Highly Sensitive Membrane-Based Pressure Sensors (MePS) for Real-Time Monitoring of Catalytic Reactions.

Functional, flexible, and integrated lab-on-chips, based on elastic membranes, are capable of fine response to external stimuli, so to pave the way for many applications as multiplexed sensors for a wide range of chemical, physical and biomedical processes. Here, we report on the use of elastic thin membranes (TMs), integrated with a reaction chamber, to fabricate a membrane-based pressure sensor (MePS) for reaction monitoring. In particular, the TM becomes the key-element in the design of a highly sensitive MePS capable to monitor gaseous species production in dynamic and temporally fast processes with high resolution and reproducibility. Indeed, we demonstrate the use of a functional MePS integrating a 2 µm thick polydimethylsiloxane TM by monitoring the dioxygen evolution resulting from catalytic hydrogen peroxide dismutation. The operation of the membrane, explained using a diffusion-dominated model, is demonstrated on two similar catalytic systems with catalase-like activity, assembled into polyelectrolyte multilayers capsules. The MePS, tested in a range between 2 and 50 Pa, allows detecting a dioxygen variation of the µmol L-1 s-1 order. Due to their structural features, flexibility of integration, and biocompatibility, the MePSs are amenable of future development within advanced lab-on-chips.

Catalytic self-propulsion of supramolecular capsules powered by polyoxometalate cargos.

Multicompartment, spherical microcontainers were engineered through a layer-by-layer polyelectrolyte deposition around a fluorescent core while integrating a ruthenium polyoxometalate (Ru4POM), as molecular motor, vis-à-vis its oxygenic, propeller effect, fuelled upon H2O2 decomposition. The resulting chemomechanical system, with average speeds of up to 25 µm s(-1), is amenable for integration into a microfluidic set-up for mixing and displacement of liquids, whereby the propulsion force and the resulting velocity regime can be modulated upon H2O2-controlled addition.

Ligand tuning of single-site manganese-based catalytic antioxidants with dual superoxide dismutase and catalase activity.

A bio-inspired manganese(ii) complex with a linear pentadentate ligand framework containing soft sulfur donors and an alternating NSNSN binding motif displays excellent dual CAT/SOD-like antioxidant activity with high turnover efficiency and good operation stability in an aqueous environment.

A Lewis acid catalytic core sandwiched by inorganic polyoxoanion caps: selective H2O2-based oxidations with [Al(III)4(H2O)10(ß-XW9O33H)2](6-) (X = As(III), Sb(III)).

The Al(III)-containing polyanions [Al(III)4(H2O)10(ß-XW9O33H)2](4-) with X = As(III) (1) and Sb(III) (2) feature four aluminum(III) centers sandwiched by two trivacant (ß-XW9O33) Keggin units, and trigger peroxide catalysis as well as substrate coordination via multiple Lewis acid site interactions.

Reactive Zr(IV) and Hf(IV) butterfly peroxides on polyoxometalate surfaces: bridging the gap between homogeneous and heterogeneous catalysis.

At variance with previously known coordination compounds, the polyoxometalate (POM)-embedded Zr(IV) and Hf(IV) peroxides with formula: [M(2)(O(2))(2)(α-XW(11)O(39))(2)](12-) (M=Zr(IV), X=Si (1), Ge (2); M=Hf(IV), X=Si (3)) and [M(6)(O(2))(6)(OH)(6)(γ-SiW(10)O(36))(3)](18-) (M=Zr(IV) (4) or Hf(IV) (5)) are capable of oxygen transfer to suitable acceptors including sulfides and sulfoxides in water. Combined (1)H NMR and electrochemical studies allow monitoring of the reaction under both stoichiometric and catalytic conditions. The reactivity of peroxo-POMs 1-5 is compared on the basis of substrate conversion and kinetic. The results show that the reactivity of POMs 1-3 outperforms that of the trimeric derivatives 4 and 5 by two orders of magnitude. Reversible peroxidation of 1-3 occurs by H(2)O(2) addition to the spent catalysts, restoring oxidation rates and performance of the pristine system. The stability of 1-3 under catalytic regime has been confirmed by FT-IR, UV/Vis, and resonance Raman spectroscopy. The reaction scope has been extended to alcohols, leading to the corresponding carbonyl compounds with yields up to 99% under microwave (MW) irradiation. DFT calculations revealed that polyanions 1-3 have high-energy peroxo HOMOs, and a remarkable electron density localized on the peroxo sites as indicated by the calculated map of the electrostatic potential (MEP). This evidence suggests that the overall description of the oxygen-transfer mechanism should include possible protonation equilibria in water, favored for peroxo-POMs 1-3.