Temperature Dependent Solubility of Thioglycerol-Ligated ZnS - - PowerPoint PPT Presentation

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Temperature Dependent Solubility of Thioglycerol-Ligated ZnS - - PowerPoint PPT Presentation

Sep 01, 2022 436 likes •1.01k views

Temperature Dependent Solubility of Thioglycerol-Ligated ZnS Nanoparticles in 4:1 MeOH:H2O Solution Daniel Scott 1 Dr. Christopher Sorensen 2 Jeff Powell 2 1 Department of Physics, University of Houston 2 Department of Physics, Kansas State

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SLIDE 1

Temperature Dependent Solubility of Thioglycerol-Ligated ZnS Nanoparticles in 4:1 MeOH:H2O Solution

Daniel Scott1

  • Dr. Christopher Sorensen2

Jeff Powell2

1 Department of Physics, University of Houston 2 Department of Physics, Kansas State University

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SLIDE 2

Background

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SLIDE 3

Background

  • Significant literature exists for solubility of bulk

materials in a wide variety of solvents

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SLIDE 4

Background

  • Significant literature exists for solubility of bulk

materials in a wide variety of solvents

  • Only in the past few decades have nanomaterials

become a topic of significant study

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SLIDE 5

Background

  • Significant literature exists for solubility of bulk

materials in a wide variety of solvents

  • Only in the past few decades have nanomaterials

become a topic of significant study ○ Nanoparticles (NPs) behave differently than bulk counterparts ○ Sparse literature on solubility of NPs

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SLIDE 6

Background

  • Treat monodisperse NP colloid in solvent as solution

with temperature dependent solubility

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SLIDE 7

Background

  • Treat monodisperse NP colloid in solvent as solution

with temperature dependent solubility

  • Construct equilibrium phase diagram

○ Enthalpy of dissolution

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SLIDE 8

Theory

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SLIDE 9

Theory

  • Surface Plasmon Resonance

○ Interaction between electrons on surface of NP with incident light ○ Causes unique light absorption profile characteristic to features such as NP material and size

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SLIDE 10

Theory

  • Surface Plasmon Resonance

○ Interaction between electrons on surface of NP with incident light ○ Causes unique light absorption profile characteristic to features such as NP material and size

  • UV-Vis spectrometer to view absorption spectrum

○ Higher concentration of dissolved NP gives greater absorption (A=ε*l*c :: Beer-Lambert Law)

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SLIDE 11

Theory

Absorption decreases with lower concentrations of dissolved NPs

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SLIDE 12

Our System

  • ZnS NPs ligated with thioglycerol (3-mercapto-1,2-propanediol)

○ Highly soluble in water ○ Insoluble in methanol ○ SPR peak at ~251nm ■ Requires UV-transparent cuvette

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SLIDE 13

Procedure

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SLIDE 14

Procedure

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SLIDE 15

Spectral results

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SLIDE 16

Spectral results

24C 40C 50C 60C 70C

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SLIDE 17

Spectral results

24C 40C 50C 60C 70C

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SLIDE 18

Spectral results

24C 40C 50C 60C 70C Absorbance decreases at higher temperatures

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SLIDE 19

Spectral results

24C 40C 50C 60C 70C Absorbance decreases at higher temperatures Less soluble when heated

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SLIDE 20

Exothermic Dissolution

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SLIDE 21

Exothermic Dissolution

In [MeOH + H2O] solution:

ZnS (sc) ⇌ ZnS (c) + heat

sc: supercluster (NP aggregates) c: cluster (NP)

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SLIDE 22

Exothermic Dissolution

In [MeOH + H2O] solution:

ZnS (sc) ⇌ ZnS (c) + heat

sc: supercluster (NP aggregates) c: cluster (NP)

Equilibrium reaction, thus Le Chatelier’s principle tells us excess heat would favor the left-hand side

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SLIDE 23

Gibbs Free Energy

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SLIDE 24

Gibbs Free Energy

  • Process is spontaneous if ΔG < 0:

○ ΔG = ΔH - ΔTΔS

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SLIDE 25

Gibbs Free Energy

  • Process is spontaneous if ΔG < 0:

