Red Light Source Research Articles

Computational study of the sensitivity of laser light scattering particle sizing to refractive index and irregularity

Measuring the size distribution of dust particles is of interest in many scientific and technological contexts. One of the most widely used techniques is laser light scattering (LLS), which provides the distribution of surface-equivalent spheres that fits the observed angular dependence of light scattered by a sample. We have revisited the problem of the uncertain lower size limit of this method by simulating laboratory measurements of the light intensity scattered by polydisperse spheres and irregular particles (agglomerated debris and pocked spheres), from which the original distributions are retrieved by regularized inversion with Mie and Fraunhofer phase functions. For the usual combination of blue (λ = 466 nm) and red (λ = 633 nm) light sources, size distributions of spheres with radii r > 0.1 μm are retrieved with Mie if the true complex refractive index (m = n – ik) is used. The retrieval for 0.1 μm < r < 3 μm is sensitive to errors in the assumed m, which results primarily from the dependence of the scattering efficiency Qsca on m. Irregular particle shape has also an impact on the Qsca vs. r curves, whose maxima are shifted towards larger r and are smoother compared to spherical particles. For a violet-blue wavelength (λ = 442 nm), good retrievals are obtained for irregular particles with r > 1 μm even if m is not very well known or the Fraunhofer model is used. Spurious slumps and enhancements appear for r < 1 μm, although if n is known, the actual lower limit decreases for increasing n. This implies that LLS size distributions of submicron irregular particles may not be accurate. Establishing the lower size limit requires inspection of the dependence on m and analysis of the irregularity of samples.

Pulsed laser deposition of a ZnO:Eu3+ thin film: Study of the luminescence and surface state under electron beam irradiation

A highly c-axis orientated Eu3+ doped ZnO (ZnO:Eu3+) thin film was successfully deposited by pulsed laser deposition in an oxygen working atmosphere. The structure, morphology, chemical analysis and luminescence properties of the sample were investigated. The effect of electron beam irradiation on the surface state, chemical and luminescence properties of the sample were studied. Successful incorporation of Eu3+ ions in the ZnO matrix was confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. XPS measurements revealed traces of the divalent (Eu2+) on the film surface while the trivalent (Eu3+) oxidation state in the bulk of the film. XPS depth profile confirmed that the film contained excess oxygen throughout the film. The film exhibited exciton and defect emission of ZnO as well as 4f – 4f characteristic emission of Eu3+ ions superimposed on the defect emission when excited at 325 nm using a He-Cd laser. Whereas only 4f – 4f characteristic emission of Eu3+ ions was recorded when the film was excited at 464 nm and also when excited with the electron beam. XPS high resolution spectra of the O 1s peak confirmed the creation of new defects during electron beam In general, ZnO:Eu3+ films show potential for applications as a source of red light in optoelectronic devices.

Optical Properties of Red-Emitting Rb2Bi(PO4)(MoO4):Eu3+ Powders and Ceramics with High Quantum Efficiency for White LEDs.

There are several key requirements that a very good LED phosphor should meet, i.e., strong absorption, high quantum efficiency, high colour purity, and high luminescence quenching temperature. The reported Rb2Bi(PO4)(MoO4):Eu3+ phosphors have all these properties. The Rb2Bi(PO4)(MoO4):Eu3+ phosphors emit bright red light if excited with near-UV radiation. The calculated colour coordinates show good stability in the 77–500 K temperature range. Moreover, sample doped with 50% Eu3+ possesses quantum efficiency close to unity. Besides the powder samples, ceramic disks of Rb2Eu(PO4)(MoO4) specimen were also prepared, and the red light sources from these disks in combination with near-UV emitting LED were fabricated. The obtained results indicated that ceramic disks efficiently absorb the emission of 375 and 400 nm LED and could be applied as a red component in phosphor-converted white LEDs.

