Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
152 Cards in this Set
- Front
- Back
|
What are the 3 categories of analytical instruments used to characterize materials? |
1. Surface characterization 2. Bulk characterization 3. Chromatographic analysis |
|
|
TRUE OR FALSE: It's standard procedure to use only one method of material characterization. |
FALSE. Multiple procedures should be performed to accurately characterize the material. |
|
|
What is one of the vital parameters that determines cell-biomaterial interactions? |
Wettability! |
|
|
What is the Contact Angle? |
The quantitative measure of the angle maintained by a liquid at the boundary where the liquid, solid, and gas phases intersect. |
|
|
What does a contact angle of 0 mean? |
COMPLETE wettability (very hydrophillic surface) |
|
|
What does a contact angle of 180 mean? |
Completely NON-wettable (very hydrophobic surface) |
|
|
What is hydrophilicity in terms of adhesive force? |
Force between molecules of liquid (cohesive force) is lower than the force between the liquid molecules and the molecules of the solid surface. |
|
|
What is hydrophobicity in terms of adhesive force? |
The cohesive force between the liquid molecules is greater than adhesive force between the liquid molecules and the molecules of the solid surface. |
|
|
What are the 2 known parameters of Young's equation? |
Surface tension between liquid and vapor and Contact angle! |
|
|
The surface energy between the solid and vapor can be determined using what 2 techniques? |
1. Zisman method 2. Solving simultaneous equations |
|
|
How does the Zisman method work? |
Plots known values of y(lv) against the contact angle measured and extrapolating the plot to the contact angle 0. This determines y(sv) |
|
|
Y(sv) is also known as what? |
Critical surface tension |
|
|
Unlike the Zisman method, what does solving simultaneous equations need to find y(sv)? |
Requires the use of two DIFFERENT liquids with known y(lv) values. |
|
|
What is a Goniometer? |
A static way to measure contact angle |
|
|
What are the 3 disadvantages of Goniometry? |
1. Drop volume control 2. the time over which the angle is measured 3. the accuracy of the operator in measuring the angles
|
|
|
Today's sessile drop system consists of what 5 things? |
1. A platform for the sample 2. A syringe that places a liquid drop on surface 3. A light source 4. a charge-coupled device camera and lens to capture the image 5. a computer to process the image |
|
|
What are the 2 methods of measuring contact angles with goniometry? |
1. One drop of liquid and one contact angle measurement 2. Measuring contact angle after additional droplets are added - angle of plateau is called the Advanced Contact Angle |
|
|
What is Receded Contact Angle? |
The contact angle obtained by REMOVING additional droplets from the surface |
|
|
What is the difference between advanced and receded contact angles? |
Contact Angle Hysteresis |
|
|
What does Contact Angle Hysteresis provide? |
Information on the homogeneity or heterogeneity of a surface |
|
|
What does a low hysteresis loop indicate? |
That the surface is HOMOGENEOUS |
|
|
What does a high hysteresis loop indicate? |
That the surface is HETEROGENEOUS |
|
|
How is the contact angle measured in a Tensiometer? |
Contact angle is measured when the liquid, solid, and vapor boundaries are in MOTION. |
|
|
What is the major difference between goniometry and tensiometry? |
The angle measured by Goniometry is dependent ONLY on the material surface in contact with the droplet whereas the angle measured by Tensiometry is dependent on the ENTIRE material in contact with the liquid. |
|
|
What are the 3 disadvantages of Tensiometry? |
1. Material surface composition must be consistent 2. Material has to be small enough to test 3. Different operators get different Contact Angles |
|
|
What are the 2 advantages of Tensiometry? |
1. Simplicity 2. Inexpensive |
|
|
When a vibrating molecule is exposed to infrared radiation (IR), what happens to the molecule? |
The molecule absorbs the portion of radiation whose frequency is equal to the frequency of the vibration. |
|
|
An analysis of the remaining portion of IR radiation transmitted through the sample provides what information? |
