1,721,090 research outputs found
Monodisperse luminescent silica nanoparticles: Synthesis, characterization and application to the dna microarray technology
No full textThe ability to modify the properties of materials by controlling their structure at nanoscale makes them extremely attractive for many applications: from fundamental scientific studies to commercially realizable technologies. In the biological context a variety of nanomaterials promise to offer sensitive, rapid and cost-effective solutions for modern clinical laboratory. In particular, dye-doped silica nanoparticles (NPs) have been demonstrated to be sensitive labeling markers for biosensing and bioimaging. Their flexible conjugation, excellent photostability, and ultrasensitivity make them a powerful tool in bioanalysis. Indeed luminescent dye-doped nanoparticles are excellent candidates for biological applications because (1) they can be analyzed with the standard existing tools (microarray scanners, optical fluorescence microscopes), which are fitted for standard fluorophore excitation and emission curves, (2) a large number of dye molecules can be incorporated in a single particle, increasing the optical signal and (3) the silica matrix provides a protective barrier minimizing photobleaching and photodegradation. A very efficient synthesis strategy for silica nanoparticles is the Stöber method, which has the advantage that it can be easily scaled up for commercial production and the possibility to effortlessly transfer the nanoparticles into aqueous solutions (typically required for bioanalysis applications). However, modifications on the synthesis process are required to obtain luminescent particles and proper investigation on the particles size control and on the dye-doping process are needed. In this chapter we describe a modifyedStöber synthesis which is based on the use of 3-Aminopropyl-triethoxysilane (APTES) for the efficient incorporation of dye molecules into the silica NPs. The parameters of the modified synthesis have been systematically investigated in order to optimize their morpho-optical properties and to maximize their optical efficiency. Moreover the application of these luminescent silica nanoparticles to DNA microarray technology is also reported for a specific case study: the detection of carcinogenic risky Human Papilloma Virus, which is one of the primary causes for cervical cancer in women worldwide. In particular, DNA microarray is a powerful tool for the parallel, high-throughput detection and quantification of many nucleic acids and other biologically significant molecules. We show that our luminescent silica nanoparticles in comparison to conventional dye labelling or commercial quantum dots allow achieving a significant tenfold increase in the optical signal, and a related decrease of the limit of detection, thus giving a remarkable improvement in this technique towards early diagnosis of the disease. It is worth noticing the fact that this result can be easily transferred to other pathologies and to other fields like for example trace level detection of dangerous biological contaminants in food or in the environment
Luminescent amino-functionalized or erbium-doped silica spheres for biological applications
No full textThis work presents the morphological and optical properties of luminescent silica spheres, discussing applications in bioimaging and biosensing. The spheres are obtained by the hydrolysis and condensation of tetraethylorthosilicate (TEOS) and can be synthesized by following either a basic or an acidic route. Luminescence emission is induced after incorporation of aminopropyltriethoxysilane (APTES) during synthesis or by introducing an optically active element, such as erbium, or other rare-earth elements. The luminescence properties of APTES-functionalized silica spheres have been investigated and optimized by varying the annealing temperature. On the other hand, erbium incorporation in silica spheres was also studied and the corresponding Er3+ luminescence emission at 1.54 mu m was evaluated for intensity and lifetime. The basic pH environment in the synthesis allows good control of the size of the spheres (similar to 200 nm in diameter), whereas the acidic route produces a wide dispersion in particle size (200-5000 nm). Both these approaches, however, can be followed to obtain an efficient photoluminescence (PL) emission for the APTES-functionalized silica spheres after 400-600 degrees C thermal treatment. If Er(NO3)(3) is introduced in the basic solution, a rapid precipitation of Er(OH)3 occurs, but erbium can be easily and efficiently incorporated in the acid-synthesized spheres, showing high PL intensity at 1.54 mu m with lifetime of 3.9 ms. Finally, I discuss perspectives for the applications of these luminescent silica spheres, in particular as biological markers for bioimaging and biosensing
A simple approach for upconversion determination using low excitation power: The photoluminescence analysis of an Er-doped aluminosilicate glass
