Photothermal Generation Research Articles

Photothermal Generation of Oxygen-Irrelevant Free Radicals with Simultaneous Suppression of Glutathione Synthesis for an Enhanced Photonic Thermodynamic Cancer Therapy.

Reactive oxygen species (ROS) as one kind of oxygen-dependent toxic free radical has been widely adopted in ROS-mediated therapies (RMT). However, two shackles, known as tumor hypoxia and high intratumor glutathione (GSH) levels, respectively, limit RMT as the former prevents ROS from generating, while the latter scavenges the ROS generated. Herein, we developed a novel nanoplatform to simultaneously overcome the two shackles by facile preparation of mesoporous carbon nanospheres (MCNs) with AIBI and raloxifene loaded inside as an initiator and inhibitor, respectively, and phase-change materials (PCMs) capped outside as gatekeepers. Upon 808 nm NIR light irradiation, the photothermal effect of MCNs melted PCMs causing the loaded AIBI and raloxifene to be released, during which the AIBI was further decomposed into oxygen-irrelevant radicals to kill cancer cells, while the raloxifene suppressed GSH synthesis, synergistically enabling an enhanced photonic thermodynamic cancer therapy.

Laser-induced photothermal generation of flexible and salt-resistant monolithic bilayer membranes for efficient solar desalination

Harvesting solar energy and generating steam through solar thermal energy are viable approaches with diverse applications such as power generation, desalination, and water purification. Particularly, for efficient and stable solar desalination, hierarchically porous materials are desired to enable the required multiple functionalities. However, high thermal/chemical energy required and time consumed remain roadblocks. In this study, a facile, fast, and scalable laser-induced photothermal method to achieve flexible monolithic bilayer sheets (MBS) of hierarchically porous graphitic carbon (HPGC) and polymeric foam for use in salt-resistant and flexible solar steam generators is reported. The MBS-based self-floating solar steam generator shows outstanding solar desalination performance with a solar thermal efficiency of 83.2% (1-sun) and a high salt-rejection ratio (99.9%). Efficient solar thermal energy transformation is achieved by the versatile multi-functionalities of the MBS, including broad-spectrum solar light absorption, heat localization, and capillary action. Anisotropic wetting properties of hydrophobic HPGC and hydrophilic polyimide (PI) foam effectively prevent salt accumulation on the HPGC surface. The salt-resistant MBS enable long-term stability for solar desalination with actual seawater. Our laser-based photothermal method has potential in the development of high-performance solar thermal systems with substantial cost reduction by scalable production of multiscale hierarchically structured materials from micro-structured polymers.

Aqueous Phase Synthesis of Cu2-x S Nanostructures and Their Photothermal Generation Study.

Size- and shape-dependent features of plasmonic nanocrystals govern the development of their applications. In the past decades, gold nanostructures, such as gold nanorods and nanoshells, have been well studied and applied for sensing, bioimaging, and photothermal generation. However, knowledge of copper chalcogenide, a new generation of plasmonic nanomaterials, is limited, especially about their preparation and size- and shape-dependent photothermal properties. In this work, controllable size and shape Cu2–xS nanocrystals (NCs) are synthesized by a facile aqueous route. Using low-molecular-weight polyethylenimine (PEI) as the reducing and capping agents, the size and shape of Cu2–xS NCs can be controlled with lengths from 6.5 to 46.5 nm and the aspect ratio from 2.2 to 7.5 by adjusting the concentration of PEI. The plasmonic peak of Cu2–xS experiences a redshift (from 1145 to 1369 nm) when the length increases from 6.5 to 44.5 nm. Under the irradiation of 1064 nm laser with 1.33 W/cm2, an excellent photothermal conversion rate (from 34.9 to 49.0%) is obtained. The characterization of Cu2–xS NCs is conducted with a UV–vis spectrometer, transmission electron microscopy, powder X-ray diffraction measurements, and 1064 nm laser.

Multifunctional Flexible Sensor Based on Laser-Induced Graphene.

