Collaborative Filler Network for Enhancing the Performance of BaTiO3/PDMS Flexible Piezoelectric Polymer Composite Nanogenerators.

Wearable sensors are gaining attention in human health monitoring applications, even if their usability is limited due to battery need. Flexible nanogenerators (NGs) converting biomechanical energy into electrical energy offer an interesting solution, as they can supply the sensors or extend the battery lifetime. Herein, flexible generators based on lead-free barium titanate (BaTiO3) and a polydimethylsiloxane (PDMS) polymer have been developed. A comparative study was performed to investigate the impact of multiwalled carbon nanotubes (MWCNTs) via structural, morphological, electrical, and electromechanical measurements. This study demonstrated that MWCNTs boosts the performance of the NG at the percolation threshold. This enhancement is attributed to the enhanced conductivity that promotes charge transfer and enhanced mechanical property and piezoceramics particles distribution. The nanogenerator delivers a maximum open-circuit voltage (VOC) up to 1.5 V and output power of 40 nW, which is two times higher than NG without MWCNTs. Additionally, the performance can be tuned by controlling the composite thickness and the applied frequency. Thicker NG shows a better performance, which enlarges their potential use for harvesting biomechanical energy efficiently up to 11.22 V under palm striking. The voltage output dependency on temperature was also investigated. The results show that the output voltage changes enormously with the temperature.

Tin Oxide Nanoparticles and SnO2 /SiO2 Hybrid Materials by Twin Polymerization Using Tin(IV) Alkoxides.

Twin polymerization was used to prepare composite materials composed of SnO2 nanoparticles entrapped in a polymer matrix. Novel, well-defined tin-containing molecular precursors, so-called twin monomers, were synthesized by transesterification starting from Sn(OR)4 (R=tBu, tAm) to give Sn(OCH2 C4 H3 O)4 (1), [Sn(OCH2 C4 H3 S)4 ⋅HOCH2 C4 H3 S]2 (2), [Sn(OCH2 -2-OCH3 C6 H4 )4 ⋅HOCH2 -2-OCH3 C6 H4 ]2 (3), [Sn(OCH2 -2,4-(OCH3 )2 C6 H3 )4 ⋅HOCH2 -2,4-(OCH3 )2 C6 H3 ]2 (4), 2,2'-spirobi[4H-1,3,2-benzodioxastannine] (5), 2,2'-spirobi[6-methylbenzo(4H-1,3,2)-dioxastannine] (6), and 2,2'-spirobi[6-methoxybenzo(4H-1,3,2)dioxastannine] (7). 13 C and 119 Sn NMR spectroscopy in the solid state and in solution as well as IR spectroscopy and elemental analysis were used to characterize the tin alkoxides. The molecular structures of compounds 2 and 3 were determined by single-crystal X-ray diffraction analysis. The moisture sensitivity of the tin(IV) alkoxides was demonstrated by the formation of the tin oxocluster [Sn3 (µ3 -O)(µ2 -OH)(µ2 -OCH2 C4 H3 S)3 (OCH2 C4 H3 S)6 (HOCH2 C4 H3 S)]2 (2 a), a hydrolysis product of compound 2. Polymerization reactions in the melt (for 1 and 5) and in solution (for 2-4) resulted in cross-linked nanocomposites of the type polymer/SnO2 . Subsequent oxidation of the composites gave SnO2 with BET surface areas up to 178 m2 g-1 . Simultaneous twin polymerization of compounds 5-7 with the silicon derivative 2,2'-spirobi[4H-1,3,2-benzodioxasiline] resulted in the formation of polymer/SnO2 /SiO2 hybrid materials. Oxidation gave porous materials with SnO2 nanoparticles embedded in a silica network with BET surface areas up to 378 m2 g-1 . The silica acts as a crystal growth inhibitor, which prevents sintering of the SnO2 nanoparticles 20-32 nm in size.