1. 1 Structurally Integrated Fluorescence-Based Bio(chemical) Sensors Excited by Organic Light Emitting Devices Students: Bhaskar Choudhury, Zhaoqun Zhou Ruth Shinar, Microelectronics Research Center Joe Shinar, Ames Laboratory, Microelectronics Research Center, & Department of Physics and Astronomy

2. 2 GOAL: Develop a flexible, lightweight, compact, and low cost platform for sensor arrays based on miniaturizable fluorescent sensors, in which the organic light-emitting device (OLED) light source is integrated with the sensing element. The sensors would:  monitor environmental gases (e.g., O 2, CO, CO 2, H 2 leaks, ammonia, hydrazine), such gases in water supplies, blood content of biochemical compounds (e.g., glucose), and biological organisms;  replace currently used fluorescence-based sensors that are bulky, costly, and therefore limited in use;  be used for basic studies of chemical, biochemical, and biological processes, in vitro and in vivo.

3. 3 Basic structure of OLEDs Low-Workfunction Cathode Electron-Transporting & Emitting layer (ETL) Hole-Transporting Layer (HTL) Transparent Conducting Anode [indium tin oxide (ITO)] Glass or Plastic Substrate + - Pe:CBP 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (DPVBi)  -NPD : DPVBi or Perylene:4,4'-bis(9-carbazolyl)biphenyl (Pe:CBP) N,N’-diphenyl-N,N’-bis(1-naphthyl phenyl)-1,1’-biphenyl-4,4’-diamine (  -NPD)

4. 4 Basic structure of an integrated OLED/fluorescent chemical sensor element Matrix array of blue DPVBi-based OLEDs; each pixel is ~1.5 mm in diameter

5. 5 Advantages of OLEDs  Can be operated at an extremely high brightness (> 10 6 Cd/m 2 ) under pulsed operation  Are the basis for commercially available bright microdisplays  Are simple to fabricate  Can be fabricated in any 2-d shape  Can be fabricated on plastic substrates  Consume little power and dissipate little heat  Their cost is expected to drop to a near-disposable level

6. 6 (a) (b) (c) Sensor device geometries: (a)Front-detection mode, (b)back-detection mode using transparent OLEDs, and (c)back-detection mode using an array of OLED pixels.

7. 7 ( 1) PL, (2) PL excitation (in air), and (3) absorption spectra of the Ru(dpp) dye immobilized within a sol-gel matrix, measured in air. (4) The EL of blue DPVBi OLEDs (peak at ~475 nm) and (5) violet CBP OLEDs (EL peaks at ~400 & ~420 nm). EL Intensity N N2N2 Air O2O2 Ruthenium (II) tris(4,7-diphenyl-1,10-phenanthroline) chloride (Ru(dpp))

8. 8 Ru(dpp) sensor response to Ar and O 2 vs time; Ru(dpp) excited by a blue ITO/NPB/ (perylene:CBP)/CsF/Al OLED. OLED biased at 16 V DC, I = 50  A, brightness ~1200 Cd/m 2. The gas flow was 7 psi for both Ar and O 2. Ar O2O2

9. 9 Time resolved PL of the oxygen sensor (solid line) and blue EL of the DPVBi OLED (dotted line), both obtained through a 15 nm band-pass filter at 600 nm, from a 4.6  sec bias pulse (dashed line) with a repetition rate c = 51.4 kHz. Inset: Time resolved EL of the DPVBi blue OLED (solid line) generated by the bias pulse (dotted line); c = 47 kHz.

10. 10 PL Lifetime and Intensity as a Function of Oxygen Concentration % O 2 020406080100 Lifetime (  s) Intensity (a.u.) 0 2 4 6 8 PL intensity PL lifetime

11. 11 Ru(dpp) Stability: OLED vs Laser Excitation Pulsed OLED excitation 3 mW laser excitation

12. 12 Rhodamine-Antibody Detection (Initial Results; lowest antibody level detected ~0.3-0.4  g)

13. 13 Fluorescent Sensor Substrate Transparent (ITO) Anode Hole Transport Layer (HTL) Emitting Layer Electron Transport Layer (ETL) Cathode Fluorescence-passing, OLED Emission-blocking Filter Photodiode or CCD detector (array) Analyte Organic LEDs CCD Microprocessor + – Zoom-in: cross section of the integrated sensing device Integrated OLED/fluorescent chemical sensor array

14. 14 Summary  Demonstrated integrated OLED/oxygen and OLED/glucose sensors  Demonstrated front- and back-detection  Demonstrated use of PL intensity and lifetime modes Next  Optimize OLED and sensing component  Expand use for various analytes, including antibody/antigen immunosensors  Enhance dynamic range and sensitivity  Develop microarrays

15. 15 Acknowledgements DOE, NASA References 1. J. W. Aylott, Z. Chen-Esterlit, J. H. Friedl, R. Kopelman, V. Savvateev, and J. Shinar, “Optical Sensors and Multisensor Arrays Containing Thin Film Electroluminescent Devices,” US Patent No. 6,331,438 (December 2001). 2. V. Savvate’ev, Z. Chen-Esterlit, J. W. Aylott, B. Choudhury, C.-H. Kim, L. Zou, J. H. Friedl, R. Shinar, J. Shinar, and R. Kopelman, “Integrated Organic Light Emitting Device/Fluorescence-Based Chemical Sensors,” Appl. Phys. Lett. 81, 4652 (2002).