Different Wavelengths Of Light Research Articles

Apochromatic X-ray focusing

Achromatic doublets are combinations of two individual lenses designed to focus different wavelengths of light in the same position. Apochromatic optics are improved versions of the achromatic schemes which extend the wavelength range significantly. Both achromatic and apochromatic optics are well-established for visible light. However, X-ray achromatic lenses did not exist until very recently, and X-ray apochromatic lenses have never been experimentally demonstrated. Here, we create an X-ray apochromatic lens system using an appropriate combination of a Fresnel zone plate and a diverging compound refractive lens with a tuned separation distance. The energy-dependent performance of this apochromat was characterized at photon energies between 6.5 and 13.0 keV by ptychographic reconstruction of the focal spot and scanning transmission X-ray microscopy of a resolution test sample. The apochromat delivered a reconstructed focal spot size of 940 × 740 nm2. The apochromatic combination shows a four-fold improvement in the chromatic aberration correction range compared to an achromatic doublet configuration. Thus, apochromatic X-ray optics have the potential to increase the focal spot intensity for a wide variety of X-ray applications.

Magnetic Nanodevices and Spin-Transport Properties of a Two-Dimensional CrSCl Monolayer

The two-dimensional intrinsic ferromagnet $\mathrm{Cr}\mathrm{S}\mathrm{Cl}$ monolayer has considerable potential for application in the development of spintronic devices because of properties such as robust ferromagnetic ordering, large spin polarization, high Curie temperature, and high carrier mobilities. Here, we investigate the electromagnetic properties of the $\mathrm{Cr}\mathrm{S}\mathrm{Cl}$ monolayer and the spin-transport properties of some conceptual magnetic devices we construct, such as p-n-junction diodes, field-effect transistors, and phototransistors, by means of first-principles calculations. The results indicate that the p-n-junction diodes of the $\mathrm{Cr}\mathrm{S}\mathrm{Cl}$ monolayer exhibit full spin-polarized transport behavior, and both the p-n and p-i-n junctions show excellent spin-filtering behavior. The phototransistor of the $\mathrm{Cr}\mathrm{S}\mathrm{Cl}$ monolayer exhibits spin-resolved photoresponse characteristics for different wavelengths of light. Furthermore, it possesses the ability to generate a fully spin-up polarized current in the visible range. Our results provide key insights into the fundamental physical properties and the underlying transport and photoresponse mechanisms of the $\mathrm{Cr}\mathrm{S}\mathrm{Cl}$ monolayer.

On the Nature of Stationary and Time-Resolved Fluorescence Spectroscopy of Collagen Powder from Bovine Achilles Tendon.

This paper presents a more systematic study of steady-state and time-resolved autofluorescence spectroscopy of collagen isolated from bovine Achilles tendon. In steady-state fluorescence measurements, the excitation and emission spectra of collagen powder, recorded at different fluorescence excitation and detection wavelengths, were compared with the fluorescence excitation and emission spectra of the amino acids phenylalanine, tyrosine, and tryptophan, as well as with similar spectra for 13 autofluorescent collagen cross-links, which have been identified and described in the literature so far. In time-resolved studies, fluorescence was excited by the pulsed light of different wavelengths, and for each excitation wavelength, fluorescence decay was recorded for several detection wavelengths. Data analysis allowed recovery of the fluorescence decay times for each experimental excitation detection event. The obtained information on the decay times of the measured fluorescent signals was discussed, taking into account the available literature data from similar studies of isolated collagen and collagen-rich tissues. Based on the obtained results, it was found that the shape and position of the measured fluorescence excitation and emission spectra of collagen strongly depend on the emission and excitation wavelengths selected in the measurements. From the recorded excitation and emission bands of collagen, it can be concluded with high probability that there are additional, so far unidentified, collagen cross-links, which can be excited at longer excitation wavelengths. In addition, the collagen excitation spectra were measured at longer emission wavelengths at which the collagen cross-links emit fluorescent light. In addition to the emission spectra obtained for excitation in the deep-UV region, the results of time-resolved fluorescence studies with excitation in the deep-UV region and detection at longer wavelengths suggest that fluorescence excitation energy transfer processes occur from the amino acids to the collagen cross-links, and also between the cross-links themselves.