No full textMaterials other than silica can offer better performance in terms of Er solubility and band broadness for integrated Er-doped optical amplifiers and a deep knowledge of their optical properties is therefore fundamental. In this work we describe a simple approach for evaluating upconversion with low pump power excitation, when the standard methods are not very accurate. This is based on the solution of an analytic model which allows the calculation of the 1540nm (I-13/2 --> I-15/2) and the 980nm (I-11/2 --> I-15/2) photoluminescence emissions by considering three energy levels for Erbium.The proposed model has been applied to analyze the luminescence properties of an Er-doped aluminosilicate glass. Firstly some of the system parameters have been evaluated in relation with the lifetimes and with the absorption cross section at 488 nm excitation wavelength. Then the model has been calibrated by comparing the calculated relation between the 980 nm and the 1540 nm emission intensities with the corresponding experimental measurements. This procedure allowed for the determination of the coefficient of cooperative upconversion using pump powers in the range 4-32 mW. An experimental check of the goodness of the method is also presented. (C) 2003 Elsevier B.V. All rights reserved
Plasmonic enhanced solar cells: Summary of possible strategies and recent results
No full textPlasmonic structures for light manipulation at sub-wavelength scale have received great interest in the field of photovoltaic (PV) solar cells for their potential to significantly enhance the cell's efficiency. The performance of any solar cell is determined by the capability to absorb incoming light and produce electric charges, which, in turn, has a number of limiting factors. One is related to the ever-reducing size and acceptance angle of the active region. Another is the limited spectral sensitivity of the active material, which cannot make use of significant parts of the solar spectrum. Correspondingly, the energy harvesting may be improved in two ways, namely by adopting light trapping schemes and by exploiting spectral modification processes to shift frequencies of the solar spectrum, which are initially not absorbed, into the region of maximum absorption of the cell. Plasmonic nanoparticles (NPs) can give a significant boost to both these aspects, by scattering and concentrating the electromagnetic field into the active region of the device, and by doing that within specific spectral regions, which can be properly tuned by optimizing the size, shape, distribution of the plasmonic NPs, and by choosing the right surrounding medium. During the last ten years, many papers have been published on very specific issues, but also on general properties of plasmonics applied to solar cells, with a strong increase between 2006 and 2012, followed by a period of significant, but stable, literature productivity. Given these premises, an organized and schematic summary of the main strategies and of the recent results on the field is given in this review, where different plasmonic approaches are compared and discussed, also by recalling specific examples from the literature and providing a few key conclusions to understand the main aspects and the future perspectives of the field
Acid synthesis of luminescent amine-functionalized or erbium-doped silica spheres for biological applications
No full textIn this work we discuss and investigate the morphological and optical properties of luminescent silica spheres which can have interesting applications in bioimaging and biosensing. The spheres are synthesized following an acid route by the hydrolysis and condensation of tetraethylortosilicate (TEOS) and can be functionalized by incorporation of aminopropyl-triethoxysilane (APTES) during the synthesis, inducing a significant luminescence that can be attributed to a recombination mechanism from localized organic defects related to –NH2 groups. It is shown that the acid synthesis route produces very regular spherical particles, but their diameter vary in the range of 200–4,000 nm. The luminescence properties have been investigated and optimized by variation of the annealing temperature for the functionalized spheres, obtaining the most efficient PL emission after a thermal treatment of 1 h at 600 °C in air. Moreover, the possibility to introduce rare earths like erbium in the spheres was also studied and the corresponding Er3 luminescence emission at 1.53 μm is reported in terms of intensity and lifetime, pointing out that erbium can be easily and efficiently incorporated during the acid synthesis giving high PL intensity with a good lifetime of 3.9 ms
State-of-the-art developments in metal and carbon-based semiconducting nanomaterials: applications and functions in spintronics, nanophotonics, and nanomagnetics
