Name: TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method (Video) | JoVE Journal
Uploaded: 2017-04-26T15:00:00.000+00:00
Duration: 7 min 37 s
Description: Learn to synthesize superhydrophobic, TiO2-coated hollow glass microspheres with high IR-reflective properties using a soft-chemistry method. This energy-efficient technique enables multifunctional materials for thermal management applications.

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5 minutes

The work described in this paper was supported by a grant from the CII-HK/PolyU Innovation Fund. Further support was provided by the Shenzhen Peacock Plan (KQTD2015071616442225) and the Chinese Government &#34;Thousand Talent&#34; Program (Y62HB31601). Also, the help from the Department of Applied Biology &#38; Chemical Technology of the Hong Kong Polytechnic University and the Hong Kong Polytechnic University Research Institute for Sustainable Urban Development (RISUD) is appreciated.

1. Pre-treatment of HGM
<ol>
	<li>Place the HGM into a 500-mL beaker with 200 mL of absolute alcohol; the low density of unbroken HGM causes it to suspend in the alcohol, but because the density of broken HGM is larger than that of alcohol, it precipitates in the solution. After 30 min, collect the suspended HGM using a clean spoon and dry at 80 &#176;C in an oven for further application.</li>
</ol>
2. Synthesis of MCHGM
<ol>
	<li>Place 5 g of unbroken HGM, 47.5 mL of ethanol, and 2.5 mL of DI water in a three-necked flask. Stir using a mixing motor at 400 r/min for 20 min (pre-mixing).</li>
	<li>Mix 15 g of TBT, 1 g of PFOTES, and 30 mL of absolute alcohol in a 200-mL beaker. Pour the mixture into a constant-pressure funnel.</li>
	<li>Insert the constant-pressure funnel into one of the holes of the three-necked flask. Drop the mixture contained in the constant-pressure funnel into the three-necked flask at a speed of 1 drop per 7 s, which is achieved by adjusting the valve of the constant-pressure funnel. Continue the reaction for 3 h.</li>
	<li>Pour the mixture from the three-necked flask into a hydrothermal reactor. Put the sealed reactor in a suitable steel sleeve in a 180 &#176;C oven for 6 h. 
	NOTE: Make sure that the reactor has a suitable cover. After it is covered, put the reactor into the steel sleeve. The sleeve should also be sealed with a cover.</li>
	<li>After the reaction is over, collect the samples suspended in the hydrothermal reactor using a big spoon. Dry the samples at 80 &#176;C for 4 h to obtain MCHGM.</li>
</ol>
3. Synthesis of F-SCHGM
<ol>
	<li>Add 5 g of unbroken HGM, 47.5 mL of absolute ethanol, and 2.5 mL of DI water to a three-necked flask. Stir using a mixing motor at 400 r/min for 20 min (pre-mixing). Mix 1 g of PFOTES and 30 mL of absolute ethanol in a 200-mL beaker. Transfer the PFOTES and absolute ethanol mixture to a constant-pressure funnel.</li>
	<li>Insert the constant-pressure funnel into the three-necked flask. Drop the mixture contained in the constant-pressure funnel into the three-necked flask at a speed of 1 drop per 7 s. Let the reaction run for 3 h.</li>
	<li>Transfer the mixture from the three-necked flask to a hydrothermal reactor. Put the sealed reactor in a 180 &#176;C oven for 6 h. After the reaction is over, collect the samples suspended in the hydrothermal reactor using a big spoon. Dry the samples at 80 &#176;C for 4 h to obtain F-SCHGM.</li>
</ol>
4. Synthesis of Ti-SCHGM
<ol>
	<li>Place 5 g of unbroken HGM, 47.5 mL of absolute ethanol, and 2.5 mL of DI water in a three-necked flask. Stir at 400 r/min for 20 min (pre-mixing). Mix 15 g of TBT and 30 mL of absolute ethanol in a 200-mL beaker. Transfer the TBT and absolute ethanol mixture to a constant-pressure funnel.</li>
	<li>Insert the constant-pressure funnel into the three-necked flask. Drop the mixture in the constant-pressure funnel into the three-necked flask at a speed of 1 drop per 7 s. Let the reaction run for 3 h.</li>
	<li>Transfer the mixture from the three-necked flask to a hydrothermal reactor. Put the sealed reactor in a 180 &#176;C oven for 6 h. Collect the samples in the hydrothermal reactor after the reaction is over. Dry the samples at 80 &#176;C for 4 h to obtain Ti-SCHGM.</li>
</ol>
5. Characterizations
<ol>
	<li>Conduct XRD characterizations on all samples. Collect the data using a highly versatile, multipurpose X-ray diffraction system with Cu K&#945; radiation (&#955; = 0.15406 nm) and a 2&#952; ranging from 10&#176; to 80&#176;.</li>
	<li>Acquire scanning electron microscope20,21 images after spraying the samples with gold. During the SEM tests, conduct the EDS is on a specific area.</li>
	<li>Measure the contact angle by using a contact-angle goniometer22; the water drop volume should be 10 &#181;L.</li>
	<li>Measure the sliding angle23 by changing the tilt angle of the surface. Minimize the angle until the water drop can just slide down.
	<ol>
		<li>Stick double-sided tape on a glass sheet (size: 26 mm x 76 mm x 2 mm). Using a spoon, uniformly place the powders (F-SCHGM or MCHGM) on the tape. Using an injector, add a water drop (volume: 0.05 mL) to the powder surface.</li>
		<li>Put the glass sheet on the motor platform of the contact-angle goniometer. Tilt the glass sheet by leaning the motor platform at a rate of 1&#176;/s. Stop the motor when the water drop starts to slide; the tilt angle is the sliding angle.</li>
	</ol>
	</li>
	<li>Measure the reflectivity spectra using a spectrophotometer24. NOTE: The wavelength is from 450 nm to 2,550 nm.</li>
	<li>Measure the thermal conductivity of all samples using a thermal conductivity meter25.</li>
</ol>

