Preparation and conductive mechanism of copper nanoparticles ink

One step and large-scale synthetic method of copper nanoparticles (NPs), with a yield of 91.36 %, has been first developed. The as-prepared oblate-shape copper NPs with a size 80 nm showed good antioxidation. The ink of the copper nanoparticles (20 wt%) onto glass slides easy formed a favorable conductive film at 300 °C. Interestingly, the coffee ring like structure, which often goes with the films by organic conductive inks, has been effectively suppressed. The experiments revealed that the size and connection of interparticles, as well as the elimination degree of organic molecules are three key factors for the conductivity of the copper films.     

Behavior of Cu nanoparticles ink under reductive calcination for fabrication of Cu conductive film

Cu nanoparticle ink was prepared from Cu nanoparticles that were coated with a gelatin layer at an average diameter of 46 nm. The Cu nanoparticle ink was applied on the polyimide substrate. Conductive films were fabricated using the Cu nanoparticle ink with a two-step annealing process consisting of oxidative pre-heating at 200 °C under 10 ppm O₂-N₂ mixed gas flow and reductive calcination at 250 °C under 3 vol.% H₂-N₂ mixed gas flow showed a low resistivity of 5 μΩ cm. The hydrolysis of the remaining gelatin layer by H₂O vapor, which was formed during the reduction of the Cu oxide by 3 vol.% H₂-N₂ mixed gas, was suggested. The results suggest the possibility of the removal of the gelatin layer without oxidative pre-heating and simultaneous sintering of Cu nanoparticles in reductive calcination.     

Synthesis and characterization of low temperature Sn nanoparticles for the fabrication of highly conductive ink

To fabricate a low cost, highly conductive ink for inkjet printing, we synthesized a gram scale of uniformly sized Sn nanoparticles by using a modified polyol process and observed a significant size-dependent melting temperature depression from 234.1?°C for bulk Sn to 177.3?°C for 11.3 nm Sn nanoparticles. A 20 wt% of Sn nanoparticles was dispersed in the 50% ethylene glycol: 50% isopropyl alcohol mixed solvent for the appropriate viscosity (11.6 cP) and surface tension (32 dyn cm(-1)). To improve the electrical property, we applied the surface treatments of hydrogen reduction and plasma ashing. The two treatments had the effect of diminishing the sheet resistance from 1 kΩ/sq to 50 Ω/sq. In addition, conductive patterns (1 cm × 1 cm) were successfully drawn on the Si wafer using an inkjet printing instrument with conductive Sn ink. The maximum resistivity for an hour of sintering at 250?°C was 64.27 μΩ cm, which is six times higher than the bulk Sn resistivity (10.1 μΩ cm).     

Green synthesis of micron-sized silver flakes and their application in conductive ink

A facile, green method for fabrication of conductive ink composed of Ag flakes was developed for use in flexible printed electronics. The Ag flakes were prepared using AgNO₃, nontoxic l-ascorbic acid (Vc) and polyvinylpyrrolidone (PVP) serving as a metal salt, reducing agent and capping agent, respectively. The prepared Ag flakes were characterized by XRD, SEM, and TGA. The combination of PVP and FeCl₃ was found to be critical for the formation of the Ag flakes, and reaction activity was affected by temperature. Samples obtained at 140 °C were composed of Ag flakes with an average size of 0.94 ± 0.3 μm. A new fabrication method for producing conductive patterns was designed using a syringe with varying dispersion areas, allowing the ink (Ag flakes and organic solvent) to be applied directly onto a flexible photo paper. The conductivity and flexibility of the pattern were experimentally tested under varying reaction temperatures and bending cycles. Increasing contact area and packing density between Ag flakes resulted in an improved conductivity of the bending pattern. After more than 5000 bending cycles, the patterns were sintered at 160 °C and the resistivity increased from 4.6 ± 0.6 to 22.4 ± 0.8 μΩ cm, acceptable values for practical applications. Sample conductive lines drawn by the Ag flake ink exhibited excellent conductive performance and mechanical integrity, demonstrating a promising method for the formation of flexible microelectrodes or electronic devices.     