MPS-Net: Learning to recover surface normal for multispectral photometric stereo

Multispectral Photometric Stereo (MPS) estimates per-pixel surface normals from one single image captured under three colored (red, green and blue) light sources. Unlike traditional Photometric Stereo, MPS can therefore be used in dynamic scenes for single frame reconstruction. However, MPS is challenging due to the tangle of the illumination, surface reflectance and camera response, causing inaccurate estimation of surface normal. Existing approaches rely on either extra depth information or materials calibration strategies, thus limiting its usage in practical applications. In this paper, we propose a Multispectral Photometric Stereo Network (MPS-Net) to solve this under-determined system. The MPS-Net takes the single multispectral image and an initial surface normal estimation obtained from this image itself, and outputs an accurate surface normal map, where no extra depth or materials calibration information is required. We show that the MPS-Net is not constrained to Lambertian surfaces and can be applied to surfaces with complex reflectance. We evaluated the MPS-Net using both synthetic and real objects of various materials. Our experiment results show that the MPS-Net outperforms the state-of-the-art approaches.

Effect of spectroradiometer characteristics on chromaticity for tricolor laser light sources.

The errors in the output of chromaticity coordinates (u',v') by two spectroradiometers caused by spectral resolution limitations, wavelength variations, and nonlinearity were investigated with three tricolor laser light sources, namely two white light sources and one red light source. Using these sources, we found chromaticity coordinate changes of up to 0.0002 due to a 3.2nm spectral resolution, 0.0010 due to a 0.6nm wavelength error, and 0.0091 due to 24% nonlinearity. These chromaticity errors demonstrate that wavelength and nonlinearity calibrations are of great importance when using a spectroradiometer to evaluate the color of a tricolor laser-based light source. Evaluating chromaticity errors due to these spectroradiometer characteristics can help us to obtain accurate color measurements for imaging and display devices based on tricolor laser light sources.

Optimization of the photodynamic inactivation of prions by a phthalocyanine photosensitizer: The crucial involvement of singlet oxygen.

Prion disorders are fatal neurodegenerative diseases caused by the autocatalytic conversion of a natively occurring prion protein (PrPC ) into its misfolded infectious form (PrPTSE ). The proven resistance of PrPTSE to common disinfection procedures increases the risk of prion transmission in medical settings. Herein, we present the effective photodynamic inactivation (PDI) of prions by disulfonated hydroxyaluminum phthalocyanine (AlPcOH(SO3 )2 ) utilizing two custom-built red light sources. The treatment eliminates PrPTSE signal in infectious mouse brain homogenate with efficiency that depends on light intensity but has a low effect on the overall protein content. Importantly, singlet oxygen (O2 (1 Δg )) is the only species significantly photogenerated by AlPcOH(SO3 )2 , and it is responsible for the PDI of prions. More intensive light conditions show not only higher O2 (1 Δg ) production but also decreases in AlPcOH(SO3 )2 photostability. Our findings suggest that PDI by AlPcOH(SO3 )2 -generated O2 (1 Δg ) represents a promising approach for prion inactivation that may be useful in future decontamination strategies for delicate medical tools.

Curettage + microneedling + topical ALA-PDT for the treatment of acral resistant warts: Our experience.

Cutaneous warts are an extremely common problem, whose eradication can be challenging. Topical PDT involves applying a porphyrin precursor, 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) to the affected area. ALA-PDT has been well documented to be successful in the treatment of recalcitrant warts. PDT has a limited role in the treatment of thicker lesions because the photosensitizer does not penetrate keratotic lesions well, though this is vehicle dependent. The aim of this study was to evaluate the efficacy and safety of curettage + microneedling + ALA-PDT for the treatment of resistant acral warts. We hypothesized that microneedling may increase the efficacy of PDT, providing a channel to deliver the ALA to deeper areas of warts. Our study was carried out between November 2017 and July 2018. Eligible participants had one or more resistant plantar or palmar warts. Thirteen patients were recruited. They underwent a thorough curettage, followed by the application of 5-ALA 10% cream on the wart, and by microneedling. Later, the pricked skin was covered for three hours by an occlusive polyurethane dressing, and finally irradiated with a red-light source. Patients performed one session every three weeks for a total of three cycles. After 3 treatments of curettage + microneedling + ALA-PDT, 11 patients (84.6%) showed complete remission (defined as complete disappearance of their warts). One patient (7.7%) showed partial remission (defined as greater than 50% decrease in the wart area) after 3 sessions; this patient needed other 2 sessions to achieve complete remission. The mean follow-up period after healing was 4.3 months. Adverse effects were recorded. We have demonstrated, for the first time to our knowledge, that the combination of curettage + microneedling + topical ALA-PDT may offer an effective and safe alternative for the treatment of acral resistant warts, even when PDT alone has already been insufficient.

