Room-temperature sintering of conductive Ag films on paper

Water-dispersible Ag nanoparticles (NPs) were synthesised with polyacrylic acid as capping agents and prepared as an Ag NP-based ink. An approach to achieve coalescence and sintering of Ag NPs at room temperature was presented. After inkjet printing Ag NP-based ink on paper substrates, the Ag NPs underwent spontaneous coalescence when they came into contact with a poly(diallyldimethylammonium chloride) (PDAC) solution even without a traditional sintering process. This phenomenon rapidly decreased the sheet resistance of the films. The room-temperature sintering mechanism was then proposed based on the electrical and the morphological properties of Ag films with and without PDAC solutions. (C) 2014 Elsevier B.V. All rights reserved

Coatings on Lithium Battery Separators: A Strategy to Inhibit Lithium Dendrites Growth

Lithium metal is considered a promising anode material for lithium secondary batteries by virtue of its ultra-high theoretical specific capacity, low redox potential, and low density, while the application of lithium is still challenging due to its high activity. Lithium metal easily reacts with the electrolyte during the cycling process, resulting in the continuous rupture and reconstruction of the formed SEI layer, which reduces the cycling reversibility. On the other hand, repeated lithium plating/stripping processes can lead to uncontrolled growth of lithium dendrites and a series of safety issues caused by short-circuiting of the battery. Currently, modification of the battery separator layer is a good strategy to inhibit lithium dendrite growth, which can improve the Coulombic efficiency in the cycle. This paper reviews the preparation, behavior, and mechanism of the modified coatings using metals, metal oxides, nitrides, and other materials on the separator to inhibit the formation of lithium dendrites and achieve better stable electrochemical cycles. Finally, further strategies to inhibit lithium dendrite growth are proposed

Effects of pH on the microstructures and optical properties of Sn3O4 crystals prepared by hydrothermal method

Intermediate tin oxide (Sn3O4) crystals have been successfully synthesized through a simple one-pot hydrothermal route by employing SnCl2 center dot 2H(2)O and NaOH as raw materials. The crystmlline structure, morphology and optical properties of Sn3O4 materials were characterized by using X-ray diffraction, field-emission scanning electron microscopy, and UV-vis absorption spectroscopy, respectively. It was found that pH value of the media had significant impacts on microstructures and optical properties of products. Products obtained from acidic media (pH=2.20) were composed of pure Sn3O4 nanosheets with grain size of 100 nm, while those prepared in alkaline conditions (pH=12.35) consisted of irregular Sn3O4 micro-flakes. Their optical band gaps were calculated to be 2.68 and 2.85 eV, correspondingly. Possible mechanism was discussed for the formation of Sn3O4 crystals in different pH. (c) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Separation of Silver Nanocrystals for Surface-enhanced Raman Scattering Using Density Gradient Centrifugation

One-dimensional silver nanocrystals (AgNCs) have been prepared by a polyol process using sodium hydroxide and nitric acid at a constant silver source concentration. Results indicate that the acidity-basicity plays an important role in silver-nanocrystal formation. Different morphologies of AgNCs were synthesized by changing the NaOH or HNO3 amount. We demonstrate that nearly monodisperse silver nanocrystals can be separated from polydisperse samples using density gradient centrifugation separation (DGCS). We also demonstrate that the separated AgNCs can be used as substrates for surface-enhanced Raman scattering (SERS) spectroscopy. The separation approach provides a method of improving the nanocrystal quality produced by large-scale synthetic methods. Copyright (C) 2015, The editorial office of Journal of Materials Science & Technology. Published by Elsevier Limited. All rights reserved

Properties of polyacrylic acid-coated silver nanoparticle ink for inkjet printing conductive tracks on paper with high conductivity

Silver nanoparticles with a mean diameter of approximately 30 nm were synthesized by reduction of silver nitrate with triethanolamine in the presence of polyacrylic acid. Silver nanoparticle-based ink was prepared by dispersing silver nanoparticles into a mixture of water and ethylene glycol. The mechanism for the dispersion and aggregation of silver nanoparticles in ink is discussed. The strong electrostatic repulsions of the carboxylate anions of the adsorbed polyacrylic acid molecules disturbed the aggregation of metal particles in solutions with a high pH value (pH > 5). An inkjet printer was used to deposit this silver nanoparticle-based ink to form silver patterns on photo paper. The actual printing qualities of the silver tracks were then analyzed by variation of printing passes, sintering temperature and time. The results showed that sintering temperature and time are associated strongly with the conductivity of the inkjet-printed conductive patterns. The conductivity of printed patterns sintered at 150 degrees C increased to 2.1 x 10(7) S m(-1), which was approximately one third that of bulk silver. In addition, silver tracks on paper substrate also showed better electrical performance after folding. This study demonstrated that the resulting ink-jet printed patterns can be used as conductive tracks in flexible electronic devices. (C) 2014 Elsevier B.V. All rights reserved

Surfactant-free Hydrothermal Synthesis and Sensitivity Characterization of Pd-doped SnO2 Nano Crystals on Multiwalled Carbon Nanotubes

