Zeitschrift für elektrische und elektronische Systeme

Light harvesting efficiency in dye sensitized solar cell is currently enhanced by the employment of an additional TiO2 scattering layer hence increasing the overall film thickness. This has limitations on effective charge transport especially in dense electrolyte media due to the increased film thickness. The additional film layer further reduces light intensity on the adsorbed dye hence decreasing photocurrent generation. Therefore, there is still the challenge of light scattering optimization versus charge transport and photocurrent generation. In addition, though TiO2 is a relatively cheap material, the addition of TiO2 layer raises the production cost of the dye sensitized solar cell effectively and rendering it not cost effective. In this study, carbon black was employed to create artificial pores in TiO2 thin films to enhance light harvesting and hence photocurrent generation. TiO2 films deposited by screen printing method had 0, 1.0, 1.5, 2.0 and 3.0 wt% carbon black. On annealing of the films at 500oC in air for 30 minutes, carbon black decomposed leaving behind voids. Transmittance, reflectance and absorbance spectra of the films determined by a UV-Vis-NIR show that transmittance decreased as the carbon black concentration increased. On the other hand, both reflectance and absorbance increased with increase in carbon black concentration. Micrograph images obtained from both Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) show that the pore size of the films increased as the carbon black concentration increased.

Furthermore, the XRD results of these films show that the TiO2 are anatase and without any carbon contamination. Conductivity of the films determined using a four point probe was found to decrease with increase in pore size due to decrease in electrical contacts among the TiO2 molecules. The values 384.61, 352.11, 103.41, 52.41 and 35.29 Siemen’s cm-1 were determined for 0, 1.0, 1.5, 2.0 and 3.0, respectively. Current-Voltage (I-V) characteristics of the cell fabricated with different pore sizes were determined using a solar cell simulator at 100 mW/cm2 illumination. The results show that photocurrent generated by these cells increased from 6.1 mA/cm2 to a maximum value of 9.9 mA/cm2 as the wt % carbon black increased from 0 wt% to 1.5 wt %, respectively. Beyond 1.5 wt%, photocurrent begun to drop until it got to its minimum value of 4.7 mA/cm2 at 3.0 wt%. The overall efficiencies for 0, 1.0, 1.5, 2.0 and 3.0 wt% were found to be 2.3, 2.6, 4.3, 2.4 and 1.4 %, respectively. The result shows an improvement in the photovoltaic performance of DSSC as a result of the artificial voids created. However, beyond the optimum concentration of 1.5 wt%, the cell performance begun to decline. This approach greatly enhanced the current density of the cells and consequently the overall conversion efficiency significantly.

Dye sensitized solar cells (DSSCs) rely on the absorption of photons by the dye molecules which are transported to the conduction band of the TiO2 electrode. The microstructure, energy gap and the absorption spectra of the TiO2 electrodes highly affects the efficiency of the cell. In this paper, the absorption spectra and energy gap has been studied by varying the thickness of the TiO2 paste. Nanocrystalline TiO2 thin films were deposited on ITO glass substrate with three different thickness (4.54µm, 7.12µm and 12.3µm) by using doctor blade method. After deposition all the samples were sintered at 450Ë?C after deposition to enhance the particle bonding and for achieving better adhesion. The samples were characterized by UV-VIS spectra for determining the absorption spectra and Scanning Electron Microscopy (SEM) for investigating the thickness and the surface morphology. Fabricating the electrodes with different thickness showed significant changes in the energy gap and from the results it can be concluded that the energy gap increases with the increased thickness. The highest energy gap of 2.25ev and absorption 3.791 was achieved by 12.3µm thick sample. The absorption spectra also shows better absorption throughout the whole visible light range but the SEM images suggests that 12.3µm thick sample shows cracks all over the deposited region which will cause current leakage when the cell is assembled. Therefore, the optimum result was achieved by 7.12µm thick sample providing 1.9 ev energy gap and 3.91 absorption peak.

