Fracture behaviour of silver nanowire films during shear deformation.

Silver nanowire films have a wide application prospect in flexible electronics, while it is a noticeable problem that the silver nanowires break due to the shear force under the mass production film cutting or extreme service conditions. In this paper, the shear fracture behaviour of silver nanowire films with different structural parameters was studied under the extreme shear failure tests. The load-displacement curve was obtained from the nano-indentation test, while the hardnessH, the elastic modulusEand the plastic properties represented by the ratio ofH3/E2of silver nanowire films with different diameters and thicknesses were calculated. On the other hand, based on the load-displacement curve, the stress-strain curve can be obtained through the finite element method simulation. The plastic properties can also be judged by the lower limit of yield strength from simulated stress-strain curve. Combined with characteristic crack propagation range, the relationship between plasticity and shear fracture was found, which was further disclosed by in-depth microstructure analysis. The results show that the better the plasticity of silver nanowire films, the stronger the resistance to shear fracture.

Highly accurate particulate matter detection assisted by an air heater based on a silver nanowire film.

Recently, many studies have been carried out to solve the particulate matter pollution problem. However, the detection accuracy for particulate matter in the atmosphere remains unsatisfactory due to the influence of the air relative humidity. Herein, we report a Ag nanowire film air heater to enhance the detection accuracy through internal heating. From air temperature and air relative humidity relationship analysis, it has been found that the Ag nanowire film air heater can form the most suitable air relative humidity in the detection system, thereby enhancing the detection accuracy. Consequently, the Ag nanowire film air heater-assisted light scattering particulate matter detector has achieved tremendous enhancement in its detection accuracy, which is comparable with the data obtained by the beta gauge method. Film resistance plays a key role in internal air temperature distribution and the resultant air relative humidity at given voltages. To achieve the most suitable air relative humidity for continuous online monitoring, response time and power consumption should be balanced. Therefore, guidance for designing Ag nanowire films with proper resistance used in an optional-sized detector has been given for quick response, high accuracy and low power consumption. This work is of significance for providing insight for future studies in particulate matter detection and pollution remediation.

Sandwich-Structured Silver Nanowire Transparent Conductive Films with 3H Hardness and Robust Flexibility for Potential Applications in Curved Touch Screens.

A sandwich-structured bottom hard-coat/silver nanowire/top hard-coat (BHC/AgNW/THC) transparent conductive film (TCF) has been prepared by embedding the functional AgNW layer between two HC layers. The BHC/AgNW/THC TCFs show high scratch resistance with a hardness of 3H due to the enhanced adhesion to the substrate. In addition, the BHC/AgNW/THC TCFs exhibit a transmittance of 90.6% and a haze of 1% at 550 nm under a sheet resistance of 72 Ω/sq. Furthermore, highly enhanced long-term stability has been guaranteed by the HC layers due to their excellent gas barrier property. The amazing fact is that hard coating has little effect on the flexibility of AgNW films especially under extreme bending conditions and negligible resistance change could be observed after bending over thousands of times. Consequently, the greatly improved performance of BHC/AgNW/THC TCFs provided by employing hard coating layers paves the way for real-world applications of flexible AgNWs in vast areas that rigid indium tin oxide is not suitable.

Tackling the Stability Issues of Silver Nanowire Transparent Conductive Films through FeCl3 Dilute Solution Treatment.

Silver nanowires (AgNWs) have been investigated as alternatives to indium tin oxide in transparent conductive films (TCFs) for electronics. However, AgNW TCFs still pose stability issues when exposed to thermal, chemical, and mechanical stimuli. Herein, we demonstrate a facile and effective route to improve stability by treating the films with dilute ferric chloride solution. Our results indicate that after treatment the films exhibit a dramatically enhanced stability against aging, high temperature oxidation, chemical etching, sulfurization, and mechanical straining. Size-dependent instability is fully explored and explained regarding surface atomic diffusion, which could be blocked by enhancing the activation energy of surface diffusion through forming a AgCl cap under ferric chloride solution treatment. Chemisorption-related Fermi level shift of silver nanowires is applied to tune their chemical reactivity to ferric chloride solution for balancing between size-dependent stability improvement and maintaining optoelectrical properties. Owing to the dilute treatment solution, the treated films exhibit a negligible change in light transmittance, whereas sheet resistance decreases by 30% and flexibility increases because of capillary-force-induced welding of contacting AgNWs and AgCl layer mediated tightening. These findings are significant for real-world applications of AgNW TCFs.

