Dynamic multifunctional devices enabled by ultrathin metal nanocoatings with optical/photothermal and morphological versatility.

Inspired by the intriguing adaptivity of natural life, such as squids and flowers, we propose a series of dynamic and responsive multifunctional devices based on multiscale structural design, which contain metal nanocoating layers overlaid with other micro-/nanoscale soft or rigid layers. Since the optical/photothermal properties of a metal nanocoating are thickness dependent, metal nanocoatings with different thicknesses were chosen to integrate with other structural design elements to achieve dynamic multistimuli responses. The resultant devices demonstrate 1) strain-regulated cracked and/or wrinkled topography with tunable light-scattering properties, 2) moisture/photothermal-responsive structural color coupled with wrinkled surface, and 3) mechanically controllable light-shielding properties attributed to the strain-dependent crack width of the nanocoating. These devices can adapt external stimuli, such as mechanical strain, moisture, light, and/or heat, into corresponding changes of optical signals, such as transparency, reflectance, and/or coloration. Therefore, these devices can be applied as multistimuli-responsive encryption devices, smart windows, moisture/photothermal-responsive dynamic optics, and smartphone app-assisted pressure-mapping sensors. All the devices exhibit high reversibility and rapid responsiveness. Thus, this hybrid system containing ultrathin metal nanocoatings holds a unique design flexibility and adaptivity and is promising for developing next-generation multifunctional devices with widespread application.

Dynamic Room Temperature Phosphorescence of Silane-Functionalized Carbon Dots Confining within Silica for Anti-Counterfeiting Applications.

Room temperature phosphorescent (RTP) materials with long-lived, excitation-dependent, and time-dependent phosphorescence are highly desirable but very hard to achieve. Herein, this work reports a rational strategy of multiple wavelength excitation and time-dependent dynamic RTP color by confining silane-functionalized carbon dots (CDs) in a silica matrix (Si-CDs@SiO2). The Si-CDs@SiO2 possesses unique green-light-excitation and a change in phosphorescence color from yellow to green. A slow-decaying phosphorescence at 500 nm with a lifetime of 1.28 s and a fast-decaying phosphorescence at 580 nm with a lifetime of 0.90 s are observed under 365 nm of irradiation, which originated from multiple surface triplet states of the Si-CDs@SiO2. Given the unique dynamic RTP properties, the Si-CDs@SiO2 are demonstrated for applications in fingerprint recognition and multidimensional dynamic information encryption. These findings will open an avenue to explore dynamic phosphorescent materials and significantly broaden their applications.

Role of Impurities in Kaolinite Intercalation and Subsequent Formation of Nanoscrolls.

Kaolinite (Kaol)-methanol (MeOH) compounds (Kaol-Me) are widely used as the starting materials for further intercalation. The conventional approach to prepare Kaol-Me compounds is to wash dimethyl sulfoxide (DMSO)-intercalated Kaol (Kaol-DMSO) for 16 days, and MeOH must be refreshed every day. Herein, we report a new and much more efficient method to prepare Kaol-Me from Kaol-DMSO by the promotion of AlCl3 under mild conditions, and the corresponding mechanism is investigated. The X-ray diffraction (XRD), Fourier transform infrared spectroscopy, and X-ray fluorescence characterization results reveal that the electric double layer resulting from the impurities absorbed on the kaolinite surface prevents weakly polar molecules from entering the kaolinite interlayers, which is probably the key reason that MeOH must be refreshed daily in the preparation of Kaol-Me compounds. After being treated with HCl to remove the impurities, Kaol-Me-HCl was successfully intercalated by cetyltrimethyl ammonium bromide and subsequently predominantly curled into nanoscrolls.

Interlayer Anions of Layered Double Hydroxides as Mobile Active Sites To Improve the Adsorptive Performance toward Cd2.