Light-Induced Bipolar Photoresponse with Amplified Photocurrents in an Electrolyte-Assisted Bipolar p-n Junction.

The p-n junction with bipolar characteristics sets the fundamental unit to build electronics while its unique rectification behavior constrains the degree of carrier tunability for expanded functionalities. Herein, a bipolar-junction photoelectrode employed with a gallium nitride (GaN) p-n homojunction nanowire array that operates in electrolyte is reported, demonstrating bipolar photoresponse controlled by different wavelengths of light. Significantly, with rational decoration of a ruthenium oxides (RuOx ) layer on nanowires guided by theoretical modeling, the resulting RuOx /p-n GaN photoelectrode exhibits unambiguously boosted bipolar photoresponse by an enhancement of 775% and 3000% for positive and negative photocurrents, respectively, compared to the pristine nanowires. The loading of the RuOx layer on nanowire surface optimizes surface band bending, which facilitates charge transfer across the GaN/electrolyte interface, meanwhile promoting the efficiency of redox reaction for both hydrogen evolution reaction and oxygen evolution reaction which corresponds to the negative and positive photocurrents, respectively. Finally, a dual-channel optical communication system incorporated with such photoelectrode is constructed with using only one photoelectrode to decode dual-band signals with encrypted property. The proposed bipolar device architecture presents a viable route to manipulate the carrier dynamics for the development of a plethora of multifunctional optoelectronic devices for future sensing, communication, and imaging systems.

Monitoring the Reversibility of GPCR Signaling by Combining Photochromic Ligands with Label‐free Impedance Analysis

AbstractG protein‐coupled cell surface receptors (GPCR) trigger complex intracellular signaling cascades upon agonist binding. Classic pharmacological assays provide information about binding affinities, activation or blockade at different stages of the signaling cascade, but real time dynamics and reversibility of these processes remain often disguised. We show that combining photochromic NPY receptor ligands, which can be toggled in their receptor activation ability by irradiation with light of different wavelengths, with whole cell label‐free impedance assays allows observing the cell response to receptor activation and its reversibility over time. The concept demonstrated on NPY receptors may be well applicable to many other GPCRs providing a deeper insight into the time course of intracellular signaling processes.

Monitoring the Reversibility of GPCR Signaling by Combining Photochromic Ligands with Label-free Impedance Analysis.

G protein-coupled cell surface receptors (GPCR) trigger complex intracellular signaling cascades upon agonist binding. Classic pharmacological assays provide information about binding affinities, activation or blockade at different stages of the signaling cascade, but real time dynamics and reversibility of these processes remain often disguised. We show that combining photochromic NPY receptor ligands, which can be toggled in their receptor activation ability by irradiation with light of different wavelengths, with whole cell label-free impedance assays allows observing the cell response to receptor activation and its reversibility over time. The concept demonstrated on NPY receptors may be well applicable to many other GPCRs providing a deeper insight into the time course of intracellular signaling processes.

High performance NIR photodetector based on Cd(1-x)CuxS colloidal quantum dots thin films

Thin films of Cd(1-x)CuxS (x = 0.0 to 0.05 with interval of 0.01) colloidal quantum dots (CQDs) are employed to develop NIR photodetectors (PDs) with significantly high performance parameters and selectivity. Two very cost effective and easy chemical routes are used to synthesize Cd(1-x)CuxS CQDs and to fabricate the PD devices. The Cd(1-x)CuxS CQDs thin films are primarily characterized by various techniques in order to study the influence of Cu doping on different properties of the films. Further, the impact of doping on device performance under the exposure of laser light of different wavelengths is investigated. The tunability in sensing range from visible (635 nm) to NIR (782 nm) of the PDs with a huge improvement in selectivity and device performance due to the incorporation of the dopant is noticed. The maximum selectivity is observed for device S2 (2% Cu in CdS) with maximum responsivity and external quantum efficiency of ∼39 A/W and ∼6.2 × 103% respectively. Whereas the device S4 (4% Cu in CdS) is found to be the fastest with response times of 102 ms/109 ms, sensitivity of ∼3 × 105%, and detectivity of ∼1 × 1014 cmHz1/2W−1. In present study, device S4shows best optimal performance parameters.