Silver Nanowire Transparent Conductive Films with High Uniformity Fabricated via a Dynamic Heating Method.

The uniformity of the sheet resistance of transparent conductive films is one of the most important quality factors for touch panel applications. However, the uniformity of silver nanowire transparent conductive films is far inferior to that of indium-doped tin oxide (ITO). Herein, we report a dynamic heating method using infrared light to achieve silver nanowire transparent conductive films with high uniformity. This method can overcome the coffee ring effect during the drying process and suppress the aggregation of silver nanowires in the film. A nonuniformity factor of the sheet resistance of the as-prepared silver nanowire transparent conductive films could be as low as 6.7% at an average sheet resistance of 35 Ω/sq and a light transmittance of 95% (at 550 nm), comparable to that of high-quality ITO film in the market. In addition, a mechanical study shows that the sheet resistance of the films has little change after 5000 bending cycles, and the film could be used in touch panels for human-machine interactive input. The highly uniform and mechanically stable silver nanowire transparent conductive films meet the requirement for many significant applications and could play a key role in the display market in a near future.

A one-step route to Ag nanowires with a diameter below 40 nm and an aspect ratio above 1000.

The synthesis of long and thin Ag nanowires is important to achieve high performance transparent conductive films. We report a one-step route to synthesizing Ag nanowires with an average diameter of ∼25 nm and an aspect ratio larger than 1000 by utilizing a mixture of poly(vinylpyrrolidone) with different molecular weights as the capping agent in a polyol reduction reaction.

Thermal response of transparent silver nanowire/PEDOT:PSS film heaters.

Thermal response behavior of transparent silver nanowire/PEDOT:PSS film heaters are intensively studied for manipulating heating temperature, response time, and power consumption. Influences of substrate heat capacity, heat transfer coefficient between air and heater, sheet resistance and dimension of Ag nanowire film, on the thermal response are investigated from thermodynamic analysis. Suggestion is given for practical applications that if other parameters are fixed, Ag nanowire coverage can be utilized as an effective parameter to adjust the thermal response. The heat transfer coefficient plays opposite roles on thermal response speed and achievable steady temperature. A value of ≈32 W m(-2) K(-1) is obtained from transient process analysis after correcting it by considering heater resistance variation during heating tests. Guidance of designing heaters with a given response time is provided by forming Ag nanowire film with a suitable sheet resistance on substrate of appropriate material and a certain thickness. Thermal response tests of designed Ag heaters are performed to show higher heating temperature, shorter response time, and lower power consumption (179 °C cm(2) W(-1)) than ITO/FTO heaters, as well as homogeneous temperature distribution and stability for repeated use. Potential applications of the Ag heaters in window defogging, sensing and thermochromism are manifested.

A route to phase controllable Cu2ZnSn(S(1-x)Se(x))4 nanocrystals with tunable energy bands.

Cu2ZnSn(S(1-x)Se(x))4 nanocrystals are an emerging family of functional materials with huge potential of industrial applications, however, it is an extremely challenging task to synthesize Cu2ZnSn(S(1-x)Se(x))4 nanocrystals with both tunable energy band and phase purity. Here we show that a green and economic route could be designed for the synthesis of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals with bandgap tunable in the range of 1.5-1.12 eV. Consequently, conduction band edge shifted from -3.9 eV to -4.61 eV (relative to vacuum energy) is realized. The phase purity of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals is substantiated with in-depth combined optical and structural characterizations. Electrocatalytic and thermoelectric performances of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals verify their superior activity to replace noble metal Pt and materials containing heavy metals. This green and economic route will promote large-scale application of Cu2ZnSn(S(1-x)Se(x))4 nanocrystals as solar cell materials, electrocatalysts, and thermoelectric materials.

