Download 2. Biosensors

Surface
Chemistry
< Analytical Chemistry >
Contents
1.
2.
3.
4.
5.
Surface Chemistry
Biosensors
TEM
SEM
AFM
1. Surface Chemistry
 What is the Surface Chemistry?
- Surface Science is the study of Physical and Chemical
Phenomena that occur at the interface of two phases. It includes
the fields of Surface Chemistry and Surface Physics.
Fig. 1. Research infrastructure at the surface science
2. Biosensors
 Sensors(1)
- Designed for the continuous monitoring of the physicochemical
or biochemical properties of specific analytes
⇒ To provide Qualitative and/or Qunatitative analytical data.
- Composition
Fig. 2. Schematic diagram of a chemical or biosensor.
2. Biosensors
 Sensors(2)
Biosensor
- A thin layer of substance incorporating an immobilized
reagent that contains Biorecognition sites
(Biorecognition : Especially as part of the Immune system)
- Reagents are immobilized by Entrapment or Binding.
- Properties of Biosensors
⇒ Robustness, Rapid and Reproducible Response, Appropriate
Selectivity/Specificity and Working Range
⇒ Stable Operation
2. Biosensors
 Electrochemical Sensors
Potentiometric Sensors
- Based on Ion Selective Electrodes, Solid State Redox Electrodes and
Field Effect Transistors(FETs).
Biosensors ;
- Can be made by coating a Glass Electrodes with a layer of an enzyme
immobilized on the surface which catalyzes a biochemical reaction.
CO(NH2)2 + 2H2O + H
+
Urease
+
→ 2NH4 + HCO3
+
NH4 + OH → NH3 + H2O
Fig. 3. Biosensor based on an enzyme-coated
ammonium ion-selective electrode.
2. Biosensors
 Optical Sensors(1)
- Responding to the absorption or fluorescent emission of
electromagnetic radiation by analytes, indicators or analytereceptor complexes at characteristics wavelengths.
- Composition
• Path of Radiation
• Optrodes
Fig. 4. Optical sensor with Y-configuration cell.
2. Biosensors
 Optical Sensors(2)
- To monitor pH, metal ions, dissolved gases and organic compounds
down to ppm and ppb concentration using Radiation in the visible,
ultraviolet and near infrared regions by absorbance, Fluorescence or
reflectance.
- Advantages of Optical Sensors
→ Not requiring an electro system
→ Providing valuable spectral information over a range of
wavelengths
- Disadvantages of Optical Sensors
→ Effecting from ambient light interference(depletion of
Immobilized reagents)
→ Slowing kinetics of the reactions between analytes and reagents
2. Biosensors
 Themal- and Mass-Sensitive Sensors
Thermal-Sensitive Sensors
- Measuring Heat of Reaction generated by the oxidation of an analyte
or its reaction with a reagent
- Thermal biosensors incorporating Thermistors measure heats of
reaction of enzymes in the detection of urea, glucose, penicillin and
cholesterol.
Mass-Sensitive Sensors
- Based on Piezoelectric Quartz Crystal Resonators covered with a
gas-absorbing organic layer.
- Absorption of an analyte gas causes a change in Resonance
frequency and which is sensitive down to ppb levels.
2. Biosensors
 Sensor arrays
- These are groups of sensors that allow simultaneous monitoring
with different instrumental parameters and/or different sensor
elements.
- Being operated at different electrical potentials, frequencies or
optical wavelengths.
- Being constructed from Three Ion-selective Field Effect
Transistors
Fig. 5. FET sensor arrays for monitoring pH, sodium and potassium.
2. Biosensors
 Applications
Nano-bio Technologies(NBT)
· Protein Chip
- To determine the presence and/or amount (referred to as
relative quantitation) of proteins in biological samples.
- Applications of Protein Chip
① Biochip
② Molecular imaging of the Cell
→ Structural Nano Imaging
→ Real-time Nano Imaging
- Detection Methods
① Fluorescence Detection
② Label-free Detection : AFM, SPR, etc.
3. TEM
 Comparison of Microscopes
•
Fig. 6. Comparison of LM, TEM, SEM.
3. TEM
 Principles (1)
- A beam of electrons is transmitted through an ultra thin specimen,
interacting with the specimen as it passes through. An image is
formed from the interaction of the electrons transmitted through
the specimen.
•
•
•
•
Electron Gun
Anode Plate
Lens System
Image Recording System
Fig. 7. Composition of TEM.
