White Lamps Research Articles

Effect of Light Intensity and Quality on Growth Rate and Composition of Chlorella vulgaris.

In this research, the effect of solar irradiance on Chlorella vulgaris cultivated in open bioreactors under greenhouse conditions was investigated, as well as of ratio of light intensity in the 420–520 nm range to light in the 580–680 nm range (I420–520/I580–680) and of artificial irradiation provided by red and white LED lamps in a closed flat plate laboratory bioreactor on the growth rate and composition. The increase in solar irradiance led to faster growth rates (μexp) of C. vulgaris under both environmental conditions studied in the greenhouse (in June up to 0.33 d−1 and in September up to 0.29 d−1) and higher lipid content in microalgal biomass (in June up to 25.6% and in September up to 24.7%). In the experiments conducted in the closed bioreactor, as the ratio I420–520/I580–680 increased, the specific growth rate and the biomass, protein and lipid productivities increased as well. Additionally, the increase in light intensity with red and white LED lamps resulted in faster growth rates (the μexp increased up to 0.36 d−1) and higher lipid content (up to 22.2%), while the protein, fiber, ash and moisture content remained relatively constant. Overall, the trend in biomass, lipid, and protein productivities as a function of light intensity was similar in the two systems (greenhouse and bioreactor).

Influence of selenium biofortification on the bioactive compounds and antioxidant activity of wheat microgreen extract

The study was conducted to confirm the effects of selenium biofortification on the bioactive compounds and antioxidant activity of wheat microgreen extract. The microgreens were cultivated in the DFT hydroponic system with different concentrations of Se (0 [control], 0.125, 0.25, 0.50, and 1.00 mg/L from sodium selenite) in a growth chamber by controlling temperature (25/20 °C, day/night), light (12 h light/dark; intensity 150 µmol‧m−2‧s−1 with white fluorescence lamp), and humidity (60%) for 10 days. Se biofortification increased the germination rate and decreased microgreen length and yield. Chlorophyll and carotenoid levels increased in the Se-biofortified microgreen extract. Bioactive compounds such as phenolics, flavonoids, vitamin C, and anthocyanin significantly increased in 0.25–0.50 mg/L of Se-biofortified microgreen extracts. Antioxidant (ABTS, DPPH, NSA and SOD-like) activity also increased at moderate levels (0.25–0.50 mg/L) of Se biofortification. Therefore, Se biofortification may be useful for the industrial manufacture of new products from wheat microgreen extract.

