Dwight Acosta

Dwight Acosta
Universidad Nacional Autónoma de México | UNAM · Institute of Physics UNAM

PhD FELICITA GARNIQUE

About

184
Publications
15,301
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
3,432
Citations
Citations since 2017
32 Research Items
1043 Citations
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
2017201820192020202120222023050100150
Introduction
1D and 2D Nanomaterials:synthesis, characterization, applications Advanced electron microscopy techniques Sonochemical synthesis of materials with quantum dots dimensions
Skills and Expertise

Publications

Publications (184)
Article
Full-text available
A study of the effect of 2.5 MeV ⁴ He ²⁺ ion irradiation on the optical, electrical, morphological and structural properties of ZnO thin films is presented. Polycrystalline zinc oxide thin films were deposited on soda lime glass substrates using the spray pyrolysis technique. During the process, the substrates’ surfaces were kept at 400, 450 and 50...
Article
Full-text available
WO3 thin films with improved electrochromic durability were deposited by pneumatic spray pyrolysis technique on top of FTO substrates; tungsten hexachloride dissolved in N,N-dimethylformamide was used as precursor. Synthetized WO3 thin films present interesting electrochromic properties with switching stability of more than 15,000 cycles. The varia...
Article
Full-text available
A proton-conducting biopolymer electrolyte system based on corn starch doped with 0.0 to 4.0 wt% of Al(OH) 3 has been prepared through the solution casting method. Scanning electron microscopy and confocal micrographs showed a partial alteration of starch granule boundary and aluminum agglomerates formation as a function of the Al(OH) 3 concentrati...
Article
Full-text available
Graphite oxide (GrO) and 2,3-Diaminomaleonitrile-doped GrO (GrODAMN) materials were synthesized by the modified Hummers method. Oxidation and N-doping treatments increase the C/O ratio from 2.49 to 2.88 for GrO and GrODAMN materials, respectively. GrODAMN material shows higher thermal resistance from room temperature to 800 °C compared with GrO mat...
Article
Fluorescent β-NaYF4 to Yb3+/Ho3+@SiO2 nanoparticles with variations in the ratios of fluorine and yttrium 4:1, 12:1, and 20:1, respectively, have been synthesized using the solvothermal method at a temperature of 200 ℃ and reaction time of 8 h and coated with SiO2 by the inverse microemulsion method. The obtained nanoparticles were characterized by...
Article
In the present study, graphite oxide, graphite oxide doped with 0.8g AgNO3 named GrO-0.5Ag, and graphite oxide doped with 1.25g AgNO3 named GrO-1.0Ag (silver-doped graphitic materials) were synthesized by the modified Hummers and chemical doping methods. Subsequently, its antimicrobial activity against Bacillus subtilis, Candida albicans, Escherich...
Chapter
Full-text available
TiO2 films were deposited by the sol–gel dip coating method assisted by ultra sonic agitation, for their use as propane gas sensors. XRD anlaysis revealed the TiO2 anatase phase for all samples. The film thickness was controlled with the number of the dip-coating immersion cycles, obtaining thicknesses from 10 to 130 nm and a growing rate of 18 nm...
Article
We addressed the deposition of silver nanoparticles (Ag NPs) onto graphene oxide (GO) in the form of powder and paper (GOP), functionalized with amines and non-functionalized, for comparison. The functionalized supports were fabricated by means of solvent-free treatment with two aliphatic amines: 1-octadecylamine (ODA) and 1,8-diaminooctane (DAO)....
Article
Full-text available
The Yb 3+-Mn 2+ codoped zinc metaphosphate glass gives rise to several processes such as upconversion, downshifting and double ion absorptions producing light from the visible to the IR wavelengths. These processes are possible since the Mn 2+ and the Yb 3+ ions replaces the Zn 2+ ion in nanoparticles of the α phase of the compound Zn(PO 3) 2. An i...
Article
Full-text available
The temperature effect on VO 2 thin films synthesized by RF sputtering on their morphological, optical, electrical properties and their activity in the photocatalytic degradation of methylene blue and naproxen was studied. Characterization results presented microcrystallinity for VO 2 films treated at 50 and 100 °C. Nevertheless, the untreated film...
Article
The structural and photoluminescent results of the lanthanum, erbium, ytterbium and lithium doped hafnium oxide phosphors; are presented. These powders were synthesized by the solvent evaporation technique, different percentages of doping of the lanthanides were carried out, obtaining monoclinic and cubic phases, also a cubic phase is present when...
