A strong and sticky hydrogel electrolyte for flexible supercapacitors

With the rapid development of flexible supercapacitors (SCs), there is increasing demand for high-performance solid electrolyte to replace the conventional liquid electrolyte. Hydrogel electrolyte is one of the promising candidates, which possesses solid state but contains plenty of water within its highly porous structure. In this paper, a strong and sticky hydrogel has been synthesized using bacterial cellulose (BC) and poly (acrylic acid) (PAA). The results of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy shows that two components are well combined. Scanning electron microscopy (SEM) test shows that BC/PAA has a highly porous structure, which is modified by the interaction between BC nanofibers and acrylic acid monomer. Double network created by BC and PAA not only enhances the mechanical property of PAA but also improves the anti-compression ability of BC. Moreover, a sticky property is recognized within BC/PAA due to PAA, which can prevent the spilt of two flexible electrodes. The high ionic strength makes PAA shrink in 1M Na2SO4. However, the swelling ratio of BC/PAA could still reach to approximately 500% and its ionic conductivity is about 0.06 S·cm-1. This prepared BC/PAA hydrogel electrolyte has a great potential to be used in flexible SCs. © 2016 Author(s)

A strong and sticky hydrogel electrolyte for flexible supercapacitors

With the rapid development of flexible supercapacitors (SCs), there is increasing demand for high-performance solid electrolyte to replace the conventional liquid electrolyte. Hydrogel electrolyte is one of the promising candidates, which possesses solid state but contains plenty of water within its highly porous structure. In this paper, a strong and sticky hydrogel has been synthesized using bacterial cellulose (BC) and poly (acrylic acid) (PAA). The results of attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy shows that two components are well combined. Scanning electron microscopy (SEM) test shows that BC/PAA has a highly porous structure, which is modified by the interaction between BC nanofibers and acrylic acid monomer. Double network created by BC and PAA not only enhances the mechanical property of PAA but also improves the anti-compression ability of BC. Moreover, a sticky property is recognized within BC/PAA due to PAA, which can prevent the spilt of two flexible electrodes. The high ionic strength makes PAA shrink in 1M Na2SO4. However, the swelling ratio of BC/PAA could still reach to approximately 500% and its ionic conductivity is about 0.06 S·cm-1. This prepared BC/PAA hydrogel electrolyte has a great potential to be used in flexible SCs. © 2016 Author(s)

Polyaniline/reduced graphene oxide hydrogel film with attached graphite current collector for flexible supercapacitors

Reduced graphene oxide (RGO) hydrogel films possess a low specific capacitance and have no flexible current collectors, which limit their use in flexible supercapacitors. To solve these problems, a novel polyaniline (PANI) modified RGO hydrogel film with an attached graphite current collector (PANI/RGO/G) was prepared. Based on this film, a flexible supercapacitor device was fabricated and characterized. PANI/RGO/G film demonstrates good flexibility and electron transport. The graphite current collector highly reduces the internal resistance of the device. It shows a high specific capacitance of 478 F g−1 at a current density of 2 mA cm−2 based on the mass of one electrode and a good cycling stability (86.5% retention after 5000 cycles). Moreover, during the fabrication of the device, a modified design was adopted to solve the problem of low extension of PANI/RGO/G hydrogel film. The obtained device also exhibits a good flexibility; its capacitance hardly changes after 500 cycles of bending at an angle of 90°. © 2017, Springer Science+Business Media, LLC, part of Springer Nature.LO1504, NPU, Northwestern Polytechnical University; 15520720500, STCSM, Science and Technology Commission of Shanghai Municipality; IGA/CPS/2015/008, ERDF, European Regional Development Fund; CZ.1.05/2.1.00/19.0409, ERDF, European Regional Development Fund; IGA/CPS/2016/003, ERDF, European Regional Development Fund; LTACH17015, MoE, Ministry of Education, Government of the People's Republic of Bangladesh; ERDF, European Regional Development Fund; Research and DevelopmentMinistry of Education, Youth, and Sports of the Czech Republic [LTACH17015]; NPU Program I [LO1504]; Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF); national budget of the Czech Republic within the framework of the CPS-strengthening research capacity [CZ.1.05/2.1.00/19.0409]; Internal Grant Agency from Tomas Bata University in Zlin, Czech Republic [IGA/CPS/2015/008, IGA/CPS/2016/003]; Shanghai Municipality Research Project [15520720500

Stabilization of chitosan-based polyelectrolyte nanoparticle cargo delivery biomaterials by a multiple ionic cross-linking strategy

