Int. Workshop Explosives Detection Valencia 2010

Nanoporous materials for gas sensing. Application to the detection of explosivesJ. Santamaria Nanoscience Institute of Aragon University of Zaragoza. Spain Int. Workshop Explosives Detection Valencia 2010

Summary1. A very short background on zeolites and related materials 2. Sensing applications: !Capacitors !SnO2 sensors !Mass sensors 4. Conclusions and outlook Int. Workshop Explosives Detection Valencia 2010

Nanoporous solids (NPS): Old family friendsNano2. Internally (and externally?) nanosized Scientists and engineers have use them for decades adsorption catalysis New synthesis methods available to tailor their porous structure and morphology A high potential exists for their combination with micro and nanostructures produced by more typical nanotech methods. Emerging applications of NPS: microreactors, membrane separations, drug delivery, sensors... Int. Workshop Explosives Detection Valencia 2010

ZeolitesMm+n/m ![Si1-n AlnO2]!nH2O A very short background on zeolites and related materials Crystalline aluminosilicates with:-A framework structure with pores of subnanometric size -High surface area: 200 900 m2/g -Exchange cations -Variable Si/Al ratio: 1 to ! Molecular sieving and selective adsorption Give rise to molecular recognition! Int. Workshop Explosives Detection Valencia 2010

1,1,4-Trimethylbencene H2O Paraffins O2MTBE Isoparaffins Methanol 0.3 0.4 0.5 0.6 0.7 0 0.1 0.2 0.8ZEOLITE NaA ZEOLITE CaA SILICALITE/ZSM-5 ZEOLITES X, Y MORDENITE ZEOLITE KA Zeolite pore size- kinetic diameter (nm) A very short background on zeolites Molecular sieving on zeolites -Strong zeolite-molecule interaction: Pores of fixed diameter, with a size comparable to small molecules -Pore size can be modified by exchange cations -Size exclusion regime -Enables molecular recognition funcions Int. Workshop Explosives Detection Valencia 2010

Adsorption on zeolites -Strong molecule-zeolite interactions (pores of molecular size) -Adsorption can be modified: -exchange cations -Si/Al ratio -Functionalization -Can be very selective -Enables molecular recognition Int. Workshop Explosives Detection Valencia 2010

3: Capacitors with zeolite filmsCharge capacity depends on the dielectric constant between the electrodes Different adsorbed chemicals produce different responses Sensitivity can be increased by increasing electrode surface A zeolite film provides selectivity Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

Support: quartz Zeolite seeds Zeolite intergrowth crystal Gold fingers "Z"Z Int. Workshop Explosives Detection Valencia 2010

ZEOLITE A OVER IDC Covalent bonding Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

SILICALITE OVER IDC Covalent bonding Int. Workshop Explosives Detection Valencia 2010

SIL-coated sensor response: ethanol-containing stream 2800 ppm 5300 ppm 9700 ppm 15000 ppm 19300 ppm 0 ppm " 0510152025303540 0.0 10.0f 20.0f 30.0f 40.0f 50.0f 60.0f 70.0f Capacity (F) Time (min) Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

Zeolite layers in SnO2 sensors Miniature, low-cost semiconductor sensors are based upon the variation of conductivity induced by the adsorption of substances.With SnO2 (n-type semiconductor) reducing gases increase conductivity. Semiconductor-based sensors suffer from lack of selectivity, reacting similarly to a variety of substances O- O- O- O- O- O- O- O- O- O- O- O- O- O- HC HC HC HC Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

doped SnO2 Pt heater Ptelectrodes resistance measurement Al2O3 substrate Zeolite layer ABCD Zeolite layer Doped SnO2 Al2O3 substrate Front Back Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

50 ppmEtOH 10 ppmEtOH 2500 ppm CH4 500 ppm CH4 measuring at 350C 50% relative humidity reference sensor sensor with zeolite layer 1 sensor with zeolite layer 2 10 4 10 5 10 6 Resistance ( #) 020406080100120140160180200220240260280 10 3 Time (min) Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

400 micron The path towards miniaturization:250 m2mSensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

Faster response while maintaining performance0 100 200 300 400 500020406080100!2 Microsensor Conventional sensor Normalized resistanceTime (s)!1Int. Workshop Explosives Detection Valencia 2010

Mass sensors: Zeolite films on QCMsQuartz Crystal Microbalances (QCMs) Oscillation frequency depending on the sensor mass Selective coatings to detect certain species in a mixture AmF F!" " # = !# 2 610 3 , 2

Int. Workshop Explosives Detection Valencia 2010

Zeolite coatings on commercial QCMsSIL seeds 1 m 1 m 5 m Hydrothermal synthesis SIL Hydrothermal synthesis LTA AlPO4-18 crystals 5 m Sensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

