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1.
Some of the old and unrealizable dreams of biomedicine have become possible thanks to the appearance of novel advanced materials such as luminescent nanothermometers, nanoparticles capable of providing a contactless thermal reading through their light emission properties. Luminescent nanothermometers have already been demonstrated to be capable of in vivo subcutaneous punctual thermal reading but their real application as diagnosis tools still requires demonstrating their actual capacity for the acquisition of in vivo, time‐resolved subcutaneous thermal images. The transfer from 1D to 2D subcutaneous thermal sensing is blocked in the last years mainly due to the lack of high sensitivity luminescent nanothermometers operating in the infrared biological windows. This work demonstrates how core/shell engineering, in combination with selective rare earth doping, can be used to develop supersensitive infrared luminescent nanothermometers. Erbium, thulium, and ytterbium core–shell LaF3 nanoparticles, operating within the biological windows, provide thermal sensitivities as large as 5% °C?1. This “record” sensitivity has allowed for the final acquisition of subcutaneous thermal videos of a living animal. Subsequent analysis of thermal videos allows for an unequivocal determination of intrinsic properties of subcutaneous tissues, opening the venue to the development of novel thermal imaging‐based diagnosis tools.  相似文献   

2.
The interfacial reaction between liquid In-49Sn solders and Ag substrates results in the formation of a thicker Ag2In intermetallic compound accompanied with the development of a thin AgIn2 layer. Through further aging of the In-49Sn/Ag soldered specimens at various temperatures ranging from room to 100°C, solid/solid trnasitions between Ag2In and AgIn2 intermetallic compounds can be observed. When the temperature drops below 75°C, Ag2In will react with the In-49Sn solder to form the dominant AgIn2 phase. Conversely, AgIn2 is consumed at a higher temperature (e.g., 100°C) when reacting with the Ag substrate to create a now dominant Ag2In phase. Lastly, the different mechanical, electrical, magnetic, and corrosion behaviors of both intermetallic compounds are respectively made known through direct measurements of the material properties of the individual Ag2In and AgIn2 bulk samples.  相似文献   

3.
Nanofiber bundles of Ag2S, Ag2Se, and Ag have been successfully synthesized by making use of Ag2C2O4 template nanofiber bundles, utilizing both anion‐exchange and redox reactions. The obtained bundles were polycrystalline nanofibers composed of nanoparticles in which the precursor morphology was well‐preserved, indicating that Ag2C2O4 nanofiber bundles acted as a general sacrificial template for the synthesis of silver‐based semiconductor and metal nanofibers. Dispersing media and transforming reactants were found to be key factors influencing the chemical transformation in the system. In particular, separate single‐crystalline Ag nanofibers were obtained via a nontemplate route when ascorbic acid was used as a relatively weak reductant. An electrical transfer and switching device was built with the obtained Ag2S and Ag nanofiber bundles, utilizing the unique ion‐conductor nature of Ag2S and revealing their potential applications in electronics.  相似文献   

4.
Cationic Au4Ag2 heterohexanuclear aromatic acetylides cluster complexes supported by bis(2‐diphenylphosphinoethyl)phenylphosphine (dpep) are prepared. The Au4Ag2 cluster structure originating from the combination of one anionic [Au(C≡CR)2]? with one cationic [Au3Ag2(dpep)2(C≡CR)2]3+ through the formation of Ag?acetylide η2‐bonds is highly stabilized by Au–Ag and Au–Au contacts. The Au4Ag2 alkynyl cluster complexes are moderately phosphorescent in the fluid CH2Cl2 solution, but exhibit highly intense phosphorescent emission in solid state and film. As revealed by theoretical computational studies, the phosphorescence is ascribable to significant 3[π (aromatic acetylide) → s/p (Au)] 3LMCT parentage with a noticeable Au4Ag2 cluster centered 3[d → s/p] triplet state. Taking advantage of mCP and OXD‐7 as a mixed host with 20 wt% dopant of phosphorescent Au4Ag2 cluster complex in the emitting layer, solution‐processed organic light‐emitting diodes (OLEDs) exhibit highly efficient electrophosphorescence with the maximum current, power, and external quantum efficiencies of 24.1 cd A?1, 11.6 lm W?1, and 7.0%, respectively. Introducing copper(I) thiocyanate (CuSCN) as a hole‐transporting layer onto the PEDOT:PSS hole‐injecting layer through the orthogonal solution process induces an obvious improvement of the device performance with lower turn‐on voltage and higher electroluminescent efficiency.  相似文献   

