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18 July, 2007 Metal Nanowires that Detect Molecules Reg Penner Institute For Surface and Interface Science (ISIS) and the Department of Chemistry University.

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Presentation on theme: "18 July, 2007 Metal Nanowires that Detect Molecules Reg Penner Institute For Surface and Interface Science (ISIS) and the Department of Chemistry University."— Presentation transcript:

1 18 July, 2007 Metal Nanowires that Detect Molecules Reg Penner Institute For Surface and Interface Science (ISIS) and the Department of Chemistry University of California, Irvine Metal Nanowires that Detect Molecules Reg Penner Institute For Surface and Interface Science (ISIS) and the Department of Chemistry University of California, Irvine

2 an objective: fast, selective testing for botulinum toxin in milk...

3 How botulinum toxin kills: It catalytically cleaves the SNARE proteins required for vesicle fusion leading to acetylcholine release. Botulinum Toxin as a Biological Weapon Medical and Public Health Management Stephen S. Arnon, MD; Robert Schechter, MD; Thomas V. Inglesby, MD; Donald A. Henderson, MD, MPH; John G. Bartlett, MD; Michael S. Ascher, MD; Edward Eitzen, MD, MPH; Anne D. Fine, MD; Jerome Hauer, MPH; Marcelle Layton, MD; Scott Lillibridge, MD; Michael T. Osterholm, PhD, MPH; Tara O'Toole, MD, MPH; Gerald Parker, PhD, DVM; Trish M. Perl, MD, MSc; Philip K. Russell, MD; David L. Swerdlow, MD; Kevin Tonat, PhD, MPH; for the Working Group on Civilian Biodefense Vol. 285 No. 8, February 28, 2001

4 “As paralysis extends beyond bulbar musculature, loss of head control, hypotonia, and generalized weakness become prominent. Dysphagia and loss of the protective gag reflex may require intubation and, usually, mechanical ventilation. Deep tendon reflexes may be present initially but diminish or disappear in the ensuing days, and constipation may occur. In untreated persons, death results from airway obstruction (pharyngeal and upper airway muscle paralysis) and inadequate tidal volume (diaphragmatic and accessory respiratory muscle paralysis).” Vol. 285 No. 8, February 28, 2001 Botulinum Toxin as a Biological Weapon Medical and Public Health Management Stephen S. Arnon, MD; Robert Schechter, MD; Thomas V. Inglesby, MD; Donald A. Henderson, MD, MPH; John G. Bartlett, MD; Michael S. Ascher, MD; Edward Eitzen, MD, MPH; Anne D. Fine, MD; Jerome Hauer, MPH; Marcelle Layton, MD; Scott Lillibridge, MD; Michael T. Osterholm, PhD, MPH; Tara O'Toole, MD, MPH; Gerald Parker, PhD, DVM; Trish M. Perl, MD, MSc; Philip K. Russell, MD; David L. Swerdlow, MD; Kevin Tonat, PhD, MPH; for the Working Group on Civilian Biodefense

5 an objective: fast, selective testing for botulinum toxin in milk...

6

7 what we’re trying to achieve... Properties of this device: ● One metal nanowire... ●...that electrically transduces the presence of molecules based on charge, dielectric constant, etc. ●...that recognizes and binds one particular molecule, ANY molecule.

8 ...this puzzle has three pieces one metal nanowire 1. electrical transduction 3. recognize and bind.

9 2. one metal nanowire (unable to sense anything) selectivity for one particular molecule (but not at a nanowire)... how can we impart “molecular sensitivity” to metal nanowires? 1. electrical transduction

10 In 1938, Fuchs* demonstrated that the resistance of very thin (l < 50 nm) metal films increases when molecules chemisorb at the surface of the film. *K. Fuchs, Proc. Cambridge Philos. Soc. 34 (1938) 100. Metal nanowires should be poor sensors of molecules, just look at metal nano-films...

