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Journal of Surface Engineered Materials and Advanced Technology 2020年第4期10卷 63-74页

作者： Yazmin Francisco Dulce Medina Miguel Barron Joan Reyes Pedro Adrian Martinez Angel de Jesus Morales elizabeth garfias Universidad Autónoma Metropolitana Departamento de Materiales Ciencias Básicas e Ingeniería Reynosa Tamaulipas México Instituto Politécnico Nacional ESIQIE UPALM S/N Mexico City México

The synthesis of the thenoyltrifluoroacetone compound doped with terbium, dysprosium and europium encapsulated in a silica matrix (TTA:Tb:Dy:Eu@SiO2) were performed by the sol-gel method. The precursors to obtain the vitreous phase (SiO2) were: Tetraethylorthosilicate (TEOS, C8H2O4Si, 98%, Aldrich), and ethyl alcohol (CH3CH2OH, 99.5%, Meyer), distilled water and 0.05 ml of hydrochloric acid (HCl, Meyer). The sample with molar ratio 20:80 TTA:Tb:Dy:Eu@SiO2 has the best emission intensity. Thermogravimetric analysis (TGA) shown that silica encapsulated samples decompose at lower temperatures than pure TTA:Tb:Dy:Eu luminescent material. Fourier Transform Infrared (IR-TF) shown the characteristic Si-O-Si bands that are presented at a wavelength of 1049, 853 and 440 cmǃ confirming that the luminescent material is encapsulated in a silica matrix, finally X-ray diffraction (XRD) shown that TTA:Tb:Dy:Eu@SiO2 composite is amorphous.

关键词： Synthesis Luminescence Composite Sol-Gel Terbium Dysprosium and Europium

Red, White and Blue Light Emission from Europium Doped Al2O3 Confined into a Silica Matrix

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Open Journal of Applied Sciences 2018年第8期8卷 338-345页

作者： Joan Reyes Dulce Y. Medina Miriam Aguilar Miguel A. Barron elizabeth garfias Angel de Jesus Morales Ciencias Básicas e Ingeniería Universidad Autónoma Metropolitana-Azcapotzalco Reynosa México Instituto Politécnico Nacional ESIQIE Mexico City México

The main drawbacks of fluorescent activated lanthanide luminescent materials in practical optoelectronic applications are the high cost of raw material and the limitation of a specific color depending on the lanthanide ion. In this work, the synthesis of red, white and blue light emitting composite powders of Al2O3:Eu3+@SiO2 were successfully synthesized by the hydrolysis and condensation reactions of TEOS as the raw precursor of silica matrix on the Al2O3:Eu3+ surface. With the aim to change the CIE coordinates different weight ratios of Al2O3:Eu3+/SiO2 powders from 13Al/87Si to 5Al/95Si were prepared. Besides, various excitation wavelength from 280 to 340 nm was used in order to change the ratio intensity;Ired/Iblue, between the red emission coming from the 5D0→7F2 transition of Eu3+ ions and the blue band of silica matrix. Chemical evolution of the hydrolysis and condensation reaction of TEOS were conducted by FTIR spectroscopy. The results indicate that from 500°C a complete TEOS to SiO2 transformation is carried out.

关键词： Luminescent Lanthanide Luminescence White Emission Aluminium Oxide

Lithium Recovery from Electrodes in Cellphone Batteries through the Leaching Process with Organic Agents Assisted by Ultrasound

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Journal of Materials Science and Chemical Engineering 2018年第9期6卷 1-5页

作者： Pedro A. Martínez Juan C. Orozco Alejandro Alonso Rosa M. Luna Miguel A. Barron Dulce Y. Medina elizabeth garfias-García División de Ciencias Básicas e Ingeniería Universidad Autónoma Metropolitana Reynosa Tamaulipas México

The present work proposes a mean for recovery of metals used in current ion-lithium batteries, like lithium, cobalt and nickel, using organic agents and ultrasound instead of the more aggressive and less environment friendly method with sulfuric acid. This is especially useful in those countries that doesn’t have lithium deposits and have a growing demand of such batteries, reducing the economic loss this represents. During the process, variables such as temperature, leaching agent concentration and ultrasound frequency were modified, using concentrations of 0.5 M (molar), 1 M and 1.5 M of sodium citrate, temperatures of 25°C, 55°C and 60°C and also ultrasound frequencies of 20 KHz, 30 KHz and 40 KHz. It was found that the best combination of these variables that yielded the most quantity of the desired metal was 0.5 M concentration for both lithium and nickel, while using 60°C and no ultrasound with Li and 55°C and 40 KHz for Ni. For Co the best variables discovered were 1.5 molar concentration, 60°C and 40 KHz.

关键词： Lithium Leaching Organic Agents Ion-Lithium Batteries Ultrasound Leaching Sodium Citrate

Blue-Red Tuning Emission of ZnO: Europium Quantum Dots with Different Excitation Wavelengths

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Open Journal of Applied Sciences 2018年第10期8卷 441-445页

作者： Primitivo Ortiz Maldonado Ana K. Chavez-Alvarado Francisco J. Rodríguez Gutierrez Joan Reyes Miranda Dulce Y. Medina Velazquez Miguel A. Barron elizabeth garfias García Universidad Autónoma Intercultural de Sinaloa El Fuerte México División de Ciencias Básicas e Ingeniería Universidad Autónoma Metropolitana Reynosa Tamaulipas México

Optoelectronic applications require the development of new fluorescent and efficient luminescent materials, free of toxicity, low in cost, and easy to produce. In this way the synthesis of zinc-oxide (ZnO) quantum dots (QDs) has recently received special attention due to their good optical, electrical and chemical properties with low production costs and blue light emission. In this work ZnO QDs were successfully doped with europium in order to obtain a tunable emission luminescence from blue emission of ZnO to red emission of europium as a function of wavelength excitation. Results show an efficient blue to red tuning when the excitation wavelength was changed from 317 nm to 395 nm, respectively. This opens the possibility of having new optical devices to produce different color emission using the same material.

关键词： Chromaticity Diagram Emission Spectra Europium Luminescence Red-Blue Tuning ZnO Quantum Dots White Light