808-nm Laser Irradiation Research Articles

Synthesis of flexible and up-converting luminescent NaYF4:Yb,Er-PET composite film for constructing 980-nm laser-driven biopower

A flexible NaYF4:Yb,Er-PET composite film has been developed for constructing 980-nm laser-driven biopower, and the resulting biopower covered with skin produces a maximal electrical output of 62 μW under 980-nm laser irradiation (intensity: 720 mW cm−2, area: 0.25 cm2).

Synthesis and antitumor activity evaluation of a novel porphyrin derivative for photodynamic therapy in vitro and in vivo.

A novel porphyrin derivative, 5, 10, 15, 20-tetrakis (5-morpholinopentyl)-21H, 23H-Porphin (MPP, 4) and its photophysical characteristics, therapeutic efficacy of photodynamic therapy (PDT) in vitro and in vivo, tumor selectivity, and clearance from normal tissues were investigated here. MPP has strong absorption at relatively long wavelength (λmax = 648nm, molar absorption coefficient ε ∼ 17,200M(-1)cm(-1)) and can emit strong fluorescence at 653 and 718nm. When administered to the animal tumor models by tail vein injection, MPP was capable of accumulating in the tumor site, as examined in vivo with the fluorescence signal of MPP. By the combination of MPP and a 650-nm laser irradiation, the viability of T24 cells could decrease by 4.37%, and inhibition rate of T24 tumor could increase up to 91.21% compared with control group, demonstrating the potential of MPP as an effective photosensitizer in PDT for tumor treatment.

Flower-like PEGylated MoS2 nanoflakes for near-infrared photothermal cancer therapy.

Photothermal cancer therapy has attracted considerable interest for cancer treatment in recent years, but the effective photothermal agents remain to be explored before this strategy can be applied clinically. In this study, we therefore develop flower-like molybdenum disulfide (MoS2) nanoflakes and investigate their potential for photothermal ablation of cancer cells. MoS2 nanoflakes are synthesized via a facile hydrothermal method and then modified with lipoic acid-terminated polyethylene glycol (LA-PEG), endowing the obtained nanoflakes with high colloidal stability and very low cytotoxicity. Upon irradiation with near infrared (NIR) laser at 808 nm, the nanoflakes showed powerful ability of inducing higher temperature, good photothermal stability and high photothermal conversion efficiency. The in vitro photothermal effects of MoS2-PEG nanoflakes with different concentrations were also evaluated under various power densities of NIR 808-nm laser irradiation, and the results indicated that an effective photothermal killing of cancer cells could be achieved by a low concentration of nanoflakes under a low power NIR 808-nm laser irradiation. Furthermore, cancer cell in vivo could be efficiently destroyed via the photothermal effect of MoS2-PEG nanoflakes under the irradiation. These results thus suggest that the MoS2-PEG nanoflakes would be as promising photothermal agents for future photothermal cancer therapy.

One-pot synthesis of PEGylated plasmonic MoO3–x hollow nanospheres for photoacoustic imaging guided chemo-photothermal combinational therapy of cancer

Engineering design of plasmonic nanomaterials as on-demand theranostic nanoagents with imaging, drug carrier, and photothermal therapy (PTT) functions have profound impact on treatment of cancer. Here, a facile ‘one-pot’ template-free hydrothermal route was firstly developed for synthesis of plasmonic oxygen deficiency molybdenum oxide hollow nanospheres functionalized by poly(ethylene glycol) (PEG-MoO3–x HNSs). The as-prepared PEG-MoO3–x HNSs not only have good biocompatibility but also exhibit obvious localized surface plasmon resonance (LSPR) absorption in the near-infrared (NIR) region. Especially, due to its intrinsic mesoporous properties and effective photothermal conversion efficiency upon 808-nm NIR laser irradiation, the PEG-MoO3–x HNSs can be applied as a pH/NIR laser dual-responsive camptothecin (CPT) drug delivery nanoplatform for chemotherapy as well as PTT to cancer cells. A remarkably improved synergistic therapeutic effect to pancreatic (PANC-1) tumor-bearing mice was obtained compared to the result of chemotherapy or PTT alone. Apart from its application for drug delivery, the PEG-MoO3–x HNSs can also be employed as an effective contrast nanoagent for photoacoustic (PAT) imaging because of its high NIR absorption, making it promising as a theranostic nanoagent for PAT imaging-guided chemo-photothermal combinational cancer therapy in the nanomedicine field.

