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Fluorescent silica MCM-41 nanoparticles based on flavonoids: Direct post-doping encapsulation and spectral characterization
Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.ORCID-id: 0000-0003-2099-7605
Laboratoire de Réactivité de Surface UMR CNRS 7197, Sorbonne Université, 4 Place Jussieu, F-75005, Paris, France.
Laboratoire de Réactivité de Surface UMR CNRS 7197, Sorbonne Université, 4 Place Jussieu, F-75005, Paris, France.
Laboratoire de Réactivité de Surface UMR CNRS 7197, Sorbonne Université, 4 Place Jussieu, F-75005, Paris, France.
Visa övriga samt affilieringar
2021 (Engelska)Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 185, Part A, artikel-id 108870Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Flavones and flavonols are naturally-occurring organic molecules with interesting biological, chemical and photophysical properties. In recent years their interaction with silica surfaces has received increasing attention. In this work, the flavonol 3-hydroxyflavone (3HF) and the flavone 7-hydroxyflavone (7HF) have been encapsulated in MCM-41 mesoporous silica nanoparticles (NP) via a post-doping procedure, and their photophysics characterized by both steady state and time-resolved spectroscopic techniques. Both flavonoid-doped NPs resulted to be highly fluorescent, even after two months of exposure to air at room temperature. UV light irradiation results in a moderate decrease of the fluorescence quantum yield. Complementary UV-Vis and fluorescence experiments of 3HF and 7HF in solutions and TD-DFT calculations to simulate absorption and emission spectra have been carried out in order to better rationalize the exact nature of the emitting species. Whereas for 3HF-doped NPs the tautomer emission in the green predominates, the fluorescence of 7HF-doped NPs is likely to arise from the cationic or the phototautomeric form of the flavonoid. The results show that organic fluorophore-based fluorescent silica NPs can be easily obtained by a post-doping procedure and represent a first step towards the development of a simple strategy for the encapsulation in MCM-41 NPs of flavonoids and other organic molecules.

Ort, förlag, år, upplaga, sidor
Elsevier, 2021. Vol. 185, Part A, artikel-id 108870
Nationell ämneskategori
Annan fysik
Forskningsämne
Experimentell fysik
Identifikatorer
URN: urn:nbn:se:ltu:diva-80873DOI: 10.1016/j.dyepig.2020.108870ISI: 000600372200007Scopus ID: 2-s2.0-85091964068OAI: oai:DiVA.org:ltu-80873DiVA, id: diva2:1469510
Anmärkning

Godkänd;2020;Nivå 0;2020-12-02 (johcin);Konferensartikel i tidskrift

Tillgänglig från: 2020-09-22 Skapad: 2020-09-22 Senast uppdaterad: 2023-10-28Bibliografiskt granskad
Ingår i avhandling
1. Nanostructured Metal Oxide Semiconductors for Functional Applications
Öppna denna publikation i ny flik eller fönster >>Nanostructured Metal Oxide Semiconductors for Functional Applications
2021 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis is about nanostructured metal oxides, their properties, and some of their applications. Semiconducting metal oxides like TiO2, ZnO,and SnO2 have a wide band gap, which means they absorb UV light andgenerate electron-hole pairs. These charge carriers can be harnessed andused for a variety of purposes, such as electricity generation in solar cells,hydrogen production by means of photolysis and electrolysis, andenvironmental remediation by mineralizing pollutants in photocatalyticreactions. However, they are typically not very efficient when comparedwith e.g. noble metals in catalysis or silicon in solar cells , and so a widevariety of strategies have been employed to remedy their weaknesses.Such strategies include structuring the materials at the nanoscale, and thefabrication of composite materials and heterostructures.In this work, some advanced hybrid materials have been studied,composed of metal oxide and various additives, such as reduced grapheneoxide (rGO), other metal oxides, and flavonoids. The materials have beenextensively characterized in order to determine how these additives affectthe processes going on in some of the mentioned applications. Thestudied systems include rGO-ZnO, SnO2-ZnO, Rh-TiO2, MoO2, SiO2coupled to 3-hydroxyflavone and 7-hydroxyflavone, and 3-hydroxyflavone-TiO2.Particles of ZnO-encapsulated rGO exhibited a good photocatalyticactivity towards the degradation of rhodamine B and phenol, but it wasfound that the main determinant of the performance was the quality ofthe semiconductor component as opposed to any favorable interactionsbetween ZnO and rGO. However, the incorporation of rGO could stillalmost double the observed performance, which was attributed to apassivation of the defects in the metal oxide host, as well as a beneficialimpact of electrochemical properties such as charge transfer resistance anddouble-layer capacitance of the resulting material.Core-shell nanoparticles consisting of a SnO2 core and a ZnO shell weresuccessfully synthesized and employed as photocatalyst and as photoanodein dye-sensitized solar cells (DSSCs). The ZnO shell improved theperformance in both photocatalysis and DSSCs by nearly a factor of two,due to a combination of the favorable properties of the two metal oxides ,and the formation of a heterojunction in the interface between them.Rhodium as an additive to TiO2 nanocrystals proved to effectivelyimprove the response in gas sensing experiments. The rhodium exhibitedcomplex speciation, however, being distributed as a homogeneouscoating of Rh(III) as well as nanocrystals of elemental rhodium,highlighting the need for deep characterization in this class of materials.Metallic MoO2 nanocrystals were synthesized and tested in photocatalysis.Due to their electronic nature, they cannot support photocatalysisaccording to the traditional reaction scheme, because metals cannotgenerate electron-hole pairs. However, they still exhibited significantphotocatalytic activity towards methylene blue, rhodamine B, andparacetamol. This was attributed to a direct sensitization mechanismwhere the dye is photoexcited and undergoes electron transfer, madepossible due to the comparatively low work function in MoO2. This alsoenables it to assist in the degradation of non-absorbing molecules in thesolution. 3-hydroxyflavone (3HF) and 7-hydroxyflavone (7HF) were combinedwith MCM-41 silica nanoparticles via a post-doping procedure, and theirphotophysics characterized by steady-state and time-resolvedspectroscopic techniques. Both flavonoid-coated nanoparticles turned outto be highly fluorescent and stable when exposed to air at roomtemperature, showing that organic fluorophore-based solid-state emitterscan be obtained by simple methods. Furthermore, 3HF was coupled toTiO2 nanoparticles with a similarly simple adsorption procedure. In thiscase the result was a chemisorption of the flavonoid, which appears to bevery similar to a chelation of the metal ions in the metal oxide substrate.The fluorescence in the resulting materials is nearly completely quenched,but when a nanometer-thin layer of Al2O3 is applied on the TiO2, it isinstead strongly enhanced. This work therefore represents a rather noveland facile way to produce flavonoid-metal complexes.

Ort, förlag, år, upplaga, sidor
Luleå University of Technology, 2021
Serie
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Nationell ämneskategori
Nanoteknik Annan fysik
Forskningsämne
Experimentell fysik
Identifikatorer
urn:nbn:se:ltu:diva-83181 (URN)978-91-7790-773-2 (ISBN)978-91-7790-774-9 (ISBN)
Disputation
2021-06-01, E632, Luleå, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2021-03-05 Skapad: 2021-03-05 Senast uppdaterad: 2022-06-30Bibliografiskt granskad

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