References of "Pàez Martinez, Carlos"
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See detailHeterogeneous singlet oxygen generation: in-operando visible light EPR spectroscopy
Mendoza Gallego, Carlos ULiege; Désert, Anthony; Khrouz, Lhoussain et al

in Environmental Science and Pollution Research (2019)

The use of photosensitizers immobilized on mesoporous materials to produce singlet oxygen (1O2) has opened a new way to synthetic and environmental applications due to the fast development of flow ... [more ▼]

The use of photosensitizers immobilized on mesoporous materials to produce singlet oxygen (1O2) has opened a new way to synthetic and environmental applications due to the fast development of flow photochemistry and continuous-flow microreactors. 1O2-based photosensitized processes can be employed for the degradation of organic pollutants in aqueous medium and the photosensitizer can be covalently attached to the support and separated from the effluent reducing the environmental impact. The aim of the present paper is to evaluate the 1O2 generation of Rose Bengal (RB) in homogeneous and heterogeneous systems using in-operando evaluation. Mesoporous SiO2 nanoparticles (MSNs) were successfully conjugated with RB (MSN-RB) and Electron Paramagnetic Resonance (EPR) spectroscopy in combination with the spin trap TEMP was employed to obtain paramagnetic TEMPO via generated 1O2 when RB or MSN-RB are exposed to visible light. Additionally, EPR/DMPO was used to exclude the possible generation of other reactive oxygen species (ROS) by the functionalized nanoparticles. We found that in situ 1O2 generation was enhanced when the same amount of RB is immobilized inside of mesoporous SiO2. [less ▲]

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See detailPorphyrin-based hybrid silica-titania as a visible-light photocatalyst
Mahy, Julien ULiege; Pàez Martinez, Carlos ULiege; Carcel, Carole et al

in Journal of Photochemistry and Photobiology A: Chemistry (2019), 373

A silylated porphyrin derivative is co-hydrolyzed with Ti(OiPr)4 to produce a hybrid TiO2 photocatalyst, and three different ratios between porphyrin and TiO2 are made. In this way, the porphyrin ... [more ▼]

A silylated porphyrin derivative is co-hydrolyzed with Ti(OiPr)4 to produce a hybrid TiO2 photocatalyst, and three different ratios between porphyrin and TiO2 are made. In this way, the porphyrin fragments are held in the resulting matrix through strong Si-O-Ti covalent bonds to limit porphyrin leaching. Thanks to its photoactive character the porphyrin fragment can act as an actuator for the TiO2 to degrade organic pollutants using light from ultra-violet to the visible range. The photocatalysts are synthesized using an easy aqueous route allowing “green conditions” for synthesis. For comparative purposes, the corresponding pure TiO2 and a grafted catalyst are also synthesized and studied. For all samples, a mixture of anatase/brookite TiO2 is obtained, resulting in crystalline materials with low temperature synthesis. The three porphyrin-doped samples prepared in water prove to be efficient photocatalysts for the degradation of p-nitrophenol (PNP) under visible light, and an improvement in photoactivity is observed when the amount of porphyrin increases. The photocatalyst activity is very stable over time as the PNP degradation remains nearly constant after 264 h of testing, showing no leaching of porphyrin. In recycling tests, the grafted sample presents bond breaking between POR-Si and TiO2 and a decrease in photoactivity towards pure TiO2 sample activity. A comparison with the commercial Evonik P25 catalyst shows that the porphyrin-doped TiO2 is nearly 6 times more photoactive under visible light for PNP degradation. [less ▲]

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See detailDurable photocatalytic thin coatings for road applications
Mahy, Julien ULiege; Pàez Martinez, Carlos ULiege; Hollevoet, Jonas et al

in Construction and Building Materials (2019), 215

In this study, 6 different coatings have been developed as photocatalytic coatings based on TiO2, which can be applied to concrete for road applications. The goal of these coatings is to degrade ... [more ▼]

