Oxidative cleavage-based upconversional nanosensor for visual evaluation of antioxidant activity of drugs

Luminescence Nanoprobe in the Near-Infrared-II Window for Ultrasensitive Detection of Hypochlorite

Sensitive and selective detection of hypochlorite is in great demand for food safety, especially in fresh cold chain products. However, the detection limit of traditional visible emission-based strategies cannot satisfy the requirement of ultrasensitive analysis in practical applications. In this work, we explored a novel luminescent nanoprobe in the near-infrared-II (NIR-II) window to greatly improve the hypochlorite detection limit for analysis of real milk samples, which was based on the fluorescence resonance energy-transfer process between the hypochlorite-responsive dye (FD1080) and the lanthanide-doped downconverted nanoparticles. Specifically, the NIR-II luminescence from Yb ions was first suppressed by FD1080 due to the energy-transfer mechanism. In the presence of hypochlorite, FD1080 was bleached to recover the luminescence. As a proof-of-concept, the optimal nanoprobe exhibited a linear luminescence recovery in the range of 0.1-1 nM with the detection limit of 0.0295 nM for hypochlorite. Real milk sample detection experiments showed that the probe had good accuracy and precision.

Surface lanthanide activator doping for constructing highly efficient energy transfer-based nanoprobes for the on-site monitoring of atmospheric sulfur dioxide

The sensitive and on-site detection of sulfur dioxide (SO₂) is in great demand in the fields of food safety and environmental protection. Here, we developed a novel upconversion nanoprobe based on the luminescence energy transfer mechanism for monitoring the atmospheric SO₂ concentrations. The lanthanide emitters, Tm³⁺ ions, were optimized to be doped on the surface layer of the upconversion nanoparticles to improve their energy transfer efficiency by minimizing the distance between the emitters and the surface quencher, a cyanine dye. As a proof-of-concept, the optimal nanoprobe was utilized to detect SO₂ water derivatives, bisulfite ions, exhibiting a linear luminescence increase in the range of 1 nM to 10 nM. Furthermore, we assembled the cyanine-modified upconversion nanoparticles onto a test paper, and used a smartphone-based detection platform to achieve portable and visual detection of SO₂. The test paper showed a strong luminescence stability, homogeneity and good anti-interference. The limit of detection for SO₂ gas was found to be 1 ng L^-1. This novel upconversion test paper was also demonstrated to directly monitor the concentration of SO₂ gas in atmosphere.

Recent Advances on Functionalized Upconversion Nanoparticles for Detection of Small Molecules and Ions in Biosystems

Significant progress on upconversion-nanoparticle (UCNP)-based probes is witnessed in recent years. Compared with traditional fluorescent probes (e.g., organic dyes, metal complexes, or inorganic quantum dots), UCNPs have many advantages such as non-autofluorescence, high chemical stability, large light-penetration depth, long lifetime, and less damage to samples. This article focuses on recent achievements in the usage of lanthanide-doped UCNPs as efficient probes for biodetection since 2014. The mechanisms of upconversion as well as the luminescence resonance energy transfer process is introduced first, followed by a detailed summary on the recent researches of UCNP-based biodetections including the detection of inorganic ions, gas molecules, reactive oxygen species, and thiols and hydrogen sulfide.

Titanium Dioxide/Upconversion Nanoparticles/Cadmium Sulfide Nanofibers Enable Enhanced Full-Spectrum Absorption for Superior Solar Light Driven Photocatalysis

In this work, we demonstrate an electrospinning technique to fabricate TiO2 /upconversion nanoparticles (UCNPs)/CdS nanofibers on large scale. In addition, the as-prepared TiO2 nanofibers are incorporated with a high population of UCNPs and CdS nanospheres; this results in Förster resonance energy-transfer configurations of the UCNPs, TiO2 , and CdS nanospheres that are in close proximity. Hence, strong fluorescent emissions for the Tm(3+) ions including the (1) G4 →(3) H6 transition are efficiently transferred to TiO2 and the CdS nanoparticles through an energy-transfer process. The as-prepared TiO2 /UCNPs/CdS nanofibers exhibit full-spectrum solar-energy absorption and enable the efficient degradation of organic dyes by fluorescence resonance energy transfer between the UCNPs and TiO2 (or CdS). The UCNPs/TiO2 /CdS nanofibers may also have enhanced energy-transfer efficiency for wide applications in solar cells, bioimaging, photodynamics, and chemotherapy.

Zinc-Dithizone Complex Engineered Upconverting Nanosensors for the Detection of Hypochlorite in Living Cells

Current chemo/biosensors for hypochlorous acid or hypochlorite detections are usually limited to the submicromolar level because of their insufficient sensitivity, which is a problem because the concentrations in biological matrices is generally on the nanomolar scale or even lower. Developing a probe with a high enough sensitivity remains a challenge. Using the minimal background fluorescence of upconversion nanocrystals to our advantage, we herein report on an energy-transfer mechanism-based upconversion luminescent nanosensor for the sensitive and selective detection of hypochlorite in aqueous solution. In this nanosensor water-dispersible upconversion nanoparticles act as the energy donor and a novel hypochlorite-responsive coordination complex Zn(DZ)3 is employed as the energy acceptor. The quenched upconversion luminescence, induced by the Zn(DZ)3 complex, can be efficiently recovered after addition of hypochlorite through the selective oxidative breakage of the Zn-S-C bonds in the Zn(DZ)3 complex, which was verified by mass spectrometry. The detection limit for hypochlorite of this sensing system is as low as 3 nM. Furthermore, this newly coordination-complex engineered upconversion nanosensor is successfully applied to image different amounts of exogenous hypochlorite in living HeLa cells.

A Rationally Designed Upconversion Nanoprobe for in Vivo Detection of Hydroxyl Radical

The detection of •OH in live organisms is crucial to the understanding of its physiological and pathological roles; while this is too challenging because of the extremely low concentration and high reactivity of the species in the body. Herein, we report the rational design and fabrication of an NIR-light excited luminescence resonance energy transfer-based nanoprobe, which for the first time realizes the in vivo detection of •OH. The nanoprobe is composed of two moieties: upconversion nanoparticles with sandwich structure and bared surface as the energy donor; and mOG, a modified azo dye with tunable light absorption, as both the energy acceptor and the •OH recognizing ligand. The as-constructed nanoprobe exhibited ultrahigh sensitivity (with the quantification limit down to 1.2 femtomolar, several orders of magnitude lower than that of most previous •OH probes), good biocompatibility, and specificity. It was successfully used for monitoring [•OH] levels in live cells and tissues.

Numerical Study of Pillar Shapes in Deterministic Lateral Displacement Microfluidic Arrays for Spherical Particle Separation

Deterministic lateral displacement (DLD) arrays containing shaped pillars have been found to be more effective in biomedical sample separation. This study aims to numerically investigate the interplay between particles and microfluidic arrays, and to find out the key factors in determining the critical size of a DLD device with shaped pillars. A new formula is thus proposed to estimate the critical size for spherical particle separation in this kind of new DLD microfluidic arrays. The simulation results show that both rectangular and I-shaped arrays have considerably smaller critical sizes. The ratio of sub-channel widths is also found to play an important role in reducing the critical sizes. This paves a valuable way toward designing high-performance DLD microfluidic arrays.