Short-wavelength Visible Light Research Articles

Visible-Light-Induced Oxidation of Poly(3-hexylthiophene-2,5-diyl) Thin Films on ZnO Surfaces under Humid Conditions: Study of Light Wavelength Dependence

The oxidation behaviors of poly(3-hexylthiophene-2,5-diyl) (P3HT) thin films (∼60 nm thickness)/ZnO irradiated with three different wavelengths of visible light (blue, green, and red) in a humid atmosphere were studied using X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy. The formation of sulfoxide states upon visible-light irradiation was observed in the S 2p core-level XPS spectra, and more importantly, this oxidation became pronounced with decreasing wavelength of incident light. Photo-oxidation of P3HT films also resulted in a reduction in optical absorption. In contrast to the XPS results, changes in the UV–vis absorption spectrum were rather insensitive to the wavelength of incident visible light. The wavelength dependency of the photo-oxidation of P3HT films seen in the XPS spectra is attributed to the more pronounced photoinduced oxidation of locally disordered thiophene rings on the surfaces of P3HT films under irradiation with shorter-wavelength visible light. The population of local-disordered sites that increases the optical transition gap compared to that of the well-ordered bulk P3HT film decreases from the top surface to the interior of P3HT films due to stronger interchain interactions in the interior portion of the films. Therefore, changes in the optical absorbance seen in the UV–vis absorption spectra of the entire P3HT film upon photoinduced oxidation are less sensitive to the wavelength of incident light in the visible regime.

Evaluating the effect of local pH on fluorescence emissions from oral bacteria of the genus Prevotella.

A number of anaerobic oral bacteria, notably Prevotellaceae, exhibit red fluorescence when excited by short-wavelength visible light due to their accumulation of porphyrins, particularly protoporphyrin IX. pH affects the fluorescence of abiotic preparations of porphyrins due to transformations in speciation between monomers, higher aggregates, and dimers. To elucidate whether the porphyrin speciation phenomenon could be manifested within a microbiological system, suspensions of Prevotella intermedia and Prevotella nigrescens were examined by fluorescence spectrophotometry while being titrated against NaOH. The initial pH of the samples was <6, which was then raised toward the maximum found within a diseased periodontal pocket, being ∼pH 8.7. The intensity of the fluorescence emissions increased between 600 and 650 nm with increasing pH. Peak fluorescence emissions occurred at 635±1 nm with a second emission peak developing with increasing pH at 622 nm. A linear relationship was demonstrated between pH and the log10 ratio of 635:622 nm excitation fluorescence intensities. These findings suggest that the pH range found within the oral cavity could affect the fluorescence of oral bacteria in vivo, which may in turn have connotations for any clinical diagnoses that may be inferred from dental plaque fluorescence.

Short Wavelength Visible Light Suppresses Innate Immunity-Related Responses by Modulating Protein S-Nitrosylation in Keratinocytes

Short Wavelength Visible Light Suppresses Innate Immunity-Related Responses by Modulating Protein S-Nitrosylation in Keratinocytes

Blue-light filtering intraocular lenses (IOLs) for protecting macular health

Blue-light filtering intraocular lenses (IOLs) for protecting macular health

Influence of macular pigment optical density spatial distribution on intraocular scatter

PurposeThis study evaluated the summed measures of macular pigment optical density (MPOD) spatial distribution and their effects on intraocular scatter using a commercially available device (C-Quant, Oculus, USA). MethodsA customized heterochromatic flicker photometer (cHFP) device was used to measure MPOD spatial distribution across the central 16° using a 1° stimulus. MPOD was calculated as a discrete measure and summed measures across the central 1°, 3.3°, 10° and 16° diameters. Intraocular scatter was determined as a mean of 5 trials in which reliability and repeatability measures were met using the C-Quant. MPOD spatial distribution maps were constructed and the effects of both discrete and summed values on intraocular scatter were examined. ResultsSpatial mapping identified mean values for discrete MPOD [0.32 (s.d.=0.08)], MPOD summed across central 1° [0.37 (s.d.=0.11)], MPOD summed across central 3.3° [0.85 (s.d.=0.20)], MPOD summed across central 10° [1.60 (s.d.=0.35)] and MPOD summed across central 16° [1.78 (s.d.=0.39)]. Mean intraocular scatter was 0.83 (s.d.=0.16) log units. While there were consistent trends for an inverse relationship between MPOD and scatter, these relationships were not statistically significant. Correlations between the highest and lowest quartiles of MPOD within the central 1° were near significance. ConclusionsWhile there was an overall trend of decreased intraocular forward scatter with increased MPOD consistent with selective short wavelength visible light attenuation, neither discrete nor summed values of MPOD significantly influence intraocular scatter as measured by the C-Quant device.

