Green Light Excitation Research Articles

Functionalized polymer waveguide optical switching devices integrated with visible optical amplifiers based on an organic gain material

In this work, polymer waveguide based optical switching devices integrated with visible optical amplifying waveguides based on an organic gain material are designed and fabricated. The gain compound is a red emissive oligomer, with good dispersibility in organic polymer matrices. Optical characteristics and thermal stabilities of the active polymer waveguide core and cladding materials are analyzed. Optical gain of the amplifier operating at 650 nm red signal wavelength with 0.1 mW input power is found to be over 3.5 dB under only 1.6 mW pumping power with 532 nm green excitation light. The on-off response time of the integrated thermo-optic switch applied is measured to be 600 μs, with switching extinction ratio of 20 dB and electric switching power of 18.5 mW. The integrated switching device capable of optical gain will be suitable for applications to optical communications at the visible wavelength range involving plastic optical fiber systems.

Additive‐Free Green Light‐Induced Ligation Using BODIPY Triggers

AbstractPhotochemical ligation is important in biomaterials engineering for spatiotemporal control of biochemical processes. Such reactions however generally require activation by high energy UV or short wavelength blue light, which can limit their use as a consequence of the potential of these high energy light sources to damage living cells. Herein, we present an additive‐free, biocompatible, chemical ligation triggered by mild visible light. BODIPY dyes with a pendant thioether attached at the meso‐position undergo photolysis of the [C−S] bond under green light (λ=530 nm) excitation, producing an ion pair intermediate that can react specifically with a propiolate group. The utility of this photochemical ligation in materials science is demonstrated by the fabrication of hydrogels with specific architectures, photo‐immobilization of biomacromolecules, and live cell encapsulation within a hydrogel scaffold.

Additive-Free Green Light-Induced Ligation Using BODIPY Triggers.

Photochemical ligation is important in biomaterials engineering for spatiotemporal control of biochemical processes. Such reactions however generally require activation by high energy UV or short wavelength blue light, which can limit their use as a consequence of the potential of these high energy light sources to damage living cells. Herein, we present an additive-free, biocompatible, chemical ligation triggered by mild visible light. BODIPY dyes with a pendant thioether attached at the meso-position undergo photolysis of the [C-S] bond under green light (λ=530 nm) excitation, producing an ion pair intermediate that can react specifically with a propiolate group. The utility of this photochemical ligation in materials science is demonstrated by the fabrication of hydrogels with specific architectures, photo-immobilization of biomacromolecules, and live cell encapsulation within a hydrogel scaffold.

Synthesis of Samarium-Based Metal Organic Compound Nanoparticles with Polychromatic-Photoluminescence for Bio-Tissue Fluorescence Imaging.

The development of nanomaterials with special optical window is critical for clinical applications and the optoelectronic industry. In this work, eight kinds of samarium-based metal organic compound nanoparticles (Sm–Fe, Sm–Ga, Sm–Mn, Sm–Na, Sm–Nb, Sm–W, Sm–Cu, and Sm–Al) were synthesized through a solution method. They show polychromatic-photoluminescence spectra extended from the UV to near-infrared (NIR) region when excited by 280 nm, 380 nm, 480 nm, 580 nm, and 785 nm light. They emit direct white light with respect to UV excitation. Tunable white-to-green fluorescence can be achieved by variation of excitation light around 300–400 nm. When they are excited by a 785 nm light source, they show intense fluorescence around 800–1100 nm, which is promising for NIR bio-imaging. Their application in multicolor ultra-wide-range bio-tissue fluorescence imaging is demonstrated by UV (359–371 nm), blue (450–490 nm), green (540–552 nm), and NIR light (central wavelength = 785 nm) excitation with pig kidney tissue samples.

