Search

A novel lotus seedpod shaped Cu2O/g-C3N4 p–n heterojunction composite was fabricated by in situ filling the g-C3N4 framework with Cu2O hollow nanospheres for efficient photocatalytic hydrogen evolution.

Photocatalytic CO2 conversion into valuable chemicals has been proved to be a promising strategy for relieving energy shortage and environmental pollution. Nevertheless, the rapid recombination of photogenerated carriers of photocatalyst greatly limits their actual application. In this work, dual CuOx and MnOx cocatalysts are decorated on g-C3N4 nanosheets via a one-step photodeposition strategy. Benefiting from the repulsion between Cu2+ and Mn2+ cations, a novel g-C3N4-based heterostructure loaded with spatially separated CuOx nanoparticles and MnOx nanosheets dual cocatalysts has been successfully fabricated. The Cu favors the trapping of electrons, while MnOx tends to collect holes. Moreover, the Cu2O/g-C3N4 p-n heterojunction also accelerates the charge separation. As a result, the photogenerated holes and electrons flow into and out of the photocatalyst, respectively, resulting in enhanced charge separation for achieving efficient CO2 photoreduction over CuOx/g-C3N4/MnOx. Impressively, the optimized CuOx/g-C3N4/MnOx exhibits an improved CO production rate of 5.49 µmol g− 1 h− 1, which exceeds over 27.5 times than bare g-C3N4. This work designs a promising photocatalyst for CO2 photoreduction and develops a novel one-step photodeposition route for decorating spatially separated dual cocatalysts on a photocatalyst.

Aim:Twin studies allow for the investigation of genetic and environmental influences on human brain development. The generalizability of their findings depends on the developmental similarity between twins and singletons. This study aimed to evaluate the structural and functional differences in a cohort of preterm-born twins and singletons at term-equivalent age.Materials and Methods:Eighteen twins and forty-seven singletons were included and scanned at the term-equivalent age. Brain volumes from 3D T1-weighted images, quantitative metrics and structural connectivity from diffusion tensor imaging, and low-frequency brain activity and functional connectivity from resting-state functional MRI (rs-fMRI) were obtained from these neonates.Results:We found no significant volumetric differences after multiple comparison correction. The diffusivity values in the cingulum cingular part, cingulate gyrus, lateral fronto-orbital gyrus, gyrus rectus, as well as medial fronto-orbital gyrus were significantly higher in the twin group than in the singleton group. Structural connectivity analysis showed higher transitivity in the twin group compared to the singletons, indicating increased local connectivity. For rs-fMRI, the twin group showed greater fractional amplitude of low-frequency fluctuation (fALFF) values in the salience network and several fronto-temporal regions compared with the singleton group. It is worth noting that we found differences both in structural and functional measurements (MD and fALFF) in the prefrontal and cingulate cortex.Conclusion:The structural and functional differences collectively indicated that preterm-born twins may have delayed brain development compared with gestational age-matched singletons at term-equivalent age, which may be related to perinatal-neonatal problems.

Herein, we report a colorful colorimetric method for semiquantitative visual identification of Staphylococcus aureus (S. aureus) based on dual enzyme-induced gold–silver (Au–Ag) alloy nanorods (NRs...

Herein, we report a colorful colorimetric method for semiquantitative visual identification of

We propose a new fluorometric method for alkaline phosphatase (ALP) determination. This method is based on the regulation of enzymatically generated poly(thymine) for the preparation of copper nanoparticles (CuNPs). 2′-Deoxythymidine 5′-triphosphate (dTTP) serves as the source for polymerization mediated by terminal deoxynucleotidyl transferase (TdT). This process generates poly(thymine), which acts as the template for synthesis of fluorescent CuNPs. However, if ALP catalyzes the hydrolysis of dTTP, the TdT-mediated polymerization will be disabled. This prevents the formation of CuNPs and causes a drop in fluorescence. The findings were used to design a sensitive and selective fluorometric method for ALP determination. A linear response in the activity range from 0.1 to 20 U L-1 and a limit of quantification of 0.3 U L-1 were obtained. The results indicate that the proposed method can be successfully applied to ALP assay in spiked diluted serum. This demonstrates the method’s reliability and practicability.

