Fluorescence enhancement of europium complexes by core-shell Ag@SiO₂ nanoparticles

MnO2 nanoparticles decorated with Ag/Au nanotags for label-based SERS determination of cellular glutathione

A novel stimulus-responsive surface-enhanced Raman scattering (SERS) nanoprobe has been developed for sensitive glutathione (GSH) detection based on manganese dioxide (MnO₂) core and silver/gold nanoparticles (Ag/Au NPs). The MnO₂ core is not only capable to act as a scaffold to amplify the SERS signal via producing "hot spots", but also can be degraded in the presence of the target and thus greatly enhance the nanoprobe sensitivity for sensing of GSH. This approach enables a wide linear range from 1 to 100 µM with a 2.95 µM (3σ/m) detection limit. Moreover, the developed SERS nanoprobe represents great possibility in both sensitive detection of intracellular GSH and even can monitor the change of intracellular GSH level when the stimulant occurs. This sensing system not merely offers a novel strategy for sensitive sensing of GSH, but also provides a new avenue for other biomolecules detection.

Enhance photoluminescence properties of Ca-Eu:Y2O3@SiO2 core-shell nanomaterial for the advanced forensic and LEDs applications

The divalent (Ca²⁺)-doped Eu:Y₂O₃@SiO₂ core-shell luminescent nanophosphors have been synthesised by a cost-effective combustion technique. Various characterizations were carried out to confirm the successful formation of the core-shell structure. The TEM micrograph reveals the thickness of the SiO₂ coating over Ca-Eu:Y₂O₃ as ∼25 nm. The optimal value of silica coating over the phosphor has been obtained as 10 vol%(TEOS) of SiO₂, with this value increasing fluorescence intensity by 34 %. Phosphor exhibits CIE coordinates as x = 0.425, y = 0.569 and a CCT value as ∼2115 K with color purity and the respective CRI of 80 % and 98 %, respectively, which make the core-shell nanophosphor suitable for warm LEDs, and other optoelectronic applications. Further, the core-shell nanophosphor has been investigated for the visualisation of latent finger prints and as security ink. The findings point towards the prospective future application of nanophosphor materials for anti-counterfeiting purposes and latent finger prints for forensic purposes.

Colorimetric/SERS dual-channel nanoprobe for reactive oxygen species monitoring in elucidating the mechanism of chemotherapeutic drugs action on cancer cells

Reactive oxygen species (ROS) are involved in drug-induced cytotoxicity by regulating cell signaling, inducing oxidative stress, and damaging the DNA and proteins. Examining ROS production in cells under the stimulation of chemotherapeutic drugs is of great importance for understanding the ROS roles and identifying the mechanism of drug-induced cytotoxicity. Here, a silver/gold (Ag/Au) nanoshell-based colorimetric and surface-enhanced Raman spectroscopy (SERS) dual-response nanoprobe was proposed for ROS sensing on the basis of Ag etching. In this study, as a kind of ROS, hydrogen peroxide (H₂O₂) was detected by the prepared nanoprobe. The linear ranges of 0.5-100 μM with a limit of detection (LOD) of 0.343 μM for the colorimetric determination and 1-50 μM with LOD of 0.294 μM for SERS determination were achieved. The detection of cellular ROS concentration after stimulation by cisplatin, paclitaxel, doxorubicin, and 5-fluorouracil was validated by the nanoprobe. The nanoprobe could also be used to detect the signal pathway of ROS production by cisplatin stimulation. This study provided a simple and novel dual-response nanoplatform for detecting and monitoring ROS in cells, which holds great potential for elucidating the mechanism of occurrence and treatment of ROS-involved diseases.

Tuning the luminescence properties of lanthanide coordination polymers with Ag@SiO2 nanoparticles

A series of core-shell Ag@SiO₂ nanoparticles with different core diameters and shell thicknesses have been prepared by a modified-Stöber method. They provide a facile route to tune the luminescence intensities, lifetimes and quantum efficiencies of lanthanide coordination polymers in the solid powder state. The coordination polymers [Tb₂(p-PTA)₃(H₂O)₂]_n, [Tb₂(o-PTA)₃(H₂O)₂]_n, [Eu₂(p-PTA)₃(H₂O)₂]_n and [Eu₂(o-PTA)₃(H₂O)₂]_n (PTA = phthalic acid) are synthesized and subsequently bound to the surface of Ag@SiO₂ nanoparticles. The luminescence intensities of the lanthanide complexes are enhanced as high as 10.8 times. The enhancement times depend on the core diameter and shell thickness of the Ag@SiO₂ nanoparticles. Importantly, by simply controlling the ratios between the complexes and the nanoparticles, the luminescence intensities, lifetimes and quantum efficiencies of the lanthanide complexes can be tuned in wide ranges. Typically, the luminescence lifetime of [Eu₂(p-PTA)₃(H₂O)₂]_n powder increases from 451 μs to 783 μs when 300 μL Ag@SiO₂ solution is added. Meanwhile, the luminescence quantum efficiency of the complex increases from 32.1% to 40.9%. The change of the luminescence properties of the lanthanide coordination polymers can be ascribed to the surface plasmon resonance effect of the Ag@SiO₂ nanoparticles as well as the decrease of the nonradiative decay rates of the complexes.

Lanthanide Fluorobenzoates as Bio-Probes: a Quest for the Optimal Ligand Fluorination Degree

The thorough study of fluorinated benzoates of lanthanides (Eu, Tb, Nd, Er, Yb, Gd, La, Lu) is reported. Their composition in single crystal and powder state revealed two predominant structural motifs. An in-depth luminescence study has been performed on the reported fluorobenzoates, showing, that terbium and europium complexes in solid state possess high luminescence intensity with the quantum yield of up to 69 %. High solubility in most organic solvents, as well as in water, combined with the high luminescence intensity in water solution and non-toxicity allowed the testing of europium complexes as bioprobes in cellulo. Among all tested fluorobenzoates, europium 2-fluorobenzoate dihydrate combined the best luminescent properties, thermodynamic stability, aqueous solubility, and non-toxicity, and was shown to be a viable bio-marker.

Study on the interaction of berberine with nucleic acids in the presence of silver nanoparticles, and the fluorometric determination of nucleic acids

The partial intercalation binding between BER and ctDNA, and the anti-photobleaching ability of BER were both strengthened by AgNPs. A metal enhanced fluorescence-based sensitive method for the determination of nucleic acids was obtained.