A molecular hybrid producing simultaneously singlet oxygen and nitric oxide by single photon excitation with green light

Combination of photosensitizers (PS) for photodynamic therapy with NO photodonors (NOPD) is opening intriguing horizons towards new and still underexplored multimodal anticancer and antibacterial treatments not based on “conventional” drugs and entirely controlled by light stimuli. In this contribution, we report an intriguing molecular hybrid based on a BODIPY light-harvesting antenna that acts simultaneously as PS and NOPD upon single photon excitation with the highly biocompatible green light. The presented hybrid offers a combination of superior advantages with respect to the other rare cases reported to date, meeting most of the key criteria for both PSs and NOPDs in the same molecular entity such as: (i) capability to generate 1O2 and NO with single photon excitation of biocompatible visible light, (ii) excellent 1O2 quantum yield and NO quantum efficiency, (iii) photogeneration of NO independent from the presence of oxygen, (iv) large light harvesting properties in the green region. Furthermore, this compound together with its stable photoproduct, is well tolerated by both normal and cancer cells in the dark and exhibits bimodal photomortality of cancer cells under green light excitation due to the combined action of the cytotoxic 1O2 and NO.

A polaron approach to photorefractivity in Fe : LiNbO3

The thermally activated, incoherent hopping of small electron polarons generated by continuous illumination in iron-doped lithium niobate is simulated by a Marcus-Holstein model for which all the input parameters are known from literature. The results of the calculations are compared with a comprehensive set of data obtained from photorefractive, photogalvanic and photoconductive measurements under green light excitation on samples with different doping levels and stoichiometries in the temperature range between and room temperature. We show that the temperature and composition dependence of the photorefractive observables can be interpreted by a change in the abundance of the different hop types that a polaron performs before being captured by a deep Fe trap. Moreover, by a comparison between experimental and numerical data we obtain new insights on the initial photo-excitation part of the photorefractive process. In particular all results are consistent if a single value of the photogalvanic length is assumed for all the samples and all the temperatures. The photo-generation efficiency ϕ under green light excitation (somewhere denoted as quantum efficiency) is also estimated. It appears to decrease from 10%–15% at room temperature to about 5% at 150 K. This behavior is qualitatively interpreted in terms of a temperature-dependent re-trapping probability of the light-emitted particles from the initial Fe donor center.

Reprint of Efficient fungal UV-screening provides a remarkably high UV-B tolerance of photosystem II in lichen photobionts

Lichen photobionts in situ have an extremely UV-B tolerant photosystem II efficiency (Fv/Fm). We have quantified the UV-B-screening offered by the mycobiont and the photobiont separately. The foliose lichens Nephroma arcticum and Umbilicaria spodochroa with 1: intact or 2: removed cortices were exposed to 0.7 Wm-2 UV-BBE for 4 h. Intact thalli experienced no reduction in Fv/Fm, whereas cortex removal lowered Fv/Fm in exposed photobiont layers by 22% for U. spodochroa and by 14% for N. arcticum. We also gave this UV-B dose to algal cultures of Coccomyxa and Trebouxia, the photobiont genera of N. arcticum and U. spodochroa, respectively. UV-B caused a 56% reduction in Fv/Fm for Coccomyxa, and as much as 98% in Trebouxia. The fluorescence excitation ratio (FER) technique comparing the fluorescence from UV-B or UV-A-excitation light with blue green excitation light using a Xe-PAM fluorometer showed that these photobiont genera did not screen any UV-B or UV-A The FER technique with a Multiplex fluorometer estimated the UV-A screening of isolated algae to be 13–16%, whereas intact lichens screened 92–95% of the UV-A. In conclusion, the cortex of N. arcticum and U. spodochroa transmitted no UV-B and little UV-A to the photobiont layer beneath. Thereby, the upper lichen cortex forms an efficient fungal solar radiation screen providing a high UV-B tolerance for studied photobionts in situ. By contrast, isolated photobionts have no UV-B screening and thus depend on their fungal partners in nature.

