Development of multiple analytical labels for volatile organic compounds based on the results of sorption on CdS quantum dots in chitosan without and with modification with Rhodamine 6G

Abstract

Analytical solutions using the luminescent labels for the analysis of gaseous media and the detection of volatile organic compounds are discussed. Such solutions can potentially be applied for the development of optical, sorption gas sensors, smart label fillers, test systems with various carriers for the detection of chemical biomarkers in living systems. To solve the problem it is proposed to develop and study the properties of modifiers based on cadmium sulfide quantum dots. The aim of the work is studying the sorption properties of CdS quantum dots prepared using a method improved in the direction of "green chemistry", with stabilizing chitosan shells (pure and modified with Rhodamine 6G). Sorption properties of various phases based on quantum dots were studied at a temperature of 22±1 °C by a highly sensitive direct piezo-quartz microweighting method with a resolution of up to 10–9 g by the mass of the sorbent in vapors of volatile compounds. The selectivity of phases based on cadmium sulfide quantum dots in low-mass chitosan (5–10 micrograms) with respect to volatile organic compounds of different classes was evaluated. The relative selectivity and sensitivity of vapor weighing on different phases were evaluated using the parameters A(i/j), showing how many times the sorption properties of CdS phases in chitosan differ without and with the addition of Rhodamine 6G. The method of direct weighing allows to estimate the rate of sorption and desorption, and the capacity of the sorbent phases. It was established that substances belonging to the same selectivity group in terms of A(i/j) values, for example, water and ethanol, have different sorption rates. This feature can be applied for solving the problems of separate detection of vapors, they can be identified at different moments of exposure of piezo balances with phases based on CdS quantum dots in chitosan without and with the addition of Rhodamine 6G. The use of cadmium sulfide quantum dots in chitosan as a sorbent of organic compound vapors significantly affects the kinetics and sorption efficiency. Modification of chitosan with Rhodamine 6G changes the sorption properties of quantum dots in chitosan, which can be used for engineering new sorbents for sensor systems. Simple algorithms are proposed for solving problems of vapor recognition of volatile compounds according to calculated parameters even for non-selective sorption systems. Programming the approach can significantly increase the expressiveness of decision-making in integrated analytical systems, for example, "electronic noses" based on sensors, including those with studied phases. It was found that the mass of the phase based on cadmium sulfide quantum dots in chitosan does not affect the sorption properties in the micromass range, which is traditional for nanostructures. Changes in the luminescent properties of phases based on cadmium sulfide, as a possible visually detectable analytical response, will be discussed in the next paper.