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1.
J Phys Chem C Nanomater Interfaces ; 128(19): 7936-7947, 2024 May 16.
Article in English | MEDLINE | ID: mdl-38774155

ABSTRACT

An aqueous colloidal suspension of gold nanoparticles (AuNPs) may be condensed into a thin fractal film at the polarizable liquid-liquid interface formed between two immiscible electrolyte solutions upon injection of millimolar concentrations of sodium chloride to the aqueous phase. By adjusting the interfacial polarization conditions (negative, intermediate, and positive open-circuit potentials), the morphology of the film is modified, resulting in unique surface plasmon properties of the film, which enable in situ surface-enhanced Raman spectroscopy (SERS). Intense SERS signals are observed at the polarizable liquid-liquid interface when micromolar concentrations of tolmetin, a nonsteroidal anti-inflammatory drug, are entrapped in the AuNP fractal film. The change in the signal intensity, averaged over multiple spectra, with respect to the concentration of tolmetin, depends on the polarization conditions and suggests the presence of chemical-induced damping effects on the surface plasmons of the gold film.

2.
Sci Adv ; 7(45): eabg4119, 2021 Nov 05.
Article in English | MEDLINE | ID: mdl-34739310

ABSTRACT

Programmed cell death via apoptosis is a natural defence against excessive cell division, crucial for fetal development to maintenance of homeostasis and elimination of precancerous and senescent cells. Here, we demonstrate an electrified liquid biointerface that replicates the molecular machinery of the inner mitochondrial membrane at the onset of apoptosis. By mimicking in vivo cytochrome c (Cyt c) interactions with cell membranes, our platform allows us to modulate the conformational plasticity of the protein by simply varying the electrochemical environment at an aqueous-organic interface. We observe interfacial electron transfer between an organic electron donor decamethylferrocene and O2, electrocatalyzed by Cyt c. This interfacial reaction requires partial Cyt c unfolding, mimicking Cyt c in vivo peroxidase activity. As proof of concept, we use our electrified liquid biointerface to identify drug molecules, such as bifonazole, that can potentially down-regulate Cyt c and protect against uncontrolled neuronal cell death in neurodegenerative disorders.

3.
Langmuir ; 37(13): 4033-4041, 2021 04 06.
Article in English | MEDLINE | ID: mdl-33761740

ABSTRACT

Interactions of a protein with a solid-liquid or a liquid-liquid interface may destabilize its conformation and hence result in a loss of biological activity. We propose here a method for the immobilization of proteins at an electrified liquid-liquid interface. Cytochrome c (Cyt c) is encapsulated in a silica matrix through an electrochemical process at an electrified liquid-liquid interface. Silica condensation is triggered by the interfacial transfer of cationic surfactant, cetyltrimethylammonium, at the lower end of the interfacial potential window. Cyt c is then adsorbed on the previously electrodeposited silica layer, when the interfacial potential, Δowϕ, is at the positive end of the potential window. By cycling of the potential window back and forth, silica electrodeposition and Cyt c adsorption occur sequentially as demonstrated by in situ UV-vis absorbance spectroscopy. After collection from the liquid-liquid interface, the Cyt c-silica matrix is characterized ex situ by UV-vis diffuse reflectance spectroscopy, confocal Raman microscopy, and fluorescence microscopy, showing that the protein maintained its tertiary structure during the encapsulation process. The absence of denaturation is further confirmed in situ by the absence of electrocatalytic activity toward O2 (observed in the case of Cyt c denaturation). This method of protein encapsulation may be used for other proteins (e.g., Fe-S cluster oxidoreductases, copper-containing reductases, pyrroloquinoline quinone-containing enzymes, or flavoproteins) in the development of biphasic bioelectrosynthesis or bioelectrocatalysis applications.


