Synthesis of Gold Nanoparticles Using Amino Acids by Light Irradiation

The synthesis of nanoparticles is generally carried out by chemical reduction, which is effective but uses a number of toxic substances, making the process potentially harmful to the environment. Thus, as part of the search for environmentally friendly or green synthetic methods, this chapter aimed to present the synthesis of gold nanoparticles (AuNPs) using only HAuCl4, Milli-Q water, white light from a xenon lamp, and amino acids. A total of 21 amino acids were studied, and the shapes and sizes of the resultant nanoparticles were evaluated. The products were characterized by ultraviolet-visible (UV-Vis) and fluorescence spectroscopy, zeta potential measurements, and transmission electron microscopy. The synthesis of the AuNPs was successful with 18 amino acids, and the best results were obtained with aspartic acid, arginine, threonine, tryptophan, and valine. The nanoparticles were spherical and their sizes ranged from 5 to 100 nm. Changes in pH were required to improve the stability of the colloidal suspensions

Hypocrellin B, a perylenequinonoid pigment, and its complexes with lanthanide ions: optical characterization and enhancements in its photodynamic properties

Hypocrellins, perylenequinonoid pigments isolated from Hypocrella bambusae, are known photodynamic agents. They exhibit several advantages over the other photosensitizers, such as ready preparation, easy purification, low aggregation tendency, high singlet oxygen generation quantum yield and rapid metabolism in vivo. However, hypocrellins do not exhibit absorption at wavelengths longer than 600 nm, which limits their application for PDT. To solve this problem our efforts were focused towards modifying the properties of hypocrellin B. in this study, hypocrellin B complexes formed with the lanthanide ions lanthanum (La(3+)), terbium (Tb(3+)) and europium (Eu(3+)), using ethanol as solvent, had their optical properties characterized through spectroscopic methods. We observed that all the lanthanide ions change the HB molecular structure, since displacements in the bands were noted in both absorption and emission spectra. Different molar ratios between the HB and the lanthanide ions were tested, and it was verified that the complexes with 1 mol of HB for 2 mol of lanthanide ions present the larger red-shift comparatively to pure HB. We also determined the dimerization constants for these complexes. Under excitation at 532 nm the singlet oxygen generation quantum yields were estimated by the emission at 1270 nm, where singlet oxygen has a well known emission peak. It can be affirmed that such complexations were responsible for an improvement in the optical properties of the HB molecule, which suggests that these complexes may find a good application at in vivo studies.IPEN CNEN SP, Ctr Laser & Aplicacoes, São Paulo, BrazilUniv Fed Sao Paulo, ICAQF, Departamento de Ciências Exatas e da Terra, Diadema, BrazilWeb of Scienc

Green synthesis of silver nanoparticles with extract of Mimusops coriacea and light

Biological methods of nanoparticle synthesis using plant extracts have been suggested as promising ecofriendly alternative to chemical and physical methods. In this study, spherical silver nanoparticles (AgNP) were synthesized from the aqueous extract of Mimusops coriacea leaves at room temperature. To accelerate the reduction of Ag+ ions was used photoreduction process with Xenon lamp. A presence of resonant surface plasmon band at approximately 415 nm confirms the formation of the nanoparticles. The shape and size of the particles were determined by transmission electron microscopy images indicating sizes from 10 to 30 nm in diameter. Zeta potential indicates good stability. To identify the products for the reduction of Ag+ ions and stability of AgNP, FTIR analysis were performed. An intense reduction in chlorophyll fluorescence was observed after formation of the nanoparticles.CapesUniv Fed Sao Paulo, Inst Ciencias Ambientais Quim & Farmaceut, Dept Fis, Diadema, SP, BrazilUniv Fed Sao Paulo, Inst Ciencias Ambientais Quim & Farmaceut, Dept Fis, Diadema, SP, BrazilWeb of Scienc

Evaluation of Steady-State and Time-Resolved Fluorescence Spectroscopy as a Method for Assessing the Impact of Photo-Oxidation on Refined Soybean Oils

The type of material used in packaging, lighting, and storage time can impact food quality during storage. This study aimed to investigate the progress of photosensitized oxidation in refined soybean oil using steady-state and time-resolved fluorescence spectroscopy. The experiment was conducted through accelerated photo-oxidation with Light-Emitting Diode (LED) in samples stored for ten days at room temperature (26.0 ± 2.0 °C) in clear polyethylene terephthalate (PET) packaging of different colors and different transmission spectra in the UV and visible range. Emission spectra were obtained with excitation at 373, 405, and 500 nm, resulting in two main emission peaks: the first with maximum emission between 430 and 555 nm and the second at around 660 nm. Fluorescence decay curves were obtained with excitation at 340 and 405 nm. The results indicated that transparent PET bottles are not effective in protecting soybean oil from photosensitized oxidation under the studied conditions. Strong correlations were observed between fluorescence parameters and peroxide and conjugated diene values, indicators of lipid oxidation progress. Fluorescence spectroscopy has several advantages over traditional methods as it is a simple, fast, low-cost, and low-waste technique

Application of Fluorescence to the Study of Crude Petroleum

Crude petroleum oils are complex mixtures of different compounds (mainly organic), which are obtained from an extensive range of different geological sources. The fluorescence of crude petroleum oils derives largely from the aromatic hydrocarbon fraction, and this fluorescence emission is strongly influenced by the chemical composition (e.g., fluorophore and quencher concentrations) and physical characteristics (e.g., viscosity and optical density) of the oil. The fluorescence spectroscopy (FS) is increasingly used in petroleum technology due the availability of better optical detection techniques, because FS offers high sensitivity, good diagnostic potential, and relatively simple instrumentation. In this work we analyzed crude petroleum at different dilution in Nujol, a transparent mineral oil. The main objective of this work was to verify the possibility to measure crude oil emission spectroscopic without use of volatile solvents. The mixtures of nujol with different -crude oil concentrations were measured with a 10 mm optical path cuvette thus simplifying the fluorescence spectroscopy signal detection. The emission spectra were obtained by exciting the samples with a 400 W Xenon lamp at 350 nm, 450 nm and 532 nm. The emissions of the samples were collected perpendicularly with the excitation axis.CAPESFAPESPPETROBRA

Eugenia uniflora L. Silver and Gold Nanoparticle Synthesis, Characterization, and Evaluation of the Photoreduction Process in Antimicrobial Activities

Eugenia uniflora linnaeus, known as Brazilian cherry, is widely distributed in Brazil, Argentina, Uruguay, and Paraguay. E. uniflora L. extracts contain phenolic compounds, such as flavonoids, tannins, triterpenes, and sesquiterpenes. The antimicrobial action of essential oils has been attributed to their compositions of bioactive compounds, such as sesquiterpenes. In this paper, the fruit extract of E. uniflora was used to synthesize silver and gold nanoparticles. The nanoparticles were characterized by UV–Vis, transmission electron microscopy, elemental analysis, FTIR, and Zeta potential measurement. The silver and gold nanoparticles prepared with fruit extracts presented sizes of ~32 nm and 11 nm (diameter), respectively, and Zeta potentials of −22 mV and −14 mV. The antimicrobial tests were performed with Gram-negative and Gram-positive bacteria and Candida albicans. The growth inhibition of EuAgNPs prepared with and without photoreduction showed the important functional groups in the antimicrobial activity