The K2 family of frequency-domain fluorometers provides researchers with a solid, well-proven instrumentation platform for the most demanding fluorescence and phosphorescence applications.

With installed units all over the world, the K2 family of Multifrequency Cross-Correlation Phase and Modulation Fluorometers represents a solid and well-proven approach to fluorescence and phosphorescence instrumentation for the research laboratory. The K2 is used by researchers at the ETH in Zurich, Switzerland, the MIT in Cambridge, MA, the NIH in Rockville, MD, and at the NASA research facility in Huntsville, AL.

Its optical design and automatic instrument control are state-of-the-art for steady-state and time-resolved fluorescence measurements. Full automation and the user-friendly Vinci software package make the instrument easy to use for both, the student and the scientist.

Key features of K2 include:

  • Lifetime measurement capabilities from 1 millisecond to 1 picosecond
  • Complete lifetime scans in less than one minute on routine samples with proprietary FastScan technology
  • A compact footprint and a short optical pathlength for maximum sensitivity and efficient light coupling into the sample
  • T-format and parallel beam optical design for fast and precise polarization measurements
  • Full automation of all instrument components (cuvette holder, polarizers, shutters, filterwheel, monochromators, and stirrers)
  • PC-controlled integration of termperature bath, titrator, stopped-flow apparatus and pressure pump
  • Measurement of fast kinetics data with one millisecond resolution in photon counting mode
  • 80 MHz pre-amplifier discriminators delivering linearity up to over eight million counts per second on each channel
  • Flexible instrument configuration
  • Upgradeable with Ti:Sapphire laser and laser diodes

Three models of K2 are available, and each comes fully automated and upgradeable.

K2-001 with K2 FastScan
The FastScan is our most popular model: lifetime data acquisition on a routine sample can be acquired in less than one minute using either a lamp or a laser. The cross-correlation is user-selectable up to 5,000Hz and data acquisition is performed through a FFT routine; the instrument covers the modulation frequency range from 300KHz up to 350MHz with a lamp and up to 450MHz using a cw laser.

K2-002 1.2GHz Upgrade
This model requires a mode-locked laser as excitation source and a microchannel plate detector (MCP-PMT) for the collection of fluorescence. Alternatively, a laser diode can be utilized as the light source to measure frequency responses up to about 1GHz. The cross-correlation is user-selectable up to 5,000Hz and data acquisition is performed through a FFT routine. It includes the FastScan upgrade and operates at modulation frequency up to 1.2GHz.

K2-003 6GHz Upgrade
The K2-003 is an upgrade of the K2-002: it operates in the frequency range up to 6GHz.

Specifications for K2

Measurements (Steady-State Fluorescence) • Corrected excitation and emission spectra
• Excitation-emission matrices
• Polarization (anisotropy) measurements
• Millisecond kinetics in photon counting mode
• Dual-wavelength-ratiometric excitation or emission measurements
Measurements (Time-Resolved Fluorescence)

• Multiple decay times from millisecond to picosecond time scale
• Anisotropy decays
• Phase- and modulation-resolved spectra (up to 3 components in a mixture)
• Time-resolved spectra

Light Sources • 300 W xenon arc lamp, 45 mW/nm brightness at 275 nm
• Laser diodes
• Light emitting diodes (LEDs)
• Continuous wave lasers (argon-ion, krypton-ion, helium-cadmium)
• Mode-locked lasers (Ti:Sapphire)
• Synchrotron light beams
Monochromators Single concave holographic grating Wavelength range: from 200 nm to 1200 nm (dependent on selected grating)
Detectors • Selected side-on photomultiplier tubes in room-temperature or cooled housing (for frequency response up to 800 MHz)
• Microchannel plate detectors (for frequency response > 800 MHz)
• Optional: CCD camera
Detection Modes • Photon counting electronics, 10 KHz, on 3 independent channels
• Analog Output on 3 channels
Frequency-Response From DC up to 10 GHz
Frequency Synthesizers • Marconi Instruments
• Programmed Test Sources
• Gigatronics
• Hewlett Packard
Light Modulation • Wide aperture Pockels cell (for lamp and cw lasers) up to 350 MHz
• Direct modulation (for laser diodes and LEDs) up to 700 MHz
• Harmonic content of pulsed sources up to 10 GHz
Polarizers • UV-grade Glan-Thompson, 10x10 mm, L/A=2.0
• UV-grade Glan-Thompson, 14x14 mm, L/A=2.0
• UV-grade Glan-Taylor, 10x10 mm, L/A=2.0 (for high power lasers)
Pre-Amplifier Discriminators 100 MHz bandwidth, TTL output
Focusing and Collection Geometry Parallel beam design for precise polarization measurements
Dynamic Range Linear up to 4 million counts/second
Wavelength Accuracy ±0.2 nm
Wavelength Reproducibility ±0.25 nm
Slew Rate 160 nm/s (optional double grating)
Lifetime Measurements Range From 100 millisecods to 20 picoseconds (depending upon the model; the shortest measurable decay time is determined by the light detectors frequency response)
OS Requirements XP, 7
Power Requirements Universal power input: 110-240 V, 50/60 Hz, 400 VAC
Dimensions 885 mm (L) x 600 mm (W) x 330 mm (H)
Weight 45 kg