Subject(s)
Cytochromes c , Silicon Dioxide , Adsorption , Electroplating
4.
Talanta ; 220: 121347, 2020 Dec 01.
Article in English | MEDLINE | ID: mdl-32928388

ABSTRACT

A novel concept is introduced for signal amplification in electrochemical sensing: the electro-oligomerisation stripping voltammetry, which has been applied here to the improved detection of the isoproturon herbicide in spring waters as a proof-of-principle. It involves a potentiostatic accumulation step onto a glassy carbon electrode (at +1.5 V vs Ag/AgCl reference electrode for 300 s) leading to the formation of an oligomeric film, which is then detected by cathodic stripping square wave voltammetry (SWV). The presence and composition of the film are confirmed by confocal Raman spectroscopy. Its characterisation by cyclic voltammetry demonstrates the reversible nature of the electrodeposited material, confirming its interest for sensitive detection by SWV. Adding a mesoporous silica membrane with vertically oriented nanochannels further enhances the sensitivity of the sensor, exhibiting a linear response in the 10-100 µM concentration range. This effect was even more interesting for real media analysis thanks to the permselective properties of such nanoporous coating in rejecting interferences and/or surface fouling agents. The method should be applicable to other analytes that are usually not detectable by conventional accumulation/stripping voltammetry.

5.
Beilstein J Nanotechnol ; 9: 2750-2762, 2018.
Article in English | MEDLINE | ID: mdl-30416926

ABSTRACT

Single-walled carbon nanotubes (SWCNTs) were functionalized by ferrocene through ethyleneglycol chains of different lengths (FcETGn) and the functionalized SWCNTs (f-SWCNTs) were characterized by different complementary analytical techniques. In particular, high-resolution scanning electron transmission microscopy (HRSTEM) and electron energy loss spectroscopy (EELS) analyses support that the outer tubes of the carbon-nanotube bundles were covalently grafted with FcETGn groups. This result confirms that the electrocatalytic effect observed during the oxidation of the reduced form of nicotinamide adenine dinucleotide (NADH) co-factor by the f-SWCNTs is due to the presence of grafted ferrocene derivatives playing the role of a mediator. This work clearly proves that residual impurities present in our SWCNT sample (below 5 wt. %) play no role in the electrocatalytic oxidation of NADH. Moreover, molecular dynamic simulations confirm the essential role of the PEG linker in the efficiency of the bioelectrochemical device in water, due to the favorable interaction between the ETG units and water molecules that prevents π-stacking of the ferrocene unit on the surface of the CNTs. This system can be applied to biosensing, as exemplified for glucose detection. The well-controlled and well-characterized functionalization of essentially clean SWCNTs enabled us to establish the maximum level of impurity content, below which the f-SWCNT intrinsic electrochemical activity is not jeopardized.

6.
Bioelectrochemistry ; 118: 131-138, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28802176

ABSTRACT

A living material was formed by self-assembly of bacterial cells (Shewanella oneidensis MR-1 or Pseudomonas fluorescens) with carbon nanotubes in the presence of cytochrome c from a bovine heart with the goal to mimic electroactive biofilms. The role of cytochrome c on self-assembly, cell viability and extracellular electron transfer was studied. Scanning electron microscopy and dynamic light scattering experiments highlighted its role on the self-assembly of bacteria­carbon nanotube aggregates within only 2h in solution. The deposition of these aggregates on glassy carbon surfaces led to a homogenous composite film in which the bacteria were embedded in a carbon nanotube network. A comparable cell density of 1cellµm-2 was achieved in the presence or in the absence of cytochrome c, but this protein allowed maintaining a higher bacterial viability. Electrochemical characterization demonstrated the role of cytochrome c on electron transfer reactions, leading to a current density of up to 300µAcm-2 in the presence of 50mM formate when a porous carbon felt electrode is used as support for the biocomposite.