Information regarding the frequencies absorbed by the sample and information regarding molecular structure |
|
|
Infrared Spectroscopy consists of what 3 things? |
1. IR radiation source 2. A monochromator 3. A detector |
|
|
What does the monochromator do? |
Disperses radiation into its constituent wavelengths and processes 1 wavelength at a time. |
|
|
What does the detector do in IR spectroscopy? |
It measures the intensities of different wavelengths |
|
|
What is the main limitation of conventional dispersive IR spectroscopy? |
Long scan time |
|
|
In Fourier Transform Infrared Spectroscopy (FTIR), the monochromator has been replaced by what? |
Interferometers which are high speed and very sensitive |
|
|
What are the 6 different modes of stretching and bending? |
1. Symmetric stretching 2. Asymmetric stretching 3. Scissoring 4. Rocking 5. Wagging 6. Twisting' |
|
|
TRUE OR FALSE: In FTIR, all wavelengths of radiation are processed simultaneously and a Fourier transformation is applied. |
TRUE |
|
|
What does the Fourier Transformation do? |
It converts the plot of signal intensity and time to a plot of wavenumber and absorbance intensity. |
|
|
What are the units of wavenumber? |
1/cm |
|
|
What is wavenumber? |
The number of waves per unit length |
|
|
TRUE OR FALSE: FTIR has very high signal-to-noise ratios. |
FALSE. FTIR has pretty low SN ratios. |
|
|
Wavenumber is directly proportional to what? |
To the energy of IR absorption |
|
|
What are the 4 sampling modes of FTIR? |
1. Attenuated Total Reflection (ATR) 2. Specular reflectance 3. IR Reflection Absorption Spectroscopy (IRRAS) 4. Diffuse reflectance IR Fourier transform spectroscopy (DRIFTS) |
|
|
How does Attenuated Total Reflection work? |
1. Sample is pressed against ZnSe or Ge crystal having high refractive index. 2. IR enters the crystal and reflects through the crystal several times. 3. Evanescent waves are produced 4. Waves penetrate sample (1-5 um) 5. Waves undergo attenuation depending on energy absorbed 6. Attenuated energy of waves is passed back to IR detector |
|
|
What can ATR tell us? |
Significant structural information about polymers and proteins |
|
|
What are Evanescent waves? |
Waves which undergo total internal reflection because they strike at an angle GREATER than the critical angle. |
|
|
In specular reflectance sampling mode of FTIR, the angle of reflection of the IR beam is equal to what? |
Its angle of incidence |
|
|
Specular reflectance is used to study what? |
Thin films on smooth and reflective surfaces |
|
|
What angle range is used in specular reflectance? |
30-45 degrees from normal |
|
|
In IR Reflection Absorption Spectroscopy (IRRAS), the angle of incidence of the IR beam is what? |
80 degrees or greater |
|
|
IRRAS is also known as what? |
Grazing angle analysis |
|
|
IRRAS is used to study what? |
Self-assembled monolayers (1-3 nm thick) on reflective gold surfaces or any films with thickness less than 10nm. |
|
|
The use of a polarizer in conjugation with IRRAS reveals what? |
Information regarding the orientation of molecules on the metal surface |
|
|
Diffuse reflectance IR Fourier Transform Spectroscopy (DRIFTS) is used for what? |
Analysis of particles, powders, and rough surfaces |
|
|
In DRIFTS, when the scattered radiation comes out of the sample, what happens? |
It is collected and focused on the detector using a large spherical mirror |
|
|
What is crucial in determining the efficiency of the DRIFTS technique? |
particle size |
|
|
What is the penetration depth of IR radiation in DRIFTS? |
~100 um |
|
|
What is XPS? Other name? |
X-Ray photoelectron Spectroscopy is also called Electron Spectroscopy for Chemical Analysis (ESCA) |
|
|
XPS consists of what 4 things? |
1. X-ray source 2. Ultrahigh vacuum chamber 3. an electron energy analyzer 4. a computer to process data |
|
|
In XPS, what is measured from ejected electrons? |
Kinetic energy! |
|
|
Binding energy in XPS is calculated using what formula? |
BE = hv - KE
h - Plank's constant v - frequency of radiation KE - kinetic energy |
|
|
What 2 x-ray sources are typically used in XPS? |
Aluminum and Magnesium |
|
|
Why are samples placed in a vacuum for XPS? |
