Bacterial Nanocellulose/MoS2 Hybrid Aerogels as Bifunctional Adsorbent/Photocatalyst Membranes for in-Flow Water Decontamination.

To address the problems associated with the use of unsupported nanomaterials, in general, and molybdenum disulfide (MoS2), in particular, we report the preparation of self-supported hybrid aerogel membranes that combine the mechanical stability and excellent textural properties of bacterial nanocellulose (BC)-based organic macro/mesoporous scaffolds with the excellent adsorption-cum-photocatalytic properties and high contaminant removal performance of MoS2 nanostructures. A controlled hydrothermal growth and precise tuning of the synthetic parameters allowed us to obtain BC/MoS2-based porous, self-supported, and stable hybrid aerogels with a unique morphology resulting from a molecular precision in the coating of quantum-confined photocatalytic MoS2 nanostructures (2-4 nm crystallite size) on BC nanofibrils. These BC/MoS2 samples exhibit high surface area (97-137 m2·g-1) and pore volume (0.28-0.36 cm3·g-1) and controlled interlayer distances (0.62-1.05 nm) in the MoS2 nanostructures. Modification of BC with nanostructured MoS2 led to an enhanced pollutants removal efficiency of the hybrid aerogels both by adsorptive and photocatalytic mechanisms, as indicated by a detailed study using a specifically designed membrane photoreactor containing the developed photoactive/adsorptive BC/MoS2 hybrid membranes. Most importantly, the prepared BC/MoS2 aerogel membranes showed high performance in the photoassisted in-flow removal of both organic dye (methylene blue (MB)) molecules (96% removal within 120 min, Kobs = 0.0267 min-1) and heavy metal ions (88% Cr(VI) removal within 120 min, Kobs = 0.0012 min-1), separately and/or simultaneously, under UV-visible light illumination as well as excellent recyclability and photostability. Samples with interlayer expanded MoS2 nanostructures were particularly more efficient in the removal of smaller species (CrO42-) as compared to larger (MB) dye molecules. The prepared hybrid aerogel membranes show promising behavior for application in in-flow water purification, representing a significant advancement in the use of self-supported aerogel membranes for photocatalytic applications in liquid media.

Microbial nanocellulose adherent to human skin used in electrochemical sensors to detect metal ions and biomarkers in sweat.

The pursuit of biocompatible, breathable and skin-conformable wearable sensors has predominantly focused on synthetic stretchable hydrophobic polymers. Microbial nanocellulose (MNC) is an exceptional skin-substitute natural polymer routinely used for wound dressing and offers unprecedented potential as substrate for wearable sensors. A versatile strategy for engineering wearable sensing platforms is reported, with sensing units made of screen-printed carbon electrodes (SPCEs) on MNC. As-prepared SPCEs were used to detect the toxic metals cadmium (Cd2+) and lead (Pb2+) with limits of detection of 1.01 and 0.43 µM, respectively, which are sufficient to detect these metal ions in human sweat and urine. SPCEs functionalized through anodic pre-treatments were used for detecting uric acid and 17ß-estradiol in artificial sweat, with detection limits of 1.8 µM and 0.58 µM, respectively. The electrochemical treatment created oxygen groups on the carbon surfaces, thus improving wettability and hydrophilicity. MNC was herein exploited as an adhesive-free, yet highly skin-adherent platform for wearable sensing devices that also benefit from the semi-permeable, non-allergenic, and renewable features that make MNC unique within the pool of materials that have been used for such a purpose. Our findings have clear implications for the developments on greener and more biocompatible but still efficient substrates and may pave the route for combining immunosensing devices with drug delivery therapies.

Nano- and macroscale structural and mechanical properties of in situ synthesized bacterial cellulose/PEO-b-PPO-b-PEO biocomposites.

Highly transparent biocomposite based on bacterial cellulose (BC) mat modified with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) block copolymer (EPE) were fabricated in situ during biosynthesis of bacterial cellulose in a static culture from Gluconacetobacter xylinum. The effect of the addition to the culture medium of water-soluble EPE block copolymer on structure, morphology, crystallinity, and final properties of the novel biocomposites was investigated at nano- and macroscale. High compatibility between components was confirmed by ATR-FTIR indicating hydrogen bond formation between the OH group of BC and the PEO block of EPE block copolymer. Structural properties of EPE/BC biocomposites showed a strong effect of EPE block copolymer on the morphology of the BC mats. Thus, the increase of the EPE block copolymer content lead to the generation of spherulites of PEO block, clearly visualized using AFM and MO technique, changing crystallinity of the final EPE/BC biocomposites investigated by XRD. Generally, EPE/BC biocomposites maintain thermal stability and mechanical properties of the BC mat being 1 wt % EPE/BC biocomposite material with the best properties. Biosynthesis of EPE/BC composites open new strategy to the utilization of water-soluble block copolymers in the preparation of BC mat based biocomposites with tunable properties.