Article
Full-text available
1. Abstract In the present work, SnO 2 quantum dots with size close to 2 nm were successfully synthesized by means of the sonochemical method. Ultrasound irradiating an aqueous solution of SnCl 4 .5 (H 2 O) 0.13M for a time of 150 min, at a constant temperature of 65ºC and using ammonium precipitation (at 25%), quantum dots SnO 2 were obtained, wit...
Article
In this work, we report the electron mobility and electron density of three graphene field effect transistors using a 280 nm titanium dioxide dielectric layer and a graphene channel of area 300 × 300 μm². We achieve electron mobilities up to 1877 cm²/V and the Dirac point appears in small gate voltages, as compared to similar SiO2 transistors. Also...
Article
Full-text available
Manganese-doped zinc oxide (Mn-doped ZnO) thin films were synthesized on soda lime glass substrates using the spray pyrolysis technique at substrates temperatures of 400, 450 and 500 °C. Compositional, optical, structural, morphological and electrical properties were studied with Rutherford Backscattering Spectrometry (RBS), Ultraviolet and Visible...
Article
Full-text available
Undoped ZnO thin films were deposited on sodocalcic glass substrates by the spray pyrolysis technique. Atomization of the starting solution was made by ultrasonic excitation. The effect of the water content in the starting solution on the structural, optical, and morphological properties of the films was studied. All films showed mirror-like finish...
Article
Full-text available
The doping reactions of graphite oxide (GO) with 3-3'-diaminobenzidine (DAB) were studied using N, N'-dicyclohexylcarbodiimide (DCC), cyanuric chloride (CC) and hexafluorophosphate (HATU) as coupling agents. The bifunctionality of the coupling agents aid to interact GO functional groups with amino groups of DAB without being part of the final produ...
Article
Silver doped zinc phosphate glass was successfully synthesized at different molar concentrations of AgCl from 1% up to 20%. Zinc phosphate glass shows a high capacity to hold silver impurities without loss of optical quality. This material shows two different centers able to emit blue and green-red light, the first one from isolated Ag⁺ ions and th...
Article
In this work, we focus on the study of structural and electrical properties of vanadium oxide thin films synthesized by RF magnetron sputtering. The samples were deposited on glass at 0%, 5%, 10% and 20%, O 2 concentration inside the vacuum of the chamber. The films were characterized by x-ray Photoelectron Spectroscopy (XPS), Scanning Electron Mic...
Article
WO 3 :Mo and WO 3 :Ti thin films have been deposited on FTO/Glass substrates by the pulsed chemical spray technique at a substrate temperature of T s = 450°C. The influence of Mo and Ti doping on the structural, electrical, and optical behavior of WO 3 thin films, has been studied by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Tran...
Article
Full-text available
SnO2 quantum dots were successfully prepared via chemical precipitation assisted by ultrasound. X-ray diffraction analysis confirmed the rutile tetragonal structure of SnO2 QDs with a crystallite size of 1.4 nm. The SEM micrographs of the obtained powder exhibited that the SnO2 QDs are agglomerated particles of around 10 nm, while TEM images confir...
Article
Full-text available
In this work, the influence of laser power on Raman spectra on different carbon based materials was studied: multilayer graphene (MLG), multilayer graphene oxide (MLGO) and reduced multilayer graphene oxide (rMLGO). The presence of oxygen and hydrogen was verified by means of Fourier-transform Infrared Spectroscopy, indicating that our oxidation an...
Article
Full-text available
Electron Microscopy Studies of SnCh Nanoparticles with Quantum Dots Dimensions Produced Using Ultrasonic Sonochemical Agitation - Volume 24 Supplement - Dwight Acosta, Natasha Kramsky, Paul Alvarado, Monica Gomez, Jose Solis
Article
A High-Resolution Electron Microscopy Study of Dislocations in Graphene Nano-Flakes Produced by Chemical Ultrasonic Exfoliation - Volume 24 Supplement - Dwight Acosta, Natasha Kramsky, Francisco Hernández, Carlos Magaña
Article
Full-text available
In this paper, a study of structural characterization of the ternary semiconductor Ag2SnSe3 is presented. The experimental work was performed using Scanning Electron Microscopy (SEM), Selected Area Electron Diffraction (SAED) patterns, High Resolution Electron Microscopy (HREM), Annular Dark field imaging (ADF), and powder synchrotron X-ray Diffrac...
Article
Full-text available
The structural and luminescent results of nondoped, terbium and dysprosium doped, and codoped Y2O3 powders are presented. Different percentages of the rare earth ions were employed. The powders were obtained by means of the solvent evaporation technique and were annealed at 1100°C for 2 h. The emission spectra of these samples are associated with t...
