Nm Of Ag Research Articles

Influence of the laser light absorption by the colloid on the properties of silver nanoparticles produced by laser ablation in stirred and stationary liquid

Silver nanoparticles were produced by nanosecond pulsed-laser ablation at 1064 nm of Ag in pure water. These experiments were performed using an alternative ablation cell design where a cylindrical shaped Ag target was horizontally irradiated, while the liquid was stirred by a stir rod coaxially arranged to the target. The repeatability of the generated colloids properties (extinction and size distribution) is assessed by statistical tools. The colloids properties prepared under stationary liquid are found to be unpredictable, while they are highly repeatable at high stirring speed. At the same time, electronic microscopy examinations of the irradiated Ag targets revealed that the width of the laser-machined grooves exponentially decays in stationary liquid and almost linearly under high stirring speed as the ablation proceeds. In the latter case, the decay rate was found to be constant from one experiment to the other, while it was not repeatable stationary liquid. We show that the decay of the groove width is due to an attenuation of the laser energy reaching the target surface due to the formation of a more or less dense NPs layer in front of the target as the ablation proceeds. Using the ablation time-dependence of the groove width, we can quantify the attenuation factor of the laser energy with exposure time. Finally, the relationship between the laser energy attenuation, stirring speed, and repeatability of the colloids properties is interpreted and discussed in terms of mass transfer.

用粉末靶在玻璃和PI衬底上制备AZO/Ag/AZO薄膜

室温下在玻璃和聚酰亚胺两种不同衬底上,采用射频磁控溅射法溅射掺铝氧化锌(AZO)粉末靶和固体Ag靶,制备了两组AZO/Ag/AZO 3层透明导电薄膜,研究了AZO层厚度对不同衬底3层膜结构和光电性能的影响。结果表明:不同衬底的两组AZO/Ag/AZO薄膜均为多晶膜。当Ag层厚度不变时,随着AZO层厚度的增加,两组薄膜电学性能变化不大,透射峰向长波方向移动。玻璃和PI衬底上制备的AZO(30 nm)/Ag(14 nm)/AZO(30 nm)薄膜,在550 nm处的透光率分别为85%和70%,方块电阻分别为2.6Ω/□和4.6Ω/□。

Controlled evaluation of silver nanoparticle sulfidation in a full-scale wastewater treatment plant.

Sulfidation of silver nanoparticles (AgNPs), which is known to alter AgNP toxicity, occurs during transport through wastewater treatment plants. In this study, arrays of immobilized AgNPs fabricated by nanosphere lithography (NSL) were used to study AgNP sulfidation in a full-scale wastewater treatment plant (WWTP). A detailed laboratory study preceded field deployment. The characteristic NSL pattern remained discernible by atomic force microscopy and transmission electron microscopy after both lab and field exposures. Growth of AgNPs due to an increase in density upon sulfidation permitted the study of sulfidation kinetics in the WWTP. Sulfidation occurred almost exclusively in anaerobic zones of the WWTP, where the initial sulfidation rate was 11-14 nm of Ag converted to Ag2S per day. Measurements of the chemical composition and crystallinity of AgNPs exposed to primary influent for ∼ 10 d confirmed that they had been converted almost entirely to Ag2S. Laboratory experiments revealed that the sulfidation process is not uniform and that partially sulfidized AgNPs retain the potential to release toxic Ag(+) ions. The results indicate that primary AgNPs are sulfidized directly without dissolving and forming secondary precipitates. This study demonstrates the utility of immobilized AgNPs for detailed, in situ investigations of nanomaterial tranformations.

Growth and Properties of ZnO:Al on Textured Glass for Thin Film Solar Cells

Aluminium induced texturing (AIT) method has been used to texture glass substrates in order to enhance the photon absorption in thin film solar cells. The resultant glass roughness has been analyzed by varying the AIT process parameters and it has been found that the deposition method of Al is a decisive factor in tuning the texture. Two types of textures, a soft (texture E) and a rough texture (texture S), were achieved from the thermally evaporated and sputtered Al layers through AIT process. Aluminium-doped zinc oxide (AZO) layers of different thickness were deposited over both textures and over smooth glass. Haze values above 30% were obtained for texture S + AZO and above 10% for texture E + AZO. The resultant morphologies were free from sharp edges or deep valleys and the transparency and the resistivity values were also good enough to be used as front contact for thin film solar cells. In order to demonstrate the light absorption enhancement in a solar cell device, 200 nm of a-Si:H followed by 300 nm of Ag were grown over the textured and smooth substrates with AZO, and an optical absorption enhancement of 35% for texture E and 53% for texture S was obtained in comparison to the smooth substrate.

