Применение перовскитных квантовых точек для обнаружения ионов тяжелых металлов
- Авторы: Рыжкова Г.Г., Ефимова Ю.А., Дудович Д.Л.
- Выпуск: № 2(25) (2024)
- Страницы: 257-262
- Раздел: Химия
- Дата публикации: 30.12.2024
- URL: https://vmuis.ru/smus/article/view/27516
- ID: 27516
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Аннотация
Данная статья посвящена последним достижениям в применении перовскитных квантовых точек для детектирования ионов тяжелых металлов. Проанализированы и систематизированы методы использования этих наночастиц для анализа ионов ртути, меди, железа и свинца. Выделены основные механизмы взаимодействия определяемых ионов и наночастиц. Оценены возможности использования перовскитных квантовых точек для флуоресцентного анализа тяжелых металлов и предложены возможные направления исследований в данной области.
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Introduction
One of the most global problems associated with rising industrial development is heavy metal pollution. Most heavy metal ions can accumulate in living organisms, have mutagenic and carcinogenic properties. Some highly toxic heavy metal ions can cause serious harm to health even in very low concentrations. For this reason, one of the important tasks is to search for new, more accurate methods for determining these ions.
To solve this problem, it is promising to use perovskite quantum dots (PQDs). They are a new class of optoelectronic nanomaterials that have been intensively studied over the past years due to their excellent optical and electrical properties. Colloidal halide perovskites have unique properties, such as photoluminescence quantum yield (PLQY) reaching 100% and high optical absorption coefficient, narrow emission full width at half maximum (FWHM), relatively high stability and tunable bandgap [1]. Thanks to them, these materials are widely used in lasers [2], solar cells [3], photodetectors [4], LEDs [5], photocatalysis [6] and chemical sensing [7].
The composition of PQDs can be described by the formula ABX3, where A represents monovalent inorganic or organic cations, such as Cs+, formamidinium (FA+) and methylammonium (MA+). B is a smaller cation, including Pb2+, Sn2+ and etc., X is Cl-, Br-, I- or their mixture. The A cations occupy every hole which is created by 8 [BX6]4- octahedra, giving the A cation 12 neighboring halide ions.
The presence of even ultratrace amounts of some metal ions can lead to the appearance of new electronic transitions in quantum dots. In this case, luminescence quenching or the emission light wavelength changes may occur. Thanks to this, the change in luminescence makes it possible to determine the concentration of metal ions with high sensitivity.
This review summarizes methods for determination of heavy metal ions using perovskite quantum dots. The purpose of this review is to classify and systematize the methods for the application of PQDs in chemical analysis of heavy metal ions, and to reveal the relationship between the quantum dots characteristics and efficiency of analysis. This work considers the possibilities of using PQDs for fluorescent analysis of heavy metal ions and also further directions of research in this area.
Mercury ions (Hg2+) sensing
Mercury is one of the most dangerous heavy metal pollutants, because it’s harmful to human health even in very low concentrations [8]. Huang Y. et al. designed a method of mercury ions determination based on the fluorescence resonance energy transfer (FRET) mechanism. [9]. FRET is a mechanism of energy transfer between two fluorescent molecules. The emission peak of the energy donor overlaps with the absorption peak of the energy acceptor and the distance between molecules is in the range of 1–100 Å are required for this effect to occur. Two-dimensional organic-inorganic perovskite (NH3(CH2)10NH3)PbBr4 were synthesized by a fast precipitation method and added in a mixture of water and dimethyl sulfoxide (DMSO) in ratio DMSO/H2O = 1/9. In the presence of Hg2+ and a rhodamine spirolactam (RBED), due to the FRET effect a pink color appears under visible light and fluorescence at 585 nm under ultraviolet light. The limit of detection (LOD) in this case was 2.4 μM.
Another mechanism of interaction between CH3NH3PbBr3 PQDs and Hg2+ based on the surface ion-exchange mechanism was described by Lu L. Q. et al. [10]. Hg2+ replaces a part of Pb2+ on the surface of nanocrystals, and makes the concentration of CH3NH3PbBr3 decrease, which leads to the fluorescence quenching. In summary, the ion-exchange on the surface of CH3NH3PbBr3 PQDs induced the highly sensitive and selective detection of Hg2+ by the PQDs. This method showed high sensitivity with the detection limit of 0.124 nM and high selectivity. The disadvantage of this method is that the analysis is carried out in toluene. In practice, metal ions most often need to be detected in an aqueous solution. PQDs are unstable in water, which limits their use in metal ion sensing.
This problem was solved by modifying the surface of all-inorganic CsPbBr3 PQDs using trifluoroacetyl lysine (Tfa-Lys) [11]. PQDs were synthesized in aqueous solution by using the method of low-temperature crystallization. After mercury ions adding one-pair electrons in N and O transfer to the empty orbitals of Hg2+, resulting in coordination bonds. The excited state electron easily loses its energy through a non-radiative transition, leading to fluorescence quenching. Limit of detection in this case was 0,374 × 10−9 (0.046 mg/L) which is almost as effective as the previous method. These PQDs also have a selective detection effect on Hg2+.