In this study, 6 different coatings have been developed as photocatalytic coatings based on TiO2, which can be applied to concrete for road applications. The goal of these coatings is to degrade pollutants such as nitrogen oxides and volatile organic compounds emitted by road transport. The coatings are synthesized by sol-gel process in organic or water solvent or by a functionalization technique with hydroxybenzoic acid on commercial TiO2 nanoparticles (P25). These suspensions are deposited by dip-coating or spray-coating on three different concrete substrates: pavement blocks, brushed or exposed aggregates road concrete. For each process, particular attention has been paid to the development of TiO2 synthesis that will be easily produced on a larger scale. The samples are characterized with photocatalytic test on NOx degradation, mechanical resistance test and resistance to freeze-thaw cycles in presence of de-icing salts. Except from the samples resulting from the sol-gel organic route, all other samples show a NOx degradation between 10 and 45%. From resistance point of view, the best coating is the TiO2 P25/E coating synthesized by functionalization of P25 nanoparticles. Results highlight that anatase TiO2 is well present at the surface of the sample and an optimal TiO2 loading exists for this coating. The TiO2 P25/E coating shows promising properties for road applications. [less ▲]

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See detailImproving Continuous Flow Singlet Oxygen Photooxygenations with Functionalized Mesoporous Silica Nanoparticles
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

in ChemPhotoChem (2018)

Continuous flow photochemistry relying on photosensitizers faces two main challenges: the photodegradation (bleaching) and the downstream removal of the photosensitizer. Rose Bengal (RB) is a common ... [more ▼]

Continuous flow photochemistry relying on photosensitizers faces two main challenges: the photodegradation (bleaching) and the downstream removal of the photosensitizer. Rose Bengal (RB) is a common photosensitizer utilized for photooxygenations with singlet oxygen (1O2), but is notoriously sensitive to photobleaching and difficult to remove from reactor effluents. The heterogenization of photosensitizers on mesoporous silica nanoparticles (MSNs) is arguably a viable option for such applications. Herein, we report on the use of RB covalently incorporated into MSNs (RB@MSNs) for photooxygenations under continuous flow conditions. RB@MSNs enable the 1O2 photooxygenation of various organic substrates upon irradiation with 540 nm LEDs. A series of organic substrates were evaluated including methionine, α‐terpinene, 2‐furoic acid, triphenylphosphine, citronellol and cyclopentadiene. These results emphasize an improved resistance to photobleaching, and the possibility to use RB@MSNs as easily recoverable catalyst, which could be removed from the reactor effluent either (a) by centrifugation or (b) in‐line membrane filtration. [less ▲]

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See detailFunctionalization of mesoporous silica nanoparticles with Rose Bengal for heterogeneous photooxygenation reactions in microfluidic systems
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

Poster (2018, July 09)

Singlet oxygen-based photocatalytic oxygenation reactions have emerged as an efficient technology to synthesize value-added organic molecules[1]. There are various methodologies for the production of ... [more ▼]

