We fabricated ultrathin metal - oxide - semiconductor (MOS) nanocapacitors using atomic layer deposition. The capacitors consist of a bilayer of Al2O3 and Y2O3 with a total thickness of ~10 nm, deposited on silicon substrate. The presence of the two materials, each slab being ~5 nm thick and uniform over a large area, was confirmed with Transmission Electron Microscopy and X-ray photoelectron spectroscopy (XPS).
View Article and Find Full Text PDFHerein, we report a detailed adsorption process of acetic acid (AA) as a model for the head group of carboxylic acid self-assembled monolayers on Cu and CuO (111) surfaces and the effect of diethyl zinc (DEZ) on its adsorption geometry on CuO (111) using quantum chemical calculations. The most stable adsorption configurations were obtained considering electrostatic potential compatibility from the molecule and surface. Overall, the adsorption behavior revealed bidentate binding as the most stable configuration.
View Article and Find Full Text PDFIn the present work, we report on a theoretical-computational study of the growth mechanism of the TiO-Graphene nanohybrid by atomic layer deposition. Hydroxyl groups (OH) are anchoring sites for interacting with the main ALD titanium precursors (Tetrakis (dimethylamino) Titanium, Titanium Tetrachloride, and Titanium Isopropoxide). Results demonstrate that the chemical nature of the precursor directly affects the reaction mechanism in each ALD growth step.
View Article and Find Full Text PDFThis research investigates the improvements of ozone (O) annealing on the optical and etching characteristics of TiO/AlO multilayer band-pass filters designed for potential optoelectronic applications. The band-pass filters were fabricated using atomic layer deposition (ALD), and their performance was systematically analyzed after the addition of O annealing at moderate temperatures (up to 300 °C). Results reveal that O annealing improves the optical transmittance of the multilayers by approximately 40% without significant spectral changes (∼6 nm).
View Article and Find Full Text PDFThe formation of heterostructures that combine a large surface area with high surface activity has attracted the attention of the scientific community due to the unique properties and applications of these heterostructures. In this work, we describe - at the atomic level - the full reaction mechanisms involved in the atomic layer deposition of a hybrid ZnO/CNT inorganic structure. First, the pristine CNTs are chemically activated with a carboxylic acid, a process unique to carbon materials.
View Article and Find Full Text PDFThe design of optoelectronic devices made with ZnO superlattices requires the knowledge of the refractive index, which currently can be done only for films thicker than 30 nm. In this work, we present an effective medium approach to determine the refractive index of ZnO layers as thin as 2 nm. The approach was implemented by determining the refractive index of ZnO layers ranging from 2 nm to 20 nm using spectroscopic ellipsometry measurements in multilayers.
View Article and Find Full Text PDFWe report the adsorption of diethylzinc on hydroxyl functionalized carbon nanotubes. This study intends to understand, at the atomic level, the initial stages of ZnO formation by atomic layer deposition. Our study begins with the molecule physisorbed on the nanotube (initial state of the reaction).
View Article and Find Full Text PDFThis is a report of a study of the nonlinear optical properties of samples based on multiple AlO/ZnO bilayers fabricated by atomic layer deposition (ALD) in silica. The multi-layer configuration for samples consists of alternated layers of constant thickness of AlO (Δx) and ZnO (Δy) nanolaminates with a total thickness of ∼ 500 nm. The physical properties of the samples were characterized by means of TEM, spectrophotometry and variable angle spectroscopic ellipsometry.
View Article and Find Full Text PDFThis work evaluated the inhibition effect of low molecular weight alcohol (ethanol) on naproxen (NAP) degradation by conventional and catalytic ozonation. The reaction system considered the ethanol as complementary organic matter in water. The conventional ozonation and in the presence of nickel oxide (O-NiO) achieved 98% NAP degradation during the first 15 min of reaction despite the presence of ethanol.
View Article and Find Full Text PDFHerein, a series of N-doped carbon nanotube (CNx) samples were obtained by modifying the synthesis temperature. Consequently, the proportion of graphitic nitrogen (Ngraph) in the samples was systematically increased as a function of temperature. This allowed evaluation of the role of the CNx graphitic nitrogen in the oxygen reduction reaction (ORR).
View Article and Find Full Text PDFThe current photodynamic therapy (PDT) is majorly hindered by the shallow penetration depth and oxygen dependency, limiting its application to deep-seated solid hypoxic tumors. Thus, it is meaningful to develop efficient X-ray mediated PDT system capable of generating reactive oxygen species (ROS) under both the normoxic and hypoxic conditions. Herein, we report the synthesis and characterization of nanocomposite, YAG:Pr@ZnO@PpIX with an amalgamation of UV-emitting YPrAlO (YAG:Pr) nanoscintillator, and zinc oxide (ZnO) and protoporphyrin IX (PpIX) as photosensitizers.
