Facile and time-resolved chemical growth of nanoporous CaxCoO2 thin films for flexible and thermoelectric applications

CaxCoO2 thin films can be promising for widespread flexible thermoelectric applications in a wide temperature range from room-temperature self-powered wearable applications (by harvesting power from body heat) to energy harvesting from hot surfaces (e.g., hot pipes) if a cost-effective and facile growth technique is developed. Here, we demonstrate a time resolved, facile and ligand-free soft chemical method for the growth of nanoporous Ca0.35CoO2 thin films on sapphire and mica substrates from a water-based precursor ink, composed of in-situ prepared Ca2+-DMF and Co2+-DMF complexes. Mica serves as flexible substrate as well as sacrificial layer for film transfer. The grown films are oriented and can sustain bending stress until a bending radius of 15 mm. Despite the presence of nanopores, the power factor of Ca0.35CoO2 film is found to be as high as 0.50 x 10-4 Wm-1K-2 near room temperature. The present technique, being simple and fast to be potentially suitable for cost-effective industrial upscaling.Comment: 16 pages, 5 figure

Design of In Situ Poled Ce³⁺-Doped Electrospun PVDF/Graphene Composite Nanofibers for Fabrication of Nanopressure Sensor and Ultrasensitive Acoustic Nanogenerator

We report an efficient, low-cost in situ poled fabrication strategy to construct a large area, highly sensitive, flexible pressure sensor by electrospun Ce³⁺ doped PVDF/graphene composite nanofibers. The entire device fabrication process is scalable and enabling to large-area integration. It can able to detect imparting pressure as low as 2 Pa with high level of sensitivity. Furthermore, Ce³⁺-doped PVDF/graphene nanofiber based ultrasensitive pressure sensors can also be used as an effective nanogenerator as it generating an output voltage of 11 V with a current density ∼6 nA/cm² upon repetitive application of mechanical stress that could lit up 10 blue light emitting diodes (LEDs) instantaneously. Furthermore, to use it in environmental random vibrations (such as wind flow, water fall, transportation of vehicles, etc.), nanogenerator is integrated with musical vibration that exhibits to power up three blue LEDs instantly that promises as an ultrasensitive acoustic nanogenerator (ANG). The superior sensing properties in conjunction with mechanical flexibility, integrability, and robustness of nanofibers enabled real-time monitoring of sound waves as well as detection of different type of musical vibrations. Thus, ANG promises to use as an ultrasensitive pressure sensor, mechanical energy harvester, and effective power source for portable electronic and wearable devices

An Effective Electrical Throughput from PANI Supplement ZnS Nanorods and PDMS-Based Flexible Piezoelectric Nanogenerator for Power up Portable Electronic Devices: An Alternative of MWCNT Filler

We demonstrate the requirement of electrical poling can be avoided in flexible piezoelectric nanogenerators (FPNGs) made of low-temperature hydrothermally grown wurtzite zinc sulfide nanorods (ZnS-NRs) blended with polydimethylsiloxane (PDMS). It has been found that conductive fillers, such as polyaniline (PANI) and multiwall carbon nanotubes (MWCNTs), can subsequently improve the overall performance of FPNG. A large electrical throughput (open circuit voltage ∼35 V with power density ∼2.43 μW/cm³) from PANI supplement added nanogenerator (PZP-FPNG) indicates that it is an effective means to replace the MWCNTs filler. The time constant (τ) estimated from the transient response of the capacitor charging curves signifying that the FPNGs are very much capable to charge the capacitors in very short time span (e.g., 3 V is accomplished in 50 s) and thus expected to be perfectly suitable in portable, wearable and flexible electronics devices. We demonstrate that FPNG can instantly lit up several commercial Light Emitting Diodes (LEDs) (15 red, 25 green, and 55 blue, individually) and power up several portable electronic gadgets, for example, wrist watch, calculator, and LCD screen. Thus, a realization of potential use of PANI in low-temperature-synthesized ZnS-NRs comprising piezoelectric based nanogenerator fabrication is experimentally verified so as to acquire a potential impact in sustainable energy applications. Beside this, wireless piezoelectric signal detection possibility is also worked out where a concept of self-powered smart sensor is introduced

Self-Poled Transparent and Flexible UV Light-Emitting Cerium Complex–PVDF Composite: A High-Performance Nanogenerator

Cerium­(III)-<i>N</i>,<i>N</i>-dimethylformamide-bisulfate [Ce­(DMF)­(HSO₄)₃] complex is doped into poly­(vinylidene fluoride) (PVDF) to induce a higher yield (99%) of the electroactive phases (β- and γ-phases) of PVDF. A remarkable enhancement of the output voltage (∼32 V) of a nanogenerator (NG) based on a nonelectrically poled cerium­(III) complex containing PVDF composite film is achieved by simple repeated human finger imparting, whereas neat PVDF does not show this kind of behavior. This high electrical output resembles the generation of self-poled electroactive β-phase in PVDF due to the electrostatic interactions between the fluoride of PVDF and the surface-active positive charge cloud of the cerium complex via H-bonding and/or bipolar interaction among the opposite poles of cerium complex and PVDF, respectively. The capacitor charging capability of the flexible NG promises its applicability as piezoelectric-based energy harvester. The cerium­(III) complex doped PVDF composite film exhibit an intense photoluminescence in the UV region, which might be due to a participation of electron cloud from negative pole of bipolarized PVDF. This fact may open a new area for prospective development of high-performance energy-saving flexible solid-state UV light emitters

Bacterial Fucose-Rich Polysaccharide Stabilizes MAPK-Mediated Nrf2/Keap1 Signaling by Directly Scavenging Reactive Oxygen Species during Hydrogen Peroxide-Induced Apoptosis of Human Lung Fibroblast Cells

