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Surface smoothing of poly(methyl methacrylate) film by laser induced photochemical etching
摘要： The surface of poly(methyl methacrylate) (PMMA) ?lm was etched by laser irradiation under O2 and vacuum conditions. By activating the O2 molecules near the rough surface, oxygen radicals will preferably etch the protrusions on the PMMA surface. Three lasers of different wavelengths were used for comparison. Laser irradiation at a short wavelength such as 325 nm resulted in high etch rates whereas a long wavelength such as 532 nm resulted in no effect on the surface pro?le. The PMMA surface was not etched under the vacuum condition, indicating the necessity of O2 molecules in etching.
关键词： surface smoothing,wavelength dependence,oxygen radicals,poly(methyl methacrylate),laser induced photochemical etching
更新于2025-09-16 10:30:52
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Determination of Infrared Laser Energy Dose for Cancer Cells Inactivation as a Candidate of Photodynamic Therapy
摘要： The aim of this research is to find out the effect of GaAlAs diode laser 808 nm exposure on MCF-7 breast cancer cells in vitro with and without the addition of a photosensitizer. Methylene blue (C16H18N3SCl) with concentration of 2 μM is used as the photosensitizer based on the preliminary results of cytotoxicity assay. Energy dose is set in the range of 23,043 to 322,062 J/cm2. Laser exposure with the addition of the photosensitizer generates the highest percentage of cell death of 20.80% at energy dose of 184,344 J/cm2 and cell death begin to decrease at energy dose above this value. This behavior is likely caused by photodegradation and photobleaching effect of the photosensitizer due to the longer exposure time. However, the percentage of cell death without the addition of photosensitizer is increased proportionally to the increase of energy dose and achieved 32,45% cell mortality at 299,559 J/cm2. This study not only shows that the exposure of infrared laser can be used to inactivate cancer cells but also determines its optimum energy dose, makes it a possible candidate for photodynamic therapy in the future.
关键词： MCF-7 cells,photodynamic therapy,photochemical,methylene blue,diode laser,photothermal
更新于2025-09-16 10:30:52
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Dibenzo[ <i>hi</i> , <i>st</i> ]ovalene as Highly Luminescent Nanographene: Efficient Synthesis via Photochemical Cyclodehydroiodination, Optoelectronic Properties, and Single-Molecule Spectroscopy
摘要： Dibenzo[hi,st]ovalene (DBOV), as a new nanographene, has demonstrated promising optical properties, such as red emission with a high fluorescence quantum yield of 79% and stimulated emission, as well as high thermal stability and photostability, which indicated its promise as a light-emitting and optical gain material. However, the previous synthetic routes required at least 12 steps. This obstructed access to different derivatives, e.g., to obtain crystals suitable for X-ray diffraction analysis and to tune the optoelectronic properties. Here, we report an efficient synthetic pathway to DBOV based on a sequential iodination-benzannulation of bi(naphthylphenyl)diyne, followed by photochemical cyclodehydroiodination (PCDHI). This protocol included a fused bischrysene as a key intermediate and furnished scalable amounts of meso-substituted DBOV derivatives with different substituents. DBOV with 2,6-dimethylphenyl groups could be used for single-crystal X-ray analysis, revealing the precise structure of the DBOV core. The optoelectronic properties of the DBOV derivatives were investigated by UV?vis absorption and fluorescence spectroscopy, cyclic voltammetry, and density functional theory calculations. Single-molecule spectroscopy at room and low temperatures provided novel insights into the photophysics of DBOV embedded in a polymer film. As a result of weak coupling of the optical transitions to the matrix, single-molecule emission spectra at 4.5 K showed narrow vibronic lines. The fluorescence autocorrelation function covering 9 orders of magnitude in time displayed high contrast photon antibunching and bunching, from which the fluorescence decay rate and the triplet population and depopulation rates could be retrieved. Remarkably, the intersystem crossing rate into the triplet state decreased by more than an order of magnitude at low temperature, demonstrating that temperature can be a crucial parameter to boost single photon emission of an aromatic hydrocarbon.
