characterization techniques of nanoparticles

Welcome1

Advancements in Characterization Techniques of Nanoparticles

Prithusayak MondalDivision of Agricultural Chemicals

Chairperson : Dr. Anupama SinghSeminar Leader : Dr. Suman Gupta 2

Characterization refers to the study of material’s features such as its composition, structure,& various properties like physical, electrical, magnetic etc.

Nano = 10-9 (extremely small) Particle = Small piece of matter

Nanoparticle is a microscopic particle whose size is measured in nanometers (nm). These particles can be spherical, tubular, or irregularly shaped and can exist in fused, aggregated or agglomerated forms. (PAS71: 2005,UK)

3

Nanoparticles are defined as particles that have at least one dimension in the nanorange (1 to 100nm). (Maurice & Hochella, 2008)

Size ranges of nanoparticles

4

5

“To understand the very large, we must understand the very small.”

- Democritus (400 BC)

Classification

6

Nanoparticle

Organic nanoparticle Inorganic nanoparticle

Novel Properties of nanoparticles

• Small size• High surface area

• Ease to suspend in liquids• Deep access to cells and organelles

• Improved physical, chemical & biological properties

Properties of nanoparticles are different from their bulk counterparts.

Extremely high surface area to volume ratio results in surface

dependent material properties.

7

Industry

UsesOf

Nanoparticles

Defence & security

Ecology & environment

Information technologyEnergy

Medical Agriculture

Consumer goods

8

Enhanced catalytic properties of surfaces of nano ceramics or those of noble metals like platinum and gold are used in the destruction of toxins and other hazardous chemicals. (Salata, 2005)

Synthesis and characterization of collagen/hydroxyapatite: magnetite nano-composite material for bone cancer treatment. (Ecaterina et al., 2010)

Antimicrobial effects of silver nanoparticles. (Kim et al.,2007)

Removal of arsenic (III) from groundwater by using different concentration of nanoscale zero-valent iron (Kanel., 2005).

Targeted drug delivery

Silver nanoparticles inhibited the binding of the virus to the host cells in vitro (Elechiguerra et al., 2005).

Cells and S layer protein nanoparticles of Bacillus sphaericus JG A12 have been found to have special capabilities for the clean up of uranium contaminated waste waters (Duran et al., 2007).

Magnetosome particles isolated from magnetotactic bacteria have been used as a carrier for the immobilization of bioactive substances such as enzymes, DNA, RNA and antibodies (Mohanpuria et al., 2007).

The gold nanoparticles synthesized from E. coli may be used for realizing the direct electrochemistry of haemoglobin (Du et al., 2007).

Metal nanoparticle embedded paints have been synthesized using vegetable oils and have been found to have good antibacterial activity (Kumar et al., 2008).

11

Nanoparticles in agrochemicals

Nano-encapsulated and solid lipid nanoparticles have been explored for the delivery of agrochemicals . (Frederiksen et al., 2003)

The development of organic–inorganic nanohybrid material for controlled release of the herbicide 2,4-dichlorophenoxyacetate. (Bin Hussein et al., 2005)

Porous hollow silica nanoparticles, developed for the controlled delivery of the water-soluble pesticide validamycin with a high loading capacity (36 wt%), have been shown to have a multistaged release pattern. (Liu et al., 2006)

The development of a nano-emulsion (water/poly-oxyethylene) non-ionic surfactant (methyl decanoate) containing the pesticide beta-cypermethrin. (Wang et al., 2007)

12

Characterization Techniques

13

Optical(Imaging) Probe Characterization Techniques

Electron Probe Characterization Techniques

Scanning Probe Characterization Techniques

Photon(Spectroscopic) Probe Characterization Techniques

Ion-particle probe Characterization Techniques

Thermodynamic Characterization Techniques

TYPES

14

Optical(Imaging) Probe Characterization Techniques

Acronym Technique Utility

CLSM Confocal laser-scanning microscopy Imaging/ultrafine morphology

SNOM Scanning near-field optical microscopy Rastered images

2PFM Two-photon fluorescence microscopy Fluorophores/biological systems

DLS Dynamic light scattering Particle sizing

BAM Brewster angle microscopy Gas-liquid interface Imaging

15

Dynamic light scattering

16

Particles, emulsions & molecules in suspension undergo Brownian motion.

If the particles are illuminated with laser, the intensity of scattered light fluctuates.

