1. Ting Gao Group meeting May 2004 Novel Chemiresistors Approaches

2. Monitor Swelling Induced Resistance Increases Time Resistance  RR R max R baseline Insulating Polymer/Carbon Black Sensors: How It Works Analyte Response of sensor is described as  R max /R b

3. Array Response Sensor Array ∆R / R Time ∆R Glass substrate Polymer/ Carbon Black Solution gap Sensor #

4.  e -2  e -Ec/KT  : core-core seperation  : ~ 1 Å  r : the relative permittivity of the dielectric medium between the cores Ec: the activation energy, essentially the Coulomb energy associated with charging two neutral particles and inversely proportional to the relative permittivity of the dielectric media  R/R ~ e -2  -1 If Ec/KT doesn’t change,  ~ 0.2 Å results in 50%  R/R changes. Resistance between the gold nanocrystals ~~~~~~~~~~~~~~~

5. HAuCl 4 (H 2 O) + RSH(Toluene) Au-SR(Toluene) NaBH 4 (C 8 H 17 ) 4 NBr Preparation of Thiol Capped Gold Nanocrystals H O N

6. Organic Ligand capped TiO 2 -CB as Chemiresistors Ti(O-isoPropoxide) 4 + 4 H 2 O  TiO 2 + 4C 2 H 5 OH H+H+ OH HO OH HOOH RCOOH OOR ROO OOR ROOOOR Analyte

7. PEO TiO2 + dye TiO2 +C15COOHAu-S-C8 Resistance Response to Eight Analytes Tested  R/R Time (S) Analytes from left to right: Hexane THF Ethanol Ethyl Acetate Cyclohexane Heptane N-octane Iso-octane

8. Time (s) R (  ) Third Try of TiO 2 + Ligand C 15 COOH  R/R Exposure Numbers

9. Third Try of TiO 2 + Ligand C 15 COOH  R/R Exposure Numbers along Time Scale

10. N C 8 H 17 + Br - OH O O O O O HO OH Br H Cl N O N HO OH N+N+ O O-O- C 6 H 4 -1,2,-[CO 2 CH 2 CH(C 2 H 5 )(CH 2 ) 3 CH 3 ] 2 Monomers Tried in This Test

11. Comparison of Monomer and Polymer to Hexane

12. OH O

13. Proposed Mechanism for Better Sensors Free space

14. Time (s)  R/R C 24 H 50 /Plastisizer to n-Hexane C 20 H 42 C 24 H 50 C 30 H 62 Time (s)  R/R Response of Several Monomer/CB to Hexane

15. C 20 H 42 C 24 H 50 C 30 H 62 Time (s)  R/R C 20 H 42 /P C 24 H 50 /P C 30 H 62 /P Time (s)  R/R

16. Reproducibility of a Typical Monomer/CB to Analytes Time (S) R (  ) C 24 H 50 /Plastisizer to analytes. Analytes from left to right: 6,6,5,4,7,5,7,1,1,4,5,1,5,5,8,1,8,7,8,4,6,7,7,3,8,5

17. Reproducibility of a Typical Monomer/CB to Analytes Time (S) O O HO OH Analytes from left to right: 6,6,5,4,7,5,7,1,1,4,5,1,5,5,8,1,8,7,8,4,6,7,7,3,8,5 R (  )

18. Reproducibility of a Typical Monomer/CB to Analytes Time (S) Analytes from left to right: 6,6,5,4,7,5,7,1,1,4,5,1,5,5,8,1,8,7,8,4,6,7,7,3,8,5 H Cl N O N R (  )

19. Dose Response to Hexane P/P o  R/R C 20 H 42 C 20 H 42 /P C 24 H 50 C 24 H 50 /P C 30 H 62 C 30 H 62 /P C 10 H 12 O 5 C 4 H 9 O 5 C 4 H 9 NO 5

20. Dose Response to Ethanol P/P o  R/R C 20 H 42 C 20 H 42 /P C 24 H 50 C 24 H 50 /P C 30 H 62 C 30 H 62 /P C 10 H 12 O 5 C 4 H 9 O 5 C 4 H 9 NO 5

21. Dose Response to Butylamine C 20 H 42 C 20 H 42 /P C 24 H 50 C 24 H 50 /P C 30 H 62 C 30 H 62 /P C 10 H 12 O 5 C 4 H 9 O 5 C 4 H 9 NO 5 P/P o  R/R

22. Experimental Setup Time (s) concentration Analyte chosen in random order All the concentrations were controlled at 0.5% P/P o

23. Stability of a Typical Monomer/CB to Analytes Exposure numbers along Time scale  R/R N C 8 H 17 + Br - with plastisizer

24. Stability of a Typical Monomer/CB to Analytes Exposure numbers along Time scale  R/R C 24 H 50 with plastisizer

25. Stability of a Typical Monomer/CB to Analytes Exposure numbers along Time scale  R/R C 30 H 62

26. Stability of a Typical Monomer/CB to Analytes Exposure numbers along Time scale  R/R O O HO OH

27. 3-D Pattern of the Sensor Array to the Analytes sensors analytes  R/R

28. Principal Components Analysis Plot of the  R/R b Response of the Detector Array

30. Conclusions Ligands capped TiO2 nanocrystals with carbon black composites are promising chemical vapor sensors. Using monomers mixed with carbon black can easily make an sensor arrays with fast response time, good reproducibility and stability, better diversity, and having the ability to classify and identify vapors. Additional tips: High density functional group More environmental friendly Fun

31. Acknowledgements Prof. Nathan S. Lewis Brian Sisk Lewis’ Group TiO2: Don, Bruce, Jordon and Tony $$$ NIH