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Brewster Angle Microscope

Brewster Angle Microscopes (BAM) enable visualization of monolayers, typically at the air-water interface in a Langmuir Trough. They create an image of the surface by detecting changes in the refractive index of the water surface in the presence of surfactant molecules. This provides information on homogeneity, phase behavior and film morphology.

 

Features & Benefits

KSV NIMA BAM

  • The best resolution (2 µm) and image quality in the field of Brewster Angle Microscopy and provides real-time and fully focused sample visualization at 20-35 fps
.
  • Easy integration with KSV NIMA L & LB Trough Large.
  • Advanced image analysis and processing with the ability to simply select domains to get their
dimensions
.
  • Adjustable incident angle (52-57°) enabling measurements with dielectric solid substrates like glass or quartz
.
  • Imaging of anisotropic layers with the motorized analyzer
.
  • On-line automatic subtraction of a constant background image
.
  • Possible desktop remote control for support purposes.

KSV NIMA MicroBAM

  • Appropriate resolution (12 µm) for most applications
.
  • Capture and save still images and real-time video footage of monolayers.
  • Compact design, small footprint
.
  • Simple, intuitive operation
.
  • Imaging and control software included
.
  • Operates with a PC or Notebook (Windows XP to Win 7)
.
  • Compatible with most Langmuir troughs and Langmuir-Blodgett troughs
.
  • Can be used as a stand-alone instrument.

KSV NIMA offers two different Brewster Angle Microscopes, the advanced KSV NIMA BAM and the compact KSV NIMA MicroBAM.

KSV NIMA BAM

The KSV NIMA BAM represents the latest in BAM instrumentation, allowing high resolution and fully focused real-time imaging of monolayers. The KSV NIMA BAM provides completely undistorted images unlike other BAMs. A precise motorized vertical lift allows fine positioning to focus the water surface. An active isolation system is integrated to the KSV NIMA BAM to eliminate disturbing environmental vibration from air conditioning, traffic etc.

A high performance camera and dedicated calibration algorithms allow quantitative measurements of reflectivity for monitoring adsorption kinetics or thickness variation. The KSV NIMA BAM is equipped with a motorized analyzer to visualize optical anisotropy due to long-range molecular orientation order in monolayers.

The software offers advanced and comprehensive image analysis and processing functionalities. A Langmuir trough can be used together with the KSV NIMA BAM for control over the monolayer packing density and recording of surface pressure. The compatible KSV NIMA Langmuir and Langmuir-Blodgett Deposition Trough Large are the recommended systems. A PC is included with the instrument.

   
 
KSV NIMA BAM
 

KSV NIMA MicroBAM

The KSV NIMA MicroBAM and KSV NIMA Stand-Alone MicroBAM are easy-to-use, entry level instruments for non-invasive imaging of mono-molecular layers at the air-water interface. The excellent image quality and good lateral resolution make them ideal instruments for the visualization of morphological film parameters (e.g. compressed film homogeneity, domain size, shape and packing). Real-time observation and recording of film structure enables dynamic activity to be captured.

Both the KSV NIMA MicroBAM and KSV NIMA Stand-Alone MicroBAM can be used with most KSV NIMA Langmuir and Langmuir-Blodgett Troughs for automatic image measurements as a function of time or surface pressure. Both instruments are easy to set up with the measurement head height adjustment either motorized, KSV NIMA MicroBAM, or manual, KSV NIMA Stand-Alone MicroBAM. Both instruments have a safety key interlock for the BAM laser.

The KSV NIMA Stand-Alone MicroBAM can also be used with most Langmuir and Langmuir-Blodgett Troughs from other manufacturers as well as freestanding vessels. The KSV NIMA Stand-Alone MicroBAM connects directly to the computer via USB making it remarkably easy to setup and use.