DSSCs has been accepted widely to be used as potential solar cell apart from traditional solid-state cells. It is considered as photo electrochemical solar cell that consists of mesoporous metal oxide semiconductor layer on transparent conductive glass, which is used as working electrode [1]. Other major components are the organic or inorganic dye material, electrolyte and the counter electrode. Oxide semiconductors possess decent stability under irradiation but due to the large bandgap this kind of material cannot absorb visible light directly [2]. In case of dye-sensitized solar cell, TiO2 is mostly used as the oxide semiconductor having 3.2ev energy gap [3]. To recover the absorption issue organic/inorganic dyes are used to sensitize the TiO2 based electrode. Dyes help to excite the electrons received from the sunlight to change its state and upon excitation; the dye molecule injects the electron towards the conduction band of the TiO2 based electrode. The semiconductor electrode then transports the electron to external load. The efficiency of this kind of solar cell highly affected depending on the performance of the TiO2 coated electrode [4]. The TiO2 paste formulation is very crucial since it helps to adsorb large amount of dye molecule to the 2 1234567890‘’“” ICAMME 2017 IOP Publishing IOP Conf. Series: Materials Science and Engineering 290 (2018) 012004 doi:10.1088/1757-899X/290/1/012004 electrode surface and using Ru-complex dye the energy conversion efficiency was achieved 11% with standard measurements [5]. The most important parameters like surface area, roughness, pore size, film thickness, sintering temperature, chemicals greatly affects the result and these properties can be controlled during the film preparation process.

 

The performance of particles is highly influenced by particle size, shape, surface chemistry, elasticity and permeability1. Electrohydrodynamic jetting technique has proven to be a versatile technique to fabricate particles with different shapes and sizes. In this work, we have fabricated topologically anisotropic cup shaped made from polylactide (PLA)/ poly[methylmethacrylate-co-2-(2-bromopropionyloxy) ethyl methacrylate]  (75/25) of ~6 μm size using electrojetting technique. Solution and processing parameters were changed to understand the mechanism of cup shape formation and to control particle’s shape from cups to discoids. Surface initiated atom transfer radical polymerization (ATRP) of stimuli responsive DMAEMA (2-dimethylamino ethyl methacrylate) was subsequently carried out for 1 h onto the surface of cup shaped particles to observe pH responsiveness of the modified anisotropic particles. An interesting change in the morphology of cup shaped particles was observed which changed to elongated cup and showed significant swelling under acidic pH (swelling ratio:~1.6), also enhanced dye adsorption at specific pH was observed by optical microscope and confocal laser scanning microscope implying that DMAEMA polymerization happened onto the surface of the composite microparticles. The Raman microscopy and FTIR spectra obtained from the particles after polymerization further confirmed the immobilization of pH responsive poly(DMAEMA) brushes onto the cup shaped particles which may potentially function as triggered/targeted drug delivery vehicles. Moreover, the brush modified cup shaped particles were found to be two times more efficient in adsorbing dye compared to disc shaped one indicating a clear advantage of using cup shaped particles over other shapes for immobilizing/adsorbing charged species e.g. sensitive biomolecules.

Responsive polymer brushes are a category of polymer brushes that are capable of conformational and chemical changes in response to external stimuli. They offer unique opportunities for the control of bio−nano interactions due to the precise control of chemical and structural parameters such as the brush thickness, density, chemistry, and architecture. The design of responsive brushes at the surface of nanomaterials for theranostic applications has developed rapidly. These coatings can be generated from a very broad range of nanomaterials, without compromising their physical, photophysical, and imaging properties. Although the use of responsive brushes for nanotheranostic remains in its early stages, in this review, the aim is to present how the systems developed to date can be combined to control sensing, imaging, and controlled delivery of therapeutics. The recent developments for such design and associated methods for the synthesis of responsive brushes are discussed. The responsive behaviors of homo polymer brushes and brushes with more complex architectures are briefly reviewed, before the applications of responsive brushes as smart delivery systems are discussed. Finally, the recent work is summarized on the use of responsive polymer brushes as novel biosensors and diagnostic tools for the detection of analytes and biomarkers.systems closely resembles that of CO2 transport through an aqueous solution. We have interpreted this to mean that the hydrate and the matrix mineral surfaces are separated by liquid-containing channels. These channels will serve as escape routes for released natural gas, as well as distribution channels for injected CO2.