The ecological hazard of artificial lighting in greenhouses

This article draws attention to the shortcomings of modern lighting systems used in greenhouses. Its content focuses on the negative effects of mismatches between the photosynthetic needs of plants and the parameters of artificial light sources. Greenhouse lamps designers often do not have the knowledge of biological cultivation dependencies. Therefore, their cooperation with specialists of plant physiology and gardeners is indispensable. This is important because it can affect the consumer quality of vegetables. Full Text: PDF ReferencesM.Kucharczyk, I.Gąsak, Ecological effects of light pollution , III International Conference on Scientific and Technical TRANSEIA, Krynica Zdrój, Poland, 6-8 December 2017. DirectLink T. H. Goldsmith, What Birds See, Scientific American Inc. (2006), CrossRef E.J. Gerl, M.R. Morris, The Causes and Consequences of Color Vision, Springer Science + Business Media, LLC, 2008. CrossRef K. Jaworski, A. Szmidt-Jaworska, J. Kopcewicz, Two calcium dependent protein kinases are differently regulated by light and have different activity patterns during seedling growth in Pharbitis nil, open access at Springerlink.com, Journal: 10725, Article: 9609, 2011. CrossRef K. Jaworski, A. Pawełek, J. Kopcewicz, A. Szmidt-Jaworska, The calcium-dependent protein kinase (PnCDPK1) is involved in Pharbitis nil flowering, Journal of Plant Physiology 169 p. 1578-1585, 2012. CrossRef A. Szmidt-Jaworska, K. Jaworski, J. Kopcewicz, Effect of light on soluble guanylyl cyclase activity in Pharbitis nil seedlings, Journal of Photochemistry and Photobiology B: Biology 93 p. 9-15, 2008. CrossRef Horticulture Lighting Group, Goniophotometer Test Report of the ELITE ECO lamp CrossRef K. Marra, E. P. LaRochelle, M. S. Chapman, P. J. Hoopes, K. Lukovits, E. V. Maytin, T. Hasan, B. W. Pogue, Comparison of Blue and White Lamp Light with Sunlight for Daylight‐Mediated, 5‐ALA Photodynamic Therapy, in vivo, Wiley Online Library, 16 April 2018 CrossRef M. Gilewski, The Ecological Harmfulness of RGB LED Light, International Conference on Energy, Power, Electrical and Environmental Engineering : EPEEE 2018, DEStech Publications, Wuhan, Hong Kong, September 27-28, 2018. CrossRef K. J. McCree, The Action Spectrum, Absorptance and Quantum Yield of Photosynthesis in Crop Plants, Agricultural Meteorology, Elsevier Publishing Company, 9 p. 191-216 , 1972. CrossRef EconoLux Indastries Ltd., What Light do Plants Need, Hong Kong CrossRef I. Ashdown, Photometry and Photosynthesis: From Photometry to PPFD, SunTracker Technologies Ltd CrossRef OSRAM Opto Semiconductors, Horticulture Lighting with LEDs, OS SSL | NR AW CH, November 2016 CrossRef M. Mottus, M. Sulev, F. Baret, R. Lopez-Lozano, A. Reinart, Photosynthetically Active Radiation: Measurement and Modeling CrossRef Heliospectra AB, Full Flexibility ELIXIA grow ligh CrossRef Heliospectra AB, Full Flexibility ELIXIA grow light CrossRef A. Szmidt-Jaworska1, K. Jaworski1, A. Tretyn, J. Kopcewicz, The involvement of cyclic GMP in the photoperiodic flower induction of Pharbitis nil, J. Plant Physiol. 161. p. 277-284, 2004. CrossRef A. Szmidt-Jaworska, K. Jaworski, J. Kopcewicz, The Involvement of Cyclic ADPR in Photoperiodic Flower Induction of Pharbitis nil, J Plant Growth Regul 25: p. 233-244, 2006. CrossRef A. Szmidt-Jaworska, K. Jaworski, A. Zienkiewicz, M. Lenartowska, J. Kopcewicz, Guanylyl cyclase activity during photoperiodic flower induction in Pharbitis nil, Plant Growth Regul 57: p. 173-184, 2009. CrossRef U.J. Błaszczak, D.A. Aziz, L. Gryko, Influence of the spectral composition of LED lighting system on plants cultivation in a darkroom, Proceedings of SPIE, vol. 10445, (2017) 1-9. CrossRef L. Gryko, U. Blaszczak, A.S. Zajac, Colorimetric characterization of the tunable LED-based light source at the output of the homogenizing rod, Proceedings of SPIE, vol. 10808, 2018. CrossRef I.Fryc, T. Dimitrova-Grekow, An automated system for evaluation of the quality of light sources, 6th IEEE Lighting Conference of the Visegrad Countries : LUMEN V4, Karpacz, September 13-16, 2016. CrossRef J. Kusznier, M. Zajkowski, L. Budzynski, D. Tyniecki, Ring optical mixer for LED with truncated surfaces, Proceedings of SPIE, vol. 10325, 2017. CrossRef W. Wojtkowski, LED Power Supply with Thermal Protection for Automotive Application, 7th Lighting Conference of the Visegrad Countries : LUMEN V4, Třebíč, September 18-20, 2018. CrossRef W. Wojtkowski, Constant Frequency Operation of the Parallel Loaded Resonant DC/DC Converter for Power LED Lighting, International Conference on Energy, Power, Electrical and Environmental Engineering : EPEEE 2018, DEStech Publications, Wuhan, Hong Kong, September 27-28, 2018. CrossRef Pashiardis S, Kalogirou SA and Pelengaris A. Characteristics of Photosynthetic Active Radiation (PAR) Through Statistical Analysis at Larnaca, Cyprus. SM J Biometrics Biostat. 2(2): 1009, 2017. DirectLink R. Inger, J. Bennie, T. W. Davies, K. J. Gaston, Potential Biological and Ecological Effects of Flickering Artificial Light, PLoS One, vol. 9(5) (2014) PMC4038456 CrossRef C. Dong, Y. Fu, G. Liu, H. Liu, "Growth, photosynthetic characteristics, antioxidant capacity and biomass yield and quality of wheat (Triticum aestivum L.) exposed to LED light sources with different spectra combinations", J Agron Crop Sci, vol. 200, p. 219-230, 2014. CrossRef