Detection of gasmixtures450 480 510 540 570 600 630 660 690 720 750 780 -1,2 -1,0 -0,8 -0,6 -0,4 -0,2 0,0 Air

Time (min) "F (a.u.) Air 18% C3H8 AlPO4-18 Silicalite 781062403130 1570 ppmSensors with zeolite films Int. Workshop Explosives Detection Valencia 2010

Int. Workshop Explosives Detection Valencia 2010

Applications. II: Gas sensors based on cantilevers"Tipycally made of Si, with lengths of a few hundred microns "Sensitivity down to femtogram (attogram?) levels "Easy to integrate as a sensor battery Int. Workshop Explosives Detection Valencia 2010

Use the molecular recognition capabilities of zeolites to impart selectivity in sensing applications Applications. II: Gas sensors based on cantilevers" BUT there is no intrinsic selectivity "The cantilvever will respond similarly to the adsorption of different molecules Int. Workshop Explosives Detection Valencia 2010

Frequency (Hz)Frequency (Hz)DNAMIC MCDL k = 3L l l3 f0 = k mef 1 2$ kesonance Irequency (f0) Module (V) Phase () Frequency (Hz)Frequency (Hz)"f"m kesonance Irequency(f) " Int. Workshop Explosives Detection Valencia 2010

The idea of coupling zeolites to cantilevers is 12 years oldScandella et al Microp. Mesop. Mat. (1998) But can be improved! Int. Workshop Explosives Detection Valencia 2010

A hybrid approach Int. Workshop Explosives Detection Valencia 2010

kkD Character|zanon L1A seedsL1A pauern2LCLI1LS USLD IN 1nIS WCkk S|]A|S 8L1 Vo|pore

P+-A Lype zeollLe (L1A sLrucLure)1.3236 m2/g0.133 cm3/g P+-? Lype zeollLe (lAu sLrucLure)3914 m2/g0.328 cm3/g nP4+-8L1A zeollLe (8LA sLrucLure)12,3620 m2/g0.226 cm3/g Co2+ /nP4+- 8L1A zeollLe (8LA sLrucLure) 12,3 309 m2/g0.219 cm3/g (16 exc.) Method of deposition: -Slip casting -Spin coating -Covalent bonding -Micro-dropping -Hydrothermal synthesis Int. Workshop Explosives Detection Valencia 2010

Int. Workshop Explosives Detection Valencia 2010

Improved microcantilever design(in collaboration with IXL group at ESIEE Bordeaux) Int. Workshop Explosives Detection Valencia 2010

Zeolite layers on top of cantilevers Int. Workshop Explosives Detection Valencia 2010

gas chamber 31 GAS DL1LC1ICN SL1-U gaschamber 100 Pz-230 kPz Int. Workshop Explosives Detection Valencia 2010

kUNNING AS1ANDAkD LkLkIMLN1 32 "f "f "f "f "fvs.ppmV Sens|nv|ty (nz]ppmV, nz]g adsorbed) S|gna| to no|se, detecnon ||m|t kesponse nmes kesponse reproduc|b|||ty Int. Workshop Explosives Detection Valencia 2010

CHIP 33 2-NI1kC1CLULNL DL1LC1ICN 1lme" Irequency Sensor l* SLNSCk ILthano|o-n|troto|uene Lresponse (mln)0,430,78 Lrecovery (mln)4,333,28 Slgnal nolse (mPz)9,78,9 SensluvlLy (mPz/ppmv)0,3818,8 SensluvlLy (mPz/ppmv. g )2.7 10-21,34 ueLecuon LlmlL (ppmv)730,S Int. Workshop Explosives Detection Valencia 2010

34 o-N|troto|ueneDL1LC1ICN w|th Co-8L1A cann|eversSLnSC8 l*SLnSC8 C CuallLyfacLor3491320 8esonance lrequency (Pz)20316 Pz37278 Pz S8L1 (m2 8L1/m2 )309 m2 8L1/m22036 m2 8L1/m2 Lresponse (mln)0,781.41 Lrecovery (mln)3,281.76 Slgnal nolse (mPz)8,94,1 SensluvlLy (mPz/ppmv) *18,89,3S SensluvlLy normallzed(mPz/ppmv. g) **1,347,79 ueLecuon LlmlL (ppmv)***0,S0,4 ueLecuon llmlL (ng)***30,1 2-NI1kC1CLULNL DL1LC1ICN !"#$%&$#'()+,-.'/( 0$-1( -+ '/( %#$23,#4-5 %&26( !! 7-,.#$28() 1(, .#00 -+ ,(%(1'-,.#'(,2#$9 !!!!"#$%&$#'() +,-. # +,(:&(5%; %/#5