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Author(s): Pinto, TV
Costa, P
Sousa, CM
Sousa, CAD
Monteiro, A
Clara Pereira
O.S.G.P. Soares
Silva, CSM
Manuel Fernando R Pereira
Coelho, PJ
Freire, C
Title: Naphthopyran-Based Silica Nanoparticles as New High-Performance Photoresponsive Materials
Issue Date: 2016
Abstract: Hybrid nanomaterials based on the covalent of silylated naphthopyrans (NPTs) onto silica nanoparticles (SiO2 NPs) were successfully prepared and studied as new photochromic materials. They were prepared by a two-step protocol consisting of (i) NPTs (derivatives from 2H-naphtho[1,2-b]pyran (2H-NPT) and 3H-naphtho-[2,1-b]pyran (3H-NPT)) silylation by a microwave-assisted reaction between hydroxyl-substituted NPTs and 3(triethoxysilyl)propyl isocyanate, followed by (ii) covalent post-grafting onto SiO2 NPs. In order to study the role-of the silylation step, the analogous non-silylated nanomaterials were also prepared by direct adsorption of NPTs. The characterization techniques confirmed the successful NPTs silylation and subsequent grafting to SiO2 NPs. All SiO2-based nanomaterials revealed photoswitching behavior, following a biexponential decay. The SiO2 NPs functionalized with silylated 3H-NPTs (SiO2@S3 and SiO2@S4) presented the most promising photochromic properties, showing fast coloration/decoloration kinetics (coloring in 1 min under UV irradiation and fading in only 2 min) and high values of total color difference (Delta E-ab* = 30-50). Also, the 2H-NPTs-based SiO2 NPs (SiO2@S1 and SiO2@S2) presented fast coloration and good color contrasts (Delta E-ab* = 54); but slower fading kinetic rates, taking more than 2 h to return to their initial color. In contrast, the SiO2 NPs functionalized with non-silylated NPTs (SiO2@1 and SiO2@3) showed weaker color contrasts (Delta E-ab* = 6-10) and slower fading kinetics, proving that the NPT silylation step was crucial to enhance the photochromic behavior of SiO2 NPs based on NPTs. Furthermore, the silylated-based nanomaterials showed good photostability upon prolonged UV light exposure) keeping their photochromic performance unchanged for at least 12 successive UV/dark cycles, anticipating interesting technological applications in several areas.
Related Information: info:eu-repo/grantAgreement/FCT - Fundação para a Ciência e Tecnologia/Projetos Estratégicos/UID/EQU/50020/2013- POCI-01-0145-FEDER-006984/Laboratório de Processos de Separação e Reação - Laboratório de Catálise e Materiais/LSRE-LCM
Document Type: Artigo em Revista Científica Internacional
Rights: restrictedAccess
Appears in Collections:FCUP - Artigo em Revista Científica Internacional
FEUP - Artigo em Revista Científica Internacional

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