Robust Ag nanoplate ink for flexible electronics packaging

Direct Z-scheme of n-type CuS/p-type ZnS@electrospun PVP nanofiber for the highly efficient catalytic reduction of 4-nitrophenol and mixed dyes

Environmental pollution has been the most critical issue on earth due to many factors, particularly the industrial chemical waste, which can be detoxified by photocatalytic methods. In this study, we demonstrate the fabrication of an electrospun composite nanofiber embedded with n-type CuS and p-type ZnS in partially carbonized-PVP nanofibers, so-called Z-type-CuS/ZnS@PVP nanofibers, to reduce 4-nitrophenol to 4-aminophenol and degrade the mixed dyes of methylene blue, rhodamine B, and methyl orange. The Z-type-CuS/ZnS@PVP nanofibers were prepared by an electrospinning method, followed by annealing at 180 °C and 400 °C under N₂ atmosphere. As-prepared CuS/ZnS@PVP nanofibrous mats were characterized by SEM, XRD, PL, DRS, TPC, and EIS analyses. The results revealed that Z-type CuS/ZnS@PVP nanofibers have enhanced optical and electrochemical properties as compared with the CuS@PVP and ZnS@PVP nanofibers. Likewise, the Z-scheme was more beneficial for promoting the electron transfer as well as for delaying the photocarrier recombination. For the applications of CuS/ZnS@PVP nanofibers, the reduction of 4-nitrophenol to 4-aminophenol occurred within 2 h and the mixed-dye degradation occurred in 90 min in 5% MeOH aqueous solution under solar light irradiation. The CuS/ZnS@PVP nanofibers also possessed excellent stability, with more than 95% remaining after five recycle runs. The photocatalytic mechanism reaction is proposed, in which the mechanism was initiated by the adsorption of organic pollutants on the nanofiber matrix, followed by the photoreaction due to e⁻ and h⁺ in CuS/ZnS after light irradiation as well as from the generated radical species. Lastly, the inorganic photocatalyst embedded in the nanofiber matrix offered an easy recovery process with excellent degradation performance as well.

Z-type CuS/ZnS@PVP nanofibers are synthesized for the photocatalytic reduction of 4-nitrophenol and for mixed-dyes degradation under mild conditions.

Simple Self-Assembly Strategy of Nanospheres on 3D Substrate and Its Application for Enhanced Textured Silicon Solar Cell

Nanomaterials and nanostructures provide new opportunities to achieve high-performance optical and optoelectronic devices. Three-dimensional (3D) surfaces commonly exist in those devices (such as light-trapping structures or intrinsic grains), and here, we propose requests for nanoscale control over nanostructures on 3D substrates. In this paper, a simple self-assembly strategy of nanospheres for 3D substrates is demonstrated, featuring controllable density (from sparse to close-packed) and controllable layer (from a monolayer to multi-layers). Taking the assembly of wavelength-scale SiO₂ nanospheres as an example, it has been found that textured 3D substrate promotes close-packed SiO₂ spheres compared to the planar substrate. Distribution density and layers of SiO₂ coating can be well controlled by tuning the assembly time and repeating the assembly process. With such a versatile strategy, the enhancement effects of SiO₂ coating on textured silicon solar cells were systematically examined by varying assembly conditions. It was found that the close-packed SiO₂ monolayer yielded a maximum relative efficiency enhancement of 9.35%. Combining simulation and macro/micro optical measurements, we attributed the enhancement to the nanosphere-induced concentration and anti-reflection of incident light. The proposed self-assembly strategy provides a facile and cost-effective approach for engineering nanomaterials at 3D interfaces.

Effects of Polydopamine Microspheres Loaded with Silver Nanoparticles on Lolium multiflorum: Bigger Size, Less Toxic

