Resumo em Inglês:

The introduction of Raman spectroscopy in South America and the development of techniques which allowed the use of radiation in the red and near infrared are discussed in this work, highlighting not only the technical aspects but also the European political and social contexts in the 1930s. When the Nazis came to power in 1933, thousands of jewish scientists, journalists and artists fled Germany, escaping from oppression, persecution and death; many of them played a pivotal role in the development of science in America. This is the case of Hans Stammreich.

Resumo em Inglês:

This paper presents a brief account of some striking aspects of Professor Hans Stammreich's life. We present in particular the highlights of his contribution to Raman spectroscopy, the contribution made to the development of molecular spectroscopy in Brazil, and details of his personal life. We also report the international recognition of his pioneering work and the legacy he left through the creation of the Molecular Spectroscopy Laboratory at the University of São Paulo.

Resumo em Inglês:

In this work we provide a revision of the studies by Raman spectroscopy carried out by Prof. Hans Stammreich in the São Paulo University. The works of Prof. Stammreich are discussed focusing on the most important conclusion of each paper and the scientific issue at the time of publication. Approximately twenty-five papers are discussed, which were separated into four groups according to the investigated systems: metal carbonyls, halogens and inter-halogens, halogen compounds, and oxoanions.

Resumo em Inglês:

In this study raw and processed silkworm (Bombyx mori) cocoons were investigated using confocal Raman spectroscopy in conjunction with differential scanning calorimetry (DSC) in order to examine the effect of temperature on the molecular conformation of silk fiber structures. Using DSC, a broad endothermic curve was observed at moderate temperatures, shedding light on the vaporization of both raw and processed cocoons, a phenomenon that could also indicate a strong interaction between silk fibroin and water molecules. Over the temperature range set for this study, Raman spectra of raw and processed cocoons were compared at different excitation radiations after drying both kinds of cocoon in an oven at 80 and 125 ºC for 60 minutes. By correlating the intensity ratios of the deconvoluted Raman bands using the broad bands characteristic of amide I and III, it was possible to evaluate the conformational changes in both materials. At excitation radiation of 532 nm, the deconvoluted Raman spectra for the amide III band indicated that, for both samples, there was a reduction in β-sheet conformation compared to α-helix conformation, and this structural disruption was driven by increased temperature. At radiation of 785 nm, the bands attributed to amino acid residues in the side chains increased in intensity, and by deconvoluting the amide I band, increased temperature was found to induce a transition from β-sheets to β-turns in both materials.

Resumo em Inglês:

The chemistry and spectroscopy of the iron(II) phenylterpyrazine complex, [Fe(phtpz)2]2+, were investigated in comparison with the analogous phenylterpyridine species, Fe(phtpy)2]2+, and the results indicated a strong electronic delocalization on the Fe(II) terimine chromophore encompassing the lateral pyrazyl groups. The delocalized nature of the molecular orbitals involved in the electronic excitation precluded a direct assignment of the pyridine and pyrazine vibrations in the complex. However, the capability of the terpyrazine complex to bind transition metal ions, such as the [Fe(CN)5]3- species, allowed to generate pentanuclear complexes displaying characteristic charge-transfer and resonance Raman spectra, revealing the pyrazine vibrations in the complex. The [Fe(CN)5]3- containing species also yielded polymeric compounds in presence of transition metal ions, exhibiting intervalence transfer bands and chemical similarities with the Prussian Blue complex.

Resumo em Inglês:

Near-field properties due to surface plasmon excitation is a key element for different applications of metal nanoparticles, such as surface-enhanced Raman scattering (SERS). Therefore, a characterization of such properties is fundamental for the correct interpretation of experimental results, such as the strong fluctuation of intensities observed at low analyte concentrations, especially at single-molecule detection level. In this paper, we investigate, by classical electrodynamics simulations, the link between the near-field properties of metal nanoclusters and the intensity distribution that is expected in a given single-molecule SERS experiment. The results presented here points to the possibility of correlating the intensity histograms shapes to properties such as degree of field amplification localization and aggregation state of metal nanoparticles.

Resumo em Inglês:

A bioanalytical method for HIV detection based on surface-enhanced Raman scattering (SERS) is described. The assay targeted the peptide p17-1. This peptide sequence is present in the protein p17, a structural protein essential in the life cycle of the human immunodeficiency retrovirus (HIV). The antibody anti-p17 was immobilized in a planar gold surface using self-assembled techniques. This planar platform was used to capture the target analyte (p17-1 peptide). The peptide detection was carried out using specially designed SERS probes, consisting of gold nanoparticles coated with a Raman reporter molecule (Nile Blue A) and functionalized with anti-p17. This sandwich assay led to the successful detection of the peptide p17-1 at 40.8 ng/mL levels. The sandwich assay described here demonstrated that the SERS technique can rival more common fluorescence methods, such as ELISA, in the detection HIV-type virus.

