Supporting Information. Anti-Fogging/Self-Healing Properties of Clay- Containing Transparent Nanocomposite Thin Films

Transcription

1 Supporting Information Anti-Fogging/Self-Healing Properties of Clay- Containing Transparent Nanocomposite Thin Films Matt W. England, Chihiro Urata, Gary J. Dunderdale, and Atsushi Hozumi* National Institute of Advanced Industrial Science and Technology (AIST), , Anagahora, Shimoshidami, Nagoya , Japan. S-1

2 Experimental Materials Ethanol (99.5 %) was purchased from Amakasu Chemical Industries. 3-aminopropyl triethoxysilane (APTES) was purchased from Gelest. Polyvinylpyrrolidone (PVP, M.W. ~1,300 kda) was purchased from Aldrich. Magnesium chloride hexahydrate (MgCl 6H 2 O) was purchased from Wako Pure Chemical Industries, Ltd. All chemicals were used without further purification. Silicon (Si) wafers (n-type [100]) were purchased from Shin-Etsu Handotai, Ltd. Glass slides were purchased from Matsunami Glass Ind. Ltd. All substrates were cleaned using an UV/ozone treatment for 30 minutes before use. Characterization Static (θ s ) and dynamic (advancing (θ A ) and receding (θ R )) contact angles (CAs) were measured using a Kyowa Interface Science, CA-V150 goniometer. θ s values of water were recorded at room temperature (~25 C). For θ A and θ R measurements, probe liquid droplet (about 5 µl of n-hexadecane) was added and withdrawn from the surface, respectively. The final CAs were determined by taking mean values of 5 different points from 3 samples. Film thicknesses were measured on films deposited onto Si wafers using a Horiba Jobin Yvon, MM-16 Ellipsometer. Measurements were taken 3 times from 5 different points on the sample surfaces, and a mean value was calculated. XRD patterns were obtained using a Rigaku, RINT 2100 diffractometer with monochromated Fe-K α radiation. UV- Vis/transmission spectra were recorded using an Agilent Technologies Inc., Cary 5000 UV- Vis-NIR Spectrophotometer. FTIR spectra were obtained using a Digilab, FTS 7000 Fourier Transform Infrared Spectrometer. Optical images were taken using a Canon, PowerShot G1 X Mark II. For film fogging images, films spin-coated onto glass slides were placed in the refrigerator at 3 C for a minimum of 1 h, then placed onto clear plastic-made holders approximately 1 cm above a patterned surface at room temperature, and photographed immediately. Preparation of films The hybrid clay (we refer to this clay as AMP-clay) was synthesized using a sol-gel based method g (3.62 mmol) of MgCl 6H 2 O was dissolved in ethanol, after which 1.3 ml (5.85 mmol) of APTES was added to the solution with rapid stirring. This mixture was left to stir overnight at room temperature. The AMP-clay was then centrifuged at 4000 rpm for 20 S-2

3 minutes to remove excess solvent, and washed using excess ethanol and a 60:40 ethanol/water mixture, a minimum of six times. AMP-clay was then dried in a fume hood at room temperature overnight. To form the composite (we refer to this composite as PVP/AMP-clay composite), the AMP-clay and PVP were dissolved into separate 1 ml aqueous solutions, and then mixed to form precursor solutions of the stated wt%. For example, for 4:1 PVP/AMP-clay composite films, 1 ml solutions of PVP at 20 wt% and AMP-clay at 5 wt% were first made up and then mixed to form a 2 ml deposition solution of PVP at 10 wt% and AMP-clay at 2.5 wt%. This mixture was then spin-coated onto UV-ozone cleaned glass slides or Si substrates using a Kyowa Riken Spin Coater, K-359S-1, and then placed in an oven at 100 C for a minimum of 3 h. For PVP films, a single 10 ml solution was made up to the stated wt% and then spin-coated onto UV-ozone cleaned glass slides or Si substrates, in a manner similar to the fabrication of PVP/AMP-clay composite films. For testing AMP-clay hydrophilicity, AMP-clay films were similarly prepared using a dispersion of finely ground AMP-clay in ethanol (10 wt%). PVP films for self-healing tests and water absorption tests were prepared by spin-coating a PVP20 wt% solution onto cleaned Si substrates for three times and then dried in an oven maintained at 100 C for 3 h. Anti-fogging tests Films deposited onto glass slides were placed in a refrigerator at 3 ºC for a minimum of 1 h. Samples were then removed from the refrigerator into the humid air of the laboratory (minimum 50 % relative humidity), and were placed above a patterned surface at room temperature, to see if fogging, or obscuring of the pattern could be observed. When multiple testing cycles were required, the samples were kept at room temperature for around 10 minutes before being returned to the refrigerator. Ambient water absorption tests Samples were prepared on pre-weighed 5 10 cm UV-ozone cleaned Si substrates (film thickness was in the range of nm). They were left in laboratory air at room temperature for 24 h (minimum 50 % relative humidity), after which they were re-weighed and their wt% water absorption was determined. Three samples of both PVP and PVP/AMPclay composite films were used, and an average water absorbance calculated. Sand abrasion tests S-3

