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Simultaneous contribution of saturation in absorption and nonlinear photoacoustic effects in CuTPP under blue laser irradiation
摘要： The nonlinear optical responses of CuTPP are studied in toluene under the irradiation of a blue laser beam focused using a convergent lens. The z-scan setup is applied in order to determine nonlinear optical responses. Besides the nonlinear absorption response, which indicates reversed saturable absorption, intensity dependence photoacoustic waves are created in both hearable sound and ultrasonic waves. Hearable sound is recorded by a microphone and analyzed by Fourier transform analyzes in order to calculate the sonic frequencies. Because of the high absorption of dye molecules, a dilute solution is prepared to enhance transmittance from the cell to analyze profile of the passing beam. Diffraction rings pattern is observed with about 30 dense rings, in which the number of rings depends on the beam intensity that could be attributed to the higher frequency photoacoustic waves and the corresponding refractive grating induced by the waves. The nonlinear refraction of the solution is a simultaneous contribution of thermal lensing and photoacoustic effects, in addition to the saturation in absorption process which influences the nonlinear absorption behavior. This compound can be proposed as a good candidate in mode locking, Q-switching devises, and short pulse generators where we need a pattern from the activity of the saturable absorber at the cross section of the beam.
关键词： OPAZ-Scan,CuTPP,Photoacoustic,Saturation in absorption,Z-scan,Diffraction rings pattern
更新于2025-09-23 15:19:57
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Mass Accommodation Coefficients of Water on Organics from Complementary Photoacoustic and Light Scattering Measurements on Laser-Trapped Droplets
摘要： The mass accommodation coefficient, αM, describes the liquid?vapor evaporation and condensation kinetics at interface. In spite of numerous experimental efforts, reliable values of αM are still not available for many substances. Here, we present a novel experimental technique, photothermal single-particle spectroscopy (PSPS), that allows for a robust retrieval of mass accommodation coefficients from three simultaneous independent measurements. PSPS combines resonant photoacoustic absorption spectroscopy with modulated Mie scattering measurements on single particles. We study the mass transport of water on organic aerosol droplets that are optically trapped using counter-propagating tweezers. We find the mass accommodation coefficient of water on a pure model organic that is fully miscible with water to be 0.021 at 296 K and to decrease by more than an order of magnitude when the temperature increases to 309 K. The experimentally observed temperature dependence of αM shows an Arrhenius behavior. Furthermore, the water content of the droplets is found to have a profound effect on αM is observed at low water concentrations, while at elevated water concentrations, we observe a 5-fold increase in αM. The technique presented in this work has the potential to become a reliable method for the retrieval of αM values at liquid?vapor interfaces, which are essential for accurate global climate and pharmaceutical aerosol inhalation modeling, to mention but a few.
关键词： temperature dependence,photoacoustic absorption spectroscopy,optical trapping,water transport,organic aerosol droplets,modulated Mie scattering,mass accommodation coefficient,Arrhenius behavior,PSPS,photothermal single-particle spectroscopy
更新于2025-09-23 15:19:57
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Biologically Responsive Plasmonic Assemblies for Second Near-Infrared Window Photoacoustic Imaging-Guided Concurrent Chem-Immunotherapy
摘要： We developed dual biologically responsive nanogapped gold nanoparticle vesicles loaded with immune inhibitor and carried with anticancer polymeric prodrug for synergistic concurrent chemo-immunotherapy against primary and metastatic tumors, along with guided cargo release by photoacoustic (PA) imaging in the second near-infrared (NIR-II) window. The responsive vesicle was prepared by self-assembly of nanogapped gold nanoparticles (AuNNPs) grafted with poly(ethylene glycol) (PEG) and dual pH/GSH-responsive polyprodrug poly(SN38-co-4-vinyl pyridine) (termed as AuNNP@PEG/PSN38VP), showing intense PA signal in the NIR-II window. The effect of the rigidity of hydrophobic polymer PSN38VP on the assembly structures and the formation mechanism of AuNNP@SN38 Ve were elucidated by computational simulations. The immune inhibitor BLZ-945 was encapsulated into the vesicles, resulting in pH-responsive release of BLZ-945 for targeted immunotherapy, followed by the dissociation of the vesicles into single AuNNP@PEG/PSN38VP. The hydrophilic AuNNP@PEG/PSN38VP nanoparticles could penetrate deep into the tumor tissues, and release the anticancer drug SN38 under the reductive environment. PA signal in the NIR-II window in the deep tumor region was obtained. The BLZ-945 loaded vesicle enabled enhanced PA imaging-guided concurrent chemo-immunotherapy efficacy, inhibiting the growth of both primary tumors and metastatic tumors.
