Lanthanoid-Doped Phosphate/Vanadate Mixed Hollow Particles as Ratiometric Luminescent Sensors

Modification of Carbon Dots for Metal‐Ions Detection

It is very appealing to develop cheap, highly sensitive and efficient metal ion fluorescence sensors as traditional instrument methods are inherently costly and time‐consuming. Carbon dots (CDs) are widely used for sensing metal ions, attributing to their merits of good biocompatibility, low toxicity, easy surface modification and excellent photostability. This article reviewed the research progress of CDs as metal ion sensors in recent years, and studied their modification methods and detection performances. Finally, the challenges and opportunities of CDs as metal ion sensors were also analyzed. This article is expected to provide inspiration and help for researchers focusing on CDs as metal ion sensors.

Synthesis and Structural Characterization of an Amorphous and Photoluminescent Mixed Eu/Zr Coordination Compound, a Potential Marker for Gunshot Residues

Hydrogels based on mixed zirconium/europium ions and benzene tricarboxylic acid were synthesized by hydrothermal reaction. A solid glass-like material is formed upon drying, showing strong reddish luminescence. The system was characterized by solid-state nuclear magnetic resonance, thermal analyses, and infrared spectroscopy. The results reveal the amorphous character of the structure and the presence of at least four types of binding modes between the metal oxide clusters and benzene tricarboxylic acid. On the other hand, thermogravimetric analysis (TGA) showed high thermal stability, with the material decomposing at temperatures higher than 500 °C. The combination of intense Eu3+ luminescence with large thermal stability makes this material a strong candidate for application as a luminescent red marker for gunshot residue (GSR). As proof of concept, we show the feasibility of this application by performing shooting tests using our compound as a GSR marker. After the shots, the residual luminescent particles could be visualized in the triggered cartridge, inner the muzzle of the firearm, and a lower amount on the hands of the shooter, using a UV lamp (λ = 254 nm). Remarkably, our results also show that the Eu3+ emission for the GSR is very similar to that observed for the original solid material. These characteristics are of huge importance since they provide a chance to use smaller amounts of the marker in the ammunition, lowering the costs of potential industrial manufacturing processes.

Highly Versatile Upconverting Oxyfluoride-Based Nanophosphor Films

Fluoride-based compounds doped with rare-earth cations are the preferred choice of materials to achieve efficient upconversion, of interest for a plethora of applications ranging from bioimaging to energy harvesting. Herein, we demonstrate a simple route to fabricate bright upconverting films that are transparent, self-standing, flexible, and emit different colors. Starting from the solvothermal synthesis of uniform and colloidally stable yttrium fluoride nanoparticles doped with Yb3+ and Er3+, Ho3+, or Tm3+, we find the experimental conditions to process the nanophosphors as optical quality films of controlled thickness between few hundreds of nanometers and several micrometers. A thorough analysis of both structural and photophysical properties of films annealed at different temperatures reveals a tradeoff between the oxidation of the matrix, which transitions through an oxyfluoride crystal phase, and the efficiency of the upconversion photoluminescence process. It represents a significant step forward in the understanding of the fundamental properties of upconverting materials and can be leveraged for the optimization of upconversion systems in general. We prove bright multicolor upconversion photoluminescence in oxyfluoride-based phosphor transparent films upon excitation with a 980 nm laser for both rigid and flexible versions of the layers, being possible to use the latter to coat surfaces of arbitrary shape. Our results pave the way toward the development of upconverting coatings that can be conveniently integrated in applications that demand a large degree of versatility.

Tuning morphology, surface, and nanocrystallinity of rare earth vanadates by one-pot colloidal conversion of hydroxycarbonates

We show that particle size, morphology, nanocrystallinity, surface area, and defect density of (Y,Eu)VO₄ structures can be tuned by one-pot colloidal conversion of rare earth hydroxycarbonates in water/ethylene glycol (EG) suspensions. Using small angle X-ray scattering, transmission electron microscopy and dynamic light scattering, we show how volume fractions of EG direct the amorphous to crystalline conversion at 1 atm/95 °C by controlling size and aggregation of hydroxycarbonate precursors. A template effect due to a Kirkendall-type conversion occurs for low EG contents, yielding solids with high densities of oxygen defects, as demonstrated by O₂ uptakes in thermogravimetry and X-ray photoelectron spectroscopy profiles. Starting from small and aggregated hydroxycarbonates high-porosity (Y,Eu)VO₄ nanoparticles were produced with expanded unit cells and short-range (<100 Å) crystalline ordering. We explored the effects of synthesis on the textural, microstructure, and defects of (Y,Eu)VO₄ solids, which were further correlated to the spectroscopic profiles of Eu³⁺-activated samples. We show that the ratios between Eu^{3+ 5}D₀ internal quantum yields and particle diameters can be directly correlated to the particle surface areas, opening new perspectives for theoretical detailing of f-f luminescence in YVO₄ solids, and enabling accurate tuning of structure and applicability of colloidal vanadate nanoparticles for sensing and catalysis applications.

HDEHP assisted solvothermal synthesis of monodispersed REPO4 (RE = La–Lu, Y) nanocrystals and their photoluminescence properties

In this paper, a novel method is reported for the preparation of spherical REPO₄ particles.

