Piezoelectric-Fenton degradation and mechanism study of Fe2O3/PVDF-HFP porous film drove by flowing water.

Piezocatalysis driven by a gentle force possesses broad application prospects for degrading organic pollutants, sterilisation, wound healing and tissue recovery. The flexible and industrially scalable poly(vinylidene fluoride) (PVDF) film is commonly used in piezocatalysis. However, under gentle force action, PVDF composite-based piezocatalysis is poor. Herein, a flexible porous film based on poly(vinylidene fluoride)-hexafluoro propylene (PVDF-HFP) is enhanced with Fenton fillers (α-Fe2O3 nanoparticles). α-Fe2O3 nanoparticles improve the piezoelectric catalysis performance of PVDF-HFP by the ß-phase enhancement and provide Fe3+ to react with H2O2 generated by the piezoelectric film itself, leading to an additional Fenton reaction. Meanwhile, the Fe3+/Fe2+ cycle in the Fenton process accelerates under the piezoelectric field, promoting the Fenton reaction for 6.9% degradation improvement. The study on Fe2O3/PVDF-HFP porous film with the piezo-Fenton reaction under flowing water may help promote new piezocatalysis designs with high efficiency for self-powered environmental purification.

Enzyme-Mimetic Molecular Selective Catalysis via Single Zr Atom Catalysis in Chelated Cage Embedded in a Flexible Piezoelectrical Matrix.

The molecularly selective catalysis in enzyme is central to life. However, their functioning mechanism remains elusive. We propose here that the synergistic effects from (i) effective orbital hybridizing and energy gap decreasing via chelating on single Zr atom as the catalytic center, (ii) selective supramolecular encapsulation in the cage, and (iii) piezoelectrical field motivation are able to achieve the enzyme-mimetic molecular selective high performance catalysis. Metal-organic polyhedra (MOPs) are added into a piezoelectrical polymer matrix to achieve the composite structure where ultrasonic treatment motivates redox reactions in the MOP-guest complex. Encapsulated and chelated guest such as Rhodamine B (RhB) is effectively converted with ratios higher than 90 % after 100 min. In comparison, molecules inefficient in either cage encapsulation or chelating with the Zr center can not be converted. This study first proposes a synergistic plot for enzyme-mimetic catalyst realization and is expected to inspire new mentality in efficient catalyst designing.

H2O2 generation enhancement by ultrasonic nebulisation with a zinc layer for spray disinfection.

With the outbreak of COVID-19, microbial pollution has gained increasing attention as a threat to human health. Consequently, many research efforts are being devoted to the development of efficient disinfection methods. In this context, hydrogen peroxide (H2O2) stands out as a green and broad-spectrum disinfectant, which can be produced and sprayed in the air directly by cavitation in ultrasonic nebulisation. However, the yield of H2O2 obtained by ultrasonic nebulisation is too low to satisfy the requirements for disinfection by spraying and needs to be improved to achieve efficient disinfection of the air and objects. Herein, we report the introduction of a zinc layer into an ultrasonic nebuliser to improve the production of H2O2 and generate additional Zn2+ by self-corrosion, achieving good disinfecting performance. Specifically, a zinc layer was assembled on the oscillator plate of a commercial ultrasonic nebuliser, resulting in a 21-fold increase in the yield of H2O2 and the production of 4.75 µg/mL Zn2+ in the spraying droplets. When the generated water mist was used to treat a bottle polluted with Escherichia coli for 30 min, the sterilisation rate reached 93.53%. This ultrasonic nebulisation using a functional zinc layer successfully enhanced the production of H2O2 while generating Zn2+, providing a platform for the development of new methodologies of spray disinfection.

Enhanced Electricity Generation and Tunable Preservation in Porous Polymeric Materials via Coupled Piezoelectric and Dielectric Processes.

