Programmable Photoluminescence via Intrinsic and DNA–Fluorophore Association in a Mixed Cluster Heterometallic MOF

A rapid and facile
design strategy to create a highly complex optical
tag with programmable, multimodal photoluminescent properties is described.
This was achieved via intrinsic and DNA–fluorophore hidden
signatures. As a first covert feature of the tag, an intricate novel
heterometallic near-infrared (NIR)-emitting mesoporous metal–organic
framework (MOF) was designed and synthesized. The material is constructed
from two chemically distinct, homometallic hexanuclear clusters based
on Nd and Yb. Uniquely, the Nd-based cluster is observed here for
the first time in a MOF and consists of two staggered Nd μ3-oxo trimers. To generate controlled, multimodal, and tailorable
emission with difficult to counterfeit features, the NIR-emissive
MOF was post-synthetically modified via a fluorescent DNA oligo labeling
design strategy. The surface attachment of several distinct fluorophores,
including the simultaneous attachment of up to three distinct fluorescently
labeled oligos was achieved, with excitation and emission properties
across the visible spectrum (480–800 nm). The DNA inclusion
as a secondary covert element in the tag was demonstrated via the
detection of SYBR Gold dye association. Importantly, the approach
implemented here serves as a rapid and tailorable way to encrypt distinct
information in a facile and modular fashion and provides an innovative
technology in the quest toward complex optical tags.