Fig. 1

Surface tension of aqueous C12E5 solutions in the absence and presence of 0.5% silica nanoparticles and the adsorbed amount of C12E5 at the silica nanoparticle-water interface as a function of initial and equilibrium C12E5 concentration, respectively, at 25 ℃"

Fig. 2

The contact angles of drops of aqueous C12E5 solution on a quartz slide in air and the contact angles of aqueous solution of C12E5 coexisting with toluene on a quartz slide（measured by captured oil droplet method）as a function of the initial surfactant concentration in water at 25 ℃. Toluene was pre-equilibrated with an equal volume of aqueous C12E5 solution for 24 h at 25 ℃"

Fig. 3

Left: Photographs of vessels containing toluene-water（7 mL/7 mL）emulsions stabilized by（A）0.5% silica nanoparticles alone,（B）C12E5 alone at different concentrations and（C, D）0.5% silica nanoparticles in combination with C12E5 at different concentrationstaken 24 h（A-C）and 1 week（D）after preparation. C12E5 concentration（B-D）in mmol/L is shown on top of the graph.Right: Optical micrographs of toluene-in-water emulsion droplets stabilized by 0.5% silica nanoparticles in combination withdifferent concentrations of C12E5（a-e）and dodecane-in-water emulsion droplets stabilized by C12E5 alone（f）taken 24 hafter preparation. C12E5 concentration（a-f, mmol/L）in water: 0.06, 0.1, 0.3, 0.6, 1.0, and 3.0. Temperature =（22±2） ℃"

Fig. 4

Photographs of（A）a toluene-in-water emulsion and（B）a dodecane-in-water emulsion stabilized by 0.5% silica nanoparticles in combination with 0.3 mmol/L C12E5 following heating under stirring to 45 ℃ and cooling to 25 ℃ followed by re-homogenization for a number of cycles, taken 24 h after preparation.（a）Initial emulsions at 25 ℃,（b）demulsified for the first time,（c）re-emulsified,（d）demulsified for the fifth time, and（e）emulsified for the sixth time"

Fig. 5

Optical micrographs of toluene-in-water emulsions taken 24 h after preparation at room temperature（22±2） ℃.（a）Initial emulsion,（c and e）emulsions formed by re-homogenization after demulsification once and fifth time, respectively"

Fig. 6

Time required for complete demulsification of a toluene-in-water emulsion stabilized by（a）0.5% silica nanoparticles in combination with 0.3 mmol/L C12E5 after warming to different temperatures with gentle stirring（100 r/min）and（b）0.5% silica nanoparticles in combination with C12E5 at different concentrations after warming to 45 ℃ with gentle stirring（100 r/min）"

Fig. 7

Photographs of toluene-in-water emulsions stabilized by（A）C12E10 alone and（B）0.5% silica nanoparticles in combination with C12E10 at different concentrations, taken 1 week after preparation at room temperature（22±2） ℃; micrographs of the emulsions stabilized by silica +C12E10（a-d）and by C12E10 alone（e）taken 24 h after preparation, as well as the emulsion（b）taken 4 h after being placed in a water bath at 45 ℃ with gentle stirring （100 r/min）（b′）. The C12E10 concentration（mmol/L）is shown on the top of the graph and micrographs"

Fig. 8

Photographs of demulsification/emulsification cycling of atoluene-in-water emulsion stabilized by 0.5% silicananoparticles in combination with 0.1 mmol/L C12E10triggered by temperature, taken 24 h after operation"

Fig. 9

Micrographs of toluene-in-water emulsion droplets during drying process at room temperature（22±2） ℃.（a）A Pickering droplet stabilized by 0.5% silica + 0.3 mmol/LC12E5, partially dried with wrinkled surface;（b）Pickering droplets stabilized by 0.5% silica + 0.3 mmol/L C12E10, fully dried displaying broken solid films;（c and d）emulsion droplets stabilized by 1 mmol/L C12E10 alone, fresh oil droplets with smooth surfaces and nearly fully dried exhibiting no surface shell, respectively"

Tab. 1

Percentage of silica nanoparticles adsorbed at oil/water interfaces in toluene-in-water emulsions stabilized by 0.5% silica nanoparticles in combination with 0.3 mmol/L C12E5 at two temperatures, obtained by measuring the concentration of particles（Cp）remaining in the aqueous phase after emulsification"

Fig. 10

Illustration of construction of temperature-responsive Pickering emulsions using silica nanoparticles in combination with nonionic surfactants via hydrogen-bonding"

Fig. 11

Photographs of liquid paraffin-in-water Pickering emulsions stabilized by 0.5% silica nanoparticles in combination with C12E9 of different concentrations without（a）and with（b）CO2 treatment, taken 24 h（a）and 15 days（b）after preparation. The concentrations（mmol/L）of C12E9 from left to right are 0.001, 0.005, 0.008, 0.01, 0.05, 0.08, and 0.1, respectively"

Fig. 12

Digital photographs of the liquid paraffin-in-water Pickering emulsion stabilized by 0.5% silica nanoparticles and 0.05 mmol/L C12E9 during switching process.（a）Homogenization of liquid paraffin and aqueous dispersion（1∶1 volume ratio）at 25 ℃, 24 h later;（b）bubbling CO2 at 25 ℃ for 30 min, followed by homogenization, 15 d later;（c）bubbling N2 at 65 ℃ for 50 min;（d）homogenization at 25 ℃, 1 h later;（e）24 h later;（f）bubbling CO2 at 25 ℃ for 30 min, followed by homogenization, 15 d later"