Efficient fungal UV-screening provides a remarkably high UV-B tolerance of photosystem II in lichen photobionts

Lichen photobionts in situ have an extremely UV-B tolerant photosystem II efficiency (Fv/Fm). We have quantified the UV-B-screening offered by the mycobiont and the photobiont separately. The foliose lichens Nephroma arcticum and Umbilicaria spodochroa with 1: intact or 2: removed cortices were exposed to 0.7 Wm-2 UV-BBE for 4 h. Intact thalli experienced no reduction in Fv/Fm, whereas cortex removal lowered Fv/Fm in exposed photobiont layers by 22% for U. spodochroa and by 14% for N. arcticum. We also gave this UV-B dose to algal cultures of Coccomyxa and Trebouxia, the photobiont genera of N. arcticum and U. spodochroa, respectively. UV-B caused a 56% reduction in Fv/Fm for Coccomyxa, and as much as 98% in Trebouxia. The fluorescence excitation ratio (FER) technique comparing the fluorescence from UV-B or UV-A-excitation light with blue green excitation light using a Xe-PAM fluorometer showed that these photobiont genera did not screen any UV-B or UV-A The FER technique with a Multiplex fluorometer estimated the UV-A screening of isolated algae to be 13–16%, whereas intact lichens screened 92–95% of the UV-A. In conclusion, the cortex of N. arcticum and U. spodochroa transmitted no UV-B and little UV-A to the photobiont layer beneath. Thereby, the upper lichen cortex forms an efficient fungal solar radiation screen providing a high UV-B tolerance for studied photobionts in situ. By contrast, isolated photobionts have no UV-B screening and thus depend on their fungal partners in nature.

Increase in perfused boundary region of endothelial glycocalyx is associated with higher prevalence of ischemic heart disease and lesions of microcirculation and vascular wall.

PBR characterizes penetration of red blood cells inside glycocalyx and its thickness can have profound impact on microcirculation and other vascular parameters. The goal of our study was to reliably quantify PBR and assess its potential use as a new marker of cardiovascular pathology. The study included 208 patients (123 men and 85 women from 40 to 65years of age) with various grades of cardiovascular SCORE risk index and IHD. PBR was quantified by sidestream dark field capillaroscopy with green light excitation. Cutaneous microcirculation was evaluated with laser Doppler fluorometry. Elevated PBR values over 2mm were associated with morphological and functional lesions of arterial wall and microcirculation and lowered levels of ApoA1 lipoprotein. Moreover, elevated PBR values were associated with 2.07-fold increase in prevalence of cerebral atherosclerosis (P=.015) and 2.42-fold increase in prevalence of IHD (P=.024). Increase in PBR was associated with elevated systolic blood pressure. Thus, PBR can be considered a new highly reproducible and promising marker candidate for non-invasive diagnostics of IHD and cerebral atherosclerosis suggesting important role of microcirculation in development and progression of cardiovascular diseases.

Pressure and Photoinduced Phase Transitions of Elemental Sulfur Confined by Open-End Single-Wall Carbon Nanohorns

Confined molecules in tubular nanospaces of nanocarbons, for example, carbon nanotubes and nanohorns (CNHs), lead to extraordinary behavior and properties different from their bulk analogues. Here, we investigated the confinement effect of CNHs on high-pressure elastic and vibrational properties of sulfur via the diamond anvil cell technique. X-ray diffraction measurements up to 40 GPa demonstrate two phase transitions of S-I → amorphous → S-II. A fit of equation of state yields a bulk modulus of ∼24.8 GPa, about 70% higher than that of soft sulfur. Different from previous Raman studies, laser with red light wavelength (694.8 nm) and high laser density (∼2 mW μm–2) was employed under the threshold for generating C–S bonds. We observed a similar photoinduced transition of S-I to amorphous sulfur at 4–6 GPa compared to the results taken from blue and green light excitation and low laser density (e.g., <28 μW μm–2), showing enhanced photothermal stability of sulfur by the aid of single-wall CNHs.

Extra green light induced ZnO ultraviolet lasing enhancement assisted by Au surface plasmons.

