Photoacoustic Technology Research Articles

Trace ethane sensor using an economic midinfrared light-emitting diode

Due to the lack of an economic midinfrared laser, especially wavelength around 3 μm, light sources are critical to trace gas sensing for the gases without absorption in the near-infrared zone. We present a trace ethane photoacoustic (PA) sensor using a midinfrared light-emitting diode (MIR LED). MIR LEDs are very attractive sources for PA technology since they are relatively high power spectral density, easy modulation, low power consumption, and low cost. The proposed PA system with a 3.36-μm MIR LED shows good linearity to ethane concentration and reaches a detection limit of 10 parts per million by volume easily. Ideas of further enhancement of the sensitivity are discussed.

Photo-acoustic technology applied to ppb level NO<sub>2</sub> detection by using low power blue diode laser

Photo-acoustic technology based on a low power blue diode laser for measuring the ppb level NO<sub>2</sub> is presented in this paper. A low-cost NO<sub>2</sub> measurement system based on traditional photo-acoustic technology is established. The 405 nm blue diode laser with an external modulation is used as a light source. The central wavelength of the laser is 403.56 nm, the half-peak full width is 0.84 nm, and the power is 65.3 mW. The effective absorption cross section of NO<sub>2</sub> is obtained, and the interference of the water vapor and other trace gasisinvestigated. The resonant frequency is tested to be 1.35 kHz by frequency scanning fitting. An internally polished and coated poly tetra fluoroethylene aluminum cylindrical cavity is used as a photo-acoustic resonator (the inner diameter is 8 mm and the length is 120 mm). The influence factors caused by cavity parameters, optical windows and power supply are studied. The system is optimized to reduce background noise and improve signal-to-noise ratio. Then the noise signal is dropped to 0.02 <inline-formula><tex-math id="M4">\begin{document}${\text{μV}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M4.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M4.png"/></alternatives></inline-formula>. An additional buffer chamber is integrated on the original buffer chamber to form a two-level buffer. The two-stage buffer structure significantly suppresses the effects of airflow noise and improves the system stability. The slope of the calibration curve of the system after linear fitting is 0.016 <inline-formula><tex-math id="M5">\begin{document}${\text{μV/ppb}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M5.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M5.png"/></alternatives></inline-formula>, and R<sup>2</sup> is 0.998. The NO<sub>2</sub> detection limit of system is 2 ppb (3<inline-formula><tex-math id="M6">\begin{document}$\sigma$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M6.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20182262_M6.png"/></alternatives></inline-formula>) with an average time of 60 s. To verify the results of the system, a diode laser cavity ring-down spectroscopy system (CRDS system, using a 409 nm the diode laser, with a system detection limit of 6.6 × 10<sup>–1</sup>) is used to measure ambient NO<sub>2</sub> simultaneouslyon Lake Dong-Pu in western Hefei, Anhui Province, China. During the experiment, the measured NO<sub>2</sub> concentration ranges from 8 to 30 ppb, with an average concentration of 20.8 ppb. The results of two systems have good consistency:alinear fitting slope of 0.94 ± 0.009, an intercept of 1.89 ± 0.18 and acorrelation coefficient of 0.87. The experimental results show that the system can realize the low-cost on-line detection of the ppb level NO<sub>2</sub>, and it can also be used for the real-time detection of NO<sub>2</sub> concentration field.

Enabling fast and high quality LED photoacoustic imaging: a recurrent neural networks based approach.

Photoacoustic (PA) techniques have shown promise in the imaging of tissue chromophores and exogenous contrast agents in various clinical applications. However, the key drawback of current PA technology is its dependence on a complex and hazardous laser system for the excitation of a tissue sample. Although light-emitting diodes (LED) have the potential to replace the laser, the image quality of an LED-based system is severely corrupted due to the low output power of LED elements. The current standard way to improve the quality is to increase the scanning time, which leads to a reduction in the imaging speed and makes the images prone to motion artifacts. To address the challenges of longer scanning time and poor image quality, in this work we present a deep neural networks based approach that exploits the temporal information in PA images using a recurrent neural network. We train our network using 32 phantom experiments; on the test set of 30 phantom experiments, we achieve a gain in the frame rate of 8 times with a mean peak-signal-to-noise-ratio of 35.4 dB compared to the standard technique.

