Ochratoxin A (OTA), a toxic mycotoxin, poses severe risks to environment and human health. Herein, we develop a ratiometric surface-enhanced Raman scattering (SERS) aptasensor based on internal standard (IS) methods for the sensitive and reproducible quantitative detection of OTA. Au−Ag Janus nanoparticles (NPs) are successfully synthesized under the guidance of 2-mercaptobenzoimidazole-5-carboxylic acid (MBIA), which possesses intrinsic Raman signals, thus no additional modification with a Raman reporter on NPs is required. In addition, Au−Ag Janus NPs exhibit amplified and stable SERS activity. MXenes nanosheets generate a unique and stable Raman signal, making them an ideal IS for quantitative Raman analysis. In principle, Au−Ag Janus NPs are assembled with MXenes nanosheets depending on hydrogen bond and the chelation interaction between MXenes nanosheets and OTA aptamers. In the presence of OTA, Au−Ag Janus NPs are dissociated from MXenes nanosheets due to the formation of aptamer/OTA complex, leading to the attenuation of Raman signal of Au−Ag Janus NPs, and meanwhile, the signal of MXenes nanosheets remain constant. Quantitatively, upon correction by the IS Raman signals, sensitive and quantitative detection can be achieved with the limit of detection (LOD) of 1.28 pM for OTA. Our results suggest that this ratiometric SERS aptasensor is a powerful tool which shows great promise for applications in complex systems.
Establishing a simple and accurate assay for detecting Microcystin-LR (MC-LR) is of significant important for the environment and human health. Herein, we develop a ratiometric surface-enhanced Raman scattering (SERS) aptasensor based on internal standard (IS) methods for the sensitive and reproducible quantitative detection of MC-LR. Gap-tethered SERS-active Au@AgAu nanoparticles (NPs) are successfully prepared and the gap sizes are adjustable by simply adjusting the acidity. Gap-tethered Au@AgAu NPs exhibit gaptunable amplified SERS activity and are served as SERS tags. The graphene oxide (GO)/Fe 3 O 4 NPs demonstrate a unique and stable Raman band from the graphitic component, making them an ideal IS for quantitative Raman analysis. In principle, Au@gap@AgAu NPs are assembled with GO/Fe 3 O 4 NPs depending on the π−π stacking interaction between GO and MC-LR aptamers. In the presence of MC-LR, Au@gap@AgAu NPs are dissociated from GO/Fe 3 O 4 NPs due to the affinity of aptamer, leading to the changes of Raman intensity of SERS tags. Quantitatively, upon correction by the IS Raman signals, the limit of detection (LOD) is as low as 9.82 pM for MC-LR. The developed protocol provides a simple and rapid approach for the sensitive and quantitative detection of MC-LR and shows great promise for applications in complex systems.
A simple magnetic
electrochemical aptasensor was established for
the detection of prostatic specific antigen (PSA). Ag/CdO nanoparticles
(NPs) were fabricated and exhibited strong electroreduction peaks
at −1.07 V, attributing to the electron transfer from Cd2+ to Cd0 and the superior electron transportation
of Ag. Aptamer-modified Ag/CdO NPs were assembled on the surface of
superparamagnetic Fe3O4/graphene oxide nanosheets
(GO/Fe3O4 NSs) through the hydrophobic and π–π
stacking interaction of aptamers and GO NSs. These assemblies possessed
superior electroactive properties, efficient electron transfer, and
superparamagnetic response and could serve as sensing units for PSA
detection with the aid of a magnetic electrode. With increasing concentrations
of PSA, the high affinity of aptamers to PSA enabled the dissociation
of Ag/CdO NPs from GO/Fe3O4 NSs, decreasing
the intensity of electroreduction peaks. The Ag/CdO NP-engineered
magnetic electrochemical aptasensor achieved sensitive and accurate
detection of PSA in the range of 50 pg/mL to 50 ng/mL. The limit of
detection (LOD) was as low as 28 pg/mL. This developed protocol can
be extended to a large set of strong electroactive labels for reliable
tumor biomarker detection with high sensitivity and specificity.
A novel
ingenious and ultrasensitive chiral electrochemical transducer
is proposed for tryptophan (Trp) isomer detection by using electroactive
Au@Ag NPs as electrochemical tags. Moreover, the large binding constant
of d-Trp on NPs and strong interaction between d-Trp and Cu2+ cause electroactive Au@Ag NP to assemble
on the electrode, generating strong differential pulse voltammetry
(DPV) signals from the oxidation of Ag0 to Ag+. In sharp contrast to d-Trp, l-Trp leads to the
assembly of Au@Ag NP oligomers on the electrode, resulting in a weak
DPV signal. The distinct DPV responses enable the developed electrochemical
chiral transducer for the sensitive and accurate quantification of d-/l-Trp. The limit of detection (LOD) is 1.21 pM for d-Trp. This established electrochemical chiral sensor also achieves
the specific determination of enantiomeric excess. In comparison to
other reported approaches, this proposed electrochemical chiral sensor
excels by its sensitivity, simplicity, and good availability of electroactive
Au@Ag NP assemblies. Target-induced colorimetric assays can be converted
into electrochemical assays for the dual signal amplification in the
field of ultrasensitive enantioselective chiral discrimination.
The
co-decomposition of non-noble metals into Ru nanoparticles
(NPs) would provide multiple active centers as well as synergistically
alter the reaction pathway, enhancing the catalytic hydrogenation
performance. Herein, a facile route for synthesizing trielement Ru–Ni–Fe
alloy NPs was proposed. The catalytic hydrogenation performance of
NPs was measured using p-nitrophenol as a model.
The synergistic effect of these three elements (Ru, Ni, and Fe) and
synergistic catalysis of multiple crystal faces greatly improved the
catalytic hydrogenation performance of Ru44Ni28Fe28 alloy NPs. Ru with more vacant orbitals showed a
strong coordination with BH4
– for the
generation of active H species. Ni played a major role in transporting
electrons and active H species, increasing the accessibility of catalytically
active sites. Fe could cooperate with BH4
– to produce active H species and promote electrons transfer. Ru44Ni28Fe28 alloy NPs could be reused
and applied for the fabrication of films at the oil–water (ethyl
acetate–water) interface. The densely packed Ru44Ni28Fe28 NP films were good Raman substrates
for monitoring the complete conversion of 4-nitrothiophenol into 4-aminothiophenol.
The rational design of Ru44Ni28Fe28 will broaden the application range of Ru-based catalysts and provide
new insights into the rational design of other multisite alloy catalysts.
Two-dimensional (2D) materials have received increasing attention in the scientific research community owing to their unique structure, which has endowed them with unparalleled properties and significant application potential. However, the expansion of the applications of an individual 2D material is often limited by some inherent drawbacks. Therefore, many researchers are now turning their attention to combine different 2D materials, making the so-called 2D heterostructures. Heterostructures can integrate the merits of each component and achieve a complementary performance far beyond a single part. MXene, as an emerging family of 2D nanomaterials, exhibits excellent electrochemical, electronic, optical, and mechanical properties. MXene-based heterostructures have already been demonstrated in applications such as supercapacitors, sensors, batteries, and photocatalysts. Nowadays, increasing research attention is attracted onto MXene-based heterostructures, while there is less effort spent to summarize the current research status. In this paper, the recent research progress of MXene-based heterostructures is reviewed, focusing on the structure, common preparation methods, and applications in supercapacitors, sensors, batteries, and photocatalysts. The main challenges and future prospects of MXene-based heterostructures are also discussed to provide valuable information for the researchers involved in the field.
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