Electrochemical biosensor based on the integration of maple leaf-like gold nanocrystal and truncated aptamer for detection of α-amanitin with high sensitivity, selectivity and rapidity.

This study reports the fabrication of three-dimensional gold nanocrystals as sensing material in the presence of l-glutathion and high-performance aptamer with 20 bases of α-amanitin via truncation and optimization of along aptamer. The resulting maple leaf-like gold nanocrystal (ML-Au) exhibits an improved catalytic activity due to more exposed high-index facets. The use of truncated aptamer increases the sensitivity by 15 times and reduces the reaction time by two times compared with those of original aptamer. An α-amanitin electrochemical biosensor constructed by integrating ML-Au nanocrystals with truncated aptamer exhibits high sensitivity, selectivity and rapidity. An increase of the α-amanitin concentration in the range of 1 × 10-14-1 × 10-9 M causes a linear decrease in the amperometric current with a limit of detection of 2.9 × 10-15 M (S/N = 3). The proposed analytical method is satisfactorily used for electrochemical sensing of α-amanitin in urine and wild mushroom samples.

Photoinduced Precise Synthesis of Diatomic Ir1 Pd1 -In2 O3 for CO2 Hydrogenation to Methanol via Angstrom-Scale-Distance Dependent Synergistic Catalysis.

The atomically dispersed metal catalysts with full atomic utilization and well-defined site structure hold great promise for various catalytic reactions. However, the single metallic site limits the comprehensive reaction performance in most reactions. Here, we demonstrated a photo-induced neighbour-deposition strategy for the precise synthesis of diatomic Ir1 Pd1 on In2 O3 applied for CO2 hydrogenation to methanol. The proximity synergism between diatomic sites enabled a striking promotion in both CO2 conversion (10.5 %) and methanol selectivity (97 %) with good stability of 100 h run. It resulted in record-breaking space-time yield to methanol (187.1 gMeOH gmetal -1  hour-1 ). The promotional effect mainly originated from stronger CO2 adsorption on Ir site with assistance of H-spillover from Pd site, thus leading to a lower energy barrier for *HCOO pathway. It was confirmed that this synergistic effect strongly depended on the dual-site distance in an angstrom scale, which was attributed to weaker *H spillover and less electron transfer from Pd to Ir site as the Pd-to-Ir distance increased. The average dual-site distance was evaluated by our firstly proposed photoelectric model. Thus, this study introduced a pioneering strategy to precisely synthesize homonuclear/heteronuclear diatomic catalysts for facilitating the desired reaction route via diatomic synergistic catalysis.

Quantitative analysis of a posterior fossa teratomas with unusual CT and MR Characteristics--illustrative case.

Background: Intracranial teratomas or other cystic lesions with atypical imaging manifestations can still be frequently seen clinically. The specific reasons for unusual imaging manifestations need to be further explored. Observations: A case of adult teratoma in the posterior fossa with unusual imaging manifestations was reported. The chemical composition of its cystic fluid was quantitatively detected, and in vitro imaging simulation experiments were performed on some fluid substances with similar cystic fluid properties to explore the reasons for special imaging manifestations. The content of inorganic substances and protein in the cystic fluid were both low, with no melanin detected. In vitro experiments revealed that MR T1 signals could increase with protein content rising and changes in MR T2 signals presented no obvious correlation with it. CT values increased gradually with protein concentration rising. The substances with similar viscosity had similar CT values, whereas substance viscosity showed no significant correlation with changes in MR signals. Conclusion: The abnormality of imaging manifestations cannot be confirmed as the result of "high protein content", nor can it be simply attributed to bleeding. Further research is required for the impact of the combination of paramagnetic particles and biofluid on imaging.

Trap remediation of CuBi2O4 nanopolyhedra via surface self-coordination by H2O2: an innovative signaling mode for cathodic photoelectrochemical bioassay.