○ ΔG = ΔH - ΔTΔS

  • Exothermic dissolution: ΔHdis < 0, so ΔHfus > 0
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SLIDE 26

Gibbs Free Energy

  • Process is spontaneous if ΔG < 0:

○ ΔG = ΔH - ΔTΔS

  • Exothermic dissolution: ΔHdis < 0, so ΔHfus > 0
  • Suppose we increase temperature, forming precipitate:
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SLIDE 27

Gibbs Free Energy

  • Process is spontaneous if ΔG < 0:

○ ΔG = ΔH - ΔTΔS

  • Exothermic dissolution: ΔHdis < 0, so ΔHfus > 0
  • Suppose we increase temperature, forming precipitate:

○ ΔHfus - ΔTΔS = (+) - (+) * ΔS

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SLIDE 28

Gibbs Free Energy

  • Process is spontaneous if ΔG < 0:

○ ΔG = ΔH - ΔTΔS

  • Exothermic dissolution: ΔHdis < 0, so ΔHfus > 0
  • Suppose we increase temperature, forming precipitate:

○ ΔHfus - ΔTΔS = (+) - (+) * ΔS ■ ΔS must be positive for ΔG to be negative so that precipitation at higher temperatures is spontaneous

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SLIDE 29

Gibbs Free Energy

  • Process is spontaneous if ΔG < 0:

○ ΔG = ΔH - ΔTΔS

  • Exothermic dissolution: ΔHdis < 0, so ΔHfus > 0
  • Suppose we increase temperature, forming precipitate:

○ ΔHfus - ΔTΔS = (+) - (+) * ΔS ■ ΔS must be positive for ΔG to be negative so that precipitation at higher temperatures is spontaneous ■ Higher entropy (disorder) in precipitate than dissolved

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SLIDE 30

Dissolved: Less Disorder

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SLIDE 31

Dissolved: Less Disorder

3-mercapto-1,2-propanediol ligand (thioglycerol)

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SLIDE 32

Dissolved: Less Disorder

Hydrogen bonding sites 3-mercapto-1,2-propanediol ligand (thioglycerol)

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SLIDE 33

Potential Explanation: Hydrogen Bonds

  • Formation of hydrogen bond is highly exothermic
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SLIDE 34

Potential Explanation: Hydrogen Bonds

  • Formation of hydrogen bond is highly exothermic

○ Hydrogen bonds have a deep potential well

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SLIDE 35

Potential Explanation: Hydrogen Bonds

  • Formation of hydrogen bond is highly exothermic

○ Hydrogen bonds have a deep potential well ○ More energy released in formation of hydrogen bond than is consumed in destruction of solute-solute (inter-NP) bond

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SLIDE 36

Potential Explanation: Hydrogen Bonds

  • Formation of hydrogen bond is highly exothermic

○ Hydrogen bonds have a deep potential well ○ More energy released in formation of hydrogen bond than is consumed in destruction of solute-solute (inter-NP) bond ○ Falls to a lower energy state with hydrogen bond

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SLIDE 37

Potential Explanation: Hydrogen Bonds

  • Formation of hydrogen bond is highly exothermic

○ Hydrogen bonds have a deep potential well ○ More energy released in formation of hydrogen bond than is consumed in destruction of solute-solute (inter-NP) bond ○ Falls to a lower energy state with hydrogen bond

  • Dissolved ZnS with hydrogen bonds is more ordered (less

disordered) than undissolved as ZnS precipitate

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SLIDE 38

Calculating ΔHdis

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SLIDE 39

Calculating ΔHdis

  • By van’t Hoff equation: ln(x) = -(ΔHdis/RT) + c

○ x: mole fraction ○ R: gas constant (8.314 x 10-3 kJ/mol K) ○ T: temperature (Kelvin) ○ c: constant related to activity coefficient

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SLIDE 40

Calculating ΔHdis

  • By van’t Hoff equation: ln(x) = -(ΔHdis/RT) + c
  • Beer-Lambert Law: absorbance (A) proportional to

concentration

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SLIDE 41

Calculating ΔHdis

  • By van’t Hoff equation: ln(x) = -(ΔHdis/RT) + c
  • Beer-Lambert Law: absorbance (A) proportional to

concentration

  • Colligative property of dilute solutions: concentration
  • approx. proportional to mole fraction
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SLIDE 42

