Absorption Of Blue Light Research Articles

Preparation of dispersed submicron YAG:Ce3+ phosphors via the molten salt method

Nano Ce-doped yttrium aluminum garnet (YAG:Ce) phosphor precursor was synthesized using the urea precipitation method, and dispersed submicron YAG:Ce phosphor was prepared using the molten salt method, with fine particle NaCl acting as the salt source. The effects of NaCl particle size on the mixing homogeneity of raw materials, particle morphology, dispersity, and luminescent properties of YAG phosphor were investigated. We found that the mixing homogeneity improved dramatically with a fine (2 µm) NaCl particle. Agglomeration and sintering of the phosphor were significantly reduced, and 200 nm dispersed YAG phosphor can be obtained at 1000 °C. The YAG phosphor obtained with fine NaCl salt also exhibits excellent luminous performance. The YAG phosphor blue light absorption ratio is 38%, and the internal quantum efficiency is 93%. The internal quantum efficiency is superior to YAG phosphors synthesized using commercial large-particle NaCl. These findings provide a new idea for preparing dispersed inorganic powder with fine particle size using the molten salt method.

Macular pigments in retinal degenerative processes

Macular pigments (MP) - carotenoids, which determine the structure of the central part of the retina, play an important role in the work of its foveolar part. The main function of MP is to maintain full functionality of the macular area of the retina, which is based on the possibility of reducing color aberrations in the absorption of blue light and patients' ability for dark adaptation. Epidemiological studies have revealed a direct correlation between the low MP and the increased risk of developing age-related macular degeneration. However, global studies on the issue such as CARMA, CARMA, AREDS I, AREDS II, Rotterdam Study, and TOZAL study have proved the possibility of correcting the level of MP in the retina when they're taken as food additives, effectively reducing the risk of developing degenerative processes in the retina. In addition, studies have determined the optimal formula for food additives to stabilize the functionality of the macular area. The most important components of the additive have been shown include lutein, zeaxanthin, ascorbic acid, selenium, zinc, α-tocopherol acetate.

Modulatory effect of carotenoid supplement constituting lutein and zeaxanthin (10:1) on anti-oxidant enzymes and macular pigments level in rats

Background:Human eye is constantly exposed to different wavelengths and intensities of light. Oxidative stress results in distinct changes to retinal organs and tissues. Macular pigments (lutein and zeaxanthin), present in the central macular region, provide protection from photodamages by absorption of high energy blue light and also by virtue of their anti-oxidant activity. Ocular phototoxicity is thus prevented by our efficient anti-oxidant system, in both young and old. One of the best commercial sources of pure lutein and zeaxanthin is Marigold flowers.Objective:In the present study, oil-soluble dietary carotenoid supplement constituting lutein and zeaxanthin in the ratio of 10:1 was evaluated for its modulatory effect on anti-oxidant enzymes and macular pigments in the serum and macula of the Swiss albino rats.Materials and Methods:Male Swiss albino rats were treated with carotenoid supplement constituting lutein and trans-Zeaxanthin (10:1) at two different doses daily, under standard experimental conditions for 42 days. End of the treatment, serum and macula were collected and used for measurement of lutein and zeaxanthin levels along with anti-oxidant parameters.Statistical Analysis Used:Statistical differences were assessed by analysis of variance (ANOVA) followed by Dunnet's test. P < 0.05 was considered statistically significant. All the results were expressed as mean ± standard deviation.Results:The supplement exhibited significant elevation of anti-oxidant enzyme levels in treated animals in dose-dependent manner. Concomitantly, the total anti-oxidant capacity has also been found to show similar increment at the end of the study period. This study revealed significant expression of the two macular pigments investigated.Conclusions:Our study, therefore, provides a strong claim for the anti-oxidant effect of the oil-soluble dietary carotenoid supplement, and thus substantiates its use in the prevention of phototoxic damage to the eye on long-term supplementation.SUMMARY Apart from its ornamental value, Marigold (Tagetes erecta L.) flowers are well known as an herbal remedy due to its antimicrobial, anti-inflammatory, and anti-oxidant activities. Epidemiological studies have implicated prolonged exposure to ultraviolet radiations & blue light and in turn oxidative stress in the pathogenesis of the majority of the eye diseases, since childhood. Studies have shown that with age a number of changes occur predisposing the retinal various organs and tissues to oxidative stress. These changes manifest in decreased levels in plasma of Vitamin C, Vitamin E, glutathione, Retinal Pigment Epithelium (RPE), Catalase (CAT), Super Oxide Dismutase (SOD), Thiobarbituric Acid Reactive Substance (TBARS), and total anti-oxidant capacity (TAC). Age- and diet-related loss of Lutein and Zeaxanthin enhance phototoxic damage to the eye, and thus supplementation of these carotenoids becomes vital for maintaining optimal eye healthIn the present study, XanMax® 2002 oil, a supplement constituting lutein and trans-Zeaxanthin, extracted from the flowers of T. erecta, was evaluated for its modulatory effect on anti-oxidant enzymes and macular pigments in the serum and macula of the Swiss albino rats. XanMax® 2002 oil exhibited significant elevation of anti-oxidant enzyme levels in treated animals in dose-dependent manner. Concomitantly, the TAC has also been found to show similar increment at the end of the study period. This study revealed significant expression of the two macular pigments investigated. Abbreviations used: AMD: Age related Macular Diseases; RPE: Retinal Pigment Epithelium; CAT: Catalase; SOD: Super Oxide Dismutase; TAC: Total Antioxidant Capacity; ROS: Reactive Oxygen Species; LC-MS: Liquid chromatography-mass spectrometry; p.o.: Per Orally; CMC Carboxymethyl cellulose.