Subject(s)
Bioelectric Energy Sources/microbiology , Biofilms , Biomimetics/methods , Pseudomonas fluorescens/metabolism , Shewanella/metabolism , Cytochromes c/chemistry , Cytochromes c/metabolism , Electrochemistry , Electron Transport , Nanotubes, Carbon/chemistry , Pseudomonas fluorescens/physiology , Shewanella/physiology , Time Factors
7.
Tissue Eng Part A ; 23(17-18): 913-922, 2017 09.
Article in English | MEDLINE | ID: mdl-28385113

ABSTRACT

We examined the respective influence of a sequential or a continuous hypoxia during expansion and transforming growth factor beta 1-driven chondrogenic differentiation of human bone marrow mesenchymal stem cells (MSCs). The differentiation was performed within alginate beads, a classical tool for the implantation of MSCs within the joint. The standard normoxic 2D (expansion) and 3D (differentiation) MSCs cultures served as reference. To determine the quality of chondrogenesis, we analyzed typical markers such as type II and X collagens, SOX9, COMP, versican, and aggrecan mRNAs using polymerase chain reaction and we assessed the production of type II collagen and hypoxia-inducible factor (HIF)-1α by histological stainings. We simultaneously assessed the expression of osteogenic mRNAs (Alkaline Phosphatase, RUNX2, and Osteocalcin) and the presence of micro-calcifications by Alizarin red and Raman spectroscopy. Chondrogenic differentiation is clearly improved by hypoxia in 3D. Best results were obtained when the entire process, that is, 2D expansion and 3D differentiation, was performed under continuous 5% hypoxic condition. In addition, no calcification (hydroxyapatite, proved by RAMAN) was observed after 2D hypoxic expansion even in the case of a normoxic differentiation, in contrast with controls. Finally, a better chondrogenic differentiation of human MSCs is achieved when a reduced oxygen tension is applied during both expansion and differentiation times, avoiding in vitro osteogenic commitment of cells and subsequently the calcification deposition.


Subject(s)
Alginates/chemistry , Calcification, Physiologic/drug effects , Cell Differentiation/drug effects , Cell Proliferation/drug effects , Chondrogenesis/drug effects , Mesenchymal Stem Cells/metabolism , Transforming Growth Factor beta/pharmacology , Aged , Cell Hypoxia/drug effects , Cells, Cultured , Female , Glucuronic Acid/chemistry , Hexuronic Acids/chemistry , Humans , Male , Mesenchymal Stem Cells/cytology , Middle Aged
8.
Environ Sci Pollut Res Int ; 23(4): 3681-706, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26498805

ABSTRACT

Mining activities release arsenopyrite into calcareous soils where it undergoes weathering generating toxic compounds. The research evaluates the environmental impacts of these processes under semi-alkaline carbonated conditions. Electrochemical (cyclic voltammetry, chronoamperometry, EIS), spectroscopic (Raman, XPS), and microscopic (SEM, AFM, TEM) techniques are combined along with chemical analyses of leachates collected from simulated arsenopyrite weathering to comprehensively examine the interfacial mechanisms. Early oxidation stages enhance mineral reactivity through the formation of surface sulfur phases (e.g., S n (2-)/S(0)) with semiconductor properties, leading to oscillatory mineral reactivity. Subsequent steps entail the generation of intermediate siderite (FeCO3)-like, followed by the formation of low-compact mass sub-micro ferric oxyhydroxides (α, γ-FeOOH) with adsorbed arsenic (mainly As(III), and lower amounts of As(V)). In addition, weathering reactions can be influenced by accessible arsenic resulting in the formation of a symplesite (Fe3(AsO4)3)-like compound which is dependent on the amount of accessible arsenic in the system. It is proposed that arsenic release occurs via diffusion across secondary α, γ-FeOOH structures during arsenopyrite weathering. We suggest weathering mechanisms of arsenopyrite in calcareous soil and environmental implications based on experimental data.