PolyElectrolyte Nanoparticles (PENs) obtained by layer-by-layer self-assembly of polycations/polyanions suffer from a lack of colloidal stability in physiological conditions. We report a simple innovative approach for increasing their stability by multiple ionic cross-linkers. Herein, a chitosan-based core was stabilized by polyanions such as tripolyphosphate and dextran sulfate at pHs of 3 (aPENs) and 8 (bPENs) to improve the quality of electrostatic interactions in the core and manage self-assembly of polyethyleneimine shell onto the core. The physicochemical properties of the particles were characterized by DLS, SEM, TEM, FT-IR, and TGA. TEM micrographs showed visible core/shell structures of bPENs. From particle size and polydispersity indices, the bPENs stability was salt concentration-dependent. The release profiles of PENs using nicotinic acid demonstrated sustained release in a pH-independent manner with a good fit of Korsmeyer-Peppas model. These results suggest that multiple ionic cross-linkers can be an efficient approach to increase the colloidal stability of PENs. © 2019 Elsevier LtdMinistry of Education, Youth, and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [LO 1504

Preparation of bacterial cellulose based hydrogels and their viscoelastic behavior

Bacterial cellulose (BC) based hydrogels have been prepared in blended with carboxymethylcellulose and polyvinyl pyrrolidone by using heat treatment. The properties of BC-CMC and BC-PVP hydrogels were compared with pure BC, CMC and PVP hydrogels. These hydrogels were investigated by measuring their structural, morphological and viscoelastic properties. Through the morphological images, alignment of the porous flake like structures could be seen clearly within the inter-polymeric network of the hydrogels. Also, the detail structure analysis of the polymers blended during the hydrogel formation confirms their interactions with each other were studied. Further, the viscoelastic behavior of all the hydrogels in terms of elastic and viscous property was studied. It is observed that at 1% strain, including CMC and PVP hydrogels, all the BC based hydrogels exhibited the linear trend throughout. Also the elastic nature of the material remains high compared to viscous nature. Moreover, the changes could be noticed in case of blended polymer based hydrogels. The values of complex viscosity (eta*) decreases with increase in angular frequency within the range of omega = 0.1-100 rad.s(-1)

A highly flexible supercapacitor based on MnO2/RGO nanosheets and bacterial cellulose-filled gel electrolyte

The flexible supercapacitors (SCs) of the conventional sandwich-type structure have poor flexibility due to the large thickness of the final entire device. Herein, we have fabricated a highly flexible asymmetric SC using manganese dioxide (MnO2) and reduced graphene oxide (RGO) nanosheet-piled hydrogel films and a novel bacterial cellulose (BC)-filled polyacrylic acid sodium salt-Na2SO4 (BC/PAAS-Na2SO4) neutral gel electrolyte. Apart from being environmentally friendly, this BC/PAAS-Na2SO4 gel electrolyte has high viscosity and a sticky property, which enables it to combine two electrodes together. Meanwhile, the intertangling of the filled BC in the gel electrolyte hinders the decrease of the viscosity with temperature, and forms a separator to prevent the two electrodes from short-circuiting. Using these materials, the total thickness of the fabricated device does not exceed 120 μm. This SC device demonstrates high flexibility, where bending and even rolling have no obvious effect on the electrochemical performance. In addition, owing to the asymmetric configuration, the cell voltage of this flexible SC has been extended to 1.8 V, and the energy density can reach up to 11.7 Wh kg-1 at the power density of 441 W kg-1. This SC also exhibits a good cycling stability, with a capacitance retention of 85.5% over 5000 cycles. © 2017 by the authors.Ministry of Education, Youth, and Sports of the Czech Republic [LTACH17015]; NPU Program I [LO1504]; Operational Program Research and Development for Innovations - European Regional Development Fund (ERDF); national budget of the Czech Republic within the framework of the CPSstrengthening research capacity [CZ.1.05/2.1.00/19.0409]; Tomas Bata University in Zlin, Czech Republic [IGA/CPS/2015/008, IGA/CPS/2016/003

Polylactide/polyvinylalcohol-based porous bioscaffold loaded with gentamicin for wound dressing applications