Waterproof Narrow-Band Fluoride Red Phosphor K2TiF6:Mn4+ via Facile Superhydrophobic Surface Modification.

With unique and efficient narrow-band red emission and broadband blue light absorption characteristics, Mn4+-activated fluoride red phosphors have gained increasing attention in warm white LEDs (WLEDs) and liquid crystal display (LCD) backlighting applications, whereas the intrinsic hygroscopic nature of these phosphors have inevitably limited their practical applications. Herein, a waterproof narrow-band fluoride phosphor K2TiF6:Mn4+ (KTF) has been demonstrated via a facile superhydrophobic surface-modification strategy. With the use of superhydrophobic surface modification with octadecyltrimethoxysilane (ODTMS) on KTF surfaces, the moisture-resistance performance and thermal stability of the phosphor KTF can be significantly improved. Meanwhile, the absorption, and quantum efficiency did not show obvious changes. The surface-modification processes and mechanism, as well as moisture-resistance performances and luminescence properties, of the phosphors have been carefully investigated. It was found that the luminous efficiency (LE) of the modified KTF was maintained at 83.9% or 84.3% after being dispersed in water for 2 h or aged at high temperature (85 °C) and high humidity (85%) atmosphere (HTHH) for 240 h, respectively. The WLEDs fabricated with modified KTF phosphor showed excellent color rendition with lower color temperature (2736 K), higher color rendering index (CRI, Ra = 87.3, R9 = 80.6), and high luminous efficiency (LE = 100.6 lm/W) at 300 mA. These results indicate that hydrophobic silane coupling agent (SCA) surface modification was a promising strategy for enhancing moisture resistance of humidity-sensitive phosphors, exhibiting great potential for practical applications.

Electron transfer pathways in a light, oxygen, voltage (LOV) protein devoid of the photoactive cysteine

Blue-light absorption by the flavin chromophore in light, oxygen, voltage (LOV) photoreceptors triggers photochemical reactions that lead to the formation of a flavin-cysteine adduct. While it has long been assumed that adduct formation is essential for signaling, it was recently shown that LOV photoreceptor variants devoid of the photoactive cysteine can elicit a functional response and that flavin photoreduction to the neutral semiquinone radical is sufficient for signal transduction. Currently, the mechanistic basis of the underlying electron- (eT) and proton-transfer (pT) reactions is not well understood. We here reengineered pT into the naturally not photoreducible iLOV protein, a fluorescent reporter protein derived from the Arabidopsis thaliana phototropin-2 LOV2 domain. A single amino-acid substitution (Q489D) enabled efficient photoreduction, suggesting that an eT pathway is naturally present in the protein. By using a combination of site-directed mutagenesis, steady-state UV/Vis, transient absorption and electron paramagnetic resonance spectroscopy, we investigate the underlying eT and pT reactions. Our study provides strong evidence that several Tyr and Trp residues, highly conserved in all LOV proteins, constitute the eT pathway for flavin photoreduction, suggesting that the propensity for photoreduction is evolutionary imprinted in all LOV domains, while efficient pT is needed to stabilize the neutral semiquinone radical.

Differential effects of changes in spectral irradiance on photoacclimation, primary productivity and growth in Rhodomonas salina (Cryptophyceae) and Skeletonema costatum (Bacillariophyceae) in simulated blackwater environments.