Subject(s)
Arsenicals/analysis , Calcium Carbonate/chemistry , Environmental Monitoring/methods , Iron Compounds/analysis , Minerals/analysis , Mining , Soil Pollutants/analysis , Soil/chemistry , Sulfides/analysis , Carbonates/analysis , Electrochemistry , Ferric Compounds/analysis , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Models, Theoretical , Oxidation-Reduction , Sulfur/analysis , Surface Properties , Weather
9.
Chemphyschem ; 16(12): 2692-701, 2015 Aug 24.
Article in English | MEDLINE | ID: mdl-26136373

ABSTRACT

The results of a study on the evolution of HiPco single-walled carbon nanotubes during the oxidizing action of H2 SO4 and HNO3 are presented. The process conditions used have been chosen so as to avoid any significant damage to the nanotube structure. The type and level of functionalization, the location of the grafted functions on the surface of the nanotube and the changes in morphological characteristics of the samples were examined by using a wide and complementary range of analytical techniques. We propose an explanation for the differences in the oxidizing action of sulfuric and nitric acids. The combined results allow us to suggest possible reaction mechanisms that occur on the surface of the nanotube.


Subject(s)
Nanotubes, Carbon , Nitric Acid/chemistry , Sulfuric Acids/chemistry , Mass Spectrometry , Microscopy, Electron, Scanning Transmission , Oxidation-Reduction , Thermogravimetry
10.
Phys Chem Chem Phys ; 16(48): 26955-62, 2014 Dec 28.
Article in English | MEDLINE | ID: mdl-25377062

ABSTRACT

Interfacial processes controlled by ion transfer voltammetry at the interface between two immiscible electrolyte solutions were studied by in situ Raman spectroscopy. Raman spectra of the interface between a 5 mM NaCl aqueous solution and 10 mM bis(triphenyl-phosphoranydieneammonium) tetrakis(4-chlorophenyl)borate in 1,2-dichloroethane were recorded at open circuit potential and at various interfacial potential differences. At open-circuit potential, Raman peaks assigned to vibrational modes of 1,2-dichloroethane are clearly visible and peaks of weak intensity are measured for the organic electrolyte ions. When a negative interfacial potential difference is applied, the intensity of the peaks of the cation of the organic electrolyte increases, confirming its transfer induced by the interfacial potential difference applied. The electrochemically assisted generation of mesoporous silica deposits was then followed by in situ confocal Raman spectroscopy. The condensation of mesoporous silica was controlled by the transfer of cetyltrimethylammonium (CTA(+)) ions to an aqueous phase containing hydrolysed silanes. The transfer of CTA(+) at the interface was monitored in situ by confocal Raman spectroscopy, and formation of silica was observed.


Subject(s)
Electrochemical Techniques/instrumentation , Electrolytes/chemistry , Silicon Dioxide/chemistry , Spectrum Analysis, Raman/instrumentation , Adsorption , Ammonium Compounds/chemistry , Cetrimonium Compounds/chemistry , Equipment Design , Ethylene Dichlorides/chemistry , Ions/chemistry , Porosity , Sodium Chloride/chemistry , Surface Properties , Tetraphenylborate/analogs & derivatives , Tetraphenylborate/chemistry
11.
Anal Chem ; 86(22): 11203-10, 2014 Nov 18.
Article in English | MEDLINE | ID: mdl-25327624

ABSTRACT

Shearforce regulated scanning electrochemical microscopy (SECM) has been associated with Raman microspectrometry in order to perform combined electrochemical and spectrochemical analysis on reactive interfaces. The interest of the method was evaluated by analyzing local corrosion phenomena in damaged Zn(Mg, Al) self-healing coatings deposited on steel. Despite the high aspect ratio of the analyzed sample displaying here more than a 50 µm depth profile, the optimized setup allowed (1) precise electrode positioning with the help of shearforce detection, (2) electrochemical measurement at a constant distance from the sample surface, and (3) local chemical analysis of the solid surface by confocal Raman microspectroscopy performed at a constant focal distance from the sample. All in all, this new setup allows one to approach the detailed reactivity involved in defective metal samples.

