Detection of nitroaromatics in aqueous media based on luminescence resonance energy transfer using upconversion nanoparticles as energy donors

Sensitive detection of picric acid in an aqueous solution using fluorescent nonconjugated polymer dots as fluorescent probes

Nonconjugated polymer dots (NPDs) were successfully used as fluorescent probes to selectively and sensitively detect picric acid (PA). The NPDs were prepared from polyethylenimine and 1,4-phthalaldehyde under mild conditions and had excitation and emission maxima of 351 and 474 nm, respectively. Fluorescence of the NPDs was efficiently quenched by PA through the inner filter effect because of the overlapping PA absorption band and NPD excitation spectrum. The NPDs allowed PA to be determined with a high degree of sensitivity. The linear range was 0-140μM and the detection limit was 0.5μM. The work involved developing a novel method for synthesizing NPDs and a promising platform for determining PA in environmental media.

Exploring Heterostructured Upconversion Nanoparticles: From Rational Engineering to Diverse Applications

Upconversion nanoparticles (UCNPs) represent a class of optical nanomaterials that can convert low-energy excitation photons to high-energy fluorescence emissions. On the basis of UCNPs, heterostructured UCNPs, consisting of UCNPs and other functional counterparts (metals, semiconductors, polymers, etc.), present an intriguing system in which the physicochemical properties are largely influenced by the entire assembled particle and also by the morphology, dimension, and composition of each individual component. As multicomponent nanomaterials, heterostructured UCNPs can overcome challenges associated with a single component and exhibit bifunctional or multifunctional properties, which can further expand their applications in bioimaging, biodetection, and phototherapy. In this review, we provide a summary of recent achievements in the field of heterostructured UCNPs in the aspects of construction strategies, synthetic approaches, and types of heterostructured UCNPs. This review also summarizes the trends in biomedical applications of heterostructured UCNPs and discusses the challenges and potential solutions in this field.

PEI-capped KMgF3:Eu2+ nanoparticles for fluorescence detection of nitroaromatics in municipal wastewater

The probing and quantitative detection of nitroaromatics is key for public safety and the monitoring of wastewater. Currently, most techniques used for the detection of nitroaromatics require ideal conditions rather than real conditions, making practical applications challenging. As nitroaromatics have strong absorption in the range of 350-370 nm, we can design a kind of KMgF₃:Eu²⁺ nanophosphor with a strong f-f transition emission located at 362 nm, and an energy resonance transfer system based on the overlap of the emission peak of nanophosphors and the absorption peak of nitroaromatics can be constructed to realize the quantitative detection of nitroaromatics in municipal wastewater. Based on this, in this paper, a fluorescence resonance energy transfer (FRET) sensor is designed by choosing polyethylenimine (PEI)-capped KMgF₃:Eu²⁺ nanoparticles as an energy donor for the ultrasensitive detection of nitroaromatics, which can also work as an energy acceptor. The KMgF₃:Eu²⁺ nanoparticle sensor shows great sensitivity and selectivity and good linear characteristics in both DI water and wastewater. The detection limits in municipal wastewater were 0.456, 0.598, 0.667, 0557 and 0.678 ng/mL for TNT, TNP, p-nitrotoluene, dinitrobenzene (DNB), and nitrobenzene (NB), respectively. The detection accuracy was identified by high-performance liquid chromatography (HPLC). The results showed that the sensor had superior sensitivity and great accuracy and could be used in practical applications.