This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles which were synthesized using a wet chemical method and functionalized with 1-dodecanethiol. This molecule allowed us to obtain a spacing of ∼2.6 nm among gold stars, which promoted the generation of SERS hotspots for single molecule detection. The gold nanoparticles were deposited on silicon substrates or on gold coated silicon substrates by using the Langmuir-Blodgett method which permitted the zeptomole detection of Rhodamine B (total moles per laser spot area). The Raman enhancement factor (EF) achieved for this level of detection was 10(12), and was obtained on the SERS substrate fabricated with the configuration: Si/Au film/Au nanoparticles. Raman spectra of the molecules TWEEN 20 and p-terphenyl were also measured in order to elucidate the effect of the molecule's length on the enhancement factor. According to these results, our SERS substrates without the gold film are useful for a minimum detection level of ∼10(-14) moles of analytes with sizes equal to or less than 1.3 nm and ∼10(-18) moles of analytes with the gold film (total moles per sample).

This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles synthesized by a wet chemical method. The SERS substrates were used for glucose detection for concentrations as low as 10(-7) M, which represents an enhancement factor (EF) of 10(9), as a result of the hot spot formed by the spike termination and appropriate distribution of the gold nanoparticles. An improvement of two orders of magnitude was obtained by coating the gold nanoparticles with albumin with the configuration: glass/Au nanoparticles/albumin. In this case the lowest detection was at a concentration of 10(-9) M for an EF of 10(11). The albumin molecule allowed us to enhance the Raman signal because of the formation of peptide bonds (COOH-NH2) generated due to the interaction of glucose with albumin, and the appropriate separation distance between the glucose molecules and gold nanoparticles. The presence of such peptide conjugates was confirmed by FTIR spectra. Thus, our results suggest that our SERS substrates can be useful for the detection of very low concentrations of glucose, which is important for the diagnosis of diabetes in the field of medicine.

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CdTe quantum dots (QDs) are widely used in bio-applications due to their size and highly efficient optical properties. However internalization mechanisms thereof for the variety of freshly extracted, not cultivated human cells and their specific molecular interactions remains an open topic for discussion. In this study, we assess the internalization mechanism of CdTe quantum dots (3.3 nm) capped with thioglycolic acid using non cultivated oral epithelial cells obtained from healthy donors. Naked gold nanoparticles (40 nm) were successfully used as nanosensors for surface-enhanced Raman spectroscopy to efficiently identify characteristic Raman peaks, providing new evidence indicating that the first interactions of these QDs with epithelial cells occurred preferentially with aromatic rings and amine groups of amino acid residues and glycans from trans-membrane proteins and cytoskeleton. Using an integrative combination of advanced imaging techniques, including ultra-high resolution SEM, high resolution STEM coupled with EDX spectroscopy together with the results obtained by Raman spectroscopy, it was determined that thioglycolic acid capped CdTe QDs are efficiently internalized into freshly extracted oral epithelial cells only by facilitated diffusion, distributed into cytoplasm and even within the cell nucleus in three minutes.

This work reports the luminescence, morphology and synthesis of ZnO quantum dots using a simple wet chemical method and different concentrations of Triethanolamine (TEA) as surfactant. Those nanoparticles emitted a strong blue emission band centered at 429 nm when they are dispersed in hexane. Spherical quantum dots with sizes ranging from 3 to 7 nm were obtained for concentrations from 0 to 0.7 ml. of TEA, whereas a mixture with oval-like nanoparticles was observed from concentrations above of 1.1 ml of TEA. It was also possible to control the values of the band gap in ZnO quantum dots depending on the content of TEA. Based on the high quantum yield of 81% measured for those ZnO nanoparticles respect to quinine sulfate dye (QS), it is suggested that such nanoparticles could be used for biolabeling and ZnO based LEDs.

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This work presents the main criteria to be considered when Surface Enhancement Raman Scattering substrate is used to detect low molecules concentrations. A comparison between hydrophilic and hydrophobic substrates is presented. SummaryActually, studies about Surface Enhancement Raman Scattering (SERS) are taking more and more importance in areas like biomedicine, toxicology, pesticide on food and water contamination. The use of SERS substrates is a powerful tool to have standard enhancement factor to all the samples under measurement.

In recent years the use of nanoparticles in medical applications has boomed. This is because the various applications that provide these materials like drug delivery, cancer cell diagnostics and therapeutics [1][2][3][4][5]. Biomedical applications of Quantum Dots (QDs) are focused on molecular imaging and biological sensing due to its optical properties. The size of QDs can be continuously tuned from 2 to 10 nm in diameter, which, after polymer encapsulation, generally increases to 5 -20 nm diminishing the toxicity. The QDs prepared in our lab have a diameter between 2 to 7 nm. Particles smaller than 5 nm can interact with the cells [2]. Some of the characteristics that distinguish QDs from the commonly used fluorophores are wider range of emission, narrow and more sharply defined emission peak, brighter emission and a higher signal to noise ratio compared with organic dyes [6]. In this paper we will show our progress in the study of the interaction of quantum dots in live cells for image and Raman spectroscopy applications. We will also show the results of the interaction of quantum dots with genomic DNA for diagnostic purposes.