Effect of robbing intensity on reproductive success of Symphytum officinale (Boraginaceae).

The intervention of nectar robbers in plant pollination systems will cause some pollinators to modify their foraging behavior to act as secondary robbers, consequently adopting a mixed foraging strategy. The influence of nectar robbing on pollinator behavior may be affected by spatio-temporal difference of robbing intensity, and consequently, may have different effects on the pollination of host plants. However, whether and how the nectar robbing might influence pollinators under different robbing intensity still needs further investigation. In this study, Symphytum officinale was used to detect the effect of nectar robbers on pollinators under different robbing intensity as well as their effects on plant reproductive success. Six robbing levels and three bumblebees with mixed foraging behaviors were used to evaluate the effect of different robbing intensity on pollinator behavior, visitation rate, flower longevity and pollen deposition. Our results indicated that the robbing rate increased gradually with the proportion of robbed flowers, but which did not affect the frequency of legitimate visits. The increase of robbing rate promoted the corolla abscission, and then enhanced the self-pollen deposition, but which had no significant effect on cross-pollen deposition. These results indicate that the overall fitness of S. officinale was improved by combined self and cross-pollination modes when visited by both pollinators and nectar robbers simultaneously. Although nectar robbing is not uncommon, its consequences for pollination in the interaction web have not been well studied. Our results emphasize the significance of indirect impacts in mediating the adaptive outcomes of species interactions.

Revealing the Effect of High Ni Content in Li-Rich Cathode Materials: Mitigating Voltage Decay or Increasing Intrinsic Reactivity.

Li-rich layered oxides are considered as one of the most promising cathode materials for secondary lithium batteries due to their high specific capacities, but the issue of continuous voltage decay during cycling hinders their market entry. Increasing the Ni content in Li-rich materials is assumed to be an effective way to address this issue and attracts recent research interests. However, a high Ni content may induce increased intrinsic reactivity of materials, resulting in severe side reactions with the electrolyte. Thus, a comprehensive study to differentiate the two effects of the Ni content on the cell performance with Li-rich cathode is carried out in this work. Herein, it is demonstrated that a properly dosed amount of Ni can effectively suppress the voltage decay in Li-rich cathodes, while over-loading of Ni, on the contrary, can cause structural instability, Ni dissolution, and nonuniform Li deposition during cycling as well as severe oxygen loss. This work offers a deep understanding on the impacts of Ni content in Li-rich materials, which can be a good guidance for the future design of such cathodes for high energy density lithium batteries.

S-Doped Carbon Fibers Uniformly Embedded with Ultrasmall TiO2 for Na+ /Li+ Storage with High Capacity and Long-Time Stability.

Building a rechargeable battery with high capacity, high energy density, and long lifetime contributes to the development of novel energy storage devices in the future. Although carbon materials are very attractive anode materials for lithium-ion batteries (LIBs), they present several deficiencies when used in sodium-ion batteries (SIBs). The choice of an appropriate structural design and heteroatom doping are critical steps to improve the capacity and stability. Here, carbon-based nanofibers are produced by sulfur doping and via the introduction of ultrasmall TiO2 nanoparticles into the carbon fibers (CNF-S@TiO2 ). It is discovered that the introduction of TiO2 into carbon nanofibers can significantly improve the specific surface area and microporous volume for carbon materials. The TiO2 content is controlled to obtain CNF-S@TiO2 -5 to use as the anode material for SIBs/LIBs with enhanced electrochemical performance in Na+ /Li+ storage. During the charge/discharge process, the S-doping and the incorporation of TiO2 nanoparticles into carbon fibers promote the insertion/extraction of the ions and enhance the capacity and cycle life. The capacity of CNF-S@TiO2 -5 can be maintained at ≈300 mAh g-1 over 600 cycles at 2 A g-1 in SIBs. Moreover, the capacity retention of such devices is 94%, showing high capacity and good stability.

ZnO-carbon nanofibers for stable, high response, and selective H2S sensors.

