The origin of interfacial delamination in Au/ceramic cofired LTCC structure

The interfacial delamination of electrode/ceramic multilayer structure will seriously damage the reliability of low temperature co-fired ceramic (LTCC) module in practical applications. In this work, three kinds of glasses employed in Au electrode are designed and prepared to study the abnormal expansion and delamination process in the Au/ceramic LTCC multilayer structure. The interfacial delamination in the co-fired structure is found to be attributed to the abnormal expansion of glass in respect to Au electrode at high temperature, which is originated from the enlarged closed pores during the co-firing process. This conclusion is further confirmed by co-firing the sample in a low-pressure condition. The mechanism and elimination of interfacial delamination here provides a feasible solution for the design of novel glasses in Au electrode for LTCC applications.     

Selective and efficient hydrogen separation of Pd–Au–Ag ternary alloy membrane

The widespread demand for clean energy stimulates great interest to hydrogen energy with high energy density and conversion efficiency. Separation technologies by membranes are increasingly applied for hydrogen separation because of its excellent performance and low consumption. In this work, density functional theory simulations is used to study hydrogen separation of Pd–Au–Ag membrane, and the performance of Pd–Au alloy is also compared and discussed. The results indicate that Pd–Au alloy shows superior selectivity to H₂ gas over CO, N₂, CH₄, CO₂ and H₂S gases, which is in line with experimental results. In particular, the separation selectivity of Pd–Au–Ag to H₂ is significantly greater than those for Pd–Au alloy and several currently reported materials. Moreover, the permeability of H₂ in Pd–Au–Ag exceeds the limits for industrial production at deferent temperatures. Our calculations demonstrate that Pd–Au–Ag alloy present excellent performance as a promising membrane for hydrogen separation.     

Colloidal synthesis of Au nanoparticles using polyelectrolytes with 1,3,4-thiadiazole as reducing agents

Heterocyclic compounds are well known for their biological activity and coordination properties. Some heterocyclic compounds have been employed in the stabilization against coalescence of metallic nanoparticles in colloidal solutions, for example, tetrazole, triazole, and pyrazole. The aim of this work is to design new polyelectrolytes with heterocyclic pendant groups useful as reducing agents of Au³⁺ and as stabilizing agents for the synthesis of colloidal Au nanoparticles. Thus, polyelectrolytes with thiosemicarbazone and 1,3,4-thiadiazole pendant groups were used as reducing agents of Au³⁺ ions and stabilizing agents of Au nanoparticles. The voltammetry study of the polyelectrolytes showed that one with thiosemicarbazone pendant groups is the better reducing agent than polyelectrolytes with heterocyclic pendant groups. The polyelectrolytes can control the growth of the nanoparticles, obtaining structures with an average size of 9 nm. In this study, it was concluded that the nature of the heterocyclic group does not have an effect on the shape of nanoparticles and quasi-spherical nanoparticles were obtained with all polyelectrolytes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47790.     

Au基MOFs双功能催化剂的制备及其催化CO2与苯胺/H2反应性能

以UiO-66(Zr)、MIL-100(Fe)、MIL-100(Cr)、MIL-101(Cr)、NH_2-MIL-101(Al)为载体,Au为活性组分,制备Au/UiO-66(Zr)、Au/MIL-100(Fe)、Au/MIL-100(Cr)、Au/MIL-101(Cr)、Au/NH_2-MIL-101(Al)双功能催化剂。采用XRD、BET、NH_3-TPD、HRTEM等表征催化剂的结构,在釜式反应器中评价催化剂对CO_2与苯胺/H_2反应生成N-甲基苯胺与N,N-二甲基苯胺的N-甲基化反应性能,考察反应条件对催化剂催化性能的影响。结果表明,催化剂的XRD特征衍射峰与相应MOFs的模拟特征峰基本一致;负载Au后催化剂仍具有高的比表面积和大的孔容、孔径;不同MOFs负载Au的催化剂具有不同的酸强度和酸量;Au纳米粒子的分散性很好,粒径为(3～7) nm。制备的催化剂均具有催化CO_2与苯胺/H_2的N-甲基化反应性能,其中质量分数2%Au/MIL-101(Cr)催化剂催化性能最好,苯胺转化率为45.26%,N-甲基苯胺和N,N-二甲基苯胺选择性分别为73.50%和26.50%,重复使用性能优异。     

Improvement of gold electrode conductivity after cofiring with CaO–B2O3–SiO2 green tapes for LTCC application

The cofiring process of Au paste containing various amount of glass additive with different properties and CaO–B₂O₃–SiO₂ (CBS) green tapes was investigated. The initial shrinkage temperature of Au paste was strongly associated with the softening point and the content of glass additive. The swell of sample and its mechanism during cofiring process was reported. The sheet resistivity of Au electrode was greatly depended on the content of CBS glass additive. When the content of CBS glass additive with the softening point of 704 °C was 3 wt %, the Au electrode exhibited the highest conductivity with the sheet resistivity of 2.4 mΩ/sq. The results obtained in this paper revealed the relationship between the glass additive and cofiring defects of Au electrode in the metal/ceramic multilayer structure, which gave an avenue to manufacture Low temperature co-fired ceramics (LTCC) modules with good quality.     