3. TEM
 Principles (2)
• Lens System
- Condensor Lens
- Objective Lens
• Image Recording System
- Projection Lens
Fig. 8. Lens system of TEM.
3. TEM
 Properties
• High Resolution : 0.4nm
• Variable Analysis
- BF(Bright Field), DF(Dark Field), etc. → By Electron
Diffraction
• Structural Analysis of Solid Sample
• Analysis in air
• Complex Sample Pre-treatment
• Slow Analysis
3. TEM
 KBSI in Jeonju
Charteristics
- Accelerated electrons : : 200keV
- Resolution : 0.1nm
4. SEM
 Principles (1)
- Accelerated electrons in an SEM carry significant amounts of kinetic energy,
and this energy is dissipated as a variety of signals produced by electronsample interactions when the incident electrons are decelerated in the solid
sample.
• Electron Gun
- Thermionic Electron Gun
- Field Emission Electron Gun
• Anode Plate
• Lens system
• Scanning Coils
• Detector
• TV Scanner
Fig. 9. Composition of SEM.
4. SEM
 Principles (2)
• Magnetic Lens
- Condenser Lens
- Objective Lens
• Aperature
• Scanning coil, Stigmator
Fig. 10. Lens system of SEM.
4. SEM
 Principles (3)
• Detection
- Topography, Morphology
⇒ SE (Secondary Electron)
- Topography, Crystallography,
Composition
⇒ BSE (Backscattered Electron),
EBSD (Electron Backscattered
Diffraction)
- Composition
⇒ X-ray (EDS : Energy Dispersive
Spectrometer), WDS : Wave
Dispersive Spectrometer), CL
(Cathode Luminescence)
Fig. 11. Scattering of electrons
4. SEM
 Properties
• High Resolution
•
•
•
•
(SEM : 3~5 nm , FE-SEM : 0.5~2 nm)
Various Range of Magnification
Deep Depth of Field
-5
High Vacuum Working (under 10 Torr)
Sample
- Coated by Au or Pt ⇒ “Charge-up Effect”
- Representative Sample
- Physical & Chemical Stability
- Clean Surface
- Roughness
4. SEM
 KBSI in Jeonju
- Manufacturer
Hitachi Japan
- Model No.
S-4700
- Year
2001
- Resolution
1.5nm
4. SEM
 KBSI in Jeonju
- Manufacturer
Hitachi Japan
- Model No.
S-5500
- Year
2006
- Resolution
0.4nm
5. AFM
 Principles (1)
- It measures the forces acting between a fine tip and a sample.
Attractive or Repulsive forces resulting from interactions between
the tip and surface will cause a positive or negative bending of
the cantilever.
Fig. 12. Principle of AFM and the scanned cantilever/tip system.
5. AFM
 Principles (2)
Force-distance Curve
Fig. 13 . Scheme of force-distance curve
5. AFM
 Modes(1)
Fig. 14. Modes of AFM
5. AFM
 Modes(2)
1. Contact mode
· Advantages
- High scan speeds
- “Atomic resolution” is possible
- Easier scanning of rough samples with extreme
changes in vertical topography
· Disadvantages
- Lateral forces can distort the image
- Capillary forces from a fluid layer can cause large
forces normal to the tip-sample interaction.
- Combination of these forces reduces spatial resolution
and can cause damage to soft samples.
5 .AFM
 Modes(3)
2. Non-contact mode
· Advantages
- Low force is exerted on the sample surface and no
damage is caused to soft samples.
· Disadvantages
- Lower lateral resolution, limited by tip-sample separation.
- Slower scan speed to avoid contact with fluid layer.
5 .AFM
 Modes(4)
3. Tapping mode
· Advantages
- Higher lateral resolution (1nm to 5nm)
- Lower forces and less damage to soft samples in air
· Disadvantages
- Slower scan speed than in contact mode
5 .AFM
 KBSI in Jeonju
- Manufacturer
Veeco
- Model No.
Nanoscope Ⅳ Multimode AFM
- Year
2004
- Resolution
Laterally : 400nm
Vertically : 400nm
5 .AFM
 KBSI in Jeonju
- Manufacturer
AFM : NT-MDT
Raman : Tokyo Instrument
- Model No.
Nanofinder 30
- Year
2004
- Resolution
Laterally : 200nm
Vertically : 500nm
+ obtaining resolution : 50nm