Simple Light-emitting Diode Research Articles

Design and Application of an In Situ Traceable Nitric OxideDonor for Promoting the Healing of Wound Infections.

Therapies for wound infections require medications with antibacterial and wound-healing functions. However, it remains a challenge to produce a single drug that can perform dual functions. Nitric oxide (NO), with its antibacterial and wound-healing activities, is an ideal solution to address this challenge. However, many controlled-release strategies for NO rely on external probes for tracing the release in situ, making it difficult to precisely assess the location and magnitude. To address this issue, this study describes a novel NO donor, DHU-NO1, capable of efficiently releasing NO under mild conditions (450nm illumination). Simultaneously, DHU-NO1 generates the fluorophore Azure B (AZB), which enables direct, non-consumptive tracing of the NO release by monitoring the fluorescence and absorption changes in AZB. Given that NO can be conveniently traced, the amount of released NO can be controlled during biological applications, thereby allowing both functions of NO to be performed. When applied to the affected area, DHU-NO1, illuminated by both a simple light-emitting diode (LED) light source and natural light, achieves significant antibacterial effects against wound infections and promotes wound healing in mice. This study offers a novel and effective approach for treating wound infections.

Monolithic Silicon-Based Photovoltaic-Nanoplasmonic Biosensor With Enhanced Limit of Detection and Minimum Detectable Power

On-chip, fully integrated electrical readout nanoplasmonic biosensors are suitable technology for the increasing demands of compact, portable, cost-efficient, and sensitive biosensors. In this paper, an ultra-compact photonic biosensor based on plasmonic nanostructure integrated with a PIN photovoltaic detector in a single chip is presented. The refractive index of different biosamples results in a shift in the surface plasmon resonance wavelength of the biosensor, and the PIN photovoltaic detector measures the intensity of transmitted light from the photonic structure at the plasmonic resonance wavelength. The biosensor shows a linear optical response of 354 nm/RIU and electrical sensitivity of about 16.9 mA/W.RIU for a wide range of biosamples. The PIN photovoltaic ultra-low dark current enables an extremely desirable limit of detection of 3 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−8</sup> RIU and minimum detectable power of −54 dBm for the biosensor. Moreover, a simple light-emitting diode is used as the light source in the biosensor's structure, which reduces its complexity and price by eliminating any extra optical setups and beam shapers. The presented structure is an important step forward for the realization of practical and handheld lab-on-chip nanophotonic biosensors, which leads to eliminating large clinical laboratories.

Double-Stranded DNA Matrix for Photosensitization Switching

Photosensitization, originated from the activation of triplet states, is the basis of many photodynamic applications, but often competes with a series of nonradiative processes. Herein, we communic...

Effect of Substrates on Structural, Morphological, Optical and Electrical Characteristics on Poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) Thin Films

Polymer light-emitting diodes using organic-inorganic heterojunctions have a lot of benefits such as excellent blue-light emission, simple fabrication procedure, and low processing cost. We report on the effect of substrates on the fabrication of poly (9,9-di-n-octylfluorenyl-2,7-diyl) or (PFO) thin films and their characterization as a simple light-emitting diode (LED) structure. The structural properties of the thin films were characterized using X-ray Diffraction (XRD). The morphological properties of the thin films were studied using Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM). The XRD results demonstrated the formation of amorphous PFO structure, with no presence of the crystalline phase of PFO. The FESEM images showed the formation of cracks due to evaporation from annealing. Optical characteristics were studied using ultraviolet-visible (UV-Vis) spectroscopy, Photoluminescence (PL) and reflectance measurements showing the presence of β phase of PFO, important for charge carrier mobility. Thin films deposited on ITO-coated glass, FTO-coated glass and Silicon n-type (110) and (111) orientation substrates were used to fabricate a simple LED structure. The devices fabricated using Si n-type substrates showed p-n junction characteristics and was a better substrate choice than ITO or FTO coated glass.