Lanthanide-Doped Photoluminescence Hollow Structures: Recent Advances and Applications

Lanthanide-doped nanomaterials have attracted significant attention for their preeminent properties and widespread applications. Due to the unique characteristic, the lanthanide-doped photoluminescence materials with hollow structures may provide advantages including enhanced light harvesting, intensified electric field density, improved luminescent property, and larger drug loading capacity. Herein, the synthesis, properties, and applications of lanthanide-doped photoluminescence hollow structures (LPHSs) are comprehensively reviewed. First, different strategies for the engineered synthesis of LPHSs are described in detail, which contain hard, soft, self-templating methods and other techniques. Thereafter, the relationship between their structure features and photoluminescence properties is discussed. Then, niche applications including biomedicines, bioimaging, therapy, and energy storage/conversion are focused on and superiorities of LPHSs for these applications are particularly highlighted. Finally, keen insights into the challenges and personal prospects for the future development of the LPHSs are provided.

Hollow particles templated from Pickering emulsion with high thermal stability and solvent resistance: Young investigator perspective

HYPOTHESIS

Hollow particles have been used in a variety of applications and many methods have been developed. Hollow particles templated from Pickering emulsions due to nanoparticle adsorption at the oil-water interface usually suffer from the collapsed morphologies and low thermal and solvent stability and enhancement of the shell can significantly improve the hollow particle performance.

EXPERIMENTS

This paper reports hollow particles templated from Pickering emulsion droplets in combination with UV photopolymerization. The Pickering emulsions were stabilized by functional silica nanoparticles at the O/W interface and the oil phase contains photosensitive reactants, initiator, catalyst and volatile solvents. The effects of nanoparticles concentration, O/W volume ratio, pH, dispersion speed and time on the stabilization of Pickering emulsion were firstly carried out and the properties of hollow particles formed by traditional interfacial crosslinking and UV photopolymerization were systematically investigated.

FINDINGS

Compared with previous interfacial crosslinking method, the UV photopolymerization method gives much more robust shells and we show in the paper that the hollow particles have much higher solvent resistance and thermal stability. The enhancement of thermal stability and solvent resistance of the hollow particle could extend its applications to more harsh fields such as self-healing coatings used in deep sea conditions.

A novel electrochemiluminescent emitter of europium hydroxide nanorods and its application in bioanalysis

The high electrochemiluminescence intensity from europium hydroxide nanorods was reported for sensitive detection of thrombin.

Design and synthesis of a vanadate-based ratiometric fluorescent probe for sequential recognition of Cu2+ ions and biothiols

YVO₄:Eu³⁺@CDs core–shell nanomaterial was synthesized through a simple self-assembly of carbon dots (CDs) with YVO₄:Eu³⁺, since the high affinity of oxygen-containing groups such as –COOH or –OH of CDs to the metal ions on the surface of YVO₄:Eu³⁺.

Fast and Selective Detection of Cr(III) in Environmental Water Samples Using Phosphovanadate Y(V0.2P0.8O4):Eu3+ Fluorescence Nanorods

Phosphovanadate Y(V_0.2P_0.8O₄):Eu³⁺ nanorods have been created via a simple hydrothermal method and used for the highly sensitive and selective fluorescence detection of Cr³⁺ over other common heavy metal ions within a 10 min period. It was found that the fluorescence intensity of Y(V_0.2P_0.8O₄):Eu³⁺ linearly decreases with Cr³⁺ concentrations ranging from 1 × 10^-9 to 1.2 × 10^-6 M. The sensing mechanism for Cr³⁺ is ascribed to the aggregation of Y(V_0.2P_0.8O₄):Eu³⁺ nanorods triggered by Cr³⁺ ions owing to the high affinity of phosphate groups to metal ions. The excellent chemical stability, photostability over a wide pH range of 3-12, and high salt-tolerance performance with ionic strength from 1× 10^-3 to 12 M of Y(V_0.2P_0.8O₄):Eu³⁺ allow these nanorods to successfully overcome the photobleaching and pH-dependent fluorescence property of traditional organic fluorescence probes. These characteristics ensure their applicability to environmental monitoring of Cr³⁺. The sensitive determination of Cr³⁺ in different environmental water samples demonstrated the potential application of Y(V_0.2P_0.8O₄):Eu³⁺ as a practical environmental probe. With the help of a UV lamp (254 nm), the visual Cr³⁺ values for dynamic monitoring in industrial wastewater further verified that this method can even exhibit on-site visible features in daytime and night easily. This allows for the direct monitoring of environmental Cr³⁺.

Facile synthesis of highly monodisperse EuSe nanocubes with size-dependent optical/magnetic properties and their electrochemiluminescence performance

We reported a facile and robust method for the synthesis of highly monodisperse EuSe nanocubes (EuSe NCs) with controllable edge lengths in the range of 8-70 nm. The EuSe NCs were formed through the aggregation of EuSe small particles (cores) and then their surface reconstruction under the influence of 1-dodecanethiol (DDT) that acted as a capping surfactant. DDT was not only found to be critical to the nucleation temperature of preparing EuSe NCs, but also played a decisive role in the formation of structurally well-defined nanocubes. The results indicated that the remarkable monodispersity and high shape consistency of EuSe NCs were highly controlled by the change in the DDT concentration. Furthermore, the size-dependent optical/magnetic properties based on the quantum size effect and the influence of edge lengths of EuSe NCs were also investigated and discussed. More importantly, the electrochemiluminescence (ECL) performance of EuSe NCs was first reported. This will make possible more biomedical applications in future.

An electrospun flexible Janus nanoribbon array endowed with simultaneously tuned trifunctionality of electrically conductive anisotropy, photoluminescence and magnetism

A flexible Janus nanoribbon array endowed with simultaneously tuned trifunctionality of electrically conductive anisotropy, photoluminescence, and magnetism was fabricated by electrospinning.