Simultaneous detection of patulin (PAT) and ochratoxin A (OTA) in food products is in great demand, which can prevent toxins from being exposed to human and animal bodies. However, simultaneous ...detection of multiple targets still faces a challenge. Herein, we developed a novel electrochemical aptasensor for the simultaneous detection of PAT and OTA in apple juice based on gold nanoparticles decorated black phosphorus (AuNPs-BP) nanomaterial. AuNPs-BP function?/work? as a sensing platform for loading much different electrochemical signal molecules functionalized aptamers. In this context, methylene blue functionalized PAT aptamers (Mb-PAT-aptamers) and ferrocene functionalized OTA aptamers (Fc-OTA-aptamers) have been introduced here to fabricate the aptasensor. Fc close to electrode surface showed a strong signal, whereas Mb was far away from electrode surface so exhibited a weak signal in the absence of OTA and PAT. Two kinds of electrochemical signal changes have been recorded dependent on target of OTA and PAT concentrations. So, simultaneous detection of OTA and PAT is achieved. Under the optimum conditions, using this developed biosensor, PAT and OTA can be quantified at a linearity range of 0.01 × 10
−7
μg·mL
−1
~ 0.10 μg·mL
−1
. In addition, it also has good selectivity, stability and repeatability. For the practical application, it shows promising performance for the simultaneous detection of PAT and OTA in apple juice.
Here, we design and synthesize a novel 2D Cu-tetrakis(4-carboxyphenyl)porphyrin (TCPP) metal–organic framework (MOF) sheet and ultrasmall Cu
5.4
O nanoparticle (Cu
5.4
O USNP) hybrid (Cu-TCPP MOF/Cu
...5.4
O nanocomposite). The graphene-like ultrathin Cu-TCPP MOF sheets offer high surface-to-volume atom ratios and many active sites, which is beneficial for loading more Cu
5.4
O USNPs. The Cu
5.4
O USNPs with ultrasmall size (<5 nm) have promising conductivity and excellent enzymatic ability for H
2
O
2
. The successfully prepared nanocomposites are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) techniques. The 2D graphene-like ultrathin Cu-TCPP MOF sheets show no H
2
O
2
-sensing signals, whereas Cu
5.4
O USNPs exhibit a clear reduction peak for detection of H
2
O
2
. Interestingly, the combination of two kinds of nanomaterials improved the H
2
O
2
sensing ability due to their synergistic effect. The properties of the unmodified electrodes and the Cu-TCPP MOF/Cu
5.4
O nanocomposite-modified electrodes were systemically studied by cyclic voltammetry (CV), current-time (
i
-
t
) response, and square-wave voltammetry (SWV) techniques. The electrochemical sensor for the detection of H
2
O
2
based on the Cu-TCPP MOF/Cu
5.4
O nanocomposite has a lower detection limit of 0.13 μmol·L
−1
and wider linear range of 0.1 × 10
−6
~ 0.59 × 10
−3
mol·L
−1
and 1.59 × 10
−3
~ 20.59 × 10
−3
mol·L
−1
when compared with the Cu
5.4
O USNPs-modified electrode. The electrochemical sensor can be further used to detect H
2
O
2
produced by cells.
Graphical abstract
The mechanism for sensing H
2
O
2
produced from cells based on a Cu-TCPP MOF/Cu
5.4
O USNPs nanocomposite-modified electrode.
A novel silver nanowire/nickel–cobalt layered double hydroxide (AgNW/NiCo LDH) nanocomposite was successfully synthesized, after which a glucose sensor was fabricated. AgNW was synthesized by ...ethylene glycol as reductant in presence of Fe3+, and NiCo LDH grafted vertically along the 1D AgNW by slow hydrolysis of urea. The morphology and composition of AgNW/NiCo LDH were characterized by Scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical investigation showed that the AgNW/NiCo LDH/GCE exhibited excellent electrocatalytic ability to glucose oxidation, with a linear range from 0.002 mM to 6 mM at a low applied potential of 0.4 V (vs. SCE) and a low detection limit of 0.66 μM at the signal-to-noise ratio of 3. It is expected that the AgNW/NiCo LDH nanocomposites appear to be a promising catalyst for non-enzymatic glucose sensor.
