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Register a new userDrastic Improvement of Air Stability in an n-type Doped Naphtalene-diimide Polymer by Thionation
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Organic thermoelectrics are attractive for the fabrication of flexible and cost-effective thermoelectric generators (TEGs) for waste heat recovery, in particular by exploiting large-area printing of polymer conductors. Efficient TEGs require both p- and n-type conductors: so far, the air instability of polymer n-type conductors, which typically loose orders of magnitude in electrical conductivity ({sigma}) even for short exposure time to air, has impeded processing under ambient conditions. Here we tackle this problem in a relevant class of electron transporting, naphthalene-diimide co-polymers, by substituting the imide oxygen with sulphur. n-type doping of the thionated co-polymer gives rise to a higher {sigma} with respect to the non-thionated one, and most importantly, owing to a reduced energy level of the lowest-unoccupied molecular orbital, {sigma} is substantially stable over 16 h of air exposure. This result highlights the effectiveness of chemical tuning to improve air-stability of n-type solution-processable polymer conductors and shows a path towards ambient large-area manufacturing of efficient polymer TEGs.
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The oxygen reduction (ORR) and oxygen evolution reactions (OER) in Zn-air batteries (ZABs) require highly efficient, cost-effective and stable electrocatalysts as replacements to traditionally high cost, inconsistently stable and low poison resistant Platinum group metals (PGM) catalysts. Although, nitrogen-doped carbon nanotube (NCNT) arrays have been developed over recent decades through various advanced technologies are now capable of catalyzing ORR efficiently, their underdeveloped bifunctional property, hydrophobic surface, and detrimental preparation strategy are found to limit practical large-scale commercialization for effective rechargeable ZABs. Here, we have demonstrated fabrication of a three-dimensional (3D) nickel foam supported NCNT arrays with CoNi nanoparticles (NPs) encapsulated within the apical domain (denoted as CoNi@NCNT/NF) that exhibits excellent bifunctional catalytic performance toward both ORR (onset potential of 0.97 V vs. RHE) and OER (overpotential of 1.54 V vs. RHE at 10 mA cm$^{-2}$). We further examined the practicability of this CoNi@NCNT/NF material being used as an air electrode for rechargeable ZAB coin cell and pouch cell systems. The ZAB coin cell showed a peak power density of 108 mW cm$^{-2}$ with an energy density of 845 Wh kg$_{Zn}^{-1}$ and robust rechargeability over 28h under ambient conditions, which exceeds the performance of PGM catalysts and leading non-PGM electrocatalysts. In addition, density functional theory (DFT) calculations revealed that the ORR and OER catalytic performance of the CoNi@NCNT/NF electrode are mainly derived from the d-orbitals from the CoNi NPs encapsulated within the apical dominant end of the NCNTs.
Much smoother surfaces and significantly improved superconducting properties of relatively thick YBa2Cu3O7 (YBCO) films have been achieved by introducing a multilayered structure with alternating main YBCO and additional NdBCO layers. The surface of thick (1 microm) multilayers has almost no holes compared to YBCO films. Critical current density (Jc) have been drastically increased up to a factor > 3 in 1 microm multilayered structures compared to YBCO films over entire temperature and applied magnetic filed range. Moreover, Jc values measured in thick multilayers are even larger than in much thinner YBCO films. The Jc and surface improvement have been analysed and attributed to growth conditions and corresponding structural peculiarities.
This work reports the strain effect on the electrical properties of highly doped n-type single crystalline cubic silicon carbide (3C-SiC) transferred onto a 6-inch glass substrate employing an anodic bonding technique. The experimental data shows high gauge factors of -8.6 in longitudinal direction and 10.5 in transverse direction along the [100] orientation. The piezoresistive effect in the highly doped 3C-SiC film also exhibits an excellent linearity and consistent reproducibility after several bending cycles. The experimental result was in good agreement with the theoretical analysis based on the phenomenon of electron transfer between many valleys in the conduction band of n-type 3C-SiC. Our finding for the large gauge factor in n-type 3C- SiC coupled with the elimination of the current leak to the insulated substrate could pave the way for the development of single crystal SiC-on-glass based MEMS applications.
NADH is a key biomolecule involved in many biocatalytic processes as cofactor and its quantification can be correlated to specific enzymatic activity. Many efforts have been taken to obtain clean electrochemical signals related to NADH presence and lower its redox overpotential to avoid interferences. Suppression of background and secondary signals can be achieved by including a switchable electroactive surface, for instance, by using semiconductors able to harvest light energy and drive the excited electrons only when irradiated. Here we present the combination of a n-type Si semiconductor with fibers made of carbon nanotubes as electroactive surface for NADH quantification at low potentials only upon irradiation. The resulting photoelectrode responded linearly to NADH concentrations from 50 {mu} M to 1.6 mM with high sensitivity (54 $mu$ A cm$^{-2}$ mM${-1}$). This system may serve as a biosensing platform for detection and quantification of dehydrogenases activity.
Magnesium alloys have been considered to be favorable biodegradable metallic materials used in orthopedic and cardiovascular applications. We introduce NH+2 to the AZ31 Mg alloy surface by ion implantation at the energy of 50 KeV with doses ranging from 1e16 ions/cm2 to 1e17 ions/cm2 to improve its corrosion resistance and biocompatibility. Surface morphology, mechanical properties, corrosion behavior and biocompatibility are studied in the experiments. The analysis confirms that the modified surface with smoothness and hydrophobicity significantly improves the corrosion resistance and biocompatibility while maintaining the mechanical property of the alloy.
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