Nickel Sulfide Nanocrystal Synthesis Using Substituted ThiophenolsJoe Veglak1,2, Jordan Rhodes1 & Janet Macdonald1

1 Department of Chemistry, Vanderbilt University, Nashville, TN2 Department of Chemical Engineering, Rose-Hulman Institute of Technology, Terre Haute, IN

Introduction

20 25 30 35 40 45 50 55 60 65 70

Inte

nsity

(A.

U.)

2θ (Degrees)

Polydymite (Ni3 S4)

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Inte

nsity

(A.

U.)

2θ (Degrees)

Heazlewoodite (Ni3 S2)

Sulfur reagents used in this synthesis:

A 1:1 ratio of Ni:S eliminated the thermodynamically stablemillerite phase (NiS) consistently found creating mixedphase products when larger quantities of sulfur werepresent.

• Oleylamine was used as thesolvent of the reaction, its stericeffects are used to help controlparticle size.

• The para-substituted thiophenolwas injected into the nickelsolution at 170°C, to form aprecursor phase, then heatedto 220°C to form the desiredphase.

Phase Characterization

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Inte

nsity

(A.

U.)

2θ (Degrees)

Heazlewoodite (Ni3 S2)Polydymite (Ni3 S4)

EWG

EDG

X-Ray Diffraction (XRD)was used to analyze thephase composition ofeach of the particles.

Sulfur rich nickel sulfide phases correlated to substituted thiophenols with the less electron donating groups.

Potential Phases:

• Starting Material (NiCl )

• Heazlewoodite(Ni S )

• Polydymite(Ni S )

Nickel Oxidation States:NiNi Ni NiNi Ni NiElectron donating groups are able to donateelectrons to the nickel atoms, lowering nickel’soxidation state, while electron withdrawing groupstake electrons and raise the oxidation state.

100 nm

A

20 nm

Cl

HS

D

50 nm

C

20 nm

B

Phase Cl Polydymite

(Ni S ) – 100%CH Polydymite (Ni S ) – 71.6%Heazlewoodite(Ni S ) – 28.4%OCH Polydymite (Ni S ) – 52.9%Heazlewoodite (Ni S ) – 47.1%NH Heazlewoodite (Ni S ) – 100%

• Transmission ElectronMicroscopy (TEM) wasused to obtain theseimages.

• A-D decreases interms of electrondonating groups, Abeing the most electrondonating and D beingthe least.

• A larger surface area tovolume ratio (smallerparticles with moreedges) typically makesfor a better catalyst .

Testing Catalytic AbilityTEM images taken by Jordan Rhodes

Future Direction and Conclusion

AcknowledgementsI would like to thank the National Science Foundation (NSF) for funding my work in the Macdonald lab,The VINSE NSF REU grant: 1560414,The VINSE program and staff,And all the members of the Macdonald lab

Electron Donating Group (EDG)

Electron Withdrawing Group (EWG)

Bruice, P. Y. (2004). Organic Chemistry 6th Edition. Upper Saddle River, NJ: Pearson/Prentice Hall

-0.006

-0.004

-0.002

0

0.002

0.004

0.006

0.008

-0.5 -0.45 -0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0Curr

ent

(mA)

Voltage (vs. Ag/AgCl) (V)

-CH3

-OCH3-Cl-NH2

We have developed a facile synthesis of nickel sulfide nanocrystalsthrough hot injection that demonstrates phase control by varying thesubstituent group of para-substituted thiophenols. In the future, we look tofurther test and enhance the particles catalytic abilities and test to see if theligands on the particles are surface or crystal bound.

Crystal bound ligands are far moredesirable as catalysts because theyleave the metal sites of nanocrystalsexposed, the catalytically active centers.Additionally crystal bound ligands aremore tightly bound and less likely tobreak. The ligands won’t contaminate thereaction solution.Turo M.J. Macdonald M.E., ACS Nano, 2014, 8 (10), pp 10206

Different phases and morphologies can largely effect thecatalytic abilities of nickel sulfide nanocrystals. While nickelsulfides contain an abundance of different phases, phasecontrol of these crystals can be difficult. One proposed methodof selectively isolating these phases involves manipulating thesulfur reagent used, where the electron donating ability ofsubstituent groups influences the reactivity of the sulfurprecursor. Para-substituted thiophenols were used as thesulfur for this work.

Preliminary Linear SweepVoltammetry in a HydrogenEvolution Reaction (HER)was used to test theparticles’ catalytic ability

Image created by Jordan Rhodes

Synthetic Process Morphological Characterization

Proposed hypothesis for phase change:

A more positive voltage when the current drops indicates particles with better catalytic abilities.

While the results are preliminary and thus inconclusive, there is already a possible

trend showing particles formed

using more electron donating substituent groups have greater

catalytic abilities.