Biological systems and artificial devices convert omnipresent low-frequency and weak mechanical stimulation into electricity for important functions. However, in-depth understanding of the energy conversion, boosting, and preservation processes of the coupled piezo-dielectric phenomenon in polymeric artificial materials is still lacking. In this study, combined experimental and simulation methods are employed to rationalize the process of energy conversion and preservation via a coupled piezo-dielectric phenomena in composite polymeric films. Both the intensity of the transmembrane electric voltages and the kinetic aspects of the energy generation and preservation process are elucidated. The study indicates that composite films consisting of a conductive filler fraction below the percolation threshold, effectively convert low-frequency mechanical stimulation to preserved electrical energy. Interestingly, film structure engineered into porous film has the ability to break the intertwined high-voltage and exhibits a low-preservation-period relationship; it can simultaneously provide high electric field intensity, high induction velocity, and a long preservation period. The model is not only supported by the experiments but is also consistent with the electricity generation and preservation features of other reported piezo-dielectric films. The systematic understanding can facilitate and inspire new device designs to better address the energy, environmental, and biomedical challenges faced by modern societies.

A self-powered delivery substrate boosts active enzyme delivery in response to human movements.

Stimulated drug releases in response to human movements are highly appealing in medical therapy and various daily uses. However, the design of a mechanically responsive substrate that presents high delivery capacities and can also preserve the activities of sensitive molecules such as enzymes is still challenging. Taking advantage of the recent development in effective piezoelectric flexible films and in molecular delivery devices, we propose a composite delivery substrate that preserves enzyme activities and enhances molecular delivery in response to human movements such as finger presses or massages. The substrate is achieved by combining two parts, which are the energy converting unit and the molecular loading and releasing unit. The energy converting unit is a piezoelectric-dielectric flexible composite film that produces enhanced electricity and preserves the electricity longer compared to a pure piezoelectric polymer. The molecular delivery unit is a layer-by-layer multilayer containing mesoporous silica particles that are assembled at pH 9 but used in neutral solutions. The releases of molecules including small molecules, peptides, and proteins are all accelerated in response to finger presses irrespective of the signs or densities of their charges. More importantly, the enzyme CAT preserves its activity after release from the composite substrates, meaning that the CAT-loaded (PAH/MS)n(PAH/DAS)n@rGO-TFB/PVDF-HFP composite substrate holds promise as a self-powered soothing pad that effectively removes residue H2O2.

A New Way to Promote Molecular Drug Release during Medical Treatment: A Polyelectrolyte Matrix on a Piezoelectric-Dielectric Energy Conversion Substrate.

Enhanced drug releases in a timely manner during urgent medical treatments would significantly enhance the prognosis of patients. Inspired by the facilitated molecular transports by the potentials, an enhanced drug release strategy driven by mechanical disturbances that widely exist in medical treatment processes is proposed. This strategy is enabled by a functional material comprised of multilayers of dendrimers as the drug reservoir, which are built on a piezoelectric-dielectric flexible film with reduced graphene oxide fillers. The generated voltages are higher and last longer than that in regular piezoelectric films. Photochemical crosslinking leads to a stable drug matrix which is even sustained in electric fields and high ionic strengths. The device enhances releases of positively, negatively, and zwitterionically charged molecules in response to mechanical stimuli and supports high cell viabilities. An illustrative application is demonstrated by preparing the material on the surface of a gastric lavage tube. The results show that the release of antiemetic drug increased by 200% within 60 min in response to forces mimicking human swallowing. This study contributes an integrative material that can realize electrically triggered releases that are previously only realized using complicated electrochemical setups. It is believed that this material can facilitate medicine applications in various emergent situations.

A self-powered porous ZnS/PVDF-HFP mechanoluminescent composite film that converts human movement into eye-readable light.