Interstitial assessment of aggressive prostate cancer by physio-chemical photoacoustics: An ex vivo study with intact human prostates.

Transrectal ultrasound (TRUS)-guided biopsy is the standard procedure for evaluating the presence and aggressiveness of prostate cancer. TRUS biopsy involves tissue removal, and suffers from low core yield as well as high false negative rate. A less invasive and more accurate diagnostic procedure for prostate cancer is therefore highly desired. Combining the optical sensitivity and ultrasonic resolution to resolve the spatial distribution of the major molecular components in tissue, photoacoustic (PA) technology could be an alternative approach for the diagnosis of prostate cancer. The purpose of this study was to examine the feasibility of identifying aggressive prostate cancer using interstitial PA measurements. Seventeen patients with prebiopsy magnetic resonance imaging (MRI), TRUS biopsies, and planned prostatectomies were enrolled in this study. The interstitial PA measurements were achieved using our recently developed needle PA probe, which was inserted into the ex vivo prostates in the fashion of a biopsy needle. A total of 70 interstitial PA measurements were acquired. The PA measurements were quantified by a previously established PA physio-chemical analysis (PAPCA) method. The histology has confirmed the nonaggressive and aggressive cancerous conditions at the insertion locations. The diagnostic accuracy was also compared to that provided by the prebiopsy MRI. The quantitative study shows significant differences between the individual parameters of the nonaggressive and the aggressive cancerous regions (P < 0.005). Multivariate analysis of the quantitative features achieved a diagnostic accuracy of 78.6% for differentiating nonaggressive and aggressive prostate cancer tissues. The proposed procedure has shown promises in the diagnosis of aggressive prostate cancer.

Highly Sensitive MoS2\u2013Indocyanine Green Hybrid for Photoacoustic Imaging of Orthotopic Brain Glioma at Deep Site

Photoacoustic technology in combination with molecular imaging is a highly effective method for accurately diagnosing brain glioma. For glioma detection at a deeper site, contrast agents with higher photoacoustic imaging sensitivity are needed. Herein, we report a MoS2–ICG hybrid with indocyanine green (ICG) conjugated to the surface of MoS2 nanosheets. The hybrid significantly enhanced photoacoustic imaging sensitivity compared to MoS2 nanosheets. This conjugation results in remarkably high optical absorbance across a broad near-infrared spectrum, redshifting of the ICG absorption peak and photothermal/photoacoustic conversion efficiency enhancement of ICG. A tumor mass of 3.5 mm beneath the mouse scalp was clearly visualized by using MoS2–ICG as a contrast agent for the in vivo photoacoustic imaging of orthotopic glioma, which is nearly twofold deeper than the tumors imaged in our previous report using MoS2 nanosheet. Thus, combined with its good stability and high biocompatibility, the MoS2–ICG hybrid developed in this study has a great potential for high-efficiency tumor molecular imaging in translational medicine.

Multimodal Intravascular Photoacoustic and Ultrasound Imaging.

The rupture of atherosclerotic plaques is the leading cause of death in developed countries. Early identification of vulnerable plaque is the essential step in preventing acute coronary events. Intravascular photoacoustic (IVPA) technology is able to visualize chemical composition of atherosclerotic plaque with high specificity and sensitivity. Integrated with intravascular ultrasound (IVUS) imaging, this multimodal intravascular IVPA/IVUS imaging technology is able to provide both structural and chemical compositions of arterial walls for detecting and characterizing atherosclerotic plaques. In this paper, we present representative multimodal IVPA/IVUS imaging systems and discuss current scientific innovations, potential limitations, and prospective improvements for characterization of coronary atherosclerosis.

