Long-wavelength Visible Light Research Articles

Highly active dye-sensitized photocatalytic H2 evolution catalyzed by a single-atom Pt cocatalyst anchored onto g-C3N4 nanosheets under long-wavelength visible light irradiation

A single-atom Pt cocatalyst anchored onto g-C3N4 nanosheets could efficiently catalyze H2 evolution from an Eosin Y-sensitized system under 520 nm irradiation.

Dinuclear PhotoCORMs: Dioxygen-Assisted Carbon Monoxide Uncaging from Long-Wavelength-Absorbing Metal–Metal-Bonded Carbonyl Complexes

We describe a new strategy for triggering the photochemical release of caged carbon monoxide (CO) in aerobic media using long-wavelength visible and near-infrared (NIR) light. The dinuclear rhenium-manganese carbonyl complexes (CO)5ReMn(CO)3(L), where L = phenanthroline (1), bipyridine (2), biquinoline (3), or phenanthrolinecarboxaldehyde (4), each show a strong metal-metal-bond-to-ligand (σMM → πL*) charge-transfer absorption band at longer wavelengths. Photolysis with deep-red (1 and 2) or NIR (3 and 4) light leads to homolytic cleavage of the Re-Mn bonds to give mononuclear metal radicals. In the absence of trapping agents, these radicals primarily recombine to reform dinuclear complexes. In oxygenated media, however, the radicals react with dioxygen to form species much more labile toward CO release via secondary thermal and/or photochemical reactions. Conjugation of 4, with an amine-terminated poly(ethylene glycol) oligomer, gives a water-soluble derivative with similar photochemistry. In this context, we discuss the potential applications of these dinuclear complexes as visible/NIR-light-photoactivated CO-releasing moieties (photoCORMs).

Purple-bacterial photosynthetic reaction centers and quantum‐dot hybrid‐assemblies in lecithin liposomes and thin films

Quantum dots (QDs) absorb ultraviolet and long-wavelength visible light energy much more efficiently than natural bacterial light-harvesting proteins and can transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion of RCs combined with QDs as antennae into liposomes opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components or inorganic components alone.RCs from Rhodobacter sphaeroides and QDs (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased. The efficiency of energy transfer between QDs and RCs and conditions of long-term stability of function of such hybrid complexes in film preparations were investigated as well. It was found that dry films containing RCs and QDs, maintained at atmospheric humidity, are capable of maintaining their functional activity for at least some months as judged by measurements of their spectral characteristics, efficiency of energy transfer from QDs to RCs and RC electron transport activity. Addition of trehalose to the films increases the stability further, especially for films maintained at low humidity. These stable hybrid film structures are promising for further studies towards developing new phototransformation devices for biotechnological applications.

Wrinkled silica/titania nanoparticles with tunable interwrinkle distances for efficient utilization of photons in dye-sensitized solar cells.

Efficient light harvesting is essential for the realization of high energy conversion efficiency in dye-sensitized solar cells (DSCs). State-of-the-art mesoporous TiO2 photoanodes fall short for collection of long-wavelength visible light photons, and thus there have been efforts on introduction of scattering nanoparticles. Herein, we report the synthesis of wrinkled silica/titania nanoparticles with tunable interwrinkle distances as scattering materials for enhanced light harvesting in DSCs. These particles with more than 20 times larger specific surface area (>400 m2/g) compared to the spherical scattering particles (<20 m2/g) of the similar sizes gave rise to the dye-loading amounts, causing significant improvements in photocurrent density and efficiency. Moreover, dependence of spectral scattering properties of wrinkled particles on interwrinkle distances, which was originated from difference in overall refractive indices, was observed.

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.

2+2] cycloaddition of 1,3-dienes by visible light photocatalysis.

