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Novel generation of hybrid photochromic vinylidene-naphthofuran silica nanoparticles through fine-tuning of surface chemistry

Abstract

Novel photochromic 1-vinylidene-naphtho[2,1-b]furan derivatives (VNF-1 and VNF-2) were successfully anchored onto silica nanoparticles (SiO2 NPs) through direct adsorption (SiO2@VNF-1) and covalent post-grafting (SiO2@VNF-2). SiO2 NPs with different size (15±3 and 123±7 nm) and surface chemistry (pHpzc in the range of 5–9) were used, offering a wide range of possibilities to fabricate tailor-made photochromic materials. Characterization of VNF-based SiO2 NPs confirmed the efficient VNFs immobilization and the integrity of both organic and inorganic components. The photochromic behavior of these new nanoparticles indicates that silica surface acidity and the type of VNF immobilization strategy (adsorption vs. covalent grafting) were crucial factors for the occurrence of photochromism in the VNF-based SiO2 NPs. Upon direct UV ( = 365 nm) or sunlight exposure during 1 min, only the SiO2@VNF-1 nanomaterials prepared by direct VNF adsorption onto SiO2 NPs with pHpzc ≈ 6.0 showed direct and reversible photochromic properties, developing fast (in seconds) and intense salmon and violet coloration, with high values of total color difference (ΔE*ab = 10.7−24.3) and optical densities (OD = 0.14−0.25); in contrast, all nanomaterials prepared by covalent grafting of VNF-2 onto SiO2 NPs (SiO2@VNF-2) did not exhibit photochromism. In the case of the photochromic SiO2@VNF-1 NPs, the decoloration process followed a bi-exponential decay with fast rate constants (k1 = 1.6×10-1–1.6 min-1 and k2 = 9.1×10-3−1.3×10-1 min-1), which were responsible for the loss of coloration in less than 10 min. Furthermore, they presented very good resistance to fatigue, showing reversibility between the colored/uncolored states without significant loss of their performance for at least 8 successive UV/dark cycles

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Publication details

The article was received on 15 Apr 2017, accepted on 13 Jun 2017 and first published on 13 Jun 2017


Article type: Paper
DOI: 10.1039/C7DT01376K
Citation: Dalton Trans., 2017, Accepted Manuscript
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    Novel generation of hybrid photochromic vinylidene-naphthofuran silica nanoparticles through fine-tuning of surface chemistry

    C. Freire, T. Pinto, C. Sousa, C. A. Sousa, M. M. Aboelhassan, A. Peixoto, C. Pereira and P. J. Coelho, Dalton Trans., 2017, Accepted Manuscript , DOI: 10.1039/C7DT01376K

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