The rapid development of nanotechnology and its widespread use have given rise to serious concerns over the potential adverse impacts of nanomaterials on the Earth’s ecosystems. Among all the nanomaterials, silver nanoparticles (AgNPs) are one of the most extensively used nanomaterials due to their excellent antibacterial property. However, the toxic mechanism of AgNPs in nature is still unclear. One of the questions under debate is whether the toxicity is associated with the size of AgNPs or the silver ions released from AgNPs. In our previous study, a sub-micron hybrid sphere system with polydopamine-stabilized AgNPs (Ag@PDS) was synthesized through a facile and green method, exhibiting superior antibacterial properties. The current study aims to explore the unique toxicity profile of this hybrid sphere system by studying its effect on germination and early growth of Lolium multiflorum, with AgNO₃ and 15 nm AgNPs as a comparison. The results showed the seed germination was insensitive/less sensitive to all three reagents; however, vegetative growth was more sensitive. Specifically, when the Ag concentration was lower than 40 mg/L, Ag@PDS almost had no adverse effects on the root and shoot growth of Lolium multiflorum seeds. By contrast, when treated with AgNO₃ at a lower Ag concentration of 5 mg/L, the plant growth was inhibited significantly, and was reduced more in the case of AgNP treatment at the same Ag concentration. As the exposures of Ag@PDS, AgNO₃, and AgNPs increased, so did the Ag content in the root and shoot. In general, Ag@PDS was proven to be a potential useful hybrid material that retains antibacterial property with light phytotoxicity.

Versatile nanocellulose-based nanohybrids: A promising-new class for active packaging applications

The food packaging industry is rapidly growing as a consequence of the development of nanotechnology and changing consumers' preferences for food quality and safety. In today's globalization of markets, active packaging has achieved many advantages with the capability to absorb or release substances for prolonging the food shelf life over the traditional one. Therefore, it is critical to developing multifunctional active packaging materials from biodegradable polymers with active agents to decrease environmental challenges. This review article addresses the recent advances in nanocelluloses (NCs)- baseds nanohybrids with new function features in packaging, focusing on the various synthesis methods of NCs-based nanohybrids, and their reinforcing effects as active agents on food packaging properties. The applications of NCs-based nanohybrids as antioxidants, antimicrobial agents, and UV blocker absorbers for prolonging food shelf-life are also reviewed. Overall, these advantages make the CNs-based nanohybrids with versatile properties promising in food and packaging industries, which will impact more readership with concern for future research.

From Silver Nanoflakes to Silver Nanonets: An Effective Trade-Off between Conductivity and Stretchability of Flexible Electrodes

Flexible and stretchable conductive materials have received significant attention due to their numerous potential applications in flexible printed electronics. In this paper, we describe a new type of conductive filler for flexible electrodes—silver nanonets prepared through the “dissolution–recrystallization” solvothermal route from porous silver nanoflakes. These new silver fillers show characteristics of both nanoflakes and nanoparticles with propensity to form interpenetrating polymer–silver networks. This effectively minimizes trade-off between composite electrode conductivity and stretchability and enables fabrication of the flexible electrodes simultaneously exhibiting high conductivity and mechanical durability. For example, an electrode with uniform, networked silver structure from the flakiest silver particles showed the lowest increase of resistivity upon extension (3500%), compared to that of the electrode filled with less flaky (3D) particles (>50,000%).

Cellulose Nanocrystal and Silver Nanobelt Gel: Cooperative Interactions Enabling Dispersion, Colloidal Gels, and Flexible Electronics

Using cellulose nanocrystals (CNCs) as a dispersant and cross-linker, we sought to enable the dispersion of silver nanobelts (AgNBs) in water for use in the manufacture of flexible electronics. In this work, we obtained a colloidal gel relying on contributions from both particles. When dried, particle interactions during gel collapse induced cooperative buckling of the AgNBs, obtaining a desirable spring-like conductive network that was not seen without the presence of CNCs. Thus, exploiting the collapse of bonded colloidal gels may represent a novel method to obtain desirable network buckling behavior for use in flexible electronics, which previously has only been obtained through printing on prestrained substrates.

Shape Stability of Metallic Nanoplates: A Molecular Dynamics Study

Metallic nanoplates have attracted widespread interests owing to their functional versatility, which relies heavily on their morphologies. In this study, the shape stability of several metallic nanoplates with body-centered-cubic (bcc) lattices is investigated by employing molecular dynamics simulations. It is found that the nanoplate with (110) surface planes is the most stable compared to the ones with (111) and (001) surfaces, and their shapes evolve with different patterns as the temperature increases. The formation of differently orientated facets is observed in the (001) nanoplates, which leads to the accumulation of shear stress and thus results in the subsequent formation of saddle shape. The associated shape evolution is quantitatively characterized. Further simulations suggest that the shape stability could be tuned by facet orientations, nanoplate sizes (including diameter and thickness), and components.

