Cytocompatibility and Dielectric Properties of Sr2+ Substituted Nano-Hydroxyapatite for Triggered Drug Release

Hydroxyapatite (Ca5(PO4)3OH) is a well-known bioceramics material used in medical applications because of its ability to form direct chemical bonds with living tissues. In this context, we investigate the biocompatibility and dielectric properties of Sr2+-substituted hydroxyapatite nanoparticles were synthesized by sol-gel method. The influence of strontium on the crystal structure, functional group, morphological, electrical properties, and biocompatibility of as-synthesized nano-hydroxyapatite samples was analyzed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FE-SEM). Dielectrical properties of the bioactive Sr-HA sample were investigated by a dielectric impedance spectroscopy method. The observed results illustrate the incorporation of Sr2+ ions in the apatite lattice could influence the pure HA properties, by reducing the crystallite size and crystallinity quite consistent with the morphology variation. The ac conductivity (σac) increased with an increasing applied frequency confirmed that prepared HA sample exhibited the universal power law nature. Further, the in vitro drug loading and release studies using doxycycline as a model drug demonstrate that the Sr2+ -HA nanoparticles show high drug adsorption capacity and sustained drug release. Thus, the improved bioceramics system could be a promising candidate for future biomedical applications

Designing piezoelectric nanogenerator from PVDFHFP nanocomposite fibers containing cellulose nanocrystals and Fedoped ZnO

Self-powering devices harvest energy from the environment and perform based on a maintenance free approach. These materials are of utmost significance as they solve the problems associated with the energy crisis and management, to greater extends. Advances in material science and the design of various polymer nanocomposites developed many self-powering devices that are flexible, sensitive, less power consuming and of low cost. The semi-crystalline polymer, poly vinylidene fluoride (PVDF) and its co-polymers are notable for mechanical energy harvesting because of the typical crystalline phases in their structure. Various nanoparticles are added to such polymers to enhance their dielectric and piezoelectric properties as well. Since the alignment of crystalline phases improve the energy harvesting properties, techniques such as electrical poling are practiced to enhance their applicability. Among various alignment procedures, electrospinning stands as unique since the high voltage applied to the polymer solution generates nanofiber scaffolds in perfect alignments. The present work aims to develop electrospun composite fibers in nano-dimensions for designing self-powering nanogenerators. The co-polymer of PVDF, polyvinylidene fluoride hexa fluoropropylene (PVDF-HFP) was used as the base polymer and the iron-doped zinc oxide (Fe-ZnO) and cellulose nanocrystals (CNC) as the filler reinforcements. Fe-ZnO nanostructures were obtained by hydrothermal synthesis method from the ZnO precursor, while the CNC were synthesized following the acid hydrolysis of cellulose microfibers. The optimized concentration of 20 wt.% was used for obtaining the electrospun fibers of neat PVDF-HFP and various concentrations of nanoparticles were mixed with this base solution. Simple solvent mixing was employed using the acetone/DMF solvent mixture to prepare the composite solutions prior to electrospinning. The electrospinning conditions were also optimized by varying the applied voltage, tip to collector distance and speed of the rotating collector. Nice fibers were obtained at a voltage of 12-13 eV and rotating collector speed of 200 rpm. Composites of CNC with PVDF-HFP, Fe-ZnO with PVDF-HFP and the hybrid material of CNC/Fe-ZnO with PVDF-HFP were prepared and properties were investigated. All the fibers were tested for the morphology, structural, thermal and dielectric properties. The mechanical energy harvesting was performed using an assembled set up containing a frequency generator, shaker and data acquisition system. At 2 wt. % of the nanofillers, the PVDF-HFP/CNC generated about 2 V, the PVDF-HFP/Fe-ZnO generated about 4 V and the hybrid nanocomposite containing both nanoparticles generated about 6 V. The filler synergy plays a major role in regulating the material properties and here the combined effect of the piezoelectric performance of the cellulose nanocrystals and the modified ZnO nanoparticles enhanced the mechanical energy harvesting capability of the final nanocomposite. A nanogenerator is designed based on the developed polymer nanocomposite fibers and the piezoelectric performance on various conditions of stretching, pressing and twisting were also investigated. In all the cases the hybrid composite showed notable performance substantiating its application in designing self-powered nanogenerators. The dielectric properties of the hybrid material showed many fold increase in its dielectric constant, making it useful in electrical energy storage. In short, the designed device by electrospinning technique is highly useful in adding to the energy management and is environmentally safe and of good efficiency.qscienc

Comparative Study on Gas-Sensing Properties of 2D (MoS2, WS2)/PANI Nanocomposites-Based Sensor

NH3 is a highly harmful gas; when inhaled at levels that are too high for comfort, it is very dangerous to human health. One of the challenging tasks in research is developing ammonia sensors that operate at room temperature. In this study, we proposed a new design of an NH3 gas sensor that was comprised of two-dimensional (TMDs, mainly WS2 and MoS2) and PANI. The 2D-TMDs metal was successfully incorporated into the PANI lattice based on the results of XRD and SEM. The elemental EDX analysis results indicated that C, N, O, W, S and Mo were found in the composite samples. The bandgap of the materials decreased due to the addition of MoS2 and WS2. We also analyzed its structural, optical and morphological properties. When compared to MoS2 and PANI, the proposed NH3 sensor with the WS2 composite was found to have high sensitivity. The composite films also exhibited response and recovery times of 10/16 and 14/16 s. Therefore, the composite PANI/2D-TMDs is a suitable material for NH3 gas detection applications.This work is supported by the Qatar National Research Fund (Project number UREP 25-057-2-023). The funding achieved herein are solely the responsibility of the autors. The characterizations of this work are accomplished in the Central Laboratories Unit, Qatar University

