and Jean-Pierre Simonato * a
Fabrication of silver nanowires (AgNWs) with fine and independent control of both the diameter (from 30 to 120 nm) and length (from 5 to 120 μm) by concomitant addition of co-nucleants and temperature con- trol is demonstrated, and used for the preparation of size standards. Percolating random networks were fabricated using these standards and their optoelectronic properties were measured and compared with regard to the nanowire dimensions. The transparentelectrodes appear suitable for various applications and exhibit excellent performances (e.g. 16 ohm sq −1 at 93% transparency), with haze values varying from 1.6 to 26.2%. Besides, in vitro toxicological studies carried out on murine macrophages with the same size stan- dards revealed that AgNWs are weakly toxic (no toxicity observed below 50 μg mL −1 Ag), in particular com- pared to other silver nanoparticles. Short AgNWs (4 μm) appeared to be slightly more toxic than longer AgNWs (10 and 20 μm). Conversely, long AgNWs (20 μm) induced a more prolonged pro-inflammatory re- sponse in murine macrophages. These results contribute, in a safer by design approach, to promoting the use of short AgNWs. The global knowledge dealing with the combination of nanowire dimensions associ- ated with optoelectronic performances and related toxicity should encourage the rational use of AgNWs, and guide the choice of the most adequate AgNW dimensions in an integrated approach.
The past few years have seen a considerable amount of research devoted to nanostructured transparent conducting materials which play a pivotal role in many modern devices such as: solar cells, flexible light-emitting devices, touch screens and flexible transparent thin film heaters. Metallic nanowire networks have recently been a heavily researched subject. Currently, the most commonly used material for such applications is Tin-doped Indium oxide (ITO). Although ITO exhibits very good physical properties, indium scarcity and brittleness have prompted the search for alternative materials. Among emerging transparentelectrodes, silver nanowire (AgNW) networks appear as a promising substitute to ITO since these percolating networks exhibit excellent properties with sheet resistance of a few Ω/sq and optical transparency of 90%, fulfilling the requirements for many applications. It also shows very good electro-mechanical properties. In addition, the fabrication of these electrodes involves low-temperature process steps and upscaling methods, thus making them very appropriate for future use as TE for flexible devices.
There is an increasing demand for optoelectronic devices such as displays, solar cells, transparent heaters, sensors, light- emitting diodes (LEDs), paper-like displays and e-skins. 1,2 In order to produce such components, the development of trans- parent and mechanically exible electrodes remains a task of major importance. 3 Most of the transparentelectrodes reported to date rely on the use of metal oxide semiconductor layers, 4 indium tin oxide (ITO) being the most common. However, the scarcity and brittleness of the latter has prompted the search for indium-free and exible transparentelectrodes. 5 Silver nano- wire (AgNW) networks constitute one of the most promising alternatives, particularly for exible applications. 6 They combine high electrical conductance with excellent optical transparency, and show minimal conductance decrease with bending. 7,8 Furthermore, low temperature processing methods exist that enable conductance and transparency values on plastics that approach those on glass. 9 It is known from the literature that networks made from longer AgNWs achieve the highly desirable goal of being more conductive at a given transparency. 10 This is because, for a given areal coverage, longer NWs overlap more than shorter NWs, decreasing the extent of NW dead ends not connected into the network. 11
Study of the effect of thin ALD oxide coatings on the stability of silver nanowire based transparentelectrodes
S. AghazadehChors 1,2 , V. Nguyen 1 , M. Lagrange 1 , A. Khan 1,3 , T. Sannicolo 1,4 , N.D. Nguyen 2 , D. Muñoz-
Rojas 1 , D. Bellet 1,*
A considerable amount of research has been devoted lately to nanostructured transparent conducting materials, which play a pivotal role in many modern devices [ 1 – 4 ] such as solar cells [ 5 , 6 ], flexible light-emitting devices [ 7 ], touch screens, electromagnetic devices, and flexible transparent thin film heaters [ 8 – 11 ]. Currently, the most commonly used material for such applications, ITO (indium tin oxide), suffers from two major drawbacks: indium scarcity and brittleness. As a consequence, several emerging transparentelectrodes (TE) have been studied lately including grapheme [ 3 ], carbon nanotubes [ 3 ], metallic grids [ 12 ], and metallic nanowire (MNW) networks [ 13 – 15 ]. Silver nanowire (AgNW) networks appear to be promising substitutes for ITO since these percolating networks exhibit excellent properties with sheet resistances of a few Ω/sq associated to optical transmittances of 90% [ 6 , 16 ], fulfilling the requirements for many applications [ 14 ]. Bending tests clearly show that MNW networks also exhibit very good electro-mechanical properties [ 13 ] which are key assets for addressing emerging flexible electronics applications. In addition, the fabrication of these electrodes involves low-temperature process steps and upscaling methods, such as spray deposition, thus making them very appropriate for future use as TE in flexible device fabrication compatible with, for instance, roll-to-roll processing [ 17 ].