We observed the dramatic enhancement of the intrinsic spontaneous and stimulated emission as well as the ensuing suppression of defect-related green emission in Au-decorated ZnO microrods. A series of spectral experiments and theoretical analysis demonstrated an electron transfer assisted process by surface plasmon (SP) resonant coupling between the Au nanoparticles and ZnO. The mechanism indicates an approach to enhance the UV emission of ZnO through an extra excitation of visible light similar to that for the defect emission of ZnO. Based on the coupling mechanism, the externally enhanced ultraviolet lasing was further improved from 1.5 to 2.8-fold by adjusting the pumping power of the green light intensity in the Au/ZnO hybrid cavity. This research not only further confirms the SPR-assisted electron transfer process but also offers an approach to improve the intrinsic UV emission even for heavily-defected ZnO through visible light excitation via a nonlinear process.

A novel laminated OLED–PSP system for measurement on moving surfaces

A novel pressure-sensitive paint (PSP) system has been developed which uses an embedded organic light-emitting diode (OLED) layer as excitation, and thus eliminates the usual requirement of an external light source. This system consists of an OLED layer, an optical filter layer and a polymer-ceramic (PC) PSP layer with fast response. The OLED provides green excitation light (around 500 nm) for PSP, while the optical filter and (550 nm short-pass) removes unwanted longer wavelength light to prevent possible interference with the PSP signal. A PC-PSP layer is applied on top of the filter with well-controlled basecoat thickness (~ 10 μm) to allow sufficient light transmittance. It is also important that the OLED is modulated with a limited duty cycle and synchronized with the camera exposure to minimize uncertainties mostly due to the inherent heating effect of OLED. This OLED-based PSP has a pressure sensitivity comparable to the regular PC-PSP, and it is well-suited for pressure measurements on moving surfaces since its illumination field is independent of the model motion. Its advantage over a conventional PSP system was demonstrated through applications on a flapping plate under the impingement of a nitrogen jet.

Large electrostrictive effect and strong photoluminescence in rare-earth modified lead-free (Bi0.5Na0.5)TiO3-based piezoelectric ceramics

In this study, new lead-free luminescent electrostrictive materials have been fabricated by introducing trivalent RE3+ (RE=Sm, Pr and Eu) as the activator into 0.93(Bi0·5Na0.5)TiO3–0.07BaTiO3 (BNBT7) ceramics. A high, purely electrostrictive effect with exceptionally good temperature-independent and fatigue-free behavior was obtained in RE-modified BNBT7 ceramics. These materials are also attractive for their strong photoluminescence with bright reddish-orange emission (RE=Sm) or red emission (RE=Pr, Eu) upon blue or green light excitation. These results suggest that this kind of materials has potential application as a multifunctional device by integrating its excellent luminescence and electrostrictive properties.

One step synthesis of maltose functionalized red fluorescent Ag cluster for specific glycoprotein detection and cellular imaging probe

The synthesis of non-cadmium based carbohydrate functionalized inorganic fluorescent nanoparticles has emerging potential applications in advanced biomedical science. Herein, we synthesized red fluorescent maltose functionalized silver clusters (AgC) using cysteamine modified maltose as a capping agent without adding any external reductant. The silver clusters had a hydrodynamic diameter of less than 5 nm with good colloidal, photochemical and fluorescent stability with a reasonably good fluorescence quantum yield. Maltose functionalized fluorescent silver clusters were produced in a one step procedure. Therefore, we exploited the maltose functionalized silver clusters for the visible detection of specific glycoprotein concanavalin-A. Because the synthesized red fluorescent maltose functionalized silver clusters possesses good photochemical stability and green light excitation, we used maltose functionalized red fluorescent AgC for HeLa cell labelling study.

Nanoscale electron transport and photodynamics enhancement in lipid-depleted bacteriorhodopsin monomers.

