Liquid Spreading Induced by In Situ Generation of Metallic Nanoparticles

Singh, Nitish Kumar; Jain, Yashaswini; Kishore, Kaushal; Ghatak, Ajoy

doi:10.1021/acs.langmuir.0c01976

Cited by 3 publications

(2 citation statements)

References 38 publications

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“…The roughness effect can possibly be attributed to diffusion of the NPs from the reacted interface. Because pure metallic gold has a surface energy of ∼1.22 J/m 2 , , it was possible that the presence of AuNPs increased the effective value of γ s . For the pool mode, in the absence of a three-phase contact line, such an effect was nonexistent.…”

Section: Resultsmentioning

confidence: 99%

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect

Singh,

Ghatak

2024

Langmuir

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We examined the effect of deformability of a solid substrate on the kinetics of a surface reaction that occurs between chemical species present in it and a liquid dispensed on it. In particular, we have dispensed aqueous solutions of gold and silver salt as sessile drops or as a liquid pool on a cross-linked film of poly(dimethylsiloxane) (PDMS). The PDMS surface contains organosilane (SiH), which reduces the salt, producing metallic nanoparticles at the solid–liquid interface. These experiments reveal that, for a sufficiently soft solid, the reaction proceeds about three times faster in the drop mode than in the pool mode. The reaction conditions in both cases remain exactly identical except that, for the drop, the vertical component of the liquid surface tension deforms the solid substrate at the three-phase contact line. We have estimated the solid–liquid and solid–air interfacial energy, which along with the surface energy of the liquid gives an estimate of excess free energy. This energy is found to be different for the drop and pool modes. By considering that this excess free energy decreases the activation energy barrier for the reaction, we have shown that the reaction rate constant in the drop mode should indeed exceed that in the pool mode by about three times.

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Section: Resultsmentioning

confidence: 99%

Enhancement of the Rate of Surface Reactions by the Elastocapillary Effect

Singh,

Ghatak

2024

Langmuir

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“…In particular, pendant lenses were made by the method described earlier 33 . Briefly, a drop of the two-phase pre-crosslinked dispersion was dispensed on an FC coated glass slide.…”

Section: Possibility Of Swelling Induced Percolation Of the Gelatin P...mentioning

confidence: 99%

Water Induced Reversible Switching of Optical Transparency of an Elastomer-Hydrogel based Two-phase Composite

Kuhar,

Ghatak

2024

Preprint

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We have examined reversible switching of optical transparency of a two-phase material consisting of hydrogel micro-spheres dispersed inside a continuous medium of crosslinked poly(dimethylsiloxane) (PDMS). Here, aqueous solution of gelatin is dispersed as drops in PDMS oligomers mixed with the crosslinker. Both phases get crosslinked to form an elastomeric material. Films of this material remain optically opaque in the unswelled state of the embedded hydrogel, but, when placed inside water for prolonged period, water diffuses through the silicone phase and gets absorbed by gelatin. At this, gelatin swells with consequent change in transparency with time. We show that the size of dispersed microspheres and the extent of crosslinking of the PDMS, both affect the kinetics of this process. In fact, for some range of parameter values, the rate of change in transparency turns more pronounced than would have been expected for simple Fickian diffusion of water through the film. We show also that selective swelling of the dispersed phase is necessary for the film to get transparent. Furthermore, it is possible to dye the dispersed phase with a water-soluble dye implying that the dye molecules can co-diffuse with water through the network. We highlight also few potential applications of this material.

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