use of surface plasmon resonance in …© 2018, djg communications llc, ... (psu≅ppt) based on...

© 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.


Outline

• Relevance & Background Theory • Work to date • Rationalising • Current work (experimental design) • Dissertation outline


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


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


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


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?


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)



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%


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


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%)


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


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)


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



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


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


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


Wav

elen

gth

(nm

)Construction of Calibration Model

For Concentration Data


0 1 2 3 4 5 6 7-1

-0.5

0

0.5

1

1.5


Pred

icte

d C

once

ntra

tion

- Tru

e C

once

ntra

tion

(wt%

) Error in Predicting Concentration At a Given Concentration


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


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)


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


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


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)


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


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


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


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


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 (?)


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)


!29

» extra images follow


!30

l

A

Usually Pt black


!31

Actual Apparent


!32

q=90°

qcrit

Air (low RI)

Water (high RI)


!33

Plastic(cladding of optical fibre)

Glass

(optical fibre)

Evanescent field

Incident ray Internallyreflected ray

Cladding (plastic)Core (glass)

Waveguidedlight ray

Light sourcea

b


!34

MirrorSensing region

q

90°- q

5mm

a

b

c

Buffer Core + Cr/Au

Core + Cr/AuBuffer


!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

use of surface plasmon resonance in …© 2018, djg communications llc, ... (psu≅ppt) based on...

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