Hydrogen sulfide (H2S), as a typical atmospheric pollutant, is neurotoxic and flammable even at a very low concentration. In this study, we design stable H2S sensors based on ZnO-carbon nanofibers. Nanofibers with 30.34 wt% carbon are prepared by a facial electrospinning route followed by an annealing treatment. The resulting H2S sensors show excellent selectivity and response compared to the pure ZnO nanofiber H2S sensors, particularly the response in the range of 102-50 ppm of H2S. Besides, they exhibited a nearly constant response of approximately 40-20 ppm of H2S over 60 days. The superior performance of these H2S sensors can be attributed to the protection of carbon, which ensures the high stability of ZnO, and oxygen vacancies that improve the response and selectivity of H2S. The good performance of ZnO-carbon H2S sensors suggests that composites with oxygen vacancies prepared by a facial electrospinning route may provide a new research strategy in the field of gas sensors, photocatalysts, and semiconductor devices.

Pipe-Wire TiO2-Sn@Carbon Nanofibers Paper Anodes for Lithium and Sodium Ion Batteries.

Metallic tin has been considered as one of the most promising anode materials both for lithium (LIBs) and sodium ion battery (NIBs) because of a high theoretical capacity and an appropriate low discharge potential. However, Sn anodes suffer from a rapid capacity fading during cycling due to pulverization induced by severe volume changes. Here we innovatively synthesized pipe-wire TiO2-Sn@carbon nanofibers (TiO2-Sn@CNFs) via electrospinning and atomic layer deposition to suppress pulverization-induced capacity decay. In pipe-wire TiO2-Sn@CNFs paper, nano-Sn is uniformly dispersed in carbon nanofibers, which not only act as a buffer material to prevent pulverization, but also serve as a conductive matrix. In addition, TiO2 pipe as the protection shell outside of Sn@carbon nanofibers can restrain the volume variation to prevent Sn from aggregation and pulverization during cycling, thus increasing the Coulombic efficiency. The pipe-wire TiO2-Sn@CNFs show excellent electrochemical performance as anodes for both LIBs and NIBs. It exhibits a high and stable capacity of 643 mA h/g at 200 mA/g after 1100 cycles in LIBs and 413 mA h/g at 100 mA/g after 400 cycles in NIBs. These results would shed light on the practical application of Sn-based materials as a high capacity electrode with good cycling stability for next-generation LIBs and NIBs.

A Phase-Separation Route to Synthesize Porous CNTs with Excellent Stability for Na+ Storage.

Porous carbon nanotubes (CNTs) are obtained by removing MoO2 nanoparticles from MoO2 @C core@shell nanofibers which are synthesized by phase-segregation via a single-needle electrospinning method. The specific surface area of porous CNTs is 502.9 m2 g-1 , and many oxygen-containing functional groups (COH, CO) are present. As anodes for sodium-ion batteries, the porous CNT electrode displays excellent rate performance and cycling stability (110 mA h g-1 after 1200 cycles at 5 A g-1 ). Those high properties can be attributed to the porous structure and surface modification to steadily store Na+ with high capacity. The work provides a facile and broadly applicable way to fabricate the porous CNTs and their composites for batteries, catalysts, and fuel cells.

Muti-component nanocomposite of nickel and manganese oxides with enhanced stability and catalytic performance for non-enzymatic glucose sensors.

A muti-component nanocomposite of nickel and manganese oxides with a uniformly dispersed microspherical structure has been fabricated by a hydrothermal synthesis method. The as-prepared nanocomposite has been employed as a sensing material for non-enzymatic glucose detection and shown excellent electrocatalytic activity, such as high sensitivities of 82.44 µA mM(-1) cm(-2) and 27.92 µA mM(-1) cm(-2) over the linear range of 0.1-1 mM and 1-4.5 mM, respectively, a low detection limit of 0.2 µM and a fast response time of <3 s. Moreover, satisfactory specificity and excellent stability have also been achieved. The results demonstrate that a muti-component nanocomposite of nickel and manganese oxides has great potential applications as glucose sensors.

Ionic liquid-assisted fabrication of copper hydroxyphosphate nanocrystals with exposed {100} facets for enhanced photocatalytic activity.

