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. Author manuscript; available in PMC: 2019 Jan 31.
Published in final edited form as: ACS Appl Mater Interfaces. 2018 Jan 16;10(4):3200–3209. doi: 10.1021/acsami.7b09071

Table 2.

Characteristics of Protein-Loaded Porous Si–SiO2 Core–Shell Particles (Large Pores)

sample
thin shell medium shell thick shell
oxidation timea 15 min 20 min 30 min
surface area (m2/g)b 239 ± 16 206 ± 30 237 ± 10
pore volume (cm3/g)c 1.04 ± 0.06 1.05 ± 0.04 1.05 ± 0.08
pore diameter (nm)b 21 ± 1 22 ± 0.2 21 ± 0.5
photoluminescence λmax (nm)d 823 783 747
Si feature size (nm)e 5.1 4.5 4.0
% BSA loaded by adsorptionf 19 ± 1.7 17 ± 1.1 16 ± 1.0
% BSA loaded by Mg silicate trappingg 29 ± 2.5 27 ± 3.6 33 ± 2.1
a

Time that pSi samples (in microparticulate form) were oxidized in air at 700 °C to generate the SiO2 shell. Preparation parameters for the particles prior to oxidation were the same for all sample types.

b

Measured by nitrogen adsorption and determined using BET (Brunnauer–Emmett–Teller) analysis of the adsorption isotherms.

c

Measured by nitrogen adsorption and determined using BJH (Barret–Joyner–Halenda) analysis of the adsorption/desorption isotherms.

d

Measured with λex = 365 nm.

e

Average size of the luminescent Si features in the sample, estimated from PL spectrum using eq 1 (Eg of Si = 1.12 eV).

f

Mass percentage. BSA loaded from pH 4 acetate buffer by electrostatic adsorption. Each value represents mean ± standard deviation (n = 3).

g

Mass percentage. BSA loaded from pH 9 tris buffer in the presence of 200 mM MgCl2(aq). Each value represents mean ± standard deviation (n = 3).