In this work a colloidal approach to synthesize water-soluble CdSe quantum dots (QDs) bearing a surface ligand, such as thioglycolic acid (TGA), 3-mercaptopropionic acid (MPA), glutathione (GSH), or thioglycerol (TGH) was applied. The synthesized material was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-Vis), and fluorescence spectroscopy (PL). Additionally, a comparative study of the optical properties of different CdSe QDs was performed, demonstrating how the surface ligand affected crystal growth. The particles sizes were calculated from a polynomial function that correlates the particle size with the maximum fluorescence position. Curve resolution methods (EFA and MCR-ALS) were employed to decompose a series of fluorescence spectra to investigate the CdSe QDs size distribution and determine the number of fraction with different particle size. The results for the MPA-capped CdSe sample showed only two main fraction with different particle sizes with maximum emission at 642 and 686 nm. The calculated diameters from these maximum emission were, respectively, 2.74 and 3.05 nm.

A obtenção de informações sobre uma rota biossintética é um procedimento complexo e trabalhoso. Neste sentido, o presente trabalho apresenta uma nova abordagem para a análise inicial da biossíntese de produtos naturais fluorescentes usando a biossíntese da violaceína como exemplo. Para tanto, uma cultura da Chromobacterium violaceum foi inoculada em um biorreator de onde alíquotas eram retiradas a cada 2 h para posterior análise por espectroscopia de fluorescência 2D. As matrizes de emissão-excitação obtidas demonstraram o comportamento dinâmico dos sinais de fluoróforos que são consumidos e produzidos pela bactéria. Estes sinais foram resolvidos pelo método PARAFAC (análise paralela de fatores) perfazendo um total de seis espécies químicas. O triptofano e a violaceína foram identificados por comparação espectral. A identificação dos outros fluoróforos mostrou-se a etapa crítica devido à falta de banco de dados de produtos naturais fluorescentes para comparação. Por fim, esta metodologia apresenta um grande potencial para fornecer informações da biossíntese de produtos naturais.

Obtaining information about a biosynthetic pathway is a complex and laborious procedure. In this sense, this work presents a new approach for the initial analysis of the biosynthesis of fluorescent natural products using as example the violacein biosynthesis. For this, a culture of Chromobacterium violaceum was grown in a bioreactor from which aliquots were collected every 2 h for subsequent analysis by multi-wavelength fluorescence spectroscopy. The excitation-emission matrices demonstrated the dynamic behavior of the fluorophores signal that are consumed and produced by the bacterium. These signals were resolved by PARAFAC (parallel factor analysis) method totalizing six pure components. Tryptophan and violacein were identified by comparison to spectra available in the literature. The identification of other fluorophores was critical step due to the lack of a database of fluorescent natural products to compare spectra. Finally, this methodology has great potential to achieve a deeper insight into the biosynthesis of natural products.