Synthesis and photoelectrochemical performance of Co doped SrTiO3 nanostructures photoanode

It is pertinent to realize that scientific research indicates that the most promising method for producing H2 is photo electrochemical water splitting through a photo anode. Cobalt-doped SrTiO3 (Co-SrTiO3) composite nanostructures were created in this study via hydrothermal synthesis. The impact of cobalt concentration change on Co-SrTiO3 has been identified using morphological, structural, and photo electrochemical research. Surface morphology of pure SrTiO3 nanoparticles using SEM and TEM reveals that the particles are intermittently agglomerated. The inclusion of Cobalt lowered the particle size of the nanostructures to 23 nm than pure SrTiO3 (41 nm). In addition, the peak profile has been influenced by cubic phase also identified from the x-ray diffraction analysis. The purity and composition of the materials were revealed by XPS analysis. The Co-SrTiO3 composite's produced the best charge transfer and recombination capabilities at 3% Co doping, according to electrochemical chemical impedance (EIS) spectroscopy. At 0.2 V applied potential, the obtained 3% Co-doped SrTiO3 photoanode system displays a photocurrent density of around 3.45 mA/cm2. The outcomes show that a promising application for the Co-doped SrTiO3 photoanode in photoelectrochemical water splitting.This publication was made possible by the support of an Qatar University Internal Grant (QUCG-CAM-20/21-6). The statements made herein are solely the responsibility of the authors. The characterizations of this work are accomplished in the Gas Processing Unit and in the Centra Laboratory Unit, at Qatar University

Corrosion behavior of Epoxy/ZnO-NiO nanocomposite coating on steel substrate

Corrosion is a very common natural phenomenon which leads to huge losses especially in the building construction, turbines in the industries and several other fields. In this research we synthesized and developed new coating materials containing ZnO-NiO. The fabricated coating was characterized by using different techniques such as SEM, XRD etc. The efficiency of the coating against corrosion was examined using the Tafel experiments and it was observed that the fabricated coating exhibit excellent anti-corrosion under seawater

Flexible piezoelectric nanogenerator based on [P(VDF-HFP)]/ PANI-ZnS electrospun nanofibers for electrical energy harvesting

Abstract Over the past decade, piezoelectric nanogenerator have attracted much attention to harvest mechanical energy from abundant resources in nature. Here, the ZnS microspheres is prepared by hydrothermal method and core-shell structured PANI/ZnS microspheres are synthesized by in situ polymerization method and then used as filler for the preparation of flexible [P(VDF-HFP)] based piezoelectric nanogenerator. The flexible P(VDF-HFP)/PANI-ZnS piezoelectric nanogenerator is prepared by Electrospinning technique. The core-shell PANI/ZnS composite improves the content of electroactive phase in [P(VDF-HFP)] and significantly improves the interfacial polarization between the PANI/ZnS particles and polymer matrix. Among all the samples, [P(VDF-HFP)]/2 wt% PANI-ZnS composite nanofibers exhibited the high piezoelectric peak-to-peak output voltage of 3 V compared with the neat [P(VDF-HFP)] (~ 120 mV). In addition, the high dielectric constant is observed for the [P(VDF-HFP)]/2 wt% PANI-ZnS composite nanofibers. These results implies that the fabricated flexible and efficient piezoelectric nanogenerator can be utilized for energy harvesting system.Other Information Published in: Journal of Materials Science: Materials in Electronics License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s10854-021-05352-4</p

A review of passivity breakdown on metal surfaces: influence of chloride- and sulfide-ion concentrations, temperature, and pH

Metals, including austenitic steels and alloys, have been extensively applied in industrial and engineering applications. Passive films on metal surfaces are very important for corrosion protection. However, localized attack, such as passive film breakdown and the initiation of pits, is found upon exposure of such metals to aggressive ion-containing environments, leading to material failure and prominent adverse economic and safety concerns. For several decades, the mechanism of passivity breakdown and pit nucleation during pitting corrosion has been widely studied. The present article provides a detailed review of passive film breakdown on metal surfaces and the effects of complicated conditions, such as chloride- and sulfide-ion concentrations, temperature, and solution pH, on passivity breakdown. The possible mechanism for passivity breakdown is reviewed and discussed. The composition, structure, and electronic properties of passive layers are of conclusive importance to understand the leading corrosion mechanism, and they have been investigated with different techniques. Furthermore, we aim to present the structure, chemical composition, and electronic properties of passive films on metal surfaces by using X-ray photoelectron spectroscopy and energy-dispersive spectroscopy. Additionally, the surface morphology of passive films is analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) techniques. Finally, the effect of chloride- and sulfide-ion concentrations, pH, and temperature on passivity breakdown is discussed in detail.Other Information Published in: Emergent Materials License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s42247-021-00194-6</p