A pseudo-Double-Network Hydrogel Built upon Layered Double Hydroxides with Self-Strengthening Properties.

While great achievements have been made in the development of mechanically robust nanocomposite hydrogels, incorporating multiple interactions on the bases of two demensional inorganic cross-linkers to construct self-strengthening hydrogels has rarely been investigated. To this end, we propose here a new method for the coupling the dynamic covalent bonds and non-covalent interactions within a pseudo double-network system. The pseudo first network, formed through the Schiff Base reation between Tris-modified layered double hydroxides (Tris-LDHs) and oxidized dextran (ODex), is linked to the second network built upon non-covalent interactions between Tris-LDHs and poly(acrylamide-co-2-acrylamido-2-methyl-propanesulfonate) (p-(AM-co-AMPS). The swelling and mechanical properties of the resulting hydrogels have been investigated as a function of the ODex and AMPS contents. The as-prepared hydrogel can swell to 420 times of its original size and retain more than 99.9 wt.% of water. Mechanical tests show that the hydrogel can bear 90 % of compression and is able to be stretched to near 30 times of its original length. Cyclic tensile tests reveal that the hydrogels are capable of self-strengthening after mechanical training. The unique energy dissipation mechanism based on the dynamic covalent and non-covalent interactions is considered to be responsible for the outstanding swelling and mechanical performances.

Polyoxometalate-Surfactant Assemblies: Responsiveness to Orthogonal Stimuli.

Integrating different types of supramolecular interactions opens the possibility to generate nanoparticle surfactants (NPSs) at the liquid-liquid interface that are responsive to multiple stimuli. Here we develop a covalently modified polyoxometalate/ß-cyclodextrin (POM/ß-CD) organic-inorganic hybrid, consisting of a negatively charged POM cluster with ß-CD host groups. The POM/ß-CD hybrid can be dispersed in water and interacts at a water/oil interface with ligands dissolved in an oil phase through electrostatic or host-guest interactions, thereby generating POM-surfactants (POMSs) having pH, redox, and guest-competitive responsiveness, respectively. By taking advantage of the jamming of POMSs at the interface, a reconfigurable all-liquid system could be produced that is responsive to orthogonal changes in the external environment.

Elucidating the paramagnetic interactions of an inorganic-organic hybrid radical-functionalized Mn-Anderson cluster.

A family of six polyoxometalate-based magnetic compounds were synthesized by anchoring N-oxide type TEMPO radicals onto an Anderson type polyoxometalate cluster. The complexes were structurally characterised by single crystal X-ray diffraction and the intramolecular paramagnetic interactions between TEMPO radicals and Mn ions of the resulting hybrids were investigated in detail by electron paramagnetic resonance and the Evans NMR method.

Structural Phase Transitions of a Molecular Metal Oxide.

The structural phase of a metal oxide changes with temperature and pressure. During phase transitions, component ions move in multidimensional metal-oxygen networks. Such macroscopic structural events are robust to changes in particle size, even at scales of around 10 nm, and size effects limiting these transitions are particularly important in, for example, high-density memory applications of ferroelectrics. In this study, we examined structural transitions of the molecular metal oxide [Na@(SO3 )2 (n-BuPO3 )4 MoV 4 MoVI 14 O49 ]5- (Molecule 1) at approximately 2 nm by using single-crystal X-ray diffraction analysis. The Na+ encapsulated in the discrete metal-oxide anion exhibited a reversible order-disorder transition with distortion of the Mo-O molecular framework induced by temperature. Similar order-disorder transitions were also triggered by chemical pressure induced by removing crystalline solvent molecules in the single-crystal state or by substituting the countercation to change the molecular packing.

Integrated Synthesis of Gold Nanoparticles Coated with Polyoxometalate Clusters.

Polyoxometalates (POMs) have been found to be good end-capping ligands for gold nanoparticles (AuNPs). Herein, we introduce a new synthetic method to synthesize gold nanoparticle-POM hybrids by heating a solution of AuNO3(PMe3) in acetonitrile in the presence of appropriate POM species with tetrabutylammonium (TBA) as a countercation at 120 °C in a microwave. This method allowed us to produce POM-capped AuNPs without over-reduction of the solution causing decomposition or reorganization of the POMs. Analysis of the resulting material by transmission electron microscopy showed that the POM's size, charge, and functionality are key factors controlling the resulting POM-AuNP hybrid structure. Additionally, the reaction was monitored by electrospray ionization mass spectrometry (ESI-MS), ultraviolet-visible spectroscopy, and dynamic light scattering. The ESI-MS studies reveal crucial information regarding the nature of the reaction that takes place, showing the cation exchange between Au(I) and TBA cations, followed by self-reduction of the Me3PAu(I)-POM complex.

A multi-species comparison of selective placement patterns of ramets in invasive alien and native clonal plants to light, soil nutrient and water heterogeneity.