Reactive Conductive Ink Capable of In Situ and Rapid Synthesis of Conductive Patterns Suitable for Inkjet Printing

We report a fabrication method of the conductive pattern based on in situ reactive silver precursor inks by inkjet printing. The reactive silver precursor inks were prepared with ethylene glycol and deionized water mixture as the solvent, and silver nitrate as silver source. Sodium borohydride solution as the reducing agent was first coated on photographic paper by screen printing process, and then dried at 50 °C for 4 h. Furthermore, the reactive silver precursor inks were printed on a photographic paper coated with sodium borohydride using inkjet printing to form silver nanoparticles in situ due to redox reaction, and thus a conductive pattern was obtained. The effects of the reactive silver precursor ink concentration and printing layer number and treatment temperature on the electrical properties and microstructures of the printed patterns were investigated systematically. The size range of in situ-formed silver nanoparticles was 50–90 nm. When the reactive silver precursor ink concentration was 0.13 g/mL, the five-layer printed pattern exhibited a sheet resistance of 4.6 Ω/γ after drying at room temperature for 2 h; furthermore, the sheet resistance of the printed pattern decreased to 1.4 Ω/γ after drying at 130 °C for 2 h. In addition, the display function circuit was printed on the photographic paper to realize the display of the numbers 0–99. It provides new research ideas for the development of environmentally friendly and low-cost flexible paper-based circuits.

Recent Progress of Metal–Air Batteries—A Mini Review

With the ever-increasing demand for power sources of high energy density and stability for emergent electrical vehicles and portable electronic devices, rechargeable batteries (such as lithium-ion batteries, fuel batteries, and metal–air batteries) have attracted extensive interests. Among the emerging battery technologies, metal–air batteries (MABs) are under intense research and development focus due to their high theoretical energy density and high level of safety. Although significant progress has been achieved in improving battery performance in the past decade, there are still numerous technical challenges to overcome for commercialization. Herein, this mini-review summarizes major issues vital to MABs, including progress on packaging and crucial manufacturing technologies for cathode, anode, and electrolyte. Future trends and prospects of advanced MABs by additive manufacturing and nanoengineering are also discussed.

Laser-Scribed Lossy Microstrip Lines for Radio Frequency Applications

Laser-direct writing has become an alternative method to fabricate flexible electronics, whereas the resistive nature of laser-scribed conductors may distort the radio-frequency characteristics of circuits for high-frequency applications. We demonstrate that the transmission characteristics of microstrip lines are insensitive to the resistance of laser-scripted conductors when the sheet resistance is not above 0.32 Ω/□. On the other hand, the transmission and reflection characteristics of the MS lines can be simply modified through the accommodation of the resistance of the conductors, because a laser can trigger the sintering and melting of laser produced silver nanostructures. This could provide an alternative way to fabricate radio frequency (RF) resistors and promote their applications to flexible radio-frequency devices and systems.

Highly Transparent, Strong, and Flexible Films with Modified Cellulose Nanofiber Bearing UV Shielding Property

This work investigates multifunctional composite films synthesized with cellulose nanofibers (CNFs) and poly(vinyl alcohol) (PVA). First, TEMPO-oxidized CNFs were modified in the heterogeneous phase with benzophenone, diisocyanate, and epoxidized soybean oil via esterification reactions. A thorough characterization was carried out via elemental analysis as well as FT-IR and X-ray photoelectron spectroscopies and solid-state NMR. Following, the surface-modified CNFs were combined with PVA to endow composite films with UV-absorbing capabilities while increasing their thermomechanical strength and maintaining a high light transmittance. Compared to neat PVF films, the tensile strength, Young modulus, and elongation of the films underwent dramatic increases upon addition of the reinforcing phase (maximum values of ∼96 MPa, ∼ 714 MPa, and ∼350%, respectively). A high UV blocking performance, especially in the UVB region, was observed for the introduced multifunctional PVA films at CNF loadings below 5 wt %. The trade-off between modified nanofibril function as interfacial reinforcement and aggregation leads to an optimum loading. The results indicate promising applications, for example, in active packaging.

Optimized inkjet-printed silver nanoparticle films: theoretical and experimental investigations

We study the influence of inkjet printing scheme and sintering parameter on the electrical resistivity of multi-layer silver nanoparticle films. A central composite Design Of Experiments (DOE) is employed to maximize experimental efficiency and improve the statistical significance of parameter estimates. The resulting mathematical correlations allow to interpret the influence of the print and sintering parameters. Detailed inspection of the correlations reveals the existence of local extrema and indicates that a structured approach such as the DOE would be significantly more effective for fabricating films with a minimum of resistivity. Furthermore, we modify the well-known Fuchs–Sondheimer Mayadas–Shatzkes model to correlate the resistivity of a multi-layer nanoparticle film with the sintering temperature and time. The modified model uses literature data but one constant inferred from two experiments. After model adjustment, the resistivities of films fabricated with different parameters can be predicted with good accuracy. This validation tremendously increases applicability and relevance of the model.

