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Gold Nanoparticle Synthesis
Published on: July 10, 2021
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pH-Responsive Mercaptoundecanoic Acid Functionalized Gold Nanoparticles and Applications in Catalysis
Siyam M Ansar1, Saptarshi Chakraborty2, Christopher L Kitchens3,4
1Department of Chemical and Biomolecular Engineering, Clemson University, Clemson, SC 29634, USA. mmohame@g.clemson.edu.
Nanomaterials (Basel, Switzerland)
|May 19, 2018
Summary
Gold nanoparticles functionalized with mercaptoundecanoic acid (AuNP-MUA) show pH-triggered aggregation and phase transfer for reusable catalysis. Optimal 90% MUA coverage balances stability, activity, and reusability in reactions.
Area of Science:
- Nanotechnology
- Catalysis
- Surface Chemistry
Background:
- Gold nanoparticles (AuNPs) are versatile nanomaterials with catalytic applications.
- Controlling nanoparticle properties like surface coverage and colloidal stability is crucial for catalytic efficiency and reusability.
- pH-responsive functionalization offers potential for dynamic control over nanoparticle behavior.
Purpose of the Study:
- To synthesize mercaptoundecanoic acid (MUA) functionalized gold nanoparticles (AuNP-MUA).
- To investigate the pH-triggered aggregation, re-dispersion, and phase transfer capabilities of AuNP-MUA.
- To evaluate AuNP-MUA as a reusable catalyst for 4-nitrophenol reduction, optimizing MUA surface coverage for performance and recovery.
Main Methods:
- Synthesis of MUA-functionalized gold nanoparticles (AuNP-MUA).
- Characterization of pH-dependent aggregation, re-dispersion, and aqueous/organic phase transfer.
- Assessment of catalytic activity and reusability in the reduction of 4-nitrophenol using borohydride.
- Investigation of varying MUA surface coverages (e.g., 100%, 60%, 90%) on catalytic performance and stability.
Main Results:
- AuNP-MUA exhibited pH-triggered aggregation around pH 4 (pK of MUA) and phase transfer to organic solvents around pH 9.
- Complete MUA coverage (100%) inhibited catalytic activity; reduced coverage increased activity but decreased stability and reusability.
- Optimal performance balancing stability, activity, and reusability was achieved at 90% MUA surface coverage.
- Catalyst recovery was demonstrated via pH-induced aggregation (pH ~4) and phase transfer (pH ~9).
Conclusions:
- AuNP-MUA demonstrates tunable pH-responsive properties for controlled catalysis.
- A 90% MUA surface coverage provides a balance for effective catalytic activity, colloidal stability, and efficient recovery/reuse.
- The dual recovery methods (aggregation and phase transfer) enhance the catalyst's applicability across various pH conditions.
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