Novel aqueous magnetic fluids stabilized by albumin for biological application

This paper demonstrates bovine serum albumin (A1) and ovalbumin (A2) can be used as stabilizer to prepare aqueous magnetic fluids for gene therapy.The content of magnetite depends on the reaction temperature and time. The reaction is performed at 70 °C for 30 min, which is appropriate to obtain stable aqueous magnetic fluids. The super paramagnetic magnetic fluids composed of Fe₃O₄ cores, which have average diameter about 8 nm. A high positive ζ-potential of +46.0 mV and suitable hydrodynamic diameters were realized.     

Adsorption of copper ions from aqueous solution by citric acid modified soybean straw

The objectives of the present study were to convert soybean straw to a metal ion adsorbent and further to investigate the potential of using the adsorbent for the removal of Cu(2+) from aqueous solution. The soybean straw was water or base washed and citric acid (CA) modified to enhance its nature adsorption capacity. The morphological and chemical characteristics of the adsorbent were evaluated by spectroscopy and N(2)-adsorption techniques. The porous structure, as well as high amounts of introduced free carboxyl groups of CA modified soybean straw makes the adsorbent be good to retain Cu(2+). The adsorption capacities increased when the solution pH increased from 2 to 6 and reached the maximum value at pH 6 (0.64 mmol g(-1) for the base washed, CA modified soybean straw (CA-BWSS)). The Cu(2+) uptake increased and percentage adsorption of the Cu(2+) decreased with the increase in initial Cu(2+) concentration from 1 mM to 20 mM. Both the Langmuir and Freundlich adsorption isotherms were tested, and the Freundlich model fited much better than the Langmuir model. It was found that CA-BWSS have the highest adsorption capacity of the four kinds of pretreated soybean straw.     

三元氯醋树脂/环氧基导电油墨的制备及性能

为提高环氧导电油墨的柔韧性,采用三元氯醋树脂（E15/45M）对环氧树脂E51增韧改性,并以2-乙基-4-甲基咪唑（2E4MI）为固化剂,银包铜粉为导电填料,制备柔性导电油墨。结果表明:导电油墨的体积电阻率随导电填料的用量增加而降低。随2E4MI用量的增加,导电油墨的体积电阻率呈现先降低后增加的趋势,2E4MI与E51的最佳质量比为1∶5。进一步探讨发现导电油墨的最佳固化温度和时间分别为105 ℃和2.5 h。E15/45M不仅可以提高导电油墨的柔韧性,还可以有效降低体积电阻率。随着E15/45M用量增加,E15/45M/E51-2E4MI胶膜的玻璃化转变温度从91.5 ℃降低至58.0 ℃,导电油墨的体积电阻率从27.5×10-4 Ω·cm降低至9.50×10-4 Ω·cm。E51-2E4MI与E15/45M的质量比为50∶50,导电填料用量为70wt%时,导电油墨体积电阻率达到9.57×10-4 Ω·cm,附着力等级为0,涂层反复折叠20次后电阻变化率小于80%。因此采用E15/45M增韧环氧树脂既可以提高导电油墨的柔韧性又可以改善其导电性。      

Highly luminescent monodisperse CdSe nanoparticles synthesized in aqueous solution

Simple routes to synthesize highly photoluminescent monodisperse thiol-capped CdSe nanoparticles are reported. The as-synthesized water-soluble CdSe nanoparticles possess higher photoluminescence quantum efficiency (up to 22%), smaller values of full width of half-maximum of photoluminescence spectra (down to 31 nm), higher photostability, and better monodispersity compared with the nanoparticles made from other aqueous routes. The quality of CdSe nanoparticles prepared by our route compares very favourably with those prepared in organic solution.     

Size-controlled synthesis and NMR characterization of mesitylene-vinylsiloxanes stabilized Pt nanoparticles in solution

Pt nanoclusters have been generated by reaction of Pt vapour and mesitylene vapour and the role of the mesitylene/platinum ratio and the Pt particle size has been evaluated, quenching the resulting mesitylene solvated Pt atoms with 1,3-divinyltetramethyldisiloxane (DVS) as additional ligand. The Pt particle sizes have been estimated on the basis of DOSY (Diffusion-Ordered SpectroscopY) analysis and information on their structure features have been obtained by combined use of 2D NMR techniques.     