关键词： the second NIR window,amphiphilic nanogapped gold nanoparticles,polymeric prodrug,chemo-immunotherapy,photoacoustic imaging
更新于2025-09-23 15:19:57
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A novel single-cavity three-wavelength photoacoustic spectrometer for atmospheric aerosol research
摘要： The spectral light-absorbing behavior of carbonaceous aerosols varies depending on the chemical composition and structure of the particles. A new single-cavity three-wavelength photoacoustic spectrometer was developed and characterized for measuring absorption coefficients at three wavelengths across the visible spectral range. In laboratory studies, several types of soot with different organic content were generated by a diffusion flame burner and were investigated for changes in mass-specific absorption cross section (MAC) values, absorption and scattering ?ngstr?m exponents (αabs and αsca), and single scattering albedo (ω). By increasing the organic carbonaceous (OC) content of the aerosol from 50 to 90 % of the total carbonaceous mass, for 660 nm nearly no change of MAC was found with increasing OC content. In contrast, for 532 nm a significant increase, and for 445 nm a strong increase of MAC was found with increasing OC content of the aerosol. Depending on the OC content, the ?ngstr?m exponents of absorption and scattering as well as the single scattering albedo increased. These laboratory results were compared to a field study at a traffic-dominated urban site, which was also influenced by residential wood combustion. For this site a daily average value of αabs(445–660) of 1.9 was found.
关键词： light absorption,carbonaceous aerosols,organic carbon,photoacoustic spectrometer,black carbon,single scattering albedo,?ngstr?m exponents
更新于2025-09-23 15:19:57
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Operando Analysis of Electron Accumulation in Titanium(IV) Oxide Particles in an Aqueous Suspension Using a Photoacoustic Spectroscopic Method
摘要： The time course of photoabsorption of an aqueous suspension of titanium(IV) oxide (TiO2) particles was studied using photoacoustic (PA) spectroscopy. In the absence of an electron acceptor and the presence of an electron donor, ultraviolet (UV) irradiation increased PA intensity because photoabsorption of the suspension increased due to trivalent titanium (Ti3+) species generated by electron accumulation in TiO2 particles. In contrast, the addition of methylene blue (MB) as an acceptor caused a decrease in PA intensity, indicating that accumulated electrons were consumed by reduction of MB to colorless leuco-MB. The results for various TiO2 particles indicated that Ti3+ density is determined by this method. Moreover, the measurement can be applicable to quantitative operando analysis for accumulated electrons in a photocatalytic reaction.
关键词： photoacoustic spectroscopy,photocatalytic reaction,Ti3+ density,electron accumulation,titanium(IV) oxide
更新于2025-09-23 15:19:57
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Lifetime-weighted photoacoustic imaging
摘要： Photoacoustic (PA) imaging has been utilized to quantify the lifetime profile of exogenous agents using a series of pump-probe pulses with a varying time delay; however, current techniques typically lead to long acquisition times which are sensitive to motion and cause absorption or photobleaching. We introduce a technique called lifetime-weighted imaging, which uses only three laser pulses to preferentially weight signals from chromophores with long lifetimes (including exogenous contrast agents with triplet excited states such as methylene blue and porphyrins) while nulling chromophores with short picosecond- to nanosecond-scale lifetimes (including hemoglobin). This technique detects the PA signal from a probe pulse either with or without a pump pulse. By subtracting the probe-only signal from the pump-present probe signal, we effectively eliminate signals from chromophores with short lifetimes while preserving PA signals from chromophores with long-lifetimes. We demonstrate the oxygen-dependent lifetime of both methylene blue and porphyrin-lipids and demonstrate both ground-state recovery and excited-state lifetime-weighted imaging. Lifetime-weighted PA imaging may have applications in many molecular imaging application including: photodynamic therapy dosimetry guidance and oxygen sensing.