关键词： fluorescence quantum yield,nanographene,single-molecule spectroscopy,optoelectronic properties,photochemical cyclodehydroiodination
更新于2025-09-16 10:30:52
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Non-Photochemical Pulsed-Laser-Induced Nucleation in a Continuous-Wave-Laser-Induced Phase-Separated Solution Droplet of Aqueous Glycine Formed by Optical Gradient Forces
摘要： A centimeter-sized, laser-induced phase-separated (LIPS) solution droplet, which was formed by tightly focusing a continuous-wave near-infrared laser beam at the glass/solution interface of a millimeter-thick layer of glycine in D2O with a supersaturation ratio, S, of 1.36 was irradiated with a single unfocused nanosecond near-infrared laser pulse in order to study the effect of non-photochemical laser-induced nucleation (NPLIN) on the droplet, as well as to help characterize the behavior of the LIPS droplet. Additionally, a control NPLIN experiment was conducted on an S = 1.50 supersaturated solution of glycine/D2O in the same cell to better understand the differences between NPLIN in a LIPS droplet and an ordinary supersaturated solution. These experiments revealed that NPLIN could nucleate crystals within a LIPS droplet, although the growth of these crystals was inhibited during the first 5 min of the droplet’s relaxation. For the first 40 min of its relaxation, the LIPS droplet was observed to be more labile to spontaneous nucleation than the control S = 1.50 solution, although the growth of spontaneously nucleated crystals was also inhibited during the first 5 min of the droplet’s relaxation. This suggests that although the macroscopic phase boundary between the LIPS droplet and the surrounding solution disappeared after approximately 5 min, the full microscopic relaxation of the LIPS droplet took at least 40 min. The resulting crystals were analyzed using powder X-ray diffraction, and 100% of crystals formed within the LIPS droplet induced by NPLIN with linearly polarized light and by spontaneous nucleation were α-glycine, while crystals formed outside of the LIPS droplet were mixtures of α- and γ-glycine. The results suggest that the LIPS droplet and the surrounding solution are not equilibrium phases of aqueous glycine, but phases in which optical gradient forces have induced a partitioning of large and small solute clusters.
关键词： Polymorphism,Optical gradient forces,Laser-induced phase separation,Non-photochemical laser-induced nucleation,Glycine
更新于2025-09-12 10:27:22
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Enhancing Double-Beam Laser Tweezers Raman Spectroscopy (LTRS) for the Photochemical Study of Individual Airborne Microdroplets
摘要： A new device and methodology for vertically coupling confocal Raman microscopy with optical tweezers for the in situ physico- and photochemical studies of individual microdroplets (? ≤ 10 μm) levitated in air is presented. The coupling expands the spectrum of studies performed with individual particles using laser tweezers Raman spectroscopy (LTRS) to photochemical processes and spatially resolved Raman microspectroscopy on airborne aerosols. This is the first study to demonstrate photochemical studies and Raman mapping on optically levitated droplets. By using this configuration, photochemical reactions in aerosols of atmospheric interest can be studied on a laboratory scale under realistic conditions of gas-phase composition and relative humidity. Likewise, the distribution of photoproducts within the drop can also be observed with this setup. The applicability of the coupling system was tested by studying the photochemical behavior of microdroplets (5 μm < ? < 8 μm) containing an aqueous solution of sodium nitrate levitated in air and exposed to narrowed UV radiation (254 ± 25 nm). Photolysis of the levitated NaNO3 microdroplets presented photochemical kinetic differences in comparison with larger NaNO3 droplets (40 μm < ? < 80 μm), previously photolyzed using acoustic traps, and heterogeneity in the distribution of the photoproducts within the drop.
关键词： optical levitation,optical traps,photochemical reactions in Earth’s atmosphere,atmospheric aerosols,laser tweezers Raman spectroscopy (LTRS)
更新于2025-09-12 10:27:22
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Shining Light on the Coiled-Flow Inverter—Continuous-Flow Photochemistry in a Static Mixer
摘要： We present the use of a coiled-flow inverter (CFI) for continuous-flow photochemistry at competitive photon efficiencies. The static mixer is placed inside a reaction chamber, while a dark adjacent chamber allows for orthogonal online reaction monitoring via fluorescence spectroscopy. The study of the aqueous visible-light induced degradation of fluorescein with ZnO-APTMS-Au photocatalyst showcases the challenge of uniformly irradiating photoreactors with non-planar surfaces. Fluorescence imaging is introduced as a simple method to visualize spatial gradients in the irradiance at the outer surface of such complex photoreactor geometries, allowing the analysis of photoreactor efficiency as a function of lighting configuration. We compared uniaxial and multiaxial lighting configurations and discuss the challenges associated with attaining uniform irradiance distribution of incident light on coiled-flow inverters, where chaotic advection combats light attenuation. A first calculation of the photochemical space-time yield (PSTY) for a “photo-CFI” is presented and contrasted with other photoreactor designs.
关键词： continuous-flow photochemistry,coiled-flow inverter,fluorescence imaging,ZnO-APTMS-Au photocatalyst,photochemical space-time yield
更新于2025-09-12 10:27:22
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Spatial Heterogeneity of Cadmium Effects on Salvia sclarea Leaves Revealed by Chlorophyll Fluorescence Imaging Analysis and Laser Ablation Inductively Coupled Plasma Mass Spectrometry
摘要： In this study, for a first time (according to our knowledge), we couple the methodologies of chlorophyll fluorescence imaging analysis (CF-IA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), in order to investigate the effects of cadmium (Cd) accumulation on photosystem II (PSII) photochemistry. We used as plant material Salvia sclarea that grew hydroponically with or without (control) 100 μM Cd for five days. The spatial heterogeneity of a decreased effective quantum yield of electron transport (ΦPSII) that was observed after exposure to Cd was linked to the spatial pattern of high Cd accumulation. However, the high increase of non-photochemical quenching (NPQ), at the leaf part with the high Cd accumulation, resulted in the decrease of the quantum yield of non-regulated energy loss (ΦNO) even more than that of control leaves. Thus, S. sclarea leaves exposed to 100 μM Cd exhibited lower reactive oxygen species (ROS) production as singlet oxygen (1O2). In addition, the increased photoprotective heat dissipation (NPQ) in the whole leaf under Cd exposure was sufficient enough to retain the same fraction of open reaction centers (qp) with control leaves. Our results demonstrated that CF-IA and LA-ICP-MS could be successfully combined to monitor heavy metal effects and plant tolerance mechanisms.