Resumo em Inglês:

There is still a significant need for low cost, fast and trustworthy diagnostic devices based on biosensors, which may impact positively for applications in developing countries. Localized surface plasmon resonance (LSPR) based biosensors have been taken as powerful alternative to deal with the above limitations. The local electromagnetic field enhancement caused by the LSPR in metallic nanomaterials allows the emergence of the surface enhanced Raman scattering (SERS) effect, which have recently been applied as biosensing platforms. In the present report, gold nanorods (AuNRs) were synthesized and modified with a sandwich immunoassay to detect bovine serum albumin antibody (anti-BSA). The sensitivity of the platform was evaluated by the extrinsic SERS signal from AuNRs in solution phase with added Nile blue as reporter molecule (AN-S-AuNRs), which was subsequently modified with bovine serum albumin (BSA); the assay consisted on capturing BSA modified AN-S-AuNRs by anti-BSA molecules immobilized on AuNRs on glass slides (AuNRs-chip). SERS mapping evidenced the analyte detection based on the substantial increase in the positive events with SERS signal of the reporter molecule in the presence of anti-BSA compared to the assay in the absence of the antibody. The present study may potentially guide the construction of efficient SERS immunosensors.

Resumo em Inglês:

The understanding of chemical and physical behavior of materials, especially metals and their alloys, is of utmost importance for industrial and technological applications, development of new materials and preservation of cultural heritage. The use of complementary analytical techniques has allowed a better understanding of corrosion mechanisms, and results obtained by Raman micro-spectroscopy, for example, have been complemented by FTIR and XRD. When focusing on the development of new materials and proposition of preservation strategies, the understanding of corrosion processes and of their very initial steps (nanometric scale) is fundamental. SERS reaches such lateral resolution if TERS is used, however, it cannot be universally applied and needs to be complemented by other techniques. In this work it is presented the potentials of a recent installed technique at the Brazilian Synchrotron Light Laboratory (LNLS), which can be used for nano-speciation of corrosion products, complementing investigation carried out by, for example, Raman micro-spectroscopy and TERS. It is Synchrotron Infrared Nano-Spectroscopy (SINS), which allows the investigation of both chemical nature and physical distribution of corrosion products. The infrastructure presented at LNLS is one of the few available in the world. As a model system, thin films of Pb exposed to formic acid were used.

Resumo em Inglês:

The preservation of Cultural Heritage is undoubtedly important for the society, and Conservation Science must dedicate itself to attempts to minimize the inherent processes of degradation to which cultural assets are susceptible. In this context, the evaluation of the chemical aspects of the composition of the objects and their relation with the environment where they are located are essential for the understanding of the decay signs observed, supporting the establishment of effective conservation strategies. These characteristics are demonstrated here by vibrational spectroscopy, scanning electron microscopy and microbiological analysis of efflorescences observed in two types of paintings: a tempera on canvas painting ("Barco com bandeirinhas e pássaros", Alfredo Volpi, 1955) and an oil mural painting of the Throne Room of the National Palace of Mafra (18th-19th century, Mafra, Portugal). The challenges involved in the investigation of the efflorescences are demonstrated in both cases, suggesting the occurrence of degradation processes of different origins: in Alfredo Volpi's tempera on canvas painting, the migration of substances from the preparation layer to the surface of the pictorial layer and microbiological colonization; and in the mural painting the migration of calcium salts from the constituent materials of plaster and of neoformation, besides associated microbiological colonization.

Resumo em Inglês:

This work shows a practical application of the group theory to a relatively simple molecular system, as well its impact in the results obtained through vibrational spectroscopic techniques. Squaraines substituted by dicyanemethylene groups have been extensively studied, and after minor approaches in the sense to facilitate the point group determination, they were classified to the C2v (Cis) and D2h (Trans) groups. The Trans squaraine presents lower irreducible representations when compared to the Cis derivative; alterations in the arrangements of such systems promotes very interesting conjugation effects, since different reactivity from spectroscopic particularities. Especially to the Trans squaraine, there was a clear convergence between the data suggest by the calculations and those observed in their vibrational spectra, mainly that related to the inversion operation; strong bands visualized in a vibrational technique are not identified in other, mainly in region between 1800-1000 cm-1. The approach of local symmetry must to be adjust to better evaluation of the spectroscopic behavior of the Cis derivative, in this case, the theory suggests low symmetry, but in the spectra can be seen clearly a bigger symmetry. Then, the vibrational analysis by using different techniques was determinant to the discussion in a supramolecular level.

Resumo em Inglês:

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) synthesis was monitored by resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies and both the oxidation of the polymer and the effects of chain length were assessed by vibrational analysis. It was supported by theoretical models of oligomers, with charge ranging from 0 to +6 and size varying from 2 to 16 3,4-ethylenedioxythiophene (EDOT) repeat units, described through density functional theory. The symmetric CαCβ stretching band observed at ca. 1426 cm-1 shifts to higher wavenumbers for reaction times varying from 2 to 9 hours and stabilizes at intermediate wavenumbers for longer times. The former behavior was ascribed to the increase of concentration of oxidized species, which was corroborated by calculated wavenumbers for oligomer models when their charges changed from neutral to +6. The behavior observed for longer reaction times was associated with the growth of chains. It was also observed through SERRS spectroscopy that small chains of the polymer, obtained in the early time of the synthesis, adsorbs on gold nanoparticle surfaces through interactions via oxidized residues. In this way, RR and SERRS spectroscopies were valuable tools to follow the synthetic procedures of PEDOT:PSS, allowing the determination of the structural evolution of the polymer.