This study reports on a self-powered mechanoluminescent flexible film that converts human movement into green, yellow, and white light that are visible to the naked eye. The film is simply a highly porous composite material that was prepared using a piezoelectric polymer and ZnS luminescent powders. The highly effective mechanoluminescence capabilities stem from both the film's porous structure and the strong interactions between poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and ZnS particles. The porous film's sensitivity helps the conversion of mechanical disturbances into electrical energies and induces the electroluminescence of ZnS particles. The particle-film interactions induced a high ß-phase, which is the most effective piezoelectric phase, in the PVDF-HFP film. Similar to polymeric materials, the composite film is highly processable and can be written into arbitrary shapes or patterns using a pipette or stamping techniques. Finger rubbing or ultrasonication makes the mechanoluminescence patterns readable. This composite mechanoluminescent film provides high potential for future applications in electronic skins, smart electronics, and information encryption techniques.

Constructing the magnetic bifunctional graphene/titania nanosheet-based composite photocatalysts for enhanced visible-light photodegradation of MB and electrochemical ORR from polluted water.

Photocatalysis is a promising strategy to address the global environmental and energy challenges. However, the studies on the application of the photocatalytically degraded dye-polluted water and the multi-purpose use of one type of catalyst have remained sparse. In this report, we try to demonstrate a concept of multiple and cyclic application of materials and resources in environmentally relevant catalyst reactions. A magnetic composite catalyst prepared from exfoliated titania nanosheets, graphene, the magnetic iron oxide nanoparticles, and a polyelectrolyte enabled such a cyclic application. The composite catalyst decomposed a methylene blue-polluted water under visible light, and then the catalyst was collected and removed from the treated water using a magnet. The photocatalytically treated water was then used to prepare the electrolyte in electrochemical reductive reactions and presented superior electrochemical performance compared with the dye-polluted water. The composite catalyst was once again used as the cathode catalyst in the electrochemical reaction. Each component in the composite catalyst was indispensable in its catalytic activity, but each component played different roles in the photochemical, magnetic recycling, and electrochemical processes. We expect the report inspire the study on the multi-functional catalyst and cyclic use of the catalytically cleaned water, which should contribute for the environmental and energy remedy from a novel perspective.

Surface-Enhanced Raman Spectra Promoted by a Finger Press in an All-Solid-State Flexible Energy Conversion and Storage Film.

Electrochemically up-regulated surface-enhanced Raman spectroscopy (E-SERS) effectively increases Raman signal intensities. However, the instrumental requirements and the conventional measurement conditions in an electrolyte cell have hampered its application in fast and on-site detection. To circumvent the inconveniences of E-SERS, we propose a self-energizing substrate that provides electrical potential by converting film deformation from a finger press into stored electrical energy. The substrate combines an energy conversion film and a SERS-active Ag nanowire layer. A composite film prepared from a piezoelectric polymer matrix and surface-engineered rGO that simultaneously presents high permittivity and low dielectric loss is the key component herein. Using our substrate, increased E-SERS signals up to 10 times from a variety of molecules were obtained in the open air. Various tests on real-life sample surfaces demonstrated the potentials of the substrate in fast on-site detection.

Achieving significantly enhanced visible-light photocatalytic efficiency using a polyelectrolyte: the composites of exfoliated titania nanosheets, graphene, and poly(diallyl-dimethyl-ammonium chloride).

A high-performance visible-light-active photocatalyst is prepared using the polyelectrolyte/exfoliated titania nanosheet/graphene oxide (GO) precursor by flocculation followed by calcination. The polyelectrolyte poly(diallyl-dimethyl-ammonium chloride) serves not only as an effective binder to precipitate GO and titania nanosheets, but also boosts the overall performance of the catalyst significantly. Unlike most titania nanosheet-based catalysts reported in the literature, the composite absorbs light in the UV-Vis-NIR range. Its decomposition rate of methylene blue is 98% under visible light. This novel strategy of using a polymer to enhance the catalytic performance of titania nanosheet-based catalysts affords immense potential in designing and fabricating next-generation photocatalysts with high efficiency.