Singlet oxygen-based photocatalytic oxygenation reactions have emerged as an efficient technology to synthesize value-added organic molecules[1]. There are various methodologies for the production of singlet oxygen, among which the most popular involves a photoinduced electronic energy transfer from an excited state of a catalytic photosensitizer (PS) to triplet oxygen (3O2)[2]. The amino acids tyrosine, tryptophan, methionine, histidine and cysteine constitute one of the most relevant families among the photooxidizable biological substrates due to their areas of high electron density because of double bonds or sulfur moieties. Of particular interest is the photooxidation of methionine (Met) to methionine sulfoxide (MetO). In general, sulfoxides are frequently used in organic synthesis, pharmaceutical science, biochemistry and material science. However, the classical methods to oxidize sulfides to sulfoxides present a high risk of overoxidation to sulfones. In particular, MetO is a particularly valuable synthetic intermediate with applications ranging from peptide sciences, material sciences, to organic synthesis. PSs are commonly organic dyes bearing a (hetero)aromatic core such as Rose Bengal, Methylene Blue, Erythrosin B, porphyrins, phtalocyanines, and related tetrapyrroles. Rose Bengal (RB) is a popular photosensitizer that has been widely utilized for the production of 1O2 upon visible light aerobic irradiation[3]. The functionalization of mesoporous silica nanoparticles (MSNs) with PSs has attracted great research attention during last years to design efficient nanoplatforms to be used in nanomedicine as drug delivery systems or in targeted photodynamic cancer therapy (PDT) owing to their biocompatibility, high RB loading capacity and ease of surface functionalization, but its use as catalyst support in photooxygenation reactions is still a challenge. Regarding the use of RB under continuous-flow photocatalytic conditions and the configuration of the flow setup, three main strategies emerge from the literature based on the use of (a) homogeneous PSs, (b) packed-bed photoreactors with heterogeneous PSs embedded on the packing material and (c) heterogeneous PSs concomitantly fed with the substrate. Although each strategy comes with assets and drawbacks, the use of free flowing heterogeneous PSs is supposedly the most interesting option, as far as, besides their efficiency, (a) they (a) are readily prepared, (b) do not accumulate within the micro/mesoreactor channels or cause clogging and (c) are easily removed downstream. RB can be protected from photobleaching during important light exposures by a mesoporous SiO2 structure[4]. Synthesis of MSNs was made following well-known methods and the immobilization of RB at the surface of SiO2 by a covalent bond was carried out by two coupling agents: 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and (1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate) (HATU). A complete characterization of RB@MSNs was made by BET, Tg-MS, UV-Vis and TEM. Finally, the influence of key parameters like RB concentration and the liquid flow were studied as a function of the coupling agent used in a microfluidic system. The efficiency of methionine photooxygenation as well as the photobleaching of the dye was followed by Proton Nuclear Magnetic Resonance (1H NMR). This work converts MSNs in interesting support for new and clean heterogeneous continuous-flow photooxygenations. Taken together, our results show that heterogenization of PS for 1O2 production in microreactors is possible by grafting RB into MSNs by a covalent bond. This attachment is able to avoid the photobleaching of the dye and allows separating the solid support with the PS from the reactor effluent and reutilizing the PS. The potential of these NPs to be used as heterogeneous catalyst for photooxygenation of methionine has been demonstrated. [less ▲]

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See detailRose Bengal@MSNs as heterogeneous photocatalysts in photooxygenation reactions
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

Conference (2018, June 19)

The functionalization of mesoporous silica nanoparticles (MSNs) with photosensitizers e.g. Rose Bengal (RB) has attracted great research attention during last years to design efficient nanoplatforms to be ... [more ▼]

The functionalization of mesoporous silica nanoparticles (MSNs) with photosensitizers e.g. Rose Bengal (RB) has attracted great research attention during last years to design efficient nanoplatforms to be used in nanomedicine as drug delivery systems or in targeted photodynamic cancer therapy (PDT) owing to their biocompatibility, high loading capacity and ease of surface functionalization. Additionally, its use as catalyst support in photooxygenation reactions via singlet oxygen (1O2) can produce high-value added organic molecules in continuous-flow microreactors decreasing the environmental impact due to the possibility to recover the solid catalyst from the reactor effluent and reutilize the photosensitizer. Various model organic substrates were tested as previously reported for homogeneous photooxygenation reactions including bio-sourced methionine [1] and α-terpinene as well as 2-furoic acid, triphenylphosphine, citronellol and cyclopentadiene. The immobilization of the dye inside mesoporous silica nanoparticles plays a strategic role in preserving the chemical integrity of the photosensitizer as demonstrated by UV-Vis spectroscopy. The mechanism of photooxygenation by 1O2 could be influenced by the state of the dye, avoiding the ground state complexation between the amino acid and the photosensitizer as occurs in homogeneous systems. Moreover, heterogeneous photooxygenation of several substrates in order to obtain high-value added organic molecules. High conversions were achieved with methionine, α-terpinene in 72 s and triphenylphosphine in 300 s. However, the heterogeneous 1O2 photooxygenation of cyclopentadiene into cis-2-cyclopentadiene-1,4-diol provided a complete conversion in 51 s of residence time. Our results show that heterogenization of PS for 1O2 production in microreactors is possible by grafting RB into MSNs by a covalent bond. This attachment is able to avoid the photobleaching of the dye and allows separating the solid support with the PS from the reactor effluent and reutilizing the PS in different cycles. The potential of these NPs to be used as heterogeneous catalyst for photooxygenation of several organic substrates has been demonstrated. [less ▲]