Optothermal Switching of Cholesteric Liquid Crystals: A Study of Azobenzene Derivatives and Laser Wavelengths.

The laser-initiated thermal (optothermal) switching of cholesteric liquid crystals (CLCs) is characterized by using different azobenzene (Azo) derivatives and laser wavelengths. Under 405-nm laser irradiation, Azo-doped CLCs undergo phase transition from cholesteric to isotropic. No cis-to-trans photoisomerization occurs when the 405-nm laser irradiation is blocked because only a single laser is used. The fast response of Azo-doped CLCs under the on–off switching of the 405-nm laser occurs because of the optothermal effect of the system. The 660-nm laser, which cannot be used as irradiation to generate the trans–cis photoisomerization of Azo, is used in Anthraquinone (AQ)-Azo-doped CLCs to examine the optothermal effect of doped Azo. The results show that the LC-like Azo derivative bearing two methyl groups ortho to the Azo moiety (A4) can greatly lower the clearing temperature and generate large amount of heat in AQ-A4-doped CLCs.

Toward NIR driven photocatalyst: Fabrication, characterization, and photocatalytic activity of β-NaYF4:Yb3+,Tm3+/g-C3N4 nanocomposite

The β-NaYF4:Yb3+,Tm3+/g-C3N4 (NYT/C3N4) photocatalyst has been successfully fabricated by a stepwise method. Firstly, the advanced near-infrared (NIR) driven photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–Vis–NIR diffuse reflectance spectroscopy. It was found that NYT/C3N4 photocatalyst consisted of uniform hexagonal phase NaYF4 nanocrystals with about 20nm diameter distributed on surface of g-C3N4 sheets, and the NYT/C3N4 composite exhibited strong near-infrared light absorption and the energy transfer from β-NaYF4:Yb3+,Tm3+ to g-C3N4 was confirmed. Secondly, the photocatalytic activities of the catalysts were evaluated by the degradation of methyl blue dye and colorless phenol under the irradiation of 980nm laser. The results suggested that NYT/C3N4 nanocomposite is an advanced NIR-driven photocatalyst. Moreover the NYT/C3N4 photocatalyst showed good stability for photocatalytic decoloration of dye in the recycled tests. This study suggested a promising system to utilize the NIR energy of sunlight for photochemical and photoelectrical applications based on g-C3N4, which will contribute to the utilization of solar energy in the future.

Graphene oxide-BaGdF5 nanocomposites for multi-modal imaging and photothermal therapy

By using a solvothermal method in the presence of polyethylene glycol (PEG), BaGdF5 nanoparticles are firmly attached on the surface of graphene oxide (GO) nanosheets to form the GO/BaGdF5/PEG nanocomposites. The resulting GO/BaGdF5/PEG shows low cytotoxicity, positive magnetic resonance (MR) contrast effect and better X-ray attenuation property than Iohexol, which enables effective dual-modality MR and X-ray computed tomography (CT) imaging of the tumor model in vivo. The enhanced near-infrared absorbance, good photothermal stability and efficient tumor passive targeting of GO/BaGdF5/PEG result in the highly efficient photothermal ablation of tumor in vivo after intravenous injection of GO/BaGdF5/PEG and the following 808-nm laser irradiation (0.5 W/cm2). The histological and biochemical analysis data reveal no perceptible toxicity of GO/BaGdF5/PEG in mice after treatment. These results indicate potential application of GO/BaGdF5/PEG in dual-modality MR/CT imaging and photothermal therapy of cancers.

