This study presents a novel noninvasive and enzyme-free dual sensor based on porous silicon for the detection of D-glucose through tear fluid analysis. The sensor incorporates NaGdF4:20% Yb3+, 2% Er3+ nanoparticles (YbEr-NPs) immobilized on a porous silicon substrate functionalized with a phenylboronic ester molecule. The YbEr-NPs enable luminescence-based sensing, exploiting the sensitivity of Er3+ ions to the OH vibrational groups present in D-glucose. Electrodes fabricated on a porous silicon substrate allow for voltammetric analysis, providing a second detection method. The voltammetric sensor achieved a limit of detection (LoD) of 20 mg/dL in the range of 20-200 mg/dL, which is suitable for detecting D-glucose concentrations in the tear fluid of diabetic patients. The luminescence-based sensor, utilizing the red-to-green emission ratio of YbEr-NPs, reached a LoD of 140 mg/dL in the range of 10-70 mg/dL, covering the hyperglycemic range. The interaction between the YbEr-NPs and the porous silicon substrate led to the appearance of new emission bands and increased intensity, attributed to surface defects acting as an additional excitation source. The 556 nm emission band showed a strong dependence on the D-glucose concentration, improving the LoD to 110 mg/dL. This provides a novel strategy for D-glucose detection based on the effect of the molecule on the interaction between the UCNPs and the Psi substrate. This triple-sensing approach offers a promising solution for noninvasive glucose monitoring, enabling detection in both the hypoglycemic and hyperglycemic ranges.

Water contamination by heavy metals poses a significant threat to human health and to the environment. Cr3+ is a common contaminant in aqueous media; therefore, innovative sensing technologies for reliable detection are in demand. In this study, we demonstrate that NaGdF4: Yb3+, Er3+ up-converting nanoparticles can be used as ratiometric luminescence probes to detect low concentrations of Cr3+ contaminating ions in water. Excitation in the near-infrared region provides a fluorescence-based detection method with large depth penetration and is autofluorescence-free. Based on this ability, a paper-based sensor was manufactured in which the incorporated up-converting nanoparticles allowed a limit of detection of Cr3+ ion concentrations as low as 2 nM. This represents a new step towards the practical application of rare-earth-doped nanoparticles in environmental monitoring, addressing the critical need for efficient detection methods of contaminating ions in water.

This work reports new soft photothermal materials based on mesomorphic nickel bis(dithiolene) complexes bearing pentakis(dodecyloxy)triphenylene units, in which the triphenylene core and the metal complex are linked through alkyl connectors.

Today, diabetes mellitus is one of the most common diseases that affects the population on a worldwide scale. Patients suffering from this disease are required to control their blood-glucose levels several times a day through invasive methods such as piercing their fingers. Our NaGdF4: 5% Er3+, 3% Nd3+ nanoparticles demonstrate a remarkable ability to detect D-glucose levels by analysing alterations in their red-to-green ratio, since this sensitivity arises from the interaction between the nanoparticles and the OH groups present in the D-glucose molecules, resulting in discernible changes in the emission of the green and red bands. These luminescent sensors were implemented and tested on paper substrates, offering a portable, low-cost and enzyme-free solution for D-glucose detection in aqueous solutions with a limit of detection of 22mg/dL. With this, our study contributes to the development of non-invasive D-glucose sensors, holding promising implications for managing diabetes and improving overall patient well-being with possible future applications in D-glucose sensing through tear fluid.

In this work, a hypoxia-sensitive nanoprobe is developed by coating the surface of upconverting core/shell nanoparticles (NaGdF4: 2%Yb3+, 3%Nd3+, 0.2%Tm3+/NaYF4) with a non-fluorescent azo-dye based on a boron-dipyrromethene functionalized azo compound. Azo-dyes are able to quench fluorescence emissions due to their N 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 N azo bond, which results in the absorption of most visible emissions of the nanoparticles. However, in a biological environment suffering hypoxia, the azo bond is reduced, which allows the recovery of the nanoparticles' upconversion emissions. Thereby a near-infrared excitable sensor with an azo-dye is created and for the first time not only enables excitation via NIR at biocompatible 808 nm but also continuous imaging and tracking of the probe in the infrared due to NIR-emissions enabled by the dopant combination since quenching only occurs in the visible. These multifunctional (imaging and sensing) nanoparticles are characterized, their behaviour in reductive and hypoxic environments is determined and the detection of reducing conditions in a hypoxic environment is demonstrated in cells.