Resumo em Inglês:

Almost 60 years ago H. Stammreich obtained the Raman spectra of two photosensitive molecules, CI4 and SnI4, using a pioneering technology developed by him. At the time the excitation source was homemade gas lamps. The same experiments were repeated by us, with the best technology available, with outstanding correlation, and some new information was obtained that wasn't possible 60 years ago. The major difference between the experiments was the use of laser, that made the Raman spectroscopist's life much easier and less time-consuming.

Resumo em Inglês:

A complete procedure including synthesizing gold nanoparticles and further hotspots stabilization is presented. Colloidal gold synthesis followed a citrate reducing reaction, then, an ideal condition for SERS enhancement with quantitative purposes was reached by searching equilibrium between salt- and analyte-induced aggregation. Under this condition, a mild aggregation is produced, along with "free sites" available on the metal surface where analyte could easily interact. As a consequence, suitable linear concentration intervals and high quality SERS spectra were obtained allowing building multivariate quantitative models. For adenine as probe molecule, LOD values were around 10-8 mol L-1, even at low laser power and short exposure time during spectral acquisition. The hotspot stabilization procedure, as shown here, allows dealing with samples or highly complex analytical matrices that can easily cause undesirable agglomerate formation like those from biological origin.

Resumo em Inglês:

The present work presents the systematic study of Nile Blue A (NB) dye, a cationic textile dye, through electronic and vibrational spectroscopies (Raman, resonant Raman scatter and infrared absorption) in the presence of distinct anions (chloride, bromide, perchlorate and sulfate) and protic and aprotic solvents of different polarities (water, ethanol, acetone, acetonitrile, chloroform and ethyl acetate). There were vibrational changes resulting from the formation and destruction of aggregates according to the chemical environment, besides the formation of a molecular conformation with higher energy in apolar aprotic solvents.

Resumo em Inglês:

The present work shows the temperature dependence of the Raman spectra of two conjugated polymers: poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). In situ resonance Raman spectra of PEDOT from 77 to 423 K at 633 nm and of MEH-PPV from 77 to 473 K at 785 nm suggest that, for both polymers, as the temperature increases there is a decrease in the chain conjugation length. Raman bands of PEDOT assigned to the νsim Cα-Cβ are the most sensitive to temperature while bands due to oxyethylene rings do not show significant shifts in this temperature range. Raman and FT-IR spectra of MEH-PPV recorded above the thermal decomposition temperature provide some insights about the thermal degradation.

Resumo em Inglês:

The oldest manuscript from the Arquivo Público do Estado de São Paulo dating back to the XVI century, which was laminated some decades ago, was analyzed by Raman and FTIR spectroscopies. A book from the XVIII century and Japanese papers were also investigated for comparison purpose. Raman microscopy is a well-known technique, which offers a non-destructive approach to informing the preservation state of paper and textile heritage. The manuscript and book were both characterized as cotton rag paper and their degradation state were evaluated from the spectroscopic features. The use of certain Raman signatures as ageing markers was discussed and questioned when different types of cellulose or even processing are compared.

Resumo em Inglês:

In this work, anhydrous titanyl sulfate (TiOSO4) was synthesized and characterized by elemental analyses and vibrational spectroscopy by the first time. In order to verify the stability of the crystallographic structure reported in the literature, an optimization calculation of the unit cell geometry was done with the CRYSTAL17 software, and the agreement with the experimental results was very good. Raman, infrared and far infrared spectra were obtained, the bands having been tentatively assigned, based on literature data for similar systems. Essentially, the spectra exhibit the vibrational modes of the sulfate anion splitted by the low local symmetry along with the bands of the TiO6 skeleton. The Raman spectra shows two intense bands, tentatively assigned to Ti-O modes.

Resumo em Inglês:

The effect of the solvent on the electronic properties of the triarylmethane dye rosolic acid (RA) is investigated by means of UV-VIS and resonance Raman (RR) spectroscopies. The comparison of the solvatochromic behavior of both neutral and dianionic species of RA in acetonitrile, dimethylsulfoxide, and methanol illustrates the effect of polarity and hydrogen bonding on their electronic transitions. The resonance Raman analysis revealed two distinct chromophores in both neutral and dianionic species: i) one located at the central carbon atom, acting as an electron acceptor, and ii) the other involving the π-system of the donor groups. The observed resonance Raman excitation profiles are solvent dependent and could be interpreted as the effect of the solvent on the planarity of the aromatic rings in relation to the central carbon atom. In the case of neutral RA species, having C2 symmetry, specific hydrogen bonding interactions are responsible for inducing a symmetry increase. The opposite effect was observed for the dianionic species [RA]2-, having D3 propeller symmetry, where the interactions with the solvent induces a lowering of the symmetry.