Blue Range Research Articles

Subcellular Optogenetics Enacted by Targeted Nanotransformers of Near-Infrared Light

Light activation of photoswitchable molecules enables control over the course of physicochemical processes with high spatiotemporal precision, offering revolutionizing potential in multiple areas of contemporary biomedicine. Yet, application of this technology in live organisms remains severely limited due to the reliance on visible light that has poor penetration in biological tissues. Herein, we introduce highly efficient upconversion nanoparticles (UCNPs) as photon nanotransformers that intracellularly convert tissue-penetrating, near-infrared light into visible light required for photoactivation. The core/shell nanoparticles described here are determined to be about six times brighter in the blue range than the canonical hexagonal (NaYF4:Yb3+30%/Tm3+0.5%)/NaYF4 core/shell UCNPs with record efficiency. An application of such efficient photon nanotransformers can significantly advance optogenetics technology, wherein the signaling of genetically modified neurons is controlled through interaction of visi...

Membrane Independence of Ultrafast Photochemistry in Pharaonis Halorhodopsin: Testing the Role of Bacterioruberin.

Ultrafast photochemistry of pharaonis halorhodopsin (p-HR) in the intact membrane of Natronomonas pharaonis has been studied by photoselective femtosecond pump-hyperspectral probe spectroscopy with high time resolution. Two variants of this sample were studied, one with wild-type retinal prosthetic groups and another after shifting the retinal absorption deep into the blue range by reducing the Schiff base linkage, and the results were compared to a previous study on detergent-solubilized p-HR. This comparison shows that retinal photoisomerization dynamics is identical in the membrane and in the solubilized sample. Selective photoexcitation of bacterioruberin, which is associated with the protein in the native membrane, in wild-type and reduced samples, demonstrates conclusively that unlike the carotenoids associated with some bacterial retinal proteins the carrotenoid in p-HR does not act as a light-harvesting antenna.

Design, synthesis and fluorescence analysis of potential fluorescent markers based on cardanol and glycerol

We report the synthesis and fluorescent properties of 1,4-disubstituted-1,2,3-triazoles (1a-c) based on pollutant wastes and by-products from the cashew and biodiesel industries as a design for fluorescent markers. The triazoles were synthesized in four steps; catalytic hydrogenation of cardanol, reaction with epichlorohydrin, azide substitution and/or epoxide opening and, Cu catalyzed click-chemistry of the azide with the ethynylanilines (6a-c). This procedure is a potential alternative to make fluorescent markers since it affords the intermediates in high yields, enabling one to produce the products in good quantities. Moreover, triazolazobenzenes (8a-c) were prepared by azo coupling of the trizoles (1a-c) with phenol to give a new option of dyes. Evaluation of the fluorescent properties of the achieved compounds showed that all triazole derivatives displayed good fluorescence emissions in the range of 325–400 nm, with a maximum of fluorescence intensity at around 350 nm when excited between 225 and 300 nm; besides, the para-triazolaniline exhibited a dual fluorescence emission, presenting an additional emission band in the blue range (400–500 nm).

Low-cost multispectral imaging for remote sensing of lettuce health

In agricultural remote sensing, unmanned aerial vehicle (UAV) platforms offer many advantages over conventional satellite and full-scale airborne platforms. One of the most important advantages is their ability to capture high spatial resolution images (1–10 cm) on-demand and at different viewing angles. However, UAV platforms typically rely on the use of multiple cameras, which can be costly and difficult to operate. We present the development of a simple low-cost imaging system for remote sensing of crop health and demonstrate it on lettuce (Lactuca sativa) grown in Hong Kong. To identify the optimal vegetation index, we recorded images of both healthy and unhealthy lettuce, and used them as input in an expectation maximization cluster analysis with a Gaussian mixture model. Results from unsupervised and supervised clustering show that, among four widely used vegetation indices, the blue wide-dynamic range vegetation index is the most accurate. This study shows that it is readily possible to design and build a remote sensing system capable of determining the health status of lettuce at a reasonably low cost (<US$100). When combined with recent advances in UAV technology, this system could lead to yield increases for lettuce growers.