12.
IEEE Trans Image Process ; 23(3): 1169-80, 2014 Mar.
Article in English | MEDLINE | ID: mdl-24723521

ABSTRACT

In this paper, we consider hyperspectral unmixing problems where the observed images are blurred during the acquisition process, e.g., in microscopy and spectroscopy. We derive a joint observation and mixing model and show how it affects end-member identifiability within the geometrical unmixing framework. An analysis of the model reveals that nonnegative blurring results in a contraction of both the minimum-volume enclosing and maximum-volume enclosed simplex. We demonstrate this contraction property in the case of a spectrally invariant point-spread function. The benefit of prior deconvolution on the accuracy of the restored sources and abundances is illustrated using simulated and real Raman spectroscopic data.


Subject(s)
Algorithms , Artifacts , Image Enhancement/methods , Image Interpretation, Computer-Assisted/methods , Microscopy/methods , Spectrum Analysis, Raman/methods
13.
J Biomed Mater Res A ; 101(11): 3211-8, 2013 Nov.
Article in English | MEDLINE | ID: mdl-23554327

ABSTRACT

Nacre (or mother of pearl) can facilitate bone cell differentiation and can speed up their mineralization. Here we report on the capability of nacre to induce differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) and the production of extracellular matrix. hBM-MSCs were encapsulated in an alginate hydrogel containing different concentrations of powdered nacre and cultured in the same environment until Day 28. Analysis of osteogenic gene expression, histochemistry, second harmonic generation (SHG) microscopy, and Raman scattering spectroscopy were used to characterize the synthesis of the extracellular matrix. In the presence of nacre powder, a significant increase in matrix synthesis from D21 in comparison with pure alginate was observed. Histochemistry revealed the formation of a new tissue composed of collagen fibers in the presence of nacre (immunostaining and SHG), and hydroxyapatite crystals (Raman) in the alginate beads. These results suggest that nacre is efficient in hBM-MSCs differentiation, extracellular matrix production and mineralization in alginate 3D biomaterials.


Subject(s)
Bone Marrow Cells/cytology , Cell Differentiation/drug effects , Hydrogel, Polyethylene Glycol Dimethacrylate/pharmacology , Mesenchymal Stem Cells/cytology , Nacre/pharmacology , Osteogenesis/drug effects , Aged , Alginates/pharmacology , Animals , Bone Marrow Cells/drug effects , Bone Marrow Cells/metabolism , Cell Differentiation/genetics , Collagen Type X/genetics , Collagen Type X/metabolism , Core Binding Factor Alpha 1 Subunit/genetics , Core Binding Factor Alpha 1 Subunit/metabolism , Gene Expression Regulation/drug effects , Glucuronic Acid/pharmacology , Hexuronic Acids/pharmacology , Humans , Microscopy, Fluorescence, Multiphoton , Microspheres , Middle Aged , Osteocalcin/genetics , Osteocalcin/metabolism , Osteogenesis/genetics , Osteopontin/genetics , Osteopontin/metabolism , Powders , Spectrum Analysis, Raman
14.
J Chem Phys ; 138(1): 014201, 2013 Jan 07.
Article in English | MEDLINE | ID: mdl-23298034

ABSTRACT

The vibrational properties of CaCO(3) aragonite have been investigated both theoretically, by using a quantum mechanical approach (all electron Gaussian type basis set and B3LYP HF-DFT hybrid functional, as implemented in the CRYSTAL code) and experimentally, by collecting polarized infrared (IR) reflectance and Raman spectra. The combined use of theory and experiment permits on the one hand to analyze the many subtle features of the measured spectra, on the other hand to evidentiate limits and deficiencies of both approaches. The full set of TO and LO IR active modes, their intensities, the dielectric tensor (in its static and high frequency components), and the optical indices have been determined, as well as the Raman frequencies. Tools such as isotopic substitution and graphical animation of the modes are available, that complement the analysis of the spectrum.

