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1.
Proc Natl Acad Sci U S A ; 115(47): E11015-E11024, 2018 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-30404911

RESUMO

Transmission-mode pulse oximetry, the optical method for determining oxygen saturation in blood, is limited to only tissues that can be transilluminated, such as the earlobes and the fingers. The existing sensor configuration provides only single-point measurements, lacking 2D oxygenation mapping capability. Here, we demonstrate a flexible and printed sensor array composed of organic light-emitting diodes and organic photodiodes, which senses reflected light from tissue to determine the oxygen saturation. We use the reflectance oximeter array beyond the conventional sensing locations. The sensor is implemented to measure oxygen saturation on the forehead with 1.1% mean error and to create 2D oxygenation maps of adult forearms under pressure-cuff-induced ischemia. In addition, we present mathematical models to determine oxygenation in the presence and absence of a pulsatile arterial blood signal. The mechanical flexibility, 2D oxygenation mapping capability, and the ability to place the sensor in various locations make the reflectance oximeter array promising for medical sensing applications such as monitoring of real-time chronic medical conditions as well as postsurgery recovery management of tissues, organs, and wounds.


Assuntos
Antebraço/irrigação sanguínea , Testa/irrigação sanguínea , Oximetria/instrumentação , Oximetria/métodos , Oxigênio/sangue , Adulto , Desenho de Equipamento , Humanos , Isquemia/sangue , Modelos Teóricos , Oxiemoglobinas/análise , Oxiemoglobinas/metabolismo
2.
Adv Mater ; 29(22)2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28394455

RESUMO

A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light-emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface-energy-patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near-infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs.

3.
J Phys Chem B ; 119(34): 11307-16, 2015 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-26053650

RESUMO

Three vinylene linked diketopyrrolopyrrole based donor-acceptor (D-A) copolymers have been synthesized with phenyl, thienyl, and selenyl units as donors. Optical and electronic properties were investigated with UV-vis absorption spectroscopy, cyclic voltammetry, near edge X-ray absorption spectroscopy, organic field effect transistor (OFET) measurements, and density functional theory (DFT) calculations. Optical and electrochemical band gaps decrease in the order phenyl, thienyl, and selenyl. Only phenyl-based polymers are nonplanar, but the main contributor to the larger band gap is electronic, not structural effects. Thienyl and selenyl polymers exhibit ambipolar charge transport but with higher hole than electron mobility. Experimental and theoretical results predict the selenyl system to have the best transport properties, but OFET measurements prove the thienyl system to be superior with p-channel mobility as high as 0.1 cm(2) V(-1) s(-1).

4.
Adv Mater ; 27(1): 93-100, 2015 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-25382072

RESUMO

Copper thiocyanate (CuSCN) is introduced as a hole-injection/hole-transport layer (HIL/HTL) for solution-processed organic light-emitting diodes (OLEDs). The OLED devices reported here with CuSCN as HIL/HTL perform significantly better than equivalent devices fabricated with a PEDOT:PSS HIL/HTL, and solution-processed, phosphorescent, small-molecule, green OLEDs with maximum luminance ≥10 000 cd m(-2) , maximum luminous efficiency ≤50 cd A(-1) , and maximum luminous power efficiency ≤55 lm W(-1) are demonstrated.

5.
Phys Chem Chem Phys ; 16(32): 17253-65, 2014 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-25017861

RESUMO

The primary role of substituted side chains in organic semiconductors is to increase their solubility in common organic solvents. In the recent past, many literature reports have suggested that the side chains play a critical role in molecular packing and strongly impact the charge transport properties of conjugated polymers. In this work, we have investigated the influence of side-chains on the charge transport behavior of a novel class of diketopyrrolopyrrole (DPP) based alternating copolymers. To investigate the role of side-chains, we prepared four diketopyrrolopyrrole-diketopyrrolopyrrole (DPP-DPP) conjugated polymers with varied side-chains and carried out a systematic study of thin film microstructure and charge transport properties in polymer thin-film transistors (PTFTs). Combining results obtained from grazing incidence X-ray diffraction (GIXD) and charge transport properties in PTFTs, we conclude side-chains have a strong influence on molecular packing, thin film microstructure, and the charge carrier mobility of DPP-DPP copolymers. However, the influence of side-chains on optical properties was moderate. The preferential "edge-on" packing and dominant n-channel behavior with exceptionally high field-effect electron mobility values of >1 cm(2) V(-1) s(-1) were observed by incorporating hydrophilic (triethylene glycol) and hydrophobic side-chains of alternate DPP units. In contrast, moderate electron and hole mobilities were observed by incorporation of branched hydrophobic side-chains. This work clearly demonstrates that the subtle balance between hydrophobicity and hydrophilicity induced by side-chains is a powerful strategy to alter the molecular packing and improve the ambipolar charge transport properties in DPP-DPP based conjugated polymers. Theoretical analysis supports the conclusion that the side-chains influence polymer properties through morphology changes, as there is no effect on the electronic properties in the gas phase. The exceptional electron mobility is at least partially a result of the strong intramolecular conjugation of the donor and acceptor as evidenced by the unusually wide conduction band of the polymer.

6.
J Am Chem Soc ; 135(6): 2040-3, 2013 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-23350611

RESUMO

We report the synthesis of a novel ladder-type fused ring donor, dithienogermolodithiophene, in which two thieno[3,2-b]thiophene units are held coplanar by a bridging dialkyl germanium. Polymerization of this extended monomer with N-octylthienopyrrolodione by Stille polycondensation afforded a polymer, pDTTG-TPD, with an optical band gap of 1.75 eV combined with a high ionization potential. Bulk heterojunction solar cells based upon pDTTG-TPD:PC(71)BM blends afforded efficiencies up to 7.2% without the need for thermal annealing or processing additives.