The paper presents the design and fabrication of a low-cost and easy-to-fabricate laser-induced graphene sensor together with its implementation for multi-sensing applications. Laser-irradiation of commercial polymer film was applied for photo-thermal generation of graphene. The graphene patterned in an interdigitated shape was transferred onto Kapton sticky tape to form the electrodes of a capacitive sensor. The functionality of the sensor was validated by employing them in electrochemical and strain-sensing scenarios. Impedance spectroscopy was applied to investigate the response of the sensor. For the electrochemical sensing, different concentrations of sodium sulfate were prepared, and the fabricated sensor was used to detect the concentration differences. For the strain sensing, the sensor was deployed for monitoring of human joint movements and tactile sensing. The promising sensing results validating the applicability of the fabricated sensor for multiple sensing purposes are presented.

Natural melanin-loaded nanovesicles for near-infrared mediated tumor ablation by photothermal conversion

Photothermal therapy requires a biocompatible material to absorb near-infrared (NIR) light and generate sufficient heat. Herein, we suggest natural melanin-loaded nanovesicles (melasicles) as photothermal therapeutic agents (PTA) for NIR mediated cancer therapy in vivo. The mean size of these melasicles was 140 ± 15 nm. They showed excellent colloidal stability. After irradiation from 808 nm NIR laser at 1.5 W cm−2, the melasicles showed good photothermal conversion efficiencies both in vitro and in vivo. In drug release study, laser irradiation increased fluidity of vesicle membrane due to photothermal generation from melanin. Initial drug release in the laser irradiation group was higher than that in the no laser irradiation group. After injecting the melasicles into tail veins of CT-26 bearing mice, tumors were suppressed or eliminated after irradiation at 1.5 W cm−2 for 5 min once or twice. These results suggest that melasicles could be used as attractive PTA for cancer therapy and localized drug release.

NIR-controlled morphology transformation and pulsatile drug delivery based on multifunctional phototheranostic nanoparticles for photoacoustic imaging-guided photothermal-chemotherapy

Stimuli-responsive nanoparticles are focused to promote the pathological specificity and controlled therapeutic activation in biomedicine, but the multifunctional modulation remains challenging. Herein, size and morphology switchable phototheranostic nanoparticles are developed for photoacoustic (PA) imaging-guided photothermal-chemotherapy. Multifunctional polypyrrole (PPy) nanoparticles with the template of upper critical solution temperature (UCST) polymers are designed to achieve light-controlled pulsatile drug release and concurrent activation of photothermal therapy (PTT). Wherein the UCST-featured inner core is loaded with camptothecin (CPT), the outer corona is tethered with thermo-cleavable doxorubicin (DOX) prodrug and further in-situ coated with PPy, affording the resultant CPT@DOX-UCST/PPy nanoparticles. Upon 808 nm continuous laser illumination, significant heating generated from light-absorbable PPy results in DOX prodrug cleavage and considerable size swelling (∼125-fold), which in turn promotes simultaneous dual drug release, and thus triggering the combined therapeutic activation of PTT and chemotherapy. When laser is switched off, the discontinued photothermal generation makes the nanoparticle shrink back, thereby avoiding the leakage of CPT and DOX. In vivo experiments demonstrate the favorable tumor accumulation and prolonged tumor retention (>24 h) for long-term PA imaging-guided combination therapy. Current multifunctional nanoparticles integrated with light-controlled swelling/shrinking and synergistic therapeutic activation/silence represent a promising platform for precision cancer theranostics.

Prediction Model of Photo-thermal Power Generation Based on G (1,1) Optimization

In this paper, the photo-thermal power generation model is obtained by studying the operation process of solar radiation , light and thermal power generation equipment. By solving the gray model parameters by particle swarm optimization, a prediction model of light and heat generation based on G (1,1) optimization is proposed. In the case of example analysis, the amount of electricity generated by the solar radiation in the past few years was based on the photo-thermal power generation model, and the light and thermal power generation prediction model is used to obtain the photo-thermal power generation in the next few years. Photo-thermal power generation will provide data support for the planning of photo-thermal power generation, and it will also verify the reasonableness of the prediction model.

Enhanced near-infrared absorption and photo-thermal generation in black iron doped indium tin oxide

Band engineering of transparent semiconductors, such as TiO2, SnO2, has recently been attempted to become black colour in order to increase photocatalytic efficiency in the visible and near infrared ranges. Here, we investigated a previously-neglected property in black oxides by using the example of iron doped indium tin oxide nanoparticles: the photo-thermal effect in the visible and near-infrared ranges. We found a significant enhancement of the photo-thermal generation in the near-infrared biological window that is due to photon absorption, with no significant contribution from surface plasmon resonance. This allows independent magnetic functionalization of the particles by iron doping. These particles may be used for in-vivo cancer treatment where heat is photo-termally generated, while keeping the magnetism as a mean for remote manipulation through permanent magnets.