New insights into the photocatalytic and magnetic activity of Co-doped BiFeO3 nanoparticles via competing structures

Cobalt was chosen as the doping element for BiFeO3 (BFO), and pure BFO and a series of BiFe1−x Co x O3 (x = 0.03, 0.05, 0.07, 0.09) nanoparticles, correspondingly labeled as nBFCO (n = 3, 5, 7, 9), were successfully prepared and investigated based on the sol-gel method in this paper. The synthesized nanoparticles were characterized by x-ray diffraction, field emission scanning electron microscopy, Brunauer−Emmett−Teller surface area, x-ray photoelectron spectroscopy and ultraviolet-visible light absorption. With the increase in the doping level of cobalt in BFO, a competing structure wandering between rhombohedral and orthorhombic structures was observed in the experiment. For instance, the microstructure characterization clearly indicates coexistence of the rhombohedral and orthorhombic structures in 7BFCO. Meanwhile, the bandgap of BFO was significantly reduced from 2.04 eV to 1.78 eV. The photocatalytic degradation of Rhodamine B of samples in an aqueous solution was investigated under different wavelengths of light. We found that 7BFCO was the optimal proportion for acquiring the photocatalytic and magnetic activity in this work, e.g. the photocatalytic efficiency can reach 98.2%. The underlying physics based on the lattice structure, size effects and energy gap is also discussed.

Multispectral Imaging for Skin Diseases Assessment-State of the Art and Perspectives.

Skin optical inspection is an imperative procedure for a suspicious dermal lesion since very early skin cancer detection can guarantee total recovery. Dermoscopy, confocal laser scanning microscopy, optical coherence tomography, multispectral imaging, multiphoton laser imaging, and 3D topography are the most outstanding optical techniques implemented for skin examination. The accuracy of dermatological diagnoses attained by each of those methods is still debatable, and only dermoscopy is frequently used by all dermatologists. Therefore, a comprehensive method for skin analysis has not yet been established. Multispectral imaging (MSI) is based on light-tissue interaction properties due to radiation wavelength variation. An MSI device collects the reflected radiation after illumination of the lesion with light of different wavelengths and provides a set of spectral images. The concentration maps of the main light-absorbing molecules in the skin, the chromophores, can be retrieved using the intensity values from those images, sometimes even for deeper-located tissues, due to interaction with near-infrared light. Recent studies have shown that portable and cost-efficient MSI systems can be used for extracting skin lesion characteristics useful for early melanoma diagnoses. This review aims to describe the efforts that have been made to develop MSI systems for skin lesions evaluation in the last decade. We examined the hardware characteristics of the produced devices and identified the typical structure of an MSI device for dermatology. The analyzed prototypes showed the possibility of improving the specificity of classification between the melanoma and benign nevi. Currently, however, they are rather adjuvants tools for skin lesion assessment, and efforts are needed towards a fully fledged diagnostic MSI device.

New cationic spiropyrans with photoswitchable NIR fluorescence

Visible-light-mediated photochromic compounds with NIR absorption and fluorescence are of great interest for use in different biomedical applications. In this work, new representatives of spiropyrans with conjugated cationic 3H-indolium substituents in different positions of 2H-chromene moiety were synthesized. The electron-donating methoxy groups were introduced in the uncharged indoline and charged indolium cycles to form the effective conjugation chain between the hetarene moiety and the cationic fragment for reaching NIR absorption and fluorescence. The molecular structure and the effects of cationic fragment position on the mutual stability of the spirocyclic and merocyanine forms of compounds were carefully studied in the solutions and solid state by NMR, IR, HRMS, single-crystal XRD, and quantum chemical calculations. It was found that the obtained spiropyrans demonstrate positive or negative photochromism depending on the cationic fragment’s position. One of spiropyrans has shown bidirectional photochromic properties induced exclusively by visible light of different wavelengths in both directions. The photoinduced merocyanine forms of compounds possessed far-red shifted absorption maxima and NIR fluorescence, which makes them prospective fluorescent probes for bioimaging.

Spectral optimization of trichromatic white LEDs based on age of lighting user and application scene.

