Nanoscale Au-ZnO heterostructure developed by atomic layer deposition towards amperometric H2O2 detection

Nanoscale Au-ZnO heterostructures were fabricated on 4-in. SiO2/Si wafers by the atomic layer deposition (ALD) technique. Developed Au-ZnO heterostructures after post-deposition annealing at 250 degrees C were tested for amperometric hydrogen peroxide (H2O2) detection. The surface morphology and nanostructure of Au-ZnO heterostructures were examined by field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), etc. Additionally, the electrochemical behavior of Au-ZnO heterostructures towards H2O2 sensing under various conditions is assessed by chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that ALD-fabricated Au-ZnO heterostructures exhibited one of the highest sensitivities of 0.53 mu A mu M(-1)cm(-2), the widest linear H2O2 detection range of 1.0 mu M-120mM, a low limit of detection (LOD) of 0.78 mu M, excellent selectivity under the normal operation conditions, and great long-term stability. Utilization of the ALD deposition method opens up a unique opportunity for the improvement of the various capabilities of the devices based on Au-ZnO heterostructures for amperometric detection of different chemicals

Microstructure and mechanical properties of an Mg-3Zn- o.5Zr-5HA nanocomposite processed by ECAE

Mg matrix composites reinforced by natural bone constituent hydroxyapatite (HA) particles have shown promising in-vitro corrosion resistance but are inconsistent in both electrochemical and mechanical performances because of severe particle segregations. The present work was carried out to investigate the feasibility of a novel technology that combines high shear solidification and equal channel angular extrusion (ECAE) for fabricating Mg-HA nanocomposites. Experiments showed that the high shear solidification resulted in a fine and uniform grain structure with a globally uniform HA nanoparticles in fine clusters and the ECAE processing of the as-cast composites resulted in further grain refinement and more importantly the breakdown of nanoparticle aggregates, leading to the formation of a dispersion of true nanoparticles in the Mg alloy matrix with improved mechanical properties. This paper describes mainly the microstructural features and mechanical performance of Mg-3Zn-0.5Zr-xHA (x 1, 3, 5, 10) nanocomposites, in which the HA was in spherical shape with an average diameter of ∼20nm © Published under licence by IOP Publishing Ltd

Low Melting Temperature Solder Materials for Use in Flexible Microelectronic Packaging Applications

The increasing application of heat-sensitive microelectronic components such as a multitude of transistors, polymer-based microchips, and so on, and flexible polymer substrates including polyethylene terephthalate (PET) and polyimide (PI), among others, for use in wearable devices has led to the development of more advanced, low melting temperature solders (<150°C) for interconnecting components in various applications. However, the current low melting temperature solders face several key challenges, which include more intermetallic compound formation (thus become more brittle), cost issues according to the addition of supplementary elements to decrease the melting point temperature, an increase in the possibility of thermal or popcorn cracking (reliability problems), and so on. Furthermore, the low melting temperature solders are still required to possess rapid electronic/electrical transport ability (high electrical conductivity and current density) and accompany strong mechanical strength sustaining the heavy-uploaded microelectronic devices on the plastic substrates, which are at least those of the conventional melting temperature solders (180–230°C). Thus, the pursuit of more advanced low melting temperature solders for interconnections is timely. This review is devoted to the research on three methods to improve the current properties (i.e., electrical and thermomechanical properties) of low melting temperature solders: (i) doping with a small amount of certain additives, (ii) alloying with a large amount of certain additives, and (iii) reinforcing with metal, carbon, or ceramic materials. In this review, we also summarize the overall recent progress in low melting temperature solders and present a critical overview of the basis of microscopic analysis with regard to grain size and solid solutions, electrical conductivity by supplementation with conductive additives, thermal behavior (melting point and melting range) according to surface oxidation and intermetallic compound formation, and various mechanical properties

Structural and Optical Properties of Cu2ZnSnS4 Nanoparticles for Solar Cell Applications

The Cu2ZnSnS4 (CZTS) nanoparticles were successfully synthesized by Chemical co-precipitation method with different synthesis temperatures. The synthesized nanoparticles were characterized by X-ray diffraction, Raman Spectroscopy, Scanning electron microscopy, Energy dispersive spectroscopy and UV-VIS-NIR spectrophotometer. XRD and Raman studies revealed that the CZTS nanoparticles exhibited Kesterite Structure with preferential orientation along the (112) direction. The CZTS nanoparticles synthesized at a temperature 150 C exhibited near stoichiometry. On further increasing the synthesis temperature sulphur composition was decreased due to volatile nature of the sulphur. The synthesized nanopar-ticles exhibited an optimum band gap of 1.4 eV. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3194