Synthesis of Er3+:Al2O3-doped and rutile-dominant TiO2 composite with increased responsive wavelength range and enhanced photocatalytic performance under visible light irradiation

Much more attentions were paid to the anatase TiO2 than rutile due to its higher photoactivety with a larger band gap. However, it is usually ignored that the relative narrow band gap of rutile TiO2 benefits to the increasing in the responsive wavelength range. In this work, spherical activated carbon-supported Er3+:Al2O3-doped rutile TiO2 (Er3+:Al2O3/TiO2-SAC) was synthesized by a sol–gel method using tetrabutyl titanate as titanium precursor, and erbium nitrate and aluminum nitrate as dopant sources. Long-wavelength visible light from a light-emitting diode source was upconverted to ultraviolet light and short-wavelength visible light by Er3+ dopant, which could then be absorbed by the synthesized photocatalyst that contained rutile TiO2. This resulted in higher photocatalytic activity of samples with rutile than those with anatase. A response surface methodology based on the central composite design model was used to determine the optimum synthesis conditions: Er concentration, 0.07mol‱; Al concentration, 0.08mol%; and calcination temperature, 700°C. The catalyst achieved a 90.0% removal efficiency for methyl orange (MO) with a reaction rate of 18.98×10−3min−1 at an initial MO concentration of 500mgL−1 in 2h under visible-light irradiation.

Short-wavelength enrichment of polychromatic light enhances human melatonin suppression potency.

The basic goal of this research is to determine the best combination of light wavelengths for use as a lighting countermeasure for circadian and sleep disruption during space exploration, as well as for individuals living on Earth. Action spectra employing monochromatic light and selected monochromatic wavelength comparisons have shown that short-wavelength visible light in the blue-appearing portion of the spectrum is most potent for neuroendocrine, circadian, and neurobehavioral regulation. The studies presented here tested the hypothesis that broad spectrum, polychromatic fluorescent light enriched in the short-wavelength portion of the visible spectrum is more potent for pineal melatonin suppression in healthy men and women. A total of 24 subjects were tested across three separate experiments. Each experiment used a within-subjects study design that tested eight volunteers to establish the full-range fluence-response relationship between corneal light irradiance and nocturnal plasma melatonin suppression. Each experiment tested one of the three types of fluorescent lamps that differed in their relative emission of light in the short-wavelength end of the visible spectrum between 400 and 500 nm. A hazard analysis, based on national and international eye safety criteria, determined that all light exposures used in this study were safe. Each fluence-response curve demonstrated that increasing corneal irradiances of light evoked progressively increasing suppression of nocturnal melatonin. Comparison of these fluence-response curves supports the hypothesis that polychromatic fluorescent light is more potent for melatonin regulation when enriched in the short-wavelength spectrum.

Lethal effects of short-wavelength visible light on insects.

We investigated the lethal effects of visible light on insects by using light-emitting diodes (LEDs). The toxic effects of ultraviolet (UV) light, particularly shortwave (i.e., UVB and UVC) light, on organisms are well known. However, the effects of irradiation with visible light remain unclear, although shorter wavelengths are known to be more lethal. Irradiation with visible light is not thought to cause mortality in complex animals including insects. Here, however, we found that irradiation with short-wavelength visible (blue) light killed eggs, larvae, pupae, and adults of Drosophila melanogaster. Blue light was also lethal to mosquitoes and flour beetles, but the effective wavelength at which mortality occurred differed among the insect species. Our findings suggest that highly toxic wavelengths of visible light are species-specific in insects, and that shorter wavelengths are not always more toxic. For some animals, such as insects, blue light is more harmful than UV light.

