M.A.R.C. Alencar

Measuring milk fat content by random laser emission

The luminescence spectra of milk containing rhodamine 6G are shown to exhibit typical signatures of random lasing when excited with 532 nm laser pulses. Experiments carried out on whole and skim forms of two commercial brands of UHT milk, with fat volume concentrations ranging from 0 to 4%, presented lasing threshold values dependent on the fat concentration, suggesting that a random laser technique can be developed to monitor such important parameter.

Third-order nonlinear optical responses of colloidal Ag nanoparticles dispersed in BMI.BF 4 ionic liquid

The third-order nonlinear optical responses of tetrafluoroborate 1-n-butyl-methylimidazolium (BMI.BF4) and colloidal Ag nanoparticles dispersed in this medium were investigated. Hybrid organic-metallic colloids consisting of silver nanoparticles dispersed in BMI.BF4 were synthesized. Using the thermally managed Z-scan technique, the electronic contribution to the nonlinear refractive indexes of the BMI.BF4 and colloids with two different nanoparticles filling factors were measured, as well as the medias nonlinear absorption. The performance of these systems for all-optical switching was also evaluated. The obtained results indicate that these are promising candidates for the development of nonlinear optical applications.

A Comparative Study of Er3+, Er3+-Eu3+, Er3+-Tb3+, and Er3+-Eu3+-Tb3+Codoped Y2O3Nanoparticles as Optical Heaters

Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of and energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of 2H11/2 and 4S3/2 energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3+, Y2O3:Er3+-Eu3+, Y2O3:Er3+-Tb3+, and Y2O3:Er3+-Eu3+-Tb3+) synthesized via PVA-assisted sol-gel route. The samples were optically heated by an 800 nm CW diode laser, while the upconverted green emissions were used to measure their temperatures in real time. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia.

Spectroscopic and electrochemical study of CdTe nanocrystals capped with thiol mixtures

Here we report the aqueous synthesis of CdTe nanocrystals capped with 3-mercaptopropionic acid (MPA) and the evaluation of the effect of mixing different thiols with MPA on the spectroscopic and electrochemical properties. Additional ligands were cysteine (CYS) and glutathione (GSH). CYS and GSH produce opposite effects on the photoluminescence quantum yield (QY) with a decrease and increase in QY in comparison to MPA, respectively. All samples exhibited monoexponential photoluminescence decays indicating the presence of high-quality nanocrystals. Electrochemical measurements evidenced the presence of several redox peaks and allowed the calculation of the electrochemical band gaps, which were in agreement with the values estimated from absorption spectra and reflected differences in nanocrystal size.

Synthesis and characterization of multicolour fluorescent nanoparticles for latent fingerprint detection

In this study, we successfully developed Y2O3 nanoparticles doped with Tb3+ and Eu3+ ions to generate fluorescent images of latent fingerprints. The optical and structural characterization of the nanoparticles was carried out and the fluorescence mechanisms are discussed. In our studies, the developed nanoparticles were effective in producing fluorescent images of latent fingerprints in shades of green, red and yellow with high-contrast colour under ultraviolet lighting.

A comparative study of Er 3+ , Er 3+ -Eu 3+ , Er 3+ -Tb 3+ , and Er 3+ -Eu 3+ -Tb 3+ codoped Y 2 O 3 nanoparticles as optical heaters

Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of and energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of 2H11/2 and 4S3/2 energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3+, Y2O3:Er3+-Eu3+, Y2O3:Er3+-Tb3+, and Y2O3:Er3+-Eu3+-Tb3+) synthesized via PVA-assisted sol-gel route. The samples were optically heated by an 800 nm CW diode laser, while the upconverted green emissions were used to measure their temperatures in real time. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia.

A Comparative Study of Er3

Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of and energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3Fluorescence intensity ratio (FIR) technique, based on the thermal coupling of 2H11/2 and 4S3/2 energy levels of erbium ions, was used to study the optical heating behavior of rare earth doped yttrium oxide nanophosphors (Y2O3:Er3+, Y2O3:Er3+-Eu3+, Y2O3:Er3+-Tb3+, and Y2O3:Er3+-Eu3+-Tb3+) synthesized via PVA-assisted sol-gel route. The samples were optically heated by an 800 nm CW diode laser, while the upconverted green emissions were used to measure their temperatures in real time. The experimental results indicate that the studied nanoparticles are promising candidates to applications such as photothermal treatments and hyperthermia.