View Article and Find Full Text PDFIn this paper, the effect of modifiers and pretreatments on the electronic states of 1 nm gold nanoparticles (AuNPs) supported on silica was systematically studied. AuNPs deposited on silica (particle size of 2-4 nm) modified with Ce, La and Fe oxides, were studied by FTIR of adsorbed CO after different redox treatments at 100, 300 and 500 °C. This study was conducted at room temperature to allow detecting the electronic states of gold, which is more likely involved in CO oxidation at the same temperature.
View Article and Find Full Text PDFEnviron Sci Pollut Res Int
November 2017
Naphthalene (NA) is a polycyclic aromatic hydrocarbon with toxic properties in aquatic systems. Ozonation (O) and catalytic ozonation (O-cat) processes are attractive alternatives of degradation for this kind of compound. NA (20 mg L) degradation by conventional and catalytic ozonation in the presence of a cosolvent (ethanol) was the aim of this study.
View Article and Find Full Text PDFJ Nanosci Nanotechnol
September 2015
Carbon Nanotubes (CNTs) are coated by an insulator (Al2O3) shell using the atomic layer deposition (ALD) technique. This is achieved in large quantities (tens of milligrams per batch) for electrical wiring purposes. Here we present a transmission electron microscopy (TEM) characterization together with a detailed high resolution elemental analysis by in-column energy dispersive X-ray spectroscopy (EDXS).
View Article and Find Full Text PDFMultifuncionality in polycrystalline multiferroic ceramics can be improved using an advanced synthesis process. In this work, core-shell design is being proposed to enhance the transport properties of biferroic YCrO3. The atomic layer deposition (ALD) thin-film growth technique was used for the YCrO3/Al2O3 (Y@Al) nanocomposite fabrication.
View Article and Find Full Text PDFSynthetic methodology and physicochemical characterization of multi-wall carbon nanotubes (MWCNTs) functionalized with a crown ether molecule is reported. The MWCNTs were synthesized by spray pyrolysis technique using toluene as carbon source and ferrocene as catalyst. The nanotubes were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
View Article and Find Full Text PDFA new technique for the silylation of pure-silica-zeolite MEL low-k films has been developed in which the spin-on films are calcined directly in trimethylchlorosilane or 1,1,1,3,3,3-hexamethyldisilazane (HMDS) in order to protect the films against corrosive wet etch chemicals and ambient moisture adsorption. In an alternative procedure, HMDS is also added to the zeolite suspension before film preparation. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, water-soak tests, and HF etch tests are performed to characterize the films.
View Article and Find Full Text PDFThe surface chemistry of atomic layer depositions (ALD) of titanium nitride films using alternate doses of TiCl4 and NH3 was characterized by using X-ray photoelectron spectroscopy. The nature of the species deposited by each half-reaction was explored first. Evidence was obtained for the partial loss of chlorine atoms and the reduction of the metal during the adsorption of the TiCl4.
View Article and Find Full Text PDFA major challenge in molecular electronics and related fields entails the fabrication of elaborate molecular architectures on electroactive surfaces to yield hybrid molecular/semiconductor systems. A method has been developed for the stepwise synthesis of oligomers of porphyrins linked covalently via imide units. A triallyl-porphyrin bearing an amino group serves as the base unit on Si(100), and the alternating use of a dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) and a porphyrin-diamine for reaction enables the rapid and simple buildup of oligomers composed of 2-5 porphyrins.
View Article and Find Full Text PDFX-ray photoelectron and Fourier transform infrared spectroscopy studies are reported for self-assembled monolayers (SAMs) of two tripodal thiol-functionalized metalloporphyrins (Zn and Cu) and three benchmark tripods on gold substrates. The tripodal unit common to all five molecules is 1-(phenyl)-1,1,1-tris(4-mercaptomethylphenyl)methane (Tpd). Both porphyrins contain S-acetyl-protected thiols and are linked to the 4-position of the phenyl ring of Tpd via a phenylethyne group.
View Article and Find Full Text PDFCharacterization of palladium catalysts, supported on alumina and alumina modified by zirconia added by impregnation, was performed by CO adsorption from 143 to 298 K and monitored by infrared spectroscopy. It was found that the population of the Al3+ octahedral sites in the alumina decreased by the addition of zirconia. In contrast to the case of the pure alumina support, where stabilization of Pd+ was observed, Pd2+ was formed preferentially on samples where zirconia was added, and higher crystallinity in the metallic palladium was observed.
View Article and Find Full Text PDFRedox kinetics were measured for two electroactive molecules attached to Si(100) surfaces, a ferrocene (Fc-BzOH) and a Zn(II) trimesitylporphyrin (Por-BzOH). Each molecule was derivatized with a benzyl alcohol linker for attachment to the Si surface via the formation of a Si-O bond. A complete protocol was developed for the preparation of stable Si(100) surfaces derivatized with the electroactive molecules.
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