Article
Full-text available
TiO 2 nanotubes were synthesized by alkaline hydrothermal treatment of TiO 2 nanoparticles with a controlled proportion of anatase and rutile. Tailoring of TiO 2 phases was achieved by adjusting the pH and type of acid used in the hydrolysis of titanium isopropoxide (first step in the sol-gel synthesis). The anatase proportion in the precursor nano...
Article
Transparent conductive and polycrystalline zinc oxide (ZnO) thin films were deposited on sodalime glass substrates using the pneumatic chemical spray technique with different amounts (30, 50 and 70 ml) of sprayed solution. During the synthesis, the surface of the substrates was kept at 400, 450 and 500 °C. The effects of the mentioned parameters on...
Article
Full-text available
Machu Rumi, or an old stone with geofagy applications used by members of the Chimpajilahuata community of Azángaro district in Puno, Peru, was chemically and mineralogically characterized. The samples were analyzed by means of the use of X-ray fluorescence (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) whose elemental abundan...
Article
Full-text available
In this paper, the presence of the crystalline phases, the size of particulate matter (PM) and chemical characterization of sediments deposited on the roofs constructed with sheet metal grooved of homes near the cement plant in the district of Caracoto, San Roman, Puno, Peru, were determined. The crystalline phases studied by X-ray diffraction (XRD...
Article
Full-text available
div class="title"> Electron Microscopy and Electrochromic Studies of V 2 O 5 Thin Films Deposited by RF Magnetron Sputtering - Volume 22 Issue S3 - Dwight R. Acosta, Argelia Pacheco, Carlos R. Magaña, Francisco Hernández
Article
Full-text available
In this paper, the presence of the crystalline phases, the size of particulate matter (PM) and chemical characterization of sediments deposited on the roofs constructed with sheet metal grooved of homes near the cement plant in the district of Caracoto, San Roman, Puno, Peru, were determined. The crystalline phases studied by X-ray diffraction (XRD...
Article
Synthesis and growth of alkali halides films by Pulsed Laser Deposition: An electron microscopy study - Volume 22 Issue S4 - Dwight R. Acosta, Elsi Mejía, Citlali Sánchez
Article
Full-text available
div class="title">Electron Microscopy and Photocatalytic Studies of 1D TiO 2 Nanostructures Synthesized by Two Different Routes - Volume 21 Issue S3 - Dwight Acosta, Julieta Cabrera, Hugo Alarcon, Alcides Lopez, Juan Rodriguez, Roberto Candal
Article
Ti:WO3 thin films were deposited by the pulsed spray pyrolysis technique on FTO/Glass substrates using WCl6, and TiCl3 precursors in the sprayed solution. The effect of Titanium concentration in the solutions on structural, electrical, optical properties and on the electrochromic behavior of Ti:WO3 films have been studied using physical and electro...
Article
Full-text available
Three compounds of the K2Ln2/3Ta2O7 (Ln = La, Nd, Pr) cation-deficient Ruddlesden-Popper series were prepared by the Pechini (polymeric complex) method. The crystal structures of the hydrated form of these compounds were determined by Rietveld analysis of the X-ray powder diffraction data and High Resolution Transmission Electron Microscopy (HRTEM)...
Article
Three compounds of the K(2)Ln(2/3)Ta(2)O(7) (Ln = La, Nd, Pr) cation-deficient Ruddlesden-Popper series were prepared by the Pechini (polymeric complex) method. The crystal structures of the hydrated form of these compounds were determined by Rietveld analysis of the X-ray powder diffraction data and High Resolution Transmission Electron Microscopy...
Article
Full-text available
Compounds with the nominal formula K2[LnTa3O10] (Ln = La, Nd, Pr), crystallising in a cation-deficient Ruddlesden-Popper structure, were prepared by the Pechini (polymeric complex) method. The crystal structures of the hydrated form of these compounds were determined by Rietveld analysis of the X-ray powder diffraction data and high-resolution tran...
Article
Full-text available
Nanowire/nanorod TiO2 structures of approximately 8 nm in diameter and around 1,000 nm long were synthesized by alkaline hydrothermal treatment of two different TiO2 nanopowders. The first precursor was TiO2 obtained by the sol-gel process (SG-TiO2); the second was the well-known commercial TiO2 P-25 (P25-TiO2). Anatase-like 1D TiO2 nanostructures...
Article
High Resolution Transmission Microscopy (HRTEM) and powder X-ray diffraction are used to investigate the disorder observed in crystalline benzilic acid. Powder synchrotron X-ray diffraction are used to solve the crystal structure of benzilic acid, (C6H5)(2)C(OH)CO2H, a compound which exhibits diffuse scattering due to disorder in the crystalline st...