Libethenite Cu2PO4OH nanocrystals with different morphologies were prepared by an ionic liquid-assisted hydrothermal route, and were further investigated as photocatalysts under visible-light irradiation. The Cu2PO4OH elongated truncated bipyramids exposing {100} facets exhibit superior photocatalytic activity compared to other particles, which can be attributed to the presence of 100% Cu5c atoms on {100} facets. It is highly expect this research can provide a useful fundamental understanding of shape-dependent photocatalytic performance of copper hydroxyphosphate.

Non-enzymatic electrochemical glucose sensor based on NiMoO4 nanorods.

A non-enzymatic glucose sensor based on the NiMoO4 nanorods has been fabricated for the first time. The electrocatalytic performance of the NiMoO4 nanorods' modified electrode toward glucose oxidation was evaluated by cyclic voltammetry and amperometry. The NiMoO4 nanorods' modified electrode showed a greatly enhanced electrocatalytic property toward glucose oxidation, as well as an excellent anti-interference and a good stability. Impressively, good accuracy and high precision for detecting glucose concentration in human serum samples were obtained. These excellent sensing properties, combined with good reproducibility and low cost, indicate that NiMoO4 nanorods are a promising candidate for non-enzymatic glucose sensors.

Giant intrinsic photovoltaic effect in one-dimensional van der Waals grain boundaries.

The photovoltaic effect lies at the heart of eco-friendly energy harvesting. However, the conversion efficiency of traditional photovoltaic effect utilizing the built-in electric effect in p-n junctions is restricted by the Shockley-Queisser limit. Alternatively, intrinsic/bulk photovoltaic effect (IPVE/BPVE), a second-order nonlinear optoelectronic effect arising from the broken inversion symmetry of crystalline structure, can overcome this theoretical limit. Here, we uncover giant and robust IPVE in one-dimensional (1D) van der Waals (vdW) grain boundaries (GBs) in a layered semiconductor, ReS2. The IPVE-induced photocurrent densities in vdW GBs are among the highest reported values compared with all kinds of material platforms. Furthermore, the IPVE-induced photocurrent is gate-tunable with a polarization-independent component along the GBs, which is preferred for energy harvesting. The observed IPVE in vdW GBs demonstrates a promising mechanism for emerging optoelectronics applications.

Monolithic integrated optoelectronic chip for vector force detection.

Sensors with a small footprint and real-time detection capabilities are crucial in robotic surgery and smart wearable equipment. Reducing device footprint while maintaining its high performance is a major challenge and a significant limitation to their development. Here, we proposed a monolithic integrated micro-scale sensor, which can be used for vector force detection. This sensor combines an optical source, four photodetectors, and a hemispherical silicone elastomer component on the same sapphire-based AlGaInP wafer. The chip-scale optical coupling is achieved by employing the laser lift-off techniques and the flip-chip bonding to a processed sapphire substrate. This hemispherical structure device can detect normal and shear forces as low as 1 mN within a measurement range of 0-220 mN for normal force and 0-15 mN for shear force. After packaging, the sensor is capable of detecting forces over a broader range, with measurement capabilities extending up to 10 N for normal forces and 0.2 N for shear forces. It has an accuracy of detecting a minimum normal force of 25 mN and a minimum shear force of 20 mN. Furthermore, this sensor has been validated to have a compact footprint of approximately 1.5 mm2, while maintaining high real-time response. We also demonstrate its promising potential by combining this sensor with fine surface texture perception in the fields of compact medical robot interaction and wearable devices.

Pushing Pressure Detection Sensitivity to New Limits by Modulus-Tunable Mechanism.

Only microstructures are used to improve the sensitivity of iontronic pressure sensors. By modulating the compressive modulus, a breakthrough in the sensitivity of the iontronic pressure sensor is achieved. Furthermore, it allows for programmatic tailoring of sensor performance according to the requirements of different applications. Such a new strategy pushes the sensitivity up to a record-high of 25 548.24 kPa-1 and expands the linear pressure range from 15 to 127 kPa. Additionally, the sensor demonstrates excellent mechanical stability over 10 000 compression-release cycles. Based on this, a well-controlled robotic hand that precisely tracks the pressure behavior inside a balloon to autonomously regulate the gripping angle is developed. This paves the way for the application of iontronic pressure sensors in precise sensing scenarios.

Non-equilibrium compression achieving high sensitivity and linearity for iontronic pressure sensors.