resistance between NWs, poor adhesion to the substrate and low stability. The blade coating method exhibits more advantages in terms of higher film uniformity and easier operation as well as more convenient process scale-up. However, this automatic technique has so far rarely been applied in the fabrication of large-area NW transparent conductive electrode, highly likely due to the relatively rough surface of the NW film processed from this technique. In our case, with the smart use of a flexible and transparent polymer, the transparent conductive electrodes showed smoother surface, better conductivity, superior mechanical flexibility as well as strong structural integrity. The polymer played multiple roles: passivation (protection), and performance and structure strengthening. Our Ag NW transparent conductive electrodes showed excellent flexibility, which can be repeatedly bent for 10,000 cycles without any performance degradation, significantly better than commercial ITO-based transparent conductive electrodes. To explore the high potential of these transparent conductive electrodes, as a proof of concept demonstration we fabricated foldable SPDs for smart window applications, using Ag NW network-based film as transparentelectrodes for the first time. Our devices showed large change in their optical transmittance (optical modulation 60.2 %) and fast switching time (21 s), as well as excellent stability. Significantly better than ITO- polyethylene terephthalate transparent conductive electrode- based electro-optic devices, the Ag NW electrode-based SPDs showed excellent mechanical flexibility, which can be folded by 180° for more than 200 cycles without obvious degradation of switching performance. The present method for fabricating large-area and ultra-flexible Ag NW transparent conductive electrode can be extended to fabricate a variety of NW-based nonplanar or curved electronic and optoelectronic devices in the future.
Hard carbons have been reported as high capacity carbon-based negative electrodes for Na-ion batteries 39 and their merit in terms of volumetric energy density should be evaluated. Hard carbons have very large surface areas and sodiation occurs through the adsorption of Na atoms onto the surfaces of nanoscopic pores throughout the hard carbon particles, which leads to low volume expansion. As a best-case scenario, we assume a zero volume expansion. The volu- metric energy density (1.7 Wh/cc) can then be calculated from the experimental hard carbon density 39 (1.5 g/cc), capacity 27 (340
The electrochemical behavior exhibited by the Nb 2 O 5 electrodes
provides a basis for distinguishing between different types of pseudo-
capacitive responses. Materials such as Nb 2 O 5 that do not undergo any
phase transformations during Li-ion intercalation can exhibit the char- acteristics of a pseudocapacitive process: i) a linear dependence of the open circuit potential with the state of charge; ii) an electrochemical process that is not limited by semi-infinite diffusion; and iii) a change in the oxidation state of the transition metal cation accompanied by high capacity values. 38 , 39 We consider such materials to be ‘intrinsic
Abu Sadat Md. Sayem, Student member, IEEE, Roy B. V. B. Simorangkir, Member, IEEE, Karu P. Esselle, Fellow, IEEE, Raheel M. Hashmi, Member, IEEE, and Hangrui Liu, Student member, IEEE
Abstract—A method to realize low-cost, optically transparent, flexible and unidirectional antennas is presented in this paper. The key to the method is making a flexible transparent reflector made using a new method- injection of pure water into a flexible transparent cavity that is made out of Polydimethylsiloxane (PDMS) polymer and integrating the flexible reflector with a flexible dipole made of transparent conducting mesh. This method is simple and inexpensive. Hence, it is useful for large scale production of transparent, flexible, robust and low-cost antennas as well as RF/microwave components for wearable body-area networks and other such systems that require flexible and transparent components. To validate the method, an antenna operating in the 2.45 GHz band was designed, fabricated and tested under various conditions. Its measured gain is 3.2 dBi and efficiency is 51%. To the best of our knowledge, this is the first water-based transparent flexible antenna. Due to the shielding effect of the water-based reflector, it produces low SAR in the human body when it is worn, as expected from a unidirectional antenna. Further, it is investigated and confirmed that the use of pure water in the reflector makes the antenna significantly more efficient as opposed to salt water.