<div><p>Continuous free radical assault upsets cellular homeostasis and dysregulates associated signaling pathways to promote stress-induced cell death. In spite of the continuous development and implementation of effective therapeutic strategies, limitations in treatments for stress-induced toxicities remain. The purpose of the present study was to determine the potential therapeutic efficacy of bacterial fucose polysaccharides against hydrogen peroxide (H₂O₂)-induced stress in human lung fibroblast (WI38) cells and to understand the associated molecular mechanisms. In two different fermentation processes, <i>Bacillus megaterium</i> RB-05 biosynthesized two non-identical fucose polysaccharides; of these, the polysaccharide having a high-fucose content (∼42%) conferred the maximum free radical scavenging efficiency <i>in vitro</i>. Structural characterizations of the purified polysaccharides were performed using HPLC, GC-MS, and ¹H/¹³C/2D-COSY NMR. H₂O₂ (300 µM) insult to WI38 cells showed anti-proliferative effects by inducing intracellular reactive oxygen species (ROS) and by disrupting mitochondrial membrane permeability, followed by apoptosis. The polysaccharide (250 µg/mL) attenuated the cell death process by directly scavenging intracellular ROS rather than activating endogenous antioxidant enzymes. This process encompasses inhibition of caspase-9/3/7, a decrease in the ratio of Bax/Bcl2, relocalization of translocated Bax and cytochrome c, upregulation of anti-apoptotic members of the Bcl2 family and a decrease in the phosphorylation of MAPKs (mitogen activated protein kinases). Furthermore, cellular homeostasis was re-established via stabilization of MAPK-mediated Nrf2/Keap1 signaling and transcription of downstream cytoprotective genes. This molecular study uniquely introduces a fucose-rich bacterial polysaccharide as a potential inhibitor of H₂O₂-induced stress and toxicities.</p></div

The effect of HFC polysaccharide on H₂O₂-induced morphological changes in WI38 cells.

<p>The cells were incubated in presence (100, 200 and 250 µg/mL) or in absence of HFC polysaccharide for 1 h followed by the treatment with 300 µM H₂O₂ in both the cases for varying periods of time (0–24 h). Cell morphology was observed under microscope in phase contrast mode. Results are representative of three independent experiments performed in triplicate. Indicated <i>scale bars</i> signify 50 µm distance and photographs were taken at 10× zoom.</p

The effects of HFC polysaccharide treatment on H₂O₂-induced regulation of mitochondrial functions.

<p>The polysaccharide prevented H₂O₂-induced changes in the expression of Bcl2 family at both mRNA and protein level. WI38 cells were incubated in presence (200 and 250 µg/mL) or in absence of HFC polysaccharide for 1 h followed by the treatment with 300 µM H₂O₂ in both the cases for varying periods of time (0–24 h). <b>A)</b> Mitochondrial membrane potential (MMP) was monitored by DiOC6 staining with flow cytometry. The mean fluorescence indices (MFI) are shown as bar graphs. <b>B)</b> Protein level expression of Bcl2, Bcl-xl, and Bad was evaluated by immunoblotting. β-actin was used as loading control. Fold changes are represented as relative values of band densitometries normalized to control and are shown as numbers below the immunoblots. Results are representative of three independent experiments performed in triplicate and are represented as mean value. <b>C)</b> The ratio between Bax and Bcl2 were calculated from band densitometries of corresponding protein level expressions and are shown as bar graphs. <b>D)</b> Fold changes of Bcl2, Bcl-xl, Bad, Bax, and cytochrome c at mRNA level were calculated using real-time RT-PCR (SYBR green method). Fold changes are represented as relative values normalized to control and quantified in the terms of 2^−ΔΔCt. GAPDH was used as internal control. Results are representative of three independent experiments performed in triplicate and are represented as mean ± SD. A one-way analysis of variance (ANOVA, Bonferroni corrections for multiple comparisons) was performed, where significant level stands for * p<0.05, ** p<0.001, *** p<0.0001.</p

Translocation of Bax and cytochrome c induced by H₂O₂ and HFC polysaccharide during the stress and polysaccharide treatment period, respectively.

<p>WI38 cells were incubated in presence (250 µg/mL) or in absence of HFC polysaccharide for 1 h followed by the treatment with 300 µM H₂O₂ in both the cases for varying periods of time (0–24 h). <b>A)</b> Protein level expression of Bax and cytochrome c in both cytosolic and mitochondrial fractions was observed by immunoblotting. β-actin and COX4 were used as loading control. Fold changes are represented as relative values of band densitometries normalized to control and are shown as numbers below the immunoblots. Results are representative of three independent experiments performed in triplicate and are represented as mean value. A one-way analysis of variance (ANOVA, Bonferroni corrections for multiple comparisons) was performed, where significant level stands for * p<0.05, ** p<0.001. <b>B)</b> H₂O₂-induced release of cytochrome c from mitochondria to cytosol and re-localization into mitochondria again during the polysaccharide treatment were monitored under fluorescence microscope using fluorescence-tagged (green florescence) specific antibodies. Similarly, mitochondrial translocation of Bax and their cytosolic re-localization was also tracked following the same procedure. The cells were treated with 100 nM MitoTracker Red (red florescence) for 30 min before cell-fixation for mitochondrial staining. Each image shown is representative of 20 random fields observed. Indicated <i>scale bars</i> signify 10 µm distance and photographs were taken at 100× zoom.</p

Plausible signaling cross-talk involved in the HFC polysaccharide treatment against H₂O₂-induced apoptosis of WI38 cells.

<p>Plausible signaling cross-talk involved in the HFC polysaccharide treatment against H₂O₂-induced apoptosis of WI38 cells.</p