Scroll-like Alloyed CdSxSe1–x Nanoplatelets: Facile Synthesis and Detailed Analysis of Tunable Optical Properties

Scroll-like colloidal quasi-two-dimensional CdSxSe1–x nanoplatelets (NPLs) with a thickness of five monolayers and average lateral dimensions of 100 nm over the whole composition range (0 ≤ x ≤ 1) were synthesized by using a mixture of chalcogenide precursors. According to X-ray diffraction and X-ray energy dispersive spectroscopy mapping in a scanning transmission electron microscope, as-synthesized NPLs are solid solutions with a uniform elemental distribution in each individual nanoplatelet. A change in composition leads to the continuous shift and gradual broadening of exciton absorption and photoluminescence (PL) lines in the visible blue and near-ultraviolet light range. Detailed analysis of optical properties, including temperature-dependent PL spectroscopy, revealed the nonmonotonic behavior of several optical parameters (average phonon temperature, electron–phonon interaction coefficient, and Stokes shift) starting from a sulfur content of ∼40% in alloyed NPLs. This behavior may be attributed to ...

External cavity diode laser setup with two interference filters

We present an external cavity diode laser setup using two identical, commercially available interference filters operated in the blue wavelength range around 450 nm. The combination of the two filters decreases the transmission width, while increasing the edge steepness without a significant reduction in peak transmittance. Due to the broad spectral transmission of such interference filters compared to the internal mode spacing of blue laser diodes, an additional locking scheme, based on H\"ansch-Couillaud locking to a cavity, has been added to improve the stability. The laser is stabilized to a line in the tellurium spectrum via saturation spectroscopy, and single-frequency operation for a duration of two days is demonstrated by monitoring the error signal of the lock and the piezo drive compensating the length change of the external resonator due to air pressure variations. Additionally, transmission curves of the filters and the spectra of a sample of diodes are given.

Bridgman growth and luminescence properties of dysprosium doped lead potassium niobate crystal

Dy-doped lead potassium niobate (Pb2KNb5O15, PKN) single crystal was grown by the modified vertical Bridgman method through spontaneous nucleation. The crystal was brownish, transparent and inclusion free. Five excitation peaks of Dy3+ ions were clearly seen from near ultraviolet region to blue range. It was unique that the excitation peaks in blue range were more intense, especially the one centered at 455nm. The emission bands consisted of blue, yellow and red emissions, which were at about 487nm, 573nm and 662nm respectively. The CIE chromaticity diagram of PKN:Dy indicated that white light and yellow light could be emitted when the crystal was excited under near ultraviolet light and blue light, respectively. Thus PKN:Dy crystal is a candidate material whose emitting light could be tunable through changing the excited light wavelength.

Two-dimensional wide-band-gap nitride semiconductors: Single-layer 1T−XN2(X=S,Se, and Te)

Recently, the two-dimensional (2D) semiconductors arsenene and antimonene, with band gaps larger than 2.0 eV, have attracted tremendous interest, especially for potential applications in optoelectronic devices with a photoresponse in the blue and UV range. Motivated by this exciting discovery, types of highly stable wide-band-gap 2D nitride semiconductors were theoretically designed. We propose single-layer $1T\ensuremath{-}X{\mathrm{N}}_{2}$ ($X=\mathrm{S}$, Se, and Te) via first-principles simulations. We compute $1T\ensuremath{-}X{\mathrm{N}}_{2}$ ($X=\mathrm{S}$, Se, and Te) with indirect band gaps of 2.825, 2.351, and 2.336 eV, respectively. By applying biaxial strain, they are able to induce the transition from a wide-band-gap semiconductor to a metal, and the range of absorption spectra of $1T\ensuremath{-}X{\mathrm{N}}_{2}$ ($X=\mathrm{S}$, Se, and Te) obviously extend from the ultraviolet region to the blue-purple light region. With an underlying graphene, we find that $1T\ensuremath{-}X{\mathrm{N}}_{2}$ can completely shield the light absorption of graphene in the range of 1--1.6 eV. Our research paves the way for optoelectronic devices working under blue or UV light, and mechanical sensors based on these 2D crystals.