Abstract P300: Fetal Status Evaluation Using Photoacoustics and 3D Power Doppler Ultrasound

Pregnancy complications can seriously impact fetal well-being. However the tools used for the evaluation of fetal oxygenation in clinic are limited to the monitoring of fetal heart rate or invasive techniques (fetal scalp pH and PO 2 ). Therefore, the development of methods enabling accurate, non-invasive and in real-time assessment of fetal status throughout pregnancy is warranted. In this study we tested the combination of photoacoustic imaging (PAI) and 3D power Doppler for the assessment of fetal distress. PAI combines optical contrast of photoacoustic laser technology with high spatial resolution of ultrasound. Power Doppler is a sensitive technique for the detection of blood flow. We hypothesize that a combination of PAI with 3D power Doppler can non-invasively and in real time establish fetal oxygenation, volume, and tissue vascularity. Pregnant C57Bl/6 mice were infused with nitric oxide synthase inhibitor, L-NAME via osmotic minipumps (50 mg/kg/day; days 11 to 14 of gestation) to induce the hypertensive phenotype. At day 14 of gestation, systolic blood pressures were higher in L-NAME-treated vs. untreated C57Bl/6 mice although these values did not reach hypertensive levels (90.8±3.1 vs. 104.4±3.7 mmHg, p&lt;0.05, n=4-5). Fetal weights were lower in the L-NAME-infused mice versus controls (0.12±0.01 vs. 0.17±0.01 g fetal weight per cm tibia length, p&lt;0.05, n=5-6). Fetal liver sO2 was lower in L-NAME-infused mice (47.5±2.1 vs. 56.1±1.6 %, n=4, p&lt;0.05), while no differences were found in fetal brain sO2. Total fetal volume was lower in L-NAME-treated mice (213.8±26.5 vs. 399±45.1 %, n=5, p&lt;0.05) and positively correlated with fetal body weights obtained postmortem in study groups. Fetal tissue vascularity was also lower in L-NAME-infused mice possibly due to limited vascular branching or blood flow (40.8±1.5 vs. 47.7±1.8%, p&lt;0.05). These changes were associated with a compensatory increase in fetal heart rate in L-NAME-treated mice (170.7±9.1 vs. 135.8±5.7 %, p&lt;0.05). We conclude that a combination of PAI with 3D power Doppler provides valuable information about fetal oxygenation and growth in association with tissue vascularity thus permitting non-invasive, in real-time analysis of fetal well-being.

Photoacoustic Drug Delivery.

Photoacoustic (PA) technology holds great potential in clinical translation as a new non-invasive bioimaging modality. In contrast to conventional optical imaging, PA imaging (PAI) enables higher resolution imaging with deeper imaging depth. Besides applications for diagnosis, PA has also been extended to theranostic applications. The guidance of PAI facilitates remotely controlled drug delivery. This review focuses on the recent development of PAI-mediated drug delivery systems. We provide an overview of the design of different PAI agents for drug delivery. The challenges and further opportunities regarding PA therapy are also discussed.

Biomedical photoacoustics: fundamentals, instrumentation and perspectives on nanomedicine.

Photoacoustic imaging (PAI) is an integrated biomedical imaging modality which combines the advantages of acoustic deep penetration and optical high sensitivity. It can provide functional and structural images with satisfactory resolution and contrast which could provide abundant pathological information for disease-oriented diagnosis. Therefore, it has found vast applications so far and become a powerful tool of precision nanomedicine. However, the investigation of PAI-based imaging nanomaterials is still in its infancy. This perspective article aims to summarize the developments in photoacoustic technologies and instrumentations in the past years, and more importantly, present a bright outlook for advanced PAI-based imaging nanomaterials as well as their emerging biomedical applications in nanomedicine. Current challenges and bottleneck issues have also been discussed and elucidated in this article to bring them to the attention of the readership.

Real-time three-dimensional visualization of blood vessels and its condition, based on photoacoustic technology

In 2014, the Japanese Government created the new innovation funding program, called “ImPACT; Impulsing PAradigm Change through disruptive Technologies” and established in the Council for Science, Technology and Innovation (CSTI), the Cabinet Office. ImPACT consists of 16 programs and its period is for 5 years (JFY2014-2018). One of ImPACT is this program; Innovative Visualization Technology to Lead to Creation of a New Growth Industry. The goal of this program is to develop the technologies for real-time 3D photoacoustic imaging of blood vessels in the human body and the physical properties of substances, and then demonstrate the value of applications in medical, healthcare, and cosmetic fields. The configuration of the program consists of six projects: “Visualization and measurement technology,” “Tunable laser technology,” “Ultrasound sensor technology,” “Wide-field visualization system” and “Micro-visualization system” for the achievement of real-time 3D visualization, and “Demonstration of value”for demonstrating the value of applications. Six research institutions and six companies will work together for a common goal. I will present the targets and strategies of the program and show recent research results.

