Electronic Supplementary Information

Measurement of filtration performance

The filter tester could deliver charge neutralized monodisperse solid NaCl aerosol particles that had a

mass mean diameter of 300 nm using electrostatic classifier and a geometric standard deviation not

exceeding 1.86. The neutralized NaCl aerosol particles were feed into a filter holder and down

through the filter with 100 cm2 of effective area. The filter air flow resistance was measured with the

combination of a flow meter and two electronic pressure transducers that detected the pressure drop

through the filtration medium under testing. All NaCl aerosol particle tests were conducted at room

temperature (25±2 oC) with a continuous airflow fixed at 10, 20, 30, 32, 40, 50, 60, 70, 80 and 90

L/min.

Fig. S1 FE-SEM images of PES fibrous membranes obtained from weight ratios of DMF/NMP (a)

3/1 and (b) 1/3, respectively.

Table S1 Properties of relevant PES solutions.

PolymerContent of BaTiO3

(wt%)

Viscosity(cps)

Conductivity(μS/cm)

Surface tension

(mN/m)

PES

0 769 2.83 33.44

0.5 732 2.47 31.23

1 689 1.99 29.67

1.5 623 1.36 28.69

2 590 1.15 26.33

Table S2 Performance summary of PES membranes fabricated from different DMF/NMP ratios.

Sample E (%) P (Pa) QF (Pa-1)

PES-0 80.02 27.6 0.058 0.215

PES-25 83.98 29.5 0.062 0.289

PES-50 91.03 30.3 0.080 0.356

PES-75 78.21 23 0.066 0.389

PES-100 36.24 7.9 0.057 0.402

E: Particle filtration efficiency; P: pressure drop; QF: quality factor; : packing density

QF=-ln(1-E%)/P, =w/(*z), w: basis weight of membrane, : density of PES, z: thickness of membrane

Fig. S2 Softness (a) and mechanical strength (b) of relevant PES/BaTiO3 NFMs.

Fig. S3 Schematic description of the electret process and the kind of electric charges existed in the

PES/BaTiO3 NFMs. (a) The hybrid nanofiber construction process along with the electret process.

(b) PES/BaTiO3 NFM. (c) Polarization charge, (d) volume charge, and (e) interfacial polarization.

Table S3 TSC data of electret membranes with different content of BaTiO3 NPs.

SamplesPeak temperature

(oC)

Peak current

(×10-1 pA)

Activation energy

(eV)

Relaxation time

(s)

PES (control) 96.6 0.607 1.268 5.82×10-18

NFM0.5 115.9 0.724 1.194 5.18×10-16

NFM1 136.3 2.086 0.676 3.12×10-8

NFM1.5 144.7 2.676 0.483 1.27×10-5

NFM2 158.5 1.197 0.549 3×10-6

Table S4 Comparison of relevant properties of NFM1.5, nylon-6/PE, Ag nanowires, and commercial

membranes.

Sample

air

permeability

(mm/s)

water vapor

permeability

(kg/m2/d)

Filtration

efficiency

(%)

Pressure

drop

(Pa)

FTIR

transmittance

(%)

NFM1.5 713 5.91 99.99 67 93.4

Nylon-6/nanoPE - 4.39 99.6 349 89.3

Ag nanowire cloth - - - - 59.2

Com-1 203 1.79 99.89 115 4.74

Com-2 190 1.57 99.97 134 0.65

Fig. S4 WCA of relevant PES/BaTiO3 NFMs.