Electrostatically Assembled Fluorescent Thin Films of Rare-Earth-Doped Lanthanum Phosphate Nanoparticles

Abstract

We report on the formation of nanostructured, ultrathin films of a new class of fluorescent nanoparticles (NPs) within the same size range as quantum dots, but with a different kind of fluorescence, by using the layer-by-layer (LbL) technique. The fluorescence of these rare-earth-doped lanthanum phosphate (LaPO4) NPs is due to the bulk properties of the material and is therefore independent of their size. Additionally, different colors are available due to variation of the dopants used in their synthesis (e.g., Ce, Tb, Eu, and Dy). These NPs were electrostatically assembled to form thin films on planar quartz supports as well as on polystyrene (PS) microspheres with the aid of oppositely charged polyelectrolyte interlayers. Regular growth of the multilayers was observed on both quartz and PS substrates, providing control over the composition and, in turn, the fluorescence intensity of the planar films and composite spheres. The resulting films exhibit the same UV and fluorescence characteristics as the corresponding aqueous NP dispersions. NPs with different fluorescence characteristics (i.e., colors) retain their individual optical properties when premixed and assembled into thin films and can be detected individually using only a single excitation wavelength. Biofunctionalization of LaPO4 NP-tagged PS spheres and of the individual LaPO4 NPs is expected to yield versatile labels that could be exploited in various biological applications.

Ionoluminescence in the Helium Ion Microscope

“…These are bulk properties and so are independent of the size of the nanocrystals. They are known to exhibit quantum yields up to 61% (Riwotzki et al, 2001), are highly stable and have a low toxicity, making them promising candidates for biotagging applications (Schuetz & Caruso, 2002). Two samples of rare earth doped LaPO 4 nanocrystals dispersed in an aqueous solution (REN-XR/REN-XG, Nanogate, Inc.) were investigated:…”

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

“…They have been widely used in phosphors for fluorescent lighting [1] and [2], semiconductors [3] and [4], or time-resolved fluorescence labels for biological detection [5]. Lanthanum, the lightest element among the lanthanides, has been extensively examined as oxide, hydroxide, phosphate, or oxychloride for optical [6] and [7], solid electrolyte [8], catalytic [9], [10] and [11], and sorbent properties [12]. Especially, lanthanum hydroxide La(OH) 3 has been used as an intermediate step in the synthesis of the oxides or sulfides through dehydration or sulfuration, because that approach is straightforward [13].…”

Controlled synthesis of Eu3+-doped La2O2S nanophosphors by refluxing method

“…In recent years, rare-earth-doped nanosized phosphors have attracted much attention due to their potential application in high resolution displaying, electroluminescent devices, optical amplifiers, and biological label and unique physical properties distinctive to the corresponding bulk [1][2][3][4][5]. Among many phosphors based on rare earth compound host materials, much work has been focused on rare-earth-doped oxide, phosphate, orthovanadate, borate and fluoride [6][7][8][9][10].…”