A tip of the HAT to C-C bond formation

Organic Chemistry Iridium and nickel are already a proven team for forging carbon-carbon bonds. The iridium harvests blue light from a simple light-emitting diode and orchestrates the coupling by the nickel. Shaw et al. now add a third player to the team, a hydrogen atom transfer (HAT) catalyst (see the Perspective by Fruit). Together, the trio of catalysts can link bromo- or chloroaryl rings directly to C-H sites adjacent to nitrogen or oxygen, with no need for prior modification. The reaction is highly selective across a broad range of substrates. Science , this issue p. [1304][1]; see also p. [1277][2] [1]: /lookup/doi/10.1126/science.aaf6635 [2]: /lookup/doi/10.1126/science.aaf8923

Research of LED Emission Cross-Section on Light Communication Systems

Visible light communication (VLC) is an optical wireless communication technology that uses visible light emitting diodes (LEDs) as a communication source. Since the LEDs are also used for illumination, the cross-section emission effects of the LEDs need to be analyzed as they apply to indoor VLC channels. In order to evaluate the illumination and communication performance according to the emission cross-section pattern, a simple LED model with a quasi-elliptic emission cross-section is proposed and compared to a circular LED model. The LEDs with a quasi-elliptic emission cross-section provide less fluctuation in the illumination and optical power distribution at the receiving plane. The four-transmitter VLC system is found to support at least at 30 and 33 Mb/s for circular and quasi-elliptic emission cross-section LEDs for the entire receiving plane, respectively.

Development of a photoelectrochemical sensor for monitoring algal biomass (Chlorella vulgaris)

Herein, we present a novel photoelectrochemical sensor system for the rapid enumeration of algal biomass. The photosynthesis-based reducing action of algal cells on the electrochemical mediator 2-hydroxyl-1,4-naphthoquinone (HNQ) was used as the basis of an amperometric sensor system. By using a simple LED (Light-Emitting Diode) installed three-electrode cell, the mediator that was reduced by algal metabolic activity was reoxidized at a platinum-working electrode and held at a positive potential. In the presence of CO2 as an electron donor, and LED illumination as an energy source for the algal cells, the reoxidation current and its rate of increase were found to depend on the concentration of algal biomass. Regression analyses plotting the initial rate of current (μAmin−1) against algal biomass concentrations (gL−1) produced a reasonable correlation coefficient (r2=0.9938). The sensor system exhibited a high sensitivity to algal biomass at a concentration as low as 0.065gL−1and a rapid response time, which is promising for further applications of the sensor system in algal-related industries.

Effect of LED emission cross-section in indoor visible light communication systems

Abstract Visible light communication (VLC) is an optical wireless communication technology that uses visible light emitting diodes (LEDs) as a communication source. Since the LEDs are also used for illumination, the cross-section emission effects of the LEDs need to be analyzed as they apply to indoor VLC channels. In order to evaluate the illumination and communication performance according to the emission cross-section pattern a simple LED model with a quasi-elliptic emission cross-section is proposed and compared to a circular LED model. The spatial distributions of the received optical power and root mean square delay spread are analyzed through calculation and comparison. The LEDs with a quasi-elliptic emission cross-section provide less fluctuation in the illumination and optical power distribution at the receiving plane. However, the RMS delay spread increases and subsequently the maximum data rate decreases for the quasi-elliptic emission cross-section LEDs. The single transmitter VLC system is found to support at least 17 and 24 Mb/s for circular and quasi-elliptic emission cross-section LEDs for the entire receiving plane, respectively. The four-transmitter VLC system is found to support at least at 30 and 33 Mb/s for circular and quasi-elliptic emission cross-section LEDs for the entire receiving plane, respectively.

