Highly conductive and transparent coatings from flow-aligned silver nanowires with large electrical and optical anisotropy

Self-Assembly of Silver Nanowire Films for Surface-Enhanced Raman Scattering Applications

The development of SERS detection technology is challenged by the difficulty in obtaining SERS active substrates that are easily prepared, highly sensitive, and reliable. Many high-quality hotspot structures exist in aligned Ag nanowires (NWs) arrays. This study used a simple self-assembly method with a liquid surface to prepare a highly aligned AgNW array film to form a sensitive and reliable SERS substrate. To estimate the signal reproducibility of the AgNW substrate, the RSD of SERS intensity of 1.0 × 10^-10 M Rhodamine 6G (R6G) in an aqueous solution at 1364 cm^-1 was calculated to be as low as 4.7%. The detection ability of the AgNW substrate was close to the single molecule level, and even the R6G signal of 1.0 × 10^-16 M R6G could be detected with a resonance enhancement factor (EF) as high as 6.12 × 10¹¹ under 532 nm laser excitation. The EF without the resonance effect was 2.35 × 10⁶ using 633 nm laser excitation. FDTD simulations have confirmed that the uniform distribution of hot spots inside the aligned AgNW substrate amplifies the SERS signal.

Aligned silver nanowires for plasmonically-enhanced fluorescence detection of photoactive proteins in wet and dry environment

We developed a method of aligning silver nanowires in a microchannel and fixing them to glass substrates via appropriate functionalization. The attachment of nanowires to the substrate is robust with no variation of their angles over minutes. Specific conjugation with photoactive proteins is observed using wide-field fluorescence imaging in real-time for highly concentrated protein solution, both in a microchannel and in a chip geometry. In the latter case we can detect the presence of the proteins in the dropcasted solution down to single proteins. The results point towards possible implementation of aligned silver nanowires as geometrically defined plasmonic fluorescence sensing platforms.

Advances in constructing silver nanowire-based conductive pathways for flexible and stretchable electronics

With their soaring technological demand, flexible and stretchable electronics have attracted many researchers' attention for a variety of applications. The challenge which was identified a decade ago and still remains, however, is that the conventional electrodes based on indium tin oxide (ITO) are not suitable for ultra-flexible electronic devices. The main reason is that ITO is brittle and expensive, limiting device performance and application. Thus, it is crucial to develop new materials and processes to construct flexible and stretchable electrodes with superior quality for next-generation soft devices. Herein, various types of conductive nanomaterials as candidates for flexible and stretchable electrodes are briefly reviewed. Among them, silver nanowire (AgNW) is selected as the focus of this review, on account of its excellent conductivity, superior flexibility, high technological maturity, and significant presence in the research community. To fabricate a reliable AgNW-based conductive network for electrodes, different processing technologies are introduced, and the corresponding characteristics are compared and discussed. Furthermore, this review summarizes strategies and the latest progress in enhancing the conductive pathway. Finally, we showcase some exemplary applications and provide some perspectives about the remaining technical challenges for future research.

Recent progress in post treatment of silver nanowire electrodes for optoelectronic device applications

Owing to the economical and practical solution synthesis and coating strategies, silver nanowires (AgNWs) have been considered as one of the most suitable alternative materials to replace commercial indium tin oxide (ITO) transparent electrodes. The primitive AgNW electrode cannot meet the requirements for preparing high performance optoelectronic devices due to its high contact resistance, large surface roughness and poor stability. Thus, various post-treatments for AgNW film optimization are needed before its actual applications, such as welding treatment to decrease contact resistance and passivation to increase film stability. This review investigates recent progress on the preparation and optimization of AgNWs. Moreover, some unique fabrication strategies to produce highly oriented AgNW films with unique anisotropic properties have also been carried out with detailed analysis. The representative devices based on the AgNW electrode have been summarized and discussed at the end of this review.

Molecular Dynamics of Janus Nanodimers Dispersed in Lamellar Phases of a Block Copolymer

We investigate structural and dynamical properties of Janus nanodimers (NDs) dispersed in lamellar phases of a diblock copolymer. By performing molecular dynamics simulations, we show that an accurate tuning of the interactions between NDs and copolymer blocks can lead to a close control of NDs' space distribution and orientation. In particular, NDs are preferentially found within the lamellae if enthalpy-driven forces offset their entropic counterpart. By contrast, when enthalpy-driven forces are not significant, the distribution of NDs, preferentially observed within the inter-lamellar spacing, is mostly driven by excluded-volume effects. Not only does the degree of affinity between host and guest species drive the NDs' distribution in the polymer matrix, but it also determines their space orientation. In turn, these key structural properties influence the long-time dynamics and the ability of NDs to diffuse through the polymer matrix.

Embedding Silver Nanowires into a Hydroxypropyl Methyl Cellulose Film for Flexible Electrochromic Devices with High Electromechanical Stability

Transparent conductive films (TCFs) based on silver nanowires (AgNWs) are becoming one of the best candidates in realizing flexible optoelectronic devices. The AgNW-based TCF is usually prepared by coating AgNWs on a transparent polymer film; however, the coated AgNWs easily detach from the polymer underneath because of the weak adhesion between them. Herein, a network of AgNWs is embedded in the transparent hydroxypropyl methyl cellulose film, which has a strong adhesion with the AgNWs. The obtained TCF shows high optical transmittance (>85%), low roughness (rms = 4.8 ± 0.5 nm), and low haze (<0.2%). More importantly, owing to the embedding structure and strong adhesion, this TCF also shows excellent electromechanical stability, which is superior to the reported ones. Employing this TCF in a flexible electrochromic device, the obtained device exhibits excellent cyclic electromechanical stability and high coloring efficiency. Our work demonstrates a promising TCF with superior electromechanical stability for future applications in flexible optoelectronics.

Paintable and writable electrodes using black conductive ink on traditional Korean paper (Hanji)

We demonstrate black conductive ink (BCI) that is writable and paintable on traditional handmade Korean paper (Hanji) for application as a high performing electrode. By optimal mixing of Ag nanowire (Ag NW) suspension and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS) solution in standard charcoal-based blank ink, we synthesized BCI suitable for writing and painting on Hanji with a normal paintbrush. Due to the shear stress induced by the paintbrush bristles, the Ag NW and PEDOT:PSS mixture was uniformly coated on the porous cellulose structure of Hanji and showed a low sheet resistance of 11.7 Ohm per square even after repeated brush strokes. Moreover, the brush-painted electrodes on Hanji showed a constant resistance during tests of inner/outer bending and folding due to the outstanding flexibility of the Ag NW and PEDOT:PSS mixture that filled the porous cellulose structure of Hanji. Therefore, the pictures drawn in the BCI on Hanji exhibited a level of flexibility and conductivity sufficiently high to enable the BCI to function as an effective electrode even when the paper substrate is wrinkled or crumpled. The successful operation of the paintable interconnector and heater on Hanji indicates the high potential of the brush-painted electrodes that can be used in various social and cultural fields, including fine art, fashion, interior design, architecture, and heating industry.