[2+2] photocycloadditions of 1,3-dienes represent a powerful yet synthetically underutilized class of reactions. We report that visible light absorbing transition metal complexes enable the [2+2] cycloaddition of a diverse range of 1,3-dienes. The ability to use long-wavelength visible light is attractive because these reaction conditions tolerate the presence of sensitive functional groups that might be readily decomposed by the high-energy UVC radiation required for direct photoexcitation of 1,3-dienes. The resulting vinylcyclobutane products are poised for a variety of further diversification reactions, and this method is consequently expected to be powerfully enabling in the synthesis of complex organic targets.

Oxidative cleavage of DNA by pentamethine carbocyanine dyes irradiated with long-wavelength visible light

Here we report the synthesis of seven symmetrical carbocyanine dyes in which two nitrogen-substituted benz[e]indolium rings are joined by a pentamethine bridge that is meso-substituted with chlorine or bromine versus hydrogen. The heteroatom of benz[e]indolium is modified with a phenylpropyl, methyl, or cationic quaternary ammonium group. In reactions containing micro molar concentrations of halogenated dye, irradiation at 575, 588, 623, or 700nm produces good photocleavage of plasmid DNA. UV–visible spectra show that the carbocyanines are in their H-aggregated and monomeric forms. Scavenger experiments point to the involvement of singlet oxygen and hydroxyl radicals in DNA photocleavage.

Nanomaterial antennae in photo-delivery of bioactive molecules

Our laboratory has developed photochemical strategies for delivery of NO and CO to physiological targets that allow control of the location, timing, and dosage of such delivery. We have explored the photoreactions of the iron/sulfur/nitrosyl clusters Fe 2 (μ-SR) 2 (NO) 4 and the Cr (III) nitrito complex trans- Cr (cyclam) ( ONO ) 2 + that release NO under visible irradiation but not at longer wavelengths. Thus, we have designed new supramolecular assemblies with water-soluble semiconductor quantum dots and lanthanide near-IR upconversion materials to serve as antennae for photosensitization of reactions from analogous precursors and increase rates of NO release using longer wavelength visible light. Certain antennae have high two photon cross-sections, a feature that allows use of NIR light (where tissue transmission is maximized) to sensitize photoreactions of these systems.

Long-Wavelength Photosensitivity in Coral Planula Larvae

Light influences the swimming behavior and settlement of the planktonic planula larvae of coral, but little is known regarding the photosensory biology of coral at this or any life-history stage. Here we used changes in the electrical activity of coral planula tissue upon light flashes to investigate the photosensitivity of the larvae. Recordings were made from five species: two whose larvae are brooded and contain algal symbionts (Porites astreoides and Agaricia agaricites), and three whose larvae are spawned and lack algal symbionts (Acropora cervicornis, Acropora palmata,and Montastrea faveolata). Photosensitivity originated from the coral larva rather than from, or in addition to, its algal symbionts as species with and without symbionts displayed similar tissue-level electrical responses to light. All species exhibited as much (or more) sensitivity to red stimuli as to blue/green stimuli, which is consistent with a role for long-wavelength visible light in the preference for substrata observed during settlement and in facilitating vertical positioning of larvae in the water column.

Fluorescent Somatostatin Receptor Probes for the Intraoperative Detection of Tumor Tissue with Long-Wavelength Visible Light

Targeted fluorescent dyes are of substantial value for the intraoperative delineation of primary tumors and metastatic lesions. For this purpose long-wavelength red light (λ=550–650 nm) offers advantages because of good tissue penetration and direct visibility. Since somatostatin receptors (SSTR) are overexpressed in a number of tumors, a series of potentially tumor-selective peptide–dye conjugates were synthesized by solid-phase peptide synthesis (SPPS). The octapeptides octreotate, Tyr3-octreotate and Tyr3-octreotide were employed and exhibited high affinity for somatostatin receptors (SSTR). The fluorescent dyes rhodamine 101, sulforhodamine B acid chloride, sulforhodamine 101 or rhodamine B isothiocyanate were conjugated either directly or via spacers, for example the peptidase-labile pentapeptide sequence Ala-Leu-Ala-Leu-Ala. The conjugates were completely assembled on the solid support: Fmoc-SPPS, cyclization via a disulfide linkage, N-terminal attachment of a spacer, and linkage to the fluorescent dye. An in vitro competition assay revealed that the conjugates bind to SSTRs with IC50 values between 0.7 and 89 nM. The conjugates were generally stable to hydrolysis at pH 7–8 in buffer or serum. However, the rhodamine 101 conjugates revealed a loss of absorption at alkaline pH due to conversion to a neutral spirolactam form, as characterized by NMR.