Analysis of these intensity fluctuations yields the particle size(radius, rk) using Stokes- Einstein relationship,

rk =kT/6πηD where k = Boltzmann’s constant T = Temperature η = Viscosity D = Diffusion coefficient

Basic principle

(Movie courtesy of Dr. Eric R. Weeks,Physics Department, Emory University.)

17

http://www.physics.emory.edu/~weeks/

What does Dynamic Light Scattering measure?

The diameter measured in DLS is called the hydrodynamic diameter and refers to how a particle diffuses within a fluid. The diameter obtained by this technique is that of a sphere that has the same diffusion coefficient as the particle being measured.

The diffusion coefficient will depend not only on the size of the particle “core”, but also on any surface structure, as well as the concentration and type of ions in the medium.

18

Instrumentation

DLS

Detector system

Optical system

Light source

Digital correlator

19

Light source

Practical requirements for a sufficiently intense light source demand a narrow-band, polarized, monochromatic, CW laser.

Type Wavelength Power Size

HeNe 632.8 nm 5-35 mW 0.40- 1.5m

Laser diodes 635-780 nm 5-100m\V 0.05-0.15 m

Ar+(air cooled) 488-514.5 nm ~100mW 1m

Ar+(water cooled) 488-514.5 nm ~1.7W 1.5-2m

DPSS (Frequ. Doubled)

532 nm 10m\V-4W 0.2 -0.5m

20

Optical system

The scattered light is focused onto a PMT at an angle 60 by another lens. Systems like this are constructed on a precision turntable with a stepper motor, and typically allow experiments to be conducted over a 10°-160° angular range.

A lens focuses the laser beam down into the sample which is enclosed in a temperature-controlled scattering cell surrounded by a refractive index matching liquid.

21

Detector system

PMTs are almost universally used as detectors in DLS experiments.

Single photon counting mode (SPCM) which incorporates an avalanche photo diode (APD), active reset and quenching electronics and a Peltier-type temperature controller in a small package.

22

Digital correlator

23

The ACF is formed by recording the number of photons arriving in each sample time, maintaining a history of this signal over a large range of sample times (time series), multiplying the instantaneous and the delayed signal for a range of time delays & accumulating these products.

Optical mixing mode : Self beating, homodyning & heterodyning

The typical measurement duration is from 1 to 10 minutes.

The DLS technique is commonly employed in the range of 0.002 to 2 microns.

The sample must be a liquid, solution or suspension & very dilute too, otherwise scattering of light can be unclear.

24

• Measurements are fast, from seconds to minutes.

• Very small quantities of sample can be measured.

• Any suitable suspending liquid (non-absorbing, relatively clear and not too viscous) can be used.

• The technique is applicable from about 0.001 to several microns.

Advantages

25

Disadvantages• It does not produce a high-

resolution histogram of the size distribution.

• Shape information is not easily obtained.

• Multiple scattering affects the data analysis.

• Dust can make measurement and interpretation difficult.

26

Electron Probe Characterization Techniques


SEM Scanning electron microscopy Raster imaging/topology morphology

EPMA Electron probe microanalysis Particle size/local chemical analysis

TEM Transmission electron microscopy Imaging/particle size-shape

HRTEM High-resolution transmission electron microscopy

Imaging structure chemical analysis

STEM Scanning transmission electron microscopy

Biological samples

LEED Low-energy electron diffraction Surface/adsorbate bonding

EELS Electron energy loss spectroscopy Inelastic electron interactions

AES Auger electron spectroscopy Chemical surface analysis

27

Scanning Electron Microscopy

28

When the beam of electrons strikes the surface of the specimen & interacts with the atoms of the sample, signals in the form of secondary electrons, back scattered electrons & characteristic X-rays are generated that contain information about the samples’ surface topography, composition etc.

Basic principleBasic principle

29

There are 3 modes –

Primary: High resolution (1-5 nm); secondary electron imaging

Secondary: Characteristic X-rays; identification of elemental composition of sample by EDX technique

Tertiary: Back-scattered electronic images; clues to the elemental composition of sample

Operation modesOperation modes

30

In a typical SEM, the beam passes through pairs of scanning coils or pairs of deflector plates in the electron column to the final lens, which deflect the beam horizontally & vertically.

Electronic devices are used to detect & amplify the signals & display them as an image on a cathode ray tube in which the raster scanning is synchronized with that of the microscope.

The image displayed is therefore a distribution map of the intensity of the signal being emitted from the scanned area of the specimen.

