CC BY
0The effect of concentrated deposition of nanoparticles during the evaporation of bicomponent droplets and its application in optical
sensors
G. Pavliuk1*, A. Zhizhchenko2, O. Vitrik2
1-Far Eastern Federal University, Ajax Bay, 10, Russky Island, Vladivostok, Russia, 690922 2- Institute of Automation and Control Processes (IACP) FEB RAS, Vladivostok, Russia, 690041
* georgii. 23542@gmail.com
The deposition of nanoparticles from liquid solutions onto a local surface area of minimal area is required in various applications related to the self-structuring of nanomaterials, surface enhanced Raman spectroscopy (SERS), matrix-assisted laser desorption and ionization spectrometry (MALDI), as well as in many other areas [1-3]. This work presents an express method for localizing nanoparticles and molecules from their liquid solutions using the features of the evaporation of bicomponent droplets. It has been established that strong toroidal Marangoni flows arising inside an evaporating droplet consisting of a mixture of isopropyl and water are capable of localizing suspended nanoparticles in the center of the droplet. In this case, at the end of the evaporation process, nanoparticles precipitate in the form of a single cluster. As it was shown, with a certain ratio of components and when selecting optimal evaporation conditions, it is possible to achieve a high degree of nanoparticles localization in the cluster without complex sample preparation and the presence of specially manufactured substrates reduce. Moreover, the cluster area is reduced by three orders of magnitude compared to the area of the initial contact of the drop. It was also be shown that the efficiency of the nanoparticle localization process can be significantly improved by additional heating of the substrate. It allows to achieve the deposit cluster with a diameter 160 ^m. To demonstrate the applicability of the described approach for sensory tasks, the organic dye Rhodamine 6G (R6G), characterized by good chemical affinity with gold, as well as intense photoluminescence signals, was added to a suspension of gold nanoparticles. After evaporation, a cluster of gold nanoparticles and rhodamine molecules was formed. The presence of rhodamine was detected in the cluster by SERS method even in case of trace initial concentrations of R6G (10-10 M) in aqueous isopropyl solution.
The developed technique can be used in a detailed study of nanoparticles synthesized in liquid media (especially at their small initial concentrations), as well as in biochemical studies and sensor applications related to the optical detection of molecular analytes contained in liquid media in ultra-low concentrations.
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[3] W. Zhou, A. Hu, S. Bai, et al, Surface-enhanced Raman spectra of medicines with large-scale self-assembled silver nanoparticle films based on the modified coffee ring effect, Nanoscale research letters, 9, 1-9 (2014).
