Wetting Modification by Photocatalysis: A Hands-on Activity To Demonstrate Photoactivated Reactions at Semiconductor Surfaces

Abstract

We present a hands-on activity designed for advanced Physical Chemistry courses for Master's students, on the application of photocatalysis to the modification of the surface properties of a semiconductor (titanium dioxide). The wetting properties of TiO 2 films, deposited from commercial powders, are studied before and after UV irradiation. Irradiation-induced superhydrophilicity is exploited to provide antifogging properties. The TiO 2 films are then functionalized with a perfluorinated alkylsilane to impart superhydrophobicity and subsequently lithographed by irradiation through a photomask: the photocatalytic degradation of the organic chains in the irradiated areas leads to a wetting contrast that can be revealed using dye solutions. This experience can be easily adapted to be suited for undergraduates or high-school students, as well as to demonstrations for science festivals.

Photocatalytic Hydrogen Production over CdS Nanomaterials: An Interdisciplinary Experiment for Introducing Undergraduate Students to Photocatalysis and Analytical Chemistry

“…In 2003, Koca developed a simple laboratory experiment for photocatalytic hydrogen production by direct sunlight . In that experiment, the volume of hydrogen evolved was determined from the displacement of liquid into the graduated pipet . The experiment nicely demonstrated that the different compositions of the CdS/ZnS photocatalysts exhibited significant effects on the volumes of hydrogen evolved .…”

“…More recently, Xiong et al used a TiO 2 -photocatalytic-oxidation process to treat methanol-containing wastewater, from which students can understand the basic principle of photocatalytic oxidation reactions and learn to assemble a specified apparatus for a chemical reaction and analytical methods . Interestingly, Rimoldi et al demonstrated the application of irradiation-induced superhydrophilicity of TiO 2 films to achieve surface-wetting properties for Master’s students . Impressively, Ma et al also introduced a new graduate course called Photocatalysis: Principles and Applications into the physical-chemistry division at the University of Chinese Academy of Sciences (UCAS), which mainly involved the teaching materials, literature discussion, and student feedback .…”

“…In that experiment, the volume of hydrogen evolved was determined from the displacement of liquid into the graduated pipet . The experiment nicely demonstrated that the different compositions of the CdS/ZnS photocatalysts exhibited significant effects on the volumes of hydrogen evolved . Notably, from a scientific point of view, the simple drainage gas-recovery technique was unfavorable for undergraduates to effectively utilize valuable laboratory skills, perform accurate analysis of H 2 , and understand the principles and use of instruments.…”

Quick and Easy Electroless Deposition and Alkanethiol Treatment To Form a Superhydrophobic Surface

“…These experiments use carbon soot, 34 polydimethylsiloxane casts to replicate taro and lotus leaf surfaces, 35 alkyl siloxanes and alkyl alkoxysilanes on glass, 36 alkyl alkoxysilanes on titanium dioxide, 37 alkyl trichlorosilanes on glass, 38 and perfluoroalkyl alkoxysilanes on titanium dioxide. 39 None use alkanethiols on metal, and only the soot coating can be prepared in a short time frame. Experiments that do use alkanethiol for preparation of self-assembled monolayers have also been published.…”

“…Previous experiments making use of superhydrophobicity have been published in this journal. These experiments use carbon soot, polydimethylsiloxane casts to replicate taro and lotus leaf surfaces, alkyl siloxanes and alkyl alkoxysilanes on glass, alkyl alkoxysilanes on titanium dioxide, alkyl trichlorosilanes on glass, and perfluoroalkyl alkoxysilanes on titanium dioxide . None use alkanethiols on metal, and only the soot coating can be prepared in a short time frame.…”