Colorimetric assays have been widely developed for the detection of toxin ochratoxin A (OTA), but most of them suffer from moderate sensitivity when they are adopted for the detection of trace OTA in a complicated food matrix. For the purpose of overcoming this issue, an innovative cascade reaction-based colorimetric aptasensor was developed for the achievement of high sensitivity. The biotin-labelled OTA aptamer was immobilized onto streptavidin magnetic beads by means of the biotin-streptavidin reaction. With OTA binding to its aptamer, the structural switching of the aptamer results in the release of the alkaline phosphatase-labelled oligonucleotide, which is partially complementary to the aptamer. Following the magnetic separation, the cascade reaction is initiated through the enzymatic conversion of ascorbic acid-2-phosphate into ascorbic acid. Subsequent to that, the generated ascorbic acid reduces MnO2 nanosheets to Mn2+ ions, accordingly destroying the oxidase-mimicking activity of MnO2 nanosheets. In consequence, it is not possible to oxidize 3,3',5,5'-tetramethylbenzidine (TMB), a substrate for oxidase, with Mn2+ for the production of the blue colour product (TMB Ox). With the increasing amount of OTA, a colour change occurs from blue to colourless. The cascade reaction has the potential of greatly amplifying the detection signal, together with remarkably improving the sensitivity, making this colorimetric sensor a universal and promising platform for the highly sensitive detection of mycotoxins in the field of public food safety monitoring.

To evaluate whether amide proton transfer (APT) MRI can be used to characterize gliomas in pediatric patients and whether it provides added value beyond relaxation times. In this prospective study, APT imaging and relaxation time mapping were performed in 203 pediatric patients suspected of gliomas from February 2018 to December 2019. The region of interest (ROI) in the tumor was automatically generated with artifact detection and ROI-shrinking algorithms. Several APT-related metrics (CESTR, CESTRnr, MTRRex, AREX, and APT#) and quantitative T1 and T2 were compared between low-grade and high-grade gliomas using the student’s t-test or Mann-Whitney U-test. The performance of these parameters was assessed using the receiver operating characteristic (ROC) analysis. A stepwise multivariate logistic regression model was used to combine the imaging parameters. Forty-eight patients (mean age: 6 ± 4 years; 23 males and 25 females) were included in the final analysis. All the APT-related metrics except APT# had significantly (p < 0.05) higher values in the high-grade group than the low-grade group. Under different ROI-shrinking cutoffs, the quantitative T1 (p = 0.045–0.200) and T2 (p = 0.037–0.171) values of high-grade gliomas were typically lower than those of low-grade ones. The stepwise multivariate logistic regression revealed that CESTRnr and APT# were combined significant predictors of glioma grades (p < 0.05), with an area under the ROC curve (AUC) of 0.86 substantially larger than those of T1 (AUC = 0.69) and T2 (AUC = 0.68). APT imaging can be used to differentiate high-grade and low-grade gliomas in pediatric patients and provide added value beyond quantitative relaxation times. • Amide proton transfer (APT) MRI showed significantly (p < 0.05) higher values in pediatric patients with high-grade gliomas than those with low-grade ones. • The area under the curve was 0.86 for APT MRI to differentiate low-grade and high-grade gliomas in pediatric patients, which was substantially higher than that for quantitative T1 (0.69) and T2 (0.68). • APT MRI demonstrated added value beyond quantitative T1 and T2 mapping in characterizing pediatric gliomas.

