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Assembly of Plasmonic Nanoparticles
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Eric H. Hill, Christoph Hanske, Cyrille Hamon, Yuebing Zheng
Later studies showed that this effect involves the suppression of Marangoni flow (a flow driven by surface tension gradients) and that Marangoni flow present in organic solvents reverses the deposition to leave material in the center of the droplet.47 A short time later, it was shown that the morphology of the suspended particles can affect the coffee ring effect. In a study by Yunker et al., it was shown that, by using ellipsoidal particles instead of spherical particles, the coffee-ring effect was not observed.48 The strong interparticle capillary interactions between the ellipsoidal particles lead to the formation of assemblies at the air–water interface, which prevent them from reaching the drop edge. This approach is highly used in plasmonic NP assembly. Curiously, compared to coffee, whiskey droplets yield much more uniform dried films. Kim et al. proposed that surface-active macromolecules and continuous mixing during the evaporation of an ethanol/water mixture causes an unexpected behavior.49 Their studies of binary model dispersions containing different combinations of low molecular surfactant and polyethylene oxide suggested that both interaction of substrate-adsorbed polymer chains with the particles and different Marangoni flows were responsible for the improved macroscopic homogeneity of the final films.
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Published in Luis Liz-Marzán, Colloidal Synthesis of Plasmonic Nanometals, 2020
Leonardo Scarabelli, Cyrille Hamon, Luis M. Liz-Marzán
A typical phenomenon related to drying upon drop casting is the so-called coffee ring effect, which induces the accumulation of colloidal particles at the edge of the drying solvent.49,84,85 As a result, supercrystals close to the dried edge typically contain a larger number of nanorods and stacked layers, whereas supercrystals in the center were composed of fewer building blocks and eventually comprised single monolayers of standing nanorods. Most research groups would try to avoid this effect so as to obtain more homogeneous substrates;73,86 on the contrary, in this context we exploited it, using dark-field microscopy to identify convenient areas containing abundant supercrystals, which were selected at different distances from the dried edge, so that they were composed of different numbers of layers. It should be stressed that all analyzed supercrystals were made of standing gold nanorod arrays, as could be confirmed by atomic force microscopy (AFM, see Fig. 22.2A). Subsequently, we used various electron microscopy techniques (HRSEM, STEM, electron tomography) to gain information about the intra- and interlayer reciprocal organization of the building blocks: the top view confirmed the vertical orientation of the nanorods, imaging their organization into a hexagonal lattice, while the formation of Moire patterns suggests an ABA type of interlamellar organization (Fig. 22.1D), which is further confirmed by the 3D reconstruction of an entire bilayer supercrystal (Fig. 22.1E).
Enhanced Oil Recovery: Wettability Alteration and Other Topics
Published in Chun Huh, Hugh Daigle, Valentina Prigiobbe, Maša Prodanović, Practical Nanotechnology for Petroleum Engineers, 2019
Chun Huh, Hugh Daigle, Valentina Prigiobbe, Maša Prodanović
An interesting analogy is the mechanism for the well-known “coffee-ring effect” (Deegan et al. 1997; Shen et al. 2010), which is the accumulation of colloidal particles at the three-phase contact line region (“ring” formation) when a particle-containing liquid drop placed on a solid surface is evaporated. Even though the particles were initially uniformly dispersed in the liquid, due to the temperature-driven surface-tension gradient, the particles are drawn to the contact line zone, causing their accumulated deposition there. Somewhat related to this phenomenon, one possible scheme to bring the colloidal or nanoparticles to the three-phase contact line zone is to utilize the recent finding by Binks et al. (2006) that, when the particles adsorbed at a liquid surface exert a sufficient lateral repulsion and consequently a strong surface pressure, the particles result in the spontaneous film climbing up the container’s wall. This novel observation warrants a further study for possible exploitation for the nanoparticle-based EOR.
Understanding the coffee ring effect: how it has led to advanced applications
Published in Drying Technology, 2023
Samuel Ariyo Okaiyeto, Hong-Wei Xiao, Arun S. Mujumdar
In biology and biotechnology, droplet drying has been used to explore the behavior of cells and proteins. In biomedical applications, the concept of exploiting patterns produced by the drying of biological fluids to diagnose disorders is interesting. By analyzing, comprehending and interpreting patterns formed by evaporating droplets, a simple and rapids means for screening a range of life-threatening illnesses may be possible. Researchers have indeed already achieved important strides on this. The coffee ring effect has also been employed in the electronics sector to deposit nanoparticles in a predetermined pattern to create conductive coatings for printed electronics. Using the coffee ring effect, anti-reflective coatings with high transmission and low reflection have been developed in the field of optics. Compared to conventional coatings, anti-reflective coatings made via the coffee ring effect have some benefits; they are inexpensive, simple to make and work with a variety of materials, such as metals, plastics and glassware.
Pattern formation of dried droplets of milk during different processes and classifying them using artificial neural networks
Published in Journal of Dispersion Science and Technology, 2022
Aswini Harindran, Sabin Hashmi, V. Madhurima
The drying patterns of milk droplets during different processes such as dilution, coagulation and staling are studied and the differences in the morphology of each pattern were explained by coffee ring effect and Marangoni effect. The coffee ring effect gave an understanding about the formation of outer rings to all the patterns whereas the inner structure varied with processes; these structural formations were explained with the help of both coffee ring and Marangoni effect. Patterns observed in the case of dilution of milk with various concentrations of water showed a clear difference between the pure and the diluted milk. Thus, this can be used as a technique for quality check applications. Also, for diluted samples (50%, 40%, 30% and 20%) concentric rings were observed which implied the presence of different sized particles thus showing a method to separate different sized particles. Similarly, in the case of coagulation, the three stages of coagulation process were detected from the dried patterns. In the case of staling process, the onset of staling was detected from the patterns. Thus, it is found that dried droplet patterns can be used to fingerprint the colloids.
Experimental and numerical research of liquid contact angles on solid surfaces under evaporation conditions: a review
Published in International Journal of Green Energy, 2021
Hongquan Yang, Songning Yu, Ronghui Qi
Droplet evaporation has a wide range of important applications in agriculture, medical treatment, combustion, air conditioning, etc., so it is a hot topic in basic science and applied research. The deposition of material on the edge of the evaporating droplet is called the coffee ring effect, which is common in colloidal and bacterial systems (Sempels et al. 2013). It is also used for disease detection, diagnosis, and drug testing in medicine (Sefiane 2010). Deen et al. (2015) studied the method of capturing DNA on the polymer surface and found that the use of droplets greatly promotes the effective deposition of DNA. Based on the heat transfer and internal flow characteristics of droplet evaporation, a cooling protection technology suitable for microelectronic components (Hsieh, Leu, and Liu 2015) was developed. Besides, as the aerosol of salt solution can be used as fire suppression, the droplet evaporation on the surface of combustible materials provides additional surface cooling, thereby reducing the possibility of re-ignition (Korobeinichev et al. 2012). The application of flowing oriented crystallization of salt solution in printed electronics has an excellent prospect (Qu, Kwok, and Diao 2016).