Influence of near-ultraviolet radiation on reproductive and immunological development in juvenile male Siberian hamsters.

The aim of this study was to characterize the lenticular ultraviolet transmission of the Siberian hamster (Phodopus sungorus) and to probe the range of near-ultraviolet (UV-A, 315-400 nm) and visible wavelengths (400-760 nm) for modulating the photoperiodic regulation of its reproductive and immune systems. Ocular lenses from adult hamsters were found to transmit UV-A wavelengths at similar levels to visible wavelengths, with a short-wavelength cut-off of 300 nm. Five separate studies compared the responses of juvenile male hamsters to long photoperiods (16 h:8 h L:D), short photoperiods (10 h:14 h L:D) and short photoperiods interrupted by an equal photon pulse of monochromatic light of 320, 340, 360, 500 or 725 nm during the night. The results show that UV-A wavelengths at 320, 340 and 360 nm can regulate both reproductive and immune short-photoperiod responses as effectively as visible monochromatic light at 500 nm. In contrast, long-wavelength visible light at 725 nm did not block the short-photoperiod responses. These results suggest that both wavelengths in the visible spectrum, together with UV-A wavelengths, contribute to hamster photoperiodism in natural habitats.

Urokinase activity in corneal fibroblasts may be modulated by DNA damage and secreted proteins.

Proteases like urokinase-type plasminogen activator (uPA) play an important role in tumor invasion. Cells derived from ultraviolet radiation (UVR)-induced corneal sarcomas of Monodelphis domestica produce relatively high levels of uPA compared to the untransformed keratocytes suggesting a mechanism for their invasiveness. Because UVR is known to stimulate uPA production in many cell types, UVR exposure may further increase uPA expression in corneal tumor cells, thus enhancing their ability to infiltrate. We investigated control of basal uPA levels and the induction of uPA by UVR in transformed and untransformed corneal keratocytes from Monodelphis. These studies took advantage of the fact that Monodelphis possesses an active photolyase that can be stimulated to remove UVR-induced pyrimidine dimers by exposure to long-wavelength visible photoreactivating light (PRL). Our studies showed that significant induction of uPA occurred in response to 200 J/m2 UVR. This induction was partially blocked by treatment with PRL, indicating that DNA damage, the pyrimidine dimer in particular, played a role in uPA induction. In untransformed cultured corneal fibroblasts, the heparin-binding protein inhibitor, suramin, reduced basal uPA levels, UVR-induced uPA production and cell proliferation. Basic fibroblast growth factor, a heparin-binding growth factor known to be UVR-inducible in mesenchymal cells, stimulated uPA production and cell proliferation; however, anti-bFGF antibodies did not significantly decrease proliferation or basal uPA production. These findings suggested that basal levels of uPA secretion were modulated in response to heparin-binding growth factors and that these growth factors may also have mediated the effect of UVR on uPA levels.