1. To avoid sample contamination 2. To maximize the photoelectrons reaching the analyzer |
|
|
XPS detects the presence of what? |
All elements EXCEPT hydrogen and helium |
|
|
XPS gives what 2 pieces of information? |
1. Elemental presence 2. Chemical bonding info |
|
|
The bonding energies of electrons coming from an atom can be different depending on what? |
On its bonding to the neighboring elements |
|
|
XPS spectrum is presented with what on the y-axis and what on the x-axis? |
y-axis: Intensity x-axis: binding energy |
|
|
What is the sampling depth of XPS? |
1-10 nm |
|
|
Although XPS is a surface sensitive technique, depth profiling can provide what information? |
Elemental information regarding the material's subsurface. |
|
|
During depth profiling in XPS, a chemically inert beam of energetic ions are used to do what? It can provide information regarding the subsurface up to what depth? |
Etch the sample surface and the new surface thus obtained is analyzed using XPS up to 1 um! |
|
|
What is the peak of C 1s always at in XPS? Why is this important? |
285 eV! This value is used to calibrate the rest of the peaks so different XPS data can be compared. |
|
|
The use of angle-resolved XPS permits the estimation of what? |
Film thickness and thickness of contaminated layers |
|
|
SIMS is able to determine what 8 things about a material surface? |
1. Molecular conformation 2. Orientation 3. Nobility 4. Sample damage 5. Extent of cross-linking 6. Molecular interactions 7. Identification of surface-active additives 8. Chemical map of surface |
|
|
What are the 6 components of SIMS? |
1. A primary ion gun 2. an ultrahigh vacuum chamber 3. An energy analyzer 4. a mass analyzer 5. an ion detector 6. a computer to process data |
|
|
What are the primary ions used in SIMS? |
Argon, Xenon, Oxygen, Gallium, and Cesium |
|
|
What kind of particles are emitted once the primary ions collide with a surface? |
Secondary particles! |
|
|
Secondary particles consist mostly of what? What else? |
Neutral species and secondary ions (1% though) |
|
|
What does the energy analyzer do? |
Separates the secondary ions from the mixture of secondary particles and passes them on to the mass analyzer |
|
|
What does the mass analyzer do? the detector? |
It separates the secondary ions based on their mass to charge ratio and the detector counts the number of ions according to their mass to charge ratio. |
|
|
What is the most commonly used mass analyzer? |
Time of Flight |
|
|
How does the Time of Flight calculate the mass to charge ratio of secondary ions? |
Based on the time taken by the ions to reach the detector |
|
|
Data from SIMS is presented with what on each axis? |
mass to charge ratio (m/z) on the x-axis intensity on the y-axis |
|
|
In SIMS, how can elements be identified? |
By their m/z ratio! |
|
|
In static SIMS, what is done? |
A low dose of primary ions is employed and involves minimal damage to a surface |
|
|
In dynamic SIMS, what is done? |
A high dose of primary ions is employed to obtain chemical composition of a surface at different depths. Surface is degraded however. |
|
|
TRUE OR FALSE: SIMS is not a destructive technique. |
FALSE. It is a destructive technique. |
|
|
SIMS provides information regarding how deep into a surface? What does it detect? |
It detects all elements including hydrogen 1 nm into the surface. |
|
|
TRUE OR FALSE: SIMS cannot detect the difference between isotopes of an element. |
FALSE. It CAN detect isotopes. |
|
|
SIMS is not commonly used for what? Why? |
Quantification of elements because the intensity of secondary ions is not directly proportional to concentrations of elements on a surface. |
|
|
Atomic force microscopy is used to obtain what information? |
3D images of material surfaces |
|
|
What are the 5 components of AFM? |
1. A flexible cantilever with a sharp tip (of a few nm) 2. A piezoelectric tube scanner capable of moving the sample in x,y, and z directions 3. A laser source 4. A photodetector 5. Computer |
|
|
In order to maintain a constant force between the probe and the sample surface in AFM, what is done? |
A piezoelectric scanner moves the sample up and down so the probe can follow the contour of the surface |