An optode membrane for determination of gold using a simple light-emitting diode-based device

A selective optode based on immobilization of 5-(p-dimethylaminobenzylidene)rhodanine on a triacetylcellulose membrane was developed for quantitative determination of Au(III). The determination procedure was performed using a simple light-emitting diode (LED)-based device as a new effort to overcome low reproducibility and repeatability problems which usually accompany optode-based determinations. The results obtained were compared with those of conventional spectrophotometric methods. The response characteristics of the sensor including dynamic range, reproducibility, response time, and lifetime are discussed in detail. This sensor was used for the determination of Au(III) in ore and electroplating liquid effluent samples with satisfactory results in comparison with flame atomic absorption spectroscopy as standard method. Under the optimum conditions, the calibration plot was linear in the concentration range of 0.3–6.0 μg cm−3. The relative standard deviations for five replicate determinations of 1.0 μg cm−3 Au(III) and the corresponding limits of detection were 1.76% and 0.12 μg cm−3, respectively.

Nanoplasmonic biosensing with on-chip electrical detection

A nanoplasmonic biosensor chip with integrated electrical detection is presented. The concept is based on the local refractive index sensitivity of nanoplasmonic gold nanodisks (110 nm in diameter and 20 nm in height) that are fabricated, through a parallel method, directly on an array of silicon solar cells or photoactive diodes. The nanoplasmonic properties of the sensor chip were investigated both optically and electrically, with excellent agreement between the two. We show that local changes in the refractive index of the surrounding environment gives changes in the nanoplasmonic properties of the gold nanodisks, which induce corresponding changes in the photocurrent at single wavelengths of the nanoplasmonic solar cells. With a simple light-emitting diode as light source, and together with a material-specific modification protocol, the photocurrent output of the nanoplasmonic sensor chip was successfully used to monitor a specific biorecognition reaction in real-time.

Lensfree microscopy on a cellphone

We demonstrate lensfree digital microscopy on a cellphone. This compact and light-weight holographic microscope installed on a cellphone does not utilize any lenses, lasers or other bulky optical components and it may offer a cost-effective tool for telemedicine applications to address various global health challenges. Weighing approximately 38 grams (<1.4 ounces), this lensfree imaging platform can be mechanically attached to the camera unit of a cellphone where the samples are loaded from the side, and are vertically illuminated by a simple light-emitting diode (LED). This incoherent LED light is then scattered from each micro-object to coherently interfere with the background light, creating the lensfree hologram of each object on the detector array of the cellphone. These holographic signatures captured by the cellphone permit reconstruction of microscopic images of the objects through rapid digital processing. We report the performance of this lensfree cellphone microscope by imaging various sized micro-particles, as well as red blood cells, white blood cells, platelets and a waterborne parasite (Giardia lamblia).

Synthesis and characterization of poly(terphenylenevinylene) derivatives containing alkoxy substituents and (or) phenyl pendant group

Abstract The blue electroluminescent polymers, poly(terphenylenevinylene) derivatives that have advantages of PPP and PPV, were prepared by Suzuki coupling reaction. The structure and properties of the polymers were analyzed by various spectroscopic methods. Poly(MHTPPV) and poly(TPPV) with phenyl pendant group in a vinyl bridge showed blue shifted absorption spectra, large band gap and enhanced thermal stability as compared with that of poly(MHTPV). The PL spectra of the films of the polymers showed maximum peaks at 450–460 nm, which are pure blue emissions. The blue electroluminescence (λ max =450–460 nm ) was obtained with the turn on voltage of 8–10 V, when the simple light-emitting diodes of ITO/polymer/Al were fabricated. The excimer emission due to interchain interaction was reduced by the introduction of substituents into the vinyl bridge and (or) the main chain.

Tetracene derivatives as potential red emitters for organic LEDs.

[structure: see text] As part of our program investigating the use of ethynylated acenes in organic electronics, we have prepared a series of functionalized tetracene derivatives in search of a material with red emission suitable for use in display technologies. A number of such compounds with functionalization on the alkyne and/or the acene ring were easily prepared in one or two steps from commercially available materials. Solution fluorescence quantum efficiencies were generally good for these derivatives, which possessed emission maxima spanning the range 540-637 nm. Simple light-emitting diodes fabricated from these compounds showed that one of the derivatives did exhibit red electroluminescence.