Table 1
Summary of Hg2+ ion sensing
PQDs type | LOD, M | mechanism | solvent | reference |
(NH3(CH2)10NH3)PbBr4 + RBED | 2,40 × 10−6 | FRET | DMSO/water (1:9) | [9] |
CH3NH3PbBr3 | 0,12 × 10−9 | surface ion-exchange | toluene | [10] |
CsPbBr3+Tfa-Lys
| 0,37 × 10−9 | electron transfer | water | [11] |
Detection of copper ions (Cu2+)
Copper is an essential mineral for human health and at the same time can be toxic, depending upon the amounts ingested. A pressing challenge in modern nutrition is to define both the copper dose and regimen of administration for safe human consumption; this is a difficult task because our knowledge about the limits of safe copper exposure (homeostasis), the consequences of moderate excess copper exposure and the indicators to detect early adverse effects are not well established [12].
It was noticed that during the work on the detection of copper ions, the mechanism of electronic transfer from the surface of quantum dots to Cu2+ ions mainly works. This is due to the special electronic configuration of Cu2+ ions d9, which is favorable for the acceptance of an electron and the transition to a relatively stable electronic configuration d10. This statement can be confirmed by the conclusions of A. Ding, D. Lei Zhou, G. Pan et al. [13]. They developed a method for detecting copper ions using europium-doped lead-free Cs3Bi2Br9 PQDs. Compared with ions of other metals, Cs3Bi2Br9:Eu3+ PQDs are highly selectively quenched by Cu2+. This is mainly due to the adsorption of Cu2+ ions on the surface of PQDs. Then the process of electron transfer from quantum dots to Cu2+ takes place, which leads to a decrease in the intensity of fluorescence in the presence of Cu2+. This method showed high sensitivity with the detection limit of 10 nM.
Similar results were obtained in a study by Jimin Wang and others [14]. The quantum dots were synthesized by hot injection method. The photoluminescence intensity of Mn-doped CsPbCl3 quantum dots decreases significantly after contact with Cu2+ solution. The quenching mechanism is also electron transfer, which has been experimentally proven by analyzing the fluorescence and absorption spectrum.
Research Y. Liu [15] and M. Raj Kapoor [16] aimed to study all possible mechanisms used in the detection of cations (cation exchange, FRET and electron transfer). In the first case, CsPbBr3 nanoparticles coated with silicon dioxide were synthesized, but the analysis is possible only in hexane. In the second case, PQDs were synthesized by hot injection. The advantage of using them is that these PQDs are coated with a polymer that allows analysis in water. Once again, the possibility of FRET and cation exchange processes has been eliminated. Both methods showed good sensitivity and great selectivity.
Table 2
Summary of Cu2+ ion sensing
PQDs type | LOD, M | mechanism | solvent | reference |
Eu3+ doped lead free Cs3Bi2Br9 | 10,00 × 10-9 | surface ion-exchange | water | [13] |
Mn-Doped CsPbCl3 | 10,00 × 10-9 | electron transfer | hexane | [14] |
CsPbBr3 | 0,10 × 10-9 | cation-exchange | hexane | [15] |
PVP/PVP-NIPAM-coated CsPbBr3 | 18,60 × 10-6 | electron transfer | water | [16] |
Fe3+ detection
Fe3+ ions are important participants in many processes occurring in the human body, such as electron transfer reactions and oxygen transport [17]. Iron imbalance in the body can lead to anemia, decreased immunity, skin diseases and other health hazards, so Fe3+ ions control is necessary. To solve this problem it is possible to use perovskite nanostructures. Zhu M. Y. et al. introduced a method for Fe3+ sensing by using 1D perovskite (C6H5NH3)2Pb3I8·2H2O nanocrystals in n N, N-dimethylformamide (DMF) solution [18]. This method demonstrated short response time, high sensitivity (LOD=75.1 × 10−9 M) and high selectivity. The quenching mechanism is explained by the Fe3+ inhibition to the radiative electron-hole recombination via capturing electrons.
Chen R. et al. managed to improve quantum dots stability in water by encapsulating CsPbBr3 PQDs in zeolitic imidazole frameworks (MAPbBr3@ZIF-8Co5%) [19]. As a result, the fluorescence characteristics of nanocrystals did not change in an aqueous solution for a long time. In this case luminescence quenching mechanism is related to the resonance energy transfer from MAPbBr3 to Fe3+. An important advantage of MAPbBr3@ZIF-8Co5% composite is the possibility of selective detection of Fe3+ even in the presence of Fe2+. However, LOD = 3.9 × 10− 5 M for this method highest among other methods.
Another way to increase stability of PQDs in aqueous solution was developed by Gao D. et al [20]. Researchers encapsulated nanoparticles into poly(styrene/acrylamide) nanospheres by modified swelling-shrinking strategy. Ion detection is based on formation of ground-state complexes Fe3+ with carboxyl groups, which causes static quenching of fluorescence. This polymer material also showed high efficiency for Fe3+ detecting in river water samples, human serum samples and tea water samples.