In the present study, a simple approach has been presented to in situ deposition of Pd-doped well-crystallized SnO2 nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution of SnCl2. The morphology, microstructure and surface chemistry of the as-prepared nanocomposites were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The HRTEM and XRD results show that the well-crystallized SnO2 nanocrystals with uniform crystal size (about 5 nm) tightly and homogenously coat on the entire surface of the MWCNTs. The carboxylic function groups on the MWCNTs surface may supply nucleation sites for facilitating the in situ deposition of SnO2 nanocrystals. The XPS results reveal that the chemical states of the nanocomposites and the dopant of Pd mainly exists in two chemical states as Pd2+ and Pd4+. The response of the 2.5 at% Pd-doped SnO2/MWCNTs nanocomposites to 1000 ppm NO at the temperature of 250 degrees C behaviors better, whose response time is about 70 s and the sensitivity is about 4.62

Trace-level ammonia detection at room temperature based on porous flexible polyaniline/polyvinylidene fluoride sensing film with carbon nanotube additives

Enhanced ammonia (NH3) sensing properties based on porous flexible polyaniline/polyvinylidene fluoride (PANI/PVDF) composite films, which used multi-wall carbon nanotubes (MWCNTs) as additives, were prepared by an in-situ polymerization process. The obtained flexible PANI/PVDF based sensing films showed a hierarchical porous structure, which enhanced their NH3 sensing performance. The results show that the addition of MWCNTs to the PANI/PVDF film further improved its stability and response to NH3. The response of the optimized MWCNT-PANI/PVDF film was found to increase by twofold to 33 %, and its recovery time was decreased 7-fold to 26 s than those of the PANI/PVDF sensing film for 1 ppm NH3 at 25 degrees C. Its lower detectable NH3 concentration was 0.1 ppm, with a response value of 8 % at 25 degrees C. Additionally, the MWCNT-PANI/PVDF film sensor presented good flexibility, showing only minor response value decline after 500 bending cycles. This work shows that the fabricated flexible MWCNT-PANI/PVDF film is promising for detecting trace-level NH3 gas at room temperature, and can be integrated with smart wearable devices for real-time environmental monitoring

Large scale preparation of surface enhanced Raman spectroscopy substrates based on silver nanowires for trace chemical detection

In this paper, a facile large-scale preparation of surface enhanced Raman spectroscopy (SERS) substrates based on silver nanowires has been developed. The SERS substrates can be easily and precisely obtained by filtering bulky amounts of silver nanostructures through hydrophilic filter membranes one time. The developed membranes can be expanded to commercial wafer-style filter membranes of large size (>47 mm in diameter). The as-prepared SERS substrates presented good uniformity and good performance for the detection of crystal violet (CV) and 1,2-di(4-pyridyl)ethylene (BPE). The relative standard deviations (RSD) were less than 5.5% (n = 11) and 5.2% (n = 11) for CV and BPE, respectively. The logarithm of characteristic SERS intensity plotted against CV and BPE concentrations presented a linear relationship over the ranges from 1.0 x 10(-4) to 1.0 x 10(-8) mol L-1 and from 5.0 x 10(-4) to 5.0 x 10(-9) mol L-1, respectively. In the detection of natural water samples of river water, Membrane Bio-Reactor (MBR) effluent and sewage disposal plant effluent, spiked with CV and BPE, the as-prepared SERS substrates also presented good performance, suggesting that such substrates possessed great potential in a broad range of analytical applications

Preparation and X-ray photoelectron spectroscopic characterization of Sn-doped C12A7:e(-) electride nanoparticles

Understanding the chemistry of dopants in electride nanoparticles is essential and challenging owing to the active nature of the electride and the low atomic concentration of the dopants. In this work, we developed conductive Sn-doped C12A7:e(-) electride nanoparticles by a modified sol-gel method, and performed a comprehensive X-ray photoelectron spectroscopic characterization on the surface chemistry of the doped electride nanoparticles. The resulting electride Ca12Al(14-x)Snx:e(-) (x = 1) exhibited an electron concentration of 1.65 x 10(21) cm(-3) and a specific area of 53.9 m(2)/g. XPS results showed that Sn was in the form of Sn4+ at the surface of the doped C12A7:e(-) nanoparticles. The depth distribution of elements was investigated by XPS Ar+ ion and Ar cluster ion sputtering. Results showed that Sn was enriched at the surface and sputtering partially reduced Sn4+ to metallic Sn, and Ar cluster ion sputtering showed much weaker effect on the reduction of Sn4+ than the Ar+ ion sputtering. The chemical states and distribution of elements Ca, Al, O did not show obvious change after sputtering. The present study provides novel insights on the chemical states analysis of doped-C12A7:e(-) nanoparticles

Effect of hydrogen-ion energy on structure of a-Si:H thin films prepared by ion-beam-assisted sputtering

In this work, hydrogenated amorphous silicon (a-Si:H) thin films were prepared by ion-beam-assisted sputtering, and the effect of hydrogen-ion energy on the structure of a-Si: H thin films were investigated using Raman spectroscopy, Fourier transform infrared spectroscopy, and spectroscopic ellipsometry. It was observed that the network structure order and defect density of states of a-Si: H films were improved with the introduction of assisted-hydrogen-ion-beam, and that of a-Si: H thin films with moderate hydrogen-ion energy of 200 eV was optimal. The a-Si: H thin films with hydrogen-ion energy of 200 eV possessed the atomic hydrogen concentration, absorption coefficient at 0.8 eV and microstructure factor of 10.2 %, 0.7 cm(-1) and 0.48, respectively. It was indicated that ion-beam-assisted sputtering was an alternative way to prepare device-quality a-Si: H thin films