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Marwa M. Al-A’qarbeh (9130134)Adv. Electroanalytical
(0303912)
1
CONTENT
INTRODUCTION History Principle Application
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19501950
20002000
20002000
fabricate glass micro fiber
.
The introduction of UMEs to electroanalytical chemistry occurred principally through the independent work of Wightman and Fleischmann and their co-workers
Application with nanoscince and nanotechnolgy
SWCNT electro studeis and used SWCNT modified electrodes
19801980
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DEFINATION (UMEs)
commonly known as microelectrode: defined as electrodes whose critical dimension is in the micrometer range, although electrodes with radii as small as (1-10) µm have been fabricated.
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DEFINATION (UMEs)
critical dimension any region at electrode or at least one dimension, with smaller than 25 µm.
where double layer thickness 25 µm
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DEFINATION (Nanoelectrods)
are electrodes with critical dimensions smaller than 10 nm
much smaller than UMEs and double layer
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..
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INTRODUCTION
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10
..
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-18000
-16000
-14000
-12000
-10000
-8000
-6000
-4000
-2000
0
2000
-0.4 -0.2 0 0.2 0.4 0.6 0.8
Ptential/V (vs. Ag/AgCl)
Cur
rent
den
sity
/(uA
/cm
2)
Macro-, Micro-, and Nano- Electrodes
-1500
-1000
-500
0
500
1000
1500
-0.4 -0.2 0 0.2 0.4 0.6 0.8
potential (vs. Ag/AgCl)
curr
ent
den
sity
(A
/cm
2)
GC2mm dia.
Carbon fiber7m dia.
Semi-infinite planar linear diffusion Semi-infinite hemispherical diffusion:Current exhibits a steady state
I total = Iplanar + Iradial
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.
Short times. at sufficiently short times the thickness of the diffusion layer that is depleted of reactant is much smaller thanthe electrode radius
The mass transport process is dominated by linear diffusion to the electrodesurface
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PRINCIPLE
Long times the spherical character of the electrode becomes
important, and the mass transport process is dominated by radial or spherical diffusion
The steady-state response arises because the electrolysis rate isequal to the rate at which molecules diffuse to the electrode surface
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Properties of UMEs & NEs
Reduced Capacitance Reduced Charging Current Minimize Baseline Current
(Background)
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Properties of UMEs & NEs
Reduce Ohmic Effects (IR-Drop) Used in aqueous, non- aqueous, solid,
and gases phase Used may without supporting
electrolyte Enhance current density, increase
sensitivity of Liner sweep voltammitry, cyclic voltammitry, single and double chronoamperommitry
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UMEs & NEs fabrication
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UMEs & NEs fabrication
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UMEs & NEs fabrication
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Effect of non polar solvant and supporting electrolyte
Cyclic voltammograms for the reduction of 1 mM TCNQ inacetonitrile at a 12 4 pm radius Pt disk electrode Concentration of supporting electrolyte (TBAP) (A) 100 mM, (B) 1 mM, (C) no supporting electrolyte deliberately added
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PH -Sensors
Detection and quantification of H2 fluxes produced from a corroding magnesium alloy
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Biosensors
Disk-Shaped Amperometric Enzymatic Biosensor for in Vivo Detection of d-serine
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Enviromantal electroanalysis
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UME arrays
um
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Scanning Prob Microscope
Mirror
PSD
PiezoScanner
LED
Cantilever with tip
sample
z-Signal
Scanning electronics
Scanning Tunnling Microscope (STM)Scanning ElectroChemical Microscope (SECM)Atomic Force Microscope (AFM)
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Characterization of SECM-AFM tips
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Imaging polycarbonate membranes
AFM image (constant force mode)
SECM image
Diffusion profile
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Imaging polycarbonate membranes
AFM image
SECM image
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LIPIDS
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Carbon Nanotube Electrodes
P. M. Ajayan et al, Nano Lett., 1(2), 87(2001).
MWCNT bundleDia. 600 m, length ~1.5 mm
MWCNT bundleDia. ~200 nm, length ~30 m
R. M. Crooks et al, J. Am. Chem. Soc., 121, 3779 (1999).
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• Vertically aligned CNTs can be used to fabricate nanoelectrode array.
• The electrical and electrochemical properties of such nanoelectrode array have been thoroughly characterized.
• Chemical functionalization has been demonstrated to be highly selective at CNT ends.
• CNT nanoelectrode array has potential applications as highly sensitive DNA sensors
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Chemical Functionalization
Highly selective reaction of primary amine with surface –COOH group
i-Pr2NEtCO2
-CO2HDMF
N C N CyCy
N
O
O
HO
H2N FcO
HNFc
O
O N
O
O
FeFc =
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Functionalization of DNA
CO2H
NC
N
CH3
N
CH3
H
Cl-
O
CH3
HN
H2N ATGCCTTCCy3
ATGCCTTCCy3
CH3
H
Cl-
TACGGAAGGGGGGGGGGCy5
N
O
O
HO
SO3Na
CH3
C
O
NH
C
N
CH3
N
O
O
O N
O
O
SO3Na
O
HN ATGCC TTCCy3TACGGAAGGGGGGGGGGCy5
+
EDC
+
Sulfo-NHS
DNA probe
Target DNA
Cy3 image
Cy5 image36
3+
2+
e
3+
2+
CNT DNA SensorUsing Electrochemical Detection
MWNT array electrode functionalized with DNA/PNA probe as an ultrasensitive
sensor for detecting the hybridization of target DNA/RNA from the sample.• Signal from redox bases in the excess DNA single strands
The signal can be amplified with metal ion mediator oxidation
catalyzed by Guanine.
Ru bPy 3
2 37
Technical Platform
Top View
Side View
Each individual electrode is electronically
addressable with an array of CNTs with
d ~ 10 to 100 nm
dnn ~ 500 nm to 5000 nm
Each Electrode Immobilized with A Specific PNA or DNA Probes
10 to 200 m
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Electrochemical Detectionof DNA Hybridization
1st, 2nd, and 3rd cycle in cyclic voltammetry 1st – 2nd scan: mainly DNA signal2nd – 3rd scan: Background
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LOGO
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