Flexible pressure sensors with high sensitivity and linearity are highly desirable for robot sensing and human physiological signal detection. However, the current strategies for stabilizing axial microstructures (e.g., micro-pyramids) are mainly susceptible to structural stiffening during compression, thereby limiting the realization of high sensitivity and linearity. Here, we report a bending-induced non-equilibrium compression process that effectively enhances the compressibility of microstructures, thereby crucially improving the efficiency of interfacial area growth of electric double layer (EDL). Based on this principle, we fabricate an iontronic flexible pressure sensor with vertical graphene (VG) array electrodes. Ultra-high sensitivity (185.09 kPa-1) and linearity (R2 = 0.9999) are realized over a wide pressure range (0.49 Pa-66.67 kPa). It also exhibits remarkable mechanical stability during compression and bending. The sensor is successfully employed in a robotic gripping task to recognize the targets of different materials and shapes based on a multilayer perception (MLP) neural network. It opens the door to realizing haptic sensing capabilities for robotic hands and prosthetic limbs.

Solvothermal synthesis of hollow urchin-like SnO2 nanospheres with superior lithium storage behavior.

Hollow urchin-like SnO2 nanospheres with ultrathin nanorods have been successfully synthesized via a simple complex solvothermal route. The formation mechanism of the as-synthesized SnO2 nanospheres was simply explained. When tested as anode, the as-obtained hollow urchin-like SnO2 nanospheres exhibit excellent rate and cycling performances. It was expected that the as-synthesized SnO2 nanospheres could be applied as anode materials for future lithium-ion batteries.

Giant Negative Thermopower Enabled by Bidirectionally Anchored Cations in Multifunctional Polymers.

The lack of high-quality ionic thermoelectric materials with negative thermopowers has stimulated scientists' broad research interest. The effective adjustment of the interaction between ions and a polymer network is an important way to achieve high-quality ion thermoelectric properties. Integrating different types of ion-polymer interactions into the same thermoelectric device seems to lead to unexpected gains. In this work, we propose a strategy for bidirectionally anchoring cations to synergistically generate a giant negative thermopower and high ionic conductivity. This is mainly achieved through synergistic ion-polymer coordination and Coulomb interactions. An ionic thermoelectric material was prepared by infiltrating a polycation electrolyte [poly(diallyldimethylammonium chloride)] with CuCl2 into the poly(vinyl alcohol)-chitosan aerogel. The confinement effect of copper-coordinated chitosan on cations, the repulsive property of the polycationic electrolyte on cations, and the unique chemical configuration of a transition metal chloride anion ([CuCl4]2-) are the fundamental guarantees for achieving a thermopower of -28.4 mV·K-1. Moreover, benefiting from the high charge density of the polycationic electrolyte, we obtain an ionic conductivity of 40.5 mS·cm-1. These findings show the application prospect of synergistic different types of ion-polymer interactions in designing multifunctional ionic thermoelectric materials.

Effects of continuous variation in vertical and lateral herkogamy on reproductive success in Euphorbia fischeriana (Euphorbiaceae).

Continuous variation in herkogamy has been well reported, however, less attention has been paid to the phenomena that the consecutive expression of two types of herkogamy in the same flower. Euphorbia fischeriana, which have both vertical and lateral herkogamy, show vertical herkogamy during the female phase. However, their gynophores bend to one side with the male phase and show lateral herkogamy. In this study, we observed the effect of successive sexual organs movement on variation in herkogamy traits. By artificially manipulating the flower to present gynophore straightened in the floral center or bend to one side, we attempted to investigate whether herkogamy movement affects pollinator access efficiency, pollen removal and deposition, and seed set ratio. Furthermore, we conducted artificial pollination in the female phase to evaluate the effect of changes in pollination environment on the variations in herkogamy traits. The results showed that gynophore straightened in female phase favors pollen deposition, whereas gynophore bending in male phase was conducive to the removal of pollen. Visitation frequency, pollen deposition and removal, and seed set ratio decreased significantly when the gynophore movement was manipulated. Finally, the bending of gynophore was obviously promoted by pollination. Therefore, the continuous variation of herkogamy in the same flower of E. fischeriana caused by the bending of the gynophore could improve the accuracy of pollination and avoid the interference of the ovary with access efficiency. That may be an adaptive strategy when pollinators are scarce. Furthermore, our study also provides good support for the hypothesis that variations in herkogamy traits are strongly selected by differences in pollination environments.