Potential future use of bacteriorhodopsin (bR) as a solid-state electron transport (ETp) material requires the highest possible active protein concentration. To that end we prepared stable monolayers of protein-enriched bR on a conducting HOPG substrate by lipid depletion of the native bR. The ETp properties of this construct were then investigated using conducting probe atomic force microscopy at low bias, both in the ground dark state and in the M-like intermediate configuration, formed upon excitation by green light. Photoconductance modulation was observed upon green and blue light excitation, demonstrating the potential of these monolayers as optoelectronic building blocks. To correlate protein structural changes with the observed behavior, measurements were made as a function of pressure under the AFM tip, as well as humidity. The junction conductance is reversible under pressure changes up to ∼300 MPa, but above this pressure the conductance drops irreversibly. ETp efficiency is enhanced significantly at >60% relative humidity, without changing the relative photoactivity significantly. These observations are ascribed to changes in protein conformation and flexibility and suggest that improved electron transport pathways can be generated through formation of a hydrogen-bonding network.

Surface enhanced fluorescence and imaging with plasmon near-fields in gold corrugated gratings

Surface plasmon-assisted fluorescence and imaging from Rhodamine 6G dye molecules in polymethyl methacrylate (PMMA) thin films deposited on gold-coated corrugated gratings of various periodicities fabricated by laser interference lithography were investigated. The fluorescence enhancement depends significantly on the periodicity of the corrugated gratings for the green light excitation centered at 548 nm with maximum enhancements at 500 and 1000 nm grating periods. A dielectric PMMA spacer layer placed between the fluorophore layer and the metal surface resulted in a further three-fold enhancement of fluorescence. The period dependent enhancement is caused by the efficient coupling of the excitation radiation to the gold gratings due to the resonant excitation of propagating surface plasmons, which assist the excitation of the fluorophores. Fluorescence imaging shows that the emitted signal is stronger from the top of the corrugated grating surface rather than from that of the valleys. It was ascertained, through surface plasmon resonant dispersion measurements and electromagnetic computations, that enhanced absorption of excitation light through propagating plasmon resonances is the prime contributor to the enhanced fluorescence.

Galactosyl Human Serum Albumin-NMP1 Conjugate: A Near Infrared (NIR)-Activatable Fluorescence Imaging Agent to Detect Peritoneal Ovarian Cancer Metastases

Patient survival depends on the completeness of resection of peritoneal ovarian cancer metastases (POCM), and therefore, it is important to develop methods to enhance detection. Previous probe designs based on activatable galactosyl human serum albumin (hGSA)-fluorophore pairs, which target lectin receptors expressed on POCM, have used only visible range dyes conjugated to hGSA. However, imaging probes emitting fluorescence in the NIR range are advantageous because NIR photons have deeper in vivo tissue penetration and result in lower background autofluorescence than those emitting in the visible range. A NIR-activatable hGSA fluorophore was synthesized using a bacteriochlorin-based dye, NMP1. NMP1 has two unique absorption peaks, one in the green range and the other in the NIR range, but emits at a NIR peak of 780 nm. NMP1, thus, has two different Stokes shifts that have the potential to allow imaging of POCM both at the peritoneal surface and just below it. hGSA was conjugated with 2 NMP1 molecules to create a self-quenching complex (hGSA-NMP1). The activation ratio of hGSA-NMP1 was measured by the fluorescence intensity before and after exposure to 10% SDS. The activation ratio of hGSA-NMP1 was ~100-fold in vitro. Flow cytometry, fluorescence microscopy, and in vivo spectral fluorescence imaging were carried out to compare hGSA-NMP1 with hGSA-IR800 and hGSA-ICG (two always-on control agents with similar emission to NMP1) in terms of comparative fluorescence signal and the ability to detect POCM in mice models. The sensitivity and specificity of hGSA-NMP1 for POCM implant detection were determined by colocalizing NMP1 emission spectra with red fluorescent protein (RFP) expressed constitutively in SHIN3 tumor implants at different depths below the peritoneal surface. In vitro, SHIN3 cells were easily detectable after 3 h of incubation with hGSA-NMP1. In vivo submillimeter POCM foci were clearly detectable with spectral fluorescence imaging using hGSA-NMP1. Among 555 peritoneal lesions, hGSA-NMP, using NIR and green excitation light, respectively, detect 75% of all lesions and 91% of lesions ~0.8 mm or greater in diameter. Few false positives were encountered. Nodules located at a depth below the small bowel surface were only depicted with hGSA-NMP1. We conclude that hGSA-NMP1 is useful in imaging peritoneal ovarian cancer metastases, located both superficially and deep in the abdominal cavity.