|
|
The force generated between the probe and the sample surface in AFM can be quantified using what law? |
Hooke's law: F = -kx |
|
|
The quantification of forces using AFM has made it possible to do what? |
To determine the force of interaction between two biomaterials |
|
|
In AFM, which mode is best for rigid samples? |
Contact mode! |
|
|
In AFM, which mode is best for soft samples? |
Tapping mode! |
|
|
AFM can provide what level of resolution of a material surface? |
Atomic resolution! |
|
|
TRUE OR FALSE: No special surface treatment is necessary for imaging samples with AFM. |
TRUE |
|
|
What are 4 disadvantages of AFM? |
1. It's limited to the vertical scan range (10 um) and the XY scan range (100x100 um) 2. Articles are common in AFM do to contamination 3. Artifacts common 4. Surface sensitive |
|
|
SEM is commonly used to image what? |
The topography of a surface |
|
|
SEM consists of what 6 things? |
1. Electron gun 2. Set of electromagnetic lenses and apertures 3. Scanning coils 4. Sample chamber 5. Detector 6. Computer |
|
|
In SEM, the collision of electrons on the sample surface causes what? |
Elastic and inelastic scattering to generate secondary electrons and backscattered electrons and X-rays. |
|
|
Secondary electrons, backscattered electrons, and X-rays are used to obtain information on what 3 things, respectively? |
Topography, atomic number, and chemical composition, respectively. |
|
|
Inelastic scattering of electrons results in what? |
the transfer of their energy (partly or all) to the colliding atoms |
|
|
What is the detector system commonly used in SEM? |
Everhart-Thornley |
|
|
In SEM, secondary electrons are attracted to the detector using what? Then what? |
A positively charged Faraday cage and then accelerated to a positive-charged scintillator at the back of the cage. |
|
|
What does the scintillator do? Then what? |
It converts electrons into photons of light which are then transferred to a photomultiplier tube |
|
|
What does the photomultiplier tube due in SEM? Then what? |
It converts photons back into electrons and the collected signal is amplified and displayed on a cathode ray tube. |
|
|
In SEM, the analysis of the energy and intensity of the X-rays emitted can be used to determine what? |
Chemical composition of the material surface |
|
|
In SEM, why is energy dispersive X-Ray analysis not considered to be a surface sensitive technique? |
Because the x-rays are produced from a depth of a micron or more within the sample |
|
|
What does a sample have to be in order to undergo SEM characterization? |
Conductive or semi-conductive! |
|
|
If a coating is not applied to non-conductive materials for SEM characterization, what happens? |
The charge-build may lead to poor quality images |
|
|
What is used extensively to study material surfaces and for visualizing cell-material interactions? |
SEM! |
|
|
What is used to study the microtexture and crystal structure of samples? |
Transmission electron microscopy (TEM) |
|
|
What is the resolution of TEM? |
Up to 0.1 nm |
|
|
Which electrons are of importance in TEM? Why? |
Non-scattered electrons because they go on to hit the fluorescent screen placed at the bottom of the microscope and an image is generated based on the density of the materials present inside the specimen |
|
|
In TEM, if the area is less dense, does a smaller or larger number of electrons pass through? |
Larger number |
|
|
In order to be characterized by the TEM, what must be true of the sample? |
It must be ultrathin (100nm) |
|
|
What three techniques are used to making ultrathin specimens? |
1. Electrolytic thinning 2. Ion milling 3. Ultramicrotomy (most common for bio and polymer samples) |
|
|
What are the 2 TEM modes? |
1. image mode 2. diffraction mode |
|
|
What is visualized in the image mode of TEM? |
Microstructure |
|
|
What is determined in the diffraction mode of TEM? |
Crystal structure by recording the electron diffraction pattetrn on the screen |
|
|
A single crystal, a polycrystalline material, and an amorphous material will produce what patterns, respectively? |
Single crystal - spots Polycrystalline - rings Amorphous - diffuse halos |
|
|
TRUE OR FALSE: TEM specimen preparation is simple and easy. |
