Chemical sensor and coating for same

An acoustic wave based-chemical sensor utilizing a crystal substrate and a coating of at least two blended materials is disclosed. The blended materials comprise a combination of (a) a high glass transition temperature polymer or a material of high melting point, and (b) a low glass transition temperature polymer or a material having a low melting point. Transducers are connected to the crystal substrate to generate an alternating potential across the crystal substrate, which in turn causes the crystal to resonate due to the converse piezoelectric effect. The blended coating absorbs the analyte, thus changing the mass of the chemical sensor, and accordingly changing its resonant frequency. The transducers detect this change in resonant frequency to indicate that the analyte is present. The use of blended materials results in a thicker coating combining the preferred properties of the blend constituents, such as improved detection sensitivities, faster response times, less acoustic wave damping, and higher operational temperature ranges

Benzobisoxazole cruciforms: a tunable, cross-conjugated platform for the generation of deep blue OLED materials

Four new cross-conjugated small molecules based on a central benzo[1,2-d:4,5-d′]bisoxazole moiety possessing semi-independently tunable HOMO and LUMO levels were synthesized and the properties of these materials were evaluated experimentally and theoretically. The molecules were thermally stable with 5% weight loss occurring well above 350 °C. The cruciforms all exhibited blue emission in solution ranging from 433–450 nm. Host–guest OLEDs fabricated from various concentrations of these materials using the small molecule host 4,4′-bis(9-carbazolyl)-biphenyl (CBP) exhibited deep blue-emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.15 ≤ x ≤ 0.17, 0.05 ≤ y ≤ 0.11), and maximum luminance efficiencies as high as ∼2 cd A−1. These results demonstrate the potential of benzobisoxazole cruciforms as emitters for developing high-performance deep blue OLEDs.We would like to thank Dr Sarah Cady, Dr Kamel Harrata and Mr Steven Veysey of Iowa State University (ISU) Chemical Instrumentation Facility for compound analysis. We thank Eeshita Manna for technical assistance. We also thank the National Science Foundation (CHE-1413173) for financial support of this work. RK and JS were partially supported by Basic Energy Sciences, Division of Materials Science and Engineering, USDOE. Ames Laboratory is operated by Iowa State University for the US Department of Energy (USDOE) under Contract No. DE-AC 02-07CH11358. Computational resources were provided in part by the MERCURY consortium (http://mercuryconsortium.org/) under NSF grants CHE-0116435, CHE-0521063, CHE-0849677, and CHE-1229354. (CHE-1413173 - National Science Foundation; Basic Energy Sciences, Division of Materials Science and Engineering, USDOE; DE-AC 02-07CH11358 - Iowa State University for the US Department of Energy (USDOE); CHE-0116435 - MERCURY consortium under NSF; CHE-0521063 - MERCURY consortium under NSF; CHE-0849677 - MERCURY consortium under NSF; CHE-1229354 - MERCURY consortium under NSF)http://pubs.rsc.org/en/Content/ArticleLanding/2016/TC/C5TC03622D#!divAbstractPublished versio

Low efficiency roll-off phosphorescent organic light-emitting devices using thermally activated delayed fluorescence hosts materials based 1, 2, 4-triazole acceptor

The host in phosphrescent organic light emitting devices (PhOLEDs), showing the thermally activated delayed fluorescence (TADF) charateristic, can effectively overcome the efficiency roll-off. Herein, six bipolar compounds with donor-π-acceptor (D-π-A) and D-π-A-π-D structures have been synthesized using 1,2,4-triazole derivative (TAZ) as an acceptor and phenothiazine (PTZ), phenoxazine (PXZ), and 9, 9-dimethylacridane (DMAC) as donors. The molecular structures were confirmed by 1H NMR, 13C NMR and X-ray single-crystal diffractions. The large steric hindrance endows these molecules with typical TADF features, including the small singlet-triplet energy splitting (Delta E-ST) of 0.08–0.30 eV and completely spatially separate highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) electron densities. The PhOLEDs hosted by these novel TADF materials display excellent performances with low efficiency roll-off

Soft lithography microlens fabrication and array for enhanced light extraction from organic light emitting diodes (OLEDs)

Provided are microlens arrays for use on the substrate of OLEDs to extract more light that is trapped in waveguided modes inside the devices and methods of manufacturing same. Light extraction with microlens arrays is not limited to the light emitting area, but is also efficient in extracting light from the whole microlens patterned area where waveguiding occurs. Large microlens array, compared to the size of the light emitting area, extract more light and result in over 100% enhancement. Such a microlens array is not limited to (O)LEDs of specific emission, configuration, pixel size, or pixel shape. It is suitable for all colors, including white, for microcavity OLEDs, and OLEDs fabricated directly on the (modified) microlens array

Soft holographic interference lithography microlens for enhanced organic light emitting diode light extraction