Adaptation luminance variation under lamps of different spectral compositions with variable surrounding luminance effects

The mesopic photometry system is expected to enable lighting designers to provide more visually effective lighting designs for appropriate outdoor lighting applications which are supposed to be more energy efficient compared to the photopic system. Studies on the adaptation characteristics are performed to define adaptation luminance and viewing conditions on the basis of peripheral adaptation state of observers for implementation of mesopic photometry system in outdoor lighting. In this work, experimentation is carried out to study the change in adaptation luminance due to various combinations of lamps with different spectral compositions and variable surrounding luminance effects caused by warm white and cool white light sources. The analysis of experimental results reveals that adaptation luminance can be considered instead of mesopic luminance for fixed area of measurement. Spectral composition of surrounding light sources imparts significant contribution on adaptation luminance. Cool white LED lamp shows most effective adaptation luminance under cool white surrounding lighting effect.

Alternating Current III-Nitride Light-Emitting Diodes With On-Chip Schottky Barrier Diode Rectifiers

We report in this paper the design and fabrication of single-chip alternating current-LEDs (AC-LEDs) by monolithically integrating, for the first time, high-breakdown Schottky barrier diodes (SBDs) and micro-LED arrays using III-nitride LED epi-wafers of standard specs for volume production. A technique of cyclic mixed-etching has been introduced to restore the surface of inductively coupled-plasma (ICP) etching processed gallium nitride to device quality for fabricating high-breakdown Schottky junctions. Proof-of-concept single-chip AC-LED devices and a prototype driver-free white AC-LED lamp were demonstrated, showing high-efficiency LED emission, high chip area utilization efficiency, low power loss of the on-chip SBD bridge rectifier, and good luminous efficacy of the prototype AC-LED lamp. This paper paves the way toward mass-producing reliable and low-cost driver-free AC-LED lamps for solid-state lighting with existing LED manufacturing infrastructures.

<strong>Behavioral response of adult caddisflies (Trichoptera) to blue and green light-emitting diode lamps</strong>

To clarify the effect of the visible spectrum, we collected Trichoptera adults using blue, green, and white light-emitting diode (LED) lamps and black light (BL) lamps. Except for white LED lamps, all lamps emitted broad-band wavelengths in the ultraviolet spectrum. A total of 212 adult Trichoptera were trapped. The most individuals were attracted by BL (96), followed blue (74), green (32), and white (10). Hydroptilidae spp. was the most abundant taxa among the lamps (183 individuals, 86.3%), followed by Cheumatopsyche brevilineata (23 individuals, 10.8%). Only Hydroptilidae spp. was common to all lamps. The Shannon–Wiener diversity index (H’) was highest at 0.96 for BL, followed by green (0.53), and blue (0.28). Trichoptera were attracted to both UV light and visible light. These results suggest that BL is the most useful for faunistic investigations of Trichoptera.