Manganese oxides (MnO

The electrolyte is one of the most important components of vanadium redox flow battery (VRFB), and its stability and solubility determines the energy density of a VRFB. The performance of current positive electrolyte is limited by the low stability of VO2+ at a higher temperature. Phosphate is proved to be a very effective additive to improve the stability of VO2+. Even though, the stabilizing mechanism is still not clear, which hinders the further development of VRFBs. In this paper, to clarify the effect of phosphate additive on the positive electrolyte stability, the hydration structures of VO2+ cations and the reaction mechanisms of precipitation with or without phosphate in the supporting electrolyte of H2SO4 solutions were investigated in detail based on calculations of electronic structure. The stable configurations of complexes were optimized at the B3LYP/6-311 + G(d,p) level of theory. The zero-point energies and Gibbs free energies for these complexes were further evaluated at the B3LYP/aug-cc-pVTZ level of theory. It shows that a structure of [VO2(H2O)2]+ surrounded by water molecules in H2SO4 solution can be formed at the room temperature. With the temperature rises, [VO2(H2O)2]+ will lose a proton and form the intermediate of VO(OH)3, and the further dehydration among VO(OH)3 molecules will create the precipitate of V2O5. When H3PO4 was added into electrolytes, the V-O-P bond-containing neutral compound could be formed through interaction between VO(OH)3 and H3PO4, and the activation energy of forming the V-O-P bond-containing neutral compound is about 7 kcal mol−1 lower than that of the VO(OH)3 dehydration, which could avoid the precipitation of V2O5 and improve the electrolyte stability.

To determine the feasibility of balanced steady-state free precession (b-SSFP) imaging for measuring hepatic steatosis in obese children and adolescents, using proton magnetic resonance spectroscopy (1H MRS) as reference standard. 182 obese Chinese paediatric patients underwent conventional T1-weighted dual echo MRI, 1H MRS and b-SSFP imaging for non-invasive assessment of hepatic steatosis. There was a strong positive correlation between liver fat fraction (FF) on T1-weighted dual echo MRI and 1H MRS-determined liver fat content (LFC) (r = 0.964, p 50 mg/g (>5 % by wet weight) showed areas under the curves for FF and L/S at 0.989 (0.976–1.000) and 0.926 (0.888–0.964), respectively. Optimal FF and L/S cut-off values identified patients with hepatic steatosis with 97.9 % and 86.5 % sensitivity and 93.4 % and 93.4 % specificity, respectively. Following further validation, b-SSFP at 1.5T has potential as a feasible technique for evaluation of hepatic steatosis in obese paediatric patients with limited breath-holding capacity. • L/S on b-SSFP images closely correlated with 1 H MRS-determined LFC. • b-SSFP has high diagnostic accuracy for hepatic steatosis in obese children. • 100% of obese paediatric subjects are imaged successfully using b-SSFP sequence. • b-SSFP has potential to evaluate hepatic steatosis in children with poor breath-hold.

Cloud Radio Access Network (C-RAN) has become one of the hot-spot research directions in both industry and academia to facilitate 5G development. Its architecture is mainly divided into three parts: i) a Virtual Base Station (VBS) pool including a number of Base Band Units (BBU) that apply for real-time cloud computing technology to carry out digital processing tasks; ii) Remote Radio Heads (RRH) that are used to collect the wireless signals from all wireless devices; iii) a front-haul network connecting the RRH to the VBS pool. The information of Base Stations (BS) resides in a centralized VBS pool, multiple operators can allow their VBS pools to exchange control data and cooperate with each other to provide high-quality 5G services. In this process, trustworthy cooperation and platform-trust authentication among multiple mobile operators are required to realize high networking performance and secure 5G environment. However, this topic has been scarcely studies and is still in its infancy. In this paper, we first propose a C-RAN Inter-Operator Cooperation Scheme (IOCS) to support the cooperation of multiple operators in C-RAN and allow them to share resources in a trustworthy and secure way based on Trusted Computing Platform (TCP). An access trust management pool including VBS trust managers (TM) is set up in IOCS to administrate an operator’s VBS pool. It allows an end user to consume other operators’ network resources in a trustworthy manner when its own operator’s network cannot satisfy the Quality of Service (QoS) requirements. Furthermore, we design a trusted cooperative platform based on OpenStack to implement IOCS. Performance evaluation and simulation results illustrate the high operation efficiency in IOCS comparing with other schemes. Game theoretical analysis shows the condition of inter-operator cooperation by taking operator trust into concern.