External electric field driven 3D ordering architecture of silver (I) oxide meso-superstructures

Summary We report an external electric field driven particle-mediated “bottom-up” assembling methodology to in situ build the Ag 2 O meso-superstructures with controlled shape and size within an electrochemical deposition system. Different shapes (rhombic hexahedron, cube and dodecahedron) and sizes (around 100 to ∼800 nm) of Ag 2 O mesocrystals have been obtained by the adjustment of the applied overpotential as well as the growth time. Various overpotentials play a crucial role in determining the shapes, structures as well as growth modes of the final product. The growth mechanism of polyhedral structures of Ag 2 O meso-superstructures is explained by the oriented attachment from the nature of crystallographic surfaces and the external electric induced ordering alignment process of primary nanoparticle building blocks. Thus, the current strategy not only provides the direct evidence of an external electric field driving in situ mesoassembling process, but also may be extended to other systems to synthesize the meso-superstructures.

Influence of Noble Metal Coating on Wettability of Copper Substrate by Sn-Ag Eutectic Solder

The influence of thin coatings (70 nm) of Au, Ag and Pd on the wettability of a Cu substrate by a Sn-3.5Ag eutectic solder was investigated using the contact angle measuring system combined with meniscograph tester. The wettability of the Cu substrate with Sn-3.5Ag was improved by the Au and Ag coatings, while reduced by a Pd coating, especially in terms of the contact angle. Namely, the contact angles were 29—30° on the Au coated-Cu substrate, 34—35° on the Ag coated-Cu substrate, 49—52° on the Pd coated-Cu substrate and 42—45° on the uncoated Cu substrate. On the wetted area, each coating layer dissolved into the solder and the Cu-Sn intermetallic compound was formed at the solder/substrate interface as well as on the uncoated Cu substrate, but the coating metal layers remained on the unwetted area. The difference in wettability of the noble metal coating on the Cu substrate was found to be attributed to the difference in the substrate-flux interfacial tensions (γsf).

Nanotechnology of transparent metals for radio frequency electromagnetic shielding

The aim of this paper is to present an innovative one-dimensional photonic bandgap structure on plastic substrate, for electromagnetic field shielding applications in the radio frequency range. A complete study is performed, from material characterization and design, to fabrication and experimental test of a prototype sample consisting of seven alternating zinc oxide and silver (Ag) layers, on Lexan polycarbonate. The transparent metal is designed to obtain high shielding effectiveness (SE), not just as a theoretical prediction, but as experimentally measured according to the standard ASTM-D 4935/89. Actually, the shielding performance of multilayered coatings having similar values of sheet resistance but different design are strongly affected by the bonding conditions. The following properties of the structure, which contains only 66 nm of Ag, are highlighted: 1) it remains transparent in the visible range; 2) it retains the conductivity of bulk metal; 3) it has SE in the 30-kHz to 1-GHz range over 40 dB; 4) the overall thickness of the multilayer shielding coating is 312 nm; and 5) it has been realized on both glass or plastic substrate.

Photochemical properties of Ag ion clusters included within ZSM-5 zeolites prepared by an ion-exchange method

Photoluminescence investigations of the Ag ion-exchanged ZSM-5 (Ag+ /ZSM-5) zeolite revealed that a Ag ion cluster (Agnm+) exists in the pore structure of ZSM-5 exhibiting photoluminesm cence at 380 nm upon excitation at 332 nm. UV irradiation (λ = 285 nm) of Ag+ /ZSM-5 at 77 K leads to the transformation of Agnm+ into a different Ag ion cluster (Agm(n-1)+) which exhibits photoluminescence at 465 nm upon excitation at 315 nm. This photo-transformation of the Ag ion clusters was found to be thermally reversible under vacuum. It was demonstrated that an electron transfer from the photo-excited Al3+ -O2- to Agnm+ plays a significant role in this process. In the presence of oxygen, UV irradiation of Ag+ /ZSM-5 leads to the formation of O2- instead of an Ag ion cluster (Agm(n-1)+), suggesting that oxygen acts as an efficient electron scavenger, which interferes with the electron capture of Agnm+ under UV irradiation at 285 nm.