3-D Quality Assurance in CyberKnife Radiotherapy Using a Novel N-(3-methoxypropyl) Acrylamide Polymer Gel Dosimeter and Optical CT

In radiotherapy, dosimetry tools are needed to record and verify complex 3-D dose distributions. A novel composition of polymer gel dosimeter based on radiation-induced polymerization of N-(3-methoxypropyl) acrylamide (NMPA) is presented and studied as a 3-D dose verification quality assurance tool (QA) in radiotherapy treatment planning. A 160 mm diameter crystal glass round bottom flask (CrystalBall) containing NMPA gel was used as a phantom. The gel was irradiated by a CyberKnife robotic radiotherapy system and scanned optically with a red light source using an optical computed tomography OCT scanner with sub-millimeter spatial resolution. Additionally, a commercial polymer gel dosimeter of BANG-GEL-QA™ was irradiated and scanned to compare its performance with that of the novel gel dosimeter. The dose distributions of a CyberKnife robotic SRS/SBRT treatment planning system (TPS) for a patient with brain metastasis were compared to the measurements of both polymers using 2-D and 3-D gamma analysis with a criteria of 5% dose difference and 2 mm distance-to-agreement. A gamma pass rate of 95% was calculated within a diameter of at least 32 mm for the 2-D and 3-D gamma analysis of both polymer gels. This suggests that the novel NMPA polymer dosimeter can provide an accurate 3-D verification of complex dose distribution in SRS/SBRT radiotherapy treatments. This study demonstrates that the newly developed CrystalBall NMPA phantom can provide a promising 3-D quality assurance tool for radiation therapy.

Photothermal-Triggered Shape Memory Polymer Prepared by Cross-Linking Porphyrin-Loaded Micellar Particles.

In this work, we fabricated porphyrin-loaded shape memory polymer (SMP) film by cross-linking micellar particles prepared by co-assembly of porphyrin compounds and amphiphilic macromolecules formulated by copolymerization of 2-butoxy ethanol (BCS), methyl methacrylate (MMA), butyl acrylate (BA) acrylic acid (AA), and diacetone acrylamide (DAAM). The experimental results revealed that this film was able to respond to the red light in terms of photothermal effect enabled by the porphyrin filler. The photothermal-triggered shape memory behaviors of the film were further examined in detail. It was noteworthy that this material was expected to have potential applications in the biomedical field due to the excellent biocompatibility of the porphyrin filler and the red-light source, which was optimal and safe enough for biomedical treatment.

Sensitization of magnetic TiO2 with copper(II) tetrahydroxylphenyl porphyrin for photodegradation of methylene blue by visible LED light

Magnetic photocatalyst (magnetite@silica@titania@copper(II) 5,10,15,20-tetrakis(4-(hydroxyl)phenyl) porphyrin, Fe3O4@SiO2@TiO2@CuIITHPP) (MSTCuP) has been synthesized, characterized, and utilized to degrade the methylene blue (MB) under a visible LED light irradiation. The structural characteristics of the MSTCuP were determined using FT-IR, SEM, EDX, XRD, BET and VSM techniques. The magnetic properties of the synthesized samples were measured by a vibrant sample magnetometer (VSM) with maximum saturation magnetization values of 10 and 8 emu g−1 for Fe3O4@SiO2@TiO2 (MST) and Fe3O4@SiO2@TiO2@CuIITHPP (MSTCuP) nanoparticles respectively. UV-DRS data show the red-shift of the absorption edge and decrease of the band gap to 1.8 eV. The degradation of MB was monitored by UV–Vis spectrometry. Maximum degradation of %98 for MB dye was attained by the use of MSTCuP nanocomposites as the catalyst and under 180 min irradiation of blue LED light. After three 180 min photocatalytic runs for MB degradation, the catalyst still showed high activity. The recovery of the catalyst was easily performed by applying the external magnetic field. The efficiency of green, red and yellow Vis-LED light sources for the photocatalytic degradation of MB was also investigated. The degradation of MB using MSTCuP nanocomposite was found to follow the pseudo-first-order kinetic.