There are challenges in developing multifunctional materials that can not only effectively adsorb but also completely eliminate organic contaminants in water. In this work, novel ZnO/biochar nanocomposites were synthesized using a facile ball-milling method. A series of characterization results showed that the ZnO nanoparticles dispersed uniformly on carbon surface within the biochar matrix. Ball milling increased the mesopores and macropores of the nanocomposites by breaking biochar and squeezing ZnO. The addition of appropriate amount of ZnO into biochar enhanced both the adsorption capacity and photocatalytic ability of the nanocomposites for methylene blue (MB) removal. When the initial concentration of MB was 160 mg/g, the nanocomposites exhibited high MB removal efficiency (up to 95.19%) under visible light through the combination of adsorption and photocatalysis. This work provides a feasible synthesis of metal oxide/biochar nanocomposites with excellent adsorption and photocatalysis properties for the treatment of organic dye wastewater.

Manganese oxides (MnO2) are widely applied in heavy metal ions removal due to their low-cost, environmental-friendly and biocompatibility. However, the adsorption capacity of MnO2 need to be further improved to satisfy the demand of practical application. Herein, a highly dispersed single layer NaxKyMnO2 nanosheet was synthesized by a facile wet-chemical method with sodium dodecyl sulfonate as surfactant. The high surface specific area, excellent dispersibility and abundant oxygen vacancies endowed NaxKyMnO2 nanosheets with potential in heavy metal ions adsorption. The adsorption experiments results showed that NaxKyMnO2 nanosheets possessed high efficiency and selectivity towards lead ion (Pb2+) with a high adsorption capacity of 2091.8 μmol g−1. The NaxKyMnO2 also showed an excellent reusability with the removal rate of 95.4% for Pb2+ even after five cycles. Moreover, both the theoretical calculation and experimental data illustrated that the single layer NaxKyMnO2 nanosheets possess high selectivity to Pb2+ adsorption.

Colorimetric aptasensors have been intensively studied for the ochratoxin A (OTA) detection, but they mostly exhibit just one-color change, resulting in poor visual resolution and limited use for semi-quantitative analysis. Thus, we designed a high-resolution colorimetric assay on the basis of aptamer structural switching and enzyme-induced metallization of gold nanorods (AuNRs). DNA-alkaline phosphatase (ALP)-immobilized magnetic beads were prepared. The aptamer bounded to OTA to form G-quadruplexes, releasing ALP-labelled complementary DNA (cDNA-ALP). After magnetic separation, cDNA-ALP catalyzed the decomposition of ascorbic acid 2-phosphate to ascorbic acid that reduced Ag+, forming an Ag shell on the surface of AuNRs. This caused a blue-shift of the longitudinal local surface plasmon resonance peak of the AuNRs and a naked eye visible multicolor change. Under optimal conditions, the assay exhibited a 9.0 nM detection limit for OTA, with high specificity. This method is promising for the on-site visual semi-quantitative detection of mycotoxins in foods.

A sensitive colorimetric method is described for the determination of the activity of alkaline phosphatase (ALP). It is based on the regulation of the oxidase-mimicking activity of MnO2 nanosheets. In the absence of ALP, MnO2 nanosheets are capable of catalyzing the oxidation of the colorless substrate 3,3′,5,5′-tetramethylbenzidine (TMB) by oxygen to form a blue oxidized product (TMB Ox) with an absorption peak at 652 nm. In the presence of ALP and its substrate ascorbic acid-2-phosphate, the latter is hydrolyzed to form ascorbic acid (AA). AA triggers the decomposition of MnO2 nanosheets by reducing MnO2 to Mn2+, thereby weakening the enzyme mimicking activity of the MnO2 nanosheets and causing a drop in absorbance. The drop in absorbance at 652 nm is related to the ALP activity in the range from 0.05–10 m-units per mL (mU·mL−1), and the detection limit is 0.05 mU·mL−1. The method was applied to the determination of ALP in spiked calf serum samples and gave satisfactory results.

