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Surface plasmon resonance spectrometer “PLASMON 6”

№12 Department of Physics and technological bases of sensory materials
Yu. M. Shirshov, Y.V. Ushenin

The most used applications:  
•    Realization of real time biokinetic, immunosensing and biosensing techniques
•    Studies of adsorption, corrosion, electrochemical reactions
•    Thin organic and inorganic film characterization and refractive index measurements
•    Gas and liquid composition detection and chemosensor applications

Ffields of application:
•    Veterinary medicine
•    Medicine
•    Biotechnology
•    Food industry
•    Ecological monitoring
•    Customs supervision

Surface plasmon resonance (SPR) is a unique optical surface sensing technique that is   responsive to refractive index changes that occur within the vicinity of a sensor surface.  Thus, SPR can be used to monitor  any physical phenomenon which alters the refractive index at the surface and has grown into a versatile technique used in variety of applications. Of special interest is its  potential for biosensing techniques.
The PLASMON-6 is a computer-controlled SPR spectrometer that implements the Kretschmann prism arrangement. A 45 nm film of gold is deposited onto a glass slide which is brought into optical contact with the prism using refractive index matching fluid. This gold film forms the sensor surface where the surface plasmons are excited using a polarized light emitted by a semiconductor laser (l=670nm). The laser light is launched into the rotating ATR prism where it can couple with the surface mode to yield the surface plasmons. Excitation of plasmons is  evidenced by a resonant dip in the reflectance of the gold film under the correct coupling conditions.
The angular dependence of this intensity (the resonance curve) reflects variation of the SPR coupling level and represents the sensor output. Its shape, especially position of the resonant dip, allows for the refractive index and the thickness of the layer coated upon the gold film to be elucidated. Surface plasmons are confined to the plane of the gold film, producing evanescent electromagnetic field. It extends over ~1 µm from the surface, that makes this technique essentially surface-sensitive.

 Depend on modification device has one or two optical channels. Second channel can be used as measuring or reference. Modification of the instrument destined for electrochemical applications features additional ADC input and software means for recording of voltamperograms simultaneously with the optical signal.

System Specifications:

Refractive index measurement range     1.0 – 1.5
Detection limit of refractive index variation     0.00005
 Angle-of-incidence setting precision     10 angular sec
Maximum angular scan    17o
Total measurement time of a single resonant curve    3 sec
Maximum time resolution of kinetics measurements:    ≤ 3 sec
Maximum time resolution for Tracing measurement mode    1 sec
Maximum time resolution for Slope measurement mode    0.2 sec
Number of optical channels    2
Light source    GaAs laser (λ=650 nm)
Additional ADC input (optional)    ±5V
Overall dimensions of the measurement unit    215x130x100 mm
Weight    2.5 kg
Computer connect    COM port, USB
Control and data processing software    Windows-95/98/ME/XP

Accessories
     Replaceable ATR prisms (1.51≤n≤1.64) for measurements in gaseous and liquid phases;
     Refractive index matched glass substrates (1.51≤n≤1.64) with plasmon-supporting layer (vacuum-deposited 45 nm thick gold thin film);
     Replaceable sample cells of different volume.