Green Light Exposure Research Articles

Effect of n + Layer Deposition Power on Light Sensing of Amorphous Silicon pin Diodes

Amorphous hydrogenated silicon (a-Si:H) is a well-explored medium for solar cells and photodetectors due to its simple fabrication process and abundance of raw materials [1,2]. The effect of the a-Si:H deposition power on the light sensing has been studied in the literature [3]. However, the influence of the n+ layer deposition power was rarely studied. In this paper, the authors investigated the effect of the n+ layer deposition power on the performance of pin a-Si:H diodes under solar, red, green, and blue light exposure conditions. The a-Si:H pin tri-layer was fabricated using plasma-enhanced chemical vapor deposition (PECVD) process in the same chamber under one pump-down at 260°C with a 50 kHz RF generator. The Corning 1737 glass was used as the substrate. The deposition conditions are listed in Table I. The n+ layer deposition power was varied. It was the top layer where the device was first exposed to the incident light. Both the top and bottom electrodes were made of the sputter deposited 8 nm thick indium tin oxide (ITO) film. No metal back reflector was included in the diode structure. While this arrangement decreases light-sensing efficiency due to the lack of light-trapping [2], it has the versatility of allowing incident light through either side of the diode for testing purposes. The final annealing was done at 200°C in air for 30 min. Each cell was tested under the red (625 nm), green (530 nm), and blue (470 nm) LED exposure, respectively. The power density on the device was fixed at 27.6 W/m2. For the solar light test, the power density was 1000 W/m2. Figure 1 shows the current density (J) – voltage (V) curve of the device. For each curve, the corresponding open circuit voltage (V OC), short circuit current (J SC), fill factor (FF), efficiency (η), and external quantum efficiency (EQE) were calculated. Under solar light exposure, all devices exhibited the same V OC of 0.85 V independent of the n + deposition condition. The J SC and η increased with the increase of the deposition power. The FF increased non-linearly with the increase of power. Optical characteristics of the device changed with the wavelength of the exposure light and the n+ layer deposition power. In general, the best characteristics were obtained at the intermediate n+ layer deposition power of 300 W. Figure 2 shows the relationship between η and the deposition power of the n+ layer with the type of exposure light as the parameter. In spite of the difference in the n+ layer deposition power, the green light gave the highest η and the blue light gave the lowest η. In general, the RF power in the PECVD process affects the characteristics of doped a-Si:H thin films. With n + layers deposited at very low and at very high power, the light sensitivity declined under the single wavelength light exposure condition. However, under the solar light exposure, the maximum efficiency was observed at the highest power deposition condition. Therefore, in addition to the n + layer deposition power, the spectrum of the exposure light affected the sensing efficiency. Separately, influences of the n + layer deposition power on the film deposition rate and sheet resistivity have been investigated. According to Learn et al. [4], the dopant concentration in the n + a-Si:H thin films is inversely proportional to the deposition rate. Also, the sheet resistivity is inversely proportional to the dopant concentration, but this relationship breaks down at higher dopant concentrations due to the high defect density in the film [5]. In this study, it was observed that the light sensing of the a-Si:H pin diode improved with the n+ layer deposition power from 200 W to 300 W. However, the efficiency decreased with the further increase of the power probably due to the high defect density in the film or at the n+ / a-Si:H interface. [1] A.V. Shah, H. Schade, M. Vanecek, J. Meier, E. Vallat-Sauvain, N. Wyrsch, U. Kroll, C. Droz, and J. Bailat. Prog. Photovolt: Res. Appl. 12, 113 (2004). [2] B. Rech and H. Wagner. Appl. Phys. A 69, 155 (1999). [3] H. Miki, S. Kawamoto, T. Maejima, H. Sakamoto, M. Hayama, and Y. Onishi. Mat. Res. Soc. Symp. Proc. 95, 431 (1987). [4] A. Learn and D. Foster. Appl. Phys. 61, 1898 (1987). [5] S. Martín de Nicolás, D. Muñoz, A.S. Ozanne, N. Nguyen, and P.J. Ribeyron. Energy Procedia 8, 226 (2011). Figure 1

Development of a light-regulated cell-recovery system for non-photosynthetic bacteria