Migratory bats are attracted by red light but not by warm-white light: Implications for the protection of nocturnal migrants.

The replacement of conventional lighting with energy‐saving light emitting diodes (LED) is a worldwide trend, yet its consequences for animals and ecosystems are poorly understood. Strictly nocturnal animals such as bats are particularly sensitive to artificial light at night (ALAN). Past studies have shown that bats, in general, respond to ALAN according to the emitted light color and that migratory bats, in particular, exhibit phototaxis in response to green light. As red and white light is frequently used in outdoor lighting, we asked how migratory bats respond to these wavelength spectra. At a major migration corridor, we recorded the presence of migrating bats based on ultrasonic recorders during 10‐min light‐on/light‐off intervals to red or warm‐white LED, interspersed with dark controls. When the red LED was switched on, we observed an increase in flight activity for Pipistrellus pygmaeus and a trend for a higher activity for Pipistrellus nathusii. As the higher flight activity of bats was not associated with increased feeding, we rule out the possibility that bats foraged at the red LED light. Instead, bats may have flown toward the red LED light source. When exposed to warm‐white LED, general flight activity at the light source did not increase, yet we observed an increased foraging activity directly at the light source compared to the dark control. Our findings highlight a response of migratory bats toward LED light that was dependent on light color. The most parsimonious explanation for the response to red LED is phototaxis and for the response to warm‐white LED foraging. Our findings call for caution in the application of red aviation lighting, particularly at wind turbines, as this light color might attract bats, leading eventually to an increased collision risk of migratory bats at wind turbines.

Impact of red versus blue light on tolerability and efficacy of PDT: a randomized controlled trial.

The aim of this study is to compare the efficacy and tolerability of therapy with red versus blue light sources, as well as the patients' evaluation of cosmetic results, clinical response, painfulness and preferred light source for future photodynamic treatments. This is a prospective, single-center, randomized, controlled, open-label study with 28 patients undergoing elective photodynamic therapy. Red and blue light sources both showed very good results with a complete response rate of 84% and 85% respectively. Pain during photodynamic therapy was 6.1 vs. 5.4 (and 2.1 vs. 1.5 eight hours after therapy) on the visual analogue scale. Although these differences were statistically significant, the clinical relevance is low, since the number of therapy interruptions were equally distributed in both groups, and patients' subjective evaluation of the treatment showed no personal preference towards the light sources. Both light sources showed very good clinical results and satisfactory tolerability in this study.

Enhanced Electron Injection and Exciton Confinement for Pure Blue Quantum-Dot Light-Emitting Diodes by Introducing Partially Oxidized Aluminum Cathode

Stable and efficient red (R), green (G), and blue (B) light sources based on solution-processed quantum dots (QDs) play important roles in next-generation displays and solid-state lighting technologies. The brightness and efficiency of blue QDs-based light-emitting diodes (LEDs) remain inferior to their red and green counterparts, due to the inherently unfavorable energy levels of different colors of light. To solve these problems, a device structure should be designed to balance the injection holes and electrons into the emissive QD layer. Herein, through a simple autoxidation strategy, pure blue QD-LEDs which are highly bright and efficient are demonstrated, with a structure of ITO/PEDOT:PSS/Poly-TPD/QDs/Al:Al2O3. The autoxidized Al:Al2O3 cathode can effectively balance the injected charges and enhance radiative recombination without introducing an additional electron transport layer (ETL). As a result, high color-saturated blue QD-LEDs are achieved with a maximum luminance over 13,000 cd m-2, and a maximum current efficiency of 1.15 cd A-1. The easily controlled autoxidation procedure paves the way for achieving high-performance blue QD-LEDs.