Article
X-Ray Diffraction, Scanning Electron Microscopy, High Resolution Transmission Electron Microscopy studies have been made of TlInS2 layered semiconductor compound to clarify its crystal structure, which has remained ambiguous through several decades. Similarly, in recent studies it has been reported at ambient conditions this semiconductor can cryst...
Article
In this work, the pulsed photoacoustic technique was used to investigate the semiconductor-metal transition of thin vanadium pentoxide films (V2O5) under increasing temperature. The V2O5 thin films were simultaneously deposited by RF magnetron sputtering at room temperature, on corning glass and SnO2:F/glass substrates, in order to compare the phot...
Article
Full-text available
Polycrystalline samples of (CuInSe 2) 1-x (RE 2 Se 3) x alloys (RE: Dy, Yb, Gd and Nd) with x=1/2 and 1/3 were prepared by the melting and annealing technique respectively and characterized by X-ray powder diffraction and Scanning electron Microscopy . It was found that all the alloys are composed by two phases (chalcopyrite + orthorhombic) in diff...
Article
Full-text available
Chromium and ruthenium-doped zinc oxide (ZnO:Cr) and (ZnO:Ru) thin solid films were deposited on soda-lime glass substrates by the sol-gel dip-coating method. A 0.6 M solution of zinc acetate dihydrate dissolved in 2-methoxyethanol and monoethanolamine was used as basic solution. Chromium (III) acetylacetonate and Ruthenium (III) trichloride were u...
Article
Full-text available
In this work, we study the crystallization and electrical resistivity of the formed oxides in a Cu/SiO2/Si thin film after thermal oxidation by ex-situ annealing at different temperatures up to 1000 °C. Upon increasing the annealing temperature, from the X ray diffractogram the phase evolution Cu → Cu + Cu2O → Cu2O → Cu2O + CuO → CuO was detected....
Article
Uniform and highly adherent thin films of CNT:TiO2 were synthesized by sol–gel dip coating method. Both TiO2 and CNT:TiO2 films showed very identical structural characteristics and no significant changes in the lattice values were observed. The crystalline size decreased from 20nm for TiO2 film to 17nm for the 4%CNT:TiO2 film. The film surface was...
Conference Paper
Full-text available
Conducting polyaniline (PANI) has been electrochemically synthesized on FTO-coated glass. The PANI films were grown at constant potentials and characterized by cyclic voltammetery (CV), UV-visible spectrophotometry, spectral reflectance techniques and SEM. PANI films thicknesses were observed in the range of 60 to 250 nm. PANI films showed optical...
Article
A structural characterization of the superconducting phases in Bi2Sr2Ca Cu2O8+x is carried out. X-Ray measurements are in agreement with recently reported diffraction patterns indicating an orthorhombic structure with large c-axis parameter (≈30Å). Twin boundaries which are commonly found in high-Tc superconducting compounds based on Y or rare eart...
Article
The effects of molybdenum [Mo] doping on the electrochromic behavior of spray pyrolised tungsten trioxide [WO3] thin films have been studied. It has been observed that the color-bleaching kinetics, coloration efficiency, and stability of electrochromic WO3 films are closely related to molybdenum doping concentration, apart from their microstructure...
Article
Catalytic isomerization of paraffines of low molecular weight is a very important process in petrochemical refination and zeolites like mordenites and erionites are used frequently as supports, due to acid properties, neccesary for a dual action in hydroisomerization processes(1–3). In the present work, we analyze the behavior of erionites intercha...
Article
Atomic force microscopy and electron microscopy were used to study surface and structural properties in SnO2:F thin films deposited by spray pyrolysis on glass at a constant substrate temperature. The influence of high levels of fluorine in the starting solution on the surface topology and morphology of thin films and correlations with electrical p...
Article
An horizontal hot-wall MOCVD reactor was used to prepare palladium and platinum catalysts supported on alumina. A conventional impregnated Pt on alumina catalyst was prepared as comparison. The solids were characterized by XRD, Auger spectroscopy, HREM and H2 -TPR. The operation conditions of the MOCVD reactor were fixed preparing several Pd cataly...
Article
Conventional MOCVD method has been explored to prepare Pd supported catalysts. Pd and PdO phases were found on the surface of the support. Small Pd particles about 1 to 3 nm and dispersions up to 19%were obtained by MOCVD. TPR results indicated that several surface Pd compounds are reduced. At temperatures below 25°C, PdO, the main compound, is com...
