Temperature evaluation of colloidal nanoparticles by the thermal lens technique

Abstract

The use of highly sensitive thermometric methods is essential for the evaluation of nanoplatforms for photothermal therapy. In this study, the thermal lens technique was introduced to assess the optically induced temperature changes in colloidal samples of gold nanoparticles. Thermal lens measurements also allowed the acquisition of the nanoparticle absorption cross-section value, regardless of knowing the nanostructure scattering properties. The developed thermometric system exhibited 0.2 °C−1 sensitivity and was capable of measuring temperature variations of metallic colloidal samples with a resolution of 0.01 °C. Measuring colloidal temperature changes allows for the estimation of the localized temperature variation reached by each nanoheater, before thermalization of the excitation volume. Our results establish a practical and effective method to evaluate optically induced temperature changes on metallic colloids.

Numerical Simulation of the Whole Thermal Lensing Process with Z-Scan-Based Methods Using Gaussian Beams

“…We can now study Equation (7) or its analogous Equation (5) using the correct values for the maximum and the minimum. We have used a nonlinear least squares routine to fit the temporal behavior at these positions obtained with the exact numerical simulation as if they were experimental acquisitions.…”

“…Indeed, as already mentioned, Equation ( 6) is obtained following a rather rough calculation, so it is not surprising to see that its extremums also do not correspond exactly to the correct values that are obtained around V ≈ ±0.7, separated therefore by a distance ≈ √ 2. We can now study Equation (7) or its analogous Equation (5) using the correct values for the maximum and the minimum. We have used a nonlinear least squares routine to fit the temporal behavior at these positions obtained with the exact numerical simulation as if they were experimental acquisitions.…”

“…Many applications use the thermal lens (TL) principle as an ultrasensitive spectrophotometric readout [1] to characterize different physical phenomena, for example (recently found in the literature) to investigate molecular/particle dynamics [2], to measure the photothermal parameters of opaque solids [3], to understand thermal lensing effects using Z-scan-based methods at multiple laser repetition rates and multiple average powers [4,5], to study the effect of highly localized thermal gradients on the catastrophic optical damage process of high-power laser diodes [6], to evaluate optically induced temperature changes in colloidal samples for photothermal therapy [7], to quantify very low concentrations in solutions [8], and to image single light-absorbing nanoparticles by photothermal microscopy [9]. Recently, we have demonstrated experimentally the feasibility of extracting an image of the phase shift induced by TL and applying this method to map an inhomogeneous thin film doped with different concentrations of silver nanoparticles transversally [10].…”

Thermal lensing: outside of the lasing medium

“…The lowest detectable concentrations he has reported were of 0.22 and 0.08 μM of the compound for distilled and tap water, respectively. Pedrosa et al [97] have shown that using TLS, it is possible to measure temperature variations of 0.01 °C, at least in case of the gold-nanoparticle they studied dissolved in water. Recently, Sebastian et al [98] have shown that using TLS, it is possible to estimate the porosity of a nanomaterial composed of nano-particles.…”

Time-Resolved cw Thermal Z-scan for Nanoparticles Scattering Evaluation in Liquid Suspension

“…Moreover, Z-scan [ 10 ] based methods were performed at different regimes of excitation to understand the origin of the third-order nonlinear optical response [ 11 ] and the influence of the accumulated thermal effect, which can be an artifact in femtosecond closed-aperture Z-scan measurements [ 12 ]. Additionally, they can be used to evaluate optically-induced temperature changes in colloidal samples for photothermal therapy [ 13 ]. Already, we have experimentally demonstrated the feasibility of extracting an image of the phase shift induced by TL and applied this method to transversally map an inhomogeneous thin film doped with different concentrations of silver nanoparticles [ 14 ].…”