Search

Your search keyword '"Barros Timmons, Ana"' showing total 317 results
Start Over Author "Barros Timmons, Ana"
317 results on '"Barros Timmons, Ana"'

1. The Recycling of Construction Foams: An Overview

Author

Gama, Nuno, Barros-Timmons, Ana, Ferreira, Artur, Chen, Sheng-Hong, Series Editor, di Prisco, Marco, Series Editor, Vayas, Ioannis, Series Editor, Bragança, Luís, editor, Cvetkovska, Meri, editor, Askar, Rand, editor, and Ungureanu, Viorel, editor

Published
2024
Full Text
View/download PDF

10. Solvolysis of Nylon: A Pathway to Sustainable Recycling and Circular Economy.

Author

Gama, Nuno, Araújo, Jéssica, Godinho, Bruno, Ferreira, Artur, and Barros-Timmons, Ana

Abstract

Polyamides (PAs) are extensively utilized across various applications, yet the accumulation of PA residues presents significant ecological and environmental challenges. Given that a substantial portion of fishing nets are composed of nylon, a type of PA, this material's disposal raises environmental concerns impacting marine life and the global ecosystem. Therefore, to enhance sustainability, they could be collected and recycled. This study introduces a method for the chemical recycling of PA waste using hydrochloric acid (HCl). Through solvolysis, a PA was depolymerized, and the effect of various reaction conditions on the depolymerization yield was analyzed, being the best conditions established in this work (100 °C, 4 h, and an HCl/PA ratio of 11:1, wt.wt−1). Next, a novel separation methodology was employed to isolate recycled products from salts formed during neutralization. Subsequently, these recycled products were incorporated as a partial substitute (up to 10% wt.wt−1) for a conventional PA in a new material production. The results indicate that the presence of recycled products enhances material stiffness due to crystallinity differences compared to the virgin matrix. In turn, the introduction of lower-molecular-weight species increases the materials' glass transition temperature (Tg) and their melt flow index (MFI). This research underscores a sustainable pathway for PA recycling aligned with circular economy principles, contributing positively to environmental conservation efforts. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

40. Biotinylation of optically responsive gold/polyelectrolyte nanostructures

Author

Pereira, Sonia O., Trindade, Tito, and Barros-Timmons, Ana

Subjects
Biotin, Nanoparticles -- Optical properties, Fluorescence -- Optical properties -- Analysis, Gold -- Optical properties, Metals, metalworking and machinery industries
Abstract

The development of analytical platforms incorporating Au nanoparticles (NPs) for optical biosensing requires approaches to produce optically responsive and target selective materials. In the present work, fluorescence emission and bioselectivity of Au NPs have been combined by a one-step surface functionalization using fluorescein isothiocyanate (FITC) and biotin. First, colloidal Au NPs (d =17.7 ± 2.7 nm) exhibiting an absorption maximum ([λ.sub.max]) at 524.5 nm have been surface-modified with the polyelectrolytes (PE) poly(allylamine hydrochloride) (PAH) and poly(sodium styrene sulfonate) (PSS). Two strategies were then assessed for the functionalization of Au NPs: (i) functionalization of PAH with biotin and subsequent coating of the NPs and (ii) surface modification of the NPs with the PE followed by postfunctionalization with biotin. The effect of the surface functionalization on the colloidal NPs was monitored by optical absorption and fluorescence emission spectroscopies, dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). Finally, the optical response and specificity of the functionalized NPs towards avidin was evaluated by optical measurements. The results have shown that these hybrid nanostructures have potential to be used in biosensing. In particular, the aggregation of biotinylated Au assemblies associated with the biorecognition of avidin could be assessed by fluorescence emission spectroscopy. Keywords Biosensor * Gold nanoparticles * Optical properties * Hybrid nanostructures * Polyelectrolytes * Biotinylation, Introduction Gold nanoparticles (Au NPs) have been widely studied for diverse bioapplications namely due to their optical properties which are dependent on the morphological characteristics and surrounding medium [1-5]. These [...]

Published
2015
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results