1,721,099 research outputs found
Utilizzo di nanoparticelle di argento per sensori ad alta sensibilità
No full textContributo orale su invito a NanoForum200
Sonda Ottica per la rilevazione di molecole SERS attive e procedimento per la sua fabbricazione
No full textFiber-optic SERS sensor with optimized geometry
No full textA novel surface enhanced Raman scattering (SERS) sensor has been developed and built. This sensor uses an “optrode” configuration in
which a single optical fiber transmits both the exciting laser radiation and the SERS signal from the molecules adsorbed onto the SERS active
substrate. The main advantage of this sensor is its unique geometry which can be obtained by means of a double static etching process achieved
with a 40% hydrofluoric acid aqueous solution covered with an organic solvent over-layer. The SERS active substrate is prepared by a standard
process of immobilizing silver nanoparticles with 3-aminopropyltrimethoxysilane. The optimized geometry permits attainment of the best limit
of detection (LOD) value ever reported in the literature for a fiber-optic SERS sensor. In particular, we are able to record SERS spectra from a
10−9M (0.018 ppb) solution of crystal violet in distilled water both with measurements performed in solution and with a “dip and dry” technique.
Moreover, the capability to detect molecules such as crystal violet at such very low concentrations make this SERS sensor very promising for
monitoring the diffuse illicit use of this molecule in aquaculture industry
Fibre-optic SERS sensor with optimized geometry
No full textPoster presentato alla Faraday Discussion 132 Imperial College Londo
Fiber-optic SERS sensor with optimized geometry: testing and optimization
No full textA unique, geometry-optimized, surface-enhanced Raman scattering (SERS) fiber-optic sensor has been recently developed and built. Though this class of sensors can be very useful in many applications, their use is greatly hindered by the fact that their
reusability can hardly be achieved because of the irreversible adsorption of the analyte molecules on the SERS-active substrate.
Different substrates have been tested on our sensor with the purpose of increasing its reusability by means of cleaning
procedures or good reproducibility in manufacturing the sensor, keeping, however, the same enhancement. We show that a
partial reusability of the sensor is possible using SERS-active substrates prepared by a standard process of immobilization of
silver nanoparticleswith 3-aminopropyltrimethoxysilane.We also show that a fairly good reproducibility can be achieved with
a low-cost substrate realized in a short time by depositing a layer of polyvinyl alcohol (PVA) containing silver nanoparticles on
the etched fiber tip.We prove as well that measurements are possible evenwith nanoparticles dispersed in the analyte solution
instead of using a substrate directlymade on the sensor tip. Finally, we have successfully tested our sensorwith somemolecules
cited in EFSA (European Food Safety Authority) and FDA (Food and Drug Administration) reports as molecules for which new
detectionmethods are necessary
A highly sensitive sensor based on Surface-Enhanced Raman Scattering
No full textposter presentato al convegno GNSR 2007 (Catania
Use of a geometry optimized fiber-optic SERS sensor in trace detection
No full textA novel SERS (surface-enhanced Raman scattering) sensor has been recently developed; its peculiar geometry is able to increase considerably both the SERS active surface and the number of internal reflections at the interface between silica and silver, thus allowing an increase of the signal intensity. The aim of this work is to demonstrate that this sensor could be efficiently used to detect some molecules such as illegally used veterinary
medicine (crystal violet and malachite green) below the ppb detection limit. The advantages of this sensor with respect to other detection techniques are not only the higher sensitivity, but also the fast response and the possibility of coupling with a portable Raman spectrometer for ‘‘on-field’’ measurements. The ability of the sensor to work under real environmental conditions in the presence of many cationic and anionic species has been tested both in solutions containing sodium and chlorine ions and in water coming from the aqueduct of Milan and from the (normally polluted) river Serio
Optical fatigue in a solid state diarylethene polymer
No full textThe issue dealt with in this Letter is the study of the optical fatigue of poly-1,2-bis(2-methylthien-3-yl)perfluorocyclopentene (I) as prototype of backbone photochromic polymers recently proposed as materials for the development of new optical devices in photonics and optical imaging. An instrument has been built and measurements have been carried out, thus showing that a film cast from a chloroform solution of the photochromic compound (I) + polymethylmethacrylate reaches the limits set by technology as acceptable (20% decrease of the absorbance with the respect to the absorbance of the stationary state) at 3400 cycles
Molecular interactions of DNA with transfectants: a study based on infrared spectroscopy and quantum chemistry in aid to fluorescence spectroscopy and dynamic light scattering analyses
No full textCationic polymers are promising non-viral agents because of their easiness of use, inexpensiveness and favorable safety profile. Being inherently cationic, they do spontaneously assemble in water with nucleic acids to give polyplexes. The more popular techniques and methods routinely applied for the characterization of such nanosupensions, unfortunately, do not afford direct observation of anion-cation interactions. We thus tackle the issue of probing at the very molecular level the interplay occurring between the PO4- groups of double stranded DNA and the NH3+ groups of the simple and representative transfectant poly(L-Lysine). By means of IR spectroscopy and Density Functional Theory (DFT) calculations we assigned the red shift of the anti-symmetric PO stretching wavenumber to the intermolecular water- mediated NH3+:PO4- interaction. These changes observed in moving from ineffective, low nitrogen (N) to DNA phosphate (P) ratios (N/Ps) to more effective conditions are in overall good agreement with changes in polyplex behavior unveiled by means of other analytical techniques such as dynamic light scattering, laser Doppler micro-electrophoresis, and fluorescence spectroscopy, but provide direct insight into the basic intermolecular DNA:transfectant interplay. The application of IR spectroscopic analysis to other non-viral gene delivery vectors may become an appealing approach to disclose molecular details on PO4- :cationic polymer interaction, taking into account conformational constraints and steric hindrance effects that the other techniques actually overlook
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