White-Light-Induced Collective Heating of Gold Nanocomposite/Bombyx mori Silk Thin Films with Ultrahigh Broadband Absorbance.

This paper describes a systematic investigation of the phenomenon of white-light-induced heating in silk fibroin films embedded with gold nanoparticles (Au NPs). The Au NPs functioned to develop an ultrahigh broadband absorber, allowing white light to be used as a source for photothermal generation. With an increase of the Au content in the composite films, the absorbance was enhanced significantly around the localized surface plasmon resonance (LSPR) wavelength, while non-LSPR wavelengths were also increased dramatically. The greater amount of absorbed light increased the rate of photoheating. The optimized composite film exhibited ultrahigh absorbances of approximately 95% over the spectral range from 350 to 750 nm, with moderate absorbances (>60%) at longer wavelengths (750-1000 nm). As a result, the composite film absorbed almost all of the incident light and, accordingly, converted this optical energy to local heat. Therefore, significant temperature increases (ca. 100 °C) were readily obtained when we irradiated the composite film under a light-emitting diode or halogen lamp. Moreover, such composite films displayed linear light-to-heat responses with respect to the light intensity, as well as great photothermal stability. A broadband absorptive film coated on a simple Al/Si Schottky diode displayed a linear, significant, stable photo-thermo-electronic effect in response to varying the light intensity.

Theranostics dye integrated zwitterionic polymer for in vitro and in vivo photothermal cancer therapy

We report that combining diagnostic bioimaging fluorescence and photothermal therapeutic (PTT) within a single nano-platform can be used to simultaneously and accurately diagnose and ablate tumors. The integrated pH with thermo-responsive poly(dimethylaminoethyl methacrylate-co-N-isopropylacylamide) sulfobetaine (PDNS) backbone carrier retained optical bioimaging from boron dipyrromethane (BODIPY) and sufficient photothermal generation is ensured by integrating IR825 within this same theranostic system. BODIPY (fluorescence dye) with IR825 (NIR dye) quaternized zwitterionic PDNS (IR825/BOD-PDNS) showed pH and temperature-dependent fluorescence emissions and NIR irradiated in vitro photothermal toxicity to cancer cells. This fluorescence platform maximizes the antitumor response, monitors treatment condition, and successfully ablates tumors with thermal energy.

Imaging Local Heating and Thermal Diffusion of Nanomaterials with Plasmonic Thermal Microscopy

Measuring local heat generation and dissipation in nanomaterials is critical for understanding the basic properties and developing applications of nanomaterials, including photothermal therapy and joule heating of nanoelectronics. Several technologies have been developed to probe local temperature distributions in nanomaterials, but a sensitive thermal imaging technology with high temporal and spatial resolution is still lacking. Here, we describe plasmonic thermal microscopy (PTM) to image local heat generation and diffusion from nanostructures in biologically relevant aqueous solutions. We demonstrate that PTM can detect local temperature change as small as 6 mK with temporal resolution of 10 μs and spatial resolution of submicrons (diffraction limit). With PTM, we have successfully imaged photothermal generation from single nanoparticles and graphene pieces, studied spatiotemporal distribution of temperature surrounding a heated nanoparticle, and observed heating at defect sites in graphene. We further show that the PTM images are in quantitative agreement with theoretical simulations based on heat transport theories.

Picosecond-to-nanosecond dynamics of plasmonic nanobubbles from pump-probe spectral measurements of aqueous colloidal gold nanoparticles.

