Plasma Based Approaches to Achieve Self-Cleaning Surfaces

The role of gaseous plasma has proven to be very beneficial in creating self-cleaning of various surfaces. Few references are there, in the published literature, on plasma enhanced hydrophilicity/hydrophobicity behavior of surfaces. A range of atmospheric pressure plasma spray systems are gaining popularity for creating self-cleaning surfaces, with some unique features, as also to fabricate new types of self-cleaning materials. In this chapter a brief introduction to essentials of plasma processing will be first presented, followed by examples of plasma assisted surface modification. This will include plasma cleaning, plasma etching, plasma polymerization/deposition, etc. Subsequently, various plasma assisted techniques to achieve a variety of self-cleaning surfaces will be highlighted. A unique combination of plasma-based approaches and sol–gel derived coating will also be discussed

ZnO/γ-Fe₂O₃ Charge Transfer Interface toward Highly Selective H₂S Sensing at a Low Operating Temperature of 30 °C

ZnO/γ-Fe₂O₃ heterostructure has been deposited in the form of thin films using a single step facile electrochemical technique. Considering the unique properties of both ZnO and γ-Fe₂O₃ toward the sensing of reducing gases, the concept of forming a heterostructure between them has been conceived. The structural characterization of the deposited material has been performed using X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy, which revealed a flowerlike morphology with the coexistence of both ZnO and γ-Fe₂O₃ leading to the formation of a heterostructure. The material showed excellent sensing properties toward the selective detection of H₂S at room temperature (30 °C) among the three test gases, namely, CH₄, H₂S, and CO. The effect of relative humidity was also studied to have an idea about the performance of the device under a real situation. The results are promising and better than those of many commercially available sensors. The room temperature selective detection will help in facile fabrication of portable gadgets

Non lithographic block copolymer directed self-assembled and plasma treated self-cleaning transparent coating for photovoltaic modules and other solar energy devices

Through a combination of sol-gel based self-assembly and plasma based approach we have developed highly transparent, self-ordered, superhydrophilic and photoactive TiO2 thin film coatings. TiO2 sol used for such coatings comprises a block copolymer which functions as a structure directing agent. This structure directing agent aid to formation of regular pores in the TiO2 thin film, thereby, remarkably reducing the refractive index values (similar to 1.31) and enhancing the transparency (4% antireflection gain) of the coatings. Further, such porous TiO2 coatings show an excellent ability to photo-decompose organic pollutants, due to the photocatalytic ability of such metal oxide semiconductor. Enhancement in the photocatalytic activity has been obtained by porous surface created using a block copolymer and shifting the band gap energy by incorporating nitrogen so as to utilize part of the visible region of the solar spectrum for photocatalysis. An optimum condition is achieved by varying the RF self-bias potential and time of plasma treatment. Nitrogen plasma treatment, in addition to enhancing the photocatalytic activity of TiO2 is also found to enhance the mechanical stability and hydrophilicity, without hampering the optical transmission of coatings. Such coatings are also found to exhibit superhydrophilicity with water contact angle (WCA) < degrees 5 under optimized condition. Thus, the coatings developed, qualify as a suitable candidate to be applied on solar PV panel and other energy devices. Treatment with nitrogen plasma extends the photocatalytic activity towards visible region of the spectrum and also ensures the mechanical stability of the otherwise porous network