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Super hydrophobic Glass

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by

Raúl Zúñiga

on 20 November 2014

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Transcript of Super hydrophobic Glass

Super hydrophofic phenomenon
"Lotus effect" : lotus leaves exhibit extremely high
water repellency and self-cleaning abilities. It is of great interest to students because of the antisticking, self-cleaning properties that can be applied to the industrial production of everyday materials (e.g., water-repelling windshields and clothing)
Method
The second slide is then immersed in a glass vial containing 10 mL of toluene to cover the entire surface of the glass. 95 μL of methyltrichlorosilane and 0.25 mL of concentrated hydrocloric acid were added before the vial was capped and stored at 4°C for 3-5 h. The third slide was treated the same way with 0.35 mL of octadecyltrichlorosilane and 0.25 mL of concentrated hydrochloric acid and stored at 4 °C (or 20 °C) for 1.5 h.
Hydrophobicity
Is the surface property of being water repellent; a surface is called hydrophobic when the water contact angle, O, is greater than 90º and superhydrophobic when it is greater than 150º
Super hydrophobic Glass
Preparation of Transparent Superhydrophobic Glass Slides:
Demonstration of Surface Chemistry Characteristics

Jessica X. H. Wong and Hua-Zhong Yu
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
dx.doi.org/10.1021/ed300809m | J. Chem. Educ. 2013, 90, 1203−1206

These are some of the water-repelling products for clothing, and also one picture of the lotus effect in cotton cloth with wax.
The contact angle measures the wettability of a surface, determined by the thermodynamic equilibrium of the interfacial tensions between the solid−vapor (gammaSV), solid−liquid (gammaSL), and liquid−vapor (gammaLV) interfaces at the three-phase contact line, as given by Young’s equation
Contac angle and Young's equation
Low-surface-tension coatings are used to prepare superhydrophobic surfaces in conjunction with the creation of nanostructures on naturally flat substrates. On the picture we can see that a coating with structures that involve an interfacial interaction between liquid and gas in a hydrophobic surface increase the hydrophobic nature of the solid.
Surface roughness at the sub-micrometer scale aids in creating cavities that trap air pockets to give a composite solid-air-liquid interface, known as the Cassie−Baxter state
The challenge of creating surface roughness to bring about a superhydrophobic surface is that hydrophobicity and transparency are opposite properties
Increasing roughness enhances the hydrophobicity to the point where transparency is reduced due to light scattering. It is therefore critical to control the surface roughness such that both needs are satisfied; transparency can be maintained when microscopic structures of the films are not greater than 100 nm.4^10
The demonstration consists of using glass slides modified with two organosilanes, methyltrichlorosilane and octadecyltrichorosilane, under varied reaction conditions, to obtain different hydrophobicities.
The water contact angles of the surfaces can be tested; then the self-cleaning effect of the superhydrophobic glass can be demonstrated and even quantified.
Measurements of contact angles are typically conducted with a digital contact angle goniometer. And should be able to visualize the difference between
hydrophilic-hydrophobic.
Demostration Overview
At least three clean glass slides should be used in the demonstration: one that unmodified (hydrofilic) and two modified (hydrofobic and superhydrofobic).
Both slides were rinsed 3 times with toluene, ethanol, a 1:1 mixture of deionized water and ethanol and deionized water, prior to drying in an oven at 100°C for 5 min.
A visual difference between the three slides should be seen immediately before optional measurement of contact angles was performed by students using a contact angle goniometer or digital camera system.
The modification with methyltrichlorosilane is an adaptation of a method by Gao and McCarthy, which had been optimized to treat glass and retain transparency
Hazards
Methyltrichlorosilane, octadecyltrichlorosilane and Silicon are airsensitive, flammable, and corrosive; they can irritate the skin and eyes on contact and should be kept under an inert gas. Concentrated hydrochloric acid is corrosive and causes burns to tissues. Toluene can be a skin and eye irritant and should not be inhaled due to its toxicity. UV light can damage the eyes and skin, potentially resulting in cataracts and skin cancer.
All solutions should therefore be prepared and handled in a fume hood in a wet laboratory. Should be used gloves, safety goggles, and lab coats.
OBSERVATIONS AND DISCUSSION
The alkyltrichorosilanes with trace amounts of water adsorbed into the glass surface leads to the formation of a
silanol.
Contact Angles.
-The water contact angles of modified glass slides were measured with digital contact angle goniometer.

-The measured contact angles indicate that the two alkyltrichlorosilanes have reacted with the hidroxylated glass surface.
Presented by:
Raúl Zúñiga Medina
Alejandra zaavik Lugo aranda
Jose armando mora navarrete
Side-view images of water droplets on the glass slides
A) Untreated glass.
B) Glass treated with octadecyltrichlorosilane.
C) Glass treated with methyltrichlorosilane.
A) Glass treated with octadecyltrichlorosilane
B) Glass treated with methyltrichlorosilane
Simply results

-At 4º resulted contact angles of 152±3 º for glass treated with methyltrichlorosilane
-And 112 ± 3° for glass treated with octadecyltrichlorosilane
The UV−vis spectra confirm that hydrophobic glass has nearly the same level of
transparency as untreated glass.
-untreated (black trace)
-hydrophobic (red line); superhydrophobic
-prepared at room temperature (green line)
-superhydrophobic glass
prepared at 4 °C (blue line)
Glass Transparency
Self-Cleaning
Image showing water droplets on a transparent superhydrophobic
glass slide covered with solid particles. Particles are
trapped by the water drop as it rolls along the surface, leaving a “trail”
of cleaned glass
Conclusion
-The method allows to obtain hydrophobic and super-hydrophobic surfaces easily.
-Good results of the contact angle, transparency and self-cleaning are obtained.
-In education serves to illustrate many concepts and implications of some equations in surface chemistry.
Reference:





Jessica X. H. Wong and Hua-Zhong Yu
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia.
Superhydrophobic Glass. Preparation of Transparent Superhydrophobic Glass Slides:Demonstration of Surface Chemistry Characteristics
. V5A 1S6, Canada
dx.doi.org/10.1021/ed300809m | J. Chem. Educ. 2013, 90, 1203−1206
Thank you!
Full transcript