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See detailTransitioning from conventional batch to microfluidic processes for the efficient singlet oxygen photooxygenation of methionine
Mendoza Gallego, Carlos ULiege; Emmanuel, Noémie ULiege; Pàez Martinez, Carlos ULiege et al

in Journal of Photochemistry and Photobiology A: Chemistry (2018), 356

Singlet oxygen-based photocatalytic oxygenation reactions have emerged as an efficient technology to synthesize value-added organic molecules. Among organic substrates, bio-sourced molecules such as ... [more ▼]

Singlet oxygen-based photocatalytic oxygenation reactions have emerged as an efficient technology to synthesize value-added organic molecules. Among organic substrates, bio-sourced molecules such as aminoacids or terpenes have a promising forecast as synthetic building blocks. A pseudo first-order kinetic study for the photocatalytic oxygenation of natural amino acid (L)-methionine was carried out in a macroscopic batch reactor. Various parameters were studied, including the effect of the photosensitizer (Rose Bengal, RB) concentration, the intensity of the light and the O2 flow in terms of apparent kinetic constants and space-time yields. The identification of important limiting parameters as pressure, gas flow or light efficiency during the photocatalytic oxygenation of methionine allowed its transition from macroscopic batch reactor to continuous-flow microreactor. [less ▲]

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See detailRole of defects on the enhancement of the photocatalytic response of ZnO nanostructures
Montero-Munoz, M.; Ramos-Ibarra, J. E.; Rodríguez-Páez, Jorge E. et al

in Applied Surface Science (2018), 448

Zinc oxide (ZnO) nanostructures have been synthesized by a simple controlled precipitation method to study the effects of the type solvent – including water, acetic acid and ethylene glycol – on the ... [more ▼]

Zinc oxide (ZnO) nanostructures have been synthesized by a simple controlled precipitation method to study the effects of the type solvent – including water, acetic acid and ethylene glycol – on the formation of ZnO and on its photocatalytic activity for the decomposition of H2O2 in aqueous solution. Scanning electron microscopy (SEM) and synchrotron-based X-ray diffraction (XRD) were used to determine the morphology, crystallinity, and chemical composition of the ZnO structures. Raman spectroscopy and photoluminescence measurements were carried out to determine the nature of the defects present in the different ZnO nanostructures and how they affect the photocatalytic activity. Based on the results, we propose plausible growth mechanisms underlying the formation of ZnO with different morphology, according to the solvent used during the synthesis. A direct relation between the photocatalytic activity and the defects type was established, suggesting that defects play a vital role in modulating the photocatalytic response. [less ▲]

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See detailInteractions between Zn2+ or ZnO with TiO2 to produce an efficient photocatalytic, superhydrophilic and aesthetic glass
Léonard, Géraldine ULiege; Pàez Martinez, Carlos ULiege; Ramirez, Alfonso et al

in Journal of Photochemistry and Photobiology A: Chemistry (2018), 350

Zinc was coupled with titanium dioxide using different methods. SiO2 and Zn-SiO2 doped TiO2 films, on the one hand, and Zn doped TiO2 on the other hand, have been produced using controlled sol-gel ... [more ▼]