Ferromagnetic Behavior of High Purity ZnO nanoparticles

ZnO nanoparticles with Wurtzite structure were prepared by chemical methods at low temperature in aqueous solution. Nanoparticles are in the range from about 10 to 30 nm. Ferromagnetic properties were observed from 2 K to room temperature and above. Magnetization vs temperature, M(T) and isothermal measurements M(H) were determined. The coercive field clearly shows ferromagnetism above room temperature. The chemical synthesis, structural defects in the bulk related to oxygen vacancies are the main factors for the observed magnetic behavior. PACS numbers: 61.46.Hk Nanocrystals, 75.50.Pp Magnetic semiconductors, 81.05.Dz II-VI semiconductor

Characterization of Zinc oxide & Aluminum Ferrite and Simulation studies of M-H plots of Cobalt/Cobaltoxide

Zinc oxide and Aluminum Ferrite were prepared Chemical route. The samples were characterized by XRD and VSM. Simulation of M-H plots of Co/CoO thin films were performed. Effect of parameters was observed on saturation magnetization.Comment: Working paper (11 pages, 8 figures

Quantum Mechanical Studies of Water Splitting Reaction With (ZNO)3 Nanoclusters as Catalysts

With the current energy crisis, H2 production through the water-splitting reaction has drawn attention recently. In this thesis, I studied the structural (geometry) and electronic properties (vertical detachment energy and electron affinity) of ZnO monomers and dimers using density functional theory. ZnO is a metal oxide with a 3.37 eV band gap and can be a commercially cheaper photocatalyst in hydrogen (H2) production. The B3LYP/DGDZVP2 pair was selected after investigating different pairs of exchange functionals and basis sets to study the hydration, hydrolysis, and water-splitting reaction. The singlet-triplet energy gaps of small (ZnO)n clusters (n=1-6) of different sizes were compared and the (ZnO)3 cluster was selected as an optimal cluster size to study the water-splitting reaction. A detailed study of water-splitting reaction pathways in the gas phase showed that oxygen is produced after hydrogen and the rate-determining step is the formation of the Zn-H bond. Graphene and graphene oxide (GO) based metal oxides play an important role as substrates for the photocatalytic reaction. The π conjugation structure of GO shows greater electron mobility and may enhance the photocatalytic performance of ZnO by increasing the electron-hole separation. In this work, I studied the impact of graphene and GO on (ZnO)3 in hydration and hydrolysis reaction using 2 water molecules and in producing H2 and O2 as products of water splitting reaction in the gas phase. I used 5 different GO models anchoring carboxyl, hydroxyl, and epoxy functional groups on a graphene layer to study the hydration and hydrolysis reaction with two water molecules. The (ZnO)3 anchored on GO model 1 was used to study the water-splitting reaction pathway

Потенциометрическое осадительное титрирование растворов солей металлов

В работе проведен сравнительный анализ процессов взаимодействия осадителей (растворов аммиака, карбоната натрия и карбамида) с растворами солей металлов. Выполнены термодинамические расчеты процессов осаждения гидроксидов и гидроксокарбонатов металлов. Полученные значения энергии Гиббса показали возможность образования гидроксидов и карбонатов металлов при взаимодействии не только с растворами аммиака и карбоната натрия, но и с продуктами гидролиза карбамида. Представлены результаты исследования процессов осаждения потенциометрическим титрованием солей (нитратов, сульфатов и хлоридов) металлов (железа, алюминия, меди, цинка, никеля) растворами осадителей (аммиака, карбоната натрия, и раствором, содержащим продукты гидролиза карбамида – аммиак и карбонат аммония). В статье проведено сравнение взаимодействия различных осадителей с растворами солей металлов, охарактеризованы различия образования гидроксидов при аммиачном и содовом осаждении, а также при осаждении продуктами гидролиза карбамида. По полученным экспериментальным данным определены условия образования осадков гидроксидов и карбонатов металлов – рН осаждения и избыточные количества осадителей для случаев аммиачного, содового и карбамидного осаждения. Это позволит обосновать выбор осадителей для получения гидроксидов или карбонатов металлов