Systematic study of printing scheme and sintering time and temperature on the conductivity of silver flims on glass.

Investigation of simultaneously existed Raman scattering enhancement and inhibiting fluorescence using surface modified gold nanostars as SERS probes

One of the main challenges for highly sensitive surface-enhanced Raman scattering (SERS) detection is the noise interference of fluorescence signals arising from the analyte molecules. Here we used three types of gold nanostars (GNSs) SERS probes treated by different surface modification methods to reveal the simultaneously existed Raman scattering enhancement and inhibiting fluorescence behaviors during the SERS detection process. As the distance between the metal nanostructures and the analyte molecules can be well controlled by these three surface modification methods, we demonstrated that the fluorescence signals can be either quenched or enhanced during the detection. We found that fluorescence quenching will occur when analyte molecules are closely contacted to the surface of GNSs, leading to a ~100 fold enhancement of the SERS sensitivity. An optimized Raman signal detection limit, as low as the level of 10-11 M, were achieved when Rhodamine 6 G were used as the analyte. The presented fluorescence-free GNSs SERS substrates with plentiful hot spots and controllable surface plasmon resonance wavelengths, fabricated using a cost-effective self-assembling method, can be very competitive candidates for high-sensitive SERS applications.

Engineering Silver Nanowire Networks: From Transparent Electrodes to Resistive Switching Devices

Metal nanowires (NWs) networks with high conductance have shown potential applications in modern electronic components, especially the transparent electrodes over the past decade. In metal NW networks, the electrical connectivity of nanoscale NW junction can be modulated for various applications. In this work, silver nanowire (Ag NW) networks were selected to achieve the desired functions. The Ag NWs were first synthesized by a classic polyol process, and spin-coated on glass to fabricate transparent electrodes. The as-fabricated electrode showed a sheet resistance of 7.158 Ω □^-1 with an optical transmittance of 79.19% at 550 nm, indicating a comparable figure of merit (FOM, or Φ_TC) (13.55 × 10^-3 Ω^-1). Then, two different post-treatments were designed to tune the Ag NWs for not only transparent electrode but also for threshold resistive switching (RS) application. On the one hand, the Ag NW film was mechanically pressed to significantly improve the conductance by reducing the junction resistance. On the other hand, an Ag@AgO_x core-shell structure was deliberately designed by partial oxidation of Ag NWs through simple ultraviolet (UV)-ozone treatment. The Ag core can act as metallic interconnect and the insulating AgO_x shell acts as a switching medium to provide a conductive pathway for Ag filament migration. By fabricating Ag/Ag@AgO_x/Ag planar structure, a volatile threshold switching characteristic was observed and an on/off ratio of ∼100 was achieved. This work showed that through different post-treatments, Ag NW network can be engineered for diverse functions, transforming from transparent electrodes to RS devices.

Sintering of multiple Cu–Ag core–shell nanoparticles and properties of nanoparticle-sintered structures

Multiple-CS-NP sintered structure of 600 K yields similar porosity as the counterpart sintered at surface premelting temperature (900 K).

Synthesis of silver nanoplate based two-dimension plasmonic platform from 25 nm to 40 μm: growth mechanism and optical characteristic investigation in situ

We show high-purity synthesis, structural engineering and in situ optical investigation of a 2D plasmonic platform using huge silver nanoplates.

Seeds triggered massive synthesis and multi-step room temperature post-processing of silver nanoink—application for paper electronics

Ink synthesis, room-temperature post-processing and applications for flexible 3D paper electronics.

