Cetyltrimethylammonium bromide

Hydrogen tetrachloroaurate trihydrate (HAuCl₄·3H₂O, 99%), chloroplatinic acid hexahydrate (H₂PtCl₆, 99%), sodium borohydride (NaBH₄, 98%), trisodium citrate (TSC, 99%), ascorbic acid (AA, 99%), iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O, 99%) and silver nitrate (AgNO₃, 99%) were purchased from Sigma-Aldrich. Cetyltrimethylammonium bromide (CTAB, 98%) was obtained from Alfa Aesar. Hydrogen peroxide solution (H₂O₂, 30 wt% in water), cetyltrimethylammonium chloride (CTAC, 97%), sodium hydroxide (NaOH, 96%), ammonia solution (NH₃·H₂O, 25 wt% in water), titanium chloride solution (TiCl₃, 15–20% in 30% HCl), sodium bicarbonate (NaHCO₃, 99%), sodium dodecyl sulfate (SDS, 98%), nitric acid (HNO₃, 67% in water), hydrochloric acid solution (HCl, 37 wt% in water), rhodamine B (RhB, 99%) and salicylic acid (SA, 99%) were purchased from Aladdin Reagent. All chemicals were used without further purification. Deionized water with a resistivity of 18.2 MΩ cm produced from a Direct-Q5 ultraviolet water purification system was used in all experiments.

The absorption spectra were acquired on Edinburgh Instruments FS5 (Edinburgh Instruments Ltd., Livingston, UK). The FTIR and XPS analysis were obtained with an FTIR SPECTROMETER FRONTIER (Perkin Elmer Inc., Waltham, MA, USA) and PHI Hybrid Quantera (ULVAC-PHI). The concentration of Au nanomaterials was measured with an OPTIMA 2000DV (Perkin Elmer Inc., Waltham, MA, USA), and TEM images were obtained using a JEM-1400 (JEOL Ltd., Akishima, Tokyo, Japan). Hydrogen tetrachloroaurate (III) trihydrate (HAuCl₄·3H₂O, ≥99.9%) and cetyltrimethylammonium bromide (CTAB, ≥99%) were purchased from Alfa Aesar (Heysham, Lancashire, UK). Sodium citrate dihydrate (≥99%) was acquired from Avantor Inc. (Radnor, PA, USA). Sodium borohydride (NaBH₄, ≥99%) was obtained from Koch-Light Laboratories Ltd. (Haverhill, England, UK). Sulfuric acid (≥98%) and L-ascorbic acid (≥99%) were purchased from Fluka (Charlotte, NC, USA). Silver nitrate (AgNO₃, 99.85%) was obtained from Acros Organics (Waltham, MA, USA). L-cysteine (≥97%) was purchased from Merck KGaA Ltd. (Darmstadt, Germany). Ultrapure deionized water (18.3 MΩ·cm⁻¹, RODA, Te Chen Instruments CO., Ltd., Taichung, Taiwan) was used for all solution preparations. All chemicals were used as received, without further purification.

Cetyltrimethylammonium bromide (CTAB, ≥98%) was obtained from Alfa Aesar (Blackfriars, MA, USA). Gold chloride trihydrate (HAuCl₄·3H₂O, ≥99.9%), silver nitrate (AgNO₃, ≥99%), L-ascorbic acid (reagent grade), sodium oleate, sodium borohydride (NaBH₄, ≥99.99%), glutaraldehyde solution (50 wt. % in water), dimethyl sulfoxide (DMSO), poly (sodium 4-styrenesulfonate) (PSS, 70 kDa), poly (allylamine hydrocholride) (PAH, 900,000), Chitosan (low molecular weight), and poly-l-lysine (PLL, 900,000) were purchased from Sigma–Aldrich, Saint Louis, MA, USA. Albumin bovine (BSA, biotechnology grade) was acquired from VWR. Hydrochloric acid (HCl, certified ACS plus) and sodium hydroxide (NaOH, 99.0%) were obtained from Fisher Scientific, Waltham, MA, USA. Hyaluronic acid (HA, 10,000) was bought from Lifecore Biomedical (Chaska, MN, USA). If not specified otherwise, all chemicals were prepared using Millipore water, Billerica, MA, USA.