15.
Sci Total Environ ; 409(19): 3971-9, 2011 Sep 01.
Article in English | MEDLINE | ID: mdl-21774966

ABSTRACT

Exploitation of polymetallic deposits from calcareous mining sites exposes galena and others sulfides to weathering factors. Galena weathering leads to the formation of lead phases (e.g., PbSO(4), PbCO(3)) with a higher bioaccessibility than galena, thus increasing the mobility and toxicity of lead. Despite the environmental impacts of these lead phases, the mechanisms of galena oxidation and the transformation of lead secondary phases, under neutral-alkaline carbonated conditions, have rarely been studied. In this work, an experimental approach, combining electrochemical and spectroscopic techniques, was developed to examine the interfacial processes involved in the galena weathering under simulated calcareous conditions. The results showed an initial oxidation stage with the formation of an anglesite-like phase leading to the partial mineral passivation. Under neutral-alkaline carbonated conditions, the stability of this phase was limited as it transformed into a cerussite-like one. Based on the surface characterization and the formation of secondary species, the weathering mechanisms of galena in calcareous soil and its environmental implications were suggested.


Subject(s)
Lead/analysis , Soil/chemistry , Sulfides/analysis , Environmental Monitoring , Lead/chemistry , Mexico , Oxidation-Reduction , Sulfides/chemistry
16.
J Hazard Mater ; 189(3): 764-72, 2011 May 30.
Article in English | MEDLINE | ID: mdl-21458156

ABSTRACT

Selenium is a known toxic element released in the environment by anthropogenic activities. The present study is devoted to the aqueous sorption behaviour of selenium oxyanions (selenate and selenite) on a reference oxide surface, namely rutile TiO(2). Batch sorption kinetics and isotherms have been studied using different physico-chemical conditions of the solution (changes of pH and ionic strength). The sorption was favoured for both anions in acidic conditions, in agreement with a surface complexation mechanism and CD-MUSIC predictions. Spectroscopic investigations of the sorbed rutile powder were also consistent with such a mechanism. EXAFS spectra confirmed that for selenite anions, an inner-sphere mechanism was the most probable process observed. Dynamic sorption experiments using a column filled with rutile powder also substantiated that a part of the surface complexes follows the inner-sphere mechanism, but also evidenced that an outer-sphere mechanism cannot be excluded, especially for selenate anions.


Subject(s)
Anions/analysis , Selenium/chemistry , Titanium/chemistry , Water Purification/methods , Adsorption , Electrolytes , Hydrogen-Ion Concentration , Ions/chemistry , Kinetics , Spectrophotometry/methods , Spectrum Analysis, Raman/methods , Surface Properties , Water Pollutants, Chemical/analysis , X-Ray Diffraction
17.
J Colloid Interface Sci ; 325(2): 363-70, 2008 Sep 15.
Article in English | MEDLINE | ID: mdl-18653195

ABSTRACT

This paper reports a comparative study of three methods for determining the surface charge and acid-base behavior of a TiO(2) rutile material. Electrophoretic mobility measurements were performed using two different batch protocols: (i) a "static" mode that consisted of immersing the rutile powder in aqueous solutions of given pH's and ionic strengths for 10 h, and (ii) a "dynamic" mode that consisted of using an automatic titrator to continuously adjust the solution pH with a contact time of 15 min. The same apparatus (a Nanosizer from Malvern) was used to measure the zeta potential of the particles in both methods. These batch experiments were next compared to the determination of the surface charge of rutile using nonlinear chromatography in column experiments. In that case, the rutile powder was compacted to enable the formation of a proper column bed. Therefore, Raman scattering and X-ray photoelectron spectra were used, as well as other physical information such as specific surface area and morphology of the particles, to verify that the rutile powder and compacted form were identical. The three approaches were then compared and discussed in relation to the acid-base behavior of the rutile material.