Fabricating Metallic Circuit Patterns on Polymer Substrates through Laser and Selective Metallization

Nowadays, with the rapid development of portable electronics, wearable electronics, LEDs, microelectronics, and bioelectronics, the fabrication of metallic circuits onto polymer substrates with strong adhesion property is an ever-increasing challenge. In this study, the high-resolution and well-defined metallic circuits were successfully prepared on the polymer surface via laser direct structuring (LDS) based on copper hydroxyl phosphate [Cu₂(OH)PO₄], and the key mechanism of the selective metallization was systematically investigated. XPS confirmed that Cu⁰ (elemental copper) was formed through photochemical reduction reaction of Cu₂(OH)PO₄, after 1064 nm NIR pulsed laser irradiation. During the electroless plating, because it is the important active catalytic center, this newly formed Cu⁰ was the key factor to achieve the successful selective metallization. SEM revealed that after the electroless plating, the copper layer actually physically anchored into the polymer substrate, giving an excellent mechanical adhesion property of the obtained metallic patterns. In addition, the micro-Raman surface imaging approved the generation of the amorphous carbon on the polymer composites' surface after NIR laser irradiation, and the chemical reaction region caused by the pulsed laser spot was found at approximately 40 μm. This environmentally friendly and effective strategy for fabricating circuit patterns on the polymer surface has a possible application in the printed circuit plate (PCB) industry.

Regulating Mid-infrared to Visible Fluorescence in Monodispersed Er3+-doped La2O2S (La2O2SO4) Nanocrystals by Phase Modulation

Rare earth doped mid-infrared (MIR) fluorescent sources have been widely investigated due to their various potential applications in the fields of communication, chemical detecting, medical surgery and so forth. However, with emission wavelength extended to MIR, multiphonon relaxation process that strongly quenched the MIR emission is one of the greatest challenges for such practical applications. In our design, we have described a controllable gas-aided annealing strategy to modulate the phase, crystal size, morphology and fluorescent performance of a material simultaneously. Uniform and monodispersed Er³⁺-doped La₂O₂S and La₂O₂SO₄ nanocrystals with a similar lattice structure, crystallinity, diameter and morphology have been introduced to investigate the impact of multiphonon relaxation on luminescence performance. Detailed spectroscopic evolutions in the region of MIR, near-infrared (NIR), visible upconversion (UC) and their corresponding decay times provide insight investigation into the fluorescent mechanism caused by multiphonon relaxation. A possible energy transfer model has also been established. Our results present direct observation and mechanistic investigation of fluorescent evolution in multiphonon relaxation process, which is conductive to design MIR fluorescent materials in the future. To the best of our knowledge, it is the first investigation on MIR fluorescent performance of La₂O₂S nanocrystals, which may find various applications in many photoelectronic fields.

Laser-Direct Writing of Silver Metal Electrodes on Transparent Flexible Substrates with High-Bonding Strength

We demonstrate a novel approach to rapidly fabricate conductive silver electrodes on transparent flexible substrates with high-bonding strength by laser-direct writing. A new type of silver ink composed of silver nitrate, sodium citrate, and polyvinylpyrrolidone (PVP) was prepared in this work. The role of PVP was elucidated for improving the quality of silver electrodes. Silver nanoparticles and sintered microstructures were simultaneously synthesized and patterned on a substrate using a focused 405 nm continuous wave laser. The writing was completed through the transparent flexible substrate with a programmed 2D scanning sample stage. Silver electrodes fabricated by this approach exhibit a remarkable bonding strength, which can withstand an adhesive tape test at least 50 times. After a 1500 time bending test, the resistance only increased 5.2%. With laser-induced in-situ synthesis, sintering, and simultaneous patterning of silver nanoparticles, this technology is promising for the facile fabrication of conducting electronic devices on flexible substrates.

Sintering mechanism of the Cu–Ag core–shell nanoparticle paste at low temperature in ambient air

Cu–Ag core–shell nanoparticles owned good anti-oxidation ability, and as-fabricated joints using the Cu–Ag core–shell nanoparticles paste showed high shear strength.

A low-cost, highly-conductive polyvinyl alcohol flexible film with Ag-microsheets and AgNWs as fillers

Low-cost, high-conductivity flexible conductive films were fabricated using Ag-microsheets, Ag-nanowires (AgNWs) and polyvinyl alcohol (PVA) as conducting agents. The flexible conductive film shows good conductivity under stretching.

Zero-dimensional to three-dimensional nanojoining: current status and potential applications

As devices have become smaller, nanomaterials have become the preferred manufacturing building blocks due to lower material and joining energy costs. This review surveys progress in nanojoining methods, as compared to conventional joining processes.

High quantum-yield luminescent MoS2 quantum dots with variable light emission created via direct ultrasonic exfoliation of MoS2 nanosheets

MoS₂ QDs with high quantum-yield, variable photoluminescence emission properties and good biocompatibility are studied and applied to the bio-imaging field.

Polyvinylpyrrolidone (PVP) in nanoparticle synthesis

The versatile role of PVP in nanoparticle synthesis is discussed in this Perspective article.