Layered double hydroxides (LDHs) have been considered important sinks for ionic contaminants in nature and effectively engineered adsorbents for environmental remediation. The availability of interlayer active sites of LDHs is critical for their adsorptive ability. However, inorganic LDHs generally have a nano-confined interlayer space of ca. 0.3-0.5 nm, and it is unclear how LDHs can utilize their interlayer active sites during the adsorption process. Thus, LDHs intercalated with SO42-, PO43-, NO3-, Cl-, or CO32- were taken as examples to reveal this unsolved problem during Cd2+ adsorption. New adsorption behaviors and pronounced differences in adsorption performance were observed. Specifically, SO42-/PO43- intercalated LDHs showed a maximum Cd2+ adsorption capacity of 19.2/9.8 times higher than other LDHs. The ligand exchange of H+ (on the surface -OH) by Cd2+ and formation of Cd-SO42-/PO43- complexes led to the efficient removal of Cd2+. Interestingly, interlayer SO42- was demonstrated to be able to move to the edges/outer surfaces of LDHs, providing abundant movable adsorption sites for Cd2+. This novel phenomenon made the SO42- intercalated LDH a superior adsorbent for Cd2+ among the tested LDHs, which also suggests that LDHs with a nano-confined interlayer space can also highly utilize their interlayer active sites based on the mobility of interlayer anions, offering a new method for constructing superior LDH adsorbents.

Tailoring the Growth of Nanosized α-Zirconium Phosphate.

Nanosized α-zirconium phosphate (α-ZrP), unlike microcrystalline α-ZrP, takes less time to prepare and is synthesized directly in organic solvents. During the synthesis of nanosized α-ZrP, the heating step is critical because during which the particle growth/aggregation is ongoing. In order to explore more details of this step, extra water molecules were intentionally introduced to the ethanol gel of nanosized α-ZrP so that the evaporation of the solvent was slowed. To heat the gels at 65 °C for different periods (1-6 days), one could control with ease the synthesized α-ZrP in size, from 63 to 155 nm, and in morphology, from amorphous to highly crystalline. Furthermore, the heating step also affects the intercalated solvent and the dangling propionate groups on the edge of the nanosized α-ZrP, which could be deduced from the intercalation/exfoliation behavior of the nanocrystals. This modified synthesis method of nanosized α-ZrP offers an alternate means to tune the size and morphology of the nanosized α-ZrP for broad applications.

Kinetics-Favorable Ultrathin NiCo-MOF Nanosheets with Boosted Pseudocapacitive Charge Storage for Quasi-Solid-State Hybrid Supercapacitors.

Bimetallic metal-organic frameworks (MOFs) with an ultrathin configuration are compelling materials for developing high-performance energy storage devices on account of their unique structural merits. Herein, a hydrangea-like NiCo-MOF is well prepared using controllable solvothermal and cation-exchange processes, synchronously achieving bimetallic nodes and hierarchical ultrathin architecture. The structural superiority enables NiCo-MOF of expanded electrons' transfer pathways and multitudinous electrolytes' diffusion channels, resulting in a significant enhancement in pseudocapacitive performance. Coupling with the bimetallic nature and constructional advantages, NiCo-MOF shows superior gravimetric capacity (832.6 C g-1 at 1 A g-1) and electrochemical kinetics to those of monometallic Ni-MOF and Co-MOF. Importantly, the quasi-solid-state hybrid supercapacitor (HSC) based on the NiCo-MOF cathode and active carbon (AC) anode delivers a desirable energy density (45.3 Wh kg-1 at 847.8 W kg-1), a favorable power density (7160.0 W kg-1 at 23.3 Wh kg-1), a remarkable cyclability (82.4% capacity retention over 7000 cycles), and a capability of driving miniature electronics, exhibiting its potential in practical applications. This work presents an efficient design strategy to develop kinetics-favorable MOF materials for energy storage.

Super Stretchable and Compressible Hydrogels Inspired by Hook-and-Loop Fasteners.

Inspired by hook-and-loop fasteners, we designed a hydrogel network containing α-zirconium phosphate (ZrP) two-dimensional nanosheets with a high density of surface hydroxyl groups serving as nanopatches with numerous "hooks," while polymer chains with plentiful amine functional groups serve as "loops." Our multiscale molecular simulations confirm that both the high density of hydroxyl groups on nanosheets and the large number of amine functional groups on polymer chains are essential to achieve reversible interactions at the molecular scale, functioning as nano hook-and-loop fasteners to dissipate energy. As a result, the synthesized hydrogel possesses superior stretchability (>2100% strain), resilience to compression (>90% strain), and durability. Remarkably, the hydrogel can sustain >5000 cycles of compression with torsion in a solution mimicking synovial fluid, thus promising for potential biomedical applications such as artificial articular cartilage. This hook-and-loop model can be adopted and generalized to design a wide range of multifunctional materials with exceptional mechanical properties.