Application of efficient photocatalytic process using a novel BiVO/TiO2-NaY zeolite composite for removal of acid orange 10 dye in aqueous solutions: Modeling by response surface methodology (RSM)

The purpose of the present study was to investigate the photocatalytic properties of a novel synthesized BiVO4/TiO2-NaY zeolite composite using the hydrothermal method for the removal of acid orange 10 (AO10), a typical azo dye, from aqueous solutions. In this respect, the experimental results revealed that the as-prepared BiVO4/TiO2-NaY zeolite composite had exhibited higher visible light photocatalytic performance for AO10 degradation than other materials under the irradiation of 12 W white LED lamp. The enhanced photocatalytic efficiency was due to the fact that reduction in the recombination of electrons and holes had been supported by zeolite. The structural properties of the studied materials were also confirmed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDXA), fourier-transform infrared spectroscopy (FT-IR), and diffuse reflectance spectroscopy (DRS). Moreover; the optimization of the experiments was performed using response surface methodology (RSM). At the optimum conditions, the observed maximum AO10 removal efficiency was reported by 99.91% of initial dye concentration: 10 mg/L, initial pH: 3, reaction time: 50 min, as well as catalyst dosage: 0.17 g/100 ml. Thus, this novel BiVO4/TiO2-NaY zeolite could be used as an effective catalyst to reduce AO10 dye from contaminated water.

Investigation of the Impact of Drive Current and Phosphor Thickness on the Reliability of High Power White LED Lamp

Lumen flux of white light-emitting diodes (LEDs) can be increased by increasing phosphor layer thickness and blue LED’s drive current. Higher LED currents will lead to an increase in blue light in the output lumen along with higher temperatures which is not acceptable, and a corresponding decrease in the yellow light emission. The physical reason for this decrease is attributed to the finite phosphor particles in the layer and re-emission occurring due to scattered or back reflected blue light rays. A parameter called blue to yellow ratio (BYR) is used which can lead to a current with maximum phosphor utilization while preventing the LED output color to shift from white toward blue. As the degree of impact on reliability from drive current and thickness is different, a careful adjustment of the drive current and phosphor layer thickness shall be made for a given lumen. Response surface method is employed to obtain an optimal combination of the current and thickness where the temperature is the minimum for a given lumen level. The temperature difference for different combinations of current and thickness for a given lumen can be as high as 15 °C as found in this paper.

Effect of Dy3+ and Eu3+ 4f Band Gap States on Luminescence and Energy Transfer in Monoclinic Lutetium Tungstate

The 4f band gap states (BGSs) of Dy and Eu ions play an important role in luminescence and energy transfer in monoclinic Lu2WO6. The corresponding white and red light emissions were ascribed to electrons’ transition from spin-down 4f states to BGSs and from BGSs to spin-up 4f states. The formation energy gradually increased or decreased with the increment of Dy or Eu content, indicating that Lu2WO6 easily introduced Eu with high concentration. Through fluorescence lifetime and Rietveld refinement, the exchange interaction energy migration mode from host to Dy and Eu ions was assumed to be electron transport from the conduction band (CB) to 4f states in the CB and 4f BGSs. From partial charge density and Bader charge analysis, electron transfer was supposed from Dy3+ BGS to Eu3+ BGS via dipole–dipole interaction in the codoping samples. The white, red, and pale red light-emitting diode (LED) lamps were fabricated using a 365 nm chip and the Dy3+/Eu3+-doped Lu2WO6. This research sheds light on the luminescence mechanism of rare-earth elements-doped Lu2WO6 and explores their potential application in lighting and displays.

Gold Nanorods Embedded in Polymeric Film for Killing Bacteria by Generating Reactive Oxygen Species with Light.

For the first time, anisotropic gold nanorods (AuNRs) were embedded with a photosensitizer dye (crystal violet) in polyurethane (PU) matrix to create the effective antimicrobial film, capable of killing Gram-negative bacteria on its surface when exposed to white light. The dye, when activated with white light, interacts with the AuNRs to generate reactive oxygen species (ROS), which kill bacteria. With a proper control of the aspect ratio (2.1–2.4) and coating of the AuNRs, the film can be tuned to reduce the bacteria population of one to four orders of magnitude (1-log to 4-log) under 11 klux of light, for an exposure to light between 1 to 3 h. Particularly it could reduce 104 cfu/cm2 to the level of 1–5 cfu/cm2 in 3 h of light exposure. This was a desired performance for use on hospital surfaces. In addition, the system showed antimicrobial effect only when exposed to light, which eliminated the concern for a cumulative toxic effect on subjects exposed to the material for a long period of time and limited the time given to the bacteria to develop resistance against the system. Furthermore, this process of sterilization could be carried out by a commercially available white light lamp, which when in use did not interrupt the normal routine operation of the environment.