Protective effects of bilberry and lingonberry extracts against blue light-emitting diode light-induced retinal photoreceptor cell damage in vitro

BackgroundBlue light is a high-energy or short-wavelength visible light, which induces retinal diseases such as age-related macular degeneration and retinitis pigmentosa. Bilberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea) contain high amounts of polyphenols (anthocyanins, resveratrol, and proanthocyanidins) and thus confer health benefits. This study aimed to determine the protective effects and mechanism of action of bilberry extract (B-ext) and lingonberry extract (L-ext) and their active components against blue light-emitting diode (LED) light-induced retinal photoreceptor cell damage.MethodsCultured murine photoreceptor (661 W) cells were exposed to blue LED light following treatment with B-ext, L-ext, or their constituents (cyanidin, delphinidin, malvidin, trans-resveratrol, and procyanidin B2). 661 W cell viability was assessed using a tetrazolium salt (WST-8) assay and Hoechst 33342 nuclear staining, and intracellular reactive oxygen species (ROS) production was determined using CM-H2DCFDA after blue LED light exposure. Activation of p38 mitogen-activated protein kinase (p38 MAPK), nuclear factor-kappa B (NF-κB), and LC3, an ubiquitin-like protein that is necessary for the formation of autophagosomes, were analyzed using Western blotting. Caspase-3/7 activation caused by blue LED light exposure in 661 W cells was determined using a caspase-3/7 assay kit.ResultsB-ext, L-ext, NAC, and their active components improved the viability of 661 W cells and inhibited the generation of intracellular ROS induced by blue LED light irradiation. Furthermore, B-ext and L-ext inhibited the activation of p38 MAPK and NF-κB induced by blue LED light exposure. Finally, B-ext, L-ext, and NAC inhibited caspase-3/7 activation and autophagy.ConclusionsThese findings suggest that B-ext and L-ext containing high amounts of polyphenols exert protective effects against blue LED light-induced retinal photoreceptor cell damage mainly through inhibition of ROS production and activation of pro-apoptotic proteins.

Noninvasive monitoring with strongly absorbed light

The transmission of light through tissue is used in noninvasive monitoring, in particular photoplethysmography. Investigations involving the transmission of wavelengths absorbed by bilirubin (short wavelength visible light) have been limited, due to strong absorption by haemoglobin. Achieving transmission of these wavelengths through tissue may advance noninvasive monitoring of substances like bilirubin. This work investigates the use of high power light sources together with improvements in signal-to-noise ratio as a means of enabling the transmission of strongly absorbed light through tissue. A custom device using multiple high-power short-wavelength visible light sources together with low power red and infrared sources, and background light cancellation to improve signal-to-noise ratio, was constructed. Transmission of 454-1200 nm light through tissue was achieved, with pulsations present in measured signals. The transmission through tissue of multiple wavelengths of strongly absorbed light can be achieved by using high power light sources in conjunction with cancelling the effect of background light. Use of these techniques may allow investigations into the noninvasive monitoring of substances such as bilirubin using photoplethysmography.

クリスタルガラス製品の製造に伴って発生するブルーライトの有害性

In factories for glassware production, workers are exposed to intense visible light emitted from hot objects such as furnaces and molten glass. High exposure to short-wavelength visible light, called blue light, can cause photoretinopathy. The objective of this study was to quantify the blue-light hazards associated with glassware production. Spectral radiances of walls and heating elements inside furnaces were measured, as well as those of molten glass placed inside furnaces in a factory producing crystal glass crafts. The factory had two reheating furnaces, three melting furnaces, and a furnace for preheating blowpipes. The effective radiances of the inner furnace walls, the heating elements, and the molten glass were calculated from the measured spectral radiances and compared with the threshold limit value (TLV) in accordance with ACGIH guidelines. The temperature of each light source was determined by comparing the measured spectral radiance with that of a black body. The measured effective radiances were in the range of 0.00498-0.708 mW/cm(2)sr and increased steeply with increasing light source temperatures in the range of 1,075-1,516 °C. The effective radiance of each light source was nearly equal to the effective radiance of the black body at the same temperature. The effective radiances of walls, heating elements, and molten glass inside the furnaces are lower than one tenth of the TLV for exposure durations longer than 10(4) s per day. Thus, it is not hazardous to view these light sources. However, the effective radiance at a higher light source temperature of approximately 1,800 °C will exceed the TLV. In this case, hot objects in a workplace for glassware production may present blue light hazards.

Samarium Ions Doped Yttrium Aluminium Garnet Glass Ceramics

Sm3+doped YAG glass ceramics containing single phase of YAG micro-crystals have been obtained by heat-treating the aluminosilicate precursor glasses. The YAG crystals grow with several preferred orientations and a dominant one (444) in the matrix, and present microcrystal sizes in the range of 3~15µm. The pilotaxitic texture existed in internal network of the YAG glass ceramics can increase yield strength and tensile strength of the sample effectively. Typical visible transition emissions of Sm3+have been observed in the YAG glass ceramics under the excitation of short-wavelength visible light, and the spectral intensity ratio between the electric dipole4G5/2→6H9/2and the magnetic dipole4G5/2→6H5/2transitions is lower than the values reported in the optical glasses specifying the enhanced symmetric nature in the Sm3+doped YAG glass ceramics. The obvious Stark splitting exhibited in emission spectrum manifests that rare-earth ions have been incorporated into YAG lattices.

