Facile Synthesis of Sustainable Biomass-Derived Porous Biochars as Promising Electrode Materials for High-Performance Supercapacitor Applications.

Preparing sustainable and highly efficient biochars as electrodes remains a challenge for building green energy storage devices. In this study, efficient carbon electrodes for supercapacitors were prepared via a facile and sustainable single-step pyrolysis method using spruce bark as a biomass precursor. Herein, biochars activated by KOH and ZnCl2 are explored as templates to be applied to prepare electrodes for supercapacitors. The physical and chemical properties of biochars for application as supercapacitors electrodes were strongly affected by factors such as the nature of the activators and the meso/microporosity, which is a critical condition that affects the internal resistance and diffusive conditions for the charge accumulation process in a real supercapacitor. Results confirmed a lower internal resistance and higher phase angle for devices prepared with ZnCl2 in association with a higher mesoporosity degree and distribution of Zn residues into the matrix. The ZnCl2-activated biochar electrodes' areal capacitance reached values of 342 mF cm-2 due to the interaction of electrical double-layer capacitance/pseudocapacitance mechanisms in a matrix that favors hydrophilic interactions and the permeation of electrolytes into the pores. The results obtained in this work strongly suggest that the spruce bark can be considered a high-efficiency precursor for biobased electrode preparation to be employed in SCs.

Low intensity electric field inactivation of Gram-positive and Gram-negative bacteria via metal-free polymeric composite.

The adhesion of pathogenic bacteria in medical implants and surfaces is a health-related problem that requires strong inhibition against bacterial growth and attachment. In this work, we have explored the enhancement in the antibacterial activity of metal free-based composites under external electric field. It affects the oxidation degree of polypyrrole-based electrodes and consequently the antibacterial activity of the material. A conductive layer of carbon nanotubes (graphite) was deposited on porous substrate of polyurethane (sandpaper) and covered by polypyrrole, providing highly conductive electrodes characterized by intrinsic antibacterial activity and reinforced by electro-enhanced effect due to the external electric field. The bacterial inhibition of composites was monitored from counting of viable cells at different voltage/time of treatment and determination of biofilm inhibition on electrodes and reactors. The external voltage on electrodes reduces the threshold time for complete bacterial inactivation of PPy-based composites to values in order of 30 min for Staphylococcus aureus and 60 min for Escherichia coli.

Extraction of plasmid DNA by use of a magnetic maghemite-polyaniline nanocomposite.

We describe the use of a hybrid magnetic nanocomposite (HMNC) for the extraction and purification of plasmid DNA (pDNA) from Escherichia coli aqueous solutions. The HMNC, which was synthesized via emulsion polymerization, was characterized by transmission electron microscopy, scanning electron microscopy, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering and magnetic measurements. The results confirmed the incorporation of polyaniline (Pani) in its conducting form onto a core formed by the magnetic iron oxide, with the hybrid particles presenting an average size of (95 ±â€¯30) nm and a saturation magnetization of 30 emu/g. The yield, purity and quality of the pDNA purified by using the Pani HMNC were evaluated by UV-Vis spectroscopy, agarose gel electrophoresis, and Polymerase Chain Reaction (PCR), respectively. An average yield of ~6.9 µg was obtained in the DNA extraction process, with the collected material presenting a good purity (a ₳260/280 ratio in the 1.68-1.82 range) and an excellent quality, as confirmed by subsequent PCR assays. Hence, this HMNC appears as a promising material for use in pDNA purification protocols, and we suggest that this novel HMNC-based methodology can be of general interest and find widespread application in different biomedical procedures.

Magnetic extraction and purification of DNA from whole human blood using a γ-Fe2O3@Chitosan@Polyaniline hybrid nanocomposite.

We examined the properties of the nanocomposite γ-Fe2O3@Chi@Pani as an adsorbent of deoxyribonucleic acid (DNA). As a model system, we used an aqueous solution of salmon sperm DNA, whose decreasing concentration was followed by monitoring the 260 nm UV-vis absorption. After adjusting the data collected to a Langmuir isotherm curve, we estimated the adsorption capacity (qe) of the nanocomposite as 49.5 mg/g. We also observed that the kinetic model of the DNA capture presents a mixed character, with both chemical mechanisms and intraparticle diffusion processes involved. When the MNC was used to extract the DNA from complex samples (human blood), a capture rate of 80 ng/µL was achieved, with the collected fraction exhibiting good quality, as evaluated by PCR analysis and electrophoresis assays. These results suggest that the γ-Fe2O3@Chi@Pani nanocomposite is a promising adsorbent for use in protocols for purification of DNA from complex samples.

Multifunctional Wearable Electronic Textiles Using Cotton Fibers with Polypyrrole and Carbon Nanotubes.

Multifunctional wearable electronic textiles based on interfacial polymerization of polypyrrole on carbon nanotubes/cotton fibers offer advantages of simple and low-cost materials that incorporate bactericidal, good electrochemical performance, and electrical heating properties. The high conductivity of doped polypyrrole/CNT composite provides textiles that reaches temperature on order of 70 °C with field of 5 V/cm, superior electrochemical performance applied as electrodes of supercapacitor prototypes, reaching capacitance in order of 30 F g-1 and strong bactericidal activity against Staphylococcus aureus. The combination of these properties can be explored in smart devices for heat and microbial treatment on different parts of body, with incorporated storage of energy on textiles.

Fabrication of Highly Flexible Hierarchical Polypyrrole/Carbon Nanotube on Eggshell Membranes for Supercapacitors.

Flexible batteries and supercapacitors (SCs) are expected to play a crucial role in energy storage and management in portable electronic devices. In addition, use of materials based on renewable resources would allow for more affordable and sustainable gadgets. In this context, eggshell membranes (ESMs) represent a promising functional platform for production of high-performance electronic components. In this work, we use ESMs for preparing flexible SCs through the incorporation of carbon nanotubes and subsequent in situ polymerization of polypyrrole, producing a highly conductive nanostructure characterized by a porous surface that exhibits both faradic and nonfaradic mechanisms for charge storage. We have found that by controlling the conducting polymer/carbon derivative relative concentration, one can maximize the corresponding capacitance to attain values up to the order 564.5 mF/cm2 (areal capacitance), 24.8 F/cm3 (volumetric capacitance), and 357.9 F/g (gravimetric capacitance). These bioinspired flexible devices exhibit a capacitance retention of 60% after 4000 cycles of charge/discharge and present negligible aging even after 500 bending repetitions (at a density of current 5 mA/cm2). The successful use of ESM-based electrodes in association with carbon derivatives/conducting polymers confirm that the exploit of biological materials offers a promising perspective for the development of new ecofriendly electronic devices.