Pretreating zinciferous surfaces

Between Late Cretaceous and Miocene time the central part of Tunisia emerged. During this period a karstic system developed in Senonian limestones of the Ain Khamouda area. It is known that three facies occur in the resulting caves: (1) red mineralised crust containing goethite, hemimorphite and smithsonite; (2) white clay containing 0.1–8.5% ZnO; (3) Miocene sand and sandstone. The white clay has been studied using STEM (scanning transmission electron microscopy) in order to determine with which minerals Zn is associated. Two zinciferous phases were found, the first being a swelling clay of sauconite type, the second a nearly amorphous Zn-hydroxide gel. Halloysite which is the main component of the white clay seems totally devoid of Zn. The difference between Zn minerals contained in the crust and in the clay can be related to pH gradients. Minute particles (3–10 nm) of pure Ag, were found in the clay, indicating that the present mineralisation is probably related to the alteration of sulphides.

Buffing apparatus suitable for thin plate work

Between Late Cretaceous and Miocene time the central part of Tunisia emerged. During this period a karstic system developed in Senonian limestones of the Ain Khamouda area. It is known that three facies occur in the resulting caves: (1) red mineralised crust containing goethite, hemimorphite and smithsonite; (2) white clay containing 0.1–8.5% ZnO; (3) Miocene sand and sandstone. The white clay has been studied using STEM (scanning transmission electron microscopy) in order to determine with which minerals Zn is associated. Two zinciferous phases were found, the first being a swelling clay of sauconite type, the second a nearly amorphous Zn-hydroxide gel. Halloysite which is the main component of the white clay seems totally devoid of Zn. The difference between Zn minerals contained in the crust and in the clay can be related to pH gradients. Minute particles (3–10 nm) of pure Ag, were found in the clay, indicating that the present mineralisation is probably related to the alteration of sulphides.

Metal overlayers on organic functional groups of self-organized molecular assemblies. V. Ion scattering spectroscopy and x-ray photoelectron spectroscopy of Ag/COOH interfaces

In the present work, x-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were used to characterize mercaptoundecanoic acid [MUA, HS(CH2)10 COOH] and mercaptohexadecanoic acid [MHA, HS(CH2)15COOH] self-assembled monolayers (SAMs) before and after depositing up to 1.0 nm Ag at ∼10−7 Torr. Results from XPS O 1s, Ag 3d, and C 1s spectra do not indicate that a complex is formed (no chemical shifts) between Ag and the COOH of MUA or MHA at 295 K. Although no direct evidence for Ag/COOH interactions is evident, the initial value for ISS Ag peak intensities for 1.0 nm of Ag on COOH of MHA is unchanged after 1 h and is only reduced to 68% of the initial value after 15 h. For MUA, the ISS Ag peak intensity for 1.0 nm is constant for about 5 min and is gradually reduced until it is not detectable about 90 min after Ag deposition. These results and those we obtained earlier for Ag on octadecanethiol [ODT, HS(CH2)17CH3] might be explained by weak or no interactions between Ag and COOH and by different defect densities in the SAMs. The initial Ag ISS peak intensity for 1.0 nm Ag on MHA increases from 295 K as the SAM temperature is reduced to reach a maximum at about 200 K. The increased ISS intensity from Ag/COOH vs Ag/CH3 is consistent with lower defect densities in the MHA vs ODT.

Analysis of zinciferous clays from central Tunisia using a scanning transmission electron microscope (STEM)

Between Late Cretaceous and Miocene time the central part of Tunisia emerged. During this period a karstic system developed in Senonian limestones of the Ain Khamouda area. It is known that three facies occur in the resulting caves: (1) red mineralised crust containing goethite, hemimorphite and smithsonite; (2) white clay containing 0.1–8.5% ZnO; (3) Miocene sand and sandstone. The white clay has been studied using STEM (scanning transmission electron microscopy) in order to determine with which minerals Zn is associated. Two zinciferous phases were found, the first being a swelling clay of sauconite type, the second a nearly amorphous Zn-hydroxide gel. Halloysite which is the main component of the white clay seems totally devoid of Zn. The difference between Zn minerals contained in the crust and in the clay can be related to pH gradients. Minute particles (3–10 nm) of pure Ag, were found in the clay, indicating that the present mineralisation is probably related to the alteration of sulphides.