BackgroundRecent advances in the understanding of photosensing in biological systems have enabled the use of photoreceptors as novel genetic tools. Exploiting various photoreceptors that cyanobacteria possess, a green light-inducible gene expression system was previously developed for the regulation of gene expression in cyanobacteria. However, the applications of cyanobacterial photoreceptors are not limited to these bacteria but are also available for non-photosynthetic microorganisms by the coexpression of a cyanobacterial chromophore with a cyanobacteria-derived photosensing system. An Escherichia coli-derived self-aggregation system based on Antigen 43 (Ag43) has been shown to induce cell self-aggregation of various bacteria by exogenous introduction of the Ag43 gene.ResultsAn E. coli transformant harboring a plasmid encoding the Ag43 structural gene under a green light-regulated gene expression system derived from the cyanobacterium Synechocystis sp. PCC6803 was constructed. Ag43 was inserted downstream of the cpcG2 promoter PcpcG2, and its expression was regulated by green light induction, which was achieved by the functional expression of cyanobacterial CcaS/CcaR by coexpressing its chromophore synthesis gene cassette in E. coli. E. coli transformants harboring this designed system self-aggregated under green light exposure and precipitated, whereas transformants lacking the green light induction system did not. The green light induction system effectively functioned before the cell culture entered the stationary growth phase, and approximately 80 % of the cell culture was recovered by simple decantation.ConclusionThis study demonstrated the construction of a cell recovery system for non-photosynthetic microorganisms induced by exposure of cells to green light. The system was regulated by a two-component regulatory system from cyanobacteria, and cell precipitation was mediated by an autotransporter protein, Ag43. Although further strict control and an increase of cell recovery efficiency are necessary, the system represents a novel tool for future bioprocessing with reduced energy and labor required for cell recovery.

MGarnet, A Far-Red Fluorescent Protein for Live-Cell Sted Imaging

Red-emitting fluorescent proteins (RFPs) with fluorescence emission above 600 nm are advantageous for cell and tissue imaging applications for various reasons. Fluorescence from an RFP is well separated from cellular autofluorescence, which is in the green region of the spectrum, and red light is scattered less, which allows thicker specimens to be imaged. Moreover, the phototoxic response of cells is lower for red than blue or green light exposure. We have selected a monomeric variant of the tetrameric RFP eqFP611 from Entacmaea quadricolor, mRuby, as a lead structure and used rational protein design to generate RFP variants with improved photochemical properties.Four point mutations were sufficient to obtain mGarnet, a robust monomeric marker protein with far-red fluorescence peaking at 670 nm. mGarnet can be efficiently excited with 640-nm light on the red edge of its 598-nm excitation band. The large Stokes shift of 72 nm allows essentially the entire fluorescence emission to be collected even with 640-nm excitation. We demonstrate an excellent performance as a live-cell fusion marker in STED microscopy.

A systematic review of light therapy on mood scores in major depressive disorder: light specification, dose, timing and delivery

<p><strong>Background:</strong> Depression is associated with prolonged disability, mortality, and morbidity. Ninety percent of patients with Major depressive disorder (MDD) have sleep problems. Light therapy has been shown to be effective in treating sleep disorders and MDD. This review aims to assess the characteristics (colour, intensity), exposure dose (duration and timing) and the mode of delivery (light boxes, visor etc) of light in reducing depression, measured by mood scores, in MDD.</p><p><strong>Method:</strong> a systematic literature search was performed on 6 major databases. The Physiotherapy Evidence Database (PEDro) Scale was applied to assess study quality.</p><p><strong>Result:</strong> Twenty-four articles satisfied the inclusion criteria. Effective light intensities varied from 176 -10,000 lux. Effective modes of delivery included light box, table lamp, visor and light emitting diode (LED) glasses. Effective light colours included white, green, and blue with the white colour being the most commonly used. The duration of light treatment ranged from 30 min to 2 h, and evening light generally improved mood.</p><p><strong>Conclusion:</strong> Light therapy, with exposure durations in the range of 30 min to 2 h per day, intensity range of 176 to 10,000 lux, in any of blue, green, or white light colour and exposure during morning mostly demonstrated a positive change in mood effects. Factors other than the light properties, such as anti-depressant medication use, depression episodes and severity, natural light exposure and sleep deprivation may confound the effects of light therapy.</p>