31

The sample must be electrically conductive at the surface.

Time consuming & expensive.

Sometimes it is not possible to clearly differentiate nanoparticle from the substrate.

SEM can’t resolve the internal structure of these domains.

SEM can yield valuable information regarding the purity as well as degree of aggregation.

32

In ESEM, samples can be looked at in a low pressure gas environment as opposed to a vacuum. GSED posseses as much as a 600-Volt positive bias on it to attract secondary electrons compared to the ET SED on a normal SEM, which ordinarily has only as much as a 300-Volt positive bias and also the former is relatively far from the sample. Thus the GSED is set up to collect secondary electrons very efficiently.

While using ESEM it is not necessary to make nonconductive samples conductive. Materials samples do not need to be desiccated and coated with gold–palladium, for example, and thus their original characteristics may be preserved for further testing or manipulation.

Environmental SEMEnvironmental SEM

33

Transmission Electron Microscopy

34

The crystalline sample interacts with the electron beam mostly by diffraction rather than by absorption. The intensity of the diffraction depends on the orientation of the planes of atoms in a crystal relative to the electron beam.

A high contrast image can be formed by blocking deflected electrons which produces a variation in the electron intensity that reveals information on the crystal structure.

This can generate both ‘bright or light field’ & ‘dark field’ images.

Basic principle

35

36

TEM enables Direct 2-D imaging of particle size, shape & surface characteristics.

Changes in nanoparticle structure as a result of interactions with gas, liquid & solid-phase substrates can also be monitored.

Sample must be able to withstand the electron beam & also the high vacuum chamber.

Time consuming.

It needs an analysis by image treatment & must be performed on a statistically significant large no. of samples.

HRTEM

Independent interaction with the sample results the electron wave to pass through the imaging system of the microscope where it undergoes further phase change & interferes as the image wave in the imaging plane.

The recorded image is not a direct representation of the samples crystallographic structure.

HRTEM is an imaging mode of TEM that allows the imaging of the crystallographic structure of a sample at an atomic scale.

37

It can be used to study local microstructures like lattice fringe, glide plane or screw axes & the surface atomic arrangement of crystalline nanoparticles.

TEM comparison

Standard TEM High resolution TEM

Courtesy of F. ErnstCourtesy of F. Ernst38

It combines the ideas of looking at the surface of the sample and into the sample with an electron beam. STEM is an invaluable tool for the characterization of nanostructures, providing a range of different imaging modes with the ability to provide information on elemental composition and electronic structure at the ultimate sensitivity.

This technique works as a mapping device unlike TEM where a stationary, parallel electron beam is used to form images. In STEM, a fine electron probe is scanned over a sample. Since it is a serial recording, the image generation takes longer time as compared to that in TEM.

Scanning Transmission Electron Microscopy

Scanning Transmission Electron Microscopy

39

The STEM works on the same principle as the normal SEM, by forming a focused beam of electrons that is scanned over the sample while some desired signal is collected to form an image. The difference with SEM is that thin specimens are used so that transmission modes of imaging are also available.

Present-day aberration corrected STEMs have a depth of field of only a few nanometers, and so it becomes possible to effectively depth slice through a sample and to reconstruct the set of images into a 3D representation of the structure. The technique is comparable to confocal optical microscopy, but provides a resolution on nanoscale.

A new possibility is opened up by the new aberration corrected STEMs. Correcting the lens aberrations allows the objective aperture to be opened up, thereby obtaining higher resolution. At the same time, as in an optical instrument like a camera, the depth of field is reduced.

40

Scanning Probe Characterization Techniques


AFM Atomic force microscopy Topology/imaging/surface structure

CFM Chemical force microscopy Chemical/surface analysis

MFM Magnetic force microscopy Magnetic materials analysis

STM Scanning tunneling microscopy Topology/imaging/surface structure

APM Atomic probe microscopy Three-dimensional imaging

FIM Field ion microscopy Chemical profiles/atomic spacing

APT Atomic probe tomography Position sensitive lateral location of atoms

41

Atomic Force Microscopy

42

Basic principle

In AFM, a probe consisting of a sharp tip(~ 10 nm) located near the end of a cantilever beam is raster scanned across the surface of a specimen using piezoelectric scanners.

Changes in the tip specimen interaction are often monitored using an optical lever detection system, in which a laser is reflected off the cantilever & onto a position-sensitive photodiode.

A particular operating parameter is maintained at a constant level & images are generated through a feedback loop between the optical detection system & the piezoelectric scanners.

