Enhancement of self-cleaning properties and durability of super-hydrophobic carbon nitride nanostructures by post-annealing treatment
Graphical abstract
Introduction
From Bullet Trains that take its inspiration from Kingfisher bird to medical adhesives inspired by spider silk, nature can inspire researchers and offer solutions to countless human problems. Among which, the remarkable non-wetting surfaces with self-cleaning properties inspired by lotus leaf received great attention and numerous technologies have been developed based on these features such as windshields of vehicles [1], body of the vehicles and mirrors in automotive [2]; glasses cameras and lenses in optics [3]; fabrics and sports shoes in textile [[4], [5], [6]]; anti-corrosion coating in marine; woods, marbles and doors in labor sector [7]; and the list is ceaseless [8,9]. One of its special features is the ability to repel water and keep the surface cleaning without any external source as well as durable to the severe environment condition and water droplets. These properties become an important aspect and widely used in coatings such as solar cell panels; which offer great reduction in maintenance cost, elimination of tedious manual effort, and also reduction in the time spent in cleaning works [[10], [11], [12]]. Due to the high water contact angle (>150°), water drops immediately bead up and readily roll off the solar cell panel's surface collecting particles, dirt and debris along the way.
The first instance of a self-cleaning surface was created in 1995 by Paz et al. which created a transparent titanium dioxide (TiO2) film that was used to coat glass and provide the ability for the glass to self-clean [13]. Since then, many approaches have been pursued to develop non-wetting surfaces with super-hydrophobic and self-cleaning properties. Cunqian Wei et al. have discussed the difference of anti-icing performance between the hydrophobic surface imitating lotus leaf and the ultra-smooth slippery liquid-infused porous surface (SLIPS) mimicking pitcher plant [14]. Ci et al. constructed an array of vertically aligned large diameter double-walled carbon nanotubes by a water assisted chemical vapour deposition process [15]. Carbon nitride materials (CNx) have also become one of the promising materials for self-cleaning applications due to its suitability in integrating with other materials such as polymer, metal etc. which increases the number of study especially that involved with self-cleaning applications. For example, Chengkai et al. reported a facile surface modification of graphitic carbon nitride nanosheets (CNNS) functionalize with textiles by directly sprayed onto the surface which creates excellent ability for photocatalytic self-cleaning and degradation of indoor volatile organic pollutants [16]. Meng Yuan et al. studied the polymer carbon nitride (PCN) integrated with polyacrylonitrile (PAN) polymers composite on fabrics which show an excellent stability, long-term durability (50circles for disinfection properties) and self-cleaning properties [17].
The most basic principle of self-cleaning is the properties of forming super-hydrophobic surfaces that can remove the dirt on the surfaces. In this work, the effects of TA have been chosen as a way to improve the characteristics of the nanostructures surfaces. Surfaces with self-cleaning properties are associated with super-hydrophobic behaviour and result from the combination of a few factors such as surface energy, surface porosity, surface morphology, sub-micron scale roughness, chemical material present on it and more [[18], [19], [20], [21], [22]]. Thus, the annealing process might be a potential method that can modify the surfaces in different forms: enhance in crystallinity, increase the film's thickness, enhance the topography of the surface etc. [23,24]. All these may contribute to an improvement of water repellent surfaces and self-cleaning properties. Here in the study, the most influenced factors of self-cleaning properties are discussed.
In our previous study, the vertically aligned CNx nanofibres were successfully produced in a simplified and cost-effective way [25]. Following up from that work, in this present study, the CNx nanostructures were grown on Si (100) substrate under the same conditions by radio frequency plasma enhanced chemical vapour deposition (RF-PECVD) and were annealed at different temperatures using conventional thermal annealing process. The surface morphology and roughness of the as-deposited and annealed CNx nanostructures have been investigated by FESEM microscopy and AFM microscopy, respectively. The effects of post-annealing temperatures on the films; and the durability of the films after 11th water dropped were investigated.
Section snippets
Film preparation
Carbon nitride (CNx) nanostructures were prepared using a parallel plate configuration of PECVD system on p-type silicon (100) wafer at a substrate temperature of 100 °C. The plasma-excitation frequency of the system was set to be 13.56 MHz. The flow rate of CH4 and N2 gases were maintained at 20 and 47 sccm, respectively. The distance between electrodes, deposition pressure, RF power and duration of deposition were kept at 1 cm, 0.8 mbar, 80 W and 90 min, respectively. In order to investigate
The effects of annealing temperatures on the contact angle, contact angle hysteresis, work of adhesion, surface energy and surface porosity
Contact angle (CA) measurements are often used to evaluate the wetting behaviour of the films due to its direct and quick measurements, while contact angle hysteresis (CAH) determined the adhesion of water to the film's surfaces when tilted at a certain angle. These measurements have always been of great interest as it determined the self-cleaning properties of the films that are important for various applications.
Fig. 1 shows water CA and CAH measurements of CNx nanostructures and its
Conclusions
The CNx nanostructures were prepared by PECVD method and were subsequently annealed at annealing temperature (TA) of 400 °C, 600 °C and 700 °C for 1 h in the nitrogen atmosphere. The influence of the annealing treatments on the water contact angle, surface morphology, roughness, surface energy, durability and chemical bonding of the CNx nanostructures have been investigated in this work. From the contact angle (CA) measurement, it showed that high TA enhanced the water repellence properties due
CRediT authorship contribution statement
Shafarina Azlinda Ahmad Kamal: Conceptualization, Methodology, Investigation, Validation, Writing – original draft. Richard Ritikos: Writing – review & editing, Supervision, Project administration, Funding acquisition. Saadah Abdul Rahman: Writing – review & editing, Supervision, Funding acquisition.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This work was supported by the Universiti Malaya Research Grant (UMRG) - AFR (Frontier Science) RG391-17AFR.