18.
FEMS Yeast Res ; 7(1): 93-101, 2007 Jan.
Article in English | MEDLINE | ID: mdl-17311587

ABSTRACT

Reduced glutathione (GSH) is involved in biochemical and physiological processes in cells. Flocculation is an important mechanism in microorganisms. The present study concerned the potential relationship between GSH metabolism and flocculation. Two yeast strains, a flocculent (Kluyveromyces lactis 5c) and a nonflocculent (Kluyveromyces lactis 5a) strain, were used. The level of intracellular GSH measured during the growth period was significantly higher in the nonflocculent than in the flocculent strain; in contrast, the flocculent strain exhibited brighter staining of vacuoles than the nonflocculent strain when observed using epifluorescence microscopy. Compounds acting either on flocculation (EDTA, galactose) or on GSH metabolism (buthionine sulfoximine, and N-acetylcysteine) were tested on the flocculent strain during the growth period. Both EDTA and galactose fully inhibited flocculation and induced GSH overproduction of 58% and 153%, respectively. Buthionine sulfoximine decreased GSH level by 76% but had no effect on flocculation; N-acetylcysteine increased the GSH level and flocculation by 106% and 41%, respectively. Combination of EDTA and N-acetylcysteine produced similar effects than with each of them. Combination of galactose and N-acetylcysteine increased the GSH level but decreased flocculation. These results demonstrated that GSH homeostasis is linked to the flocculation mechanism. A hypothesis related to stress is given.


Subject(s)
Glutathione/metabolism , Kluyveromyces/physiology , Acetylcysteine/pharmacology , Culture Media , Edetic Acid/pharmacology , Flocculation , Galactose/pharmacology , Glutathione Transferase/metabolism , Kluyveromyces/growth & development , Kluyveromyces/metabolism
19.
J Nanosci Nanotechnol ; 7(10): 3519-23, 2007 Oct.
Article in English | MEDLINE | ID: mdl-18330167

ABSTRACT

Single-wall carbon nanotubes (SWNTs) have been functionalized by a diazonium method through both a classical thermal reaction and a microwave-assisted reaction. The functionalized SWNTs have been characterized by nIR-Vis-UV absorption spectroscopy, Raman spectroscopy, and thermal gravimetric analysis. The results show that SWNTs are covalently functionalized through both reactions and that the microwave-assisted reaction is more rapid. Moreover, optimal choice of the reaction time can prevent the microwave irradiation from the adverse effect of subsequently removing the functional groups on the SWNT surface.


Subject(s)
Crystallization/methods , Diazonium Compounds/chemistry , Microwaves , Nanotechnology/methods , Nanotubes, Carbon/chemistry , Nanotubes, Carbon/ultrastructure , Diazonium Compounds/radiation effects , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Nanotubes, Carbon/radiation effects , Particle Size , Surface Properties
20.
J Phys Chem B ; 110(23): 11259-66, 2006 Jun 15.
Article in English | MEDLINE | ID: mdl-16771394

ABSTRACT

Time-resolved fluorescence spectroscopy (TRFS) was applied to an aluminate glass sample doped with Eu3+ cation as a fluorescent probe of the chemical environment and local symmetry. Conventional far-field experiments revealed the presence of two different phases: an amorphous phase featured by a highly disordered environment surrounding the Eu3+ cation and a more ordered polycrystalline phase that exhibits a significant increase in the Eu3+ fluorescence decay time compared to that of the amorphous phase. Near-field fluorescence spectra and decay kinetics were recorded in the frontier region between the two phases using a home-built scanning near-field optical microscope. SNOM-TRFS experiments confirmed the presence of local heterogeneities in this part of the glass at a sub-micrometric spatial scale. Polycrystalline sites featured an important shear-force interaction with the probing fiber optic tip, a longer fluorescence decay time, and a higher Stark splitting of the 5D0 --> 7FJ (J = 1-4) electronic transitions of the Eu3+ cations.

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