This work conveys a new philosophy of surface self-coordination mediated trap remediation for innovative cathodic photoelectrochemical (PEC) signal transduction. Initially, the surface trap states of CuBi2O4 nanopolyhedra resulting from dangling bonds can function as charge carrier recombination centers, which suppress the carrier separation efficiency and result in a low photocurrent output. Particularly, hydrogen peroxide (H2O2) spontaneously interacts with the uncoordinated Cu(II) on the surface of CuBi2O4, enabling efficient elimination of dangling bonds and remedy of trap states, thereby outputting intensified photocurrent readout. Exemplified by Flap endonuclease 1 (FEN1) as a model target, a tetrahedron DNA (THD)-based strand displacement amplification (SDA) was introduced to manipulate the formation of hemin impregnated G-quadruplex (G-quadruplex/hemin) DNAzyme and the resultant catalytic reduction for H2O2. In addition, a highly efficient and ultra-sensitive PEC sensing platform was achieved for FEN1 detection with a wide linear range from 1.0 fM to 100.0 pM and a detection limit of 0.3 fM (S/N = 3). This work not only establishes a new idea of cathodic PEC signal transduction, but also offers an efficient biosensing platform for FEN1.

The Influencing Effect of Tourism Economy on Green Development Efficiency in the Yangtze River Delta.

In the context of ecological priority and green development strategy, accelerating the upgrading of tourism structure and promoting the development of ecotourism is an important guarantee to achieve green and low-carbon economic growth and high-quality development. On the basis of constructing comprehensive evaluation indicators of tourism development (TD) and green development efficiency (GDE), this study analyzed the impulse response relationship between TD and GDE and the impact effect of TD on GDE in the Yangtze River Delta region from 2000-2018. Findings showed that: (1) During the study period, TD generally exhibited a W-shaped fluctuating upward trend and GDE showed a staggered evolution of upward and downward fluctuations, while both regional gaps of TD and GDE continued to decrease. (2) Most cities had made a leap from low to medium, high, and higher levels of tourism development, with tourism development levels decreasing along the Yangtze River basin to the north and south of the delta. The overall green development efficiency was relatively low, showing a spatial pattern of high value in the southern delta and low value in the northwest delta. (3) There was a one-way Granger causality of TD on GDE, and the impact of TD on GDE showed a significant positive cumulative effect. (4) TD exhibited a significant inverted U-shaped impact on GDE. The economic development level and government intervention had a significant positive impact on GDE. The proportion of secondary industry, energy consumption intensity, and foreign direct investment had a significant negative driving effect on GDE. While the impact of environmental regulation on GDE was insignificant positive. This study has great practical significance to alleviate the problems of urban resources and environment, and to realize a green economy and high-quality life.

Study on the coupling and coordination degree between urban tourism development and habitat environment in the Yangtze River Delta in China.

By constructing the two evaluation systems of urban tourism development (TD) and habitat environment (HE), the dynamic response relationship between the two systems in the Yangtze River Delta urban agglomeration from 2001 to 2020 is explored by using panel vector autoregression (PVAR) model and coupled coordination degree model. The study unearthed four intriguing findings: (1) the level of TD in the study area has been continuously rising from 2001 to 2020, with an initial slow growth rate and then fast. The level of HE is increasing steadily at an average annual rate of 7.05%. There exists a reciprocal response relationship between the two systems, with a strong shock effect in the short term and a synergistic evolution in the long term. (2) The coupling degree between the urban TD and HE has an increasing trend, and the coupling coordination degree of the two systems has an average annual rate of 4.165%, implying the interaction and promotion effect between the two systems is improving. (3) Most of the cities in the Yangtze River Delta gradually realize the evolution from dysfunctional type to coordinated type, but the overall coordination intensity is low. (4) The barrier degrees of TD system indicators show a small annual increasing trend, while the barrier degrees of HE system indicators show a substantial and continuous decreasing trend. In terms of the barrier degree factors, some important factors that restrict the coupled and coordinated development of the two systems are also reported. This research can provide a useful reference for the synergistic improvement of urban tourism economy and habitat environment.

Spatio-Temporal Disparity and Driving Forces of the Supply Level of Healthcare Service in the Yangtze River Delta.