The optimization of trichromatic white light emitting diodes (LEDs) spectrum for application scenes related to the age of lighting users is proposed and demonstrated. Based on the spectral transmissivity of human eyes at different ages, the visual and non-visual responses of human eyes to different wavelengths of light, we have built the blue light hazards (BLH) and circadian action factor (CAF) related to the age of the lighting user. The BLH and CAF are used to evaluate the spectral combinations of high color rendering index (CRI) white LEDs obtained from different radiation flux ratios of red, green, and blue monochrome spectrum. The best spectra of white LEDs for lighting users at different ages in work and leisure scenes are achieved due to the optimization criterion of BLH proposed by us. This research provides a solution for intelligent health lighting design applicable to light users of different ages and application scenes.

Wavelength-Dependent Effects of Photobiomodulation for Wound Care in Diabetic Wounds.

Photobiomodulation, showing positive effects on wound healing processes, has been performed mainly with lasers in the red/infrared spectrum. Light of shorter wavelengths can significantly influence biological systems. This study aimed to evaluate and compare the therapeutic effects of pulsed LED light of different wavelengths on wound healing in a diabetic (db/db) mouse excision wound model. LED therapy by Repuls was applied at either 470 nm (blue), 540 nm (green) or 635 nm (red), at 40 mW/cm2 each. Wound size and wound perfusion were assessed and correlated to wound temperature and light absorption in the tissue. Red and trend-wise green light positively stimulated wound healing, while blue light was ineffective. Light absorption was wavelength-dependent and was associated with significantly increased wound perfusion as measured by laser Doppler imaging. Shorter wavelengths ranging from green to blue significantly increased wound surface temperature, while red light, which penetrates deeper into tissue, led to a significant increase in core body temperature. In summary, wound treatment with pulsed red or green light resulted in improved wound healing in diabetic mice. Since impeded wound healing in diabetic patients poses an ever-increasing socio-economic problem, LED therapy may be an effective, easily applied and cost-efficient supportive treatment for diabetic wound therapy.

Water‐Soluble Graphite‐Phase Carbon Nitride Colloid and Its Multichannel Biological Imaging Effect

AbstractDue to the large band gap and quantum size effect, most of reported fluorescent graphite phase carbon nitride (GCN) nanosheets/quantum dot emits blue fluorescence under ultraviolet, which limits its further application in bio‐imaging. However, diversified strategies of PL wavelength tailored are rare except for heteroatom or molecule doping. In this paper, yellowish carbon nitride colloid with 508 nm PL emission was produced through structural self‐modulation method using melamine as sole precursor. The obtained colloid demonstrate nontoxicity, stability (up to 10 month), good dispersibility in water and green fluorescent under 365 nm light excitation. Associated with its broad emission peak excited by different wavelengths of light, it shows good performance in biological imaging and importantly, realizes blue, green and red three‐channels imaging. To the best of our knowledge, this is the first time to report multi‐channel biological imaging based on GCN polymer with long PL wavelength by structural self‐modulation strategy.

Performance of a PANI/MnO2 Nanocomposite-Based Supercapacitor/Diode Under DC Magnetic Field and Visible and Ultraviolet Photon Irradiation

Polyaniline/Manganese dioxide (PANI/MnO2) nanocomposite has been successfully prepared by in situ polymerization method. The X-ray Diffraction (XRD) data confirm the formation of PANI/MnO2 nanocomposites. Fourier Transform Infrared (FT-IR) spectroscopy confirms the vibrationsdominant by metal oxide and polymer in the complex format. The Scanning Electron Microscope (SEM) shows that these nanocomposites exhibits nano rods like morphologies. The optical properties were studied by UV–visible Spectroscopy and the optical band gaps were estimated to be around 1.62 eV. Also this composite follow indirect allowed transition. Cyclic Voltammetry (CV) of this composites were also studied, and from this data the specific capacitance (Cp), energy density (Ed), power density (Pd) and charge retention were also calculated. Additionally, from CV data, the energy levels such as the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were also determined. A supercapacitor of this understudy material was designed and it’s charging and discharging under different conditions (like under the exposure of different wavelengths of light and various intensities of static magnetic fields)were also studied and explained. The preliminary designed supercapacitor shows good charge retention capacity. The specific capacitance of this capacitor remainsaround 463 Fg−1 at 200 cycles. Besides this, a planner diode of this composite was also fabricated and this diode was tested for current-voltage (IV) characteristics under various conditions like under exposure to photons of various wavelengths and in presence of different static magnetic fields.The various parameters related with this diode were analyzed and studied. The dielectric studies of this material were studied. The current materials could be explored as a good candidate for modern energy storage and optoelectronics applications.

