Rhodamine 6G is a highly effective luminescent xanthene dye of the rhodamine family, which widely used for labeling oligonucleotides in biochemistry, cell imaging, as a sensitive layer of chemical sensors for metal ions \1\ and a classical analyte for optimizing SERS structures \2\, etc. At the same time, the features of the interaction of R6G with low molecular weight analytes present in most biochemical preparations have not been studied. This is important not only for understanding the possibility of the influence of non-target components on the analytical signal during analysis, but is also of great practical importance, since it also allows developing (bio)chemical sensors for specific applications. In this work, we studied the features of the interaction of R6G thin films with a number of low molecular weight analytes in the gas phase (to exclude cross-interaction etc.), namely, water vapor, acetic acid, ethyl alcohol, ammonia, benzene, pyridine, nitrobenzene, acetone, and acetonitrile. The kinetic features and adsorption capacity of the sensitive layer were compared with those for other sensitive layer materials (macrocyclic dibenzotetraazaanulenes, phthalocyanines, and their metal complexes).

Thin films (100 nm) of organic materials were obtained by thermal deposition in vacuum on one side of quartz crystal microbalance transducers (10 MHz), which were at a temperature of 297±2 ^oK. The average condensation rate was about 0.1 nm/min. Optical measurements of the absorption and emission spectra showed that R6G retains typical optical characteristics in a solid state, which indicates the preservation of its molecular structure during the deposition process. The adsorption characteristics were determined in the format of “electronic nose” devices \3\, i.e. simultaneously for the entire set of sensors with different sensitive layers (multi-sensor array).

An analysis of the obtained results unambiguously indicates that, among the used sensitive materials mentioned above, R6G has the maximum adsorption capacity with respect to all studied analytes in the gas phase. Despite the fact that the kinetics of the interaction of R6G with analytes significantly depends on the nature of the analyte, the interaction is controlled by the process of physical sorption and is a completely reversible process. We discuss possible mechanisms for such an “increased” adsorption capacity of R6G thin films and their potential impact on classical analytical procedures using this widely used reagent.

Finally, it is reasonable to emphasize the promise of R6G for the development of multisensor arrays for multivariate intelligent gas analysers, since the combination of R6G with various inorganic nanostructured materials (ZnO, etc., metal nanoparticles, etc.) makes it possible to purposefully change the selectivity profile of composite materials. This allows us to create efficient sensor arrays optimized for specific application, including environmental monitoring or as a potential bio-sniffer for acute toxicity assays \4\ or highly sensitive sensors of low molecular weight biological regulators of vital activity \5\.

1 Yujiao Wang, Xiaojun Wang, Wenyu Ma , Runhua Lu , Wenfeng Zhouand Haixiang Gao. Recent Developments in Rhodamine-Based Chemosensors: A Review of the Years 2018–2022, Chemosensors 2022, 10(10), 399; https://doi.org/10.3390/chemosensors10100399

2 Iryna Krishchenko, Sergii Kravchenko, Ivanna Kruglenko, Eduard Manoilov and Boris Snopok 3D Porous Plasmonic Nanoarchitectures for SERS-Based

Chemical Sensing Eng. Proc. 2022, 27(1), 41; https://doi.org/10.3390/ecsa-9-13200

3 I.V. Kruglenko, B.A. Snopok, Yu.M. Shirshov, F.J. Rowell Multisensor systems for gas analysis: optimization of arrays for classification of pharmaceutical products Semiconductor Physics, Quantum Electronics & Optoelectronics. 2004. V. 7, N 2. P. 207-216.

4 Kruglenko, I.; Kravchenko, S.; Burlachenko, J.; Kruglenko, P.; Snopok, B. Adsorbate Induced Transformations of Ovalbumin Layers in Volatile Organic Solvents: QCM Study of a Potential Bio-Sniffer for Acute Toxicity Assays. Eng. Proc. 2023, 35, 23. https://doi.org/ 10.3390/IECB2023-14574

5 Borys Snopok and Ivanna Kruglenko Analyte induced water adsorbability in gas phase biosensors: the influence of ethinylestradiol on the water binding protein capacity Analyst, 2015,140, 3225-3232