A sensitive colorimetric method is described for the determination of the activity of alkaline phosphatase (ALP). It is based on the regulation of the oxidase-mimicking activity of MnO

Visible-light-driven CO2 reduction yielding commodity chemicals such as ethylene holds tremendous potentials for achieving a carbon-neutral circular economy in the energy and chemical industry. Despite the success of electrochemical CO2 reduction, efficient and selective ethylene generation has not been achieved by photocatalytic means because the intermediate dimerization fails to occur on existing photocatalysts. Here, we first demonstrate that the presence of sulfur vacancies in CdS (Sv-CdS) lead to reduced Cd-Cd distance and charge enrichment on Cd atoms. This structural relaxation and associated electronic structure tuning endow successful *CHO dimerization and hence ethylene generation. The photocatalyst can be optimized by coating Sv-CdS with ZIF-8 to form a core-shell structure, which presents further lowered energy barrier for both *CO hydrogenation and *CHO dimerization. With these combined intermediate manipulation strategies, the optimized photocatalyst exhibits a record-high ethylene selectivity of 12.8 % at a production rate of 0.8 μmol g−1 h−1.

Electroreduction of CO2 to high value-added products such as hydrocarbons provides a promising way to create a carbon neutral circular economy. Copper (Cu) is the most effective metal catalyst with selectivity towards hydrocarbons but Cu catalyst alone generally produces hydrocarbons at low selectivity and yield. Operando surface enhanced infrared absorption spectroscopic (SEIRAS) analysis reveals that the low hydrocarbon yield is attributed to the poor ability of Cu to produce carbon monoxide (CO), which is a crucial intermediate for hydrocarbon formation. In the current study, an Ag-Cu dual-cathode CO2RR device is developed, which allows separate control of electrode potential. This dual-cathode cell shows increased hydrocarbon yield (83 % for methane and 106 % for ethylene) and a 200 mV lower onset potential for C2H4, compared to electrolysis with a single Cu cathode. The CO produced by the Ag cathode transfers to Cu and increase its CO coverage, facilitating methane formation as well as promoting C C coupling to form ethylene. This study also reveals a mismatch of optimum electrode potential between Ag and Cu, which results in compromised performance of the two components in an Ag-Cu bimetallic electrocatalyst, but poses no challenge in the dual-cathode cell. To optimize the performance of the dual-cathode cell, we propose the use of a single-pass dual-gas-diffusion-cathode reactor with enhanced mass transfer for maximum hydrocarbon production. This work verifies that splitting the complex CO2RR process into two separate steps is a feasible method to improve the overall efficiency and rate of advanced products while reducing the energy input.

A simple and efficient strategy based on the manganese dioxide (MnO2) nanosheet-mediated etching of gold nanorods (AuNRs) has been demonstrated, affording an effective and convenient way to develop a high-resolution multicolor colorimetric method for the visual detection of antioxidants. The UV−visible absorption spectroscopy and transmission electron microscopy results revealed that the MnO2 nanosheets etched the AuNRs quickly in weakly acidic solutions at room temperature, resulting in a significant blue shift in the AuNR longitudinal local surface plasmon resonance peak and vivid color changes. The feasibility of the etching process was theoretically evaluated by comparing the standard electron potentials of Au(I)/Au(0) and Mn(IV)/Mn(II). Changes in the chemical valencies of Au and Mn during the etching process were analyzed via X-ray photoelectron spectroscopy, which further confirmed that the etching process occurred. Key factors, including the concentrations of the MnO2 nanosheets, cetyltrimethylammonium bromide, and H+, and incubation time, were then investigated. The application of MnO2 nanosheet-mediated AuNR etching for antioxidant analysis was based on the antioxidant-induced decomposition of MnO2 nanosheets. With the merits of simplicity and user-friendliness, this method provides a promising platform for the visual detection of total antioxidant capacity in real beverages.