Zinc was coupled with titanium dioxide using different methods. SiO2 and Zn-SiO2 doped TiO2 films, on the one hand, and Zn doped TiO2 on the other hand, have been produced using controlled sol-gel processes by alcoholic, cogelation and aqueous ways. From these syntheses, films were deposited on soda lime glass. These samples were compared to ZnO samples but also to bilayer samples constituting one layer of TiO2 and one layer of ZnO. The physico-chemical properties of the films were characterized by grazing-incidence X-ray diffraction, profilometry and UV-Vis absorption analyses. The photocatalytic activity has been evaluated from the degradation of methylene blue under UV-A light, from the degradation of p-nitrophenol under visible light and from the degradation of H2O2 under halogen light (UV-A + visible light). Superhydrophilicity was evaluated from contact angle measurement after UV exposition and also from hysteresis effects. Finally, a haze measurement was performed to evaluate the impact of the coating on the aesthetic property of the coated glass. Aqueous films have better photocatalytic activity and superhydrophilicity than samples from alcoholic synthesis. The crystallization of the sample appears to be one key factor: alcoholic films required calcination to ensure the crystallization of TiO2, but the alkali migration from the glass support prevents this crystallisation, while aqueous synthesis promotes crystallized particles at low temperatures without alkali interference. It appears that the relative activity from one sample to another depends on the nature of the illumination and on the nature of the molecule to be degraded. Nevertheless, the sample with ZnO layer deposited on first TiO2 layer (ZnO 500 Alc/TiO2 100 AQ) composite is found to be the best sample, maintaining a high hydrophilicity similar to TiO2 and a good activity. [less ▲]

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See detailVisible-light TiO2 photocatalyst doped with silylated porphyrin
Mahy, Julien ULiege; Pàez Martinez, Carlos ULiege; Léonard, Géraldine ULiege et al

Conference (2017, August 15)

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See detailElectrochemical performances of Li4Mn5O12 prepared by spraycoating assisted Sol-Gel reaction
Alié, Christelle ULiege; Pàez Martinez, Carlos ULiege; Calberg, Cédric ULiege et al

Poster (2017)

There is an intense interest in the battery industry to identify ways to improve the cathodes used in terms of energy, power, safety, life, and cost. Li4Mn5O12 has attracted great interest as a potential ... [more ▼]

There is an intense interest in the battery industry to identify ways to improve the cathodes used in terms of energy, power, safety, life, and cost. Li4Mn5O12 has attracted great interest as a potential 3V cathode material for rechargeable Li batteries in recent years, due to its high specific capacity of 163 mAh/g in the 3V region. Li4Mn5O12 is conventionally synthesized via solid-state reaction where the high temperature needed makes it difficult to obtain stoichiometric Li4Mn5O12 and the solid-state reaction gives a solid that needs to be mixed with a carbon source and a binder for electrochemical characterization and application. The fabrication of thin film rechargeable lithium batteries by a Sol-Gel method combined with spray-coating technique is expected to achieve both simplification and cost reduction of fabrication process by direct deposition of the active material on the electrode during its synthesis. A precursor sol of LiCH3COO.2H2O:Mn(CH3COO)2.4H2O (4:5) and L-lysine (total metal ions:L-lysine 50:1) was sprayed onto steel coins repeatedly, dried at 280 °C by heat gun and converted to Li4Mn5O12 thin film by heating at 400 °C. This process was repeated till target mass was deposited. For a target battery capacity of 0.65 mAh, a deposit of 4 mg is necessary. The charge-discharge test of the Li/Li4Mn5O12 coin cell battery was carried out at different rates, 0.1 C to 2 C (1C = 163 mA/g), between 1.8 and 3.6V. It is important that the total capacity is close to theoretical value and stable with cycling. The table below on the evolution of the capacity with the cycles at different rates shows that even at a medium rate of C/2, the capacity decreases by 10 % after 70 cycles, result which is better than those observed in the literature [1-3] but not good enough for applications. Doping of the sol with TiO2 before spray coating is necessary to improve electrochemical performances. The figure below shows the charge-discharge curves of the TiO2-doped Li4Mn5O12 at different rates. During the successive cycles, the discharge and charge decrease only slightly at a given rate, demonstrating the high-degree stable discharge plateau at 2.8 V. Very good capacities are obtained for rates ≤ 1C but for higher rates, kinetic problems appear and part of the lithium does not take part to the insertion-extraction process, even with TiO2 doping. In the potential range of 3.6-1.8 V, TiO2-doped Li4Mn5O12 still display very good electrochemical properties in respect of the capacity (high capacity values), capacity retention (stability) and rate capability (high capacity and stability at medium rates) as shown in the table below. [less ▲]