FALSE. It's laborious. |
|
|
TEM is also extensively used to characterize what 4 things? |
1. nanoparticles 2. dendrimers 3. carbon nanotubes 4. quantum dots |
|
|
What is a non-destructive technique commonly used to characterize the crystallographic structure and physical properties of materials? |
X-Ray Diffraction (XRD) |
|
|
What are the 4 components of XRD? |
1. X-ray generator 2. A diffractormeter unit 3. detector 4. Computer |
|
|
When a beam of monochromatic x-rays are allowed to irradiate on a crystalline material, what happens to the x-rays? |
they reflect or diffract at different angles with respect to the primary beam which are related by Bragg's law |
|
|
In XRD, the spacing between the atomic planes of the crystal lattice provides what information? |
Information regarding the dimensions of the unit cell of the crystal |
|
|
The intensities of the diffraction peaks in XRD provide what information? |
Information regarding the position of atoms in the unit cell of the crystal |
|
|
In XRD data, what data is present on each axis? |
x-axis: scattering angle y-axis: intensity of diffraction peaks
|
|
|
Each peak in XRD denotes what? |
Diffraction from a certain crystallographic plane |
|
|
In XRD, sharp peaks indicates what? |
fully crystalline material |
|
|
In XRD, broad peaks indicates what? |
amorphous material |
|
|
Although XRD does not have the capability to quantify elemental or molecular composition, what does it provide? |
Inferred chemical composition once crystalline phases are identified |
|
|
What is the main component of FTIR and what does it do? |
The interferometer disperses the radiation provided by the IR source into its component frequencies |
|
|
What is the Michelson Interferometer? |
Interferometer consisting of 1 stationary and 1 moving mirror with a beam splitter made of potassium bromide coated with germanium |
|
|
ATR lets you test what 3 things? |
1. Liquid 2. Powders 3. Protein adsorption |
|
|
FTIR is only non-destructive when what is true? |
Sample is tested in DRY state |
|
|
What are the 3 disadvantages of FTIR? |
1. Information is dependent on detector/accessories used 2. Limited to molecules that exhibit changes in dipole moment 3. surface sensitive (contaminants) |
|
|
In AFM, which has a better resolution: tapping mode image or amplitude image? |
Amplitude image! |
|
|
What are 4 advantages of AFM? |
1. True atomic resolution 2. No surface treatment necessary 3. Ambient conditions 4. 3D images |
|
|
SEM/EDX allows us to find what? How is this different from XPS? |
Elemental chemistry in the BULK. XPS only shows elemental chemistry on the surface. |
|
|
What are 2 quantitative information obtained from SEM? |
1. Pore size measurement 2. Growth of thin films over time |
|
|
What is EDX? What does it give us? |
Energy Dispersive X-Ray Spectroscopy gives us Elemental Mapping |
|
|
What is the resolution depth of EDX? Probe size? |
1-5um with a probe size of 1um |
|
|
What does EDX not tell us about elements? |
How they are bonded |
|
|
What are the 4 advantages of EDX? |
1. Some surface morphology info 2. Bulk quantification of elemental composition 3. Data can be obtained in vacuum or ambient environment 4. Non-destructive as long as the sample is conductive |
|
|
What are the disadvantages of EDX? |
1. No structural information 2. Chemical info dependent on detector 3. Limited to carbon atoms and above |
|
|
What are 4 advantages of XRD? |
1. Quantification of surface and bulk 2. Quantification of crystallinity 3. Data collected in ambient environment 4. Non-destructive |
|
|
What is the difference between XPS and FTIR? |
XPS gives you ELEMENTAL composition while FTIR gives you MOLECULAR composition |
|
|
What are the 4 advantages of XPS? |
1. Quantification of surface and sub-surface chemistry 2. Some structural information 3. Non-destructive if no depth profile 4. Detects all elements EXCEPT hydrogen and helium |
|
|
What are the 5 disadvantages of XPS? |
1. No bulk information 2. Very costly 3. Has to be done in ultra-high vacuum 4. Destructive if depth profile done 5. Surface sensitive |
|
|
What is the resolution depth of XPS? Probe size? |
1-10 nm with a probe greater than 10 um |