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The authors have nothing to disclose.

In this manuscript, the critical step in the protocol is the hydrothermal process. It influences the formation of TiO2, the final reflectivity, and the superhydrophobicity. The temperature control and reaction time are also quite significant. If the reaction conditions change, the final products can be flawed.
This method provides a simple way to synthesize superhydrophobic and highly IR-reflective HGM in one step. In previous research, the superhydrophobic and reflectivity properti...

Hollow glass microspheres (HGM) are inorganic materials ranging in size from 10 to 100 &#181;m. They demonstrate many useful features, such as excellent dispersion, high flow ability, low density, and superior thermal insulation properties1,2,3,4. Because of their hollow structure, HGM have an extremely low thermal conductivity10,11. For these reasons, they are applied in many areas, including aerospace engineering5, deep-sea exploration6,7, hydrogen storage8,9, etc. However, they still demonstrate some disadvantages, such as low strength. In addition, IR light is able to transmit through HGM and heat the subject behind. Therefore, surface modifications on HGM are essential to reduce the radiative thermal transfer. An effective method is to coat an IR-blocking material onto the HGM surface. As a semiconductor, TiO2 has been used in many areas, such as photo-catalysis12,13, solar cell development, sensor fabrication14, environmental applications15, and energy storage16. In addition, it also shows low emissivity in the visible light and infrared band17,18,19. Therefore, for our purposes, TiO2 was a prudent selection due to its relatively low price and high performance.
However, the coating is quite easy for pollutants to foul, which seriously affects the reflectivity of TiO2. The reflectivity must reduce gradually. Therefore, a self-cleaning coating is essential to prevent the coating from fouling and to prolong the working time of such a coating.
In this manuscript, a soft-chemistry method was used to develop superhydrophobic TiO2-coated HGM. Tetrabutyl titanate (TBT) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES) were selected as the Ti source and superhydrophobic agent, respectively. They were hydrolyzed and deposited on the HGM surface. Then, after the hydrothermal process, the anatase TiO2 formed on the HGM surface, and the superhydrophobic properties remained. For comparison, PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The synthesis scheme is shown in Figure 1.