Abstract 029: Photoacoustic Imaging - Novel In Vivo Quantification of Placental Hypoxia in a Mouse Model of Hypertensive Pregnancy

Placental hypoxia/ischemia induces abnormal maternal and neonatal outcomes including preeclampsia and intrauterine growth restriction (IUGR). The ability to accurately determine placental oxygenation in a non-invasive way and in real-time is highly important during pregnancy as it may allow for the early diagnosis of IUGR and preeclampsia. Photoacoustic imaging (PA) is a novel preclinical and emerging clinical tool that combines optical contrast of photoacoustic laser technology with high spatial resolution of ultrasound. PA measures tissue oxygen saturation (sO2) that reflects differences in absorption spectra for oxygenated and deoxygenated hemoglobin. By using photoacoustic features of VEVO LAZR high resolution ultrasound system (VisualSonics) in a three-dimensional mode we investigated the sensitivity and accuracy of PA for placental oxygenation in C57Bl/6 mice at day 14 of gestation. Furthermore, since nitric oxide deficiency is associated with upregulation of circulatory hypoxia markers, C57Bl/6 mice were chronically treated with the nitric oxide inhibitor, L-NAME via osmotic minipumps (50 mg/kg/day; days 13 to 18 of gestation). The comparisons between scanned vs. not scanned uteroplacental units showed that PA had no effect on fetal (scanned: 0.028±0.001 vs. not scanned: 0.03±0.001 g/maternal body weight; p&gt;0.05) or placental (scanned: 0.002±0.003 vs. not scanned: 0.002±0.002 g/maternal body weight; p&gt;0.05) weights in C57Bl/6 mice. Changing inhaled O2 from 100- to 20% resulted on average in 12.5% reduction in total placental sO2. Systolic blood pressures were higher in L-NAME-treated vs. C57Bl/6 mice (215.8±0.8 vs. sham 99.3±4.4 mmHg; p&lt;0.05). L-NAME infusion decreased sO2 in all areas of the placenta: labyrinth (73.6±0.97 vs. 58.6±3.4%, p&lt;0.05), mesometrial triangle (63.0±2.0 vs. 48.9±1.0%, p&lt;0.05), and total placenta (68.2±1.7 vs. 54.4±2.2%, p&lt;0.05). Placental labyrinth had higher sO2 vs. mesometrial triangle area in both L-NAME infused (58.6±3.4 vs. 48.9±1.0%, p&lt;0.05) and in C57Bl/6 (73.6±0.97 vs. 63.0±2.0%, p&lt;0.05) mice reflecting elaborate branching morphology of the labyrinth. Our data suggest that PA imaging can detect regional differences in placental sO2 non-invasively and at different physiological states.

Photoacoustic Compound Fire Alarm System for Detecting Particles and Carbon Monoxide in Smoke

In view of the high sensitivity and high selectivity of photoacoustic technology, a compound fire alarm system used for detecting smoke particles and carbon monoxide was designed on the basis of the photoacoustic spectrometry principle. The system uses an infrared laser with a central wavelength of 1579 nm as the light source, adopts wavelength modulation technology to modulate the continuous light source, and moves the inspection frequency to high frequency with lower noise by integrating harmonic detection technology, thus realizing a measurement of the photoacoustic signal. Concurrently, the system obtains the CO concentration and extinction coefficient of smoke particles via inversion by using the measured scattered light intensity data combined with a certain algorithm. A test was carried out on the system by using three small-scale experiments, namely, cotton rope smoldering fire, polyurethane foam fire and sandalwood smoldering fire. The results show that the CO gas concentrations and extinction coefficient of smoke particles produced by these three experiments are well detected. The CO detection limit of the system was 2.98 ppm. The test results also show that pure powder (used for simulating particles) or pure CO gas will not trigger the system alarm, so unnecessary alarms caused by traditional fire detectors can be avoided and the reliability of the fire alarm can be improved.

