Surface-enhanced
Raman scattering (SERS) is a powerful and sensitive
technique for the detection of fingerprint signals of molecules and
for the investigation of a series of surface chemical reactions. Many
studies introduced quantitative applications of SERS in various fields,
and several SERS methods have been implemented for each specific application,
ranging in performance characteristics, analytes used, instruments,
and analytical matrices. In general, very few methods have been validated
according to international guidelines. As a consequence, the application
of SERS in highly regulated environments is still considered risky,
and the perception of a poorly reproducible and insufficiently robust
analytical technique has persistently retarded its routine implementation.
Collaborative trials are a type of interlaboratory study (ILS) frequently
performed to ascertain the quality of a single analytical method.
The idea of an ILS of quantification with SERS arose within the framework
of Working Group 1 (WG1) of the EU COST Action BM1401 Raman4Clinics
in an effort to overcome the problematic perception of quantitative
SERS methods. Here, we report the first interlaboratory SERS study
ever conducted, involving 15 laboratories and 44 researchers. In this
study, we tried to define a methodology to assess the reproducibility
and trueness of a quantitative SERS method and to compare different
methods. In our opinion, this is a first important step toward a “standardization”
process of SERS protocols, not proposed by a single laboratory but
by a larger community.
The paper present the synthesis of a series of nylons as constituent polymers of parts obtained by rotational molding via activated anionic copolymerization of caprolactam with laurolactam. The initial mold temperature (initial polymerization temperature) was kept constant at 160° for all experiments. The initial laurolactamn content influence was investigated in terms of nylon yield, viscosity, density, melting temperature, degree of crystallinity, water absorption, impact strength and flexural modulus. The characteristics of copolymers were compared with those of the polyamide 6. From X-ray diffraction patterns and FT JR spectra it was found that the obtained polyamides are predominantly in the α-form.
In situ anionic polymerization of °-caprolactam in the presence of SiO2 and silanated SiO2nanoparticles was promoted as a route for the synthesis of two series of nylon 6/SiO2 nanocomposites. The process was performed at 160°C well below the melting temperature of the nylon 6 ( Tm ~ 225°C) and initiated/activated with sodium dicaprolactamato-bis(2-methoxyethoxo)aluminate/ N, N′[methylene-di(4,4′phenylene)bis-carbamoyl]bis- δ-caprolactam system. The nanocomposites obtained exhibit higher onset decomposition temperatures than neat nylon 6 and a tendency of reduction of the polymer yields, degree of polymerization, water absorption and melting temperatures with silica content increasing. The crystallization temperature, Tc of the nanocomposites reaches a maximum value at 2.0 wt.% of the nanoparticles. The mechanical tests of nanocomposites revealed an increase in flexural modulus as a function of filler percentage and a decrease in notched impact strength by addition of the modified silica (over 4.0 wt.%) and unmodified silica. Furthermore, the flexural strength diminishes both the treated and untreated filler content is increased for concentration of ~ 4.0 wt.%
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