Article
Zinc oxide thin films doped with zirconium were prepared from solutions with doping material dispersed at several concentrations and using the spray pyrolysis technique.The films were deposited over sodocalcic glasses at different substrate temperatures. Effects of doping material concentration and substrate temperatures on electrical, optical, str...
Article
Full-text available
Zeolite Beta, synthesized in 1967 (1), is the first example of a large pore, high silica zeolite (SiO2O3 > 20) prepared in the presence of an organic template (Tetraethylammonium Hydroxide). Zeolite NU-2, whose synthesis has been reported in 1982 (2) seems to be related to the zeolite Beta. Although Zeolite Beta has been claimed as useful catalyst...
Article
High resolution electron microscopy observations were carried out in several zeolitic systems with different supported metallic phases in order to determine besides distributions of metallic particles, possible preferential orientations of metallic phases during impregnation processes and to detect some crystallographic relations between metallic p...
Article
Fluorine doped tin oxide thin films were prepared from solutions with high fluorine contents using the spray pyrolysis technique; the resulting films were studied by electron and X-ray diffraction methods; the resonant nuclear reaction (RNR) method was used to determine the final concentration of fluorine atoms in our films for different doping lev...
Article
In this work we present some results of a systematical study of structural and optoelectronic properties of Zn O: In thin films obtained by spray pyrolysis when the acidity and the solvent used in starting solution were varied. Structure of our samples was derived from X ray diffraction and conventional electron microscopy observations.
Article
The synthesis of hydroxyapatite on mesoporous silica SBA-15 material and the resulting composite, after a specific thermal treatment, has been followed and studied by electron microscopy. After the synthesis the samples were undergone a double thermal treatment: First the samples were hydrothermally treated from 353 y 393 K in a 10 K range interval...
Article
Transparent TiO2 thin films were deposited on soda lime glass at different substrate temperatures by a simple and reproducible spray pyrolysis technique from aqueous peroxo-polytitanic acid. Both the as-prepared and annealed films (3 h thermal treatment in air at 500 °C) were characterized by AFM, SEM, TEM, XRD, FT-IR and UV–visible spectroscopy. T...
Article
Full-text available
Purpose The purpose of this paper is a theoretical modeling use of electrochemical impedance spectroscopy (EIS) technique for different cases that could describe the possible electrochemical behaviour on steel coated with metallic and oxide thin films (of nickel) deposited by magnetron sputtering, and compare them to know if the theoretical analysi...
Article
Platinum colloidal nanoparticles were synthesized by chemical reduction of metallic salts in presence of poly (N-vinyl-2-pirrolidone) which served as a protecting agent. The preparation conditions for obtaining Pt nanoparticles were established by analyzing TEM and HRTEM images of the samples. Size of the synthesized Pt nanoparticles was in the ran...
Article
Full-text available
Nickel thin films with regular configuration and similar thickness were deposited on steel AISI 1018 (UNSG 10180) by two different techniques: magnetron sputtering and electrolytic process. The main aim of this work is to compare the surfaces deposited films made by the two techniques using the scanning electronic microscopy and to identify their m...
Article
WO3/FTO/Glass and WO3:Mo/FTO/Glass thin films were deposited using the pulsed spray pyrolysis technique. The Molybdenum doped thin films were deposited using 2,4,6,8 and 10 % at . concentration in the starting solution. The influence of molybdenum concentration on the structural, electrical, optical and electrochromic properties of WO3:Mo thin film...
Article
Zinc oxide (ZnO) is a multifunctional semiconductor with a wide direct band gap (3.3 eV); due to its tunable optoelectronic characteristics it is one of the transparent conductive oxides (TCO) materials most commonly used as front and back transparent conductors in photovoltaic cells (PVC) architecture. The electrical and optical properties of TCO...
Article
The corrosion products formed on commercial low carbon steel samples exposed to total immersion corrosion processes in a 3% wt. NaCl solution saturated with CO2(g), were identified. The immersion was realized for 10 days at 55°C and 85°C respectively. The Transmission Mössbauer Spectroscopy (TMS) showed the presence of lepidocrocite (γ-FeOOH) and/o...
Article
The goal of the present paper was to study the behavior of commercially available pristine multi-walled carbon nanotubes (MWNTs) under microwave irradiation (exposures up to 200 s) in vacuum, by means of several experimental techniques. An intense glow and heating of the nanotube samples were observed. Raman spectra, scanning electron microscopy (S...
Article
Undoped and cobalt-doped zinc oxide [ZnO:Co] thin solid films were deposited on Si(100) substrates applying the chemical spray technique (CST), using zinc acetate and cobalt chloride as precursors. The influence of both the dopant concentration in the starting solution and the substrate temperature on the composition, electrical and morphological p...