Nanotheranostics integrate diagnostic and therapeutic functions in one system and have received significant attention in the past few decades for the improvement of diagnosis, and the prevention and treatment of diseases.[1, 2] Advances in nanotheranostics benefit greatly from deeper understanding of the interactions between nanomaterials and biological systems, the refinement of multifunctional nanohybrids for simultaneous diagnosis and therapy, and the ability to harness the unique physicochemical properties of nanomaterials for specific and selective detection and treatment of diseases.[3] Although having shown promising results in many in vitro and in vivo studies, the concept of nanotheranostics remains a new paradigm and its clinical use is still in its infancy. In addition to challenges in commercialization, one of the key issues related to the translation of nanotheranostics remains the control and understanding of nano-bio interactions.[2] Upon interaction with biological systems, the physiological properties of nanoparticles determine their stability, pharmacokinetics, biodistribution, and toxicity profiles.[4] Those are crucial parameters for assessing their biocompatibility and avoid any adverse immunoreaction or inflammation,[5] but also improve efficacy as diagnostic and therapeutic tools. Hence, different techniques and modification strategies of nanomaterials have been developed and characterized to overcome these limitations. Historically, the decoration of nanomaterials with polymers has been particularly successful to tailor and design the properties of these systems.[6] This includes self-assembly of monolayers,[7] the stabilization of nanoparticles via ligand exchange methods,[8] and the coating with polyelectrolyte assemblies.[9] These strategies have enabled the improved dispersity, prolonged circulation time via PEGylation,[10] enhanced cellular uptake and loading efficiencies of the therapeutics,[11] and increased availability to link with other biomolecules for targeting[12] or other purposes.

In particular, polymer brushes, defined as thin polymer coatings in which individual polymer chains are tethered by one chain end to a solid interface, are considered among the most powerful tools to control interface properties. Polymer brushes generated via the “grafting from” approach, in which initiating moieties are coupled to surface and allow the growth of polymer chains, are extremely attractive for the precise design of biomaterials and control over bio-nano interactions. A number of controlled/“living” polymerization techniques, in particular those based on radical chemistry have been applied to generate such coatings on various types of substrates.[13] It enables the grafting density, the thickness, and the chemistry of the coating to be manipulated very readily without altering the bulk mechanical properties of biomaterials.

The Mg–12Gd–1Er–1Zn–0.9Zr (wt%) alloy with ultra-high strength and ductility was developed via hot extrusion combined with pre-deformation and two-stage aging treatment. The age-hardening behavior and microstructure evolution were inves- tigated. Pre-deformation introduced a large number of dislocations, resulting in strain hardening and higher precipitation strengthening in the subsequent two-stage aging. As a result, the alloy showed a superior strength–ductility balance with a yield strength of 506 MPa, an ultimate tensile strength of 549 MPa and an elongation of 8.2% at room temperature. The finer and denser β′ precipitates significantly enhanced the strength, and the bimodal structure, small β-Mg5RE phase as well as dense γ′ precipitates ensured the good ductility of the alloy. It is suggested that the combination of pre-deformation and two-stage aging treatment is an effective method to further improve the mechanical properties of wrought Mg alloys.

Due to the great potential for weight reduction in aerospace and automotive industries, Mg-RE(- Zn) (RE: rare earth) alloys with outstanding mechanical performance have been widely investigated for decades. Heavy RE elements such as Gd and Y are frequently selected as the main alloying elements, because they usually have high solid solubility in Mg matrix at elevated temperatures. In particular, Gd addition significantly enhances the age-hardening response due to the sharp decline in equilibrium solid solubility of Gd in Mg with decrease in temperature (from 23.5 wt% at 548 °C to only 3.8 wt% at 200 °C) [1,2,3]. The main strengthening phase formed in Mg-Gd based alloys during aging treatment is prismatic β′ precipitates with a base centered orthorhombic (bco) structure. A series of high-strength Mg-Gd(- Zn) based alloys have been successfully fabricated by deformation processing such as extrusion [3, 4] and rolling [5, 6]. For example, the Mg-8Gd-1Er-0.5Zr (wt%) alloy [5] and Mg-11.7Gd-4.5Y-1Nd-1.5Zn-0.5Zr (wt%) alloy [6] developed through extrusion, rolling and aging both have over 500 MPa yield strength. However, magnesium alloys are still restricted in engineering applications because of their lower yield strength (YS) and ductility, and hence, there are large spaces and challenges in achieving Mg alloys with ultra-high strength and ductility [7]. Besides alloy design, an effective processing method is also important to realize synchronous improvement in strength and ductility.