Green light sensitive diketopyrrolopyrrole derivatives used in versatile photoinitiating systems for photopolymerizations

The monomeric (DPPDT) and polymeric (PDQT) diketopyrrolopyrrole–thiophene derivatives combined with an iodonium salt or an amine (and optionally an additive) are used as photoinitiating systems to initiate the cationic polymerization of epoxides or divinyl ethers, radical polymerization of acrylates and thiol–ene polymerization under different irradiation sources (i.e. very soft halogen lamp, laser diodes at 473 nm, 532 nm and 808 nm). The DPPDT based systems are very efficient upon the green light exposure. Remarkably, these systems are characterized by a higher efficiency than references based on camphorquinone, a well known photosensitizer for visible light. The photochemical mechanisms are studied by steady state photolysis, fluorescence, cyclic voltammetry, laser flash photolysis and electron spin resonance spin trapping techniques.

Light-induced anatomical alterations in retinal cells

Exploring the cellular behavior and real-time evaluation of light-induced stress in retinal cells requires advanced sensitive methods. Here, an analytical application of a bioimpedance system was developed to quantify cell morphology changes in light-induced anatomical response. Hence, an unprecedented light setup was established using a bioimpedance system to generate artificial light that stresses retinal ganglion cells (RGCs), and the corresponding impedance was recorded. The dynamics of initial light-induced stress and the morphological changes were examined. This examination showed impedance drop, and the normalized variance ratios were used to quantify the changes. A rapid impedance drop was measured after exposure to the red and blue lights, whereas it was found that a minimum impedance drop was analyzed under the green light exposure. These data have revealed a strong, unconventional reliable model to detect the onset changes for photo-oxidative stress-related studies by the morphological changes of neurite retraction and cell body shrinkage. The data revealed that functions of the RGC-5 cell line under light exposure were diminished in cell strength and activity was hindered. These reduced functions might be related to the declined levels of some protein markers and stress factors. This is an effective model to study stress, morphological changes, and photodamage.

Exposure Light Wavelength Effects on Charge Trapping and Detrapping of nc-MoOx Embedded ZrHfO High-k Stack

ABSTRACTThe influence of the red and green LED light exposure on the memory function of the nanocrystalline MoOx embedded ZrHfO high-k gate dielectric has been investigated. Since the performance of the device is mainly dependent on the hole trapping and detrapping mechanisms, the light exposure affects the hole generation, transfer, and storage to and in the dielectric structure. Both the charge storage capacity and the leakage current were increased from the light exposure. The Coulomb blockade phenomenon in the leakage current density vs. gate voltage curve disappears under the light exposure condition. The light exposure effect is potentially important for practical application of the device.

Quasi-nonvolatile storage in Ru-doped Bi_12SiO_20 crystals by two-wavelength holography

Prolonged read-out process of a hologram recorded at near infrared with simultaneous green light exposure is measured in Ru-doped Bi12SiO20 crystal. The experimental results are confirmed by numerical simulations, suggesting two different traps involved in the space-charge transport mechanism. In addition, quasi-permanent holographic recording of image with fast updating speed by using two-wavelength recording is demonstrated.

Does pupil constriction under blue and green monochromatic light exposure change with age?

Many nonvisual functions are regulated by light through a photoreceptive system involving melanopsin-expressing retinal ganglion cells that are maximally sensitive to blue light. Several studies have suggested that the ability of light to modulate circadian entrainment and to induce acute effects on melatonin secretion, subjective alertness, and gene expression decreases during aging, particularly for blue light. This could contribute to the documented changes in sleep and circadian regulatory processes with aging. However, age-related modification in the impact of light on steady-state pupil constriction, which regulates the amount of light reaching the retina, is not demonstrated. We measured pupil size in 16 young (22.8±4 years) and 14 older (61±4.4 years) healthy subjects during 45-second exposures to blue (480 nm) and green (550 nm) monochromatic lights at low (7×10(12) photons/cm2/s), medium (3×10(13) photons/cm2/s), and high (10(14) photons/cm2/s) irradiance levels. Results showed that young subjects had consistently larger pupils than older subjects for dark adaptation and during all light exposures. Steady-state pupil constriction was greater under blue than green light exposure in both age groups and increased with increasing irradiance. Surprisingly, when expressed in relation to baseline pupil size, no significant age-related differences were observed in pupil constriction. The observed reduction in pupil size in older individuals, both in darkness and during light exposure, may reduce retinal illumination and consequently affect nonvisual responses to light. The absence of a significant difference between age groups for relative steady-state pupil constriction suggests that other factors such as tonic, sympathetic control of pupil dilation, rather than light sensitivity per se, account for the observed age difference in pupil size regulation. Compared to other nonvisual functions, the light sensitivity of steady-state pupil constriction appears to remain relatively intact and is not profoundly altered by age.