A novel hydrothermal method was reported to synthesize AgNW/NiCo LDH for electrocatalysis of glucose. Display omitted
•AgNW/NiCo LDH was synthesized through a facile hydrothermal method.•AgNW/NiCo LDH was employed to fabricate a novel non-enzymatic sensor.•The synergetic combination of functional AgNW and NiCo LDH materials enhanced electrocatalysis of glucose.
Zn
2+
and Cu
2+
related to transition metal ions present in foods play essential roles in the health of human and animal metabolism. However, the excess of these ions contaminates foods and causes ...many kinds of diseases. In recent years, designing chemosensors for detection of the two targets has been widespread but is still a great challenge for practical application. In this study, by reducing expenses, simplifying analytical procedures, and enabling multifunctions, a functional chemosensor was proposed by using tetraphenylethylene derivative (
H
4
tcbpe
) which could selectively and sensitively response to Zn
2+
and Cu
2+
. H
4
tcbpe can be used to detect Zn
2+
with fluorescence enhancement based on aggregation induced emission effect, while fluorescence of H
4
tcbpe can be quenched by Cu
2+
due to the disassembly of H
4
tcbpe aggregates in a solvent/nonsolvent binary mixture of EtOH and H
2
O. Fluorophotometry, UV-Vis, and SEM were used to characterize behavior of the fluorescence sensor. In this work, the detection in liquid solutions was conducted, and a fluorescent test pen for the assay of Zn
2+
and Cu
2+
on a piece of filter paper was fabricated. The proposed fluorescent test pen contained H
4
tcbpe as a “fluorescent probe ink” and made it possible to write words on the area of a filter paper spiked with solutions with different concentrations of Zn
2+
and Cu
2+
. The detection limits for Zn
2+
and Cu
2+
are 43 nM and 0.5 μM, respectively. This fluorescent sensor was applied to sense ions in black fungus samples. The proposed sensor could successfully detect Zn
2+
and Cu
2+
, and the results were in agreement with the data from inductively coupled plasma mass spectrometry, which indicated the reliability of the proposed sensor for applications in the real samples.
Climate is widely recognised as an important determinant of the latitudinal diversity gradient. However, most existing studies make no distinction between direct and indirect effects of climate, ...which substantially hinders our understanding of how climate constrains biodiversity globally. Using data from 35 large forest plots, we test hypothesised relationships amongst climate, topography, forest structural attributes (stem abundance, tree size variation and stand basal area) and tree species richness to better understand drivers of latitudinal tree diversity patterns. Climate influences tree richness both directly, with more species in warm, moist, aseasonal climates and indirectly, with more species at higher stem abundance. These results imply direct limitation of species diversity by climatic stress and more rapid (co‐)evolution and narrower niche partitioning in warm climates. They also support the idea that increased numbers of individuals associated with high primary productivity are partitioned to support a greater number of species.
Aim: Most studies on latitudinal gradients of biodiversity have focused on gradients of species richness. Here we aim to test whether, on top of these strong diversity gradients, processes of ...community assembly vary along a latitudinal gradient of more than 33°. Location: China, latitude 18.67-51.86° N. Methods: We used species abundance distribution (SAD) data collected in 32 forest tree plots, and fitted a non-neutral model of community assembly to these SADs. We then calculated the fitted deviation from neutrality, δ, and looked for correlations between δ and geographical and environmental data. Results: The fitted parameter δ was positive in most plots, and was furthermore positively correlated with latitude and negatively with temperature, indicating a less even abundance distribution and a likely increase in the strength of environmental filtering in regions further from the tropics and with decreasing temperatures. These results imply that on top of reducing the species richness, cold temperature may impact community assembly processes by strengthening local environmental filtering. Main conclusions: Our results suggest a latitudinal gradient in tree community assembly process in Chinese forests, in which deviations from neutrality increase with latitude, probably because of an increase in environmental harshness.
Arbuscular mycorrhizal (AM) and ectomycorrhizal (EcM) associations are critical for host-tree performance. However, how mycorrhizal associations correlate with the latitudinal tree beta-diversity ...remains untested. Using a global dataset of 45 forest plots representing 2,804,270 trees across 3840 species, we test how AM and EcM trees contribute to total beta-diversity and its components (turnover and nestedness) of all trees. We find AM rather than EcM trees predominantly contribute to decreasing total beta-diversity and turnover and increasing nestedness with increasing latitude, probably because wide distributions of EcM trees do not generate strong compositional differences among localities. Environmental variables, especially temperature and precipitation, are strongly correlated with beta-diversity patterns for both AM trees and all trees rather than EcM trees. Results support our hypotheses that latitudinal beta-diversity patterns and environmental effects on these patterns are highly dependent on mycorrhizal types. Our findings highlight the importance of AM-dominated forests for conserving global forest biodiversity.