The underwater light field in blackwater environments is strongly skewed toward the red end of the electromagnetic spectrum due to blue light absorption by colored dissolved organic matter (CDOM). Exposure of phytoplankton to full spectrum irradiance occurs only when cells are mixed up to the surface. We studied the potential effects of mixing-induced changes in spectral irradiance on photoacclimation, primary productivity and growth in cultures of the cryptophyte Rhodomonas salina and the diatom Skeletonema costatum. We found that these taxa have very different photoacclimation strategies. While S.costatum showed classical complementary chromatic adaption, R.salina showed inverse chromatic adaptation, a strategy previously unknown in the cryptophytes. Transfer of R.salina to periodic full spectrum light (PFSL) significantly enhanced growth rate (μ) by 1.8 times and primary productivity from 0.88 to 1.35mg C·(mg Chl-1 )·h-1 . Overall, R.salina was less dependent on PFSL than was S.costatum, showing higher μ and net primary productivity rates. In the high-CDOM simulation, carbon metabolism of the diatom was impaired, leading to suppression of growth rate, short-term 14 C uptake and net primary production. Upon transfer to PFSL, μ of the diatom increased by up to 3-fold and carbon fixation from 2.4 to 6.0mg C·(mg Chl-1 )·h-1 . Thus, a lack of PFSL differentially impairs primarily CO2 -fixation and/or carbon metabolism, which, in turn, may determine which phytoplankton dominate the community in blackwater habitats and may therefore influence the structure and function of these ecosystems.

InGaN µLEDs integrated onto colloidal quantum dot functionalized ultra-thin glass.

Red-, orange-, and green-emitting integrated optoelectronic sources are demonstrated by transfer printing blue InGaN µLEDs onto ultra-thin glass platforms functionally enhanced with II-VI colloidal quantum dots (CQDs). The forward optical power conversion efficiency of these heterogeneously integrated devices is, respectively, 9%, 15%, and 14% for a blue light absorption over 95%. The sources are demonstrated in an orthogonal frequency division multiplexed (OFDM) visible light communication link reaching respective data transmission rates of 46 Mbps, 44 Mbps and 61 Mbps.

A rhodium catalyst hogs the spotlight

Photochemistry Photochemistry offers an efficient route to constructing four-membered carbon rings, but the product geometry is hard to control precisely. Even though catalysts can selectively orient the reacting partners, it is hard to outpace the unselective background reaction stimulated by catalyst-free light absorption. Huang et al. devised a chiral rhodium catalyst that enhanced the intrinsic blue light absorption of imidazole-substituted enones by more than 100-fold, thereby accelerating their [2+2] reaction with dienes and styrene derivatives. The acceleration was sufficient to achieve 92 to 99% enantiomeric excess in a wide variety of cyclobutane products, several of which bore contiguous quaternary stereocenters. J. Am. Chem. Soc. 10.1021/jacs.7b04363 (2017).

Indium Phosphide-Based Quantum Dots with Shell-Enhanced Absorption for Luminescent Down-Conversion.

It is shown that admixing small amounts of cadmium into the shell of InP/ZnSe core/shell quantum dots results in an increased absorption of blue light and a limited redshift of the band-edge emission. These effects reflect the reduced bandgap of (Zn,Cd)Se alloys and their smaller conduction-band offset with InP. Nevertheless, adjusting the InP core size enables InP/ZnSe and InP/(Zn,Cd)Se quantum dots with identical emission characteristics to be made. Processing both materials into remote phosphor disks, it is demonstrated that the shell-enhanced absorbance of InP/(Zn,Cd)Se has the double benefit of suppressing self-absorption and reducing the amount of quantum dots by weight needed to attain a given blue-to-red color conversion.

In vitro bactericidal activity of blue light (465 nm) phototherapy on meticillin-susceptible and meticillin-resistant Staphylococcus pseudintermedius.

