Commercial substrates used for surface-enhanced Raman spectroscopy (SERS) are investigated for their reusability following cleaning with 254-nm UV light from a mercury lamp. SERS of Rhodamine 6G (Rh6G, a dye) and RDX (an explosive) is investigated. It is found that without UV irradiation, the substrate is usable only once, since it is not possible to dislodge the analyte either by prolonged immersion in distilled water or by ultrasonic cleaning. However, prolonged exposure to 254-nm UV followed by immersion in distilled water removes most of the analyte, making the substrate reusable for new SERS measurements. The technique of UV cleaning is demonstrated by recycling the same substrate several times and comparing SERS spectra taken after each cleaning cycle.
Phospholipid, which is a building block of biological membranes, plays an important role in compartmentalization of cellular reaction environment and control of the physicochemical conditions inside the reaction environment. Phospholipid bilayer membrane has been proposed as a natural biocompatible platform for attaching biological
molecules like proteins for biosensing related application. Due to the enormous potential applications of biomimetic model biomembranes, various techniques for depositions and patterning of these membranes onto solid supports and their possible biotechnological applications have been reported by different groups. In this work, patterning of
phospholipid thin-films is accomplished by interferometric lithography as well as using lithographic masks in liquid phase. Surface Enhanced Raman Spectroscopy and Atomic Force microscopy are used to characterize the model phospholipid membrane and the patterning technique. We describe an easy and reproducible technique for direct patterning of azo-dye (NBD)-labeled phospholipid (phosphatidylcholine) in aqueous medium using a low-intensity
488 nm Ar<sup>+</sup> laser and various kinds of lithographic masks.
Surface relief gratings produced on planar substrates have been widely investigated for their application as a
holographic recording medium. Much of this work has concentrated on gratings made in polymer thin films with an
azo-benzene group. We describe a novel phenomenon involving surface relief gratings which are formed by deposition
of Rhodamine 6G dye on polybutadiene thin film. This deposition as a grating pattern is photo-induced in a dye-solution
by holographic interference of low power 488 nm light from an argon-ion laser. Dynamics of this aqueousphase
grating deposition is investigated for various concentrations of the dye. A plausible mechanism of grating
formation involves photochemical reaction of polybutadiene substrate with the laser-excited dye. Surface relief
structure of the grating is characterized with an atomic force microscope.
Explosives detection for national and aviation security has been an area of concern for many years. In order to
improve the security in risk areas, much effort has been focused on direct detection of explosive materials in vapor
and bulk form. New techniques and highly sensitive detectors have been extensively investigated and developed
to detect and identify residual traces that may indicate an individual's recent contact with explosive materials.
This paper reports on the use and results of Surface Enhanced Raman Scattering (SERS) technique, to analyze
residual traces of explosives in highly diluted solutions by using low-resolution Raman spectroscopy (LRRS). An
evaluation of the detection sensitivity of this technique has been accomplished using samples of explosives such
as Trinitrotoluene(TNT), Cyclotrimethylenetrinitramine (RDX) and HMX evaluated at different concentrations.
Additionally, different SERS substrates have been studied in order to achieve the best enhancement of the Raman
spectrum for residual amounts of materials. New substrates produced by gold-coated polystyrene nanospheres
have been investigated. Two different sizes of polystyrene nanospheres, 625nm and 992nm, have been used to
produce nanopatterns and nanocavities on the surface of a glass slide which has been coated with sputtered
gold. Results from homemade substrates have been compared to a commercial gold-coated substrate consisting
of an array of resonant cavities that gives the SERS effect. Sample concentration, starting from 1000ppm
was gradually diluted to the smallest detectable amount. Raman spectrum was obtained using a portable
spectrometer operating at a wavelength of 780nm.