Ammonium-Induced Synthesis of Highly Fluorescent Hydroxyapatite Nanoparticles with Excellent Aqueous Colloidal Stability for Secure Information Storage

Abstract

In this paper, uniform hydroxyapatite (HA) nanoparticles, with excellent aqueous colloidal stability and high fluorescence, have been successfully synthesized via a citrate-assisted hydrothermal method. The effect of the molar ratio of ammonium phosphate in phosphate (RAMP) and hydrothermal time on the resultant products was characterized in terms of crystalline structure, morphology, colloidal stability, and fluorescence behavior. When the RAMP is 50% and the hydrothermal time is 4 h, the product consists of a pure hexagonal HA phase and a uniform rod-like morphology, with 120- to 150-nm length and approximately 20-nm diameter. The corresponding dispersion is colloidally stable, and transparent for at least one week, and has an intense bright blue emission (centered at 440 nm, 11.6-ns lifetime, and 73.80% quantum efficiency) when excited by 340-nm UV light. Although prolonging the hydrothermal time and increasing the RAMP had no appreciable effect on the aqueous colloidal stability of HA nanoparticles, the fluorescence intensity was enhanced. The cause of HA fluorescence are more biased towards carbon dots (which are mainly polymer clusters and/or molecular fluorophores constituents) trapped in the hydroxyapatite crystal structure. Owing to these properties, a highly fluorescent HA colloidal dispersion could find applications in secure information storage.

Tailoring the structure and self-activated photoluminescence of carbonated amorphous calcium phosphate nanoparticles for bioimaging applications

“…14,63,64 However, it is important to note that these quantum yields are primarily attributed to carbon dots acting as luminescent centers rather than solely originating from the CaP itself. 11,63,65…”

“…Only quantum yields ranging from 22% to 74% have been reported for defect-related luminescent HA. 14,63,64 However, it is important to note that these quantum yields are primarily attributed to carbon dots acting as luminescent centers rather than solely originating from the CaP itself. 11,63,65 We investigated the excitation-dependent PL emission of carbonated ACP NPs in comparison to their as-synthesized counterparts.…”

“…14,63,64 However, it is important to note that these quantum yields are primarily attributed to carbon dots acting as luminescent centers rather than solely originating from the CaP itself. 11,63,65 We investigated the excitation-dependent PL emission of carbonated ACP NPs in comparison to their as-synthesized counterparts. Fig.…”

Carriers for hydrophobic drug molecules: lipid-coated hollow mesoporous silica particles, and the influence of shape and size on encapsulation efficiency

“…The addition of ammonium hydrogen phosphate imparts directional growth, favoring elongation primarily along one axis, and adjusts the pH, influencing the condensation reactions of iron nitrate, and determining the final morphology and aspect ratio of the particles. [57][58][59][60][61] The resulting mixture was then transferred to Teflon tubes and heated at 220 °C for 6 h. Following the reaction, reddish precipitates were obtained by centrifugation at 11 000 rpm for 20 minutes. The collected precipitates were then washed with water and ethanol (4 x) to remove any impurities and dried in an oven kept at 60 °C for further analysis and characterization.…”

“…The addition of ammonium hydrogen phosphate imparts directional growth, favoring elongation primarily along one axis, and adjusts the pH, influencing the condensation reactions of iron nitrate, and determining the final morphology and aspect ratio of the particles. [57][58][59][60][61] The resulting mixture was then transferred to Teflon tubes and heated at 220°C for 6 h.…”