Combination Of Light-emitting Diodes Research Articles

Real-time optical monitoring of microbial growth using optimal combination of light-emitting diodes

We developed a real-time optical monitoring system consisting of a monochrome complementary metal-oxide semiconductor (CMOS) camera and two light-emitting diodes (LEDs) with a constant temperature incubator for the rapid detection of microbial growth on solid media. As a target organism, we used Alicyclobacillus acidocaldarius, which is an acid- ophilic thermophilic endospore-forming bacterium able to survive in pas- teurization processes and grow in acidic drink products such as apple juice. This bacterium was cultured on agar medium with a redox dye applied to improve detection sensitivity. On the basis of spectroscopic properties of the colony, medium, and LEDs, an optimal combination of two LED illuminations was selected to maximize the contrast between the colony and medium areas. We measured A. acidocaldarius and Escherichia coli at two different dilution levels using these two LEDs. From the results of time-course changes in the number of detected pixels in the detection images, a similar growth rate was estimated amongst the same species of microbes, regardless of the dilution level. This system has the ability to detect a colony of approximately 26 μm in diameter in a detection image, and it can be interpreted that the size corresponds to less than 20 μm diameter in visual inspection. © 2012 Society of Photo-Optical

Sulfur dioxide measurements using an ultraviolet light-emitting diode in combination with gas correlation techniques

The important air pollutant sulfur dioxide has a strong structured absorption band in the ultraviolet (UV) region around 300 nm. Recently, light-emitting diodes (LEDs) with structureless emission in a band about 15-nm wide in the UV region have become available. We demonstrate that they can be ideal sources for gas absorption measurements combined with the gas correlation technique, where an absorption cell with an optically thick column of the gas under investigation is used for analysing the target gas contents in a path between the LED and the measurement device. A sensitivity of 0.4 ppm sulfur dioxide was obtained with a 19-cm optical path length and 60-s integration time. Particularly compact and cost-effective monitors especially for industrial emissions can be envisaged.

Ultraviolet light emitting diodes and hydrogen peroxide in the photodegradation of aqueous phenol

The novel system of ultraviolet (UV) light emitting diodes (LED) and hydrogen peroxide (H 2O 2) was studied for the degradation of phenol as a model organic pollutant in water. The effect of different viewing angles (15 and 120°), wavelengths (255, 265 and 280 nm) and phenol and H 2O 2 concentrations were investigated in four photolytic batch reactors. Phenol degradation was observed to be most efficient with UV LEDs emitting at wavelength 280 nm, presumably due to the highest optical power. However, quantum yield for 280 nm reactor was only 0.23 compared to 0.33 of 255 nm reactor. Quantum yields for the rest of the reactors were 0.24 (265 nm, 120°) and 0.22 (265 nm, 15°). UV LEDs in combination with hydrogen peroxide are promising in wastewater treatment in degrading organic compounds, though development of both LEDs and reactor design is needed.

Cluster synthesis of branched CdTe nanocrystals for use in light-emitting diodes

Highly luminescent cadmium telluride (CdTe) nanocrystals were synthesized usingLi2[Cd4(SPh)10] as a reactive Cd cluster compound at relatively low temperature, making it a safe precursorfor the large scale synthesis of CdTe nanocrystals. Transmission electron microscopy(TEM) showed that the shape of the CdTe nanocrystals changes from nanorods tobranched structures with increasing reaction time. The nanocrystals show highluminescent quantum yields up to 37% for CdTe branched nanostructures, and ashigh as 52% for CdTe/CdS core–shell heterostructures. CdTe/CdS nanocrystalswere used to make light-emitting diodes in combination with organic layers forelectron and hole injection. The devices show a maximum luminance efficiency of0.35 cd A−1.

Clinical Experience with Light‐Emitting Diode (LED) Photomodulation

Light-emitting diode (LED) photomodulation is a novel nonthermal technology used to modulate cellular activity with light. We describe our experience over the last 2 years using 590 nm LED photomodulation within a dermatologic surgery environment. Practical use of nonthermal light energy and emerging applications in 3,500 treatments delivered to 900 patients is detailed. LED photomodulation has been used alone for skin rejuvenation in over 300 patients but has been effective in augmentation of results in 600 patients receiving concomitant nonablative thermal and vascular treatments such as intense pulsed light, pulsed dye laser, KTP and infrared lasers, radiofrequency energy, and ablative lasers. LED photomodulation reverses signs of photoaging using a new nonthermal mechanism. The anti-inflammatory component of LED in combination with the cell regulatory component helps improve the outcome of other thermal-based rejuvenation treatments.