43

AFM modesTip scans in close contact with surface (repelled)

Constant force

Highest resolution

May damage surface

Contact modeContact mode

Non-contact modeNon-contact modeTip hovers above the surface (attracted)Variable force measuredLowest resolutionNon-destructive

Tapping modeTapping modeIntermittent tip contactVariable force measuredImproved resolutionNon-destructive

Courtesy of F. ErnstCourtesy of F. Ernst44

Qualitative analysis

The AFM offers visualization in three dimensions. Resolution in the vertical, or Z, axis is limited by the vibration environment of the instrument, whereas resolution in the horizontal, or X-Y, axis is limited by the diameter of tip utilized for scanning.

Typically, AFM instruments have vertical resolutions of less than 0.1 nm and X-Y resolutions of around 1 nm.

45

Figure: Left: NIST traceable polystyrene microspheres from Duke Scientific scanned with the NANO-RP™. Mean Ø of microspheres is 102nm. Scan size is 1μm x 1μm. Right: 3D view of 1x1μm scan of calibrated spheres

Here 73nm NIST traceable microspheres are shown in both perspective view and top view. 3D information is incorporated in both views. In the perspective view, the 3D nature of the image is obvious. In the top view, the intensity of the color reflects the height of the particle.

46

Quantitative analysis

For individual particles, size information (length, width, and height) and other physical properties (such as morphology and surface texture) can be measured.

Figure: A wood particle scanned with an AFM to measure roughness. Paper products containing such wood fibers can vary in quality based on the physical properties of the particulates.

47

Statistics on groups of particles can also be measured through image analysis and data processing. Commonly desired ensemble statistics include particle counts, particle size distribution, surface area distribution and volume distribution. With knowledge of the material density, mass distribution can be easily calculated.

Figure: Left: Latex particles outlined and counted. Right: Particle size distribution of polymer nanospheres. Mean Ø = 102nm 48

AFM can be performed in liquid or gas mediums. This capability can be very advantageous for nanoparticle characterization. For example, a major component of the combustion-generated nanoparticles are volatile components that are only present in ambient conditions.

Experimental media

Dry particles can be scanned in both ambient air and in controlled environments, such as nitrogen or argon gas. Liquid dispersions of particles can also be scanned, provided the dispersant is not corrosive to the probe tip and can be anchored to the substrate.

49

Particles dispersed in a solid matrix can also be analyzed by topographical or material sensing scans of cross-sections of the composite material. Such a technique is useful for investigating spatial nanocomposites.

Fig: Left: Ni3Al precipitates in a nickel aluminum alloy. 27 μm x 27μm topography image. Right: 6.8 x 6.8 μm grain particle on super plastic ceramic. Courtesy of Dr. McCartney group, UCI.

50

In many industries, the ability to scan from the nanometer range into the micron range is important. With AFM, particles anywhere from 1nm to 5μm in height can be measured in a single scan.

51

AFM can characterize nanoparticles in multiple mediums including ambient air, controlled environments & even liquid dispersions.

Less costly & less time consuming.

The roughness of the substrate must be less than the size of nanoparticles being measured.

SEM and AFM images

Fig. SEM & AFM images of Cu Nanowires

R. Adelung et al.R. Adelung et al.

Courtesy of F. ErnstCourtesy of F. Ernst

52

Scanning Tunneling Microscopy

Basic principle

It is based on the concept of quantum tunneling. When a conducting tip is brought very near to a metallic or semi-conducting surface, a bias between the two can allow electrons to tunnel through the vacuum between them.

Variations in tunneling current as the probe passes over the surface are translated into an image.

They normally generate image by holding the current between the tip of the electrode & the specimen at some constant value by using a piezoelectric crystal to adjust the distance between the tip & the specimen surface.

54

Lateral resolution ~ 0.1 nm Depth resolution ~ 0.01 nm

STM can be used not only in ultra high vacuum but also in air & various other liquid or gas, at ambient & wide range of temperature.

STM can be a challenging technique, as it requires extremely clean surfaces & sharp tips.