The equalization of healthcare supply is not only related to the people's need for a better life, but can also provide a strong guarantee for the high-quality and sustainable development of the Yangtze River Delta integration. By using exploratory spatial analysis techniques, this study analyzed the spatio-temporal evolution characteristics and heterogeneous influence effects of the supply level of healthcare service in the Yangtze River Delta from 2007 to 2019. It was found that the supply level of healthcare service in the Yangtze River Delta had improved significantly. The differences in the supply level of healthcare service between cities had tended to narrow without polarization, and the supply level of healthcare service generally showed a high spatial pattern in the south delta and low spatial pattern in the north delta. The higher the supply level of healthcare service was, the weaker the interannual variability was. The supply level of healthcare service in the Yangtze River Delta region presented obvious spatial association and differentiated tendency of local high and low spatial clusters. The relative length and curvature of the supply level of healthcare service in the Yangtze River Delta generally presented a spatial pattern with low values in the northeast and high values in the southwest. Population density and urban-rural income gap generally exhibited negative spatio-temporal impact on the supply level of healthcare service across most cities. On the other hand, urbanization level and per capita disposable income generally had positive spatio-temporal impact on the supply level of healthcare service across most cities. Per capita gross domestic product (GDP) showed an increasingly positive spatio-temporal impact on the supply level of healthcare service across most cities. While per capita fiscal expenditure exhibited significantly negative impact on the supply level of healthcare service across most cities in space.

Highly dispersed RuO2-biomass carbon composite made by immobilization of ruthenium and dissolution of coconut meat with octyl ammonium salicylate ionic liquid for high performance flexible supercapacitor.

Poor dispersion of metal oxide-biomass carbon composite limits its further improvement in electrochemical properties. The study reports synthesis of highly dispersed RuO2-biomass carbon nanocomposite (HD-RuO2-BC). Octyl ammonium salicylate ionic liquid was combined with Ru3+ ion to form Ru-based ionic liquid. Followed by addition of coconut meat, microwave treatment to form homogeneous solution, thermal reduction in N2 and oxidation in air in sequence. The resulting HD-RuO2-BC shows three-dimensional architecture and high Ru loading of 9.2%. RuO2 nanoparticles of 6.2 nm were uniformly dispersed in biomass carbon sheets. Excellent dispersion and small size of RuO2 nanoparticles achieve to a significant synergy between RuO2 and biomass carbon. HD-RuO2-BC electrode gives high capacitance of 907.7 F g-1 at 1 A g-1. The value is more than that of BC (150.6 F g-1) and RuO2 electrodes (584.7 F g-1), verifying that introduction of RuO2 achieves to an obviously enhanced capacitance. The symmetrical flexible supercapacitor exhibits excellent supercapacitor performances, including high capacitance (403.8 F g-1 at 1.0 A g-1), rate-capacity (223.1 F g-1 at 50 A g-1), cycling stability (98.2% capacity retention after 10,000 cycles at 50 A g-1) and energy density (378.7 Wh Kg-1at power density of 5199.2 W kg-1).

Recent Advances in g-C3 N4 -Based Photocatalysts for Pollutant Degradation and Bacterial Disinfection: Design Strategies, Mechanisms, and Applications.

Emerging photocatalytic technology promises to provide an effective solution to the global energy crisis and environmental pollution. Graphite carbon nitride (g-C3 N4 ) has gained extensive attention in the scientific community due to its excellent physical and chemical properties, attractive electronic band structure, and low cost. In this paper, research progress in design strategies for g-C3 N4 -based photocatalysts in the past five years is reviewed from the perspectives of nanostructure construction, element doping, and heterostructure construction. To clarify the relationship between application requirements and structural design, variations in the morphology, electronic energy band structure, light absorption capacity, as well as interfacial charge transfer caused by various modification strategies are discussed in detail. The recent applications of g-C3 N4 -based photocatalysts for pollutant degradation and bacterial disinfection are reviewed, as well as the antimicrobial activity and degradation mechanisms. Finally, current challenges and future development directions for the practical application of g-C3 N4 -based photocatalysts are tentatively discussed.

Invoking Cathodic Photoelectrochemistry through a Spontaneously Coordinated Electron Transporter: A Proof of Concept Toward Signal Transduction for Bioanalysis.

