Abstract: The present invention concerns a luminescent particle comprising a nanoparticle of formula A1-xLnxVO4(1-y)(PO4)y??(I) in which A is selected from yttrium (Y), gadolinium (Gd), lanthanum (La), and mixtures thereof; Ln is selected from europium (Eu), dysprosium (Dy), samarium (Sm), neodymium (Nd), erbium (Er), ytterbium (Yb), and mixtures thereof; 0<x<1; and 0?y<1; characterized in that the nanoparticle on its surface has tetraalkylammonium cations in an amount such that said nanoparticle has a zeta potential, ?, of less than or equal to ?28 mV in an aqueous medium with a pH?5, more particularly with a pH?5.5, and with an ionic conductivity >100 ?S·cm?1. It also concerns a method for preparing such luminescent particles, a colloidal suspension of these particles, and the use thereof as a diagnostic agent, and also a diagnostic kit comprising such luminescent particles.

Abstract: The present invention relates to an in vitro method for detecting and/or quantifying a biological or chemical substance of interest in a liquid sample, by a capillary action test using, as probes, photoluminescent inorganic nanoparticles, of formula A1-xLnxVO4(1-y)(PO4)y (II), in which Ln is selected from europium (Eu), dysprosium (Dy), samarium (Sm), neodymium (Nd), erbium (Er), ytterbium (Yb), thulium (Tm), praseodymium (Pr), holmium (Ho) and mixtures thereof; A is selected from yttrium (Y), gadolinium (Gd), lanthanum (La), lutetium (Lu), and mixtures thereof; 0<x<1; and 0?y<1, said method employing detection of the luminescence, with an emission lifetime shorter than 100 ms, of the nanoparticles, after one-photon absorption, by excitation of the matrix at a wavelength less than or equal to 320 nm. It also relates to a capillary action test device comprising, as probes, the aforementioned nanoparticles, as well as the use of such a method for purposes of in vitro diagnostics.

Abstract: A process for ultrasensitive in vitro detection and/or quantification of a substance of interest in a sample is performed by detecting the luminescence emission by photoluminescent inorganic nanoparticles. The process includes (i) use of photoluminescent particles comprising a photoluminescent inorganic nanoparticle consisting of a crystalline matrix having at least 103 rare-earth ions, and coupled to a targeting agent for the substance to be analyzed, under conditions conducive to their association with the sample substance to be analyzed; (ii) exciting the rare-earth ions of the particles by an illumination device having a power of at least 50 mW and an excitation intensity of at least 1 W/cm2; (iii) detecting the luminescence emission by the particles after single-photon absorption; and (iv) determining the presence and/or concentration of the substance by interpreting said luminescence measurement. This process can be used for in vitro diagnostic purposes and as an in vitro diagnostic kit.

Abstract: The present invention concerns a luminescent particle comprising a nanoparticle of formula A1?xLnxVO4(1?y)(PO4)y ??(I) in which A is selected from yttrium (Y), gadolinium (Gd), lanthanum (La), and mixtures thereof; Ln is selected from europium (Eu), dysprosium (Dy), samarium (Sm), neodymium (Nd), erbium (Er), ytterbium (Yb), and mixtures thereof; 0<x<1; and 0<y<1; characterized in that the nanoparticle on its surface has tetraalkylammonium cations in an amount such that said nanoparticle has a zeta potential, ?, of less than or equal to ?28 mV in an aqueous medium with a pH?5, more particularly with a pH?5.5, and with an ionic conductivity >100 ?S.cm?1. It also concerns a method for preparing such luminescent particles, a colloidal suspension of these particles, and the use thereof as a diagnostic agent, and also a diagnostic kit comprising such luminescent particles.