Fig. Highly oriented pyrolytic graphite sheet under STM

55

Photon(Spectroscopic) Probe Characterization Techniques


UPS Ultraviolet photoemission spectroscopy Surface analysis

UVVS UV-visible spectroscopy Chemical analysis

AAS Atomic absorption spectroscopy Chemical analysis

ICP Inductively coupled plasma spectroscopy Elemental analysis

FS Fluorescence spectroscopy Elemental analysis

LSPR Localized surface Plasmon resonance Nanosized particle analysis

56

Ion-particle Probe Characterization Techniques


RBS Rutherford back scattering Quantitative-qualitative elemental analysis

SANS Small angle neutron scattering Surface characterization

NRA Nuclear reaction analysis Depth profiling of solid thin films

RS Raman spectroscopy Vibration analysis

XRD X-ray diffraction Crystal structure

EDX Energy dispersive X-ray spectroscopy Elemental analysis

SAXS Small angle X-ray scattering Surface analysis/particle sizing(1-100 nm)

CLS Cathodoluminescence Characteristic emission

NMR Nuclear magnetic resonance spectroscopy

Analysis of odd no. nuclear species

57

The use of XRD is often compared to the microscopy techniques. XRD avoids issues of representative samples and determining crystals as opposed to particles as discussed above.

X-ray DiffractionX-ray DiffractionXRD can be used to look at various characteristics of the single crystal or polycrystalline materials using Bragg’s Law ,

nλ = 2d sinθ

XRD is time consuming and requires a large volume of sample.58

Thermodynamic Characterization Techniques


TGA Thermal gravimetric analysis Mass loss vs. temperature

DTA Differential thermal analysis Reaction heats heat capacity

DSC Differential scanning calorimetry

Reaction heats phase changes

NC Nanocalorimetry Latent heats of fusion

BET Brunauer-Emmett-Teller method

Surface area analysis

Sears Sears method Colloid size, specific surface area

59

Nanoparticle tracking analysis

Tilted laser Microscopy

Turbidimetry

Field Flow Fractionation

Hydrophobic interaction Chromatography

Electrophoresis

Isopycnic Centrifugation

Zeta potential measurements

Other Important Techniques

60

Characterization of curcumin nanoparticles (Jain et al., 2011) for anti-microbial study. Instruments used :

DLS : Malvern Zetasizer S90 seriesTEM : Morgagni 268 D from FEISEM : Jeol JSM 840 microscope

Fig. Size characterization of curcumin nanoparticles (a) DLS (b) TEM (c) SEM image

30 nm

~2-40 nm

~50 nm

62

Characterization of potato & cassava starch nanoparticles (Szymońska; 2009) using AFM(Park Scientific Instrument Autoprobe CP II model & the AFM Ultralevers tips of Veeco).

Fig. High resolution nc-AFM images & dimensions of potato starch nanoparticles

Fig. High resolution nc-AFM images and dimensions of cassava starch nanoparticles

63

Characterization of a novel photodegradable insecticide nano-imidacloprid (Chi et al., 2008) .

Imidacloprid (IMI) microcrystals were directly encapsulated with nature polysaccharides chitosan (CHI) & sodium alginate (ALG) through layer-by-layer (LbL) self-assembly. The coated colloids were characterized using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM).

64

Fig. Transmission CLSM images of the IMI release process from the (CHI/ALG)10 microcapsules. (a) Morphologies of IMI microcrystal before dissolution. (b) Images of IMI microcrystal in dissolution. (c) Images of polysaccharide capsules after removal of the crystal cores

Fig. SEM images of IMI microcrystals (a) uncoated, (b) coated with 5 layers of CHI/ALG, (c) coated with 10 layers of CHI-ALG.

65

Summary

Nanoparticle - Properties - Application

Nanoparticle Characterization - Methods - Comparative analysis

Case Study

16/07/2011 Division of Agricultural Chemicals 67

Nanotechnology is the essence of molecular synthesis, manipulation, and manufacturing.

Nanoparticles, are, key components in the development of new advanced technologies.

Nanoparticle-based technologies cover different fields, ranging from environmental remediation, energy generation and most recent applications in bioscience.

Division of Agricultural Chemicals16/07/2011 68

Nanoparticle characterization is necessary to establish understanding and control of nanoparticle synthesis and applications.

Nanotechnology has a lot of potential as a futuristic approach but would be largely governed by simultaneous progress in the newer, faster, simpler & more efficient characterization techniques for nanoparticles.

Path Ahead

Integration of different techniques for better understanding of particle characters

AFM with modern probes for attachment with fluoroscent particles to study rate kinetics/degradation kinetics

Integration of surface morphology based techniques with 3D imaging techniques

69

Thank You

Thank You

70

characterization techniques of nanoparticles

Technology