Most of the cathodic photoelectrochemical (PEC) bioassays rely on electron accepting molecules for signal stimuli; unfortunately, the performances of which are still undesirable. New signal transduction strategies are still highly expected for the further development of cathodic photoelectrochemistry as a potentially competitive method. This work represents a new concept of invoked cathodic photoelectrochemistry by a spontaneously formed electron transporter for innovative operation of the sensing strategy. Specifically, the hexacyanoferrate(II) in solution easily self-coordinated with CuO nanomaterials and formed electron transporting copper hexacyanoferrate (CuHCF) on the surface, which endowed improved carrier separation for presenting augmented photocurrent readout. Exemplified by the T4 polynucleotide kinase (T4 PNK) and its inhibitors as targets, a homogenous cathodic PEC biosensing platform was achieved with the distinctive merits of label-free, immobilization-free, and split-mode readout. The mechanism revealed here provided a totally different perspective for signal transduction in cathodic photoelectrochemistry. Hopefully, it may stimulate more interests in the design and construction of semiconductor/transporter counterparts for exquisite operation of photocathodic bioanalysis.

Eccentricity forcing of East Asian monsoonal systems over the past 3 million years.

The East Asian summer monsoon and the precipitation it brings are relevant for millions of people. Because of the monsoon's importance, there has been a substantial amount of work attempting to describe the driving mechanisms behind its past variability. However, discrepancies exist, with speleothem-based East Asian monsoon reconstructions differing from those based on loess records from the Chinese Loess Plateau during the late Quaternary. The periodicity of wet and dry phases experienced by desert areas that lie on the periphery of the East Asian monsoon's influence offer another independent view of monsoonal variability. Here, we provide environmental records based on magnetic parameters for the last 3 million years from the Tengger Desert, China, one such marginal arid region. Our results reveal wet-dry cycles at a dominant frequency of 405 kiloyears, with drier intervals corresponding to eccentricity minima. These findings are consistent with previous reconstructions of East Asian summer and North African summer monsoon precipitation variability. Our records emphasize the dominant role of eccentricity in forcing East Asian monsoonal precipitation as well as monsoonal-derived environmental fluctuations experienced in peripheral desert areas. These results challenge the traditional view that high-latitude ice sheets are the primary driver of East Asian monsoon precipitation during the Quaternary based on Chinese loess records.

The in situ formation of a hole-transporting material on bismuth tungstate for innovative photoelectrochemical aptasensing.

We present the in situ formation of a hole-transporting material (bismuth hexacyanoferrate) on the surface of bismuth tungstate aimed at an innovative photoelectrochemical strategy. This approach enabled a competent aptasensing platform for chloramphenicol that was amenable to homogenous, label-free, and split-mode detection.

Establishing Interfacial Charge-Transfer Transitions on Ferroelectric Perovskites: An Efficient Route for Photoelectrochemical Bioanalysis.

This work presents the concept of establishing interfacial charge-transfer transitions (ICTT) on ferroelectric perovskites for efficient photoelectrochemical (PEC) bioanalysis. The model system was exemplified by using representative lead titanate (PbTiO3) and an enzyme tandem consisting of the isocitrate dehydrogenase (ICDH) and p-hydroxybenzoate hydroxylase (PHBH). The enzymatic generation of protocatechuic acid (PCA) can coordinate onto the surface of the PbTiO3 and hence form the ICTT that enables direct ligand-to-metal charge transfer from the highest occupied molecular orbital (HOMO) of PCA to the conduction band (CB) of PbTiO3 under light irradiation. Due to the ferroelectric polarization induced electric field of PbTiO3 and the surface polarity of PCA modification, enhanced charge separation of the ICTT contributes to the generation of anodic photocurrent and thus underlies a unique route for detecting the enzymatic activity or its substrate. For dehydrogenase detection, this strategy has better performance than some classical methodologies in terms of high sensitivity and improved selectivity. This work not only features ICTT establishment on ferroelectric perovskites for unique bioanalysis but also provides new insights into the utilization of ferroelectric perovskites for advanced PEC bioanalysis.

A 2D donor-acceptor covalent organic framework with charge transfer for supercapacitors.

An electron donor-acceptor covalent organic framework (TTF-COF1) was constructed by the imine condensation of electron donor tetraformyl-tetrathiafulvalene (TTF-fo) and electron acceptor 2,6-diaminoanthraquinone (DAQ). TTF-COF1 has intramolecular charge transfer, offering capacitance of 752 F g-1 at 1 A g-1 and an energy density of 57 W h kg-1 at a power density of 858 W kg-1.

Electrochemical biosensor for detection of MON89788 gene fragments with spiny trisoctahedron gold nanocrystal and target DNA recycling amplification.

