Electrochemically Synthesized Multi-block

Transcription

1 Electrochemically Synthesized Multi-block Nanorods Sungho Park SungKyunKwan University, Department of Chemistry & SKKU Advanced Institute of Nanotechnology (SAINT)

2 J. Am. Chem. Soc. 2003, 125, Electrochim. Acta. 2002, 47, J. Phys. Chem. B 2002, 106, Langmuir 2002, 18, J. Am. Chem. Soc. 2002, 124 (11), Langmuir 2002, 18, J. Phys. Chem. B 2001, 105, Electrochem. Comm. 2001, 3, J. Phys. Chem. B 2000, 104, J. Am. Chem. Soc. 2006, ASAP J. Phys. Chem. B 2006, 110, Science, 2005, 309, J. Am. Chem. Soc. 2005, 127, Advanced Materials 2005, 17, J. Am. Chem. Soc. 2004, 126, Angew. Chem. Int. Ed.2004, 43, Science, 2004, 303, Electrochemical Vibrational Characterization of Metal Nanoelectrodes Surface Chemistry Electrochemistry Nanoparticle electrocatalysis Nanoparticle Synthesis and Applications Nanorods Core-Shell nanoparticles DPN, Nano-Bio Chemistry

3 Nanotechnology: What is it? 1. Developing synthetic and analytical tools for characterizing and manipulating materials on the nanometer (nm) length scale. 2. Determining the chemical and physical consequences of miniaturization. 3. Exploiting the ability to miniaturize and its consequences in the development of new technology.

4 Nanometer Scale Materials Why are we interested in small particles? Single particle & Atomic species Bulk species Many fascinating potential uses: quantum dots or quantum computers and devices, chemical sensor, light-emitting diodes, industrial lithography and so on Electrochemical catalysts, SERS

5 Stability of Particles? Energy n=55 n=147 n=309 Bulk metal Kinetically stable, not thermodynamically Particle Size (a) (b)

6 Carbon Supported Nanoparticles (by K. Kinoshita)

7 Underpotential Deposition of Copper Monolayer Cu e - substrate Cu 0 UPD b' 10 μa a' b a Potential (V vs SCE)

8 Replacement of Cu UPD Adlayer with Pt Pt 2+ Pt 2+ Pt 2+ Pt 2+ Pt 2+ Pt 2+ Pt 2+ Cu 2+ Cu 2+ Cu 2+ Cu 2+ Cu 2+ Cu 2+ -2e - + 2e - + 2e - -2e - Cu Au Au Pt Cu 0 + Pt 2+ Cu 2+ + Pt 0 Au PtCl 4 2- /Pt E 0 = 0.48 V Cu 2+ /Cu upd E 0 = 0.2 V Pt

9 Pt-group metal coated gold nanoparticles CH 3 0 Au OH OH OH OH OH OH OHOH CH 3 0 Si NH 2 CH 3 0 NH NH 2 NH 2 NH 2 NH 2 NH 2 2 NH 2 Au Au ITO coated glass Silanization Pd 2+ or Pt 2+ Cu 2+ Cu overlayers Au Au Au Au Au Au Au Au Au Metal Exchange UPD

10 SERS of Pt-group modified gold nanoparticles Pt coating Pd coating SERS ua/cm ua/cm cps Relative Intensity Pt / CO 2073 Pd / CO * * * 350 Pt / C 2 H E/V vs. SCE E / V vs. SCE Au / C 2 H Raman Shift (cm -1 ) * J. Phy. Chem. B 2002, 106, 8667 JACS. 2002, 124(11), 2428

11 Nanorod Synthesis Alumina membrane Top view 150 ~200 nm Ag evaporation Ag deposition (EC) Side view Pt Ag/AgCl working electrode 1. HNO 3 Au deposition (EC) 2. NaOH Pioneered by Prof. Martin and Prof. Moskovits

12 Gold Nanorods Optical Microscope Images 5 μm 5 μm

13 Rods made from Conducting Polymers H N H N 4 N H N H Length/µm Polymer Polymer Au Au Charge/C 5 μm

14 Nanoresistors & Nanodiodes = Au Deposition Resistors Low Work Function Metal or Semiconductor Deposition = Schottky or P-N Diodes

15 Layer by Layer Assembly Ref. JPCB. 2001, 105, 8762 by T. E. Mallouk et. al.

16 Electrical Transport Measurement

17 Electrical Transport Measurement 289K 200K 175K 150K 120K At Room Temperature, conductivity ~ 3 ms cm -1 log σ(t) vs 1/T, showing a linear response (σ = σ 0 exp( E a /kt), σ: conductivity, T: temperature) the activation energy E a ~ 0.07 ev.

18 Au-Ppy-Cd-Au, Schottky Diodes A B E Reverse Bias C D Au Cd Ppy Au 150 nm

19 Conclusions (Part 2) The electrochemical deposition provides excellent control over the block length of the metal and organic regions of nanorods. They show either resistor or diode properties depending on their compositions and spatial distribution of the different compositional blocks.

20 Nano-Gap Fabrication On-Wire Lithography (OWL) 1. Removal of templates 2. Dispersion of wires Deposition of Au/Ti or SiO 2 Sonication Etching +

21 Zoomed-in SEM Images of Wires 5 nm 25 nm 50 nm 100 nm Lowest limit ~ 5 nm (at current stage) Zoomed-in Image with Au/Ti coating, after chemical etching of Ag blocks.

22 Photo-Sensitive DPN Patterns at the Gap 2.0x10-9 Current / A 1.5x x x x x10-9 Au-Gap (13nm)-Au, DPN of PEO:Ppy = 1:1 (w/w %) Without polymer Xe Light Exposure SEM Image of wire on micorelectrodes after DPN of a mixture of PEO & Ppy -1.5x x10-9 With polymer Potential / V Scanned starting from 1.0 V to +1.0 V, Xe Light was shined on the gap at 0.1 V on the way back

23 SEM Image and EDS of Disk Arrays 40 nm Au Si SEM Images of Nano-Disk Arrays after Si Deposition EDS of Nano-Disk Arrays after Si Deposition and Ag Etching

24 Conclusions (Part 3) The electrochemical deposition and selective etching provide excellent control over metal block length and nano gap distance in nanorods. They show potential application in molecular electronics and we demonstated proof-ofconcenpt experiment with and without conducting polymer at the gap.

25 Multicomponent Magnetic Nanorods for Biomolecular Separations

26 Affinity of Poly-His to Ni Blocks of Au- Ni-Au Nanorods A B A B ~ Nanorods

27 Multicomponent Magnetic Nanorods for A Biomolecular Separations B 5 μm 5 μm C D

28 Anti-PolyHis Ig G Antibody Separation by Au-Ni-Au Nanorods

29 Multi-Component Separation A B C D Dye color Nitrostreptavidin nontagged protein (protein A) Histidine tagged protein (ubiquitin) Biotin tagged protein (BSA) A Selective binding B Magnetic separation C His-tagged protein release D Biotin-tagged protein release

30 Conclusions (Part 4) Multicomponent metal nanorods have several advantages (e.g. stability and modification). Multiblock nanorods can be used for separation of various proteins by exploiting the chemical and physical properties of these nanostructures. The nanorods provide increased surface area and are a pseudo-homogeneous system, increasing the efficiency of the target binding and separation process.

31 Acknowledgements Purdue University (West Lafayette), Prof. Michael J. Weaver

32 Acknowledgements Northwestern University, Prof. Chad A. Mirkin NIH DARPA NSF ONR AFOSR