Liquid-liquid extraction and visual detection of Hg2+ in aqueous solution by luminescent CsPbBr3 perovskite nanocrystals

Sensing Utilities of Cesium Lead Halide Perovskites and Composites: A Comprehensive Review

Recently, the utilization of metal halide perovskites in sensing and their application in environmental studies have reached a new height. Among the different metal halide perovskites, cesium lead halide perovskites (CsPbX3; X = Cl, Br, and I) and composites have attracted great interest in sensing applications owing to their exceptional optoelectronic properties. Most CsPbX3 nanostructures and composites possess great structural stability, luminescence, and electrical properties for developing distinct optical and photonic devices. When exposed to light, heat, and water, CsPbX3 and composites can display stable sensing utilities. Many CsPbX3 and composites have been reported as probes in the detection of diverse analytes, such as metal ions, anions, important chemical species, humidity, temperature, radiation photodetection, and so forth. So far, the sensing studies of metal halide perovskites covering all metallic and organic-inorganic perovskites have already been reviewed in many studies. Nevertheless, a detailed review of the sensing utilities of CsPbX3 and composites could be helpful for researchers who are looking for innovative designs using these nanomaterials. Herein, we deliver a thorough review of the sensing utilities of CsPbX3 and composites, in the quantitation of metal ions, anions, chemicals, explosives, bioanalytes, pesticides, fungicides, cellular imaging, volatile organic compounds (VOCs), toxic gases, humidity, temperature, radiation, and photodetection. Furthermore, this review also covers the synthetic pathways, design requirements, advantages, limitations, and future directions for this material.

Perovskite Nanocrystals: Superior Luminogens for Food Quality Detection Analysis

With the global limited food resources receiving grievous damage from frequent climate changes and ascending global food demand resulting from increasing population growth, perovskite nanocrystals with distinctive photoelectric properties have emerged as attractive and prospective luminogens for the exploitation of rapid, easy operation, low cost, highly accurate, excellently sensitive, and good selective biosensors to detect foodborne hazards in food practices. Perovskite nanocrystals have demonstrated supreme advantages in luminescent biosensing for food products due to their high photoluminescence (PL) quantum yield, narrow full width at half-maximum PL, tunable PL in the entire visible spectrum, easy preparation, and various modification strategies compared with conventional semiconductors. Herein, we have carried out a comprehensive discussion concerning perovskite nanocrystals as luminogens in the application of high-performance biosensing of foodborne hazards for food products, including a brief introduction of perovskite nanocrystals, perovskite nanocrystal-based biosensors, and their application in different categories of food products. Finally, the challenges and opportunities faced by perovskite nanocrystals as superior luminogens were proposed to promote their practicality in the future food supply.

Synthesis of a water-stable fluorescence CsPbBr3 perovskite by dual-supersaturated recrystallization method and tuning the fluorescence spectrum for selective detection of folic acid

As an excellent fluorescent material, cesium lead halide perovskite nanocrystals (PNCs) is rarely used for analytical purposes because the PNCs are unstable in polar solvents, especially water. Developing a new synthesis method to prepare water-stable PNCs makes it promising for the detection of analytes in aqueous solutions. Herein, by using the solubility difference of the precursors in different solvents, we successfully synthesized water-stable CsPbBr3 PNCs by a dual-supersaturated recrystallization method at room temperature. We also found that the fluorescence of the as-prepared CsPbBr3 PNCs could be quenched by some small organic molecules, such as folic acid (FA) and dopamine (DA). By using a chloride-induced anion exchange reaction method, the fluorescence emission peak of the CsPbBr3 PNCs could be tuned from 518 to 418 nm and the emission color changed from green to blue. The blue emission chloride-exchanged PNCs have a good selectivity for only FA and a good linear relationship is established between the fluorescence quenching rate of the PNCs and concentration of FA from 10.0 to 140.0 μM, with a limit of detection (LOD) of 0.9 μM. This work expanded the applications of PNCs in the field of analytical chemistry and also proposed a new strategy for improving selectivity by tuning the emission spectrum of a fluorescent probe.

Synthesis of a water-stable CsPbBr3 perovskite for selective detection of mercury ion in water

By using the method of low-temperature crystallization, CsPbBr3 perovskite nanocrystals (PNCs) coated with trifluoroacetyl lysine (Tfa-Lys) and oleamine (Olam) were synthesized in aqueous solution. The structure of the CsPbBr3 PNCs was characterized by many methods, such as ultraviolet (UV)-visible absorption spectrophotometer, fluorescence spectrophotometer, transmission electron microscopy (TEM), and X-ray diffraction (XRD) pattern. The fluorescence emission of the CsPbBr3 PNCs is stable in water for about 1 day at room temperature. It was also found that the fluorescence of the PNCs could be obviously and selectively quenched after the addition of mercury ion (Hg2+ ), allowing a visual detection of Hg2+ by the naked eye under UV light illumination. The fluorescence quenching rate (I0 /I) has a good linear relationship with the addition of Hg2+ in the concentration range 0.075 to 1.5 mg/L, with a correlation coefficient (R2 ) of 0.997, and limit of detection of 0.046 mg/L. The fluorescence quenching mechanism of the PNCs was determined by the fluorescence lifetime and X-ray photoelectron spectroscopy (XPS) of the PNCs. Overall, the synthesis method for CsPbBr3 PNCs is simple and rapid, and the as-prepared PNCs are stable in water that could be conveniently used for selective detection of Hg2+ in the water environment.