Studies on the propagation of light from a light-emitting diode through a glass tube and development of an optosensor for the continuous detection of liquid level

The authors develop a new technique for continuous measurement of liquid level by an optosensor. The objectives are (i) to study the propagation of light from a light-emitting diode (LED) through a glass tube and (ii) based on this principle, to develop a continuous liquid level sensor. The attenuation of light from an LED through a glass tube with distance has been investigated and an empirical relation for it has been established. The result is applied to the detection of water level. The sensor comprises a hollow glass tube with a combined LED- photodetector assembly (the optosensor) and a light reflector inside the tube. The reflector floats on the liquid surface, and light emitted from the LED is detected after reflection from it. The detected light intensity varies with the distance between the optosensor and the reflector. The position of the float changes with the variation of the liquid level. The present level sensor can detect a change of liquid level at distances up to 80 cm with an accuracy of the order of 0.5 mm.

Lithium−Quinolate Complexes as Emitter and Interface Materials in Organic Light-Emitting Diodes

We synthesized lithium−quinolate complexes, 8-hydroxyquinolinolatolithium (Liq) and 2-methyl-8-hydroxyquinolinolatolithium (LiMeq), as emitter and electron injection/transport materials to be used in conventional two-layer organic light-emitting diodes in combination with N,N‘-bis(p-methoxyphenyl)-N,N‘-diphenylbenzidine (DMeOTPD) as hole transport material (HTL). The lithium complexes were also examined as interface materials in combination with 8-hydroxyquinolinolato-Al(III) (Alq3) as emitter material. The device efficiency with these complexes was optimized by combinatorial methods. We also compared the electron injection, transport, and emission properties of Li complexes with the well-known emitter Alq3 in the same experiment by taking advantage of the combinatorial approach. The Li quinolates are found to be efficient emitter molecules. But the efficiencies of lithium quinolate devices are lower than that of Alq3 devices. Contrary to the Alq3 emission, the Li quinolates exhibit a bathochromic shift of emission compared to the respective photoluminescence spectra. No clear evidence of exciplex formation was seen by comparing the photoluminescence spectrum of an equimolar mixture of Li quinolate and DMeOTPD with the observed electroluminescence spectrum. However, the lithium complexes increase the efficiency of an optimized indium−tin oxide (ITO)/DMeOTPD/Alq3/Al device considerably when used as a thin interface layer between Alq3 and aluminum. The improvement of device characteristics with lithium quinolates is similar to that obtained with LiF salt.

Photography and Temperature Measurements from a Remotely Piloted Vehicle

Radio-controlled model planes are useful when carrying out photography, especially from low altitudes, and meteorological soundings (air temperatures in boundary layers). Soundings were carried out with a system which stored the measured data on board the plane pending evaluation after the flight. The payload of the plane was a camera and equipment for measuring temperature and air pressure (altitude). Data were stored so that the signals from the temperature and pressure sensors (thermistor and micro aneroid respectively) lit a combination of light-emitting diodes (BCD code) that corresponded to the actual temperature and pressure (altitude). At the instant of measurement, this combination was photographed togther with the ground surface. the camera manoeuvred by means of servo-function. The position of the plane at the instant of measurement was determined on the basis of pressure values and air photographs. Photography from model planes is not a new method. However, previous results have in general been inadequate because, for safety's sake, cheap and consequently less advanced cameras were used. The determination of temperature and other soundings from such aircraft has been little tried hitherto. Photography and sounding from model planes can be of interest in ecological, physical-geographical and meteorological contexts. The method lends itself best to a rapid and handy documentation from the air of a water or land area, e.g. a severely polluted area, or a wind-eroded ground surface, or to the sounding or sampling of aif qualities such as pollution in the smoke plumes of stacks and other types of discharge, of radioactivity in the air over leaking plants, of temperature and humidity conditions in urban boundary layers and of eolian dust in the air over wind-exposed erosion surfaces in arid areas. Radio-controlled model planes could possibly also be used for dissemination of e.g. silver iodide in order to artificially release precipitation and for pollination of forest. (Less)