Spectrally resolved laser interference microscopy

We developed a new quantitative phase microscopy technique, namely, spectrally resolved laser interference microscopy (SR-LIM), with which it is possible to quantify multi-spectral phase information related to biological specimens without color crosstalk using a color CCD camera. It is a single shot technique where sequential switched on/off of red, green, and blue (RGB) wavelength light sources are not required. The method is implemented using a three-wavelength interference microscope and a customized compact grating based imaging spectrometer fitted at the output port. The results of the USAF resolution chart while employing three different light sources, namely, a halogen lamp, light emitting diodes, and lasers, are discussed and compared. The broadband light sources like the halogen lamp and light emitting diodes lead to stretching in the spectrally decomposed images, whereas it is not observed in the case of narrow-band light sources, i.e. lasers. The proposed technique is further successfully employed for single-shot quantitative phase imaging of human red blood cells at three wavelengths simultaneously without color crosstalk. Using the present technique, one can also use a monochrome camera, even though the experiments are performed using multi-color light sources. Finally, SR-LIM is not only limited to RGB wavelengths, it can be further extended to red, near infra-red, and infra-red wavelengths, which are suitable for various biological applications.

A Single Energy Conversion and Storage Device of Cobalt Oxide Nanosheets and N-Doped Reduced Graphene Oxide Aerogel

A single hybrid energy conversion and storage (HECS) cell of asymmetric Cobalt oxide (Co3O4)//N-doped reduced graphene oxide aerogel (N-rGOAE) in 6 M KOH is proposed in this work. The Co3O4 serves as a photo-positive electrode material having an energy bang gap of 2.45 eV which can absorb all visible light region. Whilst, the N-rGOAE as a negative electrode material can balance all the charges and excited electrons from the Co3O4 positive electrode due to its interconnected three-dimensional structure with nitrogen doping. Under red LED light source (627 nm = 1.98 eV), the current densities and specific capacitances of the as-fabricated asymmetric Co3O4//N-rGOAE HECS cell are 1.4-fold higher than that under dark condition due to the photovoltaic effect. In addition, the charge storage mechanism and photo-charging behaviour of the Co3O4 electrode were also investigated by in situ electrochemical X-ray absorption spectroscopy and I-V characterization, respectively.

Safest light in a combat area while performing intravenous access in the dark

IntroductionCannulation for the administration of intravenous fluids is integral to the prehospital management of injured military patients. However, this may be technically challenging to undertake during night-time conditions where the...

Cost-effective flow-through nanohole array-based biosensing platform for the label-free detection of uropathogenic E. coli in real time

Rapid, inexpensive and sensitive detection of uropathogenic Escherichia coli (UPEC), a common cause of ascending urinary tract infections (UTIs) including cystitis and pyelonephritis, is critical given the increasing number of cases and its recurrence worldwide. In this paper, we present a label-free nanoplasmonic sensing platform, built with off-the-shelf optical and electronic components, which can detect intact UPEC at concentrations lower than the physiological limit for UTI diagnosis, in real time. The sensing platform consists of a red LED light source, lens assembly, CMOS detector, Raspberry Pi interface in conjugation with a metallic flow-through nanohole array-based sensor. Detection is achieved exploiting nanoplasmonic phenomena from the nanohole arrays through surface plasmon resonance imaging (SPRi) technique. The platform has a bulk sensitivity of 212 pixel intensity unit (PIU)/refractive index unit (RIU), and a resolution in the order of 10−6 RIU. We demonstrate capture and detection of UPEC with a detection limit of ~100 CFU/ml – a concentration well below the threshold limit for UTI diagnosis in clinical samples. We also demonstrate detection of UPEC in spiked human urine samples for two different concentrations of bacteria. This work is particularly relevant for point-of-care applications, especially for regions around the world where accessibility to medical facilities is heavily dependent upon economy, and availability.