11 References: “In-plane resistivity of ultrathin gold films: A high sensitivity, Molecularly differentiated probe of mercaptan chemisorption at the liquid- metal interface” Y. Zhang, R.H. Terrill, P.W. Bohn J. Am. Chem. Soc. 120 (1998) “Chemisorption ande chemical reaction effects on the resistivity of ultrathin fold films at the liquid-solid interface”, Y. Zhang, R.H. Terrill, P.W. Bohn Anal. Chem. 71 (1999) 119. “Effect of molecular adsorption at the liquid-metal interface on electronic conductivity: the role of surface morphology”, G.A. Fried, Y. Zhang, P.W. Bohn, Thin Sol. Films 401 (2001) 171. “Surface roughness of metallic films probed by resistivity measurements”, A.L. Cabrera, E. Garrido-Molina, J. Espinosa-Ganga, I.K. Schuller, D. Lederman, Langmuir 14 (1998) “Resistance changes of cobalt and niobium films when exposed to hydrogen and carbon monoxide” A.L. Cabrera, W. Carrido-Molina, J. Colina, D. Lederman, I.K. Schuller, Phys. Rev. B 55 (1997) “Adsorbate-Induced changes in the infrared reflectance and resistivity of metals” K.C. Lin, R.G. Tobin, P. Dumas, C.J. Hirschmugl, G.P. Williams, Phys. Rev. B 48 (1993) “Multiple mechanisms for adsorbate-induced resistivity: Oxygen and formate on Cu(100)” E.T. Krastev, D.E. Kuhl, R.G. Tobin, Surf. Sci. Lett. 387 (1997) L1051. “Electron density changes and the surface resistivity of thin metal films: Oxygen on Cu(100)”, E.F. McCullen, C-L Hsu, R.G. Tobin, Surf. Sci 481 (2001) 198. “Mechanisms of Adsorbate-Induced Surface resistivity – experimental and theoretical developments”, R.G. Tobin, Surf. Sci 502 (2002) 374. ref.filmadsorbateΔR/R o, % Fuchs et al.poly Aumany< 2 % Tobin et al.Cu(100)O 2 and formate1 - 4 % Cabrera et al.poly Co & NbCO and H 2 < 0.98 % Bohn et al.poly Authiols, amines< 3.5 %...ΔR/R o is always positive, always <5%.

12 But this is not what we observe... Exposure of ≈200 nm dia. silver nanowires to ammonia causes a prompt, reversible, resistance increase of between 0.1% and 50,000%... NH 3 background: N 2 pulse duration: 5s 7% NH 3 Murray, et al. NanoLett, 4 (2004) 665. Murray, et. al., Analyt. Chem., 77 (2005) ∆R/R o = 80%

13 ...in silver wires, CRIBs are Ag 2 O point contacts interposed between particles. If this is not boundary scattering, what is it?...the Chemically Responsive Interparticle Boundary (CRIB) model...

14 ...”Bad” sensors exhibit a metallic T-dependence; “Good” sensors exhibit thermally activated conduction... For a metal: For a semiconductor: bulk Ag = 3.74 x measurements

15 Silver wires should not exhibit photoconductivity...

16 ...photoconductivity in silver wires? We often observe this for wires capable of detecting ammonia.. ΔR/R o =13% ΔR/R o =1.3%

17 ...protonation of surface hydroxyls should minimize surface charge, yielding negative ΔR/R o.

18 Experimental evidence for CRIBs? 1. The physics of conduction in “good” and “bad” ammonia sensors is very different: ● Single nanowire studies using conductive tip AFM... ● T-dependence in “good” sensors is activated, in “bad” sensors it is metallic... ● Photoconductivity? Yes!... (Murray et. al. Analytical Chemistry 77 (2005) 5205 Zubritsky, Analytical Chemistry 78 (2006) 2890). 2. Nanowires of pure Ag 2 O behave identically to “good” silver nanowires sensors... (Murray et. al. Chemistry of Materials 17 (2005) 6611). 3. “Bad” sensors can be made into “good” sensors by electrooxidation. (Murray et. al. Nano Letters 4 (2004) 665).

19 2. one metal nanowire 3. selectivity for one particular molecule (but not at a nanowire)... ✔ Based on these results, it is reasonable to expect oxidized noble metal nanowires to electrically transduce the presence of charged molecules. ✔...because of embedded oxide contacts (CRIBs)... ✔...that can be synthesized electrochemically within these nanowires. References: Zubritsky Analytical Chemistry 78 (2006) Murray et. al. Analytical Chemistry 77 (2005) Murray et. al. Chemistry of Materials 17 (2005) Murray et. al. Nano Letters 4 (2004) electrical transduction

20 2. one metal nanowire 3. selectivity for one particular molecule (but not at a nanowire)... now, how can one metal nanowire be synthesized, with control of wire position and size? 1. electrical transduction

21

22 glass Au nanowires electrodeposited gold nanowires...on glass?

23

24 Lithographically Patterned Nanowire Electrodeposition “LPNE” Menke et al. Nature Materials, 5 (2006) 914.

25 ...nanowire width and height are controlled independently, and without cross-talk.

26

27 ...presently, the smallest nanowires that can be prepared by LPNE are nm (w) x 6 nm (h). Au

28 noble metal nanowires prepared by LPNE are mechanically continuous, and quite rugged.

