LIBS as a useful tool in spatial elemental analysis of plants: Quantum dots distribution in white mustard

abstract

English

Laser-Induced Breakdown Spectroscopy (LIBS) is an optical analytical method that is used to determine the elemental composition of samples. Its tremendous advantages lie mainly in its simplicity, ability of in situ analysis with minute sample preparation, multielemental analysis, low cost and short measurement times. Together with the mentioned benefits, its capability of mapping sample surface and thus revealing the spatial distribution of elements is what opens the doors to various applications. While there are many fields where mapping of samples can be extremely useful, this work focuses entirely on the use of LIBS in analysing spatial distribution of chosen elements in plants. Every year many new nano- and micro-materials, such as various nanoparticles (NPs), are created and leek into the environment. Thus, there is emerging need for evaluation of their stability and effect on various organisms, including plants. LIBS is widely used for providing elemental distribution in plant tissues. In the previous years, the research focused mostly on essential elements (both macro- and micro-nutrients) as well as on non-essential ones. However, a very limited amount of publications deals with the toxicity of different NPs so far. This is likely caused by the major outbreak of nanomaterials in the last few years. Quantum dots (QDs) are fluorescent semiconductor spherical nanoparticles. Their fluorescence is highly stable as well as easily tuneable which makes them a promising tool for applications such as bioimaging. QDs structure usually includes two parts: core and shell. The core most commonly consists of CdTe, CdS or CdSe and the ZnS is most frequent material for encapsulation since it enhances chemical stability and fluorescence efficiency. Nowadays their use in medical applications is severely limited due to the risk of highly toxic cadmium ions (Cd2+) leaking into their surrounding environment, including tissues. This study focuses on the comparison of toxicity and bioaccumulation of two distinct types of cadmium-based QDs: core QDs (CdTe) and core/shell QDs (CdTe/SiO2) in two concentrations dispersed in aqueous environment in white mustard (Sinapis Alba) with CdCl2 used as a positive control. The exposition to QDs took place for 72 hours. After the exposure the overall content of cadmium in tested plants was assessed using Inductively Coupled Plasma Optical Emission Spectrometry and bioaccumulation factors were calculated separately for the root, that was exposed directly to the dispersion of QDs, and stem with leaves. As a toxicological end-point the length of the root was observed. LIBS was applied to determine spatial distribution of Cd in tested samples. The achieved resolution for the mapping of whole plants analysis was 100 μm. Specific areas that showed potentially interesting Cd distribution were measured with micro LIBS with a resolution of 25 μm. LIBS results have successfully shown that both Cd distribution and bioaccumulation patterns differed in QDs and positive control.

Laser Induced Breakdown Spectroscopy; Quantum Dots; White mustard; Elemental Imaging

STŘÍTEŽSKÁ, S.; MODLITBOVÁ, P.; PROCHAZKA, D.; ZEZULKA, Š.; KUMMEROVÁ, M.; POŘÍZKA, P.; KAISER, J.

20. 10. 2020

2336-7210

Czech Chemical Society Symposium Series

18

4

Czech Republic

290

291

2

http://www.ccsss.cz/index.php/ccsss/issue/viewIssue/27/39