Very uniform 2 μm-pitch square microlens arrays (μLAs), embossed on the blank glass side of an indium-tin-oxide (ITO)-coated 1.1 mm-thick glass, are used to enhance light extraction from organic light-emitting diodes (OLEDs) by ~100%, significantly higher than enhancements reported previously. The array design and size relative to the OLED pixel size appear to be responsible for this enhancement. The arrays are fabricated by very economical soft lithography imprinting of a polydimethylsiloxane (PDMS) mold (itself obtained from a Ni master stamp that is generated from holographic interference lithography of a photoresist) on a UV-curable polyurethane drop placed on the glass. Green and blue OLEDs are then fabricated on the ITO to complete the device. When the μLA is ~15 × 15 mm2, i.e., much larger than the ~3 × 3 mm2 OLED pixel, the electroluminescence (EL) in the forward direction is enhanced by ~100%. Similarly, a 19 × 25 mm2μLA enhances the EL extracted from a 3 × 3 array of 2 × 2 mm2 OLED pixels by 96%. Simulations that include the effects of absorption in the organic and ITO layers are in accordance with the experimental results and indicate that a thinner 0.7 mm thick glass would yield a ~140% enhancement

Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates

A key scientific and technological challenge in organic light-emitting diodes (OLEDs) is enhancing the light outcoupling factor ηout, which is typically \u3c20%. This paper reports experimental and modeling results of a promising approach to strongly increase ηout by fabricating OLEDs on novel flexible nanopatterned substrates that result in a \u3e2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning ηout ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed for blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost-effectively by direct room-temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome-shaped convex nanopatterns with height of ∼280–400 nm and pitch ∼750–800 nm were found to be optimal. Substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs

Bright Deep Blue TADF OLEDs: The Role of Triphenylphosphine Oxide in NPB/TPBi:PPh3O Exciplex Emission

Very bright (≈14 000 cd m−2) deep blue exciplex organic light emitting diodes (OLEDs) peaking at ≈435 nm, where the photopic response is ≈0.033, and with CIE color coordinates (0.1525, 0.0820), are described. The OLED properties are interestingly linked to PPh3O (triphenylphosphine oxide) and attributes of the emitting layer (EML) comprising NPB interfacing host:guest TPBi:PPh3O 5:1 weight ratio. A neat PPh3O layer that is central for device performance follows the EML (NPB/TPBi:PPh3O 5:1/PPh3O). The bright electroluminescence originates from NPB/TPBi:PPh3O exciplexes involving triplets via thermally activated delayed fluorescence, as evident from the strong quenching of the photoluminescence (PL) by oxygen and interestingly, the monomolecular emission process. The transient PL decay times of a NPB/TPBi:PPh3O 5:1/PPh3O film are 43 ns in air versus 136, 610, and weak ≈2000 ns in N2. For comparison, the respective PL decay times of films of NPB:TPBi are 16 ns in air versus 131 and 600 ns in N2, and of NPB:PPh3O they are 29 ns in air versus 56, 483, and weak ≈2000 ns in N2. It is suspected that slow emitting states are associated with a PPh3O aggregate interacting with NPB

Method and apparatus for magnetoresistive monitoring of analytes in flow streams

Method and apparatus for manipulating and monitoring analyte flowing in fluid streams. A giant magnetoresistive sensor has an array of sensing elements that produce electrical output signals which vary in dependence on changes in the magnetic field proximate the sensing elements. The analyte is included in a stream, such that the stream has a magnetic property which is dependent on the concentration and distribution on the analyte therein. The stream is flowed past the giant magnetoresistive sensor and in sufficiently close proximity to cause the magnetic properties of the stream to produce electrical output signals. The electrical output signals are monitored as an indicator of analyte concentration or distribution in the stream flowing past the GMR sensor. Changes in the magnetic field produced by the background stream are introduced by analyte molecules, whose presence in the flow past the GMR will effect the output reading

Novel blue fluorescent emitters structured by linking triphenylamine and anthracene derivatives for organic light-emitting devices with EQE exceeding 5%

Achieving an external quantum efficiency exceeding 5% for traditional blue fluorescent organic light emitting devices (OLEDs) is still a current challenge due to the 25% limit of the radiative exciton yield. Bipolar organic molecules with a special hybrid local-excited and charge-transfer state have showed huge potential to address this issue. Herein, we designed and synthesized two novel bipolar compounds, namely TPA-AN-NA and TPA-AN-TFP, which were structured by simply linking a donor of triphenylamine (TPA) and both acceptors of anthracene derivatives. Both resulting compounds show good blue emission with emission peaks at 468 and 471 nm and photoluminescence quantum yields of 30.68 and 23.96% in thin films for TPA-AN-NA and TPA-AN-TFP, respectively. They also exhibit good solubility and can dissolve in several organic solvents with different polarities. Further, the fabricated blue OLEDs with TPA-AN-NA and TPA-AN-TFP as emitters also realize the corresponding blue emission well with electroluminescence peaks at 464 and 472 nm, respectively. The TPA-AN-NA-based blue device achieves a high external quantum efficiency of 5.44% and a radiative exciton yield of 56.68%, exceeding the theoretical limit