Photocurrent enhancement for Ti-doped Fe2O3 thin film photoanodes by an in situ solid-state reaction method.

In this work, a higher concentration of Ti ions are incorporated into hydrothermally grown Ti-doped (2.2% by atomic ratio) micro-nanostructured hematite films by an in situ solid-state reaction method. The doping concentration is improved from 2.2% to 19.7% after the in situ solid-state reaction. X-ray absorption analysis indicates the substitution of Fe ions by Ti ions, without the generation of Fe²âº defects. Photoelectrochemical impedance spectroscopy reveals the dramatic improvement of the electrical conductivity of the hematite film after the in situ solid-state reaction. As a consequence, the photocurrent density increases 8-fold (from 0.15 mA/cm² to 1.2 mA/cm²), and it further increases up to ∼1.5 mA/cm² with the adsorption of Co ions. Our findings demonstrate that the in situ solid-state reaction is an effective method to increase the doping level of Ti ions in hematite films with the retention of the micro-nanostructure of the films and enhance the photocurrent.

Micro-nano-structured Fe2O3:Ti/ZnFe2O4 heterojunction films for water oxidation.

Iron(III) oxide photoelectrodes show promise in water oxidation applications. In this study, micro-nano-structured hematite films are synthesized, and Ti ions are doped to improve photoelectric conversion efficiency. The photocurrent increases for enhanced electrical conductivity. Further enhanced photocurrent is achieved for Fe(2)O(3):Ti/ZnFe(2)O(4) heterojunction electrodes. Cyclic voltammograms combined with optical absorbance examinations demonstrate that the conduction and valence band edges of ZnFe(2)O(4) shift from those of Ti doped Fe(2)O(3) to the negative direction, which facilitates the efficient separation of electron-hole pairs at the Fe(2)O(3):Ti/ZnFe(2)O(4) interface. These findings demonstrate that, by doping hematite and by engineering the interface between the hematite and the electrolyte, charge separation can be effectively promoted and photocurrent density can be dramatically increased.

A new route to fabricate large-area, compact Ag metal mesh films with ordered pores.

Ordered Si nanowire (SiNW) arrays can be fabricated by metal-assisted chemical etching. The metal mesh films (MMFs) are extremely important for achieving a high quality of the SiNWs. We have developed a two-step chemical deposition method to obtain compact porous Ag MMFs. By the separation of the nucleation and growth stages of the metal in the two-step deposition processes, the overgrowth of the metals to form randomly aggregated irregular metal particles can be overcome. Hexagonally arranged polystyrene (PS) latex microspheres have been employed as a template for the deposition of porous Ag MMFs. The spacing of the pores in the Ag MMFs is determined by the diameter of PS microspheres, and the pore size can also be tuned by changing Ar plasma etching time. One of the main advantages of the two-step deposition method lies in that Ag MMFs can be produced with PS microspheres that are not limited to a single layer, which dramatically simplifies the tedious processes of producing a monolayered PS template. The two-step chemical deposition method shows great potential in metal-assisted chemical etching.

An investigation of the electronic properties of MgO doped with group III, IV, and V elements: trends with varying dopant atomic number.

The electronic properties and the trends with varying dopant atomic number of III, IV, and V main group elements in MgO have been investigated using density functional theory. It is found that all of the geometry-optimized systems with the dopant atom replacing O in MgO exhibit half-metallic ferromagnetic properties regardless of metal or non-metal doping, and this agrees well with other theoretical computations. However, because of the high formation energy of metal atoms substituting for O atoms, we have calculated metal atom substitution for the Mg atom in MgO. We found that this system has a paramagnetic state and the formation energy is much lower than that of the former case. Finally, we have performed calculations for MgO doped with an F atom which shows a metallic behavior.

A facile method for effective doping of Tb3+ into ZnO nanocrystals.

A technical challenging issue in rare-earth ion doping in ZnO nanocrystals has been tackled in this communication by a novel isocrystalline core-shell protocol, and the fabricated ZnO:Tb(3+)/ZnO core/shell nanocrystals showed efficient doping and excellent optical properties.