1,657 research outputs found
Highly specific silver ion detection by fluorescent carbon quantum dots
Nitrogen-doped carbon quantum dots are easily obtainable nanomaterials endowed with remarkable fluorescence properties for the detection of contaminations by heavy metals. In this report, we show that nanometric particles with high specificity for silver cations can be prepared by hydrothermal synthesis starting from citric and folic acid solutions. Solutions of these N-CQDs give a strong fluorescence emission in the violet region (385 nm) when excited at 330 nm, which can be quenched selectively by silver (I) cations at sub-nanomolar concentrations, while other cations do not give any effect. This remarkable feature was tentatively correlated with the stronger interactions between silver ion and small portions of the nanomaterial surface by comparing Ag+ and the isoelectronic Cd2
NOVEL SYNTHESIS OF METAL OXIDE NANOPARTICLES FROM TYPE IV DEEP EUTECTIC SOLVENTS
One of the fields where DES show remarkable added-values is the synthesis of inorganic
materials, in particular nanoparticles. In this field, the inherent and highly-tunable nano homogeneities of DES structure give origin to a marked templating effect, a precious role that
has led to the recent bloom of a vast number of studies exploiting these new synthesis media to
prepare nanomaterials and composite structures of various kinds. In this contribution, the most
recent developments in the field will be reviewed and some exciting examples of novel metal
oxide nanoparticles syntheses using non-toxic type-IV Deep Eutectic Solvents will be
described. The prepared materials possess nanometric dimensions and show flower-like/thin layered shapes. Use of the prepared nanoparticles as fluorescent materials for the detection of
various contaminants is under development
Functionalization of gold nanoparticles with Ru-porphyrin and their selectivity in the oligomerization of alkynes
Gold nanoparticles (AuNPs) were functionalized by ruthenium porphyrins through a
sulfur/gold covalent bond using a three-steps reaction. The catalyst was characterized by scanning
electron microscopy (SEM) and thermogravimetric analysis (TGA) in order to control the binding
of ruthenium porphyrin on AuNPsâ surface. The catalyst was tested and compared with an analog
system not bound to AuNPs in the oligomerization reaction using 1-phenylacetylene as the substrate
Recent advances in the synthesis of inorganic materials using environmentally friendly media
Deep Eutectic Solvents have gained a lot of attention in the last few years because of their vast applicability in a large number of technological processes, the simplicity of their preparation and their high biocompatibility and harmlessness. One of the fields where DES prove to be particularly valuable is the synthesis and modification of inorganic materialsâin particular, nanoparticles. In this field, the inherent structural inhomogeneity of DES results in a marked templating effect, which has led to an increasing number of studies focusing on exploiting these new reaction media to prepare nanomaterials. This review aims to provide a summary of the numerous and most recent achievements made in this area, reporting several examples of the newest mixtures obtained by mixing molecules originating from natural feedstocks, as well as linking them to the more consolidated methods that use âclassicalâ DES, such as reline
Study of the Reactions and
We evaluate the non leptonic decays and in the limit of infinitely heavy quarks, assuming the dominance of
intermediate positive parity charmed resonances. We find that the branching
ratios are of the order .Comment: 9 pages, LaTex, BARI-TH/92-13
TNFR1 signalling is critical for the development of demyelination and the limitation of T-cell responses during immune-mediated CNS disease
In this review we summarize the essential findings about the function of tumour necrosis factor (TNF) and its cognate receptors TNFR1 and TNFR2, and lymphotoxin α (LT-α) ligands in immune-mediated CNS inflammation and demyelination. The advent of homologous recombination technology in rodents provides a new method which has been used during the last 5 years and has led to insights into the pathophysiology of experimental autoimmune encephalomyelitis (EAE) in an unprecedented way. Studies with knockout mice in which genes of the TNF ligand/receptor superfamily are not expressed and studies with transgenic mice overexpressing TNF and TNFR reveal the critical role of the TNFR1 signalling pathway in the control of CNS demyelination and inflammation. These studies provide novel findings and at the same time shed light on the complex pathophysiology of EAE. Together, these findings may contribute to better understanding of EAE and open new avenues in experimental therapies for multiple sclerosi
CuO nanoparticles and microaggregates: an experimental and computational study of structure and electronic properties