Preparation and characterisation of photoresponsive molecularly imprinting polymer nanoparticles with hollow structure for extraction and enrichment of dibutyl phthalate

Dibutyl phthalate (DBP), as a plasticizer, has been widely used in the manufacture of plastic products. However, it is generally acknowledged that DBP is an endocrine disruptor, which would cause harm to both humans and wildlife. Generally, trace DBP in river water, soil or food is hard to be detected accurately. To solve this case, a core-shell hollow structured molecularly imprinting polymer, PH-MIPs, was synthesised via surface imprinting technology. It is noteworthy that the prepared PH-MIPs can specifically absorb and release DBP irradiated by different wavelengths of light. More importantly, the absorption capacity of PH-MIPs reaches up to 5.2 mg·g−1 without obvious attenuation in absorption performance after 4 loops of photo-controlled uptake and release of DBP. Furthermore, the PH-MIPs exhibit excellent selective absorption properties, supported by an imprinting factor of 3.4. Finally, the prepared PH-MIPs were applied to enrich and extract DBP in river water samples with the recovery rate of 83.2%. In general, the proposed PH-MIPs exhibit excellent practicability, which offers a method for the content determination of DBP as a high-efficiency solid-phase extractant for the enrichment and extraction of target pollutants.

Photodynamic Light-Triggered Release of Curcumin from Hierarchical FAU Zeolite

Photodynamic therapy (PDT) is a method used in the treatment of various diseases and represents a promising alternative to classical active substance release methods. According to the United States National Institute of Health, this therapy exploits the health-promoting potential of active substances, referred to as “photosensitizers”, and radiation of specific energy. Curcumin is a natural “photosensitizer” that exhibits anti-inflammatory, antioxidant, and anti-cancer effects. Despite the novelty and innovation of PDT, the method is limited by the difficulty of using “photosensitizers” such as curcumin because of its low solubility in water, which hinders the clinical application of this technique. The use of a “photosensitizer” along with suitable carriers such as hierarchical zeolites is a potential strategy to offset this difficulty. Therefore, the objective of this study was to develop the photodynamic release of curcumin from hierarchical zeolites using the classical open-circuit release method and a novel closed-circuit release technique involving light of different wavelengths. Based on the obtained data, it was possible to unequivocally state that the speed and efficiency of curcumin release from the zeolite carrier is influenced by light with a wavelength in the range of 430–525 nm (blue-cyan-green). As much as 53.24% of the active substance was released upon light exposure.

Negative Photochromic 3-Phenylperylenyl-Bridged Imidazole Dimer Offering Quantitative and Selective Bidirectional Photoisomerization with Visible and Near-Infrared Light

Selective bidirectional photoisomerization reactions with high conversion ratios between stable and metastable isomers by irradiation of photochromic molecules with visible light of different wavelengths have been an important issue for many years. For negative photochromic molecules known so far, metastable isomers also absorb UV or visible light in the same region as stable isomers, making it difficult to selectively achieve the reverse reaction by visible-light irradiation. We have demonstrated that the absorption bands of the stable and metastable isomers of 3-phenylperylenyl-bridged imidazole dimer are largely separated by more than 140 nm and that almost quantitative and selective bidirectional photoconversion can be achieved by 660 and 460 nm light. Furthermore, the forward reaction can be achieved completely with near-infrared light of 785 nm.