FeS nanoplates as a multifunctional nano-theranostic for magnetic resonance imaging guided photothermal therapy

In this work, we develop magnetic iron sulfide (FeS) nanoplates as a theranostic agent for magnetic resonance (MR) imaging-guided photothermal therapy of cancer. FeS nanoplates are synthesized via a simple one-step method and then functionalized with polyethylene glycol (PEG). The obtained PEGylated FeS (FeS-PEG) nanoplates exhibit high NIR absorbance together with strong superparamagnetism. The r2 relaxivity of FeS-PEG nanoplates is determined to be 209.8 mm-1S-1, which appears to be much higher than that of iron oxide nanoparticles and several types of clinical approved T2-contrast agents. After intravenous (i.v.) injection, those nanoplates show high accumulation in the tumor as revealed by MR imaging. Highly effective photothermal ablation of tumors is then achieved in a mouse tumor model upon i.v. injection of FeS-PEG at a moderate dose (20 mg/kg) followed by 808-nm NIR laser irradiation. Importantly, it has been found that PEGylated FeS nanoplates after systemic administration could be gradually excreted from major organs of mice, and show no appreciable toxicity to the treated animals even at a dose (100 mg/kg) 5 times as high as that used for imaging & treatment. Our results demonstrate that PEGylated FeS nanoplates may be a promising class of theranostic nano-agents with a good potential for future clinical translation.

980-nm infrared laser modulation of sodium channel kinetics in a neuron cell linearly mediated by photothermal effect

Photothermal effect (PE) plays a major role in the near-infrared laser interaction with biological tissue. But, quite few interactions can be quantitatively depicted. Here, a two-step model is proposed to describe a 980-nm infrared laser interaction with neuron cell in vitro. First, the laser-induced temperature rises in the cell surrounding area were measured by using an open pipette method and also calculated by solving the heat conduction equation. Second, we recorded the modifications on sodium (Na) channel current in neuron cells directly by using a patch clamp to synchronize the 980-nm laser irradiation and obtained how the electrophysiological function of neuron cells respond to the temperature rise. Then, the activation time constants, τ(m), were extracted by fitting the sodium currents with the Hodgkin-Huxley model. The infrared laser modulation effect on sodium currents kinetics was examined by taking a ratio between the time constants with and without the laser irradiations. The analysis revealed that the averaged ratio at a specific laser exposure could be well related to the temperature properties of the Na channel protein. These results proved that the modulation of sodium current kinetics of a neuron cell in vitro by 980-nm laser with different-irradiation levels was linearly mediated corresponding to the laser-induced PE.

Effect of etching on the laser-induced damage properties of artificial defects under 1064-nm laser irradiation

The cracks and scratches inevitably generated by previous grinding and polishing significantly lower the ability of laser resistance of optical substrates. In this study, the artificial indentations, scratches, and structural defects imbedded with metal nanoparticles are fabricated. The laser-induced damage characteristics of such defects in different types and sizes are investigated qualitatively and quantitatively under 1064-nm laser irradiation. Moreover, the etching effect on improving the laser-induced damage threshold (LIDT) of artificial defects under different etching conditions is analyzed. LIDT is then evaluated according to the etching depth and the morphologies of artificial defects.