For precipitation hardened alloys, the size and distribution of precipitates are crucial for strengthening [7, 8]. The control of precipitation can be obtained by increasing nucleation rate and optimizing aging treatment. Introducing lattice defects has been noted to facilitate heterogeneous nucleation and enhance age-hardening response [9, 10]. A high-strength Mg-14Gd-0.5Zr (wt%) alloy was prepared by extrusion, cold rolling and aging, showing a YS of 445 MPa, an ultimate tensile strength (UTS) of 482 MPa and an elongation (EL) of 2.0% [10]. For the peak-aged alloys, pre-deformation such as cold rolling or tensile/compress deformation improves precipitation strengthening but causes severe loss of ductility at the same time. It is also reported that a rapid annealing out of dislocations at the beginning of aging would greatly reduce the strengthening effect of pre-deformation, and little further improvement in strength is expected for tensile deformation with larger strain.

The Mg-12Gd-1Er-1Zn-0.9Zr (wt%) alloy was prepared from pure Mg, pure Zn, Mg-30Gd (wt%), Mg-30Er (wt%) and Mg-12Zr (wt%) master alloys via conventional casting. The ingot was melted in an electric resistance furnace under the protection of mixed SF6 (5 vol%) + N2 (95 vol%) gas. The melt was poured into a steel mold and then cooled down in water. The actual chemical composition of the cast alloy was measured by X-ray fluorescence analyzer (XRF, Magic PW2403), which was Mg-12.39Gd-1.05Er-1.13Zn-0.88Zr (wt%). Solution treatment was performed at 520 °C for 12 h and then immediately quenched into warm water. Indirect extrusion was conducted at ~ 405 °C under an extrusion ratio of 10, followed by quenching in water at room temperature. Some extruded rods were then subjected to pre-deformation with a plastic strain of ~ 4% using a universal testing machine. Tensile deformation was conducted parallel to the extrusion direction (ED) at room temperature with a strain rate of 1 × 10-4 s-1. The extruded rods without/with pre-deformation were denoted as E and EPD samples, respectively. Subsequently, two-stage aging (TSA) was carried out by pre-aging at 100 °C for 1 h (stage I), followed by aging at 200 °C (stage II). The peak-aged samples were denoted as E + TSA and EPD + TSA.

Microstructures were observed using electron backscatter diffraction (EBSD) and transmission electron microscope (TEM, JEOL JEM-2100FX). EBSD was conducted on a scanning electron microscope (SEM, FEI QUANTA FEG 650) equipped with an HKL-EBSD system. The macro-texture of samples was measured by X-ray diffraction (XRD, BRUKER D8 DISCOVER). The hardness was measured under a load of 100 g and holding time of 10 s by Vickers hardness testing. Dog-bone shaped specimens (gauge dimensions: Ф 5 mm × 25 mm) were machined for tensile testing on a DNS-20 universal test machine with a strain rate of 5 × 10-4 s-1 at room temperature. The tensile direction was parallel to the ED.

The convergence of nanotechnologies generates synergies among different technologies to say, nanotechnologies, neurotechnology, computers and biotechnology, these technologies must converge itchier regulations, the application of medical devices in nanotechnologies should lead us to a link between the technical committee TC 210 and ISO technical committee 229 link that does not exist in our work in this moment In this do an analysis of the management of risk from an optical NC-ISO 14971. Studying the global trend in this respect as imported for manufacturers medical Devices worldwide. The convergences of technologies are a consequence of atomic precision, where the boundary between the biotic and abiotic mute blur the interaction. The interaction between nanotechnologies, biotechnology and informatics and communications (NBI) generates a synergy of unusual consequences of all is known that the industry of semiconductor)s is the one of greater precision that is atomic, the new medical devices that will be applied in the teranocis will dose Physical principles that will be governed under the laws of quantum mechanicsbut there are two problems that have not been solved even though they are one the non-existence of quantum biology and the transition from quantum to classical mechanics. On the other hand, the redefinition of the international system of units based on the universal constants that will be implemented by 2019 has a deficiency that is the second that redefirms implies redefinition of the meter the chain of traceability proposed for nanometrology presents a serious difficulty when putting the microcopy of atomic force wing of effect  tunnel situation that is changing the verification of the Wiedemann-Franz law at atomic level yields a result where the phononic component is taken into account, a result that launches STM to the cusp of the chain of traceability above inclusive of interferometry.