Photoacoustic and surface photovoltaic characteristics of L-Cysteine-capped ZnSe quantum dots with a core-shell structure

The study on photoelectronic characteristics of ZnSe quantum dots (QDs) is of significance for investigating its microelectronic structure and expanding its potential applications because ZnSe QD has low biologic toxicity. In the present paper, the surface photovoltaic and photoacoustic technologies, and laser Raman, X-ray diffraction, transmission electron microscopy and Foureier transform infrared spectroscopy spectrum are jointly used to probe the microstructures, the photoacoustic and surface photovoltaic characteristics of L-Cysteine-capped ZnSe QDs prepared by water-phase synthesis at different reflux temperatures. The results indicate that the ZnSe QDs with a mean grain size of about 3 nm has a core-shell ZnSe/ZnS/L-Cys structure, in which the sulfhydryl groups in ligand prefer reacting with Zn atom at the (220) face to form the ZnS shell layer between the core-ZnSe and ligand L-Cys. The results show that the QDs with n-type photovoltaic property display a wide range of surface photovoltaic response and weak photoacoustic signal upon the illumination of near ultraviolet to visible light as compared with others QDs with similar core-shell structures in II-VI group. Especially, the strong SPV response and the weak PA signal in a wavelength region of 350-550 nm imply that the photon energies in the range are almost all used to produce the surface photovoltaic (SPV) phenomenon instead of the thermal lattice vibration caused by non-radiative de-excitation process. This reveals the energy complementary relationship between the photoacoustic and the surface photovoltaic phenomena of the QDs. The PA signals appearing in a short wavelength range of 300-350 nm and the Raman peaks located in a high frequency ranges of 1120 cm-1, 1340 cm-1 and 1455 cm-1 are identified as relating closely to the multi-phonon vibration modes of ligand L-Cys. At low reflux temperature, the photoelectric threshold of the SPV response that relates to the core-ZnSe displays a red shift to a certain extent as compared with the bulk ZnSe. The narrowed bandgap may be attributed to quantum confinement effect of the QDs. In addition, the intensity of the SPV response that relates to the core-ZnSe gradually increases with the decrease of the reflux temperature. The results show that the above improved surface photovoltaic characteristics of the QDs may benefit from the reduced average grain size of the ZnSe QDs, thus causing its surface and small-size effects.

High-speed intravascular spectroscopic photoacoustic imaging at 1000 A-lines per second with a 0.9-mm diameter catheter.

Intravascular spectroscopic photoacoustic technology can image atherosclerotic plaque composition with high sensitivity and specificity, which is critical for identifying vulnerable plaques. Here, we designed and engineered a catheter of 0.9 mm in diameter for intravascular photoacoustic (IVPA) imaging, smaller than the critical size of 1 mm required for clinical translation. Further, a quasifocusing photoacoustic excitation scheme was developed for the catheter, producing well-detectable IVPA signals from stents and lipids with a laser energy as low as ~30 μJ/pulse. As a result, this design enabled the use of a low-energy, high-repetition rate, ns-pulsed optical parametric oscillator laser for high-speed spectroscopic IVPA imaging at both the 1.2-μm and 1.7-μm spectral bands for lipid detection. Specifically, for each wavelength, a 1-kHz IVPA A-line rate was achieved, ~100-fold faster than previously reported IVPA systems offering a similar wavelength tuning range. Using the system, spectroscopic IVPA imaging of peri-adventitial adipose tissue from a porcine aorta segment was demonstrated. The significantly improved imaging speed, together with the reduced catheter size and multiwavelength spectroscopic imaging ability, suggests that the developed high-speed IVPA technology is of great potential to be further translated for in vivo applications.

Biophysical evaluation and subjects’ clinical perception of serial PhotoAcoustic Technology pulse Q-switched Nd:YAG laser in Indonesian skin

Biophysical evaluation and subjects’ clinical perception of serial PhotoAcoustic Technology pulse Q-switched Nd:YAG laser in Indonesian skin

Targeted nanodiamonds as phenotype-specific photoacoustic contrast agents for breast cancer.