Abstract LB-508: A GSA-NMP1 conjugate: An NIR-activatable fluorescence imaging agent to detect peritoneal ovarian cancer metastases

Abstract Purpose: There is a need to improve detection of peritoneal ovarian cancer metastases before and during surgery. Previous designs of activatable GSA-fluorophore probes, which target lectin receptors, have used only visible range dyes conjugated to GSA. However, activatable agents emitting fluorescence in the NIR range are advantageous because NIR photons have deeper in vivo tissue penetration and lower background autofluorescence than those emitting in the visible range. An NIR-activatable GSA fluorophore pair can be synthesized using the dye NMP1. This NMP1 dye has two unique absorption peaks (in green and NIR wavelength ranges) with a single NIR emission peak of 780nm. NMP1 thus has two different Stoke's shifts that have the potential to allow separate imaging of tumor nodules both at the surface and at depths below the surface. Experimental Design: GSA was conjugated with 2 NMP1 molecules to create a self-quenching complex (GSA-NMP1). The activation magnitude of GSA-NMP1 was validated by adding 10% SDS. Flow cytometry, fluorescence microscopy, and in vivo spectral fluorescence imaging were carried out to compare GSA-NMP1 with GSA-IR800 (an always on control agent with similar emission to NMP1) in terms of intracellular activation and abilities to allow detection of small ovarian cancer implants in mice models. Sensitivity and specificity of GSA-NMP1 for implant detection were determined by co-localizing NMP1 emission spectra with red fluorescent protein expressed constitutively in SHIN3 tumor implants. Image processing in Java was used to subtract spectral images, with resulting images theorized to show tumor nodules at a depth below the surface. Results: The fluorescence signal of GSA-NMP1 can be activated ∼100-fold and was specifically yielded after internalization into SHIN3 cells 3h after incubation. Submillimeter ovarian cancer implants in the peritoneal cavity were clearly detectable in vivo with spectral fluorescence imaging. Among 555 peritoneal lesions, the sensitivity and specificity for GSA-NMP using NIR and green excitation light, were 75%/92% and 91%/92% for lesions ∼0.8 mm or greater in diameter, respectively. Image processing suggests that nodules at a depth below the small bowel are imaged only with GSA-NMP1 by subtraction of the two excitation images. Conclusions: GSA-NMP1 is useful in imaging peritoneal ovarian cancer metastases, located both superficially and deep in the abdominal cavity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-508. doi:1538-7445.AM2012-LB-508

Time-Resolved Fluorescence Immunoassay for C-Reactive Protein Using Colloidal Semiconducting Nanoparticles

Besides the typical short-lived fluorescence with decay times in the nanosecond range, colloidal II/VI semiconductor nanoparticles dispersed in buffer also possess a long-lived fluorescence component with decay times in the microsecond range. Here, the signal intensity of the long-lived luminescence at microsecond range is shown to increase 1,000-fold for CdTe nanoparticles in PBS buffer. This long-lived fluorescence can be conveniently employed for time-gated fluorescence detection, which allows for improved signal-to-noise ratio and thus the use of low concentrations of nanoparticles. The detection principle is demonstrated with a time-resolved fluorescence immunoassay for the detection of C-reactive protein (CRP) using CdSe-ZnS nanoparticles and green light excitation.

A multichromophoric dendrimer: from synthesis to energy up-conversion in a rigid matrix

A dendrimer with a [Ru(bpy)(3)](2+) (bpy = 2,2'-bipyridine) complex as a core and four diphenylanthracene units at the periphery was prepared from a scaffold based on a bipyridyl ligand bearing four terminal alkyne groups. Upon green light excitation, the dendrimer shows blue luminescence even in a rigid matrix at 77 K thanks to the dendritic multichromophoric structure.