关键词： methylene blue,lifetime-weighted,photoacoustic microscopy,porhpyrins,lifetime
更新于2025-09-23 15:19:57
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Quantitative analysis on <i>in vivo</i> tumor-microvascular images from optical-resolution photoacoustic microscopy
摘要： Optical-resolution photoacoustic microscopy (OR-PAM) has been shown to be an excellent imaging modality for monitoring and study of tumor microvasculature. However, previous studies focused mainly on the normal tissues and did not quantify the tumor microvasculature. In this study, we present an in vivo OR-PAM imaging of the melanomas and hepatoma implanted in the mouse ear. We quantify the vessel growth by extracting the skeletons of both dense and thin branches of the tumor microvasculature obtained by Hessian matrix enhancement followed by improved two-step multistencils fast marching method. Compared to the previous methods of using OR-PAM for normal tissues, our method was more effective in extracting the binary vascular network in the tumor images and in obtaining the complete and continuous microvascular skeleton maps. Our demonstration of using OR-PAM in improving microvasculature of tumors and quantification of tumor growth would push deep this technology for the early diagnosis and treatment of cancers.
关键词： photoacoustic imaging,tumor neovascular network,quantitative analysis,optical-resolution photoacoustic microscopy
更新于2025-09-19 17:15:36
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NIR organic dyes based on phenazine-cyanine for photoacoustic imaging-guided photothermal therapy
摘要： As non-invasive diagnosis and therapy methods, photoacoustic (PA) imaging and photothermal therapy (PTT) have attracted extensive attention. Herein, two new acceptor–donor–acceptor near-infrared organic phenazine-cyanine dyes PH-1 and PH-2 were reported for photoacoustic imaging-guided photodynamic therapy. In the strong donor phenazine molecule, the electron-withdrawing indole salt unit was introduced for absorption to the near-infrared region. To improve water solubility, the two organic dyes were assembled with human serum albumin (HSA) to form nanoparticles of appropriate sizes, i.e., PH-1@HSA and PH-2@HSA, which showed excellent stability in both weakly acidic and weakly basic environments. Moreover, the results showed that PH-1@HSA and PH-2@HSA nanoparticles can effectively transform luminous energy to thermal energy in vitro and in vivo, and they can be utilized for PA imaging. Importantly, PH-1@HSA can accumulate in mice subcutaneous tumors by enhanced permeability and retention (EPR) and damage cancer tissues effectively.
关键词： NIR organic dyes,phenazine-cyanine,nanoparticles,photoacoustic imaging,photothermal therapy
更新于2025-09-19 17:15:36
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Optimized light delivery probe using ball lenses for co-registered photoacoustic and ultrasound endo-cavity subsurface imaging
摘要： An optimized hand-held photoacoustic and ultrasound probe suitable for endo-cavity tumor subsurface imaging was designed and evaluated. Compared to previous designs, the prototype probe, consisting of four 1 mm multi-mode optical fibers attached with 1.5 mm diameter ball-shaped fiber tips sandwiched between a transvaginal ultrasound transducer and a custom-made sheath, demonstrated a higher light output and better beam homogeneity on tissue subsurface. The output power and fluence profile were simulated for different design parameters. A camera recorded fluence profiles through calibrated intralipid solution at various imaging depths. The light delivery efficiency was experimentally compared with and without the ball lenses, based on ex-vivo imaging of human colorectal cancer and in-vivo imaging of a palmar vein proximal to the human wrist. The simulations and experiments demonstrated that ball-shaped fiber tip design can achieve homogeneous fluence distribution on tissue subsurface with acceptable light output efficiency, suggesting its clinical potential for in-vivo endo-cavity imaging.
关键词： Ball-shaped fiber tip,Photoacoustic imaging,Adenocarcinoma,Optimized light delivery probe
更新于2025-09-19 17:15:36
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Photoacoustic spectroscopy telemetry of airport dangerous goods
摘要： A novel photoacoustic spectroscopy telemetry method of detecting trace acetylene gas using a quartz tuning fork is reported. A 1532-nm CW-DFB, fiber-coupled diode laser with power of 12 mW was used as the excitation source while an astronomical telescope was used to collect laser light scattered on the surface of the detected object at a distance of 6 m and the photoacoustic spectroscopy of acetylene was performed. The detection results are consistent with the standard near-infrared absorption coefficient of acetylene. This study provides a new direction for research in photoacoustic spectroscopy telemetry. Future work will quantitatively analyze acetylene gas.
关键词： Photoacoustic spectroscopy,telemetry,acetylene,dangerous goods.
更新于2025-09-19 17:15:36