© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Use of Surface Plasmon Resonance in Determination of Salinity
originally: “A Preliminary Thesis Report, Darcy Gentleman, October 29, 2002”
Modified June 2018 by Darcy J. Gentleman, DJG Communications LLC, for purposes of showing slide design revisions.
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Outline
• Relevance & Background Theory • Work to date • Rationalising • Current work (experimental design) • Dissertation outline
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
The Big Picture
• Desire to measure physicochemical properties of marine environments and hydrothermal vents with in situ sensors
• Progress understanding of oceano-climatological processes and biogeochemistry of seafloor (vent) systems
• Dip-probes welcome addition in process monitoring; small volume applications
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Salinity/Chlorinity/Conductivity• First modern (chemical) measurement in 1902 -
titration against AgNO3 • 1960’s improvements in conductivity and density
precision showed these quantities more closely related to salinity than “chlorinity” (equivalent Cl content)
• 1981 UNESCO standardised practical salinity scale (PSU≅PPT) based on conductivity (6[S/m]) because better instrumentation precision than refractometry
• Modern salinometers good to ~1ppm salt, benchtop (or shipboard), isothermal sleeve, static at time of measurement
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Refractive Index (RI) and Equations of State
• Since late 1980’s, RI instrumentation higher precision
• Equations of state appearing including RI (n) wrt salinity (S), density (D), temperature (T), pressure (P), and wavelength (8)
• N.P. Fofonoff, JGR, 90 (C2), 3332 (1985). Salinity scale and eqn of state of seawater; (P, T, 6, S, D) http://ioc.unesco.org/oceanteacher/resourcekit/M3/Converters/SeaWaterEquationOfState/Sea%20Water%20Equation%20of%20State%20Calculator.htm
• R.C. Millard, G. Seaver, Deep-Sea Res., 37 (12), 1909 (1990).; RI algorithm over T, P, S, D, 8
• X. Quan, E.S. Fry, App. Op., 34 (18), 3477 (1995).; empirical eq’n for RI
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
RI Instrumentation• Most commonly use Abbé refractometer in
cold room • Some use of flow cell or cuvette-housed
interferometry • Fibre optic based Bragg grating refractometry K. Schroeder, W. Ecke, R. Mueller, R. Willsch, A. Andreev, Meas. Sci. Technol.,
12, 757 (2001). • Surface Plasmon Resonance (SPR); Ó. Esteban, M.C. Navarette, A. González-Cano, E. Bernabeu, App. Op., 38 (25),
5267 (1999). B. Grunwald, G. Holst, manuscript, 1999?
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
kz
kx=sinΘinc
Θinc > Θcrit
Optical fibre
Medium under study Surface plasmonkSP=kx
Reflected light
Gold layer(~50nm Au over ~2nm Cr)
Evanescent field
Surface Plasmon Resonance (SPR)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Spectral Pre-Processing
550 600 650 700 7500
500
1000
1500
2000
2500
3000
3500
Wavelength (nm)
Ref
lect
ed In
tens
ity (
arb.
uni
ts)
550 600 650 700 7500
500
1000
1500
2000
2500
3000
3500
Wavelength (nm)
Ref
lect
ed In
tens
ity (
arb.
uni
ts)
550 600 650 700 7500.65
0.7
0.75
0.8
0.85
0.9
0.95
1
Wavelength (nm)
Rel
ativ
e R
efle
cted
Inte
nsity
(ar
b. u
nits
)
550 600 650 700 7500.85
0.9
0.95
1
1.05
1.1
1.15
1.2
Wavelength (nm)
Rel
ativ
e R
efle
cted
Inte
nsity
(ar
b. u
nits
)
Sample
Reference
Air Ratio
Water Ratio
0.00wt%
3.50wt%
7.00wt%
0.00wt%3.50wt%
7.00wt%
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Minima Points in Temperature Space
0 5 10 15 20 25 30625
630
635
640
645
650
655
660
Wav
elen
gth
(nm
)
Temperature (°C)
Increasing Concentration
Density Inversion
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Early Work
• Construction of P chamber, SEM • High P/T SPR attempts • Dilution series #1 (NaCl, 0.00wt%-7.00wt%,
2°C-25°C; pred. Error ~0.2wt%) • Geometry of P probes • Dilution series #2 (KCl, 0.00wt%-7.00wt%,
0°C-30°C; pred. Error ≤0.10wt%)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Spectrometer Fibre optic connector
SPR probe in stainless steel swagelok
Packing for heating or cooling (may also be immersed in T control bath)
Chamber core
HPLC pumpThermocouple
(Chromel/Alumel)
High Temperature/ Pressure Apparatus
Computer
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Effect of Hydrothermal Conditions on Silica
Bare, 0h Bare, 5h
Au coat, 0h Au coat, 4h
150X (400µm fibre)
150X (400µm fibre) 150X (400µm fibre)
2000X (400µm fibre)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Effect of Pressure on SPR Shift
y=-2.28E-4x+659
0 50 100 150 200 250657
657.5
658
658.5
659
659.5
660
Pressure (bar)
Wav
elen
gth
(nm
)
t-test: slope of regression line indistinguishable from slope zero at 97.5% confidence level
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
QTH Lamp
(Oriel)
Kaiser Holospec
Spectrometer
LED (white)
Princeton Instruments
CCD
SPR Probe (DT or ST)
Computer
SMA connector
Sample (T controlled)
Dilution Series #1 Set Up
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
temperature increase
0 1 2 3 4 5 6 7620
