Among plasmonic applications, photoacoustic (PA) generation stands out due to the emergence of nanoparticle mediated PA imaging in recent years [1]. For metallic nanoparticle mediated PA excitation, thermal effects are crucial contributors to the production of pressure waves. However, the fraction of heat converted into mechanical work has dependency on both the thermophysical constants of the medium and the nanoparticle. In this work, we investigate the effect of optimized metallic nanospheres in PA generation by nanosecond laser pulses (7ns, 10Hz) for sizes 5, 50 and 100nm at 530nm laser excitation. The results are in accordance with the theoretical prediction, based on the analysis of the NP temperature rise.
The presence of natural fluorescence in cellular structures and the use of fluorescent probes enables in vivo monitoring of biological and biophysical phenomena with high sensitivity and selectivity. In recent years, the development of on-chip lensless platforms has enabled the development of compact imaging devices. In this work we implement fluorescence detection on a contact, lensless CMOS-based image platform exploring a total internal reflection fluorescence configuration. Our fluorescent imaging platform has the potential to achieve micrometer-scale spatial resolution with a Field of View determined by the size of the semiconductor sensor (in our case 3.68mm x 2.76mm).
Highly sensitive thermometric methods are essential to the evaluation of nanoplatforms for thermal applications. In this study, the dual-beam thermal lens technique was introduced to assess the optically induced temperature changes in colloidal samples of gold nanoparticles. Dual-beam measurements were performed on a 0.05 mg/mL gold nanospheres (50 nm diameter) aqueous solution and the localized nanoparticle temperature were determined. The system was able to detect temperature variations as low as 10-2 °C, with 0.2 °C-1 sensitivity in the assessment of metallic nanoparticle colloids. Furthermore, thermal lens measurements also allowed the acquisition of the nanoparticle absorption cross-section value, regardless of its scattering properties.
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