Tuning the upconversion light emission by bandgap engineering in bismuth oxide-based upconverting nanoparticles

Abstract

In the field of novel applications involving upconverting processes, the determination of new strategies for realizing emission-tunable nanomaterials is a challenge. In this work the design of Y and Er codoped bismuth oxide-based upconverting nanoparticles is presented, evidencing that the active role of the matrix allows for the emission selectivity with chromaticity control. The bandgap of the bismuth oxide-based host can be manipulated in the range of 0.65 eV, consequently leading to upconversion emission color tunability from red to yellow-greenish. The resulting fine control of the nanoparticle chromaticity through accurate host bandgap engineering reveals a novel concept for the development of a new generation of upconverting nanophosphors.

Effective Ratiometric Luminescent Thermal Sensor by Cr3+‐Doped Mullite Bi2Al4O9 with Robust and Reliable Performances

“…In the field of Cr 3+ spectroscopy, a first important information about the crystal field experienced by Cr 3+ can be obtained by the sample's color; a red color (e.g., Al 2 O 3 :Cr 3+ , ruby) is typically correlated to “strong” crystal field while a sample's green color (e.g., Be 3 Al 2 Si 6 O 18 :Cr 3+ , emerald) is associated to “weak” crystal field. Bismuth‐based compounds are characterized by the narrow bandgaps [ 11 ] and Bi 2 Al 4 O 9 results in a yellow material, making this first assignment not always obvious. However, the green color of the sample suggests a weak/intermediate crystal field as expected from the design based on the M–O bond length.…”

“…The conduction band bottom is composed predominantly by Bi orbitals with a minor contribution from the Al orbitals while the valence band (VB) top mainly results from the 2p‐O orbitals and an admixture with the 6s and 6p orbitals of Bi, a fingerprint of the stereoactive lone pair electrons of Bi 3+ . [ 11e,12 ] Figure S1 in the Supporting Information shows the calculated electronic band structure of Bi 2 Al 4 O 9 demonstrating the direct bandgap nature of the host. The P‐DOS of Bi is in agreement with the description of the yellow‐green photoluminescence (PL) emission of Bi 2 Al 4 O 9 in terms of the typical 3 P 1 → 1 S 0 transition of Bi 3+[ 13 ] as reported by Brixner [ 14 ] and Blasse and Ho.…”

A Hollow NaGdF4/AFn Nanosystem Based on “Relay Race” Release for Therapy

“…At time points established in advance (5 and 10 min, and 0. 5,1,2,4,8,12,24,36, and 48 h), buffer solution was removed (1 mL) and fresh buffer was added back to the system. and 48 h), buffer solution was removed (1 mL) and fresh buffer was added back to the system.…”

“…We immersed the DOX-loaded AFn samples into 40 mL PBS (pH 7.4 or pH 5.0) at 37 8C. At time points established in advance (5 and 10 min, and 0.5, 1,2,4,8,12,24,36, and 48 h), buffer solution was removed (1 mL) and fresh buffer was added back to the system. DOX release was quantified by UV/Vis spectrophotometry at l 480 nm.…”

“…By multiple absorption or energy transfer, lanthanide (Ln)-doped upconversion (UC) luminescent nanomaterials are able to convert low-energye xcitation to higher-energy emission and are thus used for optical imaging. [8][9][10] Because hollow NaGdF 4 nanoparticles (NPs) possess both hollow structures and UC luminescence, they hold promise as multifunctional materials for drug delivery and imaging.…”