The photothermal generation of nanoscale vapor bubbles around noble metal nanoparticles is of significant interest, not only in understanding the underlying mechanisms responsible for photothermal effects, but also to optimize photothermal effects in applications such as photothermal cancer therapies. Here, we describe the dynamics in the 400-900 nm regime of the formation and evolution of nanobubbles around colloidal gold nanoparticles using picosecond pump-probe optical measurements. From excitations of 20-150 nm colloidal gold nanoparticles with a 355 nm, 15 ps laser, time-dependent optical extinction signals corresponding to nanobubble formation were recorded. The extinction spectra associated with nanobubbles of different diameters were simulated by considering a concentric spherical core-shell model within the Mie theory framework. In the simulations, we assumed an increase in particle temperature. From temporal changes in the experimental data of transient extinctions, we estimated the temporal evolution of the nanobubble diameter. Corrections to bubble-free temperature effects on the transient extinction decays were applied in these experiments by suppressing bubble formation using pressures as high as 60 MPa. The results of this study suggest that the nanobubbles generated around a 60 nm-diameter gold nanoparticle using a fluence of 5.2 mJ cm(-2) had a maximum diameter of 260 ± 40 nm, and a lifetime of approximately 10 ns. The combination of fast transient extinction spectral measurements and spectral simulations provides insights into plasmonic nanobubble dynamics.

Photothermal response of extracellular solution to the near-infrared laser irradiation determined by its optical absorption properties

Photothermal effect has been proved to mediate the interaction of near-infrared laser with biological tissue. However, the generation and transformation mechanism of the photothermal effect is still unclear. In this paper, we combine a patch clamp technique with the laser simulation to figure out the chromophores, which are responsible for the photothermal effect generation. This method is based on the fact that temperature dependence of solution can be measured as resistance changes. A dual-wavelength infrared light irradiating the open pipette in extracellular solution is designed to study the relation between the photothermal effect and the absorption property of solution. The principle is based on that the nearly ten times difference in the magnitude of the optical absorption coefficient in water (0.502 cm-1 at 980 nm and 0.0378 cm-1 at 845 nm), makes the corresponding proportional absorption-driven temperature rise. The photothermal effect in laser-tissue interaction can be assessed in two stages: the establishment and the dissipation of the temperature rise. In the establishment stage, an open pipette method is employed to measure the temperature rise by fabricating a glass pipette which is filled with electrolyte solution. In the dissipation stage, the electrophysiological function of a living neuron cell is studied based on a patch clamp. Theoretical calculation and experimental results show that the optical absorption properties of solution determine the photothermal effect. The results can be used to study the photothermal effect in laser-tissue interaction.

Visualizing the Effect of Gold Nanocages on Absorption, Imaging, and Lower Critical Solution Temperature Phase Transition of Individual Poly(NiPAM)-Based Hydrogel Particles by Near Infrared Multispectral Imaging Microscopy

We have successfully utilized the near-infrared multispectral imaging (NIR-MSI) microscope to observe and measure directly images and spectra of individual hydrogel particles alone or with added gold nanocages (GNs). The NIR-MSI is suited for this task because it can simultaneously record spectral and spatial information of a sample with high sensitivity (single pixel resolution) and high spatial resolution (∼0.9 μm/pixel). Because both images and spectra of the individual particles can be directly and simultaneously measured by the microscope, it is possible to detect any changes in the spectroscopic properties and/or nature (size, volume) of individual hydrogel particles induced by external factors (e.g., temperature and/or pH). These features make it possible to determine lower critical solution temperature (LCST) values based on monitoring either changes in the NIR spectra or the volume of the hydrogel particle in response to variations in temperature. More importantly, the measured volume transition temperature or LCST value is not of a collection of many hydrogel particles, but rather of individual hydrogel particles. GNs were found to significantly affect not only absorption but also images and properties of individual hydrogel particles. Specifically, GNs were found to enhance absorption of individual hydrogel particles, particularly the C-H band at 1716 nm, by about 25%. Of particular interest is the fact that not all individual hydrogel particles were enhanced by GNs; only about 50% of total number of particles were enhanced by GNs. GNs were also found to make it difficult to observe individual hydrogel particles, i.e., it seems that GNs defocused images of hydrogel particles. The defocusing effect by GNs might be due to photothermal generation of heat and vapor bubbles by the GNs. Of particular interest is the effect of GNs on the volume transition temperature of individual hydrogel particles. It seems that individual hydrogel particles lose their LCST in the presence of GNs, i.e., when heated, they undergo a gradual decrease in the volume but do not exhibit any clear and observable discontinued phase transition temperature.