关键词： effective quantum yield (ΦPSII),non-photochemical quenching (NPQ),photoprotective mechanism,photochemical quenching (qp),photosynthetic heterogeneity,phytoremediation,reactive oxygen species (ROS),bioimaging,singlet oxygen (1O2),clary sage
更新于2025-09-11 14:15:04
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A sensitive photochemical reaction-capacitively coupled contactless conductivity detection system for HPLC and its application in determination of Cyclosporin A
摘要： High performance liquid chromatography (HPLC) post-column photochemical reaction (PR) coupled capacitively coupled contactless conductivity detector (C4D) was used for the first time in analysis of weak ultraviolet (UV)-absorbing, non-fluorescence and nonpolar compound. A series of conditions including the radiation power of light source, the length of the reaction tube and the thickness of detection tube were investigated. HPLC-PR-C4D system was successfully applied to the determination of Cyclosporin A (CsA). Consequently, under optimal conditions, the detection system exhibited a detection limit of 0.04 μg/mL and wide linear range from 0.5 μg/mL to 100 μg/mL for CsA detection. Application of the HPLC-PR- C4D system to pharmaceutical formulation and biological samples revealed the system developed maybe reliably applied to clinical studies.
关键词： Photochemical reaction,Cyclosporin A,HPLC,Capacitively coupled contactless conductivity detection,Application
更新于2025-09-11 14:15:04
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Photoactive Nanocarriers for Controlled Delivery
摘要： Photoactive nanocarriers have emerged as robust and minimally invasive systems for the on-demand delivery of active payloads. The easy manipulation offered by light irradiation as an external stimulus allows precise spatiotemporal control of payload release based on the time, intensity, location, and wavelength of light exposure. Compared to conventional passive delivery systems, photoactive nanocarriers offer the possibility of tailoring the release kinetics of the encapsulated active molecules, which is of considerable clinical relevance for targeted delivery to desired sites of interest. In this progress report, the recent advances in the design and fabrication of photoactive nanoplatforms based on three main modes of mechanisms: photochemical reactions, the photothermal effect, and photosensitization mechanism mediated by reactive oxygen species are highlighted. The combination of these mechanisms provides additional flexibility for the effective delivery of therapeutics and improved synergistic therapeutic effects. Finally, challenges in future perspectives on the development of photoactive nanomaterials and their medical translation are discussed.
关键词： photothermal effects,photosensitization,photochemical reaction,nanocarriers,controlled delivery
更新于2025-09-11 14:15:04
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Antimicrobial Photodynamic Inactivation Mediated by Tetracyclines in Vitro and in Vivo: Photochemical Mechanisms and Potentiation by Potassium Iodide
摘要： Tetracyclines (including demeclocycline, DMCT, or doxycycline, DOTC) represent a class of dual-action antibacterial compounds, which can act as antibiotics in the dark, and also as photosensitizers under illumination with blue or UVA light. It is known that tetracyclines are taken up inside bacterial cells where they bind to ribosomes. In the present study, we investigated the photochemical mechanism: Type 1 (hydroxyl radicals); Type 2 (singlet oxygen); or Type 3 (oxygen independent). Moreover, we asked whether addition of potassium iodide (KI) could potentiate the aPDI activity of tetracyclines. High concentrations of KI (200–400 mM) strongly potentiated (up to 5 logs of extra killing) light-mediated killing of Gram-negative Escherichia coli or Gram-positive MRSA (although the latter was somewhat less susceptible). KI potentiation was still apparent after a washing step showing that the iodide could penetrate the E. coli cells where the tetracycline had bound. When cells were added to the tetracycline + KI mixture after light, killing was observed in the case of E. coli showing formation of free molecular iodine. Addition of azide quenched the formation of iodine but not hydrogen peroxide. DMCT but not DOTC iodinated tyrosine. Both E. coli and MRSA could be killed by tetracyclines plus light in the absence of oxygen and this killing was not quenched by azide. A mouse model of a superficial wound infection caused by bioluminescent E. coli could be treated by topical application of DMCT and blue light and bacterial regrowth did not occur owing to the continued antibiotic activity of the tetracycline.
关键词： Tetracyclines,Antimicrobial photodynamic inactivation,Photochemical mechanisms,Oxygen independent killing,Potassium iodide
更新于2025-09-11 14:15:04