From supporting wood production to mitigating climate change, forest ecosystem services are crucial to the well-being of humans. Understanding the mechanisms that drive forest dynamics can help us ...infer how to maintain forest ecosystem services and how to improve predictions of forest dynamics under climate change. Despite the growing number of studies exploring above ground biomass (AGB) dynamics, questions of dynamics in biodiversity and in number of individuals still remain unclear. Here, we first explored the patterns of community dynamics in different aspects (i.e., AGB, density and biodiversity) based on short-term (five years) data from a 25-ha permanent plot in a subtropical forest in central China. Second, we examined the relationships between community dynamics and biodiversity and functional traits. Third, we identified the key factors affecting different aspects of community dynamics and quantified their relative contributions. We found that in the short term (five years), net above ground biomass change (ΔAGB) and biodiversity increased, while the number of individuals decreased. Resource-conservation traits enhanced the ΔAGB and reduced the loss in individuals, while the resource-acquisition traits had the opposite effect. Furthermore, the community structure contributed the most to ΔAGB; topographic variables and soil nutrients contributed the most to the number of individuals; demographic process contributed the most to biodiversity. Our results indicate that biotic factors mostly affected the community dynamics of ΔAGB and biodiversity, while the number of individuals was mainly shaped by abiotic factors. Our work highlighted that the factors influencing different aspects of community dynamics vary. Therefore, forest management practices should be formulated according to a specific protective purpose.
Most of the world's terrestrial biome types can be found in China. To systematically investigate species composition and structure of China's forest communities, we launched a long-term project ...consisting forest vegetation surveys across China's mountains in the mid 1990s. Over the study period, we have conducted vegetation surveys for 65 mountains and collected vegetation data from about 1500 forest plots, using consistent sampling protocols. In this paper we first introduce the aims, protocols, and major research themes of the project, and then describe the major characteristics of forest communities and their geographic patterns and climatic controls. As latitude increased, diameter at breast height (DBH) and height of trees increased, while individual density of trees and woody species richness decreased. Total basal area (TBA) of trees and species richness of herbs did not vary with latitude. Contemporary climate seems to drive these patterns: temperature was the leading factor for DBH, precipitation was most important for tree height and individual density, actual evapotranspiration (a surrogate of productivity) determined woody (trees and shrubs) species richness, and rainfall was the major controller of the herb species richness. The species—abundance relationship showed that species dominance (measured by the number of individuals per species) declined significantly from boreal forests to evergreen broadleaf forests from north to south. Our results are in line with the idea that productivity drives woody species richness. Similarly, we find that biomass (measured as TBA) is invariant along the environmental gradients. However, individual density varies dramatically, in contrast to the assumptions underlying the metabolic theory of ecology.
Despite several decades of study in community ecology, the relative importance of the ecological processes that determine species co‐occurrence across spatial scales remains uncertain. Some of this ...uncertainty may be reduced by studying the scale dependency of community assembly in the light of environmental variation. Phylogenetic information and functional trait information are often used to provide potentially valuable insights into the drivers of community assembly. Here, we combined phylogenetic and trait‐based tests to gain insights into community processes at four spatial scales in a large stem‐mapped subtropical forest dynamics plot in central China. We found that all of the six leaf economic traits measured in this study had weak, but significant, phylogenetic signal. Nonrandom phylogenetic and trait‐based patterns associated with topographic variables indicate that deterministic processes tend to dominate community assembly in this plot. Specifically, we found that, on average, co‐occurring species were more phylogenetically and functionally similar than expected throughout the plot at most spatial scales and assemblages of less similar than expected species could only be found on finer spatial scales. In sum, our results suggest that the trait‐based effects on community assembly change with spatial scale in a predictable manner and the association of these patterns with topographic variables, indicates the importance of deterministic processes in community assembly relatively to random processes.
Trait‐based and phylogenetic tests of subtropical tree community assembly across scales.
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