Au powder

Single crystals of AuTe₂Se_4/3 were grown using the self-flux method. Total 2–4 g starting materials with high purity Au powder (99.99%, Sigma Aldrich), Te powder (99.999%, Sigma Aldrich), and Se powder (99.99%, Sigma Aldrich) were stoichiometrically weighted and sealed in an evacuated silica tube in high vacuum (10⁻⁵ mbar) and subsequently mounted into a muffle furnace. The furnace was heated up to 800 °C in 40 h and dwelled 10 h. Afterward, the furnace was slowly cooled down to 450 °C in 4 days and then shut down. Separated crystals from ingot are generally thin with maximum planar size 4 × 1 mm². The single crystals of AuTe₂Se_4/3 were ribbon shape with shining mirror-like surfaces.

Au powder (99.99%), AgI (99%), nitric acid (70%), 4-ABT (97%), ethanol (99.5%), and CMIT/MIT were purchased from Sigma Aldrich.

Purified DNA was purchased from Bioneer (Daejeon, Korea). Hg(Ac)₂, Mg(Ac)₂, Ca(Ac)₂, CrCl₂, FeCl₂, Co(Ac)₂, NiCl₂, CuCl₂, Zn(Ac)₂, Cd(Ac)₂, Pb(Ac)₂, UO₂(Ac)₂, Au powder (99.99%), and sodium dodecyl sulfate (SDS) were purchased from Sigma–Aldrich. Th(NO₃)₄ was purchased from Merck. Phosphate buffered saline (PBS) was purchased from Gibco. The natural water samples were collected from the west sea of South Korea, the Gap River, and the pond at KAIST. Samples were centrifuged to remove impurities.