625
630
635
640
645
650
655
660
665
Concentration NaCl (wt%)
Wav
elen
gth
(nm
)SPR Minima Positions Due to
NaCl(aq) Concentration
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
2°C
25°C
10°Cy=2.92x+644
y=2.75x+624
-1 0 1 2 3 4 5 6 7 8620
625
630
635
640
645
650
655
660
665
Concentration NaCl (wt%)
Wav
elen
gth
(nm
)Construction of Calibration Model
For Concentration Data
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
0 1 2 3 4 5 6 7-1
-0.5
0
0.5
1
1.5
Concentration NaCl (wt%)
Pred
icte
d C
once
ntra
tion
- Tru
e C
once
ntra
tion
(wt%
) Error in Predicting Concentration At a Given Concentration
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
0.18wt% error 0.19wt% error DAY 3 DAY 2 DAY 1
0 5 10 15 20 25-1
-0.5
0
0.5
1
1.5
Temperature (°C)
Pred
icte
d C
once
ntra
tion
- Tru
e C
once
ntra
tion
(wt%
) Error in Predicting Concentration At Given Temperature
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Dilution Series #2
QTH Lamp (Oriel)
Thermocouple Reader
(Omega) 0.01°C
K-type TC (±0.5°C)
Straight SPR Probe
Isothermal Bath (Fisher) 0.02°C
Spectrometer (Ocean Optics)
0.01nm
P3 1.1GHz 256Mb Notebook (Dell)
USB
Optical Fibre SMA Jumpers
KCl(aq)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Minima Positions in Concentration Space
0 1 2 3 4 5 6 7625
630
635
640
645
650
655
Wav
elen
gth
(nm
)
Concentration (wt%)
IncreasingTemperature
6°C
29°C
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Linear Modelling with 6°C|29C° Bounds
-1.000 0.000 1.000 2.000 3.000 4.000 5.000 6.000 7.000 8.000625
630
635
640
645
650
655
Wav
elen
gth
(nm
)
Concentration KCl(aq) (wt%)
y=2.451x + 634.82
y=2.106x + 625.98
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
5.0 10.0 15.0 20.0 25.0 30.0-0.600
-0.400
-0.200
0.000
0.200
0.400
0.600
0.800
Pre
dict
ed C
once
ntra
tion
– Tr
ue C
once
ntra
tion
(wt%
)
Temperature (°C)
Error in Predicting Concentration at a Given Temperature (6°C|29°C bounds)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Prediction Errors for Various Bounds
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
RM
SE
P fo
r Giv
en S
et (w
t%)
5|29;
5-29
6|29;
6-29
7|29;
7-29
6|16;
6-16
17|29; 17-29
19; 19
18|20
; 19
17|29
; 19
6|29;
19
9; 9
8|10;
96|1
6; 9
6|29;
9
18|2
0; 2
1
T1 | T2 (bounds); T’s Predicted
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Observations Following Statistical Analysis
• Both the linear model and multivariate (PCR) giving prediction error ~0.10wt% at best
• Prediction error improves with smaller spread of concentration/temperature
• Given wavelength shift, spectral resolution should give ~0.005wt% (50ppm), 0.02°C sensitivity
• Esteban et al. (1999) report 100ppm • Grunwald&Holst (1999) report 4000ppm • Schroeder et al. (2001) report ~400ppm • Static interferometry, conductivity give 1ppm
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Mixing Chamber Design
Isothermal Bath 0.02°C
Saltwater Pump (Lee), 50:L
Water Pump (Lee), 50:L
Mixing Chamber
LED
Ocean Optics Spectrometer
0.01nm
YSI Resistance Thermistor
Keithley 2000 Multimeter 0.001°C
YSI 3200 Conductivity Meter 3253 (K=1.0/cm) Cell
<0.01S/m (<100ppm salt)
Conductivity ProbeSPR Probe
Waste
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Special Considerations
• Probe drift: 1 probe in sample, 1 in DDI, 1 in 42ppt KCl, measure drift each day to renormalise
• Thermal equilibration: 12h down time to re-equilibrate (thermistors calibrated with 24h between measurements)
• Measurements will occur in series, not parallel
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Mix Chamber Plan
• 0.000ppt - 42.000ppt KCl, -1°C to 32°C • 24 random conc’s at each T (random
order) • Constant conc., flux T • Constant T, flux conc. • Density inversion of water (?)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
Dissertation Outline (By Expected Chapter)
• Introduction (relevance, short history of oceanographic chemical analysis)
• Theory (RI, salinity, equations of state of seawater, SPR, tie together RI&SPR)
• Apparatus • Preliminary Work • Mix Chamber • Conclusions (accomplished data, immediate future,
foreseeable future)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!29
» extra images follow
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!30
l
A
Usually Pt black
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!31
Actual Apparent
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!32
q=90°
qcrit
Air (low RI)
Water (high RI)
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!33
Plastic(cladding of optical fibre)
Glass
(optical fibre)
Evanescent field
Incident ray Internallyreflected ray
Cladding (plastic)Core (glass)
Waveguidedlight ray
Light sourcea
b
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!34
MirrorSensing region
q
90°- q
5mm
a
b
c
Buffer Core + Cr/Au
Core + Cr/AuBuffer
© 2018, DJG Communications LLC, modification of DJ Gentleman file from 2002
!35
Pump control
Chiller(with chassis de-rattling device)
KCl and H2Oreservoirs SPR probe
Conductivity cell
Thermistor
Pump control
Chiller(with chassis de-rattling device)
KCl and H2Oreservoirs SPR probe
Conductivity cell
Thermistor