Strong bulk photovoltaic effect in engineered edge-embedded van der Waals structures.

Bulk photovoltaic effect (BPVE), a second-order nonlinear optical effect governed by the quantum geometric properties of materials, offers a promising approach to overcome the Shockley-Quiesser limit of traditional photovoltaic effect and further improve the efficiency of energy harvesting. Here, we propose an effective platform, the nano edges embedded in assembled van der Waals (vdW) homo- or hetero-structures with strong symmetry breaking, low dimensionality and abundant species, for BPVE investigations. The BPVE-induced photocurrents strongly depend on the orientation of edge-embedded structures and polarization of incident light. Reversed photocurrent polarity can be observed at left and right edge-embedded structures. Our work not only visualizes the unique optoelectronic effect in vdW nano edges, but also provides an effective strategy for achieving BPVE in engineered vdW structures.

An evolution from 3D face-centered-cubic ZnSnO3 nanocubes to 2D orthorhombic ZnSnO3 nanosheets with excellent gas sensing performance.

We have successfully observed the development of three-dimensional (3D) face-centered-cubic ZnSnO(3) into two-dimensional (2D) orthorhombic ZnSnO(3) nanosheets, which is the first observation of 2D ZnSnO(3) nanostructures to date. The synthesis from 3D to 2D nanostructures is realized by the dual-hydrolysis-assisted liquid precipitation reaction and subsequent hydrothermal treatment. The time-dependent morphology indicates the transformation via a 'dissolution-recrystallization' mechanism, accompanied by a 'further growth' process. Furthermore, the 2D ZnSnO(3) nanosheets consist of smaller sized nanoflakes. This further increases the special specific surface area and facilitates their application in gas sensing. The 2D ZnSnO(3) nanosheets exhibit excellent gas sensing properties, especially through their ultra-fast response and recovery. When exposed to ethanol and acetone, the response rate is as fast as 0.26 s and 0.18 s, respectively, and the concentration limit can reach as low as 50 ppb of ethanol. All these results are much better than those reported so far. Our experimental results indicate an efficient approach to realize high-performance gas sensors.

Giant Thermopower of Hydrogen Ion Enhanced by a Strong Hydrogen Bond System.

Ionic thermoelectric materials based on organic polymers are of great significance for low-grade heat harvesting and self-powered wearable temperature sensing. Here, we demonstrate a poly(vinyl alcohol) (PVA) hydrogel that relies on the differential transport of H+ in PVA hydrogels with different degrees of crystallization. After the inorganic acid is infiltrated into the physically cross-linked PVA hydrogel, the ionic conductor exhibits a huge ionic thermopower of 38.20 mV K-1, which is more than twice the highest value reported for hydrogen ion transport thermoelectric materials. We attribute the enhanced thermally generated voltage to the movement of H+ in the strong hydrogen bond system of PVA hydrogels and the restrictive effect of the strong hydrogen bond system on anions. This ionic thermoelectric hydrogel opens up a new way for thermoelectric conversion devices using H+ as an energy carrier.

Probing interlayer shear thermal deformation in atomically-thin van der Waals layered materials.

Atomically-thin van der Waals layered materials, with both high in-plane stiffness and bending flexibility, offer a unique platform for thermomechanical engineering. However, the lack of effective characterization techniques hinders the development of this research topic. Here, we develop a direct experimental method and effective theoretical model to study the mechanical, thermal, and interlayer properties of van der Waals materials. This is accomplished by using a carefully designed WSe2-based heterostructure, where monolayer WSe2 serves as an in-situ strain meter. Combining experimental results and theoretical modelling, we are able to resolve the shear deformation and interlayer shear thermal deformation of each individual layer quantitatively in van der Waals materials. Our approach also provides important interlayer coupling information as well as key thermal parameters. The model can be applied to van der Waals materials with different layer numbers and various boundary conditions for both thermally-induced and mechanically-induced deformations.