<table><tbody><tr><td>HGM</td><td>Technical Institute of Physics and Chemistry, Chinese Academy of Science</td><td>N/A</td><td>N/A</td></tr><tr><td>TBT</td><td>Sigma-Aldrich</td><td>CAS#: 5593-70-4</td><td>Analytical grade</td></tr><tr><td>Ethyl Alcohol</td><td>Sigma-Aldrich</td><td>CAS#: 64-17-5</td><td>Analytical grade</td></tr><tr><td>PFOTES</td><td>Sigma-Aldrich</td><td>CAS#: 51851-37-7</td><td>98%</td></tr></tbody></table>

tio2-coated hollow glass microspheres with superhydrophobic and high ir-reflective properties synthesized by a soft-chemistry method

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 and a superhydrophobic agent were coated on the HGM surface in one step. TBT and PFOTES were selected as the Ti source and the superhydrophobic agent, respectively. They were both coated on the HGM, and after the hydrothermal process, the TBT turned to anatase TiO2. In this way, a PFOTES/TiO2-coated HGM (MCHGM) was prepared. For comparison, PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The PFOTES and TiO2 coatings on the HGM surface were demonstrated through X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive detector (EDS) characterizations. The MCHGM showed a higher contact angle (153&#176;) but a lower sliding angle (16&#176;) than F-SCHGM, with a contact angle of 141.2&#176; and a sliding angle of 67&#176;. In addition, both Ti-SCHGM and MCHGM displayed similar IR reflectivity values, which were about 5.8% higher than the original HGM and F-SCHGM. Also, the PFOTES coating barely changed the thermal conductivity. Therefore, F-SCHGM, with a thermal conductivity of 0.0479 W/(m&#183;K), was quite like the original HGM, which was 0.0475 W/(m&#183;K). MCHGM and Ti-SCHGM were also similar. Their thermal conductivity values were 0.0543 W/(m&#183;K) and 0.0543 W/(m&#183;K), respectively. The TiO2 coating slightly increased the thermal conductivity, but with the increase in reflectivity, the overall heat-insulation property was enhanced. Finally, since the IR-reflecting property is provided by the HGM coating, if the coating is fouled, the reflectivity decreases. Therefore, with the superhydrophobic coating, the surface is protected from fouling, and its lifetime is also prolonged.

The tests in step 4.4 reveal many features and properties of the samples. The XRD (Figure 2) reflects the formation of anatase TiO2. The SEM (Figure 3) and EDS (Figure 4) display the TiO2 and PFOTES that are coated on the HGM surface. The contact angle (Figure 5) and sliding angle (Figure 6) tests represent the superhydrophobicity. The Vis-NIR transmittance test (Figure 8</st...

This manuscript proposes a soft-chemistry method to synthesize superhydrophobic, TiO2-coated hollow glass microspheres (HGM) with high IR-reflective properties.

This manuscript proposes a soft-chemistry method to develop superhydrophobic and highly IR-reflective hollow glass microspheres (HGM). The anatase TiO2 ...

