Dielectric and Ferroelectric Properties of PZN-4.5PT Nanoparticles Thin Films on Nanostructured Silicon Substrate for Ferrophotovoltaic and Energy Storage Application

The integration of ferroelectric materials as thin films has attracted considerable attention these last years thanks to their outstanding performances that allow considering new features for the realization of photovoltaic devices. Our study focuses on investigating structural, dielectric and ferroelectric properties of undoped and Mn doped PZN-4.5PT nanoparticles thin films on Silicon substrate. We fabricate very stable PZN-4.5PT nanoparticles thin films deposited on nanostructured silicon substrate with giant relative dielectric permittivity of 2.76 × 104 and 17.7 × 104 for respectively the undoped and Mn doped thin films. These values are very large compared to those found in single crystals and might be explained by the influence of the gel in which nanoparticles were dispersed. The SEM images show the crystallization of new hexagonal phases on the film surface probably coming from interaction between Si and the gel. The hysteresis loops permitted to determine the spontaneous polarization (Ps), remnant polarization (Pr) and coercive field Ec which are equal to 11.73 μC/cm2, 10.20 μC/cm2 and 20 V/cm, respectively for the undoped nanoparticles thin film and 22.22 μC/cm2, 19.32 μC/cm2 and 20 V/cm respectively for the Mn doped one. These values are high and correspond to the best ones found in literature compared to typical ferroelectric thin films.

Fabrication and Characterization of PZN-4.5PT Inorganic Perovskites Nanoparticles Thin Films Deposited on P-Type Silicon Substrate

This work involves an investigation of nanostructures, microelectronic properties and domain engineering of nanoparticles thin layers of Pb(Zn1/ 3Nb2/3)O3-PbTiO3 (PZN-PT) ferroelectric single crystals deposited on nanostructured silicon substrate. In this study, devices made from PZN-4.5PT nanoparticles thin films successfully deposited on silicon substrate have been studied and discussed. SEM images show the formation of local black circles and hexagonal shapes probably due to the nucleation of a new Si-gel component or phase induced by annealing. Micro Xray Fluorescence mapping shows that the high values of Si and B atoms (≅7 and 4 normalized unit respectively) can be explained by the fact that the substrate is p-type silicon. The most interesting result of optical measurements is the very good absorption for all the thin films in UV, Visible and NIR regions with values from 70% to 90% in UV, from 75% to 93% in Visible and NIR. Tauc plots present particularities (rarely encountered behavior) with different segments or absorption changes showing the presence of multiple band gaps coming from the heterogeneity of the thin films (nanowires, gel and nanoparticles). Their values are 1.9 and 2.8 eV for DKRN-Gel, 2.1 and 3.1 eV for DKRN-UD and 2.1 and 3.2 eV for DKRN-D) corresponding respectively to the band gap of nanowires and that of the gel while the last ones correspond to the undoped and doped nanoparticles (3.1 and 3.2 eV respectively).

Realization of High Efficient Ferroelectric Perovskite Nanoparticles in Biopolymer-Matrix Solar Cells under Low Lighting

The idea to use ferroelectric materials (PZN-PT) came from the fact that the ferroelectric nature could facilitate electric charges accumulation on the interfaces of the solar cell. Thus, it would increase the open circuit voltage Voc which could reach more than 10 V. This would directly impact the efficiency which is proportional to Voc, thus hoping to obtain solar efficiency never equaled by the halide perovskites which are less stable and less resistant in aggressive environments. In this work, the solar cells produced gave an exceptional record efficiency of 39.32% with a very high open circuit voltage (Voc) of 3.50 V, a short-circuit current density (Jsc) of 0.118 mA/cm2 and an FF of 0.72 measured in the positive polarization direction under 3825 lux (5.6 W/m2) lighting. The negative polarization direction under 4781 lux (7 W/m2) lightning gave a current density of 2 mA/cm2, an open circuit voltage of 2.30 V and an FF of 0.35.

