Randomly deposited or partially aligned electrospun nylon-6 nanofibers were prepared by using a rotating collector with linear velocity from 0 to 900 m/min, and their molecular orientation was characterized with polarized Fourier-transform infrared (FT-IR) spectroscopy. At a linear velocity of 0 m/min, electrospun nylon-6 nanofibers are randomly deposited onto a collector owing to the bending instability of the charged jet. In this case the parallel polarized FT-IR spectrum (obtained at two mutually perpendicular directions) is the same as the perpendicular polarized spectrum, indicating that there is no molecular orientation in the electropun membrane. When the linear velocity of the collector was increased from 0 to 300 m/min, several changes in IR band intensity are observed, including the NH stretching band at 3303 cm -1 and the amide I and II vibrations (1647 and 1543 cm -1 , respectively) in the two polarized FTIR spectra. Also, the intensity of the amide II vibration is observed to gradually increase in the parallel polarized FT-IR spectrum, with an increase in the linear velocity of the collector, whereas its intensity is observed to decrease in the perpendicularly polarized spectrum. This indicates that the polymer chains are preferentially oriented along the fiber axis. Also, a decrease in the average fiber diameter (from 250 to 125 nm) is observed in SEM micrographs, indicating that the fibers are stretched and aligned by the high-speed rotating collector.

A 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.

A 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\ud reusability can hardly be achieved because of the irreversible adsorption of the analyte molecules on the SERS-active substrate.\ud Different substrates have been tested on our sensor with the purpose of increasing its reusability by means of cleaning\ud procedures or good reproducibility in manufacturing the sensor, keeping, however, the same enhancement. We show that a\ud partial reusability of the sensor is possible using SERS-active substrates prepared by a standard process of immobilization of\ud silver nanoparticleswith 3-aminopropyltrimethoxysilane.We also show that a fairly good reproducibility can be achieved with\ud a low-cost substrate realized in a short time by depositing a layer of polyvinyl alcohol (PVA) containing silver nanoparticles on\ud the etched fiber tip.We prove as well that measurements are possible evenwith nanoparticles dispersed in the analyte solution\ud instead of using a substrate directlymade on the sensor tip. Finally, we have successfully tested our sensorwith somemolecules\ud cited in EFSA (European Food Safety Authority) and FDA (Food and Drug Administration) reports as molecules for which new\ud detectionmethods are necessary