4 The mechanical resistance and self-healing ability of our PVP/AMP-clay composite films were investigated by sand abrasion tests. During the tests, the composite film (PVP10 wt%) was mounted at an incline of 45o, and 20 g of sea sand (300 to 600 µm in diameter) was continuously dropped onto it from a height of 40 cm. After this, the sample was kept under high humidity conditions (~80 % relative humidity at room temperature) for 48 h. Changes in transparency of our samples were monitored using relative optical transmission (T/T0, where T0 is initial transmission, and T is transmission after test). Figure S1. Optical images of a) as-synthesized AMP-clay, and b) opaque 2:1 PVP/AMPclay composite film (PVP10 wt%) on a glass slide, after water was placed on the surface. a) b) Glass Si Cu PMMA Figure S2. Optical images of a) bulk 4:1 PVP/AMP-clay composite gel (PVP10 wt%), and b) various 4:1 PVP/AMP-clay composite film (PVP10 wt%)-covered substrates. S-4

5 (d 001 ) 600 Intensity (a.u.) (d 002 ) (d 020, 200 ) θ (Degrees, Fe Kα) Figure S3. Typical XRD patterns of AMP-clay Transmission (%) Wavelength (nm) iii iv v i ii Figure S4. Transmission spectra of i) an uncoated glass slide, and glass slides coated with ii) PVP, iii) PVP/AMP-clay composite films (PVP10 wt%), iv) sample iii) after multiple antifogging tests, and v) sample iii) after exposure to humid air (minimum 50 % relative humidity at room temperature) for 30 days. S-5

6 a) nm b) nm c) nm d) nm Figure S5. Typical AFM images of a) spin-coated AMP-clay (Rrms= 8.30 nm), b) PVP/AMPclay composite film (PVP10 wt%, Rrms = 3.34 nm), c) PVP film (10 wt%, thickness = about 45 nm, Rrms = 1.01 nm), and d) uncoated glass slide (Rrms = 0.42 nm) surfaces, in a scanning area of µm2. a) i b) i 15.1 o ii c) i 5.2 o ii 23.7 o iii ii 6.1 o iii 27.9 o 22.3 o 25.9 o iii <5 o 10.0 o Figure S6. a) Optical micrographs of a water droplet profile (5 µl) on a glass slide surface coated with AMP-clay: i) after deposition, ii) after anti-fogging testing, and iii) after drying at 100 C for 3 h, then cooling to room temperature. Because of adsorption of impurities, this hydrophilicity quickly worsened after anti-fogging testing and drying. Also shown are S-6

7 optical micrographs of a n-hexadecane droplet profile (5 µl) on b) a dried PVP/AMP-clay composite film (PVP10 wt%) surface, and c) a water-swollen surface b) after 48 h exposure to humid air (minimum 50 % relative humidity at room temperature); micrographs i, ii, and iii show θ S, θ A and θ R, respectively. Figure S7. Optical images of PVP/AMP-clay composite (prepared at different PVP concentrations, top) and PVP (bottom) films on glass slides during anti-fogging tests. S-7

8 Scheme S1. Predicted self-healing mechanism for our PVP/AMP-clay composite film: a) PVP/AMP-clay composite film is scratched/damaged; b) newly-exposed surface absorbs ambient water, causing it to swell; c) swollen composite migrates across surface until the scratch is closed, and re-forms non-covalent bond structure. Figure S8. Typical SEM images of a-c) ~100 nm and d-f) ~60 nm-thick PVP/AMP-clay composite films (PVP10 wt%) after damaging with a scalpel (a and d) and after exposure to humid air (minimum 50 % relative humidity at room temperature) for 24 h (b and e) and 36 h (c and f). S-8

9 Figure S9. Typical SEM images of a PVP/AMP-clay composite film (PVP10 wt%, ~900 nm thick): (a) immediately after damage with an abrasive sponge, and (b) after 24 h exposure to humid air (minimum 50 % relative humidity at room temperature). c) shows an identical surface which was damaged immediately after one cycle of anti-fogging tests, and d) shows surface c) after 24 h exposure to humid air (minimum 50 % relative humidity at room temperature). Figure S10. Optical images of a PVP/AMP-clay composite film (PVP10 wt%): a) immediately after a sand abrasion test, and b) after 48 h exposure to high humidity conditions (~80 % relative humidity at room temperature, abraded areas are highlighted with a yellow circle). c) shows the relative optical transmittance of samples a) and b) (T/T 0, where T 0 is initial transmission, and T is transmission after test), shown in red and blue, respectively. S-9