Exfoliation of Nanosized α-Zirconium Phosphate in Methanol.

The exfoliation of microcrystalline α-zirconium phosphate (α-ZrP) in an organic solvent is very difficult to achieve. Surprisingly, the addition of tetra(n-butyl)ammonium hydroxide (TBAOH) into a methanol dispersion of a nanosized α-ZrP brings about the complete exfoliation of nanosheets. To understand the mechanism, we examined the stepwise intercalation/exfoliation of the nanosized α-ZrP using TBAOH in four different solvents (water, methanol, ethanol, and butanol). Propionate groups on the edge of the nanosized α-ZrP prevent TBA cations from entering the galleries. Due to the formation of unstable solvent-intercalated α-ZrP with an increased interlayer distance in methanol and ethanol, TBA cations can overcome the steric hindrance and move into nanosheet layers to exchange with solvent molecules. However, the movability of the cations into the center of the galleries is preferred at a certain interlayer distance range, which leads to exfoliation of α-ZrP in methanol but intercalation only in ethanol. In water, in the beginning, neither intercalation nor exfoliation by TBA cations occurs. An additional amount of TBAOH causes the deformation of propionate groups and removes the barriers on the edges, followed by late intercalation and then exfoliation. On the other hand, butanol, as the solvent, is bulky and effectively limits the intercalation behavior of TBA cations. The weaker polarity of ethanol and butanol, compared with water and methanol, lowers the ion interactions in the solvent, which is another reason why they do not lead to exfoliation.

Transparency Change Mechanochromism Based on a Robust PDMS-Hydrogel Bilayer Structure.

Hydrogels and polydimethylsiloxane (PDMS) are complementary to each other, since the hydrophobic PDMS provides a more stable and rigid substrate, while the water-rich hydrogel possesses remarkable hydrophilicity, biocompatibility, and similarity to biological tissues. Herein a transparent and stretchable covalently bonded PDMS-hydrogel bilayer (PHB) structure is prepared via in situ free radical copolymerization of acrylamide and allylamine-exfoliated-ZrP (AA-e-ZrP) on a functionalized PDMS surface. The AA-e-ZrP serves as cross-linking nano-patches in the polymer gel network. The covalently bonded structure is constructed through the addition reaction of vinyl groups of PDMS surface and monomers, obtaining a strong interfacial adhesion between the PDMS and the hydrogel. A mechanical-responsive wrinkle surface, which exhibs transparency change mechanochromism, is created via introducing a cross-linked polyvinyl alcohol film atop the PHB structure. A finite element model is implemented to simulate the wrinkle formation process. The implication of the present finding for the interfacial design of the PHB and PDMS-hydrogel-PVA trilayer (PHPT) structures is discussed.

Prediction of posttraumatic stress disorder by acute stress disorder in traffic accident survivors.

BACKGROUND: To investigate the predictive effect of different symptoms of early acute stress disorder (ASD) on posttraumatic stress disorder (PTSD) in traffic accident survivors. METHODS: A total of 206 traffic accident survivors were assessed with the acute stress disorder scale (ASDS) within 2-23 days after accidents, as well as with 17-item PTSD checklist-specific stressor version (PCL-S) during 4-12 months after accidents. All into the first group of subjects by senior surgeon assessment, based on the clinical, radiological and laboratory examination, excluded traumatic brain injuries, and mild brain injury. And then, assessment by clinical psychological practitioner. RESULTS: The severity of ASD can significantly predict the severity of PTSD symptoms. ASD reexperience symptoms and avoidance symptoms can significantly predict PTSD reexperience symptoms and avoidance symptoms. ASD hyperarousal symptoms can significantly predict PTSD hyperarousal symptoms. DISCUSSION: ASD and PTSD are common psychological disorders among traffic accident survivors. ASD can predict the symptoms and severity of PTSD.