A polished blue

Researchers at the University of California, Santa Barbara, have achieved the highest ever power output and efficiency for a blue laser diode on a semipolar GaN substrate. Semipolar substrates are cut at a different angle from the standard c-plane of the crystal, and are predicted to result in more effective laser operation. Despite the advantages, such as higher gain and efficiency, several technological challenges have limited the efficacy of these semipolar substrates in most applications. Blue laser diodes can excite other phosphors to emit different wavelengths, resulting in white light The Santa Barbara team, however, have overcome these challenges through a polishing process, and the resulting laser demonstrates stable, continuous wave operation with high optical power densities. This could lead to greatly improved solid-state systems in all lighting, imaging, and display systems. Solid-state lighting systems are lighting systems based on semiconductor devices, typically diodes, and use considerably less power than traditional light sources, as explained by Robert Farrell, one of the authors and a researcher at UC Santa Barbara: “they are used primarily because they are more efficient than traditional white light sources such as incandescent or fluorescent lighting.” Quantifying this difference in efficiency makes the advantages of solid-state systems very clear, said Farrell, telling us that “incandescent bulbs and linear florescent bulbs use ∼15 lm/W and ∼100 lm/W, respectively, while state-of-the-art solid-state lighting systems operate at ∼150 lm/W and this is expected to surpass 200 lm/W as further developments in the technology are made.” The current generation of commercially available systems use LEDs for excitation. For lighting purposes, “the semiconductor device emits photons in the violet or blue range of the spectrum,” said Farrell, “and these excite one or more phosphors that emit in other regions of the visible spectrum. The combined emission of light from the semiconductor devices and the phosphors is used to produce high quality white light.” While LED lighting technology is relatively mature and developed, laser diode approaches show even more promise in terms of power and efficiency. Efficiency is not the only advantage, however, as the laser diodes have both the potential to decrease the cost of solid-state lighting systems, as well as to improve the directional control of light emission as lasers are a natural point source. Laser diodes naturally require a substrate cavity for operation. This cavity can be oriented at various angles to the substrate's crystal structure. Standard (polar or c-plane substrate) lasers use mirror facets formed by cleaving the semiconductor wafer along a crystallographic plane. This is not, however, the best solution. Non-polar substrates show greater promise than their polar counterparts, but for laser cavity orientations on semipolar crystal planes “there is not an orthogonal crystallographic plane that can be used for cleaving mirror facets,” explained Farrell. The consequences of this are fairly drastic as other techniques, such as dry etching or polishing, are therefore necessary. Unfortunately, it has not been clear if these techniques are stable under high optical power densities. The achievement of the UC Santa Barbara team has been, according to Farrell, “to show that polishing can be used to create mirror facets for semipolar blue laser diodes that are smooth, perpendicular to the laser cavity, and stable under CW operation with high optical power densities (greater than 30 MW/cm2).” Showing that blue semipolar laser diodes with polished mirror facets are stable during CW operation with high optical power densities firmly establishes them as a viable alternative to c-plane laser diodes. Is the story then complete? The team's results certainly represent an important step in the development of semipolar laser diodes for laser-based solid-state lighting. However, laser diode lighting is still at an early stage - shortcomings in the technology are still apparent. “In particular,” said Farrell, “the wall plug efficiency (currently around 40%) needs to be improved, and new phosphor geometries need to be developed for integration with laser diodes.” The mechanically polished facet Once these issues have been addressed, Farrell told us that the team expect, as the efficiency of laser diodes improves over time, “it will be possible for laser-based solid-state lighting systems to find applications in all areas of general lighting.”