This study explores the feasibility of modifying the surface liquid spraying method to prepare porous bioscaffolds intended for wound dressing applications. For this purpose, gentamicin sulfate was loaded into polylactide-polyvinyl alcohol bioscaffolds as a highly soluble (hygroscopic) model drug for in vitro release study. Moreover, the influence of inorganic salts including NaCl (10 g/L) and KMnO4 (0.4 mg/L), and post-thermal treatment (T) (80◦ C for 2 min) on the properties of the bioscaffolds were studied. The bioscaffolds were characterized by scanning electron microscopy, Fourier Transform infrared spectroscopy, and differential scanning calorimetry. In addition, other properties including porosity, swelling degree, water vapor transmission rate, entrapment efficiency, and the release of gentamicin sulfate were investigated. Results showed that high concentrations of NaCl (10 g/L) in the aqueous phase led to an increase of around 68% in the initial burst release due to the increase in porosity. In fact, porosity increased from 68.1 ± 1.2 to 94.1 ± 1.5. Moreover, the thermal treatment of the Polylactide-polyvinyl alcohol/NaCl (PLA-PVA/NaCl) bioscaffolds above glass transition temperature (Tg ) reduced the initial burst release by approximately 11% and prolonged the release of the drug. These results suggest that thermal treatment of polymer above Tg can be an efficient approach for a sustained release. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth, and Sports of the Czech RepublicMinistry of Education, Youth & Sports - Czech Republic [RP/CPS/2020/002]; Internal Grant Agency of TBU in Zlin [IGA/CPS/2020/002]IGA/CPS/2020/002; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: RP/CPS/2020/00

Development of all-solid-state Li-ion batteries: From key technical areas to commercial use

Innovation in the design of Li-ion rechargeable batteries is necessary to overcome safety concerns and meet energy demands. In this regard, a new generation of Li-ion batteries (LIBs) in the form of all-solid-state batteries (ASSBs) has been developed, attracting a great deal of attention for their high-energy density and excellent mechanical-electrochemical stability. This review describes the current state of research and development on ASSB technology. To this end, study of the literature and patents as well as market analysis over the last two decades were carried out, highlighting how scientific achievements have informed the application of commercially profitable ASSBs. Analyzing the patents registered over the past 20 years revealed that the number of them had increased exponentially-from only few per year in early 2000 to more than 342 in 2020. Published literature and patents on the topic declare a solid-state electrolyte (SSE) to be the main component of ASSBs, and most patented examples are referred to as solid inorganic electrolytes (SIEs), followed by solid polymer electrolytes (SPEs) and solid hybrid electrolytes (SHEs) in popularity. Investigation of company websites, social media profiles, reports, and academic publications identified 93 companies associated with ASSBs. A list of leading businesses in the solid-state battery sector was compiled, out of which 36 provided information on the ASSB units in their product portfolio for detailed analysis.Technology Agency of the Czech Republic, TACR: TK03030157Technology Agency of the Czech Republic, Theta Program [TK03030157

Near-field coupling and resonant cavity modes in plasmonic nanorod metamaterials

Plasmonic resonant cavities are capable of confining light at the nanoscale, resulting in both enhanced local electromagnetic fields and lower mode volumes. However, conventional plasmonic resonant cavities possess large Ohmic losses at metal-dielectric interfaces. Plasmonic near-field coupling plays a key role in a design of photonic components based on the resonant cavities because of the possibility to reduce losses. Here, we study the plasmonic near-field coupling in the silver nanorod metamaterials treated as resonant nanostructured optical cavities. Reflectance measurements reveal the existence of multiple resonance modes of the nanorod metamaterials, which is consistent with our theoretical analysis. Furthermore, our numerical simulations show that the electric field at the longitudinal resonances forms standing waves in the nanocavities due to the near-field coupling between the adjacent nanorods, and a new hybrid mode emerges due to a coupling between nanorods and a gold-film substrate. We demonstrate that this coupling can be controlled by changing the gap between the silver nanorod array and gold substrate

Nanoparticle-based rifampicin delivery system development

The alkaline milieu of chronic wounds severely impairs the therapeutic effect of antibiotics, such as rifampicin; as such, the development of new drugs, or the smart delivery of existing drugs, is required. Herein, two innovative polyelectrolyte nanoparticles (PENs), composed of an amphiphilic chitosan core and a polycationic shell, were synthesized at alkaline pH, and in vitro performances were assessed by H-1 NMR, elemental analysis, FT-IR, XRD, DSC, DLS, SEM, TEM, UV/Vis spectrophotometry, and HPLC. According to the results, the nanostructures exhibited different morphologies but similar physicochemical properties and release profiles. It was also hypothesized that the simultaneous use of the nanosystem and an antioxidant could be therapeutically beneficial. Therefore, the simultaneous effects of ascorbic acid and PENs were evaluated on the release profile and degradation of rifampicin, in which the results confirmed their synergistic protective effect at pH 8.5, as opposed to pH 7.4. Overall, this study highlighted the benefits of nanoparticulate development in the presence of antioxidants, at alkaline pH, as an efficient approach for decreasing rifampicin degradation.Ministry of Education, Youth and Sport of the Czech Republic-DKRVO [RP/CPS/2020/005