Complexing Agent Directed Growth of α-Zirconium Phosphate-Based Hexagonal Prisms.

A layered prism is an ideal system for fundamental studies due to its unique structure with uniform-sized sheets. However, there are very limited reports in the last few decades on the preparation of such materials. In this contribution, we report for the first time the preparation of α-ZrP intercalation compound-based hexagonal prisms. Preferential crystal growth perpendicular to the (001) crystal plane of α-ZrP intercalation compounds was achieved by incorporating a complexing agent and a layer growth coordinator into a crystal growth reaction system. With the presence of a layer growth coordinator to coordinate the crystal growth perpendicular to the (001) crystal plane and the presence of a complexing agent to slow down the crystal growth rate, the previously unknown layer growth coordination effect is revealed. After a facile ion exchange treatment, pure α-ZrP hexagonal prisms can also be obtained.

Exfoliation of α-Zirconium Phosphate Using Tetraalkylammonium Hydroxides.

α-Zirconium phosphate (α-ZrP), a classical layered compound, has found widespread application. Exfoliation of α-ZrP has been mainly achieved by propylamine (PA) or tetrabutylammonium hydroxide (TBAOH), but the exact mechanism of exfoliation has not been completely elucidated. We examined the feasibility of exfoliation utilizing tetraalkylammonium hydroxide (TXAOH) and investigated the stepwise intercalation/exfoliation mechanism of α-ZrP. All of the TXAOHs examined (carbon number of the branches: 1-4) were able to exfoliate α-ZrP in an aqueous dispersion under ultrasonication. Furthermore, exfoliation of α-ZrP by two different exfoliators (either a mixture of two or sequentially) was also investigated to pinpoint the exfoliation mechanism. Our results indicate that small TXA cations are kinetically preferred to diffuse into the galleries of α-ZrP, while large TXA cations can help open up the galleries and facilitate transport of the already intercalated cations. These findings should help fellow researchers to choose the most suitable exfoliators for their own projects and develop better intercalation/exfoliation systems.

High-Resolution U-Net: Preserving Image Details for Cultivated Land Extraction.

Accurate and efficient extraction of cultivated land data is of great significance for agricultural resource monitoring and national food security. Deep-learning-based classification of remote-sensing images overcomes the two difficulties of traditional learning methods (e.g., support vector machine (SVM), K-nearest neighbors (KNN), and random forest (RF)) when extracting the cultivated land: (1) the limited performance when extracting the same land-cover type with the high intra-class spectral variation, such as cultivated land with both vegetation and non-vegetation cover, and (2) the limited generalization ability for handling a large dataset to apply the model to different locations. However, the "pooling" process in most deep convolutional networks, which attempts to enlarge the sensing field of the kernel by involving the upscale process, leads to significant detail loss in the output, including the edges, gradients, and image texture details. To solve this problem, in this study we proposed a new end-to-end extraction algorithm, a high-resolution U-Net (HRU-Net), to preserve the image details by improving the skip connection structure and the loss function of the original U-Net. The proposed HRU-Net was tested in Xinjiang Province, China to extract the cultivated land from Landsat Thematic Mapper (TM) images. The result showed that the HRU-Net achieved better performance (Acc: 92.81%; kappa: 0.81; F1-score: 0.90) than the U-Net++ (Acc: 91.74%; kappa: 0.79; F1-score: 0.89), the original U-Net (Acc: 89.83%; kappa: 0.74; F1-score: 0.86), and the Random Forest model (Acc: 76.13%; kappa: 0.48; F1-score: 0.69). The robustness of the proposed model for the intra-class spectral variation and the accuracy of the edge details were also compared, and this showed that the HRU-Net obtained more accurate edge details and had less influence from the intra-class spectral variation. The model proposed in this study can be further applied to other land cover types that have more spectral diversity and require more details of extraction.

CO2 Nanoenrichment and Nanoconfinement in Cage of Imine Covalent Organic Frameworks for High-Performance CO2 Cathodes in Li-CO2 Batteries.