Rare-earth-doped inorganic nanocrystals are an important class of nanoparticles for bioimaging applications due to the facility of providing them with tailored emissions in the visible and near-infrared regions of the electromagnetic spectrum. Recently it has become of interest to engineer the dopant composition of these materials in order to enable multiplexed lifetime imaging for autofluorescence-free in vivo bioimaging. Herein we report a simple approach to obtain different fluorescence lifetimes for the Yb3+emission (2F5/2 → 2F7/2) in Nd3+, Yb3+, Tm3+ co-doped NaGdF4 nanoparticles by only changing their crystal size while keeping their hydrodynamic diameter constant. This allowed straightforward transformation of infrared images in the time domain into lifetime maps. The particles were then deployed as in vivo contrast agents for near-infrared imaging in a mouse demonstrating their multiplexing capability.

Functionalized upconverting nanoparticles (UCNPs) are promising theragnostic nanomaterials for simultaneous therapeutic and diagnostic purposes. We present two types of non-toxic eosin Y (EY) nanoconjugates derived from UCNPs as novel nanophotosensitizers (nano-PS) and deep-tissue bioimaging agents employing light at 800 nm. This excitation wavelength ensures minimum cell damage, since the absorption of water is negligible, and increases tissue penetration, enhancing the specificity of the photodynamic treatment (PDT). These UCNPs are uniquely qualified to fulfil three important roles: as nanocarriers, as energy-transfer materials, and as contrast agents. First, the UCNPs enable the transport of EY across the cell membrane of living HeLa cells that would not be possible otherwise. This cellular internalization facilitates the use of such EY-functionalized UCNPs as nano-PS and allows the generation of reactive oxygen species (ROS) under 800 nm light inside the cell. This becomes possible due to the upconversion and energy transfer processes within the UCNPs, circumventing the excitation of EY by green light, which is incompatible with deep tissue applications. Moreover, the functionalized UCNPs present deep tissue NIR-II fluorescence under 808 nm excitation, thus demonstrating their potential as bioimaging agents in the NIR-II biological window.

The development of selective and controlled photo-thermal therapies requires luminescent nanoparticles capable of simultaneous heating and contactless thermal sensing. Until now, thermal therapies have suffered from a lack of control over the absolute temperature of the treated tissue because the nanothermometers used for thermal feedback, based on a spectral analysis of emitted radiation, were affected by the inhomogeneous extinction of the tissues. This work shows how this deficiency can be overcome by using core-shell-shell nanostructures doped with lanthanide ions (Nd3+ and Yb3+). Thermal reading was achieved from the analysis of the Yb3+ luminescence lifetime whereas simultaneous heating was achieved thanks to the non-radiative deexcitations of Nd3+ ions. Simple proof-of-concept experiments show the great potential of these lanthanide-doped nanostructures for the development of in vivo photo-thermal treatments with absolute and reliable thermal feedback.

Persistent phosphorescence nanoparticles emitting in the red and near-infrared spectral regions are strongly demanded as contrast nanoprobes for autofluorescence free bioimaging and biosensing. In this work, we have developed Sr4Al14O25:Eu2+, Cr3+, Nd3+ nanopowders that produce persistent red phosphorescence peaking at 694 nm generated by Cr3+ ions. This emission displays temperature sensitivity in the physiological temperature range (20–60 °C), which makes these nanoparticles potentially useful as fluorescence (contactless) nanothermometers operating without requiring optical excitation. Nd3+ ions, which act as shallow electron traps for the red Cr3+ persistent emission, also display infrared emission bands, extending the fluorescence imaging capability to the second biological window. This unique combination of properties makes these nanoparticles multifunctional luminescent probes with great potential applications in nanomedicine.