Search results for "silica"
showing 10 items of 1092 documents
NanoSIMS: insights into the organization of the proteinaceous scaffold within Hexactinellid sponge spicules.
2010
The giant basal spicules (GBS) from Monorhaphis chuni (Porifera [sponges], Hexactinellida) represent the largest biosilica structures on Earth and can reach lengths of 300 cm (diameter of 1.1 cm). The amorphous silica of the inorganic matrix is formed enzymatically by silicatein. During this process, the enzyme remains trapped inside the lamellar-organized spicules. In order to localize the organic silicatein scaffold, the inside of a lamella has been analyzed by nano-secondary ion mass spectrometry (NanoSIMS). It is shown that the GBSs are composed of around 245 concentrically arranged individual siliceous lamellae. These surround an internal siliceous axial cylinder. The lamellae adjacent…
Transport of Mobile Particles in an Immobile Environment: Computer Simulations of Sodium Silicates
2007
Molecular dynamics (MD) simulations of various sodium silicate melts, (Na2O)x(SiO2) with x=2, 3, 20, are presented. In these systems, the mobility of sodium ions is much higher, often by orders of magnitude, than that of the silicon and oxygen atoms forming a tetrahedral network structure. We show that the high mobility of sodium is intimately related to the chemical ordering in sodium silicates. A network of percolating sodium-rich channels is formed in the static structure that serve as diffusion channels for the sodium ions. This channel network is revealed in static structure factors by a prepeak at the wavenumber q=0.95 A-1. Inelastic neutron scattering experiments of sodium silicate m…
Ordered mesoporous hybrid materials containing cobalt(ii) Schiff base complex
2002
Immobilisation of Co-salen and Co-fluomine onto ordered mesoporous silica has been achieved through coordination of the cobalt to pyridine or imidazole groups covalently attached to the silica matrix. Two routes have been investigated to obtain mesoporous hybrid materials containing coordinating ligands: post synthesis grafting of 4-[2-(trimethoxysilyl)ethyl]pyridine 1 and N-trimethoxysilylpropylimidazole 2 on hexagonally ordered mesoporous silica via SiOH groups or direct synthesis method i.e. co-hydrolysis and polycondensation of the same functionalised organotrimethoxysilane with a number of equivalents of TEOS in the presence of n-hexadecylamine as structure directing agent. The first m…
Nanosensor for Sensitive Detection of the New Psychedelic Drug 25I-NBOMe.
2020
[EN] This work reports the synthesis, characterization, and sensing behavior of a hybrid nanodevice for the detection of the potent abuse drug 25I-NBOMe. The system is based on mesoporous silica nanoparticles, loaded with a fluorescent dye, functionalized with a serotonin derivative and capped with the 5-HT2A receptor antibody. In the presence of 25I-NBOMe the capping antibody is displaced, leading to pore opening and rhodamine B release. This delivery was ascribed to 5-HT2A receptor antibody detachment from the surface due to its stronger coordination with 25I-NBOMe present in the solution. The prepared nanodevice allowed the sensitive (limit of detection of 0.6 mm) and selective recogniti…
From common and used to rare and forgotten: Past and present distribution of the archaeophyte Euphorbia lathyris L. (Euphorbiaceae) in southern Italy…
2019
Our study aimed at clarifying the current and previous occurrence, distribution and status (native vs. introduced) of Euphorbia lathyris L., the caper spurge, in S Italy and Sicily: most of the recent Italian floras and checklists, in fact, do not report this species for this area. To do this, a multi-disciplinary research was carried out taking into account not only botanical but also ethnobotanical and dialectological sources and a survey of the main herbaria of central and southern Italy. Our results point out that E. lathyris was much more frequent, well-known and commonly used in the whole southern Italy and in Sicily until 2-3 centuries ago, and that it probably experienced isolated c…
Hieracium racemosum subsp. lucanum (Asteraceae), a new hawkweed from southern Italy
2019
A new endemic taxon of Hieracium belonging to the H. racemosum aggregate is described from Basilicata (southern Italy) and named H. racemosum subsp. lucanum. Information on its morphology, distribution, ecology and taxonomic relationship is provided.
The integrated action framework of Rete Natura 2000 Basilicata
2012
Basilicata Natura 2000 network consists of 50 Sites of Community Importance (SCI) and 17 Special Protection Zones (SPZs), covering alltogether more than 17% of the regional area. This network, partially overlapping other forms of land protection, represents a valuable environmental, agricultural and cultural heritage, in which the safeguard of natural resources and landscapes has to be coupled with the needs of the local population; especially in relation to development and social welfare. The Natura 2000 project involved a panel of experts belonging to 15 different institutions, to form a steering committee with the following professional and scientific skills: vegetation, landscape, fauna…
Biocompatibility and staining properties of CdSe\CdS\SiO2 nanoparticles for in-vitro biomaterials characterization
2015
Semiconductor nanocrystals, known as quantum dots (QDs) display well-tuned emission spectra from ultraviolet to the infrared region. Their photostability is greatly enhanced compared to fluorophores making them suitable for optical bio-imaging. In this work we have studied the cytocompatibility of CdSe\CdS\SiO2 QDs towards bovine articular chondrocytes in order to establish if these nanoparticles could be used as staining system forcells in tissue engineering purposes. Studies of QDs uptake and cell viability were conducted through morphology evaluation and MTS test. The adhesion behavior of chondrocytes deposited onto scaffolds of a derivative of hyaluronic acid functionalized with octadec…
Rare-earth doped silica optical fibres for ionizing radiation detection
2016
Scintillating silica optical fibre sensors have shown interesting results for ionizing radiation monitoring and therefore can be useful for dosimetry applications in medical field. In fact, they enable a remote, punctual and real-time dose assessment (Mones et al., 2008). In addition, the high radiation hardness that characterizes silica optical fibers, makes these systems promising for radiation detection in high energy physics experiments (Chiodini et al., 2014). This work aims to review the recent progresses in the development and characterization of rare-earth doped silica fibres. The radioluminescent and dosimetric properties of Ce, Eu, Yb and Pr-doped silica matrices are described and…
Effects of thermal treatments in controlled atmosphere on the Ce oxidation state in Ce-Ti-Eu doped SiO2 sol-gel glasses
2011
We report an experimental study by optical absorption, photoluminescence and Raman spectroscopies of the modifications induced on Ce–Ti-Eu doped SiO2 glasses by thermal treatments in controlled atmosphere. Samples with Ce content varying up to 5,000 part per million by weight (ppm) and with Ti and Eu content fixed at 40 and 300 ppm respectively, have been investigated. The treatments were done in inert atmosphere of He and in O2 atmosphere at 390 C and 100 bar. Our experiments show that only Ce4? ions are affected by He treatments, whereas both Ce4? and Ce3? ions are affected by O2 treatments. The obtained results are interpreted on the basis of microstructural changes induced by the therma…