Thermodynamic models of the adsorption and desorption of molecular oxygen at the UV and blue emitting centers in mesoporous silica under variable oxygen pressure

The UV excited emission properties of mesoporous silica in the blue and UV range are modified by the adsorption and desorption of oxygen molecules at the two defect sites. To interpret the experimental purging cycles we model the oxygen-silica interaction at thermodynamic level, succeeding in explaining the interaction mechanism and the trend of UV centre to undergo photo-bleaching when excited under vacuum conditions. The analysis called for the presence of two different set of defects for both the centres, pinpointed as defects liable to interact with O2 and non-interacting isolated defects. To support the thermodynamic analysis, we simulated the O2 adsorption and desorption processes within the first principles DFT cluster framework. The calculated atomic configurations and the potential energy curves along selected probable reaction paths allow suggesting the kinetics of molecular oxygen interaction on examined surface silica defects and pointing at an oxygen vacancy E’-like defect as the possible result of the UV centre photo-bleaching.

Design and fabrication of two-stack tandem-type all-phosphorescent white organic light-emitting diode for achieving high color rendering index and luminous efficacy.

White organic light-emitting diodes (WOLEDs) are regarded as the general lighting source. Although color rendering index (CRI) and luminous efficacy are usually in trade-off relation, we will discuss about the optimization of both characteristics, particularly focusing on the spectrum of a blue emitter. The emission at a shorter wavelength is substantially important for achieving very high CRI (> 90). The luminous efficacy of a phosphorescent blue emitter is low as its color falls in the deeper blue range; however, that does not show any significant influence on the WOLEDs. WOLEDs with different blue dopants are compared to confirm the calculation of the CRI and luminous efficacy, and the optimized WOLEDs exhibit luminous efficacy of 38.3 lm/W and CRI of 90.9.

Theoretical investigation of the electronic structure and optical properties of zinc-doped magnesium oxide

In this work, the electronic structure and optical properties of $$\hbox {Mg}_{1-x}\hbox {Zn}_{x}\hbox {O}$$Mg1-xZnxO ($$0\le x \le 0.5$$0≤x≤0.5) are investigated within the framework of the density functional theory (DFT), the GW method, and the Bethe---Salpeter equation (BSE). We find that zinc doping can lower the band gap of pure MgO via the Zn 4s states near the Fermi level and reduce the lattice symmetry, both of which will affect the optical properties. The energy of the first absorption peak decreases as the concentration of zinc increases, so are the exciton energy and binding energy of the lowest excited state. The results nicely fit to published experimental results and are compared to those of the simple hydrogen-like atom model for excitons. As the lowest excited state is closely related to light emission at that energy according to Kasha's rule, zinc doping will lower the light emission energy of pure MgO, while still exhibiting an exciton binding energy much higher than that of $${k}_{\mathrm{B}}{T}$$kBT at room temperature. This means that $$\hbox {Mg}_{1-x}\hbox {Zn}_{x}\hbox {O}$$Mg1-xZnxO materials are perfectly suited for optoelectronic devices operating in the deep blue and near-ultraviolet (UV) range.

Clinical Study of Sensory Recovery of Artificial Nerve Grafts (Nerbridge®)

Purpose: To examine postoperative sensory recovery of patients who used Nerbridge® for sensory nerves, and the indications. Subjects and methods: We investigated length of the transplanted nerve, postoperative sensory evaluation, and Disabilities of Arm, Shoulder and Hand (DASH) score in patients who underwent surgery at our center and could be followed up for at least 6 months. The participants were 11 patients (8 men and 3 women) with 17 nerves for study whose mean age at the time of injury was 48 years (15-64 years) and mean follow-up period was 14.4 months (6-28 months). We used the Semmes Weinstein (SW) test for postoperative sensory evaluation. Results: Mean length of the transplanted nerve was 17.3 mm (3-41 mm); the sensory evaluation had 8 patients in the blue range, 6 in the purple range, and 3 in the red range; and the mean DASH score was 16.3 points (1.7-37.5 points). The results tended to be unfavorable for patients with severe injuries such as an amputated finger and those with relatively long transplanted nerves. The results of this study indicated that Nerbridge® worked well with digital nerve deficits on the order of 20 mm. Discussion: When the results following artificial nerve transplants were as good as or better than nerve autografts, the donor site was not problematic and the transplantations with artificial nerves were clearly useful. The product would be decomposed and absorbed in vivo in approximately 3 months. Although the product can be used for a maximum length of 50 mm, in a deficit over 30 mm, the regenerating nerve might be metabolized before reaching its distal nerve stump; thus, a nerve autograft would be preferred in that situation.