Assuntos
Fontes de Energia Elétrica , Compostos Heterocíclicos de 4 ou mais Anéis/química , Compostos Organometálicos/química , Polímeros/química , Energia Solar , Estrutura Molecular , Polimerização , Polímeros/síntese química
7.
Adv Mater ; 25(10): 1504-9, 2013 Mar 13.
Artigo em Inglês | MEDLINE | ID: mdl-23280854

RESUMO

The wide bandgap and highly transparent inorganic compound copper(I) thiocyanate (CuSCN) is used for the first time to fabricate p-type thin-film transistors processed from solution at room temperature. By combining CuSCN with the high-k relaxor ferroelectric polymeric dielectric P(VDF-TrFE-CFE), we demonstrate low-voltage transistors with hole mobilities on the order of 0.1 cm(2) V(-1) s(-1) . By integrating two CuSCN transistors, unipolar logic NOT gates are also demonstrated.


Assuntos
Tiocianatos/química , Transistores Eletrônicos , Cobre , Temperatura
8.
Chem Commun (Camb) ; 49(39): 4154-6, 2013 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-23223555

RESUMO

The optical, structural and charge transport properties of solution-processed films of copper(I) thiocyanate (CuSCN) are investigated in this work. As-processed CuSCN films of ~20 nm in thickness are found to be nano-crystalline, highly transparent and exhibit intrinsic hole transporting characteristics with a maximum field-effect mobility in the range of 0.01-0.1 cm(2) V(-1) s(-1).

9.
Chem Commun (Camb) ; 48(90): 11130-2, 2012 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-23044933

RESUMO

We report the first synthesis of a tetrafluorinated 4,7-bis(3,4-difluorothiophen-2-yl)-2,1,3-benzothiadiazole monomer and its polymerisation with dithieno[3,2-b:2',3'-d]germole by Stille coupling to afford a low band gap polymer with a high ionisation potential. Direct comparison to the non-fluorinated analogue demonstrates that fluorination results in an increase in ionisation potential with no change in optical band gap, and enhanced aggregation over the non-fluorinated polymer. These desirable properties result in a significant enhancement in OPV device performance in blends with PC(71)BM.


Assuntos
Polímeros/química , Energia Solar , Tiofenos/química , Halogenação , Teoria Quântica , Tiadiazóis/química
10.
J Am Chem Soc ; 134(40): 16532-5, 2012 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-23017114

RESUMO

In this communication, we report the synthesis of a novel diketopyrrolopyrrole-diketopyrrolopyrrole (DPP-DPP)-based conjugated copolymer and its application in high-mobility organic field-effect transistors. Copolymerization of DPP with DPP yields a copolymer with exceptional properties such as extended absorption characteristics (up to ~1100 nm) and field-effect electron mobility values of >1 cm(2) V(-1) s(-1). The synthesis of this novel DPP-DPP copolymer in combination with the demonstration of transistors with extremely high electron mobility makes this work an important step toward a new family of DPP-DPP copolymers for application in the general area of organic optoelectronics.

11.
ACS Nano ; 6(4): 3128-33, 2012 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-22390408

RESUMO

We show that it is possible to combine several charge generation strategies in a single device structure, the performance of which benefits from all methods used. Exploiting the inherent type II heterojunction between layered structures of CdSe and CdTe colloidal quantum dots, we systematically study different ways of combining such nanocrystals of different size and surface chemistry and with different linking agents in a bilayer solar cell configuration. We demonstrate the beneficial use of two distinctly different sizes of NCs not only to improve the solar spectrum matching but also to reduce exciton binding energy, allowing their efficient dissociation at the interface. We further make use of the ligand-induced quantum-confined Stark effect in order to enhance charge generation and, hence, overall efficiency of nanocrystal-based solar cells.

12.
Nat Mater ; 10(12): 974-9, 2011 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-21983889

RESUMO

Inorganic nanocrystals are attractive materials for solar-cell applications. However, the performance of such devices is often limited by an insufficient alignment of energy levels in the nanocrystals. Here, we report that by attaching two different molecules to a single quantum dot or nanocrystal one can induce electric fields large enough to significantly alter the electronic and optoelectronic properties of the quantum dot. This electric field is created within the nanocrystals owing to a mixture of amine- and thiol-anchor-group ligands. Examining the steady state as well as temporal evolution of the optical properties and the nuclear magnetic resonances of the nanocrystals we found that the first excitonic peak shifts as a function of the capping-layer composition. We also demonstrate that the use of a mixed-ligand-induced electric field markedly enhances the charge generation efficiency in layer-by-layer CdSe-nanocrystal-based solar cells, thus improving the overall cell efficiency.

13.
Nano Lett ; 8(2): 678-84, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18179278

RESUMO

We demonstrate tuning of the electronic level positions with respect to the vacuum level in colloidal InAs nanocrystals using surface ligand exchange. Electrochemical as well as scanning tunneling spectroscopy measurements reveal that the tuning is largely dependent on the nanocrystal size and the surface linking group, while the polarity of the ligand molecules has a lesser effect. The implications of affecting the electronic system of nanocrystal through its capping are illustrated through prototype devices.


Assuntos
Cristalização/métodos , Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/instrumentação , Pontos Quânticos , Transferência de Energia , Desenho de Equipamento , Análise de Falha de Equipamento , Teste de Materiais , Nanotecnologia/métodos , Tamanho da Partícula , Propriedades de Superfície
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