A lead-free Cs2ZnCl4 perovskite nanocrystals fluorescent probe for highly selective detection of norfloxacin

The abuse of antibiotics would seriously affect human health and has become of worldwide critical concern, thus it is urgent to develop an environmentally friendly and nontoxic fluorescent probe for antibiotics sensing. In this work, a lead-free Cs₂ZnCl₄ perovskite nanocrystals (PNCs) probe was fabricated for sensing norfloxacin (NOR) employing a modified ligand-assisted reprecipitation method. The prepared Cs₂ZnCl₄ PNCs probe had strong blue emission around 440 nm, and the characteristics of PNCs were systematically characterized by X-ray photoelectric spectroscopy (XPS), Fourier transforms infrared spectroscopy (FTIR), transmission electron microscope (TEM) and powder X-ray diffraction (XRD). The results revealed that the fluorescence intensity of the Cs₂ZnCl₄ PNCs was significantly enhanced after the introduction of norfloxacin. The Cs₂ZnCl₄ PNCs can be used as a fluorescent probe to selectively and sensitively detect norfloxacin in the concentration range from 0.2 to 50.0 μM, with a correlation coefficient (R²) of 0.9954 and the limit of detection (LOD, 3σ) of 0.1499 µM. The preparation and application of a lead-free perovskite fluorescent probe for norfloxacin would promote the application of perovskite fluorescent probes in biochemical assays.

Microwave-Assisted Synthesis of Red Emitting Copper Nanoclusters Using Trypsin as a Ligand for Sensing of Pb2+ And Hg2+ Ions in Water and Tobacco Samples

In this work, a microwave assisted method was developed for synthesis of red fluorescent copper nanoclusters (NCs) using trypsin as a template (trypsin-Cu). The as-synthesized trypsin-Cu NCs are stable and water soluble, exhibiting fluorescence emission at 657 nm when excited at 490 nm. The as-prepared red-emitting trypsin-Cu NCs were characterized by using several analytical techniques such as ultraviolet-visible (UV-Vis) and fluorescence, fluorescence lifetime, Fourier transform infrared, and X-ray photoelectron spectroscopic techniques. Red-emitting trypsin-Cu NCs acted as a nanosensor for sensing both Pb2+ and Hg2+ ions through fluorescence quenching. Using this approach, good linearities are observed in the range of 0.1-25 and of 0.001-1 μM with the lower limit of detection of 14.63 and 56.81 nM for Pb2+ and Hg2+ ions, respectively. Trypsin-Cu NCs-based fluorescence assay was successfully applied to detect both Hg2+ and Pb2+ ions in water and tobacco samples.

Ultrasensitive detection of mercury(II) in aqueous solutions via the spontaneous precipitation of CsPbBr3 crystallites

Mercury(II) is one of the most toxic ions and has the lowest allowed concentration in water. Lowering the detection limits of Hg²⁺ based on fluorescence methods is challenging compared to the detection of other heavy metal ions. Co-precipitation of the CsPbBr₃ precursor and mercury ions in aqueous solutions was developed for the ultra-trace level detection of Hg²⁺. It was found that the formed CsPbBr₃ crystals with sizes in the range of nanometers to micrometers exhibited strong fluorescence in the solid state free of water, and the incorporation of Hg²⁺ in the crystals would cause fluorescence quenching. Therefore, the decrease in fluorescence intensity could be used to quantitatively detect Hg²⁺. A microwell array was designed by dispersing the sample solution with the perovskite probe and evaporating water for 3 min to form solid fluorescent crystals, leading to the incorporation of Hg²⁺ in the crystals. This evaporation-induced co-precipitation strategy successfully solved the problem of the instability of perovskite materials in water. The concentration of Hg²⁺ can be obtained according to the decrease in the fluorescence intensity, which is caused by the replacement of Pb²⁺ by Hg²⁺ in the crystals during the crystallization process. The CsPbBr₃ crystallites can be used to detect ultra-trace levels of Hg²⁺ simply and quickly, with a linear range of 5-100 nM and limit of detection (LOD) as low as 0.1 nM. More importantly, no organic molecules are required to prepare crystals since the micron-sized crystals have obvious fluorescence. This method demonstrates great promise in detecting low concentrations of Hg²⁺ in aqueous solutions.

A simulation study of an electro-membrane extraction for enhancement of the ion transport via tailoring the electrostatic properties

Membrane technology with advantages such as reduced energy consumption due to no phase change, low volume and high mass transfer, high separation efficiency for solution solutions, straightforward design of membranes, and ease of use on industrial scales are different from other separation methods. There are various methods such as liquid-liquid extraction, adsorption, precipitation, and membrane processes to separate contaminants from an aqueous solution. The liquid membrane technique provides a practical and straightforward separation method for metal ions as an advanced solvent extraction technique. Stabilized liquid membranes require less solvent consumption, lower cost, and more effortless mass transfer due to their thinner thickness than other liquid membrane techniques. The influence of the electrostatic properties, derived from the electrical field, on the ionic transport rate and extraction recovery, in flat sheet supported liquid membrane (FSLM) and electro flat sheet supported liquid membrane (EFSLM) were numerically investigated. Both FSLM and EFSLM modes of operation, in terms of implementing electrostatic, were considered. Through adopting a numerical approach, Poisson-Nernst-Planck, and Navier-Stokes equations were solved at unsteady-state conditions by considering different values of permittivity, diffusivity, and viscosity for the presence of electrical force and stirrer, respectively. The most important result of this study is that under similar conditions, by increasing the applied voltage, the extraction recovery increased. For instance, at EFSLM mode, by increasing the applied voltage from [Formula: see text] to [Formula: see text], the extraction recovery increased from [Formula: see text] to [Formula: see text]. Furthermore, it was also observed that the presence of nanoparticles has significant effects on the performance of the SLM system.