The shape-controlled synthesis of gold nanocrystals via shape induction of hexadecyltrimethylammonium chloride, potassium bromide, and potassium iodide and enantioselective direction of L-cysteine is reported. The resulting gold nanocrystals (STO-Au) offer spiny trisoctahedron nanostructures with good monodispersity and enhanced exposed high-index facets and high catalytic activity. Construction of the electrochemical sensing platform for MON89788 gene involves the modification of STO-Au, thionine (Thi), and labeled bipedal DNA probe 1 or 2 (P1 or P2) for target DNA-induced recycling amplification. In the detection, two surface DNA probes were immobilized on gold electrode via the Au-S bond. Then, hairpin DNA 1 (H1), Thi-STO-Au-P1, and Thi-STO-Au-P2 self-assemble into two-dimensional DNA nanopores (DNPs) on the electrode surface. Target DNA hybridizes with hairpin DNA 2 (H2) to open hairpin structure of H2. The opened H2 binds with H1 in the DNPs to release Thi-STO-Au-P1, Thi-STO-Au-P2, and target DNA by toehold-mediated strand-displacement. The utilization of target DNA-induced recycling allows one target DNA to release 2N STO-Au-labeled DNA strands, promoting significant signal amplification. The detection signal is further enhanced by the catalyzed redox reaction of Thi with STO-Au. The differential pulse voltammetric signal, best measured at - 0.18 V vs. Ag/AgCl, decreases linearly with increasing concentration of MON89788 in the range 0.02-8 × 104 fM, and the detection limit is 0.0048 fM (S/N = 3). The proposed method was successfully applied for electrochemical detection of MON89788 gene fragments in the PCR products from genetically modified soybean. Graphical Abstract We develop l-cysteine controlled synthesis of spiny trisoctahedron gold nanocrystals with good monodispersity and highly exposed high-index facets. The architecture achieves to ultrahigh catalytic activity. The electrochemical biosensor based on gold nanocrystals and target DNA recycling amplification provides advantage of sensitivity, repeatability, and regeneration-free.

High-throughput photoelectrochemical determination of E. coli O157:H7 by modulation of the anodic photoelectrochemistry of CdS quantum dots via reversible deposition of MnO2.

A method is described for modulating the anodic photoelectrochemistry of netlike CdS quantum dots through the deposition and dissolution of the electron acceptor manganese dioxide (MnO2) on the surface of the photoelectrode. Specifically, the photocurrent of a CdS-modified indium tin oxide (ITO/CdS) electrode is inhibited by chemical deposition of MnO2. However, the photocurrent becomes recovered by oxidative removal of MnO2 with H2O2. This deposition-dissolution reaction modulates the photoelectrochemistry of CdS effectively. A bioassay for Escherichia coli (E. coli) O157:H7 is designed that uses the antimicrobial peptide magainin I as the recognition element. Glucose oxidase (GOx) acts as a catalytic label tracer to produce the signaling molecule H2O2 in the microwell plates. The enzymatically generated H2O2 etches the deposited MnO2 on the photoelectrode and thus enhances the photocurrent. This detection scheme does not cause any damage to biomolecules. It also avoids the adverse effects of immobilized biomolecules for retarding signal production and leads to improved detection when compared to conventional PEC configurations. E. coli can be detected in the 10 to 5.0 × 106 CFU·mL-1 concentration range, and the limit of detection is 3 CFU·mL-1. Graphical abstractSchematic representation of the photoelectrochemical assay of E. coli through the deposition and dissolution of electron accepting manganese dioxide (MnO2) on the surface of the photoelectrode.

Ultrasensitive Fluorometric Angling Determination of Staphylococcus aureus in Vitro and Fluorescence Imaging in Vivo Using Carbon Dots with Full-Color Emission.