Calculating ΔHdis

  • By van’t Hoff equation: ln(x) = -(ΔHdis/RT) + c
  • Beer-Lambert Law: absorbance (A) proportional to

concentration

  • Colligative property of dilute solutions: concentration
  • approx. proportional to mole fraction
  • Then x=bA

○ ln(bA) = -(ΔHdis/RT) + c

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SLIDE 43

Calculating ΔHdis

  • ln(bA) = -(ΔHdis/RT) + c

○ Slope of ln(bA) vs (1/T): -(ΔHdis/R)

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SLIDE 44

Calculating ΔHdis

  • ln(bA) = -(ΔHdis/RT) + c

○ Slope of ln(bA) vs (1/T): -(ΔHdis/R) ○ Calculating slope ■ [ln(bA2) - ln(bA1)] / [(1/T2) - (1/T1)]

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SLIDE 45

Calculating ΔHdis

  • ln(bA) = -(ΔHdis/RT) + c

○ Slope of ln(bA) vs (1/T): -(ΔHdis/R) ○ Calculating slope ■ [ln(bA2) - ln(bA1)] / [(1/T2) - (1/T1)] ■ [(ln(b) + ln(A2)) - (ln(b) + ln(A1))] / [(1/T2) - (1/T1)]

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SLIDE 46

Calculating ΔHdis

  • ln(bA) = -(ΔHdis/RT) + c

○ Slope of ln(bA) vs (1/T): -(ΔHdis/R) ○ Calculating slope ■ [ln(bA2) - ln(bA1)] / [(1/T2) - (1/T1)] ■ [(ln(b) + ln(A2)) - (ln(b) + ln(A1))] / [(1/T2) - (1/T1)] ■ [ln(A2) - ln(A1)] / [(1/T2) - (1/T1)]

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SLIDE 47

Calculating ΔHdis

  • ln(bA) = -(ΔHdis/RT) + c

○ Slope of ln(bA) vs (1/T): -(ΔHdis/R) ○ Calculating slope ■ [ln(bA2) - ln(bA1)] / [(1/T2) - (1/T1)] ■ [(ln(b) + ln(A2)) - (ln(b) + ln(A1))] / [(1/T2) - (1/T1)] ■ [ln(A2) - ln(A1)] / [(1/T2) - (1/T1)]

  • Proportionality b does not affect slope
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SLIDE 48

Calculating ΔHdis

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SLIDE 49

Calculating ΔHdis

  • Slope 1000/T: m = 4
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SLIDE 50

Calculating ΔHdis

  • Slope 1000/T: m = 4

○ Slope 1/T: m = 4000

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SLIDE 51

Calculating ΔHdis

  • Slope 1000/T: m = 4

○ Slope 1/T: m = 4000

  • 4000 = -(ΔHdis/R)

○ R = 8.314 x 10-3 kJ/mol K

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SLIDE 52

Calculating ΔHdis

  • Slope 1000/T: m = 4

○ Slope 1/T: m = 4000

  • 4000 = -(ΔHdis/R)

○ R = 8.314 x 10-3 kJ/mol K

  • ΔHdis = -3 x 101 kJ/mol K
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SLIDE 53

Conclusions

  • Thioglycerol-ligated ZnS becomes less soluble at higher

temperatures in MeOH/H2O solution

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SLIDE 54

Conclusions

  • Thioglycerol-ligated ZnS becomes less soluble at higher

temperatures in MeOH/H2O solution

  • Dissolution is exothermic
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SLIDE 55

Conclusions

  • Thioglycerol-ligated ZnS becomes less soluble at higher

temperatures in MeOH/H2O solution

  • Dissolution is exothermic
  • ΔHdis = -3 x 101 kJ/mol K (for 4:1 ratio MeOH:H2O in the region of

40C-70C)

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SLIDE 56

Acknowledgements

For providing the nanoparticles used in this experiment:

Doris Segets, Sebastian Süß

Friedrich-Alexander-Universität Erlangen-Nürnberg For providing the grant funding this REU program:

National Science Foundation

For their mentorship:

Jeff Powell and Dr. Chris Sorensen