One‐step deposition of nano‐Ag‐TiO2 coatings by atmospheric pressure plasma jet for water treatment: Application to trace pharmaceutical removal using solar photocatalysis

AbstractIn this study, micrometer thick Ag‐TiO2 coatings were deposited in a single and facile step by spraying the precursor in an atmospheric pressure plasma jet with different concentrations of Ag nanoparticles. The homogenous distribution of Ag decreased the TiO 2 crystal size and increased the surface area. The coatings were characterized to be porous with an anatase phase with improved charge separation and visible light absorption. The photocatalytic activity of the materials was investigated for degrading rhodamine B using a white lamp as a screening method to optimize Ag‐TiO 2 coatings. Then the photodegradation of trace pharmaceutical compounds (TrPCs) was investigated by using a solar light simulator at the optimal condition of a TiO 2 coating with 0.4wt% Ag.

Photo-stability of perovskite solar cells with Cu electrode

Towards higher stability of perovskite solar cells, Cu has been observed to be more suitable electrode material compared to conventional Al and Ag electrodes. The photo-stability of such devices has not been explored much in the literature, therefore we present here the investigation carried out towards the photo-stability of PSCs based on top Cu electrodes. The PSCs were prepared in normal geometry and stored in dark, under continuous illumination of a white LED lamp inside the laboratory and under direct sunlight outside the laboratory and tested as per the international summit on organic photovoltaics stability protocols. In dark storage the encapsulated solar cells exhibited highest stability but under illumination they exhibited degradation in their performance and the degradation was fastest in the direct sunlight. Degradation under illumination has been attributed to the photo-oxidation of the perovskite film. Cu has been observed to diffuse into and react with the underlying perovskite film and the ultraviolet and infrared contents in direct sunlight accelerated the photo-oxidation and chemical reactions between Cu and perovskite film. The chemical reactions of Cu electrode with perovskite constituents made it disappear after some time. These investigations suggest that Cu too is not a very stable electrode material for PSCs under natural operating conditions.

Propagação in vitro de cultivares de alpinia em diferentes fontes de luz

The light source in tissue culture is often one of the punctual factors for the adequacy of plant production. For this, light emitting diodes (LEDs) have been used in order to increase the growth and development of the plants propagated in vitro. The objective was to evaluate the in vitro propagation of cultivars of Alpinia purpurata ‘Red Ginger’ and ‘Pink Ginger’ in two different light sources (fluorescent or LEDs tubes). The experiment was conducted in a completely randomized design, factorial scheme (2x2), totaling four treatments with ten replicates, and the experimental unit composed of one flask containing five explants. After 55 days, white LED and the ‘Red Ginger’ provided the highest number of shoots. For the number of leaves, the cultivar ‘Red Ginger’ and white LED lamps provided superior results. For shoot length (cm), the cultivar ‘Red Ginger’ kept under fluorescent lamps was superior, and ‘Pink Ginger’ presented superiority when cultivated under LED lights. Thus, even with differentiated responses among genotypes, the use of white LED lamps in the in vitro propagation of Alpinia purpurata ‘Red Ginger’ and ‘Pink Ginger’ cultivars is suggested.

Identification of dual luminescence centers from a single site in a novel blue-pumped Ca3Sc2Ge3O12:Ce3+ phosphor.

