Preparation, characterization and Hg(II)-sensing behavior of an up-conversion nanocomposite grafted by a rhodamine derived probe: a potential application for eco-industrial park

Up-Converting Nanocrystals Modified With Fluorescent Markers for the Detection of Amino Acids: Preparation, Characterization, and Sensing Performance

The present work was devoted to developing rhodamine-like chemosensing systems for cysteine (Cys) optical recognition. Aiming at low background light and minimal photobleaching effect, up-converting nanocrystals were firstly synthesized and latterly coated by α-cyclodextrin, and finally used as an exciting host. An energy transfer procedure from these nanocrystals and rhodamine sensors was established via their spectroscopic analysis and emissive decay dynamics comparison. The binding dynamics of our chemosensors for Cys were revealed to have uncomplicated recognition with a stoichiometric ratio of 1 vs. 1. The addition of cysteine increased the emission intensity of the chemosensors. As a consequence, the luminescence off-on effect with sensing selectivity and linear sensing behavior for Cys was demonstrated. Sulfur modification on our chemosensors was shown to be effective in improving their selectivity and photostability.

Lanthanide Doped Near Infrared Active Upconversion Nanophosphors: Fundamental Concepts, Synthesis Strategies, and Technological Applications

Near infrared (NIR) light utilization in a range of current technologies has gained huge significance due to its abundance in nature and nondestructive properties. NIR active lanthanide (Ln) doped upconversion nanomaterials synthesized in controlled shape, size, and surface functionality can be combined with various pertinent materials for extensive applications in diverse fields. Upconversion nanophosphors (UCNP) possess unique abilities, such as deep tissue penetration, enhanced photostability, low toxicity, sharp emission peaks, long anti-Stokes shift, etc., which have bestowed them with prodigious advantages over other conventional luminescent materials. As new generation fluorophores, UCNP have found a wide range of applications in various fields. In this Review, a comprehensive overview of lanthanide doped NIR active UCNP is provided by discussing the fundamental concepts including the different mechanisms proposed for explaining the upconversion processes, followed by the different strategies employed for the synthesis of these materials, and finally the technological applications of UCNP, mainly in the fields of bioimaging, drug delivery, sensing, and photocatalysis by highlighting the recent works in these areas. In addition, a brief note on the applications of UCNP in other fields is also provided along with the summary and future perspectives of these materials.

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.

Characterization and cysteine sensing performance of nanocomposites based on up-conversion excitation host and rhodamine-derived probes

Optical sensing for cysteine (Cys) recognition is an interesting topic due to Cys biological participation. In this paper, two rhodamine-based chemosensors were designed for Cys optical sensing. For chemosensor photostability improvement, up-conversion nanocrystals were synthesized and used as excitation host. These nanocrystals were modified with a phase transfer reagent α-cyclodextrin (α-CD) to improve their compatibility with chemosensors. An efficient energy transfer from these nanocrystals to chemosensors under 980nm radiation was observed and confirmed by spectral match analysis, energy transfer radius calculation and emission decay lifetime comparison. A direct bonding mechanism between Cys and chemosensors with bonding stoichiometry of 1:1 was established by Job's plot experiment. Given the presence of Cys, chemosensor emission was increased, showing emission turn on effect. These two chemosensors showed good selectivity, improved photostability and linear sensing response towards Cys.

Cysteine optical sensing with an up-conversion host and two chemosensors derived from rhodamine: Construction, characterization and performance

This paper focused on two rhodamine chemosensors for cysteine optical sensing. To minimize their photobleaching caused by excitation light, up-conversion NaYF₄:Yb³⁺/Er³⁺ nanocrystals were prepared and used as excitation host. Photophysical measurement on this host and the two chemosensors suggested that chemosensor absorption matched well with host emission. An efficient energy transfer between them was discussed and confirmed by their spectral analysis and emission lifetime comparison. Job's plot suggested that our chemosensors followed a simple recognition mechanism towards cysteine with binding stoichiometry of 1:1. Both chemosensors showed emission "off-on" effect triggered by cysteine and good photostability. Linear working curves with maximum sensitivity of 2.61 were obtained. S substituent was positive to improve selectivity.

Two rhodamine derived chemosensors excited by up-conversion lattice for cysteine detection: Synthesis, characterization and sensing behavior

In this paper, two chemosensors derived from rhodamine were reported for cysteine optical recognition. An up-conversion NaYF4 lattice was applied as excitation host to minimize chemosensor photobleaching. This NaYF4 lattice was firstly modified with α-cyclodextrin, making it water dispersible. It was found that chemosensor absorption matched well with host emission. The energy transfer between this excitation host and our chemosensors was analyzed and confirmed by their spectral analysis and emission decay lifetime comparison. Detailed analysis suggested that the recognition mechanism between our chemosensors and cysteine was a simple one with binding stoichiometry of 1:1. Our chemosensors showed emission "off-on" effect towards cysteine with good photostability. Maximum sensitivity was obtained as 7.90 for our chemosensors with a linear working curve. S substituent was found positive to improve selectivity.

An optical sensing composite for cysteine detection using up-conversion nanoparticles and a rhodamine-derived chemosensor: Construction, characterization, photophysical feature and sensing performance

In this paper, we reported an optical sensing composite for cysteine detection. A chemosensor derived from rhodamine 6G was synthesized and characterized. To minimize its photobleaching, up-conversion nanocrystals β-NaYF4:Yb(3+)/Er(3+) were prepared and modified with α-cyclodextrin, serving as excitation host. Under 980nm laser excitation, emission of these up-conversion nanocrystals overlapped well with the absorption of our chemosensor. Energy transfer between them was analyzed and confirmed by emission decay analysis. Job's analysis suggested that the complexation equilibrium between our chemosensor and cysteine was a simple one with binding stoichiometry of 1:1. A sensing system was constructed with up-conversion nanocrystals (modified with α-cyclodextrin) and this chemosensor. Emission "turn-on" effect was observed only for cysteine but immune to other competing amino acids and thiols, showing a good selectivity.

Highly sensitive and selective detection of mercury ions based on up-conversion FRET from NaYF4:Yb3+/Er3+ nanophosphors to CdTe quantum dots

The detection of Hg²⁺ has attracted considerable attention because of the serious health and environmental problems caused by it.

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

In this work, we reported a simple and effective upconversional nanoprobe for selective detection of hydroxyl radical (OH) and visual evaluation of OH-scavenging activities of drugs for the first time. The upconversion luminescence from NaYF4:Yb,Er nanoparticles was first quenched by carminic acid (CA) through luminescence resonance energy transfer (LRET) mechanism, and then hydroxyl radical-initiated oxidative cleavage of CA can recover the luminescence by inhibition of LRET. The nanosensors exhibited high selectivity towards other reactive oxygen species and many common metal ions with the detection limit down to 0.21 μM, and displayed a relative standard deviation ranging from 1.17% to 3.13%. More attractively, the nanosensors have efficiently avoided the interference of autofluorescence upon near-infrared excitation, and provided a robust platform to study hydroxyl radical scavenging abilities of several common antioxidants such as tannic acid, ascorbic acid and ferulic acid, and visually evaluate antioxidant activities of five traditional Chinese medicines by luminescent images. This newly developed nanosensor could be further exploited for many applications in pharmaceutical, biomedical and environmental engineering areas.