Not only cesium lead halide CsPbBr3 PQDs may be used for Fe3+ detecting. Gao D. et al. synthesized the Pb-free cesium–tin halide CsSnX3 QDs covering with bone gelatin [21]. Due to this, the stability of PQDs in water and the quantum yield increase. The presence of Fe3+ leads to the luminescence quenching, which occurs according to the FRET mechanism.
Table 3
Summary of Fe3+ ion sensing
PQDs type | LOD, M | mechanism | solvent | reference |
(C6H5NH3)2Pb3I8·2H2O | 75,10 × 10−9 | electron transfer | DMF | [18] |
CsPbBr3@poly(styrene/ acrylamide) | 2,20 × 10− 6 | static quenching | water | [19] |
CsSnX3@bone gelatin | 8,00 × 10− 6 | FRET | water | [20] |
MAPbBr3@ZIF-8Co5% | 3,90 × 10− 5 | FRET | water | [21] |
Pb2+ detection
The toxicity of lead is of serious concern due to its source in the environment in developing countries. Such poisoning occurs as a result of various human-related activities such as house painting, smoking-related activities, leaded gasoline, contaminated food and drinking water, and especially in industry where production processes are carried out. It is also found in breast milk. Excessive exposure to lead on the human body leads to impaired body functions: it can destroy the nervous and the digestive system, such as memory degradation, dizziness, and gastrointestinal ulcer even at very low dose level [22].
- Juan, H. Yuchun and others took up the solution to this problem. In their study [23], they were based on the rapid chemical reaction of MABr with lead ions to form CH3NH3PbBr3. The MABr solution detects the Pb2+ due to the luminescence enhancing effect which is different from the quenching mechanisms of lead halide perovskite fluorescent probes. All of the solutions were transparent under ambient light. Solution without PbBr2 only reflects the purple color of the UV light under the UV lamp illumination, indicating that the MABr solution is nonfluorescent under the UV lamp illumination. Introduction of a small amount of PbBr2 to the MABr solution leads to the formation of the MABr@MAPbBr3 solution, and it emits pale-yellow color under UV light illumination. As the Pb2+ concentration of the MABr@MAPbBr3 solutions increased from 1.6×10−3 to 2×10−1 M, the emission colors of these solutions changed quickly from pale yellow to bright green.
Another research belongs to L. Dongyu, X. Wan and their colleagues [24]. Firstly, the all-inorganic perovskite CsSnX3 (X = Cl, Cl/Br, or Br) QDs were synthesized through a hot injection method with Cs2CO3 and SnX2 (X = Cl, Cl/Br, or I). The detection of lead is based on the mechanism of cation exchange: all the samples show higher emission intensity with increasing the Pb2+ ion concentration, suggesting the Pb2+ ions enter into the lattice of CsSnX3. In addition, the PL of CsSnX3 QDs is highly selectively enhanced by Pb2+ ions other than metal ions. The PL intensity of QDs reaches maximum in 6 min after adding lead ions and remains stable in more than 10 days. The long response time further implies that the Pb2+ ions do not adsorb to the surface of the CsSnBr3 QDs but enter the lattice. These methods are based on obtaining lead bromide PQDs. Disadvantage of these methods is the impossibility of application in aqueous solution, which is extremely important for the determination of metal ions.
Table 4
Summary of Pb2+ ion sensing
PQDs type | LOD, M | mechanism | solvent | reference |
CH3NH3Br | 1,60 × 10-3 | formation of luminescent nanoparticles | DMF | [23] |
CsSnX3 | 3,50 × 10−9 | cation-exchange | ODE | [24] |
Conclusions
We have summarized the methods proposed for sensing heavy metal ions, such as Hg2+, Cu2+, Fe3+ and Pb2+ , using perovskite quantum dots. The use of these nanoparticles has great potential for application in analysis, since these methods show high efficiency and selectivity. However, the instability of nanocrystals in aqueous solution limits their use in metal ion detection. Encapsulation of PQDs in different polymers or zeolites improves their stability, but detection efficiency is significantly lower, than using nanocrystals in organic solvents. A more promising method for increasing stability is use of a short-chain ligand with polar groups at the ends. Unlike other methods, in this case efficiency decreases slightly. However, ions can react differently with ligands, so the type of ligand must be selected individually for each ion. Therefore, the main direction of research is to find ways to increase stability without loss of efficiency.
This method can also find application in the deteсtion of other heavy metal ions. This is possible if interaction between quantum dots, ligands and metal ions leads to change in the luminescence. The main mechanisms of interaction include ion exchange, electron transfer, static quenching and FRET. Therefore, another possible direction of research may be the search for combinations of quantum dots and ligands that interact through one of these mechanisms with metal ions such as cadmium, chromium, cobalt and others.
Об авторах
Галина Геннадьевна Рыжкова
Автор, ответственный за переписку.
Email: gala.ryzhckova@yandex.ru
Россия
Юлия Алексеевна Ефимова
Email: ufm233@yandex.ru
Дарья Леонидовна Дудович
Email: dudovich.dl@ssau.ru
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