5.
The effect of electric current on the Sn/Ag interfacial reaction was studied at 140°C and 200°C, by examining the growth of phase (ε-Ag3Sn) in the Sn/Ag reaction couples with a constant current density. Only at 140°C was the growth of phase affected by the passage of electric current. The growth rate was enhanced when diffusion of Sn and electron flow were in the same direction, and retarded when they were in the opposite direction. It was found that the diffusion coefficient of Sn through Ag3Sn was 3.37 μm2/h and the apparent effective charge for Sn in Ag3Sn was −90, at 140°C.  相似文献   

6.
A setup is developed for measuring the thermal properties of Ag2Te and Ag2Se near the main phase transition and in the region of it in high vacuum. The samples are of stoichiometric composition with an excess of Ag, Te, and Se. Differential thermal analysis is performed and the temperature differences across and along the samples are measured by the pulsed light method. Using data on the thermal diffusivity a(T), the temperature dependence of the thermal conductivity K = apc is determined, where p is the density and c is the specific heat. The measurement technique used allows us to establish that the main phase transitions are accompanied by intense heat release. New phase transitions before and after the main structural phase transition with heat absorption are found. According to the DTA data, in the Ag2Te sample with an excess of Ag (0.25 at.%, cn = 1.2 × 1019 cm?3) the phase transition at 365 K is also accompanied by heat absorption. Thus, it is established that all of the phase transitions in Ag2Te and Ag2Se are first-order.  相似文献   

7.
Intermetallic compounds formed during the soldering reactions between Sn-3.5Ag and Cu at temperatures ranging from 250°C to 375°C are investigated. The results indicate that scallop-shaped η-Cu6(Sn0.933 Ag0.007)5 intermetallics grow from the Sn-3.5Ag/Cu interface toward the solder matrix accompanied by Cu dissolution. Following prolonged or higher temperature reactions, ɛ-Cu3 (Sn0.996 Ag0.004) intermetallic layers appear behind the Cu6(Sn0.933 Ag0.007)5 scallops. The growth of these interfacial intermetallics is governed by a kinetic relation: ΔX=tn, where the n values for η and ɛ intermetallics are 0.75 and 0.96, respectively. The mechanisms for such nonparabolic growth of interfacial intermetallics during the liquid/solid reactions between Sn-3.5Ag solders and Cu substrates are probed.  相似文献   

8.
The morphology and growth kinetics of intermetallic compounds formed during the reaction of liquid In 10Ag on Ag substrates in the temperature range between 250°C and 375°C are studied. The results indicate that the Ag2In intermetallic compounds that appear at the interface are in the columnar shape, enveloped by thin AgIn2 shells. The growth kinetics of intermetallic compounds are parabolic, indicating that the reaction is diffusion-controlled. The Arrhenius reaction activation energy was found to be 44.9 kJ/mol. Also, the wetting behavior of the In10Ag on Ag substrates was studied. The results show that there exists a transient plateau of the contact angle variation. Such a phenomenon can be explained by the intermetallic compound precursor halo formation preceding the edge of the solder drop.  相似文献   

9.
The interfacial reactions between In49Sn solders and Ag thick films at temperatures ranging from 200°C to 350°C have been studied. The intermetallic compound formed at the Ag/In49Sn interface is Ag2In enveloped in a thin layer of AgIn2. Through the measurement of the thickness decrease of Ag thick films, it has been determined that the reaction kinetics of Ag2In has a linear relation to reaction time. Morphology observations indicated that the linear reaction of Ag2In was caused by the floating of Ag2In into the In49Sn solder as a result of the In49Sn solder penetrating into the porous Ag thick film. A sound joint can be obtained when a sufficient thickness of the Ag thick film (over 19.5 μm) reacts with the In49Sn solder. In this case, the tensile tested specimens fracture in the In49Sn matrix.  相似文献   

10.
Novel visible-light-driven Ag3PO4@C3N4PO4 loaded with metal Ag were synthesised via an anion-exchange precipitation method and regenerated by H2O2 and NaNH3HPO4. The obtained Ag/Ag3PO4@C3N4 and regenerated Ag/Ag3PO4@C3N4 were characterised by XRD, XPS, SEM and UV–vis. The XRD and UV–vis results revealed that the crystal structure and light adsorption property of Ag/Ag3PO4@C3N4 were similar to that of regenerated Ag/Ag3PO4@C3N4. The XPS result showed that the metallic Ag0 deposited on the surface of Ag/Ag3PO4@C3N4 and regenerated Ag/Ag3PO4@C3N4. The Ag/Ag3PO4@C3N4 hybrids displayed remarkable photocatalytic activity and stability after regeneration. Compared with pure Ag3PO4 or C3N4, the Ag/Ag3PO4@C3N4 and regenerated Ag/Ag3PO4@C3N4 enhancement in the photodegradation rate towards methyl orange is observed over under visible light irradiation. The enhanced photocatalytic performance was attributed to the synergistic effect between Ag3PO4 and C3N4 and a small amount of Ag0 which suppresses the charge recombination during photocatalytic process. This work could provide new insights into the fabrication of high stability visible photocatalysts and facilitate their practical application in environment issues.  相似文献   

