of Pregnant Women With Antenatal Depression During the Pandemic.

Purpose: The COVID-19 epidemic has been a threat to the health of people all over the world. Various precautions during COVID-19 in China have kept a large number of people in isolation, and this has inconvenienced and placed enormous stress on pregnant women. Pregnant women are more likely to suffer from antenatal depression (ANDP) with social isolation or low social support. This research aims to investigate the neurobiological mechanisms underlying ANDP, which impedes early detection and intervention in this disorder. Methods: A total of 43 singleton pregnant women who experienced isolation were recruited, including 21 treatment-naïve ANDP patients and 22 healthy pregnant women (HPW). To explore the intrinsic cerebral activity alternations in ANDP using resting-state functional MRI (rsfMRI), we assessed the local regional homogeneity (ReHo) differences in two groups using the voxel-based whole-brain analysis. The correlation between the regional functional abnormalities and clinical variables in ANDP patients was also examined. Results: Compared with HPW, ANDP patients showed decreased ReHo in the left dorsolateral prefrontal cortex, right insular and the cluster coving the right ventral temporal cortex (VTC), amygdala (AMG), and hippocampus (HIP). The Edinburgh Postnatal Depression Scale (EPDS) scores of ANDP patients negatively correlated with the ReHo in the right VTC, AMG, and HIP. Conclusion: Elucidating the neurobiological features of ANDP patients during COVID-19 is crucial for evolving adequate methods for early diagnosis, precaution, and intervention in a future epidemic.

Cane Molasses Graphene Quantum Dots Passivated by PEG Functionalization for Detection of Metal Ions.

Poly(ethylene glycol) passivated graphene quantum dots (PEG-GQDs) were synthesized based on a green and effective strategy of the hydrothermal treatment of cane molasses. The prepared PEG-GQDs, with an average size of 2.5 nm, exhibit a brighter blue fluorescence and a higher quantum yield (QY) (up to approximately 21.32%) than the QY of GQDs without surface passivation (QY = 10.44%). The PEG-GQDs can be used to detect and quantify paramagnetic transition-metal ions including Fe3+, Cu2+, Co2+, Ni2+, Pb2+, and Mn2+. In the case of ethylenediaminetetraacetic acid (EDTA) solution as a masking agent, Fe3+ ions can be well selectively determined in a transition-metal ion mixture, following the lowest limit of detection (LOD) of 5.77 µM. The quenching mechanism of Fe3+ on PEG-GQDs belongs to dynamic quenching. Furthermore, Fe3+ in human serum can be successfully detected by the PEG-GQDs, indicating that the green prepared PEG-GQDs can be applied as a promising candidate for the selective detection of Fe3+ in clinics.

Manganese(ii) enhanced fluorescent nitrogen-doped graphene quantum dots: a facile and efficient synthesis and their applications for bioimaging and detection of Hg2+ ions.

Manganese ion (Mn2+) bonded nitrogen-doped graphene quantum dots (Mn(ii)-NGQDs) with water solubility have been successfully synthesized by a simple, one-pot hydrothermal carbonization, using sodium citrate, glycine and manganese chloride as raw materials. The photoluminescence (PL) characteristics of Mn(ii)-NGQDs were studied in detail. The resulting Mn(ii)-NGQDs show a remarkably enhanced PL intensity and quantum yield (QY = 42.16%) compared with the product without Mn(ii)-doped (named as NG, QY = 27.06%) and the product doped with other metal ions. The Mn(ii)-NGQDs not only display low toxicity and high cellular uptake efficiency for fluorescence live cell imaging in biological evaluations but also exhibit a fast, highly selective and sensitive fluorescence quenching effect toward Hg2+ ions, with a detection limit of 3.4 × 10-8 mol L-1.

Photocatalytic activity of ZnWO4: band structure, morphology and surface modification.

Photocatalytic degradation of organic contaminants is an important application area in solar energy utilization. To improve material photocatalytic properties, understanding their photocatalytic mechanism is indispensable. Here, the photocatalytic performance of ZnWO4 nanocrystals was systematicly investigated by the photodegradation of tetraethylated rhodamine (RhB) under simulated sunlight irradiation, including the influence of morphology, AgO/ZnWO4 heterojunction and comparison with CoWO4 nanowires. The results show that the photocatalytic activity of ZnWO4 is higher than that of CoWO4, and the ZnWO4 nanorods exhibit better photocatalytic activity than that of ZnWO4 nanowires. In addition, the mechanism for the difference of the photocatalytic activity was also investigated by comparison of their photoluminescence and photocurrents. AgO nanoparticles were assembled uniformly on the surface of ZnWO4 nanowires to form a heterojunction that exhibited enhanced photocatalytic activity under irradiation at the initial stage. We found that a good photocatalyst should not only have an active structure for electrons directly to transfer from the valence band to the conduction band without the help of phonons but also a special electronic configuration for the high mobility, to ensure more excited electrons and holes in a catalytic reaction.