29 ...by repeating the LPNE process twice, electrically continuous nanowires can be overlaid in patterns on a surface.

30 Au Pd nanowire now we’ve got something that LOOKS approximately right...

31 2. one metal nanowire 3. selectivity for one particular molecule (but not at a nanowire)... ✔ LPNE = Lithographically Patterned Nanowire Electrodeposition. ✔ Photolithographic control of wire position, length, contour. ✔ Fully parallel. ✔ Independent control of nanowire width and thickness. ✔ NOTE: most of these data were generated in a chemistry laboratory, using a handheld UV lamp and contact masks.

32 2. one metal nanowire (unable to sense anything) sensitivity to molecules (with many nanowires and little selectivity)... how can we engineer a metal surface capable of recognizing and binding a particular molecule, ANY molecule? our collaborator: Prof. Greg Weiss, UCI Chemistry 3. recognize and bind.

33 wait, isn’t this a solved problem? What’s wrong with antibodies?

34 Three objectives: 1. Covalently attach virus to a gold surface using surface chemistry that rejects nonspecific binding. 3. Electrically detect this recognition and binding.

35 Full disclosure: NO NANOWIRES HERE.

36 Our Chemical Recognition Element: M13 Penner and Weiss, Analytical Chemistry, 2007

37 ...from a library of adhesive “flavors”, we select members that strongly and selectively stick to our target molecule, “T”...

38 what’s “T”? Today, in the Greg Weiss lab at UCI: Biodefense proteins anthrax lethal factor vaccinia (smallpox vaccine) proteins Francisella tularemia (highly infectious agent) proteins Cholera toxin botulinum toxin (toxin, in progress) SARS S protein Human proteins human growth factor (drug of abuse) CD4, p56lck, actin, and Fyn (cell signaling proteins) prostate specific membrane antigen (prostate cancer marker) Others DNA by engrailed homeodomain displayed on phage EF-Tu (bacterial marker) BSA various antibodies

39 how are viruses attached to the gold surface? Yang et al. Analytical Chemistry 78 (2006) 3265.

40 The resulting phage layer is dense, and completely passivating of the gold surface...

41 attached viruses retain the ability to recognize and binding their target molecules... PSMA = Prostate Specific Membrane Antigen. Yang et al. Analytical Chemistry 78 (2006) 3265.

42 20 nM linear mass loading and release of p-Ab from covalent virus surface as monitored by QCM (LOD ≈ 20 nM). Yang et al. (2007).

43 where, in terms of frequency and phase, can we detect the virus electrode response?

44 where, in terms of frequency and phase, can we detect the virus electrode response?

45 sensitivity is marginally better at 100 kHz. LOD for p-Ab is ≈26 nM. NOTE: Each data point here is a different electrode! LOD = 26 nM [p-Ab], µg ml -1

46 wash 1: 0.5 M HCl wash 2: 0.5 M HCl 1 x 1 µm AFM images...

47 why does electrochemical transduction fail after two HCl washes? A working hypothesis: Phage bundling coupled with monolayer desorption. electrochemical transduction works here......but fails here....in spite of the fact that QCM still works.

48 2. one metal nanowire (unable to sense anything) sensitivity to molecules (with many nanowires and little selectivity)... ✔ Viruses, engineered by Phage Display, can recognize and bind molecules at metal surfaces. ✔...permitting a modular sensor design... ✔...tailorable to ANY target molecule, in principle. ✔...rugged (...surviving, right now, 6 hours in high ionic strength buffers...) ✔...electrically detectible... References: Yang et al. Analytical Chemistry 78 (2006) recognize and bind.

49 remaining objective: Put these pieces together.

50 this is stupid nm Two problems with this: 1.A nm sensing “layer” is doing all the work. 2.R soln is included in sensor signal, requiring recalibration for every sample.

51 ...let’s just measure the conductivity of the membrane, by putting the conductivity cell inside it. In principle, this accomplishes two things: 1.Increases the electrical path length through the sensing medium (bound phage). 2.Short circuits R soln.

52 photoresist channel

53 ...Phage are electrostatically bound to the APTES-modified glass channel...

54 ...Phage are electrostatically bound to the APTES-modified glass channel... so far: 6 experiments; 6 nanochannel sensors. 40 nm wire height 11 mm channel width 50 nM p-Ab 150 nM n-Ab

55 Michael Thompson Chengxiang Xiang Not shown: Erik Menke, Ben Murray Penner Group, Aug NSF - CHE, DMR, & NIRT ACS - PRF Coworkers: Funding: Li-Mei Yang


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