Chemical and biochemical sensing 1 with silicon nanostructures

OECD Conference on Potential Environmental Benefits of Nanotechnology: Fostering Safe Innovation-Led Growth Paris, France, July 2009

Professor Michael J. Sailor UC San Diego Dept. of Chemistry and Biochemistry [email protected] http://chem-faculty.ucsd.edu/sailor/ Environmental sampling

Samples collected in the field are transported back to the laboratory for more detailed analysis. The delay reduces the effectiveness of remediation efforts. Santa Margarita Ecological Reserve, Aug 2002 Sensor miniaturization

BAWS III Miniaturization provides: photonic crystal Lower cost microsensor Redundancy Highly distributed devices At a price: Lower sensitivity Lower specificity 100 mm Nature Materials 2002, 1, 39-41. There is a great need for functional nanostructures 4 Sensor Networks using Smart Dust Kris Pister, UCB (1996) Advantages of wireless sensor networks: • Highly distributed, fine granularity gives faster, more redundant response to toxin release • Lower cost, smaller infrastructure • Readily moved or reconfigured 5 Small Sensors-Applications

Wireless sensor networks • Indoor air quality • Industrial process monitors • Environmental monitoring • Water quality

Volume-constrained environments • Portable instrumentation • Gas masks • On-body chemical hazard monitors

Medical • In vivo diagnostics • Point-of-care (blood, saliva, breath) • Biomedical research 6

“The promise of nanotechnology is that it can allow us to design some of the key sample preparation, processing, and signal conversion steps directly into the sensor element.”

Sailor, M. J., “Color Me Sensitive: Amplification and Discrimination in Photonic Silicon Nanostructures.” ACS Nano 2007, 1, (4), 248-252. 7 Challenges for nanosensors

•Specificity: Identification and amount of a chemical or biological compound in a complex mixture

•Fouling: Accumulation of impurities leads to degradation of sensitivity

•Zero Point Drift: From sensor to sensor; from day to day

•Sample collection: •Air: Need efficient collector or sensor network with fine granularity •Water: Bioassays are sample volume limited--need high sensitivity, need to reject most of the matrix

Sailor, M. J., ACS Nano 2007, 1, (4), 248-252. 8 Etching porous layers in silicon H + + 2Si + 6 HF + 2 h Si + H2SiF 6 + 2H + 1/2 H2

Porous Si Surface

20 m

Porosity (index) ~ current density Thickness ~ etch time Pore size: (1 nm - 1 m) ~ current, [F-] 9 Etching porous layers in silicon

2 600 layer 1 500

400

300 20 m

200 layer 2

100

Current Density, mA/cm 0 0 10 20 30 40 50 60 70 Time, s Porosity (index) ~ current density Thickness ~ etch time

Pore size: (1 nm - 1 m) ~ current, [F-] Pepsin-loaded reactor detects 10 cleavage of -casein

9.24 10 3 16.02 103

Layer 2 3 9.22 10 16.00 103

9.20 10 3 15.98 103

2nL, nm 9.18 10 3 15.96 103 9.16 10 3 2nL, nm 2nL, Layer 1 15.94 103 9.14 10 3

3 9.12 10 3 15.92 10

9.10 10 3 15.90 103 -50.0 0.00 50.0 100 150 200 Time, min

Orosco, M. M., et al. Nature Nanotech. 2009, 4, 255 - 2581 1-D Photonic Crystals 11 Calloodes grayanus Porous Si multilayers

2 mm

1 mm

PARKER, A. R., et al., J. Exper. Biol. 1998 201, 1307-1313. Orosco, Manuel and Oakes, Melanie Modulation of pore dimensions 12 using current modulation H + + 2Si + 6 HF + 2 h Si + H2SiF 6 + 2H + 1/2 H2

Porous Si Surface Pt Current

HF/Ethanol

Time Porosity

Silicon

Depth Background: Lehmann, V. Electrochemistry of Silicon AC (Wiley-VCH, Weinheim, Germany, 2002). 13 Porous photonic crystal sensor

Analyte-induced color change: • Visual detection • Sensitive • Specific?

air ethanol

Sailor, M. J.; Link, J. R. Chem. Commun. 2005, 1375-1383. 14 Porous photonic crystal sensor

OH

Si O O Si O Si Si Si Si Si Si

Surface chemistry and nanostructure control infiltration 15 Protease Biosensor

• Detection of protease activity in water, the environment, and patient samples pepsin concentration • red shift in 1-D 45 pmol photonic crystal spectrum when enzyme is present 23 pmol • Presence of protease is amplified. • 2 pmol detection limit 0 pmol