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See detailOrganic dyes anchoring in anatase photocatalysts to decontaminate water with solar light
Tasseroul, Ludivine; Pirard, Sophie ULiege; Lambert, Stéphanie ULiege et al

Conference (2017)

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See detailCharacterization of photoactive coatings of SiO2 nanoparticles and Rose Bengal onto glass surfaces
Mendoza Gallego, Carlos ULiege; Lismont, Marjorie ULiege; Pàez Martinez, Carlos ULiege et al

Conference (2016)

The fluorescence emission and singlet oxygen (1O2) production have been widely investigated over the last decade due to high-value added applications such as organic chemical synthesis1, wastewater ... [more ▼]

The fluorescence emission and singlet oxygen (1O2) production have been widely investigated over the last decade due to high-value added applications such as organic chemical synthesis1, wastewater treatment2 or photodynamic cancer therapy3. This work is dedicated to the synthesis and deposition of SiO2 nanoparticles on glass surfaces using Stober’s process and dip coating, respectively. The adherence was improved through the incorporation of different concentrations of these nanoparticles into a TiO2 matrix. Additionally, the speed of dip coating was used to modify SiO2 thicknesses. Rose bengal was covalently anchored to SiO2 coatings through (3-aminopropyl)triethoxysilane (APTES) linker. UV, IR, fluorescence, SEM and profilometry were used to characterize the corresponding films and the efficiency for singlet oxygen production was measured by oxidation of the amino acid methionine. The immobilization of SiO2 nanoparticles photosensitized with rose bengal showed promising results for the production of singlet oxygen. [less ▲]

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See detailMethod for the wet deposition of thin films
Pàez Martinez, Carlos ULiege; Liquet, Dimitri ULiege; Calberg, Cédric ULiege et al

Patent (2016)

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See detailProtoporphyrin IX Functionalised AgSiO2 Core-shell Nanoparticle: Plasmonic Enhancement of Fluorescence and Singlet Oxygen Production
Lismont, Marjorie ULiege; Dreesen, Laurent ULiege; Heinrichs, Benoît ULiege et al

in Photochemistry and Photobiology (2016), 92

Metal-enhanced processes arising from the coupling of a dye with metallic nanoparticles (NPs) have been widely reported. However, few studies have simultaneously investigated these mechanisms from the ... [more ▼]

Metal-enhanced processes arising from the coupling of a dye with metallic nanoparticles (NPs) have been widely reported. However, few studies have simultaneously investigated these mechanisms from the viewpoint of dye fluorescence and photoactivity. Herein, protoporphyrin IX (PpIX) is grafted onto the surface of silver core silica shell NPs in order to investigate the effect of silver (Ag) localized surface plasmon resonance (LSPR) on PpIX fluorescence and PpIX singlet oxygen (1O2) production. Using two Ag core sizes, we report a systematic study of these photophysical processes as a function of silica (SiO2) spacer thickness, LSPR band position and excitation wavelength. The excitation of Ag NP LSPR, which overlaps the PpIX absorption band, leads to the concomitant enhancement of PpIX fluorescence and 1O2 production independently of the Ag core size, but in a more pronounced way for larger Ag cores. These enhancements result from the increase in the PpIX excitation rate through the LSPR excitation and decrease when the distance between PpIX and Ag NPs increases. A maximum fluorescence enhancement of up to 14-fold, together with an increase in photogenerated 1O2 production of up to five times are obtained using 100 nm Ag cores coated with a 5 nm thick silica coating. [less ▲]

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