Thin films of binary amorphous Zn-Zr alloys developed by magnetron co-sputtering for the production of degradable coronary stents:A preliminary study

1.Introduction Vascular stents are endo-prostheses that allow the restoration of blood flow in case of obstruction of a vessel.A stent usually consists of a corrosion-resistant metal such as Nitinol,316L steel or a CoCr alloy[1].Many studies have been undertaken for the production of polymer degradable stents[2,3]or metallic stents[4,5]and,among these,devices made of pure zinc or crystallized alloy based on zinc obtained by molding and extrusion are promising in terms of biodegradability,biocompatibility and mechanical properties[6],but also concerning the degradation rate of the stent which should to be effective until arterial remodeling and tissue healing are complete[5].The objective of this preliminary study is the comparison of the degradation in simulated biological medium and the endothelial cytotoxicity of amorphous and crystallized thin ZnZr films according to their composition and structure.In this work,the thin layers were deposited on silicon substrates by magnetron co-sputtering.This technology is already used to make metal stents[7,8].

Real-time in situ magnetic measurement of the intracellular biodegradation of iron oxide nanoparticles in a stem cell-spheroid tissue model

The use of magnetic nanoparticles in nanomedicine keeps expanding and,for most applications,the nanoparticles are internalized in cells then left within,bringing the need for accurate,fast,and easy to handle methodologies to assess their behavior in the cellular environment.Herein,a benchtop-size magnetic sensor is introduced to provide real-time precise measurement of nanoparticle magnetism within living cells.The values obtained with the sensor,of cells loaded with different doses of magnetic nanoparticles,are first compared to conventional vibrating sample magnetometry(VSM),and a strong correlation remarkably validates the use of the magnetic sensor as magnetometer to determine the nanoparticle cellular uptake.The sensor is then used to monitor the progressive intracellular degradation of the nanoparticles,over days.Importantly,this real-time in situ measure is performed on a stem cell-spheroid tissue model and can run continuously on a same spheroid,with cells kept alive within.Besides,such continuous magnetic measurement of cell magnetism at the tissue scale does not impact either tissue formation,vibility,or stem cell function,including differentiation and extracellular matrix production.

Advances in the engineering of the outer blood-retina barrier:From in-vitro modelling to cellular therapy

The outer blood-retina barrier(oBRB),crucial for the survival and the proper functioning of the overlying retinal layers,is disrupted in numerous diseases affecting the retina,leading to the loss of the photoreceptors and ultimately of vision.To study the oBRB and/or its degeneration,many in vitro oBRB models have been developed,notably to investigate potential therapeutic strategies against retinal diseases.Indeed,to this day,most of these pathologies are untreatable,especially once the first signs of degeneration are observed.To cure those patients,a current strategy is to cultivate in vitro a mature oBRB epithelium on a custom membrane that is further implanted to replace the damaged native tissue.After a description of the oBRB and the related diseases,this review presents an overview of the oBRB models,from the simplest to the most complex.Then,we propose a discussion over the used cell types,for their relevance to study or treat the oBRB.Models designed for in vitro applications are then examined,by paying particular attention to the design evolution in the last years,the development of pathological models and the benefits of co-culture models,including both the retinal pigment epithelium and the choroid.Lastly,this review focuses on the models developed for in vivo implantation,with special emphasis on the choice of the material,its processing and its characterization,before discussing the reported pre-clinical and clinical trials.

Recent advances in Fe-based bioresorbable stents:Materials design and biosafety

Fe-based materials have received more and more interests in recent years as candidates to fabricate bioresorbable stents due to their appropriate mechanical properties and biocompatibility.However,the low degradation rate of Fe is a serious limitation for such application.To overcome this critical issue,many efforts have been devoted to accelerate the corrosion rate of Fe-based stents,through the structural and surface modification of Fe matrix.As stents are implantable devices,the released corrosion products(Fe^(2+)ions)in vessels may alter the metabolism,by generating reactive oxygen species(ROS),which might in turn impact the biosafety of Fe-based stents.These considerations emphasize the importance of combining knowledge in both materials and biological science for the development of efficient and safe Fe-based stents,although there are still only limited numbers of reviews regarding this interdisciplinary field.This review aims to provide a concise overview of the main strategies developed so far to design Fe-based stents with accelerated degradation,highlighting the fundamental mechanisms of corrosion and the methods to study them as well as the reported approaches to accelerate the corrosion rates.These approaches will be divided into four main sections,focusing on(i)increased active surface areas,(ii)tailored microstructures,(iii)creation of galvanic reactions(by alloying,ion implantation or surface coating of noble metals)and(iv)decreased local pH induced by degradable surface organic layers.Recent advances in the evaluation of the in vitro biocompatibility of the final materials and ongoing in vivo tests are also provided.