Electrochemical Detection of Lead Ions with Ordered Mesoporous Silica–Modified Glassy Carbon Electrodes

The development of methods for lead ion determination in various biological and environmental samples is both necessary and challenging. In this context, considering the properties of both SBA-15 and MCM-41 mesoporous materials and the role of NH2-functional groups grafted on the silica surface (SBA-15-NH2 and MCM-41-NH2), the aim of the study was to investigate the electrochemical detection of Pb2+ by means of silica-modified glassy carbon electrodes (GCEs). The square wave anodic stripping voltammetry (SWASV) was used to characterize the modified electrodes with four different samples of ordered mesoporous silica (OMS) powders, mentioned above. Additionally, scanning electron microscopy (SEM) was used to characterize these modifiers. Pb2+ exhibits a well-defined oxidation peak (around − 0.5 V vs. Ag/AgCl/KClsat) and high peak current at either bare or OMS-modified glassy carbon electrodes, but the best response was recorded in the case of GC/SBA-15-NH2-modified electrode in 0.1 M acetate buffer. The performance of the prepared electrodes is highlighted by good analytical parameters (satisfies the requirements of low cost and rapid results), which recommends them to be used for real sample analysis

Continuity and diversity of Roman pottery production at Famars (northern France) in the 2nd–4th centuries AD: insights from the pottery waste

© 2020, Springer-Verlag GmbH Germany, part of Springer Nature. Grey and cream ware were widely produced and traded in Roman towns in Northern France (a region known as Civitas Nerviorum). A large production centre of grey and cream ware in northern France was Famars, where 15 pottery kilns functioned between the 2nd and 4th centuries ad. In order to identify the raw materials and to reconstruct the technology of grey and cream ware produced at Famars, 51 sherds found in the pottery waste, associated with kilns, were investigated by means of optical microscopy, X-ray fluorescence spectrometry, cold field emission scanning electron microscopy and electron microprobe analysis. The optical microscopy analysis allowed to define the Quartz (Qz), Microfossil-Glauconite (MFG) and Quartz-Microfossil-Glauconite (QzMFG) petrographic groups, as well as the Quartz + Argillaceous Rocks Fragments (QZ + ARF), Microfossil-Glauconite Fine (MFG Fine) and Microfossil-Glauconite + Chamotte (MFG + Chm) variants. The defining components for all groups are quartz, glauconite pellets and microfossils, but in variable proportions. The chemical data support the optical microscopy analysis and reveal the differences between the petrographic groups: Qz sherds are rich in Si and Fe, whereas MFG sherds contain more Ca, Al and K. Firing phases, as seen in scanning electron microscopy analysis, include glass, melilite, clinopyroxene and an Fe aluminosilicate. The matrix of most sherds of the MFG and QzMFG groups shows low sintering and initial vitrification, while the matrix of the Qz group displays mostly extensive and continuous vitrification. The results permitted to identify two kinds of raw materials, most likely originating from local georesources. One raw material, with high Si and Fe, was fired in a reducing kiln atmosphere in order to produce grey ware, while the other, with high Ca, Al and K, was fired in oxidising conditions in order to produce cream ware

Structural and luminescence effects of Ga co-doping on Ce-doped yttrium aluminate based phosphors

WOS: 000369581800062Herein, we primarily focus on luminescence spectrum measurements of various types of green emitting yttrium aluminate phosphors modified with gallium (Y3Al5-xGaxO12) synthesised by solid state reaction. The luminescent emission of samples depends on sample temperature and excitation radiation such as incident X-ray, electron and laser beam. Here, we measured radioluminescence (RL), cathodoluminescence (CL), photoluminescence (PL) along with XRD in order to clarify relationship between lattice defects and the spectral luminescence emissions. The RL and CL spectra of YAG:Ce exhibit an emission band ranging from 300 to 450 nm related to Y-Al antisite defects. The broad emission band of garnet phosphors is shifted from 526 nm to 498 nm with increasing of Ga3+ content, while full width at half maximum (FWHM) of the band tends to be greater than the width of unmodified YAG: Ce garnet. Deconvolution of the spectrum reveals that three emission bands centred at 139, 234 and 294 degrees C occur in aluminate host garnets. (C) 2016 Elsevier B.V. All rights reserved

The Influence of the Au Nanoparticles Dimension on the Photocatalytic Performances of TiO2−AuTiO_2-Au Porous Composites

The influence of Au nanoparticles dimension on the photocatalytic performances of the $TiO_2$ aerogels-Au composites was evaluated. Structural and morphological peculiarities of the $TiO_2$ aerogel, unloaded and loaded with 5 and 22 nm Au nanoparticles, were studied by transmission electron microscopy technique, X-ray diffraction and $N_2$-sorption measurements. UV-Vis diffuse reflectance measurements were performed to determine the band gap energies. The photocatalytic activity was evaluated by monitoring the salicylic acid photodegradation. It was found that the Au nanoparticles promote the anatase phase crystallization and produce the decrease of the specific surface area and band gap energy values. The porous composite with the smallest Au nanoparticles dimension exhibits the best photocatalytic performances

Optical spectroscopy of the Ce-doped multicomponent garnets

Here, we report our results referring to the preparation of Ce doped YMgGaAlSiO, YMgAlSiO and YGdGaAlO using solid state reaction at high temperature. Several complementary methods (i.e. powder x-ray diffraction (XRPD), energy dispersive analysis of X-rays (EDX), scanning electron microscopy (SEM) and Fourier transforms infrared spectroscopy (FTIR)) were studied to examine the effects of the synthesis procedure on the morphology and structure. XRD analyses revealed that all compounds include yttrium aluminate phase with garnet structure. Cathodoluminescence (CL), radioluminescence (RL) and photoluminescence (PL) measurements were carried out for clarification of relationship between host lattice defects and the spectral luminescence emissions. Luminescence emission of phosphors is peaked at 530 nm assigned to 5d-4f transitions of the dopant Ce ions with a broad emission band in 400-700 nm range. Under electron irradiation, the emission spectrum of Ce doped (YGd)GaAlO is well defined and has a characteristic fairly narrow and sharp emission band peaking at 312 nm and 624 nm corresponding to transition of P →S and G→P (Gd), respectively. We suggest some of phosphors might be excellent phototherapy phosphor materials under electron excitation.This work was supported by a grant of the Romanian National Authority for Scientific Research, CNCS – UEFISCDI, project number PN-II-RU-TE-2012–3-0360.Peer Reviewe