The Li-CO2 battery is an emerging green energy technology coupling CO2 capture and conversion. The main drawback of present Li-CO2 batteries is serious polarization and poor cycling caused by random deposition of lithium ions and big insulated Li2 CO3 formation on the cathode during discharge. Herein, covalent organic frameworks (COF) are identified as the porous catalyst in the cathode of Li-CO2 batteries for the first time. Graphene@COF is fabricated, graphene with thin and uniform imine COF loading, to enrich and confine CO2 in the nanospaces of micropores. The discharge voltage is raised by higher local CO2 concentration, which is predicted by the Nernst equation and realized by CO2 nanoenrichment. Moreover, uniform lithium ion deposition directed by the graphene@COF nanoconfined CO2 can produce smaller Li2 CO3 particles, leading to easier Li2 CO3 decomposition and thus lower charge voltage. The graphene@COF cathode with 47.5% carbon content achieves a discharge capacity of 27833 mAh g-1 at 75 mA g-1 , while retaining a low charge potential of 3.5 V at 0.5 A g-1 for 56 cycles.

Preparation of two dimensional layered double hydroxide nanosheets and their applications.

Layered double hydroxides (LDHs) with their highly flexible and tunable chemical composition and physical properties have attracted tremendous attention in recent years. LDHs have found widespread application as catalysts, anion exchange materials, fire retardants, and nano-fillers in polymer nanocomposites. The ability to exfoliate LDHs into ultrathin nanosheets enables a range of new opportunities for multifunctional materials. In this review we summarize the current available LDH exfoliation methods. In particular, we highlight recent developments for the direct synthesis of single-layer LDH nanosheets, as well as the emerging applications of LDH nanosheets in catalyzing oxygen evolution reactions and preparing light emitting devices, supercapacitors, and flame retardant nanocomposites.

Study on Thermal Decomposition Behaviors of Terpolymers of Carbon Dioxide, Propylene Oxide, and Cyclohexene Oxide.

The terpolymerization of carbon dioxide (CO2), propylene oxide (PO), and cyclohexene oxide (CHO) were performed by both random polymerization and block polymerization to synthesize the random poly (propylene cyclohexene carbonate) (PPCHC), di-block polymers of poly (propylene carbonate⁻cyclohexyl carbonate) (PPC-PCHC), and tri-block polymers of poly (cyclohexyl carbonate⁻propylene carbonate⁻cyclohexyl carbonate) (PCHC-PPC-PCHC). The kinetics of the thermal degradation of the terpolymers was investigated by the multiple heating rate method (Kissinger-Akahira-Sunose (KAS) method), the single heating rate method (Coats-Redfern method), and the Isoconversional kinetic analysis method proposed by Vyazovkin with the data from thermogravimetric analysis under dynamic conditions. The values of ln k vs. T-1 for the thermal decomposition of four polymers demonstrate the thermal stability of PPC and PPC-PCHC are poorer than PPCHC and PCHC-PPC-PCHC. In addition, for PPCHC and PCHC-PPC-PCHC, there is an intersection between the two rate constant lines, which means that, for thermal stability of PPCHC, it is more stable than PCHC-PPC-PCHC at the temperature less than 309 °C and less stable when the decomposed temperature is more than 309 °C. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analysis/infrared spectrometry (TG/FTIR) techniques were applied to investigate the thermal degradation behavior of the polymers. The results showed that unzipping was the main degradation mechanism of all polymers so the final pyrolysates were cyclic propylene carbonate and cyclic cyclohexene carbonate. For the block copolymers, the main chain scission reaction first occurs at PC-PC linkages initiating an unzipping reaction of PPC chain and then, at CHC⁻CHC linkages, initiating an unzipping reaction of the PCHC chain. That is why the T-5% of di-block and tri-block polymers were not much higher than that of PPC while two maximum decomposition temperatures were observed for both the block copolymer and the second one were much higher than that of PPC. For PPCHC, the random arranged bulky cyclohexane groups in the polymer chain can effectively suppress the backbiting process and retard the unzipping reaction. Thus, it exhibited much higher T-5% than that of PPC and block copolymers.

Versatile Nanostructures from Rice Husk Biomass for Energy Applications.