Human phase response curve to a single 6.5 h pulse of short‐wavelength light

The photic resetting response of the human circadian pacemaker depends on the timing of exposure, and the direction and magnitude of the resulting shift is described by a phase response curve (PRC). Previous PRCs in humans have utilized high-intensity polychromatic white light. Given that the circadian photoreception system is maximally sensitive to short-wavelength visible light, the aim of the current study was to construct a PRC to blue (480 nm) light and compare it to a 10,000 lux white light PRC constructed previously using a similar protocol. Eighteen young healthy participants (18-30 years) were studied for 9-10 days in a time-free environment. The protocol included three baseline days followed by a constant routine (CR) to assess initial circadian phase. Following this CR, participants were exposed to a 6.5 h 480 nm light exposure (11.8 μW cm(-2), 11.2 lux) following mydriasis via a modified Ganzfeld dome. A second CR was conducted following the light exposure to re-assess circadian phase. Phase shifts were calculated from the difference in dim light melatonin onset (DLMO) between CRs. Exposure to 6.5 h of 480 nm light resets the circadian pacemaker according to a conventional type 1 PRC with fitted maximum delays and advances of -2.6 h and 1.3 h, respectively. The 480 nm PRC induced ∼75% of the response of the 10,000 lux white light PRC. These results may contribute to a re-evaluation of dosing guidelines for clinical light therapy and the use of light as a fatigue countermeasure.

A Novel Source of Methylglyoxal and Glyoxal in Retina: Implications for Age-Related Macular Degeneration

Aging of retinal pigment epithelial (RPE) cells of the eye is marked by accumulations of bisretinoid fluorophores; two of the compounds within this lipofuscin mixture are A2E and all-trans-retinal dimer. These pigments are implicated in pathological mechanisms involved in some vision-threatening disorders including age-related macular degeneration (AMD). Studies have shown that bisretinoids are photosensitive compounds that undergo photooxidation and photodegradation when irradiated with short wavelength visible light. Utilizing ultra performance liquid chromatography (UPLC) with electrospray ionization mass spectrometry (ESI-MS) we demonstrate that photodegradation of A2E and all-trans-retinal dimer generates the dicarbonyls glyoxal (GO) and methylglyoxal (MG), that are known to modify proteins by advanced glycation endproduct (AGE) formation. By extracellular trapping with aminoguanidine, we established that these oxo-aldehydes are released from irradiated A2E-containing RPE cells. Enzyme-linked immunosorbant assays (ELISA) revealed that the substrate underlying A2E-containing RPE was AGE-modified after irradiation. This AGE deposition was suppressed by prior treatment of the cells with aminoguanidine. AGE-modification causes structural and functional impairment of proteins. In chronic diseases such as diabetes and atherosclerosis, MG and GO modify proteins by non-enzymatic glycation and oxidation reactions. AGE-modified proteins are also components of drusen, the sub-RPE deposits that confer increased risk of AMD onset. These results indicate that photodegraded RPE bisretinoid is likely to be a previously unknown source of MG and GO in the eye.

Optical effects of exposing intact human lenses to ultraviolet radiation and visible light

BackgroundThe human lens is continuously exposed to high levels of light. Ultraviolet radiation is believed to play a causative role in the development of cataract. In vivo, however, the lens is mainly exposed to visible light and the ageing lens absorbs a great part of the short wavelength region of incoming visible light. The aim of the present study was to examine the optical effects on human lenses of short wavelength visible light and ultraviolet radiation.MethodsNaturally aged human donor lenses were irradiated with UVA (355 nm), violet (400 and 405 nm) and green (532 nm) lasers. The effect of irradiation was evaluated qualitatively by photography and quantitatively by measuring the direct transmission before and after irradiation. Furthermore, the effect of pulsed and continuous laser systems was compared as was the effect of short, intermediate and prolonged exposures.ResultsIrradiation with high intensity lasers caused scattering lesions in the human lenses. These effects were more likely to be seen when using pulsed lasers because of the high pulse intensity. Prolonged irradiation with UVA led to photodarkening whereas no detrimental effects were observed after irradiation with visible light.ConclusionsIrradiation with visible light does not seem to be harmful to the human lens except if the lens is exposed to laser irradiances that are high enough to warrant thermal protein denaturation that is more readily seen using pulsed laser systems.