Infrared nanosecond pulsed laser irradiation of stainless steel: Micro iron-oxide zones generation

Nanosecond-pulsed, infrared (1064nm) laser irradiation was used to create periodic metal oxide coatings on the surface of two samples of commercial stainless steel at ambient conditions. A pattern of four different metal oxide zones was created using a galvanometer scanning head and a focused laser beam over each sample. This pattern is related to traverse direction of the laser beam scanning. Energy-dispersive X-ray spectroscopy (EDS) was used to find the elemental composition and Raman spectroscopy to characterize each oxide zone. Pulsed laser irradiation modified the composition of the stainless steel samples, affecting the concentration of the main components within each heat affected zone. The Raman spectra of the generated oxides have different intensity profiles, which suggest different oxide phases such as magnetite and maghemite. In addition, these oxides are not sensible to the laser power of the Raman system, as are the iron oxide powders reported in the literature. These experiments show that it is possible to generate periodic patterns of various iron oxide zones by laser irradiation, of stainless steel at ambient conditions, and that Raman spectroscopy is a useful punctual technique for the analysis and inspection of small oxide areas.

Nonlinear optical properties of systems based on (tetra-15-crown-5-phthalocyaninato)indium(III)

The nonlinear optical properties of solutions of (2,3,9,10,16,17,23,24-tetra-15-crown-5-phthalocyaninato)indium(III) [(15C5)4Pc]In(OH) in tetrachloroethane (TCE) have been studied by the z-scan method. It has been found that a nonlinear optical response is due to supramolecular associates formed in a tetrachloroethane solution by heating to 90°C/slow cooling to room temperature cycling. The formation of the supramolecular associates has been studied by atomic force microscopy (AFM) and electronic absorption spectroscopy (EAS). It has been shown that a single thermal treatment of [(15C5)4Pc]In(OH) solutions in TCE results in the predominant formation of dimers, as evidenced by both a short-wavelength shift of the Q-absorption band of the monomeric complex (λmax = 692 nm) to the band of λmax = 653 nm and height doubling of molecular entities as measured by AFM. The dimers are responsible for the two-photon absorption measured in the femtosecond range, which has a relatively high cross section of σ2 = 1.38 × 10−46 cm4 s/(molecule, photon) or 1.38 × 104 GM. According to the AFM data, three cycles of heat treatment of the solution leads to the formation of supramolecular assemblies of about 200 nm length. The optical spectrum exhibits long-wavelength absorption at λmax = 841 nm and the long-wavelength edge near 1300 nm. In the case of nanosecond 1064-nm laser irradiation, the linear absorption S 0 → S 1 is primary, having the cross section of σ0 = α0/N = 2.3 × 10−20 cm2. The known high quantum yield (close to unity) of triplet states of indium phthalocyanines suggests that the main nonlinear optical effect is determined by intersystem crossing S 1 → T 1 and triplet-triplet absorption T 1 → T 2. The absorption cross section is σ T-T = 1.14 × 10−19 cm2.

Protein modified upconversion nanoparticles for imaging-guided combined photothermal and photodynamic therapy

In this work, we develop a multifunctional nano-platform by coating upconversion nanoparticles (UCNPs) with bovine serum albumin (BSA), obtaining UCNP@BSA nanoparticles with great solubility and stability in physiological environments. Two types of dye molecules, including a photosensitizer, Rose Bengal (RB), and an NIR-absorbing dye, IR825, can be simultaneously loaded into the BSA layer of the UCNP@BSA nanoparticles. In this carefully designed UCNP@BSA-RB&; IR825 system, RB absorbs green light emitted from UCNPs under 980-nm excitation to induce photodynamic cancer cell killing, while IR825 whose absorbance shows no overlap with upconversion excitation and emission wavelengths, offers nanoparticles a strong photothermal perform under 808-nm laser irradiation. Without showing noticeable dark toxicity, the obtained dual-dye loaded nanoparticles are able to kill cancer via combined photothermal and photodynamic therapies, both of which are induced by NIR light with high tissue penetration, by a synergetic manner both in vitro and in vivo. In addition, the intrinsic paramagnetic and optical properties of Gd3+-doped UCNPs can further be utilized for in vivo dual modal imaging. Our study suggests that UCNPs with well-designed surface engineering could serve as a multifunctional nano-platform promising in cancer theranostics.