Converting biomass into valuable products has great benefits in terms of both economic and environmental considerations, and has attracted considerable attention in recent years. Rice husk biomass was initially utilized to produce bulk materials for conventional applications while a variety of advanced nanostructures (NSs) have been fabricated over the past few years. In addition to their low cost and environmental friendliness, RH-derived NSs (RH-NSs) exhibit versatile properties, which are promising for broad applications in various fields. In this Review, we summarize the latest research on RH-NSs, covering their design, fabrication, properties, and applications in the modern energy field. Based on the unique structure and components of RHs, a series of carbon/silicon-based novel NSs with outstanding performances have been exploited, which are difficult to be synthesized using conventional chemical reagents. We also discuss perspective uses of RH-NSs on the basis of the current research progress.

Synthesis of Layered Double Hydroxide Single-Layer Nanosheets in Formamide.

Layered double hydroxide (LDH) single-layer nanosheets were synthesized through a single-step process in the presence of formamide. This one-step process is simple, fast, and efficient and thus is potentially viable for large-scale production. Two key factors for the growth of LDH single-layer nanosheets, formamide concentration and LDH layer charge, were investigated thoroughly. A higher formamide concentration and a higher LDH layer charge are favorable for the growth of LDH single-layer nanosheets. The LDH single-layer nanosheets obtained at the premium formamide concentration and LDH layer charge were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and atomic force micrscopy (AFM). Poly(vinyl alcohol) (PVA)/LDH nanocomposite coatings were also prepared. The coated polyethylene terephthalate (PET) and poly(lactic acid) (PLA) films exhibited significantly improved oxygen gas barrier properties thanks to the well-dispersed and -aligned LDH single-layer nanosheets in the coating.

Hexagon wreaths: self-assembly of discrete supramolecular fractal architectures using multitopic terpyridine ligands.

In this study, we overcame a challenge in conventional self-assembly of macrocycles that uses ditopic 2,2':6',2″-terpyridine (tpy) building blocks with a 120° angle between two ligating moieties, which generally produces a mixture of multiple macrocycles instead of a single hexagon. Two supramolecular hexagon wreaths, [Zn9LA6] and [Zn12LB6], were designed and self-assembled from tritopic and tetratopic tpy ligands with Zn(II) ions, respectively. These multitopic ligands, bearing multiple binding sites, increased the total density of coordination sites and provided high geometric constraints to induce the formation of discrete structures. Such hexagon wreaths, which were constructed by simple recursion of small hexagons around a central hexagon, exhibit fractal geometry features with self-similarity at different levels. The shapes, sizes, and structures were fully characterized by NMR, ESI-MS, traveling-wave ion mobility mass spectrometry (TWIM-MS), and transmission electron microscopy. With diameters around 5.5 nm for [Zn9LA6] and 5.8 nm for [Zn12LB6], the remarkable rigidity of these fractal architectures was supported by TWIM-MS, in contrast to the high flexibility of macrocycles assembled by ditopic tpy ligands.

Privacy Barriers in Health Monitoring: Scoping Review.

BACKGROUND: Health monitoring technologies help patients and older adults live better and stay longer in their own homes. However, there are many factors influencing their adoption of these technologies. Privacy is one of them. OBJECTIVE: The aim of this study was to provide an overview of the privacy barriers in health monitoring from current research, analyze the factors that influence patients to adopt assisted living technologies, provide a social psychological explanation, and propose suggestions for mitigating these barriers in future research. METHODS: A scoping review was conducted, and web-based literature databases were searched for published studies to explore the available research on privacy barriers in a health monitoring environment. RESULTS: In total, 65 articles met the inclusion criteria and were selected and analyzed. Contradictory findings and results were found in some of the included articles. We analyzed the contradictory findings and provided possible explanations for current barriers, such as demographic differences, information asymmetry, researchers' conceptual confusion, inducible experiment design and its psychological impacts on participants, researchers' confirmation bias, and a lack of distinction among different user roles. We found that few exploratory studies have been conducted so far to collect privacy-related legal norms in a health monitoring environment. Four research questions related to privacy barriers were raised, and an attempt was made to provide answers. CONCLUSIONS: This review highlights the problems of some research, summarizes patients' privacy concerns and legal concerns from the studies conducted, and lists the factors that should be considered when gathering and analyzing people's privacy attitudes.