Students undertaking courses in the field of sciences and engineering need to learn practical skills and conceptual knowledge, and the experimental classes are the best moment for this. In this paper, we propose a practical experiment to aid nanotechnology learning by synthesizing gold nanoparticles (AuNPs) and their application as a colorimetric sensor of sulfathiazole. AuNPs were prepared using sodium citrate as a reducing and capping agent. The existence of the synthesized AuNPs was detected using the Tyndall effect while their optical properties were investigated by molecular absorption spectrophotometry. The gold nanoparticles exhibit spherical-like shape morphology and an average size of 13.6 nm, determined by transmission electron microscopy. The AuNPs were applied as a colorimetric sensor for the detection of sulfathiazole in mixed water/ethanol solution by simple visual inspection and using molecular absorption spectrophotometry. Due to the simplicity of the experimental steps, this activity is well-suited for a hands-on introduction of nanoparticles synthesis and its application as a molecular sensor. In addition, the experiment encompasses knowledge from different fields being suitable for interdisciplinary classes.

Abstract Target molecules adsorbed onto metallic nanoparticles can have their Raman and/or fluorescence signals enhanced, leading to the called surface-enhanced [resonance] Raman scattering (SE[R]RS) or surface-enhanced fluorescence (SEF). Here we have applied Au nanorods (AuNRs) coated with a surfactant bilayer leading to a positive surface charge to investigate the role played by these AuNRs in colloidal suspension on SERRS and SEF effects of charged molecules. In the case of the anionic nickel (II) tetrasulfonated phthalocyanine (NiTsPc), besides achieving SERRS with an enhancement factor (EF) of ca. 105, the AuNRs allowed the analytical application of the SERRS effect for the NiTsPc between 8.3x10-6 and 4.0x10-5 mol L-1. The limit of detection of 4.8x10-7 mol L-1 (at 752 cm-1) and 1.3x10-6 mol L-1 (at 1338 cm-1) was found. In the case of the cationic methylene blue, the SEF effect was achieved reaching an EF of ca. 10. Besides, fundamental discussions are carried out considering the results presented here.

In this work is reported the investigation of the 4-aminobenzenethiol (4-ABT) surface-enhanced Raman scattering (SERS) response for different 4-ABT concentrations as well as when this molecule is intercalated between Ag and Au nanoparticles (AgNP and AuNP). SERS substrates consisting of the individual AgNP or AuNP and bi-layer AgNP/4-ABT/AuNP or AuNP/4-ABT/AgNP were prepared on glass slides. It was observed a decreasing trend of the bands intensity ratios b2/a1 as a function of the 4-ABT solutions concentration. Since the b2 modes are enhanced through the charge transfer (CT) mechanism, this result indicates that this mechanism is less effective for low concentration of 4-ABT. Also, a dependence between a1 and b2-type bands intensities could be identified for the samples where 4-ABT molecules were intercalated between AgNP and AuNP. A significantly increase in the SERS intensities of the a1 mode around 1074 cm-1 and b2 mode around 1142 cm-1 is observed when AgNP are present in the samples. This result indicates that AgNP promote amplifications of the Raman signal thorough the CT and electromagnetic (EM) mechanisms, whereas for the AuNP the SERS effect is related manly to EM mechanism. These results show that the 4-ABT SERS response can provide more information than the SERS substrate activity. Its SERS signal pattern is rich in information, allowing investigations about the local where the molecule is, details about the substrate surface, and also on the mechanisms present in the system under study.

Glass-ceramics are prepared by controlled separation of crystal phases in glasses, leading to uniform and dense grain structures. On the other hand, chemical leaching of soluble crystal phases yields porous glass-ceramics with important applications. Here, glass/ceramic interfaces of niobo-, vanado- and titano-phosphate glasses were studied by micro-Raman spectroscopy, whose spatial resolution revealed the multiphase structures. Phase-separation mechanisms were also determined by this technique, revealing that interface composition remained unchanged as the crystallization front advanced for niobo- and vanadophosphate glasses (interface-controlled crystallization). For titanophosphate glasses, phase composition changed continuously with time up to the equilibrium composition, indicating a spinodal-type phase separation.

Resultados preliminares de XRD, IR, Raman e SEM mostraram que monólitos vitrocerâmicos porosos (pgc-LVCP) com esqueleto tridimensional constituído pelas fases V(PO3)3 e Ca3(VO4)2 foram obtidos utilizando um vidro original de Li2O-V2O3-CaO-P 2O5 como precursor. O pgc-LVCP pode ser um hospedeiro poroso promissor para sistemas químicos integrados visto que a fase Ca3(VO4)2 apresenta propriedades ferroelétricas e de luminescência enquanto a fase V(PO3)3 exibe propriedades magnéticas associadas com elevada estabilidade mecânica, química e térmica.

Preliminary XRD, IR, Raman and SEM data indicate that porous glass-ceramic monoliths (pgc-LVCP) with skeleton of V(PO3)3 and Ca3(VO4)2 with three-dimensional network structure using an original Li2O-V2O3-CaO-P 2O5 glass as precursor was obtained. The pgc-LVCP is a promising porous host for integrated chemical systems because the Ca3(VO4)2 has ferroelectric and luminophor properties while V(PO3)3 exhibits magnetic properties associated with high degree of mechanical, chemical and thermal stability.