Staphylococcus pseudintermedius is the most common cause of bacterial skin infections in dogs. Meticillin-resistant infections have become more common and are challenging to treat. Blue light phototherapy may be an option for treating these infections. The objective of this study was to measure the in vitro bactericidal activity of 465 nm blue light on meticillin-susceptible Staphylococcus pseudintermedius (MSSP) and meticillin-resistant Staphylococcus pseudintermedius (MRSP). We hypothesized that irradiation with blue light would kill MSSP and MRSP in a dose-dependent fashion in vitro as previously reported for meticillin-resistant Staphylococcus aureus (MRSA). In six replicate experiments, each strain [MSSP, n = 1; MRSP ST-71 (KM1381) n = 1; and MRSA (BAA-1680) n = 1] were cultivated on semisolid media, irradiated using a 465 nm blue light phototherapeutic device at the cumulative doses of 56.25, 112.5 and 225 J/cm2 and incubated overnight at 35°C. Controls were not irradiated. Colony counts (CC) were performed manually. Descriptive statistics were performed and treatment effects assessed using the Wilcoxon-Mann-Whitney rank-sum test. Bonferroni-corrected rank-sum tests were performed for post hoc analysis when significant differences were identified. There was a significant decrease in CC with blue light irradiation at all doses for MRSA (P = 0.0006) but not for MSSP (P = 0.131) or MRSP (P = 0.589). Blue light phototherapy significantly reduced CC of MRSA, but not of MSSP or MRSP. The mechanism for the relative photosensitivity of the MRSA isolate is unknown, but is hypothesized to be due to an increased concentration of porphyrin in S. aureus relative to S. pseudintermedius, which would modulate blue light absorption.

Macular Pigments

Yellowish pigmentation of the macula results from macular pigments called lutein, zeaxanthin, and mesozeaxanthin. Anatomical, biochemical (antioxidative) and optical (short-wavelength blue light absorption) properties of the macular pigments have increased the interest in vision and macular health. Macular pigments have been shown to have a protective role for age-related macular degeneration which is one of the leading causes of blindness all over the world. Macular pigments play an important role in the evaluation of the fundus imaging and diagnostic systems such as autofluorescence and angiography.

Volumetric Spatial Correlations of Neurovascular Coupling Studied using Single Pulse Opto-fMRI

Neurovascular coupling describes the link between neuronal activity and cerebral blood flow. This relationship has been the subject of intense scrutiny, with most previous work seeking to understand temporal correlations that describe neurovascular coupling. However, to date, the study of spatial correlations has been limited to two-dimensional mapping of neuronal or vascular derived signals emanating from the brain’s surface, using optical imaging techniques. Here, we investigate spatial correlations of neurovascular coupling in three dimensions, by applying a single 10 ms pulse of light to trigger optogenetic activation of cortical neurons transduced to express channelrhodopsin2, with concurrent fMRI. We estimated the spatial extent of increased neuronal activity using a model that takes into the account the scattering and absorption of blue light in brain tissue together with the relative density of channelrhodopsin2 expression across cortical layers. This method allows precise modulation of the volume of activated tissue in the cerebral cortex with concurrent three-dimensional mapping of functional hyperemia. Single pulse opto-fMRI minimizes adaptation, avoids heating artefacts and enables confined recruitment of the neuronal activity. Using this novel method, we present evidence for direct proportionality of volumetric spatial neurovascular coupling in the cerebral cortex.

Selective photocatalytic oxidation of benzyl alcohol into benzaldehyde with high selectivity and conversion ratio over Bi4O5Br2 nanoflakes under blue LED irradiation

Novel Bi4O5Br2 nanoflakes with a thickness of approximately 5nm and a band gap energy of 2.54eV were synthesized by a rapid and energy-saving microwave route. Under blue light emitting diode (LED) irradiation and using the Bi4O5Br2 nanoflakes as a photocatalyst, selective catalytic oxidation of benzyl alcohol (BA) into benzaldehyde (BAD) was successfully achieved with a high selectivity and conversion ratio. Compared to Bi12O17Cl2, which has a similar blue LED light absorption capability and a band gap energy of 2.37eV, these Bi4O5Br2 nanoflakes exhibit superb conversion efficiency (>99%) and selectivity (>99%) toward the photocatalytic oxidation of BA into BAD. Based on the structural characterization of the as-synthesized photocatalyst, comparison of photocatalytic performances, investigation of active radicals, and quantum chemical calculations, a possible photoreaction pathway is explored and proposed. It is revealed that the high selectivity of the system comes from direct hole oxidation of alkoxide anions (BA−) and the appropriate valence band potential (+2.41V vs. NHE) of Bi4O5Br2. And the high conversion ratio is attributed to the positively charged surface, large specific surface area with micro-nano structures, and effective separation of photogenerated carriers of the as-synthesized photocatalyst. In addition, the as-synthesized Bi4O5Br2 catalyst remains stable during the photocatalytic conversion process and can be utilized repeatedly, suggesting its potential for practical applications.