Carbon dots coated with vitamin B12 as selective ratiometric nanosensor for phenolic carbofuran

A carbon quantum dots (CQDs) based ratiometric nanosensor exhibiting dual emission fluorescence was developed. The spherical fluorescent carbon nanoparticles were obtained from lactose using a hydrothermal method. Under a single excitation at 355nm they showed the typical blue emission at 417nm and a red emission at 550nm attributed to the coating effect of vitamin B12. The latter is explained by the fluorescence resonance energy transfer (FRET) and it consists of 61% of total emission. Upon the presence of carbofuran phenol 3-Keto, a phenolic metabolite of carbofuran, the red emission was quenched, resulting in a ratiometric fluorescence response in the blue range. This ratiometric nanosensor exhibited a good selectivity to carbofuran phenol 3-Keto. The ratio of I417/I550 linearly decreased with an increasing carbofuran phenol 3-Keto concentration in the range 9.8μM–1.40×10−4M. A detection limit for carbofuran phenol 3-Keto pesticide was 12.2μM. The pesticide tested was extracted from soy sauce. Recovery values ranged from 98% to 114% with RSD values from 1.50% to 6.50%.

En Route to Stimuli-Responsive Boron-, Nitrogen-, and Sulfur-Doped Polycyclic Aromatic Hydrocarbons.

Replacing both meso carbon atoms of the polycyclic aromatic hydrocarbon (PAH) bisanthene by boron atoms creates an efficient blue fluorophore with a strong electron-accepting character. The corresponding meso-B,S-doped bisanthene exhibits a solvent-dependent green-to-orange photoluminescence and undergoes a reversible reduction at E1/2 =-2.06 V (vs. FcH/FcH(+) ). After oxidation of the sulfur atom, the resulting sulfoxide emits in the blue range of the spectrum, shows only negligible solvatochromism, and a reversible redox transition at E1/2 =-1.74 V. Several related B, N- and B, S-containing PAHs have been prepared following the same modular synthetic procedure and are also described herein. In order to systematically compare their optoelectronic properties, all products have been investigated by cyclic voltammetry as well as UV/Vis absorption/emission spectroscopy.

Preparation of PbSeO3 as a new material, sensitive to the electromagnetic radiation in UV range

The new technology of the formation of photoresistive structures sensitive in ultraviolet range of electromagnetic spectrum based on lead selenide and lead selenite composite is discussed. Studies of photosensitivity were carried out using a set of LEDs in the visible and ultraviolet spectral range. Obtained structures show considerable sensitivity in ultraviolet and blue range of radiation, meanwhile that in red and yellow region of light turned to be small. The structures were formed by oxidation of PbSe crystals. Diffusion of the oxygen through the surface layer of PbSe was suggested to be a key mechanism of oxidation. Oxidation kinetics were studied by means of roentgen lines chemical shift and roentgen diffraction.

Graphene oxide modified with aminoazobenzol group stabilized blue phase liquid crystals

ABSTRACTLiquid-crystalline blue phases are stable only for very narrow temperature range between the isotropic and the chiral nematic phase that severely hinders their applicability. Herein, aminoazobenzol group was chemically grafted onto graphene oxide (GO) via amidization reaction. Successful grafting of aminoazobenzol group was confirmed using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), UV-vis absorption spectra and Thermogravimetric analysis (TGA). The resultant aminoazobenzol group modified GO sheets which is reduced (GO-Az) were easily redispersed in common organic solvents. By doping different contents of GO-Az nanosheets could stabilize blue phase and increase the blue phase range. When doped with 0.5 wt% GO-Az, the mixtures show the wider range with 5.4°C than the range with 3.6°C of blue phase liquid crystals without GO-Az. Meanwhile, the phase sequence and the range of the aforementioned phases are reproducible upon heating and cooling, which shows that the blue phases doped with GO-Az nanosheets are thermodynamically stable.