Civilian Pilot Exposure to Ultraviolet and Blue Light and Pilot Use of Sunglasses

Population and animal studies indicate that long-term exposure to short-wavelength visible light and ultraviolet (UV) radiation causes increased risk of certain ocular pathologies such as cataracts and maculopathy. The potential risk to flight crew is unknown. The UK Civil Aviation Authority (CAA) has issued guidance to pilots regarding sunglass selection; however, it is not known if this guidance is appropriate given pilots' unique occupational environment. A search and appraisal of the relevant literature was conducted which showed that within the airline pilot population, there is limited evidence of a higher prevalence of cataracts. There are no data of other known UV-related ocular pathology. There is some evidence of higher prevalence of skin melanomas. Studies measuring cockpit UV radiation levels are limited and leave unanswered questions regarding airline pilot exposure. Data from optical transmission of cockpit windshields demonstrates the UV blocking properties at sea level. No studies have addressed the occupational use of sunglasses in airline pilots. Although it is likely that an aircraft windshield effectively blocks UV-B, the intensity of UV-A and short wavelength blue light present within the cockpit at altitude is unknown. Pilots may be exposed to solar radiation for periods of many hours during flight where UV radiation is known to be significantly greater. Aircraft windshields should have a standard for optical transmission, particularly of short-wavelength radiation. Clear, untinted prescription glasses will offer some degree of UV protection; however, sunglasses will offer superior protection. Any sunglasses used should conform to a national standard.

Invisibility Cloaks for Visible Light Must Remain Tiny, Theorists Predict

Efforts to make an invisibility cloak for shorter-wavelength visible light will never lead to something you can hide in, one team of researchers predicts. The researchers say a cloak for visible light would be so small it could hide only objects almost too tiny to be seen.

Polyscale technology for developing near infrared fluorescence bioimaging system based on novel synthese approaches for rare-earth doped nanophspors

Fluorescence bioimaging is one of the key technologies for biomedical science and engineering. Major issues of the current fluorescence bioimaiging are colour fading of the fluorescent probes, phototoxicity and strong light scattering due to the use of a short wavelength excitation light, an ultraviolet or visible light. The use of fluorescent probes to be excited by longer wavelength excitation light, i.e. near infrared light, should solve all of the above issues. In this paper, materials and system developments for the fluorescence bioimaging system with near infrared excitation are reviewed. The development of the system is based on 'polyscale technology,' a post-nanotechnology by cooperative works of the technologies in various scales. The concept and example of the 'polyscale technology' are also described.

Visible light induced bending and unbending behavior of crosslinked liquid-crystalline polymer films containing azotolane moieties

Monodomain crosslinked liquid-crystalline polymer (CLCP) films with three crosslinking densities were prepared by thermal polymerization of the mixtures of mono and diacrylates, both of which contain azotolane chromophores. Thermodynamic properties of the monomer, the crosslinker, their mixtures and the CLCP films were determined by differential scanning calorimetry. Mesomorphic properties were studied using a polarizing optical microscope and a polarized UV-vis absorption spectrometer. Due to a longer conjugated structure of the azotolane moieties in side chains, free-standing CLCP films underwent photoinduced bending upon exposure to short-wavelength visible light at 436 nm and the bent films returned to their initial states by alternating the wavelength of the actinic visible light to 577 nm. The bending could also be induced by 530 nm visible light though the bending speed decreased with the increasing of the wavelength of the actinic light. It was also observed that the bending speed of the films was related to the order parameter, the light intensity and the temperature. The mechanical force of the films generated upon exposure to visible light at 436 nm increased with the increasing of the crosslinking density and the light intensity but decreased with the increment of the temperature.

Hazards of solar blue light

Short-wavelength visible light (blue light) of the Sun has caused retinal damage in people who have stared fixedly at the Sun without adequate protection. The author quantified the blue-light hazard of the Sun according to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines by measuring the spectral radiance of the Sun. The results showed that the exposure limit for blue light can be easily exceeded when people view the Sun and that the solar blue-light hazard generally increases with solar elevation, which is in accordance with a model of the atmospheric extinction of sunlight. Viewing the Sun can be very hazardous and therefore should be avoided except at very low solar elevations.