Aerobic photooxidation and C–C bond cleavage of the acetylacetonate ligand in (2-arylazo)arylpalladium(II) complexes induced by visible light

(Arylazo)aryl(acetylacetonato)palladium(II) complexes [Pd(4-RC6H3NNC6H4R-4′)(O,O-acac)](R = H 1a, Me 1b or OMe 1c; Hacac = acetylacetone), upon irradiation of their acetone solutions at room temperature by UV, or even long-wavelength visible (λ > 500 nm) light, were readily oxidized by atmospheric oxygen to give the corresponding acetato derivatives [Pd(4-RC6H3NNC6H4R-4′)(µ-O2CMe)]2(R = H 2a, Me 2b or OMe 2c), providing a model for some chemical and biological processes. The oxidation reaction of complex 1b was first order in the complex when [1b]0⩽ 2 × 10–3 mol dm–3. Complexes 1b and 1c were photooxidized at approximately twice the rate of complex 1a. In the presence of a scavenger of C-centred radicals (CCl4) the rate of complex 2b accumulation was reduced. When pyridine was added or co-ordinating solvents (acetonitrile or nitromethane) were used no photooxidation of complex 1 occurred. In the presence of PPh3 an induction period was observed and the oxidation of 1 started only after all the PPh3 was oxidized under irradiation into OPPh3. Spectroscopic data suggested that these ligands inhibit this photochemical oxidation because they change the type of co-ordination of the azobenzene chromophore and/or the acac ligands inducing a disconnection between the chromophore (antenna) and the acac ligand.

Vibronic excitation of oxygen-atom transfer from nitrogen dioxide to ethylene by long-wavelength visible light in a cryogenic matrix

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTVibronic excitation of oxygen-atom transfer from nitrogen dioxide to ethylene by long-wavelength visible light in a cryogenic matrixMunetaka. Nakata, Kazuhiko. Shibuya, and Heinz. FreiCite this: J. Phys. Chem. 1990, 94, 21, 8168–8175Publication Date (Print):October 1, 1990Publication History Published online1 May 2002Published inissue 1 October 1990https://doi.org/10.1021/j100384a035RIGHTS & PERMISSIONSArticle Views56Altmetric-Citations19LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Observations of natural fluorescence with an underwater radiometer

Measurements of subsurface irradiance spectra in the ocean consistently indicate intensities of long-wavelength visible light (λ≧589 nm) greater than could be derived from the penetration of sunlight. This can be attributed to natural fluorescence and/or to spectral crosstalk due to light leakage through the blocking filters of each discrete detector. A comparison of observed profiles with modelled contributions from these two possible sources indicates that both factors are contributing. At 671 and 694 nm wavelength, the excess signal appears to be predominantly fluorescence while that at 589 nm is mostly crosstalk. Both effects appear to be important at 625 nm although the amount of excess light is small compared to the other wavelengths.

THE CONTROL OF PLANT GROWTH AND DEVELOPMENT BY LIGHT

THE CONTROL OF PLANT GROWTH AND DEVELOPMENT BY LIGHT

Die Wirkung von hellroter und blauer Strahlung auf die Chloroplastenausbildung

Growth and morphogenesis of the young fern gametophytes. e. g. Dryopteris filix-mas, is completely controlled by light. This remarkable light effect has nothing to do with photosynthesis but is a good example of photomorphogenesis, i. e. direct control of growth and development by light (MOHR und OHLENROTH)1. — Only short-wave-length visible light (“blue light”) has been found to the photomorphogenically effective. Under longer wave length visible light (“red light”) the sporelings continue to grow as “etiolated” filaments very similar to those formed in darkness, while under blue light “normal” two dimensional growth and prothallium formation can occur. The induction of morphogenesis by blue light is causally connected with an increase of protein synthesis. Sporelings growing in the blue contain much more protein (as related to dry weight) than sporelings growing in the red at about the same photosynthetic rate (OHLENROTH und MOHR)2. In the present paper it has been shown that the size of the chloroplasts in cells of these sporelings can be controlled by light. In darkness the chloroplasts are smaller than in red or blue but in blue they become much larger than in the red. This control of plastid size by light is reversible, e. g. if sporelings which have been grown in the red are kept under blue light the chloroplast size increases rapidly up to a certain value but if they are brought back into the red the original size will be regained within a few days. It has been concluded that the protein content of the plastids is controlled by light and that changes of the plastid size are manifestations of a change in protein content of the plastids.