11.
《Microelectronics Reliability》2015,55(11):2306-2315
We found the failure mechanisms in Ag wire bonded to Al pads during the high-temperature-storage lifetime test (HTST) and the unbiased highly-accelerated temperature and humidity storage test (uHAST). The native oxide layer on the Al pads caused a ball lift. The moisture and the thermal energy during uHAST along with the Cl ion in epoxy molding compounds (EMCs) induced repetitive oxidation and reduction reactions of the Ag–Al intermetallic compounds (IMCs) with the Al pads. These repetitive reactions formed H2 gas as a by-product causing the formation of a micro-crack. In addition, the alumina layer acted as a resistive layer in the Ag–Al IMCs. The phases of the Ag–Al IMCs were identified as Ag2Al and Ag3Al, and the growth rates of those IMCs were measured at 150 and 175 °C for 2000 h.  相似文献   

12.
Thin film of silver tin sulfides (Ag–Sn–S) has been deposited on indium tin oxide coated glass (ITO) substrates using potentiostatic cathodic electrodeposition technique. New procedure for the growth of Ag–Sn–S film is presented. An electrolyte solution containing Silver Nitrate (AgNO3), Tin(II) Chloride (SnCl2) and Sodium Thiosulfate (Na2S2O3)in acidic solution (pH ~2) and at temperature of the bath 55 °C were used for the growth of Ag–Sn–S thin film. Prior to the deposition, a cyclic voltammetry technique was performed in binary (Ag–S, Sn–S) and ternary (Ag–Sn–S) systems. This study was carried out to examine the behavior of electroactive species at the electrode surface. Based on these results, the cathodic applied potential was fixed at −1000 mV versus Ag/AgCl to obtain a uniform and good adhesion of ternary thin film. After that, structural, morphological and optical performances of films have been investigated. The X-ray diffraction patterns of the samples demonstrate the presence of the orthorhombic phase of Ag8SnS6 at applied potential of −1000 mV versus Ag/AgCl. Based on the scanning electron microscopy (SEM), it was found that the surface morphology and grain size were strongly influenced by the presence of Sn and/or Ag in the electrolyte bath. The band gaps of binaries and ternary compound are evaluated from optical absorption measurements. Band gap of Ag8SnS6 determined from transmittance spectra is in the range 1.56 eV. Flat-band potential and free carrier concentration have been determined from Mott–Schottky plot and are estimated to be around 0.18 V and 2.21×1014 cm−3 respectively. The photoelectrochemical test of Ag8SnS6 was studied and the experimental observations are discussed in detail.  相似文献   

13.
Accurate, noninvasive, and self‐referenced temperature measurements at the submicrometer scale are of great interest, prompted by the ever‐growing demands in the fields of nanotechnology and nanomedicine. The thermal dependence of the phosphor's luminescence provides high detection sensitivity and spatial resolution with short acquisition times in, e.g., biological fluids, strong electromagnetic fields, and fast‐moving objects. Here, it is shown that nanoparticles of [(Tb0.914Eu0.086)2(PDA)3(H2O)]·2H2O (PDA = 1,4‐phenylenediacetic acid), the first lanthanide–organic framework prepared by the spray‐drying method, are excellent nanothermometers operating in the solid state in the 10–325 K range (quantum yield of 0.25 at 370 nm, at room temperature). Intriguingly, this system is the most sensitive cryogenic nanothermometer reported so far, combining high sensitivity (up to 5.96 ± 0.04% K?1 at 25 K), reproducibility (in excess of 99%), and low‐temperature uncertainty (0.02 K at 25 K).  相似文献   

14.
Anisotropic Ag2S‐edged Au‐triangular nanoprisms (TNPs) are constructed by controlling preferential overgrowth of Ag2S as plasmonic photocatalysts for hydrogen generation. Under visible and near‐infrared light irradiation, Ag2S‐edged Au‐TNPs exhibit almost fourfold higher efficiency (796 µmol h−1 g−1) than those of Ag2S‐covered Au‐TNPs (216 µmol h−1 g−1) and pure Au‐TNPs in hydrogen generation. A single‐particle photoluminescence study demonstrates that the plasmon‐induced hot electrons transfer from Au‐TNPs to Ag2S for hydrogen generation. Finite‐difference‐time‐domain simulations verify that the corners/edges of Au‐TNPs are high‐curvature sites with maximum electric field distributions facilitating hot electron generation and transfer. Therefore, Ag2S‐edged Au‐TNPs are efficient plasmonic photocatalyst with the desired configurations for charge separation boosting hydrogen generation.  相似文献   