Green light affects blue-light-based phototropism in hypocotyls of Arabidopsis thaliana1

Abstract Light affects all aspects of plant growth and development from seed germination to senescence. While there has been intensive investigation of the effects of blue and red light on development and tropisms, much less is known about the specific effects of green light exposure in plants. Several recent studies demonstrate that monochromatic green light has a number of physiological effects including antagonizing light-mediated growth inhibition in hypocotyls and reversing blue-light-induced stomatal opening. In this paper, we report on the effects of green light pulses on phototropism in both light- and dark-grown seedlings of Arabidopsis thaliana. Green light had no effect on either red-light or blue-light-based phototropism in roots. However, in hypocotyls of dark-grown seedlings, pulses of green light significantly reduced blue-light positive phototropism while the growth rate was increased. In contrast, in hypocotyls of light-grown seedlings, green pulses significantly increased positive photot...

Green light radiation effects on free radicals inhibition in cellular and chemical systems

Free radicals generation is inhibited through green light (GL) irradiation in cellular systems and in chemical reactions. Standard melanocyte cultures were UV-irradiated and the induced cellular reactive oxygen species (ROS) were quantified by the fluorescence technique. The same cell cultures, previously protected by a 24 h GL exposure, displayed a significantly lower ROS production. A simple chemical reaction is subsequently chosen, in which the production of free radicals is well defined. Paraffin wax and mineral oil were GL irradiated during thermal degradation and the oxidation products checked by chemiluminescence [CL] and Fourier transform infrared spectra [FT-IR]. The same clear inhibition of the radical oxidation of alkanes is recorded. A quantum chemistry modeling of these results is performed and a mechanism involving a new type of Rydberg macromolecular systems with implications for biology and medicine is suggested.

Photoinduced broadening of cholesteric liquid crystal reflectors

The selective reflection of cholesteric liquid crystals (CLCs) is well-known and has been utilized in a number of dynamic optical applications. This work presents a novel approach to passively (e.g., all-optically) cue reflection notch broadening in photoresponsive CLC formulations based on high helical twisting power (HTP) bis(azo) chiral dopants. The original reflection bandwidth of approximately 100 nm is increased to as much as 1700 nm, by exposing 36 μm thick cells to UV light. The maximum attainable bandwidth is shown to be a function of cell thickness, light intensity, and strongly related to the HTP of the photoresponsive chiral dopants. An all-optical technique of simultaneous UV and green light exposure is demonstrated to trap the reflection notch at a predetermined position and bandwidth.

AGE-DEPENDENT ALTERATIONS IN HUMAN PER2 LEVELS AFTER EARLY MORNING BLUE LIGHT EXPOSURE

In our modern society, we are exposed to different artificial light sources that could potentially lead to disturbances of circadian rhythms and, hence, represent a risk for health and welfare. Investigating the acute impact of light on clock-gene expression may thus help us to better understand the mechanisms underlying disorders rooted in the circadian system. Here, we show an overall significant reduction in PER2 expression in oral mucosa with aging in the morning, noon, and afternoon. In the afternoon, 10 h after exposure to early morning blue light, PER2 was significantly elevated in the young compared to green light exposure and to older participants. Our findings demonstrate that human buccal samples are a valuable tool for studying clock-gene rhythms and the response of PER2 to light. Additionally, our results indicate that the influence of light on clock-gene expression in humans is altered with age. (Author correspondence: urs.albrecht@unifr.ch)

Age-Related Changes in Acute and Phase-Advancing Responses to Monochromatic Light

