3 research outputs found
Plasmonic Vertically Coupled Complementary Antennas for Dual-Mode Infrared Molecule Sensing
Here we report an
infrared plasmonic nanosensor for label-free,
sensitive, specific, and quantitative identification of nanometer-sized
molecules. The device design is based on vertically coupled complementary
antennas (VCCAs) with densely patterned hot-spots. The elevated metallic
nanobars and complementary nanoslits in the substrate strongly couple
at vertical nanogaps between them, resulting in dual-mode sensing
dependent on the light polarization parallel or perpendicular to the
nanobars. We demonstrate experimentally that a monolayer of octadecanethiol
(ODT) molecules (thickness 2.5 nm) leads to significant antenna resonance
wavelength shift over 136 nm in the parallel mode, corresponding to
7.5 nm for each carbon atom in the molecular chain or 54 nm for each
nanometer in analyte thickness. Additionally, all four characteristic
vibrational fingerprint signals, including the weak CH<sub>3</sub> modes, are clearly delineated experimentally in both sensing modes.
Such a dual-mode sensing with a broad wavelength design range (2.5
to 4.5 μm) is potentially useful for multianalyte detection.
Additionally, we create a mathematical algorithm to design gold nanoparticles
on VCCA sensors in simulation with their morphologies statistically
identical to those in experiments and systematically investigate the
impact of the nanoparticle morphology on the nanosensor performance.
The nanoparticles form dense hot-spots, promote molecular adsorption,
enhance near-field intensity 10<sup>3</sup> to 10<sup>4</sup> times,
and improve ODT refractometric and fingerprint sensitivities. Our
VCCA sensor structure offers a great design flexibility, dual-mode
operation, and high detection sensitivity, making it feasible for
broad applications from biomarker detection to environment monitoring
and energy harvesting
Picomolar-Level Sensing of Cannabidiol by Metal Nanoparticles Functionalized with Chemically Induced Dimerization Binders
Simple and fast detection of small molecules is critical for health and environmental
monitoring.
Methods for chemical detection often use mass spectrometers or enzymes;
the former relies on expensive equipment, and the latter is limited
to those that can act as enzyme substrates. Affinity reagents like
antibodies can target a variety of small-molecule analytes, but the
detection requires the successful design of chemically conjugated
targets or analogs for competitive binding assays. Here, we developed
a generalizable method for the highly sensitive and specific in-solution
detection of small molecules, using cannabidiol (CBD) as an example.
Our sensing platform uses gold nanoparticles (AuNPs) functionalized
with a pair of chemically induced dimerization (CID) nanobody binders
(nanobinders), where CID triggers AuNP aggregation and sedimentation
in the presence of CBD. Despite moderate binding affinities of the
two nanobinders to CBD (equilibrium dissociation constants KD of ∼6 and ∼56 μM), a scheme
consisting of CBD–AuNP preanalytical incubation, centrifugation,
and electronic detection (ICED) was devised to demonstrate a high
sensitivity (limit of detection of ∼100 picomolar) in urine
and saliva, a relatively short sensing time (∼2 h), a large
dynamic range (5 logs), and a sufficiently high specificity to differentiate
CBD from its analog, tetrahydrocannabinol. The high sensing performance
was achieved with the multivalency of AuNP sensing, the ICED scheme
that increases analyte concentrations in a small assay volume, and
a portable electronic detector. This sensing system is readily applicable
for wide molecular diagnostic applications
Novel CO<sub>2</sub> Fluorescence Turn-On Quantification Based on a Dynamic AIE-Active Metal–Organic Framework
Traditional
CO<sub>2</sub> sensing technologies suffer from the disadvantages
of being bulky and cross-sensitive to interferences such as CO and
H<sub>2</sub>O, these issues could be properly tackled by innovating
a novel fluorescence-based sensing technology. Metal–organic
frameworks (MOFs), which have been widely explored as versatile fluorescence
sensors, are still at a standstill for aggregation-induced emission
(AIE), and no example of MOFs showing a dynamic AIE activity has been
reported yet. Herein, we report a novel MOF, which successfully converts
the aggregation-caused quenching of the autologous ligand molecule
to be AIE-active upon framework construction and exhibits bright fluorescence
in a highly viscous environment, resulting in the first example of
MOFs exhibiting a real dynamic AIE activity. Furthermore, a linear
CO<sub>2</sub> fluorescence quantification for mixed gases in the
concentration range of 2.5–100% was thus well-established.
These results herald the understanding and advent of a new generation
in all solid-state fluorescence fields