Sodium oleate

Gold (III) chloride trihydrate (HAuCl₄·3H₂O, ≥99.9%), hexadecyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride solution (CTAC, 25 wt% in H₂O), and L-ascorbic acid (AA, ≥99%) were purchased from Sigma Aldrich. Sodium Oleate (NaOL, 98%), sodium borohydride (NaBH₄, ≥99%), silver nitrate (AgNO₃, 99.99%), Hydrochloric Acid (HCl, 37 wt% in H₂O), Tetrahydrofuran (THF, 99%) and Chloroform (99%) were obtained from MACKLIN. Thiol-functionalized polystyrene (M_n = 50,000 g mol⁻¹, M_w/M_n= 1.06) was obtained from Polymer Source Inc. Bovine serum albumin (BSA, Fraction V) was obtained from Solarbio. Quantifoil holey carbon films (400 mesh with 37 μm × 37 μm square holes) and Gilder Square Grids (2,000 mesh with 7.5 × 5 μm² and 300 mesh with 54 × 54 μm² square holes) were purchased from Zhongjingkeyi Technology Co., Ltd.
All chemicals were used as-received unless otherwise indicated. Demineralized water was used in all aqueous solutions, which were further purified with a Milli-Q system (Millipore). All glassware used in the following procedures were cleaned in a bath of freshly prepared aqua regia and were rinsed thoroughly in H₂O prior to use.

Oleic acid (OA, >90%), 1-octadecene (ODE, >90%), Arg-Gly-Asp (RGD, 97%), polyacrylamide (PAM, M_n = 40 000), (3-aminopropyl)triethoxysilane (APTS, 99%), sodium hydroxide (NaOH, 97%), and hydrochloric acid (HCl, 37%) were purchased from Sigma-Aldrich. Cyclohexane (99.5%), N-hexane (97%), ethanol (99.7%), and diethylene glycol (DEG, 98%) were purchased from General-Reagent. Sodium oleate (NaOL, 98%), gadolinium chloride hexahydrate (GdCl₃·6H₂O, 99.99%), and citric acid (CA, 99.5%) were purchased from Macklin. N,N-Dimethylformamide (DMF, 99.8%) and oleylamine (OM, 80–90%) were purchased from Aladdin. Poly(acrylic acid) (PAA5000, M_w = 5000, 50 wt%) and Poly(acrylic acid) (PAA2000, M_w = 2000, 63 wt%) were purchased from Acros Organics.