Modeling of Influence of Fluctuations of Laser Irradiation Frequency on Photochemical Reactions

F2 excimer laser (157 nm) irradiation was applied to modify sol–gel-derived amorphous Al2O3 thin films at ambient temperature. The surface morphology and density of the film were significantly altered by the laser irradiation (power: 2 mW/cm2/pulse). The surface properties of the film were also changed from hydrophilic to hydrophobic. These alterations were not observed when using ArF excimer laser (193 nm) irradiation at the same laser power as that of the F2 laser. It was found that the changes induced by F2 laser irradiation mainly arose from the direct photoexcitation of C = O groups in ethylacetoacetate, which was added as a chelating agent of aluminum-alkoxides. Consequently, photochemical reactions of the Norrish-type occur, resulting in the formation of hydrocarbon or olefin and the elimination of carbon monoxide (CO) or decomposition products. The elimination of CO is considered to cause the marked change in structure and surface properties of the film. Patterning of the gel films was successfully performed by using these findings.

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Effectiveness of bacterial biofilms photodynamic inactivation mediated by curcumin extract, nanodoxycycline and laser diode

Biomedical Photonics ◽

10.24931/2413-9432-2020-9-4-4-14 ◽

2021 ◽

Vol 9 (4) ◽

pp. 4-14

Author(s):

S. D. Astuti ◽

A. F. Mahmud ◽

A. P. Putra ◽

E. M. Setiawatie ◽

D. Arifianto

Keyword(s):

Photodynamic Therapy ◽

Laser Irradiation ◽

Diode Laser ◽

Laser Diode ◽

Irradiation Time ◽

Photochemical Reactions ◽

Bacterial Biofilm ◽

Bacterial Biofilms ◽

Turmeric Extract ◽

Significant Difference

Biofilms have higher levels of antibiotic resistance compared to bacteria, so the alternatives are needed as therapy for diseases caused by biofilm infections. Photodynamic Therapy (PDT) has the advantage of being a safe alternative that involves molecular-level photochemical reactions. The use of different types of exogenous photosensitizers (PS) was done to compare their effectiveness. Turmeric extract containing curcumin has good effectiveness in PDT, whereas nanodoxycycline as an antibiotic has a fairly broad absorption spectrum and is effective as PS. The purpose of this study is to compare the effectiveness of photodynamic therapy on infections by Aggregatibacter actinomycetemcomitans causing periodontitis using exogenous organic and non-organic photosensitisers (PS). The A. actinomycetemcomitans biofilm had been grown on 96-well microplate for 72 hours incubation time. The samples were divided into three groups, treated with Laser diode, Laser + Turmeric Extract 0.5%, and Laser + Nanodoxycycline 0.1%. Treatment was done with a variety of exposure times: 30, 60, 90, 120, and 150 seconds. The data were analyzed using ANOVA test. The results of data analysis showed that diode laser irradiation treatment with endogenous porphyrin, diode laser with Curcumin and diode laser with nanodoxycycline produced significantly different biofilm reductions. Treatment with diode laser irradiation at various energy densities (4.15, 8.28, 12.44, 16.59, and 20.73 J/cm2) showed no significant difference in reducing bacterial biofilm. The treatment with diode and curcumin, and the treatment with diode laser irradiation and nanodoxycyclin showed a significant difference. Diode laser irradiation of 20.73 J/cm2 with irradiation time of 150 seconds resulted in the greatest reduction of biofilm 14.94%, diode laser irradiation + Curcumin 47.82%, and diode laser irradiation + nanodoxycyclin 53.76%. Therefore, PDT using a diode laser combined with exogenous PS extract of curcumin and nanodoxycycline is more effective to reduce bacterial biofilms.

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Chronic Laser Exposure Effects on Rabbit Retina

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100093523 ◽

1972 ◽

Vol 30 ◽

pp. 54-55

Author(s):

Burton B. Silver ◽

Theodore Lawwill

Keyword(s):

Laser Irradiation ◽

Laser Light ◽

Broad Band ◽

Argon Laser ◽

Atropine Sulfate ◽

Ultrastructural Changes ◽

Laser Exposure ◽

Rabbit Retina ◽

Histological Changes ◽

Threshold Doses

Dutch-belted 1 to 2.5 kg anesthetized rabbits were exposed to either xenon or argon laser light administered in a broad band, designed to cover large areas of the retina. For laser exposure, the pupil was dilated with atropine sulfate 1% and pheny lephrine 10%. All of the laser generated power was within a band centered at 5145.0 Anstroms. Established threshold for 4 hour exposures to laser irradiation are in the order of 25-35 microwatts/cm2. Animals examined for ultrastructural changes received 4 hour threshold doses. These animals exhibited ERG, opthalmascopic, and histological changes consistent with threshold damage.One month following exposure the rabbits were killed with pentobarbitol. The eyes were immediately enucleated and dissected while bathed in 3% phosphate buffered gluteraldehyde.

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Microstructural changes of Aluminum Nitride after laser irradiation and electroless copper deposition

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100170918 ◽

1994 ◽

Vol 52 ◽

pp. 636-637

Author(s):

S. Cao ◽

A. J. Pedraza ◽

L. F. Allard

Keyword(s):

Aluminum Nitride ◽

Laser Irradiation ◽

Electroless Deposition ◽

Thermal Evaporation ◽

Surface Region ◽

Near Surface ◽

Laser Patterning ◽

Electroless Copper ◽

Excimer Laser Irradiation ◽

Laser Effect

Excimer-laser irradiation strongly modifies the near-surface region of aluminum nitride (AIN) substrates. The surface acquires a distinctive metallic appearance and the electrical resistivity of the near-surface region drastically decreases after laser irradiation. These results indicate that Al forms at the surface as a result of the decomposition of the Al (which has been confirmed by XPS). A computer model that incorporates two opposing phenomena, decomposition of the AIN that leaves a metallic Al film on the surface, and thermal evaporation of the Al, demonstrated that saturation of film thickness and, hence, of electrical resistance is reached when the rate of Al evaporation equals the rate of AIN decomposition. In an electroless copper bath, Cu is only deposited in laser-irradiated areas. This laser effect has been designated laser activation for electroless deposition. Laser activation eliminates the need of seeding for nucleating the initial layer of electroless Cu. Thus, AIN metallization can be achieved by laser patterning followed by electroless deposition.

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