KSV NIMA MicroBAM
KSV NIMA Stand-Alone MicroBAM

 

KSV NIMA BAM
KSV NIMA MicroBAM
KSV NIMA SA MicroBAM

Measurement

   
Angle-of-incidence range (°)

52…57, motorized

53, fixed
Angle-of-incidence resolution (°)
0.001
Light source power (mW)
50 50
Light source wavelength (nm)
658 659
Image resolution (µm)

2 (horizontal image direction)1

12 (horizontal image direction, center)1
Field of view (µm)
720×400 3600×4000
Polarizer
Glan-Thompson prism, motorized Fixed2
Polarizing resolution (°)
0.001
Analyzer
Motorized Fixed
Analyzing resolution (°)
0.001

Camera

   
Type
CCD USB
Resolution (px)
1360×1024 640×480
Framerate (fps)
20-35 30
Adjustable exposure time and gain
AVI video recorder

Image processing

   
Background compensation
Automatic
Geometric image deformation for unskewed images
Image resizing
Scale bar overlay
 √
Contrast enhancement
Profile
Image filtering
Various image formats
Particle size determination
 Advanced

Hardware

   
Instrument dimensions (L×W×H, cm)
85×47×65 22×27.7×40.2
Measuring head dimensions (L×W×H, cm)
45×10×25  5.7×16.2×7.2
Power supply (V, Hz)
100-240, 50/60 100-240, 50/60
Weight (kg)
45 10

Compatibility with L & LB Troughs

 
Medium
Large
High Compression
Alternate

1According to Rayleigh’s criterion

2P-polarization of the incident beam

 

Brewster Angle Microscopes (BAM) enable the visualization of Langmuir monolayers or adsorbate films at the air-water interface. In conjunction with a Langmuir Trough it is possible to study:

  • Monolayer/film behavior. It is possible to observe phase changes, phase separation, domain size, shape and packing.
  • Monolayer/film homogeneity. When combined with a KSV NIMA L & LB Trough, observation can be performed during compression/expansion at known surface pressures.
  • Influence of sub-phase conditions on film structures. Observe and study monolayer/film behavior and formation in different sub-phase conditions including salt concentrations, pH and temperature etc.
  • Monitoring of surface reactions. For example, photochemical reactions, polymerization reactions as well as enzyme kinetics can be followed in real-time.
  • Monitoring and detection of surface active materials.
 For example protein adsorption and nanoparticle flotation. BAMs are primarily designed for the air-water interface. However under some conditions the KSV NIMA BAM can be used for other interfaces such as air-glass.

Application examples

Chemical exfoliation of graphite in the production of graphene

Chemical exfoliation of graphite is recognized as one of the most potential methods for producing graphene in industrial scale. The result of the exfoliation process is graphene oxide, which is known to disperse well in water due to its ionizable –COOH groups. However, the basal plane of graphene is essentially a network of hydrophobic benzene rings. In a study by Kim and coworkers, the properties of graphene oxide were investigated by examining the amphiphilic nature of the molecule in a Langmuir trough.

Langmuir isotherms and Brewster angle microscopy were used to examine the properties and observe the formation of graphene oxide sheets at air-water interfaces. The study showed how monolayer imaging can improve solution processing and to help finding the optimal deposition parameters for graphene oxide materials.

Kim et al., ‘J of American Chemical Society’ (2010), 132, pp. 8180-8186

   
In Situ BAM images of A) freshly prepared graphene oxide—water solution and B) graphene
oxide with flotation.

Structure of asphaltene model compounds

Asphaltenes, a class of compounds in crude oil, are known to stabilize emulsions by forming elastic interfacial films. Despite the ongoing research regarding the structure and functional groups of these polyaromatic hydrocarbons, the exact chemical composition remains unknown.

Langmuir isotherm experiments show that the presence of acidic groups in asphaltene molecules is crucial for their film forming properties and interfacial activity. The packing morphology was further examined using a Brewster angle microscope. The study shows how Brewster angle microscopy can be used to correlate the structural properties and different phase transitions of Langmuir monolayers at air-water interfaces.

For more information, see:

   

   

BAM images of Langmuir compression of an acidic asphaltene model compound A) before
compression, B) at 4 mN/m and C) after film collapse. BAM images of a non-acidic asphaltene
model compound D) before compression and E) and at 2 mN/m. With permission from ‘Langmuir
(2008), 24 (16), pp 8742-8751. Copyright 2008 American Chemical Society.

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