The link between morphology and properties is well-established in the nanoparticle literature. In this report, we show that different approaches in the synthesis of copper oxide can lead to nanoparticles (NPs) of different size and morphology. The structure and properties of the synthesized NPs are investigated with powder X-ray diffraction, scanning electron microscopy (SEM), and diffuse reflectance spectroscopy (DRS). Through detailed SEM analyses, we were able to correlate the synthetic pathways with the particlesâ shape and aggregation, pointing out that bare hydrothermal pathways yield mainly spheroidal dandelion-like aggregates, whereas, if surfactants are added, the growth of the nanostructures along a preferential direction is promoted. The effect of the morphology on the electronic properties was evaluated through DRS, which allowed us to obtain the electron bandgap in every system synthesized, and to find that the rearrangement of threaded particles into more compact structures leads to a reduction in the energy difference. The latter result was compared with Density Functional Theory (DFT) computational models of small centrosymmetric CuO clusters, cut from the tenorite crystal structure. The computed UV-Vis absorption spectra obtained from the clusters are in good agreement with experimental findings
Comparative treatments of a green tattoo ink with Ruby, Nd: YAG nano- and picosecond lasers in normal and array mode
The tattoos removal has become an issue upon spread of the tattooing practice worldwide and
hindsight regrets. Lasers are typically used for the purpose, though some colours such as green are
considered ârecalcitrantâ to the treatment. In the current investigation, we aim at determining the
efcacy of removal of a green ink water dispersion, using 5 laser treatments: Nd:YAG nano- and
picosecond lasers in normal and array mode and Ruby nanosecond laser, keeping the total irradiated
energy constant. The UVâVis spectroscopy of the treated samples indicate that Nd:YAG picosecond
laser is most efective, and the Ruby nanosecond laser is the least efcient. Fragment compounds
generated from the pigment and siloxanes are common to all treatments, whereas hydrocarbon
emerge by a larger amount upon Nd:YAG nanosecond treatment. Fibres are formed upon picosecond
treatments and when operating in array mode, and lamellae are achieved by Ruby nanosecond laser
treatment. Residual particles suspensions are very heterogeneous upon nanosecond treatments
âFor Asia market onlyâ: a green tattoo ink between safety and regulations
Due to the increasing tattoo practicing in Eastern countries and general concern on tattoo ink composition and safety, the green tattoo inks Green Concentrate by Eternal, for European and âfor Asia Market Onlyâ were analyzed, under the premise that only the former falls under a composition regulation. A separation of the additives from the pigment was carried out by successive extraction in solvents of different polarities, i.e., water, acetone and dichloromethane. The solid residues were analyzed by IR and Raman spectroscopies, the liquid fractions by GC/mass spectrometry. The relative pigment load and element traces were also estimated. We found that the European and the Asian inks are based on the same pigment, PG7, restricted in Europe, though at different loads. They have a similar content of harmful impurities, such as Ni, As, Cd and Sb and both contain siloxanes, including harmful D4. Furthermore, they have different physical-chemical properties, the European ink being more hydrophilic, the Asian more hydrophobic. Additionally, the Asian ink contains harmful additives for the solubilization of hydrophobic matrices and by-products of the phthalocyanine synthesis. Teratogenic phthalates are present as well as chlorinated teratogenic and carcinogenic compounds usually associated to the laser treatment for removal purposes, to a larger extent in the European ink. The composition of the inks does not seem to reflect regulatory restrictions, where issued
Room temperature syntheses of ZnO and their structures
ZnO has many technological applications which largely depend on its properties, which
can be tuned by controlled synthesis. Ideally, the most convenient ZnO synthesis is carried out
at room temperature in an aqueous solvent. However, the correct temperature values are often
loosely defined. In the current paper, we performed the synthesis of ZnO in an aqueous solvent
by varying the reaction and drying temperatures by 10 âŠC steps, and we monitored the synthesis
products primarily by XRD). We found out that a simple direct synthesis of ZnO, without additional
surfactant, pumping, or freezing, required both a reaction (TP) and a drying (TD) temperature of
40 âŠC. Higher temperatures also afforded ZnO, but lowering any of the TP or TD below the threshold
value resulted either in the achievement of Zn(OH)2 or a mixture of Zn(OH)2/ZnO. A more detailed
Rietveld analysis of the ZnO samples revealed a density variation of about 4% (5.44 to 5.68 gcmâ3
)
with the synthesis temperature, and an increase of the nanoparticlesâ average size, which was also
verified by SEM images. The average size of the ZnO synthesized at TP = TD = 40 âŠC was 42 nm, as
estimated by XRD, and 53 ± 10 nm, as estimated by SEM. For higher synthesis temperatures, they
vary between 76 nm and 71 nm (XRD estimate) or 65 ± 12 nm and 69 ± 11 nm (SEM estimate) for
TP = 50 âŠC, TD = 40 âŠC, or TP = TD = 60 âŠC, respectively. At TP = TD = 30 âŠC, micrometric structures
aggregated in foils are obtained, which segregate nanoparticles of ZnO if TD is raised to 40 âŠC. The
optical properties of ZnO obtained by UV-Vis reflectance spectroscopy indicate a red shift of the band
gap by ~0.1 eV
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