Designing stimuli-responsive upconversion nanoparticles based on a mimetic immunoassay for potential accurate diabetic nephropathy diagnosis.

Diabetic nephropathy (DN) is the most common microvascular complication associated with incurable diabetes. The gold standard diagnostic method for DN is based on the detection of proteinuria but it overlooks cases of non-proteinuria (NP-DN). To address this limitation, urinary sialic acid (SA) has been confirmed as an effective biomarker for various DNs. Herein, we constructed an ultrasensitive non-proteinuria assay platform to accurately diagnose DN within 20 min. This platform utilized the ninhydrin reaction between acidic ninhydrin and urinary sialic acid (SA) as an effective biomarker for various DNs. A compound with a maximum absorption peak at 470 nm was produced in this reaction and contributed to the fluorescence decrease of the blue-emission core-shell upconverting nanoparticles through the inner filter effect (IFE). By integrating the inner filter effect (IFE) with a mimetic immunoassay, the imperceptible color was converted into highly sensitive fluorescence signals. This protocol shows a stable and high sensitivity with a detection limit of 20 nmol L-1 and provides 100% positive prediction for urine samples, demonstrating its potential for clinical diagnosis and long-term monitoring of DN.

Multi-color luminescence and anticounterfeiting application of upconversion nanoparticle.

Multi-color luminescence materials are important in the illumination, solid-state three-dimensional display, information storage, biological labelling and anticounterfeiting fields. Herein, we designed a novel core-shell structure upconversion nanoparticle (UCNP) material (NaYF4) with lanthanide ion doping to achieve multi-color luminescence under a single NIR excitation laser. Different from the typical single-sensitizer materials, the core-shell structure utilizes Nd3+, Yb3+, Tm3+ and Er3+ ions to obtain tuning of the color and brightness. The doping of Nd3+ ions enhances the weak color (red) light source to maintain the light color balance. Benefiting from the color adjustment of the sensitizers and the change of the core-shell coating, bright-white emission and flexible color emission from red to green, cyan and blue can be achieved via the diverse doped rare earth ions in a single UCNP under continuous-wave laser excitation (980 nm). Simultaneously, the emission color of the UCNPs can change with the intensity of the excitation light source and the wavelength. The bright-white emission can be used for lighting displays, and the flexible full-color emission can be applied in the anticounterfeiting and information storage fields.

Quantifying contrast of latent fingerprints developed by fluorescent nanomaterials based on spectral analysis.

Fluorescent nanoparticles (NPs) have been used to develop latent fingerprints with enhanced contrast. However, a method for quantifying the contrast is still lacking, making it impossible to achieve quantitative comparison in the contrast enhancement between different fingerprint developing agents. Here we proposed a new method to quantify the developed contrast using two indexes when fluorescent NPs were used to develop the latent fingerprint. One is the intensity index (I) defined as the ratio between the integrated fluorescence intensities of the signal and background in the fluorescence spectra of the developed fingerprint. Another is the chroma index (C) determined from the color difference between developed fingerprints and their substrates in the chromaticity graph. We defined the developed contrast as the product of the chroma index and the common logarithm of the intensity index (C·lg I), and validated this method using both down- and up-conversion fluorescent NPs and on a variety of different substrates (glass, marble, red paper and money). We showed that the developed contrast quantified by our method effectively reflected the true contrast but the intensity or chroma index alone was not always effective. This work opens up a new avenue to quantifying and enhancing the developed contrast.

Preparation, Energy Transfer Characteristics and Colorimetric Properties of Na2Dy4(WO4)7:Eu³âº Nanophosphors.

Eu³âº-doped Na2Dy4(WO4)7 nanophosphors were synthesized via a co-precipitation method. The crystal structure and morphology of the nanophosphors were characterized by X-ray diffraction analysis and field emission scanning electron microscopy, respectively. For all Eu³âº doping concentrations, spherical particles with an average diameter of about 40 nm and consisting of a pure Na2Dy4(WO4)7 phase were obtained. The excitation and emission properties of the nanophosphors were examined by fluorescence spectroscopy and the energy transfer between Eu³âº and Dy³âº was studied. Furthermore, the influence of the Eu³âº concentration on the color coordinates and luminescence intensity is discussed. The nanophosphors could easily be excited by ultraviolet (UV) and near-UV light corresponding to the f-f transitions of Dy³âº. The color coordinates of the nanophosphors light emission are in the white light region and the Commission Internationale de l'Éclairage (CIE) coordinates of the nanophosphors light emission varied between (0.331, 0.354) and (0.405, 0.368) depending on the Eu³âº doping concentration.