Abstract
Nanoparticles, particularly quantum dots (QDs), are commonly used for the sensitive detection of various objects. A number of target molecules may be determined using QDs sensing systems. Depending on their chemical nature, physicochemical properties, and spatial arrangement, QDs can selectively interact with given molecules of interest. This can be performed in complex systems, including microorganisms or tissues. Efficient fluorescence enables low exposure of QDs and high sensitivity for detection. One disadvantage of quantum dots fluorophores is fluorescence decay. However, for given applications, this property may be an advantage, e.g., for highly sensitive detection based on correlation images in the time domain. This experimental work deals with the measurement of fluorescence decay of Lumidot TMCdSe/ZnS (530 nm) quantum dots. These nanoparticles were transferred to the surface of various planar chromatographic stationary phases. Fluorescence of formed spots was recorded at room temperature over a long period of time, namely 15.7824 × 105 min (three years). The resulting signal profiles in the time domain were analyzed using classical approach (luminescence model comparison involving different mathematical models).Moreover, fluorescence behavior on different TLC/HPTLC supports was investigated using multivariate statistics (principal component analysis, PCA). Eight planar chromatographic stationary phases were investigated, including cellulose, octadecylsilane, polyamide, silica gel and aluminium oxide in different forms (TLC and HPTLC types). The presented research revealed significantly different and non-linear long-term QDs behavior on these solids. Two different fluorescence signal trajectories were recorded, including typical signal decay after QDs application to the plates and long-term intensity increase. This was particularly visible for given planar chromatographic adsorbents, e.g., cellulose or octadecylsilane. To the author’s knowledge, these findings were not reported before using the stationary chromatographic phases, and enable the design of future experiments toward sensing of low molecular mass chemicals using, e.g., advanced quantification approaches. This may include signal processing computations based on correlation images in the time domain. Additionally, the reported preliminary data indicates that the investigated nanoparticles can be applied as efficient and selective fluorophores. This was demonstrated on micro-TLC plates where separated bioactive organic substances quenching from cyanobacteria extracts were sensitively detected. The described detection protocol can be directly applied for different planar chromatographic systems, including paper-based microfluidic devices, planar electrophoresis and/or miniaturized microfluidic chip devices.
Highlights
This article is an open access articleThere is increasing interest in developing simple analytical devices, which can generate qualitative or quantitative data that may be acquired and transmitted by digital cameras, especially those built into mobile phones/smartphones devices [1]
They include parallel/multiple samples development, low consumption of chemicals for mobile phases, ability to work without external pumps, degassers, pre-columns, injectors or different large and complex auxiliary devices, the possibility for direct analysis of heavily loaded matrices without sample pre-purification, fast-developing mode [5]
Quantum dots based on CdSe or CdTe particles have been found to be efficient sensing components of paper-based analytical devices for detecting toxic inorganic elements, including Cu (II) and complex organic biomolecules like enzymes [13,14]
Summary
There is increasing interest in developing simple analytical devices, which can generate qualitative or quantitative data that may be acquired and transmitted by digital cameras, especially those built into mobile phones/smartphones devices [1] Such inexpensive and robust hybrid analytical systems can be used in remote sampling areas, for fast screening of various micropollutants and/or biomarkers. It should be noted that planar chromatography is fairly efficient as a separation tool with several advances on their counterpart: column liquid chromatography (high-performance liquid chromatography; HPLC) They include parallel/multiple samples development, low consumption of chemicals for mobile phases, ability to work without external pumps, degassers, pre-columns, injectors or different large and complex auxiliary devices (mobile phase movement is driven by capillary forces), the possibility for direct analysis of heavily loaded matrices without sample pre-purification (due to single-use of stationary phase), fast-developing mode (in case of micro-TLC, the analysis time can be completed within 1–2 min) [5]. Planar chromatographic analysis can be manual or fully automated, significantly decreasing the relative low repeatability of such analysis [6]
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