Two roads diverged in a yellow photolyase

Biophysics Photolyase enzymes repair DNA that has been damaged by ultraviolet sunlight. The repair process begins when blue light absorption by a cofactor drives an electron transfer step. Zhang et al. applied ultrafast absorption spectroscopy to study the dynamics of this step. A bifurcation in the

Dual wavelength stimulation of polymeric nanoparticles for photothermal therapy

Photothermal therapy (PTT) has several applications in the areas of wound healing, pain management, bacterial infection control, and cancer treatment dependent on the temperature that is generated. PTT is often used exclusively with near infrared (NIR) light and most nanoparticles (NP) used for PTT are designed to absorb within one narrow range of wavelengths. We have developed a dual-wavelength photothermal therapy by capitalizing on the dual absorption of nanoparticles in the blue and NIR range. Our lab has previously developed NP based on the semiconducting, conjugated polymer poly[4,4-bis(2-ethylhexyl)-cyclopenta[2,1-b;3,4-b']dithiophene-2,6-diyl-alt-2,1,3-benzoselenadiazole-4,7-diyl] (PCPDTBSe). The NP have strong absorption in the blue and NIR regions. In this report, we have explored the heat generated by PCPDTBSe NP using simultaneous delivery of 450 and 800 nm light, either independently or together for photothermal ablation of mouse colorectal cancer cells. The heat generation studies indicated that the use of either 450 or 800 nm wavelengths at the same fluences produced approximately the same temperature change of deionized water. Fluences of 114.6 and 229.2 J/cm2 , utilizing 450 or 800 nm light applied individually resulted in temperatures of 8-47°C above ambient temperature, leading to a 90% reduction in cell viability. Simultaneous stimulation of the PCPDTBSe NP with 450 and 800 nm light effectively doubles the effective power delivered, resulting in temperatures 18-63°C above ambient and 100% photothermal ablation of the colorectal cancer cells. The results of this study demonstrate that PCPDTBSe polymer NP can be utilized as effective PTT agents by capitalizing on their dual absorption of both blue and NIR light. Lasers Surg. Med. 48:893-902, 2016. © 2016 Wiley Periodicals, Inc.

Ambient exposure of the ocular tissues to optical radiation

SummaryOptical radiation is usually considered as radiation between 1 nm and 1 mm. The visible part of optical radiation typically extends from 400 and 760 nm. Optical radiation with wavelengths shorter than visible is referred to as ultraviolet radiation (UVR) and optical radiation with wavelengths longer than visible as infrared radiation (IRR). The most abundant source of optical radiation on the earth is daylight sun. The spectral emission of the sun is determined by the sun temperature, 5,778 K and the atmospheric attenuation. In environments with high backhground reflection of UVR the UVR from the sun at the surface of the earth may cause photochemical damage to the human eye. Humans have continuously increased the light load on the visual system by inventions like the fire, the incandescent‐ and the halogen‐ lamp, fluorescent tubes and recently the LED lamp. The primary emission from halogen lamps and fluorescent tubes contains enough UVR to cause photochemical damage to the eye if not fitted with suitable filters. Even when fitted with UVR blocking filters these sources increase the load of blue light on the retina that potentially causes photochemical damage. LED lamps used for illumination typically are blue emitting diodes with fluorescent coating that provides a white light sensation to the visual system. The spectral output typically has a strong peak in the blue balanced by a broad peak in red. The blue light potentially causes photochemical damage in the retina. The deviation of the spectral distribution of the LED lamp from that of the sun challenges the color perception of the visual system in the aging eye and after cataract surgery with blue blocking IOLs due to increased selective blue light absorption. Increasing use of IRR LEDs for remote sensing and control is a potential hazard to the anterior segment of the eye.

Blue-Black or White-Gold? Early Stage Processing and the Color of 'The Dress'.