Tetramethylthiourea (TMTU) as an alternative redox mediator for electrochromic devices

Iodide/triiodide (I−/I3−) redox electrolyte in hybrid electrochromic (EC) devices provides high charge capacity and thereby a high optical modulation can be achieved. However, its corrosive nature and absorption in UV and in blue range of light forming an unpleasant yellowish coloration limits smart window application. In this regard, tetramethylthiourea/tetramethylformaminium disulphide (TMTU/TMFDS2+), 2,2,6,6-tetramethyl-1-piperidinyl-oxy (TEMPO)/TEMPO+ and potassium ferrocyanide/potassium ferricyanide (K4[Fe(CN)6]/K3[Fe(CN)6]) are studied as alternative redox couples. Their characterisation is performed considering electrochemical and optical properties. The redox potential is evaluated by cyclic voltammetry. The charge transfer resistance (Rct) is determined by electrochemical impedance spectroscopy on sputtered and sol–gel tungsten trioxide (WO3), sol–gel titanium oxide (TiO2), fluorine doped tin oxide (F:SnO2) as well as on sputtered platinum (Pt). TMTU/TMFDS2+ has demonstrated an appropriate redox potential as well as a high charge transfer resistance on oxides and low on Pt layers for high bias potentials. Furthermore, the kinetics of the change in transmission of the EC devices is compared considering the loss current. The EC device comprising TMTU/TMFDS2+ exhibits excellent optical modulation in visual transmission from 71 down to 14% at −795mV within 5min.

Artificial Optical Radiation photobiological hazards in arc welding

Occupational Health and Safety (OHS) is associated with crucial social, economic, cultural and technical issues. A highly specialized OHS sector deals with the photobiological hazards from artificial optical radiation (AOR), which is divided into visible light, UV and IR emitted during various activities and which is legally covered by European Directive 2006/25/EC. Among the enormous amount of sources emitting AOR, the most important non-coherent ones to consider for health effects to the whole optical range, are arcs created during metal welding. This survey presents the effort to assess the complicated exposure limits of the Directive in the controlled environment of a welding laboratory. Sensors covering the UV and blue light range were set to measure typical welding procedures reproduced in the laboratory. Initial results, apart from apparently justifying the use of Personal Protective Equipment (PPE) due to even subsecond overexposures measured, also set the basis to evaluate PPE’s properties and support an integrated risk assessment of the complex welding environment. These results can also improve workers’ and employer’s information and training about radiation hazards, which is a crucial OHS demand.

Spectroscopic investigation on thermally stable Dy3+ doped zinc phosphate glasses for white light emitting diodes

Optically transparent dysprosium ions doped lead zinc phosphate glasses have been prepared via melt quenching technique to study the luminescent properties and their applications for white light emitting diodes (w-LEDs). X-ray diffraction (XRD) pattern confirmed the amorphous nature of the as-prepared glass. The glass transition temperature (Tg) and thermal stability (ΔT) were determined by using Differential Scanning Calorimetry (DSC). The vibrational features were characterized by Raman and FT-IR, which indicate the presence of poly-phosphate structure dominated by Q2 and Q1 structural units. The intense emission bands observed at 482 nm (blue) and 574 nm (yellow), where the yellow to blue intensity ratio for all excitation wavelengths (NUV to blue range) were found to lie in the vicinity of unity, yielding to intense white light emission. The evaluated CIE chromaticity coordinates (0.309, 0.341) for the optimized glass (GP10) at 350 nm excitation fall in the pure white region, which is in proximity with commercial w-LED (Blue LED + YAG:Ce3+) and NTSC system for white light emission. The correlated color temperature (CCT) of the optimized glass is 6547 K, which represents cool white light emission. The decay profiles have been measured for the excited 4F9/2 level and analyzed.