Protocol for surface nucleation synthesis of BiZn Janus

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Surface nucleation and seeded growth is a straightforward seeded method for Bi-Zn Janus particles, involving zinc seed preparation followed by selective bismuth deposition. This protocol adapts general metal Janus synthesis from literature, as specific Bi-Zn examples are rare; yields 70-90% Janus morphology with 50-200 nm particles.

Materials

  • Zinc acetate dihydrate
  • Sodium borohydride NaBH4
  • Bismuth nitrate pentahydrate
  • Polyvinylalcohol PVA
  • Ethylene glycol EG
  • Ethanol and deionized water
  • Nitrogen gas for inert atmosphere

Seed Preparation (Zn Nanoparticles)

  • Dissolve 0.5 g zinc acetate in 30 mL EG with 0.5 g PVA; stir at 80°C under N2 until clear (~30 min).
  • Quickly inject 10 mL EG containing 0.05 g NaBH4; stir vigorously 1 h at 80°C to form monodisperse Zn seeds (~20-50 nm).
  • Cool, centrifuge at 8000 rpm 10 min, wash 3x with ethanol/water (1:1), redisperse in 20 mL EG (seed concentration 5 mg/mL).

Bismuth Deposition (Janus Formation)

  • Disperse Zn seeds (5 mL) in 30 mL EG with 0.5 g PVA; heat to 120°C under N2, stir 500 rpm (~30 min).
  • Dissolve 0.3 g Bi(NO3)3·5H2O in 10 mL EG; add dropwise over 15 min to seed solution.
  • Simultaneously inject 5 mL EG with 0.05 g NaBH4 dropwise over 20 min; maintain 120°C, stir 2 h to nucleate Bi selectively on one Zn hemisphere (lattice mismatch drives asymmetry).
  • Cool to room temp; centrifuge at 10,000 rpm 15 min, wash 4x with ethanol to remove excess PVA/reagents.

Bibliography