Reduced sensitivity to short-wavelength (blue) light with age has been shown for light-induced melatonin suppression. The current research aimed to determine if a similar age-related reduction occurs in subjective alertness, mood, and circadian phase-advancing responses. Young (n = 11, 23.0 +/- 2.9 years) and older (n = 15, 65.8 +/- 5.0 years) healthy males participated in laboratory sessions that included a 2-h intermittent monochromatic light exposure, individually timed to begin 8.5 h after their dim light melatonin onset (DLMO) determined in a prior visit. In separate sessions, pupil-dilated subjects were exposed to short-wavelength blue (lambda max 456 nm) and medium-wavelength green (lambda max 548 nm) light matched for photon density (6 x 1013 photons/cm2/sec). Subjective alertness, sleepiness, and mood were verbally assessed every 15 to 30 min before, during, and up to 5 h after the light exposure. The magnitude of phase advance was assessed as the difference in plasma melatonin rhythm phase markers before and after light exposure. Following blue light exposure, responses in older men were significantly diminished compared with young men for subjective alertness (p < 0.0001), sleepiness (p < 0.0001), and mood (p < 0.05) during and after light exposure. There was no significant effect of age on these parameters following green light exposure. The phase advances to both blue and green light were larger in the young than older subjects, but did not reach statistical significance. In general, phase advances to blue light were slightly larger than to green light in both young and old, but did not reach statistical significance. The current results add to previous findings demonstrating reduced responsiveness to the acute effects of blue light in older people (melatonin suppression, alertness). However, under the study paradigm, the phase-advancing response to light does not appear to be significantly impaired with age.

Wavelength-Dependent Modulation of Brain Responses to a Working Memory Task by Daytime Light Exposure

In addition to classical visual effects, light elicits nonvisual brain responses, which profoundly influence physiology and behavior. These effects are mediated in part by melanopsin-expressing light-sensitive ganglion cells that, in contrast to the classical photopic system that is maximally sensitive to green light (550 nm), is very sensitive to blue light (470-480 nm). At present, there is no evidence that blue light exposure is effective in modulating nonvisual brain activity related to complex cognitive tasks. Using functional magnetic resonance imaging, we show that, while participants perform an auditory working memory task, a short (18 min) daytime exposure to blue (470 nm) or green (550 nm) monochromatic light (3 x 10(13) photons/cm2/s) differentially modulates regional brain responses. Blue light typically enhanced brain responses or at least prevented the decline otherwise observed following green light exposure in frontal and parietal cortices implicated in working memory, and in the thalamus involved in the modulation of cognition by arousal. Our results imply that monochromatic light can affect cognitive functions almost instantaneously and suggest that these effects are mediated by a melanopsin-based photoreceptor system.

Reduction of indocyanine green-associated photosensitizing toxicity in retinal pigment epithelium by sodium elimination.

To determine if eliminating sodium affects indocyanine green (ICG) photosensitizing toxicity and uptake in cultured human retinal pigment epithelial (RPE) cells. Cultured human RPE cells were exposed to ICG (2.5 mg/mL) in balanced salt solution and sodium-free balanced salt solution for 2 minutes. Afterwards, ICG was removed, and the cells were irradiated with a light beam (4 x 10(4) lux) for 40 minutes. Toxicity was monitored using light microscopy, calcein AM-ethidium homodimer 1 staining, trypan blue exclusion test, and 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium viability assay. Indocyanine green uptake was measured by optical absorption at 790 nm. Photoreactive changes occurred in RPE cells exposed to ICG and light. These changes included cell shrinkage, cell death, pyknotic nuclei, reduced viability, and reduced mitochondrial dehydrogenase activity. These changes were less severe when ICG was dissolved in sodium-free balanced salt solution. In addition, ICG uptake was reduced when the solvent was sodium-free balanced salt solution. Indocyanine green and intense light exposure in RPE cells caused photosensitizing toxicity that was reduced when sodium in the solvent was eliminated and replaced with other cations. Eliminating sodium from the solvent reduced ICG uptake into RPE and its associated photosensitizing toxicity. This reconstitution method of ICG may be helpful for safer intravitreal ICG use in macular hole surgery.

