Exploring the Potential of Nucleic Acid Bases in Organic Light Emitting Diodes.

Naturally occurring biomolecules have increasingly found applications in organic electronics as a low cost, performance-enhancing, environmentally safe alternative. Previous devices, which incorporated DNA in organic light emitting diodes (OLEDs), resulted in significant improvements in performance. In this work, nucleobases (NBs), constituents of DNA and RNA polymers, are investigated for integration into OLEDs.

DNA bases thymine and adenine in bio-organic light emitting diodes.

We report on the use of nucleic acid bases (NBs) in organic light emitting diodes (OLEDs). NBs are small molecules that are the basic building blocks of the larger DNA polymer. NBs readily thermally evaporate and integrate well into the vacuum deposited OLED fabrication.

Nanocomposite approaches for enhancing the DC and photoconductivity of DNA films.

Enhanced DC conductivity and photoconductivity of cationic carbazole tethered deoxyribonucleic acid (Cz-DNA) in film devices is achieved by incorporating mobility enhancers. An anthracene-based organic semiconductor (namely 4HPA-Ant) and the inorganic semiconductor cadmium sulfide (CdS) multipod nanocrystal (NC) were used as the mobility enhancers. Space charge limited current (SCLC) experiments show that hole mobility in CdS:Cz-DNA composite film is improved significantly, by about an order of magnitude, compared to the Cz-DNA film.

Optimized half-wave voltage and insertion loss in a strip-loaded waveguide electro-optic polymer modulator.

A strip-loaded waveguide, electro-optic modulator was designed and analyzed in terms of single mode conditions, optical loss due to the metal electrodes, modulation efficiency, and mode size. Two designs were compared: Design 1 optimized the half-wave voltage (V(π)=1.1 V) with a nearly symmetric waveguide by maximizing modulation efficiency and minimizing the overall thickness of the waveguide; Design 2 optimized the insertion loss by reducing coupling loss by 4.

Three dye energy transfer cascade within DNA thin films.

An efficient cascade FRET was realized in solid state DNA-CTMA thin films using a three chromophore system without any covalent attachments. The extent of energy transfer from Cm102 to SRh was studied and found to improve eight-fold using the bridging dye Pm567.

DNA electron injection interlayers for polymer light-emitting diodes.

Introduction of a DNA interlayer adjacent to an Al cathode in a polymer light-emitting diode leads to lower turn-on voltages, higher luminance efficiencies, and characteristics comparable to those observed using a Ba electrode. The DNA serves to improve electron injection and also functions as a hole-blocking layer. The temporal characteristics of the devices are consistent with an interfacial dipole layer adjacent to the electrode being responsible for the reduction of the electron injection barrier.

Vitamin D(3) is more potent than vitamin D(2) in humans.

Background: Current unitage for the calciferols suggests that equimolar quantities of vitamins D(2) (D2) and D(3) (D3) are biologically equivalent. Published studies yield mixed results.

Objective: The aim of the study was to compare the potencies of D2 and D3.

DNA-based polymers as chiral templates for second-order nonlinear optical materials.

The unique symmetry properties of chiral systems allow the emergence of coherent second harmonic generation in polymeric materials lacking polar order. Deoxyribonucleic acid (DNA) treated with the surfactant cetyltrimethylammonium (CTMA) was drop-cast to spontaneously form films that are active for coherent second harmonic generation (SHG). SHG images acquired as a function of incident and exigent polarization are in good agreement with theoretical predictions assuming nonpolar D(infinity) symmetry for the double-stranded DNA chains.

White luminescence from multiple-dye-doped electrospun DNA nanofibers by fluorescence resonance energy transfer.

A DNA spin-off: Electrospinning of DNA complexes gives nanofibers with a highly ordered morphology that allows homogeneous distribution of encapsulated multiple chromophores. The emission color can be controlled by suitable choice of the donor-acceptor pair and the doping ratio. Pure white-light emission from nanofibers is demonstrated (see picture).

Highly efficient quantum-dot light-emitting diodes with DNA-CTMA as a combined hole-transporting and electron-blocking layer.

Owing to their narrow bright emission band, broad size-tunable emission wavelength, superior photostability, and excellent flexible-substrate compatibility, light-emitting diodes based on quantum dots (QD-LEDs) are currently under intensive research and development for multiple consumer applications including flat-panel displays and flat lighting. However, their commercialization is still precluded by the slow development to date of efficient QD-LEDs as even the highest reported efficiency of 2.0% cannot favorably compete with their organic counterparts.

Enrichment of (6,5) single wall carbon nanotubes using genomic DNA.

Single wall carbon nanotubes (SWNTs) have attracted attention because of their potential in a vast range of applications, including transistors and sensors. However, immense technological importance lies in enhancing the purity and homogeneity of SWNTs with respect to their chirality for real-world electronic applications. In order to achieve optimal performance of SWNTs, the diameter, type, and chirality have to be effectively sorted.

Enhanced fluorescence in electrospun dye-doped DNA nanofibers.

Nanoscale fibers and non-woven meshes composed of DNA complexed with a cationic surfactant (cetyltrimethylammonium chloride, or CTMA) have been fabricated through electrospinning. The DNA-CTMA complex can be electrospun far more easily than DNA alone. Incorporation of a hemicyanine chromophore resulted in materials that demonstrated amplified emission as compared to thin films of identical composition.

Molecular beam deposition of DNA nanometer films.

The development of novel photonic devices which incorporate biological materials is strongly tied to the development of thin film forming processes. Solution-based ("wet") processes when used with biomaterials in device fabrication suffer from dissolution of underlying layers, incompatibility with clean environment, inconsistent film properties, etc. We have investigated ultra-high-vacuum molecular beam deposition of surfactant-modified deoxyribonucleic acid (DNA).

Infrared two-photon-excited visible lasing from a DNA-surfactant-chromophore complex.

Infrared two-photon-pumped and cavity-enhanced frequency upconversion lasing has been achieved in a novel DNA-surfactant-chromophore complex (DSCC) gel system, which is a new step toward producing a biological laser. Once the focused intensity of the 150 fs and approximately 775 nm pump laser beam is higher than a certain threshold level, highly directional stimulated emission at approximately 582 nm wavelength can be observed from a 1 cm long DSCC complex gel cell. With cavity feedback provided by the two optical windows, the pump threshold can be further reduced, the highly directional output lasing can be greatly enhanced, and the output spectral linewidth can be reduced to less than 1/5 of the spontaneous fluorescence spectral bandwidth.