Study of spatial thermal distribution of gold nanourchins in saline by combined transverse probe beam deflection and beam wavefront sensor: biomedical implications

Abstract

Combined probe beam deflection (PBD) and wavefront sensor (WFS) technique are used to investigate the thermal distribution of gold nanourchins (GNU) in physiological saline (PS) using a low-power continuous NIR diode laser. Three different samples were prepared for the experiment: (S1) 0.5 mg/mL GNU only, (S2) 0.5 mL PS and 0.3 mL GNU, and (S3) 0.5 mL PS and 0.1 mL GNU. The laser transmission initially increases linearly as S3 > S2 > S1, but reaches a plateau and remains constant. The probe beam response in an adjective statistics process exhibited a stochastic behaviour at different positions and constant power in x- and y-directions. The beam view profiles showed a non-uniform intensity distribution and the addition of PS dramatically caused a blue shift indicating its cooling effect, S1 (20) warmer > S1(10) medium > S2 (20) cooler. S1 (10), S1 (20), and S2 (20) correspond to the samples irradiated with the laser power (mW) shown in the bracket. The peak-to-valley (PV) and root-mean-square (RMS) values demonstrated a non-linear intensity distribution during the scanning process. The greater PV values in deeper positions may well due to agglomeration, hence the sedimentation process. The Zernike coefficients with high absolute values represent the aberrations that cause the greatest distortion of the wavefront and found in the order of S2(20) > S1(10) > S1(20). This is consistent with PV wavefront slope and spatial period aberration relation. The opto-thermal coefficients were obtained as S2 (− 7.86 × 10−4) > S3: 0.5 mL PS and 0.1 ml GNU (− 6.3 × 10−4), respectively.