In addition, composite films with a Nb2O5 mass loading up to 4 mg cm −2 were fabricated and cycled at 1 mV s −1 and 20 mV s −1 (Figure 4). Area-normalized capacitance values of 1.5 F cm −2 (425 F g −1 ) and 0.98 F cm −2 (270 F g −1 ) were measured for a 3.6 mg cm −2 film depending on rate. This shows that decent specific and areal ca- pacitance values can be obtained for thick electrodes of Nb2 O5 by us- ing standard electrode formulation methods, Nonetheless, electrodes in the 4 mg cm −2 range exhibit a stronger sweep rate dependence compared to the 1.2 mg cm −2 electrodes shown in Figures 3b and 3c. The causes of the rate dependence are currently being studied as both ionic and electronic conductivities decrease upon increasing the sample loading. We tend to consider that the lower level of electronic conduction is more important here because Nb2O5 is a wide bandgap material and even upon lithium intercalation, the conductivity is on the order of 3 × 10 −5 S cm −1 . 15 It is evident that improving the elec- trode formulation in terms of film composition (conducting agent and binder systems) as well as electrode fabrication and architecture will be necessary in order to achieve fast charge storage when the film thickness exceeds 40 μm.
The Enhancing the QUAlity and Transparency Of health Re- search (EQUATOR) network is a global initiative with the aim of improving the quality of research publications and research itself. A key mission in this context is to achieve accurate, complete and transparent reporting of health research studies to support repro- ducibility and usefulness. A core activity of the network is to as- sist in the development, dissemination and implementation of ro- bust reporting guidelines, where a guideline is deﬁned as “a check- list, ﬂow diagram or structured text to guide authors in report- ing a speciﬁc type of research” ( TheEQUATORNetwork (2008) ). Be- tween 2006 and 2019, more than 400 reporting guidelines have been published under the umbrella of the equator network. A well- known guideline is the CONSORT statement ( Moher et al., 2001 ; Schulz et al., 2010 ) developed for reporting of randomized con- trolled trials. Prominent journals, such as Lancet, JAMA or the British Medical Journal require the CONSORT checklist to be sub- mitted along with the actual paper when reporting results of a randomized controlled trial.
In this paper, we propose a scheme that addresses both of these problems: we ensure that voters get unique trackers and we close off the coercer’s window of opportunity by ensuring that the voters only learn their track- ing numbers after votes have been posted. The resulting scheme provides receipt-freeness, and indeed a good level of coercion-resistance while also providesinga more immediately understandable form of verifiability. The cryptographyis under the bonnet as far as the voter is concerned. The basic scheme still has a problem in some contexts: if the coercer is himself a voter there is a chance that the coerced voter might light on the coercer’s tracker, or the coercer simply claims that it is his. We argue that in many contexts this may be an acceptable threat when weighed against the more transparent verification provided by the scheme. Nonetheless, we describe some elaborations of the basic scheme to mitigate such threats.
Concluding Remarks and Future Perspectives
MXene chemistry is continuing to grow, with almost 30 compositions today and more being dis- covered routinely. Thanks to their key features (high accessible surface area and metallic-like electrical conductivity), 2D MXenes have emerged as promising candidates in many applications, one of the most promising being electrochemical energy storage. For instance, ultrahigh volumet- ric capacitance beyond 1500 F cm –3 can be achieved with Ti 3 C 2 MXenes when used as EC elec- trodes in aqueous acidic electrolytes and high power can be obtained by designing speciﬁc 3D porous or vertically aligned MXene electrodes. However, the narrow potential window that can be reached in aqueous electrolytes limits the energy density of these devices and their further use in practical applications.
4. The persistence layer must be memory-friendly, by using on-demand element loading and by removing from memory unused objects.
5. The persistence layer must outperform the execution time of current persis- tence layers when executing queries on VLMs using the standard API. In Figure 2, we show the high-level architecture of our proposal particular- ized for the EMF framework. Our solution consist in a transparent persistence manager behind the model-management interface, so that tools built over the modeling framework would be unaware of it. The persistence manager communi- cates with a map-database by a driver and supports a pluggable caching strategy. In particular we implement the NeoEMF/Map tool as a persistence manager for EMF on top of MapDB. NeoEMF also supports a graph backend .