TY - JOUR
T1 - Surface-plasmon resonance with infrared excitation
T2 - Studies of phospholipid membrane growth
AU - Lirtsman, Vladislav
AU - Ziblat, Roy
AU - Golosovsky, Michael
AU - Davidov, Dan
AU - Pogreb, Roman
AU - Sacks-Granek, Vered
AU - Rishpon, Judith
N1 - Funding Information:
This work was supported by the Israeli Ministry of Science. We are grateful to the late Dr. Mark Levin for his help in system design during the initial stages of this research. One of the authors (D.D.) would like to acknowledge helpful correspondence with J. R. Sambles concerning SPR in the infrared range. FIG. 1. Upper panel: the scheme of the surface-plasmon excitation. The arrows show the directions of the incident and the reflected beams. α is the the external angle of incidence and θ is the internal angle of incidence. The k 0 is the incident beam wave vector in vacuum, k 1 = k 0 ε 1 1 ∕ 2 is the wave vector in the prism with the dielectric constant ε 1 , and k x is its projection on the glass-metal interface. Lower panel: SPR-FTIR experimental setup. A glass prism coated with a thin metallic (gold or silver) film is illuminated with a collimated, polarized beam from the FTIR spectrometer (Bruker Equinox 55). The reflected beam is detected with an InGaAs (D427) detector. The beam collimation is produced by a pair of BK-7 lenses L1 and L2 (with 62.9 and 150 mm focal lengths, respectively) and a 0.5 mm pinhole. A third BK-7 lens, L3 ( D = 25 mm , focal length 62.9 mm ), focuses the beam into the detector. The sample (liquid in the flow cell or thin film) is in tight contact with the metallic substrate. The flow cell is mounted on the prism on a rotation stage. FIG. 2. A typical FTIR-SPR reflectivity vs wavelength for the Au/Air interface and for different angles of incidence θ . The solid lines represent the Fresnel prediction for the experimental data. FIG. 3. Dispersion relation for the surface plasmons at the Au/air interface. The circles are experimental points. The solid line is a prediction of Eq. (2) using the dielectric constants of Refs. 13 and 14 . The dashed line is the dispersion relation in air. The two extreme points (squares) in the figure were taken from the different SPR experiments using C O 2 ( λ = 10.6 μ m ) and HeNe ( λ = 0.6328 μ m ) laser excitations. FIG. 4. Angular-dependent SPR. The data at 1.4 and 1.2 μ m are extracted from Fig. 2 . The data for 10.6 and 0.6328 μ m show angular-dependent measurements using excitation from C O 2 and HeNe lasers, respectively. For the mid-IR we have used a special filter composed of two ZnSe lenses and a pin hole to decrease the beam divergence to 2 mrad or better. A gold film with a thickness of 9 nm was deposited directly on the base of the ZnSe right-angle prism. For the visible range we have used an SF-10 glass 60° prism and 47 - nm -thick gold film. Vertical arrows indicate the critical angles of the prisms. FIG. 5. Angular width of the SPR reflectivity minimum. Filled symbols show experimental data from Fig. 4 . The solid line describes the imaginary part of the surface-plasmon wave vector k sp ″ , as found from Eq. (2) and Ref. 14 . FIG. 6. FTIR-SPR minima at different growth stages of the decanethiol-phospholipid bilayer on thin gold film under the flow mode. FIG. 7. SPR minimum vs time for POPC adsorption onto the gold-coated decanethiol monolayer for (a) flow mode and (b) injection mode. The solid line in (a) represents a stretched exponential fit: P sat [ 1 − exp ( − t ∕ τ ) d ] , where d = 2.1 , τ = 143 min , and P sat = 95 % . The solid line in (b) is a fit for the Langmuir-type exponential behavior: P sat [ 1 − exp ( − t ∕ τ ) ] , where P sat = 55 % , τ = 80 min .
PY - 2005/11/1
Y1 - 2005/11/1
N2 - We report on a surface-plasmon resonance (SPR) technique based on a Fourier transform infrared spectrometer for biological and surface-sensitive applications. In contrast with conventional surface-plasmon techniques, which operate at a fixed wavelength and a variable angle of incidence, our setup allows independent variation of the wavelength and the angle of incidence. By the proper choice of these parameters, we achieve optimal coupling to the surface plasmon and high sensitivity. Moreover, by using infrared rather than visible light, we achieve an extremely narrow angular-dependent surface-plasmon resonance. This results in a very sensitive SPR technique that can easily sense one molecular layer. We take advantage of the extremely narrow SPR in the infrared range and use it to study the growth dynamics of the phospholipid layer, which is the main constituent of the biological cell membrane. In particular, we distinguish the difference in the growth dynamics of this artificial membrane from a solution under different conditions of liquid flow (continuous flow or injection).
AB - We report on a surface-plasmon resonance (SPR) technique based on a Fourier transform infrared spectrometer for biological and surface-sensitive applications. In contrast with conventional surface-plasmon techniques, which operate at a fixed wavelength and a variable angle of incidence, our setup allows independent variation of the wavelength and the angle of incidence. By the proper choice of these parameters, we achieve optimal coupling to the surface plasmon and high sensitivity. Moreover, by using infrared rather than visible light, we achieve an extremely narrow angular-dependent surface-plasmon resonance. This results in a very sensitive SPR technique that can easily sense one molecular layer. We take advantage of the extremely narrow SPR in the infrared range and use it to study the growth dynamics of the phospholipid layer, which is the main constituent of the biological cell membrane. In particular, we distinguish the difference in the growth dynamics of this artificial membrane from a solution under different conditions of liquid flow (continuous flow or injection).
UR - http://www.scopus.com/inward/record.url?scp=27844507212&partnerID=8YFLogxK
U2 - 10.1063/1.2123370
DO - 10.1063/1.2123370
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:27844507212
SN - 0021-8979
VL - 98
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 9
M1 - 093506
ER -