Cetyltrimethylammonium bromide

Cetyltrimethyl-ammonium bromide (CTAB, 99.0%) as surfactant and the alkoxide precursor tetraethyl orthosilicate (TEOS, 99.0%) were purchased from Dae-Jung Chemicals (Siheung-si, Korea). VLP was generously donated by Ameer & Adnan Pharmaceutical Pvt. Ltd. (Lahore, Pakistan). Acetonitrile (≥98%) was also purchased from Dae-Jung Chemicals (Siheung-si, Korea). The rest of the chemicals used in this research were of analytical grade and used as such.

Yttrium nitrate hexa-hydrate (Y(NO₃)₃∙6H₂O, 99.8%), ytterbium nitrate penta-hydrate (Yb(NO₃)₃∙5H₂O, 99.9%), erbium nitrate penta-hydrate (Er(NO₃)₃∙5H₂O, 99.9%), sodium fluoride (NaF, ≥99.0%), diethylene glycol (DEG, 99.0%), polyacrylic acid, N-(3-dimethylaminopropyl)-Nʹ-ethylcarbodimide hydrochloride (EDC), and N-hydroxy-succinimide (NHS, 98.0%) were obtained from Sigma-Aldrich (St. Louis, MO, USA). Sodium citrate (C₆H₅Na₃O₇∙2H₂O, >99.0%) was provided by APS Biotech, Seoul. Nitric acid (HNO₃, 60.0%) was purchased from Samchun (Seoul, Korea), ethyl alcohol (C₂H₅OH) was provided by Emsure (Billerca, MA, USA), and cetyltrimethylammonium bromide (CTAB, >99.0%) was obtained from Daejung (Seoul). Sodium hydroxide (NaOH) was obtained from KANTO chemical (Tokyo), and dimethylsulfoxide (DMSO, 99.9%) was provided by Alfa Aesar (Ward Hill, MA, USA). All the purchased reagents were of analytical grade. Solutions were prepared using deionized (DI) water (Direct–Q^® Water Purification System, Millipore, Billerica, MA, USA).