References (41)
- et al.
Effect of surface wettability on boiling and evaporation
Energy
(2005) - et al.
Surface technology for automotive engineering
CIRP Ann.
(2009) - et al.
Self cleaning TiO2 coating on polycarbonate: surface treatment, photocatalytic and nanomechanical properties
Surf. Coat. Technol.
(2010) - et al.
Fabrication of coral-reef structured nano silica for self-cleaning and super-hydrophobic textile applications
Chemical Engineering Journal
(2020) - et al.
Self–cleaning superhydrophobic coatings: Potential industrial applications
Progress in Organic Coatings
(2019) - et al.
A new method to determine the effects of hydrodynamic surface coatings on the snow shedding effectiveness of solar photovoltaic modules
Sol. Energy Mater. Sol. Cells
(2013) - et al.
A review of icing prevention in photovoltaic devices by surface engineering
Renew. Sust. Energ. Rev.
(2014) - et al.
Anti-icing performance of super-wetting surfaces from icing-resistance to ice-phobic aspects: robust hydrophobic or slippery surfaces
J. Alloys Compd.
(2018) - et al.
Facile surface modification of textiles with photocatalytic carbon nitride nanosheets and the excellent performance for self-cleaning and degradation of gaseous formaldehyde
J. Colloid Interface Sci.
(2019) - et al.
Polymeric carbon nitride modified polyacrylonitrile fabrics with efficient self-cleaning and water disinfection under visible light
Chemical Engineering Journal
(2020)
Functionalization of graphene oxide via gamma-ray irradiation for hydrophobic materials
Corrosion behavior of superhydrophobic surfaces: a review
Arab. J. Chem.
Reversible transformation of hydrophobicity and hydrophilicity of aligned carbon nanotube arrays and buckypapers by dry processes
Carbon
The effects of annealing temperature on the characteristics of carbon counter electrodes for dye-sensitized solar cells
Curr. Appl. Phys.
Wettability and surface energy of oxidized and hydrogen plasma-treated diamond films
Diam. Relat. Mater.
Effect of contact angle hysteresis on water droplet evaporation from super-hydrophobic surfaces
Appl. Surf. Sci.
Influence of annealing temperature on thermal stabilities of hydrogenated amorphous carbon on silicon nitride balls
Vacuum
Carbon and nitrogen 1s energy levels in amorphous carbon nitride systems: XPS interpretation using first-principles
Diam. Relat. Mater.
Self-cleaning coatings
J. Mater. Chem.
Self-cleaning fibers via nanotechnology: a virtual reality
J. Mater. Chem.
Cited by (9)
Lattice Boltzmann simulation of condensation on self-cleaning porous membrane
2023, International Communications in Heat and Mass TransferCitation Excerpt :Chehrghani et al. [19] pointed that superhydrophobic surfaces enhance condensation heat transfer performance due to the discrete droplet formation and rapid removal and hydrophobic surfaces help droplets to nucleate easier and faster. Despite all the strategies of surface treatments mentioned above, continuous and long lasting dropwise condensation is still a rough task for practical application, since most hydrophobic or super-hydrophobic surfaces have short life time [20,21] and the removal performance of condensate is usually related to the direction on the cold surface. On vertical surface condensation could be enhanced while on horizontal surface, the removal rate will be greatly impaired [7].
Properties of poly(titanium oxide)-containing polymeric materials exhibiting UV-induced superhydrophilicity under simulated climate test conditions
2022, Results in EngineeringCitation Excerpt :An example of hydrophobic coatings can be surfaces on which nanostructures of carbon nitride CNx are applied. They have excellent water repellent properties, as evidenced by the value of the edge wetting angle of 160° [12]. Fluoropolymers modified with binding agents to improve their adhesion and durability are widely used to create hydrophobic coatings [13].
Corrosion Investigation of Self-cleaning Film Prepared on Surface of Hot-dip Galvanized Steel in Chloride-bisulphite Mixed Solution
2022, International Journal of Electrochemical ScienceInfluence of roughness on polar and dispersed components of surface free energy and wettability properties of copper and steel surfaces
2021, Surface and Coatings TechnologyCitation Excerpt :The application areas of metals, including copper and steel, depend not only on the physicomechanical and tribological properties, but also on the near-surface properties, the main of which is wettability. It is known that wettability affects such functional properties as self-cleaning [1,2], resistance to icing [3,4], fogging [5,6], corrosion [7,8], biofouling [9,10] abrasive and cavitation wear [11,12], protection against bacteria [13,14]. Wetting is contingent on the elemental composition of the subsurface layer and roughness (texture) [15,16], as well as broadly studied for molecularly smooth and chemically homogeneous surfaces [17,18].
Impact of processing parameters on the superhydrophobic and self-cleaning properties of CaO nanoparticles derived from oyster shell for electrical sheathing insulator applications
2023, International Journal of Advanced Manufacturing Technology