Quantifying the radiant exposure and effective dose in patients treated for actinic keratoses with topical photodynamic therapy using daylight and LED white light

Daylight photodynamic therapy (dl-PDT) is as effective as conventional PDT (c-PDT) for treating actinic keratoses but has the advantage of reducing patient discomfort significantly. Topical dl-PDT and white light-PDT (wl-PDT) differ from c-PDT by way of light sources and methodology. We measured the variables associated with light dose delivery to skin surface and influence of geometry using a radiometer, a spectral radiometer and an illuminance meter. The associated errors of the measurement methods were assessed. The spectral and spatial distribution of the radiant energy from the LED white light source was evaluated in order to define the maximum treatment area, setup and treatment protocol for wl-PDT. We compared the data with two red LED light sources we use for c-PDT. The calculated effective light dose is the product of the normalised absorption spectrum of the photosensitizer, protoporphyrin IX (PpIX), the irradiance spectrum and the treatment time. The effective light dose from daylight ranged from 3 ± 0.4 to 44 ± 6 J cm−2due to varying weather conditions. The effective light dose for wl-PDT was reproducible for treatments but it varied across the treatment area between 4 ± 0.1 J cm−2 at the edge and 9 ± 0.1 J cm−2 centrally. The effective light dose for the red waveband (615–645 nm) was 0.42 ± 0.05 J cm−2 on a clear day, 0.05 ± 0.01 J cm−2 on an overcast day and 0.9 ± 0.01 J cm−2 using the white light. This compares with 0.95 ± 0.01 and 0.84 ± 0.01 J cm−2 for c-PDT devices. Estimated errors associated with indirect determination of daylight effective light dose were very significant, particularly for effective light doses less than 5 J cm−2 (up to 83% for irradiance calculations). The primary source of error is in establishment of the relationship between irradiance or illuminance and effective dose. Use of the O’Mahoney model is recommended using a calibrated logging illuminance meter with the detector in the plane of the treatment area.

Flavonoid accumulation in common buckwheat (Fagopyrum esculentum) sprout tissues in response to light

The content and accumulation patterns of flavonoids in response to light were investigated in common buckwheat (Fagopyrum esculentum) sprouts over the course of 9 days. Buckwheat sprouts were grown under fluorescent (FL), red (RL), and blue (BL) light sources, as well as in darkness, and their extracts were analyzed. Sprout elongation and chlorophyll content were high in the presence of red light. The contents of the major buckwheat sprout flavonoids, orientin, isoorientin, vetexin, isovetexin, and rutin all peaked 5 days after germination under all four growth conditions, then gradually decreased. Sprouting cotyledons accumulated around 1.5-fold more orientin, isoorientin, quercetin-3-O-robinobioside, and rutin in the presence of red light, including from the RL and FL light sources, than in blue light alone. The C-glycosyl flavones, orientin, isoorientin, vetexin, and isovetexin, were not detected in the stem tissues of the hypocotyls, but C-glycosyl flavonols, such as quercetin-3-O-robinobioside and rutin, were present, and were twice as abundant under BL and FL than in the RL and darkness conditions. In the root tissues, a small amount of C-glycosyl flavonols was detected after BL exposure only; however, the other flavonoids were not detected at all. These results indicated that red light induces flavonoid biosynthesis in the cotyledons of buckwheat seedlings, but blue light has a greater effect on the accumulation of C-glycosyl flavonols in other seedling tissues.

Multifunctional luminescent magnetic cryocooler in a Gd5Mn2 pyramidal complex.

Magnetic cooling is a highly efficient refrigeration technique with the potential of replacing expensive and rare helium-3 in the field of ultra-low temperature cooling. However, the visualization of a cryogen at an extremely low temperature and in a strong magnetic field is challenging, but it is crucial for the precise positioning and in situ thermal probe measurements in potential practical applications. Here, the activation of a red-emissive Mn(ii) ion using 3d/4f chemistry produces a luminescent molecule cooler, [Gd5Mn2(LOMe)2(OH)4(Ac)6(MeOH)10Cl2]Cl3·2MeOH (1), with the core of an Mn(ii)-anchored heptanuclear [GdIII5MnII2] pyramid. The photoluminescence (PL) of the Mn2+ emission, with a large Stokes shift (λem ∼ 690 nm) from 4T1(4G) → 6A1(6S), shows not only a sensitive temperature sensing property but also reversible mechanoluminescence (ML). More attractively, these findings reveal a considerable magnetocaloric effect (MCE) coupled with a tunable emission window, opening up new opportunities in the multifunctional applications of PL, ML, and the MCE involving red-light sources, thermometers, and stress imaging. In particular, this provides a novel resolution to design visualized PL coolers.