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.

Sugarcane waste ash, a Si-rich waste product, is generated in large quantities and creates a serious disposal problem in the Brazilian ethanol-sugar industry, affecting the environment and public health. Here, a simple method capable of generating bare silica nanoparticles utilizing this residue is demonstrated. Firstly, the crystalline silica present in sugarcane waste ash (SWA) was converted into amorphous by melting a mixture of sodium hydroxide and SWA at 550 ºC for 1 h. The silica nanoparticles (SiO2NPs) were formed by lowing pH. This production process of SiO2NPs from SWA was optimized varying the ash:NaOH mass ratio, increasing the silica extraction up to 96%. The sample’s composition was characterized by total X-ray fluorescence spectroscopy, morphology and physical-chemical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, specific surface area measurements, Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA), followed by use as adsorbent for the removal of methylene blue dye. With this process of extraction, nanoparticles smaller than 100 nm were generated, with a surface area of 63 m2 g-1 and a maximum adsorption capacity of 37 mg g-1 for methylene blue. The results indicate a successful process for obtaining an adsorbent from an industrial waste product using a cost effective and rapid synthesis procedure rendering renewable product.

This work investigates the conceptions of undergraduate chemistry students regarding environmental chemistry and green chemistry within the structure of chemical knowledge. This study was carried out by the analysis of fourteen concept maps produced by third year students at the University of São Paulo. Analysis of the concept maps considered the manifested conceptions about environmental chemistry and green chemistry, and the relations established between them and the five traditional areas of chemistry (analytical chemistry, inorganic chemistry, organic chemistry, physical-chemistry and biochemistry). In general, students presented difficulties in expressing inclusive and integrated conceptions on the topics of environmental chemistry and green chemistry, as suggested by today's purposes for chemical education. The obtained results express the strong influence of the curricular structures of the different chemistry majors, and of the disciplinary didactic textbooks on the students' conceptions.

Este trabajo investiga las concepciones de los alumnos de la carrera de Química de la Universidad de Sao Paulo respecto al estatus de la Química Ambiental y la Química Verde con relación al conjunto del conocimiento químico. El estudio fue realizado sobre un conjunto de catorce mapas conceptuales producidos por alumnos del tercer año. En el análisis de los mapas se consideraron las concepciones manifestadas respecto a la Química Ambiental y la Química Verde, y a sus relaciones establecidas entre ellas y las cinco áreas tradicionales de la química (analítica, inorgánica, orgánica, fisicoquímica y bioquímica). De modo general, los alumnos encontraron dificultades en expresar concepciones incluyentes e integradoras respecto de la Química Ambiental y la Química Verde conforme sugieren los objetivos actuales de la enseñanza de la química. Los resultados muestran una influencia fuerte sobre las concepciones de los estudiantes de la estructura curricular de los diferentes cursos ofrecidos por la Universidad de Sao Paulo, así como de los libros de textos disciplinarios didácticos.

This paper reports the use of Raman and infrared techniques for the qualitative and quantitative analysis of plasticizers in polyvinylchloride (PVC) commercial films. FT-Raman marker bands were indentified for di-2-ethyl-hexyl adipate (DEHA) and di-2-ethyl-hexyl phthalate (DEHP), allowing for the rapid identification of these species in the commercial film. Quantitative analysis by FT-IR resulted in plasticizers concentrations ranging from 11 to 27% (w/w). Considering the little sample preparation and the low cost of the techniques, FT-IR and FT-Raman are viable techniques for a first assessment of plasticizers in commercial samples.

Este trabalho apresenta o estudo do comportamento fotoquímico de hidrocarbonetos policíclicos aromáticos (HPAs), potenciais poluentes secundários em reações em aerossóis, através de espectroscopia Raman em comparação com seu comportamento eletroquímico. Os HPAs estudados incluem pireno, antraceno, fenantreno e fluoreno. Esses foram adsorvidos sobre o catalisador TiO2 e irradiados com radiação ultravioleta (254 nm). A oxidação eletroquímica foi estudada via espectroscopia Raman intensificada pela superfície (SERS) in situ e levou à formação de produtos carbonilados. Intermediários oxidados contendo o grupo C=O foram também observados nos processos de fotodegradação. A comparação entre os intermediários formados nos processos fotoquímicos e eletroquímicos revela produtos idênticos para o antraceno, mas não para o pireno. Esse resultado advém da diferença de mecanismo para esses dois processos. A degradação fotocatalítica sobre TiO2 é iniciada por radicais hidroxila, enquanto a oxidação eletroquímica é iniciada por transferência eletrônica direta com o HPA adsorvido no eletrodo, gerando cátions radicais do HPA que desencadeiam as reações subseqüentes.

This paper presents the study of photochemical behavior of polycyclic aromatic hydrocarbons (PAHs), potential pollutants in secondary reactions in aerosols, through Raman spectroscopy compared with its electrochemical behavior. The PAHs studied include pyrene, anthracene, phenanthrene and fluorene. These were adsorbed onto TiO2 and irradiated with ultraviolet light (254 nm). Their electrochemical oxidation was studied by in situ Surface-enhanced Raman Scattering (SERS) and led to the formation of carbonyl-containing products. Oxidized intermediates bearing the C=O group were also formed during photodegradation. The joint analysis of the photodegradation data with those produced by electrochemical means - using spectroscopic techniques for the identification and characterization of the products - revealed the formation of identical products for anthracene, but not for pyrene. A reasonable explanation for this difference in results is that photochemical and electrochemical oxidation reactions proceed via different mechanisms. While photocatalytic degradation over TiO2 is initiated by hydroxyl radicals, electrochemical oxidation is initiated by the direct electron transfer from adsorbed PAH to the electrode, generating PAH cation radicals that undergo subsequent reactions.

Surface-Enhanced Raman Scattering - SERS - underwent huge advances since a single-molecule Raman spectrum was obtained in 1997. New theoretical and experimental approaches emerged since then leading to a better understanding of the enhancement mechanisms and to a significant improvement in the Raman signal. This review presents the current status of the SERS effect and the promising ways of designing and preparing high performance SERS-active substrates.

The structural characterization of molecules used in the sterilization of blood for transfusions, such as crystal violet (CV), is relevant for understanding the action of these prophylactic drugs. The characterization is feasible by surface enhanced resonance Raman spectroscopy (SERRS) of CV in solution or on surfaces. The limit of detection of CV by SERRS, in the presence of colloidal particles, using 514.5 nm as excitation radiation, was found to be around 1 ppb. The characterization of CV was also made by SERS, by using different active-particles-containing substrates, proving the versatility of this technique for the study of such structures. The results suggest that the controlled production of highly efficient SERS-active substrates may allow qualitative and quantitative analysis, with high sensitivity, with potential applications in medical and environmental fields.