Highly efficient piezocatalytic composite with chitosan biopolymeric membranes and bismuth ferrite nanoparticles for dye decomposition and pathogenic S. aureus bacteria killing.

Untreated wastewater harbors dangerous pathogens, chemicals, and pollutants, posing grave public health threats. Nowadays, there is a rising demand for eco-friendly technologies for wastewater treatment. Recently, piezoelectric materials-based wastewater treatment technology has captured considerable interest among researchers because of its noninvasiveness and rapidity. Herein, a highly efficient piezoelectric composite material is designed with chitosan-incorporated bismuth ferrite (BFO) nanocrystals, to decompose pollutants and ablate bacteria in wastewater. On one hand, piezoelectric BFO has shown exclusive piezo-coefficient for ultrasound-mediated reactive oxygen species (ROS) production. On the other hand, chitosan depicts its biocompatible nature, which not only promotes cellular adhesion but also significantly elevates the ROS production capabilities of BFO under ultrasound. The synergistic effect of these two piezoelectric units in one composite entity shows an improved ROS production, eradicating ∼87.8% of Rhodamine B within 80 min under soft ultrasound treatment (rate constant, k ≈ 0.02866 min-1). After performing the scavenger experiment, it has been found that hydroxyl radicals are the dominating factor in this case. Further, the reusability of the composite piezocatalyst is confirmed through multiple cycles (five times) of the same experiment. The high polarizability of the composite material facilitates the generation of piezoelectric power through finger tapping (∼12.05 V), producing substantial instantaneous piezo-voltage. Moreover, the sample exhibits remarkable antibacterial activity, with nearly 99% bacterial eradication within 30 min. This indicates a significant advancement in utilizing biopolymeric composites incorporated with BFO for fabricating versatile devices with multidimensional applications.

Improvement of consolidation properties of clay soil using fine-grained construction and demolition waste.

As urbanization spreads rapidly, more structures are being built, and more construction and demolition waste (CDW) is produced, occupying about 36-40% of the total solid waste generation in the world; hence, CDW has become a burden nowadays. Moreover, the construction of low-rise buildings on weak soil is always challenging and costly due to the soil's high compressibility and low bearing capacity. Sand or other granular materials are commonly used to improve the compressibility behavior and associated settlement, drainage, and shear strength of weak soil. The massive use of natural sand for construction purposes of different civil engineering structures have lessened their reserves in recent times, increasing their price and destroying the balance in the environment. Among the several methods of improving soil, this research uses fine-grained CDW to improve the geotechnical behavior of weak soil under study. The main objective of this research is to observe the changes in soil properties after mixing with CDW. Recycled waste mortar powder has been selected as CDW mixed in different percentages in the soil. In addition, CDW powder was inserted into soil mass as a circular powder column in triangular and square grid patterns as an alternative to the sand column. CDW in the soil samples improved consolidation settlement, and reduced settlement time and compression index. Increments in the pre-consolidation pressure, consolidation rate, and permeability of the clay-CDW mixtures were also remarkable. Soil improvement through reusing CDW is a sustainable way to solve problems in solid waste management and the soft soil settlement issue under a shallow foundation, ultimately reducing the environmental footprints, saving natural resources, and supporting the circular economy concept.

Development of a Sustainable and Biodegradable Sonchus asper Cotton Pappus Based Piezoelectric Nanogenerator for Instrument Vibration and Human Body Motion Sensing with Mechanical Energy Harvesting Applications.

Energy harvesting from natural resources has gained much attention due to the huge increase in the demand for portable electronic devices and the shortage of conventional energy resources in general. In the present work, the fabrication and realistic applications of a piezoelectric nanogenerator (PENG) using polydimethylsiloxane (PDMS) and the abundantly available, environment-friendly natural fiber Sonchus asper (SA) have been discussed. The biocompatible, low-cost SA fibers were flexible enough and showed high piezoelectric properties as active materials in the study. The SA pappus based piezoelectric nanogenerator demonstrated its ability to convert the harvested biomechanical energy into electrical energy from the various mechanical energy sources available in our environment. The SA pappus/PDMS thin film based piezoelectric nanogenerator (SPENG) fabricated in the laboratory showed colossal output performances (open circuit output voltage, V OC ∼81.2 V; short circuit current, I SC ∼1.0 µA) by continuous finger impartation. Uniform output performance was also obtained by the application of uniform force on the devices (e.g., ∼42 V for 5 N force at 10 Hz frequency). The SPENG was capable to charge a 2.2 µF capacitor to 3.2 V within a short time span (16 s) under continuous finger impartation and illuminate 39 commercial high-power blue LEDs that were connected in series. Thus, the fabricated SPENG can be used as a green and portable energy source to power up portable electronic devices. Apart from this, the SPENG may also be used as a self-powered energy supply for pacemakers or different types of health care units if properly improvised.