15.
TiO2? Ag‐nanocomposites exhibit various desirable properties that make them suitable for a variety of applications, for example in photocatalysis and as bactericidal coatings. In this work, a new method for processing TiO2? Ag nanocomposites is presented. The nanocomposite films are fabricated from one precursor solution with high silver loading of up to 50%. The resulting films exhibit a microstructure consisting of TiO2? AgxO nanocomposites with a largely XRD‐amorphous TiO2 matrix containing brookite nanocrystals. This specific microstructure absorbs in the visible range so that photoreduction of Ag ions can be accomplished by using visible light. The thin films can be patterned using simple shadow masks. The illuminated areas show a high density of self‐organized nanoparticles (SNPs) and nanorods (SNRs), which are templated by the TiO2 porous network. The particle size can be tuned by varying the irradiation time. Most of the SNPs and SNRs form faceted crystals, which are mostly a combination of {111} and {110}. The application of these films as substrates for surface‐enhanced Raman scattering is shown. Enhancement factors as high as 4.6 × 106 could be obtained using rhodamine 6G dye molecules. More applications should involve photocatalytic water purification using visible light.  相似文献   

16.
In this study, solid-state interfacial reactions between Ag and Sn-Zn alloys with varying Zn content (0.1 wt.% to 9 wt.%) were investigated at 170°C. The reaction couples were prepared by electroplating Ag on the Sn-Zn alloy to avoid dissolution of Ag into the molten solder during soldering. The Zn content greatly influenced the reaction products and the interfacial microstructures. When the Zn content was less than 4 wt.%, Ag3Sn and AgZn layers were simultaneously formed. Notably, Zn could actively diffuse through the Ag3Sn layer and react with Ag to form the AgZn phase. With the proceeding reaction, small α-Ag particulates were produced within the AgZn phase. With 9 wt.% Zn, the dominant reactions formed Ag5Zn8 and AgZn layers. The interfacial microstructure evolved significantly with reaction time. Interface instability due to Zn depletion in the solder resulted in massive spalling of the Ag5Zn8 layer. The Ag3Sn phase was then produced next to the AgZn layer. Moreover, another reaction couple, Sn-9 wt.%Zn/Sn(15 μm)/Ag, was prepared, in which fast interdiffusion between Zn and Ag across the Sn layer was demonstrated due to the strong chemical affinity of Zn.  相似文献   

17.
The interfacial reaction between two prototype multicomponent lead-free solders, Sn-3.4Ag-1Bi-0.7Cu-4In and Sn-3.4Ag-3Bi-0.7Cu-4In (mass%), and Ag, Cu, Ni, and Pd substrates are studied at 250°C and 150°C. The microstructural characterization of the solder bumps is carried out by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis. Ambient temperature, isotropic elastic properties (bulk, shear, and Young’s moduli and Poisson’s ratio) of these solders along with eutectic Sn-Ag, Sn-Bi, and Sn-Zn solders are measured. The isotropic elastic moduli of multicomponent solders are very similar to the eutectic Sn-Ag solder. The measured solubility of the base metal in liquid solders at 250°C agrees very well with the solubility limits reported in assessed Sn-X (X=Ag, Cu, Ni, Pd) phase diagrams. The measured contact angles were generally less than 15° on Cu and Pd substrates, while they were between 25° and 30° on Ag and Ni substrates. The observed intermediate phases in Ag/solder couples were Ag3Sn after reflow at 250°C and Ag3Sn and ζ (Ag-Sn) after solid-state aging at 150°C. In Cu/solder and Ni/solder couples, the interfacial phases were Cu6Sn5 and (Cu,Ni)6Sn5, respectively. In Pd/solder couples, only PdSn4 after 60-sec reflow, while both PdSn4 and PdSn3 after 300-sec reflow, were observed.  相似文献   

