Search results for "silica nanoparticle"
showing 10 items of 59 documents
Multiband light emission and nanoscale chemical analyses of carbonized fumed silica
2018
Fumed silica with a specific area of 295 m2/g was carbonized by successive phenyltrimethoxysilane treatments followed by annealing in inert atmosphere up to 650 °C. Emission, excitation, kinetics, and photo-induced bleaching effects were investigated by steady state and time-resolved photoluminescence spectroscopies. The local chemistry was also studied by infrared transmission spectroscopy. Strong ultraviolet and visible photoluminescence was observed in the samples after the chemical treatments/modifications and thermal annealing. It has been shown that ultraviolet photoluminescence in chemically modified fumed silica is associated with phenyl groups, while near ultraviolet and visible em…
Insight into the defect-molecule interaction through the molecular-like photoluminescence of SiO2 nanoparticles
2016
Luminescence properties due to surface defects in SiO2 are the main keystone with particles that have nanoscale dimensions, thus motivating their investigation for many emission related applications in the last few decades. A critical issue is the role played by the atmosphere that, by quenching mechanisms, weakens both the efficiency and stability of the defects. A deep knowledge of these factors is mandatory in order to properly limit any detrimental effects and, ultimately, to offer new advantageous possibilities for their exploitation. Up to now, quenching effects have been interpreted as general defect conversion processes due to the difficulty in disentangling the emission kinetics by…
Entrapping of O2 Molecules in Nanostructured Silica Probed by Photoluminescence
2013
We studied the emission of the O2 molecules embedded in fumed silica (amorphous silicon dioxide) nanoparticles differing for diameters and specific surface. By using a 1064 nm laser as a source we recorded both the O2 emission and the Raman signal of silica. Our experimental data show that the O2 emission/Raman signal (at 800cm-1) ratio decreases with increasing the specific surface both for the as received and the loaded samples. By performing a thermal treatment (600 °C for 2h) we modified the structure and the water content of the smallest nanoparticles without observing any significant change in the O2 emission/Raman signal ratio. Our data are explained by a shell model showing that the…
Visible-ultraviolet vibronic emission of silica nanoparticles
2014
We report the study of the visible-ultraviolet emission properties and the structural features of silica nanoparticles prepared through a laboratory sol-gel technique. Atomic force microscopy, Raman and Infrared investigations highlighted the 10 nm size, purity and porosity of the obtained nanoparticles. By using time resolved photoluminescence techniques in air and in a vacuum we were able to single out two contributions in the visible emission: the first, stable in both atmospheres, is a typical fast blue band centered around 2.8 eV; the second, only observed in a vacuum around the 3.0-3.5 eV range, is a vibrational progression with two phonon modes at 1370 cm(-1) and 360 cm(-1). By fully…
Visible luminescence peculiar to sintered silica nanoparticles: Spectral and decay properties
2015
We report that the sintering at 1000 degrees C of silica nanoparticles (an average diameter of 14 nm) produces a transparent sample that exhibits a bright visible emission under UV excitation. The use of time resolved luminescence spectroscopy and a tunable laser source allows us to single out three contributions centered at 1.96 eV, 2.41 eV and 3.43 eV. The excitation spectra of these emissions evidence bell shaped bands consistent with transitions between localized defects' states. For each emission we study the intensity and the lifetime in the temperature range from 300 K down to 10 K, thus evidencing the competition between radiative and non-radiative processes in the optical cycle of …
Functionalization of mesoporous silica nanoparticles through one-pot co-condensation in w/o emulsion
2022
In this work, three different functionalized mesoporous silica nanoparticles (MSNs) were synthesized through the co-condensation synthesis in oil/water emulsion. Hexadecyltrimethoxysilane, triethoxy-3-(2-imidazolin-1-yl)propylsilane and (3-mercaptopropyl)triethoxysilane were used as organo-substituted silica precursors with variable molar ratio with respect to tetraethylorthosilicate (TEOS, 1:4, 1:9, 1:19). The occurred functionalization was investigated by Infrared Spectroscopy and FT-Raman and 29Si {1H} CP-MAS-NMR spectroscopy. Results show that the three materials were successfully functionalized. The influence of the different pendant groups and their concentration on the mesostructured…
Biocompatibility and internalization assessment of bare and functionalised mesoporous silica nanoparticles
2021
[EN] We report herein an evaluation of the effect of several mesoporous silica nanoparticles (MSNs) on the cellular uptake and in vitro cytotoxicity in human cells. Bare MSNs and MSNs functionalized with polyethylene glycol or hyaluronic acid are employed to evaluate uptake efficiency and mechanisms of endocytosis in cancer (MDA-MB-231) and non-cancer (MCF10A) cells. Moreover, changes in viability, cell cycle, oxidative stress, and mitochondrial membrane potential are evaluated. Our results confirm that MSNs are internalized efficiently by human cells and that uptake mechanisms differ for cell types and particles. We also confirm that MSNs are biocompatible materials that do not induce ROS/…
Use of Silica Based Materials as Modulators of the Lipase Catalyzed Hydrolysis of Fats under Simulated Duodenal Conditions
2020
[EN] The effect of silica materials and their functionalization in the lipase catalyzed fat hydrolysis has been scarcely studied. Fifteen silica materials were prepared and their effect on the fat hydrolysis was measured, under simulated duodenal conditions, using the pH-stat method. The materials are composed of the combination of three supports (Stober massive silica nanoparticles, Stober mesoporous nanoparticles and UVM-7) and four surface functionalizations (methyl, trimethyl, propyl and octyl). In addition, the non-functionalized materials were tested. The functional groups were selected to offer a hydrophobic character to the material improving the interaction with the fat globules an…
Catalytic and photocatalytic epoxidation of limonene: Using mesoporous silica nanoparticles as functional support for a Janus-like approach
2020
Abstract Mesoporous silica nanoparticles (MSN) were used as a platform to design novel active materials for the catalytic and photocatalytic epoxidation of limonene. Binary systems comprised of TiO2 and MSN were used for the catalytic reaction when doped with manganese, and for the photocatalytic reaction when functionalised with hexadecyl chains or imidazolinyl groups. All of the MSN based systems were synthesized by condensation in emulsion. A thorough characterization of the powders has been performed by means of Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES), X-ray diffraction (XRD), FT-IR, Raman and EPR Spectroscopy, Fluorescence and diffuse reflectance UV–vis (DR…
A Sensitive Nanosensor for the In Situ Detection of the Cannibal Drug.
2020
[EN] A bio-inspired nanodevice for the selective and sensitive fluorogenic detection of 3,4- methylenedioxypyrovalerone (MDPV), usually known as Cannibal drug, is reported. The sensing nanodevice is based on mesoporous silica nanoparticles (MSNs), loaded with a fluorescent reporter (rhodamine B) and functionalized on their external surface with a dopamine derivative (3), which specifically interacts with the recombinant human dopamine transporter (DAT), capping the pores. In the presence of MDPV, DAT detaches from the MSNs consequently causing rhodamine B release and allowing drug detection. The nanosensor shows a detection limit of 5.2 µM and it is able to detect the MDPV drug both in sali…