Women's Knowledge, Attitude, and Perceptions Toward COVID-19 in Lower-Middle-Income Countries: A Representative Cross-Sectional Study in Bangladesh.

The coronavirus disease 2019 (COVID-19) is a global health emergency of unprecedented proportions. Countries around the world have taken extraordinary steps to control the disease. The preventive measures face challenges in low and lower middle income countries (LICs and LMICs). Especially the marginalized communities, e.g., women are the hardest hit of the virus. This study took Bangladesh as a representative LMIC and aimed to determine the level of knowledge, perception, attitude, and preparedness related to COVID-19 among the adult women in the country. Using a comprehensive questionnaire, we channeled a cross-sectional study among adult women in Bangladesh. Participant's self-reported data on the knowledge, attitude, and preparedness were tabulated and analyzed using suitable statistical tools. A total of 1,869 adults from 61 districts of Bangladesh took part in this study. Ninety seven percentage of the participants claimed to have heard of COVID-19 before it arrived in Bangladesh. Regarding the general knowledge related to COVID-19's causal agent, symptoms, and treatment, the positive response rate was nearly 80%, with a mean of 10.68 ± 1.72. Younger and educated women had better knowledge levels compared to the older and lower-educated participants (p < 0.01). More efforts are required to educate women with older age and lower socioeconomic status. An overall positive attitude and perception were observed, although a significant proportion of the participants opined that the Government's efforts in controlling the outbreak were not adequate. Although the participants had a satisfactory level of knowledge and a positive attitude in adopting preventive measures against COVID-19, greater efforts are needed from the healthcare authorities and Government.

Essential oil impregnated luminescent hydroxyapatite: Antibacterial and cytotoxicity studies.

In this study, porous fluorescent nanocrystalline erbium doped hydroxyapatite (eHAp) was synthesized via hydrothermal assisted co-precipitation method. Eucalyptus oil (EU), frankincense oil (FO), Tea tree oil (TTO), wintergreen oil (WO) were successfully absorbed into eHAp pellet by vacuum filtration technique using Buckner funnel. Phase crystallization, fluorescence property and microstructure of eHAp were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Photoluminiscence spectroscopy (PL) and Field emission scanning electron microscopy (FESEM). Strong antimicrobial activity was observed for EU, TTO and WO on both E. coli and S. aureus mediated by cell membrane damage and leakage of cytoplasmic components. The oil absorbed eHAp nanocomposites were found to be moderately biocompatible with normal WI-38 cells up to MIC concentration various time scale. The nanocomposites showed significant cytotoxic activity on breast cancer cell line MDA-MB 468 and the fluorescent property of the eHAp was utilized to visualize internalization of particles in the cells. The release profile of the oils from the eHAp matrix showed pH dependent release indicated that the porous matrix can be used as a suitable carrier for modulated and sustained release of bioactive components. Thus, given the multifunctional attributes these natural essential oil-based nanocomposites show great promise as an alternative to conventional therapeutic treatments.

Re-usable self-poled piezoelectric/piezocatalytic films with exceptional energy harvesting and water remediation capability.

The need for sustainable technologies to address environmental pollution and energy crisis is paramount. Here we present a novel multifunctional nanocomposite, free standing film by combining piezoelectric molybdenum sulphide (MoS2) nanoflower with poly vinylidene fluoride (PVDF) polymer, which can harness otherwise wasted mechanical energy for useful energy generation and/or water purification. The unique MoS2 nanoflower morphology is exploited to render the whole nanocomposite piezo active. A number of features are demonstrated to establish potential practical usage. Firstly, the nanocomposite is piezoelectric and piezocatalytic simultaneously without requiring any poling step (i.e. self-poled). Secondly, the self-poled piezoelectricity is exploited to make a nanogenerator. The nanogenerator produced >80 V under human finger tapping with a remarkable power density, reaching 47.14 mW cm-3. The nanocomposite film is made by simple solution casting, and the corresponding nanogenerator powers up 25 commercial LEDs by finger tapping. Last but not the least, the developed films show efficient, fast and stable piezocatalytic dye degradation efficiency (>90% within 20 min) against four different toxic and carcinogenic dyes under dark condition. Reusability of at least 10 times is also demonstrated without any loss of catalytic activity. Overall, our nanocomposite has clear potential for use as self-powered sensor and energy harvester, and in water remediation systems. It should potentially also be deployable as a surface mounted film/coating in process engineering, industrial effluent management and healthcare devices systems.

