Core–Shell Lanthanide-Doped Nanoparticles@Eu-MOF Nanocomposites for Anticounterfeiting Applications

Abstract

Heterogeneous nanocomposites constructed by lanthanide-doped nanoparticles and metal–organic frameworks (MOFs) have broad application prospects in therapy, catalysis, optical encoding, etc. However, the assembly of MOFs normally acquires delicate premodification of the surface of the nanoparticles. Herein, we demonstrate a simplified growth strategy of europium/1,3-benzenedicarboxylic acid (1,3-BDC) MOF on NaYF4:Ce/Tb@NaYF4 nanoparticles through a one-step reaction. Carboxylic acid groups are grafted on the surface of the nanoparticles via the ligand-exchange process between oleic acid and 1,3-BDC in the precursors of MOFs, which become growth sites for Eu-MOF under the reaction condition. An acid–base stimuli-responsive ligand N-(2-pyridinyl)­benzoylacetamide (HPBA) is coordinated with Eu3+ in the Eu-MOF, thereafter resulting in NaYF4:Ce/Tb@NaYF4@Eu-MOF@HPBA nanocomposites. The luminescence lifetime of Tb3+ could be controlled by the NaYF4 inert layer. After exposure to NH3/HAc vapor, the decay curve of Eu3+ centered at 615 nm has a corresponding change. Thus, the luminescence lifetime of Tb3+ and Eu3+ can be effectively tuned. This work sheds light on the synthesis of nanoparticle@MOF hybrid structures and time-resolved anticounterfeiting applications.

Review of Mn-Doped Semiconductor Nanocrystals for Time-Resolved Luminescence Biosensing/Imaging

“…Lanthanide-doped polymer particles, silica nanoparticles, and fluoride nanoparticles with long luminescence lifetimes are also in development. − However, they also need high-energy UV light for excitation. Specifically, for lanthanide-doped fluoride nanoparticles, although they can be excited by near-infrared (NIR) light through upconversion for bioapplications, NIR excitation of these particles still requires high-power lasers and costly laser drivers. , These fluoride nanoparticles also suffer from low brightness or low QYs at 0.1–5%, which necessitates the need for more sensitive but expensive CCD cameras. , …”

Orthogonal luminescence lifetime encoding by intermetallic energy transfer in heterometallic rare-earth MOFs

“…In agreement with this premise, several recently published works have described potential options for secure encoding 1 , 6 – 9 , drawn from many classes of materials, including carbon dots 2 , 10 , metallic nanoparticles 11 , 12 , and perovskites 3 . However, existing materials suffer from critical drawbacks: (i) monochromatic and/or broad emission bands, unsuited for multi-tiered screening 3 , 13 ; (ii) complex synthesis methods, which are time-consuming and cost-ineffective 11 , 14 ; and (iii) highly specialized interrogation equipment, which restricts real-life implementation 2 , 15 .…”

“…(ii) complex synthesis methods, which are time-consuming and costineffective 11,14 ; and (iii) highly specialized interrogation equipment, which restricts real-life implementation 2,15 .…”

Photo-functionalized metal–organic frameworks for anti-counterfeiting applications

“…26,27 Effective combinations of fluorescent sources have been used to construct PMOFs, which have been universally applied to fluorescence regulation, chemical sensing and optical anticounterfeiting. 28 An ideal PMOF-based optical anticounterfeiting material should have the following characteristics: (1) a combination of covert tags that simultaneously emit adjustable optical properties under UV light; 29,30 (2) different fluorescence combinations allow orthogonal information confirmation of the photo-response signal; 31 (3) a tunable fluorescence lifetime feature helps to encode the tag as an additional encryption difficulty. 32,33 PMOFs, as optical anti-counterfeiting materials, have more advantages than other types of fluorescent materials.…”