WGs & MC Meeting at SOFIA (BG), December 2015

Transcription

1 European Network on New Sensing Technologies for Air Pollution Control and Environmental Sustainability EuNetAir COST Action TD115 WGs & MC Meeting at SOFIA (BG), 1618 December 215 New Sensing Technologies for Indoor Air Quality Monitoring: Trends and Challenges Action Start date: 1/7/212 Action End date: 3/4/216 Year 4: 1 July April 216 MSDI HETEROJUNCTIONS, FROM IMPEDANCE AND CHEMO SENSING STUDIES TO GAS SENSORS IN TRUE ATMOSPHERE COST is supported by the EU Framework Programme Marcel Bouvet SubWG 1.3 leader, MC member University of Burgundy Dijon / France Andreas Schütze WG 2 leader, MC member Saarland University/ Germany ESF provides the COST Office through a European Commission contract

2 Scientific context and objectives in the Action Background / Problem statement: Guidelines for Best Coupling AirPollutant and Transducer (SIG 3) Objective: To operate a same conductometric device in different ways to achieve a better selectivity? Outline: Presentation of the device Current = f(t) Impedance = f(frequency) 2

3 Conductometric Gas Sensors Resistor Conductivity: s = n e m For redox active species, variation of n by doping or neutralization of charge carriers: D[Gas] Dn Ds Thus, in a ptype material, a donating species like NH 3 can give 1 electron to the material, neutralizing the positive charge carriers, leading to a decrease of s. But for non redox active species, variation of m due to the variation of the dielectric constant of the sensing material: D[Gas] De Dm Ds M. Bouvet, A. Pauly, "Molecular Semiconductor Based Gas Sensors" in The Encyclopedia of Sensors, ed. by C.A. Grimes, E.C. Dickey, M. V. Pishko, American Scientific Publishers, vol 6, 26, pp

4 Conductometric Gas Sensors resistor diode MSDI transistor 4

5 E / ev vs. Vacuum Level Molecular Semiconductor Doped Insulator heterojunctions (MSDI) Semiconductor Doped insulator SOMO LuPc 2 E ox E red =.48 V E gap LuPc 2 CuPc F 8 (CuPc) F 16 (CuPc) V. Parra, J. Brunet, A. Pauly, M. Bouvet, Molecular semiconductor doped insulator (MSDI) heterojunctions: An alternative transducer for gas chemosensing", Analyst, 134, , 29. 5

6 i/ A i/ A i/ A MSDI heterojunctions 1.x1 2 LuPc 2 /F. Semiconductor 1.x1 4.x1. 4.x1 8.x LuPc 2 /F LuPc 2 /F MSDI Doped insulator The energy barrier increases from F (ptype) to F16 (ntype) since LuPc 2 is of ptype in air,. M. Bouvet, V. Parra, Patent Application n 7/729, filed on 15/1/27 by UPMC and CNRS; and PCT 28/1325, 24/9/28. 8.x Bias / V V. Parra, J. Brunet, A. Pauly, M. Bouvet*, "Molecular semiconductor doped insulator (MSDI) heterojunctions, an alternative transducer for gas chemosensing", Analyst, 134, , 29 6

7 i/a i/a Sensitivity to Ammonia of p and nmsdis MSDI Molecular Semiconductor Doped insulator An energy barrier E pn exists at the interface between the two layers pmsdi, [LuPc 2+ ] and I nmsdi, E pn and I 2.7x x x1 6 Ar ammonia 2.4x t/s Ar 6 3.x1 Ar 6 2.9x x x x1 ammonia Ar t/s 7

8 Sensitivity to Humidity of nmsdis rh I H 2 O is a donating species like NH 3 But s 8

9 Relative Humidity (%) Sensitivity to Ammonia of nmsdis NH 3 : s H 2 O : s 9

10 ,3 Discrimination between NH 3 and H 2 O Relative response: I/I = (I I )/I =f(relative Humidity) +,1 +,1 m = 1,49 D e = 22 +,1,4 O +,2 H H +,2 m = 1,85 D e = 8 Good discrimination of NH 3 concentrations whatever the RH in the 17 % range 1

11 Impedance = f(frequency) nmsdi Nyquist plot Bode plot LuPc 2 resistor M. Bouvet*, P. Gaudillat, A. Kumar, T. Sauerwald, M. Schüler, A. Schütze*, J.M. Suisse, "Revisiting the electronic properties of Molecular Semiconductor Doped Insulator (MSDI) heterojunctions through impedance and chemosensing studies", Org. Electron., 26 (215),

12 Equivalent circuit Z CPE = 1/(Q. (jw) a ) with w = 2pf, where Q is the capacity, f the frequency and a a coefficient. For the special case of a = 1, a CPE equals an ideal capacitor with Q = C. It can also represent a normal resistor (a = ), or a socalled Warburg element (a =.5). M. Bouvet*, P. Gaudillat, A. Kumar, T. Sauerwald, M. Schüler, A. Schütze*, J.M. Suisse, "Revisiting the electronic properties of Molecular Semiconductor Doped Insulator (MSDI) heterojunctions through impedance and chemosensing studies", Org. Electron., 26 (215),

13 Conclusion MSDIs: New heterojunctions based on molecular materials were demonstrated to be promising transducers for gas chemosensing (Ex.: For O 3 in the ppb range and for NH 3 in the ppm range) MSDIs are a new conductometric transducer; they can be operated in different ways : Current = f(t): simple Impedance = f(frequency): more powerful because more data, but requires more data treatment LuPc 2 /Cu(F 16 Pc) ntype MSDI exhibits a very good stability of the response to NH 3 over a broad range of RH. Research directions: To tune the electrodesublayer interface, by chemical or electrochemical modifications, and study it by impedance spectroscopy 13

14 Acknowledgments Drs Thibaut Sizun, Guillaume Barochi and Pierre Gaudillat, Amélie Wannebroucq, Ph. D student, Dr JeanMoïse Suisse, ICMUB, University of Burgundy, Dijon (Univ. Bourgogne FrancheComté) Dr Vicente Parra, Postdoctorant, DC Wafers then PV Silicon Advisor (Spain) Prof. Yanli Chen, China University of Petroleum (Qingdao, China) Dr Tilman Sauerwald and Marco Schüler, Saarland University, Germany Financial supports: The ESPCI ParisTech and the City of Paris The Agence Nationale de la Recherche (ANR) The Conseil Régional de Bourgogne 14