The luminescence spectra of some trivalent rare-earth ions in a garnet host present interesting multisite structures; however, their mechanism is still not fully understood. In this study, for the first time, we directly observed two luminescence centers of Ce3+ at a single site in a novel garnet Ca3Sc2Ge3O12 phosphor. The spectral characteristics of the two luminescence centers were clearly identified using site-selective and time-resolved spectroscopy. Luminescence excitation was observed at 425 nm and 450 nm, corresponding to emissions at 490 (Ce(i)) nm and 530 (Ce(ii)) nm. The decay curves confirmed the existence of energy transfer from Ce(i) to Ce(ii). The potential mechanisms of the multisite luminescence are also discussed. This study gives a new insight into the concentration-dependent red-shift and inhomogeneous broadening of the Ce3+ emission band in the garnet phosphor. The title phosphor showed excellent thermal stability, with more than 90% of the initial intensity at the functioning temperature (323 K). Finally, a white LED lamp was fabricated, which exhibited an excellent color rendering index (82.3) and a proper correlated color temperature (3582 K). These results demonstrate that Ca3Sc2Ge3O12:Ce3+ is highly promising to serve as a blue-pumped phosphor for white LEDs.

Water Disinfection by Immobilized Photosensitizers

Fresh water shortage has become a global problem. A partial solution for this problem is the use of treated and disinfected wastewater for irrigation. However, most existing wastewater disinfection methods are based on the use of aggressive chemicals or power-consuming physical processes. Photodynamic eradication of waterborne bacteria by immobilized photosensitizers may be a good alternative to conventional methods. In the present work, the photosensitizers Rose Bengal sodium salt, Rose Bengal lactone, methylene blue, and hematoporphyrin were immobilized in polyethylene or polypropylene using a “green” method of co-extrusion, without addition of any chemicals, yielding polymeric strips and beads containing the photosensitizers. The antibacterial efficiency of these immobilized photosensitizers was tested against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli in batch and continuous regimes upon illumination with a white luminescent lamp. All examined photosensitizers demonstrated a good ability to decrease the bacterial concentration, up to their total eradication. Immobilized photosensitizers are proposed for batch or continuous disinfection of wastewater after secondary treatment.

Symmetry Breaking-Induced Plasmonic Mode Splitting in Coupled Gold-Silver Alloy Nanodisk Array for Ultrasensitive RGB Colorimetric Biosensing.

We report the first observation of symmetry breaking-induced mode splitting in coupled gold-silver alloy nanodisk array (ANA). According to the plasmonic hybridization picture, the original localized surface plasmon resonance (LSPR) of individual nanodisk is split into a pair of high and low energy modes when placed in between a superstrate and a substrate. Although well studied in single silver nanoparticles, the high energy mode has been largely suppressed in gold nanoparticles, which nevertheless are more chemically robust and have superior environmental stability. Herein, we show that the high energy mode can be partially restored and precisely engineered to ∼540 nm for silver-rich alloy nanodisk which has excellent environmental stability. However, peak broadening and red-shifting occur due to plasmonic dephasing when the nanodisk diameter increases. We next demonstrate that a far-field coupled ANA fabricated by low-cost nanosphere lithography can fully restore the high energy mode with electric field concentration extended into the superstrate, thereby imparting greater sensitivity to local refractive index changes. The high energy mode at 540 nm is of key importance for color change detection using low-cost RGB cameras/human vision and broadband light sources (e.g., the sun). The index sensitivity of ANA is the highest among existing plasmonic arrays (particles or holes) within a similar resonance wavelength region. We demonstrate colorimetric detection of sub-nanomolar and sub-monolayer biotin-streptavidin surface binding with a smartphone camera and a white light lamp. The high performance yet low-cost fabrication and detection technology could potentially result in affordable point-of-care biosensing technologies.