No full textNanomaterials composed of metals and metal alloys are the most valuable components in emerging micro-and nano-electronic devices and innovations to date. The composition of these nanomaterials, their quantum chemical and physical properties, and their production methods are in critical need of summarization, so that a complete state of the art of the present and future of nanotechnologies can be presented. In this review, we report on the most recent activities and results in the fields of spintronics, nanophotonics, and nanomagnetics, with particular emphasis on metallic nanoparticles in alloys and pure metals, as well as in organic combinations and in relation to carbon-based nanostructures. This review shows that the combinatory synthesis of alloys with rare metals, such as scandium, yttrium, and rare earths imparts valuable qualities to high-magnetic-field compounds, and provides unique properties with emphasis on nanoelectronic and computational components. In this review, we also shed light on the methods of synthesis and the background of spintronic, nanomagnetic, and nanophotonic materials, with applications in optics, diagnostics, nanoelectronics, and computational nanotechnology. The review is important for the industrial development of novel materials, and for summarizing both fabrication and manufacturing methods, as well as principles and functions of metallic nanoparticles
Rare-earth doped glasses and light managing in solar cells
Full text linkGlasses doped with rare earth elements possess unique photoluminescence properties. They find application in several devices, such as lasers, optical amplifiers, and sensors. More recently, rare-earth doped glass thin films have been the subject of investigation for the development of frequency-converting layers able to increase the efficiency of silicon solar cells. Another approach to the improvement of the performance of a solar cell is based on the capture of a larger flux of light by the detector, which can be obtained by surface texture, plasmonics, or waveguide structures. Here, the recent advances in this area will be briefly reviewed
Rare-earth doped glasses and light managing in solar cells
Full text linkGlasses doped with rare earth elements possess unique photoluminescence properties. They find application in several devices, such as lasers, optical amplifiers, and sensors. More recently, rare-earth doped glass thin films have been the subject of investigation for the development of frequency-converting layers able to increase the efficiency of silicon solar cells. Another approach to the improvement of the performance of a solar cell is based on the capture of a larger flux of light by the detector, which can be obtained by surface texture, plasmonics, or waveguide structures. Here, the recent advances in this area will be briefly reviewed
Signal enhancement in DNA microarray using dye doped silica nanoparticles: Application to Human Papilloma Virus (HPV) detection
No full textDNA microarray is a powerful tool for the parallel of nucleic acids and other biologically significant molecules. In this communication we report an easy and cheap synthesis route for incorporating organic dyes into monodisperse inorganic silica nanoparticles and their application on the detection of carcinogenic risky Human Papilloma Virus using DNA microarray technology. We correlate our system with conventional direct dyes and commercial quantum dots, with a promising increase in optical signal, and a related decrease of the limit of detection, thus giving a remarkable improvement in this technique towards early diagnosis of diseases and trace level detection of dangerous biological contaminants. (c) 2010 Elsevier B.V. All rights reserved
Modified Stöber synthesis of highly luminescent dye-doped silica nanoparticles
No full textDye-doped silica nanoparticles (NPs) have been demonstrated to be sensitive labeling markers for biosensing and bioimaging. Their flexible conjugation, excellent photostability and ultrasensitivity make them a powerful tool in biological analysis. Although there have been many reports on the basic research and application of these NPs, they are far from reaching their full potential. Silica NPs can be obtained through two principal approaches: the Stober synthesis and the microemulsion method. The Stober synthesis has the advantage of being easily scaled up for commercial applications and the possibility to effortlessly transfer the NPs into aqueous solutions (typical of bioanalysis). However, further investigation on the impact of the synthesis parameters on the particles size and on the doping process are needed in order to obtain highly luminescent particles. In this study a modified Stober synthesis is proposed and a systematic study of the different reagents is reported, which provides a better picture on the influence of ethanol, ammonia, water, silica precursors, and dye concentration on the final morpho-optical properties. As a result, samples of luminescent silica NPs from 10 to 300 nm have been synthesized and optimized to be highly promising labels for biological applications
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