Microwave-assisted hydrothermal synthesis and temperature sensing application of Er3+/Yb3+ doped NaY(WO4)2 microstructures

Laurustinus shaped NaY(WO4)2 micro-particles assembled by nanosheets were synthesized via a microwave-assisted hydrothermal (MH) route. The growing mechanisms for the obtained resultants with various morphologies were proposed based on the observation of scanning electron microscopic (SEM) images. It was found that Na3Cit added into the reaction solution greatly influenced the formation and size dimension of the nano-sheets, furthermore determined assembling of the laurustinus shaped micro-particles. The temperature sensing performance of NaY(WO4)2:Er3+/Yb3+ was evaluated. Thermal effect induced by the 980nm laser irradiation in laurustinus-shaped NaY(WO4)2:Er3+/Yb3+ phosphor was studied. It was found that the green upconversion luminescence intensity increased in the first stage of laser irradiation, and then decreased after reaching a maximum. Based on the thermal sensing technology the laurustinus NaY(WO4)2:Er3+/Yb3+ microparticles were used as thermal probe to discover thermal effect of upconversion luminescence in laurustinus NaY(WO4)2:Tm3+/Yb3+ micro-particles.

Laser-damage growth characteristics of fused silica under 1064- and 532-nm laser irradiation

The laser-damage growth characteristics of initial damage sites play an important role in investigating the laser-induced damage mechanisms and determining the lifetime of the optics in application. We investigate the damage growth behaviors of fused silica under 1064, and 532-nm nanosecond-pulsed laser irradiation. The relationships between the sizes of initial damage sites and the laser fluence, as well as the initial damage morphology evolutions and the laser shot numbers, are discussed. Moreover, the growth characteristics of the initial damage sites generated by the same fluence but under different subsequent fluence irradiation are compared with those of initial damage sites generated by different fluence but under the same subsequent fluence irradiation. Finally, the differences between the damage morphologies and the growth features at the same conditions under different wavelengths are also provided and discussed.

Low-level laser therapy for spinal cord injury in rats: effects of polarization

The effects of laser polarization on the efficacy of near-infrared low-level laser therapy for spinal cord injury (SCI) are presented. Rat spinal cords were injured with a weight-drop device, and the lesion sites were directly irradiated with a linearly polarized 808-nm diode laser positioned either perpendicular or parallel to the spine immediately after the injury and daily for five consecutive days. Functional recovery was assessed daily by an open-field test. Regardless of the polarization direction, functional scores of SCI rats that were treated with the 808-nm laser irradiation were significantly higher than those of SCI alone group (Group 1) from day 5 after injury. The locomotive function of SCI rats irradiated parallel to the spinal column (Group 3) was significantly improved from day 10 after injury, compared to SCI rats treated with the linear polarization perpendicular to the spinal column (Group 2). There were no significant differences in ATP contents in the injured tissue among the three groups. We speculate that the higher efficacy with parallel irradiation is attributable to the deeper light penetration into tissue with anisotropic scattering.

Lifetime test of photoemission from Cs3Sb photocathode coated with W or Cr film

Cs3Sb photocathodes were fabricated at 8–16°C with sandwiched layers of Sb, Cs, and Sb deposited onto the fine tips of three cathodes at 15°C. After examining the influence of the cathode tip temperature on the changes in the quantum efficiencies of the Cs3Sb photocathodes during and after additional Cs depositions, we performed lifetime tests of the three Cs3Sb photocathodes using a 405-nm semiconductor laser and 488-nm Ar ion laser. The decrease in the photocurrent with time was more rapid with the 488-nm laser irradiation than with the 405-nm laser irradiation, and continuous laser irradiation caused a much more rapid decrease in photoelectrons with time than intermittent laser irradiation did. We deposited a 0.32–0.64-nm-thick W film or a 0.43-nm-thick Cr film onto the Cs3Sb photocathode during the lifetime test at 0.9–1.0×10−7Pa. We found that the passive WO3 or Cr2O3 film, which was formed at a reduced vacuum level of 1.6×10−7Pa or during the continuous 405-nm laser irradiation, increased the lifetime of the Cs3Sb photocathode by effectively protecting its surface against oxidation and evaporation of Cs. This protection effect was most effective at approximately 90°C.

