Optoacoustic Conversion in Suspensions: The Competition of Mechanisms and Statistical Characteristics

Size-dependent effect of gold nanospheres on the acoustic pressure pulses from laser-irradiated suspensions

“…S1S3. undergoes a phase transition from liquid to vapor [7][8][9][10][11][12][13][14][15][16][17]; this is out of our scope in the present study.…”

“…Subsequently, a vapor layer appears on the surface of every NP to undergo rapid expansion, thus giving rise to an effective photoacoustic signal. This cavitation-induced enhancement of the photoacoustic signal at high laser fluence has been investigated in several experimental and theoretical studies [7][8][9][10][11][12][13][14][15][16][17], the principal focus of which was placed on direct observations and theoretical descriptions of bubble formation around heated particles and the resultant enhanced amplitude of the acoustic signal. On the other hand, very few studies have reported experimental results and physical modeling in the case of low-level laser irradiation that help us to better understand the fundamentals of the acoustic signal resulting from the thermoacoustic response of the heated NPs and heated host liquid in the absence of cavitation, except for the following studies.…”

Acoustic pressure pulses from laser-irradiated suspensions containing gold nanospheres in water: Experimental and theoretical study

“…Let us consider the case of low laser fluence, where the photoacoustic pressure observed from a laser-irradiated suspension containing NPs increases linearly with the laser fluence [31,[38][39][40][41][42]. If the laser fluence exceeds a threshold, the photoacoustic pressure experiences a sharp nonlinear increase, where the water layer adjacent to heated metal NPs undergoes a phase transition from liquid to vapor [31,32,[38][39][40][41][42][43][44][45][46][47][48]; this is out of our scope in the present study. It should be pointed out that the theoretical description given in this section is not limited to the spherical particles, but applicable to the particles with arbitrary shapes in principle.…”

Optical wavelength dependence of photoacoustic signal of gold nanofluid

“…Previous works demonstrated that adding exogenous agents in the biological tissue can enhance PA contrast [7] , [8] , [9] , [10] , [11] . In particular, noble metal nanoparticles have been used as exogenous agents to enhance the PA contrast in imaging applications [12] , [13] , [14] , [15] .…”

“…Indeed, several works have been devoted to modeling the PA response of liquid-embedded nanoparticles, somehow accounting for a T-dependent α wat and/or the presence of a TBC [ [8] , [9] , [10] , [11] , 14 ]. Calasso et al [34] developed an analytical expression for the pressure field, under the assumption of heat deposited at a point in space.…”