The aim is to develop irradiated nanodiamonds (INDs) as a molecularly targeted contrast agent for high-resolution and phenotype-specific detection of breast cancer with photoacoustic (PA) imaging. The surface of acid treated radiation-damaged nanodiamonds was grafted with PEG to improve its stability and circulation time in blood, followed by conjugation to an anti-HER2 peptide with a final nanoparticle size of approximately 92 nm. Immunocompetent mice bearing orthotopic HER2-positive or negative tumors were administered INDs and PA imaged using an 820-nm near-infrared laser. PA images demonstrated that INDs accumulate in tumors and completely delineated the entire tumor within 10 h. HER2 targeting significantly enhanced imaging of HER2-positive tumors. Pathological examination demonstrated INDs are nontoxic. PA technology is adaptable to low-cost bedside medicine, and with new contrast agents described herein, PA can achieve high-resolution (sub-mm) and phenotype-specific monitoring of cancer growth.

Noninvasive photoacoustic measurement of the composite indicator dilution curve for cardiac output estimation.

Recently, the measurement of indicator dilution curves using a photoacoustic (PA) technology was reported, which showed promising results on the noninvasive estimation of cardiac output (CO) that is an important hemodynamic parameter useful in various clinical situations. However, in clinical practice, measuring PA indicator dilution curves from an arterial blood vessel requires an ultrasound transducer array capable of focusing on the targeted artery. This causes several challenges on the clinical translation of the PA indicator dilution method, such as high sensor cost and complexity. In this paper, we theoretically derived that a composite PA indicator dilution curve simultaneously measured from both arterial and venous blood vessels can be used to estimate CO correctly. The ex-vivo and in-vivo experimental results with a flat ultrasound transducer verified the developed theory. We believe this new concept would overcome the main challenges on the clinical translation of the noninvasive PA indicator dilution technology.

Measurement of cardiac output by use of noninvasively measured transient hemodilution curves with photoacoustic technology

We present the theoretical basis and experimental verification for cardiac output measurements using noninvasively measured hemodilution curves afforded with an indicator dilution technique and the emerging photoacoustic technology. A photoacoustic system noninvasively tracks a transient hemodilution effect induced by a bolus of isotonic saline as an indicator. As a result, a photoacoustic indicator dilution curve is obtained, which allows to estimate cardiac output from the developed algorithm. The experiments with a porcine blood circulatory phantom system demonstrated the feasibility of this technology towards the development of a noninvasive cardiac output measurement system for patient monitoring.

Parameter Estimation of Photoacoustic Signal for Glucose Solutions Using Laplace Wavelet Correlation Filtering and Least Square Estimation

In photoacoustic (PA) technology, piezoelectrical transducer (PZT) is the most frequently used detector for the PA signal generated by weakly absorbing liquids. Although PZT has high sensitivity, its output signals are distorted and become exponentially damped sinusoidal signal [, which is a barrier to extract correct information of glucose. Therefore it is necessary to find a proper way to extract glucose information. In this paper, a method of parameter estimation based on Laplace wavelet correlation filtering and Least Square Estimation is proposed to extract the information of PA signals, which includes signal decomposition, fitting and glucose parameter extraction. The Laplace wavelet correlation filtering is introduced to decompose piezoelectrical signals into impulse responses of single mode subsystems [2], followed by a Least Square Estimator to fit PA signal and estimate parameters of the exponentially damped sinusoidal model [3]. Good agreement between the fitting model and the PA signal is obtained. Experiments are carried out on finding meaningful parameters indicating glucose among estimated parameters of the exponentially damped sinusoidal model.

Research of the Reactivity Photoacoustic Characteristics of PETN and HNS Induced by Laser

The reactivity photoacoustic technology was used to detect the laser induced photoacoustic spectroscopy characteristics of explosives (PETN and HNS). The results showed that: the reflectivity of pure PETN and HNS under laser irradiation was large and the photoacoustic signal was weak. After doping with carbon nanotubes (CNTs) and carbon black (CB), the reflectivity decreased. The photothermal conversion and the optical absorption coefficient rate increased and the photoacoustic signal enhanced. For the same sample, the intensity of the signal was proportional to the incident laser energy. For the same explosives and under the same doping amount, the photoacoustic signal of the CNTs doped sample is greater than that of the CB doped sample. For the same sample and the same dopant, the greater the amount of doping, the stronger the photoacoustic signal. There was optimum ignition energy. By using TG-DSC technology for thermal analysis of the samples, the results from the thermal analysis could explain the reactivity photoacoustic experiment.