Technological convergence, in general, refers to the trend or phenomenon where two or more independent technologies integrate and form a new outcome. One example is the smartphone. A smartphone integrated several independent technologies—such as telephone, computer, camera, music player, television (TV), and geolocating and navigation tool—into a single device. The smartphone has become its own, identifiable category of technology, establishing a $350 billion industry.

 

Of the three closely associated convergences—technological convergence, media convergence, and network convergence—consumers most often directly engage with technological convergence. Technological convergent devices share three key characteristics. First, converged devices can execute multiple functions to serve blended purpose. Second, converged devices can collect and use data in various formats and employ machine learning techniques to deliver enhanced user experience. Third, converged devices are connected to a network directly and/or are interconnected with other devices to offer ubiquitous access to users.

Technological convergence may present a range of issues where Congress may take legislative and/or oversight actions. Three selected issue areas associated with technological convergence are regulatory jurisdiction, digital privacy, and data security. First, merging and integrating multiple technologies from distinct functional categories into one converged technology may pose challenges to defining regulatory policies and responsibilities. Determining oversight jurisdictions and regulatory authorities for converged technologies can become unclear as the boundaries that once separated single-function technologies blend together. A challenge for Congress may be in delineating which government agency has jurisdiction over various converged technologies. Defining policies that regulate technological convergence industry may not be simple or straightforward. This may further complicate how Congress oversees government agencies and converged industries due to blending boundaries of existing categories.

Second, converged technologies collect and use personal and machine data which may raise digital privacy concerns for consumers. Data collection and usage are tied to digital privacy issues because a piece or aggregation of information could identify an individual or reveal patterns in one’s activities. Converged or smart technologies leverage large volumes of data to try to improve the user experience by generating more tailored and anticipatory results. However, such data can potentially identify, locate, track, and monitor an individual without the person’s knowledge. Such data can also potentially be sold to third-party entities without an individual’s awareness. As the use of converged technologies continues to propagate, digital privacy issues will likely remain central.

 

Third, data security concerns are often associated with smart devices’ convenient ubiquitous features that may double as vulnerabilities exploited by malicious actors. Data security, a component of cybersecurity, protects data from unauthorized access and use. Along with digital privacy, data security is a pertinent issue to technological convergence. As converged devices generate and consume large volumes of data, multiple data security concerns have emerged: potentially increased number of access points susceptible to cyberattacks, linkage to physical security, and theft of data.

Relatively few policies are in place for specifically overseeing technological convergence, and current federal data protection laws have varied privacy and data security provisions for different types of personal data. To address regulatory, digital privacy, and data security issues, Congress may consider the role of the federal government in an environment where technological evolution changes quickly and continues to disrupt existing regulatory frameworks. Regulating technological convergence may entail policies for jurisdictional deconfliction, harmonization, and expansion to address blended or new categories of technology. One approach could be for Congress to define the role of federal government oversight of digital privacy and data security by introducing new legislation that comprehensively addresses digital privacy and data security issues or by expanding the current authorities of federal agencies. When considering new legislation or expanding the authorities of federal agencies, three potential policy decisions are (1) whether data privacy and data security should be addressed together or separately, (2) whether various types of personal data should be treated equally or differently, and (3) which agencies should be responsible for implementing any new laws.

 