A worth noticing pattern in current invasive biology is the clonal ability of many of the world's worst invasive plants. Selective placement of ramets (i.e. foraging behavior) can intensify ramet performance and allocation, and place more ramets in the more favorable microhabitats, which can maximum utilize resource and share risk in heterogeneous environments. Still little is known about whether invasive alien and native clonal plants differ in the selective placement patterns of ramets in invasive clonal plants or not. We used five congeneric pairs of naturally co-occurring invasive alien and native clonal plant species in China. In a glasshouse, we grew all species in pots under a homogeneous and three heterogeneous conditions (i.e. light, soil nutrients or water) subjected to resource-high or -low patches. All biomass parameters and number of ramets significantly increased in resource-high patches in all three types of heterogeneous environments. Interestingly, growth of invasive alien plants benefited significantly more from resource-high patches than native plants in all heterogeneous environments. Overall, invasive had higher biomass parameters per ramet than natives. Ramet parameters of invasive plants also benefited more from resource-low patches than natives. Three different selective placement patterns of ramets in resource-low patches were exhibited in invasive plants: ramet increasing shoot investment (above pattern), increasing root investment (below pattern) and increasing both investments (complete pattern) in the light, soil water and nutrient heterogeneity, respectively. Investment on less, larger ramet was the adaptive strategy of invasive plants in resource-poor patches. The results suggest that adaptively selective placement patterns of ramets promote a higher morphology plasticity and performance in invasive clonal plants over natives. When alien clonal plants spread new areas with light, soil nutrients or water heterogeneity, selective placement patterns of ramets might play an important role in plant performance and competitive superior by capitalizing more on additional resources.

Synthesis, structural characterization and fluorescence enhancement of chromophore-modified polyoxometalates.

Intramolecular charge transfers between π-conjugated molecules and polyoxometalate (POM) clusters have been observed in donor-acceptor systems based on organic donors and inorganic POM acceptors, which unfortunately results in a general quenching of the chromophore luminescence. The development of POM-chromophore dyads that are capable of tackling the quenching process and enhancing the fluorescence intensity of such systems remains a highly challenging area of study. A family of organic-inorganic polyoxometalate hybrids, {[(n-C4H9)4N]3[(MnMo6O24){(CH2)3CR}2]} [1, R = -NHCH2C14H9, namely (anthracen-9-ylmethyl)amino; 2, R = -NHCH2C13H9, (9H-fluoren-2-ylmethyl)amino; 3, R = -NHCH2C10H7, (naphthalen-2-ylmethyl)amino; 4, R = -NHCH2C16H9, (pyren-2-ylmethyl)amino], were synthesized by covalently tethering π-conjugated molecules onto an Anderson cluster. The resulting POM-chromophore dyads were fully characterized by various spectroscopic techniques, single-crystal X-ray diffraction analysis and ESI-MS. The fluorescence features of these dyads were studied in detail to verify a dramatic emission enhancement that can be achieved by fine-tuning the microenvironment in solution and suppressing the intrinsic photo-induced electron-transfer process.

Digital Control of Multistep Hydrothermal Synthesis by Using 3D Printed Reactionware for the Synthesis of Metal-Organic Frameworks.

Hydrothermal-synthesis-based reactions are normally single step owing to the difficulty of manipulating reaction mixtures at high temperatures and pressures. Herein we demonstrate a simple, cheap, and modular approach to the design reactors consisting of partitioned chambers, to achieve multi-step synthesis under hydrothermal conditions, in digitally defined reactionware produced by 3D printing. This approach increases the number of steps that can be performed sequentially and allows an increase in the options available for the control of hydrothermal reactions. The synthetic outcomes of the multi-stage reactions can be explored by varying reaction compositions, number of reagents, reaction steps, and reaction times, and these can be tagged to the digital blueprint. To demonstrate the potential of this approach a series of polyoxometalate (POM)-containing metal-organic frameworks (MOFs) unavailable by "one-pot" methods were prepared as well as a set of new MOFs.

3D printing of versatile reactionware for chemical synthesis.

In recent decades, 3D printing (also known as additive manufacturing) techniques have moved beyond their traditional applications in the fields of industrial manufacturing and prototyping to increasingly find roles in scientific research contexts, such as synthetic chemistry. We present a general approach for the production of bespoke chemical reactors, termed reactionware, using two different approaches to extrusion-based 3D printing. This protocol describes the printing of an inert polypropylene (PP) architecture with the concurrent printing of soft material catalyst composites, using two different 3D printer setups. The steps of the PROCEDURE describe the design and preparation of a 3D digital model of the desired reactionware device and the preparation of this model for use with fused deposition modeling (FDM) type 3D printers. The protocol then further describes the preparation of composite catalyst-silicone materials for incorporation into the 3D-printed device and the steps required to fabricate a reactionware device. This combined approach allows versatility in the design and use of reactionware based on the specific needs of the experimental user. To illustrate this, we present a detailed procedure for the production of one such reactionware device that will result in the production of a sealed reactor capable of effecting a multistep organic synthesis. Depending on the design time of the 3D model, and including time for curing and drying of materials, this procedure can be completed in ∼3 d.

Step-by-step covalent modification of Cr-templated Anderson-type polyoxometalates.

A series of tripodal alcohols substituted Anderson-type polyoxometalates (POMs) including mono-substituted (compounds and ), asymmetrical bi-substituted (compound ), and symmetrical bi-substituted ones (compounds and ) have been synthesized under hydrothermal conditions using a pre-designed step-by-step strategy, and compounds , and have been fully characterized by single-crystal X-ray diffraction, ESI-MS, and elemental analysis.