Direct synthesis of monodispersed ZnO nanoparticles in an aqueous solution

Monodispersed ZnO nanoparticles with mesopores were successfully prepared via a simple route through the transformation of Zn(NH₃)₄²⁺ precursor in the presence of sodium oleate and hydrazine at 80 °C with the pH of 8.5. Hydrazine and sodium oleate were used to control the size at 30-60 nm and to improve dispersion properties of ZnO nanoparticles. The samples were characterized by TEM, XRD, IR and TG-DTA, and the results suggest that the grains are composed of ZnO and a small quantity of oleate. The oleate plays an important role in preventing the ZnO nanoparticles from aggregating.     

Facile synthesis of silver malonate conductive MOD ink for screen printing

At present, screen printing is the most widely used technique in the printed electronics industry and the printed pattern can satisfy certain electronic application requirements. Ink development is the most important part of the printing process. In this paper, a new particle-free MOD ink (MOD?=?metal–organic-decomposition) was synthesized from silver malonate, diethanolamine (DEA) and ethylene glycol (EG). Silver malonate was the precursor of silver. DEA was the complexing agent that maked silver malonate soluble. EG acted not only as a solvent to regulate the rheological properties of the ink, but also as a reducing agent to reduce silver ions. The decomposition temperature was reduced from 210 °C to about 100 °C by the formation of silver-amine complex, thus the selection range of substrate could be broadened. The ink was spread on the polyimide (PI) substrate by screen printing. The silver film was formed after heat treatment at 150 °C for 1 h and its electrical conductivity can reach 1.0?×?10⁴ S cm^?1, which corresponded to one sixty-third of the theoretical conductivity of the bulk silver (6.3?×?10⁵ S cm^?1).

     

Chemical reaction between Ag nanoparticles and TCNQ microparticles in aqueous solution

The chemical reaction between Ag nanoparticles (Ag NPs) and 7,7',8,8'- tetracycanoquinodimethane (TCNQ) microparticles (MPs) in aqueous solution for the formation of Ag-NP-decorated Ag-TCNQ nanowires is reported. Based on the results obtained by UV-vis spectroscopy and scanning electron microscopy (SEM), it is proposed that the reaction between Ag NPs and TCNQ MPs includes three stages, namely, aggregation of NPs and MPs, diffusion and reaction between NPs and MPs, and formation of Ag-TCNQ nanowires. The as-synthesized semiconducting Ag-TCNQ nanowires show good performance in nonvolatile memory devices with multiple write-read-erase-read (WRER) cycles in air.     

Sonochemical preparation of bimetallic Co/Cu nanoparticles in aqueous solution

Co/Cu bimetallic nanocrystallites, with average diameter of 50 nm, were prepared by a sonochemical method in the hydrazine solution of copper chloride and cobalt chloride. Cobalt was face-centered cubic phase when synthesized and remained fcc phase throughout the annealing process. X-ray diffractometer (XRD), transmission electron microscope (TEM), differential scanning calorimetry (DSC), vibrating sample magnetometry (VSM), inductively coupled plasma-atomic emission spectrometer (ICP-AES) measurements were carried out to investigate their structural and magnetic properties. It was found that the magnetic properties of bimetallic nanocrystallites were close to that of the sputtered alloys.     

Au+-cetyltrimethylammonium bromide solution: A novel precursor for seed-mediated growth of gold nanoparticles in aqueous solution

The appropriate choice of chemical composition of a metallic precursor, which produces the basic structure units in the growth process of nanocrystals, is a high priority in the synthesis of metal-especially Au-nanoparticles. In the present work, Au seeds (prepared by the reduction of Au³⁺ solution with NaBH4 in the presence of cetyltrimethylammonium bromide (CTAB)) have been used to initiate the growth of Au nanoparticles from two different Au precursors. When an aqueous Au⁺ solution prepared in the presence of CTAB micelles was treated with ascorbic acid in the presence of the gold seeds, a high yield (up to 92%) of gold nanoparticles was obtained. By varying the volume of the seed solution with a fixed amount of Au⁺, we can effectively control the morphological transformation of the resulting Au nanoparticles from cubes to octahedra. When an aqueous Au³⁺ solution was prepared in the presence of CTAB micelles and treated with ascorbic acid in the presence of the gold seeds, smaller yields of Au nanoparticles were obtained. A preliminary growth mechanism has been proposed based on the changes induced by varying the amount of ascorbic acid and the ratio of the concentration of Au⁺ to the number of seeds.      

