K2co3

S53P4 and 13-93B20 BaG were prepared from analytical grade K₂CO₃ (Alfa Aesar, Thermo Fischer, Kandel, Germany),
Na₂CO₃, NH₄H₂PO₄, (CaHPO₄)(2(H₂O)), CaCO₃, MgO,
H₃BO₃ (Sigma-Aldrich, Saint-Louis, MS), and
Belgian quartz sand. The nominal oxide compositions of the experimental
BaGs are presented in Table 1 in mol %.
The reagents
were melted in a platinum crucible at 1450 °C
in an electrical furnace. The molten glass was then cast into a preheated
graphite mold to obtain a rod with a diameter of 14 mm. The glass
rods were then annealed overnight at 500 °C and let to cool down
to room temperature. The rods were then cut into 2 mm thick discs
and polished with SiC paper (grit #320, #500, #800, #1200, #2400,
and #4000, from Struers, Copenhagen, Denmark). All samples were dried
and kept in a desiccator until further use.
Membranes were directly
deposited onto untreated or surface-modified
BaG discs. Discs with both BaGs composition were surface treated by
either silanization or conditioning. The surface treatment protocols
are as follows.

Tannic acid (TA, M_w = 1701.23 g·mol⁻¹, CAS 1401-55-4), ferroceneboronic acid ≥ 95% (FcB(OH)₂, M_w = 229.85 g·mol⁻¹, CAS 12152-94-2), glucose oxidase from Aspergillus Niger sp. Type X-S (GOx, ~168 U·mg⁻¹, M_w = 160 kDa, G7141, CAS 9001-37-0), horseradish peroxidase (HRP, ~250 U·mg⁻¹, M_w = 44 kDa, CAS 9003-99-0), hydrogen peroxide solution 30 wt.% (H₂O₂, M_w = 34.01 g·mol⁻¹, CAS 7722-84-1), Bradford reagent (reference B6916), and phosphate buffered saline tablets were purchased from Sigma-Aldrich (St. Louis, MO, USA). Ferrocene methanol (FcOH ≥ 95%, Mw = 216.1 g·mol⁻¹, CAS 1273-86-5) was retrieved from FluoroChem (Hadfield, UK). Hydrogen tetrachloroaurate(III) hydrate (HAuCl₄, M_w = 393.83 g·mol⁻¹, CAS 27988-77-8), d-(+)-glucose anhydrous 99% (M_w = 180.16 g·mol⁻¹, CAS 50-99-7), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS 98 %, M_w = 548.68 g·mol⁻¹, CAS 30931-67-0) were purchased from Alfa Aesar (Haverhill, MA, USA). Sodium chloride ≥99.5% (NaCl, M_w = 58.44 g·mol⁻¹, CAS 7631-99-4), and potassium carbonate ≥99.5% (K₂CO₃, M_w) =138.21 g·mol⁻¹, CAS 209-529-3) were purchased from Fischer (Pittsburgh, PA). All chemicals were used as received and solution were prepared using Milli-Q water with 18.2 MΩ·cm resistivity.