18.
New bis(ω‐hydroxyalkyl)imidazolium and 1,2‐bis[N‐(ω‐hydroxyalkyl)imidazolium]ethane salts are synthesized and characterized; most of the salts are room temperature ionic liquids. These hydroxyl end‐functionalized ionic liquids are polymerized with diacid chlorides, yielding polyesters containing imidazolium cations embedded in the main chain. By X‐ray scattering, four polyesters are found to be semicrystalline at room temperature: mono‐imidazolium‐C11‐sebacate‐C6 ( 4e ), mono‐imidazolium‐C11‐sebacate‐C11 ( 4c ), bis(imidazolium)ethane‐C6‐sebacate‐C6 ( 5a ), and bis(imidazolium)ethane‐C11‐sebacate‐C11 ( 5c ), all with hexafluorophosphate counterions. The other imidazolium polyesters, including all those with bis(trifluoromethanesulfonyl)imide (TFSI?) counterions, are amorphous at room temperature. Room temperature ionic conductivities of the mono‐imidazolium polyesters (4 × 10?6 to 3 × 10?5 S cm?1) are higher than those of the corresponding bis‐imidazolium polyesters (4 × 10?9 to 8 × 10?6 S cm?1), even though the bis‐imidazolium polyesters have higher ion concentrations. Counterions affect ionic conduction significantly; all polymers with TFSI? counterions have higher ionic conductivities than the hexafluorophosphate analogs. Interestingly, the hexafluorophosphate polyester, 1,2‐bis(imidazolium)ethane‐C11‐sebacate‐C11 ( 5c ), displays almost 400‐fold higher room temperature ionic conductivity (1.6 × 10?6 S cm?1) than the 1,2‐bis(imidazolium)ethane‐C6‐sebacate‐C6 analog ( 5a , 4.3 × 10?9 S cm?1), attributable to the differences in the semicrystalline structure in 5c as compared to 5a . These results indicate that semicrystalline polymers may result in high ionic conductivity in a soft (low glass tranition temperature, Tg) amorphous phase and good mechanical properties of the crystalline phase.  相似文献   

19.
The quantitative detection of microRNA (miR) and multimode‐imaging‐induced photothermal therapy in vivo have become the focus of much attention. Platinum (Pt) decorated gold nanorods (AuNR‐Pt) and Ag2S core–satellite (AuNR‐Pt@Ag2S) multifunctional nanostructures are fabricated to quantify intracellular miRs (miR‐21), near‐infrared fluorescence cell quantitative imaging, and tumor ablation in vivo. When combined with miR‐21, the nanoassembly displays significant fluorescence intensity in the second window of the near‐infrared region (1000–1700 nm) after 808 nm excitation. The Ag2S fluorescence intensity has a good linear relationship with the amount of intracellular miR in the range of 0.054–20.45 amol ngRNA ?1 and a limit of detection of 0.0082 amol ngRNA ?1. The nanoassembly is also used to develop multimodal bioimaging, including near‐infrared, X‐ray computed tomographic, and photoacoustic imaging in HeLa‐tumor‐bearing mice. Moreover, the tumors are completely eliminated by the high photothermal capacity of the AuNR‐Pt@Ag2S assembly. This nanoassembly provides a multifunctional nanoplatform for the ultrasensitive detection of miRs and tumor diagnosis and therapy in vivo.  相似文献   

20.
We have investigated the structural and electrical characteristics of the Ag/n-TiO2/p-Si/Al heterostructure. Thin films of pure TiO2 were deposited on p-type silicon (100) by optimized pulsed laser ablation with a KrF-excimer laser in an oxygen-controlled environment. X-ray diffraction analysis showed the formation of crystalline TiO2 film having a tetragonal texture with a strong (210) plane as the preferred direction. High purity aluminium and silver metals were deposited to obtain ohmic contacts on p-Si and n-TiO2, respectively. The current–voltage (IV) characteristics of the fabricated heterostructure were studied by using thermionic emission diffusion mechanism over the temperature range of 80–300 K. Parameters such as barrier height and ideality factor were derived from the measured IV data of the heterostructure. The detailed analysis of IV measurements revealed good rectifying behavior in the inhomogeneous Ag/n-TiO2/p-Si(100)/Al heterostructure. The variations of barrier height and ideality factor with temperature and the non-linearity of the activation energy plot confirmed that barrier heights at the interface follow Gaussian distributions. The value of Richardson’s constant was found to be 6.73 × 105 Am?2 K?2, which is of the order of the theoretical value 3.2 × 105 Am?2 K?2. The capacitance–voltage (CV) measurements of the heterostructure were investigated as a function of temperature. The frequency dependence (Mott–Schottky plot) of the CV characteristics was also studied. These measurements indicate the occurrence of a built-in barrier and impurity concentration in TiO2 film. The optical studies were also performed using a UV–Vis spectrophotometer. The optical band gap energy of TiO2 films was found to be 3.60 eV.  相似文献   

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