Abstract

Generation of the photoacoustic effect through chemical reaction of particulate carbon in chemically reactive solutions is presented. Experiments are carried out using a Q-switched Nd:YAG laser to heat carbon nanoparticles, initiating chemical reaction which results in sound production. The amplitude of the photoacoustic signal from a carbon suspension in H2O2–H2O mixtures is shown to increase dramatically as the percentage of H2O2 in solution increases. Laser induced chemical generation of sonoluminescence in aqueous carbon suspensions is also reported. Following irradiation and chemical reaction, highly compressed gas bubbles are formed. The expansion of the gas bubble past its equilibrium diameter results in oscillation of the bubble diameter. Tens of μs after the initial formation of the bubble, sonoluminescence is found to take place on collapse of the bubble. Experiments show that the sonoluminescent intensity is increased by a factor of more than 10 as the external pressure is increased from 1 to 6 atm. The time of appearance of optical radiation following the initial firing of the laser is found to decrease with increasing external pressure as well.

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