Magnetite nanoparticles as adsorbent material for Cu2+ ions from aqueous solution

Cu²⁺ ions can cause serious injuries to human health, at both high and low concentrations. Therefore, it is important not only to remove Cu²⁺ ions from aqueous media, but also to develop analytical methods for their accurate determination at low concentrations. Magnetite is one of the most used sorbents for Cu²⁺ removal. This work aims at synthesizing magnetite nanoparticles and at evaluating their adsorption capacity toward Cu²⁺ ions in aqueous solution by means of atomic absorption spectroscopy. Magnetite nanoparticles were characterized by means of a vibrational magnetometer, Fourier transformer infrared spectrum (FTIR), x-ray diffraction (XRD) and Thermal gravimetric analysis (TGA). Magnetic nanoparticles showed Ms values of 52 and 62?emu/g. By taking into consideration the precipitation of Cu(OH)₂ as a function of pH in the evaluation of the adsorption capacity of magnetite, we found that the maximum Cu²⁺ adsorption occurs at pH?=?7 and that the adsorption equilibrium of the two samples is reached at 490 and 445?min. The use of blank solution avoids the overestimation of the adsorption capacity due to the presence of insoluble Cu(OH)₂. Finally, two models are considered as a liquid/solid phase reaction, pseudo-first- and pseudo-second-order reaction. Batch adsorption kinetics agrees with a pseudo-second-order model, suggesting that chemisorption is the rate-limiting step.     

Self-assembly of silver nanoparticles into dendritic flowers from aqueous solution

Similar to folding of proteins into three-dimensional (3D) structure, self-assembly of metallic nanoparticles (NPs) into dendritic or other supramolecular structures is of greater interest, yet less understood. We observed spontaneous, template-free organisation of silver NPs into 3D, dendritic, elegant, flower-like structures from an aqueous solution containing AgNO₃ and L-cysteine (Cys). The resultant NPs and dendritic structures were characterised using UV–Vis spectroscopy and scanning and transmission electron microscopy. The process initiated most likely by diffusion-limited aggregation in the liquid phase, which were further grown into elegant, dendritic flowers probably by evaporation of residual wetting layer of larger NPs. Electrostatic attraction between –COO^? and –NH₃ ⁺ groups of L-Cys on the surface of silver NPs may also have a role in their growth.     

Magnetic chitosan nanoparticles for removal of Cr(VI) from aqueous solution

A simple method was introduced to prepare magnetic chitosan nanoparticles by co-precipitation via epichlorohydrin cross-linking reaction. The average size of magnetic chitosan nanoparticles is estimated at ca. 30 nm. It was found that the adsorption of Cr(VI) was highly pH-dependent and its kinetics follows the pseudo-second-order model. Maximum adsorption capacity (at pH 3, room temperature) was calculated as 55.80 mg·g^? 1, according to Langmuir isotherm model. The nanoparticles were thoroughly characterized before and after Cr(VI) adsorption. From this result, it can be suggested that magnetic chitosan nanoparticles could serve as a promising adsorbent for Cr(VI) in wastewater treatment technology.     

Some amino acids as corrosion inhibitors for copper in nitric acid solution

The inhibition effect of five amino acids (AA) on the corrosion of copper in molar nitric solution was studied by using weight loss and electrochemical polarization measurements. Valine (Val) and Glycine (Gly) accelerate the corrosion process; but Arginine (Arg), Lysine (Lys) and Cysteine (Cys) inhibit the corrosion phenomenon. Cysteine is the best inhibitor. Its efficiency increases with the concentration to attain 61% at 10^− 3 M. Correlation between the quantum chemical calculations and inhibition efficiency was discussed using semi-empirical methods (AM1 and MNDO).     

PVP水溶液中纳米Pd粒子的生长过程及形貌控制

在微量聚乙烯吡咯烷酮(PVP)存在下,超声还原氯化钯水溶液,合成纳米Pd粒子,利用透射电镜、紫外-可见吸收光谱、X射线光电子能谱等技术对纳米Pd粒子的生长过程进行了研究。考察了PVP用量对纳米粒子形貌的影响。结果表明,当PVP与PdCl2的质量比为10∶1、超声反应50min时,得到规则的单分散球型纳米Pd粒子,粒径大约8nm左右。根据紫外-可见特征吸收波峰和X射线光电子能谱中结合能的变化,提出了纳米粒子的稳定分散是借助于纳米Pd与PVP之间的配位作用来实现的。