It is well know that zinc oxide (ZnO) is one of the most significant II-VI semiconductor materials attracting enormous interests and research, especially in the application of optoelectronic, electromechanical, electrochemical, photovoltaic devices, etc. owing to its excellent intrinsic properties. In addition, innovative designs of various configuration structures of ZnO nanowires (NWs)/substrate have been developed for enhancing performance and multifunctional applications as piezoelectric nano-generators and sensors. In our project, the vertically aligned ZnO NW arrays exhibiting a 1031 nm length and 80-100 nm diameter, are grown on a 40nm-thick ZnO seed layer deposited on top of a 500µm-thick silicon substrate, and are embedded in a 1464 nm dielectric layer of polymethyl-methacrylate (PMMA). Up to now, a lot of publications has been reported on exploiting piezoelectric behavior of ZnO nanowire for various applications but very few of them provided a reliable method of characterization for these materials. Thus, the idea of this study focuses on characterizing the electromechanical response of vertically aligned ZnO NW arrays/polymer composite structure via an experimental test bench. Under dynamic mechanical excitation at 1 Hz , two electric configurations were performed including an application of a dynamic electric excitation from a sinusoidal voltage of 1 kHz and a short-circuit condition. The static electrical measurment confirmed the capacitive property of composite is dominant with respect to the resistive one and electromechanical characterization demonstrated an existence of piezoelectric property of the ZnO structure (d33 ~ 1.25 pC/N). The results will lead to a better understanding of the multi-physic coupling of ZnO materials in order to validate its feasibility for flexible sensors adapted to biological media. In the future, different designs of tunable ZnO NW length and radius, together with optimization of base structure and polymer matrix will be explored in order to drastically boost the electromechanical coupling of the proposed material. Nanowires (NW) are defined here as metallic or semiconducting particles having a high aspect ratio, with cross-sectional diameters « 1 μm, and lengths as long as tens of microns. Well-aligned one-dimensional nanowire arrays have been widely investigated as photoelectrodes for solar energy conversion because they provide direct electrical pathways ensuring the rapid collection of carriers generated throughout the device , as well as affording large junction areas and low reflectance owing to light scattering and trapping. Solar energy conversion is a highly attractive process for clean and renewable power for the future. Excitonic solar cells (SCs), including organic and dye-sensitized solar cells (DSSC), appear to have significant potential as a low cost alternative to conventional inorganic photovoltaic (PV) devices. The synthesis and application of nanostructures in solar cells have attracted much attention. Metal oxide nanowire (NW) arrays with large surface area and short diffusion length for minority carriers represent a new class of photoelectrode materials that hold great promise for photoelectrochemical (PEC) hydrogen generation applications. Up to now, various metal oxide nanostructures such as TiO2, ZnO, Fe2O3, ZrO2, Nb2O5, Al2O3, and CeO2 have been successfully employed as photoelectrodes in SCs. Among the above-mentioned metal oxide nanostructures, the study of TiO2 and ZnO is of particular interest due to the fact that they are the best candidates as photoelectrode used in SCs. However, the advantage offered by the increased surface area of the nanoparticle film is compromised by the effectiveness of charge collection by the electrode. For DSSCs, the traditional nanoparticle film was replaced by a dense array of oriented, crystalline nanostructures to obtain faster electron transport for improving solar cell efficiency. A typical high-efficiency DSSC (Grätzel, 2009) consists of a TiO2 nanocrystal thin film that has a large surface area covered by a monolayer of dye molecules to harvest sunlight. Comparedwith TiO2, ZnO shows higher electron mobility with similar bandgap and conduction band energies. ZnO is a direct wide bandgap semiconductor (Eg = 3.4 eV) with large exciton binding energy (~60 meV), suggesting that it is a promising candidate for stable room temperature luminescent and lasing devices. Therefore, ZnO nanowires is an alternative candidate for high efficient SCs. So far, various ZnO nanostructures have been extensively investigated for SCs. In the early reports on ZnO-based DSSCs, ZnO nanoparticles were often used as the photoanode prepared by a conventional doctor blade technique (Keis et al., 2002; Keis et al., 2002). Lévy-Clément et al. (2005) reported experimental results on a new ETA solar cell fabricated from an electron-accepting layer of free-standing ZnO nanowires. Law et al. (2005) presented first the ordered nanowire DSSC. The nanowire DSSC is an exciting variant of the most successful of the excitonic photovoltaic devices. As an ordered topology that increases the rate of electron transport, a nanowire electrode may provide a means to improve the quantum efficiency of DSSCs in the red region of the spectrum, where their performance is currently limited. Raising the efficiency of the nanowire cell to a competitive level depends on achieving higher dye loadings through an increase in surface area. Law et al. (2006) described the construction and performance of DSSCs based on arrays of ZnO nanowires coated with thin shells of amorphous Al2O3 or anatase TiO2 by atomic layer deposition.