Biodiesel, a mixture of fatty acids alkyl esters (FAAE), has recently received great concern as an excellent alternative to the petro-based diesel fuel. However, the production of biodiesel at commercial scale is obstructed by both cost of feedstock and the homogeneous catalyst system. To overcome these challenges, Amberlyst-15/Poly (vinyl alcohol) membrane (A-15/PVA) with catalytic and water-adsorbing dual functions have been prepared by a simple phase inversion method. The as-prepared A-15/PVA exhibited excellent catalytic activity and reusability in both batch and continuous esterification of acidified oil from waste cooking oil (WCO) with methanol for biodiesel production. The produced biodiesel exhibited high qualified properties and stability and can be directly applied in current diesel engines without modifying the engines. The exhaust of the biodiesel and biodiesel-blend could decrease the smoke opacity, carbon monoxide, hydrocarbon, while increase the nitrogen oxide emissions. The A-15/PVA demonstrated great potential in industrial production of biodiesel with high qualities from WCO.

An innovative colorimetric method based on enzyme-induced gold nanoparticle aggregation was developed to detect the activity of alkaline phosphatase (ALP), and it was further applied to construct an aptasensor to monitor ochratoxin A (OTA) concentrations. In the presence of ALP, the substrate ascorbic acid 2-phosphate was hydrolyzed to generate ascorbic acid (AA). Subsequently, reduction of MnO2 nanosheets by AA produced manganese ions, which mediated gold nanoparticle aggregation. The color of the detection solution changed from brown-red to purple to blue as the ALP concentration increased, and a detection limit of 0.05 U·L-1 was achieved. Furthermore, this strategy was successfully utilized to devise a target-responsive aptasensor for colorimetric detection of an important mycotoxin, OTA, which causes food poisoning and has various toxic effects on humans. The proposed method offers high sensitivity with a detection limit as low as 5.0 nM together with high specificity. When applied to analyze red wine and grape juice samples, no complex sample pretreatment or bulky instruments were required. Overall, a colorimetric platform based on enzyme-induced gold nanoparticle aggregation was successfully established to improve the simplicity and sensitivity of ALP and OTA detection. This platform appears highly promising for mycotoxin-related food safety monitoring.

A fluorescence enhancement method is presented for the determination of ochratoxin A (OTA). The interaction of OTA with its aptamer causes structural changes which, in turn, change fluorescence of enzymatically generated polythymine-coated copper nanoparticles (CuNPs) (with excitation/emission maxima at 340/625 nm). The OTA-binding aptamer was immobilized on magnetic beads. When it binds OTA, it is partially released and exposes a region with a partly complimentary DNA strand (cDNA). After magnetic separation, the cDNA was employed as a primer to trigger the terminal deoxynucleotidyl transferase-mediated polymerization. This process generates polythymine which act as a template for synthesis of the CuNPs. The method is sensitive in having a 2.0 nM detection limit for OTA. It was successfully applied to the determination of OTA in spiked diluted red wine. Graphical abstract Schematic presentation of a fluorometric enhancement method for ochratoxin A assay based on ochratoxin A inducing structure switching of its aptamer and enzymatically generated polythymine for copper nanoparticles formation.

While 4G is speeding up its steps towards global markets, 5G has initiated its full development to satisfy an increasing demand on mobile data traffic and big data bandwidth. Centralized data processing, collaborative radio, real-time cloud infrastructure and Cloud Radio Access Network (C-RAN), along with their excellent advantages are being sought by more and more operators to meet end-user requirements. As a promising mobile wireless network architecture, compared with traditional RAN, C-RAN has incomparable advantages in terms of low power consumption, reduced Base Station (BS) numbers, and economic capital and operating expenditure. It can also improve network capacity and BS utilization rate. Recently, C-RAN security has aroused special attention and concern. However, the literature still lacks an overall review on it in order to guide current and future research. In this paper, we first overview the architecture, deployment scenarios and special characteristics of C-RAN. We then provide a thorough review on the existing security studies in the field of C-RAN based on its three logic layers and corresponding security threats and attacks. Particularly, we discuss whether the current literature can satisfy the expected security requirements in C-RAN. Based on this, we indicate open research issues and propose future research trends.