Dynamics of Photothermally Created Vaporous, Gaseous, and Mixed Microbubbles

Carbon nanotubes suspended in various liquids act as absorbers of low-power (mW), continuous-wave laser (1064 nm) light and cause photothermal generation of microbubbles. Three types of microbubbles, gaseous, vaporous, and mixed, are experimentally and theoretically characterized, allowing diverse applications to be identified where one or the other kind may be better suited. Bubbles collapse after reaching a certain size. Imploding cavitational collapse of vaporous bubbles produces exploding shockwaves while nonspherical collapse generates high-speed liquid jets, resulting in spectacular disruption of proximate matter; localized temperatures in excess of 4000 K are predicted. Small fractions of noncondensable gases in vaporous bubbles are found to significantly alter the dynamics.

Synergistic cell-killing by photocatalytic and plasmonic photothermal effects of Ag@TiO 2 core–shell composite nanoclusters against human epithelial carcinoma (HeLa) cells

The Ag metal core–TiO 2 shell (Ag@TiO 2) composite nanocluster with uniform size, shape and core–shell structures was successfully synthesized by a new simple citrate reduction method. The core–shell structure of Ag@TiO 2 nanocluster was characterized by using TEM, SEM, XPS, EDX, XRD, and photoluminescence spectra analysis. It was found that the Ag core is in metallic form which is covered by TiO 2 shell within 3–5 nm thickness and the core–shell particles size was about 30 nm. The photocatalytic and photothermal cell killing efficiency of colloidal Ag@TiO 2 core–shell nanocluster was evaluated against cancer (HeLa) cells under UV–vis irradiation. It was found that the Ag@TiO 2 nanocluster with an adequate Ag ratio to TiO 2 killed more malignant (HeLa) cells by 80% compared to TiO 2 nanoparticles alone. The comparative study of the cell viability using UV only, visible only and UV–visible light revealed that the synergy effect of photocatalytic hydroxyl radical formation and Ag-plasmonic photothermal generation plays a vital role for the cancer cell killing. Based on the obtained results, a plausible mechanism was also proposed.

Spatially resolved thermal diffusivity measurements on functionally graded materials

Photothermal generation of thermal waves was used in combination with the probe beam deflection technique to study the thermal diffusivity of functionally graded materials (FGMs) quantitatively. An amplitude modulated Ar ion laser was used as a heat source and the HeNe probe laser was reflected from the specimen surface at almost normal incidence. It is demonstrated that this measuring technique can be used for a precise determination of the thermal diffusivity for a wide variety of materials if appropriate measuring conditions are chosen. The precision of the thermal diffusivity measurement was better than 5% for all materials studied. The achieved spatial resolution of the thermal diffusivity measurement was about 100 μm, but higher spatial resolutions can be achieved if necessary. In a graded Al2O3/Al composite local fluctuations of the thermal diffusivity were observed due to the coarseness of the microstructure, but the overall behaviour of the thermal conductivity could be described well by the Maxwell-Eucken relationship. In a functionally graded AlCu alloy, a smooth thermal diffusivity profile was observed in the region where the alloy consisted of a solid solution of Cu in Al.

Interference Analysis of Photothermal Generation of Waves in Layered Structures

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Energy relaxations in CS2 and in NO2–N2O4 vapors following pulsed laser excitation at 337.1 nm by probe beam deflection measurements

The pulsed photothermal generation and probe-beam deflection technique was applied to monitor nonradiative relaxation and transport processes in CS2 and in NO2–N2O4 vapors following nitrogen laser excitation at 337.1 nm. A theoretical model is developed to describe the signal shape, and to derive the thermal diffusivity and energy relaxation time. The experiments were performed over a vapor pressure range of typically 1–100 Torr with a time resolution of 1 μs. In CS2 vapor of pressure above 10 Torr at room temperature, a slow heat release component is observed attributed to the photochemical formation of (CS)n particulates (‘‘laser-snow’’). In NO2–N2O4 vapor, the experimental data provide the thermal diffusivity values in the pressure range of 1–100 Torr; these measurements support a ‘‘frozen equilibrium’’ model and indicate that any contribution due to the diffusional transport of chemical enthalpy for this system is small in this pressure range at room temperature. These experiments demonstrate that the photothermal probe-beam deflection technique can provide useful information on heat-release rates, for example, due to particulate formation, as well as measurement of thermal diffusivity, for example, in hostile and dissociative gas systems.

Photothermal Generation of Thermoelastic Waves in Composite Media

L'accent est mis sur la comprehension des effets des parametres du materiau et dynamiques, sur le processus de generation thermoelastique. On decrit le couplage thermoelastique des modes de propagation et de non-propagation