Synthesis of Spherical Mn2O3 Nanozymes from Different Green Precursors for their Innovative Applications in Catalytic Properties and Bioactivity.

Here, spherical Mn2O3 nanozymes were synthesized via a one-step green method using different green precursors, and their physicochemical properties and biological activities were monitored with various green precursors. Powder X-ray diffraction (PXRD) was performed to determine the crystalline properties and phases involved in the formation of cubic Mn2O3 nanozymes. The synthesized nanozymes were spherical and examined by SEM and FESEM studies. All of the samples synthesized using different green precursors exhibited different sizes but similar spherical shapes. Moreover, all green-synthesized nanozymes catalyzed the oxidation reaction of the chromogenic substrate 3,3'5,5' tetramethylbenzidine (TMB) in the absence of H2O2, and A2 (lemon-mediated Mn2O3 nanozymes), which the followed Michaelis-Menten kinetics, showed the best activity. Therefore, A2 (lemon-mediated nanozyme) showed oxidase-mimicking activity with distinct Km and Vmax values calculated by the Lineweaver-Burk plot. Furthermore, the current nanozymes demonstrated a significant ability to kill both Gram-negative and Gram-positive bacteria as well as effectively destroy biofilms under physiological conditions. Moreover, the green-mediated nanozymes also displayed ROS-scavenging activity. Our nanozymes exhibited scavenging activity toward OH and O2-• radicals and metal chelation activity, which were investigated colorimetrically. Therefore, these nanozymes might be used as effective antibacterial agents and also for the consumption of reactive oxygen species.

A self-powered mechanical energy harvester based on CH3NH3PbI3 doped P(VDF-HFP)/PANI composite films.

Piezoelectric polymers, particularly poly(vinylidene fluoride) (PVDF) and its copolymers attract attention from researchers due to their stretchability, flexibility, lightweight, and most importantly their biocompatible nature. In this research work, we report on the preparation of polymer composite films as flexible piezoelectric generators (PGs) and their electroactive phase (ß- and γ-phase) formation. The piezoelectric properties of copolymer poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) have been enhanced by incorporating polyaniline (PANI) and methylammonium lead iodide (CH3NH3PbI3) into it for a higher yield of the electroactive phases where a traditional electrical poling treatment was avoided. The remarkable enhancement in the piezoelectric phase (i.e., ß-phase) of the P(VDF-HFP) copolymer has been reported in this work, and it is found that the overall improvement of the piezoelectric ß-phase and the conversion of the degree of crystallinity is governed by the incorporation of the PANI and CH3NH3PbI3 fillers as revealed by the attenuated total reflectance (ATR) and X-ray diffraction (XRD) analysis. The X-ray photoelectron spectroscopy (XPS) analysis further confirmed the interfacial dipole-dipole interaction of PANI with the P(VDF-HFP) copolymer matrix. Piezoelectric generators (PGs) fabricated from the composite films show an open circuit piezoelectric voltage output of 5 volts and an output power of 8.2 nW. The capacitor charging capability by simple repetitive finger touch and release motions (a pressure amplitude of ∼14 kPa) of the flexible PGs promises their applicability as a piezoelectric-based energy harvester where different mechanical vibrations can be utilized.

Enhanced electro-active phase in a luminescent P(VDF-HFP)/Zn2+ flexible composite film for piezoelectric based energy harvesting applications and self-powered UV light detection.

We have prepared a flexible polymer composite film containing poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) and Zn2+ for the fabrication of a multifunctional piezoelectric based nanogenerator (MFNG), where a traditional electrical poling treatment was avoided. The desirable amount of Zn2+ yields more than 99% of electro-active phases in the P(VDF-HFP) matrix that co-operates to enhance the dielectric properties of the composite film via hydrogen bonding interactions. In situ thermal Fourier transform infrared (FT-IR) spectroscopy affirms the improved thermal stability of the electro-active ß-phase and the ß→γ phase transition temperature in the Zn2+ doped composite film. It also shows UV absorption and intense blue light emission confirmed by a CIE 1931 chart that gives it applicability as a flexible optical sensor. The MFNG behaves as an efficient mechanical energy harvester that delivers an open-circuit voltage ∼6 V and an output power of 2.4 µW and successfully enables the charging of a capacitor by simple repetitive finger touch and release motions (a pressure amplitude of ∼14 kPa). The UV light sensing ability of the MFNG is confirmed under the continuous application and removal of applied stress, which is very promising for designing versatile self-powered optoelectronic smart sensors. Our approach is very simple and cost effective for the construction of a new class of flexible multifunctional energy harvesters that have wonderful applications in the areas of piezo-photonics, wireless detection and flexible self-powered opto-electronics.

Improved sensitivity of wearable nanogenerators made of electrospun Eu3+ doped P(VDF-HFP)/graphene composite nanofibers for self-powered voice recognition.

Composite nanofibers of Eu3+ doped poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP))/graphene are prepared by the electrospinning technique for the fabrication of ultrasensitive wearable piezoelectric nanogenerators (WPNGs) where the post-poling technique is not necessary. It is found that the complete conversion of the piezoelectric ß-phase and the improvement of the degree of crystallinity is governed by the incorporation of Eu3+ and graphene sheets into P(VDF-HFP) nanofibers. The flexible nanocomposite fibers are associated with a hypersensitive electronic transition that results in an intense red light emission, and WPNGs also have the capability of detecting external pressure as low as ~23 Pa with a higher degree of acoustic sensitivity, ~11 V Pa-1, than has ever been previously reported. This means that ultrasensitive WPNGs can be utilized to recognize human voices, which suggests they could be a potential tool in the biomedical and national security sectors. The capacitor's ability to charge from abundant environmental vibrations, such as music, wind, body motion, etc, drives WPNGs as a power source for portable electronics. This fact may open up the prospect of using the Eu3+ doped P(VDF-HFP)/graphene composite electrospun nanofibers, with their multifunctional properties such as vibration sensitivity, wearability, red light emission capability and piezoelectric energy harvesting, for various promising applications in portable electronics, health care monitoring, noise detection and security monitoring.

The co-operative performance of a hydrated salt assisted sponge like P(VDF-HFP) piezoelectric generator: an effective piezoelectric based energy harvester.

We have prepared hydrated salt filler assisted sponge like P(VDF-HFP) micro-porous electroactive films to fabricate a high performance flexible piezoelectric generator (FPG). These FPGs deliver up to 8 V of open circuit voltage under external stress and also generate enough power to turn on at least fifteen commercial blue light emitting diodes (LEDs) instantly. Furthermore, capacitors have been successfully charged by repeated finger touches indicating the potential of the FPGs to be used as self-powered devices where different types of mechanical vibrations can be applied. The high performance of FPGs might be attributed to the co-operative contribution from the porous electret structure and electroactive nature of the P(VDF-HFP) film, as they also enhance the dielectric permittivity. This approach is simple, cost-effective, and well-suited for large-scale fabrication of high-performance FPGs.

Self-poled transparent and flexible UV light-emitting cerium complex-PVDF composite: a high-performance nanogenerator.

Cerium(III)-N,N-dimethylformamide-bisulfate [Ce(DMF)(HSO4)3] complex is doped into poly(vinylidene fluoride) (PVDF) to induce a higher yield (99%) of the electroactive phases (ß- 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 ß-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.