Portable Self-Powered Piezoelectric Nanogenerator and Self-Charging Photo-Power Pack Using In Situ Formed Multifunctional Calcium Phosphate Nanorod-Doped PVDF Films.

Herein, biocompatible Ca3(PO4)2 nanorod-incorporated poly(vinylidene) difluoride films have been prepared via an in situ process. A good piezoelectricity (d33 ≈ 56.6 pC/N) along with a large dielectric constant of ∼3.48 × 105 at frequency 20 Hz has been achieved. Then, we have designed a biocompatible, highly durable, low-cost piezoelectric nanogenerator (CPNG) which shows the superiority in open-circuit voltage ∼47 V and current ∼1.8 µA generation with power density ∼47.4 mW cm-3 under the gentle touch of a finger. Excellent mechanical to electrical energy conversion efficiency (∼65.5%) of our developed CPNG leads to fast charging of a capacitor of 1 µF in 18 s and glowing of 26 light-emitting diodes (LEDs) under finger impartation. Further, a portable light-charging power pack (LCPP) has been developed using the high dielectric film as the storage function. Under light illumination, our LCPP generates open-circuit output voltage ∼1.29 V with short-circuit current 5.7 mA cm-2. Areal capacitance ∼1779 F m-2 and storage efficiency ∼88% are achieved. The device is able to lighten up 22 LEDs for 10 days after charging once.

Photo-Rechargeable Organic-Inorganic Dye-Integrated Polymeric Power Cell with Superior Performance and Durability.

In the present work, we propose a simple and unique approach to design a lightweight, low-cost, self-charging power cell with considerable capacity to generate and store photocharges named self-charged photo-power cell (SCPPC). Initially, highly electroactive sodium dodecyl sulfate (SDS)-incorporated poly(vinylidene fluoride) (PVDF) composite thin films with a large dielectric constant of ∼525 are synthesized via a simplistic solution casting process. Then, the as-prepared high-dielectric SDS/PVDF thin film is used as a charge-storage medium in combination with an inorganic-organic dye film, i.e., ZnO nanoparticles-eosin Y-poly(vinylpyrrolidone) film, as a photoelectron generator in our SCPPC. An open-circuit voltage of ∼1.2 V is attained after charging SCPPC under illumination light with intensity ∼110 mW/cm2 and then discharging fully with a constant current density of ∼4.5 mA/cm2. A specific areal capacitance of ∼450 F/m2 is obtained with large energy and power densities of ∼90 mWh/m2 and 54 W/m2, respectively. The improved overall efficiency, ∼3.78%, along with 89% storage efficiency leads to promising application possibilities of our rechargeable photo-power cell. The recyclability, i.e., rechargeability and storage durability, of the photo-power cell are also checked for 35 days without no such reduction in voltage generation and storage. Also, multicolored light-emitting diodes are lightened up using the photo-power cell as power source.

Antimicrobial and biocompatible fluorescent hydroxyapatite-chitosan nanocomposite films for biomedical applications.

Development of fluorescent erbium doped hydroxyapatite (eHAp)-chitosan nanocomposite film is reported. Nanocrystalline eHAp has been synthesized by hydrothermal assisted precipitation method using erbium (III) ions as dopant. Physico-chemical characterization by UV/Visible spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), photoluminiscence spectroscopy (PL) and Field emission scanning electron microscopy(FESEM) confirmed incorporation and uniform distribution of eHAp in the chitosan films. Strong antimicrobial activity was observed using eHAp incorporated chitosan films against E. coli and S. aureus by contact inhibition on agar plates. On the other hand, excellent biocompatibility was observed with human lung fibroblast cells (WI-38) which showed strong attachment and proliferation on the chitosan films with minimal cytotoxicity. Moreover, the doped films showed good biodegradation and mineralization behavior after 2 weeks in simulated body fluid. Thus the doped fluorescent chitosan films with multifunctional attributes can be a strong candidate for diverse applications like in antimicrobial treatments, wound healing, tissue scaffolds and bioimaging.

Er3+/Fe3+ Stimulated Electroactive, Visible Light Emitting, and High Dielectric Flexible PVDF Film Based Piezoelectric Nanogenerators: A Simple and Superior Self-Powered Energy Harvester with Remarkable Power Density.