PurposeIn Feb 2015 an image of a dress posted on Tumblr triggered an internet phenomenon: Is the Dress blue and black (BB) or white and gold (WG)? Many claim BB and others insist WG while the true colors are BB. The prevailing theory is that assumptions about the illuminant govern perception of the Dress with WG due to bluish lighting and BB due to yellowish. Our purpose was to determine if early stage optical, retinal and/or neural factors also impact perception of the Dress.MethodsThirty-nine subjects were categorized as BB or WG based on their initial perception of the Dress and their perception reported when viewing the Dress on iPhone 5, iPad, and 22” LCD displays. Macular pigment optical density (MPOD) measured with the QuantifEye™ MPS II and visual brainwaves (VEPs) in response to brief presentations of a transparency of the Dress illuminated by a flashing light were measured on each subject and compared between BB and WG groups. Additionally, CIE chromaticity (color) and luminance (brightness) were measured from multiple areas of the Dress image to determine cone stimulation and contrast.ResultsMean MPOD was higher in the WG group (0.49) vs. the BB (0.41, p = 0.04) and median values were higher as well (WG = 0.46, BB = 0.36, p = 0.03). There was no difference in VEP amplitude between groups (p > 0.85) but mean VEP latency was longer in WG (130 msec.) vs. the BB group (107 msec., p = 0.0005). Colorimetry of the Dress showed significantly greater stimulation of blue cones (contrast = 73%) vs. red and green sensitive cones (contrast = 13%).ConclusionsOur findings indicate that observers with denser MPOD may be predisposed to perceive the Dress as WG due to great absorption of blue light by the macular pigment. Moreover, the novel, substantial stimulation of blue cones by the Dress may contribute to ambiguity and dichotomous perception since the blue cones are so sparse in the retina. Finally, the delayed WG VEPs indicate distinct neural processing in perception of the consistent with fMRI evidence that the WG percept is processed at higher cortical levels than the BB. These results do not fully explain the dichotomous perception of the Dress but do exemplify the need to consider early stage processing when elucidating ambiguous percepts and figures.

Squarylium and rubrene based filterless narrowband photodetectors for an all-organic two-channel visible light communication system

In this paper, based on 1,3-bis[(3,3-dimethylindolin-2-ylidene)methyl]squaraine (ISQ), which has narrowband red-light absorption, and Rubrene, which possesses significant blue-light absorption, two color-selective organic photodetectors (OPDs) are developed. By quantum chemistry calculation, the mechanism of ISQ's sharp absorption spectrum is analyzed. Without input filtering, the two OPDs are well suited for two-channel visible light communications (VLC) system due to their good orthogonality of response spectrum and exceptional features, such as flexibility and ability to realize large-area thin-film manufacturing. With the two OPD as receivers and corresponding organic light emitting diodes (OLEDs) as data transmitters respectively, a two-channel VLC system delivering a bit-rate of 530 kb/s in the blue-light channel and 180 kb/s in the red-light channel was experimentally demonstrated. The two channels have good orthogonality when they operate together. This all-organic VLC system demonstrates the feasibility and benefit for the application of organic electronics in the communication field.

Organic Dye Graphene Hybrid Structures with Spectral Color Selectivity

This study characterizes a hybrid structure formed between graphene and organic dye molecules for use in photodetectors with spectral color selectivity. Rhodamine‐based organic dye molecules with red, green, or blue light absorption profiles are deposited onto a graphene surface by dip‐coating. UV–vis absorption spectroscopy, charge transport measurements, and density functional theory based calculations reveal that the photoresponses of the dye graphene hybrid films are governed by the light absorption of the dye molecules and also by the photo‐excited‐charge‐transfer‐induced photocurrent gain. The hybrid films respond only to photons with an energy exceeding the band gap of the immobilized dye. Dye‐Graphene charge transfer is affected by the distance and direction of the dipole moment between the two layers. The resulting hybrid films exhibit spectral color selectivities with responsivities of ≈103 A W−1 and specific detectivities of ≈1010 Jones. This study demonstrates the successful operation of photodetectors with a full‐color optical bandwidth using hybrid graphene structures coated with a mixture of dyes. The strategy of building a simple hybrid photodetector can further offer many opportunities to be also tuned for other optical functionalities using a variety of commercially available dye molecules.

Optogenetic activation of axon guidance receptors controls direction of neurite outgrowth.

Growth cones of extending axons navigate to correct targets by sensing a guidance cue gradient via membrane protein receptors. Although most signaling mechanisms have been clarified using an in vitro approach, it is still difficult to investigate the growth cone behavior in complicated extracellular environment of living animals due to the lack of tools. We develop a system for the light-dependent activation of a guidance receptor, Deleted in Colorectal Cancer (DCC), using Arabidopsis thaliana Cryptochrome 2, which oligomerizes upon blue-light absorption. Blue-light illumination transiently activates DCC via its oligomerization, which initiates downstream signaling in the illuminated subcellular region. The extending axons are attracted by illumination in cultured chick dorsal root ganglion neurons. Moreover, light-mediated navigation of the growth cones is achieved in living Caenorhabditis elegans. The photo-manipulation system is applicable to investigate the relationship between the growth cone behavior and its surrounding environment in living tissue.