Rapid, accurate, and safe screening of foodborne pathogenic bacteria is essential to effectively control and prevent outbreaks of foodborne illness. Fluorescent sensors constructed from carbon dots (CDs) and nanomaterial-based quenchers have provided an innovative method for screening of pathogenic bacteria. Herein, an ultrasensitive magnetic fluorescence aptasensor was designed for separation and detection of Staphylococcus aureus (S. aureus). Multicolor fluorescent CDs with a long fluorescent lifetime (6.73 ns) and high fluorescence stability were synthesized using a facile hydrothermal approach and modified cDNA as a highly sensitive fluorescent probe. CD fluorescence was quenched by Fe3O4 + aptamer via fluorescence resonance energy transfer (FRET). Under optimal conditions, the FRET-based aptasensor can detect S. aureus accompanied by a wide linear range of 50-107 CFU·mL-1 and a detection limit of 8 CFU·mL-1. Compared with other standard methods, this method was faster and more convenient, and the entire test was finished within 30 min. The capability of the aptasensor was simultaneously investigated on food samples. Additionally, the developed CDs exhibited excellent biocompatibility and were thus applied as fluorescent probes for bioimaging both in vitro and in vivo. This new platform provided an excellent application of the CDs for detecting and bioimaging pathogenic bacteria.

In situ chemical redox and functionalization of graphene oxide: toward new cathodic photoelectrochemical bioanalysis.

This report outlines the first exploration of graphene oxide (GO) itself as a light harvesting material with an innovative in situ chemical redox and functionalization (CRF) strategy for versatile and high-throughput cathodic photoelectrochemical (PEC) bioanalysis.

Switched photoelectrochemistry of carbon dots for split-type immunoassay.

A novel and general strategy of split-type immunoassay is developed based on redox chemical reaction modulated photoelectrochemistry of carbon dots (CDs). Specifically, the photocurrent of the CDs sensitized titanium dioxide nanoparticles (TiO2 NPs) modified fluorine doped indium tin oxide (FTO) (that is the FTO/TiO2/CDs) electrode was inhibited obviously by KMnO4 due to the oxidation of surface hydroxyl groups of CDs to electron accepting carbonyls. While the inhibited photocurrent of the KMnO4 treated FTO/TiO2/CDs electrode can be restored by ascorbic acid (AA) because of the regeneration of electron donating hydroxyls to promote electron-hole separation. Take carcinoembryonic antigen (CEA) as a model analyte and alkaline phosphate (ALP) as a catalytic label tracer to hydrolyze ascorbic acid 2-phosphate (AAP) for producing AA, which greatly stimulated the photocurrent of the transducer of KMnO4 treated FTO/TiO2/CDs photoelectrode for signal output. This redox chemical reaction modulated PEC strategy enabled the separation of the immunoreaction from the photoelectrode (that is, a split-type PEC detection), eliminating potential damage of biomolecules during the PEC detection processes and leading to enhanced throughput detection as compared to conventional PEC configurations. A low detection limit of 7.0 fg/mL was achieved for CEA. This convenient, split-type PEC immunoassay with high throughput may be easily extended to other bioaffinity assays for versatile targets.

Synthesis of gold-palladium nanowaxberries/dodecylamine-functionalized graphene quantum dots-graphene micro-aerogel for voltammetric determination of peanut allergen Ara h 1.

The paper reports synthesis of gold-palladium nanowaxberries(AuPd NWs)/dodecylamine-functionalized graphene quantum dots(D-GQDs)-graphene micro-aerogel(GMA). D-GQDs was used as a solid particle surfactant for stabilizing Pickering emulsion of toluene-in-graphene oxide aqueous dispersion. Graphene oxide sheets in the aqueous phase are reduced by hydrazine hydrate, diffused into the toluene droplet and self-assembled into graphene oxide micro-gels. Followed by freeze-drying, thermal annealing and hybridized with AuPd NWs. The as-prepared AuPd NWs/D-GQDs-GMA shows an unique three-dimensional structure with the size of microns. The small size and strong polarity make it can be directly dispersed in ethanol to form stable dispersion for sensor preparation. The hybrid of GMA, D-GQDs and AuPd NWs greatly improves the electron transfer, electroactive surface area and ion diffusion. The architecture of conductor/semiconductor/conductor achieves to a significant amplification of detection signal. The DNA biosensor based on the AuPd NWs/D-GQDs-GMA exhibits ultrasensitive differential pulse voltammetric (DPV) response towards peanut allergen Ara h 1. The DPV signal linearly increases with increasing DNA concentration in the range of 1.0 × 10-22-1.0 × 10-17 M with the detection limit of 4.7 × 10-23 M (S/N = 3). The analytical method was successfully applied to voltammetric determination of peanut allergen Ara h 1 in peanut milk beverage.