Advanced near-infrared-driven photocatalyst: Fabrication, characterization, and photocatalytic performance of β-NaYF4:Yb3+,Tm3+@TiO2 core@shell microcrystals

The β-NaYF4:Yb3+,Tm3+@TiO2 core@shell photocatalyst has been successfully fabricated by a simply hydrothermal method followed by hydrolysis of titanium isopropoxide (TTIP) with polyvinylpyrrolidone K-30 (PVP) as the coupling agent. The advanced near-infrared-driven photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, fluorescence spectrometer and UV–vis–NIR diffuse reflectance spectroscopy. It is found that β-NaYF4:Yb3+,Tm3+@TiO2 core@shell photocatalyst consists of uniform hexagonal phase NaYF4 microcrystals rods and anatase TiO2 shells, and the β-NaYF4:Yb3+,Tm3+@TiO2 exhibits strong near-infrared light absorption and the energy transfers from β-NaYF4:Yb3+,Tm3+ to TiO2 is confirmed. The photocatalytic activities of the catalysts were evaluated by the discoloration of Methylene Blue, Methyl Orange and Rhodamine B under the irradiation of 980nm laser. The results suggest that β-NaYF4:Yb3+,Tm3+@TiO2 core@shell composite is an advanced near-infrared-driven photocatalyst. Moreover the NIR-driven photocatalyst shows good stability for photocatalytic decoloration of dye in the recycled tests. This study suggests a promising system to utilize the NIR energy of sunlight for photochemical and photoelectrical applications based on TiO2, which will contribute to the utilization of solar energy in the future.

Nanosecond pulsed laser irradiation of stainless steel 304L: Oxide growth and effects on underlying metal

Nanosecond-pulsed, infrared (1064nm) laser irradiation was used to create metal oxide coatings on the surface of polished stainless steel 304L austenite for application as color markings and unique tags/identifiers. By rastering a Gaussian-shaped, focused laser beam across a specimen in air, continuous metal oxide coatings were grown to thicknesses in the range of 20 to ~500nm. Oxide coating thickness generally increased with laser fluence. However, for large accumulated fluences in excess of ~600–800J/cm2, oxide growth was affected by evaporation and particle ejection resulting in a decreased coating thickness. Transmission electron microscopy and X-ray diffraction revealed that oxide coatings developed a polycrystalline, spinel structure having a lattice constant=8.4Å (consistent with MnCr2O4 and Fe3O4). Pulsed laser irradiation and oxide growth modified the composition of stainless steel substrates by reducing the Cr and Mn concentration within the melt zone. The reflectance and chromaticity of laser-fabricated oxide coatings were characterized using spectrophotometry. These optical properties are described in the context of measured oxide thicknesses.

Mechanism of anti-stokes photoluminescence in Ag0.05Ga0.05Ge0.95S2-Er2S3 glassy alloys

The absorption and up-conversion photoluminescence spectra of alloys of the Ag0.05Ga0.05Ge0.95S2−xEr2S3 system (100 − x), excited with 980-nm laser irradiation, where x = 0.42, 0.25, and 0.18 mol %, have been studied. Green, intensive red, and infrared luminescence, which is caused by electronic 2H11/2 → 4I15/2, 4F9/2 → 4I15/2, 4S3/3 → 4I13/2 transitions in Er3+ ions, respectively, and connected with two photon up-conversion processes was recorded in all samples. The changes in the intensities of glassy alloys of radiation bands with different erbium contents and the influence of large structure defects on the processes of the occupation and the devastation of the energetic levels of erbium ions.