Embryonic Growth, Hatching Time and Hatchability Performance of Meat Breeder Eggs Incubated under Continuous Green Light

The effects of dark-control (D) and continuous green light (GL) exposure of incubated meat-type breeder eggs (Hybro) on embryonic growth from 5 to 15 days of age, hatching time, hatchability per cent and chick hatching weight were investigated in three consecutive experiments at 33, 38, and 41 weeks of age. A total of 798 eggs were used in this study. Eggs were set in an incubator on trays either in the D or under two tubes of 20-watt green fluorescent light during the first 18 days of incubation. Eggs from both treatments were transferred to the dark hatching compartment at 19 days of incubation. The light intensity was in the range of 1,340 to 1,730 lux at the surface of the eggs. GL incubation of eggs significantly (p<0.01) increased weight (expressed as an absolute value) and daily weight gain of embryos at 11 and continued to 15 days of age, hatchability per cent by 4.8%, reduced dead embryos per cent and chick weight at hatch by 37 and 2%, respectively and accelerated hatching time by about 24 h when compared with the D-control incubation. Chicks hatched at 504 h of incubation had significantly (p<0.01) higher body weight, expressed as an absolute value or as a percentage of egg weight, than those hatched earlier at 456 h of incubation. It was concluded that the GL incubation of meat breeder eggs reduced incubation period and chick weight at hatch and increased embryonic growth and hatchability per cent. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1702-1707)

Photochemical and Photoorientational Behavior of Liquid Crystalline Carbosilane Dendrimer with Azobenzene Terminal Groups

The photochemical and photooptical properties of the first-generation LC dendrimer with terminal azobenzene groups which forms a SmA mesophase in a wide temperature range have been studied. A comparative analysis of its photochemical behavior in a dilute solution and a thin film was carried out. Under the action of UV irradiation, the E/Z photoisomerization of the azobenzene group takes place both in the solution and in the film. This process is found to be photochemically and thermally reversible. The kinetics of the thermal Z/E process is studied, and the activation energy of the process is calculated. The process of the photoinduced orientation of the terminal azobenzene groups in films of the dendrimer upon irradiation with linearly polarized UV light (365 nm) and with the green light of an Ar+ laser (488 nm) was studied. Under irradiation with linearly polarized UV light, the E/Z isomerization takes place, but photoorientation is not observed. However, in the case of linearly polarized green light exposure (488 nm), a well pronounced linear dichroism is generated. The kinetics of the process was studied, and the photoinduced orientational order parameter was calculated.

Effect of light on choroidal blood flow in the fovea centralis

To investigate whether light and dark exposures induce a response of choroidal blood flow (ChBF) in the foveal region in humans. In a group of healthy volunteers (age 25-60 years) ChBF was measured using a new confocal laser Doppler flowmeter (probing laser at 785 nm, power at the cornea = 90 microW). ChBF was recorded at room light, in darkness, at room light following dark adaptation, and during strong light exposure following room light. While ChBF was stable during room light condition, it decreased significantly by 15% (p < 0.01) during darkness. After 6 min of room light following darkness, ChBF was back to baseline. Strong diffuse, green light exposure over a field of 45 degrees had no detectable effect on ChBF. In all the experiments, no significant change of blood pressure was detected. Our findings did not confirm the presence of an active process of ChBF regulation in response to strong light exposure in humans. They demonstrate, however, a reversible decrease in ChBF occurring after a transition from room light to darkness.

Cells, bilirubin and light: formation of bilirubin photoproducts and cellular damage at defined wavelengths.

Cultured cells from one human and one murine cell line were treated with bilirubin and irradiated with visible light of different wavelengths, either from phototherapy lamps or from a Xenon/Mercury lamp equipped with a monochromator. Bilirubin bound to human serum albumin was also irradiated with light. After irradiation, the bilirubin and its photoisomers were extracted and analysed with High Pressure Liquid Chromatography. The formation of single strand breaks in the DNA of treated cells was studied using a fluorescence marker. Cytotoxicity in the mouse skin cell line was measured by loss of the ability to form visible colonies in vitro. Green light exposure favours the production of lumirubin, while blue light causes more DNA damage and cytotoxicity. Green light may be more efficient and safer than shorter wavelength exposure when treating jaundiced newborns with phototherapy.