Electrochemically Synthesized Multi-block Nanorods Sungho Park SungKyunKwan University, Department of Chemistry & SKKU Advanced Institute of Nanotechnology (SAINT)
J. Am. Chem. Soc. 2003, 125, 2282-2290 Electrochim. Acta. 2002, 47, 3611-3620 J. Phys. Chem. B 2002, 106, 8667-8670 Langmuir 2002, 18, 5792-5798 J. Am. Chem. Soc. 2002, 124 (11), 2428-2429 Langmuir 2002, 18, 3233-3240 J. Phys. Chem. B 2001, 105, 9719-9725 Electrochem. Comm. 2001, 3, 509-513 J. Phys. Chem. B 2000, 104, 8250-8258 J. Am. Chem. Soc. 2006, ASAP J. Phys. Chem. B 2006, 110, 2150-2154 Science, 2005, 309, 113-115 J. Am. Chem. Soc. 2005, 127, 5312-5313 Advanced Materials 2005, 17, 1027-1031 J. Am. Chem. Soc. 2004, 126, 11772-11773 Angew. Chem. Int. Ed.2004, 43, 3048-3050 Science, 2004, 303, 348-351 Electrochemical Vibrational Characterization of Metal Nanoelectrodes Surface Chemistry Electrochemistry Nanoparticle electrocatalysis Nanoparticle Synthesis and Applications Nanorods Core-Shell nanoparticles DPN, Nano-Bio Chemistry
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.
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
Stability of Particles? Energy n=55 n=147 n=309 Bulk metal Kinetically stable, not thermodynamically Particle Size + + + + + + + + + + + + (a) (b)
Carbon Supported Nanoparticles (by K. Kinoshita)
Underpotential Deposition of Copper Monolayer Cu 2+ + 2e - substrate Cu 0 UPD b' 10 μa a' b a -0.2 0.0 0.2 0.4 0.6 Potential (V vs SCE)
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
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
SERS of Pt-group modified gold nanoparticles Pt coating Pd coating SERS 2080 478 100 ua/cm 2 100 ua/cm 2 2500 cps Relative Intensity Pt / CO 2073 Pd / CO 1969 1504 1224 * * * 350 Pt / C 2 H 4 1540 1278 0.0 0.5 1.0 E/V vs. SCE 0.0 0.5 1.0 E / V vs. SCE Au / C 2 H 4 2000 1500 1000 500 Raman Shift (cm -1 ) * J. Phy. Chem. B 2002, 106, 8667 JACS. 2002, 124(11), 2428
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
Gold Nanorods Optical Microscope Images 5 μm 5 μm
Rods made from Conducting Polymers H N H N 4 N H N H Length/µm 3 2 1 Polymer Polymer Au Au 0 0 1 2 3 4 5 6 Charge/C 5 μm
Nanoresistors & Nanodiodes = Au Deposition Resistors Low Work Function Metal or Semiconductor Deposition = Schottky or P-N Diodes
Layer by Layer Assembly Ref. JPCB. 2001, 105, 8762 by T. E. Mallouk et. al.
Electrical Transport Measurement
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.
Au-Ppy-Cd-Au, Schottky Diodes A B E Reverse Bias C D Au Cd Ppy Au 150 nm
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.
Nano-Gap Fabrication On-Wire Lithography (OWL) 1. Removal of templates 2. Dispersion of wires Deposition of Au/Ti or SiO 2 Sonication Etching +
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.
Photo-Sensitive DPN Patterns at the Gap 2.0x10-9 Current / A 1.5x10-9 1.0x10-9 5.0x10-10 0.0-5.0x10-10 -1.0x10-9 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 -1.5x10-9 -2.0x10-9 With polymer -1.0-0.5 0.0 0.5 1.0 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
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
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.
Multicomponent Magnetic Nanorods for Biomolecular Separations
Affinity of Poly-His to Ni Blocks of Au- Ni-Au Nanorods A B A B ~ 4 10 9 Nanorods
Multicomponent Magnetic Nanorods for A Biomolecular Separations B 5 μm 5 μm C D
Anti-PolyHis Ig G Antibody Separation by Au-Ni-Au Nanorods
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
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.
Acknowledgements Purdue University (West Lafayette), Prof. Michael J. Weaver
Acknowledgements Northwestern University, Prof. Chad A. Mirkin NIH DARPA NSF ONR AFOSR