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Open AccessArticle

Synthesization, Characterization, and in Vitro Evaluation of Cytotoxicity of Biomaterials Based on Halloysite Nanotubes

Antonio Sánchez-Fernández

Viviana C. Zomosa-Signoret

Ana M. Rivas-Estilla

and

Paulina Riojas

Materials 2014, 7(12), 7770-7780; https://doi.org/10.3390/ma7127770 - 04 Dec 2014

Cited by 28 | Viewed by 7315

Abstract

Halloysite is an aluminosilicate clay that has been widely used for controlled drug delivery, immobilization of enzymes, and for the capture of circulating tumor cells (CTCs). Surface modification of halloysite by organosilanes has been explored to improve their properties. In this study halloysite clay nanotubes (HNTs) were functionalized by two different organosilanes: Trimethoxy(propyl)silane (TMPS), and Triethoxy(octyl)silane (EOS). Untreated and modified samples were characterized by scanning electron microscopy (SEM), X-ray diffractometry (XRD), thermogravimetrical analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). Results showed a strong interaction of organosilanes with the chemical groups present in HNTs. Biocompatibility and cytotoxicity of these nanomaterials were determined using C6 rat glioblastoma cells. Our results indicate that prior to functionalization, HNTs show a high biocompatibility and low cytotoxicity. However, HNTs functionalized with EOS and TMPS showed high cytotoxicity by inducing apoptosis. These results allow the identification of potential applications in biomedical areas for HNTs. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International e-Conference on Materials)

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Open AccessArticle

Electrical Properties of CZO Films Prepared by Ultrasonic Spray Pyrolysis

Lung-Chien Chen

Cheng-An Hsieh

and

Xiuyu Zhang

Materials 2014, 7(11), 7304-7313; https://doi.org/10.3390/ma7117304 - 05 Nov 2014

Cited by 15 | Viewed by 5794

Abstract

CuZnO (CZO) films have attracted increasing amounts of attention due to their promising potential applications in semiconductor devices. ZnO shows n-type conductivity, and attempts have been made to dope several elements in ZnO to improve the electrical properties. This study investigated the electrical property transitions of CZO films and determined the copper concentration at which the conductivity of CZO films will change from n-type to p-type. In this study, CZO films were fabricated by ultrasonic spray pyrolysis with copper acetate, zinc acetate, and ammonium acetate precursor solution. The concentrations of Cu ions in the CZO films were controlled by the concentration ratios of copper acetate to zinc acetate in the precursor solutions. In addition, these samples were analyzed by Hall effect measurements, X-ray diffraction, transmittance measurements, and photoluminescence measurements. The results show that the conductivity of the CZO film changes from n-type to p-type when the copper ion concentration in the film is 5%. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International e-Conference on Materials)

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Open AccessArticle

Property Relationship in Organosilanes and Nanotubes Filled Polypropylene Hybrid Composites

Alejandra J. Monsiváis-Barrón

Jaime Bonilla-Rios

and

Antonio Sánchez-Fernández

Materials 2014, 7(10), 7073-7092; https://doi.org/10.3390/ma7107073 - 20 Oct 2014

Cited by 2 | Viewed by 5985

Abstract

Polypropylene composites with different filler contents were prepared by creating a masterbatch containing 3 wt%. filler. A variety of silanol groups were used to synthetized three compounds in different media trough a sol-gel process with acetic acid, formic acid and ammonium hydroxide as catalysts. Besides, four different nanotubular fillers were also used to analyze their behavior and compare it with the effect caused by the silanol groups. These tubular structures comprise: unmodified halloysite, carbon nanotubes and functionalized halloysite and carbon nanotubes. Morphological characterization in SEM and STEM/TEM showed dispersion in the polypropylene matrix. According to TGA and DSC measurements thermal behavior remain similar for all the composites. Mechanical test in tension demonstrate that modulus of the composites increases for all samples with a major impact for materials containing silanol groups synthetized in formic acid. Rheological measurements show a significantly increment in viscosity for samples containing unmodified and modified carbon nanotubes. No difference was found for samples containing silanol groups and halloysite when compared to neat polypropylene. Finally, the oxygen transmission rate increased for all samples showing high barrier properties only for samples containing natural and functionalized halloysite nanotubes. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International e-Conference on Materials)

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Open AccessArticle

Sol-Gel Synthesis and Antioxidant Properties of Yttrium Oxide Nanocrystallites Incorporating P-123

Rebeca Mellado-Vázquez

Margarita García-Hernández

Arturo López-Marure

, Perla Yolanda López-Camacho,

Ángel De Jesús Morales-Ramírez

and

Hiram Isaac Beltrán-Conde

Materials 2014, 7(9), 6768-6778; https://doi.org/10.3390/ma7096768 - 19 Sep 2014

Cited by 22 | Viewed by 6594

Abstract

Yttrium oxide (Y₂O₃) nanocrystallites were synthesized by mean of a sol-gel method using two different precursors. Raw materials used were yttrium nitrate and yttrium chloride, in methanol. In order to promote oxygen vacancies, P-123 poloxamer was incorporated. Synthesized systems were heat-treated at temperatures from 700 °C to 900 °C. Systems at 900 °C were prepared in the presence and absence of P-123 using different molar ratios (P-123:Y = 1:1 and 2:1). Fourier transform infrared spectroscopy (FTIR) results revealed a characteristic absorption band of Y–O vibrations typical of Y₂O₃ matrix. The structural phase was analyzed by X-ray diffraction (XRD), showing the characteristic cubic phase in all systems. The diffraction peak that presented the major intensity corresponded to the sample prepared from yttrium chloride incorporating P-123 in a molar ratio of P-123:Y = 2:1 at 900 °C. Crystallites sizes were determined by Scherrer equation as between 21 nm and 32 nm. Antioxidant properties were estimated by 2,2-diphenyl-1-picrylhydrazyl (DPPH•) assays; the results are discussed. Full article

(This article belongs to the Special Issue Selected Papers from the 1st International e-Conference on Materials)

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