1 mm Orosco, M. M., Pacholski, C., Miskelly, G. M. & Sailor, M. J. Adv. Mater. 2006,18, 1393-1396. 16 “Smart Dust” sensor on an optical fiber Films, microparticles, and 17 nanoparticles of porous Si H + + 2Si + 6 HF + 2 h Si + H2SiF 6 + 2H + 1/2 H2

Porous Si Surface 18 Porous Si microparticles Smart Dust: 19 Optical sensors for chemical pollutants

“Smart Dust” particles as remote 20 sensors Advantages •Highly distributed, rapid response •Environmentally degradable •Low cost Challenges •Sensitivity •Specificity

Schmedake, T. A.; Cunin, F.; Link, J. R.; Sailor, M. J. Adv. Mater. 2002, 14, 1270-1272 21 Hazards of nanotechnology

50 mm

Electron Microscope Image of US EPA: Attic Containing UW Asbestos Management Asbestos Fibers Asbestos-Laden Vermiculite Program: Heating/Chilling Insulation Plant Furnace/Boiler . . . . Asbestos (crocidolite): Na2O Fe2O3 3FeO 8SiO2 H2O Toxicity: Chemical composition, form, dose, and availability 22 3 Laws of NanoRobotics*

1. The structure must not self- replicate 2. The structure must degrade 3. The degradation products must not be harmful

Are the chemical constituents toxic? Is it going to end up in the environment?

*apologies to Isaac Asimov How does Si degrade?

Si + O2 SiO2

SiO2 + 2H2O Si(OH)4 Nanostructure determines dissolution rate subcutaneous 0 weeks Studies in Simulated Human Plasma. L T Canham, implant in Adv Mater 7, 1033, (1995) Guinea pig. pSiMedica, inc. “…thin, high porosity and high surface area mesoporous layers were observed to be completely removed…within a day or so.” 4 weeks S H C Anderson, H Elliott, D J Wallis, L T Canham, J J Powell. Phys Stat Solidi (a) 197, 331 (2003)

“porous silicon films release Si(OH)4 in aqueous solutions in the physiological pH range…high and 12 weeks very high porosity films showed the greatest dissolution”

36 Biodegradable silicon quantum dots

Etching in HF Lift-off

210mA/cm2, 150s Si substrate (P++) Porous Si Free-standing film

Ultrasonic fracture H2O, 24h

Activation Filtering

200nm pores Luminescent Nanoparticles Microparticles Nanoparticles

Park, J.-H. et al. Nature Mater. 2009, 8, 331-336. In vivo degradation of porous Si nanoparticles

Color map of fluorescence intensity @ 850 nm •Si nanoparticles injected via tail vein •Localize to MDA-MB-435 tumor •Fluoresce @ 850 nm •Degrade and clear in 3 d Park, J.-H. et al. Nature Mater. 2009, 8, 331-336. 26 Conclusions •Silicon electrochemistry provides programmed nanostructures with built-in sample and signal processing features •Nanotechnology can enable higher fidelity, smaller and lower cost microsensors •Silicon and silica nanostructures can be degraded in the environmentally (or in vivo) •Degradable nanomaterials are needed 27 Acknowledgements

Coworkers: Manuel Orosco, Claudia Pacholski, Anne Ruminski, Brian King, Jamie Link, Luo Gu, Thomas Schmedake, Elizabeth Wu

Collaborators: Dr. Jay Snyder, NIOSH Prof. Sangeeta N. Bhatia, Geoff von Maltzahn (MIT Bioengineering) Prof. Erkki Ruoslahti (Burnham Institute at UCSB) Dr. Frederique Cunin, Prof. Jean-Marie Devoisselle (CNRS Montpellier, FR) Prof. Gordon Miskelly, Corrina Thompson (University of Auckland, NZ) Prof. Yukio H. Ogata, T. Sakka, M.S. Salem (Kyoto University) Dr. William Freeman, Dr. Lingyun Cheng (UCSD Jacobs Retina Center) Prof. Kenneth Vecchio (UCSD Nanoengineering)

Funding: NSF, NIH, NIOSH, Hitachi Chemical Research Center, Elintrix, Cellular Bioengineering, inc.

Michael J. Sailor, Department of Chemistry and Biochemistry