The overall goal of this experiment is to synthesize superhydrophobic, highly IR-reflective hollow glass microspheres in a single step. This technique can help with the development of simple masses to synthesize HGM with multiple functions, such as the self-cleaning and IR-reflective properties. The advantage of this mass is that it is a performer in the single-stat, making the mass simple and energy-saving compared with the existing mass.The implications of this technique extended toward a better understanding of sliding angles as HGM samples with different coatings can have similar connected angles but different sliding angles. To prepare the hollow glass microspheres, first place over five grams of original HGM in a 500-milliliter beaker. Add 200 milliliters of absolute ethanol to the mixture of broken and unbroken HGM.Allow the mixture to sit for 30 minutes to ensure that all unbroken HGM have floated to the top, leaving only broken HGM at the bottom of the beaker. Use a clean scoop to collect the unbroken HGM from the surface of the ethanol. Dry the unbroken HGM at 80 degrees Celsius for four hours.Repeat this process as needed to obtain five grams of unbroken HGM. To begin the synthesis, combine five grams of unbroken HGM, 47.5 milliliters of absolute ethanol, and 2.5 milliliters of deionized water. Add it into a three-necked flask.And then stir the mixture at 400 RPM for 20 minutes. Place 30 milliliters of absolute ethanol, 15 grams of tetrabutyl titanate, and one gram of PFOTES in a beaker and stir until dissolved. Pour the mixture into a pressure-equalized dropping funnel.Connect the dropping funnel to the three-necked flask and reduce the stirring rate 350 RPM. Add the TBT-PFOTES mixture to the HGM suspension at a rate of one drop every seven seconds. The dropping speed must be carefully set to the correct rate and stay in that rate until the mixture have been completely added.Once addition of the TBT-PFOTES mixture is complete, continue stirring at 350 RPM until three hours have elapsed since the start of addition. Then, pour the HGM mixture into a hydrothermal reactor with a well-fitting cover. Insert the reactor into an appropriately-sized steel sleeve and seal the reactor.Heat the HGM mixture at 180 degrees Celsius for six hours. Once the reaction is complete, allow the reactor to cool to room temperature. Open the hydrothermal reactor and use a large, clean scoop to collect the suspended HGM samples.Dry the samples at 80 degrees Celsius for four hours to obtain MCHGM. To synthesize PFOTES or titanium oxide single-coated HGM, follow this procedure without addition of TBT or PFOTES respectively. Perform X-ray defraction and measure the reflectivity and thermal conductivity of the coated and uncoated HGM samples.Acquire scanning electron microscopy images and perform energy dispersive X-ray spectroscopy. Use a contact angle goniometer to measure the contact angle between the HGM surface and a 10-microliter drop of water. To measure the sliding angle, first apply double-sided tape to a glass slide.Evenly distribute the HGM powder sample over the double-sided tape. Place 0.05 milliliter drop of water on the powder surface. Place the coated slide on the goniometer motor platform.While monitoring the water drop, tilt the glass slide at a rate of one degree per second. When the water drop begins to move, stop tilting the slide and record the sliding angle. The successful coating of HGM samples was confirmed by EDS.Fluorine was detected in both F-SCHGM and MCHGM, and titanium was detected in both titanium-SCHGM and MCHGM. The single PFOTES coating was not observable by SEM. But rough coatings were observed for titanium-SCHGM and MCHGM.The coated HGM samples were compared to the starting material and to standard anatase titanium oxide by X-ray defraction. The MCHGM and titanium-SCHGM samples both showed peaks matching anatase titanium oxide indicating that the titanium coating was in the anatase form. Both titanium-SCHGM and MCHGM showed about 5%higher reflectivity values than uncoated or F-SCHGM.A small increase in thermal conductivity was also observed for titanium-SCHGM and MCHGM. The measured contact angle of uncoated HGM was 59 degrees. Titanium SCHGM did not show a large increase from this contact angle, but both F-SCHGM and MCHGM did.Further, MCHGM had a much lower sliding angle than F-SCHGM, indicating greater hydrophobicity compared to F-SCHGM. Once mastered, this technique can be done in nine hours if it is performed properly. While attempting this procedure, it is important to remember to precisely set the TBT-PFOTES addition rate to one drop every seven seconds.After its development, this technique paved the way for the researchers in the hidden civilization field to explore highly IR-reflective HGM with superhydrophobic self-cleaning properties to protect the surface from falling.

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Chemistry

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We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Herein, we present detailed protocols for solution-processed silver-bismuth-iodine (Ag-Bi-I) ternary semiconductor thin films fabricated on TiO2-coated transparent electrodes and their potential application as air-stable and lead-free optoelectronic devices.

Solution-Processed "Silver-Bismuth-Iodine" Ternary Thin Films for Lead-Free Photovoltaic Absorbers

This article describes a synthetic method to obtain bismuth oxyiodide microspheres, which are highly functional to perform the photocatalytic removal of organic pollutants, such as ciprofloxacin, in water under UV-A/visible light irradiation.

A Facile Synthetic Method to Obtain Bismuth Oxyiodide Microspheres Highly Functional for the Photocatalytic Processes of Water Depuration

This work presents microfabrication protocols for achieving cavities and pillars with reentrant and doubly reentrant profiles on SiO2/Si wafers using photolithography and dry etching. Resulting microtextured surfaces demonstrate remarkable liquid repellence, characterized by robust long-term entrapment of air under wetting liquids, despite the intrinsic wettability of silica.

Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars

Learn to synthesize superhydrophobic, TiO2-coated hollow glass microspheres with high IR-reflective properties using a soft-chemistry method. This energy-efficient technique enables multifunctional materials for thermal management applications.

TiO2-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method (Video) | JoVE Journal

TiO₂-coated Hollow Glass Microspheres with Superhydrophobic and High IR-reflective Properties Synthesized by a Soft-chemistry Method

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