The design of an energy-harvesting unit with superior output characteristics, i.e., high power density, is a great technological challenge in the present time. Here, simple, lightweight, flexible, and cost-effective piezoelectric nanogenerators (PENGs) have been fabricated by integrating the aluminum electrodes onto Er3+/Fe3+ stimulated electroactive, visible-light-emitting, and large dielectric PVDF films in which ErCl3·6H2O and Fe(NO3)3·9H2O act as the catalytic agents for electroactive ß polymorph nucleation and the enhancement of dielectric properties. The developed PENGs exhibit excellent energy-harvesting performance with very high power density and very fast charging ability compared with the previously reported PVDF-assisted prototype nanogenerators. The PENGs lead to very large power density (∼160 and ∼55.34 mW cm-3) under periodic finger imparting for Er3+- and Fe3+-stimulated PVDF-film-based energy-harvester units, respectively. The fabricated self-powered PENG is also able to light up 54 commercially available light-emitting diodes.

Electroactive and High Dielectric Folic Acid/PVDF Composite Film Rooted Simplistic Organic Photovoltaic Self-Charging Energy Storage Cell with Superior Energy Density and Storage Capability.

Herein we report a simplistic prototype approach to develop an organic photovoltaic self-charging energy storage cell (OPSESC) rooted with biopolymer folic acid (FA) modified high dielectric and electroactive ß crystal enriched poly(vinylidene fluoride) (PVDF) composite (PFA) thin film. Comprehensive and exhaustive characterizations of the synthesized PFA composite films validate the proper formation of ß-polymorphs in PVDF. Significant improvements of both ß-phase crystallization (F(ß) ≈ 71.4%) and dielectric constant (ε ≈ 218 at 20 Hz for PFA of 7.5 mass %) are the twosome realizations of our current study. Enhancement of ß-phase nucleation in the composites can be thought as a contribution of the strong interaction of the FA particles with the PVDF chains. Maxwell-Wagner-Sillars (MWS) interfacial polarization approves the establishment of thermally stable high dielectric values measured over a wide temperature spectrum. The optimized high dielectric and electroactive films are further employed as an active energy storage material in designing our device named as OPSESC. Self-charging under visible light irradiation without an external biasing electrical field and simultaneous remarkable self-storage of photogenerated electrical energy are the two foremost aptitudes and the spotlight of our present investigation. Our as fabricated device delivers an impressively high energy density of 7.84 mWh/g and an excellent specific capacitance of 61 F/g which is superior relative to the other photon induced two electrode organic self-charging energy storage devices reported so far. Our device also proves the realistic utility with good recycling capability by facilitating commercially available light emitting diode.

Synthesis of eucalyptus/tea tree oil absorbed biphasic calcium phosphate-PVDF polymer nanocomposite films: a surface active antimicrobial system for biomedical application.

A biocompatible poly(vinylidene) difluoride (PVDF) based film has been prepared by in situ precipitation of calcium phosphate precursors. Such films were surface absorbed with two essential oils namely eucalyptus and tea tree oil. Physico-chemical characterization of the composite film revealed excellent stability of the film with 10% loading of oils in the PVDF matrix. XRD, FTIR and FESEM measurements confirmed the presence of hydroxyapatite and octacalcium phosphate in the PVDF matrix which showed predominantly ß phase. Strong bactericidal activity was observed with very low minimum bactericidal concentration (MBC) values on both E. coli and S. aureus. The composite films also resisted biofilm formation as observed by FESEM. The release of essential oils from the film showed an initial burst followed by a very slow release over a period of 24 hours. Antibacterial action of the film was found to be primarily due to the action of essential oils which resulted in leakage of vital fluids from the microorganisms. Both necrotic and apoptotic morphologies were observed in bacterial cells. Biocompatibility studies with the composite films showed negligible cytotoxicity to mouse mesenchymal and myoblast cells at MBC concentration.

In situ synthesis of Ni(OH)2 nanobelt modified electroactive poly(vinylidene fluoride) thin films: remarkable improvement in dielectric properties.

A facile and low cost synthesis of Ni(OH)2 nanobelt (NB) modified electroactive poly(vinylidene fluoride) (PVDF) thin films with excellent dielectric properties has been reported via in situ formation of Ni(OH)2 NBs in the PVDF matrix. The formation and morphology of the NBs are confirmed by UV-visible spectroscopy and field emission scanning electron microscopy respectively. A remarkable improvement in electroactive ß phase nucleation (∼82%) and the dielectric constant (ε ∼ 3.1 × 10(6) at 20 Hz) has been observed in the nanocomposites (NCs). The interface between the NBs and the polymer matrix plays a crucial role in the enhancement of the electroactive ß phase and the dielectric properties of thin films. Strong interaction via hydrogen bonds between Ni(OH)2 NBs and the PVDF matrix is the main reason for enhancement in ß phase crystallization and improved dielectric properties. The NC thin films can be utilized for potential applications as high energy storage devices like supercapacitors, solid electrolyte batteries, self-charging power cells, piezoelectric nanogenerators, and thin film transistors and sensors.