Fluorene-Based Copolymers for Red-Light-Emitting Diodes

The syntheses of new fluorene-based π-conjugated copolymers; namely, poly((5,5″-(3′,4′-dihexyl-2,2′;5′,2″-terthiophene 1′,1′-dioxide))-alt-2,7-(9,9-dihexylfluorene)) (PFTORT), poly((5,5″″-(3″,4″-dihexyl-2,2′:5′,2′:5″,2‴:5‴,2″″-quinquethiophene 1″,1″-dioxide))-alt-2,7-(9,9-dihexylfluorene)) (PFTTORTT), and poly((5,5-E-α-(2-thienyl)methylene)-2-thiopheneacetonitrile)-alt-2,7-(9,9-dihexylfluorene)) (PFTCNVT), are reported. In the solid state, PFTORT and PFTCNVT present red–orange emission (with a maximum at 610 nm) while PFTTORTT shows a red emission with a maximum at 666 nm. In all cases, electrochemical measurements have revealed p- and n-dopable copolymers. All these copolymers have been successfully tested in simple light-emitting diodes and show promising results for orange- and red-light-emitting devices.

Electronic coupling and structural ordering of quantum dots using InAs quantum dot columns

In this article, recent investigations of vertically aligned quantum dot columns conducted at Stanford University are reviewed. The quantum dots are InAs in a matrix of GaAs. Both the quantum dots and quantum dot columns are formed through strain-induced islanding, without lithography. Two aspects of these columns are discussed. First, the electronic coupling of quantum dots within columns of up to ten quantum dots is demonstrated. The coupling is adjusted and improvements to a simple light-emitting diode are shown. Second, increased uniformity of a surface quantum dot layer is shown when a subsurface layer of these columns are used. The most impressive results occur when the columns contain a large number of islands. Reduced variations in average ensemble height and diameter, called size uniformity, and average nearest neighbor distances, called structural uniformity, are shown. A surface unit cell of islands is demonstrated and the lack of a surface lattice is discussed.

Anisotropy-Based Sensing with Reference Fluorophores

We describe a new approach to fluorescence sensing based on measurements of steady-state anisotropies in the presence of reference fluorophores with known anisotropies. The basic concept is that the anisotropy of a mixture reflects a weighted average of the anisotropies of the emitting species. By use of reference fluorophores the starting anisotropy can be near zero, or near 0.9 for oriented films which contain the reference fluorophore. Changing intensities of the analyte result in changes in anisotropy. A wide dynamic range of anisotropies is available because of the freedom to select high or low starting values. Anisotropy-based sensing was demonstrated for pH using 6-carboxyfluorescein and for protein affinity or immunoassay using an oriented film with high anisotropy and a protein labeled with a metal–ligand complex. The latter measurements were performed with a simple light-emitting diode excitation source without an excitation polarizer. The sensitive range of the assay can be adjusted by changing the intensity of the reference fluorophore. Anisotropy-based sensing can have numerous applications in clinical and analytical chemistry.

Selective area solution growth of Ge and GaAs on Si

Ge and GaAs have been grown on Si substrates by selective area solution growth from saturated metal solutions. Prior to this work, the growth of GaAs on Si has been almost exclusively done by molecular-beam epitaxy or metalorganic chemical vapor deposition. A primary advantage of the solution growth process is the prospect for selective area growth where growth is limited solely to openings in a SiO2 mask. The selectively grown Ge and GaAs crystal compositions were determined by energy dispersive analysis by x ray with the GaAs material demonstrating stoichiometry without detectable Si or Ge incorporation. The GaAs crystals on Si were also fabricated into simple light-emitting diode structures that emitted infrared light at 0.7–0.8 V forward bias.