We developed a pump-probe photothermal lens spectrophotometer that uses a broadband arc-lamp and a set of interference filters to provide tunable, nearly monochromatic radiation between 370 and 730 nm as the pump light source. This light is focused onto an absorbing sample, generating a photothermal lens of millimeter dimensions. A highly collimated monochromatic probe light from a low-power He-Ne laser interrogates the generated lens, yielding a photothermal signal proportional to the absorption of light. We measure the absorption spectra of scattering dye solutions using the device. We show that the spectra are not affected by the presence of scattering, confirming that the method only measures the absorption of light that results in generation of heat. By comparing the photothermal spectra with the usual absorption spectra determined using commercial transmission spectrophotometers, we estimate the quantum yield of scattering of the sample. We discuss applications of the device for spectroscopic characterization of samples such as blood and gold nanoparticles that exhibit a complex behavior upon interaction with light.
Spark plasma sintering (SPS) technique was used to densify 7 mol% yttria-stabilized zirconia (7YSZ) powder with Gd 2 O 3 -particles, at temperatures ranging between 1000 and 1200 • C. Fine dispersion of Gd 2 O 3 -particles into a full-densified matrix was achieved. Shrinkage and microstructure, as well as porosity were investigated. The fine Gd 2 O 3 -particles distributed into 7YSZ matrix have influence over the sintering consolidation and final microstructure. An increment in the spark plasma sintering temperature around 70 • C is detected when Gd 2 O 3 particles are present. The thermal characterization was performed using the photothermal infrared radiometry technique. Both thermal diffusivity and thermal conductivity display a similar sigmoidal (Boltzmann type) behavior with the Gd 2 O 3 concentration in the samples.
We present a method for measurement of the thermal diffusivity of metallic samples in the form of thin filaments, which is inspired in both the photothermal beam deflection and the shadowgraph techniques. The method utilizes the shadow projected by the sample when put against a collimated light source (a probe beam). The sample is then heated periodically by another light beam (the pump beam), giving rise to thermal waves, which propagate across it and through its surroundings. Changes in the refraction index of the surrounding media due to the heating distort the shadow. The periodical time evolution of the shadow is recorded by a FLIR SC2500 Infrared Camera and lock-in amplified in order to determine the sample´s thermal diffusivity by the well-known phase slope method.
We detect the absorption spectra of scattering dye solutions using a white light photothermal lens spectrophotometer. We estimate the quantum yield of scattering by comparing the obtained photothermal spectra with the usual absorbance spectra.
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