Gold Drugs with {Au(PPh3)}+ Moiety: Advantages and Medicinal Applications

Following the success of Auranofin as an anti-arthritic drug, search for novel gold drugs has afforded a large number of [L−Au(PPh₃)] complexes that exhibit notable salutary effects. Unlike Au(III)-containing species, these gold complexes with {Au(PPh₃)}⁺ moiety are stable in biological media and readily exchange L with S- and Se-containing enzymes or proteins. Such exchange leads to rapid reduction of microbial loads or induction of apoptotic cell death at malignant sites. In many cases the lipophilic {Au(PPh₃)}⁺ moiety delivers a desirable toxic L to the specific cellular target in addition to exhibiting its own beneficial activity. Further research and utilization of this synthon in drug design could lead to novel chemotherapeutics for treatment of drug-resistant pathogens and cancers.     

Facile synthesis of PdAu/C by cold plasma for efficient dehydrogenation of formic acid

Decomposition of formic acid biomass to generate hydrogen is vital for coping with fossil energy depletion, environmental pollution, and developing clean, efficient, safe, and sustainable modern energy system. In this study, a PdAu/C−C bimetallic catalyst was prepared by the co-impregnation method followed by an atmospheric pressure (AP) cold plasma treatment to synthesize PdAu/C−P catalysts. The resulting PdAu/C−P showed excellent catalytic activity for the formic acid dehydrogenation (FAD) reaction. The total volume of H₂ and CO₂ released from the FAD reaction was about 375 mL after 4 h at 50 °C, and the initial turnover frequency (TOF_initial) was 808.6 h⁻¹. We used X−ray diffractometry (XRD), temperature programmed reduction (TPR) and high-resolution transmission electron microscopy (HRTEM) to show that plasma can effectively promote the redispersion of Pd−Au particles on the surface of the support. The average particle size of PdAu/C−P (3.5 ± 1.5 nm) was less than PdAu/C−C (4.4 ± 1.9 nm) and uniformly distributed. X-ray photoelectron spectroscopy (XPS), TPR, and HRTEM showed that PdAu/C−P has a higher degree of alloying. In addition, the strong electric field in the plasma facilitated more metal sites located on the outer surface of the support in PdAu/C−P, and the atomic ratio of M/C (M = Pd and Au) (0.0134) was much larger than that of PdAu/C−C (0.0060). The apparent activation energy (E_a) of PdAu/C−P for the FAD reaction was only 27.25 kJ mol⁻¹, and it had much higher activity and stability than the commercial Pd/C (Sigma−Aldrich). The total volume of H₂ and CO₂ produced over the PdAu/C−P for three cycles was 1.33, 5.87, and 8.56 times that of commercial Pd/C. Overall, the cold plasma enhanced the degree of alloying, promoted the redispersion of agglomerated particles, and regulated the surface enrichment of the active metal components. This is of great significance for guiding the preparation of high−performance multi-metal catalysts by cold plasma.     

Embedding Ag or Au nanoparticles within the nano-sized wall of YbPO4:Er3+ inverse opals and resulting enhanced upconversion luminescence

Metal nanoparticles preparation in the interior of nanoscale skeleton of inverse opals made up of crystallized matrix is more difficult than the preparation of pure inverse opals. In the present work, the Ag or Au nanoparticles embedded YbPO₄:Er³⁺ inverse opals were prepared by a simple approach, which involved the infiltration of opal template by using the transparent YbPO₄:Er³⁺ sol including silver nitrate or chloroauric acid and the sintering at high temperature. The 20–30?nm Au or 5–10?nm Ag nanoparticles were formed in the interior of nanoscale skeleton in the YbPO₄:Er³⁺ inverse opals, and the Ag or Au nanoparticles embedded YbPO₄:Er³⁺ inverse opals were prepared. The influence of Ag or Au nanoparticles on the upconversion photoluminescence of YbPO₄:Er³⁺ inverse opal was studied, and the upconversion luminescence enhancement induced by the Ag or Au nanoparticles was observed. The mechanisms of upconversion luminescence enhancement of YbPO₄:Er³⁺ inverse opals induced by Ag or Au nanoparticles were discussed. The enhancement of upconversion luminescence induced by Ag nanoparticles was attributed to the enhancement of the excitation field, and the enhancement of upconversion emission induced by Au nanoparticles was related to the increasing of the radiation decay rate of Er³⁺.