Non-mechanical Lidar beamforming enabled by combined wavelength-division- and time-division-multiplexing

We propose and demonstrate a Lidar beam-forming scheme without moving parts, enabled by the combination of wavelength-division-multiplexing (WDM) and time-division-multiplexing (TDM). The lights of different wavelength are demultiplexed into N different waveguides to form N WDM channels; each of them is further switched into M waveguides to form M TDM channels with their exiting ends placed in the focal plane of a lens. The lights exiting from the N × M array at different positions in the focal plane of the lens are collimated into different beams pointing to different directions. Two-dimensional beam-forming of N × M beams is realized in the space-wavelength domain (the WDM channels) and space-time domain (the TDM channels), in which the N WDM beams can be simultaneously directed into different direction by the TDM switches sequentially. The scheme has been successfully demonstrated with the off-the-shelf discrete fiber optic components using 4 WDM channels and 1 × 4 optical fiber switches for beam forming, together with the time-of-flight (ToF) technique for distance measurement for obtaining the three dimensional (3D) point cloud data. In particular, we have experimentally realized four different beam scanning modes using different configurations of the time- and wavelength-channels. The addition of the TDM channels helps to reduce the required number of wavelength channels in the pure wavelength-multiplexed scheme, and vice versa, to overcome the technical limitations on the number of WDM or TDM channels. Furthermore, adding the WDM channels helps to relax the speed requirement of the switches and related electronics of the TDM channels. We believe our Lidar beam-forming scheme combining both TDM and WDM may provide an attractive alternative to the MEMS and optical phased array based beam scanning, as well as the pure WDM beam-forming schemes.

Window films increase avoidance of collisions by birds but only when applied to external compared with internal surfaces of windows.

Window collisions are one of the largest human-caused causes of avian mortality in built environments and, therefore, cause population declines that can be a significant conservation issue. Applications of visibly noticeable films, patterns, and decals on the external surfaces of windows have been associated with reductions in both window collisions and avian mortality. It is often logistically difficult and economically prohibitive to apply these films and decals to external surfaces, especially if the windows are above the first floor of a building. Therefore, there is interest and incentive to apply the products to internal surfaces that are much easier to reach and maintain. However, there is debate as to whether application to the internal surface of windows renders any collision-reduction benefit, as the patterns on the films and decals may not be sufficiently visible to birds. To address this knowledge gap, we performed the first experimental study to compare the effectiveness of two distinct window films when applied to either the internal or external surface of double-glazed windows. Specifically, we assessed whether Haverkamp and BirdShades window film products were effective in promoting the avoidance of window collisions (and by inference, a reduction of collisions) by zebra finches through controlled aviary flight trials employing a repeated-measures design that allowed us to isolate the effect of the window treatments on avoidance flight behaviors. We chose these two products because they engage with different wavelengths of light (and by inference, colors) visible to many songbirds: the BirdShades film is visible in the ultraviolet (shorter wavelength) range, while the Haverkamp film includes signals in the orange (longer wavelength) range. We found consistent evidence that, when applied to the external surface of windows, the BirdShades product resulted in reduced likelihood of collision and there was marginal evidence of this effect with the Haverkamp film. Specifically, in our collision avoidance trials, BirdShades increased window avoidance by 47% and the Haverkamp increased avoidance by 39%. However, neither product was effective when the films were applied to the internal surface of windows. Hence, it is imperative that installers apply these products to exterior surfaces of windows to render their protective benefits and reduce the risk of daytime window collision.

Green means go: Green light promotes hypocotyl elongation via brassinosteroid signaling.

Although many studies have elucidated the mechanisms by which different wavelengths of light (blue, red, far-red, or ultraviolet-B [UV-B]) regulate plant development, whether and how green light regulates plant development remains largely unknown. Previous studies reported that green light participates in regulating growth and development in land plants, but these studies have reported conflicting results, likely due to technical problems. For example, commercial green light-emitting diode light sources emit a little blue or red light. Here, using a pure green light source, we determined that unlike blue, red, far-red, or UV-B light, which inhibits hypocotyl elongation, green light promotes hypocotyl elongation in Arabidopsis thaliana and several other plants during the first 2-3 d after planting. Phytochromes, cryptochromes, and other known photoreceptors do not mediate green-light-promoted hypocotyl elongation, but the brassinosteroid (BR) signaling pathway is involved in this process. Green light promotes the DNA binding activity of BRI1-EMS-SUPPRESSOR 1 (BES1), a master transcription factor of the BR pathway, thus regulating gene transcription to promote hypocotyl elongation. Our results indicate that pure green light promotes elongation via BR signaling and acts as a shade signal to enable plants to adapt their development to a green-light-dominant environment under a canopy.