Schematic Diagram for K2

Measurement Examples from K2

2-Aminopurine in Water

Frequency responses (phase and modulation) of 2-Aminopurine in water acquired on K2 using a Xenon lamp. The excitation wavelength was 290-nm with a 2 mm slit size. The emission was collected through a 345 high pass filter. The data is best fitted with a single exponential decay time of 11.69 ns (θ2 = 1.32).

Rose Bengal in Water

Time-domain anisotropy decays of Rose Bengal in water acquired on ChronosBH using a 447-nm pulsed laser diode. The emission was collected through a long pass filter KV 505. Calculated values for θ = 0.16 ns with R0 = 0.39 and τ = 0.075 ns, T = 20-21°C.

Selected publications featuring K2

Below is a list of selected publications featuring K2. Click here to browse our complete library of publications.

Coordinatively Induced Length Control and Photoluminescence of W18O49 Nanorods
Woo, K., Hong, J., Ahn, J.-P., Park, J.-K., Kim, K.J.
Inorg. Chem., 2005, 44(20), 7171-7174.
Modeling of Spherical Fluorescent Glucose Microsensor Systems: Design of Enzymatic Smart Tattoos
Brown, J.Q., McShane, M.J.
Biosens. Bioelectron., 2006, 21(9), 1760-9.
Fluorescence Lifetimes and Spectral Properties of Protochlorophyllide in Organic Solvents in Relation to the Respective Parameters in Vivo
Mysliwa-Kurdziel, B., Kruk, J., Strzalka, K.
Photochemistry and Photobiology, 2004, 79(1), 62-67.
Hg2+ Reacts with Different Components of the NADPH: Protochlorophyllide Oxidoreductase Macrodomains
Solymosi, K., Lenti, K., Mysliwa-Kurdziel, B., Fidy, J., Strzalka, K., Böddi, B.
Plant Biology, 2004, 6, 358-367.
A New Competitive Fluorescence Assay for the Detection of Patulin Toxin
de Champdoré, M., Bazzicalupo, P., De Napoli, L., Montesarchio, D., Di Fabio, G., Cocozza, I., Parracino, A., Rossi, M., D'Auria, S.
Anal. Chem., 2007, 79, 751-757.
Thermosensitive Poly(organophosphazene) Hydrogels for a Controlled Drug Delivery
Kang, G.D., Cheon, S.H., Khang, G., Song, S.-C.
European Journal of Pharmaceutics and Biopharmaceutics, in press, Available online 9 March 2006.
Daunomycin Binding to Detergent Micelles: A Model System for Evaluating the Hydrophobic Contribution to Drug-DNA Interactions
Dignam, J.D., Qu, X., Ren, J., Chaires, J.B.
J. Phys. Chem. B, 2007, 111(39), 11576-11584.

Accessories available for K2

The following accessories are available for K2. For more information please visit our Fluorescence Accessories page.

  • Xenon Arc Lamp
  • Laser Diodes & Light Emitting Diodes (Modulated and Pulsed)
  • Two-cuvette Sample Compartment
  • Three-cuvette Sample Compartment
  • Four-cuvette, Peltier-controlled, Sample Compartment
  • Absorption Measurements Accessory
  • Dewar Flask
  • The HPCell™ High Pressure Cell System
  • Total Internal Reflection Fluorescence(TIRF) Flow Cell
  • Variable-angle, Front-Surface Sample Compartment
  • Vacuum Chamber
  • Microwell Plate Reader Accessory
  • UV Glan-Thompson Prism Polarizers
  • Single Syringe Titrator
  • Double Syringe Titrator
  • Stopped-Flow Devices
  • Fiber Optics
  • Computer-controlled Filter Wheels
  • Filters & Filter Holders
  • Variable-Angle Cover Slip
  • Cuvettes amp; Cuvette Holders
  • Light Detectors