Self-template construction of honeycomb-like mesoporous YPO4:Ln3+ (Ln = Eu, Tb) phosphors with tuneable luminescent properties

Rare earth (RE)-based phosphors with mesoporous structure that can improve the absorption and utilization of light have attracted much attention recently. Herein, we develop a novel and facile self-template strategy to synthesize honeycomb-like mesoporous YPO4:Ln3+ (Ln = Eu, Tb) phosphors using Y4O(OH)9NO3: Ln3+ as the precursor through a simple H3PO4 etching process. The maximum specific surface area of the mesoporous YPO4:Ln3+ phosphors can reach 406 m2 g−1. The influence of mesoporous structure, crystallinity, and the concentration of rare earth ions on the photoluminescence performance of mesoporous YPO4:Ln3+ phosphors was investigated. The results of fluorescence measurements indicate the mesoporous YPO4:Ln3+ phosphors exhibit better photoluminescence performance after calcination at 900 °C due to the large surface area and high crystallinity. The optimum doped concentrations of Eu3+ ions and Tb3+ ions are 0.12 and 0.08, respectively, and the concentration quenching occurs among nearest-neighbor ions. This work provide a new sight on preparation of phosphors for white light-emitting diodes lamps.

Green-emitting CaF2:Ce3+,Tb3+ phosphor: selection for improving luminous flux and color quality of conformal geometry white LED lamps

Abstract In the last decades, new solutions for improving lighting properties of white LED lamps (WLEDs) have been the main research direction in optoelectronics. In this paper, a modern approach for enhancing luminous flux and color quality of white LED lamps was presented. By mixing green-emitting CaF2:Ce3+,Tb3+ phosphor with yellow-emitting YAG:Ce phosphor compound, the luminous flux and color quality of white LED lamps with conformal phosphor geometry (CPG) increased significantly. From the obtained results it follows that, the luminous flux increased more than 1.5 times, and the correlated color temperature deviation decreased more than 4 times in comparison with the non-green-emitting CaF2:Ce3+,Tb3+ phosphor. The presented research shows that the green-emitting CaF2:Ce3+,Tb3+ phosphor could become a good candidate for enhancing luminous flux and color quality of white LED lamps.

Novel highly efficient blue-emitting SrHfSi2O7:Eu2+ phosphor: A potential color converter for WLEDs and FEDs

A novel blue-emitting phosphor SrHfSi2O7: Eu2+ (SHSO: Eu2+) was designed and prepared via solid-state reaction, and the relationship between their crystal structure and luminescence properties were explored in detail. The structure and phase formation were determined by Rietveld refinements and transmission electron microscopy. Under excitation by n-UV light, the obtained samples have blue emission band with peaking at 456 nm. The dipole−dipole interaction is a dominant concentration quenching mechanism and the testing of fluorescence lifetimes proves the existing of energy transfer among Eu2+ ions. The phosphor shows moderate temperature dependence and, with substitution of 10% of Sr2+ by Ba2+, its thermal stability is noticeably improved. Besides, we fabricated a white LED lamp which can exhibit bright white light with a low color temperature of 4531 K and a high color rendering index of 90.2. Furthermore, under the excitation by low voltage electron, the phosphor will emit blue emission with high current saturation and resistance. All the results indicate that the SHSO: Eu2+ phosphor is a promising candidate for applying to both WLEDs and field emission displays.

On the development of an effective image acquisition system for diamond quality grading.

In this paper, an effective diamond image acquisition system is proposed for capturing images of the diamond sample under inspection separately with transmitted and reflected light. The proposed system consists of two parts: a lighting system and an imaging system. The lighting system is a newly designed integrating sphere that can control the light distribution in the image plane and provide uniform illumination to the diamond sample while it is being inspected under white LED lamps with a specific spectral power distribution. The imaging system comprises industrial-grade lenses, cameras, and a sample loading plate. One set of lenses and a camera is installed at the port of the lower hemisphere. This arrangement ensures that all light rays illuminated to the image plane are transmitted light. On the other hand, all light captured by the other set of lenses and a camera installed on the upper hemisphere is reflected light. The proposed design utilizes the ray tracing processing method based on the physical properties of materials and adjusts the parameters of each optical component. When properly designed, the signal-to-noise ratio of captured diamond images is significantly improved, so that imperfections inside the diamond or on its surface can be clearly distinguished. The proposed image acquisition system is cost-effective and compact. The experimental results agree well with the theoretical analysis and verify the effectiveness of the proposed image acquisition system. The proposed system will facilitate, improve, and simplify automated diamond quality grading.